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Lithium-rich materials exhibit high capacity and high voltage properties due to the charge compensation mechanism, but the disadvantages such as material voltage decay and poor cycling stability limit their practical application. The fixation and stabilizations of surface lattice oxygen is considered the most challenging problem the materials. We have successfully prepared a lithium-rich cathode material with a triad of oxygen vacancies, surface spinel and polyanionic SO42- doping by a mild surface preactivation treatment, and systematically investigated the stabilization mechanism of surface oxygen vacancies in the materials. The VS-LR0.25 material with multiple stabilizations of oxygen vacancies exhibited excellent cycling stability and rate performance, with an initial Coulomb efficiency of 82.7%, and capacity retention of 95.1% after 200 cycles at 1 C. [ABSTRACT FROM AUTHOR]

Broadening the portfolio of cathode active materials for Li-ion battery applications is now more important than ever. Recent focus on enabling diversity and security in supply chains, as well as concerns over sustainability of a massively growing energy storage market, have put emphasis on enabling more Earth-abundant cathode materials as an attractive strategy. With respect to relatively near-term options, manganese-based cathodes are particularly interesting. Herein we discuss some of the challenges associated with advancing the development of manganese-based oxides and, in particular, those that take advantage of complex local structures and/or over-lithiated compositions. Discussion centers on the representative, lithium- and manganese-rich class of cathodes and considerations to future development are given that range from the atomic-scale to the electrode level. [ABSTRACT FROM AUTHOR]

Degradation phenomena in Li-ion batteries are highly complex, coupled, and sensitive to use history and operating conditions. In this study, we show how tracking model parameters in continuum-level physics-based models, expedited by machine learning, can be useful in testing hypotheses for degradation mechanisms. An exemplary analysis using this approach is presented for a set of lithium trivanadate (LixV3O8) cathodes cycled over a range of current rates. A simple cell revival process is combined with the parameter estimates over the course of cycling to extract valuable insights into cathode evolution and eliminate hypothesized degradation mechanisms for these cathodes. The presented approach is expected to be broadly applicable for degradation analysis of other electrodes. [ABSTRACT FROM AUTHOR]

The electrochemical performance of Li-rich layered manganese oxide (LMO) cathodes is greatly affected by the oxygen release and irreversible transition metal (TM) migration. Such structural instabilities are the driving force behind structural reconstruction, rapid voltage decay, and capacity fade in LMR cathodes. This is due to the inability to retain a layered-layered phase during cycling hence the inability to maintain a consistent conductive ion flow (lithiums). Herein, we report for the first time, exploration of manganese and oxygen-compensated nanostructures to investigate its role in the structural morphology and microstructure. The nanostructures were studied using the molecular dynamics simulation method owing to its ability to simulate nucleation and crystal growth. According to the analysis, the simulated nanospheres yielded multi-grained and single crystalline phases for Mn and O compensation, respectively. Further analysis illustrated severe Li/O loss in the structure when the role of oxygen is neglected. Moreover, the formation of layered-layered-spinel composites is demonstrated together with the comparison of temperaturedependent diffusion coefficients. This goes to show that both oxygen and manganese play a crucial role during the cycling process of Li-rich cathode materials. These findings can provide important insights into understanding diffusion and ageing mechanisms in cathode materials during the cycling processes. [ABSTRACT FROM AUTHOR]

Lattice oxygen loss during cathode charging significantly limits the charge storage capacity of lithium-ion batteries (LiBs). Therefore, elucidating the oxygen loss and subsequent surface reconstruction phenomena remains an ongoing pursuit with practical implications. In this article, we report an in situ oxygen detection strategy using scanning electrochemical microscopy (SECM) that reveals an unprecedented two-stage oxygen evolution behavior from commercial cathodes. This highly sensitive SECM method captured an unreported transient oxygen release at less than 3.3 V vs Li+/Li during the first charge cycle of LiCoO2, LiNi0.33Mn0.33Co0.33O2 and LiNi0.8Mn0.1Co0.1O2. At the main oxygen loss process above 3.3 V vs Li+/Li, SECM mapping highlighted spatial and temporal heterogeneities. Finite element simulations were used to quantify the rate of instantaneous oxygen release, with rates of ∼30 pmol cm−2 s for the steady-state oxygen evolution. This SECM approach revealed incipient degradation processes and created new quantitative and spatially resolved opportunities for investigating degradation in operating LiB cathodes. [ABSTRACT FROM AUTHOR]

Aqueous zinc-ion batteries (ZIBs) are a promising technology that can satisfy the present requirements for battery systems because of their excellent characteristics (e.g., low cost, recurrent availability of zinc metal resources, high chemical/physical stability, and safety). However, the growth of zinc dendrites in alkaline electrolytes makes ZIBs unsuitable for many applications. To address this problem, we developed a novel ZIB using a solid-state electrolyte based on polyacrylamide hybridized with layered double hydroxide (PAM-LDH). The hydrogel electrolyte exhibited an excellent ionic conductivity. The result also indicates that a PAMLDH electrolyte combined with NH4F-treated MnO2 shows an ultra-high capacity of 354.3 mAh g−1 at a current density of 0.1 A g−1 and an energy density of 484.3 Wh kg−1 at a peak power density of 136 W kg−1 (based on the weight of the cathode). Moreover, the cycle retention of the cell was significantly improved to 88.8% after 1000 cycles compared with that of the untreated MnO2/PAM-LDH/Zn cell (79.5%). These results demonstrate that − F -doped cathode and hydrogel electrolyte can form the foundation for practically usable solid-state ZIBs. [ABSTRACT FROM AUTHOR]

P2-Na0.67Ni0.15Mn0.85O2 layered sodium transition metal oxides have drawn much attention as a promising candidate cathode due to its high specific capacity and high working voltage. However, undesired cyclability and poor rate performance originated from the serve Jahn-Teller effect and mixed Na+/vacancy ordering during the cycle process. To address this issue, we designed a series P2-type Na0.67Ni0.15Mn0.85−xTixO2 (x = 0, 0.05, 0.10, 0.15) cathode by using a modified sol-gel method, and comprehensively investigated the influence of Ti doping Mn sites with the structural and electrochemical properties. It was found that Ti-substitution not only increases the interlayer distance to suppress Na+/vacancy ordering, but also reduces Mn3+ content to alleviate the JahnTeller effect. Notable, the Na0.67Ni0.15Mn0.80Ti0.05O2 electrode exhibited a remarkable cycling stability (85.36% capacity retention after 200 cycles at 1 C). Ti-substitution would greatly increase charge/discharge reversibility and boosts Na+ diffusion mobility kinetics, which were clearly elucidated by Ex-situ X-ray Diffraction (XRD), cyclic voltammetry (CV) and Galvanostatic Intermittent Titration Technique (GITT), respectively. This simple and effective work provides a novel strategy for developing high-performance cathode materials for practical SIBs. [ABSTRACT FROM AUTHOR]

