JP2020004542A - Negative electrode and electrochemical device - Google Patents

Abstract

To provide a negative electrode that can reduce the resistance of an electrochemical device.SOLUTION: There is provided a negative electrode including a negative electrode current collector and a negative electrode mixture layer, and the negative electrode mixture layer contains a compound represented by the following formula (1). [In the formula (1), Rto Reach independently represent an alkyl group or a fluorine atom, Rrepresents an alkylene group, and Rrepresents an organic group containing a sulfur atom.]SELECTED DRAWING: None

Description

  The present invention relates to a negative electrode and an electrochemical device.

  In recent years, with the spread of portable electronic devices and electric vehicles, high-performance electrochemical devices such as non-aqueous electrolyte secondary batteries represented by lithium ion secondary batteries and capacitors have been required. As a means for improving the performance of an electrochemical device, for example, a method of adding a predetermined additive to an electrolytic solution has been studied. Patent Literature 1 discloses an electrolyte for a non-aqueous electrolyte battery containing a specific siloxane compound in order to improve internal resistance characteristics.

JP-A-2005-005329

  As described in Patent Document 1, it is important to reduce the resistance of an electrochemical device. Therefore, an object of the present invention is to provide a negative electrode that can reduce the resistance of an electrochemical device. Another object of the present invention is to provide an electrochemical device with reduced resistance.

  The present inventors have found that the resistance of an electrochemical device can be reduced by including a specific compound containing a silicon atom and a sulfur atom in a negative electrode.

［式（１）中、Ｒ^１〜Ｒ^３は、それぞれ独立に、アルキル基又はフッ素原子を示し、Ｒ^４はアルキレン基を示し、Ｒ^５は、硫黄原子を含む有機基を示す。］ The present invention provides, as a first aspect, a negative electrode including a negative electrode current collector and a negative electrode mixture layer, wherein the negative electrode mixture layer contains a compound represented by the following formula (1).

[In the formula (1), R ^{1 to} R ³ each independently represent an alkyl group or a fluorine atom, R ⁴ represents an alkylene group, and R ⁵ represents an organic group containing a sulfur atom. ]

  In the first embodiment, the number of silicon atoms in one molecule of the compound represented by the formula (1) is preferably one.

［式（２）中、Ｒ^６はアルキル基を示し、＊は結合手を示す。］

［式（３）中、Ｒ^７はアルキル基を示し、＊は結合手を示す。］

［式（４）中、Ｒ^８はアルキル基を示し、＊は結合手を示す。］ R ⁵ is preferably a group represented by any of the following formulas (2), (3) and (4).

[In the formula (2), R ⁶ represents an alkyl group, and * represents a bond. ]

[In the formula (3), R ⁷ represents an alkyl group, and * represents a bond. ]

[In the formula (4), R ⁸ represents an alkyl group, and * represents a bond. ]

At least one of R ^{1 to} R ³ is preferably a fluorine atom.

  The content of the compound represented by the formula (1) is preferably 10% by mass or less based on the total amount of the negative electrode mixture layer.

  The negative electrode mixture layer preferably further contains a carbon material. The carbon material preferably contains graphite.

  The negative electrode mixture layer preferably further contains an inorganic material containing at least one element of the group consisting of silicon and tin.

  The present invention provides, as a second aspect, an electrochemical device including a positive electrode, the above-described negative electrode, and an electrolytic solution.

  The electrochemical device is preferably a non-aqueous electrolyte secondary battery or capacitor.

  ADVANTAGE OF THE INVENTION According to this invention, the negative electrode which can reduce the resistance of an electrochemical device can be provided. Further, according to the present invention, an electrochemical device with reduced resistance can be provided.

1 is a perspective view showing a non-aqueous electrolyte secondary battery as an electrochemical device according to one embodiment. FIG. 2 is an exploded perspective view illustrating an electrode group of the secondary battery illustrated in FIG. 1. It is a graph which shows the evaluation result of the cycle characteristic of an Example and a comparative example.

  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.

