Preventing Degradation of NMC811 with Bimetallic Oxide Coatings

Abstract

High nickel-content cathodes such as NMC811 (LiNi0.8Mn0.1Co0.1O2) offer high practical capacities but undergo rapid degradation during cycling due to multiple mechanisms, such as surface phase transformations, reactive oxygen release and transition metal dissolution. Coatings using metal oxides have been proposed to provide surface protection against these processes. In this work we have used bespoke bimetallic alkoxide precursors to deliver unique bimetallic oxide coatings onto NMC811 secondary particles. Bimetallic combinations of lithium and zirconium or magnesium and zirconium showed enhanced electrochemical performance compared to uncoated NMC811 and only zirconium-based coatings, particularly at high charging voltages (4.6 V). Examining the cathodes post-cycling with XPS revealed a significant difference in the cathode electrolyte interface (CEI) of the different coated cathodes, suggesting different surface chemical reactions occur with different coating materials. These bimetallic coatings could offer a route to accessing further capacity available only at higher potentials. Figure 1