Li-ion battery electrode electronic properties, including bulk conductivity and contact resistance, are critical parameters affecting cell performance and fast-charge capability. Contact resistance between the coating and current collector is often the largest electronic resistance in an electrode and is affected by chemical, microstructural, and interfacial variations. Direct measurements of contact resistance and bulk conductivity have proven to be challenging. In their absence, a mechanical electrode peel test is often used to compare adhesion and electrical contact resistance. However, using a micro-flexible-surface probe, contact resistance can be directly determined. This work compares contact resistance and mechanical peel strength of multiple commercial-grade HE5050 and NCM523 cathodes and graphite and silicon anodes. It was found that peel strength correlates well with contact resistance in a carefully curated data set (p < 0.05) and in some situations may be a good metric to estimate electrical properties. However, there were distinct outliers in the data set, indicating that peel strength may not accurately reflect electrical properties when there is significant variation in electrode composition. These results illustrate the value of the micro-flexible-surface probe in quantifying contact resistance and bulk conductivity to better understand how battery composition and processing steps affect microstructure and resulting cell performance. [ABSTRACT FROM AUTHOR]

In this manuscript, the impact of operating conditions such as voltage window, and operating temperature on electrochemical performance and cycle life of Zn-substituted Na3.2V1.8Zn0.2(PO4)3 (NVZP) vs hard carbon (HC) coin cells filled with 1 mol dm−3 NaBF4 in tetraglyme is presented. Initially, the cells are cycled for 500 times at C/2 charge and 1 C discharge in three different voltage windows (4.20–1.00 V, 4.05–1.00 V and 4.05–1.50 V) and at two temperatures (28 °C and 40 °C) and are subjected to periodic internal resistance and impedance measurements. The elemental composition of the electrodes harvested after cycling reveals that vanadium dissolution with accompanying deposition on the HC electrode and irreversible loss of sodium causes increased cell impedance. The identified degradation mechanisms, which causes severe capacity fade, are found to be accelerated in the cells cycled over wider voltage windows, particularly at elevated temperature. The best cycling performance and lowest impedance are recorded for the cells cycled within 4.05–1.50 V at 28 °C owing to negligible vanadium dissolution. Under these optimized testing conditions, a prototype 18650 cell, shows impressive capacity retention of 77% after 1000 cycles. [ABSTRACT FROM AUTHOR]

In this work, novel near-zero volume expanding Si-dominant electrodes are presented as promising anodes for next-generation Liion batteries. The electrodes contain micrometer-size nano-porous Silicon particles with a carefully tuned morphology and synthesized via a scalable and cost-effective route. Volume expansion during electrochemical Li-Si alloying/de-alloying is found to be almost completely suppressed. Bi-layer pouch cells manufactured with the abovementioned Si-anodes, having industrial relevant areal capacities (⩾3 mAh cm−2 ), and LiNi0.6Mn0.2Co0.2O2 cathodes, show indeed negligible volume expansion as demonstrated by operando dilatometric measurements during galvanostatic cycling and post-mortem SEM cross-sectional analysis. [ABSTRACT FROM AUTHOR]

A parametric analysis is presented using a previously validated 1D model for a cathode catalyst layer (CL). The results show that maximum power density at low Pt loading can be maximized with relatively thin CLs (thickness ∼ 2 μm) featuring a high carbon volume fraction (low ionomer-to-carbon weight ratio, I/C) compared to high Pt loading CLs. The shift of the optimal carbon volume fraction (I/C ratio) is caused by the dominant role of the local oxygen transport resistance at low Pt loading, which is lowered by a reduction of the average ionomer film thickness (better ionomer distribution among carbon particles). In contrast, at high Pt loading, higher porosity and pore radius (lower carbon volume fraction) is beneficial due to an increase of bulk effective diffusivity despite thickening of ionomer films. Moreover, the results show that performance at low Pt loading is significantly improved with increasing mass-specific activity. The effect of average saturation and ionomer permeability on performance at low Pt loading is lower compared to dry CL composition and mass-specific activity. [ABSTRACT FROM AUTHOR]

The performance of a hydrogen-powered, electrochemically-driven CO2 separator (EDCS) was demonstrated at cathode inlet CO2 concentrations from 400 ppm to 5,000 ppm. The impact of current density and CO2 concentration were evaluated to predict operating windows for various applications. The single-cell data was used to scale a 100 cm², multi-cell stack using a shorted-membrane design for four applications: direct air capture (DAC), hydroxide exchange membrane fuel cell (HEMFC) air pretreatment, submarine life support, and space habitation. For DAC, a 339-cell EDCS stack (7.7 L, 17 kg) was projected to remove 1 tonne CO2 per year. The addition of the EDCS in HEMFC systems would result in nearly a 30% increase in volume, and therefore further improvements in performance would be necessary. A module containing five 338-cell EDCS stacks (38 L, 85 kg) in parallel can support a 150 person crew at 2.1% of the volume of the liquid amine system employed in submarines. For space habitation, a 109-cell EDCS stack (3.2 L, 10 kg) is adequate for 6 crewmembers, and is less than 1% the size and 5% the weight of the current CO2 removal system installed on the International Space Station. [ABSTRACT FROM AUTHOR]

With high theoretical specific capacity and favorable electrochemical properties, CuS is considered to be the ideal cathode material for hybrid Mg-Li ion batteries. However, the traditional CuS cathodes exhibit inferior rate performance and poor cycle stability, which limits the development and application of CuS. In this work, CuS@MoS2 with core–shell structure was prepared by two-step hydrothermal synthesis. When utilized for hybrid Mg-Li batteries, CuS@MoS2 displayes high special capacity and stable cycling performance. At current density of 50, 100 and 300 mAg−1, the first discharge capacity is 337.40, 276.28 and 254.58 mAhg−1 which are all higher than those of single CuS and MoS2. More importantly, the discharge capacity of core–shell CuS@MoS2 can remain 104.70 mAhg−1 at 100 mAg−1 after 50 cycles. These performance improvements are contributed to rich reaction sites and high conductivity of mixed metal sulfides. Furthermore, core–shell structure could relieve the volumetric change and remain structure stability for active materials. In conclusion, core–shell CuS@MoS2 could offer a new strategy for the design of high-performance cathode. [ABSTRACT FROM AUTHOR]

