JP2003045489A - Manufacturing method for non-aqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a non-aqueous electrolyte battery having a low internal resistance and a long charging/discharging cycle life. SOLUTION: This manufacturing method comprises a process for impregnating, an electrode group 2 including positive and negative electrodes with a gel electrolyte precursor including monomers having a molecular weight of 200 to 100,000 having two or more polymerizable functional groups in one molecule; non-aqueous electrolyte; and a surface active agent (phosphoric trialkyl and the like having a 3-10C alkyl group), and the process of gelating the gel electrolyte precursor.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing a non-aqueous electrolyte battery.

[0002]

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

Recently, carbonaceous materials (for example, coke, graphite,
Active development and commercialization of lithium secondary batteries using carbon fiber, resin fired body, pyrolysis gas phase carbon) and positive electrode containing lithium cobalt oxide or lithium manganese composite oxide. It is being appreciated.

Meanwhile, a polymer lithium secondary battery has been developed for the purpose of further weight reduction and size reduction of the secondary battery. As a polymer lithium secondary battery, for example, a layer containing an active material, a non-aqueous electrolytic solution, and a polymer holding the electrolytic solution as disclosed in US Pat. No. 5,296,318 serves as a current collector. A positive electrode having a supported structure,
A carbonaceous material that absorbs and releases lithium, a nonaqueous electrolytic solution, and a layer containing a polymer that holds this electrolytic solution are disposed between a negative electrode having a structure in which a current collector supports the nonaqueous electrolytic solution. There is known a separator including a liquid and a gel solid electrolyte containing a polymer holding the electrolytic solution.

On the other hand, Japanese Patent Laid-Open No. 11-283673 discloses a polymer lithium electrolyte prepared by injecting a gel electrolyte precursor consisting of a polymerizable compound and an electrolyte solution into a power generating element not impregnated with the electrolyte solution, and then polymerizing and hardening the gel electrolyte precursor. A secondary battery is disclosed.

However, since the viscosity of the gel electrolyte precursor is much higher than that of the non-aqueous electrolyte, it is difficult to spread the gel electrolyte precursor throughout the power generating element, and the internal resistance of the secondary battery is high. Therefore, there is a problem that the initial capacity and the charge / discharge cycle life are reduced.

The molecular weight of the polymerizable compound may be reduced in order to reduce the viscosity of the gel electrolyte precursor, but the gel stability obtained by the gel electrolyte obtained by reducing the molecular weight of the polymerizable compound is low. Therefore, a long life cannot be obtained.

Further, in order to improve the permeation rate of the gel electrolyte precursor, it is conceivable that the gel electrolyte precursor is impregnated into the power generating element while being kept at a high temperature. However, due to the high temperature, gelation starts during the impregnation, and the power generation element is not impregnated thereafter, which causes a problem that both the initial capacity and the cycle life are inferior.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing a non-aqueous electrolyte battery having a low internal resistance and a long charge / discharge cycle life.

[0010]

According to the method for producing a non-aqueous electrolyte battery of the present invention, an electrode group including a positive electrode and a negative electrode has a molecular weight of 20 having two or more polymerizable functional groups in one molecule.
It is characterized by comprising a step of impregnating a gel electrolyte precursor containing 0 to 100,000 monomers, a non-aqueous electrolyte solution and a surfactant, and a step of gelling the gel electrolyte precursor. .

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An example of a method for manufacturing a non-aqueous electrolyte battery according to the present invention will be described.

(First Step) An electrode group including a positive electrode and a negative electrode is charged with a monomer having two or more polymerizable functional groups in one molecule and having a molecular weight of 200 to 100,000, a non-aqueous electrolyte and a surfactant. Impregnate with a gel electrolyte precursor containing.

The electrode group includes, for example, the following (a) to (c):
The shape described in can be used.

(A) A shape in which a laminate including a positive electrode and a negative electrode is wound into a flat shape.

