A laminated structure, pole piece assembly and wound battery core

Abstract

A laminated structure, a pole piece assembly, and a wound battery cell, belonging to the field of wound batteries. The laminated structure includes: a combination layer and a second separator. The combination layer has at least one first separator and an even number of current collectors greater than 2 stacked in layers, with each first separator flanked by a current collector of opposite polarity; the even number of current collectors greater than 2 includes at least one composite current collector and one metal foil current collector of opposite polarity, and the number of composite current collectors is less than or equal to the number of metal foil current collectors, and the composite current collector includes a polymer substrate and a conductive layer bonded to the substrate; the second separator is optionally stacked on the top or bottom surface of the combination layer. The arrangement of the current collectors in the laminated structure facilitates the welding of the tabs, thereby eliminating the need for transfer welding processes or equipment.

Description

Technical Field

[0001] The present application relates to the field of wound batteries, and more specifically, to a laminated structure, a pole piece assembly, and a wound battery cell. Background Art

[0002] In traditional lithium-ion batteries, conventional cells use metal foil as the current collector, for example, copper foil for the negative electrode and aluminum foil for the positive electrode. These metal foil current collectors offer advantages such as good conductivity, softness, and good environmental stability (for example, an oxide film forms on the aluminum surface, preventing further reactions).

[0003] However, the traditional foil current collectors mentioned above also have some problems. Therefore, the industry has proposed a type of composite current collector. The use of composite current collectors can improve battery safety, reduce battery cost and weight, and increase energy density. However, composite current collectors have the problem of requiring copper or aluminum foil for transfer welding. Summary of the Invention

[0004] To address the problem of transfer welding required in battery cells using composite current collectors, the present application proposes a laminated structure, a pole piece assembly, and a wound battery cell.

[0005] This application is implemented as follows:

[0006] In a first aspect, examples of the present application provide a laminate structure for a wound battery cell. The laminate structure includes a separator and a current collector, and also includes a sandwich structure. The sandwich structure is composed of a composite current collector of a second polarity or a foil current collector of a second polarity sandwiched between a composite current collector and a foil current collector of a first polarity, where the first polarity and the second polarity are opposite.

[0007] In a second aspect, the examples of the present application provide a laminate structure for a wound battery cell. The laminate structure includes a combination layer and a second diaphragm optionally stacked on the top surface or bottom surface of the combination layer. The combination layer has at least one first diaphragm and an even number of current collectors stacked in layers. Moreover, each first diaphragm is flanked by a current collector of opposite polarity. Among these even-numbered current collectors, at least one composite current collector and one metal foil current collector of opposite polarity are included, and the number of composite current collectors is less than or equal to the number of metal foil current collectors. The composite current collector includes a polymer substrate and a conductive layer bonded to the substrate.

[0008] Since the composite current collector and the foil current collector are matched, the tabs of the composite current collector can be matched with the tabs of the foil current collector accordingly, thereby avoiding the operation of transfer welding.

[0009] In some examples of the present application, the combined layer has three first separators and four current collectors; wherein the four current collectors include a first metal foil current collector A1 and a second metal foil current collector C1 with opposite polarities, a first composite current collector A2 and a second composite current collector C2 with opposite polarities; the arrangement order of the four current collectors in the combined layer is: A2C2A1C1, or A1C2A2C1, or A2C1A1C2, or A1C1A2C2.

[0010] In some examples of the present application, the combined layer has five first separators and six current collectors; wherein, the six current collectors include a first composite current collector A2 and a second composite current collector C2 with opposite polarities, a first metal foil current collector A1 and a second metal foil C1 with opposite polarities, the number of first metal foil current collectors A1 is two, and the number of second metal foils C1 is two; the arrangement order of the six current collectors in the combined layer is: A2C2A1C1A1C1, or A1C2A2C1A1C1, or A2C1A1C2A1C1, or A1C1A2C2A1C1.

[0011] In some examples of the present application, among all current collectors of the combined layer, the negative electrode current collector covers the positive electrode current collector.

[0012] In a third aspect, the present application provides an example of a pole piece assembly, which includes an even number of current collectors greater than 2 as described above, and each of the current collectors is electrically connected to a pole ear one by one.

