JP4635589B2 - Bipolar battery, assembled battery, composite battery and vehicle equipped with these - Google Patents

Description

  The present invention relates to a bipolar battery, an assembled battery, a composite battery, and a vehicle equipped with these.

  Lithium secondary batteries include those using a solid electrolyte, those using a liquid electrolyte, and those using a polymer gel electrolyte as the electrolyte enclosed therein.

  For the solid electrolyte, an all solid polymer electrolyte such as polyethylene oxide is used, while a 100% electrolytic solution is used for the liquid electrolyte. The polymer gel electrolyte should be said to be an intermediate between them. For example, polyvinylidene fluoride (PVDF) itself has an electrolyte solution held in a polymer skeleton having no lithium ion conductivity ( For example, see Patent Document 1).

  When a liquid electrolyte or a polymer gel electrolyte is used as the electrolyte, a seal member surrounding the single battery layer is provided between the current collectors (for example, Patent Document 2). If there is no sealing member, the electrolyte oozes out between the respective unit cell layers, and contacts with the electrolytes of the other unit cell layers, causing a short circuit between the unit cell layers called a liquid junction. Here, the single battery layer includes a positive electrode active material layer, a gel electrolyte layer, and a negative electrode active material layer.

In order to provide the seal member, a single cell layer is sandwiched between the current collectors, and a heat-sealing resin for sealing is sandwiched between the outer peripheral parts, and the heat-sealing resin part is heated and pressed to heat-fuse the current collector. There is a method of heat-sealing resin. The heat sealing resin serves as a seal member.
JP-A-11-204136 JP-A-08-007926 (paragraph "0012")

  However, as described above, when the sealing member is hot-pressed and heat-sealed on the current collector, there are the following problems.

  When the seal member is pressurized in a state where it is softened by heating, the seal member is compressed without being able to maintain its shape, and the distance between the current collectors is shortened. In this case, the insulation distance between the current collectors may not be ensured.

  Moreover, in order to adhere | attach in the state which maintained the shape, when heating of a sealing member is reduced and a pressurizing force is improved, stress will be applied to the adhesion part periphery of a collector. In this case, the current collector is deformed, and the battery performance may be deteriorated.

  The present invention has been made in view of the above problems, and provides a bipolar battery, an assembled battery, a composite battery, and a vehicle on which these are mounted while maintaining the shape of the seal member and generating no stress on the current collector. For the purpose.

The bipolar battery of the present invention comprises a bipolar electrode having a positive electrode active material layer formed on one surface of a current collector and a negative electrode active material layer formed on the other surface, and an electrolyte laminated alternately between the bipolar electrodes. And between the current collectors so as to surround the periphery of the unit cell layer including the adjacent positive electrode active material layer, the electrolyte, and the negative electrode active material layer, and when being heat-sealed A resin layer having a softening point lower than the temperature and a resin layer having a softening point higher than the temperature at which the heat fusion is performed, and is heated to the temperature at which the heat fusion is performed to sandwich the current collector And a seal member that is partially bonded to each other .

  According to the bipolar battery of the present invention, when the sealing member is thermally welded between the current collectors, the soft resin layer reaches the softening point by heating at a lower softening point or higher and lower or higher softening point. Thus, a strong resin layer can be obtained without reaching the softening point. Since the flexible resin layer can absorb the stress due to the pressurization during welding, the current collector can be prevented from being deformed by the stress. Since the strong resin layer can withstand pressure and maintain its shape, the distance between the current collectors can be maintained.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
(overall structure)
1 is a plan view of the bipolar battery, FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. 1, and FIG. 3 is a cross-sectional view taken along line 3-3 in FIG.

  As shown in FIGS. 1 to 3, the bipolar battery has a positive electrode tab and a negative electrode tab drawn from a flat main body.

  As shown in FIG. 2, the bipolar battery 10 has a positive electrode active material layer 12 and a negative electrode active material layer 13 formed at the center of both surfaces of a current collector 11 other than both ends. A single battery layer 15 is formed by sandwiching a separator 14 between the layer 12 and the negative electrode active material layer 13, and a plurality of single battery layers 15 are stacked in the same order. A material in which the positive electrode active material layer 12 is formed on one surface of the current collector 11 and the negative electrode active material layer 13 is formed on the other surface is referred to as a bipolar electrode 16. A current collector (referred to as an end current collector 17) at both ends is connected to electrodes of the entire bipolar battery.

  A structure in which the positive electrode active material layer 12 and the negative electrode active material layer 13 are provided with the current collector 11 interposed therebetween is called a bipolar electrode.

  Here, the separator 14 is, for example, a polymer skeleton formed of a resin selected from the group consisting of a polyester resin, an aramid resin, and a polyolefin resin, either alone or in combination. The separator 14 constitutes an electrolyte layer by holding a gel electrolyte or a liquid electrolyte containing an electrolytic solution of about several to 98% by weight. Moreover, the separator 14 can also hold | maintain an electrolyte by being formed with a solid electrolyte itself. In the first embodiment, a case where a gel electrolyte is held in the separator 14 will be described.

