Pole piece structure, battery cell and battery

Abstract

The utility model belongs to the technical field of batteries, and particularly relates to a pole piece structure, a battery cell and a battery. The pole piece structure comprises a current collector and an active material layer arranged on at least one surface of the current collector, an expansion conductive part is arranged between the current collector and the active material layer; when the pole piece structure is wound into a roll core, the pole piece structure is provided with at least one corner section; and the expansion conductive part is arranged at the corner section. According to the utility model, the stability of the whole structure can be improved, the infiltration effect between electrolyte and the pole piece is facilitated, and the phenomenon of lithium precipitation by black spots at corners is improved.

Description

Technical Field

[0001] This utility model belongs to the field of battery technology, and in particular relates to an electrode structure, a battery cell and a battery. Background Technology

[0002] Currently, lithium-ion batteries are composed of components such as a positive electrode, a negative electrode, a separator, and an electrolyte. The cell is manufactured through processes including slurry preparation, coating, rolling, slitting, winding, electrolyte injection, assembly, and formation. Improving the energy density of the cell can be addressed by considering factors such as the specific capacity and thickness of each component material. For the positive electrode, energy density can be achieved by introducing high-specific-capacity positive electrode materials, increasing the areal density of the positive electrode, and improving the compaction of the positive electrode. It should be noted that lithium-ion batteries are divided into hard-case batteries and pouch batteries.

[0003] In some existing technologies, as the number of battery cell cycles increases, the space between the positive and negative electrodes at the cell corners is compressed due to the expansion of the positive and negative electrodes during the cycle. This causes the electrolyte at the corners to easily form broken bridges, reducing the electrolyte storage capacity and eventually resulting in black spots and lithium plating. Utility Model Content

[0004] The purpose of this invention is to provide an electrode structure that addresses the shortcomings of existing technologies and solves the technical problem of low liquid storage capacity in existing technologies.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An electrode structure includes a current collector and an active material layer disposed on at least one surface of the current collector; and an expansion conductive component is provided between the current collector and the active material layer;

[0007] When the electrode structure is wound into a core, the electrode structure has at least one corner segment; and the expansion conductive component is disposed at the corner segment.

[0008] Preferably, the number of the expanding conductive components is at least two, and they are respectively disposed on two opposite surfaces of the current collector;

[0009] In the thickness direction of the electrode structure, the projection of one of the expanded conductive components toward the current collector is misaligned with the projection of the other expanded conductive component toward the current collector.

[0010] Preferably, the thickness h1 of the expanded conductive component satisfies: 1um ≤ h1 ≤ 8um.

[0011] Preferably, the expandable conductive component includes an expandable layer and a conductive agent layer connected to each other; the expandable layer is connected to the current collector and / or the active material layer; the conductive agent layer is connected to the current collector and / or the active material layer.

[0012] Preferably, the expansion layer is one of polyurethane thermoplastic elastomer, styrene thermoplastic elastomer, olefin thermoplastic elastomer, dynamically vulcanized thermoplastic elastomer, polyester thermoplastic elastomer, and polyamide thermoplastic elastomer;

[0013] And / or, the conductive agent layer is one of carbon black, conductive graphite, carbon fiber, carbon nanotubes, and graphene.

[0014] Preferably, the expansion layer and the conductive agent layer are stacked, and the expansion layer is connected to the active material layer; the conductive agent layer is connected to the current collector.

[0015] Preferably, there are two conductive agent layers, and the expansion layer is disposed between the conductive agent layers; one conductive agent layer is connected to the active material layer; and the other conductive agent layer is connected to the current collector.

[0016] Preferably, when the electrode structure is in contact with the electrolyte, at least one bump is provided on the active material layer; the bump and the expanding conductive component are disposed opposite to each other on the two sides of the active material layer.

[0017] This utility model also discloses a battery cell, including a first electrode and a second electrode, and a separator disposed between the first electrode and the second electrode; wherein the first electrode, the separator and the second electrode are sequentially stacked and wound to form a core; the first electrode and / or the second electrode are the battery cell electrodes described above.

[0018] This utility model also discloses a battery, including the aforementioned battery cell.

[0019] The beneficial effects of this utility model are that, by adding at least one expanding conductive component to each corner segment of the winding state, the expanding conductive component can absorb and expand the electrolyte after contacting it, thereby restoring the uniformity of the electrode thickness to a certain extent and improving the electrolyte storage capacity of the corner segment of the core; furthermore, it is beneficial to the wetting effect between the electrolyte and the electrode, improving the black spot lithium deposition phenomenon at the corner; and improving the battery cycle performance. Attached Figure Description

[0020] The following will refer to the appendix. Figures 1-7 This section describes the features, advantages, and technical effects of exemplary embodiments of the present invention.

