Electrode assembly, battery cell and battery

Abstract

The utility model discloses an electrode assembly, a battery cell and a battery, the electrode assembly comprises a positive plate and a negative plate, and the positive plate and the negative plate are laminated; the positive plate comprises a first current collector, a positive active material layer and a liquid retaining coating, the positive active material layer is arranged on the surface of the first current collector and comprises a main body part and a thinned part, the thinned part is arranged at at least one end of the main body part in the length direction of the electrode assembly, and the thickness of the main body part is greater than that of the thinned part; the liquid retaining coating is arranged on one surface, deviating from the first current collector, of the thinned part; at least one end of the negative plate in the length direction of the electrode plate assembly forms an edge area, and the edge area, the thinned part and the liquid retaining coating are correspondingly arranged in the thickness direction of the electrode assembly. According to the electrode assembly disclosed by the utility model, the thinned part corresponding to the edge area of the negative plate and the liquid retaining coating are arranged on the positive plate, so that the condition of lithium precipitation in the edge area of the negative plate can be improved.

Description

Technical Field

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

[0002] Currently, with the increasing prevalence of electronic products, lithium-ion batteries have become the preferred energy source for most electronic products due to their high energy density, long cycle life, and environmental friendliness. As people use electronic products more frequently and for longer periods, the requirements for battery cycle life are also increasing.

[0003] The inventors discovered during the disassembly of the cycled battery that lithium plating was more severe in the edge region of the negative electrode than in the middle region. Furthermore, the lithium plating in the edge region of the negative electrode became more severe as the charging rate increased, which could lead to battery failure in the later stages of cycling. Utility Model Content

[0004] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes an electrode assembly, a battery cell, and a battery that can improve the situation of lithium plating in the edge region of the negative electrode.

[0005] According to a first aspect of the present invention, the electrode assembly includes a positive electrode sheet and a negative electrode sheet, which are stacked together.

[0006] The positive electrode includes a first current collector, a positive active material layer, and a liquid-retaining coating. The positive active material layer is disposed on the surface of the first current collector. The positive active material layer includes a main body and a thinned portion. The thinned portion is disposed at at least one end of the main body along the length direction of the electrode assembly. The thickness of the main body is greater than the thickness of the thinned portion. The liquid-retaining coating is disposed on the side of the thinned portion away from the first current collector.

[0007] The negative electrode sheet forms an edge region at at least one end along the length direction of the electrode assembly, and the edge region, the thinned portion, and the liquid-retaining coating are correspondingly arranged along the thickness direction of the electrode assembly.

[0008] The electrode assembly according to the embodiments of the present invention has at least the following beneficial effects:

[0009] By providing a thinned portion with a small thickness at at least one end of the main body along the length direction X of the electrode assembly, the areal density of the active material layer of the positive electrode at the location of the thinned portion is reduced, and the N / P value of the positive and negative electrodes is increased. This results in more lithium intercalation sites in the edge region of the negative electrode corresponding to the thinned portion, thereby improving the charging window and mitigating lithium deposition in the edge region of the negative electrode. Furthermore, considering that the current density of the positive and negative electrodes is high and the electrolyte consumption rate is fast in the corresponding edge regions, which can easily lead to insufficient electrolyte and lithium deposition in the edge region of the negative electrode, this embodiment of the invention provides a liquid-retaining coating on the side of the thinned portion away from the first current collector. The liquid-retaining coating can absorb and accumulate electrolyte in the positive electrode at the location corresponding to the edge region, preventing lithium deposition in the edge region of the negative electrode due to insufficient electrolyte in the later stages of cycling, thus preventing cycle failure.

[0010] According to some embodiments of the present invention, the liquid-retaining coating covers the thinned portion along the width direction of the electrode assembly.

[0011] According to some embodiments of this utility model, the width of the first current collector is The width of the thinned part is The width of the liquid-retaining coating is , = = .

[0012] According to an embodiment of the present invention, the electrode assembly has a main body thickness of [missing information]. The thickness of the liquid-retaining coating is 0.25* ≤ ≤0.5* .

[0013] According to some embodiments of this utility model, the size of the liquid-retaining coating along the length of the electrode assembly is L, where 2mm≤L≤6mm.

