JPH11185733A - Manufacture of lithium polymer secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method superior in adhesion and adhesiveness between respective constituting layer boundaries, and reducing internal impedance being a problem in the case of electron movement between the layer boundaries. SOLUTION: In a manufacturing method for a lithium polymer secondary battery formed by applying at least a primer layer, electrode layers containing active materials, and two layers or more selected among polymer electrolyte layers to a conductive support body, a method superimposing the coatings of at least two or more layers among them into layer-like in a liquid state, and applying the whole as one layer thereto simultaneously is used, or a method applying one layer onto other wet state applied layer without any post- treatment, repeating the same process, and finally conducting post-treatment for all layers simultaneously is used, and the viscosity of the respective layer coatings used in that case shows in a range of 10<-3> to 5×10<2> Pa.s in dynamic viscosity coefficient when shearing velocity of 2×1<2> s<-1> is imparted. Further coating viscosity difference between adjoining layers is within 10<2> Pa.s in the comparison of dynamic viscosity coefficients at the above mentioned shearing velocity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating a positive electrode coating layer, a negative electrode coating layer, a polymer-containing electrolyte layer, and associated layers of a lithium polymer secondary battery.

[0002]

2. Description of the Related Art In recent years, various devices such as a camera-integrated VTR device, an audio device, a portable computer, and a cellular phone have been reduced in size and weight, and there has been a demand for higher performance of a battery as a power supply for these devices. Is growing. Above all, development of lithium secondary batteries capable of realizing high voltage, high energy density and excellent cycle characteristics as batteries for power sources of electric vehicles has been active.

A lithium secondary battery comprises a positive electrode capable of inserting and extracting lithium ions, a negative electrode, and a non-aqueous electrolyte solution.
Conventionally, non-aqueous electrolytes have been used as electrolytes for these high-voltage batteries. However, since batteries using a non-aqueous electrolyte have a risk of filtrate and ignition, in recent years, non-aqueous electrolytes have been added to improve safety, for example, a gel polymer contains an electrolyte. Electrolyte development is underway. In particular, in a lithium secondary battery, heat generation and ignition resulting from an internal short circuit due to precipitation of lithium dendrites when a liquid electrolyte is used poses a problem, and application of a polymer electrolyte has been desired.

Further, unlike the conventional lithium secondary battery, a polymer electrolyte including an electrolyte containing an electrolyte solution in a gel polymer as described above can be used without using a separator.
Since it is possible to recommend a substitute for the separator used in the secondary battery system, the positive electrode and the negative electrode can be used by joining the polymer electrolyte. Since such a polymer is lighter and has shape flexibility compared to a liquid system,
For example, there is an advantage that a thin battery such as a sheet can be formed, and a lightweight and space-saving battery can be manufactured.

[0005] There are a variety of methods for producing a lithium polymer secondary battery, and among them, various coating methods are often used for forming a positive / negative electrode film and an electrolyte layer mainly using an active material as a main constituent material. . However, as a coating method for forming each of the necessary constituent layers, a wet-on-dry method in which coating and post-processing are repeated as many times as the number of layers is a general method. In many cases, an increase in internal impedance and a variation in performance due to insufficient degree are problems.

[0006]

In such a polymer battery, the ionic conduction of the electrolyte is mainly carried out through the non-aqueous electrolyte phase in the electrolyte. Although the main part of the properties follows the non-aqueous electrolyte, the polymer matrix containing this non-aqueous electrolyte has a very low fluidity to maintain its mechanical strength,
There is a problem that charge / discharge at a high rate is poor because the bonding interface between the positive electrode and the negative electrode with the active material is small.

Here, in the charging / discharging process of the lithium secondary battery, electrons are exchanged between the lithium ion moving through the electrolyte and the electrode (the active material in the electrode). It is necessary to have electron conductivity. In the case of a lithium secondary battery using a liquid electrolyte, the ion conductivity in the electrolyte is higher when the conductivity of lithium ions in the active material in the electrode is compared with that in the electrolyte. As a result, the movement of electrons in the electrode is performed by an active material in the electrode and a conductive material such as carbon black,
The movement of lithium ions is mainly performed by the electrolyte that has penetrated into pores existing in the electrode.

