JP7423120B2 - Electrolyte slurry composition, electrolyte sheet manufacturing method, and secondary battery manufacturing method - Google Patents

Description

The present invention relates to an electrolyte slurry composition, a method for manufacturing an electrolyte sheet, and a method for manufacturing 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. BACKGROUND ART Conventionally, as a method for improving the safety of lithium secondary batteries, there has been known a method of gelling components used in an electrolytic solution to form a gel electrolyte (see, for example, Patent Documents 1 and 2).

Japanese Patent Application Publication No. 2000-164254 Japanese Patent Application Publication No. 2007-141467

Incidentally, an electrolyte layer formed from an electrolyte is required to have improved mechanical strength from the viewpoint of reducing the weight and thickness of a lithium secondary battery. However, the electrolyte layer formed from gel electrolyte is not strong enough, and there is still room for improvement.

Therefore, the main object of the present invention is to provide an electrolyte slurry composition that can form an electrolyte layer having excellent strength.

A first aspect of the present invention includes one or more polymers, oxide particles, and at least one electrolyte salt selected from the group consisting of lithium salts, sodium salts, calcium salts, and magnesium salts; It contains at least one of a compound represented by the following general formula (10) (hereinafter sometimes referred to as "glyme") and an ionic liquid, and an organic solvent, and the organic solvent has a heating rate of 5°C/min. This electrolyte slurry composition has a temperature at which a mass reduction rate of 95% occurs when the temperature is raised at 120° C. or lower (hereinafter sometimes simply referred to as "mass reduction rate 95% temperature").
R ^A O-(CH ₂ CH ₂ O) _y -R ^B (10)
[In formula (10), R ^A and R ^B each independently represent an alkyl group having 1 to 4 carbon atoms, and y represents an integer of 1 to 6. ]

The oxide particles preferably contain 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 . It is a particle.

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

The ionic liquid preferably contains at least one anion component represented by the following general formula (A) as an anion component.
N(SO ₂ C _m F _2m+1 ) (SO ₂ C _n F _2n+1 ) ^- (A)
[In formula (A), m and n each independently represent an integer of 0 to 5. ]

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

The polymer preferably has a first structural unit and a second structural unit selected from the group consisting of hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate, and methyl methacrylate in the structural units constituting the polymer. is included.

The electrolyte salt is preferably an imide-based lithium salt.

The compound represented by general formula (10) preferably contains tetraethylene glycol dimethyl ether.

A second aspect of the present invention includes a step of disposing the electrolyte slurry composition described above on a base material, and a step of removing an organic solvent from the disposed electrolyte slurry composition to form an electrolyte layer on the base material. A method for manufacturing an electrolyte sheet, comprising:

A third aspect of the present invention includes a step of forming a positive electrode mixture layer on a positive electrode current collector to obtain a positive electrode, a step of forming a negative electrode mixture layer on a negative electrode current collector to obtain a negative electrode, and a step of forming a negative electrode mixture layer on a negative electrode current collector to obtain a negative electrode. This is a method for manufacturing a secondary battery, comprising the step of arranging an electrolyte layer of an electrolyte sheet obtained by the manufacturing method described above between a positive electrode and a negative electrode.

According to the present invention, an electrolyte slurry composition capable of forming an electrolyte layer having excellent strength can be provided. Further, according to the present invention, it is possible to provide a method for manufacturing an electrolyte sheet using such an electrolyte slurry composition. Furthermore, according to the present invention, it is possible to provide a method for manufacturing a secondary battery using an electrolyte sheet manufactured from an electrolyte slurry composition.

FIG. 1 is a perspective view showing a secondary battery according to a first embodiment. 2 is an exploded perspective view showing one embodiment of an electrode group in the secondary battery shown in FIG. 1. FIG. 2 is a schematic cross-sectional view showing one embodiment of an electrode group in the secondary battery shown in FIG. 1. FIG. (a) is a schematic cross-sectional view showing an electrolyte sheet according to one embodiment, and (b) is a schematic cross-sectional view showing an electrolyte sheet according to another embodiment. FIG. 7 is a schematic cross-sectional view showing one embodiment of an electrode group in a secondary battery according to a second embodiment.

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.

[First embodiment]
FIG. 1 is a perspective view showing a secondary battery according to a first 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 in the secondary battery 1 shown in FIG. FIG. 3 is a schematic cross-sectional view showing one embodiment of the electrode group 2 in the secondary battery 1 shown in FIG. As shown in FIGS. 2 and 3, the electrode group 2A according to this embodiment 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. 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 the negative electrode current collector 11. A negative electrode current collector tab 5 is provided on the negative electrode current collector 11 .

The positive electrode current collector 9 may be made of aluminum, stainless steel, titanium, or the like. Specifically, the positive electrode current collector 9 may be, for example, a perforated aluminum foil having holes with a diameter of 0.1 to 10 mm, an expanded metal, a foamed metal plate, or the like. In addition to the above, the positive electrode current collector 9 may be formed of any material as long as it does not undergo changes such as dissolution or oxidation during use of the battery, and its shape, manufacturing method, etc. Not restricted.

The thickness of the positive electrode current collector 9 may be 10 μm or more and 100 μm or less, and preferably 10 μm or more and 50 μm or less from the viewpoint of reducing the overall volume of the positive electrode. From the viewpoint of rotation, it is more preferably 10 μm or more and 20 μm or less.

In one embodiment, the positive electrode mixture layer 10 contains a positive electrode active material, a conductive agent, and a binder.

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 ₂ 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 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 (1)
[In formula (1), ^M2 is at least one member selected from the group consisting of Al, Mn, Mg, and Ca, and a, b, c, d, and e are each 0.2≦a≦ A number that satisfies 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 It is. ]

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 At least one element selected from the group consisting of Zr).

