JPH1186844A - Battery electrode and battery using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode superior in handling property and having high capacity, high output characteristic, good cycle characteristic, and high safety by integrally forming an electrically insulating fine porous film, having specific strength and elastic modulus on an electrode substrate by the wet coagulation method. SOLUTION: A fine porous film made mainly of a thermoplastic resin is integrally provided on an electrode substrate provided with an active material made of a lithium composite oxide or a carbon material on a conductive material via a binder. A fluorine-containing polymer containing α-polyvinylidene fluoride 40 wt.% or above and/or a sulfur-containing polymer is preferably used for this thermoplastic resin. The fine porous film is made of a wet coagulation paint film with the thickness of about 200 μm or below, having a strength of 0.1-10 MPa, preferably 0.5-2 MPa, an elastic modulus of 10-200 MPa, preferably 10-100 MPa, the median diameter of the fine bore diameter of 40-1500 mm, and the porosity of 40-90%, preferably 65-90%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery electrode and a battery using the same, and more particularly to a battery having high capacity and excellent safety.

[0002]

2. Description of the Related Art In recent years, with the spread of portable devices such as video cameras and notebook personal computers, demand for small and high capacity secondary batteries has been increasing. Most of the secondary batteries that have been used in the past are nickel-cadmium batteries or nickel-hydrogen batteries using an alkaline electrolyte, but the battery voltage is as low as about 1.2 V, and there is a problem in improving the energy density. . Thus, a lithium secondary battery using lithium metal for the negative electrode was developed, but a problem occurred in safety due to the generation of lithium dendrite, and it did not reach full-scale spread. After that, a lithium ion secondary battery using a carbon intercalation compound, which is said to generate less dendrite, as a negative electrode instead of a metal lithium negative electrode was developed, and is now being widely used as a secondary battery for portable equipment.

[0003] However, although the safety of the lithium ion secondary battery has been greatly improved compared to the lithium metal secondary battery, the technology has not yet been established in terms of safety, and in particular, the battery capacity has been increased. With the increased number of batteries, securing safety is an issue.

In a conventional battery, a method is used in which a microporous membrane separator film such as polyethylene or polypropylene is interposed between the positive electrode and the negative electrode. The flowing current
It also has a shutdown function that shuts off due to microporous blockage due to heat generation, which is indispensable for improving battery safety. In particular, polyethylene having a low melting point is effective for improving safety and is currently most commonly used. However, safety has not yet been secured with lithium ion secondary batteries, and examples of smoke and fire accidents have been reported.

The present inventors have conducted intensive studies to further improve the safety of such a battery, and as a result, by appropriately selecting the strength, elastic modulus, pore size, etc. of the microporous membrane directly coated on the electrode. And improved safety. Conventionally used separators require high strength and elastic modulus due to electrode entanglement and the like.
A film of about MPa and an elastic modulus of about 2 GPa is used. However, as described above, safety is not ensured even if these separators are used.

On the other hand, in a solid polymer electrolyte which is said to suppress the generation of lithium dendrite and improve safety, a solvent such as an electrolytic solution solvent is added in order to enhance ionic conductivity and is used as a gel polymer. ing. However, these solid electrolytes have an elastic modulus of 10 ⁻⁴ to 10 ⁻⁵ Pa
In other words, the retention between the electrodes becomes a problem, and a separator which should be unnecessary is interposed between the electrodes in many cases.

Conventionally, measures for ensuring safety (especially passing a destructive test such as a nail penetration test or a crush test) include (1) a method devised for an electrode material and an electrolytic solution; 2) There is a device devised for a battery configuration, a safety device, and the like (for example, JP-A-5-326017, JP-A-6-203827, JP-A-6-215749, JP-A-6-325755, JP-A-6-33
No. 3548). As (1), use of LiMn ₂ O ₄ having relatively high thermal stability as a positive electrode active material, use of a flame-retardant electrolytic solution, and a separator having a shutdown effect have been attempted. As (2), a pressure rupture disk, a PTC element, a current cutoff valve, and the like have been tried.

However, it is difficult to secure the safety of a battery having high energy density and high output characteristics only by these measures. In particular, when a LiNiO ₂ -based positive electrode active material, which is expected to have a high capacity but has a problem in safety, is used, it was practically impossible.

In addition, the countermeasure (2) is categorized as follows. A positive electrode equipotential exposed metal portion and a negative electrode exposed metal portion are provided on the outermost peripheral portion and / or innermost peripheral portion of the wound electrode body.
A battery having a configuration in which the batteries are opposed to each other over a length equal to or longer than the circumference has been proposed (Japanese Patent Application Laid-Open No. 8-153542). However, the publication does not specifically describe a specific safety improvement effect such as a battery capacity.

[0010]

On the other hand, the present inventors have studied and found that a battery using a microporous membrane-coated electrode manufactured by a wet coagulation method is excellent in high energy density and high output characteristics. (See Japanese Patent Application No. 8-254330). Furthermore, as a result of intensive studies, the present inventors found that the outermost and / or innermost portions of the above-mentioned microporous membrane-coated electrode and the wound electrode body were
The positive electrode equipotential conductor and the negative electrode equipotential conductor are
It has been found that the safety can be more reliably ensured by using a configuration in which the components are opposed to each other over the length of the circumference.

Accordingly, an object of the present invention is to provide a battery electrode having high capacity, high output characteristics, good cycle characteristics, and high safety, and a battery using the same.

[0012]

That is, the present invention has the following arrangement to solve the above-mentioned problems.

(1) An electrode for a battery, wherein an electrically insulating microporous film is provided integrally on an electrode substrate.

(2) The battery electrode according to the above (1), wherein the microporous film contains a thermoplastic resin as a main component.

(3) The battery electrode as described in (2) above, wherein the thermoplastic resin contains a fluorine-containing polymer and / or a sulfur-containing polymer.

(4) The battery electrode as described in (3) above, wherein the content of α-type polyvinylidene fluoride in the thermoplastic resin is 40% by weight or more.

(5) The battery electrode as described in (4) above, wherein the content of α-type polyvinylidene fluoride in the thermoplastic resin is 80% by weight or more.

(6) The battery electrode according to the above (1), wherein the microporous film is a wet solidified coating film.

(7) The battery electrode according to the above (1), wherein the microporous membrane is a membrane solidified on the electrode.

(8) The strength of the microporous membrane is 0.1 MPa
(1) wherein the pressure is not less than 10 MPa.
An electrode for a battery according to item 1.

(9) The strength of the microporous membrane is 0.5 MPa
The battery electrode according to the above (8), which is at least 2 MPa or less.

(10) The microporous membrane has an elastic modulus of 10 MP
The electrode for a battery according to the above (1), which has a of not less than a and not more than 200 MPa.

(11) The elastic modulus of the microporous membrane is 10MP
The battery electrode according to the above (10), which is not less than a and not more than 100 MPa.

(12) The battery electrode according to the above (1), wherein the median diameter of the pore diameter of the microporous membrane is 40 nm to 1500 nm.

(13) The porosity of the microporous membrane is 40 to 9
The battery electrode according to the above (1), which is 0%.

(14) The porosity of the microporous membrane is 65 to 9
The battery electrode according to the above (13), which is 0%.

(15) The microporous membrane according to (1), wherein the microporous membrane is a porous membrane containing at least one material selected from a heat absorbing material, a flame retardant material and an antioxidant. Electrodes for batteries.

