WO2015045519A1

WO2015045519A1 - Secondary battery and production method therefor

Info

Publication number: WO2015045519A1
Application number: PCT/JP2014/066172
Authority: WO
Inventors: 卓哉長谷川
Original assignee: Ｎｅｃエナジーデバイス株式会社
Priority date: 2013-09-27
Filing date: 2014-06-18
Publication date: 2015-04-02

Abstract

A secondary battery having: a power generation element (4) having positive electrodes (1) and negative electrodes (2) laminated therein, via separators (3); and an outer case (5) housing the power generation element (4) and an electrolyte (6), and having the outer circumference thereof sealed. The electrolyte (6) has a static viscosity at 25°C of 4-30 cP. The positive electrodes (1) and negative electrodes (2) include collectors (1a, 2a) and active substances (1b, 2b) coated on one or both surfaces of the collectors (1a, 2a). Both the active substance (1b) for the positive electrodes (1) and the active substance (2b) for negative electrodes (2) have an overall porosity of at least 30% but less than 50%.

Description

Secondary battery and manufacturing method thereof

The present invention relates to a secondary battery and a manufacturing method thereof.

2. Description of the Related Art Secondary batteries having a configuration in which a power generation element in which a positive electrode and a negative electrode are stacked via a separator are housed in an outer package together with an electrolyte are used as a power source for various electronic devices. Examples of such secondary batteries are described in

Patent Documents

1 and 2. In the secondary battery of Patent Document 1, the porosity of the positive electrode active material (mixture layer) is specified. In the secondary battery of Patent Document 2, the average porosity of the positive electrode active material and the negative electrode active material is defined.

JP 2012-138322 A JP 2003-272609 A

In the secondary battery of Patent Document 1, only the porosity of the positive electrode active material is specified, but the porosity of the negative electrode active material is not mentioned. Although there is a possibility that the permeability of the electrolytic solution is lowered depending on the porosity of the negative electrode active material, Patent Document 1 does not consider this point. Further, the operating voltage of the secondary battery is not taken into consideration, and the problem in the case of using a high dielectric electrolyte required when the operating voltage is high is not recognized.

In the secondary battery of Patent Document 2, the average porosity of the active material of the positive electrode and the active material of the negative electrode is specified, but since it is an average value, there should be a portion where the porosity is partially low or high. Is allowed. If there is a part with a low porosity, a part of the composition in the electrolytic solution (for example, lithium) may be deposited on the electrode at that part. Further, if a part with a high porosity is present partially, the part does not function sufficiently as a battery because the amount of the active material is small. Also in Patent Document 2, there is no particular recognition about the problem in the case of using a high dielectric electrolyte required when the operating voltage is high.

Although not taken into account in

Patent Documents

1 and 2, a high dielectric electrolyte solution required for a secondary battery having a high operating voltage (for example, 4 V or more) has a problem of high static viscosity (unit cP). Static viscosity is a numerical value representing the difficulty of movement of a substance in a liquid. The charge / discharge of the secondary battery is determined by the ease of movement of metal ions (for example, lithium ions) in the electrolyte. That is, in a high static viscosity electrolytic solution used for a secondary battery having a high operating voltage, metal ions are difficult to move, and the charge / discharge characteristics of the battery may be degraded. Such problems are not particularly considered in

Patent Documents

1 and 2.

Patent Document 1 mentions the kinematic viscosity (unit St) of the electrolytic solution, but the kinematic viscosity is a numerical value representing the difficulty of flowing of the liquid itself, and is different from the static viscosity. As described above, the charge / discharge performance of the secondary battery is determined by the ease of movement of the metal ions in the electrolytic solution, and thus depends on the static viscosity and is not directly related to the kinematic viscosity. That is, a high dielectric electrolyte used for a secondary battery having a high operating voltage has a problem that metal ions in the liquid are difficult to move (high static viscosity) and deteriorate the charge / discharge characteristics of the battery. It is not recognized in any of 1 and 2.

The object of the present invention is to solve the above-mentioned problems, taking into account that the permeability of the electrolytic solution depends on the porosity of the negative electrode active material. And a secondary battery that solves the deterioration of the charge / discharge characteristics of the battery due to the high static viscosity of the high dielectric electrolyte used in the secondary battery having a high operating voltage It is in providing the manufacturing method.

