Effects Of Capacitive Carbon On Rate Capability Of Lithium Ion Battery

LiFePO₄（LFP） due to its outstanding safety performance advantages, LiNi_1-x-yCo_xAl_yO₂ system（NCA） ternary cathode material due to its specific capacity, highest and excellent cycle performance and comparative low price, had become a research focus in the electric vehicle power supply. However, the material of LiFePO₄（LFP） and NCA ternary lithium battery was not a perfect battery technology.There were many problems both in the process of realizing industrialization, such as slower charging speed, lower the utilization of active material under the condition of big ratio.In this research, LiFePO₄ material, ternary lithium anode material, graphite anode materials capacitance carbon was added to improve the electrode material, improve the LiFePO₄ lithium ion batteries and NCA ternary lithium battery materials utilization of active material and dynamic properties in high ratio.The method of using directly mixed LiFePO₄/capacitance carbon composite electrode was prepared.And the effection of the capactive carbon on the rate capability of LiFePO₄ lithium ion battery was researched. When adding five percent of the mechanical grinding capacitive carbon, the rate performance of the battery is best. When the battery was charged in 5C, 10 C and 20 C, its specific capacity can reach 160 m Ah/g, constant current time for 10 min, 6 min, 2 min respectively, discharge specific capacity could be as high as 160 m Ah/g, 120 m Ah/g, 80 m Ah/g. In addition, the discharge time was 18 s and 12 s respectively when charged by 90 C and 100 C. By EIS and CV analysis, the battery internal impedance was minimum, the deviation of peak position between the oxidation peak and the reduction peak was very small, the peak current was quite large. These represented the good reaction kinetics and reversibility.NCA ternary materials/capacitance carbon composite electrode cathode material was synthesized by the method of directly mixed. And the effection of capactive carbon on the rate capability of ternary lithium ion battery. When adding five percent of the artificial ground capacitive carbon, its rate capability was optimal. The constant current period of the battery was 8 min, 4 min, 2 min, and the discharge specific capacity was as high as 140 m Ah/g, 134 m Ah/g, 120 m Ah/g respectively, when charged by 5C, 10 C and 20 C ratio for fast charged fast discharged. In addition, in a 90 C, 100 C for discharged, the discharge time was 17 s and 11 s respectively. By analyzing of the EIS and CV, when adding capacitive carbon, the battery charge-discharge impedance decreased, and on the 3.8 V / 4.0 V peak position, its peak voltage deviation was small, on 4.15 V / 4.15 V peak position, the corresponding peak current was big. Compared with the quality of active substances were 1.16 mg, 2.88 mg and 4.96 mg, the performance of the battery of active substances 2.88 mg was the best, And its discharge specific capacity is 110 m Ah/g, 100 m Ah/g, 90 m Ah/g respectively, when 5C, 10 C and 20 C fast charged fast discharged.Selecting optimal proportion 5% artificial ground capacitive carbon/NCA ternary composite electrode as battery anode, respectively by 5% pre-grinded capacitive carbon/graphite composite electrode, 5% artificial grounded capacitive carbon/graphite composite electrode, 5% mechanical grinded capacitive carbon as battery cathode, assembled the whole battery. And the effection of capactive carbon on the capability of graphite was researched. Only adding 5% graphite mechanical/ grinded capacitive carbon, whose charged and discharged performance was better than that of graphite blank cells under the ration of 5C. Under the condition of 10 C, adding 5% pre-grinded capacitive carbon and mechanical grinded capacitive carbon to graphite, the performance of these batteries was better than that of blank graphite. When the ration was 20 C, adding 5% mechanical grinded capacitive carbon,5% artificial grounded capacitive carbon,5% pre-grinded capacitive carbon, their charge specific capacity are 70 m Ah/g、50 m Ah/g 、40m Ah/g respectively,whose performance were better than graphite blank.