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 0.1 μm or more, more preferably 1 μm or more. Moreover, it 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 (D50) when the ratio (volume fraction) to the total volume of the positive electrode active material is 50%. The average particle diameter (D50) of the positive electrode active material can be determined by measuring a suspension of the positive electrode active material in water using a laser scattering method using a laser scattering particle size measuring device (e.g. Microtrack). It can be obtained with

The content of the positive electrode active material may be 70% by mass or more, 80% by mass or more, or 85% by mass or more based on the total amount of the positive electrode mixture layer. The content of the positive electrode active material may be 95% by mass or less, 92% by mass or less, or 90% by mass or less based on the total amount of the positive electrode mixture layer.

The conductive agent may be a carbon material such as graphite, acetylene black, carbon black, carbon fiber, carbon nanotube, etc., but is not particularly limited. 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 0.1% by mass or more, 1% by mass or more, or 3% by mass or more based on the total amount of the positive electrode mixture layer. The content of the conductive agent is preferably 15% by mass or less, more preferably 15% by mass or less, based on the total amount of the positive electrode mixture layer, from the viewpoint of suppressing an increase in the volume of the positive electrode 6 and a corresponding decrease in the energy density of the secondary battery 1. It is 10% by mass or less, more preferably 8% by mass or less.

The binder is not limited as long as it does not decompose on the surface of the positive electrode 6, but it is selected from the group consisting of tetrafluoroethylene, vinylidene fluoride, hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate, and methyl methacrylate. The rubber may be a polymer containing at least one of the following as a monomer unit, a rubber such as styrene-butadiene rubber, isoprene rubber, or acrylic rubber. The binder is preferably a copolymer containing tetrafluoroethylene and vinylidene fluoride as structural units.

The content of the binder may be 0.5% by mass or more, 1% by mass or more, or 3% by mass or more based on the total amount of the positive electrode mixture layer. The content of the binder may be 20% by mass or less, 15% by mass or less, or 10% by mass or less based on the total amount of the positive electrode mixture layer.

The positive electrode mixture layer 10 may further contain an ionic liquid.

As the ionic liquid, an ionic liquid used in the electrolyte slurry composition described below can be used. The content of the ionic liquid contained in the positive electrode mixture layer 10 is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, based on the total amount of the positive electrode mixture layer. The content of the ionic liquid contained in the positive electrode mixture layer 10 is preferably 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less, based on the total amount of the positive electrode mixture layer.

An electrolyte salt may be dissolved in the ionic liquid contained in the positive electrode mixture layer 10. As the electrolyte salt, an electrolyte salt used in the electrolyte slurry composition described below can be used.

The thickness of the positive electrode mixture layer 10 is, from the viewpoint of further improving the conductivity, a thickness greater than or equal to the average particle diameter of the positive electrode active material, specifically, 10 μm or more, 15 μm or more, or 20 μm or more. good. The thickness of the positive electrode mixture layer 10 may be 100 μm or less, 80 μm or less, or 70 μm or less. By setting the thickness of the positive electrode mixture layer to 100 μm or less, bias in charging and discharging caused by variations in the charge level of the positive electrode active material near the surface of the positive electrode mixture layer 10 and near the surface of the positive electrode current collector 9 is suppressed. can.

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 gravimetric 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, and preferably 10 μm or more and 50 μm or less from the viewpoint of reducing the volume of the entire negative electrode, and the negative electrode may be wound with a small curvature when forming a battery. From the viewpoint of rotation, it is more preferably 10 μm or more and 20 μm or less.

In one embodiment, the negative electrode mixture layer 12 contains a negative electrode active material and a binder.

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 metal lithium, lithium titanate (Li ₄ Ti ₅ O ₁₂ ), lithium alloys or other metal compounds, carbon materials, metal complexes, organic polymer compounds, etc. . 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 black. Examples include carbon black such as. 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 increases 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 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. The content of the negative electrode active material may be 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.

The binder and its content may be the same as the binder and its content in the positive electrode mixture layer 10 described above.

The negative electrode mixture layer 12 may further contain a conductive agent from the viewpoint of further lowering the resistance of the negative electrode 8. The conductive agent and its content may be the same as the conductive agent and its content in the positive electrode mixture layer 10 described above.

The negative electrode mixture layer 12 may further contain an ionic liquid.

As the ionic liquid, an ionic liquid used in the electrolyte slurry composition described below can be used. The content of the ionic liquid contained in the negative electrode mixture layer 12 is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, based on the total amount of the negative electrode mixture layer. The content of the ionic liquid contained in the negative electrode mixture layer 12 is preferably 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less, based on the total amount of the negative electrode mixture layer.

An electrolyte salt similar to the electrolyte salt that can be used in the above-described positive electrode mixture layer 10 may be dissolved in the ionic liquid contained in the negative electrode mixture layer 12.

The thickness of the negative electrode mixture layer 12 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 100 μm or less, 80 μm or less, or 70 μm or less.

Electrolyte layer 7 is formed by producing an electrolyte sheet on a base material using an electrolyte slurry composition. The electrolyte slurry composition comprises one or more polymers, oxide particles, at least one electrolyte salt selected from the group consisting of lithium salts, sodium salts, calcium salts, and magnesium salts, and the general formula (10 ) and at least one of an ionic liquid and an organic solvent. The organic solvent has a temperature of 120° C. or lower at which the mass reduction rate is 95% when the temperature is increased at a heating rate of 5° C./min.

The electrolyte slurry composition contains one or more polymers. The polymer preferably has a first structural unit selected from the group consisting of tetrafluoroethylene and vinylidene fluoride.

The structural units constituting the polymer include the first structural unit and a second structural unit selected from the group consisting of hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate, and methyl methacrylate. You can leave it there. 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.

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

The content of the polymer is preferably 3% by mass or more based on the total amount of the components of the electrolyte slurry composition excluding the organic solvent. The content of the polymer is preferably 50% by mass or less, more preferably 40% by mass or less, based on the total amount of components excluding the organic solvent of the electrolyte slurry composition. The content of the polymer is preferably 3 to 50% by mass, more preferably 3 to 40% by mass, based on the total amount of the components of the electrolyte slurry composition excluding the organic solvent.

Since the polymer according to the present embodiment has excellent affinity with the ionic liquid contained in the electrolyte slurry composition, it retains the electrolyte in the glyme or the ionic liquid when the electrolyte layer 7 is formed. This suppresses leakage of grime or ionic liquid when a load is applied to the electrolyte layer 7.

