Analysis on pulse charging–discharging strategies for improving capacity retention rates of lithium-ion batteries

Abstract

The capacity fade of lithium-ion batteries (LIBs) are intimately dependent upon charging–discharging strategies. In this work, a pseudo-two-dimensional model coupled with thermal effects was developed to investigate the effects of pulse current charging–discharging strategies on the capacity fade for LIBs, in which the growth of solid electrolyte interphase (SEI) and the lithium ion migration process are highlighted. LiFePO4/graphite (LFP) batteries were taken as samples. The capacity fading processes of the LFP batteries under different pulse current charging–discharging strategies were studied by numerical simulations. The impacts of the growth of the SEI layer at the negative electrode on the capacity degradation were studied by using eleven charging–discharging cases. The results show that, compared with the constant current-constant voltage (CC-CV) strategy, the pulse current-constant voltage (PC-CV) strategies can effectively alleviate the capacity fade of the LFP batteries due to the relaxation process in the pulse charging process. Under the PC-CV strategies, the relaxation duration and the peak current were altered. The relaxation process renders the decrease of the current density of side reactions in the batteries, which is conducive to the recovery of the aged batteries, thus improving the capacity retention rates of the batteries. The advantages of the PC-CV strategies were demonstrated in this work. The results will provide theoretical guidance for the rapid charging–discharging strategies of LIBs.