Search

A protocol of evaluating 2D anode materials that was applied in our previous study has been refined. With the updated Li/Na potential profiles, the two-dimensional biphenyl network (BPN_C) and its isoelectronic structure, boron nitride (BPN_BN), were comprehensively investigated as potential anode materials. The electronic properties, the mechanic strength and the storage capacities were computed accordingly. The band structure results show that the BPN_C and BPN_BN exhibit the nature of conductor and wide-band semi-conductor, respectively. The calculated mechanic strengths of BPN_BN and BPN_C are competent for anode materials. The storage capacities of BPN_C and BPN_BN were addressed by means of the stepwise binding energies (E ad2) and ab initio molecular dynamic simulations. Higher storage capacities were identified as compared with those of the graphene structure. Furthermore, the calculated open-circuit voltages (OCVs) for both BPN_C and BPN_BN can meet the requirements of adequate anode materials. Finally, the diffusivities of Li/Na atoms on the surface of BPN_C and BPN_BN were investigated and found to be suitable for the application as anodes. Our results suggest that the BPN structures can be used as potential anode materials for both LIBs and SIBs. [Display omitted] • Li/Na potential profiles can lead to rational Li/Na adsorption energies and OCVs. • StepWise Adsorption Energies and AIMD can solve Li/Na storage capacities. • CI-NEB results and the diffusion results are consistent and proper. • Results show the potential of BPN be applied in designing anodes. [ABSTRACT FROM AUTHOR]

Developing a self-rechargeable transparent electrochromic energy storage device (EESD) is highly demanding for advancing electrochromic technology and energy harvesting capabilities. In this study, we introduce a room-temperature photo-annealing method to fabricate electrospun titanium oxide (TiO 2) nanofibers, serving as an ion-storage layer (ISL) on the counter electrode. By monitoring the composition and morphology of the precursor before and after ultraviolet/ozone irradiation, we confirm the formation of oxide nanostructures in electrospun TiO 2 nanofibers, which enhances ion transport in the fabricated EESDs. The structural and surface properties of the photo-annealed ISL are comprehensively analyzed using various characterization techniques. Enhanced electrochromic performances are evidenced through cyclic voltammetry, spectroelectrochemical measurements, and charge storage assessments. The Zn-based EESDs with ISL (ISL Zn-EESDs) display rapid electrochemical kinetics, high charge-storing capacities, and long lifespans, with open-circuit potential of 1.2 V, optical contrast of 77 %, discharge capacity of 92 mA h/g, coloration efficiency of 58.63 cm2/C, and 99.9 % efficiency retention up to 250 cycles in both flat and bent states. Furthermore, the practical viability of the ISL Zn-EESDs is demonstrated by powering an LED lamp for several minutes. This approach highlights the potential of ISL Zn-EESDs for developing flexible smart windows, opening up a range of promising applications. • A self-rechargeable electrochromic energy storage device (EESD) was fabricated. • The electrospun TiO 2 nanofibers were prepared by room-temperature photo-annealing. • TiO2 nanofibers served as an ion-storage layer (ISL) on the counter electrode. • The ISL Zn-EESD displayed good electrochemical kinetics and charge-storing capacity. • The ISL Zn-EESD could power an LED lamp for several minutes. [ABSTRACT FROM AUTHOR]

To explain the degradation mechanism of lithium-ion batteries, a nondestructive diagnosis technology to estimate the degree of degradation of the cell components is required. A technology that satisfies that requirement is widely used to analyze the open-circuit voltage (OCV) curve of a cell and estimate the positive-electrode and negative-electrode capacities and the amount of deactivated lithium. However, it has been difficult to estimate the degradation of electrodes composed of active materials with flat electrode potentials, such as lithium iron phosphate (LFP). The novel nondestructive method developed in this study can estimate the degradation state of battery components using LFP by analyzing the "internal resistance curve" of the battery. This method is used to determine the degradation parameters that explain both the measured OCV curve and the measured internal resistance curves of the cell by comparing the internal resistance curves of the cells with those of the positive and negative electrodes. The results of calendar life tests of lithium-ion batteries using LFP at elevated temperature and high voltage were analyzed by using this method, and the results of the analysis show that the degradation of the LFP positive electrode was progressing. • Degradations of cell components can be estimated with the internal resistance curve. • Usable capacities of electrodes in cells using LFP were evaluated in the analysis. • LFP positive electrode deteriorated in calendar life tests at elevated temperature. [ABSTRACT FROM AUTHOR]

Harvesting energy from the natural environment has garnered significant interest due to its eco-friendliness and spontaneity. Here, we present a novel carbon-based rope hydrovoltaic generator, fabricated by a straightforward dip-coating method. Water infiltrates the rope and flows driven by capillary forces, creating a wet/dry interface. An electrical double layer (EDL) forms at the carbon-water interface where wetting occurs, causing protons to accumulate between the wet and dry regions and establishing a substantial potential difference. Under environmental conditions, this setup can induce an open circuit voltage of approximately 0.4 V when a 0.01 mL droplet is applied to the carbon-based rope (with a resistance of 1 MΩ). As a proof of concept, the output performance can be scaled through series and parallel connections, successfully charging a 100 μF capacitor that powers a digital calculator. This simple and flexible hydrovoltaic device provides a new method for clean energy harvesting in practical applications. • A new carbon-based rope hydrovoltaic generator is proposed. • Synergy effects of water flows and electrical double layer induces the electricity. • Exposing such device generates ∼0.4 V voltage when a droplet is applied. • Digital calculator is driven through the capacitor scaled by series connections. [ABSTRACT FROM AUTHOR]

Organic Photovoltaics (OPVs) have emerged as leading materials for next-generation energy sources. Despite the advancements in organic photoactive materials, research on parallel tandem organic photovoltaics (PT-OPVs) has been limited. The efficiency of PT-OPVs can be improved by reducing the difference in the open-circuit voltages (V OC) between the front and back subcells. However, there is a significant gap in research on the middle transparent electrode (MTE), which is crucial for achieving the desired energy-level alignment between the photoactive layers of these subcells and establishing electrical connectivity between them. This gap limits the utilization of reported high-performance photoactive materials in PT-OPV devices. To address this issue, a novel MTE is developed by depositing a copper (I) thiocyanate (CuSCN) hole transport layer on a molybdenum oxide/thin silver/molybdenum oxide (MAM) multilayer structure. The MAM/CuSCN MTE is distinguished by its higher work function and reduced surface roughness. As a result, integrating the MAM/CuSCN MTE in the PT-OPVs substantially increases the V OC of the back subcells (from 714 mV to 773 mV) while simultaneously minimizing the difference in V OC between the front and back subcells; thus, improving the performance of the device. Our findings provide valuable insights into the engineering of MTEs to enhance PT-OPVs' efficiency. [Display omitted] • High-performance parallel tandem organic photovoltaics (PT-OPV) are fabricated. • Single-junction (opaque and semi-transparent) and PT-OPV devices are evaluated. • V OC disparity between the front subcell and back subcell is minimized. • MAM/CuSCN as middle TEs—higher work function & reduced surface roughness. [ABSTRACT FROM AUTHOR]

The integrated design of solar energy conversion and storage systems has attracted increasing attention, and non-spontaneous redox reactions driven by dual photoelectrodes provide a potential solution to this issue. This study presents a solar rechargeable flow battery (SRFB) that combines dual photoelectrodes (BiVO 4 or Mo–BiVO 4 as photoanode, polyterthiophene (pTTh) as photocathode) with cost-effective redox pairs (Fe3+/Fe2+ and Br 3 −/Br−). The system charges under simulated solar illumination (100 mW∙cm−2, AM 1.5G) and releases stored energy controllably as electrical energy. Research indicates the Mo–BiVO 4 photoanode and pTTh photocathode achieve an open-circuit voltage of 0.34 V and a short-circuit current density of 0.38 mA cm−2. Using a specially designed Fe3+/Fe2+-Br 3 −/Br− (Fe–Br) SRFB device made via 3D printing, a charging photocurrent of approximately 1.9 mA cm−2 is attained. In constant current discharge tests, an initial discharge voltage of 0.23 V is observed at 0.1 mA∙cm−2 within the 10 discharge cycles, demonstrating system stability and offering a viable solution for low-cost, large-scale solar energy storage and conversion. • A novel all-in-one solar rechargeable flow battery was designed. • Mo–BiVO 4 and pTTh dual photoelectrodes enables solar-charging of Fe–Br flow battery. • The proposed SRFB system achieved a photocharging current of 1.9 mA cm−2. • The SRFB exhibits stable charge-discharge performance in multiple cycles. • The construction of SRFB provides cost-effective promise for the utilization of solar energy. [ABSTRACT FROM AUTHOR]

