Understanding Boron Chemistry as the Surface Modification and Electrolyte Additive for Co‐Free Lithium‐Rich Layered Oxide

Abstract

Lithium‐rich layered oxide (LRLO) stands out as a highly promising cathode material for the next generation of Li‐ion batteries, owing to its exceptional lithium storage capacity. The absence of cobalt in LRLO's composition provides an additional advantage, enabling cost‐effective production and thereby improving the feasibility of large‐scale manufacturing. Despite these promising attributes, LRLO has encountered challenges related to poor cycling performance and severe voltage decay, impeding its practical application. In addressing these challenges, a surface modification technique involving lithium borate (LBO) is employed through a dry coating method. The LBO‐coated LRLO exhibits a uniform surface layer with a thickness of 15 nm. Furthermore, the performance of LBO‐coated LRLO in a full cell is synergistically enhanced when combined with lithium bis(oxalato)borate (LiBOB) as an electrolyte additive. A discharge capacity retention of 82% is achieved after 400 cycles at room temperature. These substantial improvements are attributed to the continual reaction between boron species on the LRLO cathode surface and PF6− anions in the electrolyte. This reaction generates BF4− and suppresses HF acid formation during the high voltage charging process, demonstrating LRLO's potential for practical implementation.