JP5343500B2 - Bipolar electrode and bipolar secondary battery using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bipolar electrode using a collector having lighter weight as compared with a metal foil collector and for preventing liquid junction between a cathode layer and an anode layer in the bipolar electrode. <P>SOLUTION: The bipolar electrode 16 is composed of a collector 11 containing conductive resin layers 2a-2c, a cathode layer 13 electrically connected with one face of the collector 11, and an anode layer 15 electrically connected with the other face of the collector 11. The collector 11 includes thin metal layers 1a, 1b thinner than the resin layers 2a-2c, and the metal layer 1a is pinched by the resin layers 2a, 2b and the metal layer 1b is pinched by the resin layers 2b, 2c. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a bipolar electrode comprising a current collector made of a resin layer having conductivity (hereinafter also referred to simply as a resin layer) formed using a resin or a conductive polymer to which a conductive filler is added, and The present invention relates to a bipolar secondary battery using the electrode. The bipolar secondary battery using the bipolar electrode of the present invention is used as a driving power source for an electric vehicle, a hybrid electric vehicle and the like, for example.

  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.

  In general, a lithium ion secondary battery is configured by applying a positive electrode or a negative electrode active material or the like to a positive electrode or negative electrode current collector using a binder. In the case of a bipolar battery, a positive electrode active material is applied to one surface of the current collector using a binder and a positive electrode layer is applied to the opposite surface, and a negative electrode active material is applied to the opposite surface using a binder. A bipolar electrode having a negative electrode layer is formed.

In such a lithium ion secondary battery, conventionally, a metal foil (metal current collector foil) has been used as a current collector. In recent years, so-called resin current collectors composed of a resin layer having a conductivity formed by using a resin or a conductive polymer to which a conductive filler is added instead of a metal foil have been proposed (for example, Patent Document 1). Such a resin current collector is lighter than a metal current collector foil, and is expected to improve battery output.
JP-A 61-285664

  However, when the conventional resin current collector described in Patent Document 1 is applied to a bipolar lithium ion secondary battery, ions are transmitted through the resin current collector of the bipolar electrode, and the positive electrode in the bipolar electrode It has been found that there is a problem that a liquid junction occurs between the layer and the negative electrode layer.

  Accordingly, an object of the present invention is a bipolar electrode using a current collector that is lighter than a metal foil current collector and can prevent a liquid junction between the positive electrode layer and the negative electrode layer in the bipolar electrode. Is to provide.

  In the present invention for achieving the above object, the current collector comprises a resin layer having conductivity and a metal layer thinner than the resin layer, and the metal layer is sandwiched between the resin layers. A bipolar electrode characterized by having a structure.

  According to the present invention, the resin collector of the bipolar electrode has a structure in which a metal layer thinner than the conductive resin layer is sandwiched between the resin layers, so that the metal layer transmits ions of the resin layer. By blocking the movement, a liquid junction between the positive electrode layer and the negative electrode layer in the bipolar electrode due to ion permeation in the current collector can be prevented, and a lighter bipolar electrode can be provided compared to the metal foil current collector. . As a result, a bipolar secondary battery using a bipolar electrode with improved lifetime characteristics and excellent long-term reliability can be constructed. Furthermore, since a conductive resin layer is used for a part of the current collector, the bipolar type is lighter than the metal foil current collector and can improve battery output when viewed as a whole. A bipolar secondary battery using electrodes can be constructed.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the technical scope of the present invention should be determined based on the description of the scope of claims, and is not limited only to the following embodiments. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

<I> General basic configuration of a bipolar secondary battery using the bipolar electrode of the present invention A bipolar secondary battery using the bipolar electrode of the present invention has a plurality of bipolar electrodes as a general basic configuration. A bipolar electrode and an electrolyte layer are alternately stacked, each of which includes a mold electrode and an electrolyte layer disposed between the bipolar electrodes. The bipolar electrode includes a current collector, a positive electrode layer electrically coupled to one surface of the current collector, and a negative electrode layer electrically coupled to the other surface of the current collector. It has the composition which becomes.

  The kind of the bipolar secondary battery of the present invention is not particularly limited, and examples thereof include a bipolar secondary battery using a non-aqueous electrolyte, preferably a bipolar lithium ion secondary battery. This is because a bipolar lithium ion secondary battery has a large cell (single cell layer) voltage, can achieve high energy density and high output density, and is excellent as a vehicle driving power source or an auxiliary power source. In addition, when distinguished by the structure and form of the battery, it is not particularly limited such as a stacked (flat) battery or a wound (cylindrical) battery, and can be applied to any conventionally known structure.

  When viewed in terms of the electrical connection form (electrode structure) in the bipolar secondary battery, it can be said that the bipolar type is an internal series connection type secondary battery.

  Similarly, there is no particular limitation even when distinguished by the electrolyte form of the bipolar secondary battery. For example, the present invention can be applied to any of a liquid electrolyte type battery in which a separator is impregnated with a nonaqueous electrolytic solution, a polymer gel electrolyte type battery also called a polymer battery, and a solid polymer electrolyte (all solid electrolyte) type battery. With respect to the polymer gel electrolyte and the solid polymer electrolyte, these can be used alone, or the polymer gel electrolyte or the solid polymer electrolyte can be used by impregnating the separator.

  FIG. 1 shows an outline of a general basic configuration of a bipolar lithium ion secondary battery (hereinafter also simply referred to as “bipolar secondary battery”), which is a typical embodiment of the bipolar secondary battery of the present invention. It is the cross-sectional schematic diagram which represented typically. In the present specification, a bipolar lithium ion secondary battery will be described in detail as an example, but the technical scope of the present invention is not limited to such a form.

  The bipolar secondary battery 10 shown in FIG. 1 has a structure in which a substantially rectangular power generation element 21 in which a charge / discharge reaction actually proceeds is sealed inside a laminate sheet that is a battery exterior material 29.

  Here, the battery element 21 has a plurality of bipolar electrodes 16 in which the positive electrode layer 13 is formed on one surface of the current collector 11 and the negative electrode layer 15 is formed on the other surface. Each bipolar electrode 16 is laminated via an electrolyte layer 17 to form a power generation element 21. At this time, each bipolar electrode is arranged such that the positive electrode layer 13 of one bipolar electrode 16a and the negative electrode layer 15 of another bipolar electrode 16b adjacent to the one bipolar electrode 16a face each other through the electrolyte layer 17. 16 and electrolyte layers 17 are alternately laminated. That is, the electrolyte layer 17 is sandwiched between the positive electrode layer 13 of one bipolar electrode 16a and the negative electrode layer 15 of another bipolar electrode 16b adjacent to the one bipolar electrode 16a.

  The positive electrode layer 13 of one bipolar electrode 16 a, the electrolyte layer 17, and the negative electrode layer 15 of another adjacent bipolar electrode 16 b constitute one single battery layer (= battery unit or single cell) 19. Therefore, it can be said that the bipolar secondary battery 10 has a configuration in which a plurality of single battery layers 19 are stacked. Further, in order to prevent leakage of the electrolyte layer 17, a seal portion 31 is disposed around the unit cell layer 19. By providing the seal portion 31, the adjacent current collectors 11 can be insulated. The positive electrode layer 13 is formed on only one side of the outermost current collector 11a on the positive electrode layer side located in the outermost layer of the power generation element 21. Further, the negative electrode layer 15 is formed on only one side of the outermost current collector 11b on the negative electrode layer side located in the outermost layer of the power generation element 21.

  Furthermore, in the bipolar secondary battery 10, the outermost layer current collector 11 a on the positive electrode layer side is extended to form a positive electrode tab 25, which is derived from a laminate sheet that is a battery outer packaging material 29. On the other hand, the outermost layer current collector 11 b on the negative electrode layer side is extended to form a negative electrode tab 27, which is similarly derived from a laminate sheet that is a battery exterior material 29.

  In the bipolar secondary battery, the current flows in the thickness direction (stacking direction) due to the above configuration, so the electron conduction path is significantly shorter than that of the non-bipolar stacked battery. Become.

  However, in the present invention, the bipolar electrode 16 in which the positive electrode layer 13 is formed on one surface and the negative electrode layer 15 is formed on the other surface also in the outermost layer current collector 11a on the positive electrode layer side located in the outermost layer. May be used. Similarly, the outermost current collector 11b on the negative electrode layer side located in the outermost layer also uses a bipolar electrode 16 in which the positive electrode layer 13 is formed on one surface and the negative electrode layer 15 is formed on the other surface. Also good.

<II> About the structure of the current collector, which is a characteristic part of the bipolar electrode of the bipolar secondary battery of the present invention. The bipolar secondary battery according to the present invention is characterized by the bipolar type having the above-described general basic structure. In the secondary battery, the current collector of the bipolar electrode includes a conductive resin layer and a metal layer thinner than the resin layer, and the metal layer is sandwiched between the resin layers. By adopting such a configuration, it is possible to prevent a liquid junction between the positive electrode layer and the negative electrode layer in the bipolar electrode due to ion permeation in the resin layer, and the bipolar type with improved long-term reliability with improved life characteristics. A secondary battery can be constructed. Furthermore, since a conductive resin layer is used for a part of the current collector, the bipolar type is lighter than the metal foil current collector and can improve battery output when viewed as a whole. A bipolar secondary battery using electrodes can be constructed. In addition, the structure in which the metal layer is sandwiched between the resin layers (laminated structure of the metal layer and the resin layer) is made into a multilayer structure of three or more layers, so that the bipolar secondary battery using bipolar electrodes Vibration resistance can be improved. For this point, refer to the charge / discharge characteristics of the two-layer structure of Comparative Example 2, the three-layer structure of Example 1, and the five- to six-layer structures of Examples 6-8. Moreover, it is possible to form a current collector in which the resin layer and the metal layer that can withstand the positive electrode potential and the negative electrode potential for a long period of time are selectively disposed on the positive electrode layer and the negative electrode layer side surface layer. With this configuration, it is possible to construct a bipolar secondary battery using a bipolar electrode with further improved lifetime characteristics and excellent long-term reliability.

(1) About the structure of lamination | stacking arrangement | positioning with the metal layer in an electrical power collector, and the resin layer which has electroconductivity The electrical power collector which is the characteristic part of the bipolar electrode of this invention is demonstrated using drawing. 2A to 2H are each a bipolar type battery schematically showing an example of a laminated arrangement of a metal layer in a current collector and a resin layer having conductivity in the bipolar type electrode of the bipolar type secondary battery of the present invention. It is the cross-sectional schematic of the arbitrary bipolar electrodes in a secondary battery.

(A) One Configuration Example Arranged with Three Layers In the bipolar electrode 16 shown in FIG. 2A, the current collector 11 is made of conductive resin layers 2a and 2b and a metal layer 1 thinner than the resin layers 2a and 2b. It is configured. And the said metal layer 1 has the structure pinched | interposed by the said resin layers 2a and 2b (clamped). In other words, the current collector 11 has a resin layer 2a-metal layer 1-resin layer 2b 3 in which the metal layer 1 is an intermediate layer and the resin layers 2a and 2b are joined via the metal layer 1. It has a layered structure. That is, in this configuration example, from the viewpoint of reducing the weight of the resin current collector and ensuring safety against micro short-circuits, the resin layer having a conductive property is thickened, and from the viewpoint of weight reduction and imparting ion permeation prevention, the resin A metal layer thinner than the layer is formed in an intermediate layer (structure sandwiched between resin layers).

  Further, in this configuration example, the conductive resin layer 2a is disposed on the positive electrode layer 13 side, and the conductive resin layer 2b is disposed on the negative electrode layer 15 side. The metal layer 1 that is in contact with the resin layer 2 b on the surface layer on the negative electrode layer 15 side is disposed at the center of the current collector 11.

Here, the metal layer 1 in contact with the conductive resin layer 2b on the surface layer on the negative electrode layer 15 side is disposed in the center of the current collector 11, as shown in FIG. thickness D ₂ center (center) M ₂ is means that is disposed at a position coincident with the center (center) M ₁ in the thickness D ₁ of the current collector 11.

