WO2019035190A1 - Battery member for secondary batteries, and secondary battery - Google Patents

Abstract

The present invention provides a battery member for secondary batteries which is provided with: a collector; and a positive electrode mixture layer which is provided on the collector. The positive electrode mixture layer includes: a positive electrode active material; an ionic liquid; at least one kind of electrolytic salt selected from the group consisting of lithium salts, sodium salts, calcium salts, and magnesium salts; and a conductive material including carbon. The conductive material includes a first conductive material, and a second conductive material different to the first conductive material.

Description

Battery member for secondary battery and secondary battery

The present invention relates to a battery member for a secondary battery and a secondary battery.

2. Description of the Related Art In recent years, with the spread of portable electronic devices, electric vehicles and the like, high-performance secondary batteries are required. Among them, since lithium secondary batteries have high energy density, they are used as power sources for portable electronic devices, electric vehicles and the like.

For example, in the 18650-type lithium secondary battery, a rolled-up electrode body is housed inside a cylindrical battery can. The wound-up electrode body is formed by sandwiching a microporous separator between a positive electrode and a negative electrode, and winding them in a spiral. Since the separator in the rolled-up electrode body is impregnated with a flammable electrolyte, for example, when the temperature of the battery suddenly rises in an abnormal situation, the electrolyte evaporates and the internal pressure rises, thereby causing the lithium secondary battery to There is a possibility of rupture and ignition of the electrolyte. It is important in lithium secondary battery design to prevent lithium secondary battery from bursting and firing. That is, in the lithium secondary battery, in order to further increase the energy density and increase the size, it is required to further improve the safety.

Development of an all-solid-state battery is in progress as a radical solution for improving the safety of lithium secondary batteries. In the all-solid-state battery, a layer of a solid electrolyte such as a polymer electrolyte or an inorganic solid electrolyte is provided on the electrode mixture layer instead of the electrolytic solution (for example, Patent Document 1). In recent years, development of an all-solid-state battery in which various battery characteristics such as discharge characteristics are improved has been promoted.

JP, 2006-294326, A

Then, this invention aims at providing the battery member for secondary batteries which can improve the discharge characteristic of a secondary battery, and the secondary battery excellent in the discharge characteristic.

According to a first aspect, the present invention includes a current collector and a positive electrode mixture layer provided on the current collector, and the positive electrode mixture layer includes a positive electrode active material, an ionic liquid, a lithium salt, A conductive material comprising: at least one electrolyte salt selected from the group consisting of a sodium salt, a calcium salt, and a magnesium salt; and a conductive material containing carbon, the conductive material comprising a first conductive material, and a first conductive material And a second conductive material different from the second conductive material.

Both the first conductive material and the second conductive material may be in the form of particles. In this case, the specific surface area of the first conductive material is preferably smaller than the specific surface area of the second conductive material. The average particle size of the second conductive material is preferably smaller than the average particle size of the first conductive material. The content of the second conductive material is preferably 20 parts by mass or less with respect to 100 parts by mass in total of the content of the first conductive material and the content of the second conductive material.

The first conductive material may be particulate, and the second conductive material may be fibrous. In this case, the content of the second conductive material is preferably 50 parts by mass or less with respect to 100 parts by mass in total of the content of the first conductive material and the content of the second conductive material.

The total of the content of the first conductive material and the content of the second conductive material is the total of the content of the positive electrode active material, the content of the first conductive material, and the content of the second conductive material. Preferably it is 0.5 to 10 mass parts with respect to a mass part.

The ionic liquid preferably contains at least one member selected from the group consisting of a linear quaternary onium cation, a piperidinium cation, a pyrrolidinium cation, a pyridinium cation, and an imidazolium cation as a cation component, and an anion component As at least one of the anion component represented by the following general formula (1) is contained.
_{N (SO 2 C m F 2m} + 1) (SO 2 C n F 2n + 1) - (1)
[M and n each independently represent an integer of 0 to 5] ]

According to a second aspect of the present invention, there is provided a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte layer provided between the positive electrode and the negative electrode, the positive electrode comprising a current collector, a current collector, and A positive electrode mixture layer provided thereon, the positive electrode mixture layer comprising at least one selected from the group consisting of a positive electrode active material, an ionic liquid, a lithium salt, a sodium salt, a calcium salt, and a magnesium salt And a conductive material containing carbon, wherein the conductive material includes a first conductive material and a second conductive material different from the first conductive material, and the electrolyte layer is of one type. Or a secondary battery containing two or more polymers, an oxide particle, at least one electrolyte salt selected from the group consisting of lithium salt, sodium salt, calcium salt, and magnesium salt, and an ionic liquid I will provide a.

The one or more polymers preferably have a first structural unit selected from the group consisting of tetrafluoroethylene and vinylidene fluoride.

Among structural units constituting one or more polymers, preferably, it is selected from the group consisting of a first structural unit, hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate, and methyl methacrylate And a second structural unit.

The average particle size of the oxide particles is preferably 0.005 μm or more and 5 μm or less.

The ionic liquid contained in the electrolyte layer preferably contains, as a cationic component, at least one selected from the group consisting of linear quaternary onium cation, piperidinium cation, pyrrolidinium cation, pyridinium cation, and imidazolium cation. It contains and contains at least 1 sort (s) of the anion component represented by following General formula (1) as an anion component.
_{N (SO 2 C m F 2m} + 1) (SO 2 C n F 2n + 1) - (1)
[M and n each independently represent an integer of 0 to 5] ]

ADVANTAGE OF THE INVENTION According to this invention, the battery member for secondary batteries which can improve the discharge characteristic of a secondary battery, and the secondary battery excellent in the discharge characteristic can be provided.

It is a perspective view showing the rechargeable battery concerning a 1st embodiment. It is a disassembled perspective view which shows one Embodiment of the electrode group in the secondary battery shown in FIG. (A) is a schematic cross section which shows the battery member for secondary batteries which concerns on one Embodiment, (b) is a schematic cross section which shows the battery member for secondary batteries which concerns on other embodiment. It is an exploded perspective view showing the electrode group of the rechargeable battery concerning a 2nd embodiment. (A) is a schematic cross section which shows the battery member for secondary batteries which concerns on one Embodiment in the secondary battery shown in FIG. 4, (b) is two which concerns on other embodiment in the secondary battery shown in FIG. It is a schematic cross section which shows the battery member for secondary batteries.

Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including steps) are not essential unless otherwise specified. The sizes of components in the respective drawings are conceptual, and the relative relationship between the sizes of the components is not limited to those shown in the respective drawings.

The numerical values and the ranges in the present specification do not limit the present invention. In the present specification, a numerical range indicated using “to” indicates a range including numerical values described before and after “to” as the minimum value and the maximum value, respectively. In the numerical ranges that are described stepwise in the present specification, the upper limit or the lower limit described in one numerical range may be replaced with the upper limit or the lower limit described in the other stepwise descriptions. In addition, in the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the example.

First Embodiment
FIG. 1 is a perspective view showing a secondary battery according to the first embodiment. As shown in FIG. 1, the secondary battery 1 includes an electrode group 2 configured of a positive electrode, a negative electrode, and an electrolyte layer, and a bag-like battery exterior body 3 accommodating the electrode group 2. The positive electrode current collection tab 4 and the negative electrode current collection tab 5 are provided on the positive electrode and the negative electrode, respectively. The positive electrode current collecting tab 4 and the negative electrode current collecting tab 5 protrude from the inside of the battery outer package 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.

