JP2010033918A - Manufacturing method of lithium battery, and lithium battery obtained by the same - Google Patents

Abstract

A method of manufacturing a lithium battery having an electrode adjusted to a desired thickness and having excellent production efficiency is provided.
An active material slurry is prepared by dispersing an active material in a solvent containing a lithium ion conductive binder, and a sulfide-based solid electrolyte is dispersed in the solvent containing the binder to form a solid. A step of preparing an electrolyte slurry, and a step of dropping each of the slurry onto a substrate having a side guard, adjusting the slurry thickness with a blade, and further forming an active material sheet and a solid electrolyte sheet by heating and drying and peeling. Cutting the side guard side portions of the active material sheet and the solid electrolyte sheet, sandwiching the cut solid electrolyte sheet between the two cut active material sheets, and forming a laminate, A step of sandwiching the laminate with two current collector sheets to form a laminate, and vacuum hot pressing at a temperature equal to or higher than the melting point of the lithium ion conductive binder Step method for producing a lithium battery including.
[Selection] Figure 1

Description

  The present invention relates to a method for producing a lithium battery and a lithium battery obtained therefrom.

  Conventionally, most electrolytes exhibiting high lithium ion conductivity at room temperature are liquids, and many of the commercially available lithium ion secondary batteries use organic electrolytes. However, since the electrolyte of a lithium ion secondary battery using an organic electrolyte is a liquid, there is a risk of leakage and ignition of the electrolyte, and an all-solid battery with higher safety has been desired. However, the ionic conductivity of solid electrolytes is generally low and it is difficult to put it to practical use.

Lithium ion conductive ceramics based on Li ₃ N are known as solid electrolytes exhibiting high ion conductivity of 10 ⁻³ Scm ⁻¹ at room temperature. However, since the decomposition voltage is low, a battery that operates at 3 V or more cannot be constructed.

The lithium-ion conducting ceramic of addition, Patent Document 1 discloses a ^1E -4 S / cm base of the sulfide-based solid electrolyte, Patent Document 2 is synthesized from Li ₂ S and _P 2 _{S 5,} 1E ^- A sulfide-based solid electrolyte exhibiting ion conductivity on the order of ⁴ S / cm is disclosed.

Patent Document 3 discloses a sulfide crystal in which ionic conductivity on the order of 1E ⁻³ S / cm is achieved by synthesizing Li ₂ S and P ₂ S ₅ in a ratio of 68 to 74 mol%: 26 to 32 mol%. Disclosed is a glass.
However, although it is the solid electrolyte of patent document 3 which is excellent in ion conductivity, when manufacturing a battery using this, the method of maintaining an interface with each electrode is difficult, and it has not necessarily resulted in obtaining sufficient performance. .

Regarding Li ₂ S, which is a raw material for the above-described sulfide-based solid electrolyte, Patent Document 4 discloses a method for synthesizing Li ₂ S from lithium hydroxide and hydrogen sulfide.

As a method of forming a battery using a sulfide-based solid electrolyte, Patent Document 5 laminates a composite powder composed of positive and negative electrode active materials and a solid electrolyte on a current collector, and sandwiches the solid electrolyte between these composite materials. A method is disclosed in which the laminated body is subjected to pressure molding at a pressure of about 5 to 1000 MPa.
However, although the manufacturing method of Patent Document 5 can be applied to a battery having an area of about 1 cm ² , it is difficult to use for a battery having a large area (100 cm ² or more).

Patent Document 6 discloses a method of preparing a battery by preparing a slurry using a positive electrode mixture, a negative electrode mixture, and a solid electrolyte, forming a multilayer film by coating formation, and then pressurizing. In addition to the above, Patent Document 7 and Non-Patent Document 1 also disclose a method of press molding after applying a solid electrolyte slurry.
However, the manufacturing method disclosed in Patent Document 6 has many problems such as the solid electrolyte re-dissolved in the solvent at the time of slurry formation, and the film thickness fluctuates due to a change in viscosity due to the slurry concentration.

  In the case of using an oxide solid electrolyte, Patent Document 8 applies each of the conventionally known methods for preparing ceramic green sheets to produce each active material green sheet and solid electrolyte green sheet. A method of forming a battery by removing the binder resin by firing the laminate at a temperature of 700 ° C. or higher is disclosed.

However, in the production method of Patent Document 8, there are many problems such as generation of cracks due to shrinkage ratio during firing, generation of distortion due to non-uniformity of heat conduction, and the yield is extremely low. In addition to these problems, when the method of Patent Document 8 is applied to a sulfide-based solid electrolyte, decomposition at a temperature of 700 ° C. or higher causes the decomposition reaction of the solid electrolyte to progress, and the high ion expected to progress through the oxidation reaction A conductive battery could not be formed.
JP-A-4-202024 JP 2002-109955 A JP 2005-228570 A Japanese Patent Laid-Open No. 7-330312 JP 2000-106154 A JP 2008-121401 A JP-A-4-133209 JP 2007-227362 A New Energy Industry Technology Development Organization 2001 Results Report

  An object of this invention is to provide the manufacturing method of the lithium battery which can adjust the thickness of the sheet | seat which comprises a lithium battery to desired thickness, and has the outstanding production efficiency.