  As described above, when a plurality of conductive resin layers are stacked and arranged, each conductive resin layer may be composed of one kind of component (resin component) like a conductive polymer. And you may be comprised by 2 or more types of components like a conductive filler (metal component) and resin (resin component). The same can be said for other configuration examples shown below having the same configuration.

  In this configuration example, the resin collector of the bipolar electrode is used as an example of a structure in which the metal layer is sandwiched between the resin layers, and an alternate lamination having a three-layer laminated structure of resin layer 2a-metal layer 1-resin layer 2b. By adopting a structure, ion permeation in the resin layer can be prevented by the metal layer 1 as an intermediate layer. Thereby, a liquid junction between the positive electrode layer and the negative electrode layer in the bipolar electrode can be prevented, and a bipolar secondary battery with improved long-term reliability and improved life characteristics can be constructed. The same can be said for other configuration examples shown below having the same configuration.

  Furthermore, in this configuration example, since a conductive resin layer is used for a part of the current collector, it is lighter than the metal foil current collector and the output of the battery is improved when viewed as a whole. It is possible to construct a bipolar secondary battery using a possible bipolar electrode. Further, it is particularly excellent to make the thickness of the metal layer 1 thinner than the thickness of the conductive resin layer 2 from the viewpoints of weight reduction, ensuring safety against a short circuit, and imparting ion permeation prevention. However, in the present invention, a metal layer thinner than any one of the conductive resin layers may be included as in Example 9 described later, and the remaining conductive resin layer has the same thickness as the metal layer ( Example 9) may be used, or it may be thinner than the metal layer. Preferably, as in Examples 1 to 8, it is desirable that all metal layers are thinner than all resin layers. The same can be said for the other configuration examples shown below (including the present invention in general). In addition, from the viewpoint of productivity and economy, a configuration example in which three layers including the present configuration example are arranged is desirable.

  In addition, as an example of the structure in which the metal layer is sandwiched between the resin layers, the vibration resistance performance of the bipolar secondary battery is improved by making the alternating layered structure of the metal layer and the resin layer into a multilayer structure. This is particularly noticeable when the positive electrode layer 13 and the negative electrode layer 15 are in contact with the resin layers 2a and 2c as in this configuration example. This is because when the active material in the positive electrode layer 13 and the negative electrode layer 15 expands and contracts due to charge and discharge, the conductive resin layer in contact with the positive electrode layer and the negative electrode layer relieves stress due to the expansion and contraction. Can be expanded and contracted. In addition, even with external vibrations and shocks, the conductive resin layer can be expanded and contracted to ease external loads such as vibrations and shocks, improving the vibration resistance of bipolar secondary batteries. It is to do. The same can be said for other configuration examples shown below having the same configuration.

  In addition, when the positive electrode layer 13 and the negative electrode layer 15 are in contact with the conductive resin layers 2a and 2c as in this configuration example, when an internal short circuit occurs as in the case of a metal current collector foil, current flows in the plane direction. It is excellent in that it can effectively prevent flow and local heat generation.

  In the bipolar battery, the conductive resin layers 2a and 2c have a conductive resin layer, which will be described later, depending on the volume resistivity, when a current flows for a very short distance in the thickness direction. If it is about the thickness range, the resistance in the thickness direction of the conductive resin layer is a region that can be almost ignored with respect to the entire internal resistance of the battery. Therefore, there is no problem with the conductivity of the bipolar electrode. On the other hand, when a current is attempted to flow in the surface direction of the resin layer having conductivity, the surface resistance of the resin layer having conductivity is very large, and the current flows in the surface direction when an internal short circuit occurs. This is because it can be effectively suppressed and a local heat generation phenomenon can be prevented. The same can be said for other configuration examples shown below having the same configuration.

  Furthermore, it is possible to form a current collector that can withstand the positive electrode potential and the negative electrode potential for a long period of time. That is, in this configuration example, the conductive resin layer 2a disposed on the positive electrode layer side is provided with a conductive resin that can withstand the positive electrode potential, and the conductive resin layer 2b disposed on the negative electrode layer side is provided on the negative electrode layer side. Therefore, it is possible to select a resin having conductivity that can withstand the negative electrode potential. Therefore, it is possible to form a current collector that can withstand a positive electrode potential and a negative electrode potential for a long period of time, and a bipolar electrode. In addition, in the configuration in which the positive electrode layer 13 and the negative electrode layer 15 are in contact with the conductive resin layers 2 a and 2 c, there is no metal layer in the vicinity of the positive electrode layer 13 and the negative electrode layer 15. The same can be said for other configuration examples shown below having the same configuration.

  The reason why the two-layer laminated structure of the metal layer and the conductive resin layer was not adopted is as follows. That is, compared with the present invention in which a current collector is provided with a structure in which a metal layer of a three-layer structure or more of the resin layer-metal layer-resin layer is sandwiched between the resin layers, the capacity retention rate is not sufficient, This is because it has been found that it is difficult to sufficiently suppress ion permeation in the current collector (see comparison of the capacity maintenance rate of Comparative Example 2 and Examples 1 to 9 in Table 2 and the capacity improvement rate of Comparative Example 1). This is because if a metal layer is arranged so as to be in contact with only the positive electrode layer or the negative electrode layer, a current flows in the plane direction of the metal layer when an internal short circuit occurs like a metal current collector foil, and local heat generation phenomenon is caused. It is thought to cause. Therefore, it is necessary to reduce the thickness of the metal layer to increase the resistance in the surface direction of the metal layer when an internal short circuit occurs, thereby making it difficult for current to flow. However, if the metal layer in contact with only the positive electrode layer or the negative electrode layer is made very thin, the active material in the positive electrode layer or the negative electrode layer during the process of contracting the positive electrode layer or the negative electrode layer by the pressing process in the manufacturing stage or during charge / discharge It was found that the metal layer in contact with the positive electrode layer and the negative electrode layer was torn or peeled during the process of expansion and contraction. Thus, it was found that the metal layer was torn or ions were transmitted through the peeled part (= pinhole part), and a liquid junction was generated between the positive electrode layer and the negative electrode layer in the bipolar electrode. . For this reason, in Comparative Example 2 in Table 2, it is considered that the result of the ion permeation in the current collector is hardly suppressed. Therefore, in the present invention, the metal layer is disposed so as to be in contact with only the positive electrode layer and the negative electrode layer, and the two-layer laminated structure including the resin layer and the metal layer is not included.

(B) Another configuration example in which three layers are stacked The bipolar electrode 16 shown in FIG. 2B is a modification of the bipolar electrode shown in FIG. 2A.

  Also in the bipolar electrode 16 shown in FIG. 2B, the current collector 11 is composed of conductive resin layers 2a and 2b and a metal layer 1 that is at least thinner than the resin layer 2a. And the said metal layer 1 has the structure pinched | interposed by the said resin layers 2a and 2b (clamped). In other words, the current collector 11 has a resin layer 2a-metal layer 1-resin layer 2b 3 in which the metal layer 1 is an intermediate layer and the resin layers 2a and 2b are joined via the metal layer 1. It has a layered structure. The resin layer 2a is disposed on the positive electrode layer 13 side, and the resin layer 2b is disposed on the negative electrode layer 15 side. In this configuration example, the resin layer 2b is thinner than the metal layer 1, but preferably a metal layer 1 thinner than the resin layers 2a and 2b (a configuration in which the resin layers 2a and 2b are thicker than the metal layer 1). It is more preferable to use (refer to Examples 1 to 8 described later).

Here, the metal layer 1 in contact with the resin layer 2b on the surface layer on the negative electrode layer 15 side is disposed on the negative electrode layer 15 side from the center of the current collector 11, as shown in FIG. The center M ₂ of the thickness D ₂ of the current collector 11 is arranged at a position closer to the negative electrode layer 15 than the center M ₁ of the thickness D ₁ of the current collector 11.

  Even in this configuration example, the same effects as those described in the configuration example (a) can be obtained. That is, the life characteristics are improved by reducing the liquid junction, the weight is reduced by the resin layer having conductivity, and the vibration resistance performance of the bipolar secondary battery is improved. In addition, it is possible to form a current collector that can withstand a positive electrode potential and a negative electrode potential for a long period of time.

Further, in the present configuration example, the metal layer 1 in contact with the resin layer 2 b on the negative electrode layer 15 side of the current collector 11 on the positive electrode layer side is disposed on the negative electrode layer side from the center of the current collector 11. Specifically, in this configuration example, the metal layer 1 in contact with the conductive resin layer 2b on the negative electrode layer 15 side (particularly the surface layer) of the current collector 11 is disposed on the negative electrode layer 15 side from the center of the current collector 11. Has been. Therefore, in this configuration example, the negative electrode layer 15 side (particularly the surface layer) thickness D ₃ of the resin layer 2b having conductivity of the thickness D of the resin layer 2a having the other conductivity of the current collector 11 _The configuration is thinner than ₄ . In such a configuration, the following effects can be achieved by using the conductive resin layer 2b on the negative electrode layer 15 side as a layer in which a conductive metal filler is dispersed in a polymer material. The layer in which the conductive metal filler is dispersed in the polymer material referred to here is a layer in which only the conductive metal filler is dispersed as the conductive filler in the polymer material, and at least the conductive metal as the conductive filler. A layer in which a filler is dispersed is included. The same applies to other configuration examples. In addition, the “conductive metal filler” in the present invention refers to a conductive filler that reacts with lithium at the negative electrode potential to reduce the capacity. Specifically, in addition to conductive carbon, a metal filler made of a metal such as silver or Al or an alloy thereof, a filler obtained by coating the surface of a non-conductive filler such as a resin with a metal or alloy such as silver or Al, etc. Can be mentioned. The same can be said for other configuration examples shown below having the same configuration.

  That is, a battery having excellent long-term reliability and improved charge / discharge efficiency can be constructed. In addition, vibration resistance can be further improved. Specifically, by reducing the thickness of the resin layer 2b between the negative electrode layer 15-resin layer 2b-metal layer 1, the conductive metal filler, which is a conductive material contained in the resin layer 2b, can be reduced. Therefore, capacity deterioration of the conductive metal filler can be suppressed and long-term reliability can be improved. As a cause of the capacity deterioration of the conductive metal filler, the conductive carbon material which is one of the conductive metal fillers in the resin layer 2b functions as an active material. It is considered that the carbon material is deactivated by being pulverized due to cracks caused by expansion and contraction of the carbon material, leading to capacity loss (deterioration). In addition, when a metal filler, which is a kind of conductive metal filler, or a filler in which the surface of a resin filler is coated with the metal also reaches the reduction potential of the negative electrode, lithium is consumed by the electrochemical reaction on the metal surface, resulting in capacity deterioration. It is thought to be a cause. Therefore, in the current collector used for the bipolar electrode of the present invention, the conductive metal filler in the resin layer 1 absorbs and relaxes stress due to the polymer material when it expands and contracts. It is possible to suppress the deterioration of the conductive metal filler, build a battery with excellent long-term reliability, and improve the charge / discharge efficiency. Further, it is considered that the vibration resistance can be further improved. Further, by reducing the conductive metal filler in the resin layer 2b, capacity loss (= capacity deterioration) due to irreversible reaction between the conductive metal filler which is a conductive material and lithium ions can be suppressed, and long-term reliability can be achieved. It is considered that an excellent battery can be constructed and charge / discharge efficiency can be improved.

  A method for reducing the conductive metal filler of the resin layer 2b on the negative electrode layer 15 side (particularly the surface layer) includes a method of thinning the resin layer. Further, a method in which the metal layer 1 in contact with the resin layer 2b on the negative electrode layer 15 side is arranged on the negative electrode layer 15 side from the center of the current collector 11 as in this configuration example is applicable. In addition to this, for example, among the conductive fillers of the resin layer on the negative electrode layer 15 side (particularly the surface layer), the content of the conductive metal filler is reduced, and other conductive fillers that do not function as an active material are contained. A method of increasing the amount is also conceivable. Further, for example, the conductive metal filler is reduced by reducing the total content of the conductive material (conductive filler) of the resin layer 2b on the negative electrode layer 15 side (particularly the surface layer) within a range not impairing the conductivity of the bipolar electrode. The content of may be reduced. Further, the average particle diameter and material (including those modified by surface treatment) of the conductive metal filler may be changed to one having less capacity loss (= capacity deterioration). Furthermore, you may use combining these methods suitably.