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

FIG. 2 is an exploded perspective view showing an embodiment of the electrode group 2 in the secondary battery 1 shown in FIG. As shown in FIG. 2, the electrode group 2A according to the present embodiment includes the positive electrode 6, the electrolyte layer 7, and the 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. The negative electrode current collector 11 is provided with a negative electrode current collection tab 5.

In one embodiment, the electrode group 2A includes the battery member (positive electrode member) 13 for the secondary battery including the positive electrode current collector 9 and the positive electrode mixture layer 10 provided on the positive electrode current collector 9. Can be seen. Fig.3 (a) is a schematic cross section which shows the battery member (positive electrode member) for secondary batteries which concerns on one Embodiment. As shown to Fig.3 (a), the battery member 13 for secondary batteries is a positive electrode member provided with the positive electrode collector 9 and the positive mix layer 10 provided on the positive electrode collector 9. As shown in FIG. The positive electrode 6 is configured by the battery member 13 for a secondary battery according to an embodiment. Hereinafter, the “battery member for secondary battery” may be simply referred to as “battery member”.

The positive electrode current collector 9 may be formed of aluminum, stainless steel, titanium or the like. Specifically, the positive electrode current collector 9 may be, for example, a perforated aluminum foil having a hole with a hole 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 cause a change such as dissolution or oxidation during use of the battery, and its shape, manufacturing method, etc. It is not restricted.

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

In one embodiment, the positive electrode mixture layer 10 includes a positive electrode active material, an ionic liquid, at least one electrolyte salt selected from the group consisting of lithium salt, sodium salt, calcium salt, and magnesium salt, and carbon. And a conductive material.

The positive electrode active material may be a lithium transition metal compound such as lithium transition metal oxide or lithium transition metal phosphate. The lithium transition metal oxide may be, for example, lithium manganate, lithium nickelate, lithium cobaltate and the like. The lithium transition metal oxide is a transition metal such as Mn, Ni, or Co contained in lithium manganate, lithium nickelate, lithium cobaltate, etc., as a part of one or more other transition metals, or It may be a lithium transition metal oxide substituted by 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 transition metal). Specifically, the lithium transition metal oxide is 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 ₄ mag.

The lithium transition metal oxide is preferably a compound represented by the following formula (2) from the viewpoint of further improving the energy density.
Li _a Ni _b Co _c M ² _d O _{2+ e} (2)
[In Formula (2), M ² is at least one 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, 0.5 ≦ b ≦ 0.9, 0.1 ≦ c ≦ 0.4, 0 ≦ d ≦ 0.2, −0.2 ≦ e ≦ 0.2, and a number satisfying b + c + d = 1 . ]

The lithium transition metal phosphate is 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. And at least one element selected from the group consisting of

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

The particle diameter 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 the positive electrode active material contains coarse particles having a particle diameter equal to or larger than the thickness of the positive electrode mixture layer 10, the coarse particles are previously removed by sieve classification, air flow classification or the like, and the particles having a thickness smaller than the thickness of the positive electrode mixture layer 10 The positive electrode active material having a diameter is sorted out.

The average particle diameter of the positive electrode active material is 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 diameter of the positive electrode active material is the particle diameter (D ₅₀ ) when the ratio (volume fraction) to the volume of the entire positive electrode active material is 50%. The average particle diameter (D ₅₀ ) of the positive electrode active material is measured by using a laser scattering particle size measuring device (for example, Microtrack) to measure a suspension of the positive electrode active material suspended in water by a laser scattering method. It is obtained by

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

The ionic liquid contained in the positive electrode mixture layer 10 contains the following anion component and cation component. The ionic liquid in the present embodiment is a liquid substance at −20 ° C. or higher.

The anion component of the ionic liquid is not particularly limited, but anions of halogen such as Cl ⁻ , Br ⁻ , I ⁻ , etc., inorganic anions such as BF ₄ ⁻ , N (SO ₂ F) ₂ ^−, etc., 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 - And the like. The anion component of the ionic liquid preferably contains at least one anion component represented by the following general formula (1).
_{N (SO 2 C m F 2m} + 1) (SO 2 C n F 2n + 1) - (1)
m and n each independently represent an integer of 0 to 5; m and n may be the same as or different from each other, and preferably are the same as each other.

Anion component represented by formula (1) may, 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} ^- a. Anion component of the ionic liquid, together with further improve the ionic conductivity at a relatively low viscosity, from the viewpoint of even further improve charge-discharge characteristics, more ^{_{preferably, N (SO 2 C 4 F}} 9) 2 -, CF 3 SO _It contains at least one selected from the group consisting of ₂ O ⁻ , N (SO ₂ F) ₂ ⁻ , N (SO ₂ CF ₃ ) ₂ ⁻ , and N (SO ₂ C ₂ F ₅ ) ₂ ^−, more preferably is _{N (SO 2 F)} 2 ^- containing.

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 -, bis oxalate borate anion _{^{[f3C] -: C (SO}} 2 F) 3 -, tris (fluorosulfonyl) carbanions

The cationic component of the ionic liquid contained in the positive electrode mixture layer 10 is preferably at least one member selected from the group consisting of linear quaternary onium cation, piperidinium cation, pyrrolidinium cation, pyridinium cation, and imidazolium cation. It is.

The linear quaternary onium cation is, for example, a compound represented by the following general formula (3).

[In Formula (3), R ¹ to R ⁴ each independently represent a linear alkyl group having 1 to 20 carbon atoms, or a linear 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 carbon number of the alkyl group represented by R ¹ to R ⁴ is preferably 1 to 20, more preferably 1 to 10, and still more preferably 1 to 5. ]

The piperidinium cation is, for example, a nitrogen-containing six-membered ring cyclic compound represented by the following general formula (4).

[In Formula (4), R ⁵ and R ⁶ each independently represent an alkyl group having 1 to 20 carbon atoms, or an alkoxyalkyl group represented by R—O— (CH ₂ ) _n — (R is methyl Represents a group or an ethyl group, n represents an integer of 1 to 4). The carbon number of the alkyl group represented by R ⁵ and R ⁶ is preferably 1 to 20, more preferably 1 to 10, and still more preferably 1 to 5. ]

The pyrrolidinium cation is, for example, a five-membered cyclic compound represented by the following general formula (5).

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

The pyridinium cation is, for example, a compound represented by the following general formula (6).

[In Formula (6), R ⁹ to R ¹³ each independently represent an alkyl group having 1 to 20 carbon atoms, or an alkoxyalkyl group represented by R—O— (CH ₂ ) _n — (R is a methyl group Or represents an ethyl group, n represents an integer of 1 to 4) or a hydrogen atom. The carbon number of the alkyl group represented by R ⁹ to R ¹³ is preferably 1 to 20, more preferably 1 to 10, and still more preferably 1 to 5. ]

The imidazolium cation is, for example, a compound represented by the general formula (7).

