JPH0896838A - Lithium ion secondary battery - Google Patents

Abstract

PURPOSE: To provide a large lithium ion secondary battery having 'improved stiffness, vibration resistance, and shock resistance by feeding a refrigerant to the surfaces of the metal faces of the conductors of a negative electrode and a positive electrode, and removing the heat generated in unit cells. CONSTITUTION: A positive electrode coated with a positive electrode active material mix on a metal material and a negative electrode coated with a negative electrode active material mix on a metal material are laminated in turn across a separator to obtain a unit cell. Metal foil lug portions 4', 5' of the electrodes of the unit cells are separated for the positive electrodes and negative electrodes, and they are bundled and welded to form metal faces 10, 13. The metal faces 10, 13 are pinched by conductors 8, 11 and fastened by bolts 9, 12 to form a metal plate, and this metal plate is integrated with the metal foils of the electrodes to form a current collector. The metal faces 10, 13 and an electrolyte in the unit cells are separated, a refrigerant is fed to the metal faces 10, 13 to extract the heat accumulated in the unit cells at the time of a charge and a discharge, the temperature rise in the unit cells is prevented, and electricity is extracted through the current collector.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium-ion secondary battery, and particularly to a field of large capacity, high energy density, and high maintenance-free demand for electric vehicles, load leveling of electric power, and the like. The present invention relates to a prismatic lithium ion secondary battery used in.

[0002]

2. Description of the Related Art In recent years, in response to the miniaturization and weight reduction of electronic equipment, a lithium-ion secondary battery for electronics, which is lightweight and small in size and has a large capacity, has been put into practical use as a power source for handheld video cameras and It is used in portable personal computers. However, its capacity is large, 5-20
It is about Wh, and there are many cylindrical types. On the other hand, electric vehicles are attracting public attention due to environmental issues and the need for load leveling of electric power to effectively use nighttime electric power is increasing. Therefore, there is an increasing demand for a secondary battery which has a large capacity, is inexpensive, and is maintenance-free, which is required for these. However, lead-acid batteries widely used in this field have low energy density, are heavy, and are difficult to use. Further, in terms of maintenance, in addition to the need for water replenishment and the like, the charge / discharge cycle life is as short as about 600 cycles, and as a result, the cost for the battery is high. Nickel-cadmium batteries are also used in some parts, but they are not widely used because their energy density is not high enough and their cost is higher than that of lead-acid batteries. In addition to these, nickel-zinc batteries and sodium-sulfur batteries have also been experimentally used for electric vehicles, but the former has shortcomings such as a short charge / discharge cycle life and the latter has a high risk. .

Since the lithium ion secondary battery has a high energy density, is sealed and maintenance-free,
Although suitable for these applications, large ones have not been put to practical use in the past. To use for these purposes 1,
It is necessary to have a capacity of about 000 to 5,000 Wh, and to manufacture a capacity of 100 times or more of that which has been put into practical use. Cylindrical type is the mainstream of lithium-ion secondary batteries that have been put to practical use, but 1,000 to 5, which are required for electric vehicles, load leveling, etc.
The 000 Wh class is a 3 to 4 V unit cell having a structure in which a positive electrode in which a positive electrode active material mixture is applied to a metal foil or the like and a negative electrode in which a negative electrode active material mixture is applied to a metal foil or the like are alternately laminated with a separator interposed therebetween. It is a prismatic battery that comprises two or more batteries connected in series to form an assembled battery. Such a prismatic lithium ion secondary battery has not yet been put to practical use. Further, conventionally, a large-sized lithium-ion secondary battery having excellent toughness, vibration resistance, and impact resistance, which is suitable for electric vehicles, has not been put into practical use.

[0004]

When a lithium-ion secondary battery is used as a large-capacity secondary battery required for electric vehicles, load leveling, etc., it is first necessary to increase the capacity. . In that case, the lithium ion secondary battery is a so-called prismatic type. It consists of several tens to about 100 electrodes of each unit cell, which are laminated with alternating negative and positive electrodes with a separator sandwiched between them. Normally, these cells are connected in series to form an assembled battery. .
In particular, when it is used for an electric vehicle or the like, it is required to have large size and toughness, vibration resistance, and impact resistance. For that purpose, the charge / discharge cycle life of the electrode itself, toughness, vibration resistance, and impact resistance are required to be high, but the structure of a single cell in which electrodes are laminated in multiple layers also has toughness, vibration resistance, and
It is necessary to devise so that impact resistance becomes high. As described above, it is required to increase the size of the lithium ion secondary battery and enhance the toughness, vibration resistance and impact resistance.

