JP2001085060A - Electrochemical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemical device having enhanced capacity with improved maintaining rate during the charging-discharging cycles. SOLUTION: The electrochemical device is equipped with at least one of the electrodes 1 and 2 furnished with electrode layers 5 and 7 containing a resin including vinylidene fluoride(VdF) component and a non-aqueous electrolytic solution retained by the resin and electricity collectors 4 and 6 whereby the electrode layers are carried and a separator 3 containing resin including vinylidene fluoride(VdF) component and non-aqueous electrolytic solution retained by the resin, wherein the resin melt viscosity at 230 deg.C/100 s-1 of at least one of the electrodes is 5000 Pa.sec or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrochemical device such as a polymer lithium secondary battery and an electric double layer capacitor.

[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.

Meanwhile, in order to further reduce the weight and size of the secondary battery, for example, US Pat.
As disclosed in US Patent No. 6,318, a polymer lithium secondary battery has been developed. A polymer lithium secondary battery includes a positive electrode having a structure in which a positive electrode layer containing an active material, a non-aqueous electrolyte, and a polymer holding the electrolyte is supported on a current collector, an active material, a non-aqueous electrolyte, and the electrolyte. A negative electrode having a structure in which a negative electrode layer containing a polymer holding
A separator comprising a non-aqueous electrolyte and an electrolyte sheet containing a polymer holding the electrolyte, the separator being provided between the positive and negative electrodes; This polymer lithium secondary battery contains substantially no liquid component because the non-aqueous electrolyte is held by the polymer, and since the positive and negative electrodes and the separator are integrated, the exterior material is like a laminate film. Simple simple ones can be used. For this reason, the secondary battery has features of being thin, lightweight, and excellent in safety.

[0005]

In this polymer lithium secondary battery, a copolymer of vinylidene fluoride (VdF) and hexafluoropropylene (HFP) is used as a polymer for holding a non-aqueous electrolyte. ing. Although this copolymer has a high non-aqueous electrolyte retention power, it is difficult to keep the positive electrode layer (or the negative electrode layer) and the positive electrode current collector (or the negative electrode current collector) in close contact with each other. When this is repeated, the positive electrode layer is separated from the positive electrode current collector, and the negative electrode layer is separated from the negative electrode current collector. As a result, there is a problem that the charge / discharge cycle life is short because the internal resistance increases with the progress of the charge / discharge cycle.
The reduction in cycle life is more remarkable when a film-made exterior material is used.

An object of the present invention is to provide an electrochemical device having an improved capacity retention during a charge / discharge cycle.

[0007]

According to the present invention, there is provided an electrochemical device comprising: a resin containing a vinylidene fluoride (VdF) component; an electrode layer containing a non-aqueous electrolyte held by the resin; At least one electrode having a current collector to be used, and vinylidene fluoride (Vd
F) In an electrochemical device comprising a resin containing a component and a separator containing a non-aqueous electrolyte held by the resin, at least one of the electrodes has a melt viscosity of the resin (230 ° C./100 s ^{−). 1} ) is 5000 Pa
/ Sec or more.

According to the present invention, a positive electrode layer containing a resin containing a vinylidene fluoride (VdF) component, a non-aqueous electrolyte held by the resin, and a positive electrode current collector carrying the positive electrode layer are provided. A negative electrode comprising a negative electrode layer containing a resin containing a vinylidene fluoride (VdF) component and a non-aqueous electrolyte held by the resin, and a negative electrode current collector carrying the negative electrode layer; A resin containing a vinylidene fluoride (VdF) component and a separator containing a non-aqueous electrolyte held by the resin; The resin has a melt viscosity (230
(° C./100 s ⁻¹ ) is 5000 Pa / sec or more.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electrochemical device according to the present invention will be described using a polymer lithium secondary battery as an example.

The polymer lithium secondary battery comprises a binder containing a resin containing a vinylidene fluoride (VdF) component, a positive electrode layer containing a non-aqueous electrolyte held (or impregnated) in the resin, and a positive electrode layer containing the nonaqueous electrolyte. And a positive electrode provided with a positive electrode current collector carrying vinylidene fluoride (VdF)
A negative electrode including a binder containing a resin containing a component and a negative electrode layer containing a non-aqueous electrolyte held (or impregnated) in the resin, and a negative electrode current collector on which the negative electrode layer is supported; A power generating element disposed between the negative electrodes and having a resin containing a vinylidene fluoride (VdF) component and a separator containing a non-aqueous electrolyte held (or impregnated) in the resin; an exterior in which the power generating element is housed Material.

In the power generating element, the positive electrode, the negative electrode, and the separator are integrated. The resin of at least one of the positive electrode and the negative electrode has a melt viscosity (viscosity at 230 ° C. when a shear rate of 100 s ⁻¹ is applied) of 5000 Pa / sec or more.

The positive electrode, the negative electrode, the separator, and the exterior material will be described.

(1) Positive Electrode In this positive electrode, the positive electrode layer comprises a positive electrode active material, a binder containing a resin containing a vinylidene fluoride (VdF) component, and a non-aqueous electrolyte held or impregnated in the resin. including.

