Battery cell and negative electrode

Abstract

The invention relates to a battery cell and a negative electrode. A battery cell includes: an electrode body formed by stacking a positive electrode, a negative electrode, and a separator; and a laminated film that seals the electrode body in a state where the electrode body is housed, the negative electrode is configured so as to include a current collector that is coated with a negative electrode mixture containing a negative electrode active material, and the negative electrode active material contained in the negative electrode mixture is less in the center portion than in the end portion.

Description

Technical Field

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

[0002] A battery module in which an electrode assembly is housed in a case is disclosed in U.S. Patent Application Publication No. 2018 / 287184. Further, by surrounding the outside of the electrode assembly (battery cell) with a heat-shrinkable protective layer, a structure for suppressing thermal expansion of the electrode assembly has been achieved. Summary of the Invention

[0003] However, in the structure of the above-mentioned U.S. Patent Application Publication No. 2018 / 287184, in order to suppress thermal expansion, it is necessary to prepare a dedicated heat-shrinkable protective layer, and the manufacturing cost and man-hours may increase.

[0004] In consideration of the above facts, an object of the present invention is to obtain a battery cell and a negative electrode capable of suppressing thermal expansion with a simple structure.

[0005] The battery cell according to Technical Solution 1 includes:

[0006] an electrode body formed by laminating a positive electrode, a negative electrode, and a separator; and

[0007] a laminated film that seals the electrode body in a state where the electrode body is housed,

[0008] The negative electrode is configured to

[0009] include a current collector coated with a negative electrode mixture containing a negative electrode active material,

[0010] compared with the end portion, the amount of the negative electrode active material contained in the negative electrode mixture is less in the central portion.

[0011] In the battery cell according to Technical Solution 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 laminated film. Here, the negative electrode is configured to include a current collector coated with a negative electrode mixture containing a negative electrode active material, and the amount of the negative electrode active material contained in the negative electrode mixture is less in the central portion than in the end portion of the negative electrode. Thus, particularly for the central portion of the negative electrode where the volume change due to thermal expansion is large, thermal expansion can be suppressed. In addition, there is no need to separately prepare a member for suppressing thermal expansion. Further, the "end portion" and "central portion" mentioned herein are not limited to the end portion and central portion with respect to a plurality of directions, but broadly include the concept of the end portion and central portion with respect to one direction. In addition, the "negative electrode mixture" mentioned herein refers to a mixture containing a negative electrode active material, a binder, and a conductive additive.

[0012] According to Technical Solution 1, the battery cell related to Technical Solution 2 has a lower density of the negative electrode active material contained in the negative electrode mixture in the central portion of the negative electrode than in the end portion.

[0013] In the battery cell related to Technical Solution 2, by varying the density of the negative electrode active material contained in the negative electrode mixture in the central portion and the end portion of the negative electrode, the thermal expansion of the battery cell is suppressed. Thereby, the thickness of the negative electrode active material can be made the same in the central portion and the end portion.

[0014] According to Technical Solution 1, the battery cell related to Technical Solution 3 has a thinner thickness of the negative electrode mixture in the central portion of the negative electrode than in the end portion.

[0015] In the battery cell related to Technical Solution 3, by making the thickness of the negative electrode mixture in the central portion of the negative electrode thinner than in the end portion, the thermal expansion of the battery cell is suppressed. Thereby, the thermal expansion of the battery cell can be suppressed only by reducing the negative electrode mixture in the central portion of the negative electrode.

[0016] According to any one of Technical Solutions 1 to 3, the battery cell related to Technical Solution 4 has the negative electrode active material containing a silicon element.

[0017] In the battery cell related to Technical Solution 4, the negative electrode active material is composed of a silicon element. The silicon element is particularly excellent in specific capacity. On the other hand, the volume change is large, but by making the negative electrode active material in the central portion less than that in the end portion, the thermal expansion of the battery cell can be effectively suppressed.

[0018] The negative electrode related to Technical Solution 5 is a negative electrode that forms an electrode body together with a positive electrode and a separator.

[0019] It includes a current collector and a negative electrode mixture containing a negative electrode active material coated on the current collector.

