High-Performance Solid Polymer Electrolytes Filled with Vertically Aligned 2D Materials

Solid state lithium metal batteries are the most promising next-generation power sources owing to their high energy density and safety. Solid polymer electrolytes (SPE) have gained wide attention due to the excellent flexibility, manufacturability, lightweight, and low-cost processing. However, fatal drawbacks of the SPE such as the insufficient ionic conductivity and Li + transference number at room temperature restrict their practical application. Here vertically aligned 2D sheets are demonstrated as an advanced filler for SPE with enhanced ionic conductivity, Li + transference number, mechanical modulus, and electrochemical stability, using vermiculite nanosheets as an example. The vertically aligned vermiculite sheets (VAVS), prepared by the temperature gradient freezing, provide aligned, continuous, run-through polymer-filler interfaces after infiltrating with polyethylene oxide (PEO)-based SPE. As a result, ionic conductivity as high as 1.89 × 10 −4 S cm −1 at 25 °C is achieved with Li + transference number close to 0.5. Along with their enhanced mechanical strength, Li|Li symmetric cells using VAVS–CSPE are stable over 1300 h with a low overpotential. LiFePO 4 in all-solid-state lithium metal batteries with VAVS–CSPE could deliver a specific capacity of 167 mAh g −1 at 0.1 C at 35 °C and 82% capacity retention after 200 cycles at 0.5 C.