According to the present invention, the following lithium battery manufacturing method and the like are provided.
1. A method for manufacturing a lithium battery including a solid electrolyte layer, an active material layer, and a current collector layer, the method including the following steps:
A step of dispersing an active material in a solvent containing a lithium ion conductive binder to prepare an active material slurry;
A step of preparing a solid electrolyte slurry by dispersing a sulfide-based solid electrolyte in a solvent containing a lithium ion conductive binder;
The step of forming the active material sheet and the solid electrolyte sheet by dropping the active material slurry and the solid electrolyte slurry onto a substrate having side guards respectively, adjusting the slurry thickness with a blade, and further drying by heating and peeling. When,
Cutting the side guard side portions of the active material sheet and the solid electrolyte sheet;
The solid electrolyte sheet with the side guard side portion cut is sandwiched between two active material sheets with the side guard side portion cut, and two more active material sheets with the two side guard side portions cut are further sandwiched. A step of forming a laminate by sandwiching it with a current collector sheet, and a step of vacuum hot pressing the laminate at a temperature equal to or higher than the melting point of the lithium ion conductive binder.
2. 2. The method for producing a lithium battery according to 1, wherein the sulfide-based solid electrolyte is obtained from lithium sulfide, one or more sulfides selected from the group consisting of phosphorus sulfide, silicon sulfide, and germanium sulfide.
3. 3. The method for producing a lithium battery according to 1 or 2, wherein the lithium ion conductive binder is polyethylene glycol or polymethyl methacrylate.
4). The manufacturing method of the lithium battery in any one of 1-3 in which the board | substrate which has the said side guard consists of a metal which has a softness | flexibility, and the surface is coated with the fluorine.
5). The manufacturing method of the lithium battery in any one of 1-4 in which the said electrical power collector sheet | seat consists of 1 or more metals selected from the group which consists of Al, Ti, and SUS.
6). The method for producing a lithium battery according to any one of 1 to 5, wherein the vacuum hot pressing is performed at a temperature equal to or higher than a melting point of the lithium ion conductive polymer and at a pressure of 1 MPa to 1000 MPa.
A lithium battery pack obtained by further laminating a lithium battery obtained by the method for producing a lithium battery according to any one of 7.1 to 6.
The apparatus provided with the lithium battery obtained from the manufacturing method of the lithium battery in any one of 8.1-6.

  ADVANTAGE OF THE INVENTION According to this invention, the thickness of the sheet | seat which comprises a lithium battery can be adjusted to desired thickness, and the manufacturing method of the lithium battery which has the outstanding production efficiency can be provided.

  The method for producing a lithium battery of the present invention is a method for producing a lithium battery comprising a solid electrolyte layer, an active material layer and a current collector layer, wherein the active material is dispersed in a solvent containing a lithium ion conductive binder. A step of preparing a material slurry (hereinafter sometimes referred to as a first step); a step of preparing a solid electrolyte slurry by dispersing a sulfide-based solid electrolyte in a solvent containing a lithium ion conductive binder (hereinafter referred to as a first step). The active material slurry and the solid electrolyte slurry are each dropped onto a substrate having a side guard, the thickness of the slurry is adjusted with a blade, and the active material sheet and A step of forming each of the solid electrolyte sheets (hereinafter sometimes referred to as a third step); a side material of the active material sheet and the solid electrolyte sheet; A step of cutting the side surface portion (hereinafter sometimes referred to as a fourth step); sandwiching the solid electrolyte sheet from which the side guard side surface portion has been cut between two active material sheets from which the side guard side surface portion has been cut; A step of forming a laminated body by sandwiching an active material sheet obtained by cutting two side guard side portions between two current collector sheets (hereinafter also referred to as a fifth step); A step of vacuum hot pressing at a temperature equal to or higher than the melting point of the lithium ion conductive binder (hereinafter sometimes referred to as a sixth step).

[First step]
In the first step, an active material slurry is prepared by dispersing an active material in a solvent containing a lithium ion conductive binder.
As the lithium ion conductive binder used for the preparation of the active material slurry, polyethylene glycol or polymethyl methacrylate is preferably used. Moreover, you may add lithium salts, such as LiPF ₆ , as needed.

  As a solvent for the lithium ion conductive binder, alcohols such as ethanol, n-butyl acetate, ethyl acetate, toluene and the like can be used, and preferably toluene.

  The content of the lithium ion conductive binder in the solvent containing the lithium ion conductive binder is about 1 wt% to 30 wt%, more preferably 1 wt% to 20 wt%.

