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Triplite-type LiFeSO4F has attracted considerable attention as a promising cathode for next-generation lithium-ion batteries because of its high redox potential based on earth-abundant Fe2+/3+. However, successful extraction/reinsertion of all the lithium ions in triplite host is challenging even at a low current rate, resulting in a low specific capacity. These experimental findings contrast with previous theoretical works that predicted that the triplite structure would be a fast ionic conductor with low activation barriers for lithium-ion hopping. Origin of this discrepancy is elusive to date. Herein, combined first-principles calculations and high-angle annular dark-field scanning transmission electron microscopy analyses reveal that typical triplite structure is composed of nanodomains consisting of corner-shared FeO4F2 octahedra, whereas their domain boundaries are regions of mixed corner/edge-shared FeO4F2 octahedra. More importantly, these locally disordered domain boundaries significantly reduce the overall lithium diffusivity of the materials. Inspired by these findings, this study redesigns triplite structure with sufficiently small sizes to avoid local bottlenecks arising from the domain boundaries, successfully achieving nearly full lithium extraction/reinsertion with high power and energy density. This work represents the first direct observation of the presence of domain boundaries within a crystalline structure playing a critical role in governing the lithium diffusivity in a battery electrode.

Abstract: Triplite‐type LiFeSO4F has attracted considerable attention as a promising cathode for next‐generation lithium‐ion batteries because of its high redox potential based on earth‐abundant Fe2+/3+. However, successful extraction/reinsertion of all the lithium ions in triplite host is challenging even at a low current rate, resulting in a low specific capacity. These experimental findings contrast with previous theoretical works that predicted that the triplite structure would be a fast ionic conductor with low activation barriers for lithium‐ion hopping. Origin of this discrepancy is elusive to date. Herein, combined first‐principles calculations and high‐angle annular dark‐field scanning transmission electron microscopy analyses reveal that typical triplite structure is composed of nanodomains consisting of corner‐shared FeO4F2 octahedra, whereas their domain boundaries are regions of mixed corner/edge‐shared FeO4F2 octahedra. More importantly, these locally disordered domain boundaries significantly reduce the overall lithium diffusivity of the materials. Inspired by these findings, this study redesigns triplite structure with sufficiently small sizes to avoid local bottlenecks arising from the domain boundaries, successfully achieving nearly full lithium extraction/reinsertion with high power and energy density. This work represents the first direct observation of the presence of domain boundaries within a crystalline structure playing a critical role in governing the lithium diffusivity in a battery electrode. [ABSTRACT FROM AUTHOR]

Submicrosized chevrel Mo6S8 powder is synthesized using mechanical milling of the starting materials and the powder yield is increased by using modified synthesis method. The effect of particle size is investigated using various electrochemical techniques. The submicrosized chevrel shows enhanced discharge capacity compared with that of microsized chevrel, and voltage profile indicates that the low capacity arising from Mg trapping at the Mg-1 site is improved for submicrosized chevrel. Mg trapping is also verified by ex situ X-ray diffraction measurement and the results are in good agreement with the electrochemical profile. Open-circuit voltage measurements and AC-impedance spectroscopy are used to identify the kinetics of Mg2+ insertion. The improved electrochemical properties obtained with the submicrosized chevrel are attributed to the smaller particles that provide shorter diffusion lengths for Mg2+ ions. [ABSTRACT FROM AUTHOR]

Abstract: The positive effect of AlF3 (Al–F) coating on the over-lithiated transition metal oxide with a composition of 0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 has been investigated to address its potential use in lithium ion batteries. On the basis of various structural and electrochemical characterizations, we elucidate a correlation between surface structure and its electrochemical performance. After the controlled coating with AlF3 (Al–F), we observed notable improvements on cyclic performance and rate capability as well as thermal stability. We found that uniformly introduced AlF3 (Al–F) not only preserves the electrochemical kinetics at the surface of the oxide but also stabilizes its surface as a protective layer against electrolyte oxidation during the high voltage charging. Such improvements will provide a further progress on the development of high-capacity cathode materials fulfilled with the stringent safety requirements. [Copyright &y& Elsevier]

