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Herein, we report the transition metal dependent deprotonation of layered type materials during their high voltage (>4.5 V vs. Li/Li+) operation as a potential degradation cause in an electrochemical system.

We present the first monolithic fabrication of a-IGZO TFTs on a GaN-based micro-LED array at a low temperature to overcome the weak thermal endurance constraint of the organic planarization layer for high resolution and stable low-cost LED displays.

Phosphate doped hard carbons have shown a significant capacity increase accompanied by an additional plateau in its voltage profile. The work reveals the co-contribution of oxygen atoms in phosphate and carbon atoms for the additional Na-ion storage.

Na3V2(PO4)3 is regarded as one of the promising cathode materials for next-generation sodium ion batteries, but its undesirable electrochemical performances due to inherently low electrical conductivity have limited its direct use for applications. Motivated by the limit, this study employed a porous carbon network to obtain a porous carbon network–Na3V2(PO4)3 composite by using poly(vinylalcohol) assised sol-gel method. Compared with the typical carbon-coating approach, the formation of a porous carbon network ensured short ion diffusion distances, percolating electrolytes by distributing nanosized Na3V2(PO4)3 particles in the porous carbon network and suppressing the particle aggregation. As a result, the porous carbon network–Na3V2(PO4)3 composite exhibited improved electrochemical performances, i.e., a higher specific discharge capacity (~110 mAh g−1 at 0.1 C), outstanding kinetic properties (~68 mAh g−1 at 50 C), and stable cyclic stability (capacity retention of 99% over 100 cycles at 1 C).

We scrutinized the barrier capability of SiOx, plasma Al2O3 (P-Al2O3)/SiOx, and SiNx/SiOx passivation layers (PLs) on the environmental stabilities of back-channel etched Al-doped InSnZnO (Al-ITZO) TFTs at 85 °C with a relative humidity of 85 % for 30 days. Turn-on voltage (VON) of SiNx/SiOx-passivated TFTs was dramatically shifted to the negative direction and became conductive. Compared to those of SiOx and P-Al2O3/SiOx films, more hydroxyl groups existed at the PL/active interface of SiNx/SiOx-passivated Al-ITZO films. Water vapor transmission rates showed that abnormal behavior was not attributed to barrier capability of PL against the water vapor. When all TFTs were kept at 85 °C for 30 days in an air-drying oven, only the VON of SiNx/SiOx-passivated TFTs shifted negative direction and finally became conductive. Secondary ion mass spectroscopy (SIMS) results revealed that this abnormal behavior originates from the formation of oxygen vacancy due to highly existed hydroxyl group at SiOx/Active interface at an elevated temperature.

The use of iodide as the positive redox-active species in redox flow batteries has been highly anticipated owing to its attractive features of high solubility, excellent reversibility, and low cost. However, the electro-oxidation reaction of iodide (I

Iodide and iodine comprise a promising redox couple in aqueous energy storage systems (aqua-ESSs). However, the corresponding half-redox reaction on the cathode of an aqua-ESS has most often been considered as simply I2 (or I3−)/I−. Here, we describe for the first time reversible electrochemical formation and dissolution of insoluble iodine–halide coordination networks, [(I2)n·X−] (X− = Br− and I−), in confined nanopores with microporous carbon (micro-C) serving as a positive electrode in an aqua-ESS and using I− as the redox active electrolyte during charging. In an electrochemical cell without added Br−, the main half-redox reaction changed from I2/I− to [(I2)n·I−]/I− (n = 1 and 2) as charging and discharging accelerated (i.e., as current densities increased). When Br− was added to the electrolyte with I−, [(I2)n·Br−] was formed by electro-oxidation of I−, which was stably encapsulated in nanopores of micro-C regardless of the charging/discharging rate. Our findings suggest that [(I2)n·Br−]/I− half-redox reactions can produce superior energy and power densities in an aqua-ESS with porous carbon electrodes through the addition of Br− to their electrolytes compared with electrodes with I− only.

We present a unique composite assembly of rhombohedral Li3V2(PO4)3 and carbon nanofiber, which simultaneously facilitates Li-ion transport as well as electron transfer. For the synthesis of this composite, the inorganic precursors were confined in electron-spun nanofibers, and then, through controlled annealing, Na3V2(PO4)3 particulates were grown with controllable crystallite size and partially embedded into carbon nanofibers with precisely controlled diameter. The rhombohedral Li3V2(PO4)3 could be successfully obtained by ion exchange from Na to Li in the prepared Na3V2(PO4)3. The final rhombohedral Li3V2(PO4)3 particles anchored onto the carbon nanofibers exhibited excellent electrochemical performance with fast kinetics for Li-ion batteries. Suprisingly it maintains 69 and 41 mAh/g even at 100C as cathode and anode. Several advanced characterizations revealed that its ultrafast kinetics could be attributed to synergistic effect resulting from the distinctive microstructure of the composite and the structural superiority of highly symmetric rhombohedral Li3V2(PO4)3 over its monoclinic homologue for Li-ion transport.

