JP3246596B2 - Rechargeable battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery, and more particularly, to a secondary battery in which dendritic (dendritic) growth of lithium or zinc generated by repeated charge and discharge is suppressed.

[0002]

2. Description of the Related Art Recently, the amount of CO ₂ gas contained in the atmosphere is increasing, and it is predicted that the greenhouse effect will cause global warming. Thermal power plants convert thermal energy obtained by burning fossil fuels and the like into electrical energy, but burning large amounts of CO ₂ gas makes new thermal power plants difficult to construct. Are coming. Therefore, as an effective use of electric power generated by generators such as thermal power plants, surplus electric power at night is stored in secondary batteries installed in ordinary households and used during the daytime when power consumption is high. In other words, a so-called load leveling in which the load is leveled has been proposed.

[0003] In addition, development of a secondary battery having a high energy density is expected for electric vehicles which are characterized in that they do not emit air pollutants including CO _x , NO _x , CH and the like. Furthermore, for the power supply of portable devices such as book-type personal computers, word processors, video cameras, and mobile phones, there is an urgent need to develop small, lightweight, and high-performance secondary batteries.

The above-mentioned small, lightweight and high-performance secondary battery is formed, for example, by using a lithium intercalation compound which deintercalates lithium ions by a reaction during charging as a positive electrode material and lithium ions as carbon atoms. A rocking chair type “lithium-ion battery” using a carbon material typified by graphite as the negative electrode material, which can be intercalated between layers of a six-membered ring network plane
Has been developed and some have been put to practical use.

However, the above-mentioned "lithium ion battery"
Then, the negative electrode composed of carbon material is theoretically C
Since only a maximum of 1/6 lithium atoms can be intercalated per atom, a secondary battery having a high energy density comparable to a lithium primary battery when, for example, metallic lithium is used for the negative electrode material cannot be realized. If it is attempted to store more lithium than the amount of lithium that can be inserted between the carbon layers of the negative electrode during charging, metallic lithium grows on the surface of the carbon in dendrite and causes a short circuit, so the amount of lithium that can be inserted between the layers was stored. High capacity secondary batteries have not been realized.

On the other hand, in a high-capacity lithium battery using lithium metal as a negative electrode, repetition of charge and discharge tends to generate lithium dendrite, which is a main cause of a short circuit.
It is not easy to suppress the dendrite growth of lithium, which makes it difficult to make a lithium battery a secondary battery.

In addition, lithium metal precipitates during charging,
A lithium secondary battery using a metal such as lithium metal or aluminum for the negative electrode can be expected to have a high energy density, and has been studied, but a battery having a lifespan up to a practical area has not been put into practical use.

In both the secondary battery using carbon as the negative electrode and the secondary battery using the negative electrode on which lithium metal precipitates when charged, lithium dendrite grows and the negative electrode and the positive electrode are short-circuited. In some cases, heat is generated by consuming the energy of the battery in a short time, the solvent of the electrolyte is decomposed and gas is generated, the internal pressure is increased, and the battery may be damaged in some cases. As a countermeasure, ensuring the safety of lithium secondary batteries including the above-mentioned lithium ion batteries (hereinafter, secondary batteries utilizing the oxidation-reduction reaction of lithium ions are collectively referred to as lithium secondary batteries) For this purpose, a porous film of polyethylene or polypropylene with a melting point of 120 ° C to 170 ° C is used for the separator between the positive electrode and the negative electrode. If the battery short-circuits for some reason and the internal temperature rises to the melting point of the material, the separator will melt. A mechanism has been attempted in which the pores are closed and the negative electrode and the positive electrode are electrically insulated to stop the battery reaction. However, although it is a safety measure,
It has not been a definitive method for dramatically extending the life of the negative electrode in a lithium secondary battery.

In addition, a lithium secondary battery using a porous film made of the above-mentioned organic polymer as a separator does not function unless the battery temperature reaches a high temperature of 120 ° C. or higher. Even if the temperature decreases, the insulation state between the positive electrode and the negative electrode remains, and the performance of the battery does not recover. For this reason, it is desired to develop means capable of realizing a high capacity battery, suppressing the dendrite growth of lithium during charging, and extending the cycle life.

[0010] Also, in a secondary battery composed of a nickel zinc battery and an air zinc battery, zinc dendrites are generated by repetition of charge / discharge similarly to the lithium secondary battery, and penetrate the separator to form a zinc negative electrode and a positive electrode. However, there is a problem similar to that of the above-described lithium secondary battery that the cycle life is short because of the short circuit. Therefore, there is a strong demand for lithium secondary batteries and zinc secondary batteries that have a high capacity and a sufficient cycle life.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a long cycle life in a secondary battery in which the negative electrode active material is lithium or zinc.
Another object is to provide a secondary battery having a high energy density.

[0012]

The secondary battery of the present invention comprises a negative electrode, a positive electrode, and an electrolyte between the positive electrode and the negative electrode.
A secondary battery includes a layer having communication holes having pore diameters in which ions involved in a battery reaction can move and can vary according to the environment, and a battery housing for accommodating them. The “ion involved in the battery reaction” is an ion that undergoes oxidation / reduction in the charge / discharge reaction of the secondary battery and participates in the reaction.

[0013] The secondary battery according to the present invention has a diameter (width) that allows ions involved in a battery reaction to move in a layer interposed between the positive electrode and the negative electrode and that can vary according to the environment. It is characteristic in that there is a communication hole (through hole) communicating there between. Here, the “communication hole” is a hole communicating between the positive electrode and the negative electrode in the secondary battery, and can be a passage through which the ions involved in the battery reaction move between the positive electrode and the negative electrode through the communication hole. In particular, the diameter (width) of the communication hole varies in accordance with a change in voltage and temperature in the vicinity of the position where the electrode exists between the positive electrode and the negative electrode, and the resistance between the positive electrode and the negative electrode in the communication hole decreases. Change. For example, in a battery reaction, when the voltage is locally high around the series communication hole and / or when the temperature is high, the width of the communication hole changes so as to be narrow, and the resistance near the communication hole becomes high. And the progress of the battery reaction is suppressed.

In the charging reaction of a secondary battery, a high electric field is locally generated between the positive electrode and the negative electrode due to the non-uniformity of the surface shape and composition of the positive electrode and the negative electrode, and the temperature is locally reduced. As a result, the reaction proceeds excessively, and depending on the constituent materials of the battery and the reaction mechanism, the anode active material may grow into a dendrite shape or the electrolyte may be decomposed as described above. Eventually, the possibility of a short circuit between the positive electrode and the negative electrode at such a location increases. Therefore, by forming the region between the positive electrode and the negative electrode of the battery from a communication hole whose width varies so that the resistance increases near the place where the high electric field or the temperature rises, the battery reaction proceeds. With the suppression of the short circuit, the short circuit is prevented.

The secondary battery of the present invention is a battery that can be expected to have a high energy density and suppresses the dendrite growth described above. Preferably, the secondary battery contains at least a lithium element in the negative electrode during charging (lithium secondary battery). Battery) or a battery containing at least zinc element (zinc secondary battery).

In the secondary battery according to the present invention, the layer between the positive electrode and the negative electrode has pores, and a polymer film or pores whose pore diameters are reduced at locations where the electric field strength is higher than the surroundings. It is preferable to use a polymer film having a polymer film whose pore diameter decreases at a location where the temperature rise is larger than that of the surroundings.

It is preferable that the polymer film is composed of at least a polymer liquid crystal or a composite of a polymer and a liquid crystal. When the liquid crystal part of the polymer film is at rest when no voltage is applied, the liquid crystal part is oriented vertically or obliquely to the negative electrode plane, and a high electric field is locally generated during charging in a place where dendrite growth of the active material is likely to occur. When the voltage is applied and / or the temperature rises, it is preferable that the orientation is parallel or random (random) to the negative electrode plane, and the length of the pores in the negative electrode plane direction (pore diameter) is reduced. It is preferable that the polymer liquid crystal or the liquid crystal of the polymer film is composed of a liquid crystal having at least negative dielectric anisotropy.

Further, it is preferable that the above-mentioned polymer film is made of at least a polymer gel.

The inventor of the present invention has carefully investigated the locations and conditions under which lithium dendrite growth occurs during charging of a lithium secondary battery using metallic lithium, aluminum, or a carbon material for the negative electrode. It was found that a portion where dendrite growth was easy was a portion where the electric field strength was high, such as a projection on the negative electrode surface, and a large current flowed to generate heat. Similar findings were obtained in nickel zinc secondary batteries and zinc zinc batteries using zinc as the negative electrode. Based on this finding, they found that the resistance of the above-mentioned portions was selectively increased, and confirmed that dendrite growth of lithium and zinc was suppressed during charging.

