JP2020061221A - Bipolar secondary battery - Google Patents

Abstract

To stably detect a voltage of a single cell even in a case where exfoliation of a cathode collector or an anode collector with respect to an insulation member occurs.SOLUTION: A bipolar secondary battery 10 comprises a battery element 11 in which single cells 20 are stacked. The single cell includes a cathode 30a, an anode 30b, a separator 40 and an insulation member 50. The bipolar secondary battery comprises a voltage detection terminal 70 which is disposed, in an outer periphery of the battery element, between a front face of a cathode collector 31a at a side not in contact with the insulation member between both front and rear faces thereof and a front face of an anode collector 31b at a side not in contact with the insulation member between both front and rear faces thereof, and detecting a voltage of the single cell. The bipolar secondary battery comprises an adhesive layer 80 for bonding any one collector of the cathode collector 31a and the anode collector 31b with the voltage detection terminal.SELECTED DRAWING: Figure 4B

Description

  The present invention relates to a bipolar secondary battery.

  In recent years, various electric vehicles have been expected to become popular for solving environmental and energy problems. Batteries have been earnestly developed as in-vehicle power sources such as motor driving power sources that hold the key to the spread of these electric vehicles. Batteries intended for application to in-vehicle power supplies are required to have extremely high output characteristics as compared with batteries used in mobile phones, notebook computers, and the like.

  For example, Patent Document 1 discloses a bipolar secondary battery in which a plurality of single cells are stacked and connected in series in order to improve the output characteristics of the battery. Here, the single cell includes a positive electrode having a positive electrode active material layer containing a positive electrode active material formed on the surface of a positive electrode current collector, and a negative electrode having a negative electrode active material layer containing a negative electrode active material formed on the surface of a negative electrode current collector. Are laminated via a separator. In Patent Document 1, in order to prevent a short circuit due to electrolyte leakage, an insulating member (sealing member) is arranged so as to surround the outer periphery of the electrode active material layer, and the outer periphery of the positive electrode current collector and the negative electrode current collector is arranged. It is sealed.

JP-A-2004-349156

  In a bipolar secondary battery in which single cells are connected in series, it is necessary to detect and control the voltage of each single cell so as not to overcharge or overdischarge.

  By the way, the electrode may expand due to the characteristics of the material forming the electrode or the deterioration of the electrode over time. The expansion of the electrode increases the thickness of the electrode, and while maintaining the normal function as a battery, the positive electrode current collector may be slightly peeled from the insulating member or the negative electrode current collector may be slightly peeled from the insulating member. It may happen. Even when the current collector is peeled off from the insulating member, the voltage of the single cell must be stably detected.

  Therefore, the present invention provides a bipolar secondary battery capable of stably detecting the voltage of a single cell even when the positive electrode collector or the negative electrode collector is separated from the insulating member. The purpose is to do.

  The bipolar secondary battery of the present invention for achieving the above object has a battery element in which single cells are laminated. The single cell is a positive electrode having a positive electrode active material layer formed on a positive electrode current collector, a negative electrode having a negative electrode active material layer formed on a negative electrode current collector, and a separator sandwiched by the positive electrode and the negative electrode. The positive electrode active material layer is sealed between the positive electrode current collector and the separator between the positive electrode current collector and the negative electrode current collector, and the positive electrode active material layer is sealed between the negative electrode current collector and the separator. And an insulating member that seals the negative electrode active material layer. The bipolar secondary battery has, on the outer periphery of the battery element, a surface of the front and back surfaces of the positive electrode current collector that is not in contact with the insulating member and a surface of the negative electrode current collector that contacts the insulating member. It has a voltage detection terminal for detecting the voltage of the unit cell, the voltage detection terminal being arranged between the non-side surface and the surface. The bipolar secondary battery has an adhesive layer that bonds one of the positive electrode current collector and the negative electrode current collector to the voltage detection terminal.

  According to the bipolar secondary battery of the present invention, the voltage of a single cell can be stably detected even when the positive electrode current collector or the negative electrode current collector is separated from the insulating member.

1 is a perspective view showing a bipolar secondary battery according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1, which is a cross-sectional view schematically showing the overall structure of a bipolar secondary battery. It is sectional drawing which shows the single cell of a bipolar secondary battery. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 1, showing a voltage detection terminal and an adhesive layer in the bipolar secondary battery. FIG. 4B is a cross-sectional view corresponding to FIG. 4A in a state in which the thickness of the negative electrode is increased due to the expansion of the negative electrode and the negative electrode current collector is partially separated from the insulating member. FIG. 4B is a cross-sectional view corresponding to FIG. 4A in a state in which the thickness of the negative electrode is increased due to the expansion of the negative electrode and the positive electrode current collector is partly separated from the insulating member. 9 is a cross-sectional view showing a voltage detection terminal and an adhesive layer in a bipolar secondary battery according to Modification 1. FIG. FIG. 9 is a cross-sectional view showing a voltage detection terminal and an adhesive layer in a bipolar secondary battery according to Modification 2. FIG. 9 is a cross-sectional view of a bipolar secondary battery of Modification 2 in a state where the thickness of the negative electrode is increased due to the expansion of the negative electrode. 11 is a cross-sectional view showing a voltage detection terminal and an adhesive layer in a bipolar secondary battery according to Modification 3. FIG. FIG. 9 is a cross-sectional view showing a voltage detection terminal and an adhesive layer in a bipolar secondary battery according to Modification 4. It is sectional drawing which shows a comparative battery. FIG. 7 is a cross-sectional view showing a state in which the negative electrode current collector is separated from the insulating member due to an increase in the negative electrode thickness due to the expansion of the negative electrode in the battery of the comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the technical scope of the present invention should be determined based on the description of the claims, and is not limited to the following embodiments. It should be noted that the dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios. In the present specification, “X to Y” indicating a range means “X or more and Y or less”.

