Comparative Analysis on the Electrical State-of-Health Degradation of 21700 LiNiCoAlO2 based on Alternating and Direct Currents

The rapid increase in energy consumption has generated considerable interest in energy storage systems (ESSs) for stable power supply. Lithium-ion batteries with high energy density, high power density, and long life cycles are widely used in ESSs. In addition, to improve energy use efficiency through battery charging and discharging, a grid-connected power conversion system (PCS) is applied. In particular, power factor correction (PFC) based on gallium-nitride (GaN) totem-pole PFC has been widely applied to increase efficiency. However, in ESS and grid-connected PCS structures, a pulsating component with a frequency twice the grid frequency affects the battery. Therefore, an experimental-based analysis of the effect of AC ripple on the aging of lithium-ion batteries is presented hear. A total of 200 cycles of calendar experiments were performed, and 21700 cylindrical lithium-ion battery was used. A DC-only and DC + AC (120 Hz) current profile was applied. Based on the experimental results, direct current internal resistance (DCIR), incremental capacity (IC), and surface temperature were analyzed. The results indicated that the AC ripple does not directly contribute to aging and can improve the battery life after a certain number of cycles. These results can help improve filter design in battery-based PCSs in applications experiencing AC ripples.