(B) A shape in which a laminate including a positive electrode and a negative electrode is bent.

(C) A laminate containing a positive electrode and a negative electrode.

A separator can be arranged between the positive electrode and the negative electrode. Hereinafter, the positive electrode, the negative electrode, and the separator will be described.

1) Positive Electrode This positive electrode has a positive electrode layer containing an active material and a positive electrode current collector carrying the positive electrode layer.

This positive electrode is produced, for example, by the method described below. A positive electrode sheet is prepared by forming a paste prepared by mixing an active material, a binder, and a conductive material in an organic solvent such as acetone to form a film. The obtained positive electrode sheet is laminated on a current collector and heated and pressed to obtain the positive electrode. Alternatively, the positive electrode may be produced by applying the paste to a current collector, drying it, and applying heat and pressure.

Examples of the positive electrode active material include various oxides (eg, lithium-containing manganese oxides such as LiMn ₂ O ₄ ; manganese dioxide, lithium-containing nickel oxides such as LiNiO ₂ ; lithium-containing cobalt such as LiCoO _2). Examples thereof include oxides, lithium-containing nickel-cobalt oxides, lithium-containing amorphous vanadium pentoxide, etc.), chalcogen compounds (eg, titanium disulfide, molybdenum disulfide, etc.), and the like. Above all, it is preferable to use lithium-containing manganese oxide, lithium-containing cobalt oxide, and lithium-containing nickel oxide.

Examples of the binder include polyvinylidene fluoride copolymer, styrene-butadiene copolymer, carboxymethyl cellulose and derivatives thereof. The binder preferably has a function of holding the non-aqueous electrolytic solution. Among the above binders, a polyvinylidene fluoride copolymer is preferable.

Examples of the conductive material include artificial graphite, carbon black (for example, acetylene black, etc.), nickel powder and the like.

The current collector is, for example, a mesh,
It is possible to use one having a porous structure such as expanded metal or punched metal, or a metal plate (for example, metal foil). Further, the current collector is preferably formed of aluminum or an aluminum alloy.

2) Negative Electrode This negative electrode has a negative electrode layer containing an active material and a negative electrode current collector carrying the negative electrode layer.

This negative electrode is produced, for example, by the method described below. A negative electrode sheet is produced by forming a paste prepared by mixing an active material and a binder in an organic solvent such as acetone to form a film. The obtained negative electrode sheet is laminated on a current collector and heated and pressed to produce the negative electrode. Alternatively, the negative electrode may be prepared by applying the paste to a current collector, drying it, and applying heat and pressure.

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

As the binder, the same binder as described above for the positive electrode is used. Among the above binders, a polyvinylidene fluoride copolymer is preferable.

The negative electrode layer is made of artificial graphite,
It is allowed to include fillers such as natural graphite, carbon black, acetylene black, Ketjen black, nickel powder, conductive material of polyphenylene derivative, olefin polymer and carbon fiber.

As the current collector, for example, a mesh,
It is possible to use one having a porous structure such as expanded metal or punched metal, or a metal plate (for example, metal foil). Further, the current collector is preferably formed of copper or a copper alloy.

3) Separator For the separator, for example, an insulating porous sheet can be used. Examples of the porous sheet include woven cloth, non-woven cloth, microporous film, and the like. As the insulating material forming the porous sheet, a material having non-aqueous electrolyte resistance such as polyolefin (eg, polyethylene, polypropylene) is desirable. The porous sheet may be made of one kind of insulating material or two or more kinds of insulating materials.

Next, the gel electrolyte precursor will be described.

4) Non-Aqueous Electrolyte Solution The non-aqueous electrolyte solution is prepared, for example, by dissolving an electrolyte such as a lithium salt in a non-aqueous solvent.

Examples of the lithium salt include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆₎ , lithium borotetrafluoride (LiB)
F ₄ ), lithium hexafluoroarsenide (LiAsF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ S)
O ₃ ) and the like can be mentioned.

