A Ternary (P, Se, S) Covalent Inorganic Framework as a Shuttle Effect-Free Cathode for Li-S Batteries.

Abstract

Developing new cathode materials to avoid shuttle effect of Li-S batteries at source is crucial for practical high-energy applications, which, however, remains a great challenge. Herein, a new class of sulfur-containing ternary covalent inorganic framework (CIF), P₄ Se₆ S₄₀ , is explored, by simply comelting powders of P, S, and Se. The P₄ Se₆ S₄₀ CIF with open framework enables all active sites available during electrochemical reactions, giving a high capacity delivery. Moreover, introducing Se atoms can improve intrinsic electronic conductivity of S chains yet without remarkably compromising the capacity because Se is also electrochemical active to lithium storage. More importantly, Se atoms in S-Se chains can serve as a heteroatom barrier to block the bonding of S atoms around, effectively avoiding the formation of long-chain polysulfides during cycling. Besides, stable Li₃ PS₄ with a tetrahedral configuration formed after lithiation works as not only a good ionic conductor to promote Li ion diffusion, but a three-dimensional spatial barrier and chemical anchor to suppress the dissolution and diffusion of lithium polysulfides (LiPS), further inhibiting the shuttle effect. Consequently, the P₄ Se₆ S₄₀ cathode delivers high capacity and excellent capacity retention with even a high loading of 10.5 mg cm^-2 which far surpasses the requirement for commercial applications.