[0021] Figure 1This is a schematic diagram of the electrode structure according to an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the electrode structure in the winding state according to an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the electrode structure according to an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of the structure of the expansion conductive component in the electrode structure according to an embodiment of the present invention;

[0025] Figure 5 This is a schematic diagram of the structure of the expansion conductive component in the electrode structure according to an embodiment of the present invention;

[0026] Figure 6 This is a schematic diagram of the structure of a battery cell according to an embodiment of the present invention;

[0027] Figure 7 This is a schematic diagram of the structure of the battery cell before winding, according to an embodiment of the present invention.

[0028] In the figure: 1-current collector; 2-active material layer; 21-bump; 3-expanding conductive component; 31-expanding layer; 32-conductive agent layer; 41-corner section; 42-straight section; 100-first electrode; 200-second electrode; 300-separating membrane. Detailed Implementation

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0030] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0031] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0032] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or multiple situations existing alone. In addition, the character " / " in this document generally indicates that the related objects before and after are in an "or" relationship.

[0033] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0034] The following is in conjunction with the appendix Figures 1 to 7 The present invention will be described in further detail, but this is not intended to limit the scope of the present invention.

[0035] like Figure 1 and 2 As shown, in one embodiment of the present invention, the electrode structure includes a current collector 1 and an active material layer 2 disposed on at least one surface of the current collector 1; and an expansion conductive component 3 is provided between the current collector 1 and the active material layer 2.

[0036] When the electrode structure is wound into a core, the electrode structure has at least one corner segment 41 and a straight segment 42 that are alternately arranged; and the expansion conductive component 3 is disposed at the corner segment 41.

[0037] The technical solution of this utility model adds at least one expanding conductive component to each corner segment of the winding state, so that the expanding conductive component can absorb and expand the electrolyte after contacting it, thereby restoring the uniformity of the electrode thickness to a certain extent and improving the electrolyte storage capacity of the corner segment of the core; furthermore, it is beneficial to the wetting effect between the electrolyte and the electrode, improves the black spot lithium deposition phenomenon at the corner; and improves the battery cycle performance.

[0038] Specifically, in some implementations, such as Figure 1 and3 As shown, there are at least two expanding conductive components 3, which are respectively disposed on two opposite surfaces of the current collector 1; and in the thickness direction of the electrode structure, the projection of one expanding conductive component 3 toward the current collector 1 is offset from the projection of the other expanding conductive component 3 toward the current collector 1. That is, the expanding conductive components 3 on the upper and lower surfaces of the current collector 1 are staggered to avoid the deformation of the overall structure caused by the simultaneous expansion of expanding conductive components 3 at the same thickness position, thereby improving the stability of the overall structure and facilitating the wetting effect between the electrolyte and the electrode, and improving the phenomenon of black spot lithium deposition at the corners.

[0039] Specifically, in some implementations, such as Figure 3 As shown, the thickness h1 of the expanding conductive component 3 satisfies: 1µm ≤ h1 ≤ 8µm; h1 can be 1µm, 2µm, 4µm, 6µm, 7µm, 8µm, etc. That is, by controlling the thickness of the expanding conductive component 3 within the range of 1µm to 8µm, the expanding conductive component can be more stably expanded after contacting the electrolyte, thus facilitating the wetting effect between the electrolyte and the electrode, improving the black spot lithium deposition phenomenon at corners, and enhancing battery cycle performance. In some embodiments, such as... Figure 3 As shown, the relationship between the thickness h1 of the expanding conductive component 3 and the thickness h2 of the active material layer 2 satisfies: 1% * h2 ≤ h1 ≤ 8% * h2. Here, h1 can be 1% * h2, 2% * h2, 3% * h2, 4% * h2, 5% * h2, 8% * h2, etc. In other words, by controlling the proportion of the expanding conductive component 3 in the active material layer 2, excessive thickness is avoided, which would affect the structural stability; excessive thinness is avoided, which would affect the expansion effect. This, in turn, facilitates the wetting effect between the electrolyte and the electrode, improves the black spot lithium deposition phenomenon at the corners, and enhances the battery cycle performance.

