JP2012216561A - Bipolar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bipolar battery comprising a collector available at low cost and having oxidation resistance.SOLUTION: A bipolar lithium ion battery comprises: a plurality of electrodes comprising a collector, a positive electrode electrically coupled to one side of the collector, and a negative electrode electrically coupled to the other side of the collector; and an electrolyte layer between the electrodes. The collector contains a material containing simple silicon (Si) as a component of a conductive material coupling the positive electrode and the negative electrode with electronic conductivity, and the collector comprises a layer where silicon is in the form of particles or fibers and disposed in a state of allowing continuity between both sides in a resin.

Description

  The present invention relates to a bipolar battery having an electrode in which a positive electrode, a current collector, and a negative electrode are stacked in this order. The bipolar battery of the present invention is used, for example, as a motor driving power source for an electric vehicle or the like.

  In recent years, reduction of carbon dioxide emissions has been strongly desired for environmental protection. In the automobile industry, there are high expectations for reducing carbon dioxide emissions by introducing electric vehicles (EVs) and hybrid electric vehicles (HEVs), and we are eager to develop secondary batteries for motor drives that hold the key to their practical application. Has been done. As a secondary battery, attention is focused on a lithium ion secondary battery that can achieve a high energy density and a high output density. However, in order to apply to an automobile, it is necessary to use a plurality of secondary batteries connected in series in order to ensure a large output.

  However, when a battery is connected via the connection portion, the output is reduced due to the electrical resistance of the connection portion. Further, the battery having the connection portion has a disadvantage in terms of space. In other words, the output volume and energy density of the battery are reduced due to the occupied volume of the connection portion.

  In order to solve this problem, a bipolar battery in which a positive electrode active material and a negative electrode active material are arranged on both sides of a current collector has been developed (see, for example, Patent Document 1). Conventionally, SUS or a clad material has been used as a current collector of such a bipolar battery (see, for example, Patent Document 2).

JP 2004-95400 A Japanese translation of PCT publication No. 2004-523091

  However, the SUS material that has been used as the current collector of the bipolar battery as described in the cited document 2 has oxidation resistance, but SUS is also oxidized in the long term and has a problem in durability and has a long term. There was a problem that it was not reliable and the cladding material was expensive and could not be thinned.

  Therefore, an object of the present invention is to provide a bipolar battery using a current collector that is inexpensive and has oxidation resistance.

The present invention comprises an electrode comprising a current collector, a positive electrode electrically coupled to one surface of the current collector, and a negative electrode electrically coupled to the other surface of the current collector;
In a bipolar battery comprising an electrolyte layer disposed between a plurality of the electrodes,
The current collector is made of a material containing simple silicon (Si) as a main component for bonding the positive electrode and the negative electrode by electronic conductivity,
The layer constituting the current collector can be achieved by a bipolar lithium ion battery characterized in that silicon is in the form of particles or fibers and is arranged in a resin in a state where conduction between the front and back sides can be taken. it can.

  In the bipolar battery according to the present invention, a silicon material is used as a main component for bonding a current collector between the back and front surfaces (between the positive electrode and the negative electrode) by electronic conductivity, so that the current collector is inexpensive and has oxidation resistance. It can be a body. As a result, a bipolar battery having long-term reliability can be made at low cost.

It is a cross-sectional schematic diagram which shows the basic composition (power generation element) of the bipolar battery of this invention. It is a cross-sectional schematic diagram which shows one preferable form of the electrical power collector of the bipolar battery of this invention. It is a cross-sectional schematic diagram which shows another preferable form of the collector of the bipolar battery of this invention. It is a cross-sectional schematic diagram which shows another preferable one form of the collector of the bipolar battery of this invention. 1 is an external perspective view of a bipolar battery of the present invention. 4 is an external view of the assembled battery of the present invention, FIG. 4A is a plan view of the assembled battery, FIG. 4B is a front view of the assembled battery, and FIG. 4C is a side view of the assembled battery. It is a conceptual diagram of the vehicle carrying the assembled battery of this invention.

  The bipolar battery of the present invention comprises a current collector, a positive electrode electrically coupled to one surface of the current collector, and an electrode comprising a negative electrode electrically coupled to the other surface of the current collector, In the bipolar battery comprising the electrolyte layer disposed between the electrodes, the current collector electrically couples the positive electrode (positive electrode active material layer) and the negative electrode (negative electrode active material layer) by electronic conductivity. A silicon material is used as the main component.

  This is because, in a series assembled battery represented by a bipolar battery, the current collector is required to have oxidation resistance on the surface in contact with the positive electrode active material, and reduction resistance is required on the surface in contact with the negative electrode active material. In addition, conductivity and non-ion conductivity (which means that the current collector does not have conductivity with respect to ions and does not mean that it has conductivity with respect to non-ions) are also required items. For this reason, in order to provide oxidation resistance on the positive electrode side, it is necessary to prevent oxidation by using an oxide film and to prevent oxidation by using a noble metal such as Au or Pt. On the other hand, on the negative electrode side, it is necessary for the reduction resistance to have a characteristic that does not react with highly reactive lithium, and it is necessary to use Cu, Ni, stainless steel alloy that does not alloy with lithium. One of the methods for satisfying these is a method of bonding and using a material that can be used for the positive electrode and the negative electrode, such as a clad material, but there is a problem that it is expensive and cannot be thinned. Another method includes a method using a material that can withstand both poles, such as SUS stainless alloy, gold, and platinum. However, gold and platinum have a problem of being expensive. Then, although SUS was used like patent document 2, here SUS was also oxidized in the long term, and there existed a problem in durability. In particular, when lithium cobalt oxide, lithium nickel oxide, or lithium manganese oxide having a full charge voltage of 4 V or more is used, there is a problem that SUS is rapidly deteriorated. In the present invention, a silicon material is used as a main component for bonding the positive electrode active material layer and the negative electrode active material layer by electronic conduction, so that it has oxidation resistance and is conductive and nonionic conductive. By using it as an electric body, a bipolar battery that solves the above problems can be obtained.

On the other hand, silicon may produce a compound with Li when the potential is very low, but this can be avoided by selecting a negative electrode active material. Since silicon does not form a compound with Li unless it has a very low potential of 0.1 V vs Li / Li ⁺ , general carbon (0.1 to 1 V) can be used as the negative electrode active material. Also, with respect to oxidation resistance, since the oxidation of silicon does not proceed due to the formation of the SiO ₂ film, it does not dissolve. For this reason, it is possible to provide a current collector that can stably exist on both the positive electrode side and the negative electrode side in the operating voltage range of the battery. Obtainable. In addition, if thin metal foils that are different on the positive electrode side and the negative electrode side are used together such as a clad material, pinholes are likely to occur, and the thickness can be reduced to a thickness that can be used as a current collector of a bipolar battery. Can not. In the present invention, since a current collector can be formed using a silicon material without being clad, an ultra-thin current collector can be obtained at a lower cost than conventional clad materials.

When silicon (Si) is used for the current collector of the bipolar battery, the resistance increases as compared with conventional Au and SUS, but slightly increases compared to the total resistance of the battery. Compared to Au: 2.0 × 10 ⁻⁸ Ωm and SUS: 100 × 10 ⁻⁸ Ωm, Si is about 100 to 10000 × 10 ⁻⁸ Ωm, depending on the amount of impurities. When this value is applied to a stacked bipolar battery, for example, in the case of a 10 cm × 10 cm battery, when the current collector thickness is 20 μm, the resistance of the Si current collector is about 0.02 mΩ. In this case, since the resistance of the entire battery is about 0.1 to 1Ω, it can be said that an increase in resistance of about 0.02 mΩ is completely within the error range.