The secondary battery of the present invention includes a power generation element in which a positive electrode and a negative electrode are stacked with a separator interposed therebetween, and an exterior body that houses the power generation element and an electrolyte solution and has an outer peripheral portion sealed. The electrolytic solution has a static viscosity at 25 ° C. of 4 cP or more and 30 cP or less. The positive electrode and the negative electrode include a current collector and an active material applied to both or one side of the current collector. Each of the positive electrode active material and the negative electrode active material has a porosity of 30% or more and less than 50%.

In the method for producing a secondary battery of the present invention, the active material is applied to both or one side of the current collector, and the active material applied to the current collector is pressed to make the porosity of the active material 30% or more as a whole. And an electric power generation element forming step of using the electrode forming step, the electrode formed by the electrode forming step as a positive electrode and a negative electrode, and laminating the positive electrode and the negative electrode through a separator, A housing step of housing an electrolytic solution having a static viscosity at 4 ° C. of 4 cP or more and 30 cP or less in the exterior body, and a sealing step of sealing an outer peripheral portion of the exterior body housing the power generation element and the electrolytic solution. Including.

According to the present invention, it is possible to satisfactorily impregnate the electrode with the electrolytic solution while suppressing the deterioration of the charge / discharge characteristics, and it is possible to suppress the metal deposition on the electrode and the deterioration of the electrochemical characteristics.

It is a schematic sectional drawing showing the basic structure of the laminated type secondary battery of this invention. It is a schematic sectional drawing which expands and shows the positive electrode of the secondary battery shown in FIG. It is a schematic sectional drawing which expands and shows the negative electrode of the secondary battery shown in FIG. It is a graph which shows the relationship between the apparent density of the active material of the positive electrode of a secondary battery, and electrolyte solution penetration time. It is a graph which shows the relationship between the apparent density of the active material of the negative electrode of a secondary battery, and electrolyte solution penetration time.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, the basic structure of the secondary battery manufactured in the present invention will be described. As shown in FIG. 1, two types of electrodes (positive electrode 1 and negative electrode 2) are stacked via a separator 3 to form a stacked body (power generation element) 4, and this power generation element 4 is accommodated in an exterior body 5. ing. The exterior body 5 of the present embodiment includes a pair of

laminate films

5a and 5b. Specifically, the

laminate films

5a and 5b positioned above and below so as to sandwich the power generation element 4 are joined to each other at the outer peripheral portion. . The

laminate films

5a and 5b are bonded and sealed by a method such as welding. A power generation element 4 and an electrolytic solution 6 are accommodated in an exterior body 5 made of

laminate films

5a and 5b. In FIG. 1, a part of each layer constituting the power generation element 4 (a layer located at an intermediate portion in the thickness direction) is omitted, and the electrolytic solution 6 impregnated in the power generation element 4 is schematically illustrated. In addition, it is also possible to form the exterior body 5 by bending one long laminate film to cover the power generation element 4 and joining the outer peripheral portions of the laminated laminate film.

The positive electrode 1 included in the power generation element 4 has a configuration in which the positive electrode active material 1b is applied to both surfaces (or only one surface) of the positive electrode current collector 1a as shown in FIG. 2a. Similarly, the negative electrode 2 has a configuration in which the negative electrode active material 2b is applied to both surfaces (or only one surface) of the negative electrode current collector 2a as shown in FIG. 2b. And in the exterior body 5, the electrolyte solution 6 is impregnated with the positive electrode active material 1b and the negative electrode active material 2b. In the present invention, the porosity of both the positive electrode active material 1b and the negative electrode active material 2b is set to 30% or more and less than 50%. Thereby, the electrolyte impregnation property of the electrode is good, and the deterioration of the cycle characteristics due to the deposition of metal (for example, lithium) or the like on the electrode surface and the capacity deterioration can be suppressed. This will be described below.