The present invention has been made in order to improve various problems in the prior art, and has excellent adhesion and adhesion between boundaries of constituent layers. This has the effect of reducing the internal impedance of the battery, which is a problem when moving, and as a result has the effect of reducing the variation in the performance of the battery, and at the same time has the merit of significantly shortening the process from the viewpoint of manufacturing. An object of the present invention is to provide a method for producing a lithium polymer secondary battery having such excellent performance and stability.

[0009]

According to the study of the present inventors, the present invention relates to a polymer electrolyte containing a lithium ion complex, a polymer electrolyte containing a plasticizer, a gel polymer electrolyte or a lithium polymer secondary battery containing a completely solid electrolyte. Here, it has been found that the problem of adhesion and adhesion between the constituent layers greatly affects battery performance as compared with the case of a lithium-ion battery called a normal liquid system. As a result of intensive research to solve this problem, we improved the coating process of each constituent layer in battery production, that is, a single layer coating and post-treatment for each constituent layer, which is a conventional method A so-called multi-layer simultaneous coating method in which a multi-layer state is formed and applied simultaneously in a liquid state, or a so-called multi-layer coating method in which a coating layer in a sufficiently wet state is overcoated with another layer without post-processing, rather than a wet-on-dry method in which the layers are overlapped. Multilayer wet-on-
By adopting the wet method, it was found that variations in battery performance related to internal impedance and charge / discharge can be significantly reduced, and the present invention has been achieved.

The gist of the present invention is to provide a lithium polymer secondary battery in which at least two layers selected from a primer layer, an electrode layer containing an active material, and a polymer electrolyte layer are coated on a conductive support. A production method, wherein at least two or more layers of the paint are layered in a liquid state,
The method of simultaneously applying the whole as a single layer is used, and the viscosity of the coating material of each layer used at that time is 10 ^{−3 in} terms of the dynamic viscosity when a shear rate of 2 × 10 ² s ⁻¹ is applied.
５5 × 10 ² Pa · s, and the difference in the viscosity of the paint between adjacent layers is within 10 ² Pa · s in comparison of the dynamic viscosity at the above shear rate. A method for producing a lithium polymer secondary battery or a conductive support, on which at least two layers selected from a primer layer, an electrode layer containing an active material, and a polymer electrolyte layer, are coated with a lithium polymer secondary A method for producing a battery, wherein a method of repeatedly applying another layer without post-processing on one coating layer in a wet state, and finally performing post-processing simultaneously on all layers, and each layer used at that time The viscosity of the paint is 10 ^{−3 to} 5 × 10 ² P in the dynamic viscosity when a shear rate of 2 × 10 ² s ⁻¹ is applied.
In the comparison of the dynamic viscosity at the shear rate, the viscosity of the upper layer is lower than the viscosity of the lower layer by 10 ² Pa · s.
A method for producing a lithium polymer secondary battery, characterized in that:

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The layers in the present invention are Al, C
u is a layer formed by being applied directly or indirectly on a conductive support such as u, and in addition to the electrode layers that are various active material-containing layers, between this electrode layer and the conductive support. It refers to all the layers required for battery performance, such as a layer provided, that is, a primer layer having an anchor effect for enhancing conductivity and adhesion, or a polymer electrolyte layer provided on an electrode layer.

In these batteries, the reason why the present invention improves the adhesion / adhesion between the respective layers and consequently the internal impedance is reduced is that the layers are brought into contact with each other while they are in a sufficiently wet state. By causing a drying and curing reaction to occur, first, the compatibility between the wet layers is improved by the interfacial tension between them, and when the layers are contacted in a sufficiently wet state, a very small amount of the layer interfaces are mixed with each other, and It is considered that this is to create an anchor effect. In the conventional sequential wet-on-dry method, since a sequential post-treatment is performed for each layer, the above-mentioned affinity in terms of interfacial tension and an anchor effect are hardly generated, and as a result, a state close to interfacial peeling occurs and the original material is removed. It is considered that the performance has not been sufficiently brought out.

The coating device is not particularly limited,
In the case of the multi-layer simultaneous application of the first invention of the present application, each paste is formed into a multi-layer state in a liquid (semi-solid) state, and is then placed on a support to realize multi-layer simultaneous application. This includes slide coating and extrusion type die coating. The latter extrusion method is usually the best method in consideration of paste viscosity and coating film thickness.

