Preparation and Electrochemical Performances of Vanadium or Nickel Doped Lithium Iron Phosphates
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摘要: 以水/乙醇作溶剂,采用溶剂热法制备合成了钒/镍离子掺杂的锂离子电池正极材料LiFePO4,利用X射线衍射仪(XRD)和扫描电镜(SEM)对试验所得样品进行物相和形貌分析,通过恒流充放电测试仪以及电化学工作站对样品的电化学性能进行了研究。结果表明:掺杂钒和镍离子后样品的充放电电压平台差均比未掺杂样品小,当钒离子掺杂量1%以及镍离子掺杂量为1%时,在2.5~4.3 V、0.2C和常温下电池的首次放电比容量分别为124.9、113.5 mAh/g。常温下钒离子掺杂量1%时循环性能最佳,循环50次后放电比容量为114.4 mAh/g,容量保持率为91.59%。镍掺杂量为1%样品在低温条件(0℃)下具有最高的首次放电比容量103.1 mAh/g。Abstract: In this paper,the vanadium or nickel doped cathode material LiFePO4 for lithium ion battery was synthesized by solvothermal method,using water/ethanol as the solvent.The crystal phases and microstructures of the samples were characterized by XRD and SEM,respectively.Furthermore,the electrochemical performances of LiFePO4/carbon composites were studied by the methods of constant AC impedance and cyclic voltammetry.Through the constant current charge and discharge test,the results indicate that the difference between the charge and discharge voltage of the samples doped by vanadium and nickel ions is smaller than that of the undoped sample.The samples with 1% vanadium ion doping and 1% nickel ion doping respectively have an initial discharge specific capacity of 124.9 mAh/g and 113.5 mAh/g at 2.5～4.3 V,0.2 C and room temperature.And the sample with 1% vanadium ion doping has the best cycle performance with 114.4 mAh/g of specific discharge capacity and 91.59% of capacity retention rate after 50 cycles.The sample with 1% nickel ion doping has the highest initial discharge specific capacity of 103.1 mAh/g at 0 ℃.
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Key words:
- lithium ion battery /
- cathode material /
- LiFePO4 /
- doping modification /
- electrochemical performances
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