  FIG. 1 is a perspective view showing an electrochemical device according to one embodiment. In this embodiment, the electrochemical device is a non-aqueous electrolyte secondary battery. As shown in FIG. 1, the non-aqueous electrolyte secondary battery 1 includes an electrode group 2 including a positive electrode, a negative electrode, and a separator, and a bag-shaped battery case 3 containing the electrode group 2. The positive electrode and the negative electrode are provided with a positive electrode current collecting tab 4 and a negative electrode current collecting tab 5, respectively. The positive electrode current collecting tab 4 and the negative electrode current collecting tab 5 protrude from the inside of the battery exterior body 3 to the outside such that the positive electrode and the negative electrode can be electrically connected to the outside of the nonaqueous electrolyte secondary battery 1, respectively. . The battery exterior 3 is filled with an electrolyte (not shown). The non-aqueous electrolyte secondary battery 1 may be a battery (coin type, cylindrical type, stacked type, etc.) having a shape other than the so-called “laminated type” as described above.

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

  FIG. 2 is an exploded perspective view showing one embodiment of the electrode group 2 in the nonaqueous electrolyte secondary battery 1 shown in FIG. As shown in FIG. 2, the electrode group 2 includes a positive electrode 6, a separator 7, and a negative electrode 8 in this order. The positive electrode 6 and the negative electrode 8 are arranged such that the surfaces on the positive electrode mixture layer 10 side and the negative electrode mixture layer 12 side face the separator 7, respectively.

  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 collection tab 4.

  The positive electrode current collector 9 is made of, for example, aluminum, titanium, stainless steel, nickel, calcined carbon, conductive polymer, conductive glass, or the like. The positive electrode current collector 9 may be one obtained by treating a surface of aluminum, copper, or the like with carbon, nickel, titanium, silver, or the like for the purpose of improving adhesiveness, conductivity, and oxidation resistance. The thickness of the positive electrode current collector 9 is, for example, 1 to 50 μm in terms of electrode strength and energy density.

  In one embodiment, the positive electrode mixture layer 10 contains a positive electrode active material, a conductive agent, and a binder. The thickness of the positive electrode mixture layer 10 is, for example, 20 to 200 μm.

The positive electrode active material may be, for example, a lithium oxide. The lithium oxide, for _{example, Li x CoO 2, Li x} NiO 2, Li x MnO 2, Li x Co y Ni 1-y O 2, Li x Co y M 1-y O z, Li x Ni 1- _{y M y O z, Li x} Mn 2 O 4 and _{Li x Mn 2-y M y} O 4 ( in each formula, M represents, Na, Mg, Sc, Y , Mn, Fe, Co, Cu, Zn, Al , Cr, Pb, Sb, V and B, at least one element selected from the group consisting of M and X (where M is an element different from the other elements in each formula). , Y = 0 to 0.9 and z = 2.0 to 2.3.). The lithium oxide represented by Li _x Ni _1-y M _y O _z is Li _x Ni _{1- (y1 + y2)} Co _{y1 Mny 2} O _z (where x and z are the same as those described above, and y1 = 0 to 0.9, y2 = 0 to 0.9, and y1 + y2 = 0 to 0.9), for example, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , It may be LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O _{2, or} LiNi _0.8 Co _0.1 Mn _0.1 O ₂ . Li _x Ni _1-y lithium oxide represented by M y _{O z is, Li x Ni 1- (y3 +} y4) Co y3 Al y4 O z ( here, x and z are the same as those described above, y3 = 0 to 0.9, y4 = 0 to 0.9, and y3 + y4 = 0 to 0.9.) For example, LiNi _0.8 Co _0.15 Al _0.05 O ₂ There may be.

The positive electrode active material may be, for example, a lithium phosphate. Examples of the lithium phosphate include lithium manganese phosphate (LiMnPO ₄ ), lithium iron phosphate (LiFePO ₄ ), cobalt iron phosphate (LiCoPO ₄ ), and vanadium phosphate (Li ₃ V ₂ (PO ₄ ) ₃ ). ).

  The content of the positive electrode active material may be 80% by mass or more, or 85% by mass or more, and may be 99% by mass or less based on the total amount of the positive electrode mixture layer.

  The conductive agent may be a carbon material such as carbon black such as acetylene black and Ketjen black, graphite, graphene, and carbon nanotube. The content of the conductive agent may be, for example, 0.01% by mass or more, 0.1% by mass or more, or 1% by mass or more, based on the total amount of the positive electrode mixture layer, and 50% by mass or less, 30% by mass or less. Or less, or 15% by mass or less.

