KR20130105448A - Layer structure battery - Google Patents

Abstract

PURPOSE: A lamellar structure battery is provided to prevent the difference of the ion permeability of each resin layer by preventing the lack of a melting uniformity between the inner side and the outer side of a laminating direction. CONSTITUTION: A lamellar structure battery is formed by laminating three or more of unit battery layers (19). The unit battery layer has a positive electrode (13), a negative electrode (15), and an electrolyte layer (17) including a separator, is formed by inserting the positive electrode, negative electrode, and electrolyte layer, is additionally has a resin layer (18) which is located between at least one of the positive and negative electrode and the separator and is formed by attaching the separator with at least one of the positive electrode and the negative electrode. At least one of the melting temperature, softening temperature, heat deflection temperature, and deflection load temperature of the center part is smaller than that of a side part.

Description

Stacked Structure Batteries {LAYER STRUCTURE BATTERY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated structure battery, which is one kind of electrical device that works externally by electrons and ions acting electrochemically. Specifically, it is related with the laminated structure battery represented by a lithium ion secondary battery etc. of a laminated type (laminated structure).

In recent years, in order to cope with air pollution and global warming, reduction of the amount of carbon dioxide is eagerly desired. In the automobile industry, there is an expectation that reduction of carbon dioxide emission by introduction of an electric vehicle (EV) or a hybrid electric vehicle (HEV) is expected, and development of the motor drive secondary battery which holds the key of these practical use is actively performed.

As a motor drive secondary battery, what has a very high output characteristic and high energy is calculated | required compared with the civil lithium ion secondary battery used for a mobile telephone, a notebook, etc. Therefore, the lithium ion secondary battery which has the highest theoretical energy among all the batteries attracts attention, and development is progressing rapidly now.

In general, a lithium ion secondary battery includes a positive electrode in which a positive electrode active material or the like is coated on both surfaces of a positive electrode current collector using a binder, and a negative electrode in which the negative electrode active material or the like is coated on both surfaces of the negative electrode current collector using a binder. It is connected through and has a structure accommodated in a battery exterior material. For example, in Patent Document 1, a battery group (power generation element) in which a positive electrode and a negative electrode are alternately stacked via a separator is accommodated in an outer case of a laminate sheet, and after the electrolyte is injected, a certain pressure is applied to the outer edge of the laminate sheet. A lithium ion secondary battery (laminated structure battery) is described, which is sealed under an environment of.

Japanese Patent Publication No. 2009-211937

However, in the conventional laminated structure lithium ion secondary battery (laminated structure battery) such as patent document 1, in order to prevent the short circuit by the thermal contraction of a separator, when pressing the outer edge of the laminated sheet which is the above-mentioned exterior materials, Sealing under the environment was not enough.

Accordingly, the inventors of the present invention provide a resin layer between an electrode-separator in order to prevent a short circuit due to thermal contraction of a separator, apply a load between the electrodes with a hot press, and partially melt the resin layer by applying a load between the electrodes. -We devised a construction method to connect the separators.

However, in a laminated structure battery, it is necessary to heat-press (hot press) from the up-down direction of the power generation element (battery group) of a laminated structure. Therefore, in a large-sized laminated structured battery such as a laminated structured battery, particularly a vehicle mounted battery, there is a difference in the amount of heat received at the end side and the center side of the laminated structured battery, and at the center portion and the end portion in the lamination direction, It turned out that a deviation generate | occur | produces (refer FIG. 2). As a result, it turned out that there exists a problem that deterioration accelerates because a difference arises in the ion permeability in the said resin layer in the center part and the edge part of a lamination direction (refer Example and Table 1 of Table 1).

Accordingly, an object of the present invention is to prevent melt unevenness of resin layers in the inner (inner) and outer (outer) directions of the lamination direction in a laminated structure battery having a resin layer between the electrode and the separator, and ion permeability for each of the resin layers. It is to provide a laminated structure battery which can reduce the difference between the two.

In the laminated structure battery of the present invention, in a laminated structure battery having a resin layer between an electrode and a separator, at least one of a melting point, a softening point, a heat deflection temperature, and a load deflection temperature of the resin layer is a lamination direction (thickness direction of the battery). ) Is characterized by a point on the center <end side.

According to the present invention, melt non-uniformity is prevented in the lamination direction by using a resin layer having a high melting point (hard to melt) on the end side of the laminated structure battery and a resin layer having a low melting point (easy to melt) along the middle of the lamination direction. The resistance between the electrodes can be maintained uniformly. As a result, uneven distribution of reactions for each unit cell layer (single cell) is prevented, and durability of the entire multilayer structure battery is improved.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional schematic drawing which shows the basic structure of the laminated (flat type) nonaqueous electrolyte lithium ion secondary battery which is one typical embodiment of a laminated structure battery.
FIG. 2 is a partial cross-sectional view of a power generating element of the laminated structure battery of FIG. 1, which schematically illustrates a state in which heat is transmitted when a hot press (hot press) is performed from a vertical direction of the power generating element of the laminated structure battery. drawing.
FIG. 3A is a plan view showing a stripe resin portion provided on an electrode surface, and FIG. 3B and FIG. 3C have a dot resin portion formed on an electrode surface. Plan view showing the angle.
4 is a perspective view showing the appearance of a flat lithium ion secondary battery as a typical embodiment of a secondary battery.
FIG. 5 is a schematic cross-sectional view schematically showing a state in which the laminated structure battery produced in the example is hot pressed (hot pressed) using a pressing jig having a heat press function. FIG.

In the laminated structure battery of this embodiment, there is further a resin layer adhering therebetween between at least one of the stationary electrodes and the separator, and the melting point, softening point, thermal modification temperature, thermal deformation temperature, and load deflection temperature of the resin layer. At least one of the features is characterized in that the center side <end end side in the stacking direction. Here, the laminated structure battery refers to a battery having a laminated structure in which at least three single cell layers having an electrolyte layer including at least a positive electrode, a negative electrode, and a separator and facing the positive electrode and the negative electrode through the electrolyte layer are laminated. With such a configuration, the effects of the invention described above can be exhibited.

As a preferable embodiment of a laminated structure battery, although a laminated (laminated structure) nonaqueous electrolyte lithium ion secondary battery is demonstrated, it is not limited only to the following embodiment. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimension ratio of drawing is exaggerated on account of description, and may differ from an actual ratio.

Although the lithium ion secondary battery of the laminated type (lamination structure) of this embodiment is especially preferable to apply to large sized batteries, such as a vehicle-mounted battery, it is not restrict | limited to the size and use of a battery. It can be applied to a lithium ion secondary battery of a laminated structure used for any size and use conventionally known.

There is no restriction | limiting in particular also when the lithium ion secondary battery of the laminated type (lamination structure) of this embodiment is distinguished by the form of electrolyte. For example, it can be applied to both of a liquid electrolyte type battery in which a nonaqueous electrolyte solution is impregnated in a separator, a polymer gel electrolyte type battery also called a polymer battery, and a solid polymer electrolyte (all-solid electrolyte) type battery. In this embodiment, also about a polymer gel electrolyte and a solid polymer electrolyte, what impregnated these polymer gel electrolyte and a solid polymer electrolyte in the separator is used.

In the following description, a lithium ion secondary battery of a bipolar (internal parallel connection type) stacked type (laminated structure) is described with reference to the drawings, but the present invention should not be limited thereto.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the basic structure of one Embodiment of a laminated (flat type) nonaqueous electrolyte lithium ion secondary battery (henceforth simply a "laminated structure battery"). As shown in FIG. 1, the laminated structure battery 10 of this embodiment has a structure in which the substantially rectangular power generation element 21 in which the charge / discharge reaction actually proceeds is sealed inside the battery packaging material 29 which is an exterior body. Have Here, the power generation element 21 has a structure in which a positive electrode, a separator (electrolyte layer) 17 containing an electrolyte, and a negative electrode are laminated. The positive electrode has a structure in which the positive electrode active material layer 13 is disposed on both surfaces of the positive electrode collector 11. The negative electrode has a structure in which the negative electrode active material layer 15 is disposed on both surfaces of the negative electrode collector 12. In addition, in this embodiment, between the separator (electrolyte layer) 17 and the negative electrode (active material layer) 15, the resin layer 18 which adheres between these is further arrange | positioned. In addition, the resin layer 18 formed by adhering between the separator (electrolyte layer) 17 and the positive electrode (active material layer) 13 by inverting arrangement | positioning of the resin layer 18 from FIG. It may be arranged. Further, both sides of the separator (electrolyte layer) 17 and the negative electrode (active material layer) 15 and between the separator (electrolyte layer) 17 and the positive electrode (active material layer) 13 are bonded to both of them. The resin layers 18 may be arranged respectively.

Specifically, one positive electrode active material layer 13 and the negative electrode active material layer 15 adjacent thereto are opposed to each other via the electrolyte layer 17 and the resin layer 18, so that the negative electrode, the resin layer, the electrolyte layer, and the like. The positive electrodes are stacked in this order. Thereby, the adjacent positive electrode, electrolyte layer, resin layer, and negative electrode comprise one single cell layer (single cell) 19. Therefore, the laminated structure battery 10 of this embodiment can also be said to have a structure by which the single cell layer (single cell) 19 is laminated | stacked and electrically connected in parallel. In addition, in the lithium ion secondary battery of the bipolar type (internal series connection type) stacked type (stacked structure), a plurality of unit cell layers (single cells) are stacked, whereby it can be said to have a configuration that is electrically connected in series.

The positive electrode active material layer 13 is disposed on only one side of the outermost positive electrode current collector located on both outermost layers of the power generation element 21, but an active material layer may be provided on both sides. In other words, the current collector having the active material layer on both sides may be used as the current collector of the outermost layer, without being used as the outermost current collector having only the active material layer provided on one side. In addition, as shown in FIG. 1, the arrangement of the positive electrode and the negative electrode is reversed, so that the outermost negative electrode current collector is positioned at both outermost layers of the power generation element 21, and the negative electrode active material layer is disposed on one or both surfaces of the outermost negative electrode current collector. It may be arranged.

In the present embodiment, the electrode (positive electrode or negative electrode) includes a freestanding electrode. The freestanding electrode ensures shape even when there is no metal foil (current collector). That is, the self-supporting electrode (self-supporting structure) can secure the shape only by the active material layer even without the metal foil (current collector) structurally (or in strength). However, even if it is a self-supporting electrode (independent structure), as an electrode element, an electrical power collector (however, in addition to metal foil, it may be a metal deposition film, plating thin film, metal wiring, etc. which are lower in mechanical strength than metal foil, and cannot ensure shape) And an active material layer are required. The self-supporting electrode defined above has an active material layer (positive electrode active material layer, negative electrode active material layer) and a current collector (positive electrode current collector, negative electrode current collector) formed directly on one side of the active material layer. The active material layer includes a porous skeleton and an active material (positive electrode active material, negative electrode active material) held in the pores of the porous skeleton.