The electrolyte slurry composition contains oxide particles. The oxide particles 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 preferably contain 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 . It is a particle. Since the oxide particles have polarity, they can promote dissociation of the electrolyte in the electrolyte layer 7 and improve battery characteristics.

Oxide particles generally consist of primary particles that integrally form a single particle (particles that do not constitute secondary particles) and multiple primary particles, judging from their apparent geometric form. may also include secondary particles formed by aggregation.

The specific surface area of the oxide particles is 2 to 380 m ² /g, and may be 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 380 m ² /g, the secondary battery tends to have better discharge characteristics. From the same viewpoint, the specific surface area of the oxide particles may be 5 m ² /g or more, 10 m ² /g or more, or 15 m ² /g or more, and 100 m ² /g or less, 80 m ² /g or less, or It may be 60 m ² /g or less. The specific surface area of oxide particles 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 is preferably 0.005 μm (5 nm) or more, more preferably 0.01 μm (10 nm) or more, from the viewpoint of further improving the electrical conductivity. It is more preferably 0.015 μm (15 nm) or more. From the viewpoint of making the electrolyte layer 7 thinner, the average primary particle size of the oxide particles is preferably 1 μm or less, more preferably 0.1 μm or less, and even more preferably 0.05 μm or less. The average primary particle size of the oxide particles is preferably from 0.005 to 1 μm, from 0.01 to 1 μm, from the viewpoint of making the electrolyte layer 7 thin and suppressing the protrusion of the oxide particles from the surface of the electrolyte layer 7. It is 0.1 μm or 0.015 to 0.05 μm. The average primary particle size of the oxide particles can be measured by observing the oxide particles using a transmission electron microscope or the like.

The average particle diameter of the oxide particles 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 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 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 shape of the oxide particles may be, for example, massive or approximately spherical. The aspect ratio of the oxide particles is preferably 10 or less, more preferably 5 or less, still more preferably 2 or less, from the viewpoint of facilitating thinning of the electrolyte layer 7. The aspect ratio is calculated from the scanning electron micrograph of an oxide particle, and is calculated from the length in the long axis direction of the particle (maximum length of the particle) and the length in the short axis direction of the particle (minimum length of the particle). is defined as the ratio of The length of the particle is determined by statistically calculating the photograph using a commercially available image processing software (for example, image analysis software Azo-kun (registered trademark) manufactured by Asahi Kasei Engineering Co., Ltd.).

The oxide particles may be surface treated with a surface treatment agent. Examples of the surface treatment agent include silicon-containing compounds. Silicon-containing compounds include methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethoxydiphenylsilane, n-propyltrimethoxysilane, hexyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyl Alkoxysilane such as diethoxysilane, n-propyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, Epoxy group-containing silanes such as 3-glycidoxypropylmethyldiethoxysilane and 3-glycidoxypropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(amino Silanes containing amino groups such as ethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, silazane such as hexamethyldisilazane, dimethylsilicone oil, etc. It may also be siloxane or the like.

As the oxide particles surface-treated with a surface treatment agent, those produced by a known method may be used, or commercially available products may be used as they are.

The content of oxide particles is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, particularly preferably The content is 20% by mass or more, and preferably 60% by mass or less, more preferably 50% by mass or less, and still more preferably 40% by mass or less.

The electrolyte slurry composition contains an electrolyte salt. The electrolyte salt is at least one selected from the group consisting of lithium salts, sodium salts, calcium salts, and magnesium salts. The electrolyte salt is a compound used to transfer cations between the positive electrode 6 and the negative electrode 8. The above-mentioned electrolyte salt has a low degree of dissociation at low temperatures and is easily diffused in glyme or ionic liquid. In addition, it does not decompose thermally at high temperatures, so it is preferable that the secondary battery can be used at a wide range of environmental temperatures. The electrolyte salt may be an electrolyte salt used in fluoride ion batteries.

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 represented by formula (A), such as N(SO ₂ F) ₂ ^- , N(SO ₂ CF ₃ ) ₂ ^-, etc., as exemplified by the anion components of ionic liquids described below. component, PF ₆ ^- , BF ₄ ^- , B(O ₂ C ₂ O ₂ ) ₂ ^- , or ClO ₄ ^- .

Note that the following abbreviations may be used below.
[FSI] ⁻ :N(SO ₂ F) ₂ ⁻ , bis(fluorosulfonyl)imide anion [TFSI] ⁻ :N(SO ₂ CF ₃ ) ₂ ⁻ , bis(trifluoromethanesulfonyl)imide anion [BOB] ⁻ :B (O ₂ C ₂ O ₂ ) ₂ ⁻ , bisoxalate borate anion [f3C] ⁻ :C(SO ₂ F) ₃ ⁻ , tris(fluorosulfonyl) carbanion

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 , CF ₃ SO ₂ OLi, CF ₃ COOLi, and R'COOLi (R' is a carbon number of 1 to 4 (alkyl group, 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 , CF ₃ SO ₂ ONa, CF ₃ COONa, and R'COONa (R' is a carbon number of 1 to 4 (alkyl group, 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 , (CF ₃ SO ₂ O) ₂ Ca, (CF ₃ COO) ₂ Ca, and (R'COO) ₂ Ca (R' is alkyl having 1 to 4 carbon atoms) group, phenyl group, 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 , Na(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 , (CF ₃ SO ₃ ) ₂ Mg, (CF ₃ COO) ₂ Mg, and (R'COO) ₂ Mg (R' is an alkyl group having 1 to 4 carbon atoms) , phenyl group, or naphthyl group).

The electrolyte salt is preferably one selected from the group consisting of imide-based lithium salts, imide-based sodium salts, imide-based calcium salts, and imide-based magnesium salts, and more preferably imide-based lithium salts.

The imide-based lithium salt may be Li[TFSI], Li[FSI], or the like. The imide-based sodium salt may be Na[TFSI], Na[FSI], or the like. The imide calcium salt may be Ca[TFSI] ₂ , Ca[FSI] ₂ or the like. The imide-based magnesium salt may be Mg[TFSI] ₂ , Mg[FSI] ₂ or the like.