Thermocells generate voltage from the temperature difference between a pair of electrodes immersed in a liquid electrolyte. Recent studies showed that natural convection in the liquid thermocells brings a significant amount of heat into the electrolyte, minimizes the temperature gradient, and reduces the open-circuit voltage. Herein, bipolar electrodes (BPEs) are integrated into a thermocell containing aqueous electrolyte of hexacyanoferrate/ferrite to control the natural convection of the thermocell. Simulation of the fluid velocity of the electrolyte showed that the convective flow can be reduced to the half after insertion of one BPE and to the one-third after insertion of two BPEs. The experimental measurement shows the open-circuit voltage was increased by 39% with one BPE and by 55% with two BPEs, because of the enlarged temperature gradient. Further optimization of the position of BPE increased the power output by 54% and the conversion efficiency by 160%, respectively, compared to the conventional single cell. Integration of BPEs is a simple approach to control natural convection in thermocells and can universally be applied to various types of thermocells for increasing the power output and the conversion efficiency for waste-heat recovery. [Display omitted] • Bipolar electrodes (BPEs) are integrated into thermocells for the first time. • Simulation shows that the convective flow of the electrolyte is suppressed by BPEs. • Simulation and experiment show that the temperature gradient is enhanced by BPEs. • Number and position of BPEs are optimized to maximize the power output. • Carbon sheet is used as a cost-effective alternative to replace platinum-made BPEs. [ABSTRACT FROM AUTHOR]

Pressurized operation of Solid Oxide Cells (SOCs) enhances the performance in the fuel cell mode and is mandatory for coupling with gas turbines. For electrolysis, energy demand and balance of plant to pressurize hydrogen or syngas can be reduced. Today's facilities for pressurization of SOCs rely on voluminous pressure vessels that enclose the cells/stacks. Inside such vessel, fuel- and oxidant pressures have to match the vessel pressure to avoid a deterioration of the cells/stacks. Here, a single cell is operated without a pressure vessel in a metallic cell housing sealed towards the cell by a glass-ceramic sealant. Any differential pressure is avoided by a downstream combustor, an approach that is limited to test benches. In our experiments we found that this sealing concept can withstand pressure drops of up to 10 bar towards ambient pressure even after a full thermal cycle. As to be expected from numerous previous studies, open-circuit voltage as well as performance increased significantly with increasing pressure. The power density increased by 20 % in air/dry H 2 at 850 °C and 11 bar a. • Pressurized operation of SOCs without pressure vessel. • Glass ceramic sealed SOC gastight up to 11 bar a. • Open circuit voltages of up to 1.42 V achieved at 850 °C. • SOC performance increase of 20 % achieved at 11 bar a. [ABSTRACT FROM AUTHOR]

As the demand for lithium titanate oxide (LTO) batteries increases in high-power applications, their health estimation, especially the degradation mode diagnostics, is critical for the safe and economical operation of battery systems. However, various operation and environmental conditions can alter the aging of LTO cells, with few related studies. In this study, the changes in the electrode open-circuit potential (OCP) after aging are investigated and their effects on the full-cell open-circuit voltage (OCV) are discussed. An aging-aware modified electrode model is developed to simulate the evolution of the electrode OCP and used to diagnose the degradation mode by reconstructing the full-cell OCV curve. Unlike traditional polynomial models that lack physical meaning, the proposed aging-aware modified model reveals the changes in the phase transition process by identifying the warping paths of the incremental capacity curves. Compared with using only the pristine or aged OCP curves, using the synthesized OCP curves from the proposed model improves the accuracy of reconstructing full-cell OCV curves over the full life cycle, reducing the average RMSE from 80 mV to less than 8 mV. Moreover, the proposed model improves the validity of degradation mode diagnosis and adapts to different cycling conditions and different battery samples. [Display omitted] • The shape change of the electrode OCP curves of LTO batteries is investigated. • An aging-aware modified electrode model based on the DTW method is developed. • Improving the validity of degradation mode diagnosis despite changes in OCV curve. • The proposed model is robust to different cycling conditions and battery samples. [ABSTRACT FROM AUTHOR]

A potential opportunity to improve the integrated betavoltaic batteries and low-power cells performance is the radionuclide-activation method, which is an integrated combination of an injection source and an energy converter in the one material. Energy converters that contain an activated SiC thin film as the Si 14 C-Si barrier heterojunctions energy converter in betavoltaic cell are considered. The Si 14 C-Si heterojunction is positioned as by 14 C beta source doped direct energy converting material two-in-one, for the device structure with an emitter of Si 14 C with optimized thickness is 0. 4 μ m and the doping concentrations of N-SiC/p-Si are 15. 7 ÷ 15. 9 × 1 0 17 / 16. 2 × 1 0 17 ÷ ∼ 1 0 19 cm − 3. To ensure efficient operation of a betavoltaic element, the mathematical model determines: the short circuit current density is up to 900 nA cm−2, the open circuit voltage is up to 1.21 V, the fill factor is 0.9, the maximum output power density is up to 300 nW cm−2, the conversion efficiency is up to 16% and up to 0.5 V voltage per load in the experiment. The calculation and experimental verification results indicate that the Si 14 C-Si structure improved output performance of the nuclear cell by reducing the radioactive source self-absorption energy losses and due to better energy deposition distributions of inner injector. The results are valuable for optimizing the integrated betavoltaic elements production. [Display omitted] • SiC thin film is integrated with Carbon-14 as activated converter for betavoltaic cell. • Si14C-Si heterojunction reduces energy loss by improving energy deposition. • Optimal Si14C-Si reaches 21.31% energy conversion, J sc =900 nA/cm2, V oc =1.2 V, FF=0.9. • Potential profile determines transfer and separation of nonequilibrium EHPs. [ABSTRACT FROM AUTHOR]

The development of new cathode materials for aqueous zinc ion batteries (AZIBs) is a critical step toward developing robust and large-scale electrochemical energy conversion and storage systems. Recent studies in this field have witnessed the emergence of manganese-based oxide cathode materials, with manganese dioxide (MnO 2) growing as a promising one owing to its high capacity, impressive energy density, high operating voltage, and cost-effectiveness. Nevertheless, the practical utilization of MnO 2 cathodes confronts substantial challenges like sluggish diffusion kinetics, low electronic conductivity, and structural instability during the cycling process. In this review, we present a thorough examination of the key approaches adopted by researchers to address the prevailing challenges and improve the MnO 2 cathode's electrochemical performance. We first discuss the structures of different MnO 2 polymorphs, followed by various synthesis techniques commonly employed to obtain electrochemically engineered MnO 2. Then we discuss the challenges associated with MnO 2 cathode when employed in AZIB. Next we thoroughly investigate three main strategies (preintercalation, defect engineering, and composite formation) opted to enhance MnO 2 performance. In conclusion, we outline the challenges and prospects inherent in these strategies, to further improve MnO 2 performance thereby advancing its utility as a cathode material for AZIB. [Display omitted] • MnO 2 is the most promising cathode material for zinc-ion battery. • It offers high theoretical capacity and open circuit voltage. • Poor structural stability and slow reaction kinetics hinder its utility as a cathode. • Methods to improve MnO 2 are: pre-intercalation, defect engineering and composites. • This is a consolidated and a comprehensive review of all the strategies adopted. [ABSTRACT FROM AUTHOR]

The global energy transition is based on renewable energy sources and batteries to store electrical energy. Efficient use of batteries requires accurate state estimation algorithms and proper control. In this paper, a data-driven method for estimating a battery dynamic model using a Tensor Train (TT) is designed and tested. The method intrinsic efficiency in handling high-dimensional data allows one to develop an algorithm, that can use a batch of observable variables to reconstruct a system dynamics with negligible computational costs and reliable accuracy, as well as without any preliminary characterization test data. Here, the method is applied to reconstruct a dynamic battery model from operational data and tested upon a solid state lithium-ion battery cell. Furthermore, the explanatory power of the method is demonstrated by extracting the open circuit voltage and the impedance in the form of a relaxation times distribution, as well as the activation energy related to temperature dependence, and its accuracy is further validated against the results of standard battery characterization tests. Due to intrinsic scalability and low computational costs, the method can become a part of AI-driven battery management systems, thus improving battery durability and safety, as well as helping to optimize time-consuming battery characterization tests. • TT-based method allows to reconstruct a battery electric model with error within 5%. • Battery operation data only are used without time-consuming characterization tests. • Meaningful information (OCV, impedance, and activation energy) is extracted. • The method computational efficiency allows one to use it in real-time systems. [ABSTRACT FROM AUTHOR]