When the lithium ion secondary battery is upsized, the heat generated inside the battery during charging / discharging accumulates inside the battery and the internal temperature of the battery rises, which may exceed the allowable temperature of the battery. It is necessary to dissipate this outside. Particularly for electric vehicles, there is a strong demand for secondary batteries that can withstand rapid charging / discharging, and conventional lithium-ion secondary batteries accumulate heat inside the batteries during rapid charging and repeated charging / discharging, and the internal temperature of the batteries increases. There is a problem that the temperature rises and exceeds the allowable temperature of the battery. The present inventor previously disclosed in Japanese Patent Application No. 6-67246 that heat generated inside a lithium-ion secondary battery is passed through a wall of a battery container by a conductor of a current collector for each single battery. We proposed a lithium-ion secondary battery that is configured to be discharged to the outside and then contacted with a refrigerant to dissipate. However, in this case, since heat conduction and heat transfer of the metal of the conductor are not sufficiently large, further improvement is required. Therefore, the present inventor has arrived at the present invention by conducting various studies to solve these problems.

[0006]

The summary of the present invention is as follows.
In a lithium-ion secondary battery consisting of a single battery in which a positive electrode in which a positive electrode active material mixture is applied to a metal material and a negative electrode in which a negative electrode active material mixture is applied to a metal material are alternately laminated with a separator interposed therebetween, the electrodes are laminated in multiple layers. , The electrode metal material ears are separated into the positive electrode and the negative electrode and electrically and thermally connected to the conductors respectively to form the current collector, and the metal material ears of the positive electrode and the negative electrode are separated. , Separate and bundle a plurality of each, sandwiched by this conductor, the end of the ear portion of the electrode and a metal surface formed by welding this conductor from the tip side of this end, the refrigerant The lithium ion secondary battery is characterized in that it is configured so that the heat generated inside the unit cell is dissipated and the electricity is taken out through this conductor. Hereinafter, the present invention will be described in detail.

First, the constituent elements of the lithium ion secondary battery according to the present invention are at least a negative electrode, a positive electrode, a separator and a non-aqueous electrolyte, and the negative electrode active material is generally a carbon material capable of intercalating or doping with lithium. The positive electrode active material is a metal oxide compound such as Li _x CoO ₂ capable of occluding or intercalating lithium, a chalcogenite compound such as Li _x TiS ₂ .

The negative electrode is a negative electrode active material and a binder.
A slurry of [negative electrode mixture] in a solvent is applied to a foil of a metal such as copper, dried, and optionally roll-treated. The positive electrode is obtained by applying a slurry of a positive electrode active material, a binder (binder), and a conductive agent [positive electrode mixture] in a solvent to a metal foil such as aluminum or the like,
It is dried and, if necessary, roll-treated. As the separator, a thin film of porous synthetic resin, for example, a thin film of polypropylene resin having a thickness of 25 μm, a thin film of polyethylene resin having a thickness of 20 μm, or the like is used, but the separator is not limited thereto.

As the non-aqueous electrolyte, a solution obtained by dissolving a lithium salt in an organic solvent is used. The lithium salt is not particularly limited, and examples thereof include LiPF ₆ , LiBF ₄ , and LiCl.
O ₄ , LiAsF ₆ , LiCF ₃ SO _{3 and the} like can be mentioned. The organic solvent is not particularly limited, for example, carbonates, ethers, ketones, sulfolane compounds,
Lactones, nitriles, chlorinated hydrocarbons, amines, esters, amides, phosphoric acid ester compounds and the like can be used.