(16) The electrode for a battery according to the above (15), wherein the heat absorbing material is an organic compound containing zinc and / or manganese.

(17) The method according to (15) or (16), wherein the flame retardant is a bromine-containing organic compound.
An electrode for a battery according to item 1.

(18) The battery electrode according to the above (15), wherein the antioxidant is a hindered amine organic compound.

(19) The battery electrode according to the above (15), wherein the electrode material comprises an active material and / or a binder and a conductive material.

(20) The battery electrode according to the above (19), wherein the active material is a lithium composite oxide.

(21) The lithium composite oxide is Li _X
CoO ₂ (0 <x ≦ 1.0), Li _X NiO ₂ (0 <x
≦ 1.0) or an electrode for a battery according to the above (20), wherein a part of these metal elements is replaced with an alkaline earth metal element and / or a transition metal element.

(22) The battery electrode according to the above (21), wherein the active material is a carbonaceous material.

(23) The method according to (2), wherein the carbonaceous material comprises carbon fiber and / or graphite powder.
The battery electrode according to 2).

(24) The battery electrode according to the above (23), wherein the carbon fibers are in the form of short fibers having an average length of 30 μm or less.

(25) A battery using the electrode according to any one of (1) to (24).

(26) The battery according to (25), further comprising a separator between the electrodes.

(27) The above-mentioned (25), wherein a conductor having an equipotential with the positive electrode and a conductor having an equipotential with the negative electrode are wound and laminated so as to face one or more turns via a separate material.
Or the battery according to (26).

(28) The battery according to (27), wherein the opposed conductor is provided on the outermost and / or innermost portion of the wound electrode body.

(29) The battery according to (27), wherein the separate substance is a microporous film containing a thermoplastic resin as a main component.

(30) The battery according to (25), wherein the battery is a secondary battery.

(31) The battery according to the above (30), wherein a non-aqueous electrolyte is used.

(32) The battery according to the above (31), wherein the non-aqueous electrolyte contains an alkali metal salt electrolyte.

(33) The battery according to (32), wherein the alkali metal salt is a lithium salt.

(34) The volume energy density is 265 W
h / l or more, wherein the battery according to the above (25),

(35) The volume energy density is 300
The battery according to the above (34), which is at least Wh / l.

(36) The weight energy density is 110 W
h / kg or more, the battery according to (25) above,

(37) The weight energy density is 125 W
h / kg or more, the battery according to (36) above.

[0050]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the fact that the microporous film is provided integrally on the electrode substrate means that there is no layered gap between the microporous film and the electrode substrate, and that the microporous film can be processed or used normally. In the state, it means that both are joined to an extent sufficient to behave integrally. Therefore, this is different from a conventional separator or polymer electrolyte simply interposed between electrode substrates and laminated. For example, it can be usually manufactured by forming a film directly on an electrode substrate.

The microporous membrane used in the present invention has a strength of 0.1 MPa or more and 10 MPa or less, an elastic modulus of 10 MPa or more and 200 MPa or more, and more preferably a strength of 0.5 MPa or more. It is used at an elastic modulus of 10 MPa or more and 100 MPa or less. For those lower than these strength and elastic modulus ranges,
In use, the microporous membrane is easily broken, and problems such as difficulty in holding between the electrodes also occur. On the other hand, if the strength or the elastic modulus is too high, the effect of maintaining the electrical resistance between the electrodes when the battery is pierced as described below does not occur, so that a short circuit occurs and the safety of the battery decreases. In other words, it is not clear why batteries using such microporous membranes having such mechanical properties have improved safety.However, these microporous membranes have a lower mechanical strength than separators, and therefore, these fragments when nailing are used. Is left on the electrode surface, and the contact between the positive electrode and the negative electrode maintains a slight resistance without reaching a complete short circuit, so that it is considered that rupture and ignition were suppressed. Although the strength of the microporous membrane in the present invention is lower by two to three orders of magnitude than that of the conventional separator, the microporous membrane in the present invention is directly coated on the electrode, so that particularly high strength is not required.

For measurement of the mechanical properties of the microporous membrane, a general measuring instrument is used, and the measurement is performed at room temperature. The strength is
The value obtained by dividing the maximum load by the apparent initial cross-sectional area of the test piece was used. The elastic modulus was a value obtained by calculating the gradient in the weight-crosshead movement amount diagram, multiplying the largest value of the gradient by the grip interval, and dividing the result by the cross-sectional area of the test piece. In addition,
As the test piece of the microporous film, a film peeled off from the electrode surface or a film obtained by coating a metal foil with an equivalent method and then dissolving the metal was used.

In the present invention, for example, α-type PVDF
The microporous membrane containing as a main component is also electrically insulating and ion-permeable, so that it can also serve as a separator film. That is, when the electrode is used as at least one of the positive and negative electrodes, it is possible to configure a battery without interposing a separator film between the electrodes. In this case, without using a conventional expensive separator film, it is possible to simplify the current process having a complicated manufacturing process, and furthermore, the yield due to conduction (short circuit) between the positive electrode and the negative electrode due to the occurrence of winding deviation during electrode fabrication. There is an advantage that a decrease can be prevented.
Furthermore, the gap between the electrodes can be reduced as compared with the conventional separator film due to the membrane characteristics of the coated separator, so that not only the electrode filling amount in the battery can can be increased (battery capacity improvement), but also the distance between the electrodes can be shortened. Can be
In addition, since the resistance to ion permeability is small, a decrease in capacity during high-power discharge can be reduced. In the case of a conventional separator, if the film thickness is not about 25 μm, a short circuit occurs when the electrode is entangled, but the separator directly coated on the electrode material of the present invention can sufficiently prevent the short circuit even with a film thickness of about 10 μm. .

Of course, at least one of the positive and negative electrodes may be the electrode of the present invention, and a separator film may be interposed between the electrodes. This is preferable in some cases because the yield is improved. Further, by using the microporous membrane and the separator together, there is also an advantage that the above-mentioned shutdown effect can be reliably performed in a short time.

As a method of using a PVDF ion-permeable membrane for a battery, a method as a polymer solid electrolyte and a method as a microporous membrane are known. Examples of the former are disclosed in US Pat. No. 5,296,318, WO95 / 0.
6332. These are all related to a homogeneous polymer electrolyte, and have no voids or pores in the polymer film to suppress the generation of dendrites, and a copolymer with hexafluoropropylene to reduce the crystallinity of the polymer. It is characterized by doing.

On the other hand, as a known example of a battery using a microporous PVDF membrane, there is JP-A-8-250127. Here, the microporous membrane is a structure holding a separator film or an electrode active material, and for application to a battery, only by interposing the porous membrane between electrodes,
There is no description of a method of directly coating the porous membrane on the electrode surface to cover the surface, and no description is given of the mechanical properties of the microporous membrane. In the known example,
It is described that a β-type structure is required as a crystal structure of PVDF in order to increase ionic conductivity, and it is necessary to apply stretching or tension for that purpose. Part of the present invention is
Surprisingly, by coating the electrode surface with a porous α-type PVDF, which has been considered to have little effect on improving safety and low ionic conductivity, surprisingly, battery safety is improved. It is based on the finding.

The present inventors have found that the battery of the present invention is also effective for an electrochemical safety test such as an overcharge test and a heating test. In other words, safety devices such as a pressure rupture plate, a PTC element, and a current cutoff valve are usually tried for troubles in battery use such as overcharge and heating, but these are applied to the battery of the present invention. At least, they found that they passed electrochemical safety tests such as overcharge tests and heating tests. Although the clear reason for this effect is not clear, it is speculated that it may be due to the shutdown effect of the microporous membrane.

