Regulating interfacial chemistry of layered lithium-rich oxide by weakly solvating electrolyte

Abstract

Layered lithium-rich oxide (LLRO) cathodes for lithium-ion batteries exhibit outstanding specific capacity but suffer from irreversible oxygen release, which leads to continuous voltage decay. The interfacial chemistry between electrolyte and cathode material is crucial for improving the stability of LLRO. Commercial carbonate electrolytes (CCE) tend to form an organic-rich interphase, which is susceptible to dissolution during cycling. On the contrary, an inorganic-rich interphase is robust and electrochemically stable. To achieve this goal, lithium difluoro-oxalate borate (LiDFOB) and tris(2,2,2-trifluoroethyl) phosphate (TFEP) are used to formulate a weakly solvating electrolyte (WSE). In this design, DFOB^- anion participates in the primary solvation sheath (PSS), forming an anion-dominated structure that facilitates the formation of an inorganic-rich, LiF-based cathode electrolyte interphase (CEI). Electrochemical performance indicates that voltage decay is significantly suppressed in WSE, with an average voltage drop of only 0.45 mV/cycle, compared to 2.51 mV/cycle in CCE. The anion-derived interphase slows the failure process of LLRO, providing valuable insights into electrolyte design for enhancing material stability.