Typical examples of these are listed below: propylene carbonate, ethylene carbonate, vinylene carbonate, tetrahydrofuran, 2 methyl tetrahydrofuran, 1,4 dioxane, 4 methyl 2 pentanone, sulfolane, 3 methyl sulfolane, γ-butyrolactone and dimethoxyethane. , Diethoxyethane, acetonitrile, propionitrile, benzonitrile, butyronitrile, valeronitrile, 1,2 dichloroethane, dimethylformamide, dimethylsulfoxide, trimethyl phosphate, triethyl phosphate and the like and mixed solvents thereof.

Examples of the binder for the negative and positive electrodes include polyvinylidene fluoride, polytetrafluoroethylene, and EP.
DM (ethylene-propylene-diene terpolymer),
SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber and the like are used, but not limited to these. As the positive electrode conductive agent, fine particles of graphite, carbon black such as acetylene black, fine particles of amorphous carbon such as needle coke,
Etc. are used, but not limited to these.

As the solvent for making the negative electrode mixture of the negative electrode and the positive electrode mixture of the positive electrode into a slurry, an organic solvent capable of dissolving the binder is usually used. For example, N-methylpyrrolidone, dimethylformamide, dimethylacenamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, NN dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc. are used, but not limited to these. .

Further, the negative electrode mixture and the positive electrode mixture are made into a slurry by adding a dispersant, a thickener, etc. to water, or SBR.
In some cases, the electrode active material or the like is slurried with a latex such as the above and applied to a metal foil or the like to manufacture an electrode. The negative electrode active material is a carbon material capable of intercalating or doping with lithium, and the carbon material is not particularly limited, and examples thereof include graphite and coal-based coke, petroleum-based coke, carbide of coal-based pitch, and carbide of petroleum-based pitch. Carbides such as needle coke, pitch coke, phenol resin and crystalline cellulose, and the like, and carbon materials obtained by partially graphitizing these, furnace black, acetylene black, pitch-based carbon fiber, and the like.

The positive electrode active material occludes or intercalates lithium.
Metal oxide compounds that can be curated, chalcogena
Ito-based compounds and the like, but are not particularly limited, for example,
Li _xCoO₂, Li_xMnO₂, Li_xMn₂O_Four,
Li_xV₂O_Five, Li_xTiS₂Etc. are used. Negative electrode
The current collector materials are copper, nickel, and stainless steel.
Steel, nickel-plated steel, etc. are used for the positive electrode current collector.
Materials are aluminum, stainless steel, nickel
Plated steel, etc. are used, but are not limited to these
Not of.

The lithium ion secondary battery according to the present invention comprises a single battery in which a positive electrode in which a positive electrode active material mixture is applied to a metal material and a negative electrode in which a negative electrode active material mixture is applied to a metal material are alternately laminated with a separator interposed therebetween. Become. This stacking can be selected according to the purpose, but in order to increase the size of the battery, it is necessary to stack ten or more electrodes, and in some cases, 100 or more multilayers. As a metal material for applying the positive or negative electrode active material mixture, a thin material such as a metal foil, a metal plate, a metal porous plate, or a wire mesh is suitable.

In the present invention, the ears, which are the portions of the metal material to which the electrode active material mixture is not applied, are electrically and thermally connected to a conductor by separating the positive electrode and the negative electrode. Then, a current collector is formed. When forming the current collector by connecting the ears of the metal material to the conductor, separate the ears of the metal material of the positive electrode and the negative electrode and bundle them into a plurality, and sandwich them with the conductor. , Weld this conductor to the edge of the metal material ear portion of the electrode. As a welding method, TIG welding, high frequency welding, and ultrasonic welding are preferable, but the welding method is not limited to these.

According to the present invention, in a lithium ion secondary battery, in order to prevent the heat generated inside the unit cell during charging / discharging from being stored inside the unit cell and preventing the internal temperature of the unit cell from exceeding an allowable temperature, Provided is a lithium-ion secondary battery configured to effectively dissipate heat from a single battery. The present invention is configured to remove the heat generated inside the unit cell by directly contacting the coolant with the end of the ear portion of the metal material and the metal surface formed by welding the conductor. A lithium ion secondary battery is provided. Usually, this metal surface is inside the assembled battery and is in contact with the electrolytic solution, but the purpose can be achieved by separating this metal surface from the electrolytic solution.