Examples of the positive electrode active material include various oxides (eg, lithium-manganese composite oxide such as LiMn ₂ O ₄ , manganese dioxide, lithium-containing nickel oxide such as LiNiO _2, and lithium-containing cobalt oxide such as LiCoO ₂ , for example). Oxide, lithium-containing nickel-cobalt oxide, lithium-containing amorphous vanadium pentoxide and the like, and chalcogen compounds (for example, titanium disulfide and molybdenum disulfide). Among them, it is preferable to use a lithium manganese composite oxide, a lithium-containing cobalt oxide, and a lithium-containing nickel oxide.

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

As the resin containing the VdF component, for example, a resin containing VdF as one component such as a copolymer of vinylidene fluoride (VdF) and hexafluoropropylene (HFP), or polyvinylidene fluoride ( PVdF) can be used alone or in combination of two or more. Among them, a VdF-HFP copolymer is preferred. In the copolymer, VdF contributes to the improvement of the mechanical strength in the skeleton of the copolymer, and HFP is incorporated in the copolymer in an amorphous state, and the non-aqueous electrolyte is retained and the non-aqueous electrolyte is retained. It functions as a lithium ion transmission part.

The resin containing the VdF component has a melt viscosity (230 ° C./100 s ⁻¹ ) of 5000 Pa / sec or more. The melt viscosity varies depending on the molecular weight of the resin and the branched structure of the resin. The melt viscosity is 50
When it is less than 00 Pa / sec, the resin strength is extremely reduced by holding or impregnating the non-aqueous electrolyte, and the solvent resistance (non-aqueous electrolyte resistance) at high temperatures is reduced. as a result,
When the charge / discharge cycle is repeated, the positive electrode layer is separated from the positive electrode current collector, so that the internal resistance increases and the cycle life is shortened. More preferably, the melt viscosity is 6000 Pa / sec or more. The upper limit of the melt viscosity is preferably set to 10,000 Pa / sec. When the melt viscosity is higher than 10,000 Pa / sec,
There is a possibility that the preparation of the paste (dissolution of the VdF component-containing resin) in the production of the positive electrode, which will be described later, becomes difficult, or the cost of synthesizing the VdF component-containing resin increases, which may cause problems.

The resin containing the VdF component preferably has a content of the VdF component in the range of 88 to 95 mol%. This is due to the following reasons. If the content is less than 88 mol%, the resin is likely to swell when impregnated with a non-aqueous electrolyte, which may make it difficult to sufficiently suppress an increase in internal resistance during a charge / discharge cycle. On the other hand, when the content exceeds 95 mol%,
Since the non-aqueous electrolyte holding amount of the resin decreases, the internal resistance may increase from the beginning of the charge / discharge cycle. A more preferred range is 90 to 93 mol%.

The positive electrode layer may contain VdF component-containing resins having different melt viscosities, or may contain VdF component-containing resins having different VdF component contents.

The content of the VdF component-containing resin in the positive electrode layer is preferably in the range of 3 to 15% by weight.

[0024] The positive electrode layer may further contain a conductive material from the viewpoint of improving conductivity. Examples of the conductive material include artificial graphite, carbon black (eg, acetylene black), nickel powder, and the like.

As the current collector, for example, a mesh,
A material having a porous structure such as expanded metal or punched metal, or a metal plate can be used.
Preferably, the current collector is made of aluminum or an aluminum alloy.

The VdF component-containing resin in the negative electrode layer has a melt viscosity (230 ° C./100 s ⁻¹ ) of 5000 Pa / sec.
c or more, the melt viscosity (230 ° C./100 s ⁻¹ ) of the VdF component-containing resin in the positive electrode layer is 5000 Pa / s.
It may be less than ec. In addition, the melt viscosity is 5000P
Even if it is less than a / sec, the content of the VdF component in the resin is 88 to 95 mol for the same reason as described above.
% Is preferable.

(2) Negative Electrode In the negative electrode, the negative electrode layer comprises a negative electrode active material, a binder containing a resin containing a vinylidene fluoride (VdF) component, and a non-aqueous electrolyte held or impregnated in the resin. including.

Examples of the negative electrode 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. Among them, it is preferable to use a carbonaceous material obtained by firing the mesophase pitch at a temperature of 500 ° C. to 3000 ° C. in an inert gas atmosphere such as an argon gas or a nitrogen gas under normal pressure or reduced pressure.

As the non-aqueous electrolyte, those similar to those described above for the positive electrode are used.

As the resin containing the VdF component, the same types of resins as those described above for the positive electrode can be used alone or in combination. Among them, VdF-H
FP copolymers are preferred.

The resin containing the VdF component has a melt viscosity (230 ° C./100 s ⁻¹ ) of 5000 Pa / sec or more. When the melt viscosity is less than 5000 Pa / sec, the charge / discharge cycle is repeated, so that the negative electrode layer is separated from the negative electrode current collector, so that the internal resistance increases and the cycle life is shortened. More preferably, the melt viscosity is 6000 Pa / sec or more. The upper limit of the melt viscosity is preferably set to 10,000 Pa / sec. When the melt viscosity is higher than 10,000 Pa / sec, the paste preparation (Vd
F component-containing resin) or VdF
There is a possibility that problems such as an increase in the synthesis cost of the component-containing resin may occur.

The resin containing the VdF component preferably has a content of the VdF component in the range of 88 to 95 mol%. This is due to the following reasons. If the content is less than 88 mol%, the resin is likely to swell when impregnated with a non-aqueous electrolyte, which may make it difficult to sufficiently suppress an increase in internal resistance during a charge / discharge cycle. On the other hand, when the content exceeds 95 mol%,
Since the non-aqueous electrolyte holding amount of the resin decreases, the internal resistance may increase from the beginning of the charge / discharge cycle. A more preferred range is 90 to 93 mol%.

