g-C3N4@COF heterojunction filler for polymer electrolytes enables fast Li+ transport and high mechanical strength

Solid polymer electrolytes (SPEs) show great promise for high-energy and high-safety lithium metal batteries. However, current SPEs suffer from low ionic conductivity and poor mechanical strength. Herein, the g-C₃N₄@COF heterojunction filler is constructed for SPEs for fast Li⁺ transport and high Li⁺ transference number. In addition, a robust 3D network is fabricated by using g-C₃N₄@COF heterojunction filler in order to further improve the mechanical robustness and electrochemical stability. As a consequence, the g-C₃N₄@COF-3D network/polymer electrolyte displays an ionic conductivity of 1.25×10⁻⁴ S cm⁻¹ at 30 ℃, an electrochemical window of 5.0 V and the tensile strength of 8.613 MPa. Furthermore, the assembled LiFePO₄//Li battery with the g-C₃N₄@COF-3D network/polymer electrolyte presents remarkable cycling stability with a capacity retention of 99.71% after 600 cycles. The above results indicate the great potential of the g-C₃N₄@COF-3D network/polymer electrolyte for advanced energy storage devices.