JP2019212464A - Manufacturing method of lithium ion battery - Google Patents

Abstract

To provide a manufacturing method of a lithium ion battery, capable of immersing uniformly an electrolyte.SOLUTION: A manufacturing method of a lithium ion battery, comprising: a lamination unit in which an electrode active material layer A and an electrode active material layer B opposite to the A are laminated via a separator; an electrolyte; and an outer casing that houses them, includes a lamination step of obtaining the lamination unit made of laminating the A and B. At least one of the B contains the electrolyte before the formation of the lamination unit. The A and the B satisfy at least one condition of the following 1 and 2: 1. a total area of a fine hole of the A in the state where all fine holes held in a separator are filled with the electrolyte, and the electrolyte is not included is larger than a volume of the electrolyte included in the A; and 2. at least B contains the electrolyte, a ratio of the volume of the electrolyte contained in the B for the total volume of the fine hole included by the B in the state of excluding the electrolyte is larger than the ratio of the volume of the electrolyte contained in the A for the total volume of the fine hole of the A in the state of excluding the electrolyte.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing a lithium ion battery.

In recent years, reduction of carbon dioxide emissions has been strongly desired for environmental protection. In the automobile industry, there are high expectations for reducing carbon dioxide emissions by introducing electric vehicles (EVs) and hybrid electric vehicles (HEVs), and we are eager to develop secondary batteries for motor drives that hold the key to their practical application. Has been done. As a secondary battery, attention is focused on a lithium ion battery (also referred to as a lithium ion secondary battery) that can achieve high energy density and high output density.

A lithium ion battery is manufactured by laminating or winding a positive electrode, a negative electrode, and a separator to form a power generation element, and injecting an electrolyte therethrough. By the way, when it is set as the high capacity | capacitance battery used for an electric vehicle (EV) etc., since an electrode becomes large and the quantity of the active material contained there increases, electrolyte solution is uniformly impregnated in an electrode, and electrolyte solution It is necessary to prevent or suppress the impregnation unevenness.
As a liquid injection method for preventing or suppressing the uneven impregnation of the electrolytic solution, for example, the inside of the laminate container having the housing portion containing the power generation element and the space in which the electrolytic solution is stored is set to a negative pressure, and electrolysis in the space is performed. A method of gradually penetrating a liquid into a power generation element (see Patent Document 1) is known.

JP 2009-76248 A

However, in the method described in Patent Document 1, the electrolyte is injected from the lateral direction of the laminate, and the active material layer is impregnated by gradually spreading in the lateral direction, so that the electrode area is increased. In some cases or when only a short time has passed since the electrolyte solution was injected, it was difficult to uniformly impregnate the electrolyte solution, and there was a problem that impregnation unevenness could not be sufficiently prevented or suppressed.

The present invention has been made in view of the above problems, even when impregnating an electrolyte with a large area electrode, or even when only a short time has passed since the electrolyte was injected, It aims at providing the manufacturing method of the lithium ion battery which can be uniformly impregnated with electrolyte solution.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have reached the present invention.
That is, the present invention provides a laminate unit in which an electrode active material layer (A) and an electrode active material layer (B) as a counter electrode of the electrode active material layer (A) are laminated via a separator, an electrolytic solution, and A method of manufacturing a lithium ion battery including an exterior body that accommodates the laminated unit and the electrolytic solution, wherein the electrode active material layer (A), the separator, and the electrode active material layer (B) are laminated. A stacking step for obtaining a stack unit, and before forming the stack unit, at least one of the separator and the electrode active material layer (B) contains the electrolyte solution, and the electrode active material layer (A), the separator and the negative electrode active material layer (B) relate to a method for producing a lithium ion battery, characterized in that at least one of the following conditions (1) to (2) is satisfied.
(1) The total volume of the pores of the electrode active material layer (A) in the state where all of the pores of the separator are filled with the electrolyte and does not contain the electrolyte is the electrode active material It is larger than the volume of the electrolyte solution that the layer (A) has.
(2) The electrode active material layer (B) relative to the total volume of pores of the electrode active material layer (B) in a state where at least the electrode active material layer (B) contains the electrolyte solution and does not contain the electrolyte solution The volume ratio of the electrolyte solution contained in the electrode active material layer (A) with respect to the total volume of pores of the electrode active material layer (A) in a state where the electrolyte solution is not contained. It is larger than the liquid volume ratio.

The method for producing a lithium ion battery according to the present invention provides a uniform electrolyte solution even when an electrode with a large area is impregnated with the electrolyte solution or when only a short time has elapsed since the electrolyte solution was injected. Can be impregnated.

FIG. 1 is a diagram schematically illustrating an example of a stacking process. FIG. 2 is an explanatory view schematically showing an example of the movement of the electrolytic solution immediately after forming the laminated unit. FIG. 3 is an explanatory view schematically showing another example of the movement of the electrolytic solution immediately after forming the laminated unit.

Hereinafter, the present invention will be described in detail.
Note that in this specification, a lithium ion battery includes a lithium ion secondary battery.

The method for producing a lithium ion battery according to the present invention includes a laminate unit in which an electrode active material layer (A) and an electrode active material layer (B) serving as a counter electrode of the electrode active material layer (A) are laminated via a separator, A method of manufacturing a lithium ion battery including an electrolytic solution and an exterior body that houses the laminated unit and the electrolytic solution, the electrode active material layer (A), the separator, and the electrode active material layer (B ) Is provided, and before forming the laminated unit, at least one of the separator and the electrode active material layer (B) contains the electrolytic solution, The electrode active material layer (A), the separator, and the negative electrode active material layer (B) satisfy at least one of the following conditions (1) to (2).
(1) The total volume of the pores of the electrode active material layer (A) in the state where all of the pores of the separator are filled with the electrolyte and does not contain the electrolyte is the electrode active material It is larger than the volume of the electrolyte solution that the layer (A) has.
(2) The electrode active material layer (B) relative to the total volume of pores of the electrode active material layer (B) in a state where at least the electrode active material layer (B) contains the electrolyte solution and does not contain the electrolyte solution The volume ratio of the electrolyte solution contained in the electrode active material layer (A) with respect to the total volume of pores of the electrode active material layer (A) in a state where the electrolyte solution is not contained. It is larger than the liquid volume ratio.

In the method for producing a lithium ion battery of the present invention, before forming the laminated unit, at least one of the separator and the electrode active material layer (B) contains an electrolytic solution, and the following (1) to (2) Satisfies at least one of the following conditions.
(1) The total volume of the pores of the electrode active material layer (A) in the state where all of the pores of the separator are filled with the electrolyte and does not contain the electrolyte is the electrode active material It is larger than the volume of the electrolyte solution that the layer (A) has.
(2) The electrode active material layer (B) relative to the total volume of pores of the electrode active material layer (B) in a state where at least the electrode active material layer (B) contains the electrolyte solution and does not contain the electrolyte solution The volume ratio of the electrolyte solution contained in the electrode active material layer (A) with respect to the total volume of pores of the electrode active material layer (A) in a state where the electrolyte solution is not contained. It is larger than the liquid volume ratio.

In the case of (1), all the pores of the separator are filled with the electrolyte solution, but the total volume of the pores of the electrode active material layer (A) in the state not containing the electrolyte solution is the electrode active material. Since it is larger than the volume of the electrolyte solution which a layer (A) has, it can be said that the electrode active material layer (A) has the pore which does not contain electrolyte solution. Accordingly, a part of the electrolyte contained in the separator is supplied to the electrode active material layer (A).
At this time, since the electrode active material layer (A) and the separator are in contact with each other, the rate at which the electrolytic solution is supplied from the separator to the electrode active material layer (A) is adjusted by a normal method (the electrolytic solution in the exterior body). Compared with the method of injecting liquid).

