Pole piece and battery cell

Abstract

The utility model provides a pole piece and a battery cell, and relates to the technical field of batteries. Comprising a current collector, a carbon-coated layer and an active substance layer, the carbon-coated layer is arranged on the surface of the current collector, the active substance layer is arranged on the side, away from the current collector, of the carbon-coated layer, and a groove part is formed in the side, facing the active substance layer, of the carbon-coated layer. In the application, the groove part is arranged on one side, facing the active material layer, of the carbon coating layer, so that the problem that the electrolyte infiltrates the pole piece poorly in the use process of the battery can be improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a pole piece and a battery cell. Background Art

[0002] With the rapid development of the information age, the rapid development of lithium batteries has also come along. In recent years, people have put forward higher requirements for the performance of electronic products, so high-performance lithium-ion secondary batteries with large capacity, high energy density, and fast charging and discharging have attracted widespread attention.

[0003] In the related art, the pole piece includes a current collector and an active material layer arranged in the thickness direction of the current collector. Usually, a carbon coating layer is arranged between the active material layer and the current collector to reduce the contact impedance between the active material layer and the current collector, thereby achieving the purpose of reducing the DCR (direct current resistance) of the battery cell, and further achieving the effect of reducing the heat generation inside the battery cell. In this way, the rate performance of the battery cell can be improved.

[0004] During the use of the battery, the current collector will expand, causing the active material layers of the positive and negative electrodes to approach and squeeze each other, which in turn reduces the electrolyte storage space between the positive and negative electrodes. When the active material layers of the positive and negative electrodes squeeze each other, the electrode liquid in the active material layer is squeezed out. As a result, the positive and negative electrodes are not sufficiently wetted, which is not conducive to the normal operation of the battery. Utility Model Content

[0005] In view of this, the present application provides a pole piece and a battery cell to improve the problem of poor electrolyte wetting of the pole piece during battery use.

[0006] The technical solution adopted by this application to solve the above technical problems is:

[0007] In a first aspect, an embodiment of the present application provides a pole piece, comprising a current collector, a carbon coating layer and an active material layer, wherein the carbon coating layer is arranged on the surface of the current collector, the active material layer is arranged on the side of the carbon coating layer away from the current collector, and a groove portion is provided on the side of the carbon coating layer facing the active material layer.

[0008] In some embodiments of the present application, along the thickness direction of the pole piece, the groove portion penetrates through both sides of the carbon coating layer.

[0009] In some embodiments of the present application, the extension direction of the groove portion is parallel to the length direction of the pole piece.

[0010] In some embodiments of the present application, the extension direction of the groove portion is parallel to the width direction of the pole piece.

[0011] In some embodiments of the present application, the groove portion includes a plurality of first grooves and a plurality of second grooves, the plurality of first grooves are arranged in sequence along the length direction of the pole piece, the plurality of second grooves are arranged in sequence along the width direction of the pole piece, and the plurality of first grooves and the plurality of second grooves are arranged alternately.

[0012] In some embodiments of the present application, both ends of the groove portion along its extension direction are connected to the external space, or both ends of the groove portion are closed.

[0013] In some embodiments of the present application, the width of the groove portion is W, satisfying: 0.1mm≤W≤10mm.

[0014] In some embodiments of the present application, the thickness of the carbon coating layer is d, satisfying: 1 μm≤d≤2 μm.

[0015] In some embodiments of the present application, the distance between adjacent groove portions is c, satisfying: 0<c≤5mm.

[0016] In some embodiments of the present application, the carbon-coated layer includes a first carbon-coated layer and a second carbon-coated layer, and the first carbon-coated layer and the second carbon-coated layer are respectively located on both sides of the current collector, and the active material layer includes a first active material layer and a second active material layer, and the first active material layer and the second active material layer are respectively located on the side of the first carbon-coated layer or the second carbon-coated layer away from the current collector.

[0017] In a second aspect, an embodiment of the present application further provides a battery cell, which includes a pole piece as described in any one of the above items.

