Performance Improvement of Li6PS5Cl Solid Electrolyte Modified by Poly(ethylene oxide)-Based Composite Polymer Electrolyte with ZSM-5 Molecular Sieves

Abstract

All-solid-state lithium metal batteries (ASSLMBs) with argyrodite-type Li6PS5Cl solid electrolyte (SE) show potential to replace current commercially available lithium-ion batteries by virtue of their potentially high energy density and safety. However, the interface incompatibility between sulfide solid electrolyte and lithium metal leads to an increase in interfacial resistance and the rapid growth of lithium dendrites, which greatly impede its commercial application. To alleviate the above problems, here a cell construction model has been put forward, in which composite polymer electrolytes (CPEs) with high ionic conductivity and good interface compatibility against lithium metal are employed as the interphase between Li6PS5Cl solid electrolyte and lithium metal. CPEs can prevent direct contact between lithium anode and Li6PS5Cl, and a soft CPE layer can solve the problem of high interfacial resistance caused by bad contact between the Li6PS5Cl solid electrolyte and the lithium metal anode. As a result, the symmetric cells Li/CPEs/Li6PS5Cl/CPEs/Li show stable polarization voltage over 140 h at a current density of 0.2 mA at 60 °C. Compared with the rapidly decaying capacity of the LiFePO4/Li6PS5Cl/Li cell, the initial discharge capacity of LiFePO4/Li6PS5Cl/CPEs/Li is 93.74 mAh/g, and after 15 cycles at 0.5 C, the capacity retention rate is still 75.1%. Therefore, the successful design of this cell structure based on the interface modification of Li6PS5Cl solid electrolyte provides good prospects for the commercial application of ASSLMBs.