Fast Li-ion transport and uniform Li-ion flux enabled by a double–layered polymer electrolyte for high performance Li metal battery

Abstract

Polymer–based lithium metal batteries are considered to be one of the most promising Li–based energy storage systems for portable devices and flexible technologies. However, low ionic conductivity of polymer electrolytes and poor compatibility in electrode–electrolyte interfaces restrict the wide applications of polymer–based lithium metal batteries. Here we report a novel polycarbonate–polyethylene oxide based polymer electrolyte with a double layered structure to achieve fast Li–ion conduction and uniform Li-ion flux. Comprehensive experiments and simulations show the ion-dipolar pair of [C=O...Li+] is the main reason for Li+ conduction, and the balances of coupling/decoupling in Li+…TFSI– and Li+…PAN/PVEC synergistically facilitate a fast Li+ transport on the cathode side, which results in high Li+ transference number (0.602) and high ionic conductivity (1.56 × 10–4 S cm–1, 20 °C) of DLPE. Besides, uniform Li+ flux in PEGDMA-SiO2-Pyr14TSFI achieves stable Li/electrolyte interface rich in LiF and Li3N on the anode side. Benefit from this design, the DLPE–based LiFePO4 and LiNi0.8Co0.1Mn0.1O2 battery deliver high safety and high stable performances under various extreme conditions.