In the case of (2), the ratio of the volume of the electrolyte solution contained in the electrode active material layer (B) to the total volume of the pores of the electrode active material layer (B) in the state where the electrolyte solution is not contained is the electrolyte solution. It is larger than the ratio of the volume of the electrolyte solution contained in the electrode active material layer (A) to the total volume of the pores of the electrode active material layer (A) when not included.
Therefore, a part of the electrolytic solution contained in the electrode active material layer (B) in which the amount of the electrolytic solution occupies the total volume of the pores in a state where the electrolytic solution is not included is relatively large does not include the electrolytic solution. Thus, the amount of the electrolyte solution in the total volume of the pores is supplied to the electrode active material layer (A) having a relatively small amount. At this time, a part of the electrolytic solution contained in the electrode active material layer (B) is supplied to the electrode active material layer (A) via a separator that is in contact with the electrode active material layer (B) surface-to-face. The rate at which the electrolytic solution is supplied from the electrode active material layer (B) to the electrode active material layer (A) through the separator is faster than that of a normal method (method of injecting the electrolytic solution into the exterior body). .
In the case of (2), the electrode active material layer (A) may or may not contain an electrolytic solution. When the electrode active material layer (A) does not contain an electrolyte solution, the electrolyte solution contained in the electrode active material layer (A) with respect to the total volume of pores of the electrode active material layer (A) in a state where the electrode solution does not contain the electrolyte solution The volume ratio of is 0%.

In the case of (1) and (2) above, the movement of the electrolytic solution between the electrode active material layer (A) and the separator and the movement of the electrolytic solution between the separator and the electrode active material layer (B) Since it is performed on the contact surface with the electrode active material layer (A) or the electrode active material layer (B) and diffuses in the thickness direction, the diffusion distance of the electrolytic solution is short, and variations in the concentration of the electrolytic solution are unlikely to occur.
Therefore, the electrolyte can be uniformly impregnated into the lithium ion battery electrode. This effect is more remarkable as the area of the electrode is larger.

In the method for producing a lithium ion battery of the present invention, in the case of (2) above, the electrode active material layer (B) is included in the total volume of pores of the electrode active material layer (B) in a state where the electrolyte solution is not included. The ratio of the volume of the electrolyte solution (hereinafter also referred to as the electrolyte solution ratio of the electrode active material layer (B)) and the electrode relative to the total volume of the pores of the electrode active material layer (A) in a state that does not include the electrolyte solution The difference in the volume ratio of the electrolyte solution contained in the active material layer (A) (hereinafter also referred to as the electrolyte solution ratio of the electrode active material layer (A)) is not particularly limited, but is preferably 45% or more.
When the difference in the electrolytic solution ratio is 45% or more, the electrolytic solution can be rapidly supplied from the electrode active material layer (B) to the electrode active material layer (A).

In the method for producing a lithium ion battery of the present invention, at least one of the above conditions (1) to (2) is satisfied before the stacked unit is formed, but both the conditions (1) and (2) are satisfied. preferable.
When both conditions (1) and (2) are satisfied, the electrode active material layer (A) can be rapidly and uniformly impregnated with a sufficient amount of the electrolytic solution.

As a method of satisfying the above (1) before forming the laminated unit, for example, before forming the laminated unit, the electrode active material layer (A) is not impregnated with the electrolytic solution, but the separator is impregnated with the electrolytic solution. Methods and the like.
Examples of the method of impregnating the separator with the electrolytic solution include a method of putting (immersing) the separator into a container containing a predetermined amount of the electrolytic solution, a method of dropping the electrolytic solution on the surface of the separator with a dropper, and the like. .
Whether or not all the pores of the separator are filled with the electrolytic solution can be confirmed by changing the appearance of the separator surface from white to translucent.
Note that an electrolytic solution having a volume larger than the total volume of the pores may be added to the separator. In this case, the electrolyte solution that has not entered the pores is retained on the surface of the separator.

As a method of satisfying the above (2) before forming the laminated unit, for example, a method of putting (immersing) the electrode active material layer (B) in a container containing a predetermined amount of electrolyte, or an electrode active material Examples thereof include a method of dropping an electrolyte solution on the surface of the layer (B) with a dropper or the like.
Furthermore, when producing the electrode active material layer (B), in addition to each component constituting the electrode active material layer, an electrolytic solution was added, and this was mixed and molded to contain the electrolytic solution. A method for producing the electrode active material layer (B) is also included.

The lamination process which comprises the manufacturing method of the lithium ion battery of this invention is demonstrated concretely with reference to FIG.
FIG. 1 is a diagram schematically illustrating an example of a stacking process.
As shown in FIG. 1, in the stacking step, the electrode active material layer (A) 10 and the electrode active material layer (B) 30 serving as a counter electrode are stacked via a separator 20 to obtain a stack unit 100.
The electrode active material layer (A) 10 and the electrode active material layer (B) 30 are both porous bodies having pores that can contain an electrolytic solution. The separator 20 is also a porous body having pores that can contain an electrolytic solution therein.
At least one of the electrode active material layer (B) 30 and the separator 20 contains an electrolytic solution.

The movement of the electrolytic solution after forming the laminated unit will be described.
FIG. 2 is an explanatory view schematically showing an example of the movement of the electrolytic solution immediately after forming the laminated unit. FIG. 2 shows an example in which the electrolyte solution is contained only in the separator before forming the laminated unit.
In the case shown in FIG. 2, the electrolyte is initially contained only in the separator 20. When the separator 20 is brought into contact with the electrode active material layer (A) 10 and the electrode active material layer (B) 30 by forming the laminated unit 100, the electrode active material layer (A) 10 and the electrode active material are contacted from the contact surface. The electrolytic solution moves toward the material layer (B) 30 (the arrow shown in FIG. 2 indicates the direction in which the electrolytic solution diffuses).

FIG. 3 is an explanatory view schematically showing another example of the movement of the electrolytic solution immediately after forming the laminated unit. FIG. 3 shows an example of the case where the electrolytic solution is contained only in the electrode active material layer (B) before forming the laminated unit.
In the case shown in FIG. 3, the electrolytic solution is initially contained only in the electrode active material layer (B) 30. When the separator 20, the electrode active material layer (A) 10, and the electrode active material layer (B) 30 come into contact with each other by forming the laminated unit 100, the separator is separated from the contact surface between the electrode active material layer (B) 30 and the separator 20. First, the electrolyte moves with respect to 20. Thereafter, the electrolyte solution moves from the contact surface between the separator 20 and the electrode active material layer (A) 10 to the electrode active material layer (A) 10 (the arrow shown in FIG. 3 indicates the direction in which the electrolyte solution diffuses). Is shown.)
In addition, even when it contains electrolyte solution in both a separator and an electrode active material layer (B) before forming a lamination | stacking unit, electrolyte solution moves from a separator to an electrode active material layer (A).

The electrode active material layer is a porous body that includes an electrode active material and has pores that can contain an electrolytic solution. In addition to the electrode active material, the electrode active material layer may contain a conductive additive, an adhesive resin, and an electrode binder.

In the method for producing a lithium ion battery of the present invention, different types of electrode active materials are used for the electrode active material layer (A) and the electrode active material layer (B).
That is, the electrode active material is either a positive electrode active material or a negative electrode active material, and when the electrode active material layer (A) is a positive electrode active material layer using a positive electrode active material as an electrode active material, (B) is a negative electrode active material layer using a negative electrode active material as an electrode active material.

The positive electrode active material layer is a porous body that includes a positive electrode active material and has pores that can contain an electrolytic solution.

As the positive electrode active material, a composite oxide of lithium and a transition metal (a composite oxide having one kind of transition metal (such as LiCoO ₂ , LiNiO ₂ , LiAlMnO ₄ , LiMnO _2, and LiMn ₂ O ₄ ), a transition metal element is used. Two kinds of complex oxides (for example, LiFeMnO ₄ , LiNi _1-x Co _x O ₂ , LiMn _1-y Co _y O ₂ , LiNi _1/3 Co _1/3 Al _1/3 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ ) and a composite oxide having three or more transition metal elements [for example, LiM _a M ′ _b M ″ _c O ₂ (M, M ′, and M ″ are different transition metals, respectively) an element, satisfy a + b + c = 1. for example _{LiNi 1/3 Mn 1/3 Co 1/3 O 2} ) , etc.] or the like}, lithium-containing transition metal phosphate (e.g. LiFePO _4, Li OPO _4, LiMnPO ₄ and LiNiPO _4), transition metal oxides (e.g., MnO ₂ and _V 2 _O 5), transition metal sulfides (e.g., MoS ₂ and TiS ₂₎ and the conductive polymer (such as polyaniline, polypyrrole, polythiophene, Polyacetylene, poly-p-phenylene, and polyvinylcarbazole), and the like may be used in combination.
The lithium-containing transition metal phosphate may be one in which a part of the transition metal site is substituted with another transition metal.

