MIXTURE, ELECTRODE FOR ELECTROCHEMICAL DEVICE, AND ELECTROCHEMICAL DEVICE

Abstract

To provide a novel mixture that is liquid at room temperature.SOLUTION: A mixture is provided, including a lithium salt and a compound represented by the following general formula (1). [In the formula (1), R1 and R2 each independently represent a hydrogen atom, an alkyl group, or a substituted amino group. R3 and R4 each independently represent an alkyl group. R1 and R3 and R2 and R4 may be bonded to each other to form a ring together with the atoms to which they are bonded. R5 represents an alkylene group].SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a mixture, an electrode for an electrochemical device, and an electrochemical device. [Background technology]

[0002] In recent years, eutectic mixtures of hydrogen bond donors and hydrogen bond acceptors have attracted attention as new organic materials or organic fluids. Eutectic mixtures have the property of exhibiting a melting point lower than the melting points of the hydrogen bond donors and hydrogen bond acceptors due to the eutectic (eutectic) structure, and those that are liquid at around room temperature are also called deep eutectic solvents. Eutectic mixtures have been actively researched and developed because their physical properties can be adjusted by the combination of the mixtures (e.g., Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2016-538405 [Patent Document 2] Special Publication No. 2016-534958 Summary of the Invention [Problem to be solved by the invention]

[0004] The primary objective of the present disclosure is to provide novel mixtures that are liquid at room temperature. [Means for solving the problem]

[0005] According to the investigations of the present inventors, it has been found that by mixing a lithium salt with a compound represented by general formula (1), a mixture that is liquid at room temperature can be obtained.

[0006] One aspect of the present disclosure relates to a mixture, which includes a lithium salt and a compound represented by the following general formula (1): [ka] [In formula (1), R 1 and R 2 each independently represents a hydrogen atom, an alkyl group, or a substituted amino group. R 3 and R 4 each independently represents an alkyl group. R 1 and R 3 and R 2 and R 4 may be bonded to each other to form a ring together with the atoms to which they are bonded. R 5 represents an alkylene group.

[0007] R 1 and R 2 may be a substituted amino group.

[0008] The compound represented by general formula (1) may be a compound represented by the following general formula (3). [ka] [In formula (3), R A , R B , R C , R D , R E , and R F each independently represents an alkyl group having 1 to 4 carbon atoms. R G represents an alkylene group having 1 to 4 carbon atoms.]

[0009] The lithium salt may be lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethanesulfonyl)imide.

[0010] Another aspect of the present disclosure relates to an electrode for an electrochemical device. The electrode for an electrochemical device includes a current collector and an electrode mixture layer provided on at least one main surface of the current collector. The electrode mixture layer contains an electrode active material, an electrolyte salt, and the above-mentioned mixture.

[0011] Another aspect of the present disclosure relates to an electrochemical device. The electrochemical device includes the above-described electrode for an electrochemical device. The electrochemical device may be a secondary battery. [Effects of the Invention]

[0012] The present disclosure provides a novel mixture that is liquid at room temperature. The present disclosure also provides an electrode for an electrochemical device using such a mixture, and an electrode for an electrochemical device. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view showing an electrochemical device according to a first embodiment. [Figure 2] FIG. 2 is an exploded perspective view showing an electrode group of the electrochemical device shown in FIG. [Figure 3] FIG. 3(a) is a cross-sectional view taken along line II in FIG. 2 to explain an electrode for electrochemical devices (positive electrode) according to one embodiment, and FIG. 3(b) is a schematic cross-sectional view showing an electrode for electrochemical devices (positive electrode) according to another embodiment. [Figure 4] FIG. 4(a) is a cross-sectional view taken along line II-II in FIG. 2 to explain an electrode for electrochemical devices (negative electrode) according to one embodiment, and FIG. 4(b) is a schematic cross-sectional view showing an electrode for electrochemical devices (negative electrode) according to another embodiment. [Figure 5] FIG. 5 is an exploded perspective view showing an electrode group of an electrochemical device according to a second embodiment. [Figure 6]FIG. 6(a) is a cross-sectional view taken along the line III-III in FIG. 2 for explaining an electrode for electrochemical devices (bipolar electrode) according to another embodiment, and FIG. 6(b) is a schematic cross-sectional view showing an electrode for electrochemical devices (bipolar electrode) according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings as appropriate. However, the present disclosure is not limited to the following embodiments. In the following embodiments, the components (including steps, etc.) are not essential unless specifically stated. The sizes of the components in each figure are conceptual, and the relative size relationships between the components are not limited to those shown in each figure.

[0015] The same applies to numerical values ​​and ranges in this specification and do not limit the present disclosure. In this specification, numerical ranges indicated using "to" indicate ranges that include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In addition, in numerical ranges described in this specification, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. In addition, the upper and lower limits described individually can be arbitrarily combined. Furthermore, "A or B" may include either A or B, or may include both. Furthermore, unless otherwise specified, the materials exemplified below may be used alone or in combination of two or more. When multiple substances corresponding to each component are present in the composition, the content of each component in the composition refers to the total amount of those multiple substances present in the composition, unless otherwise specified.

[0016] In this specification, the term "electrode" refers to a positive electrode or a negative electrode. The same applies to other similar expressions such as an electrode current collector, an electrode mixture layer, an electrode active material, an electrode active material layer, and an electrode precursor.

[0017] In this specification, the following abbreviations may be used: [Nf2] - : Bis(fluorosulfonyl)imide anion [NTf2] - :Bis(trifluoromethanesulfonyl)imide anion [f3C] - : Tris(fluorosulfonyl)carbanion [BOB] - : Bis(oxalato)borate anion

[0018] In this specification, "room temperature" means 25°C.