Further, another layer is coated on the layer in the wet state according to the second invention of the present application, that is, so-called sequential wet-on-wet.
It has been confirmed that, when a multilayer coating is performed by a method, the performance is almost the same as that produced by the multilayer simultaneous coating method of claim 1. In this method, the extrusion die method is used. Besides, a reverse roll, a gravure, a knife coater, a kiss coater, a microgravure, a knife coater, a rod coater, a blade coater, etc., if possible, the application method is not limited at all,
More various coating methods can be used in combination than the multilayer simultaneous method. Further, depending on the wet state and viscosity of the lower layer, another layer in a wet state, which has been applied to another support, may be transfer-laminated and applied as an upper layer.

Regarding the coating liquid, regardless of whether it contains a solvent or not, even if it is a monomer-containing type that does not contain an organic solvent called a so-called plasticizer, it can be cured by heat, light, electron beam, etc. after coating. If the wet coating can be carried out by selecting the appropriate coating method and the wet state coating is possible, all the processes fall within the scope of the present invention.

In the first invention of the present application, when two or more layers are simultaneously coated, the viscosity of the paint in each layer is 2 × 10 ² s ^−1.
Dynamic viscosity at a shear rate of 10
^{-3 to} 5 × 10 ² Pa · s, and the difference in viscosity between paints between adjacent layers is within 10 ² Pa · s in comparison of the dynamic viscosity at the above shear rate. It is characterized by. There is no particular limitation on the viscoelasticity of each liquid.
When a specific layer is applied as a thin film, it is usually desirable that the difference between the respective liquids is within 1 Pa · s in dynamic viscosity, and Casson's sp.
It is more desirable to make the slope in lot as close as possible.

By using the viscosity paste in the range of the thin film of the present invention, mutual disturbance of the liquid between the multilayered fluids is reduced, and the interface can be kept uniform. By approaching the slope at this Caasson 'plot, the fluid has more approximate liquid properties, and hence from the hydrodynamic point of view, disturbance at the interface is reduced, and it is thought that the film can be made thinner. From these facts, the short circuit between the positive electrode and the negative electrode in the battery is reduced, which leads to variation in the performance of the battery and improvement in the yield.

According to the second invention of the present application, two or more sequential wet-o
When n-wet coating is performed, the viscosity of the paint in each layer is 2 ×
When the shear viscosity of 10 ² s ^{−1 is applied} , a dynamic viscosity of 10 ^{−3 to} 5 × 10 ² Pa · s is used. Is characterized in that the viscosity of the lower layer is equal to or lower than the viscosity of the lower layer + 10 ² Pa · s with respect to the viscosity of the lower layer. There is no particular limitation on the viscoelasticity of each liquid.

In the case of a condition outside the above range, for example,
Over 10 on electrolyte of viscosity ^TwoHigh viscosity over Pa · s
When applying a positive electrode or a negative electrode, the lower electrolyte paste
Interface cannot support the stress received from the upper electrode paste
Of the battery, resulting in a short circuit between the positive and negative electrodes in the battery.
Because of the interfacial mixing described above, variations in performance and yield
It is thought that this will lead to a lower rate.

The lithium secondary battery of the present invention mainly comprises a positive electrode, a negative electrode and a polymer electrolyte. First, the electrodes in the lithium secondary battery of the present invention will be described. Generally, a positive electrode and a negative electrode in a lithium secondary battery are formed by forming a positive electrode (negative electrode) active material, a conductive material, and a binding resin (binder) on a current collector such as an aluminum plate or a copper plate.
It is manufactured by applying and drying a paint containing a solvent and the like.

The compound capable of inserting and extracting lithium ions, which is an active material used for the positive electrode in the present invention, includes:
Examples of the inorganic compound include transition metal oxides of transition metals such as Fe, Co, Ni, and Mn, composite oxides of lithium and transition metals, and transition metal sulfides. Specifically, M
transition metal oxide powders such as nO, V ₂ O ₅ , V ₆ O ₁₃ and TiO ₂ , composite oxide powders of lithium and transition metal such as lithium nickelate and lithium cobalt oxide, TiS ₂ ,
Transition metal sulfide powder such as FeS can be used. Examples of the organic compound include a conductive polymer such as polyaniline. Further, an inorganic compound, an organic compound and the like may be mixed and used.

