JP2001085061A - Electrochemical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemical device having a reduced rate of internal short-circuiting in a high-temperature environment. 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 having a melt viscosity at 230 deg.C/100 s-1 of 5000 Pa.sec or more and non-aqueous electrolytic solution retained by the resin.

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 is excellent in the holding power of the non-aqueous electrolyte, the fluidity increases at high temperatures. For this reason,
If the secondary battery is used in a high-temperature environment, an internal short circuit may occur, causing heat or ignition.

An object of the present invention is to provide an electrochemical device having a reduced internal short-circuit occurrence rate in a high-temperature environment.

[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) containing a component and having a melt viscosity (230 ° C./100 s)
^-1 ) is 5000 Pa / sec or more, and a separator containing a non-aqueous electrolyte held by the resin.

In the electrochemical device according to the present invention, in at least one of the electrodes, the resin has a melt viscosity (230 ° C./100 s ⁻¹ ) of 1,000 to 3,000.
It is preferably Pa / sec.

Further, according to the present invention, a resin containing a vinylidene fluoride (VdF) component, a positive electrode layer containing 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, wherein the resin of the separator has a melt viscosity (230 ° C. / 100 s ^-1 ) is 5000 Pa /
An electrochemical device is provided, wherein the length is not less than sec.

In such an electrochemical device, the resin of at least one of the positive electrode and the negative electrode has a melt viscosity (230 ° C./100 s ⁻¹ ) of 1000 to 1000.
It is preferably 3000 Pa / sec.

[0011]

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 the separator has a melt viscosity (100 at 230 ° C.).
(viscosity when shear rate of s ^-1 is added) is 5000 Pa / s
ec or more.

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

(1) 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.

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 the pressure is less than 00 Pa / sec, the resin strength is extremely reduced when the resin is held or impregnated with the electrolytic solution. As a result, when the secondary battery is used in a high temperature environment, the separator is easily melted, and the internal short circuit occurrence rate is increased. 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,
In the production of the positive electrode described later, there may be problems such as difficulty in preparing the paste (dissolving the VdF component-containing resin) or decreasing the yield when synthesizing the VdF component-containing resin and increasing the synthesis cost. is there.

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. When the content is less than 88 mol%, the resin easily swells when impregnated with the non-aqueous electrolyte, so that the internal resistance tends to increase during a charge / discharge cycle, and a long life may not be obtained. On the other hand, when the content exceeds 95 mol%,
Since the non-aqueous electrolyte holding amount of the resin decreases, the internal resistance tends to increase from the beginning of the charge / discharge cycle, and a long life may not be obtained. A more preferred range is from 90 to
93 mol%.

The VdF component-containing resin contained in the separator may have one or more melt viscosities and VdF component contents.

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

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.

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.

(2) 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.

[0027] As the positive electrode active material, various oxides (e.g., lithium manganese composite oxides such as LiMn ₂ O _4, manganese dioxide, for example, lithium-containing nickel oxides such as LiNiO _2, for example, lithium-containing cobalt such as LiCoO ₂ 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.

Examples of the non-aqueous electrolyte include those similar to those described above for the separator.

As the resin containing the VdF component, the same types of resins as those described above for the separator can be used alone or in combination.
F-HFP 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
If the pressure is less than 000 Pa / sec, the positive electrode layer is likely to peel off from the current collector when the charge / discharge cycle is repeated, so that a long life may not be obtained. On the other hand, if the melt viscosity exceeds 3,000 Pa / sec, the difference between the melt viscosity of the resin in the separator and the melt viscosity of the resin in the separator becomes small, so that the melt viscosity of the resin in the separator may be close to a state where the melt viscosity is reduced. May increase the internal short circuit occurrence rate. A more preferred range of the melt viscosity is 1500
~ 2500 Pa / sec.