Examples of the non-aqueous solvent include ethylene carbonate (EC) and propylene carbonate (P
C), butylene carbonate (BC), dimethyl carbonate (DMC), 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 etc. can be mentioned.
The non-aqueous solvent may be used alone or in combination of two or more.

The amount of the lithium salt dissolved in the non-aqueous solvent is preferably 0.2 mol / L to 2 mol / L.

5) Monomer polymerizable functional groups having two or more polymerizable functional groups in one molecule and having a molecular weight of 200 to 100,000 include, for example, acryloyl group,
An allyl group etc. can be mentioned.

The number of polymerizable functional groups in one molecule of the monomer is preferably 3 or more. Moreover, it is desirable that the upper limit of the number of functional groups be 6.

The reason for defining the molecular weight in the above range will be described. When the molecular weight is less than 200, the stability of the gel decreases, so that liquid leakage easily occurs and the charge / discharge cycle life decreases. On the other hand, if the molecular weight exceeds 100,000, even if a surfactant is added, the permeation rate of the gel electrolyte precursor into the electrode group does not increase, increasing the internal resistance, decreasing the initial capacity or deteriorating the charge / discharge cycle life. Occurs. A more preferable range of the molecular weight is 500 to 10,000.

Examples of the monomer having two or more polymerizable functional groups in one molecule and having a molecular weight of 200 to 100,000 include, for example, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyether-based polyfunctional acrylates, and polyester-based polyfunctional polyesters. A functional acrylate etc. can be mentioned.

The type of the monomer contained in the gel electrolyte precursor may be one type or two or more types. When the number of kinds of monomers is two or more, it is necessary to set the molecular weight of each monomer within the above range.

The content of the monomer in the gel electrolyte precursor is
It is desirable to set it within the range of 3 to 10 mass% with respect to the gel electrolyte precursor.

6) Surfactant Examples of the surfactant include trialkyl phosphate surfactants, carboxylic acid surfactants, fluorine surfactants, linear alkylcarboxylic acid surfactants, and oleic acid amides. Examples thereof include a system surfactant. The type of surfactant used may be one type or two or more types. Among them, trialkyl phosphate having an alkyl group having 3 to 10 carbon atoms is preferable because it is less likely to cause a side reaction during the charge / discharge reaction. The reason why the carbon number of the alkyl group is defined in the above range will be described. If the carbon number is less than 3, the permeation rate of the gel electrolyte precursor will not be sufficiently increased, which may make it difficult to improve the internal resistance, the initial capacity and the cycle life. On the other hand, when the carbon number exceeds 10, the balance between hydrophilicity and hydrophobicity of the surfactant is deteriorated, so that phase separation easily occurs in the gel electrolyte precursor.

The content of the surfactant is preferably in the range of 0.01 to 3% by mass with respect to the non-aqueous electrolyte.
This is due to the following reasons. If the content is 0.
If it is less than 01% by mass, the impregnating property of the gel electrolyte precursor into the electrode group may be insufficient and the initial capacity and the cycle life may be reduced. On the other hand, if the content exceeds 3% by mass, the lithium conductivity of the gel electrolyte may decrease and the internal resistance may increase. A more preferable range of the content is
It is 0.1 to 1 mass%.

A polymerization initiator may be added to the gel electrolyte precursor. Examples of the polymerization initiator include t-
Examples thereof include peroxide thermal polymerization initiators such as butyl-peroxy 2-ethylhexanate, azo thermal polymerization initiators such as azobisisobutyronitrile, and photopolymerization initiators such as benzyl methyl ketal.

The temperature of the gel electrolyte precursor is preferably maintained near room temperature. When the temperature of the gel electrolyte precursor is maintained at a high temperature (for example, 45 ° C.), gelation of the gel electrolyte precursor starts during the injection into the electrode group and the gel electrolyte is not retained inside the electrode group. It may not be possible to obtain a long life.

