Unveiling the inherent functions of the rock-salt phase character and multi-dimensional structural engineering of the NiCoO2 anode for high-power and long-life lithium ion batteries

Abstract

NiCoO₂ (NCO) with a desirable redox activity, high lithium storage capacity and distinct rock-salt structure has gained increasing attention toward application in next-generation lithium ion batteries (LIBs) in comparison with other transition metal oxides (TMOs). However, the volumetric change and pulverization of the NCO electrode during the charge/discharge processes hugely limit its utilization in LIBs. In this study, we present a novel assembling protocol via integrating different structural configurations to address the general limitations of TMO anodes, which effectively improves the rate and cycling performance of the NCO anode. In addition, we provide an insightful understanding of the electrochemical behaviors of NCO through various ex situ characterization techniques and first-principles DFT calculations for the first time. This study reveals that the inherent rock-salt phase character of NCO could not only preserve 3D channels toward efficient ionic/electrical interdiffusion, but also retain high electrochemical reversibility during the long cycling process in comparison to the spinel NiCo₂O₄. Potential application of the NCO anode for LIBs has also been evaluated through assembling full cells. This study demonstrates the synergistic influences of the innate structure of NCO and elaborate composite architecture on the performance, paving the way for future design and manufacture of TMO anodes for practical applications.