Economic and Effective Construction of a P/Sn Multifunctional Layer on the Li/Garnet Interface via Transformation Reactions

Garnet-based solid-state electrolytes (SSEs) have been regarded as one of the most promising ideal candidates for applications in all-solid-state lithium metal batteries (ASSLMBs) due to their high electrochemical stability, wide potential window, and superior safety performance. However, their practical utilization is currently limited by their poor interfacial compatibility and short cycling life. Here, a low-cost and effective interfacial modification method is proposed to improve the interfacial contact by introducing a thin uniform modified layer of Sn4P3 on the surface of garnet-type Li6.4La3Zr1.4Ta0.6O12 SSE. According to experimental results and theoretical calculations, it has been discovered that Li and Sn4P3 undergo a transformation reaction, resulting in the production of a multifunctional interfacial layer consisting of Li22Sn5/Li8SnP4. Specifically, due to the presence of this layer, the interfacial impedance of the Li–Li symmetric cell is just approximately 1 Ω cm–2 and the symmetric cell exhibits a critical current density of 1.7 mA cm–2 at room temperature. The remarkable features of the electrolyte interface ensure that the symmetric cells are capable of stable electrochemical cycling for >1800 h at 0.5 mA cm–2. Additionally, the ASSLMBs demonstrate favorable cycling and rate performance. This effective transformation reaction-driven interfacial modification strategy offers a beneficial means of resolving the interfacial issues of Li/garnet-state SSEs.