Salt, electrolyte, electrolyte solution, secondary battery

Abstract

This invention provides a salt that can be used as an electrolyte or electrolyte solution, exhibiting good solubility and chemical stability. [Solution] A salt comprising an organic cation and an anion, wherein the organic cation does not have hydrogen at the β-carbon, has an asymmetric structure, and is 170 Å 3 A salt having the above molecular volume.

Description

[Technical Field]

[0001] This invention relates to salts, electrolytes, electrolyte solutions, and secondary batteries. [Background technology]

[0002] The shift towards sustainable power generation and the increasing reliance on variable renewable energy (VRE) are major driving forces behind new energy storage technologies. While lithium-ion batteries have reached an energy density of 300 Wh / kg, batteries with even higher energy densities are desired for weight-sensitive applications such as electric vehicles. Fluoride-ion batteries (FIBs) are a promising alternative to lithium-ion technology due to their high theoretical capacity of over 800 mAh / g (Non-Patent Literature 1).

[0003] Liquid electrolytes maintain high ionic conductivity at room temperature, but solvent-fluoride salt systems that combine high solubility and stability are not readily found. Tetramethylammonium fluoride (TMAF) has low solubility in organic solvents. Tetrabutylammonium fluoride (TBAF) has higher solubility in organic solvents than TMAF, but above 0°C it becomes F - The ions react with the β-protons of the butyl side chains to self-decompose (Hofmann elimination). There is a strong demand for electrolyte salts with excellent properties such as improved solubility in organic solvents, high ionic conductivity, and improved thermodynamic and electrochemical stability.

[0004] One way to lower the operating temperature of a battery is to switch to a liquid electrolyte that maintains high ionic conductivity down to room temperature. Liquid fluoride ion batteries exhibit excellent performance, but are largely limited to the use of aprotic solvents. Recent research has focused on quaternary ammonium-based ionic liquids, which are highly promising for improving battery performance due to their favorable electrochemical properties. Despite this potential, these ionic liquids face challenges mainly due to their low stability to highly reactive fluoride anions and low solubility to fluoride salts. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] AW Xiao, G. Galatolo and M. Pasta, Joule, Vol.5, No.11, p.2823-2844 (2021). [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] To construct more efficient and stable fluoride-ion battery systems, there is a need for electrolytes with excellent solubility and chemical stability, as well as electrolyte solutions that exhibit high solubility in the electrolyte and excellent chemical stability.

[0007] The present invention aims to provide a salt that can be used as an electrolyte or electrolyte solution with good solubility and chemical stability. [Means for solving the problem]

[0008] To achieve the aforementioned objective, the salt of the present disclosure comprises an organic cation and an anion, wherein the organic cation does not have a hydrogen atom at the β-carbon, has an asymmetric structure, and is 170 Å 3 It has the above molecular volume. [Effects of the Invention]

[0009] The present invention provides a salt that can be used as an electrolyte or electrolyte solution with good solubility and chemical stability. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows the compounds of the examples and comparative examples. [Figure 2] This diagram shows an overview of the synthesis scheme for Experiment 1. [Figure 3]This figure shows Scheme S1 (synthesis of MeDMBBF4) and Scheme S2 (synthesis of MeDMBF). [Figure 4] This figure shows scheme S3 (synthesis of NpDMBBF4) and scheme S4 ​​(synthesis of NpDMBF). [Figure 5] This figure shows scheme S5 (composition of NpADMBF4) and scheme S6 (composition of NpADMF). [Figure 6] 19F,1H HOESY spectra of 0.9M MeDMBF and NpDMBF in BTFE. [Figure 7] This is a snapshot diagram of the contact ion pair configuration, obtained from molecular dynamics simulations of 0.9 M solutions of MeNp1F and MeNp2F in BTFE at room temperature. [Figure 8] (a) Radial distribution functions of four chemically distinct hydrogen atoms (Ha, Hb, Hs, N) and F-anions in MeDMB / BTFE. (b) Radial distribution functions of four chemically distinct hydrogen atoms (Ha, Hb, Hs, N) and F-anions in NpDMBF / BTFE. [Figure 9] Cyclic voltammograms of (a) 0.1M MeDMBF and (b) 0.1M NpDMBF in GBL and BTFE (scan rate 1mV / s). [Figure 10] Graphs showing half-cell performance. (a) Cyclic voltammograms (CV) of bismuth fluoride and carbon electrodes in 0.9M Np2F / BTFE electrolyte, 298K, scan rate 1mV / s, (b) Charge / discharge curves (0.1C) of BiF3 electrodes in 0.9M Np2F / BTFE, (c) Charge / discharge curves (0.1C) of BiF3 electrodes in 0.9M MeDMBF / BTFE, (d) Charge / discharge curves (0.1C) of BiF3 electrodes in 0.9M NpDMBF / BTFE. Voltage is referenced to a double-junction electrode based on Ag / AgOTf in MPPy-FSI. [Figure 11] This figure shows the molecular design of the ammonium cation in Experiment 2. [Figure 12](a) A commercially available TFSI salt using a quaternary ammonium cation, (b) a TFSI salt synthesized based on an alkylammonium cation that does not contain a β-proton, and (c) MNPA and NPPA, which are cations for ionic liquids in Examples 4 and 5. [Figure 13] This diagram shows an overview of the synthesis scheme for Experiment 2. [Figure 14] This figure shows scheme S2-1 (combination of [MNPA][TFSI]). [Figure 15] This figure shows scheme S2-2 (combination of [NPPA][TFSI]). [Figure 16] This figure shows schemes S2-3 (combination of [MeDMB][TFSI]), S2-4 (combination of [Np2][TFSI]), and S2-5 (combination of [NpDMB][TFSI]). [Figure 17] (a) DSC traces of [MNPA][TFSI] and (b) DSC traces of [NPPA][TFSI]. [Figure 18] TGA traces of [MNPA][TFSI] and [NPPA][TFSI]. [Figure 19] This figure shows the crystal structures of [MNPA][TFSI](a,c,e,h) and [NPPA][TFSI](b,d,f,i) as ellipsoids with a 50% probability. [Figure 20] [MNPA][TFSI], 0.1M Np2F / [MNPA][TFSI], [NPPA][TFSI], 0.1M Np2F / [NPPA][TFSI] potential window (scan speed 1mV / s). [Figure 21] (a) Graphs of the diffusion coefficient D as a function of temperature T for cations and (b) anions. [Figure 22] Voltage profile of the Pb / PbF2 electrode when charged and discharged at 1 μA / cm2 in a 0.5 M Np2F / [MNPA][TFSI] electrolyte. [Figure 23] Voltage profile of the Pb / PbF2 electrode when charging and discharging in a 0.5M Np2F / [NPPA][TFSI] electrolyte at 1 μA / cm2. [Modes for carrying out the invention]

[0011] The embodiments of the present invention (hereinafter referred to as "these embodiments") will be described below. This embodiment relates to salts, electrolytes, and electrolyte solutions.

[0012] [Definition] In this specification, ○~△ (for example, ○%~△%) means ○ or more and △ or less (○% or more and △% or less). Also in this specification, the terms "includes" or "contains" mean including the specified components, but do not exclude the existence of other components. Also in this specification, the expression "A and / or B" includes "A only," "B only," and "both A and B." Also in this specification, "room temperature" means 25°C.

[0013] [1. Salt] The salt of this embodiment comprises an organic cation and an anion, the organic cation does not have hydrogen at the β-carbon, has an asymmetric structure, and is 170 Å 3 It has the above molecular volume.

[0014] In the salt of this embodiment, the organic cation does not have a hydrogen atom (β-proton) at the β-carbon. Furthermore, the organic cation may not have a carbon atom at the β-position. Conventional organic cations self-decompose by reacting with the hydrogen atom (β-proton) at the carbon adjacent to the carbon atom to which the leaving group is attached (the carbon at the β-position, β-carbon) (Hofmann elimination). Organic cations that do not have a hydrogen atom at the β-carbon, such as ammonium cations, exhibit superior stability.

[0015] In the salt of this embodiment, the organic cation has an asymmetric structure. An asymmetric molecular structure of the organic cation improves its solubility in organic solvents. The method for making the molecular structure of the organic cation asymmetric is not particularly limited, but examples include selecting substituents R1 and R2 such that the molecular structure becomes asymmetric in the general formula (I) described later.

[0016] In the salt of the present embodiment, the organic cation has a molecular volume of 170 Å 3 or more. When the molecular volume (size) of the organic cation is increased, the diffusion constant of the fluoride salt in the solvent increases, and the ionic conductivity increases. From the viewpoint of increasing the ionic conductivity, the molecular volume of the organic cation is preferably 150 Å 3 or more, more preferably 170 Å 3 or more, still more preferably 200 Å 3 or more, even more preferably 220 Å 3 or more, particularly preferably 240 Å 3 or more, 250 Å 3 or more. When the molecular volume of the organic cation is increased, the heat resistance of the corresponding fluoride salt decreases. Therefore, the molecular volume of the organic cation is preferably 400 Å 3 or less, more preferably 350 Å 3 or less, still more preferably 320 Å 3 or less, even more preferably 300 Å 3 or less, particularly preferably 290 Å 3 or less, 280 Å 3 or less, 270 Å 3 or less, 260 Å 3 or less. From the viewpoints of ionic conductivity and heat resistance, the molecular volume of the organic cation is preferably 150 Å 3 to 400 Å 3 , more preferably 170 Å 3 to 350 Å 3 , still more preferably 170 Å 3 to 300 Å 3 , even more preferably 170 Å 3 to 280 Å 3 , particularly preferably 180 Å 3 to 280 Å 3 , 200 Å 3 to 280 Å 3 , 235 Å 3 to 275 Å 3 is.

[0017] The molecular volume of the organic cation was first optimized using the ORCA5.0.3 software package with theory at the M062X / Def2-TZVPP level, and then calculated based on the van der Waals radius using the GROMACS2022.4 software package.

[0018] In the salt of this embodiment, the charge center of the organic cation is not particularly limited, but it is preferably N (nitrogen), P (phosphorus), S (sulfur), or O (oxygen). It is preferable that the charge center of the organic cation is N (nitrogen).

[0019] [1-1. Salt of the first embodiment] The following describes the salt of the first embodiment. The salt of the first embodiment is characterized in that the organic cation is represented by the following general formula (I). [ka] (In general formula (I), R1 and R2 are each independently H, substituted or unsubstituted C1-C 20 Alkyl, C3-C 20 Cycloalkyl, C5-C 30 Aryl, C5-C 30 Heteroaryl, C1-C 20 Asyl, C2-C 20 Alkenil, C3-C 20 Cycloalkenyl, C2-C 20 Alkinyl, C5-C 20 Alkylaryl, C2-C 20 (It is an alkoxycarbonyl or halogen group.)

[0020] In the above general formula (I), it is preferable that R1 and R2 are independently represented by the following general formulas (II-1) to (II-10) and the following general formula (III). [ka] [ka] (In general formula (III), R5 is either H or a fluoroalkyl group.)

[0021] In the salt of the first embodiment, the organic cation is represented by the above general formula (I), and the anion is a fluoride ion (F - In that case, it is preferable to use it as an electrolyte.

[0022] Preferred examples of the salts of the first embodiment include, but are not limited to, N,N,N,2,2-pentamethylbutane-1-aminium fluoride (MeDMBF) represented by formula (VI), N,N,2,2-tetramethyl-N-neopentylbutane-1-aminium fluoride (NpDMBF) represented by formula (VII), and N-((adamantan-1-yl)methyl)-N,N,2,2-tetramethylpropane-1-aminium fluoride (NpADMF) represented by formula (VIII). [ka] [ka] [ka]

[0023] When the salt of the first embodiment is used as an electrolyte, its solubility in bis(2,2,2-trifluoroethyl) ether (BTFE) at 25°C is preferably 2.6 M or higher, more preferably 2.7 M or higher, even more preferably 2.8 M or higher, even more preferably 2.9 M or higher, and particularly preferably 3.0 M or higher.