We present an out-of-equilibrium thermodynamics method for lithium-ion batteries' (LIB) state-of-charge (SOC) assessment during ultra-fast charging using the non-linear voltammetry (NLV) algorithm. NLV consists of applying short constant voltage pulses followed by a very short relaxation period. The out-of-equilibrium open-circuit voltage during the relaxation period is addressed to as pseudo-open-circuit voltage (p-OCV). From the p-OCV temperature dependence, pseudo-entropy and pseudo-enthalpy are determined, denoted as p- Δ S and p- Δ H , respectively. It is found that the SOC follows the "Yazami theorem", which theorizes that SOC is a linear function of p- Δ S and p- Δ H. Out-of-equilibrium p- Δ S and p- Δ H together with incremental capacity (IC) analysis reveal different steps during the charging process, which are assigned to phase transitions in the LIB's anode and cathode materials. • Estimation of out-of-equilibrium thermodynamics during the fast charging process. • Analysis of non-linear voltammetry fast charging under various operating conditions. • High accuracy SOC assessment from out-of-equilibrium thermodynamics. • Battery temperature prediction during NLV ultra-fast charging. [ABSTRACT FROM AUTHOR]

Rapid and reversible performance loss in proton exchange membrane fuel cells (PEMFCs) has been observed due to membrane chemical degradation. Despite various experimental efforts, challenges persist in studying the membrane degradation dynamics and its connection to performance loss. While many membrane degradation models exist, they significantly underestimate the performance decay and fail to replicate its reversibility, limiting their predictive capacity. To address this gap, we present a physics-based membrane degradation model that effectively captures the decay and recovery of both open circuit voltage (OCV) and performance by incorporating the release and transport of sulfate and sulfonate, byproducts of membrane degradation, as well as their interactions with catalyst layers. Simulation results are compared with experimental data from the literature, successfully replicating sulfate adsorption, OCV/performance loss/recovery, and byproduct release rates. Further analyses reveals the role of membrane degradation in reversible performance loss, suggesting that the performance decay is primarily attributed to catalyst poisoning, while the reduced resistance is due to membrane thinning from the much faster mainchain degradation process. Our results also indicate that the H 2 /N 2 recovery protocol is less effective than H 2 /air due to the fast condensation of supersaturated gases in channels and the absence of water generated by electrochemical reactions. [Display omitted] • A membrane degradation model with effects of decomposition products is presented. • The reversible performance loss and release of anions in experiments is replicated. • The OCV loss is mainly due to the poisoning of membrane decomposition products. • A faster degradation of mainchain can lead to smaller proton transport resistance. • H 2 /N 2 recovery protocol is found to be less effective than the H 2 /air protocol. [ABSTRACT FROM AUTHOR]

Overcoming the formidable challenge of achieving multifunctionality and a seamless bio-interface for triboelectric nanogenerators (TENGs) is a persistent pursuit. Here, a biomaterial-based nanocomposite designed for both energy harvesting and storage is presented. Molybdenum disulfide nanosheets (MoS 2 -NSs) are securely and uniformly incorporated into silk fibroin (SF). The resulting MoS 2 -NS/SF TENG, in conjunction with a tribo-negative polymer, exhibits an open-circuit voltage (V oc) of 0.95 kV, an average short-circuit current (I sc) of 2.2 μA, and an output power density of 60 μW/cm2—sufficient to illuminate 40 light-emitting diodes (LEDs). Notably, exposure to light triggers a substantial increase in V oc s by more than 26 %. Additionally, the MoS 2 -NS/SF nanocomposite enables efficient energy storage, with a frequency-dependent dielectric constant ranging from 28.2 to 2.6. This underscores its potential as a versatile electronic material platform for wearable devices, seamlessly integrating motion sensing, energy harvesting, and charge storage capabilities. [Display omitted] • A Silk fibroin-MoS 2 (MoS 2 -NS/SF) nanocomposites based TENG device is presented. • MoS 2 -NS/SF and PVBVA act as positive and negative triboelectric material. • A high V oc (∼0.95 kV), I sc (∼2.2 μA), and a power density (∼78 mW/cm2) are obtained. • The TENG device shows a high sensitivity against light illumination. • MoS 2 -NS/SF nanocomposite can also be utilized as a charge storing device. [ABSTRACT FROM AUTHOR]

In light of the immense potential solid-state photo-rechargeable batteries hold in the efficient utilization of renewable solar energy, there is a rapidly growing demand for materials that possess both energy harvesting and storage capabilities. In this study, a solid-state photo-rechargeable battery has been designed based on the FTO(Fluorine-doped SnO 2 transparent conductive glass)/TiO 2 /Cs 3 Bi 2 Br 9 /Pt/FTO system, which achieves dual functions of photoelectric conversion and energy storage. The inorganic bismuth-based material employed in these batteries exhibits commendable cyclic stability. Under photo-rechargeable conditions, a single cell can maintain an open-circuit voltage as high as 0.45 V in the absence of illumination. By connecting multiple cells in series, we succeed in powering an LED (Light-emitting diode) continuously for 1 min without light exposure. The findings of this research open new avenues for the design and development of novel materials that could enable highly efficient solid-state photo-rechargeable batteries. [Display omitted] • Open new avenues for the design and development of novel materials for photo-rechargeable batteries. • The inorganic Cs 3 Bi 2 Br 9 employed in these batteries exhibits commendable cyclic stability. • LED was continuously powered for 1 min. [ABSTRACT FROM AUTHOR]

The tin dioxide (SnO 2) layer is commonly used as a traditional electron transport layer (ETL) in perovskite solar cells. However, it exists numerous defects in interior and on surface, diminishing the electron transport rate and causing energy level mismatches, thereby limiting the photoelectric conversion efficiency (PCE). In this study, cadmium p-aminobenzoate (PABACd) is synthesized using the displacement reaction and applied to modify the interface between the SnO 2 ETL and CsPbI 2 Br film to achieve bidirectional passivation. Cd2+ effectively passivates defects in the ETL and penetrates perovskite crystals, contributing to defect passivation. Furthermore, PABA− stabilizes the [PbX 6 ]4− octahedron, enhancing the stability of CsPbI 2 Br perovskite solar cells (PSCs). As a result of these interactions, the PABACd-optimized device achieved a maximum PCE of 14.34 % and an outstanding open-circuit voltage of 1.27 V. Simultaneously, the PCE of the optimized CsPbI 2 Br PSCs remains at 92 % of the initial efficiency after 30 days of aging in an air environment with 15–20 % humidity. [Display omitted] • Passivating agent cadmium p-aminobenzoate (PABACd) is prepared. • PABACd is used to bidirectionally passivate the ETL and CsPbI 2 Br interface. • The carbon-based CsPbI 2 Br PSC yields a high PCE of 14.34 % with a Voc of 1.27 V. [ABSTRACT FROM AUTHOR]

This study investigates the durability of high temperature proton exchange membrane fuel cells (HT-PEMFCs) under various thermal cycling conditions: temperature changes between 140 °C and 180 °C (TC1), simulated 50 °C to 160 °C start–stop cycles (TC2), and 50 °C to 160 °C start–stop cycles under open circuit voltage (TC3). Accelerated stress tests and electrochemical evaluations were used to study voltage degradation, shifts in polarization curves, electrochemical impedance spectroscopy (EIS), and phosphoric acid (PA) leaching. The findings indicate escalating voltage degradation rates, peaking at 75.6 μ V h−1 in TC3, significantly higher than the 14.2 μ V h−1 observed at a steady 160 °C. Additionally, a decline in polarization curves and increased PA leaching were noted, with the most significant escalation in TC3, where it reached 36.1 ng cm−2 h−1, compared to 6.9 ng cm−2 h−1 in TC1 and 8.3 ng cm−2 h−1 under constant temperature. Furthermore, EIS analysis indicated substantial increases in charge transfer and ohmic resistance under the various thermal cycling tests. These results underscore the crucial need for improved thermal management strategies in HT-PEMFCs to enhance their durability under fluctuating thermal conditions. • Thermal cycling accelerates degradation in HT-PEMFCs. • OCV cycles increase resistances due to membrane and acid loss. • Start/stop and OCV cycles worsen voltage degradation. • Acid loss reduces proton conductivity and performance. [ABSTRACT FROM AUTHOR]

The key component of a polymer electrolyte membrane (PEM) water splitting electrolyzer is its membrane. Despite decades of research, the transport phenomena occurring within the membrane during electrolysis – which are vital to the device's efficiency – have yet to be fully understood. In this work, controlling the anolyte concentration can effectively be used to tune the PEM water gradient, but it comes with a tradeoff in electrochemical performance. Infrared (IR) imaging is coupled with electrochemical impedance spectroscopy and distribution of relaxation times to elucidate the relationship between membrane hydration and ohmic, kinetic, and mass transport losses. Varied H 2 SO 4 anolyte concentrations manifested water diffusion gradients through the PEM of the electrolyzer, where the strongest water diffusion gradients | Δ λ f i t ‾ | (relative to open circuit voltage) were observed for the most concentrated anolyte. However, tuning the anolyte concentration came with a tradeoff between a lower ohmic resistance (from 4.4 Ω cm−2 to 4.0 Ω cm−2 for 0.1 mol L−1 to 1.0 mol L−1 H 2 SO 4 anolyte) and higher kinetic and mass transport losses accompanied by increasingly unstable performance. These findings showcase the potential of IR imaging when coupled with a microfluidic PEM electrolyzer and electrochemical characterization techniques, and the influence of anolyte concentration for manipulating the PEM water gradient. [Display omitted] • IR imaging visualized membrane water diffusion across the PEM during electrolysis. • PEM water transport can be tailored through the supplied electrolyte concentration. • The combination of EIS and DRT diagnosed voltage losses during electrolysis. • Varied electrolytes yield tradeoff between ohmic and kinetic/mass transport losses. [ABSTRACT FROM AUTHOR]