[0019] [Mixture] A mixture according to one embodiment includes a lithium salt and a compound represented by general formula (1). The lithium salt and the compound represented by general formula (1) are typically solid at room temperature. The inventors have discovered that a mixture in a liquid state at room temperature can be obtained by mixing a lithium salt with a compound represented by general formula (1). While the interaction between the lithium salt and the compound represented by general formula (1) in the mixture is not entirely clear, it is presumed that the oxygen atom of the carbonyl group in the compound represented by general formula (1) strongly interacts with the lithium cation of the lithium salt. The inventors believe that this interaction is responsible for the liquid state. The mixture according to this embodiment is expected to have properties similar to those exhibited in ionic liquids, eutectic mixtures (deep eutectic solvents), and the like. Furthermore, the physical properties can be adjusted by adjusting the type of lithium salt, the type of compound represented by general formula (1), the molar ratio of the combination of the two, and the like.

[0020] (lithium salts) The lithium salt may be LiPF, LiBF, Li[Nf], Li[NTf], Li[fC], Li[BOB], LiClO, LiBF(CF), LiBF(C), LiBF(C), LiBF(C), LiBF(C), LiC(SOCF), LiCFSO, LiCFCOO, or LiRCOO (where R is an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a naphthyl group). Among these, the lithium salt may be Li[Nf] or Li[NTf] from the viewpoint of thermal or electrochemical stability and dissociation. Using a highly dissociable lithium salt can enhance the ionic conductivity of the mixture of this embodiment and is expected to maintain a liquid state even at lower temperatures. Commercially available lithium salts can be used.

[0021] (Compound represented by general formula (1)) [ka] [In formula (1), R 1 and R 2 each independently represents a hydrogen atom, an alkyl group, or a substituted amino group. R 3 and R 4 each independently represents an alkyl group. R 1 and R 3 and R 2 and R 4 may be bonded to each other to form a ring together with the atoms to which they are bonded. R 5 represents an alkylene group.

[0022] R 1 and R 2Examples of the alkyl group include linear, branched, and cyclic alkyl groups. Specific examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl, n-hexyl, cyclohexyl, n-heptyl, and n-octyl groups. The number of carbon atoms in the alkyl group may be 1 to 10, 1 to 8, 1 to 6, 1 to 4, or 1 to 2. The alkyl group may be, for example, a methyl group.

[0023] R 1 and R 2 Examples of the substituted amino group include a dialkylamino group, a dicycloalkylamino group, and a diarylamino group. The substituted amino group may be, for example, a dialkylamino group. The alkyl group in the dialkylamino group may be, for example, R 1 and R 2 Examples of the dialkylamino group include the same as the alkyl group in the above. The number of carbon atoms in the alkyl group may be 1 to 10, 1 to 8, 1 to 6, 1 to 4, or 1 to 2. Specific examples of the dialkylamino group include a dimethylamino group, a diethylamino group, and a di(n-propyl)amino group. The dialkylamino group may be, for example, a dimethylamino group.

[0024] R 1 and R 2 may be the same or different, but from the viewpoint of compound synthesis, it is preferable that they are the same. 1 and R 2 may be a substituted amino group from the viewpoint of the reduction stability of the compound.

[0025] R 3 and R 4 The alkyl group of R 1 and R 2 Examples of the alkyl group include the same as those of the alkyl group in R. The number of carbon atoms in the alkyl group may be 1 to 10, 1 to 8, 1 to 6, 1 to 4, or 1 to 2. The alkyl group may be, for example, a methyl group. 3 and R4 may be the same or different, but are preferably the same from the viewpoint of compound synthesis.

[0026] R 5 Examples of the alkylene group include linear, branched, and cyclic alkylene groups. Specific examples of the alkyl group include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a decanylene group, and a dodecanylene group. The number of carbon atoms in the alkyl group may be 1 to 20, 1 to 16, 1 to 12, 1 to 8, or 1 to 4. The alkylene group may be, for example, an ethylene group.

[0027] R 1 and R 3 and R 2 and R 4 may be bonded to each other to form a ring together with the atoms to which they are bonded. The ring may be a 4-membered ring, a 5-membered ring, or a 6-membered ring, or may be a 5-membered ring. 1 and R 2 When is a substituted amino group, examples of compounds forming such a ring include compounds represented by general formula (2).

[0028] [ka] [In formula (2), n1 and n2 each independently represent an integer of 1 to 3. R 5 is synonymous with the above. R 6 and R 7 each independently represents an alkyl group. R 8 and R 9 Each of R independently represents a hydrogen atom or an alkyl group. 8 may be the same or different. 8 may be the same or different.]

[0029] n1 and n2 are 1 to 3, may be 2 or 3, or may be 2. That is, the formed ring is a 4-membered ring, a 5-membered ring, or a 6-membered ring, or may be a 5-membered ring or a 6-membered ring, or may be a 5-membered ring. n1 and n2 may be the same or different, but are preferably the same.

[0030] R 6 and R 7 The alkyl group of R 1 and R 2 Examples of the alkyl group include the same as those of the alkyl group in R. The number of carbon atoms in the alkyl group may be 1 to 10, 1 to 8, 1 to 6, 1 to 4, or 1 to 2. The alkyl group may be, for example, a methyl group. 6 and R 7 may be the same or different, but are preferably the same.

[0031] R 8 and R 9 The alkyl group of R 1 and R 2 The alkyl group may have 1 to 10, 1 to 8, 1 to 6, 1 to 4, or 1 to 2 carbon atoms.

[0032] Multiple Rs 8 It is preferable that each of R is the same. 9 It is preferable that R 8 and R 9 may be the same or different, but are preferably the same. 8 and R 9 may be a hydrogen atom.

[0033] The compound represented by general formula (1) may be a compound represented by the following general formula (3).

[0034] [ka] [In formula (3), R A , R B , R C , R D , R E , and R F each independently represents an alkyl group having 1 to 4 carbon atoms. R G represents an alkylene group having 1 to 4 carbon atoms.]