[0013] In some examples of the present application, the plurality of pole tabs are respectively located on the same side of the pole piece assembly.

[0014] In some examples of the present application, the plurality of tabs are located on two opposite sides of the pole piece assembly, and the polarities of the tabs on the same side are the same.

[0015] In some examples of the present application, the plurality of tabs are composed of a composite tab corresponding to the composite current collector and a foil tab corresponding to the metal foil current collector, and the composite tab is located between the two foil tabs.

[0016] In some examples of the present application, the plurality of tabs are composed of a composite tab corresponding to a composite current collector and a foil tab corresponding to a metal foil current collector, and one composite tab and one foil tab are matched.

[0017] In the fourth aspect, the example of the present application provides a wound battery cell, which is wound using the aforementioned pole piece assembly, and the winding method of the pole piece assembly is defined by the following method: the pole piece assembly is wound in a manner such that the second diaphragm of the laminated structure is located in the outermost layer, and the pole ears of the composite current collector with the same polarity are welded to the metal foil current collector.

[0018] In the above implementation process, the laminated structure provided by the embodiments of the present application simultaneously configures mutually matching composite current collectors and metal foil current collectors. Since the current collectors are connected to the tabs, the tabs can also form corresponding discharge structures corresponding to the arrangement of different types of current collectors in the above-mentioned laminated structure. On this basis, the composite tabs and metal foil are combined, and the metal foil tabs can provide electrical connections for the composite tabs, eliminating the need for separate lead welding for the composite substrate tabs, that is, no transfer welding is required. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 This is a schematic diagram of the structure of the smallest unit in a traditional wound battery cell;

[0021] Figure 2 Shown Figure 1 Schematic diagram of the smallest unit winding structure;

[0022] Figure 3 Schematic diagram of the structure of the composite current collector in the example of this application;

[0023] Figure 4 shows the current collector based on foil and Figure 3 Schematic diagrams of four structures of a composite current collector having a stacked structure of four current collectors;

[0024] Figure 5 Four other schematic structural diagrams of a stacked structure with four current collectors are shown;

[0025] Figure 6 shows the current collector based on foil and Figure 3 A schematic structural diagram of a composite current collector having a stacked structure of six current collectors;

[0026] Figure 7 shows the current collector based on foil and Figure 3 Another structural schematic diagram of a composite current collector having a stacked structure of six current collectors;

[0027] Figure 8 Based on Figure 4 Four structural schematic diagrams of pole piece assemblies made of a laminated structure;

[0028] Figure 9 To show Figure 8 The structural diagram represented by II-1 in the pole piece assembly;

[0029] Figure 10 Based on Figure 5 Schematic diagrams of four other structures of pole piece assemblies made of a laminated structure;

[0030] Figure 11 Based on Figure 6 Two structural schematic diagrams of pole piece assemblies made of a laminated structure;

[0031] Figure 12 Based on Figure 11 Schematic diagram of the winding methods of two pole piece assemblies;

[0032] Figure 13 Based on Figure 12 A schematic diagram of the structure of a wound battery cell formed by the winding method of the electrode assembly;

[0033] Figure 14 Based on Figure 8 and Figure 10 Schematic diagram of eight winding methods of pole piece assemblies;

[0034] Figure 15 Based on Figure 14 A schematic diagram of the structure of a wound battery cell formed by the winding method of the electrode assembly;

[0035] Figure 16 A schematic structural diagram of a square hard-shell battery cell implemented based on the laminated structure of the present application is shown.

[0036] Icon: 100-four-layer structure; 101-diaphragm; 102-positive electrode sheet; 103-diaphragm; 104-negative electrode sheet; 200-composite current collector; 201-polymer film; 202-aluminum layer; 301-aluminum foil tab; 302-composite positive electrode tab; 401-copper foil tab; 402-composite negative electrode tab. DETAILED DESCRIPTION

[0037] The smallest unit of a conventional wound cell is generally a four-layer structure 100, which includes a separator 101, a positive electrode sheet 102, a separator 103 and a negative electrode sheet 104, and the structure is as follows: Figure 1 The positive electrode sheet 102 is usually made of aluminum foil, and the negative electrode sheet 104 is usually made of copper foil.