The volume average particle diameter of the positive electrode active material is preferably 0.01 to 100 μm, more preferably 0.1 to 35 μm, and more preferably 1 to 30 μm, from the viewpoint of the electrical characteristics of the lithium ion battery. Further preferred.

The negative electrode active material layer includes a negative electrode active material and is a porous body having pores that can contain an electrolytic solution.

Examples of the negative electrode active material include carbon materials [for example, hard carbon, non-graphitizable carbon, amorphous carbon, resin fired bodies (for example, those obtained by firing and carbonizing phenol resin, furan resin, etc.), cokes (for example, pitch coke). , Needle coke and petroleum coke, etc.), silicon carbide and carbon fiber, etc.], conductive polymers (eg, polyacetylene and polypyrrole, etc.), metals (tin, silicon, aluminum, zirconium, titanium, etc.), metal oxides (titanium oxide, etc.) , Lithium / titanium oxide, silicon oxide, etc.) and metal alloys (for example, lithium-tin alloy, lithium-silicon alloy, lithium-aluminum alloy, lithium-aluminum-manganese alloy, etc.) and the like and mixtures of these with carbon-based materials Etc.
Among the above negative electrode active materials, those that do not contain lithium or lithium ions may be subjected to a pre-doping treatment in which lithium or lithium ions are included in part or all of the negative electrode active material in advance.

The volume average particle diameter of the negative electrode active material is preferably from 0.01 to 100 μm, more preferably from 0.1 to 40 μm, and even more preferably from 2 to 35 μm, from the viewpoint of the electrical characteristics of the lithium ion battery.

In this specification, the volume average particle diameter of the electrode active material means the particle diameter (Dv50) at an integrated value of 50% in the particle size distribution determined by the microtrack method (laser diffraction / scattering method). The microtrack method is a method for obtaining a particle size distribution using scattered light obtained by irradiating particles with laser light. In addition, Nikkiso Co., Ltd. microtrack etc. can be used for the measurement of a volume average particle diameter.

The conductive aid is selected from materials having conductivity.
Specifically, metals [nickel, aluminum, stainless steel (SUS), silver, copper, titanium, etc.], carbon [graphite and carbon black (acetylene black, ketjen black, furnace black, channel black, thermal lamp black, etc.), etc. , And mixtures thereof, but are not limited thereto.
These conductive assistants may be used alone or in combination of two or more. Further, these alloys or metal oxides may be used. From the viewpoint of electrical stability, aluminum, stainless steel, carbon, silver, copper, titanium and a mixture thereof are preferable, silver, aluminum, stainless steel and carbon are more preferable, and carbon is more preferable. Moreover, as these conductive support agents, what coated the electroconductive material (metal thing among the above-mentioned conductive support agents) by plating etc. around the particulate ceramic material or the resin material may be used.

The average particle diameter of the conductive auxiliary agent is not particularly limited, but is preferably 0.01 to 10 μm and more preferably 0.02 to 5 μm from the viewpoint of the electrical characteristics of the lithium ion battery. More preferably, the thickness is 0.03 to 1 μm.
The “particle diameter” means the maximum distance L among the distances between any two points on the particle outline. As the value of “average particle diameter”, the average value of the particle diameter of particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted.

The shape (form) of the conductive auxiliary agent is not limited to the particle form, but may be a form other than the particle form, or may be a form put into practical use as a so-called filler-based conductive material such as a carbon nanotube.

The conductive auxiliary agent may be a conductive fiber having a fibrous shape.
Examples of conductive fibers include carbon fibers such as PAN-based carbon fibers and pitch-based carbon fibers, conductive fibers obtained by uniformly dispersing highly conductive metal and graphite in synthetic fibers, and metals such as stainless steel. Examples thereof include fiberized metal fibers, conductive fibers in which the surface of organic fiber is coated with metal, and conductive fibers in which the surface of organic fiber is coated with a resin containing a conductive substance. Among these conductive fibers, carbon fibers are preferable. A polypropylene resin in which graphene is kneaded is also preferable.
When a conductive support agent is a conductive fiber, it is preferable that the average fiber diameter is 0.1-20 micrometers.

The electrode active material may be a coated electrode active material in which at least a part of its surface is coated with a coating agent containing a coating resin. The coated electrode active material can be molded under simpler conditions because the coating agent containing the electrolyte swells and exhibits adhesiveness.
Therefore, it becomes easy to produce an electrode active material layer containing an electrolytic solution from the beginning.
The coated electrode active material when the electrode active material is a positive electrode active material is also referred to as a coated positive electrode active material, and the coated electrode active material when the electrode active material is a negative electrode active material is also referred to as a coated negative electrode active material.

The coating agent includes a coating resin, and may further include a conductive material as necessary.
Examples of the coating resin include thermoplastic resins and thermosetting resins. For example, fluorine resins, acrylic resins, urethane resins, polyester resins, polyether resins, polyamide resins, epoxy resins, polyimide resins, silicone resins, Examples thereof include phenol resins, melamine resins, urea resins, aniline resins, ionomer resins, polycarbonates, polysaccharides (such as sodium alginate), and mixtures thereof. Among these, acrylic resins, urethane resins, polyester resins or polyamide resins are preferable, and acrylic resins are more preferable.
Among these, a coating resin having a liquid absorption rate of 10% or more when immersed in an electrolytic solution and a tensile elongation at break in a saturated liquid absorption state of 10% or more is more preferable.
Among the above-described coating resins, those described as a coating resin in International Publication No. 2015/005117 constitute a coating agent in the method for producing an electrode composition molded body for a lithium ion battery of the present invention. It can be particularly suitably used as a coating resin.

The coated active material can be obtained by a known method described in International Publication No. 2015/041184.

The electrode active material layer may be a porous body formed by forming a mixture containing an electrode active material and an electrode binder and / or an adhesive resin. The electrode active material layer is preferably a porous body formed by molding a mixture containing an electrode active material and an adhesive resin without containing an electrode binder.
As the binder for electrodes, known binder drying agents for lithium ion batteries (starch, polyvinylidene fluoride, polyvinyl alcohol) used for binding and fixing the electrode active materials to each other and the electrode active material and the current collector , Carboxymethylcellulose, polyvinylpyrrolidone, tetrafluoroethylene, styrene-butadiene rubber, polyethylene, polypropylene and styrene-butadiene copolymer, etc., which are used by dissolving or dispersing in a solvent, volatilizing and distilling off the solvent. A material that binds by being precipitated as a solid).
When the electrode binder is dried by volatilizing the solvent component, the surface is solidified without showing adhesiveness, and the electrode active materials and the electrode active materials and the current collector are firmly fixed. . On the other hand, the adhesive resin means a resin having adhesiveness without solidifying even if the solvent component is volatilized and dried. Here, the term “adhesion” means “a phenomenon seen in high-viscosity liquids that adheres to an adherend by applying a slight pressure” as defined in the term JIS Z0109: 2015 adhesive tape / adhesive sheet. An adhesive resin is a resin that can be adhered to an adherend by applying a slight pressure. The solid electrode binder and the adhesive resin, which cannot be adhered to the adherend only by applying a slight pressure, are different materials and are distinguished from each other. The electrode binder is also simply called a binder or a binder.

An adhesive resin is a resin that can be reversibly adhered to an adherend with a slight pressure at room temperature for a short time. From vinyl acetate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, butyl acrylate, and butyl methacrylate It is preferable to include at least one low Tg monomer selected from the group as an essential constituent monomer. The total weight ratio of the low Tg monomer is preferably 45% by weight or more based on the total weight of the constituent monomers.
The coating resin does not exhibit adhesiveness unless a solvent that dissolves a part thereof is used, whereas the adhesive resin is an electrode active material composition without using a solvent that dissolves a part thereof. The resin for coating and the adhesive resin are distinguished from each other in that the adhesiveness is developed.

As said adhesive resin, the polymer containing 2-hydroxyethyl methacrylate, acrylic acid, etc. other than the said essential constituent monomer may be sufficient.

When the adhesive resin is used, it is preferable to use 0.01 to 10% by weight of the adhesive resin with respect to the total weight of the electrode active material and the conductive additive.

As the conductive material, the same conductive agent as described above can be suitably used.
However, the conductive material is contained in the coating material constituting a part of the coated electrode active material, whereas the conductive auxiliary agent can be clearly distinguished in that it is not contained in the coating material.