<Bipolar secondary battery>
A bipolar lithium ion secondary battery, which is one type of non-aqueous electrolyte secondary battery, will be described as an example of the bipolar secondary battery according to the embodiment of the present invention. Here, the bipolar lithium-ion secondary battery is a secondary battery that includes bipolar electrodes connected in series and that charges or discharges when lithium ions move between a positive electrode and a negative electrode. In the following description, the bipolar lithium ion secondary battery will be simply referred to as “battery”.

  FIG. 1 is a perspective view showing a battery 10 according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line 2-2 of FIG. 1, showing a schematic overall structure of the battery 10. is there. FIG. 3 is a sectional view showing a single cell 20 of the battery 10. FIG. 4A is a cross-sectional view taken along line 4-4 of FIG. 1, showing a voltage detection terminal and an adhesive layer in the battery.

  The battery 10 of the present embodiment will be outlined with reference to FIGS. The battery 10 has a battery element 11 in which unit cells 20 are stacked. The unit cell 20 includes a positive electrode 30a, a negative electrode 30b, a separator 40, and an insulating member 50. The positive electrode 30a has a positive electrode current collector 31a and a positive electrode active material layer 32a formed thereon. In the negative electrode 30b, the negative electrode active material layer 32b is formed on the negative electrode current collector 31b. The separator 40 is sandwiched between the positive electrode 30a and the negative electrode 30b. The insulating member 50 seals the positive electrode active material layer 32a between the positive electrode current collector 31a and the negative electrode current collector 31b and between the positive electrode current collector 31a and the separator 40, and the negative electrode current collector 31b and the separator 40. The negative electrode active material layer 32b is sealed with the gap 40. The battery 10 includes, on the outer periphery of the battery element 11, one of the front and back surfaces of the positive electrode current collector 31 a which is not in contact with the insulating member 50 and the other one of the front and back surfaces of the negative electrode current collector 31 b which is not in contact with the insulating member 50. It has a voltage detection terminal 70 for detecting the voltage of the unit cell 20, which is arranged between the surface and the surface. The battery 10 includes an adhesive layer 80 that bonds the current collector 31 (the negative electrode current collector 31b in the illustrated example) of either one of the positive electrode current collector 31a and the negative electrode current collector 31b to the voltage detection terminal 70. Have. Hereinafter, the configuration of the battery 10 will be described in detail.

  As shown in FIG. 2, the battery 10 has a structure in which a battery element 11 formed by stacking a plurality of unit cells 20 is sealed inside an outer casing 12 in order to prevent external impact and environmental deterioration. Have. The battery element 11 is a laminated body of the single cells 20, and is a portion that contributes to the charge / discharge reaction. In addition, it is preferable to adjust the number of stacking of the single cells 20 according to a desired voltage. Further, in this specification, a direction in which the plurality of unit cells 20 are stacked is referred to as a “stacking direction” and is indicated by an arrow Z in the drawing. A plane orthogonal to the stacking direction is referred to as a "plane direction" and is indicated by an arrow X and an arrow Y in the drawing.

  As shown in FIG. 2, the positive electrode 30 a and the negative electrode 30 b have a positive electrode active material layer 32 a that is electrically coupled to one surface of a current collector 31 and that is electrically connected to the other surface of the current collector 31. A bipolar electrode 35 having the combined negative electrode active material layer 32b is formed. The current collector 31 has a laminated structure (two-layer structure) in which a positive electrode current collector 31a and a negative electrode current collector 31b are combined.

  In the battery 10, a positive electrode collector plate (positive electrode tab) 34a is arranged adjacent to the positive electrode collector 31a, and a negative electrode collector plate (negative electrode tab) 34b is arranged adjacent to the negative electrode collector 31b. There is. As shown in FIG. 1, the positive electrode current collector plate (positive electrode tab) 34 a is extended and led out from the exterior body 12. Similarly, the negative electrode current collector plate (negative electrode tab) 34 b is extended and led out from the exterior body 12.

[Single cell]
As shown in FIGS. 2 and 3, the single cell 20 includes a positive electrode 30a, a negative electrode 30b, a separator 40, and an insulating member 50. By holding the electrolyte in the separator 40, an electrolyte layer is formed. In the unit cell 20 of the present embodiment, the positive electrode active material layer 32a and the negative electrode active material layer 32b contain an electrolytic solution.

  The positive electrode active material layer 32a and the negative electrode active material layer 32b are arranged so as to face each other via the separator 40. The positive electrode current collector 31a and the negative electrode current collector 31b are located in the outermost layer of the single cell 20.