  When the separator 14 holds the gel electrolyte, in order to prevent liquid leakage from the single cell layer 15, it surrounds each single cell layer 15 and is between the current collectors 11 or between the current collectors 11 and the end portions. A seal member 18 disposed between the current collectors 17 is provided.

  The seal member 18 is formed in a two-layer structure in which different resin layers 181 and 182 are laminated. The seal member 18 is softened by heating and welded to the current collector 11. By using such a material for the seal member 18, it is possible to prevent liquid leakage from the single cell layer 15, and it is possible to prevent a short circuit due to contact between the current collectors 11.

  As described above, the separators 14 and the bipolar electrodes 16 are alternately stacked, and the sealing member 18 is disposed around the unit cell layer 15 to form the battery element 20.

  The battery element 20 is connected to electrode tabs 30a and 30b for drawing current. The electrode tab 30a is connected to the positive electrode side of the battery element 20, and the electrode tab 30b is connected to the negative electrode side. The electrode tabs 30a and 30b are pulled out from the exterior 40 as shown in FIG.

  The exterior 40 is formed by two laminate sheets 41. The laminate sheet 41 has a three-layer structure in which both surfaces of an aluminum layer are covered with a resin layer. At least one of the laminate sheets 41 is processed into a medium-high shape in order to provide a space that encloses the battery element 20. The edge of the laminate sheet 41 is bonded by heat fusion or the like. Thereby, the battery element 20 is sealed inside the exterior 40.

  As described above, the bipolar battery 10 of the present embodiment is characterized by having the two-layered sealing member 18. The seal member 18 will be described in detail.

(Seal member)
FIG. 4 is a cross-sectional view showing the battery element.

  As described above, the seal member 18 has a two-layer structure. The resin layer 181 and the resin layer 182 constituting the sealing member 18 are formed of different resins.

  For example, the resin layer 181 is formed of a material having a softening point smaller than that of the resin layer 182. Hereinafter, the resin layer 181 is referred to as a softened layer 181. Further, the resin layer 182 is referred to as a maintenance layer 182.

  The softening layer 181 is made of, for example, a material having a low softening point such as low-density polyethylene or ethylene-vinyl acetate copolymer (EVA), or a material that can operate with a low softening point such as modified polypropylene. As the modified propylene, maleic acid modification is effective. However, it is not limited to this. Any material can be used for the softening layer 181 as long as the softening point is lower than the material used for the sustaining layer 182.

  The maintenance layer 182 is formed of a resin having a relatively high melting point / softening point, such as polyethylene terephthalate (PET) or polyether nitrile (PEN). By selecting such a resin having a high softening point, the range of materials that can be used for the softening layer 181 is widened. The maintenance layer 182 preferably has a softening point higher by 40 degrees or more than the softening layer 181.

  As shown in FIG. 4, the battery element 20 is heated and pressurized from above and below the stack in a state where the seal member 18 is disposed so as to surround the single cell layer 15, whereby the seal member 18 is collected from the current collector 11. Welded in between. Thereby, the single battery layer 15 is sealed between the current collectors 11.

  Thereafter, the battery element 20 is further heated and pressurized at the portion indicated by the alternate long and short dash line in FIG. 4 to weld the seal members 18 together. Thereby, the sealing members 18 are welded together, and the whole battery element 20 is maintained integrally. In FIG. 4, the current collector 11 appears to have a large gap between the seal members 18. However, since the current collectors 11 are actually thin, the current collectors 11 can be welded together without being disturbed by the thickness of the current collectors 11.

  In FIG. 4, the softening layer 181 is the upper layer, and the sustaining layer 182 is disposed in the lower layer. However, the softening layer 181 may be disposed in the lower layer and the maintenance layer 182 may be disposed in the upper layer.

(effect)
Next, the effect of the seal member 18 will be described.

  As described above, in this embodiment, the sealing member 18 is formed in a two-layer structure by combining the softening layer 181 having a low softening point and the maintenance layer 182 having a high softening point.

  Therefore, by heating the sealing member 18 at a temperature equal to or higher than the softening point of the softening layer 181 and lower than the softening point of the sustaining layer 182, the softening layer 181 that reaches the softening point and reaches the softening point without reaching the softening point can be obtained. A strong maintenance layer 182 is obtained.

  The softened layer 181 absorbs stress generated in a region surrounded by a dotted line in FIG. 4 due to elasticity and deformation. Therefore, the stress applied to the current collector 11 is reduced. As a result, metal deterioration of the current collector 11 due to stress and poor welding of the seal member 18 can be prevented.

  On the other hand, the shape of the maintenance layer 182 is maintained without being deformed. Accordingly, at least the thickness of the sustain layer 182 ensures the distance between the current collectors 11. As a result, a short circuit of the single battery layer 15 due to contact between the current collectors 11 can be prevented.

