JP2012186020A - Manufacturing method of lithium ion secondary battery and lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a lithium ion secondary battery with high charge and discharge performance of positive and negative electrode plates and high safety, and a lithium ion secondary battery by the same.SOLUTION: A manufacturing method of a lithium ion secondary battery formed by laminating a positive electrode plate, a negative electrode plate, and an electrolyte membrane comprises: a first step of applying nonaqueous electrolyte to one plate surface of the positive electrode plate and the negative electrode plate; a second step of forming a gel-like electrolyte membrane on the one plate surface of the positive electrode plate and the negative electrode plate after the first step; and a third step of alternately laminating the positive electrode plate and the negative electrode plate so that the electrolyte membrane intervenes therebetween after the second step.

Description

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

  Conventionally, lithium ion secondary batteries using solid electrolyte membranes or gel electrolyte membranes have been developed in order to avoid problems such as liquid leakage of lithium ion secondary batteries using electrolyte solutions. In particular, the gel electrolyte membrane contains an electrolyte component, and is more easily soaked into the active material layer of the positive electrode plate and the negative electrode plate than the solid electrolyte membrane and has better charge / discharge performance. As a method for manufacturing such a battery, for example, a method for manufacturing a lithium ion secondary battery described in Patent Document 1 has been proposed.

  The method of manufacturing a lithium ion secondary battery described in Patent Document 1 includes a gel electrolyte membrane in which the concentration of the gel paint is lowered, that is, the viscosity of the gel paint is lowered, and a gel-like electrolyte in which the concentration of the gel paint is increased. Separately from the electrolyte membrane, first, an electrolyte solution having a low concentration of gel paint is applied to the positive electrode plate and the negative electrode plate to form a gel electrolyte membrane.

JP 2000-173656 A

  However, according to the method of manufacturing a lithium ion secondary battery of Patent Document 1, the positive electrode plate and the active material layer of the positive electrode plate and the negative electrode plate are not sufficiently soaked even when an electrolyte solution having a low concentration is first applied. There was a problem that the charge / discharge performance of the negative electrode plate could not be fully exploited.

Therefore, the present invention provides the following means in order to solve the above problems.
The invention according to claim 1 is a method of manufacturing a lithium ion secondary battery formed by laminating a positive electrode plate, a negative electrode plate, and an electrolyte membrane, and a nonaqueous electrolytic solution is provided on one plate surface of the positive electrode plate and the negative electrode plate. A second step of forming a gel electrolyte membrane on the one plate surface of the positive electrode plate and the negative electrode plate after the first step, and the second step. And a third step of alternately stacking the positive electrode plate and the negative electrode plate so that the electrolyte membrane is interposed therebetween.
In the present invention, since the non-aqueous electrolyte is applied to the positive electrode plate and the negative electrode plate before forming the gel electrolyte membrane, the non-aqueous electrolyte can be sufficiently infiltrated into the active material layers of the positive electrode plate and the negative electrode plate. it can. Therefore, more lithium ions are exchanged inside the positive electrode plate and the negative electrode plate. In addition, the amount of electrolyte used is smaller than that of a battery having only an electrolyte, and the nonaqueous electrolyte penetrates into the positive electrode plate and the negative electrode plate.

The invention of claim 2 is the method for producing a lithium ion secondary battery according to claim 1, wherein the non-aqueous electrolyte and the non-aqueous electrolyte contained in the gel electrolyte membrane are prepared by a combination of the same materials. It is characterized by being.
In the present invention, the non-aqueous electrolyte is adjusted by a combination of the same materials as the non-aqueous electrolyte contained in the gel electrolyte membrane, so that the interface between the positive electrode plate and the gel electrolyte membrane permeated with the non-aqueous electrolyte is obtained. In addition, lithium ions are more smoothly exchanged at the interface between the negative electrode plate and the gel electrolyte membrane into which the nonaqueous electrolytic solution has permeated.