[0024] When the salt of the first embodiment is used as an electrolyte, the ionic conductivity when dissolved in bis(2,2,2-trifluoroethyl) ether at a concentration of 0.9 M at 25°C is preferably 3.0 mS / cm or higher, more preferably 3.2 mS / cm or higher, even more preferably 3.4 mS / cm or higher, even more preferably 3.6 mS / cm or higher, and particularly preferably 3.8 mS / cm or higher.

[0025] [1-2. Salt of the second embodiment] The following describes the salt of the second embodiment. In the salt of the second embodiment, the anion is a sulfonylimid anion and / or a fluorine-containing anion.

[0026] The fluorine-containing anions are not particularly limited, but examples include trifluoromethanesulfonic acid anions, bis(fluorosulfonyl)imide anions, bis(perfluoroalkylsulfonyl)imide anions, tetrafluoroborate anions, and hexafluorophosphate anions. Of these fluorine-containing anions, bis(fluorosulfonyl)imide anions and bis(perfluoroalkylsulfonyl)imide anions are preferred.

[0027] In the salt of the second embodiment, it is preferable that the fluorine-containing anion is a fluorine-containing sulfonylimid anion represented by the following general formula (IV). [ka] (In general formula (IV), R 7 and R 8 Each independently represents either a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms. 7 and R 8 These may bond to each other to form a perfluoroalkylene group having 3 to 5 carbon atoms.

[0028] Examples of perfluoroalkyl groups having 1 to 6 carbon atoms include linear or branched perfluoroalkyl groups having 1 to 6 carbon atoms, and more specifically, perfluoromethyl group, perfluoroethyl group, perfluoro-n-propyl group, perfluoroisopropyl group, perfluoro-n-butyl group, perfluoroisobutyl group, perfluoro-t-butyl group, perfluoro-n-pentyl group, and perfluoro-n-hexyl group. It is preferable that the perfluoroalkyl group is a linear perfluoroalkyl group.

[0029] Examples of perfluoroalkylene groups having 3 to 5 carbon atoms include -CF2-CF2-CF2-, -CF2-CF2-CF2-CF2-, and -CF2-CF2-CF2-CF2-CF2-, with perfluoroalkylene groups having 3 carbon atoms being preferred.

[0030] In the fluorine-containing sulfonyliimide anion represented by general formula (IV), R 7 and R 8 Each independently represents a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms. In general formula (IV), R 7 and R 8 When each independently represents a perfluoroalkyl group having 1 to 6 carbon atoms, R 7 and R 8 Each of these groups is preferably a perfluoroalkyl group having 1 to 4 carbon atoms, more preferably a perfluoroalkyl group having 1 to 3 carbon atoms, even more preferably a perfluoromethyl group or a perfluoroethyl group, and most preferably both are trifluoromethyl groups.

[0031] In the salt of the second embodiment, preferred anions include, for example, bis(fluorosulfonyl)imide anion and bis(trifluoromethanesulfonyl)imide (TFSI) anion. The anions can be used individually or in combination of two or more.

[0032] In the salt of this embodiment, when the anion is a sulfonylimid anion and / or a fluorine-containing anion, the organic cation is preferably represented by the following general formula (V). [ka] (In general formula (V), R 9 CH3, CF3, CH2CF3, CF2CF 3、 CH2CH2CF 3、 (It is CH2CF2CF3 or CF2CF2CF3)

[0033] As preferred examples of the salt of the second embodiment, examples include a salt ([MNPA][TFSI]) in which the organic cation is 3-methoxy-N,N,N,2,2-pentamethylpropane-1-aminium (MNPA, molecular volume 182 Å) and the anion is bis(trifluoromethanesulfonyl)imide (TFSI), and a salt ([NPPA][TFSI]) in which the organic cation is N,N,N,2,2-pentamethyl-3-(2,2,2-trifluoroethoxy)propane-1-aminium (NPPA, molecular volume 219 Å) and the anion is bis(trifluoromethanesulfonyl)imide (TFSI), but the salt is not limited to these compounds. The molecular volume of the organic cation in the salt of the second embodiment is preferably 150 Å. 3 ~400Å 3 , more preferably 160 Å 3 ~350Å 3 , more preferably 170 Å 3 ~300Å 3 , more preferably 170 Å 3 ~280Å 3 Particularly preferred is 170 Å 3 ~260Å 3 , 175Å 3 ~250Å 3 , 180 Å 3 ~240Å 3 That is the case.

[0034] The salt of the second embodiment is preferably a liquid at 25°C, i.e., an ionic liquid. When the salt of this embodiment is an ionic liquid, it is preferably used as an electrolyte. When the salt of the second embodiment is an ionic liquid, the ionic conductivity at 25°C is 1.0 mS / cm or more, preferably 1.1 mS / cm or more, and more preferably 1.2 mS / cm or more.

[0035] When the salt of the second embodiment is used as the electrolyte, the solubility of N,N-dimethyl-N,N-dineopentylammonium fluoride (Np2F, electrolyte) at 25°C is preferably 0.5M or higher, more preferably 0.6M or higher, even more preferably 0.7M or higher, even more preferably 0.8M or higher, and particularly preferably 1.0M or higher. Also, when the salt of the second embodiment is used as the electrolyte, the solubility of TMAF (tetramethylammonium fluoride, electrolyte) at 25°C is preferably 0.1M or higher, more preferably 0.3M or higher, even more preferably 0.5M or higher, even more preferably 0.6M or higher, and particularly preferably 0.7M or higher.

[0036] [2. Electrolytes or electrolytes] The salt of this embodiment can be used as an electrolyte or electrolyte solution. Specifically, the salt of this embodiment (for example, the salt of the first embodiment) can be used as an electrolyte, either alone or in mixture with a solvent commonly used in electrolyte solutions. Furthermore, the salt of this embodiment (for example, the salt of the second embodiment) can be used as an electrolyte, either alone or in mixture with an electrolyte commonly used in electrolyte solutions.

[0037] [2-1. Uses as an electrolyte] The solvent used when the salt of this embodiment is used as an electrolyte is not particularly limited as long as it is capable of dissolving the salt of this embodiment, but for example, various organic solvents and ionic liquids can be used. Examples of solvents that can be used include nitriles, amines, ethers, carbonates, esters, furans, lactones, nitro compounds, aromatic compounds, sulfur compounds, amides, oxolanes, heterocyclic compounds, pyrrolidones, boric acid compounds, phosphate ester compounds, chain ammonium ionic liquids, cyclic ammonium ionic liquids, aromatic ionic liquids, phosphonium ionic liquids, and sulfonium ionic liquids.

[0038] It is preferable to use a fluorinated non-aqueous solvent as the solvent. A fluorinated non-aqueous solvent is, for example, [X-(CH2) n -Y] (wherein n=1 or 2), where X and Y are polar functional groups (electron-withdrawing groups) that have the effect of being bonded to a CH2 group or group thereof to impart a partial positive charge. For example, Y may be O (oxygen) or S (sulfur). X may be a functional group and is not particularly limited, but examples include ethers, esters, acid anhydrides, amines, amides, carbonates, sulfones, sulfonyl esters, phosphites (phosphate or phosphorous esters), phosphates (phosphates), nitriles, nitros, aldehydes, acetates, SF5, or fluorocarbons (carbon fluoride) (e.g., -CF3, -CF2CF3).

[0039] When using the salt of this embodiment as an electrolyte, the salt and solvent are mixed to dissolve the salt in the solvent. The mixing ratio of the salt and solvent is not particularly limited, but the lower limit of the salt concentration in the solvent is preferably 0.01 M, more preferably 0.05 M, and even more preferably 0.09 M. The upper limit of the salt concentration in the solvent is preferably 10 M, more preferably 5 M, and even more preferably 3 M.

[0040] [2-2. Uses as a solvent] The electrolyte used when the salt of this embodiment is used as a solvent is not particularly limited as long as it is soluble in the salt of this embodiment, but for example, a fluoride salt can be used. The fluoride salt that can be used as an electrolyte is not particularly limited, but examples include inorganic fluoride salts and organic fluoride salts.

[0041] The inorganic fluoride salt is not particularly limited, but for example, formula MF n Examples of inorganic fluoride salts include those having the following properties, where M is a metal and n is an integer greater than 0. Examples of inorganic fluoride salts include lithium fluoride (LiF), sodium fluoride (NaF), potassium fluoride (KF), rubidium fluoride (RbF), cesium fluoride (CsF), and ammonium fluoride (NH4F).

[0042] Examples of organic fluoride salts are not limited to those mentioned above, but include tetramethylammonium fluoride, neopentyltrimethylammonium fluoride, trineopentylmethylammonium fluoride, tetraneopentylammonium fluoride, 1,3,3,6,6-hexamethylpiperidinium fluoride, 1-methyl-1-propylpiperidinium fluoride, tetramethylphosphonium fluoride, tetraphenylphosphonium fluoride, and trimethylsulfonium fluoride.

[0043] The electrolyte may contain only one type of fluoride salt or two or more types of fluoride salts.

[0044] When using the salt of this embodiment as a solvent, the salt and electrolyte are mixed to dissolve the electrolyte in the salt. The mixing ratio of salt and electrolyte is not particularly limited, but the lower limit of the electrolyte concentration in the salt is preferably 0.01 M, more preferably 0.05 M, and even more preferably 0.09 M. The upper limit of the electrolyte concentration in the salt is preferably 10 M, more preferably 5 M, and even more preferably 3 M.

[0045] [3.Battery] The salt of this embodiment can be used as an electrolyte or electrolyte solution to constitute a battery. The battery is not particularly limited, but examples include primary batteries, secondary batteries, fuel cells, and solar cells such as dye-sensitized solar cells. The battery has a positive electrode (cathode), a negative electrode (anode), and an electrolyte solution provided between the positive electrode and the negative electrode.

[0046] [3-1. Secondary battery] The salt of this embodiment is preferably used as an electrolyte or electrolyte solution to constitute a secondary battery. The secondary battery is not particularly limited, but examples include fluoride ion batteries.

[0047] [3-2. Fluoride-ion batteries] The salt of this embodiment is preferably used as an electrolyte or electrolyte solution to constitute a fluoride ion battery. The fluoride ion secondary battery of this embodiment includes a positive electrode, a negative electrode, and an electrolyte having fluoride ion conductivity. Conventional known components can be used for the positive electrode, negative electrode, separator, etc. of the fluoride ion secondary battery.

[0048] The active materials for the positive and negative electrodes of the fluoride-ion secondary battery of this embodiment include a fluoride ion host capable of accommodating fluoride ions from the electrolyte during discharge and charging. Accommodation of fluoride ions includes insertion of fluoride ions into the host, intercalation of fluoride ions into the host, and / or reaction between the host and fluoride ions. In the fluoride-ion secondary battery of this embodiment, it is preferable to use a host capable of reversibly exchanging fluoride ions with the electrolyte without significantly degrading the host during charge-discharge cycles.

[0049] The fluoride ion host for the negative electrode of a fluoride ion secondary battery is not particularly limited, but for example, LaF x CaF x AlF x , EuF x LiC6, Li x Si, Li x Ge, Lix (CoTiSn), SnF x , InF x , VF x , CdF x , CrF x , FeF x , ZnF x , GaF x , TiF x , NbF x , MnF x , BiF x , YbF x , ZrF x , SmF x , LaF x and CeFx are included. A preferred fluoride host for the negative electrode of a fluoride ion secondary battery is MF x where M is an alkaline earth metal (Mg, Ca, Ba), M is a transition metal, M belongs to Group 13 (B, Al, Ga, In, Tl), or M is a rare earth element (atomic number Z is between 57 and 71).

