JP2012209218A - Method for manufacturing lithium ion secondary battery, and lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery high in discharge capacity and excellent in capacity retention ratio, and a method for manufacturing the lithium ion secondary battery.SOLUTION: A lithium ion secondary battery at least includes: a negative electrode including a carbon material 100; a gel electrolyte; and a positive electrode. The carbon material 100 has a hollow structure involving mutually connected pores, where a void 102 comprising a plurality of connected pores penetrates in the thickness direction, and contains metal 103 capable of forming an alloy with lithium, inside of the void. A method for manufacturing the lithium ion secondary battery at least includes: a first step of impregnating the carbon material 100 with a nonaqueous electrolyte; and a second step of arranging the gel electrolyte between the negative electrode and the positive electrode after the first step.

Description

  The present invention relates to a method for producing a lithium ion secondary battery and a lithium ion secondary battery.

Carbon materials made of carbonaceous fired bodies are used for electrode materials such as lithium ion secondary batteries, electric double layer capacitors, and capacitors. For example, in a lithium ion secondary battery, a carbon material is used as the negative electrode active material, and lithium ions are occluded (intercalated) in the carbon material when the battery is charged, and desorbed (deintercalated) when discharged. "Rocking chair type" battery configuration is adopted.

  On the other hand, in recent years, electronic devices have been rapidly reduced in size or performance, and there has been an increasing demand for higher energy density of lithium ion secondary batteries. However, since graphite constituting the carbon material has a theoretical lithium ion storage / release capacity limited to 372 mAh / g, a negative electrode material having a larger lithium ion storage / release capacity is required.

  Therefore, a method using a silicon material instead of a carbon material having a low charge / discharge capacity has been studied. However, the silicon material has a problem that the volume change due to charging / discharging is large and the electrode material may be damaged by performing continuous charging / discharging. Therefore, carbon-silicon composite materials are being studied. However, even with these carbon-silicon composite materials, the problem of material breakage due to volume change has not been sufficiently solved. On the other hand, a negative electrode material using a carbon material having a specific hollow structure and containing a metal capable of forming an alloy with lithium as a negative electrode active material has been proposed, and high charge / discharge as a lithium ion secondary battery is proposed. It has been disclosed that efficiency and durability can be realized (see Patent Document 1).

International Publication No. 10/074243 Pamphlet

Although the lithium ion secondary battery described in Patent Document 1 is excellent in charge and discharge efficiency and durability, further enhancement of performance is strongly desired.
This invention is made | formed in view of the said situation, and makes it a subject to provide the lithium ion secondary battery which was large in discharge capacity, and was excellent in the capacity | capacitance maintenance factor, and its manufacturing method.

The method for producing a lithium ion secondary battery according to claim 1 of the present invention is a method for producing a lithium ion secondary battery comprising at least a negative electrode containing a carbon material, a gel electrolyte, and a positive electrode, wherein the carbon material Has a continuous cell hollow structure in which a void formed by connecting a plurality of holes is penetrated in the thickness direction, and contains a metal capable of forming an alloy with lithium in the void. It has at least a first step of impregnating with a non-aqueous electrolyte and a second step of arranging the gel electrolyte between the negative electrode and the positive electrode after the first step.
According to Claim 2 of the present invention, in the method for producing a lithium ion secondary battery according to Claim 1, the carbon material is a continuum of particles formed by contacting carbon particles with each other, and the carbon particles The non-contact site | part of mutual forms the said cavity part, It is characterized by the above-mentioned.
The method for producing a lithium ion secondary battery according to claim 3 of the present invention is characterized in that, in claim 1 or 2, the negative electrode further contains a binder resin.
The method for producing a lithium ion secondary battery according to claim 4 of the present invention is the method according to any one of claims 1 to 3, wherein the negative electrode further comprises graphite, carbon black, carbon nanotube, graphene, and fullerene. It contains one or more conductive aids selected from the group consisting of:
The method for producing a lithium ion secondary battery according to claim 5 of the present invention is the gel electrolyte according to any one of claims 1 to 4, wherein the gel electrolyte is formed on the surface of the negative electrode or the positive electrode in the second step. The raw material solution is applied, the applied raw material solution is dried and gelled to obtain the gel electrolyte, and the obtained gel electrolyte is sandwiched between the positive electrode and the negative electrode.
The method for producing a lithium ion secondary battery according to claim 6 of the present invention is the method according to any one of claims 1 to 4, wherein the gel is formed on the surface of the negative electrode or the positive electrode in the second step. A separator impregnated with a raw material liquid for electrolyte is placed, and the raw material liquid in the separator is dried and gelled to obtain the gel electrolyte, and the obtained gel electrolyte is divided into the positive electrode and the negative electrode. It is characterized by pinching.
The method for producing a lithium ion secondary battery according to claim 7 of the present invention is characterized in that, in claim 5 or 6, the raw material liquid is heated in the second step.
The method for producing a lithium ion secondary battery according to claim 8 of the present invention is the method according to any one of claims 1 to 7, wherein the gel electrolyte includes a non-aqueous electrolyte, and the carbon material is used in the first step. The non-aqueous electrolyte to be impregnated into the gel and the non-aqueous electrolyte contained in the gel electrolyte have the same composition.
A lithium ion secondary battery according to a ninth aspect of the present invention is manufactured by the method for manufacturing a lithium ion secondary battery according to any one of the first to eighth aspects.

  According to the method for manufacturing a lithium ion secondary battery of the present invention, nonaqueous electrolysis is performed in the continuous hollow structure of the carbon material by including a nonaqueous electrolyte in the carbon material included in the negative electrode in the first step. The liquid can be sufficiently penetrated. Further, in the second step, by covering the surface of the negative electrode with the gel electrolyte, it is possible to prevent the nonaqueous electrolytic solution permeated into the carbon material from being lost by evaporation. As a result, in the negative electrode of the manufactured lithium ion secondary battery, the diffusion efficiency of lithium ions is increased, and the effective value of the discharge capacity of the lithium ion secondary battery can be made close to the theoretical value. The maintenance rate can be increased.

It is a schematic diagram which illustrates the carbon material in this invention. It is typical sectional drawing which illustrates the lithium ion secondary battery in this invention.

Hereinafter, the present invention will be described in detail.
<< Method for producing lithium ion secondary battery >>
The present invention is a method for producing a lithium ion secondary battery comprising at least a negative electrode containing a carbon material, a gel electrolyte, and a positive electrode.
The carbon material has a continuous cell hollow structure in which a void formed by connecting a plurality of holes penetrates in the thickness direction, and contains a metal capable of forming an alloy with lithium in the void.
The carbon material, the negative electrode, the gel electrolyte, and the positive electrode will be described in detail later.
The method for producing a lithium ion secondary battery according to the present invention includes a first step of impregnating the carbon material with a nonaqueous electrolyte, and the gel between the negative electrode and the positive electrode after the first step. And a second step of disposing an electrolyte.

