JP2000030746A - Bipolar lithium-ion secondary battery - Google Patents

Abstract

(57) [Problem] To provide a bipolar lithium-ion secondary battery having a large capacity, a compact size, and an improved insulating property. SOLUTION: A positive electrode active material is formed on a positive electrode current collector foil, and a negative electrode active material is formed on a negative electrode current collector foil. These positive electrode active material and negative electrode active material are disposed to face each other via a separator,
This is wound to form a battery structure 26. The same battery structure 26 is further wound around such a battery structure 26 via an insulating container 28, and a predetermined number of battery structures 2 are formed.
After winding 6a to 6d, they are electrically connected in series from the inner battery structure 26 to the outer battery structure 26 to obtain a bipolar lithium ion secondary battery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement in the structure of a bipolar type lithium ion secondary battery.

[0002]

2. Description of the Related Art Conventionally, a bipolar lithium ion secondary battery in which a plurality of lithium ion secondary batteries are connected in series as one battery has been used. In such a bipolar lithium ion secondary battery, a battery structure is formed by sandwiching a lithium ion conductive separator containing an electrolyte between a positive electrode and a negative electrode, and the battery structure is laminated in the electrode direction. It was formed by connecting the bodies in series. An example of such a bipolar type lithium ion secondary battery is disclosed in JP-A-59-90359.

FIG. 15 is a sectional view of a conventional bipolar lithium ion secondary battery. In FIG. 15, a battery case 100 is formed by applying a positive electrode active material 12 on a positive electrode current collector foil 10 and a negative electrode active material 16 on a negative electrode current collector foil 14. A bipolar type lithium ion secondary battery having a structure in which a separator 18 having lithium ion conductivity is interposed between the negative electrode and a negative electrode and having a structure in which the battery components are stacked in a plurality of electrode directions is accommodated. . Both stacked end faces of the bipolar type lithium ion secondary battery thus configured are a positive electrode current collector foil 10 and a negative electrode current collector foil 14, respectively, on which a positive terminal lead 20 and a negative terminal lead 22 are provided. It is connected.

[0004]

However, in the above-mentioned conventional bipolar type lithium ion secondary battery, each battery component can be made thin in the stacking direction.
At the same time, in order to obtain a large capacity, it is necessary to increase the areas of the positive electrode and the negative electrode. For this reason, there has been a problem that it is difficult to reduce the size of the positive electrode and the negative electrode in the area direction.

[0005] Further, the interval between the respective battery components is several tens to one.
Since it is as thin as 00 μm, there is also a problem that it is difficult to perform insulation treatment around the battery structure.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a bipolar lithium ion secondary battery which has a large capacity, can be made compact, and has an improved insulating property. It is in.

[0007]

In order to achieve the above object, the present invention relates to a bipolar type lithium ion secondary battery, which is wound with a separator sandwiched between a positive electrode and a negative electrode. A plurality of components are wound concentrically via an insulator, and are electrically connected in series from the inner battery component to the outer battery component.

In a bipolar type lithium ion secondary battery, a plurality of battery components wound concentrically with a separator sandwiched between a positive electrode and a negative electrode are formed concentrically. From the body to the outer battery structure, they are electrically connected in series sequentially, and at each connection point, the current collector foil of the positive or negative electrode of the inner battery structure and the negative or positive electrode of the outer battery structure And a current collecting foil.

Further, the bipolar lithium ion 2
The secondary battery is characterized in that a current collecting foil constituting a connection portion between the inner battery structure and the outer battery structure has a structure surrounding the entire outer periphery of the inner battery structure.

In addition, the bipolar lithium ion 2
In the secondary battery, the positive electrode and the negative electrode of each battery structure have an active material laminated only on one side of the current collector foil, and the laminated end surface of each battery structure has the current collector foil of the positive electrode and the negative electrode. At the connection between the structure and the outer battery structure, the positive or negative current collector foil of the inner battery structure and the negative or positive current collector foil of the outer battery structure are in electrical contact. It is characterized by the following.

The bipolar type lithium ion 2
In the next battery, the inner battery structure and the outer battery structure have the same electric capacity, and the internal resistance is higher for the inner battery structure.