The electrode active material layer is prepared by mixing the electrode active material and electrode binder, adhesive resin, and the like to be used by using a known powder agitating and mixing device such as a planetary mixer, a universal mixer and a tumbler mixer. And can be obtained by molding the mixture by a known method. Examples of the molding method include compression molding, extrusion molding, and calendar molding.
In addition, when the electrode active material layer is a porous body formed by molding a mixture containing an electrode active material and an adhesive resin, the electrode active material layer is used as needed after adhering the adhesive resin to the surface of the electrode active material. The electrode active material, the adhesive resin, and the conductive assistant used as necessary may be mixed and molded together with a conductive aid or the like.

The mixture may be a dry body or a wet body, but is preferably a wet body. The wet body is obtained by adding a small amount of liquid (electrolytic solution or solvent constituting the electrolytic solution) to the dried mixture. When the mixture is wet, it is preferably in a pendular state or a funicular state.

The ratio of the electrolytic solution in the case of a wet body is not particularly limited, but in order to obtain a pendular state or a funicular state, in the case of a positive electrode, the ratio of the electrolytic solution is 0.5 to 15% by weight of the entire wet body In the case of a negative electrode, the ratio of the electrolyte is preferably 0.5 to 25% by weight of the entire wet body.

Examples of a method for obtaining an electrode active material layer by compression molding include a method in which the mixture is put into a mold having an arbitrary shape and compressed using a known compression device.
The shape of the mold only needs to have a bottom surface and side surfaces, and other shapes are not particularly limited. Moreover, the type | mold which comprises a side surface, and the type | mold which comprises a bottom face may be comprised so that isolation | separation is possible.

Examples of the material constituting the mold include general materials such as metals used for molds.
In order to reduce the friction generated between the mold and the electrode composition molded body, the surface of the mold may be coated with fluorine.
The shape of the space formed in the mold (hereinafter also simply referred to as a space) may be adjusted according to the shape of the electrode active material layer desired to be obtained, and preferably has no shape change in the compression direction. A cylindrical shape, a prismatic shape or the like is preferable.
An electrode composition molded body having a substantially circular shape in plan view when a space shape is used and a rectangular shape in plan view when a space shape is used is obtained.

As a method for obtaining an electrode active material layer by extrusion molding, a method using a known extrusion molding machine can be mentioned.
As an extrusion molding machine, for example, a raw material cylinder to which a raw material (the above mixture) is supplied, a die (also referred to as a mold) attached to the raw material discharge side of the raw material cylinder, and a raw material disposed in the raw material cylinder One having a rotating shaft-like screw for extruding in the direction.
A cylindrical shaped body can be obtained by putting the mixture into the raw material cylinder and extruding the mixture that has moved the raw material cylinder by the rotation of the screw from the die. The shape of the molded body can be appropriately adjusted by adjusting the shape of the die and the rotational speed of the screw.

The shape of the cylindrical molded body discharged from the die is not particularly limited, but is preferably a cylindrical shape or a quadrangular prism shape. An electrode active material layer is obtained by cutting a cylindrical molded body discharged from a die with a predetermined length.

Examples of the method for obtaining the electrode active material layer by calendering include a method using a known roll press apparatus.
A sheet-like molded product can be obtained by charging the mixture from a continuous mixer such as a kneader and roll-pressing the mixture spread to a certain thickness on a smooth surface such as a film by a doctor blade or the like. An electrode active material layer is obtained by cutting the sheet-like molded body at a predetermined length.

The ratio of the pore volume of the electrode active material layer to the apparent volume of the electrode active material layer (hereinafter referred to as the porosity of the electrode active material layer) is not particularly limited, but is 35 to 50 in the case of the positive electrode active material layer. %, And in the case of the negative electrode active material layer, it is preferably 30 to 45%.
The porosity of the electrode active material layer can be adjusted by adjusting the pressure in the molding method described above.
Note that the porosity of the electrode active material layer is a ratio of the total volume of pores contained in the electrode active material layer to the apparent volume of the electrode active material layer in a state where the electrolyte solution is not included. The total volume of the pores contained in the electrode active material layer is obtained by subtracting the total volume of the electrode active material used for forming the electrode active material layer from the apparent volume of the electrode active material layer in a state where the electrolyte solution is not included. Is a value calculated by The volume of the electrode active material used for forming the electrode active material layer can be obtained by multiplying the mass of the electrode active material and the true density.
Note that the true density of the electrode active material is OECD Test No. 109, OECD GUIDLINE FOR THE TESTING OF CHEN | MICALS, Density of Liquids and Solids.

Of the electrode active material layers, at least the electrode active material layer (A) is preferably a non-binding body in which the electrode active materials are not bound to each other by the electrode binder.
The electrode active material layer (A) which is a non-binding body can be obtained by preparing and molding a mixture without using an electrode binder.
When the electrode active material constituting the electrode active material layer (A) is a coated electrode active material, the coating resin is present in the electrode active material layer. However, the coating resin coats the surface of the electrode active material particles, and does not irreversibly bond the electrode active material particles to each other. The bonding is temporary (reversible) and can be easily performed. Can be loosened. Therefore, even when a mixture containing a coated electrode active material is formed, by not adding an electrode binder, it is possible to obtain a non-bound body in which the electrode active materials are not bound to each other by the electrode binder. it can.

Moreover, when an adhesive resin is included in the mixture for obtaining the electrode active material layer, the surface of the electrode active material is reversibly fixed by the adhesive resin. In this case, the electrode active materials can be easily separated from each other, and even if the electrode active material is a coated electrode active material, the coated electrode active materials can be separated without destroying the coating resin. Can do.
Therefore, even when the electrode active material (or the coated electrode active material) and the adhesive resin are used and the mixture is prepared using the prepared mixture without using the electrode binder, the electrode active materials are separated by the electrode binder. Non-bound bodies that are not bound to each other can be obtained.

As a separator used in the method for producing a lithium ion battery of the present invention, a known separator for a lithium ion battery can be used. Known separators for lithium-ion batteries include separators made of porous polyolefins (Hypore manufactured by Asahi Kasei Co., Ltd., Celgard manufactured by Asahi Kasei Co., Ltd., Upore manufactured by Ube Industries, Ltd.) and the like. You may use what provided the porous film which consists of insulating particles, such as an alumina.
The ratio of the total volume of the pores to the apparent volume of the separator (hereinafter referred to as the separator porosity) is preferably 40 to 60%, and if the porosity falls within this range, a commercially available separator is used. It can be used as it is.
In addition, the porosity of the separator can be confirmed with the values described in the specifications for commercially available separators, and can be obtained using a porosimeter that quantifies the pore distribution by injecting a liquid such as mercury into the pores. This can be confirmed by calculating the total volume of the pores from the pore distribution and calculating the ratio of the total volume of the pores to the apparent volume calculated from the outer dimensions of the separator.

Although the thickness of a separator is not specifically limited, It is preferable that it is 5-200 micrometers.
When the thickness of the separator is within the above range, the thickness of the separator is sufficiently thin, and the rate of supplying the electrolytic solution from the electrode active material layer (B) to the electrode active material layer (A) through the separator is good. is there.
Furthermore, when the thickness of the separator is within the above range, the amount of electrolyte solution that the separator can contain is the amount of electrolyte solution that the electrode active material layer (A) and the electrode active material layer (B) can contain. Since the ratio is smaller than that of the electrode active material layer (B), the separator contains the electrolyte when the ratio of the electrolyte solution of the electrode active material layer (A) is larger (that is, the condition (2)). Even if not, the electrolyte contained in the electrode active material layer (B) is supplied not only to the separator but also to the electrode active material layer (A).

As the electrolytic solution, an electrolytic solution containing an electrolyte and a non-aqueous solvent used for manufacturing a lithium ion battery can be used.

As the electrolyte, those used in ordinary electrolytic solutions can be used, and preferable examples include LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , and LiN (SO ₂ F) _2. And lithium salts of organic anions such as LiN (SO ₂ CF ₃ ) ₂ and LiN (SO ₂ C ₂ F ₅ ) ₂ . Among these, LiPF ₆ and LiN (SO ₂ F) ₂ are preferable from the viewpoint of battery output and charge / discharge cycle characteristics.

