Electrodes for Li-ion batteries: From high-voltage LiCoO₂ to Co-reduced /Co-free layered oxides with potential anodes

Li-ion batteries (LIBs) are one type of more and more widely used devices for energy storage and power supply in which cathode materials are playing a relatively more decisive role at current stage. In this review, we start with pioneeringly commercialized LiCoO₂ (LCO) with a layered rhombohedral structure (space group $R\overline{3}m$) to discuss novel sequentially emerging LCO-derived layered oxides from the perspectives of both cobalt content reduction and performance improvement. Emphasis is placed on the improvement of high-voltage performance of LCO and Co-reduced/free layered oxides, including Co-reduced high-nickel layered oxides, Co-free Li-rich layered oxides, and Ni-based layered oxides cathodes, and their underlying mechanisms via different strategies. Also, possibly matched carbon and silicon-based anode materials are briefly discussed. The common issues and prospects of the layered oxides cathodes and their potential anodes are summarized and commented on. This review can help understand the emergence logics of novel layered oxides with gradually vanishing cobalt involved, provide insights about the underlying mechanisms of performance enhancement pertaining to particular strategies, and even inspire the discovery of novel cathode materials with high performance and low cost.