The negative electrode layer may contain VdF component-containing resins having different melt viscosities, or may contain VdF component-containing resins having different VdF component contents.

The content of the VdF component-containing resin in the negative electrode layer is preferably in the range of 3 to 15% by weight.

As the current collector, for example, a mesh,
A material having a porous structure such as expanded metal or punched metal, or a metal plate can be used.
Preferably, the current collector is formed of copper or a copper alloy.

The VdF component-containing resin in the positive electrode layer has a melt viscosity (230 ° C./100 s ⁻¹ ) of 5000 Pa / sec.
c or more, the melt viscosity (230 ° C./100 s ⁻¹ ) of the VdF component-containing resin in the negative electrode layer is set to 5000 Pa / s.
It may be less than ec. The melt viscosity is 5000 Pa
/ Sec, the content of the VdF component in the resin is 88 to 95 mol% for the same reason as described above.
Is preferably within the range.

(3) Separator This separator is made of vinylidene fluoride (VdF).
It includes a resin containing components and a non-aqueous electrolyte held or impregnated in the resin.

Examples of the nonaqueous electrolyte include the same ones as described for the positive electrode.

As the resin containing the VdF component, the same kinds of resins as those described for the positive electrode described above can be used alone or in combination. Among them, VdF-H
FP copolymers are preferred.

The resin containing the VdF component has a melt viscosity (230 ° C./100 s ⁻¹ ) of 1000 to 3000 Pa /
sec. The melt viscosity is 1
When it is less than 000 Pa / sec, the positive electrode and the negative electrode are easily peeled off from the separator when the charge / discharge cycle is repeated, so that it may be difficult to sufficiently suppress an increase in the internal resistance during the charge / discharge cycle. On the other hand, if the melt viscosity exceeds 3,000 Pa / sec, the lithium ion conductivity of the separator decreases, and the internal resistance may increase from the beginning of the charge / discharge cycle. A more preferable range of the melt viscosity is 1500 to 2500 Pa / s.
ec.

The resin containing the VdF component preferably has a VdF component content of 88 to 95 mol%. This is due to the following reasons. If the content is less than 88 mol%, the resin is likely to swell when impregnated with a non-aqueous electrolyte, which may make it difficult to sufficiently suppress an increase in internal resistance during a charge / discharge cycle. On the other hand, when the content exceeds 95 mol%,
Since the non-aqueous electrolyte holding amount of the resin decreases, the internal resistance may increase from the beginning of the charge / discharge cycle. A more preferred range is 90 to 93 mol%.

The separator has Vd having different melt viscosities.
It may contain an F component-containing resin, or may contain VdF component-containing resins having different VdF component contents.

The content of the resin containing the VdF component in the separator is preferably in the range of 30 to 70% by weight.

It is preferable that the separator further includes a reinforcing material. As the reinforcing material, for example, one or more kinds selected from silicon oxide (SiO ₂ ), mica group, alumina and the like can be used. The form of the reinforcing material is particulate,
It can be fibrous or scaly. Further, for example, two or more kinds having different forms such as particles and fibers may be mixed and used.

(4) Exterior material As the exterior material, it is preferable to use a film having a barrier function against moisture. Examples of such a film-made exterior material include a laminated 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, a laminated film of acid-modified polypropylene (PP) / polyethylene terephthalate (PET) / Al foil / PET laminated from the sealing portion side to the outer surface; a laminated film of acid-modified PE / nylon / Al foil / PET A laminate film of ionomer / Ni foil / PE / PET; ethylene vinyl acetate (EV
A) A laminated film of / PE / Al foil / PET; an ionomer / PET / 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 has moisture resistance, gas permeability, and chemical resistance.

The polymer lithium secondary battery according to the present invention can be manufactured, for example, by the method described below. First, a positive electrode, a negative electrode and a separator not impregnated with a non-aqueous electrolyte are prepared by a method described below.

The positive electrode not impregnated with the nonaqueous electrolyte is, for example, a paste prepared by mixing an active material, a binder containing a resin containing a VdF component, a conductive material, and a plasticizer in an organic solvent such as acetone. To form a positive electrode sheet, the obtained positive electrode sheet is laminated on a current collector, and heated and pressurized to fuse the positive electrode sheet to the current collector. Alternatively, the positive electrode may be manufactured by applying the paste to a current collector, drying the paste, and applying heat and pressure.

The negative electrode not impregnated with the non-aqueous electrolyte is formed, for example, by forming a paste prepared by mixing an active material, a binder containing a resin containing a VdF component, and a plasticizer in an organic solvent such as acetone. Then, a negative electrode sheet is prepared, and the obtained negative electrode sheet is laminated on a current collector, and heated and pressed to fuse the negative electrode sheet to the current collector. Alternatively, the paste may be applied to a current collector, dried, and then heated and pressed to produce the negative electrode.

The separator not impregnated with the non-aqueous electrolyte is prepared by, for example, mixing a resin containing a VdF component, a plasticizer, and a reinforcing material in an organic solvent such as acetone to prepare a paste and forming a film.

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.