  Examples of the binder include resins such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), and fluorine rubber Rubber such as isoprene rubber, butadiene rubber and ethylene-propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / butadiene / Thermoplastic elastomers such as ethylene copolymer, styrene / isoprene / styrene block copolymer or hydrogenated product thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate Soft resins such as copolymers and propylene / α-olefin copolymers; polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer, polytetrafluoroethylene / Examples thereof include a fluorine-containing resin such as a vinylidene fluoride copolymer; a resin having a nitrile group-containing monomer as a monomer unit; and a polymer composition having ion conductivity of an alkali metal ion (for example, lithium ion).

  The content of the binder may be, for example, 0.1% by mass or more, 1% by mass or more, or 1.5% by mass or more, based on the total amount of the positive electrode mixture layer, and 30% by mass or less, 20% by mass or less. % Or 10% by mass or less.

  The separator 7 is not particularly limited as long as it electrically insulates the positive electrode 6 and the negative electrode 8 while allowing ions to permeate, and has resistance to oxidizing property on the positive electrode 6 side and reducing property on the negative electrode 8 side. Not done. Examples of the material (material) of such a separator 7 include a resin and an inorganic substance.

  Examples of the resin include an olefin-based polymer, a fluorine-based polymer, a cellulose-based polymer, polyimide, and nylon. The separator 7 is preferably a porous sheet or a nonwoven fabric formed of a polyolefin such as polyethylene or polypropylene from the viewpoint of being stable with respect to the electrolytic solution and having excellent liquid retention properties.

  Examples of the inorganic substance include oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate. The separator 7 may be, for example, a separator in which a fibrous or particulate inorganic substance is adhered to a thin film substrate such as a nonwoven fabric, a woven fabric, or a microporous film.

  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.

  The negative electrode current collector 11 is formed of copper, stainless steel, nickel, aluminum, titanium, calcined carbon, conductive polymer, conductive glass, aluminum-cadmium alloy, or the like. The negative electrode current collector 11 may be one obtained by treating a surface of copper, aluminum, or the like with carbon, nickel, titanium, silver, or the like for the purpose of improving adhesion, conductivity, and reduction resistance. The thickness of the negative electrode current collector 11 is, for example, 1 to 50 μm in terms of electrode strength and energy density.

式（１）中、Ｒ^１〜Ｒ^３は、それぞれ独立に、アルキル基又はフッ素原子を示し、Ｒ^４はアルキレン基を示し、Ｒ^５は、硫黄原子を含む有機基を示す。 In one embodiment, the negative electrode mixture layer 12 contains a compound represented by the following formula (1), a negative electrode active material, and a binder.

In the formula (1), R ^{1 to} R ³ each independently represent an alkyl group or a fluorine atom, R ⁴ represents an alkylene group, and R ⁵ represents an organic group containing a sulfur atom.

The number of carbon atoms of the alkyl group represented by R ^{1 to} R ³ may be 1 or more, and may be 3 or less. R ^{1 to} R ³ may be a methyl group, an ethyl group, or a propyl group, and may be linear or branched. At least one of R ^{1 to} R ³ is preferably a fluorine atom.

The carbon number of the alkylene group represented by R ⁴ may be 1 or more, or 2 or more, and may be 5 or less or 4 or less. The alkylene group represented by R ⁴ may be a methylene group, an ethylene group, a propylene group, a butylene group, or a pentylene group, and may be linear or branched.

式（２）中、Ｒ^６はアルキル基を示す。アルキル基は、上述したＲ^１〜Ｒ^３で表されるアルキル基と同様であってよい。＊は結合手を示す。 In one embodiment, R ⁵ may be a group represented by the following formula (2) from the viewpoint of further reducing the resistance of the electrochemical device.

In the formula (2), R ⁶ represents an alkyl group. The alkyl group may be the same as the alkyl group represented by R ^{1 to} R ³ described above. * Indicates a bond.

式（３）中、Ｒ^７はアルキル基を示す。アルキル基は、上述したＲ^１〜Ｒ^３で表されるアルキル基と同様であってよい。＊は結合手を示す。 R ⁵ may be a group represented by the following formula (3) in another embodiment from the viewpoint of further reducing the resistance of the electrochemical device.