[0012]

Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

Embodiment 1 FIG. 1 and FIG. 2 show an example of a battery structure constituting the bipolar lithium-ion secondary battery according to the present embodiment. In FIG. 1, between a positive electrode formed by applying a positive electrode active material 12 on a positive electrode current collector foil 10 and a negative electrode formed by applying a negative electrode active material 16 on a negative electrode current collector foil 14. The battery component 26 is configured with the separator 18 having lithium ion conductivity interposed therebetween. The battery assembly 26 is wound as shown in FIG.
In this case, the insulating film 2 is provided outside the negative electrode current collector foil 14.
4 are stacked. Thereby, the battery structure 26
When the coil is wound, the short-circuit between the positive electrode current collector foil 10 and the negative electrode current collector foil 14 is prevented. FIG. 2 shows a cross-sectional view of the battery structure 26 thus wound. As shown in FIG. 2, in the battery assembly 26, the positive electrode current collector foil 10 is exposed inside and the negative electrode current collector foil 14 is exposed outside.

In the example shown in FIG. 1, the positive electrode current collector foil 10 and the negative electrode current collector foil 14 have the positive electrode active material 1 on one side.
2 and the negative electrode active material 16 are applied.
As shown in (2), a configuration may be adopted in which the positive electrode active material 12 and the negative electrode active material 16 are applied to both sides of each of the current collecting foils 10 and 14. In this case, a separator 18a is sandwiched between the positive electrode active material 12 and the negative electrode active material 16 located inside the positive electrode current collector foil 10 and the negative electrode current collector foil 14 among the stacked layers. Further, the same separator 18b is arranged further outside the negative electrode active material 16 outside the negative electrode current collector foil 14. When this is wound in the direction of arrow A, the inner positive electrode active material 12 and the negative electrode active material 16 described above are arranged to face each other with the separator 18a interposed therebetween, and the outer positive electrode active material 12 and the negative electrode active material
Also, a separator 18 disposed outside the negative electrode active material 16
b will be opposed to each other. In this case, if the length of the portion of the negative electrode current collector foil 14 on which the negative electrode active material 16 is not applied is sufficiently ensured, the positive electrode current collector foil will be disposed inside when wound in the direction of arrow A in FIG. 10 is exposed, and a battery structure 26 having a structure in which the negative electrode current collector foil 14 is exposed to the outside can be obtained.

The battery structure 26 shown in FIG. 2 is covered with an insulator, and the outer periphery thereof is further covered with the battery structure 2 shown in FIG.
6 is concentrically wound. As described above, the plurality of battery components 26 are concentrically wound via the insulator, and are sequentially electrically connected in series from the inner battery component to the outer battery component. A bipolar lithium ion secondary battery according to the embodiment is configured. in this way,
By winding the battery structure 26, a bipolar lithium ion secondary battery having a large capacity and a compact capacity can be obtained as compared with a case where the battery structure 26 is stacked without being wound.

FIG. 4 is a sectional view of the above-mentioned bipolar type lithium ion secondary battery. In FIG. 4, the innermost battery component 26a is changed to the outermost battery component 26d.
Are wound concentrically via an insulating container 28. These are accommodated in the battery case 100, and the battery components 26b, 26c, 2
The connection is performed in series by the series connection lead wire 30 in the order of 6d. As described above, the positive electrode current collector foil 10 is exposed at the innermost part of the battery assembly 26, and the positive electrode terminal lead 20 is connected to this. Since the foil 14 is exposed, the negative electrode terminal lead 22 is connected thereto.

FIG. 5 is a sectional view of the bipolar lithium-ion secondary battery according to the embodiment shown in FIG. 4 taken along line VV. However, the battery case 100 is omitted. In the present embodiment, four battery components 26a,
26b, 26c, and 26d are sequentially wound concentrically outward from the inner battery component 26a, and are connected in series from the inner battery component 26a to the outer battery component 26d. When using this bipolar lithium ion secondary battery, the positive electrode terminal lead 20
And charge / discharge via the negative terminal lead 22.

In this embodiment, a positive electrode is provided at the innermost part.
Although the negative electrode is formed at the outermost part, the arrangement of the positive electrode and the negative electrode can be reversed by reversing the stacking order or winding direction of the battery assembly 26.

Hereinafter, a specific example of the bipolar type lithium ion secondary battery according to the present embodiment will be described as Example 1.

Embodiment 1 LiMn as the positive electrode active material 12
₂ O ₄ was used and applied on an aluminum foil as the positive electrode current collector foil 10 to form a positive electrode. In addition, graphite was used as the negative electrode active material 16, and this was applied on a copper foil as the negative electrode current collector foil 14 to form a negative electrode. Further, a nonwoven fabric was used as the separator 18. These were laminated as shown in FIG. 1 and wound to form a battery structure 26.
The battery structure 26 thus configured is put in a polypropylene (PP) bag as an insulating container 28, and the same battery structure 26 as described above is wound around the bag, and the whole is also made of polypropylene. In a bag. In this manner, the battery structure is further wound around the outer periphery of the battery structure placed in the polypropylene bag, and as shown in FIG. The components 26a, 26b, 26c, 26d were wound concentrically.