Subsequently, a non-aqueous electrolyte-unimpregnated separator is placed between the non-aqueous electrolyte-unimpregnated positive electrode and the non-aqueous electrolyte-unimpregnated negative electrode, and then heated and pressurized to integrate them. To produce a laminate. Next, after removing the plasticizer from the laminate by, for example, solvent extraction, the laminate is impregnated with a non-aqueous electrolyte and sealed with an exterior material to obtain a polymer lithium secondary battery according to the present invention.

The electrochemical device according to the present invention described in detail above carries a resin containing a vinylidene fluoride (VdF) component, an electrode layer containing a non-aqueous electrolyte held by the resin, and the electrode layer. At least one electrode provided with a current collector, and vinylidene fluoride (Vd
F) a resin containing the component and a separator containing a non-aqueous electrolyte held by the resin, wherein at least one of the electrodes has a melt viscosity (230 ° C./1
00s ^-1 ) is 5000 Pa / sec or more. Since the resin having such a melt viscosity has a high molecular weight and a structure having many branches, the resin has low fluidity. As a result, the adhesion between the electrode layer and the current collector can be improved, so that the electrode layer can be prevented from peeling off from the current collector when charge and discharge are repeated. For this reason, an increase in internal resistance can be suppressed, and the capacity retention rate during charging and discharging can be improved. In addition, since the electrode layer does not peel from the current collector even when a film-made exterior material is used, the use of a film-made exterior material is possible, and the electrochemical device is thin and has a high capacity retention rate during charge and discharge. It becomes possible to realize the device.

In the electrochemical device according to the present invention,
Melt viscosity of the resin in the separator (230 ° C./1
00s ^-1 ) of 1000 to 3000 Pa / sec, the lithium ion conductivity of the separator can be improved while maintaining the adhesion between the separator and the electrode. Therefore, the initial internal resistance can be reduced. Can,
The capacity retention rate during charge / discharge can be further improved.

[0054]

Embodiments of the present invention will be described below in detail.

(Examples 1 to 23 and Comparative Examples) <Preparation of positive electrode not impregnated with nonaqueous electrolyte> 70% by weight of a lithium-cobalt composite oxide represented by a composition formula of LiCoO ₂ as an active material, and the following Table 1 Melt viscosity and copolymerization ratio ΔV / H; V is vinylidene fluoride (CH ₂ —CF ₂ )
8% by weight of a VdF-HFP copolymer powder having a mole ratio (mol%) of H, and H being a mole ratio (mol%) of hexafluoropropylene {CF ₂ -CF (CF ₃ )}. 7% by weight and dibutyl phthalate (DB
P) was mixed in acetone with 15% by weight to prepare a paste. The resulting paste is placed on a PET film for 160
g / m ^2, and dried to produce a non-aqueous electrolyte-unimpregnated positive electrode sheet. The obtained positive electrode sheet is placed on both sides of a current collector made of expanded metal made of aluminum (thickness converted into aluminum foil is 30 μm and porosity is 60%), and is pressed with a rigid roll heated to 140 ° C. Thus, a positive electrode not impregnated with a non-aqueous electrolyte was prepared.

<Preparation of Negative Electrode Impregnated with Nonaqueous Electrolyte> 70% by weight of mesophase pitch carbon fiber as an active material, melt viscosity and copolymerization ratio ΔV / H shown in Table 1 below, where V is the mole of vinylidene fluoride Ratio (mol%), H indicates the molar ratio (mol%) of hexafluoropropylene VdF of｝
A paste was prepared by mixing 9% by weight of -HFP copolymer powder and 18% by weight of dibutyl phthalate (DBP) in acetone. Put the obtained paste on PET film
The coating was applied so as to be 60 g / m ^2, and dried to prepare a non-aqueous electrolyte-unimpregnated negative electrode sheet. The obtained negative electrode sheet is made of a copper expanded metal (having a thickness of 30 μm in terms of copper foil).
m, and a negative electrode not impregnated with a non-aqueous electrolyte was prepared by placing the collector on both sides of a current collector having a porosity of 60%) and pressing with a rigid roll heated to 140 ° C.

<Preparation of Separator Impregnated with Nonaqueous Electrolyte>
The melt viscosity and copolymerization ratio shown in Table 1 below (V / H; V is the molar ratio of vinylidene fluoride (mol%), H is the molar ratio of hexafluoropropylene (mol%)) V
30 parts by weight of the dF-HFP copolymer powder, 30 parts by weight of the silicon oxide powder, and 40 parts by weight of dibutyl phthalate (DBP) were mixed in acetone to prepare a paste. The resulting paste is dried on a PET film to a thickness of 50
The resultant was coated so as to have a thickness of μm and dried to prepare a non-aqueous electrolyte-unimpregnated separator.

<Preparation of Nonaqueous Electrolyte> A nonaqueous solvent in which ethylene carbonate (EC) and dimethyl carbonate (MEC) 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
Sheet, one sheet of non-aqueous electrolyte unimpregnated negative electrode and two sheets of non-aqueous electrolyte unimpregnated separator were prepared, and these were laminated so that the separator was interposed between the positive electrode and the negative electrode. The positive and negative electrodes and the separator are fused by applying heat and pressure with a rigid roll heated to
A power generation element not impregnated with a non-aqueous electrolyte was obtained.