[0040] Specifically, in some implementations, such as Figure 1 , 3 As shown in Figure 6, the relationship between the length L1 of the expanding conductive component 3 and the width h0 of the entire winding core satisfies: 0.25*h0≤L1≤h0. Where L1 can be 0.25*h0, 0.30*h0, 0.40*h0, 0.50*h0, 0.60*h0, h0, etc. This structure, with a suitable length range for the liquid-absorbing conductive component 3 in each turn, ensures the amount of expansion protrusion, which is beneficial for the wetting effect between the electrolyte and the electrode, improves the black spot lithium deposition phenomenon at the corners, and enhances the battery cycle performance.

[0041] Specifically, in some embodiments, the expandable conductive component 3 includes an expandable layer 31 and a conductive agent layer 32 interconnected (including hybrid interconnection forms); the expandable layer 31 is connected to the current collector 1 and / or the active material layer 2; the conductive agent layer 32 is connected to the current collector 1 and / or the active material layer 2. The expandable layer 31 can be one or more of polyurethane thermoplastic elastomers (TPU), styrene thermoplastic elastomers (TPS), olefin thermoplastic elastomers (TPO), dynamically vulcanized thermoplastic elastomers (TPV), polyester thermoplastic elastomers (TPEE), and polyamide thermoplastic elastomers (TPA). The conductive agent layer 32 can be one or more of carbon black, conductive graphite, carbon fiber (VGCF), carbon nanotubes (CNT), and graphene. The shape of the expandable conductive component 3 can be uniform dots, stripes, waves, etc., and is not limited to any particular shape. In other words, this structure combines one of the following materials—carbon black, conductive graphite, carbon fiber (VGCF), carbon nanotubes (CNTs), and graphene—with one of the following thermoplastic elastomers: polyurethane (TPU), styrene (TPS), olefinic thermoplastic elastomers (TPO), dynamically vulcanized thermoplastic elastomers (TPV), polyester thermoplastic elastomers (TPEE), and polyamide thermoplastic elastomers (TPA). This allows for slight expansion and deformation at the corners when in contact with the electrolyte, restoring the electrode structure and improving the electrolyte storage capacity at the corners of the core. Furthermore, it facilitates the wetting effect between the electrolyte and the electrode, mitigating the black spot lithium deposition phenomenon at the corners, and improving battery cycle performance.

[0042] Specifically, in some of these implementations, such as Figure 4 As shown, the expansion layer 31 and the conductive agent layer 32 are stacked sequentially, with the expansion layer 31 abutting against the active material layer 2; the conductive agent layer 32 is connected to the current collector 1. That is, by coating the conductive agent layer 32 first and then the expansion layer 31, the expansion can improve the liquid retention level at the corner and reduce damage to the current collector 1, thereby improving the black spot lithium deposition at the corner. In other embodiments, such as... Figure 5 As shown, there are two conductive agent layers 32, and an expansion layer 31 is disposed between the conductive agent layers 32; one conductive agent layer 32 is connected to the active material layer 2; the other conductive agent layer 32 is connected to the current collector 1. This structure, through an upper, middle, and lower sandwich structure, improves the electrolyte retention level at the corner through expansion and reduces damage to the current collector 1, thereby improving lithium plating at the corner. In another embodiment, the expansion layer 31 and the conductive agent layer 32 are mixed in a preset ratio; the mixture is disposed between the active material layer 2 and the current collector 1. Further, the preset ratio can be 1:1, 1:2, 1:3, etc., for example, where the expansion layer 31: conductive agent layer 32 is 1:1, 1:2, or 1:3. After the mixture is formed, the electrode is well wetted by the electrolyte, which improves the lithium plating effect at the corner during circulation.

[0043] Specifically, in some implementations, such as Figure 1 and 3 As shown, when the electrode structure comes into contact with the electrolyte, at least one bump 21 is provided on the active material layer 2; the bump 21 and the expanding conductive component 3 are disposed opposite to each other on the two sides of the active material layer 2; the bump 21 protrudes from the current collector 1 toward the active material layer 2. That is to say, before the electrode structure is immersed in the electrolyte, the surface of the active material layer 2 is flat. When the electrode structure comes into contact with the electrolyte, the expanding conductive component 3 has the characteristic of easily expanding after being immersed in the electrolyte, thereby achieving the purpose of creating gaps on the electrode. Among them, as shown in the figure... Figure 3 As shown, the relationship between the length L1 of the expanding conductive component 3 and the length L2 of the protrusion 21 satisfies: L2≤L1. The relationship between the thickness h1 of the expanding conductive component 3 and the thickness h3 of the protrusion 21 satisfies: h3≤h1.

