JP2019153545A - Secondary battery negative electrode and secondary battery - Google Patents

Abstract

To provide a secondary battery negative electrode capable of improving the discharge characteristics of a secondary battery and a secondary battery excellent in the discharge characteristics.SOLUTION: A secondary battery negative electrode according to the present invention includes a negative electrode current collector and a negative electrode mixture layer provided on the negative electrode current collector, and the negative electrode mixture layer includes a fibrous carbon material, a negative electrode active material other than the carbon material, an ionic liquid, and at least one electrolyte salt selected from the group consisting of lithium salt, sodium salt, calcium salt, and magnesium salt.SELECTED DRAWING: None

Description

  The present invention relates to a negative electrode for a secondary battery and a secondary battery.

  In recent years, with the widespread use of portable electronic devices, electric vehicles, etc., high performance secondary batteries are required. Among them, lithium secondary batteries have high energy density and are used as power sources for portable electronic devices, electric vehicles, and the like.

  For example, in a 18650 type lithium secondary battery, a winding electrode body is accommodated in a cylindrical battery can. The wound electrode body is configured by sandwiching a microporous separator between a positive electrode and a negative electrode and winding them in a spiral shape. Since the separator in the winding electrode body is impregnated with a flammable electrolyte, for example, when the temperature of the battery suddenly rises during an abnormal situation, the electrolyte is vaporized and the internal pressure rises, so that the lithium secondary battery is There is a possibility of rupture and the electrolyte may ignite. Preventing rupture and ignition of a lithium secondary battery is important in the design of lithium secondary batteries. That is, in the lithium secondary battery, it is required to further improve safety in order to further increase the energy density and size.

  As a fundamental solution for improving the safety of lithium secondary batteries, development of an all-solid battery is underway. In an all-solid battery, a layer of a solid electrolyte such as a polymer electrolyte or an inorganic solid electrolyte is provided on an electrode mixture layer instead of an electrolyte solution (for example, Patent Document 1). In recent years, development of all-solid-state batteries in which various battery characteristics such as discharge characteristics have been improved (for example, Patent Document 2).

JP 2006-294326 A JP 2017-050109 A

  Then, an object of this invention is to provide the secondary battery excellent in the negative electrode for secondary batteries which can improve the discharge characteristic of a secondary battery, and the discharge characteristic.

  The present invention includes, as a first aspect, a negative electrode current collector and a negative electrode mixture layer provided on the negative electrode current collector, wherein the negative electrode mixture layer is a fibrous carbon material, and the fibrous material A negative electrode for a secondary battery comprising a negative electrode active material other than the carbon material, an ionic liquid, and at least one electrolyte salt selected from the group consisting of a lithium salt, a sodium salt, a calcium salt, and a magnesium salt. .

  The content of the fibrous carbon material is preferably 0.1% by mass or more and 10% by mass or less based on the total amount of the negative electrode mixture layer.

  The negative electrode mixture layer may further contain a binder. In this case, the binder includes polyvinylidene fluoride, a copolymer containing ethylene tetrafluoride and vinylidene fluoride as structural units, and vinylidene fluoride. And at least one selected from the group consisting of copolymers containing hexafluoropropylene as a structural unit.

The ionic liquid preferably contains 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 as a cation component, and an anionic component As, it contains at least one kind of 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 represents an integer of 0 to 5. ]

  The present invention, as a second aspect, is a secondary battery comprising a positive electrode, the negative electrode according to the first aspect described above, and an electrolyte layer provided between the positive electrode and the negative electrode, wherein the electrolyte layer is One or two or more polymers, oxide particles, at least one electrolyte salt selected from the group consisting of a lithium salt, a sodium salt, a calcium salt, and a magnesium salt, and an ionic liquid, Provide the next battery.

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

  Among the structural units constituting one or more polymers, the first structural unit is preferably selected from the group consisting of the first structural unit and hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate, and methyl methacrylate. 2 structural units.

  The average particle diameter 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 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 as a cation component. And at least one anion component represented by the 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 represents an integer of 0 to 5. ]

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

1 is a perspective view showing a secondary battery according to a first 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 negative electrode for secondary batteries which concerns on one Embodiment, (b) is a schematic cross section which shows the negative electrode for secondary batteries which concerns on other embodiment. It is a disassembled perspective view which shows the electrode group of the secondary battery which concerns on 2nd Embodiment. (A) is a schematic cross-sectional view showing a battery member for a secondary battery according to an embodiment of the secondary battery shown in FIG. 4, and (b) is a diagram of a second embodiment according to another embodiment of the secondary battery shown in FIG. It is a schematic cross section which shows the battery member for secondary batteries.

