Self‐Supporting Solid Electrolyte Based on Supramolecular Interaction for Stable Li Metal Batteries

Abstract Li metal batteries based on solid polymer electrolytes offer the benefits of high energy density and safety, as well as extended cycling life, making them an excellent candidate for the next‐generation battery system. However, current solid polymer electrolytes still suffer from low ion conductivity and Li + transfer number, which seriously restricts its practical application. Herein, a self‐supporting composite solid polymer electrolyte was prepared, where phenolic resin rich in hydroxyl groups (BR) and polyethylene oxide (PEO) are mixed evenly and poured onto a cellulose membrane in one step. In such an electrolyte, PEO and BR combine to form intermolecular hydrogen bonds, lowering the crystallinity of PEO and increasing the Li + transfer number. Lastly, the obtained solid electrolytes exhibited a high ion conductivity (1.1×10 −4 S cm −1 ) and Li + transfer number (0.53), as well as improved electrochemical window. Consequently, Li || Li symmetrical cells can run stably for more than 700 h at 0.1 mA cm −2 /0.25 mAh cm −2 . And full cells with LiFePO 4 cathode can also demonstrate high discharge capacity of 152.12 mAh g −1 and rate performance. We believe that such a design based on supramolecular interaction offer a new avenue to advanced solid polymer electrolytes.