Degradation Behavior of Lithium-Ion Capacitors during Calendar Aging

Lithium-Ion Capacitors (LICs) are a new technology of hybrid supercapacitors that aims to deliver relatively high energy and high power. Therefore, they arc known for their constitution inspired from lithium-ion batteries and conventional supercapacitors. Due to their hybrid structure, they have a unique behavior during aging. This paper concerns the effects of high temperatures (60 degrees C and 70 degrees C) and two states of charge (fully charged and fully discharged) on the acceleration of aging of LICs. Fully charged and fully discharged cells were mounted at high temperatures and the evolution of their properties was monitored during 12 months. Electrochemical impedance spectroscopy was the tool for regularly measuring their capacity. Results showed that fully discharged LICs encounter huge deterioration of performance. For example, at 60 degrees C, a capacity decrease of 45 % was found. On another hand, fully charged cells lost around 12 % of their initial capacity Therefore, the state of charge that should be avoided when leaving LICs at rest is introduced for the first time in a paper. Moreover, based on the comparison of capacity decrease of fully discharged cells at different temperatures, the parameters of Arrhenius equation were analyzed. A physicochemical interpretation of the results was made according to the established results.