Electro-Thermal Behavior of Four Fast Charging Protocols for a Lithium-Ion Cell at Different Temperatures

Electric vehicles applications calls for improved fast-charging protocols reducing charging time and meeting safety constraints. This paper contributes by comparing four fast charging protocols (constant current, multistep, pulse and voltage trajectory charging) at 3 different temperatures (5, 25 and 45°C) on a lithium-ion cell. Results shows that pulse charging displays similar charging time compared to constant current protocol of same mean value, but leads to higher heat generation at all temperatures. The multistep protocol, with different current levels corresponding to different voltage limits, allows for a finer charge control and provides a good capacity utilization despite a slight increase in charging time. The defined voltage trajectory protocol results in the longest charging time, but minimize cell temperature rise by reducing current at low temperatures. Advantages and disadvantages of charging protocols are discussed to give additional insights into protocol selection for practical fast-charging applications.