[0035] R A , R B , R C , R D , R E , and R F The alkyl group in R may be, for example, a linear or branched alkyl group having 1 to 4 carbon atoms, or may be a methyl group. A , R B , R C , R D , R E , and R F may be the same or different, but are preferably the same.

[0036] R G The alkylene group may be, for example, a linear or branched alkylene group having 1 to 4 carbon atoms, and may be a methyl group or an ethylene group, or may be an ethylene group.

[0037] The compound represented by general formula (1) can be obtained, for example, by reacting a compound represented by the following general formula (4), a compound represented by the following general formula (5), and a compound represented by the following general formula (6). The reaction may be carried out in the presence of a base, if necessary.

[0038] [ka]

[0039] In the compound represented by general formula (1), R 1 and R 2When the same group is introduced as above, the compound represented by general formula (4) can be reacted with a compound represented by general formula (5) in an amount about twice (or more) the molar amount of the compound represented by general formula (4) to obtain the desired compound represented by general formula (1).

[0040] Examples of the base include amines such as pyridine and triethylamine, metal hydroxides such as sodium hydroxide, and carbonates such as sodium carbonate and sodium hydrogencarbonate. The amount of the base added is not particularly limited, but may be 2 times or more by mole relative to the compound represented by general formula (4).

[0041] In the compound represented by general formula (1), R 1 and R 2 When a different group is introduced as a base, a compound represented by general formula (4) is reacted with a compound represented by general formula (5) in an amount approximately equimolar (1 fold molar) relative to the compound to obtain an intermediate represented by general formula (7) below. The amount of base added is not particularly limited, but may be approximately equimolar (1 fold molar) relative to the compound represented by general formula (4). The intermediate represented by general formula (7) is then reacted with a compound represented by general formula (6) in an amount approximately equimolar (1 fold molar) relative to the compound represented by general formula (7), thereby obtaining the desired compound represented by general formula (1). The amount of base added is not particularly limited, but may be approximately equimolar (1 fold molar) relative to the compound represented by general formula (7).

[0042] [ka]

[0043] The reaction conditions for synthesizing the compound represented by general formula (1) can be appropriately selected depending on the raw materials used. Examples of reaction conditions include stirring in the absence or presence of a solvent at a reaction temperature of -30 to 200°C for a reaction time of 0.5 to 48 hours. The solvent can be appropriately selected from organic solvents commonly used in organic synthesis, water, aqueous organic solvents, etc., depending on the raw materials, reaction conditions, etc.

[0044] The mixture of this embodiment can be obtained by mixing a lithium salt with a compound represented by general formula (1).

[0045] When mixing the lithium salt and the compound represented by general formula (1), the molar ratio of the compound represented by general formula (1) to the lithium salt (moles of the compound represented by general formula (1) / moles of the lithium salt) may be 1 to 20, since a predetermined mixture is easily obtained. The molar ratio of the compound represented by general formula (1) to the lithium salt may be 1.5 or more, 2 or more, 2.5 or more, 3 or more, 4 or more, or 5 or more, and may be 18 or less, 15 or less, 12 or less, or 10 or less. The molar ratio of the compound represented by general formula (1) to the lithium salt in the resulting mixture (moles of the compound represented by general formula (1) / moles of the lithium salt) may be the same as the molar ratio when mixing the lithium salt and the compound represented by general formula (1).

[0046] When synthesizing the mixture, the mixture may be heated as needed. The reaction temperature may be, for example, 25 to 200°C.

[0047] The mixture may consist of a lithium salt and a compound represented by general formula (1), but may also contain other components, such as additives for secondary batteries, such as vinylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, and succinonitrile.

[0048] In this way, the mixture of this embodiment can be obtained. The mixture of this embodiment is expected to be excellent in ionic conductivity, flame retardancy, non-volatility, high-temperature decomposition resistance, etc. The mixture of this embodiment can be suitably used, for example, for forming an interface between an electrode active material and an electrolyte salt in an electrode mixture layer of an electrochemical device (secondary battery).

[0049] [Electrodes for electrochemical devices and electrochemical devices] <Electrochemical Device (First Embodiment)> 1 is a perspective view showing an electrochemical device according to a first embodiment. The electrochemical device may be, for example, a secondary battery. Hereinafter, an embodiment of the secondary battery will be described.

[0050] As shown in FIG. 1, a secondary battery 1 includes an electrode group 2 composed of electrodes for electrochemical devices and a separator, a bag-shaped battery exterior 3 that houses the electrode group 2, and an electrolyte (not shown) that is poured into the battery exterior 3. The electrodes for electrochemical devices may be positive electrodes or negative electrodes. The electrodes for electrochemical devices (positive electrodes and negative electrodes) are provided with a positive electrode current collecting tab 4 and a negative electrode current collecting tab 5, respectively. The positive electrode current collecting tab 4 and the negative electrode current collecting tab 5 protrude from the inside to the outside of the battery exterior 3 so that the positive electrode and the negative electrode, respectively, can be electrically connected to the outside of the secondary battery 1.

[0051] The battery outer casing 3 may be formed of, for example, a laminate film. The laminate film may be a laminate film in which a resin film such as a polyethylene terephthalate (PET) film, a metal foil such as aluminum, copper, or stainless steel, and a sealant layer such as polypropylene are laminated in this order.

[0052] FIG. 2 is an exploded perspective view showing one embodiment of the electrode group 2 in the secondary battery 1 shown in FIG. 1. As shown in FIG. 2, the electrode group 2A includes a positive electrode 6, a separator 7, and a negative electrode 8, in this order. The positive electrode 6 includes a positive electrode current collector 9 and a positive electrode mixture layer 10 provided on at least one main surface of the positive electrode current collector 9. The positive electrode current collector 9 is provided with a positive electrode current collector tab 4. The negative electrode 8 includes a negative electrode current collector 11 and a negative electrode mixture layer 12 provided on at least one main surface of the negative electrode current collector 11. The negative electrode current collector 11 is provided with a negative electrode current collector tab 5.

