JP7416426B2 - Method for manufacturing battery components for secondary batteries - Google Patents

Description

The present invention relates to a method for manufacturing a battery member for a secondary battery.

In recent years, with the spread of portable electronic devices, electric vehicles, etc., high-performance secondary batteries are required. Among them, lithium secondary batteries have high energy density and are therefore attracting attention as power sources for electric vehicle batteries, power storage batteries, and the like. Specifically, lithium secondary batteries as batteries for electric vehicles are used in zero-emission electric vehicles without an engine, hybrid electric vehicles with both an engine and a secondary battery, and plug-in hybrids that are directly charged from the power grid. It is used in electric vehicles such as electric cars. In addition, lithium secondary batteries as power storage batteries are used in stationary power storage systems and the like that supply previously stored power in an emergency when the power grid is cut off.

For use in such a wide range of applications, lithium secondary batteries with higher energy density are required and are being developed. In particular, lithium secondary batteries for electric vehicles require high safety in addition to high input/output characteristics and high energy density, so more advanced technology is required to ensure safety. As a method of improving the safety of lithium secondary batteries, a method of changing the electrolyte to a solid electrolyte is known (for example, Patent Document 1).

Japanese Patent Application Publication No. 2004-107641

In a lithium secondary battery using a solid electrolyte, depending on the application, it may be important to improve the discharge characteristics when discharging at a relatively low current, for example, about 0.2C. Therefore, an object of the present invention is to provide a method for manufacturing a battery member for a secondary battery that can improve the discharge characteristics when the secondary battery is discharged at a relatively low current.

One aspect of the present invention includes a step of forming an electrode mixture intermediate layer containing an electrode active material on one surface of a current collector, and a step of forming an electrode mixture intermediate layer containing an electrode active material on a surface of the electrode mixture intermediate layer opposite to the current collector. applying a slurry containing oxide particles, a polymer, an ionic liquid, and an electrolyte salt, wherein the total content of the ionic liquid and electrolyte salt relative to the content of the oxide particles is greater than 4/1 in volume ratio. Provided is a method for manufacturing a battery member for a secondary battery that is significantly smaller than 12/1.

The specific surface area of the oxide particles is preferably 2 to 400 m ² /g.

The concentration of electrolyte salt per unit volume of ionic liquid is preferably greater than 0.5 mol/L.

The ionic liquid preferably contains N(SO ₂ F) ₂ ^- as an anion component.

According to the present invention, it is possible to provide a method for manufacturing a battery member for a secondary battery that can improve discharge characteristics when a secondary battery is discharged at a relatively low current. More specifically, it is possible to provide a method for manufacturing a battery member for a secondary battery that can improve the discharge characteristics of the secondary battery when discharged at 0.2C.

FIG. 1 is a perspective view showing a secondary battery according to an embodiment. FIG. 2 is an exploded perspective view showing one embodiment of the electrode group of the secondary battery shown in FIG. 1. FIG. FIG. 1 is a schematic cross-sectional view showing a method of manufacturing a battery member for a secondary battery according to an embodiment. It is an exploded perspective view showing one embodiment of an electrode group of a secondary battery concerning a modification.

Embodiments of the present invention will be described below with appropriate reference to the drawings. However, the present invention is not limited to the following embodiments. In the following embodiments, the constituent elements (including steps, etc.) are not essential unless otherwise specified. 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.

The numerical values and ranges herein are not intended to limit the invention. In this specification, a numerical range indicated using "-" indicates a range that includes the numerical values written before and after "-" as the minimum and maximum values, respectively. In the numerical ranges described stepwise in this specification, the upper limit or lower limit described in one numerical range may be replaced with the upper limit or lower limit described in another stepwise manner. Furthermore, in the numerical ranges described in this specification, the upper limit or lower limit of the numerical range may be replaced with the values shown in the examples.

Note that the following abbreviations may be used in this specification.
[Py13] ⁺ : N-methyl-N-propylpyrrolidinium cation [EMI] ⁺ : 1-ethyl-3-methylimidazolium cation [DEME] ⁺ : N,N-diethyl-N-methyl-N-(2 -Methoxyethyl) ammonium cation [FSI] ^- :N(SO ₂ F) ₂ ^- , bis(fluorosulfonyl)imide anion [TFSI] ^- :N(SO ₂ CF ₃ ) ₂ ^- , bis(trifluoromethanesulfonyl)imide anion [f3C] ⁻ :C(SO ₂ F) ₃ ⁻ , tris(fluorosulfonyl)carbanion [BOB] ⁻ :B(O ₂ C ₂ O ₂ ) ₂ ⁻ , bisoxalate borate anion [P(DADMA)] [Cl]: Poly(diallyldimethylammonium) chloride [P(DADMA)][TFSI]: Poly(diallyldimethylammonium)bis(trifluoromethanesulfonyl)imide

FIG. 1 is a perspective view showing a secondary battery according to one embodiment. As shown in FIG. 1, the secondary battery 1 includes an electrode group 2 composed of a positive electrode, a negative electrode, and an electrolyte layer, and a bag-shaped battery exterior body 3 that houses the electrode group 2. A positive electrode current collector tab 4 and a negative electrode current collector tab 5 are provided on the positive electrode and the negative electrode, respectively. The positive electrode current collector tab 4 and the negative electrode current collector tab 5 protrude from the inside of the battery exterior body 3 to the outside so that the positive electrode and the negative electrode can be electrically connected to the outside of the secondary battery 1, respectively.

The battery exterior body 3 may be formed of, for example, a laminate film. The laminate film may be, for example, a laminated 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.

FIG. 2 is an exploded perspective view showing one embodiment of the electrode group 2 of the secondary battery 1 shown in FIG. As shown in FIG. 2, the electrode group 2A includes a positive electrode 6, an electrolyte layer 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 the positive electrode current collector 9. A positive electrode current collector tab 4 is provided on the positive electrode current collector 9 of the positive electrode 6 . The negative electrode 8 includes a negative electrode current collector 11 and a negative electrode mixture layer 12 provided on the negative electrode current collector 11. A negative electrode current collector tab 5 is provided on the negative electrode current collector 11 of the negative electrode 8 .

In one embodiment, the electrode group 2A includes a first secondary battery battery member (positive electrode member) that includes a positive electrode current collector 9, a positive electrode mixture layer 10, and an electrolyte layer 7 in this order. You can see it there. Similarly, the electrode group 2A includes a second secondary battery battery member (negative electrode member) comprising a negative electrode current collector 11, a negative electrode mixture layer 12, and an electrolyte layer 7 in this order. You can also see it. A method for manufacturing a battery member for a secondary battery (hereinafter also simply referred to as a "battery member") according to each embodiment of the present invention is a method for manufacturing this positive electrode member or negative electrode member.

FIG. 3 is a schematic cross-sectional view showing a method for manufacturing a battery member for a secondary battery according to one embodiment. In this manufacturing method, first, as shown in FIG. 3(a), an electrode active material is contained on one surface (principal surface) 13a of the current collector 13 (positive electrode current collector 9 or negative electrode current collector 11). An electrode mixture intermediate layer 14 (positive electrode mixture intermediate layer or negative electrode mixture intermediate layer) is formed (electrode mixture intermediate layer forming step).

In the electrode mixture intermediate layer forming step, the method for forming the electrode mixture intermediate layer 14 on the one surface 13a of the current collector 13 includes applying an electrode mixture slurry onto the one surface 13a of the current collector 13 in one embodiment. This is the way to do it. The electrode mixture slurry is a slurry (positive electrode mixture slurry or negative electrode mixture slurry) in which the material contained in the positive electrode mixture layer 10 or the negative electrode mixture layer 12 is dispersed in a dispersion medium. The electrode mixture slurry of this embodiment contains at least an electrode active material (positive electrode active material or negative electrode active material) and a dispersion medium.

When the battery member is a positive electrode member, the current collector 13 is the positive electrode current collector 9. The positive electrode current collector 9 may be made of metal such as aluminum, titanium, tantalum, or an alloy thereof. The positive electrode current collector 9 is preferably made of aluminum or an alloy thereof because it is lightweight and has a high weight energy density. The thickness of the positive electrode current collector 9 may be 10 μm or more and 100 μm or less.

When the battery member is a negative electrode member, the current collector 13 is the negative electrode current collector 11. The negative electrode current collector 11 may be made of metal such as aluminum, copper, nickel, 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 viewpoint of ease of processing into a thin film and cost. The thickness of the negative electrode current collector 11 may be 10 μm or more and 100 μm or less.

