JP2008300692A - Power storage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve durability in a power storage device by adopting a structure coping with heat. <P>SOLUTION: The power storage device 10 has an outer package case 12 within which a plurality of power storage cells 11 are stored. A laminated film 13 of the power storage cell 11 stores an electrode lamination unit, with alternating laminated positive and negative electrodes. The armored case 12 is filled with a resin material 22, and respective storage cells 11 are covered with the resin material 22. In this manner, since the power storage cells 11 are covered with the resin material 22, heat from the outside and the power storage cell 11 by the resin material 22 is absorbed, suppressing excessive temperature rise and an abrupt temperature change in the power storage cell 11 and stabilizing the cell temperature, to avoid deterioration in the performance of the power storage cell 11. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique effective when applied to an electricity storage device including an electrode unit.

Lithium ion capacitors, lithium ion secondary batteries, and the like are listed as candidates for power storage devices mounted on electric vehicles, hybrid vehicles, and the like. In these electricity storage devices, if the cell temperature rises excessively, it will deteriorate, so it is important to converge the cell temperature to a predetermined range. In view of this, a power storage device has been proposed in which a heat sink is sandwiched between a plurality of stacked power storage cells to release the heat of the power storage cell from the heat sink to the outside air, thereby suppressing an excessive rise in cell temperature. (For example, see Patent Document 1).
Japanese Patent Laid-Open No. 2004-3281

  However, since the power storage device described in Patent Document 1 has a structure in which a heat sink is assembled to each power storage cell, there is a problem in that the number of parts increases and the manufacturing cost of the power storage device increases. There is. In addition, since the electricity storage device of Patent Document 1 has a cooling structure for releasing heat generated by charging and discharging to the outside, it is difficult to cope with heat applied to the electricity storage device in a high temperature environment. Met. In particular, when an electricity storage device is used as a power source for a hybrid vehicle or the like, the electricity storage device is often used in a high-temperature environment, and in order to ensure the durability and safety of the electricity storage device, only its own heat generation is required. In addition, a structure for protecting the electricity storage device from external heat has been demanded.

  An object of the present invention is to improve durability and safety of an electricity storage device by adopting a structure for dealing with heat.

  An electricity storage device of the present invention includes an electrode unit including a positive electrode and a negative electrode facing the positive electrode, an inner container that accommodates the electrode unit, an outer container that accommodates the inner container, and the inner container that is filled in the outer container. And a protective material covering the container.

  In the electricity storage device of the present invention, a heat radiating member that contacts the protective material is inserted into the outer container, and a part of the heat radiating member is exposed outside the outer container.

  The electricity storage device of the present invention is characterized in that the protective material causes phase transition due to endotherm in a range of 40 ° C. or higher and 100 ° C. or lower.

  In the electricity storage device of the present invention, an electricity storage cell is formed by the inner container and the electrode unit, and a heat capacity of the protective material is 1 kJ / K or more and 5 kJ / K or less with respect to 1 kg of the electricity storage cell. To do.

  The electricity storage device of the present invention is characterized in that the protective material is a liquid.

  The electricity storage device of the present invention is characterized in that a plurality of the inner containers are accommodated in the outer container.

  The electricity storage device of the present invention is characterized in that the electricity storage device is a lithium ion capacitor.

  The electricity storage device of the present invention is characterized in that the electricity storage device is a lithium ion secondary battery.

  According to the present invention, the inner container is accommodated in the outer container, and the outer container is filled with the protective material. Therefore, the inner container accommodating the electrode unit can be covered with the protective material. Thereby, an electrode unit can be protected by a protective material, and it becomes possible to improve the durability and safety of an electricity storage device.

  FIG. 1 is a perspective view showing an electricity storage device 10 according to an embodiment of the present invention, FIG. 2 is a perspective view showing an electricity storage cell 11 constituting the electricity storage device 10, and FIG. 3 is an AA view of FIG. It is sectional drawing which shows schematically the internal structure of the electrical storage cell 11 along a line. As shown in FIG. 1, the power storage device 10 includes an outer case 12 as an outer container, and a plurality of power storage cells 11 are accommodated in the outer case 12 substantially in parallel. In addition, the some electrical storage cell 11 accommodated in the exterior case 12 is connected in series via the bus bar etc. which are not shown in figure, and the high voltage of the electrical storage device 10 modularized is achieved.

  As shown in FIG. 2 and FIG. 3, an electrode stack unit (electrode unit) 14 is accommodated in a laminate film 13 that is an inner container of the storage cell 11, and the electrode stack unit 14 is alternately arranged via separators 15. It is comprised by the positive electrode 16 and the negative electrode 17 which are laminated | stacked. In addition, a lithium electrode 18 is disposed on the outermost part of the electrode laminate unit 14 so as to face the negative electrode 17, and the electrode laminate unit 14 and the lithium electrode 18 constitute a three-electrode laminate unit 19. Note that an electrolyte solution made of an aprotic organic solvent containing a lithium salt is injected into the laminate film 13. That is, the electrical storage cell 11 is comprised by the laminate film 13, the electrode lamination | stacking unit 14, and electrolyte solution.

