Acta Phys. -Chim. Sin. ›› 2021, Vol. 37 ›› Issue (2): 2009001.doi: 10.3866/PKU.WHXB202009001

Special Issue: Lithium Metal Anodes

• ARTICLE • Previous Articles     Next Articles

Influence of Interfacial Concentration Polarization on Lithium Metal Electrodeposition

Yitao He1, Fei Ding2,*(), Li Lin3, Zhihong Wang1, Zhe Lü1, Yaohui Zhang1,*()   

  1. 1 School of Physics, Harbin Institute of Technology, Harbin 150001, China
    2 Science and Technology on Power Sources Laboratory, Tianjin Institute of Power Sources, Tianjin 300384, China
    3 Wuhan Institute of Marine Electric Propulsion, Wuhan 430064, China
  • Received:2020-09-01 Accepted:2020-09-30 Published:2020-10-21
  • Contact: Fei Ding,Yaohui Zhang E-mail:fding@nklps.org;hitcrazyzyh@hit.edu.cn
  • About author:Yaohui Zhang, Email: hitcrazyzyh@hit.edu.cn (Y.Z.)
    Fei Ding, Email: fding@nklps.org (F.D.)
  • Supported by:
    the Foundation of National Key Laboratory of China(6142808180202);the Pre-Research Foundation of China(61407210406);the Pre-Research Foundation of China(61407210208);the Pre-Research Foundation of China(41421080401);the Open Fund of Jiangsu Key Laboratory of Electrochemical Energy Storage Technologies(EEST2019-1)

Abstract:

As an ideal negative electrode material for next-generation high-energy-density batteries, lithium (Li) metal has received extensive attention from the global research community. However, the safety hazards and short cycle life caused by the growth of Li dendrites have seriously hampered the application of Li metal batteries. Based on electrochemical phenomena and theory, this paper discusses the mechanism of dendritic growth, dead Li formation, and full battery failure from the perspective of concentration polarization. During the electrodeposition process, the consumption of Li ions on the surface induces concentration polarization. After the initial deposition, a relatively loose dendrite layer appears on the Li metal surface; the electrolyte can penetrate this dendrite layer to reach the dense Li metal surface. When the grown dendrites penetrate the concentration polarization layer, the interface concentration battery is short-circuited. In this case, the concentration difference battery tends to release all stored power and reach a potential balance between the high- and low-concentration regions, which causes the deposition of Li ions over the dendrites to reduce the ion concentration in the surrounding electrolyte. Meanwhile, the dissolution of Li ions that occurs at the roots of the dendrites increases the local ion concentration. This process accelerates the formation of a dead Li layer. A similar electrochemical process often occurs in columnar Li, as reported in other studies. When columnar Li is cycled several times, each Li column degenerates into a matchstick shape with a large head and thin neck. Therefore, eliminating concentration polarization is necessary for the application of columnar Li. Furthermore, in this work, concentration polarization and dendrite suppression in state-of-the-art porous host electrodes are analyzed. The larger specific surface area of the porous electrode greatly reduces the local current density on the electrode surface, which can reduce the interface concentration polarization and thus prevent dendrite growth. In charge-discharge cycling, a constant-voltage charging or shelving step is often inserted in each cycle in order to eliminate the influence of concentration polarization. However, if a dendritic layer has been formed on the Li metal surface after charging, in addition to the self-diffusion of ions, the self-discharge process of the interface concentration battery causes the detachment of the dendrite layer, thus resulting in the above-mentioned dead Li. Therefore, a larger amount of deposited Li yields a thicker Li dendritic layer, thus accelerating the capacity decay and failure of the battery, especially to those with high-capacity, high-voltage positive electrodes. The conclusions obtained in this paper can provide a theoretical basis for researchers to further explore Li metal protection strategies.

Key words: Lithium metal, Concentration polarization, Dendrite suppression, Interface concentration difference battery, Porous host electrode

MSC2000: 

  • O643