[0018] In summary, due to the adoption of the above technical solution, this application has at least the following beneficial effects:

[0019] A pole piece and a battery cell provided in the present application are provided with a groove portion for storing electrolyte on the side of the carbon coating layer facing the active material layer. Thus, when the current collector expands and the active material layers of the positive and negative pole pieces are squeezed against each other, the active material layer can absorb the electrolyte from the groove portion to replenish the needs of the active material layer, thereby improving the wetting effect of the pole piece in the expanded state, which is beneficial to improving the reliability of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings of the embodiments are briefly introduced below. Obviously, the drawings described below only relate to some embodiments of the present application, but are not intended to limit the present application, wherein:

[0021] Figure 1 A schematic diagram of the structure of a pole piece provided in an embodiment of the present application;

[0022] Figure 2 A cross-sectional schematic diagram of a pole piece provided in an embodiment of the present application;

[0023] Figure 3 The embodiments of the present application provide Figure 2 Schematic diagram of electrolyte flow in the middle electrode;

[0024] Figure 4 Another cross-sectional schematic diagram of a pole piece provided in an embodiment of the present application;

[0025] Figure 5 The embodiments of the present application provide Figure 4 Schematic diagram of the electrolyte flow in the middle electrode.

[0026] The accompanying drawings are as follows:

[0027] 1. Current collector; 2. Carbon coating layer; 21. First carbon coating layer; 22. Second carbon coating layer; 3. Active material layer; 31. First active material layer; 32. Second active material layer; 4. Groove portion. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0029] In the description of this application, it should be understood that the words "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0030] In this application, the word "exemplary" is used to mean "used as an example, illustration, or description". Any embodiment described in this application as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. The following description is given to enable any technician in the field to implement and use the present application. In the following description, details are listed for the purpose of explanation. It should be understood that a person of ordinary skill in the art can recognize that the present application can be implemented without using these specific details. In other instances, known structures and processes are not elaborated in detail to avoid obscuring the description of the present application with unnecessary details. Therefore, the present application is not intended to be limited to the embodiments shown, but is consistent with the widest scope consistent with the principles disclosed in this application.

[0031] Before introducing the embodiments of the present application, the related technology of the present application is first introduced. In the related technology, taking lithium battery as an example, it is usually composed of the following structure:

[0032] (1) Positive electrode: including active material layer and current collector. The active material layer is generally lithium manganese oxide, lithium cobalt oxide, or nickel cobalt lithium manganese oxide. The current collector is usually electrolytic aluminum foil with a thickness of 10-20 μm.

[0033] (2) Diaphragm, a polymer film with a microporous structure that allows lithium ions to pass freely but prevents electrons from passing through;

[0034] (3) Negative electrode: including an active material layer and a current collector. The active material layer is graphite or carbon with a structure similar to graphite. The current collector is an electrolytic copper foil with a thickness of 7-15 μm.

[0035] (4) an electrolyte, usually a carbonate solvent in which lithium hexafluorophosphate is dissolved;

[0036] (5) Battery cell casing: includes a shell and a top cover. The shell can be made of steel, aluminum, nickel-plated iron, aluminum-plastic film, etc. The positive and negative terminals of the battery cell are arranged on the top cover.

[0037] When the battery is charged, lithium ions are generated on the positive electrode of the battery, and the generated lithium ions move to the negative electrode through the electrolyte. The carbon used as the negative electrode has a layered structure and has many micropores. The lithium ions that reach the negative electrode are embedded in the micropores of the carbon layer. The more lithium ions are embedded, the higher the charging capacity. Similarly, when the battery is discharged (that is, the process of using the battery), the lithium ions embedded in the carbon layer of the negative electrode escape and move back to the positive electrode. The more lithium ions that return to the positive electrode, the higher the discharge capacity. When the battery is charged, the current collector expands. When the charging state changes to the non-charging state, the current collector shrinks.

[0038] Based on this, an embodiment of the present application provides a pole piece and a battery cell, and the pole piece is described in detail below.

[0039] See also Figure 1 and Figure 2 As shown, Figure 1 A schematic diagram of the structure of a pole piece provided in an embodiment of the present application, Figure 2 A cross-sectional schematic diagram of a pole piece provided in an embodiment of the present application, the pole piece comprises a current collector 1, a carbon coating layer 2 and an active material layer 3. The carbon coating layer 2 is arranged on the surface of the current collector 1, the active material layer 3 is arranged on the side of the carbon coating layer 2 facing away from the current collector 1, and a groove portion 4 is provided on the side of the carbon coating layer 2 facing the active material layer 3.

[0040] It can be understood that the current collector 1 can be copper foil, aluminum foil, or foil of other materials, and the thickness of the current collector 1 can be adjusted according to actual conditions.

[0041] It can be understood that the raw material of the carbon coating layer 2 may include a mixture of graphite, carbon black, a conductive agent and a binder.

[0042] It can be understood that the active material layer 3 can be lithium manganese oxide, lithium cobalt oxide, or nickel cobalt lithium manganese oxide material.