Direct borohydride fuel cells (DBFCs) outperform the other direct liquid fuel cells by a higher open circuit voltage and energy density. However, their benign performance and efficiency are highly dependent on high-performance anode catalysts. This study delves into the enhancement of borohydride oxidation reaction (BOR) kinetics through an octahedral Pt–Ni/C catalyst. The Pt(111) facets of the catalyst exhibit a combination of abundant active sites exposed for BOR and the inherent ability to suppress hydrolysis reaction. Furthermore, the synergistic incorporation of Ni modifies the electronic structure of Pt, resulting in enhanced OH− adsorption and hydrogen oxidation reaction (HOR) activity. This multifaceted approach not only mitigates hydrogen accumulation but also boosts the overall BOR efficiency. The elaborate electrochemical measurements along with comprehensive characterizations elucidate the superior catalytic activity and stability of Pt–Ni/C over commercial Pt/C catalysts. Specifically, DBFCs employing the Pt–Ni/C catalyst manifest considerably higher open circuit voltage (1.05 V), peak power density (1.82 W cm−2) and fuel efficiency (63.96 %) than those of DBFCs employing Pt/C catalyst. Through these efforts, we provide significant insight into the design of high-performance anode catalyst for DBFCs. • Pt(111) facets have abundant active sites for BH 4 − oxidation. • Incorporating Ni into the Pt catalyst promotes efficient OH− adsorption. • Pt–Ni/C enhances HOR activity and minimizes hydrogen accumulation in the anode. • Pt–Ni/C delivers high power output and excellent fuel efficiency. [ABSTRACT FROM AUTHOR]

The highly coupled nature of the reaction process and the multitude of model parameters in proton exchange membrane fuel cell pose significant challenges in establishing a high-confidence and high-precision model. In this paper, a multi-physics model is developed, which couples electrochemical reactions, multiphase water conversion, together with mass and charge transport processes. Through single-factor sensitivity analysis involving physical, mass transfer, heat transfer, and electrochemical parameters, seven sensitive parameters with their overlapping relationships related to open circuit voltage loss, activation loss, and ohmic loss under both low and high current densities have been identified. A detailed model parameter identification method specifically designed for low current densities is proposed based on parameter decoupling and the analytical Butler-Volmer equation. Finally, polarization curve and ohmic impedance experiments are conducted using a proton exchange membrane fuel cell with single serpentine flow channel at various temperatures and pressures to obtain voltage losses for parameter identification. The results show that the maximum relative error in the polarization curves is 2.08% with an average relative error of 0.81% under different conditions, thus validating the effectiveness of the proposed method. • The open circuit loss based on hydrogen crossover is considered. • The sensitive parameters and their overlapping relationships of voltage losses are discovered. • Reveal the reason for parameter identification from low current density to high current density. • A fast and accurate parameter identification method for PEMFC model is proposed. [ABSTRACT FROM AUTHOR]

Quantitative analysis of the aging process of lithium-ion batteries by using electrochemical thermodynamic and kinetic parameters such as electrochemical potential, Li stoichiometry, and Li inventory loss is a key research topic in the development of Li-ion battery for electric vehicles and smart grids. It is generally known the above parameters can be acquired through the analysis of Electromotive Force (EMF) or Open-Circuit Voltage (OCV) curves. In this work, we proposed and applied five EMF measurement techniques to obtain the EMF-SoC relationships in LFP/Gr single-layer laminated pouch cells at different temperatures and States of Health (SoH), and comprehensively examined them from the viewpoints of eight evaluation dimensions. A Python program, named Degradation Modes Analysis (DMA), is used to diagnose the thermodynamic degradation modes of the battery automatically. Furthermore, electrochemical kinetic parameters were also extracted along with the depolarization process. For faster and more accurate aging diagnosis, we recommend an optimal blend of short relaxation time GITT (Short-Rest-GITT) and extrapolated EMF (Extrap-EMF) to reach the most precise EMF measurements and gain the most comprehensive information about battery thermodynamics and kinetics at the same time. [Display omitted] • Five EMF measurement techniques for Li-ion batteries are compared. • LFP/Gr batteries aged at three temperatures are analyzed. • A written DMA Python program is presented. • Kinetic parameters are extracted during the depolarization process. [ABSTRACT FROM AUTHOR]

Enzymatic biofuel cells (EBFCs) are emerged as promising power sources for implantable devices, offering excellent form factor and performance. For these applications, EBFCs require customer tailored structure and more than 10 μW power. In this study, flexible and stretchable EBFCs are suggested, assessing their performance using tube-type artificial blood vessel (TABV) cell kit with sheep blood fuel. To fabricate the EBFCs, buckypaper (BP) is molded to polydimethylsiloxane (PDMS) to fabricate BP@PDMS electrode that shows excellent strain rate (95 %) and durability (1500 cycles) in tensile and fatigue tests. Additionally, electrochemical evaluations are implemented to measure the performance of anode and cathode fabricated with BP@PDMS. In anode including 1,10-phenanthroline-5,6-dione and glucose dehydrogenase, maximum reactivity of glucose oxidation is 1.05 mA/cm2, while in cathode including bilirubin oxidase, that of oxygen reduction is 0.61 mA/cm2. Regarding flexibility, anode and cathode are little affected by current density irrespective of bending angle, proving that the fabricated anode and cathode have good flexibility. To emulate the behavior of EBFCs in actual blood vessel, EBFCs are implanted in TABV cell kit, fueling sheep blood. Observed open circuit voltage of 0.59 V and maximum power of 26 μW reveals that fabricated EBFCs have superior potential to be considered as power sources for implantable devices. [Display omitted] • Performance of flexible/stretchable EBFCs is assessed by in-house tube cell. • EBFCs including sheep blood fuel are well operated. • PDMS molded BP electrode shows excellent strain rate and durability. • Current density of electrodes is little affected by bending angle. • EBFCs shows excellent open circuit voltage (0.59 V) and maximum power (26 μW). [ABSTRACT FROM AUTHOR]

The glucose fuel cells (GFCs) leverage the implant surface as an electrode, representing an optimal approach for miniaturizing implantable power sources. A conductive hydrogel electrode membrane is crafted through in situ reduction and electrochemical co-deposition techniques by employing bacterial cellulose as a scaffold. This process enables the seamless integration of the GFC directly onto the implant surface. The integrated GFC exhibits an impressive open-circuit voltage peak of 0.894 V and a peak power density of 94.7 μW cm−2. Additionally, the fuel cell demonstrates resistance to chloride ion toxicity under simulated interstitial fluid conditions. Although performance within horse serum is moderate, the methodology presents a viable strategy for developing GFCs on implant surfaces. • Cell's cathode and anode utilize bacterial cellulose and platinum nanoparticles. • Bacterial cellulose templating and electrochemical co-deposition are utilized. • The GFC exhibits a Voc of 0.894 V, along with a power density of 94.7 μW cm−2. • The anode membrane resists chloride ion poisoning, enhancing cell stability. [ABSTRACT FROM AUTHOR]

When two electrode open-circuit potentials form a full-cell OCV (open-circuit voltage) model, cell-level SOH (state of health) parameters related to LLI (loss of lithium inventory) and LAM (loss of active materials) naturally appear. Such models have been used to interpret experimental OCV measurements and infer these SOH parameters associated with capacity fade. In this work, we first re-parametrize a popular OCV model formulation by the N/P (negative-to-positive) ratio and Li/P (lithium-to-positive) ratio, which have more symmetric and intuitive physical meaning, and are also pristine-condition-agnostic and cutoff-voltage-independent. We then study the modal identifiability of capacity fade by mathematically deriving the gradients of electrode slippage and cell OCV with respect to these SOH parameters, where the electrode differential voltage fractions, which characterize each electrode's relative contribution to the OCV slope, play a key role in passing the influence of a fixed cutoff voltage to the parameter sensitivity. The sensitivity gradients of the total capacity also reveal four characteristic regimes regarding how much lithium inventory and active materials are limiting the apparent capacity. We show the usefulness of these sensitivity gradients with an application regarding degradation mode identifiability from OCV measurements at different SOC (state of charge) windows. [Display omitted] • An electrode-specific OCV model parametrized by N/P and Li/P ratio. • Degradation modes and electrode SOC based on material-specific usable stoichiometry range. • Electrode differential voltage fractions indicating the limiting electrode. • Four regimes of degradation identifiability characterized by Li/N and Li/P ratio. • Informative SOC windows for degradation mode estimation by Fisher information. [ABSTRACT FROM AUTHOR]

