JP6962032B2 - Method for manufacturing lithium negative electrode complex - Google Patents

Description

The present invention relates to a method for producing a lithium negative electrode composite by forming a lithium layer on a Si-containing negative electrode active material layer.

A lithium ion secondary battery is a secondary battery having a high charge / discharge capacity and capable of increasing output. Lithium-ion secondary batteries are currently mainly used as a power source for portable electronic devices, and are expected to be a power source for electric vehicles, which are expected to become widespread in the future. The lithium ion secondary battery has an active material capable of adsorbing and releasing lithium at the positive electrode and the negative electrode, respectively. Then, the lithium ion secondary battery operates by moving lithium ions, which are charge carriers, in the electrolytic solution existing between the two electrodes.

As a negative electrode active material used for the negative electrode of a lithium ion secondary battery, a technique of using a Si-containing negative electrode active material, that is, a Si-containing negative electrode active material is known. Theoretically, Si has a higher lithium ion occlusion capacity per element than a negative electrode active material such as graphite. Therefore, it is considered that the capacity of the lithium ion secondary battery can be increased by selecting the Si-containing negative electrode active material.

For example, Patent Document 1 and Patent Document 2 describe a lithium ion secondary battery in which the negative electrode active material is silicon. Patent Document 3 and Patent Document 4 describe a lithium ion secondary battery in which the negative electrode active material is SiO.

In Patent Document 5, _{a layered silicon compound containing CaSi 2} as a main component and layered polysilane from which Ca has been removed is synthesized by reacting CaSi 2 with an acid, and the layered silicon compound is heated at 300 ° C. or higher to release hydrogen. It describes that the material was manufactured and that the lithium ion secondary battery includes the silicon material as a negative electrode active material.

Japanese Unexamined Patent Publication No. 2014-203595 JP 2015-57767 JP-A-2015-185509 JP 2015-179625 International Publication No. 2014/08608

By the way, it is known that the Si-containing negative electrode active material has a large capacity but also a large irreversible capacity. The inventor of the present invention considered to introduce in advance an amount of lithium ions corresponding to the irreversible capacity of the Si-containing negative electrode active material into the Si-containing negative electrode active material in order to cancel the irreversible capacity of the Si-containing negative electrode active material. Hereinafter, introducing lithium ions into the negative electrode active material is referred to as doping lithium. Further, unless otherwise specified, the negative electrode active material refers to a Si-containing negative electrode active material, and the negative electrode active material layer refers to a Si-containing negative electrode active material layer.

As a lithium doping method, a method of manufacturing a lithium battery for doping using a negative electrode and metallic lithium as a counter electrode and doping the negative electrode with lithium is known. Hereinafter, this doping method is referred to as an electrical doping method. In the electrical doping method, by charging the above-mentioned lithium battery for doping, lithium ions at the counter electrode are moved to the negative electrode, and lithium is doped into the negative electrode. The lithium-doped negative electrode is removed from the lithium battery for doping and used as a negative electrode for a lithium ion secondary battery.

Although such an electrical doping method is effective as a lithium doping method, it requires a large amount of man-hours and is not practical as a method for industrially producing a lithium ion secondary battery.

As another lithium doping method, a method is also proposed in which a lithium layer is further formed on the negative electrode active material layer formed on one side of the current collector, and lithium ions are directly doped from the lithium layer to the negative electrode active material. The lithium layer can be composed of a thinly rolled lithium foil. Hereinafter, this type of doping method is referred to as a direct doping method. If the direct doping method is adopted, there is a possibility that the man-hours required for lithium doping can be reduced.

However, the method for producing a lithium negative electrode complex used in such a direct doping method, that is, a method in which a lithium layer is formed on a negative electrode active material layer of a negative electrode, has not been sufficiently studied at present. , A method for producing a lithium negative electrode composite suitable for the direct doping method has been desired.

The present invention has been made in view of such circumstances, and provides a new method for producing a lithium negative electrode composite suitable for a direct doping method by forming a lithium layer on a Si-containing negative electrode active material layer. With the goal.

The inventor of the present invention has actually produced a lithium negative electrode complex for the direct doping method under various conditions. Then, as one of the problems in producing the lithium negative electrode composite, attention was paid to the volume change of the Si-containing negative electrode active material.

That is, the volume of the Si-containing negative electrode active material layer increases by the amount of the doped lithium ions. The negative electrode is composed of a current collector and a Si-containing negative electrode active material layer, but lithium ions in the lithium layer are doped only in the Si-containing negative electrode active material layer, not in the current collector. Depending on the difference in volume change between the Si-containing negative electrode active material layer and the current collector during this doping, the negative electrode may be distorted or warped in some cases. Specifically, when the Si-containing negative electrode active material layer is provided on only one side of the current collector, or when lithium is doped on only one of the Si-containing negative electrode active material layers provided on both sides of the current collector. In particular, the above-mentioned negative electrode is liable to be distorted or warped.
Since the warped negative electrode may be damaged during the manufacturing of the battery, it cannot be said that such a manufacturing method is suitable as a manufacturing method of the lithium negative electrode composite.

In the method for producing a lithium negative electrode composite of the present invention, Si-containing negative electrode active material layers are formed on both sides of a current collector, and lithium layers are simultaneously formed on each of the negative electrode active material layers to obtain a lithium negative electrode composite. This is a method for producing a lithium negative electrode composite having a composite forming step.

The method for producing a lithium negative electrode composite of the present invention is a new method for producing a lithium negative electrode composite suitable for a direct doping method by forming a lithium layer on a Si-containing negative electrode active material layer.

It is explanatory drawing which shows typically the manufacturing apparatus of the lithium negative electrode complex of Example 1. FIG. It is explanatory drawing which shows typically the main part of the manufacturing apparatus of the lithium negative electrode complex of Example 1. FIG. It is explanatory drawing which shows typically the lithium negative electrode complex of Example 1. FIG. It is explanatory drawing which shows typically the main part of the manufacturing apparatus of the lithium negative electrode complex of Example 1. FIG. It is explanatory drawing which shows typically the manufacturing method of the lithium-doped negative electrode of Example 1. FIG. It is explanatory drawing explaining Test Example 1. FIG. It is explanatory drawing which shows typically the manufacturing apparatus of the lithium negative electrode complex of Example 2.

The best mode for carrying out the present invention will be described below. Unless otherwise specified, the numerical range "x to y" described in the present specification includes the lower limit x and the upper limit y. Then, a numerical range can be constructed by arbitrarily combining these upper and lower limit values and the numerical values listed in the examples. Further, the numerical value arbitrarily selected from the numerical range can be set as the upper limit and the lower limit of the new numerical range.

In the method for producing a lithium negative electrode composite of the present invention, Si-containing negative electrode active material layers are formed on both sides of a current collector, and lithium layers are simultaneously formed on each of the negative electrode active material layers to obtain a lithium negative electrode composite. It has a complex forming step.
That is, in the method for producing a lithium negative electrode composite of the present invention, Si-containing negative electrode active material layers are formed on both sides of the current collector, and lithium layers are formed on each of the negative electrode active material layers directly. A lithium negative electrode composite suitable for the target doping method is produced.

In the method for producing a lithium negative electrode composite of the present invention, in the above-mentioned complex forming step, Si-containing negative electrode active material layers are formed on both sides of the current collector, and a lithium layer is simultaneously placed on each of the Si-containing negative electrode active material layers. To form. Si-containing negative electrode active material layers are formed on both sides of the current collector, and lithium is doped into any of the Si-containing negative electrode active material layers. Therefore, the lithium obtained by the method for producing a lithium negative electrode composite of the present invention. Even if lithium is doped into the negative electrode active material layer, the negative electrode composite is unlikely to warp or the like. As described above, the method for producing a lithium negative electrode complex of the present invention can be said to be a very suitable method as a method for producing a lithium negative electrode complex. Hereinafter, unless otherwise specified, the Si-containing negative electrode active material layer is simply referred to as a negative electrode active material layer.

In the method for producing a lithium negative electrode composite of the present invention, the composite forming step may include a negative electrode forming step and a pressing step.

The negative electrode forming step is a step of forming negative electrode active material layers on both sides of the current collector to form a negative electrode, and a general method for forming a negative electrode active material layer can be used.

In the pressing process, a lithium foil is laminated on each negative electrode active material layer and pressed between the two rolls to form a current collector, a negative electrode having two negative electrode active materials, and a two-layer lithium layer. This is a step of obtaining a lithium negative electrode composite to have. According to the method for producing a lithium negative electrode composite of the present invention having such a composite forming step, a lithium foil can be pressure-bonded to the two negative electrode active material layers at substantially the same time. The doping of lithium into the negative electrode active material layer gradually progresses even if lithium comes into contact with the negative electrode active material layer. As described above, each negative electrode active material layer and the lithium foil are pressed at the same time, and both are pressed at the same time. By doing so, lithium doping into the two negative electrode active material layers can be performed substantially at the same time, and the above-mentioned warpage of the negative electrode and the like can be suppressed more efficiently.

In the pressing step, the negative electrode laminate of the current collector, the negative electrode active material layer, and the lithium foil may be pressed between the two rolls, and a pressing device called a roll pressing device can be used. The number of rolls in the press device, the load acting on the negative electrode laminate from each roll, and the like may be appropriately set according to the specifications of the negative electrode to be manufactured, and are not particularly limited in the present invention.
However, if the load acting on the negative electrode laminate from the roll is too small, the lithium foil may not adhere to the negative electrode active material layer, and lithium doping to the negative electrode active material layer may not be performed satisfactorily. Further, if the load acting on the negative electrode laminate from the roll is excessive, the negative electrode active material layer may be damaged. In consideration of such circumstances, the load acting on the negative electrode laminate from the roll is preferably in the range of 0.01 N / mm to 20 N / mm, preferably in the range of 0.1 N / mm to 10 N / mm. It is more preferable to have it.

In the pressing process, it is more preferable to interpose a film between the roll and the negative electrode laminate. This is to prevent the roll and the lithium foil from firmly adhering to each other and efficiently manufacture the lithium negative electrode composite.

Lithium has the property of being soft and easily deformed. Since such a lithium foil made of lithium is inferior in handleability, it is very difficult to laminate a lithium foil that is not deformed or damaged on the negative electrode active material layer. For example, when the lithium foil is transported for laminating on the negative electrode active material layer, the lithium foil may be deformed due to its own weight. Further, for example, when the negative electrode laminate in which the lithium foil is laminated on the negative electrode active material layer is roll-pressed, the lithium foil firmly adheres to the roll, and when the roll is peeled off from the negative electrode laminate, the lithium foil is deformed. Or it may be damaged.

In the lithium negative electrode composite having the damaged lithium foil, the thickness of the lithium layer on the negative electrode active material layer may be uneven, or a portion where the lithium layer may not be formed may occur on the negative electrode active material layer. When such a lithium negative electrode complex is used in the direct doping method, lithium is not uniformly doped in the negative electrode active material, and it is difficult to preferably perform lithium doping. Therefore, it is very useful in the production of the lithium negative electrode composite to insert a film between the roll and the negative electrode laminate in the pressing step to avoid strong adhesion between the lithium foil and the roll.

Further, even before the pressing process, if the lithium foil and the film are handled in a stacked state, for example, deformation due to the weight of the lithium foil during the above-mentioned transportation can be suppressed, and as described above, the roll and the negative electrode are laminated in the pressing process. A film can be placed between the bodies. Therefore, it can be said that this aspect is more suitable as a method for producing a lithium negative electrode complex.

The film is not particularly limited, but for the purpose of reinforcing the lithium foil, it is preferable to select a material having relatively excellent strength and rigidity. Further, in consideration of cost and reactivity with the lithium foil, the film is preferably a resin film. For example, polyolefins typified by polyethylene and polypropylene, polyester typified by polyethylene terephthalate and polybutylene terephthalate, and the like can be preferably used because they are relatively inexpensive and can sufficiently function as a resin film for reinforcing lithium foil. ..

In the pressing process, it is more preferable to interpose a lubricant, a release layer, or the like between the resin film and the negative electrode laminate. This is to avoid the strong adhesion between the lithium foil and the resin film and to efficiently manufacture the lithium negative electrode composite.
Hereinafter, the release layer and the lubricant will be described.

It suffices that the release layer and the lubricant are interposed between the resin film and the negative electrode laminate in the pressing step so that strong adhesion between the two can be suppressed. Even when the resin film is not used, if the release layer and / or the lubricant is interposed between the roll and the negative electrode laminate in the pressing process, strong adhesion between the lithium foil and the roll can be suppressed, and the lithium foil can be suppressed. Damage etc. can be suppressed. In any case, the release layer and the lubricant are not particularly limited as long as they can exhibit the above functions.

Here, in the present specification, the release layer is a layer containing a release agent, and the release agent is a material capable of exhibiting a certain degree of lubricating function and having low fluidity to the extent that it can form a layer. Point to. The lubricant has a higher fluidity than the release agent, and has a fluidity that cannot be formed as a layer.
At least one of the release layer and the lubricant may be interposed between the resin film and the negative electrode laminate, but at least one of the release layers is preferably interposed, and both the release layer and the lubricant are interposed. Is more preferable.

