钾、氯离子共掺杂纳米Li_(2)FeSiO_(4)/C正极材料的电化学性能

Performance of nano Li_(2)FeSiO_(4)/C cathode material co⁃doped by potassium and chlorine ions

利用K^(+)、Cl^(-)共掺杂来优化纳米Li_(2)Fe Si O_(4)/C正极材料的结构及电化学性能,通过固相反应制备了纳米Li_(2-x)K_(x )Fe Si O_(4-0.5x)Cl_(x)/C(x=0、0.01、0.02)正极材料。采用X射线衍射、扫描电子显微镜、透射电子显微镜、X射线光电子能谱和恒电流充放电等对比研究了3种正极材料的微观结构特征和电化学性能。研究表明纳米Li_(1.99)K_(0.01)Fe Si O_(3.995)Cl_(0.01)/C正极材料的晶面间距和晶胞体积最大,颗粒粒径最小,平均粒径为32 nm。这些特定的微观结构使其表现出最优的电化学性能。纳米Li_(1.99)K_(0.01)Fe Si O_(3.995)Cl_(0.01)/C在0.1C下的首次放电比容量高达203 m Ah·g^(-1),在1C下充放电循环100次的容量保持率为97.72%。

Herein,the structure and electrochemical properties of nano Li_(2)FeSiO_(4)/C cathode materials were opti-mized through co-doping potassium and chlorine ions.A series of nano Li_(2-x)K_(x )Fe Si O_(4-0.5x)Cl_(x)/C(x=0,0.01,0.02)com-posites were prepared by a solid-state reaction.The microstructure and electrochemical performance of the three kinds of composites were analyzed using X-ray diffraction,scanning electron microscopy,transmission electron microscopy,X-ray photoelectron spectroscopy,constant current charge-discharge test,etc.The results showed that nano Li_(1.99)K_(0.01)Fe Si O_(3.995)Cl_(0.01)/C cathode material owned the largest interplanar spacing,biggest cell volume,and smallest average particle size among the three materials.The average particle size of nano Li_(1.99)K_(0.01)Fe Si O_(3.995)Cl_(0.01)/C cathode material was as small as 32 nm.These particular structures made it exhibit the best electrochemical performance.The initial specific discharge capacity of the nano Li1.99K0.01FeSiO_(3).995Cl0.01/C cathode material at 0.1C was as high as 203 mAh·g^(-1).In addition,a capacity retention rate of 97.72%was acquired for the nano Li_(1.99)K_(0.01)Fe Si O_(3.995)Cl_(0.01)/C cathode material at 1C after 100 charge-discharge cycles.