A Novel Equivalent Circuit Model for Lithium-ion Battery with Complex Electrical Element Parameters

An equivalent circuit model for lithium-ion battery including capacitor and inductor with complex parameters is proposed. The imaginary part of the complex-valued capacitor expresses diffusion processes instead of constant phase element, which leads to a higher computational efficiency by removing the exponential variant calculation. The inductor with the complex parameter, the imaginary part accounting for the frequency-dependent magnetic hysteresis loss of battery current collectors and cables, can accurately regenerate the impedance characteristics at high frequencies with various linear slope angles to the real axis in a Nyquist plot. The fitted electrochemical impedance spectrum of a lithium iron phosphate/graphite battery with this proposed model is compared to the measured data. The maximum relative error of the impedance magnitude is 4.94% at the frequencies between 0.01 Hz and 10 kHz. The electrical component parameters of the proposed equivalent circuit model are calculated and analyzed.