Magnesium-ion batteries (MIBs) are emerging as a promising alternative to lithium-ion batteries (LIBs) due to their superior safety features and cost-effectiveness. In this work, heteroatoms-co-doped oxo-triarylmethyl (B/N/P@oxTAM) as a favorable anode material for MIBs was investigated using density functional theory calculations. The B/N/P@oxTAM is a highly porous structure and has a better affinity for Mg-ions to attach to vacancy site. Partial density of states, open-circuit voltage, theoretical specific capacity, and diffusion energy barrier were calculated and discussed. A significant decrease in the HOMO-LUMO gap with no structural deformation occurred, suggesting the high cycling performance of B/N/P@oxTAM for MIBs. Moreover, the designed anode material demonstrated full loading with six Mg-ions at different active sites, indicating a high theoretical specific capacity of 513.75 mAh g−1 and a low open-circuit voltage of 0.07 V. The presence of a heterocyclic ring (borabenzene) with a diffusion energy barrier of 0.039 eV increased the diffusion of Mg-ions. Therefore, B/N/P@oxTAM can be used as a viable anode material for MIBs with extended life cycle and quick charge-discharge rates due to its low open-circuit voltage and diffusion energy barrier, as well as its high theoretical specific capacity value. [Display omitted] • The B/N/P@oxTAM is designed as an anode material for Mg-ion batteries. • The co-doping enhances the electrical conductivity of the pristine oxTAM. • The anode can store six Mg-ions with specific capacity of 513.75 mAh g−1. [ABSTRACT FROM AUTHOR]

Developing a dual-functional photocatalytic fuel cell (PFC) with improved solar-to-electricity energy conversion efficiency and renewable biomass sensitivity performance is of great significance for clean energy conservation and utilization. Herein, a novel PFC device with stable signal output and glucose sensing performance is fabricated, of which polyaniline (PANI) functionalized p-type silicon nanowire arrays (SiNWs) and In 2 S 3 modified n-type SiNWs are utilized as the photocathode and photoanode, respectively. The optimal PFC exhibits excellent cell performance under AM 1.5G illumination with an open circuit voltage of 0.83 V and a high-power density of 163.010 μW cm−2. The PFC also achieves effective glucose detection performance with a low detection limit of 0.998 μM and a broad linear range of 0∼50 mM, as well as excellent selectivity and stability. The enhanced performance is attributed to the efficient carrier separation and charge transfer rate at the interface of the heterojunctions, which is facilitated by the high conductivity of uniform PANI film on the p-SiNWs and S-scheme band alignment formed in the photoanodes. This work opens a new path for improving the energy conversion efficiency in traditional PFCs and offers guidance for sensing strategies toward renewable biomass using PFCs. A dual-functional photocatalytic fuel cell (PFC) with improved solar-to-electricity energy conversion efficiency and renewable biomass sensitivity performance was developed. [Display omitted] • Novel SiNWs-based PFC to achieve the dual-function of solar-to-electricity conversion and self-powered glucose detection. • The uniform conductive PANI films on the p-SiNWs photocathode accelerate the charge transfer rate at the interface. • The S-scheme band alignments in the n-SiNWs/In 2 S 3 heterojunction improve the carrier separation and transfer efficiency. • Excellent energy conversion and effective detection performance towards glucose. [ABSTRACT FROM AUTHOR]

In this publication we extend a state-of-the-art electrode open circuit potential model for blend electrodes and inhomogeneous lithiation. We introduce a bi-level optimization algorithm to estimate the open parameters of the electrode model using measurements conducted on the full-cell level with state-of-the-art testing equipment. As input for the optimization algorithm, we use data from a pseudo open-circuit voltage aging study to estimate the electrode potential curves, the electrode capacities, and the capacity of cyclable lithium over lifetime without opening the cell. We validate our method against measurements on commercial lithium-ion cells with the electrode materials LFP-C, NMC-SiC and NCA-SiC, and compare the estimated electrode pseudo open-circuit potential curves to measurements conducted on harvested half-cells. We conclude that the presented non-destructive method of half-cell open-circuit potential modeling offers an alternative to complex cell disassembly and electrode material harvesting for degradation mode analysis. [Display omitted] • Physical motivated model for blend electrodes and inhomogeneous lithiation; • Non-destructive estimation of electrode potential curves; • Validation on commercial LFP-C, NMC-SiC and NCA-SiC Li-ion cells; • Novel non-destructive degradation mode analysis. • Achievement of model-based fitting voltage RMSE < 6 mV over lifetime; [ABSTRACT FROM AUTHOR]

Self-powered visible-blind ultraviolet (UV) photodetectors have emerged as sustainable alternatives in various sectors, including security, surveillance, and environmental monitoring. So, we report a vanadium oxide (V 2 O 5) hollow nanofibers-based supercapacitor-inspired triboelectric nanogenerator (STENG) as a self-powered visible-blind UV photodetector. A novel designed STENG is fabricated using electrospun V 2 O 5 hollow nanofibers-based coated on indium tin oxide coated polyethylene terephthalate sheet (ITO/PET) on top side and a layer of polyvinyl alcohol (PVA) & sulphuric acid over multi-walled carbon nanotubes (MWCNT) coated graphite sheet on bottom side. The optimized STENG demonstrates 34 V peak-to-peak open circuit voltage (Voc) and 2 μA of peak-to-peak short circuit current (Isc) by applying force via finger tapping. However, STENG's performance improves significantly to deliver 280 V Voc (peak-to-peak), and 6 μA Isc (peak-to-peak) with 0.49 W/m2 power density at 100 MΩ load resistance due to electrochemical charging. The output voltage of the STENG increases by 400 % under UV light, which refers to the excellent performance of STENG as a self-powered visible-blind UV photodetector with 266 V/W responsivity at 2.5 mW/cm2 intensity. Hence, the as-fabricated V 2 O 5 hollow nanofibers-based STENG not only paves the way to fabricate a high-performance energy harvester, but can also be used as a self-powered UV-photodetector. [Display omitted] • A novel V 2 O 5 hollow nanofibers based triboelectric nanogenerator(TENG) is proposed. • The TENG is developed by mimicking solid-state hybrid supercapacitors (SC). • The Performance of SC-inspired TENG(STENG) is improved by electrochemical charging. • The STENG is demonstrated as a self-powered visible blind UV photodetector. [ABSTRACT FROM AUTHOR]

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) have attract much attention from academic and industry, which can improve the catalyst activity, reduce Pt loading, enhance CO tolerance, and simplify water and heat management. High-temperature proton exchange membrane (HT-PEM) is the key component for HT-PEMFCs. Here, we provide an investigation of newly developed HT-PEM to evaluate its properties and performances in fuel cells above 90 °C. The HT-PEM exhibits an excellent proton conductivity of 136.1 mS cm−1 at 90 °C and 95% RH, and remarkable power density of 0.95 Wcm−2 at 105 °C and 80% RH. The stability and durability of HT-PEM are studied with varied testing methods. After the continuous operation at open circuit voltage (OCV) for 500 h and continuous dry-wet circulation for 20000 cycles at 90 °C, negligible change of OCV and hydrogen permeation current density are recorded, indicating good chemical and mechanical stability for HT-PEM. The improved property and performance originate from the new PFSA base material and improved morphology, in which the larger ionic clusters and continuous proton-transfer channels contribute to the superior performance, and the high glass transition temperature (T g ∼132 °C) induces good stability. • A newly developed perfluorosulfonic acid proton exchange membrane (HT-PEM) was evaluated for fuel cells above 90 °C. • The larger ionic clusters and continuous proton-transfer channels contribute to the superior performance, and the high glass transition temperature (T g ∼132 °C) induces good stability. [ABSTRACT FROM AUTHOR]

The chemical degradation of the proton exchange membrane (PEM) causes the changes in membrane properties and morphology, which directly affects the cell performance and membrane degradation. In this work, the changes of PEM during the chemical degradation are theoretically analyzed at both microscopic and mesoscopic levels. Based on the theoretical study, a bidirectionally coupled physical model of PEM fuel cell (PEMFC) performance and PEM chemical degradation is developed, which is used to investigate the evolutions of cell performance and chemical degradation. It can be found that the open circuit voltage first increases slightly and then decreases with time, and the ohmic loss increases rapidly under accelerated degradation conditions. The membrane chemical degradation is analyzed in terms of four aspects: the mass loss rate of the membrane, the region of pronounced degradation, the contribution of different degradation mechanisms and the proportion of ionomer species remaining. Furthermore, the effect of operating conditions on the degradation is examined. The degradation is most sensitive to voltage and has the fastest rate at high voltage, high temperature, high gas pressure and relative humidity of 60%. This work provides a deep insight into the PEM chemical degradation, which is instructive for the long-term prediction of PEMFC lifetime. [Display omitted] • The changes of PEM are analyzed from both micro and mesoscopic levels. • Bidirectional coupling of PEMFC performance and PEM decay models. • The evolutions of PEM, PEMFC performance and degradation are analyzed. • Effects of operating conditions on degradation have been considered. [ABSTRACT FROM AUTHOR]