Given that the performance of a lithium–oxygen battery (LOB) is determined by the electrochemical reactions occurring on the cathode, the development of advanced cathode nanoarchitectures is of great importance for the realization of high‐energy‐density, reversible LOBs. Herein, a robust cathode design is proposed for LOBs based on a dual‐phasic carbon nanoarchitecture. The cathode is composed of an interwoven network of porous metal–organic framework (MOF) derived carbon (MOF‐C) and conductive carbon nanotubes (CNTs). The dual‐phasic nanoarchitecture incorporates the advantages of both components: MOF‐C provides a large surface area for the oxygen reactions and a large pore volume for Li2O2 storage, and CNTs provide facile pathways for electron and O2 transport as well as additional void spaces for Li2O2 accommodation. It is demonstrated that the synergistic nanoarchitecturing of the dual‐phasic MOF‐C/CNT material results in promising electrochemical performance of LOBs, as evidenced by a high discharge capacity of ≈10 050 mAh g−1 and a stable cycling performance over 75 cycles. [ABSTRACT FROM AUTHOR]

A uniform surface coating and control over residual Li on the surface of high-Ni layered transition metal oxides is crucial for development of highly reliable and high-performance cathode materials for lithium ion batteries (LIBs). To suppress undesirable side reactions at the surface of high-Ni layered transition metal oxides, we propose a one-pot TiO 2 surface coating process using a bifunctional hybrid solution. We demonstrate that the uniformity and thickness of a TiO 2 coating layer can be controlled, and residual Li can be simultaneously reduced during the surface coating process. Structural and electrochemical characterizations support the utilization of an essential bifunctional hybrid solution composed of titanium (IV) isopropoxide (TTIP) in isopropyl alcohol (IPA) and tetrabutyl-ammonium hydroxide (TBAOH) in water for introducing a uniform TiO 2 coating layer and eliminating undesirable Li residues on the surface without yielding significant structural degradation. Our approach provides a practical guide to develop advanced cathode materials and simplify the synthetic process for mass production. A one-pot TiO 2 surface coating process using a bifunctional hybrid solution composed of titanium (IV) isopropoxide (TTIP) in isopropyl alcohol (IPA) and tetrabutyl-ammonium hydroxide (TBAOH) in water for introducing a uniform TiO 2 coating layer and eliminating undesirable Li residues on the surface without yielding significant structural degradation. Image 1 • A one-pot TiO 2 surface coating process using a bifunctional hybrid solution is proposed. • A bifunctional hybrid solution is essential for introducing a uniform TiO 2 coating and eliminating undesirable Li residues. • TiO 2 coated NCM811 exhibits a high reversible capacity of more than 200 mAh g−1 and stable cycle performance. [ABSTRACT FROM AUTHOR]

Prussian blue and its analogues that have three-dimensional open frameworks are promising cathode materials for sodium-ion batteries owing to their high theoretical capacity and low production cost. Unfortunately, these materials are electrically insulating, which results in adverse effects on their electrochemical performance, such as limited practical capacity and rate capability. In this study, we demonstrate a simple overlaying of a conductive polymer— poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)—on the surface of Prussian blue nanocubes at room temperature, with the aim to secure sufficient electrical conduction pathways and, by extension, improve the electrochemical performance of the nanocubes. The proposed surface-engineered Prussian blue nanocubes with 3.0 wt% poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) show a high reversible capacity (130.9 mA g−1) with stable cycle performance. Moreover, they exhibit a reversible capacity of approximately 112.6 mAh g−1 at the high rate of 1220 mA g−1, which corresponds to 86.0% of the capacity obtained at a current density of 12.2 mA g−1. Such improvements are mainly attributed to the formation of additional networks of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) that facilitate electric conduction in the electrode. Our proposed approach could be a practical solution to improving the electrochemical properties of Prussian blue and its analogues as potential cathode materials for high-performance sodium-ion batteries. Image 1 • PEDOT:PSS overlaid the PB nanocubes prepared by a one-pot mixing process. • Spontaneous formation of 3D conductive networks in electrode by PEDOT:PSS layer. • Improved rate capability of PED-PB electrode by additional pathways of electrons. [ABSTRACT FROM AUTHOR]

