Cycle-life Energy Analysis of LiFePO_4 Batteries for Energy Storage

The correlation between the accumulative transfer(AT) energy of LiFePO4 battery and battery aging degreewas investigated by controlling the depth of discharge(DOD) in the range from 40% DOD to 100% DOD and 1C rate charge/discharge cycle experiments.By analyzing results of long-term cycle experiments,the AT energy and cycle number accorded with Box Lucas model,meanwhile,the influence of battery aging on the ability of LiFePO4 battery to transfer energy was gradually reduced with the increase of DOD.By calculating instant capacity fading rates of all samples,the state of LiFePO4 battery was divided into two stages:the battery inclined to a self-stabilization state in the former stage and then experienced an accelerated aging state in the latter stage.The influence of lighter charge/discharge usage mode on the ability of LiFePO4 battery to transfer energy was identical to deeper charge/discharge usage mode before battery capacity decayed to 85%,however,when the capacity decayed to 75%,the latter usage mode was superior to the former usage mode in AT energy and energy output/input efficiency.