Study On Preparation Of Batterty-Grade LiBF₄ By The Solution Method And Electrochemical Performance

With the rapid development of economy,environmental pollution and the shortage of energy have become the issues that everyone must face.Lithium-ion batteries has attracted wide attention,from all aspects of enery,environment,transportation and aerospace ect,because of its high specific energy,long cycle life,no memory effect,safety,environmental protection and other advantages.The electrolyte is most certainly an indispensable part of lithium-ion battery.The excellent performance electrolyte is essential for lithium-ion battery to obtain a high voltage and high energy density etc.Lithium tetrafluoroborate?LiBF₄?has the advantages of good thermal stability,no sensitivity to water environment,low toxicity,high safety and cost-effective production,as electrolyte material for lithium-ion battery.Beside,it can effectively prevent corrosion of Al-collector.It is one of the necessary functional composition in electrolyte for lithium-ion battery.And it has a good prospect for wide applications.This paper has adopted solution method in the preparation process.Lithium tetrafluoroborate of battery level has been prepared by taking hydrofluoric acid,boric acid,lithium carbonate as the raw material.The lithium tetrafluoroborate were characterized by means of IR,XRD,AAS,ICP-AES,and DTA ect.The electrochemical properties of lithium tetrafluoroborate were tested through the battery test system and the electrochemical workstation.This paper studied the topic by the following aspects:First,This paper places emphasis on preparing LiBF₄ of battery level by adopting solution method and taking hydrofluoric acid and boric acid as the raw material.The influences on the product's purity and yield were investigated,whose various factors had reaction temperature,the mole ratio of the raw material,evaporation capacity and crystallization temperature.Technological parameters were optimized by conducting single factor experiment and orthogonal experiment,and the optimal technological parameters were determined as 7.5? about reaction temperature,the mole ration 4.05:1.00:0.56about raw material of HF:H3BO3:Li2CO3,65%about alcohol evaporation capacity,15? about crystallization temperature.LiBF₄ prepared under such conditions has the purity of 99.22%?AAS?and yield of 90.08%.Second,it was tested that the self-made target product was LiBF₄ by using infrared spectroscopy for structural analysis and X ray diffraction method.The results indicated that the samples of optimum conditions had high purity,up to 99.00%,by using AAS to test the amount of lithium ion in the target product LiBF₄,ICP-AES to analyze the other metal ions and the weight method?precipitation method and titration method of weight?to determine fluoroborate of samples.The lithium tetrafluoroborate was characterized by thermal analysis and the endothermic peak appeared at 290?300? of the DTA pattern,which indicated that the target product LiBF₄ has good thermal stability..Third,the button battery was made by using the electrolyte of self-made LiBF₄,and the electrochemical properties were tested by cell testing system and electrochemical workstation.The results proved that it had high charge discharge voltage and good cycle performance.The results of experiments showed that the process of preparing lithium tetrafluoroborate of battery level by solution method was feasible.The process has mild reaction condition,and the by-products are water and carbon dioxide which can be easily removed.The product of the process has high product purity,and the solvent in the preparation process can recycle,which solve the fatal disadvantage of using strongly corrosive and toxic reagents in traditional methods.