(C) Still another configuration example in which three layers are stacked The bipolar electrode 16 shown in FIG. 2C is also a modification of the bipolar electrode shown in FIG. 2A.

  Also in the bipolar electrode 16 shown in FIG. 2C, the current collector 11 is composed of the conductive resin layers 2a and 2b and the metal layer 1 that is at least thinner than the resin layer 2b. And the said metal layer 1 has the structure pinched | interposed by the said resin layers 2a and 2b (clamped). In other words, the current collector 11 includes a resin layer 2a-metal layer 1-resin layer in which the metal layer 1 is an intermediate layer and conductive resin layers 2a and 2b are joined via the metal layer 1. 2b has a three-layer structure. Further, the conductive resin layer 2a is disposed on the positive electrode layer 13 side, and the conductive resin layer 2b is disposed on the negative electrode layer 15 side. In this configuration example, the metal layer 1 in contact with the conductive resin layer 2 b on the surface layer on the negative electrode layer 15 side of the current collector 11 is disposed on the positive electrode layer 15 side from the center of the current collector 11. In this configuration example, the configuration example in which the resin layer 2a is thinner than the metal layer 1 is shown, but preferably the metal layer 1 thinner than the resin layers 2a and 2b (the configuration in which the resin layers 2a and 2b are thicker than the metal layer 1). It is more preferable to use (refer to Examples 1 to 8 described later).

The metal layer 1 in contact with the resin layer 2b having conductivity of the negative electrode layer 15 side surface layer is disposed on the positive electrode layer 15 side from the center of the collector 11, the center of the thickness D ₂ of the metal layer 1 It means that M ₂ is arranged at a position closer to the positive electrode layer 13 than the center M ₁ of the thickness D ₁ of the current collector 11.

  Even in this configuration example, the same effects as those described in the configuration example (a) can be obtained. That is, the life characteristics are improved by reducing the liquid junction, the weight is reduced by the resin layer having conductivity, and the vibration resistance performance of the bipolar secondary battery is improved. In addition, it is possible to form a current collector that can withstand the positive electrode potential and the negative electrode potential for a long period of time (the capacity retention ratio of Example 9 and Example 1 in Table 2 and the capacity improvement ratio relative to Comparative Example 1). See contrast).

(D) Configuration example in which five layers are stacked In the bipolar electrode 16 shown in FIG. 2D, the current collector 11 is thinner than the resin layers 2a, 2b, and 2c having conductivity and the resin layers 2a, 2b, and 2c. It consists of metal layers 1a and 1b. The metal layer 1a is sandwiched between the resin layers 2a and 2b, and the metal layer 1b is sandwiched (sandwiched) between the resin layers 2b and 2c. In other words, the current collector 11 has a resin layer 2a-metal layer 1a-resin layer 2b-metal layer 1b-resin layer in which a plurality of metal layers 1 and conductive resin layers 2 are alternately laminated. It has a two-layer structure of 2c. In this configuration example, the surface layer on the positive electrode layer 13 side and the negative electrode layer 15 side of the current collector 11 is composed of resin layers 2 a and 2 c having conductivity.

  Even in this configuration example, the metal layer 1b in contact with the conductive resin layer 2c on the negative electrode layer 15 side (particularly the surface layer) of the current collector 11 is disposed on the negative electrode layer 15 side from the center of the current collector 11. ing.

  Even in this configuration example, the life characteristics can be improved by reducing the liquid junction, and the weight can be reduced by the resin layer having conductivity. Further, in this configuration example, both the positive electrode layer and the negative electrode layer are in contact with a conductive resin layer. Therefore, as described in the configuration example (a) above, the vibration resistance performance of the bipolar secondary battery can be improved, and a current collector that can withstand the positive electrode potential and the negative electrode potential for a long time can be formed. become. In addition, the vibration resistance performance of the bipolar secondary battery is further improved by forming the current collector 11 in a multi-layer structure of five layers. Specifically, in addition to the two surface layers that are in contact with the positive electrode layer and the negative electrode layer, a conductive resin layer is disposed on the inner layer sandwiched between the surface layers. The presence of the conductive resin layer 2b in the inner layer of the current collector further improves the peel strength between the current collector and the positive electrode layer or negative electrode layer. In addition to adhesion and buffering role (stress relaxation function) by the surface layer, the resin layer 2b having inner conductivity also plays a buffering role (stress relaxation function), and the surface layer, positive electrode layer and negative electrode layer It is presumed that this is because the adhesion and vibration resistance performance are further enhanced.

  Also in this configuration example, as described in the above (b), the metal layer 1 b in contact with the resin layer 2 c on the negative electrode layer 15 side of the current collector 11 on the positive electrode layer side is the center of the current collector 11. It has the structure arrange | positioned more by the negative electrode layer 15 side. That is, the resin layer 2c on the negative electrode layer 15 side (particularly the surface layer) is thinner than the other conductive resin layers 2a and 2b. In such a configuration, the following functions and effects can be achieved by using the conductive resin layer 2c on the negative electrode layer 15 side (surface layer) as a layer in which a conductive metal filler is dispersed in a polymer material. .

  That is, a battery having excellent long-term reliability and improved charge / discharge efficiency can be constructed. In addition, vibration resistance can be further improved. Specifically, the conductive metal filler of the conductive material (conductive filler) contained in the resin layer 2c is reduced by thinning the resin layer 2c between the negative electrode layer 15-resin layer 2c-metal layer 1b. be able to. Therefore, capacity deterioration of the conductive metal filler can be suppressed and long-term reliability can be improved. That is, in the current collector of this structural example, the conductive metal filler in the resin layer 2c is absorbed and relaxed by the surrounding polymer material when it expands and contracts. It is considered that the vibration resistance can be improved and the vibration resistance can be further improved. In addition, it is considered that by reducing the conductive metal filler in the resin layer 2c, it is possible to suppress capacity loss (= capacity deterioration) due to irreversible reaction between the conductive metal filler which is a conductive filler and lithium ions. It is.

(E) One Configuration Example Arranged in Six Layers In the bipolar electrode 16 shown in FIG. 2E, the current collector 11 includes conductive resin layers 2a, 2b, and 2c, and these resin layers 2a, 2b, and 2c. It is composed of thin metal layers 1a, 1b and 1c. The metal layer 1b is sandwiched between the resin layers 2a and 2b, and the metal layer 1c is sandwiched (sandwiched) between the resin layers 2b and 2c. In other words, the current collector 11 has a metal layer 1a-resin layer 2a-metal layer 1b-resin layer 2b-metal layer in which a plurality of metal layers 1 and conductive resin layers 2 are alternately laminated. It has a 6-layer laminated structure of 1c-resin layer 2c. In this configuration example, the surface layer on the positive electrode layer 13 side of the current collector 11 is composed of the metal layer 1a, and the surface layer on the negative electrode layer 15 side is composed of the resin layer 2c. Thus, in the “structure in which the metal layer is sandwiched between resin layers” in the present invention, the metal layer 1a that is one of the metal layers included in the bipolar electrode 16 of the present configuration example is used. A structure in which the layer 1a is sandwiched (clamped) between the resin layer 2a and the positive electrode layer 13 is also included. However, in the bipolar electrode of the present invention, it is necessary to have “a structure in which a metal layer is sandwiched between resin layers” in at least a part of the current collector as in this configuration example, and this structure is not included at all. A two-layer structure composed of a resin layer and a metal layer is not included.

  Also in this configuration example, the metal layer 1c in contact with the conductive resin layer 2c on the negative electrode layer 15 side (particularly the surface layer) of the current collector 11 is disposed on the negative electrode layer 15 side from the center of the current collector 11. ing.

  Even in this configuration example, the life characteristics can be improved by reducing the liquid junction, and the weight can be reduced by the resin layer having conductivity. Further, in this configuration example, the negative electrode layer is in contact with the conductive resin layer. Therefore, as described in the configuration example (a) above, the vibration resistance performance of the bipolar secondary battery can be improved, and a current collector that can withstand a negative electrode potential for a long period of time can be formed. For the positive electrode potential, the metal layer 1a may be able to withstand the positive electrode potential for a long period of time. In addition, by making the current collector 11 into a multi-layer laminate structure of six layers, as described in (d) above, the resin layer having the inner conductivity also plays a buffer role (stress relaxation function), The adhesion between the surface layer, the positive electrode layer and the negative electrode layer and the vibration resistance are further enhanced. Therefore, it is considered that the vibration resistance performance of the bipolar secondary battery is further improved.

  In addition, when the positive electrode layer 13 and the metal layer 1a are in contact with each other as in this configuration example, current flows in the plane direction when an internal short circuit occurs like a metal current collector foil, causing a local heat generation phenomenon. I think so. However, by adopting a multilayer laminated structure as in this configuration example, other metal layers 1a to 1b held on both sides by resin layers 2a, 2b to 2c having conductivity can be present. Therefore, ion permeation can be effectively prevented by the other metal layer held on both sides by the resin layer having conductivity. Therefore, the thickness of the metal layer 1a can be suppressed to be very thin as compared with existing metal current collector foils (that is, a very thin vapor deposited metal thin film by vapor deposition or the like is sufficient). For this reason, when an internal short circuit occurs, if a current flows in a concentrated manner in the surface direction, a function of interrupting (burning out) the current flow in a very short time can be provided. As a result, it is excellent in that a local heat generation phenomenon can be effectively prevented when an internal short circuit occurs. In addition, since the current flow can be interrupted in a very short time, it is excellent in that the current collecting performance is not deteriorated in the laminated structure portion of other current collectors.

(F) Another Configuration Example Arranged in Six Layers The bipolar electrode 16 shown in FIG. 2F is a modification of the bipolar electrode shown in FIG. 2E.

  In the bipolar electrode 16 shown in FIG. 2F, the current collector 11 includes conductive resin layers 2a, 2b, and 2c and metal layers 1a, 1b, and 1c thinner than these resin layers 2a, 2b, and 2c. Yes. The metal layer 1a is sandwiched between the resin layers 2a and 2b, and the metal layer 1b is sandwiched (sandwiched) between the resin layers 2b and 2c. In other words, the current collector 11 is a resin layer 2a-metal layer 1a-resin layer 2b-metal layer 1b-resin layer in which a plurality of metal layers 1 and conductive resin layers 2 are alternately laminated. It has a 6-layer laminated structure of 2c-metal layer 1c. In this configuration example, the surface layer on the positive electrode layer 13 side of the current collector 11 is composed of a conductive resin layer 2a, and the surface layer on the negative electrode layer 15 side is composed of a metal layer 1c. Thus, in the “structure in which the metal layer is sandwiched between the resin layers” in the present invention, the metal layer 1c which is one of the metal layers included in the bipolar electrode 16 of the present configuration example is used. A structure in which the layer 1c is sandwiched (clamped) between the resin layer 2c and the negative electrode layer 15 is also included. However, in the bipolar electrode of the present invention, it is necessary to have “a structure in which a metal layer is sandwiched between resin layers” in at least a part of the current collector as in this configuration example, and this structure is not included at all. A two-layer structure composed of a resin layer and a metal layer is not included.

  In this configuration example, the metal layer 1 c on the negative electrode layer 15 side (particularly the surface layer) of the current collector 11 is disposed on the negative electrode layer 15 side from the center of the current collector 11.

  Even in this configuration example, the life characteristics can be improved by reducing the liquid junction, and the weight can be reduced by the resin layer having conductivity. Further, in this configuration example, the positive electrode layer is in contact with the conductive resin layer. Therefore, as described in the configuration example (a) above, the vibration resistance performance of the bipolar secondary battery can be improved, and a current collector that can withstand the positive electrode potential for a long time can be formed. For the negative electrode potential, the metal layer 1c may be able to withstand the negative electrode potential for a long time. In addition, by making the current collector 11 into a multi-layer laminate structure of six layers, as described in (d) above, the resin layer having the inner conductivity also plays a buffer role (stress relaxation function), The adhesion between the surface layer, the positive electrode layer and the negative electrode layer and the vibration resistance are further enhanced. Therefore, it is considered that the vibration resistance performance of the bipolar secondary battery is further improved.