When preparing the positive electrode active material slurry, a commercially available positive electrode active material can be used without particular limitation, and a composite oxide of lithium and transition metal can be suitably used. Specifically, the following materials and similar materials having different composition ratios of the respective elements can be used, and LiCoO ₂ , LiNiCoO ₂ , LiNiO ₂ , LiNiMnCoO ₂ , LiFeMnO ₂ , Li ₂ PtO ₃ , LiMnNiO ₄ , LiMn ₂ Examples include O ₄ , LiNiMnO ₂ , LiNiVO ₄ , LiCrMnO ₄ , LiFePO ₄ , LiFe (SO ₄ ) ₃ , LiCoVO ₄ , LiCoPO ₄ , S, and the like. Although there is no restriction | limiting in particular regarding a particle size, The thing with an average particle diameter of several micrometers-10 micrometers can be used suitably.

Moreover, when preparing a negative electrode active material slurry, as a negative electrode active material to be used, what is marketed can be used without particular limitation, and a carbon material, Sn metal, In metal, etc. can be used conveniently. Specifically, natural graphite, various graphites, metal powders such as Sn, Si, Al, Sb, Zn, and Bi, metals such as Sn ₅ Cu ₆ , Sn ₂ Co, Sn ₂ Fe, Ti—Sn, and Ti—Si Examples include alloy powder, oxide (Li4 / 3Ti5 / 3O), nitride (LiCoN), and other amorphous alloys and plating alloys. Although there is no restriction | limiting in particular regarding a particle size, A thing with an average particle diameter of several micrometers-80 micrometers can be used suitably.

In the active material slurry of the present invention, the active material is preferably dispersed in a solvent containing a lithium ion conductive binder, and a sulfide-based solid electrolyte is further added (electrode mixture slurry). The sulfide solid electrolyte used will be described later.
The addition amount of the sulfide-based solid electrolyte varies depending on the active material to be used, but is preferably in the range of 50:50 to 80:20 (weight ratio) of the active material: sulfide-based solid electrolyte.

[Second step]
In the second step, a solid electrolyte slurry is prepared by dispersing a sulfide-based solid electrolyte in a solvent containing a lithium ion conductive binder.
The lithium ion conductive binder and solvent used are the same as in the first step.

  The sulfide-based solid electrolyte used for the preparation of the solid electrolyte slurry is not particularly limited, and a known sulfide-based solid electrolyte can be used, preferably one or more selected from the group consisting of phosphorus sulfide, silicon sulfide, and germanium sulfide. This is a sulfide-based solid electrolyte obtained from sulfides and lithium sulfide.

  Since lithium ion conductivity is high, lithium sulfide and diphosphorus pentasulfide, or lithium sulfide and simple phosphorus and simple sulfur, as well as sulfides generated from lithium sulfide, diphosphorus pentasulfide, simple phosphorus and / or simple sulfur More preferably, a solid electrolyte is used. Hereinafter, preferred sulfide-based solid electrolytes will be described.

The sulfide-based solid electrolyte can be produced from lithium sulfide and diphosphorus pentasulfide (P ₂ S ₅ ) and / or simple phosphorus and simple sulfur. Specifically, it can be produced by melting these raw materials and then rapidly cooling them. In addition, sulfide glass obtained by treating these raw materials by a mechanical milling method (hereinafter, sometimes referred to as MM method), or a heat-treated product thereof.

As lithium sulfide, those commercially available without limitation can be used, but those having high purity are preferable as described below.
Lithium sulfide has at least a total content of lithium salt of sulfur oxide of 0.15% by mass or less, preferably 0.1% by mass or less, and a content of lithium N-methylaminobutyrate of 0.15% by mass. Hereinafter, it is preferably 0.1% by mass or less. When the total content of the lithium salt of sulfur oxide is 0.15% by mass or less, the solid electrolyte obtained by the melt quenching method or the mechanical milling method described later is a glassy electrolyte (fully amorphous). That is, when the total content of the lithium salt of sulfur oxide exceeds 0.15% by mass, the obtained electrolyte is a crystallized product from the beginning, and the ionic conductivity of this crystallized product is low. Furthermore, even if the crystallized product is subjected to the following heat treatment, the crystallized product is not changed, and a sulfide-based solid electrolyte having high ion conductivity cannot be obtained.

  Further, when the content of lithium N-methylaminobutyrate is 0.15% by mass or less, a deteriorated product of lithium N-methylaminobutyrate does not deteriorate the cycle performance of the lithium battery.

  Thus, in order to obtain a high ion conductive electrolyte, it is necessary to use lithium sulfide with reduced impurities.

