物理化学学报 >> 2021, Vol. 37 >> Issue (1): 2008081.doi: 10.3866/PKU.WHXB202008081

所属专题: 金属锂负极

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锂金属负极的可逆性与沉积形貌的关联

黄凡洋, 揭育林, 李新鹏, 陈亚威, 曹瑞国, 章根强, 焦淑红()   

  • 收稿日期:2020-08-27 录用日期:2020-09-28 发布日期:2020-10-19
  • 通讯作者: 焦淑红 E-mail:jiaosh@ustc.edu.cn
  • 作者简介:第一联系人:

    These authors contribute equally to this work.

  • 基金资助:
    国家重点研发计划(2017YFA0402802);国家重点研发计划(2017YFA0206700);国家自然科学基金(51902304);国家自然科学基金(21776265);安徽省自然科学基金(1908085ME122);中央高校基本科研基金(Wk2060140026)

Correlation between Li Plating Morphology and Reversibility of Li Metal Anode

Fanyang Huang, Yulin Jie, Xinpeng Li, Yawei Chen, Ruiguo Cao, Genqiang Zhang, Shuhong Jiao()   

  • Received:2020-08-27 Accepted:2020-09-28 Published:2020-10-19
  • Contact: Shuhong Jiao E-mail:jiaosh@ustc.edu.cn
  • About author:Jiao Shuhong. E-mail:jiaosh@ustc.edu.cn; Tel.: +86-551-63601807
  • Supported by:
    the National Key Research and Development Program of China(2017YFA0402802);the National Key Research and Development Program of China(2017YFA0206700);the National Natural Science Foundation of China(51902304);the National Natural Science Foundation of China(21776265);the Anhui Provincial Natural Science Foundation(1908085ME122);the Fundamental Research Funds for the Central Universities, China(Wk2060140026)

摘要:

高能量密度二次电池的商业化将会推动便携式电子设备和电动车的飞速发展。锂金属电池因具有较高的理论能量密度而受到研究者的广泛关注。然而,锂金属负极较低的库仑效率(CE)和枝晶生长等问题,严重制约了锂金属电池的发展。库仑效率是衡量电池体系可逆性的关键参数之一,锂金属负极的库仑效率在不同电解液中存在较大的差异,本文以四种常见的电解液为例,包括1 mol·L-1六氟磷酸锂-碳酸乙烯酯/碳酸二甲酯电解液,1 mol·L-1六氟磷酸锂-碳酸乙烯酯/碳酸二甲酯+ 5% (w)氟代碳酸乙烯酯电解液,1 mol·L-1双(三氟甲烷磺酰)亚胺锂-乙二醇二甲醚/1, 3二氧戊环+ 2% (w)硝酸锂电解液,以及4 mol·L-1双氟磺酰亚胺锂-乙二醇二甲醚电解液,利用原子力显微镜研究了不同电解液体系中锂金属的生长行为,探讨了锂金属沉积形貌与其库仑效率之间的联系,为发展高效的锂金属负极提供了参考依据。

关键词: 锂金属负极, 库仑效率, 沉积形貌, 电解液, 原子力显微镜

Abstract:

Commercialization of high-energy rechargeable batteries can promote the rapid development of portable electronics and electric vehicles. Li metal batteries (LMBs) have attracted considerable attention owing to their high theoretical energy density. Li metal anodes (LMAs) used in LMBs suffer from the disadvantages of high reactivity, interface instability and dendrite growth, which impede the practical development of the LMBs. Coulombic efficiency (CE), which depends on the type of electrolyte used, is one of the key parameters for evaluating the reversibility of battery systems. Herein, we use atomic force microscopy (AFM) to study the initial plating stages and growth of the lithium metal in different electrolytes, such as 1 mol·L-1 lithium hexafluorophosphate (LiPF6)-ethylene carbonate/dimethyl carbonate (EC/DMC, 1 : 1, V/V), 1 mol·L-1 LiPF6-EC/DMC (1 : 1, V/V) + 5% (mass fraction, w) fluoroethylene carbonate (FEC), 1 mol·L-1 lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)-1, 3-dioxolane/dimethoxyethane (DOL/DME, 1 : 1, V/V) + 2% (w) lithium nitrate (LiNO3), and 4 mol·L-1 lithium bis(fluorosulfonyl)imide (LiFSI)-DME, and further investigate the correlation between the CE of LMA and Li plating morphology. There are two types of Li morphologies in these electrolytes: strip-like and particle-like morphology. Since the specific surface area of particle-like deposits is much smaller than that of strip-like deposits, the particle-like morphology facilitates higher CE. (1) In the conventional carbonate electrolyte (1 mol·L-1 LiPF6-EC/DMC), Li predominantly forms strip-like deposits with large specific surface area, consuming much active Li (due to the side reaction between Li and the electrolyte). The dendrite morphology of the Li deposits lead to the formation of dead Li during the stripping process, which results in low CE. (2) FEC, an effective additive often used in carbonate electrolyte, can induce the transformation of Li plating morphology from strip-like to particle-like morphology. Therefore, the CE in FEC-containing electrolytes has been significantly improved with stable electrode/electrolyte interphase and small specific surface area of deposited Li. (3) In ether electrolytes, which have better compatibility with LMAs than carbonate electrolytes, Li metal exhibits a particle-like morphology and achieves high CE. (4) In the highly concentrated electrolyte (4 mol·L-1 LiFSI-DME), Li metal grows into large particles without dendrite formation, which hampers the parasitic side reactions, and further enhances CE.

Key words: Li metal anode, Coulombic efficiency, Plating morphology, Electrolyte, Atomic force microscopy

MSC2000: 

  • O646