Na3V2(PO4)3 is regarded as one of the promising cathode materials for next-generation sodium ion batteries, but its undesirable electrochemical performances due to inherently low electrical conductivity have limited its direct use for applications. Motivated by the limit, this study employed a porous carbon network to obtain a porous carbon network–Na3V2(PO4)3 composite by using poly(vinylalcohol) assised sol-gel method. Compared with the typical carbon-coating approach, the formation of a porous carbon network ensured short ion diffusion distances, percolating electrolytes by distributing nanosized Na3V2(PO4)3 particles in the porous carbon network and suppressing the particle aggregation. As a result, the porous carbon network–Na3V2(PO4)3 composite exhibited improved electrochemical performances, i.e., a higher specific discharge capacity (~110 mAh g−1 at 0.1 C), outstanding kinetic properties (~68 mAh g−1 at 50 C), and stable cyclic stability (capacity retention of 99% over 100 cycles at 1 C).

The main drawback of organic electrode materials is their solubility in the electrolyte, leading to the shuttle effect. Using N,N'-dimethylphenazine (DMPZ) as a highly soluble cathode material, and its PF6 - and triflimide salts as models for its first oxidation state, a poor correlation was found between solubility and battery operability. Extensive electrochemical experiments suggest that the shuttle effect is unlikely to be mediated by molecular diffusion as commonly understood, but rather by electron-hopping via the electron self-exchange reaction based on spectroscopic results. These findings led to two counter-strategies to prevent the hopping process: the pre-treatment of the anode to form a solid-electrolyte interface and using DMPZ salt rather than neutral DMPZ as the active material. These strategies improved coulombic efficiency and capacity retention, demonstrating that solubility of organic materials does not necessarily exclude their applications in batteries.

A simple and scalable method for producing graphite anode material for lithium-ion batteries is developed and demonstrated. A low-cost, earth abundant iron powder is used to catalyze the conversion of softwood, hardwood, cellulose, glucose, organosolv lignin, and hydrolysis lignin biomaterials to crystalline graphite at relatively low temperatures ( 99% coulombic efficiency.

Flexible and wearable pressure sensors, which can detect various pressures generated by the human body and convert them into electrical signals, are of great interest because they have a wide variety of applications for an interface between humans and external devices. Elastomeric dielectric materials for commercial piezocapacitive pressure sensors need to be manufactured quickly and easily via cost-effective methods. Herein, we report a piezocapacitive pressure sensor based on a three-dimensional macroporous dielectric layer fabricated by a rapid and facile baking-inspired foaming process. The pressure sensor showed high sensitivities of 0.16 ± 0.03 kPa−1 (at

Aqueous zinc (Zn)-based flow batteries are an attractive option for energy storage systems due to their inflammability and high energy density. However, Zn dendrite formation, which causes internal short circuiting and capacity drop, limits the long-term operation of Zn-based flow batteries. Here, we present highly stable Zn deposition/dissolution achieved by a defective carbon surface. DFT calculations and electrochemical analysis demonstrate that a single vacancy carbon defect prevents the surface diffusion of Zn and consequent aggregative Zn growth by forming a strong orbital hybridization between Zn and the dangling bonds of the defect. Triggered by the interatomic interaction, a defective carbon-decorated electrode achieves dendrite-free Zn deposition and excellent cycling stability in zinc–bromine flow batteries (ZBBs) over 5000 cycles at 100 mA cm−2 and 20 mA h cm−2, while maintaining coulombic efficiency above 97%. The deeper understanding of defect chemistry provides a new scientific strategy to engineer advanced Zn-based aqueous batteries.

The popularization of electric vehicles and the increasing use of electronic devices highlight the importance of fast charging technology. The charging process of lithium secondary battery is basically limited by a series of processes on the anode side, which include desolvation of lithium ions as well as lithium diffusion through SEI and the anode material. These series of reactions are kinetically sluggish, leading to insufficient power density. Therefore, to unravel this problem, we need to either accelerate each step or skip over some of the steps to make the whole charging process shorter. A solvated ion cointercalation into graphite has turned out to successfully exclude both desolvation of lithium ions and SEI film formation to achieve high kinetics with graphite. Herein, the solvated ion cointercalation into MoS2 demonstrated that it can help to remove desolvation of alkali ions as well as SEI formation, and thereby ultrahigh kinetics and long-term cyclability are attained by the characteristic ps...

