Alloy anode materials, such as Si, Sn, have attracted much attention due to their much higher theoretical capacities than that of the commercially used graphite electrodes. However, their commercial applications are limited because of the short cycle life due to the large volume changes and non-healable fracture during electrochemical cycling. In this work, we prepared metal Ga thin film electrodes on stainless steel substrate (diameter 1.4 cm, mass load 1.5～2 mg/cm2) to study the self-healing behavior of Ga anodes. After 25 cycles, the cells were disassembled in Ar-filled glove box and the metal Ga thin film electrodes were washed by dimethyl carbonate (DMC) to remove residual LiPF6 and then dried in the vacuum chamber for more than 2 hours before SEM analysis. Based on SEM observation and crack size statistical distribution, we found that the characteristic size of the self-healing area reduced to 34 μm after 25 cycles and gradually reduced with the increasing cycles using low-melting point metal Ga film electrodes at a temperature above the melting point of Ga. Energy dispersive spectrometer (EDS) analysis showed that there was a large amount of F, O and C at the surface of metal Ga thin film electrodes, which are considered as main components of the solid electrolyte interface (SEI) layer. The formation of the SEI layer degrades the self-healing capability of Ga metal thin films because the layer may attach on the crack surfaces after full delithiation, hindering self-healing of the Ga films. Metal Ga powder electrodes (mass load 4.3 mg/cm2) were prepared by simple liquid dispersion method. The size of the Ga metal powder was 3.43 μm, which is smaller than that of effective self-healing area. Electrochemical performance showed improved durability of the metal Ga powder electrodes compared to the metal Ga thin film electrodes. After 25 cycles, the average crack size of the metal Ga powder electrodes was 1 μm based on SEM images. This shows that the self-healing ability of metal Ga in liquid electrolyte is limited. Metal Ga is expected to be used as crack healing agent in non-liquid electrolyte systems, such as the solid-state batteries.
罗飞, 郑杰允, 褚赓, 刘柏男, 张素林, 李泓, 陈立泉. 高容量金属镓薄膜和粉体作为锂离子电池负极材料的自修复行为研究[J]. 化学学报, 2015, 73(8): 808-814.
Luo Fei, Zheng Jieyun, Chu Geng, Liu Bonan, Zhang Sulin, Li Hong, Chen Liquan. Self-healing Behavior of High Capacity Metal Gallium Thin Film and Powder as Anode Material for Li-ion Battery. Acta Chim. Sinica, 2015, 73(8): 808-814.