  Furthermore, since the softening points of the softening layer 181 and the maintenance layer 182 are 40 degrees or more apart, it is not necessary to increase the heating control accuracy when the seal member 18 is welded. Manufacturing flexibility is large, and manufacturing efficiency can be improved.

(Improved example 1)
The bipolar battery 10 can be applied under vibration generation of an automobile or the like. Therefore, it is preferable to improve the vibration isolation performance. In order to improve the anti-vibration performance, it is preferable that the hardness of the sealing member 18, particularly the hardness of the softened layer 181, is in the range of JIS-A 5 to 95 degrees. If the hardness JIS-A of the softened layer 181 is less than 5 degrees, it is too soft and the deformation of the softened layer 181 at the time of pressurization is too large. If the hardness JIS-A is greater than 95 degrees, it is too hard and the anti-vibration effect is obtained. It will be smaller.

  A vibration system model of the battery element 20 is shown in FIG.

  FIG. 5 is a diagram showing a mass spring model of the battery element.

  The battery element 20 shown in FIG. 5 includes the same bipolar electrode 16 as in FIGS. 2 and 4, and two cell layers 15 are provided.

  As shown in FIG. 5, the battery element 20 is modeled as a vibration system including masses 51 and 52, springs 53 and 54, and dampers 55 and 56.

  The masses 51 and 52 correspond to the bipolar electrode 16 (the positive electrode active material layer 12 is formed on one surface of the current collector 11 and the negative electrode active material layer 13 is formed on the other surface). The springs 53 and 54 and the dampers 55 and 56 correspond to the seal member 18. Strictly speaking, the separator 14 also has the effects of the springs 53 and 54 and the dampers 55 and 56.

  The weights of the masses 51 and 52 are M1 and M2, the spring coefficients of the springs 53 and 54 are K1 and K2, and the damping coefficients of the dampers 55 and 56 are C1 and C2. Usually, M1 = M2, K1 = K2, and C1 = C2, so that an anti-vibration effect is obtained. In particular, in order to increase the vibration damping effect, the damping coefficients C1 and C2 of the seal member 18 when modeled are increased, and the spring coefficients K1 and K2 are reduced. By changing the hardness of the resin of the seal member 18, the damping coefficients C1 and C2 and the spring coefficients K1 and K2 can be adjusted.

  As described above, by selecting the hardness of the resin of the seal member 18, the vibration isolation effect can be improved. The anti-vibration effect also has the effect that the impact of the seal member 18 on the current collector 11 can be reduced.

Further, considering the case where the bipolar battery 10 of the present embodiment is applied to a vehicle regarding vibration isolation, it is necessary to determine the resin used for the seal member 18 based on the situation where the vehicle is placed. The vehicle may be placed in an environment having a temperature of -30 degrees to 80 degrees, and vibrations with a vibration frequency of 10 Hz to 1 KHz are applied during traveling. In this situation, the resin used for the seal member 18 preferably has a dielectric loss tangent of 1.0 × 10 ^{−3 to} 5.0 × 10 ⁻¹ . This is because when the dielectric loss tangent is less than 1.0 × 10 ^{−3, the} dielectric loss tangent is too soft, and when the dielectric loss tangent is larger than 5.0 × 10 ⁻¹ , the dielectric loss tangent is too hard.

  FIG. 6 is a diagram showing the relationship between the frequency of vibration applied to the bipolar battery and the acceleration of the bipolar battery when a resin having a preferable dielectric loss tangent is used for the seal member.

  In the conventional structure, as shown in FIG. 6, the acceleration is large when the frequency is 80 Hz, 120 Hz, and 200 Hz. That is, it can be seen that the image stabilization is not achieved.

  On the other hand, in the structure of the embodiment, the acceleration hardly increases even at the same frequency. It can be seen that the image stabilization is possible.

  The vibration reducing effect depends on the loss tangent, which is obtained by a dynamic viscoelastic test. However, since it is difficult to accurately measure a relatively soft resin in this test, characteristics can be predicted by using a dielectric loss tangent that is substantially equivalent to the loss tangent. Therefore, the range of the dielectric loss tangent is determined as described above.

However, when the loss tangent can be measured accurately, the loss tangent is preferably in the range of 1.0 × 10 ^{−3 to} 5.0 × 10 ⁻¹ .

(Improvement example 2)
In the above embodiment, the seal member 18 is formed in a two-layer structure. However, it is not limited to this. The sealing member 18 can be formed in a multilayer structure having more than two layers. For example, as shown in FIG. 6, the seal member 18 ′ can be formed in a three-layer structure.

  FIG. 7 is a view showing a seal member having a three-layer structure.

  In the sealing member 18 ′ shown in FIG. 7, the resin layer 181 in contact with the current collector 11 has a low softening point, and one resin layer 182 sandwiched therebetween has a high softening point. That is, the maintenance layer 182 is sandwiched between the softening layers 181. Here, the materials used for the softening layer 181 and the sustaining layer 182 are the same as those described above. The softening layers 181 disposed at both ends can be formed of different resins having a difference in softening point of less than 40 degrees. However, the softened layers 181 at both ends are preferably formed of the same material.

