Pole piece, battery cell and battery

Abstract

The utility model belongs to the technical field of battery production and manufacturing, and particularly relates to a pole piece which comprises a current collector and an active material layer coated on the current collector, a tab groove is formed in the middle area of the active material layer, tab glue is arranged in the tab groove, the size of the tab glue is smaller than that of the tab groove, and the active material layer is coated on the active material layer. The tab glue comprises a barrier layer and a swelling layer which are stacked in sequence, the tab is located between the swelling layer and the tab groove, and the swelling rate of the swelling layer after being heated and absorbing liquid is 110%-180%. After the swelling layer is formed by hot pressing, the swelling layer extends and fills the tab groove, so that the thickness of the tab glue can be reduced, and the thickness of a corresponding position of a battery cell formed by the tab glue can be reduced; meanwhile, the expanded swelling layer can permeate into the edge area of the active material layer to block a lithium ion channel, so that the lithium precipitation condition is improved, and the safety performance is improved. In addition, the utility model also discloses a battery cell and a battery comprising the pole piece.

Description

Technical Field

[0001] The utility model belongs to the technical field of battery production and manufacturing, and specifically relates to a pole piece, a battery core and a battery. Background Art

[0002] Nowadays, with the development of modern society and the enhancement of people's environmental awareness, more and more devices choose lithium-ion batteries as power sources, such as mobile phones, laptops, power tools and electric vehicles, which provides a broad space for the application and development of lithium-ion batteries.

[0003] At present, the centering of the pole ear is a common method for installing the pole ear in the existing battery cell, and the centering structure of the pole ear often causes the thickness of the pole sheet in the pole ear installation part to increase, affecting the energy density. To solve the above problems, there is a patent for a centering structure of the pole ear (Chinese patent, application number: 202222435090.X), including a square pole ear slot of the pole ear in the length direction of the positive electrode sheet or the negative electrode sheet, a current collector, an electrode active material coating and a protective tape, characterized in that: the pole ear slot includes a protective tape groove and a pole ear welding groove, and the pole ear welding groove is provided with protective tape grooves on both sides to form a stepped pole ear slot with a bilaterally symmetrical cross-sectional shape. Although the above patent can improve the thickness of the pole ear area, its process steps are complicated and the cost is high. To this end, it is urgent to propose a new technical solution to solve the above problems. Utility Model Content

[0004] One of the purposes of the utility model is to provide a pole piece in view of the deficiencies of the prior art, which prevents lithium deposition at the pole ear groove without increasing the thickness of the pole piece by arranging a pole ear glue in the groove.

[0005] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0006] A pole piece comprises a current collector and an active material layer coated on the current collector, wherein the active material layer is provided with a pole ear groove in the central region thereof, the pole ear groove is used to accommodate a pole ear, a pole ear glue is arranged in the pole ear groove, the volume of the pole ear glue is smaller than the volume of the pole ear groove, the pole ear glue comprises a barrier layer and a swelling layer stacked in sequence, the pole ear is located between the swelling layer and the pole ear groove, and the liquid absorption expansion rate of the swelling layer is 110%-180%.

[0007] In the utility model, the material of the barrier layer is polymethacrylate or polyethylene terephthalate, and the barrier layer has high physical strength, which can prevent burrs from penetrating; the swelling layer is composed of α-olefin polymer, modified polyolefin, styrene block copolymer and petroleum resin. After hot pressing, the swelling layer absorbs electrolyte to expand and can fill the pole ear groove, thereby not increasing the thickness of the battery cell composed of the pole pieces of the utility model, and can also prevent lithium deposition from occurring in the pole ear groove.

[0008] As an improvement of the pole piece described in the utility model, under the environment of 95° C. and standard atmospheric pressure, the melt index of the swelling layer is greater than 90 g / 10 min.

[0009] As an improvement of the pole piece described in the utility model, the volume of the pole ear glue accounts for 70%-85% of the volume of the pole ear groove.

[0010] As an improvement of the pole piece described in the utility model, the distance between the edge of the pole ear glue and the edge of the pole ear groove is R, and R is set to 0.5mm-1mm.