[In Formula (7), R ¹⁴ to R ¹⁸ each independently represent an alkyl group having 1 to 20 carbon atoms, or an alkoxyalkyl group represented by R—O— (CH ₂ ) _n — (R represents a methyl group Or represents an ethyl group, n represents an integer of 1 to 4) or a hydrogen atom. The carbon number of the alkyl group represented by R ¹⁴ to R ¹⁸ is preferably 1 to 20, more preferably 1 to 10, and still more preferably 1 to 5. ]

Ionic liquid contained in the positive electrode mixture layer 10, it is enough include any anionic component and a cationic component as described above, preferably, as an anionic _{component, N (SO 2 F) 2} - wherein the cationic component As pyrrolidinium cation. Such an ionic liquid is, for example, N-methyl-N-propylpyrrolidinium bis (fluorosulfonyl) imide (Py13-FSI).

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 still 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.

The electrolyte salt contained in the positive electrode mixture layer 10 may be at least one selected from the group consisting of lithium salt, sodium salt, calcium salt, and magnesium salt.

Anionic component of the electrolyte salt contained in the positive electrode mixture layer 10, a halide ion ^{(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 ^{− and the} like. Anionic component of the electrolyte salt, ^{_{preferably, N (SO 2 F) 2}} -, N (SO 2 CF 3) 2 - above anion component represented by formula (1), such _as, ^PF 6 -, BF ₄ ^- _{, B (O 2 C 2 O} 2) 2 -, or ClO ₄ ^- is.

The lithium salt is LiPF ₆ , LiBF ₄ , Li [FSI], Li [TFSI], Li [f ₃ C], 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 RCOOLi (wherein R represents an alkyl group having 1 to 4 carbon atoms , A phenyl group, or a naphthyl group), and at least one selected from the group consisting of

The sodium salt is 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 RCOONa (R is an alkyl group having 1 to 4 carbon atoms , A phenyl group, or a naphthyl group), and at least one selected from the group consisting of

The calcium salt is Ca (PF ₆ ) ₂ , Ca (BF ₄ ) ₂ , Ca [FSI] ₂ , Ca [TFSI] ₂ , Ca [f 3 C] 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 (RCOO) ₂ Ca (R is an alkyl group having 1 to 4 carbon atoms, phenyl Or a naphthyl group) may be at least one selected from the group consisting of

The magnesium salt is Mg (PF ₆ ) ₂ , Mg (BF ₄ ) ₂ , Mg [FSI] ₂ , Mg [TFSI] ₂ , Mg [f 3 C] 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 (RCOO) ₂ Mg (R is an alkyl group having 1 to 4 carbon atoms, a phenyl group Or a naphthyl group) may be at least one selected from the group consisting of

Among them, from the viewpoint of dissociativeness and electrochemical stability, the electrolyte salt is preferably LiPF ₆ , LiBF ₄ , Li [FSI], Li [TFSI], Li [f 3 C], 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, At least one selected from the group consisting of CF ₃ COOLi and RCOOLi (wherein R is an alkyl group having 1 to 4 carbon atoms, a phenyl group or a naphthyl group), more preferably Li [TFSI], Li _{[FSI], LiPF 6, LiBF} 4, Li [BOB], and at least one selected from the group consisting of LiClO _4, more preferably Li [TF I], and is one selected from the group consisting of Li [FSI].

The electrolyte salt contained in the positive electrode mixture layer 10 may be dissolved and contained in the ionic liquid. The total content of the electrolyte salt and 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, still more preferably 10% based on the total amount of the positive electrode mixture layer. The content is preferably not less than 30% by mass, more preferably not more than 25% by mass, still more preferably not more than 20% by mass.

The concentration of the electrolyte salt per unit volume of the ionic liquid contained in the positive electrode mixture layer 10 is preferably 0.5 mol / L or more, more preferably 0.7 mol / L or more, from the viewpoint of further improving the discharge characteristics. Preferably, it is 0.8 mol / L or more, preferably 2.0 mol / L or less, more preferably 1.8 mol / L or less, and still more preferably 1.5 mol / L or less.

The conductive material containing carbon includes a first conductive material and a second conductive material different from the first conductive material. The type of conductive material may be graphite, acetylene black, carbon black, carbon fiber or the like. The shape of the conductive material may be particulate, fibrous or the like. For example, the first conductive material and the second conductive material may be different from each other in at least one of the type and the shape (including the size and the like) of the conductive material. In the present specification, the particulate conductive material means a conductive material having an aspect ratio of 2 or less, and the fibrous conductive material means a conductive material having an aspect ratio of more than 20. The aspect ratio is the ratio of the particle length in the long axis direction (maximum particle length) to the particle length in the short axis direction (minimum particle length) calculated from the scanning electron micrograph of the conductive material (maximum particle length) Defined as maximum length / minimum length). The length of the particles can be obtained by statistically calculating the photograph using commercially available image processing software (for example, image analysis software manufactured by Asahi Kasei Engineering Corporation, A-image-kun (registered trademark)).

In one embodiment, the first conductive material and the second conductive material may both be in the form of particles. That is, the conductive material containing carbon may include the first particulate conductive material and the second particulate conductive material. Specifically, the particulate conductive material may be particulate graphite, acetylene black, carbon black or the like.

The first particulate conductive material and the second particulate conductive material may be different from each other by having different specific surface areas. For example, the specific surface area of the first particulate conductive material is the second Smaller than the specific surface area of the particulate conductive material. In this case, the types of the first particulate conductive material and the second particulate conductive material may be the same as or different from each other. The specific surface area can be measured by the BET method by nitrogen adsorption desorption measurement.

The specific surface area of the first particulate conductive material is preferably 10 m ² / g or more, more preferably 20 m ² / g or more, and still more preferably 30 m ² / g or more. The specific surface area of the first particulate conductive material is preferably 100 m ² / g or less, more preferably 70 m ² / g or less, and still more preferably 50 m ² / g or less.

The specific surface area of the second particulate conductive material is preferably 100 m ² / g or more, more preferably 120 m ² / g or more, and still more preferably 130 m ² / g or more. The specific surface area of the second particulate conductive material is preferably 200 m ² / g or less, more preferably 170 m ² / g or less, and still more preferably 150 m ² / g or less.

The first particulate conductive material and the second particulate conductive material may be different from each other by having different average particle sizes (D ₅₀ ), for example, the average of the second particulate conductive material The particle size is smaller than the average particle size of the first particulate conductive material. In this case, the types of the first particulate conductive material and the second particulate conductive material may be the same as or different from each other. The mean particle size is measured by the same method as the mean particle size (D ₅₀ ) of the positive electrode active material described above.

The average particle diameter of the first conductive material is preferably 30 nm or more, more preferably 35 nm or more, and still more preferably 40 nm or more. The average particle diameter of the first conductive material is preferably 100 nm or less, more preferably 80 nm or less, and still more preferably 60 nm or less.

The average particle diameter of the second conductive material is preferably 10 nm or more, more preferably 15 nm or more, and still more preferably 20 nm or more. The average particle diameter of the first conductive material is preferably 30 nm or less, more preferably 28 nm or less, and still more preferably 25 nm or less.