[0050] The fluoride ion host of the positive electrode of a fluoride ion secondary battery is an intercalation host capable of accommodating fluoride ions so as to form an intercalation compound of fluoride ions. The fluoride ion host for the positive electrode of a fluoride ion secondary battery is not particularly limited. For example, CF x , AgF x , CuF x , NiF x , CoF x , PbF x , CeF x , MnF x , AuF x , PtF x , RhF x , VF x , OsF x , RuF x and FeF x are included. The fluoride ion host of the positive electrode is of the formula CF xThe carbonaceous material is a partially fluorinated carbonaceous material having the formula, where x is the average atomic ratio of fluorine atoms to carbon atoms, preferably in the range of about 0.3 to about 1.0. Suitable carbonaceous materials for the cathode are not particularly limited, but include, for example, graphite, graphene, coke, single-walled or multi-walled carbon nanotubes, multi-layered carbon nanofibers, multi-layered carbon nanoparticles, carbon nanowhiskers, and carbon nanorods.

[0051] [4. Other uses] The salt of this embodiment, taking advantage of its excellent solubility and chemical stability, can be used not only in battery applications but also as an electrolyte and / or electrolyte in capacitors such as electric double-layer capacitors, an electroviscous fluid, a heat storage medium, a catalyst, a solvent for various organic synthesis reactions, an extraction solvent for separation and purification, and an electrolyte for plating. [Examples]

[0052] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0053] [Experiment 1: Synthesis and Evaluation of Asymmetric Quaternary Ammonium Fluorides] In Experiment 1, the quaternary ammonium fluorides of Examples 1-3 and Comparative Example 1 shown in Figure 1 were synthesized, and their various properties were evaluated. Since fluorides are strong bases, quaternary ammonium fluorides such as tetrabutylammonium fluoride (TBAF) are known to self-decompose by Hoffmann elimination. Therefore, removing the reactivity with β-protons on the quaternary ammonium cation is essential in molecular design. The reference compound, N,N-dimethyl-N,N-dineopentylammonium fluoride (Np2F, Comparative Example 1), is characterized by a symmetrical cation with two tert-butyl groups on a tetramethylammonium skeleton and was used as a benchmark.

[0054] N,N,2,2-tetramethyl-N-neopentylbutane-1-aminium fluoride (NpDMBF, Example 2) is obtained by replacing one tert-butyl group of Np2F with a 1,1-dimethylpropyl group, resulting in a larger asymmetric cation. N-((adamantan-1-yl)methyl)-N,N,2,2-tetramethylpropane-1-aminium fluoride (NpADMF, Example 3) incorporates a bulky and rigid adamantyl group, resulting in an even larger overall size. On the other hand, compound N,N,N,2,2-pentamethylbutane-1-aminium fluoride (MeDMBF, Example 1) is obtained by replacing the tert-butyl group of NpDMBF with a hydrogen atom, resulting in an asymmetric cation that is significantly smaller than both Np2F and NpDMBF. Theoretical calculations show that MeDMB + , Np2 + NpDMB + NpADM + The volume of each cation is 172 Å. 3 , 233Å 3 , 246Å 3 , 263Å 3 This was the estimated result. Using these four fluoride salts, we investigated how asymmetric substituents affect solubility, ionic conductivity, and chemical stability.

[0055] [Overview of Synthesis] Figure 2 shows an overview of the synthesis schemes for the anhydrous quaternary ammonium fluorides MeDMBF (Example 1), NpDMBF (Example 2), and NpADMF (Example 3). Tertiary amines were synthesized from commercially available compounds as starting materials (Schemes S1, S3, S5). To obtain the anhydrous fluoride salts, the corresponding ammonium tetrafluoroborate was used as a key intermediate, and a simple and safe anion exchange reaction with KF in methanol was employed. MeDMBBF4, NpDMBBF4, and NpADMBF4 were synthesized by oxinium methylation of the corresponding tertiary amines in dichloromethane using the Meerwein salt (trimethyloxynium tetrafluoroborate), yielding 93%, 96%, and 91% yields, respectively. These three borate salts were prepared, and anionic ion exchange between the borate salts and KF in dry methanol was performed to obtain aqueous solutions of the fluorides. After removing KBF4 by filtration, the resulting solution was further vacuum-dried at 90°C to obtain solids of anhydrous MeDMBF, NpDMBF, and NpADMF in yields of 76%, 43%, and 44%, respectively.

[0056] Detailed synthesis procedures are described in schemes S2, S4, and S6 below. The purity of the product was determined in a deuterated organic solvent. 1 H, 13 C, 19 Confirmed by F NMR, HF2 - No species were detected. The water content of MeDMBF and NpDMBF was 15 ppm and 16 ppm, respectively, in 0.1 M BTFE, while NpADMF had a water content of 34 ppm in 0.1 M dichloromethane (DCM). Fluoride salts are highly hygroscopic substances. The solubility of MeDMBF, NpDMBF, and NpADMF in water exceeded 24 M, 28 M, and 5 M, respectively.

[0057] (material) Neopentylamine, 1-(adamantan-1-yl)methaneamine, pivalaldehyde, sodium triacetoxyborohydride, MeI, formaldehyde, trimethyloxonium tetrafluoroborate, LiAlH4, BTFE (bis(2,2,2-trifluoroethyl) ether), PN (propionitrile), DMA (N,N-dimethylacetamide), DME (dimethyl ether), DEC (diethyl carbonate), TEGDME (triethylene glycol dimethyl ether), and DMI (1,3-dimethyl-2-imidazolidinone) were purchased from Tokyo Chemical Industries Ltd. (TCI). Hydrochloric acid and anhydrous magnesium sulfate were purchased from Nacalai Tesque Co., Ltd. Formic acid, sodium hydroxide, Et3N, dibutyl ether, super-dehydrated MeOH, DMSO (dimethyl sulfoxide), GBL (γ-butyrolactone), NMP (N-methyl-2-pyrrolidone), siRNA (ethyl acetate), and MeCN (acetonitrile) were purchased from Fujifilm Wako Pure Chemical Industries. The dehydrating solvents, dichloromethane, diethyl ether, DMF (N,N-dimethylformamide), Et2O (diethyl ether), and THF (tetrahydrofuran), were purchased from Kanto Chemical Co., Ltd. 2,2-dimethylbutanoyl chloride, dimethylamine hydrochloride, and KF were purchased from Sigma-Aldrich. PN, DMA, DME, DEC, TEGDME, DMI, and BTFE were dried on a 4Å molecular sieve, and KF was dried at 250°C for 8 hours. Deuterated solvents were purchased from Eurosotop or Cambridge Isotope Laboratories, Inc. All deuterated solvents were used as received, with the exception of CD3CN dried on a 4Å molecular sieve.

[0058] (NMR measurement) 1 H, 13 C, 19 F NMR spectra were recorded using a Bruker Advance III 400,600 MHz spectrometer equipped with a BBFO probe. Chemical shifts are reported in δ ppm, with residual protonated solvent in 1H deuterated solvent as the internal standard. The peak in the deuterated solvent is13 Used as an internal standard for 13C NMR, 19 CFCl3 (0 ppm) was used as the external standard for 1F NMR. Anhydrous sample solutions were prepared in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm). A Wilmud low-pressure / vacuum NMR tube (LPV) was used.

[0059] [Example 1: Synthesis of MeDMBF] MeDMBBF4 was synthesized according to scheme S1 in Figure 3. To a room temperature solution of dimethylamine hydrochloride (14.5 g, 0.177 mol) and triethylamine (48.6 mL, 35.3 g, 0.349 mol) in dichloromethane (300 mL), 20.4 mL of 2,2-dimethylbutanoyl chloride (18.0 g, 0.149 mol) was slowly added, and the mixture was stirred at room temperature for 16 hours. After the reaction, the mixture was washed with water. The organic layer was dried over anhydrous magnesium sulfate, filtered, and then evaporated under low vacuum to obtain N,N,2,2-tetramethylbutanamide (1) in 87% yield. 5.0 g of lithium aluminum hydride (0.14 mol) was suspended in dibutyl ether at 0°C, and 15.0 g of N,N,2,2-tetramethylbutanamide (0.105 mol) was added. The mixture was stirred at 80°C for 6 hours. The solution was cooled to room temperature, treated with an aqueous NaOH solution, and then filtered. The resulting solution was treated with concentrated hydrochloric acid until the pH was 1. After removing most of the solvent under vacuum, the mixture was transferred to a water bath (<295K), treated with concentrated sodium hydroxide solution until the pH was 14, and extracted with diethyl ether. The organic layer was dried on anhydrous magnesium sulfate, filtered, and then partially removed from the residual solvent by low-vacuum evaporation.

[0060] The obtained N,N,2,2-tetramethylbutan-1-amine(2) (10.6 g (77.8 mmol) in diethyl ether (52 wt%)) was slowly added to a suspension of Meerwein salt (trimethyloxonium tetrafluoroborate, 13.3 g, 89.9 mmol) in 200 mL of dichloromethane (<100 ppm water, Ar atmosphere). The suspension was stirred at room temperature for 12 hours, and most of the solvent was evaporated to obtain a white solid. The crude product was further purified by recrystallization from methanol / diethyl ether to obtain MeDMBBF4, which was dried under vacuum at 80°C for 14 hours to obtain anhydrous MeDMBBF4 (17.1 g, 74.0 mmol) in 93% yield. 1 H NMR (400MHz, DMSO-d6): δ3.26(s,2H),3.14(s,9H),1.40(q,2H,J=7.6Hz),1.09(s,6H),0.85(t,3H,J=7.6Hz); 13 C NMR(101MHz,DMSO-d6):δ74.25,54.76,35.56,34.50,26.14,8.01; 19 F NMR (376MHz, DMSO-d6): δ-150(s).

[0061] MeDMBBF was synthesized according to scheme S2 in Figure 3. 3.0 g of anhydrous MeDMBBF4 (13 mmol) was dissolved in 20 mL of methanol (water content <30 ppm). After adding 1 g of KF (17 mmol, dried at 250°C for 8 hours), a precipitate of KBF4 was instantly formed and filtered. BF4 - The conversion rate from ions to fluoride 19 Monitored by F NMR: BF4 - If ions are detected, BF4 - KF was further added to the solution until no ionic impurities were observed in the product. Methanol in the resulting solution was removed by vacuum evaporation. Excess KF was removed by precipitation from methanol / diethyl ether (water content <30 ppm) to obtain a colorless solution, which was further dried under vacuum at 90°C for 19 hours. 1.7 g (10 mmol) of white solid product was recovered with a purification yield of 76%. 11H NMR (400 MHz, MeCN-d3): δ 3.42 (s, 2H), 3.35 (s, 9H), 1.43 (q, 2H, J = 7.6 Hz), 1.09 (s, 6H), 0.87 (t, 3H, J = 7.6 Hz); 13 13C NMR (101 MHz, MeCN-d3): δ 75.51, 55.67, 36.59, 35.72, 26.90, 8.35; 19 19F NMR (376 MHz, MeCN-d3): δ -73 (s), -147 (t, J D-F = 18 Hz).