The method for producing lithium sulfide used for producing the high ion conductive electrolyte is not particularly limited as long as it is a method that can reduce at least the impurities.
For example, it can also be obtained by purifying lithium sulfide produced by the following method.
Among the following production methods, the method a or b is particularly preferable.
a. A method in which lithium hydroxide and hydrogen sulfide are reacted at 0 to 150 ° C. in an aprotic organic solvent to produce lithium hydrosulfide, and this reaction solution is then desulfurized at 150 to 200 ° C. -330312).
b. A method of directly producing lithium sulfide by reacting lithium hydroxide and hydrogen sulfide at 150 to 200 ° C. in an aprotic organic solvent (Japanese Patent Laid-Open No. 7-330312).
c. A method of reacting lithium hydroxide and a gaseous sulfur source at a temperature of 130 to 445 ° C. (Japanese Patent Laid-Open No. 9-283156).

  There is no restriction | limiting in particular as a purification method of the lithium sulfide obtained as mentioned above. As a preferable purification method, for example, the method described in International Publication No. WO2005 / 40039 and the like can be mentioned.

  Specifically, the lithium sulfide obtained as described above is washed at a temperature of 100 ° C. or higher using an organic solvent. The organic solvent used for washing is preferably an aprotic polar solvent, and more preferably, the aprotic organic solvent used for lithium sulfide production and the aprotic polar organic solvent used for washing are the same. .

  Examples of the aprotic polar organic solvent preferably used for washing include aprotic polar organic compounds such as amide compounds, lactam compounds, urea compounds, organic sulfur compounds, cyclic organophosphorus compounds, Or it can use suitably as a mixed solvent. In particular, N-methyl-2-pyrrolidone (NMP) is selected as a good solvent.

  The amount of the organic solvent used for washing is not particularly limited, and the number of times of washing is not particularly limited, but is preferably 2 or more. Cleaning is preferably performed under an inert gas such as nitrogen or argon.

  The washed lithium sulfide is dried at a temperature equal to or higher than the boiling point of the organic solvent used for washing for 5 minutes or more, preferably about 2 to 3 hours or more under an inert gas stream such as nitrogen under normal pressure or reduced pressure. Thus, lithium sulfide suitably used in the present invention can be obtained.

P ₂ S ₅ can be used without particular limitation as long as it is industrially manufactured and sold. In place of P ₂ S ₅ , elemental phosphorus (P) and elemental sulfur (S) in a corresponding molar ratio can also be used. Simple phosphorus (P) and simple sulfur (S) can be used without particular limitation as long as they are industrially produced and sold.

  In the present invention, as the solid electrolyte, both a glassy solid electrolyte and a solid electrolyte containing a crystal component can be used. The type should be selected according to the required characteristics. Both may be used.

The mixing molar ratio of the lithium sulfide to diphosphorus pentasulfide or simple phosphorus and simple sulfur is usually 50:50 to 80:20, preferably 60:40 to 75:25.
Particularly preferably, it is about Li ₂ S: P ₂ S ₅ = 68: 32 to 74:26 (molar ratio).

  Examples of the method for producing a sulfide glass that is a glassy electrolyte include a melt quenching method and a mechanical milling method.

In the case of the melt quenching method, a predetermined amount of P ₂ S ₅ and Li ₂ S are mixed in a mortar, and the pellets are placed in a carbon-coated quartz tube and sealed in a vacuum. After reacting at a predetermined reaction temperature, the glass is put into ice and quenched to obtain a sulfide glass.

  The reaction temperature at this time is preferably 400 ° C to 1000 ° C, more preferably 800 ° C to 900 ° C. Moreover, reaction time becomes like this. Preferably it is 0.1 to 12 hours, More preferably, it is 1 to 12 hours. The quenching temperature of the reaction product is usually 10 ° C. or lower, preferably 0 ° C. or lower, and the cooling rate is about 1 to 10,000 K / sec, preferably 1 to 1000 K / sec.

In the case of the MM method, sulfide glass is obtained by mixing a predetermined amount of P ₂ S ₅ and Li ₂ S in a mortar and reacting for a predetermined time by a mechanical milling method.

  The mechanical milling method using the above raw materials can be reacted at room temperature. According to the MM method, since a glassy electrolyte can be produced at room temperature, there is an advantage that a raw material is not thermally decomposed and a glassy electrolyte having a charged composition can be obtained. Further, the MM method has an advantage that the glassy electrolyte can be made into fine powder simultaneously with the production of the glassy electrolyte.

  Although various types of pulverization methods can be used for the MM method, it is particularly preferable to use a planetary ball mill. The planetary ball mill can efficiently generate very high impact energy by rotating the platform while the pot rotates.

  Although the rotation speed and rotation time of the MM method are not particularly limited, the faster the rotation speed, the faster the glassy electrolyte production rate, and the longer the rotation time, the higher the conversion rate of the raw material into the glassy electrolyte.

The electrolyte thus obtained is a glassy electrolyte and usually has an ionic conductivity of about 1.0 × 10 ^{−5 to} 8.0 × 10 ⁻⁴ (S / cm).

