Improving high-voltage electrochemical performance of LiCoO2 by Nd2O3 modification

Abstract

High-voltage LiCoO2 (LCO) is currently the most promising cathode material for portable electronic devices, however, its further development is hindered by the accelerated structural decline that results from increasing the cut-off voltage. This article presents a facile solid-phase sintering approach for synthesizing Nd2O3-modified LCO in a one-step process. The crystal parameters of LCO after Nd2O3 modification increase, and a coating layer of Nd2O3 was formed on the surface. Meanwhile, a fraction of Nd3+ ions diffused into the surface layer of LCO to replacing Li + sites, which leads to an increase in lattice parameters. The electrochemically inert Nd3+ can serve as an anchoring pillar within the Li layer, playing a role in enhancing lattice stability. Moreover, the proportion of lattice oxygen in the Nd4000 structure was determined to be 56.82%, which is significantly higher than that of bare LCO (51.81%), leading to an improved structural stability. The Nd2O3 modification also significantly suppressed the side reactions at the electrode-electrolyte interface, thereby reducing the thickness of the CEI film and increasing the Li+ diffusion rate, ultimately resulting in superior electrochemical performance. Notably, the optimized Nd4000 exhibited a capacity retention of 86.19% after 300 cycles at 1.0C and 3.0∼4.5 V, while bare LCO only retained 38.63% of its initial capacity.