In the lithium ion secondary battery thus constructed, the heat generated inside the unit cell is transferred from the layer of the electrode active material mixture to the metal foil of the metal material, and the like.
The heat is transferred to the conductor by heat conduction through the metal material, and is effectively removed by the refrigerant in contact with the conductor.
When separating the ears of the metal material of the positive electrode and the negative electrode and bundling a plurality of them separately, when bundling a plurality of cells per single cell, in order to achieve the above-mentioned object, it is necessary to use conductors that sandwich adjacent bunches. It is necessary to make them integral with each other so that the conductors of the positive electrode and the negative electrode are each one metal plate.

The method for separating the metal surface from the electrolytic solution is as follows: (1) When the container of the assembled battery for accommodating the unit cell has a structure in which the metal surface is liquid-sealed with a sealing material or the like, (2) Each cell may have a structure capable of containing an electrolytic solution. For both the former and the latter, as a method for liquid sealing, usually, a method of mechanically tightening using a gasket, a method of using an adhesive material that plastically deforms, such as an asphalt seal, or a plastic seal, for liquid sealing, or a container with an adhesive is used. Examples include a method of adhering the frame and the surface of the unit cell and a method of combining these.

In the present invention, a structure in which the electrolytic solution is contained in each unit cell is more preferably applied. Usually, the shape of the lithium-ion secondary battery in the present invention is a rectangular parallelepiped, but the following method is suitable for liquid sealing the corners. That is, it is suitable as a method for separating the electrolytic solution from the unit cell or the outside that a structure in which a sealing material that resists corrosion of the electrolytic solution is sandwiched in the corner portion or a structure is press-fitted. Polyvinylidene fluoride, SBR, NBR, EPDM, and the like are suitable as the sealing material that is resistant to the corrosion of the electrolytic solution.

As the refrigerant, so-called air cooling, which uses cooling air, is preferable, but a liquid refrigerant is more effective.
In the case of air cooling, the structure that sends air by natural convection is the simplest, but in order to cope with higher loads such as rapid charging,
It is necessary to forcefully blow air with a blower. A blower for blowing air can be provided for each battery pack,
It may be provided for a plurality of assembled batteries. In the case of using a liquid refrigerant, in order to flow the cooled refrigerant on the metal surface made of the electric conductor of the single cell, for each assembled battery or for each assembled battery, the cooling medium provided with the cooler and the circulation pump is used. It is generally configured to include a cooling system.

As the refrigerant, it is preferable to use a solvent which does not react even when mixed with the electrolytic solution. This is to prevent a problem from immediately occurring even if a coolant leaks in the cooling system and a coolant as a cold source is mixed in the electrolytic solution of the lithium ion secondary battery. The solvent is preferably the same as the solvent used for the electrolytic solution of the lithium ion secondary battery, but is not limited thereto. Also, when equipped with a blower for air cooling or a circulation pump when using a liquid refrigerant, the temperature inside the cell is detected, and when this temperature rises, it starts, and when it falls, it stops. It is preferable to provide a mechanism.

Further, in the present invention, in order to make the unit cell have a solid structure, when the positive electrodes and the negative electrodes are alternately laminated with the separators sandwiched therebetween, the intervals between the positive electrodes and the positive electrodes and between the negative electrodes and the negative electrodes are kept constant. In addition, it is possible to have a structure in which non-conductive spacers are sandwiched and stacked, and the electrode layer of the unit cell is clamped from the outside with a non-conductive frame. By making the unit cell have such a structure, the unit cell is tougher and is excellent in vibration resistance and impact resistance. As the non-conductive frame, a frame made of a synthetic resin such as polypropylene, or a frame made of metal which is in contact with the positive electrode and the negative electrode on the surface of the frame and is covered with a non-conductive material at a portion necessary for insulation is used.