In this specification, when it describes as a "current collector", it may refer to both a positive electrode electrical power collector and a negative electrode electrical power collector, may point only one side, and may refer to the electrical power collector for bipolar electrodes of a bipolar battery. . Similarly, when describing as "active material layer", it may refer to both a positive electrode active material layer and a negative electrode active material layer, and may point to only one side. Similarly, when describing as "active substance", it may refer to both a positive electrode active material and a negative electrode active material, and may point to only one side. Similarly, when describing as "electrode", it may refer to both a positive electrode and a negative electrode, and may only refer to a single side | surface.

In the positive electrode current collector 11 and the negative electrode current collector 12, one of the positive electrode current collector tab (positive current collector plate) 25 and the negative electrode current collector tab (negative current collector plate) 27, which are connected to each electrode (positive electrode and negative electrode), is provided. The tip of each side is attached. Moreover, the other front end part of the positive electrode current collector tab 25 and the negative electrode current collector tab 27 has a structure which is led to the edge part of the battery exterior material 29, and leads to the exterior of the battery exterior material 29. As shown in FIG. Each of the positive electrode current collector tab 25 and the negative electrode current collector tab 27 is interposed between the positive electrode current collector 11 of each electrode and an electrode terminal lead (positive electrode terminal lead and negative electrode terminal lead) (not shown), as necessary. The negative electrode current collector 12 may be attached by ultrasonic welding, resistance welding, or the like.

Moreover, as a characteristic structure of the laminated structure battery 10 of this embodiment, at least one of melting | fusing point, the softening point, heat deformation temperature, and the load deflection temperature of the said resin layer 18 is a center side <end side side in a lamination direction. It is characterized by. Preferably, the melting point of the resin layer is a center side <end end side in the lamination direction. This is because the softening point, the heat deflection temperature, and the load deflection temperature generally tend to be the same as the melting point, so that only the melting point, which already has measurement data for most resins, is used so as to be the center side <end side side in the lamination direction. Because it becomes. Therefore, unless otherwise indicated, including description of the effect of this invention mentioned above, it shall demonstrate using melting | fusing point of a resin layer.

FIG. 2 is a partial cross-sectional view of a power generating element of a laminated structure battery, and is a diagram schematically showing how heat is transmitted when hot pressing (hot press) is performed from the vertical direction of the power generating element of the laminated structure battery. In addition, the arrow in the figure shows typically how heat is transmitted. As shown in FIG. 2, heat is propagated toward the center part (center side) from the top and bottom (end part) by hot-pressing by the apparatus 20 which heat-presses the power generation element 21 from up and down. do. Therefore, it heats up quickly from the apparatus 20 at the end side of the lamination direction, and becomes high temperature in a short time = It is easy to melt. On the other hand, in the center part of a lamination direction, time is required for heat transfer from the apparatus 20, and in the time which heat-presses, it does not become high temperature to the same extent as an edge part side, but it is difficult to melt | dissolve in a hot press state Is terminated.

Therefore, when melting | fusing point of a resin layer is made into the center side = end part side (all the same resin material) in a lamination direction, melt nonuniformity arises in a lamination direction, and melting and adhesion of a resin layer are inadequate in the center part of a lamination direction. There is a risk of loss. As a result, the separator heat-contracts when abnormal heat is generated, and the ends of the opposing electrodes are in contact with each other, and there is a fear of causing a short circuit.

In addition, when melting | fusing point of a resin layer is made into the center side = end side (all the same resin material) in a lamination direction, and when time to heat-press a process is extended until melt | dissolution and adhesion of the center part of a lamination direction are sufficient, The load is applied to the end side in the stacking direction for a long time in a high temperature state. Therefore, there exists a possibility that it may melt too much and cannot maintain the desired thickness of a resin layer, or it will become difficult to maintain a desired porosity (size of a public). Therefore, the porosity (space amount = electrolyte holding amount) and the pore size (path width through which Li ions diffuse) in the center side and the end are changed, and the ion conductivity of Li is changed at the center side and the end, and the lamination is changed. There exists a possibility that a nonuniformity may arise in an ion conductivity (= interelectrode resistance) in the direction.

Therefore, the above-described configuration of the present embodiment, that is, the resin layer 18 having a high melting point (which is difficult to be melted (heat-sealed)) is used for the end side of the laminated structure battery 10, and has a low melting point depending on the middle of the stacking direction [ By using the resin layer 18 which is easy to melt (heat fusion), melt nonuniformity can be prevented in a lamination direction. That is, as shown in FIG. 2, when hot-pressing the power generating element 21 with the apparatus 20 which heat-presses from top to bottom, melting | fusing point is high [melting (heat welding) to the end side of the laminated structure battery 10 Difficult to use). By doing in this way, predetermined time is also needed until adhesiveness arises in the resin layer 18 also in the end side of a lamination direction, and it does not change the thickness of a resin layer and a space | gap (space ratio, pore diameter, etc.), It can melt and adhere suitably within press time. On the other hand, when hot-pressing the power generating element 21 by the apparatus 20 which heat-presses from the top and bottom, the resin layer with a low melting point [easy to melt (heat-fusion)] is used for the center side of the laminated structure battery 10. do. By doing so, the predetermined time is sufficient until adhesion occurs to the resin layer 18 even in the center side of the lamination direction, and the heat press time is performed without changing the thickness or the pore (space ratio or pore diameter, etc.) of the resin layer. It can melt and adhere suitably in a inside. As a result, melt nonuniformity and also thickness of a resin layer and a nonuniformity of a resin can be prevented in a lamination direction. Thereby, the resistance between electrodes can be kept uniform. Furthermore, the reaction distribution nonuniformity for every single cell layer (single cell) 19 can be prevented, and the durability of the whole laminated structure battery 10 can be improved.

Moreover, also in the resin layer 18 of the center side which is easy to melt (heat-fusion), the temperature (usually about 95 degreeC; see Example) of the apparatus (jig) 20 which heat-presses the power generating element 21 from up and down. Resin having a higher melting point is used. This is because the softening start has softened from a temperature lower than the melting point of the resin layer 18. This is because the resins (including copolymers and polymer alloys) used in the resin layer 18 are not the same (uniform) in molecular weight, molecular structure, resin shape, etc., and have a constant distribution. In practice, the surface of the resin layer is sufficiently softened (heat melted) at a temperature lower than the melting point obtained. Therefore, since adhesiveness comes out at lower temperature, it can fully adhere | attach with an electrode or a separator. However, since the temperature (the temperature at which the adhesion becomes possible) that starts to soften is proportional to the melting point of the resin layer 18, the melting point of the resin layer 18 is set in the lamination direction by making the melting point of the resin layer 18 the center side <end side side. Melt nonuniformity can be prevented and the said effect can be exhibited.

Here, as the range where the melting point of the resin layer 18 is suitable for the difference in resistance between the center side (inner side: center portion) and the end side (outer side: end portion) in the stacking direction, the object of the present embodiment can be achieved and the desired effect can be achieved. All you need is That is, melting nonuniformity can be prevented in the lamination direction by making melting | fusing point of the resin layer of an end side high, making it difficult to melt (thermal fusion), and making melting (thermal fusion) low by lowering the melting | fusing point of the center side. Thereby, the resistance between electrodes can be kept uniform. Thereby, the reaction distribution nonuniformity for every unit cell layer (single cell) 19 can be prevented, and the durability of the whole laminated structure battery 10 can be improved.

Specifically, the melting point of the resin layer on the end side in the stacking direction may be higher than the melting point of the resin layer in the center portion, although it is also dependent on the stacking number of the single cells of the battery and the electrode size, and preferably 3 to 15 ° C higher. And it is more preferable that it is 5-10 degreeC high. If the melting point of the resin layer on the end side in the stacking direction is higher than the melting point of the resin layer in the center portion at a temperature of 3 ° C., preferably at 5 ° C. or more, the resin layer at the center portion is also sufficiently adhered by the hot press, although it depends on the number of laminations. It is possible to prevent the occurrence of melt nonuniformity in the stacking direction. As a result, the above objects and effects can be sufficiently achieved. On the other hand, if the melting point of the resin layer on the end side in the stacking direction is higher than the melting point of the resin layer in the center portion in the range of 15 ° C, preferably 10 ° C or less, the outer side is excessively melted and crushed by the hot press (desired number). The thickness of the layer can not be maintained), and can be bonded while maintaining an appropriate porosity. As a result, a good diffusion path for Li ions can be ensured, the resistance between electrodes can be maintained uniformly, and generation of melt nonuniformity in the stacking direction can be prevented. As a result, the above objects and effects can be sufficiently achieved.

In addition, melting | fusing point, softening point, heat distortion temperature, and load deflection temperature of the resin layer 18 can be measured with the following method.

(1) melting point

Melting | fusing point is calculated | required from the endothermic peak at the time of heating up at 20 degree-C / min with a differential scanning calorimeter (DSC).

Specifically, it measures on the following conditions using the differential scanning calorimeter made by Seiko Denshi Co., Ltd., for example.

Sample amount: about 5mg

Atmosphere gas: Nitrogen (flow rate 20 ml / min)

Temperature condition: After holding for 10 minutes at 230 ° C., the temperature is lowered to 30 ° C. at 10 ° C./min, and then the endothermic behavior of melting when the temperature is raised at a heating rate of 10 ° C./min is measured.

(2) softening point

The softening point temperature is measured according to JIS K7206 as Vicat softening temperature (Vicat softening temperature, VST). Explaining the outline of JIS K7206, a test piece having a prescribed size is provided in a heating bath, and the temperature of the bath is raised in a state where the end face of a constant cross-sectional area (1 mm 2 in JIS K7206) is brought into contact with the center part. The temperature at which the end face penetrates to the test piece to a certain depth is referred to as Vicat softening temperature (unit: ° C).

(3) heat deflection temperature

The heat deflection temperature is according to the ASTM D648 standard, and the resin pellets are molded into a heat deflection temperature measurement specimen based on ASTM D648 by an injection molding machine, annealed at 80 ° C. for 24 hours, and then under reduced conditions of 4.6 kg / cm 2. The temperature measured by

For implementation, the dumbbell test piece which was injection-molded at the conditions of the molding temperature of 270 degreeC and the mold temperature of 80 degreeC using the IS55EPN injection molding machine manufactured by Toshiba Corp. was heat-treated at 120 degreeC for 5 hours, and according to ASTMD-648, the load of 0.45 Mpa You may measure heat distortion temperature on conditions.

