JP2000331673A - Manufacture of polymer lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the discharge capacity in the discharge with a high load by manufacturing a positive electrode and/or a negative electrode through a process of applying a paste containing a polymer retainable of nonaqueous electrolyte and an active material to a porous substrate arranged on the upper surface of a paste spread preventing sheet. SOLUTION: A strip layer product 9 is carried from unwinding side to a back roll 1. The strip layer product 9 is carried to a paste storing vessel 5, a paste P is adhered to the porous substrate of the strip layer product 9. Since the paste P has flowing property, it is fallen into the through-holes of the porous substrate but banked by a paste spread preventing sheet arranged closely in contact with the lower surface of the porous substrate to prevent the paste P from being adhered to the lower surface of the porous substrate. The strip layer product 9 having the paste P adhered thereto is passed in a slit formed by the back roll 1 and a doctor blade 2, the thickness of the paste P adhered to the upper surface of the porous substrate is set to a desired value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a polymer lithium secondary battery.

[0002]

2. Description of the Related Art In recent years, with the development of electronic equipment, there has been a demand for the development of a non-aqueous electrolyte secondary battery that is small, lightweight, has a high energy density, and can be repeatedly charged and discharged. Such a secondary battery includes a negative electrode using lithium or a lithium alloy as an active material, a positive electrode containing an oxide, sulfide, or selenide such as molybdenum, vanadium, titanium, or niobium as an active material, and a nonaqueous electrolyte. There is known a lithium secondary battery including:

In recent years, a negative electrode containing a carbonaceous material that absorbs and releases lithium ions, such as coke, graphite, carbon fiber, a resin fired body, and pyrolytic gas phase carbon, has been used as a negative electrode. The development and commercialization of lithium ion secondary batteries using lithium and lithium manganese oxide-containing batteries are being actively pursued.

On the other hand, in order to further reduce the weight and size of the secondary battery, for example, US Pat.
As disclosed in No. 18, a polymer lithium secondary battery has been developed. Polymer lithium secondary batteries are
It is manufactured by the method described below. That is, a positive electrode having a structure in which a non-aqueous electrolyte non-impregnated positive electrode layer containing a polymer having a function of holding a non-aqueous electrolyte and an active material is supported on a conductive substrate, and has a function of holding a non-aqueous electrolyte. A negative electrode having a structure in which a negative electrode layer not impregnated with a non-aqueous electrolyte containing a polymer and an active material is supported on a conductive substrate, and a separator containing a polymer having a function of holding the non-aqueous electrolyte is manufactured. A separator is arranged between the obtained positive and negative electrodes and integrated by, for example, heating and pressing to obtain a laminate. Next, an operation of removing the plasticizer in the laminate is performed as necessary, and then the battery is impregnated with a non-aqueous electrolyte and sealed with an exterior material to obtain a secondary battery.

This polymer lithium secondary battery contains substantially no liquid component because the nonaqueous electrolyte is held by the polymer, and the positive and negative electrodes and the separator are integrated. A simple material such as a film can be used. For this reason, the secondary battery has features of being thin, lightweight, and excellent in safety.

The positive and negative electrodes of the secondary battery not impregnated with the non-aqueous electrolyte are prepared by applying (a) a paste containing a polymer having a function of holding the non-aqueous electrolyte and an active material to a conductive substrate, Is passed through a slit to adjust the coating thickness, then dried, and heated and pressurized, or contains (b) a polymer having a function of holding a nonaqueous electrolyte and an active material. The sheet is obtained by laminating a sheet obtained by forming a paste on a conductive substrate and applying heat and pressure to the sheet.

[0007]

However, in a polymer lithium secondary battery in which a positive electrode or a negative electrode is manufactured by such a method, at least one of the positive electrode and the negative electrode is used in order to increase the rate of penetration of the electrolyte into the laminate. When a conductive substrate having a porous structure such as expanded metal is used, the following problems occur.

