Enhancing the interfacial stability between argyrodite sulfide-based solid electrolytes and lithium electrodes through CO2 adsorption

Abstract

Argyrodite sulfide-based solid electrolyte Li₆PS₅Cl (LPSC) is considered to have great potential in solid-state battery applications due to its ion conductivity being comparable to that of liquid electrolytes. However, interfacial instability between LPSC and Li during cycling, resulting in battery polarization, is an ongoing problem. Here, we report that CO₂ adsorption can play a crucial role in improving both interfacial and electrochemical stability between lithium and LPSC. Investigating the formation of the new S–CO₂ bond, examined here using various analytical techniques, is pivotal to modifying interfacial behavior. It enhances the interfacial stability between lithium and LPSC and reduces cell resistance. Moreover, the Li|CO₂@LPSC|LTO shows an amazing result, with 62% capacity retention and ultra-high coulombic efficiency of 99.91% after 1000 cycles. Interestingly, the same concept was also applied to the high ionic conductivity sulfide-based superionic conductor Li₁₀GeP₂S₁₂ (LGPS) system, which also has the PS₄³⁻ moiety. It also enhanced the stability at the lithium and LGPS interface. This work offers a new direction toward reducing the interfacial resistance of sulfide-based solid electrolytes; it increases the possibility of realizing sulfide-based all-solid-state lithium metal batteries.