Stalling oxygen evolution in high-voltage cathodes by lanthurization

Abstract

Coatings and surface passivation are sought to protect high-energy-density cathodes in lithium-ion batteries, which suffer from labile oxygen loss and fast degradations. Here we develop the theory underlying the high-voltage-induced oxygen evolution crisis and report a lanthurizing process to regulate the near-surface structure of energy materials beyond conventional surface doping. Using LiCoO2 as an example and generalizing to Co-lean/free high-energy-density layered cathodes, we demonstrate effective surface passivation, suppressed surface degradation and improved electrochemical performance. High-voltage cycling stability has been greatly enhanced, up to 4.8 V versus Li+/Li, including in practical pouch-type full cells. The superior performance is rooted in the engineered surface architecture and the reliability of the synthesis method. The designed surface phase stalls oxygen evolution reaction at high voltages. It illustrates processing opportunities for surface engineering and coating by high-oxygen-activity passivation, selective chemical alloying and strain engineering using wet chemistry.