Study On Preparation And Properties Of LiFePO₄ Cathode Materials For Hybrid Capacitors

In order to meet the development needs of high energy density and high power density of electrochemical hybrid capacitors,the development of electrode materials with high specific energy,high specific power and good cycle efficiency has become an urgent problem to be solved.Lithium iron phosphate has the most potential electrode material because of its high specific capacity,stable cycle performance.Therefore,the research on lithium iron phosphate cathode material is significant.LiFePO₄ cathode materials were prepared by solid phase reaction and sol-gel method respectively,and the effects on the electrochemical performance of the hybrid capacitors were investigated by changing the process parameters.XRD and SEM were used to characterize the crystal structure and microstructure of the material.Electrochemical performance of the material was tested by electrochemical workstation and blue battery test system.The results show that the calcination temperature of solid phase reaction is 700 ^oC,the holding time is 12 h,and the electrochemical performance of LiFePO₄ with lithium-iron element ratio of 1.3:1 is the best.The first discharge specific capacity at a charging current of 0.2C was 167.3 mAh·g^-1.When the mixed capacitor was composed of a soft carbon negative electrode material having a mass ratio of 0.8:1.1,the specific capacitance retention rate was 96.4%after 500 cycles under a charging current of 1C.The carbon element prepared by the sol-gel method was added in an amount of 12 wt.%,the calcination temperature was 700^oC,and the holding time was 15 h.The electrochemical performance of L was good.The first discharge specific capacity was 179 mAh·g^-11 at a charging current of 0.2C.After circulating 250 times at a charging current of 1C,the specific discharge capacity was 167.6 mAh·g^-1,accounting for 136.7%of the first discharge specific capacity.When the hybrid capacitor was composed of the negative soft carbon material,the retention ratio of the discharge specific capacity after the 500 cycles of the charging current of 1C was 96.1%Figure 57;Table 2;Reference 53.