That is, when a positive electrode or a negative electrode impregnated with a non-aqueous electrolyte is prepared by the method (a) described above, when the paste is applied to the porous substrate, the paste travels through the pores in the porous substrate and faces the opposite side. And the paste thickness on the application surface becomes thinner by that amount, so that the paste application thickness becomes uneven. As a result, the active material filling density of the positive electrode or the negative electrode becomes non-uniform, so that when discharging under a high load, a battery reaction occurs locally and a high discharge capacity cannot be obtained.

On the other hand, when a positive electrode or a negative electrode not impregnated with a non-aqueous electrolyte is produced by the method (b) described above, it is difficult to uniformly adhere the sheet and the porous substrate.
Not only high load discharge characteristics but also cycle life is reduced.

According to the present invention, there is provided a polymer lithium prepared by a method comprising a step of applying a paste containing a polymer having a function of holding a non-aqueous electrolyte and an active material to a porous substrate on at least one of the positive and negative electrodes. It is an object of the present invention to provide a method for manufacturing a polymer lithium secondary battery capable of improving a discharge capacity when discharged under a high load.

[0011]

According to a method of manufacturing a polymer lithium secondary battery according to the present invention, at least one of a positive electrode and a negative electrode contains a polymer having a function of holding a nonaqueous electrolyte and an active material. It is characterized by being produced by a method including a step of applying a paste to a porous substrate disposed on an upper surface of a paste wraparound prevention sheet.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a polymer lithium secondary battery according to the present invention will be described below with reference to FIGS.

FIG. 1 is a side view showing a coating and drying step in the method for producing a polymer lithium secondary battery according to the present invention.
FIG. 2 is an enlarged sectional view showing a portion A of FIG. 1, and FIG. 3 is an enlarged sectional view showing a portion B of FIG.

(First Step) A positive electrode, a negative electrode and a separator not impregnated with a non-aqueous electrolyte are prepared.

A positive electrode and a negative electrode not impregnated with a non-aqueous electrolyte are prepared by the method described below.

(1) A paste containing a polymer having a function of retaining a non-aqueous electrolyte and an active material is applied to a porous substrate disposed on the upper surface of a paste wraparound prevention sheet, and then dried.

First, a coating apparatus with a drying oven used in this step will be described.

As shown in FIG. 1, a knife coater as a coating means includes a back roll 1 and the back roll 1.
The doctor blade 2 is arranged above the doctor blade and moves up and down to adjust the gap with the back roll 1.
And a take-up side free roller 3 and a take-up side free roller 4. Further, the knife coater is adapted to adjust a traveling speed by a winding-side drive unit.
The paste container 5 is disposed in front of the back roll 1 so as to be close to the back roll 1. The drying furnace 6 is disposed between the back roll 1 and the take-up side free roller 4.

The coating and drying steps using such an apparatus will be described.

The paste P is supplied to the paste container 5 and, at the same time, as shown in FIG. 2, a belt-like laminate 9 having a porous substrate 8 closely arranged on the paste wraparound sheet 7 is unwound. 3 to the back roll 1. The band-like laminate 9 is the paste-containing container 5
When the paste P is transported, the paste P adheres to the porous substrate 8 of the band-shaped laminate 9. Although the paste P flows into the through-holes 10 of the porous substrate 8 because it has fluidity, the paste P is blocked by the paste wrap-around prevention sheet 7 closely arranged on the lower surface of the porous substrate 8, so that the paste P Adhesion to the lower surface of the porous substrate 8 is prevented. When the belt-like laminate 9 to which the paste P is attached passes through the slit formed by the back roll 1 and the doctor blade 2, the thickness of the paste P attached to the upper surface of the porous substrate 8 is desired as shown in FIG. To the value of. The paste-applied strip-shaped laminate 9 is dried in a drying furnace 6 and is subsequently rolled by a winding-side free roller 4 as a porous substrate having a nonaqueous electrolyte-unimpregnated positive electrode layer (or negative electrode layer) held on one side. It is transported to the process.

(2) The positive and negative electrodes which are not impregnated with the non-aqueous electrolyte are obtained by applying heat and pressure to the porous substrate having undergone the above-mentioned step (1).

