Revealing the Effect of the [CoO]₆ Microstructure in Pseudocapacitance by Controlled Delithium of LiCoO₂.

Abstract

Revealing the in-depth structure-property relationship and designing specific capacity electrodes are particularly important for supercapacitors. Despite many efforts made to tune the composition and electronic structure of cobalt oxide for pseudocapacitance, insight into the [CoO]₆ octahedron from the microstructure is still insufficient. Herein, we present a tunable [CoO]₆ octahedron microstructure in LiCoO₂ by a chemical delithiation process. The c-strained strain of the [CoO]₆ octahedron is induced to form higher valence Co ions, and the (003) crystalline layer spacing increases to allow more rapid participation of OH^- in the redox reaction. Interestingly, the specific capacity of L_0.75CO₂ is nearly four times higher than that of LiCoO₂ at 10 mA g^-1. The enhanced activity originated from the asymmetric strain [CoO]₆ octahedra, resulting in enhanced electronic conductivity and Co-O hybridization for accelerated redox kinetics. This finding provides new insights into the modification strategy for pseudocapacitive transition metal oxides.