物理化学学报 >> 2021, Vol. 37 >> Issue (1): 2009012.doi: 10.3866/PKU.WHXB202009012

所属专题: 金属锂负极

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金属锂负极的成核机制与载体修饰

邱晓光, 刘威, 刘九鼎, 李俊志, 张凯, 程方益()   

  • 收稿日期:2020-09-02 录用日期:2020-09-23 发布日期:2020-10-09
  • 通讯作者: 程方益 E-mail:fycheng@nankai.edu.cn
  • 作者简介:程方益,南开大学杰出教授。2009年在南开大学化学学院获博士学位后留校,2009、2011、2016年分别被聘为讲师、副教授、研究员。从事能源材料、先进电池、电催化研究
  • 基金资助:
    国家重点研发计划(2017YFA0206702);国家重点研发计划(2016YFA0202500);国家自然科学基金(21925503);国家自然科学基金(21835004);中国科协青年人才托举工程项目(2019QNRC001)

Nucleation Mechanism and Substrate Modification of Lithium Metal Anode

Xiaoguang Qiu, Wei Liu, Jiuding Liu, Junzhi Li, Kai Zhang, Fangyi Cheng()   

  • Received:2020-09-02 Accepted:2020-09-23 Published:2020-10-09
  • Contact: Fangyi Cheng E-mail:fycheng@nankai.edu.cn
  • About author:Fangyi Cheng, Email: fycheng@nankai.edu.cn. Tel.: +86-22-23497716
  • Supported by:
    the Ministry of Science and Technology(2017YFA0206702);the Ministry of Science and Technology(2016YFA0202500);the National Natural Science Foundation of China(21925503);the National Natural Science Foundation of China(21835004);Young Elite Scientists Sponsorship Program by CAST(2019QNRC001)

摘要:

金属锂具有电位低、比容量高等突出优点,是极具吸引力的下一代高能量密度电池的负极材料,然而存在枝晶、死锂、副反应严重、库伦效率低、循环稳定性差等问题,限制了其实际应用。金属锂负极的成核是电化学沉积过程中的重要步骤,锂在集流体或导电载体上的均匀成核和稳定生长对于抑制枝晶死锂、提高充放电效率和循环性能具有关键作用。本文从成核机制与载体效应的角度概述了锂金属负极的研究进展,介绍了锂成核驱动力、异相成核模型、空间电荷模型等内容,分析了锂核尺寸及分布与过电位和电流密度的关系,并通过三维载体分散电流密度、异相晶核/电场诱导成核、晶格匹配等方面的研究实例讨论了载体修饰对锂负极的性能提升。

关键词: 金属锂电池, 枝晶, 成核机制, 载体改性

Abstract:

Li is highly attractive anode material for next-generation high-energy-density batteries, such as Li-air, Li-sulfur, and solid-state Li-based systems because of its exceedingly low electrode potential (-3.04 V vs the standard hydrogen electrode) and ultra-high theoretical capacity (3860 mAh-g-1). However, Li metal anodes and Li-based batteries are plagued by issues, including unstable solid electrolyte interface (SEI), dead Li formation, and uncontrollable dendritic growth. These limitations result in low cycling stability and could induce short circuits, thermal runaway, and safety hazards. In recent years, a variety of efficient strategies have been proposed to alleviate the challenges faced by Li anodes. For example, the design of Li-free anodes (with Li supplied from the lithiated cathode) or Li-composite anodes has attracted significant attention. Their population can be ascribed to the use of non-excessive Li metal that could be potentially safer and easier to produce. In Li-free and Li-composite anodes, the initial nucleation sites play a crucial role in influencing the subsequent Li electroplating behavior. Stable, homogenous Li electrodeposition is crucial for improving Coulomb efficiency and inhibiting dendrite formation. Moreover, it is also desirable to explore the nucleation and growth mechanism of Li metal on substrates or current collectors. Therefore, in this article, we aim to provide an overview of the mechanism of Li nucleation and strategies to enhance Li metal batteries via substrate modification. The mechanisms of Li nucleation are discussed in terms of nucleation-driven forces and the relation between nuclei size/distribution and overpotential/current density. Heterogeneous nucleation and Chazalviel space charge models are introduced to describe the deposition behaviors of Li in the initial nucleation stage. In the heterogeneous nucleation process, the formation of Li nuclei and its kinetics depend on the nucleation barrier, which correlates with the properties of substrates, such as their crystal structure, lattice matching, facets, and defects. The space charge model can be applied to low-concentration electrolytes or rapid Li deposition, where the decrease in ion concentration on the electrode surface induces a localized space charge and polarized electric field. This subsequently affects the microstructure and morphology of the deposited Li. After discussing the nucleation mechanism and substrate effect, strategies to stabilize nucleation and suppress dendrite are highlighted, such as three-dimensional frameworks, heterogeneous crystal nuclei, Li storage buffer layers, electric field effects, and lattice matching engineering. Information gained from the perspective of Li nucleation and the substrate effect might enlighten the development of strategies to upgrade metallic Li anodes for application in Li-based batteries.

Key words: Lithium metal battery, Dendrite, Nucleation mechanism, Framework modification

MSC2000: 

  • O646