Study On 50 Ah Aluminum LiFePO₄ Battery

In this paper,four different LiFePO4(LFP) purchased from different companiesand the corresponding as-prepared electrodes were characterized by X-ray diffractometer(XRD) and scanning electron microscopy(SEM). Afterwards, four kinds of LFP/Li half-cells were assembled and the performance of LFP cathode plates was investigated. On this basis,aluminum-shell LFP/C full battery with 50 Ah was successfully prepared. Charge and discharge performance, high temperature and low temperature properties of LiFePO4 materials were studied.The grainsize of all the four different LiFePO4 materials is up to the using standard of lithium-ion battery. The grain size of the four materials is from 47.24 to 52.61 nm. The smallest particle size of LFP-1 was less than 0.5 ?m, the particle size of LFP-2 and LFP-4 was 1 ?m,the particle size of LFP-3 was distributed from 0.5 to 1?m.The ohmic resistance of LFP/Li half-cells assembled by the four different materials is also the same, the electrochemical resistance of LFP-1 is the largest one, the electrochemical resistance of LFP-2 and LFP-3 is approximately equaland the smallest, and that of LFP-4 is more than 100 ?. The capacity retention after 45 cycles of four different half-cellsis still above 95%. The performance of LFP-1 material is the best.Aluminum-shell LFP/C full battery with 50 Ah was prepared by the four different materials and assembled. The capacity retention after 380 cycles of LFP-1 is the best in the four materials. The performance of LFP-2 is less than that of LFP-1. The capacity retention after 840 cycles of LFP-2 is up to 90.20%, which shows a good long-circulating properties.Moreover, the capacity retention after 380 cycles of LFP-3 and LFP-4 is 83.49% and 85.24%, respectively. However, the capacity retention after 700 cycles of LFP-3 is better than that of LFP-4.The capacity retention after 400 cycles at high temperature of 45 ? of LFP-2 is high to 92.20%, and the charge-discharge efficiency is almost 100%. These materials may meet the requirement for communications back-up power working at the high temperature. The discharge voltage plateau of LFP-2 appears at 2.94 V and 2.39 V at -20 and -25 ?,respectively. The final discharge capacity is 26441 and 27201 mAh at -20 and -25 ?,respectively. The low-temperature performance of LFP-2 is unsatisfied.