When the battery member is a positive electrode member, the electrode active material is a positive electrode active material. The positive electrode active material may be a lithium transition metal compound such as a lithium transition metal oxide or a lithium transition metal phosphate.

The lithium transition metal oxide may be, for example, lithium manganate, lithium nickelate, lithium cobaltate, or the like. Lithium transition metal oxides include a part of transition metals such as Mn, Ni, and Co contained in lithium manganate, lithium nickelate, lithium cobaltate, etc., and one or more other transition metals, or It may also be a lithium transition metal oxide substituted with a metal element (typical element) such as Mg or Al. That is, the lithium transition metal oxide may be a compound represented by LiM ¹ O ₂ or LiM ¹ O ₄ (M ¹ contains at least one type of transition metal). Specifically, lithium transition metal oxides include Li(Co _1/3 Ni _1/3 Mn _1/3 ) O ₂ , LiNi _1/2 Mn _1/2 O ₂ , LiNi _1/2 Mn _3/2 O It may be _4th grade.

From the viewpoint of further improving 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 (1)
[In formula (1), M ² is at least one member selected from the group consisting of Al, Mn, Mg, and Ca, and a, b, c, d, and e each satisfy 0.2≦a≦1. 2. A number that satisfies 0.5≦b≦0.9, 0.1≦c≦0.4, 0≦d≦0.2, -0.2≦e≦0.2, and b+c+d=1 . ]

Lithium transition metal phosphates include LiFePO ₄ , LiMnPO ₄ , LiMn _x M ³ _1-x PO ₄ (0.3≦x≦1, M ³ is Fe, Ni, Co, Ti, Cu, Zn, Mg and Zr (at least one element selected from the group consisting of).

The positive electrode active material may be ungranulated primary particles or granulated secondary particles.

The particle size of the positive electrode active material is adjusted to be equal to or less than the thickness of the positive electrode mixture layer 10. If there are coarse particles in the positive electrode active material that have a particle size larger than the thickness of the positive electrode mixture layer 10, remove the coarse particles in advance by sieve classification, wind current classification, etc. A positive electrode active material having a diameter is selected.

The average particle size of the positive electrode active material is preferably 0.1 μm or more, more preferably 1 μm or more. The average particle size of the positive electrode active material is preferably 30 μm or less, more preferably 25 μm or less. The average particle size of the positive electrode active material is the particle size (D ₅₀ ) when the ratio (volume fraction) to the total volume of the positive electrode active material is 50%. The average particle diameter (D ₅₀ ) of the positive electrode active material is determined by measuring a suspension of the positive electrode active material in water by a laser scattering method using a laser scattering particle size measuring device (e.g. Microtrac). You can get it by doing that.

The content of the positive electrode active material is 70% by mass or more, 80% by mass or more, or 90% by mass, based on the total amount of nonvolatile components (components excluding the dispersion medium from the positive electrode mixture slurry. The same applies hereinafter) in the positive electrode mixture slurry. The amount may be greater than or equal to 99% by mass. Thereby, the content of the positive electrode active material in the obtained positive electrode mixture layer becomes the same as the content described above.

When the battery member is a negative electrode member, the electrode active material is a negative electrode active material. As the negative electrode active material, those commonly used in the field of energy devices can be used. Specific examples of negative electrode active materials include metallic lithium, lithium titanate (Li ₄ Ti ₅ O ₁₂ ), lithium alloys or other metal compounds, carbon materials, metal complexes, and organic polymer compounds. . The negative electrode active material may be one of these materials or a mixture of two or more thereof. Carbon materials include natural graphite (scaly graphite, etc.), graphite such as artificial graphite, amorphous carbon, carbon fiber, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal. Examples include carbon black such as black. From the viewpoint of obtaining a larger theoretical capacity (for example, 500 to 1500 Ah/kg), the negative electrode active material may be silicon, tin, or a compound containing these elements (oxide, nitride, alloy with other metals). good.

The average particle diameter (D ₅₀ ) of the negative electrode active material is preferably 1 μm or more from the viewpoint of obtaining a well-balanced negative electrode that suppresses an increase in irreversible capacity due to a decrease in particle size and enhances the electrolyte salt retention ability. It is more preferably 5 μm or more, still more preferably 10 μm or more, preferably 50 μm or less, more preferably 40 μm or less, and still more preferably 30 μm or less. The average particle size (D ₅₀ ) of the negative electrode active material is measured by the same method as the average particle size (D ₅₀ ) of the positive electrode active material described above.

The content of the negative electrode active material is 60% by mass or more, 65% by mass or more, or 70% by mass, based on the total amount of nonvolatile components (components excluding the dispersion medium from the negative electrode mixture slurry. The same applies hereinafter) in the negative electrode mixture slurry. It may be 99% by mass or less, 95% by mass or less, or 90% by mass or less. Thereby, the content of the negative electrode active material in the obtained negative electrode mixture layer becomes the same as the content described above.

The dispersion medium may be water or an organic solvent. The organic solvent may be N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide, methyl ethyl ketone, toluene, 2-butanol, cyclohexanone, ethyl acetate, 2-propanol, etc., preferably NMP. The content of the dispersion medium in the electrode mixture slurry is, for example, 20 parts by mass per 100 parts by mass of nonvolatile components (components obtained by removing the dispersion medium from the electrode mixture slurry. The same applies hereinafter) in the electrode mixture slurry. The amount may be more than 1,000 parts by mass or less.

The electrode mixture slurry may further contain a conductive agent, a binder, etc. as other components. In this case, an electrode mixture intermediate layer 14 further containing these materials is formed.

The conductive agent is not particularly limited, but may be a carbon material such as graphite, acetylene black, carbon black, or carbon fiber. The conductive agent may be a mixture of two or more of the above-mentioned carbon materials. The content of the conductive agent may be 1 to 70% by mass based on the total amount of nonvolatile matter in the electrode mixture slurry. Thereby, the content of the conductive agent in the obtained electrode mixture layer becomes the same content as described above.

The binder is not particularly limited, but contains as a monomer unit at least one member selected from the group consisting of tetrafluoroethylene, vinylidene fluoride, hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate, and methyl methacrylate. It may be a polymer, a rubber such as styrene-butadiene rubber, isoprene rubber, acrylic rubber, or the like. The binder is preferably a copolymer containing hexafluoropropylene and vinylidene fluoride as structural units. The content of the binder may be 1 to 70% by mass based on the total amount of nonvolatile content in the electrode mixture slurry. Thereby, the content of the binder in the obtained electrode mixture layer becomes the same content as described above.

The electrode mixture slurry may further contain an ionic liquid and an electrolyte salt, which will be described later, but preferably does not contain an ionic liquid and an electrolyte salt.

In the electrode mixture intermediate layer forming step, methods for applying the electrode mixture slurry include, for example, a method of applying using an applicator, a method of applying by spraying, and the like. By these methods, the electrode mixture slurry is applied onto one surface 13a of the current collector 13. As a result, an electrode mixture intermediate layer 14 is formed on one surface 13a of the current collector 13, as shown in FIG. 3(a).

In the electrode mixture intermediate layer forming step, after applying the electrode mixture slurry, the dispersion medium in the slurry may be volatilized. In other words, the "electrode mixture intermediate layer" in this specification includes a layer formed of an electrode mixture slurry and a layer formed by volatilization of part or all of the dispersion medium from the electrode mixture slurry. It will be done. The method of volatilizing the dispersion medium may be, for example, a method of drying by heating, a method of reducing pressure, a method of combining reduced pressure and heating, etc. In the method of reducing the pressure, the pressure may be reduced to a vacuum state. The heating temperature during drying may be 50 to 150°C. The heating time may be changed depending on the temperature as long as the dispersion medium is sufficiently volatilized, and may be, for example, from 1 minute to 48 hours.

Following the electrode mixture intermediate layer forming step, as shown in FIG. 3(b), oxide particles 16, polymer 17, A slurry 15 containing an ionic liquid, an electrolyte salt, and a dispersion medium is applied. Hereinafter, this slurry will also be referred to as "electrolyte slurry", and the process of applying electrolyte slurry 15 will also be referred to as "electrolyte slurry application process".

