Battery cell and negative electrode

Abstract

To provide a battery cell which can be prevented from thermally expanding by a simple structure, and a negative electrode.SOLUTION: A battery cell 20 includes: an electrode body 19 formed by laminating a positive electrode, a negative electrode 30, and a separator; and a laminate film for sealing the electrode body 19 while storing the electrode body 19. The electrode body 30 includes a collector 30 on which a negative electrode mixture material including a negative electrode active material 34 is applied. The amount of the negative electrode active material 34 contained in a center part 34A is less than that in an edge part 34B.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a battery cell and a negative electrode.

Background Art

[0002] Patent Document 1 discloses a battery module in which an electrode assembly is housed in a case. Further, by surrounding the outside of the electrode assembly (battery cell) with a heat-shrinkable protective layer, a structure is formed that suppresses the thermal expansion of the electrode assembly.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the structure of Patent Document 1 described above, it is necessary to prepare a dedicated heat-shrinkable protective layer to suppress thermal expansion, which may increase the manufacturing cost and man-hours.

[0005] In consideration of the above facts, an object of the present invention is to obtain a battery cell and a negative electrode that can suppress thermal expansion with a simple structure.

Means for Solving the Problems

[0006] The battery cell according to claim 1 includes an electrode body formed by laminating a positive electrode, a negative electrode, and a separator, and a laminate film that seals the electrode body in a housed state. The negative electrode includes a current collector coated with a negative electrode composite material containing a negative electrode active material, and the amount of the negative electrode active material contained in the negative electrode composite material is less in the central portion than in the end portions.

[0007] In the battery cell according to claim 1, the electrode body is formed by laminating a positive electrode, a negative electrode, and a separator. Further, the electrode body is sealed with a laminate film. Here, the negative electrode is composed of a current collector coated with a negative electrode composite material containing a negative electrode active material, and the negative electrode active material contained in the negative electrode composite material is less in the central portion than in the end portion of the negative electrode. Thereby, thermal expansion can be suppressed with respect to the central portion of the negative electrode where the volume change due to thermal expansion is particularly large. In addition, it is not necessary to separately prepare a member for suppressing thermal expansion. Here, the "end portion" and "central portion" referred to herein are not limited to the end portion and the central portion in a plurality of directions, but are concepts widely including the end portion and the central portion in one direction. Further, the "negative electrode composite material" referred to herein refers to a mixture containing a negative electrode active material, a binder, and a conductive assistant.

[0008] In the battery cell according to claim 2, in claim 1, the density of the negative electrode active material contained in the central portion of the negative electrode is lower than that in the end portion.

[0009] In the battery cell according to claim 2, the thermal expansion of the battery cell is suppressed by changing the density of the negative electrode active material contained in the central portion and the end portion of the negative electrode. Thereby, the thickness of the negative electrode active material can be made the same in the central portion and the end portion.

[0010] In the battery cell according to claim 3, in claim 1, the thickness of the negative electrode composite material in the central portion of the negative electrode is thinner than that in the end portion.

[0011] In the battery cell according to claim 3, the thermal expansion of the battery cell is suppressed by making the thickness of the negative electrode composite material in the central portion of the negative electrode thinner than that in the end portion. Thereby, the thermal expansion of the battery cell can be suppressed only by reducing the negative electrode composite material in the central portion of the negative electrode.

[0012] In the battery cell according to claim 4, in any one of claims 1 to 3, the negative electrode active material contains a silicon element.

[0013] In the battery cell according to claim 4, the negative electrode active material is composed of silicon element. Although the silicon element is excellent in terms of specific capacity, it has a large volume change. However, by reducing the negative electrode active material in the central portion rather than the end portion, the thermal expansion of the battery cell can be effectively suppressed.

[0014] The negative electrode according to claim 5 is a negative electrode that constitutes an electrode body together with a positive electrode and a separator, and includes a current collector and a negative electrode composite material including a negative electrode active material coated on the current collector, and the negative electrode active material contained in the negative electrode composite material in the central portion is less than that in the end portion.

[0015] In the negative electrode according to claim 5, it includes a current collector and a negative electrode composite material, and the negative electrode active material contained in the negative electrode composite material in the central portion is less than that in the end portion of the negative electrode. Thereby, the thermal expansion can be suppressed particularly with respect to the central portion of the negative electrode where the volume change due to thermal expansion is large.