  Thus, by making the sealing member 18 ′ into a three-layer structure, the softened layers 181 at both ends become soft and easily welded to the current collector 11 when being sandwiched between the current collector 11 and thermally fused. Therefore, the sealing performance can be further improved.

  Further, by using the same material for the softened layers 181 at both ends, the adhesiveness when welding the seal members 18 'is improved, and the seal strength can be further improved.

(Bipolar battery configuration)
The configuration of the bipolar battery of the present invention is not particularly limited as long as a known material used for a general lithium ion secondary battery is used, except for those specifically described. The current collector, positive electrode active material layer, negative electrode active material layer, electrolyte, and the like that can be used for this bipolar battery will be described below for reference.

[Positive electrode active material layer]
The positive electrode includes a positive electrode active material. In addition to this, an electrolyte, a lithium salt, or the like may be included in order to increase ion conductivity. Moreover, in order to improve electronic conductivity, a conductive support agent, NMP (N-methyl-2-pyrrolidone) as a slurry viscosity adjusting solvent, AIBN (azobisisobutyronitrile), etc. as a polymerization initiator may be included. In particular, it is desirable that at least one of the positive electrode and the negative electrode contains an electrolyte, preferably a solid polymer electrolyte. However, in order to further improve the battery characteristics of the bipolar battery, it is preferable to contain them in both.

As the positive electrode active material, a composite oxide of transition metal and lithium, which is also used in a solution-type lithium ion battery, can be used. Specifically, Li · Co-based composite oxide such as LiCoO _2, Li · Ni-based composite oxide such as LiNiO _2, Li · Mn-based composite oxide such as spinel LiMn ₂ O _4, Li · such LiFeO ₂ Examples thereof include Fe-based composite oxides. In addition, transition metal and lithium phosphate compounds and sulfuric acid compounds such as LiFePO ₄ ; transition metal oxides and sulfides such as V ₂ O ₅ , MnO ₂ , TiS ₂ , MoS ₂ , and MoO ₃ ; PbO ₂ , AgO, NiOOH etc. are mentioned.

  The positive electrode active material may have any particle diameter as long as the positive electrode material can be formed into a paste by spray coating or the like. Further, in order to reduce the electrode resistance of the bipolar battery, it is preferable to use a battery whose electrolyte is smaller than a particle diameter generally used in a solution type lithium ion battery which is not solid. Specifically, the average particle diameter of the positive electrode active material is preferably 10 to 0.1 μm.

  As the electrolyte contained in the positive electrode, a solid polymer electrolyte, a polymer gel electrolyte, a laminate of these, and the like can be used. That is, the positive electrode can have a multi-layer structure, and on the collector side and the electrolyte side, a layer in which the type of electrolyte constituting the positive electrode, the type and particle size of the active material, and the mixing ratio thereof are changed is formed. You can also.

  The polymer gel electrolyte is a solid polymer electrolyte having ion conductivity containing an electrolyte solution usually used in a lithium ion battery. Further, in the polymer skeleton having no lithium ion conductivity, In addition, those holding the same electrolytic solution are also included.

Here, the electrolyte solution (electrolyte salt and plasticizer) contained in the polymer gel electrolyte may be any one that is normally used in lithium ion batteries. For example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiTaF ₆ , inorganic acid anion salts such as LiAlCl ₄ and Li ₂ B ₁₀ Cl ₁₀ , organic acid anions such as LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, and Li (C ₂ F ₅ SO ₂ ) ₂ N Including at least one lithium salt (electrolyte salt) selected from ionic salts, cyclic carbonates such as propylene carbonate and ethylene carbonate; chain carbonates such as dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate; tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxa , Ethers such as 1,2-dimethoxyethane, 1,2-dibutoxyethane; lactones such as γ-butyrolactone; nitriles such as acetonitrile; esters such as methyl propionate; amides such as dimethylformamide; Those using an organic solvent (plasticizer) such as an aprotic solvent in which at least one selected from methyl and methyl formate are mixed can be used. However, it is not necessarily limited to these.

  For example, polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), etc. are used as the polymer having no lithium ion conductivity used in the polymer gel electrolyte. it can. However, it is not necessarily limited to these. Note that PAN, PMMA, etc. are in a class that has almost no ionic conductivity, and therefore can be a polymer having the above ionic conductivity, but here, they are used for a polymer gel electrolyte. This is exemplified as a polymer having no lithium ion conductivity.

As the lithium salt, for _{example, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10 and the like inorganic acid anion _{salts, Li (CF 3 SO 2)} 2 N, An organic acid anion salt such as Li (C ₂ F ₅ SO ₂ ) ₂ N or a mixture thereof can be used. However, it is not necessarily limited to these.

