Battery cell capable of improving lithium precipitation and battery

Abstract

The utility model discloses a battery cell capable of improving lithium precipitation and a battery. The battery cell comprises a negative plate, a negative tab, a positive plate and a diaphragm, the negative plate is provided with a tab connecting area; the negative tab is connected to the tab connecting area of the negative plate; the positive plate and the negative plate are stacked; the diaphragm is arranged between the negative plate and the positive plate; and a resistive layer is arranged at the position, opposite to the tab connecting area, of the positive plate. The resistive layer is arranged at the position, opposite to the tab connecting area, of the positive plate, the resistive layer can increase the impedance of the area corresponding to the positive plate, during charging, the lithium removal rate of the area, provided with the resistive layer, of the positive plate is reduced, the current density of the area, provided with the resistive layer, of the positive plate is reduced, and therefore the current density of the tab connecting area of the negative plate is also reduced; therefore, the lithium separation risk of the negative plate at the position near the negative tab is reduced, and the safety of the battery cell is improved.

Description

Technical Field

[0001] The utility model relates to the field of batteries, in particular to a battery cell and a battery for improving lithium deposition. Background Art

[0002] Some existing battery cells consist of stacked negative and positive electrodes with a separator between them. The negative electrode has a negative tab welded to it, while the positive electrode has a positive tab. During charging, the current flow is uneven across the positive and negative electrodes. Typically, the current density is highest near the negative tab, making lithium deposition more likely. Lithium dendrites can pierce the separator, causing a short circuit between the positive and negative electrodes and potentially posing a safety risk. Utility Model Content

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a battery cell with improved lithium deposition, which can reduce the risk of lithium deposition near the negative electrode tab of the negative electrode sheet and improve the safety of the battery cell.

[0004] The utility model also provides a battery having the above-mentioned battery core with improved lithium deposition.

[0005] According to an embodiment of the first aspect of the present invention, a battery cell for improving lithium deposition comprises a negative electrode sheet, a negative electrode tab, a positive electrode sheet, and a separator. The negative electrode sheet is provided with a tab connection area; the negative electrode tab is connected to the tab connection area of the negative electrode sheet; the positive electrode sheet and the negative electrode sheet are stacked; the separator is provided between the negative electrode sheet and the positive electrode sheet; wherein a resistor layer is provided at a position on the positive electrode sheet opposite the tab connection area.

[0006] The battery cell with improved lithium plating according to the embodiment of the first aspect of the present invention has at least the following beneficial effects: a resistance layer is provided at a position relative to the positive electrode sheet and the tab connection area, and the resistance layer can increase the impedance of the area corresponding to the positive electrode sheet. During charging, the lithium desorption rate of the area where the resistance layer is provided on the positive electrode sheet is reduced, thereby reducing the current density in the area where the resistance layer is provided on the positive electrode sheet. Therefore, the current density in the tab connection area of the negative electrode sheet is also reduced, making the lithium insertion of the negative electrode sheet more uniform, thereby reducing the risk of lithium plating of the negative electrode sheet near the negative tab and improving the safety of the battery cell.

[0007] According to some embodiments of the present invention, the negative electrode sheet includes a negative electrode current collector, negative electrode active material layers are provided on both sides of the negative electrode current collector, and the negative electrode current collector is provided with an empty foil area, and the empty foil area forms the tab connection area.

[0008] According to some embodiments of the present invention, the length of the resistance layer is greater than the length of the corresponding tab connection area, the width of the resistance layer is greater than the width of the corresponding tab connection area, and the projections of the tab connection areas on the positive electrode sheet are all located within the projection range of the resistance layer on the positive electrode sheet.

[0009] According to some embodiments of the present invention, the length of the tab connection area is A, and the length of the resistance layer is B, satisfying A+5mm≤B≤A+10mm.

[0010] According to some embodiments of the present invention, the width of the tab connection area is C, and the width of the resistance layer is D, satisfying C+10mm≤D≤C+20mm.

[0011] According to some embodiments of the present invention, the positive electrode sheet includes a positive electrode current collector, positive electrode active material layers are respectively provided on both sides of the positive electrode current collector, the resistance layer is provided on the side of the positive electrode current collector close to the tab connection area, and the resistance layer is located between the positive electrode current collector and the positive electrode active material layer.