  In the present specification, the positive electrode current collector 31a, the negative electrode current collector 31b, and the outer peripheral portion 60 of the separator 40 are heat-sealed via the insulating member 50 (a region surrounded by a broken line in FIG. 3). It is defined as As shown in FIG. 3, when the insulating member 50 is interposed between the outer peripheral portion of the positive electrode current collector 31 a and the outer peripheral portion of the negative electrode current collector 31 b, the outer peripheral portion of the current collector 31 and the separator 40. The region including the outer peripheral portion of the single cell 20 and the insulating member 50 corresponds to the outer peripheral portion of the single cell 20.

  The insulating member 50 liquid-tightly seals the periphery of the positive electrode active material layer 32a, the negative electrode active material layer 32b, and the separator 40 to prevent a liquid junction due to leakage of the electrolytic solution. Further, the positive electrode current collector 31a and the negative electrode current collector 31b are electrically separated in the single cell 20 to prevent a short circuit due to the contact between the positive electrode current collector 31a and the negative electrode current collector 31b.

  The material forming the insulating member 50 may be any material having an insulating property, a sealing property (liquid tightness), a heat resistance at a battery operating temperature, and the like. For example, acrylic resin, urethane resin, epoxy resin, polyethylene resin, polypropylene resin, polyimide resin, rubber (ethylene-propylene-diene rubber: EPDM), or the like can be used. Further, an isocyanate adhesive, an acrylic resin adhesive, a cyanoacrylate adhesive, or the like may be used, or a hot melt adhesive (urethane resin, polyamide resin, polyolefin resin) or the like may be used. Of these, polyethylene resin and polypropylene resin are preferably used as the constituent material of the insulating layer from the viewpoints of corrosion resistance, chemical resistance, easiness of production (film-forming property), economical efficiency, etc., and amorphous polypropylene resin is the main component. It is preferable to use a resin obtained by copolymerizing ethylene, propylene and butene.

[Voltage detection terminal]
As shown in FIG. 4A, the voltage detection terminal 70 is provided on the outer periphery of the battery element 11 between the front and back surfaces of the positive electrode current collector 31a that are not in contact with the insulating member 50 and the front and back surfaces of the negative electrode current collector 31b. Of these, it is arranged between the surface not in contact with the insulating member 50 and the surface. A lead wire 71 is connected to the voltage detection terminal 70. The lead wire 71 is connected to a controller (not shown), and a detection signal is input to the controller.

  The material forming the voltage detection terminal 70 may be any material as long as it has conductivity, and is made of a conductive material. Examples of the conductive material include metal materials. Examples of the metal material include aluminum, nickel, iron, stainless steel, titanium and copper.

[Adhesive layer]
As shown in FIG. 4A, the adhesive layer 80 of the present embodiment is disposed between the negative electrode current collector 31b and the voltage detection terminal 70, and bonds the negative electrode current collector 31b and the voltage detection terminal 70.

  As a material for forming the adhesive layer 80, a material that has an adhesive property between the negative electrode current collector 31b and the voltage detection terminal 70 and a conductivity that does not hinder the electrical conductivity between the negative electrode current collector 31b and the voltage detection terminal 70 is used. It only needs to be provided, and is composed of a conductive adhesive. The conductive adhesive is, for example, a conductive epoxy adhesive.

  Hereinafter, the operation and effect of this embodiment will be described with reference to a comparative example. FIG. 4B is a cross-sectional view corresponding to FIG. 4A in a state where the thickness of the negative electrode 30b is increased by the expansion of the negative electrode 30b and the negative electrode current collector 31b is partially peeled from the insulating member 50. FIG. 4C is a cross-sectional view corresponding to FIG. 4A in a state where the thickness of the negative electrode 30b is increased due to the expansion of the negative electrode 30b and the positive electrode current collector 31a is partially separated from the insulating member 50. FIG. 9A is a cross-sectional view showing a battery in contrast. FIG. 9B is a cross-sectional view in a state where the thickness of the negative electrode 30b is increased due to the expansion of the negative electrode 30b and the negative electrode current collector 31b is partially separated from the insulating member 110.

  As shown in FIG. 9A, in the battery of proportionality, the voltage detection terminal 120 is arranged between the insulating member 110 and the negative electrode current collector 31b while being in contact with the negative electrode current collector 31b.

  The electrode 30 may expand due to the characteristics of the material forming the electrode 30 or the deterioration of the electrode 30 over time. For example, as shown in FIG. 9B, the thickness of the negative electrode 30b increases due to the expansion of the negative electrode 30b, and the negative electrode current collector 31b may be somewhat peeled from the insulating member 110 while maintaining the normal function as a battery. Sometimes. The voltage detection terminal 120 is bonded (easily bonded) to the insulating member 110 side of the negative electrode current collector 31b. Therefore, when the negative electrode current collector 31b is peeled off from the insulating member 110, the negative electrode current collector 31b is peeled off from the voltage detection terminal 120. The contact state between the voltage detection terminal 120 and the negative electrode current collector 31b changes, and the contact resistance between the two changes from the initial state. Therefore, it becomes difficult to stably detect the voltage of the single cell.

  On the other hand, in the present embodiment, as shown in FIG. 4A, in the battery 10, on the outer periphery of the battery element 11, the voltage detection terminal 70 is provided on the side of the positive and negative electrode current collector 31a that is not in contact with the insulating member 50. Of the negative electrode current collector 31b and the surfaces of the front and back surfaces of the negative electrode current collector 31b that are not in contact with the insulating member 50. Further, in the battery 10, the negative electrode current collector 31b and the voltage detection terminal 70 are bonded to each other with the adhesive layer 80.

