Collective Surface Enabling an Ultralong Life of LiCoO<sub>2</sub> at High Voltage and Elevated Temperature
Wen Zhang, Fangyuan Cheng, Meng Wang, Jia Xu, Yuyu Li, Shixiong Sun, Yue Xu, Liang Wang, Leimin Xu, Qing Li, Chun Fang, Yuhao Lu, Jiantao Han
Abstract
Abstract Rapidly increasing demand for energy density in consumer electronics is eager for developing high‐voltage LiCoO 2 (LCO). However, some great challenges such as severe phase transition and surface instability negate the cycle life of LCO operated at high‐voltages (≥4.6 V). Herein, a chemical reconstruction strategy is proposed to form a collective surface of LCO through an interdiffusion reaction of MgHPO 4 ·3H 2 O (MP) so as to extend the cycle life of high‐voltage LCO. The collective surface renders a three‐layer configuration that demonstrates an amorphous Li 3 PO 4 outmost layer, a spinel‐like layer beneath, and a Mg diffusion layer within LCO bulk. MP with relatively low hardness enables the uniform precoating via mechanical mixing, followed by a sintering process to undergo an interdiffusion reaction. Li 3 PO 4 is an intrinsic electrochemical stabilizer against interfacial side reactions. The spinel‐like compounds build a high‐voltage‐stable surface against irreversible O 2 release. In addition, Mg diffuses into the bulk lattice to suppress irreversible phase transition during the deep delithiation of LCO. Therefore, such modified LCO with a collective surface exhibits ultralong life with capacity retention of 82% after 1000 cycles at 1 C within 3.0–4.6 V and stable operating at 4.7 V or elevated temperature (45 °C).