JP2013101867A - Nonaqueous electrolyte secondary battery, and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery including a heat-resistant layer capable of limiting an increase in the internal resistance, and to provide a manufacturing method therefor.SOLUTION: A lithium ion secondary battery is manufactured by a manufacturing method including a dispersion step S11 for preparing a paste by dispersing an insulating filler and a binding agent into a solvent, a granulation step S12 for granulating composite particles compounding the insulating filler and binding agent by drying the paste prepared in the dispersion step S11, a molding step S13 for forming a particle layer composed of a large number of composite particles by molding the composite particles prepared in the granulation step S12 so as to cover a negative electrode mixture layer 12, and a press step S14 for changing the particle layer to a heat-resistant layer by pressing the particle layer formed in the molding step S13.

Description

  The present invention relates to a nonaqueous electrolyte secondary battery and a method for producing the same, and more particularly to a technique for forming a heat-resistant layer on an electrode mixture layer.

In general, lithium ion secondary batteries and non-aqueous electrolyte secondary batteries such as nickel / hydrogen storage batteries are formed by laminating a pair of electrodes (a positive electrode and a negative electrode) formed in a sheet shape via a separator and winding them. The electrode body which comprises is comprised.
In such a non-aqueous electrolyte secondary battery, a short circuit may occur between the positive and negative electrodes due to foreign matters mixed into the electrode body, and the separator may melt.

Conventionally, a technique for forming a heat-resistant layer on the surface of an electrode mixture layer in order to prevent an internal short circuit due to melting of a separator or the like is known (for example, see Patent Document 1).
The heat-resistant layer is formed by applying a paste obtained by dispersing an insulating filler and a binder in a solvent to the surface of the electrode mixture layer using a coating machine such as a die coater and then drying the paste. .

  However, in the nonaqueous electrolyte secondary battery in which the above heat-resistant layer is formed, the solvent and the binder in the paste permeate into the electrode mixture layer, so that the active material in the electrode mixture layer is the binder. This causes a problem that the internal resistance is increased.

JP 2006-120604 A

  This invention makes it a subject to provide the nonaqueous electrolyte secondary battery which comprises the heat-resistant layer which can suppress a raise of internal resistance, and its manufacturing method.

  A method for producing a nonaqueous electrolyte secondary battery according to the present invention comprises a nonaqueous electrolyte secondary comprising a sheet-like current collector and a pair of electrodes each having an electrode mixture layer formed on the surface of the current collector. A method for producing a battery, comprising: a dispersion step in which an insulating filler and a binder are dispersed in a solvent to prepare a paste; and the paste produced in the dispersion step is dried to obtain the insulating filler and the binder. A granulation step of granulating composite particles combined with an adhesive, and forming the composite particles produced in the granulation step so as to cover at least one electrode mixture layer of the pair of electrodes, A molding step for forming a particle layer composed of a large number of composite particles; and a pressing step for applying a pressing process to the particle layer formed in the molding step to change the particle layer into a heat-resistant layer. .

  In the method for manufacturing a non-aqueous electrolyte secondary battery according to the present invention, in the molding step, the particle layer is preferably formed so as to cover a surface and a side surface of the electrode mixture layer.

  In the method for manufacturing a non-aqueous electrolyte secondary battery according to the present invention, it is preferable to form the heat-resistant layer only on the negative electrode.

  A non-aqueous electrolyte secondary battery according to the present invention is a non-aqueous electrolyte secondary battery comprising a sheet-shaped current collector and an electrode comprising an electrode mixture layer formed on the surface of the current collector, A heat-resistant layer made of composite particles in which an insulating filler and a binder are combined is formed on the electrode mixture layer, and the heat-resistant layer is formed so as to cover the surface and side surfaces of the electrode mixture layer.

  According to the nonaqueous electrolyte secondary battery and the manufacturing method thereof according to the present invention, it is possible to suppress an increase in internal resistance when a heat-resistant layer is formed on the surface of the electrode mixture layer.