[0011] As an improvement of the pole piece described in the utility model, the softening point of the swelling layer is 50°C-95°C, and the melting point of the barrier layer is 130°C-185°C.

[0012] As an improvement of the pole piece described in the utility model, the liquid absorption swelling degree of the barrier layer is less than 5%, and the thickness of the barrier layer is set to 5 μm-20 μm.

[0013] As an improvement of the pole piece described in the utility model, the width D of the pole ear groove is 8mm-20mm, and the length L of the pole ear groove is 10mm-47mm.

[0014] As an improvement of the pole piece described in the utility model, the thickness of the active material layer is set to 50mm-100mm, and the thickness of the swelling layer is set to 20mm-50mm. The setting of the size, distance parameter and volume relationship of the pole ear glue and the pole ear groove, together with the characteristics of the swelling layer, can ensure that the pole ear glue does not protrude from the pole ear groove after hot pressing, further ensuring that the thickness of the battery cell formed in actual application does not increase, and improving the volume energy density of the battery cell.

[0015] The second purpose of the utility model is to provide a battery core, including the pole piece as described above.

[0016] The second purpose of the present utility model is to provide a battery, comprising the battery cell as described above.

[0017] The beneficial effect of the utility model lies in that the pole piece of the utility model comprises a current collector and an active material layer coated on the current collector, the active material layer is provided with a pole ear groove in the central region thereof, the pole ear groove is used to accommodate the pole ear, the pole ear glue is arranged in the pole ear groove, the volume of the pole ear glue is smaller than the volume of the pole ear groove, the pole ear glue comprises a barrier layer and a swelling layer stacked in sequence, the pole ear is located between the swelling layer and the pole ear groove, and the liquid absorption expansion rate of the swelling layer is 110%-180%. The ear glue in the utility model is provided with a swelling layer. After the swelling layer is hot-pressed, it expands and fills the ear groove, thereby reducing the thickness of the ear glue, and reducing the thickness of the battery cell composed of it at the corresponding position, thereby improving the volume energy density of the battery cell; at the same time, the active material layer is a porous structure. Since the active material layer is provided with the ear groove, lithium deposition is prone to occur at the edge of the active material layer close to the ear groove. The expanded swelling layer of the utility model can penetrate into the edge area of ​​the active material layer, which can firstly prevent powder loss, and secondly block the lithium ion channel, thereby improving the lithium deposition situation and enhancing the safety performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The features, advantages and technical effects of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings.

[0019] Figure 1 It is a structural schematic diagram of the utility model.

[0020] Figure 2 It is a bottom view of the pole ear groove in the utility model.

[0021] Figure 3 It is a schematic diagram of the structure of the utility model after hot pressing.

[0022] The reference numerals are described as follows:

[0023] 1-current collector;

[0024] 2-active material layer; 21-ear groove;

[0025] 3-Pole ear;

[0026] 4-ear glue; 41-barrier layer; 42-swelling layer. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are 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 ordinary technicians in this field without creative work are within the scope of protection of this application.

[0028] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific implementation methods and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0029] Reference to "embodiment" in this application means that a particular feature, structure or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments.

[0030] In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, as well as the overall thickness, length, width and other dimensions of the integrated device are only exemplary descriptions and should not constitute any limitation to the present application.

[0031] The battery includes a cell and an electrolyte. The cell is composed of a positive electrode sheet, a negative electrode sheet and a separator. The battery mainly relies on the movement of metal ions between the positive electrode sheet and the negative electrode sheet to work. The positive electrode sheet includes a positive electrode collector and a positive electrode active material layer. The positive electrode active material layer is coated on the surface of the positive electrode collector. The positive electrode collector not coated with the positive electrode active material layer protrudes from the positive electrode collector coated with the positive electrode active material layer. The positive electrode collector not coated with the positive electrode active material layer serves as the positive electrode tab. Taking lithium-ion batteries as an example, the material of the positive electrode collector can be aluminum, and the positive electrode active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganese oxide, etc. The negative electrode sheet includes a negative electrode collector and a negative electrode active material layer. The negative electrode active material layer is coated on the surface of the negative electrode collector. The negative electrode collector not coated with the negative electrode active material layer protrudes from the negative electrode collector coated with the negative electrode active material layer. The negative electrode collector not coated with the negative electrode active material layer serves as the negative electrode tab. The material of the negative electrode collector can be copper, and the negative electrode active material can be carbon or silicon, etc. In order to ensure that a large current does not melt, the number of positive electrode tabs is multiple and stacked together, and the number of negative electrode tabs is multiple and stacked together. The material of the isolation film can be PP (polypropylene) or PE (polyethylene).