The method for producing a microporous film according to the present invention includes (1) immersing a polymer film containing a good solvent in a poor solvent to replace the good solvent with the poor solvent, and (2) containing a foaming agent. (3) dipping a polymer film containing a solvent-soluble substance into the solvent to elute the substance, and the like.

First, (1) will be described in detail. A raw material solution is prepared by dissolving the polymer in a solvent. That is, PV
DF is dissolved in N-methyl-2-pyrrolidone at about 1% to 20% by weight. Next, the electrode substrate prepared in a sheet shape is placed in the raw material solution for a predetermined time, preferably 1 second to 1 second.
It is immersed for about 0 minutes and pulled up by, for example, a dip method. If necessary, excess material solution attached to the electrode substrate is removed. The immersed electrode substrate is immersed in an extraction solvent such as water, methanol, ethanol, acetone or hexane (one or a mixture of two or more may be used) for a predetermined time, preferably 10 seconds to 100 minutes. After the lifting, the solvent in the PVDF film directly coated on the electrode substrate is replaced with the extraction solvent to make the PVDF film microporous. Thereafter, the electrode is dried and, if necessary, pressed by a roll press method or the like to obtain the electrode of the present invention in which the microporous film is directly coated on the electrode substrate. In addition, although the pores of the coating may be slightly deformed by the above-described press working, the separator is selected by selecting the pressing conditions (pressure, temperature, etc.), the type and the mixing ratio of the conductive material and the binder, and the like. A film that does not impair the performance is obtained. The film density of the microporous film of the present invention is about 0.1 to 3.0 g / cm ³ . This method is characterized in that the thickness and the porosity of the porous film can be controlled relatively easily by appropriately selecting the manufacturing conditions.

Regarding (2), a raw material solution prepared in the same manner as (1) is mixed with an inorganic blowing agent such as ammonia carbonate, sodium bicarbonate, an equimolar mixture of sodium nitrite and ammonium chloride, and dinitrosopentamethylenetetramine (DP).
T), nitroso compounds such as N, N'dimethyl N, N'dinitrosoterephthalamide, benzenesulfonyl hydrazide, P-
Toluenesulfonyl hydrazide, P-P'oxybis, 3-3 '
1 selected from organic blowing agents such as sulfohydrazide compounds such as disulfone hydrazide diphenyl sulfone, azo compounds such as azobisisobutyronitrile, azodicarbonamide (AC), barium azodicarboxylate, and diethyl azodicarboxylate. Add more than one kind of blowing agent,
After uniform mixing, the sheet-shaped electrode material is immersed in the raw material solution containing the foaming agent for several seconds to 10 minutes, and pulled up by, for example, a dip method. If necessary, excess raw material solution attached to the electrode material is removed. After this, Equation 1
The electrode of the present invention is dried at a temperature of about 0 ° C. to 200 ° C., foamed, and if necessary, pressed in the same manner as (1) to directly coat the electrode material with the porous separator membrane. can get. Here, among the foaming agents, DP having a high foaming temperature is used.
For T and AC, it is effective to use a foaming aid such as salicylic acid, stearic acid, zinc white, and urea.

Regarding (3), for example, a fine powder of sodium chloride is added to the inside of the coating in the same manner as in the foaming agent of (2).
The sodium chloride can be eluted by immersion in water to make it porous.

The thickness of the porous film is preferably 200 μm or less in order to reduce the internal resistance of the battery.
More preferably 50 μm or less, particularly preferably 25 μm
m or less.

As the crystal structure of PVDF, α-form, β-form
Types, γ-type and δ-type are known, and the PVDF microporous membrane used in the present invention preferably has an α-type structure. The identification of the crystal structure was performed by the usual wide-angle X-ray diffraction method. The α-type structure is 18-1 which was observed by X-ray diffraction measurement using CuKα radiation.
This was confirmed by strong (100), (020), and (001) diffraction lines near 9 degrees.

In the above description, a microporous membrane composed of only PVDF has been described. However, if PVDF exhibits α-type,
A mixed system with another polymer, such as a blend with another polymer, is also preferably used.

The porosity of the microporous membrane is preferably large from the viewpoint of ionic conductivity. If the porosity is too large, the effect of covering the electrode surface is reduced.
5-90% is preferably used. Note that the porosity of the microporous membrane used in the present invention is difficult to measure in a state where the microporous membrane is coated on the electrode. Therefore, a microporous membrane formed on a support such as a metal foil is shown below. It was measured by the mercury porosimeter method. That is, after the cell in which the sample is placed is degassed (attained to about 0.7 Pa), mercury is injected, and attached to a porosimeter device (Model 2000 manufactured by Carlo Elba), and the measurement pressure range; porosity at about 100 kPa to 190 MPa Was measured. The pore distribution is also measured by a porosimeter. The median diameter of the pore diameter used in the present invention is preferably 40 nm to 1500 nm. 40n
m, it affects the high output characteristics of the battery.
If it is larger than nm, the improvement in safety is impaired, which is not preferable.

Next, another important component of the present invention is that “a conductor having the same potential as the positive electrode and a conductor having the same potential as the negative electrode are wound one or more times via a separate material. The fact that they are stacked will be described below.

Normally, when there is a physical impact from the outside of the battery can such that the battery can is deformed (such as a nail penetration test or a crush test), for example, the separator is broken due to deformation of the positive electrode or the negative electrode, and the positive electrode material is damaged. And the negative electrode material or the respective current collectors contact each other (electrically short-circuit). The short-circuit current concentrates on this short-circuit portion, Joule heat is generated, and the temperature rise causes the final reaction due to the reaction between the negative electrode and / or positive electrode and the electrolytic solution and the release of active oxygen due to the decomposition of the charged positive electrode active material. It eventually explodes and ignites. Therefore, in the present invention, the conductor having the same potential as the positive electrode and the conductor having the same potential as the negative electrode are wound and laminated so as to face one or more turns via a separate material, By generating heat in the initial short-circuit area where there is no unstable active material in the charged state, it is possible to suppress the decomposition of the positive electrode active material in the charged state and reduce the degree of battery rupture and ignition I guess it could be prevented. In addition,
In connection with this invention, the present inventors have already filed Japanese Patent Application No. 8-85.
313 (in the patent, there is a description of "electrically connected conductor" in the claims, but the term "conductor" as used herein is apparent from the description in the specification and examples. Thus, it may be integrated with the current collector).

Further, when the conductor-facing portion is located at the outermost periphery of the wound electrode body, heat is easily radiated to the outside of the battery can, and an initial short circuit occurs at the outermost periphery as in a nail penetration test. It is considered effective. Further, when the conductor facing portion is located at the innermost periphery of the wound electrode body, it is considered to be effective when an initial short circuit easily occurs at the innermost periphery having a small winding radius as in a crush test. Can be Therefore, it is preferable to use them in combination, since a battery more effective for a nail penetration test and a crush test can be produced. Further, the battery can may be an equipotential conductor with the positive electrode or the negative electrode. Alternatively, an external electrode having a polarity different from that of the battery can may be provided outside the battery can, and the battery may be wound around the battery can via a separate substance. This can be applied to all batteries as a safety device, and may be excellent in versatility and compatibility.