As the non-aqueous solvent, an aprotic solvent can be preferably used.
An aprotic solvent is a solvent that does not have a hydrogen ion donating group (a group having a dissociative hydrogen atom, for example, an amino group, a hydroxyl group, and a thio group). Is a lactone compound, a cyclic or chain carbonate ester, a chain carboxylate ester, a cyclic or chain ether, a phosphate ester, a nitrile compound, an amide compound, a sulfone and the like, and more preferably a cyclic carbonate ester, It is a mixed solvent of a chain carbonate ester and a cyclic carbonate ester and a chain carbonate ester.

Examples of the lactone compound include a 5-membered ring (γ-butyrolactone, γ-valerolactone, etc.) and a 6-membered lactone compound (δ-valerolactone, etc.).

Examples of the cyclic carbonate include propylene carbonate, ethylene carbonate, butylene carbonate and vinylene carbonate.
Examples of the chain carbonate include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, and di-n-propyl carbonate.

Examples of chain carboxylic acid esters include methyl acetate, ethyl acetate, propyl acetate, and methyl propionate.
Examples of the cyclic ether include tetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 1,4-dioxane and the like.
Examples of the chain ether include dimethoxymethane and 1,2-dimethoxyethane.

Examples of phosphate esters include trimethyl phosphate, triethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate, tripropyl phosphate, tributyl phosphate, tri (trifluoromethyl) phosphate, tri (trichloromethyl) phosphate, Tri (trifluoroethyl) phosphate, tri (triperfluoroethyl) phosphate, 2-ethoxy-1,3,2-dioxaphospholan-2-one, 2-trifluoroethoxy-1,3,2- Examples include dioxaphospholan-2-one and 2-methoxyethoxy-1,3,2-dioxaphosphoran-2-one.
Examples of the nitrile compound include acetonitrile. Examples of the amide compound include N, N-dimethylformamide (hereinafter also referred to as DMF). Examples of the sulfone include chain sulfones such as dimethyl sulfone and diethyl sulfone, and cyclic sulfones such as sulfolane.
The aprotic solvent may be used alone or in combination of two or more.

The concentration of the electrolyte contained in the electrolytic solution is preferably 0.3 to 3 mol / L from the viewpoint of battery characteristics at a low temperature.

In the method for producing a lithium ion battery of the present invention, when the condition (2) is satisfied, the electrode active material layer (B) with respect to the total pore volume of the electrode active material layer (B) in a state in which no electrolyte solution is contained. ) Of the volume of the electrolyte contained in the electrode active material layer (A) with respect to the total volume of the pores of the electrode active material layer (A) in the state where the electrolyte is not contained. If it is larger than the ratio, the amount of the electrolyte contained in the electrode active material layer (A), the separator and the electrode active material layer (B) used in the laminating step is not particularly limited.
In particular, from the viewpoint of uniformly impregnating the electrolytic solution, the volume of the electrolytic solution contained in the electrode active material layer (A) with respect to the total volume of pores of the electrode active material layer (A) in a state where the electrolytic solution is not contained. Is preferably 0 to 90%, more preferably 0 to 50%.

The ratio of the volume of the electrolyte contained in the electrode active material layer (B) to the total volume of the pores of the electrode active material layer (B) in a state not containing the electrolyte may exceed 100%. When the said ratio exceeds 100%, an electrode active material layer (B) turns into an active material layer with fluidity | liquidity.

The method for producing a lithium ion battery of the present invention preferably further includes a liquid absorption step of containing the electrolytic solution in at least one of the separator and the electrode active material layer (B) before the stacking step.

In the liquid absorption step, the electrode active material layer (B) is placed (immersed) in a container containing a predetermined amount of electrolyte solution, and the electrolyte solution is dropped onto the surface of the electrode active material layer (B) with a dropper or the like. And an electrode active material layer (B), in addition to each component constituting the electrode active material layer, an electrolytic solution is added, and this is mixed and molded to contain the electrolytic solution. The electrode active material layer (B) can be produced by a method or the like.

In addition, as a method of obtaining the electrode active material layer (B) in which the electrolytic solution ratio exceeds 100%, for example, pores are formed with respect to the electrode active material layer (B) obtained by molding a mixture containing the electrode active material. More than the amount that the pores of the molded electrode active material (B) can contain with respect to the method of adding a larger amount of electrolyte solution than the amount that can be contained, and the mixture containing the electrode active material A method of forming after adding an amount of the electrolytic solution in advance is included.

In the liquid-absorbing step, the separator may contain the electrolytic solution. The separator is put (immersed) in a container containing a predetermined amount of electrolytic solution, or the electrolytic solution is dropped onto the surface of the separator with a dropper or the like. Methods and the like.

It is preferable that the manufacturing method of the lithium ion battery of the present invention further includes a housing step of obtaining a housing body in which the laminated unit is housed in an exterior body.
The housing step may be performed by housing the laminated unit in an exterior body after the above-described laminating step, and the electrode active material layer (A), the separator, and the electrode active material layer (B) directly inside the exterior body. ) May be laminated to form a lamination unit (that is, the lamination process and the accommodation process are performed simultaneously).

Before the container is sealed, the positive electrode current collector is connected to the positive electrode active material layer, and the negative electrode current collector is connected to the negative electrode current collector.
The positive electrode current collector is preferably provided on the main surface opposite to the separator of the electrode active material layer to be the positive electrode. The negative electrode current collector is preferably provided on the main surface opposite to the separator of the electrode active material layer to be the negative electrode.

As the exterior body, a known metal can case and a laminate film containing aluminum can be used. As the laminate film, a laminate film having a three-layer structure in which polypropylene, aluminum, and nylon are laminated in this order can be used. Of these, a laminate film is preferred because it is easy to promote the impregnation of the electrolytic solution by applying pressure to the laminated unit after storage.

As the positive electrode current collector and the negative electrode current collector, a metal current collector or a resin current collector can be used. As the metal current collector, a known metal current collector can be used. For example, the metal current collector is selected from the group consisting of copper, aluminum, titanium, nickel, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, and alloys containing one or more of these, and stainless steel alloys. It is preferable that it consists of 1 or more types. The metal current collector may be formed of a thin plate or a metal foil, or a metal layer may be formed on the surface of the substrate by a technique such as sputtering, electrodeposition, and coating.

The resin current collector is a current collector made of a polymer composition having conductivity, and preferably made of a mixture of a non-conductive polymer material and a conductive filler, and Japanese Patent Publication No. 2012-150905. And those described in International Publication No. WO2015 / 005116 and the like can be used.
Polymer materials include polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polycycloolefin (PCO), polyethylene terephthalate (PET), polyether nitrile (PEN), polytetrafluoroethylene (PTFE) Styrene butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVdF), epoxy resin, silicone resin, and mixtures thereof.
From the viewpoint of electrical stability, polyethylene (PE), polypropylene (PP), polymethylpentene (PMP) and polycycloolefin (PCO) are preferable, and polyethylene (PE), polypropylene (PP) and polymethylpentene are more preferable. (PMP).

The conductive filler is selected from materials having conductivity, and from the viewpoint of suppressing ion permeation in the current collector, it is preferable to use a material that does not have conductivity with respect to ions used as the charge transfer medium. Specific examples include, but are not limited to, carbon materials, aluminum, gold, silver, copper, iron, platinum, chromium, tin, indium, antimony, titanium, nickel, and the like. These conductive fillers may be used alone or in combination of two or more. Moreover, these alloy materials, such as stainless steel (SUS), may be used. From the viewpoint of corrosion resistance, aluminum, stainless steel, carbon material, nickel, and more preferably carbon material are preferred. In addition, these conductive fillers may be those obtained by coating the metal shown above with a plating or the like around a particulate ceramic material or resin material.

The resin current collector can be obtained by a known method described in Japanese Patent Publication No. 2012-150905 and International Publication No. WO2015 / 005116, and 5-20 parts of acetylene black as a conductive filler in polypropylene. After the dispersion, those rolled by a hot press machine can be mentioned. Moreover, the thickness is not particularly limited, and can be applied in the same manner as known ones or with appropriate changes.

After the laminated unit is accommodated in the exterior body, a step of injecting an electrolytic solution into the exterior body may be performed. By further injecting the electrolytic solution into the exterior body, the amount of the electrolytic solution in the lithium ion battery can be adjusted.