[0043] It can be understood that the position of the groove portion 4 on the current collector 1 is not fixed, and can be evenly distributed on the entire current collector 1, or evenly distributed on a part of the surface of the current collector 1, for example, the groove portion 4 is only provided at the portion where the carbon coating layer 2 is immersed in the electrolyte; it can be understood that the shape of the cross-section of the groove portion 4 is not fixed, including but not limited to rectangular, trapezoidal, conical or arc-shaped, etc.

[0044] See also Figure 3 As shown, Figure 3 The embodiments of the present application provide Figure 2 Schematic diagram of electrolyte flow in the middle electrode. It can be understood that after the battery cell is assembled, the electrode is wetted and electrolyte is stored in the groove portion 4. Specifically, when the groove portion 4 has a groove port connected to the outside, the electrolyte directly enters the groove portion 4 through the groove port; when the groove port of the groove portion 4 is a closed structure, the electrolyte enters the groove portion 4 through the active material layer 3.

[0045] During the use of the battery, when the current collector 1 expands, the active material layers 3 of the positive and negative electrode sheets approach and squeeze each other, resulting in a reduction in the electrolyte storage space between the positive and negative electrode sheets, and the electrolyte in the active material layer 3 is squeezed out. At this time, as the electrolyte in the active material layer 3 is squeezed out, the active material layer 3 absorbs the electrolyte in the groove portion 4 to replenish the electrolyte required by the active material layer 3, thereby improving the wetting effect of the electrode sheet in the expanded state, and further helping to improve the reliability of the battery.

[0046] When the current collector shrinks and returns to its original state, the electrolyte directly enters the groove portion 4 or enters the groove portion 4 through the active material layer 3 to fill the groove portion 4 to prepare for the next expansion of the current collector 1 .

[0047] In addition, the end of the groove portion 4 may be connected to the outside world or not. When the groove end of the groove portion 4 is connected to the outside world, during the initial electrode infiltration or after the battery is discharged, the electrolyte can directly enter the groove portion 4 through the groove end of the groove portion 4 to prepare for the electrolyte replenishment of the electrode that expands next time.

[0048] The beneficial effects of the embodiments of the present application are as follows: by providing a groove portion 4 for storing electrolyte on the side of the carbon-coated layer 2 facing the active material layer 3, when the current collector 1 expands and causes the active material layers 3 of the positive and negative electrode sheets to squeeze each other, the active material layer 3 can absorb the electrolyte from the groove portion 4 to replenish the needs of the active material layer 3, thereby improving the wetting effect of the electrode sheet in the expanded state, which is beneficial to improving the reliability of the battery.

[0049] In some embodiments of the present application, both ends of the groove portion 4 along its extension direction are connected to the external space.

[0050] It can be understood that the two ends of the groove portion 4 are connected to the external space, so that the electrolyte can directly enter the groove portion 4 from the two ends of the groove portion 4, so that the electrode liquid can infiltrate the active material layer 3 through the groove portion 4 to meet the rapid charging and discharging requirements of the battery. Especially during the initial infiltration, the contact area between the active material layer and the electrolyte can be increased, thereby accelerating the infiltration efficiency of the electrode sheet.

[0051] In some embodiments of the present application, both ends of the groove portion 4 along its extension direction are closed.

[0052] It can be understood that the ends of the groove portion 4 are closed, so that when the positive electrode and the negative electrode are close to each other due to being in an expanded state, the electrolyte can only pass through the active material layer 3 and then enter the groove portion 4. At this time, the groove portion 4 only discharges the electrolyte through the active material layer 3, so that the electrolyte discharge speed in the groove portion 4 is low, so that the electrolyte in the groove portion 4 can continuously replenish the active material layer 3, thereby improving the reliability of the electrode piece.

[0053] In some embodiments of the present application, the extension direction of the groove portion 4 is parallel to the length direction of the pole piece.

[0054] It can be understood that when the groove portion 4 has a groove port connected to the outside, compared with the groove portion 4 extending in a direction perpendicular to the length direction of the pole piece, when the groove portion 4 extends in a direction parallel to the length direction of the pole piece, its length dimension is larger, and the path of the electrolyte in the groove portion 4 when discharged from the port of the groove portion 4 is longer, so that the flow resistance of the electrolyte in the groove portion 4 discharged from the groove port of the groove portion 4 can be larger, so as to reduce the speed of the electrode liquid in the groove portion 4 being discharged from the port of the groove portion 4, and further, the groove portion 4 can continuously replenish the electrolyte to the active material layer 3. In this way, the wetting effect of the active material layer 3 can be improved.

[0055] In some embodiments of the present application, the extension direction of the groove portion 4 is perpendicular to the length direction of the pole piece.

