Mg~(2+)、Zr~(4+)离子掺杂对Li_4Ti_5O_(12)电化学性能的影响

以固相反应法合成了尖晶石型Li4Ti5O12电极材料,进行了金属离子掺杂以提高其导电性及综合性能,以适应用于大电流充放电的目的。采用XRD、室温恒流充放电循环、交流阻抗和循环伏安等测试手段,考察了A位掺杂Mg(Li4-xMgxTi5O12,x=0.15),B位掺杂Zr(Li4ZrxTi5-xO12,x=0.15)对Li4Ti5O12结构和电化学性能的影响。结果表明:掺杂少量的Mg2+、Zr4+未引起材料结构的变化,明显降低了Li4Ti5O12电荷转移阻抗,使导电性得到有效提高。0.1 C放电倍率下放电,未掺杂及掺杂Mg2+、Zr4+的Li4Ti5O12首次放电容量分别为159.8、144.9、161.2mAh/g,循环40次后,容量分别保持为113.8、130.6、133.6 mAh/g。与未掺杂的Li4Ti5O12相比,掺杂后的电极材料极化减小、循环容量及稳定性提高。

Effects of Mg2+ and Zr4+ Doping on Electrochemical Performance of Li4Ti5O12

Spinel-type electrode material Li4Ti5O12 was prepared by a solid-state reaction method,and doped with metal ions to improve the conductivity and integrated performance,in order to be suited for big rate application.Mg2 and Zr4 doped respectively at A and B site were studied,and the effects of Mg2 and Zr4 doping on the structure and electrochemical properties were investigated by X-ray diffractometry,constant current charge-discharge cycling tests,AC impedance and cyclic voltammogram.The results indicate that the structure of Li4Ti5O12 is not changed with small doping content,but the conductivity is efficiently improved due to obvious reduction of the charge transfer impedance.At 0.1 C discharging rate,the first discharge specific capacities of pure and Mg2 and Zr4 doped lithium titanate are 159.8,144.9 and 161.2 mAh/g,respectively.After 40 cycles,the capacities are 113.8,130.6 and 133.6 mAh/g respectively.Compared with pure Li4Ti5O12,the cyclic capacity and stability of the doped material are improved.