(Second Step) The gel electrolyte precursor impregnated in the electrode group is gelled.

Gelation can be carried out, for example, by heating, electron beam irradiation, light irradiation or the like.

(Third Step) The electrode group is sealed in the outer package.

This outer package can be formed of, for example, a film having a barrier function against moisture, a metal, or the like. The film exterior body can reduce the thickness and weight of the battery. Examples of such a film include a laminate film in which a heat-fusible resin is disposed at least in a sealing portion and a metal thin film such as aluminum (Al) is interposed inside. Specifically, acid-modified polypropylene (PP) / polyethylene terephthalate (PE) laminated from the sealing portion side to the outer surface.
T) / Al foil / PET laminated film; acid-modified P
Laminated film of E / nylon / Al foil / PET;
Ionomer / Ni foil / PE / PET laminated film; ethylene vinyl acetate (EVA) / PE / A
l foil / PET laminated film; ionomer / P
A laminated film of ET / Al foil / PET or the like can be used. Here, the films other than the acid-modified PE, the acid-modified PP, the ionomer, and EVA on the sealing portion side are moisture-proof,
Has breathability and chemical resistance.

An example of the non-aqueous electrolyte battery manufactured by the method according to the present invention will be described in detail with reference to FIGS.

FIG. 1 is a plan view showing a non-aqueous electrolyte battery manufactured by the method according to the present invention, FIG. 2 is a perspective view showing an electrode group used in the non-aqueous electrolyte battery of FIG. 1, and FIG. , Figure 1
4 is a sectional view showing the non-aqueous electrolyte battery of FIG. 4, and FIG. 4 is an enlarged sectional view showing a portion A of FIG.

As shown in FIG. 1, an electrode group 2 is housed in a bag-shaped exterior body 1 made of, for example, a film. The electrode group 2 has a structure in which a laminate including a positive electrode 3, a separator 4 and a negative electrode 5 is wound into a flat shape. Positive electrode 3
Includes a positive electrode current collector 6 and a positive electrode layer 7 carried on one surface or both surfaces of the positive electrode current collector 6. On the other hand, the negative electrode 5 includes a negative electrode current collector 8 and a negative electrode layer 9 carried on one surface or both surfaces of the negative electrode current collector 8. The strip-shaped positive electrode lead 10 is
One end is connected to the positive electrode current collector 6 of the electrode group 2, and the other end is extended from the exterior body 1. On the other hand, the strip-shaped negative electrode lead 11 has one end connected to the negative electrode current collector 8 of the electrode group 2 and the other end extending from the outer package 1.

(Operation) According to the method for producing a non-aqueous electrolyte battery of the present invention, an interface between a monomer having two or more polymerizable functional groups in one molecule and having a molecular weight of 200 to 100,000, a non-aqueous electrolyte, and Since the gel electrolyte precursor containing the activator is used, the gel electrolyte precursor can be quickly permeated into the entire electrode group without applying heat treatment or the like to the gel electrolyte precursor. Then, the gel electrolyte precursor with which the electrode group is impregnated is gelated, whereby a highly stable gel electrolyte can be obtained. A nonaqueous electrolyte battery in which such an electrode group is sealed in an outer package can have a low internal resistance, so that the initial capacity and charge / discharge cycle life can be improved.

In the production method according to the present invention, the surfactant containing trialkyl phosphate having an alkyl group having 3 to 10 carbon atoms is used to further lower the internal resistance of the non-aqueous electrolyte battery. You can

[0055]

EXAMPLES Examples of the present invention will be described in detail below.