The content of the second particulate conductive material is from the viewpoint of enhancing the dispersibility of the conductive material in the positive electrode mixture layer, the content of the first particulate conductive material and the content of the second particulate conductive material The content is preferably 1 part by mass or more, more preferably 5 parts by mass or more, still more preferably 10 parts by mass or more, and preferably 40 parts by mass or less, based on 100 parts by mass of the total content. More preferably, it is 30 mass parts or less, More preferably, it is 20 mass parts or less. The content of the second particulate conductive material is from the viewpoint of enhancing the dispersibility of the conductive material in the positive electrode mixture layer, the content of the first particulate conductive material and the content of the second particulate conductive material Preferably, 1 to 40 parts by weight, 1 to 30 parts by weight, 1 to 20 parts by weight, 5 to 40 parts by weight, per 100 parts by weight of the total content. It is 5 parts by mass to 30 parts by mass, 5 parts by mass to 20 parts by mass, 10 parts by mass to 40 parts by mass, 10 parts by mass to 30 parts by mass, or 10 parts by mass to 20 parts by mass.

In another embodiment, the first conductive material may be particulate and the second conductive material may be fibrous. That is, the conductive material containing carbon may contain a particulate conductive material and a fibrous conductive material. The particulate conductive material may be the same as the first or second particulate conductive material described above. Specifically, the fibrous conductive material may be carbon fiber such as vapor grown carbon fiber (VGCF (registered trademark)) or carbon nanotube.

The average fiber diameter of the fibrous conductive material is preferably 50 nm or more, more preferably 80 nm or more, and still more preferably 120 nm or more. The average fiber diameter of the second conductive material is preferably 250 nm or less, more preferably 200 nm or less, and still more preferably 170 nm or less. The average fiber diameter can be measured by a transmission electron microscope (TEM).

The average length of the fibrous conductive material is preferably 1 μm or more, more preferably 2.5 μm or more, and still more preferably 5 μm or more. The length of the fibrous conductive material is preferably 30 μm or less, more preferably 20 μm or less, and still more preferably 15 μm or less. The average length refers to the average value of the dimensions in the longitudinal direction of the fibrous conductive material and can be measured by a transmission electron microscope (TEM).

The content of the fibrous conductive material is preferably 1 part by mass with respect to a total of 100 parts by mass of the content of the particulate conductive material and the content of the fibrous conductive material from the viewpoint of further enhancing the discharge characteristics. Or more, more preferably 5 parts by mass or more, further preferably 10 parts by mass or more, preferably 70 parts by mass or less, more preferably 60 parts by mass or less, still more preferably 50 parts by mass Part or less. The content of the fibrous conductive material is preferably 1 mass to a total of 100 parts by mass of the content of the particulate conductive material and the content of the fibrous conductive material, from the viewpoint of further enhancing the discharge characteristics. Parts to 70 parts by mass, 1 to 60 parts by mass, 1 to 50 parts by mass, 5 to 70 parts by mass, 5 to 60 parts by mass, 5 to 50 parts by mass Hereinafter, 10 parts by mass or more and 70 parts by mass or less, 10 parts by mass or more and 60 parts by mass or less, or 10 parts by mass or more and 50 parts by mass or less.

The total of the content of the first conductive material and the content of the second conductive material is a total of 100 mass of the content of the positive electrode active material, the content of the first conductive material, and the content of the second conductive material. Preferably it is 0.5 mass part or more, More preferably, it is 1 mass part or more, More preferably, it is 3 mass parts or more, Preferably, it is 20 mass parts or less, More preferably, it is It is 15 parts by mass or less, more preferably 10 parts by mass or less. The total of the content of the first conductive material and the content of the second conductive material is a total of 100 mass of the content of the positive electrode active material, the content of the first conductive material, and the content of the second conductive material. 0.5 parts by mass or more and 20 parts by mass or less, 0.5 parts by mass or more and 15 parts by mass or less, 0.5 parts by mass or more and 10 parts by mass or less, and 1 parts by mass or more and 20 parts by mass or less 1 to 15 parts by mass, 1 to 10 parts by mass, 3 to 20 parts by mass, 3 to 15 parts by mass, or 3 to 10 parts by mass.

The positive electrode mixture layer 10 may further contain a binder.

The binder is not particularly limited, and contains at least one member selected from the group consisting of ethylene tetrafluoride, vinylidene fluoride, hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate, and methyl methacrylate as a monomer unit. It may be rubber, such as polymer, styrene-butadiene rubber, isoprene rubber, acrylic rubber and the like. The binder is preferably a copolymer containing tetrafluoroethylene and vinylidene fluoride as structural units, or a copolymer containing vinylidene fluoride and hexafluoropropylene 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 thickness of the positive electrode mixture layer 10 may be 10 μm or more, 15 μm or more, or 20 μm or more from the viewpoint of further improving the conductivity. 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, uneven charge / discharge due to the variation in charge level of the positive electrode active material in the vicinity of the surface of the positive electrode mixture layer 10 and in the vicinity of the surface of the positive electrode current collector 9 is suppressed. it can.

In one embodiment, the electrolyte layer 7 includes, in one embodiment, one or more polymers, an oxide particle, and at least one electrolyte salt selected from the group consisting of lithium salt, sodium salt, calcium salt and magnesium salt, And an ionic liquid.

The one or more polymers preferably have a first structural unit selected from the group consisting of tetrafluoroethylene and vinylidene fluoride.

The one or more polymers preferably have 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. It may be included. That is, the first structural unit and the second structural unit may be included in one type of polymer to constitute a copolymer, and each may be included in another polymer and have the first structural unit. And at least two polymers of a second polymer having a second structural unit.

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

The content of the one or more polymers is preferably 3% by mass or more based on the total amount of the electrolyte layer. The content of the polymer is preferably 70% by mass or less, more preferably 60% by mass or less, based on the total amount of the electrolyte layer.

The polymer according to the present embodiment is excellent in the affinity to the ionic liquid contained in the electrolyte composition, and thus retains the electrolyte salt in the ionic liquid. This suppresses the leakage of the ionic liquid when a load is applied to the electrolyte composition.

The oxide particles are, for example, particles of inorganic oxide. 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 and the like as constituent elements. Good. The oxide particles 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 . It is a particle. Since the oxide particles have polarity, the dissociation of the electrolyte in the electrolyte layer 7 can be promoted, and the battery characteristics can be enhanced.

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

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. If the specific surface area is 2 to 380 m ² / g, a secondary battery using an electrolyte composition containing such oxide particles tends to be excellent in 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, 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 the oxide particles means the specific surface area of the whole oxide particles including the primary particles and the secondary particles, and is measured by the BET method.

The average primary particle size of the oxide particles (average particle size of the primary 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 conductivity. And more preferably 0.015 μm (15 nm) or more. The average primary particle size of the oxide particles 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 thinning the electrolyte layer 7. The average primary particle size of the oxide particles can be measured by observing the oxide particles with a transmission electron microscope or the like.

The average particle size of the oxide particles is preferably 0.005 μm or more, more preferably 0.01 μm or more, and still more preferably 0.03 μm or more. The average particle size of the oxide particles is preferably 5 μm or less, more preferably 3 μm or less, and still more preferably 1 μm or less. The average particle diameter of the oxide particles is preferably 0.005 to 5 μm, 0.005 to 3 μm, 0.005 to 1 μm, 0.01 to 5 μm, 0.01 to 3 μm, 0.01 to 0.2 μm. It is 1 μm or less, 0.03 μm to 5 μm, 0.03 μm to 3 μm, or 0.03 μm to 1 μm.