As the negative electrode material, in addition to the Li metal foil, Li
Graphite, coke, or the like is used as a compound capable of inserting and extracting ions. The particle size of the active material of the positive electrode and the negative electrode may be appropriately selected in consideration of the other constituent elements of the battery, but is usually 1 to 30 μm, and particularly preferably 5 to 20 μm, whereby the battery characteristics are good. Is preferred. The binder needs to be stable to an electrolytic solution or the like, and is desired to have weather resistance, chemical resistance, heat resistance, flame retardancy, and the like. Further, a material having excellent ion conductivity is desirable, and examples thereof include a cross-linkable polyethylene oxide resin. More preferably, it is desirable to introduce an acryl group, a methacryl group, or the like into the terminal of the polyethylene oxide resin and to crosslink with heat, ultraviolet rays, or the like.

The conductive substance is not particularly limited as long as it is a substance capable of imparting conductivity by mixing a proper amount of lithium with a compound powder capable of inserting and extracting lithium, and carbon-based powders such as acetylene black, carbon black and graphite can be used. And a metal powder that is stable at the electrode potential used. The DBP oil absorption of these conductive substances is preferably 120 cc / 100 g or more, particularly preferably 150 cc / 100 g or more because the electrolyte retains the electrolyte. The weight ratio between the active material and the binder is preferably in the range of 98/2 to 80/20.

An aluminum foil is generally used as a current collector of the positive electrode. A copper foil is used as a current collector of the negative electrode. It is preferable that the surface of the current collector be subjected to a roughening treatment in advance, since the binding effect is enhanced. Examples of the surface roughening method include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method. As the mechanical polishing method, abrasive cloth paper to which abrasive particles are fixed,
A method of polishing the surface of the current collector with a wire brush provided with a grindstone, emery buff, steel wire, or the like can be given.

Next, the polymer electrolyte will be described.
Generally, a polymer electrolyte containing an electrolyte solution in a gel polymer (hereinafter, this may be simply referred to as a polymer electrolyte) is used as the polymer electrolyte. A non-aqueous electrolytic solution is preferably used as the electrolytic solution to be contained in the gel polymer. In general, a solution obtained by dissolving an electrolyte in a non-aqueous solvent is used. As the electrolyte solution used for the polymer electrolyte, the electrolyte is stable with respect to the positive electrode active material and the negative electrode active material, and lithium ions can move to perform an electrochemical reaction with the positive electrode active material or the negative electrode active material. Any non-aqueous substance can be used.

Specifically, LiPF ₆ , LiAsF ₆ , L
iSbF ₆ , LiBF ₄ , LiClO ₄ , Lil, Li
Br, LiCl, LiAlCl, LiHF ₂ , LiSC
N, LiSO ₃ CF _{2 and the} like. Among them, LiPF ₆ and LiClO ₄ are particularly preferable. The content of these electrolytes in the electrolyte is generally 0.5 to
2.5 mol / l.

The solvent for dissolving the polymer electrolyte is not particularly limited, but a solvent having a relatively high dielectric constant is preferably used. Specifically, ethylene carbonate, cyclic carbonates such as propylene carbonate, dimethyl carbonate, diethyl carbonate, acyclic carbonates such as ethyl methyl carbonate, tetrahydrofuran,
One or a mixture of two or more of glymes such as 2-methyltetrahydrofuran and dimethoxyethane, lactones such as γ-butyllactone, sulfur compounds such as sulfolane, and nitriles such as acetonitrile can be mentioned. Among these, one or more mixed solutions selected from cyclic carbonates such as ethylene carbonate and propylene carbonate, and acyclic carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate are particularly suitable.

The above-mentioned electrolyte solution is immersed in a polymer such as polyethylene oxide, polypropylene oxide, a crosslinked isocyanate of polyethylene oxide, phenylene oxide, or a phenylene sulfide polymer to prepare a gel electrolyte. The shape of the lithium secondary battery of the present invention can be various shapes such as a cylindrical shape, a box shape, a paper type, a card type, and a circular shape.

