A diaphragm and battery cell

Abstract

The utility model relates to battery separator technology field discloses a kind of separator and electric core, separator has mutually perpendicular first direction and second direction, comprising: base film layer, first coating, second coating and protective layer, base film layer has the first side and second side of opposite arrangement along second direction, base film layer has the second part and third part along first direction arrangement;First coating is located at first side, the surface of first coating forms second vacant area along second direction corresponding third part;Second coating is located at second side, the surface of second coating forms fourth vacant area along second direction corresponding third part;Protective layer is set on the surface of first coating and / or second coating, and protective layer and the second part of base film layer are oppositely arranged along second direction;Protective layer at least corresponds to the bending part of anode sheet or cathode sheet winding start segment.

Description

Technical Field

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

[0002] Currently, with the rapid growth in demand for consumer batteries, users are placing higher demands on cell energy density and charging rate. Due to silicon's high specific capacity, silicon-doped anodes have become an important development direction for improving energy density.

[0003] In wound battery cell structures, the bending radius of the anode and cathode plates at the initial winding position is small, resulting in sharp angles. This makes it easy for graphite or silicon particles on the electrodes to be exposed and puncture the separator, causing micro-short circuits. An improvement in existing technology is to completely coat the separator surface with a ceramic coating to improve its puncture resistance. However, completely coating the separator with a ceramic coating increases its overall thickness, affecting the cell's energy density.

[0004] In summary, the existing method of completely coating the membrane surface with a ceramic coating cannot simultaneously meet the requirements of puncture resistance of the membrane and improving the energy density of the battery cell. Utility Model Content

[0005] The technical problem to be solved by this utility model is that the existing method of completely coating the diaphragm surface with a ceramic coating cannot simultaneously meet the requirements of diaphragm puncture resistance and improve cell energy density.

[0006] To solve the above-mentioned technical problems, this utility model provides a diaphragm technical solution:

[0007] A diaphragm having a first direction and a second direction perpendicular to each other includes:

[0008] A base film layer having a first side surface and a second side surface arranged opposite to each other along a second direction, and a second portion and a third portion disposed along the first direction;

[0009] A first coating is disposed on the first side, and the surface of the first coating forms a second vacant area along the second direction corresponding to the third part;

[0010] A second coating is disposed on the second side, and the surface of the second coating forms a fourth vacant area along the second direction corresponding to the third part;

[0011] A protective layer is disposed on the surface of the first coating and / or the second coating, and the protective layer is arranged opposite to a second portion of the base film layer along the second direction; the protective layer corresponds at least to a curved portion of the starting section of the anode or cathode sheet.

[0012] Furthermore, the base film layer also has a first portion, the first portion, the second portion and the third portion are arranged sequentially along the first direction, the surface of the first coating forms a first vacant area along the second direction corresponding to the first portion, the surface of the second coating forms a third vacant area along the second direction corresponding to the first portion, the length of the first vacant area and the third vacant area along the first direction is L1, and the length of the protective layer along the first direction is L2, satisfying: L2>L1.

[0013] Furthermore, both the first coating and the second coating are adhesive coatings, and the protective layer is a ceramic coating.

[0014] Furthermore, the thickness of the base film layer in the second direction is T1, the thickness of the first coating layer in the second direction is T2, the thickness of the second coating layer in the second direction is T3, and the thickness of the protective layer in the second direction is T4, satisfying: T1 = 2μm ~ 10μm, T2 = 0.3μm ~ 3μm, T3 = 0.3μm ~ 3μm, and T4 = 0.5μm ~ 2μm.

[0015] Furthermore, both the first coating and the second coating are mixed coatings of adhesive and ceramic, and the protective layer is a thickened portion of the mixed coating of adhesive and ceramic.

[0016] Furthermore, the thickness of the base film layer in the second direction is T1, the thickness of the first coating layer in the second direction is T2, the thickness of the second coating layer in the second direction is T3, and the thickness of the protective layer in the second direction is T4, satisfying: T1 = 2μm ~ 10μm, T2 = 0.3μm ~ 3μm, T3 = 0.3μm ~ 3μm, T4 = 0.5*T2 ~ 2*T2.

[0017] To solve the above-mentioned technical problems, this utility model provides a technical solution for a battery cell:

[0018] Battery cell, including the separator in the above scheme.

[0019] Furthermore, the battery cell also includes an anode plate and a cathode plate, the diaphragm is stacked between the anode plate and the cathode plate along the second direction, and the anode plate, the diaphragm and the cathode plate are wound together along the first direction.

