(Invited) Quantifying Outgassing, Surface Oxygen Depletion and Solid Carbonate Evolution to Understand Interfacial Reactivity in Cathode Active Materials

Abstract

Complex degradation processes at the cathode-electrolyte interface limit the high voltage application of conventional and emerging cathode materials (e.g., Li or Ni-rich LiMO2, M= Li, Ni, Mn, Co, (NMC) layered oxides and Li-excess disordered rocksalt materials). We will present results in which quantitative gas evolution and acid titrations are used to identify key contributions to these high voltage instabilities in Ni-rich and Li-rich NMC materials, including electrolyte degradation evolution and the impact that residual solid carbonate has on parasitic reactions.1-2 This presentation will emphasize the need to accurately quantify these minor side reactions to fully understand their large influence on battery performance. We show that by using a short aqueous rinse on NMC powders prior to their integration into porous electrodes, adventitious carbonates are removed from the material surface, which also undergoes a structural change. Both of these effects dramatically reduce parasitic gas evolution from the materials and, in certain cases, improve the active material’s long term cyclability without compromising its capacity.3-4