Electrochemical ion storage behaviors of Fe3O4 nanoparticles, as a representative transition metal oxide for an environmentally benign and low cost anode for a sodium ion battery, are thoroughly investigated through a combination of electrochemical analysis and diagnostics of Fe3O4 electrode cells, X-ray based and spectroscopic analysis of material structure evolution as functions of depth of discharge (DoD) and state of charge (SoC), and first principle modeling. The gravimetric capacity is found to be 50 mAh/g for bulk Fe3O4 (50 nm average crystallite size) and 100 mAh/g—about a tenth of the theoretical prediction for complete conversion—for Fe3O4 nanoparticles (8.7 nm average particle size), respectively. A fundamental and mechanistic study of material evolution as functions DoD and SoC shows that Fe3O4 does not allow electrochemical incorporation of Na+ ions into the empty cation positions of the inverse spinel structure, leading to our assertion that electrochemical intercalation of Na+ ions to conversion of Fe3O4 anode in sodium ion batteries is nonviable. Density Functional Theory investigation points to the impracticality of the intercalation of Na+ ions into Fe3O4, and further validates our experimental findings. We propose several possible mechanisms corresponding to the observed low capacity, including formation of solid electrolyte interphases with unfavorable properties, adsorption of Na+ ions onto surfaces of nanoparticles and/or at hetero-interfaces in Fe3O4 composite electrodes in a NaPF6-based electrolyte system.

A detailed understanding of the surface modification or coating of materials is becoming more important for the design and development of hybrid materials for their advanced applications. The characteristics of polydopamine-coated surfaces were explored by varying dopamine concentration and polymerization time for noble metal deposition, which is a key for the development of advanced catalysts. The variation of these parameters for dopamine coating on carbon nanofibers (CNFs) finally modulated the amount of palladium (Pd) nanoparticles deposited on the dopamine-coated surface, which is CNFs. The results showed that the higher the dopamine concentration, the larger the amount of deposited Pd, while the polymerization time is inversely proportional to the amount of Pd deposited. Thereby, the optimally functionalized surface for Pd deposition was found with a dopamine concentration of 3 mg mL−1 and a reaction time of 6 hours (PDAT1). This optimum Pd/CNF hybrid material showed very promising electrochemical and catalytic performances with a high discharge capacity of about 5.26 mA h cm−2 which could be maintained up to the 67th cycle at a cut-off capacity of 0.2 mA h cm−2 in non-aqueous Li–O2 batteries and an impressive catalytic activity for the oxygen reduction reaction via the preferred 4 electron pathway in aqueous electrolyte.

We present a unique composite assembly of rhombohedral Li

The surface structure of solid catalysts has been regarded as a critical descriptor for determining the catalytic activities in various applications. However, structure-dependent catalytic activities have been rarely understood for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) within Li-O2 batteries. Here, we succeeded in the preparation of a Pt catalyst with an anisotropic structure and demonstrated its high catalytic activity in non-aqueous Li-O2 batteries. The cathode incorporating Pt exposed with high-index {411} facets showed greatly enhanced ORR and OER performance in comparison to commercial Pt/C cathode. The anisotropic Pt catalyst improved ORR activity with a large capacity of 12,985 mAh gcarbon-1, high rate performance, and stable cyclic retention up to 70 cycles with the capacity limited to 1,000 mAh gcarbon-1 of capacity. Furthermore, the anisotropic Pt catalyst exhibited high round-trip efficiency of ~87% with a low OER potential (3.1 V) at a current density of 200 m...

Reduced graphene oxide (RGO) have been regarded as promising electrode material for supercapacitors. However, restacking of layers limits its surface area and pore volume which, in turn, suppress the electrochemical performances. Herein, we functionalize RGO with para-phenylenediamine (p-PDA) to suppress the problem and thus preserve the surface area and pore volume. p-PDA functionalized RGO (p-PDA-RGO) is explored as electrode materials for organic electrolytes based supercapacitors. The structural characteristics are characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and FT-IR. Electron microscopy demonstrates formation of randomly oriented 3D structure after functionalization. Effect of p-PDA functionalization toward surface area and pore volume is analyzed by Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) analysis. The effect of p-PDA functionalization toward electrochemical performances is evaluated in symmetrical supercapacitors in organic electrolytes. p-PDA-RGO shows an improvement in capacitance over 10,000 cycles while attaining stability with high power capability.