  Further, as described in the above (e), even when the negative electrode layer 15 and the metal layer 1c are in contact with each other as in this configuration example, when an internal short circuit occurs like the metal current collector foil, It seems that current flows and causes a local heat generation phenomenon. However, by adopting a multilayer laminated structure as in this configuration example, other metal layers 1a to 1b held on both sides by resin layers 2a, 2b to 2c having conductivity can be present. Therefore, ion permeation can be effectively prevented by the other metal layer held on both sides by the resin layer having conductivity. Therefore, the thickness of the metal layer 1c can be suppressed to be very thin as compared with the existing metal current collector foil (that is, a very thin vapor deposited metal thin film by vapor deposition or the like is sufficient). For this reason, when an internal short circuit occurs, if a current flows in a concentrated manner in the surface direction, a function of interrupting (burning out) the current flow in a very short time can be provided. As a result, it is excellent in that a local heat generation phenomenon can be effectively prevented when an internal short circuit occurs. In addition, since the current flow can be interrupted in a very short time, it is excellent in that the current collecting performance is not deteriorated in the laminated structure portion of other current collectors.

  From the above viewpoints, in this configuration example, the conductive resin layer in contact with the metal layer on the negative electrode layer side surface layer has a capacity in which the filler reacts with lithium at a negative electrode potential such as a carbon material or a metal filler as a conductive filler. It is a resin layer having conductivity formed using a resin to which a material that can be down (conductive metal filler) is added, and the thickness of the resin layer having conductivity is 10 to 100 μm. Is desirable.

  In addition, each structural example of said (a)-(f) is only one example of the structural example of the electrical power collector by which the electrical power collector used by this invention is laminated | stacked. Therefore, other than the above-described configuration example, the metal layer thinner than the resin layer having conductivity is sandwiched between the resin layers (a structure in which the metal layer and the resin layer are laminated). That is, it is included in the technical scope of the present invention.

  For example, a resin layer having a first conductivity and a resin layer having a second conductivity having different characteristics are continuously laminated, such as a resin layer-metal layer- (first resin layer-second resin layer). Even in the form, any metal layer having a structure in which a metal layer thinner than the resin layer having conductivity is sandwiched between the resin layers is included in the technical scope of the present invention. Similarly, in the form of continuously laminating the first metal layer and the second metal layer having different characteristics, such as resin layer- (first metal layer-second metal layer) -resin layer, the resin layer having conductivity Any structure having a thin metal layer sandwiched between the resin layers is included in the technical scope of the present invention. Further, the first metal layer and the second metal layer having different characteristics are continuously laminated such as resin layer- (first metal layer-second metal layer)-(first resin layer-second resin layer), Even if the first conductive resin layer and the second conductive resin layer are differently laminated, the metal layer thinner than the conductive resin layer has a structure sandwiched between the resin layers. If it exists, it is included in the technical scope of the present invention. The above-mentioned (first metal layer-second metal layer) and (first resin layer-second resin layer) are replaced with a metal material or conductive filler in one metal layer or one resin layer. It may be included in the configuration examples of FIG. 2A and FIG.

(2) Each constituent element of the metal layer and the conductive resin layer in the current collector (2-1) Metal layer (a) The constituent material of the metal layer As the metal layer in the current collector, ion permeation in the current collector Is not particularly limited as long as it can function to prevent liquid junction between the positive electrode layer and the negative electrode layer in the bipolar electrode, and the same material as the existing metal current collector foil is used. Can be formed. Specifically, a plating material such as aluminum, nickel, copper, stainless steel, or a combination of these metals (including alloys) is preferably used. From the viewpoints of corrosion resistance, ease of production, economy, etc., it is preferable to use aluminum as a material for forming the metal layer. 2E and 2F, the metal layer disposed on the positive electrode layer side or the negative electrode layer side surface layer is mainly composed of Fe and alloyed with Cr and Ni from the point that it can withstand the positive electrode potential and the negative electrode potential. It is preferable to use the stainless steel as the metal layer forming material. Moreover, in the metal layer arrange | positioned at the negative electrode layer side surface layer, it is preferable to use SUS316L which has Mo component as a formation material of a metal layer at the point which can pass a voltage to 0V.

(B) Thickness of the metal layer The thickness of the metal layer in the current collector has a function of preventing ion permeation in the current collector and preventing a liquid junction between the positive electrode layer and the negative electrode layer in the bipolar electrode. Any material can be used as long as it can be expressed. However, from the viewpoint of weight reduction, it can be said that it is desirable to make it thinner than the resin layer having conductivity within a range where the function can be expressed. However, as described with reference to FIG. 2F, in the case where a plurality of metal layers are provided, at least one of the metal layers may be thinner than the conductive resin layer. Preferably, even when a plurality of metal layers are provided, it is desirable that all metal layers be thinner than all conductive resin layers.

  From the above viewpoint, for example, as shown in FIGS. 2A to 2C, in the case of a current collector having a three-layer structure including a conductive resin layer-metal layer-conductive resin layer, The thickness is 0.01 to 20 μm, preferably 0.05 to 10 μm, more preferably 0.1 to 5 μm. If the thickness of the metal layer is 0.01 μm or more, it is excellent in that the occurrence of pinholes can be suppressed and a high liquid junction prevention function can be effectively expressed. Moreover, if the thickness of a metal layer is 20 micrometers or less, it is excellent at the point which can be reduced in thickness and weight in addition to the said liquid junction prevention function. Further, since the relatively conductive resin layer can be thickened, this is superior in that it can contribute to exhibiting a sufficient stress relaxation function (vibration resistance) against external loads such as vibration and impact.

  However, when arranging a plurality of metal layers as shown in FIGS. 2D to 2F, the number of metal layers may be any as long as the above-described liquid junction prevention function can be effectively expressed in the entire metal layers. According to the above, the thickness of each metal layer may be appropriately adjusted. Therefore, when using a plurality of metal layers, the thickness of each metal layer may be substantially the same (see FIGS. 2D to 2F) or may be different from each other.

(2-2) Resin layer having conductivity (a) Constituent material The resin layer having conductivity in the current collector has conductivity required for a current collector for a bipolar battery, and the entire current collector If it can reduce in weight compared with the existing metal foil electrical power collector, it will not be restrict | limited especially, It can form using the material similar to the existing resin electrical power collector. That is, it can be composed of a resin having conductivity such as a resin to which a conductive filler is added or a conductive polymer.

  Specifically, the resin layer having conductivity has conductivity and essentially contains a polymer material (resin). In order for the resin layer having conductivity to have conductivity, as a specific form, 1) a form in which the polymer material (resin) is a conductive polymer, 2) a resin layer having conductivity is a conductive filler ( Examples include a form including a conductive material), 3) a form combining the forms 1) and 2) above, and the like.

Here, the resin layer having conductivity means that the conductivity is generally a conductor whose electrical conductivity (conductivity) is equal to or higher than that of graphite (electric conductivity: 10 ⁶ S / m), 10 ⁻ Those having ⁶ S / m or less are classified as non-conductors (insulators), and those having intermediate values are classified as semiconductors. However, in the present invention, they may not be insulators, and the electrical conductivity (conductivity) is 10 ^−. It may be ⁶ S / m or more. In the present invention, since a current collector including a conductive resin layer is used for a bipolar electrode, the volume resistivity in the thickness direction of the conductive resin layer is 10 ² Ω · cm or less. It can be said that the resin layer having conductivity has conductivity. In a resin layer having conductivity in which conductive metal fillers such as carbon materials and metal fillers are dispersed in the epoxy resin of Examples described later, the thickness is in the range of 10 ⁻² to 10 ^{−1 in} the range of 10 to 100 μm. The range of Ω · cm satisfies the requirement of 10 ² Ω · cm or less. Therefore, although it has not put up to an experimental result, the resin layer which has electroconductivity without any problem has electroconductivity.

Further, the volume resistivity in the thickness direction of the current collector is preferably in the range of 10 ² to 10 ⁻⁵ Ω · cm. If the volume resistivity in the thickness direction of the current collector is in such a range, it is suitable as a current collector for a bipolar electrode. The volume resistivity can be measured using a commercially available measuring instrument that conforms to JIS standards.

(I) Conductive polymer The conductive polymer used in the embodiment 1) is selected from materials having conductivity. Preferably, from the viewpoint of suppressing ion permeation in the resin layer having conductivity, it is desirable to use a material that does not have conductivity with respect to ions used as the charge transfer medium. These conductive polymers are considered to be conductive because the conjugated polyene system forms an energy band. As a typical example, a polyene-based conductive polymer that has been put into practical use in an electrolytic capacitor or the like can be used. Specifically, polyaniline, polypyrrole, polythiophene, polyacetylene, polyparaphenylene, polyphenylene vinylene, polyacrylonitrile, polyoxadiazole, or a mixture thereof is preferable. Polyaniline, polypyrrole, polythiophene, and polyacetylene are more preferable from the viewpoint of conductivity (electron conductivity) and stable use in the battery.

  In addition, when the conductive polymer is used for the resin layer having conductivity on the surface layer in contact with the positive electrode layer or the negative electrode layer, it alone becomes a good material that can withstand the applied positive electrode potential or negative electrode potential. However, since it has not been developed at this stage, it is desirable to add a conductive filler (conductive material) described later so that it can withstand the applied positive electrode potential and negative electrode potential.

(Ii) Conductive filler (conductive material)
The conductive filler (conductive material) used in the form 2) is selected from materials having conductivity. Preferably, from the viewpoint of suppressing ion permeation in the resin layer having conductivity, it is desirable to use a material that does not have conductivity with respect to ions used as the charge transfer medium. Further, the conductive filler is selected from materials that can withstand the applied positive electrode potential and negative electrode potential when it is arranged on the surface layer on the positive electrode layer side or the negative electrode layer side, although it depends on the position of the laminated arrangement. Is desirable.

  Specific examples include, but are not limited to, aluminum materials, stainless steel (SUS) materials, carbon materials such as graphite and carbon black, silver materials, gold materials, copper materials, and titanium materials. These conductive fillers may be used alone or in combination of two or more. Moreover, these alloy materials may be used. Silver material, gold material, aluminum material, stainless steel material, carbon material is preferable, and carbon material is more preferable. These conductive fillers (conductive materials) may be those obtained by coating a conductive material (the conductive material) around the particle ceramic material or resin material with plating or the like.

(Ii-1) Shape of conductive filler (conductive material) The shape (form) of the conductive filler (conductive material) may be used in the form of particles, but is not limited to the form of particles, and so-called fillers such as carbon nanotubes. It may be in a form other than the particle form that has been put to practical use as a conductive resin composition.

(Ii-2) Distribution of conductive filler The distribution of the conductive filler in the conductive resin layer may not be uniform, and the distribution of the conductive filler particles is changed inside the conductive resin layer. Also good. In addition, since a plurality of conductive resin layers are used for the current collector, a plurality of conductive fillers are used, and the distribution, content, and material distribution of the conductive filler particles are also used between the conductive resin layers. The type or the like may be changed. For example, the resin layer having conductivity near the positive electrode layer and the resin layer having conductivity close to the positive electrode layer, and the resin layer having conductivity near the negative electrode layer and the conductivity close to positive electrode layer A preferable conductive filler material may be properly used for the resin layer.

  As the conductive filler suitably used for the resin layer having conductivity in contact with the positive electrode layer or the resin layer having conductivity close to the positive electrode layer (the resin layer having conductivity on the positive electrode layer side), the conductive filler has high conductivity and high dispersibility. From the viewpoint, aluminum particles in the form of particles, SUS particles, gold particles and carbon particles are preferable. Among these, carbon particles are more preferable.