In the formula (3), R ⁷ represents an alkyl group. The alkyl group may be the same as the alkyl group represented by R ^{1 to} R ³ described above. * Indicates a bond.

式（４）中、Ｒ^８はアルキル基を示す。アルキル基は、上述したＲ^１〜Ｒ^３で表されるアルキル基と同様であってよい。＊は結合手を示す。 In another embodiment, R ⁵ may be a group represented by the following formula (4) from the viewpoint of further reducing the resistance of the electrochemical device.

In the formula (4), R ⁸ represents an alkyl group. The alkyl group may be the same as the alkyl group represented by R ^{1 to} R ³ described above. * Indicates a bond.

In one embodiment, the number of silicon atoms in one molecule of the compound represented by the formula (1) is one. That is, in one embodiment, the organic group represented by R ⁵ does not include a silicon atom.

  From the viewpoint of further reducing the resistance of the electrochemical device, the content of the compound represented by the formula (1) is preferably 0.2% by mass or more, more preferably 0% by mass, based on the total amount of the negative electrode mixture layer. 0.3% by mass or more, more preferably 0.5% by mass or more. From the same viewpoint, the content of the compound represented by the formula (1) is preferably 10% by mass or less, more preferably 7% by mass or less, and further preferably, based on the total amount of the negative electrode mixture layer. It is at most 5% by mass, particularly preferably at most 3% by mass. From the viewpoint of further reducing the resistance of the electrochemical device, the content of the compound represented by the formula (1) is preferably from 0.2 to 10% by mass, from 0.2 to 10% by mass, based on the total amount of the negative electrode mixture layer. 7% by mass, 0.2 to 5% by mass, 0.2 to 3% by mass, 0.3 to 10% by mass, 0.3 to 7% by mass, 0.3 to 5% by mass, 0.3 to 3% by mass %, 0.5 to 10% by mass, 0.5 to 7% by mass, 0.5 to 5% by mass, or 0.5 to 3% by mass.

  The negative electrode active material is not particularly limited as long as it can absorb and release lithium ions. Examples of the negative electrode active material include a carbon material, a metal composite oxide, an oxide or nitride of a Group 14 element such as tin, germanium, and silicon; a simple substance of lithium; a lithium alloy such as a lithium aluminum alloy; And the like which can form an alloy with lithium. The negative electrode active material is preferably at least one selected from the group consisting of a carbon material and a metal composite oxide from the viewpoint of safety. The negative electrode active material may be a single type of these or a mixture of two or more types. The shape of the negative electrode active material may be, for example, a particle shape.

  Examples of the carbon material include an amorphous carbon material, natural graphite, a composite carbon material in which a coating of an amorphous carbon material is formed on natural graphite, artificial graphite (a resin material such as an epoxy resin and a phenol resin, or oil, coal, etc.). Obtained by firing the pitch-based raw material obtained from the above). From the viewpoint of high current density charge / discharge characteristics, the metal composite oxide preferably contains one or both of titanium and lithium, and more preferably contains lithium.

The negative electrode active material may include an inorganic material containing at least one element selected from the group consisting of silicon and tin. The inorganic material containing at least one element selected from the group consisting of silicon and tin may be a simple substance of silicon or tin, or a compound containing at least one element selected from the group consisting of silicon and tin. The compound may be an alloy containing at least one element selected from the group consisting of silicon and tin. For example, in addition to silicon and tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver , An alloy containing at least one selected from the group consisting of titanium, germanium, bismuth, antimony, and chromium. The compound containing at least one element selected from the group consisting of silicon and tin may be an oxide, a nitride, or a carbide, and specifically, for example, silicon oxide such as SiO, SiO ₂ , and LiSiO. Material, silicon nitride such as Si ₃ N ₄ and Si ₂ N ₂ O, silicon carbide such as SiC, and tin oxide such as SnO, SnO ₂ and LiSnO. The inorganic material containing at least one element selected from the group consisting of silicon and tin may not contain a sulfur atom. That is, the inorganic material containing at least one element selected from the group consisting of silicon and tin is a material different from the compound represented by the formula (1).