In the secondary battery of the present invention, in a secondary battery in which the negative electrode active material is lithium or zinc, the negative electrode is located at a place where the electric field strength is high such as a projection on the surface of the negative electrode and / or a place where the temperature rises sharply locally. A layer comprising a communication hole in which the diameter of the communication hole between the positive electrodes is reduced is provided, and the resistance is increased by the communication hole to prevent a short circuit. Thus, the growth of lithium or zinc in the form of dendrite during charging can be suppressed, and as a result, the cycle life during charging and discharging can be significantly extended. Accordingly, a high energy density secondary battery having a long cycle life can be realized.

In the present invention, the term "active material" refers to a substance that participates in (returns) the electrochemically reversible reaction of charging and discharging in a battery, and furthermore, a substance that itself participates in the above-mentioned reaction. , And substances holding other substances involved in the above reaction. In addition, in the lithium secondary battery,
As a negative electrode active material, lithium is held on the negative electrode side during charging, and dissolves in the electrolytic solution during discharging to become lithium ions. In a zinc secondary battery, zinc as a negative electrode active material reacts with hydroxide ions during discharge to change to zinc hydroxide or zinc oxide.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1, 2 and 5. FIG. FIG. 1 is a conceptual diagram showing a cross section of an example of the secondary battery of the present invention. In the secondary battery of the present invention shown in FIG. 1, the negative electrode 101 is opposed to the positive electrode 102 via the separator 103 which holds the electrolytic solution or also serves as an electrolyte, and is located between the opposed negative electrode 101 and the positive electrode 102. It has a communication hole having a pore diameter that allows ions involved in the battery reaction, which is a feature of the present invention, to be movable and can vary depending on the environment. A structure provided with a porous polymer film 100 having pores as a layer having communication holes is accommodated in a battery housing 104. Although the porous polymer membrane 100 can pass ions associated with the battery reaction, the pores are narrowed where a high electric field is applied and where the temperature rises, so that the passage of the ions associated with the battery reaction is controlled and charging is performed. It has the function of restricting the transmission of the metal which is sometimes deposited, and increasing the resistance. The positive terminal 106 connected to the positive electrode 102 and the negative terminal 105 connected to the negative electrode 101 are respectively connected to the housing 1.
04 has been drawn out.

This function will be described with reference to FIG. FIG. 5 is a conceptual diagram illustrating the function of the secondary battery of the present invention.
This is an example of charging a secondary battery of the present invention by connecting a DC power supply. When the electric field concentrating portion 107 such as a projection has a high electric field strength on the negative electrode surface of the secondary battery of FIG. 1, a high electric field is applied to the electric field concentrating portion 107 from the periphery, and the current density becomes high. Fever, then
At a portion 108 of the polymer film 100 where a high electric field is applied and the temperature rises, the pores are narrowed and the resistance rises. As a result, the electric field concentration portion 107 where the high electric field is applied on the negative electrode surface has a dendritic shape during charging. The deposition of the negative electrode active material is suppressed, and the internal short circuit between the negative electrode and the positive electrode is suppressed.

FIG. 2 is a conceptual diagram showing an arrangement example of a negative electrode, a positive electrode, a separator, and a polymer film as a means for preventing dendrite growth of a negative electrode active material in a secondary battery of the present invention. 2A, 2B and 2C show examples of the arrangement of the negative electrode 101, the positive electrode 102, the separator / electrolyte 103, and the porous polymer film 100 in the cross section of the secondary battery of FIG. It is a thing. FIG. 2A shows an example in which the polymer film 100 is provided between the negative electrode 101 and the separator 103. In FIG. 2B, the polymer film 10
0 is an example provided between the positive electrode 102 and the separator 103. FIG. 2C shows an example in which the polymer film 100 is provided between the negative electrode 101 and the positive electrode 102 also as the separator 103.

The secondary battery of the present invention has at least a positive electrode and a negative electrode, and a layer having the above-described communication hole between the positive electrode and the negative electrode, specifically, a porous polymer film and an electrolyte. Although it has a battery housing, each component will be described below.

(Polymer film) A diameter (width) provided between a negative electrode and a positive electrode constituting a secondary battery, which is a feature of the present invention, in which ions involved in a battery reaction can move and can be varied according to the environment. The porous polymer film (the film 100 in the example shown in FIG. 1) as a region layer formed of communication holes having a function of preventing dendrite growth of the negative electrode active material during charging has the function of It is necessary to have pores through which ions involved are transmitted, and to have such a property that the pore diameter is narrowed when a high electric field is applied or the temperature rises.

As the material of the polymer film, for example, a liquid crystal polymer, a composite material of a polymer serving as a base material and liquid crystal, and a polymer gel can be used. As the liquid crystal polymer as a material of the polymer film or a composite material of a polymer and a liquid crystal as a base material, a liquid crystal in which the major axes of molecules are aligned perpendicular to the electric field when an electric field is applied is preferable. Liquid crystals having negative anisotropy are more preferable. When the long axes of the molecules of the liquid crystal portion of the polymer film are arranged in a direction perpendicular to the electric field, the pores (communication holes described above) penetrating in the direction of the electric field are narrowed. Further, in the polymer gel forming the polymer film, it is preferable that a large volume expansion of 20% or more occurs due to a temperature rise. The pores in the polymer gel are narrowed by the volume expansion.

Further, when this polymer gel is provided on the negative electrode side, it is preferable that the polymer gel is a cationic polymer gel having a positive charge. At the time of charging, lithium cations gather near the surface of the negative electrode, and the cationic polymer gel expands by expanding molecules to maintain neutralization conditions. When this polymer gel is provided on the positive electrode side, an anionic polymer gel having a negative charge is desirably used. At the time of charging, anions collect near the surface of the positive electrode, and the anionic polymer gel expands by expanding the molecules in order to maintain neutralization conditions.

As described above, the characteristic pores of the polymer film constituting the secondary battery of the present invention are formed when a high electric field is locally generated near the pores or when the temperature is increased. This can prevent the ions contributing to the battery reaction and the negative electrode active material precipitated during charging from penetrating through the polymer film and the pores of the separator to the positive electrode and causing an internal short circuit.

The size of the pores formed in the polymer membrane may be any size as long as they can transmit ions involved in the battery reaction, and is usually 1 μm or less, preferably 2 to 10 μm.
00 °.

Further, the pore diameter of the pores of the polymer membrane decreases when a high electric field is applied or the temperature rises, but the contraction rate of the pore diameter decreases the resistance when ions move. Any range is possible as long as the function for raising the pressure can be obtained. Usually, the ratio of shrinkage to the original pore diameter is 10%.
% Or more, preferably 20 to 98%.

When the above-mentioned polymer film is used particularly in a lithium secondary battery, at least before the electrolyte solution is incorporated into the battery and the electrolyte solution is sufficiently injected, the film is sufficiently dried by a method such as drying under reduced pressure to remove water. Need to be kept. If the dehydration had not been performed sufficiently, lithium that would precipitate during charging and this water would react to form lithium compounds such as lithium hydroxide that could not be used during discharging, resulting in a decrease in the amount of discharged electricity. Become.

As a method for forming a porous polymer film having the above-mentioned communicating holes using a polymer liquid crystal material, a solution obtained by dissolving a polymer liquid crystal material in a solvent is formed by a casting method, or A film is formed by directly coating the surface of the negative electrode, the separator, and the positive electrode. It is then dried to remove the solvent and form pores. In addition to formation using a polymer liquid crystal material, it is also possible to form a polymer film simultaneously with the polymerization reaction by using a monomer obtained by polymerizing the polymer liquid crystal. In some cases, in order to adjust the pore distribution, a membrane can be formed by adding an electrolyte or the like that can be extracted and removed at the time of film formation, and after drying, the substance added during membrane preparation can be extracted and removed to adjust the pore distribution. I do.

As a method for preparing the pores, a substance which can be removed later is added so as to have a desired porosity at the time of forming the polymer film, and then a solvent is added if necessary, and the material is removed at or after the film formation. Prepare the pores by removing possible substances. Examples of the removable substance include an elutable electrolyte and an organic solvent used for an electrolytic solution. When the electrolyte is used as a removable additive material, it has little effect on battery characteristics. As another removable substance, it is also possible to remove by evaporation or decomposition under heating or reduced pressure, or to use a solvent having a low boiling point which is mixed uniformly with the solvent to be removed.