When the release layer is interposed between the resin film and the negative electrode laminate, the release layer may be integrally provided with the above resin film, or may be formed between the negative electrode laminate and the resin film before the pressing process. You may. When the resin film and the lithium foil are handled in layers, it is naturally preferable that the release layer is integrally provided with the resin film in advance.
When the release layer is interposed between the roll and the negative electrode laminate, the release layer may be provided integrally with the roll or may be formed between the negative electrode laminate and the roll before the pressing process. However, considering the work efficiency of the pressing process, it is preferable that the release layer in this case is integrally provided on the roll.

The release layer may contain a known release agent, and is not particularly limited, but is preferably a layer containing silicone. Hereinafter, the release layer containing silicone is referred to as a silicone layer, if necessary.

The silicone constituting the silicone layer is a compound having a main skeleton formed by a siloxane bond, and has various properties mainly derived from the siloxane bond. Among the characteristics of silicone, the property of being hard to adhere to the mating material is considered to greatly contribute to pressing the negative electrode laminate without crimping the resin film or roll with the lithium foil. When the inventor of the present invention actually rolled a lithium foil with a silicone layer interposed between the roll and the lithium foil, another release agent was interposed between the roll and the lithium foil. Compared with the case where the roll and the lithium foil were strongly adhered to each other, the strong adhesion was greatly suppressed. Further, when the lithium foil is rolled with the silicone layer and the lubricant interposed between the resin film and the lithium foil, when only the lubricant is interposed between the resin film and the lithium foil. In comparison, the strong adhesion between the resin film and the lithium foil was greatly suppressed.

The silicone layer is preferably made of a silicone material that is relatively easily deformed, exhibits a certain degree of adhesiveness to the mating material, and is difficult to firmly adhere to the mating material. Specifically, the silicone material may be a silicone resin described later, but is preferably an addition-curable or peroxide-curable silicone pressure-sensitive adhesive. This type of silicone adhesive is used as an adhesive for adhesive tapes typified by labels and masking tapes because it exhibits an excellent pressure-sensitive adhesive action.

The addition-curable silicone pressure-sensitive adhesive preferably has a siloxane unit represented by the following general formula (1) as a repeating unit, and may have a linear structure having the repeating unit as a main chain.
R ⁵ _y SiO _{(4-y) x 0.5} (1)
(R ⁵ in the formula is a monovalent or divalent hydrocarbon group having 1 to 20 carbon atoms which may be substituted independently, and y is 1.0 to 3.0.)

Examples of y in the above equation (1) include 1.5 to 2.05.

The number of carbon atoms of the monovalent or divalent hydrocarbon group represented by ^{R 5} in the above formula (1) include a range of 1～14,1～12. Examples of the hydrocarbon group include at least one selected from an alkyl group, an alkenyl group, an aryl group, an aralkyl group or an alkylene group. Two or more of R ⁵ may be an alkenyl group. Specific examples of the alkyl group include a methyl group. Specific examples of the alkenyl group include at least one selected from a vinyl group, an allyl group, a butenyl group, a pentenyl group, a hexenyl group or a heptenyl group. Specific examples of the aryl group include a phenyl group.

Examples of the addition-curing type silicone pressure-sensitive adhesive include those in which a silicone pressure-sensitive adhesive raw material containing an organopolysiloxane having an alkenyl group and an organohydrogenpolysiloxane is cured by an addition reaction. An addition reaction catalyst may be used to increase the rate of the addition reaction.

When the addition-curable silicone pressure-sensitive adhesive uses the siloxane unit represented by the above formula (1) as a repeating unit, the organopolysiloxane includes a compound containing a siloxane unit represented by the following general formula (1-1). Be done.
R ⁶ _y SiO _{(4-y) x 0.5} (1-1)
(In the formula, R ⁶ is an alkenyl group independently, and y is 1.0 to 3.0.)

The organopolysiloxane preferably has a siloxane unit represented by the above general formula (1-1) as a repeating unit, and may have a linear structure having the repeating unit as a main chain. The organopolysiloxane may be linear or may have a branched and / or cyclic partial structure as well as a linear partial structure. The molecular weight of the organopolysiloxane is not particularly limited.

The organohydrogenpolysiloxane has a SiH group in the molecule, and the organic group thereof is not particularly limited. The number of SiH groups in one molecule of organohydrogenpolysiloxane is not particularly limited, and may range from 2 to 300, 3 to 200, and 4 to 150. The SiH groups may react with the alkenyl group R ⁶ in the organopolysiloxane, which contributes to curing of the addition curing type silicone adhesive. Therefore, the number of SiH groups in one molecule of organohydrogenpolysiloxane is preferably 2 or more. The organohydrogenpolysiloxane may be linear or branched.

As raw materials for the addition-curable silicone pressure-sensitive adhesive, KS-774, KS-775, KS-778, KS-779H, KS-847H, KR3700, KR3701, X-40-3237-1, X-40-3240, X-40-3291-1, X-40-3229, X-40-3270, X-40-3306 (above, manufactured by Shin-Etsu Chemical Co., Ltd.), SD4584, SD4585, SD4560, SD4570, SD4600PFC, SD4593, (above) , Toray Dow Corning Co., Ltd.), TSR1512, TSR1516, XR37-B9204 (all manufactured by Momentive Performance Materials Co., Ltd.) and the like. As the addition-curing type silicone pressure-sensitive adhesive, these may be used alone or in combination of two or more. As a specific combination when two or more kinds of silicone adhesives are used in combination, a combination of KS-847H manufactured by Shin-Etsu Chemical Co., Ltd. and SD4584 manufactured by Toray Dow Corning Co., Ltd. can be mentioned. , Not limited to this.
Further, the silicone layer may be formed by combining the raw material of the silicone resin described later with the raw material of the silicone pressure-sensitive adhesive. SD4584 manufactured by Toray DouConning Co., Ltd. contains a trifunctional or tetrafunctional siloxane unit, and the silicone adhesive obtained by using the raw material exhibits the same characteristics as the silicone resin. However, it is considered that a silicone layer having a good balance between adhesiveness and peelability can be formed.

As the addition reaction catalyst, one that can function as the catalyst for the above-mentioned addition reaction may be used. For example, various platinum-based catalysts such as platinum, platinum compounds, and various complexes of platinum, rhodium-based catalysts such as rhodium chloride, and palladium. , Palladium-based catalysts such as palladium chloride can be exemplified.

The peroxide-curing type silicone pressure-sensitive adhesive is different from the above-mentioned addition-curing type silicone pressure-sensitive adhesive in that it performs a curing reaction of organopolysiloxane in the presence of an organic peroxide. As the organopolysiloxane used as a material for the peroxide-curable silicone pressure-sensitive adhesive, the same organopolysiloxane as described in the above-mentioned addition-curable silicone pressure-sensitive adhesive may be used, but R ⁶ has an alkyl group. Is preferable.

As the organic peroxide, one that decomposes to generate free oxygen radicals may be used, and is not particularly limited. Examples of organic peroxides that can be used as raw materials for peroxide-curable silicone pressure-sensitive adhesives include dibenzoyl peroxide, 4,4'-dimethylbenzoyl peroxide, and 3,3'-dimethylbenzoyl peroxide. Examples thereof include 2,2'-dimethylbenzoyl peroxide.

In order to form a silicone layer with each of the above-mentioned silicone pressure-sensitive adhesives, each of the above-mentioned raw materials may be mixed with a solvent such as an organic solvent, if necessary, and applied to a resin film to carry out a curing reaction. Before and after the curing reaction, the silicone pressure-sensitive adhesive or the raw material of the silicone pressure-sensitive adhesive on the resin film may be heated. By heating, it is possible to remove the solvent and accelerate the curing reaction.

As the material of the silicone layer provided on the resin film, the following silicone resin can also be used in addition to the above-mentioned silicone pressure-sensitive adhesive. As described above, the silicone resin may be used in combination with the silicone adhesive. The silicone layer containing a silicone resin can form a release layer that is less likely to be deformed and has lower adhesiveness than the silicone layer containing a silicone pressure-sensitive adhesive. Further, due to this property, the silicone resin is suitable as a material for the silicone layer integrally provided on the roll. Further, the silicone layer made of silicone resin may be formed on the surface of the roll used in the lithium foil rolling step described later. Since the lithium foil for doping is required to be thin and not damaged, suppressing the strong adhesion between the lithium foil and the roll when rolling the lithium foil to obtain a thin lithium foil is a lithium negative electrode composite. It is very useful in the manufacture of.
Hereinafter, the silicone resin will be described.

As described above, the silicone resin has the property of being relatively hard to be deformed and having low adhesiveness. Specifically, the silicone resin is a bifunctional siloxane unit represented by the following general formula (2), a trifunctional siloxane unit represented by the following general formula (3), or the following general formula (4). ), It is preferable to include a polyorganosiloxane material containing a tetrafunctional siloxane unit.
R ¹ R ² SiO _{(0.5 × 2)} (2)
R ¹ SiO _{(0.5 × 3)} (3)
SiO _{(0.5 × 4)} (4)
(In the formula, R ¹ and R ² are independently any of an alkyl group having 1 to 3 carbon atoms, a phenyl group, a vinyl group, and an amino group. Even if R ¹ and R ² are the same. It may be good or different.)

The polyorganosiloxane material containing any of the siloxane units of the general formulas (2) to (4) can form a relatively hard silicone layer having a three-dimensional network structure.

Examples of the raw material of the polyorganosiloxane material containing any of the siloxane units of the general formulas (2) to (4) include compounds represented by the following general formulas (2-1) to (4-1), respectively. Be done.
R ¹ R ² Si (OR ³ ) ₂ (2-1)
R ¹ Si (OR ³ ) ₃ (3-1)
Si (OR ³ ) ₄ (4-1)
(In the formula, R ¹ and R ² are independently any of H, an alkyl group having 1 to 3 carbon atoms, a phenyl group, a vinyl group, and an amino group. R ³ has 1 to 3 carbon atoms. It is an alkyl group. R ^{1 to} R ³ may be the same or different.)

As the raw material of the polyorganosiloxane material, the bifunctional compound represented by the general formula (2-1), the trifunctional compound represented by the general formula (3-1), or the general Any of the tetrafunctional compounds represented by the formula (4-1) may be used, and the proportion of the bifunctional compound, the trifunctional compound and the tetrafunctional compound in the raw material is not particularly limited. .. Of these compounds contained in the raw material, when the proportion of the bifunctional compound is large, the flexibility of the silicone layer is increased, and when the proportion of the trifunctional compound is large, the silicone layer is hardened and the tetrafunctional compound is quadrature. It is said that the silicone layer becomes harder when the proportion of the sex compound is large.

The silicone resin for rolls preferably contains a trifunctional siloxane unit, and more preferably contains a trifunctional siloxane unit and a bifunctional siloxane unit. Examples of R ¹ , R ² and R ³ include a methyl group, a propyl group and a phenyl group, respectively. Further, the mass average molecular weight of the silicone resin may be in the range of 300 or more and 30,000 or less, and the residual alkoxy amount in the silicone resin may be in the range of 2% by mass or more and 50% by mass or less.

Examples of the raw material of the silicone resin containing the siloxane unit of the general formula (2) include methylhydrogendimethoxysilane, methylhydrogendiethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methylethyldimethoxysilane, diethyldimethoxysilane, and diethyl. Examples thereof include diethoxysilane, methylpropyldimethoxysilane, methylpropyldiethoxysilane, phenylmethyldimethoxysilane, and vinylmethyldimethoxysilane. These are bifunctional alkoxysilanes.

As raw materials for the silicone resin containing the siloxane unit of the general formula (3), KR220L, KR242A, KR271, KR282, KR300, KR311, KK89, KR500, KR212, KR213, KR9218, KR251, KR400, KR255, KR216, KR152 ( (Made by Shin-Etsu Chemical Co., Ltd.), 804RESIN, 805RESIN, 806ARESIN, 840RESIN, SR2400, 3037INTERMEDIATE, 3074INTERMEDIATE, Z-6018, 217FLAKE, 220FLAKE, 233FLAKE, 249FLAKE, 249FLAKE, QP862-14 Examples thereof include AY42-163 (all manufactured by Toray Dow Corning Co., Ltd.), SY231, SY550, SY300, SY409, SY430, and IC836 (all manufactured by Asahi Kasei Wacker Co., Ltd.). These contain trifunctional alkoxysilanes and / or derivatives thereof.

Examples of the raw material of the silicone resin containing the siloxane unit of the general formula (4) include tetramethoxysilane, tetraethoxysilane, and tetraisopropoxysilane. In addition, M silicate 51, silicate 35, silicate 45, FR-3 (above, manufactured by Tama Chemical Corporation), MSI51, ESI40, ESI48, EMCi48 (above, manufactured by Corcote), MS51, MS56 (above, Mitsubishi Chemical Corporation) (Made by a company) can be illustrated. These contain tetrafunctional alkoxysilanes and / or derivatives thereof.

