物理化学学报 >> 2021, Vol. 37 >> Issue (2): 2008044.doi: 10.3866/PKU.WHXB202008044

所属专题: 金属锂负极

综述 上一篇    下一篇

锂金属电池用高浓度电解液体系研究进展

吴晨, 周颖, 朱晓龙, 詹忞之, 杨汉西, 钱江锋()   

  • 收稿日期:2020-08-16 录用日期:2020-09-10 发布日期:2020-09-16
  • 通讯作者: 钱江锋 E-mail:jfqian@whu.edu.cn
  • 作者简介:钱江锋,副教授,武汉大学珞珈青年学者,物理化学学报青年编委,2019年度爱思唯尔中国高被引学者(能源领域)。主要从事锂离子电池预锂化技术、金属锂负极枝晶抑制策略、以及储钠电极材料结构设计等方面研究
  • 基金资助:
    国家自然科学基金(21773177);中央高校基本科研基金(2042020gf0007)

Research Progress on High Concentration Electrolytes for Li Metal Batteries

Chen Wu, Ying Zhou, Xiaolong Zhu, Minzhi Zhan, Hanxi Yang, Jiangfeng Qian()   

  • Received:2020-08-16 Accepted:2020-09-10 Published:2020-09-16
  • Contact: Jiangfeng Qian E-mail:jfqian@whu.edu.cn
  • About author:Jiangfeng Qian, Email: jfqian@whu.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(21773177);the Fundamental Research Funds for the Central Universities, China(2042020gf0007)

摘要:

锂金属二次电池具有极高的能量密度,是下一代储能电池的研究热点。然而,金属锂负极在传统碳酸酯电解液1 mol·L-1 LiPF6-EC/DEC (ethylene carbonate/diethyl carbonate)中充放电时,存在严重的枝晶生长和循环效率低下等问题,阻碍了其商业化应用。因此,开发与锂负极兼容的新型电解液体系是目前重要的研究任务。与传统稀溶液相比,高浓度电解液体系具有独有的物化性质和优异的界面相容性,并且能有效抑制锂枝晶生长、显著提升锂负极的循环可逆性,因而格外受到关注。本文综述了高浓度电解液及局部高浓电解液体系的最新研究进展,分析了其溶液化学结构和物化性质,对其与锂负极的界面相容性、枝晶抑制效果、效率提升能力及界面稳定性机制进行了探讨;文章着重介绍了高浓与局部高浓电解液体系在锂金属二次电池中的应用,同时从基础科学研究和应用研究两个层面对高浓电解液和局部高浓电解液存在的主要问题进行了简要分析,并对其未来发展方向进行了展望。

关键词: 锂金属电池, 高浓度电解液, 局部高浓电解液, 电解液溶剂化结构, 界面性质

Abstract:

Improvement in the energy density of conventional lithium-ion batteries (LIBs), based on the intercalation-extraction chemistry of graphite and transition metal layered oxides, has apparently lagged behind the advances in consumer electronics and electric vehicles. Secondary Li-metal batteries (LMBs), utilizing metallic Li as the anode material, have incomparable advantages in terms of energy density due to their high specific capacity (3860 mAh·g-1) and low redox potential (-3.04 V vs. standard hydrogen electrode) of Li metal. Irrespective of whether Li anodes are coupled with intercalation-type cathodes (e.g. LiFePO4, LiCoO2, LiNixCoyMnzO2, etc.) or conversion-type cathodes (S, O2), the energy density of LMBs is much higher than that of traditional LIBs, which should solve the range concern of electric vehicles. However, the intrinsically high reactivity between metallic Li and organic electrolytes could induce the formation of a solid electrolyte interface (SEI). The heterogeneous SEI, consisting of a flexible organic outer layer and a brittle inorganic inner layer, suffers from repeated rupture and regeneration due to infinite volume expansions associated with Li deposition and dissolution reactions. Meanwhile, Li is preferentially deposited on the "hot sites" and is stripped from the root of sediments, resulting in uncontrolled dendrite growth during charging and formation of electrochemically isolated Li ("dead" Li) during discharging. Thus, the Columbic efficiency of Li metal full cells is greatly limited by interfacial side effects and continuous loss of active Li, especially in conventional carbonate-based electrolyte, viz. 1 mol·L-1 LiPF6-EC/DEC (ethylene carbonate/diethyl carbonate), which impedes the large-scale employment of Li metal batteries. Recently, novel electrolytes with high or localized-high salt concentrations have attracted considerable attention because of their unique physiochemical properties and excellent electrochemical performance. In high-concentration electrolytes, the reduction in the population of free solvent molecules inhibits irreversible electrolyte decomposition at the electrode-electrolyte interface. In localized-high-concentration electrolytes, the introduction of a dilute reagent retains the desired solvation structure, while improving the physicochemical properties (conductivity and viscosity) of the electrolyte. Herein, we systemically review the latest progress in high-concentration and localized-high-concentration electrolytes for use in Li metal batteries. The solvation chemistry structure, physicochemical properties, and interfacial-stabilizing mechanisms are analyzed in detail, and special attention is devoted to their superior interfacial compatibility with Li metal anodes. Finally, we briefly clarify the current problems associated with the research of high-concentration and localized-high-concentration electrolytes from the viewpoints of basic scientific research and practical applications, and some possible solutions are provided to further pave the way to practical Li metal batteries.

Key words: Li metal battery, High concentration electrolyte, Localized high concentration electrolyte, Electrolyte solvation structure, Interfacial property

MSC2000: 

  • O646