[0062] [Example 2: Synthesis of NpDMBBF] NpDMBBF4 was synthesized according to scheme S3 in Figure 4. To 15.4 mL of 2,2-dimethylbutanoyl chloride (14.4 g, 0.107 mol), a solution of triethylamine (15.4 mL, 11.2 g, 0.111 mol) and neopentylamine (8.1 g, 0.093 mol) in chloroform (80 mL) was slowly added and refluxed for 18 hours. The mixture was washed with water, the organic layer was dried over anhydrous magnesium sulfate, filtered, and then evaporated under low vacuum to quantitatively obtain 2,2-dimethyl-N-neopentylbutanamide. 5.4 g of lithium aluminum hydride (0.14 mol) was suspended in dibutyl ether at 0°C, and 17.5 g of N,N,2,2-tetramethylbutanamide (3) (94.6 mmol) was added. The mixture was stirred at 80°C for 6 hours. The solution was cooled to room temperature, treated with aqueous NaOH solution, and then filtered. The resulting solution was treated with concentrated hydrochloric acid until the pH was 1. After removing most of the solvent under vacuum, the mixture was transferred to a water bath (<295K) and treated with concentrated sodium hydroxide solution until the pH was 14, followed by extraction with diethyl ether. The organic layer was dried over anhydrous magnesium sulfate, filtered, and then partially removed from the residual solvent by low-vacuum evaporation to obtain 2,2-dimethyl-N-neopentylbutane-1-amine (4) in 88% yield (14.2 g, 83.0 mmol, 57 wt%) in ether. The resulting colorless solution was transferred to an ice bath, and formic acid (10.3 g, 0.223 mol) was added, followed by formaldehyde (aq. 37 wt%, 10.2 g, 0.126 mol). The mixture was refluxed for 3 hours. The solution was cooled to room temperature and treated with concentrated hydrochloric acid until the pH was 1. The solvent was partially removed under vacuum at 45°C until a white solid appeared. The mixture was then transferred to a water bath (<295K), treated with concentrated sodium hydroxide solution to pH=14, and extracted with diethyl ether. The organic layer was dried over anhydrous magnesium sulfate, filtered, and then partially removed by low-vacuum evaporation.

[0063] The obtained N,2,2-trimethyl-N-neopentylbutane-1-amine (5) (10.7 g (57.8 mmol) in diethyl ether (53 wt%)) was slowly added to a suspension of Meerwein salt (trimethyloxonium tetrafluoroborate, 9.3 g (63 mmol)) in 100 mL of dichloromethane (<100 ppm water, Ar atmosphere). The suspension was stirred at room temperature for 12 hours to evaporate most of the solvent and remove it, obtaining a white solid. The crude product was further purified by recrystallization from methanol / diethyl ether to obtain NpDMBBF4, which was then dried under vacuum at 80°C for 14 hours to obtain 16.0 g of anhydrous NpDMBBF4 (55.7 mmol) in 96% yield. 1 H NMR(400MHz,MeCN-d3):δ3.37(s,2H),3.34(s,2H),3.27(s,6H),1.47(q,2H,J=7.6Hz),1.21(s,9H),1.18(s,6H),0.91(t,3H,J=7.6Hz); 13 C NMR(101MHz,MeCN-d3): δ78.87,77.05,53.81,36.71,35.90,34.87,30.44,27.08,8.31; 19 F NMR (376MHz, MeCN-d3): δ-150 (s).

[0064] NpDMBF was synthesized according to scheme S4 ​​in Figure 4. 3.0 g of anhydrous NpDMBBF4 (10 mmol) was dissolved in 20 mL of methanol (water content <30 ppm). After adding 0.8 g of KF (14 mmol, dried at 250°C for 8 hours), a precipitate of KBF4 was instantly formed and filtered. BF4 - The conversion rate from ions to fluoride 19 Monitored by F NMR: BF4 - If ions are detected, BF4 -KF was further added to the solution until no ionic impurities were observed in the product. Methanol in the resulting solution was removed by vacuum evaporation. Excess KF was removed by precipitation from methanol / diethyl ether (water content <30 ppm) to obtain a colorless solution, which was further dried under vacuum at 90°C for 19 hours. 0.95 g (4.3 mmol) of a white solid product was recovered in a purification yield of 43%. 1 H NMR(400MHz,MeCN-d3)δ3.36(s,2H),3.34(s,2H),3.23(s,6H),1.48(q,2H,J=7.6Hz),1.18(s,9H),1.16(s,6H),0.90(t,3H,J=7.6Hz); 13 C NMR(101MHz,MeCN-d3): δ78.78,77.33,54.38,37.22,36.50,34.52,30.47,29.30,27.26,8.57; 19 F NMR(376MHz,MeCN-d3):δ-76(s),-144(t,J D-F (=18Hz).

[0065] [Example 3: Synthesis of NpDMBBF] NpADMBF4 was synthesized according to scheme S5 in Figure 5. 5.0 g of 1-(adamantan-1-yl)methaneamine (30 mmol) was added to a room temperature solution of pivalaldehyde (3.3 mL, 2.6 g, 30 mmol) in dichloromethane (50 mL) and stirred for 30 minutes. The solution was then transferred to a water bath (<295 K). 9.1 g of sodium triacetoxyborohydride (43 mmol) was added, and the mixture was stirred for 16 hours (NMR confirmed that the reaction was complete after 2 hours). After the reaction, the mixture was quenched with aqueous NaHCO3 solution and extracted with diethyl ether. The organic layer was treated with concentrated hydrochloric acid to quantitatively obtain the corresponding hydrochloride salt. The hydrochloride salt (6) and 12.0 g of K2CO3 (87.0 mmol) were added to 50 mL of MeOH, and 5.0 mL of MeI (11.4 g, 80.9 mmol) was added to this mixture, which was then heated at 40°C for 26 hours. The mixture was filtered, and the solvent was removed by low vacuum evaporation to obtain a colorless liquid of 5.1 g (21 mmol) of N-(adamantan-1-ylmethyl)-N,2,2-trimethylpropan-1-amine (7) in 70% yield.

[0066] The obtained amine was slowly added to a suspension of Meerwein salt (trimethyloxonium tetrafluoroborate, 4.0 g, 21 mmol) in 20 mL of dichloromethane. The suspension was stirred at room temperature for 16 hours, and most of the solvent was evaporated to obtain a white solid. The crude product was further purified by recrystallization from methanol / diethyl ether to obtain NPADMBF4, which was dried under vacuum at 80°C for 14 hours to obtain anhydrous NpADMBF4 (6.4 g, 15 mmol, 2 ppm water) in 71% yield. 1 H NMR(400MHz,MeCN-d3)δ3.27(s,2H),3.16(s,6H),3.09(s,2H),2.02(m,3H),1.81(m,6H),1.72(m,6H),1.18(s,9H); 13 C NMR(101MHz,MeCN-d3):δ80.33,79.16,55.01,42.37,37.17,36.90,34.64,30.34,29.34; 19 F NMR (376MHz, MeCN-d3): δ-153.

[0067] NpADMF was synthesized according to scheme S6 in Figure 5. 2.0 g of anhydrous NPADMBF4 (5.7 mmol) was dissolved in 20 mL of methanol (water content <30 ppm). After adding 0.4 g of KF (6.9 mmol, dried at 250°C for 8 hours), a precipitate of KBF4 was instantaneously formed and filtered. BF4 - The conversion rate from ions to fluoride 19 Monitored by F NMR: BF4 - If ions are detected, BF4 - KF was further added to the solution until no ionic impurities were observed in the product. Methanol in the resulting solution was removed by vacuum evaporation. Excess KF was removed by precipitation from methanol / diethyl ether (water content <30 ppm), and a colorless solution was obtained after vacuum drying at 90°C for 19 hours. 0.7 g (2.5 mmol) of the white solid product was recovered in a purification yield of 44%. 1 H NMR(400MHz,MeCN-d3)δ3.49(s,2H),3.33(m,8H),3.23(s,6H),1.96(m,3H),1.78(m,6H),1.68(m,6H),1.15(s,9H); 13 C NMR(101MHz,MeCN-d3): δ79.56,78.32,54.66,42.53,37.01,34.49,30.54,29.39; 19 F NMR(376MHz,MeCN-d3):δ-73(s),-147(t,J D-F (=18Hz).

[0068] [Results of Experiment 1] (Solubility) Table 1 summarizes the solubility of MeDMBF, Np2F, NpDMBF, and NpADMF in 19 different solvents, and Table 2 summarizes the residual water content of the dried solvent. MeDMBF, Np2F, and NpDMBF showed high solubility (>1M) in bis(2,2,2-trifluoroethyl) ether (BTFE), dimethyl sulfoxide (DMSO), acetonitrile (MeCN), γ-butyrolactone (GBL), and dichloromethane (DCM). Np2F and NpDMBF also showed high solubility (>1M) in propionitrile (PN). MeDMBF, Np2F, and NpDMBF had low solubility (<0.3M) in hydrocarbon ethers such as N,N-dimethylformamide (DMF) and 1,2-dimethoxyethane (DME). MeDMBF also had low solubility in PN (<0.3M). NpDMBF exhibits higher solubility in DMF compared to MeDMBF and Np2F, which is thought to be due to the increased flexibility of the methyl-substituted alkyl chain. In contrast, NpADMF showed very low solubility (<0.1M) in all aprotic solvents tested, which is thought to be due to the large and rigid structure of the adamantyl substituent.

[0069] [Table 1]

[0070] [Table 2]

[0071] (stability) Anhydrous quaternary ammonium fluoride is F - Due to its small ionic radius and high electronegativity of 3.98, it is strongly basic, and the stability of its fluoride salt in solvents is a concern. Therefore, the stability of MeDMBF, Np2F, NpDMBF, and NpADMF in aprotic solvents was evaluated. 19 Table 3 summarizes the chemical shifts of the F NMR spectrum for all compounds in DCM. - A signal was observed at around -100 ppm, HF2 -Signals for CH2ClF and CH2F2 were observed at -150, -172, and -145 ppm, respectively. This suggests that halogen exchange occurred. In contrast, the compounds in acetonitrile (MeCN), dimethyl sulfoxide (DMSO), γ-butyrolactone (GBL), and propionitrile (PN) showed F - The signal was observed in the lower bound (-73 to -80 ppm), while HF2 - A signal from appeared at the upper limit (-144 to -152 ppm), confirming that the F-anion can deprotonate these solvents. In PN and GBL, HF2 - F is dominant, - From HF2 - This shows an almost complete conversion to HF2 in the fluorinated solvent BTFE. - The signal analysis is ambiguous. 1 From the 1H NMR spectrum, trace amounts of HF2 were detected. - Only one was detected. MeDMBF and NpDMBF may show some reactivity with BTFE, but their potential for broader applications remains promising.

[0072] [Table 3]

[0073] (Thermogravimetric analysis) To investigate the thermal stability of ammonium fluoride salts, thermogravimetric analysis (TGA) was performed in an argon-filled glove box. The mass loss up to 70°C for compounds MeDMBF, Np2F, NpDMBF, and NpADMF was less than 1 wt%, confirming the salts' stability at room temperature. MeDMBF exhibited exceptional stability, with a mass loss up to 108°C of less than 1 wt%, compared to 2%, 3%, and 4% for Np2F, NpDMBF, and NpADMF, respectively. The trend in heat resistance indicates that the reactivity of the fluoride increases with increasing cation size. The long-term stability of these fluoride salts in BTFE is being investigated. 1The reaction was monitored by 1H NMR for 11 months. In all cases, the fluoride did not deprotonate the BTFE solvent, but rather partially reacted with the quaternary cation to form a tertiary amine and fluoromethane.

[0074] (Theoretical calculation 1) DFT calculations were performed using the ORCA5.0.3 software package. The ground state molecular shape was optimized using DFT with the RIJCOSX approximation and TightSCF convergence, based on the M062X / Def2-TZVPP theory. Vibrational analysis of all steady-state structures confirmed the absence of imaginary or negative frequencies. Molecular dynamics simulations were performed at 300K and 1atm using the Gromacs2022.4 software package. The initial dimensions for the simulations were set to 33Å×33Å×33Å, generated by the Packmol program.