The silicone resin constituting the silicone layer is produced by a dehydration condensation reaction between a raw material of the silicone resin, that is, an alkoxysilane and / or a derivative thereof. As the raw material of the silicone resin, only one kind of the alkoxysilanes (2-1) to (4-1) and / or a derivative thereof may be used, or two or more kinds thereof may be used in combination.

The method of providing the silicone layer on the roll or the resin film is not particularly limited, and a known coating method may be used. Further, the thickness of the silicone layer may be appropriately set according to the stress acting on the lithium foil during pressing.

When the silicone layer is provided on the roll, the silicone layer may be provided on only one roll or both rolls. However, in consideration of suppressing damage to the lithium foil when performing a pressing process for pressing the negative electrode laminate without using a resin film or when rolling the lithium foil in the lithium foil rolling process described later, silicone is used. It is preferable to provide the layer on both rolls.

The silicone layer may be provided on both the roll and the resin film. That is, even when the resin film is used in the pressing step of the method for producing the lithium negative electrode composite of the present invention, a roll having a silicone layer may be used as the roll for pressing the negative electrode laminate. For example, the lithium layer formed on one negative electrode active material layer is in direct contact with the roll, and the negative electrode laminate is further laminated with a resin film on the lithium layer formed on the other negative electrode active material layer. When pressing, it is preferable to use a roll having a silicone layer as a roll in contact with the lithium foil. Further, when rolling the lithium foil, when the resin film provided with the silicone layer is overlaid on only one surface of the lithium foil and rolled, the side of the two surfaces of the lithium foil where the resin film is not overlaid is not overlapped. It is preferable that a roll having a silicone layer faces the surface of the surface.

By the way, as described above, it is preferable to use a silicone resin as the silicone layer provided on the roll, and it is preferable to use a silicone adhesive as the silicone layer provided on the resin film. This is because the timing of peeling from the lithium foil differs between the silicone layer provided on the roll and the silicone layer provided on the resin film. Hereinafter, a pressing method in which a resin film is interposed between a roll and a lithium foil is referred to as a film press, and a pressing method in which a resin film is not interposed between a roll and a lithium foil is referred to as a direct press.

When the negative electrode laminate having the lithium foil is pressed by the two rolls, the compressive stress acting on the lithium foil from the two rolls is the position where the distance between the two rolls is closest (hereinafter, if necessary, the close position). (Call) is considered to be the maximum. In the case of direct pressing, when the lithium foil reaches a close position, the lithium foil and the roll are brought into close contact with each other due to the above-mentioned compressive stress. Then, when the lithium foil passes through a close position, the roll that is in close contact with the lithium foil is peeled off from the lithium foil, and it is considered that stress at that time acts on the lithium foil.
Considering any point of the lithium foil as a reference, in the case of direct pressing, the time for the lithium foil to contact the silicone layer provided on the roll is very short, and the compressive stress and the stress when the roll is peeled off Acts on the lithium foil at relatively short intervals. Therefore, the silicone layer provided on the roll is preferably made of a silicone material having a small adhesive force to the lithium foil and easily peeling off from the lithium foil, that is, a silicone resin, in order to suppress deformation and breakage of the lithium foil.

On the other hand, in the case of the film press, the compressive stress acting on the lithium foil from the roll is maximum at the above-mentioned close position, but the stress acting on the lithium foil immediately after that is smaller than that in the case of the above-mentioned direct press. .. That is, in the case of a film press, a resin film having a silicone layer is interposed between at least one roll and the lithium foil, and the resin film may be peeled off from the lithium foil after pressing. Therefore, in this case, unlike the case of direct pressing, the stress of peeling the resin film from the lithium foil does not act on the lithium foil immediately after the compressive stress is applied. Therefore, the silicone layer formed on the resin film is not required to have as low an adhesive force and easy peeling from the lithium foil as the silicone layer formed on the roll. Rather, the silicone layer formed on the film is desired to have an adhesive force that can remain between the resin film and the lithium foil from the time of pressing until the resin film is peeled off. In that respect, the silicone pressure-sensitive adhesive is considered to be suitable as a silicone material for the silicone layer formed on the film because it has a larger adhesive strength than the above-mentioned silicone resin.

By the way, a silicone adhesive that adheres to a mating material such as lithium foil has a property that the adhesive strength is relatively large when peeling from the mating material at high speed, and the adhesive strength is relatively small when peeling from the mating material at low speed. Have. Therefore, when the resin film is peeled off from the lithium foil at a low speed after pressing, the stress acting on the lithium foil, that is, the stress of the resin film peeling off from the lithium foil is not excessive, and the deformation and breakage of the lithium foil are sufficiently suppressed. It is thought that it will be done. From this, it is considered that the silicone pressure-sensitive adhesive is suitable as a silicone material for the silicone layer formed on the film.

In the method for producing a lithium negative electrode composite of the present invention, the thickness of the lithium foil laminated on the Si-containing negative electrode active material layer, that is, the amount of lithium doped in the Si-containing negative electrode active material layer is determined by the Si-containing negative electrode active material layer. It may be set based on the irreversible capacity. Further, since the lithium foil is laminated on the Si-containing negative electrode active material layer, the amount of lithium and the irreversible capacity of the Si-containing negative electrode active material layer may be designed as the amount per unit area of both.
That is, the amount of lithium in the lithium foil per unit area is preferably an amount corresponding to the amount of lithium that can cancel the irreversible capacity of the Si-containing negative electrode active material layer per unit area.

The amount of lithium in a lithium foil per unit area correlates with the thickness of the lithium foil. If the thickness of the lithium foil is too small, the amount of lithium in the lithium foil per unit area is too small, and the irreversible capacity of the Si-containing negative electrode active material layer on which the lithium foil is overlapped is not sufficiently canceled, and the lithium ion battery is not sufficiently canceled. The capacity of the next battery does not improve sufficiently. On the other hand, if the thickness of the lithium foil is excessive, excess lithium may become a foreign substance in the lithium ion secondary battery, and the cost of the lithium ion secondary battery increases.
In order to consider the irreversible capacity of the Si-containing negative electrode active material layer and reduce excess lithium as much as possible, the thickness of the lithium foil is preferably 1 μm to 25 μm, preferably 3 to 20 μm. More preferably, it is 5 to 15 μm.
When the method for producing a lithium negative electrode composite of the present invention includes a lithium foil rolling step of rolling a lithium foil, the suitable thickness of the lithium foil obtained in the lithium foil rolling step is also within the above range.

The above-mentioned "amount of lithium capable of canceling the irreversible capacity of the Si-containing negative electrode active material layer per unit area" may be calculated as follows.
First, the "irreversible capacity of the Si-containing negative electrode active material layer per unit area" is a test lithium secondary battery actually manufactured with the negative electrode having the Si-containing negative electrode active material layer as the reference electrode and metallic lithium as the counter electrode. It may be calculated based on the measured value of the so-called half cell). Specifically, the irreversible capacity per mass of the Si-containing negative electrode active material is calculated based on the irreversible capacity of the negative electrode active material layer of the half cell calculated by (initial charge capacity) − (initial discharge capacity). Then, from the calculation result, the irreversible capacity per unit area of the negative electrode active material layer in the lithium-doped negative electrode of the present invention is calculated.
The initial charge capacity means the capacity when the lithium counter electrode and the negative electrode are initially charged until the potential difference becomes 0.01 V. The initial discharge capacity refers to the capacity when the half cell after the initial charge is discharged until the potential difference between the lithium counter electrode and the negative electrode becomes 0.8 V. Charging here means that the lithium ion of the counter electrode moves to the reference electrode, and discharge means that the lithium ion moves from the reference electrode after charging to the counter electrode. At this time, charging / discharging shall be performed with a low current of about 0.01C to 0.05C. 1C means the current value required to fully charge or completely discharge the battery in 1 hour at a constant current.
The above-mentioned "amount of lithium that can cancel the irreversible capacity of the Si-containing negative electrode active material layer per unit area" is the same amount of lithium as the above-mentioned "irreversible capacity of the Si-containing negative electrode active material layer per unit area". The quantity. As the capacity of lithium, 3861 mAh / g, which is the theoretical capacity of metallic lithium, may be used.

Further, assuming that the amount of lithium in the lithium foil per unit area is (A) and the amount of lithium that can cancel the irreversible capacity of the Si-containing negative electrode active material layer per unit area is (B), the (A) and (B) ) Should satisfy 0.8 <(A) / (B) <1.2.

Further, in general, in a lithium ion secondary battery, the battery is designed so that extra lithium, which is a foreign substance, is not generated in the lithium ion secondary battery. Specifically, assuming that the amount of lithium that can be accepted by the negative electrode is (C) and the amount of lithium that can be emitted by the positive electrode is (D), the relationship of C> D may be satisfied.
In consideration of this, in the lithium ion secondary battery of the present invention having the lithium-doped negative electrode of the present invention, the battery is designed so as to satisfy the relationship of 1.05 <C / (D + lithium amount of lithium foil) <1.5. Is preferable.
Here, the amount of lithium (C) that can be accepted by the negative electrode can be calculated based on the capacity of the negative electrode active material per unit mass calculated from the initial charge capacity of the half cell described above. The amount of lithium (D) that can be emitted by the positive electrode is the maximum capacity that can be reversibly charged and discharged by manufacturing a lithium ion secondary battery having a positive electrode used for the lithium ion secondary battery to be manufactured. Just do it.

The material of the roll used in the pressing process is not particularly limited, but it is preferable to use a hard material in order to apply a sufficient load to the lithium foil. Each of the two rolls may be made of different materials or have different sizes, but in order to easily set the load, the rotation speed of the rolls, etc., they are made of the same material and have the same size. Is preferable.
Specifically, the material of the roll preferably has a Vickers hardness of 50 HV or more, more preferably 70 HV or more, further preferably 100 HV or more, and even more preferably 150 HV or more. Examples of materials with Vickers hardness of 50 HV or more are stainless steel, nickel, nickel steel, nickel molybdenum chrome alloy, nickel chrome iron alloy, tungsten, tungsten steel, molybdenum, titanium, titanium alloy, aluminum bronze, brass, copper alloy. , Metallic materials such as carbon steel. Considering the price, workability, etc., it is particularly preferable to use stainless steel.

The roll material referred to here refers to a material other than the release layer when the roll is provided with a release layer such as a silicone layer. That is, it can be said that the roll having the release layer integrally is composed of the roll base material and the release layer provided on the roll base material. In this case, the material of the roll is the roll base material. Refers to the material.

In the pressing step, a lubricant may be used in combination with the above-mentioned release layer or instead of the release layer. The lubricant is preferably interposed between the roll and the lithium foil, or between the resin film and the lithium foil, and in any case, it is preferably interposed between the release layer and the lithium foil. By using the release layer and the lubricant together, it is considered that the pressure bonding of the lithium foil to the roll or the resin film can be suppressed, and the deformation and breakage of the lithium foil by the press can be further suppressed. In particular, when a silicone layer is used as the release layer, the effect of suppressing damage to the lithium foil can be further enhanced by using the release layer and the lubricant in combination. As the lubricant, it is preferable to use a lubricant that has good compatibility with a release layer such as a silicone layer and has low reactivity with lithium.

As the lubricant, a lubricant capable of suppressing the strong adhesion of the lithium foil to the release layer, the roll and the resin film is used. Further, the lubricant has a property of being low in volatility to the extent that it stays between the release layer, the roll or the film and the lithium foil at the time of pressing, and has a property of being high in volatility to the extent that it can be easily removed from the lithium negative electrode composite. preferable. Examples of the lubricant satisfying these conditions include an aprotic organic solvent. Specifically, it is preferable to use one having a vapor pressure at 20 ° C. in the range of 0.3 to 65.0 kPa or a vapor pressure at 25 ° C. in the range of 0.5 to 100 kPa.

Specific examples of the lubricant include pentane, hexane, heptane, octane, nonane, decane, ethylmethyl carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, fluoromethylmethyl carbonate, difluoromethylmethyl carbonate, 2,2,2-. Trifluoroethyl methyl carbonate, bis (2,2,2-trifluoroethyl) carbonate, acetonitrile, propionitrile, butyronitrile, acrylonitrile, dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, 1,2 -Dioxane, 1,3-dioxane, 1,4-dioxane, 2,2-dimethyl-1,3-dioxolane, 2-methyltetrahydropyran, 1,3-dioxolane, N, N-dimethylacetamide, isopropylisocyanate, n -Propyl isocyanate, chloromethylisocyanate, dimethylacetal, diethyl ether, methylisobutylketone, 1,2-dimethoxyethane, 1,2-diethoxyethane, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, butyl acetate , Propyl acetate, isopropyl acetate, isobutyl acetate, methyl propionate, vinyl acetate, methyl acrylate, methyl methacrylate, glycidyl methyl ether, epoxybutane, 2-ethyloxylan, oxazole, 2-ethyloxazole, oxazoline, 2-methyl-2- Examples thereof include oxazoline, acetone, methyl ethyl ketone, methyl isobutyl ketone, anhydrous acetic acid, 1-nitropropane, 2-nitropropane, furan, γ-butyrolactone, thiophene, pyridine, 1-methylpyrrolidin, N-methylmorpholin and the like. In the method for producing a lithium negative electrode composite of the present invention, one or a combination of two or more of these aprotic organic solvents may be used as a lubricant.