DBP was removed from this power generating element by solvent extraction with methanol until the DBP concentration in methanol became 20 ppm or less, and then dried. Then, after connecting the positive and negative electrode leads to the power generating element, it is immersed in a non-aqueous electrolytic solution having the above composition for 30 minutes, and laminated from the outermost layer in order of a polyethylene terephthalate (PET) film, an aluminum foil and a heat-fusible resin film. 1 and 2 by sealing with an exterior material made of a laminated film.
And a capacity of 100 mAh was manufactured.

That is, the polymer lithium secondary battery is
A power generating element mainly includes a positive electrode 1, a negative electrode 2, and an electrolyte layer 3 disposed between the positive electrode 1 and the negative electrode 2. The positive electrode 1 includes a porous current collector 4
And a positive electrode layer 5 adhered to both surfaces of the current collector 4. On the other hand, the negative electrode 2 includes a porous current collector 6 and a negative electrode layer 7 bonded to both surfaces of the current collector 6. The strip-shaped positive electrode terminal 8 is obtained by extending the current collector 4 of each of the positive electrodes 1 in a strip shape. On the other hand, the strip-shaped negative electrode terminal 9 is obtained by extending the current collector 6 of the negative electrode 2 in a strip shape. For example, a positive electrode lead 10 made of a strip-shaped aluminum plate is connected to the two positive electrode terminals 8. For example, a negative electrode lead 11 made of a strip-shaped copper plate is connected to the negative electrode terminal 9. The power generating element having such a configuration is hermetically sealed in a state in which the positive electrode lead 10 and the negative electrode lead 11 extend from the exterior material 12 within an exterior material 12 having a barrier function against moisture.

(Example 24) <Preparation of positive electrode not impregnated with non-aqueous electrolyte> A lithium-cobalt composite oxide having a composition formula of LiCoO ₂ as an active material of 70% by weight and a melt viscosity shown in Table 1 below were obtained. 8% by weight of polyvinylidene fluoride powder and 7% of carbon black
% By weight and 15% by weight of dibutyl phthalate (DBP) were mixed in acetone to prepare a paste. The obtained paste was applied on a PET film so as to be 160 g / m ^2, and dried to produce a positive electrode sheet not impregnated with a non-aqueous electrolyte. The obtained positive electrode sheet is made of expanded metal made of aluminum (having a thickness of 30 μm in terms of aluminum foil).
In this case, the porosity is 60%).
A positive electrode not impregnated with a non-aqueous electrolyte was produced by pressing with a rigid roll heated to 160 ° C.

<Production of Negative Electrode Impregnated with Nonaqueous Electrolyte> 70% by weight of mesophase pitch carbon fiber as an active material, 9% by weight of polyvinylidene fluoride powder having a melt viscosity shown in Table 1 below, and dibutyl phthalate ( DBP) was mixed in acetone at 18% by weight to prepare a paste. The obtained paste was applied on a PET film so as to be 160 g / m ^2, and dried to prepare a non-aqueous electrolyte-unimpregnated negative electrode sheet. The obtained negative electrode sheet is made of a copper expanded metal (thickness converted to copper foil is 30 μm and porosity is 60%)
A negative electrode not impregnated with a non-aqueous electrolyte was prepared by disposing on both sides of a current collector composed of and pressing with a rigid roll heated to 150 ° C.

<Preparation of Non-Aqueous Electrolyte-Unimpregnated Separator>
30 parts by weight of polyvinylidene fluoride powder having a melt viscosity shown in Table 1 below, 30 parts by weight of silicon oxide particles, and 40 parts by weight of dibutyl phthalate (DBP) were mixed in acetone to prepare a paste. The obtained paste was applied on a PET film so as to have a thickness after drying of 50 μm, and dried to prepare a non-aqueous electrolyte-unimpregnated separator.

A polymer lithium secondary battery was manufactured in the same manner as in Example 1 except that the obtained positive electrode, negative electrode and separator were used.

The melt viscosity of the VdF-HFP copolymer and the polyvinylidene fluoride was 100 seconds at 230 ° C.
^This is the viscosity when a shear rate of ^-1 is added.

After charging the obtained secondary batteries of Examples 1 to 24 and Comparative Example to 4.2 V at 1.0 C,
A charge / discharge cycle test in which the battery was discharged to 3.0 V at 1.0 C was performed, and the capacity retention ratio at every 50 cycles was compared with the discharge capacity at the first cycle being 100. The results are shown in Table 2 below and FIG.

The secondary batteries of Examples 1 to 24 and Comparative Example were charged at 0.2 C and the battery voltage was 4.2.
After measuring the AC resistance (1 kHz) at the point of V, the battery was charged to 4.2 V at 1.0 C and then at 1.0 C,
A charge / discharge cycle test for discharging to 3.0 V was performed and 50
The AC resistance for each cycle was measured, and the results are shown in Table 3 below and FIG.

Further, the degree of swelling of the VdF-HFP copolymer and polyvinylidene fluoride was measured by the following method, and the results are shown in Table 4 below. Table 4 shows the VdF component content and melt viscosity (230 ° C./100
s ^-1 ).

That is, each resin is dissolved in a solvent and cast to prepare four types of test sheets. LiBF ₄ is dissolved in a solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) are mixed at a volume ratio of 2: 1 to a concentration of 1 mol / l to prepare a test solution. Each test sheet is immersed in 1 L of the test solution for 1 hour at 25 ° C. After immersion, the weight of each test sheet is measured. Next, each test sheet is washed with alcohol, and it is confirmed that weight loss does not occur by washing. The swelling ratio (%) of each resin in the non-aqueous electrolyte is calculated from the following mathematical formula (1).

