Moisture-uptake by the positive active material from the casting solvent and the ambient environment

Abstract

It is widely recognized that the presence of residual moisture has significant detrimental effects on the performance of lithium ion batteries. Studies have shown that the positive active material can be a major source of moisture contributors to the overall cell moisture. The aim of the present study is to understand the factors affecting moisture uptake by the doped-lithium nickel cobalt oxide material from the casting solvent, acetone, and the ambient environment. As-is and the air-dried powders under various conditions (300 °C for 24 h, 500 °C for 8 h, and 500 °C for 24 h) were exposed to ambient and humid air for various lengths of time. Similarly, all these powders were exposed to extra dry (47 ppm) and wet (5789 ppm) acetone. Karl Fisher measurements at 160 °C and 290 °C show that humidity levels (80–85% relative humidity versus 20–25%) and the exposure times are the critical factors. Acetone wetness and the length of exposure in it do not contribute significantly to the moisture uptake by the active material. Cathode powder drying helps in minimizing the amount of moisture uptake from the environment.