[0020] Compared with the end portion, the amount of the negative electrode active material contained in the negative electrode mixture in the central portion is reduced.

[0021] In the negative electrode related to Technical Solution 5, it includes a current collector and a negative electrode mixture. Compared with the end portion of the negative electrode, the amount of the negative electrode active material contained in the negative electrode mixture in the central portion is reduced. Thereby, especially for the central portion of the negative electrode where the volume change due to thermal expansion becomes large, the thermal expansion can be suppressed.

[0022] As described above, according to the battery cell and the negative electrode of the present invention, thermal expansion can be suppressed with a simple structure. Description of the Drawings

[0023] Hereinafter, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, in which like reference numerals denote like elements, and in which:

[0024] Figure 1 is a schematic plan view showing a main part of a vehicle equipped with a battery pack having a battery cell according to an embodiment.

[0025] Figure 2 is a schematic perspective view of a battery module housing the battery cell according to an embodiment.

[0026] Figure 3 is a plan view of a state in which the upper cover of the battery module is removed.

[0027] Figure 4 is a schematic view of the battery cell according to an embodiment as viewed in the thickness direction.

[0028] Figure 5 is a schematic view of the negative electrode constituting the battery cell according to an embodiment as viewed in the thickness direction.

[0029] Figure 6 is a schematic view of the negative electrode constituting the battery cell according to a modification as viewed in the thickness direction. Detailed Embodiments

[0030] With reference to the accompanying drawings, the battery module 11 having the battery cell 20 according to the embodiment will be described.

[0031] Overall Configuration of Vehicle 100

[0032] Figure 1 is a schematic plan view showing a main part of a vehicle 100 equipped with a battery pack 10 having the battery module 11 according to the present embodiment. As Figure 1 shown, the vehicle 100 is a battery electric vehicle (BEV) having the battery pack 10 mounted under the floor. In addition, the arrows UP, FR, and LH in each figure respectively 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. When the directions of front, rear, left, right, up, and down are used for description, unless otherwise specified, front and rear in the vehicle front-rear direction, left and right in the vehicle width direction, and up and down in the vehicle up-down direction are meant.

[0033] 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 with respect to the battery pack 10. In addition, a motor 108, a transmission (gearbox) 110, an inverter 112, and a charger 114 are arranged on the vehicle rear side with respect to the battery pack 10.

[0034] 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. In addition, power is supplied to the motor 108 via the inverter 112, so that the rear wheels rotate to make the vehicle 100 travel.

[0035] A charging port 116 is provided on the right side part of the rear portion of the vehicle 100. By connecting a charging plug of an external charging device (not shown) to the charging port 116, power can be stored in the battery pack 10 via the in-vehicle charger 114.

[0036] In addition, the configuration and structure of each component constituting the vehicle 100 are not limited to the above configuration. For example, it can also be applied to a hybrid electric vehicle (HV) equipped with an engine or a plug-in hybrid electric vehicle (PHEV). In addition, in the present embodiment, the vehicle is a rear-wheel drive vehicle with the motor 108 mounted on the rear portion of the vehicle, but it is not limited thereto. It can also be a front-wheel drive vehicle with the motor 108 mounted on the front portion of the vehicle, or a pair of motors 108 can be mounted on the front and rear of the vehicle. Moreover, it can also be a vehicle having in-wheel motors at each wheel.

[0037] Here, the battery pack 10 is composed of a plurality of battery modules 11. In the present embodiment, as an example, 10 battery modules 11 are provided. Specifically, 5 battery modules 11 are arranged in the vehicle front-rear direction on the right side of the vehicle 100, and 5 battery modules 11 are arranged in the vehicle front-rear direction on the left side of the vehicle 100. In addition, each battery module 11 is electrically connected.

[0038] Figure 2 It is a schematic perspective view of the battery module 11. As Figure 2 shown, the battery module 11 is formed in a substantially rectangular parallelepiped shape with the vehicle width direction as the long side direction. In addition, the housing 13 of the battery module 11 is formed of aluminum alloy. For example, by joining aluminum die-castings to both ends of an extruded material of aluminum alloy by laser welding or the like, the housing 13 of the battery module 11 is formed.