[0014] According to some embodiments of the present invention, the side of the liquid-retaining coating that is away from the first current collector is flush with the side of the main body that is away from the first current collector.

[0015] According to some embodiments of the present invention, the main body is connected to two ends of the electrode assembly along the length direction, and each thinned part is connected to a liquid-retaining coating on the side of the thinned part facing away from the first current collector.

[0016] The negative electrode sheet forms two edge regions at both ends along the length of the electrode assembly. One edge region corresponds to the thinned portion and liquid-retaining coating at one end of the main body along the length of the electrode assembly, and the other edge region corresponds to the thinned portion and liquid-retaining coating at the other end of the main body along the length of the electrode assembly.

[0017] According to some embodiments of the present invention, both opposite surfaces of the first current collector are provided with a positive electrode active material layer and a liquid-retaining coating.

[0018] According to a second aspect embodiment of the present invention, the battery cell includes a separator and an electrode assembly as described above, wherein the separator is disposed between the positive electrode and the negative electrode.

[0019] The battery cell of this utility model embodiment has the beneficial effects of the electrode assembly, which will not be described in detail here.

[0020] According to a third aspect embodiment of the present invention, the battery includes a casing and a battery cell as described above, the battery cell being disposed inside the casing.

[0021] The battery of this utility model embodiment has the beneficial effects of a battery cell, which will not be elaborated here.

[0022] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0024] Figure 1 This is a schematic diagram of the structure of an electrode assembly provided in one embodiment of the present invention;

[0025] Figure 2 for Figure 1 The diagram shows the structure of the positive electrode.

[0026] Figure 3 for Figure 1 The diagram shows another angle of the positive electrode structure.

[0027] Figure label:

[0028] Electrode assembly 100;

[0029] Positive electrode 10; First current collector 11; Positive electrode active material layer 12; Main body 121; Thinned portion 122; Liquid-retaining coating 13;

[0030] Negative electrode 20; Edge region 201; Second current collector 21; Negative electrode active material layer 22;

[0031] Length direction X; width direction Y; thickness direction Z. Detailed Implementation

[0032] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0033] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0034] In the description of this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0035] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0036] In the description of this utility model, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0037] In related technologies, since the surface density of the active material layer in the edge region of the positive electrode is roughly the same as that in the middle region of the positive electrode, and the current density and electrolyte consumption rate are relatively high in the corresponding edge regions of the positive and negative electrodes, lithium plating is prone to occur in the edge region of the negative electrode due to insufficient electrolyte. The lithium plating in the edge region of the negative electrode is more serious than that in the middle region of the negative electrode, and the lithium plating in the edge region of the negative electrode becomes more serious as the charging rate increases. This can lead to battery failure in the later stages of cycling.

[0038] In view of this, this utility model embodiment provides an electrode assembly 100 to improve the situation of lithium plating in the edge region of the negative electrode.

[0039] Please see Figures 1 to 3 The electrode assembly 100 includes a positive electrode 10 and a negative electrode 20, which are stacked together. The positive electrode 10 includes a first current collector 11, a positive active material layer 12, and a liquid-retaining coating 13. The positive active material layer 12 is disposed on the surface of the first current collector 11. The positive active material layer 12 includes a main body 121 and a thinned portion 122. The thinned portion 122 is disposed at at least one end of the main body 121 along the length direction X of the electrode assembly 100. The thickness of the main body 121 is... Thickness greater than the thinned portion 122 The liquid-retaining coating 13 is disposed on the side of the thinned portion 122 facing away from the first current collector 11; the negative electrode sheet 20 forms an edge region 201 at at least one end along the length direction X of the electrode assembly 100, and the edge region 201, the thinned portion 122 and the liquid-retaining coating 13 are disposed correspondingly along the thickness direction Z of the electrode assembly 100.

[0040] The electrolyte-retaining coating 13 can absorb and store the electrolyte and allow the electrolyte to pass through. The electrolyte can be absorbed and stored in the electrolyte-retaining coating 13, and the electrolyte in the electrolyte-retaining coating 13 can wet the thinned portion 122 through the electrolyte-retaining coating 13.