  From the viewpoint of further reducing the resistance of the electrochemical device and improving the cycle characteristics, the negative electrode mixture layer 12 preferably contains a carbon material as the negative electrode active material, more preferably contains graphite, and is more preferably a carbon material. And a mixture of an inorganic material containing at least one element selected from the group consisting of silicon and tin, and particularly preferably a mixture of graphite and silicon oxide. The content of the inorganic material (silicon oxide) containing at least one element selected from the group consisting of silicon and tin in the mixture is 1% by mass or more, or 3% by mass or more based on the total amount of the mixture. And may be 30% by mass or less.

  The content of the negative electrode active material may be 80% by mass or more, or 85% by mass or more, and may be 99% by mass or less based on the total amount of the negative electrode mixture layer.

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

  The negative electrode mixture layer 12 may further contain a thickener in order to adjust the viscosity. The thickener is not particularly limited, but may be carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, salts thereof, and the like. The thickener may be one of these alone or a mixture of two or more thereof.

  When the negative electrode mixture layer 12 contains a thickener, its content is not particularly limited. The content of the thickener may be 0.1% by mass or more, and preferably 0.2% by mass or more, based on the total amount of the negative electrode mixture layer, from the viewpoint of applicability of the negative electrode mixture layer. , More preferably 0.5% by mass or more. The content of the thickener may be 5% by mass or less, preferably 3% by mass, based on the total amount of the negative electrode mixture layer, from the viewpoint of suppressing a decrease in battery capacity or an increase in resistance between the negative electrode active materials. %, More preferably 2% by mass or less.

  The present inventors have studied compounds having various structures and functional groups. As a result, by applying the compound represented by the above formula (1) to the negative electrode, the resistance of the nonaqueous electrolyte secondary battery 1 is reduced. It was evident that it was significantly reduced. The present inventors have inferred the following effects of using the compound represented by the formula (1) for the negative electrode. The compound represented by the formula (1) forms a stable and low-resistance film on the negative electrode. This suppresses an increase in resistance due to the decomposition of the electrolyte salt. As a result, the resistance of the non-aqueous electrolyte secondary battery 1 decreases. Furthermore, since the compound represented by the formula (1) itself has a skeleton containing Si, generation of gas derived from the compound is reduced, and volume expansion when the nonaqueous electrolyte secondary battery 1 is stored at a high temperature. Can also be suppressed.

  In one embodiment, the electrolytic solution contains an electrolyte salt and a non-aqueous solvent.

The electrolyte salt may be, for example, a lithium salt. Lithium salts include, for example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiB (C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , CF ₃ SO ₂ OLi, LiN (SO ₂ F) ₂ (Li [FSI], lithium bis At least one member selected from the group consisting of fluorosulfonylimide), LiN (SO ₂ CF ₃ ) ₂ (Li [TFSI], lithium bistrifluoromethanesulfonylimide), and LiN (SO ₂ CF ₂ CF ₃ ) ₂ Good. The lithium salt preferably contains LiPF ₆ from the viewpoint of more excellent solubility in a solvent, charge / discharge characteristics of a secondary battery, output characteristics, cycle characteristics, and the like.

  The concentration of the electrolyte salt is preferably 0.5 mol / L or more, more preferably 0.7 mol / L or more, and still more preferably 0.8 mol / L or more, based on the total amount of the nonaqueous solvent, from the viewpoint of excellent charge / discharge characteristics. And preferably 1.5 mol / L or less, more preferably 1.3 mol / L, and still more preferably 1.2 mol / L or less.

  Non-aqueous solvents, for example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyl lactone, acetonitrile, 1,2-dimethoxyethane, dimethoxymethane, tetrahydrofuran, dioxolan, methylene chloride, methyl acetate, etc. It may be. The non-aqueous solvent may be used alone or as a mixture of two or more thereof, and is preferably a mixture of two or more thereof.

  The electrolytic solution may further contain other materials other than the electrolyte salt and the non-aqueous solvent. Other materials may be, for example, nitrogen, sulfur, or a heterocyclic compound containing nitrogen and sulfur, a cyclic carboxylate, a fluorine-containing cyclic carbonate, or a compound having an unsaturated bond in a molecule.