  As shown in FIG. 4B, the thickness of the negative electrode 30b increases due to the expansion of the negative electrode 30b, and the negative electrode current collector 31b may be somewhat peeled from the insulating member 50 while maintaining the normal function as a battery. is there. Even if such a situation occurs, since the voltage detection terminal 70 is bonded to the negative electrode current collector 31b by the adhesive layer 80, it is possible to prevent the negative electrode current collector 31b from peeling off from the voltage detection terminal 70. The contact state between the voltage detection terminal 70 and the negative electrode current collector 31b does not change, and the contact resistance between the two does not change from the initial state. Therefore, it is possible to stably detect the voltage of the unit cell 20.

  Further, as shown in FIG. 4C, the expansion of the negative electrode 30b increases the thickness of the negative electrode 30b, so that the positive electrode current collector 31a may be slightly peeled from the insulating member 50 while maintaining the normal function as a battery. Sometimes. Even if such a situation occurs, since the voltage detection terminal 70 is adhered to the negative electrode current collector 31b by the adhesive layer 80, it is possible to prevent the negative electrode current collector 31b from peeling off from the voltage detection terminal 120. The contact state between the voltage detection terminal 70 and the negative electrode current collector 31b does not change, and the contact resistance between the two does not change from the initial state. Therefore, it is possible to stably detect the voltage of the unit cell 20.

[Current collector]
The current collector 31 (adjacent positive electrode current collector 31a and negative electrode current collector 31b) mediates transfer of electrons from one surface in contact with the positive electrode active material layer 32a to the other surface in contact with the negative electrode active material layer 32b. Have the function to The material forming the current collector 31 is not particularly limited, but, for example, a conductive resin or metal can be used.

  From the viewpoint of reducing the weight of the current collector 31, it is preferable that the current collector 31 is a resin current collector formed of a resin having conductivity. From the viewpoint of blocking the movement of lithium ions between the unit cells 20, a metal layer may be provided on a part of the resin current collector.

  Specifically, examples of the conductive resin that is a constituent material of the resin current collector include a resin in which a conductive filler is added to a conductive polymer material or a non-conductive polymer material as necessary. . Examples of the conductive polymer material include polyaniline, polypyrrole, polythiophene, polyacetylene, polyparaphenylene, polyphenylenevinylene, and polyoxadiazole. Since such a conductive polymer material has sufficient conductivity without adding a conductive filler, it is advantageous in facilitating the manufacturing process and reducing the weight of the current collector.

  Examples of the non-conductive polymer material include polyethylene (PE; high density polyethylene (HDPE), low density polyethylene (LDPE), etc.), polypropylene (PP), polyethylene terephthalate (PET), polyether nitrile (PEN), polyimide. (PI), polyamideimide (PAI), polyamide (PA), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA). , Polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), polystyrene (PS), and the like. Such a non-conductive polymer material may have excellent potential resistance or solvent resistance.

  The conductive filler can be used without particular limitation as long as it is a substance having conductivity. For example, as a material having excellent conductivity, potential resistance, or lithium ion barrier property, metal and conductive carbon can be cited. The metal is not particularly limited, but at least one metal selected from the group consisting of nickel, titanium, aluminum, copper, platinum, iron, chromium, tin, zinc, indium, antimony, and potassium, or a metal thereof. It is preferable to include an alloy or a metal oxide containing The conductive carbon is not particularly limited. Preferably, from the group consisting of acetylene black, Vulcan (registered trademark), black pearl (registered trademark), carbon nanofiber, Ketjenblack (registered trademark), carbon nanotube (CNT), carbon nanohorn, carbon nanoballoon, and fullerene. It is preferable to include at least one selected.

  The amount of the conductive filler added is not particularly limited as long as it can provide the current collector 31 with sufficient conductivity, and is preferably about 5 to 35% by volume.

  When the current collector 31 is made of metal, examples of the metal include aluminum, nickel, iron, stainless steel, titanium, and copper. In addition to these, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plated material of these metals can be preferably used. Further, it may be a foil having a metal surface coated with aluminum. Of these, aluminum, stainless steel, copper, and nickel are preferable from the viewpoints of electron conductivity, battery operating potential, and adhesion of the negative electrode active material to the current collector 31 by sputtering.

[Electrode active material layer (positive electrode active material layer, negative electrode active material layer)]
The electrode active material layer (positive electrode active material layer 32a, negative electrode active material layer 32b) 32 includes an electrode active material (positive electrode active material or negative electrode active material) and an electrolytic solution. In addition, the electrode active material layer 32 may include a coating material (coating resin, conductive auxiliary agent), a conductive member, or the like, if necessary. Furthermore, the electrode active material layer 32 may include an ion conductive polymer or the like, if necessary.

  The electrolytic solution contained in the electrode active material layer 32 functions as a dispersion medium of the electrode active material in the slurry preparation step. The electrolytic solution of the electrode active material layer 32 has the same composition as the electrolytic solution contained in the separator 40 of the battery 10 from the viewpoint of reducing the number of steps by omitting the step of injecting the electrolytic solution in the step after forming the electrode 30. It is preferable.

  In the battery 10, the positive electrode active material layer 32a and the negative electrode active material layer 32b contain an electrolytic solution. In this configuration, after the electrode active material slurry is applied to obtain a coating film, it is not necessary to subject the obtained coating film to a drying treatment by heating. As a result, cracking of the electrode active material layer 32 can be suppressed, and the manufacturing cost required for the drying process can be reduced.