[0071]

(Equation 1)

However, in the above equation, W₁Is before immersion
Test sheet weight (g), W_TwoIs the test sheet after immersion.
Weight (g), X_ELIs the specific gravity of the test solution (g / c
m^Three), X _PIs the specific gravity of the test sheet (g / cm^Three)
You. However, the specific gravity of the test solution shall be constant weight and constant volume.
Was measured with a hydrometer using a cup of

Further, each test sheet was immersed in a solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (MEC) were mixed at a volume ratio of 2: 1 and the solvent absorption was calculated from the weight increase. The result is shown in FIG.

[0074]

[Table 1]

[0075]

[Table 2]

[0076]

[Table 3]

[0077]

[Table 4]

As is apparent from Tables 1 to 3 and FIGS. 3 and 4, at least one of the positive electrode and the negative electrode has Vd.
F component and melt viscosity (230 ° C / 100
It can be seen that the secondary batteries of Examples 1 to 23 containing a resin having s ^-1 ) of 5000 Pa / sec or more have a small increase in internal resistance with the progress of the charge / discharge cycle and a high discharge capacity retention ratio. In particular, the melt viscosity (230 ° C./100 s ⁻¹ ) of the VdF component-containing resin contained in the separator is 1000 to 1000.
The secondary batteries of Examples 1 to 21 at 3000 Pa / sec have a lower initial internal resistance and a lower discharge capacity retention ratio than the secondary battery of Example 22 in which the melt viscosity of the VdF component-containing resin in the separator is high. It turns out that it is high. The melt viscosity (230 ° C./100
s ^-1) as compared with the case of using a VdF component-containing resin is 5000 Pa / sec or more, the melt viscosity on both the positive electrode and the negative electrode (230 ℃ / 100s ^-1) is 5000 Pa / se
It can be seen that the use of a VdF component-containing resin having a value of c or more has a higher effect of suppressing an increase in internal resistance.

On the other hand, in the secondary battery of the comparative example in which the VdF component-containing resin of both the positive electrode and the negative electrode had a melt viscosity of less than 5000 Pa / sec, the internal resistance rapidly increased and the discharge capacity retention rate was low. Understand.

On the other hand, as apparent from Table 4 and FIG.
It is understood that the resin containing 88 to 95 mol% of the VdF component can absorb a large amount of the non-aqueous electrolyte and has an appropriate swelling ratio when impregnated with the non-aqueous electrolyte. Actually, from Tables 1 to 3 and FIGS. 3 and 4 described above, the copolymerization ratio of the VdF component in the VdF component-containing resin is 88 to 95 m.
ol%, the secondary battery of Examples 1 to 21 has a lower internal resistance increase rate and a higher discharge capacity retention rate than the secondary battery of Example 23 in which the copolymerization ratio is lower than 88 mol%.
It can be seen that the initial internal resistance is lower and the discharge capacity retention ratio is higher than the secondary battery of Example 24 in which the copolymerization ratio is higher than 95 mol%.

In the embodiment described above, the positive electrode,
Although the VdF component-containing resin having the same VdF component content was used for the negative electrode and the separator, the VdF component content of the resin contained in the positive electrode, the negative electrode, and the separator may be different from each other.

In the above-described embodiment, the positive electrode layer is supported on both surfaces of the porous current collector. However, the positive electrode layer may be supported on only one surface of the porous current collector.

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

In the above-described embodiment, an example in which the present invention is applied to a polymer lithium secondary battery has been described. However, the activated carbon and the melt viscosity (230 ° C./100 s ⁻¹ ) are 5000 Pa /
A paste obtained by mixing a copolymer of VdF-HFP (sec copolymerization ratio of VdF component is 92 mol%) for more than sec in acetone is applied on an aluminum foil, and pressure-bonded by a roll press to obtain a polarizable electrode. Make two sets,
Melt viscosity (230 ° C / 100s) between these polarizable electrodes
^-1 ) is interposed with a separator containing a 2500 Pa / sec copolymer of VdF-HFP (the copolymerization ratio of the VdF component is 92 mol%), integrated with a hot roll, and impregnated with a non-aqueous electrolyte. When the electric double layer capacitor was assembled by sealing in a laminate film, it was confirmed that the capacity retention rate during charge and discharge could be improved.

[0085]

As described in detail above, according to the present invention, it is possible to provide an electrochemical device having an improved capacity retention rate during a charge / discharge cycle.

[Brief description of the drawings]

FIG. 1 is a plan view showing a polymer lithium secondary battery of Example 1.

FIG. 2 is a sectional view showing the polymer lithium secondary battery of FIG. 1;

FIG. 3 is a characteristic diagram showing the relationship between the number of charge / discharge cycles and the discharge capacity retention ratio in the polymer lithium secondary batteries of Examples 1 to 24 and Comparative Example.

FIG. 4 shows the number of charge / discharge cycles and the internal resistance (1 kHz) in the polymer lithium secondary batteries of Examples 1 to 24 and Comparative Example.
FIG. 3 is a characteristic diagram showing a relationship with z).

FIG. 5 is a characteristic diagram showing a relationship between a VdF component content in a resin and a solvent absorption amount.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... positive electrode, 2 ... negative electrode, 3 ... separator, 4 ... positive electrode current collector, 5 ... positive electrode layer, 6 ... negative electrode current collector, 7 ... negative electrode layer, 12 ... exterior material.