  Embodiments of the present invention will be described below 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 and the like) are not essential unless otherwise specified. The size of the component in each figure is conceptual, and the relative relationship of the size between the components is not limited to that shown in each figure.

  The numerical values and ranges thereof herein are not intended to limit the invention. In the present specification, a numerical range indicated using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value described in another stepwise description. Further, in the numerical ranges described in the present specification, the upper limit value or the lower limit value of the numerical range may be replaced with the values shown in the examples.

[First Embodiment]
FIG. 1 is a perspective view showing the secondary battery according to the 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 outer package 3 that houses the electrode group 2. A positive electrode current collecting tab 4 and a negative electrode current collecting 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, respectively.

  The battery outer package 3 may be formed of a laminate film, for example. 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 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. The negative electrode current collector 11 is provided with a negative electrode current collector tab 5.

  In one embodiment, it is assumed that the electrode group 2 </ b> A includes a negative electrode member 13 for a secondary battery that includes a negative electrode current collector 11 and a negative electrode mixture layer 12 provided on the negative electrode current collector 11. be able to. Fig.3 (a) is a schematic cross section which shows the negative electrode member for secondary batteries which concerns on one Embodiment. As shown in FIG. 3A, the secondary battery negative electrode member 13 is a negative electrode member including a negative electrode current collector 11 and a negative electrode mixture layer 12 provided on the negative electrode current collector 11. The negative electrode 8 is comprised by the negative electrode member 13 for secondary batteries which concerns on one Embodiment. Hereinafter, the “secondary battery negative electrode member” may be simply referred to as “negative electrode”.

  The negative electrode current collector 11 may be a metal such as aluminum, copper, nickel, stainless steel, or an alloy thereof. Since the negative electrode current collector 11 is lightweight and has a high weight energy density, it is preferably aluminum or an alloy thereof. The negative electrode current collector 11 is preferably copper from the viewpoint of ease of processing into a thin film and cost. In addition to the above, the negative electrode current collector 11 may be formed of any material as long as it does not cause changes such as dissolution and oxidation during use of the battery, and its shape, manufacturing method, etc. Not limited.

  The thickness of the negative electrode current collector 11 may be 10 μm or more and 100 μm or less, and is preferably 10 μm or more and 50 μm or less from the viewpoint of reducing the volume of the whole negative electrode. From the viewpoint of turning, it is more preferably 10 μm or more and 20 μm or less.

  In one embodiment, the negative electrode mixture layer 12 is composed of a fibrous carbon material, a negative electrode active material other than the fibrous carbon material, an ionic liquid, a lithium salt, a sodium salt, a calcium salt, and a magnesium salt. And at least one electrolyte salt selected from the group.

  The fibrous carbon material is a conductive carbon material (conductive material) having a fibrous shape, and means a carbon material having an aspect ratio exceeding 20 in the shape. The aspect ratio is calculated from the scanning electron micrograph of the carbon material. The length of the carbon material in the long axis direction (the maximum length of the carbon material) relative to the length of the carbon material in the short axis direction (minimum length of the carbon material). ) Ratio (maximum length / minimum length). The length of the carbon material is obtained by statistically calculating the above-mentioned photograph using commercially available image processing software (for example, image analysis software manufactured by Asahi Kasei Engineering Co., Ltd., Image A (registered trademark)).

  Specifically, the fibrous carbon material may be a carbon fiber such as a vapor-grown carbon fiber (VGCF (registered trademark)), a carbon nanotube, or the like.

  The average fiber diameter of the fibrous carbon 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 fibrous carbon 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 with a transmission electron microscope (TEM).

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

  From the viewpoint of further improving discharge characteristics, the content of the fibrous carbon material contained in the negative electrode mixture layer 12 is preferably 0.1% by mass or more, more preferably 0.00%, based on the total amount of the negative electrode mixture layer. 3% by mass or more, more preferably 0.5% by mass or more, preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 3% by mass or less, and particularly preferably 1% by mass or less. is there.

The negative electrode active material is not particularly limited as long as it is a negative electrode active material other than the fibrous carbon material described above, and those commonly used in the field of energy devices can be used. 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 (however, excluding fibrous carbon materials), metal complexes, organic high Examples include molecular compounds. The negative electrode active material may be one of these alone or a mixture of two or more. Carbon materials include natural graphite (such as flake graphite), graphite such as artificial graphite, amorphous carbon, and carbon such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black. Black etc. are mentioned, and it is preferable to contain graphite among them. The negative electrode active material may be 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 content of the negative electrode active material contained in the negative electrode mixture layer 12 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 ionic liquid contained in the negative electrode mixture layer 12 contains the following anion component and cation component. In addition, the ionic liquid in this embodiment is a liquid substance at −20 ° C. or higher.

