Novel Inorganic Coatings for Li2s Cathodes

Abstract

While Li2S cathodes are extremely attractive due to their high theoretical capacity (1166 mAh/g), low cost, and compatibility with non-lithium metal anodes, the lithiation/delithiation reaction pathway between Li2S and S includes the formation of soluble polysulfides, which leads to poor cycle life. One strategy to improve cycle life is to coat Li2S particles with a protective layer, preventing polysulfide dissolution. Leveraging a proprietary high-throughput synthesis workflow, Wildcat Discovery Technologies has demonstrated the reactive deposition of an inorganic coating onto Li2S particles. The coating method, based on the reaction of precursors with Li2S, is shown to be a general method and used to deposit coatings with different compositions on the surface of Li2S. Galvanostatic cycling of coated cathodes shows reduced formation of soluble polysulfides which in turn increases cycle life with 95% capacity retention between cycles 1-3 and also improves long term cycle life. This coating also improves conductivity thus improving cycle 1 discharge capacity. The approach described in this presentation is unique in: 1) it focuses on the charged state of the cathode versus the uncharged state (Li2S vs S) which would enable cell chemistries that do not rely on a Li metal anode, 2) it is a novel type of coating for the active material which is compatible with any base Li2S, and 3) demonstrates the power of high-throughput screening in developing new chemistries for next generation batteries.