The recent surge of research in the development of sodium-ion batteries (SIBs) as an alternative to the lithium-ion batteries (LIBs) has shown that the SIBs can reduce the load of the LIBs in certain areas. However, the development of SIBs in the commercial arenas is yet to be tapped. This perspective delineates the importance of Ni-rich cathodes and various strategies to ameliorate the performance of the Ni-rich cathodes in the SIBs. Also, discussed various synthesis routes for the industrial-scale synthesis of Nirich materials and tried to elucidate the importance of SC cathodes and the necessity to develop those in SIBs. [ABSTRACT FROM AUTHOR]

Li2FeSiO4, as a highly promising polyanionic cathode material, has the advantages of high energy density, low cost, good thermal stability, high safety and environmental friendliness. However, its electrochemical performance has been affected by the drawbacks such as low electrical conductivity, low Li-ion diffusion rate and crystal instability. Over the years, in order to solve these problems and truly realize the commercial application of Li2FeSiO4 cathode materials, researchers have proposed more and more preparation or modification methods to optimize the electrochemical performance of Li2FeSiO4. This paper lists the electrochemical performance improvement of modified Li2FeSiO4 and its innovation points. The realistic problems that still exist in the application of Li2FeSiO4 cathode materials at this stage were discussed. This paper provides a basis for the next innovative research and application of cathode materials for Li-ion batteries. [ABSTRACT FROM AUTHOR]

Battery performance is strongly correlated with electrode microstructure and weight loading of the electrode components. Among them are the carbon-black and binder additives that enhance effective conductivity and provide mechanical integrity. However, these both reduce effective ionic transport in the electrolyte phase and reduce energy density. Therefore, an optimal additive loading is required to maximize performance, especially for fast charging where ionic transport is essential. Such optimization analysis is however challenging due to the nanoscale imaging limitations that prevent characterizing this additive phase and thus quantifying its impact on performance. Herein, an additive-phase generation algorithm has been developed to remedy this limitation and identify percolation threshold used to define a minimal additive loading. Improved ionic transport coefficients from reducing additive loading has been then quantified through homogenization calculation, macroscale model fitting, and experimental symmetric cell measurement, with good agreement between the methods. Rate capability test demonstrates capacity improvement at fast charge at the beginning of life, from 37% to 55%, respectively for high and low additive loading during 6C CC charging, in agreement with macroscale model, and attributed to a combination of lower cathode impedance, reduced electrode tortuosity and cathode thickness. [ABSTRACT FROM AUTHOR]

Sulfurized polyacrylonitrile (SPAN) is considered one of the most promising cathode materials to overcome the operational challenges that plague lithium-sulfur (Li-S) batteries. However, material properties and electrochemical performance implications of SPAN prepared under different synthesis conditions are not yet fully investigated. In this study, we show the impacts of different synthesis conditions on the formation of sulfur to PAN bonds and redox reaction mechanisms of multi-phase SPAN via comprehensive material and electrochemical characterizations. In-situ Raman analysis was first applied to study the multi-phase SPAN-based Li-S cells. We found that both elemental sulfur and chemically bonded sulfur are present under the synthesis condition of 300 °C/3 h along with unreacted PAN. The incompletely sulfurized, multi-phase SPAN exhibited an unusually rapid capacity degradation in the resultant Li-S cells, which is attributed to polysulfide formation and continuously growing interfacial impedance in the Li-S cells. On the other hand, SPAN samples prepared under the synthesis condition of 350 °C/3 h are found completely sulfurized with chemically bonded sulfur to the PAN backbone without the presence of free elemental sulfur. Complete sulfurization of SPAN led to exceptionally stable cycle performance due to excellent reversible redox processes of chemically bonded sulfur with Li+ in the Li-S cells. [ABSTRACT FROM AUTHOR]

(Ba0.95La0.05)(Fe0.8Zn0.2)O3-δ (BLFZ) is a good candidate for protonic ceramic fuel cell cathodes owing to its high proton concentration and decent electronic conductivity. However, the poor catalytic activity of BLFZ limits the electrochemical reaction on the cathode surface, resulting in poor fuel cell performance in hydrocarbon fuels. In this study, to enhance the catalytic activity of BLFZ, Fe cations were substituted with cobalt (Co) cations to synthesize (Ba0.95La0.05)(CoxFe0.8-xZn0.2)O3−δ (BLCFZ) (x = 0–0.8). A single-phase perovskite structure was obtained when the mol% of Co (x) was 0.2 and 0.4, while secondary phases were observed at x = 0.6 and 0.8. The cathode performance was improved by doping Co into BLFZ. The polarization resistances of the fuel cell with BLCFZ (x = 0.2) in H2 and CH4 fuels at 600 °C were smaller than those of the fuel cell with BLFZ (x = 0) and the power density in H2 fuel at 600 °C increased from 0.7 to 0.9 Wcm−2 . Equivalent circuit models were used to analyze the contribution of Co in improving the catalytic activity of the cathode. [ABSTRACT FROM AUTHOR]

This study was conducted to understand the effect of well-known water-washing process on Ni-rich LiNi0.885Co0.100Al0.015O2 (NCA) cathode material, which reduces the amount of residual lithium compounds in NCA to improve lithium-ion batteries (LIBs) characteristics. X-ray absorption fine structure (XAFS) analysis revealed that the oxidation state of the surface nickel in washed NCA particles was reduced. The fact was consistent with the increase in charge transfer resistance (Rct) measured by the electrochemical impedance spectroscopy (EIS) method. From X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) analyses, it was found that the residual lithium compounds were washed away not only from the surface of NCA particles but also from grain boundaries or voids in between primary particles of NCA, by water-washing process. Differential scanning calorimetry (DSC) measurements suggested that an increase in specific surface area of NCA particles by water-washing was attributed a rapid heat release from the charged cathode material during heating to. On the other hand, cross-sectional scanning electron microscope (SEM) images showed that the crack formation inside washed NCA particles were suppressed after charge/discharge cycling. As a result, the capacity retention of washed NCA electrode at 60 °C cycling was improved. [ABSTRACT FROM AUTHOR]

In this study, we investigate the spatial variations of discharge precipitate and cathode reaction rate in lithium (Li)-air battery both theoretically and experimentally: (1) the reaction variation of local oxygen reduction reaction (ORR) rate is theoretically analyzed, with analytical solutions as a function of the Damköhler (Da) number; (2) a novel experimental method is proposed to probe local ORR rate by designing a multi-layer cathode which consists of three identical Toray® carbon clothes that have a porosity of 0.8 and a thickness of about 0.4 mm. The morphology of insoluble Li compounds at different thickness locations is uncovered by SEM images. An overall very small volume fraction of precipitates was observed in the air cathode. It is found that the local ORR rate decreases from the air side of cathode to the separator side in the case of study, which is consistent with our model predictions for two orders of the cathode reaction. The theoretical analysis and experimental method can be applied to design and optimize materials for the air cathode of Li-air batteries. [ABSTRACT FROM AUTHOR]