Anion component of the ionic liquid is not particularly ^{limited, Cl -, Br -, I} - halogen anions _{^{such, BF 4 -, N (SO}} 2 F) 2 - or the like of the inorganic _{anion, 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 - Or an organic anion. The anionic component of the ionic liquid preferably contains at least one anionic 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 represents an integer of 0 to 5. m and n may be the same as or different from each other, and are preferably 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. The anionic component of the ionic liquid is more preferably N (SO ₂ C ₄ F ₉ ) ₂ ⁻ , CF ₃ SO from the viewpoint of further improving the ionic conductivity with a relatively low viscosity and further improving the charge / discharge characteristics. _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 ^—, and more preferably. Contains N (SO ₂ F) ₂ ^— .

In the following, the following abbreviations may be used.
[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 cation component of the ionic liquid contained in the negative electrode mixture layer 12 is preferably 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. It is.

  The chain quaternary onium cation is, for example, a compound represented by the following general formula (2).

［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。］

[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, and n represents an integer of 1 to 4), and X represents a nitrogen atom or a phosphorus atom. The number of carbon atoms of the alkyl group represented by R ¹ to R ⁴ is preferably 1 to 20, more preferably 1 to 10, more preferably from 1 to 5. ]

  The piperidinium cation is, for example, a nitrogen-containing six-membered cyclic compound represented by the following general formula (3).

［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。］

[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 Represents a group or an ethyl group, and n represents an integer of 1 to 4. Carbon number of the alkyl group represented by R ⁵ and R ⁶ is preferably 1-20, more preferably 1-10, and still more preferably 1-5. ]

  The pyrrolidinium cation is, for example, a five-membered cyclic compound represented by the following general formula (4).

［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。］

[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 Represents a group or an ethyl group, and n represents an integer of 1 to 4. Carbon number of the alkyl group represented by R ⁷ and R ⁸ is preferably 1-20, more preferably 1-10, and still more preferably 1-5. ]

  The pyridinium cation is, for example, a compound represented by the following general formula (5).

［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。］

Wherein ^{(5), R} 9 ~R ¹³ independently represents an alkyl group having a carbon number of _{1~20, R-O- (CH 2} ) n - alkoxyalkyl group represented by (R is a methyl group Or represents an ethyl group, and n represents an integer of 1 to 4, or represents a hydrogen atom. 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 (6).

［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。］

Wherein ^{(6), R} 14 ~R ¹⁸ independently represents an alkyl group having a carbon number of _{1~20, R-O- (CH 2} ) n - alkoxyalkyl group represented by (R is a methyl group Or represents an ethyl group, and n represents an integer of 1 to 4, or represents a hydrogen atom. Carbon number of the alkyl group represented by R ^{14 to} R ¹⁸ is preferably 1 to 20, more preferably 1 to 10, and further preferably 1 to 5. ]

Ionic liquid contained in the negative electrode mixture layer 12, 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 a 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 negative electrode mixture layer 12 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 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, and still more preferably 20% by mass or less, based on the total amount of the negative electrode mixture layer.

  The electrolyte salt contained in the negative electrode mixture layer 12 may be at least one selected from the group consisting of a lithium salt, a sodium salt, a calcium salt, and a magnesium salt.

The anion component of the electrolyte salt contained in the negative electrode mixture layer 12 includes halide ions (I ⁻ , Cl ⁻ , Br ^{− and the} like), SCN ⁻ , BF ₄ ⁻ , BF ₃ (CF ₃ ) ⁻ , and 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 ^— .

Lithium salts include 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 (R is an alkyl group having 1 to 4 carbon atoms) , A phenyl group, or a naphthyl group).

Sodium salts include NaPF ₆ , NaBF ₄ , Na [FSI], Na [TFSI], Na [f ₃ C], 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).

The calcium salts are 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 (RCOO) ₂ Ca (R is an alkyl group having 1 to 4 carbon atoms, phenyl Or at least one selected from the group consisting of a naphthyl group).

Magnesium salts are 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 these, from the viewpoint of dissociation property 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, CF ₃ COOLi and RCOOLi (R is an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a naphthyl group), and 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 negative electrode mixture layer 12 may be dissolved in the ionic liquid and contained. The total content of the electrolyte salt and 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, and further preferably 10%, based on the total amount of the negative electrode mixture layer. It is at least mass%, preferably at most 30 mass%, more preferably at most 25 mass%, still more preferably at most 20 mass%.

