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电化学 ›› 2021, Vol. 27 ›› Issue (1): 56-62.  doi: 10.13208/j.electrochem.191230

• 研究论文与评述 • 上一篇    下一篇

Na3V2(PO4)2O2F的合成及其在钠离子电池中的应用

吴凯*()   

  1. 宁德时代新能源科技股份有限公司,福建 宁德 352106
  • 收稿日期:2020-12-30 修回日期:2021-03-10 出版日期:2021-02-28 发布日期:2020-03-16
  • 通讯作者: 吴凯 E-mail:WuK@catlbattery.com

Syntheses of Na3V2(PO4)2O2F as a Cathode for Sodium Ion Battery Application

Kai Wu*()   

  1. Ningde Contemporary Amperex Technology Co., Ltd., Ningde 352106, Fujian, China
  • Received:2020-12-30 Revised:2021-03-10 Online:2021-02-28 Published:2020-03-16
  • Contact: Kai Wu E-mail:WuK@catlbattery.com

摘要:

目前,合成Na3V2(PO4)2O2F(NVPF)材料的方法包括高温固相法、水热法、溶剂热法等,这些方法均不利于该材料的大规模工业化生产。本文开发了温和的低温共沉淀法合成NVPF材料,该材料首次放电容量为105.6 mAh·g-1,首次效率为90.16%。经过简单的热处理过程,可以有效去除由于液相合成带来的结晶水以及吸附在材料表面的羟基,同时还可以提高材料的结晶度,使得材料的首次放电容量提高到124.3 mAh·g-1,首次效率提高到96.06%。以热处理后的NVPF材料为正极,商业化硬碳为负极组装的全电池表现出了优异的循环性能和倍率性能,1C下循环1200次后容量保持率仍有94.6%,4C倍率下的放电容量仍有基准倍率(0.33 C)的86%。该方法有助于NVPF材料的大规模工业化生产。

关键词: Na3V2(PO4)2O2F, NVPF, 共沉淀法, 电化学性能, 钠离子电池

Abstract:

High-temperature solid-state method, hydro-thermal method and solvo-thermal method have been mainly employed to synthesize Na3V2(PO4)2O2F (NVPF) cathode materials. However, these methods are energy consuming and complicated, which is not applicable for a large scale industrial production. In this study, a rather low-temperature (70℃) co-precipitation strategy was proposed to synthesize NVPF cathode materials. The as-prepared NVPF cathode materials showed a spherical shape with a diameter of 400 ~ 500 nm, and exhibited a sodium storage of 105.6 mAh·g-1 and an efficiency of 90.06%. After a simple thermal process, the specific capacity of the material increased to 124.3 mAh·g-1, and the first cycle efficiency increased to 96.06%. More specifically, a series of experiments with different heat temperatures were done and the results revealed that the best electrochemical performance of NVPF cathode material was achieved with the heat treatment of 600℃ for 2 h under argon atmosphere. Techniques including XRD, SEM, FT-IR, TG-MS, and carbon content analysis and Rietveld analysis were used in order to figure out the effect of the thermal process. The results revealed that the heat treatment could remove the crystal water that led to many side reactions and lowered the cycle efficiency, remove the adsorbed hydroxyl resulted from liquid-phase synthesis, as well as increase the crystallinity of NVPF cathode materials and coated a tinny amount of carbon on the surface of the materials through the decomposition of the remained C2O42-, thus, improving the electrochemical performance of the NVPF cathode materials. Additionally, a full cell with a capacity of 24 mAh composed of a NVPF cathode and a commercial hard carbon anode was fabricated and tested. The cell exhibited an excellent cycle and rate performance. It remained 94.6% of its initial capacity after 1200 cycles at 1 C and 86% of the reference rate (0.33 C) capacity even at 4 C. Furthermore, this method is attractive to the large-scale industrial production of NVPF cathode materials.

Key words: Na3V2(PO4)2O2F, NVPF, co-precipitation, electrochemical performance, sodium ion battery