[0053] <Electrode for electrochemical device (first electrode for electrochemical device)> Fig. 3(a) is a cross-sectional view taken along the arrow II in Fig. 2. The positive electrode 6 constitutes a first electrode for electrochemical devices. That is, as shown in Fig. 3(a), the first electrode for electrochemical devices 13A includes a positive electrode current collector 9 and a positive electrode mixture layer 10 provided on at least one main surface of the positive electrode current collector 9.

[0054] Fig. 3(b) is a schematic cross-sectional view showing a first electrode for electrochemical devices according to another embodiment. As shown in Fig. 3(b), the first electrode for electrochemical devices 13B includes a positive electrode current collector 9, a positive electrode mixture layer 10, and a separator 7, in this order.

[0055] The positive electrode current collector 9 may be formed of a metal such as aluminum, titanium, or tantalum, or an alloy thereof. The positive electrode current collector 9 is preferably formed of aluminum or an alloy thereof because it is lightweight and has a high weight energy density.

[0056] The thickness of the positive electrode current collector 9 may be 1 μm or more, 5 μm or more, or 10 μm or more. The thickness of the positive electrode current collector 9 may be 100 μm or less, 50 μm or less, or 20 μm or less.

[0057] In one embodiment, the positive electrode mixture layer 10 contains a positive electrode active material, an electrolyte salt, and the above mixture.

[0058] The positive electrode active material may be, for example, a lithium transition metal compound such as a lithium transition metal oxide or a lithium transition metal phosphate.

[0059] The lithium transition metal oxide may be, for example, lithium manganate, lithium nickelate, lithium cobaltate, etc. The lithium transition metal oxide may be a lithium transition metal oxide in which a part of the transition metal, such as Mn, Ni, or Co, contained in lithium manganate, lithium nickelate, lithium cobaltate, etc., is substituted with one or more other transition metals, or a metal element (typical element), such as Mg or Al. That is, the lithium transition metal oxide may be LiM 1 O2 or LiM 1 2O4(M1 The lithium transition metal oxide may be a compound represented by Li(Co 1 / 3 Ni 1 / 3 Mn 1 / 3 )O2, LiNi 1 / 2 Mn 1 / 2 O2, LiNi 1 / 2 Mn 3 / 2 It may be O4 etc.

[0060] From the viewpoint of further improving the energy density, the lithium transition metal oxide is preferably a compound represented by the following formula (1). Li a Ni b Co c M 2 d O 2+e (A) [In formula (A), M 2 is at least one selected from the group consisting of Al, Mn, Mg, and Ca, and a, b, c, d, and e are numbers that satisfy 0.2≦a≦1.2, 0.5≦b≦0.9, 0.1≦c≦0.4, 0≦d≦0.2, −0.2≦e≦0.2, and b+c+d=1.

[0061] Lithium transition metal phosphates include LiFePO4, LiMnPO4, and LiMn x M 3 1-x PO4(0.3≦x≦1、M 3 is at least one element selected from the group consisting of Fe, Ni, Co, Ti, Cu, Zn, Mg, and Zr), etc.

[0062] The content of the positive electrode active material may be 70% by mass or more, 80% by mass or more, or 90% by mass or more, based on the total amount of the positive electrode mixture layer, and may be 99% by mass or less, based on the total amount of the positive electrode mixture layer.

[0063] The electrolyte salt may be at least one selected from the group consisting of lithium salts, sodium salts, calcium salts, and magnesium salts.

[0064] The anion of the electrolyte salt is a halide ion (I - , Cl - , Br - etc.), SCN - , BF4 - , BF3(CF3) - , BF3(C2F5) - , PF6 - , ClO4 - , SbF6 - , [Nf2] - , [NTf2] - , N(SO2C2F5)2 - , BPh4 - , B(C2H4O2)2 - , [f3C] - , C(CF3SO2)3 - , CF3COO - , CF3SO2O - , C6F5SO2O - , [BOB] - Among these, the anion of the electrolyte salt is preferably PF6 - , BF4 - , [Nf2] - , [NTf2] - , [BOB] - , and ClO4 - At least one selected from the group consisting of, more preferably [NTf2] - or [Nf2] - is.

[0065] Examples of the lithium salt include the same as those in the mixture. The lithium salt may be LiPF6, LiBF4, Li[Nf2], Li[NTf2], Li[f3C], Li[BOB], LiClO4, LiBF3(CF3), LiBF3(C2F5), LiBF3(C3F7), LiBF3(C4F9), LiC(SO2CF3)3, LiCF3S02O, LiCF3COO, LiRCOO (wherein R is an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a naphthyl group), etc.

[0066] The sodium salt may be at least one selected from the group consisting of NaPF6, NaBF4, Na[Nf2], Na[NTf2], Na[f3C], Na[BOB], NaClO4, NaCF3BF3, NaC2F5BF3, NaC3F7BF3, NaC4F9BF3, Na[C(SO2CF3)3], NaCF3SO3, NaCF3COO, and NaRCOO (R is an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a naphthyl group).

[0067] The calcium salt may be at least one selected from the group consisting of Ca(PF6)2, Ca(BF4)2, Ca[Nf2]2, Ca[NTf2]2, Ca[f3C]2, Ca[BOB]2, Ca(ClO4)2, Ca(CF3BF3)2, Ca(C2F5BF3)2, Ca(C3F7BF3)2, Ca(C4F9BF3)2, Ca[C(SO2CF3)3]2, Ca(CF3SO3)2, Ca(CF3COO)2, and Ca(RCOO)2 (R is an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a naphthyl group).