  The concentration of the electrolyte salt per unit volume of the ionic liquid contained in the negative electrode mixture layer 12 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 3.0 mol / L or less, more preferably 2.7 mol / L or less, and still more preferably 2.3 mol / L or less.

  The negative electrode mixture layer 12 may further contain a binder.

  The binder is not particularly limited, but contains as a monomer unit at least one selected from the group consisting of ethylene tetrafluoride, vinylidene fluoride, hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate, and methyl methacrylate. It may be a polymer, rubber such as styrene-butadiene rubber, isoprene rubber or acrylic rubber. The binder is preferably a copolymer containing polyvinylidene fluoride, tetrafluoroethylene and vinylidene fluoride as structural units, and 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 negative 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 negative electrode mixture layer.

  From the viewpoint of further improving the conductivity, 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. By controlling the thickness of the negative electrode mixture layer to 50 μm or less, charging and discharging unevenness caused by variations in the charge level of the negative electrode active material in the vicinity of the surface of the negative electrode mixture layer 12 and in the vicinity of the surface of the negative electrode current collector 11 are suppressed. it can.

  In one embodiment, the electrolyte layer 7 includes one or more polymers, oxide particles, and at least one electrolyte salt selected from the group consisting of a lithium salt, a sodium salt, a calcium salt, and a magnesium salt; An ionic liquid.

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

  Preferably, the one or more polymers are preferably composed of 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 kind of polymer to form a copolymer, and each of the first structural unit and the second structural unit may be included in another polymer and have the first structural unit. And at least two types of polymers, the second polymer having the second structural unit.

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

  The content of 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.

  Since the polymer according to the present embodiment is excellent in affinity with the ionic liquid contained in the electrolyte composition, the polymer retains the electrolyte salt in the ionic liquid. Thereby, the leakage of the ionic liquid when a load is applied to the electrolyte composition is suppressed.

The oxide particles are, for example, inorganic oxide particles. The inorganic oxide is an inorganic oxide containing, for example, 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 . Particles. Since the oxide particles have polarity, it is possible to promote dissociation of the electrolyte in the electrolyte layer 7 and improve battery characteristics.

  The oxide particles may be rare earth metal oxides. Specifically, the oxide particles include scandium oxide, yttrium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, eurobium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, and 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. When the specific surface area is ² to 380 m ² / g, the secondary battery using the 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 primary particles and 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 electrical conductivity. More preferably 0.015 μm (15 nm) or more. From the viewpoint of making the electrolyte layer 7 thin, 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 can be measured by observing the oxide particles with 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 further 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 even more preferably 1 μm or less. The average particle size of the oxide particles is preferably 0.005 μm to 5 μm, 0.005 μm to 3 μm, 0.005 μm to 1 μm, 0.01 μm to 5 μm, 0.01 μm to 3 μm, 0.01 μm or more. 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, or 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 negative electrode mixture layer 12 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 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).

  From the viewpoint of suitably producing the electrolyte layer 7, 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.

  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 a lithium salt, a sodium salt, a calcium salt, and a 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 negative electrode mixture layer 12 described above.

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

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-based 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 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 reduction of the secondary battery. It is 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 still more preferably, from the viewpoint of further improving charge / discharge characteristics. Is 0.8 mol / L or more, preferably 3.0 mol / L or less, more preferably 2.7 mol / L or less, and still more preferably 2.3 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 increasing strength and improving safety. The thickness of the electrolyte layer 7 is preferably 200 μm or less, more preferably 150 μm or less, and still more preferably 100 μm or less, from the viewpoint of further reducing the internal resistance of the secondary battery and further improving the large current characteristics.

  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, an aluminum perforated foil having 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 changes such as dissolution and oxidation during use of the battery, and its shape, manufacturing method, etc. Not limited.

  The thickness of the positive electrode current collector 9 may be 10 μm or more and 100 μm or less, and is preferably 10 μm or more and 50 μm or less from the viewpoint of reducing the volume of the entire positive electrode, and the positive electrode current collector 9 has a small curvature when forming a battery. From the viewpoint of turning, 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.

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 oxide is a part of transition metals such as Mn, Ni, Co, etc. contained in lithium manganate, lithium nickelate, lithium cobaltate, etc., one or more other transition metals, or A lithium transition metal oxide substituted with a metal element (typical element) such as Mg or Al may also be used. That is, the lithium transition metal oxide may be a compound represented by LiM ¹ O ₂ or LiM ¹ O ₄ (M ¹ includes at least one transition metal). Specifically, lithium transition metal oxides are 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.