For batteries with high energy density and good fast-charge capability, NCM cathode active materials with ⩾80 mol% nickel are promising due to their high specific capacities. Unfortunately, the increase in nickel content is accompanied by a high susceptibility to moisture. Therefore, nickel-rich NCM is coated or doped by the manufacturers to increase its stability. However, it is unclear if special requirements regarding ambient humidity must still be met during the whole production chain, or only after post-drying and during cell assembly. Therefore, the structure and properties of three different nickel-rich NCM active materials (one doped monocrystalline, two coated polycrystalline materials) processed at ambient atmosphere were investigated. At every process step, moisture content and microstructure were examined. Prior to cell assembly, two different post-drying procedures were applied and investigated. As validation, electrochemical tests were performed. Both polycrystalline cathodes demonstrated good physical and electrochemical properties, despite the ambient process atmosphere. Higher moisture reduction led to improved electrochemical performances at higher C-rates. Finally, a comparison between dry and normal atmosphere of the best performing material indicates that a production of high-quality nickel-rich electrodes at ambient atmosphere is possible if their exposure to moisture is short and well-designed post-drying techniques are applied. [ABSTRACT FROM AUTHOR]

Cycling lithiated metal oxides to high potential (>4.5 V vs Li) is of significant interest for the next generation of lithium ion batteries as this significantly increases the capacity and energy of cells. However, cells cycled to high potential suffer from rapid capacity fade due to a combination of thickening of the anode solid electrolyte interphase (SEI) and impedance growth on the cathode. While transition metal catalysed degradation of the anode SEI has been widely proposed as a primary source of capacity loss, a related acid induced degradation of the anode SEI is proposed. A systematic investigation of LiNi0.5Co0.2Mn0.3O2, and LiNi0.8Co0.1Mn0.1O2 cathodes cycled to 4.2 and 4.6 V has been conducted and the oxidative generation of the strong acid difluorophosphoric acid (F2PO2H) has been quantified by solution Nuclear Magnetic Resonance (NMR) spectroscopy. Ex-situ surface analysis of the electrodes with X-ray Photo Electron spectroscopy (XPS) suggests that the generation of F2PO2H correlates with a thickening of the anode SEI and an increase in the fluorophosphate content of the SEI. Changes to the LiNi0.8Co0.1Mn0.1O2 surface for cells cycled to 4.6 V are also consistent with the generation of acidic species. There is good correlation between the concentration F2PO2H, anode SEI degradation and the capacity loss of the cells. [ABSTRACT FROM AUTHOR]

Water has now become the standard process solvent for graphite-based anodes, eliminating the use of toxic and costly N-Methylpyrrolidone (NMP) in anode manufacturing. Ideally, water could also become the standard for cathodes; however, water-based processing of NMC cathode materials induces lithium leaching, which reduces their specific capacity and leads to capacity fade. Here, we demonstrate that leached lithium ions can be exploited during aqueous slurry preparation to create a Li-containing polymer binder that enables cathode performance comparable to those fabricated using NMP. Specifically, we show that leached lithium ions from LiNi0.8Mn0.1Co0.1O2 (NMC 811) particles react with polyacrylic acid (PAA) to form a lithium polyacrylate (LPA) surface coating and binder. Because the resulting LPA binder is water soluble, aqueous-based recycling of the cathode particles is feasible and over 90% capacity retention is shown in recycled material after 100 cycles. [ABSTRACT FROM AUTHOR]

Solid-state sulfur cathodes based on inorganic sulfide solid electrolytes can enable energy-dense lithium batteries. However, volume changes and chemical decomposition can drive delamination and degradation during cycling. To overcome these challenges, this paper reports an in situ approach to encapsulate the solid-state sulfur cathode with a gel polymer electrolyte (GPE). The GPE is covalently bonded with the sulfide solid electrolyte and acts as a barrier that suppresses chemical decomposition between the sulfide solid electrolyte and cathode active material. The elastic GPE maintains interfacial contact within the sulfur cathode allowing for greater sulfur utilization. The solid-state sulfur cathode with GPE demonstrates capacities nearing 700 mAh g−1 and capacity retention over 100 cycles. [ABSTRACT FROM AUTHOR]

The high pH environment in hydroxide exchange membrane fuel cells (HEMFCs) has the potential to reach lower costs than the current proton exchange membrane fuel cells (PEMFCs), the incumbent technology. A significant difference between HEMFCs and PEMFCs is the location of water production within the cell. In PEMFCs, the water is produced on the cathode, limiting oxygen transport. In HEMFCs, the water is produced on the anode where the fuel is pure hydrogen. This allows the cathode to be optimized for oxygen transport without the presence of excess liquid water. Limiting current analysis, a technique previously used in PEMFCs, is adopted in HEMFCs to evaluate the oxygen mass transport resistances for different sections of the cathode. Through elimination of the microporous layer (MPL), gas diffusion layer (GDL), and traditional flow field and using porous nickel foam for gas distribution, the transport resistance at an operating condition of 150 kPa(g) and with the cell temperature at 80 °C was decreased from 112 s m-1 to 48 s m-1, effectively halved. The optimal configuration for performance was found with Ni foam and a GDL, eliminating the MPL and traditional flow field, which vastly improved oxygen transport while maintaining adequate electrical contact with the cathode catalyst layer. [ABSTRACT FROM AUTHOR]

Cathode material with high nickel content is a promising candidate for the future generation of Li-ion batteries (LIBs). However, severe structural degradation during cycling limits its practical use, especially for electric vehicles. Herein, AlPO4 nanoparticles were synthesized and then coated onto the surface of a high-nickel layer-structured cathode via a dry coating method. The AlPO4 nanoparticles coating significantly improved the cycling stability from 69.2% to over 80% capacity retention after 140 cycles. Furthermore, the structure and chemical composition of the AlPO4-coated cathode was investigated by XRD, SEM, XPS, and STEM. Compared with the non-coated cathode, we revealed a dual protective mechanism for enhanced cycling stability, where Al doping and Li3PO4 coating play synergistic roles in protecting cathode material through long-term cycling. This work demonstrates a facile and environmentally friendly approach toward improving the performance of high-nickel LIB cathodes, which can be easily scaled up for industrial applications. [ABSTRACT FROM AUTHOR]