The separator between the conductor having the same potential as the positive electrode and the conductor having the same potential as the negative electrode may be a separator such as a polyethylene microporous membrane commonly used for batteries or the separator according to the present invention. A coated microporous membrane may be used.
The combined use of these is also effective for preventing short circuit during normal use.

The above configuration is effective not only for instantaneous energy consumption but also for the outermost and / or innermost portions even if the wound electrode body continues to be pierced by a nail in a nail piercing test, for example. It is expected that the resistance of the short-circuited portion between the positive and negative electrodes and the conductor having the same potential is the smallest, and the short-circuit current is concentrated on the short-circuited portion, so that the safety is considered to be higher.

FIG. 1 shows an example of an embodiment relating to the configuration of the present invention, but the present invention is not limited to this.
An electrically insulating separate substance 12 is provided on the outer periphery of the battery can 5 having the same potential as the negative electrode, and a conductor 13 electrically connected to the battery lid 7 having the same potential as the positive electrode is laminated thereon as an external electrode. It has a structure.

The material of the separate substance 12 is not particularly limited as long as the electrical insulation between the battery can 5 and the conductor 13 can be maintained. Specifically, polymers such as polyethylene, polypropylene, polyester, Teflon, and polyethylene glycol (molecular weight of 1,000 or more) and laminates thereof (for example, polypropylene / polyethylene / polypropylene), fluorine-containing rubber, silicon, chloroprene rubber, and the like. Examples include a sheet-like material made of various rubbers, nonwoven fabric, papers, glass, and the like, a coating film (for example, a microporous film in the present invention), a bead-like material, and the like.

The thickness of the separate substance 12 is not particularly limited, and is determined by the size of the battery to be manufactured, the material used as the separate substance, and the like.

Further, these separate substances do not need to be present on the entire outer peripheral portion of the battery can, and may be present only on a part of the outer peripheral portion of the battery can as long as the electrical insulation of the conductor 13 is maintained. Further, when there is a physical impact such as deformation of the battery can from the outside (a nail penetration test, a crush test, etc.), it is preferable that the battery can 5 and the conductor 13 contact immediately. When the inside of the battery can generates heat for some reason or the battery itself is exposed to a high temperature, the separate substance is melted, and the battery can 1 and the conductor 13 come into contact (short circuit).
It is desirable to be able to release energy.

Regarding the method of attaching the separate substance 12, it may be wound around or applied to the outer periphery of the battery can in advance, or may be installed after the battery is manufactured. In addition, it may be pasted or applied to the conductor 13 in advance. Also,
As an example of a method for installing the separate substance 12 and the conductor 13 on the inner peripheral portion of the battery can, usually, a positive electrode sheet, a separator and a negative electrode sheet are rolled up to produce a wound electrode body. At the time, the portion of the positive electrode current collector not coated with the positive electrode active material is left in the latter half of the winding,
At least one part of the current collector only and the separator
After the winding, the battery is manufactured by a generally known method. Thereby, even if the battery can is deformed or a nail or the like is stabbed, the battery can and the portion of the positive electrode current collector where the positive electrode active material is not applied are short-circuited first. In addition, by winding not only the positive electrode but also the negative electrode, the conductors are short-circuited with lower resistance, so that the safety is more effectively improved. In the case of the innermost peripheral portion, on the contrary, the portion of the positive electrode current collector that is not coated with the positive electrode active material is taken to the first half of the winding, and the current collector only portion and the separator are wound at least one or more times, Thereafter, a battery is manufactured by a generally known method. By winding not only the positive electrode but also the negative electrode in the same manner, short-circuiting is achieved with lower resistance and the safety is more effectively improved as in the case where the conductor facing portion is provided on the outermost periphery. Further, even if the battery can is connected to be at the same potential as the positive electrode,
It is obvious that the same effect can be obtained by reversing the positive electrode and the negative electrode.

Further, an electrode having the same potential as that of the battery can is laminated on the outer peripheral portion and / or the inner peripheral portion of the battery can via a separate material, and the other outer and / or inner peripheral portion is provided on the outer periphery and / or the inner peripheral portion. There is no problem with the configuration in which the electrode and the electrode body having the same potential are stacked via a separate substance as long as the object of the present invention can be achieved. Further, even if an active material layer is provided on a surface of the conductor which is not opposed to the other conductor, there is no problem as long as the object of the present invention can be achieved.

The conductor 13 is not particularly limited as long as it has conductivity, and examples thereof include a metal material and a carbonaceous material.
In particular, metal materials such as aluminum, copper, nickel, stainless steel, and iron are preferable from the viewpoint of workability and cost. The conductor 13 may be separately electrically connected to the current collector,
An uncoated portion of the active material layer may be provided on the current collector, and a part of the current collector may be used as the conductor 13. In addition, there is no problem even if a protective film such as a heat-shrinkable film, which is applied to a normal battery, is provided on the outer peripheral portion of the conductor 13.

Further, even if the battery itself is not provided with the safety mechanism of the present invention, a battery pack in which a plurality of batteries are connected in series and / or in parallel, the whole or a part thereof is covered with a separate substance, and the battery can and Even if conductors connected to different polarities are stacked, there is no problem as long as the same safety mechanism as in the present invention works effectively, and various devices for applying the same safety mechanism as in the present invention are possible.

The carbon material used in the present invention is not particularly limited, and generally, a carbon material obtained by calcining an organic substance or graphite is used. As the form of the carbon body, a powdered or fibrous carbon body is preferably used. Examples of the powdered carbon include natural graphite, artificial graphite, coke such as fluid coke, pitch such as coal or petroleum, fired bodies such as mesocarbon microbeads, polyacrylonitrile (PAN) or a copolymer thereof, cellulose, and polyvinyl alcohol. , Lignin, polyvinyl chloride, polyamide, polyimide, phenol resin, and furfuryl alcohol. Examples of the fibrous carbon body include a PAN-based carbon fiber obtained from PAN or a copolymer thereof, a pitch-based carbon fiber obtained from a pitch such as coal or petroleum, a cellulosic carbon fiber obtained from cellulose, and a gas of a low molecular organic substance. And carbon fibers obtained by sintering the above-mentioned polyvinyl alcohol, lignin, polyvinyl chloride, polyamide, polyimide, phenol resin, furfuryl alcohol, and the like. .

Among them, a carbon body satisfying the characteristics is appropriately selected according to the characteristics of the electrode and the battery in which the carbon body is used. In the case where the carbon material is used for a negative electrode of a secondary battery using a non-aqueous electrolyte containing an alkali metal salt, a PAN-based carbon material, a pitch-based carbon material, and a vapor-grown carbon material are preferable. In particular, a PAN-based carbon body is preferably used in that the doping of an alkali metal ion, particularly, a lithium ion is good. The particle size of the powdered carbon body is
Preferably 0.1 to 100 μm is used, and more preferably 1 to 50 μm. The diameter of the carbon fiber should be determined so as to easily adopt each form, but is preferably 1 to 1000 μm, more preferably 1 to 20 μm, and particularly preferably 3 to 15 μm. It is also preferable to use several types of carbon fibers having different particle sizes. The average length of the carbon fibers is 1 mm or less, more preferably 50 μm or less, and even more preferably 8 to 30 μm. The lower limit is the ratio of the fiber length to the fiber diameter (aspect ratio)
Is preferably 1 or more. If the average length is 1 mm or more,
When a slurry is used to form a sheet-like electrode, the coatability is poor, and when the electrode is used, a short circuit between the positive and negative electrodes is liable to occur. Aspect ratio is 1
If the ratio is less than the above, the ratio of the active carbon surface exposed by cleavage during powdering becomes excessively large, so that the cycle characteristics deteriorate. The average length of the fiber is determined by measuring the length of at least 20 carbon bodies in the fiber direction by microscopic observation such as SEM. In order to cut or pulverize the carbon fiber to 1 mm or less, various pulverizers can be used.

