To demonstrate a new family of ionic liquids (ILs), i.e., "solvate" ionic liquids, the properties (thermal, transport, and electrochemical properties, Lewis basicity, and ionicity) of equimolar molten mixtures of glymes (triglyme (G3) and tetraglyme (G4)) and nine different lithium salts (LiX) were investigated. By exploring the anion-dependent properties and comparing them with the reported data on common aprotic ILs, two different classes of liquid regimes, i.e., ordinary concentrated solutions and "solvate" ILs, were found in the glyme-Li salt equimolar mixtures ([Li(glyme)]X) depending on the anionic structures. The class a given [Li(glyme)]X belonged to was governed by competitive interactions between the glymes and Li cations and between the counteranions (X) and Li cations. [Li(glyme)]X with weakly Lewis basic anions can form long-lived [Li(glyme)](+) complex cations. Thus, they behaved as typical ionic liquids. The lithium "solvate" ILs based on [Li(glyme)]X have many desirable properties for lithium-conducting electrolytes, including high ionicity, a high lithium transference number, high Li cation concentration, and high oxidative stability, in addition to the common properties of ionic liquids. The concept of "solvate" ionic liquids can be utilized in an unlimited number of combinations of other metal salts and ligands, and will thus open a new field of research on ionic liquids.

Innovation in the design of electrolyte materials is crucial for realizing next-generation electrochemical energy storage devices such as Li–S batteries. The theoretical capacity of the S cathode is 10 times higher than that of conventional cathode materials used in current Li–ion batteries. However, Li–S batteries suffer from the dissolution of lithium polysulfides, which are formed by the redox reaction at the S cathode. Herein, we present simple solvate ionic liquids, glyme–Li salt molten complexes, as excellent electrolyte candidates because they greatly suppress the dissolution of lithium polysulfides. The molten complexes do not readily dissolve other ionic solutes, which leads to the stable operation of the Li–S battery over more than 400 cycles with discharge capacities higher than 700 mAh g-sulfur−1 and with coulombic efficiencies higher than 98% throughout the cycles. Such high performance has not been realized to the best of our knowledge. Furthermore, the addition of a nonflammable fluorinated solvent, which does not break the solvate structure of the glyme–Li salt molten complexes, greatly enhances the power density of the Li–S battery. The strategic design of electrolyte properties provides opportunities for the development of new electrochemical devices with many different electrode materials.

Certain glymeLi salt complexes, which are composed of equimolar mixtures of a glyme and a Li salt, are liquid under ambient conditions with physicochemical properties such as high thermal stability, wide potential window, high ionic conductivity, and high Li + transference number and can be regarded as a new family of room-temperature ionic liquids.Room-temperature ionic liquids (RTILs), which are liquid at room temperature and composed entirely of ions, have attracted much attention because of their unique properties such as nonflammability, low-volatility, high chemical stability, and high ionic conductivity.1 RTILs are expected to be applied to electrochemical devices, including electric double-layer capacitors, 2 fuel cells, 3 dye-sensitized solar cells, 4 and lithium ion batteries (LIBs).5 Most of the RTILs reported to date can be classified as combinations of weakly Lewis-acidic cations and weakly Lewis-basic anions, which leads to ionic dissociation without strong coordination of solvent molecules around each ion. Thus, the most common compositions of RTILs are combinations of onium cations such as imidazolium cations, quaternary ammonium cations, and quaternary phosphonium cations and soft anions such as bis(trifluoromethylsulfonyl)-amide (TFSA ¹ ), tetrafluoroborate (BF 4 ¹ ), and hexafluorophosphate (PF 6 ¹ ). There are few reports of RTILs consisting of strongly Lewis-acidic cations such as Li + and Na + and strongly Lewis-basic anions such as F ¹ and Cl ¹ . Melting points of salts consisting of strongly Lewis-acidic cations and strongly Lewisbasic anions are generally much higher than room temperature, resulting in the formation of ionic crystals at room temperature. So far, we have reported the preparation of lithium ionic liquids consisting of lithium salts of borates having electron-withdrawing groups, to reduce the anionic basicity, and lithium coordinating ether-ligands, to dissociate the lithium cations from the anionic centers.6 However, possibly due to the strong Lewis acidity of Li + , the viscosity and ionicity (dissociativity) of the lithium ionic liquids at room temperature are as high as 500 mPa s and as low as 0.10.2, respectively, resulting in a low ionic conductivity of 10 ¹5 S cm ¹1 at its maximum. Weakly Lewis-basic anions such as BF 4 ¹ and PF 6 ¹ are prepared by the reactions between Lewis acids (BF 3 and PF 5 ) and a Lewis base (F ¹ ) by forming coordination bonds. However, the preparation of weakly Lewis-acidic cations for RTILs by the reaction between a Lewis acid and a Lewis base has not been proposed. It is anticipated that weakly Lewis-acidic cations can be prepared by the combination of alkali metal cations (Lewis acid) and suitable ligands (Lewis base).Ethers are relatively strong Lewis bases, and alkali metal cations are strongly coordinated with ethers. It is well-known that particular molar ratio mixtures of Li salts and oligoethers such as crown ethers, triglyme (G3), and tetraglyme (G4) form complexes. Henderson et al. have conducted a systematic study of glymeLi salt...

Lithium ion batteries (LIBs), with high energy and power densities, have become essential to modern society as power sources for portable electronic devices. 1À3 Furthermore, electric vehicles (EVs) equipped with LIBs are now commercialized. The conventional electrolyte of LIBs is composed of mixed organic solvents (cyclic carbonate and linear carbonate) and LiPF 6 . 4 Linear carbonate solvents are extremely flammable, with flash points below room temperature, and LiPF 6 decomposes into HF with the presence of a slight amount of water at temperatures higher than 60 °C. 5 Thus, LIBs have thermal instability problems at elevated temperatures. To achieve a high degree of safety of LIBs, the development of thermally stable electrolytes is crucial.Room-temperature ionic liquids (RTILs), which consist entirely of cations and anions, have attracted much attention owing to their unique properties such as low volatility, high thermal stability, high ionic conductivity, wide potential window, and high chemical stability. 5À7 RTILs are called "designer solvents" because their physicochemical properties can be easily tuned

Two-dimensional polymeric nanosheets have recently gained much attention, particularly top-down nanosheets such as graphene and metal chalcogenides originating from bulk-layered mother materials. Although molecule-based bottom-up nanosheets manufactured directly from molecular components can exhibit greater structural diversity than top-down nanosheets, the bottom-up nanosheets reported thus far lack useful functionalities. Here we show the design and synthesis of a bottom-up nanosheet featuring a photoactive bis(dipyrrinato)zinc(II) complex motif. A liquid/liquid interfacial synthesis between a three-way dipyrrin ligand and zinc(II) ions results in a multi-layer nanosheet, whereas an air/liquid interfacial reaction produces a single-layer or few-layer nanosheet with domain sizes of >10 μm on one side. The bis(dipyrrinato)zinc(II) metal complex nanosheet is easy to deposit on various substrates using the Langmuir–Schäfer process. The nanosheet deposited on a transparent SnO2 electrode functions as a photoanode in a photoelectric conversion system, and is thus the first photofunctional bottom-up nanosheet.