Sodium ion batteries are being highlighted as a promising energy storage system to resolve the critical issues associated with lithium ion battery usage due to a limited quantity of lithium resources on the earth. Although recent advances in sodium ion battery technology have been remarkable, the reversible capacities and cyclic performance of sodium ion batteries should be further advanced prior to their successful implementation. Herein, we demonstrate dual-textured Prussian blue nanocubes prepared via simple acid etching as a reliable sodium storage material. Taking advantage of their hybrid microstructure composed of porous and non-porous domains, dual-textured Prussian blue nanocubes exhibit high reversible capacities, good rate capabilities, and stable cyclic performance. Moreover, the nanocubes exhibit excellent dimensional stability even after 100 cycles, offering new opportunities for the development of robust and high-performance sodium rechargeable batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • LiTaO 3 surface layer is integrated onto SNCM cathode for high-energy LIBs and ASSBs. • The crystallinity of LiTaO 3 affects the reversibility and long-term cycling performance of SNCM cathode. • Tailoring the crystallinity of LiTaO 3 is beneficial for effective surface stabilization of SNCM cathode. Various functional materials have been explored as surface-coating layers for Ni-rich cathode materials used in lithium-ion batteries (LIBs) aiming to enhance their long-term cycling performance and electrochemical stability under high-voltage operation. In particular, lithium tantalate (LiTaO 3) has received considerable attention as a promising candidate due to its distinct physicochemical properties, including high ionic conductivity, wide voltage window, low band-gap energy, and excellent mechanical strength. These characteristics are beneficial for effective surface stabilization of Ni-rich cathode materials, which currently suffer from poor cycling performance, mainly due to issues related to structural instability with elevated Ni concentrations. In this respect, we report the benefits of surface coating with LiTaO 3 on the electrochemical properties of single-crystalline Ni-rich cathode materials (SNCM) for successful implementation in high-energy LIBs. The controlled crystallinity of the LiTaO 3 surface layer directly affects the reversibility as well as interfacial stability of the SNCM cathode under various operating conditions. The tailored crystallinity of LiTaO 3 surface layer is mainly responsible for enhancing the cycle performance of SNCM cathodes under high-temperature (60 °C) and high-voltage (4.5 V vs. Li/Li+) operations. Our findings will significantly contribute to the development of robust and reliable cathode materials for high-energy LIBs. [ABSTRACT FROM AUTHOR]

Improving cycle performance and rate-capability of lithium ion batteries is necessary in moving toward their use in electric vehicles. Working towards this goal, we propose an amorphous Li-Zr-O coating on the surface of a high-Ni layered transition metal oxide (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ) via a simple wet process. By using residual Li on the surface of as-prepared LiNi 0.8 Co 0.1 Mn 0.1 O 2 particles as a Li source, a non-stoichiometric Li-Zr-O compound can be successfully formed on the surface of LiNi 0.8 Co 0.1 Mn 0.1 O 2 particles at a low temperature of 400 °C. The formation of an amorphous Li-Zr-O layer is beneficial in minimizing undesirable side reactions associated with residual Li at the surface and, by extension, improving the cycle performance and rate-capability of LiNi 0.8 Co 0.1 Mn 0.1 O 2 . The amorphous Li-Zr-O coated LiNi 0.8 Co 0.1 Mn 0.1 O 2 exhibits a high reversible capacity of more than 190 mAh g −1 with improved cycle performance. This simple approach offers easy control of the surface characteristics of LiNi 0.8 Co 0.1 Mn 0.1 O 2 , improving the surface stability and enhancing the thermal stability. [ABSTRACT FROM AUTHOR]

The thermal stability of a fully delithiated cathode, coupled with an inorganic salt, organic solvents, and electrolyte, was evaluated with differential scanning calorimetry (DSC) to address the safety issue of lithium-ion batteries. The DSC experiments revealed that vinylene carbonate (VC)-based systems exhibit decreased thermal stability compared to other coexisting systems. The DSC analysis of the cathode and electrolyte in the presence of VC, employed as additives, confirmed the reduction in thermal stability. Our results suggested that VC additives, which have been recently employed to enhance the electrochemical performance in anodes, negatively affect the thermal properties and safety characteristics of the cathode in lithium-ion batteries. [ABSTRACT FROM AUTHOR]

The mechanical properties of cathode materials are among the critical factors that directly affect the lifespan of lithium-ion batteries (LIBs). However, a significant challenge remains in understanding the exact mechanism of mechanical degradation of present cathode materials that results in significant loss of performance during long-term operation. Herein, a comparative study on the correlation between mechanical strength (e.g. particle hardness) and cycle performance of the cathode materials (particularly those with layered structures) is presented. By improving the particle hardness of cathode materials via Mg doping, the formation of undesirable microcracks within the particles during cycling can be effectively suppressed, thus improving cycle performance. Structural and electrochemical analyses are performed in order to further elucidate the mechanical degradation mechanism of LIBs during repeat cycles, and identify a possible approach to the enhancement of electrochemical performance and long-term durability in present cathode materials. Image 1 • A strategy for improving the cycle performance of NCM cathode is presented. • The particle hardness of NCM can be effectively enhanced by Mg doping. • The enhanced particle hardness of Mg-NCM positively affects the cycle performance. • The formation of microcracks within Mg-NCM can be suppressed during cycles. [ABSTRACT FROM AUTHOR]