¡Electrolyte 6 having a high static viscosity is used for a secondary battery having a high operating voltage. For example, an electrolyte 6 having a static viscosity of 4 cP or less at 25 ° C. can be used for a secondary battery having an average operating voltage of 3 V or more and less than 4 V (so-called 4 V type secondary battery), but the average operating voltage is 4 V or more and 5 V. The electrolyte solution 6 having a high dielectric property and high static viscosity (static viscosity at 25 ° C. of about 20 cP) is used for a secondary battery of less than 5V (so-called 5V type secondary battery). As described above, when the electrolytic solution 6 having a high static viscosity is used as the operating voltage increases, the metal ions (for example, lithium ions) in the electrolytic solution 6 are difficult to move, and the electrolytic solution 6 is the electrode 1, It becomes difficult to penetrate into the second

active material

1b, 2b. When the metal ions in the electrolytic solution 6 are difficult to move, the charge / discharge performance of the battery is degraded. In addition, if the electrolytic solution 6 is not sufficiently impregnated in the

active materials

1b and 2b, a substance (for example, lithium) in the electrolytic solution 6 is deposited on the surfaces of the

electrodes

1 and 2 as a metal, and has electrochemical characteristics such as cycle characteristics. Or drop. The density of the electrolytic solution 6 is approximately 1.2 g / ml or more.

Therefore, in the present invention, even when the static viscosity of the electrolytic solution 6 is high, sufficient charge / discharge performance can be obtained, and the

active materials

1b and 2b of the

electrodes

1 and 2 can be satisfactorily impregnated with the electrolytic solution 6. Therefore, attention was paid to the porosity of the

active materials

1b and 2b. By increasing the porosity, the amount of the electrolytic solution 6 held in the

active materials

1b and 2b increases, and the amount of the electrolytic solution 6 that floats in the outer package 5 without being impregnated in the

electrodes

1 and 2 decreases. Therefore, a part of the composition of the electrolytic solution 6 is deposited as a metal, and the capacity reduction associated therewith is suppressed.

Thus, in the present invention, the porosity of the

active materials

1b and 2b of the

electrodes

1 and 2 is specified in order to solve the problem associated with the increase in the static viscosity of the electrolytic solution, which has not been noticed until now. As a result, the electrolyte impregnation property is also improved. The improvement of the electrolyte impregnation property is recognized while improving the charge / discharge performance as compared with the general configuration when the porosity of the

active materials

1b and 2b is approximately 30% or more. However, if the porosity is too large, the amount of the

active materials

1b and 2b is so small that the original function may not be sufficiently exhibited. Therefore, the porosity is preferably less than 50%. That is, in the present invention, the porosity of the

active materials

1b and 2b of the

electrodes

1 and 2 is preferably 30% or more and less than 50%.

Generally, the size of one hole in the

active materials

1b and 2b is about 1 μm to 20 μm, and it is desirable that the holes are evenly dispersed in the

active materials

1b and 2b. If the pores are partly aggregated, the reaction state is non-uniform and uneven, and a part of the electrolyte composition (for example, lithium) is deposited on the electrode or the cycle characteristics are deteriorated. In addition, if the

electrode

1 or 2 has a part where the amount of the

active material

1b or 2b is too small, the part may not sufficiently contribute to the generation of electric power. Therefore, the porosity should be 30% or more and less than 50% throughout the

active materials

1b and 2b, in other words, the porosity of the

active materials

1b and 2b is less than 30%. It is preferable that no part or part having a porosity of 50% or more is present. And it is preferable that the porosity is always 30% or more and less than 50% on each surface of the active material or in any cross section.

In the present invention, by defining the porosity of the

active materials

1b and 2b of the

electrodes

1 and 2, the electrolyte 6 injected into the exterior body 5 is used as efficiently as possible. That is, as many metal ions as possible contained in the electrolytic solution 6 can be contributed to charge / discharge of the battery without being deposited as metal. Therefore, the present invention is particularly effective in a 5V type secondary battery in which the electrolytic solution 6 having a high static viscosity is used or a battery having a higher operating voltage.

A method for manufacturing the secondary battery will be described. First, as a secondary battery electrode, a positive electrode 1 in which a positive electrode active material 1b is applied to both surfaces (or one surface) of a positive electrode current collector 1a as shown in FIG. 2a, and a negative electrode current collector 2a as shown in FIG. 2b. The negative electrode 2 in which the negative electrode active material 2b is applied to both sides (or one side) is manufactured. Specifically, a predetermined amount of the positive electrode active material 1b is applied to the positive electrode current collector 1a. Thereafter, the positive electrode active material 1b on the positive electrode current collector 1a is pressed at an appropriate pressure, so that the porosity is made 30% or more and less than 50% throughout the positive electrode active material 1b as described above. In the same manner, after applying the negative electrode active material 2b to the negative electrode current collector 2a, the negative electrode active material 2b is pressed so that the porosity is 30% or more and less than 50% throughout. The positive electrode 1 and the negative electrode 2 manufactured in this manner are alternately stacked via the separator 3 to form a stacked body (power generation element) 4. The number of layers of the positive electrode 1 and the negative electrode 2 to be stacked is determined according to the use of the secondary battery.