[0032] In the battery, the method of centering the lug is to take a suitable position in the middle of the length direction of the positive or negative electrode sheet, and remove the active material on the positive or negative current collector by mechanical scraping, foam glue sticking and laser cleaning, so as to obtain a square lug slot, so that the lug can be in the center of the positive or negative electrode sheet. Compared with the traditional winding method, the method of centering the lug can effectively reduce the area of ​​the empty foil area at the lug welding point, thereby effectively improving the energy density of the battery. However, the structure of centering the lug requires glue sticking at the lug, resulting in the thickness here being greater than the thickness of the active coating on the current collector, which ultimately increases the thickness of the wound battery, which is not conducive to improving the energy density of the battery.

[0033] In view of this, the present embodiment arranges the pole ear glue inside the pole ear groove, and the pole ear glue is composed of a swelling layer. The swelling layer is extended after hot pressing and can fill the pole ear groove to improve the lithium precipitation phenomenon; at the same time, the thickness of the battery cell composed of the pole piece of the present invention at the pole ear groove can be maintained without increasing, thereby ensuring the volume energy density of the battery cell.

[0034] The following is combined with Figures 1 to 3 The utility model is further described in detail with specific implementation modes, but is not intended to limit the utility model.

[0035] like Figure 1As shown, a pole piece includes a current collector 1 and an active material layer 2 coated on the current collector 1, wherein the active material layer 2 has a pole ear groove 21 in the central region thereof, the pole ear groove 21 is used to accommodate a pole ear 3, a pole ear glue 4 is arranged in the pole ear groove 21, the pole ear glue 4 includes a barrier layer 41 and a swelling layer 42 stacked in sequence, and the pole ear 3 is located between the swelling layer 42 and the pole ear groove 21.

[0036] In practical applications, the material of the barrier layer 41 is polymethacrylate or polyethylene terephthalate, and the barrier layer 41 has high physical strength, which can prevent burrs from piercing; the swelling layer 42 is composed of α-olefin polymer, modified polyolefin, styrene block copolymer and petroleum resin. After hot pressing, the swelling layer 42 absorbs the electrolyte to expand and can fill the pole ear groove 21, thereby not increasing the thickness of the battery cell composed of the pole pieces of this embodiment, and can also prevent lithium deposition from occurring in the pole ear groove 21.

[0037] Preferably, the liquid absorption expansion rate of the swelling layer 42 is 110%-180%, the liquid absorption swelling degree of the barrier layer 41 is less than 5%, the softening point of the swelling layer 42 is 50℃-95℃, the melting point of the barrier layer 41 is 130℃-185℃, and under the environment of 95℃ and standard atmospheric pressure, the melting index of the swelling layer 42 is greater than 90g / 10min. The setting of the above parameters further ensures the fluidity of the pole ear glue 4, so that the pole ear glue 4 can extend to fill the pole ear groove 21 after hot pressing.

[0038] like Figure 2 As shown, the width D of the pole ear groove 21 is 8mm-20mm, and the length L of the pole ear groove 21 is 10mm-47mm; the thickness of the active material layer 2 is set to 50mm-100mm, and the thickness of the swelling layer 42 is set to 20mm-50mm; the thickness of the barrier layer 41 is set to 5μm-20μm; the distance between the edge of the pole ear glue 4 and the edge of the pole ear groove 21 is R, and R is set to 0.5mm-1mm; the volume of the pole ear glue 4 accounts for 70%-85% of the volume of the pole ear groove 21; the setting of the size, distance parameters and volume relationship of the pole ear glue 4 and the pole ear groove 21, together with the characteristics of the swelling layer 42, can ensure that the pole ear glue 4 does not protrude from the pole ear groove 41 after hot pressing, further ensure that the thickness of the battery cell formed in actual application does not increase, and improve the volume energy density of the battery cell.

