Huang Weiyuan, Hu Jiangtao, Yang Luyi, Zhao Wenguang, Wang Ziqi, Wang Hongbin, Guo Zheng, Li Yiwei, Liu Jiajie, Yang Kai, Pan Feng
School of Advanced Materials , Peking University Shenzhen Graduate School , Shenzhen 518055 , China.
ACS Appl Mater Interfaces. 2019 Jan 9;11(1):957-962. doi: 10.1021/acsami.8b18930. Epub 2018 Dec 18.
The commercial application of LiMn FePO materials has always been a great challenge because of their unsatisfactory structure stability during cycling and the safety issue. Herein, single-particle (SP) electrodes, where aggregated LiMn FePO is dispersed into SPs so they can distribute homogeneously in the carbon-nanotube networks, have been prepared and characterized to probe the degradation mechanism of LiMn FePO for the first time. Compared with a conventionally prepared cathode, the SP LiMn FePO cathode shows prominent capacity-fading with cycle numbers, which can be attributed to the formation of the MnF nanocrystals on the surface of LiMn FePO because of the reaction between F and dissolved Mn at the interface between the electrolyte and LiMn FePO. The different electrochemical behaviors can be ascribed to LiMn FePO SPs surface reconstruction with MnF nucleation and growth by the interfacial reactions. In addition, by applying a thin protecting layer of AlO on the surface of LiMn FePO, the interfacial side reactions can be suppressed. This work demonstrates that the SP method is a powerful tool to extract the information of interfacial reactions, which sometimes appear to be negligible compared with bulk reactions.
由于LiMnFePO材料在循环过程中结构稳定性不尽人意以及存在安全问题，其商业应用一直是一项巨大挑战。在此，制备并表征了单颗粒（SP）电极，即将团聚的LiMnFePO分散成单颗粒，使其能够均匀分布在碳纳米管网络中，从而首次探究LiMnFePO的降解机制。与传统制备的阴极相比，SP LiMnFePO阴极的容量随循环次数显著衰减，这可归因于在电解质与LiMnFePO的界面处，F与溶解的Mn发生反应，在LiMnFePO表面形成了MnF纳米晶体。不同的电化学行为可归因于通过界面反应，LiMnFePO单颗粒表面发生了MnF成核和生长的表面重构。此外，通过在LiMnFePO表面施加一层薄的AlO保护层，可以抑制界面副反应。这项工作表明，SP方法是提取界面反应信息的有力工具，而界面反应有时与本体反应相比似乎微不足道。