[0075] (Theoretical calculation 2) To further understand the relative stabilities of different compounds, theoretical calculations were performed using the ORCA package. The gas phase shapes of the ground state of the initial salt, the decomposition products, and the corresponding transition states were fully optimized using theory at the M06-2X / Def2-TZVPP level. The overall decomposition reaction was exothermic for all compounds, and the decomposition energy (ΔG) was -125, -144, -149, and -152 kJ / mol for MeDMBF, Np2F, NpDMBF, and NpADMF, respectively. The activation energy barrier (ΔG) was also calculated. ‡ The activation energies were calculated to be 123, 112, 109, and 107 kJ / mol for MeDMBF, Np2F, NpDMBF, and NpADMF, respectively. Increasing the size of the ammonium cation decreases the activation energy and increases the reactivity of the fluoride. These results are consistent with experimental observations in TGA and NMR.

[0076] (HOESY) MeDMBF and NpDMBF in 0.9M BTFE 19 F and 1The detailed ion pair structure was revealed by heteronuclear Overhauser effect spectroscopy (HOESY) (Figure 6). - From Anion to MeDMB + α proton (H a ,H b Strong contact between ) and BTFE and α-protons (Hs) was observed. Also, F - From Anion to NpDMB + α proton (H e H f H g ) and the α-proton (H) of BTFE s Strong contact with ) was observed, F - The presence of contact ion pairs or associated structures involving ammonium cations and BTFE was demonstrated.

[0077] (DOSY) In various solvents, F - To gain a more detailed understanding of how anions interact with cations of different sizes, diffusion order spectroscopy (DOSY) measurements were also performed on 0.9 M solutions of MeDMBF, Np2F, and NpDMBF in CD3OD and BTFE, respectively. The ion diffusion coefficient D at room temperature was determined from the DOSY measurements. The ionic conductivity of MeDMBF, Np2F, and NpDMBF was determined from the diffusion coefficient using the Nernst-Einstein relationship, and was 14.9, 17.5, and 19.4 mS / cm, respectively. This trend is consistent with the electrochemical measurements, and the ionic conductivity of MeDMBF, Np2F, and NpDMBF is 2.8, 3.0, and 4.0 mS / cm, respectively, which is comparable to the values ​​of electrolytes used in lithium-ion batteries.

[0078] (Hydrophilic radius of an ion) The hydrodynamic radius of an ion is given by the Stokes-Einstein relationship (r), as shown in Table 4. H =k BThis can be estimated from the diffusion coefficient using T / 6πηD). Increasing the size of the cation effectively reduces the hydrodynamic radius of the corresponding fluoride. The hydrodynamic radius of the fluoride of MeDMBF / BTFE is 8.75 Å, while the radii of the fluorides of Np2F and NpDMBF are smaller, at 7.02 Å and 6.56 Å, respectively. The hydrodynamic radius of F- in all three quaternary ammonium salts is the same as that of bare F. - The ionic radius of the anion (1.2 Å) was much larger, confirming significant ion pair formation. The corresponding hydrodynamic radius of the protic CD3OD was slightly reduced compared to BTFE, but F - Strong contact between the anion and the ammonium cation was also observed by HOESY NMR. These results suggest that ammonium cation and F - A strong interaction between the anions was confirmed. Despite methanol being a protic polar solvent and not normally promoting ion pair formation in solution, it can be concluded that a significant proportion of ion pairs still exist in CD3OD.

[0079] [Table 4]

[0080] (Molecular dynamics simulation) We explored the most likely structures of the contact ion pair between MeDMBF and NpDMBF in BTFE solution using molecular dynamics (MD) simulations. As shown in Figure 7, MeDMBF is mainly F - Four BTFE solvent molecules and one MeDMB around the anion + It has a 5-coordinate contact ion pair structure due to cations, but NpDMBF is NpDMB + Due to the bulkiness of the cation, it has a four-coordinate contact ion pair structure with three BTFE solvent molecules. The radial distribution function (RDF) is shown in Figures 8(a) and (b). F - Cation and BTFE-F - The radii of the coordination shells are 2.5 Å and 2.6 Å, respectively. These small radii are 19 F, 1This is consistent with the strong contact observed in 1H HOESY NMR.

[0081] (Electrochemical stability) Cyclic voltammetry (CV) was performed in a glove box (H2O < 0.1 ppm, O2 < 0.1 ppm) using an HZ-Pro analyzer (Hokuto Denko). A three-electrode cell with platinum as the working electrode and counter electrode was used. A silver wire immersed in 1-methyl-1-propylpyrrolidinium bis(fluorosulfonyl)imide (MPPy-FSI) containing 0.1 M silver trifluoromethanesulfonate was placed in a compartment filled with MPPy-FSI, and a reference electrode (vs. reference) immersed in 0.9 M Np2F / BTFE electrolyte was used. The potentials of Fc / Fc+ in 0.2 M LiTFSI / DMSO solution were determined as follows. -0.42V vs. ref. This value was then determined based on previously published literature (PKR Kottam, D. Kalkan, M. Wohlfahrt-Mehrens and M. Marinaro, J. Electrochem. Soc., 2019, 166, A1574.) for Li + The values ​​were converted to / Li. The water content was measured using a Karl Fischer water titrator (MKH-710M, Kyoto Electronics Manufacturing Co., Ltd.).

[0082] Focusing on electrochemical stability, the voltage windows of these anhydrous fluoride salts in GBL and BTFE were investigated by cyclic voltammetry. The voltage windows of MeDMBF and NpDMBF in BTFE were relatively wide, at 3.3V (0.9-4.2V vs. Li). + / Li) and 3.5V (0.7-4.2V vs. Li) + / Li) and the reference for Np2F is [3.5V (0.7-4.2V vs. Li + It was equivalent to [ / Li)]. Next, the solvent was changed to GBL. GBL makes these fluoride salts highly soluble. However, F - HF2 derived from the deprotonation of GBLs by anions - Due to the high concentration of seeds, the voltage window is 2.3V (1.2-3.5V vs. Li) in the MeDMBF. +The voltage decreased to 2.4V with NpDMBF and 2.4V with Np2F (Figure 9). These results highlight how low HF2 concentrations are essential for achieving a wide voltage window.

[0083] (Half-cell performance) Half-cell devices with bismuth fluoride and carbon electrodes were fabricated using 0.9 M Np2F / BTFE, MeDMBF / BTFE, and NpDMBF / BTFE electrolytes, and their charge-discharge performance in FIB was evaluated. Measurements were performed at 298 K. The double-junction reference electrode consisted of a silver (Ag) wire immersed in a mixture of 1-methyl-1-propylpyrrolidinium bis(fluorosulfonyl)imide (MPPy-FSI) and 0.1 M silver trifluoromethanesulfonate (AgOTf). The electrode was placed in a small compartment filled with MPPy-FSI and immersed in the electrolyte. As a typical example, the cyclic voltammogram of this half-cell using 0.9 M Np2F / BTFE electrolyte is shown in Figure 10(a). In the first cycle, starting from -2.3 V (vs. reference), the current increases sharply during the cathode sweep. This corresponds to the reduction (defluorination) reaction from BiF3 to metallic bismuth. In the next sweep, an oxidation peak pointing towards a positive potential of -1.8V was observed, which corresponds to the oxidation (fluorination) of metallic bismuth. The subsequent cyclic voltammograms overlapped over a considerable range, confirming a stable defluorination / fluorination reaction.

[0084] Figures 10(b), (c), and (d) show the total charge / discharge performance (below 0.1C) of 0.9M Np2F / BTFE, 0.9M MeDMBF / BTFE, and 0.9M NpDMBF / BTFE, respectively. In the case of Np2F / BTFE, the open-circuit voltage (OCV) before charging and discharging was -1.5V. In the initial reduction phase, the potential remained at -2.0V until the capacity reached 100mAh / g, then gradually decreased to the lower limit of -2.5V. Subsequently, in the initial oxidation phase, the potential stabilized around -1.9V before rising sharply. The discharge capacity was 244mAh / g (81% of the theoretical capacity of 302mAh / g), and the charge capacity was 227mAh / g (75% of the theoretical capacity). The discharge and charge capacities of MeDMBF and NpDMBF were equivalent, at 241 mAh / g and 246 mAh / g, and 208 mAh / g and 210 mAh / g, respectively. These results indicate that the three quaternary ammonium fluorides—MeDMBF, NpDMBF, and the reference compound Np2F—are promising as electrolytes for fluoride-ion batteries.

[0085] [Summary of Experiment 1] We investigated quaternary ammonium fluoride-based liquid electrolytes for room-temperature FIB. Three novel anhydrous quaternary ammonium fluorides with different alkyl substituents were synthesized via anion exchange reactions of corresponding tetrafluoroborates and KF in methanol. Two novel compounds with asymmetric substituents, MeDMBF and NpDMBF, exhibited excellent solubility (>1.7 M) and high conductivity (>2 mS / cm). In contrast, the fluoride salt NpADMF, synthesized with a bulky, rigid adamantyl group, showed low solubility (<0.1 M) in all aprotic solvents tested. DOSY and HOESY NMR and theoretical calculations revealed a tendency for increased cation size to lead to higher diffusion constants and thus higher ionic conductivity of the fluoride salt in BTFE solution. Furthermore, it was found that there is a trade-off relationship between ionic conductivity and heat resistance depending on the size of the ammonium cation. The ionic conductivity of electrolytes using MeDMBF / BTFE, Np2F / BTFE, and NpDMBF / BTFE increases with increasing cation size, but the heat resistance of the corresponding fluoride salt decreases. While increasing cation size improves conductivity, stability is compromised. MeDMBF and NpDMBF exhibited a wide voltage window exceeding 3V at room temperature in BTFE. The performance of these electrolytes at room temperature was evaluated by the charge-discharge behavior of a half-cell device using a BiF3 electrode. MeDMBF, NpDMBF, and the reference compound Np2F achieved over 80% of the theoretical capacity (302 mAh / g) in the first charge-discharge cycle.

[0086] The results of Experiment 1 showed that quaternary ammonium fluoride is suitable as an electrolyte for fluoride-ion batteries (FIBs). Furthermore, these findings provide valuable guidance for developing electrolyte systems with excellent solubility and chemical stability.

[0087] [Experiment 2: Synthesis and evaluation of ionic liquid quaternary ammonium TFSI] In Experiment 2, quaternary ammonium bis(trifluoromethylsulfonyl)imide was selected for its excellent chemical stability and good ionic conductivity in order to optimize the ionic liquid molecule for fluoride ion batteries (FIBs). However, the high reactivity of fluoride anions may lead to the formation of tertiary amines by reacting with fluoride, such as 1-methyl-1-propylpyrrolidinium TFSI([P 13 This poses a significant risk to commercially available ionic liquids such as TFSI (N-methyl-N-propylpyrrolidinium-bis(trifluoromethanesulfonyl)imide). To mitigate this risk, it is essential to use ammonium cations that do not contain β-protons.

[0088] In Experiment 2, to overcome the low stability and solubility of quaternary ammonium fluorides, two new ionic liquids based on 3-alkoxy-N,N,2,2-pentamethylpropane-1-ammoniumbis(trifluoromethylsulfonyl)imide were designed and synthesized. Specifically, 3-methoxy-N,N,N,2,2-pentamethylpropane-1-aminium (MNPA)TFSI (Example 4, [MNPA][TFSI]) and N,N,N,2,2-pentamethyl-3-(2,2,2-trifluoroethoxy)propane-1-aminium (NPPA)TFSI (Example 5, [NPPA][TFSI]) were synthesized and evaluated.