[0041] In this embodiment of the invention, by providing a thinned portion 122 with a smaller thickness at at least one end of the main body 121 along the length direction X of the electrode assembly 100, the areal density of the active material layer of the positive electrode 10 at the location of the thinned portion 122 is reduced, and the N / P (Negative-to-Positive) ratio of the positive and negative electrodes is increased. The ratio value allows for more lithium insertion sites in the edge region 201 corresponding to the thinned portion 122 in the negative electrode 20, thereby improving the charging window and mitigating lithium deposition in the edge region 201 of the negative electrode 20. Furthermore, given the high current density and rapid electrolyte consumption rate in the corresponding edge regions 201 of the positive and negative electrodes, which can easily lead to insufficient electrolyte and lithium deposition in the edge region 201 of the negative electrode 20, this embodiment of the invention provides a liquid-retaining coating 13 on the side of the thinned portion 122 facing away from the first current collector 11. The liquid-retaining coating 13 can absorb and accumulate electrolyte at the position corresponding to the edge region 201 in the positive electrode 10, preventing lithium deposition in the edge region 201 of the negative electrode 20 due to insufficient electrolyte in the later stages of cycling, thus preventing cycle failure.

[0042] In some embodiments, the first current collector 11 can be an aluminum foil, and the positive electrode active material layer 12 can be lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide, or ternary lithium, etc.

[0043] In some embodiments, the negative electrode 20 includes a second current collector 21 and a negative electrode active material layer 22, wherein the negative electrode active material layer 22 is disposed on the surface of the second current collector 21.

[0044] In some embodiments, the negative electrode active material layer 22 is disposed on the opposite surfaces of the second current collector 21.

[0045] In some embodiments, the second current collector 21 may be a copper foil, and the negative electrode active material layer 22 may be carbon or silicon, etc.

[0046] like Figure 3 As shown, the electrolyte-retaining coating 13 covers the thinned portion 122 along the width direction Y of the electrode assembly 100. In this way, the electrolyte-retaining coating 13 can absorb and accumulate electrolyte on each unit width of the thinned portion 122. The electrolyte can wet each unit width of the thinned portion 122 through the electrolyte-retaining coating 13, which is beneficial to improve the situation where lithium is deposited in the edge region 201 of the negative electrode 20 due to insufficient electrolyte.

[0047] Please continue reading. Figure 3 In some embodiments, the width of the first current collector 11 is The width of the thinned portion 122 is , = Thus, in the width direction Y of the electrode assembly 100, the end faces of the first current collector 11 and the thinned portion 122 are flush. The thinned portion 122 covers the first current collector 11 along the width direction Y of the electrode assembly 100, which can significantly reduce the surface density of the active material layer of the positive electrode 10 at the location of the thinned portion 122, thereby significantly increasing the N / P value of the positive and negative electrodes; the width of the liquid-retaining coating 13 is... , = Thus, in the width direction Y of the electrode assembly 100, the end face of the thinned portion 122 and the liquid-retaining coating 13 are flush. The liquid-retaining coating 13 covers the thinned portion 122 along the width direction Y of the electrode assembly 100, so that the liquid-retaining coating 13 can absorb and accumulate electrolyte to a greater extent at the position corresponding to the edge region 201, which is beneficial to improve the situation of lithium plating in the edge region 201 of the negative electrode sheet 20 due to insufficient electrolyte.

[0048] like Figure 2 As shown, in some embodiments, the thickness of the main body 121 is The thickness of the liquid-retaining coating 13 is 0.25* ≤ ≤0.5* Among them, by increasing the thickness of the liquid-retaining coating 13 Greater than or equal to 0.25 times the thickness of the main body 121 The parameter design can avoid the problem caused by the thickness of the liquid-retaining coating 13. If the thickness is too small, its ability to absorb and accumulate electrolyte will be weak. Therefore, it is necessary to ensure that the electrolyte-retaining coating 13 has a certain ability to absorb and accumulate electrolyte in the edge region, and to ensure that the electrolyte-retaining coating 13 improves the lithium plating effect on the edge region 201 of the negative electrode 20. This is achieved by adjusting the thickness of the electrolyte-retaining coating 13. Less than or equal to 0.5 times the thickness of the main body 121 The parameter design can avoid the problem caused by the thickness of the liquid-retaining coating 13. Setting the value too high results in the positive electrode sheet 10 having an excessively large proportion of its thickness, leading to a decrease in the battery's energy density.