The electrolyte slurry composition contains at least one of a compound represented by general formula (10) (glyme) and an ionic liquid. Glyme and ionic liquids are not included in organic solvents. The electrolyte slurry composition preferably contains an ionic liquid from the viewpoint of ionic conductivity and discharge characteristics.

Glyme is a compound represented by general formula (10).
R ^A O-(CH ₂ CH ₂ O) _y -R ^B (10)

In formula (10), R ^A and R ^B each independently represent an alkyl group having 1 to 4 carbon atoms, and y represents an integer of 1 to 6. The alkyl group as R ^A and R ^B may be a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, etc. Among these, the alkyl group is preferably a methyl group or an ethyl group.

Examples of glyme include triethylene glycol dimethyl ether (sometimes called "triglyme" or "G3"), tetraethylene glycol dimethyl ether (sometimes called "tetraglyme" or "G4"), and pentaethylene glycol dimethyl ether (sometimes called "penta glyme" or "G4"). (sometimes referred to as "glyme" or "G5"), hexaethylene glycol dimethyl ether (sometimes referred to as "hexaglyme" or "G6"), and the like. These may be used alone or in combination of two or more. Among these, glyme is preferably triglyme or tetraglyme, more preferably tetraglyme. These grimes tend to have a temperature at which a mass reduction rate of 95% occurs when the temperature is increased at a heating rate of 5°C/min (mass reduction rate 95% temperature) exceeding 120°C.

The ionic liquid contains the following anionic components and cationic components. Note that the ionic liquid in this embodiment is a substance that is liquid at −20° C. or higher. Ionic liquids are known to have almost no vapor pressure, unlike molecular liquids such as water and organic solvents, due to strong electrostatic interactions between their constituent cations and anions. Therefore, when an ionic liquid is heated at a heating rate of 5°C/min, the temperature at which the mass reduction rate is 95% tends to exceed 120°C.

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 includes at least one anion component represented by the following general formula (A).
N(SO ₂ C _m F _2m+1 ) (SO ₂ C _n F _2n+1 ) ^- (A)

In formula (A), 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 (A) 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 Contains N(SO ₂ F) ₂ ^- .

The cation component of the ionic liquid is not particularly limited, but 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（２）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 general formula (2).

[In formula (2), 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 R-O-(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（３）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 general formula (3).

[In formula (3), 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（４）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 general formula (4).

[In formula (4), 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（５）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 general formula (5).

[In formula (5), 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（６）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 general formula (6).

[In formula (6), 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. ]

From the viewpoint of suitably producing the electrolyte layer 7, the total content of glyme and ionic liquid may be 10% by mass or more, and 80% by mass, based on the total amount of components of the electrolyte slurry composition excluding the organic solvent. It may be the following. The content of the ionic liquid is preferably 20% by mass or more based on the total amount of components of the electrolyte slurry composition excluding the organic solvent, from the viewpoint of enabling charging and discharging of the lithium secondary battery at a high load rate. The content is more preferably 30% by mass or more.

The concentration of the electrolyte salt per unit volume of the total of glyme and ionic liquid in the electrolyte layer 7 is preferably 0.5 mol/L or more, more preferably 0.7 mol/L or more, from the viewpoint of further improving charge/discharge characteristics. More preferably, it is 1.0 mol/L or more, and preferably 3.0 mol/L or less, more preferably 2.5 mol/L or less, and even more preferably 2.3 mol/L or less.

The electrolyte slurry composition contains an organic solvent. However, the above-mentioned glyme and ionic liquid are not included in the organic solvent. The organic solvent has a temperature at which the mass reduction rate is 95% (mass reduction rate 95% temperature) when the temperature is raised at a heating rate of 5°C/min.

The organic solvent can be used without particular limitation as long as the temperature at which the 95% mass reduction rate is 120° C. or lower. One type of organic solvent may be used alone, or two or more types may be used in combination as a mixed solvent. The mass reduction rate 95% temperature can be adjusted to a desired range by adjusting the ratio of two or more organic solvents having different mass reduction rate 95% temperatures. Therefore, even if a single organic solvent does not satisfy this condition, it may be possible to satisfy this condition by combining two or more types to form a mixed solvent. The mass reduction rate of 95% temperature can be determined by increasing the temperature at a heating rate of 5°C/min using a thermogravimetric measuring device and measuring the temperature when the mass reduction rate of 95% is reached. .

The 95% mass reduction rate temperature of the organic solvent is 120°C or lower, preferably 115°C or lower, more preferably 110°C or lower, even more preferably 105°C or lower. When the 95% mass reduction rate temperature of the organic solvent is 120° C. or lower, the electrolyte layer 7 formed from the electrolyte slurry composition tends to have excellent strength. The reason for this is not necessarily clear, but it is thought that it is because the organic solvent becomes easier to volatilize, which improves the drying rate and forms a dense layer (film). The lower limit of the 95% mass reduction rate temperature of the organic solvent is not particularly limited, but is preferably 50°C or higher, more preferably 60°C or higher, and still more preferably 70°C or higher. When the 95% mass reduction rate temperature of the organic solvent is 50° C. or higher, the drying rate can be easily controlled and a uniform film tends to be obtained.

The electrolyte slurry composition may contain other components. Examples of other components include cellulose fibers, resin fibers, and glass fibers. The content of other components may be 0.1 to 20% by mass based on the total amount of components excluding the organic solvent of the electrolyte slurry composition.

The concentration of the components contained in the electrolyte slurry composition may be 5 to 70% by weight based on the total weight of the electrolyte slurry composition.

The electrolyte slurry composition comprises one or more polymers, oxide particles, at least one electrolyte salt selected from the group consisting of lithium salts, sodium salts, calcium salts, and magnesium salts, represented by general formula (10). It can be prepared by mixing and kneading at least one of the compound and ionic liquid, an organic solvent, and other components. Mixing and kneading can be carried out using an appropriate combination of dispersing machines such as a conventional stirrer, a sieve machine, a three-roll mill, a ball mill, and a bead mill.