[0068] The magnesium salt may be at least one selected from the group consisting of Mg(PF6)2, Mg(BF4)2, Mg[Nf2]2, Mg[NTf2]2, Mg[f3C]2, Mg[BOB]2, Mg(ClO4)2, Mg(CF3BF3)2, Mg(C2F5BF3)2, Mg(C3F7BF3)2, Mg(C4F9BF3)2, Mg[C(SO2CF3)3]2, Mg(CF3SO3)2, Mg(CF3COO)2, and Mg(RCOO)2 (R is an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a naphthyl group).

[0069] Among these, from the viewpoint of dissociation property and electrochemical stability, the electrolyte salt is preferably a lithium salt, more preferably at least one selected from the group consisting of LiPF, LiBF, Li[Nf], Li[NTf], Li[fC], Li[BOB], and LiClO, and even more preferably Li[NTf] or Li[Nf].

[0070] The content of the electrolyte salt may be, for example, 0.1 to 5 mass % based on the total amount of the positive electrode mixture layer.

[0071] The positive electrode mixture layer 10 contains the above mixture. The content of the mixture may be, for example, 0.1 to 10 mass % based on the total amount of the positive electrode mixture layer.

[0072] The positive electrode mixture layer 10 may further contain a conductive agent, a binder, a molten salt, a carbonate ester, and the like.

[0073] The conductive agent may be carbon black, graphite, carbon fiber, carbon nanotubes, acetylene black, or the like.

[0074] The content of the conductive agent may be, for example, 1 to 15 mass % based on the total amount of the positive electrode mixture layer.

[0075] The binder may be a resin such as polyvinylidene fluoride, polyacrylonitrile, styrene-butadiene rubber, carboxymethyl cellulose, fluororubber, ethylene-propylene rubber, polyacrylic acid, polyimide, polyamide, or a copolymer resin having these resins as the main skeleton (e.g., polyvinylidene fluoride-hexafluoropropylene copolymer, etc.).

[0076] The content of the binder may be, for example, 1 to 15 mass % based on the total amount of the positive electrode mixture layer.

[0077] The molten salt is composed of a cation component and an anion component. The molten salt is not particularly limited, and a normal ionic liquid or a plastic crystal can be used. Note that the "molten salt" referred to here does not include the above-mentioned mixture.

[0078] In this specification, "ionic liquid" means a molten salt that is liquid at 30°C, i.e., a molten salt having a melting point of 30°C or less, and "plastic crystal" means a molten salt that is solid at 30°C, i.e., a molten salt having a melting point higher than 30°C.

[0079] The content of the molten salt may be, for example, 1 to 15 mass % based on the total amount of the positive electrode mixture layer.

[0080] Examples of carbonate esters include cyclic carbonate esters such as ethylene carbonate and propylene carbonate, and chain carbonate esters such as dimethyl carbonate and diethyl carbonate.

[0081] The content of the carbonate ester may be, for example, 1 to 15 mass % based on the total amount of the positive electrode mixture layer.

[0082] The thickness of the positive electrode mixture layer 10 is not particularly limited, but may be 10 μm or more, 20 μm or more, or 30 μm or more. The thickness of the positive electrode mixture layer 10 may be 100 μm or less, 80 μm or less, or 60 μm or less.

[0083] The mixture density of the positive electrode mixture layer 10 is, for example, 1 g / cm 3 It may be more than that.

[0084] The separator 7 is disposed between the positive electrode and the negative electrode to insulate them from each other. There are no particular limitations on the separator as long as it has oxidation resistance on the positive electrode side and reduction resistance on the negative electrode side, and separators used in the field of ordinary liquid electrolyte ion batteries can be used. Examples of separators include porous polyolefin membranes such as polyethylene and polypropylene; and nonwoven fabrics such as polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), glass fibers, cellulose fibers, and polyimide fibers.

[0085] The electrolyte may be one that is commonly used as an electrolyte in the field of ordinary electrolyte-type ion batteries. The electrolyte may contain, for example, a non-aqueous solvent and an electrolyte salt. The electrolyte may further contain a molten salt, the above-mentioned mixture, or the like. Furthermore, an electrolyte containing a mixture may be used as the electrolyte. The electrolyte containing a mixture may be an electrolyte consisting of only the mixture, or may be an electrolyte containing the mixture and an electrolyte salt.

[0086] The non-aqueous solvent may be, for example, a carbonate ester, such as cyclic carbonate esters such as ethylene carbonate, propylene carbonate, and vinylene carbonate, and chain carbonate esters such as dimethyl carbonate and diethyl carbonate.

[0087] Examples of the electrolyte salt include the same electrolyte salts that can be contained in the positive electrode mixture layer 10. Examples of the molten salt include the same molten salts that can be contained in the positive electrode mixture layer 10.

[0088] <Electrode for electrochemical device (electrode for second electrochemical device)> Fig. 4(a) is a cross-sectional view taken along the arrows II-II in Fig. 2. The negative electrode 8 constitutes a second electrode for electrochemical devices. That is, as shown in Fig. 4(a), the second electrode for electrochemical devices 14A includes a negative electrode current collector 11 and a negative electrode mixture layer 12 provided on at least one main surface of the negative electrode current collector 11.

[0089] Fig. 4(b) is a schematic cross-sectional view showing a second electrode for electrochemical devices according to another embodiment. As shown in Fig. 4(b), the second electrode for electrochemical devices 14B includes, in this order, a negative electrode current collector 11, a negative electrode mixture layer 12, and a separator 7. The separator 7 is the same as the separator 7 in the above-described first electrode for electrochemical devices, and therefore will not be described below.

[0090] The negative electrode current collector 11 may be made of a metal such as aluminum, copper, nickel, or stainless steel, or an alloy thereof. The negative electrode current collector 11 is preferably made of aluminum or an alloy thereof because it is lightweight and has a high weight energy density. The negative electrode current collector 11 is preferably made of copper from the viewpoints of ease of processing into a thin film and cost.