Vanadium redox flow batteries (VRFBs) have attracted considerable attention for potential use in the development of large-scale energy storage systems. However, the commercialization of VRFBs is still challenging because of their various overpotentials, which are due to the poor reversibility and electrochemical activity of graphite felt (GF) electrodes. In this study, we fabricated a NiO-decorated GF electrode that exhibited a clear electrocatalytic effect on the V2+/V3+ and VO2+/VO2+ redox reactions. Vanadium ions preferentially attached to each NiO site because of strong electrostatic affinity to the local negatively charged O2− species. In particular, a significant amount of NiO bound to graphite by replacement of hydrogen from the hydroxyl groups with nickel ion, leading to an increase in the ratio of carboxyl groups to hydroxyl groups. The increase in the number of carboxyl groups also improved the VRFB performance, since the carboxyl functional group on GF surface acts as effective catalyst for the vanadium redox reactions. Furthermore, NiO nanoparticles enhanced the mass-transfer property of vanadium ions by the increased area and hydrophilicity of the electrode surface. To optimize the electrode structure for high electrochemical performance, the crystallinity and morphology of the NiO catalyst on GF were controlled via the operating temperature and precursor concentration. When optimized NiO/GF300 was applied to VRFBs, it exhibited high energy efficiency (74.5%) at a high current rate (125 mA cm−2), compared with GF without the catalyst (55.4%). Moreover, NiO-decorated GF exhibited durability and stability in acidic electrolyte during long-term operation for 300 cycles.

A great challenge in the application of carbon-based materials to Li–O2 batteries is to prevent the formation of carbonate-based side products, thereby extending the cycle life of Li–O2 batteries. Herein, for the first time, CNT@Ni@NiCo silicate core–shell nanocomposite is designed and used as a cathode catalyst in Li–O2 batteries. This nanocomposite shows a promising electrochemical performance with a discharge capacity of 10 046 mA h gcat−1 and a low overpotential of 1.44 V at a current density of 200 mA gcat−1, and it can sustain for more than 50 cycles within the voltage range of 2–4.7 V. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) characterizations prove that the formation of Li2CO3 and other side products are prevented, likely due to the encapsulation of CNTs by NiCo silicates and Ni nanoparticles, which may help decompose the side products. Finally, the synergistic effects, which are contributed by the high electrical conductivity of CNTs, high surface area, the high oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities of NiCo silicate, and the simple decomposition of side products by Ni nanoparticles enable outstanding performance of the CNT@Ni@NiCo silicate core–shell nanocomposite as a cathode catalyst for Li–O2 batteries.

FeCo alloy nanoparticles were nucleated onto graphitic carbon layers through the pyrolysis of polydopamine (PDA) sub-micrometer spheres to form a highly active electrocatalytic system that exhibits excellent oxygen conversion catalytic activity in both alkaline and acidic media. Owing to the strong metal chelation capability during the chemical modification and high sp2-dominant carbon yield of PDA, an abundance of non-precious-metal ions were easily trapped and absorbed into the PDA segments at room temperature by catechol and amine functional groups, followed by the in situ nucleation of FeCo alloy nanoparticles on graphitic carbon layers during the pyrolysis. The contents of graphitic nitrogen and pyridinic nitrogen were significantly increased by the presence of the non-precious-metal ions during carbonization as well, which is a result of the chelation effect of non-precious-metal atoms. Meanwhile, the FeCo nanoparticles (diameter < 5 nm) were protected by the multi-layer-graphene-like carbon layer from the harsh acid and uniformly anchored on graphitic carbon sub-microspheres, which can greatly improve the catalytic durability, particularly in acidic media. From the perspective of the whole catalytic system being used as an air electrode in rechargeable Zn–air batteries, the porous nitrogen-doped graphitic carbon framework was functionalised as a continuous conductive framework due to its catalytic activity towards high oxygen conversion and good electrical conductivity.

There is increasing interest in vanadium redox flow batteries (VRFBs) for large scale-energy storage systems. Vanadium electrolytes which function as both the electrolyte and active material are highly important in terms of cost and performance. Although vanadium electrolyte technologies have notably evolved during the last few decades, they should be improved further towards higher vanadium solubility, stability and electrochemical performance for the design of energy-dense, reliable and cost-effective VRFBs. This timely review summarizes the vanadium electrolyte technologies including their synthesis, electrochemical performances, thermal stabilities, and spectroscopic characterizations and highlights the current issues in VRFB electrolyte development. The challenges that must be confronted to further develop vanadium electrolytes may stimulate more researchers to push them forward.

