锂离子电池Na_2Li_2Ti_6O_(14)负极材料的合成与电化学性能

采用高温固相法成功合成了新型钛基负极材料Na_2Li_2Ti_6O_(14),并研究了其结构及电化学性能。利用高分辨透明电镜(HRTEM)、X射线衍射(XRD)及其Rietveld精修、扫描电子显微镜(SEM)及能谱分析(EDS)表征分析了材料的物相和显微结构。结果表明,合成的Na_2Li_2Ti_6O_(14)负极材料为纯相,具有Fmmm空间群结构;Na_2Li_2Ti_6O_(14)颗粒约为500~800 nm,Na、Ti和O三种元素分布均匀。循环伏安(CV)、充放电及电化学阻抗谱(EIS)测试表明,材料具有较好的锂离子脱嵌可逆性,较好的倍率性能和循环稳定性。钛电流密度为500 m A/g充放电时,Na_2Li_2Ti_6O_(14)材料的首次脱锂(充电)容量为180 m A·h/g,100次循环后可逆容量为136 m A·h/g;100次循环后,Na_2Li_2Ti_6O_(14)材料的电荷转移电阻增加,锂离子扩散系数略有下降,表明Na_2Li_2Ti_6O_(14)材料在循环后SEI膜的生成,降低了材料的电化学活性。

Electrochemical Performance and Synthesis of Na2Li2Ti6O14Anode Materials for Lithium-ion Batteries

Na2Li2Ti6O14 anode material was synthesized by a solid-state method, and the physical and electrochemical properties of the material were investigated. XRD patterns and the Rietveld refinement show that the prepared Na2Li2Ti6O14 with Fmmm space group is pure phase. SEM indicates Na2Li2Ti6O12 particle has a narrow size distribution between 500 and 800 nm. The coincidence degree of the three curves is good, indicating that the material has good reversibility of the extraction and insertion of Li+. Na2Li2Ti6O12 material has good rate capability and cycling stability. The initial delithiation (charge) capacity is 180 mAh/g at a current density of 500 mA/g, and the reversible capacity is 136 mAh/g after 100 cycles, revealing a well fast charge-discharge performance. EIS indicates that the charge transfer resistance of Na2Li2Ti6O12 material increases after 100 cycles, and the Li-ion diffusion coefficient slightly decreases, revealing that the formed solid electrolyte interphase (SEI) layer reduces the electrochemical activity of Na2Li2Ti6O12 material after cycles.