(4) load bending temperature

The load deflection temperature is measured at 1.81 MPa (18.5 kg load) using a 1/4 inch test piece by a method according to ASTM D648. When the outline of ASTM-D648 is explained, the temperature at which the temperature of the sample is increased in a state in which a load determined by the standard of the test method is applied, and the size of the warp becomes a constant value is called the load warping temperature. That is, the temperature at which the displacement becomes a constant value by applying a static load to the needle, but the temperature at which the flexural modulus becomes 2,514 kgf / cm 2 = 0.25 kPa (or 10,000 kgf / cm 2 = 1 kPa) is called the load bending temperature.

From the characteristic of the temperature change of the elasticity modulus of resin, since an elasticity modulus falls rapidly when it exceeds a glass transition point, load bending temperature may become a temperature value near a glass transition point.

When the outline of JIS 7191 is explained, the both ends of the test piece of the prescribed dimension are supported and installed in a heating bath, and the temperature of a bathtub is raised in the state which applied the load to the center part. The temperature at which constant warpage occurs in the test piece is taken as the load warping temperature (unit: ° C) and used as an index of heat resistance. Since the test result depends on the size and the weight of the test piece, these values are written together. This load deflection temperature (Heat Deflection Temperature, HDT) is generally correlated with the glass transition point in the case of amorphous resin and the melting point in the case of crystalline resin.

In addition, load deflection temperature is one of the test methods of evaluating the heat resistance of a synthetic resin, and is also called a heat deflection temperature.

Hereinafter, each structural requirement (structural member) of the laminated structure battery 10 of this embodiment is demonstrated. In addition, about each structural requirement (structural member) of the laminated structure battery 10, it is not limited only to the following form, A conventionally well-known form can also be employ | adopted similarly.

(1) The whole house

The current collector is made of a conductive material, and an active material layer is disposed on one or both surfaces thereof. There is no restriction | limiting in particular in the material which comprises an electrical power collector, For example, the resin which has electroconductivity to which the conductive filler was added to a metal, a conductive polymer material, or a nonelectroconductive polymer material can be employ | adopted.

Examples of the metal include aluminum, nickel, iron, stainless steel, titanium and copper. Besides these, a cladding material of nickel and aluminum, a cladding material of copper and aluminum, or a plating material of a combination of these metals can be preferably used. Moreover, the foil in which aluminum is coat | covered on the metal surface may be sufficient. Especially, aluminum, stainless steel, and copper are preferable from a viewpoint of electroconductivity and battery operation potential.

As a form of the electrical power collector using metal, you may use a metal vapor deposition layer, a metal plating layer, a conductive primer layer, and metal wiring other than metal foil. The metal deposition layer and the metal plating layer can form (arrange) a very thin metal deposition layer or a metal plating layer on one surface of the active material layer by a vacuum deposition method or various plating methods. Metallic wirings can also be formed (arranged) on one side of the active material layer by vacuum deposition or various plating methods. In addition, the primer layer can be impregnated into the metal wiring to be attached by thermocompression bonding. In addition, when using a punching metal sheet or an expanded metal sheet as metal wiring, the metal wiring interposed between the active material layer by apply | coating and drying an electrode slurry on both surfaces of a punching metal sheet or an expanded metal sheet (current collector) Can be placed. Even when metal foil is used, metal foil (current collector) can be arrange | positioned on the single side | surface of an active material layer by apply | coating and drying an electrode slurry on metal foil (one side or both sides). The conductive primer layer can be produced by mixing a resin with carbon (chain, fibrous) or metal filler (aluminum, copper, stainless steel, nickel powder, etc. used for current collector materials). Mixtures vary. It can form (arrangement) by apply | coating this to single side | surface of an active material layer, and drying.

The said electroconductive primer layer contains the electrical power collector resin layer. Suitably, a conductive primer layer consists of a collector resin layer which has electroconductivity. In order for an electroconductive primer layer to have electroconductivity, as a specific aspect, 1) the aspect which the polymer material which comprises resin is a conductive polymer, and 2) the aspect in which the collector resin layer contains resin and a conductive filler (conductive material) are mentioned.

The conductive polymer is selected from materials that are conductive and not conductive to ions that can be used as charge transfer media. It is thought that these conductive polymers exhibit the conductivity by the conjugated polyene system forming an energy band. As a representative example, a polyene-based conductive polymer that has been put into practical use as an electrolytic capacitor or the like can be used. Specifically, polyaniline, polypyrrole, polythiophene, polyacetylene, polyparaphenylene, polyphenylenevinylene, polyacrylonitrile, polyoxadiazole or a mixture thereof is preferable. Polyaniline, polypyrrole, polythiophene, and polyacetylene are more preferable from the viewpoint that they can be used stably in electronic conductivity and in a battery.

The conductive filler (conductive material) used in the above 2) is selected from conductive materials. Preferably, from the viewpoint of suppressing ion permeation in the conductive current collecting resin layer, it is preferable to use a material having no conductivity with respect to ions that can be used as the charge transfer medium.

Although an aluminum material, a stainless steel (SUS) material, a carbon material, a silver material, a gold material, a copper material, a titanium material etc. are mentioned specifically, It is not limited to these. These conductive fillers may be used singly or in combination of two or more. Moreover, these alloy materials may be used. Preferably a silver material, a gold material, an aluminum material, a stainless material, a carbon material, and more preferably a carbon material. The conductive filler (conductive material) may be one obtained by coating a conductive material (the conductive material) with a plating or the like around the particulate ceramic material or the resin material.

Examples of the carbon material include at least one member selected from the group consisting of acetylene black, balkan, black pearl, carbon nanofiber, ketjen black, carbon nanotube, carbon nanohorn, carbon nano balloon, hard carbon, and fullerene. Can be. These carbon materials have a very wide potential window, are stable in a wide range with respect to both of the positive electrode potential and the negative electrode potential, and are excellent in conductivity. In addition, since the carbon material is very lightweight, the increase in mass is minimized. Moreover, since carbon materials are often used as a conductive support agent of an electrode, even if it contacts with these conductive support agents, since they are the same material, contact resistance becomes very low. In addition, when using carbon material as electroconductive particle, it is also possible to reduce the wettability of electrolyte by giving hydrophobic treatment to the surface of carbon, and can make the situation which electrolyte is hard to permeate | transmit the electrolyte in an electrical power collector.

There is no restriction | limiting in particular in the shape of an electroconductive filler (conductive material), Well-known shapes, such as a particulate form, a powder state, a fibrous form, plate shape, block shape, cloth shape, or mesh shape, can be selected suitably. For example, when it is going to give electroconductivity widely over resin, it is preferable to use a particulate conductive material. On the other hand, in order to improve the electroconductivity to a specific direction in resin, it is preferable to use the electrically-conductive material which has a certain directivity to shapes, such as fibrous form.

Although the average particle diameter of an electroconductive filler is not specifically limited, It is preferable that it is about 0.01-10 micrometers. In addition, in this specification, a "particle diameter" means the largest distance L among the distance between arbitrary two points on the outline of an electrically conductive filler. As a value of an "average particle diameter", the value calculated as an average value of the particle diameter of the particle observed in several to several tens of visual fields is employ | adopted using observation means, such as a scanning electron microscope (SEM) and a transmission electron microscope (TEM). I shall do it. The particle diameter and average particle diameter, such as active material particle mentioned later, can also be defined similarly.

In the case where the current collecting resin layer includes a conductive filler, the resin forming the current collecting resin layer may contain a non-conductive polymer material for binding the conductive filler in addition to the conductive filler. By using a polymer material having no conductivity as a constituent material of the current collecting resin layer, the binding property of the conductive filler can be improved, and the reliability of the battery can be improved. The polymer material is selected from a material capable of withstanding the applied positive electrode potential and negative electrode potential.

Examples of the non-conductive polymer material are preferably polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyethernitrile (PEN), polyimide (PI), polyamide ( PA), polyamideimide (PAI), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethylacrylate (PMA), polymethyl methacrylate (PMMA) ), Polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), polyvinylidene chloride (PVDC) or a mixture thereof. These materials have a wide potential window and are stable to either the positive electrode potential or the negative electrode potential. Moreover, since it is light weight, the high output density of a battery is attained.

The content of the conductive filler is not particularly limited. Particularly, when the resin contains a conductive polymer material and can secure sufficient conductivity, it is not always necessary to add the conductive filler. However, in the case where the resin is made of only the non-conductive polymer material, the addition of the conductive filler is essential to impart conductivity. Content of the electrically conductive filler at this time becomes like this. Preferably it is 5-90 mass% with respect to the total mass of a nonelectroconductive polymer material, More preferably, it is 30-85 mass%, More preferably, it is 50-80 mass%. . By adding such an amount of the conductive filler to the resin, sufficient conductivity can be imparted to the non-conductive polymer material while suppressing increase in the mass of the resin.

The conductive primer layer may contain other additives in addition to the conductive filler and the resin, but is preferably made of the conductive filler and the resin.

Of the materials constituting the current collector, examples of the conductive polymer material include polyaniline, polypyrrole, polythiophene, polyacetylene, polyparaphenylene, polyphenylene vinylene, polyacrylonitrile and polyoxadiazole And the like. Since such conductive polymer material has sufficient conductivity without adding a conductive filler, it is advantageous in terms of facilitating the manufacturing process or reducing the weight of the current collector.

As a nonelectroconductive high molecular material, it is polyethylene [PE; (HDPE), low density polyethylene (LDPE)], polypropylene (PP), polyethylene terephthalate (PET), polyether nitrile (PEN), polyimide (PI), polyamideimide ), Polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethylmethacrylate (PMMA) , Polyvinylidene fluoride (PVdF), and polystyrene (PS). Such a non-conductive polymer material may have excellent anti-satellite or solvent resistance.

To the above conductive polymer material or non-conductive polymer material, a conductive filler may be added if necessary. In particular, when the resin serving as the base material of the current collector is made of only the non-conductive polymer, an electrically conductive filler is inevitably necessary in order to impart conductivity to the resin. The conductive filler can be used without particular limitation as long as it is a conductive material. For example, metal, electroconductive carbon, etc. are mentioned as a material excellent in electroconductivity, electric potential resistance, or lithium ion barrier property. The metal is not particularly limited, but at least one kind of metal selected from the group consisting of Ni, Ti, Al, Cu, Pt, Fe, Cr, Sn, Zn, In, Sb and K, It is preferable to include a metal oxide. The conductive carbon is not particularly limited, but includes at least one selected from the group consisting of acetylene black, balkan, black pearl, carbon nanofibers, ketjen black, carbon nanotubes, carbon nanohorns, carbon nano balloons and fullerenes. It is desirable to. There is no restriction | limiting in particular if the addition amount of an electroconductive filler is a quantity which can provide sufficient electroconductivity to an electrical power collector, Generally, it is about 5-35 mass%.