[0089] [Design and Composition] As shown in Figures 11 and 12, tetramethylammonium (TMA, Figure 12(a)) TFSI lacks a β-proton, but its high melting point of 134°C makes it unsuitable as a room-temperature electrolyte. Since no alternatives are available, three TFSI salts based on alkylammonium cations lacking β-protons were initially synthesized to help identify suitable TFSI salts with lower melting points. The results showed that replacing one of the methyl groups in the TMA skeleton with a flexible 2,2-dimethylbutyl group lowered the melting point to 48°C (MeDMB, Figure 12(b)). Substitution with two neopentyl groups (Np2), or one neopentyl group and one 2,2-dimethylbutyl group (NpDMB), resulted in melting points of 78°C and 53°C, respectively (Figure 12(b)). These results confirm that flexible substituents on the quaternary ammonium cation are important for keeping the TFSI salt liquid at room temperature. For this reason, alkoxy functional groups have long been used to synthesize ionic liquids with low melting points, low viscosity, and high conductivity. Therefore, to lower the melting point below room temperature, tetramethylammonium (TMA) was substituted with a 1-alkoxy-2,2-dimethylbutyl group. One substitution involved a simple methoxy group, yielding methoxy-N,N,N,2,2-pentamethylpropane-1-aminium (MNPA), while the other involved a trifluoroethoxy group (CF3CH2O-), yielding N,N,N,2,2-pentamethyl-3-(2,2,2-trifluoroethoxy)propane-1-aminium (NPPA). The strongly acidic proton on the trifluoroethoxy group is expected to increase the solubility of the quaternary ammonium fluoride salt through hydrogen bonding. Indeed, both [MNPA][TFSI] and [NPPA][TFSI] were liquid at room temperature (Figure 12(c)).

[0090] The synthesis of these alkyloxy-substituted quaternary ammonium TFSI salts using inexpensive and readily available starting materials employed a simple and safe approach involving Williamson ether synthesis, oxonium methylation of borate, and ion exchange between tetrafluoroborate and LiTFSI. The alkoxy-substituted quaternary ammonium TFSI salts were synthesized according to the scheme shown in Figure 13. To prepare the amino ether intermediates (2a,2b), the commercially available starting material 3-(dimethylamino)-2,2-dimethylpropan-1-ol (1) was first deprotonated with potassium hydride (KH). After deprotonation, an electrophile (RL) was added to substitute the terminal group to obtain the amino ether intermediate. Next, the product of the Williamson ether synthesis was methylated in dichloromethane by oxonium methylation of borate using Meerwein's salt (trimethyloxonium tetrafluoroborate) to obtain tetrafluoroborate (3a,3b). The TFSI salt solution was formed by mixing borate and LiTFSI in dichloromethane. After removing LiBF4 and excess LiTFSI by extraction, the solution was vacuum-dried at 80°C to obtain the TFSI salts ([MNPA][TFSI] and [NPPA][TFSI]) as colorless liquids. The procedure is described in detail below. The purity of the product was determined by the deuterated organic solvent. 1 H, 13 C, and 19 The solid structure was confirmed by 1F NMR, and the low-temperature solid structure was confirmed by single-crystal X-ray diffraction analysis. (1) No toxic chemicals are used, (2) No special handling considerations are required, (3) All reagents are commercially available, (4) The reaction proceeds rapidly, and (5) No complex and expensive purification methods are required for product isolation.

[0091] (material) 3-(dimethylamino)-2,2-dimethylpropan-1-ol, MeI, TsOCH2CF3, trimethyloxonium tetrafluoroborate, and LiTFSI were purchased from Tokyo Chemical Industry Co., Ltd. (TCI). [P 13[TFSI], [DEME], [TFSI], dehydrating solvent, dichloromethane, and THF were purchased from Kanto Chemical Co., Ltd. Potassium hydride, KH, and trimethyloxonium tetrafluoroborate were purchased from Sigma-Aldrich. All chemicals were used as received. Deuterated solvents were purchased from Eurisotop or Cambridge Isotope Laboratories. All deuterated solvents were used as received, with the exception of CD3CN dried on a 4Å molecular sieve. Np2F was prepared based on previous reports. The Pb / PbF2 electrode was prepared based on previous reports.

[0092] [Example 4: Synthesis of [MNPA][TFSI]] [MNPA][TFSI] was synthesized according to scheme S2-1 in Figure 14. 26.2 g of KH (30 wt% dispersion, 0.197 mol) was added to 300 mL of THF at 0°C, and 24.9 g (29.0 mL, 0.190 mol) of 3-(dimethylamino)-2,2-dimethylpropan-1-ol (1) was slowly added. Next, 29.4 g of methyl iodide (12.9 mL, 0.209 mol) was slowly added at 0°C. The mixture was stirred at room temperature for 18 hours. By low-pressure distillation, 17.2 g (0.119 mol) of the 3-methoxy-N,N,2,2-tetramethylpropan-1-amine product was obtained (2a). 9.5 g (0.065 mol) of 3-methoxy-N,N,2,2-tetramethylpropan-1-amine (2a) was slowly added to a suspension of Meerwein salt (trimethyloxonium tetrafluoroborate, 10.0 g, 0.0680 mol) in 150 mL of dichloromethane. The suspension was stirred at room temperature for 2 hours, and 19.7 g (0.0686 mol) of LiTFSI was added to the solution and stirred at room temperature for 1 hour. The reaction mixture was washed with water to remove the solvent and obtain a colorless liquid. This was further dried under vacuum at 80°C for 14 hours to obtain 26.7 g (0.0607 mol) of [MNPA][TFSI] in 93% yield. [MNPA][TFSI]: 1H NMR(400MHz,CD2Cl2):δ3.36(s,3H),3.28(s,2H),3.27(s,2H),3.22(s,9H),1.16(s,6H); 13 C NMR(101MHz,DMSO-d6):δ119.62,78.94,72.64,58.36,54.54,36.91,24.92; 19 F NMR (376 MHz, CD2Cl2): δ-79.

[0093] [Example 5: Synthesis of [NPPA][TFSI]] [NPPA][TFSI] was synthesized according to scheme S2-2 in Figure 15. 20.0 g of KH (30 wt% dispersion, 0.150 mol) was added to 400 mL of THF at 0°C, and 24.9 g (29.0 mL, 0.190 mol) of 3-(dimethylamino)-2,2-dimethylpropan-1-ol (1) was slowly added. Next, 37.0 g (0.168 mol) of 2,2,2-trifluoroethyl-4-methylbenzenesulfonate was slowly added at 0°C. The mixture was stirred at 70°C for 18 hours. By low-pressure distillation, 22.1 g (0.104 mol) of the N,N,2,2-tetramethyl-3-(2,2,2-trifluoroethoxy)propan-1-amine product was obtained (2b). To a suspension of Meerwein salt (trimethyloxonium tetrafluoroborate, 10.0 g, 0.0680 mol) in 150 mL of dichloromethane, 13.8 g (0.0647 mol) of N,N,2,2-tetramethyl-3-(2,2,2-trifluoroethoxy)propan-1-amine (2b) was slowly added. The suspension was stirred at room temperature for 2 hours, and 19.7 g (0.0686 mol) of LiTFSI was added to the solution and stirred at room temperature for 1 hour. The reaction mixture was washed with water to remove the solvent and obtain a colorless liquid. This was further dried under vacuum at 80°C for 14 hours to obtain 29.1 g (0.0573 mol) of [NPPA][TFSI] in 88% yield. [NPPA][TFSI]: 1 H NMR(400MHz,CD2Cl2):δ3.92(q,2H,J H-F =9.4Hz),3.55(s,2H),3.32(s,2H),3.21(s,9H),1.20(s,6H); 13C NMR(101MHz,CD2Cl2):δ126.68,120.33,78.71,74.83,68.85,54.64,37.02,24.54; 19 F NMR (376MHz, CD2Cl2): δ-74,-79.

[0094] [Synthesis of TFSI salts based on alkylammonium cations that do not contain β-protons] [Example 1: Synthesis of [MeDMB] and [TFSI]] [MeDMB][TFSI] was synthesized according to scheme S2-3 in Figure 16. 20 mg (0.086 mol) of [MeDMB][BF4] was dissolved in dichloromethane, and 27 mg (0.095 mol) of LiTFSI was added to the solution and shaken. BF4 - Conversion from ions to TFSI ions 19 The results were monitored using 1F NMR. BF4 - If ions were detected, LiTFSI was added until no more impurities were observed. The mixture was then... 7 The product was washed with water until no Li species were detected by Li NMR. After removing the solvent by vacuum evaporation, the crude product [MeDMB][TFSI] was further dried under vacuum at 90°C for 18 hours to obtain [MeDMB][TFSI] (23 mg, 0.071 mol) as a colorless solid in 83% yield. Melting point: 48°C. 1 H NMR(400MHz,CDCl3):3.22(s,2H),3.21(s,9H),1.48(q,2H,J=7.2Hz),1.17(s,6H),0.92(t,3H,J=7.2Hz); 19 F NMR (376 MHz, CDCl3): δ-77.

[0095] [Example 2: Synthesis of [Np2][TFSI]] [Np2][TFSI] was synthesized according to scheme S2-4 in Figure 16. 20 mg (0.073 mol) of [Np2][BF4] was dissolved in dichloromethane, and 23 mg (0.080 mol) of LiTFSI was added to the solution and shaken. BF 4- Conversion from ions to TFSI ions19 The results were monitored using 1F NMR. BF4 - If ions were detected, LiTFSI was added until no more impurities were observed. The mixture was then... 7 The product was washed with water until no Li species were detected by Li NMR. After removing the solvent by vacuum evaporation, the crude product [Np2][TFSI] was further dried under vacuum at 90°C for 18 hours to obtain 27 mg (0.071 mol) of [Np2][TFSI] as a colorless solid in 97% yield. Melting point: 78°C. 1 H NMR(400MHz,CDCl3):δ3.27(s,4H),3.20(s,6H),1.18(s,18H); 19 F NMR (376 MHz, CDCl3): δ-78.

[0096] [Reference Example 3: Synthesis of [NpDMB] and [TFSI]] [NpDMB][TFSI] was synthesized according to scheme S2-5 in Figure 16. 20 mg (0.070 mol) of [NpDMB][BF4] was dissolved in dichloromethane, and 22 mg (0.077 mol) of LiTFSI was added to the solution and shaken. BF4 - Conversion from ions to TFSI ions 19 The results were monitored using 1F NMR. BF4 - If ions were detected, LiTFSI was added until no more impurities were observed. The mixture was then... 7 The product was washed with water until no Li species were detected by Li NMR. After removing the solvent by vacuum evaporation, the crude product [NpDMB][TFSI] was further dried under vacuum at 90°C for 18 hours to obtain 25 mg (0.066 mmol) of [NpDMB][TFSI] as a colorless solid in 94% yield. Melting point: 53°C; 1 H NMR (400MHz, CDCl3): δ3.31(s,2H),3.29(s,2H),3.25(s,6H),1.48(q,2H,J=7.6Hz),1.22(s,9H),1.18(s,6H),0.92(t,3H,J=7.6Hz); 19 F NMR (376 MHz, CDCl3): δ-78.

