Interfacial and cycle stability of sulfide all-solid-state batteries with Ni-rich layered oxide cathodes

The interfacial compatibility between sulfide solid electrolyte (SSE) and Ni-rich layered oxide (NRLO) cathode is critical for high-performance sulfide all-solid-state Li-ion batteries (SASSLIBs). However, the reasons for interfacial/capacity degradation of SASSLIBs are not yet clearly resolved. Herein, the impacts of surface structures and chemical environments of LiNi0.83Co0.11Mn0.06O2 (NCM83) on SASSLIB performances are systematically investigated. Surface lithium vacancies of NCM83 facilitate Li ion migration from SSE to NCM83 side, suppressing the H1 phase transformation of NCM83 and expanding the space charge layer. Surface LixNi1−xO type rock salt phases inhibit oxygen-participating interfacial reactions at high voltages due to their low susceptibility to oxygen evolutions, enhancing the H2/H3 phase transformation of NCM83. Surface Li2O and Li2CO3 mitigate the space charge layer effect and interfacial reactions at high voltages, activating H1 and H2/H3 phase transformations of NCM83. On the other hand, the combination of LiOH and Li2CO3 causes severe side reactions with SSE, resulting in escalated interfacial resistance and drastic capacity fading over cycling. Importantly, while the suppression of H1 and H2/H3 transformations reduces the reversible capacity, it mitigates the internal stress and micro-cracks in NCM83 particles, contributing to superior cycling stability of NCM83-sulfide ASSLIBs (94.1 % capacity retention over 500 cycles).