Aqueous organic redox flow batteries (AORFBs) operated at neutral pH are considered a promising energy storage technology for massive-scale renewable energy storage. The development of suitable electrolytes is of particular significance because they determine the performances and cost of AORFBs. Viologen based redox-active materials are typical negative electrolytes for pH-neutral AORFBs. However, the widespread adoption of most reported viologen derivatives is limited by their solubility in water and the complicated synthesis. Herein, we propose a densely hydroxylated viologen, which can be obtained readily through a one-step synthesis with a yield of 70%, promising an ideal negative electrolyte for pH-neutral AORFBs. When operated in a 0.1 M practical pH-neutral AORFB against NMe-TEMPO, the battery displays an open-circuit voltage of 1.32 V, and delivers a capacity retention rate of 99.979% per cycle (temporal capacity fade rate of 0.18% per hour) over 600 consecutive cycles. An energy-dense pH-neutral AORFB based on this densely hydroxylated viologen is demonstrated and the mechanism leading to battery capacity fade is analyzed. [Display omitted] • A densely hydroxylated viologen is proposed as a negolyte for pH-neutral AORFBs. • The highly water soluble BDiOH-Vi is obtained by a facile one-step synthesis. • The degradation mechanism of BDiOH-Vi during AORFB cycling is disclosed. [ABSTRACT FROM AUTHOR]

Zinc-bromine flow batteries (ZBFBs) are regarded as one of the most appealing technologies for stationary energy storage due to their excellent safety, high energy density, and low cost. Nevertheless, their power efficiency and cycling life are still limited by the sluggish reaction kinetics of the Br 2 /Br− redox couple and the shuttle effect of bromine species. Herein, we report a catalytic cathode for ZBFBs enabled by graphite felt electrode functionalized by cobalt and nitrogen-containing carbon nanocomposites (Co-N/C@GF). The nitrogen-rich groups and metallic cobalt nanocrystal inculsions in the Co-N/C@GF promote the absorption of Br 2 and provide abundant catalytic active sites for the Br 2 /Br− redox reaction. Consequently, the electrochemical performance of ZBFB has been significantly enhanced. The ZBFB using Co-N/C@GF exhibits a high voltage efficiency of 86.06% and excellent energy efficiency of 84.7% at a current density of 80 mA cm−2. It also demonstrates suppressed self-discharge characteristic (keep high open circuit voltage within 84 h) and long cycle life of more than 400 cycles. Furthermore, the ZBFB can also operate stably at ultra-high current density of 180 mA cm−2, and the voltage efficiency reaches 62.8%. Therefore, this work provides an effective approach to developing high-performance ZBFBs. Cobalt and nitrogen-containing carbon nanostrutures are successfully grown on graphite fiber electrode (Co-N/C@GF), which catalyse the Br 2 /Br− redox reaction, suppresses the shuttling effect of polybromine ions and enhance the electrochemical performance of Zinc-bromine flow battery. [Display omitted] • An ultra-hydrophilic composite cathode with catalytic Co-N/C doping is designed. • Co-N/C@GF greatly improves the redox kinetics and reversibility of Br 2 /Br−. • The battery achieves excellent energy efficiency of 84.7% at 80 mA cm−2. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries exhibit path-dependent aging behavior. Degradation mode (DM) estimation is a first step towards accurate state of health (SOH) representations by clustering degradation mechanisms. Mechanistic models shift and scale pristine half-cell open circuit potential (OCP) curves of both electrodes to reconstruct the open circuit voltage (OCV) curve by minimizing the difference between measured and reconstructed OCV. Alignment parameters describe the shift and scaling of the OCPs and can be used to estimate SOH and DMs. This study introduces the Δ Q -method, which relies on relaxed voltage points and accumulated charge between these points. It is independent of current rates and applicable after almost every event. The optimization problem minimizes deviation between measured and reconstructed Δ Q. The method is developed with an automotive cell dataset and validated with real-world vehicle data from the BMW i3. The Δ Q -method achieves a mean absolute SOH estimation error of 2.52 % and a mean absolute OCV reconstruction error of 7.19 mV. Reliable estimations are ensured by predefined filters. The method remains effective with restricted state of charge (SOC) windows or limited data points. It is robust against variations in input data, solver choice, and optimization settings. Convergence is improved by constraining the solution space. [Display omitted] • A novel method for full OCV curve reconstruction is introduced. • Method utilizes captured relaxed voltage points within the last month. • Method works with only three relaxed voltage points within a SOC window of 30 % to 75 %. • Method is validated with real-world vehicle data from the BMW i3. [ABSTRACT FROM AUTHOR]

In order to improve corrosion resistance and electric conductivity of titanium bipolar plate (BPP) for proton exchange membrane water electrolyser (PEMWE), three different metal nitride (i.e.Ta/TaN, Cr/CrN and Nb/NbN) coated titanium bipolar plates are prepared by magnetron sputtering. The coated BPP is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscope (AFM), and their electrochemical performance is assessed by electrochemical corrosion tests including open circuit voltage (OCP), potentiodynamic and potentiostatic polarization tests in the simulated PEMWE anode environment. It is revealed that the surface roughness of titanium substrates is decreased after coating, implicating the reduced interfacial contact resistance (ICR). Potentiodynamic and potentiostatic tests demonstrate that Ta/TaN and Nb/NbN coatings can significantly improve the corrosion resistance of titanium bipolar plate. The corrosion current density of coated substrate is reduced by approximately 67 % upon coating with Ta/TaN and Nb/NbN under the simulated PEMWE anode environment. However, the ICR of Ta/TaN coating is the lowest (3.9 mΩ × cm2), which is reduced by 74 % compared with pristine titanium substrate (14.9 mΩ × cm2). Hence, the Ta/TaN coated BPP is tested in single electrolytic cell and demonstrates significantly improved electrolysis efficiency. • Metal nitride coated titanium bipolar plate is prepared by magnetron sputtering. • Surface roughness of coated samples is reduced, indicating low contact resistance. • Corrosion current density and interface contact resistance are reduced upon coating. • Improved electrolysis efficiency is demonstrated using Ta/TaN coated bipolar plate. [ABSTRACT FROM AUTHOR]

High-frequency supercapacitors (HF–SCs) are promising electric energy storage devices and alternating current line filters. However, severe self-discharge of HF–SCs causes significant energy loss and limits their applications. Current self-discharge suppression methods for supercapacitors typically lead to decreased rate performance and hence cannot be applied to HF–SCs directly. In this work, barium titanate (BTO) nanoparticles are employed as an electrolyte additive for HF–SCs to reduce self-discharge. By adding BTO nanoparticles into the electrolyte, both leakage current and decay of open circuit voltage of the devices are reduced without sacrificing the specific capacitance and high-frequency response. At a charging voltage of 2 V, the leakage current is reduced by 49 % (3.91 vs. 1.98 μA), while the time for the voltage to drop from 2.0 to 1.0 V is extended by 4.5 times (2300 vs. 10240 sec). When the HF–SCs with BTO electrolyte are employed to store the energy generated by a triboelectric nanogenerator, the time for charging the cells to 2.0 V is reduced by 82 %. Mechanistic analysis indicates that the reduced self-discharge can be attributed to the fluid electrorheological effect and the enhanced localized electric field within the gaps among BTO nanoparticles that lead to sluggish diffusion and migration of reactive species, so the diffusion-controlled faradaic reaction process is suppressed. [Display omitted] • Carbonized melamine foams were synthesized for high-frequency supercapacitors (HF–SCs). • BaTiO 3 nanoparticles were employed as electrolyte additive to reduce self-discharge. • Rate performances and high frequency responses of the HF–SCs were well retained. • Improved charging efficiency of the HF–SCs by a triboelectric nanogenerator was demonstrated. [ABSTRACT FROM AUTHOR]

Highly durable ether-linkage-free polyfluorene–based electrolytes with different ion exchange capacities (IECs) were synthesized, followed by the preparation and evaluation of cast and pore-filling (PF) membranes as anion exchange membranes (AEMs). The performance of these membranes was tested in direct formate fuel cells (DFFCs). The membrane properties, including formate permeability, were investigated to clarify the relationship between membrane performance and the performance of DFFCs. The formate permeability of the membrane was drastically affected by the existence of OH− anion, as OH− ions induce larger membrane swelling. In addition, the PF method was more effective in reducing the formate permeation than the cast membranes. The PF membrane using the polyelectrolyte with a low IEC value showed 20-fold lower formate permeability compared to that of the original cast membrane, leading to a higher improvement in open-circuit voltage (OCV), from 0.55 to 0.95 V in DFFCs. For the first time, a quantitative correlation between the formate permeability of AEMs and OCV values in DFFCs was established. From this correlation, formate permeation less than 0.03 mol L−1 h−1 is necessary to keep high OCV value. Using the developed membrane, we also demonstrated the high stability of DFFC at 80 °C for 5 days. [Display omitted] • Higher formate permeability was observed in OH− form of AEMs. • Pore-filling method reduced formate permeation more effectively than cast membranes. • Quantitative correlation between formate permeability and OCV values was founded. • Pore-filling method considerably improves the OCV value (from 0.55 to 0.95 V). • Ether-free AEM–based MEA exhibits stability during DFFC operation at 80 °C. [ABSTRACT FROM AUTHOR]