Next, the liquid of EC: DEC = 1: 1 is converted into Li
The PF ₆ dissolved 1 mol / l solution and PVDF-HF
A mixture of P and P in a weight ratio of 7: 1 was prepared as an electrolytic solution. Each of the battery components 26, 26 contained in the above-described polypropylene bag is
b, 26c and 26d were impregnated, heated to 120 ° C., returned to room temperature, and the electrolyte was gelled in the positive electrode, the negative electrode and the separator 18. Thereafter, the opening of the polypropylene bag is closed by hot pressing, and each of the battery components 26, 26b, 26
c and 26d were completely sealed and separated. Thereafter, the batteries were electrically connected in series from the inner battery assembly 26a to the outer battery assembly 26d by the serial connection lead wire 30. Finally, these are sealed in the battery case 100, and the innermost positive electrode current collector foil 10 and the outermost negative electrode current collector foil 14 are sealed.
And a positive electrode terminal lead 20 and a negative electrode terminal lead 22, respectively, to obtain a bipolar lithium ion secondary battery according to this example.

When the bipolar lithium ion secondary battery obtained in this way was evaluated, the average voltage was 1
5.8 V could be obtained. The voltage was maintained at 15.6 V even after being left in the charged state for 10 days. As a comparative example, a bipolar lithium-ion secondary battery in which the battery structure 26 shown in FIG. 1 was laminated without being wound and the periphery thereof was insulated was similarly evaluated. As a result, a voltage of 15.8 V was obtained at first, but dropped to 10.8 V after being left for 10 days. This is presumably because the thickness of each of the battery components 26 is as thin as about several tens to 100 μm, which makes it difficult to insulate the surroundings.

Embodiment 2 FIG. FIG. 6 shows a cross-sectional view of the configuration of the bipolar lithium ion secondary battery according to the present embodiment. FIG. 7 is a cross-sectional view of a battery structure 26 constituting the bipolar lithium ion secondary battery shown in FIG.

In FIG. 7, a positive electrode active material 12 is applied to both surfaces of a positive electrode current collector foil 10 to form a positive electrode. A negative electrode active material 16 is applied to both sides of the negative electrode current collector foil 14 to form a negative electrode. Of the positive electrode active material 12 and the negative electrode active material 16, those disposed inside are opposed to each other via a separator 18a. A separator 18b is further formed on the positive electrode active material 12 formed on the side (outside) of the positive electrode current collector foil 10 opposite to the negative electrode. As a result, when the battery structure 26 is wound, the positive electrode active material 12 and the negative electrode active material 16 disposed outside are opposed to each other via the separator 18b. In such a battery structure 26, one positive electrode current collector foil 10 and the other negative electrode current collector foil 14 are connected at a connection portion 32, and a plurality of battery members 26 are connected in series. As described above, by directly connecting the positive electrode current collector foil 10 to the other negative electrode current collector foil 14, the contact resistance can be reduced.

When the battery thus constructed is wound in the direction of arrow A shown in FIG. 7, a bipolar type lithium ion secondary battery having the structure shown in FIG. 6 is obtained. Can be. FIG. 6 shows a structure in which a plurality of battery components 26 wound in a state where separators 18a and 18b are sandwiched between a positive electrode and a negative electrode are concentrically wound. Also, as shown in FIG. 7, since the battery members 26 are connected in series by the connection part 32, also in FIG. 6, the battery members 26 are sequentially shifted from the inner battery members 26 to the outer battery members 26. It has a structure electrically connected in series.

At this time, the length in the winding direction of the positive electrode current collector foil 10 and the negative electrode current collector foil 14 connecting the one battery structure 26 and the other battery structure 26 is determined in the case where the winding is performed. The length is set so that the outer circumference of the inner battery assembly 26 can be wound one or more times only by the current collector foils 10 and 14. Thus, the entire outer periphery of the inner battery assembly 26 is wrapped by the current collector foil, and short-circuiting between the positive and negative electrodes of the inner battery assembly 26 and the outer battery assembly 26 can be prevented. At this time, it is desirable that the width in the winding direction and the vertical direction of the connection portion 32 of the current collecting foils 10 and 14 connecting the two battery components be larger than the portion where the electrodes are formed. This is to prevent the electrolyte from migrating from the upper and lower ends of the bipolar lithium ion secondary battery having a cylindrical shape after winding the battery structure 26 to the adjacent battery structure and causing an electrolyte short circuit. .

