物理化学学报

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ZrO2包覆高镍LiNi0.8Co0.1Mn0.1O2正极材料提高其循环稳定性的作用机理

苏岳锋1,2, 张其雨1,2, 陈来1,2, 包丽颖1, 卢赟1,2, 陈实1, 吴锋1,2   

  1. 1 北京理工大学材料学院, 环境科学与工程北京市重点实验室, 北京 100081;
    2 北京理工大学重庆创新中心, 重庆 401120
  • 收稿日期:2020-05-25 修回日期:2020-06-02 录用日期:2020-06-08 发布日期:2020-06-12
  • 通讯作者: 陈来, 吴锋 E-mail:chenlai144@sina.com;wufeng863@vip.sina.com
  • 基金资助:
    国家重点研发项目(2016YFB0100301), 国家自然科学基金(21875022, 51802020, U1664255), 北京理工大学重庆创新中心科技创新计划项目(2020CX5100006), 北京理工大学“青年教师学术启动计划”项目和中国科学技术协会青年人才托举计划(2018QNRC001)资助

Effects of ZrO2 Coating on Ni-rich LiNi0.8Co0.1Mn0.1O2 Cathodes with Enhanced Cycle Stabilities

Yuefeng Su1,2, Qiyu Zhang1,2, Lai Chen1,2, Liying Bao1, Yun Lu1,2, Shi Chen1, Feng Wu1,2   

  1. 1 School of Materials Science and Engineering, Beijing Key Laboratory of Environmental Science and Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China;
    2 Beijing Institute of Technology Chongqing Innovation Center, Chongqing 401120, P. R. China
  • Received:2020-05-25 Revised:2020-06-02 Accepted:2020-06-08 Published:2020-06-12
  • Supported by:
    The project was supported by the National Key R&D Program of China (2016YFB0100301), the National Natural Science Foundation of China (21875022, 51802020, U1664255), the Science and Technology Innovation Foundation of Beijing Institute of Technology Chongqing Innovation Center, China (2020CX5100006), the Beijing Institute of Technology Research Fund Program for Young Scholars, and the Young Elite Scientists Sponsorship Program by CAST, China (2018QNRC001).

摘要: 高镍三元材料作为一种锂离子电池正极材料,因其较高的放电比容量而得到科学界和工业界的广泛关注。研究表明,高镍三元材料的比容量与材料中的Ni含量呈正相关,但Ni含量的增加也会加剧循环过程中的界面副反应,材料表面释氧以及结构转变等问题。本文采用ZrO2包覆LiNi0.8Co0.1Mn0.1O2材料,利用X射线衍射证明,在高温处理下ZrO2包覆物中的Zr4+会掺杂进LiNi0.8Co0.1Mn0.1O2材料表面晶格中,使得X射线衍射谱中的(003)衍射峰左移。电化学测试证明在4.3和4.5 V的截止电压下,改性最优的材料在1C循环100周后容量保持率分别从84.89%和75.60%提高到97.61%和81.37%,同时发现循环稳定性的提升主要来自材料表面的Zr4+掺杂。X射线光电子能谱证明Zr4+表层掺杂后材料的Ni化合价由Ni3+向Ni2+转变,透射电子显微镜观察到Zr4+的表层掺杂使得材料表面的层状结构发生重构,从而稳定了材料体相结构,提高了材料整体的循环稳定性。

关键词: 锂离子电池, LiNi0.8Co0.1Mn0.1O2, 正极材料, ZrO2包覆, Zr4+掺杂, 表层结构重构

Abstract: With the development of electric vehicles (EVs) and hybrid electric vehicles (HEVs), the demand for lithium ion power batteries with high energy density and long cycle life has continuously increased in the recent years. According to the “Made in China 2025” plan, the energy densities of lithium ion batteries need to reach 300 Wh·kg-1 in 2020. Due to their high discharge capacities and work voltages, Ni-rich layered materials have attracted considerable attention from the science and industry fields as one of the most promising cathodes to achieve high energy density. According to previous reports, the discharge capacities of Ni-rich cathodes were positively correlated to their Ni content. However, the increased Ni content can aggravate the side reactions between the cathode and electrolyte, induce O loss, and trigger structural transformation from the surface to bulk. In this study, ZrO2 was coated on LiNi0.8Co0.1Mn0.1O2 with a simple wet chemical method to improve its cycle performance. The scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) demonstrated that Zr was only detected in the ZrO2-coated samples and was mainly distributed at the surface of the secondary particles of the LiNi0.8Co0.1Mn0.1O2 cathodes. The X-ray diffraction (XRD) indicated that Zr4+ in ZrO2 migrated into the layered surface structure of LiNi0.8Co0.1Mn0.1O2 based on the shift of the (003) peak to a lower angle, which was considered as a lattice expansion along the c axis. Under the cut-off voltage of 4.3 and 4.5 V, the capacity retentions of the LiNi0.8Co0.1Mn0.1O2 cathodes improved from 84.89 to 97.61% and 75.60 to 81.37%, respectively, after 100 cycles at 1C. This was mainly attributed to the doped Zr4+ in surface structure as opposed to the ZrO2 coating. The X-ray photoelectron spectroscopy (XPS) indicated that the Ni3+ at the surface of LiNi0.8Co0.1Mn0.1O2 was reduced to Ni2+ after the Zr4+ surface doping due to charge balance. Rietveld refinement also indicated that the Li+/Ni2+ cation disordering improved after the Zr4+ in ZrO2 doped into NCM surface structure. The raised cation disordering may be triggered by the increased content of Ni2+ and their migration into Li layers due to the similar ion radius of Li+ (0.076 nm) and Ni2+ (0.069 nm). A structure-reconstructed layer at the surface of LiNi0.8Co0.1Mn0.1O2 was formed after the Zr4+ doping, which had been confirmed by transmission electron microscope (TEM). It was determined that this structure-reconstructed layer can hinder the side reactions at the interface and stabilize the bulk structure during cycles; thus, the cycle stability of LiNi0.8Co0.1Mn0.1O2 material was improved.

Key words: Lithium ion battery, LiNi0.8Co0.1Mn0.1O2, Cathode material, ZrO2 coating, Zr4+ doping, Surface structural reconstruction

MSC2000: 

  • O646