As the lubricant, among the above-mentioned aprotic organic solvents, those having a vapor pressure at 20 ° C. in the range of 0.5 to 10 kPa or a vapor pressure at 25 ° C. in the range of 1.0 to 20 kPa. Is particularly preferable to use. Further, as the lubricant, it is particularly preferable to use a saturated hydrocarbon having 7 or less carbon atoms.
Specifically, as the lubricant, it is particularly preferable to use at least one selected from hexane, heptane, octane, nonane, decane, methyl isobutyl ketone, ethyl methyl carbonate, and dimethyl carbonate. It should be noted that these aproton organic solvents not only satisfy the above conditions, but are also used in the electrolytic solution of the lithium ion secondary battery, or are not sufficiently volatilized and are not sufficiently volatilized. Even if it is brought into the market, it has the advantage that it does not easily deteriorate the performance of the lithium-ion secondary battery.

Further, the lubricant is expected to exhibit a degree of fluidity that can be uniformly spread between the roll and the lithium foil or between the resin film and the lithium foil at the vicinity of the two rolls described above. NS. In the present specification, the fluidity of the lubricant is defined by the viscosity of the lubricant. The viscosity of the lubricant at 20 ° C. is preferably 2.00 pascal seconds or less, and more preferably 1.00 pascal seconds or less. The viscosity of hexane at 20 ° C. is about 0.0003 pascal seconds, and the viscosity of ethyl methyl carbonate at 20 ° C. is about 0.0007 pascal seconds.

As the lithium foil used in the pressing process, a commercially available one may be used, but since it is preferable to use a thin lithium foil in the method for producing the lithium negative electrode composite of the present invention, the commercially available lithium foil is further rolled. You may use it. That is, the method for producing a lithium negative electrode composite of the present invention may include a lithium foil rolling step for obtaining a thin lithium foil. The lithium foil rolling step is a step of rolling a relatively thick lithium foil to obtain a thin lithium foil. Hereinafter, if necessary, the lithium foil before rolling is referred to as a lithium raw foil, and the lithium foil after rolling is referred to as a rolled lithium foil.

As the rolling apparatus used in the lithium foil rolling step, a press roll similar to the above-mentioned pressing step may be used. The strong adhesion between the roll and lithium, which is a problem when rolling the negative electrode laminate, is also a problem that occurs when rolling the lithium foil. Therefore, even in the lithium foil rolling process, between the roll and the lithium foil. It is preferable to interpose a resin film in the roll, and it is preferable to interpose a release layer and / or a lubricant between the roll or the resin film and the lithium foil. The roll, resin film, release layer and lubricant are as described above. Hereinafter, if necessary, a mode in which a lithium raw foil on which a resin film is laminated is rolled with a roll is referred to as film rolling, and a mode in which a lithium raw foil without a resin film is rolled as it is is referred to as direct rolling.

As described above, lithium has the property of being soft and easily deformed. In order to thinly process a lithium foil having such properties, the inventor of the present invention repeatedly rolls the lithium foil under various conditions to produce a thin lithium foil with suppressed breakage that can withstand the use of lithium dope. I tried. In the process, it was found that when rolled by a press roll, the amount of deformation of the lithium foil in the rolling direction of the lithium foil is large, but the amount of deformation is almost nonexistent in the width direction of the lithium foil orthogonal to the rolling direction. .. The rolling direction of the lithium foil referred to here can be said to be the direction in which the lithium foil rolled by the two rolls is conveyed. In other words, the rolling direction can be said to be the rear-front direction in FIG. 1, which will be described later. Further, the width direction of the lithium foil can be said to be the direction from the back side of the paper surface to the front side of the paper surface in FIG. 1 which will be described later. Based on this discovery, the inventor came to optimize the lithium foil rolling process.

That is, since the width of the lithium foil does not change before and after rolling, the width of the lithium raw foil can be set based on the width of the negative electrode active material layer. This is due to the following reasons.

A so-called roll-to-roll method is known in which a material wound on an unwinding roll is processed while being unwound and then wound on a winding roll. In the pressing step in the method for producing a lithium negative electrode composite of the present invention, for example, as in Example 1 described later, a rolled lithium foil is laminated on the negative electrode active material layer of the negative electrode while unwinding the negative electrode from the unwinding roll. A roll-to-roll method can be adopted in which the lithium negative electrode composite is formed by pressing and rewinding on a take-up roll. When the press process is performed by the roll-to-roll method, the width of the negative electrode active material layer wound on the unwinding roll and the width of the rolled lithium foil laminated on the negative electrode active material layer are precisely determined. Must be set.

That is, for example, if the width of the rolled lithium foil is excessive with respect to the width of the negative electrode active material layer, the rolled lithium foil greatly protrudes from the negative electrode active material layer. Therefore, in order to prevent excess lithium, that is, lithium that is not doped in the negative electrode active material layer, into the lithium ion secondary battery, a step such as cutting the protruding rolled lithium foil is required. Specifically, the width of the rolled lithium foil should be slightly smaller than the width of the negative electrode active material layer.
Further, for example, if the width of the rolled lithium foil is smaller than the width of the negative electrode active material layer, many portions of the negative electrode active material layer are not doped with lithium, so that the excess negative electrode active material layer is cut off. Step is required.
If the above cutting is performed in the state of the lithium negative electrode composite in which the rolled lithium foil is laminated on the negative electrode, the negative electrode active material layer and the lithium foil may be damaged and a manufacturing loss may occur. It is hard to say that it is preferable in manufacturing a negative electrode composite or a lithium ion secondary battery.

In order to avoid this problem, it is necessary to appropriately shape the width of the rolled lithium foil and the width of the negative electrode active material layer before the pressing process. Specifically, the rolled lithium foil or the negative electrode must be shaped before the pressing process. It is considered that a process such as cutting is required.

However, as described above, if the width of the lithium foil does not change before and after rolling, a lithium raw foil having a width corresponding to the width of the negative electrode active material layer to be manufactured may be prepared, and the rolled lithium foil or the negative electrode described above may be prepared. The step of cutting is not required. If the lithium negative electrode composite is manufactured by such a method, there is a great effect in reducing the manufacturing cost of the lithium negative electrode composite.

For reference, the width of the positive electrode active material layer at the positive electrode should be slightly smaller than the width of the rolled lithium foil. This is the case where the lithium negative electrode composite and the positive electrode are stacked and placed in a battery container as described later, and the negative electrode active material layer is doped with lithium by a doping step of injecting an electrolytic solution into the battery container. Especially useful. In this case, at the time of manufacturing the lithium ion secondary battery, there is an advantage that the lithium ion secondary battery in which the entire surface of the positive electrode active material layer faces the lithium-doped negative electrode active material layer can be easily manufactured.

It is preferable that the width of the lithium raw foil is equal to or less than the width of the negative electrode active material layer, and the difference between the width of the lithium raw foil and the width of the negative electrode active material layer is 5 mm or less. The width of the lithium raw foil is less than the width of the negative electrode active material layer, and the difference between the width of the lithium raw foil and the width of the negative electrode active material layer is more preferably 3 mm or less, and further preferably 1 mm or less. .. Further, it is preferable that the width of the lithium raw foil is equal to or larger than the width of the positive electrode active material layer, and the difference between the width of the lithium raw foil and the width of the positive electrode active material layer is 5 mm or less. The width of the lithium raw material exceeds the width of the positive electrode active material layer, and the difference between the width of the lithium raw material and the width of the negative electrode active material layer is more preferably 3 mm or less, and further preferably 1 mm or less.

In the lithium foil rolling step, the load acting on the lithium raw foil from the roll is preferably 0.1 kN to 3.0 kN. If the load exceeds this range, the lithium raw foil may be crimped to the roll during rolling, and the rolled lithium foil may be deformed or damaged. Further, if the load is less than this range, it is necessary to perform roll pressing many times, which may increase the manufacturing cost of the rolled lithium foil. The load acting on the lithium raw foil from the roll during rolling is more preferably 0.5 kN to 2.0 kN, and further preferably 1.0 kN to 1.5 kN.
Further, the load acting on the lithium raw foil from the roll in the lithium foil rolling step is preferably 1.0 N / mm to 30 N / mm, and more preferably 0.5 N / mm to 20 N / mm.

By the way, in the lithium foil rolling process, the lithium raw foil rolled between the two rolls is not only compressed by the two rolls, but also conveyed by the rotation of the two rolls. That is, at this time, it can be said that not only the compressive force in the thickness direction but also the tension in the transport direction acts on the lithium raw foil.
As described above, the lithium foil is very soft and easily stretched and deformed. Therefore, when a very thin lithium raw foil is used in direct rolling, the lithium raw foil cannot withstand the tension during rolling and is damaged. There is a risk.
Further, considering the handleability, it is considered that the rolled lithium foil obtained by the lithium foil rolling step should be wound on a take-up roll. However, when a very thin rolled lithium foil is wound on a take-up roll in direct rolling, or when the wound rolled lithium foil is unwound and used, the rolling is applied to the tension at the time of winding or unwinding. The lithium foil cannot resist and may be damaged.

On the other hand, when the film is rolled, the lithium raw foil is lined with the resin film, so that there is an advantage that the above-mentioned lithium raw foil and the rolled lithium foil can be suppressed from being damaged by the tension.
Examples of the thickness of the very thin lithium raw foil and the thickness of the very thin rolled lithium foil referred to here are 20 μm or less in thickness and 10 μm or less in thickness. That is, it can be said that the lithium foil rolling step by film rolling is useful as a step of rolling a lithium raw foil having a thickness of 20 μm or less or a thickness of 10 μm or less, and a step of manufacturing a rolled lithium foil having the thickness. Further, the lithium foil rolling step by film rolling may include a step of winding the rolled lithium foil of the thickness together with the resin film.

Examples of the roll for rolling the lithium foil include a resin roll in addition to the metal roll described above. Since the resin roll has lower compatibility with the lithium foil than the metal roll, it is possible to suppress the pressure bonding of the lithium foil to the roll in the lithium foil rolling process by using the resin roll.
However, on the other hand, the resin roll tends to have an eccentric shape because the molding accuracy is lower than that of the metal roll. If the rolls are eccentric, it is difficult to roll the lithium foil with the rolls with high dimensional accuracy.
For example, when the target thickness of the rolled lithium foil is 20 μm, a rolled lithium foil having a thickness of about 20 μm ± 1 to 2 μm can be obtained according to the metal roll, but the rolling obtained by the resin roll can be obtained. The thickness of the lithium foil remains at about 20 μm ± 5 μm.
For this reason, conventionally, it is preferable to use a resin roll in consideration of crimping the lithium foil to the roll, but there is a contradictory situation that it is better to use a metal roll in consideration of the dimensional accuracy of the rolled lithium foil. rice field.

In the lithium foil rolling process, by interposing a silicone layer between the roll and the lithium foil, it is possible to suppress the crimping of the lithium foil to the roll, so a metal roll can be used and the rolled lithium foil with high dimensional accuracy can be used. There are advantages that can be manufactured. The metal roll referred to here may be a roll used for film rolling or a roll base material used for direct rolling. That is, regardless of whether the rolling method in the lithium foil rolling process is film rolling or direct rolling, there is an advantage that rolled lithium foil can be manufactured with high dimensional accuracy by using a metal roll or a metal roll base material. There is.

The doping of lithium in the lithium negative electrode composite obtained by the method for producing a lithium negative electrode composite of the present invention gradually proceeds even if the lithium negative electrode composite is left as it is. However, the lithium doping rate can be increased by bringing the lithium negative electrode complex into contact with the electrolytic solution.

Specifically, as the electrolytic solution, one containing an organic solvent and a lithium salt may be used. As the organic solvent and the lithium salt, those that can be used in the electrolytic solution for the lithium ion secondary battery described later may be used. The step of bringing the lithium negative electrode complex into contact with the electrolytic solution is called a doping step. By the doping step, the lithium in the lithium layer provided on the negative electrode active material layer is transferred to the negative electrode active material layer. Therefore, in the lithium negative electrode composite after the doping step, the lithium layer is substantially eliminated, and only the negative electrode active material layer having a one-layer structure in which lithium is integrated remains on the current collector. Therefore, the lithium negative electrode composite after the doping step does not need to consider peeling of lithium and the like, and the handleability is improved.