The oxide particles 16 are, for example, inorganic oxide particles. The inorganic oxide is, for example, an inorganic oxide containing Li, Mg, Al, Si, Ca, Ti, Zr, La, Na, K, Ba, Sr, V, Nb, B, Ge, etc. as constituent elements. good. The oxide particles 16 are preferably at least one selected from the group consisting of SiO ₂ , Al ₂ O ₃ , AlOOH, MgO, CaO, ZrO ₂ , TiO ₂ , Li ₇ La ₃ Zr ₂ O ₁₂ , and BaTiO ₃ particles. Since the oxide particles 16 have polarity, they can promote dissociation of the electrolyte in the electrolyte layer and improve battery characteristics.

The oxide particles 16 may be oxides of rare earth metals. Specifically, the oxide particles 16 include scandium oxide, yttrium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, eurobium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, It may be thulium oxide, ytterbium oxide, lutetium oxide, or the like.

Oxide particles 16 may have a hydrophobic surface. Oxide particles usually have hydroxyl groups on their surfaces and tend to be hydrophilic. Oxide particles with a hydrophobic surface have fewer hydroxyl groups on the surface than oxide particles without a hydrophobic surface. Therefore, if oxide particles having a hydrophobic surface are used, it is expected that the affinity between the oxide particles and the ionic liquid will improve since the ionic liquid is hydrophobic. Therefore, it is considered that the liquid retention property of the ionic liquid in the electrolyte layer 7 is further improved, and as a result, the ionic conductivity of the electrolyte layer 7 is improved. When oxide particles with a hydrophobic surface are used, the discharge characteristics are improved not only when the secondary battery is discharged at a relatively low current, but also when it is discharged at a relatively high current (for example, about 0.5C). be able to.

Oxide particles having a hydrophobic surface can be obtained, for example, by treating oxide particles exhibiting hydrophilicity with a surface treatment agent capable of imparting a hydrophobic surface. That is, oxide particles having a hydrophobic surface mean oxide particles whose surface has been treated with a surface treatment agent. The surface treatment agent may be a silicon-containing compound or the like.

The oxide particles 16 may be surface-treated with a silicon-containing compound. That is, the oxide particles 16 may be those in which the surface of the oxide particles and the silicon atoms of the silicon-containing compound are bonded via oxygen atoms. The silicon-containing compound is preferably at least one selected from the group consisting of halogen-containing alkylsilanes, alkoxysilanes, epoxy group-containing silanes, amino group-containing silanes, silazane, and siloxanes.

The halogen element in the halogen-containing alkylsilane may be chlorine, fluorine, or the like. The halogen-containing alkylsilane (alkylchlorosilane) containing chlorine may be methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, n-octyldimethylchlorosilane, or the like. The halogen-containing alkylsilane (fluoroalkylsilane) containing fluorine may be trifluoropropyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, or the like.

Alkoxysilanes include methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethoxydiphenylsilane, n-propyltrimethoxysilane, hexyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, and dimethyldiphenylsilane. Ethoxysilane, n-propyltriethoxysilane, etc. may also be used.

Epoxy group-containing silanes include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropylmethyldiethoxysilane. Silane, 3-glycidoxypropyltriethoxysilane, etc. may also be used.

The amino group-containing silanes include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N- Phenyl-3-aminopropyltrimethoxysilane and the like may also be used.

The silazane may be hexamethyldisilazane or the like. The siloxane may be dimethyl silicone oil or the like. These may have a reactive functional group (eg, carboxyl group, etc.) at one or both ends.

As the oxide particles having a hydrophobic surface (surface-treated oxide particles), those manufactured by a known method may be used, or commercially available products may be used as they are.

Judging from the apparent geometrical form, the oxide particles 16 generally consist of primary particles (particles that do not constitute secondary particles) that integrally form a single particle, and multiple primary particles. It may also include secondary particles formed by aggregation of particles.

The specific surface area of the oxide particles 16 is preferably 2 to 400 m ² /g, 5 to 100 m ² /g, 10 to 80 m ² /g, or 15 to 60 m ² /g. When the specific surface area is 2 to 400 m ² /g, a secondary battery equipped with an electrolyte layer containing such oxide particles tends to have excellent discharge characteristics. From the same viewpoint, the specific surface area of the oxide particles 16 may be 2 m ² /g or more, 5 m ² /g or more, 10 m ² /g or more, 15 m ² /g or more, or 50 m ² /g or more, 400 m ² /g or less, 350 m ² /g or less, 300 m ² /g or less, 200 m ² /g or less, 100 m ² /g or less, 90 m ² /g or less, 80 m ² /g or less, or 60 m ² /g or less. You can. The specific surface area of the oxide particles 16 means the specific surface area of the entire oxide particles including primary particles and secondary particles, and is measured by the BET method.

The average primary particle size (average particle size of primary particles) of the oxide particles 16 is preferably 0.005 μm (5 nm) or more, more preferably 0.01 μm from the viewpoint of improving the electrical conductivity of the secondary battery 1. (10 nm) or more, more preferably 0.015 μm (15 nm) or more. The average primary particle size of the oxide particles 16 is preferably 1 μm or less, more preferably 0.1 μm or less, and still more preferably 0.05 μm or less, from the viewpoint of making the electrolyte layer 7 thinner. The average primary particle size of the oxide particles 16 can be measured by observing the oxide particles 16 using a transmission electron microscope or the like.

The average particle diameter of the oxide particles 16 is preferably 0.005 μm or more, more preferably 0.01 μm or more, and even more preferably 0.03 μm or more. The average particle diameter of the oxide particles 16 is preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 1 μm or less. The average particle diameter of the oxide particles 16 is measured by a laser diffraction method, and corresponds to the particle diameter at which the volume accumulation is 50% when a volume cumulative particle size distribution curve is drawn from the small particle size side.

The content of the oxide particles 16 is preferably 1% by mass or more, more preferably 3% by mass, based on the total amount of nonvolatile components (components excluding the dispersion medium from the electrolyte slurry; the same applies hereinafter) in the electrolyte slurry 15. % or more, more preferably 5% by mass or more, particularly preferably 7% by mass or more, and preferably 30% by mass or less, more preferably 27% by mass or less, still more preferably 25% by mass or less. % by mass or less.

In the electrolyte slurry 15, the content of the oxide particles 16 is preferably 5% by volume or more, more preferably 7% by volume or more, even more preferably 9% by volume, based on the total amount of nonvolatile content in the electrolyte slurry 15. % or more, and preferably 20 volume % or less, more preferably 17 volume % or less, and still more preferably 15 volume % or less.

Polymer 17 preferably has a first structural unit selected from the group consisting of tetrafluoroethylene and vinylidene fluoride.

The polymer 17 is preferably one or more kinds of polymers, and the structural units constituting the one or more kinds of polymers include the above-mentioned first structural unit, hexafluoropropylene, acrylic A second structural unit selected from the group consisting of acid, maleic acid, ethyl methacrylate, and methyl methacrylate may be included. That is, the first structural unit and the second structural unit may be contained in one type of polymer to form a copolymer, or the first structural unit and the second structural unit may be contained in different polymers to form a copolymer. and a second polymer having a second structural unit.

More specifically, the polymer 17 may be polytetrafluoroethylene, polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, or the like.

The content of the polymer 17 may be preferably 3% by mass or more, preferably 60% by mass or less, and more preferably 50% by mass or less, based on the total amount of nonvolatile content in the electrolyte slurry 15. , more preferably 40% by mass or less.

The ionic liquid contains the following anionic components and cationic components. Note that the ionic liquid in this specification is a substance that is liquid at −20° C. or higher. In the secondary battery 1, the types of ionic liquids contained in the positive electrode member and the negative electrode member may be the same or different.

The anion component of the ionic liquid is not particularly limited, but includes halogen anions such as Cl ^- , Br ^- and I ^-, inorganic anions such as BF ₄ ^- and N(SO ₂ F) ₂ ^- , and B(C ₆ H ₅ ). ₄ ⁻ , CH ₃ SO ₂ O ⁻ , CF ₃ SO ₂ O ⁻ , N(SO ₂ C ₄ F ₉ ) ₂ ⁻ , N(SO ₂ CF ₃ ) ₂ ⁻ , N(SO ₂ C ₂ F ₅ ) ₂ ⁻ It may be an organic anion such as. The anion component of the ionic liquid preferably contains at least one anion component represented by the following formula (2).
N(SO ₂ C _m F _2m+1 ) (SO ₂ C _n F _2n+1 ) ^- (2)
[In formula (2), m and n each independently represent an integer of 0 to 5. m and n may be the same or different, preferably the same. ]

The anion component represented by formula (2) is, for example, N(SO ₂ C ₄ F ₉ ) ₂ ⁻ , N(SO ₂ F) ₂ ⁻ , N(SO ₂ CF ₃ ) ₂ ⁻ and N(SO ₂ C ₂ F ₅ ) ₂ ^- . The anionic component of the ionic liquid is more preferably N(SO ₂ C ₄ F ₉ ) ₂ ⁻ or CF ₃ SO from the viewpoint of further improving ionic conductivity with a relatively low viscosity and further improving charge/discharge characteristics. ₂ O ⁻ , N(SO ₂ F) ₂ ⁻ , N(SO ₂ CF ₃ ) ₂ ⁻ , and N(SO ₂ C ₂ F ₅ ) ₂ ⁻ .