  Examples of the conductive assistant include acetylene black, carbon black, and graphite. However, it is not necessarily limited to these.

  The amount of the positive electrode active material, electrolyte (preferably solid polymer electrolyte), lithium salt, and conductive additive in the positive electrode is determined in consideration of the intended use of the battery (output priority, energy priority, etc.) and ion conductivity. Should. For example, if the amount of the electrolyte in the positive electrode, particularly the solid polymer electrolyte, is too small, the ionic conduction resistance and the ionic diffusion resistance in the active material layer will increase, and the battery performance will deteriorate. On the other hand, when the amount of the electrolyte in the positive electrode, particularly the solid polymer electrolyte, is too large, the energy density of the battery decreases. Therefore, in consideration of these factors, the solid polymer electrolysis mass suitable for the purpose is determined.

  The thickness of the positive electrode is not particularly limited, and should be determined in consideration of the intended use of the battery (emphasis on output, emphasis on energy, etc.) and ion conductivity, as described for the blending amount. A typical positive electrode active material layer has a thickness of about 10 to 500 μm.

[Negative electrode active material layer]
The negative electrode includes a negative electrode active material. In addition, an electrolyte, a lithium salt, a conductive auxiliary agent, and the like may be included to increase ion conductivity. Except for the type of the negative electrode active material, the contents are basically the same as those described in the section “Positive electrode active material layer”, and thus the description thereof is omitted here.

  As the negative electrode active material, a negative electrode active material such as a crystalline carbon material or an amorphous carbon material that is also used in a solution-based lithium ion battery can be used. For example, metal oxide, lithium-metal composite oxide metal, hard carbon and the like are preferable. More preferred are carbon, transition metal oxide, and lithium-transition metal composite oxide. More preferred are titanium oxide, lithium-titanium composite oxide, and carbon. These may be used alone or in combination of two or more.

[Electrolytes]
Examples of the electrolyte include a liquid electrolyte and a polymer gel electrolyte. A liquid electrolyte or a polymer gel electrolyte is held in the separator 14. The electrolyte can also have a multilayer structure, and a layer in which the type of electrolyte and the component mixing ratio are changed can be formed on the positive electrode side and the negative electrode side. When the polymer gel electrolyte is used, the ratio (mass ratio) between the polymer constituting the polymer gel electrolyte and the electrolytic solution is 20:80 to 2:98, which is a range in which the ratio of the electrolytic solution is relatively large.

  As such a polymer gel electrolyte, a solid polymer electrolyte having ion conductivity includes an electrolytic solution usually used in a lithium ion battery. Those in which the same electrolyte solution is held in the molecular skeleton are also included. Since these are the same as the polymer gel electrolyte described as one of the electrolytes included in the [positive electrode], description thereof is omitted here.

  These solid polymer electrolytes or polymer gel electrolytes can be included in the positive electrode and / or the negative electrode as described above in addition to the polymer electrolyte constituting the battery, but depending on the polymer electrolyte, positive electrode, and negative electrode constituting the battery. Different polymer electrolytes may be used, the same polymer electrolyte may be used, or different polymer electrolytes may be used depending on the layer.

  The thickness of the electrolyte constituting the battery is not particularly limited. However, in order to obtain a compact bipolar battery, it is preferable to make it as thin as possible as long as the function as an electrolyte can be secured. The thickness of a general solid polymer electrolyte layer is about 10 to 100 μm. However, the shape of the electrolyte can be easily formed so as to cover the upper surface of the electrode (positive electrode or negative electrode) as well as the outer periphery of the side surface, taking advantage of the characteristics of the manufacturing method. It is not always necessary to have a substantially constant thickness.

[Exterior body (battery case)]
From the viewpoint of weight reduction, the exterior body has a polymer-metal composite laminate film or aluminum laminate pack in which a metal (including an alloy) such as aluminum, stainless steel, nickel, or copper is covered with an insulator such as a polypropylene film. A bipolar battery is housed and sealed using a conventionally known material.

  In this case, the positive electrode and the negative electrode lead may be structured so as to be sandwiched between the heat-sealed portions and exposed to the outside of the battery outer package. In addition, the use of polymer-metal composite laminate films and aluminum laminate packs with excellent thermal conductivity allows heat to be efficiently transferred from the heat source of the automobile and the inside of the battery to be quickly heated to the battery operating temperature. preferable.

[Positive electrode and negative electrode terminal plate]
The positive electrode and the negative electrode terminal plate have functions as terminals and are preferably as thin as possible from the viewpoint of thinning, but the electrodes, electrolytes, and current collectors that are laminated by film formation have low mechanical strength. For this reason, it is desirable to have sufficient strength to sandwich and support them from both sides. Furthermore, it can be said that the thickness of the positive electrode and the negative electrode terminal plate is usually preferably about 0.1 to 2 mm from the viewpoint of suppressing the internal resistance at the terminal portion.