  As conditions for the MM method, for example, when a planetary ball mill is used, the rotational speed may be set to several tens to several hundreds of revolutions / minute, and the treatment may be performed for 0.5 hours to 100 hours.

  Although specific examples of the sulfide glass by the melt quenching method and the MM method have been described above, manufacturing conditions such as temperature conditions and processing time can be appropriately adjusted according to the equipment used.

  Thereafter, the obtained sulfide glass is heat-treated at a predetermined temperature to produce a solid electrolyte containing a crystal component.

  The heat treatment temperature for producing such a solid electrolyte is preferably 190 ° C to 340 ° C, more preferably 195 ° C to 335 ° C, and particularly preferably 200 ° C to 330 ° C. When the temperature is lower than 190 ° C., it may be difficult to obtain a crystal with high ion conductivity. When the temperature is higher than 340 ° C., a crystal with low ion conductivity may be generated.

  The heat treatment time is preferably 3 to 240 hours, particularly preferably 4 to 230 hours, when the temperature is 190 ° C or higher and 220 ° C or lower. When the temperature is higher than 220 ° C and not higher than 340 ° C, 0.1 to 240 hours are preferable, 0.2 to 235 hours are particularly preferable, and 0.3 to 230 hours are more preferable. If the heat treatment time is shorter than 0.1 hour, it may be difficult to obtain a crystal with high ion conductivity. If the heat treatment time is longer than 240 hours, a crystal with low ion conductivity may be formed.

The sulfide-based solid electrolyte containing the crystal component thus obtained usually has an ionic conductivity of about 7.0 × 10 ^{−4 to} 5.0 × 10 ⁻³ (S / cm). .

  This sulfide-based solid electrolyte has 2θ = 17.8 ± 0.3 deg, 18.2 ± 0.3 deg, 19.8 ± 0.3 deg, 21.X in X-ray diffraction (CuKα: λ = 1.5418４). It is preferable to have a diffraction peak at 8 ± 0.3 deg, 23.8 ± 0.3 deg, 25.9 ± 0.3 deg, 29.5 ± 0.3 deg, 30.0 ± 0.3 deg. A solid electrolyte having such a crystal structure has extremely high lithium ion conductivity.

  The addition amount of the sulfide-based solid electrolyte may be appropriately selected in consideration of the viscosity of the slurry, the film thickness after drying, etc., but is usually 5 wt% to 30 wt% with respect to the solvent containing the lithium ion conductive binder. Yes, preferably in the range of 10 wt% to 20 wt%.

[Third step]
In the third step, the active material slurry and the solid electrolyte slurry are respectively dropped onto a substrate having a side guard, the slurry thickness is adjusted with a blade, and the active material sheet and the solid electrolyte sheet are formed by drying and peeling, respectively. To do.

  FIG. 1 is a schematic diagram showing the third step. As shown in FIG. 1, slurry is dropped onto a substrate 20 supplied from a substrate supply roll 10 using a nozzle 30. The slurry on the substrate 20 is heat-treated and dried to form a battery sheet (active material sheet or solid electrolyte sheet) 40, and the thickness thereof is adjusted by the blade 50. The battery sheet 40 and the substrate 20 are peeled off by the substrate take-up roll 60 and the battery sheet take-up roll 70, respectively, and taken up.

FIG. 2 is an enlarged schematic view of slurry dropping and battery sheet production in FIG. As shown in FIG. 2, the thickness of the battery sheet 40 can be adjusted by adjusting the amount of dripping by appropriately increasing or decreasing the number of nozzles in accordance with the width of the sheet (FIG. 2 (1)). And it can adjust also with the conditions of drying processing, and the moving speed of the battery sheet 40 (FIG. 2 (2)).
In the third step, as shown in FIG. 2, a battery sheet can be easily produced by using an ink jet printing technique.

  In FIG. 1, the battery sheet 40 and the substrate 20 are separated by winding, but when it is difficult to wind in a roll shape, the sheet is recovered in the A5 sheet or business card sheet by cutting in the width direction. It is also possible. In FIG. 2 (2), the battery sheet 40 and the substrate 20 are cut in the width direction using the wedge-shaped peeling member 24.

  Since the active material slurry and the solid electrolyte slurry of the present invention contain a lithium ion conductive binder, for example, unlike the case where an insulating resin or the like is used as the binder, the resulting battery sheet has insulation derived from the binder. That can be suppressed.

As shown in FIG. 2, the substrate 20 has side guards 22. In the present invention, the substrate 20 having the side guard 22 is preferably made of a flexible metal, and the surface thereof is coated with fluorine.
The metal having flexibility is preferably a metal foil such as Al or SUS.