In consideration of the balance between cycle characteristics and capacity performance, a system in which graphite powder and carbon fiber, or amorphous carbon powder and carbon fiber are appropriately mixed may be preferable.

Further, other than the carbon body, for example,
Periodic Table IV-B as shown in JP-A-235293
And / or V-B semimetals (Ge, Sn, Pb, S
Compounds such as b, Bi) or a metal oxide selected from In, Zn, and Mg, and polyacene are also used as the negative electrode active material.

In the negative electrode of the present invention, metals such as copper and stainless steel can be used as a current collector in order to enhance the current collecting effect. The metal current collector is not particularly limited, such as a foil shape, a fiber shape, and a mesh shape.
For example, when a foil-like metal current collector is used, a sheet-like electrode is produced by applying a slurry on a metal foil. In order to further enhance the current collecting effect, carbon black such as acetylene black, Ketjen black, and furnace black is added to the sheet-shaped electrode. Further, conductive powder such as carbon powder and metal powder may be added for the purpose of improving conductivity.

As the positive electrode active material used for the electrode used in the present invention, artificial or natural graphite powder, inorganic compounds such as carbon fluoride and metal oxide, organic polymer compounds and the like are used. In this case, when an inorganic compound such as a metal oxide is used as the positive electrode, a charge / discharge reaction occurs using doping and undoping of the cation. In the case of an organic polymer compound, a charge / discharge reaction occurs by doping and undoping of an anion. As described above, various charge / discharge reaction modes are adopted depending on the substance, and these are appropriately selected according to the required positive electrode characteristics of the battery. Specifically, inorganic compounds such as transition metal oxides and transition metal chalcogens containing alkali metals, conjugated polymers such as polyacetylene, polyparaphenylene, polyphenylenevinylene, polyaniline, polypyrrole, and polythiophene, and crosslinked polymers having disulfide bonds For example, positive electrode active materials used in ordinary secondary batteries can be mentioned. Among these, in the case of a secondary battery using a non-aqueous electrolyte containing a lithium salt, transition metal oxides and transition metals such as cobalt, manganese, nickel, molybdenum, vanadium, chromium, iron, copper, and titanium are used. Chalcogens are preferably used. In particular, Li _x CoO ₂ (0 <x ≦ 1.
0), Li _x NiO ₂ (0 <x ≦ 1.0), or a lithium composite oxide obtained by substituting a part of these metal elements with an alkaline earth metal element and / or a transition metal element (see, for example, 17430) and Li _x MnO ₂ (0 <x
≦ 1.0), Li _x Mn ₂ O ₄ (0 <x ≦ 1.3) and the like are preferably used.

For the positive electrode used in the present invention, a metal such as aluminum, nickel, stainless steel or titanium can be used as a current collector in order to enhance the current collecting effect as in the case of the negative electrode. As in the case of the negative electrode, carbon black such as acetylene black and Ketjen black is added as a conductive agent. Furthermore, carbon powder for the purpose of improving conductivity,
A conductive powder such as a metal powder may be added.

The method for producing these positive and negative electrodes is not particularly limited, but a paste obtained by kneading a binder, an active material, and a conductive agent with an organic solvent or water on the above-mentioned current collector is applied. It is dried, pressed and formed into a sheet. The solvent and the solid content concentration used for the pasting are not particularly limited, but are appropriately determined in consideration of the resin used, the coating method, the drying conditions, and the like. Also, in the paste, a surfactant for improving applicability, an antifoaming agent, a dispersant,
Various additives such as an ultraviolet absorber and a stabilizer for improving storage stability can be added.

The electrolytic solution used in the present invention is not particularly limited, and a conventional electrolytic solution can be used, and examples thereof include an aqueous acid or alkali solution, and a non-aqueous solvent. Among these, propylene carbonate (PC), ethylene carbonate (EC), and γ are used as electrolytes for a secondary battery composed of a non-aqueous electrolyte containing the above-described alkali metal salt.
-Butyrolactone (BL), N-methylpyrrolidone (N
MP), acetonitrile (AN), N, N-dimethylformamide, dimethylsulfoxide, tetrahydrofuran (THF), 1,3-dioxolan, methyl formate,
Sulfolane, oxazolidone, thionyl chloride, 1,2-
Dimethoxyethane (DME), dimethyl carbonate (DMC), diethylene carbonate (DEC), dimethylimidazolidinone, a derivative thereof, a mixture of two or more thereof, and the like are preferably used. As the electrolyte contained in the electrolytic solution, alkali metal, especially lithium halide, perchlorate, thiocyanate, borofluoride,
Phosphorus fluoride, arsenic fluoride, aluminum fluoride,
Trifluoromethyl sulfate and the like are preferably used.

The present invention can be used for various types of batteries, and there is no particular limitation on what kind of battery it is used for, such as a primary battery and a secondary battery. It is preferably used as a lithium metal secondary battery, which is a liquid secondary battery, and further as a lithium ion secondary battery. The form of the battery is not particularly limited, such as a square type, a cylindrical type, a card type, and a coin type.

Since the safety of a battery generally tends to decrease as the battery energy increases, it is said that a high energy battery, for example, a lithium ion secondary battery having a high energy does not use a lithium metal negative electrode. However, technology for ensuring safety is an important issue. The present invention is preferably used as a safety measure for such a high energy battery. Specifically, the volume energy density 26
5 Wh / l or more, and / or weight energy density 1
It is effectively used as a measure for improving safety of a battery having a capacity of 10 Wh / kg or more, more preferably a battery having a volume energy density of 300 Wh / l or more and / or a weight energy density of 125 Wh / kg or more.

According to the present invention, a battery with high capacity, high output characteristics, good cycle characteristics, and high safety can be provided.

The secondary battery using the electrode of the present invention can be used in video cameras, personal computers, word processors, radio cassettes,
Mobile phone, handy terminal, CD player, MD
It can be widely used for portable small electronic devices such as players, electric shavers, liquid crystal televisions and toys, and portable small electronic devices such as electric vehicles.

[0092]

EXAMPLES Specific embodiments of the present invention will be described below with reference to examples, but the present invention is not limited thereto.

Example 1 (1) Preparation of Positive Electrode Commercially available lithium carbonate (Li ₂ CO ₃ ) and basic cobalt carbonate (2CoCO ₃ .3Co (OH) ₂ were used in a molar ratio of Li.
/ Co = 1/1, weighed so as to be 1/1, wet-mixed with a zirconia ball mill (using ethanol as a grinding solvent), and then heat-treated at 900 ° C. in the air for 20 hours to synthesize LiCoO ₂ . This was pulverized by the ball mill to obtain a LiCoO ₂ powder as a positive electrode active material.

The cathode active material was 91% by weight, PVDF
6% by weight (KF polymer # 1100 manufactured by Kureha Chemical Co., Ltd.) and 3% by weight of acetylene black ("Denka Black", manufactured by Denki Kagaku) are added, and the same amount of NMP is added, kneaded and paste. I made it.