In this work, a hybrid direct ammonia fuel cell, consisting of an alkaline anode, a cation exchange membrane, and an acid cathode, is developed. Taking the advantage of hybrid configuration, this fuel cell exhibits an extremely high theoretical voltage of 2.55 V, which helps to boost the cell performance. Experimental results depict that this hybrid direct ammonia fuel cell achieves an open-circuit voltage of 1.42 V and a power density of over 600 mW cm−2 at 95 °C. Furthermore, this study explores the effects of species concentrations, operating temperatures, and thicknesses of the membrane on cell performance to gain insights into mass/charge transport mechanisms inside the cell and develop performance-enhancing strategies. [Display omitted] • A hybrid direct ammonia fuel cell prototype is designed and tested. • An open-circuit voltage of 1.42 V and a power density of over 600 mW cm−2 at 95 °C. • An insight into mass/charge transport mechanisms inside the cell are proposed. [ABSTRACT FROM AUTHOR]

Cycling lithium-ion batteries causes capacity fade, but also changes the shape of the open-circuit voltage (OCV) curve, due to loss of active material (LAM) and loss of lithium inventory (LLI). To model this change, we recently proposed a novel empirical calendar aging model that is parameterized on component states of health (SOH s) instead of capacity fade only. In this work, we present a mechanistic aging model for cycle aging, allowing prediction of capacity fade, OCV curve change and component degradation. The model is parameterized on cycling data of 59 commercial lithium-ion batteries with NCA cathode and silicon–graphite anode, which were cycled for 2500 equivalent full cycles under varying conditions. We propose a stepwise approach to identify the most relevant stress parameters causing LLI and LAM , where we also separate between loss of accessible graphite and silicon in the blend anode. Stress parameter dependence is modeled with linear combinations of exponential functions and the model predicts capacity fade with 1.04 % mean absolute error (MAE). For all test conditions, LLI is the dominating degradation mode and loss of accessible graphite is negligible. Reconstructed OCV curves reduce the median voltage MAE by a factor of 8, compared to not updating the OCV. [Display omitted] • Empirical algorithm for degradation rates enables first mechanistic cycle aging model. • Degradation rates for all components mainly driven by DOD , SOC and temperature. • Modeling aged OCV curves reduces voltage error by factor 8, compared to no update. • Predicted capacity fade values exhibit an average error of 1.04% on validation data. • Hidden degradation of electrodes does not explain onset of non-linear capacity fade. [ABSTRACT FROM AUTHOR]

The direct carbon solid oxide fuel cell (DC-SOFC) is a new-type energy conversion device that converts chemical energy stored in solid carbon into electricity efficiently with environmental benignity and low cost for abundant carbon resources, which reveals upward impetus recently. To accelerate the practical application of DC-SOFC, here, we report a high-performance La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3−δ (LSGM) electrolyte-supported tubular DC-SOFC stack for portable applications, in which Ag– Ce 0.8 Gd 0.2 O 1.9 (Ag-GDC) is used as symmetrical electrodes and camellia oleifera shell char as fuel. The performance of the 3-cell-stack stands out, with an open circuit voltage (OCV) of 3.18 V, an output power of 2.65 W, and a maximum volumetric power density of 605 mW cm−3 at 800 °C. In addition, the stack can survive for 5.82 and 1.12 h under the constant discharging currents of 200 and 800 mA, respectively, exhibiting discharge capacities of 3492 and 2688 mA h. Furthermore, adopting the external anode design can sextuple the fuel load and lead to remarkably improved output performance, discharge time, and discharge capacity of the stack (3.71 W, 9.2 h, 22080 mA h). The above results indicate that LSGM electrolyte-supported tubular DC-SOFC stacks show great potential for developing into high-performing, efficient, and environmentally friendly portable power sources for distributed applications. • A LSGM electrolyte-supported tubular DC-SOFC stack is assembled. • The stack achieves an output performance of 2.65 W and 605 mW cm−3 at 800 °C. • The external anode design can lead to remarkably improved output performance. [ABSTRACT FROM AUTHOR]

Like li- and Na-ion batteries, electrolyte reactivity (i.e., salt and solvent decomposition) is important in the electrochemical performance of K-ion batteries (KIBs). Indeed, X-ray photoelectron spectroscopy (XPS) analysis of a solid electrolyte interphase (SEI) in KIBs is still based on K-ion half-cells. This may lead to incorrect interpretations of the results considering the contamination of the studied electrode SEI due to the high K metal reactivity. Therefore, this study aims to provide a reliable XPS study without potassium metal, investigating the impact of various parameters, including open-circuit voltage (OCV) temperature, upper cut-off voltage (UCV), depth of discharge (DOD), and vanadium dissolution, on the electrochemical performance of KVPO 4 F 0.5 O 0.5 /graphite full cells. This work highlights the importance of SEI preformation, which is more pronounced at higher OCV temperatures. At specific UCV and DOD, the cell provides the best trade-off between the organic and inorganic passivation layer, leading to good electrochemical performance. The study also demonstrates that vanadium dissolution is a potential mechanism affecting capacity fading in K-ion batteries. Finally, understanding these SEI growth mechanisms should help researchers get reliable XPS analysis of the SEI in KIBs and move forward with the practical passivation layer characterizations. • K-ion Full-cell: XPS Unveils SEI/CEI impact on Electrochemical Performance. • The graphite and KVPFO surface layer is thicker at 60 °C than at 40 °C and 25 °C. • High upper cut-off voltage induces more electrolyte degradation and vanadium dissolution. • High depth of discharge induces more passivation layer dissolution. [ABSTRACT FROM AUTHOR]

Cell-to-cell variations inside a battery pack can result in inhomogeneities, leading to an accelerated, uneven aging. Until today these variations are solely quantified by parameter-based studies, which only offer a limited interpretability. To tackle this inconclusiveness, cell-to-cell variations and their effects on the electrode processes of lithium-ion batteries are investigated in this work. For this purpose 92 cells are characterized by impedance, pulse, and pseudo open-circuit voltage measurements, and the data obtained is compiled as publicly available data set. The data is examined by a holistic distribution of relaxation times analysis, comprising complementary distribution of relaxation times approaches. This enables a reliable identification of process variations between cells. First, the confidence intervals of both the raw data and the distribution of relaxation times are examined. Subsequently, the individual processes, their characteristic time constants, and their polarization are determined. The analysis reveals that a normal distribution only applies in one of the examined cases and can even be excluded in four cases. Finally, a correlation analysis is conducted, allowing the categorization of the identified processes into cell winding, electrochemical interface processes, and solid-state diffusion. The potential physicochemical reasons behind are discussed and the work thus contributes to a deeper understanding of cell-to-cell variations. [Display omitted] • Development of a combined distribution of relaxation times analysis. • Process identification and correlation of lithium-ion batteries. • Statistical analysis of processes in lithium-ion batteries. • Provision of a cell-to-cell variation data set of 92 cells. [ABSTRACT FROM AUTHOR]

Zn-quinone batteries, with the merit of high reversibility, show great potential in the energy storage and conversion system, but the low working voltage and power density limit their application. We here report a rechargeable asymmetric alkali-acid electrolyte Zn-quinone battery (AAAZQB, 3AZQB) with the Zn anode in alkali and the highly reversible quinone cathode in acid. The elaborate asymmetric alkali-acid electrolyte design, enables the redox of Zn and quinone can act in their optimal conditions, the electrochemical neutralization energy can be harvested simultaneously. As a result, the 3AZQB delivers an open circuit voltage of 1.95 V, a peak power density up to 315 mW cm−2 and a highly strong stability with a reversible charging/discharging voltage gap of 200 mV, which are much better than those of Zn-air batteries and Zn-quinone batteries reported before. Image 1 • Zn-quinone battery was employed to harvest electrochemical neutralization energy. • An open circuit voltage of 1.95 V can be achieved. • The device shows a power density up to 315 mW cm−2. • A long-term stability with ultralow voltage gap of 200 mV is realized. [ABSTRACT FROM AUTHOR]