In the bipolar type lithium ion secondary battery shown in FIG. 6 configured as described above, the positive electrode current collector foil 10 is exposed inside and the negative electrode current collector foil 14 is exposed outside. A positive terminal lead 20 and a negative terminal lead 22 are connected to each. In this embodiment,
It is also possible to reverse the innermost and outermost positive and negative electrodes. 6, the battery case 100 is omitted.

FIGS. 8A and 8B show a modification of the battery structure 26 according to the present embodiment. A characteristic point of this modification is that the positive electrode current collector foil 1 of one battery
In order to connect 0 to the negative electrode current collector foil 14 of the other battery structure 26, a connection current collector foil 34 made of stainless steel or the like is used. This connection current-collecting foil 34 is used for the battery construct 2
The width in the direction of 90 ° with respect to the winding direction of No. 6 is larger than that of the electrode portion. Thus, when the battery structure 26 is wound, it is possible to prevent the electrolyte from leaking from the upper and lower ends of the cylindrical bipolar lithium ion secondary battery and causing a short circuit.

In the bipolar type lithium ion secondary battery according to the present embodiment, similarly to the first embodiment, an aluminum foil is used as the positive electrode current collector foil 10 and the negative electrode current collector foil 14 is used.
Used copper foil. LiMn ₂ O ₄ was used as the positive electrode active material 12, and graphite was used as the negative electrode active material 16. These active materials are formed by applying a mixture of the binder and PVDF on the above-mentioned current collector foils 10 and 14. Further, a non-woven fabric was used as the separator 18. These positive electrode, negative electrode, and separator 18 are impregnated with the same electrolytic solution as in Embodiment 1, heated to 120 ° C., and then returned to room temperature to be gelled.

Embodiment 3 FIG. 9 shows a cross-sectional view of the configuration of the bipolar lithium ion secondary battery according to the present embodiment. FIGS. 10A and 10B are a cross-sectional view and a plan view of a battery structure 26 constituting the bipolar lithium-ion secondary battery shown in FIG.

As shown in FIG. 10A, the battery structure 26 in this embodiment has the positive electrode active material 12 formed on only one side of the positive electrode current collector foil 10 and the negative electrode current collector foil 14.
The negative electrode active material 16 is formed only on one side of the substrate. These positive electrode active material 12 and negative electrode active material 16
8 are disposed opposite to each other. In addition, the positive electrode current collector foil 10 of one battery element 26 and the negative electrode current collector foil 14 of the other cell element 26 are connected at a connection portion 32, and the battery elements 26 are connected in series.

A feature of the present embodiment is that each of the battery components 26 is covered with an insulating film 36 made of a polypropylene film or the like except for the connection portion 32. With such a configuration, as in the second embodiment,
When the outer battery structure 26 is wound around the outer periphery of the inner battery structure 26, the inner battery structure 26 and the inner battery structure 26 do not need to be wound over one or more circumferences of the outer periphery of the inner battery structure 26. There is no short circuit with the outer battery structure 26. Therefore, as shown in FIG. 9, in the bipolar lithium-ion secondary battery according to the present embodiment, the positive electrode current collector foil 10 and the negative electrode current collector foil 1
4 can be used to reduce the length of the current collector foil to be used, thereby increasing the electric capacity per volume.

In FIG. 9, three battery components are wound around the outer periphery of the inner one, and the outer one is wound around the outer periphery.
An example in which they are connected in series from the inside to the outside, respectively, is shown. The number of battery components is not limited to three, and four or more battery components can be sequentially wound.

Hereinafter, a specific example of the bipolar lithium ion secondary battery according to this embodiment will be described as Example 2.

Embodiment 2 FIG. Aluminum foil was used as the positive electrode current collector foil 10, and copper foil was used as the negative electrode current collector foil 14. LiMn ₂ O ₄ was used as the positive electrode active material 12 and graphite was used as the negative electrode active material 16. These active materials were mixed with the binder PVDF to form a paste, which was applied to only one surface of each current collector foil. Further, a non-woven fabric is used as the separator 18, and EC: DEC =
An electrolytic solution mixed so that the weight ratio of a solution obtained by dissolving 1 mol / l of LiPF ₆ in a 1: 1 liquid and PVDF-HFP was 7: 1 was impregnated. This was heated to 120 ° C., then returned to room temperature, and the impregnated electrolytic solution was gelled. The electrolyte is impregnated not only into the separator 18 but also into the above-described positive electrode and negative electrode.

