Preparation Of LiFePO₄/c Nanofiber Cathode Material For Lithium Ion Battery By Electrospinning

Olivine structure lithium iron phosphate（LiFePO₄） is widely recognized as apromising cathode material for lithium ion battery, especially as the motive powerbatteries and energy storage battery materials because of its abundant resources, lowcost, good thermal stability, excellent cycling performance and so on. Currentlithium-ion batteries were depended on using active powder materials to storeenergy. However, powder materials have a long diffus ion path for lithium ions andslow electrode reaction kinetics, and as a result, the performance of currentlithium-ion batteries has not reached their potential. Electrospinning is a verypromising technique to obtain large scale nanofibers for its simple process, low-costadvantages. In this paper, having certain morphology carbon-coated or otherwisemodified LiFePO₄composite nanofibers cathode material were synthesized byelectrospinning technology, with the recent progress in the materials andexperimental means, combining with the optimization of the electrode preparation,and studied its performance.The LiFePO₄materials were produced by electrospinning. The effects ofsolvent, inorganic precursor and polymer were investigated. The electrospinningsolution consisting of the water as solvent, ferric citrate and lithium dihydrogenphosphate as raw material, polyethylene oxide （PEO） ethane andpolyvinylpyrrolidone （PVP） hybrid polymer as the thickening a gent of precursorsolution system showed good spinnability, prepared the small size uniformdistribution, into three dimensional non-woven shaped nanometer fiber membrane.The problems of fiber poor film-forming properties, not easy to receive,hygroscopicity have been well overcomed. A pure LiFePO₄was obtained after heattreatment by optimize the stoichiometric ratio of iron citrate and lithium dihydrogenphosphate, removed the impact of the iron impurities on the material properties. In0.1C charging and discharging rate, discharge capacity of115mAh/g; in0.5C rate,the discharge capacity of about80mAh/g.Subsequently, the effect of nickel doping on LiFePO₄/C nano fiber werestudyed. It found that nickel doping no change the crystal type of LiFePO₄, butreduce the charge transfer resistance between the material, thereby improve theelectrochemical properties of the material. At0.1C charging and discharging rate,the discharge specific capacity reached143mAh/g, after five cycle, capacity did notappear degradation; In0.5C ratio discharge specific capacity still reached90mAh/g.With high conductive phase Fe2P of LiFePO₄/C composite nanofibers weresuccessfully synthesized through increasing the sintering temperature at750°C or higher. In0.1C charge and discharge ratio, the preparation of composite material of750°C discharge specific capacity reached165mAh/g; In0.5C ratio, dischargespecific capacity reached about105mAh/g; In1C ratio, discharge specific capacityreached76mAh/g. After five0.1C cycles and twenty0.5C cycles and twenty five1C ratio cycles, the capacity of composite material of750°C no degradation, traceamounts of Fe2P can remarkable upgrade the performance of LiFePO₄/C cathodematerial.