[0097] (thermodynamic properties) To investigate the phase transition process, differential scanning calorimetry (DSC) was performed on both [MNPA][TFSI] and [NPPA][TFSI]. No clear crystallization was detected during the cooling process down to -50°C. However, when the temperature was raised from -30°C to -5°C, multiple phase transitions were observed in [MNPA][TFSI] at -23, -20, -11, and -7°C (Figure 17(a)), and in [NPPA][TFSI] at -27, -23, and -17°C (Figure 17(b)), suggesting the possibility of multiple packing modes existing in each ionic liquid. Subsequently, both samples melted at 11°C for [MNPA][TFSI] and 26°C for [NPPA][TFSI]. Both [MNPA][TFSI] and [NPPA][TFSI] remained in a liquid state at room temperature (25°C), exhibiting behavior reminiscent of a supercooled liquid. Thermogravimetric analysis (TGA) was employed to investigate thermal stability. The mass loss of [MNPA][TFSI] and [NPPA][TFSI] up to 292°C was less than 1%, demonstrating the high thermodynamic stability of the synthesized ionic liquids (Figure 18).

[0098] (Single crystal analysis) The crystal structures of [MNPA][TFSI] and [NPPA][TFSI] were determined. The molecular volume of MNPA is 182 Å. 3 The molecular volume of NPPA is 219 Å. 3Single crystal analysis provided further insights into ion-ion arrangement and interactions. Ion-ion interactions in the solid state are often known to correlate with those in the corresponding liquid state. Single crystals for analysis were grown by slowly heating the TFSI salt from -70°C to the crystallization temperature and maintaining it below 0°C using liquid nitrogen. [MNPA][TFSI] has a low melting point, requiring extremely fast mounting (<5 seconds). All samples were measured at -173°C. As shown in Figure 19, intermolecular interactions via CH…O hydrogen bonds were observed, with CH…O distances of 3.151(2) Å for [MNPA][TFSI] and 3.2422(2) Å for [NPPA][TFSI]. The TFSI anion was observed to be in a transoid conformation with CS…SC at 180° in both crystal structures. In these crystal structures, a total of four types of ion-ion interactions exist with respect to the ammonium cation. In [MNPA][TFSI] and [NPPA][TFSI], there are three cation-anion interactions via CH…O, CH…N, and CH…F hydrogen bonds, and one cation-cation interaction via CH…O and CH…F hydrogen bonds, respectively. In [MNPA][TFSI], there are eight molecules around one cation, and there are cation-anion interactions via CH…O, CH…N, and CH…F hydrogen bonds, with the minimum distances between CH…O, CH…N, and CH…F being 3.396(3), 3.609(3), and 3.496(3) Å, respectively. On the other hand, in the crystal structure of [NPPA][TFSI], the minimum distances between CH…O, CH…N, and CH…F decreased to 3.353(5), 3.583(6), and 3.282(7) Å, respectively. In [MNPA][TFSI], a cation-cation interaction between the oxygen of the methoxy group and the α-proton of the methyl group was observed at a CH...O distance of 3.482(3) Å, while in [NPPA][TFSI], a cation-cation interaction between the fluorine of the trifluoroethoxy group and the α-proton of the ammonium group was observed at a CH...F distance of 3.352(5) Å.In [NPPA][TFSI], the short distance between atoms involved in hydrogen bonding indicates that the introduction of the trifluoroethoxy group strengthens anion-cation and cation-cation interactions, resulting in decreased ion diffusion and increased viscosity.

[0099] To determine the energies associated with ion-ion interactions, theoretical calculations were performed using the DLPNO-CCSD(T) method with the def2-TZVPP basis set. The initial shape was extracted from crystal data. For [NPPA][TFSI], the cation-anion attraction was calculated to be -382.6 kJ / mol, and the cation-cation repulsion to be 100.4 kJ / mol. On the other hand, for [MNPA][TFSI], the cation-anion attraction was low at -303.8 kJ / mol, and the cation-cation repulsion was high at 142.6 kJ / mol. Although no significant difference was observed in the partial charge of the α-proton on the MNPA cation and the NPPA cation, it was considered that the strongly electron-withdrawing trifluoroethoxy group enhances the ion-ion attraction not by inductively influencing the partial charge of the α-proton on the ammonium cation, but by providing an additional interaction point. Specifically, the trifluoroethoxy group introduces additional hydrogen bond donors (protons on the trifluoroethoxy group) and additional hydrogen bond acceptors (fluorine atoms on the trifluoroethoxy group). Due to these interactions, the cation-anion attraction is stronger and the cation-cation repulsion is reduced in [NPPA][TFSI], so the melting point of [NPPA][TFSI] is slightly higher at 26°C compared to 11°C for [MNPA][TFSI].

[0100] (Solubility) We first investigated the solubility of two ammonium fluoride salts with different bond energies (TMAF and NP2F) in [MNPA][TFSI] and [NPPA][TFSI]. For comparison, we also investigated the solubility of a commercially available ionic liquid, [P 13 [TFSI] was used as the benchmark. Both TMAF and NP2F were [P 13 Solubility in [MNPA][TFSI] was low (<0.3M). Despite its high bond energy, TMAF showed good solubility in [MNPA][TFSI] (<0.7M), and even higher solubility in [NPPA][TFSI] due to the high acidity of the proton of the 2,2,2-trifluoroethoxy group (<0.9M). Furthermore, NP2F, which has a low bond energy, showed increased solubility in [MNPA][TFSI] and [NPPA][TFSI], reaching 0.8M and 1.1M, respectively.

[0101] (chemical stability) Anhydrous quaternary ammonium fluoride is F - Due to its small ionic radius and high electronegativity of 3.98, Np2F exhibits strong basicity, raising repeated concerns about the stability of its fluoride salts in solvents. Therefore, evaluating the stability of fluoride salts in ionic liquids is extremely important. The stability of [MNPA][TFSI] and [NPPA][TFSI] after dissolving Np2F is important. 1 The stability was investigated by 1H NMR. For comparison, the stability of Np2F in commercially available N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide ([DEME][TFSI]) was also tested. [MNPA][TFSI] and [NPPA][TFSI] showed good stability with respect to fluoride at room temperature. In contrast, [DEME][TFSI] showed decomposition of the DEME cation by Hoffmann elimination, indicating that the absence of a reactive β-proton on the ammonium cation is important for maintaining stability.

[0102] (Electrochemical stability) Turning to electrochemical stability, the voltage window for these ionic liquids is, firstly, 100 μA cm. -2 Any current density cutoff (J)cutoff The stability was evaluated by linear sweep voltammetry defined as (Figure 20). [MNPA][TFSI] showed a wide voltage window of 5.6V, from 0.5V (vs. Li+ / Li) to 6.1V. On the other hand, the oxidation stability of [NPPA][TFSI] improved to 6.3V, and the reduction stability was maintained at 0.5V, resulting in a voltage window of 5.8V. The improved oxidation stability of [NPPA][TFSI] is thought to be due to the introduction of a fluorinated ether functional group into the molecular skeleton, which reduced the oxidation tendency. This is based on reports that electron-withdrawing substituents reduce the electron density on oxygen, thereby increasing stability against oxidation. The excellent electrochemical stability of [MNPA][TFSI] and [NPPA][TFSI] was maintained even after dissolving 0.1M Np2F fluoride salt, with voltage windows of 5.4V (0.5~5.9V vs. Li+ / Li+) respectively. + / Li) and 5.7V (0.5~6.2V vs. Li) + The voltage window for these ionic liquid-based electrolytes is 2V wider than that of the previously reported Np2F / BTFE electrolyte (3.5V).

[0103] (Ionic conductivity) The ionic conductivity of [MNPA][TFSI] and [NPPA][TFSI] was first measured by electrochemical measurements. At 25°C, [MNPA[TFSI]] showed a higher conductivity of 1.92 mS / cm compared to [NPPA][TFSI]'s 1.27 mS / cm. At 55°C, [NPPA][TFSI] reached 8.69 mS / cm, 1.9 times the value at 25°C, while [MNPA][TFSI] was 4.60 mS / cm. In contrast, the conductivity of 0.5M [MNPA][TFSI] / Np2F and 0.5M [NPPA][TFSI] / Np2F decreased to approximately 0.83 mS / cm and 0.82 mS / cm respectively at 25°C, compared to their respective original ionic liquids. This similarity in conductivity persisted even as the temperature rose to 40°C.

[0104] (NMR dynamic behavior) To better understand the dynamics and structural interactions of these ionic liquid mixtures containing fluoride salts (TMAF, Np2F), diffusion order spectroscopy (DOSY) measurements were applied to collect information on the translational motion of individual cations and anions in the mixtures, respectively. The diffusion coefficients D of the anions and cations in all samples were, respectively. 19 F and 1 Measurements were taken in the frequency domain of H. D showed temperature dependence in the range of 298 K (25 °C) to 328 K (55 °C) (Figure 21), and the activation energy barrier for ion translation was determined using Arrhenius's equation. The correlation between D and viscosity (η) was fitted using the fractional Stokes-Einstein (FSE) relation (D∝(T / η)m). Table 5 shows the diffusion coefficients, viscosity, and activation energies of 0.5 M mixtures of these ionic liquids and Np2F. In the 1H spectra of these ionic liquid mixtures, most peaks overlap, especially in the [MNPA][TFSI] mixture, so the corresponding diffusion coefficient is the average value of the two cations.

[0105] [Table 5]

[0106] In pure ionic liquids, TFSI anions diffuse faster than NMPA and NPPA cations, and the transition number (D TFSI / D Total The values ​​were 0.52 and 0.54, respectively. [MNPA][TFSI] total is 17.16 × 10 -12 m 2 s -1 Therefore, because the viscosity of [MNPA] and [TFSI] is low, D total 7.94 × 10 -12 m 2 s -1 It diffused faster than [NPPA][TFSI]. The same was true for the ionic liquid mixture of 0.5M TMAF and Np2F. totalThe same trend was observed, and the ionic liquid using [MNPA][TFSI] diffused faster than the mixture using [NPPA][TFSI]. When comparing the mixed solutions of TMAF and Np2F, since the dissociation energy of Np2F is lower, the mixed solution of Np2F showed faster diffusion than TMAF. The transference number of anions increased in the order of ionic liquid with TMAF added < ionic liquid with TMAF added < ionic liquid with Np2F added, and the activation energy increased in the order of ionic liquid with TMAF added < ionic liquid with TMAF added < ionic liquid with Np2F added. These results indicate that by introducing strong anion-cation interactions between fluoride anions and ammonium cations using ammonium fluoride with a large cation, the anion-cation interactions between TFSI anions and ammonium cations are reduced.

[0107] Regarding the D value of fluoride anions, F in [NPPA][TFSI] / TMAF - Only the diffusion coefficient of anions was determined to be 1.03×10 -12 m 2 s -1 at 298 K using a diffusion probe in the frequency region of 752 MHz. The D value of fluoride anions in [NPPA][TFSI] / TMAF is lower than that of ammonium cations and TFSI anions, but since the activation energy of fluoride anions is the lowest among these ions, it was shown that the mobility of fluoride anions in the ionic liquid mixture is high.