Advantages of the Invention

[0016] As described above, according to the battery cell and the negative electrode according to the present invention, the thermal expansion can be suppressed with a simple structure.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0018] The battery module 11 including the battery cell 20 according to the embodiment will be described with reference to the drawings.

[0019] (Overall configuration of the vehicle 100) FIG. 1 is a schematic plan view showing a main part of a vehicle 100 to which a battery pack 10 having a battery module 11 according to the present embodiment is applied. As shown in FIG. 1, the vehicle 100 is a battery electric vehicle (BEV) with the battery pack 10 mounted under the floor. In addition, the arrows UP, FR, and LH in each figure indicate the upper side in the vehicle up-down direction, the front side in the vehicle front-rear direction, and the left side in the vehicle width direction, respectively. When explaining using the front-rear, left-right, and up-down directions of the vehicle, unless otherwise specified, the front and rear in the vehicle front-rear direction, the left and right in the vehicle width direction, and the up and down in the vehicle up-down direction are shown.

[0020] As an example, in the vehicle 100 of the present embodiment, a DC / DC converter 102, an electric compressor 104, and a PTC (Positive Temperature Coefficient) heater 106 are arranged on the vehicle front side of the battery pack 10. Also, on the vehicle rear side of the battery pack 10, a motor 108, a gearbox 110, an inverter 112, and a charger 114 are arranged.

[0021] The direct current output from the battery pack 10 is supplied to the electric compressor 104, the PTC heater 106, the inverter 112, etc. after the voltage is adjusted by the DC / DC converter 102. Also, by supplying power to the motor 108 via the inverter 112, the rear wheels rotate to make the vehicle 100 run.

[0022] A charging port 116 is provided on the right side at the rear of the vehicle 100, and by connecting a charging plug of an external charging facility (not shown) from the charging port 116, power can be stored in the battery pack 10 via the in-vehicle charger 114.

[0023] Note that the arrangement and structure of each component constituting the vehicle 100 are not limited to the above-described configuration. For example, it may be applied to a hybrid vehicle (HV) or a plug-in hybrid electric vehicle (PHEV) equipped with an engine. Also, in the present embodiment, the vehicle is a rear-wheel drive vehicle with the motor 108 mounted at the rear of the vehicle, but it is not limited to this. It may be a front-wheel drive vehicle with the motor 108 mounted at the front of the vehicle, or a pair of motors 108 may be mounted at the front and rear of the vehicle. Furthermore, a vehicle equipped with in-wheel motors for each wheel may also be used.

[0024] Here, the battery pack 10 is configured to include a plurality of battery modules 11. In the present embodiment, as an example, 10 battery modules 11 are provided. Specifically, five battery modules 11 are arranged in the vehicle front-rear direction on the right side of the vehicle 100, and five battery modules 11 are arranged in the vehicle front-rear direction on the left side of the vehicle 100. Also, each of the battery modules 11 is electrically connected.

[0025] FIG. 2 is a schematic perspective view of the battery module 11. As shown in FIG. 2, the battery module 11 is formed in a substantially rectangular parallelepiped shape with the vehicle width direction as the longitudinal direction. Also, the case 13 of the battery module 11 is formed of an aluminum alloy. For example, the case 13 of the battery module 11 is formed by joining aluminum die-casts to both ends of an extruded material of an aluminum alloy by laser welding or the like.

[0026] A pair of voltage terminals 12 and connectors 14 are provided at both ends in the vehicle width direction of the battery module 11. A flexible printed circuit board 21 described later is connected to the connector 14. Also, bus bars (not shown) are welded to both ends in the vehicle width direction of the battery module 11.

[0027] The vehicle-width direction length MW of the battery module 11 is, for example, 350 mm to 600 mm, the vehicle longitudinal direction length ML is, for example, 150 mm to 250 mm, and the vehicle vertical direction height MH is, for example, 80 mm to 110 mm.

[0028] FIG. 3 is a plan view of the battery module 11 with the upper lid removed. As shown in FIG. 3, inside the battery module 11, a battery cell group in which a plurality of battery cells 20 are arranged is accommodated. In this embodiment, as an example, 24 battery cells 20 are arranged in the vehicle longitudinal direction and adhered to each other.