In the case where a positive electrode (or negative electrode layer) not impregnated with a nonaqueous electrolyte is held on both sides of a porous substrate to form a positive electrode and a negative electrode not impregnated with a nonaqueous electrolyte, the above-mentioned (1) )
After the above-mentioned paste is applied to the surface of the porous substrate on which the positive electrode layer (or the negative electrode layer) has not been formed, and the paste is dried,
It can be obtained by applying heat and pressure. Here, since the paste is applied to the porous substrate on which the positive electrode layer (or the negative electrode layer) has already been formed on one side, it is not necessary to use a paste wraparound prevention sheet during the application.

Hereinafter, the composition of the paste, the porous substrate, and the paste prevention sheet will be described.

The positive electrode paste is prepared, for example, by mixing an active material, a polymer having a function of holding a non-aqueous electrolyte, a conductive material, and a plasticizer in an organic solvent such as acetone.

Examples of the active material include various oxides (eg, lithium manganese composite oxide such as LiMn ₂ O ₄ );
Manganese dioxide, for example, a lithium-containing nickel oxide such as LiNiO ₂ , for example, a lithium-containing cobalt oxide such as LiCoO ₂ , a lithium-containing nickel cobalt oxide, and an amorphous vanadium pentoxide containing lithium.
And chalcogen compounds (for example, titanium disulfide, molybdenum disulfide, and the like). Among them, it is preferable to use a lithium manganese composite oxide, a lithium-containing cobalt oxide, and a lithium-containing nickel oxide.

It is desirable that the polymer has a binding function in addition to the function of holding the non-aqueous electrolyte. Examples of such a polymer include a polyethylene oxide derivative, a polypropylene oxide derivative, a polymer containing the derivative, a polytetrafluoropropylene, a copolymer of vinylidene fluoride (VdF) and hexafluoropropylene (HFP), and a polyvinylidene fluoride ( PVdF) or the like can be used. As the polymer, one or more kinds selected from the above types can be used. Among them, a VdF-HFP copolymer is preferred.

Examples of the conductive material include artificial graphite, carbon black (eg, acetylene black), nickel powder, and the like. The conductive material includes one or two selected from the above-described types.
More than one species can be used.

Examples of the plasticizer include dibutyl phthalate (DBP), dimethyl phthalate (DMP), and ethyl phthalyl ethyl glycolate (EPEG). As the plasticizer, one or more selected from the above types can be used.

It is preferable to use a porous substrate having a two-dimensional structure as the porous substrate for the positive electrode. Specifically, mesh, expanded metal, punched metal, or the like can be used. Preferably, the porous substrate is formed of, for example, aluminum or an aluminum alloy.

On the other hand, the negative electrode paste is prepared, for example, by mixing an active material, a polymer having a function of holding a non-aqueous electrolyte, and a plasticizer in an organic solvent such as acetone.

Examples of the active material include carbonaceous materials that occlude and release lithium ions. Such carbonaceous materials include, for example, those obtained by firing organic polymer compounds (eg, phenolic resin, polyacrylonitrile, cellulose, etc.), those obtained by firing coke and mesophase pitch, and those made by artificial graphite. And carbonaceous materials represented by natural graphite and the like. Above all, in an inert gas atmosphere such as argon gas or nitrogen gas,
It is preferable to use a carbonaceous material obtained by firing the mesophase pitch at a temperature of 500 ° C to 3000 ° C under normal pressure or reduced pressure.

As the polymer and the plasticizer,
The same one as described for the positive electrode described above can be used.

From the viewpoint of improving the conductivity of the negative electrode, the negative electrode paste desirably contains the same conductive material as that described for the positive electrode.

It is preferable to use a porous substrate having a two-dimensional structure as the porous substrate for the negative electrode. Specifically, mesh, expanded metal, punched metal, or the like can be used. The porous substrate is desirably formed of, for example, copper or a copper alloy.

The paste wraparound prevention sheet can be formed from, for example, a metal such as aluminum or a synthetic resin such as polyethylene terephthalate (PET). Such a sheet may be formed from one type of material, or may have a multilayer structure in which two or more types of sheets are stacked.