[0049] Please continue reading. Figure 2 In some embodiments, the size of the electrolyte-retaining coating 13 along the length direction X of the electrode assembly 100 is L, where 2mm ≤ L ≤ 6mm. By designing the size L of the electrolyte-retaining coating 13 to be greater than or equal to 2mm, it avoids a situation where the size L of the electrolyte-retaining coating 13 is too small, resulting in a weak ability to absorb and accumulate electrolyte. This ensures that the electrolyte-retaining coating 13 has a certain ability to absorb and accumulate electrolyte in the edge region, and also ensures that the electrolyte-retaining coating 13 improves the lithium plating effect on the edge region 201 of the negative electrode sheet 20. Conversely, by designing the size L of the electrolyte-retaining coating 13 to be less than or equal to 6mm, it avoids a situation where the size L of the electrolyte-retaining coating 13 is too large, resulting in an excessive proportion in the length of the positive electrode sheet 10, which would reduce the energy density of the battery.

[0050] like Figure 2 and Figure 3 As shown, in some embodiments, the side of the electrolyte-retaining coating 13 facing away from the first current collector 11 is flush with the side of the main body 121 facing away from the first current collector 11. This arrangement ensures that the outermost surface of the positive electrode 10 furthest from the first current collector 11 is a flat surface, allowing both the main body 121 and the thinned portion 122 to be quickly wetted by the electrolyte. Furthermore, the positive electrode 10 does not become excessively thick due to the electrolyte-retaining coating 13, enabling the battery to have a higher energy density.

[0051] In some embodiments, the electrolyte-retaining coating 13 includes an electrolyte-retaining additive, which is used to absorb electrolyte. The electrolyte-retaining additive has good electrolyte affinity and can lock in the electrolyte, thereby increasing its electrolyte retention at the location of the positive electrode 10.

[0052] The liquid-retaining additive includes at least one of the following: a blend powder of nitrile butadiene and polyvinyl chloride, polypropylene micro powder, ultra-high molecular weight polyethylene powder, and linear crystalline polyvinylidene fluoride polymer.

[0053] In some embodiments, the electrolyte-retaining coating 13 further includes ceramic microspheres for storing electrolyte. The ceramic microspheres have numerous pores in which the electrolyte can be stored. Furthermore, the ceramic microspheres can increase the hardness of the positive electrode 10 at the location of the positive electrode 10, preventing deformation or even damage caused by external forces at the location of the positive electrode 10.

[0054] Among them, ceramic microsphere powder includes at least one of the following spherical powders: bermite, silicon dioxide, magnesium hydroxide, aluminum oxide, zirconium oxide, magnesium oxide, mullite, and cordierite.

[0055] like Figure 1 and Figure 2 As shown, in some embodiments, the main body 121 has thinned portions 122 connected to both ends along the length X of the electrode assembly 100. Each thinned portion 122 has a liquid-retaining coating 13 connected to its side facing away from the first current collector 11. The negative electrode 10 has two edge regions 201 formed at both ends along the length X of the electrode assembly 100. One edge region 201 corresponds to the thinned portion 122 and the liquid-retaining coating 13 at one end of the main body 121 along the length X of the electrode assembly 100, and the other edge region 201 corresponds to the thinned portion 122 and the liquid-retaining coating 13 at the other end of the main body 121 along the length X of the electrode assembly 100. This configuration simultaneously improves the lithium plating situation in the two edge regions 201 of the negative electrode 10 along the electrode assembly 100, preventing lithium plating in the edge regions 201 of the negative electrode 20 due to insufficient electrolyte during the later stages of cycling, which could ultimately lead to cycle failure.

[0056] Please continue reading. Figure 1 and Figure 2 In some embodiments, a positive electrode active material layer 12 and a liquid-retaining coating 13 are provided on both opposite surfaces of the first current collector 11. That is, a positive electrode active material layer 12 is provided on both surfaces of the first current collector 11 along the thickness direction Z of the positive electrode sheet 10, and a liquid-retaining coating 13 is provided on the side of the thinned portion 122 of the positive electrode active material layer 12 on each surface that is away from the first current collector 11. In this way, after the positive electrode sheet 10 and the negative electrode sheet 20 are stacked, along the stacking direction, the opposite sides of one positive electrode sheet 10 located between two adjacent negative electrode sheets 20 can improve the lithium plating effect on the edge regions 201 of the two negative electrode sheets 20. This can prevent the edge regions 201 of each negative electrode sheet 20 from plating lithium due to insufficient electrolyte in the later stage of the cycle, which would eventually lead to cycle failure.