[0038] When the four-layer structure 100 is wound, the separator 101 is the outermost layer and the negative electrode sheet 104 is the innermost layer. The winding is started from one end and the winding is continued for an appropriate number of turns. The winding method and structure are as follows: Figure 2 (It is rolled up once in the picture).

[0039] In some attempts, a composite current collector is selected. The smallest unit of such a wound cell may be, for example, the separator 101, the positive composite current collector, the separator 103, and the negative composite current collector.

[0040] See Figure 3 The composite current collector 200 generally includes an insulating polymer film 201 and a deposited metal film, such as an aluminum layer 202, attached to both surfaces of the polymer film 201. Therefore, the composite current collector 200 is a positive polarity composite current collector. Correspondingly, a negative polarity composite current collector can also be made of a Figure 3 The structure shown is different from Figure 3 The aluminum layer 202 in the composite current collector 200 is replaced by a copper layer.

[0041] However, in actual use, there are some problems that need to be solved, as described below.

[0042] In actual use, since ultrasound cannot penetrate the polymer layer and the metal conductive layer of the composite current collector at the same time, the composite current collector tab cannot be directly ultrasonically welded and needs to be transfer-welded with copper foil or aluminum foil.

[0043] In other words, while the use of composite current collectors can improve the performance of wound batteries to a certain extent, for example, the problems of current collectors made of foil materials (such as copper foil and aluminum foil) such as large thickness, high cost, and poor safety can be improved by using composite current collectors. Furthermore, the use of composite current collectors in batteries can also improve battery safety (for example, by passing abuse tests such as needle penetration), reduce costs, reduce battery weight, and thus increase energy density.

[0044] However, the use of composite current collectors also requires transfer welding equipment and the corresponding transfer welding process. In short, in cells with a traditional wound structure, the tabs of the composite current collector cannot be directly welded. Transfer welding requires additional equipment and a modified process, making it difficult to integrate with existing production lines.

[0045] Furthermore, cells with pure composite current collectors have poorer heat dissipation than traditional cells. This is because composite current collectors have a lower heat dissipation capacity than metal foil current collectors of the same thickness. Consequently, it is difficult to use composite current collectors for both positive and negative electrodes in a wound cell.

[0046] In view of this reality, the present application proposes a new wound cell structure. In such a structure, a positive polarity composite current collector and a negative polarity composite current collector can be used at the same time, and the operation of transfer welding can be avoided, thereby also avoiding the use of transfer welding equipment and processes. In addition, in this new wound cell structure, while using positive and negative composite current collectors at the same time, a foil current collector is also used, which can improve the heat dissipation effect to a certain extent. Therefore, such a wound cell takes into account the advantages of both heat dissipation and the use of composite current collectors.

[0047] In general, the laminated structure in the examples of the present application includes a separator and a current collector. The separator and the current collector are provided with different numbers of layers as needed. The positive electrode current collector and the negative electrode current collector are separated by a separator. Furthermore, the laminated structure also includes a sandwich structure. The sandwich structure is composed of a composite current collector of the second polarity or a foil current collector of the second polarity sandwiched between a composite current collector and a foil current collector of the same first polarity, and the first polarity and the second polarity are opposite. For example, a negative polarity copper foil current collector or a copper composite current collector is sandwiched between two positive polarity aluminum composite current collectors and aluminum foil current collectors. Alternatively, a positive polarity aluminum foil current collector or an aluminum composite current collector is sandwiched between two negative polarity copper composite current collectors and copper foil current collectors.

[0048] In other examples, the wound battery cell described above has a laminated structure as a basic unit. The laminated structure includes a composite layer and a second separator. The second separator can be laminated on the top surface of the composite layer or on the bottom surface of the composite layer.

[0049] As the name suggests, the second separator is the outermost layer of the wound battery cell. That is, the laminated structure is wound from the second separator to the combined layer.