Based on this technical idea, the present invention can also be regarded as an invention relating to a method for manufacturing a lithium-doped negative electrode having the doping step.

In the doping step, the lithium negative electrode composite may be brought into contact with the electrolytic solution by itself, or may be brought into contact with the electrolytic solution in the battery container together with the battery constituent materials other than the negative electrode such as the positive electrode.

When the lithium negative electrode composite is brought into contact with the electrolytic solution by itself to perform the doping step, the handleability of the lithium negative electrode composite is improved as described above, and the assembly work of the lithium ion secondary battery becomes easy. Further, the negative electrode active material layer is porous having a large number of pores, and it is considered that an increase in density can be tolerated by the volume integral of the pores. Therefore, it is considered that the negative electrode active material layer doped with lithium in the doping step substantially has a smaller outer shape by the amount of the lost lithium layer, while increasing the density. As a result, the thickness of the lithium-doped negative electrode after the doping process is considered to be thinner than the thickness of the lithium negative electrode composite before the doping process.
Therefore, the amount of the lithium-doped negative electrode that can be put in the battery container of the same size is larger than the amount of the lithium negative electrode complex. In other words, the lithium-doped negative electrode can be filled in the battery container at a higher density than the lithium negative electrode composite. Therefore, in this case, it can be said that a lithium ion secondary battery having a large capacity can be manufactured.

On the other hand, when the lithium negative electrode composite is brought into contact with the electrolytic solution in the battery container together with the battery constituent material other than the negative electrode such as the positive electrode, the number of steps for manufacturing the lithium ion secondary battery is reduced. Further, as described above, the volume of the lithium-doped negative electrode after lithium doping is smaller than the volume of the lithium negative electrode composite before lithium doping. Therefore, when the lithium negative electrode composite is brought into contact with the electrolytic solution in the battery container to proceed with lithium doping, the difference between the volume of the lithium negative electrode composite before lithium doping and the lithium-doped negative electrode after lithium doping is calculated. There is a space in the battery container. Therefore, in this case, even when the negative electrode is expanded, a large stress is unlikely to act on the battery components such as the negative electrode, and a lithium ion secondary battery that can withstand the expansion of the negative electrode due to charging and discharging for a long period of time, that is, excellent in durability. It can be said that a lithium ion secondary battery can be obtained.

By the way, when the negative electrode laminate is pressed with a film interposed between the roll and the lithium foil in the pressing step, the film remains on the surface of the lithium negative electrode composite after pressing. As described above, when the film is peeled off from the lithium negative electrode composite, stress acts on the lithium layer made of the lithium foil, and if the stress is excessive, the lithium layer may be damaged. ..

However, if the lithium negative electrode composite is subjected to the doping step with the films stacked, damage to the lithium layer and the like can be suppressed. That is, since lithium in the lithium layer is transferred to the negative electrode active material layer by the doping step, the film after the doping step lacks the lithium foil, and the adhesion between the film and the negative electrode active material layer is also low. Therefore, the film after the doping step is easily peeled off from the lithium negative electrode composite. Further, since the lithium foil is doped in the negative electrode active material layer and disappears, the lithium foil cannot be damaged.

The lithium ion secondary battery of the present invention having the lithium negative electrode composite of the present invention includes the lithium negative electrode composite, a positive electrode body, an electrolytic solution and, if necessary, a separator. The positive electrode body has a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector. The lithium negative electrode composite has a negative electrode current collector, a negative electrode active material layer provided on both sides of the negative electrode current collector, and a lithium layer provided on each negative electrode active material layer. Further, the negative electrode active material layer is a Si-containing negative electrode active material layer, and Si contained in the negative electrode active material layer is derived from the negative electrode active material.

Examples of the Si-containing negative electrode active material include elemental silicon, elemental silicon and _{silicon-based materials such as SiO x} (0.3 ≤ x ≤ 1.6) that disproportionate to silicon dioxide, elemental silicon or silicon-based materials, and carbon described later. Examples thereof include a composite in which system materials and the like are combined. Furthermore, it is also preferable to use the silicon material disclosed in Patent Document 5 as the silicon-based material. Patent Document 5 discloses a silicon material having a structure in which a plurality of plate-shaped silicon bodies are laminated in the thickness direction. Then, in Patent Document 5, _{a layered silicon compound containing polysilane as a main component from which Ca is removed by reacting CaSi 2} with an acid is synthesized, and the layered silicon compound is heated at 300 ° C. or higher to release hydrogen. It describes the production of a silicon material and a lithium ion secondary battery containing the silicon material as an active material.

Other negative electrode active materials may be used in combination with the Si-containing negative electrode active material layer. The other negative electrode active materials include general negative electrode active materials, that is, Group 14 elements such as carbon, germanium and tin, Group 13 elements such as aluminum and indium, Group 12 elements such as zinc and cadmium, antimony and bismuth. At least one simple substance, compound or alloy of Group 15 elements such as, alkaline earth metals such as magnesium and calcium, and Group 11 elements such as silver and gold may be selected. Specific examples of the alloy or compound include tin-based materials such as Ag-Sn alloys, Cu-Sn alloys, and Co-Sn alloys, and carbon-based materials such as various graphites. Further, as the negative electrode active material, oxides such _{as Nb 2} O ₅ , TIO ₂ , Li ₄ Ti ₅ O ₁₂ , WO ₂ , MoO ₂ , Fe ₂ O _{3 or Li 3-x} M _x N (M = Co). , Ni, Cu) may be used. One or more of these can be used as the negative electrode active material.

In addition to the Si-containing negative electrode active material, the negative electrode active material layer may contain an appropriate amount of additives such as a conductive auxiliary agent, a binder, and a dispersant, if necessary. Similarly, since the positive electrode active material layer can also contain these additives in an appropriate amount in addition to the positive electrode active material described later, the following section includes the negative electrode active material layer and the positive electrode active material layer. I will explain. Hereinafter, if necessary, the negative electrode and the positive electrode are collectively referred to as an electrode, the negative electrode active material and the positive electrode active material are collectively referred to as an active material, and the negative electrode active material layer and the positive electrode active material layer are collectively referred to as an active material layer. That is.

The conductive auxiliary agent is added to increase the conductivity of the electrode. The conductive auxiliary agent may be a chemically inert electron high conductor, and examples thereof include carbon black, which are carbonaceous fine particles, graphite, Vapor Grown Carbon Fiber, and various metal particles. .. Examples of carbon black include acetylene black, Ketjen black (registered trademark), furnace black, and channel black. These conductive auxiliary agents can be added to the active material layer alone or in combination of two or more.

The binder plays a role of binding the active material or the like to the surface of the current collector. Examples of the binder include fluororesins such as polyvinylidene fluoride, polytetrafluoroethylene and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, and alkoxysilyl group-containing resins. be able to. Further, a polymer having a hydrophilic group may be adopted as the binder. Examples of the hydrophilic group of the polymer having a hydrophilic group include a carboxyl group, a sulfo group, a silanol group, an amino group, a hydroxyl group, and a phosphoric acid group. Specific examples of the polymer having a hydrophilic group include polyacrylic acid, carboxymethyl cellulose, polymethacrylic acid, and poly (p-styrenesulfonic acid).
Known additives such as dispersants other than the conductive auxiliary agent and the binder can be adopted.

A current collector is a chemically inert electronic high conductor that keeps current flowing through the electrodes during the discharge or charging of a lithium ion secondary battery. As the current collector, at least one selected from silver, copper, gold, aluminum, magnesium, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel. Metallic materials such as, etc. can be exemplified.

The current collector may be coated with a known protective layer. A current collector whose surface is treated by a known method may be used as the current collector.
Further, the current collector can take the form of a foil, a sheet, a film, a linear shape, a rod shape, a mesh or the like. Therefore, as the current collector, for example, a metal foil such as a copper foil, a nickel foil, an aluminum foil, or a stainless foil can be preferably used.

To form an active material layer on the surface of the current collector, a conventionally known method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method is used to collect electricity. An electrode mixture having an active material may be applied to the surface of the body. Specifically, the active material, the solvent, and if necessary, the binder and the conductive auxiliary agent are mixed to form a slurry-like electrode mixture, and after the slurry-like electrode mixture is applied to the surface of the current collector. ,dry. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. The dried one may be compressed in order to increase the electrode density.
When the lithium ion secondary battery of the present invention has a plurality of negative electrodes, at least one negative electrode may be the lithium-doped negative electrode of the present invention. That is, the lithium ion secondary battery of the present invention may have a negative electrode other than the lithium-doped negative electrode of the present invention. The negative electrode may have a negative electrode active material layer on only one side of the current collector, or may not be lithium-doped.

The positive electrode active material used for the positive electrode is not particularly limited, and a general positive electrode active material for a lithium ion secondary battery can be used.
Common cathode active material for lithium ion secondary batteries, the general formula of the layered rock salt _{structure: Li a Ni b Co c Mn} d D e O f (0.2 ≦ a ≦ 2, b + c + d + e = 1,0 ≦ e <1, D are W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr, Cu, Ca, Ir, Hf, It is represented by at least one element selected from Rh, Fe, Ge, Zn, Ru, Sc, Sn, In, Y, Bi, S, Si, Na, K, P, and V (1.7 ≦ f ≦ 3). Lithium composite metal oxide, Li ₂ MnO ₃ , can be mentioned. Further, as the positive electrode active material, _{a metal oxide having a spinel structure such as LiMn 2} O ₄ , a solid solution composed of a mixture of a metal oxide having a spinel structure and a layered compound, LiMPO ₄ , LiMVO ₄ or Li ₂ MSiO ₄ (in the formula). M is selected from at least one of Co, Ni, Mn, and Fe) and the like. Furthermore, as the positive electrode active material, tavorite compound (the M a transition metal) LiMPO ₄ F, such as LiFePO ₄ F represented by, Limbo ₃ such LiFeBO ₃ (M is a transition metal) include borate-based compound represented by be able to. Any metal oxide used as the positive electrode active material may have the above composition formula as the basic composition, and those in which the metal element contained in the basic composition is replaced with another metal element can also be used.

The above-mentioned lithium negative electrode composite or lithium-doped negative electrode of the present invention may be placed in a battery container together with a positive electrode and, if necessary, a known separator, and an electrolytic solution may be injected to obtain a lithium ion secondary battery.

The electrolytic solution contains an organic solvent and a lithium salt dissolved in the organic solvent.
As the organic solvent, cyclic esters, chain esters, ethers and the like can be used. Examples of the cyclic esters include ethylene carbonate, propylene carbonate, butylene carbonate, gamma-butyrolactone, vinylene carbonate, 2-methyl-gamma-butyrolactone, acetyl-gamma-butyrolactone, and gamma-valerolactone. Examples of chain esters include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, ethyl methyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester. Examples of ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane. These organic solvents may be used alone or in combination of two or more as the electrolytic solution.

Examples of the lithium salt include LiClO ₄ , LiAsF ₆ , LiPF _{6 , LiBF 4} , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) _{2, and the} like.

_{As the electrolytic solution, lithium salts such as LiClO 4} , LiPF ₆ , LiBF ₄ , and LiCF ₃ SO ₃ are added to an organic solvent such as ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, and dimethyl carbonate from 0.5 mol / l. An example is an example of a solution dissolved at a concentration of about 1.7 mol / l.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. As long as it does not deviate from the gist of the present invention, it can be carried out in various forms with modifications, improvements, etc. that can be made by those skilled in the art. In addition, each component shown in the present specification including the embodiment and the following examples can be arbitrarily extracted and combined.

Hereinafter, the present invention will be described in more detail with reference to Test Examples and Examples. The present invention is not limited to these examples.

(Example 1)
(Manufacturing of lithium negative electrode complex)
FIG. 1 shows an explanatory diagram schematically showing a method for manufacturing the lithium negative electrode complex of Example 1 using the apparatus for manufacturing the lithium negative electrode complex of Example 1, and FIG. 2 is an enlarged view of a main part of part A in FIG. Shown in. FIG. 3 shows an explanatory diagram schematically showing the lithium negative electrode complex of Example 1 obtained by the method for producing the lithium negative electrode complex of Example 1. An enlarged view of a main part of the B portion in FIG. 1 is shown in FIG. FIG. 5 shows an explanatory diagram schematically showing the method for producing the lithium-doped negative electrode of Example 1. Hereinafter, the terms "upper, lower, front, and rear" refer to the top, bottom, front, and rear shown in FIG.

The method for producing the lithium negative electrode composite of Example 1 is carried out using the roll press apparatus 1 shown in FIG.
As shown in FIG. 1, the roll press device 1 includes a roll press unit 2, a transport unit 3, and a lithium foil supply unit 4.

The roll press unit 2 has a first roll 21 and a second roll 22, and a press drive unit (not shown) that rotationally drives the first roll 21 and the second roll 22. The first roll 21 and the second roll 22 are made of stainless steel and are arranged vertically so as to be parallel to each other.