[0029] On the battery cell 20, a flexible printed circuit (FPC) 21 is arranged. The flexible printed circuit 21 is formed in a strip shape with the vehicle-width direction as the longitudinal direction, and thermistors 23 are provided at both ends of the flexible printed circuit 21, respectively. The thermistor 23 is not adhered to the battery cell 20 and is configured to be pressed toward the battery cell 20 side by the upper lid of the battery module 11.

[0030] Also, inside the battery module 11, one or more buffer plates (not shown) are accommodated. For example, the buffer plate is a thin plate-like member that can be elastically deformed and is arranged between adjacent battery cells 20 with the arrangement direction of the battery cells 20 as the thickness direction. In this embodiment, as an example, buffer materials are arranged at both longitudinal ends and the central portion in the longitudinal direction of the battery module 11, respectively.

[0031] FIG. 4 is a schematic view of the battery cell 20 accommodated in the battery module 11 viewed from the thickness direction. As shown in FIG. 4, the battery cell 20 is formed in a substantially rectangular plate shape, and a long electrode body 19 is accommodated inside. The electrode body 19 is formed by laminating a positive electrode, a negative electrode, and a separator, and is sealed with a laminate film 22.

[0032] In this embodiment, as an example, the housing portion of the electrode body 19 is formed by folding and bonding an embossed sheet-like laminate film 22. Note that both a single cup emboss structure with one embossing and a double cup emboss structure with two embossings can be adopted, but in this embodiment, a single cup emboss structure with a drawing depth of about 8 mm to 10 mm is used.

[0033] The upper ends at both longitudinal ends of the battery cell 20 are bent, and the corners form the outer shape. Also, the upper end portion of the battery cell 20 is bent, and a fixing tape 24 is wound along the longitudinal direction on the upper end portion of the battery cell 20.

[0034] Here, terminals (tabs) 26 are provided at both longitudinal ends of the battery cell 20. In this embodiment, as an example, the terminals 26 are provided at positions offset downward from the center in the vertical direction of the battery cell 20. The terminals 26 are joined to a bus bar (not shown) by laser welding or the like.

[0035] The length CW1 of the battery cell 20 in the vehicle width direction is, for example, 530 mm to 600 mm, the length CW2 of the region where the electrode body 19 is accommodated is, for example, 500 mm to 520 mm, and the height CH of the battery cell 20 is, for example, 80 mm to 110 mm. Therefore, the battery cell 20 is formed in a long shape, and the directions of the lengths CW1 and CW2 are the longitudinal directions.

[0036] Also, the thickness of the battery cell 20 is 7.0 mm to 9.0 mm, and the height TH of the terminal 26 is 40 mm to 50 mm.

[0037] FIG. 5 is a schematic view of the negative electrode 30 constituting the battery cell 20 according to the embodiment as viewed from the thickness direction. As shown in FIG. 5, the negative electrode 30 includes a current collector 32 and a negative electrode active material 34 applied to the surface of the current collector 32.

[0038] The current collector 32 is composed of a metal foil, and is formed, for example, into a substantially rectangular sheet shape by a copper foil or the like. The negative electrode active material 34 held by the current collector 32 forms a negative electrode composite material together with a binder and a conductive assistant, and occludes lithium ions, which are charge carriers, from the non-aqueous electrolyte during charge and discharge, and releases them into the non-aqueous electrolyte. The negative electrode active material 34 of the present embodiment uses a material containing a silicon element such as porous silicon or a silicon-based carbon composite material, but is not limited thereto. For example, as the negative electrode active material, a known negative electrode active material such as artificial graphite or a lithium alloy (LiXM) may be used. In LiXM, M is C, Si, Sn, Sb, Al, Mg, Ti, Bi, Ge, Pb, P, or the like, and X is a natural number. Further, the negative electrode active material layer formed by the negative electrode active material 34 may contain a known binder such as a styrene-butadiene copolymer.

[0039] Note that the positive electrode constituting the electrode body 19 includes a current collector formed of an aluminum foil or the like and a positive electrode active material. The positive electrode active material releases or occludes lithium ions into or from the non-aqueous electrolyte. As the positive electrode active material, a known positive electrode active material such as LiNiO2 or LiNi1 / 3Co1 / 3Mn1 / 3O2 is used. Further, it may further contain carbon black, trilithium phosphate, and a known binder.