The size of the current collector is determined depending on the intended use of the battery. For example, if it is used in a large-sized battery requiring a high energy density, a collector having a large area is used.

The thickness of the current collector is preferably 1 to 100 µm, more preferably 3 to 80 µm, still more preferably 5 to 40 µm. In the self-supporting electrode mentioned later, since thin film formation is possible, it is 1-18 micrometers, More preferably, it is 2-15 micrometers, More preferably, it is 3-13 micrometers. When manufacturing a freestanding electrode, this can be manufactured, without going through the conventional coating and drying process. Therefore, when using an electrical power collector with a metal vapor deposition layer, a metal plating layer, a conductive primer layer, or a metal wiring which do not need to go through the conventional coating and drying process, it has the tensile strength required by the coating and drying process. no need. As the need arises, the thickness of the current collector can be made thinner as necessary, which improves the freedom of designing the current collector and contributes to the weight reduction of the electrode and the battery.

In the case of using a punching metal sheet or expanded metal sheet having a plurality of through holes as the current collector, as the shape of the through holes, quadrangular, rhombus, bone shape, hexagon, circle, square, star, cross, etc. Can be mentioned. The so-called punching metal sheet or the like is formed by pressing a plurality of holes of such a predetermined shape, for example, in a zigzag arrangement or a parallel arrangement. In addition, what is called expanded metal sheet | seat etc. which extended | stretched the sheet | seat which inserted the zigzag-shaped perforation line, and formed many rhombic through-holes was formed.

When the current collector having the plurality of through holes is used in the current collector, the opening ratio of the through holes of the current collector is not particularly limited. However, the target of the lower limit of the opening ratio of the current collector is preferably 10 area% or more, more preferably 30 area% or more, still more preferably 50 area% or more, still more preferably 70 area% or more, further preferably Is more than 90 area%. Thus, in the electrode of this embodiment, the electrical power collector which has an aperture ratio of 90 area% or more can also be used. Moreover, as an upper limit, it is 99 area% or less, or 97 area% or less, for example. As described above, the laminated structure battery 10 including the electrode formed with the current collector having a significantly large aperture ratio can significantly reduce its weight, and further increase its capacity, thereby enabling high density. Do.

In the case where the current collector having the plurality of through holes described above is used for the current collector, the hole diameter (opening diameter) of the through holes of the current collector is similarly not particularly limited. However, the lower limit of the opening diameter of the current collector is preferably 10 µm or more, more preferably 20 µm or more, still more preferably 50 µm or more, and particularly preferably 150 µm or more. The upper limit is, for example, about 300 μm or less, preferably about 200 μm or less. In addition, the opening diameter here is the diameter of the circumference circle of a through-hole = opening part. The diameter of the circumscribed circle is obtained by observing the surface of the current collector with a laser microscope or a tool microscope, fitting the circumscribed circle to the opening, and averaging it.

(2) An electrode (positive electrode and negative electrode) and an electrode active material layer

The positive electrode and the negative electrode have a function of generating electrical energy by sorghum of lithium ions. The positive electrode essentially includes a positive electrode active material, and the negative electrode active essentially includes a negative electrode active material.

In the case of a laminated structure battery, these electrode structures are structures in which an active material layer containing an active material is formed on the surface of the current collector as in the embodiment of FIG. 1. On the other hand, in the case of a bipolar secondary battery, a positive electrode active material layer containing a positive electrode active material is formed on one surface of a current collector, and a negative electrode active material layer containing a negative electrode active material is formed on the other surface. It has a structure formed. That is, it has the form which integrated the positive electrode (positive electrode active material layer) and the negative electrode (negative electrode active material layer) through an electrical power collector. In addition to the active material, the active material layer may include additives such as an electrolyte salt (lithium salt) and an ion conductive polymer as necessary, in addition to the active material.

(2a) Positive electrode active material

As a positive electrode active material, a conventionally well-known thing can be used.

As the positive electrode active material, for example, LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni, Co, Mn) O ₂ , Li ₂ MnO ₃ , Li ₂ MnO ₃ -LiMO _{2 type} (M = Co, Ni, etc.) And a lithium-transition metal composite oxide, a lithium-transition metal phosphate compound, a lithium-transition metal sulfate compound, and the like, in which a solid solution and a part of these transition metals are substituted by other elements. In some cases, two or more kinds of positive electrode active materials may be used in combination. Preferably, from the viewpoints of capacity and output characteristics, a lithium-transition metal composite oxide is used as the positive electrode active material. It goes without saying that other positive electrode active materials may be used. In addition, a high-energy-density positive electrode active material such as LiNiO ₂ , Li (Ni, Co, Mn) O ₂ , or Li ₂ MnO ₃ is easy to increase the capacity of the battery, And it is also advantageous in that it is possible to extend the distance.

Although the average particle diameter of a positive electrode active material is not specifically limited, From a viewpoint of high output, Preferably it is 1-25 micrometers.

The amount of the positive electrode active material is not particularly limited, but is preferably 50 to 99% by mass, more preferably 70 to 97% by mass, still more preferably 80 to 96% by mass relative to the total amount of the raw material for forming the positive electrode active material layer. Range.

(2b) Negative electrode active material

A negative electrode active material has a composition which can discharge lithium ion at the time of discharge, and can occlude lithium ion at the time of charge. The negative electrode active material is not particularly limited as long as it can resorb and release lithium. Examples of the negative electrode active material include metals such as Si and Sn, or TiO, Ti ₂ O ₃ , TiO ₂ , or SiO ₂ , SiO, SnO. _2, and a metal _{oxide, Li 4/3 Ti 5/} 3 O 4 or Li ₇ composite oxide of lithium and transition metals and the like MnN, Li-Pb alloy, Li-Al alloy, Li, or natural graphite, artificial graphite Carbon materials, such as carbon black, activated carbon, carbon fiber, coke, soft carbon, or hard carbon, etc. are mentioned preferably. Among these, by using the element alloying with lithium, it becomes possible to obtain the battery of the high capacity | capacitance and the outstanding output characteristic which has a high energy density compared with the conventional carbon-type material. The negative electrode active material may be used alone or in the form of a mixture of two or more kinds. Examples of the element alloyed with lithium include, but are not limited to, Si, Ge, Sn, Pb, Al, In, Zn, H, Ca, Sr, Ba, Ru, Rh, Ir, Pd, Pt. , Ag, Au, Cd, Hg, Ga, Tl, C, N, Sb, Bi, O, S, Se, Te, Cl and the like.

It is preferable to contain a carbon material and / or at least 1 or more types of elements chosen from the group which consists of Si, Ge, Sn, Pb, Al, In, and Zn among the said active material, and the element of a carbon material, Si, or Sn is included. It is more preferable to include. Among the carbon materials, graphite having a discharge potential lower than that of lithium is more preferably used.

When using the said negative electrode active material as a negative electrode, you may shape | mold the negative electrode active material layer containing a negative electrode active material in plate shape, and may make it as a negative electrode as it is, and even if it forms a negative electrode active material layer containing the said negative electrode active material particle on the surface of an electrical power collector, and makes it a negative electrode do. The average particle diameter of the negative electrode active material particles in the latter aspect is not particularly limited, but is preferably 1 to 100 μm from the viewpoint of high capacity, reactivity, and cycle durability of the negative electrode active material, and from the viewpoint of high output, Preferably it is 1-25 micrometers. If it is this range, the secondary battery can suppress the increase of the internal resistance of the battery at the time of charge / discharge under high output conditions, and can take out sufficient electric current. In addition, when the negative electrode active material is a secondary particle, it can be said that it is preferable that the average particle diameter of the primary particle which comprises the said secondary particle is the range of 10 nm-1 micrometer, However, in this embodiment, it is necessarily in the said range. It is not limited. However, although it is based also on a manufacturing method, it cannot be overemphasized that the negative electrode active material does not need to be secondary particle | grains by aggregation, agglomeration, etc. The median diameter obtained using the laser diffraction method can be used for the particle diameter of such a negative electrode active material and the particle size of a primary particle. In addition, the shape of the negative electrode active material particles is different in the shape that can be taken by the kind, manufacturing method, and the like, and examples thereof include spherical shape (powder shape), plate shape, needle shape, columnar shape, and angular shape. It is not limited to this, Any shape can be used without a problem. Preferably, it is preferable to appropriately select an optimal shape capable of improving battery characteristics such as charge / discharge characteristics.

The amount of the negative electrode active material is not particularly limited, but is preferably 50 to 99% by mass, more preferably 70 to 97% by mass, still more preferably 80 to 96% by mass relative to the total amount of the raw material for forming the negative electrode active material layer. Range.

(2b) challenge aids

A conductive support agent means the additive mix | blended in order to improve the electroconductivity of an active material layer. Examples of the conductive auxiliary agent include carbon powder such as acetylene black, carbon black, Ketjen black and graphite, various carbon fibers such as vapor grown carbon fiber (VGCF; registered trademark), and expanded graphite. However, needless to say, the conductive assistant is not limited to these. When the active material layer contains a conductive auxiliary agent, an electronic network inside the active material layer is effectively formed, contributing to the improvement of the output characteristics of the battery.

Content of the conductive support agent mixed in the positive electrode active material layer is 1 mass% or more with respect to the total amount of the raw material for positive electrode active material layer formation, More preferably, it is 3 mass% or more, More preferably, it is the range of 5 mass% or more. In addition, content of the conductive support agent mixed in the positive electrode active material layer is 15 mass% or less with respect to the total amount of the raw material for positive electrode active material layer formation, More preferably, it is 10 mass% or less, More preferably, it is the range of 7 mass% or less to be. The following effects are exhibited by defining the compounding ratio (content) of the conductive support agent in the positive electrode active material layer which can reduce the electrode resistance by the quantity of a conductive support agent because the electronic conductivity of an active material itself is low. That is, the effect of the present embodiment can be expressed without inhibiting the electrode reaction. In addition, the electronic conductivity can be sufficiently secured, and the decrease in the energy density due to the decrease in the electrode density can be suppressed, and further, the energy density can be improved by the increase in the electrode density.

As content of the conductive support agent mix | blended with a negative electrode active material layer, since it changes with a negative electrode active material, it cannot be specified uniquely. That is, when using carbon materials and metal materials, such as graphite (graphite), soft carbon, and hard carbon which have the outstanding electron conductivity excellent in the negative electrode active material itself, containing of the conductive support agent to a negative electrode active material layer does not need in particular. Even if it contains a conductive support agent, it is enough in the range of 0.1-1 mass% with respect to the total amount of the electrode structural material of a negative electrode side. On the other hand, similar to the positive electrode active material, the electronic conductivity is low, and the electrode resistance can be reduced by the amount of the conductive assistant. In the case of using a negative electrode active material such as a lithium alloy negative electrode material or a lithium-transition metal composite oxide (for example, Li ₄ Ti ₅ O ₁₂ ), the content is about the same as the content of the conductive assistant mixed in the positive electrode active material layer. It is preferable to set it as. That is, the content of the conductive assistant mixed in the negative electrode active material layer is also preferably 1 to 10% by mass, more preferably 2 to 8% by mass, particularly preferably 3 to the total amount of the electrode constituent material on the negative electrode side. It is preferable to set it as the range of -7 mass%.