<First step>
In the first step, the carbon material contained in the negative electrode is impregnated (included) with the non-aqueous electrolyte solution. The non-aqueous electrolyte solution can be infiltrated into the open cell hollow structure constituting the carbon material. The method is not particularly limited. For example, a method of applying the non-aqueous electrolyte to the carbon material or the negative electrode, a method of spraying the non-aqueous electrolyte to the carbon material or the negative electrode (spray method), the carbon material or the negative electrode A method of dipping the electrode in the non-aqueous electrolyte (dipping method) can be mentioned.

  In the dipping method, the nonaqueous electrolytic solution is more sufficiently obtained by ultrasonically treating or heating the nonaqueous electrolytic solution with the carbon material or the negative electrode immersed in the nonaqueous electrolytic solution. The carbon material can be penetrated into the solid cell hollow structure.

<Second step>
In the second step, as the method of arranging the gel electrolyte between the negative electrode and the positive electrode, the gel electrolyte is in contact with the surface of the negative electrode, and the gel electrolyte is on the surface of the positive electrode. If it is the method of arrange | positioning so that it may contact, it will not restrict | limit in particular.

As the method of arranging, for example, a gel electrolyte raw material liquid is applied to the surface of the negative electrode and / or the surface of the positive electrode, and this is gelled by a drying treatment or a heating treatment, and the gel. A method of fixing the electrolyte by sandwiching the electrolyte between the negative electrode and the positive electrode is preferable. Since the surface of the gel electrolyte usually has adhesiveness, the gel electrolyte can be easily fixed to the surface of the negative electrode and the surface of the positive electrode. In this manner, the negative electrode and the positive electrode are electrochemically connected with the gel electrolyte interposed therebetween, thereby functioning as a lithium ion secondary battery.
The gelation may be performed after the raw material liquid is applied and disposed between the negative electrode and the positive electrode. That is, after applying a raw material liquid for gel electrolyte on the surface of the negative electrode and / or the surface of the positive electrode, the applied raw material liquid is disposed between the negative electrode and the positive electrode, Then, it may be gelled and the raw material liquid may be used as a gel electrolyte.

As another method of arranging, for example, a separator impregnated with a raw material solution for gel electrolyte is placed (placed) on the surface of the negative electrode and / or the surface of the positive electrode, and this is dried. A method of gelling by a treatment or a heating treatment and fixing the separator containing the gel electrolyte between the negative electrode and the positive electrode is preferable. Since the surface of the gel electrolyte is usually sticky, the separator containing the gel electrolyte can be easily fixed on the surface of the negative electrode and the surface of the positive electrode. In this manner, the negative electrode and the positive electrode are electrochemically connected with the separator containing the gel electrolyte interposed therebetween, thereby functioning as a lithium ion secondary battery.
The gelation may be performed after a separator impregnated with the raw material liquid is disposed between the negative electrode and the positive electrode. That is, after a separator impregnated with a gel electrolyte raw material liquid is placed on the surface of the negative electrode and / or the surface of the positive electrode, the separator is interposed between the negative electrode and the positive electrode. The material solution may be used as a gel electrolyte.

[Carbon material]
The carbon material has an open cell hollow structure in which a gap formed by connecting a plurality of holes penetrates in the thickness direction. Here, the open cell hollow structure refers to a structure in which the voids are arbitrarily extended in a three-dimensional direction to be porous in the entire area of the carbon material. The gap portion also has portions that intersect each other. And in the said carbon material, it has the structure which penetrated in the thickness direction between two points where many said space | gap parts differ. Here, the thickness direction corresponds to the movement direction of lithium ions (Li ⁺ ) in the lithium ion secondary battery.
Such a continuous hollow structure can be confirmed by, for example, imaging data obtained by an electron microscope in a cross section of the carbon material.

  Examples of the preferable carbon material include those in which the continuous cell hollow structure is a continuous body of particles formed by contacting carbon particles with each other. The continuum of carbon particles refers to those formed by gathering a large number of carbon particles, and the average particle diameter of the carbon particles is preferably 1 nm to 200 nm. In such a continuous body of carbon particles, a non-contact portion between the carbon particles forms the void.

  The carbon material is preferably in the form of particles having the voids. In this case, the average particle diameter of the carbon material is preferably 10 nm to 1 mm, and more preferably 1000 nm to 500 μm. By setting it to the lower limit value or more, in the method for producing a carbon material described later, coalescence during firing is suppressed and single particles can be easily formed. Moreover, by setting it as below an upper limit, negative electrode material can be shape | molded more easily to a desired shape and magnitude | size.

The carbon material contains a metal capable of forming an alloy with lithium in the void (hereinafter, simply referred to as “metal”).
Examples of the metal include silicon (Si), tin (Sn), magnesium (Mg), titanium (Ti), vanadium (V), cadmium (Cd), selenium (Se), iron (Fe), cobalt (Co), Examples thereof include simple metals such as nickel (Ni), manganese (Mn), platinum (Pt), and boron (B), and alloys composed of two or more of these. Among these, silicon or tin is preferable and silicon is more preferable because lithium ion storage / release capacity is particularly high.
The metals may be used alone or in combination of two or more, and in the case of two or more, the combination and ratio may be appropriately selected according to the purpose.

  The metal is preferably in the form of particles, and the average particle diameter is preferably 1 μm or less. By setting it to 1 μm or less, the lithium ion storage / release capacity of the carbon material is further improved.

It is preferable that the surface of the metal is treated with a pigment dispersant. By doing in this way, the dispersibility in a monomer containing mixture improves in the manufacturing method of the carbon material mentioned later, and the negative electrode material of a more favorable characteristic is obtained.
Examples of the pigment dispersant include a high molecular weight polyester acid amidoamine salt, an acrylic polymer, an aliphatic polyvalent carboxylic acid, a polyester amine salt, polyvinyl alcohol, polyvinylpyrrolidone, and methylcellulose.

The lower limit of the content of the metal in the carbon material is preferably 1% by mass, and preferably 5% by mass. By setting it as such a range, the lithium ion occlusion-release capacity | capacitance of a carbon material becomes higher.
Further, the carbon material has a higher lithium ion storage / release capacity as the content of the metal is larger, but the upper limit of the content of the metal is preferably 95% by mass. By setting it as such a range, the influence of the volume change of the said metal at the time of continuous charging / discharging becomes small, and the higher effect which suppresses the failure | damage of a carbon material is acquired. Further, the conductivity is further improved.

The carbon material preferably has a porosity of 5 to 95%. By setting it to the lower limit value or more, the effect of reducing the influence of the volume change of the metal at the time of continuous charge / discharge is increased, and a higher effect of suppressing the breakage of the carbon material is obtained. Moreover, the intensity | strength and electroconductivity of a carbon material improve more by setting it as an upper limit or less.
The porosity of the carbon material can be calculated by, for example, the Archimedes method from the specific gravity measured by a pycnometer true density measuring instrument or the like.

As an embodiment of the carbon material, FIG. 1 illustrates a schematic diagram of a continuum of particles formed by contacting carbon particles with each other.
The carbon material 100 shown here is in the form of particles and is a continuous body of fine carbon particles 101, and the voids 102 are formed from non-contact portions between the carbon particles 101. Similarly, the void 102 is formed by connecting a plurality of holes formed from non-contact sites between the carbon particles 101. Further, a large number of voids 102, 102,... Penetrate in the thickness direction of the carbon material 100. Further, a metal 103 that can form an alloy with lithium is contained in the gap 102. However, the carbon material 100 is just an example of the carbon material in the present invention, and the carbon material is not limited to this.