[0012] According to some embodiments of the present invention, the resistance layer is a non-metallic resistance layer.

[0013] According to some embodiments of the present invention, the thickness of the resistance layer is E, the thickness of the positive electrode active material layer covering the resistance layer is H1, and the thickness of the positive electrode active material layer around the resistance layer is H2, satisfying E+H1=H2.

[0014] According to some embodiments of the present invention, the negative electrode tab is connected to the negative electrode current collector by welding.

[0015] The battery according to the embodiment of the second aspect of the present invention includes the above-mentioned battery cell with improved lithium deposition.

[0016] The battery according to the embodiment of the second aspect of the present invention has at least the following beneficial effects: due to the use of the above-mentioned battery cell, lithium deposition is not likely to occur near the negative electrode ear of the battery, thereby improving the overall safety of the battery.

[0017] Additional aspects and advantages of the present invention will be given in part in the following description and will become apparent from the following description or learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0019] Figure 1 A top cross-sectional view of a portion of the structure of a battery cell according to an embodiment of the present invention;

[0020] Figure 2 This is a front view schematic diagram of a negative electrode sheet according to an embodiment of the present invention;

[0021] Figure 3 This is a front view schematic diagram of the positive electrode sheet of an embodiment of the utility model;

[0022] Figure 4 This is a top cross-sectional view of the positive electrode sheet according to an embodiment of the present invention.

[0023] Reference numerals:

[0024] Negative electrode sheet 100, tab connection area 101, negative electrode current collector 110, negative electrode active material layer 120;

[0025] Negative electrode ear 200;

[0026] Positive electrode sheet 300, resistance layer 310, positive electrode current collector 320, positive electrode active material layer 330;

[0027] Diaphragm 400. DETAILED DESCRIPTION

[0028] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0029] In the description of the present invention, it should be understood that descriptions involving orientation, such as the orientation or positional relationship indicated by up, down, etc., are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0030] In the description of this utility model, "a plurality" means more than two. The use of "first" or "second" is solely for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of technical features indicated, or implicitly indicating the order of the technical features indicated.

[0031] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0032] Reference Figures 1 to 4The battery cell for improving lithium deposition according to an embodiment of the present invention includes a negative electrode sheet 100, a negative electrode tab 200, a positive electrode sheet 300, and a separator 400. The negative electrode sheet 100 is provided with a tab connection area 101; the negative electrode tab 200 is connected to the tab connection area 101 of the negative electrode sheet 100; the positive electrode sheet 300 is stacked with the negative electrode sheet 100; the separator 400 is disposed between the negative electrode sheet 100 and the positive electrode sheet 300; and a resistive layer 310 is disposed on the positive electrode sheet 300 at a position opposite the tab connection area 101.

[0033] A resistance layer 310 is provided at a position opposite to the positive electrode sheet 300 and the tab connection area 101. The resistance layer 310 can increase the impedance of the area corresponding to the positive electrode sheet 300. During charging, the lithium desorption rate of the area where the resistance layer 310 is provided on the positive electrode sheet 300 is reduced, thereby reducing the current density in the area where the resistance layer 310 is provided on the positive electrode sheet 300. Therefore, the current density of the tab connection area 101 of the negative electrode sheet 100 is also reduced, making the lithium insertion of the negative electrode sheet 100 more uniform, thereby reducing the risk of lithium plating of the negative electrode sheet 100 near the negative electrode tab 200.

[0034] In the embodiment, the negative electrode sheet 100 includes a negative electrode current collector 110, with negative electrode active material layers 120 disposed on both sides of the negative electrode current collector 110. The negative electrode current collector 110 is provided with a hollow foil area, which forms the tab connection area 101. In the above-mentioned negative electrode sheet 100, the negative electrode current collector 110 can be directly connected to the negative electrode tab 200, which has a better performance.