The content of the oxide particles may be 5% by mass or more, 10% by mass or more, or 15% by mass or more based on the total amount of the electrolyte layer. The content of the oxide particles may be 60% by mass or less, 50% by mass or less, and 40% by mass or less based on the total amount of the electrolyte layer.

The ionic liquid contained in the electrolyte layer 7 may be the same as the ionic liquid that can be used for the positive electrode mixture layer 10 described above. The ionic liquid contained in the electrolyte layer 7 is preferably an ionic liquid containing N (SO ₂ CF ₃ ) ₂ ⁻ as an anion component and containing a chain quaternary onium cation as a cation component. Such an ionic liquid is, for example, N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) imide (DEME-TFSI).

The content of the ionic liquid contained in the electrolyte layer 7 may be 10% by mass or more and 80% by mass or less based on the total amount of the electrolyte layer from the viewpoint of suitably producing the electrolyte layer 7.

The electrolyte salt contained in the electrolyte layer 7 may be dissolved and contained in the ionic liquid. The electrolyte salt may be at least one selected from the group consisting of lithium salt, sodium salt, calcium salt, and magnesium salt. The electrolyte salt contained in the electrolyte layer 7 may be the same as the electrolyte salt that can be used for the positive electrode mixture layer 10 described above.

The electrolyte salt contained in the electrolyte layer 7 is preferably one selected from the group consisting of an imide lithium salt, an imide sodium salt, an imide calcium salt, and an imide magnesium salt.

The imide lithium salt may be Li [TFSI], Li [FSI] or the like. The imide 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 magnesium salt may be Mg [TFSI] ₂ , Mg [FSI] ₂ or the like.

The total content of the electrolyte salt and the ionic liquid contained in the electrolyte layer 7 is preferably 10% by mass based on the total amount of the electrolyte layer, from the viewpoint of further improving the conductivity and suppressing the capacity decrease of the secondary battery. It is the above, More preferably, it is 25 mass% or more, More preferably, it is 40 mass% or more. The total content of the electrolyte salt and the ionic liquid is preferably 80% by mass or less based on the total amount of the electrolyte layer from the viewpoint of suppressing the strength reduction of the electrolyte layer.

The concentration of the electrolyte salt per unit volume of the ionic liquid contained in the electrolyte layer 7 is preferably 0.5 mol / L or more, more preferably 0.7 mol / L or more, and further preferably from the viewpoint of further improving the charge / discharge characteristics. Is 0.8 mol / L or more, preferably 2.0 mol / L or less, more preferably 1.8 mol / L or less.

The thickness of the electrolyte layer 7 is preferably 5 μm or more, more preferably 10 μm or more, from the viewpoint of enhancing the strength and improving the safety. The thickness of the electrolyte layer 7 is preferably 200 μm or less, more preferably 150 μm or less, and further preferably 100 μm or less from the viewpoint of further reducing the internal resistance of the secondary battery and the viewpoint of further improving the large current characteristics.

The negative electrode current collector 11 may be a metal such as aluminum, copper, nickel, stainless steel, an alloy thereof, or the like. The negative electrode current collector 11 is preferably aluminum and an alloy thereof because of its light weight and high weight energy density. The negative electrode current collector 11 is preferably 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, preferably 10 μm or more and 50 μm or less from the viewpoint of reducing the volume of the entire negative electrode. From the viewpoint of winding, 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.

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

The average particle size (D ₅₀ ) of the negative electrode active material is preferably 1 μm or more from the viewpoint of obtaining a well-balanced negative electrode in which the retention capacity of electrolyte salt is enhanced while suppressing the increase in irreversible capacity accompanying the particle size reduction. More preferably, it is 5 μm or more, more preferably 10 μm or more, and 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 negative electrode mixture layer 12 may further contain an ionic liquid, an electrolyte salt, a conductive material, and a binder.

The type and content of the ionic liquid and the electrolyte salt contained in the negative electrode mixture layer 12 may be the same as the type and the content of the ionic liquid and the electrolyte salt in the positive electrode mixture layer 10 described above.

The conductive material is not particularly limited, but may be a carbon material such as graphite, acetylene black, carbon black, carbon fiber and the like. The conductive material may be a mixture of two or more of the above-described carbon materials.

The content of the conductive material contained in the negative electrode mixture layer 12 may be 0.1 mass% or more, 1 mass% or more, or 3 mass% or more, 15 mass% or less, based on the total amount of the negative electrode mixture layer. , 10% by mass or less, or 8% by mass or less.

The negative electrode mixture layer 12 may further contain a binder similar to the binder that can be used for the positive electrode mixture layer 10 described above. The content of the binder contained in the negative electrode mixture layer 12 may be the same as the content of the binder in the positive electrode mixture layer 10 described above.

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 60 μm or less, 55 μm or less, or 50 μm or less.

In another embodiment, the electrode group 2A can be considered to include a battery member provided with the positive electrode current collector 9, the positive electrode mixture layer 10, and the electrolyte layer 7 in this order. FIG.3 (b) is a schematic cross section which shows the battery member for secondary batteries which concerns on other embodiment. As shown in FIG. 3 (b), the battery member 14 includes a positive electrode current collector 9, a positive electrode mixture layer 10 provided on the positive electrode current collector 9, and an electrolyte provided on the positive electrode mixture layer 10. It is a battery member provided with the layer 7 in this order. The electrolyte layer 7, the positive electrode current collector 9, and the positive electrode mixture layer 10 are the same as the electrolyte layer 7, the positive electrode current collector 9, and the positive electrode mixture layer 10 in the above-described battery member 13, respectively.

Then, the manufacturing method of the secondary battery 1 mentioned above is demonstrated. In the method of manufacturing the secondary battery 1, a first step of forming the positive electrode mixture layer 10 on the positive electrode current collector 9 to obtain the positive electrode 6 and forming the negative electrode mixture layer 12 on the negative electrode current collector 11 And a third step of providing the electrolyte layer 7 between the positive electrode 6 and the negative electrode 8.

In the first step, for example, after the material used for the positive electrode mixture layer is dispersed in a dispersion medium to obtain a slurry-like positive electrode mixture, the positive electrode 6 is coated with the positive electrode mixture on the positive electrode current collector 9. It is then obtained by volatilizing the dispersion medium. The dispersion medium is preferably an organic solvent such as N-methyl-2-pyrrolidone (NMP). The electrolyte salt contained in the positive electrode mixture layer 10 can be dissolved in the ionic liquid and then dispersed in the dispersion medium together with other materials. The first step is the step of obtaining the above-described battery member 13.

The mixing ratio of the positive electrode active material, the conductive agent, the binder, and the ionic liquid in which the electrolyte salt is dissolved in the positive electrode mixture layer 10 is, for example, a positive electrode active material: conductive material: binder: ionic liquid in which electrolyte salt is dissolved. = 69 to 82: 0.1 to 10: 5 to 12: 10 to 17 (mass ratio). However, it is not necessarily limited to this range.

