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 LixSiSy inorganic components on lithium metal surfaces and the formation of an organic–inorganic hybrid stable SEI layer in conjunction with LixSiOy, 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.