[0035] In an embodiment, the length of the resistive layer 310 is greater than the length of the corresponding tab connection area 101, the width of the resistive layer 310 is greater than the width of the corresponding tab connection area 101, and the projection of the tab connection area 101 on the positive electrode sheet 300 is entirely located within the projection range of the resistive layer 310 on the positive electrode sheet 300. Specifically, the tab connection area 101 is rectangular, which facilitates the installation and connection of conventional tabs. The length and width of the resistive layer 310 are both greater than the length and width of the tab connection area 101, so that the projection of the tab connection area 101 on the positive electrode sheet 300 can be entirely located within the projection range of the resistive layer 310 on the positive electrode sheet 300, which can reduce the current density of the negative electrode sheet 100 near the negative tab 200, thereby making the lithium insertion of the negative electrode sheet 100 more uniform, further reducing the risk of lithium plating of the negative electrode sheet 100 near the negative tab 200, and improving the safety of the battery cell.

[0036] Specifically, in this embodiment, the tab connection area 101 is rectangular, which is convenient for connecting and installing conventional tabs; the corresponding resistance layer 310 is also rectangular.

[0037] Specifically, the tab connection area 101 is actually an empty foil area on the negative electrode sheet 100 for welding the negative electrode tab 200. In actual production, the area of the tab connection area 101 is slightly larger than the area where the negative electrode tab 200 is overlapped with the negative electrode sheet 100, which facilitates the connection between the two during production.

[0038] If the size of the resistor layer 310 is too large, it is easy to excessively affect the current density of the positive electrode sheet 300 in the resistor layer 310 area and the negative electrode sheet 100 near the negative electrode ear 200, ultimately affecting the charging efficiency of the battery cell; if the size of the resistor layer 310 is too small, the effect of suppressing lithium deposition of the negative electrode sheet 100 near the negative electrode ear 200 may not be obvious enough. Therefore, the resistor layer 310 needs to be of an appropriate size to reduce the problem of lithium deposition of the negative electrode sheet 100 near the negative electrode ear 200, improve safety, and reduce the impact on the charging efficiency of the battery. Therefore, the following improvements are made:

[0039] In an embodiment, the length of the tab connection area 101 is A, and the length of the resistor layer 310 is B, satisfying A+5mm≤B≤A+10mm. The above-mentioned length of the resistor layer 310 can relatively appropriately reduce the current density in the tab connection area 101 and the vicinity, so that the lithium insertion speed of the negative electrode sheet 100 is relatively appropriate and the use effect is better. Specifically, the length of the resistor layer 310 can be, for example, 5mm, 6mm, 7mm, 8mm, 9mm or 10mm longer than the length of the tab connection area 101, or other values within the selected range. Those skilled in the art can make specific configurations according to actual needs.

[0040] In an embodiment, the width of the tab connection area 101 is C, and the width of the resistor layer 310 is D, satisfying C+10mm≤D≤C+20mm. The above-mentioned width of the resistor layer 310 can relatively appropriately reduce the current density in the tab connection area 101 and the vicinity, so that the lithium insertion speed of the negative electrode sheet 100 is relatively appropriate and the use effect is better. Specifically, the width of the resistor layer 310 can be, for example, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm or 20mm larger than the width of the tab connection area 101, or other values within the selected range. Those skilled in the art can make specific configurations according to actual needs.

[0041] In the embodiment, the positive electrode sheet 300 includes a positive electrode current collector 320, with positive electrode active material layers 330 disposed on both sides of the positive electrode current collector 320. A resistor layer 310 is disposed on the side of the positive electrode current collector 320 near the tab connection area 101, and the resistor layer 310 is located between the positive electrode current collector 320 and the positive electrode active material layer 330. The location of the resistor layer 310 makes the production process of the positive electrode sheet 300 relatively convenient and can reduce the current density of the negative electrode sheet 100 near the negative tab 200.

[0042] In this embodiment, the resistor layer 310 is a non-metallic resistor layer 310. Specifically, the resistor layer 310 includes a non-metallic conductive agent and an adhesive. The non-metallic conductive agent is at least one of conductive carbon black, conductive graphite sheets, and conductive carbon nanotubes; the adhesive is at least one of polyvinylidene fluoride, acrylic acid-modified PVDF, carboxylic acid-modified PVDF, styrene-butadiene rubber, acrylic acid-modified styrene-butadiene rubber, polymethyl methacrylate, and polyimide. Using the above materials for the resistor layer 310 achieves a relatively moderate increase in the impedance of the corresponding region of the positive electrode sheet 300, with little negative impact on the original function of the positive electrode sheet 300.