In the second step, the negative electrode 8 is obtained by the same method as the above-described positive electrode 6. That is, after a material used for the negative electrode mixture layer 12 is dispersed in a dispersion medium to obtain a slurry-like negative electrode mixture, the negative electrode mixture is applied to the negative electrode current collector 11 and then the dispersion medium is volatilized. can get.

The mixing ratio of the negative electrode active material, the conductive agent, the binder, and the ionic liquid in which the electrolyte salt is dissolved in the negative electrode mixture layer 12 is, for example, negative electrode active material: conductive agent: binder: ionic liquid in which electrolyte salt is dissolved. It may be 70 to 80: 0.1 to 10: 5 to 10: 10 to 17 (mass ratio). However, it is not necessarily limited to this range.

In the third step, in one embodiment, after the material used for the electrolyte layer 7 is dispersed in a dispersion medium to obtain a slurry-like electrolyte composition, the electrolyte layer 7 is coated on a substrate and then dried. It is obtained as a sheet-like electrolyte layer by volatilizing the dispersion medium. The dispersion medium is preferably water, NMP, toluene or the like. In this case, in the third step, the positive electrode 6, the electrolyte layer 7, and the negative electrode 8 are laminated by, for example, lamination, to obtain the secondary battery 1. At this time, the electrolyte layer 7 is positioned 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, and the electrolyte layer 7. The negative electrode mixture layer 12 and the negative electrode current collector 11 are stacked in this order.

In the third step, in another embodiment, the electrolyte layer 7 is formed by coating on at least one of the positive electrode mixture layer 10 side of the positive electrode 6 and the negative electrode mixture layer 12 side of the negative electrode 8, preferably a positive electrode. Both the positive electrode mixture layer 10 side of 6 and the negative electrode mixture layer 12 side of the negative electrode 8 are formed by application. This step is, in other words, the step of obtaining the battery member 14 described above. In this case, for example, the secondary battery 1 is formed by laminating the positive electrode 6 (battery member 14) provided with the electrolyte layer 7 and the negative electrode 8 provided with the electrolyte layer 7 such that the electrolyte layers 7 are in contact with each other. Is obtained.

In the method of forming the electrolyte layer 7 on the positive electrode mixture layer 10, for example, after a material used for the electrolyte layer 7 is dispersed in a dispersion medium to obtain a slurry-like electrolyte composition, this electrolyte composition is used as a positive electrode mixture It is a method of applying on the layer 10 using an applicator. The dispersion medium is preferably an organic solvent such as NMP. The electrolyte salt contained in the electrolyte layer 7 can be dissolved in the ionic liquid and then dispersed in the dispersion medium together with other materials.

The mixing ratio of the oxide particles, the ionic liquid in which the electrolyte salt is dissolved, and the polymer in the slurry for forming the electrolyte layer 7 is, for example, oxide particles: ionic liquid in which the electrolyte salt is dissolved: polymer = 5 to 60: 10 to It may be 80: 5 to 50 (mass ratio). However, the mixing ratio is not necessarily limited.

The method of forming the electrolyte layer 7 in the negative electrode mixture layer 12 may be the same method as the method of forming the electrolyte layer 7 in the positive electrode mixture layer 10.

Second Embodiment
Next, a secondary battery according to a second embodiment will be described. FIG. 4 is an exploded perspective view showing an electrode group of a secondary battery according to a second embodiment. As shown in FIG. 4, the secondary battery in the second embodiment is different from the secondary battery in the first embodiment in that the electrode group 2 </ b> B includes a bipolar electrode 15. That is, the electrode group 2B includes the positive electrode 6, the first electrolyte layer 7, the bipolar electrode 15, the second electrolyte layer 7, and the negative electrode 8 in this order.

The bipolar electrode 15 includes a bipolar electrode current collector 16, a positive electrode mixture layer 10 provided on the surface (positive electrode surface) of the bipolar electrode current collector 16 on the negative electrode 8 side, and a positive electrode 6 side of the bipolar electrode current collector 16. And the negative electrode mixture layer 12 provided on the negative electrode surface. That is, since the bipolar electrode 15 has both the function of the positive electrode and the function of the negative electrode, in addition to the positive electrode 6 and the negative electrode 8 in the electrode group 2B in the second embodiment, the bipolar electrode current collector 16 and the bipolar electrode Another positive electrode including the positive electrode mixture layer 10 provided on the current collector 16 and another negative electrode mixture layer 12 provided on the bipolar electrode current collector 16 and the bipolar electrode current collector 16 It can be seen that the negative electrode is included.

In one embodiment, the bipolar electrode 15 can be viewed as a battery member for a secondary battery including the bipolar electrode current collector 16 and the positive electrode mixture layer 10 provided on the bipolar electrode current collector 16. Fig.5 (a) is a schematic cross section which shows the battery member for secondary batteries which concerns on one Embodiment. As shown in FIG. 5A, the battery member 17 includes a bipolar electrode current collector 16, a positive electrode mixture layer 10 provided on one surface of the bipolar electrode current collector 16, and a positive electrode mixture layer 10 is a battery member provided with the bipolar electrode current collector 16 and the negative electrode mixture layer 12 provided on the opposite side.

In the bipolar electrode current collector 16, the positive electrode surface may be preferably made of a material excellent in oxidation resistance, and may be made of aluminum, stainless steel, titanium or the like. The negative electrode surface of the bipolar electrode current collector 16 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 16 may be a clad material in which different metal foils are laminated. However, in the case of using the negative electrode 8 operating at a potential not forming an alloy with lithium as lithium titanate, the above limitation is eliminated, and the negative electrode surface may be the same material as the positive electrode current collector 9. In that case, the bipolar electrode current collector 16 may be a single metal foil. The bipolar electrode current collector 16 as a single metal foil may be a perforated aluminum foil, an expanded metal, a foam metal plate or the like having holes with a hole diameter of 0.1 to 10 mm. In addition to the above, the bipolar electrode current collector 16 may be made of any material as long as it does not cause a change such as dissolution or oxidation during use of the battery, and its shape, manufacturing method, etc. Nor is it limited.

The thickness of the bipolar electrode current collector 16 may be 10 μm or more and 100 μm or less, preferably 10 μm or more and 50 μm or less from the viewpoint of reducing the volume of the entire positive electrode, and the bipolar electrode with a small curvature when forming a battery. In view of winding, it is more preferably 10 μm or more and 20 μm or less.

The positive electrode mixture layer 10 in the battery member 17 may be made of the same material as the positive electrode mixture layer 10 in the battery member 13 of the first embodiment described above. In the electrode group 2B, the positive electrode mixture layer 10 on the bipolar electrode current collector 16 in the battery member 17 includes the second conductive material different from the first conductive material and the first conductive material described above. A combination of a first conductive material and a second conductive material contained in the positive electrode mixture layer 10 on the positive electrode current collector 9 of the positive electrode 6 and a positive electrode mixture layer on the bipolar electrode current collector 16 in the battery member 17 The combination of the first conductive material and the second conductive material included in 10 may be the same combination as each other or a different combination, but is preferably the same combination as each other.