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. When the content is less than 88 mol%, the resin easily swells when impregnated with the non-aqueous electrolyte, so that the internal resistance tends to increase during a charge / discharge cycle, and a long life may not be obtained. On the other hand, when the content exceeds 95 mol%,
Since the non-aqueous electrolyte holding amount of the resin decreases, the internal resistance tends to increase from the beginning of the charge / discharge cycle, and a long life may not be obtained. A more preferred range is from 90 to
93 mol%.

The VdF component-containing resin of the positive electrode layer may have one or more melt viscosities and 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.

[0034] 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.

(3) Negative Electrode In this 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 separator are used.

As the resin containing the VdF component, the same types of resins as those described above for the separator can be used alone or in combination.
F-HFP 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
If it is less than 000 Pa / sec, the negative electrode layer is likely to be peeled off from the current collector when the charge / discharge cycle is repeated, so that a long life may not be obtained. On the other hand, if the melt viscosity exceeds 3,000 Pa / sec, the difference between the melt viscosity of the resin in the separator and the melt viscosity of the resin in the separator becomes small, so that the melt viscosity of the resin in the separator may be close to a state where the melt viscosity is reduced. May increase the internal short circuit occurrence rate. A more preferred range of the melt viscosity is 1500
~ 2500 Pa / sec.

The resin containing the VdF component preferably has a VdF component content of 88 to 95 mol%. This is due to the following reasons. When the content is less than 88 mol%, the resin easily swells when impregnated with the non-aqueous electrolyte, so that the internal resistance tends to increase during a charge / discharge cycle, and a long life may not be obtained. On the other hand, when the content exceeds 95 mol%,
Since the non-aqueous electrolyte holding amount of the resin decreases, the internal resistance tends to increase from the beginning of the charge / discharge cycle, and a long life may not be obtained. A more preferred range is from 90 to
93 mol%.

The melt viscosity and the VdF component content of the VdF component-containing resin of the negative electrode layer can be one or more.

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.

(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
Chair contains vinylidene fluoride (VdF) component
Including a resin to be treated and a non-aqueous electrolyte held by the resin.
An electrode comprising a pole layer and a current collector on which the electrode layer is carried;
At least one kind and vinylidene fluoride (Vd
F) containing a component and having a melt viscosity (230 ° C./100 s)
^-1) Is 5000 Pa / sec or more and the resin
And a separator containing a non-aqueous electrolyte held by the fat.
You. The resin having a melt viscosity has a high molecular weight and is branched.
, The fluidity is low. The result
As a result, when the electrochemical device is used in a high temperature environment,
To prevent the melter from melting.
Short circuits can be reduced, improving safety in high temperature environments.
Can be up.

Further, according to the present invention, it is possible to reduce the internal short-circuit occurrence rate during manufacturing. That is, in the electrochemical device, for example, a non-aqueous electrolyte unimpregnated separator containing a VdF component-containing resin is interposed between a positive electrode and a non-aqueous electrolyte-unimpregnated positive electrode containing a VdF component-containing resin, and the obtained laminate is obtained. After integrating the objects by heating and pressing, impregnated with non-aqueous electrolyte,
It is manufactured by sealing with an exterior material. The melt viscosity of the resin of the separator not impregnated with the non-aqueous electrolyte was 5,000.
By setting the pressure to Pa / sec or more, the separator can be prevented from melting at the time of heating and pressurizing, so that an internal short circuit can be reduced. Therefore, an electrochemical device having excellent safety in a high temperature environment can be manufactured with a high yield.

In the electrochemical device according to the present invention,
The melt viscosity (230 ° C./100 s ⁻¹ ) of at least one of the resins among the electrodes is 1000 to 3000 Pa /
By setting to sec, it is possible to further reduce the internal short-circuit occurrence rate at a high temperature while maintaining the adhesion between the current collector and the electrode layer.