From the viewpoint of further improving the energy density, the lithium transition metal oxide is preferably a compound represented by the following formula (7).
^{_{Li a Ni b Co c M 2}} d O 2 + e (7)
Wherein (7), ^{M 2} is at least one Al, Mn, selected from the group consisting of Mg and Ca, a, b, c, d and e are each 0.2 ≦ a ≦ 1. 2, 0.5 ≦ b ≦ 0.9, 0.1 ≦ c ≦ 0.4, 0 ≦ d ≦ 0.2, −0.2 ≦ e ≦ 0.2, and b + c + d = 1. . ]

Lithium transition metal phosphates are 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) Or at least one element selected from the group consisting of:

  The positive electrode active material may be primary particles that are not granulated, or may be secondary particles that are granulated.

  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. When there are coarse particles having a particle size equal to or larger than the thickness of the positive electrode mixture layer 10 in the positive electrode active material, the coarse particles are removed in advance by sieving classification, wind classification, etc. A positive electrode active material having a diameter is selected.

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 diameter 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 suspending the positive electrode active material in water by a laser scattering method using a laser scattering particle size measuring device (for example, Microtrack). Can be obtained.

  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 positive electrode mixture layer 10 may further contain an ionic liquid, an electrolyte salt, a conductive material, and a binder.

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

  The conductive material included in the positive electrode mixture layer 10 is not particularly limited, and may be a carbon material such as graphite, acetylene black, carbon black, and carbon fiber. The conductive material may be a mixture of two or more of the carbon materials described above.

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

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

  From the viewpoint of further improving the conductivity, the thickness of the positive electrode mixture layer 10 may be 10 μm or more, 15 μm or more, or 20 μm or more. 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 making the thickness of the positive electrode mixture layer 100 μm or less, charging and discharging unevenness due to variations in the 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 are suppressed. it can.

  In other embodiments, the electrode group 2 </ b> A can also be regarded as including a negative electrode member including the negative electrode current collector 11, the negative electrode mixture layer 12, and the electrolyte layer 7 in this order. FIG.3 (b) is a schematic cross section which shows the negative electrode member for secondary batteries which concerns on other embodiment. As shown in FIG. 3B, the negative electrode member 14 includes a negative electrode current collector 11, a negative electrode mixture layer 12 provided on the negative electrode current collector 11, and an electrolyte provided on the negative electrode mixture layer 12. It is a negative electrode member provided with the layer 7 in this order. The electrolyte layer 7, the negative electrode current collector 11, and the negative electrode mixture layer 12 are the same as the electrolyte layer 7, the negative electrode current collector 11, and the negative electrode mixture layer 12 in the negative electrode member 13 described above.

  Then, the manufacturing method of the secondary battery 1 mentioned above is demonstrated. The manufacturing method of the secondary battery 1 includes the 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. The second step of obtaining the negative electrode 8 and the third step of providing the electrolyte layer 7 between the positive electrode 6 and the negative electrode 8 are included.

  In the first step, the positive electrode 6 is obtained by, for example, dispersing a material used for the positive electrode mixture layer in a dispersion medium to obtain a slurry-like positive electrode mixture, and then applying the positive electrode mixture to the positive electrode current collector 9. Then, it is 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 an ionic liquid and then dispersed in a dispersion medium together with other materials.

  The mixing ratio of the positive electrode active material, the conductive material, the binder, and the ionic liquid in which the electrolyte salt is dissolved in the positive electrode mixture layer 10 is, for example, positive electrode active material: conductive material: binder: ionic liquid in which the electrolyte salt is dissolved. = 69-82: 0.1-10: 5-12: 10-17 (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 positive electrode 6 described above. That is, by dispersing the material used for the negative electrode mixture layer 12 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 second step is a step of obtaining the negative electrode member 13 described above.

  The mixing ratio of the negative electrode active material, the fibrous carbon material, 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: fibrous carbon material: binder: electrolyte. The ionic liquid in which the salt is dissolved = 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, the electrolyte layer 7 is obtained by dispersing a material used for the electrolyte layer 7 in a dispersion medium to obtain a slurry-like electrolyte composition, and then applying the slurry on the substrate. 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 secondary battery 1 is obtained by laminating the positive electrode 6, the electrolyte layer 7 and the negative electrode 8 by, for example, laminating. 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 laminated so as to be arranged 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 the positive electrode 6 on both the positive electrode mixture layer 10 side and the negative electrode 8 on the negative electrode mixture layer 12 side. This step is a step of obtaining the negative electrode member 14 described above. In this case, for example, the secondary battery 1 is formed by laminating the negative electrode 8 (negative electrode member 14) provided with the electrolyte layer 7 and the positive electrode 6 provided with the electrolyte layer 7 so that the electrolyte layers 7 are in contact with each other. Is obtained.