[Fourth step]
In the fourth step, the side guard side portions of the active material sheet and the solid electrolyte sheet are cut.
FIG. 3 is a schematic cross-sectional view of the battery sheet obtained in the third step. As shown in FIG. 3 (1), although it depends on the conditions of the heat treatment and the drying treatment, the film thickness of the side guard side surface portion of the battery sheet usually tends to be thick. This is due to the surface tension of the side surface of the side guard, and it is necessary to cut the side end of the battery sheet in order to prevent the resulting battery from being distorted. On the other hand, FIG. 3 (2) is a schematic cross-sectional view of a battery sheet produced using the above-described substrate having a fluorine-coated side guard. As shown in FIG. 3 (2), the surface of the fluorine-coated side guard is excellent in releasability, so that it repels each other and the obtained battery sheet has a thin side guard side portion. Even if the battery sheet has a thin side guard side film thickness, it is necessary to cut the side edge, but the amount of cutting can be reduced, so that the efficiency of using the slurry can be increased and the resulting battery can be obtained. The yield of the seat can be improved.

[Fifth step and sixth step]
In the fifth step, the solid electrolyte sheet cut from the side guard side part is sandwiched between the active material sheets cut from the two side guard side parts, and the active material sheet cut from the two side guard side parts is further A laminated body is formed by being sandwiched between two current collector sheets.
In the sixth step, the laminate obtained in the fifth step is vacuum hot pressed at a temperature equal to or higher than the melting point of the lithium ion conductive binder.

FIG. 4 is a schematic cross-sectional view of a process of stacking a positive electrode active material sheet, a solid electrolyte sheet, a negative electrode active material sheet, and a current collector sheet, and manufacturing the battery by vacuum hot pressing the obtained laminate.
As shown in FIG. 4, the solid electrolyte sheet 42 from the solid electrolyte sheet supply roll 80, the positive electrode active material sheet 44 from the positive electrode active material sheet supply roll 90, and the negative electrode active material sheet 46 from the negative electrode active material sheet supply roll 100. Each is supplied to form a laminate in which the positive electrode active material sheet 44, the solid electrolyte sheet 42, and the negative electrode active material sheet 46 are laminated in this order. Two current collector sheets 112 supplied from the current collector sheet supply roll 110 are further laminated from both sides of the positive electrode active material sheet 44 and the negative electrode active material sheet 46 of the laminate, and vacuum hot pressing is performed by the press roll 120. By doing so, a lithium battery is obtained.

As shown in FIG. 4, since the present invention can continuously perform the production of the laminate and the batch pressing of the laminate, the production efficiency of the lithium battery can be greatly increased.
As a method of forming a laminated body, there are a method of laminating while sequentially drawing from the roll-shaped sheet shown in FIG. 4, and a method of laminating each sheet after cutting it to a desired size. From the viewpoint of productivity, a method of directly laminating from a roll sheet is desirable, but distortion may occur when the sheet is transferred.

  The current collector sheet is preferably a current collector sheet made of one or more metals selected from the group consisting of Al, Ti and SUS.

FIG. 5 is an enlarged cross-sectional view of the pressing step of FIG.
As shown in FIG. 5, in the present invention, the laminate is vacuum hot pressed at a temperature equal to or higher than the melting point of the lithium ion conductive binder to fuse each sheet of the laminate. A hot press under an inert atmosphere can be applied instead of the vacuum hot press, but there is a possibility that the slurry solvent cannot be completely removed or the gas in the film cannot be removed. The pressing method includes a surface pressing method and a roll pressing method, but is not particularly limited.

  The press pressure of the vacuum hot press is preferably 1 MPa or more and 1000 MPa or less, more preferably 1 MPa or more and 500 MPa or less.

  The method for producing a lithium battery of the present invention has excellent production efficiency, and the obtained lithium battery can be further laminated to form a lithium battery pack.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments.

Preparation example [Preparation of lithium sulfide]
Lithium sulfide was produced according to the method of the first aspect (two-step method) in JP-A-7-330312. This will be specifically described below.
First, N-methyl-2-pyrrolidone (NMP) 3326.4 g (33.6 mol) and lithium hydroxide 287.4 g (12 mol) were charged into a 10 liter autoclave equipped with a stirring blade, and at 300 rpm and 130 ° C. The temperature was raised to. After the temperature rise, hydrogen sulfide was blown into the liquid at a supply rate of 3 liters / minute for 2 hours.

  Subsequently, the temperature of the reaction solution was raised under a nitrogen stream (200 cc / min), and the reacted lithium hydrosulfide was dehydrosulfurized to obtain lithium sulfide. As the temperature increased, water produced as a by-product due to the reaction between the hydrogen sulfide and lithium hydroxide started to evaporate, but this water was condensed by the condenser and extracted out of the system. While water was distilled out of the system, the temperature of the reaction solution rose, but when the temperature reached 180 ° C., the temperature increase was stopped and the temperature was kept constant. The reaction was completed after the dehydrosulfurization reaction of lithium hydrosulfide (about 80 minutes) to prepare lithium sulfide.

