Rational Design of a Gel–Polymer–Inorganic Separator with Uniform Lithium-Ion Deposition for Highly Stable Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries have received intense interest as next-generation electrochemical energy storage systems because of their high specific energy and natural abundance potential. However, its practical reality is seriously limited by the safety concerns from heterogeneous lithium deposition and the so-called “shuttle effect”. Herein, this work reports a novel gel–polymer–inorganic separator specifically for the lithium–sulfur battery, which could enable homogeneous lithium deposition and inhibit the diffusion of polysulfides, simultaneously. The composite separator exhibits a superior electrochemical performance up to 500 cycles at 0.5 C with a capacity retention of 718.2 mA h g–1. It is worth noting that the corresponding fade rate for 1000 cycles was 0.04%/cycle even tested at 2 C. This outstanding cycling stability can be attributed to the strong anchoring effect of polar carboxymethylcellulose sodium to polysulfides, which is confirmed by the permeation experiments and X-ray photoelectron spectroscopy analyses. Besides, the Al2O3 coating layer on the anode side could achieve relatively uniform lithium deposition and inhibit the growth of dendrite to some extent. As a result, this study may provide a novel strategy for the effective design of separators toward the practical reality of the high-performance lithium–sulfur battery.