The separator not impregnated with the non-aqueous electrolyte is formed by, for example, forming a paste prepared by mixing a polymer having a function of holding the non-aqueous electrolyte and a plasticizer in an organic solvent such as acetone. It is produced by

As the polymer and the plasticizer,
The same one as described for the positive electrode described above can be used.

In the separator, an organic filler or an inorganic filler such as silicon oxide powder may be added to the electrolyte from the viewpoint of further improving the strength.

(Second step) A non-aqueous electrolyte-unimpregnated separator is disposed between the non-aqueous electrolyte-unimpregnated positive electrode and the non-aqueous electrolyte-unimpregnated negative electrode, and these are integrated by, for example, heating and pressing. Obtain a laminate.

(Third Step) The plasticizer is removed from the laminate.

(Fourth Step) The laminate is impregnated with a non-aqueous electrolyte and sealed with an exterior material.

The non-aqueous electrolyte is prepared by dissolving an electrolyte in a non-aqueous solvent.

Examples of the non-aqueous solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and dimethyl carbonate (D
MC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone (γ-
BL), sulfolane, acetonitrile, 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran and the like. The non-aqueous solvents may be used alone or as a mixture of two or more.

Examples of the electrolyte include lithium perchlorate (LiClO ₄ ) and lithium hexafluorophosphate (L
iPF _6), boric tetrafluoride lithium (LiBF _4), lithium hexafluoroarsenate (LiAsF _6), lithium salts such as lithium trifluoromethane sulfonate (LiCF ₃ SO ₃₎ may be mentioned. The electrolytes may be used alone or as a mixture of two or more.

The amount of the electrolyte dissolved in the non-aqueous solvent is desirably 0.2 mol / l to 2 mol / l.

The exterior material desirably has a barrier function against moisture. Examples of such an exterior material include a laminate film in which a heat-fusible resin is disposed at least in a sealing portion and a metal thin film such as aluminum (Al) is interposed inside. Specifically, acid-modified polypropylene (PP) / polyethylene terephthalate (PE) laminated from the sealing portion side to the outer surface
T) / Al foil / PET laminated film; acid-modified P
E / nylon / Al foil / PET laminated film;
Laminated film of ionomer / Ni foil / PE / PET; ethylene vinyl acetate (EVA) / PE / A
1 foil / PET laminated film; ionomer / P
An ET / Al foil / PET laminated film or the like can be used. Here, the film other than the acid-modified PE, the acid-modified PP, the ionomer, and the EVA on the sealing portion side is moisture-proof,
It is responsible for breathability and chemical resistance.

In the method for producing a polymer lithium secondary battery according to the present invention, when a positive electrode not impregnated with a non-aqueous electrolyte is produced by the method using the above-mentioned paste detent sheet, A negative electrode is prepared by applying a negative electrode paste to a metal foil such as a copper foil, drying and applying heat and pressure, or a non-aqueous electrolyte solution not impregnated obtained by forming a negative electrode paste into a film. It is allowed to laminate the negative electrode layer on the metal foil and apply heat and pressure to these layers. Further, the method for producing a polymer lithium secondary battery according to the present invention, in the case where the non-aqueous electrolyte non-impregnated negative electrode is produced by the method using the above-described paste detent prevention sheet, the non-aqueous electrolyte non-impregnated positive electrode, Apply positive electrode paste to metal foil such as aluminum foil, dry,
It is produced by applying heat and pressure or by laminating a non-aqueous electrolyte unimpregnated positive electrode layer obtained by forming a positive electrode paste on the metal foil, and applying heat and pressure to these. Allow to do.

As described in detail above, according to the method for manufacturing a polymer lithium secondary battery according to the present invention, at least one of the positive electrode and the negative electrode is provided with a polymer having a function of retaining a non-aqueous electrolyte and an active material. Is applied to a porous substrate disposed on the upper surface of the paste wraparound prevention sheet.

When the paste is applied to the porous substrate, the paste flows into the holes of the porous substrate because of the fluidity of the paste. However, the paste is blocked by the paste wrap-around preventing sheet disposed on the lower surface of the porous substrate, so that the paste is applied. Adhesion to the surface opposite to the application surface of the porous substrate can be prevented, and the applied thickness of the paste can be made uniform. As a result, the active material filling density can be made uniform, so that the discharge capacity under a high load can be improved.