A third aspect of the present invention is the method of manufacturing a lithium ion secondary battery according to the first or second aspect, wherein, in the second step, the gel electrolyte membrane is formed by applying a gel electrolyte to a substrate. It is characterized by being formed.
In the present invention, by applying the gel electrolyte to the base material, it is possible to prevent a short circuit between the positive electrode plate and the negative electrode plate, and to increase the strength of the laminate obtained by laminating the positive electrode plate and the negative electrode plate. Further, the thickness can be easily controlled in the manufacturing process of the lithium ion secondary battery.

According to a fourth aspect of the present invention, in the method for producing a lithium ion secondary battery according to any one of the first to third aspects, the gel electrolyte membrane in the second step is applied with the gel electrolyte. It is formed by heating.
In the present invention, the gel electrolyte membrane is formed by heating the gel electrolyte solution, so that the viscosity of the gel electrolyte solution is reduced and the fluidity of the gel electrolyte solution is increased. It can form uniformly between a positive electrode plate and a negative electrode plate.

The invention of claim 5 is a lithium ion secondary battery, which is manufactured by the method of manufacturing a lithium ion secondary battery according to any one of claims 1 to 4.
In this invention, it can be set as the lithium ion secondary battery with high charging / discharging performance and being hard to leak.

According to the method for manufacturing a lithium ion secondary battery of the present invention, the following effects can be achieved by the above-described solving means.
That is, according to the present invention, since the non-aqueous electrolyte is applied to the positive electrode plate and the negative electrode plate before forming the gel electrolyte membrane, the non-aqueous electrolyte is sufficiently applied to the active material layer of the positive electrode plate and the negative electrode plate. Can penetrate. Therefore, more lithium ions are exchanged inside the positive electrode plate and the negative electrode plate. Further, the amount of non-aqueous electrolyte used is smaller than that of a battery having only an electrolyte, and the non-aqueous electrolyte penetrates into the positive electrode plate and the negative electrode plate. Therefore, it is possible to produce a lithium ion secondary battery that has high charge / discharge performance and is difficult to leak.

Hereinafter, embodiments of the present invention will be described.
A lithium ion secondary battery manufactured by the manufacturing method of the present invention has a positive electrode plate in which a tab for terminals protrudes from an end and a nonaqueous electrolyte is applied to at least one plate surface, a gel electrolyte membrane, A multi-layer membrane electrode assembly formed by alternately laminating a negative electrode plate with a non-aqueous electrolyte applied to at least one plate surface by projecting a terminal tab from an end portion was wrapped and sealed with a laminate film. Is.

The positive electrode plate is formed by forming a positive electrode active material layer on a positive electrode current collector made of, for example, an aluminum foil, and having a terminal tab connected to an end of the positive electrode current collector. Is cut into, for example, 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 formed by forming a negative electrode active material layer on a negative electrode current collector made of, for example, copper (Cu) and the like, and a terminal tab is connected to an end 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.

The nonaqueous electrolytic solution is applied to the positive electrode plate and the negative electrode plate, and includes a nonaqueous solvent and an electrolyte salt.
The non-aqueous solvent used in this non-aqueous electrolyte is a lactone compound such as γ-butyrolactone; a carbonate compound such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, or methyl ethyl carbonate; methyl formate, methyl acetate, propionic acid Carboxylic acid ester compounds such as methyl; 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; It is prepared by mixing the above.

The electrolyte membrane is a gel formed by applying a gel electrolyte, or a gel formed by applying a gel electrolyte to a substrate made of a nonwoven fabric or the like.
The material of the substrate is not particularly limited, and polyolefin resins (polypropylene, polyethylene, etc.), polyester resins, polyimide resins and the like are used.

The electrolyte solution for gel is gelled by adding a polymer matrix to a non-aqueous electrolyte solution (that is, an electrolyte solution using a non-aqueous solvent), thereby producing adhesiveness on the surface. The gel electrolyte may contain a diluting solvent. Moreover, what has adhesiveness is used for the electrolyte solution for gels, when it apply | coats or impregnates to a base material.
In addition, it is preferable that an electrolyte membrane forms the self-supporting film | membrane which does not isolate | separate from the surface of a positive electrode plate, a negative electrode plate, or a base material.