  The method for forming the electrolyte layer 7 on the negative electrode mixture layer 12 includes, for example, dispersing a material used for the electrolyte layer 7 in a dispersion medium to obtain a slurry-like electrolyte composition, and then using this electrolyte composition as the negative electrode mixture It is a method of applying on the layer 12 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 an ionic liquid and then dispersed in a 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. It may be 80: 5-50 (mass ratio). However, it is not necessarily limited to this mixing ratio.

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

[Second Embodiment]
Next, the secondary battery according to the second embodiment will be described. FIG. 4 is an exploded perspective view showing an electrode group of the secondary battery according to the 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 a surface (positive electrode surface) on the negative electrode 8 side of the bipolar electrode current collector 16, and a positive electrode 6 side of the bipolar electrode current collector 16. And a negative electrode mixture layer 12 provided on the surface (negative electrode surface). That is, since the bipolar electrode 15 has both a positive electrode function and a negative electrode function, the electrode group 2B in the second embodiment includes a bipolar electrode current collector 16 and a bipolar electrode in addition to the positive electrode 6 and the negative electrode 8. 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 regarded as a battery member for a secondary battery including a bipolar electrode current collector 16 and a negative electrode mixture layer 12 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. And a negative electrode mixture layer 12 provided on the opposite side of the bipolar electrode current collector 16 on the battery member 10.

  In the bipolar electrode current collector 16, the positive electrode surface may be preferably formed of a material excellent in oxidation resistance, and may be formed 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, specifically, stainless steel, nickel, iron, titanium, or the like. It may be formed. When different types of 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, when the negative electrode 8 that operates at a potential that does not form an alloy with lithium, such as lithium titanate, is used, 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 foil made of aluminum having 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 bipolar electrode current collector 16 may be formed of any material as long as it does not cause changes such as dissolution and oxidation during use of the battery, and its shape, manufacturing method, etc. Is not limited.

  The thickness of the bipolar electrode current collector 16 may be not less than 10 μm and not more than 100 μm, and is preferably not less than 10 μm and not more than 50 μm from the viewpoint of reducing the volume of the entire bipolar electrode, and bipolar with a small curvature when forming a battery. From the viewpoint of winding the electrode, it is more preferably 10 μm or more and 20 μm or less.

  The negative electrode mixture layer 12 in the battery member 17 may be made of the same material as the negative electrode mixture layer 12 in the negative electrode member 13 of the first embodiment described above.

  In another embodiment, the electrode group 2 </ b> B can also be regarded as including 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 of 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 12, and a first electrolyte layer 7 provided on the opposite side of 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, positive electrode mixture layer 10, and negative electrode mixture layer 12 in the battery member 17 described above. It may be composed of the same material.

  The 1st electrolyte layer 7 and the 2nd electrolyte layer 7 in the battery member 18 may be comprised with the material similar to the electrolyte layer 7 in the negative electrode member 14 of 1st Embodiment mentioned above. The first electrolyte layer 7 and the second electrolyte layer 7 may be the same type or different types, and preferably the same type.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to 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 size 0.04 μm, specific surface area 50 m ² / g) and 60 parts by mass of a copolymer of vinylidene fluoride and hexafluoropropylene are mixed, and then N-methyl-2-2, which is a dispersion medium, is mixed. Pyrrolidone (NMP) was added and kneaded to obtain a mixture of SiO ₂ particles and a copolymer. Also, lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) dried in a dry argon atmosphere is used as an electrolyte salt, and N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium bis, which is an ionic liquid, is used. LiTFSI was dissolved in (trifluoromethanesulfonyl) imide (DEME-TFSI) at a concentration of 1.5 mol / L (hereinafter, the electrolyte salt concentration in the ionic liquid in which the electrolyte salt was dissolved, the type of the electrolyte salt, and the ionic liquid The type is also expressed as “electrolyte salt concentration (mol / L) / type of electrolyte salt / type of ionic liquid”). Next, a slurry containing an electrolyte composition was prepared by mixing a mixture of SiO ₂ particles and a copolymer and an ionic liquid in which an electrolyte salt was dissolved. 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 polyethylene terephthalate base material and heated to volatilize the dispersion medium to obtain an electrolyte sheet. The thickness of the electrolyte layer in the obtained electrolyte sheet was 20 ± 2 μm.