The electrolytic solution has a form in which a lithium salt is dissolved in a solvent. Examples of the solvent that constitutes the electrolytic solution include carbonates such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate. The lithium _{salt, LiPF 6, LiBF 4, LiSbF} 6, LiAsF 6 LiClO 4, Li [(FSO 2) 2 N] (LiFSI) lithium salts of inorganic acids such _{as, LiN (CF 3 SO 2)} 2, LiN ( Examples thereof include lithium salts of organic acids such as C ₂ F ₅ SO ₂ ) ₂ and LiC (CF ₃ SO ₂ ) ₃ .

(Cathode active material)
As the positive electrode active material, for example, lithium such as those _{LiMn 2 O 4, LiCoO 2,} LiNiO 2, Li (Ni-Mn-Co) O 2 , and some of these transition metals are replaced by other elements - Examples thereof include transition metal composite oxides, lithium-transition metal phosphate compounds, lithium-transition metal sulfate compounds, and the like. Depending on the case, two or more positive electrode active materials may be used in combination. From the viewpoint of capacity and output characteristics, a lithium-transition metal composite oxide is preferably used as the positive electrode active material. More preferably, a composite oxide containing lithium and nickel is used. More preferably Li (Ni-Mn-Co) O 2 , and in which a part of these transition metals are replaced by other elements (hereinafter, simply referred to as "NMC composite oxide"), or a lithium - nickel - cobalt -Aluminum composite oxide (hereinafter also simply referred to as "NCA composite oxide") or the like is used. The NMC composite oxide has a layered crystal structure in which lithium atomic layers and transition metal (Mn, Ni, and Co are arranged in order) atomic layers are alternately stacked with oxygen atomic layers interposed. One Li atom is contained per atom of the transition metal, and the amount of Li that can be taken out is twice as large as that of the spinel-based lithium manganese oxide, that is, the supply capacity is twice as large, and a high capacity can be obtained.

(Negative electrode active material)
Examples of the negative electrode active material include carbon materials such as graphite, soft carbon, hard carbon, lithium-transition metal composite oxides (eg, Li ₄ Ti ₅ O ₁₂ ), metal materials (tin, silicon), lithium. Examples thereof include alloy-based negative electrode materials (for example, lithium-tin alloy, lithium-silicon alloy, lithium-aluminum alloy, lithium-aluminum-manganese alloy). Depending on the case, two or more negative electrode active materials may be used in combination. From the viewpoints of capacity and output characteristics, carbon materials, lithium-transition metal composite oxides, and lithium alloy-based negative electrode materials are preferably used as the negative electrode active material. Needless to say, a negative electrode active material other than the above may be used. In addition, a coating resin such as a (meth) acrylate-based copolymer has a property that it is particularly easily attached to a carbon material. Therefore, from the viewpoint of providing a structurally stable electrode material, it is preferable to use a carbon material as the negative electrode active material.

(Conductive agent)
The conductive auxiliary agent is used as a coating agent for coating the surface of the electrode active material together with the coating resin. The conduction aid forms an electron conduction path in the coating material and reduces the electron transfer resistance of the electrode active material layer 32, thereby contributing to the improvement of the output characteristics at a high rate of the battery.

  Examples of the conductive aid include metals such as aluminum, stainless steel, silver, gold, copper, and titanium, alloys or metal oxides containing these metals; graphite, carbon fibers (specifically, vapor-grown carbon fibers ( VGCF) and the like), carbon nanotubes (CNT), carbon black (specifically, acetylene black, Ketjen black (registered trademark), furnace black, channel black, thermal lamp black, etc.) and the like. Not limited to. Further, a granular ceramic material or resin material coated with the above metal material by plating or the like can also be used as the conductive additive. Among these conductive aids, from the viewpoint of electrical stability, it is preferable to contain at least one selected from the group consisting of aluminum, stainless steel, silver, gold, copper, titanium, and carbon. Aluminum and stainless steel It is more preferable to contain at least one kind selected from the group consisting of silver, gold, and carbon, and it is more preferable to contain at least one kind of carbon. These conductive aids may be used alone or in combination of two or more.

  The shape of the conductive additive is preferably particulate or fibrous. When the conductive additive is in the form of particles, the shape of the particles is not particularly limited and may be any shape such as powder, spherical, rod-shaped, needle-shaped, plate-shaped, column-shaped, irregular-shaped, scaly, and spindle-shaped. It doesn't matter. When the conductive additive is in the form of particles, the average particle size (primary particle size) is preferably 100 nm or less. In addition, in this specification, a "particle diameter" means the largest distance among the distances between arbitrary two points on the outline of a conductive support agent. The value of the “average particle diameter” is an average value of the particle diameters of particles observed in several to several tens of visual fields by using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted.

(Conductive member)
The conductive member has a function of forming an electron conduction path in the electrode active material layer 32. In particular, it is preferable that at least a part of the conductive member forms a conductive path that electrically connects the two main surfaces of the electrode active material layer 32. By having such a form, the electron transfer resistance in the thickness direction in the electrode active material layer 32 is further reduced, so that the output characteristics of the battery at a high rate can be further improved. Whether or not at least a part of the conductive member forms a conductive path that electrically connects the two main surfaces of the electrode active material layer 32 is determined by using an SEM or an optical microscope. It can be confirmed by observing the cross section.

