物理化学学报 >> 2021, Vol. 37 >> Issue (1): 2007016.doi: 10.3866/PKU.WHXB202007016

所属专题： 金属锂负极

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一种有助于稳定锂金属循环的富氟化位点框架结构

王木钦1,2, 彭哲2,*(), 林欢1,2, 李振东2, 刘健1,2, 任重民1,2, 何海勇2,*(), 王德宇1,2,3,*()   

  1. 1 江汉大学，光电化学材料与器件教育部重点实验室，武汉 430056
    2 中国科学院宁波材料技术与工程研究所，浙江 宁波 315201
    3 天目湖先进储能技术研究院，江苏 溧阳 213300
  • 收稿日期:2020-07-06 录用日期:2020-07-29 发布日期:2020-07-31
  • 通讯作者: 彭哲,何海勇,王德宇 E-mail:pengzhe@nimte.ac.cn;hehaiyong@nimte.ac.cn;wangdeyu@aesit.com.cn
  • 基金资助:
    国家自然科学基金(51872304);宁波市2025计划(2018B10061);宁波市2025计划(2019B10044);国家重点研发计划(2018YFB0905400)

A Framework with Enriched Fluorinated Sites for Stable Li Metal Cycling

Muqin Wang1,2, Zhe Peng2,*(), Huan Lin1,2, Zhendong Li2, Jian Liu1,2, Zhongmin Ren1,2, Haiyong He2,*(), Deyu Wang1,2,3,*()   

  1. 1 Key Laboratory of Optoelectronic Chemical Materials and Devices of Ministry of Education, Jianghan University, Wuhan 430056, China
    2 Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, Zhejiang Province, China
    3 Tianmu Lake Institute of Advanced Energy Storage Technologies, Liyang 213300, Jiangsu Province, China
  • Received:2020-07-06 Accepted:2020-07-29 Published:2020-07-31
  • Contact: Zhe Peng,Haiyong He,Deyu Wang E-mail:pengzhe@nimte.ac.cn;hehaiyong@nimte.ac.cn;wangdeyu@aesit.com.cn
  • About author:Wang Deyu, Email:wangdeyu@aesit.com.cn
    He Haiyong, Email:hehaiyong@nimte.ac.cn
    Peng Zhe, Email: pengzhe@nimte.ac.cn
  • Supported by:
    the National Natural Science Foundation of China(51872304);Ningbo 2025 Project, China(2018B10061);Ningbo 2025 Project, China(2019B10044);the National Key R & D Program of China(2018YFB0905400)

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摘要：

锂金属是下一代高能量密度二次电池的理想负极材料，然而它的应用仍然受制于较差的循环稳定性。近期，二维氟化界面被广泛用于改善锂金属负极的成核机制、沉积形貌和循环稳定性。本工作通过将体积缩小化的氟化石墨颗粒与锂离子传导网络结合，获得了一种富氟化位点的三维框架结构。实验结果证明此类三维氟化结构可显著提升锂金属负极在不同电流密度和容量下的循环稳定性，且优于二维氟化界面结构。通过本工作的研究，证明了相较于单纯的二维氟化界面，三维锂离子传导网络和富氟化位点的合理结合可以成为一种改进的界面结构用于锂金属负极保护，为高能量密度锂金属电池的负极保护提供了新的设计思路。

关键词: 锂金属电池, 锂金属负极, 氟化石墨, 固液界面, 库伦效率

Abstract:

In past decades, lithium-ion batteries (LIBs) were the dominant energy storage systems for powering portable electronic devices because of their reliable cyclability. However, further increase in the energy density of LIBs was met by a bottleneck when low-specific- capacity graphite was used at the anode. Li metal has long been regarded as the ideal anode material for building the next high-energy-density batteries due to its ultrahigh capacity of 3860 mAh·g-1, which is ten times higher than that of graphite. However, using Li metal as an anode in rechargeable batteries is challenging due to its high uncontrolled volume expansion and aggressive side reactions with liquid electrolytes. In this study, we demonstrate the effect of a three-dimensional (3D) framework with enriched fluorinated sites for Li metal protection. This framework is obtained via a facile integration of down-sized fluorinated graphite (CFx) particles into Li+ conducting channels. Thermogravimetry, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy results show that Li+ conducting channels rich in lithium fluoride (LiF) are formed in situ across the embedded CFx particles during the initial lithiation process, leading to fast Li+ transfer. Scanning electron microscopy results show that residual CFx particles could act as high-quality nucleation sites for uniform Li deposition inside the framework. These features could not be achieved with a 2D structure consisting of large CFx flakes, due to the limited Li+ transfer paths and low utilization ratio of CFx for conversion into LiF-based solid electrolyte interphase (SEI) layers. Consequently, better performance of Li metal anodes in a 3D framework with enriched fluorinated sites is demonstrated. Stable Li plating/stripping over 240 cycles is obtained at a current density of 0.5 mA·cm-2 for a fixed capacity of 1 mAh·cm-2 by maintaining a voltage hysteresis below 80 mV. Improved Li-LiFePO4 full cell performance with a practical negative/positive capacity ratio of 3 is also demonstrated. These results show the rational combination of well-developed 3D Li+ transfer channels and enriched fluorinated sites as an optimized interfacial design beyond the single use of a 2D fluorinated interface, giving new insight into the protection of Li metal anodes in high-energy-density batteries.

Key words: Li metal battery, Li metal anode, Fluorinated graphite, Solid electrolyte interphase, Coulombic efficiency