Charging Optimization Strategy Of Lithium-ion Batteries Based On Impedance Characteristics

The demand for Lithium-ion batteries has of late been rapidly increasing in diverse fields of applications such as portable electronics,electric vehicles,power tools,renewable energy support,and many others.These applications require very efficient charging strategies to maintain a longer life cycle of the Li-ion batteries.A new recently proposed charging strategy referred to as the Sinusoidal Ripple Current（SRC）charging technique claimed in certain publications to achieve improved charging performance on Li-ion batteries than the traditional Constant-Current Constant-Voltage charging（CC-CV）strategies.The charging performance of the SRC charging method applied to a cylindrical18650 Lithium-ion battery is investigated in this thesis.Electrochemical impedance spectrums of the battery have been obtained using electrochemical impedance spectroscopy（EIS）.The minimum impedance Z_min and the corresponding frequency fopt of the lithium-ion battery was obtained from the spectrums,which is consistent with the theoretical value calculated in the electrochemical impedance model.The charging circuit of the lithium-ion battery based on d SPACE Micro Lab Box and LM338K is constructed to realize the sinusoidal current charging at the optimum frequency.It can measure the charging time,the charging current,the battery voltage,and temperature,and achieve different frequencies of sinusoidal current charging,pulse current charging,and the typical CC-CV charge.The experimental results show that the charging time and charging efficiency are improved by 6.93%and 1.66%,respectively,and the maximum temperature rise is reduced by 38.23%compared with CC-CV charging strategy.