Revealing the influence of in-situ formed LiCl on garnet/Li interface for dendrite-free solid-state batteries

Inadequate interfacial contact between lithium and solid-state electrolytes(SSEs) leads to elevated impedance and the growth of lithium dendrites, presenting significant obstacles to the practical viability of solid-state batteries(SSBs). To ameliorate interfacial contact, optimizing the surface treatment of SSEs has been widely adopted. However, the formation of LiCl through acid treatment, an equally crucial factor impacting SSB performance, has received limited attention, leaving its underlying mechanism unclear.Our study aims to shed light on SSE characteristics following LiCl formation and the removal of Li2CO3through acid treatment. We seek to establish quantifiable links between SSE surface structure and SSB performance, focusing on interfacial resistance, current distribution, critical current density(CCD), and lithium deposition. The formation of LiCl, occurring as Li2CO3is removed through acid treatment, effectively mitigates lithium dendrite formation on SSE surfaces. This action inhibits electron injection and reduces the diffusion rate of Li atoms. Simultaneously, acid treatment transforms the SSE surface into a lithiophilic state by eliminating surface Li2CO3. Consequently, the interfacial resistance between lithium and SSEs substantially decreases from 487.67 to 35.99 Ω cm2at 25℃. This leads to a notably high CCD of 1.3 mA cm-2and a significantly extended cycle life of 1,000 h. Furthermore, in full SSBs incorporating LiCoO2cathodes and acid-treated garnet SSEs, we observe exceptional cyclability and rate capability.Our findings highlight that acid treatment not only establishes a fundamental relationship between SSE surfaces and battery performance but also offers an effective strategy for addressing interfacial challenges in SSBs.