  The conductive member is preferably a conductive fiber having a fibrous form. Specifically, carbon fibers such as PAN-based carbon fibers and pitch-based carbon fibers, conductive fibers obtained by uniformly dispersing metal with good conductivity or graphite in synthetic fibers, and metals such as stainless steel are made into fibers. The metal fibers, the conductive fibers obtained by coating the surface of the organic fibers with a metal, the conductive fibers obtained by coating the surface of the organic fibers with a resin containing a conductive substance, and the like. Among them, carbon fiber is preferable because it has excellent conductivity and is lightweight.

  In the battery 10 of the present embodiment, the thickness of the electrode active material layer 32 is preferably 150 to 1500 μm, more preferably 180 to 950 μm, and further preferably 200 to 800 μm for the positive electrode active material layer 32a. is there. The thickness of the negative electrode active material layer 32b is preferably 150 to 1500 μm, more preferably 180 to 1200 μm, and further preferably 200 to 1000 μm. When the thickness of the electrode active material layer 32 is at least the above lower limit value, the energy density of the battery can be sufficiently increased. On the other hand, if the thickness of the electrode active material layer 32 is equal to or less than the above-mentioned upper limit value, the structure of the electrode active material layer 32 can be sufficiently maintained.

  In addition, in the battery 10 of the present embodiment, as a constituent member of the electrode active material layer 32, the above-mentioned electrode active material, a conductive member optionally used, an ion conductive polymer, a lithium salt, a coating agent (for coating) Members other than the resin and the conductive additive may be used as appropriate. However, from the viewpoint of improving the energy density of the battery, it is preferable not to include a member that does not contribute much to the progress of the charge / discharge reaction. For example, it is preferable not to use the binder added to bind the electrode active material and other members and maintain the structure of the electrode active material layer 32 as much as possible. Examples of the binder having the above function include solvent-based binders such as polyvinylidene fluoride (PVdF) and water-based binders such as styrene-butadiene rubber (SBR). Specifically, the content of the binder is preferably 10% by mass or less, more preferably 5% by mass or less, and still more preferably 100% by mass of the total solid content contained in the electrode active material layer 32. Is 2% by mass or less, particularly preferably 1% by mass or less, and most preferably 0% by mass.

[Separator]
The separator 40 holds the electrolyte and is located between the positive electrode active material layer 32a and the negative electrode active material layer 32b and prevents them from directly contacting each other. The electrolyte used for the separator 40 of the present embodiment is not particularly limited, and examples thereof include an electrolytic solution or a gel polymer electrolyte. High lithium ion conductivity can be ensured by using these electrolytes.

  Examples of the form of the separator 40 include a separator of a porous sheet made of a polymer or fiber that absorbs and holds the electrolyte, a nonwoven fabric separator, and the like.

  The electrolytic solution may be the same as the electrolytic solution used for the electrode active material layer 32 described above. The concentration of the lithium salt in the electrolytic solution is preferably 0.1 to 3.0M, more preferably 0.8 to 2.2M. The amount of the additive used is preferably 0.5 to 10% by mass, more preferably 0.5 to 5% by mass, based on 100% by mass of the electrolytic solution before the additive is added. is there.

  As the additive, for example, vinylene carbonate, methyl vinylene carbonate, dimethyl vinylene carbonate, phenyl vinylene carbonate, diphenyl vinylene carbonate, ethyl vinylene carbonate, diethyl vinylene carbonate, vinyl ethylene carbonate, 1,2-divinyl ethylene carbonate, 1-methyl- 1-vinyl ethylene carbonate, 1-methyl-2-vinyl ethylene carbonate, 1-ethyl-1-vinyl ethylene carbonate, 1-ethyl-2-vinyl ethylene carbonate, vinyl vinylene carbonate, allyl ethylene carbonate, vinyloxymethyl ethylene carbonate, Allyloxymethyl ethylene carbonate, acryloxymethyl ethylene carbonate, methacryloxymethyl Ji Ren carbonate, ethynyl ethylene carbonate, propargyl carbonate, ethynyloxy methylethylene carbonate, propargyloxy ethylene carbonate, methylene carbonate, etc. 1,1-dimethyl-2-methylene-ethylene carbonate. Among them, vinylene carbonate, methylvinylene carbonate and vinylethylene carbonate are preferable, and vinylene carbonate and vinylethylene carbonate are more preferable. These cyclic carbonates may be used alone or in combination of two or more.

  The gel polymer electrolyte has a structure in which the above electrolytic solution is injected into a matrix polymer (host polymer) made of an ion conductive polymer. The use of the gel polymer electrolyte as the electrolyte is excellent in that the fluidity of the electrolyte is lost and the ion conductivity between the layers is blocked to facilitate the process. Examples of the ion conductive polymer used as the matrix polymer (host polymer) include polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polyvinylidene fluoride-hexafluoropropylene ( PVdF-HEP), polymethylmethacrylate (PMMA), copolymers thereof, and the like.

  The matrix polymer of the gel polymer electrolyte can exhibit excellent mechanical strength by forming a crosslinked structure. In order to form a crosslinked structure, a suitable polymerization initiator may be used to perform thermal polymerization, ultraviolet polymerization, radiation polymerization, electron beam polymerization, etc. on a polymerizable polymer for forming a polyelectrolyte (for example, PEO or PPO). Polymerization may be performed.