  FIG. 4 is a cross-sectional view showing a partially enlarged internal structure of the storage cell 11. As shown in FIG. 4, the positive electrode 16 includes a positive electrode current collector 16b having a large number of through holes 16a and a positive electrode mixture layer 16c applied to the positive electrode current collector 16b. The negative electrode 17 includes a negative electrode current collector 17b having a large number of through holes 17a and a negative electrode mixture layer 17c applied to the negative electrode current collector 17b. A plurality of positive electrode current collectors 16b connected to each other are connected to positive electrode terminals 20 projecting outside from the laminate film 13, and a plurality of negative electrode current collectors 17b connected to each other are connected to the laminate film 13 A negative electrode terminal 21 protruding from the outside is connected. Furthermore, the lithium electrode 18 disposed on the outermost part of the electrode laminate unit 14 is composed of a lithium electrode current collector 18a made of a conductive porous material such as stainless steel mesh, and metal lithium 18b attached thereto. The lithium electrode current collector 18a is connected to the negative electrode current collector 17b.

  The positive electrode mixture layer 16 c of the positive electrode 16 contains a positive electrode active material capable of reversibly doping and dedoping lithium ions, and the negative electrode mixture layer 17 c of the negative electrode 17 contains lithium ions. The negative electrode active material which can be reversibly doped / dedoped is contained. Then, the negative electrode mixture layer 17 c of the negative electrode 17 is doped with lithium ions from the metal lithium 18 b, thereby reducing the negative electrode potential and improving the energy density of the storage cell 11. The positive electrode current collector 16b and the negative electrode current collector 17b are formed with a large number of through holes 16a and 17a, and lithium ions can freely move between the respective electrodes through the through holes 16a and 17a. Therefore, it is possible to smoothly dope lithium ions to all the positive electrode mixture layers 16c and the negative electrode mixture layers 17c to be laminated. In the present invention, doping means doping, loading, adsorption, insertion, etc., and means a state in which lithium ions, anions, or the like enter the positive electrode active material or the negative electrode active material. . De-doping (de-doping) means release, desorption, and the like, and means a state in which lithium ions, anions, and the like are emitted from the positive electrode active material and the negative electrode active material.

  FIG. 5 is a cross-sectional view schematically showing the internal structure of the electricity storage device 10 along the line AA of FIG. As shown in FIG. 5, not only the storage cells 11 are accommodated in the outer case 12, but also a resin material 22 that is a protective material is filled so as to cover the individual storage cells 11. Polyethylene oxide is used as the resin material 22 filled in the outer case 12, and this polyethylene oxide has a characteristic of causing a phase transition (melting point) from a solid phase to a liquid phase at 65 ° C. When filling the exterior case 12 with the resin material 22, the resin material 22 is melted at 65 ° C. and the liquid resin material 22 is injected.

  In addition, it is preferable that the resin material 22 is filled so as to correspond to a heat capacity of 1 kJ / K or more and 5 kJ / K or less per unit weight (1 kg) of the storage cell 11. For example, when a polypropylene having a specific heat of 1.93 kJ / (kg · K) is filled, the filling amount is 0.5 kg to 2.6 kg.

  As described above, the outer case 12 and the laminate film 13 form a double-structured container, and the laminate film 13 is covered with the resin material 22 filled in the outer case 12. And safety can be dramatically improved. That is, since the resin material 22 that covers the storage cell 11 can absorb heat from the outside and the storage cell 11, it is possible to suppress an excessive temperature rise or rapid temperature change of the storage cell 11. It becomes possible to stabilize cell temperature and to avoid the performance fall and deterioration of the electrical storage cell 11. FIG. In particular, when the resin material 22 that causes a phase transition from a solid phase to a liquid phase at 65 ° C. is adopted, it is possible to cause the resin material 22 to absorb a large amount of heat in the phase transition process, and to increase the cell temperature by 65. It becomes possible to suppress to below ℃. Thereby, even when the power storage device 10 is used in a high temperature environment or when the power storage device 10 generates heat due to rapid charge / discharge, an excessive increase or fluctuation in cell temperature can be suppressed. The durability and safety of the device 10 can be improved. In addition, since the outer case 12 is simply filled with the resin material 22, it is possible to stabilize the cell temperature while suppressing an increase in the cost of the power storage device 10. In particular, when considering the case where the electricity storage device 10 is installed in the engine room, the temperature rise in the engine room while the vehicle is running is suppressed by a cooling fan or running wind. Immediately after turning off, there is a case where the engine room becomes a temperature environment close to 100 ° C. due to the heat of the engine, and in order to protect the electricity storage device 10, filling of the resin material 22 is extremely effective.