Irreversible phase transformation of layered structure into spinel structure is considered detrimental for most of the layered structure cathode materials. Here we report that this presumably irreversible phase transformation can be rendered to be reversible in sodium birnessite (NaxMnO2·yH2O) as a basic structural unit. This layered structure contains crystal water, which facilitates the formation of a metastable spinel-like phase and the unusual reversal back to layered structure. The mechanism of this phase reversibility was elucidated by combined soft and hard X-ray absorption spectroscopy with X-ray diffraction, corroborated by first-principle calculations and kinetics investigation. These results show that the reversibility, modulated by the crystal water content between the layered and spinel-like phases during the electrochemical reaction, could activate new cation sites, enhance ion diffusion kinetics and improve its structural stability. This work thus provides in-depth insights into the intercalating materials capable of reversible framework changes, thereby setting the precedent for alternative approaches to the development of cathode materials for next-generation rechargeable batteries., The irreversible layered-to-spinel phase transformation is detrimental for many cathode materials. Here, the authors show that reversibility can be realized in crystal water containing sodium birnessite by controlled dehydration, leading to enhanced ion diffusion kinetics and improved structural stability.

Next-generation electrodes for rechargeable lithium-ion batteries (LiBs) promise higher energy and power storage at lower cost. For example, silicon has a theoretical capacity approximately 10 times higher compared to current state-of-the-art anodes based on graphite, 3580 mAhg-1 vs 372 mAhg-1, respectively.1 On the other side of the cell, it has been shown that increasing the Ni content in cathodes based on lithium nickel manganese cobalt oxide (LiNi1-x-yMnxCoyO2 or NMC) increases their specific capacity up to 280 mAhg-1.2, 3. Unfortunately, the improvements in energy storage provided by these next-gen materials is currently offset by their rapid degradation due to the undesirable (electro)chemical reactions, taking place at electrode surface in contact with a reactive liquid organic electrolyte, which form the unstable electrode-electrolyte interphase (EEI).2, 4-8 Understanding the complex reactions taking place in each phase, as well as the compositional, morphological, and structural formation and evolution of the EEI is essential to the development of mitigation strategies enabling longer battery life. Over the decades of battery R&D, many spectroscopic and analytical techniques have been developed to characterize the properties of battery components and understand cell capacity fade, but most often, these techniques are applied ex situ to a component of the battery that has been harvested from a disassembled cell after testing.9, 10 While informative, ex situ measurements cannot elucidate changes happening to the cell during testing, thus potentially failing to provide critical information about correlated processes underpinning the cell performance. Here we present a summary of our recently-developed in situ Raman and FTIR spectroscopic techniques and in situ gas chromatography-mass spectrometry-flame-ionization detection (GC-MS-FID) analytical methods applied to custom battery cells under test11-13. By monitoring the EEI “in real-time” during cell charging and discharging cycles, we gain a better understanding of the critical mechanisms occurring near the electrode surfaces. For example, with our in situ FTIR spectroscopic methods, we have investigated the voltage dependent electrolyte solution structure changes at the interface, electrode changes correlated to redox chemistry, and the electrode/electrolyte interfacial layer evolution in LiBs employing high-Ni cathodes. In an electrochemical cell, gas evolution from electrolyte degradation is controlled by many factors, including the electrolyte’s physical and (electro)chemical properties, electrode compositions, and the applied stress to the cell (voltage, current, temperature, etc.), and we have used GC-MS-FID to elucidate mechanistic relationships between gas evolution/interface formation in novel Si-anode LiBs. Our various in situ cell designs provide both sensitive detection and reliable electrochemical device testing. Ultimately, we aim to develop in-situ gas analysis tools to be coupled with in situ spectroscopic techniques enabling a holistic understanding of the battery. References: K. Feng, M. Li, W. Liu, A. G. Kashkooli, X. Xiao, M. Cai, and Z. Chen, Small, 14 (8), 1702737 (2018). F. Schipper, E. M. Erickson, C. Erk, J.-Y. Shin, F. F. Chesneau, and D. Aurbach, Journal of The Electrochemical Society, 164 (1), A6220-A6228 (2017). N. Nitta, F. Wu, J. T. Lee, and G. Yushin, Materials Today, 18 (5), 252-264 (2015). J. Kasnatscheew, S. Röser, M. Börner, and M. Winter, ACS Applied Energy Materials, 2 (11), 7733-7737 (2019). M. Wetjen, D. Pritzl, R. Jung, S. Solchenbach, R. Ghadimi, and H. A. Gasteiger, Journal of The Electrochemical Society, 164 (12), A2840-A2852 (2017). J.-H. Kim, H.-H. Ryu, S. J. Kim, C. S. Yoon, and Y.-K. Sun, ACS Applied Materials & Interfaces, 11 (34), 30936-30942 (2019). H.-H. Ryu, K.-J. Park, C. S. Yoon, and Y.-K. Sun, Chemistry of Materials, 30 (3), 1155-1163 (2018). M. Ashuri, Q. He, and L. L. Shaw, Nanoscale, 8 (1), 74-103 (2016). A. M. Tripathi, W.-N. Su, and B. J. Hwang, Chemical Society Reviews, 47 (3), 736-851 (2018). P. B. Balbuena and Y. X. Wang, Lithium-ion Batteries: Solid-electrolyte Interphase, World Scientific Publishing Company (2004). B. J. Tremolet de Villers, Y. Ha, and S.-D. Han, in "236th ECS Meeting (October 13-17, 2019)". ECS, 2019. Y. Ha, B. J. Tremolet de Villers, Z. Li, Y. Xu, P. Stradins, A. Zakutayev, A. Burrell, and S. D. Han, J Phys Chem Lett, 11 (1), 286-291 (2020). B. Tremolet de Villers, S.-M. Bak, J. Yang, and S.-D. Han, Batteries & Supercaps, under revision (2020).