More preferably, the electrolyte slurry 15 contains N(SO ₂ F) ₂ ^- as an anion component. When N(SO ₂ F) ₂ ^- is included as an anion component, a good interface can be formed between the electrode mixture layer and the electrolyte layer in the resulting battery member. This effect is particularly remarkable in the negative electrode member. That is, in the method for manufacturing a negative electrode member, the ionic liquid contained in the electrolyte slurry preferably contains N(SO ₂ F) ₂ ^- as an anion component.

The cation component of the ionic liquid is preferably at least one selected from the group consisting of chain quaternary onium cations, piperidinium cations, pyrrolidinium cations, pyridinium cations, and imidazolium cations.

［式（３）中、Ｒ^１～Ｒ^４は、それぞれ独立に、炭素数が１～２０の鎖状アルキル基、又はＲ－Ｏ－（ＣＨ_２）_ｎ－で表される鎖状アルコキシアルキル基（Ｒはメチル基又はエチル基を表し、ｎは１～４の整数を表す）を表し、Ｘは、窒素原子又はリン原子を表す。Ｒ^１～Ｒ^４で表されるアルキル基の炭素数は、好ましくは１～２０、より好ましくは１～１０、更に好ましくは１～５である。］The chain quaternary onium cation is, for example, a compound represented by the following formula (3).

[In formula (3), R ¹ to R ⁴ are each independently a chain alkyl group having 1 to 20 carbon atoms, or a chain alkoxyalkyl group represented by RO-(CH ₂ ) _n - (R represents a methyl group or an ethyl group, n represents an integer of 1 to 4), and X represents a nitrogen atom or a phosphorus atom. The alkyl group represented by R ¹ to R ⁴ preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and still more preferably 1 to 5 carbon atoms. ]

［式（４）中、Ｒ^５及びＲ^６は、それぞれ独立に、炭素数が１～２０のアルキル基、又はＲ－Ｏ－（ＣＨ_２）_ｎ－で表されるアルコキシアルキル基（Ｒはメチル基又はエチル基を表し、ｎは１～４の整数を表す）を表す。Ｒ^５及びＲ^６で表されるアルキル基の炭素数は、好ましくは１～２０、より好ましくは１～１０、更に好ましくは１～５である。］The piperidinium cation is, for example, a nitrogen-containing six-membered cyclic compound represented by the following formula (4).

[In formula (4), R ⁵ and R ⁶ are each independently an alkyl group having 1 to 20 carbon atoms, or an alkoxyalkyl group represented by R-O-(CH ₂ ) _n - (R is methyl or ethyl group, and n represents an integer of 1 to 4). The alkyl group represented by R ⁵ and R ⁶ preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and still more preferably 1 to 5 carbon atoms. ]

［式（５）中、Ｒ^７及びＲ^８は、それぞれ独立に、炭素数が１～２０のアルキル基、又はＲ－Ｏ－（ＣＨ_２）_ｎ－で表されるアルコキシアルキル基（Ｒはメチル基又はエチル基を表し、ｎは１～４の整数を表す）を表す。Ｒ^７及びＲ^８で表されるアルキル基の炭素数は、好ましくは１～２０、より好ましくは１～１０、更に好ましくは１～５である。］The pyrrolidinium cation is, for example, a five-membered cyclic compound represented by the following formula (5).

[In formula (5), R ⁷ and R ⁸ are each independently an alkyl group having 1 to 20 carbon atoms, or an alkoxyalkyl group represented by R-O-(CH ₂ ) _n - (R is methyl or ethyl group, and n represents an integer of 1 to 4). The alkyl group represented by R ⁷ and R ⁸ preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and still more preferably 1 to 5 carbon atoms. ]

［式（６）中、Ｒ^９～Ｒ^１３は、それぞれ独立に、炭素数が１～２０のアルキル基、Ｒ－Ｏ－（ＣＨ_２）_ｎ－で表されるアルコキシアルキル基（Ｒはメチル基又はエチル基を表し、ｎは１～４の整数を表す）、又は水素原子を表す。Ｒ^９～Ｒ^１３で表されるアルキル基の炭素数は、好ましくは１～２０、より好ましくは１～１０、更に好ましくは１～５である。］The pyridinium cation is, for example, a compound represented by the following formula (6).

[In formula (6), R ⁹ to R ¹³ are each independently an alkyl group having 1 to 20 carbon atoms, an alkoxyalkyl group represented by RO-(CH ₂ ) _n - (R is a methyl group) or represents an ethyl group, n represents an integer of 1 to 4), or represents a hydrogen atom. The alkyl group represented by R ⁹ to R ¹³ preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and still more preferably 1 to 5 carbon atoms. ]

［式（７）中、Ｒ^１４～Ｒ^１８は、それぞれ独立に、炭素数が１～２０のアルキル基、Ｒ－Ｏ－（ＣＨ_２）_ｎ－で表されるアルコキシアルキル基（Ｒはメチル基又はエチル基を表し、ｎは１～４の整数を表す）、又は水素原子を表す。Ｒ^１４～Ｒ^１８で表されるアルキル基の炭素数は、好ましくは１～２０、より好ましくは１～１０、更に好ましくは１～５である。］The imidazolium cation is, for example, a compound represented by the following formula (7).

[In formula (7), R ¹⁴ to R ¹⁸ are each independently an alkyl group having 1 to 20 carbon atoms, an alkoxyalkyl group represented by RO-(CH ₂ ) _n - (R is a methyl group) or represents an ethyl group, n represents an integer of 1 to 4), or represents a hydrogen atom. The alkyl group represented by R ¹⁴ to R ¹⁸ preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and still more preferably 1 to 5 carbon atoms. ]

The ionic liquid contained in the electrolyte slurry 15 is preferably N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium-bis(trifluoromethanesulfonyl)imide (DEME-TFSI), N,N- Diethyl-N-methyl-N-(2-methoxyethyl)ammonium-bis(fluorosulfonyl)imide (DEME-FSI), 1-ethyl-3-methylimidazolium-bis(trifluoromethanesulfonyl)imide (EMI-TFSI) , 1-ethyl-3-methylimidazolium-bis(fluorosulfonyl)imide (EMI-FSI), N-methyl-N-propylpyrrolidinium-bis(trifluoromethanesulfonyl)imide (Py13-TFSI), N-methyl -N-propylpyrrolidinium-bis(fluorosulfonyl)imide (Py13-FSI), N-ethyl-N-methylpyrrolidinium-bis(trifluoromethanesulfonyl)imide (Py12-TFSI), or N-ethyl- N-methylpyrrolidinium-bis(fluorosulfonyl)imide (Py12-FSI). The ionic liquid contained in the electrolyte slurry 15 is more preferably DEME-FSI, EMI-FSI, Py13-FSI, or Py12-FSI from the viewpoint of further improving discharge characteristics at relatively high currents. The ionic liquid contained in the electrolyte slurry 15 is more preferably EMI-FSI from the viewpoint of further improving discharge characteristics at relatively high currents.