[0050] The combined layer has a layered structure and is composed of different numbers of structural layers stacked together. The combined layer includes at least one first diaphragm and an even number of current collectors stacked in layers. And the stacking method is that each first diaphragm is provided with a current collector of opposite polarity on both sides. At the same time, among all the even number of current collectors, at least one composite current collector and one metal foil current collector of opposite polarity are included, and the number of composite current collectors is less than or equal to the number of metal foil current collectors, and the composite current collector includes a polymer substrate and a conductive layer bonded to the substrate. The number of even number of current collectors is 2n, and n is an integer greater than or equal to 2. That is, in the combined layer, the number of current collectors is four or more.

[0051] In the above description, the stacking layout of each film layer that can be used in the pole piece assembly is described through the laminated structure. In some examples, therefore, such a laminated structure is not an independent product or intermediate product. In the actual battery manufacturing process, the surface of the current collector in the laminated structure can be attached with a film layer composed of a corresponding layered electrode slurry (at least including an electrode active material), and then stacked in layers with the diaphragm in the manner described above to form a pole piece assembly.

[0052] Based on such a laminated structure, when configuring the tabs to form a pole piece assembly, the tabs of the composite current collector and the tabs of the foil current collector can be matched, thereby eliminating the need for additional transfer welding operations. The tabs of the composite current collector and the tabs of the foil current collector can be, for example:

[0053] A positive polarity composite current collector tab is matched with a positive polarity foil tab;

[0054] Alternatively, a negative composite current collector tab is combined with a negative foil tab;

[0055] Alternatively, two positive-polarity foil tabs sandwich a positive-polarity composite current collector tab;

[0056] Alternatively, two negative-polarity foil tabs sandwich one negative-polarity composite current collector tab.

[0057] In some other examples of the present application, as an eight-layer laminate structure, it has four separators (G) and four current collectors, which are a pair of positive and negative composite current collectors and a pair of positive and negative foil current collectors. For the convenience of description, the positive foil current collector is denoted as C1, the positive composite current collector is denoted as C2, the negative foil current collector is denoted as A1, and the negative composite current collector is denoted as A2. Therefore, the structure of the eight-layer laminate structure (such as Figure 4 As shown, the four structures are as follows:

[0058] (I) G0A2GC2GA1GC1; or (II) G0A1GC2GA2GC1;

[0059] or (III) G0A2GC1GA1GC2; or (IV) G0A1GC1GA2GC2.

[0060] exist Figure 4 In the figure, the dotted line represents the diaphragm, and the Figure 4 The diaphragm on the top layer (top surface) is the aforementioned second diaphragm G0. Corresponding to the aforementioned, the surface diaphragm can be located on the top surface and the bottom surface of the combined layer.

[0061] For example, Figure 4 In I, the three current collectors A2C2A1 form a sandwich structure. Figure 4 The I structure can contain two sandwich structures (the other is C1A1C2). Obviously, there is a separator between A2 and C2, and between C2 and A1. A2 and A1 have the same polarity, while C2 has the opposite polarity; polarity here refers to positive or negative polarity.

[0062] Figure 4 In some examples, the second diaphragm is located on the top surface of the combined layer. In other examples, the second diaphragm can also be located on the bottom surface of the combined layer, for example Figure 5 As shown. Figure 4 and Figure 5 It has a roughly symmetrical structure. Figure 5 In the structure shown, as another eight-layer laminate structure. It has four separators (G) and four current collectors, which are a pair of positive and negative composite current collectors and a pair of positive and negative foil current collectors. For the convenience of description, the positive foil current collector is denoted as C1, the positive composite current collector is denoted as C2, the negative foil current collector is denoted as A1, and the negative composite current collector is denoted as A2. Therefore, the structure of the eight-layer laminate structure (such as Figure 5 As shown, the four structures are as follows:

[0063] (V)GC1GA1GC2GA2; or (VI)GC1GA2GC2GA1;

[0064] or (VII) GC2GA1GC1GA2; or (VIII) GC2GA2GC1GA1.

[0065] In other examples, the combined layer in the stacked structure can further increase the number of current collectors as needed. For example, the combined layer has five first separators and six current collectors. The six current collectors include a first composite current collector A2 and a second composite current collector C2 of opposite polarity, and a first metal foil current collector A1 and a second metal foil C1 of opposite polarity. The number of first metal foil current collectors A1 is two, and the number of second metal foils C1 is two.

