Internal Low-Temperature Heating of Lithium-Ion Cells Using Alternating Current: Thermal Performance and Aging Behavior

Lithium-ion batteries commonly used today may only be charged at temperatures above 0 °C. However, the heating elements currently used to warm the battery packs make the battery heavier and more complicated in design. In addition, heat is transferred from outside into the cell, causing the temperature inside the cell to rise slowly. The aim is to heat the cells without additional components by applying alternating current and without significantly accelerating aging. To this end, a series of measurements were carried out at temperatures between 0 °C and -20 °C and at frequencies between 50 Hz and 10 mHz. A square wave signal and an amplitude of 5 A were kept constant in all measurement series. The cells were heated for 30 minutes and then cooled for 60 minutes. After every 50 heating cycles, the state of health (SOH) of the cells was determined, and a total of 400 heating cycles were carried out. Aging due to heating is independent of temperature and frequency, with the SOH ending at 99 %. The heating depends on temperature and frequency, amounting to up to 14 K for individual cells. The lower the temperature of the cells and the lower the frequency of the alternating current, the higher the heating of the cells. This type of heating is particularly suitable for simpler battery-electric applications without thermal management, such as e-bikes or power tools. However, it can also be interesting for applications with thermal management, as it simplifies the design of the battery packs.