Abstract
High ionic carrier mobilities are important for the electrolyte solutions used in high-performance batteries. Based on the functional sharing concept, we fabricated mixed electrolytes consisting of solvate ionic liquids (SIL), which are highly concentrated solution electrolyte, and the non-coordinating low-viscosity dilution solvent 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (HFE). We investigated the thermal, transport, and static properties of electrolytes with different ratios of SIL to HFE. In particular, the interactions between the SILs and HFE and static correlations of the coordinating (ether-based molecules), non-coordinating (HFE), and carrier ionic species (lithium salt) were clarified by applying the excess density concept. Ether molecules always formed strong complexes with lithium cations regardless of the absence or presence of HFE. The repulsion force between the SILs and HFE was strongly affected by lithium salt concentration. From our results, we proposed dissociation/association models for these electrolyte systems.
Highlights
Renewable energy technology or industry such as solar, wind power, geothermal heat, and biomass are prospective contributors to achieve a sustainable low-carbon society because they do not emit greenhouse gases.[1]
Renewable energy needs to meet the demands of low cost, high energy density, and long life to realize its effective use
Glyme molecules and Li cations can form quite stable coordinated cations, such as [Li(Glyme)]+, which exist in the liquid state at room temperature, and have weak basicity with similar complex structures.[13,14]
Summary
(1) Capacity degradation of the S electrode by decreasing of the net positive S electrode mass. Glyme molecules and Li cations can form quite stable coordinated cations, such as [Li(Glyme)]+, which exist in the liquid state at room temperature, and have weak basicity with similar complex structures.[13,14] SILs are a type of room-temperature ionic liquid because of their liquid properties at room temperature and composition of complex cations and counter anions.[15] As room-temperature ionic liquids, SILs show high thermal stability and low volatility and high ionic conductivity and a wide electrochemical window.[13] SILs hardly interact with Li2Sx, and can control the dissolution of the reactive intermediate Li2Sx into electrolyte solution.[12] Long cycle life (over 800 cycles) and high coulombic efficiencies (over 97%) have been realized by using Li–S batteries.[16] the glyme and Li salt are not equimolar near the electrode/ electrolyte interface owing to the Li alloying and de-alloying into the electrode associated with charge/discharge process, even if the equimolar mixture is used for the electrolyte.[17] Li2Sx can dissolve into the electrolyte through dynamic electrochemical reactions because of the presence of free glyme molecules[18] originating from the desolvated SIL. The interactions between coordinated solvent (glyme) and noncoordinated solvent (HFE) molecules and dissolved salts are clari ed
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