The battery assembly 26 thus configured was covered with a polypropylene film except for the end portions of the positive electrode current collector foil 10 and the negative electrode current collector foil 14, and sealed by thermocompression bonding. In this state, the battery characteristics were evaluated, and short circuits, variations in capacity, and the like were checked.

Next, each of the battery components 2 thus configured
The positive electrode current collector foil 10 and the negative electrode current collector foil 14 of FIG. 6 are connected by spot welding, and wound in the winding direction A shown in FIGS. The following battery was obtained. At this time, the positive electrode terminal lead 20 was attached to the innermost exposed positive electrode current collector foil 10, and the negative electrode terminal lead 22 was attached to the outermost exposed negative electrode current collector foil 14. The negative electrode terminal lead is connected to the outermost negative electrode current collector foil 14 by a battery case 100 containing the battery assembly 26.
(Not shown), and the negative electrode terminal lead 22 may be attached to the battery case 100. Also,
Also in this embodiment, the innermost part can be a negative electrode and the outermost part can be a positive electrode.

According to the above method, the four battery members 26
A lithium ion secondary battery was constructed and the electrical characteristics thereof were evaluated.

In the battery assembly 26 according to the present embodiment, the positive electrode active material 12 and the negative electrode active material 16 are formed only on one side of the positive electrode current collector foil 10 and the negative electrode current collector foil 14, respectively. Since the battery is completed as a lithium ion secondary battery before performing, the capacity check and short-circuit check of each battery component can be performed. The battery structure 26 used in this example has a maximum variation of 20% in the capacity. However, as described above, the capacity of each battery structure 26 can be measured in advance. It is possible to construct a bipolar lithium ion secondary battery using only the body. Thereby, cycle characteristics can be improved.

Battery structure 26 having a capacity variation within 5%
Are connected in series, and are wound in the winding direction A shown in FIGS.
A secondary battery was constructed and charged and discharged with a constant current of 1 C between 12 V and 17 V. As a result, a good capacity retention rate of 87% after 100 cycles was obtained.

Embodiment 4 FIG. FIG. 11 shows a cross-sectional view of the configuration of the bipolar lithium ion secondary battery according to the present embodiment. FIGS. 12A and 12B show FIG.
2A and 2B are a cross-sectional view and a plan view of a battery structure 26 constituting the bipolar type lithium ion secondary battery shown in FIG.

In FIG. 12A, a positive electrode was formed by forming a positive electrode active material 12 on only one surface of the positive electrode current collector foil 10. Further, only one side of the negative electrode current collector foil 14 has the negative electrode active material 16
Was formed to form a negative electrode. These positive and negative electrodes are
The respective active materials 12 and 16 are arranged so as to face each other with the separator 18 interposed therebetween, and constitute a battery assembly 26. The battery structure 26 according to the present embodiment includes the positive electrode active material 1
2, insulating members 38 are provided at both ends of the negative electrode active material 16 and the separator 18, whereby the positive electrode current collector foil 10 and the negative electrode current collector foil 14 of the battery structure 26 are adhered to each other.
Thereby, the contents composed of the positive electrode active material 12 and the negative electrode active material 16 and the separator 18 are sealed, and leakage of the electrolyte can be prevented. Therefore, a voltage drop due to a short circuit of the electrolyte can be prevented.

FIG. 12B shows the current collector foils 10 and 14 on which the active materials 12 and 16 are applied and the separator 18 surrounded by an insulating member 38. When the battery assembly 26 is formed by these, the active materials 12 and 16 are accommodated in a portion surrounded by the insulating member 38, and the positive electrode and the negative electrode are fitted to the insulating member 38 so as to be in contact with the separator 18. Thereby, a battery structure 26 as shown in FIG. 12A can be obtained.

Such a battery structure 26 is shown in FIG.
As shown in (a), a current collector foil, an active material, and a separator are laminated, and the upper and lower laminated end faces of the laminated structure are a positive electrode current collector foil 10 and a negative electrode current collector foil 14. . Therefore, this is represented by the arrow A shown in FIG.
, So that the positive electrode current collector foil is on the innermost side, and the negative electrode current collector foil is on the outermost side. The positive electrode current collector foil 10 can be wound outward so as to make electrical contact.
Thereafter, in a similar manner, a predetermined number of battery components 26 are sequentially wound outward. Thereby, as shown in FIG.
A bipolar lithium ion secondary battery in which the battery components 26 are connected in series from the inside to the outside can be obtained. In the bipolar type lithium ion secondary battery assembled in this way, the positive electrode terminal lead 20 is connected to the innermost positive electrode current collector foil, and the negative electrode terminal lead 22 is connected to the outermost negative electrode current collector foil. Also in the present embodiment, the innermost part can be a negative electrode and the outermost part can be a positive electrode.

