Capacity fade of Sony 18650 cells cycled at elevated temperatures: Part II. Capacity fade analysis

A complete capacity fade analysis was carried out for Sony 18650 cells cycled at elevated temperatures. The major causes of capacity loss were identified and a complete capacity fade balance was carried out to account for the total capacity loss of Li-ion battery as a function of cycle number and temperature. The three most significant parameters that cause capacity loss were loss of secondary active material (LiCoO2/carbon) and primary active material (Li+) and the rate capability losses. Intrinsic capacity measurements for both positive and negative electrode has been used to estimate the capacity loss due to secondary active material and a charge balance gives the capacity lost due to primary active material (Li+). Capacity fade has been quantified with secondary active material loss dominating the other losses.