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

The anion components of the electrolyte salt include halide ions (I ⁻ , Cl ⁻ , Br ^{− ,} etc.), SCN ⁻ , BF ₄ ⁻ , BF ₃ (CF ₃ ) ⁻ , BF ₃ (C ₂ F ₅ ) ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , SbF ₆ ⁻ , N(SO ₂ F) ₂ ⁻ , N(SO ₂ CF ₃ ) ₂ ⁻ , N(SO ₂ C ₂ F ₅ ) ₂ ⁻ , B(C ₆ H ₅ ) ₄ ⁻ , B(O ₂ C ₂ H ₄ ) ₂ ⁻ , C(SO ₂ F) ₃ ⁻ , C(SO ₂ CF ₃ ) ₃ ⁻ , CF ₃ COO ⁻ , CF ₃ SO ₂ O ⁻ , C ₆ F ₅ SO ₂ O ^- , B(O ₂ C ₂ O ₂ ) ₂ ^- , etc. The anion component of the electrolyte salt is preferably an anion component represented by the above formula (2) such as N(SO ₂ F) ₂ ^- , N(SO ₂ CF ₃ ) ₂ ^- , PF ₆ ^- , BF ₄ ^- , B(O ₂ C ₂ O ₂ ) ₂ ⁻ , or ClO ₄ ⁻ .

Lithium salts include LiPF ₆ , LiBF ₄ , Li[FSI], Li[TFSI], Li[f3C], Li[BOB], LiClO ₄ , LiBF ₃ (CF ₃ ), LiBF ₃ (C ₂ F ₅ ), LiBF ₃ (C ₃ F ₇ ), LiBF ₃ (C ₄ F ₉ ), LiC (SO ₂ CF ₃ ) ₃ , LiCF ₃ SO ₂ O, LiCF ₃ COO, and LiRCOO (R is an alkyl group having 1 to 4 carbon atoms) , phenyl group, or naphthyl group).

Sodium salts include NaPF ₆ , NaBF ₄ , Na[FSI], Na[TFSI], Na[f3C], Na[BOB], NaClO ₄ , NaBF ₃ (CF ₃ ), NaBF ₃ (C ₂ F ₅ ), NaBF ₃ (C ₃ F ₇ ), NaBF ₃ (C ₄ F ₉ ), NaC (SO ₂ CF ₃ ) ₃ , NaCF ₃ SO ₂ O, NaCF ₃ COO, and NaRCOO (R is an alkyl group having 1 to 4 carbon atoms) , phenyl group, or naphthyl group).

Calcium salts include Ca(PF ₆ ) ₂ , Ca(BF ₄ ) ₂ , Ca[FSI] ₂ , Ca[TFSI] ₂ , Ca[f3C] ₂ , Ca[BOB] ₂ , Ca(ClO ₄ ) ₂ , Ca [BF ₃ (CF ₃ )] ₂ , Ca [BF ₃ (C ₂ F ₅ )] ₂ , Ca [BF ₃ (C ₃ F ₇ )] ₂ , Ca [BF ₃ (C ₄ F ₉ )] ₂ , Ca [C(SO ₂ CF ₃ ) ₃ ] ₂ , Ca(CF ₃ SO ₂ O) ₂ , Ca(CF ₃ COO) ₂ , and Ca(RCOO) ₂ (R is an alkyl group having 1 to 4 carbon atoms, phenyl or naphthyl group).

Magnesium salts include Mg(PF ₆ ) ₂ , Mg(BF ₄ ) ₂ , Mg[FSI] ₂ , Mg[TFSI] ₂ , Mg[f3C] ₂ , Mg[BOB] ₂ , Mg(ClO ₄ ) ₂ , Mg [BF ₃ (CF ₃ )] ₂ , Mg [BF ₃ (C ₂ F ₅ )] ₂ , Mg [BF ₃ (C ₃ F ₇ )] ₂ , Mg [BF ₃ (C ₄ F ₉ )] ₂ , Mg [C(SO ₂ CF ₃ ) ₃ ] ₂ , Mg(CF ₃ SO ₃ ) ₂ , Mg(CF ₃ COO) ₂ , and Mg(RCOO) ₂ (R is an alkyl group having 1 to 4 carbon atoms, a phenyl group or a naphthyl group).

Among these, from the viewpoint of dissociability and electrochemical stability, the electrolyte salt is preferably LiPF ₆ , LiBF ₄ , Li[FSI], Li[TFSI], Li[f3C], Li[BOB], LiClO ₄ , _LiBF3 ( _CF3 ), _{LiBF3 ( C2F5} ), _LiBF3 ( _C3F7 ) _{, LiBF3} ( _C4F9 ), LiC _{( SO2CF3 ) 3} , _{LiCF3SO2O ,} At least one member selected from the group consisting of LiCF ₃ COO and LiRCOO (R is an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a naphthyl group), more preferably Li [TFSI], Li At least one selected from the group consisting of [FSI], LiPF ₆ , LiBF ₄ , Li[BOB], and LiClO ₄ , more preferably one selected from the group consisting of Li[TFSI] and Li[FSI] It is a seed.

The electrolyte slurry may contain an ionic liquid and an electrolyte salt as an "ionic liquid electrolyte" in which the electrolyte salt is dissolved in the ionic liquid. In the ionic liquid electrolyte, the salt concentration of the electrolyte salt per unit volume of the ionic liquid is preferably greater than 0.5 mol/L. By increasing the salt concentration of the electrolyte salt per unit volume of the ionic liquid to more than 0.5 mol/L, even when the secondary battery is discharged at a relatively high current (for example, when discharged at 0.5 C), The discharge characteristics of the secondary battery can be improved, and as a result, the discharge characteristics of the secondary battery can be further improved. From the same viewpoint, the salt concentration of the electrolyte salt per unit volume of the ionic liquid is more preferably 0.7 mol/L or more, and still more preferably 1.0 mol/L or more. The salt concentration of the electrolyte salt per unit volume of the ionic liquid is preferably 3.0 mol/L or less, more preferably 2.0 mol/L or less, from the viewpoint of suppressing a decrease in ionic conductivity due to excessive inclusion of the electrolyte salt. It is 7 mol/L or less, more preferably 2.5 mol/L or less.

The content of the ionic liquid electrolyte (the total content of the ionic liquid and electrolyte salt) is determined from the viewpoint of obtaining a uniform dispersion state in the electrolyte slurry 15, and from the viewpoint of obtaining a uniform dispersion state in the electrolyte slurry 15, and from the viewpoint of obtaining a uniform dispersion state in the electrolyte slurry 15, 12) and the electrolyte layer 7, the content is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably It is 30% by mass or more. Thereby, the ionic conductivity of the electrolyte layer 7 can be increased, and the battery characteristics of the secondary battery can be further improved. The content of the ionic liquid electrolyte may be 90% by mass or less, 85% by mass or less, or 80% by mass or less based on the total amount of nonvolatile content in electrolyte slurry 15.

In the electrolyte slurry 15, the content of the ionic liquid electrolyte (the total content of the ionic liquid and the electrolyte salt) is determined from the viewpoint of obtaining a uniform dispersion state in the electrolyte slurry 15, and from the viewpoint of obtaining a uniform dispersion state in the electrolyte slurry 15, and from the viewpoint of obtaining a uniform dispersion state in the electrolyte slurry 15, Alternatively, from the viewpoint of forming a good interface between the negative electrode mixture layer 12) and the electrolyte layer 7, it is preferably 35% by volume or more, more preferably 40% by volume or more, based on the total amount of nonvolatile content in the electrolyte slurry 15. The content is more preferably 45% by volume or more. Thereby, the ionic conductivity of the electrolyte layer 7 can be increased, and the battery characteristics of the secondary battery can be further improved. The content of the ionic liquid electrolyte may be 90% by volume or less, 85% by volume or less, or 80% by volume or less based on the total nonvolatile content in electrolyte slurry 15.

The dispersion medium in the electrolyte slurry 15 may be the same as the dispersion medium used in the electrode mixture slurry described above. The content of the dispersion medium in the electrolyte slurry 15 may be, for example, 5 parts by mass or more and 1000 parts by mass or less based on 100 parts by mass of the nonvolatile content in the electrolyte slurry 15.

In the electrolyte slurry 15, the ratio of the total content of the ionic liquid and electrolyte salt to the content of the oxide particles 16 is larger than 4/1 in terms of volume ratio (volume of ionic liquid electrolyte/volume of oxide particles), and is 12 /1. Thereby, when the secondary battery is discharged at a relatively low current (for example, when discharged at 0.2C), the discharge characteristics of the secondary battery can be improved. From the viewpoint of further improving the discharge characteristics of the secondary battery, the ratio of the total content of the ionic liquid and the electrolyte salt to the content of the oxide particles 16 is preferably 5/1 or more in terms of volume ratio, and more preferably is 6/1 or more. In order to suppress the deterioration of the properties of the electrolyte slurry due to the high content of the ionic liquid and electrolyte salt, or to suppress the liquid leakage from the electrode after drying, the ionic liquid and electrolyte are adjusted according to the content of the oxide particles 16. The ratio of the total salt content, in terms of volume ratio, is preferably 11/1 or less, more preferably 10/1 or less, still more preferably 9/1 or less, particularly preferably 8/1 or less. It is.