[0043] In the embodiment, the thickness of the resistor layer 310 is E, the thickness of the positive electrode active material layer 330 covering the resistor layer 310 is H1, and the thickness of the positive electrode active material layer 330 surrounding the resistor layer 310 is H2, satisfying E + H1 = H2. Because the resistor layer 310 occupies a portion of the thickness of the positive electrode active material layer 330, the amount of active material in the positive electrode active material layer 330 covering the resistor layer 310 is reduced. This reduces the surface density of the positive electrode active material of the positive electrode sheet 300 in the region of the resistor layer 310, thereby increasing the CB value there. This allows the negative electrode sheet 100 to have more lithium insertion vacancies, thereby increasing the lithium plating window, further suppressing lithium plating, and improving the safety of the battery cell.

[0044] Specifically, since the resistor layer 310 replaces a portion of the active material of the original positive electrode active material layer 330, the surface density of the active material of the positive electrode active material layer 330 in the resistor layer 310 region is reduced. If the thickness of the resistor layer 310 is too large, the capacity of the battery cell will be affected; if the thickness of the resistor layer 310 is too small, the lithium deposition suppression effect near the negative electrode tab 200 of the negative electrode sheet 100 is not significant. Therefore, the following improvements are made:

[0045] In an embodiment, the thickness of the resistor layer 310 is E, satisfying 5μm≤E≤10μm. The aforementioned thickness of the resistor layer 310 has little effect on the capacity of the battery cell, and the negative electrode sheet 100 has a relatively good effect in suppressing lithium deposition near the negative electrode tab 200. Specifically, the thickness of the resistor layer 310 can be, for example, 5μm, 6μm, 7μm, 9μm, or 10μm, or other values within the selected range. Those skilled in the art can configure the thickness according to actual needs.

[0046] It should be understood that since the resistance layer 310 is located between the positive current collector 320 and the positive active material layer 330 , the thickness of the positive active material layer 330 should be greater than the thickness of the resistance layer 310 .

[0047] In the embodiment, the negative electrode tab 200 is connected to the negative electrode current collector 110 by welding, which is relatively convenient to produce and has a good connection effect. It is conceivable that in other embodiments, the negative electrode tab 200 can also be fixedly connected to the negative electrode current collector 110 by riveting or other methods.

[0048] Specifically, in this embodiment, the positive electrode current collector 320 is aluminum foil. During production, the resistor layer 310 is first coated on the positive electrode current collector 320, and then the positive electrode active material is coated on the positive electrode current collector 320. During this process, the positive electrode active material will also directly cover the resistor layer 310 to form the positive electrode sheet 300. The negative electrode current collector 110 is usually copper foil. During production, the negative electrode active material is directly coated on the negative electrode current collector 110, and then the negative electrode tab 200 is welded to the tab connection area 101.

[0049] When producing battery cells, a separator 400 is placed between the positive electrode sheet 300 and the negative electrode sheet 100, and the negative electrode ear 200 of the negative electrode sheet 100 is centered and aligned with the resistance layer 310 of the positive electrode sheet 300. The cells are then wound to form a wound battery cell, or stacked to form a laminated battery cell. The battery cells are then packaged, baked, injected, formed, repackaged, and capacity divided to produce a finished battery.

[0050] The utility model also discloses a battery that uses the above-mentioned battery core for improving lithium deposition. Due to the use of the above-mentioned battery core, lithium deposition is not likely to occur near the negative electrode tab 200 of the battery, thereby improving the overall safety of the battery.

[0051] Specifically, two types of batteries were fabricated for testing. One battery had a resistor layer 310 disposed in the region of the positive electrode current collector 320 facing the negative electrode tab 200, serving as Example 1 of this solution. The other battery had no resistor layer 310 disposed on the positive electrode current collector 320, serving as Comparative Example 1. After several cycles of charge and discharge, the following data was obtained:

[0052] Table 1: Battery disassembly results:

[0053]

[0054] As can be seen from Table 1, Example 1 has a certain effect of suppressing lithium deposition in the area near the negative electrode tab 200 of the negative electrode sheet 100 , that is, adding the resistance layer 310 can suppress the lithium deposition problem in the area near the negative electrode tab 200 of the negative electrode sheet 100 .

