Effects of Environmental Humidity on Self-Discharging Behaviour and Electrochemical Performance of Lithium-Ion Batteries

Abstract

The application of lithium ion batteries (LIBs) have been widen from IT devices to electric vehicles (EVs). To be precise, EVs adopting LIBs are being increased because LIBs guarantee high energy density and cycle life. LIBs are also sensitive to external environmental factors such as temperature, humidity, vibration, etc. In order words, these conditions should be controlled for better battery performance and reliability. Most of the studies on LIBs have been focused on temperature as the key environmental factor, however, other variables such as humidity should be also considered carefully for EV application. Hence, this work focuses on the effect of humidity on self-discharging and battery degradation behaviour. Herein, we try to unveil the effect of relative humidity on self-discharging behaviour of fully charged LIBs by monitoring open-circuit voltages (OCVs), capacity and power retention, and electrochemical impedance before and after storage. Pouch-type LIBs having LiNi1/3Co1/3Mn1/3O2/graphite chemistry are fabricated, and then stored at room temperature under high humidity condition (>90%). As a result, the OCV drop is much higher at high humidity condition, which causes more degradation of capacity and power than expected. This abnormal result will be discussed in more detail via various case studies and analysis.