[0020] Furthermore, the battery cell has a bending area and a straight area along its width direction. The end of the cathode sheet located inside the battery cell is the winding start end. The cathode sheet is wound along the first direction. Along the winding direction of the battery cell, the cathode sheet has multiple bending portions. The multiple bending portions are located in the bending area. The bending portion connected to the winding start end is the first bending portion. The second portion is arranged opposite to the first bending portion of the cathode sheet along the second direction.

[0021] Furthermore, the second portion is arranged opposite to the first five bends of the cathode sheet along the second direction.

[0022] Compared with existing technologies, the diaphragm and battery cell of this invention have the following advantages: The diaphragm adopts a design of a base film layer, a first coating layer, a second coating layer, and a protective layer. The base film layer has a first side surface and a second side surface arranged opposite to each other along a second direction, and a second part and a third part arranged along the first direction. The first coating layer is disposed on the first side surface, and the second coating layer is disposed on the second side surface. The protective layer is disposed on the surface of the first coating layer and / or the second coating layer, and the protective layer is arranged opposite to the second part of the base film layer. The second part corresponds to the winding start part of the anode or cathode sheet. By specifically enhancing the strength of key parts of the diaphragm, it can effectively resist the puncture force generated by the sharp bends of the electrode sheets, and improve the local puncture resistance of the diaphragm in the second part.

[0023] In this design, the surface of the first coating forms a second vacant area corresponding to the third part, and the surface of the second coating forms a fourth vacant area corresponding to the second part. During actual winding, the second and fourth vacant areas are located in the later part of the diaphragm winding. Here, the bending radius of the anode and cathode plates is larger, preventing puncture damage caused by sharp corners. This effectively reduces the thickness of the diaphragm. At the same time, during charging and discharging, the vacant areas allow ions to pass through the diaphragm more smoothly, ensuring ion migration speed and efficiency, thereby significantly improving the energy density of the cell. Attached Figure Description

[0024] Figure 1 This is a cross-sectional schematic diagram of the diaphragm in an embodiment of this utility model;

[0025] Figure 2 This is a cross-sectional schematic diagram of the diaphragm in another embodiment of the present invention;

[0026] Figure 3 This is a cross-sectional schematic diagram of the battery cell in an embodiment of this utility model;

[0027] In the figure: 1. Diaphragm; 11. Base film layer; 11a. First side surface; 11b. Second side surface; 111. First part; 112. Second part; 113. Third part; 12. First coating layer; 121. First vacant area; 122. Second vacant area; 13. Second coating layer; 131. Third vacant area; 132. Fourth vacant area; 14. Protective layer; 2. Anode plate; 3. Cathode plate; 30. Bending part; 31. First bending part; a. Bending area; b. Straight area; X. First direction; Y. Second direction. Detailed Implementation

[0028] The specific embodiments of this utility model will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this utility model, but are not intended to limit its scope.

[0029] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise" used to indicate the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or component 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.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0031] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in this utility model can be understood according to the specific circumstances.

[0032] like Figure 1As shown, a diaphragm according to an embodiment of the present invention has a first direction X and a second direction Y that are perpendicular to each other, and includes: a base film layer 11, a first coating layer 12, a second coating layer 13, and a protective layer 14. The base film layer 11 has a first side surface 11a and a second side surface 11b arranged opposite to each other along the second direction Y. The base film layer 11 has a second portion 112 and a third portion 113 disposed along the first direction X.

[0033] The first coating 12 is disposed on the first side 11a, and the surface of the first coating 12 forms a second vacant area 122 along the second direction Y corresponding to the third part 113; the second coating 13 is disposed on the second side 11b, and the surface of the second coating 13 forms a fourth vacant area 132 along the second direction Y corresponding to the third part 113.

[0034] The protective layer 14 is disposed on the surface of the first coating 12 and / or the second coating 13, and the protective layer 14 is arranged opposite to the second portion 112 of the base film layer 11 along the second direction Y; the protective layer 14 corresponds at least to a curved portion of the starting section of the anode sheet 2 or the cathode sheet 3.

[0035] The diaphragm 1 adopts a design of a base film layer 11, a first coating layer 12, a second coating layer 13, and a protective layer 14. The base film layer 11 has a first side 11a and a second side 11b arranged opposite to each other along the second direction Y. The base film layer 11 has a second part 112 and a third part 113 arranged along the first direction X. The first coating layer 12 is disposed on the first side 11a, and the second coating layer 13 is disposed on the second side 11b.