The electrolyte sheet used as the electrolyte layer 7 is produced by the steps of disposing the above-mentioned electrolyte slurry composition on a base material, and removing an organic solvent from the disposed electrolyte slurry composition to form an electrolyte layer on the base material. It is produced by a manufacturing method comprising steps. FIG. 4(a) is a schematic cross-sectional view showing an electrolyte sheet according to one embodiment. As shown in FIG. 4(a), the electrolyte sheet 13A includes a base material 14 and an electrolyte layer 7 provided on the base material 14. The electrolyte layer 7 may be composed of an electrolyte slurry composition excluding the organic solvent.

The method for disposing the electrolyte slurry composition on the substrate is not particularly limited, and examples thereof include coating by a doctor blade method, a dipping method, a spray method, and the like.

The method for removing the organic solvent from the electrolyte slurry composition is not particularly limited, but examples thereof include a method of heating the electrolyte slurry composition to volatilize the organic solvent. The heating temperature can be appropriately set according to the organic solvent used.

The base material 14 is not limited as long as it has heat resistance that can withstand heating during volatilization of the organic solvent, does not react with the electrolyte slurry composition, and does not swell with the electrolyte slurry composition, but for example, , made of resin. Specifically, the base material 14 may be a film made of resin (general-purpose engineered plastic) such as polyethylene terephthalate, polytetrafluoroethylene, polyimide, polyether sulfone, or polyether ketone.

The base material 14 only needs to have a heat resistance temperature that can withstand the treatment temperature for volatilizing the organic solvent in the process of manufacturing the electrolyte layer. When the base material 14 is made of resin, the heat-resistant temperature is the lower of the softening point (temperature at which plastic deformation begins) or melting point of the base material 14. The heat resistance temperature of the base material 14 is preferably 50°C or higher, more preferably 100°C or higher, and still more preferably 150°C or higher, from the viewpoint of compatibility with the grime and ionic liquid used in the electrolyte layer 7. For example, the temperature may be 400° C. or lower. If a base material having the above-mentioned allowable temperature limit is used, the above-mentioned organic solvents can be suitably used.

The thickness of the base material 14 is preferably as thin as possible while maintaining strength enough to withstand the tensile force of the coating device. The thickness of the base material 14 is preferably 5 μm or more, more preferably 10 μm, from the viewpoint of reducing the overall volume of the electrolyte sheet 13A and ensuring strength when applying the electrolyte slurry composition to the base material 14. or more, more preferably 25 μm or more, preferably 100 μm or less, more preferably 50 μm or less, still more preferably 40 μm or less.

The electrolyte sheet can also be manufactured continuously by winding it up into a roll. In that case, the surface of the electrolyte layer 7 comes into contact with the back surface of the base material 14 and a part of the electrolyte layer 7 sticks to the base material 14, which may cause damage to the electrolyte layer 7. In order to prevent such a situation, the electrolyte sheet may be one in which a protective material is provided on the side of the electrolyte layer 7 opposite to the base material 14 as another embodiment. FIG. 4(b) is a schematic cross-sectional view showing an electrolyte sheet according to another embodiment. As shown in FIG. 4(b), the electrolyte sheet 13B further includes a protective material 15 on the side of the electrolyte layer 7 opposite to the base material 14.

The protective material 15 may be any material as long as it can be easily peeled off from the electrolyte layer 7, and is preferably a nonpolar resin film such as polyethylene, polypropylene, polytetrafluoroethylene, or the like. When a non-polar resin film is used, the electrolyte layer 7 and the protective material 15 do not stick to each other, and the protective material 15 can be easily peeled off.

The thickness of the protective material 15 is preferably 5 μm or more, more preferably 10 μm, and preferably 100 μm or less, from the viewpoint of ensuring strength while reducing the overall volume of the electrolyte sheet 13B. Preferably it is 50 μm or less, more preferably 30 μm or less.

The heat resistance temperature of the protective material 15 is preferably −30° C. or higher, more preferably 0° C. or higher, from the viewpoint of suppressing deterioration in a low-temperature environment and suppressing softening in a high-temperature environment. Preferably it is 100°C or less, more preferably 50°C or less. When the protective material 15 is provided, the above-mentioned volatilization process of the dispersion medium is not required, so there is no need to increase the heat resistance temperature.

The thickness of the electrolyte layer 7 is preferably 5 μm or more, more preferably 10 μm or more, from the viewpoint of increasing conductivity and strength. From the viewpoint of suppressing the resistance of the electrolyte layer 7, the thickness of the electrolyte layer 7 is preferably 200 μm or less, more preferably 150 μm or less, still more preferably 100 μm or less, and particularly preferably 50 μm or less.

Next, a method for manufacturing the above-mentioned secondary battery 1 will be explained. The method for manufacturing a secondary battery 1 according to the present embodiment includes a first step of forming a positive electrode mixture layer 10 on a positive electrode current collector 9 to obtain a positive electrode 6, and a first step of forming a positive electrode mixture layer 10 on a positive electrode current collector 9 to obtain a positive electrode 6; A second step of forming the layer 12 to obtain the negative electrode 8, and a third step of arranging the electrolyte layer 7 of the electrolyte sheet obtained by the above manufacturing method between the positive electrode 6 and the negative electrode 8. .

In the first step, the positive electrode 6 is produced by, for example, dispersing the material used for the positive electrode mixture layer in a dispersion medium using a kneader, a dispersing machine, etc. to obtain a slurry-like positive electrode mixture; is applied onto the positive electrode current collector 9 by a doctor blade method, a dipping method, a spray method, etc., and then the dispersion medium is volatilized. After volatilizing the dispersion medium, a compression molding step using a roll press may be provided as necessary. The positive electrode mixture layer 10 may be formed as a positive electrode mixture layer with a multilayer structure by performing the steps described above from applying the positive electrode mixture to volatilizing the dispersion medium multiple times.

The dispersion medium used in the first step may be water, 1-methyl-2-pyrrolidone (hereinafter also referred to as NMP), or the like. Note that the dispersion medium is a compound other than the above-mentioned glyme and ionic liquid.