Next, as shown in FIG. 1, a pair of

laminate films

5 a and 5 b are arranged so as to sandwich the power generation element 4, and the

laminate films

5 a and 5 b are overlapped with each other outside the power generation element 4. And the outer peripheral part of the

laminated film

5a, 5b which overlaps is mutually joined by welding etc. except the part used as the liquid injection port which is not shown in figure. A pair of

electrode terminals

9 and 10 are connected to the positive electrode 1 and the negative electrode 2, respectively, and extend to the outside of the exterior body 5. Therefore, the portions through which the

electrode terminals

9 and 10 pass are not directly welded to the

laminate films

5a and 5b. However, the

laminate films

5a and 5b are substantially bonded to each other around the

electrode terminals

9 and 10. It is sealed without gaps. Then, the electrolytic solution 6 is injected from the liquid injection port into the exterior body 5 in a state where the power generation element 4 is accommodated in the sealed exterior body 5 except for the liquid injection port. The unbonded portions of the outer peripheral portions of the

laminate films

5a and 5b are joined to each other by welding or the like so as to seal the liquid injection port of the outer package 5 containing the power generation element 4 and the electrolyte 6. Thereby, the outer package 5 is sealed over the entire circumference.

In such a battery manufacturing method, in order to obtain good electrochemical characteristics as a battery, the electrolytic solution 6 injected into the exterior body 5 is well impregnated (absorbed) into the positive electrode active material 1b and the negative electrode active material 2b. ) Is desirable. If the impregnation property is poor, the time required to sufficiently impregnate the electrolytic solution 6 becomes long, and the productivity is deteriorated.

As a specific example, in FIG. 3, one drop (about 0.1 μl) of an electrolytic solution 6 having a static viscosity of 23 cP at 25 ° C. is dropped into the outer package 5 and completely penetrates into the positive electrode 1 (impregnated). And the result of measuring the time until it is judged visually. In this experiment, the porosity was 36.57% (apparent density 2.56 g / cm ³ ), 34.13% (apparent density 2.65 g / cm ³ ), 32.1% (apparent density) the positive electrode having a positive electrode active material 1b of density 2.73 g ^/ cm 3), 29.23% (density of 2.85 g ^/ cm 3 apparent), 26.47% (density of 2.96 g / cm ³ apparent) 6 pieces of 1 were prepared for each of 30 positive electrodes 1 in total. As a result, when the porosity of the positive electrode active material 1b is 30% or more, the permeation time is 120 seconds or less, and it can be said that the impregnation property is good. In addition, the graph of FIG. 3 shows the average of the permeation time of the six positive electrodes 1 having the positive electrode active materials 1b having the same porosity.

In FIG. 4, a similar experiment was conducted with a porosity of 39.69% (apparent density 1.30 g / cm ³ ), 35.25% (apparent density 1.40 g / cm ³ ), 30. Six negative electrodes 2 each having 64% (apparent density 1.50 g / cm ³ ) of the negative electrode active material 2b were prepared, and a total of 18 negative electrodes 2 were prepared. As the porosity of the negative electrode active material 2b is larger, the permeation time tends to be shorter. In addition, the graph of FIG. 4 shows the average of the permeation time of the six negative electrodes 2 having the negative electrode active material 2b having the same porosity.

Here, the relationship between the apparent density and the porosity shown on the horizontal axis of FIGS. The porosity means the ratio of the volume of vacancies existing in and on the surface of the substance to the total volume of the substance. Therefore, in a substance having the same volume, the higher the porosity, the more pores, the smaller the amount of the substance itself, and the smaller the mass. On the other hand, since the density is the mass per unit volume, it is considered that the substance of the same volume has a larger amount of the substance itself and a smaller number of pores as the apparent density is higher. Thus, when the porosity is high, the apparent density is low, and when the porosity is low, the apparent density is high.

