Constructing an Organic–Inorganic Hybrid Solid-Electrolyte Interface In Situ via an Organo-Polysulfide Electrolyte Additive for Lithium–Sulfur Batteries

Lithium (Li) metal's extremely high specific energy and low potential make it critical for high-performance batteries. However, uncontrolled dendrite growth and an unstable solid-electrolyte interphase (SEI) during repeated cycling still seriously hinder its practical application in Li metal batteries. Herein, we demonstrate a facile and effective approach to fabricate a flexible and robust hybrid SEI layer using two kinds of organo-polysulfides with different sulfur chain lengths [bis(3-(triethoxysilyl)propyl)disulfide (Si-O-2S) and bis(3-(triethoxysilyl)propyl)tetrasulfide (Si-O-4S)] as the additives in the electrolyte. Compared to Si-O-2S, the siloxane and the long sulfur chain in Si-O-4S are conducive to the production of Li_<i>x</i>SiS_<i>y</i> inorganic components on lithium metal surfaces and the formation of an organic-inorganic hybrid stable SEI layer in conjunction with Li_<i>x</i>SiO_<i>y</i>, thereby improving the stability of the SEI layer and inhibiting the growth of lithium dendrites. Specifically, with 10 wt % Si-O-4S as the additive, an excellent cycling lifespan (1400 h) was achieved with a low hysteresis voltage of ∼17 mV at 1.0 mA cm^-2 in a Li-Li symmetrical cell. Moreover, the lithium-sulfur battery also exhibits long cycling stability (850 mA h g^-1 at 0.5 C after 200 cycles) and good Coulombic efficiency (99.5%). This study provides an electrolyte additive strategy for the Li anode fabricating a stable SEI layer and long cycling batteries.