[Purification of lithium sulfide]
After decanting NMP in the prepared 500 mL slurry reaction solution (NMP-lithium sulfide slurry), 100 mL of dehydrated NMP was added and stirred at 105 ° C. for about 1 hour. NMP was decanted at the same temperature. Further, 100 mL of NMP was added, stirred for about 1 hour at 105 ° C., NMP was decanted at the same temperature, and the same operation was repeated a total of 4 times. After completion of the decantation, lithium sulfide was dried at 230 ° C. (temperature higher than the boiling point of NMP) under a nitrogen stream for 3 hours under normal pressure.

The impurity content in the obtained purified lithium sulfide was measured. The content of each sulfur oxide of lithium sulfite (Li ₂ SO ₃ ), lithium sulfate (Li ₂ SO ₄ ), lithium thiosulfate (Li ₂ S ₂ O ₃ ), and lithium N-methylaminobutyrate (LMAB) Quantification was performed by ion chromatography.
As a result, the total content of sulfur oxides of purified lithium sulfide was 0.13% by mass, and LMAB was 0.07% by mass.

[Preparation of sulfide-based solid electrolyte]
500 ml of purified lithium sulfide (Li ₂ S) having an average particle size of about 30 μm and 67.46 g of P ₂ S ₅ (manufactured by Aldrich) having an average particle size of about 50 μm containing 175 10 mmφ alumina balls Sealed in an alumina container. The above weighing and sealing operations were all carried out in the glove box, and all the equipment used was previously dehydrated with a dryer.

  The sealed alumina container was mechanically milled at room temperature for 36 hours with a planetary ball mill (PM400 manufactured by Lecce) to obtain white yellow solid electrolyte glass particles. The recovery rate at this time was 78%.

As a result of X-ray diffraction measurement (CuKα: λ = 1.5418４) of the obtained solid electrolyte glass particles, the peak of the raw material Li ₂ S was not observed, and it was a halo pattern resulting from the solid electrolyte glass.
The solid electrolyte glass particles were sealed in a SUS tube under an Ar atmosphere in a glove box, and subjected to heat treatment at 300 ° C. for 2 hours to obtain solid electrolyte glass ceramic particles (average particle size 14.52 μm). In the X-ray diffraction measurement of the obtained solid electrolyte glass ceramic particles, peaks were observed at 2θ = 17.8, 18.2, 19.8, 21.8, 23.8, 25.9, 29.5, 30.0 deg. Was observed.
The conductivity of the solid electrolyte glass ceramic particles was 1.3 × 10 ⁻³ S / cm.

Example 1
[Preparation of solid electrolyte slurry]
43 g of the produced solid electrolyte (solid electrolyte glass ceramic particles) was added to 500 ml of a toluene solvent in which 10 g of polyethylene glycol was dissolved to obtain a solid electrolyte slurry having a solid concentration of about 10 wt%.

[Preparation of positive electrode mixture slurry]
12.9 g of the produced solid electrolyte (solid electrolyte glass ceramic particles) and 30.1 g of LiCoO ₂ (manufactured by Toda Kogyo Co., Ltd.) which is a positive electrode active material are added to 500 ml of a toluene solvent in which 10 g of polyethylene glycol is dissolved. A mixture slurry was obtained.

[Preparation of negative electrode mixture slurry]
The prepared solid electrolyte (solid electrolyte glass ceramic particles) 17.2 g and the negative electrode active material carbon (SFG75, manufactured by Kimcal) 25.8 g were added to 500 ml of toluene solvent in which 10 g of polyethylene glycol was dissolved, and the negative electrode mixture A slurry was obtained.

[Production of solid electrolyte sheet and active material sheet]
A solid electrolyte sheet, a positive electrode mixture sheet, and a negative electrode mixture sheet were produced along the steps shown in FIG.
The board | substrate which has a side guard was transferred with the roll, and the slurry layer which has a desired depth was formed by dripping each prepared slurry suitably. The thickness of the slurry is determined by the amount of slurry dropped and the transfer speed of the substrate, but the side guard height was 500 μm so that it could be formed in the range of 50 μm to 500 μm. The board | substrate which has a side guard was produced by welding the guard part which deformed the Al wire at the edge part of the Al sheet. The width is not particularly limited, but is 10 cm and the length is 30 m. In consideration of the peelability after drying, Teflon (registered trademark) processing was applied to the substrate surface.

  As shown in FIG. 2, each nozzle was dropped at a rate of 1 drop / 10 seconds with a nozzle provided with a valve adjustment function so that a certain amount of each slurry could be dropped. The substrate transfer speed was transferred at a rate of 5 cm / min so that the slurry was sufficiently filled. The transfer speed and the dropping amount need to be adjusted depending on the desired film thickness. In this example, the transfer speed and the dropping amount were set based on obtaining a sheet thickness of about 100 μm.

