On the role of water contamination in rechargeable Li batteries

Many cathode materials such as LiMnO₂ can be highly hygroscopic and thus, introduce considerable water contamination into Li batteries. Water reacts with the Li anode, and this strongly affects its surface chemistry. In this work, we investigated some phenomena related to water contamination due to the cathode material in Li-Li_xMnO₂ cells containing 1-3 dioxolane/LiAsF₆ solutions. When these cells contain cathodes which were exposed to air, their electrolyte solutions become contaminated with water, which reacts with lithium and thus, hydrogen gas is formed. We discovered that discharging cells containing wet cathodes stops this liberation of hydrogen. We explored several possible explanations for this phenomenon. It was concluded that lithiation of water-containing Li_xMnO₂ considerably inhibits the liberation of water into the electrolyte solution. The effect of the presence of water in solutions on the properties of the Li anode is discussed.