Green Preparation Of Lithium Iron Phosphate And Study On Its Electrochemical Properties

Olivine-structured lithium iron phosphate has many advantages,such as excellent cycling performance,high safety factor,considerable specific capacity,abundant raw material,green and non-toxic property,so it is considered as one of the most promising cathode material for lithium-ion battery.In recent years,many researchers have paid attention to LiFePO₄ cahode material.In this study,LiFePO₄/C composite material was prepared by precipitation and solid phase method.First,the precursor of iron phosphate was prepared by precipitation method.The preparation process of precursor is free from waste water and pollution.The lithium iron phosphate cathode material was prepared by solid phase sintering with the mixture of precursor and lithium source.Solid phase sintering process is green and non-toxic after simple tail gas treatment.The feasibility of the experimental scheme was proved by exploring the preparation parameters.Finally,the suitable preparation parameters were obtained as follows:the preparation temperature of precursor was 85?,the pH value was controlled at about 4,the milling time was 9 h,the carbon content was 2%,and the sintering time was 10 h.The optimum preparation parameters were used to prepare lithium iron phosphate powder with a particle size of about 100-200 nm.Its excellent performance is that the discharge capacity of the battery is 161 mA·h·g^-1 at a small rate of 0.1 C,which is equivalent to 95%of the theoretical capacity of LiFePO₄.At high rate of 10 C and 20 C,the discharge capacity of lithium-ion batteries can reach 119 mA·h·g^-1 and93 mA·h·g^-1,respectively.After 100 cycles at 1 C,the specific discharge capacity of the battery is 142 mA·h·g^-1,and the capacity retention rate is 98%.In addition,it has excellent ion diffusion rate through comparison with commercialized material.In addition,spherical particles of LiFePO₄/C were prepared by spray pyrolysis.The sintering temperature parameters in the preparation process were taken as the core of the basic research.The best preparation temperature parameter is obtained by comparing the physical and electrochemical properties of the materials.The prepared materials have excellent electrochemical properties.Lithium iron phosphate material with excellent properties was prepared at 640?sintering temperature.The constant current charge-discharge test results show that the specific capacity is 165 mA·h·g^-1 at 0.1 C and 80 mA·h·g^-1 at 20 C,respectively.In this study,the amorphous properties of the materials prepared at lower temperatures were analyzed.We found that the materials containing amorphous phase exhibited certain pseudocapacitive properties.The contribution ratio of pseudocapacitance varies with sintering temperature.The lower the sintering temperature,the greater the contribution of capacitance.The battery and capacitance regions in the charge-discharge curve of the battery have a good correspondence with the characteristics of the battery and capacitance calculated from the CV curve,and the process of lithium iron phosphate charging and discharging is further understood.