Controlling the Phase Separation of Dimethyl Carbonate Solvents Using a Dual-Cation System: Applications in High-Power Lithium Ion-Based Hybrid Capacitors
Controlling the Phase Separation of Dimethyl Carbonate Solvents Using a Dual-Cation System: Applications in High-Power Lithium Ion-Based Hybrid Capacitors
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DOI：
10.1021/acs.jpcc.2c03004
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发表时间：
2022-08
期刊：
影响因子：
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通讯作者：
Y. Chikaoka;Riko Ochi;K. Fujii;Takaaki Ariga;Masatoki Sakurai;Ayuna Matsumoto;Tsukasa Ueda;Etsuro Iwama;K. Naoi
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文献类型：
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作者：
Y. Chikaoka;Riko Ochi;K. Fujii;Takaaki Ariga;Masatoki Sakurai;Ayuna Matsumoto;Tsukasa Ueda;Etsuro Iwama;K. Naoi
为了实现具有高功率密度和稳定性的基于锂离子的能量存储装置，使用低粘度和低介电常数的溶剂[例如碳酸二甲酯（DMC）]以及化学稳定的基于BF 4的盐（例如LiBF 4或季铵盐[螺-（1，1）-联吡咯烷四氟硼酸盐（SBPBF 4）]）有望应用于下一代电解质。然而，这些组合由于几个原因是不切实际的，包括LiBF 4/DMC的低离子电导率和SBPBF 4/DMC系统的相分离。因此，我们开发了一种基于DMC的双阳离子系统（1 M LiBF 4 + 1 M SBPBF 4/DMC），其具有比单阳离子系统（1 M LiBF 4/DMC，0.5 mS cm-1）更高的离子电导率（5.7 mS cm-1），并实现了稳定的单相溶液。拉曼测量表明，双阳离子系统构成一个DMC和两个或三个BF 4-配合物（非中性带电状态），这将导致高离子电导率。此外，基于DMC的双阳离子系统在Li 4 Ti 5 O 12//活性炭混合电容器中表现出比单阳离子系统更高的功率性能（在50 mA cm-2下分别为88%和13%的容量保持率），并表现出高Li+电导率（双阳离子：1.6 mS cm-1，单阳离子：0.2 mS cm-1）。因此，双阳离子策略可以帮助开发涉及盐和溶剂的各种电解质组合，这些组合被认为是不切实际的。
To achieve lithium ion-based energy storage devices having high power densities and stabilities, the use of a low-viscosity and low-dielectric-constant solvent [such as dimethyl carbonate (DMC)] as well as a chemically stable BF4–-based salt (such as LiBF4or quaternary ammonium salts [spiro-(1,1)-bipyrrolidinium tetrafluoroborate (SBPBF4))] is promising for application in next-generation electrolytes. However, these combinations are impractical for several reasons, including the low ionic conductivity of LiBF4/DMC and the phase separation of SBPBF4/DMC systems. Thus, we developed a DMC-based dual-cation system (1 M LiBF4+ 1 M SBPBF4/DMC) possessing a higher ionic conductivity (5.7 mS cm–1) than that of single-cation systems (1 M LiBF4/DMC, 0.5 mS cm–1) and realizing a stable single-phase solution. Raman measurements suggest that the dual-cation system constitutes one DMC and two or three BF4–complexes (not neutral-charged states), which should result in high ionic conductivity. Furthermore, the DMC-based dual-cation system exhibited a higher power performance in a Li4Ti5O12//activated carbon hybrid capacitor than the single-cation system (88 and 13% capacity retention at 50 mA cm–2, respectively) and demonstrated high Li+conductivity (dual-cation: 1.6 mS cm–1, single-cation: 0.2 mS cm–1). Therefore, the dual-cation strategy could aid the development of diverse electrolyte combinations involving salts and solvents that have been considered impracticable.