In order to increase the dissolution stability in the electrolytic solution after the formation of the film, it is preferable to cause a crosslinking reaction to cause crosslinking. Examples of the cross-linking method include a method in which a cross-linking agent is added during film formation to cause a cross-linking reaction, or a method in which a cross-linking reaction is caused by irradiating ultraviolet rays or radiation after film formation.

As a method for forming a porous polymer film having the above-mentioned communicating holes by a composite of a polymer material and a liquid crystal material, a polymer solution in which a polymer serving as a base material is dissolved in a solvent is used.
A liquid crystal material is mixed, and the obtained mixed solution is cast on a rotating flat and uniform metal support to form a film, or directly applied to the negative electrode, separator, or positive electrode surface to form a film After drying, the solvent is removed to prepare a polymer film. In some cases, as in the above-described formation of a polymer liquid crystal film, it is also possible to form a polymer film by adding an additive substance such as an electrolyte that can be removed later to adjust the pore distribution. . Further, it is also preferable to cause a cross-linking reaction after the formation of the film to cross-link it, in order to increase the stability to the electrolytic solution. As the cross-linking method, a method similar to the above-described cross-linking method for a polymer liquid crystal film can be employed.

In the secondary battery of the present invention, the polymer liquid crystal film is a polymer film used as a layer region having a communication hole whose hole (width) can be varied according to the environment between the positive electrode and the negative electrode.
It is preferable that the liquid crystal of the composite film of the polymer and the liquid crystal is oriented vertically or obliquely to the plane of the negative electrode during film formation.

As the orientation method, a method in which a magnetic field or an electric field is applied in a direction perpendicular to, or inclined to, or parallel to the plane of the negative electrode before the solidification of the polymer film can be used. Other orientation methods are controlled by applying stress, orienting the surface of a substrate on which a film is formed, heating or cooling, selecting an optimum solvent and an optimum concentration, and the like.

As a specific example of the orientation treatment of the substrate surface on which the film is formed, a vertical orientation treatment method includes p- (octyloxy) -p'-hydroxyazobezen, dimethylhexadecyl ammonium bromide, N- [11-
Bromoundecanoyl] -L-glutamic acid didodecyl ester, hexadecyltributylphosphonium bromide, stearyltributylphosphonium bromide,
Examples include physical adsorption of amphipathic molecules such as lecithin and cetyltrimethylammonium bromide and chemical adsorption of organometallic coupling agents such as steryltrichlorosilane.

As the tilt alignment, a method of forming an alignment film by obliquely depositing a metal or an organic polymer on a substrate surface by a vacuum evaporation method such as sputtering or electron beam evaporation is used.

On the other hand, as a method for forming a porous polymer film having the above-mentioned communicating holes using a polymer gel material, (a) a polymer gel is formed by direct polymerization and crosslinking reaction from a monomer, or a polymer is formed. (B) immersing the separator in the monomer solution to form a polymer gel by the crosslinking reaction, or immersing the separator in the polymer solution to cause the crosslinking reaction Forming a polymer gel, (c) forming a polymer gel powder by polymerization and crosslinking reaction from a monomer, then dispersing and solidifying the polymer gel powder in a polymer solution, (d) forming a negative electrode surface, After casting the polymer solution on the positive electrode surface or on the separator surface, a polymer gel is formed by a crosslinking reaction,
After casting the monomer solution, a polymerization reaction and a crosslinking reaction are caused to form a polymer gel. The thickness of the polymer gel is adjusted during the formation during polymerization or crosslinking and used as it is, or it is used after drying after forming and uniformly adjusting the thickness by pressing or the like. The thickness of the polymer gel can be adjusted by the type and concentration of the solvent at the time of formation, the depth of the reaction vessel, and the like. The expansion rate of the polymer gel can be adjusted by the monomer type, the degree of polymerization, the degree of crosslinking, the type and concentration of the solvent, the concentration of the electrolyte contained in the solvent, and the like.

Other methods for producing a porous polymer film formed of a polymer liquid crystal, a composite of a polymer and a liquid crystal, or a polymer gel as a film or a sheet include a polymer dissolved in a solvent. In addition to the casting method (solution casting method), in which the solution is cast on a rotating flat and uniform metal support to form a film, the polymer liquid melted by heat is extruded from a T-die to form an extract. A lubrication method (melt extrusion method), a calendering method in which a polymer substance is rolled between two or more rolls to form a film can be used. In the extrusion method, a polymer before cross-linking is used, and after forming a film, a cross-linking reaction occurs to obtain a polymer film. In the calendar method, a film is prepared using a dried polymer.

(Liquid Crystal Material) Examples of the polymer organic liquid crystal as the material of the porous polymer film or the liquid crystal material used in the composite of the polymer and the liquid crystal include a thermotropic material exhibiting a liquid crystal layer through a melting process. And a lyotropic material exhibiting liquid crystallinity in the presence of a solvent. Nematic liquid crystal, cholesteric liquid crystal, smectic liquid crystal, discotic liquid crystal,
Examples thereof include ferroelectric liquid crystals exhibiting spontaneous polarization, and are preferably liquid crystals exhibiting negative dielectric anisotropy, and more preferably exhibiting a nematic liquid crystal phase or a cholesteric liquid crystal phase.

When the voltage is not applied, the liquid crystal portion is vertically or obliquely aligned with the plane of the negative electrode when the voltage is not applied, and a high electric field is locally applied during charging to cause a temperature rise. It is more preferable that the orientation is parallel to the negative electrode plane or disordered at an easy place.

Further, it is preferable to use a plurality of liquid crystals by blending them so as to function according to the operating temperature of the secondary battery. It is preferable that the liquid crystal is subjected to an orientation treatment or a tilt orientation treatment perpendicular to the negative electrode plane of the secondary battery, and the liquid crystal is initially oriented (perpendicular or inclined to the negative electrode surface). The tilt angle of the liquid crystal molecules with respect to the negative electrode plane in the initial state by these alignment treatments is 45 °.
That is all.

The liquid crystal material having a negative dielectric anisotropy used in the present invention includes 2,3-difluorobenzene derivative, pyridazine derivative, fluorinated hydroquinone cyclohexane carboxylate compound, fluorinated tolan compound, cyanobenzene Carboxylic acid ester compounds, cyanocyclohexane compounds, and the like, among which,
3,6-2 substituted-1,2-dicyanobenzenes, 3,6
Compare 2-substituted pyridazine, 3,6-substituted-1,2-difluorobenzenes, 3,6-substituted-1-cyanobenzenes, 1,4-2-substituted-1-cyanocyclohexanes, etc. It can be cited as an example showing an extremely large negative dielectric anisotropy.

The structure of the liquid crystal polymer used in the present invention is as follows:
A mesogen group that is a linear conjugated atomic group, or a main chain polymer in which mesogen groups and alkyl chains or oxyethylene chains are alternately and linearly linked, and a mesogen group whose main chain is directly or via an alkyl chain Is a side chain type polymer bonded as a side chain. Examples of the mesogen group include benzylidene aniline, azobenzene, azoxybenzene,
Examples include stilbene, phenylbenzoate, benzoylaniline, biphenyl, benzylideneacetophenone, benzylideneazine, and the like.

(Polymer in Polymer-Liquid Crystal Composite) As the polymer material which becomes a solid in the composite of a polymer and a liquid crystal which is a porous polymer film, a polymer which is insoluble in an electrolyte solution of a battery A material or a polymer material which has been crosslinked so as to be insoluble in the electrolytic solution can be used. Further, an organic polymer soluble in a solvent used for preparing the polymer-liquid crystal composite or a raw material monomer thereof can be used (when a monomer is used, polymerization is performed at the stage of preparing the composite). Examples of the polymer material include polyolefins such as polyethylene and polypropylene, fluororesins, polyvinyl chloride,
Examples thereof include polyvinyl alcohol, polyacrylamide, polyester, polyamide, and polyethylene oxide.

(Polymer Gel) In the present invention, the polymer gel used as the material of the porous polymer film described above includes:
Preferably, a polymer having a three-dimensional network structure that is insoluble in a solvent or a material that is swollen by absorbing a solvent is used as a means for preventing internal short circuit of a lithium secondary battery.