[0050]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described below in detail with reference to the drawings.

(Example) <Preparation of a positive electrode not impregnated with a non-aqueous electrolyte> A lithium manganese composite oxide having a composition formula of LiMn ₂ O ₄ as an active material was 56% by weight, and carbon black was 5% by weight. And vinylidene fluoride-hexafluoropropylene (VdF-H) as a polymer having a function of retaining a non-aqueous electrolyte.
A paste was prepared by mixing 17% by weight of the copolymer powder of FP) and 22% by weight of dibutyl phthalate (DBP) in acetone.

The paste P is supplied to the paste storage container 5 of the coating apparatus with a drying oven shown in FIG. 1 and the polyethylene terephthalate having a thickness of 50 μm as the paste wraparound sheet 7 as shown in FIG. On the upper surface of the (PET) sheet, as a porous substrate 8, a band-shaped laminate 9 made of a material in which aluminum expanded metal (thickness: 20 μm, porosity: 60%) is closely arranged is unwound from the roller 3 to the back. The paste P was conveyed to the roll 1 and adhered to the porous substrate 8 of the band-shaped laminate 9. Although the paste P flows into the through-holes 10 of the porous substrate 8 because it has fluidity, the paste P is blocked by the paste wrap-around prevention sheet 7 closely arranged on the lower surface of the porous substrate 8, so that the paste P Adhesion to the lower surface of the porous substrate 8 was prevented. Next, the thickness of the paste P attached to the upper surface of the porous substrate 8 was reduced to 200 μm by passing the band-shaped laminate 9 to which the paste P was attached through a slit formed by the back roll 1 and the doctor blade 2. The thickness was uniform. The paste-applied strip-shaped laminate 9 is placed in a drying oven 6.
The positive electrode layer not impregnated with the nonaqueous electrolyte was transported to the next step by the winding-side free roller 4 as a porous substrate held on one side.

Next, the paste was applied to the surface of the porous substrate on which the positive electrode layer was not formed so that the thickness after drying was 200 μm, and the paste was dried. Subsequently, a positive electrode not impregnated with a non-aqueous electrolyte was produced by pressing with a hot roll.

<Production of Negative Electrode Impregnated with Nonaqueous Electrolyte> Mesophase pitch carbon fiber was 58% by weight as an active material, and VdF-
17% by weight of HFP copolymer powder and 25% by weight of dibutyl phthalate (DBP) were mixed in acetone to prepare a paste.

The paste P is supplied to the paste storage container 5 of the coating apparatus with a drying oven shown in FIG. 1 and the polyethylene terephthalate having a thickness of 50 μm as the paste wraparound sheet 7 as shown in FIG. (PET) On the upper surface of the sheet, a copper expanded metal (thickness 30 μm, porosity 6
(0%) was conveyed from the unwinding roller 3 to the back roll 1 and the paste P was adhered onto the porous substrate 8 of the band-shaped laminate 9. Although the paste P flows into the through-holes 10 of the porous substrate 8 because it has fluidity, the paste P is blocked by the paste wrap-around prevention sheet 7 closely arranged on the lower surface of the porous substrate 8, so that the paste P Adhesion to the lower surface of the porous substrate 8 was prevented. Next, the thickness of the paste P attached to the upper surface of the porous substrate 8 was reduced to 200 μm by passing the band-shaped laminate 9 to which the paste P was attached through a slit formed by the back roll 1 and the doctor blade 2. The thickness was uniform.
The paste-applied strip-shaped laminate 9 was dried in a drying furnace 6 and transported to the next step by the winding-side free roller 4 as a porous substrate having a non-aqueous electrolyte-unimpregnated negative electrode layer held on one surface.

Next, the paste was applied to the surface of the porous substrate on which the negative electrode layer had not been formed so that the thickness after drying was 200 μm, and dried. Subsequently, a non-aqueous electrolyte-unimpregnated negative electrode was prepared by pressing with a hot roll.