In the electrolyte slurry 15, the ratio of the content of oxide particles 16 to the content of polymer 17 is preferably a mass ratio (content of oxide particles/content of polymer) from the viewpoint of improving the strength of the electrolyte layer. is 1/5 or more, more preferably 1/4 or more, still more preferably 1/3 or more, particularly preferably 1/2 or more. The ratio of the content of oxide particles 16 to the content of polymer 17 is preferably 5/1 or less, more preferably 3/1 in terms of mass ratio, from the viewpoint of improving discharge characteristics at relatively high currents. or less, more preferably 1/1 or less, particularly preferably 2/3 or less.

In the electrolyte slurry 15, the content ratio of the oxide particles 16, the polymer 17, and the ionic liquid electrolyte is oxide particles:polymer:ionic liquid electrolyte=7 to 25:4 to 60:20 to 85 in terms of mass ratio. It may be.

In the electrolyte slurry application step, the method of applying the electrolyte slurry 15 onto one surface (principal surface) 14a of the electrode mixture intermediate layer 14 is the same as the method of applying the electrode mixture slurry described above onto the one surface 13a of the current collector 13. It may be similar. The method for applying the electrolyte slurry 15 may be the same as or different from the method for applying the electrode mixture slurry.

After the electrolyte slurry application step, the dispersion medium contained in the electrode mixture intermediate layer 14 and the electrolyte slurry 15 is volatilized. The method of volatilizing the dispersion medium may be the same as the method of volatilizing the dispersion medium in the electrode mixture slurry described above. As a result of volatilizing the dispersion medium of the electrode mixture intermediate layer 14 and the electrolyte slurry 15, as shown in FIG. 12) and the electrolyte layer 7 in this order, a secondary battery battery member 19 (positive electrode member or negative electrode member) can be obtained.

A secondary battery using the battery member 19 obtained by the manufacturing method of this embodiment has particularly excellent discharge characteristics when the secondary battery is discharged at a relatively low current.

Further, in the manufacturing method of this embodiment, when the electrolyte slurry 15 is applied on the electrode mixture intermediate layer 14, the ionic liquid electrolyte is mixed with the dispersion medium and the electrolyte as shown by the arrow in FIG. 3(b). The slurry 15 moves to the electrode mixture intermediate layer 14 . This movement is presumed to be based on an effect of reducing the concentration difference of the ionic liquid electrolyte between the electrode mixture intermediate layer 14 and the electrolyte slurry 15, an effect of gravity, or a capillary phenomenon.

According to the manufacturing method of this embodiment, since the electrolyte layer 7 is formed by applying the electrolyte slurry 15 on the electrode mixture intermediate layer 14, fine irregularities are present on the surface of the electrode mixture intermediate layer 14. The electrolyte slurry 15 is also arranged so as to fill the recessed portion and flatten it. As a result, in the obtained battery member 19, a good interface is formed in which the electrode mixture layer 18 and the electrolyte layer 7 are in close contact with each other. In addition, in the battery member 19, the ionic liquid electrolyte may move between the electrolyte slurry 15 and the electrode mixture intermediate layer 14 in the electrolyte slurry application process, so the ionic liquid electrolyte may move in the electrode mixture layer 18. tends to exist around the electrode active material. Therefore, in the battery member 19, the electrode active material/electrolyte interface is well formed.

In this way, in the battery member 19, the electrode mixture layer 18/electrolyte layer 7 interface is well formed and has excellent adhesion, and the electrode active material/electrolyte interface is also well formed. Ru. Therefore, a secondary battery using this battery member 19 has even better battery characteristics.

Another embodiment of the method for manufacturing a secondary battery includes a step of permeating a polymer-containing solution (polymer solution) into the electrode mixture intermediate layer 14 before applying the electrolyte slurry 15 (polymer solution permeation). The method may further include a step).

In one embodiment, the polymer solution contains a polymer having a structural unit represented by the following formula (8), an ionic liquid, and an electrolyte salt.

In formula (8), X ⁻ represents a counter anion. Examples of X ^- include BF ₄ ^- (tetrafluoroborate anion), PF ₆ ^- (hexafluorophosphate anion), [FSI] ^- , [TFSI] ^- , [f3C] ^- , [BOB] ^- , BF ₃ (CF ₃ ) ^- , BF ₃ (C ₂ F ₅ ) ^- , BF ₃ (C ₃ F ₇ ) ^- , BF ₃ (C ₄ F ₉ ) ^- , C (SO ₂ CF ₃ ) ₃ ^- , CF ₃ SO ₂ O ⁻ , CF ₃ COO ⁻ , RCOO ⁻ (R is an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a naphthyl group), and the like. Among these, X ^- is preferably at least one selected from the group consisting of BF ₄ ^- , PF ₆ ^- , [FSI] ^- , [TFSI] ^- , and [f3C] ^- , more preferably [TFSI] ^- or [FSI] ^- .

The viscosity average molecular weight Mv (g mol ⁻¹ ) of the polymer having the structural unit represented by formula (8) is not particularly limited, but is preferably 1.0×10 ⁵ or more, more preferably 3.0 ×10 ⁵ or more. The viscosity average molecular weight of the polymer is preferably 5.0×10 ⁶ or less, more preferably 1.0×10 ⁶ . When the viscosity average molecular weight of the polymer is 5.0×10 ⁶ or less, the handling property when the polymer solution is permeated tends to be improved.

In this specification, "viscosity average molecular weight" can be evaluated by the viscosity method, which is a general measurement method, and for example, from the intrinsic viscosity number [η] measured based on JIS K 7367-3:1999. It can be calculated.

From the viewpoint of ionic conductivity, the polymer having the structural unit represented by formula (8) is preferably a polymer consisting only of the structural unit represented by formula (8), that is, a homopolymer.

The polymer having the structural unit represented by the formula (8) may be a polymer represented by the following formula (8A).

In formula (8A), n is 300 to 4000, and Y ⁻ represents a counter anion. Y ⁻ can be the same as those exemplified for X ⁻ .

n is 300 or more, preferably 400 or more, more preferably 500 or more, and may be 4000 or less, preferably 3500 or less, and more preferably 3000 or less. n is 300 to 4000, preferably 400 to 3500, more preferably 500 to 3000.

The method for producing the polymer having the structural unit represented by formula (8) is not particularly limited, and for example, the production method described in Journal of Power Sources 2009, 188, 558-563 can be used.

A polymer having a structural unit represented by formula (8) (X ⁻ =[TFSI] ⁻ ) can be obtained, for example, by the following manufacturing method.

First, poly(diallyldimethylammonium) chloride ([P(DADMA)][Cl]) is dissolved in deionized water and stirred to prepare a [P(DADMA)][Cl] aqueous solution. For [P(DADMA)][Cl], for example, a commercially available product can be used as is. Next, separately, Li[TFSI] is dissolved in deionized water to prepare an aqueous solution containing Li[TFSI].

After that, the molar ratio of Li[TFSI] to [P(DADMA)][Cl] (molar amount of Li[TFSI]/molar amount of [P(DADMA)][Cl]) was set to 1.2 to 2.0. The two aqueous solutions are mixed and stirred for 2 to 8 hours to precipitate a solid, and the resulting solid is collected by filtration. By washing the solid with deionized water and vacuum drying for 12 to 48 hours, a polymer ([P(DADMA)][TFSI]) having a structural unit represented by formula (8) can be obtained. .

The content of the polymer having the structural unit represented by formula (8) is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, based on the total amount of the polymer solution. Moreover, it is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less.

The ionic liquid and electrolyte salt included in the polymer solution may be similar to those used in the embodiments described above. The ionic liquid and electrolyte salt contained in the polymer solution may be the same or different from the ionic liquid and electrolyte salt contained in the electrolyte slurry 15.

The ionic liquid and electrolyte salt may be added to the polymer solution as an ionic liquid electrolyte. In this case, in the ionic liquid electrolyte, the salt concentration of the electrolyte salt per unit volume of the ionic liquid may be 0.3 mol/L or more, 0.5 mol/L or more, or 1.0 mol/L or more, and 3 It may be .0 mol/L or less, 2.7 mol/L or less, or 2.5 mol/L or less.

