Study On Directional Arrangement And Properties Of Lithium Cobalt Phosphate Cathode Materials

Lithium cobalt phosphate has olivine structures and theoretical specific capacity,similar to lithium iron phosphate,and high voltage discharge platform of 4.8V,which leads to a higher energy density.It is expected to become the cathode material for high-voltage,high-energy density power batteries in the future.However,its actual electrochemical performance of the material could not reach the theoretical values.Doping and coating are dominant methods to improve the perporities,which are mainly based on chemical technology.This work intends to improve the peroformance based on the magnetic properties of lithium cobalt phosphate.In this paper,single crystal lithium cobalt phosphate with?020?crystal plane was synthesized by a solvothermal method using sucrose as an additive.It was found that lithium cobalt phosphate crystals growing along the?020?crystal plane could be synthesized in the EG-water system.Compared with the DEG-water system and the TEG-water system,the lithium cobalt phosphate crystal synthesized by the EG-water system?LCP-EG-S?has smaller grain size with its length in the[010]direction is about 300⁶00 nm,which is benefit for Li-ion diffusion.The LCP-EG-S has the highest specific capacity of 128.9mAh/g at 0.1 C with better cyclic and rate performance than the others.It could be contributed to the fast Li-ion diffusion of LCP-EG-S.The hydroxyl group of the alcohol organic solvent can inhibit the growth in the[010]direction and inhibit the growth of crystals during the growth of the lithium cobalt phosphate crystal.According to the anisotropy of the magnetic susceptibility of lithium cobalt phosphate crystals,oriented alignment of LCP-EG-S cathode parellel to[010]direction was prepared by appling a static magnetic field of 0.5 T.By comparing with the electrochemical performance of the LCP-EG-S electrode without magnetic orientation?LCP-O?,it was found that the initial discharge specific capacity of the LCP-EG-S electrode after magnetic field treatment?LCP-M?was increased by about7mAh/g,at 0.1C,and after 25 cycles,the cycle performance was improved by 7%,the rate performance was improved by 20mAh/g at 5C.The magnetic properties also showed a stronger macro magnetization,which it was increased by 0.00139emu/mg at5000Oe.Finally,the composite material of?1-x?LiCoPO₄/xLiFePO₄?x=0,0.1,0.3 and 0.5?was synthesized by coating lithium cobalt phosphate with lithium iron phosphate.When the compounding amount of lithium iron phosphate was 10%,it has the best cyclic and rate rate performance.After 20 cycles at 0.1 C,its the cycle performance was 20%higher,and its the discharge rate at 5C was 65 mAh/g higher.