  Further, since the power storage cell 11 is covered with the resin material 22, the power storage cell 11 can be protected from impact and vibration, and from this point, the durability and safety of the power storage device 10 can be improved. Become. Furthermore, in the power storage device 10 shown in the figure, since the plurality of power storage cells 11 accommodated in the outer case 12 are positioned and fixed by filling the resin material 22, the plurality of power storage cells 11 are accommodated and modularized. As a result, the number of parts and the manufacturing cost of the power storage module can be reduced. Further, when the power storage device 10 is used as a power source for a hybrid vehicle or the like, the power storage device 10 can be disposed in an engine room or the like that is in a high temperature environment, so that the degree of freedom in vehicle design is dramatically increased. Is possible.

  Further, although the resin material 22 having a specific heat capacity (specific heat) of 1.93 kJ / (kg · K) is used as the protective material, the specific heat capacity of the protective material is not limited to the above-described numerical values, and the storage cell 11 It is possible to set a protective material having an appropriate specific heat capacity by comprehensively judging the amount of heat generated, the temperature of the use environment, the filling amount of the protective material, the price of the protective material, and the like. For example, when an installation condition is set in which 1 kg of the storage cell 11 absorbs the heat amount from room temperature to 100 ° C., the heat capacity of the protective material per unit weight (1 kg) of the storage cell 11 is 1 kJ / K. As mentioned above, it is preferable that it is 5 kJ / K or less, but in order to keep the energy density of the electrical storage device 10 high, the smaller the filling amount of the resin material 22, the better. It is preferable because the effect can be obtained. Similarly, in the above description, the resin material 22 that causes a phase transition at 65 ° C. is used as a protective material. However, the temperature at which the protective material causes a phase transition is not limited to 65 ° C. It is possible to set a protective material having an appropriate phase transition temperature by comprehensively judging the heat generation amount of the cell 11, the temperature of the use environment, the filling amount of the protective material, the price of the protective material, and the like. For example, when charging / discharging in a high temperature environment, the deterioration of the storage cell is accelerated. In particular, if the temperature exceeds 60 ° C., internal resistance may suddenly increase and capacity may deteriorate due to gas generation. Therefore, from the viewpoint of durability, the temperature range in which the protective material causes a phase transition is preferably 40 ° C. or higher and 100 ° C. or lower. If it is less than 40 ° C., the deterioration rate is slow, so the effect is small and not preferable. Moreover, since it will deteriorate violently when it exceeds 100 degreeC, it is not preferable. More preferably, it is 40 degreeC or more and 80 degrees C or less.

  In the above description, the outer case 12 is filled with the resin material 22 as a protective material. However, the present invention is not limited to this, and the outer case 12 is filled with liquid paraffin as a protective material. You may do it. In this manner, when liquid paraffin, which is liquid, is filled, liquid paraffin flows into the storage cell 11 even if the laminate film 13 is damaged due to gas generation due to overcharge or the like. It becomes possible to block the contact of outside air to the electrode lamination unit 14 in the laminate film 13. Thereby, since supply of oxygen and moisture to electrode lamination unit 14 can be intercepted, it becomes possible to suppress promotion of heat generation accompanying oxidation, and it becomes possible to improve safety of power storage device 10.

  Further, in the above description, only the resin material 22 is filled in the outer case 12 in which the power storage cell 11 is accommodated. However, in order to improve the cooling performance of the power storage device, a heat radiating member is provided in the outer case 12. It may be inserted. Here, FIG. 6 is a cross-sectional view showing the internal structure of an electricity storage device 30 according to another embodiment of the present invention. The same members as those shown in FIG. Omitted. As shown in FIG. 6, the electricity storage device 30 includes a heat dissipation member 31 formed using a metal material such as aluminum having high thermal conductivity. The heat radiating member 31 includes a heat absorbing portion 31a that is inserted into the outer case 12 and contacts the resin material 22, and a heat radiating portion 31b that is exposed to the outside from the outer case 12 and contacts the outside air. Thus, by providing the heat radiating member 31 in contact with the resin material 22 and the outside air, not only the heat of the storage cell 11 is absorbed by the resin material 22 but also the absorbed heat is absorbed from the resin material 22 through the heat radiating member 31. Heat can be radiated to the outside air, and the storage cell 11 can be actively cooled. In particular, when it is arranged in the engine room, the side surface on which the heat radiating member 31 is not arranged is arranged on the engine side, and the heat radiating member 31 is arranged at a position far from the engine, so It can be cooled efficiently. A plurality of heat radiating fins 31c are formed in the heat radiating portion 31b, and heat can be efficiently radiated from the heat radiating member 31 to the outside air.