The figure which shows the negative electrode of the nonaqueous electrolyte secondary battery which concerns on this invention. The figure which shows the manufacturing process of the nonaqueous electrolyte secondary battery which concerns on this invention. The figure which shows the particle layer formed on the negative mix layer. The figure which shows the electrode in which the conventional heat-resistant layer was formed.

  Below, with reference to FIG. 1, the lithium ion secondary battery which is one Embodiment of the nonaqueous electrolyte secondary battery which concerns on this invention is demonstrated.

  The lithium ion secondary battery includes a container forming an exterior and an electrode body housed in the container.

  The container is a metal can made of aluminum, stainless steel, or the like, and is configured to accommodate the electrode body therein. In the state where the electrode body is stored in the container, the electrolyte solution is impregnated into the electrode body by filling the inside of the container with the electrolyte solution.

  The electrode body is a wound body that is formed into a predetermined shape by laminating a positive electrode and a negative electrode 10 (a pair of electrodes) via a separator and winding them. The electrode body becomes a power generation element when impregnated with the electrolytic solution.

The positive electrode is an electrode including a sheet-like positive electrode current collector and a positive electrode mixture layer formed on the surface of the positive electrode current collector.
The positive electrode current collector is a current collector made of a metal foil such as aluminum, titanium, or stainless steel.
The positive electrode mixture layer is an electrode mixture layer made of a positive electrode mixture in which a positive electrode active material is dispersed in a solvent together with a conductive additive and a binder. The positive electrode mixture layer is formed by drying the paste-like positive electrode mixture coated on a surface of the positive electrode current collector by a coating machine such as a die coater and then pressing the positive electrode mixture. Formed by.

As shown in FIG. 1, the negative electrode 10 includes a sheet-like negative electrode current collector 11, a negative electrode mixture layer 12 formed on the surface of the negative electrode current collector 11, and a heat resistance formed on the negative electrode mixture layer 12. It is an electrode provided with a layer (HRL: Heat Resistance Layer) 13.
The negative electrode current collector 11 is a current collector made of a metal foil such as copper, nickel, or stainless steel.
The negative electrode mixture layer 12 is an electrode mixture layer made of a negative electrode mixture in which a negative electrode active material is dispersed in a solvent together with a conductive additive and a binder. The negative electrode mixture layer 12 is obtained by drying the paste-like negative electrode mixture coated on the surface of the negative electrode current collector 11 by a coating machine such as a die coater and then pressing the negative electrode mixture. Formed by.
The heat-resistant layer 13 is a layer for suppressing an internal short circuit caused by the melting of the separator, and covers the surface (upper surface in FIG. 1) and side surfaces (both left and right in FIG. 1) of the negative electrode mixture layer 12. Is formed. The heat-resistant layer 13 is formed by pressing a large number of particles in which an insulating filler and a binder are combined.
The surface of the electrode mixture layer (negative electrode mixture layer 12) according to the present invention is the surface of the current collector (negative electrode current collector 11) according to the present invention (surface on which the electrode mixture layer is formed). The side surface of the electrode mixture layer (negative electrode mixture layer 12) according to the present invention is substantially parallel to the surface of the current collector (negative electrode current collector 11) according to the present invention. It is a vertical surface.

  The separator is an insulator made of a polyolefin resin such as polyethylene or polypropylene, and is interposed between the positive electrode and the negative electrode 10.

  Below, with reference to FIGS. 2-4, the manufacturing process of the said lithium ion secondary battery which is one Embodiment of the manufacturing method of the nonaqueous electrolyte secondary battery which concerns on this invention is demonstrated.

  The manufacturing process of the lithium ion secondary battery includes a positive electrode manufacturing process for manufacturing the positive electrode and a negative electrode manufacturing process for manufacturing the negative electrode 10.

In the positive electrode preparation step, first, the positive electrode mixture is applied to the surface of the positive electrode current collector using a coating machine such as a die coater, and then the positive electrode mixture is dried.
Next, the positive electrode mixture layer is formed on the surface of the positive electrode current collector by pressing the positive electrode mixture on the surface of the positive electrode current collector.
Thus, the positive electrode is produced.

