稀土元素掺杂对LiFePO4正极材料电导率和电化学性能的影响

The conductivity and electrochemical performance of lanthanon doped lithium iron phosphate cathode materials

橄榄石型LiFePO4因其安全性能突出、价格低廉、绿色环保、循环性能优良等优点已成为最具应用潜力的新一代锂离子电池用正极材料。由于LiFePO4电子导电能力较低，因此其充放电容量有待进一步改进。采用水热合成法制备了纯LiFePO4和稀土元素La、Ce、Nd掺杂的LiFePO4纳米粉末。研究表明，掺杂后材料的电导率比未掺杂试样高2-3个数量级。电化学测试显示掺杂后LiFePO4的首次充放电容量提高2-5倍，其中掺Nd的效果最好。水热合成产物经高温碳包覆后，掺杂的LiFePO4/C复合材料也比纯的LiFePO4/C复合材料的放电容量高，表明掺杂稀土元素能有效提高橄榄石型LiFePO4的充放电容量。

Olivine-structured LiFePO4 is gaining particular interest as a potential candidate cathode material for rechargeable lithium-ion batteries from both economic and environmental points of view. In order to improve the performance of LiFePO4, the poor conductivity must be ameliorated. The powder of pure LiFePO4 and LiFePO4 doped with La, Ce and Nd have been synthesized by solvothermal method. As a result, the conductivities of hot pressed samples with doped elements were 100-1000 times higher than the undoped sample evidently, and the electrochemical performance of the composites was improved greatly by doping, With the capacities about 2-5 times higher than the pure sample, especially for the composite with Nd which had the largest range. The capacities of corresponding carbon-coated LiFePO4 composites were also improved by doping markedly, which proved that the performance of olivine-structured LiFePO4 could be improved by doping.