<Preparation of positive electrode>
70 parts by mass of layered lithium / nickel / manganese / cobalt composite oxide (positive electrode active material), acetylene black (conductive material, average particle size 48 nm, specific surface area 39 m ² / g, product name: HS-100, manufactured by Denka Corporation ) 7 parts by mass, 9 parts by mass of a vinylidene fluoride-hexafluoropropylene copolymer (binder), an ionic liquid (1 mol / L / lithium bis (fluoromethanesulfonyl) imide) (LiFSI) in which a lithium salt is dissolved as an electrolyte salt ) / N-methyl-N-propylpyrrolidinium bis (fluorosulfonyl) imide (Py13-FSI)) 14 parts by mass were mixed. Next, a slurry-like positive electrode mixture was prepared by adding NMP as a dispersion medium and kneading. This positive electrode mixture is applied onto a positive electrode current collector (aluminum foil having a thickness of 20 μm) at a coating amount of 125 g / m ² , heated at 80 ° C. to volatilize the dispersion medium, and the mixture density is set to 2. It consolidated to 60 g / cm < ³ > and formed the positive mix layer. This was punched out into a 13.5 cm ² square to obtain a positive electrode.

<Production of negative electrode>
Negative electrode active material A (graphite, product name: SMG-KB3, manufactured by Hitachi Chemical Co., Ltd.) 81.2 parts by mass, fibrous carbon material (average fiber diameter 150 nm, product name: VGCF, manufactured by Showa Denko Co., Ltd.) 52 parts by mass, binder A (copolymer of vinylidene fluoride and hexafluoropropylene) 4.30 parts by mass, electrolyte salt (ionic liquid in which lithium salt is dissolved (1 mol / L / LiFSI / Py13-FSI)) 14 parts by mass The parts were mixed. Next, NMP as a dispersion medium was added and kneaded to prepare a slurry-like negative electrode mixture. This negative electrode mixture was applied onto a negative electrode current collector (copper foil having a thickness of 10 μm) at a coating amount of 60 g / m ² , heated at 80 ° C. to volatilize the dispersion medium, and the mixture density 1. It consolidated to 60 g / cm < ³ > and formed the negative mix layer. This was punched into a square shape of 13.9 cm ² to form a negative electrode.

<Production of secondary battery>
An electrode group in which the positive electrode prepared above, the electrolyte layer, and the negative electrode were superposed in this order was manufactured. This electrode group was put in an aluminum laminate container (product name: aluminum laminate film, manufactured by Dai Nippon Printing Co., Ltd.), and the laminate container was heat-sealed to produce a secondary battery for evaluation.

[Example 2]
A secondary battery was produced in the same manner as in Example 1, except that 79.1 parts by mass of negative electrode active material A and 2.58 parts by mass of fibrous carbon material were used in the negative electrode mixture layer.

[Example 3]
In the negative electrode mixture layer, 79.1 parts by mass of negative electrode active material A and 2.06 of negative electrode active material B (graphite, product name: J-SP-α, manufactured by Nippon Graphite Industries Co., Ltd.) were used as the negative electrode active material. A secondary battery was produced in the same manner as in Example 1 except that the parts by mass were used.

[Example 4]
In the negative electrode mixture layer, 79.1 parts by mass of negative electrode active material A and negative electrode active material C (acetylene black, average particle size 48 nm, specific surface area 39 m ² / g, product name: HS-100, A secondary battery was produced in the same manner as in Example 1 except that 2.06 parts by mass of Denka Co., Ltd. was used and 0.52 parts by mass of a fibrous carbon material was used.

[Example 5]
In the negative electrode mixture layer, 79.1 parts by mass of negative electrode active material A, 0.52 parts by mass of negative electrode active material B, and 2.06 parts by mass of fibrous carbon material were used as the negative electrode active material. A secondary battery was fabricated in the same manner as in Example 1 except for the above.

[Example 6]
In the negative electrode mixture layer, 76.5 parts by mass of the negative electrode active material A, 4.13 parts by mass of the negative electrode active material B, and 1.03 parts by mass of the fibrous carbon material were used as the negative electrode active material. A secondary battery was fabricated in the same manner as in Example 1 except for the above.