(2c) Binder (binder)

A binder is added in order to bind | conclude the structural members in an active material layer, or to bind an active material layer and an electrical power collector, and to maintain an electrode structure. As a binder, as an insulating material which can achieve the said objective, what is necessary is just a material which does not produce a side reaction (redox reaction) at the time of charge and charge, and it is although it does not specifically limit, For example, the following materials are mentioned. Polyethylene, polypropylene, polyethylene terephthalate (PET), polyethernitrile, polyacrylonitrile, polyimide, polyamide, cellulose, carboxymethyl cellulose (CMC), ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene butadiene Rubber (SBR), isoprene rubber, butadiene rubber, ethylene propylene rubber, ethylene propylene diene copolymer, styrene butadiene styrene block copolymer and its hydrogenated substance, styrene isoprene styrene block copolymer and its hydrogenated substance Thermoplastic polymer, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), tetrafluoroethylene hexafluoropropylene copolymer (FEP), tetrafluoroethylene perfluoro alkyl vinyl ether copolymer ( PFA), ethylene tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), Fluorine resins such as methylene chlorotrifluoroethylene copolymer (ECTFE) and polyvinyl fluoride (PVF), vinylidene fluoride-hexafluoropropylene fluorine rubber (VDF-HFP fluorine rubber), vinylidene fluoride- Hexafluoropropylene-tetrafluoroethylene fluorine rubber (VDF-HFP-TFE fluorine rubber), vinylidene fluoride-pentafluoropropylene fluorine rubber (VDF-PFP fluorine rubber), vinylidene fluoride-penta Fluoropropylene-tetrafluoroethylene-based fluororubbers (VDF-PFP-TFE-based fluororubbers), vinylidene fluoride-perfluoromethylvinylether-tetrafluoroethylene-based fluororubbers (VDF-PFMVE-TFE-based fluororubbers) And vinylidene fluoride-based fluorine rubbers such as vinylidene fluoride-chlorotrifluoroethylene-based fluorine rubber (VDF-CTFE-based fluorine rubber) and epoxy resins. Among these, polyvinylidene fluoride, polyimide, styrene-butadiene rubber, carboxymethylcellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile and polyamide are more preferable. These suitable binders are excellent in heat resistance and are very wide in the potential window, so that they are stable to both the positive electrode potential and the negative electrode potential, and thus can be used for the active material layer. These binders may be used alone or in combination of two or more. However, needless to say, the binder is not limited to these.

Although the quantity of a binder will not be specifically limited if it is an quantity which can bind an active material etc., Preferably it is 0.5-15 mass% with respect to the total amount of the raw material for electrode active material layer formation, More preferably, it is 1-10 mass%. .

(2d) Electrolyte salt (lithium salt)

Examples of the electrolyte salt (lithium salt) include Li (C ₂ F ₅ SO ₂ ) ₂ N, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ and LiCF ₃ SO ₃ . Furthermore, the electrolyte salt (lithium salt) used for the electrolyte layer mentioned later can be used suitably.

(2e) ion conductive polymers

Examples of the ion conductive polymer include polymers based on polyethylene oxide (PEO) and polypropylene oxide (PPO). Furthermore, the electrolyte salt (lithium salt) used for the electrolyte layer mentioned later can be used suitably.

(2f) Porous Skeletal Body Used for Freestanding Electrodes

As a porous skeleton, a nonwoven fabric, a woven fabric, a metal foam (or a metal porous body), carbon paper, etc. are preferable. Among these, the nonwoven fabric used for the porous skeleton is formed by overlapping fibers in different directions. Resin materials are used for the nonwoven fabric, and for example, fibers such as polypropylene, polyethylene, polyethylene terephthalate, cellulose, nylon, and EVA resin (ethylene-vinyl acetate copolymer resin) can be applied. Moreover, as a form other than a nonwoven fabric as a porous skeleton body, the resin woven fabric (regular resin porous body), a metal foam, or a metal porous body, carbon paper, etc. are mentioned. Examples of the resin used for the woven fabric made of resin include polypropylene, polyethylene, polyethylene terephthalate, EVA resin, and the like, but are not limited thereto. As a metal foam or a metal porous body, Preferably at least 1 sort (s) of metal foam, a metal porous body, etc. of Cu, Ni, Al, Ti, etc. can be illustrated, but it is not restrict | limited to these at all. Preferably, it is a nonwoven fabric made of at least one metal porous body of Cu or Al, carbon paper, polypropylene, polyethylene or EVA resin.

The proportion of the porous skeleton of the skeleton portion in the active material layer is in the range of 2% by volume or more, preferably 7% by volume or more. On the other hand, the proportion of the porous skeleton of the skeleton portion in the active material layer is 28% by volume or less, preferably 12% by volume or less. It is excellent in the point which does not inhibit an electrode reaction, if the ratio of the porous skeleton which occupies for an active material layer exists in the said range.

As porosity (porosity) of a porous skeleton, Preferably it is 70%-98%, More preferably, it is 90-95%. Within the above range, the effect of the present invention can be effectively obtained.

As a pore diameter of a porous skeleton, about 50-100 micrometers which can fully fill the active material used for time is preferable. Within the above range, the effect of the present invention can be effectively obtained. That is, if the pore diameter of the porous skeleton is 100 μm or less, the effect of the present embodiment is effectively obtained, and if the pore diameter is 50 μm or more, an appropriate active material is appropriately selected depending on the intended use without restriction of the particle size of the active material to be used. Excellent in terms of choice.

The thickness of the porous skeleton may be smaller than the thickness of the active material layer, and is usually about 1 to 120 µm, preferably 1 to 20 µm.

Although there is no restriction | limiting in particular also about the thickness of each active material layer, From a viewpoint of suppressing an electronic resistance, it is preferable that the thickness (one side) of each active material layer is about 1-120 micrometers.

About the porosity of each active material layer, the porosity of each active material layer is about 10 to 40% from a viewpoint of increasing the electroconductivity (diffusion) of Li ion by impregnation and holding | maintenance of electrolyte solution, or suppressing an electronic resistance. Is preferably.

(3) The electrolyte layer

The electrolyte layer of this embodiment consists of an electrolyte and the separator which impregnates or hold | maintains the said electrolyte in the vacancy. The electrolyte layer having a separator functions as a space partition (spacer) between the positive electrode and the negative electrode. In addition, it also has a function of holding an electrolyte which is a moving medium of lithium ions between the stationary electrodes during charging and discharging. In addition, in this embodiment, the short circuit by the heat shrink of a separator can be prevented by adhering between a separator and an electrode using the resin layer 18 as mentioned above.

There is no restriction | limiting in particular in the electrolyte which comprises an electrolyte layer, A polymer electrolyte, such as a liquid electrolyte and a polymer gel electrolyte and a polymer solid electrolyte, can be used suitably.

(3a) Liquid electrolyte

The liquid electrolyte is obtained by dissolving a lithium salt as a supporting salt in a solvent. Examples of the solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propionate (MP), methyl acetate (MA), and methyl formate (MF). , 4-methyldioxolane (4MeDOL), dioxolane (DOL), 2-methyltetrahydrofuran (2MeTHF), tetrahydrofuran (THF), dimethoxyethane (DME), ethylene carbonate (EC), propylene carbonate (PC ), Butylene carbonate (BC), γ-butyrolactone (GBL), and the like. These solvents may be used singly or as a mixture of two or more kinds. The supporting salt (lithium salt) is not particularly limited, but LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiTaF ₆ , LiSbF ₆ , LiAlCl ₄ , Li ₂ B ₁₀ Cl ₁₀ , LiI, LiBr, LiCl, LiAlCl , Inorganic acid anion salts such as LiHF ₂ , LiSCN, LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiBOB (lithium bisoxide boron), LiBETI (lithium bis (perfluoroethylenesulfonylimide); Li And organic acid anion salts such as (C ₂ F ₅ SO ₂ ) ₂ N). These electrolytic salts may be used singly or in the form of a mixture of two or more kinds.

On the other hand, the polymer electrolyte is classified into a gel electrolyte containing an electrolyte solution and a polymer solid electrolyte containing no electrolyte solution.

(3b) Gel electrolyte

The gel electrolyte has a configuration in which the liquid electrolyte is injected into a matrix polymer having lithium ion conductivity. Examples of the matrix polymer having lithium ion conductivity include polymer (PEO) having polyethylene oxide in the main chain or side chain, polymer (PPO) having polypropylene oxide in the main chain or side chain, polyethylene glycol (PEG), polyacrylonitrile (PAN), polymethacrylic acid ester, polyvinylidene fluoride (PVdF), a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP), polyacrylonitrile (PAN) ) (PMA), and poly (methyl methacrylate) (PMMA). In addition, a mixture, a modified product, a derivative, a random copolymer, an alternate copolymer, a graft copolymer, a block copolymer and the like of the polymer and the like may be used. Among these, it is preferable to use PEO, PPO and copolymers thereof, PVdF, and PVdF-HFP. In such a matrix polymer, electrolyte salts, such as a lithium salt, can be melt | dissolved well.

(3c) Polymer solid electrolyte

The polymer solid electrolyte has a structure in which a supporting salt (lithium salt) is dissolved in the matrix polymer and does not contain an organic solvent. Therefore, when the electrolyte layer is composed of a polymer solid electrolyte, there is no worry of leakage from the battery, and the reliability of the battery can be improved.

The matrix polymer of the polymer gel electrolyte or the polymer solid electrolyte can exhibit excellent mechanical strength by forming a crosslinked structure. In order to form a crosslinked structure, a polymerization treatment such as thermal polymerization, ultraviolet polymerization, radiation polymerization, electron beam polymerization or the like may be performed on a polymerizable polymer for forming a polymer electrolyte (for example, PEO or PPO) using an appropriate polymerization initiator. do. In addition, the said electrolyte may be contained in the active material layer of an electrode.

(3d) Separator

There is no restriction | limiting in particular as a separator, A conventionally well-known thing can be used suitably. For example, a separator or a nonwoven fabric separator of a porous sheet made of a polymer or a fiber absorbing and retaining the electrolyte may be mentioned.