The carbon material includes, for example, a step of preparing a monomer-containing mixture by mixing a monomer, an organic solvent and the metal, a step of preparing a suspension by dispersing the monomer-containing mixture in an aqueous phase, In a suspension, a production method comprising: polymerizing the monomer in the mixture to prepare resin particles; and firing the resin particles, wherein the monomer and the organic solvent are the resin Can be produced by a production method characterized by low compatibility.
Hereinafter, the method for producing the carbon material will be described more specifically.

  “The monomer and the organic solvent have low compatibility with the resin” means that the difference between the solubility parameter (SP value) of the monomer and the organic solvent and the solubility parameter (SP value) of the resin is 1. .5 or more. Here, the “solubility parameter (SP value)” is a value defined as the square root of the intermolecular bond energy (a value obtained by subtracting the energy of gas from the latent heat of vaporization) of 1 mL of solvent at 25 ° C. It means a value that can be calculated by the Fedors equation.

In the method for producing the carbon material, first, a monomer, an organic solvent, and the metal are mixed to prepare a monomer-containing mixture.
The monomer constitutes a resin by polymerization described later, and constitutes a carbon component of the carbon material after firing.
Examples of the monomer include divinylbenzene, vinyl chloride, acrylonitrile and the like.
The said monomer may be used individually by 1 type, and may use 2 or more types together. When two or more kinds are used in combination, the combination and ratio may be appropriately selected according to the purpose. For example, a carbon material can be easily obtained by using only one kind.

The organic solvent functions as a hollow agent and forms voids in the carbon material.
The organic solvent may be appropriately selected according to the type of the monomer. For example, when divinylbenzene is used as the monomer, a linear hydrocarbon such as n-heptane or an alicyclic carbonization such as cyclohexane is used. Hydrogen or the like is preferred.
The said organic solvent may be used individually by 1 type, and may use 2 or more types together. When two or more kinds are used in combination, the combination and ratio may be appropriately selected according to the purpose.

  In the monomer-containing mixture, the content of the organic solvent is preferably 20 to 150 parts by mass, more preferably 40 to 130 parts by mass, per 100 parts by mass of the monomer. By making the lower limit value or more, a carbon material having a more sufficiently formed void is obtained, and as a result, the effect of mitigating the influence of volume change of the metal during continuous charge and discharge is increased, and the carbon material is damaged. A higher effect can be obtained. Moreover, the intensity | strength of a carbon material improves more by setting it as below an upper limit, and a shape can be maintained more stably.

  When using a metal whose surface is treated with a pigment dispersant, the pigment dispersant may be added to the monomer mixture together with the metal.

In the monomer-containing mixture, the lower limit value of the metal content is preferably 1 part by mass and more preferably 3 parts by mass per 100 parts by mass of the monomer content. By setting it as such a range, the lithium ion occlusion-release capacity | capacitance of a carbon material becomes higher.
Further, in the monomer-containing mixture, the metal has a higher lithium ion storage / release capacity as the content increases, but the upper limit of the metal content is 95 parts by mass per 100 parts by mass of the monomer. It is preferable that By setting it as such a range, the effect of the volume change of the said metal becomes small at the time of continuous charging / discharging, and the higher effect which suppresses the damage of a carbon material is acquired. Further, the conductivity is further improved.

Examples of the polymerization initiator used for the polymerization of the monomer include known ones such as organic peroxides, azo compounds, metal ion redox initiators, photopolymerization initiators, and persulfates.
The content of the polymerization initiator in the monomer-containing mixture is not particularly limited, and may be adjusted as appropriate. If the content is too small, the polymerization of the monomer may be insufficient and a carbon material may not be formed. If the content is too large, the molecular weight of the resin will not increase, and post-treatment of the resulting carbon material will be hindered. Sometimes.

The monomer-containing mixture may further contain other additives in addition to the monomer, the organic solvent, the metal, and the polymerization initiator.
Examples of the additive include conductive assistants such as graphite, carbon black, carbon nanotubes, graphene, and fullerene. By containing the conductive aid, the carbon material obtained is more improved in conductivity. In particular, when the monomer-containing mixture contains graphite, the graphite not only functions as a conductive additive but also has an effect of increasing the discharge capacity.
The said additive may be used individually by 1 type, and may use 2 or more types together. When two or more kinds are used in combination, the combination and ratio may be appropriately selected according to the purpose.

  The monomer-containing mixture can be prepared, for example, by adding the monomer, an organic solvent, a metal, a polymerization initiator, and an additive as necessary, and mixing by a known means such as ultrasonic dispersion.

In the production method, the monomer-containing mixture is then dispersed in an aqueous phase to prepare a suspension. The monomer-containing mixture is dispersed as oil droplets.
Examples of the aqueous medium (aqueous solvent) constituting the aqueous phase include water, alcohols, ketones (excluding lactones) and the like.
The aqueous medium may be one kind or two or more kinds. In the case of two kinds or more, the combination and ratio may be appropriately selected according to the purpose.

The aqueous medium preferably contains, for example, a dispersant such as polyvinyl alcohol, methyl cellulose, polyvinyl pyrrolidone, insoluble inorganic fine particles, or a polymer surfactant that does not fall under this category.
The dispersant may be only one kind, or two or more kinds. In the case of two or more kinds, the combination and ratio may be appropriately selected according to the purpose.

  The suspension is prepared by, for example, adding the monomer-containing mixture to an aqueous medium and stirring with a stirring device such as a homogenizer, a static static mixer, an ultrasonic mixer, an ultrasonic homogenizer, a shirasu porous filter, or a stirring blade. Can be prepared. At this time, by adjusting the stirring conditions, the size of the oil droplets of the monomer-containing mixture in the suspension can be controlled, and as a result, the particle diameter of the resulting carbon material can be adjusted.

In the carbon material manufacturing method, resin particles are then prepared by polymerizing the monomers in the mixture in the suspension.
The polymerization conditions of the monomer may be appropriately adjusted in consideration of the raw materials to be used. For example, a method in which the suspension is stirred at 30 to 95 ° C. in a nitrogen stream for about 1 to 50 hours can be exemplified.
The obtained resin particles are separated from the suspension and may be used in the subsequent steps through operations such as washing with water, drying, and classification.

In the carbon material manufacturing method, the resin particles are then fired.
The firing conditions may be appropriately selected according to the type of resin particles. Examples of preferable firing temperatures include three types of 1000 ° C. or lower, 1000 to 2500 ° C., and 2500 ° C. or higher.
When the firing temperature is 1000 ° C. or lower, the negative electrode material obtained from such a carbon material has a very high lithium ion storage / release capacity, and the lithium ion secondary battery has a higher output although the output may vary. Output is obtained.
When the firing temperature is 1000 to 2500 ° C., the negative electrode material obtained from such a carbon material has more stable output characteristics and high durability, although the lithium ion storage / release capacity may decrease.
When the firing temperature is 2500 ° C. or higher, the negative electrode material obtained from such a carbon material has an extremely high lithium ion storage / release capacity, and the lithium ion secondary battery can obtain higher output.

