储能科学与技术 ›› 2020, Vol. 9 ›› Issue (6): 1702-1713.doi: 10.19799/j.cnki.2095-4239.2020.0149

• 储能材料与器件 • 上一篇    下一篇

助熔剂法制备单晶LiNi0.8Co0.1Mn0.1O2正极材料

任思佳1,2(), 田雷武1,2, 邵钦君1,2, 陈剑1()   

  1. 1.中国科学院大连化学物理研究所，辽宁 大连 116023
    2.中国科学院大学，北京 100049
  • 收稿日期:2020-04-19 修回日期:2020-04-27 出版日期:2020-11-05 发布日期:2020-10-28
  • 通讯作者: 陈剑 E-mail:rensijia@dicp.ac.cn;chenjian@dicp.ac.cn
  • 作者简介:任思佳(1995—)，女，硕士研究生，主要研究方向为锂离子电池正极材料，E-mail：rensijia@dicp.ac.cn；
  • 基金资助:
    大连化物所与青岛能源所两所融合基金项目(DICP&QIBE-BTUN201702)

Synthesis of single-crystal LiNi0.8Co0.1Mn0.1O2 by flux method

Sijia REN1,2(), Leiwu TIAN1,2, Qinjun SHAO1,2, Jian CHEN1()   

  1. 1.Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China
    2.University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2020-04-19 Revised:2020-04-27 Online:2020-11-05 Published:2020-10-28
  • Contact: Jian CHEN E-mail:rensijia@dicp.ac.cn;chenjian@dicp.ac.cn

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摘要：

高镍三元材料LiNi0.8Co0.1Mn0.1O2(NCM811)具有比容量高、成本较低和安全性较高等优点，已成为新一代高能量密度锂离子电池的首选正极材料之一。但材料晶胞在充电和放电过程中发生收缩和膨胀，导致多晶态的NCM811由于晶间应力而产生微裂纹，材料的循环寿命尚不理想。与多晶态的三元材料相比，单晶三元材料具有更优的力学性能、热稳定性和循环稳定性。本文优选了低熔点混合助熔剂LiNO3-LiOH，并将其应用于合成单晶NCM811材料，借助X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和电化学测试等方法，研究了助熔剂用量和烧结温度对产物NCM811材料的结构、形貌、电化学性能的影响，并通过掺杂Mg元素对材料进行进一步的改性。结果表明，助熔剂在“助熔剂-前体”混合物中的摩尔分数为90%、烧结温度为800 °C时，制备的单晶NCM811材料的粒径为1～2 μm，结晶性良好，且具有优异的电化学性能和循环稳定性。Mg元素掺杂的单晶NCM811材料的循环稳定性得到进一步提高，以1 C倍率进行充放电，经过100次循环后的放电比容量为165.4 mA·h/g，容量保持率为97.7%。而采用商品前体制备的多晶态的NCM811材料，以1 C倍率进行充放电，循环100次后的放电比容量为132.9 mA·h/g，容量保持率为75.0%。表明单晶NCM811材料的循环稳定性和电化学性能均明显优于多晶态的NCM811材料。

关键词: 单晶高镍三元材料, 助熔剂合成法, 元素掺杂, 锂离子电池

Abstract:

The nickel-rich ternary material LiNi0.8Co0.1Mn0.1O2 (NCM811) is one of the cathode material candidates for new-generation high-energy density lithium-ion batteries due to its advantages of high specific capacity, low cost, and high safety. However, the inter-granular fracture cannot be avoided in polycrystalline NCM811 materials due to the contraction and expansion of the lattice volume during the charge and discharge processes, which causes an unsatisfied cycling life of the materials. Compared to polycrystalline materials, single-crystal materials have better mechanical property and thermal and cycle stabilities. In this work, the LiNO3-LiOH mixed flux with a low-melting point is applied to prepare the single-crystal LiNi0.8Co0.1Mn0.1O2 (NCM811) material. The influence of the synthesis conditions on the structure, morphology, and electrochemical performances of the final products (e.g., flux dosage) and the sintering temperature are systematically investigated through X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and electrochemical measurements. The results show that the molar ratio of flux in the mixture of the precursors and the flux is optimized to be 90 mol%, and the optimized sintering temperature is 800 °C. The as-prepared NCM811 material measuring 1-2 μm exhibits an excellent electrochemical performance. Furthermore, the Mg-doped single-crystal NCM 811 material achieves a large discharge specific capacity of 165.4 mA·h/g and a capacity retention of 97.7% after 100 cycles at 1 °C. For comparison, the discharge specific capacity of the polycrystalline NCM811 material synthesized from the commodity precursors is only 132.9 mA·h/g, and the capacity retention is 75.0% after 100 cycles at 1 °C. In conclusion, the electrochemical performance and the cycling capability of the single-crystal NCM811 material are superior to those of the polycrystalline NCM811 material.

Key words: single crystal nickel-rich ternary material, flux method, element doping, lithium-ion batteries

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