[0055] Table 2: Battery capacity retention rate table; Battery capacity retention rate = cycle discharge capacity / initial discharge capacity*100%.

[0056] Cycle times 200 400 600 800 Example 1 Capacity retention rate 97.8％ 94.3％ 89.6％ 85.9％ Comparative Example 1 Capacity retention rate 95.4％ 89.5％ 82.5％ 76.3％

[0057] It can be seen from Table 2 that Example 1 also has a certain effect of suppressing the decrease in battery capacity, that is, adding the resistance layer 310 can extend the charge and discharge service life of the battery.

[0058] Table 3: Battery thickness expansion rate table;

[0059] Cycle times 200 400 600 800 Example 1 Expansion Rate 3.62％ 4.72％ 5.57％ 6.17％ Comparative Example 1 Expansion Rate 4.56％ 6.46％ 7.51％ 8.39％

[0060] It can be seen from Table 3 that Example 1 can suppress the expansion of the battery to a certain extent, that is, adding the resistance layer 310 can suppress the expansion problem of the battery after long-term use.

[0061] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative use of the above terms does 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 any one or more embodiments or examples.

[0062] Although the embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and purpose of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A battery cell for improving lithium deposition, characterized in that: include: A negative electrode sheet (100) is provided with a tab connection area (101); A negative electrode tab (200) connected to the tab connection region (101) of the negative electrode sheet (100); A positive electrode sheet (300) is stacked with the negative electrode sheet (100); a separator (400) disposed between the negative electrode sheet (100) and the positive electrode sheet (300); Wherein, a resistance layer (310) is provided at a position of the positive electrode sheet (300) opposite to the tab connection area (101).

2. The battery cell for improving lithium deposition according to claim 1, characterized in that: The negative electrode sheet (100) comprises a negative electrode current collector (110), negative electrode active material layers (120) are provided on both sides of the negative electrode current collector (110), and the negative electrode current collector (110) is provided with an empty foil area, and the empty foil area forms the tab connection area (101).

3. The battery cell for improving lithium deposition according to claim 1 or 2, characterized in that: The length of the resistance layer (310) is greater than the length of the corresponding tab connection area (101), the width of the resistance layer (310) is greater than the width of the corresponding tab connection area (101), and the projection of the tab connection area (101) on the positive electrode sheet (300) is entirely located within the projection range of the resistance layer (310) on the positive electrode sheet (300).

4. The battery cell for improving lithium deposition according to claim 3, characterized in that: The length of the tab connection area (101) is A, and the length of the resistance layer (310) is B, satisfying A+5mm≤B≤A+10mm.

5. The battery cell for improving lithium plating according to claim 3, characterized in that: The width of the tab connection area (101) is C, and the width of the resistance layer (310) is D, satisfying C+10mm≤D≤C+20mm.

6. The battery cell for improving lithium deposition according to claim 1, characterized in that: The positive electrode sheet (300) includes a positive electrode current collector (320), and positive electrode active material layers (330) are respectively provided on both sides of the positive electrode current collector (320). The resistance layer (310) is provided on the side of the positive electrode current collector (320) close to the tab connection area (101), and the resistance layer (310) is located between the positive electrode current collector (320) and the positive electrode active material layer (330).

7. The battery cell for improving lithium deposition according to claim 6, characterized in that: The resistance layer (310) is a non-metal resistance layer (310).

8. The battery cell for improving lithium deposition according to claim 6, characterized in that: The thickness of the resistance layer (310) is E, the thickness of the positive electrode active material layer (330) covered on the resistance layer (310) is H1, and the thickness of the positive electrode active material layer (330) around the resistance layer (310) is H2, satisfying E+H1=H2.

9. The battery cell for improving lithium plating according to claim 2, characterized in that: The negative electrode tab (200) is connected to the negative electrode current collector (110) by welding.

10. A battery, characterized in that: A battery cell with improved lithium plating performance comprising the battery cell according to any one of claims 1 to 9.

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