In the manufacture of the lithium ion secondary battery of the present invention, when a spacer is sandwiched between electrodes, the following method can be preferably adopted in order to improve the productivity. (I) A metal foil or the like of the positive electrode and the negative electrode, to which a spacer is attached in advance with an adhesive, is used. By doing so, by performing the work of laminating the positive electrode, the separator, the negative electrode, the separator, and the positive electrode in this order,
Since the unit cell in which the spacer is sandwiched is completed, the work of sandwiching the spacer is omitted, and the productivity of the manufacturing process of the lithium ion secondary battery is significantly improved. (Ii) As the spacer, an elongated spacer that matches the length of the electrode in the lengthwise direction is used. By doing so, the number of operations for sandwiching the small spacer is reduced, and the workability is also improved.

[0025]

[Example 1]

(Negative electrode) Coal-based needle coke is crushed to an average particle size of 1
90 parts of 0 μm was added to polyvinylidene fluoride 10
Part is dissolved in 150 parts of N-methylpyrrolidone to form a negative electrode mixture slurry, which is applied to both sides of a copper foil having a thickness of 40 μm, dried to evaporate the solvent, and roll-treated to form a negative electrode. The size of the negative electrode mixture application part is 10 cm x 1
The thickness was 8 cm and the thickness was 150 μm on each side. Although the copper foil is not particularly sensitive to the top and bottom, the left and right sides are 30 mm on the left and 3 on the right.
It is designed to be applied with the negative electrode mixture leaving the mm ear. It should be noted that the electrodes constituting the end portions of the unit cells are those in which the negative electrode mixture is applied to only one surface.

(Positive electrode) 1 mol of lithium carbonate and 2 mol of cobalt carbonate were mixed and pulverized in a ball mill, heat-treated in air at 850 ° C. for 5 hours, mixed and pulverized again in a ball mill, and further in air at 850 ° C. for 5 hours. Heat-treated with 9
An aluminum foil having a thickness of 80 μm was prepared by adding 5 parts of acetylene black as a conductive agent to 0 part and mixing the mixture with 5 parts of polyvinylidene fluoride dissolved in 150 parts of N-methylpyrrolidone to prepare a positive electrode mixture slurry. Is coated on both surfaces, dried to evaporate the solvent and roll-processed to prepare a positive electrode. The size of the positive electrode mixture application part is 10 cm x 18
cm, and the thickness was 140 μm on each side. The aluminum foil doesn't take much ears up and down, but to the left and right, 30m to the right.
It is designed so that the negative electrode mixture is applied while leaving a 3 mm left ear. It should be noted that the electrodes forming the end portion of the unit cell are those in which the positive electrode mixture is applied to only one surface.

(Assembly of Unit Cell) The unit cell is assembled by alternately stacking the negative electrode and the positive electrode with a porous polypropylene sheet having a thickness of 35 μm sandwiched as a separator. At that time, the electrodes on both ends were prepared by applying the electrode mixture only on one side, and a polypropylene vertical spacer was sandwiched between the negative electrodes on the left negative electrode ears, and the right positive electrode ears were Longitudinal polypropylene spacers are also sandwiched between the positive electrodes and laminated on the portions.

Approximately 15 sheets of the end portion of the left negative electrode are bundled, each of which is sandwiched by two copper conductors and fastened with a bolt to electrically and thermally join the two. , Weld the ends of the ears and these two copper conductors. In this case, since the negative ears of the unit cell are 91 sheets, they will be bundled in 6 groups and bonded to the conductors, but the conductors that tighten the adjacent groups will be integrated, and After tightening, joining, and welding of the end portion of the ear portion of the negative electrode and the copper conductor, the negative electrode conductor becomes a welded single metal plate. Thus, the negative electrode current collector in which the metal foil coated with the negative electrode active material mixture and the conductor metal are firmly bonded together is formed.

Similarly, the end portion of the right side of the positive electrode is also bundled by about 15 sheets each, sandwiched by two aluminum conductors each, and crimped with a rivet to electrically and thermally join them. Then, the ends of the ears are welded to the two aluminum conductors. In this case, since there are 91 positive electrode ears of the unit cell, they will be bundled in 6 groups and bonded to the conductors, but the conductors that clamp the adjacent groups will be integrated, and After tightening, joining, and welding of the end portion of the ear portion of the negative electrode and the aluminum conductor, the negative electrode conductor becomes a welded single metal plate. Thus, the negative electrode current collector in which the metal foil coated with the negative electrode active material mixture and the conductor metal are firmly bonded together is formed.