Use of physics-based models to interpret battery degradation data over the course of cycling can provide deeper physical insight into the internal states of the system and how they evolve. We present a neural network trained on simulations generated by a previously published physics-based model for a lithium trivanadate (LVO) cathode to estimate parameters that evolve over the course of cycling. We focus on the robustness of the neural network through two case studies that probe different kinds of discrepancies between model and experiment: nonideal data and imperfect model. In the former, the experimental protocols do not meet the assumption made in the training data generated by the physics-based model, while in the latter, the physics-based model fails to describe all of the measured cathode behavior even under ideal conditions. When there is total model-experiment agreement, a neural network estimates parameters with improved accuracy compared to a maximum likelihood analysis using the same set of simulations. However, in both types of model-experiment discrepancy, the neural network returned biased parameter estimates. We introduce a data augmentation procedure into the neural network training to mitigate these effects and improve robustness, and employ it to estimate parameters for a cycling LVO cathode. [ABSTRACT FROM AUTHOR]

A major drawback of today's Li-ion batteries is inadequate performance at low temperatures, which slows down the userfriendliness and thus market expansion of electromobility. Due to the complexity of the system, many possible low-temperature limitations and various dependencies on the operating conditions exist. As a result, the origin of the performance limitations at low temperatures is still controversial and not completely clarified to date. We herein demonstrate a comprehensive analysis of the performance limitations at low temperatures using a LiNi0.5Co0.2Mn0.3O2-based cathode as an example. To separate the overpotential phenomena, the complex system is decomposed as much as possible and individual aspects are investigated separately. Complementary electrochemical methods are employed to quantify the C-rate and SOC dependence of the individual overpotential phenomena. Based on the comprehensive analysis of the intercalation kinetics, mass and charge transport, we obtain a coherent picture of the performance limitations as a function of operating conditions. This can serve for targeted optimization or parameterizing models to simulate battery behavior. However, the present work is not only concerned with identifying the lowtemperature limits of the system studied but also shows how the rate-determining step of the electrode reaction can be efficiently identified as a function of temperature, SOC, and C-rate, which can serve as a guide for future work. [ABSTRACT FROM AUTHOR]

A binder-free AgCl@Ag (SPL-A) cathode was prepared via a facile one-step synthesis by the in situ growth of AgCl active material on the surface of Ag foil substrate. Compared with the AgCl cathode (SPL-B) prepared by the traditional smelting-rolling method, the coarse-grained particulates of AgCl in AgCl@Ag cathode facilitated the permeation of the electrolyte. In addition, it exhibited a preferred growth orientation of the (111), (222), and (311) crystal planes to reduce the charge transfer resistance. The electrochemical behaviors of the optimized SPL-A-24 cathode (prepared with reaction time of 24 h) and the SPL-B cathode were also compared. The galvanostatic discharge results showed that SPL-A-24 cathode had a more positive electrode potential than SPL-B cathode (-0.06 V vs -0.19 V at 50 mA cm-2). Moreover, SPL-A cathode exhibited a stable discharge process that SPL-B cathode could not achieve at 100 mA cm-2 and 250 mA cm-2. The magnesium seawater-activated battery assembled with SPL-A-24 cathode displayed a shorter time to reach the voltage plateau (0.2 s), a higher maximum discharge voltage (1.69 V), a larger specific power (255.5 mWh g-1), and higher specific capacity (167.7 mAh g-1) at the discharge current density of 50 mA cm-2. © 2022 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited. [ABSTRACT FROM AUTHOR]

Lithium ion batteries (LIBs) have dominated the energy industry due to their unmatchable properties that include a high energy density, a compact design, and an ability to meet a number of required performance characteristics in comparison to other rechargeable systems. Both government agencies and industries are performing intensive research on Li-ion batteries for building an energy-sustainable economy. LIBs are single entities that consist of both organic and inorganic materials with features covering multiple length scales. Two vital parameters for LIBs are their stable and safe operation. Critical insights should be made for understanding the structure to property relationships and the behavior of components under the working condition of LIBs. Since, the cathode serves as a central component of LIBs, the overall cell performance is significantly affected by the chemical and physical properties of the cathode. Cathodes tend to react with the electrolytes and, hence, to undergo surface modifications accompanied by degradation. These side-reactions result in an erosion of battery performance, thereby causing a reduced battery life and power capacity. Recently, techniques for preparing surface coatings on cathode materials have been widely implemented as a measure to improve their stability, to enhance their electrochemical performance, and to prevent detrimental surface reactions between the electrode materials and electrolyte. This review will cover different types of surface coatings for cathode materials, as well as a comparison of the changes in electrochemical performance between those materials with and without an applied coating. In addition, a brief outlook is included for different cathode materials and their coatings. [ABSTRACT FROM AUTHOR]

Batteries capable of extreme fast-charging (XFC) are a necessity for the deployment of electric vehicles. Material properties of electrodes and electrolytes along with cell parameters such as stack pressure and temperature have coupled, synergistic, and sometimes deleterious effects on fast-charging performance. We develop a new experimental testbed that allows precise and conformal application of electrode stack pressure. We focus on cell capacity degradation using single-layer pouch cells with graphite anodes, LiNi0.5Mn0.3Co0.2O2 (NMC532) cathodes, and carbonate-based electrolyte. In the tested range (10–125 psi), cells cycled at higher pressure show higher capacity and less capacity fading. Additionally, Li plating decreases with increasing pressure as observed with scanning electron microscopy (SEM) and optical imaging. While the loss of Li inventory from Li plating is the largest contributor to capacity fade, electrochemical and SEM examination of the NMC cathodes after XFC experiments show increased secondary particle damage at lower pressure. We infer that the better performance at higher pressure is due to more homogeneous reactions of active materials across the electrode and less polarization through the electrode thickness. Our study emphasizes the importance of electrode stack pressure in XFC batteries and highlights its subtle role in cell conditions. [ABSTRACT FROM AUTHOR]

LiNiO2, a promising cobalt-free cathode, suffers from poor cyclic stability and inferior rate performance due to structural degradation. A strategy based on the synergistic effect of a strong Nb–O bond (753 kJ mol−1 ), high valence state (Nb5+), and larger ionic radius (0.64 Å) was developed to improve the properties of LiNiO2. The synergistic effects can effectively improve lattice stability, lower Li+/Ni2+ cation mixing, expand LiO6-slab spaces, enhance the conductivity and inhibit the H2–H3 phase transition, which can enhance the stability of the layered structure, accelerate Li+ diffusion and alleviate mechanical damage. Therefore, LiN0.99Nb0.01O2 exhibits higher capacity retention (91.4% after 100 cycles at 0.5C) and superior rate capability (143 mAh g−1 at 5C). As a comparison, the data of bare LiNiO2 is 69.2% and 127 mAh g−1 under the same conditions. These results further demonstrate the effectiveness of the proposed doping strategy. [ABSTRACT FROM AUTHOR]