[0108] Spin-lattice (longitudinal relaxation, T1) and spin-spin (transverse relaxation, T2) are sensitive to intramolecular and intermolecular relaxation mechanisms and can be used to explore the reorientation dynamics of the system. Therefore, for both cations and anions, in the temperature range of 298 K - 328 K, respectively 1 H and 19T1 and T2 were measured using 1F NMR. The inversion recovery method and the Carr-Purcell-Meiboom-Gill (CPMG) method were used to estimate T1 and T2, respectively. Because the fluoride signal was weak, the T2 of the observed fluoride anion was determined by the full width at half maximum (ΔLW). For these ionic liquid mixtures... 1 In the H spectrum, especially for [MNPA][TFSI] and its fluoride salt mixture, most peaks overlap, so the corresponding relaxation time is the average of the two cation species. The T1 / T2 ratio is a useful parameter for investigating the local order of the system. The T1 / T2 ratio is equal to 1 in isotropic fluids, and a larger value indicates the presence of local structure. (H) a Table 6 summarizes the T1 / T2 ratios of cations and fluorine α-protons at room temperature. The T1 / T2 ratio of cations and anions in ionic liquid electrolytes containing Np2F is higher than that of ionic liquids without ammonium fluoride salts. On the other hand, the T1 / T2 ratio of Np2F / [NPPA][TFSI] is higher than that of Np2F / [MNPA][TFSI]. In particular, the T1 / T2 ratio of TFSI anions in Np2F / [NPPA][TFSI] increased to more than 10 after dissolving Np2F, indicating the presence of a localized structure. These results are consistent with the stronger ion-ion interactions observed in the single crystal structure (Figure 19). [NPPA][TFSI], which has a trifluoroethoxy group, has high solubility in fluoride salts, but its diffusivity is lower compared to [MNPA][TFSI] due to the resulting increase in viscosity. Based on this evaluation, we concluded that Np2F / [MNPA][TFSI] is a more suitable electrolyte for fluoride-ion batteries.

[0109] [Table 6]

[0110] (Battery performance) Finally, the performance of 0.5 M Np2F / [MNPA][TFSI] and 0.5 M Np2F / [NPPA][TFSI] electrolytes was evaluated in an operating test cell at 25°C. In the three-electrode test cell, Pb / PbF2, Pb foil, and silver trifluoromethanesulfonate (AgOTf) / Ag electrodes were used as the working electrode, counter electrode, and reference electrode, respectively. Np2F / [MNPA][TFSI] showed a 1 μA / cm² higher flow rate than Np2F / [NPPA][TFSI]. 2 The system showed a stable charge-discharge voltage plateau for 100 hours (Figures 22 and 23). These results confirm a stable and reversible (de)fluorination reaction at the Pb / PbF2 working electrode using the Np2F / [MNPA][TFSI] electrolyte, suggesting that Np2F / [MNPA][TFSI] is a promising electrolyte candidate for fluoride-ion batteries.

[0111] [Summary of Experiment 2] We investigated liquid electrolytes based on quaternary ammonium TFSI ionic liquids for room temperature FIB. Two novel quaternary ammonium TFSIs, [MNPA][TFSI] and [NPPA][TFSI], possessing a 3-alkyloxy-N,N,N,2,2-pentamethylpropane-1-aminium skeleton, were designed and synthesized using a simple and safe approach involving Williamson ether synthesis, oxonium methylation of borate, and ion exchange with tetrafluoroborate and LiTFSI, using inexpensive and readily available starting materials. [MNPA][TFSI] and [NPPA][TFSI] showed good stability against Hoffmann elimination and exhibited excellent electrochemical stability with broad potential windows of 5.5V and 5.7V, respectively. The excellent electrochemical stability of [MNPA][TFSI] and [NPPA][TFSI] was maintained even after dissolving 0.1M Np2F fluoride salt, resulting in potential windows of 5.4V (0.5-5.9V vs. Li) respectively. + / Li) and 5.7V (0.4-6.2V vs. Li) +The result was / Li). The high voltage window and improved solubility of Np2F / [NPPA][TFSI] are attributed to the fluorinated ether functional group (trifluoromethoxy group) of the ammonium skeleton. Intramolecular / intermolecular interactions were evaluated by single crystal analysis, DOSY NMR, and T1,T2 relaxation times, and the Np2F / [MNPA][TFSI] combination was found to be the optimal combination with the highest diffusivity, lowest viscosity, and lowest T1 / T2 ratio. Finally, in a preliminary study of battery performance using a Pb / PbF2 working electrode with an MNPATSI / Np2F electrolyte, 1 μA / cm² was observed at 100 hours. 2 A stable plateau in charge and discharge voltage was observed. In terms of battery performance, a stable and reversible (de)fluorination reaction was demonstrated using a Pb / PbF2 working electrode with an Np2F / [MNPA][TFSI] electrolyte. These findings provide valuable guidance for developing electrolyte systems with excellent solubility and chemical stability in order to develop high-performance FIBs.

[0112] Although the present invention has been described above with reference to embodiments and examples, the present invention is not limited to the above embodiments and examples. Various modifications to the configuration and details of the present invention can be understood by those skilled in the art within the scope of the present invention.

[0113] The patents, patent applications, and documents cited herein are incorporated herein by reference in the same manner as their contents are specifically described herein.

[0114] <Note> Some or all of the above embodiments and examples may be described as follows, but are not limited to the following. <Salt> (Note 1) It is salt, It contains organic cations and anions, The aforementioned organic cation does not have hydrogen at the β-carbon, has an asymmetric structure, and is 170 Å. 3 Having the above molecular volume, salt. (Note 2) The salt according to Appendix 1, wherein the charge center of the organic cation is N, P, S, or O. (Note 3) The aforementioned organic cation is 200 Å 3 A salt according to Appendix 1 or 2 having the above molecular volume. (Note 4) A salt described in any of the appendices 1 to 3, having a solubility of 2.6 M or higher in bis(2,2,2-trifluoroethyl) ether at 25°C. (Note 5) A salt as described in any of the appendices 1 to 4, wherein the ionic conductivity when dissolved in bis(2,2,2-trifluoroethyl) ether at a concentration of 0.9 M at 25°C is 3.0 mS / cm or higher. (Note 6) The aforementioned organic cation is a salt represented by the following general formula (I), as described in any of the appendices 1 to 5. [C1] JPEG2026092491000016.jpg1652 (In general formula (I), R1 and R2 are, independently, H, substituted or unsubstituted C1-C 20 Alkyl, C3-C 20 Cycloalkyl, C5-C 30 Aryl, C5-C 30 Heteroaryl, C1-C 20 Asyl, C2-C 20 Alkenil, C3-C 20 Cycloalkenyl, C2-C 20 Alkinyl, C5-C 20 Alkylaryl, C2-C 20 (It is an alkoxycarbonyl or halogen group.) (Note 7) In the above general formula (I), R1 and R2 are, independently, the salts described in Appendix 6, represented by the following general formulas (II-1) to (II-10) and general formula (III). [Case 2] JPEG2026092491000017.jpg91148[3] JPEG2026092491000018.jpg1764 (In general formula (III), R5 is H or a fluoroalkyl group.) (Note 8) The aforementioned anion is a fluoride ion, A salt used as an electrolyte, as specified in any of the appendices 1 to 7. (Note 9) The salt according to any of the appendices 1 to 7, wherein the anion is a sulfonylimid anion. (Note 10) The salt described in Appendix 9, wherein the anion is a fluorine-containing anion. (Note 11) The salt described in Appendix 10, wherein the fluorine-containing anion is a fluorine-containing sulfonylimide anion represented by the following general formula (IV). [C4] JPEG2026092491000019.jpg2277 (in general formula (IV), R 7 and R 8 Each independently represents either a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms. 7 and R 8 These may bond to each other to form a perfluoroalkylene group having 3 to 5 carbon atoms. (Note 12) The aforementioned organic cation is a salt represented by the following general formula (V), as described in any of the appendices 9 to 11. [5] JPEG2026092491000020.jpg1564 (in general formula (V), R 9 CH3, CF3, CH2CF3, CF2CF 3、 CH2CH2CF 3、 (It is CH2CF2CF3 or CF2CF2CF3) (Note 13) A salt described in any of the appendices 9 to 11, wherein the solubility of N,N-dimethyl-N,N-dineopentylammonium fluoride at 25°C is 0.5 M or higher. (Note 14) A salt that is liquid at 25°C, as described in any of appendices 9 to 12. (Note 15) The salt described in Appendix 13, used as an electrolyte. <Electrolytes> (Note 16) An electrolyte containing a salt as described in any of the notes 1 to 8. <Electrolyte> (Note 17) An electrolyte containing one of the salts listed in any of the appendices 9 to 15. <Secondary battery> (Note 18) A secondary battery using the electrolyte described in Appendix 16. (Note 19) A secondary battery using the electrolyte described in Appendix 17. (Note 20) A secondary battery, which is a fluoride ion battery, as described in Appendix 18 or 19. [Industrial applicability]

[0115] As described above, the salts of this disclosure have good solubility and chemical stability and can be used as electrolytes and electrolyte solutions. For this reason, this disclosure is useful, for example, in secondary batteries such as fluoride-ion batteries.

Claims

1. It is salt, It contains organic cations and anions, The aforementioned organic cation does not have hydrogen at the β-carbon, has an asymmetric structure, and is 170 Å. ３ Having the above molecular volume, salt.

2. The salt according to claim 1, wherein the charge center of the organic cation is N, P, S, or O.

3. The aforementioned organic cation is 200 Å. ３ The salt according to claim 1 or 2 having the above molecular volume.

4. The salt according to any one of claims 1 to 3, wherein its solubility in bis(2,2,2-trifluoroethyl) ether at 25°C is 2.6 M or higher.

5. The salt according to any one of claims 1 to 4, wherein the ionic conductivity when dissolved in bis(2,2,2-trifluoroethyl) ether at a concentration of 0.9 M at 25°C is 3.0 mS / cm or more.

6. The organic cation is a salt according to any one of claims 1 to 5, represented by the following general formula (I). 【Chemistry 1】 (In general formula (I), R １ and R ２ are each independently H, substituted or unsubstituted C １ -C ２０ alkyl, C ３ -C ２０ cycloalkyl, C ５ -C ３０ aryl, C ５ -C ３０ heteroaryl, C １ -C ２０ acyl, C ２ -C ２０ alkenyl, C ３ -C ２０ cycloalkenyl, C ２ -C ２０ alkynyl, C ５ -C ２０ alkylaryl, C ２ -C ２０ alkoxycarbonyl, or a halogen group.)

7. In the above general formula (I), R １ and R ２ The salt according to claim 6, wherein each of these is independently represented by the following general formulas (II-1) to (II-10) and the following general formula (III). 【Chemistry 2】 【Transformation 3】 (In general formula (III), R ５ (This is either H or a fluoroalkyl group.)

8. The aforementioned anion is a fluoride ion, A salt according to any one of claims 1 to 7, used as an electrolyte.

9. The salt according to any one of claims 1 to 7, wherein the anion is a sulfonylimid anion.

10. The salt according to claim 9, wherein the anion is a fluorine-containing anion.

11. The salt according to claim 10, wherein the fluorine-containing anion is a fluorine-containing sulfonylimide anion represented by the following general formula (IV). 【Chemistry 4】 (In general formula (IV), R ７ and R ８ Each of these independently represents either a fluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms. ７ and R ８ These may bond to each other to form a perfluoroalkylene group having 3 to 5 carbon atoms.

12. The organic cation is represented by the following general formula (V), and is a salt according to any one of claims 9 to 11. 【Transformation 5】 (In general formula (V), R ９ CH ３ CF ３ ,CH ２ CF ３ CF ２ CF ３、 CH ２ CH ２ CF ３、 CH ２ CF ２ CF ３ or CF ２ CF ２ CF ３ (is)

13. The salt according to any one of claims 9 to 11, wherein the solubility of N,N-dimethyl-N,N-dineopentylammonium fluoride at 25°C is 0.5 M or higher.

14. A salt according to any one of claims 9 to 12, which is liquid at 25°C.

15. The salt according to claim 13, used as an electrolyte.

16. An electrolyte comprising the salt according to any one of claims 1 to 8.

17. An electrolyte containing the salt described in any one of claims 9 to 15.

18. A secondary battery using the electrolyte described in claim 16.

19. A secondary battery using the electrolyte described in claim 17.

20. A secondary battery according to claim 18 or 19, which is a fluoride ion battery.

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