In the method for manufacturing a lithium ion battery according to the present invention, an exhaust process for discharging the gas in the container may be performed.
When the exhaust process is performed, the discharge of gas from the pores of the electrode active material layer (A), the separator, and the electrode active material layer (B) is promoted, and the electrolyte solution is rapidly transferred to the pores. It becomes easier to impregnate the liquid more uniformly.
For exhausting the gas in the container, connect a known decompression device (rotary vacuum pump, aspirator, etc.) to the opening of the exterior body to decompress the interior of the housing and exhaust the gas. A method of discharging the gas in the container by placing the container in a decompressed dry chamber or the like and placing the container in a decompressed environment, and compressing the stacking unit by applying pressure from the outside of the container The method can be performed by a method of exhausting the gas in the container, and the method of exhausting the gas in the container by placing the container in a reduced pressure environment is particularly preferable.
Further, in the exhaust process of discharging the gas in the container, excess electrolyte may be discharged to the outside of the container simultaneously with the gas.

With respect to the above container, after performing an exhaust stroke, a lithium ion battery can be obtained by sealing the opening of the container by heat sealing or the like. The container is preferably sealed in a state where the gas in the container is exhausted.
When the exhaust process is performed by placing the container in a sealed container such as a dry chamber that has been decompressed, the inside of the sealed container remains in a decompressed state (that is, the container is left in a decompressed environment). It is preferable to seal the opening.
When the container is sealed in a reduced pressure environment, when the container is returned to the normal pressure environment, atmospheric pressure is uniformly applied from the outside of the container, and the electrode active material layer (A) constituting the laminated unit The adhesion between the electrode active material layer (B) and the separator and the adhesion between the laminated unit and the current collector can be improved, and the electric resistance of the battery can be lowered.

EXAMPLES Next, the present invention will be specifically described with reference to examples, but the present invention is not limited to the examples without departing from the gist of the present invention. Unless otherwise specified, “part” means “part by weight” and “%” means “% by weight”.

<Production Example 1: Production of adhesive resin>
A 4-neck Kolben equipped with a stirrer, thermometer, reflux condenser, dropping funnel and nitrogen gas inlet tube was charged with 5.0 parts of vinyl acetate, 23.7 parts of 2-ethylhexyl acrylate, and 185.5 parts of ethyl acetate 75 The temperature was raised to ° C. 11.1 parts vinyl acetate, 21.0 parts 2-ethylhexyl acrylate, 28.1 parts 2-hydroxyethyl methacrylate, 11.1 parts acrylic acid and 2,2′-azobis (2,4-dimethylvaleronitrile). 200 parts and 0.200 parts of 2,2′-azobis (2-methylbutyronitrile) were mixed. The resulting monomer mixture was continuously dropped with a dropping funnel over 4 hours while nitrogen was blown into Kolben to carry out radical polymerization. After completion of the dropwise addition, 8 hours after the start of polymerization using a dropping funnel, a solution prepared by dissolving 0.800 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) in 12.4 parts of ethyl acetate It was added continuously over time. Furthermore, the polymerization was continued at the boiling point for 2 hours, and 702.4 parts of ethyl acetate was added to obtain an adhesive resin solution having a resin concentration of 10% by weight. Then, the ethyl acetate was removed by putting in a 100 degreeC vacuum dryer for 3 hours, and adhesive resin was obtained. The obtained adhesive resin had a weight average molecular weight (hereinafter abbreviated as Mw) of 420,000.
Mw was determined by gel permeation chromatography measurement under the following conditions.
Apparatus: “HLC-8120GPC” [manufactured by Tosoh Corporation]
Column: “TSKgel GMHXL” (2), “TSKgel Multipore HXL-M each connected” [all manufactured by Tosoh Corporation]
Sample solution: 0.25 wt% tetrahydrofuran solution solution injection amount: 10 μL
Flow rate: 0.6 mL / min Measurement temperature: 40 ° C
Detector: Refractive index detector Reference material: Standard polystyrene [manufactured by Tosoh Corporation]

<Production Example 2: Preparation of electrolyte solution>
LiN (FSO ₂ ) ₂ was dissolved in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) (volume ratio EC: PC = 1: 1) at a rate of 2 mol / L, and an electrolyte for a lithium ion battery was obtained. Prepared. The specific gravity (20 ° C.) of the electrolytic solution measured by a floating hydrometer in JIS B 7525-3: 2013 was 1.4.

[Preparation of mixture of adhesive resin and negative electrode active material (granulated mixture for negative electrode)]
<Production Example 3>
235 parts of hard carbon powder [manufactured by Kureha Co., Ltd., true density 1.5 g / cm ³ ] in a universal mixer and stirred at room temperature and 150 rpm, the adhesive resin solution (resin obtained in Production Example 1) 50 parts of solid content concentration 10% by weight) was dropped and mixed over 60 minutes, and further stirred for 30 minutes.
Next, 10 parts of carbon nanofibers [manufactured by Teijin Limited, true density 2.2 g / cm ³ ] and acetylene black [Denka Black by Denki Kagaku Kogyo Co., true density 1.8 g / cm ³ ] in a stirred state. The mixture was mixed with 10 parts, heated to 70 ° C. with stirring for 30 minutes, depressurized to 0.01 MPa and held for 30 minutes to distill off ethyl acetate contained in the adhesive resin solution. By this operation, 260 parts of a granulated mixture for negative electrode (NM-1) was obtained.

<Production Example 4>
Put 595 parts of hard carbon powder in a universal mixer and stir at room temperature and 150 rpm, and drop-mix the 130 parts of the adhesive resin solution (resin solid content concentration 10 wt%) obtained in Production Example 1 over 60 minutes. And stirred for another 30 minutes.
Next, 26 parts of carbon nanofibers and 26 parts of acetylene black were mixed while stirring, and the temperature was raised to 70 ° C. while stirring for 30 minutes, and the pressure was reduced to 0.01 MPa and held for 30 minutes to form an adhesive resin solution. The ethyl acetate contained was distilled off. By this operation, 660 parts of a granulation mixture for negative electrode (NM-2) was obtained.

<Production Example 5>
Put 926 parts of hard carbon powder in a universal mixer and stir at room temperature and 150 rpm, and drop-mix the 200 parts of the adhesive resin solution (resin solid content concentration 10 wt%) obtained in Production Example 1 over 60 minutes. And stirred for another 30 minutes.
Next, 37 parts of carbon nanofibers and 37 parts of acetylene black were mixed while stirring, and the temperature was raised to 70 ° C. while stirring for 30 minutes, and the pressure was reduced to 0.01 MPa and held for 30 minutes to form an adhesive resin solution. The ethyl acetate contained was distilled off. By this operation, 1000 parts of a granulated mixture for negative electrode (NM-3) was obtained.

<Production Example 6>
Put 926 parts of hard carbon powder in a universal mixer and stir at room temperature and 150 rpm, and drop-mix the 200 parts of the adhesive resin solution (resin solid content concentration 10 wt%) obtained in Production Example 1 over 60 minutes. And stirred for another 30 minutes.
Next, 74 parts of acetylene black was mixed with stirring, the temperature was raised to 70 ° C. while stirring for 30 minutes, the pressure was reduced to 0.01 MPa and held for 30 minutes, and the ethyl acetate contained in the adhesive resin solution was distilled off. did. By this operation, 1000 parts of a granulated mixture for negative electrode (NM-4) was obtained.

[Preparation of mixture of adhesive resin and positive electrode active material (granulated mixture for positive electrode)]
<Production Example 7>
950 parts of nickel-based positive electrode powder [manufactured by Toda Kogyo Co., Ltd., true density 4.8 g / cm ³ ] in an all-purpose mixer and stirred at room temperature and 150 rpm, the adhesive resin obtained in Production Example 1 200 parts of a solution (resin solid content concentration: 10% by weight) and 30 parts of carbon nanofibers were added and mixed, stirred for 30 minutes, further heated to 70 ° C. with stirring, reduced to 0.01 MPa and held for 30 minutes. The ethyl acetate contained in the adhesive resin solution was distilled off. By this operation, 1000 parts of a granulation mixture for positive electrode (PM-1) was obtained.

