Thin aluminum film improving the cycle performance of positive electrode of lithium ion battery

A novel method was investigated to improve the cycle performance of the spinel LiMn2O4. It is widely different from the traditional way of modifying LiMn2O4 particle with compounds or metals. In our study, instead of coating LiMn2O4 particle itself with compounds or metals, first we covered the current collector with the mixture of LiMn2O4 particle, conductive agents and binders, and then deposited an aluminum film onto it by vacuum evaporation technique. Both of the pristine electrode and the modified one were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and charge-discharge tests. The results of SEM and XRD demonstrate that the aluminum film was formed successfully onto the positive electrode. And the charge-discharge tests show that the capacity retention of pristine electrode and modified one are 63.7% and 93.5% at C/2 rate in the voltage range of 3.5-4.3 V after 200 cycles, respectively. The modified electrode also shows better rate capability in comparison with the pristine one. The improved cycling stability is attributed to the minimizing of Mn dissolution into electrolyte solution and the good electronic conductivity of deposited aluminum film.