  The carbon material obtained by firing the resin particles has an open cell hollow structure, and has a high lithium occlusion / release capacity by containing the metal capable of forming an alloy with lithium in the void. Further, the effect of alleviating the influence of the volume change of the metal during continuous charge / discharge is enhanced, and an excellent effect of suppressing breakage of the carbon material is obtained. In the carbon material, the volume change of the metal occurs during continuous charge / discharge, but it is presumed that the breakage of the carbon material is suppressed because the solid cell hollow structure disperses and absorbs the stress caused by the volume change. .

[Negative electrode]
In this invention, a negative electrode contains the said carbon material, and can be set as the structure similar to the conventional negative electrode except this point. For example, the negative electrode material containing the carbon material may be laminated on a copper (Cu) plate or the like. Hereinafter, the laminated negative electrode material may be referred to as a negative electrode active material layer.

Preferred examples of the negative electrode material include those containing the carbon material and a binder resin.
The binder resin functions as a binder for bonding the carbon materials, and by using the binder resin, the carbon material can be formed into an arbitrary shape.
Examples of the binder resin include polyvinylidene fluoride and styrene butadiene rubber.
Although the usage-amount of the said binder resin is not specifically limited, It is preferable that it is 3-50 mass parts with respect to 100 mass parts of carbon materials. By using more than a lower limit, the effect which uses binder resin is fully acquired, and the electroconductivity of negative electrode material improves more by setting it as an upper limit or less.

The negative electrode material preferably further contains a conductive additive. By including the conductive assistant, the conductivity of the negative electrode material is further improved.
Examples of the conductive aid include graphite, carbon black, carbon nanotube, graphene, and fullerene.
The conductive auxiliary agent may be one kind or two or more kinds. In the case of two or more kinds, the combination and ratio may be appropriately selected according to the purpose.

In the negative electrode material (excluding the organic solvent at the time of preparing the mixture described later), the content of the conductive auxiliary agent is preferably 1 to 90% by mass. By setting it to the lower limit value or more, a more sufficient conductivity improvement effect can be obtained, and by setting the upper limit value or less, the lithium ion storage / release capacity of the negative electrode material becomes higher.
In addition, the function of the binder which couple | bonds carbon materials may be exhibited by mix | blending the said conductive support agent more than predetermined amount. In this case, higher conductivity can be obtained by reducing the amount of the binder resin used.

The negative electrode material can be produced, for example, by mixing the carbon material, a conductive additive, a binder resin and the like and then molding the obtained mixture. And the said mixture may contain the organic solvent so that shaping | molding may become easy.
The organic solvent is preferably one that can dissolve the binder resin, and examples thereof include N-methylpyrrolidone and N, N-dimethylformamide.
In the case of using a mixture containing the organic solvent, for example, the mixture may be applied or laminated at a predetermined location, and then the organic solvent may be removed and dried to form a desired shape.

[Non-aqueous electrolyte]
In the present invention, the non-aqueous electrolytic solution is an electrolytic solution containing a non-aqueous solvent and an electrolyte salt, and can be infiltrated into the carbon material. There is no particular limitation as long as the performance of the carbon material is not impaired, and an electrolytic solution used in a conventional lithium ion secondary battery can be used.

  The non-aqueous solvent refers to a solvent that does not substantially contain an aqueous solvent such as water and alcohol, and is preferably an organic solvent. Here, the content of water and alcohol in the non-aqueous solvent is preferably 1% by volume or less, more preferably 0.5% by volume or less, still more preferably 0.1% by volume or less, and 0.01% by volume or less. Is particularly preferable, and 0.001% or less is most preferable.

Examples of the non-aqueous solvent include lactone compounds such as γ-butyrolactone; carbonate ester compounds such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; carboxylic acids such as methyl formate, methyl acetate, and methyl propionate. Ester compounds; ether compounds such as tetrahydrofuran and dimethoxyethane; ether compounds such as tetrahydrofuran and dimethoxyethane; nitrile compounds such as acetonitrile; sulfone compounds such as sulfolane; amide compounds such as dimethylformamide; Among these non-aqueous solvents, those having high solubility of the electrolyte salt are preferable. Tetrahydrofuran (THF), dimethyl carbonate (DMC), and acetonitrile, which have high lithium salt solubility described later, are preferably used.
The non-aqueous solvent may be used singly or in combination of two or more. In the case of two or more, the combination and ratio may be appropriately selected according to the purpose. Good.

As the electrolyte salt, an electrolyte salt used in an electrolytic solution of a conventional lithium ion secondary battery can be used. For example, bis (trifluoromethylsulfonyl) imide lithium (LiN (SO ₂ CF ₃ ) ₂ ), Lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), lithium boron tetrafluoride (LiBF ₄ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium hexafluoroantimonate (LiSbF _6), hexafluoroarsenate arsenate periodate lithium (LiAsF _6), lithium tetraphenylborate _{(LiB (C 6 H 5)} 4) can be exemplified.
The said lithium salt may be used individually by 1 type, and may use 2 or more types together. When two or more kinds are used in combination, the combination and ratio may be appropriately selected according to the purpose.

  The concentration of the lithium salt in the electrolytic solution is preferably 0.05 to 10 mol / L, and more preferably 0.1 to 5 mol / L.

  The non-aqueous electrolyte preferably contains lithium bis (oxalate) borate (abbreviated as “LiBOB”) and / or fluoroethylene carbonate (abbreviated as “FEC”). By using LiBOB or FEC, the durability of the negative electrode material is significantly improved without impairing the charge / discharge efficiency of the lithium ion secondary battery according to the present invention.

  The total content of LiBOB and FEC in the electrolyte is a molar ratio of [total number of moles of LiBOB and FEC] / [total number of moles of lithium atoms] with respect to the total amount of lithium atoms in the lithium salt contained. Preferably satisfies 0.05 to 0.5, more preferably 0.1 to 0.4. By setting the lower limit value or more, the durability of the negative electrode material is further improved. Moreover, LiBOB and FEC can be more stably dissolved in electrolyte solution by setting it as below an upper limit.

  The non-aqueous electrolyte can be prepared by appropriately blending, for example, a lithium salt and an organic solvent, and LiBOB and / or FEC as necessary. Each condition such as the order of addition, temperature, time and the like at the time of blending each component can be arbitrarily adjusted according to the type of the blended component.

The nonaqueous electrolytic solution preferably constitutes the gel electrolyte. That is, it is preferable that the non-aqueous electrolyte is contained in the polymer matrix in the gel electrolyte.
In the production of the lithium ion secondary battery of the present invention, the composition of the non-aqueous electrolyte contained in the carbon material is preferably the same as or close to the composition of the non-aqueous electrolyte contained in the gel electrolyte. After the lithium ion secondary battery is assembled, the carbon material and the gel electrolyte are in contact with each other, so that the non-aqueous electrolyte and / or the electrolyte salt contained in both are mixed by diffusion. At the time of this mixing, it is preferable that the composition of the non-aqueous electrolyte contained in both is the same or close, so that the compatibility is excellent and unnecessary chemical reaction can be prevented from occurring.