As the separator of the porous sheet made of the above polymer or fiber, for example, microporous (microporous membrane) can be used. Specific examples of the porous sheet made of the polymer or the fiber include polyolefins such as polyethylene (PE) and polypropylene (PP); (For example, a laminate having a three-layer structure of PP / PE / PP or the like), a polyimide, an aramid, and a hydrocarbon-based material such as polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) And a microporous (microporous membrane) separator made of resin, glass fiber or the like.

The thickness of the microporous (microporous membrane) separator is different depending on the intended use and cannot be defined uniquely. As an example, in applications such as a secondary battery for driving a motor such as an electric vehicle EV, a hybrid electric vehicle HEV, a fuel cell vehicle FCV, or the like, the thickness is preferably 4 to 60 µm in a single layer or a multilayer. It is preferable that the micropore diameter of the said microporous (microporous membrane) separator is at most 1 micrometer or less (usually pore diameter of about several tens nm), and the porosity (porosity) is 20 to 80%.

As said nonwoven fabric separator, conventionally well-known things, such as polyolefins, such as cotton, rayon, acetate, nylon, polyester; PP, PE; polyimide, aramid, are used individually or in mixture. The bulk density of the nonwoven fabric is not particularly limited as long as it can obtain sufficient battery characteristics by the impregnated polymer gel electrolyte.

It is preferable that the porosity (porosity) of the said nonwoven fabric separator is 45 to 90%. In addition, the thickness of a nonwoven fabric separator should just be the same as an electrolyte layer, Preferably it is 5-200 micrometers, Especially preferably, it is 10-100 micrometers. If the thickness is less than 5 µm, the electrolyte retainability deteriorates, and if the thickness exceeds 200 µm, the resistance increases.

(4) resin layer

What is necessary is just to provide a resin layer in order to prevent the short circuit by the thermal contraction of a separator, even if it adheres to either an electrode (positive electrode or negative electrode) and a separator.

As a material used for a resin layer, as an insulating material which can achieve the said objective, what is necessary is just a material which does not produce a side reaction (redox reaction) at the time of charge and discharge, and is not specifically limited, For example, the following materials are mentioned. have. Olefin-based resins such as polyethylene (PE) and polypropylene (PP), polyethylene terephthalate (PET), polyethernitrile, polyacrylonitrile, polyimide, polyamide, cellulose, carboxymethyl cellulose (CMC), ethylene-acetic acid Vinyl copolymer, polyvinyl chloride, styrene butadiene rubber (SBR), isoprene rubber, butadiene rubber, ethylene propylene rubber, ethylene propylene diene copolymer, styrene butadiene styrene block copolymer and its hydrogenated substance, styrene and Thermoplastic polymers such as isoprene styrene block copolymers and hydrogenated products thereof, polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), polytetrafluoroethylene (PTFE), tetrafluoro Ethylene hexafluoropropylene copolymer (FEP), tetrafluoroethylene perfluoro alkyl vinyl ether copolymer (PFA), ethylene Fluororesins such as trifluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride (PVF), vinylidene fluoride-hexa Fluoropropylene-based fluororubbers (VDF-HFP-based fluororubbers), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based fluororubbers (VDF-HFP-TFE-based fluororubbers), vinylidene fluoride-pentafluoro Low-propylene fluorine rubber (VDF-PFP-based fluororubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene-based fluorine rubber (VDF-PFP-TFE-based fluororubber), vinylidene fluoride-perfluoro Vinylidene fluorine such as methyl vinyl ether tetrafluoroethylene fluorine rubber (VDF-PFMVE-TFE fluorine rubber) and vinylidene fluoride-chlorotrifluoroethylene fluorine rubber (VDF-CTFE fluorine rubber) Id based include fluorine rubber, epoxy resins, (meth) acrylic resin, an aramid or the like. Among these, polyvinylidene fluoride, polyimide, styrene-butadiene rubber, carboxymethylcellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile and polyamide are more preferable. The material used for these suitable resin layers is excellent in heat resistance, and has a very large potential window, and is stable to both a positive electrode potential and a negative electrode potential, and can be used for a resin layer. The material used for these resin layers may be used independently and may use 2 or more types together. However, it goes without saying that the material used for the resin layer is not limited to these. Among them, for example, polyvinylidene fluoride (PVdF), (meth) acrylic resin, olefin resin, and the like are strong to the potential of any one of the positive electrode side and the negative electrode side, and therefore can be applied to both. Moreover, since SBR etc. are strong to a negative electrode potential, it is preferable to use it on the negative electrode side. Moreover, since PTFE etc. are strong to a positive electrode potential, it is preferable to use it on the positive electrode side.

In this embodiment, it is preferable that at least one resin layer in a lamination direction, Preferably all the resin layers 18 contain polyvinylidene fluoride (PVDF). By constituting the resin layer 18 of each unit cell layer (single cell) 19 with a material containing PVDF or PVDF, the adhesion temperature (the surface of the resin layer starts to soften, and has adhesiveness; softening point temperature) It can set in temperature lower than a separator deformation temperature area | region (softening point temperature). Therefore, since battery reaction is not inhibited as much as possible, there exists an effect further to an output characteristic. In addition, the material containing PVDF and PVDF has a large amount of modification from the softening start temperature, so that it can be directly adhered, and the heat press time can be shortened or the heat press temperature can be set low.

As a material containing PVDF, a homopolymer of PVDF, a substituent (for example, a carboxyl group) is introduced into a part of PVDF (for example, a side chain of a repeating unit, etc.), and PVDF is different from one or more polymers. Random, block, alternating, graft copolymers (binary copolymers, ternary copolymers, quaternary copolymers, etc.), polymer alloys containing PVDF and one or more other (co) polymers; In particular, it is made of a carboxyl group incorporated in the PVDF (e.g., structure ;-( having a carboxyl group in the side chain portion _{CH (COOH) -CF 2) n} -, or _{- (CH 2 -CF (COOH)} ) n - Or-(CH ₂ -CF _2- ) _n- (CH (COOH) -CF ₂ ) _m- , or-(CH ₂ -CF _2- ) _n- (CH ₂ -CF (COOH)) _m -etc.) This is preferred. By mixing carboxyl groups with PVDF, the melting point can be lowered by 1 to 10 ° C (adjustable), and by adjusting the amount of carboxyl groups mixed, the variation of melting point (= resin layer on the end and center side) can be easily made. Excellent in terms of However, in order to exhibit the effect of this invention, it is enough to lower about 10 degreeC, It is preferable to have melting point about 2 to 3 degreeC preferably.

In this embodiment, it is preferable that the said resin layer 18 contains styrene butadiene rubber (SBR). In the case of SBR, since it is a copolymer of styrene and butadiene, by increasing the ratio of styrene, the melting point can be increased by about 1 to 10 ° C, so that the deviation of the melting point (= resin layer on the end side and the center side) can be easily made. Excellent in terms of

It is preferable that the thickness of the resin layer can be made as thin as possible within the range in which the above object can be achieved, in that it can suppress the diffusion distance of Li ions from becoming long and contribute to the weight reduction of the battery. In particular, in the present embodiment, the desired purpose and effect can be realized by changing the melting point without changing the thickness of the resin layer (= without changing the thickness of the resin layer of each unit cell layer) at the end side and the center side in the stacking direction. will be. Thereby, it is not necessary to change production equipment (especially thickness adjustment) etc., and is excellent in production efficiency. From this point of view, the thickness of the resin layer depends on the form of the resin layer, but in the case where the resin layer is present on the entire surface of the separator and the electrode (whole surface), it is 0.1 to 5 µm, preferably 1 to 2 µm. to be. If the thickness of a resin layer is 0.1 micrometer or more, since manufacture can be made easy, it is preferable, because when the thickness of a resin layer is 5 micrometers or less, since there is little possibility that it may adversely affect the load characteristic of a battery, it is preferable.

Moreover, when the resin part (resin layer) exists in stripe shape or dot shape in the separator and the whole electrode surface, the thickness of a resin layer is 0.1-5 micrometers, Preferably it is the range of 1-2 micrometers. If the thickness of a resin layer is 0.1 micrometer or more, since manufacture can be made easy, it is preferable, because when the thickness of a resin layer is 5 micrometers or less, since there is little possibility that it may adversely affect the load characteristic of a battery, it is preferable.

Since the thickness of a resin layer may recede and may not peel easily, a thickness of a resin layer can be disassembled, a cross-section is taken out, and can be measured from the cross-sectional image of SEM (scanning electron microscope).

The porosity (also referred to as porosity) of the resin layer depends on the separator porosity and the shape of the resin layer, but the resin portion is present in the form of a stripe or a dot when the resin layer is present on the separator and the entire electrode surface (whole surface). When present, it is 60% or more, Preferably it is 60 to 90%. When it is 60% or more, the diffusion of Li ions is not disturbed. In addition, the porosity of the resin layer mentioned above is an example when the separator porosity is about 45 to 55%, and when the porosity of the separator increases or decreases, if the porosity of the resin layer also increases or decreases proportionally do. As described above, the porosity of the resin layer is slightly higher than the porosity of the separator (see Examples) in order to prevent the diffusion of Li ions due to the presence of the resin layer formed on the electrode surface. In addition, in this embodiment, a desired objective and an effect by changing melting | fusing point on the end side and center side of a lamination direction, without changing the porosity of a resin layer (= without changing the porosity of the resin layer of each unit cell layer). It can be realized. Thereby, there is no need to change production facilities or raw materials (adjustment of the porosity by adjusting the viscosity of the resin layer forming slurry), and the production efficiency is excellent.

On the other hand, when the resin portion is provided in a dot shape, when the ratio of the resin portion is very small, the porosity of the resin portion (resin layer) is more preferably smaller, and is 10% or less, preferably 0%. . This is because a large non-resin portion functions effectively as a new electrolyte solution holding portion. What is necessary is just to determine the ratio of the resin part in the case where the ratio of resin part is very small in consideration of adhesiveness and battery performance. However, as mentioned above, even if the porosity of the said resin part (resin layer) is 60% or more, Preferably it is 60 to 90%, there is no problem in particular.

The porosity present in the resin layer can be measured by using a mercury porosimetry or the like after first dismantling the battery, taking out each resin layer, washing and removing the electrolyte, and drying. However, when the resin layer is subdued and cannot be peeled off well, the battery may be disassembled and cross-sectionalized to count (measure) the spatial portion of the resin layer by mapping from a cross-sectional image of a SEM (scanning electron microscope). have.

In addition, the ratio of the resin part (or non-resin part) which exists in the separator and the electrode surface can be computed by disassembling a battery, making it cross-sectional, and counting (measure | bonding) the adhesion part (dot) by mapping from the cross-sectional image of SEM. have.