The content of the ionic liquid electrolyte is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, and preferably 80% by mass or more, based on the total amount of the polymer solution. It is at most 75% by mass, more preferably at most 70% by mass, and even more preferably at most 70% by mass.

The polymer solution may further contain a dispersion medium. The dispersion medium may be an organic solvent, such as acetone, ethyl methyl ketone, γ-butyrolactone, and the like.

In the polymer solution infiltration step, the method for infiltrating the electrode mixture intermediate layer 14 with the polymer solution is, for example, a method of applying the polymer solution on the surface 14a of the electrode mixture intermediate layer 14 on the side opposite to the current collector 13. be. Application may be by application with an applicator, application by spray, or the like. The polymer solution applied onto the electrode mixture intermediate layer 14 permeates into the electrode mixture intermediate layer 14, and an electrode mixture intermediate layer containing a polymer having a structural unit represented by formula (8) is formed. Ru.

Another method for infiltrating the polymer solution into the electrode mixture intermediate layer 14 may be a method in which the current collector 13 on which the electrode mixture intermediate layer 14 is formed is immersed in the polymer solution.

Thereafter, an electrolyte slurry 15 is applied onto the surface 14a of the electrode mixture intermediate layer 14 (the electrode mixture intermediate layer permeated with the polymer solution) on the side opposite to the current collector 13. (Electrolyte slurry application process). The composition and application method of electrolyte slurry 15 may be the same as in the embodiments described above.

In the battery member 19 obtained by the manufacturing method including the polymer solution coating step, the electrode mixture layer 18 contains the polymer represented by the above formula (8). Thereby, the ionic conductivity of the electrode mixture layer 18 can be increased, and the battery characteristics of the secondary battery using this battery member 19 can be further improved.

A secondary battery including a battery member manufactured by the manufacturing method described above can take various modifications.

As a first modification, the method of manufacturing a battery member according to each of the embodiments described above can also be used as a method of manufacturing a battery member used in a so-called bipolar secondary battery. FIG. 4 is an exploded perspective view showing an embodiment of an electrode group of a secondary battery according to a modification. The secondary battery in this modification differs from the secondary battery in the embodiment described above in that the electrode group 2B includes a bipolar electrode 21. That is, as shown in FIG. 4, the electrode group 2B includes a positive electrode 6, a first electrolyte layer 7, a bipolar electrode 21, a second electrolyte layer 7, and a negative electrode 8 in this order. The bipolar electrode 21 includes a bipolar current collector 22 , a positive electrode mixture layer 10 provided on the negative electrode 8 side surface (positive electrode surface) of the bipolar current collector 22 , and a positive electrode mixture layer 10 provided on the negative electrode 8 side surface (positive electrode surface) of the bipolar current collector 22 ( The negative electrode mixture layer 12 is provided on the negative electrode surface.

This bipolar type secondary battery includes a first electrolyte layer 7, a positive electrode mixture layer 10, a bipolar current collector 22, a negative electrode mixture layer 12, and a second electrolyte layer 7 in this order. It can be seen that a battery member for a battery (bipolar electrode member) is included. A method for manufacturing a battery member according to an embodiment of the present invention is a method for manufacturing this bipolar electrode member.

A method for manufacturing a bipolar electrode member according to one embodiment includes a step of forming a positive electrode mixture intermediate layer on one surface (one main surface) of the bipolar current collector 22 (positive electrode mixture intermediate layer forming step); A step of applying a first electrolyte slurry on the surface of the positive electrode mixture intermediate layer opposite to the bipolar current collector 22 (first electrolyte slurry application step); forming a negative electrode mixture intermediate layer (negative electrode mixture intermediate layer forming step) on the main surface of the negative electrode mixture intermediate layer (main surface of (second electrolyte slurry application step). Each step may be performed using the same materials and methods as those in each of the embodiments described above (electrode mixture intermediate layer forming step, electrolyte slurry application step). Note that the first electrolyte slurry and the second electrolyte slurry may have the same composition or different compositions, but preferably have the same composition.

Also in this embodiment, before the electrolyte slurry application step, a solution containing a polymer having a structural unit represented by the above formula (8) is infiltrated into the positive electrode mixture intermediate layer or the negative electrode mixture intermediate layer. The method may further include a step (polymer solution infiltration step). The polymer solution infiltration step may be performed using the same materials and methods as the polymer solution infiltration step in the embodiment described above.

After the electrolyte slurry application step, the dispersion medium of the positive electrode mixture intermediate layer and the first electrolyte slurry is volatilized. Similarly, the dispersion medium of the negative electrode mixture intermediate layer and the second electrolyte slurry is volatilized. The method of volatilizing the dispersion medium may be the same method as in the embodiment described above. As a result of volatilizing the dispersion medium, a battery member for a secondary battery is obtained, which includes the first electrolyte layer 7, the positive electrode mixture layer 10, the bipolar current collector 22, the negative electrode mixture layer 12, and the second electrolyte layer 7 in this order. (bipolar electrode member) can be obtained.

Even in a secondary battery using the bipolar electrode member obtained in this manner, the discharge characteristics of the secondary battery when discharged at a relatively low current can be improved.

As a second modification, in the method for manufacturing a battery member according to each of the embodiments described above, after forming the electrolyte layer 7, another electrolyte layer (second electrolyte layer) is formed on the electrolyte layer (first electrolyte layer) 7. The method may further include a step of laminating an electrolyte layer). In this case, since the first electrolyte layer serves to form a good interface between the electrode mixture layer and the second electrolyte layer, the first electrolyte layer can also be called an interface forming layer. A secondary battery using a battery member obtained by this manufacturing method includes, as an electrode group, a positive electrode current collector, a positive electrode mixture layer, a first interface forming layer, an electrolyte layer (second electrolyte layer), a second An interface forming layer, a negative electrode mixture layer, and a negative electrode current collector are provided in this order.

In one embodiment, this electrode group includes a first battery member (positive electrode member) comprising a positive electrode current collector, a positive electrode mixture layer, a first interface forming layer, and an electrolyte layer in this order. You can see it. Similarly, this electrode group includes a second battery member (negative electrode member) comprising a negative electrode current collector, a negative electrode mixture layer, a second interface forming layer, and an electrolyte layer in this order. It can also be seen as The manufacturing method according to the second modification is a method of manufacturing this positive electrode member and negative electrode member.

The interface forming layer may have the same composition as the electrolyte layer in the battery member of each embodiment described above. That is, the manufacturing method according to this modification is a method in which the electrolyte layer in each of the above-described embodiments is replaced with the interface forming layer.

In this manufacturing method, a battery member can be manufactured by arranging an electrolyte layer on the surface of the positive electrode member on the first interface forming layer side or on the surface of the negative electrode member on the second interface forming layer side. . In one embodiment, the electrolyte layer at this time may be one in which the electrolyte slurry 15 described above is formed into a sheet shape. That is, an electrolyte sheet is produced by preparing a base material such as a resin film, coating the electrolyte slurry 15 on the base material, and then volatilizing the dispersion medium. Then, by peeling off the base material from this electrolyte sheet, an electrolyte layer can be obtained.

In other embodiments, the electrolyte layer may have a composition different from that of the electrolyte layer prepared from the electrolyte slurry 15, for example, a known electrolyte composition such as an organic polymer solid electrolyte or an inorganic solid electrolyte. may be formed into a sheet shape in advance. In this case, the organic polymer solid electrolyte may be polyethylene oxide, etc., and the inorganic solid electrolyte is Li ₇ La ₃ Zr ₂ O ₁₂ , Li _6.75 La ₃ Zr _1.75 Nb _0.25 O ₁₂ (LLZ- Nb), Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ , Li _1+c+d Al _c (Ti, Ge) _2-c Si _d P _3-d O ₁₂ (where 0≦c<2 (Ti, Ge) means either Ti or Ge, or both Ti and Ge.), Li ₁₀ GeP ₂ S ₁₂ , Li _9.54 Si _1.74 P _1.44 S _11.7 Cl _0.3 , etc.

Also in a secondary battery using the battery member obtained in this way, the discharge characteristics of the secondary battery when discharged at a relatively low current can be improved. Furthermore, by containing the ionic liquid electrolyte in the interface forming layer, ionic conduction between the interface forming layer and the electrolyte layer becomes easier. As a result, it can be said that the secondary battery using the battery member according to this modification has excellent battery characteristics because the interface between each layer is well formed.