[0055]

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

(Examples 1 to 9 and Comparative Examples 1 and 2) <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: The melt viscosity and copolymerization ratio ΔVdF / HFP shown in Table 1 below, where VdF is vinylidene fluoride (C
H ₂ -CF ₂₎ molar ratio (mol%), HFP 8 weight VdF-HFP copolymer powder shows the molar ratio of hexafluoropropylene _{{CF 2 -CF (CF 3)} } (mol%)} %, 7% by weight of carbon black 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 was expanded with aluminum expanded metal (having a thickness of 30 μm in terms of aluminum foil and a porosity of 6).
0%) and pressed with a rigid roll heated to 140 ° C. to produce a non-aqueous electrolyte-unimpregnated positive electrode.

<Preparation of Negative Electrode Impregnated with Nonaqueous Electrolyte> 70% by weight of mesophase pitch carbon fiber as active material and 9% by weight of VdF-HFP copolymer powder having a melt viscosity and a copolymerization ratio shown in Table 1 below. And dibutyl phthalate (DBP) 1
8% by weight was mixed in acetone to prepare a paste.
The obtained paste was coated on a PET film at 160 g / m ^2.
And dried to produce a non-aqueous electrolyte-unimpregnated negative electrode sheet. The obtained negative electrode sheet is placed on both sides of a current collector made of copper expanded metal (thickness converted to copper foil is 30 μm and porosity is 60%), and is pressed with a rigid roll heated to 140 ° C. Thus, a non-aqueous electrolyte-unimpregnated negative electrode was produced.

<Preparation of non-aqueous electrolyte non-impregnated separator>
VdF-HFP with melt viscosity and copolymerization ratio shown in Table 1 below
30 parts by weight of the 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 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.

<Preparation of Nonaqueous Electrolyte> LiPF ₆ as an electrolyte was added to a nonaqueous solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of 2: 1 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.

The 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.

The melt viscosity of the VdF-HFP copolymer is a viscosity at 230 ° C. when a shear rate of 100 s ⁻¹ is applied.

When 10 pieces of the obtained secondary batteries of Examples 1 to 9 and Comparative Examples 1 and 2 were prepared and charged to 4.2 V at 0.2 C, and left for 1 hour in an environment of 150 ° C. Were measured for the number of internal short circuits, and the results are shown in Table 1 below.
However, for this test, one that did not cause an internal short circuit during manufacturing was used.

For the secondary batteries of Examples 1 to 9 and Comparative Examples 1 and 2, when 100 batteries were manufactured, the number of internal short-circuits generated in the heating and pressurizing step in battery assembly was measured. Also shown in Table 1.

Further, the secondary batteries of Examples 1 to 9 and Comparative Examples 1 and 2 were charged at 1.0 C to 4.2 V and then discharged at 1.0 C to 3.0 V. And the discharge capacity in the first cycle is set to 100, and 1
The capacity retention rates at the 00th cycle were compared, and the results are shown in Table 1 below. However, for this test, one that did not cause an internal short circuit during manufacturing was used.

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 2 below. Table 2 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).

[0069]

(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

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. , And the results are shown in FIG.

[0072]

[Table 1]

[0073]

[Table 2]

As is clear from Table 1, the V of the separator
Melt viscosity of dF component-containing resin (230 ° C / 100s ^-1 )
It can be seen that the secondary batteries of Examples 1 to 9 having a value of 5,000 Pa / sec or more have no internal short-circuit occurrence in a high-temperature environment and a small number of internal short-circuits during manufacturing. In particular,
The melt viscosity (230 ° C./100 s ⁻¹ ) of the VdF component-containing resin contained in the positive electrode and the negative electrode is 1000 to 3000 Pa /
It can be seen that the secondary batteries of Examples 1 to 7 and 9, which have a sec.

On the other hand, the secondary batteries of Comparative Examples 1 and 2 in which the VdF component-containing resin of the separator had a melt viscosity of less than 5000 Pa / sec had an internal short-circuit occurrence rate during use in a high-temperature environment and during manufacture. It turns out that it is high.