  Here, that one nonaqueous electrolytic solution and the other nonaqueous electrolytic solution are “approximate” means that the solvents of at least both of the nonaqueous electrolytic solutions are the same type. In addition to the same solvent type, if the electrolyte types dissolved in both non-aqueous electrolytes are the same and the electrolyte concentrations are different, both non-aqueous electrolytes are It is more approximate. ”

[Gel electrolyte]
The gel electrolyte is a gel electrolyte, and includes a non-aqueous electrolyte and / or an electrolyte salt in a polymer matrix constituting the gel.
As the gel electrolyte in the present invention, a gel electrolyte (solid electrolyte) used in a conventional lithium ion secondary battery can be used.
The gel electrolyte can be produced by applying a raw material solution containing the non-aqueous electrolyte and the polymer matrix to a substrate.
In addition, when the said raw material liquid contains the dilution solvent, after apply | coating or impregnating this raw material liquid to a base material, it can be gelatinized by volatilizing a dilution solvent.

In the method for producing a lithium ion secondary battery according to the present invention, the gel electrolyte disposed between the electrodes in the second step is to apply the raw material liquid on the surface of the negative electrode or the positive electrode, and to gel the gel. May be used as a gel electrolyte, or a gel electrolyte previously gelled may be disposed on the surface of the negative electrode or the positive electrode.
It is preferable to apply the raw material liquid to the electrode surface and gel the electrode liquid on the electrode surface because the adhesion between the gel electrolyte and the electrode surface is increased. In the second step, it is preferable to warm the raw material liquid when applying the raw material liquid. By heating, the viscosity of the raw material liquid temporarily decreases, and the raw material liquid can be uniformly applied to the coated surface (coating property can be improved).

  The temperature of the heating is not particularly limited, and may be appropriately adjusted within a temperature range in which components contained in the raw material liquid are not decomposed. For example, what is necessary is just to heat in the range of 40-90 degreeC.

  The raw material liquid may be applied as it is to the electrode surface, or a material made by impregnating the raw material liquid into a separator made of a nonwoven fabric or a resin porous sheet may be placed on the electrode surface. In any method, the gel electrolyte can be formed on the electrode surface by gelation.

Although the content rate of the nonaqueous solvent contained in the gel electrolyte gelled by the drying is not particularly limited, it may be, for example, 50 to 99% by mass. In this range, the content is preferably 60 to 98% by mass. By setting the lower limit value or more, the mobility of lithium ions in the gel electrolyte can be further increased. By setting it to the upper limit or less, it becomes easier to increase the structural strength (elasticity) of the gel electrolyte and maintain the shape of the membrane autonomously.
The strength of the gel electrolyte tends to decrease as the content of the nonaqueous solvent of the gel electrolyte increases. Moreover, there exists a tendency for the adhesiveness of the surface of the said gel electrolyte to increase, so that the said content rate of the nonaqueous solvent of the said gel electrolyte is high.

  As the separator, a separator used in a conventional lithium ion secondary battery can be used. The material of the separator is not particularly limited, and for example, polyolefin resin (polypropylene, polyethylene, etc.), polyester resin, polyimide resin, glass fiber, etc. are used.

The polymer matrix is not particularly limited, and those that satisfy the following conditions (i) to (iii) are preferable.
(I) A raw material liquid can be formed by blending with the non-aqueous electrolyte, and the viscosity of the raw material liquid can be increased. (Ii) The raw material liquid is gelled by evaporating the non-aqueous solvent from the raw material liquid. What can be made (iii) What is difficult to chemically react with the non-aqueous electrolyte As such a polymer matrix, for example, a polymer obtained by polymerizing a compound having a polymerizable unsaturated bond is preferred. It is done. More specifically, for example, polyvinylidene fluoride (PVDF), PVDF-hexafluoropropylene copolymer (PVDF-HFP), polyacrylonitrile, alkylene ethers such as polyethylene oxide and polypropylene oxide, polyester, polyamine, polyphosphazene, and Polysiloxane etc. are mentioned.

  As a density | concentration of the said polymer matrix in the said raw material liquid, 1-40 mass% is preferable, 3-30 mass% is more preferable, and 5-20 mass% is still more preferable. By being more than a lower limit, the viscosity and coating property of the said raw material liquid can be improved, and it can be made to gelatinize by drying the said raw material liquid. By being below an upper limit, it can prevent that the viscosity of a raw material liquid increases too much, and it is easy to obtain favorable coating property.

The raw material liquid can be prepared by appropriately blending, for example, a lithium salt, a non-aqueous solvent (organic solvent), a polymer, and LiBOB and / or FEC as necessary. The raw material solution is preferably prepared by appropriately blending the non-aqueous electrolyte and the polymer. That is, the raw material liquid is preferably prepared by blending the non-aqueous electrolyte.
Each condition such as the order of addition, temperature, time and the like at the time of blending each component can be arbitrarily adjusted according to the type of the blended component.

[Positive electrode]
In the present invention, the positive electrode can have the same configuration as the positive electrode in a conventional lithium ion secondary battery. For example, a positive electrode material containing a lithium compound may be stacked on an aluminum (Al) plate. Hereinafter, the laminated positive electrode material may be referred to as a positive electrode active material layer.

Preferred examples of the positive electrode material include those containing the lithium compound and a binder resin.
The binder resin functions as a binder that holds the lithium compound in the positive electrode material, and by using this, the positive electrode material can be formed into an arbitrary shape.
Examples of the binder resin include polyvinylidene fluoride and styrene butadiene rubber.
Although the usage-amount of the said binder resin is not specifically limited, It is preferable that it is 3-30 mass parts with respect to 100 mass parts of lithium compounds. By using more than a lower limit, the effect which uses binder resin is acquired more fully, and the electroconductivity of positive electrode material improves more by setting it as an upper limit or less.

The lithium compound is not particularly limited, and a lithium compound used for a positive electrode of a conventional lithium ion secondary battery can be used. Examples thereof include transition metal oxides such as lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium manganate (LiMn ₂ O ₄ ), and olivine type lithium iron phosphate (LiFePO ₄ ).
As content of the lithium compound in the said positive electrode material (except the organic solvent at the time of the mixture preparation mentioned later), 10-98 mass% is preferable, for example, 70-98 mass% is more preferable, and 80-98 mass% is further. preferable. By setting the lower limit value or more, the amount of lithium ions in the electrolyte can be made more sufficient. By setting the upper limit value or less, other components such as a binder resin for forming the positive electrode active material layer are contained. can do.

The positive electrode material preferably further contains a conductive additive. By including the conductive assistant, the conductivity of the positive electrode material is further improved.
Examples of the conductive aid include graphite, carbon black, carbon nanotube, graphene, and fullerene.
The conductive auxiliary agent may be one kind or two or more kinds. In the case of two or more kinds, the combination and ratio may be appropriately selected according to the purpose.

