Asymmetric gel polymer electrolyte with high lithium ion conductivity for dendrite-free lithium metal batteries

Lithium metal has been intensively investigated as a promising anode for next generation rechargeable Li metal batteries (LMBs). However, the safety concern on Li anodes caused by uncontrolled Li dendrite growth in liquid electrolytes hinders their application. Herein, a novel poly(vinylidene fluoride- co -hexafluoropropylene) (PVDF-HFP) based gel polymer electrolyte (GPE) with an asymmetric structure has been designed and developed to effectively retard the growth of lithium dendrites. Atomistic simulations confirm the strong interactions between PF 6 − and dipoles in the polymer matrix, which can anchor PF 6 − in the GPE and slow down its mobility to prevent space charge formation. In addition, this unique asymmetric membrane with a channel upper layer greatly enhances the mobility of Li + in the GPE due to its low tortuosity and high porosity. The synergistic effect of the ion-dipole interaction and asymmetric structure increases the Li + transference number to 0.66 and ionic conductivity to 3.36 mS cm −1 (20 °C). Using this superior asymmetric GPE, Li|Li symmetric cells show more stable cycle performance than those using a liquid electrolyte. Li|LiFePO 4 batteries with the asymmetric GPE also deliver an impressive electrochemical performance, i.e. , coulombic efficiency of 99.5% at 2C after 600 cycles. In consequence, this novel asymmetric GPE possesses potential application in high energy LMBs. An asymmetric gel polymer electrolyte is designed for regulating ions and suppressing Li dendrite growth in high-performance Li metal batteries.