Search

Constructing stable electrode/electrolyte interphase with fast interfacial kinetics is vital for fast‐charging batteries. Herein, we investigate the interphase that forms between a high‐voltage Na3V2(PO4)2F3 cathode and the electrolytes consisting of 3.0, 1.0, or 0.3 M NaClO4 in an organic carbonate solvent (47.5 : 47.5 : 5 mixture of EC: PC: FEC) during charging up to 4.5 V at 55 °C. It is found that a higher anion/solvent ratio in electrolyte solvation structure induces anion‐dominated interphase containing more inorganic species and more anion derivatives (CxClOy), which leads to a larger interfacial Na+ transport resistance and more unfavorable gas evolution. In comparison, a low anion/solvent ratio derives stable anion‐tuned interphase that enables better interfacial kinetics and cycle ability. Importantly, the performance of a failed cathode is restored by triggering the decomposition of CxClOy species. This work elucidates the role of tuning interphase in fast‐charging batteries. [ABSTRACT FROM AUTHOR]

In commercial Li-ion batteries, the internal short circuits or over-lithiation often cause structural transformation in electrodes and may lead to safety risks. Herein, we investigate the over-discharged mechanism of LiCoO2/graphite pouch cells, especially spatially resolving the morphological, surface phase, and local electronic structure of LiCoO2 electrode. With synchrotron-based X-ray techniques and Raman mapping, together with spectroscopy simulations, we demonstrate that over-lithiation reaction is a surface effect, accompanied by Co reduction and surface structure transformation to Li2CoO2/Co3O4/CoO/Li2O-like phases. This surface chemical distribution variation is relevant to the depth and exposed crystalline planes of LiCoO2 particles, and the distribution of binder/conductive additives. Theoretical calculations confirm that Li2CoO2-phase has lower electronic/ionic conductivity than LiCoO2-phase, further revealing the critical effect of distribution of conductive additives on the surface chemical heterogeneity evolution. Our findings on such surface phenomena are non-trivial and highlight the capability of synchrotron-based X-ray techniques for studying the spatial chemical phase heterogeneity. Over-lithiation often causes structural transformation in electrodes and may lead to safety issues in Li-ion batteries. Here, authors investigate the over-discharged mechanism of LiCoO2/graphite pouch cells, and spatially resolve the morphological, surface phase, and local electronic structure of LiCoO2 electrode. [ABSTRACT FROM AUTHOR]

Abstract High-capacity electrode materials are needed for electrochemical energy storage. Spinel (Ni 0.4 Co 0.4 Mn 0.2) 3 O 4 nanoparticles have been prepared by simplified and efficient coprecipitation in combination with thermal decomposition. As conversion-type anodes for lithium ion batteries (LIBs), the materials exhibit high capacities of 779 mAh g−1 after 600 cycles at the optimal current density of 0.5 A g−1. The enhanced cycling performance of (Ni 0.4 Co 0.4 Mn 0.2) 3 O 4 electrodes benefits from multiple metal species providing synergic effects in electrical processes, nanosize favorable for releasing stress and optimal rate lithiation for generating unique solid electrolyte interphase (SEI) with reactivation ability. And, the SEI layer is critical for the cycling properties. Optimal rate lithiation offers in designing long-lived electrodes. Additionally, the spinel materials are evaluated in sodium systems. The different capacity fading behaviors of the (Ni 0.4 Co 0.4 Mn 0.2) 3 O 4 electrodes between lithium and sodium ion cells are concerned. [ABSTRACT FROM AUTHOR]