A coolant is caused to flow on the surfaces of the metal surfaces of the electric conductors of the negative electrode and the positive electrode thus formed, and the heat generated inside the unit cell is removed. Therefore, it is necessary to seal the electrolytic solution in the unit cell, so that the unit cell bottom plate is first attached to the bottom surface of the assembled unit cell, and then the unit cell side wall plate is attached to the side surface. The unit cell side wall plate has a unit cell side wall plate adhesive portion, and is superposed on the unit cell side wall plate and firmly joined thereto. Finally, the cell top lid is attached to the top surface of the cell. The unit cell upper lid is provided with a unit cell upper lid adhesive portion, and overlaps with the unit cell side wall and is firmly bonded thereto. As a method of pasting, an adhesive material can be used for adhesion, or a gasket can be sandwiched and mechanically tightened. Also, these may be combined. Polypropylene filled with glass fiber was used for the unit cell bottom plate, unit cell side wall plate, unit cell upper lid and the like.

The unit cell in which the unit cell body is thus sealed is first subjected to an airtight test, then the inside is evacuated to inject a predetermined amount of the electrolytic solution, and then the injection hole is sealed. The electrolyte is propylene carbonate and dimethoxyethane 1: 1
A solution obtained by dissolving 1 mol / L of lithium hexafluorophosphate in the mixed solvent of is used. When 90 sets of electrodes of the above size and half are laminated (the electrodes on both ends are half because the electrode mixture is applied on only one surface), a single cell having a charge / discharge capacity of about 625 Wh is obtained.

1 to 4 show a lithium ion secondary battery cell thus obtained. FIG. 1 is a plan view (sectional view taken along the line AA ′ in FIG. 2), in which the metal foil ears 4 ′ and 5 ′ of the electrodes of the unit cell are bundled into four sets, and the positive electrode and the negative electrode are separately conductive. Sandwiched between bodies 8 and 11, bolts 9 and 1
The one tightened in 2 is shown. 10 and 13 are welded portions of the metal foil ears 4'and 5'and the conductors 8 and 11. The conductors 8 and 11 are integrated so as to tighten the ears of adjacent metal foils, and as a result, the conductors 8 and 11 are formed into a single metal plate by welding. The one metal plate and the metal foil of the electrode are integrated to form a current collector. Reference numeral 1 denotes an electrode active material mixture application portion, and 7 is a portion sandwiching a spacer. 15,17
Is a unit cell terminal and is directly welded to the conductors 8 and 11. Reference numeral 42 denotes a unit cell side plate, which plays a role of pressing an electrode at an end of the unit cell, tightening an electrode layer, and a role of separating the electrolytic solution of the unit cell from the outside. The material of the cell side plate is polypropylene with glass fiber. The side plate of the unit cell and the side wall of the unit cell may be bonded by an adhesive, a gasket may be sandwiched between them, or both may be combined.

FIG. 2 is a front view (cross section BB 'in FIG. 1). Reference numeral 1 is an electrode active material mixture application portion, and 6 is a separator. Numeral 7 is a spacer, which sandwiches the ears 4 ', 5'of the metal foil of the electrode with the conductors 8, 11, and the bolts 9, 1
Tighten with 2. 10 and 13 are the electrode ears 4 ',
5'shows a welded portion where the conductors 8 and 11 are welded. 15,
Reference numeral 17 denotes a unit cell terminal, which is directly welded to the conductors 8 and 11. Electricity is generated from electrode active material mixture, metal foil, conductor,
It is transmitted from the unit cell terminal and taken out from the unit cell. The heat generated inside the unit cell is removed by heat conduction from the electrode active material mixture to the metal foil and the conductor, and is removed by the cooling liquid flowing on the surface of the conductor. 24 is the liquid level of the electrolytic solution in the unit cell.
Reference numeral 41 denotes a unit cell bottom plate and 44 is a unit cell upper lid, which serves to separate the electrolytic solution of the unit cell from the outside. These materials are polypropylene with glass fiber. Reference numeral 43 denotes a unit cell side plate adhesive portion that is integral with the unit cell side plate, and serves to strengthen the joint between the bottom plate and the side plate. The bottom surface of the cell and the cell bottom plate, and the top surface and the cell lid may be bonded with an adhesive, a gasket may be sandwiched between them, or both may be combined.

