Ionic liquid molecular brush-functionalized gel polymer electrolyte with vertically aligned channels for high performance lithium metal batteries

Gel polymer electrolytes (GPEs), benefiting from strong contact with electrodes and leakage resistance, are considered as a compromised strategy to reconcile the dilemma of solid polymer electrolytes and liquid electrolytes. However, the discontinuous and random transport channels in GPEs could impede the fast Li+ migration and result in the dendritic growth. Herein, a molecular-level designed GPE (IL@SiO2@PVDF) has been fabricated via grafting ionic liquid molecular brushes onto the vertically aligned channels in PVDF-based polymer electrolyte to improve the electrochemical performance of lithium metal batteries. The vertically aligned channels can reduce the ionic transport distance, and the grafted ionic liquid molecular brushes on the channels are capable of immobilizing the anions of TFSI-, which can enhance the Li-ion transference number of GPE. The IL@SiO2@PVDF displays an outstanding ionic conductivity of 3.2 x 10-3 S cm-1 at room temperature and a high Li+ transference number (tLi+) of 0.72. Consequently, the symmetric Li||Li cell with IL@SiO2@PVDF delivers excellent plating/stripping stability at a current density of 0.5 mA cm-2 . The Li||LiFePO4 cell with IL@SiO2@PVDF shows a superior long cycling life and remains an excellent specific capacity of 107 mAh g-1 after 1000 cycles. This work opens a new avenue for developing superior GPE with aligned structure through molecular brush-functionalized engineering.