The effect of ball miling and temperature treatment on the electrochemical properties of LiMn_2O_4 electrodes

摘要

In this paper we report on the preparation of positive electrodes for rechargeable lithium batteries, based on LiMn_2O_4. Two aspects are stressed. (i) The homogenization of the electrode mass (oxide, carbon, and binder) with a ball mill. For a good electric contact between oxide particles and carbon a milling time of 5 min is enough, as demonstrated by the low polarization of the electrode during cycling. After a longer period of milling, the specific capacity of the oxide decreases due to mechanical degradation of the oxide. (ii) The water content adsorbed at the surface of the electrode mass should be as small as possible. Therefore, a drying step is needed, but it can result in chemical reduction of LiMn_2O_4 by carbon if the temperature is higher than 175 deg C.