Water-based processing of positive Li-ion battery electrodes is becoming increasingly important to enable green and sustainable electrode production. Although already widely established for carbon-based anodes, the water-based coating process still poses challenges if applied to cathode materials containing high contents of nickel. Positive electrodes using Ni-rich cathode materials with areal capacities of 2.6 mAh cm−2 were prepared either with Epoxy, a polyisocyanate-based (ICN) binder or polyacrylic acid (PAA). All three binders can cross-link with Na-carboxymethyl cellulose (CMC) used in the formulation. In bi-layer pouch-cells, such cathodes based on Epoxy or ICN binders reach an excellent long-term 1 C charge/discharge capacity retention of 85% and 88% after 1000 cycles, whereas electrodes with PAA only reach 65%. Post-mortem analysis of cells after cycling suggests aging of the cathode electrode as main source of deactivation. According to scanning electron microscopy data, the aqueous processing does not lead to a stronger cracking of the secondary CAM particles and no enhanced dissolution of transition metals was found on the anode side. However, a stronger increase in charge-transfer impedance is observed for the aged water-based cathodes. Thus, the formation of a blocking surface layer appears to be the major reason for performance deterioration with increasing cycle number. [ABSTRACT FROM AUTHOR]

Layered NaxMO2 cathodes are of immense interest as rechargeable sodium batteries further their development as a lithium-ion battery alternative. However, two primary intrinsic structural issues hinder their practicality—sodium ordering and transition-metal layer gliding during cycling. These phenomena plague the electrochemical profiles of these materials with several unwanted voltage plateaus. A Na+ and Fe3+ substitution for Ni2+ strategy is employed here to obtain a series of Na3+xNi2–2xFexSbO6 (0 ⩽ x ⩽ 0.5) materials to suppress the structural phenomena that are apparent in O’3-layered Na3Ni2SbO6 cathode material. This strategy is successful in obtaining a sloping voltage curve without distinct plateaus—an indication of suppression of the underlying structural phenomena that cause them—at doping concentrations of x ⩾ 0.3. The first-cycle coulombic efficiency of the doped compounds is much greater than the starting compound, presumably owing to a kinetic barrier to reforming the full O’3-layered starting materials within the voltage range of 2.5–4.3 V vs Na+/Na. Sodium doping into the MO2 layer thus remains a promising strategy for enabling commercial NaxMO2 cathodes, but further development is required to lower the kinetic barrier for sodium reinsertion into these materials in a useful voltage range to maximize their reversible capacity. [ABSTRACT FROM AUTHOR]

Lithiated nickel-cobalt-manganese oxides, such as NCM523, are used in the positive electrode (cathode) of Li-ion cells. Using operando X-ray diffraction profilometry, lithiation gradients in the cathode matrix can be observed and quantified by expansion into Legendre polynomials with time-dependent weights. These weights (referred to as gradients) increase in magnitude when electric current flows through the cell, decrease during potentiostatic hold and finally relax to zero when the current is interrupted during open circuit rest. Both physics-based electrochemical models and operando X-ray experiments suggest that the time constants for gradient growth and abatement are primarily determined by ionic diffusion in the oxide particles, which in turn depends on their lithium content. In contrast, the magnitude of gradients depends mainly on the applied current. The X-ray profilometry provides a way of directly probing the formation and disappearance of Li gradients across the cathode during fast cycling, which can help to diagnose the effects of material degradation in the cells. [ABSTRACT FROM AUTHOR]

A model for impedance of a PEM fuel cell cathode taking into account oxygen transport in the cathode catalyst layer (CCL), gas-diffusion layer (GDL) and in channel is solved analytically. A formula for the cathode impedance is valid for the cell current densities below 100 mA cm-2 and air flow stoichiometries exceeding 10. Least-squares fitting of experimental spectrum using the analytical result takes about 5 s on a standard PC. Fitting returns Tafel slope of the oxygen reduction reaction, double layer capacitance, CCL proton conductivity and oxygen diffusivities of the CCL and GDL. Analytical impedance can be coded as a user-defined function for a standard spectra fitting software supplied with EIS-meters. [ABSTRACT FROM AUTHOR]

The dissolution of lithium polysulfide (Li2Sx, 4 < x < 8, LiPS) during charge/discharge testing is a critical issue hindering the practical application of lithium-sulfur batteries (LSBs). To suppress LiPS dissolution, we propose a facile method to fabricate a Liion-conductive polymer layer by photopolymerization. The electrochemical performance of LSBs was investigated by preparing small pouch cells containing a three-dimensional (3D) structured sulfur-based cathode that either was or was not layered with the new polymer. Analysis of the electrolyte in the LSB pouch cell by UV-Vis spectroscopy revealed that a 3D S cathode with polymer layer shows a good discharge capacity of 535 mA h g-1 and a coulombic efficiency (CE) of over 96% after 40 cycles. In comparison, the 3D S cathode without a polymer layer has a poor discharge capacity of 389 mA h g-1 and a CE of over 22% after 40 cycles. The dissolution suppressing ability of our new polymer layer demonstrates promise for the practical application of LSBs. [ABSTRACT FROM AUTHOR]

The resurgence of electromobility drives the need for high energy density cathode materials. LiNiO2 (LNO) meets this demand, based on its high specific capacity in a narrow voltage range and without relying on scare elements. Yet, it has been plagued by various issues, such as poor cycling performance and thermal instability. Adding dopants, such as widely available Mg2+, is a common strategy to balance cycling performance and energy density. Most prior studies focused on large Mg content ranges and were based on laboratory X-ray diffraction. Hence, the influence of Mg2+ addition on the crystal structure remains ambiguous, especially when small amounts are used (< 5 mol%; particularly interesting for industrial applications). Here, we present a systematic study of LiNi1-yMgyO2 (0 ≤ y ≤ 0.05) investigated by high-resolution synchrotron-based X-ray diffraction combined with elemental analysis, electron microscopy and electrochemical testing. The synthetic route relies on the addition of 10 nm Mg(OH)2 nanoparticles prior to the final calcination, as well as on co-precipitation. It is found that Mg2+ mostly occupies the Ni site until saturating at ~1.7%, then the Li site becomes preferred. This trend in the site occupancies influences the lattice parameters, oxygen coordinate within the unit cell and Ni-O bond distances. Doping also modifies the electrochemical behavior as a cathode material, stabilizing the capacity retention during cycling but sacrificing specific discharge capacity. Laboratory-based operando X-ray diffraction reveals that the increase in capacity retention is due to the suppression of the H2-H3 phase transition and interlayer distance collapse already in 3% Mg-doped LNO. The combination of structural and electrochemical characterization of doped LNO provides useful insights into the structural chemistry of the Mg2+ dopant and can serve as a starting point to understand Mg as a component in multiple dopant strategies for cathode material design and application. [ABSTRACT FROM AUTHOR]