Example 1 (Production of Positive Electrode) 78% by mass of lithium-containing manganese oxide represented by LiMn ₂ O ₄ , 5% by mass of carbon black, and a binder having a function of holding a non-aqueous electrolyte. As a paste, 17% by mass of polyvinylidene fluoride powder was mixed in acetone to prepare a paste. The obtained paste was applied on a PET film to prepare a positive electrode layer. The obtained positive electrode layer was placed on both sides of a current collector made of expanded metal made of aluminum, and the positive electrode layer was fused to the current collector by pressing with a hot roll, and then cut to a thickness of 130 μm. A positive electrode was produced.

(Preparation of Negative Electrode) A paste was prepared by mixing 83% by mass of mesophase pitch carbon fiber and 17% by mass of polyvinylidene fluoride powder as a binder having a function of holding a non-aqueous electrolyte in acetone. Was prepared. Apply the obtained paste on a PET film,
A negative electrode layer was produced. The negative electrode layer thus obtained was placed on both sides of a current collector made of expanded metal made of copper, and the negative electrode layer was fused to the current collector by pressing with a heat roll, and then cut to form a negative electrode having a thickness of 150 μm. Was produced.

(Preparation of Gel Electrolyte Precursor) LiBF ₄ as an electrolyte was dissolved in a non-aqueous solvent in which ethylene carbonate and γ-butyrolactone were mixed at a volume ratio of 1: 2 so that the concentration was 1 mol / L. Then, a non-aqueous electrolyte was prepared. In this non-aqueous electrolytic solution, trioctyl phosphate as a surfactant was added in an amount of 0.5% by mass, and a monomer having three polymerizable functional groups in one molecule had a molecular weight of 1,000.
0% by weight of polyether-based trimethacrylate
And 0.25 as a peroxide-based polymerization initiator as a polymerization initiator.
Mass% was dissolved to prepare a liquid gel electrolyte precursor.

(Assembly of Battery) One piece of the obtained positive electrode, one piece of the negative electrode, and one piece of a polyethylene microporous film having a thickness of 30 μm and a porosity of 50% as a separator were prepared.
A separator is placed so as to enclose the negative electrode, then laminated with the positive electrode, wound into a coil shape, and fused by applying heat and pressure, and then the positive electrode lead 10 and the negative electrode lead 1
By connecting 1 to each other, the electrode group 2 having the structure shown in FIG. 2 and not holding the gel electrolyte was obtained.

A laminated film in which a polyethylene terephthalate (PET) film, an aluminum foil and a heat-fusible resin film are laminated in this order from the outermost layer is folded in two, and two sides are heat-sealed to form a bag, The outer package 1 was obtained. The electrode group 2 was housed in the outer package 1 such that the positive electrode lead 10 and the negative electrode lead 11 were extended to the outside of the outer package 1. Subsequently, the gel electrolyte precursor described above was injected from the opening of the outer package 1 to impregnate the electrode group 2 with the gel electrolyte precursor. Next, the opening of the outer package 1 was sealed by heat sealing with the positive electrode lead 10 and the negative electrode lead 11 extending out of the outer package 1. This is heated at 80 ° C. for 1 hour and then cooled at room temperature to gelate the gel electrolyte precursor, which has the structure shown in FIGS. 1 to 4 described above and has a capacity of 600 mAh.
A thin polymer lithium secondary battery was manufactured.

Example 2 A thin polymer lithium secondary battery was manufactured in the same manner as described in Example 1 except that trimethyl phosphate was used as the surfactant.

Example 3 A thin polymer lithium secondary battery was manufactured in the same manner as described in Example 1 except that tridodecyl phosphate was used as the surfactant.

Example 4 A thin polymer lithium secondary battery was manufactured in the same manner as described in Example 1 except that ethyl caprylate was used as the surfactant.

Example 5 A thin polymer lithium secondary battery was manufactured in the same manner as described in Example 1 except that oleic acid amide was used as the surfactant.

Example 6 In the same manner as described in Example 1 above, except that the temperature of the gel electrolyte precursor is maintained at 45 ° C. when the gel electrolyte precursor is injected into the electrode group. A thin polymer lithium secondary battery was manufactured.