Embodiments of the present invention will be described below. However, the present invention is not limited to the following embodiments. In the following, when expressing the composition of an ionic liquid in which an electrolyte salt is dissolved (ionic liquid electrolyte), it may be expressed as "concentration of electrolyte salt/type of electrolyte salt/type of ionic liquid". .

<Example 1>
[Preparation of positive electrode member]
92.5 parts by mass of layered lithium-nickel-manganese-cobalt composite oxide (positive electrode active material) and 2.5 parts of acetylene black (conductive agent, product name: HS-100, average particle size 48 nm, manufactured by Denka Corporation) parts by mass and 5 parts by mass of a copolymer solution of vinylidene fluoride and hexafluoropropylene (solid content 12% by mass) are dispersed in an appropriate amount of N-methyl-2-pyrrolidone (NMP) as a dispersion medium to form a positive electrode mixture. A slurry was prepared. This positive electrode mixture slurry was coated on a positive electrode current collector (aluminum foil with a thickness of 20 μm) at a coating weight of 125 g/m ² , heated at 80°C for 12 hours to dry, and then pressed. A positive electrode mixture intermediate layer having a density of 2.7 g/cm ³ was formed. After cutting this into a width of 30 mm and a length of 45 mm, a positive electrode current collecting tab was attached.

25 parts by mass of PVDF-HFP and 12 parts by mass of SiO ₂ particles (specific surface area: 50 m ² /g, surface treatment: hexamethyldisilazane, average primary particle size: 40 nm, product name: AEROSIL RX50, Nippon Aerosil Co., Ltd.) and 63 parts by mass of an ionic liquid electrolyte (2.0 mol/L/Li[FSI]/EMI-FSI) were dispersed in an appropriate amount of NMP as a dispersion medium to prepare an electrolyte slurry. Based on the total nonvolatile content of the electrolyte slurry, the content of SiO ₂ particles was 9% by volume, and the content of the ionic liquid electrolyte was 70% by volume. The obtained electrolyte slurry was applied onto the surface of the positive electrode mixture intermediate layer opposite to the positive electrode current collector, and heated at 80° C. for 12 hours to volatilize the dispersion medium to form an electrolyte layer. Thereby, a positive electrode member including a positive electrode current collector, a positive electrode mixture layer, and an electrolyte layer in this order was obtained. The thickness of the electrolyte layer in the obtained positive electrode member was 15±2 μm.

[Preparation of negative electrode member]
92 parts by mass of graphite (negative electrode active material, manufactured by Hitachi Chemical Co., Ltd.), 3 parts by mass of acetylene black (conductive agent, product name: HS-100, average particle size 48 nm, manufactured by Denka Corporation), vinylidene fluoride and hexa A negative electrode mixture slurry was prepared by dispersing 5 parts by mass of a fluoropropylene copolymer solution (solid content: 12% by mass) in an appropriate amount of NMP as a dispersion medium. This negative electrode mixture slurry was coated on a current collector (copper foil with a thickness of 10 μm) at a coating amount of 60 g/ ^m2 , heated at 80°C for 12 hours, dried, and pressed to determine the mixture density. A 1.8 g/cm ³ negative electrode mixture intermediate layer was formed. After cutting this to a width of 31 mm and a length of 46 mm, a negative electrode current collecting tab was attached.

By a method similar to the method for manufacturing the positive electrode member, the electrolyte slurry described above is applied on the surface of the negative electrode mixture intermediate layer opposite to the negative electrode current collector, and then the dispersion medium is evaporated to form an electrolyte layer. Ta. Thereby, a negative electrode member including a negative electrode current collector, a negative electrode mixture layer, and an electrolyte layer in this order was obtained. The thickness of the electrolyte layer in the obtained negative electrode member was 15±2 μm.

[Fabrication of lithium ion secondary battery]
An electrode group was produced by stacking the produced positive electrode member and negative electrode member so that their respective electrolyte layers were in contact with each other. As shown in FIG. 1, this electrode group was housed in a battery exterior made of an aluminum laminate film. A lithium ion secondary battery was produced by sealing the opening of the battery container in this battery case so that the above-mentioned positive electrode current collecting tab and negative electrode current collecting tab could be taken out to the outside. Note that the aluminum laminate film is a laminate of polyethylene terephthalate (PET) film/aluminum foil/sealant layer (polypropylene, etc.). The designed capacity of the produced lithium ion secondary battery was 20 mAh.

<Examples 2-22, Reference Examples 1-2>
A lithium ion secondary battery was produced in the same manner as in Example 1, except that the composition of the electrolyte slurry was changed to that shown in Table 1 in producing the positive electrode member and the negative electrode member. Regarding the oxide particles, in the table, those with an average primary particle size of 40 nm and surface treated are the same SiO ₂ particles as in Example 1, and those with an average primary particle size of 40 nm and not surface treated. The material is AEROSIL OX50 (product name) manufactured by Nippon Aerosil Co., Ltd., and the material with an average primary particle size of 7 nm is S5130 (product name) manufactured by SIGMA-ALDRICH.

<Evaluation of discharge characteristics>
Constant current charging at 0.1C was performed to an upper limit voltage of 4.2V. Thereafter, constant current discharge was performed at a current value of 0.1C and a final voltage of 2.7V, and the capacity during this discharge was defined as the discharge capacity at a current value of 0.1C. Next, constant current charging at 0.1C is performed to the upper limit voltage of 4.2V, constant current discharge is performed at a current value of 0.2C with a final voltage of 2.7V, and the capacity at the time of this discharge is measured at a current value of 0.2C. Discharge capacity. The discharge capacity retention rate (0.2C/0.1C) was calculated using the following formula. Similarly, the discharge capacity at 0.5C was also measured to determine the discharge capacity retention rate (0.5C/0.1C). The results are shown in Table 1.
Discharge capacity maintenance rate (%) = (discharge capacity at current value 0.2C or 0.5C/discharge capacity at current value 0.1C) x 100

DESCRIPTION OF SYMBOLS 1... Secondary battery, 6... Positive electrode, 7... Electrolyte layer, 8... Negative electrode, 9... Positive electrode current collector, 10... Positive electrode mixture layer, 11... Negative electrode current collector, 12... Negative electrode mixture layer, 13... Collection Electric body, 14... Electrode mixture intermediate layer, 15... Slurry (electrolyte slurry), 16... Oxide particles, 17... Polymer, 18... Electrode mixture layer, 19... Battery member for secondary battery.

Claims (4)

forming an electrode mixture intermediate layer containing an electrode active material on one surface of the current collector;
a step of applying a slurry containing oxide particles, a polymer, an ionic liquid, and an electrolyte salt on the surface of the electrode mixture intermediate layer opposite to the current collector;
The ratio of the total content of the ionic liquid and the electrolyte salt to the content of the oxide particles is larger than 4/1 and smaller than 12/1 in terms of volume ratio,
The polymer is one or more kinds of polymers, and the structural units constituting the one or more kinds of polymers include a first one selected from the group consisting of tetrafluoroethylene and vinylidene fluoride. a structural unit and a second structural unit selected from the group consisting of hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate, and methyl methacrylate,
The ionic liquid is N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium-bis(trifluoromethanesulfonyl)imide (DEME-TFSI), N,N-diethyl-N-methyl-N- (2-Methoxyethyl)ammonium-bis(fluorosulfonyl)imide (DEME-FSI), 1-ethyl-3-methylimidazolium-bis(trifluoromethanesulfonyl)imide (EMI-TFSI), 1-ethyl-3-methyl Imidazolium-bis(fluorosulfonyl)imide (EMI-FSI), N-methyl-N-propylpyrrolidinium-bis(trifluoromethanesulfonyl)imide (Py13-TFSI), N-methyl-N-propylpyrrolidinium- Bis(fluorosulfonyl)imide (Py13-FSI), N-ethyl-N-methylpyrrolidinium-bis(trifluoromethanesulfonyl)imide (Py12-TFSI), or N-ethyl-N-methylpyrrolidinium-bis A method for producing a battery member for a secondary battery, which is (fluorosulfonyl)imide (Py12-FSI) . The manufacturing method according to claim 1, wherein the oxide particles have a specific surface area of 2 to 400 m ² /g. The manufacturing method according to claim 1 or 2, wherein the concentration of the electrolyte salt per unit volume of the ionic liquid is greater than 0.5 mol/L. The manufacturing method according to any one of claims 1 to 3, wherein the ionic liquid contains N(SO ₂ F) ₂ ^- as an anion component.

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