[0091] The thickness of the negative electrode current collector 11 may be 1 μm or more, 5 μm or more, or 10 μm or more. The thickness of the negative electrode current collector 11 may be 100 μm or less, 50 μm or less, or 20 μm or less.

[0092] In one embodiment, the negative electrode mixture layer 12 contains a negative electrode active material, an electrolyte salt, and the above mixture.

[0093] The negative electrode active material can be any material commonly used in the field of energy devices such as secondary batteries. Examples of negative electrode active materials include metallic lithium, lithium alloys, metal compounds, carbon materials, metal complexes, and organic polymer compounds. These materials may be used alone or in combination of two or more. Among these, the negative electrode active material is preferably a carbon material. Examples of carbon materials include graphite such as natural graphite (e.g., flake graphite) and artificial graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, amorphous carbon, and carbon fiber.

[0094] The content of the negative electrode active material may be 60% by mass or more, 65% by mass or more, or 70% by mass or more, based on the total amount of the negative electrode mixture layer, and 99% by mass or less, 95% by mass or less, or 90% by mass or less, based on the total amount of the negative electrode mixture layer.

[0095] Examples of the electrolyte salt include the same as the electrolyte salt in the positive electrode mixture layer 10. The content of the electrolyte salt may be, for example, 0.1 to 5 mass % based on the total amount of the negative electrode mixture layer.

[0096] The negative electrode mixture layer 12 contains the above mixture. The content of the mixture may be, for example, 0.1 to 10 mass % based on the total mass of the negative electrode mixture layer.

[0097] The negative electrode mixture layer 12 may further contain a conductive agent, a binder, a molten salt, a carbonate ester, and the like that may be contained in the positive electrode mixture layer 10. The contents of these may be the same as those of the positive electrode mixture layer 10.

[0098] The thickness of the negative electrode mixture layer 12 is not particularly limited, but may be 10 μm or more, 15 μm or more, or 20 μm or more. The thickness of the negative electrode mixture layer 12 may be 50 μm or less, 45 μm or less, or 40 μm or less.

[0099] The mixture density of the negative electrode mixture layer 12 is 1 g / cm 3 It may be more than that.

[0100] Next, we will explain the method for manufacturing the secondary battery 1. The method for manufacturing the secondary battery 1 according to the first embodiment includes a first step of manufacturing a first electrode for electrochemical devices 13A (cathode 6), a second step of manufacturing a second electrode for electrochemical devices 14A (negative electrode 8), and a third step of placing a separator 7 between the first electrode for electrochemical devices 13A (cathode 6) and the second electrode for electrochemical devices 14A (negative electrode 8), injecting an electrolyte solution, and sealing the secondary battery (battery exterior of the secondary battery).

[0101] The manufacturing method of the first electrode for electrochemical devices 13A (cathode 6) in the first step includes the steps of preparing a cathode precursor having a cathode active material layer containing a cathode active material provided on at least one main surface of a cathode current collector, adding a slurry containing an electrolyte salt, a mixture, etc., and a dispersion medium to the cathode active material layer of the cathode precursor, and removing volatile components from the slurry added to the cathode active material layer to form a cathode mixture layer. Since the volatile components (dispersion medium) have been removed, the cathode mixture layer can be composed of the cathode active material, the electrolyte salt, the mixture, etc.

[0102] The positive electrode active material layer in the positive electrode precursor can be produced, for example, by preparing a positive electrode active material layer-forming slurry in which materials including a positive electrode active material, a conductive agent, a binder, etc. are dispersed in a dispersion medium, and then applying and drying the positive electrode active material layer-forming slurry to the positive electrode current collector 9. The dispersion medium is not particularly limited, and may be an aqueous solvent such as water, a mixed solvent of alcohol and water, or an organic solvent such as N-methyl-2-pyrrolidone.

[0103] Next, a slurry (slurry for forming a positive electrode mixture layer) is prepared by dispersing materials including an electrolyte salt, a mixture, a molten salt, etc. in a dispersion medium, and the slurry is added to the positive electrode active material layer. The method for adding the slurry is not particularly limited, and examples thereof include dropping, coating, printing, etc. The dispersion medium is not particularly limited, and may be acetone, ethyl methyl ketone, γ-butyrolactone, etc.

[0104] Thereafter, the volatile components are removed from the slurry added to the positive electrode active material layer to form the positive electrode mixture layer 10. The method for removing the volatile components is not particularly limited, and can be any commonly used method.

[0105] The second electrode for electrochemical devices 14A (negative electrode 8) in the second step can be produced by the same manufacturing method as the first electrode for electrochemical devices 13A (cathode 6) in the first step. That is, the manufacturing method of the second electrode for electrochemical devices 14A (negative electrode 8) includes the steps of preparing a negative electrode precursor having a negative electrode active material layer containing a negative electrode active material provided on at least one main surface of a negative electrode current collector; adding a slurry containing an electrolyte salt, a mixture, etc., and a dispersion medium to the negative electrode active material layer of the negative electrode precursor; and removing volatile components from the slurry added to the negative electrode active material layer to form a negative electrode mixture layer. Since the volatile components (dispersion medium) have been removed, the negative electrode mixture layer can be composed of the negative electrode active material, the electrolyte salt, the mixture, etc.

[0106] In the third step, a separator 7 is placed between the first electrode for electrochemical devices 13A (positive electrode 6) and the second electrode for electrochemical devices 14A (negative electrode 8), an electrolyte solution is injected, and the secondary battery (battery exterior of the secondary battery) is sealed to obtain a secondary battery 1. After the electrolyte solution is injected, a step of immersing the first electrode for electrochemical devices 13A (positive electrode 6), the second electrode for electrochemical devices 14A (negative electrode 8), and the separator 7 in the electrolyte solution in a reduced pressure environment may be included.