After dropping the slurry, the height of the side guard was regulated by a doctor blade for the purpose of securing the liquid level and obtaining the level of the substrate. Subsequently, in order to dry the slurry, it was passed through a hot air drying area. Since the distance (time) of the hot air drying area depends on the solid content concentration (solvent amount) of the slurry, a condition for ensuring a sufficient distance for drying is required.
As shown in FIG. 3, the side guard side edge part was cut | disconnected with the cutter after drying. In this example, cutting was performed using an acute blade.

[Production of lithium battery]
The produced solid electrolyte sheet, the positive electrode mixture sheet and the negative electrode mixture sheet were formed into a roll and combined with a current collector roll to produce a laminate in the step shown in FIG. Then, the laminated body was vacuum hot roll pressed at 100 ° C. to produce a lithium battery.
The current collector roll is not particularly limited as long as the most suitable positive electrode and negative electrode are selected. In consideration of conventional stability, a 0.1 mm-thick In sheet and SUS sheet are used. Carried out.

  The manufactured lithium battery was punched out so that the peripheral portion was not short-circuited, and set in an HS cell, and charge / discharge evaluation was performed. The cut-off voltage was set to a lower limit of 1.5 V and an upper limit of 3.7 V, and the discharge capacity was a ratio of the discharge capacity to the charge capacity after charging and a discharge output that was an integrated value thereof. As a result, the obtained lithium battery had a discharge capacity of 120 mAh / g in terms of positive electrode active material at a rate of 0.2C.

The method for producing a lithium battery of the present invention can produce a lithium battery efficiently.
The lithium battery pack of the present invention can be used as a battery for portable information terminals, portable electronic devices, household small-sized power storage devices, motorcycles using electric power as a motor, electric vehicles, hybrid electric vehicles, and the like.

It is a schematic diagram which shows a 3rd process. It is an expansion schematic diagram of the slurry dripping process and battery sheet preparation process of FIG. It is a schematic sectional drawing of the battery sheet obtained at the 3rd process. It is a schematic sectional drawing of the process of laminating | stacking a positive electrode active material sheet, a solid electrolyte sheet, a negative electrode active material sheet, and a collector sheet, and manufacturing the battery by pressing the obtained laminated body. It is an expanded sectional view of the press process of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Substrate supply roll 20 Substrate 22 Side guard 24 Wedge-shaped peeling member 30 Nozzle 40 Battery sheet 42 Solid electrolyte sheet 44 Positive electrode active material sheet 46 Negative electrode active material sheet 50 Blade 60 Substrate winding roll 70 Battery sheet take-up roll 80 Solid electrolyte sheet supply Roll 90 Positive electrode active material sheet supply roll 100 Negative electrode active material sheet supply roll 110 Current collector sheet supply roll 112 Current collector sheet 120 Press roll

Claims (8)

A method for manufacturing a lithium battery including a solid electrolyte layer, an active material layer, and a current collector layer, the method including the following steps:
A step of dispersing an active material in a solvent containing a lithium ion conductive binder to prepare an active material slurry;
A step of preparing a solid electrolyte slurry by dispersing a sulfide-based solid electrolyte in a solvent containing a lithium ion conductive binder;
The step of forming the active material sheet and the solid electrolyte sheet by dropping the active material slurry and the solid electrolyte slurry onto a substrate having side guards respectively, adjusting the slurry thickness with a blade, and further drying by heating and peeling. When,
Cutting the side guard side portions of the active material sheet and the solid electrolyte sheet;
The solid electrolyte sheet with the side guard side portion cut is sandwiched between two active material sheets with the side guard side portion cut, and two more active material sheets with the two side guard side portions cut are further sandwiched. A step of forming a laminate by sandwiching it with a current collector sheet, and a step of vacuum hot pressing the laminate at a temperature equal to or higher than the melting point of the lithium ion conductive binder.   The method for producing a lithium battery according to claim 1, wherein the sulfide-based solid electrolyte is obtained from lithium sulfide, one or more sulfides selected from the group consisting of phosphorus sulfide, silicon sulfide, and germanium sulfide.   The method for producing a lithium battery according to claim 1, wherein the lithium ion conductive binder is polyethylene glycol or polymethyl methacrylate.   The method for manufacturing a lithium battery according to any one of claims 1 to 3, wherein the substrate having the side guard is made of a flexible metal, and the surface thereof is coated with fluorine.   The method for manufacturing a lithium battery according to claim 1, wherein the current collector sheet is made of one or more metals selected from the group consisting of Al, Ti, and SUS.   The method for producing a lithium battery according to claim 1, wherein the vacuum hot pressing is performed at a temperature equal to or higher than a melting point of the lithium ion conductive polymer and a pressure of 1 MPa to 1000 MPa.   The lithium battery pack obtained by further laminating the lithium battery obtained from the manufacturing method of the lithium battery in any one of Claims 1-6.   The apparatus provided with the lithium battery obtained from the manufacturing method of the lithium battery in any one of Claims 1-6.

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