Defects easily form in organic-inorganic hybrid perovskite (CH 3 NH 3 PbX 3) absorber layers acting as recombination centers which reduce the performance of solar cells. Therefore, defect passivation is an efficient method to improve the performance of solar cells. Herein, ethylamine alcohol chlorides is introduced into perovskite films to passivate defects. The hydroxyl group and ammonium group in ethylamine alcohol chlorides can interact with halogen in MAPbI x Cl 3-x to form hydrogen bonds suppressing ion migration. In addition, the crosslinking neighbouring perovskite grains through hydrogen bonds can also improve the perovskite grain size and film coverage. The data demonstrate that the obvious reduction of the defect concentration via defect passivation contributes to an enhancement of the open-circuit voltage from 0.87 V to 0.92 V and the device efficiency from 14.52% to 16.97%. • Ethylamine alcohol chlorides were interacted with perovskite to form hydrogen bonds. • The hydrogen bond interaction suppressed ion migration and passivated defects. • The crosslinking perovskite grains improved the grain size and film coverage. • Defect passivation contributes to enhancement of solar cell performance. [ABSTRACT FROM AUTHOR]

A polythiophene homopolymer with conjugated side chains (2D-PT) was applied as a hole transport material (HTM) of perovskite solar cells (PSCs). The all-conjugated two-dimensional structure effectively increases the ionization potential, realizing a high open-circuit voltage near 1 V for the 2D-PT-based PSC. Very interestingly, the two-dimensional wide-angle X-ray scattering measurements show that the 2D-PT molecules are self-assembled into ordered structure with a face-on dominant orientation and exhibit a hole mobility, which is ∼1.6 times faster than that of poly(3-hexylthiophene) (P3HT). Consequently, the power conversion efficiency of PSC is noticeably increased by ∼30% as 2D-PT replaces P3HT as HTM. Moreover, the densely packed 2D-PT slows down the moisture induced degradation of perovskite crystals, leading to a better environmental stability. This work demonstrates that two-dimensional non-donor-acceptor structural conjugated polymers can be utilized as promising HTM of PSCs. Image 1 • 2D comb-like polythiophenes exhibit good crystallinity and a face-on orientation. • 2D polythiophene is a promising hole transport material of perovskite solar cells. • 2D-PT-based perovskite solar cell achieves a high open-circuit voltage near 1 V. • The champion 2D-PT-cell exhibits an excellent PCE of 14.8%. [ABSTRACT FROM AUTHOR]

Doping in organic–inorganic perovskite semiconductors is an effective method to tailor their optoelectronic properties. In this work, manganese-doped perovskite films with different Mn/Pb ratios ranging from 0% to 2% were systematically studied. The device performance of 0.2% Mn-doped devices was improved compared to that of a device without Mn. However, a further increase of the doping concentration induced a decrease in performance. Several characteristics (especially different scanning probe microscopy characteristics) reveal that an increased dopant concentration results in reduced crystallinity and a change in the film morphology and causes a deterioration in photovoltaic performance for higher dopant concentrations. In the best-performing samples (0.2%), a shift in the valence band level and band gap are found which are responsible for the increased open circuit voltage, while increased grain boundaries and lower surface charge density are responsible for a small reduction in the short circuit current. Thus, multifunctional scanning probe microscopy approaches, combined with different film characterization techniques, offer us effective tools to investigate the impact of doping in the perovskite materials and the corresponding device performance. • Scanning Kelvin Probe Microscopy is used to test the open circuit voltage of films. • Conductive atomic force microscopy is used to study the short-circuit of films. • Electrostatic force microscopy is used to distinguish the surface charge change of films. [ABSTRACT FROM AUTHOR]

Abstract Nitrogen-doped carbon matrix (Co/NC) has been synthesized with NaCl as a template and peptone as a carbon/nitrogen source. Subsequently, mesoporous nitrogen-doped CoSe/NC was prepared by solvothermal selenization. The obtained CoSe/NC is useful as highly efficient bifunctional electrocatalyst for hydrogen evolution and oxygen reduction reactions. Structures of the CoSe/NC material have been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N 2 adsorption desorption analysis and X-ray photoelectron spectroscopy. Results demonstrate the role of NaCl as efficient low cost template to form mesoporous nitrogen doped carbon, which could significantly simplify and reduce the cost of the synthetic procedure. During hydrogen evolution reaction in a 1 M KOH electrolyte, the best performing sample with formula Co 0.88 Se/NC produces an overpotential of 72 ± 0.1 mV at a current density of 10 mA cm−2. This material also shows excellent electrocatalytic activity and stability in oxygen reduction reaction, superior even to a commercial Pt/C catalyst. A primary zinc-air battery containing Co 0.88 Se/NC as a oxygen reduction reaction catalyst reaches an open circuit voltage of 1.44 ± 0.02 V, higher than that of a Pt/C containing zinc-air battery and delivers superior power and current density combination. Graphical abstract Herein, highly efficient mesoporous CoSe/N-doped carbon materials was developed as HER and ORR electrocatalysts for water splitting and zinc-air batteries. Image 1 Highlights • CoSe/NC are developed as catalysts for HER and ORR. • NaCl is used to form the porous structure at high temperature. • Co 0.88 Se/NC displays significantly high electrocatalytic performance. [ABSTRACT FROM AUTHOR]

Abstract Commercial carbon-based perovskite solar cells have rapidly developed due to its low cost and long-term stability. However, commercial carbon paste as counter electrode always produces a large number of defects at the perovskite interface, thereby greatly affecting the performance of the perovskite solar cells. In this work, a grinding process is used to compact the thin carbon film. The process effectively eliminates defects and improves the extraction efficiency of holes from the photoexcited layer, resulting in 21.2% increase in the efficiency of the carbon-based perovskite solar cells. In addition, open-circuit voltage decay on the order of tens of seconds is analyzed in detail. A new capacitor-like model is established to successfully explain the hysteresis phenomenon. Perovskite solar cells show 700 h of stability with ground carbon counter electrode. Highlights • The interface quality of the carbon electrode is improved by a grinding process. • This grinding process increases PSC efficiency by 21.2%. • The mechanism of Open Circuit Voltage Decay generation is discussed in detail. • A new capacitor-like model is established to successfully explain the hysteresis. • PSCs show 700 h of stability with ground carbon counter electrode. [ABSTRACT FROM AUTHOR]

Abstract Though numerous researches regarding the influence of annealing atmospheric condition of ZnO have been carried out, the impact of annealing atmosphere on the carrier transporting properties and the performance of the ZnO-based optoelectronics has not been well-established. Here, the effects of annealing atmosphere (i.e. , N 2 , ambient air, and O 2) used to generate ZnO nanoparticle (NP) layers are elucidated. The chemical nature of ZnO layers, especially the amount of oxygen vacancies in ZnO NPs, is modulated by the annealing atmosphere. As the composition of O 2 gas increases in the annealing atmosphere, a notable reduction of oxygen vacancies of ZnO NPs and electron mobility enhancement are observed, indicating that O 2 gas contributes to a reduction of surface defects on ZnO NPs during the annealing process. In addition, trap-filling by reduced oxygen vacancies of air- and O 2 -annealed ZnO layers, induces the enhanced built-in potential in colloidal quantum-dot photovoltaic (CQDPV) devices. As expected, PbS CQDPVs with an air- and O 2 -annealed ZnO layer demonstrate significantly improved power conversion efficiencies than CQDPVs with an N 2 -annealed ZnO layer. Further analysis shows that the interfacial recombination is reduced for CQDPVs with an air- and O 2 -annealed ZnO layer due to the reduced trap states of ZnO NPs. Graphical abstract Image 1 Highlights • Effects of annealing atmosphere on the surface defects of ZnO were elucidated. • PbS quantum dot solar cell with an O 2 -annealed ZnO showed enhanced open-circuit voltage. • As increasing O 2 concentration during annealing, the defects of ZnO were passivated. • Defect passivation suppressed interfacial charge recombination in the solar cell. • The suppression of charge recombination induced the improved V OC of the solar cell. [ABSTRACT FROM AUTHOR]

Abstract Parallel-connection of lithium-ion cells is of increasing research interest, caused by the commercialization of large-scale applications and their needed amount of energy. However, correlations of cell parameters on the current distribution of parallel-connected cells are not given in present literature. This paper provides an insight into the influence of cell resistance and capacity on the current distribution, open circuit voltage (OCV) differences and the corresponding time constants for parallel-connected cells. Cell currents and OCV differences are evaluated via an analytical model for two parallel-connected cells. The system can be described by four characteristic values, what is mathematically shown. The analytical solution and characteristic values are extended to n parallel-connected (n p) cells by a transformation of the n p equivalent circuit model (ECM) to a corresponding 2p ECM. The models are used in order to investigate the effects of Gaussian distributed cell parameters on the current distribution by Monte Carlo simulations. Thereby, the influence of the number of parallel-connected cells and the product of cell resistance and capacity is examined. Simulations show increasing cell currents with increasing number of parallel-connected cells and an accelerated SoC balance within the logical cell by decreasing product of cell resistance and capacity. Highlights • Analytical model of the current distribution of parallel-connected cells. • Reduction to four characteristic values. • Impact of Gaussian distributed cell resistances and capacities on the current distribution. • Mathematical description of the balancing effect of parallel-connected cells. [ABSTRACT FROM AUTHOR]