  As the conductive filler suitably used for the resin layer having conductivity in contact with the negative electrode layer and the resin layer having conductivity close to the negative electrode layer (resin layer having conductivity on the negative electrode layer side), the conductive filler has high conductivity and high dispersibility. From the viewpoint, silver particles, gold particles, aluminum metal particles, copper particles, titanium particles, SUS particles, and carbon particles are preferable. These conductive fillers may be those obtained by coating a conductive material around the particle ceramic material or resin material with plating or the like. Among these, carbon particles are more preferable.

  Examples of the carbon particles include carbon black and graphite. This is because these carbon particles such as carbon black and graphite have a very wide potential window, are stable in a wide range with respect to both the positive electrode potential and the negative electrode potential, and are excellent in conductivity. Also, since the carbon particles are very light, the increase in mass is minimized. Furthermore, since carbon particles are often used as conductive aids for electrodes (particularly the positive electrode layer), even if they come into contact with these conductive aids, the contact resistance is very low because of the same material. In addition, when a carbon material is used for the conductive resin layer in contact with the negative electrode layer, the thickness of the conductive resin layer is reduced, the other conductive material is added in a compounding ratio, etc. It is desirable to reduce the carbon material (conductive material) contained in the conductive resin layer. That is, the carbon material (conductive material) in the conductive resin layer in contact with the negative electrode layer can also function as the negative electrode active material. Therefore, it is effective in suppressing a part of the carbon material (conductive material) from being deactivated by an irreversible reaction with lithium ions in the charge / discharge process (especially the first charge / discharge process) and the deterioration of the conductive performance. In addition, when carbon particles are used as the conductive filler, the compatibility of the electrolyte is lowered by applying a hydrophobic treatment to the surface of the carbon so that the electrolyte does not easily penetrate into the pores of the resin layer having conductivity. Is also possible.

(Ii-2) Average particle diameter of conductive filler The average particle diameter of the conductive filler is not particularly limited, but is desirably about 0.01 to 10 μm. In the present specification, “particle diameter” means the maximum distance L among the distances between any two points on the contour line of the conductive filler. As the value of “average particle diameter”, the average particle diameter of particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted. Particle diameters and average particle diameters of active material particles to be described later can be defined similarly.

(Ii-3) Addition amount of conductive filler The addition amount of the conductive filler in the resin layer having conductivity is desirably 1 to 30 wt%. If the addition amount of the conductive filler in the resin layer having conductivity is 1 wt% or more, the conductive performance necessary for the current collector of the bipolar electrode can be effectively expressed. On the other hand, if the addition amount of the conductive filler is 30 wt% or less, an increase in the weight of the conductive resin layer containing the conductive filler can be suppressed.

(Iii) Polymer material (resin matrix)
When the conductive resin layer includes a conductive filler as in the above 2), the polymer material forming the conductive resin layer is conductive for adding the conductivity. Insulating polymer material (polymer material having no electrical conductivity) to which the filler is bound is included. In the above-described 3), the polymer material forming the conductive resin layer may be either a non-conductive polymer material that binds the conductive filler or the conductive polymer of 1) above. These may be used in combination.

  By using a polymer material as a constituent material of the resin layer having conductivity, the binding property of the conductive filler can be increased and the reliability of the battery can be increased. The polymer material is desirably selected from materials that can withstand the applied positive electrode potential and negative electrode potential. Further, in the resin layer having conductivity, in order to heat-seal the metal layer, the positive electrode layer, or the negative electrode layer, the non-conductive polymer material contained in the conductive resin layer or the conductivity of the above 1) The polymer is preferably thermoplastic. However, since it is possible to form a conductive resin layer by applying ordinary slurry, the resin layer is not necessarily limited to thermoplastic.

  As an example of a conductive polymer, what was illustrated with the form of said 1) can be used.

  Examples of the non-conductive polymer material include, for example, polyolefins such as polyethylene (PE) and polypropylene (PP); polyesters such as polyethylene terephthalate (PET) and polyethernitrile (PEN); silicones and polyimide (PI); Polyamide (PA); Polyvinylidene fluoride (PVdF); Epoxy resin; Polytetrafluoroethylene (PTFE); Synthetic rubber materials such as styrene butadiene rubber (SBR); Polyacrylonitrile (PAN); Polymethyl acrylate (PMA); Polymethyl Methacrylate (PMMA); polyvinyl chloride (PVC). These polymer materials may be used alone or in combination of two. Especially, an epoxy resin is preferable at the point which does not swell with respect to electrolyte (organic solvent). Moreover, from the following viewpoints, polyolefin, polyester, polyimide, polyamide, and polyvinylidene fluoride are preferable. These materials have a very wide potential window and are stable to both positive and negative electrode potentials. In addition, since it is lightweight, it is possible to increase the output density of the battery. Furthermore, it is easy to melt by applying heat, and it is easy to fuse to a metal layer, a positive electrode layer, or a negative electrode layer.

(Iii) Compounding ratio of polymer material In the case where the conductive resin layer includes a conductive filler as in the modes 2) and 3) above, the polymer material and the conductivity in the conductive resin layer The ratio with the filler is as defined in (ii-3). Preferably, 2 to 20 wt% of the conductive filler is present with respect to the total of the polymer material and the conductive filler. This is because the presence of a sufficient amount of the conductive filler can ensure sufficient conductivity in the current collector.

(Iv) Other additives For the resin layer having conductivity, in addition to the conductive filler and the polymer material, a water repellent and a binder are provided as long as the effects of the present invention are not affected. A suitable amount of other additives may be contained.

(B) Thickness of Resin Layer Having Conductivity The thickness of the resin layer having conductivity may be thicker than at least one metal layer as described above. To increase the output density of the battery by reducing the weight, The thinner, the better. In a bipolar secondary battery, the current collector existing between the positive electrode layer and the negative electrode layer of the bipolar electrode may have a high electric resistance in the direction parallel to the stacking direction. The thickness of the resin layer having conductivity in the current collector can be reduced. Therefore, it is possible to construct a battery having excellent battery output characteristics and excellent long-term reliability.

  From the above viewpoint, for example, in the case of a current collector having a three-layer structure including a conductive resin layer-metal layer-conductive resin layer as shown in FIGS. The thickness of the resin layer (for one layer) is 1 to 200 μm, preferably 10 to 100 μm, and more preferably 10 to 50 μm. Although depending on the volume resistivity of the resin layer having conductivity, the resistance in the thickness direction of the resin layer having conductivity within the above range is a region that can be substantially ignored with respect to the entire internal resistance of the battery. Therefore, it is possible to increase the output density of the battery by reducing the weight while securing the conductivity of the current collector. In addition to improving the life characteristics by reducing liquid junction, the vibration resistance performance of the bipolar secondary battery is improved. In addition, it is possible to form a current collector that can withstand a positive electrode potential and a negative electrode potential for a long period of time.

  However, even when more conductive resin layers are arranged as shown in FIGS. 2D to 2F, it is only necessary that these conductive resin layers can achieve the above-described conductivity and thin film weight reduction. The thickness of each conductive resin layer may be adjusted as appropriate in accordance with the number of conductive resin layers. Therefore, when using two or more resin layers which have electroconductivity, the thickness of each resin layer which has electroconductivity may be substantially the same thickness, and may be different thickness, respectively.

  Preferably, as described in FIGS. 2B and 2F, the negative electrode layer side (particularly the surface layer) of the current collector is a conductive metal filler such as a conductive carbon or metal filler (such as silver or Al) as a polymer material. In the case of a layer in which is dispersed, the thickness of the conductive resin layer on the negative electrode layer side (particularly the surface layer) is desirably thinner than the thickness of other conductive resin layers. By thinning the conductive resin layer between the negative electrode layer-conductive resin layer-metal layer, a conductive metal filler contained in the conductive resin layer (conductive carbon or metal filler) Etc.) can be reduced. As a result, the irreversible reaction between the conductive metal filler (conductive carbon, metal filler, etc.) and lithium ions can be suppressed, the charge / discharge efficiency is increased, and a battery with excellent long-term reliability can be constructed.

(C) Thickness ratio between the metal layer and the conductive resin layer (conductive resin layer / metal layer)
The thickness ratio of the metal layer to the conductive resin layer (for one layer) (conductive resin layer / metal layer) is the thickness of the metal layer and the conductive resin layer (for one layer). As long as it is within the thickness range, there is no particular limitation. A metal layer having an arbitrary thickness and a resin layer having conductivity can be combined.

  For example, in a current collector having a three-layer structure including a conductive resin layer-metal layer-conductive resin layer, the thickness ratio between the metal layer and the conductive resin layer (for one layer) (conductive (Resin layer / metal layer) is 0.05 to 20000, preferably 0.5 to 2000, and more preferably 2 to 500. By having a thickness ratio (conductive resin layer / metal layer) in such a range, life characteristics due to liquid junction reduction are improved, and vibration resistance performance of the bipolar secondary battery is improved. In addition, it is possible to form a current collector that can withstand a positive electrode potential and a negative electrode potential for a long period of time. As a result, a bipolar secondary battery excellent in long-term reliability can be constructed.

(3) Configuration Requirements for Entire Current Collector (3-1) Thickness of Current Collector The thickness of the current collector is preferably as thin as possible to increase the output density of the battery by reducing the weight. In a bipolar secondary battery, the current collector existing between the positive electrode layer and the negative electrode layer of the bipolar electrode may have a high electric resistance in the direction parallel to the stacking direction. It is possible to make it thinner. Therefore, it is possible to construct a battery having excellent battery output characteristics and excellent long-term reliability.

  From the above viewpoint, the thickness of the current collector is 1 to 200 μm, preferably 5 to 150 μm, and more preferably 10 to 100 μm. If it is this range, while ensuring the electroconductivity of an electrical power collector, the output density of the battery by weight reduction can be raised. In addition to improving the life characteristics by reducing liquid junction, the vibration resistance performance of the bipolar secondary battery is improved. In addition, it is possible to form a current collector that can withstand a positive electrode potential and a negative electrode potential for a long period of time.

(3-1) Resistance value of current collector The resistance value of the current collector is not particularly limited as long as the conductivity in the stacking direction required for the current collector for bipolar batteries is sufficiently secured. It is not a thing. Preferably, the metal layer of the current collector has conductivity so that the resistance value in the stacking direction of the current collector is 1/100 or less, preferably 1/1000 or less, relative to the resistance value of the entire battery. It is desirable to select the arrangement, material, thickness, etc. of the resin layer.

  Note that the outermost layer current collector 11a on the positive electrode layer side and the outermost layer current collector 11b on the negative electrode layer side shown in FIG. 1 do not need to have a bipolar electrode structure, and therefore, the positive electrode layer and the negative electrode layer of the bipolar electrode are not required. On the other hand, there is no concern about liquid junction between them, but conductivity in a direction (plane direction) horizontal to the stacking direction is required. Therefore, for these outermost layer current collectors, existing metal foil current collectors (those composed of only metal layers) may be used, and the amount of conductive filler added to the resin layer having conductivity is as described above. It may be used in an amount higher than the amount specified in.

<III> About the configuration other than the current collector (characteristic portion) of the bipolar secondary battery of the present invention The above is an explanation of the current collector that is a characteristic component of the bipolar secondary battery of the present invention. There are no particular restrictions on other components. Therefore, in the following, regarding the other constituent elements other than the current collector, which is a characteristic constituent element of the bipolar secondary battery of the present invention, a bipolar lithium ion secondary battery will be described as an example. However, it is not limited to these.

[Positive electrode layer and negative electrode layer]
The electrode layers (positive electrode layer 13 and negative electrode layer 15) include an active material, and further include other additives as necessary.

The positive electrode layer 13 includes a positive electrode active material. As the positive electrode active material, for example, LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni—Co—Mn) O _2, and lithium-such as those in which a part of these transition metals are substituted with other elements Examples include transition metal composite oxides, lithium-transition metal phosphate compounds, and lithium-transition metal sulfate compounds. In some cases, two or more positive electrode active materials may be used in combination. Preferably, a lithium-transition metal composite oxide is used as the positive electrode active material from the viewpoint of capacity and output characteristics. Of course, positive electrode active materials other than those described above may be used.