  FIG. 1 is a conceptual diagram showing the structure of a stacked bipolar battery. The bipolar battery has a structure in which the current collector 10, the positive electrode 20, the electrolyte layer 30, the negative electrode 40, and the current extraction tab 11 are stacked, and the current collector 10 existing between the batteries connected in series is a positive electrode. A battery that functions as both a current collector and a negative electrode current collector. Hereinafter, the constituent members of the bipolar battery of the present invention will be described in detail.

[Current collector]
The current collector of a normal battery that is not a bipolar type transfers charge through a tab attached to the end of the current collector, and the current collector collects the charge generated on the negative electrode side into the tab or supplies it from the tab. A function of transmitting the generated electric charge to the positive electrode side. Therefore, the current collector needs to have a low electric resistance in the horizontal direction (surface direction) in which charges move, and a metal foil having a certain thickness is used to reduce the electric resistance in the horizontal direction. For this reason, it led to the increase in the weight of a battery.

  On the other hand, in the current collector 10 of a bipolar battery, unlike a normal battery, the charge generated on the negative electrode 40 side is directly supplied to the positive electrode 20 existing on the opposite side of the current collector 10. For this reason, the current flows in the stacking direction of the components of the bipolar battery, and does not need to flow in the horizontal direction. Therefore, in order to reduce the electrical resistance in the horizontal direction, even if Si is not a low resistance material such as conventional Au or SUS, the resistance of the entire battery is about 0.1 to 1Ω as described above, so It can be said that an increase in resistance of about 0.02 mΩ is completely within the error range. Further, since the electrical resistance in the horizontal direction may be high, the current collector can be made very thin. Moreover, regarding the tab from which the current is finally extracted, it is desirable to use a metal tab that is in surface contact with the current collector.

  In view of the situation peculiar to such a bipolar battery, in the present invention, by configuring the current collector 10 using a silicon material as a main component for coupling the positive electrode active material layer and the negative electrode active material layer by electronic conduction. Thus, the current collector can be reduced in weight and ultrathin without impairing the battery characteristics, and the energy density of the bipolar battery can be improved.

  The layer (also referred to as current collector layer) 10 constituting the current collector of the present invention may be composed of one or more layers including a silicon layer. Thereby, it can be set as the structure which can add another function as needed.

  By using silicon in the current collector of the present invention, it is possible to obtain durability in addition to conductivity and ion blocking properties required for the current collector of the series assembled battery. Other layers may be added to the body surface. For example, by adding carbon having a large surface area such as carbon black, a function of reducing resistance can be exhibited (see Reference Example 2). Even in such a case, it is cheaper than the conventional clad material and can be made thin. However, in this invention, it is not limited to this carbon layer, You may combine with another functional layer so that it can improve in function more.

  When the current collector layer 10 is composed of two or more layers including a silicon layer, the ratio of the thickness of the silicon layer and the other layer may be appropriately determined according to the purpose of use of the other layer, Although not particularly limited, it is desirable to optimize the thickness of each layer so that the entire current collector layer 10 is thin. For example, as described above, when the layer (current collector layer) 10 constituting the current collector is a silicon layer and a carbon layer having a large surface area such as carbon black, the silicon layer: the thickness of the carbon layer The ratio is in the range of 1: 0.001 to 10, preferably 1: 0.01 to 1. When the thickness of the carbon layer is less than 0.001 with respect to the thickness of the silicon layer 1, it is not possible to improve the conductivity and it is difficult to sufficiently achieve the purpose of reducing the resistance by the carbon layer. It may become. On the other hand, when the thickness of the carbon layer exceeds 10 with respect to the thickness 1 of the silicon layer, the bulk is large, but the function cannot be expressed because the thickness of the silicon layer is insufficient.

  In addition, as shown in FIGS. 2A to 2C described later, the silicon layer has a layer structure made of silicon (FIG. 2C), as well as silicon resin particles (FIG. 2A) or fibers (FIG. 2C). 2B) and a layer structure in which the film is made conductive is also included.

  In the present invention, the current collector layer 10 may be silicon or particles, or may be disposed in the resin in a state where conduction between the front and back surfaces can be obtained.

  2A, 2B, and 2C are schematic cross-sectional views respectively showing preferred embodiments of the current collector 10 of the bipolar battery according to the present invention.

  In the current collector layer 10 shown in FIG. 2A, silicon (Si) is the particle 50 and is arranged in the resin 60 in a state where conduction between the front and back surfaces can be obtained. In the current collector layer 10 shown in FIG. 2B, silicon is in a fibrous form 52 and is disposed in the resin 60 in a state where conduction between the front and back surfaces can be obtained. Further, the current collector layer 10 shown in FIG. 2C is entirely composed of a sheet (foil) 54 of silicon (Si), and is in a state where conduction between the front and back surfaces can be taken. In the current collector 10 existing between the electrodes, the current flows in the vertical direction of the current collector 10 (in the direction indicated by the arrow in the figure), but the vertical direction is caused by the conductive material silicon (Si) 50, 52, 54. Conductivity is ensured. For this reason, it is possible to reduce the mass of the current collector 10. 2A and 2B, from the viewpoint of improving molding processability and flexibility (flexibility), when the resin 60 is used in addition to the siliceous materials 50 and 52 of the conductive material, the conductive material is used. These particles or fibrous Si may be arranged in a state where conduction between the front and back surfaces can be taken. 2A to C show an example in which the current collector layer 10 is composed of a silicon layer, but in reality, the current collector layer 10 may be composed of two or more layers including a silicon layer. In that case, FIG. It can be considered that it represents the silicon layer of the body layer.

  As shown in FIG. 2, silicon used in the current collector layer (or silicon layer) may form a complete layer structure and exist between the positive electrode active material and the negative electrode active material (see FIG. 2). As another method, it is also possible to apply a method in which silicon is dispersed in particles (FIG. 2A) or fibers (FIG. 2B) in a film-like resin, and the film is made conductive (implementation). (See Examples 1 and 4). Si is relatively poor in mechanical bending strength and ductility compared to conventional metal foil current collectors such as SUS and Au. Therefore, when making a large battery, it can be handled by combining it with a resin. It is preferable to facilitate. By combining with the resin, the resistance of the current collector increases by an order of magnitude, but since the original resistance is low, the increase in resistance can be ignored. In particular, in a bipolar battery, an ultra-thin film can be formed as described above, and an increase in (conducting) resistance in the thickness direction (stacking direction) due to the resin can be suppressed to a lower level by reducing the film thickness.

  The average particle diameter of the silicon particles constituting the current collector layer (or silicon layer) 10 as shown in FIG. 2A may be appropriately determined according to the thickness of the current collector layer (or silicon layer). Specifically, it is in the range of 10 nm to 100 μm, preferably 100 nm to 10 μm, more preferably 500 nm to 5 μm. When the average particle diameter of the silicon particles is less than 10 nm, it is difficult to manufacture the particles themselves and it is difficult to manufacture due to aggregation, and when it exceeds 100 μm, it is difficult to maintain the denseness, There is a possibility that it is difficult to reduce the thickness of the current collector layer (or silicon layer).

  The shape of the silicon particles is not particularly limited, and a spherical shape, an elliptical cross-sectional shape, a columnar shape (bar shape), an indefinite shape, and the like can be used as appropriate, but are not limited thereto.