Due to inherent properties of the silicon (Si)-electrolyte interphase (SEI)—complexity, high reactivity and continuous evolution—it remains a poorly understood topic in advanced Si-based Li-ion battery (LiB) research,1,2 and its detailed and real-time analysis is a great challenge. Vibrational spectroscopy, such as Raman and Fourier-transform infrared spectroscopy (FTIR), is one of the most important analytical tools for understanding and quantifying the interfacial chemical reactions. These techniques are used extensively by the battery community in their ex situ form, but developing in situ variants of these techniques and combing in situ analyses from both techniques can provide new insight and help to elucidate the mechanism of interfacial failure in battery systems. We have optimized in situ vibrational spectroscopy methods that show reproducible and stable performance over multiple cycles in terms of both electrochemistry and spectroscopy, which enables us to monitor the surface chemistry and evolution of the SEI. This is essential to gaining a better understanding of the electrochemical performance of Si-based LiBs.3-5 Further, the reactions leading to SEI growth and evolution in Si-based LiBs may be more comprehensively probed by monitoring changes in the gas and liquid phases. To this end, we are developing novel in situ gas chromatography (GC) techniques, which may be applied to both coin-type cells and larger-format pouch cells. Using custom cell designs, we track the evolution of electrolyte and degradation species in the gaseous and liquid6 phases at various stages of battery cycling. We achieve both qualitative identification and quantification through coupled mass-spectrometry (MS) and flame ionization detection (FID). This GC-MS-FID analysis complements our in situ vibrational spectroscopy studies, providing a true multi-modal and multi-phase approach to SEI analysis. Taken together, these studies can provide an in-depth understanding of the underlying chemistry and physics and mechanical explanation of various reactions/interactions within the SEI, thus enabling the rational design of electrolytes and electrodes to stabilize the SEI. Additionally, we have developed advanced techniques to assess the structural and electronic properties of Si-based composite electrodes. Comprehensive characterization of pristine and cycled composite electrode architectures is complicated by several inherent properties. During battery operation, Si-based composite electrodes experience localized lithiation and reaction rates due to heterogeneous conditions and distributions of electrode components. Further, (electro)chemical and structural properties continuously evolve during cycling. Finally, the nanoscale diameter of particles falls beneath the lateral and depth resolution of most laboratory-based instruments. To address these challenges, we have utilized scanning spreading resistance microscopy (SSRM) to image the three-dimensional nanostructure of composite anodes via contrast in the electronic properties of the distinct components.7 Specifically, Si-based composite anode components, such as SiOx nanoparticles, graphite, carbon black, and lithium polyacrylate binder, are all readily distinguished by their intrinsic electronic properties, with measured electronic resistivity closely matching known material properties. In combination with scanning electron microscopy/energy dispersive X-ray (SEM-EDX) and electron energy loss spectroscopy (EELS), we expect to compare the electrical, chemical and structural changes of Si-based composite electrodes before and after cycling. This can provide a fundamental understanding of localized degradation mechanisms, which informs our understanding of SEI formation and evolution. This technique may also be applied to assess heterogeneous aging within the electrode, and is more broadly applicable to other battery systems. In particular, it may be used to better understand particle dispersion, localized lithiation, electrolyte-electrode interphase formation/evolution, and degradation processes in composite electrodes for the development of next-generation batteries. References: Xu, C. Stetson, K. Wood, E. Sivonxay, C. Jiang, G. Teeter, S. Pylypenko, S.-D. Han, K. A. Persson, A. Burrell and A. Zakutayev, ACS Appl. Mater. Interfaces 2018, 10, 38558-38564. -D. Han,* K. N. Wood, C. Stetson, A. G. Norman, M. T. Brumbach, J. Coyle, Y. Xu, S. P. Harvey, G. Teeter, A. Zakutayev and A. K. Burrell, ACS Appl. Mater. Interfaces 2019, 11, 46993-47002. Ha, B. J. Tremolet de Villers, Z. Li, Y. Xu, P. Stradins, A. Zakutayev, A. Burrell and S.-D. Han,* J. Phys. Chem. Lett. 2020, 11, 286-291. Yin, R. Pekarek, C. Stetson, M. Schnabel, E. Arca, S. Harvey, B. Tremolet de Villers, S.-D. Han, S. DeCaluwe, G. Teeter, C. Ban and N. Neale, 2021, under revision. J. Tremolet de Villers, J. Yang, S.-M. Bak and S.-D. Han,* 2021, under revision. Ha, C. Stetson, S. P. Harvey, G. Teeter, B. J. Tremolet de Villers, C.-S. Jiang, M. Schnabel, P. Stradins, A. Burrell and S.-D. Han,* ACS Appl. Mater. Interfaces 2020, 12, 49563-49573. C. Stetson, Z. Huey, A. Downard, Z. Li, B. To, A. Zakutayev, C.-S. Jiang, M. Al-Jassim, D. P. Finegan, S.-D. Han* and S. C. DeCaluwe, Nano Lett. 2020, 20, 8081-8088.