[0039] A pair of voltage terminals 12 and connectors 14 are respectively provided at both ends of the battery module 11 in the vehicle width direction. A flexible printed circuit board 21 described later is connected to the connector 14. In addition, bus bars (not shown) are welded to both ends of the battery module 11 in the vehicle width direction.

[0040] The length MW of the battery module 11 in the vehicle width direction is, for example, 350 mm to 600 mm, the length ML in the vehicle front-rear direction is, for example, 150 mm to 250 mm, and the height MH in the vehicle up-down direction is, for example, 80 mm to 110 mm.

[0041] Figure 3 It is a plan view of the state where the upper cover of the battery module 11 is removed. As Figure 3 shown, inside the battery module 11, a battery cell group in which a plurality of battery cells 20 are arranged is housed. In the present embodiment, as an example, 24 battery cells 20 are arranged in the vehicle front-rear direction and bonded to each other.

[0042] A flexible printed circuit (FPC) board 21 is disposed on the battery cell 20. The flexible printed circuit board 21 is formed in a strip shape with the vehicle width direction as the length direction, and thermistors 23 are respectively provided at both ends of the flexible printed circuit board 21. The thermistors 23 are not bonded to the battery cell 20 and are configured to be pressed from the upper cover of the battery module 11 toward the battery cell 20 side.

[0043] In addition, one or more buffer plates (not shown) are housed inside the battery module 11. For example, the buffer plate is a thin plate-like member that can elastically deform and is disposed between adjacent battery cells 20 with the arrangement direction of the battery cells 20 as the thickness direction. In the present embodiment, as an example, buffer materials are respectively disposed at both ends and the central portion in the long side direction of the battery module 11.

[0044] Figure 4 It is a schematic view of the battery cell 20 housed in the battery module 11 as viewed from the thickness direction. As Figure 4 shown, the battery cell 20 is formed in a substantially rectangular plate shape, and a long strip-shaped electrode body 19 is housed inside. The electrode body 19 is formed by laminating a positive electrode, a negative electrode, and a separator, and is sealed with a laminated film 22.

[0045] In the present embodiment, as an example, a housing portion for the electrode body 19 is formed by folding and bonding the embossed sheet-like laminated film 22. In addition, two structures, a single embossing structure with one embossing process and a double embossing structure with two embossing processes, can be adopted. In the present embodiment, it is a single embossing structure with an embossing depth of about 8 mm to 10 mm.

[0046] The upper ends of both ends of the battery cell 20 in the longitudinal direction are bent, and the corners form the outer shape. In addition, the upper end portion of the battery cell 20 is bent, and a fixing band 24 is wound along the longitudinal direction at the upper end portion of the battery cell 20.

[0047] Here, terminals (connectors) 26 are provided at both ends of the battery cell 20 in the longitudinal direction. In the present embodiment, as an example, the terminal 26 is provided at a position offset downward from the center in the vertical direction of the battery cell 20. The terminal 26 is joined to a bus bar (not shown) by laser welding or the like.

[0048] 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 accommodating the electrode body 19 is, for example, 500 mm to 520 mm. 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 strip shape, and the directions of the lengths CW1 and CW2 are the longitudinal directions.

[0049] In addition, 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.

[0050] Figure 5 It 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 Figure 5 shown, the negative electrode 30 is configured to include a current collector 32 and a negative electrode active material 34 coated on the surface of the current collector 32.

[0051] The current collector 32 is made of a metal foil, and is formed, for example, into a substantially rectangular sheet shape such as a copper foil. The negative electrode active material 34 held by the current collector 32 forms a negative electrode mixture together with a binder and a conductive additive, and occludes lithium ions as charge carriers from the non-aqueous electrolyte during charge and discharge, and releases the non-aqueous electrolyte. The negative electrode active material 34 of the present embodiment uses a silicon-containing material such as porous silicon or a silicon-based carbon composite material, but is not limited thereto. For example, as the negative electrode active material, known negative electrode active materials such as artificial graphite and lithium alloy (LiXM) can also be used. In addition, M in LiXM is C, Si, Sn, Sb, Al, Mg, Ti, Bi, Ge, Pb, or P, etc., and X is a natural number. In addition, the negative electrode active material layer formed of the negative electrode active material 34 may also contain a known binder such as styrene-butadiene copolymer.