  As the fiber diameter (average value) of the fibrous silicon constituting the current collector layer (or silicon layer) 10 as shown in FIG. 2B, the thickness and resistance of the current collector layer (or silicon layer) and the impregnation of resin What is necessary is just to determine suitably in consideration of ease of operation. Specifically, it is in the range of 10 nm to 50 μm, preferably 100 nm to 10 μm, more preferably 500 nm to 5 μm. When the fiber diameter (average value) of the fibrous silicon is less than 10 nm, it is difficult to produce the fibrous silicon itself. When the fiber diameter exceeds 50 μm, it is not dense, and is a current collector as compared with the electrode layer. The layer (or silicon layer) may be difficult to be thinned or formed.

  As the length (average value) of the fibrous silicon constituting the current collector layer (or silicon layer) 10 as shown in FIG. 2B, the thickness of the current collector layer (or silicon layer) and the bending property of the fiber It may be determined appropriately in consideration of resistance, ease of manufacture, and the like. Specifically, it is in the range of 0.1 to 1000 μm, preferably 0.2 to 500 μm, more preferably 0.5 to 200 μm. If the length (average value) of the fibrous silicon is less than 0.1 μm, it is difficult to produce the fiber, and if it exceeds 1000 μm, it is difficult to include the fiber in the sheet.

  The shape of the fibrous silicon is not particularly limited, and fibrous materials such as silicon nanotubes, silicon microtubes, silicon nanofibers, silicon microfibers, silicon nanocoils, and silicon microcoils can be used as appropriate. There are, but are not limited to these.

  The particle diameter of the silicon particles and the fiber diameter of fibrous silicon can be measured by, for example, SEM (scanning electron microscope) observation, TEM (transmission electron microscope) observation, or the like. The fiber cross section of silicon particles or fibrous silicon may contain particles or fibrous silicon having different aspect ratios as described above, instead of being spherical or circular. Therefore, the particle diameter, fiber diameter, and the like mentioned above are expressed by the absolute maximum length because the particle shape and fiber cross-sectional shape are not uniform. Here, the absolute maximum length is the maximum length among the distances between any two points on the contour line of the particle or fiber cross section.

  Whether silicon is particulate or fibrous is not particularly a problem. That is, in this invention, it is because silicon may be arrange | positioned in resin in the state which can carry out the conduction | electrical_connection between back and front, as for a silicon | silicone as a collector layer. The silicon particles have an aspect ratio (aspect ratio) in the range of 1 to 10, preferably 1 to 2, and the aspect ratio (fiber length / fiber diameter) of the fibrous silicon exceeds the aspect ratio of the silicon particles. , Preferably in the range of 10 to 1000.

  The type of the resin 60 constituting the current collector layer (or silicon layer) 10 as shown in FIGS. 2A and 2B is not particularly limited, but it needs to be extremely small even if there is no ion permeability. There is. Moreover, since it is necessary to endure heating and a solvent in the formation process of an electrode, resin which satisfy | fills this condition is preferable. Specifically, one of polyolefin, polyamide, polyimide, polyamideimide, epoxy resin, bakelite, or a plurality thereof is desirable.

  Further, the blending ratio of the particulate or fibrous silicon and the resin in FIGS. 2A and 2B is not particularly limited as long as each of the above blending purposes can be achieved. However, silicon: resin (mass ratio) = 1: 99 to 80:20, preferably 10:90 to 75:25, more preferably 25:75 to 50:50. When silicon is less than 1% by mass, there is a problem that the resin is not sufficiently filled and the liquid penetrates. When it exceeds 80% by mass, electronic conductivity cannot be expected.

  In the present invention, the silicon-containing layer 10 preferably contains carbon (see FIGS. 2A and 2B).

  Specifically, when silicon (silicon particles 50 or fibrous silicon 52) is contained in the resin 60 of the silicon-containing layer 10 that is the current collector layer 10 shown in FIGS. 2A and 2B, the silicon itself has a large surface area. Is not large, and there is a case where the electronic resistance is increased without sufficient contact. In this case, it is possible to add some carbon in addition to silicon particles and / or fibrous silicon. Even in such a case, it is preferable that silicon and carbon, which are conductive materials, be arranged in the resin in a state where conduction between the front and back surfaces can be obtained.

  In this case, the particles 50 made of silicon particles and carbon particles may be arranged in the resin in a state where conduction between the front and back surfaces can be taken (FIG. 2A). Or the fiber 52 which consists of fibrous silicon and fibrous carbon may be arrange | positioned in resin in the state which can connect between back and front (FIG. 2B). Alternatively, carbon particles and / or silicon particles and fibrous silicon and / or fibrous carbon may be arranged in the resin in a state where conduction between the front and back surfaces can be taken (so to speak, FIG. 2A and FIG. 2). A state where the states of 2B are combined; not shown).

  Note that a current collector using a silicon material as a main component for bonding the positive electrode and the negative electrode by electron conduction has a silicon material having electron conductivity as a main component, and has electronic conductivity such as carbon as required. An auxiliary material may be used as long as the electron conductive material is disposed in the resin in a state where conduction between the front and back surfaces (= between the electrodes) can be obtained (see FIGS. 2A and 2B). Further, a layer (silicon sheet or film or carbon-containing silicon sheet or film) is composed of only silicon or a material having electronic conductivity such as silicon and carbon, and the entire layer (entire surface) has a back-and-front space (= It may be formed in a state where conduction between the electrodes) can be taken (see FIG. 2C). Further, another carbon layer or the like may be laminated on such a silicon layer or silicon-containing layer to form a multilayer, and the entire multilayer structure may be formed in a state where conduction between the back and front (= between electrodes) can be obtained.

  The shape of the carbon is not particularly limited, and the particle shape such as a spherical shape, an elliptical cross section, a columnar shape (bar shape), and an indefinite shape, carbon nanotube, carbon microtube, carbon nanofiber, carbon microfiber, carbon nano Any of fiber shapes such as a coil and a carbon microcoil can be used as appropriate, but is not limited thereto.

  In the case of carbon particles, the average particle size may be appropriately determined according to the thickness of the current collector layer (or silicon layer). Specifically, it is in the range of 1 nm to 20 μm, preferably 10 nm to 5 μm, more preferably 50 nm to 0.5 μm. When the average particle size of the carbon particles is less than 1 nm, there is a problem that the conductivity is inferior. When the average particle size exceeds 20 μm, there is a possibility that carbon having lithium ion conductivity may short-circuit between the back and front of the electrode. There is a risk that it is difficult to reduce the thickness of the electrical layer (or silicon layer).

  In the case of the fibrous carbon, the fiber diameter (average value) may be appropriately determined in consideration of the thickness of the current collector layer (or silicon layer), resistance, resin filling property, and the like. Specifically, it is in the range of 10 nm to 50 μm, preferably 100 nm to 10 μm, more preferably 500 nm to 5 μm. If the fiber diameter (average value) of the fibrous carbon is less than 10 nm, the production is difficult, and if it exceeds 5 μm, the possibility of allowing lithium ions to move between the front and back of the current collector layer is increased. There is a risk that the current collector layer (or silicon layer) may be difficult to be thinned or formed.

  The length (average value) of the fibrous carbon may be appropriately determined in consideration of the thickness of the current collector layer (or silicon layer), the bendability of the fiber, resistance, presence / absence of penetration of the current collector layer, and the like. Good. Specifically, it is in the range of 0.05 to 20 μm, preferably 0.1 to 10 μm, more preferably 0.2 to 5 μm. If the length (average value) of the fibrous carbon is less than 0.05 μm, the production is difficult, and if it exceeds 20 μm, there is a possibility of penetrating the current collector layer.