In the positive electrode material (excluding an organic solvent at the time of preparing the mixture described later), the content of the conductive auxiliary agent is preferably 1 to 90% by mass. By setting the lower limit value or more, a more sufficient conductivity improvement effect can be obtained, and by setting the upper limit value or less, the lithium ion storage / release capacity of the positive electrode material becomes higher.
In addition, the function to hold | maintain the said lithium compound may be exhibited by mix | blending the said conductive support agent more than predetermined amount. In this case, higher conductivity can be obtained by reducing the amount of the binder resin used.

The positive electrode material can be produced, for example, by mixing the obtained components such as the lithium compound, conductive additive and binder resin, and then molding the resulting mixture. And the said mixture may contain the organic solvent so that shaping | molding may become easy.
The organic solvent is preferably one that can dissolve the binder resin, and examples thereof include N-methylpyrrolidone and N, N-dimethylformamide.
In the case of using a mixture containing the organic solvent, for example, the mixture may be applied or laminated at a predetermined location, and then the organic solvent may be removed and dried to form a desired shape.

  The lithium ion secondary battery of the present invention may be manufactured in a glove box or in a dry air atmosphere.

[Lithium ion secondary battery]
The lithium ion secondary battery of this invention is manufactured by the manufacturing method of the lithium ion secondary battery of this invention. If it is a lithium ion secondary battery formed through said 1st process and said 2nd process, the main structure can be set as the structure similar to the conventional lithium ion secondary battery. For example, the negative electrode, the gel electrolyte, and the positive electrode (counter electrode) may be arranged in this order. Furthermore, a separator may be provided between the negative electrode and the positive electrode as necessary.

The form of the lithium ion secondary battery of the present invention is not particularly limited, and can be adjusted to a known form such as a cylindrical shape, a square shape, a coin shape, or a sheet shape. For example, FIG. 2 shows a schematic cross-sectional view of an example of the coin-type battery.
The lithium ion secondary battery 1 shown here is a coin type, and a positive electrode 11, a gel electrolyte (electrolyte film) 12, and a negative electrode 13 are laminated in this order in a case 14, and this laminate forms an insulating gasket 15. It is sealed with a cap 16 and has a schematic configuration. However, the lithium ion secondary battery shown here is merely an example of the present invention, and the present invention is not limited to the one shown here.

Hereinafter, a method for producing a laminate-type lithium ion secondary battery will be exemplified.
The laminate-type lithium ion secondary battery includes a positive electrode plate having a terminal tab protruding from an end and a non-aqueous electrolyte applied to at least one plate surface, a gel electrolyte membrane, and a terminal from the end. A multilayer membrane electrode assembly formed by alternately laminating a negative electrode plate with a non-aqueous electrolyte applied to at least one plate surface with protruding tabs is wrapped and sealed with a laminate film.

The positive electrode plate is formed by forming a positive electrode active material layer on a positive electrode current collector made of, for example, aluminum foil, and the terminal tab is connected to the end of the positive electrode current collector. For example, it is cut into a rectangle so as to fit on the surface of the electrolyte membrane.
Examples of the material for the terminal tab of the positive electrode plate include aluminum.

The positive electrode active material layer is formed by, for example, applying a positive electrode slurry in which a positive electrode active material, a conductive additive, and a binder serving as a binder are dispersed in a solvent to one or both sides of the positive electrode current collector, Is obtained by drying. After application, pressing may be performed as necessary.
As the positive electrode active material, for example, a metal acid lithium compound represented by the general formula LiMxOy (where M is a metal and x and y are composition ratios of the metal M and oxygen O) is used. Specifically, lithium cobaltate, lithium nickelate, lithium manganate and the like are used as the metal acid lithium compound.
For example, acetylene black or the like is used as the conductive assistant, and polyvinylidene fluoride or the like is used as the binder.

The negative electrode plate is obtained by forming a negative electrode active material layer on a negative electrode current collector made of, for example, copper (Cu) and the like, and connecting terminal tabs from the edge of the negative electrode current collector. For example, the material layer is cut into a rectangular shape so as to fit on the surface of the electrolyte membrane.
An example of the material for the negative terminal tab is nickel.

  The negative electrode active material layer is made of, for example, a negative electrode slurry obtained by dispersing a carbon material made of carbon powder or graphite powder and a binder such as polyvinylidene fluoride in a solvent on one or both surfaces of the negative electrode current collector. It is obtained by coating and drying the negative electrode slurry. After application, pressing may be performed as necessary.

  Next, each process (A)-(C) of the manufacturing method of the said laminate type lithium ion secondary battery is demonstrated. The laminate type lithium ion secondary battery manufacturing method includes (A) a step A of applying a non-aqueous electrolyte to at least one plate surface of the positive electrode plate and the negative electrode plate, and (B) after the first step. Step B of forming a gel electrolyte membrane on at least one plate surface of the positive electrode plate and the negative electrode plate, and (C) after the second step, the positive electrode plate and the negative electrode plate are placed between them. And a step C of alternately laminating so as to interpose a film.

(A) Step A of applying a non-aqueous electrolyte to at least one plate surface of the positive electrode plate and the negative electrode plate
First, a positive electrode plate formed by forming a positive electrode active material layer on a positive electrode current collector such as an aluminum foil and wound on a roll is stretched, and a nonaqueous electrolytic solution is applied to the plate surface of the electrode plate. This positive electrode plate may be previously cut to a predetermined dimension.
The application method is not particularly limited, and for example, a dipping method or a spray method is employed.
Further, the application amount of the non-aqueous electrolyte is not particularly limited, but it is preferable that the non-aqueous electrolyte spreads over the entire plate surface of the negative electrode plate and does not sufficiently soak and drip into the negative electrode active material layer. For example, it is preferable that the coating amount of the electrolyte is (1 microliter / cm ^{2 to} 100 microliter / cm ² ) per unit volume of the electrode.
Similarly to the negative electrode plate, the positive electrode plate is formed by applying a non-aqueous electrolyte.
In addition, it is preferable that the nonaqueous electrolytic solution applied to the plate surfaces of the positive electrode plate and the negative electrode plate and the nonaqueous electrolytic solution contained in the gel electrolyte membrane are adjusted by a combination of the same materials.

(B) Step B of forming a gel electrolyte membrane (gel electrolyte)
The gel electrolyte membrane can be applied by directly applying the electrolyte solution for gel to the surface of the positive electrode plate and the negative electrode plate applied with the nonaqueous electrolyte solution formed in the step A, or the electrolyte solution for gel (the raw material solution). ) Is impregnated into the base material and then bonded to the plate surface to which the nonaqueous electrolyte solution of the positive electrode plate and the negative electrode plate is applied.
In this case, the gel electrolyte may be preheated in the range of 40 ° C. to 120 ° C. to reduce the viscosity of the gel electrolyte.
Examples of the method for applying or impregnating the gel electrolyte include various coater methods using a doctor blade method, dipping, a gravure coater, a comma coater, a lip coater, and the like.
In addition, when the dilution solvent is contained in the electrolyte solution for gels to apply | coat or impregnate, after apply | coating or impregnating this electrolyte solution for gels, a dilution solvent is volatilized and it gelatinizes.