The press drive unit (not shown) is composed of an electric motor. Driven by the press drive unit, the first roll 21 rotates counterclockwise in FIG. 1, and the second roll 22 rotates clockwise in FIG. 1.

The transport unit 3 includes a negative electrode unwinding roll 31, a negative electrode take-up roll 32, a negative electrode unwinding roll 31 and a negative electrode take-up roll 32, and four auxiliary rolls (first auxiliary). It is composed of a roll 33, a second auxiliary roll 34, a third auxiliary roll 35, and a fourth auxiliary roll 36). A negative electrode 90 is wound around the negative electrode unwinding roll 31. As will be described later, the negative electrode take-up roll 32 winds up the lithium negative electrode composite 95 having the negative electrode 90. Therefore, the negative electrode 90 is bridged between the negative electrode unwinding roll 31 and the negative electrode winding roll 32.

As shown in FIG. 2, the negative electrode 90 includes a negative electrode current collector 91, a first negative electrode active material layer 92 formed on one surface of the negative electrode current collector 91, and a negative electrode current collector 91. It has a second negative electrode active material layer 93 formed on the other surface. The negative electrode 90 bridged between the negative electrode unwinding roll 31 and the negative electrode winding roll 32 faces the first negative electrode active material layer 92 upward and the second negative electrode active material layer 93 downward.

The negative electrode unwinding roll 31 is arranged on the rear side of the roll press unit 2, and the negative electrode winding roll 32 is arranged on the front side of the roll press unit 2. A transport drive unit (not shown) composed of an electric motor is connected to the negative electrode unwinding roll 31 and the negative electrode winding roll 32. Driven by the transport drive unit, the negative electrode unwinding roll 31 and the negative electrode winding roll 32 rotate clockwise in FIG. That is, the negative electrode unwinding roll 31 unwinds the negative electrode 90 from the rear side to the front side in FIG. 1, and the negative electrode winding roll 32 winds the lithium negative electrode composite 95 from the rear side to the front side. The first auxiliary roll 33 to the fourth auxiliary roll 36 will be described later.

A lithium foil supply unit 4 is arranged between the negative electrode unwinding roll 31 and the roll press unit 2. The lithium foil supply unit 4 is composed of a first foil unwinding unit 41, a second foil unwinding unit 42, and a foil unwinding drive unit (not shown). The first foil unwinding portion 41 is arranged above the negative electrode 90 between the negative electrode unwinding roll 31 and the roll press portion 2. The second foil unwinding portion 42 is arranged below the negative electrode 90 between the negative electrode unwinding roll 31 and the roll press portion 2.

The first foil unwinding portion 41 has a first unwinding roll 41a and a first winding roll 41b. The second foil unwinding portion 42 has a second unwinding roll 42a and a second winding roll 42b. The first film lithium laminate 61 is wound around the first unwinding roll 41a, and the second film lithium laminate 62 is wound around the second unwinding roll 42a. Although the details will be described later, the first film lithium laminate 61 and the second film lithium laminate 62 are the same, and each is a rolled lithium foil 65 and two films laminated on both sides of the rolled lithium foil 65, respectively. It is composed of 68 and.

One film 68 of the first film lithium laminate 61 is peeled off from the first film lithium laminate 61 at the front side of the first unwinding roll 41a in the unwinding direction, and is peeled off from the first film lithium laminate 61 via the first auxiliary roll 33. 1 Winding is wound on the winding roll 41b. The portion of the first film lithium laminate 61 other than the film 68, that is, the first film lithium laminate main body 61a having the other film 68 and the rolled lithium foil 65 passes through the second auxiliary roll 34 and the rolled lithium foil. 65 is placed on the upper surface of the negative electrode 90 with the 65 facing downward.

One film 68 of the second film lithium laminate 62 is peeled off from the second film lithium laminate 62 at the front side of the second unwinding roll 42a in the unwinding direction, and is peeled off from the second film lithium laminate 62 via the third auxiliary roll 35. 2 Winding is wound on the winding roll 42b. The portion of the second film lithium laminate 62 other than the film 68, that is, the second film lithium laminate main body 62a having the other film 68 and the rolled lithium foil 65 passes through the fourth auxiliary roll 36 and the rolled lithium foil. 65 is placed on the lower surface of the negative electrode 90 with the 65 facing upward. The first film lithium laminated main body 61a and the second film lithium laminated main body 62a are passed between the first roll 21 and the second roll 22 together with the negative electrode 90, and further wound on the negative electrode winding roll 32.

The foil unwinding drive unit (not shown) comprises an electric motor and is connected to a first unwinding roll 41a, a first winding roll 41b, a second unwinding roll 42a, and a second winding roll 42b. The first unwinding roll 41a, the first winding roll 41b, the second unwinding roll 42a, and the second winding roll 42b rotate in synchronization with each other. More specifically, driven by the foil unwinding drive unit, the first unwinding roll 41a rotates counterclockwise in FIG. 1, the first winding roll 41b rotates clockwise in FIG. 1, and the second The unwinding roll 42a rotates clockwise in FIG. 1, and the second winding roll 42b rotates counterclockwise in FIG. 1.

Hereinafter, a method for producing the lithium negative electrode complex of Example 1 using the apparatus for producing the lithium negative electrode complex of Example 1 will be described. The method for producing a lithium negative electrode composite of Example 1 includes a lithium foil rolling step and a composite forming step. The complex forming step includes a negative electrode forming step and a pressing step.

(Lithium foil rolling process)
As the lithium raw foil which is the material of the rolled lithium foil 65, a lithium foil having a thickness of 100 μm was used. Lubricant was applied to both sides of the lithium raw foil, and a film 68 was further laminated on the respective surfaces and rolled by a roll press device to obtain a rolled lithium foil 65 having a thickness of 20 μm.

Specifically, hexane was used as the lubricant.
As the film 68, a film 68 manufactured by Lintec Corporation and having a thickness of about 25 μm was used. The film 68 has a silicone layer formed on a resin film made of polyethylene terephthalate. The raw material of the silicone layer is KS-847H (manufactured by Shin-Etsu Chemical Co., Ltd.), which is an addition-curable silicone adhesive, in an amount of 30 parts by mass in terms of solid content, and SD4584 (Toray Industries, Inc.), which is also an addition-curable silicone adhesive. 18 parts by mass of Doukoning Co., Ltd. in terms of solid content, and 1.6 parts by mass of PL-50T (manufactured by Shin-Etsu Chemical Co., Ltd.), which is a platinum catalyst, by adding toluene as a solvent to solid content. The concentration is about 30% by mass. The raw material of the silicone layer was applied onto the resin film described above, heated at 130 ° C. for 2 minutes to cure, and the solvent was volatilized to form the silicone layer. The thickness of the silicone layer is 0.05 μm, and the thickness of the resin film is 25 μm. The film 68 thus obtained was laminated on both sides of the lithium raw foil to which the lubricant was sufficiently applied with the silicone layer facing the lithium raw foil, respectively, to obtain a laminate of the lithium raw foil and the film 68.

In this state, the laminated body was sandwiched and rolled with a predetermined load by two rolls of the roll press device (not shown). The rolled laminates are wound around a roll core as a first film lithium laminate 61 and a second film lithium laminate 62, respectively, and the first unwinding roll 41a and the second unwinding roll of the lithium foil supply unit 4 are taken up, respectively. Used for 42a. The first film lithium laminate 61 and the second film lithium laminate 62 are each composed of a rolled lithium foil 65 and a film 68 laminated on both sides of the rolled lithium foil 65, respectively.

(Complex formation step)
(Negative electrode forming process)
(Manufacturing of silicon material)
Concentrated hydrochloric acid containing 1% by mass of hydrogen fluoride is prepared, and under an ice bath at 0 ° C., 5 g of CaSi ₂ is added to 20 ml of the concentrated hydrochloric acid and stirred for 1 hour, then water is added and stirred for another 5 minutes. The reaction solution was obtained. The yellow solid content obtained by filtering the reaction solution was washed with water and ethanol, and dried under reduced pressure to obtain layered polysilane. This layered polysilane was heated at 500 ° C. under an argon atmosphere to obtain a silicon material in which hydrogen was released from the polysilane.
Using the silicon material as a Si-containing negative electrode active material, the negative electrode 90 was manufactured by the following method.

(Manufacturing of negative electrode)
70 parts by mass of the above silicon material as a Si-containing negative electrode active material, 15 parts by mass of natural graphite as another negative electrode active material, 5 parts by mass of acetylene black as a conductive auxiliary agent, and 15 parts by mass of polyamide-imide as a binder are mixed. At the same time, an appropriate amount of N-methyl-2-pyrrolidone was added to this mixture to obtain a slurry-like negative electrode mixture. A 20 μm electrolytic copper foil is prepared as the negative electrode current collector 91, and a negative electrode mixture is applied to both sides of the negative electrode current collector 91 using a doctor blade, and the negative electrode mixture is used as the negative electrode mixture. A negative electrode precursor having a layer and a current collector 91 for a negative electrode was obtained. The negative electrode precursor was dried to volatilize N-methyl-2-pyrrolidone in the negative electrode mixture. The dried negative electrode precursor was rolled by a roll press device (not shown) so that the thickness of the negative electrode mixture layer was 70 μm. By this rolling, the negative electrode mixture layer and the negative electrode current collector 91 were firmly integrated. The density of the negative electrode mixture layer at this time was 1.2 g / cm ³ .
The rolled negative electrode precursor is further heated at 200 ° C. for 2 hours under reduced pressure to form a first negative electrode active material layer formed on one surface of the negative electrode current collector 91 and the negative electrode current collector 91. A negative electrode 90 having 92 and a second negative electrode active material layer 93 formed on the other surface of the negative electrode current collector 91 was obtained. The negative electrode 90 was wound around a roll core and used for the negative electrode unwinding roll 31. The negative electrode 90 was subjected to the following pressing steps together with the first film lithium laminate 61 and the second film lithium laminate 62 described above.

(Press process)
Using the roll press apparatus 1 shown in FIG. 1, the lithium negative electrode complex 95 of Example 1 was produced by the following pressing steps.
First, the negative electrode 90 obtained in the above negative electrode forming step was unwound from the negative electrode unwinding roll 31 and passed between the first roll 21 and the second roll 22. Further, as shown in FIG. 4, one film 68 of the first film lithium laminate 61 was peeled off from the first unwinding roll 41a of the first foil unwinding portion 41 and wound on the first winding roll 41b. .. As shown in FIGS. 1 and 2, the remaining first film lithium laminated main body 61a was superposed on the upper surface of the negative electrode 90 while the rolled lithium foil 65 was directed toward the first negative electrode active material layer 92. Similarly, one film 68 of the second film lithium laminate 62 is peeled off from the second unwinding roll 42a of the second foil unwinding portion 42 and wound on the second winding roll 42b, and the remaining second film lithium The laminated main body 62a was laminated on the lower surface of the negative electrode 90 while the rolled lithium foil 65 was directed toward the second negative electrode active material layer 93. The first film lithium laminated main body 61a and the second film lithium laminated main body 62a were passed between the first roll 21 and the second roll 22 together with the negative electrode 90 and wound on the negative electrode winding roll 32. When passing between the first roll 21 and the second roll 22, the laminate (referred to as the film negative electrode laminate 94) of the negative electrode 90, the first film lithium laminated body 61a, and the second film lithium laminated body 62a , The loads from the first roll 21 and the second roll 22 acted. The rolled lithium foil 65 of the first film lithium laminated main body 61a and the rolled lithium foil 65 of the second film lithium laminated main body 62a are formed on the first negative electrode active material layer 92 and the second negative electrode active material layer 93, respectively, by the load. It was crimped and integrated.

In the method for producing the lithium negative electrode composite of Example 1, since the rolled lithium foil 65 was subjected to the pressing process while being reinforced with the film 68, the lithium negative electrode composite 95 was manufactured while suppressing damage to the rolled lithium foil 65. can.

Further, in the method for producing the lithium negative electrode composite of Example 1, since the pressing step was performed with the film 68 interposed between the rolled lithium foil 65 and the first roll 21 and the second roll 22, the rolled lithium foil was formed. Strong adhesion between the 65 and the first roll 21 and the second roll 22 can be suppressed, and damage to the rolled lithium foil 65 in the pressing process can be further suppressed.

As shown in FIG. 3, by peeling the film 68 from the film negative electrode laminate 94 after the pressing step, the negative electrode 90 and the layer of the rolled lithium foil 65 integrated with the negative electrode 90 (that is, the lithium layer 66) are provided. A lithium negative electrode composite 95 can be obtained.

In the method for producing the lithium negative electrode composite of Example 1, a silicone layer is formed on the film 68. That is, in the method for producing the lithium negative electrode composite of Example 1, a release layer is interposed between the film 68 and the rolled lithium foil 65. Therefore, the strong adhesion between the film 68 and the rolled lithium foil 65 in the pressing process is further suppressed, and further, damage to the lithium layer 66 can be suppressed even when the film 68 is peeled off after the pressing process.