  In addition, the particle diameter of the said carbon particle and the fiber diameter of fibrous carbon can be measured by SEM (scanning electron microscope) observation, TEM (transmission electron microscope) observation, etc., for example. In addition, in the fiber cross section of carbon particles or fibrous carbon, particles or fibrous carbon having different aspect ratios as described above may be included instead of spherical or circular shapes. Therefore, the particle diameter and fiber diameter mentioned above are also expressed by the absolute maximum length because the particle shape and fiber cross-sectional shape are not uniform.

  As the amount of carbon, the silicon itself has a very small surface area, and the purpose is to complement the increase in electronic resistance without sufficient contact. Silicon: carbon (mass ratio) = 100: 0.01 to 50, preferably 100: 0.1 to 20, more preferably 100: 0.5 to 10 is desirable. When carbon is less than 0.01 part by mass with respect to 100 parts by mass of silicon, the effect of addition cannot be expected, and when it exceeds 50 parts by mass, ionic conductivity appears in the film.

  The blending ratio of the resin with respect to the total amount of silicon and carbon as the conductive material is (silicon + carbon): resin (mass ratio) = 1: 99 to 85:15, preferably 10:90 to 80:20. More preferably, the range of 25:75 to 60:40 is desirable. When the total amount of silicon and carbon is less than 1 part by mass, there is a problem that the resin is not sufficiently filled and the liquid penetrates. When it exceeds 85 parts by mass, electronic conductivity cannot be expected.

  The thickness of the current collector 10 is not particularly limited. Preferably, by reducing the resistance in the stacking direction by reducing the thickness of the battery, it is possible to achieve a reduction in weight and thickness of the battery as a whole. It can be said that it is desirable to have various characteristics required for the current collector, such as mechanical strength, conductivity, and durability. From this point of view, the thickness of the current collector 10 is desirably 0.1 to 100 μm, preferably 1 to 50 μm, and more preferably 5 to 30 μm because it is desirable that the current collector 10 be made thinner. In addition, the thickness of a collector here means the thickness of these whole layers, when it consists of two or more layers containing a silicon layer.

  The above is the description of the configuration of the current collector that is a characteristic part of the bipolar battery of the present invention. There are no restrictions on the configuration requirements of the bipolar battery other than the current collector. Therefore, in the following description, the bipolar lithium ion secondary battery will be described as an example with respect to other constituent elements other than the current collector of the bipolar battery of the present invention, but the present invention is not limited to these.

[Electrodes (positive electrode and negative electrode)]
The configurations of the positive electrode (also referred to as positive electrode active material layer) 20 and the negative electrode (also referred to as negative electrode active material layer) 40 are not particularly limited, and known positive electrodes and negative electrodes are applicable. The electrode includes a positive electrode active material if the electrode is a positive electrode and a negative electrode active material if the electrode is a negative electrode. What is necessary is just to select a positive electrode active material and a negative electrode active material suitably according to the kind of battery.

For example, when the bipolar battery is a lithium ion secondary battery, as a cathode active material, Li · Co-based composite oxide such as LiCoO _2, Li · Ni-based composite oxide such as LiNiO _2, spinel LiMn ₂ Examples thereof include Li · Mn composite oxides such as O ₄ and Li · Fe composite oxides such as LiFeO ₂ . In addition, transition metal and lithium phosphate compounds and sulfate compounds such as LiFePO ₄ ; transition metal oxides and sulfides such as V ₂ O ₅ , MnO ₂ , TiS ₂ , MoS ₂ , and MoO ₃ ; PbO ₂ , AgO, NiOOH etc. are mentioned. In some cases, two or more positive electrode active materials may be used in combination. In particular, when lithium cobalt oxide, lithium nickel oxide, or lithium manganese oxide with a full charge voltage of 4 V or more is used as the positive electrode active material, there is a problem that the positive electrode side is rapidly deteriorated in the conventional SUS current collector. However, the current collector of the present invention has the advantage that the formation of the SiO ₂ film has a very high oxidation resistance on the positive electrode side and is stable for a long period of time, and can provide a battery with excellent durability. The thickness of the positive electrode may be appropriately determined according to the purpose of use, and is usually about 1 to 500 μm.

  Furthermore, in the present invention, as described later, the positive electrode can be formed by any one of sputtering, vapor deposition, CVD, PVD, ion plating, and thermal spraying.

  As a positive electrode active material suitable for such a forming method, in addition to lithium cobaltate described in Reference Example 5 described later, lithium nickelate, lithium manganate, lithium cobalt nickelate, lithium nickel manganate, cobalt nickel lithium manganate, An olivine type lithium iron phosphate can be suitably used.

  When such a forming method is used, the thickness of the positive electrode can be reduced to 0.001 to 10 μm, preferably 0.01 to 1 μm.

In addition, examples of the negative electrode active material in the case where the bipolar battery is a lithium ion secondary battery include carbon materials such as crystalline carbon material and amorphous carbon material, and metal materials such as Li ₄ Ti ₅ O _12. . Specific examples include natural graphite, artificial graphite, carbon black, acetylene black, graphite, activated carbon, carbon fiber, coke, soft carbon, and hard carbon. In some cases, two or more negative electrode active materials may be used in combination. In particular, the main component silicon that bonds the positive electrode and the negative electrode of the current collector of the present invention by electronic conduction may form a compound with Li when the potential is very low. This is the selection of the negative electrode active material. Can be avoided. Specifically, since silicon does not form a compound with Li unless it has a very low potential of 0.1 V vs Li / Li ⁺ or less, the above-described crystalline carbon material or non-crystalline material can be used as the negative electrode active material. It can be said that it is desirable to use a carbon material (carbon material) (0.1 to 1 V) such as a carbon material. The thickness of the negative electrode may be appropriately determined according to the purpose of use, and is usually about 1 to 500 μm.

  Further, in the present invention, as described later, the negative electrode can be formed by any one of sputtering, vapor deposition, CVD, PVD, ion plating, and thermal spraying.

  As a negative electrode active material suitable for such a forming method, carbon, lithium metal, lithium aluminum alloy, lithium tin alloy, lithium silicon alloy and the like can be suitably used in addition to lithium titanate described in Reference Example 5 described later. .

  When such a forming method is used, the thickness of the negative electrode can be reduced to 0.001 to 10 μm, preferably 0.01 to 1 μm.

  Electrodes include conductive aids, binders, electrolytes (polymer matrix, ion conductive polymers, electrolytes, etc.) to increase electronic conductivity, electrolyte support salts (lithium salts), etc. to increase ion conductivity. obtain.

  Examples of the conductive assistant include acetylene black, carbon black, graphite, and carbon fiber. By including a conductive additive, the conductivity of electrons generated at the electrode can be increased, and the battery performance can be improved.

  Examples of the binder include polyvinylidene fluoride (PVdF), styrene butadiene rubber, and polyimide.

  Examples of the electrolyte include polyethylene oxide (PEO), polypropylene oxide (PPO), and ion conductive polymers (solid polymer electrolytes) such as copolymers thereof.

An electrolyte supporting salt for increasing ion conductivity may be selected according to the type of battery. Bipolar battery, in the case of bipolar lithium ion secondary battery, as the electrolyte support _{salt, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10, LiCF Examples of the lithium salt include ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, and Li (C ₂ F ₅ SO ₂ ) ₂ N.

  The amount of electrode constituent materials such as active materials, conductive assistants, binders, electrolytes (polymer matrix, ion conductive polymers, electrolytes, etc.), electrolyte support salts (lithium salts), etc. It is preferable to determine in consideration of ionic conductivity.

