Acta Chim. Sinica ›› 2019, Vol. 77 ›› Issue (7): 625-633.

Article

### 钾掺杂对钒酸钠纳米片储钠性能的影响

1. a 湘潭大学化学学院 教育部环境友好化学和应用重点实验室 湘潭 411105;
b 西安理工大学先进电化学能源研究院 西安 710048;
c 湘潭大学土木与力学工程学院 湘潭 411105
• 投稿日期:2019-01-23 发布日期:2019-07-02
• 通讯作者: 李朝晖, 李喜飞 E-mail:lzh69@xtu.edu.cn;xfli2011@hotmail.com
• 基金资助:

项目受国家自然科学基金（Nos.51572194，51672189）和湖南省自然科学基金（Nos.2018JJ2386，2018JJ2393）资助.

### Effect of K-Doping on the Sodium-storage Performance of Sodium Vanadate Nanoplates

Song Xuexia,b, Li Jichenga, Li Zhaohuia, Li Xifeib, Ding Yanhuaic, Xiao Qizhena, Lei Gangtiea

1. a Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education, College of Chemistry, Xiangtan University, Xiangtan 411105;
b Institute of Advanced Electrochemical Energy, Xi'an University of Technology, Xi'an 710048;
c College of Civil Engineering and Mechanics, Xiangtan University, Xiangtan 411105
• Received:2019-01-23 Published:2019-07-02
• Supported by:

Project supported by the National Natural Science Foundation of China (Nos. 51572194, 51672189), and the Hunan Provincial Natural Science Foundation (Nos. 2018JJ2386, 2018JJ2393).

Na-ion batteries with lower cost than Li-ion batteries would be developed to large-scale energy-storage device to store solar and wind energies. However, large radius renders Na+ ions to insert into/extract out the layered transition metal oxides (LTMOs) sluggishly. To improve the intercalation dynamics of Na+ ions, the interlayer spacing of crystals has to be expanded for those LTMOs that are capable of fast lithiation and delithiation. Herein, a LTMO based on vanadium is firstly doped with larger K+ ions to expand the interlayer spacing to yield K+-doped sodium vanadate (Na5KxV12O32) cathode material by a hydrothermal method at 200℃ for 24 h followed by calcination at 500℃ for 3 h. The samples were characterized by scanning electron microscope (SEM)/transmission electron microscope (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) technologies. Effect of the doping amount of K+ on the structure and sodium-storage performance of the sample was studied in detail. The synthesized materials display nanoplate morphology viewing from the TEM images. K+ ions are doped into the interlayer of the sodium vanadate crystallites, which is proved by analysis of the XRD patterns and XPS spectra. Expanded interlayer spacing favors Na+ ions' intercalation and deintercalation between the[V3O8]- layers, which is testified by the chemical diffusion coefficient of cathodes, thus enhancing the rate capability. On the other hand, the chemically pre-intercalated K+ ions are pinned in the crystallites during insertion and extraction of Na+ ions and act as pillars to stabilize the layered structure, improving the cycliability of the cathode. However, excessive doping of K+ leads to a discounted rate capability of the cathode, suggesting an optimized amount of K+ doping into the crystal. The results from galvanostatic charge-discharge tests indicate that the obtained NVO(3K) sample, in which 0.118 mol of K+ ions are doped into per mol of Na5V12O32, presents the best electrochemical performance among the various samples. It can deliver the maximum capacities of 169, 160, 148, 132, 98 and 69 mAh·g-1 at the rates of 0.1C, 0.2C, 0.5C, 1C, 3C and 10C after activated for several times over the voltage window of 4.0~1.5 V (vs. Na+/Na), respectively. Even run at 3C rate, it can retain 93.0% of the maximum capacity after 1000 cycles, exhibiting excellent rate capability and stable cycliability. The results suggest that doping of K+ ions into the interlayer of crystallites can significantly improving the rate capability as well as cycling performance of the obtained Na5V12O32. Our investigation demonstrates that design of K+-doped sodium vanadate cathode materials is beneficial for harvesting superior performance, of which the Na5K0.118V12O32 nanoplates can be developed into a novel cathode material for sodium-ion batteries in the future.