  Next, the configuration of the above-described power storage device will be described in detail in the following order. [A] positive electrode, [B] negative electrode, [C] positive electrode current collector and negative electrode current collector, [D] lithium electrode, [E] separator, [F] electrolyte, [G] inner container and outer container, H] protective material.

[A] Positive Electrode The positive electrode has a positive electrode current collector and a positive electrode active material layer integrated with the positive electrode current collector, although it varies depending on the type of power storage device. When the electricity storage device is a lithium ion capacitor, the positive electrode active material layer contains a positive electrode active material capable of reversibly supporting lithium ions and anions (eg, tetrafluoroborate). The positive electrode active material is not particularly limited as long as it can reversibly carry lithium ions and anions, and examples thereof include activated carbon, a conductive polymer, and a polyacene-based material. In addition, when PAS, which is a heat-treated product of aromatic condensed resin material and H / C is 0.50 to 0.05, is used as the positive electrode active material, it is preferable because the capacity can be increased. It is. In the case where the power storage device is a lithium ion secondary battery, a metal oxide such as LiCoO ₂ or V ₂ O ₅ , a conductive polymer, or the like can be used.

The positive electrode active material such as PAS and V ₂ O ₅ described above is formed into a powder form, a granular form, a short fiber form, etc., and this positive electrode active material is mixed with a binder to form a slurry. Then, a positive electrode active material layer is formed on the positive electrode current collector by applying a slurry containing the positive electrode active material to the positive electrode current collector and drying the slurry. As the binder mixed with the positive electrode active material, for example, a rubber-based binder such as SBR, a fluorine-containing resin such as polytetrafluoroethylene or polyvinylidene fluoride, or a thermoplastic resin such as polypropylene or polyethylene can be used. . Moreover, you may make it add electrically conductive materials, such as acetylene black, a graphite, and a metal powder, with respect to a positive electrode active material layer suitably.

[B] Negative electrode The negative electrode has a negative electrode current collector and a negative electrode active material layer integrated with the negative electrode current collector, depending on the type of the electricity storage device. When the electricity storage device is a lithium ion capacitor or a lithium ion secondary battery, the negative electrode active material layer contains a negative electrode active material capable of reversibly doping and dedoping lithium ions. The negative electrode active material is not particularly limited as long as it can reversibly carry lithium ions. Examples thereof include graphite, various carbon materials, polyacene-based materials, tin oxide, and silicon oxide. it can. Particularly, a polyacene organic semiconductor (PAS) that is a heat-treated product of an aromatic condensed resin material and has a hydrogen atom / carbon atom ratio (H / C) of 0.50 to 0.05 is used as a negative electrode active material. Is preferred. Since this PAS has an amorphous structure, there is no structural change such as swelling / shrinkage with respect to doping / dedoping of lithium ions, and it has excellent cycle characteristics, and isotropic to doping / dedoping of lithium ions. Due to its molecular structure, it has excellent characteristics for rapid charge and rapid discharge.

  The negative electrode active material such as PAS described above is formed into a powder form, a granular form, a short fiber form, etc., and this negative electrode active material is mixed with a binder to form a slurry. And the negative electrode active material layer is formed on a negative electrode collector by applying the slurry containing a negative electrode active material to a negative electrode collector, and making it dry. As the binder mixed with the negative electrode active material, for example, a rubber binder such as SBR, a fluorine-containing resin such as polytetrafluoroethylene or polyvinylidene fluoride, or a thermoplastic resin such as polypropylene or polyethylene is used. Among these, it is preferable to use a fluorine-based binder. In addition, a conductive material such as acetylene black, graphite, or metal powder may be appropriately added to the negative electrode active material layer.

[C] Positive electrode current collector and negative electrode current collector As the positive electrode current collector and the negative electrode current collector, generally, a highly conductive sheet such as metal or carbon can be used although it varies depending on the type of the electricity storage device. . In particular, in lithium ion capacitors and lithium ion secondary batteries that require a step of pre-doping lithium ions from the lithium ion supply source (lithium electrode) to the negative electrode and / or positive electrode (pre-doping), a through-hole penetrating the front and back surfaces is provided. What is provided is suitable, for example, an expanded metal, a punching metal, a net | network, a foam etc. can be mentioned. The shape and number of the through holes are not particularly limited, and can be appropriately set as long as they do not inhibit the movement of lithium ions. As materials for the positive electrode current collector and the negative electrode current collector, various materials generally proposed for organic electrolyte batteries can be used. For example, aluminum, stainless steel, or the like can be used as the material of the positive electrode current collector, and stainless steel, copper, nickel, or the like can be used as the material of the negative electrode current collector.

