Electrolyte Oxidation and the Role of Acidic Fluorophosphates in Capacity Loss for Lithium Ion Batteries

Abstract

Cycling lithiated metal oxides to high potential (>4.5 V vs Li) is of significant interest for the next generation of lithium ion batteries. Cathodes cycled to high potential suffer from rapid capacity fade due to a combination of thickening of the anode solid electrolyte interphase (SEI) and impedance growth on the cathode. While transition metal catalyzed degradation of the anode SEI has been widely proposed as a primary source of capacity loss, we propose a related acid induced degradation of the anode SEI. A systematic investigation of LiMn2O4, LiNi0.5Mn1.5O4, LiNi0.6Mn0.2Co0.2O2, and LiNi0.8Mn0.1Co0.1O2 cathodes will be presented. The role of potential on the generation of soluble acidic fluorophosphates crossover species and the impact of these species on the structure and stability of the SEI will be presented.