On the other hand, as is clear from Table 2 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 Table 1 described above, the VdF component-containing resin
The secondary batteries of Examples 1 to 8 in which the copolymerization ratio of the dF component is 88 to 95 mol% are the secondary batteries of Example 9 in which the copolymerization ratio is lower than 88 mol%, and the copolymerization ratio is 95 mol%.
It can be seen that the capacity retention after 100 cycles is higher than that of the secondary battery of Comparative Example 2 which is higher.

In the above-described embodiment, 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.

Further, in the above-described 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 2500 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 5000 Pa / sec copolymer of VdF-HFP (the copolymerization ratio of the VdF component is 92 mol%), interposed 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 internal short-circuit occurrence rate in a high-temperature environment and during manufacture could be reduced, and the capacity retention rate during charge and discharge could be improved. .

[0081]

As described above in detail, according to the present invention, it is possible to provide an electrochemical device in which an internal short circuit in a high-temperature environment is suppressed.

[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 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) containing a component and having a melt viscosity (230 ° C./100 s)
^-1 ) is 5000 Pa · sec or more, and a separator containing a non-aqueous electrolyte held by the resin.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

In the electrochemical device according to the present invention, in at least one of the electrodes, the resin has a melt viscosity (230 ° C./100 s ⁻¹ ) of 1,000 to 3,000.
It is preferably Pa · sec.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

Further, according to the present invention, a resin containing a vinylidene fluoride (VdF) component, a positive electrode layer containing 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, wherein the resin of the separator has a melt viscosity (230 ° C. / 100s ^-1) is 5000Pa ·
An electrochemical device is provided, wherein the length is not less than sec.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

In such an electrochemical device, the resin of at least one of the positive electrode and the negative electrode has a melt viscosity (230 ° C./100 s ⁻¹ ) of 1000 to 1000.
It is preferably 3000 Pa · sec.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

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

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0017

[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
When the pressure is less than 00 Pa · sec, the resin strength is extremely reduced when the resin is held or impregnated with the electrolytic solution. As a result, when the secondary battery is used in a high temperature environment, the separator is easily melted, and the internal short circuit occurrence rate is increased. 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,
In the production of the positive electrode described later, there may be problems such as difficulty in preparing the paste (dissolving the VdF component-containing resin) or decreasing the yield when synthesizing the VdF component-containing resin and increasing the synthesis cost. is there.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0030

[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
If the pressure is less than 000 Pa · sec, the positive electrode layer is likely to peel off from the current collector when the charge / discharge cycle is repeated, so that a long life may not be obtained. On the other hand, when the melt viscosity exceeds 3,000 Pa · sec, the difference between the melt viscosity of the resin in the separator and the melt viscosity of the resin in the separator becomes small, so that the melt viscosity of the resin in the separator may be close to a state where the melt viscosity is reduced. May increase the internal short circuit occurrence rate. A more preferred range of the melt viscosity is 1500
２2500 Pa · sec.

[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
If the pressure is less than 000 Pa · sec, the negative electrode layer is likely to be peeled off from the current collector when the charge / discharge cycle is repeated, so that a long life may not be obtained. On the other hand, when the melt viscosity exceeds 3000 Pa · sec, the difference between the melt viscosity of the resin in the separator and the melt viscosity of the resin in the separator is reduced, and the melt viscosity of the resin in the separator may be close to a state where the melt viscosity is reduced. May increase the internal short circuit occurrence rate. A more preferred range of the melt viscosity is 1500
２2500 Pa · sec.

[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
Chair contains vinylidene fluoride (VdF) component
Including a resin to be treated and a non-aqueous electrolyte held by the resin.
An electrode comprising a pole layer and a current collector on which the electrode layer is carried;
At least one kind and vinylidene fluoride (Vd
F) containing a component and having a melt viscosity (230 ° C./100 s)
^-1) Is 5000 Pa・resin and the above tree
And a separator containing a non-aqueous electrolyte held by the fat.
You. The resin having a melt viscosity has a high molecular weight and is branched.
, The fluidity is low. The result
As a result, when the electrochemical device is used in a high temperature environment,
To prevent the melter from melting.
Short circuits can be reduced, improving safety in high temperature environments.
Can be up.