<Preparation of Separator Impregnated with Nonaqueous Electrolyte>
Vd as a polymer having a function of retaining a non-aqueous electrolyte
22.2 parts by weight of F-HFP copolymer powder, 44.5 parts by weight of dibutyl phthalate (DBP), and silicon oxide powder 3
3.3 parts by weight were mixed in acetone to prepare a paste. The paste was applied on a PET film and dried to prepare a non-aqueous electrolyte non-impregnated separator having a thickness of 100 μm.

<Preparation of Nonaqueous Electrolyte> A nonaqueous solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of 2: 1 was mixed with LiPF ₆ as an electrolyte at a concentration of 1 mol / mol. 1 to prepare a non-aqueous electrolyte.

<Battery Assembly> A positive electrode not impregnated with a non-aqueous electrolyte was
Sheets, one negative electrode not impregnated with the non-aqueous electrolyte and two separators not impregnated with the non-aqueous electrolyte were prepared, and these were stacked so that the separator was interposed between the positive electrode and the negative electrode. It was integrated by applying heat and pressure with a rigid roll. After removing the DBP from the obtained laminate and drying, impregnated with a non-aqueous electrolyte having the above composition, laminated from the outermost layer in order of polyethylene terephthalate (PET) film, aluminum foil and heat-fusible resin film. Sealing with a packaging material made of a laminated film having the structure shown in FIG. 4 and FIG.
A 10 mAh polymer lithium secondary battery was manufactured.

That is, the polymer lithium secondary battery is
Positive electrode 21, negative electrode 22, positive electrode 21 and negative electrode 2
A power generating element mainly composed of a unit integrated with a separator 23 disposed between the two. The positive electrode 21 includes a porous substrate 24 and a positive electrode layer 25 adhered to both surfaces of the porous substrate 24. On the other hand, the negative electrode 22 includes a porous substrate 26 and a negative electrode layer 27 adhered to both surfaces of the porous substrate 26. The strip-shaped positive electrode terminal 28 is obtained by extending the porous substrate 24 of each of the positive electrodes 21 into a strip shape. On the other hand, the strip-shaped negative electrode terminal 29 is obtained by extending the porous substrate 26 of the negative electrode 22 into a strip shape. For example, a positive electrode lead 30 made of a strip-shaped aluminum plate is connected to the two positive electrode terminals 28. For example, a negative electrode lead 31 made of a strip-shaped copper plate is connected to the negative electrode terminal 29. The power generating element having such a configuration is hermetically sealed in a state in which the positive electrode lead 30 and the negative electrode lead 31 extend from the exterior material 32 in an exterior material 32 having a barrier function against moisture.

(Comparative Example) <Preparation of positive electrode not impregnated with non-aqueous electrolyte> A paste similar to that described in the above-described embodiment is supplied to a paste container of a coating apparatus with a drying oven, and the above-described embodiment is used. Only the porous substrate similar to that described in the above section was unwound and transported from the roller to the back roll, and the paste was adhered onto the porous substrate. The paste adhered to the lower surface of the porous substrate through the through holes of the porous substrate to have fluidity. Next, when the porous substrate to which the paste was adhered was passed through a slit formed by a back roll and a doctor blade, the paste applied thickness at a portion corresponding to the lower surface where the paste was not adhered was 200 μm.
However, the thickness of the paste applied at the portion corresponding to the lower surface where the paste was adhered became thinner than 200 μm. The paste-coated porous substrate was dried in a drying oven, and transported to the next step by a winding-side free roller as a porous substrate having a nonaqueous electrolyte-unimpregnated positive electrode layer held on one surface.

Next, the paste was applied to the surface of the porous substrate on which the positive electrode layer was not formed so as to have a thickness of 200 μm, and dried. Subsequently, a positive electrode not impregnated with a non-aqueous electrolyte was produced by pressing with a hot roll.