[0066] The arrangement order of the six current collectors and the second separator (G0) in the combined layer is: G0A2GC2GA1GC1GA1GC1, or G0A1GC2GA2GC1GA1GC1;

[0067] Or G0A2GC1GA1GC2GA1GC1, or G0A1GC1GA2GC2GA1GC1.

[0068] Alternatively, the order can be:

[0069] G0C1A1C1A1C2A2, or G0C1A1C1A2C2A1;

[0070] G0C1GA1GC2GA1GC1GA2;G0C1GA1GC2GA2GC1GA1.

[0071] The five first separators and six current collectors mentioned above can also be combined in other ways, which are not listed here one by one to avoid redundancy. Figure 6 The structural diagram of G0A1GC1GA2GC2GA1GC1 is given. Figure 6 In the orientation shown, the membrane on the top layer (top surface) is the aforementioned second membrane G0. Figure 7 The structural diagram of G0C1GA1GC2GA2GC1GA1 is given. Figure 7 In the orientation shown, the membrane on the top layer (top surface) is the aforementioned second membrane G0.

[0072] Based on the above-mentioned laminated structure and based on a specific application example, this application further proposes a pole piece assembly, which includes: a laminated structure and a plurality of pole tabs corresponding to and electrically connected to the current collectors therein. Specifically, the number of pole tabs is equal to the number of current collectors, with one pole tab corresponding to each current collector.

[0073] Generally, the wound cell or battery can be a columnar structure (e.g. cylindrical) or a square structure. In this application, the square hard shell cell JR (Jelly Roll) is mainly used as an example for explanation. Figure 16 Therefore, the tabs generally extend from the upper and lower sides or one side of the square hard shell. Correspondingly, in the pole piece assembly, all the tabs can be on the same side of the pole piece assembly. For example, all the tabs extend from the upper bottom side of the square hard shell, or all the tabs extend from the lower bottom side of the square hard shell. Alternatively, in some other examples, the tabs are located on opposite sides of the pole piece assembly, and the polarity of the tabs on the same side is the same.

[0074] It should be noted that when all the tabs extend from the same side, in order to avoid interference between the spatial positions of the positive and negative tabs, the positive and negative tabs are staggered / interlaced.

[0075] Figure 8 Shown, based on Figure 4 The arrangement of the tabs in the structure of the pole piece assembly made of the laminated structure shown in FIG. Figure 8 The structure is such that all the tabs extend from the same side of the electrode assembly, that is, the positive tab and the negative tab extend from the same side. Therefore, it can be understood that the positive tab and the negative tab are staggered as described above. Figure 8 The tab distribution in the pole piece assembly shown in II-1 can also be found in Figure 9(The separator is not shown), wherein the positive electrode tab includes an aluminum foil tab 301 and a composite positive electrode tab 302; the negative electrode tab includes a composite negative electrode tab 402 and a copper foil tab 401.

[0076] Figure 10 Shown, based on Figure 5 The arrangement of the tabs in the structure of the pole piece assembly made of the laminated structure shown in FIG. Figure 10 The structure is such that all the tabs extend from both sides of the pole piece assembly. Figure 10 The tab extending from the top is the positive electrode tab (including aluminum foil tabs and composite positive electrode tabs), and the tab extending from the bottom is the negative electrode tab (including copper foil tabs and composite negative electrode tabs). In these two-end tab solutions, the tabs can adopt a full-tab structure. Full tabs can significantly increase the current conduction area and greatly shorten the current conduction distance, thereby reducing the internal resistance of the wound battery, which in turn helps reduce heat generation, extend life, and increase peak charge and discharge power.

[0077] The wound cell can be manufactured by performing a winding operation based on the above-mentioned pole piece assembly. During the winding, the second separator of the laminated structure is located at the outermost layer.