[Electrolyte layer]
The electrolyte layer may be a liquid, gel, or solid phase. In consideration of safety when the battery is damaged and prevention of liquid junction, the electrolyte layer is preferably a gel polymer electrolyte layer or an all-solid electrolyte layer. In consideration of safety when the battery is damaged and prevention of liquid junction, the electrolyte layer is preferably a gel polymer electrolyte layer or an all-solid electrolyte layer.

  Further, by using a gel polymer electrolyte layer as the electrolyte layer, the fluidity of the electrolyte is lost, the electrolyte is prevented from flowing out to the current collector, and the ion conductivity between the layers can be blocked. Examples of the gel electrolyte host polymer include PEO, PPO, PVdF, polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), PAN, PMA, and PMMA. Moreover, as a plasticizer, it is possible to use the electrolyte solution normally used for a lithium ion battery.

  Also, when an all-solid electrolyte layer is used as the electrolyte layer, the electrolyte does not flow, so that the electrolyte does not flow out to the current collector, and the ion conductivity between the layers can be blocked. When the all solid electrolyte layer is used, the current collector may have a high porosity because there is no fear of permeation of the electrolyte solution from the electrolyte layer. In particular, it is desirable to be an all-solid battery using an all-solid electrolyte layer (further using an all-solid electrolyte as an electrolyte component in the electrodes (positive electrode and negative electrode)). In the present invention, the electrolyte used for the bipolar battery may be a liquid, a gel or a solid. However, particularly when it is a solid, the oxidation reaction is unlikely to occur and the electrolyte is more durable. It is for improving.

  The gel polymer electrolyte is produced by adding an electrolyte solution usually used in a lithium ion battery to an all solid polymer electrolyte such as PEO or PPO. It may be produced by holding an electrolytic solution in a polymer skeleton having no lithium ion conductivity, such as PVdF, PAN, or PMMA. The ratio of the polymer constituting the gel polymer electrolyte to the electrolytic solution is not particularly limited. If 100% of the polymer is an all solid polymer electrolyte and 100% of the electrolytic solution is a liquid electrolyte, all of the intermediates are the concept of a gel polymer electrolyte. include. The all solid electrolyte includes all electrolytes having Li ion conductivity such as polymer or inorganic solid.

The electrolyte layer preferably contains a supporting salt in order to ensure ionic conductivity. When the battery is a lithium secondary battery, LiBF ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , or a mixture thereof is used as the supporting salt. it can. However, it is not necessarily limited to these. As described above, polyalkylene oxide polymers such as PEO and PPO often dissolve lithium salts such as LiBF ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , and LiN (SO ₂ C ₂ F ₅ ) _2. Yes. Moreover, excellent mechanical strength is exhibited by forming a crosslinked structure.

  Specifically, as the electrolyte layer, conventionally known materials include (a) polymer gel electrolyte (gel polymer electrolyte), (b) polymer solid electrolyte (all solid polymer electrolyte), (c) liquid electrolyte ( (Electrolyte solution) or (d) Separators (including nonwoven fabric separators) impregnated with these electrolytes can be used. Preferably, a gel electrolyte material that is excellent in output characteristics, capacity, reactivity, and cycle durability and is a low-cost material can be suitably used.

(A) Polymer gel electrolyte The polymer gel electrolyte refers to a polymer matrix in which an electrolytic solution is held. The polymer matrix (polymer) used as the polymer gel electrolyte is, for example, a polymer having polyethylene oxide in the main chain or side chain (PEO), a polymer having polypropylene oxide in the main chain or side chain (PPO), polyethylene glycol (PEG ), Polyacrylonitrile (PAN), polymethacrylic acid ester, polyvinylidene fluoride (PVdF), a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP), poly (methyl methacrylate) (PMMA) and their co-weights It is desirable to use PEO, PPO and their copolymers, or PVdF-HFP. The electrolyte solution, which electrolyte salt dissolved in a solvent, as the _{electrolyte, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl ₁₀ and the like inorganic acid anion As the solvent, at least one selected from organic acid anion salts such as salts, LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, etc. Ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), dimethyl carbonate (DMC), diethyl carbonate (DEC) and mixtures thereof are desirable.

  The ratio of the electrolytic solution in the gel electrolyte in the present invention is not particularly limited, but is preferably about several mass% to 98 mass% from the viewpoint of ionic conductivity. The present invention is particularly effective for a gel electrolyte having a large amount of electrolytic solution in which the proportion of the electrolytic solution is 70% by mass or more.

(B) Polymer solid electrolyte Examples of the all solid polymer electrolyte include known solid polymer electrolytes such as PEO, PPO, and copolymers thereof. The solid polymer electrolyte contains a lithium salt in order to ensure ionic conductivity. As the lithium salt, LiBF ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , or a mixture thereof can be used.

(C) Liquid electrolyte (electrolyte)
Examples of the electrolytic solution include those obtained by dissolving an electrolyte salt in a solvent. Here, as the _{electrolyte, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10 inorganic acid anion salts such _{as, LiCF 3 SO 3, Li (} CF 3 SO 2 ) At least one selected from organic acid anion salts such as ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, and the solvent is EC, PC, GBL, DMC, DEC and mixtures thereof Is desirable.

  Among electrolytes, a separator impregnated with a gel electrolyte is preferable. This is because a battery having excellent capacity and output characteristics can be configured.

(D) Separator impregnated with the electrolyte (including non-woven separator)
As the electrolyte that can be impregnated in the separator, the same electrolytes as those already described (a) to (c) can be used.

  Examples of the separator include a porous sheet and a nonwoven fabric made of a polymer that absorbs and holds the electrolyte.

  As the porous sheet, for example, a microporous separator can be used. Examples of the polymer include polyolefins such as polyethylene (PE) and polypropylene (PP); laminates having a three-layer structure of PP / PE / PP, polyimide, and aramid. The thickness of the separator cannot be unambiguously defined because it varies depending on the intended use, but a secondary battery for driving a motor such as an electric vehicle (EV), a hybrid electric vehicle (HEV), a fuel cell vehicle (FCV), etc. In the above application, it is desirable that the thickness is 4 to 60 μm in a single layer or multiple layers. The separator preferably has a fine pore size of 1 μm or less (usually a pore size of about several tens of nm) and a porosity of 20 to 80%.

As the nonwoven fabric, cotton, rayon, acetate, nylon, polyester; polyolefins such as PP and PE; conventionally known materials such as polyimide and aramid are used alone or in combination. The bulk density of the nonwoven fabric is not particularly limited as long as sufficient battery characteristics can be obtained by the impregnated polymer gel electrolyte. The porosity of the nonwoven fabric separator is preferably 50 to 90%. Furthermore, the thickness of the nonwoven fabric separator may be the same as that of the electrolyte layer, preferably 5 to 200 μm, particularly preferably 10 to 100 μm. When the thickness is less than 5 μm, the electrolyte retention deteriorates, and when it exceeds 200 μm, the resistance increases.

  Further, in the present invention, as described later, the electrolyte layer can be formed by any one of sputtering, vapor deposition, CVD, PVD, ion plating, and thermal spraying.

As an electrolyte layer suitable for such a forming method, in addition to lithium phosphate oxynitride glass described in Reference Example 5 described later, lithium phosphate, a thiolysicon compound, Li ₃ PO ₄ —Li ₂ S—SiS ₂ glass, Li ₂ S-P ₂ S ₅ glass or the like can be suitably used.

[Appearance structure of bipolar battery]
FIG. 3 is an external view of a bipolar battery according to the present invention.