Examples of such a polymer gel include polyacrylamide, N, N-diethylacrylamide polymer, N-isopropylacrylamide polymer, N-isopropylacrylamide-sodium acrylate copolymer, N, N-diethylacrylamide-sodium acrylate Copolymer, acrylamide- (methacrylamidopropyl) trimethylammonium chloride copolymer, acrylamide-trimethyl (N-acryloyl-
3-aminopropyl) ammonium iodide copolymer, polystyrene, styrene-styrene sulfonate copolymer, polyvinyl methyl ether, polyvinyl alcohol-polyacrylic acid composite gel, polyacrylic acid, polymethacrylic acid, methacrylic acid-2- Examples include hydroxyethyl, cellulose, polyethylene glycol, polyethylene oxide, polyvinyl alcohol, and the like. Among them, N-isopropylacrylamide-sodium acrylate copolymer, N, N-diethylacrylamide-sodium acrylate copolymer, acrylamide- (methacrylamidopropyl) trimethylammonium chloride copolymer, acrylamide-trimethyl (N- Polymer gels having an ion dissociating group such as acryloyl-3-aminopropyl) ammonium iodide copolymer and styrene-styrene sulfonate copolymer are preferably used. Also, among the above polymer gels,
Polymer gels such as polyacrylamide and N, N-diethylacrylamide polymer, in which the polymer chains are contracted at room temperature, are also preferable for use in the present invention because they expand at high temperatures.

As a method for forming a polymer gel usable in the present invention, for example, a method using a chemical bond or a method using an intermolecular bond is employed. Methods of forming a gel by chemical bonding include a method of crosslinking during a polymerization reaction and a method of crosslinking after polymerization.Methods of crosslinking between polymer chains by bonding between molecules include crosslinking by hydrogen bonding and ionic bonding. There are crosslinks and crosslinks by coordination bonds.

The crosslinking method includes, for example, formation of a crosslinked structure by polycondensation of a divinyl compound or a polyfunctional compound, simultaneous polymerization and crosslinking by energy such as heat, light, radiation, or plasma, or linear polymerization. There is also a method of crosslinking after synthesizing a polymer.

As a method of crosslinking at the time of the polymerization reaction, for example, polymerization with a radical initiator using ethylene glycol dimethacrylate or methylene bisacrylamide as a crosslinking agent, radiation polymerization by irradiating gamma rays or electron beams, or the same as the absorption wavelength of a vinyl monomer. Photopolymerization by irradiating light in the presence of a crosslinking agent or by adding a photosensitizer to irradiate light. .

As a method for later crosslinking between polymer chains, for example, a polymer having an amino acid is used to crosslink cellulose or polyvinyl alcohol having a hydroxyl group by a chemical reaction such as aldehyde, N-methylol compound, dicarboxylic acid, and bisepoxide. Is a method of gelling with aldehydes or glycidyl groups, a method of crosslinking polyvinyl alcohol or polymethyl vinyl ether in water by irradiation with gamma rays, or a method of crosslinking polyvinyl alcohol or N-vinylpyrrolidone with diazo resin, bisazide, dichromate, etc. A method of photodimerizing a polymer having a photosensitive group such as stilbazolium salt in a water-soluble polymer such as polyvinyl alcohol, which is cross-linked with a cross-linking agent, and cross-linking by contacting plasma generated by gas discharge with a polymer material Method.

A gel can also be formed by hydrogen bonding, ionic bonding, chelate formation or the like between polymers, and hydrogen bonds are formed between polymers by freeze vacuum drying, freeze thawing, or the like. A gel can be formed by mixing two different polymers, such as acid and polyethylene glycol, polyacrylic acid and polyvinyl alcohol. By mixing a polycation such as polyvinylbenzyltrimethylammonium and a polyanion such as sodium polystyrenesulfonate, a polyion complex gel can be formed. A strongly acidic polymer such as polycarboxylic acid such as polyacrylic acid or polystyrene sulfonic acid can be combined with an alkali or alkaline earth metal to form a gel.

(Negative Electrode) As the material of the negative electrode material (the negative electrode 101 in the example shown in FIG. 1) in the secondary battery of the present invention, a material containing a lithium element at the time of charging (lithium secondary battery) or zinc An element containing an element is used (a zinc secondary battery). Preferably, a negative electrode is obtained by molding a negative electrode material on a current collector.

As a negative electrode material for a lithium secondary battery,
For example, lithium metal, a carbon material including graphite, a metal material, and a material in which lithium is intercalated such as a transition metal compound can be used. As the above-mentioned metal material, a metal material such as aluminum which forms an alloy with lithium, a metal such as porous nickel having pores for accommodating deposited lithium and also serving as a current collector, and the like are preferable.

The negative electrode material can be used as it is as long as it has a foil or plate shape. In the case of a powder, a binder is mixed, and in some cases, a conductive auxiliary material is also added to form a coating film on the current collector to form a negative electrode. Further, as a method for forming a thin film of the above material on the current collector, plating or vapor deposition can be used. As the vapor deposition method, CVD (Chemical Vapor De) is used.
position), electron beam evaporation, sputtering and the like. It is necessary that all negative electrodes for lithium secondary batteries be sufficiently dried under reduced pressure.

As a negative electrode for a zinc secondary battery, a zinc foil or plate, a zinc plated film or a vapor-deposited film formed on a current collector, a zinc oxide powder or a binder containing zinc powder and zinc oxide powder (Optionally with the addition of conductive aids)
What formed the coating film on the current collector can be used for a negative electrode.

(Positive Electrode) The positive electrode (the positive electrode 102 in the example shown in FIG. 1) in the secondary battery of the present invention is made of a material such as a current collector, a positive electrode active material, a conductive auxiliary material, and a binder. is there. This positive electrode is manufactured by molding a mixture of a positive electrode active material, a conductive auxiliary material, a binder, and the like on the surface of a current collector.

Examples of the conductive auxiliary material used for the positive electrode include graphite, carbon black such as Ketjen black and acetylene black, and fine metal powder such as nickel.

As the binder used for the positive electrode, for example,
When the electrolytic solution is a non-aqueous solvent system, a polyolefin such as polyethylene or polypropylene, or a fluororesin such as polyvinylidene fluoride or tetrafluoroethylene polymer, and when the electrolytic solution is an aqueous solution, polyvinyl alcohol, cellulose or polyamide And the like.

In a lithium secondary battery in which the negative electrode active material is lithium, a transition metal oxide, a transition metal sulfide, a lithium-transition metal oxide, or a lithium-transition metal sulfide is generally used as the positive electrode active material. . As the transition metal element of the transition metal oxide or the transition metal sulfide, for example, an element partially having a d-shell or an f-shell,
Sc, Y, lanthanoid, actinoid, Ti, Zr,
Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc,
Re, Fe, Ru, Os, Co, Rh, Ir, Ni, P
d, Pt, Cu, Ag, and Au. In particular, the first transition series metals Ti, V, Cr, Mn, Fe, C
o, Ni, Cu are preferably used.

In a nickel zinc secondary battery in which the negative electrode active material is zinc, nickel oxide hydroxide is used as the positive electrode active material.

In an air zinc secondary battery in which the negative electrode active material is zinc, oxygen is used as the positive electrode active material, and the positive electrode comprises a current collector, a catalyst, and a water repellent material. As the catalyst, for example, porous carbon, porous nickel, copper oxide, and nickel oxide are used. As the water repellent material, a porous resin such as a porous tetrafluoroethylene polymer or polyvinylidene fluoride is used. In a zinc bromine secondary battery in which the negative electrode active material is zinc, bromine is used as the positive electrode active material.

(Current Collector for Negative Electrode and Positive Electrode) The current collector used for the negative electrode and the positive electrode in the secondary battery of the present invention efficiently supplies the current consumed in the electrode reaction during charging and discharging or collects the current generated. Has the role of electricity. Therefore,
As a material forming the current collectors of the negative electrode and the positive electrode, a material having high conductivity and being inert to a battery reaction is desirable.

Preferred materials include nickel, titanium, copper, aluminum, stainless steel, platinum,
Examples include palladium, gold, zinc, various alloys, and two or more composite metals of the above materials. As the shape of the current collector,
For example, a formed shape such as a plate shape, a foil shape, a mesh shape, a sponge shape, a fibrous shape, a punching metal, an expanded metal and the like can be adopted.

(Separator) The separator (103 in the example shown in FIG. 1) in the secondary battery of the present invention is disposed between the negative electrode and the positive electrode, and has a role of preventing a short circuit therebetween. Also,
In some cases, it has a role of holding the electrolytic solution.

The separator must have pores through which lithium ions or hydroxide ions can move, and must be insoluble and stable in the electrolytic solution. Accordingly, as the separator, for example, a nonwoven fabric such as glass, polyolefin such as polypropylene or polyester, a fluororesin, or polyamide, or a material having a micropore structure is suitably used.

