Storage characteristics of lithium ion cells

Abstract

This report provides the results of simple preliminary tests on the storage characteristics of lithium ion cells in relation to their use for uninterrupted power supplies (UPS). Cylindrical 18650 size cells were used in the experiments. Cells were stored for 1 to 6 months and then their capacity was measured after constant voltage charging at 4.1 or 4.2 V and 21 or 60 °C. After measuring the capacity, the cells were crashed with a round bar as a fundamental abuse test. The residual cell capacity after 10 years of 4.2 V constant charging at 20 °C was predicted to be approximately 67 %. This exceeds our tentative target of 50 %.