The battery structure 26 according to the present embodiment is
Can obtain a bipolar lithium-ion secondary battery even if they are laminated in the same manner as before without winding.

Hereinafter, a specific example of the bipolar type lithium ion secondary battery according to the present embodiment will be described as Example 3.

Embodiment 3 FIG. An aluminum foil was used as the positive electrode current collector foil 10, a blank was formed on only one side of the current collector foil, and the active material was printed and dried to form a positive electrode. LiMn ₂ O ₄ was used as the positive electrode active material 12, and natural graphite was mixed with the LiMn ₂ O ₄ as a conductive agent. EC: DE as gel electrolyte
A solution obtained by dissolving LiPF ₆ at 1 mol / l in a liquid of C = 1: 1 and PVDF-HFP at a ratio of 3: 1 was used. In addition, tetrahydrofuran (THF) was used as an organic solvent for forming a paste. These were mixed at a mixing ratio of LiMn ₂ O ₄ : natural graphite: gel electrolyte: organic solvent = 10: 1: 10: 30, and a positive electrode paste was applied to the positive electrode current collector foil 10.

Further, a copper foil was used as the negative electrode current collector foil 14, a margin was formed on only one side thereof, and the active material was printed and dried to form a negative electrode. Natural graphite was used as the negative electrode active material, and the same material as the positive electrode was used as the gel electrolyte and the organic solvent. These were mixed at a mixing ratio of natural graphite: gel electrolyte: organic solvent = 1: 1: 4 to form a negative electrode paste, which was applied to the negative electrode current collector foil 14.

The separator 18 was obtained by impregnating a non-woven fabric with a gel electrolyte and an organic solvent and drying it. As a gel electrolyte, a solution obtained by dissolving 1 mol / l of LiPF ₆ in a liquid of EC: DEC = 1: 1 and PVD
Using a mixture of F-HFP at a ratio of 5: 1,
THF was used as the organic solvent. The mixing ratio between the gel electrolyte and the organic solvent was 1: 2. The separator 18 thus formed was surrounded by an insulating member 38 made of a polypropylene film so that the gel electrolyte did not leak. Further, the positive and negative electrode active materials 12 and 14 described above are arranged to face each other with the separator 18 interposed therebetween, and are hot-pressed to form a positive electrode current collector foil 10-an insulating member 38-a separator 18-an insulating member 38-a negative electrode. Current collector foil 14
Was thermocompressed to seal the contents. By this hot pressing, the gel electrolyte in the positive electrode active material 12, the separator 18, and the negative electrode active material 16 is also re-gelled after thermal melting, eliminating voids between the gels and improving ionic conductivity.

The battery structure 26 constructed as described above
After checking its capacity and whether there is a short circuit, it is quadruple wound in a battery case (not shown) to
The battery was electrically connected in series from No. 6 to the outer battery structure 26 to obtain a bipolar lithium ion secondary battery.

As described above, the voltage of the bipolar lithium ion secondary battery according to the present embodiment only dropped to 15.6 V even when the battery was initially charged to 16.4 V and left for 10 days. On the other hand, without surrounding the separator 18 with the insulating member 38 in advance,
6. After winding, the part where the electrolyte was exposed was insulated with an epoxy resin or the like, and then left for 10 days.
The voltage of 4V was reduced to 3.8V. This allows
It can be seen that the bipolar lithium ion secondary battery according to this example has extremely good insulation properties.

Embodiment 5 FIG. In the bipolar lithium ion secondary battery according to each of the embodiments described above, when the charge / discharge current is increased, the battery structure 2 on the inner side
The temperature rises about six. For this reason, the inner battery structure 2
The better the lithium ion conductivity is, the lower the internal resistance is compared to the outer battery structure 26. Each battery structure 2
6 are connected in series, and a current of the same magnitude flows, so that the voltage of the outer battery structure 26 having a higher internal resistance is higher. For this reason, when a high voltage is applied, there is a possibility that the battery may be deteriorated particularly due to the deterioration of the electrolytic solution of the outer battery structure 26 or the elution of the current collector foil. Therefore, it is preferable to adjust the internal resistances of the individual battery components 26 to be equal in use.

