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Computational Screening of Cathode Coatings for Solid-State Batteries

  • Author(s): Xiao, Y;
  • Miara, LJ;
  • Wang, Y;
  • Ceder, G
  • et al.
Abstract

Solid-state batteries are on the roadmap for commercialization as the next generation of batteries because of their potential for improved safety, power density, and energy density compared with conventional Li-ion batteries. However, the interfacial reactivity and resulting resistance between the cathode and solid-state electrolyte (SSE) lead to deterioration of cell performance. Although reduction of the cathode/SSE interfacial impedance can be achieved using cathode coatings, optimizing their compositions remains a challenge. In this work, we employ a computational framework to evaluate and screen Li-containing materials as cathode coatings, focusing on their phase stability, electrochemical and chemical stability, and ionic conductivity. From this tiered screening, polyanionic oxide coatings were identified as exhibiting optimal properties, with LiH2PO4, LiTi2(PO4)3, and LiPO3 being particularly appealing candidates. Some lithium borates exhibiting excellent (electro)chemical stability at various interfaces are also highlighted. These results highlight the promise of using optimized polyanionic materials as cathode coatings for solid-state batteries. The flammability of organic liquid electrolytes in Li-ion batteries is a serious safety risk. Solid-state batteries (SSBs) replace the liquid with an inorganic solid, dramatically improving the safety. Unfortunately, solid-solid contacts at the cathode/electrolyte interface are often unstable, leading to high interfacial impedance that grows during operation. Buffering this interface with another layer effectively improves stability; however, optimized buffer materials have not been found by previous research. This work develops and uses a computational framework to screen a wide range of chemistries for use as buffer layers between oxide cathodes and sulfide solid electrolytes and identifies the key factors such as Li content and oxygen bonding covalency that affect the stability of these materials. Many of these materials are polyanionic oxides that substantially outperform conventional oxide buffers. Our work provides guidance for material selection for the next-generation SSBs. Solid-state batteries are considered the next generation of batteries, but they still suffer from high interfacial resistance. One strategy to mitigate the problem is to use coating. We performed a computational screening to find promising cathode coating compositions. Polyanionic oxides are highlighted for good overall characteristics, and LiH2PO4, LiTi2(PO4)3, and LiPO3 are particularly appealing candidates. Furthermore, factors including oxygen bond covalency and Li content are identified to affect oxidation stability of polyanionic oxide coatings.

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