溶液pH对水热法合成钠离子电池Na3V2O2(PO4)2F正极材料结构和电化学性能的影响-中国材料进展

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Title:: Effects of the pH of Solution on the Structure and Electrochemical Performance of Na3V2O2 (PO4)2F Cathode Material for Sodium-Ion Battery Synthesized via Hydrothermal Method

作者:: 李汶交; 杨晓平; 辛亚男; 韩慧果; 段建国; 王丁; 1.昆明理工大学锂离子电池及材料制备技术国家地方联合工程研究中心，云南昆明 650093 2.攀钢集团研究院有限公司钒钛资源综合利用国家重点实验室，四川攀枝花 617000

Author(s):: Li Wenjiao; Yang Xiaoping; Xin Yanan; Han Huiguo; Duan Jianguo; Wang Ding; 1 National and local joint engineering research center of lithium-ion batteries and materials preparation technology，Kunming 650093，China 2 State Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization，Panzhihua Iron & Steel Group Research Institute Co.Ltd.Panzhihua 617000，China

Keywords:: sodium-ion batteries; cathode material; Na3V2O2(PO4)2F; hydrothermal insulation

摘要:: 以V2O5、NH4H2PO4、Na2CO3和NaF为原料，二水合草酸为还原剂，在150 ℃水热条件下，通过水热法合成了钠离子电池Na3V2O2(PO4)2F（NVPOF）正极材料，并系统研究了溶液pH对NVPOF材料储钠结构及电化学性能的影响。溶液pH影响NVPOF材料的晶体结构、形貌及粒度分布。随着溶液pH值(1.8~4.0)升高，NVPOF材料粒度逐渐增大，形貌逐渐由絮状演变成立方体状。当溶液pH值为2.0时合成的材料(NVPOF-pH2.0)的结晶度好，晶胞参数值和晶胞体积均为最小，粒度细小均匀，有利于充放电过程中Na+的输运和存储。电化学性能测试结果表明，相比于在其他pH值的溶液中合成的NVPOF材料，NVPOF-pH2.0无论是循环性能还是倍率性能都是最佳的。特别地，NVPOF-pH2.0在1C条件下经过500次循环后放电比容量为72.7 mAh·g-1，容量保持率为66.0%。

Abstract:: Adopting V2O5, NH4H2PO4, Na2CO3 and NaF as the raw materials, oxalic acid dihydrate as reducing agents, hydrothermal insulation at 150 ℃ as synthetic conditions, Na3V2O2(PO4)2F(NVPOF), has been successfully synthesized.Meanwhile, the effect of pH values of the solution on materials-sodium-storage structure and electrochemical performance is systematically studied. To be specific, the pH value generates influences on the lattice structure, morphology and particle size distribution of NVPOF. As the increasing of the pH values (1.8~4.0) of the solution, the particle sizes are increased with the morphology morphing from flocculent to cube. When the pH value of the solution reaches at 2.0, the synthesized material (NVPOF-pH2.0) possesses excellent crystallinity, minimum cell parameter value and cell volume, tiny and uniform particle size, which is conducive to the transportation and storage of Na+ during the charge/discharge process. As is shown from the results of electrochemical tests, compared with NVPOF synthesized from the other solutions with different pH values, NVPOF-pH2.0 shows the optimal cycling performances and rate performances. Particularly, even after 500 cycling periods under 1C, NVPOF-pH2.0 exhibits the discharging specific capacity at 72.7 mAh·g-1 and retention rate at 66.0%.