In another embodiment, it can be considered that the electrode group 2B includes a battery member including the first electrolyte layer 7, the bipolar electrode 15, and the second electrolyte layer 7 in this order. FIG.5 (b) is a schematic cross section which shows the battery member for secondary batteries which concerns on other embodiment. As shown in FIG. 5B, the battery member 18 includes a bipolar electrode current collector 16, a positive electrode mixture layer 10 provided on one surface of the bipolar electrode current collector 16, and a positive electrode mixture layer 10, a second electrolyte layer 7 provided on the opposite side to the bipolar electrode current collector 16, a negative electrode mixture layer 12 provided on the other surface of the bipolar electrode current collector 16, and a negative electrode mixture layer And a first electrolyte layer 7 provided on the opposite side to the bipolar electrode current collector 16.

The bipolar electrode current collector 16, the positive electrode mixture layer 10 and the negative electrode mixture layer 12 in the battery member 18 are the bipolar electrode current collector 16, the positive electrode mixture layer 10 and the negative electrode mixture layer 12 in the battery member 17 described above. And may be made of the same material.

The first electrolyte layer 7 and the second electrolyte layer 7 in the battery member 18 may be made of the same material as the electrolyte layer 7 in the battery member 14 of the first embodiment described above. The first electrolyte layer 7 and the second electrolyte layer 7 may be the same as or different from each other, and are preferably the same as each other.

Hereinafter, the present invention will be more specifically described by way of examples, but the present invention is not limited to these examples.

Example 1
<Preparation of electrolyte layer>
40 parts by mass of SiO ₂ particles (average particle diameter 0.04 μm, specific surface area 50 m ² / g), 60 parts by mass of a copolymer of vinylidene fluoride and hexafluoropropylene are mixed, and then a dispersion medium N-methyl-2- Pyrrolidone (NMP) was added and kneaded to obtain a mixture of SiO ₂ particles and a copolymer. In addition, lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) dried under a dry argon atmosphere is used as an electrolyte salt, and an ionic liquid N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium bis is used. LiTFSI was dissolved in (trifluoromethanesulfonyl) imide (DEME-TFSI) at a concentration of 1.5 mol / L (hereinafter referred to as the concentration of electrolyte salt in the ionic liquid in which the electrolyte salt is dissolved, the type of electrolyte salt, and the ionic liquid The type is also described as "electrolyte salt concentration (mol / L) / type of electrolyte salt / type of ionic liquid". Next, a mixture of SiO ₂ particles and a copolymer was mixed with an ionic liquid in which an electrolyte salt was dissolved to prepare a slurry containing an electrolyte composition. At this time, the SiO ₂ particles, the volume ratio of ionic liquid obtained by dissolving an electrolyte salt, SiO ₂ particles: the ionic liquid by dissolving an electrolyte salt = 25: was 75. The obtained slurry was applied to a substrate made of polyethylene terephthalate and heated to volatilize the dispersion medium to obtain an electrolyte sheet. The thickness of the electrolyte layer in the obtained electrolyte sheet was 25 ± 2 μm.

<Production of positive electrode (positive electrode member)>
70 parts by mass of layered lithium-nickel-manganese-cobalt composite oxide (positive electrode active material), particulate acetylene black as a first conductive material (conductive material A, average particle diameter 48 nm, specific surface area 39 m ² / g, Product name: 6.3 parts by mass of HS-100, manufactured by Denka Co., Ltd., particulate acetylene black as a second conductive material (conductive material B, average particle diameter 23 nm, specific surface area 133 m ² / g, product name: 0.7 part by mass of Denka Co., Ltd. 9 parts by mass of copolymer (binder) of vinylidene fluoride and hexafluoropropylene, ionic liquid in which lithium salt is dissolved as electrolyte salt (1 mol / L / lithium bis (fluorocarbon) Methanesulfonyl) imide (LiFSI) / N-methyl-N-propylpyrrolidinium bis (fluorosulfonyl) imide (Py13-FSI)) 1 4 parts by mass were mixed. Next, NMP, which is a dispersion medium, was added and kneaded to prepare a slurry-like positive electrode mixture. This positive electrode mixture is coated on a positive electrode current collector (aluminum foil with a thickness of 20 μm) at a coating amount of 160 g / m ² , heated at 80 ° C. to volatilize the dispersion medium, and pressed with a mixture density of 2. It was consolidated to 60 g / cm ³ to form a positive electrode mixture layer. This was punched into a square of 13.5 cm ² and used as a positive electrode. In the positive electrode, the content of the second conductive material is 10 parts by mass with respect to a total of 100 parts by mass of the content of the first conductive material and the content of the second conductive material. The total of the content of the first conductive material and the content of the second conductive material is a total of 100 mass of the content of the positive electrode active material, the content of the first conductive material, and the content of the second conductive material. It is 9.1 mass parts with respect to parts.

<Fabrication of negative electrode>
Graphite (negative electrode active material, manufactured by Hitachi Chemical Co., Ltd.) 76.9 parts by mass, scale-like graphite (conductive material, average particle diameter 7 μm, product name: manufactured by Nippon Graphite Industry Co., Ltd.) 2.06 parts by mass, VGCF (conductive material , Average fiber diameter 150 nm, product name: VGCF-H, 0.52 parts by mass, Showa Denko Co., Ltd. 0.52 parts by mass, copolymer of vinylidene fluoride and hexafluoropropylene (binder) 6.52 parts by mass, lithium salt as electrolyte salt Were mixed with 14 parts by mass of an ionic liquid (1 mol / L / LiFSI / Py13-FSI) in which Next, NMP, which is a dispersion medium, was added and kneaded to prepare a slurry-like negative electrode mixture. This negative electrode mixture is coated on a negative electrode current collector (copper foil with a thickness of 10 μm) at a coating amount of 70 g / m ² , heated at 80 ° C. to volatilize the dispersion medium, and pressed with the mixture density 1. It was consolidated to 70 g / cm ³ to form a negative electrode mixture layer. This was punched into a square of 13.9 cm ² and used as a negative electrode.

<Fabrication of secondary battery>
An electrode group was manufactured by overlapping the positive electrode manufactured above, the electrolyte layer, and the negative electrode in this order. This electrode group was placed in an aluminum laminate container (product name: aluminum laminate film, manufactured by Dainippon Printing Co., Ltd.), and the laminate container was thermally welded to prepare a secondary battery for evaluation.

Example 2
A secondary battery was produced in the same manner as in Example 1, except that in the positive electrode mixture layer, 5.6 parts by mass of the conductive material A and 1.4 parts by mass of the conductive material B were used. In the positive electrode, the content of the second conductive material is 20 parts by mass with respect to a total of 100 parts by mass of the content of the first conductive material and the content of the second conductive material. The total of the content of the first conductive material and the content of the second conductive material is a total of 100 mass of the content of the positive electrode active material, the content of the first conductive material, and the content of the second conductive material. It is 9.1 mass parts with respect to parts.

[Example 3]
In the positive electrode mixture layer, 6.3 parts by mass of the conductive material A is used as the first conductive material, and VGCF (conductive material C, average fiber diameter 150 nm, average length 10 μm, product name: VGCF as the second conductive material A secondary battery was produced in the same manner as in Example 1 except that 0.7 parts by mass of -H (manufactured by Showa Denko KK) was used. In the positive electrode, the content of the second conductive material is 10 parts by mass with respect to a total of 100 parts by mass of the content of the first conductive material and the content of the second conductive material. The total of the content of the first conductive material and the content of the second conductive material is a total of 100 mass of the content of the positive electrode active material, the content of the first conductive material, and the content of the second conductive material. It is 9.1 mass parts with respect to parts.