(C) Step C of alternately laminating the positive electrode plate and the negative electrode plate after the second step so that the electrolyte membrane is interposed therebetween.
The positive electrode plate and the negative electrode plate formed as described above were alternately laminated and bonded so that the gel electrolyte membrane was interposed therebetween, and protruded outward from the positive electrode plate and the negative electrode plate. The terminal tabs are joined by ultrasonic welding to obtain a multilayer membrane electrode assembly.
At this time, it is desirable to heat the gel electrolyte membranes of the positive electrode plate and the negative electrode plate in the range of 40 ° C. to 120 ° C. and melt the gel electrolyte solution gelled in the electrolyte membrane.

When the positive electrode plate and the negative electrode plate are laminated as described above, since the electrolyte membrane has adhesiveness in a gelled state or a molten state, the positive electrode plate and the negative electrode plate are adhered to the electrolyte membrane. .
When the electrolyte membrane is heated, the electrolyte membrane is then placed at room temperature again to gel the electrolyte membrane again.
The multilayer membrane electrode assembly obtained as described above is accommodated in a casing such as a laminate type. In this case, the terminal tabs protruding from the positive electrode plate and the negative electrode plate are protruded outward of the aluminum laminate film, and the outer periphery of the film is laminated and sealed to complete the lithium ion secondary battery.

  According to the method for manufacturing a laminate type lithium ion secondary battery of this embodiment, before forming the gel electrolyte membrane, at least one plate surface of the positive electrode plate and at least one plate surface of the negative electrode plate are subjected to nonaqueous electrolysis. Since the liquid is applied, the non-aqueous electrolyte can be sufficiently infiltrated into the active material layers of the positive electrode plate and the negative electrode plate. And since the gel-like electrolyte membrane is formed on the plate surface coated with the non-aqueous electrolyte, it is possible to produce a battery excellent in charge / discharge performance of the positive electrode plate and the negative electrode plate. In addition, since the gel electrolyte membrane is formed after the non-aqueous electrolyte is applied, a lithium ion secondary battery that makes it easy to adsorb the gel electrolyte membrane, hardly volatilizes, and does not leak easily is manufactured. The effect that it can do is acquired.

  In addition, when the gel electrolyte is heated when the gel electrolyte membrane is formed on the positive electrode plate and the negative electrode plate, the gel electrolyte solution is uniformly applied to the entire surface of the positive electrode plate and the negative electrode plate. In addition, since the electrolyte solution can be uniformly applied or impregnated on the base material, an effect that a battery excellent in charge / discharge performance of the positive electrode plate and the negative electrode plate can be produced is obtained.

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

<Manufacture of carbon materials>
[Production Example 1]
100 parts by weight of divinylbenzene as a monomer, 100 parts by weight of n-heptane as a hollow agent, 10 parts by weight of silicon particles (silicon nanopowder manufactured by Aldrich, average particle diameter 50 nm) as metal particles, and a pigment dispersant (manufactured by Enomoto Kasei Co., Ltd.) DA-7301) After mixing 10 parts by mass and ultrasonically dispersing, 1.5 parts by mass of an organic peroxide as a polymerization initiator was further added to prepare a monomer mixture as an oil phase component.
Further, 500 parts by mass of pure water and 5 parts by mass of polyvinyl alcohol as a dispersant were mixed to prepare an aqueous phase component.
The obtained oil phase component and aqueous phase component were mixed and stirred and dispersed with a homogenizer to prepare a suspension. The resulting suspension was stirred and held at 80 ° C. for 12 hours under a nitrogen stream to conduct a polymerization reaction. And the particle | grains obtained by superposition | polymerization were washed and dried, and the resin particle was obtained. The obtained resin particles were heat-treated at 300 ° C. for 3 hours in an air atmosphere, and then fired at 1000 ° C. for 3 hours in a nitrogen atmosphere to obtain carbon particles as a carbon material for the negative electrode.
The obtained carbon particles had an average particle size of 20 μm, a particle size Cv value of 40%, and a porosity of 40%. The average particle size and Cv value were determined by observing about 100 arbitrary particles using an electron microscope (S-4300SE / N, manufactured by Hitachi High-Technology Corporation).

(1) Production of negative electrode plate of lithium ion secondary battery 10 parts by weight of carbon black (Mitsubishi Chemical Co., Ltd., # 3230B) as a conductive auxiliary agent and 100% by weight of polyurethane as a binder resin with respect to 100 parts by weight of the obtained carbon particles for electrodes. A mixed liquid (negative electrode material) was prepared by mixing 10 parts by weight of vinylidene chloride and N-methylpyrrolidone as an organic solvent.
The obtained liquid mixture was apply | coated to the single side | surface of 18-micrometer-thick Cu foil, and it was set as the negative electrode active material layer by drying. The laminate having the negative electrode active material layer disposed on the surface was pressure-formed with a roll press to obtain a negative electrode plate.

(2) Production of positive electrode plate of lithium ion secondary battery 89 parts by mass of LiCoO ₂ (lithium cobaltate Nippon Chemical Industry Co., Ltd. Cellseed C-5H) and PVDF (polyvinylidene fluoride, Kureha KF Polymer L # 1120) ) 6 parts by mass, 5 parts by mass of carbon black (Denka Black, Denki Kagaku Kogyo), and 100 parts by mass of N-methylpyrrolidone (NMP) 1 in Disper (TK homodisper 2.5 type, manufactured by Primix Corporation) By mixing for a time, a mixed solution (positive electrode material) was prepared.
The obtained mixed liquid was applied to one side of an aluminum foil having a thickness of 20 μm, and further dried under reduced pressure (100 ° C., −0.1 MPa, 10 hours) to obtain a positive electrode active material layer. The laminate having the positive electrode active material layer disposed on the surface was pressure-formed with a roll press to obtain a positive electrode plate.

(3) Preparation of non-aqueous electrolyte for lithium ion secondary battery LiPF ₆ (manufactured by Kishida Chemical Co., Ltd.) as an electrolyte in a mixed solvent of ethylene carbonate and dimethyl carbonate in a volume ratio of 1: 2 has a concentration of 1 mol / L. It was made to melt | dissolve so that it might become, and it was set as the nonaqueous electrolyte solution.

(4) Preparation of gel electrolyte of lithium ion secondary battery 90 parts by mass of the non-aqueous electrolyte and 10 parts by mass of PVDF-HFP (polyvinylidene fluoride / hexafluoropropylene copolymer, manufactured by Aldrich) as a polymer matrix Were stirred with a disper (Primix Co., Ltd., TK homodisper 2.5 type) for 1 hour to obtain a gel electrolyte raw material liquid. This raw material solution was applied to the electrode surface, and a solvent was volatilized appropriately as needed to obtain a gel electrolyte.

<Manufacture of lithium ion secondary batteries>
[Example 1]
The negative electrode plate was cut into a size of 80 × 80 mm square to obtain a negative electrode. A tab made of Cu foil was attached to the negative electrode as a current-carrying wiring. The design capacity of this negative electrode was estimated to be 205 mAh / cm ² based on its size.
The positive electrode plate was cut into a 78 × 78 mm square size to obtain a positive electrode. An aluminum foil tab was attached to the positive electrode as a wiring for energization. The design capacity of this positive electrode was estimated to be 183 mAh / cm ² based on its size.

