(665a) Analysis of Cathode-Electrolyte Interfaces in Lithium-Ion Batteries

Lithium-ion batteries (LIBs) have been widely used in portable electronics and electric vehicles. The future development and improvement of LIBs require a better understanding of electrochemical activities at battery electrode/electrolyte interfaces. The formation of interfacial layers on the anodes has been extensively studied, however, the formation of cathode-electrolyte interfaces (CEI) layers may also accelerate LIB degradation. Therefore, the characterization of CEI is critical for understanding the interfacial processes, including transition metal dissolution, oxygen release, and electrolyte oxidation. In this presentation, we will focus on characterizing oxidative processes occurring at Pt, glassy carbon, and model LIB cathode materials by scanning electrochemical microscopy. Electrochemical measurement analysis indicates multiple anodic reaction processes occurring at Pt and glassy carbon at high voltage due to the electrolyte oxidation. The electrolyte oxidation processes generate reducible products from metal oxide cathodes that are detected at different voltage ranges, which can be associated with the metal dissolution of the electrochemically active materials from cathodes. We propose a preliminary model mechanism that connects transition metal dissolution with catalytic electrolyte oxidation and potential interfacial film formation. Our observation offers insights into the CEI formation and evolution mechanism, providing information on LIB interfacial processes associated with cathode degradation.