  As shown in FIG. 3, the stacked bipolar battery 100 has a rectangular flat shape, and a positive electrode tab 11 </ b> A and a negative electrode tab 11 </ b> B for taking out electric power are drawn out from both sides thereof. The power generation element 160 is wrapped by an outer packaging material 180 of the bipolar battery 100, and the periphery thereof is heat-sealed. The power generation element 160 is sealed with the positive electrode tab 11A and the negative electrode tab 11B pulled out. Here, the basic configuration of the bipolar battery shown in FIG. 1 described above corresponds to the power generation element, and the power generation element 160 includes the current collector 10, the positive electrode 20, the electrolyte layer 30, and the negative electrode 40. A plurality of the single cells are stacked.

  The bipolar battery is not limited to a flat shape as shown in FIG. 3, and a wound bipolar battery may have a cylindrical shape or such a cylindrical shape. It is not particularly limited, for example, the shape may be deformed into a rectangular flat shape. In the said cylindrical shape thing, a laminate film may be used for the exterior material, and the conventional cylindrical can (metal can) may be used, for example, It does not restrict | limit.

  In addition, the tab and take-out shown in FIG. 3 are not particularly limited, and the positive electrode tab and the negative electrode tab may be pulled out from the same side, or the positive electrode tab and the negative electrode tab are divided into a plurality of parts respectively. It is not limited to the one shown in FIG. 3 such as taking out from each side.

[Battery exterior materials]
As a battery exterior material, a conventionally known metal can case can be used, and a bag-like case that can cover a unit cell using a laminate film containing aluminum can be used. For example, a laminate film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order can be used as the laminate film, but the laminate film is not limited thereto.

[Spacer (sealant or peripheral insulating layer)]
Spacers (also called sealants or peripheral insulating layers) are used for the purpose of preventing adjacent collectors in the battery from contacting each other and short-circuiting due to slight unevenness at the end of the laminated electrode. It is formed around the electrode. As the spacer (sealant or peripheral insulating layer), for example, polyolefin resin such as PE and PP, epoxy resin, rubber, polyimide and the like can be used from the viewpoint of corrosion resistance, chemical resistance, film forming property, economical efficiency, and the like. Is preferably a polyolefin resin. However, it is not limited to these (see Example 1 and Reference Example 5 described later).

  Further, in the present invention, as described later, the spacer (sealant or peripheral insulating layer) can be formed by any one of sputtering, vapor deposition, CVD, PVD, ion plating, and thermal spraying.

  As a spacer suitable for such a forming method, silica, magnesia, yttria and the like can be suitably used in addition to alumina described in Reference Example 5 described later.

[Positive electrode and negative electrode terminal plate]
The positive electrode and the negative electrode terminal plate are used as necessary. For example, when the output electrode terminal (tab) is directly taken out from the outermost current collector, the positive electrode and the negative electrode terminal plate may not be used.

  As a material for the positive electrode and the negative electrode terminal plate, a material used in a conventionally known lithium ion battery can be used. For example, aluminum, copper, titanium, nickel, stainless steel, and alloys thereof can be used. Aluminum is preferably used from the viewpoints of corrosion resistance, ease of production, economy, and the like. Furthermore, from the viewpoint of suppressing internal resistance at the terminal portion, the thickness of the positive electrode and the negative electrode terminal plate is usually preferably about 0.1 to 2 mm.

[Positive electrode and negative electrode lead]
The positive electrode and the negative electrode lead are also used as necessary. For example, when the output electrode terminal (tab) is directly taken out from the outermost current collector (see FIG. 3), the positive electrode and the negative electrode lead may not be used.

  As a material for the positive electrode and the negative electrode lead, a lead used in a known lithium ion battery can be used. In addition, the parts removed from the battery exterior material should be heat-insulating so that they do not affect products (for example, automobile parts, especially electronic devices) by touching peripheral devices or wiring and causing leakage. It is preferable to coat with a heat shrinkable tube or the like.

  The bipolar battery of the present invention is used as a power source for driving a vehicle or an auxiliary power source that requires a high volume energy density and a high volume output density as a large capacity power source for an electric vehicle, a hybrid electric vehicle, a fuel cell vehicle, and a hybrid fuel cell vehicle. It can be suitably used.

[Battery]
The bipolar battery of the present invention may constitute a battery pack by combining a plurality of the serial batteries in series, in parallel, or in series and parallel. Capacitance and voltage can be freely adjusted by paralleling in series.

  The number of batteries in the assembled battery and the manner of connection may be determined according to the output and capacity required of the battery. When the assembled battery is configured, the stability of the battery is increased as compared with the unit cell. By configuring the assembled battery, the influence on the entire battery due to the deterioration of one cell can be reduced.

  FIG. 4 is an external view schematically showing a typical embodiment of the assembled battery according to the present invention.

  As shown in FIG. 4, the assembled battery 300 according to the present invention includes a plurality of bipolar batteries connected in series or in parallel to form an assembled battery module 250, and the assembled battery modules 250 are further connected in series or The assembled battery 300 can also be formed by connecting in parallel. FIG. 4 shows a plan view (FIG. 4A), a front view (FIG. 4B), and a side view (FIG. 4C) of the assembled battery 300, and the assembled battery module 250 is electrically connected like a bus bar. The assembled battery modules 250 are stacked in a plurality of stages using the connection jig 310. How many bipolar batteries are connected to create the assembled battery module 250, and how many assembled battery modules 250 are stacked to create the assembled battery 300 depends on the vehicle (electric vehicle) to be mounted. It may be determined according to the battery capacity and output.

[vehicle]
The bipolar battery of the present invention or an assembled battery formed by combining a plurality of these batteries can be preferably used as a power source for driving a vehicle. When the battery or the assembled battery of the present invention is used in a hybrid vehicle, an electric vehicle, or a fuel cell vehicle, the life and reliability of the vehicle can be improved. However, the application is not limited to automobiles. For example, it can be applied to various power sources for moving bodies such as trains, and can also be used as a mounting power source for uninterruptible power supplies. is there.

  FIG. 5 is a conceptual diagram of a vehicle equipped with the assembled battery of the present invention.

  As shown in FIG. 5, in order to mount the assembled battery 300 on a vehicle such as the electric vehicle 400, the battery pack 300 is mounted under the seat at the center of the vehicle body of the electric vehicle 400. This is because if it is installed under the seat, the interior space and the trunk room can be widened. The place where the assembled battery 300 is mounted is not limited to the position under the seat, but may be a lower part of the rear trunk room or an engine room in front of the vehicle. The electric vehicle 400 using the assembled battery 300 as described above has high durability and can provide sufficient output even when used for a long period of time. Furthermore, it is possible to provide electric vehicles and hybrid vehicles that are excellent in fuel efficiency and running performance. A vehicle equipped with the assembled battery of the present invention can be widely applied to a hybrid vehicle, a fuel cell vehicle and the like in addition to an electric vehicle as shown in FIG.

[Production method of bipolar battery]
The manufacturing method of the bipolar battery of the present invention is not particularly limited, and a conventionally known manufacturing method can be used.

  In particular, regarding the formation of the silicon layer of the current collector, which is a characteristic part of the bipolar battery of the present invention, and further the formation of the carbon layer (carbon layer), the current collector can be formed using a vacuum process. Specifically, PVD (Physical Vapor Deposition) represented by sputtering, vapor deposition, ion plating and thermal spraying, CVD (Chemical Vapor Deposition); Chemical Vapor Deposition or Chemical It is desirable to form by any one of the vapor deposition method.

  Examples of the sputtering method include, as shown in Reference Example 5, an electron cyclotron resonance sputtering method suitable for forming a current collector and an electrode, a radio frequency (RF) sputtering method suitable for forming an electrolyte layer and a peripheral insulating layer, Examples include, but are not limited to, a magnetron sputtering method, a counter target sputtering method, a mirrortron sputtering method, and an ion beam sputtering method.