FIG. 3 is a side view (section CC ′ in FIG. 2), which is a front view of a metal surface formed by welding conductors. This side is the negative electrode (copper) and the opposite side is the positive electrode (aluminum) of exactly the same shape. The portion surrounded by the broken line in the center is the electrode active material mixture application portion 1. The upper part 24 indicates the liquid surface of the electrolytic solution. The negative electrode single battery terminal 15 is welded to the center of the metal surface. The positive electrode single battery terminal 16 is welded to the opposite surface. As shown in this figure, the unit cell bottom plate 41, the unit cell side plate 42, the unit cell side plate adhesive portion 43, the unit cell upper lid 44, and the unit cell upper lid adhesive portion 45 surround the bottom surface, the top surface, and the side surface of the unit cell. Separates the electrolyte from the appearance. The unit cell side plate also plays a role of clamping the electrode layers of the unit cell.

FIG. 4 shows an enlarged view of the X portion of FIG. In this figure, three negative electrode ears 4'are bundled, sandwiched between conductors 8 and tightened with bolts 9. Reference numeral 10 indicates a welded portion in which the negative electrode ear portion 4'and the conductor 8 are welded. The conductors 8 that sandwich the adjacent negative electrode ears are integrated. Reference numerals 2 and 4 are negative electrodes, 3 and 5 are positive electrodes, 6 is a separator, and 7 is a spacer. Reference numeral 42 is a unit cell side plate.

(Assembly of Batteries) The above four cells are divided into partition walls of the cells, a chamber in which the cooling liquid flows on the surface of the conductor of the cells, an inlet for the cooling liquid, and a cooling liquid having distribution holes connected to the inlet. Place in a polypropylene container equipped with a distribution pipe and a cooling liquid outlet, and close the top lid. At this time, the cells are connected in series inside the container, and the positive and negative terminals are drawn from the cells at both ends to the outside of the vessel. The charge / discharge capacity of this lithium ion secondary battery is 2,500 Wh, the battery voltage is 14 V, and the energy density is 100 Wh / kg.

FIGS. 5 to 7 show the assembled battery of the lithium ion secondary battery thus obtained. 5 is a front view (EE 'cross section of FIG. 6), FIG. 6 is a plan view (DD' cross section of FIG. 5), and FIG. 7 is a side view (FF 'cross section of FIG. 6). 20
Indicates the cell body. Four unit cells are connected in series, housed in an assembled battery container body 21 having an assembled battery partition wall 22, and separated from the outside by an assembled battery container lid 23. Reference numeral 15 indicates a negative electrode single battery terminal, and 17 indicates a positive electrode single battery terminal. Adjacent single batteries are set by changing the + -direction. The middle is connected with the unit cell terminal connecting rod 14, and both ends are the battery assembly negative electrode terminal 18,
The battery pack is connected to the positive electrode terminal 19 of the battery pack, and electricity is taken out of the battery pack container body.

The left and right electric conductors 8 and 11 of the unit cell are welded to form a single metal plate, respectively.
On the surface of the metal plate of the above, the cooling liquid is supplied to the distribution pipe 28 for the cooling liquid from the bottom of the outside of the assembled battery (the cooling liquid sent from the cooling liquid inlet 26 flows upward. That is, the heat generated inside the unit cell is , The heat is removed from the electrode active material mixture by heat conduction with the metal foil and the conductor, and is removed by the cooling liquid flowing on the surface of the conductor (2
9: Coolant distribution hole). The cooling liquid warmed by the heat generated inside the unit cell returns from the upper part of the battery through the cooling liquid outlet 27 to the finned cooler and the circulation pump provided outside the assembled battery, and is cooled and circulated. The finned cooler is cooled by air for air cooling sent from the outside. Reference numeral 10 indicates a negative electrode welded portion, and 12 indicates a positive electrode welded portion.

[0039]

EFFECTS OF THE INVENTION According to the present invention, a lithium ion secondary battery suitable for upsizing can be obtained.