  As the material of the positive electrode and the negative electrode terminal plate, materials usually used in lithium ion batteries can be used. For example, aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof can be used. Aluminum is preferably used from the viewpoints of corrosion resistance, ease of production, economy, and the like.

  The material of the positive electrode terminal plate and the negative electrode terminal plate may be the same material or different materials. Furthermore, the positive electrode and the negative electrode terminal plate may be a laminate of different materials.

  The shape of the positive electrode and the negative electrode terminal plate is a shape obtained by tracing the outer surface of a heat source of an automobile when used also as a template, and the terminal plate is installed in a terminal plate provided at a position opposite to the template. Any shape that traces the outer surface of the current collector may be used, and it may be formed by tracing by press molding or the like. Note that the terminal plate provided at a position opposite to the template may be formed by spray coating in the same manner as the current collector.

[Positive electrode and negative electrode lead]
As for the positive electrode and the negative electrode lead, known leads usually used in lithium ion batteries can be used. In addition, since the part taken out from the battery exterior material (battery case) does not have a distance from the heat source of the automobile, it does not affect the automobile parts (particularly electronic equipment) by contacting with them and causing electric leakage. In addition, it is preferable to coat with a heat-resistant insulating heat-shrinkable tube or the like.

(Example)
Next, an example in which a bipolar battery that actually employs the configuration of the above battery element was manufactured and evaluated was described.

<Sample preparation>
As examples, bipolar batteries of Examples 1 to 8 having different specifications were prepared.

  FIG. 8 is a diagram showing the specifications of the bipolar batteries of Examples 1-8. The detailed configuration of each embodiment is as follows.

Example 1
A positive electrode active material (average particle size: 5 μm) made of Li / Mn composite oxide on SUS 15 μm as a current collector is coated and dried to a thickness of 15 μm, and an amorphous carbon material is formed on the opposite surface of the positive electrode. The hard carbon negative electrode active material (average particle size 6 μm) was applied and dried to a thickness of 15 μm to prepare a bipolar electrode.

  Then, an electrolyte layer formed by impregnating the precursor of the cross-linked gel electrolyte with a polyester nonwoven fabric separator having a thickness of 25 μm and a hardness of JIS-A 60 was overlaid on the bipolar electrode.

  For both ends of the laminate, only the positive electrode active material or the negative electrode active material was applied to one side of the current collector to produce an electrode.

  About the electrode obtained here, the sealing member was heat-sealed to 4 sides and temporarily fixed.

  These electrodes were overlapped to form a 10-layer structure of 1 layer on each side and 8 layers on the center, and then the entire sealing member was heat-sealed to produce a battery element.

  An aluminum tab having a thickness of 200 μm and a width of 55 μm was vibration welded on the positive electrode end side of the battery element, and a copper tab having a thickness of 200 μm and a width of 55 μm was vibration welded on the negative electrode end side.

  The battery element to which this tab was attached was sealed with a laminate and thermally crosslinked at about 80 ° C. for about 2 hours to produce a 10-layer bipolar battery.

  The seal member used was a three-layer structure as shown in FIG. PET was used for the maintenance layer of the sealing member, and resin A shown in the table of FIG. 8 was used for the softening layer. The resin A is low density polyethylene (PE) having a hardness of about 40 degrees and a dielectric loss tangent of about 0.01 at a frequency of 1 kHz. A sealing member having a three-layer structure in which PET is sandwiched between the resins A was used.

  In the following Examples 2 to 8, bipolar batteries were produced by the same manufacturing process as in Example 1. In the second to eighth embodiments, only portions different from the first embodiment will be described.

(Example 2)
In Example 2, PEN was used instead of PET for the maintenance layer of the seal member of Example 1.

(Example 3)
In Example 3, PEN was used instead of PET for the maintenance layer of the sealing member of Example 1, and Resin B was used for the softening layer instead of Resin A. The resin B is a modified polypropylene (PP) having a hardness of about 60 degrees and a dielectric loss tangent of about 0.005 at a frequency of 1 kHz.

Example 4
In Example 4, PEN was used instead of PET for the maintenance layer of the sealing member of Example 1, and Resin C was used instead of Resin A for the softening layer. Resin C is an ethylene-vinyl acetate copolymer (EVA) having a hardness of about 30 degrees JIS-A and a dielectric loss tangent of about 0.01 at a frequency of 1 kHz.

(Example 5)
In Example 5, PEN was used instead of PET for the maintenance layer of the sealing member of Example 1, and Resin A and Resin B were used for the softening layer. That is, the resin A was used for one of the two softening layers included in the three-layer structure of the sealing member, and the resin B was used for the other.

(Example 6)
In Example 6, a two-layer structure was adopted instead of the three-layer structure of the seal member of Example 1. The sealing member has a two-layer structure in which PET and resin A are overlapped. In the bipolar electrode of Example 1, a crystalline carbon material was used as the negative electrode active material.

