关键词： 水系混合电池, 正极材料, 磷酸钒锂, 冷冻干燥, 掺杂

Abstract: In this design,Li₃V_2-xCo_x(PO₄)₃ materials were synthesized by freeze-drying assisted sol-gel method,with ammonium metavanadate,lithium acetate dihydrate,and ammonium dihydrogen phosphate as raw materials,and cobalt acetate tetrahydrate as Co doping source.The effect of Co doping on the structural and electrochemical properties of the materials was investigated.The results show that Monoclinic crystals with good crystallinity can be obtained by freeze-drying assisted sol-gel method,and the crystal structure of lithium vanadium phosphate is not changed by proper Co doping.The positive electrode materials synthesized by freeze-drying assisted sol-gel have microporous structure.The proper amount of Co doping helps to increase the number of micropores and obtain the material with more uniform particle size.With the increase of Co doping amount,the ion diffusion rate,charge/discharge and cycling performance of the materials all presents a trend of first increasing and then decreasing,while the charge transfer impedance presents a trend of first decreasing and then increasing.When x=0.04,the electrochemical performance of the lithium vanadium phosphate cathode material is the best,the ion diffusion rate reached 8.99×10^-13 cm/s,the charge transfer impedance is the lowest,233.6 Ω,and the initial discharge capacity  increases from undoped 53.4 mAh/g to 81.7 mAh/g at 2C discharge rate.After 50 weeks of 2C rate cycle,the discharge capacity retention rate is 91.11%,which is 13.54% higher than that of the undoped sample.

Key words: aqueous hybrid battery, cathode material, lithium vanadium phosphate, freeze-drying, doping