Soy protein as a dual-functional bridge enabling high performance solid electrolyte for Li metal batteries

A high-performance solid electrolyte is critical for all-solid-state Li metal batteries which possess good safety and high energy densities. In this study, inspired by the unique ionic transport function and excellent adhesive properties of natural proteins, we successfully generated a novel solid electrolyte by applying soy protein as a dual-functional bridge to enable additional ion-conduction pathways and improve mechanical performance. The solid electrolyte with soy protein that interacts with both SiO 2 nanofabrics and polypolyethylene oxide (PEO) exhibits high ionic conductivity of 10 −5  S cm −1 (vs. 10 −6  S cm −1 of SiO 2 /PEO), improved Li + transference number of 0.550 (vs. 0.446 of SiO 2 /PEO), high Young's modulus of 1.862 MPa (vs. 0.356 MPa of SiO 2 /PEO) and excellent flexibility. As a result, the solid-state batteries with LiFePO 4 as cathode demonstrate a stable discharge capacity. This work provides a new strategy to advance the performance of solid electrolytes for achieving long-lifespan all-solid-state batteries.