[0040] The separator is a sheet-like member that electrically insulates the positive electrode and the negative electrode 30 and provides a migration path for lithium ions between the positive electrode active material and the negative electrode active material 34. Examples of the separator include a porous membrane formed of polyethylene and polypropylene. Note that the separator may have a single-layer structure or a multilayer structure.

[0041] Here, in the present embodiment, the negative electrode active material 34 is provided in a portion excluding the peripheral end portion of the current collector 32, and is applied in a substantially rectangular shape when viewed from the thickness direction. Further, the central portion 34A of the negative electrode active material 34 contained in the negative electrode composite material is less than the end portion 34B.

[0042] Specifically, in the negative electrode composite material of the present embodiment, the density of the negative electrode active material 34 in the central portion 34A is lower than that in the end portion 34B. In other words, the basis weight of the central portion 34A is smaller than that of the end portion 34B. For example, when pressing the negative electrode active material 34, the density of the central portion 34A may be relatively reduced by reducing the pressing pressure of the central portion 34A compared to the end portion 34B. As another method, two types of negative electrode active materials 34 having different densities may be prepared in advance, and the negative electrode active material 34 having a lower density may be disposed in the central portion 34A.

[0043] In the present embodiment, the central portion 34A where the density of the negative electrode active material 34 is low is the region surrounded by the two-dot chain line in the figure. That is, it is the central portion in the longitudinal direction of the negative electrode 30 and the central portion in the short-side direction of the negative electrode 30.

[0044] On the other hand, the end portion in the longitudinal direction of the negative electrode 30 and the end portion in the short-side direction of the negative electrode 30 are the end portions 34B where the density of the negative electrode active material 34 is relatively high.

[0045] Note that the present invention is not limited to the configuration of FIG. 5, and the structure of the modification shown in FIG. 6 may be adopted.

[0046] FIG. 6 is a schematic view of a negative electrode constituting the battery cell 20 according to the modification as viewed from the thickness direction. As shown in FIG. 6, in the battery cell 20 of the present modification, the negative electrode active material 34 is provided in a portion excluding the end portion of the current collector 32 and is coated in a substantially rectangular shape as viewed from the thickness direction. Further, the central portion 34A in the short-side direction of the negative electrode active material 34 is less than the end portion 34B.

[0047] (Operation) Next, the operation of the battery cell 20 according to the present embodiment will be described.

[0048] As shown in FIG. 4, the battery cell 20 according to the present embodiment is formed in a long shape by sealing the electrode body 19 with the laminate film 22.

[0049] Further, as shown in FIG. 5, the negative electrode 30 includes a current collector 32 coated with a negative electrode composite material containing a negative electrode active material 34, and the negative electrode active material 34 contained in the negative electrode composite material is less in the central portion 34A than in the end portion 34B of the negative electrode 30. Thereby, the thermal expansion can be suppressed particularly with respect to the central portion 34A of the negative electrode 30 where the volume change due to thermal expansion is large. Also, there is no need to separately prepare a member for suppressing thermal expansion. As a result, the thermal expansion of the battery cell 20 can be suppressed with a simple structure.

[0050] Furthermore, in the present embodiment, the thermal expansion of the battery cell 20 is suppressed by changing the density of the negative electrode active material 34 between the central portion 34A and the end portion 34B of the negative electrode 30. Thereby, the thickness of the negative electrode active material 34 can be made the same between the central portion 34A and the end portion 34B.

[0051] In particular, the negative electrode active material 34 of the present embodiment is configured to contain a silicon element. The silicon element is excellent in terms of specific capacity in particular, while having a large volume change. However, by reducing the silicon in the central portion 34A compared to the end portion 34B as in the present embodiment, the thermal expansion of the battery cell 20 can be effectively suppressed.