As a form of a resin layer, what is necessary is just to be able to achieve the said objective, and it is not specifically limited. For example, (i) the resin layer may exist in the whole surface (whole surface) of a separator and an electrode. In this case, in order for the said resin part to have a liquid retention space, it is necessary to be a porous layer (refer the said porosity). Alternatively, (ii) the resin layer may be present at intervals such that the resin portion in which the resin layer is present and the non-resin portion in which the resin layer does not exist are formed on the surface of the separator and the electrode. It is preferable that a resin part is arrange | positioned so that uniformity may be maintained on a separator and an electrode surface. In the case of (ii), since the non-resin portion functions effectively as a liquid retaining space, the resin layer (resin layer) may be a porous layer having a liquid retaining space. Alternatively, it may be non-porous (= porosity (porosity) 0%) in which no liquid retention space exists. In particular, when the resin portion is provided in a dot shape (= when the ratio of the resin portion is very small), the resin portion may be made nonporous (= porosity (porosity) 0%) in which no liquid-retaining space exists.

FIG. 3A is a plan view showing a state where a stripe-shaped resin portion is provided on an electrode surface. 3B and 3C are plan views showing a state in which a dot-shaped resin portion is provided on the electrode surface.

Specifically, (iia) as shown in Fig. 3A, a non-resin portion 35 is formed on the separator and the electrode surface 31 between the stripe-shaped resin portion 33a and the stripe 33a. The resin layer 33a may exist at intervals as much as possible. (iib) As shown in FIGS. 3B and 3C, the separator and the electrode surface 31 have a dot-shaped resin portion 33b between the dot 33b and the dot 33b. The resin layer 33b may exist interspersed at intervals so that the non-resin part 35 may be formed in it. As an example of (iib), the resin part 33b of a dot shape exists only in the neck of the separator and the electrode surface 31, and the separator and electrode surface 31 other than the dot (resin part 33b) of the corner are present. The resin layer may exist at intervals so that the non-resin part 35 is formed in () (FIG. 3B). Or (b2) the dot-shaped resin portion 33b is interspersed on the separator and the electrode surface 31 so as to maintain uniformity, and the non-resin portion (3) is disposed on the separator and the electrode surface 31 between the dot 33b and the dot 33b. The resin layer may exist at intervals so that 35) is formed. For example, a dot-shaped resin portion 33b of 12 points in total, 3 points in length and 4 points in length, is dotted on the separator and the electrode surface 31 at equal intervals, and 12 dots (resin part 33b) are provided. The resin layer may exist at intervals so that the non-resin part 35 is formed in the separator and electrode surface 31 other than] (FIG. 3C). However, the present invention is not limited to these forms at all, and the above-described objects such as ring shapes, polygonal shapes, waveform shapes, semicircle shapes, and irregular shapes such as lattice shapes, rhombus lattice shapes, rectangles, continuous or discontinuous circles or ellipses, etc. are achieved. Anything you can do can be anything.

 In addition, in this embodiment, it is preferable that the softening point of a resin layer is lower than the softening point of a separator. This is because the electrode-separator can be sufficiently bonded by softening the surface of the resin layer to give adhesiveness while maintaining the shape of the separator. From this viewpoint, it is preferable that the softening point of the resin layer of the center side of the lamination direction with the lowest softening point is lower than the softening point of a separator. Specifically, the softening point of the resin layer on the center side in the lamination direction having the lowest softening point is preferably 5 to 10 ° C. lower than the softening point of the separator. In addition, it is preferable to use the same thing for the separator of each unit cell of a lamination direction from a viewpoint of a production efficiency or a part management.

Here, the softening point temperature of a resin layer and the softening point temperature of a separator can be measured by JISK7206 as both a bicat softening temperature (Vicat softening temperature, Vicat Softening Temperature, VST). Explaining the outline of JIS K7206, a test piece having a prescribed size is provided in a heating bath, and the temperature of the bath is raised in a state where the end face of a constant cross-sectional area (1 mm 2 in JIS K7206) is brought into contact with the center part. The temperature at which the end face penetrates to the test piece to a certain depth is the vicat softening temperature (unit: ° C).

Formation of the resin layer, as shown in Examples, desires a resin slurry (in which the porosity of the resin layer can be adjusted depending on the concentration change) in which the resin material for forming the resin layer is previously dissolved on a separator surface with a suitable solvent. It is apply | coated and dried by thickness and a shape (whole surface, stripe shape, dot shape, etc.). Thereby, a separator and a resin layer can be integrated (it is called a resin separator). In addition, in the case where the resin layer is provided on either side of the stationary electrode, the effects of the present embodiment are all the same. However, when the electrode size is different, the one provided on the larger electrode side (usually, the negative electrode side) is opposed until the separator of the same size as the larger electrode is thermally contracted and smaller than the smaller electrode. It can also be said to be advantageous because the electrodes do not contact each other. The resin separator is placed in the same manner as a normal separator, and the power generation element 21 is formed between the positive electrode and the negative electrode. Thereafter, by hot pressing from the vertical direction of the power generating element 21 to the heat press device (see FIGS. 2 and 5) 20, the surface portion of the resin layer 18 (resin portion) of the resin separator is softened and adhesive It also adheres to the electrode. Thereby, the resin layer 18 formed by bonding between electrode and separator can be formed. Moreover, you may apply | coat a resin slurry to the electrode (positive electrode or negative electrode) side previously, and may produce the resin electrode (integrating an electrode and a resin layer). Thereafter, the power generation element 21 is similarly formed and hot-pressed to form a resin layer 18 formed by adhering the electrode-separator.

(5) Current collector plate (current collector tab; external lead)

In the lithium ion secondary battery (laminated structure battery) 10, the current collector plates (current collector tabs) 25 and 27 may be used for the purpose of taking out a current to the outside of the battery. The current collector plates (current collector tabs) 25 and 26 are electrically connected to the current collectors 11 and 12, and are taken out to the outside such as a laminate film as an exterior material.

The material constituting the current collector plates 25 and 27 is not particularly limited, and a known highly conductive material conventionally used as a current collector plate for a lithium ion secondary battery can be used. As the constituent material of the collector plate, for example, a metal material such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof is preferable. From the viewpoints of light weight, corrosion resistance and high electrical conductivity, aluminum, copper and aluminum are particularly preferable. In the positive electrode current collector (positive electrode tab) 25 and the negative electrode collector (negative electrode tab) 27, the same material or different materials may be used.

(5a) Electrode (positive and negative electrodes) Terminal lead (inner lead)

In the stacked structure battery 10 shown in FIG. 1, the current collectors 11 and 12 are current collector plates (current collector tabs) 25 and 27 via negative electrode terminal leads and positive electrode terminal leads (not shown), respectively. And may be electrically connected to each other. However, a part of the current collectors 11 and 12 may be extended like an electrode terminal lead (internal lead), and may be electrically connected to the current collector plates (current collector tabs) 25 and 27 directly. Therefore, what is necessary is just to use an electrode terminal lead (not shown) suitably as needed, and it can be said to be an arbitrary structural member.

As a material of a negative electrode and a positive electrode terminal lead, the lead used by a well-known laminated secondary battery can be used. In addition, the portion taken out from the battery packaging material may be covered with a heat-shrinkable heat-shrink tube or the like so as not to short-circuit by contact with peripheral devices or wirings and to affect the product (for example, automobile parts, especially electronic devices, etc.). desirable.

(6) Battery exterior material

As the battery packaging material, a conventionally known metal can case can be used. In addition, you may pack the power generation element 21 using the laminated film 29 as shown in FIG. 1 as an exterior material. The laminate film can be configured as, for example, a three-layer structure in which polypropylene, aluminum, and nylon are laminated in this order. By using such a laminated film, it is possible to easily open the casing, add the capacity recovery material, and re-seal the casing. Moreover, a laminated film exterior material is preferable also from the viewpoint of being excellent in high output and cooling performance, and being suitably used for the battery for large apparatus for EV and HEV.

The lithium ion secondary battery 10 of the said laminated structure can be manufactured by a conventionally well-known manufacturing method.

[Outline structure of lithium ion secondary battery]

4 is a perspective view showing an appearance of a flat laminated (laminated structure) lithium ion secondary battery, which is a typical embodiment of a laminated structure battery.

As shown in FIG. 4, in the flat-layered lithium ion secondary battery 30, it has a rectangular flat shape, and the positive electrode tab 38 and the negative electrode tab 39 for extracting electric power from both sides thereof are provided. It is withdrawn. The power generation element 37 is enclosed by the battery packaging material 32 of the lithium ion secondary battery 30, and the surroundings are heat-sealed, and the power generation element 37 connects the positive electrode tab 38 and the negative electrode tab 39. It is sealed in the state drawn out to the outside. Here, the power generation element 37 corresponds to the power generation element 21 of the stacked lithium ion secondary battery (laminated structure battery) 10 shown in FIG. 1 described above. The power generation element 37 is formed by stacking a plurality of unit cell layers (single cells) 19 composed of a positive electrode, an electrolyte layer, and a negative electrode.

In addition, the extraction of the tabs 38 and 39 shown in FIG. 4 is not particularly limited. The positive electrode tab 38 and the negative electrode tab 39 may be drawn out from the same side or the positive electrode tab 38 and the negative electrode tab 39 may be divided into a plurality of portions and taken out from each side, The present invention is not limited thereto.

The lithium ion secondary battery (laminated structure cell) 10 is a large-capacity power source for an electric vehicle, a hybrid electric vehicle, a fuel cell vehicle, a hybrid fuel cell vehicle, or the like, and is used for driving a vehicle in which solid energy density and solid output density are obtained. It can use suitably for a power supply or an auxiliary power supply.

In addition, although the said embodiment illustrated the laminated lithium ion secondary battery as a laminated structure battery, it is not limited to this, It is applicable to other types of secondary batteries and also a primary battery.

The above-described laminated structure battery of the present embodiment has the following effects.

In the battery 10 of the present embodiment, the melting point of the resin layer or the like is set at the center side <end side side in the stacking direction, so that melt unevenness can be prevented in the stacking direction, and the inter-electrode resistance can be maintained uniformly.

As a result, the reaction distribution nonuniformity for every unit cell layer (monocell) is prevented, and the durability of the whole laminated structure battery is improved. Uniform output can be obtained for each unit cell to be stacked, and battery durability can be improved.

Since the resin layer contains polyvinylidene fluoride (PVDF), the adhesion temperature (the surface of the resin layer starts to soften, the temperature having adhesiveness; the softening point temperature) is set to a temperature lower than the separator deformation temperature region (softening point temperature). Can be. Therefore, since battery reaction is not inhibited as much as possible, the effect which was further added to an output characteristic can be exhibited.

By making the softening point of the resin layer lower than the softening point of the separator, the surface of the resin layer is softened while giving the adhesiveness while maintaining the shape of the separator, so that the electrode-separator can be sufficiently bonded. Therefore, since battery reaction is not inhibited as much as possible, the effect which was further added to an output characteristic can be exhibited.