Comparative Example 1 A thin polymer lithium secondary battery was manufactured in the same manner as described in Example 1 except that the surfactant was not added.

The secondary batteries of Examples 1 to 6 and Comparative Example 1 were subjected to a charge / discharge cycle test in which the secondary batteries were charged at 1.0C to 4.2V and then discharged at 1.0C to 3.0V.
Measure the resistance value at 0th cycle and 300th cycle,
The results are shown in Table 1 below. In addition, the discharge capacity of the first cycle in this charge / discharge cycle test is 100
The capacity retention ratios at the third cycle and the 300th cycle were compared, and the results are shown in Table 1 below.

[0068]

[Table 1]

As is clear from Table 1, the secondary batteries of Examples 1 to 6 had lower internal resistances after 100 cycles and 300 cycles than the secondary batteries of Comparative Example 1, and further after 100 cycles. And that the capacity retention rate after 300 cycles is excellent. Particularly, according to the secondary batteries of Examples 1 to 3 using the trialkyl phosphate having an alkyl group having 3 to 10 carbon atoms, the internal resistance is lower than that of the secondary batteries of Examples 4 to 5 and the capacity is maintained. It turns out that the rate becomes high.

Examples 7 to 10 and Comparative Examples 2 to 3 Example 1 described above except that the monomers shown in Table 2 below are used as monomers having two or more polymerizable functional groups in one molecule. A thin polymer lithium secondary battery was manufactured in the same manner as described above.

The obtained Examples 7 to 10 and Comparative Examples 2 to 3 were obtained.
For the secondary battery of Example 1, the internal resistance after 100 cycles and after 300 cycles and the capacity retention rate after 100 cycles and after 300 cycles were measured in the same manner as described in Example 1 above, and the results are shown in the table below. 2 shows. Table 2 also shows the results of Example 1 described above.

[0072]

[Table 2]

As is clear from Table 2, the molecular weight of the monomer having two or more polymerizable functional groups in one molecule is 20.
In the secondary batteries of Examples 1 and 7 to 10 in the range of 0 to 100,000, Comparative Examples 2 to 3 in which the monomer molecular weight is out of the range.
It can be seen that the internal resistance after 100 cycles and 300 cycles is low and the capacity retention rate after 100 cycles and 300 cycles is superior to that of the secondary battery of No.

[0074]

As described above in detail, according to the present invention, it is possible to provide a method for producing a non-aqueous electrolyte battery having a low internal resistance and an improved charge / discharge cycle life.

[Brief description of drawings]

FIG. 1 is a plan view showing a non-aqueous electrolyte battery manufactured by a method according to the present invention.

FIG. 2 is a perspective view showing an electrode group used in the non-aqueous electrolyte battery of FIG.

3 is a cross-sectional view showing the non-aqueous electrolyte battery of FIG.

FIG. 4 is an enlarged cross-sectional view showing a portion A of FIG.

[Explanation of symbols]

1 ... Exterior body, 2 ... Electrode group, 3 ... Positive electrode, 4 ... separator, 5 ... Negative electrode, 6 ... Positive electrode current collector, 7 ... Positive electrode layer, 8 ... Negative electrode current collector, 9 ... Negative electrode layer, 10 ... Positive electrode lead, 11 ... Negative electrode lead.

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Claims (2)

[Claims] 1. An electrode group including a positive electrode and a negative electrode having a molecular weight of 200 to 2 having two or more polymerizable functional groups in one molecule.
A non-aqueous electrolyte battery comprising: a step of impregnating a gel electrolyte precursor containing 100,000 monomers, a non-aqueous electrolyte solution, and a surfactant; and a step of gelling the gel electrolyte precursor. Production method. 2. The method for producing a non-aqueous electrolyte battery according to claim 1, wherein the surfactant contains trialkyl phosphate having an alkyl group having 3 to 10 carbon atoms.