Further, a metal oxide film having fine pores or a resin film in which a metal oxide is compounded can be used. In particular, when a metal oxide film having a multilayered structure is used, the dendrite hardly penetrates, which is effective in preventing a short circuit. When a fluororesin film which is a flame retardant material, or a glass or metal oxide film which is a nonflammable material is used, safety can be further improved.

(Electrolyte) The electrolyte in the secondary battery of the present invention is, for example, a layer having a communication hole through which ions involved in the above-described battery reaction can move, and which has a diameter that can be varied according to the environment such as voltage or temperature. (The polymer film 100 in the example shown in FIG. 1) and the separator 103. The use of such an electrolyte includes the following three methods. (1) A method used as it is. (2) A method of using as a solution dissolved in a solvent. (3) A method in which a gelling agent such as a polymer is added to a solution to be used as an immobilized one.

In general, an electrolytic solution obtained by dissolving an electrolyte in a solvent is retained on a porous separator for use. The conductivity of the electrolyte is preferably 1 × as a value at 25 ° C.
10 ^-3 S / cm or more, more preferably 5 × 10 ^-3 S / c
m or more.

In a lithium battery in which the negative electrode active material is lithium, the following electrolyte and its solvent are suitably used. As the electrolyte, for example, H ₂ SO ₄ , HCl, HN
Acids such as O ₃ , lithium ions (Li ⁺ ) and Lewis acid ions (BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , ClO ₄ ⁻ , C
^{_{F 3 SO 3 -, BPh 4}} -: salt consisting of (Ph phenyl group)), and these mixed salts thereof. Further, salts composed of cations such as sodium ion, potassium ion, and tetraalkylammonium ion and Lewis acid ions can also be used. It is desirable that the salt is sufficiently dehydrated and deoxygenated by heating under reduced pressure.

Examples of the solvent for the electrolyte include acetonitrile, benzonitrile, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethylformamide, tetrahydrofuran, nitrobenzene, dichloroethane, diethoxyethane, 1,2-dimethoxyethane, chlorobenzene, and the like. γ
-Butyrolactone, dioxolan, sulfolane, nitromethane, dimethyl sulfide, dimethyl sulphoxide, methyl formate, 3-methyl-2-oxidazolidinone,
2-Methyltetrahydrofuran, 3-propylsidnone, sulfur dioxide, phosphoryl chloride, thionyl chloride, sulfuryl chloride or a mixture thereof can be used.

The solvent may be dehydrated with, for example, activated alumina, molecular sieve, phosphorus pentoxide, calcium chloride, or the like, or may be distilled in an inert gas in the presence of an alkali metal to remove impurities and dehydrate. Good to do.

In order to prevent the electrolyte from leaking, it is preferable to gel. As the gelling agent, it is desirable to use a polymer that absorbs the solvent of the electrolytic solution and swells.
As such a polymer, polyethylene oxide, polyvinyl alcohol, polyacrylamide and the like are used.

In a nickel zinc battery or an air zinc battery in which the negative electrode active material is zinc, the following electrolytes are preferably used. Water is used as a solvent for the electrolyte. As the electrolyte, for example, an alkali (such as potassium hydroxide, sodium hydroxide, or lithium hydroxide) is used. In a zinc bromine battery in which the negative electrode active material is zinc, a salt such as zinc bromide is used.

In order to prevent the electrolyte solution from leaking, it is preferable to form a gel. As the gelling agent, it is desirable to use a polymer that absorbs the solvent of the electrolytic solution and swells.
As such a polymer, for example, a polymer such as polyethylene oxide, polyvinyl alcohol, and polyacrylamide, and starch are used.

(Battery Shape and Structure) Specific shapes of the secondary battery of the present invention include, for example, a flat shape, a cylindrical shape, a rectangular parallelepiped shape, and a sheet shape. The structure of the battery is as follows:
For example, there are a single layer type, a multilayer type, a spiral type, and the like. Among them, the spiral cylindrical battery has a feature that the electrode area can be increased by winding the separator between the negative electrode and the positive electrode with the separator interposed therebetween, and a large current can flow during charging and discharging. In addition, the rectangular or sheet-shaped battery has a feature that the storage space of a device configured to store a plurality of batteries can be effectively used.

Hereinafter, the shape and structure of the battery will be described in more detail with reference to FIGS. 3 and 4. FIG. 3 is a sectional view of a single-layer flat (coin-shaped) battery, and FIG. 4 is a sectional view of a spiral cylindrical battery. These have basically the same configuration as in FIG. 1 and include a negative electrode, a positive electrode, an electrolyte / separator, a battery housing, and an output terminal.

3 and 4, reference numerals 301 and 402 denote negative electrodes (a negative electrode 402 comprises a negative electrode current collector 400 and an active material layer 401), and reference numerals 303 and 408 denote positive electrodes (a positive electrode 408 denotes a positive electrode current collector 404 and an active material layer). Layer 403), 305 and 40
5 is a negative electrode terminal (negative electrode cap), 306 and 406 are positive electrode terminals (positive can), 307 and 407 are separators / electrolyte, 310 and 410 are gaskets, 411 is an insulating plate,
12 is a negative electrode lead, 413 is a positive electrode lead, and 414 is a safety valve.

In the flat-type (coin-type) secondary battery shown in FIG. 3, a positive electrode 303 including a positive electrode active material layer and a negative electrode 301 including a negative electrode material layer have a separator 307 holding at least an electrolytic solution, and the above-described separator 307. These layers are stacked via a polymer film 315 as a layer having such communication holes, and the stacked body is accommodated from the positive electrode side in a positive electrode can 306 as a positive electrode terminal, and the negative electrode side is covered by a negative electrode cap 305 as a negative electrode terminal. Coated. Then, a gasket 310 is arranged in another portion inside the positive electrode can.

In the spiral cylindrical secondary battery shown in FIG. 4, the positive electrode (active material) formed on the positive electrode current collector 404
A positive electrode having a layer 403 and a negative electrode 402 having a negative electrode (active material) layer 401 formed on a negative electrode current collector 400 have at least a separator 407 holding an electrolytic solution, and further, a communication hole as described above. Polymer film 41 as layer
5, a multilayer body having a cylindrical structure wound in multiple layers is formed. The laminate having the cylindrical structure is accommodated in a positive electrode can 406 as a positive electrode terminal. Further, a negative electrode cap 405 as a negative electrode terminal is provided on the opening side of the positive electrode can 406, and a gasket 410 is disposed in another portion inside the negative electrode can. The stacked body of electrodes having a cylindrical structure is separated from the inside of the positive electrode can and the inside of the negative electrode cap via an insulating plate 411. The positive electrode 408 is connected to a positive electrode can 406 via a positive electrode lead 413. The negative electrode 402 is connected to a negative electrode cap 405 via a negative electrode lead 412. A safety valve 414 for adjusting the internal pressure inside the battery is provided on the negative electrode cap side.

In the following, an example of a method of assembling the battery shown in FIGS. 3 and 4 will be described. (1) A negative electrode layer (301, 401) covered with a polymer film (315, 415) and a molded positive electrode layer (303, 40)
3), the separators (307, 407) are sandwiched between
It is incorporated in the positive electrode cans (306, 406). (2) After injecting the electrolyte, the negative electrode cap (305, 4
05) and gaskets (310, 410). (3) The battery is completed by caulking the above (2).

The above-mentioned material preparation for the lithium battery,
It is desirable that the battery be assembled in dry air from which moisture has been sufficiently removed or in a dry inert gas.

A description will be given of aspects of the members in the above-described example of the secondary battery. (Gasket) As a material of the gasket (310, 410), for example, polyolefin resin, fluorine resin, polyamide resin, polysulfone resin, and various rubbers can be used. As a method for sealing the battery, a method such as glass sealing tube, adhesive, welding, soldering, or the like is used other than “caulking” using a gasket as shown in FIGS. Also,
As the material of the insulating plate (411) in FIG. 4, various organic resin materials and ceramics are used.

(Battery Housing / Positive Electrode Can, Negative Cap) As the battery housing for accommodating each member in the secondary battery of the present invention, for example, as shown in FIG. 3 and FIG. Also serves as a can and negative electrode cap. In the example shown in FIG. 3, the positive electrode can 306 and the negative electrode cap 3
In the example shown in FIG. 4, the positive electrode can 406 and the negative electrode cap 405 are battery housings that also serve as input / output terminals. As a material of the battery housing also serving as the input / output terminal, stainless steel is preferably used. In particular,
A titanium-clad stainless steel plate, a copper-clad stainless steel plate, a nickel-plated steel plate and the like are often used.