[Brief description of drawings]

FIG. 1 shows a plan view of an example of a unit cell according to the present invention.

FIG. 2 shows a front view (BB ′ cross section of FIG. 1) of an example of a unit cell according to the present invention.

FIG. 3 shows a side view (CC ′ cross section of FIG. 2) of an example of a unit cell according to the present invention.

FIG. 4 is an enlarged view of an X part in FIG.

FIG. 5 shows a front view of an example of an assembled battery according to the present invention.

FIG. 6 is a plan view showing a DD ′ cross section of FIG. 5;

7 is a side view showing a cross section taken along the line FF ′ of FIG.

[Explanation of symbols]

 1 Electrode Active Material Mixing Part 2, 4 Negative Electrode 3,5 Positive Electrode 6 Separator 7 Spacer 8, 11 Conductor 24 Electrolyte Liquid Level 26 Coolant Inlet 27 Coolant Outlet 28 Coolant Distribution Pipe

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Minor Inoue 1 Fukuda-cho, Joetsu City, Niigata Prefecture Naoetsu Plant, Mitsubishi Kasei Co., Ltd. (72) Tomiichi Koyama 1 Fukuda-cho, Joetsu City, Niigata Mitsubishi Kasei Co., Ltd. in the factory

Claims (12)

[Claims] 1. A lithium ion secondary battery comprising a unit cell in which a positive electrode in which a positive electrode active material mixture is applied to a metal material and a negative electrode in which a negative electrode active material mixture is applied to a metal material are alternately laminated with a separator interposed therebetween. In order to form a current collector by stacking electrodes in multiple layers and separating the ears of the metal material of the electrode into a positive electrode and a negative electrode and electrically and thermally connecting them to conductors, respectively, a metal material for the positive electrode and the negative electrode. The ears are separated and bundled in multiple pieces, sandwiched between the conductors, and the end of the ears of the electrode and the metal surface formed by welding the conductor are electrolyzed inside the cell. Separated from the liquid, a coolant is flown on this metal surface to take out the heat accumulated inside the cell during charging and discharging, prevent the temperature rise inside the cell, and take out electricity through this conductor. Lithium Y characterized by On secondary battery. 2. The ears of metal material of the positive electrode and the negative electrode are
When separating and bundling a plurality of cells, when bundling a plurality of cells per cell, the conductors sandwiching the adjacent bundles should be integrated, and the conductors of the positive electrode and the negative electrode should be 1 each.
The lithium ion secondary battery according to claim 1, wherein the lithium ion secondary battery is configured to be a single metal plate. 3. The lithium ion secondary battery according to claim 1, which has a structure in which an electrolytic solution is enclosed in each single battery. 4. The lithium ion secondary battery according to claim 1 or 2, wherein the welding of the end portion of the ear portion of the electrode and the conductor is performed by TIG welding, high frequency welding or ultrasonic welding. 5. The lithium ion secondary battery according to claim 1 or 2, wherein a spacer that regulates a gap between the electrodes is sandwiched between the ears of the metal material of the electrodes when assembling the unit cell. 6. The lithium ion secondary battery according to claim 5, wherein the spacer is made of a metal material which is previously bonded to the ear portion. 7. The lithium ion secondary battery according to claim 3, wherein a sealing material that resists corrosion of the electrolytic solution is sandwiched or pressed into the corner portion. 8. The lithium-ion secondary battery according to claim 1, further comprising a blower for sending cooling air to a cooling surface of the unit cell for each assembled battery or for each of a plurality of assembled batteries. 9. The lithium ion secondary battery according to claim 1, 2 or 3, further comprising a circulation pump for feeding a cooling medium as a cooling source to the cooling surface of the unit cell and a cooler for each of the plurality of assembled batteries. 10. A mechanism for controlling the operation of the circulation pump or the blower blower according to the internal temperature of the battery.
Alternatively, the lithium ion secondary battery according to item 9. 11. The lithium-ion secondary battery according to claim 1, wherein cooling air flows on the cooling surface of the unit cell by natural convection. 12. The lithium ion secondary battery according to claim 9, wherein a solvent that does not react even when mixed with an electrolytic solution is used as a refrigerant as a cold source.