(Example 7)
In Example 7, the two-layer structure of the sealing member was adopted, and the resin C was used for the softening layer.

(Example 8)
In Example 8, a bipolar battery of 100 layers was produced instead of the 10 layers of Example 1. Resin C was used for the softening layer of the sealing member.

(Comparative example)
As a comparative example, a bipolar battery was manufactured by the same manufacturing process as in Example 1 above. In the bipolar battery of the comparative example, a one-layer structure was adopted with respect to the three-layer structure of the seal member of Example 1.

<Test>
The following tests were performed on the bipolar batteries of Examples 1 to 8 and Comparative Example manufactured as described above.

(Seal test)
The obtained bipolar battery was fully charged (equivalent to a single layer of 4.2 V) and stored for 30 days in an environment of 60 degrees.

  The results are shown in FIG. 8 with “O” indicating that no seal failure occurred and “X” indicating that a seal failure occurred. Whether or not a seal failure occurred was judged from the appearance of whether or not the electrolyte oozed out.

  As shown in FIG. 8, no leakage of liquid was observed in the seal resins of Examples 1 to 8 having a multilayer structure. On the other hand, in the comparative example, liquid leakage was observed.

  From this test, it can be seen that the sealing performance is improved by making the sealing member a multilayer structure.

(Measurement of average attenuation rate)
With respect to the obtained bipolar battery, an acceleration pickup was provided in the approximate center of the single battery layer of the battery element, and the vibration spectrum of the acceleration pickup when hammered by an impulse hammer was measured. Various settings for the measurement were in accordance with JIS B 0908 (vibration and shock pickup calibration method / basic concept).

  The measured spectrum was analyzed with an FFT analyzer and converted to frequency and acceleration dimensions. The obtained frequency was averaged and smoothed to obtain a vibration transmissibility spectrum (see FIG. 6).

  About the said vibration transmissibility spectrum, about each said Examples 1-8 and a comparative example, the ratio with respect to the comparison reference value of the area of the 1st peak which appears on the lowest frequency side was made into the average attenuation rate, respectively. A larger value means that vibration is reduced. As a comparison reference value, the spectrum of the comparative example was used.

  Referring to the results of FIG. 8, it can be seen that all of Examples 1 to 8 are attenuated by 20% or more with respect to the comparative example. In particular, as shown in Example 4, the attenuation rate was as high as 35% when PEN was used for the maintenance layer of the sealing member and resin C was used for the softening layer. As shown in Examples 1, 2, and 5, when the resin A was used for the softening layer of the sealing member, the attenuation factor was as high as 30%.

  From the above, it can be seen that Examples 1 to 8 can improve both the sealing performance and the vibration attenuation amount. In particular, the amount of attenuation can be improved when the seal member has a three-layer structure. It can be seen that PEN is particularly suitable for the maintenance layer of the sealing member, and resin C and resin A are particularly suitable for the softening layer.

(Second Embodiment)
In the second embodiment, an assembled battery is obtained by connecting a plurality of the bipolar batteries 10 of the first embodiment in parallel and / or in series.

  9 is a diagram showing an assembled battery in which a plurality of bipolar batteries are connected in parallel, FIG. 10 is a diagram showing an assembled battery in which a normal battery equivalent to a bipolar battery is connected in parallel, and FIG. 11 is a diagram showing a composite assembled battery. is there.

  As shown in FIG. 9, the assembled battery 60 can be configured by connecting two bipolar batteries 10 in series and connecting them in parallel. The assembled battery 60 can be further combined to form a composite assembled battery. Between the batteries 10, the electrodes 30 a and 30 b of each battery are connected by a conductive bar 61. The assembled battery is provided with electrode terminals 62 and 63 on one side as electrodes.

  In addition, ultrasonic welding, heat welding, laser welding, rivets, caulking, an electron beam, or the like can be used as a connection method when the batteries 10 are directly connected and connected in parallel. By adopting such a connection method, a long-term reliable assembled battery can be manufactured.

  In addition, the connection of the battery 10 as an assembled battery may connect all the batteries 10 in parallel, and may connect all the batteries 10 in series.

  In addition, as shown in FIG. 10, an assembled battery can be configured by connecting a bipolar battery 10 and a normal battery 90 having a voltage equivalent to that of the bipolar battery 10 in parallel. Here, the normal battery 90 is a lithium ion secondary battery or the like. The lithium ion secondary battery preferably includes the same positive electrode active material and negative electrode active material as the bipolar battery 10. Then, lithium ion secondary batteries 80 having a voltage equivalent to that of the single battery layer 15 of the bipolar battery 10 are connected in series by the number of the single battery layers 15 of the bipolar battery 10. Furthermore, the voltage of the several lithium ion secondary battery connected in series and the bipolar battery 10 can be match | combined, and it can connect in parallel.

  Thus, by connecting in parallel, an assembled battery having the characteristics of the bipolar battery 10 and the lithium ion secondary battery can be obtained. That is, an instantaneous high output can be obtained by the bipolar battery 10, and a continuous output can be obtained by the lithium ion secondary battery.

