A Novel Filler for Gel Polymer Electrolyte with a High Lithium-Ion Transference Number toward Stable Cycling for Lithium-Metal Anodes in Lithium–Sulfur Batteries

Although the lithium metal is considered as the most promising anode for high energy density batteries, uncontrolled lithium dendrite growth and continuous side reactions with electrolyte hinder its practical applications for rechargeable batteries. Herein, we prepared a gel polymer electrolyte by synthesizing a novel 250 nm filler (KMgF3), which is greatly beneficial to the formation of a uniformly deposited lithium-metal anode. This is due to the regulation effect of KMgF3 that double the lithium-ion transference number up to 0.63 and adjust the solid electrolyte interphase layer full of dense LiF and flexible polycarbonates, which greatly reduces the side reactions on the lithium-metal surface and inhibits the growth of lithium dendrites. Consequently, the composite gel polymer electrolyte guarantees a stable long cycle performance of more than 1400 h with 1 mA h cm–2 for symmetric cells. Moreover, the composite gel polymer electrolyte demonstrates high compatibility and great promise for rechargeable lithium–sulfur (Li–S) batteries.