Capacity Fade of 20Ah Power Lithium-ion Batteries Cycled at High Discharge Rates

Capacity fade of 20 Ah power Li-ion batteries cycled by using different discharge rates was studied at ambient temperature.The capacity losses were estimated after 200 cycles at 2C and 3C discharges rates and were found to be 25.28 % and 34.85 % of the initial capacity,respectively.At 1 C discharge rate the capacity lost was only 20.28 %.The cell cycled at high discharge rate(3C) showed that the largest internal resistance increased of 32.9 % relatively to the resistance of the fresh cells.Half-cell study indicated carbon loss after cycles dominated the capacity fade of the whole cell at high discharge rates,the main reason of capacity fading at high discharge rates was the thickness increase of anode SEI film,which induced resistance enhancement of Li+ deintercalation on the surface of anode by EIS testing.