The negative electrode active material layer disposed on the surface of the negative electrode is impregnated with the non-aqueous electrolyte by a dipping method, and before the non-aqueous electrolyte is evaporated and lost, the gel electrolyte raw material solution is added to the negative electrode active material layer. Using a bar coater on the material layer, it was applied to a thickness of 20 μm to obtain a gel electrolyte. The positive electrode is placed on the obtained negative electrode-gel electrolyte laminate, laminated so that the gel electrolyte is held between the negative electrode and the positive electrode, and laminated lithium ion secondary The next battery was obtained.
In the dipping method, the coating amount of the non-aqueous electrolyte was adjusted to 15 μl to 25 μl per square centimeter.

[Example 2]
A positive electrode and a negative electrode were prepared in the same manner as in Example 1, and the negative electrode active material layer was impregnated with a non-aqueous electrolyte, and before the non-aqueous electrolyte was evaporated and lost, on the negative electrode active material layer Then, a separator (manufactured by Hirose Paper Co., Ltd., non-woven fabric; model number = HOP-6, thickness 24 μm) impregnated with the gel electrolyte raw material solution was placed. The positive electrode is placed on the obtained negative electrode-gel electrolyte laminate, laminated so that the gel electrolyte is held between the negative electrode and the positive electrode, and laminated lithium ion secondary The next battery was obtained.

[Comparative Example 1]
A laminate type lithium ion secondary battery was produced in the same manner as in Example 1 except that the negative electrode active material layer was not impregnated with the non-aqueous electrolyte.

[Comparative Example 2]
The gel electrolyte raw material liquid is referred to as a first raw material liquid. The first raw material liquid has a polymer matrix concentration of 10% by mass.
The non-aqueous electrolyte is 97 parts by mass, and the PVDF-HFP which is a polymer matrix is mixed with the disper so that the mass is 3 parts by mass and stirred for 1 hour to obtain a second raw material liquid for gel electrolyte. It was. The second raw material liquid has a polymer matrix concentration of 3% by mass.
Next, a positive electrode and a negative electrode are prepared in the same manner as in Example 1. The negative electrode active material layer is not impregnated with a non-aqueous electrolyte, and the second raw material liquid is placed on the negative electrode active material layer with a bar coater. The gel electrolyte was obtained by coating so as to have a thickness of 10 μm. The first raw material liquid was applied onto the gel electrolyte with a bar coater so as to have a thickness of 10 μm to obtain a gel electrolyte. The positive electrode is placed on the obtained negative electrode-gel electrolyte laminate, laminated so that the gel electrolyte is held between the negative electrode and the positive electrode, and laminated lithium ion secondary The next battery was obtained.

(5) Evaluation of lithium ion secondary battery <Evaluation of discharge capacity (battery capacity) and capacity maintenance ratio>
The laminated batteries of each of the examples and the comparative examples were charged at 0.2 C (36.6 mAh / cm ² ) with respect to the design capacity of the positive electrode until reaching 4.2 V, and then 0.2 C or 1 C (183 mAh / It discharged until it reached 2.7V on the conditions of cm < ² >). Using this charging and discharging as the first cycle, charging and discharging for a total of 10 cycles were repeated. Before the charge of each cycle, the rest period which does not perform charging / discharging was put for 10 minutes. The discharge capacity was calculated from the energization amount at the discharge of each cycle. Tables 1 and 2 show the discharge capacities of the second cycle (2cyc.) And the tenth cycle (10cyc.). Tables 1 and 2 show the discharge capacity of the second cycle with respect to the discharge capacity (theoretical capacity) that can be theoretically exhibited.
Further, the capacity retention ratio, which is the cycle characteristic of the secondary battery, was calculated by the formula of “10th cycle discharge capacity / second cycle discharge capacity × 100 (%)”. The results are shown in Tables 1 and 2.

From the above results, the lithium ion secondary batteries of Examples 1 and 2 according to the present invention can express a discharge capacity closer to the theoretical capacity than the lithium ion secondary batteries of Comparative Examples 1 and 2, Further, it is clear that the capacity retention rate when charging and discharging are repeated is also excellent.
Thus, the lithium ion secondary battery of the present invention is superior in discharge capacity and capacity retention rate as compared with conventional lithium ion secondary batteries.

  The present invention can be used in the field of lithium ion secondary batteries.

DESCRIPTION OF SYMBOLS 1 ... Lithium ion secondary battery, 11 ... Positive electrode, 12 ... Electrolyte membrane, 13 ... Negative electrode, 14 ... Case, 15 ... Insulating gasket, 16 ... Cap, 100 ... Carbon material, 101 ... Carbon particle, 102 ... Cavity part, 103. Metal capable of forming an alloy with lithium

Claims (9)

A method for producing a lithium ion secondary battery comprising at least a negative electrode containing a carbon material, a gel electrolyte, and a positive electrode,
The carbon material has a continuous cell hollow structure in which a void formed by connecting a plurality of holes penetrates in the thickness direction, and contains a metal capable of forming an alloy with lithium in the void.
It has at least a first step of impregnating the carbon material with a non-aqueous electrolyte and a second step of arranging the gel electrolyte between the negative electrode and the positive electrode after the first step. A method for producing a lithium ion secondary battery.   The carbon material is a continuum of particles formed by contacting carbon particles with each other, and a non-contact portion between the carbon particles forms the void. Method for producing a lithium ion secondary battery.   The method for producing a lithium ion secondary battery according to claim 1, wherein the negative electrode further contains a binder resin.   The said negative electrode further contains 1 or more types of conductive support agents selected from the group which consists of graphite, carbon black, a carbon nanotube, a graphene, and fullerene, The Claim 1 characterized by the above-mentioned. Method for producing a lithium ion secondary battery.   In the second step, the gel electrolyte raw material liquid was applied to the surface of the negative electrode or the positive electrode, and the applied raw material liquid was dried and gelled to obtain the gel electrolyte. The method for producing a lithium ion secondary battery according to any one of claims 1 to 4, wherein the gel electrolyte is sandwiched between the positive electrode and the negative electrode.   In the second step, a separator impregnated with the raw material liquid for the gel electrolyte is placed on the surface of the negative electrode or the positive electrode, and the raw material liquid in the separator is dried and gelled. The method for producing a lithium ion secondary battery according to any one of claims 1 to 4, wherein the gel electrolyte is sandwiched between the positive electrode and the negative electrode.   The method of manufacturing a lithium ion secondary battery according to claim 5 or 6, wherein in the second step, the raw material liquid is heated.   The gel electrolyte includes a non-aqueous electrolyte, and the non-aqueous electrolyte to be impregnated in the carbon material in the first step and the non-aqueous electrolyte included in the gel electrolyte have the same composition. The manufacturing method of the lithium ion secondary battery as described in any one of claim | item 1 -7.   A lithium ion secondary battery manufactured by the method for manufacturing a lithium ion secondary battery according to claim 1.

Images