  Polymer matrices include polyvinylidene fluoride (PVDF), hexafluoropropylene copolymer (PVDF-HFP), polyacrylonitrile, alkylene ethers such as polyethylene oxide and polypropylene oxide, polyester, polyamine, polyphosphazene, and polysiloxane. Etc. are used.

The non-aqueous solvent is a lactone compound such as γ-butyrolactone; a carbonic acid ester compound such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, or methyl ethyl carbonate; a carboxylic acid ester compound such as methyl formate, methyl acetate, or methyl propionate; 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; .
In addition, it is desirable that the nonaqueous electrolytic solution applied to the positive electrode plate and the negative electrode plate and the nonaqueous electrolytic solution contained in the electrolyte membrane are prepared by a combination of the same materials. Thereby, the transfer of lithium ions is performed more smoothly between the positive electrode plate and the negative electrode plate infiltrated with the non-aqueous electrolyte and the gel electrolyte interface.

The electrolyte salt is not particularly limited, and lithium salts such as lithium hexafluorophosphate, lithium perchlorate, and lithium tetrafluoroborate can be used.
When the diluting solvent is mixed, dimethyl carbonate (DMC), tetrohydrofuran (THF), acetonitrile, or the like having a boiling point lower than that of the nonaqueous electrolytic solution is used.

  Next, each process (I)-(III) of the manufacturing method of a lithium ion secondary battery is demonstrated. The method for producing a lithium ion secondary battery includes (I) a first step of applying a non-aqueous electrolyte to at least one plate surface of a positive electrode plate and a negative electrode plate, and (II) a positive electrode plate after the first step. And a second step of forming a gel electrolyte membrane on at least one surface of the negative electrode plate, and (III) a gel electrolyte between the positive electrode plate and the negative electrode plate after the second step. And a third step of alternately laminating with the film interposed.

(I) First step of applying non-aqueous electrolyte to at least one plate surface of positive electrode plate and negative electrode plate First, a positive electrode active material layer is formed on a positive electrode current collector such as an aluminum foil, and then wound on a roll. The rotated positive electrode plate is stretched and a non-aqueous electrolyte is applied to at least one 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 amount of the nonaqueous electrolyte applied is not particularly limited, but the nonaqueous electrolyte may be spread over the entire surface of the one of the positive electrode plates, so that the positive electrode active material layer is not sufficiently soaked and dripped. Desirably, for example, the application amount of the nonaqueous electrolytic solution per unit volume of the electrode is preferably (1 microliter / cm2 to 100 microliter / cm2).
Similarly to the positive electrode plate, the negative electrode plate is formed by applying a non-aqueous electrolyte.
In addition, it is preferable that the nonaqueous electrolytic solution applied to the one plate surface 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.

(II) Second Step of Forming Gelled Electrolyte Membrane The gelled electrolyte membrane was coated with the nonaqueous electrolytic solution of the positive electrode plate and the negative electrode plate formed in the first step. It is formed by directly applying to the plate surface, or by impregnating the substrate with a gel electrolyte, and then bonding the positive electrode plate and the negative electrode plate to the plate surface to which the nonaqueous electrolyte solution 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.

(III) After the second step, the third step of alternately stacking the positive electrode plate and the negative electrode plate so that the electrolyte membrane is interposed therebetween. The positive electrode plate and the negative electrode plate formed as described above These are laminated alternately and joined so that the gel electrolyte membrane is interposed between them, and the terminal tabs protruding outward from the positive electrode plate and the negative electrode plate are joined by ultrasonic welding or the like, A membrane electrode assembly is obtained.
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. The
When the electrolyte membrane is heated, the electrolyte membrane is then placed at room temperature again, and the electrolyte membrane is gelled again.
The multilayer membrane electrode assembly obtained as described above is housed in a cylindrical, square, or laminate type housing, but has a higher energy density and heat dissipation than other housings. A good laminate type battery structure is preferable. For example, when housed in a laminate-type housing, the terminal tabs protruded from the positive electrode plate and the negative electrode plate are protruded outward from the aluminum laminate film, and the outer periphery of the film is laminated and sealed. An ion secondary battery is completed.