The negative electrode layer 15 includes a negative electrode active material. Examples of the negative electrode active material include carbon materials such as graphite, soft carbon, and hard carbon, lithium-transition metal composite oxides (for example, Li ₄ Ti ₅ O ₁₂ ), metal materials, lithium alloy negative electrode materials, and the like. . In some cases, two or more negative electrode active materials may be used in combination. Preferably, from the viewpoint of capacity and output characteristics, a carbon material or a lithium-transition metal composite oxide is used as the negative electrode active material. Of course, negative electrode active materials other than those described above may be used.

  Although the average particle diameter of each active material contained in each positive electrode layer 13 and negative electrode layer 15 is not particularly limited, it is preferably 1 to 20 μm from the viewpoint of high output.

  The electrode layers (the positive electrode layer 13 and the negative electrode layer 15) include a binder polymer material (also simply referred to as a binder).

  Although it does not specifically limit as a binder used for the electrode layers 13 and 15, For example, the following materials are mentioned. Polypropylene; Polyester such as polyethylene terephthalate (PET) and polyether nitrile (PEN); Polyimide; Polyamide; Polyvinylidene fluoride (PVdF); Epoxy resin; Synthetic rubber. Among them, polypropylene, polyester such as polyethylene terephthalate (PET), polyether nitrile (PEN), polyimide, polyamide, polyvinylidene fluoride (PVdF), epoxy resin, and synthetic rubber are preferable. These suitable binders are excellent in heat resistance, have a very wide potential window, are stable at both the positive electrode potential and the negative electrode potential, and can be used for the electrode layers 13 and 15. These binders may be used alone or in combination of two. PVdF, an epoxy resin, or the like is preferable as the binder used for the electrode layer that is bonded by heat fusion to the conductive resin layer of the current collector. This is because these materials are easy to heat-seal and improve the productivity during production. Moreover, since it is easy to perform heat fusion even if a binder is thermosetting, it is preferable. Suitable thermosetting binders include thermosetting polyimides, thermosetting polyamides, epoxy resins, synthetic rubbers, and more preferably epoxy resins.

  Examples of other additives that can be included in the active material layer include a conductive additive, an electrolyte salt (lithium salt), and an ion conductive polymer.

  The conductive assistant refers to an additive that is blended in order to improve the conductivity of the positive electrode active material layer or the negative electrode active material layer. Examples of the conductive assistant include carbon materials such as carbon black such as acetylene black, graphite, and vapor grown carbon fiber. When the active material layer contains a conductive additive, an electronic network inside the active material layer is effectively formed, which can contribute to improvement of the output characteristics of the battery.

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 , LiCF ₃ SO _{3 and the} like.

  Examples of the ion conductive polymer include polyethylene oxide (PEO) -based and polypropylene oxide (PPO) -based polymers.

  The compounding ratio of the components contained in the positive electrode layer 13 and the negative electrode layer 15 is not particularly limited. The mixing ratio can be adjusted by appropriately referring to known knowledge about the non-aqueous solvent secondary battery.

  The thicknesses of the electrode layers 13 and 15 are not particularly limited, and may be appropriately determined in consideration of the purpose of use of the battery (output importance, energy importance, etc.) and ion conductivity. Reference may be made as appropriate. If an example is given, the thickness of each electrode layers 13 and 15 is about 2-100 micrometers.

[Electrolyte layer]
The electrolyte constituting the electrolyte layer 17 is not particularly limited as long as it has a function as a lithium ion carrier that moves between positive and negative electrodes during charge and discharge, and is a liquid electrolyte, a polymer electrolyte, an inorganic solid electrolyte (oxide type) Solid electrolytes, sulfide-based solid electrolytes) and the like can be used.

The liquid electrolyte has a form in which a lithium salt as a supporting salt is dissolved in an organic solvent as a plasticizer. Examples of the organic solvent that can be used as the plasticizer include carbonates such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), and diethyl carbonate (DEC). As the supporting salt (lithium _{salt), Li (CF 3 SO 2} ) 2 N, Li (C 2 F 5 SO 2) 2 N, LiPF 6, LiBF 4, LiAsF 6, LiTaF 6, LiClO 4, LiCF 3 Compounds that can be added to the electrode mixture layer, such as SO _3, can be employed as well.

  On the other hand, the polymer electrolyte is classified into a gel electrolyte containing an electrolytic solution and an intrinsic (all solid) polymer electrolyte containing no electrolytic solution.

  The gel polymer electrolyte has a configuration in which the liquid electrolyte is injected into a matrix polymer (host polymer). Using a gel polymer electrolyte as the electrolyte is superior in that the fluidity of the electrolyte is lost, the electrolyte is prevented from flowing out to the current collector layer, and the ionic conductivity between the layers can be easily blocked. The matrix polymer (host polymer) is not particularly limited. For example, polyethylene oxide (PEO), polypropylene oxide (PPO), polyvinylidene fluoride (PVdF), a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP). ), Polyethylene glycol (PEG), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and copolymers thereof.

  Examples of the intrinsic polymer electrolyte include polyether polymer electrolytes such as polyethylene oxide (PEO) and polypropylene oxide (PPO). Usually, it has a structure in which a supporting salt (lithium salt) is dissolved in an intrinsic polymer electrolyte, and does not include an organic solvent that is a plasticizer. Therefore, by using the intrinsic polymer electrolyte as the electrolyte, the fluidity of the electrolyte is lost, the electrolyte is prevented from flowing out to the current collector layer, and the ion conductivity between the layers can be easily blocked.

  The matrix polymer of gel polymer electrolyte or intrinsic polymer electrolyte can express excellent mechanical strength by forming a crosslinked structure. In order to form a crosslinked structure, thermal polymerization, ultraviolet polymerization, radiation polymerization, electron beam polymerization, etc. are performed on a polymerizable polymer (for example, PEO or PPO) for forming a polymer electrolyte using an appropriate polymerization initiator. A polymerization treatment may be performed.

  In addition, when an electrolyte layer is comprised from a liquid electrolyte or a gel electrolyte, you may use a separator for an electrolyte layer. Specific examples of the separator include a microporous film made of polyolefin such as polyethylene or polypropylene.

[Outermost layer current collector]
As the outermost layer current collectors 11a and 11b, the current collector 11 for bipolar electrodes can be used as described above, and an existing metal current collector foil can be used. For example, an aluminum foil, a stainless steel (SUS) foil, a nickel and aluminum clad material, a copper and aluminum clad material, or a plating material of a combination of these metals may be used. Of these, aluminum foil and stainless steel foil are preferred in order to obtain an outermost layer current collector that can withstand the positive electrode potential and the negative electrode potential.

  However, a bipolar current collector may be used for the outermost layer current collector as in the embodiments described later. Furthermore, a bipolar electrode formed using the bipolar collector may be applied to the outermost layer. In this case, for example, in the outermost bipolar electrode connected to the positive electrode tab, the negative electrode layer positioned on the outermost surface does not substantially contribute to the charge / discharge reaction. Similarly, in the outermost bipolar electrode connected to the negative electrode tab, the positive electrode layer located on the outermost surface does not substantially contribute to the charge / discharge reaction. However, the number of components of the battery can be reduced by using bipolar electrodes in the outermost layer as in the embodiment. In addition, the production line reconfiguration (or switching) and production management (quality control) for forming only the positive electrode layer 13 and only the negative electrode layer 15 using the outermost layer current collectors 11a and 11b dedicated to the outermost layer electrode are performed. There is no need. Furthermore, it is excellent in that it is possible to prevent the occurrence of a problem that the outermost layer and other bipolar electrodes are mixed.

[Seal part]
A seal portion (also referred to as a sealant or a peripheral insulating layer) 31 is disposed in the peripheral portion of the unit cell layer 19 in order to prevent the electrolyte layer 17 from leaking. In addition to this, it is possible to prevent the adjacent current collectors in the battery from contacting each other and the occurrence of a short circuit due to slight unevenness at the end of the laminated electrode. For example, polyolefin resin such as PE and PP, epoxy resin, rubber, polyimide and the like can be used as the seal portion 31. From the viewpoint of corrosion resistance, chemical resistance, film forming property, economy, and the like, polyolefin resin is used. preferable. However, it is not limited to these.

  The seal part 31 can also be formed by any of sputtering, vapor deposition, CVD, PVD, ion plating, and thermal spraying. As the seal portion 31 suitable for such a forming method, alumina, silica, magnesia, yttria, or the like can be suitably used.

[Tab (positive tab and negative tab)]
Tabs (positive electrode tab 25 and negative electrode tab 27) that are electrically connected to each current collector are taken out of the battery exterior material for the purpose of taking out the current outside the battery. Specifically, as shown in FIG. 3, a positive electrode tab 25 electrically connected to the outermost layer positive electrode current collector 11 a and a negative electrode tab 27 electrically connected to the outermost layer negative electrode current collector 11 b include a battery. It is taken out of the laminate sheet as the exterior material 29.

  The material constituting the tabs (the positive electrode tab 25 and the negative electrode tab 27) is not particularly limited, and a known highly conductive material conventionally used as a tab for a lithium ion secondary battery can be used. As a constituent material of the tab, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable, and aluminum, copper, and the like are more preferable from the viewpoint of light weight, corrosion resistance, and high conductivity. Is preferred. Note that the same material may be used for the positive electrode tab 25 and the negative electrode tab 27, or different materials may be used. Moreover, it is good also as the positive electrode tab 25 and the negative electrode tab 27 by extending a part of outermost layer collector 11a and 11b, and the positive electrode tab 25 and the negative electrode tab 27 which were prepared separately are made into outermost layer collector 11a and 11b. You may connect.

[Positive electrode and negative electrode current collector]
A positive electrode and a negative electrode current collector plate (also referred to as an electrode terminal plate, a high voltage terminal, etc.) are used as necessary. For example, when the positive electrode tab 25 and the negative electrode tab 27 are directly taken out from the outermost current collectors 11a and 11b, the positive electrode and the negative electrode current collector plate need not be used. It is good also as the positive electrode tab 25 and the negative electrode tab 27 by extending a part of this electrode current collecting plate (high electric terminal; refer to an Example). Or you may connect the positive electrode tab 25 and the negative electrode tab 27 which were prepared separately, and a positive electrode and a negative electrode terminal lead to a positive electrode and a negative electrode current collector plate.

  As a material for the positive electrode and the negative electrode current collector 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 the internal resistance at the electrode current collector plate, the thickness of the positive electrode and negative electrode current collector plate is usually preferably about 0.1 to 2 mm.

[Positive electrode and negative electrode lead]
The positive terminal lead and the negative terminal lead are also used as necessary. For example, when the positive electrode tab 25 and the negative electrode tab 27 which are output electrode terminals are directly taken out from the outermost layer current collectors 11a and 11b, the positive electrode terminal lead and the negative electrode terminal lead may not be used.

  As the material of the positive terminal lead and the negative terminal lead, a terminal lead used in a known lithium ion secondary battery can be used. It should be noted that the part taken out from the battery outer packaging material 29 has a heat insulating property so as not to affect the product (for example, automobile parts, particularly electronic devices) by contacting with peripheral devices or wiring and causing leakage. It is preferable to coat with a heat shrinkable tube or the like.

[Battery exterior materials]
As the battery exterior material 29, a known metal can case can be used, and a bag-like case using a laminate film containing aluminum that can cover the power generation element 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. A laminate film that is excellent in high output and cooling performance and that can be suitably used for a battery for large equipment for EV and HEV is desirable.

[Appearance structure of bipolar secondary battery]
FIG. 3 is a perspective view showing the appearance of a stacked flat bipolar lithium ion secondary battery which is a typical embodiment of the bipolar secondary battery according to the present invention.

  As shown in FIG. 3, the laminated flat bipolar lithium ion secondary battery 50 has a rectangular flat shape, and a positive electrode tab 58 and a negative electrode tab for taking out electric power from both sides thereof. 59 is pulled out. The power generation element 57 is wrapped by the battery outer packaging material 52 of the bipolar lithium ion secondary battery 50, and the periphery thereof is heat-sealed. The power generation element 57 is in a state in which the positive electrode tab 58 and the negative electrode tab 59 are pulled out to the outside. It is sealed with. Here, the power generation element 57 corresponds to the power generation element 21 of the bipolar lithium ion secondary battery 10 shown in FIG. 1 described above. Further, a plurality of single battery layers (single cells) 19 composed of the positive electrode layer 13, the electrolyte layer 17, and the negative electrode layer 15 are stacked.

