LiNiO2 (LNO) is a promising cathode material for next‐generation Li‐ion batteries due to its exceptionally high capacity and cobalt‐free composition that enables more sustainable and ethical large‐scale manufacturing. However, its poor cycle life at high operating voltages over 4.1 V impedes its practical use, thus motivating efforts to elucidate and mitigate LiNiO2 degradation mechanisms at high states of charge. Here, a multiscale exploration of high‐voltage degradation cascades associated with oxygen stacking chemistry in cobalt‐free LiNiO2, is presented. Lattice oxygen loss is found to play a critical role in the local O3–O1 stacking transition at high states of charge, which subsequently leads to Ni‐ion migration and irreversible stacking faults during cycling. This undesirable atomic‐scale structural evolution accelerates microscale electrochemical creep, cracking, and even bending of layers, ultimately resulting in macroscopic mechanical degradation of LNO particles. By employing a graphene‐based hermetic surface coating, oxygen loss is attenuated in LNO at high states of charge, which suppresses the initiation of the degradation cascade and thus substantially improves the high‐voltage capacity retention of LNO. Overall, this study provides mechanistic insight into the high‐voltage degradation of LNO, which will inform ongoing efforts to employ cobalt‐free cathodes in Li‐ion battery technology.
All-solid-state batteries (ASSBs) comprising solidified cathodes, electrolytes, and Li-metal anodes have attracted notable attention as promising future batteries for electric vehicles owing to their exceptional stability and expectation of achieving high energy density. However, its permanent operation has been hindered by Li dendrite growth, chemo-mechanical degradation, and interfacial instability, leading to Li exhaustion, increased resistance, and internal short-circuiting. Herein, for the first time, the authors report the effects of a lithium nitride (Li 3 N) sacrificial cathode on the cycling performance of ASSBs combined with a Li-free In layer. Through in situ evolved gas and internal pressure change analyses of the cells, it is found that, as with the liquid electrolyte cell, the decomposed Li 3 N compensates for active Li consumed by side reactions in the cell. Moreover, it is demonstrated that the improved interparticle contact by volume expansion of In through additionally supplied Li as well as the interfacial stability at the anode side by the dendrite-free In layer, are strongly responsible for the improved cyclability of the ASSBs. The findings reveal the effectiveness of the Li compensation approach for the stable cycling of ASSBs based on the secured interfacial stability at the anode side.
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