In particular, in the example shown in FIGS.
The above-mentioned stainless steel is preferable because 6, 406 also serves as the battery housing. On the other hand, when the positive electrode can and the like do not double as the battery housing, as the material of the battery housing, other than stainless steel, for example, a metal such as zinc, a plastic such as polypropylene, or a composite material of metal or glass fiber and plastic is used. Can be

(Safety Valve) The secondary battery of the present invention is preferably provided with a safety valve (414 in the example shown in FIG. 4) as a safety measure when the internal pressure of the battery increases. As the safety valve, for example, rubber, spring, metal ball, bursting foil, or the like can be used.

[0090]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. Note that the present invention is not limited to these examples.

Example 1 In the present invention, a coin-shaped lithium secondary battery having the cross-sectional structure shown in FIG. 3 was manufactured. On the negative electrode surface, a negative electrode coated with a polymer-liquid crystal composite film for preventing internal short circuit due to lithium dendrite growth during charging was used. Hereinafter, with reference to FIG. 3, a description will be given of a procedure for manufacturing each component of the battery and an assembly of the battery. All operations were performed in argon gas.

(1) Procedure for Producing Negative Electrode (Active Material) Layer 301 A negative electrode layer 301 was produced by pressing a metallic lithium foil on copper expanded metal.

(2) Coating of Negative Electrode with Polymer-Liquid Crystal Composite Film Polyvinyl chloride and liquid crystal ZLI-4519 manufactured by Merck having negative dielectric anisotropy were mixed at a weight ratio of 40/60. Dichloroethane was added to prepare a coating solution.

After applying the coating solution prepared above on the surface of the metal lithium foil pressed against the expanded copper metal prepared in the above (1), a magnetic field is applied in a direction perpendicular to the surface of the metal lithium foil, followed by drying. The negative electrode (active material) layer 301 of a lithium metal foil covered with a polymer film 315 in which liquid crystal was dispersed by irradiation with ultraviolet rays was crosslinked.

(3) Production procedure of positive electrode (active material) layer 303 Electrolytic manganese dioxide and lithium carbonate were mixed at a molar ratio of 1: 0.4, and then heat-treated at 800 ° C. to remove lithium-manganese oxide. Prepared. N-methyl-2-pyrrolidone was added to the lithium-manganese oxide prepared above after mixing 3 wt% (weight) of carbon powder of acetylene black and 5 wt% of polyvinylidene fluoride powder. The paste obtained above was applied to an aluminum foil and dried, and then dried under reduced pressure at 150 ° C. to form a positive electrode (active material) layer 303.

(4) Procedure for producing electrolyte solution 307 Ethylene carbonate (EC) from which water was sufficiently removed
And dimethyl carbonate (DMC) were mixed in an equal amount to prepare a solvent. A solution obtained by dissolving lithium tetrafluoroborate 1M (mol / 1) in the solvent obtained above was used as an electrolytic solution.

(5) Separator 307 Using a polyethylene microporous separator, the electrolyte prepared in (4) was retained.

(6) Assembly of Battery The negative electrode layer 301 and the positive electrode layer 30 covered with the polymer film 315
3, a separator 307 holding an electrolytic solution was sandwiched therebetween, and inserted into a positive electrode can 306 made of a titanium clad stainless steel material. Further, the above-mentioned electrolytic solution was injected into the positive electrode can 306, and the electrolytic solution was retained in the polymer film 315. The positive electrode can 306 obtained above was covered with a gasket 310 of polypropylene and a negative electrode cap 305 of titanium clad stainless steel material, and were caulked to produce a lithium secondary battery.

(Evaluation of Battery Characteristics) Hereinafter, performance evaluation of the manufactured battery will be described. The performance evaluation was performed on the energy density per unit volume of the battery and the cycle life obtained in the charge / discharge cycle test.

The conditions of the cycle test are based on the electric capacity calculated from the positive electrode active material, and a large current density such that dendrite growth of the negative electrode active material easily occurs during charging.
That is, charging and discharging of 1C (current of one time of capacity / time),
A cycle consisting of a 30-minute rest period was defined as one cycle. The charge / discharge test of the battery used HJ-106M manufactured by Hokuto Denko. The charge / discharge test was started from charging, the battery capacity was the discharge amount in the third cycle, and the cycle life was the number of cycles less than 60% of the battery capacity.

The energy density per unit volume (Wh /
l) [Average operating voltage (V) × discharged electricity (A)
h)] / Battery volume (1). The volume of the battery was calculated as the outer volume of the cell of the unit composed of the negative electrode / separator / positive electrode. In the case of a lithium battery, the cutoff voltage for charging was set to 4.5 V, and the cutoff voltage for discharging was set to 2.5 V.

Comparative Example 1 In this example, a negative electrode (active material) layer not coated with a polymer-liquid crystal composite film was used as the negative electrode. Except that the coating operation of the liquid crystal composite film was not performed, the other points were the same as those in Example 1.
A battery was prepared in the same manner as in Example 1 and evaluated in the same manner.

Table 1 summarizes the performance evaluation (cycle life) of the lithium secondary batteries produced in Example 1 and Comparative Example 1. The evaluation results regarding the cycle life were described by standardizing the value of Example 1 with the value of Comparative Example 1 being 1.0.

[0104]

[Table 1]

Separately, the batteries prepared in Example 1 and Comparative Example 1 were subjected to 10 charge / discharge tests under the above conditions, the battery can was opened, and the state of dendrite growth on the anode of the battery was observed under a microscope. In the battery of Example 1, no generation of dendrites was observed, but in Comparative Example 1, generation of dendrites was observed. Therefore, Example 1
It was found that in the secondary battery in which the negative electrode was coated with the polymer liquid crystal composite film, no dendrite was generated even after long-term use, and a long cycle life was obtained.

Example 2 In this example, a coin-shaped lithium secondary battery having the cross-sectional structure shown in FIG. 3 was manufactured. A secondary battery was fabricated in the same manner as in Example 1, except that an aluminum foil covered with a polymer liquid crystal film was used as a negative electrode and lithium-nickel oxide was used as a positive electrode active material.

Hereinafter, the procedure for producing the negative and positive electrodes of the battery will be described with reference to FIG. (1) Production procedure of negative electrode The surface of an aluminum foil was etched with a 5% by weight aqueous solution of potassium hydroxide, neutralized with an aqueous solution of nitric acid, washed with water, and an aqueous solution of hydrochloric acid was used as an electrolyte, and glassy carbon was used as a counter electrode. The treated aluminum foil was electrolytically etched, washed with water and dried under reduced pressure, to prepare an aluminum foil having an increased surface area. At the time of charging in a battery, lithium as a negative electrode active material is deposited on the aluminum surface to form a negative electrode active material layer.

(2) Coating of Negative Electrode with Polymer Liquid Crystal Film Poly (4,4'-dioxy-2,2'-dimethylazoxybenzene (+3) -methylhexanedioil) cholesteric polymer liquid crystal was coated with Lithium chloride 2% by weight
Azobisisobutyronitrile was added to a tetrahydrofuran solution mixed with to prepare a coating solution. After applying the coating solution prepared above on the surface of the aluminum foil prepared in the above (1) using a spin coater, the coating solution was applied under reduced pressure for 1 hour.
Heat treatment was performed at 00 ° C. to prepare an aluminum foil negative electrode covered with a polymer liquid crystal film.

(3) Procedure for Producing Positive Electrode Active Material Layer 303 After mixing lithium nitrate and nickel carbonate at a molar ratio of 1: 1, the mixture was heat-treated in an air stream at 750 ° C. to prepare a lithium-nickel oxide. . N-methyl-2-pyrrolidone was added to the lithium-nickel oxide prepared above after mixing 3 wt% (weight) of carbon powder of acetylene black and 5 wt% of polyvinylidene fluoride powder. The paste obtained above is applied to an aluminum foil and dried, and then dried under reduced pressure at 150 ° C. to form a positive electrode active material layer 30.
3 was produced. In other respects, a battery was manufactured in the same manner as in Example 1.

Comparative Example 2 In this example, except that the negative electrode was not coated with a polymer liquid crystal film, that is, in this example,
A battery was fabricated in the same manner as in Example 2 except that the coating operation of the polymer liquid crystal film in was not performed, and the same evaluation was performed.