<Preparation of Negative Electrode Unimpregnated with Non-Aqueous Electrolyte> A paste similar to that described in the above-described embodiment is supplied to a paste container of a coating device with a drying oven, and the paste described in the above-described embodiment is used. Only the same porous substrate as in Example 1 was fed from the unwinding roller to the back roll, and the paste was adhered onto the porous substrate. The paste adhered to the lower surface of the porous substrate through the through holes of the porous substrate to have fluidity. Next, when the porous substrate to which the paste was adhered was passed through a slit formed by a back roll and a doctor blade, the paste application thickness at a portion corresponding to the lower surface where the paste was not adhered was 200 μm. The thickness of the paste applied at the portion corresponding to the lower surface where the paste was attached became thinner than 200 μm. The paste-coated porous substrate was dried in a drying oven and transported to the next step by a winding-side free roller as a porous substrate having a nonaqueous electrolyte-impregnated negative electrode layer held on one surface.

Next, the paste was applied to the surface of the porous substrate on which the negative electrode layer was not formed so that the thickness became 200 μm, and dried. Subsequently, a non-aqueous electrolyte-unimpregnated negative electrode was prepared by pressing with a hot roll.

<Battery assembly> The positive electrode not impregnated with the non-aqueous electrolyte was
Sheets, one non-aqueous electrolyte-unimpregnated negative electrode and two non-aqueous electrolyte-unimpregnated separators similar to those described in the above-described examples were prepared, and these were placed between the positive electrode and the negative electrode. The layers were laminated with a separator interposed therebetween, and were integrated by applying heat and pressure with a heated rigid roll. After removing the DBP from the obtained laminate and drying it, the laminate was impregnated with a non-aqueous electrolyte having the same composition as described in the above-described embodiment, and the same exterior material as described in the above-described embodiment. Then, a polymer lithium secondary battery having the above-described structure shown in FIGS. 4 and 5 and having a theoretical capacity of 110 mAh was manufactured.

The obtained secondary batteries of Examples and Comparative Examples were charged to 4.5 V at a current of 0.2 C, and then charged at a current of each rate (0.2 C, 0.5 C or 1.0 C). The discharge capacity at the time of discharging to 0.0 V was measured, and the results are shown in Table 1 below, where the discharge capacity at 0.2 C is expressed as 100.

[0067]

[Table 1]

As is clear from Table 1, the secondary battery of the embodiment in which the positive electrode and the negative electrode are manufactured by a method including the step of applying the paste to the porous substrate disposed on the upper surface of the paste rotation preventing sheet is used. The discharge capacity when discharged at a higher rate (higher load) compared to the secondary battery of the comparative example in which a positive electrode and a negative electrode are produced by a method including a step of applying a paste to a porous substrate without using a stopper sheet. It can be seen that the decrease can be suppressed.

In the above-described embodiment, the positive electrode,
An example in which a five-layer power generation element in which an electrolyte layer, a negative electrode, an electrolyte layer, and a positive electrode are stacked in this order has been described. However, the present invention is not limited thereto.
A power generation element having a layered structure may be used.

[0070]

As described above in detail, according to the present invention, there is provided a method for producing a polymer lithium secondary battery in which at least one of the positive electrode and the negative electrode is prepared by a method including a step of applying a paste to a porous substrate. In the method, remarkable effects such as improvement of the discharge capacity under a high load can be obtained.

[Brief description of the drawings]

FIG. 1 is a side view showing a coating / drying step in a method for producing a polymer lithium secondary battery according to the present invention.

FIG. 2 is an enlarged sectional view showing a portion A in FIG.

FIG. 3 is an enlarged sectional view showing a portion B in FIG. 1;

FIG. 4 is a plan view showing a polymer lithium secondary battery of an example.

FIG. 5 is a sectional view showing the polymer lithium secondary battery of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Back roll, 2 ... Doctor blade, 3 ... Unwinding side free roller, 4 ... Winding side free roller, 5 ... Paste storage container, 6 ... Drying furnace, 9 ... Strip laminate.

Claims (1)

[Claims] At least one of a positive electrode and a negative electrode applies a paste containing a polymer having a function of holding a non-aqueous electrolyte and an active material to a porous substrate disposed on an upper surface of a paste wraparound prevention sheet. A method for producing a polymer lithium secondary battery, wherein the method is produced by a method including a step.