This paste was coated on one surface of an aluminum foil having a thickness of 16 μm with a positive electrode active material weight per unit area of 200 μm.
g / m ² , and dried at 100 ° C. for 15 minutes, then applied to the other surface, dried at 100 ° C. for 30 minutes, and further dried at 180 ° C. for 15 minutes to form a sheet electrode using LiCoO _2. Was prepared. The sheet electrode is applied with a linear pressure of about 1
After being pressed with a roller press at 00 kg / cm and pressed against an aluminum current collector, slitting was performed to obtain a positive electrode having a total thickness of 190 μm.

(2) Preparation of Negative Electrode 85% by weight of short fibrous carbon fiber ("Treca" milled fiber: MLD-30, manufactured by Toray Industries, Inc.) was used as the negative electrode active material.
10% by weight of DF (described above), acetylene black (described above)
Was weighed, and about 1.4 times NMP was added thereto and kneaded to form a paste.

This paste was applied to one surface of a copper foil having a thickness of 10 μm, dried at 100 ° C. for 15 minutes, and the other surface was slightly reduced in the basis weight (the amount of active material per unit area). And dried at 100 ° C for 30 minutes.
And dried in a nitrogen stream for 15 minutes to produce a sheet electrode using short fibrous carbon fibers. A linear pressure of about 10
After being pressed with a roller press at 0 kg / cm and pressure-bonded to the copper foil current collector, a slit was obtained to obtain a 200 μm-thick battery electrode.

(3) Preparation of Raw Material Solution for Microporous Membrane NMP was added to PVDF (described above), and the mixture was completely dissolved by stirring.
A solution was prepared.

(4) Preparation of Microporous Membrane The positive electrode prepared in (1) was immersed in the solution prepared in (3), pulled up by a dipping method, and placed in a methanol solution.
Then, the electrode was dried at 60 ° C. for 20 minutes to produce an electrode. The thickness of the microporous film coated on the electrode material was 15 μm as observed by a scanning electron microscope (SEM).
The microporous film was coated on the negative electrode prepared in (2) in the same manner. The thickness of the obtained microporous membrane was 12 μm. The crystal structure of the microporous film coated on these electrodes was measured by X-ray diffraction using CuKα radiation.
Strong diffraction lines belonging to (100), (020), and (001) planes were observed at 7.87 °, 18.39 °, and 19.19 °, respectively, indicating that the microporous PVDF membrane has an α-type structure. It was confirmed.

A microporous film was formed on an aluminum metal foil in the same manner as described above, and the aluminum metal foil was dissolved to obtain a microporous film. Ten films were stacked and subjected to a tensile test using a universal material testing machine (Model 1185; manufactured by Instron), and the strength and elastic modulus were determined by the crosshead displacement method. Table 3 shows the results. Further, Table 3 also shows the results of measuring the pore median diameter and the porosity by the mercury intrusion method (Mercury porosimeter 2000 manufactured by Carlo Elba).

(5) Electrolyte solution LiPF ₆ was prepared by dissolving LiPF ₆ at a ratio of 1 mol / l in a mixed solvent of equal volumes of PC and DMC.

(6) Preparation of Battery FIG. 2 is a schematic longitudinal sectional view of the nonaqueous electrolyte secondary battery of the present invention. The microporous film top-coated positive electrode 1 and negative electrode 2 obtained in the above (4) are rolled up, and are housed in a battery can 5 with insulators 4 installed above and below.

The battery lid 5 is provided with a sealing gasket 6 on the battery can 5.
And are electrically connected to the negative electrode 1 and the positive electrode 2 via the negative electrode lead 11 and the positive electrode lead, respectively, and are configured to function as a battery.

Such a non-aqueous electrolyte secondary battery was produced as follows. A negative electrode lead 10 made of nickel and a positive electrode lead 11 made of aluminum were previously welded to the current collector portions of the negative electrode 1 and the positive electrode 2. After partially using a conventional separator for the current collector portions of the negative electrode 1 and the positive electrode 2,
The negative electrode 1 and the positive electrode 2 were spirally wound while being stacked to obtain a spirally wound electrode having an outer diameter of about 17 mm. Here, as a method of preventing an electrical short circuit between the current collector of the positive electrode 2 and the negative electrode 1, even if a room-temperature-curable epoxy resin (electrically insulating) is uniformly applied and cured, the above-described microporous film is topped. You may coat. In addition to the above-described coating of the electrically insulating resin, any method may be used as long as it achieves the purpose of preventing the electrical short circuit between the positive and negative electrodes, for example, by attaching an electrically insulating tape.

After the insulating plates 4 are arranged on the upper and lower end surfaces of the spirally wound electrode thus produced, the battery can 5
, And insert the positive electrode lead 11 into the battery lid and the negative electrode lead 10
Was welded to the battery can 5. An electrolytic solution was injected into the battery can 5 in a glove box in an argon atmosphere. The battery lid 7 is fixed by caulking the battery can 5 through the insulating sealing gasket 6 coated on the surface with asphalt, and the airtightness is maintained in the battery, so that the 18650-size cylindrical non-aqueous electrolyte secondary battery is formed. Eleven were assembled.

One of these batteries was charged at a constant current / constant voltage for 3 hours under the conditions of a charge end voltage of 4.2 V and a charge current of 1 A, and then a discharge end voltage of 2.75 V and a discharge current of 0.2 A The initial capacity was determined by discharging at a constant current under the following conditions. Next, the same charge is performed, and after the charge, the discharge end voltage is set to 3.0.
V, a charge / discharge cycle in which constant current discharge is performed under a high output condition of a discharge current of 2.0 A is repeated 300 times, and the discharge capacity of the 300th charge / discharge cycle and the first discharge capacity are compared. Capacity retention rate was determined.

Capacity retention (%) = {(300th discharge capacity) / (1st discharge capacity)} × 100 Weight energy density and volume energy density, capacity retention, and high output represented by the following equation Table 1 shows the evaluation results of the retention.

High output retention rate (%) = ｛(capacity at 2.0A discharge) / (battery capacity at 0.2A discharge) × 100 Further, the charge end voltage of the remaining 10 batteries is 4.0. After performing constant-current / constant-voltage charging for 3 hours under the conditions of 2 V and charging current of 1 A, three safety tests (crush test and nail penetration test) were performed in accordance with UL standards. The results are also shown in Table 1.

Further, the remaining four batteries were subjected to an overcharge test and a heating test (n = 2 each). Both the overcharge test and the heating test were performed in accordance with the “Safety Evaluation Guidelines for Lithium-Ion Secondary Batteries” issued by the Japan Storage Battery Association Standardization Committee. The results are shown in Table 2.

Example 2 Example 1 was repeated except that the microporous membrane was not directly coated on the positive electrode.
Was performed in the same manner as described above. Table 1 shows the evaluation results of the charge / discharge characteristics and the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Example 3 Example 1 was repeated except that the microporous film was not directly coated on the negative electrode.
Was performed in the same manner as described above. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Example 4 The same procedure as in Example 1 was carried out except that the raw material for the microporous membrane was changed to polyacrylonitrile (PAN). Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test.
Table 2 shows the evaluation results of the overcharge test and the heating test.
Table 3 shows the results of measuring the mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.
It was shown to.