[0057] This utility model embodiment also provides a battery cell, which includes a separator and an electrode assembly 100 as described above. The separator is disposed between the positive electrode 10 and the negative electrode 20, and the positive electrode, the separator and the negative electrode are stacked in sequence to form the battery cell.

[0058] It is understandable that the battery cell can be a stacked cell structure or a wound cell structure.

[0059] The battery cell of this embodiment has the beneficial effects of the electrode assembly 100, which will not be described in detail here.

[0060] This utility model embodiment also provides a battery, which includes a casing and an electrode assembly 100 as described above, with the battery cell disposed inside the casing.

[0061] In some embodiments, the battery further includes a positive tab and a negative tab, the positive tab being connected to a first current collector and the negative tab being connected to a second current collector. The positive tab and the negative tab are used to connect to an external electrical device or an external power supply device to enable the battery to supply power to the external electrical device or the external power supply device to charge the battery.

[0062] The battery of this utility model embodiment has the beneficial effects of a battery cell, which will not be elaborated here.

[0063] It should be noted that the battery provided in this embodiment only shows the part related to the technical problem to be solved by this embodiment. It is understood that the battery provided in this embodiment also includes other structures or media for realizing the function of the battery, including but not limited to electrolytes for wetting the positive electrode, negative electrode and separator.

[0064] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. An electrode assembly, characterized by, The electrode assembly includes a positive electrode sheet and a negative electrode sheet; The positive electrode sheet includes a first current collector, a positive electrode active material layer, and a liquid retaining coating, the positive electrode active material layer is disposed on a surface of the first current collector, the positive electrode active material layer includes a main body portion and a thinned portion, the thinned portion is disposed on at least one end of the main body portion along a length direction of the electrode assembly, a thickness of the main body portion is greater than a thickness of the thinned portion, and the liquid retaining coating is disposed on a side of the thinned portion away from the first current collector; The negative electrode sheet forms an edge region on at least one end along the length direction of the electrode assembly, the edge region, the thinned portion, and the liquid retaining coating are disposed correspondingly along a thickness direction of the electrode assembly.

2. The electrode assembly of claim 1, wherein, The liquid retaining coating covers the thinned portion along a width direction of the electrode assembly.

3. The electrode assembly of claim 1, wherein, The first current collector has a width of , the width of the thinning portion is , the width of the liquid retaining coating is , = = .

4. The electrode assembly of claim 1, wherein, The thickness of the main body part is , the thickness of the liquid retaining coating is , 0.25 ≤ ≤ 0.5 .

5. The electrode assembly of claim 1, wherein, Along the length direction of the electrode assembly, a size of the liquid retaining coating is L, and 2 mm≤L≤6 mm.

6. The electrode assembly of claim 1, wherein, The side of the liquid retaining coating away from the first current collector is flush with the side of the main body portion away from the first current collector.

7. The electrode assembly of any one of claims 1 to 6, wherein, The main body portion is connected with the thinned portion on each of two ends along the length direction of the electrode assembly, and the side of each of the thinned portions away from the first current collector is connected with the liquid retaining coating. The negative electrode sheet forms two edge regions on two ends along the length direction of the electrode assembly, one of the edge regions is disposed correspondingly with the thinned portion and the liquid retaining coating located on one end of the main body portion along the length direction of the electrode assembly, and the other of the edge regions is disposed correspondingly with the thinned portion and the liquid retaining coating located on the other end of the main body portion along the length direction of the electrode assembly.

8. The electrode assembly of any one of claims 1 to 6, wherein, Both surfaces of the first current collector are provided with the positive electrode active material layer and the liquid retaining coating.

9. An electric cell characterized by The electrode assembly includes a separator and any one of claims 1 to 8, the separator is disposed between the positive electrode sheet and the negative electrode sheet.

10. A battery, characterized by The battery cell includes a housing and claim 9, the battery cell is disposed inside the housing.

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