<Production Example 8>
855 parts of the nickel-based positive electrode material powder was put into a universal mixer and stirred at room temperature and 150 rpm, 180 parts of the adhesive resin solution (resin solid content concentration 10% by weight) obtained in Production Example 1, carbon nanofiber 27 The parts were added and mixed, stirred for 30 minutes, further heated to 70 ° C. with stirring, depressurized to 0.01 MPa and maintained for 30 minutes to distill off ethyl acetate contained in the adhesive resin solution. By this operation, 900 parts of a granulated mixture for positive electrode (PM-2) was obtained.

[Preparation of negative electrode active material layer]
<Production Example 9>
260 parts of the granulation mixture for negative electrode (NM-1) produced in Production Example 3 and 740 parts of the electrolytic solution obtained in Production Example 2 were mixed with a planetary agitation type kneading apparatus {Awatori Kentaro [manufactured by Shinky Co., Ltd.] } And mixed at 2000 rpm for 5 minutes to prepare a negative electrode active material composition. The negative electrode active material composition was applied to the entire surface of a 10 cm × 10 cm copper foil with a current extraction terminal using a film applicator with a film thickness adjusting function so that the coating amount per 1 cm ^{2 of} copper foil was 163.4 mg. Then, a negative electrode active material layer (N-1) having a thickness of 1143 μm was formed on the copper foil. The weight of the hard carbon powder placed on the copper foil per 1 cm ² area is 38.4 mg. Value obtained by subtracting the total volume of hard carbon, which is the negative electrode active material particles contained in the negative electrode active material layer, from the volume of the negative electrode active material layer (total volume of pores of the negative electrode active material layer in a state in which no electrolyte solution is included) The ratio of the volume of the electrolytic solution contained in the negative electrode active material layer to that of the negative electrode active material layer (that is, the ratio of the electrolytic solution in the negative electrode active material layer) is 97%.

<Production Example 10>
660 parts of the granulation mixture for negative electrode (NM-2) produced in Production Example 4 and 340 parts of the electrolytic solution obtained in Production Example 2 were mixed with a planetary agitation type mixing and kneading apparatus {Awatori Kentaro [manufactured by Shinky Co., Ltd.] } And mixed at 2000 rpm for 5 minutes to prepare a negative electrode active material composition, and the same coating on a copper foil as in Production Example 9 was applied per 1 cm ^{2 of} copper foil using a film applicator with a film thickness adjusting function. It apply | coated so that quantity might be set to 104.6 mg, and formed the negative electrode active material layer (N-2) with a thickness of 715 micrometers on copper foil. The weight of the hard carbon powder placed on the copper foil per 1 cm ² area is 62.2 mg. Value obtained by subtracting the total volume of hard carbon, which is the negative electrode active material particles contained in the negative electrode active material layer, from the volume of the negative electrode active material layer (total volume of pores of the negative electrode active material layer in a state in which no electrolyte solution is included) The ratio of the volume of the electrolytic solution contained in the negative electrode active material layer to the negative electrode (that is, the proportion of the electrolytic solution in the negative electrode active material layer) is 86%.

<Production Example 11>
The negative electrode granulation mixture (NM-3) produced in Production Example 5 is placed on the same copper foil as in Production Example 9 at a weight of 53.8 mg per cm ² of copper foil, and 3400 kgf / cm using a tableting machine. A negative electrode active material layer (N-3) having a thickness of 511 μm was formed on the entire surface of the copper foil by compression molding at a pressure of ² . The weight of the hard carbon powder placed on the copper foil per 1 cm ² area is 38.4 mg. Value obtained by subtracting the total volume of hard carbon, which is the negative electrode active material particles contained in the negative electrode active material layer, from the volume of the negative electrode active material layer (total volume of pores of the negative electrode active material layer in a state in which no electrolyte solution is included) The ratio of the volume of the electrolyte contained in the negative electrode active material layer to the negative electrode (that is, the ratio of the electrolyte in the negative electrode active material layer) is 0%.

<Production Example 12>
The negative electrode granulation mixture (NM-4) produced in Production Example 6 is placed on the same copper foil as in Production Example 9 at a weight of 53.8 mg per cm ² of copper foil, and 3400 kgf / cm using a tableting machine. A negative electrode active material layer (N-4) having a thickness of 521 μm was formed on the entire surface of the copper foil by compression molding at a pressure of ² . The weight of the hard carbon powder placed on the copper foil per 1 cm ² area is 38.4 mg. Value obtained by subtracting the total volume of hard carbon, which is the negative electrode active material particles contained in the negative electrode active material layer, from the volume of the negative electrode active material layer (total volume of pores of the negative electrode active material layer in a state in which no electrolyte solution is included) The ratio of the volume of the electrolyte contained in the negative electrode active material layer to the negative electrode (that is, the ratio of the electrolyte in the negative electrode active material layer) is 0%.

[Preparation of positive electrode active material layer]
<Production Example 13>
The positive electrode granulation mixture (PM-1) produced in Production Example 7 is placed on a 10 cm × 10 cm carbon-coated aluminum foil to which a current extraction terminal is attached at a weight of 84.2 mg per 1 cm ^{2 of the} carbon-coated aluminum foil, Using a tableting machine, compression molding was performed at a pressure of 3400 kgf / cm ² to form a positive electrode active material layer (P-1) having a thickness of 352 μm on the entire surface of the carbon-coated aluminum foil. The weight of the nickel-based positive electrode material placed per 1 cm ² on the carbon-coated aluminum foil is 80.0 mg. Positive electrode active material with respect to a value obtained by subtracting the total volume of positive electrode active material particles contained in the positive electrode active material layer from the volume of the positive electrode active material layer (the total volume of pores of the positive electrode active material layer in a state where no electrolyte solution is included) The volume ratio of the electrolyte solution contained in the layer (P-1) (that is, the electrolyte solution ratio of the positive electrode active material layer) is 0%.

<Production Example 14>
900 parts of the positive electrode granulation mixture (PM-2) produced in Production Example 8 and 100 parts of the electrolytic solution obtained in Production Example 2 were mixed with a planetary agitation type mixing and kneading apparatus {Awatori Netaro [Sinky Corp. ] And mixed at 2000 rpm for 5 minutes to produce a positive electrode active material composition, which is placed on the same carbon coated aluminum foil as in Production Example 13 at a weight of 92.2 mg per 1 cm ^{2 of} carbon coated aluminum foil, Using a tableting machine, compression molding was performed at a pressure of 3400 kgf / cm ² to form a positive electrode active material layer (P-2) having a thickness of 347 μm on the entire surface of the carbon-coated aluminum foil. The weight of the nickel-based positive electrode material placed per 1 cm ² on the carbon-coated aluminum foil is 80.0 mg. Positive electrode active material with respect to a value obtained by subtracting the total volume of positive electrode active material particles contained in the positive electrode active material layer from the volume of the positive electrode active material layer (the total volume of pores of the positive electrode active material layer in a state where no electrolyte solution is included) The volume ratio of the electrolyte solution contained in the layer (P-2) (that is, the electrolyte solution ratio of the positive electrode active material layer) is 37%.

<Production Example 15>
[Preparation of separator impregnated with electrolyte solution]
5500 parts of the electrolytic solution obtained in Production Example 2 was dropped into 100 parts of a separator (Celgard (trademark) 3501, manufactured by Celgard, Inc., thickness 25 μm, porosity 55%) (S-0), and impregnated with the electrolytic solution. A separator (S-1) was produced. When about 85 parts of the electrolytic solution was dropped, all the pores of the separator were filled with the electrolytic solution, and the electrolytic solution did not penetrate into the separator. Thereafter, the remaining electrolyte was slowly dropped so as not to spill from the separator surface, and the entire amount was placed on the surface of the separator. In addition, it was able to be put on the surface without spilling from the separator surface due to the surface tension of the electrolytic solution. In the separator (S-1), the excess electrolyte solution that did not enter the pores was on the separator surface.

<Production Example 16>
A separator (S-2) having pores impregnated with an electrolytic solution was produced in the same manner as in Production Example 15 except that the electrolytic solution was changed to 450 parts. The excess electrolyte solution that did not enter the pores was on the separator surface.