The negative electrode manufacturing step is a step of manufacturing the negative electrode 10, and includes a heat-resistant layer forming step S 10 for forming the heat-resistant layer 13 on the negative electrode mixture layer 12.
In the negative electrode preparation step, after the step of forming the negative electrode mixture layer 12 on the surface of the negative electrode current collector 11, the heat resistant layer forming step S10 is performed.
In addition, since the process of forming the negative mix layer 12 on the surface of the negative electrode collector 11 is substantially the same as the positive electrode preparation process, detailed description thereof is omitted.

  As shown in FIG. 2, the heat-resistant layer forming step S10 includes a dispersing step S11, a granulating step S12, a molding step S13, and a pressing step S14.

The dispersion step S11 is a step of producing a paste by dispersing the insulating filler and the binder in a solvent.
In the dispersion step S11, using a suitable disperser, the powdery insulating filler and the binder are dispersed in a solvent to prepare a paste.
As the insulating filler, magnesium oxide, titanium oxide, aluminum oxide, zirconium oxide, tungsten oxide, zinc oxide, silicon oxide and the like can be adopted. Even if one of them is used alone, You may use combining more than a seed.
As the binder, polyacrylonitrile (PAN), polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyethylene (PE), styrene-butadiene rubber (SBR), etc. are adopted. One of them may be used alone, or two or more may be used in combination.
As the solvent, N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMA) or the like can be employed.
For example, magnesium oxide (MgO) is used as the insulating filler, polyacrylonitrile (PAN) is used as the binder, N-methylpyrrolidone (NMP) is used as the solvent, and the mixing ratio is MgO: PAN = 96: 4 (wt%). ), A paste is prepared so that the solid content is 35 wt%.

The granulation step S12 is a step of drying the paste produced in the dispersion step S11 to granulate particles (hereinafter referred to as “composite particles”) in which the insulating filler and the binder are combined. is there.
In the granulation step S12, the paste is dried by spray drying, freeze drying, fluidized bed granulation, or the like, and composite particles in which the insulating filler and the binder are combined are granulated. At this time, it is preferable to appropriately classify the granulated composite particles.

As shown in FIG. 3, the molding step S13 is a step of molding the composite particles produced in the granulation step S12 so as to cover the negative electrode mixture layer 12 and forming a particle layer 14 composed of a large number of composite particles. is there.
In the molding step S13, the particle layer 14 is formed by molding composite particles on the negative electrode mixture layer 12 formed on the surface of the negative electrode current collector 11 by a squeegee method, an inter-roll press method, an electrostatic screen method, or the like. Form.
At this time, it is preferable to form the particle layer 14 so as to cover the surface (upper surface in FIG. 3) and the side surfaces (left and right both surfaces in FIG. 3) of the negative electrode mixture layer 12. Specifically, the surface of the negative electrode mixture layer 12 and the negative electrode mixture layer 12 so that the distance between the surface of the particle layer 14 (upper end surface in FIG. 3) and the surface of the negative electrode current collector 11 is substantially uniform. Composite particles are molded on the surface of the negative electrode current collector 11 in the vicinity of the side surface of the electrode. That is, the amount of composite particles molded on the surface of the negative electrode mixture layer 12 is smaller than the amount of composite particles molded on the surface of the negative electrode current collector 11 in the vicinity of the side surface of the negative electrode mixture layer 12 ( The thickness dimension of the composite particles molded on the surface of the negative electrode mixture layer 12 is smaller than the thickness dimension of the composite particles molded on the surface of the negative electrode current collector 11 in the vicinity of the side surface of the negative electrode mixture layer 12). Control molding of composite particles. Since the composite particles are powder, they are deposited, and the particle layer 14 can be easily formed into a desired shape.

The pressing step S14 is a step of pressing the particle layer 14 formed in the molding step S13.
In the pressing step S <b> 14, the particle layer 14 is changed to the heat-resistant layer 13 by pressing the particle layer 14 using a flat plate press or a roll press.

