| In the case of the increasingly serious global energy and environmental issues,the areas of development of the lithium-ion batteries by mobile phones,laptop computers,digital cameras,submarines,aerospace,aviation is gradually moving towards electric bicycles,electric vehicle power fields,it is considered to be an ideal choice for high-capacity,high-power battery.In this study,taking LiNi0.5Co0.2Mn0.3O2/Li4Ti5O12 Lithium-ion power battery as the research object,focusing studies on the charge-discharge performance,cycle performance and safety performance.The preparation and performance characteristics of the 18650 cylindrical Lithium-ion power batteries have been systematically studied.In the preparation process,the article have mainly studied from the cathode conductive agent content,the electrolyte injection fluid volume,positive/negative ratio of material,formation technology on the battery performance.The results showed that:(1)the battery electrical properties and cycle performance was more excellent when the positive electrode conductive agent was 8%.The battery performance was relatively stable with the increase of the content of the positive electrode conductive agent at 1C rate.The 5C rate discharge capacity was 94.5%of the 1C rate capacity,the average discharge voltage was 1.92V.The battery capacity retention rate and the cycle life of the battery were improved with an appropriate increase in the content of the conductive agent.(2)Through calculations,18650 cylindrical LiNi0.5Co0.2Mn0.3O2/Li4Ti5O12 lithium-ion power batteries's theoretical injected volume was 5.23g.The capacity retention rate of the batteries was 96.13%and the internal resistance was 14.7m? when the actual injected volume was 6.0 g.Add appropriate amount of electrolyte,not only can reduce the internal resistance of the battery and improve the efficiency of charging and discharging,but also can enhance the battery cycle life and safety.(3)When the negative/positive was 1.05,the battery capacity retention rate was 95.8%after 50 cycles.The only proper amount excessive of the negative electrode material can be provided for the sufficient of the space for lithium in the positive electrode and also can improve the utilization rate of the lithium and increase the cycle life of the battery.(4)Different formation technology for the first time charging the battery performance had a certain impact.The results showed that the total capacity was 1506.1 mAh after small-current formation technology and the total capacity was 1499.5 mAh after high-current formation technology when the charging constant voltage was 3V.The batteries's initial discharging performance and cycling performance were almost no affect.Different performance tests were made for the LiNi0.5Co0.2Mn0.3O2/Li4Ti5O12 Li-ion power battery.The results showed that the performance of routine and fast charge-discharge was good.The time when charge rate achieved 100%was 39.9min at the 5C rate,and the battery capacity was 1235mAh.At 1C rate charge-discharge,the battery capacity retention rate were 95.7%at room temperature and 98.28%at 55?after cycle of 60,indicating that the battery had a high temperature performance.The discharge capacity of the battery was 1347mAh,and the discharge voltage was 2.23 V at 55?.The battery discharge capacity was 792.7mAh at-20?,it can be indicated that the battery had no good electrical properties at low temperatures.Through different safety tests,the results indicated that the battery's safety and adaptation to environment were uniform to GB/T18287-2000. |
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