  According to the method for manufacturing a lithium ion secondary battery of this embodiment, before forming the gel electrolyte membrane, the nonaqueous electrolyte is applied to at least one plate surface of the positive electrode plate and at least one plate surface of the negative electrode plate. Therefore, the non-aqueous electrolyte can be sufficiently permeated 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, more lithium ions are transferred inside and outside the positive electrode plate and the negative electrode plate. Further, the amount of non-aqueous electrolyte used is smaller than that of a battery having only an electrolyte, and the non-aqueous electrolyte penetrates into the positive electrode plate and the negative electrode plate. Therefore, it is possible to produce a lithium ion secondary battery that is excellent in charge / discharge performance and hardly leaks.

  In addition, when the non-aqueous electrolyte applied to the positive electrode plate and the negative electrode plate is made of the same material as the non-aqueous electrolyte contained in the gel electrolyte membrane, the electrode and the gel infiltrated with the non-aqueous electrolyte Lithium ions are more smoothly exchanged with the electrolyte interface. Therefore, the effect of improving the charge / discharge performance of the lithium ion secondary battery can be obtained.

  Moreover, while the gel electrolyte membrane is formed by impregnating a base material such as a nonwoven fabric with gel electrolyte and gelling, it can effectively prevent a short circuit between the positive electrode plate and the negative electrode plate. The effect of improving the strength of the laminate of the positive electrode plate and the negative electrode plate is obtained. Furthermore, the effect that it becomes easy to control the thickness of a lithium ion secondary battery in the manufacturing process of a lithium ion secondary battery 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 viscosity of the gel electrolyte decreases and the fluidity of the gel electrolyte increases. Thus, since the electrolyte membrane can be uniformly formed between the positive electrode plate and the negative electrode plate, an effect that a lithium ion secondary battery excellent in charge / discharge performance of the positive electrode plate and the negative electrode plate can be produced.

Hereinafter, the present invention will be specifically described with reference to examples.
1) Fabrication of lithium ion secondary battery <Electrode>
<Positive electrode plate> 89 parts by mass of LiCoO 2 (lithium cobaltate Nippon Chemical Industry Co., Ltd., Cellseed C-5H), 6 parts by mass of PVDF (polyvinylidene fluoride, Kureha KF Polymer L # 1120), carbon black (electric Chemical Industry Denka Black) 5 parts by mass and N-methylpyrrolidone (NMP) 100 parts by mass were mixed with a disper (Primix Co., Ltd., TK homodisper 2.5 type) for 1 hour, and the resulting mixture was mixed with 20 μm. Both surfaces were coated on an aluminum foil, and further dried under reduced pressure (100 ° C., −0.1 MPa, 10 hours) and roll-pressed.

  <Negative Electrode Plate> 90 parts by mass of graphite (Nippon Graphite Industries Co., Ltd. CGB-10), 10 parts by mass of PVDF (polyvinylidene fluoride, Kureha KF Polymer L # 1120), 120 parts by mass of N-methylpyrrolidone (NMP) Were mixed with the disper for 1 hour, and the resulting mixture was coated on both sides of a 20 μm copper foil, dried under reduced pressure (100 ° C., −0.1 MPa, 10 hours), and roll-pressed.

  The positive electrode plate and the negative electrode plate were cut into a substantially rectangular shape in advance. The portion covered with the active material layer was 80 × 80 mm for the negative electrode and 78 × 78 mm for the positive electrode. The portion not covered with the active material layer (tab portion) was cut to leave about 2 × 5 cm.