As described above, the heat-resistant layer 13 is formed on the negative electrode mixture layer 12 through the heat-resistant layer forming step S10 (see FIG. 1).
Unlike the conventional heat-resistant layer, the heat-resistant layer 13 is produced from a large number of composite particles in which no solvent is present, so that the binder does not penetrate into the negative electrode mixture layer 12 together with the solvent.
Thereby, the raise of the internal resistance of the said lithium ion secondary battery resulting from the said binder coat | covering the negative electrode active material in the negative mix layer 12 can be suppressed.

Further, since the particle layer 14 is formed so as to cover the surface and the side surface of the negative electrode mixture layer 12, the heat-resistant layer 13 is formed so as to cover not only the surface of the negative electrode mixture layer 12 but also the side surface of the negative electrode mixture layer 12. It is formed.
Thereby, the short circuit by the foreign material in the side surface of the negative mix layer 12 can be suppressed.
As shown in FIG. 4, in the conventional non-aqueous electrolyte secondary battery, the problem that the heat-resistant layer which covers the side surface (left and right both surfaces of FIG. 4) of an electrode mixture layer cannot be formed has arisen. This is because, in a conventional nonaqueous electrolyte secondary battery, a heat-resistant layer is formed by applying a paste in which the insulating filler and the binder are dispersed in a predetermined solvent using a coating machine such as a die coater. It is for forming. A coating machine such as a die coater is configured to apply paste with a uniform thickness on a flat surface. Therefore, if there is a step in the coating target, the amount of paste applied to the stepped portion is insufficient. End up.
However, according to the present invention, such a problem can be solved.

  After the positive electrode preparation step and the negative electrode preparation step, a storage step of storing the electrode body in the container, a liquid injection step of injecting the electrolyte into the container in which the electrode body is stored, and the like. As a result, the lithium ion secondary battery is manufactured.

In this embodiment, the heat-resistant layer 13 is formed only on the negative electrode 10, but the heat-resistant layer according to the present invention is formed only on the positive electrode, or the heat-resistant layer according to the present invention is formed on both the positive electrode and the negative electrode 10. It is also possible to form
However, in consideration of dendrite precipitation or the like in the negative electrode 10, it is preferable to form at least the heat-resistant layer 13 on the negative electrode 10, and considering the time and cost required for manufacturing the lithium ion secondary battery, the heat-resistant layer is formed only on the negative electrode 10. More preferably, 13 is formed.

10 Negative electrode (electrode)
11 Negative electrode current collector (current collector)
12 Negative electrode mixture layer (electrode mixture layer)
13 Heat-resistant layer 14 Particle layer

Claims (4)

A method for producing a non-aqueous electrolyte secondary battery comprising a sheet-shaped current collector and a pair of electrodes comprising an electrode mixture layer formed on the surface of the current collector,
A dispersion step of producing a paste by dispersing an insulating filler and a binder in a solvent;
A granulation step of drying the paste prepared in the dispersion step and granulating composite particles in which the insulating filler and the binder are combined;
A molding step of molding the composite particles produced in the granulation step so as to cover at least one electrode mixture layer of the pair of electrodes, and forming a particle layer composed of a large number of composite particles;
Pressing the particle layer formed in the molding step, and changing the particle layer into a heat-resistant layer,
A method for producing a non-aqueous electrolyte secondary battery. In the molding step, the particle layer is formed so as to cover the surface and side surfaces of the electrode mixture layer.
The manufacturing method of the nonaqueous electrolyte secondary battery of Claim 1 characterized by the above-mentioned. Forming the heat-resistant layer only on the negative electrode,
The method for producing a non-aqueous electrolyte secondary battery according to claim 1, wherein: A non-aqueous electrolyte secondary battery comprising a sheet-like current collector and an electrode comprising an electrode mixture layer formed on the surface of the current collector,
A heat-resistant layer composed of composite particles in which an insulating filler and a binder are combined is formed on the electrode mixture layer,
The heat-resistant layer is formed so as to cover the surface and side surfaces of the electrode mixture layer.
A non-aqueous electrolyte secondary battery characterized by the above.

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