锂离子电池Na_2Li_2Ti_6O_(14)负极材料的合成与电化学性能

Electrochemical Performance and Synthesis of Lithium-ion Battery Na_2Li_2Ti_6O_(14) Anode Material

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。

A new type of negative electrode material,Na2Li2Ti6O14,was successfully synthesized by high temperature solid-state method,and its structure and electrochemical properties were studied.HRTEM,XRD and Rietveld refinement indicated that the synthesized Na2Li2Ti6O14 anode material was pure phase with Fmmm space group structure; SEM showed that Na2Li2Ti6O14 particles had a particle size of about 500 —800 nm; EDS mapping showed that Na,Ti and O were the three elements evenly distributed. The CV test of Na2Li2Ti6O14 material shows that the material has better reversibility of lithium ion deintercalation. Na2Li2Ti6O14 material has better rate performance and cycle stability. When the current density is 500 m A/g,the first delithiation（ charge） capacity of Na2Li2Ti6O14 material is180 m A·h/g,and the reversible capacity is 136 m A · h/g after 100 cycles,demonstrating a good rapid charge-discharge performance. The EIS test showed that after 100 cycles,the charge transfer resistance of Na2Li2Ti6O14 material increased, and the lithium ion diffusion coefficient decreased slightly,indicating that the formation of SEI film of Na2Li2Ti6O14 material reduces the electrochemical activity of the material.