[Procedure amendment]

[Submission date] April 24, 2000 (200.4.2
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

[0007]

According to the present invention, there is provided an electrochemical device comprising: a resin containing a vinylidene fluoride (VdF) component; an electrode layer containing a non-aqueous electrolyte held by the resin; At least one electrode having a current collector to be used, and vinylidene fluoride (Vd
F) In an electrochemical device comprising a resin containing a component and a separator containing a non-aqueous electrolyte held by the resin, at least one of the electrodes has a melt viscosity of the resin (230 ° C./100 s ^{−). 1} ) is 5000 Pa
- it is characterized in that sec or more.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

According to the present invention, a positive electrode layer containing a resin containing a vinylidene fluoride (VdF) component, a non-aqueous electrolyte held by the resin, and a positive electrode current collector carrying the positive electrode layer are provided. A negative electrode comprising a negative electrode layer containing a resin containing a vinylidene fluoride (VdF) component and a non-aqueous electrolyte held by the resin, and a negative electrode current collector carrying the negative electrode layer; A resin containing a vinylidene fluoride (VdF) component and a separator containing a non-aqueous electrolyte held by the resin; The resin has a melt viscosity (230
(° C./100 s ⁻¹ ) is 5000 Pa · sec or more.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

In the power generating element, the positive electrode, the negative electrode, and the separator are integrated. The resin of at least one of the positive electrode and the negative electrode has a melt viscosity (viscosity at 230 ° C. when a shear rate of 100 s ⁻¹ is applied) of 5000 Pa · sec or more.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

The resin containing the VdF component has a melt viscosity (230 ° C./100 s ⁻¹ ) of 5000 Pa · sec or more. The melt viscosity varies depending on the molecular weight of the resin and the branched structure of the resin. The melt viscosity is 50
If the pressure is less than 00 Pa · sec, the resin strength is extremely reduced by holding or impregnating the non-aqueous electrolyte, and the solvent resistance (non-aqueous electrolyte resistance) at high temperatures is reduced. as a result,
When the charge / discharge cycle is repeated, the positive electrode layer is separated from the positive electrode current collector, so that the internal resistance increases and the cycle life is shortened. More preferably, the melt viscosity is 6000 Pa · sec or more. Further, the upper limit of the melt viscosity is preferably set to 10,000 Pa · sec. When the melt viscosity is higher than 10000 Pa · sec,
There is a possibility that the preparation of the paste (dissolution of the VdF component-containing resin) in the production of the positive electrode, which will be described later, becomes difficult, or the cost of synthesizing the VdF component-containing resin increases, which may cause problems.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

The VdF component-containing resin in the negative electrode layer has a melt viscosity (230 ° C./100 s ⁻¹ ) of 5000 Pa · sec.
c or more, the melt viscosity (230 ° C./100 s ⁻¹ ) of the VdF component-containing resin in the positive electrode layer is 5000 Pa · s.
It may be less than ec. In addition, the melt viscosity is 5000P
Even if less than a · sec, the content of the VdF component in the resin is 88 to 95 mol for the same reason as described above.
% Is preferable.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction contents]

The resin containing the VdF component has a melt viscosity (230 ° C./100 s ⁻¹ ) of 5000 Pa · sec or more. When the melt viscosity is less than 5000 Pa · sec, the charge and discharge cycle is repeated, so that the negative electrode layer is separated from the negative electrode current collector, so that the internal resistance increases and the cycle life is shortened. More preferably, the melt viscosity is 6000 Pa · sec or more. Further, the upper limit of the melt viscosity is preferably set to 10,000 Pa · sec. When the melt viscosity is higher than 10000 Pa · sec, the paste preparation (Vd
F component-containing resin) or VdF
There is a possibility that problems such as an increase in the synthesis cost of the component-containing resin may occur.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0036

[Correction method] Change

[Correction contents]

The melt viscosity (230 ° C./100 s ⁻¹ ) of the VdF component-containing resin in the positive electrode layer was 5000 Pa · sec.
c or more, the melt viscosity (230 ° C./100 s ⁻¹ ) of the VdF component-containing resin in the negative electrode layer is 5000 Pa · s.
It may be less than ec. The melt viscosity is 5000 Pa
- be less than sec, the content of VdF components in the resin, 88~95mol% by the same reason as described above
Is preferably within the range.

[Procedure amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0040

[Correction method] Change

[Correction contents]

The resin containing the VdF component has a melt viscosity (230 ° C./100 s ⁻¹ ) of 1000 to 3000 Pa ·
sec. The melt viscosity is 1
When the pressure is less than 000 Pa · sec, the positive electrode and the negative electrode are easily separated from the separator when the charge / discharge cycle is repeated, so that it may be difficult to sufficiently suppress an increase in the internal resistance during the charge / discharge cycle. On the other hand, if the melt viscosity exceeds 3,000 Pa · sec, the lithium ion conductivity of the separator decreases, and the internal resistance may increase from the beginning of the charge / discharge cycle. A more preferable range of the melt viscosity is 1500 to 2500 Pa · s.
ec.