Herein, we describe the design and operation of an indirect coal liquefaction plant with integrated coal-water slurry manufacturing, entrained flow gasification, Rectisol, and Fischer–Tropsch processes to produce liquid fuels for vehicles. The above plant contained an entrained flow gasifier (10 t/d test rig) operated using oxygen as a gasifying agent (21 bar, 1100 °C) and could stably produce synthesis gas (37.8 vol% H2, 36.4 vol% CO) at 600 Nm3/h. Due to the importance of impurities in synthetic liquid fuel production, more than 99% of H2S contained in synthesis gas was removed by the Rectisol process employing refrigerated methanol. An iron-based catalyst allowed liquid fuels containing wax, light/heavy oil, and alcohol fractions to be obtained by the Fischer–Tropsch process at a rate of 5 barrel per day, with detailed analysis confirming their compliance with various quality standards and thus their suitability for use as automobile diesel after distillation.

A zinc–bromine redox flow battery (ZBB) has attracted increasing attention as a potential energy-storage system because of its cost-effectiveness and high energy density. However, its aqueous zinc bromide phase and non-aqueous polybromide phase are inhomogeneously mixed in the positive electrolyte. Furthermore, various equilibrium reactions, e.g., charge-transfer reactions, polybromide formation, and complexation, simultaneously occur in the battery. Because of these complex reactions, it is difficult to systematically analyze its electrolyte, which a component crucial for the stable operation of the battery. Especially, although the state-of-charge (SoC) of an electrolyte is crucial for preventing overcharging or discharging and side reactions, its accurate estimation is difficult. As a result, there have been few studies on estimation of the SoC in ZBBs. In this study, in situ Raman spectroscopy is employed for the real-time estimation of the SoC in 25 charge–discharge cycles. To exclude errors arising from the inhomogeneous dispersion of the non-aqueous phase, SoC is monitored on the negative electrolyte. External standard solutions are measured, and the calibration curve is constructed just before in situ measurements at every cycle to minimize instrumental errors, e.g., those caused by alignment. This in situ methodology exhibits high accuracy and reproducibility.