[0052] As described above, the battery cell 20 and the negative electrode 30 according to the embodiment have been described, but the present invention is not limited thereto. Of course, the present invention can be implemented in various modes without departing from the gist of the present invention. In the above embodiment, as shown in FIG. 5, the density of the central portion 34A of the negative electrode active material 34 contained in the negative electrode composite material is made lower than that of the end portion 34B. However, the present invention is not limited thereto, and any other structure may be adopted as long as the structure is such that the negative electrode active material 34 in the central portion 34A is less than that in the end portion 34B. For example, the central portion 34A of the negative electrode active material 34 may be formed to be thinner than the end portion 34B. As a method of making the central portion 34A of the negative electrode active material 34 thinner, a method of scraping off a part of the negative electrode active material 34 only from the central portion 34A after applying and pressing the negative electrode active material 34 by a normal procedure may be used.

[0053] By making the central portion 34A of the negative electrode active material 34 thinner than the end portion 34B, the thermal expansion of the battery cell 20 is suppressed. As a result, the thermal expansion of the battery cell 20 can be suppressed only by reducing the negative electrode active material 34 in the central portion of the negative electrode 30.

[0054] Also, the central portion 34A of the negative electrode active material 34 may be made thinner than the end portion 34B, and the density of the central portion 34A of the negative electrode active material 34 may be made lower than that of the end portion 34B. Further, without changing the density of the negative electrode active material, the concentration of silicon contained in the negative electrode active material may be changed. That is, the same effect can be obtained by making the concentration of silicon in the central portion of the negative electrode active material lower than the concentration of silicon in the end portion.

[0055] Furthermore, in the above embodiment, the central portion 34A with a low density of the negative electrode active material 34 and the end portion 34B with a high density are formed with the two-dot chain line in FIG. 5 as a boundary, but the present invention is not limited to this. For example, the density of the negative electrode active material 34 may be changed stepwise from the end portion 34B toward the central portion 34A, or the density of the negative electrode active material 34 may be changed continuously from the end portion 34B toward the central portion 34A.

[0056] Regarding the above embodiment, the following supplementary notes are disclosed.

[0057] (Supplementary Note 1) An electrode body formed by laminating a positive electrode, a negative electrode, and a separator, A laminate film that seals the electrode body in a contained state, having, The negative electrode includes a current collector coated with a negative electrode composite material containing a negative electrode active material, and the negative electrode active material contained in the negative electrode composite material is less in the central portion than in the end portion. Battery cell. (Supplementary Note 2) In the central portion of the negative electrode, the density of the negative electrode active material contained in the negative electrode composite material is lower than that in the end portion. The battery cell according to Supplementary Note 1. (Supplementary Note 3) In the central portion of the negative electrode, the thickness of the negative electrode composite material is thinner than that in the end portion. The battery cell according to Supplementary Note 1 or 2. (Supplementary Note 4) The battery cell according to any one of Supplementary Notes 1 to 3, wherein the negative electrode active material contains silicon element. (Supplementary Note 5) A negative electrode that constitutes an electrode body together with a positive electrode and a separator, comprising a current collector and a negative electrode composite material containing a negative electrode active material applied to the current collector, wherein the negative electrode active material contained in the negative electrode composite material is less in a central portion than in an end portion. Negative electrode.

Explanation of Reference Signs

[0058] 19 Electrode body 20 Battery cell 22 Laminate film 30 Negative electrode 32 Current collector 34 Negative electrode active material 34A Central portion 34B End portion

Claims

1. An electrode body formed by laminating a positive electrode, a negative electrode, and a separator; A laminate film that seals the electrode body in a state where the electrode body is accommodated; having; The negative electrode includes a current collector coated with a negative electrode composite material containing a negative electrode active material, and the negative electrode active material contained in the negative electrode composite material is less in the central portion than in the end portions. A battery cell.

2. The battery cell according to claim 1, wherein the central portion of the negative electrode has a lower density of the negative electrode active material contained in the negative electrode composite material than the end portions.

3. The battery cell according to claim 1, wherein the central portion of the negative electrode has a thinner thickness of the negative electrode composite material than the end portions.

4. The battery cell according to any one of claims 1 to 3, wherein the negative electrode active material contains a silicon element.

5. A negative electrode that constitutes an electrode body together with a positive electrode and a separator, comprising a current collector and a negative electrode composite material containing a negative electrode active material coated on the current collector, wherein the negative electrode active material contained in the negative electrode composite material in the central portion is less than that in the end portions. A negative electrode.

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