[Procedure amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0052

[Correction method] Change

[Correction contents]

The electrochemical device according to the present invention described in detail above carries a resin containing a vinylidene fluoride (VdF) component, an electrode layer containing a non-aqueous electrolyte held by the resin, and the electrode layer. At least one electrode provided with a current collector, and vinylidene fluoride (Vd
F) a resin containing the component and a separator containing a non-aqueous electrolyte held by the resin, wherein at least one of the electrodes has a melt viscosity (230 ° C./1
00s ⁻¹ ) is 5000 Pa · sec or more. Since the resin having such a melt viscosity has a high molecular weight and a structure having many branches, the resin has low fluidity. As a result, the adhesion between the electrode layer and the current collector can be improved, so that the electrode layer can be prevented from peeling off from the current collector when charge and discharge are repeated. For this reason, an increase in internal resistance can be suppressed, and the capacity retention rate during charging and discharging can be improved. In addition, since the electrode layer does not peel from the current collector even when a film-made exterior material is used, the use of a film-made exterior material is possible, and the electrochemical device is thin and has a high capacity retention rate during charge and discharge. It becomes possible to realize the device.

[Procedure amendment 11]

[Document name to be amended] Statement

[Correction target item name] 0053

[Correction method] Change

[Correction contents]

In the electrochemical device according to the present invention,
Melt viscosity of the resin in the separator (230 ° C./1
00s ⁻¹ ) of 1000 to 3000 Pa · sec can improve the lithium ion conductivity of the separator while maintaining the adhesion between the separator and the electrode, so that the initial internal resistance can be reduced. Can,
The capacity retention rate during charge / discharge can be further improved.

[Procedure amendment 12]

[Document name to be amended] Statement

[Correction target item name] 0077

[Correction method] Change

[Correction contents]

[0077]

[Table 4]

[Procedure amendment 13]

[Document name to be amended] Statement

[Correction target item name] 0078

[Correction method] Change

[Correction contents]

As is apparent from Tables 1 to 3 and FIGS. 3 and 4, at least one of the positive electrode and the negative electrode has Vd.
F component and melt viscosity (230 ° C / 100
It can be seen that the secondary batteries of Examples 1 to 23 containing a resin having s ⁻¹ ) of 5000 Pa · sec or more have a small increase in internal resistance as the charge / discharge cycle progresses and a high discharge capacity retention rate. In particular, the melt viscosity (230 ° C./100 s ⁻¹ ) of the VdF component-containing resin contained in the separator is 1000 to 1000.
The secondary batteries of Examples 1 to 21 at 3000 Pa · sec have a lower initial internal resistance and a lower discharge capacity retention ratio than the secondary battery of Example 22 in which the melt viscosity of the VdF component-containing resin in the separator is high. It turns out that it is high. The melt viscosity (230 ° C./100
s ^-1) as compared with the case of using a VdF component-containing resin is 5000 Pa · sec or more, the melt viscosity on both the positive electrode and the negative electrode (230 ℃ / 100s ^-1) is 5000 Pa · se
It can be seen that the use of a VdF component-containing resin having a value of c or more has a higher effect of suppressing an increase in internal resistance.

[Procedure amendment 14]

[Document name to be amended] Statement

[Correction target item name] 0079

[Correction method] Change

[Correction contents]

On the other hand, in the secondary battery of the comparative example in which the VdF component-containing resin of both the positive electrode and the negative electrode had a melt viscosity of less than 5000 Pa · sec, the internal resistance rapidly increased and the discharge capacity retention rate was low. Understand.

[Procedure amendment 15]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

In the above-described embodiment, an example in which the present invention is applied to a polymer lithium secondary battery has been described. However, activated carbon and melt viscosity (230 ° C./100 s ⁻¹ ) are 5000 Pa ·
A paste obtained by mixing a copolymer of VdF-HFP (sec copolymerization ratio of VdF component is 92 mol%) for more than sec in acetone is applied on an aluminum foil, and pressure-bonded by a roll press to obtain a polarizable electrode. Make two sets,
Melt viscosity (230 ° C / 100s) between these polarizable electrodes
^-1 ) with a separator containing a VdF-HFP copolymer (the copolymerization ratio of the VdF component is 92 mol%) of 2500 Pa · sec, integrated with a hot roll, and impregnated with a non-aqueous electrolyte solution. When the electric double layer capacitor was assembled by sealing in a laminate film, it was confirmed that the capacity retention rate during charge and discharge could be improved.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideki Kaito 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Inside Toshiba Battery Corporation (72) Inventor Aiichiro Fujiwara 3-4-1 Minamishinagawa, Shinagawa-ku, Tokyo No.Toshiba Battery Corporation (72) Inventor Tetsuo Okuyama 72 Horikawa-cho, Saiwai-ku, Kawasaki City, Kanagawa Prefecture 5H029 AJ03 AJ05 AK02 AK03 AK05 AL06 AL07 AM02 AM03 AM04 AM05 AM07 AM16 BJ04 DJ04 DJ07 EJ12 HJ10 HJ14

Claims (2)

[Claims] 1. An electrode comprising a resin containing a vinylidene fluoride (VdF) component, an electrode layer containing a non-aqueous electrolyte held by the resin, and a current collector carrying the electrode layer. And a resin containing a vinylidene fluoride (VdF) component and a separator containing a non-aqueous electrolyte held by the resin, wherein at least one of the electrodes has a melt viscosity of the resin ( 230 ° C./100 s ⁻¹ ) is 5000 Pa / sec or more. 2. The resin of the separator has a melt viscosity.
(230 ° C / 100s ^-1) Is 1000 to 3000 Pa /
2. The electrochemical according to claim 1, wherein
device.