储能科学与技术 ›› 2023, Vol. 12 ›› Issue (5): 1604-1615.doi: 10.19799/j.cnki.2095-4239.2023.0072

• 储能材料与器件 • 上一篇    下一篇

调控LiPF6 基电解液溶剂化结构稳定富锂锰基正极界面

胡川1(), 胡志伟2, 李振东2, 李帅1, 王豪1, 王丽平1()   

  1. 1.电子科技大学,四川 成都 611731
    2.天目湖先进储能技术研究院,江苏 常州 213300
  • 收稿日期:2023-02-14 修回日期:2023-03-12 出版日期:2023-05-05 发布日期:2023-05-29
  • 通讯作者: 王丽平 E-mail:2130388134@qq.com;lipingwang@uestc.edu.cn
  • 作者简介:胡川(1998—),男,硕士研究生,从事富锂锰基正极功能电解液研究,E-mail:2130388134@qq.com
  • 基金资助:
    四川省自然科学基金杰出青年科学基金(2023NSFSC1914)

Tailoring LiPF6-base electrolyte solvation structure toward a stable Lithium-rich manganese-based cathode interface

Chuan HU1(), Zhiwei HU2, Zhendong LI2, Shuai LI1, Hao WANG1, Liping WANG1()   

  1. 1.University of Electronic Science and Technology, Chengdu 611731, Sichuan, China
    2.Tianmu Lake Institute of Advanced Energy Storage Technologies, Changzhou 213300, Jiangsu, China
  • Received:2023-02-14 Revised:2023-03-12 Online:2023-05-05 Published:2023-05-29
  • Contact: Liping WANG E-mail:2130388134@qq.com;lipingwang@uestc.edu.cn

摘要:

富锂锰基正极材料具有高比容量和低成本的优势,有望成为下一代高能量密度金属锂电池的正极材料。然而在实际应用中,其相对于金属锂高达4.8 V的充电截止电压,会引发电解液氧化分解失效,导致正极与电解液的界面恶化使得电池难以稳定循环。为此本文开发了以1,1,2,2-四氟乙基-2,2,3,3-四氟丙基醚(TTE)充当促配位溶剂的六氟磷酸锂(LiPF6)基新型高电压电解液。实验与表征结果说明,适量TTE引入后具有更多锂盐阴离子参与锂离子配位的溶剂化结构的电解液,能够在正极表面形成5 nm厚且富含氟元素的正极电解液中间相(CEI),稳定正极界面并抑制正极层状结构的退化。使用新型电解液的富锂锰基正极对金属锂扣式电池,以99.8%的平均效率循环400次后,仍有83.9%的容量保持率(0.5 C)。组装1.25 Ah的富锂锰基正极对金属锂软包电池,在0.04 C下能够提供370 Wh/kg的质量能量密度,在0.08 C下循环45次后,仍有80%的容量保持率,表现出良好的应用前景。本研究有助于推动富锂锰基正极的应用,为高能量密度金属锂电池的研发提供实验依据。

关键词: 富锂锰基正极, 高电压, 电解液, 正极-电解液中间相, 层状结构, 金属锂软包电池

Abstract:

Li-rich Mn-based cathode has the advantages of high specific capacity and low cost, which is expected to be the cathode material for the next generation of high-energy density Li-metal batteries. However, in practical applications, its charging cutoff voltage is 4.8 V versus Li, leading to the failure of electrolyte oxygenation decompositions, thereby deteriorating the interface between the cathode and electrolyte, making stable battery cycling challenging. A novel high-voltage electrolyte based on LiPF6 is developed, in which 1, 1, 2, 2-tetrafluoroethyl-2, 2, 3, 3-tetrafluoropropylether (TTE) is used as a solvent to promote coordination. The experimental and characterization results show that many Li anions participate in the solvated structure of Li+ coordination after introducing appropriate TTE in the electrolyte, which can form a 5-nm-thick fluorine-rich cathode electrolyte interphase (CEI) on the surface of the cathode, stabilizing its interface and inhibiting the degradation of the cathode layer structure. The Li-rich Mn-based cathode Li-metal battery with the new electrolyte has an 83.9% capacity retention rate after 400 cycles with an average efficiency of 99.8% (0.5 C). The 1.25-Ah Li-rich Mn-based cathode Li-metal battery pouch cell can provide 370 Wh/kg mass-energy density at 0.04 C and still has an 80% capacity retention rate after 45 cycles at 0.08 C, showing a good application prospect. This study is helpful to promote the application of Li-rich Mn-based cathode and provide an experimental basis for the research and development of high energy density Li-metal batteries.

Key words: lithium-rich manganese-based cathode, high voltage, electrolyte solvent, cathode-electrolyte interphase, layered structure, lithium metal pouch cell

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