[0078] The structures of the pole piece assemblies of some examples of the six current collectors are as follows: Figure 11 As shown, and the winding method refers to Figure 12 (The arrow in the figure indicates the winding direction), the structure after winding is as follows Figure 13 ( Figure 13 The portion in medium to light color that extends to the end of the current collector is the separator. The winding structure of the positive electrode in the inner layer is shown in (3); the winding structure of the negative electrode in the inner layer is shown in (4).

[0079] For the winding method of the four current collector electrode assemblies, please refer to Figure 14 (The arrow in the figure indicates the winding direction), the structure after winding is as follows Figure 15 ( Figure 15 The light-colored portion extending to the end of the current collector is the separator. The winding structure of the positive electrode in the inner layer is shown in (2); the winding structure of the negative electrode in the inner layer is shown in (1).

[0080] In the aforementioned coiled structure, since the innermost current collector has no current collector of opposite polarity facing it, it is coated with active material on a single side. The innermost negative electrode current collector has active material coated on only one side along a portion of its length at the start of the coil. Similarly, since the outermost current collector has no current collector of opposite polarity facing it, it is also coated with active material on a single side. The innermost negative electrode current collector has active material coated on only one side along a portion of its length at the start of the coil.

[0081] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A pole piece assembly, characterized in that: include: A laminated structure, the laminated structure being used for winding a battery core, the laminated structure comprising: A composite layer comprising at least one first separator and an even number greater than 2 current collectors stacked in layers, wherein each first separator is flanked by a current collector of opposite polarity; the even number greater than 2 current collectors include at least one composite current collector and one metal foil current collector of opposite polarity, and the number of composite current collectors is less than or equal to the number of metal foil current collectors, and the composite current collector includes a polymer substrate and a conductive layer bonded to the substrate; a second diaphragm, optionally laminated to the top or bottom surface of the combined layer; The combined layer has three first separators and four current collectors, wherein the four current collectors include a first metal foil current collector A1 and a second metal foil current collector C1 with opposite polarities, a first composite current collector A2 and a second composite current collector C2 with opposite polarities, and the arrangement order of the four current collectors in the combined layer is: A2C2A1C1, or A1C2A2C1, or A2C1A1C2, or A1C1A2C2; or, The combined layer has five first separators and six current collectors. The six current collectors include a first composite current collector A2 and a second composite current collector C2 with opposite polarities, a first metal foil current collector A1 and a second metal foil C1 with opposite polarities, two first metal foil current collectors A1, and two second metal foils C1. The arrangement order of the six current collectors in the combined layer is: A2C2A1C1A1C1, or A1C2A2C1A1C1, or A2C1A1C2A1C1, or A1C1A2C2A1C1; Wherein, each of the even number of current collectors greater than 2 is electrically connected to a tab in a one-to-one correspondence, and two foil tabs of the same polarity clamp a composite current collector tab of the same polarity.

2. The pole piece assembly according to claim 1, characterized in that: Among all the current collectors in the combined layer, the negative electrode current collector covers the positive electrode current collector.

3. The pole piece assembly according to claim 1, characterized in that: The pole tabs are respectively located on the same side of the pole piece assembly.

4. The pole piece assembly according to claim 3, characterized in that: When the electrode tabs are respectively located on the same side of the electrode assembly, the positive electrode tabs and the negative electrode tabs are arranged alternately.

5. The pole piece assembly according to claim 1, characterized in that: The pole tabs are located on two opposite sides of the pole piece assembly, and the pole tabs on the same side have the same polarity.

6. The pole piece assembly according to any one of claims 1 to 5, characterized in that: The tab is composed of a composite tab corresponding to the composite current collector and a foil tab corresponding to the metal foil current collector, and the composite tab is located between the two foil tabs; Alternatively, the tab is composed of a composite tab corresponding to the composite current collector and a foil tab corresponding to the metal foil current collector, and one composite tab and one foil tab are matched.

7. A wound battery cell, characterized in that: The pole piece assembly as described in any one of claims 1 to 6 is wound, and the winding method of the pole piece assembly is defined by the following method: the pole piece assembly is wound in such a way that the second diaphragm of the laminated structure is located in the outermost layer, and the pole tabs of the composite current collector of the same polarity are welded to the pole tabs of the metal foil current collector.

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