[D] Lithium electrode The lithium electrode is used in the above-described lithium ion capacitor or lithium ion secondary battery that requires pre-doping, and a lithium electrode current collector made of a conductive porous material such as a stainless mesh, and affixed thereto. It consists of attached metal lithium. Further, instead of metallic lithium constituting the lithium electrode, an alloy capable of supplying lithium ions, such as a lithium-aluminum alloy, may be used. In addition, while supporting lithium metal with a lithium electrode current collector and bringing lithium ions into contact, the negative electrode current collector and the lithium electrode current collector are brought into contact with each other, and the metal lithium is lost between the electrodes. The gap can be reduced, and lithium ions can be smoothly supported on the negative electrode. Further, the thickness of the lithium electrode current collector is preferably about 10 to 200 μm, and the thickness of the metal lithium is preferably about 50 to 300 μm although it depends on the amount of the negative electrode active material. Note that the lithium electrode current collector can be formed of the same material as the negative electrode current collector or the positive electrode current collector.

[E] Separator As the separator, a porous body having durability against an electrolytic solution, a positive electrode active material, a negative electrode active material, and the like and having continuous air holes is used as the separator. be able to. As the material of the separator, known materials such as cellulose (paper), polyethylene, and polypropylene can be used in the case of a lithium ion capacitor or a lithium ion secondary battery. In addition, the separator disposed between the negative electrode and the lithium electrode is not limited to the above-described material, and this insulation can be achieved by forming an insulating film on the surface of the negative electrode current collector or the lithium electrode current collector. It is also possible to make the coating function as a separator.

[F] Electrolyte The electrolyte varies depending on the type of power storage device, but in the case of a lithium ion capacitor or lithium ion secondary battery, it does not cause electrolysis even at high voltages, and lithium ions can exist stably. Therefore, it is preferable to use an aprotic organic solvent containing a lithium salt. Examples of the aprotic organic solvent include solvents in which ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, acetonitrile, dimethoxyethane, tetrahydrofuran, dioxolane, methylene chloride, sulfolane and the like are used alone or in combination. Examples of the lithium salt include _{LiI, LiClO 4, LiAsF 6,} LiBF 4, LiPF 6 , and the like. The electrolyte concentration in the electrolytic solution is preferably at least 0.1 mol / l or more in order to reduce the internal resistance due to the electrolytic solution, and should be in the range of 0.5 to 1.5 mol / l. Is more preferable.

[G] Inner container and outer container As the inner container and the outer container, various materials generally used for batteries can be used, and metal materials such as iron and aluminum, and resin materials such as polypropylene are used. Also good. Further, the shape of the inner container and the outer container is not particularly limited, and can be appropriately selected according to the use such as a cylindrical shape or a rectangular shape. From the viewpoint of reducing the size and weight of the storage cell, it is preferable to use an aluminum laminate film as the inner container. In general, a three-layer laminate film having a nylon film on the outside, an aluminum foil in the center, and an adhesive layer such as modified polypropylene on the inside is used. In addition, the laminate film is generally deep-drawn according to the size of the electrode and the like to enter, after installing the electrode lamination unit in the deep-drawn laminate film and injecting the electrolyte, The outer peripheral part of the laminate film is sealed by heat welding or the like.

[H] Protective material As the protective material to be filled in the outer case, an insulating material such as synthetic resin, polymer, liquid paraffin, etc. can be used. It is possible to set an appropriate protective material by comprehensively judging the price of the protective material. Further, the type of protective material to be filled is not limited to one type, and a plurality of protective materials may be mixed. Further, when selecting the protective material, the heat capacity of the protective material per 1 kg of the storage cell is 1 kJ / K or more, 5 kJ / Although it is preferable that it is K or less, in order to keep the energy density of the electricity storage device high, the smaller the resin material to be filled, the better. Therefore, the higher the specific heat capacity of the resin material, the better the effect can be obtained with a smaller filling amount. Further, when charging / discharging in a high temperature environment, the deterioration of the storage cell is accelerated. In particular, if the temperature exceeds 60 ° C., internal resistance may suddenly increase and capacity may deteriorate due to gas generation. Therefore, from the viewpoint of durability, the temperature range in which the protective material causes a phase transition is preferably 40 ° C. or higher and 100 ° C. or lower. If it is less than 40 ° C., the deterioration rate is slow, so the effect is small and not preferable. Moreover, since it will deteriorate violently when it exceeds 100 degreeC, it is unpreferable. More preferably, it is 40 degreeC or more and 80 degrees C or less.

  Hereinafter, based on an Example, this invention is demonstrated in detail. In the above description, a power storage device is described in which a plurality of power storage cells are accommodated in one outer case. However, in the following embodiments, one power storage cell is accommodated in one outer case. The power storage device described above will be described.