  Next, a method for manufacturing the nonaqueous electrolyte secondary battery 1 will be described. The method for manufacturing the non-aqueous electrolyte secondary battery 1 includes a first step of obtaining the positive electrode 6, a second step of obtaining the negative electrode 8, and a third step of housing the electrode group 2 in the battery package 3. And a fourth step of injecting the electrolyte into the battery exterior body 3.

  In the first step, the material used for the positive electrode mixture layer 10 is dispersed in a dispersion medium using a kneader, a disperser, or the like to obtain a positive electrode mixture in a slurry form. The positive electrode 6 is obtained by coating the positive electrode current collector 9 by dipping, spraying, or the like, and then volatilizing the dispersion medium. After volatilizing the dispersion medium, a compression molding step using a roll press may be provided as necessary. The positive electrode mixture layer 10 may be formed as a positive electrode mixture layer having a multilayer structure by performing the above-described steps from application of the positive electrode mixture to volatilization of the dispersion medium a plurality of times. The dispersion medium may be water, 1-methyl-2-pyrrolidone (hereinafter, also referred to as NMP) or the like.

  The second step may be the same as the first step described above, and the method of forming the negative electrode mixture layer 12 on the negative electrode current collector 11 may be the same method as the first step described above. .

  In the third step, the electrode group 2 is formed by sandwiching the separator 7 between the prepared positive electrode 6 and negative electrode 8. Next, the electrode group 2 is accommodated in the battery exterior body 3.

  In the fourth step, the electrolytic solution is injected into the battery case 3. The electrolytic solution can be prepared, for example, by first dissolving the electrolyte salt in a solvent and then dissolving other materials.

  In another embodiment, the electrochemical device may be a capacitor. The capacitor may include an electrode group composed of a positive electrode, a negative electrode, and a separator, and a bag-shaped battery case housing the electrode group, similarly to the nonaqueous electrolyte secondary battery 1 described above. The details of each component of the capacitor may be the same as those of the nonaqueous electrolyte secondary battery 1.

  Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

(Example 1)
[Preparation of positive electrode]
Acetylene black (AB) (5% by mass) as a conductive agent is bound to lithium nickel cobalt manganate (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , 91% by mass) as a positive electrode active material. (4% by mass) were sequentially added and mixed. NMP as a dispersion medium was added to the obtained mixture and kneaded to prepare a slurry-like positive electrode mixture. A predetermined amount of this positive electrode mixture was uniformly and uniformly applied to a 20 μm-thick aluminum foil as a positive electrode current collector. Thereafter, the dispersion medium was volatilized, and then pressed to a density of 2.8 g / cm ³ by pressing to obtain a positive electrode.

[Preparation of negative electrode]
A binder and carboxymethyl cellulose as a thickener were added to graphite as a negative electrode active material. The mass ratio of the negative electrode active material: the binder: the thickener was 98: 1: 1. To the obtained mixture, 1.1% by mass (based on the total solid content of the negative electrode mixture) of compound A represented by the following formula (5) is added, and water as a dispersion medium is added and kneaded. To prepare a negative electrode mixture in the form of a slurry. A predetermined amount of this negative electrode mixture was uniformly and uniformly applied to a 10 μm-thick rolled copper foil as a negative electrode current collector. Thereafter, the dispersion medium was volatilized, and then pressed to a density of 1.6 g / cm ³ by pressing to obtain a negative electrode.

[Production of lithium ion secondary battery]
The positive electrode cut into a square of 13.5 cm ² is sandwiched between polyethylene porous sheets (trade name: Hypore (registered trademark), manufactured by Asahi Kasei Corporation, thickness: 30 μm) as a separator, and further a square of 14.3 cm ² . The electrode group was prepared by superposing the cut negative electrodes. This electrode group was housed in a container (battery exterior) formed of an aluminum laminated film (trade name: aluminum laminated film, manufactured by Dai Nippon Printing Co., Ltd.). Next, 1 mL of an electrolytic solution was added to the container, and the container was thermally welded to produce a lithium ion secondary battery for evaluation. As an electrolytic solution, a mixture solution of ethylene carbonate, dimethyl carbonate and diethyl carbonate containing 1 mol / L LiPF ₆ added with 1% by mass of vinylene carbonate (VC) based on the total amount of the mixed solution (based on the total amount of the electrolytic solution) It was used.

