Study On Performance Of Positive And Negative Electrode In LiFePO₄/Li₄Ti₅O₁₂ Battery

Compared with conventional lithium-ion battery using graphite as negative electrode,LiFePO₄/Li₄Ti₅O₁₂（LFP/LTO） lithium-ion battery has the advantages of high safety, longcycle life and fast charging ability. It has potential applications in energy storage of windand solor electricity as well as in power system of electrical buses. Nowadays, tremendousefforts have been made to investigate the preparation and modification of LiFePO₄andLi₄Ti₅O₁₂materials. However, studies on the overall performance of batteries using LiFePO₄and Li₄Ti₅O₁₂as cathode and anode, repectively, are rare. So, it is necessary to study theelectrochemical performance of LiFePO₄and Li₄Ti₅O₁₂as positive and negative electrode,respectively, in a whole battery. In this theis, different commercial LiFePO₄and Li₄Ti₅O₁₂were evulated as the electrode materials of LiFePO₄/Li₄Ti₅O₁₂pouch battery in terms oftheir power performance, cycle performance and low temperature performance by CV, EISand constant current charge-discharge tests.For the positive electrode material, five LiFePO₄samples from different manufactureswere evulated. It was found that the sample LFP-1shows the best power performanceamong all the samples. The discharge capacity of LFP-1is105.3mAh·g^-1at thecharge-discharge rate of5C measured in a LiFePO₄/Li half cell. While, for the10AhLFP/LTO pouch battery with LFP-1positive electrode, the capacity is about8.75Ah and atthe charge rate of10C and is9.33Ah at the discharge rate of5C. The sample LFP-3exhibits the best cycle performance. After50cycles at1C, the discharge capacity retentionof LFP-3is98.3%in the half cell test. And the discharge capacity retention of the LFP/LTOpouch battery with LFP-3postive electrode is97.6%at the rate of2C. The sample LFP-2displys the best low temperature performance. The discharge capacity of LFP/LTO pouchbattery with LFP-2positive electrode at-20℃and-30℃is75.7%and71.2%of thenominal capacity, respectively.For the negative electrode material, three Li₄Ti₅O₁₂samples from differentmanufactures were investigated. The discharge capacity of LTO-1is112.2mAh·g^-1at thecharge-discharge rate of10C in the Li₄Ti₅O₁₂/Li half cell. The charge and dischargecapacity of the LFP/LTO pouch battery with LTO-1negative electrode is about128.7mAh·g^-1and136.4mAh·g^-1, respectively at the rate of5C. Although the capacity retention of LTO-1is not the highest in the100cycle test at1C in the half cell, the discharge capacityof LTO-1is always the highest. And the discharge capacity retention of the LFP/LTO pouchbattery with LTO-1negative electrode is94.0%at the rate of2C, which is the best amongall the three samples. The sample LTO-1also shows the best low temperature performance.The discharge capacity of the LFP/LTO pouch battery with LTO-1negative electrode at-20℃and-30℃reaches70.3%and54.0%of the nominal capacity.