储能科学与技术 ›› 2022, Vol. 11 ›› Issue (9): 2989-2994.doi: 10.19799/j.cnki.2095-4239.2022.0194

• 创刊十周年专刊 • 上一篇    下一篇

锂离子电池硅基负极循环过程中的膨胀应力

牛少军1,2(), 吴凯2, 朱国斌1, 王艳1, 曲群婷1, 郑洪河1,3()   

  1. 1.苏州大学能源学院，苏州纳米科技协同创新中心，江苏 苏州 215006
    2.宁德时代新能源科技股份有限公司，福建 宁德 352100
    3.苏州华赢新能源材料科技有限公司，江苏 苏州 215000
  • 收稿日期:2022-04-07 修回日期:2022-04-15 出版日期:2022-09-05 发布日期:2022-08-30
  • 通讯作者: 郑洪河 E-mail:niushj@catl.com;hhzheng@suda.edu.cn
  • 作者简介:牛少军（1981—），男，博士研究生，研究方向为锂离子电池关键材料与技术，E-mail：niushj@catl.com；
  • 基金资助:
    国家重点研发计划(2016YFB0100400);国家自然科学基金项目(21875154)

Studies on the swelling force during cycling of Si-based anodes in lithium ion batteries

Shaojun NIU1,2(), Kai WU2, Guobin ZHU1, Yan WANG1, Qunting QU1, Honghe ZHENG1,3()   

  1. 1.College of Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006, Jiangsu, China
    2.Contemporary Amperex Technology Limited, Ningde 352100, Fujian, China
    3.Highwin New Energy Materials Co. , Suzhou 215000, Jiangsu, China
  • Received:2022-04-07 Revised:2022-04-15 Online:2022-09-05 Published:2022-08-30
  • Contact: Honghe ZHENG E-mail:niushj@catl.com;hhzheng@suda.edu.cn

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摘要：

研究硅基负极在充放电及循环过程中的膨胀对开发下一代高比能锂离子动力电池具有重要意义。本工作采用商业化的SiO x /Graphite为负极匹配高比能镍钴锰酸锂［Li(Ni0.8Mn0.1Co0.1)O2，NCM811］正极，组装了60 Ah大软包电池，并对其进行循环膨胀应力、应力增长机理与膨胀应力的改善等方面的研究。结果表明SiO x 材料的构成为3～5 nm Si颗粒分散在无定形的SiO2内部，首次充放电比容量为1840.9/1380 mAh/g，库仑效率为75%。大软包电池单次充放电膨胀应力的变化为7320 N，约为石墨负极的4倍。工作温度越高容量衰减越快，衰减到70% SOH时，25、45和60 ℃对应的循环次数分别为980、850和500次，对应的最大膨胀应力分别为25107、25490、23667 N。此外，机理分析发现电池循环膨胀应力的增长和容量衰减之间为线性相关，CP(cross section polisher)-SEM分析发现膨胀应力的增加主要来自于SiO x 颗粒表面的破裂及副反应导致的SEI (solid electrolyte interphase)增厚。通过测定缓冲垫压缩曲线的方法筛选了合适的聚氨酯类缓冲垫，验证对循环无影响，但可以显著改善膨胀应力的增加，膨胀应力降低50%，这些结果将为更好地应用高比容量的硅基负极材料奠定基础。

关键词: 锂离子电池, 硅基负极, 膨胀应力, 聚氨酯缓冲垫

Abstract:

Studying the swelling force of Si-based anodes for the next generation of high energy lithium-ion batteries is crucial. In this study, we assembled 60-Ah large pouch batteries with commercialized SiO x /Graphite and NCM811 cathode, tested their cycle life and swelling force increase, and studied the relevant mechanisms and strategies for reducing the swelling force. The structure of SiO x was a 3～5 nm Si core distributed in amorphous SiO2, and the specific capacity of SiO x in the first cycle was 1380 mAh/g and the first columbic efficiency was ca. 75%. The swelling force increase during the first cycle was 7320 N, which was 4 times higher than that of graphite-based batteries. The cycling tests under different ambient temperatures showed high temperature-dependent tendency. At 25 ℃, 45 ℃, and 60 ℃, the cycle numbers were 980, 850, and 500, corresponding to 70% SOH, with the maximum swelling force being 25107, 25490, and 23667 N, respectively. The root cause for the swelling force increase was the solid electrolyte interface growth and thickening with repeated electrochemical cycles. The compression curve was applied to sorting appropriate cushion that can accommodate the swelling force. The results showed that polyurethane cushion had the best compression properties, reducing the swelling force by 50%. This study provides a foundation for using SiO x in large-scale lithium-ion batteries.

Key words: lithium-ion batteries, SiO x /graphite anode, swelling force, polyurethane cushion

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