The relationship between the apparent density and the porosity is not the same between the positive electrode active material 1b shown in FIG. 3 and the negative electrode active material 2b shown in FIG. This is because the material of the positive electrode active material 1b and the material of the negative electrode active material 2b are different and the true densities are different. That is, even with the same porosity, an active material made of a material having a high true density has a high apparent density, and an active material made of a material having a low true density has a low apparent density. Therefore, the apparent density necessary to obtain a desired porosity in the present invention can be calculated based on the true density of the active material. At the time of manufacturing the secondary battery electrode, conditions (pressure, etc.) for pressing the active material are set so that the apparent density obtained based on such calculation is obtained. For example, in order to make an active material made of a material having a true density of 4 g / cm ³ to have a porosity of 35%, the apparent density may be 2.6 g / cm ³ . Assuming that the area of the part to which the active material of the current collector is applied is 10,000 mm ² , 3.1 g of the active material (material) is applied to this part and pressed to a thickness of 0.12 mm. The apparent density is 2.6 g / cm ³ and a porosity of 35% is achieved. When the active material is a mixture of a plurality of materials, the above-described calculation may be performed after obtaining the true density of the mixture itself by adding the products of the true density and the mixing rate of each material.

As the positive electrode active material 1b of the positive electrode 1 of the present invention, for example, LiCoO ₂ , LiNiO ₂ , LiNi _(1-x) CoO ₂ , LiNi _x (CoAl) _(1-x) O ₂ , Li ₂ MO ₃ —LiMO ₂ , layered oxide materials such as LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiMn ₂ O ₄ , LiMn _1.5 Ni _0.5 O ₄ , LiMn _(2-x) M _x O spinel type material such as _4, olivine-based material such as LiMPO _{_4,} Li ₂ MPO _{4 F,} fluoride olivine-based material, such as Li 2 MSiO ₄ _F, vanadium oxide-based materials such as V 2 _{O 5,} and these 1 type of these, or a mixture of 2 or more types can be used.

As the negative electrode active material 2b, carbon materials such as graphite, amorphous carbon, diamond-like carbon, fullerene, carbon nanotube, and carbon nanohorn, lithium metal materials, alloy materials such as silicon and tin, Nb ₂ O ₅ and TiO _{2 are used.} An oxide-based material such as these, or a composite thereof can be used.

The positive electrode active material 1b and the negative electrode active material 2b can be appropriately added with a binder, a conductive auxiliary agent, and the like. As the conductive auxiliary agent, one or more of carbon black, carbon fiber, graphite and the like are used. Can be used. As the binder, polyvinylidene fluoride, polytetrafluoroethylene, carboxymethylcellulose, modified acrylonitrile rubber particles, and the like can be used.

As the positive electrode current collector 1a, aluminum, stainless steel, nickel, titanium, or an alloy thereof can be used, and aluminum is particularly preferable. As the negative electrode current collector 2a, copper, stainless steel, nickel, titanium, or an alloy thereof can be used.

The electrolyte 6 includes cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, butylene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC). ), Etc., aliphatic carboxylic acid esters, γ-lactones such as γ-butyrolactone, chain ethers, cyclic ethers, organic solvents such as fluorine compounds, or Two or more kinds of mixtures can be used, and lithium salts and functional additives can be dissolved in these organic solvents.

Examples of the resin component of the separator 3 include a porous film, a woven fabric, and a nonwoven fabric. For example, a polyolefin resin such as polypropylene or polyethylene, a polyester resin, an acrylic resin, a styrene resin, or a nylon resin can be used. In particular, a polyolefin-based microporous membrane is preferable because of its excellent ion permeability and performance of physically separating the positive electrode and the negative electrode. If necessary, the separator 3 may be formed with a layer containing inorganic particles, and examples of the inorganic particles include insulating oxides, nitrides, sulfides, carbides, etc. It is preferable to contain TiO ₂ or Al ₂ O ₃ . In terms of improving the impregnation property of the electrolytic solution 6, it is preferable to select a material that reduces the contact angle between the electrolytic solution 6 and the separator 3.

As the

laminate films

5a and 5b constituting the exterior body 5, those in which a resin layer is provided on the front and back surfaces of a metal layer serving as a base material can be used. As the metal layer, a metal layer having a barrier property such as prevention of leakage of electrolyte solution or entry of moisture from the outside can be selected, and aluminum, stainless steel, or the like can be used. On at least one surface of the metal layer, a heat-fusible resin layer such as a modified polyolefin is provided. The heat-sealing resin layers of the

laminate films

5a and 5b are opposed to each other, and the outer container is formed by heat-sealing the periphery of the portion that houses the electrode laminate. A resin layer such as a nylon film or a polyester film can be provided on the surface of the exterior body that is the surface opposite to the surface on which the heat-fusible resin layer is formed.

