Sulfide-based all-solid-state lithium-ion batteries (ASSLIBs) are considered as a promising candidate for next-generation energy storage devices that can meet the safety requirements of electric vehicles by utilizing nonflammable solid-state electrolytes (SSEs). However, the poor interfacial compatibility in composite cathodes (SSE/cathode/carbon) is challenging the stable delivery of electrochemical performance. At the SSE/cathode interface, the severe side reactions between sulfide SSEs and cathodes trigger the oxidative decomposition of sulfide SSEs. Moreover, because of the volume change of cathodes, sulfide-based ASSLIBs suffers from severe contact loss between cathode particles and sulfide SSEs. In our study, a two-in-one strategy by a dual-functional Li3PO4 (LPO) modification is designed to suppress both the side-reactions and contact loss at the SSE/cathode interface. As a result, a stable long-term cycling is achieved with a low capacity degradation rate of 0.22 mAh g-1 per cycle for 300 cycles at 0.2C. Although the cycling stability is much improved by the LPO modification, the underlying degradation mechanism at the SSE/cathode interface, especially the origin of the oxidation of sulfide SSEs, is still not clear. Therefore, a surface-cleaning strategy is adopted to investigate the underlying degradation mechanism at SSE/cathode interface. The results indicate that residual lithium compounds on the surface of cathodes, rather than the cathode particles themselves, are the main reason that triggering the oxidation of sulfide SSEs, therefore inducing severe side-reactions at the SSE/cathode interface and structural degradation of cathodes. The degradation of the cathode interface can be significantly suppressed when the cathode surface is cleaned. At the SSE/carbon interface, carbon provides sufficient electronic percolation pathways in composite cathodes, therefore accelerating the decomposition of sulfide SSEs. In our study, a poly(3,4-ethylenedioxythiophene) (PEDOT) modification is designed as a semiconductive additive for composite cathodes. The modified ASSLIB demonstrates a competitive rate capacity, which is 10 times greater than that of the bare cathode. The comprehensive characterizations indicate the PEDOT modification not only significantly suppresses the side reactions but also realizes effective electron transfer at the SSE/cathode/carbon three-phase interface.

Rational design of cathode interface for high-performance all-solid-state lithium-ion batteries

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.