  Examples of the vapor deposition method include CVD (chemical vapor deposition method) and PVD (physical vapor deposition method).

  Examples of the CVD include, but are not limited to, thermal CVD, plasma CVD, photo CVD, epitaxial CVD, and atomic layer CVD.

  Examples of PVD include, but are not limited to, sputtering, pulsed laser deposition, vacuum deposition, ion plating, molecular beam epitaxy, electron beam deposition, and thermal spraying.

  The silicon layer may be a thin plate as it is, or may be formed using sputtering, vapor deposition, ion plating, thermal spraying, or other PVD or CVD, which are vacuum processes as described above. In this method, it is possible to produce a current collector layer that is considerably thinner than in the past, and it is possible to produce an ultra-high density battery. In addition, by stacking thin-layer current collectors like silicon layer-carbon layer-silicon layer-carbon layer-, current collectors are suitable for series assembled batteries that are resistant to bending and have both conductivity and ion blocking characteristics. You can also get the electric body.

  In addition, regarding the current collector layer as shown in FIGS. 2A and 2B, as shown in the examples described later, silicon (particles or fibers), a resin, and if necessary, an appropriate solvent is added. A sheet-shaped current collector with a predetermined thickness can be produced by kneading and dispersing (uniformly) silicon (particles or fibers) in the resin (uniformly) and thinning it by T-die molding or the like. However, the present invention is not limited to these production methods.

  In addition, as above-mentioned as a manufacturing method of another battery structural member, a conventionally well-known manufacturing method can be used as above-mentioned. For example, in the electrode formation method, each of the positive electrode and negative electrode active materials, which is a general battery manufacturing method, is slurried together with components constituting other electrodes such as a binder, and the positive electrode slurry is formed on one surface of the current collector layer. By using a method of applying a negative electrode slurry to the other surface of the current collector layer, a bipolar electrode formed by forming a positive electrode and a negative electrode can be formed. Furthermore, in the present invention, as another method for producing an electrode, there is a method of forming electrodes (positive electrode, negative electrode) and further battery constituent members such as an electrolyte layer and a peripheral insulating layer using a vacuum process. Specifically, the current collector is formed by sputtering, vapor deposition, ion plating, thermal spraying, other PVD, CVD, etc., on the electrode active material of at least one of the positive electrode and the negative electrode, and further on the battery constituent members such as the electrolyte layer and the peripheral insulating layer. The layers may be sequentially formed. Thereby, battery constituent members such as an electrode and further an electrolyte membrane and a peripheral insulating layer can be thinned, and the entire battery can be made thin and light. A method of forming battery components such as electrodes and further electrolyte membranes and peripheral insulating layers using such a vacuum process is a conventional coating method particularly when the current collector is formed into a thin film using the same vacuum process. Compared to the case where the current collector is produced, the durability of the current collector is low, which is realistic. In this case, each battery component such as a current collector, electrode, and electrolyte membrane and peripheral insulating layer is extremely thin, so that a very large electrode area can be accommodated in the same volume, resulting in ultra-high output. (Refer to Reference Example 5).

  Hereinafter, the present invention will be described in detail using examples.

Example 1
<Creation of current collector>
70 vol% of polypropylene and 30 vol% of silicon (silicon) particles having an average particle diameter of 1 μm were kneaded and dispersed at 220 ° C. by a twin screw extruder. This was thinned by T-die molding to prepare a 30 μm thick sheet, which was used as a current collector.

<Formation of electrode>
LiMn ₂ O ₄ is used for the positive electrode active material, acetylene black is used for the conductive auxiliary agent, and polyvinylidene fluoride (PVdF) is used for the binder. The positive electrode active material, the conductive auxiliary agent, and the binder are 85% by mass, 5% by mass, and 10% by mass, respectively. 60 parts by mass of NMP was added as a slurry viscosity adjusting solvent to 40 parts by mass of the compounding agent and mixed to prepare a positive electrode slurry.

  The positive electrode slurry is applied to a portion other than the margin portion on one side of the current collector having a thickness of 30 μm and 125 mm × 75 mm so that the entire circumference of the current collector becomes a margin portion having a width of 5 mm and dried. Thus, a positive electrode was formed.

  Hard carbon is used for the negative electrode active material, PVdF is used for the binder, the negative electrode active material and the binder are blended in 90% by mass and 10% by mass, respectively, and 60 parts by mass of NMP is adjusted for slurry viscosity with respect to 40 parts by mass of the compounding agent. A negative electrode slurry was prepared by adding as a solvent and mixing.

  The negative electrode slurry is applied to the opposite surface of the current collector on which the positive electrode has been applied, and the negative electrode slurry is applied to a portion other than the margin portion and dried so that the entire circumference of the current collector becomes a margin portion having a width of 5 mm. Formed.

  Thereby, a bipolar electrode having a positive electrode and a negative electrode formed on both sides of the current collector was prepared.

<Formation of gel electrolyte>
Polyvinylidene fluoride (PVdF) 10% by mass, electrolyte solution 1.0M LiPF ₆ , propylene carbonate (PC) + ethylene carbonate (EC) (1: 1) 90% by mass, and PVdF and electrolyte total amount 100% A pregel solution was prepared by mixing 200 parts by mass of dimethyl carbonate (DMC) with respect to the parts.

  The pregel solution is applied on the bipolar electrode formed in advance and on a polypropylene separator having a thickness of 30 μm, DMC is removed by vacuum drying, and gel electrolyte is contained in the positive electrode and the negative electrode (the void portion thereof). Thus, a bipolar electrolyte electrode and a gel electrolyte layer comprising a polypropylene separator (a porous portion thereof) containing a gel electrolyte were obtained.

<Configuration of electrode laminate>
As shown in FIG. 2, two bipolar electrodes were stacked so that the positive electrode and the negative electrode face each other with the gel electrolyte layer interposed therebetween to form a single cell layer.

  By repeating this operation, a bipolar electrode and a gel electrolyte layer are sequentially laminated so that 12 single battery layers are formed, and a negative electrode is provided on one side of the current collector and a positive electrode is provided on the other side of the current collector. An electrode laminate (power generation element) was constructed.

<Tab for voltage detection>
A voltage monitoring tab was disposed on the current collector of each cell layer of the obtained electrode laminate.

  The tab disposed on the current collector of the single cell layer at the center of the electrode stack has a width of 30 mm, and the next two tabs to be attached to the current collector of the single cell layer close to the center are each wide. Use a tab of 10 mm and a tab of 5 mm in width to attach to the current collector of the single cell layer on the outermost part of the battery, and adhere with a carbon-based conductive adhesive at intervals so that the tabs do not touch each other vertically did.

  The tabs were all 20 μm thick and made of aluminum.

<Structure of stacked bipolar battery>
A sealant was sandwiched between the current collectors in the peripheral portion (margin) of the current collector so that the gel electrolyte did not move beyond the current collector adjacent to the electrode laminate.

  Next, this electrode laminate was vacuum-sealed using an aluminum laminate exterior material, and the outer periphery was sealed by thermal fusion, to produce a 12-layer laminated bipolar battery.

<Test>
In this way, five laminated bipolar batteries with 12 direct structures were prepared, and 1 kHz AC impedance immediately after the production was measured and recorded. After 0.2C to 50V charge and 0.2 to 30V discharge, charge and discharge 10 times at 1C, and finally 50V full charge state (average voltage 4.17V), and then 60 ° C storage test I did it. In this test, the voltage of each layer of each battery is monitored periodically via the voltage monitoring tab, and a cell layer that has dropped by 0.1 V or more from the average voltage of each cell layer is regarded as an abnormal cell layer. The number was recorded. In addition, it was excluded from the aggregation of average values.

