In Situ Electrooxidation of Electrolyte Additive to Improve Capacity Retention in Li-Rich Layered Oxide Cathode, Li2RuO3

Abstract

Conventional positive electrode materials for Li-ion technology utilize a Li+ intercalation mechanism charge-balanced by redox on transition metals within an oxide host lattice. Moving forward, multi-electron cathodes that gain capacity by contribution to the redox from the structural anions are of interest for the hybrid intercalation- and conversion-type chemistry during cycling. One such material, Li2RuO3, first studied by Goodenough and coworkers, exhibits high capacity but also a significant capacity loss after the first charge and long-term capacity fade. We suspect the capacity loss is due to structural distortions induced as the lattice accommodates the removal of Li+. Electrolyte additives with tailored chemistry can be an efficient and cost-effective way to stabilize structural changes and promote reversible cycling. Here, in situ, irreversibleelectrooxidation of soluble electrolyte additives at the cathode-electrolyte interface was investigated as a route to stabilizing the cathode surface. Electrooxidation causes dramatically improved capacity retention and stabilizes high-voltage oxidation processes in Li2RuO3. Through understanding how to stabilize structural distortions in Li-rich layered oxide cathodes, we hope to promote reversible cycling near theoretical capacity and target design principles for active electrolyte additives that enhance battery performance.