Self-directed chemical synthesis of lithium-rich layered oxide Li[Li0.2Ni0.2Mn0.6]O2 with tightly interconnected particles as cathode of lithium ion batteries with improved rate capability

A novel method, self-directed chemical method, is proposed to synthesize lithium-rich layered oxide Li[Li0.2Ni0.2Mn0.6]O2 as cathode of lithium ion batteries with improved rate capability. In this method, Li2CO3 powder that has low dissolvability in aqueous solution is introduced as precipitating agent to induce the formation of transition-metal carbonate, resulting in the precursor Ni0.25Mn0.75CO3 with a hierarchical structure: secondary particles assembled with interconnected primary particles. This hierarchical structure remains in subsequent product (Li[Li0.2Ni0.2Mn0.6]O2-T). Electrochemical measurements indicates that Li[Li0.2Ni0.2Mn0.6]O2-T delivers a capacity of 222 mAh g−1 at 1st cycle (0.05 C, 1 C = 263 mAh g−1) and holds 207 mAh g−1 at 50th cycle, which is slightly better than the sample from a traditional co-precipitation method (Li[Li0.2Ni0.2Mn0.6]O2-L). More importantly, Li[Li0.2Ni0.2Mn0.6]O2-T is able to stably offer 156 mAh g−1 at 0.5 C, 136 mAh g−1 at 1 C and 108 mAh g−1 at 2 C, much better than Li[Li0.2Ni0.2Mn0.6]O2-L. The improved performance is attributed to the tightly interconnected structure and smaller particle size, which facilitates the diffusion of Li+ ions in the material bulk and reduces the barrier of charge transfer reaction.