[0044] This utility model also proposes a battery cell, such as Figure 6 and 7 As shown, the battery cell includes a first electrode 100, a second electrode 200, and a separator 300 disposed between the first electrode 100 and the second electrode 200; the first electrode 100, the separator 300, and the second electrode 200 are sequentially stacked and wound to form a core; the first electrode 100 and / or the second electrode 200 are electrode structures. The specific structure of this electrode structure is described in the above embodiments. Since this battery cell adopts all the technical solutions of all the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be elaborated further here. The positive electrode includes a positive current collector and a positive active material layer, the positive active material layer being coated on the surface of the positive current collector; the positive active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The negative electrode includes a negative current collector and a negative active material layer, the negative active material layer being coated on the surface of the negative current collector; the material of the negative current collector can be copper, and the negative active material layer includes a negative active material, which can be carbon or silicon, etc. The material of the separator 300 can be PP (polypropylene) or PE (polyethylene), etc.

[0045] Example 1

[0046] Positive electrode sheet: An expanded conductive component 3, consisting of a polyurethane thermoplastic elastomer as an expansion layer 31 and a carbon nanotube (CNT) as a conductive agent layer 32, is coated onto the aluminum current collector at the corner section to control the thickness of the expanded conductive component 3 to 1 μm; then, the active material LiCoO2 is fully dispersed and uniformly coated onto the aluminum current collector with the expanded conductive component 3, and then cold-pressed, slit, and die-cut to obtain the positive electrode sheet.

[0047] Negative electrode sheet: Negative electrode active material, conductive agent, and binder are mixed in a weight ratio of 97.6:1.1:1.3 to prepare a negative electrode active material slurry. This slurry is then coated, cold-pressed, slit, laser-etched, and die-cut to obtain the negative electrode sheet. The negative electrode sheet includes a negative electrode current collector. The negative electrode active material slurry is fully and uniformly dispersed and coated onto the negative electrode current collector, followed by cold pressing, slitting, and die-cutting to obtain the negative electrode sheet.

[0048] Separator: A ceramic mixture is coated on the PE surface to serve as a separator.

[0049] Electrolyte: Ethyl carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and propyl propionate (PP) are mixed in a volume ratio of 1:1:4:4. Then, fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent at a ratio of 1 mol / L to prepare the electrolyte.

[0050] Full cell preparation: The above-mentioned positive electrode, separator and negative electrode are stacked to make a bare cell, which is then packaged and injected with electrolyte to make a finished lithium-ion battery.

[0051] The lithium plating interface is obtained by disassembling the battery cell after 500 cycles.

[0052] Example 2

[0053] The difference between Example 2 and Example 1 is that the thickness of the expanded conductive component 3 is 2 μm.

[0054] Example 3

[0055] The difference between Example 3 and Example 1 is that the thickness of the expanded conductive component 3 is 3 μm.

[0056] Example 4

[0057] The difference between Example 4 and Example 1 is that the thickness of the expanded conductive component 3 is 4 μm.

[0058] Example 5

[0059] The difference between Example 5 and Example 1 is that the thickness of the expanded conductive component 3 is 5 μm.

[0060] Example 6

[0061] The difference between Example 6 and Example 1 is that the thickness of the expanded conductive component 3 is 6 μm.

[0062] Example 7

[0063] The difference between Example 7 and Example 1 is that the thickness of the expanded conductive component 3 is 7 μm.

[0064] Example 8

[0065] The difference between Example 8 and Example 1 is that the thickness of the expanded conductive component 3 is 7 μm.

[0066] Comparative Example 1

[0067] The difference between Comparative Example 1 and Example 1 is that the expansion conductive component 3 is not coated between the active material layer on the positive electrode and the current collector.

[0068] Comparative Example 2

[0069] The difference between Comparative Example 2 and Example 1 is that the thickness of the expanded conductive component 3 is 0.5 μm.

[0070] Comparative Example 3

[0071] The difference between Comparative Example 3 and Example 1 is that the thickness of the expanded conductive component 3 is 9 μm.

[0072] Comparative Example 4

[0073] The difference between Comparative Example 4 and Example 1 is that the thickness of the expanded conductive component 3 is 10 μm.