(Example 1)
<Manufacture of negative electrode>
A 0.5 mm thick phenolic resin molded plate was placed in a siliconite electric furnace, heated to 500 ° C. at a rate of 50 ° C./hour in a nitrogen atmosphere, and further heated to 700 ° C. at a rate of 10 ° C./hour. The PAS was synthesized by heat treatment. The PAS plate thus obtained was pulverized with a disk mill to obtain a PAS powder. The H / C ratio of this PAS powder was 0.17. Next, 100 parts by weight of the PAS powder was sufficiently mixed with a solution obtained by dissolving 10 parts by weight of polyvinylidene fluoride powder in 80 parts by weight of N-methylpyrrolidone to prepare a slurry for a negative electrode. The negative electrode slurry was coated on both sides of a negative electrode current collector made of a copper expanded metal having a thickness of 32 μm with a die coater to form a negative electrode mixture layer. The negative electrode current collector formed with the negative electrode mixture layer was vacuum-dried to obtain a negative electrode having a negative electrode active material weight per unit area of 4.0 mg / cm ² .

<Production of positive electrode>
By fully mixing 85 parts by weight of commercially available activated carbon powder having a specific surface area of 2000 m ² / g, 5 parts by weight of acetylene black powder, 6 parts by weight of an acrylic resin binder, 4 parts by weight of carboxymethyl cellulose and 200 parts by weight of water, A slurry was obtained. The positive electrode current collector in which a conductive layer is formed by coating this positive electrode slurry on both surfaces of an aluminum expanded metal having a thickness of 35 μm with a non-aqueous carbon-based conductive paint by a spray method and then drying. Got. The total thickness (the total of the current collector thickness and the conductive layer thickness) was 52 μm, and the through hole was almost blocked by the conductive paint. And the slurry for positive electrodes was coated with the roll coater on both surfaces of the positive electrode electrical power collector, and the positive mix layer was shape | molded. The positive electrode current collector formed with the positive electrode mixture layer is vacuum-dried, so that the total thickness of the positive electrode (the total of the positive electrode mixture layer thickness on both sides, the conductive layer thickness on both sides, and the positive electrode collector thickness) is 129 μm. A positive electrode was obtained. The thickness of the positive electrode mixture layer was 77 μm on both sides, and the basis weight of the positive electrode active material was 3.5 mg / cm ² on both sides.

<Capacitance measurement per unit weight of negative electrode>
The negative electrode was cut into a size of 1.5 cm × 2.0 cm to obtain a negative electrode for evaluation. A simulation cell was assembled by making metallic lithium (1.5 cm × 2.0 cm size, thickness 200 μm) as a counter electrode opposed to the negative electrode for evaluation through a separator made of a polyethylene nonwoven fabric having a thickness of 50 μm. As the reference electrode, metallic lithium was used, and as the electrolytic solution, a solution obtained by dissolving LiPF ₆ in propylene carbonate at a concentration of 1.2 mol / l was used. The negative electrode active material was charged with 620 mAh / g of lithium ions at a charge current of 1 mA, and then discharged until the negative electrode potential reached 1.5 V at a discharge current of 1 mA. The capacitance per unit weight of the negative electrode was determined to be 1021 F / g based on the discharge time until a potential change of 0.2 V further occurred from the negative electrode potential one minute after the start of discharge.

<Capacitance measurement per unit weight of positive electrode>
The positive electrode was cut into a size of 1.5 cm × 2.0 cm to obtain a positive electrode for evaluation. A simulation cell was assembled by making metallic lithium (1.5 cm × 2.0 cm size, thickness 200 μm) as a counter electrode opposed to this evaluation positive electrode through a separator made of a polyethylene nonwoven fabric having a thickness of 50 μm. As the reference electrode, metallic lithium was used, and as the electrolytic solution, a solution obtained by dissolving LiPF ₆ in propylene carbonate at a concentration of 1.2 mol / l was used. Then, constant voltage charging was performed after charging to 3.6 V with a charging current of 1 mA, and after a total charging time of 1 hour, discharging was performed with a discharging current of 1 mA until the positive electrode potential reached 2.5 V. Based on the discharge time until the positive electrode potential reached 3.5 V to 2.5 V, the capacitance per unit weight of the positive electrode was determined to be 140 F / g.

<Production of electrode lamination unit>
The negative electrode was cut to 6.0 cm × 7.5 cm (excluding the terminal welded portion), the positive electrode was cut to 5.8 cm × 7.3 cm (excluding the terminal welded portion), and the cellulose / rayon mixed nonwoven fabric (thickness) as the separator 35 μm) was cut into 6.2 × 7.7 cm 2. Then, the terminal welds of the positive electrode current collector and the negative electrode current collector are arranged on opposite sides, the opposing surfaces of the positive electrode and the negative electrode are 40 layers, and the outermost electrode of the stacked electrodes is the negative electrode It laminated | stacked so that it might become. Subsequently, after placing separators on the uppermost part and the lowermost part and tapering the four sides, the positive electrode terminal made of aluminum (width 50 mm, length 50 mm, Ultrasonically weld a copper negative electrode terminal (width 50 mm, length 50 mm, thickness 0.2 mm) to the terminal welded portion (21 sheets) of the negative electrode current collector. An electrode laminate unit was produced. In the electrode stacking unit, 20 positive electrodes are used, and 21 negative electrodes are used. The weight of the positive electrode active material is 0.8 times the weight of the negative electrode active material, but is 0.9 times the weight of the negative electrode active material contained in the negative electrode surface area facing the positive electrode. Furthermore, the positive electrode surface area is 94% of the negative electrode surface area.