In the method for producing a lithium negative electrode composite of Example 1, a lithium foil rolling step was performed by film rolling in which a film 68 having a silicone layer was interposed between a roll (not shown) and a lithium raw foil. As a result, the crimping of the lithium raw foil to the roll shown in the drawing during rolling is suppressed, so that a metal roll having high molding accuracy can be used as the roll for the lithium foil rolling process. Then, by using the metal roll, it becomes possible to obtain a rolled lithium foil 65 having high dimensional accuracy. Therefore, according to the method for producing a lithium negative electrode composite of Example 1, the amount of lithium as intended is obtained. It can be said that a lithium negative electrode composite in which is laminated can be produced. Furthermore, according to the method for producing a lithium-doped negative electrode of Example 1 including the method for producing a lithium negative electrode composite of Example 1, it can be said that a lithium-doped negative electrode to which a target amount of lithium is doped can be produced.

Further, in the lithium foil rolling step, by rolling and winding the rolled lithium foil 65 together with the film 68, the rolled lithium foil 65 can be reinforced by the film 68, and the tension in the transport direction acting during rolling and winding can be resisted. , It is possible to obtain a rolled lithium foil 65 in which damage is suppressed. The rolled lithium foil 65 is wound around the first unwinding roll 41a and the second unwinding roll 42a together with the film 68, and is used in the pressing process. Therefore, even when unwinding from the first unwinding roll 41a and the second unwinding roll 42a, the rolled lithium foil 65 is reinforced by the film 68, so that the rolled lithium foil 65 is suppressed from being damaged.

Hereinafter, a method for producing a lithium-doped negative electrode of Example 1 using the lithium negative electrode complex 95 of Example 1 obtained by the method for producing a lithium negative electrode composite of Example 1 will be described.
The method for producing a lithium-doped negative electrode of Example 1 includes a doping step.

(Dope process)
Lithium was doped by bringing the film negative electrode laminate 94 after the above pressing step into contact with the electrolytic solution without peeling off the film 68. _{As the electrolytic solution, a solution obtained by dissolving LiPF 6} at a concentration of 1 M in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 was used. As shown in FIG. 5, when the lithium contained in the lithium layer 66 of the film negative electrode laminate 94 is rapidly doped into the first negative electrode active material layer 92 and the second negative electrode active material layer 93 in the presence of the electrolytic solution. As a result, the lithium layer 66 of the film negative electrode laminate 94 is considered to disappear. If the lithium layer 66, which may be deformed or damaged when peeled from the film 68, disappears, the step of peeling the film 68 is easy. Therefore, the lithium negative electrode composite 95 is brought into contact with the electrolytic solution and doped in the presence of the film 68. By performing the above, a lithium-doped negative electrode 99 having excellent quality can be easily manufactured. The lithium-doped negative electrode 99 after the doping step was one in which distortion and warpage were suppressed.

According to the method for producing the lithium negative electrode composite of Example 1, the first negative electrode active material layer 92 and the second negative electrode active material layer 93 are provided on both sides of the negative electrode current collector 91, respectively, and the first negative electrode active material layer 92 is provided. A lithium layer 66 was formed on each of the second negative electrode active material layer 93 and the second negative electrode active material layer 93 to form a lithium negative electrode composite 95. By arranging the negative electrode active material layers 92 and 93 and the lithium layer 66 in this way, it is possible to obtain a lithium-doped negative electrode 99 in which distortion and warpage are suppressed even when the lithium negative electrode composite 95 is subjected to the doping step. can.

Hereinafter, the effects of the method for producing a lithium negative electrode composite, the method for producing a lithium-doped negative electrode, and the method for producing a battery of the present invention will be examined by giving a test example.

(Test Example 1)
Using the roll press apparatus shown in FIG. 6, the lithium raw foil 64 was rolled under various conditions with different loads, and the shape and transport state of the lithium foil before and after rolling were measured. During rolling, a sufficient amount of hexane was applied to both surfaces of the lithium raw foil 64. As the two rolls 28 and 29 of the roll press device, those having a silicone layer integrally were used.

Specifically, as a raw material for the silicone layer, KR216 (manufactured by Shin-Etsu Chemical Co., Ltd.), which is a silicone resin, was used. The raw materials were each applied on a stainless steel roll base material with a spray gun and held at room temperature for 24 hours to cure the silicone layer. Then, the surface roughness of the silicone layer was measured, and if necessary, the surface of the silicone layer was polished with sandpaper so that the surface roughness Ra was about 1.0 μm.
The lithium raw foil 64 was rolled using the rolls 28 and 29 integrally having the silicone layer obtained as described above.

The load of the roll press device, that is, the load acting on the lithium raw foil 64 from the two rolls 28 and 29 was set to 0.5 tons, 1 ton, 2 tons, and 4 tons. As the lithium raw foil 64, one having a thickness t1 of 100 μm, a width w1 of 80 mm, and a density of 0.53 g / cm ³ was used. Further, as shown in FIG. 6, the transport speed of the lithium foil on the rear side of the two rolls 28 and 29 in the transport direction, that is, the transport speed s1 of the lithium raw foil 64 was measured. The transport speed s1 of the lithium raw foil 64 was set to 0.5 m / min. The base point speeds of the rolls 28 and 29 and the transfer speed of the lithium foil were adjusted so that a constant tension was generated in each of the rolled lithium foil 65.
The thickness t2, width w2 and density of the lithium foil rolled by the above method, that is, the rolled lithium foil 65 were measured. Further, the transport speed s2 of the rolled lithium foil 65, that is, the transport speed of the lithium foil on the front side of the two rolls 28 and 29 in the transport direction was measured. The results are shown in Table 1.

As shown in Table 1, the width and density of the lithium foil did not change before and after rolling. Instead, the transfer speed s2 of the lithium foil after rolling is higher than the transfer speed s1 of the lithium foil before rolling.

As described above, since the width and density of the lithium foil do not change before and after rolling, the amount of lithium present in the rolled lithium foil 65 is the length of the rolled lithium foil 65 in the rolling direction and the thickness of the rolled lithium foil 65. It can be grasped almost accurately based on it. Therefore, if the thickness and length of the rolled lithium foil 65 are measured and the rolled lithium foil 65 is shaped so as to contain the desired amount of lithium, that is, the amount corresponding to the irreversible capacity, the desired amount of lithium is obtained. Can be doped into the negative electrode active material layer.

(Test Example 2)
When the lithium negative electrode complex of Example 1 was brought into contact with the electrolytic solution, when it was left as it was without being brought into contact with the electrolytic solution, and when it was brought into contact with an organic solvent containing no electrolyte, respectively. The degree of lithium doping was evaluated. As the electrolytic solution, the same electrolytic solution used in the above doping step was used. The organic solvent used for this electrolytic solution was used as the organic solvent.
The lithium negative electrode composite left as it was without contacting the electrolytic solution was designated as Test Example 2-1 and the lithium negative electrode composite contacted with the electrolytic solution was designated as Test Example 2-2, and the lithium negative electrode composite contacted with an organic solvent was designated as Test Example 2-1. As Test Example 2-3, the change over time in the thickness of the lithium layer was measured for each lithium negative electrode composite. Since the lithium negative electrode complex after the test is lithium-doped, it can be said to be a lithium-doped negative electrode.
The results of Test Example 2-1 and Test Example 2-2 are shown in Table 2.

As shown in Table 2, in the lithium negative electrode complex of Test Example 2-1 left in contact with the electrolytic solution, the rate of decrease of the lithium layer was very slow, and the lithium layer gradually disappeared 48 hours after the start of the test. .. On the other hand, in the lithium negative electrode composite of Test Example 2-2 which was brought into contact with the electrolytic solution, the rate of decrease of the lithium layer was very fast, and the lithium layer disappeared 3 hours after the start of the test. Since the lost lithium layer is considered to have been doped into the negative electrode active material layer, it can be said from this result that the lithium doping proceeds rapidly in the presence of the electrolytic solution. In addition, it can be said that lithium doping proceeds very slowly even in the absence of the electrolytic solution.

On the other hand, in the lithium negative electrode complex of Test Example 2-3, the lithium layer was gradually formed 48 hours after the start of the test, as in the case of the lithium negative electrode complex of Test Example 2-1 which was left without contacting the electrolytic solution. It disappeared. This result suggests that lithium doping proceeds via lithium ions in the electrolytic solution.

The layer thickness of the lithium negative electrode complex was measured before and after lithium doping. As a result, in both the lithium negative electrode composites of Test Example 2-1 and Test Example 2-2, the thickness of the negative electrode active material layer was 70 μm and the thickness of the lithium layer was 20 μm at an elapsed time of 0 hours, and the lithium negative electrode was used. The thickness of the composite layer, that is, the total thickness of the negative electrode active material layer and the lithium layer was 90 μm. On the other hand, the thickness of the lithium negative electrode composite layer when the thickness of the lithium layer is 0 μm, that is, the thickness of the negative electrode active material layer is 88 μm in the lithium negative electrode composite of Test Example 2-1. The lithium negative electrode composite of Test Example 2-2 was 80 μm.

In the lithium negative electrode complex of Test Example 2-2 in which lithium doping was performed while in contact with the electrolytic solution, it can be said that the thickness of the layer of the lithium negative electrode complex after doping was significantly reduced as compared with that before doping. Further, in the lithium negative electrode composite of Test Example 2-2 in which lithium doping was performed without contacting with the electrolytic solution, it can be said that the thickness of the layer of the lithium negative electrode composite after doping was substantially the same as that before doping. When lithium doping is performed while the lithium negative electrode composite is in contact with the electrolytic solution, lithium is dispersed and doped over the entire porous negative electrode active material layer, and the negative electrode active material expands due to the lithium doping, but the expansion It is presumed that the increased volume of the negative electrode active material was canceled by the volume of the pores in the negative electrode active material layer. Further, when lithium doping was performed without contacting the electrolytic solution, a large amount of lithium was doped in the surface layer portion of the negative electrode active material layer, so that the volume of the negative electrode active material layer increased by the lithium doping was difficult to cancel. Guess. That is, from this result, when lithium doping is performed while the lithium negative electrode composite is in contact with the electrolytic solution, the negative electrode active material layer is compared with the case where lithium doping is performed without contacting the lithium negative electrode composite with the electrolytic solution. It is presumed that the lithium doping to is uniformly performed.

(Test Example 3)
The effects of the release layer and the lubricant during rolling with a roll press were evaluated. Specifically, the thickness of the rolled lithium foil that is not deformed or damaged by rolling the lithium raw foil as it is or sandwiching it between resin films while changing the gap between the two rolls and the load of the two rolls in various ways. The limit value of was measured. The effect of the release layer and / or the lubricant was evaluated by performing the measurement in the presence or absence of the release layer and / or the lubricant.

(Test Example 3-1)
In Test Example 3-1, a 100 μm-thick lithium raw foil was sandwiched between films having a release layer, and hexane as a lubricant was interposed between the release layer of the film and the lithium raw foil to laminate film lithium. Constructed the body. As the roll, one made of stainless steel was used. The film lithium laminate was rolled, and the thickness of the rolled lithium foil obtained was 10 μm. The results of Test Example 3-1 are shown in Table 3 together with the results of Test Examples 3-2-3-10 described later.
As the film, a film having a thickness of 25 μm manufactured by Lintec Corporation was used in the same manner as in the lithium foil rolling step of Example 1 described above. The film contains a silicone adhesive in the release layer.

(Test Example 3-2)
In Test Example 3-2, the lithium foil was rolled in the same manner as in Test Example 3-1 except that the lithium raw foil was rolled using a roll provided with a release layer without using a film. As the two rolls, the same rolls as those used in Test Example 1 having a silicone layer containing a silicone resin were used.
The thickness of the rolled lithium foil measured in Test Example 3-2 was 10 μm.

(Test Example 3-3)
In Test Example 3-3, a film having no release layer and composed only of a resin film was used, a lubricant was present only between one film and the lithium raw foil, and the other film was a lithium raw film. It was brought into direct contact with the foil. Other than that, the lithium foil was rolled in the same manner as in Test Example 3-1. The thickness of the rolled lithium foil measured in Test Example 3-3 was 80 μm.

(Test Example 3-4)
In Test Example 3-4, the lithium foil was rolled in the same manner as in Test Example 3-1 except that a film composed of only a resin film without a release layer was used.
The thickness of the rolled lithium foil measured in Test Example 3-4 was 30 μm.

(Test Example 3-5)
In Test Example 3-5, the lithium foil was rolled in the same manner as in Test Example 3-2, except that a roll made of high-density polyethylene having no release layer was used as the roll.
The thickness of the rolled lithium foil measured in Test Example 3-5 was 50 μm.

(Test Example 3-6)
In Test Example 3-6, the lithium foil was rolled in the same manner as in Test Example 3-2, except that a roll made of polyacetal having no release layer was used as the roll.
The thickness of the rolled lithium foil measured in Test Example 3-6 was 30 μm.