Table 2 summarizes the performance evaluation (cycle life) of the lithium secondary batteries produced in Example 2 and Comparative Example 2. The evaluation results regarding the cycle life were described by standardizing the value of Example 2 with the value of Comparative Example 2 being 1.0.

[0112]

[Table 2] Therefore, it was found that the cycle life of the secondary battery of Example 2 in which the negative electrode was covered with the polymer liquid crystal film was prolonged.

Example 3 In this example, a coin-shaped lithium secondary battery having the cross-sectional structure shown in FIG. 3 was manufactured. Graphite is used as a negative electrode as an intercalation substance that stores lithium between layers during charging,
Example 2 differs from Example 1 in that a lithium-cobalt oxide was used as a positive electrode active material and a polymer gel film was provided between the negative electrode and the positive electrode. Otherwise, a secondary battery was fabricated in the same manner as in Example 1.

Hereinafter, the procedure for producing the negative and positive electrodes of the battery will be described with reference to FIG. (1) Preparation procedure of polymer gel membrane A microporous polypropylene film subjected to hydrophilic treatment was applied to an aqueous solution of N, N-diethylacrylamide, which is a polymer monomer, and sodium acrylate, which had been deoxidized by flowing nitrogen gas. After immersion and irradiation with gamma rays, the polymer was washed with water to remove unreacted monomers and dried under reduced pressure to obtain a microporous polypropylene film with a polymer gel.

(2) Preparation of Negative Electrode After 5 wt% of polyvinylidene fluoride powder was mixed with fine powder of natural graphite heat-treated at 2000 ° C. in an argon gas stream, N-methyl-2-pyrrolidone was added to prepare a paste. did. The paste obtained above was applied to a copper foil and dried, and then dried under reduced pressure at 150 ° C. to produce a negative electrode. At the time of charging, lithium is intercalated into the graphite to form a negative electrode (active material) layer 301.

(3) Preparation procedure of positive electrode (active material) layer 303 Lithium carbonate and cobalt carbonate were mixed at a molar ratio of 1: 2, and then heat-treated in an air stream at 800 ° C.
A cobalt oxide was prepared. N-methyl-2-pyrrolidone was added to the lithium-cobalt oxide prepared above after mixing 3 wt% (weight) of carbon powder of acetylene black and 5 wt% of polyvinylidene fluoride powder. After applying and drying the paste obtained above on a current collector that is an expanded metal aluminum foil,
The positive electrode active material layer 303 was formed by drying under reduced pressure at 0 ° C.

(4) Assembly of Battery A microporous polypropylene film with a polymer gel, prepared in (1) and holding an electrolytic solution (the electrolytic solution is the same as in Example 1), is sandwiched between the positive electrode and the negative electrode. As shown in FIG. 2C, a positive electrode 102, a polymer film 100 holding an electrolytic solution, and a negative electrode 10
The laminated structure of No. 1 was formed and inserted into a positive electrode can 306 made of a titanium clad stainless steel material.

The positive electrode can 306 obtained above was covered with a polypropylene gasket 310 and a negative electrode cap 305 made of a titanium clad stainless steel material, and then caulked to produce a lithium secondary battery. That is, in the structure shown in FIG. 3, the polymer film 315 has the same function as the separator 307 in the same layer. Example 1 about the obtained secondary battery
The performance was evaluated in the same manner as in.

Comparative Example 3 In this example, a secondary battery was fabricated in the same manner as in Example 3 except that no polymer gel film was used between the positive electrode and the negative electrode. That is, a microporous polypropylene film was used as a separator.

Table 3 summarizes the performance evaluation (cycle life) of the lithium secondary batteries produced in Example 3 and Comparative Example 3. The evaluation result on the cycle life was described by standardizing the value of Example 3 with the value of Comparative Example 3 being 1.0.

[0121]

[Table 3] Therefore, it was found that the cycle life was improved in the lithium secondary battery of Example 3 in which the polymer gel film was interposed between the positive electrode and the negative electrode.

The energy density per unit volume of the secondary battery of Comparative Example 3 was set to 1.0, and the energy density per unit volume of the secondary batteries of Examples 1, 2, and 3 was standardized. As a result, 1.9, 1.6,
1.0. From the comparison of the energy densities, it was found that all of the lithium secondary batteries of Examples 1 to 3 have a long cycle life and can be obtained with a higher energy density.

In Examples 1 to 3, lithium-cobalt oxide, lithium-nickel oxide, and lithium-manganese oxide were used as a positive electrode active material in a lithium secondary battery. However, the present invention is not limited to this, and various positive electrode active materials such as lithium-vanadium oxide and lithium-iron oxide can be employed. In addition, as a negative electrode material,
Graphite, aluminum and lithium metal were used. However, the present invention is not limited to this, and various carbon materials, transition metal oxides, transition metal sulfides, and the like obtained by firing an organic resin can also be employed.

Also, one type of electrolyte solution was used in Examples 1 to 3, but the present invention is not limited to this.

Example 4 In this example, a coin-shaped nickel-zinc secondary battery having the sectional structure shown in FIG. 3 was manufactured.

Hereinafter, with reference to FIG. 3, a description will be given of a procedure for manufacturing each component of the battery and an assembly of the battery. (1) Procedure for Producing Polymer Gel Film 315 Acrylamide and trimethyl (N-acryloyl-3-aminopropyl) ammonium iodide as polymer monomers and N, N'-methylenebisacrylamide as a crosslinking agent were dissolved in water. Thereafter, a nitrogen gas is flown to deoxidize, soak the hydrophilically treated microporous polypropylene film, add ammonium persulfate as a polymerization initiator and tetramethylethylenediamine to this liquid, and react for about 30 minutes to form a gel. After that, it was washed with water to remove unreacted monomers and dried under reduced pressure to obtain a microporous polypropylene film with a polymer gel.

(2) Preparation procedure of negative electrode (active material) layer 301 A mixture of zinc powder and zinc oxide powder was used on both sides of a copper punching metal, and polyvinyl alcohol was used as a binder.
Water was added and kneaded to form a paste, which was applied to a nickel metal punched metal plate, dried, and pressed to obtain a negative electrode active (material) layer 301.

(3) Procedure for Producing Positive Electrode (Active Material) Layer 303 Nickel powder is added to nickel hydroxide, carboxymethylcellulose and water are added as a binder to prepare a paste, and a nickel foam ( After filling in Sumitomo Electric Co., Ltd., Celmet), it was dried and pressed to produce.

(4) Procedure for Producing Electrolyte Solution 307 A 30 wt% aqueous solution of potassium hydroxide to which lithium hydroxide was added was used. (5) Separator 307 Sandwiched hydrophilic non-woven polypropylene nonwoven fabric with hydrophilic microporous polypropylene film
One having a thickness of 0 μm was used.

(6) Battery Assembly Between the negative electrode (active material) layer 301 and the positive electrode (active material) layer 303, the positive electrode 102, the separator / electrolyte 103, the polymer film 100, and the negative electrode shown in FIG. As in the laminated structure of No. 101, the microporous polypropylene film with the polymer gel prepared in the above (1) is sandwiched on the negative electrode side, and the separator 307 holding the above-mentioned electrolyte is sandwiched on the positive electrode side. Of the positive electrode can 306. Further, the electrolytic solution was injected into the positive electrode can 306 and the polymer film 315 retained the electrolytic solution.

A positive electrode can 306 obtained above was covered with a polypropylene gasket 310 and a negative electrode cap 305 made of stainless steel material clad with titanium, and caulked to produce a nickel-zinc secondary battery.

Hereinafter, performance evaluation of the manufactured nickel-zinc battery will be described. The performance evaluation was performed on the cycle life obtained in the charge / discharge cycle test.

The conditions for the cycle test were as follows: 1 C (capacity / time 1
A cycle consisting of charging / discharging at twice the current and a rest time of 30 minutes was defined as one cycle. The charge / discharge test of the battery used HJ-106M manufactured by Hokuto Denko. The charge / discharge test was
Starting from charging, the battery capacity was defined as the amount of discharge in the third cycle, and the cycle life was defined as the number of cycles less than 60% of the battery capacity. In the case of a nickel-zinc battery, the charge cutoff voltage is 2.0 V, and the discharge cutoff voltage is 0.1 V.
It was set to 9V.

Comparative Example 4 In this example, a nickel-zinc secondary battery was manufactured in the same manner as in Example 4 except that the polymer gel film was not used, and the performance was evaluated in the same manner. .

Table 4 summarizes the performance evaluation (cycle life) of the nickel-zinc secondary batteries produced in Example 4 and Comparative Example 4. The evaluation results regarding the cycle life were described by standardizing the value of Example 4 with the value of Comparative Example 4 being 1.0.