Iron (Fe)-based layered oxide cathodes that employ Fe3+/Fe4+ redox reaction present a family of attractive cathode materials for sodium-ion batteries as iron is abundant, low-cost, and environmentally benign. However, their electrochemical performance is not yet satisfactory and requires further improvement. In this study, we investigate the effect of electrolytes on the electrochemical performance of α-NaFeO2, a prototypical model of Fe-based layered cathodes. First, we established the critical impact of the poor cathode-electrolyte interfacial stability on cell performances. Systematic electrochemical tests and material characterizations further revealed the degradation mechanism in which the highly reactive Fe4+ state in the charged Na1-xFeO2 electrodes promotes severe electrolyte decomposition and subsequent growth of a thick interface layer that leads to impedance rise and performance degradation. In addition, the superior performance of NaPF6 over NaClO4 and the beneficial effect of the FEC additive are reported. [ABSTRACT FROM AUTHOR]

Zinc manganese spinel composite oxide ZnMn2O4 is an important inorganic material, which is rich in natural resources and environment-friendly. Herein, pure phase ZnMn2O4 was prepared by a simple sol-gel process as cathode material for zinc ion batteries. In order to improve the cycle performance of the material while maintaining the capacity, acetonitrile/aqueous co-solvent electrolyte (0.5 M Zn(CF3SO3)2/AN-H2O) was used as the electrolyte of the zinc ion battery. The influence of different experimental conditions on the electrochemical properties of ZnMn2O4 was studied by orthogonal experiment. In order to improve its electrochemical performance and cycling ability, the non-equivalent substitution of pure ZnMn2O4 was performed by adding Al3+. The non-equivalent substitution of Al3+ reduced the cell volume of ZnMn2O4 and the mixed manganese valence appeared. The specific capacity of initial discharge increases from 52.9 mAh·g-1 to 109.4 mAh·g-1 at 0.05C, and the cycle stability is also greatly improved. After 100 cycles, the capacity retention rate was 82.3%. This work shows that ZnMn2O4 is a promising cathode material for zinc ion batteries, which expands the application of spinel oxide in zinc ion batteries. [ABSTRACT FROM AUTHOR]

A large-format pouch cell with a nominal capacity of 78 Ah from the Volkswagen ID.3 was disassembled and analyzed to characterize the state of the art of industrial-scale cells in automotive applications. The cell components were separated from each other, geometrically measured, and weighed to quantify the volume and weight fractions from electrode to cell level. Material samples from the electrodes were characterized by scanning electron microscopy (SEM), elemental analysis, and mercury porosimetry. Half cells were built post mortem and assessed in electrochemical tests. The results revealed a stacked cell of laminated electrode layers. The cathode showed a bi-modal particle distribution and its active material ranged with LiNi0.65Mn0.2Co0.15O2 in between NMC622 and NMC811. Silicon-free graphite was used as the anode active material. Over 75% of the cell mass and over 81% of the cell volume directly contribute with its active material to the specific energy of 268 Wh kg-1 and energy density of 674 Wh L-1 at cell level. 91% of the anode and 93% of the cathode were utilized in the pristine cell, respectively. In charge rate tests, the anode was identified as the limiting electrode. The results provide valuable insights into the state of the art of automotive lithium-ion batteries and serve as a reference for scientific research. [ABSTRACT FROM AUTHOR]

For lithium-sulfur batteries, porous carbon/sulfur composite cathodes are the primary solution to compensate the non-conductive nature of sulfur. The composition and structure of this class of cathodes are crucial to the electrochemical performance, achieved energy density and the stability of the cell. Electrochemical impedance spectroscopy is employed to investigate and correlate the electrochemical performance of lithium-sulfur batteries to the composition and microstructure of differently fabricated carbon/sulfur composite cathodes. A transmission line model is applied to identify different underlying electrochemical processes appearing in the impedance response of a range of porous carbon/sulfur cathodes. The integration of a lithium ring serving as a counter electrode coupled with advanced wiring has allowed an artifact-free recording of the cathode impedance at different states of charge with the aim to investigate the evolution of impedance during discharge/charge and the kinetics of charge transfer depending on the infiltration method and the utilized carbon host. It is shown that impedance response of this class of cathodes is highly diverse and the plausible underlying processes are discussed in details. To this end, quasi-solid-state and various polysulfide-based charge transfer mechanisms are identified and their time constants are reported. [ABSTRACT FROM AUTHOR]

The O2-type layered oxide cathode materials have attracted strong research interest recently because of their high specific capacity and their unique lattice structure that may help suppress the detrimental layer-to-spinel phase transition. These materials are metastable and commonly prepared through Li-Na exchange methods from the Na-containing P2-type oxides. Here we investigated the structural, chemical, and morphological changes during the ion-exchange processes in both the LiBr/hexanol solution and the LiNO3/LiCl molten salts. The solution method was more favorable in preparing high-capacity O2-type cathode materials, even though the structural reorganization was slower compared with the molten-salt method. The as-made O2-type cathode materials, contrary to the previous belief, were actually Li-deficient at their pristine states, but could accept more Li ions than that it was extracted during the first charge/discharge cycle. The O2-type cathode materials exhibited high capacities (up to 266 mAh g-1) but the cycle performance requires further improvements. XRD and Raman spectroscopy studies indicated that the structural changes in the bulk were quite reversible. Using a fluorinated electrolyte to address the interface instability improved the cycle performance. Our results provide a more complete understanding of the O2-type cathode materials and useful guidance in the design of low-cost, high-energy cathode materials for LIBs. [ABSTRACT FROM AUTHOR]