(Test Example 3-7)
In Test Example 3-7, the same method as in Test Example 3-2 was used except that a roll made of FRP (fiber reinforced plastic) composed of an epoxy resin having no release layer and glass fiber was used as the roll. The lithium foil was rolled.
The thickness of the rolled lithium foil measured in Test Example 3-7 was 90 μm.

(Test Example 3-8)
In Test Example 3-8, the lithium foil was rolled in the same manner as in Test Example 3-2, except that a roll made of polyetheretherketone resin having no release layer was used as the roll.
The thickness of the rolled lithium foil measured in Test Example 3-8 was 90 μm.

(Test Example 3-9)
In Test Example 3-9, the lithium foil was rolled in the same manner as in Test Example 3-2, except that a stainless steel roll having no release layer was used as the roll.
The thickness of the rolled lithium foil measured in Test Example 3-9 was 90 μm.

(Test Example 3-10)
In Test Example 3-10, the lithium foil was rolled in the same manner as in Test Example 3-2, except that a roll having a DLC (diamond-like carbon) layer was used as the release layer.
The thickness of the rolled lithium foil measured in Test Example 3-10 was 80 μm.

As shown in Table 3, in Test Example 3-1 in which a silicone layer as a release layer was interposed between the roll and the lithium foil and rolled, only a resin film was interposed between the roll and the lithium foil. A thinner rolled lithium foil could be obtained as compared with Test Example 3-4 in which the release layer was not interposed. Further, in Test Example 3-2 in which a silicone layer as a peeling layer was provided on the surface of the roll and the silicone layer was interposed between the roll and the lithium foil and rolled, a roll without the peeling layer was used, and the roll and lithium were used. A rolled lithium foil that was significantly thinner than that of Test Example 3-9 in which no release layer was interposed between the foil and the foil could be obtained. From this result, it can be seen that the lithium foil can be rolled while suppressing the strong adhesion between the lithium foil and the roll by interposing a silicone layer as a release layer between the roll and the lithium foil. Further, also in the production of the lithium negative electrode composite of the present invention in which the negative electrode laminate having the lithium foil is pressed to produce the lithium negative electrode composite, the lithium layer is formed by interposing the silicone layer between the roll and the lithium foil. It can be said that a good lithium negative electrode composite without damage can be produced.

Further, in Test Example 3-2 in which rolling was performed with a roll integrally provided with a silicone layer, Test Example 3-5 to Test Example 3-8 in which rolling was performed with a roll composed of various resin materials, and a DLC layer. It can be said that a very thin rolled lithium foil can be obtained as compared with Test Example 3-10 in which the rolls are integrally provided. That is, it can be said that the silicone layer is very excellent as a release layer interposed between the roll and the lithium foil during rolling.

(Reference example)
A battery was manufactured using the negative electrode 90 before the pressing process, which was manufactured in the section (Manufacturing of the negative electrode) of Example 1. The counter electrode was a metallic lithium foil (thickness 500 μm), and the electrolytic solution was the same electrolytic solution used in the above-mentioned doping step.

The counter electrode was cut to φ13 mm and the lithium-doped negative electrode was cut to φ11 mm, and a separator (a glass filter manufactured by Hoechst Celanese and “Celgard 2400” manufactured by Celgard) was interposed between the two electrodes to form an electrode body. This electrode body was placed in a battery container (CR2032 type coin battery member, manufactured by Hosen Co., Ltd.). An electrolytic solution was injected into the battery container, and the battery container was sealed to manufacture a lithium ion secondary battery as a reference example.

The lithium ion secondary battery of the reference example was charged and discharged at a constant current of 0.2 mA. As a result, the initial discharge capacity was 1200 mAh / g, the initial charge capacity was 803 mAh / g, and the initial efficiency calculated by (initial charge capacity / initial discharge capacity) × 100 was 66.9%. From this result, it is demonstrated that the irreversible capacitance is large in the Si-containing negative electrode which is not subjected to lithium doping.

(Example 2)
FIG. 7 shows an explanatory diagram schematically showing the method for producing the lithium negative electrode composite of Example 2.
The roll press apparatus used in the method for manufacturing the lithium negative electrode composite of Example 2 has a fifth auxiliary roll and a sixth auxiliary roll in the transport section, and a third take-up roll and a fourth take-up roll in the lithium foil supply section. Except for having a roll, it is substantially the same as the roll press apparatus used in the method for producing a lithium negative electrode composite of Example 1.
Further, the method for producing the lithium negative electrode composite of Example 2 is carried out except that the film is peeled off from the film negative electrode laminate after the pressing process and before winding, and the lithium negative electrode composite is wound on the negative electrode winding roll. It is substantially the same as the method for producing the lithium negative electrode composite of Example 1.
Hereinafter, the roll press apparatus of Example 2 and the method for producing the lithium negative electrode composite will be described focusing on the differences from Example 1.

As shown in FIG. 7, the roll press device 1 of the second embodiment has a fifth auxiliary roll 37 and a sixth auxiliary roll 38 in the transport unit 3, and a third take-up roll 43 and a third winding roll 43 in the lithium foil supply unit 4. It has 4 take-up rolls 44.
The fifth auxiliary roll 37 and the third take-up roll 43 are arranged on the upper side of the film negative electrode laminate 94 on the front side of the first roll 21 and on the rear side of the negative electrode take-up roll 32. The sixth auxiliary roll 38 and the fourth take-up roll 44 are arranged on the front side of the second roll 22 and on the rear side of the negative electrode take-up roll 32, and on the lower side of the film negative electrode laminate 94. The third take-up roll 43 and the fourth take-up roll 44 are connected to the foil unwinding drive unit (not shown), and the first take-up roll 41a, the first take-up roll 41b, the second take-up roll 42a, and the second take-up roll 42a are connected. It rotates in synchronization with the take-up roll 42b. The third take-up roll 43 rotates counterclockwise in FIG. 7, and the fourth take-up roll 44 rotates clockwise in FIG. 7.

The first film lithium laminate 61 wound around the first unwinding roll 41a is composed of rolled lithium foil 65a, films 68a and 68b. One of the films 68a is peeled off from the rolled lithium foil 65a before the rolled lithium foil 65a is overlaid on the negative electrode 90 and pressed, that is, after the roll press portion 2, and the first take-up roll 41b. It is rolled up. The other film 68b is laminated on the upper surface of the negative electrode 90 together with the rolled lithium foil 65a and pressed by the roll press unit 2 to form the film negative electrode laminate 94 together with the rolled lithium foil 65a and the negative electrode 90.
Similarly, one of the rolled lithium foil 65b, the films 68c and 68d constituting the second film lithium laminate 62, the film 68c, is peeled off from the rolled lithium foil 65b and wound on the second take-up roll 42b. The other film 68d constitutes the film negative electrode laminate 94 together with the film 68b, the negative electrode 90, and the two rolled lithium foils 65a and 65b.

Since the films 68b and 68d contained in the film negative electrode laminate 94 are unnecessary for the lithium ion secondary battery, they need to be peeled off from the film negative electrode laminate 94 at any stage. In Example 2, the films 68b and 68d were peeled off from the film negative electrode laminate 94 after the pressing process by the roll press unit 2 and before winding by the negative electrode winding roll 32. Specifically, the film 68b was wound on the third winding roll 43 via the fifth auxiliary roll 37. Further, the film 68d was wound on the fourth winding roll 44 via the sixth auxiliary roll 38. The film negative electrode laminate 94 from which the films 68b and 68d were peeled off, that is, the lithium negative electrode composite 95, was wound on the negative electrode take-up roll 32.

In the method for producing the lithium negative electrode composite of Example 2, the lithium negative electrode composite 95 from which the films 68b and 68d were peeled off was wound around the negative electrode winding roll 32. Since the rolled lithium foils 65a and 65b in the lithium negative electrode composite 95 are superposed on the negative electrode current collector 91 made of copper foil, they have relatively high strength and are not easily deformed. Therefore, the lithium negative electrode composite 95 can be wound around the negative electrode winding roll 32 without damage without reinforcing the films 68b and 68d. Similarly, when the lithium negative electrode composite 95 is used, that is, when the lithium negative electrode composite 95 is unwound from the negative electrode take-up roll 32 during the doping process or during the manufacture of the lithium ion secondary battery, the current collector for the negative electrode is also used. The lithium negative electrode composite 95 reinforced by 91 is not easily damaged.

1: Roll press device 2: Roll press unit 3: Conveyance unit 4: Lithium foil supply unit 21: First roll 22: Second roll 31: Negative electrode unwinding roll 32: Negative electrode winding roll 33: First auxiliary roll 34: 2nd auxiliary roll 35: 3rd auxiliary roll 36: 4th auxiliary roll 37: 5th auxiliary roll 38: 5th auxiliary roll 41: 1st foil unwinding portion 41a: 1st unwinding roll 41b: 1st winding roll 42: 2nd foil unwinding portion 42a: 2nd unwinding roll 42b: 2nd winding roll 43: 3rd winding roll 44: 4th winding roll 61: 1st film lithium laminate 61a: 1st film lithium Laminated body 62: Second film lithium laminated body 62a: Second film lithium laminated body 64: Lithium raw foil 65, 65a, 65b: Rolled lithium foil 66: Lithium layer 68, 68a, 68b, 68c, 68d: Film 90: Negative electrode 91: Current collector for negative electrode 92: First negative electrode active material layer 93: Second negative electrode active material layer 94: Film negative electrode laminate 95: Lithium negative electrode composite 98: Lubricant

Claims (13)

A method for producing a positive electrode body having a current collector and a positive electrode active material layer, a lithium negative electrode composite, and a lithium ion secondary battery having an electrolytic solution.
The lithium foil rolling process of rolling lithium foil to obtain rolled lithium foil,
Collector to form a Si-containing negative electrode active material layer on both sides of, and forms the shape of the lithium layer simultaneously by laminating the rolled lithium foil on each of the anode active material layer, and the lithium layer and the negative electrode To obtain the lithium negative electrode composite having the above .
A method for producing a lithium ion secondary battery, wherein the width of the lithium foil is equal to or less than the width of the negative electrode active material layer and equal to or larger than the width of the positive electrode active material layer facing the lithium foil. The method for manufacturing a lithium ion secondary battery according to claim 1, wherein the difference between the width of the lithium foil and the width of the negative electrode active material layer is within 5 mm. The method for manufacturing a lithium ion secondary battery according to claim 2, wherein the difference between the width of the lithium foil and the width of the negative electrode active material layer is within 1 mm. The method for manufacturing a lithium ion secondary battery according to any one of claims 1 to 3, wherein the difference between the width of the lithium foil and the width of the positive electrode active material layer is within 5 mm. Assuming that the amount of lithium in the lithium foil per unit area is (A) and the amount of lithium that can cancel the irreversible capacity of the negative electrode active material layer per unit area is (B), 0.8 <(A) / (B). ) The method for manufacturing a lithium ion secondary battery according to any one of claims 1 to 4 , which satisfies <1.2. The complex forming step is
A negative electrode forming step of forming the negative electrode active material layer on both sides of the current collector to form a negative electrode.
It has a pressing step of laminating the rolled lithium foil on each of the negative electrode active material layers and pressing between the two rolls to obtain a lithium negative electrode composite having the negative electrode and the two lithium layers. The method for manufacturing a lithium ion secondary battery according to any one of claims 1 to 5 . In the pressing process
The method for manufacturing a lithium ion secondary battery according to claim 6 , wherein the rolled lithium foil is pressed in a state where films are stacked. The lithium ion secondary battery according to claim 7 , wherein the film is composed of a resin film and a release layer laminated on the resin film, and the release layer is directed toward the lithium foil and laminated on the lithium foil. Manufacturing method . The lithium ion secondary according to any one of claims 1 to 8 , further comprising a doping step of contacting the lithium negative electrode composite with an electrolytic solution containing an organic solvent and a lithium salt to obtain a lithium-doped negative electrode. Battery manufacturing method . The lithium ion II according to claim 7 or 8 , further comprising a doping step of contacting the lithium negative electrode composite with an electrolytic solution containing an organic solvent and a lithium salt while the films are stacked to obtain a lithium-doped negative electrode. How to manufacture the next battery . The invention according to any one of claims 1 to 8, further comprising a step of injecting an electrolytic solution into a battery container containing the lithium negative electrode composite and a positive electrode body having a current collector and a positive electrode active material layer. The method for manufacturing a lithium ion secondary battery according to the above. The lithium ion secondary according to claim 9 or 10 , further comprising a step of injecting an electrolytic solution into a battery container containing the lithium-doped negative electrode and a positive electrode body having a current collector and a positive electrode active material layer. Battery manufacturing method. Assuming that the amount of lithium that can be accepted by the negative electrode is (C) and the amount of lithium that can be emitted by the positive electrode is (D), the relationship of 1.05 <C / (D + lithium amount of lithium foil) <1.5 is satisfied. The method for manufacturing a lithium ion secondary battery according to any one of claims 1 to 12.

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