[Example]

Although this invention is demonstrated in more detail using the following example and a comparative example, it is not limited to a following example at all.

1. Fabrication of Positive Electrode

LiMn ₂ O ₄ (average particle diameter 20 μm) as the positive electrode active material, acetylene black as the conductive aid, and polyvinylidene fluoride (PVDF) as the binder were mixed in a mass ratio of positive electrode active material: conductive aid: binder = 90: 5: 5 A positive electrode slurry was obtained.

The slurry was coated with NMP (N-methyl-2-pyrrolidone) to adjust the viscosity, so that the amount of active material per unit area was 20 mg / cm 2 on one side on both sides of the Al foil (thickness 20 µm). After sufficiently drying, the thickness of the positive electrode (total thickness of the positive electrode current collector + positive electrode active material layer (both sides)) was processed to a thickness of 159 µm using a roll press. The porosity of the positive electrode active material layer was 23%.

2. Production of negative electrode

Natural graphite (average particle diameter 20 micrometers) as a negative electrode active material, polyvinylidene fluoride (PVDF) as a binder was mixed by the mass ratio of negative electrode active material: binder = 95: 5, and the negative electrode slurry was obtained.

The slurry was coated with NMP (N-methyl-2-pyrrolidone) to adjust the viscosity, so that the amount of active material per unit area was 6 mg / cm 2 on one side on both sides of Cu foil (thickness 10 µm). After sufficiently drying, the thickness of the negative electrode (total thickness of the negative electrode current collector + negative electrode active material layer (both sides)) was processed to a thickness of 90 μm using a roll press. The porosity of the negative electrode active material layer was 30%.

3. Preparation of Separator + Resin Layer A (hereinafter referred to simply as Resin Separator A)

A low-density polyethylene layer (melting point 105 ° C, softening point temperature 90 ° C) as a resin layer is formed on the entire surface of the laminated microporous membrane of polyethylene and polypropylene (thickness 20 µm, porosity 50%, softening point temperature 105 ° C) so as to have a thickness of 2 µm. It was applied. The porosity of the low density polyethylene layer (resin layer) was 65%.

4. Preparation of Separator + Resin Layer B (hereinafter, simply referred to as Resin Separator B)

A high-density polyethylene layer (melting point 108 ° C, softening point temperature 85 ° C) as a resin layer is formed on the entire surface of the laminated microporous membrane (polyethylene and polypropylene) (thickness 20 µm, porosity 50%, softening point temperature 105 ° C) so as to have a thickness of 2 µm. It was applied. The porosity of the high density polyethylene layer (resin layer) was 65%.

5. Preparation of Separator + Resin Layer C (hereinafter, referred to simply as Resin Separator C)

A polyvinylidene fluoride layer (melting point 175 ° C, softening point temperature 110 ° C) is applied as a resin layer to a laminated microporous film of polyethylene and polypropylene (thickness 20 µm, porosity 50%, softening point temperature 120 ° C) so as to have a thickness of 2 µm. It was constructed. The porosity of the polyvinylidene fluoride layer (resin layer) was 70%.

6. Preparation of Separator + Resin Layer D (hereinafter also referred to simply as Resin Separator D)

Polyvinylidene fluoride (having a carboxyl group in some side chain) layer (melting point 165 degreeC, softening point temperature 105 degreeC) as a resin layer in the laminated microporous film (thickness 20 micrometers, porosity 50%, softening point temperature 120 degreeC) of polyethylene and a polypropylene. ) Was applied to a thickness of 2 μm. The porosity of the polyvinylidene fluoride layer (resin layer) was 70% (as can be seen in comparison with resin separator C, in the case of polyvinylidene fluoride used in the resin layer, the melting point can be easily lowered by incorporating a carboxyl group).

7. Description of Examples

The laminated structure battery (cell stack) which produced five laminated single cell layers (single cells) was produced by combining the structure site | part (member) of the said single cell layer (single cell) of said 1-6.

As the positive electrode and the negative electrode of each unit cell layer (single cell) of all the examples, the members produced in the above 1 and 2 were used.

In addition, the lamination number of each single cell of the laminated structure battery in which five single cell layers (single cells) are laminated is set to 1 to 5 in order from the bottom.

Example 1

The adhesive separator B was used for the 1st stage, the 2nd stage, the 4th stage, and the 5th stage, and the adhesive separator A was used for the 3rd stage.

Example 2

The adhesive separator C was used for the 1st stage, the 2nd stage, the 4th stage, and the 5th stage, and the adhesive separator D was used for the 3rd stage.

Example 3

An adhesive separator A was used for the first stage and the fifth stage, an adhesive separator C was used for the second stage and the fourth stage, and an adhesive separator D was used for the third stage.

Comparative Example 1

The adhesive separator A was used for all the layers (1st stage-5th stage).

Comparative Example 2

The adhesive separator B was used for all the layers (1st stage-5th stage).

Comparative Example 3

The adhesive separator C was used for all the layers (1st stage-5th stage).

Comparative Example 4

Adhesive separator D was used for all the layers (1st-5th stage).

8. Fabrication of Laminated Structure Cells

In the above procedure, the positive electrode, the negative electrode, and the adhesive separators A to D were cut to have a size of 20 cm (vertical, 20 cm wide) (at which time, the tabs were not cut), and five single cell layers (single cells) were laminated. At this time, the adhesive separators A to D were arranged so that the resin layer side adhered to the surface of the negative electrode (active material layer) in all the unit cell layers (single cells). After that, the stacked tabs (current collector tabs formed by extending a part of the current collector; the thickness of the current collector tabs are the same as the current collectors) are connected to each other, and the parallel type (internal parallel connection type) is laminated. The power generation elements (stacked bodies) (see Figs. 1 and 5) of the structural battery were stacked (stacked up). In order to adhere | attach (heat-seal) the resin layer of adhesive separator A-D, the constant pressure load is heated, heating from the up-down direction of the power generation element 21 using the heat press apparatus (pressing jig) 20 shown in FIG. Was added (hot pressed). At this time, the load was 10 MPa, and in the hot press condition 1 (Comparative Examples 1, 2, and Example 1), the temperature of the jig was 95 ° C, the press time was 5 minutes, and the hot press condition 2 (Comparative Examples 3, 4, In Examples 2 and 3, the jig temperature was 110 ° C and the press time was 6 minutes. In the hot press, the result of having measured the temperature (maximum temperature) by attaching a temperature sensor to each resin layer (in-plane center part) in the battery of each Example and a comparative example is shown in Table 1 below.

The number in a table | surface shows the maximum temperature (unit; degreeC) of a resin layer. In addition, each unit cell layer (single cell) of the laminated body laminated | stacked five layers was made into 1 layer (top layer), 2 layer, 3 layer (center layer), 4 layer, and 5 layer (lower layer) in order from the top.

Each power generation element 21 (laminated body) was placed in an aluminum laminate outer package, a desired electrolyte solution (see the composition of the above reference value) was injected into a vacuum, and then vacuum sealed to fabricate a laminated structure battery. The mixed solution (molar ratio of 5: 5) of EC and DEC containing 1 M LiPF ₆ was used for electrolyte solution at this time.

9. Evaluation Method

The cycle test (durability test) was done under 50 degreeC storage using the laminated structure battery produced by the said procedure. Cycle conditions were 400 cycles between 4.2V-3.0V at 1C rate.

10. Results

The capacity retention rate (%) before and after the endurance test is shown in Table 2 below.

Capacity retention rate (%) = (discharge capacity (Ah) of the 400th cycle) / (discharge capacity (Ah) of the 1st cycle) x 100.

In Table, A-D abbreviate | omits the adhesive separators A-D used for each layer (1st-5th stage) of each Example.

From the results shown in Table 2, the capacity retention rate of 75 to 77% was ensured by gradating the melting point of the resin layer for each of the unit cell layers (single cells) to be laminated as in Examples 1 to 3. Moreover, compared with the capacity retention ratio (67-70%) of the laminated structure battery which does not gradient the melting point of the resin layer for every single cell layer (single cell) laminated like Comparative Examples 1-4, the lamination of Examples 1-3. In the structural battery, it was confirmed that the durability was improved.

As can be seen from Table 2, in the present invention, the melting point of the resin layer for each single cell from the center side to the end side may be gradientd. It may be gradient-graded in step shape so that melting | fusing point of the resin layer for every several cell number may change. For example, in the case where five single cell layers (single cells) are laminated in the same manner as in the embodiment, the melting point of the resin layer is in the order of A> B> C> D, and the melting point of the resin layer is as follows in order from the end side. Includes changing forms. A> B> C <B <A, A> B> D <B <A, A> C> D <C <A, B> C> D <C <B so that the melting point of the resin layer for each single cell changes. It may be gradient as shown. In addition, A = A> B <A = A, A = A> C <A = A, A = A> D <A = A, B = B> C <so that the melting point of the resin layer for every single cell changes. B = B, B = B> D <B = B, C = C> D <C = C, A> B = B = B <A, A> C = C = C <A, A> D = D = D <A, B> C = C = C <B, B> D = D = D <B, C> D = D = D <C may be gradientd in a step shape. However, if melting | fusing point of the resin layer of a single cell satisfy | fills center side <end side side, it will not be limited to these.

10, 30: lithium ion secondary battery of a laminated structure
11: positive electrode current collector
12: anode collector
13: Positive electrode active material layer
15: Negative electrode active material layer
17: Electrolyte layer (separator)
18: Resin layer
19: Short layer (single cell)
20: heat press device (press jig)
21, 37: Power generation elements
25: positive pole collector plate
27: negative electrode collector plate
29, 32: Battery enclosure
31: electrode (separator) surface
33a: resin part of stripe shape
33b: dot-shaped resin part
35: non-resin part
38:
39: Negative electrode tab

Claims (4)

In a laminated structure battery having an electrolyte layer including a positive electrode, a negative electrode, and a separator, and stacking three or more layers of a single cell layer formed by opposing a positive electrode and a negative electrode through an electrolyte layer,
There is further a resin layer formed by adhering between at least one of the stationary poles and the separator, and at least one of the stationary poles and the separator,
At least one of a melting point, a softening point, a heat deflection temperature, and a load deflection temperature of the resin layer is a center side <end end side in the lamination direction. The method of claim 1,
Melting | fusing point of the said resin layer is a center side <end side in a lamination direction, The laminated structure battery characterized by the above-mentioned. 3. The method according to claim 1 or 2,
At least one resin layer of the said stacking direction contains polyvinylidene fluoride (PVDF), The laminated structure battery characterized by the above-mentioned. 3. The method according to claim 1 or 2,
The softening point of the said resin layer is lower than the softening point of the said separator, The laminated structure battery characterized by the above-mentioned.

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