[0029]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples, and may be carried out by appropriately changing the scope of the present invention. Is possible. The viscosity measurement of the following paste was performed using RE-550 manufactured by Toki Sangyo.
U was used.

[Preparation of Positive Electrode Paste] Composition (1) Lithium cobaltate (Cellseed C10 manufactured by Nippon Chemical Industry) 88.0 wt% Acetylene black (Denka Black manufactured by Denki Kagaku Kogyo) 4.0 wt% Binder (Photomer 4050 manufactured by Henkel) 8 0.0 wt% Polymerization initiator (Trignox 42 manufactured by Akuzo Nobel) 0.1 wt% Solvent (propylene carbonate manufactured by Mitsubishi Chemical) 100.0 wt%

From the above composition, all the raw materials except the polymerization initiator were kneaded for 2 hours by a kneader. A polymerization initiator was added to the prepared paste immediately before use, followed by stirring to obtain a positive electrode paste. For this paste, 2 × 10 ² s
The dynamic viscosity at a shear rate of ^-1 is 1 × 1
0 ² Pa · s was shown.

Composition (2) Lithium cobaltate (Cell seed C10 manufactured by Nippon Chemical Industry) 88.0 wt% Acetylene black (Denka Black manufactured by Denki Kagaku Kogyo) 4.0 wt% Binder (Photomer 4050 manufactured by Henkel) 8.0 wt% Polymerization initiator (Trignox42 manufactured by Akuzo Nobel) 0.1 wt% Solvent (propylene carbonate manufactured by Mitsubishi Chemical) 70.0 wt%

From the above composition, all the raw materials except the polymerization initiator were kneaded for 2 hours by a kneader. A polymerization initiator was added to the prepared paste immediately before use, followed by stirring to obtain a positive electrode paste. For this paste, 2 × 10 ² s
The dynamic viscosity at a shear rate of ^-1 is 4 × 1
0 ² Pa · s was shown.

[Preparation of Negative Electrode Paste] Coke (MBC manufactured by Mitsubishi Chemical) 92.0 wt% Binder (Photomer 4050 manufactured by Henkel) 8.0 wt% Polymerization initiator (Trignox 42 manufactured by Akuzo Nobel) 0.1 wt% Solvent (manufactured by Mitsubishi Chemical) Propylene carbonate) 100.0wt%

As in the case of the positive electrode, all the raw materials in the above composition except for the polymerization initiator were kneaded for 2 hours by a kneader.
A polymerization initiator is added to the prepared paste immediately before use,
The mixture was stirred to obtain a negative electrode paste. About this paste,
The dynamic viscosity at the time of applying a shear rate of 2 × 10 ² s ⁻¹ was 8 × 10 ¹ Pa · s.

[Preparation of Polymer-Containing Electrolyte] Binder (Photomer 4050 manufactured by Henkel) 20.0 wt% Binder (polyethylene oxide) 2.0 wt% Lithium perchlorate 15.0 wt% Polymerization initiator (Trignox 42 manufactured by Akuzo Nobel) 0.5 wt% % Solvent (Mitsubishi Chemical propylene carbonate) 100.0wt%

All of the above compositions were mixed, stirred and dissolved to obtain a polymer-containing electrolyte paste. About this paste, 2
The dynamic viscosity at the time of applying a shear rate of × 10 ² s ⁻¹ was 2 × 10 Pa · s.

[Substrate] Aluminum foil (made by Toyo Aluminum) 20 μm thick Copper foil (made by Japanese foil) 20 μm [Thickness of each layer coated] Positive layer 100 μm Negative layer 100 μm Electrolyte layer 30 μm

Example 1 By an extrusion die multi-layer simultaneous coating method, these three layers were simultaneously extruded to a predetermined film thickness in the order of the positive electrode paste (1), the electrolyte, and the negative electrode paste. Coated on top. Then, during the untreated state, a copper foil was laminated on the coated body to obtain an untreated coated body composed of all five layers. About 80 ° C
Heat curing was performed for 10 minutes, processed into a predetermined shape, and evaluated for battery performance.