[0107] <Electrochemical Device (Second Embodiment)> Next, a secondary battery according to a second embodiment will be described. FIG. 5 is an exploded perspective view showing an electrode group of the secondary battery according to the second embodiment. As shown in FIG. 5, the secondary battery according to the second embodiment differs from the secondary battery according to the first embodiment in that the electrode group 2B further includes a bipolar electrode 15. That is, the electrode group 2B includes a positive electrode 6, a first separator 7A, a bipolar electrode 15, a second separator 7B, and a negative electrode 8, in this order. When a liquid electrolyte is used, the secondary battery according to the second embodiment requires structural design to suppress the movement of the electrolyte (liquid junction) between the positive electrode 6 and the negative electrode 8 of the bipolar electrode 15. Furthermore, in terms of liquid junction (short circuit), the secondary battery according to the second embodiment preferably uses a gel or solid electrolyte layer instead of the first separator 7A, the second separator 7B, and the electrolyte. Examples of such an electrolyte layer include a gel electrolyte, which is a gelled electrolyte, and the solid electrolyte described below.

[0108] The bipolar electrode 15 includes a bipolar electrode current collector 16, a positive electrode mixture layer 10 provided on the surface of the bipolar electrode current collector 16 facing the negative electrode 8, and a negative electrode mixture layer 12 provided on the surface of the bipolar electrode current collector 16 facing the positive electrode 6.

[0109] Fig. 6(a) is a cross-sectional view taken along the line III-III in Fig. 5. The bipolar electrode 15 constitutes a third electrode for electrochemical devices. That is, as shown in Fig. 6(a), the third electrode for electrochemical devices 17A is a bipolar electrode member including a bipolar electrode current collector 16, a positive electrode mixture layer 10 provided on one surface of the bipolar electrode current collector 16, and a negative electrode mixture layer 12 provided on the other surface of the bipolar electrode current collector 16.

[0110] Fig. 6(b) is a schematic cross-sectional view showing a third electrode for electrochemical devices (bipolar electrode member) according to another embodiment. As shown in Fig. 6(b), the third electrode for electrochemical devices 17B includes a bipolar electrode current collector 16, a positive electrode mixture layer 10 provided on one surface of the bipolar electrode current collector 16, a second separator 7B provided on the side of the positive electrode mixture layer 10 opposite the bipolar electrode current collector 16, a negative electrode mixture layer 12 arranged on the other surface of the bipolar electrode current collector 16, and a first separator 7A arranged on the side of the negative electrode mixture layer 12 opposite the bipolar electrode current collector 16.

[0111] The bipolar electrode current collector 16 may be made of aluminum, stainless steel, titanium, or the like, or may be a clad material made by rolling and bonding aluminum and copper or stainless steel and copper.

[0112] The first separator 7A and the second separator 7B may be made of the same or different materials.

[0113] Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above embodiments. For example, in the above embodiments, a secondary battery including an electrode group composed of electrochemical device electrodes and a separator, and an electrolyte solution has been illustrated, but the secondary battery may include an electrode group composed of electrochemical device electrodes and an electrolyte layer.

[0114] The electrolyte layer can be formed from a slurry for forming the electrolyte layer, which is prepared by dispersing a material containing, for example, a solid electrolyte, an electrolyte salt, a molten salt, or a mixture thereof in a dispersion medium. The dispersion medium is not particularly limited, but may be an organic solvent such as acetone or N-methyl-2-pyrrolidone.

[0115] Examples of solid electrolytes include polymer electrolytes and inorganic solid electrolytes. The polymer electrolyte and inorganic solid electrolyte are not particularly limited, and those commonly used as polymer electrolytes and inorganic solid electrolytes for ordinary secondary batteries can be used. The polymer electrolyte may be, for example, a polymer electrolyte having a structural unit represented by the following general formula (B):

[0116] [ka] [In formula (C), X C - indicates a counter anion.]

[0117] X C - Examples of the counter anion include the same anions as those of the electrolyte salts.

[0118] The inorganic solid electrolyte is, for example, Li7La3Zr2O 12 (LLZ) and the like.

[0119] Examples of the electrolyte salt and molten salt include the same electrolyte salt and molten salt that can be contained in the positive electrode mixture layer described above.

[0120] The electrolyte layer-forming slurry may further contain additives having lithium salt dissociation ability, such as borate esters and aluminate esters, as needed.

[0121] The thickness of the electrolyte layer may be, for example, 5 to 200 μm from the viewpoint of increasing strength and improving safety. [Example]

[0122] The present disclosure will be explained in more detail below using examples, but the present disclosure is not limited to these examples.

[0123] (Production Example 1) <N,N'-Dimethyl-N,N'-bis(dimethylaminocarbonyl)ethylenediamine (Compound (1A), R A 、R B 、R C 、R D 、R E 、and R F is a methyl group, and R G is an ethylene group, synthesis of the compound represented by the general formula (3))> Into a nitrogen-substituted eggplant flask on an ice bath, dichloromethane (42 mL), N,N'-dimethylethylenediamine (1.11 g, 12.6 mmol), and triethylamine (3.82 g, 37.8 mmol) were added. Next, dimethylcarbamoyl chloride (1.49 g, 13.86 mmol) was added dropwise to the eggplant flask on an ice bath and stirred for 1 hour. Then, it was stirred at room temperature for 24 hours. Then, the obtained solution was filtered, and the filtered solution was separated with aqueous sodium hydrogen carbonate to remove unnecessary moisture with sodium carbonate to obtain a yellow liquid. The yellow liquid was used to remove the solvent using an evaporator to obtain Compound 1A (0.72 g) as a white solid. The 1 1H-NMR of the obtained compound is shown below.

[0124] 1 1H-NMR (300 MHz, CDCl3): δ (ppm) 3.37 (s, 4H), 2.86 (s, 6H), 2.77 (s, 12H).