[0074] Table 1 Performance parameters for all embodiments and comparative examples

[0075]

[0076] From the table above, we can see that: 1. The positive electrode in the battery cell includes a positive current collector. At least one expanded conductive component 3, consisting of alumina as a polyurethane thermoplastic elastomer 31 and carbon nanotubes (CNTs) as a conductive agent layer 32, is added between the surface of the positive current collector and the negative electrode active material layer. Its thickness is in the range of 1µm to 8µm, which is equivalent to the thickness of the cathode active layer, effectively improving lithium plating during cycling. 2. An excessively thick expanded conductive component 3 can cause excessive deformation of the positive electrode active material, affecting structural stability and leading to lithium plating. An excessively thin or absent expanded conductive component 3 results in poor liquid retention at the corners. 3. Battery cells with excessively thin, absent, or excessively thick expanded conductive components 3 develop corner black spots and lithium plating after 300–400 cycles.

[0077] This utility model also proposes a battery, which includes a cell. The specific structure of the cell is as described in the above embodiments. Since this battery adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here.

[0078] A battery is a device that converts chemical energy into electrical energy. It contains an electrolyte solution and metal electrodes to generate an electric current. With technological advancements, the term "battery" now generally refers to any small device that generates electrical energy, such as a solar cell. The main performance parameters of a battery are electromotive force, capacity, specific energy, and resistance. The principle of a battery is that chemical energy is directly converted into electrical energy through spontaneous oxidation and reduction reactions within the battery. These reactions occur at the two electrodes. The negative electrode active material consists of a reducing agent with a negative potential and stable in the electrolyte, such as active metals like zinc, cadmium, and lead, and hydrogen or hydrocarbons. The positive electrode active material consists of an oxidizing agent with a positive potential and stable in the electrolyte, such as metal oxides like manganese dioxide, lead dioxide, and nickel oxide, oxygen or air, halogens and their salts, and oxyacids and their salts. The electrolyte is a material with good ionic conductivity, such as aqueous solutions of acids, bases, and salts, organic or inorganic non-aqueous solutions, molten salts, or solid electrolytes.

[0079] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is merely for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0080] Based on the disclosure and teachings of the above specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, this utility model is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on this utility model are within the protection scope of this utility model. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on this utility model.

Claims

1. A pole piece structure, characterized by: The electrode sheet structure comprises a current collector and an active material layer arranged on at least one surface of the current collector; and an expansion conductive component is arranged between the current collector and the active material layer. When the electrode sheet structure is wound into a core, the electrode sheet structure has at least one corner segment; and the expansion conductive component is arranged on the corner segment.

2. The pole piece structure of claim 1, wherein: The number of the expansion conductive components is at least two, and each is arranged on two opposite surfaces of the current collector. In the thickness direction of the electrode sheet structure, the projection of one expansion conductive component towards the current collector is arranged in a staggered manner with the projection of another expansion conductive component towards the current collector.

3. The pole piece structure of claim 1, wherein: The thickness h1 of the expansion conductive component satisfies: 1um≤h1≤8um.

4. The pole piece structure of claim 1, wherein: The expansion conductive component comprises an expansion layer and a conductive agent layer connected with each other; the expansion layer is connected to the current collector and / or the active material layer; and the conductive agent layer is connected to the current collector and / or the active material layer.

5. The pole piece structure of claim 4, wherein: The expansion layer is one of polyurethane thermoplastic elastomer, styrene thermoplastic elastomer, olefin thermoplastic elastomer, dynamic vulcanized thermoplastic elastomer, polyester thermoplastic elastomer, and polyamide thermoplastic elastomer. The conductive agent layer is one of carbon black, conductive graphite, carbon fiber, carbon nanotube, and graphene.

6. The pole structure of claim 4 or 5, wherein: The expansion layer and the conductive agent layer are arranged in a stacked manner, and the expansion layer is connected to the active material layer; and the conductive agent layer is connected to the current collector.

7. The pole structure of claim 4 or 5, wherein: The number of the conductive agent layers is two, and the expansion layer is arranged between the two conductive agent layers; one of the conductive agent layers is connected to the active material layer; and the other is connected to the current collector.

8. The pole structure of claim 1, wherein: When the electrode sheet structure is in contact with electrolyte, at least one protrusion is arranged on the active material layer; and the protrusion is arranged on the two side surfaces of the active material layer in a manner opposite to the expansion conductive component.

9. An electric cell characterized by: The battery cell comprises a first electrode sheet and a second electrode sheet and a separator arranged between the first electrode sheet and the second electrode sheet; and the first electrode sheet, the separator, and the second electrode sheet are sequentially stacked and wound to form a core; and the first electrode sheet and / or the second electrode sheet is the electrode sheet of any one of claims 1 to 8.

10. A battery, characterized by: The battery cell comprises the battery cell of claim 9.

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