The presence of nitrogen atoms in reduced graphene oxide (RGO) sheets considerably modulates their intrinsic physical and chemical properties to finally improve their electrochemical properties in electric double layer supercapacitors. However, this also accelerates the restacking phenomena of RGO, which results in a decreased active surface area and pore volume. To solve this problem, we fabricated para-phenylenediamine (p-PDA) functionalized nitrogen doped RGO (NRGO) to inhibit the restacking phenomenon and thus preserve the active surface area and pore volume via chemical bonding between RGO and p-PDA. Finally, we realized an impressive electrochemical performance through the synergistic effect of nitrogen doping and p-PDA functionalization.

Even though Na3V2(PO4)3 (NVP) is regarded as one of the next-generation cathode materials in sodium-ion batteries (SIBs), its undesirable rate performance due to its inherently low electrical conductivity has limited its application in demanding fields such as electric vehicles. Motivated by this fact, the present study profitably employed a conductive carbon grown in situ to obtain an NVP@C composite with a pomegranate-like structure by a simple sol–gel assisted hydrothermal technique. The as-prepared NVP@C composite consists of small carbon-coated NVP particles (∼200 nm) embedded in a conductive carbon matrix, which ensures short ion diffusion distances, percolating electron/ion conduction pathways and stable structural integrity. As a result, the pomegranate-structured NVP@C composite displayed remarkable overall electrochemical performance: a high discharge capacity (110 mA h g−1 at 1C), excellent rate capability (92 mA h g−1 even at 50C) and impressive cycling stability (capacity retention of 91.3% over 2000 cycles at 10C). Such a feasible and beneficial design provides a good strategy for other materials that require both size reduction and high electronic/ionic conductivity.

Silicon (Si) has attracted much attention as a promising anode material for Li ion battery because of its high theoretical specific capacity and low working potential. However, Si has shown poor cycling behavior and reversibility, which result from its huge volume change and the following pulverization. In this study, an electrospinning method was adopted to synthesize Pitch-incorporated into Si/Carbon nanofibers (Si/Pitch CNFs), which has high crystalline carbon network compared to other Si/Carbon nanofibers without the carbon matrix obtained from the decomposition of pitch. We demonstrated that this high crystalline carbon network in the form of nanofiber has two kinds of merits: it not only reduced the diffusion length for Li ion transport thanks to its 1D morphology but also helped to tolerate high strain of Si and maintain electron transport throughout the entire electrode. As a result, Si/Pitch CNFs showed a greatly enhanced kinetic performance, even at 10C, thus showing its feasibility as a high-power material for future applications like electric vehicles (EV) and energy storage systems (ESS).

Because of their outstanding features such as safety, long cycle life, and design flexibility, vanadium redox flow batteries (VRFBs) have attracted much attention from those involved in the development of electrical energy-storage system. However, the performance of VRFBs remains limited due to their significant polarization. Here, we report a new fabrication method for highly porous graphenated graphite felt electrode with high-performance, which enables operation of VRFBs at high current rates by alleviating polarization. The etched graphite felt (EGF) electrode is optimized by repetition of a NiO/Ni redox reaction cycle, which is a facile, scalable, and controllable etching process that produces a high surface area. The EGF also has stepped edges, which act as preferred sites for incorporating oxygen defects. The plentiful oxygen defects on the stepped edges show catalytic effect and good wettability for vanadium electrolyte, leading to substantially reduced overpotentials. VRFBs with the EGF electrode exhibit a strongly enhanced electrochemical performance with respect to energy efficiency and discharge capacity at 150 mA cm−2. Furthermore, the robustness of the graphenated structure provides stability and durability in acidic electrolyte during long-term battery operation, facilitating stable cycling performance for 200 cycles at high current rates.

In a zinc–bromine redox flow battery, a nonaqueous and dense polybromide phase formed because of bromide oxidation in the positive electrolyte during charging. This formation led to complicated two-phase flow on the electrode surface. The polybromide and aqueous phases led to different kinetics of the Br/Br − redox reaction; poor mixing of the two phases caused uneven redox kinetics on the electrode surface. As the Br/Br − redox reaction was coupled with the zinc deposition reaction, the uneven redox reaction on the positive electrode was accompanied by nonuniform zinc deposition and zinc dendrite formation, which degraded battery stability. A single-flow cell was operated at varying electrolyte circulation rates and current densities. Zinc dendrite formation was observed after cell disassembly following charge–discharge testing. In addition, the flow behavior in the positive compartment was observed by using a transparent version of the cell. At low rate of electrolyte circulation, the polybromide phase clearly separated from the aqueous phase and accumulated at the bottom of the flow frame. In the corresponding area on the negative electrode, a large amount of zinc dendrites was observed after charge–discharge testing. Therefore, a minimum circulation rate should be considered to avoid poor mixing of the positive electrolyte.