FIG. 13 shows such a battery structure 26.
FIG. 1 is a cross-sectional view of a configuration of a bipolar lithium ion secondary battery in which the internal resistance becomes equal during use. FIG.
FIG. 4 is a cross-sectional view of a battery structure 26 for constituting the bipolar lithium-ion secondary battery shown in FIG. In FIG. 14, when the bipolar type lithium ion secondary battery shown in FIG. 13 is configured, the battery structure 26 is wound in the direction of arrow A in the figure. Is the battery structure 26 on the right side of the figure.
Inside. Therefore, the battery structure 2 on the left side of the drawing
If the internal resistance of the battery assembly 26 on the right side of the drawing in the figure is increased even if the internal resistance of the battery assembly 26 becomes high during use and the internal resistance becomes low,
Can be made equal to the internal resistance. Thereafter, similarly, the internal resistance of the battery component 26 arranged outside is reduced in advance in advance.

As a method of adjusting the internal resistance, the total amount of the active material and the porosity of each electrode are kept constant, and the thickness of the active material is adjusted. There is a method of controlling the area of the active material layer. That is, as the thickness increases, the effective area decreases and the resistance increases.

On the other hand, the internal resistance can also be adjusted by keeping the basis weight, that is, the weight of the active material per unit area and the effective area constant, adjusting the thickness of the active material, and changing the porosity. . That is, as the thickness of the active material is changed by pressing and the porosity is reduced, the amount of electrolyte existing between the active materials decreases, the ionic conductivity decreases, and the resistance increases.

As described above, the resistance is adjusted with the effective area by changing the thickness while the total amount and the porosity of the active material are kept constant, or the porosity of the active material is reduced by keeping the basis weight and the effective area constant. It is considered that a method of adjusting the internal resistance is preferable.

Specific examples of the method for adjusting the internal resistance as described above will be described as Embodiments 4 and 5.

Embodiment 4 FIG. In this embodiment, four battery components 26 are used, and the respective internal resistances are changed. The four battery components 26 are arranged in the order of I, II, III, and I from the innermost to the outermost.
Table 1 shows the value of the effective area of each positive electrode and negative electrode as IV. In this example, the total active material amount and the porosity of each electrode were kept constant, and the effective area was changed by changing the basis weight.

[0059]

[Table 1] The porosity of each active material was 45% for both the positive electrode and the negative electrode.

Example 5 Four Battery Structures 26I, I
The basis weight of each of the positive electrodes and negative electrodes of I, III, and IV was 2
0.4mg / cm ^2, a constant of 10.2mg / cm ^2,
The effective area was also constant at 100 cm ² . Such positive electrode and negative electrode active materials were pressed to have the following thicknesses, and the porosity was adjusted.

[0061]

[Table 2] In the case of the battery component IV, the porosity is 50%. If the porosity is further increased, the contact resistance between the active materials increases, and the resistance increases with an increase in film thickness. . Below the thickness of the battery component IV, the porosity decreases as the thickness decreases, the mass of the electrolyte between the active materials decreases, the ionic conductivity decreases, and the resistance increases. That is, the resistance increases as the pressing pressure of the active material increases.

In contrast to the above two embodiments, all of the four battery components I, II, III, and IV had a positive electrode basis weight of 2
0.4 mg / cm ² , the basis weight of the negative electrode is 10.2 mg / c
A sample having m ² and a porosity of 45% was prepared and evaluated together with the above two examples.

When the bipolar lithium ion secondary battery obtained as described above was charged and discharged at a constant current of 1 C at a voltage of 12 to 17 V, the capacity retention after 100 cycles was 90% in Example 4. %, Example 5 was 91%, and Comparative Example was 87%. For this reason, as in Example 4 and Example 5, the cycle characteristics were able to be improved by increasing the internal resistance as the inner battery structure was increased.

[0064]

As described above, according to the present invention,
Since the battery structure is wound to form a bipolar lithium ion secondary battery, a compact and large capacity battery can be obtained.

Further, since the electrical connection between the inner battery structure and the outer battery structure is made by directly connecting the current collectors, the contact resistance can be reduced.

Further, since the current collector foil is wound around the outer periphery of the inner battery structure one or more times, it is possible to prevent electrolyte short-circuit, improve insulation, and prevent short-circuit only with the current collector foil. It is not necessary to use an insulating film, and the size can be reduced accordingly.

Further, since the outermost current collecting foil of the inner battery structure and the innermost current collecting foil of the outer battery structure are brought into direct contact with each other and electrically connected, the contact area is increased. Internal resistance can be reduced.