[0052] In addition, the positive electrode constituting the electrode body 19 includes a current collector formed of aluminum foil or the like and a positive electrode active material. The positive electrode active material releases or occludes lithium ions from the non-aqueous electrolyte. The positive electrode active material uses LiNiO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3Well-known positive electrode active materials such as O2. Additionally, carbon black, lithium phosphate, and well-known binders may also be included.

[0053] 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 porous membranes formed of polyethylene, polypropylene, etc. In addition, the separator may have a single-layer structure or a multi-layer structure.

[0054] Here, in the present embodiment, the negative electrode active material 34 is provided on a portion of the current collector 32 other than the peripheral end portion, and is coated in a substantially rectangular shape when viewed from the thickness direction. Additionally, the central portion 34A of the negative electrode active material 34 included in the negative electrode mixture is less than the end portion 34B.

[0055] Specifically, the density of the central portion 34A of the negative electrode active material 34 included in the negative electrode mixture of the present embodiment is lower than that of the end portion 34B. In other words, the weight per unit area of the central portion 34A is smaller than that of the end portion 34B. For example, the density of the central portion 34A can be relatively reduced by making the pressing pressure of the central portion 34A smaller than that of the end portion 34B when pressing the negative electrode active material 34. Additionally, as another method, two types of negative electrode active materials 34 with different densities can be prepared in advance, and the negative electrode active material 34 with a lower density can be disposed in the central portion 34A.

[0056] In the present embodiment, the central portion 34A with a lower density of the negative electrode active material 34 is the region surrounded by the double-dot dash line in the figure. That is, it is the central portion in the long side direction of the negative electrode 30 and is also the central portion in the short side direction of the negative electrode 30.

[0057] In contrast, the end portion in the long side direction of the negative electrode 30 and the end portion in the short side direction of the negative electrode 30 become the end portion 34B with a relatively higher density of the negative electrode active material 34.

[0058] In addition, without being limited to Figure 5 the configuration of Figure 6 the structure of the modified example shown can also be adopted.

[0059] Figure 6 is a schematic view of the negative electrode constituting the battery cell 20 according to the modified example when viewed from the thickness direction. As shown in this Figure 6 figure, in the battery cell 20 of the present modified example, the negative electrode active material 34 is provided on a portion of the current collector 32 other than the end portion, and is coated in a substantially rectangular shape when viewed from the thickness direction. Additionally, the central portion 34A in the short side direction of the negative electrode active material 34 becomes less than the end portion 34B.

[0060] Function

[0061] Next, the function of the battery cell 20 according to this embodiment will be described.

[0062] As Figure 4 shown, the battery cell 20 according to this embodiment is formed in a strip shape by sealing the electrode body 19 with a laminate film 22.

[0063] In addition, as Figure 5 shown, the negative electrode 30 is configured to include a current collector 32 coated with a negative electrode mixture containing a negative electrode active material 34. Compared with the end portion 34B of the negative electrode 30, the amount of the negative electrode active material 34 contained in the negative electrode mixture is less in the central portion 34A. Thus, especially for the central portion 34A of the negative electrode 30 where the volume change due to thermal expansion is large, thermal expansion can be suppressed. In addition, 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.

[0064] Moreover, in this embodiment, the thermal expansion of the battery cell 20 is suppressed by changing the density of the negative electrode active material 34 in the central portion 34A and the end portion 34B of the negative electrode 30. Thus, the thickness of the negative electrode active material 34 can be the same in the central portion 34A and the end portion 34B.

[0065] In particular, the negative electrode active material 34 of this embodiment is configured to contain a silicon element. The silicon element is particularly excellent in terms of specific capacity. On the other hand, the volume change is large, but by making the silicon in the central portion 34A less than that in the end portion 34B as in this embodiment, the thermal expansion of the battery cell 20 can be effectively suppressed.