<Electrolytic solution for gel>
10 parts by mass of PVDF-HFP (polyvinylidene fluoride / hexafluoropropylene copolymer, manufactured by Aldrich), which is a polymer matrix, and non-aqueous electrolyte (LiPF6 (manufactured by Kishida Chemical Co., Ltd.)) with a lithium salt concentration of 1 mol / l 90 parts by mass of dimethyl carbonate: ethylene carbonate (2: 1, volume ratio) dissolved in a mixed solvent was mixed. This mixed solution was stirred with the disper for 1 hour to obtain an electrolyte solution for gel (1).
Moreover, the amount of the PVDF-HFP used is 3 parts by mass instead of 10 parts by mass, and the amount of the nonaqueous electrolyte used is 97 parts by mass instead of 90 parts by mass. In the same manner as in 1), an electrolyte solution for gel (2) was obtained.

[Example 1]
A LiPF6 solution was applied as a nonaqueous electrolyte solution to both the positive electrode plate and the negative electrode plate by a dipping method. The non-aqueous electrolyte was applied so that the application amount of LiPF6 was (15 microliters / cm2 to 25 microliters / cm2) per unit volume of the electrode. Next, the obtained electrolyte solution for gel (1) was applied on the positive electrode plate and the negative electrode plate to which the nonaqueous electrolyte solution was applied using a bar coater so as to have a thickness of 20 μm, dried, and laminated. The battery was processed to produce a lithium ion secondary battery.

[Example 2]
A non-aqueous electrolyte solution was applied to the positive electrode plate and the negative electrode plate in the same manner as in Example 1, and then the gel electrolyte solution (1) was impregnated and applied to a base material (HOP6 manufactured by Hirose Paper Co., Ltd.). After the laminated ones were laminated, the laminated battery was processed to produce a lithium ion secondary battery.

[Comparative Example 1]
A lithium ion secondary battery was produced in the same manner as in Example 1 except that the non-aqueous electrolyte was not applied to the positive electrode plate and the negative electrode plate.

[Comparative Example 2]
After applying the electrolyte solution for gel (2) to the positive electrode plate and the negative electrode plate, the electrolyte solution for gel (1) was further applied thereon to process the laminated battery to produce a lithium ion secondary battery. Table 1 shows details of Examples 1 and 2 and Comparative Examples 1 and 2.

2) Evaluation result It charges until it reaches 4.2V with 0.2C (18.2mAh / cm2) with respect to the design capacity of the electrode of the lithium ion secondary battery of each of the above examples and comparative examples, and then 0.2C It discharged until it reached 2.7 V under the condition of 1 C (91 mAh / cm 2), and the discharge capacity at that time was compared with the design capacity, ie, the discharge capacity / design capacity × 100 (%), and each example and the comparative example were compared. . The results are shown in Table 2 below. When the lithium ion secondary battery according to each example is charged, the discharge capacity ratio to the design capacity is higher than that of the conventional lithium ion secondary battery according to the comparative example. Both secondary batteries had a lower discharge capacity ratio than the lithium ion secondary batteries of Examples 1 and 2.

Claims (5)

In the method for producing a lithium ion secondary battery formed by laminating a positive electrode plate, a negative electrode plate, and an electrolyte membrane,
A first step of applying a non-aqueous electrolyte to one plate surface of the positive electrode plate and the negative electrode plate;
A second step of forming a gel electrolyte membrane on the one plate surface of the positive electrode plate and the negative electrode plate after the first step;
A lithium ion battery comprising: a third step of alternately stacking the positive electrode plate and the negative electrode plate so that the electrolyte membrane is interposed between the positive electrode plate and the negative electrode plate after the second step. Production method. In the manufacturing method of the lithium ion secondary battery according to claim 1,
The method for producing a lithium ion secondary battery, wherein the non-aqueous electrolyte and the non-aqueous electrolyte contained in the gel electrolyte membrane are prepared by a combination of the same materials. In the manufacturing method of the lithium ion secondary battery according to claim 1 or 2,
In the second step, the gel electrolyte membrane is formed by applying an electrolyte solution for gel to a base material. In the manufacturing method of the lithium ion secondary battery as described in any one of Claim 1 to 3,
The method for producing a lithium ion secondary battery, wherein the gel electrolyte membrane in the second step is formed by heating the electrolyte solution for gel.   A lithium ion battery manufactured by the method for manufacturing a lithium ion secondary battery according to any one of claims 1 to 4.