Study On Optimum Control Of Production Process Parameters Of Battery-grade Ferric Phosphate

With the development of society and the increasing awareness of environmental protection,the demand for rechargeable batteries and battery materials increases accordingly.As the mainstream batteries in the world,Lithium-ion batteries have been paid close attention by researchers.Lithium ferric phosphate which has good chemical properties,strong stability and the characteristic of environmental protection has become the main representative of cathode materials for lithium-ion batteries.As the main raw material of lithium ferric phosphate,ferric phosphate is particularly important.Because the control of manufacture process and the quality of ferric phosphate will directly affect the quality of lithium ferric phosphate.In the preparation of lithium ferric phosphate cathode material,which need to make use of ferric phosphate dihydrate,the uncertainty of crystalline water content and material water content makes the actual ratio of raw material inaccurate.As a result,the performance control of the product,the product quality and the economic efficiency will be affected.Based on the study of the technology of dehydration of ferric phosphate dihydrate and milling time of ferric phosphate,the present paper concems itself with the best technological and economic path ferric phosphate production by combining the actual production of enterprises with the technology.The main work is as follows:1.Theoretical calculation shows the initial precipitation pH of ferric phosphate and impurity ferric hydroxide,it is concluded that the pH is related to the concentration of the raw material.The higher the concentration of the raw material,the lower the initial pH and the more difficult it is to control.Therefore,in order to prepare the purified ferric phosphate,the raw material concentration is controlled to be about 1.0 mol/L-2.0 mol/L.2.By making use of ferric chloride,ammonium dihydrogen phosphate solution and ammonia water as main raw materials and reaction at a certain temperature and pH to produce ferric phosphate dihydrate as production route,the samples were characterized and analyzed by infrared spectroscopy and XRD.The results showed that the samples were ferric phosphate dihydrate.By controlling the synthesis temperature at 55?,changing the synthesis pH?0.85-1.3?and dehydrating at300?/2h+530?/2h,the grinding process of dehydrated products was studied.The results are as follows.First,the lower of the pH value is,the larger of the specific surface area becomes.Under such conditions,the gMilling time will become faster,the particle size of grinding for 30 minutes will become smaller and the production requirements will be met.Second,with the increase of synthesis temperature,the specific surface area of products increases correspondingly.In conclusion,the optimum pH value is 0.9 to 1.0,and the optimum synthesis temperature is 75 to80?.3.The influence of temperature on the dehydration process of ferric phosphate dihydrate was studied.The samples were characterized and analyzed by infrared spectroscopy,XRD and thermogravimetry.The results showed that the ratio of phosphorus to iron was unchanged at different dehydration temperatures,which was consistent with that before dehydration,and the content of iron and phosphorus reached the standard.Specific surface area decreased with the increase of dehydration temperature.Compared with pure low temperature and pure high temperature dehydration test,the combination of low temperature and high temperature can meet the requirements of the indicators and is economical.The results show that the optimum dehydration conditions of FePO₄ dihydrate are 300?,a two-hour dehydration and 530-550?,one to two hours of dehydration.To analyze the grinding rate of dehydrated products,the effects of different dehydration temperatureon product particle size were studied.The results show that the above element has little effect on the grinding rate of the product.Based on theoretical calculations,the synthesis conditions of ferric phosphate dihydrate were studied.The effects of synthetic pH,temperature and dehydration temperature on the grinding rate of ferric phosphate were investigated,which provided a reference for the production of battery grade ferric phosphate.Figure[21]table[11]reference[59]...