<Example 1>
In a dry chamber, the outer body produced by heat-sealing three sides of two rectangular laminate films is not impregnated with carbon-coated aluminum foil, positive electrode active material layer (P-1), or electrolyte. A separator (S-0), a negative electrode active material layer (N-1), and a copper foil were laminated in this order. Next, the inside of the dry chamber is depressurized to -1 atm, a Teflon plate (Teflon is a registered trademark) is placed on the exterior body in the dry chamber, and compression is performed by applying a load from above, and an excess electrolyte solution is obtained from the exterior body. Compression was continued until 6.4 g was discharged. Subsequently, the battery was sealed with the terminal for taking out a current from the opening, and then the inside of the dry chamber was returned to normal pressure with dry air to produce an evaluation battery. Thereafter, the following cycle characteristics were evaluated.

[Evaluation of cycle characteristics]
The terminal for taking out the current of the evaluation battery was connected to a charge / discharge measuring device “Battery Analyzer 1470 type” [manufactured by Toyo Technica Co., Ltd.].
Subsequently, using the above charge / discharge measuring apparatus, after discharging the laminate unit at a current of 0.05 C until the potential of the positive electrode becomes 2.5 V (vs. Li ⁺ / Li) and resting for 10 minutes. Then, the battery was charged until the potential of the positive electrode was 4.2 V (vs. Li ⁺ / Li), and preliminary charging was performed.
Subsequently, the battery for evaluation after the preliminary charging step was further discharged at a current of 0.05 C until the potential of the positive electrode became 2.5 V (vs. Li ⁺ / Li), paused for 10 minutes, 0.05 C The cycle of charging and resting for 10 minutes was repeated three times until the potential of the positive electrode reached 4.2 V (vs. Li ⁺ / Li) at a current of 3 times.
The ratio of the third charge capacity to the first charge capacity (the third cycle capacity maintenance rate) was determined with the first charge capacity set to 100%, and the results are shown in Table 1.
If the electrode active material layer contains an electrolyte nonuniformly, the portion of the electrode active material not impregnated with the electrolyte cannot participate in the movement of lithium ions, so the first charge capacity is smaller than the design value. Thus, as the time passes, the electrolytic solution spreads over the whole while repeating the charge / discharge cycle, and the charge capacity becomes larger than the first time. That is, the third cycle capacity retention rate exceeds 100%.
On the other hand, when the electrolyte solution is uniformly contained from the first cycle, the charge capacity close to the design value is shown in the third cycle. Since the design value is a value obtained by subtracting the irreversible capacity from the first cycle capacity, the third cycle capacity retention rate when the electrolyte is uniformly contained is smaller than 100%.

<Example 2>
In a dry chamber, the same outer package as in Example 1 was coated with carbon coated aluminum foil, positive electrode active material layer (P-2), separator not impregnated with electrolyte (S-0), negative electrode active material layer ( N-2) and copper foil were laminated in this order. Subsequently, the inside of the dry chamber was depressurized to -1 atm. Thereafter, the battery was sealed in a state where a current extraction terminal was taken out from the opening, and then the inside of the dry chamber was returned to normal pressure with dry air to produce an evaluation battery. An evaluation battery was produced.
The cycle characteristics were evaluated in the same manner as in Example 1, and the results are shown in Table 1.

<Example 3>
In the dry chamber, the same outer package as in Example 1 was coated with carbon coated aluminum foil, positive electrode active material layer (P-1), separator impregnated with electrolyte (S-1), and negative electrode active material layer (N -3) and copper foil were laminated in this order. Subsequently, the inside of the dry chamber was depressurized to -1 atm. Thereafter, the battery was sealed with the terminal for taking out the current from the opening, and the inside of the dry chamber was returned to normal pressure with dry air to produce an evaluation battery.
The cycle characteristics were evaluated in the same manner as in Example 1, and the results are shown in Table 1.

<Example 4>
Inside the dry chamber, the same outer package as in Example 1 was coated with carbon coated aluminum foil, positive electrode active material layer (P-1), separator impregnated with electrolyte (S-2), and negative electrode active material layer (N -4) and copper foil were laminated in this order. Next, 5.6 g of an electrolytic solution was added from the opening. Next, the inside of the exterior body is evacuated from the opening of the exterior body using a vacuum pump while the inside of the draft chamber is at normal pressure, and then sealed in a state in which the terminal for extracting current is taken out to produce a battery for evaluation. did.
The cycle characteristics were evaluated in the same manner as in Example 1, and the results are shown in Table 1.

<Comparative Example 1>
Inside the dry chamber, the same outer package as in Example 1 was coated with carbon coated aluminum foil, positive electrode active material layer (P-1), separator not impregnated with electrolyte (S-0), negative electrode active material layer ( N-4) and copper foil were laminated in this order. Next, 6.2 g of electrolytic solution was added from the opening. Subsequently, the inside of the dry chamber was depressurized to -1 atm. Thereafter, the battery was sealed with the terminal for taking out the current from the opening, and the inside of the dry chamber was returned to normal pressure with dry air to produce an evaluation battery.
The cycle characteristics were evaluated in the same manner as in Example 1, and the results are shown in Table 1.

All the electrodes of the battery for evaluation described in Table 1 are 10 cm × 10 cm squares.
Moreover, in Table 1, the positive electrode active material with respect to the value which remove | excluding the total volume of the positive electrode active material contained in the positive electrode active material layer from the volume of "S-0" and the positive electrode active material layer in the separator which is not impregnated with electrolyte solution The ratio of the volume of the electrolyte contained in the layer is the value obtained by subtracting the total volume of the anode active material contained in the anode active material layer from the volume of the anode active material layer and the ratio of the electrolyte solution in the cathode active material layer [%] The ratio of the volume of the electrolyte contained in the negative electrode active material layer to the negative electrode active material layer was described as “electrolyte ratio of negative electrode active material layer [%]”.
In both the separators (S-1) and (S-2), the pores are all filled with the electrolyte solution, and the excess electrolyte solution that has not entered the pores is placed on the separator surface, and the separator (S-1) There are more electrolytes on it.

If the electrode active material layer contains a non-uniform amount of electrolyte, the portion of the electrode active material that does not contain the electrolyte cannot participate in the movement of lithium ions. The charge / discharge capacity increases as the liquid is contained throughout.
From the results of Table 1, the evaluation battery according to the example manufactured by the method for manufacturing a lithium ion battery of the present invention has a capacity retention rate at the third cycle of less than 100% as compared with the evaluation battery according to the comparative example. It can be seen that the electrolyte solution could be uniformly impregnated.

10 Electrode active material layer (A)
20 Separator 30 Electrode active material layer (B)
100 stacking unit

Claims (5)

A laminated unit in which an electrode active material layer (A) and an electrode active material layer (B) serving as a counter electrode of the electrode active material layer (A) are laminated via a separator, an electrolytic solution, and the laminated unit and the electrolytic A method for producing a lithium ion battery including an exterior body that contains a liquid,
A lamination step of obtaining a lamination unit in which the electrode active material layer (A), the separator and the electrode active material layer (B) are laminated,
Before forming the laminated unit, at least one of the separator and the electrode active material layer (B) contains the electrolytic solution, and the electrode active material layer (A), the separator, and the electrode active material are contained. The material layer (B) satisfies at least one of the following conditions (1) to (2):
(1) The total volume of the pores of the electrode active material layer (A) in a state where all of the pores of the separator are filled with the electrolyte and does not contain the electrolyte is the electrode active material The volume of the electrolyte solution contained in the layer (A) is larger.
(2) The electrode active material layer (B) with respect to the total volume of pores of the electrode active material layer (B) in a state in which at least the electrode active material layer (B) contains the electrolyte solution and does not contain the electrolyte solution The electrolytic solution contained in the electrode active material layer (A) with respect to the total volume of pores of the electrode active material layer (A) when the volume ratio of the electrolytic solution contained in the electrode active material layer does not contain the electrolytic solution. It is larger than the liquid volume ratio. The method for producing a lithium ion battery according to claim 1, further comprising a liquid absorption step in which at least one of the separator and the electrode active material layer (B) contains the electrolytic solution before the stacking step. The manufacturing method of the lithium ion battery of Claim 1 or 2 further equipped with the accommodation process which obtains the container in which the said lamination | stacking unit was accommodated in the said exterior body. The method for manufacturing a lithium ion battery according to claim 3, further comprising an exhaust process of discharging the gas in the container by placing the container in a reduced pressure environment. The said electrode active material layer (A) and / or the said electrode active material layer (B) are the manufacturing methods of the lithium ion battery in any one of Claims 1-4 containing adhesive resin.

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