(Example 2)
A lithium ion secondary battery was produced in the same manner as in Example 1, except that the content of Compound A was 2.3% by mass (based on the total solid content of the negative electrode).

(Example 3)
Lithium was prepared in the same manner as in Example 1 except that Compound B represented by the following formula (6) was added in an amount of 0.3% by mass (based on the total solid content of the negative electrode mixture) in place of Compound A. An ion secondary battery was manufactured.

(Comparative Example 1)
A lithium ion secondary battery was fabricated in the same manner as in Example 1 except that Compound A was not used.

[Initial charge / discharge]
For the lithium ion secondary batteries of Examples 1 to 3 and Comparative Example 1, the initial charge / discharge was performed by the following method. First, under an environment of 25 ° C., constant current charging was performed up to an upper limit voltage of 4.2 V at a current value of 0.1 C, and then constant voltage charging was performed at 4.2 V. The charge termination condition was a current value of 0.01C. Thereafter, a constant current discharge at a final voltage of 2.5 V was performed at a current value of 0.1 C. This charge / discharge cycle was repeated three times ("C" used as a unit of the current value means "current value (A) / battery capacity (Ah)").

[Resistance measurement by AC impedance measurement (upper limit voltage 4.2V)]
After the initial charge and discharge, the resistance of the lithium ion secondary batteries of Examples 1 to 3 and Comparative Example 1 was evaluated by AC impedance measurement. The prepared lithium ion battery was subjected to constant current charging at a current value of 0.1 C up to an upper limit voltage of 4.2 V in a 25 ° C. environment, followed by constant voltage charging at 4.2 V. The charge termination condition was a current value of 0.01C. The resistance of these lithium ion secondary batteries was measured in an environment of 25 ° C. with an amplitude of 10 mV and a frequency range of 20 mHz to 200 kHz using an AC impedance measurement device (Type 1260, manufactured by Solartron). FIG. 3 shows the measurement results.

  As shown in FIG. 3, the lithium ion secondary batteries of Examples 1 to 3 using the negative electrodes containing a predetermined amount of the compound A and the compound B are the lithium ion secondary batteries of Comparative Example 1 using the negative electrode not containing the compound A or the compound B. The resistance was lower than that of the ion secondary battery. Although this mechanism is not always clear, it is considered that the resistance of the battery was reduced because the compound A and the compound B formed a low-resistance film on the negative electrode.

  1: Non-aqueous electrolyte secondary battery (electrochemical device), 6: Positive electrode, 7: Separator, 8: Negative electrode.

Claims (10)

Comprising a negative electrode current collector and a negative electrode mixture layer,
The negative electrode, wherein the negative electrode mixture layer contains a compound represented by the following formula (1).

[In the formula (1), R ^{1 to} R ³ each independently represent an alkyl group or a fluorine atom, R ⁴ represents an alkylene group, and R ⁵ represents an organic group containing a sulfur atom. ]   The negative electrode according to claim 1, wherein the number of silicon atoms in one molecule of the compound represented by the formula (1) is one. 3. The negative electrode according to claim 1, wherein R ⁵ is a group represented by any of the following formulas (2), (3), and (4). 4.

[In the formula (2), R ⁶ represents an alkyl group, and * represents a bond. ]

[In the formula (3), R ⁷ represents an alkyl group, and * represents a bond. ]

[In the formula (4), R ⁸ represents an alkyl group, and * represents a bond. ] The negative electrode according to claim 1, wherein at least one of R ^{1 to} R ³ is a fluorine atom.   The negative electrode according to any one of claims 1 to 4, wherein the content of the compound represented by the formula (1) is 10% by mass or less based on the total amount of the negative electrode mixture layer.   The negative electrode according to any one of claims 1 to 5, wherein the negative electrode mixture layer further contains a carbon material.   The negative electrode according to claim 6, wherein the carbon material contains graphite.   The negative electrode according to any one of claims 1 to 7, wherein the negative electrode mixture layer further contains an inorganic material containing at least one element selected from the group consisting of silicon and tin.   An electrochemical device comprising a positive electrode, the negative electrode according to any one of claims 1 to 8, and an electrolytic solution. The electrochemical device according to claim 9, wherein the electrochemical device is a non-aqueous electrolyte secondary battery or a capacitor.

Images