[0056] It can be understood that the extension direction of the groove portion 4 can also be perpendicular to the length direction of the pole piece, so that when the pole piece is used for a winding core, on the one hand, the resistance of winding the pole piece can be reduced, which is conducive to the smooth winding of the pole piece and improves the efficiency of winding core manufacturing; on the other hand, the stress state of the pole piece in the winding state can be improved, thereby improving the reliability of the pole piece.

[0057] In some embodiments of the present application, the groove portion includes multiple first grooves and multiple second grooves, the multiple first grooves are arranged in sequence along the length direction of the pole piece, the multiple second grooves are arranged in sequence along the width direction of the pole piece, and the multiple first grooves and the multiple second grooves are arranged alternately.

[0058] It can be understood that the groove portion 4 includes a plurality of mutually staggered first grooves and second grooves along the outer surface parallel to the active material layer 3, which can make the groove portion 4 have a larger storage space for the electrolyte, a larger wetting area for the bottom of the electrode, and a faster chemical reaction on the electrode.

[0059] It can be understood that the width of the groove portion 4 includes but is not limited to 0.1mm, 0.3mm, 0.5mm, 0.7mm, and 0.9mm. The width of the groove portion 4 must be at least less than a certain threshold to meet the condition that a single active substance cannot enter the groove portion 4. The depth and length of the groove portion 4 can be adjusted according to the actual width of the groove portion 4.

[0060] In this embodiment, by limiting the width of the groove portion 4, on the one hand, it can be avoided that the width is too small, resulting in the groove portion 4 being collapsed during rolling and being unfavorable for the electrolyte to enter the groove portion 4; on the other hand, it can be avoided that the width is too large, resulting in the contact impedance between the current collector 1 and the active material layer 3 not meeting the requirements.

[0061] In some embodiments of the present application, the minimum distance between adjacent groove portions 4 is c, satisfying: 0<c≤5mm.

[0062] It can be understood that the distance c includes but is not limited to 0.1mm, 0.2mm, 0.3mm, 0.4mm, and 0.5mm.

[0063] In this embodiment, by limiting the minimum distance between adjacent groove portions 4, the problem of insufficient electrolyte infiltration effect in the electrode caused by excessive distance between adjacent groove portions 4 can be avoided, so that the carbon coating layer 2 can have enough groove portions 4 to make the contact area between the active material layer 3 and the electrolyte larger, thereby improving the electrolyte infiltration effect. At the same time, when there are more groove portions 4, the contact area between the electrode and the electrolyte can be increased, so that the electrode can quickly dissipate heat through the electrolyte. Since the more groove portions 4, the better, and the carbon coating layer 2 has good rolling resistance, the distance c can be small enough.

[0064] In some embodiments of this application, see Figure 3As shown, the thickness of the carbon coating layer 2 is d, which satisfies: 1 μm≤d≤2 μm.

[0065] It can be understood that the thickness d includes but is not limited to 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, and 2 μm.

[0066] In this embodiment, by limiting the thickness of the carbon coating layer 2, on the one hand, it can be avoided that the contact impedance between the current collector 1 and the active material layer 3 does not meet the requirements due to the thickness being too small, and on the other hand, it can be avoided that the thickness of the electrode is too large and the energy density is reduced.

[0067] In some embodiments of this application, see Figure 3 As shown, the width of the groove portion 4 is W, which satisfies: 0.1 mm ≤ W ≤ 10 mm.

[0068] In some embodiments of this application, see Figure 4 As shown, Figure 4 Another cross-sectional schematic diagram of a pole piece provided in an embodiment of the present application, Figure 5 The embodiments of the present application provide Figure 4 Schematic diagram of electrolyte flow in the middle electrode, the carbon-coated layer 2 includes a first carbon-coated layer 21 and a second carbon-coated layer 22, the first carbon-coated layer 21 and the second carbon-coated layer 22 are respectively located on both sides of the current collector 1, the active material layer 3 includes a first active material layer 31 and a second active material layer 32, the first active material layer 31 and the second active material layer 32 are respectively located on the side of the first carbon-coated layer 21 or the second carbon-coated layer 22 away from the current collector 1.

[0069] It can be understood that the first carbon coating layer 21 and the second carbon coating layer 22 are respectively arranged on both sides of the current collector 1, and then the first active material layer 31 and the second active material layer 32 are arranged on the outer sides of the first carbon coating layer 21 and the second carbon coating layer 22, so that when the electrode itself expands, the two sides of the current collector 1 can have a better ability of electrolyte to infiltrate the active material layer 3 compared with the method of only arranging the carbon coating layer 2 and the active material layer 3 on one side of the current collector 1.

