一步固相合成Nb掺杂LiFePO_4/C及其电化学性能

Electrochemical properties of Nb doped LiFePO_4/C prepared by one-step solid-state synthesis

用廉价的三价铁离子化合物为铁源，以聚丙烯为还原剂和碳源，在一步固相法合成Nb掺杂LiFePO4的同时实现颗粒表面碳导电膜的原位包覆。结果表明：一步固相合成的Nb掺杂LiFePO4／C具有完整的橄榄石型LiFePO4晶体结构和近似球状的颗粒形貌，颗粒尺寸为100～500nm；聚丙烯分解后在颗粒表面和颗粒之间形成连通的网络状碳膜。电化学测试结果表明，当Nb的掺入量为1．0％（摩尔分数）时具有最好的倍率放电性能和循环性能；在2C充放电时具有130mA·h／g的放电容量，循环100次容量无衰减，在4C充放电时仍具有105mA·h／g的放电容量。

Nb-doped lithium iron phosphates were synthesized and in-situ carbon coated by one-step solid-state reaction using ferrous compound as the iron source and polypropylene as the reductive agent and carbon source. The results show that the one-step solid-state synthesized Nb doped LiFePO4/C powders are near-spherical particles of 100 -500 nm with the olivine type LiFePO4 structure, and wrapped with carbon nets decomposed from polypropylene. Electrochemical analyses show that LiFePO4/C with 1.0% Nh（in mole fraction） doping has the best rate perforrnances and cycling stability with a discharge capacity of 130 mA· h/g retained up to 100 cycles at 2 C rate and 105 mA· h/g at 4 C rate.