Ti^(4+)掺杂对Li_2FeSiO_4/C电化学性能的影响

Effects of Ti^(4+) Doping on the Electrochemical Performance of Li_2FeSiO_4/C

用溶胶-凝胶法制备Ti 4+掺杂的Li2Fe1-xTixSiO4/C正极材料。用XRD、HRTEM和电化学方法研究了该材料的结构、形貌和电化学性能。结果表明,掺杂适量的Ti 4+不会改变Li2FeSiO4的正交晶系结构,可以稳定材料的结构,改善高倍率充放电性能。在室温下,Li2Fe0.97Ti0.03SiO4/C以0.1C倍率放电的首次放电比容量为149.1mA.h/g,20次循环后放电比容量为127.3mA.h/g,且不同倍率下的电化学性能明显优于未掺杂的Li2FeSiO4/C。交流阻抗谱研究表明,适量的Ti 4+掺杂,减小了正极材料在充放电过程中的电荷传递电阻,增加了材料的电子电导率,改善了材料的电化学性能。

Ti4＋-doped Li2Fe1-xTixSiO4/C cathode material was prepared by a sol - gel method. The structure and image and electrochemical performance of cathode material were tested by XRD HRTEM and electrochemical meth- ods. The results show that the orthorthombic structure of Li2 FeSiO4/C is not changed while the structure is more stable and the electrochemical properties is better at high rate due to doping appropriate amount of Ti4＋. The initial specific capacity of Li2 FeSiO4/C is 149.1 mA · h/g at 0, 1 C discharge rate under the condition of room temperature and possesses a discharge capacity of 127.3 mA · h/g after 20 cycles. And the different magnification electrochemi- cal performance is significantly better than undoped Li2FeSiO4/C . Electrochemical impedance analysis shows that Ti4＋ doping decreases charge transfer resistance of Li2 FeSiO4/C, and moreover, Ti4＋ doping increases the electronic conductivity of the material,and the electrochemical properties of cathode material is improved.