Example 4
A secondary battery was produced in the same manner as in Example 3 except that 5.6 parts by mass of the conductive material A and 1.4 parts by mass of the conductive material C were used in the positive electrode mixture layer. In the positive electrode, the content of the second conductive material is 20 parts by mass with respect to a total of 100 parts by mass of the content of the first conductive material and the content of the second conductive material. The total of the content of the first conductive material and the content of the second conductive material is a total of 100 mass of the content of the positive electrode active material, the content of the first conductive material, and the content of the second conductive material. It is 9.1 mass parts with respect to parts.

[Example 5]
A secondary battery was produced in the same manner as in Example 3, except that 4.2 parts by mass of the conductive material A and 2.8 parts by mass of the conductive material C were used in the positive electrode mixture layer. In the positive electrode, the content of the second conductive material is 40 parts by mass with respect to a total of 100 parts by mass of the content of the first conductive material and the content of the second conductive material. The total of the content of the first conductive material and the content of the second conductive material is a total of 100 mass of the content of the positive electrode active material, the content of the first conductive material, and the content of the second conductive material. It is 9.1 mass parts with respect to parts.

[Example 6]
A laminate type battery was produced in the same manner as in Example 3 except that 3.5 parts by mass of the conductive material A and 3.5 parts by mass of the conductive material C were used in the positive electrode mixture layer. In the positive electrode, the content of the second conductive material is 50 parts by mass with respect to a total of 100 parts by mass of the content of the first conductive material and the content of the second conductive material. The total of the content of the first conductive material and the content of the second conductive material is a total of 100 mass of the content of the positive electrode active material, the content of the first conductive material, and the content of the second conductive material. It is 9.1 mass parts with respect to parts.

Comparative Example 1
In the positive electrode mixture layer, 7.0 parts by mass of the conductive material A was used, and a secondary battery was produced in the same manner as in Example 1 except that the conductive material B was not used.

Comparative Example 2
An ionic liquid in which 81.4 parts by mass of a positive electrode active material, 8.1 parts by mass of a conductive material A, and 10.5 parts by mass of a binder are used to dissolve a conductive material B and a lithium salt in a positive electrode mixture layer A secondary battery was produced in the same manner as in Example 1 except that the above was not used.

<Evaluation of discharge characteristics>
The discharge capacity at 25 ° C. of the obtained secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 2 was measured using the charge / discharge device (made by Toyo System Co., Ltd.) under the following charge / discharge conditions: did.
(1) After performing constant current constant voltage (CCCV) charging at final voltage 4.2 V, 0.1 C, perform one cycle of discharging constant current (CC) to final voltage 2.7 V at 0.1 C, discharging I asked for the capacity. C means "current value (A) / battery capacity (Ah)".
(2) Next, one cycle of constant current constant voltage (CCCV) charging with a final voltage of 4.2 V, 0.1 C and then constant current (CC) discharging with a 0.5 C to a final voltage of 2.7 V The discharge capacity was determined.
From the obtained discharge capacity, the discharge characteristic was calculated using the following equation.
The discharge capacity discharge characteristic obtained by the discharge capacity = (2) / (1) is 0.9 or more and 1.0 or less as “A”, and 0.8 or more and less than 0.9 as “B "Less than 0.7" was evaluated in three steps as "C", and A was made the best evaluation result. The obtained results are shown in Table 1.

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, 14 17, 18, ... Battery members for secondary batteries.

Claims (13)

1. A current collector, and a positive electrode mixture layer provided on the current collector;
   The positive electrode mixture layer is
   A positive electrode active material,
   Ionic liquid,
   At least one electrolyte salt selected from the group consisting of lithium salts, sodium salts, calcium salts, and magnesium salts;
   Containing a conductive material containing carbon;
   A battery member for a secondary battery, wherein the conductive material includes a first conductive material and a second conductive material different from the first conductive material.
2. The first conductive material and the second conductive material are both in the form of particles,
   The battery member according to claim 1, wherein a specific surface area of the first conductive material is smaller than a specific surface area of the second conductive material.
3. The first conductive material and the second conductive material are both in the form of particles,
   The battery member according to claim 1, wherein an average particle size of the second conductive material is smaller than an average particle size of the first conductive material.
4. The content of the second conductive material is 20 parts by mass or less with respect to a total of 100 parts by mass of the content of the first conductive material and the content of the second conductive material. The battery member as described in 2 or 3.
5. The battery member according to claim 1, wherein the first conductive material is particulate, and the second conductive material is fibrous.
6. The content of the second conductive material is 50 parts by mass or less with respect to a total of 100 parts by mass of the content of the first conductive material and the content of the second conductive material. The battery member as described in.
7. The total of the content of the first conductive material and the content of the second conductive material is the content of the positive electrode active material, the content of the first conductive material, and the content of the second conductive material. The battery member according to any one of claims 1 to 6, which is 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass in total.
8. The ionic liquid contains, as a cation component, at least one selected from the group consisting of a linear quaternary onium cation, a piperidinium cation, a pyrrolidinium cation, a pyridinium cation, and an imidazolium cation, and as the anion component, The battery member according to any one of claims 1 to 7, which contains at least one anion component represented by the following general formula (1).
   _{N (SO 2 C m F 2m} + 1) (SO 2 C n F 2n + 1) - (1)
   [M and n each independently represent an integer of 0 to 5] ]
9. A secondary battery comprising a positive electrode, a negative electrode, and an electrolyte layer provided between the positive electrode and the negative electrode,
   The positive electrode includes a current collector and a positive electrode mixture layer provided on the current collector,
   The positive electrode mixture layer is
   A positive electrode active material,
   Ionic liquid,
   At least one electrolyte salt selected from the group consisting of lithium salts, sodium salts, calcium salts, and magnesium salts;
   Containing a conductive material containing carbon;
   The conductive material includes a first conductive material and a second conductive material different from the first conductive material,
   The electrolyte layer is
   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;
   A secondary battery containing an ionic liquid.
10. The secondary battery according to claim 9, wherein the one or more polymers have a first structural unit selected from the group consisting of tetrafluoroethylene and vinylidene fluoride.
11. The second structural unit selected from the group consisting of the first structural unit, hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate, and methyl methacrylate among structural units constituting the one or more polymers The secondary battery according to claim 10, comprising the structural unit of
12. The secondary battery according to any one of claims 9 to 11, wherein an average particle diameter of the oxide particles is 0.005 μm or more and 5 μm or less.
13. The ionic liquid contained in the electrolyte layer contains, as a cationic component, at least one selected from the group consisting of a linear quaternary onium cation, a piperidinium cation, a pyrrolidinium cation, a pyridinium cation, and an imidazolium cation. And
    The secondary battery according to any one of claims 9 to 12, which contains at least one of anion components represented by the following general formula (1) as the anion component.
    _{N (SO 2 C m F 2m} + 1) (SO 2 C n F 2n + 1) - (1)
    [M and n each independently represent an integer of 0 to 5] ]

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