Example 5 The same procedure as in Example 1 was carried out except that the raw material for the microporous membrane was changed to polyimide (PI). Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Example 6 The same procedure as in Example 1 was carried out except that the raw material for the microporous membrane was changed to aramid (AM). Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Example 7 The same procedure as in Example 1 was carried out except that the raw material for the microporous membrane was changed to polymethyl acrylate (PAM). Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test.
Table 2 shows the evaluation results of the overcharge test and the heating test.
Table 3 shows the results of measuring the mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.
It was shown to.

Example 8 The same procedure as in Example 4 was carried out except that the raw material for the microporous membrane was changed to polysulfone (PSF). Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Also,
Table 3 shows the results of measuring the mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Example 9 The same procedure as in Example 1 was conducted except that 50% of PVDF was replaced with zinc stearate (St-Zn; reagent grade: manufactured by Wako Pure Chemical Industries, Ltd.). Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.
It was shown to.

Example 10 50% of PVDF was made of manganese stearate (St-M
n; reagent: manufactured by Wako Pure Chemical Industries, Ltd.), except that the procedure was as in Example 1. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Example 11 25% of PVDF was St-Zn (described above), and 25% was St
The same procedure as in Example 1 was performed, except that -Mn (described above) was used. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Example 12 An experiment was carried out in the same manner as in Example 1 except that 10% of PVDF was replaced with hexabromobenzene (HBB; reagent: manufactured by Wako Pure Chemical Industries, Ltd.). Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Example 13 The same procedure as in Example 1 was carried out except that 10% of PVDF was replaced with hindered amine (HA; Adekastab LA-82: manufactured by Asahi Denka Kogyo KK). Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1. Example 14 The same procedure as in Example 1 was carried out except that the method of applying the microporous membrane solution to the electrode was changed from the dipping method to the knife coater method. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Example 15 The same procedure as in Example 1 was carried out except that the following active material was used as the positive electrode active material. Lithium hydroxide (Li (O
H)), nickel hydroxide (Ni (OH) _2), strontium hydroxide octahydrate _{(Sr (OH) 2 · 8H} 2 O),
Cobalt hydroxide (Co (OH) ₂ ) is converted to Li
_It was weighed so as to be _0.98 Sr _0.002 Ni _0.90 Co _0.10 O ₂ , held at 650 ° C. for 16 hours, and pre-baked. After cooling to room temperature, the mixture was pulverized again in an automatic mortar for 30 minutes to break up aggregation of secondary particles. Then, in the same atmosphere as in the preliminary firing, main firing was performed at 750 ° C. for 8 hours, cooled to room temperature, and then pulverized again with an automatic mortar to obtain a positive electrode active material powder. Table 1 shows the evaluation results of the charge / discharge characteristics and the safety test of the battery according to the present invention using the positive electrode active material. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Example 16 The same procedure as in Example 1 was carried out except that the MLD-30 was heat-treated at 1150 ° C. for 4 hours in a nitrogen atmosphere. Table 1 shows the charge / discharge characteristics of this battery and the results of the safety test.
It was shown to. Table 2 shows the evaluation results of the overcharge test and the heating test.
It was shown to. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Example 17 The same procedure as in Example 15 was carried out except that the negative electrode used in Example 16 was used. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Example 18 The length of the electrode-coated portion was not changed, and the uncoated portion of the double-sided active material layer was provided at the outermost periphery of the electrode sheet for the outermost periphery of the wound electrode body at two ends of the outermost periphery of the positive electrode sheet. The same procedure as in Example 15 was carried out, except that a conductor having the same potential as the positive electrode (a current collector aluminum foil) was provided twice around the outermost periphery of the wound electrode body. The electrical insulation between the positive electrode and the conductor having the same potential, the negative electrode, and the battery can was ensured by partially using a polyethylene separator. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Example 19 A microporous film was formed on the positive and negative electrodes, and the same method as in Example 18 was carried out except that the above-mentioned separator was used between the positive and negative electrodes. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Example 20 Example 19 was repeated except that a microporous film was formed only on the negative electrode.
Was performed in the same manner as described above. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Example 21 Example 19 was repeated except that a microporous film was formed only on the positive electrode.
Was performed in the same manner as described above. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Example 22 Graphite powder (KS-25, manufactured by Lonza KK) was used for 75% by weight of the negative electrode active material, and the heat-treated carbon fiber used for Example 16 was used for 25% by weight. Example 20 was carried out in the same manner as in Example 20, except that an electrolytic solution in which LiPF ₆ was dissolved at a ratio of 1 mol / L in a mixed solvent of an equal volume with DMC was used. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test.

Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Example 23 Graphite powder (KS-25, manufactured by Lonza Co., Ltd.) was used as the negative electrode active material.
Except using only, it carried out by the method similar to Example 22. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Further, for the microporous membrane, as in Example 1, the crystal structure, mechanical properties, pore median diameter,
Table 3 shows the results of the measurement of the porosity.

Example 24 By providing the uncoated portion of the double-sided active material layer at the outermost periphery of the wound electrode body at one end of the electrode sheet at the outermost periphery of the negative electrode without changing the length of the electrode-coated portion, The same procedure as in Example 22 was carried out, except that a conductor having a potential equal to that of the negative electrode (a copper foil of a current collector) was also provided once around the outermost periphery of the wound electrode body. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.
It was shown to.

Example 25 The uncoated portion of the double-sided active material layer was provided at the end of the electrode sheet at the innermost periphery of the positive electrode for the two innermost periphery of the wound electrode body without changing the length of the electrode-coated portion. Thus, the same method as in Example 22 was carried out except that two rounds of a conductor (a current collector aluminum foil) having the same potential as the positive electrode were provided on the outermost and innermost circumferences of the wound electrode body. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Example 26 The length of the double-sided electrode-coated portion was not changed, and the uncoated portion of the single-sided active material layer was applied to the edge of the electrode sheet at the outermost periphery of the positive electrode so as to face the battery can. By providing the outermost circumference for one round,
Example 22 was carried out in the same manner as in Example 22 except that a conductor having the same potential as the positive electrode (a current collector aluminum foil) was provided once around the outermost periphery of the wound electrode body. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane in the same manner as in Example 1.

Comparative Example 1 The same procedure as in Example 24 was carried out except that the microporous film was not provided on the negative electrode, and the negative electrode equipotential conductor and the positive electrode equipotential conductor were not provided. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the mechanical properties, pore median diameter, and porosity of the separator in the same manner as in Example 1.

Comparative Example 2 The same procedure as in Comparative Example 1 was carried out except that the electrode lengths of the positive and negative electrodes were shortened to reduce the battery capacity. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the mechanical properties, pore median diameter, and porosity of the separator in the same manner as in Example 1.

Comparative Example 3 A 15% by weight NMP solution of PVDF was applied on an aluminum foil and then immersed in methanol to form a microporous film on the aluminum foil and further immersed in dilute hydrochloric acid for 1 minute. To separate a PVDF microporous independent membrane. This microporous independent membrane was wound in the same manner as in Example 24 except that a wound electrode body was produced by winding the membrane together with positive and negative electrodes together with a polyethylene separator. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, the mechanical properties, the pore median diameter, and the porosity of the microporous membrane in the same manner as in Example 1.

Comparative Example 4 A negative electrode was coated with a 15% by weight NMP solution of PVDF and then immersed in an equal volume solution of methanol and NMP instead of immersed in methanol. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, mechanical properties, pore median diameter, and porosity of the microporous membrane as in Example 1.

