Toward robust solid-state lithium metal batteries by stabilizing a polyethylene oxide-based solid electrolyte interface with a biomass polymer filler

[Display omitted] •The cost-effective filler of bacterial cellulose was applied in PEO-based electrolyte.•The Li/Li symmetric cell with BC-PEO/LiTFSI can cycle for more than 1000 h.•All-solid-state Li–LFP and Li–S batteries were successfully fabricated. Achieving all-solid-state lithium-based batteries with high energy densities requires lightweight and ultrathin solid-state electrolytes (SSEs) with high Li+ conductivity, but this still poses significant challenges. Herein, we designed a robust and mechanically flexible SSE (denoted BC-PEO/LiTFSI) by using an environmentally friendly and low-cost approach that involves bacterial cellulose (BC) as a three-dimensional (3D) rigid backbone. In this design, BC-PEO/LiTFSI is tightly integrated and polymerized through intermolecular hydrogen bonding, and the rich oxygen-containing functional groups from the BC filler also provide the active site for Li+ hopping transport. Therefore, the all-solid-state Li-Li symmetric cell with BC-PEO/LiTFSI (containing 3% BC) showed excellent electrochemical cycling properties over 1000 h at a current density of 0.5 mA cm−2. Furthermore, the Li-LiFePO4 full cell showed steady cycling performance under 3 mg cm−2 areal loading at a current of 0.1 C, and the resultant Li–S full cell maintained over 610 mAh g−1 for upward of 300 cycles at 0.2 C and 60 °C.