  The bipolar secondary battery of the present invention is not limited to the stacked flat shape as shown in FIG. The wound bipolar secondary battery may have a cylindrical shape, or may have a shape that is flattened by deforming such a cylindrical 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.

  Also, the removal of the tabs 58 and 59 shown in FIG. 3 is not particularly limited. The positive electrode tab 58 and the negative electrode tab 59 may be pulled out from the same side, or the positive electrode tab 58 and the negative electrode tab 59 may be divided into a plurality of parts and taken out from each side, as shown in FIG. It is not limited to. In addition, in a wound bipolar secondary battery, a terminal may be formed using, for example, a cylindrical can (metal can) instead of a tab.

[Battery]
The assembled battery of the present invention is constructed by connecting a plurality of bipolar secondary batteries of the present invention. Specifically, at least two or more are used, and are configured by serialization, parallelization, or both. Capacitance and voltage can be freely adjusted by paralleling in series. In the assembled battery of the present invention, a combination of the bipolar secondary battery of the present invention and another non-bipolar lithium ion secondary battery is used in series, in parallel, or in series and in parallel. An assembled battery can also be configured by combining them.

  4 is an external view of a typical embodiment of the assembled battery according to 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. It is a side view of an assembled battery.

  As shown in FIG. 4, the assembled battery 300 according to the present invention forms a small assembled battery 250 in which a plurality of bipolar lithium ion secondary batteries are connected in series or in parallel to be detachable. A large capacity and large output suitable for a vehicle driving power source and an auxiliary power source that require a high volume energy density and a high volume output density by connecting a plurality of these detachable small assembled batteries 250 in series or in parallel. It is also possible to form an assembled battery 300 having 4A is a plan view of the assembled battery, FIG. 4A is a front view, and FIG. 4C is a side view. The small assembled battery 250 that can be attached / detached has an electrical connection means such as a bus bar. The assembled battery 250 is stacked in a plurality of stages using the connection jig 310. How many bipolar lithium ion secondary batteries are connected to produce the assembled battery 250 and how many assembled batteries 250 are laminated to produce the assembled battery 300 are determined by the mounted vehicle (electric vehicle). ) Can be determined according to the battery capacity and output.

[vehicle]
The vehicle of the present invention is equipped with the battery of the present invention or an assembled battery formed by combining a plurality of these. Since the bipolar secondary battery of the present invention has a high output, when the battery is mounted, a plug-in hybrid electric vehicle having a long EV travel distance or an electric vehicle having a long charge travel distance can be configured. In other words, the bipolar secondary battery of the present invention or an assembled battery formed by combining a plurality of these batteries can be used as a power source for driving a vehicle. Examples of vehicles include hybrid vehicles, fuel cell vehicles, and electric vehicles (all are automobiles (commercial vehicles such as passenger cars, trucks, buses, light vehicles, etc.), motorcycles, and tricycles. ). However, the application is not limited to automobiles, and it can be applied to various power sources for other vehicles, for example, moving bodies such as trains, and can be used as a power source for mounting such as an uninterruptible power supply. It is also possible to do.

  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 can provide a sufficient output.

<IV> About the manufacturing method of the bipolar secondary battery of the present invention Next, the manufacturing method of the bipolar secondary battery of the present invention is not particularly limited, and is manufactured by applying a conventionally known method. be able to.

  The method for forming the current collector of the bipolar secondary electrode, which is a feature of the present invention, is not particularly limited. As a technique for alternately laminating and arranging conductive resin thin films and metal thin films, existing resin thin films and metal thin film deposition techniques, lamination / bonding techniques, and the like can be used in appropriate combinations.

  That is, the current collector is formed by (1) a method in which a conductive resin layer and a metal foil are bonded together by thermal fusion (thermosetting). (2) It is also formed by applying a conductive resin slurry containing a conductive resin material such as a resin or a conductive polymer with a conductive filler added on both sides of the metal foil. Further, (3) a metal layer is coated on the conductive resin layer by vapor deposition, sputtering, or the like. (A) A technique in which another conductive resin layer is bonded to the surface of the metal layer by thermal fusion (thermosetting) using the technique in (1) above, or (b) in (2) above. It is formed by a method of further applying a conductive resin slurry using a method. A current collector having a laminated structure of three or more layers can be obtained by repeating the above methods (1) to (3) to obtain a current collector in which a large number of metal layers and conductive resin layers are alternately laminated. Can be produced. However, the manufacturing method other than this may be used.

  Next, the method for manufacturing the bipolar secondary battery of the present invention is not particularly limited except that the current collector is formed by the appropriate method described above, and a conventionally known manufacturing method is used. Can be applied.

Example 1
1. Current collector manufacturing process A current collector having a three-layer laminated structure of Example 1 shown in Table 1 was constructed.

  Specifically, a conductive resin layer 1 (thickness 50 μm) in which a carbon material is dispersed in an epoxy resin is used, and a surface of the conductive resin layer 1 is coated with stainless steel by a vapor deposition method. Layer 1 (thickness 20 μm) was formed. A film in which a conductive resin layer 2 (thickness of 50 μm) in which a carbon material is dispersed in an epoxy resin is placed on the surface of the metal layer 1 is placed between the metal layer 1 and the conductive resin layer 2. Bonding (adhesion) was performed by curing and bonding the epoxy resin of the resin layer 2 having conductivity by heating.

  In addition, current collectors (Examples 6 to 8) having a laminated structure of more than this were also produced in the same manner as described above, and metal layers 2 and 3 and conductive resin layer 3 were produced. In Comparative Example 1, a so-called resin current collector composed of only conductive resin layers 1 (thickness: 100 μm) having different thicknesses was used. Comparative Example 2 was a current collector having a two-layer structure in which the metal layer 1 (thickness 20 μm) was formed on the conductive resin layer 1 (thickness 50 μm).

  Here, the resin layers 1 to 3 having conductivity are all liquid uncured epoxy resin (95 wt%) which is a polymer material (resin) having no conductivity, and carbon particles (carbon A solid content consisting of black; average particle size: 0.1 μm) (5 wt%) was kneaded at a temperature of 50 ° C. to prepare a conductive resin slurry. A conductive resin slurry was applied on the release film and dried to form a conductive resin layer in which a carbon material was dispersed in an epoxy resin. The release film was used by removing it when forming a positive electrode layer, a negative electrode layer, or a metal layer on the release film surface of the conductive resin layer. Moreover, the 1-component uncured epoxy resin which is a prepolymer before thermosetting was used for the epoxy resin. Furthermore, PET having excellent release properties and heat resistance was used for the release film.

  Moreover, as for the said metal layers 1-3, all used SUS316 as stainless steel.

2. Formation process of positive electrode layer As a positive electrode active material, LiMn ₂ O ₄ (average particle size: 10 μm) 85 wt%, acetylene black 5 wt% as a conductive assistant, and PVdF 10 wt% as a binder, slurry viscosity adjusting solvent An appropriate amount of N-methyl-2-pyrrolidone (NMP) was added to prepare a positive electrode slurry.

  The positive electrode slurry is mixed with the 1. One side of the current collector fabricated in step 1 (surface layer opposite to the conductive resin layer 1 side of the current collector surface layer; see Table 1 for details) and dried to form a positive electrode layer did. Pressing was performed so that the thickness of this positive electrode layer was 36 μm on one side.

3. Formation of negative electrode layer and completion of bipolar electrode Add appropriate amount of NMP, a slurry viscosity adjusting solvent, to the solid content of 90wt% hard carbon (average particle size: 10μm) as the negative electrode active material and 10wt% PVdF as the binder Thus, a negative electrode slurry was prepared.

  The other side of the current collector with the positive electrode layer formed on one side (resin layer 1 having electrical conductivity of the current collector surface layer; that is, the surface of the negative electrode layer side in each example and comparative example) The layer was applied to the conductive resin layer 1. (See Table 1) and dried to form a negative electrode layer. Pressing was performed so that the thickness of the negative electrode layer was 30 μm on one side.

  This formed a bipolar electrode in which a positive electrode layer was formed on one side of the current collector and a negative electrode layer was formed on the other side.

  The obtained bipolar electrode was cut into 140 mm × 90 mm, and the peripheral portion of the electrode 10 mm was prepared with a portion where no electrode layer (both positive electrode layer and negative electrode layer) was previously applied. Thus, a bipolar electrode having a 120 mm × 70 mm electrode portion and a 10 mm seal margin in the peripheral portion was produced.

  Next, the following materials were mixed at a predetermined ratio to prepare an electrolyte material (pregel solution).

As an electrolytic solution, 90 wt% of propylene carbonate (PC) -ethylene carbonate (EC) (1: 1 (volume ratio)) containing 1.0 M LiPF ₆ was used. As the host polymer, 10 wt% of polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP) containing 10 wt% of the HFP component was used. DMC was used as a viscosity adjusting solvent. An electrolyte material (pregel solution) was prepared by mixing an electrolyte solution, a host polymer, and a viscosity adjusting solvent.

  The electrolyte material (pregel solution) was applied to the entire surface of the positive electrode layer and the negative electrode layer on both sides of the bipolar electrode formed in advance, and the DMC was removed by drying at room temperature, so that the gel electrolyte was infiltrated. A bipolar electrode was completed. Note that the thickness of the positive electrode layer remained 36 μm, and the thickness of the negative electrode layer remained 30 μm.

4). Gel Polymer Electrolyte Layer Fabrication Process The electrolyte material (pregel solution) is applied on both sides of a polypropylene porous film separator (thickness 20 μm), and the DMC is dried at room temperature, thereby the gel polymer electrolyte layer (thickness 20 μm). )

5. Lamination Step A gel electrolyte layer was placed on the positive electrode layer of the bipolar electrode obtained above, and a PE (polyethylene) film having a width of 12 mm and a thickness of 100 μm was placed around it as a sealing material. After laminating 6 layers of such bipolar electrodes, the sealing material is pressed (heat and pressure) from above and below, and each layer is sealed (press conditions: 0.2 MPa, 160 ° C., 5 s) to seal Part was formed.

  A part (electrode tab: electrode tab: part of a 130 μm × 80 mm 100 μm thick Al plate (electrode current collector plate) that can cover the entire projection surface of the obtained battery element. An electrode current collector (high voltage terminal) having a width of 20 mm was produced. The battery element is sandwiched between the current collector plates so as to cover them, and is vacuum-sealed with a laminate film containing aluminum as a battery exterior material. The whole battery element is pressurized by pressing both sides at atmospheric pressure, and the electrode current collector plate- A bipolar secondary battery having a five-line structure (configuration in which five cells are connected in series) with improved contact between battery elements was completed.

(Example 2)
A bipolar secondary battery was fabricated in the same manner as in Example 1 except that the metal layer 1 (thickness 10 μm) having a different thickness was used as the metal layer 1 of the current collector.

(Example 3)
A bipolar secondary battery was fabricated in the same manner as in Example 1 except that the metal layer 1 (thickness: 5 μm) having a different thickness was used as the metal layer 1 of the current collector.

Example 4
Example 1 with the exception of using conductive resin layer 1 (20 μm), metal layer 1 (thickness 5 μm), and conductive resin layer 2 (80 μm) having different thicknesses as the current collector A bipolar secondary battery was produced in the same manner.

(Example 5)
Example 1 except that the conductive resin layer 1 (10 μm), the metal layer 1 (thickness 5 μm) and the conductive resin layer 2 (90 μm) having different thicknesses were used as the current collector. A bipolar secondary battery was produced in the same manner.

(Example 6)
As the current collector, conductive resin layer 1 (20 μm), metal layer 1 (thickness 5 μm), conductive resin layer 2 (20 μm), metal layer 2 (thickness 5 μm), and conductive resin A bipolar secondary battery was produced in the same manner as in Example 1 except that a current collector having a five-layer structure composed of layer 3 (20 μm) was used.