  A composite battery pack 90 as shown in FIG. 11 can also be configured by further stacking the battery packs 70 shown in FIG. 10 and connecting them in series. Since the sub-module such as the assembled battery 70 can be combined into the composite assembled battery 90, the composite assembled battery 90 having an appropriate output can be easily created according to the specifications of the vehicle. Thereby, it is not necessary to manufacture an assembled battery for every vehicle, and the manufacturing cost of an assembled battery can be reduced.

  As described above, according to the assembled battery of the second embodiment, by forming the assembled battery using the bipolar battery 10 according to the first embodiment described above, high capacity and high output can be obtained. Since the reliability of the battery is high, long-term reliability as an assembled battery can be improved.

(Third embodiment)
In the third embodiment, a vehicle 100 is obtained in which the bipolar battery 10 of the first embodiment, or the assembled batteries 60 and 70 and the composite assembled battery 90 of the second embodiment are mounted as a driving power source. The vehicle using the bipolar battery 10 or the assembled batteries 60 and 70 and the composite assembled battery 90 as a motor power source is an automobile whose wheels are driven by a motor, such as an electric vehicle or a hybrid vehicle.

  For reference, FIG. 12 shows a schematic diagram of an automobile 100 on which the assembled battery 60 is mounted. The assembled battery 60 mounted on the automobile has the characteristics described above. For this reason, the automobile on which the assembled battery 60 is mounted has high durability and can provide a sufficient output even after being used for a long period of time.

  Since the bipolar battery 10 and the assembled battery 60 can achieve a light and small battery, it is possible to meet the demand for space when mounted on a vehicle. For example, the battery can be installed under the floor of the vehicle, behind the seat back, or under the seat.

It is a top view of a bipolar battery. FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 1. It is sectional drawing which shows a battery element. It is the figure which made the battery element a mass spring model. It is a figure which shows the relationship between the frequency of the vibration added to a bipolar battery when the resin which has a preferable dielectric loss tangent is used for a sealing member, and the acceleration of a bipolar battery. It is a figure which shows the sealing member of 3 layer structure. It is a figure which shows the specification of the bipolar battery of Examples 1-8. It is a figure which shows the assembled battery which connected multiple bipolar batteries in parallel. It is a figure which shows the assembled battery which connected the normal battery equivalent to a bipolar battery in parallel. It is a figure which shows a composite assembled battery. It is the schematic of the motor vehicle carrying an assembled battery.

Explanation of symbols

10 ... Bipolar battery,
11 ... current collector,
12 ... positive electrode active material layer,
13 ... negative electrode active material layer,
14 ... separator
15 ... single cell layer,
16: Bipolar electrode,
17 ... End current collector,
18 ... seal member,
181 ... softening layer,
182 ... maintenance layer,
20 ... Battery element,
30a, 30b ... electrodes,
40 ... exterior,
41 ... Laminate sheet,
51 ... trout,
53 ... Spring,
55 ... Damper,
60, 70 ... assembled battery,
80 ... Composite battery pack,
100 ... an automobile.

Claims (7)

A bipolar electrode in which a positive electrode active material layer is formed on one surface of a current collector and a negative electrode active material layer is formed on the other surface;
An electrolyte layered alternately with the bipolar electrode;
From the temperature at which the current collector is fixed and heat-sealed so as to surround the unit cell layer including the adjacent positive electrode active material layer, the electrolyte, and the negative electrode active material layer Including a resin layer having a low softening point and a resin layer having a softening point higher than the temperature at which the heat fusion is performed, and is heated to the temperature at which the heat fusion is performed and sandwiched between the current collectors. A sealing member whose parts are bonded to each other ;
Bipolar battery having   2. The bipolar battery according to claim 1, wherein the sealing member has a temperature difference of 40 degrees or more of a softening point of a resin layer to be laminated.   The said sealing member contains at least 3 layers, The resin layer which contacts the said electrical power collector has a low softening point, The at least 1 resin layer pinched | interposed has a high softening point. The bipolar battery described in 1.   The resin layer having a lower softening point among the sealing members is formed of a material selected from low density polyethylene, an ethylene-vinyl acetate copolymer, and a modified polypropylene. Bipolar battery.   The bipolar battery according to any one of claims 1 to 4, wherein a resin layer having a lower softening point among the seal members has a hardness of JIS-A of 5 to 95 degrees. The dielectric loss tangent of the sealing member is 1.0 × 10 ^{−3 to} 5.0 × 10 ⁻¹ when the frequency is 10 Hz to 1 KHz and the temperature is in the range of −30 degrees to 80 degrees. The bipolar battery according to any one of the above. For the positive electrode active material layer, a Li · Mn-based composite oxide is used,
The bipolar battery according to any one of claims 1 to 6, wherein a crystalline carbon material or an amorphous carbon material is used for the negative electrode active material layer.

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