Comparative Example 5 The same procedure as in Comparative Example 1 was carried out except that an 8% by weight solution of PVDF in NMP was applied to the negative electrode and a microporous film was top-coated. Table 1 shows the charge / discharge characteristics of the battery and the evaluation results of the safety test. Table 2 shows the evaluation results of the overcharge test and the heating test. Table 3 shows the results of measuring the crystal structure, the mechanical properties, the pore median diameter, and the porosity of the microporous membrane in the same manner as in Example 1.

Table 4 summarizes the materials and characteristics of the positive electrode, the negative electrode, the microporous film, etc. of the batteries described in the examples and comparative examples.

[0141]

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[0142]

According to the present invention, by employing the above-described structure, it is possible to provide a battery having high capacity, high output characteristics, good cycle characteristics, and high safety.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing an example of a secondary battery of the present invention.

FIG. 2 is a schematic longitudinal sectional view showing an example of the secondary battery of the present invention described in Example 1.

FIG. 3 is a schematic diagram showing the outermost peripheral portion of the secondary battery of the present invention described in Example 18.

FIG. 4 is a schematic view showing the outermost peripheral portion of the secondary battery of the present invention described in Example 19.

FIG. 5 is a schematic diagram showing the outermost peripheral portion of the secondary battery of the present invention described in Example 20.

FIG. 6 is a schematic diagram showing the outermost peripheral portion of the secondary battery of the present invention described in Example 21.

FIG. 7 is a schematic diagram showing the outermost peripheral portion of the secondary battery of the present invention described in Example 24.

FIG. 8 is a schematic diagram showing the innermost periphery of the secondary battery of the present invention described in Example 25.

FIG. 9 is a schematic diagram showing the outermost peripheral portion of the secondary battery of the present invention described in Example 26.

[Explanation of symbols]

 1: negative electrode 2: positive electrode 3: microporous film 4: insulating plate 5: battery can 6: sealing gasket 7: battery cover 8: negative electrode current collector 9: positive electrode current collector 10: negative electrode lead 11: positive electrode lead 12: separate Material 13: Negative equipotential conductor 14: Positive equipotential conductor

 ──────────────────────────────────────────────────続 き Continued on the front page (31) Priority claim number Japanese Patent Application No. Hei 9-183866 (32) Priority date Hei 9 (July 9) (33) Priority claim country Japan (JP) (72) Inventor Keijiro Takanishi 1-1-1, Sonoyama, Otsu-shi, Shiga Prefecture Toray Industries, Inc. Shiga Works (72) Inventor Takeharu Inoue 1-1-1, Sonoyama, Otsu-shi, Shiga Prefecture Toray Industries, Shiga Works (72) Invention Person: Tsurutsu Tsukamoto 1-1-1, Sonoyama, Otsu-shi, Shiga Prefecture, Toga Corporation Shiga Plant (72) Inventor Naoki Shimoyama 1-1-1, Sonoyama, Otsu-shi, Shiga Prefecture Toga Company Shiga Plant (72) Invention Naoki Iwasaki 1-1-1, Sonoyama, Otsu City, Shiga Prefecture Toray Industries, Inc. Shiga Plant

Claims (37)

[Claims] An electrode for a battery, wherein an electrically insulating microporous film is provided integrally on an electrode substrate. 2. The battery electrode according to claim 1, wherein the microporous film contains a thermoplastic resin as a main component. 3. The battery electrode according to claim 2, wherein the thermoplastic resin contains a fluorine-containing polymer and / or a sulfur-containing polymer. 4. The battery electrode according to claim 3, wherein the content of the α-type polyvinylidene fluoride in the thermoplastic resin is 40% by weight or more. 5. The battery electrode according to claim 4, wherein the content of the α-type polyvinylidene fluoride in the thermoplastic resin is 80% by weight or more. 6. The battery electrode according to claim 1, wherein said microporous film is a wet solidified coating film. 7. The battery electrode according to claim 1, wherein the microporous membrane is a membrane solidified on an electrode. 8. The strength of the microporous membrane is not less than 0.1 MPa and not more than 1 MPa.
The battery electrode according to claim 1, wherein the pressure is 0 MPa or less. 9. The strength of the microporous membrane is 0.5 MPa or more and
9. The battery electrode according to claim 8, wherein the pressure is not more than MPa. 10. The battery electrode according to claim 1, wherein the microporous membrane has an elastic modulus of 10 MPa or more and 200 MPa or less. 11. The battery electrode according to claim 10, wherein the microporous membrane has an elastic modulus of 10 MPa or more and 100 MPa or less. 12. The battery electrode according to claim 1, wherein the median diameter of the pore diameter of the microporous membrane is 40 nm to 1500 nm. 13. The battery electrode according to claim 1, wherein the porosity of the microporous membrane is 40 to 90%. 14. The battery electrode according to claim 13, wherein the porosity of the microporous membrane is 65 to 90%. 15. The battery according to claim 1, wherein the microporous film is a porous film containing at least one material selected from a heat absorbing material, a flame retardant material and an antioxidant. electrode. 16. The battery electrode according to claim 15, wherein said heat absorbing material is a zinc and / or manganese-containing organic compound. 17. The battery electrode according to claim 15, wherein the flame retardant is a bromine-containing organic compound. 18. The electrode according to claim 15, wherein the antioxidant is a hindered amine organic compound. 19. The battery electrode according to claim 15, wherein the electrode material is composed of an active material, a binder, and a conductive material. 20. The battery electrode according to claim 19, wherein said active material is a lithium composite oxide. 21. The lithium composite oxide is Li _x CoO.
₂ (0 <x ≦ 1.0), Li _x NiO ₂ (0 <x ≦ 1.
21. The battery electrode according to claim 20, wherein 0) or a part of these metal elements is replaced with an alkaline earth metal element and / or a transition metal element. 22. The battery electrode according to claim 21, wherein the active material is a carbonaceous material. 23. The battery electrode according to claim 22, wherein said carbonaceous material is made of carbon fiber and / or graphite powder. 24. The battery electrode according to claim 23, wherein the carbon fibers are short fibers having an average length of 30 μm or less. 25. A battery using the electrode according to any one of claims 1 to 24. 26. The battery according to claim 25, further comprising a separator between the electrodes. 27. The conductor according to claim 25, wherein a conductor having an equipotential with the positive electrode and a conductor having an equipotential with the negative electrode are wound and laminated so as to face one or more turns via a separate material. 27. The battery according to 26. 28. The battery according to claim 27, wherein the opposing conductor is provided at an outermost peripheral portion and / or an innermost peripheral portion of the wound electrode body. 29. The separation material according to claim 27, wherein the separation material is a microporous film containing a thermoplastic resin as a main component.
The battery according to 1. 30. The battery according to claim 25, wherein the battery is a secondary battery. 31. The battery according to claim 30, wherein a non-aqueous electrolyte is used. 32. The battery according to claim 31, wherein the non-aqueous electrolyte contains an alkali metal salt electrolyte. 33. The battery according to claim 32, wherein the alkali metal salt is a lithium salt. 34. A volume energy density of 265 Wh / l
26. The battery according to claim 25, wherein: 35. The volume energy density is 300 Wh /
35. The battery according to claim 34, wherein the number is 1 or more. 36. A weight energy density of 110 Wh / k
The battery according to claim 25, wherein the battery is not less than g. 37. The weight energy density is 125 Wh / k.
The battery according to claim 36, wherein the battery is not less than g.