In the second step, the method for forming the negative electrode mixture layer 12 on the negative electrode current collector 11 may be the same method as in the first step described above.

In the third step, the method of arranging the electrolyte layer 7 between the positive electrode 6 and the negative electrode 8 using the electrolyte sheet 13A includes, for example, peeling the base material 14 from the electrolyte sheet 13A, removing the positive electrode 6, the electrolyte layer 7, The secondary battery 1 is obtained by laminating the negative electrode 8 and the negative electrode 8, for example, by laminating. At this time, the electrolyte layer 7 is located on the positive electrode mixture layer 10 side of the positive electrode 6 and on the negative electrode mixture layer 12 side of the negative electrode 8, that is, the positive electrode current collector 9, the positive electrode mixture layer 10, the electrolyte layer 7 , the negative electrode mixture layer 12 and the negative electrode current collector 11 are stacked in this order.

[Second embodiment]
Next, a secondary battery according to a second embodiment will be described. FIG. 5 is a schematic cross-sectional view showing one embodiment of an electrode group in a secondary battery according to a second embodiment. As shown in FIG. 5, the secondary battery in the second embodiment differs from the secondary battery in the first embodiment in that the electrode group 2B includes a bipolar electrode 16. That is, the electrode group 2B includes a positive electrode 6, a first electrolyte layer 7, a bipolar electrode 16, a second electrolyte layer 7, and a negative electrode 8 in this order.

The bipolar electrode 16 includes a bipolar electrode current collector 17 , a positive electrode mixture layer 10 provided on the negative electrode 8 side surface (positive electrode surface) of the bipolar electrode current collector 17 , and a positive electrode mixture layer 10 provided on the negative electrode 8 side (positive electrode surface) of the bipolar electrode current collector 17 . The negative electrode mixture layer 12 is provided on the surface (negative electrode surface).

In the bipolar electrode current collector 17, the positive electrode surface may preferably be made of a material with excellent oxidation resistance, and may be made of aluminum, stainless steel, titanium, or the like. The negative electrode surface of the bipolar electrode current collector 17 using graphite or an alloy as the negative electrode active material may be formed of a material that does not form an alloy with lithium, and specifically, stainless steel, nickel, iron, titanium, etc. It may be formed. When different metals are used for the positive electrode surface and the negative electrode surface, the bipolar electrode current collector 17 may be a clad material in which different metal foils are laminated. However, when using a negative electrode 8 that operates at a potential that does not form an alloy with lithium, such as lithium titanate, the above-mentioned limitation is eliminated, and the negative electrode surface may be made of the same material as the positive electrode current collector 9. In that case, bipolar electrode current collector 17 may be a single metal foil. The bipolar electrode current collector 17 as a single metal foil may be a perforated aluminum foil having holes with a diameter of 0.1 to 10 mm, an expanded metal, a foamed metal plate, or the like. In addition to the above, the bipolar electrode current collector 17 may be formed of any material as long as it does not undergo changes such as dissolution or oxidation during use of the battery, and its shape, manufacturing method, etc. is not restricted either.

The thickness of the bipolar electrode current collector 17 may be 10 μm or more and 100 μm or less, and preferably 10 μm or more and 50 μm or less from the viewpoint of reducing the overall volume of the positive electrode. From the viewpoint of winding, the thickness is more preferably 10 μm or more and 20 μm or less.

Next, a method for manufacturing a secondary battery according to the second embodiment will be described. The method for manufacturing a secondary battery according to the present embodiment includes a first step of forming a positive electrode mixture layer 10 on a positive electrode current collector 9 to obtain a positive electrode 6, and a first step of forming a negative electrode mixture layer 10 on a negative electrode current collector 11. 12 to obtain the negative electrode 8; and a second step in which the positive electrode mixture layer 10 is formed on one side of the bipolar electrode current collector 17, and the negative electrode mixture layer 12 is formed on the other side to form the bipolar electrode. 16, and a fourth step of disposing the electrolyte layer 7 of the electrolyte sheet obtained by the above manufacturing method between the positive electrode 6 and the bipolar electrode 16 and between the negative electrode 8 and the bipolar electrode 16. and has.

The first step and the second step may be the same method as the first step and the second step in the first embodiment.

In the third step, the method for forming the positive electrode mixture layer 10 on one surface of the bipolar electrode current collector 17 may be the same method as the first step in the first embodiment. The method for forming the negative electrode mixture layer 12 on the other surface of the bipolar electrode current collector 17 may be the same method as the second step in the first embodiment.

A method of arranging the electrolyte layer 7 of the electrolyte sheet obtained by the above manufacturing method between the positive electrode 6 and the bipolar electrode 16 in the fourth step, and a method of arranging the electrolyte layer 7 of the electrolyte sheet obtained by the above manufacturing method between the negative electrode 8 and the bipolar electrode 16. The method for arranging the electrolyte layer 7 of the electrolyte sheet may be the same as the third step in the first embodiment.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to these examples.

[Example 1]
<Preparation of electrolyte slurry composition>
Lithium bis(trifluoromethanesulfonyl)imide (Li[TFSI]) dried under a dry argon atmosphere was used as an electrolyte salt, and the electrolyte salt was added to glyme tetraethylene glycol dimethyl ether (G4) at a concentration of 2.3 mol/L. A G4 solution of Li[TFSI] was prepared by dissolving Li[TFSI]. ). Next, a copolymer of vinylidene fluoride and hexafluoropropylene (PVDF-HFP) as a polymer and SiO ₂ particles as oxide particles (product name: AEROSIL OX50, manufactured by Nippon Aerosil Co., Ltd., specific surface area: 50 m ² / g, average primary particle size: about 40 nm), dimethylacetamide (DMAc, 100% by mass) is added as an organic solvent, and the G4 solution of Li[TFSI] prepared above is further added and mixed. In this way, an electrolyte slurry composition was obtained. At this time, the mass ratio of the polymer, oxide particles, and G4 solution of Li[TFSI] was polymer:oxide particles:G4 solution of Li[TFSI]=34:23:43. The concentration of the components contained in the electrolyte slurry composition was 45% by mass based on the total mass of the electrolyte slurry composition. The 95% mass reduction rate temperature of DMAc (100% by mass) was 95°C.