Example 2 By an extrusion die multi-layer simultaneous coating method, these three layers are simultaneously extruded to a predetermined film thickness in the order of the negative electrode paste, the electrolyte, and the positive electrode paste (1). Coated on top. And, unprocessed,
An aluminum foil was laminated on the coated body to obtain an untreated coated body composed of all five layers. About 10
It was heat-cured for a minute, processed into a predetermined shape, and evaluated for battery performance.

Example 3 A positive electrode paste (1) was applied to a predetermined thickness on an aluminum foil by an extrusion die single layer coating method.
An electrolyte layer was applied to the untreated layer so as to have a predetermined thickness by the same single-layer coating method. Further, a negative electrode paste was applied on a copper foil by the same method so as to have a predetermined film thickness, and was laminated on the above-mentioned coated aluminum foil without any treatment to obtain an untreated coated body composed of all five layers. About 1
It was heat-cured for 0 minutes, processed into a predetermined shape, and evaluated for battery performance.

Example 4 A positive electrode paste (1) was applied to a predetermined thickness on an aluminum foil by an extrusion die single layer coating method.
An electrolyte layer and further a negative electrode paste were applied thereon by a single-layer coating method so as to have a predetermined thickness. Thereafter, a copper foil was laminated on the coated body to obtain an untreated coated body composed of all five layers. About 1
It was heat-cured for 0 minutes, processed into a predetermined shape, and evaluated for battery performance.

Comparative Example 1 A positive electrode paste (1) and a negative electrode paste were respectively applied to an aluminum foil and a copper foil so as to have a predetermined thickness by an extrusion die single layer coating method.
A 10 μm-thick polyethylene terephthalate film having a surface roughness Ra of 10 nm was laminated thereon, respectively, and thermally cured at 80 ° C. for 10 minutes. After that, by peeling off the laminated film, a predetermined positive electrode,
A negative electrode film was obtained. An electrolyte layer is coated on the positive electrode layer by the same coating method so as to have a predetermined thickness. Similarly, it was laminated and heat-cured with a polyethylene terephthalate film, and after peeling off the film, it was overlapped with the cured negative electrode film. This laminated film was passed through a metal roll having a linear pressure of 0.1 kgf / cm three times in order to further improve the adhesion between the layers.

Comparative Example 2 A positive electrode paste was applied on an aluminum foil to a predetermined thickness by an extrusion die single layer coating method, and a 10 μm thick polyethylene terephthalate film having a surface roughness Ra of 10 nm was applied thereon. Were respectively laminated and thermally cured at 80 ° C. for 10 minutes. Thereafter, the laminate film was peeled off to obtain a predetermined positive electrode film. An electrolyte layer is coated on the positive electrode layer by the same coating method so as to have a predetermined thickness. Similarly, lamination and heat curing were performed with a polyethylene terephthalate film, and the film was peeled off. According to the same coating method, a negative electrode paste was applied on a copper foil so as to have a predetermined thickness, and was untreated and laminated on the electrolyte surface coated with the negative electrode / electrolyte. About this laminated film, 10
After heat-curing for 3 minutes, in order to further improve the adhesion between the layers, the sheet was passed through a metal roll having a linear pressure of 0.1 kgf / cm three times. This was processed into a predetermined shape, and the battery performance was evaluated.

Comparative Example 3 A positive electrode paste (1) was applied on an aluminum foil so as to have a predetermined film thickness by an extrusion die single layer coating method, and a surface roughness Ra of 10 μm was applied to the aluminum foil.
Each of the m-thick polyethylene terephthalate films was laminated and thermally cured at 80 ° C. for 10 minutes. Then, by peeling this laminate film,
A predetermined positive electrode film was obtained. An electrolyte layer is coated on the positive electrode layer by the same coating method so as to have a predetermined thickness. Further, the negative electrode layer is applied on the copper foil to have a predetermined thickness by the same coating method. While untreated, it was laminated on the above-mentioned positive electrode / untreated electrolyte film. This laminated film was heat-cured at 80 ° C. for 10 minutes, and then passed between metal rolls having a linear pressure of 0.1 kgf / cm three times in order to further improve the adhesion between layers. This was processed into a predetermined shape, and the battery performance was evaluated.

