Comprehensive Recovery And Regeneration Of-waste Lithium Iron Phosphate Battery

LiFePO4,a lithium battery cathode material,has been widely used in mobile phones and electric vehicles because of its high discharge specific capacity,smooth discharge platform,good cycle stability,thermal stability and low price.In recent years,the output of lithium iron phosphate batteries has gradually increased,resulting in a gradual increase in the scrap amount of lithium iron phosphate batteries.The separate recovery of lithium directly from the spent lithium iron phosphate battery will waste iron and phosphorus,and will not maximize the recovery value of the spent lithium iron phosphate battery.Therefore,this paper through the leaching of waste lithium iron phosphate,comprehensive recovery of iron phosphate and lithium carbonate and lithium iron phosphate regeneration research.In this paper,li-containing leaching solution and iron phosphate were obtained from the leaching of waste lithium iron phosphate.The effects of leaching conditions such as HZSO4/LiFePO4 molar ratio,H2O2/LiFePO4 molar ratio,H2SO4 concentration and reaction temperature on the recovery of iron phosphate were studied.The research shows that the molar ratio of H2SO4:H2O2:LIFePO4 is 0.65:2.81:1,the concentration of H2SO4 is 1.0 mol/L,the reaction temperature is 60?,the stirring speed is 200 r/min,and the reaction time is 120 min.The optimum leaching conditions for lithium,the leaching rate of lithium can reach 98.5%,the recovery rate of iron phosphate can reach 98%and the purity is about 98%,and the particle size D50 of the iron phosphate sample is 2.67 ?m.In this paper,lithium in the leachate was recovered by precipitation crystallization method.The effects of pH value,type of precipitant and amount of precipitant on lithium carbonate recovery were studied.The research shows that the pH of the Li-containing leachate is adjusted to 9.4 with ammonia water,and the Li-containing secondary filtrate is obtained by filtration.The ratio of the actual amount of sodium carbonate added to the theoretical amount during the precipitation crystallization is 105%,and separated by filtration.And after the drying,the recovered product Li2CO3 was obtained,the recovery of lithium was 82%,and the purity of lithium carbonate was 96.7%.In this paper,iron phosphate and lithium carbonate recovered from waste lithium iron phosphate were used as raw materials,and lithium iron phosphate was successfully regenerated using a carbothermal reduction method.The regenerated lithium iron phosphate was assembled into a button cell for testing.It was found that the sample had a first discharge specific capacity of 143.3 mAh/g at 0.1 C and a specific discharge capacity of 129.7 mAh/g at 1C.The first discharge specific capacities at 0.1C,0.2C,0.5C,1C,3C,and 5C rates were 143.3,137.4,134.5,129.7,110.8,and 102.1 mAh/g,respectively,and the charge transfer resistance Ret was 122.6?.