The temperature at which the mass reduction rate is 95% when the temperature is increased at a heating rate of 5°C/min (the temperature at which the mass reduction rate is 95%) is determined using a differential thermal thermogravimeter (Hitachi High-Tech Science Co., Ltd., TG-DTA). -6200 model) at a heating rate of 5° C./min, and the temperature was measured when the mass reduction rate reached 95%.

<Preparation of electrolyte sheet>
Adding DMAc, which is an organic solvent, to the obtained electrolyte slurry composition so that the concentration of the components contained in the electrolyte slurry composition is 28% by mass based on the total mass of the electrolyte slurry composition, The viscosity was adjusted. An electrolyte slurry composition with adjusted viscosity was applied onto a polyethylene terephthalate base material (product name: Theonex R-Q51, manufactured by Teijin DuPont Films Ltd., thickness 38 μm) using an applicator. The applied electrolyte slurry composition was heated and dried at 80° C. for 1 hour to evaporate the organic solvent and obtain an electrolyte sheet having an electrolyte layer on the base material.

<Measurement of tensile strength>
The obtained electrolyte sheet was cut to a width of 5 mm, sandwiched between zippers, and then fixed to a pedestal with tape to a length of 20 mm. Then, the electrolyte sheet was pulled using a force gauge (Nidec-Shimpo Corporation, FGP-5), and the strength when the electrolyte sheet broke was measured. The results are shown in Table 1.

<Measurement of ionic conductivity>
The obtained electrolyte sheet was punched out to a diameter of 10 mm to prepare a sample for ionic conductivity measurement. This sample was placed in a two-electrode sealed cell (manufactured by Hosen Co., Ltd., HS cell), and measured using an AC impedance measuring device (manufactured by Solartron, model 1260). AC impedance was measured at room temperature (25° C.) at 10 mV in the range of 1 Hz to 10 MHz. The resistance value was calculated from the width of the arc of the Nyquist plot, and the ionic conductivity was calculated from the resistance value. Note that the samples were placed in the closed cell in a dry room. The results are shown in Table 1.

<Preparation of positive electrode>
78.5 parts by mass of layered lithium-nickel-manganese-cobalt composite oxide (positive electrode active material), 5 parts by mass of acetylene black (conductive agent, average particle size 48 nm, product name: HS-100, Denka Corporation), fluoride 2.5 parts by mass of a copolymer solution of vinylidene chloride and hexafluoropropylene (binder, solid content 12% by mass) and 14 parts by mass of an ionic liquid (1.5M/LiFSI/Py13FSI) in which an electrolyte salt was dissolved were mixed. A positive electrode mixture slurry was prepared. By coating this positive electrode mixture slurry on a current collector (aluminum foil with a thickness of 20 μm) at a coating amount of 147 g/m ² and drying it at 80°C, a positive electrode with a mixture density of 2.9 g/cm ³ was applied. A mixture layer was formed. This was punched out to a diameter of 15 mm and used as a positive electrode.

<Preparation of negative electrode>
78 parts by mass of graphite A (negative electrode active material, manufactured by Hitachi Chemical Co., Ltd.), 2.4 parts by mass of graphite B (manufactured by Nippon Graphite Industries Co., Ltd.), carbon fiber (conductive agent, product name: VGCF-H, Showa Denko K.K.) ) 0.6 parts by mass, 5 parts by mass of a copolymer solution of vinylidene fluoride and hexafluoropropylene (binder, solid content 12% by mass), ionic liquid in which an electrolyte salt is dissolved (1.5M/LiFSI/Py13FSI) A negative electrode mixture slurry was prepared by mixing 14 parts by mass. By coating this negative electrode mixture slurry on a current collector (copper foil with a thickness of 10 μm) at a coating amount of 68 g/m ² and drying it at 80°C, a negative electrode with a mixture density of 1.9 g/cm ³ was applied. A mixture layer was formed. This was punched out to a diameter of 16 mm and used as a negative electrode.

<Production of coin-type battery for evaluation>
The obtained electrolyte sheet was punched out to a diameter of 16 mm, and the base material was peeled off to obtain an electrolyte layer. A coin-type battery for evaluation was produced using a positive electrode, an electrolyte layer, and a negative electrode. Here, lithium bis(fluorosulfonyl)imide (Li[FSI]) dried under a dry argon atmosphere was used as an electrolyte salt, and N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide ([Py13][ A [Py13][FSI] solution of Li[FSI] was prepared by dissolving the electrolyte salt in 1.5 mol/L of Li[FSI]. After adding a [Py13][FSI] solution of Li[FSI] into a coin cell container of the CR2016 type and arranging the positive electrode, electrolyte layer, and negative electrode one on top of the other in this order, the top of the battery container was placed through an insulating gasket. It was crimped and sealed.

<Measurement of battery discharge rate characteristics>
The discharge rate characteristics of the obtained coin-shaped battery at 25° C. were measured using a charging and discharging device (manufactured by Toyo System Co., Ltd.) under the following charging and discharging conditions.
(1) After performing constant current constant voltage (CCCV) charging at a final voltage of 4.2 V and 0.05 C, two cycles of constant current (CC) discharging at 0.05 C and a final voltage of 2.7 V were performed. Note that C means "current value (A)/battery capacity (Ah)".
(2) Then, one cycle of constant current constant voltage (CCCV) charging at a final voltage of 4.2 V and 0.05 C, followed by constant current (CC) discharging at 0.1 C to a final voltage of 2.7 V. went. Furthermore, the rate of constant current (CC) discharge was changed to 0.2, 0.3, 0.5, and 1.0 C for each cycle, and the discharge rate characteristics were evaluated. The results are shown in Table 1.