[0070] In some embodiments of the present application, the groove portion 4 is formed by intermittently coating the carbon coating layer 2 on the current collector 1, or,

[0071] The groove portion 4 is formed by laser burning the carbon coating layer 2 on the side surface of the current collector 1 .

[0072] It can be understood that the method of realizing the groove portion 4 is not fixed, and the groove portion 4 can be formed by, but is not limited to, intermittent coating or laser burning. Compared with the method of forming the groove portion 4 by roller pressing, the above two methods are not easy to crush the pore structure inside the carbon coating layer 2 to collapse and close the pores, thereby making the chemical reaction on the electrode more sufficient and rapid.

[0073] Based on the same inventive concept, an embodiment of the present application provides a battery cell, comprising a pole piece as described in any one of the above items.

[0074] It can be understood that since the battery cell in the embodiment of the present application has the effect of improving the problem of poor electrolyte infiltration of the electrode during battery use, the electrode of the battery cell provided in the embodiment of the present application also has this effect, which will not be repeated here.

[0075] The basic concepts have been described above. Obviously, for those skilled in the art, the above detailed disclosure is only for example and does not constitute a limitation of the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements and amendments to the present application. Such modifications, improvements and amendments are suggested in the present application, so such modifications, improvements and amendments still belong to the spirit and scope of the exemplary embodiments of the present application.

[0076] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0077] Similarly, it should be noted that in order to simplify the description of the disclosure of this application and thus help understand one or more application embodiments, in the above description of the embodiments of this application, multiple features are sometimes merged into one embodiment, figure or description thereof. However, this disclosure method does not mean that the features required by the object of this application are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

[0078] Each patent, patent application, patent application publication, and other materials, such as articles, books, specifications, publications, documents, etc., cited in this application is hereby incorporated by reference in its entirety, except for application history documents that are inconsistent with or conflicting with the content of this application, and documents that limit the broadest scope of the claims of this application (currently or later attached to this application). It should be noted that if the descriptions, definitions, and / or use of terms in the attached materials of this application are inconsistent or conflicting with the content of this application, the descriptions, definitions, and / or use of terms in this application shall prevail.

Claims

1. A pole piece, characterized in that: The invention comprises a current collector (1), a carbon coating layer (2) and an active material layer (3), wherein the carbon coating layer (2) is arranged on the surface of the current collector (1), the active material layer (3) is arranged on the side of the carbon coating layer (2) facing away from the current collector (1), and a groove portion (4) is provided on the side of the carbon coating layer (2) facing the active material layer (3).

2. The pole piece according to claim 1, characterized in that: The extending direction of the groove portion (4) is parallel to the length direction of the pole piece.

3. The pole piece according to claim 1, characterized in that: The extending direction of the groove portion (4) is parallel to the width direction of the pole piece.

4. The pole piece according to claim 1, characterized in that: The groove portion (4) comprises a plurality of first grooves and a plurality of second grooves, wherein the plurality of first grooves are sequentially arranged along the length direction of the pole piece, and the plurality of second grooves are sequentially arranged along the width direction of the pole piece, and the plurality of first grooves and the plurality of second grooves are staggered.

5. The pole piece according to any one of claims 1 to 4, characterized in that: Both ends of the groove portion (4) along its extension direction are connected to the external space, or both ends of the groove portion (4) are closed.

6. The pole piece according to any one of claims 1 to 5, characterized in that: The width of the groove portion (4) is W, which satisfies: 0.1 mm ≤ W ≤ 10 mm.

7. The pole piece according to any one of claims 1 to 5, characterized in that: The thickness of the carbon coating layer (2) is d, which satisfies: 1 μm≤d≤2 μm.

8. The pole piece according to any one of claims 1 to 5, characterized in that: The minimum distance between adjacent groove portions (4) is c, satisfying: 0<c≤5mm.

9. The pole piece according to any one of claims 1 to 5, characterized in that: The carbon-coated layer (2) comprises a first carbon-coated layer (21) and a second carbon-coated layer (22), the first carbon-coated layer (21) and the second carbon-coated layer (22) being located on both sides of the current collector (1), respectively; the active material layer (3) comprises a first active material layer (31) and a second active material layer (32), the first active material layer (31) and the second active material layer (32) being located on a side of the first carbon-coated layer (21) and the second carbon-coated layer (22) facing away from the current collector (1), respectively.

10. A battery cell, characterized in that: Comprising a pole piece as described in any one of claims 1 to 9.

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