Further, since the internal resistance of the battery components located on the inner side becomes higher, the internal resistances of all the battery components become substantially equal during use, and the voltages applied to the respective battery components can be made substantially equal. Deterioration can be suppressed.

[Brief description of the drawings]

FIG. 1 shows a bipolar lithium ion 2 according to the present invention.
It is sectional drawing of the battery structure used for Embodiment 1 of a next battery.

FIG. 2 is an explanatory diagram of a case where the battery structure shown in FIG. 1 is wound.

FIG. 3 is a cross-sectional view showing a modification of the battery structure used in the first embodiment.

FIG. 4 is a cross-sectional view of a configuration of a bipolar lithium ion secondary battery according to Embodiment 1.

FIG. 5 is a sectional view taken along line VV of the bipolar type lithium ion secondary battery shown in FIG.

FIG. 6 shows a bipolar lithium ion 2 according to the present invention.
It is sectional drawing of Embodiment 2 of a secondary battery.

FIG. 7 is a cross-sectional view of a battery constituting the bipolar lithium ion secondary battery shown in FIG.

FIG. 8 is a view showing a modification of the battery structure constituting the bipolar type lithium ion secondary battery shown in FIG.

FIG. 9 shows a bipolar lithium ion 2 according to the present invention.
It is sectional drawing of Embodiment 3 of a next battery.

10A and 10B are a cross-sectional view and a plan view of a battery constituting the bipolar lithium-ion secondary battery shown in FIG.

FIG. 11 is a cross-sectional view of a bipolar lithium-ion secondary battery according to Embodiment 4 of the present invention.

12A and 12B are a cross-sectional view and a plan view of a battery constituting the bipolar lithium-ion secondary battery shown in FIG.

FIG. 13 is a sectional view of a bipolar lithium-ion secondary battery according to Embodiment 4 of the present invention.

FIG. 14 is a cross-sectional view of a battery constituting the bipolar lithium-ion secondary battery shown in FIG.

FIG. 15 is a cross-sectional view of a conventional bipolar lithium ion secondary battery.

[Explanation of symbols]

REFERENCE SIGNS LIST 10 positive electrode current collector foil, 12 positive electrode active material, 14 negative electrode current collector foil, 16 negative electrode active material, 18 separator, 20 positive terminal lead, 22 negative terminal lead, 24 insulating film, 26 battery structure, 28 insulating container, 30 series Connection lead wire, 32 connection part, 34 connection current collector foil, 3
6. Insulating film, 38 insulating member, 100 battery case.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H022 AA09 AA18 AA20 BB03 CC19 CC21 5H028 AA01 AA05 BB05 CC05 CC08 CC12 CC19 HH10 5H029 AJ03 AJ12 AJ14 AK03 AL07 AM00 AM03 AM05 AM07 BJ02 BJ14 BJ17 CJ05 DJ01 DJ07

Claims (5)

[Claims] 1. A plurality of battery components wound around a separator between a positive electrode and a negative electrode are concentrically wound with an insulator interposed between the inner battery component and the outer battery. A bipolar lithium-ion secondary battery, which is electrically connected in series toward a structure. 2. A plurality of battery components wound in a state in which a separator is interposed between a positive electrode and a negative electrode are wound concentrically, and from the inner battery component toward the outer battery component, It is electrically connected in series sequentially, and at each connection part, the positive or negative electrode current collector foil of the inner battery structure and the negative or positive electrode current collector foil of the outer battery structure are connected. A bipolar type lithium ion secondary battery characterized by the above-mentioned. 3. A bipolar lithium ion secondary battery according to claim 1, wherein the current collector foil forming a connection portion between the inner battery structure and the outer battery structure includes an inner battery. A bipolar lithium-ion secondary battery having a structure surrounding the entire outer periphery of a structure. 4. The bipolar type lithium ion secondary battery according to claim 1, wherein the positive electrode and the negative electrode of each of the battery structures have an active material laminated only on one surface of a current collector foil. The laminated end face of the battery structure is a current collector foil of a positive electrode and a negative electrode, and a connection portion between the inner battery structure and the outer battery structure is formed by connecting the positive or negative current collector foil of the inner battery structure to the outer surface. A bipolar lithium ion secondary battery, wherein the negative electrode or the positive electrode current collector foil of the battery structure according to any one of the above, is in electrical contact with the battery. 5. The bipolar type lithium ion secondary battery according to claim 1, wherein the inner battery structure and the outer battery structure have the same electric capacity and have the same internal resistance. A bipolar lithium ion secondary battery, wherein the inner battery structure is made higher.