[Example 2]
The same method as in Example 1 was used except that a mixed solvent of N-methyl-2-pyrrolidone (NMP) and cyclohexanone (CHN) mixed at a mass ratio of 1:1 was used as the organic solvent instead of DMAc. An electrolyte sheet was prepared. The 95% mass reduction rate temperature of the mixed solvent of NMP (50% by mass) and CHN (50% by mass) was 87°C. The same evaluation as in Example 1 was performed using the produced electrolyte sheet. The results are shown in Table 1.

[Example 3]
An electrolyte sheet was produced in the same manner as in Example 1, except that a mixed solvent of NMP and methyl ethyl ketone (MEK) mixed at a mass ratio of 1:1 was used as the organic solvent instead of DMAc. The mass reduction rate 95% temperature of the mixed solvent of NMP (50% by mass) and MEK (50% by mass) was 103°C. The same evaluation as in Example 1 was performed using the produced electrolyte sheet. The results are shown in Table 1.

[Example 4]
An electrolyte sheet was produced in the same manner as in Example 1, except that a mixed solvent of NMP and 2-butanol (2-BuOH) at a mass ratio of 4:1 was used as the organic solvent instead of DMAc. . The 95% mass reduction rate temperature of the mixed solvent of NMP (80% by mass) and 2-BuOH (20% by mass) was 97°C. The same evaluation as in Example 1 was performed using the produced electrolyte sheet. The results are shown in Table 1.

[Example 5]
An electrolyte sheet was produced in the same manner as in Example 4, except that a [Py13][FSI] solution of Li[FSI] was used instead of the G4 solution of Li[TFSI]. Evaluations similar to those in Example 1 were performed using the produced electrolyte sheet. The results are shown in Table 1.

[Reference example 1]
An electrolyte sheet was produced in the same manner as in Example 1, except that NMP (100% by mass) was used as the organic solvent instead of DMAc. The 95% mass reduction rate temperature of NMP (100% by mass) was 136°C. The tensile strength was measured in the same manner as in Example 1 using the produced electrolyte sheet. The results are shown in Table 1. Note that the electrolyte sheet of Reference Example 1 did not have a good tensile strength evaluation, so measurements of ionic conductivity and discharge rate characteristics of the battery were not performed.

[Reference example 2]
The same method as in Example 5 was used, except that NMP (100% by mass) was used as the organic solvent instead of a mixed solvent in which NMP and 2-butanol (2-BuOH) were mixed at a mass ratio of 4:1. An electrolyte sheet was prepared. The tensile strength was measured in the same manner as in Example 1 using the produced electrolyte sheet. The results are shown in Table 1. Note that the electrolyte sheet of Reference Example 2 did not have a good evaluation of tensile strength, so measurements of ionic conductivity and discharge rate characteristics of the battery were not performed.

The electrolyte sheets of Examples 1 to 5 were superior to the electrolyte sheets of Reference Examples 1 and 2 in terms of the tensile strength of the electrolyte layer. These results confirmed that the electrolyte slurry composition of the present invention was capable of forming an electrolyte layer with excellent strength.

DESCRIPTION OF SYMBOLS 1... Secondary battery, 2, 2A, 2B... Electrode group, 3... Battery exterior body, 4... Positive electrode current collection tab, 5... Negative electrode current collection tab, 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, 13A, 13B... Electrolyte sheet, 14... Base material, 15... Protective material, 16... Bipolar electrode, 17... Bipolar electrode current collector.

Claims (11)

one or more polymers,
oxide particles;
At least one electrolyte salt selected from the group consisting of lithium salts, sodium salts, calcium salts, and magnesium salts;
At least one of a compound represented by the following general formula (10) and an ionic liquid,
an organic solvent;
Contains
The organic solvent has a temperature at which a mass reduction rate of 95% when heated at a heating rate of 5° C./min is 120° C. or less,
The electrolyte slurry composition , wherein the organic solvent includes N-methyl-2-pyrrolidone .
R ^A O-(CH ₂ CH ₂ O) _y -R ^B (10)
[In formula (10), R ^A and R ^B each independently represent an alkyl group having 1 to 4 carbon atoms, and y represents an integer of 1 to 6. ] The oxide particles are at least one particle 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 . The electrolyte slurry composition of claim 1 , wherein the electrolyte slurry composition is: 2. The ionic liquid includes, as a cation component, at least one selected from the group consisting of a chain quaternary onium cation, a piperidinium cation, a pyrrolidinium cation, a pyridinium cation, and an imidazolium cation. The electrolyte slurry composition described in . The electrolyte slurry composition according to any one of claims 1 to 3, wherein the ionic liquid contains at least one anion component represented by the following general formula (A) as an anion component.
N(SO ₂ C _m F _2m+1 ) (SO ₂ C _n F _2n+1 ) ^- (A)
[In formula (A), m and n each independently represent an integer of 0 to 5. ] The electrolyte slurry composition according to any one of claims 1 to 4, wherein the polymer has a first structural unit selected from the group consisting of tetrafluoroethylene and vinylidene fluoride. The structural units constituting the polymer include the first structural unit and a second structural unit selected from the group consisting of hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate, and methyl methacrylate. , the electrolyte slurry composition according to claim 5. The electrolyte slurry composition according to any one of claims 1 to 6, wherein the electrolyte salt is an imide-based lithium salt. The electrolyte slurry composition according to any one of claims 1 to 7, wherein the compound represented by the general formula (10) contains tetraethylene glycol dimethyl ether. The electrolyte slurry composition according to any one of claims 1 to 8, wherein the organic solvent further includes any one of cyclohexanone, methyl ethyl ketone, and 2-butanol. disposing the electrolyte slurry composition according to any one of claims 1 to 9 on a substrate;
forming an electrolyte layer on the base material by removing the organic solvent from the disposed electrolyte slurry composition;
A method for manufacturing an electrolyte sheet, comprising: forming a positive electrode mixture layer on the positive electrode current collector to obtain a positive electrode;
forming a negative electrode mixture layer on the negative electrode current collector to obtain a negative electrode;
arranging the electrolyte layer of the electrolyte sheet obtained by the manufacturing method according to claim 10 between the positive electrode and the negative electrode;
A method for manufacturing a secondary battery, comprising:

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