Aqueous zinc batteries are increasingly gaining attention of the researchers in recent years because of their environmental and user friendliness as well as the economic benefits of the zinc metal. Herein we report a ferrocene based organic cathode synthesized by following green chemistry principle and stabilized by low temperature thermal encapsulation in multiwalled carbon nano tubes (MWCNTs) for stable electrochemical performance. Successful intercalation was confirmed by XRD, Raman, FTIR spectra, TEMHAADF imaging. Without encapsulation, material exhibited initial capacity of 64.7 mAhg-1 which was drastically faded with time due to dissolution of active material. However, by low temperature thermal encapsulation, the capacity was remarkably improved to 71.3 mAhg-1 with 94% columbic efficiency and 91% capacity retention at a current density of 75 mAg-1 in a 100 charge/discharge cycles. The stability of the electrode has been explained on the basis of a friendly host-guest interaction between CNTs and the organic molecules by π-π stacking, dipole-dipole and dipole induced dipole interactions with detailed electrochemical and spectroscopic characterization. From this study we conclude that the thermal intercalation in MWCNTs has been found to be excellent method to stabilize the electrode materials in battery application. [ABSTRACT FROM AUTHOR]

Developing efficient and stable ORR catalysts for Mg-air batteries is crucial to enabling extensive applications. Herein, CuMnO2 nanoflakes were synthesized with a facile one-step hydrothermal way and applied as the cathode catalyst for Mg-air batteries. The ORR activities in alkaline and neutral electrolyte were then investigated. The half-wave potential has a minus variation of 22 mV after 5000 cycles, indicating the outstanding stability of the CuMnO2. The electron transfer number of the CuMnO2 is 3.70 under neutral condition, which demonstrates that the reaction process of ORR is equivalent to the commercial Pt catalyst. Moreover, the primary Mg-air battery with CuMnO2 as the cathode catalyst was assembled and the discharge properties were tested. The open circuit voltage achieved was 1.78 V and the operating voltage remained about 1.36 V after 22 h operation at 1.0 mA·cm-2. It is evident that the CuMnO2 nanoflake is an effective catalyst to accelerate the reaction rate of ORR process in Mg-air battery. This work provides a novel approach for the subsequent exploration of non-noble metal catalysts for Mg-air batteries. [ABSTRACT FROM AUTHOR]

The heterogeneous nature of the cathode catalyst layer has been a major obstacle toward the comprehension of the mechanisms hindering the PEMFC performance at high current densities. To deconvolute these, an approach coupling multiscale modeling and multiscale electron microscopy characterization--allowing to move from the local to the cathode catalyst layer scale--is adopted. Here, an agglomerate scale model is developed and coupled with a MEA-scale model. Different structures are analyzed and the effects of certain structural parameters (Pt particle size, agglomerate structure and Nafion layer thickness) on the electrode performance are quantified and discussed. Reducing the Pt particle size is found to improve performance in most cases, though the improvement margin is highly dependent on the structure, and to a certain extent, on the particle spatial distribution. It is found that thickening the Nafion film is detrimental for performance only when the porosity is not sufficiently large. Performance gains upon structure rearrangement into an ideal-type structure (Nafion and pore tortuosities minimized to unity) are also quantified. These analyses have unvealed the main mechanism limiting performance when shifting to moderate/high current densities and allowed quantifying and ranking the physical phenomena hampering performance by order of importance. [ABSTRACT FROM AUTHOR]

Rechargeable alkaline zinc batteries (RAZBs) have attracted great attention due to their inexpensive use of electrode materials and high safety features. However, the development of RAZBs is restricted by their low capacity and volumetric energy density, mainly suffering from poor electric conductivity of the cathode. Aluminium-doped SrTiO3 (1.0% Al-STO) has successfully enhanced the capacity of pristine STO from 387 to 646 mAh cm-3 at a current density of 2 mA cm-2. This may be attributed to the fact that Al doping improves electrical conductivity as well as promoting the transportation of ions/electrons. Based on the Nyquist plot, the charge-transfer resistance of Al-STO was reduced from 7.8 to 1.2 Ω, indicating the enhancement of electrical conductivity after Al doping. This outstanding electrochemical performance of Al-STO as cathode provide valuable insights for designing high-performance electrode for RAZBs. [ABSTRACT FROM AUTHOR]

Rechargeable aqueous zinc-ion batteries (ZIBs) with cost-effective and environmentally friendly characteristics show great potential for large-scale energy storage systems. Among all cathode material candidates, layered vanadates are promising owing to their suitable open structure for accommodating Zn2+/H+. However, the unsatisfactory rate capability and cycling stability of vanadate cathodes have hindered the practical application. Thus, the exploration of high-performance and structural stable cathode materials is urgently needed. In this study, a La0.14V2O5/reduced graphene oxide composite material (denoted as LaVO/rGO) can be successfully synthesized by a facile hydrothermal procedure. With the pillar La3+ ions and highly conductive rGO, the layered LaVO/rGO has the merits of large interlayer distance (14.7 Å), low charge transfer resistance, and high diffusion coefficient that guarantee fast kinetics of Zn2+/H+ intercalation/de-intercalation. As a result, the LaVO/rGO cathode delivers a high-rate performance which obtains high capacity of 298 mAh g-1 at 0.3 A g-1. Even up to 8 A g-1, high capacity of 166 mAh g-1 can be achieved. Stable cycle performance with the capacity retention of 88% over 6000 cycles is attained, benefiting from fast and reversible Zn2+/H+ storage in the host material. [ABSTRACT FROM AUTHOR]

Lithium-rich disordered rocksalts such as Li1.3Nb0.3Mn0.4O2 and Li2MnO2F are being investigated as high energy density cathodes for next generation Li-ion batteries. They can support the (de) lithiation of lithium ions over large compositional ranges while preserving the same overall structure. Here, we present a new Ni-rich oxyfluoride cathode, Li2NiO2F, with a disordered rocksalt structure. Li2NiO2F and can deliver a discharge capacity of 200 mAh g-1 at an average voltage of 3.2 V. [ABSTRACT FROM AUTHOR]

Different forms of δ-MnO2 were constructed with their reduction sites anchored on non-support or other supports. Morphology, composition, and electrochemical properties of MnO2 and its hybrids were analyzed. Results revealed that MnO2/reduced graphene oxide (rGO) layered hybrid showed a higher BET surface area due to the synergistic effect on the introduction of rGO and the morphologic transformation of anchored MnO2. MnO2/rGO-2 exhibits a higher ratio of Mn3+: Mn4+ content, a better adsorption performance for O2, and a lower charge-transfer resistance when respect to pristine δ-MnO2. Compared with other MnO2/rGO hybrids, porous MnO2/rGO-2 layered hybrid exhibits the best electrochemical property: a closer four-electron process (3.95), a more positive Eonset (0.92 V vs RHE), and superior long-term durability (98.5% after 25,000 s). Especially, a mechanically reusable Mg-air battery with MnO2/rGO-2 cathode catalyst only exhibits a 5% decay for 264 h. [ABSTRACT FROM AUTHOR]