[0125] (Example 1-1) <Synthesis of the mixture> Li[NTf2] was prepared. Li[NTf2] and Compound (1A) were added to a sample bottle so that the molar ratio of Compound (1A) to Li[NTf2] was 5. The cap of the sample bottle was closed, and the sample bottle was heated on a hot plate at 100 °C for 2 hours to obtain the mixture of Example 1 in a liquid state. The mixture remained liquid even when left at room temperature for 2 hours.

[0126] <Measurement of ionic conductivity of the mixture> A silicone rubber sheet (manufactured by AS ONE Corporation, 1 mm thick) was punched out to a diameter of 16 mm, and the 16 mm silicone rubber was further punched out to a diameter of 10 mm to obtain a doughnut-shaped silicone rubber for sample fixation. The silicone rubber for sample fixation was attached to a SUS plate, and the mixture from Example 1, which was liquid at 25°C, was placed inside the silicone rubber for sample fixation. The mixture was then dried under reduced pressure at 60°C for 24 hours and then left to stand for 24 hours in an argon atmosphere with a dew point of -90°C or lower to remove moisture. A SUS plate with a diameter of 16 mm was then placed on the silicone rubber for sample fixation and the resulting mixture was then sealed in a two-electrode cell (manufactured by Toyo Systems Co., Ltd.) to prepare a cell for ionic conductivity measurement. The cell for ionic conductivity measurement was assembled in a glove box under an argon atmosphere with a dew point of -90°C or lower. The ionic conductivity was measured using a Frequency Response Analyzer Model 1260 connected to a Potentio Galvanostat Model 1287 (both manufactured by Solartron) by sweeping the range of 2 MHz to 1 Hz at 70°C, 55°C, 40°C, or 25°C. The value at the intersection with the real axis in the Nyquist plot was taken as the bulk resistance of the electrolyte, and the ionic conductivity of the mixture of Example 1 was calculated based on the following formula (X). The results are shown in Table 1.

[0127]

number

[0128] In formula (X), σ represents ionic conductivity (S / cm), R represents bulk resistance of the electrolyte (Ω), L represents the distance between the electrodes (0.1 cm), and S represents the electrode area (0.78 cm 2 ) is shown.

[0129] <Measurement of 10% weight loss temperature (T(d10)) of mixture> The 10% weight loss temperature was measured using a thermogravimetric and differential thermal analyzer (TG / DTA7200, manufactured by Seiko Instruments Inc.). Approximately 10 mg of the mixture was placed in an aluminum pan, and measurements were taken at a temperature increase rate of 5°C / min under a nitrogen gas flow of 200 mL / min. The results are shown in Table 1. Note that "-" in Table 1 indicates that the measurement was not performed.

[0130] (Example 1-2) A liquid mixture of Example 1-2 was obtained in the same manner as in Example 1-1, except that the molar ratio of compound (1A) to Li[NTf2] was changed to 10. The mixture remained liquid even after being left at room temperature for 2 hours. The ionic conductivity of the mixture of Example 1-2 was calculated in the same manner as in Example 1-1. The results are shown in Table 1.

[0131] Example 2-1 A liquid mixture of Example 2-1 was obtained in the same manner as in Example 1-1, except that Li[NTf2] was replaced with Li[Nf2]. The mixture remained liquid even after being left at room temperature for 2 hours. The ionic conductivity of the mixture of Example 2-1 was calculated in the same manner as in Example 1-1. The results are shown in Table 1.

[0132] (Example 2-2) A liquid mixture of Example 2-2 was obtained in the same manner as in Example 2-1, except that the molar ratio of compound (1A) to Li[Nf2] was changed to 10. The mixture remained liquid even after being left at room temperature for 2 hours. The ionic conductivity of the mixture of Example 2-2 was calculated in the same manner as in Example 1-1. The results are shown in Table 1.

[0133] [Table 1]

[0134] As described above, it was confirmed that the mixture of the present disclosure is a mixture of solids and is liquid at room temperature. As shown in Table 1, it was found that the mixture of the present disclosure has ionic conductivity and heat resistance. [Explanation of symbols]

[0135] 1... secondary battery, 2, 2A, 2B... electrode group, 3... battery outer casing, 4... positive electrode current collecting tab, 5... negative electrode current collecting tab, 6... positive electrode, 7... separator, 8... negative electrode, 9... positive electrode current collector, 10... positive electrode mixture layer, 11... negative electrode current collector, 12... negative electrode mixture layer, 13A, 13B... first electrochemical device electrodes, 14A, 14B... second electrochemical device electrodes, 15... bipolar electrode, 16... bipolar electrode current collector, 17A, 17B... third electrochemical device electrodes.

Claims

1. A mixture comprising a lithium salt and a compound represented by the following general formula (1): 【Chemistry 1】 [In formula (1), R １ and R ２ each independently represents a hydrogen atom, an alkyl group, or a substituted amino group. R ３ and R ４ each independently represents an alkyl group. R １ and R ３ and R ２ and R ４ may be bonded to each other to form a ring together with the atoms to which they are bonded. R ５ represents an alkylene group.

2. The R １ and the R ２ The mixture of claim 1 , wherein is a substituted amino group.

3. The mixture according to claim 1 or 2, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (3): 【Chemistry 2】 [In formula (3), R Ａ , R Ｂ , R Ｃ , R Ｄ , R Ｅ , and R Ｆ each independently represents an alkyl group having 1 to 4 carbon atoms. R Ｇ represents an alkylene group having 1 to 4 carbon atoms.

4. 4. The mixture of claim 1, wherein the lithium salt is lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethanesulfonyl)imide.

5. a current collector; and an electrode mixture layer provided on at least one main surface of the current collector; An electrode for electrochemical devices, wherein the electrode mixture layer contains an electrode active material, an electrolyte salt, and the mixture according to any one of claims 1 to 4.

6. An electrochemical device comprising the electrode for electrochemical devices according to claim 5 .

7. The electrochemical device according to claim 6 , which is a secondary battery.

Images