[0066] As described above, the battery cell 20 and the negative electrode 30 according to the embodiment have been described, but are not limited thereto. Of course, various technical solutions can be implemented without departing from the gist of the present invention. In the above embodiment, as Figure 5 shown, the density of the central portion 34A of the negative electrode active material 34 contained in the negative electrode mixture is lower than the density of the end portion 34B. However, it is not limited thereto. 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, other structures can also be adopted. For example, it can also be formed such that the thickness of the central portion 34A of the negative electrode active material 34 is thinner than the thickness of the end portion 34B. As a method of thinning the thickness of the central portion 34A of the negative electrode active material 34, the following method can also be used: after coating the negative electrode active material 34 in a normal step and pressing it, only a part of the negative electrode active material 34 in the central portion 34A is shaved off.

[0067] By making the thickness of the central portion 34A of the negative electrode active material 34 thinner than that of the end portion 34B, the thermal expansion of the battery cell 20 can be suppressed. Thus, by simply reducing the negative electrode active material 34 in the central portion of the negative electrode 30, the thermal expansion of the battery cell 20 can be suppressed.

[0068] In addition, it is also possible to make the thickness of the central portion 34A of the negative electrode active material 34 thinner than that of the end portion 34B and make the density of the central portion 34A of the negative electrode active material 34 lower than that of the end portion 34B. Moreover, without changing the density of the negative electrode active material, the concentration of silicon contained in the negative electrode active material can be changed. That is, by making the concentration of silicon in the central portion of the negative electrode active material lower than that in the end portion, the same effect can also be obtained.

[0069] Moreover, in the above-described embodiment, Figure 5 Taking the double-dot dash line as the boundary, a central portion 34A with a low density and an end portion 34B with a high density of the negative electrode active material 34 are formed, but it is not limited thereto. 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.

[0070] Regarding the above-described embodiment, the following remarks are disclosed.

[0071] Remark 1

[0072] A battery cell having:

[0073] An electrode body formed by laminating a positive electrode, a negative electrode, and a separator; and

[0074] A laminated film that seals the electrode body in a housed state,

[0075] The negative electrode is configured to

[0076] include a current collector coated with a negative electrode mixture containing a negative electrode active material,

[0077] The amount of the negative electrode active material contained in the negative electrode mixture in the central portion is less than that in the end portion.

[0078] Remark 2

[0079] The battery cell according to Remark 1,

[0080] The density of the negative electrode active material contained in the negative electrode mixture in the central portion of the negative electrode is lower than that in the end portion.

[0081] Remark 3

[0082] The battery cell according to Remark 1 or 2,

[0083] The thickness of the negative electrode mixture in the central portion of the negative electrode is thinner than that in the end portion.

[0084] Supplementary Note 4

[0085] The battery cell according to any one of Supplementary Notes 1 to 3,

[0086] The negative electrode active material contains silicon element.

[0087] Supplementary Note 5

[0088] A negative electrode, which together with a positive electrode and a separator constitutes an electrode body,

[0089] The negative electrode includes a current collector and a negative electrode mixture containing a negative electrode active material coated on the current collector,

[0090] The amount of the negative electrode active material contained in the negative electrode mixture in the central portion is less than that in the end portion.

Claims

1. A battery cell comprising: an electrode body formed by laminating a positive electrode, a negative electrode, and a separator; and The laminate film is sealed in a state where the electrode body is housed therein, The negative electrode is composed of: The invention comprises a current collector coated with a negative electrode mixture containing a negative electrode active material, The negative electrode active material contained in the negative electrode mixture is smaller in the center portion than in the end portions.

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

3. The battery cell according to claim 1, The thickness of the negative electrode mixture is thinner in the central portion of the negative electrode than in the end portions.

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

5. A negative electrode, It is the negative electrode that forms the electrode body together with the positive electrode and the separator. The negative electrode comprises a current collector and a negative electrode mixture containing a negative electrode active material applied to the current collector. The negative electrode active material contained in the negative electrode mixture in the center portion is smaller than that in the end portion.

Images