Experimental investigation of the impact of high-frequency alternating current on heating a Li-ion cell at subzero temperatures and its effect on lifetime

Abstract

At low temperatures, lithium-ion cells exhibit poor performance, and especially during subzero temperature charging, specific ageing processes such as lithium plating can occur, leading to safety issues. An effective approach to heat up cells is to generate alternating current to produce power losses inside the cells. While many studies focus on the heating aspect, they often do not consider the ageing effects. Conversely, some research investigates the influence of current ripples on the cells’ lifetime. This study seeks to integrate the effects of current ripples and the heating process in relation to the ageing of the cell.

The research findings indicate that current ripples with a peak-to-peak value of approximately 40 A for a 3.5 Ah 18650 cell, as well as a cell voltage close to 0 V alternating with double the cell voltage at a high frequency of 250 kHz, have little to no effect on ageing at room temperature. However, when the cell was subjected to heating, specifically after 1800 heating cycles from −9 °C to 10 °C and an overall heating time exceeding 52 h with an average heat rate of nearly 11 K/Min, a capacity fade of approximately 7% linked to the heating was observed. This capacity fade is presumed to be due to mechanical stress resulting from rapid thermal changes in the cell.