[0136]

[Table 4] Therefore, it was found that a longer cycle life was obtained in the nickel-zinc secondary battery of Example 4 in which the polymer gel film was interposed between the positive electrode and the negative electrode.

Example 5 In this example, a coin-shaped air zinc secondary battery having the cross-sectional structure shown in FIG. 3 was manufactured.

In the following, referring to FIG. 3, a description will be given of the procedure for manufacturing each component of the battery and the assembly of the battery. (1) Preparation procedure of polymer-liquid crystal composite film 315 Polyvinyl chloride and liquid crystal ZLI-2806 manufactured by Merck exhibiting negative dielectric anisotropy were mixed at a weight ratio of 40/60, and then dissolved in dichloroethane. The solution was applied to a hydrophilically-treated microporous polypropylene film which was previously coated with an ethanol solution of lecithin and dried, and then polymer-
A liquid crystal composite film 315 was obtained.

(2) Preparation procedure of negative electrode (active material) layer 301 A paste prepared by adding polyvinyl alcohol and water to a mixture of zinc powder and zinc oxide powder and kneading the mixture was applied to both surfaces of a copper punching metal. By performing dry pressing, a negative electrode (active material) layer 301 was obtained.

(3) Manufacture Procedure of Positive Electrode Acetylene black was mixed with manganese dioxide, nickel oxide, cobalt oxide, and tetrafluoroethylene polymer powder. The paste obtained by adding the solution was applied to a nickel-plated copper mesh, cured at 170 ° C., and formed through a pressure heater roller to obtain a positive electrode. At the time of discharge, air diffuses to the positive electrode and oxygen of the active material reacts.

(4) Procedure for Producing Electrolyte Solution 307 A 30 wt% aqueous solution of potassium hydroxide to which lithium hydroxide was added was used. (5) Separator 307 Sandwiched hydrophilic non-woven polypropylene nonwoven fabric with hydrophilic microporous polypropylene film
One having a thickness of 0 μm was used.

(6) Assembly of Battery Between the negative electrode (active material) layer 301 and the positive electrode (active material) layer 303, the positive electrode 102, the separator / electrolyte 103, the polymer film 100, and the negative electrode shown in FIG. As in the laminated structure of No. 101, the microporous polypropylene film with the polymer-liquid crystal composite film prepared in the above (1) is sandwiched on the negative electrode side, and the separator 307 holding the electrolyte is sandwiched on the positive electrode side. And a titanium can clad stainless steel material into which a polytetrafluoroethylene film of a water-repellent film was inserted. Further, the positive electrode can 30
An electrolytic solution was injected into 6 and the electrolytic solution was held on a polypropylene film.

The positive electrode can 306 obtained above was covered with an insulating backing 310 made of polypropylene and a negative electrode cap 305 made of a stainless steel material clad with titanium.
An air zinc secondary battery was produced by caulking.

Comparative Example 5 In this example, an air zinc secondary battery was produced in the same manner as in Example 5, except that the polymer-liquid crystal composite film was not used for the positive electrode and the negative electrode.

The performance of the batteries produced in Example 5 and Comparative Example 5 was evaluated under the same conditions as in the nickel-zinc battery of Example 4.

Table 5 summarizes the performance evaluations of the air-zinc secondary batteries produced in Example 5 and Comparative Example 5. The evaluation result on the cycle life was described by standardizing the value of Example 5 with the value of Comparative Example 5 being 1.0.

[0147]

[Table 5] Therefore, it was found that by using the air-zinc secondary battery in which the polymer liquid crystal composite film was sandwiched between the positive electrode and the negative electrode of Example 5, a secondary battery having a better cycle life was obtained.

[0148]

As described above, according to the present invention,
In particular, in a secondary battery in which the negative electrode active material is lithium or zinc, it is possible to suppress the growth of dendrite which is generated in the negative electrode during charging and causes performance degradation. As a result, it is possible to produce a lithium secondary battery, a nickel zinc secondary battery, an air zinc secondary battery, and the like, which have a long cycle life and a high energy density.

[Brief description of the drawings]

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

FIG. 2 is a conceptual diagram showing an arrangement example of a negative electrode, a positive electrode, a separator, and a polymer film as a means for preventing dendrite growth of a negative electrode active material in a secondary battery of the present invention.

FIG. 3 is a cross-sectional view illustrating an example of a single-layer flat battery according to the present invention.

FIG. 4 is a sectional view showing an example of a spiral cylindrical battery of the present invention.

FIG. 5 is a conceptual diagram illustrating functions of a secondary battery of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Short-circuit preventing polymer film 101 Negative electrode 102 Positive electrode 103 Separator / electrolyte 104 Battery case (battery housing) 105 Negative terminal 106 Positive terminal 107 Electric field concentration portion 108 High resistance portion of short-circuit preventing polymer film 109 Charging power supply 301 Negative electrode layer 401 Negative electrode (active material) layer 303 Positive electrode layer 403 Positive electrode (active material) layer 305,405 Negative cap (negative electrode terminal) 306,406 Positive electrode can (positive electrode terminal) 307,407 Separator 310,410 holding electrolyte solution Gasket 400 Negative current collector 402 Negative electrode 404 Positive current collector 408 Positive electrode 411 Insulating plate 412 Negative lead 413 Positive lead 414 Safety valve 315, 415 Short-circuit preventing polymer film

Claims (19)

(57) [Claims] 1. A negative electrode, a positive electrode, a layer having a communication hole having a pore diameter capable of moving an electrolyte and ions involved in a battery reaction between the positive electrode and the negative electrode and varying according to the environment, possess a battery housing for accommodating the communication
The through hole increases the electric field strength in the area around the through hole.
A secondary battery characterized in that the pore size becomes smaller due to an increase in temperature and / or temperature . 2. The secondary battery according to claim 1, wherein the layer having the communication holes is a polymer film having pores whose diameter changes according to a change in electric field strength and / or temperature. 3. The secondary battery according to claim 2, wherein the polymer film is made of a polymer liquid crystal. 4. The polymer liquid crystal is vertically or obliquely aligned with respect to the negative electrode plane when no electric field is applied, and in the vicinity of pores where electric field intensity and / or temperature have increased. 4. The secondary battery according to claim 3 , wherein the secondary battery is substantially parallel or randomly oriented with respect to the negative electrode plane. 5. The secondary battery according to claim 3 , wherein the polymer liquid crystal has a negative dielectric anisotropy. 6. The secondary battery according to claim 2, wherein the polymer film comprises a composite of a polymer and a liquid crystal. 7. A liquid crystal in the polymer film is vertically or obliquely aligned with respect to a negative electrode plane without application of an electric field, and around a pore in which electric field intensity and / or temperature have increased. The secondary battery according to claim 6 , wherein the secondary battery is oriented substantially parallel or randomly with respect to the negative electrode plane. 8. The secondary battery according to claim 6 , wherein the dielectric anisotropy of the liquid crystal in the polymer film is negative. 9. The secondary battery according to claim 2, wherein the polymer film is made of a polymer gel. 10. The method according to claim 1, wherein the temperature of the polymer gel is increased by increasing the temperature.
The secondary battery according to claim 9, which expands in volume by 0% or more. 11. The secondary battery according to claim 2 , further comprising a separator, wherein the positive electrode, the separator, the polymer film, and the negative electrode are laminated in this order to form a laminated structure. 12. The secondary battery according to claim 11, wherein the polymer film is made of a cationic polymer gel having a positive charge. 13. The secondary battery according to claim 2 , further comprising a separator, wherein the positive electrode, the polymer film, the separator, and the negative electrode are laminated in this order to form a laminated structure. 14. The secondary battery according to claim 13, wherein the polymer film is made of an anionic polymer gel having a negative charge. 15. The secondary battery according to claim 2, wherein the polymer film also has a function of a battery separator and is sandwiched between a positive electrode and a negative electrode. 16. The secondary battery according to claim 2, wherein the polymer membrane has pores having a pore size of 2 to 1000 °. 17. The shrinkage ratio of the pore diameter when a high electric field is locally applied and / or the temperature locally rises in the polymer film is 20 to 98% of the original pore diameter. 2
The secondary battery according to any one of the preceding claims. 18. The secondary battery according to claim 1, wherein the negative electrode at the time of charging the secondary battery contains at least a lithium element. 19. The secondary battery according to claim 1, wherein the negative electrode at the time of charging the secondary battery contains at least zinc element.