The present invention is useful for the production of an electrode of a lithium ion secondary battery and the production of a lithium ion secondary battery using the electrode, but it is also effective when applied to a secondary battery other than a lithium ion battery.

As described above, the present invention is characterized by defining the porosity of the active material 1b of the positive electrode 1 and the active material 2b of the negative electrode 2, and the other configurations are not particularly limited. Therefore, various modified examples adopted in a general secondary battery can be adopted in the present invention. For example, FIG. 1 illustrates a secondary battery having a so-called laminated power generation element 4 formed by alternately and repeatedly laminating a plurality of positive electrodes 1 and a plurality of negative electrodes 2 with separators 3 interposed therebetween. is doing. However, one long positive electrode 1 and one long negative electrode are laminated via a long separator 3, and the laminated positive electrode 1, separator 3 and negative electrode 2 are integrally wound. The present invention can also be applied to a secondary battery having a so-called wound type power generation element 4 formed by doing so.

Further, in the laminated power generation element 4, instead of preparing a plurality of separators 3 sandwiched between the positive electrode 1 and the negative electrode 2, one long separator 3 is provided for each length corresponding to the positive electrode 1 and the negative electrode 2. It is also possible to interpose between each positive electrode 1 and each negative electrode 2 by being alternately folded. That is, a configuration may be adopted in which a plurality of bag-like portions are formed by alternately folding the long separator 3 every predetermined length, and the positive electrode 1 or the negative electrode 2 is accommodated in each bag-like portion.

Although the present invention has been described above with reference to some embodiments, the present invention is not limited to the configurations of the above-described embodiments, and the scope of the technical idea of the present invention is not limited to the configurations and details of the present invention. Various modifications that can be understood by those skilled in the art can be made.

This application claims priority based on Japanese Patent Application No. 2013-201541 filed on September 27, 2013, and incorporates the entire disclosure of Japanese Patent Application No. 2013-201541.

Claims

A power generation element in which a positive electrode and a negative electrode are laminated via a separator, and an exterior body that contains the power generation element and an electrolyte and has an outer peripheral portion sealed;
The electrolytic solution has a static viscosity at 25 ° C. of 4 cP or more and 30 cP or less,
The positive electrode and the negative electrode include a current collector and an active material applied to both or one side of the current collector,
The active material of the positive electrode and the active material of the negative electrode each have a porosity of 30% or more and less than 50% throughout.
The secondary battery according to claim 1, wherein the active material does not include a portion having a porosity of less than 30% or 50% or more.
The secondary battery according to claim 1 or 2, wherein the average operating voltage is 4 V or more.
The secondary battery according to any one of claims 1 to 3, wherein the power generation element is formed by alternately and repeatedly laminating a plurality of the positive electrodes and a plurality of the negative electrodes through the separators. .
The power generation element is formed by laminating one positive electrode and one negative electrode through the separator, and the laminated positive electrode, separator, and negative electrode are integrally wound. The secondary battery according to any one of claims 1 to 3.
The secondary battery according to any one of claims 1 to 5, wherein the electrolytic solution contains at least one of cyclic carbonate, chain carbonate, cyclic fluorinated ether, and chain fluorinated ether.
An electrode in which an active material is applied to both sides or one side of a current collector, and the active material applied to the current collector is pressed to make the porosity of the active material 30% or more and less than 50% throughout. Forming process;
Using the electrode formed by the electrode forming step as a positive electrode and a negative electrode, and laminating the positive electrode and the negative electrode through a separator,
A housing step of housing the power generation element and an electrolytic solution having a static viscosity at 25 ° C. of 4 cP or more and 30 cP or less within the exterior body;
A method for manufacturing a secondary battery, comprising: a sealing step of sealing an outer peripheral portion of the exterior body containing the power generation element and the electrolytic solution.
The method for manufacturing a secondary battery according to claim 7, wherein in the power generation element forming step, a plurality of the positive electrodes and a plurality of the negative electrodes are alternately and repeatedly stacked via the separators.
The said power generation element formation process WHEREIN: One said positive electrode and one said negative electrode are laminated | stacked through the said separator, and the laminated | stacked said positive electrode, the said separator, and the said negative electrode are integrally wound. The manufacturing method of the secondary battery as described in any one of.