The effect of pulse charging on commercial lithium nickel cobalt oxide (NMC) cathode lithium-ion batteries

Fast charging is essential for high energy applications such as electric vehicles. Many methods have been proposed for faster charging and increased energy efficiencies. Pulse charging is considered as one of the promising methods for faster and efficient charging. Researchers have proposed pulse charging methods using different pulse frequencies and duty cycles for better performance. However, the effect of pulse charging frequencies on charging time and cycle life is seldom investigated. In this study, rectangular pulse-CV charging experiments on lithium nickel manganese cobalt oxide (NMC) cathode commercial lithium-ion batteries were performed at 50 Hz, 100 Hz, and 1 kHz and compared with benchmark constant current - constant voltage (CC-CV) charging. From the results, it was determined that pulse-CV charging is significantly faster than CC-CV charging. It was also observed that pulse-CV charging at 1 kHz showed comparable discharge capacities to CC-CV charging throughout cycling with an approximate reduction of 17% in charging time. Battery impedance characteristics were examined using electrochemical impedance spectroscopy (EIS) measurements, and equivalent circuit parameters (ECPs) were obtained for analyzing the behavior of the batteries.