Comparative Example 4 The three layers were simultaneously extruded to a predetermined thickness so that the positive electrode paste (2), the electrolyte, and the negative electrode paste were formed in the order of the extrusion die multi-layer simultaneous coating method. Coated on top. Then, during the untreated state, a copper foil was laminated on the coated body to obtain an untreated coated body composed of all five layers. About 80 ° C
Heat curing was performed for 10 minutes, processed into a predetermined shape, and evaluated for battery performance.

Comparative Example 5 A negative electrode paste was applied to a predetermined thickness on a copper foil by an extrusion die single-layer coating method, and an untreated electrolytic paste was applied thereon by the same single-layer coating method. Was applied with a positive electrode paste (2) so as to have a predetermined film thickness. Thereafter, an aluminum foil was laminated on the coated body to obtain an untreated coated body composed of all five layers. About 1
It was heat-cured for 0 minutes, processed into a predetermined shape, and evaluated for battery performance.

Table 1 shows the number of samples that could be initially charged and discharged for 20 condition samples for the above Examples and Comparative Examples. Further, the initial discharge capacity of Example 1 was set to 1
Table 1 also shows the discharge capacity ratio of each example when it was set to 00.
Here, the results when charging was performed at 0.2 C (the amount of current that would be fully charged in 5 hours) and discharging was performed at 0.2 C and 1 C are shown. Table 2 shows the number of the samples which were capable of initial charge / discharge and achieved a discharge capacity retention ratio of 80% after the charge / discharge cycle test of each of the 20 samples.

[0049]

[Table 1] Table 1 Initial chargeable / dischargeable number Initial discharge capacity ratio 0.2C 1C ──────────────────────────── Example 1 20 100 100 Example 2 1999 9 98 Example 3 20 96 98 Example 4 19 98 98 Comparative Example 1 12 76 61 Comparative Example 2 15 81 66 Comparative Example 3 16 90 78 Comparative Example 4 10 96 82 Comparative Example 5 8 92 80

[0050]

Table 2 Number of charge / discharge cycles (times) 50 100 150 200 300 ───────────────────────────── Example 1 20 20 20 19 19 Example 2 20 20 19 19 19 Example 3 20 20 20 19 19 Example 4 20 20 19 19 18 Comparative Example 1 8 2 0 0 Comparative Example 2 10 5 2 10 Comparative Example 3 15 10 8 5 3 Comparative Example 4 18 16 15 12 10 Comparative Example 5 16 13 10 9 7

[0051]

According to the present invention, compared to the conventional coating method,
Adhesiveness and interface uniformity at the electrode-electrolyte interface are greatly improved, which can lead to a reduction in internal impedance related to the interfacial resistance of the battery and an improvement in battery capacity. In addition, the cycle characteristics of the batteries can be greatly improved, and variations among the batteries can be reduced. In terms of production, it greatly contributes to shortening the production process.

Claims (2)

[Claims] 1. A method for producing a lithium polymer secondary battery, comprising applying at least two layers selected from a primer layer, an electrode layer containing an active material, and a polymer electrolyte layer on a conductive support. A method is used in which at least two or more layers of the paints are layered in a liquid state in a liquid state, and the whole is coated simultaneously as a single layer, and the viscosity of the paint in each layer used at that time is 2 × 10 ² s ^−1. 10 ^{−3 to} 5 × 10 ² P in the dynamic viscosity when a shear rate of
a.s is used, and the difference in viscosity of the paint between adjacent layers is within 10 ² Pa · s in comparison of the dynamic viscosity at the above-mentioned shear rate. Manufacturing method of secondary battery. 2. A method for producing a lithium polymer secondary battery, comprising applying at least two layers selected from a primer layer, an electrode layer containing an active material, and a polymer electrolyte layer on a conductive support. Repeating the application of another layer without post-processing on one application layer in the wet state,
Finally, the method of performing post-treatment simultaneously on all layers is used, and the viscosity of the paint of each layer used at that time is 10 ^{−3 to} 5 in dynamic viscosity when a shear rate of 2 × 10 ² s ⁻¹ is applied. ×
Used as indicating the scope of the 10 ² Pa · s, also the upper layer of the viscosity at the time of recoating, in comparison of the dynamic viscosity at a shear rate, with respect to the lower viscosity, lower viscosity +10 ²
A method for producing a lithium polymer secondary battery, which is not more than Pa · s.