[Positive electrode current collector and negative electrode current collector]
The material that constitutes the current collector 31 (the positive electrode current collector 31a and the negative electrode current collector 31b) is not particularly limited, and a known high-conductivity material that has been conventionally used as a current collector for a lithium ion secondary battery. Can be used. As a constituent material of the current collector 31, for example, a metal material such as aluminum, copper, titanium, nickel, stainless steel, or an alloy thereof is preferable. From the viewpoint of light weight, corrosion resistance, and high conductivity, aluminum and copper are more preferable, and aluminum is particularly preferable. The same material may be used for the positive electrode current collector 31a and the negative electrode current collector 31b, or different materials may be used.

[Exterior body]
In the present embodiment shown in FIG. 2, the outer casing 12 is formed of a flexible laminated film into a bag shape, but is not limited to this. For example, a cell case formed of a material having rigidity may be used. You may use. From the standpoint that it is excellent in high output and cooling performance and can be suitably used for batteries for large-sized equipment for EVs and HEVs, the outer casing 12 is preferably made of a laminated film, and a laminated film containing aluminum. Is particularly preferable. As the laminate film containing aluminum, for example, a laminate film having a three-layer structure obtained by laminating polypropylene (PP), aluminum, and nylon in this order can be used, but the laminate film is not limited thereto.

  As described above, the battery 10 according to the present embodiment has the battery element 11 in which the single cells 20 are stacked, and the outer periphery of the battery element 11 contacts the insulating member 50 on both the front and back surfaces of the positive electrode current collector 31a. It has a voltage detection terminal 70 for detecting the voltage of the single cell 20, which is arranged between the surface on the non-contact side and the surface on both sides of the negative electrode current collector 31b which is not in contact with the insulating member 50. The battery 10 has an adhesive layer 80 that adheres the negative electrode current collector 31b and the voltage detection terminal 70.

  With this configuration, even if the positive electrode current collector 31a or the negative electrode current collector 31b is separated from the insulating member 50, the adhesion of the voltage detection terminal 70 to the negative electrode current collector 31b is reduced. Therefore, the contact state between the voltage detection terminal 70 and the negative electrode current collector 31b does not change. Therefore, the contact resistance between the voltage detection terminal 70 and the negative electrode current collector 31b does not change from the initial state. Therefore, the voltage of the unit cell 20 can be stably detected.

  In the battery 10, the positive electrode current collector 31a and the negative electrode current collector 31b are resin current collectors.

  With this configuration, the weight of the battery 10 can be reduced by reducing the weight of the current collector 31 (the positive electrode current collector 31a and the negative electrode current collector 31b).

  In the battery 10, the positive electrode active material layer 32a and the negative electrode active material layer 32b contain an electrolytic solution.

  With this configuration, when the battery 10 is manufactured, it is not necessary to apply the electrode active material slurry to obtain a coating film and then subject the obtained coating film to a drying treatment by heating. . As a result, cracking of the electrode active material layer 32 (the positive electrode active material layer 32a and the negative electrode active material layer 32b) can be suppressed, and the manufacturing cost required for the drying process can be reduced.

(Modification 1)
FIG. 5 is a cross-sectional view showing the voltage detection terminal 70 and the adhesive layer 80 in the battery 10 according to Modification 1.

  In the embodiment described above, the form in which the negative electrode current collector 31b and the voltage detection terminal 70 are adhered by the adhesive layer 80 has been shown. The present invention is not limited to this case, and the adhesive layer 80 may be formed by bonding one of the positive electrode current collector 31a and the negative electrode current collector 31b to the voltage detection terminal 70. Good.

  Therefore, as shown in FIG. 5, the positive electrode current collector 31a and the voltage detection terminal 70 may be bonded by the adhesive layer 80.

  Even in the case of such a configuration, the same operation and effect as those of the above-described embodiment are exhibited. That is, even if the positive electrode current collector 31a or the negative electrode current collector 31b is separated from the insulating member 50, the contact state between the voltage detection terminal 70 and the positive electrode current collector 31a does not change, and both of them do not change. The contact resistance does not change from the initial state. Therefore, the voltage of the unit cell 20 can be stably detected.

  Note that the first adhesive is placed between the negative electrode current collector 31b and the voltage detection terminal 70, and the second adhesive is also placed between the positive electrode current collector 31a and the voltage detection terminal 70. Furthermore, the adhesive strength of the first adhesive and the adhesive strength of the second adhesive are made different. Such an aspect should be understood not to be included in the “adhesive layer 80 for adhering any one of the positive electrode current collector 31a and the negative electrode current collector 31b to the voltage detection terminal 70”. I won't. This is because, when the positive electrode current collector 31a or the negative electrode current collector 31b is peeled off from the insulating member 50, the contact state between the one current collector 31 and the voltage detection terminal 70 is brought about by the adhesive having a high adhesive strength. Is maintained and the voltage of the unit cell 20 can be detected stably.

(Modification 2)
FIG. 6A is a cross-sectional view showing the voltage detection terminal 70 and the adhesive layer 80 in the battery 10 according to Modification 2. FIG. 6B is a cross-sectional view of the battery 10 of Modification 2 in a state where the thickness of the negative electrode 30b is increased due to the expansion of the negative electrode 30b.