(Example 7)
As the current collector, conductive resin layer 1 (10 μm), metal layer 1 (thickness 5 μm), conductive resin layer 2 (20 μm), metal layer 2 (thickness 5 μm), and conductive resin A bipolar secondary battery was fabricated in the same manner as in Example 1 except that a current collector having a five-layer structure composed of layer 3 (30 μm) was used.

(Example 8)
As a current collector, conductive resin layer 1 (10 μm), metal layer 1 (thickness 5 μm), conductive resin layer 2 (20 μm), metal layer 2 (thickness 5 μm), conductive resin A bipolar secondary battery was fabricated in the same manner as in Example 1 except that a current collector having a six-layer structure composed of layer 3 (20 μm) and metal layer 3 (thickness 5 μm) was used.

Example 9
As a current collector, a current collector having a six-layer structure composed of a resin layer 1 (80 μm) having different thicknesses, a metal layer 1 (thickness 20 μm), and a resin layer 2 (20 μm) having conductivity is used. A bipolar secondary battery was produced in the same manner as in Example 1 except that it was used.

(Comparative Example 1)
A bipolar secondary battery was fabricated in the same manner as in Example 1 except that a so-called resin current collector consisting only of a conductive resin layer 1 (100 μm) was used as the current collector.

(Comparative Example 2)
As the current collector, a bipolar type was used in the same manner as in Example 1 except that a current collector having a two-layer structure composed of a conductive resin layer 1 (50 μm) and a metal layer 1 (thickness 20 μm) was used. A secondary battery was produced.

  Table 1 shows the stacked arrangement configuration of the current collectors used in each example and comparative example 1. The conductive resin layer 1 shown in Table 1 is the negative electrode layer side surface layer. However, since Comparative Example 1 is a resin current collector composed only of the resin layer 1 having conductive conductivity, both surfaces of the conductive resin layer 1 become the positive electrode layer side surface and the negative electrode layer side surface.

(Evaluation 1: charge / discharge test)
The first charge / discharge test was performed on the batteries of Examples 1 to 9 and Comparative Examples 1 and 2. In the test, constant current charging (CC) was performed at a current of 0.5 C up to 21.0 V, charging (CV) was then performed at a constant voltage, charging was performed for 10 hours, and then the capacity was measured with a discharge capacity of 1 C.

  After the initial charge / discharge, vibration and heat (70 ° C.) were applied for a long time with 50% SOC (State of charge: the amount of electricity charged relative to the electric capacity). Thereafter, a charge / discharge test (1C CCCV charge for 2 hours, 1C CC discharge) was performed to confirm the discharge capacity. The capacity before vibration is 100%, and the discharge capacity after vibration is shown in Table 2 (charging / discharging is performed by constant current (CC) charging / discharging, full charging is 21.0V, and discharge is 12.5V). .

  The vibration (test) was performed by applying a monotonous vibration with an amplitude of 3 mm and 50 Hz in a direction perpendicular to the battery (stacking direction) for 200 hours.

  The capacity retention rate (%) in Table 2 represents the ratio of the discharge capacity after vibration to the initial discharge capacity. That is, capacity retention ratio = discharge capacity after vibration (Ah) / initial discharge capacity (Ah) × 100 (%).

  The capacity improvement rate (−) for Comparative Example 1 in Table 2 is the ratio (relative value) of the capacity maintenance rates of other examples or comparative examples when the capacity maintenance rate of Comparative Example 1 is 1.00. Represent. That is, capacity improvement rate relative to Comparative Example 1 = capacity maintenance rate (%) of other examples or comparative examples / capacity maintenance rate (%) of Comparative Example 1.

(Discussion)
From the results of Table 2 above, the structure in which the metal layer is sandwiched by the conductive resin layer in the current collector from the capacity retention rate results of the example and the comparative example (conductive resin layer-metal layer-conductive property) It was confirmed that the ion permeation in the current collector can be suppressed by providing a three-layer laminated structure or more having a resin layer structure.

  In Examples 4 and 5, the capacity retention ratio is improved by making the resin layer 1 having conductivity, which is the surface layer on the negative electrode layer side, thinner than the resin layers 2 and 3 having other conductivity. This is because the amount of carbon (conductive metal filler) in the conductive resin layer 1 which is the surface layer on the negative electrode layer side is reduced, and thus the capacity deterioration of the carbon during the long-term reliability test is suppressed. it is conceivable that. The cause of this carbon capacity deterioration is that the conductive carbon material in the conductive resin layer 1 also functions as an active material. However, as charging and discharging are repeated, the carbon material is pulverized due to cracks caused by expansion and contraction of the carbon material. It is thought that it is inactivated by doing so, leading to capacity loss (deterioration). In the current collector of the example, the conductive carbon (conductive metal filler) in the conductive resin layer 1 is absorbed and relaxed by the polymer material (epoxy resin) when expanded and contracted. It is considered that the deterioration of the carbon material can be further suppressed.

  In Examples 6, 7, and 8, the capacity retention ratio is slightly improved by forming a multi-layered structure of five or more layers as compared to the three-layer structure (Examples 1 to 5 and 9). The vibration resistance is further improved by adopting a multi-layer structure, which is considered to have led to an improvement in life characteristics.

  Even in the two-layer structure in which the metal layer is provided together with the conductive resin layer in the current collector as in the comparative example 2, the current collector is more in comparison with the existing resin current collector (Comparative Example 1). It was confirmed that the ion permeation can be suppressed and the life characteristics are improved by reducing the liquid junction. However, from the capacity retention rate results of Comparative Example 2 and Examples 1 to 9, the structure in which the metal layer is sandwiched between the conductive resin layers in the current collector (the conductive resin layer-metal layer-conductive It is confirmed that the ion permeation in the current collector can be significantly suppressed by providing a three-layer structure having a resin layer structure having a metal layer with a conductive resin layer. It was done.

  In addition, compared with the metal collector foil of the same thickness, the current collectors of Examples 1 to 9 each having a conductive resin layer are all lightweight, and the output of the battery is improved. Since it has already been confirmed from 1 etc., the same experiment was not conducted.

BRIEF DESCRIPTION OF THE DRAWINGS It is the cross-sectional schematic which represented typically the outline | summary of the bipolar lithium ion secondary battery which is one typical embodiment of the bipolar secondary battery of this invention. As an example of the current collector laminated arrangement in the bipolar electrode of the bipolar secondary battery of the present invention, a three-layer laminated structure of a conductive resin layer-metal layer-conductive resin layer, wherein the metal layer is It is the cross-sectional schematic of the arbitrary bipolar electrodes in the bipolar secondary battery which represented the structure arrange | positioned in the center typically. An example of a laminated arrangement in a current collector in a bipolar electrode of the bipolar secondary battery of the present invention is a three-layer laminated structure of a conductive resin layer-metal layer-conductive resin layer, the metal layer FIG. 3 is a schematic cross-sectional view of an arbitrary bipolar electrode in a bipolar secondary battery, schematically showing a structure in which is disposed closer to the negative electrode layer side. An example of a laminated arrangement in a current collector in a bipolar electrode of the bipolar secondary battery of the present invention is a three-layer laminated structure of a conductive resin layer-metal layer-conductive resin layer, the metal layer FIG. 3 is a schematic cross-sectional view of an arbitrary bipolar electrode in a bipolar secondary battery, schematically showing a structure in which is disposed closer to the positive electrode layer side. As an example of the lamination arrangement of the metal layer in the current collector and the conductive resin layer in the bipolar electrode of the bipolar secondary battery of the present invention, the conductive resin layer-metal layer-conductive resin layer -Metal layer-It is the cross-sectional schematic diagram of the arbitrary bipolar electrodes in the bipolar secondary battery which represented typically the 5 layer laminated structure of the resin layer which has electroconductivity. And in this drawing, the inside of the bipolar secondary battery schematically showing the structure in which the conductive resin layer on the negative electrode layer side surface layer is arranged to be thinner than the other conductive resin layers. It is the cross-sectional schematic of arbitrary bipolar electrodes. As an example of the lamination arrangement in the current collector in the bipolar electrode of the bipolar secondary battery of the present invention, (positive electrode layer side) metal layer-conductive resin layer-metal layer-conductive resin layer-metal layer -It is the cross-sectional schematic diagram of the arbitrary bipolar electrodes in the bipolar secondary battery which represented typically the 6 layer laminated structure of the resin layer (negative electrode layer side) which has electroconductivity. In this drawing, a bipolar secondary that schematically shows a structure in which the conductive resin layer on the negative electrode layer side surface layer has the same thickness as other conductive resin layers. It is the cross-sectional schematic of the arbitrary bipolar electrodes in a battery. As an example of the laminated arrangement in the current collector in the bipolar electrode of the bipolar secondary battery of the present invention, (positive electrode layer side) conductive resin layer-metal layer-conductive resin layer-metal layer-conductive It is the cross-sectional schematic of the arbitrary bipolar electrodes in the bipolar secondary battery which represented typically the 6 layer laminated structure of the resin layer-metal layer (negative electrode layer side) which has. And in this drawing, in the bipolar secondary battery schematically showing a structure in which the conductive resin layer closer to the negative electrode layer side is arranged to be thinner than other conductive resin layers. It is the cross-sectional schematic of arbitrary bipolar electrodes. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view schematically showing an appearance of a stacked flat bipolar secondary battery that is a typical embodiment of a bipolar secondary battery according to the present invention. FIG. 4A is an external view schematically showing a typical embodiment of a bipolar secondary battery module according to the present invention, and FIG. 4A is a plan view of the bipolar secondary battery module, and FIG. 4B is a bipolar secondary battery module. FIG. 4C is a front view of the battery module, and FIG. 4C is a side view of the bipolar secondary battery module. It is a conceptual diagram of the vehicle carrying the assembled battery (module) of the bipolar secondary battery of this invention.

Explanation of symbols

1, 1a, 1b, 1c metal layer,
2, 2a, 2b, 2c conductive resin layer,
10 Bipolar lithium ion secondary battery,
11 Current collector,
11a Outermost layer current collector on the positive electrode layer side,
11b The outermost layer current collector on the negative electrode layer side,
13 positive electrode layer,
15 negative electrode layer,
16, 16a, 16b bipolar electrode,
17 electrolyte layer (gel electrolyte layer),
19 single battery layer (= battery unit or single cell),
25 positive electrode tab,
27 negative electrode tab,
29 Battery exterior materials (eg laminate films),
31 seal part,

50 Bipolar lithium ion secondary battery, 250 Battery pack (module) of a detachable small bipolar secondary battery,
300 battery pack (module) of bipolar secondary battery,
310 connection jig,
400 Electric car.

Claims (5)

A current collector including a conductive resin layer; a positive electrode layer electrically coupled to one surface of the current collector; and a negative electrode layer electrically coupled to the other surface of the current collector. A bipolar electrode,
The current collector includes a metal layer thinner than the resin layer,
The metal layer includes a structure sandwiched between the resin layers ,
In the case of the current collector having a three-layer structure including the resin layer, the metal layer, and the resin layer, the resin layer (for one layer) having conductivity in the current collector has a thickness of 10 to 200 μm ( However, a bipolar electrode characterized in that it is 10 μm) . The resin layer closest to the negative electrode layer side of the current collector is a layer in which a conductive metal filler is dispersed in a polymer material, and the metal that is in contact with the resin layer closest to the negative electrode layer side on the positive electrode layer side The bipolar electrode according to claim 1, wherein the layer is disposed on the negative electrode layer side from the center in the thickness direction of the current collector. The resin layer closest to the negative electrode layer side of the current collector is a layer in which a conductive metal filler is dispersed in a polymer material, and the thickness of the resin layer closest to the negative electrode layer side is other than The bipolar electrode according to claim 1, wherein the bipolar electrode is thinner than the resin layer. The bipolar electrode according to any one of claims 1 to 3, wherein a surface layer on a positive electrode layer side and a negative electrode layer side of the current collector is formed of a resin layer. Bipolar secondary battery with bipolar electrodes and the electrolyte layer, characterized in that the layers are alternately formed of any one of claims 1-4.

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