<Production of film capacitor cell>
As the lithium electrode, a metal lithium foil (thickness 122 μm, size 6.0 cm × 7.5 cm, equivalent to 300 mAh / g) bonded to an 80 μm thick stainless mesh was used. Also, one lithium electrode was placed on each of the upper and lower portions of the electrode laminate unit so as to completely face the outermost negative electrode, and four sides were taped to produce a three-pole laminate unit. The terminal welded part (two sheets) of the lithium electrode current collector was resistance welded to the negative electrode terminal welded part. The above three-pole laminated unit is installed inside a laminate film deeply drawn to 7.5 mm, the opening is covered with the laminate film, and the three sides are fused. A solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / l in a mixed solvent with a ratio of 3: 4: 1 is vacuum impregnated, and the other side is fused to form a film type lithium ion capacitor cell (hereinafter referred to as a film type capacitor). 5 cells were assembled. Next, the film type capacitor cell is inserted into a resin outer case, and filled with polyethylene oxide (melting point 65 ° C.) as a protective material dissolved at 65 ° C. Five cells of a double structure type lithium ion capacitor cell (hereinafter referred to as a double structure type capacitor cell, which corresponds to the above-mentioned electricity storage device) having a double structure of a film and an outer case were assembled. In addition, the metallic lithium arrange | positioned in a film type capacitor cell is equivalent to 600 mAh / g per negative electrode active material weight.

<Pre-dope>
After assembling the double structure type capacitor cell and leaving it to stand for 20 days, when one double structure type capacitor cell was disassembled, metallic lithium was completely lost. From this, it was judged that lithium ions for obtaining a capacitance of 1021 F / g or more per unit weight of the negative electrode active material were surely doped by charging in advance. The electrostatic capacity per unit weight of the negative electrode is 7.3 times the electrostatic capacity per unit weight of the positive electrode.

<Initial evaluation of the cell>
The remaining four double-structured capacitor cells are charged at a constant current of 1.5 A until the cell voltage reaches 3.8 V, and then a constant current-constant voltage charge is applied for 1 hour by applying a constant voltage of 3.8 V went. Subsequently, the battery was discharged at a constant current of 1.5 A until the cell voltage reached 2.2V. Such a cycle test of 3.8V-2.2V was repeated, and the cell capacitance (initial cell capacitance) after the tenth discharge was measured.

<Evaluation of cell characteristics>
Further, after charging the double-structure capacitor cell in a constant temperature bath at 60 ° C. with a constant current of 100 A until the cell voltage becomes 3.8 V, 2 at a constant current of 100 A Charge / discharge of discharging to 2 V was repeated 50,000 times. Thereafter, the cell temperature was returned to room temperature (25 ° C.), and the cell capacitance after 50000 cycles was measured by the same method as the initial cell capacitance measurement method. The results are shown in FIG. 7 together with the initial cell capacitance.

(Comparative Example 1)
Using the film type capacitor cell produced in Example 1, the initial cell capacitance was measured by the same measurement method as in Example 1. Thereafter, the film type capacitor cell was placed in a constant temperature bath at 60 ° C., and charge and discharge were repeated 50000 times by the same cycle test method as in Example 1, followed by 50000 cycles by the same measurement method as in Example 1. The subsequent cell capacitance was measured. The result is shown in FIG.

(Example 2)
The double structure type capacitor cell used in Example 2 is obtained by changing the polyethylene oxide of the double structure type capacitor cell produced in Example 1 to isododecane which is a kind of liquid paraffin. Since the specific heat of isododecane is 2.19 kJ / (kg · K), 1 kg of film type capacitor cell was filled with 1.37 kg equivalent of isododecane (equivalent to 3 kJ / K). The initial cell capacitance was measured by the same measurement method as in Example 1. Thereafter, the film-type capacitor cell was placed in a constant temperature bath at 60 ° C., and charge / discharge was repeated 50000 times by the same cycle test method as in Example 1, and then the cell capacitance after 50000 cycles was measured. . The result is shown in FIG.