  As shown in FIG. 6A, in the battery 10 according to the modified example 2, the thickness t1 of the insulating member 50 along the stacking direction of the single cells 20 is the total thickness t0 of the positive electrode 30a, the negative electrode 30b, and the separator 40 in the single cell 20. Thinner than. Further, the negative electrode current collector 31b and the voltage detection terminal 70 are bonded by the adhesive layer 80. On the outer periphery of the battery element 11, a minute space is formed between the voltage detection terminal 70 and the positive electrode current collector 31a.

  As shown in FIG. 6B, when the thickness of the negative electrode 30b increases due to the expansion of the negative electrode 30b, the outer periphery of the battery element 11 can move in the vertical direction in the figure. Therefore, peeling of the positive electrode current collector 31a or the negative electrode current collector 31b from the insulating member 50 is unlikely to occur in the first place. Even if the negative electrode current collector 31b is peeled off from the insulating member 50, the negative electrode current collector 31b is peeled off from the voltage detection terminal 70 because the voltage detection terminal 70 is bonded to the negative electrode current collector 31b by the adhesive layer 80. Can be suppressed. The contact state between the voltage detection terminal 70 and the negative electrode current collector 31b does not change, and the contact resistance between the two does not change from the initial state. Therefore, the voltage of the unit cell 20 can be stably detected.

(Modification 3)
FIG. 7 is a cross-sectional view showing the voltage detection terminal 70 and the adhesive layer 80 in the battery 10 according to Modification 3.

  In the second modification, the negative electrode current collector 31b and the voltage detection terminal 70 are bonded by the adhesive layer 80. The present invention is not limited to this case, and the adhesive layer 80 may be formed by bonding one of the positive electrode current collector 31a and the negative electrode current collector 31b to the voltage detection terminal 70. Good.

  Therefore, as shown in FIG. 7, the positive electrode current collector 31a and the voltage detection terminal 70 may be bonded by the adhesive layer 80.

  Even in the case of such a configuration, the same operation and effect as in the second modification can be obtained. That is, since the outer periphery of the battery element 11 can move in the vertical direction in the figure, the positive electrode current collector 31a or the negative electrode current collector 31b is unlikely to be separated from the insulating member 50. Even if the positive electrode current collector 31a is peeled off from the insulating member 50, since the voltage detection terminal 70 is bonded to the positive electrode current collector 31a by the adhesive layer 80, the positive electrode current collector 31a is peeled off from the voltage detection terminal 70. Can be suppressed. The contact state between the voltage detection terminal 70 and the positive electrode current collector 31a does not change, and the contact resistance between the two does not change from the initial state. Therefore, the voltage of the unit cell 20 can be stably detected.

(Modification 4)
FIG. 8 is a cross-sectional view showing the voltage detection terminal 70 and the adhesive layer 80 in the battery 10 according to Modification 4.

  The voltage detection terminal 70 of the modified example 4 is bonded to the negative electrode current collector 31b by the adhesive layer 80 as in the modified example 2. On the outer periphery of the battery element 11, a minute space is formed between the voltage detection terminal 70 and the positive electrode current collector 31a. Therefore, the thickness of the voltage detection terminal 70 of the modification 4 along the stacking direction of the unit cell 20 is larger than that of the voltage detection terminals 70 of the modifications 2 and 3.

  Even in the case of such a configuration, the same operation and effect as in the second modification can be obtained. Further, even if the thickness of the voltage detection terminal 70 is increased, the height dimension of the battery 10 does not increase.

10 Bipolar rechargeable battery,
11 battery elements,
12 exterior body,
20 single cells,
30 electrodes,
30a positive electrode,
30b negative electrode,
31 current collector,
31a Positive electrode current collector,
31b Negative electrode current collector,
32 electrode active material layer,
32a positive electrode active material layer,
32b negative electrode active material layer,
35 bipolar electrodes,
40 separator,
50 insulating member,
60 outer periphery,
70 Voltage detection terminal,
71 lead wire,
80 adhesive layer,
110 insulating member,
120 Voltage detection terminal.

Claims (4)

A positive electrode having a positive electrode active material layer formed on a positive electrode current collector, a negative electrode having a negative electrode active material layer formed on a negative electrode current collector, a separator sandwiched between the positive electrode and the negative electrode, and the positive electrode current collector. The positive electrode active material layer is sealed between the positive electrode current collector and the separator between the current collector and the negative electrode current collector, and the negative electrode active material layer is interposed between the negative electrode current collector and the separator. A battery element in which single cells are laminated, including an insulating member for sealing
In the outer periphery of the battery element, between the surface of the front and back surfaces of the positive electrode current collector that is not in contact with the insulating member and the surface of the front and back surfaces of the negative electrode current collector that is not in contact with the insulating member. And a voltage detection terminal for detecting the voltage of the single cell,
A bipolar secondary battery comprising: an adhesive layer that bonds one of the positive electrode current collector and the negative electrode current collector to the voltage detection terminal.   The bipolar secondary battery according to claim 1, wherein a thickness of the insulating member along the stacking direction of the single cells is smaller than a total thickness of the positive electrode, the negative electrode, and the separator in the single cells.   The bipolar secondary battery according to claim 1 or 2, wherein the positive electrode current collector and the negative electrode current collector are resin current collectors.   The bipolar secondary battery according to claim 1, wherein the positive electrode active material layer and the negative electrode active material layer contain an electrolytic solution.