Reference example 2
In Example 1, silicon having a thickness of 2 μm was deposited on the surface of a carbon sheet having a thickness of 30 μm, and a current collector having a two-layer structure composed of a carbon layer and a silicon layer was used. Of these, a stacked bipolar battery was prepared and tested in the same manner as in Example 1 except that the silicon layer was used as the negative electrode side and the positive electrode side was used as the carbon layer.

Reference example 3
In Example 1, a laminated bipolar battery was prepared and tested in the same manner as in Example 1 except that a silicon substrate having a thickness of 200 μm was used as the current collector.

Example 4
In Example 1, 65 vol% polypropylene, 30 vol% silicon (silicon) particles having an average particle diameter of 1 μm, and 5 vol% carbon black having an average secondary particle diameter of 0.4 μm at 220 ° C. by a twin screw extruder. Kneaded and dispersed. This was thinned by T-die molding to prepare a 30 μm thick sheet. A laminated bipolar battery was prepared and tested in the same manner as in Example 1 except that this was used as a current collector.

Reference Example 5
<Creation of thin film battery>
Silicon having a thickness of 2 mm × length 50 mm × width 50 mm was used as a base material, and a lithium titanate thin film as a negative electrode was attached to the center of the surface by electron cyclotron resonance sputtering in a shape of 1 μm thickness × length 40 mm × width 40 mm. Next, lithium phosphate oxynitride glass having a thickness of 2 μm × length of 45 mm × width of 45 mm was formed by a radio frequency (RF) sputtering method to obtain an electrolyte membrane. Further, a lithium cobaltate thin film was applied as a positive electrode by electron cyclotron resonance sputtering in a shape of 1 μm thick × 40 mm long × 40 mm wide. Here, as a peripheral insulating layer for preventing a short circuit at the peripheral portion, alumina was formed by RF sputtering in an outer shape of 50 mm × 50 mm and a central portion of 40 mm × 40 mm in a square shape with a thickness of 1 μm. On top of this, a silicon thin film as a current collector was attached by RF sputtering in a shape of 2 μm thickness × 40 mm length × 40 mm width to form a battery for one cell. Further thereon, a laminated bipolar battery having a three-cell series structure was formed by repeating the negative electrode, the electrolyte layer, the positive electrode, the peripheral insulating layer, and the current collector twice in this order.

<Test>
In this way, 20 stacked bipolar batteries were prepared, 0.2C to 8V charged and 0.2 to 5V discharged, then charged and discharged 10 times at 1C, and finally 8V full charged. After making it into a state, a 60 ° C. storage test was conducted. In this test, the number of batteries with a voltage drop of 0.1 V or more from the average voltage of each laminated battery was recorded as an abnormal battery. Since the assembled battery of this example was not provided with a voltage monitor terminal, the number of abnormal cells was determined for each stacked battery. Therefore, “total number of cells” in Reference Example 5 in Table 1 below is read as “total number of batteries”.

Comparative Example 1
In Example 1, a laminated bipolar battery was prepared and tested in the same manner as in Example 1 except that 30 μm SUS304 foil was used as a current collector.

Comparative Example 2
In Example 1, a laminated bipolar battery was prepared and tested in the same manner as in Example 1 except that 30 μm aluminum foil was used as the current collector. In this experiment, only one stacked battery was used.

  The results of the tests of Examples 1 and 4, Reference Examples 2, 3, 5 and Comparative Examples 1 and 2 are shown in Table 1 below.

From the results of Table 1 above, in Examples 1, 4 and Reference Examples 2, 3, and 5, abnormal cells after 90 days were not detected, and the current collector was stable for a long time and had excellent durability. It was confirmed that a bipolar battery was formed. On the other hand, it was confirmed that the existing metal foil current collectors such as SUS foil and aluminum foil used in Comparative Examples 1 and 2 were oxidized in the long term and had a problem in durability as described in the background art. It was. In particular, since lithium manganese oxide (LiMn ₂ O ₄ ) having a full charge voltage of 4 V or more was used as the positive electrode active material, an SUS foil having oxidation resistance was used for Examples 1 and 4 and Reference Examples 2 and 3. In Comparative Example 1 used for the current collector, all abnormalities were observed after 15 days. In Comparative Example 2 using the aluminum foil as the current collector, liquid leakage occurred between the electrodes during initial charging, and the battery did not function. As a result, the deterioration appeared very quickly (Note that this test is an acceleration life test, and the battery life can be diagnosed in a short period of time).

10 Current collector (current collector layer, silicon layer or silicon-containing layer),
11 electrode tabs,
11A positive electrode tab,
11B negative electrode tab,
20 positive electrode (positive electrode active material layer),
30 electrolyte layer,
40 negative electrode (negative electrode active material layer),
50 silicon particles (silicon particles + carbon particles),
52 Fibrous silicon (fibrous silicon + fibrous carbon),
54 Silicon sheet (carbon-containing silicon sheet),
60 resin,
100 bipolar battery,
160 power generation elements,
180 exterior materials (eg laminate films),
250 battery module,
300 battery packs,
310 connection jig,
400 Electric car.

Claims (7)

An electrode comprising a current collector, a positive electrode electrically coupled to one surface of the current collector, and a negative electrode electrically coupled to the other surface of the current collector;
In a bipolar battery comprising an electrolyte layer disposed between a plurality of the electrodes,
The current collector uses a material containing single silicon (Si) as a component of a conductive material that bonds the positive electrode and the negative electrode by electronic conductivity,
The bipolar lithium ion battery is characterized in that, as a layer constituting the current collector, silicon is in the form of particles or fibers, and is arranged in a resin in a state where conduction between the front and back sides can be taken.   2. The bipolar lithium ion battery according to claim 1, wherein the resin is one of polyolefin, polyamide, polyimide, polyamideimide, epoxy resin, bakelite, or a plurality thereof. The layer constituting the current collector is
The silicon is in the form of particles or fibers, and the silicon layer is disposed in the resin in a state where conduction between the front and back sides can be taken, or the silicon is in the form of particles or fibers and further has electronic conductivity other than the silicon A silicon-containing layer that includes an auxiliary material and is disposed in the resin in a state where conduction between the front and back surfaces of the silicon and the auxiliary material can be taken;
The bipolar lithium ion battery according to claim 1, wherein the bipolar lithium ion battery comprises one or more layers including The layer constituting the current collector is in a state where the silicon is particles or fibers, and further includes an auxiliary material having electronic conductivity other than the silicon, and the silicon and the auxiliary material can be electrically connected between the front and back surfaces. Having a silicon-containing layer disposed in the resin;
The bipolar lithium ion battery according to claim 1, wherein carbon is contained as the auxiliary material in the silicon-containing layer.   A bipolar lithium ion battery, wherein the battery according to any one of claims 1 to 4 is an all-solid battery. In the manufacturing method of the battery of any one of Claims 1-5,
Formation of the layer constituting the current collector is carried out by adding particles or fibrous silicon and the resin, and if necessary, adding the auxiliary material and an appropriate solvent and kneading the particles or fibrous silicon. Further, the bipolar material is produced by dispersing the auxiliary material added if necessary in the resin and making it into a thin film. In the manufacturing method of the battery of any one of Claims 1-6,
Production of bipolar lithium ion battery characterized in that at least one of positive electrode and negative electrode active material is formed on current collector layer by any of sputtering, vapor deposition, CVD, PVD, ion plating and thermal spraying methods Method.

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