[Example 7]
In the negative electrode mixture layer, 74.0 parts by mass of negative electrode active material A, 6.19 parts by mass of negative electrode active material B, and 2.06 parts by mass of fibrous carbon material were used as the negative electrode active material. A secondary battery was fabricated in the same manner as in Example 1 except for the above.

[Example 8]
In the negative electrode mixture layer, a secondary battery was prepared in the same manner as in Example 1 except that 4.30 parts by mass of binder B (polyvinylidene fluoride) was used instead of binder A as the binder. Was made.

[Example 9]
In the negative electrode mixture layer, 73.1 parts by mass of negative electrode active material A and negative electrode active material D (graphite, product name: SMG-N-HP1-10, manufactured by Hitachi Chemical Co., Ltd.) are used as the negative electrode active material. A secondary battery was produced in the same manner as in Example 1 except that 1 part by mass was used.

[Reference Example 1]
In the negative electrode mixture layer, the same method as in Example 1 except that 95 parts by mass of the negative electrode active material A, 5 parts by mass of the binder A were used, and the fibrous carbon material and the electrolyte salt were not used. Thus, a secondary battery was produced.

<Evaluation of discharge characteristics>
About the obtained secondary battery of Examples 1-9 and Reference Example 1, the discharge capacity in 25 degreeC was measured on the following charging / discharging conditions using the charging / discharging apparatus (made by Toyo System Co., Ltd.).
(1) After performing constant current and constant voltage (CCCV) charging at a final voltage of 4.2 V and 0.1 C, one cycle of discharging at a constant current (CC) to a final voltage of 2.7 V at 0.1 C is performed and discharged. The capacity was determined. C means “current value (A) / battery capacity (Ah)”.
(2) Next, after performing constant current and constant voltage (CCCV) charging at a final voltage of 4.2 V and 0.1 C, one cycle of discharging at a constant current (CC) to 0.5 V at a final voltage of 2.7 V is performed. The discharge capacity was determined.
From the obtained discharge capacity, discharge characteristics were calculated using the following formula.
Discharge characteristics = Discharge capacity obtained by (2) / Discharge capacity obtained by (1). ”, Less than 0.9 and less than 0.9 was evaluated as“ C ”, and less than 0.8 was evaluated as“ D ”in four stages. 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 collector, 10 ... Positive electrode mixture layer, 11 ... Negative electrode collector, 12 ... Negative electrode mixture layer, 13, 14 ... negative electrode member for secondary battery, 17, 18 ... battery member for secondary battery.

Claims (10)

A negative electrode current collector, and a negative electrode mixture layer provided on the negative electrode current collector,
The negative electrode mixture layer is
Fibrous carbon material,
A negative electrode active material other than the carbon material;
An ionic liquid,
A negative electrode for a secondary battery, comprising at least one electrolyte salt selected from the group consisting of a lithium salt, a sodium salt, a calcium salt, and a magnesium salt.   2. The negative electrode according to claim 1, wherein the content of the carbon material is 0.1% by mass or more and 10% by mass or less based on the total amount of the negative electrode mixture layer.   The negative electrode according to claim 1, wherein the negative electrode mixture layer further contains a binder.   The binder is at least selected from the group consisting of a copolymer containing polyvinylidene fluoride, tetrafluoroethylene and vinylidene fluoride as structural units, and a copolymer containing vinylidene fluoride and hexafluoropropylene as structural units. The negative electrode of Claim 3 containing 1 type. The ionic liquid contains 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 as a cation component, and as an anion component, The negative electrode as described in any one of Claims 1-4 containing at least 1 sort (s) of the anion component represented by 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 represents an integer of 0 to 5. ] A secondary battery comprising a positive electrode, a negative electrode according to any one of claims 1 to 5, and an electrolyte layer provided between the positive electrode and the negative electrode,
The electrolyte layer is
One or more polymers,
Oxide particles,
At least one electrolyte salt selected from the group consisting of lithium salt, sodium salt, calcium salt and magnesium salt;
A secondary battery containing an ionic liquid.   The secondary battery according to claim 6, wherein the one or more kinds of polymers have a first structural unit selected from the group consisting of tetrafluoroethylene and vinylidene fluoride.   A second unit selected from the group consisting of the first structural unit and hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate, and methyl methacrylate, among the structural units constituting the one or more polymers. The secondary battery according to claim 7, wherein:   The secondary battery according to any one of claims 6 to 8, wherein an average particle diameter of the oxide particles is 0.005 µm or more and 5 µm or less. The ionic liquid contained in the electrolyte layer contains, 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. And the secondary battery as described in any one of Claims 6-9 containing 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 represents an integer of 0 to 5. ]

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