  As shown in FIG. 7, the results of Example 1 and Example 2 were higher than those of Comparative Example 1 in terms of cell capacitance after 50000 cycles. This is considered to be due to the fact that the deterioration of the film type capacitor cell of Comparative Example 1 was increased to 60 ° C. or more due to the cycle test performed at a large current of 100 A in a constant temperature bath at 60 ° C. . On the other hand, the double structure type capacitor cell of Example 1 has a double structure and is covered with a resin material having a melting point of 65 ° C. However, it was considered that the cell capacitance after 50000 cycles could be maintained high because the cell temperature did not increase so much. Similarly, in Example 2, since the heat capacity is covered with isododecane equivalent to 3 kJ / K, it is considered that the cell temperature did not rise much higher than 60 ° C.

(Example 3 and Comparative Example 2)
In Example 3, the double structure type capacitor cell filled with isododecane prepared in Example 2 was used. The film type capacitor cell used in Comparative Example 2 is the same as the film type capacitor cell used in Comparative Example 1.

  An overcharge test was performed on the double structure type capacitor cell of Example 3 and the film type capacitor cell of Comparative Example 2 at a constant current of 50A. When this overcharge test was carried out, any film type capacitor cell was expanded by gas generation, and the laminate film of the film type capacitor cell was torn. In the film type capacitor cell of Comparative Example 2, the cell temperature exceeded 100 ° C., but in the double structure type capacitor cell of Example 2, the cell temperature was 50 ° C. or less. This is because, since the laminate was broken, air (oxygen) was supplied into the film type capacitor cell in Comparative Example 2 and heat generation due to oxidation progressed, whereas in Example 3, the film type capacitor cell was liquid. Since it is covered with liquid paraffin such as isododecane, it is considered that liquid paraffin flows into the torn capacitor cell, heat generation is suppressed by blocking air (oxygen), and temperature rise is small.

  It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. In the above description, activated carbon is used as the positive electrode active material, carbon material such as graphite, hard carbon, coke and the like that can reversibly carry lithium ions as the negative electrode active material, polyacene-based material (PAS), and lithium as the electrolyte. Although the present invention is applied to a lithium ion capacitor using a non-aqueous organic solvent solution containing a salt, the present invention can also be effectively applied to other capacitors and secondary batteries. .

For example, as the positive electrode active material, lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), and composite oxides thereof (LiCo _x Ni _y Mn _z O ₂ , x + y + z = 1) , Lithium manganate spinel (LiMn ₂ O ₄ ), lithium vanadium oxide, olivine-type LiMPO ₄ (M: Co, Ni, Mn, Fe, etc.), V ₂ O ₅ , M _x O _y (MnO ₄ , Fe ₂ O) ₃ ), a polyacene-based material (PAS), a carbon material made of graphitizable carbon material or graphite, or a non-carbon material made of silicon, tin, or the like as the negative electrode active material. The present invention can be effectively applied to a lithium ion secondary battery in which a nonaqueous organic solvent solution containing a lithium salt is used.

It is a perspective view which shows the electrical storage device which is one embodiment of this invention. It is a perspective view which shows the electrical storage cell which comprises an electrical storage device. FIG. 3 is a cross-sectional view schematically showing the internal structure of the storage cell along the line AA in FIG. 2. It is sectional drawing which expands and shows the internal structure of an electrical storage cell partially. It is sectional drawing which shows schematically the internal structure of an electrical storage device along the AA line of FIG. It is sectional drawing which shows the internal structure of the electrical storage device which is other embodiment of this invention. 3 is a table showing test results of Example 1, Comparative Example 1 and Example 2.

Explanation of symbols

10 Power Storage Device 12 Exterior Case (Outside Container)
13 Laminate film (inner container)
14 Electrode stacking unit (electrode unit)
31 Heat dissipation member

Claims (8)

An electrode unit comprising a positive electrode and a negative electrode facing the positive electrode;
An inner container containing the electrode unit;
An outer container containing the inner container;
A power storage device comprising: a protective material filled in the outer container and covering the inner container. The electricity storage device according to claim 1, wherein
The heat storage device, wherein a heat radiating member that contacts the protective material is inserted into the outer container, and a part of the heat radiating member is exposed to the outside of the outer container. The electricity storage device according to claim 1 or 2,
The power storage device, wherein the protective material causes phase transition due to endotherm in a range of 40 ° C or higher and 100 ° C or lower. The electricity storage device according to claim 1 or 2,
A power storage cell is formed by the inner container and the electrode unit, and a heat capacity of the protective material is 1 kJ / K or more and 5 kJ / K or less with respect to 1 kg of the power storage cell. In the electrical storage device of any one of Claims 1-4,
The electrical storage device, wherein the protective material is a liquid. In the electrical storage device of any one of Claims 1-5,
A plurality of the inner containers are accommodated in the outer container. In the electrical storage device of any one of Claims 1-6,
The electricity storage device is a lithium ion capacitor. In the electrical storage device of any one of Claims 1-7,
The electricity storage device is a lithium ion secondary battery.

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