[Procedure amendment 11]

[Document name to be amended] Statement

[Correction target item name] 0053

[Correction method] Change

[Correction contents]

Further, according to the present invention, it is possible to reduce the internal short-circuit occurrence rate during manufacturing. That is, in the electrochemical device, for example, a non-aqueous electrolyte unimpregnated separator containing a VdF component-containing resin is interposed between a positive electrode and a non-aqueous electrolyte-unimpregnated positive electrode containing a VdF component-containing resin, and the obtained laminate is obtained. After integrating the objects by heating and pressing, impregnated with non-aqueous electrolyte,
It is manufactured by sealing with an exterior material. The melt viscosity of the resin of the separator not impregnated with the non-aqueous electrolyte was 5,000.
When the pressure is equal to or more than Pa · sec, the separator can be prevented from melting at the time of heating and pressing, so that an internal short circuit can be reduced. Therefore, an electrochemical device having excellent safety in a high temperature environment can be manufactured with a high yield.

[Procedure amendment 12]

[Document name to be amended] Statement

[Correction target item name] 0054

[Correction method] Change

[Correction contents]

In the electrochemical device according to the present invention,
The melt viscosity (230 ° C./100 s ⁻¹ ) of at least one of the resins among the electrodes is set to 1000 to 3000 Pa ·
By setting to sec, it is possible to further reduce the internal short-circuit occurrence rate at a high temperature while maintaining the adhesion between the current collector and the electrode layer.

[Procedure amendment 13]

[Document name to be amended] Statement

[Correction target item name] 0073

[Correction method] Change

[Correction contents]

[0073]

[Table 2]

[Procedure amendment 14]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

As is clear from Table 1, the V of the separator
Melt viscosity of dF component-containing resin (230 ° C / 100s ^-1 )
It can be seen that the secondary batteries of Examples 1 to 9 in which the internal short-circuiting is 5000 Pa · sec or more have no internal short-circuiting occurrence in a high temperature environment and a small number of internal short-circuiting occurrences during manufacturing. In particular,
The melt viscosity (230 ° C./100 s ⁻¹ ) of the VdF component-containing resin contained in the positive electrode and the negative electrode is 1000 to 3000 Pa ·
It can be seen that the secondary batteries of Examples 1 to 7 and 9, which have a sec.

[Procedure amendment 15]

[Document name to be amended] Statement

[Correction target item name] 0075

[Correction method] Change

[Correction contents]

On the other hand, the secondary batteries of Comparative Examples 1 and 2 in which the VdF component-containing resin of the separator had a melt viscosity of less than 5000 Pa · sec had an internal short circuit occurrence rate during use in a high temperature environment and during manufacture. It turns out that it is high.

[Procedure amendment 16]

[Document name to be amended] Statement

[Correction target item name] 0080

[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, the activated carbon and the melt viscosity (230 ° C./100 s ⁻¹ ) are 2500 Pa · s
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 ) after interposing a separator containing a 5000 Pa · sec VdF-HFP copolymer (the copolymerization ratio of the VdF component is 92 mol%) with a hot roll and impregnating with a non-aqueous electrolyte, When the electric double layer capacitor was assembled by sealing in a laminate film, it was confirmed that the internal short-circuit occurrence rate in a high-temperature environment and during manufacture could be reduced, and 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 Co., Ltd. BJ04 DJ04 DJ09 HJ02 HJ10

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. , A vinylidene fluoride (VdF) component, and a melt viscosity (230 ° C./1
(00s ^-1 ) is 5000 Pa / sec or more, and a separator containing a non-aqueous electrolyte held by the resin. 2. The electrochemical device according to claim 1, wherein in at least one of the electrodes, the resin has a melt viscosity (230 ° C./100 s ⁻¹ ) of 1,000 to 3,000 Pa / sec.