[0039] Battery Cell

[0040] A battery cell includes the electrode as described above, wherein the electrode may be a positive electrode or a negative electrode. After being hot pressed, the structure of the electrode is as follows: Figure 3As shown, after the swelling layer 42 is hot-pressed, it extends and fills the pole ear groove 21, thereby reducing the thickness of the pole ear glue 4, and can reduce the thickness of the battery cell composed of it at the corresponding position, thereby increasing the volume energy density of the battery cell; at the same time, the active material layer 2 is a porous structure. Since the active material layer 2 is provided with the pole ear groove 21, lithium deposition is prone to occur at the edge of the active material layer 2 close to the pole ear groove 21, and the expanded swelling layer 42 can penetrate into the edge area of ​​the active material layer 2, which can firstly prevent powder loss, and secondly block the lithium ion channel, thereby improving the lithium deposition situation and enhancing the safety performance.

[0041] Battery

[0042] A battery, comprising the battery cell as described above, and the battery can be a lithium ion battery, a sodium ion battery, a magnesium ion battery, etc., which is not limited in the embodiments of the present application; the battery can be cylindrical, flat, rectangular or other shapes, etc., which is not limited in the embodiments of the present application.

[0043] According to the disclosure and teaching of the above description, the technicians in the field of the utility model can also change and modify the above implementation. Therefore, the utility model is not limited to the above specific implementation, and any obvious improvement, replacement or modification made by the technicians in this field on the basis of the utility model belongs to the protection scope of the utility model. In addition, although some specific terms are used in this specification, these terms are only for the convenience of explanation and do not constitute any limitation to the utility model.

Claims

1. A pole piece, comprising a current collector (1) and an active material layer (2) coated on the current collector (1), wherein the active material layer (2) is provided with a pole ear groove (21) in the middle region thereof, wherein the pole ear groove (21) is used to accommodate a pole ear (3), characterized in that: A tab glue (4) is arranged in the tab groove (21); the volume of the tab glue (4) is smaller than the volume of the tab groove (21); the tab glue (4) comprises a barrier layer (41) and a swelling layer (42) stacked in sequence; the tab (3) is located between the swelling layer (42) and the tab groove (21); and the liquid absorption expansion rate of the swelling layer (42) is 110%-180%.

2. The pole piece according to claim 1, characterized in that: The volume of the tab glue (4) accounts for 70%-85% of the volume of the tab groove (21).

3. The pole piece according to claim 1, characterized in that: The distance between the edge of the tab glue (4) and the edge of the tab groove (21) is R, and R is set to 0.5 mm-1 mm.

4. The pole piece according to claim 1, characterized in that: The softening point of the swelling layer (42) is 50°C-95°C, and the melting point of the barrier layer (41) is 130°C-185°C.

5. The pole piece according to claim 1, characterized in that: Under the environment of 95° C. and standard atmospheric pressure, the melt index of the swelling layer ( 42 ) is greater than 90 g / 10 min.

6. The pole piece according to claim 1, characterized in that: The liquid absorption swelling degree of the barrier layer (41) is less than 5%, and the thickness of the barrier layer (41) is set to be 5 μm-20 μm.

7. The pole piece according to claim 1, characterized in that: The width D of the pole lug groove (21) is 8 mm to 20 mm, and the length L of the pole lug groove (21) is 10 mm to 47 mm.

8. The pole piece according to claim 1, characterized in that: The thickness of the active material layer (2) is set to 50 mm-100 mm, and the thickness of the swelling layer (42) is set to 20 mm-50 mm.

9. A battery cell, characterized in that: A pole piece comprising any one of claims 1 to 8.

10. A battery, characterized in that: Comprising the battery cell as claimed in claim 9.

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