[0036] The protective layer 14 is disposed on the surface of the first coating 12 and / or the second coating 13, and the protective layer 14 is arranged opposite to the second part 112 of the base film layer 11. The second part 112 corresponds to the starting part of the winding of the anode sheet 2 or the cathode sheet 3. By specifically enhancing the strength of the key parts of the diaphragm 1, it can effectively resist the puncture force generated by the sharp bend of the electrode sheet and improve the local puncture resistance of the diaphragm 1 in the second part 112.

[0037] In this design, the surface of the first coating 12, corresponding to the area of ​​the third part 113, forms a second vacant area 122, and the surface of the second coating 13, corresponding to the area of ​​the second part 112, forms a fourth vacant area 132. During actual winding, the second vacant area 122 and the fourth vacant area 132 are located in the later part of the winding of the separator 1. Here, the bending radius of the anode plate 2 and the cathode plate 3 is relatively large, and puncture damage will not be caused by sharp corners. This can effectively reduce the main body thickness of the separator 1. At the same time, during charging and discharging, the vacant areas allow ions to pass through the separator 1 more smoothly, ensuring ion migration speed and efficiency, thereby significantly improving the energy density of the battery cell.

[0038] In this embodiment, the base film layer 11 further has a first portion 111. The first portion 111, the second portion 112, and the third portion 113 are arranged sequentially along the first direction X. The surface of the first coating layer 12 forms a first vacant area 121 along the second direction Y corresponding to the first portion 111. The surface of the second coating layer 13 forms a third vacant area 131 along the second direction Y corresponding to the first portion 111. The length of the first vacant area 121 and the third vacant area 131 along the first direction X is L1, and the length of the protective layer 14 along the first direction X is L2, satisfying L2>L1. During actual winding, the winding start portion of the diaphragm 1 protrudes along the second direction Y relative to the winding start portion of the anode sheet 2 and / or the cathode sheet 3. The length L1 of the first vacant area 121 and the second vacant area 122 along the first direction X is the pre-winding length of the diaphragm 1, which can meet the requirement of flexible folding deformation of the winding start portion, and at the same time provides effective anti-puncture protection for the winding start portion of the anode sheet 2 and / or the cathode sheet 3.

[0039] As a further preferred embodiment, both the first coating 12 and the second coating 13 are adhesive coatings, and the protective layer 14 is a ceramic coating. Specifically, the thickness of the base film layer 11 in the second direction Y is T1, the thickness of the first coating 12 in the second direction Y is T2, the thickness of the second coating 13 in the second direction Y is T3, and the thickness of the protective layer 14 in the second direction Y is T4, satisfying: T1 = 2μm~10μm, T2 = 0.3μm~3μm, T3 = 0.3μm~3μm, T4 = 0.5μm~2μm.

[0040] To verify the relationship between the thickness of the ceramic coating and the yield of the cell's K-value (K-value: self-discharge rate), taking the fabrication of a battery cell with a centrally located tab as an example, the ceramic coating covers the first five bends of the cathode sheet. Along the winding direction of the battery cell, the cathode sheet has multiple bends, with the bend connected to the starting end of winding being the first bend, and so on. Therefore, the first five bends refer to the portion from the starting end of winding to the fifth bend. The different thicknesses of the ceramic coating were verified as follows:

[0041] T1(μm) T2(μm) T3(μm) T4(μm) K-value yield Experimental Example 1 5 0.75 0.75 0 96.2％ Experiment Example 2 5 0.75 0.75 0.5 98.6％ Experimental Example 3 5 0.75 0.75 1 99.2 Experiment Example 4 5 0.75 0.75 1.5 99.6％ Experimental Example 5 5 0.75 0.75 2 99.9％ Experimental Example 6 5 0.75 0.75 2.5 99.9％ Experimental Example 7 5 0.75 0.75 3 99.9％

[0042] As shown in Experiments 1 to 7 above, the thickness of the protective layer 14 in the second direction Y, T4, is approximately 0.5. μ m to 2 μ Within the m range, the yield of cell K-value is significantly improved, the risk of cell short circuit is reduced, and the high energy density of the cell is guaranteed.

[0043] like Figure 2As shown, a diaphragm according to another embodiment of the present invention has a first direction X and a second direction Y that are perpendicular to each other, and includes: a base film layer 11, a first coating layer 12, a second coating layer 13, and a protective layer 14. The base film layer 11 has a first side surface 11a and a second side surface 11b arranged opposite to each other along the second direction Y. The base film layer 11 has a second portion 112 and a third portion 113 disposed along the first direction X.

[0044] The first coating 12 is disposed on the first side 11a, and the surface of the first coating 12 forms a second vacant area 122 along the second direction Y corresponding to the third part 113; the second coating 13 is disposed on the second side 11b, and the surface of the second coating 13 forms a fourth vacant area 132 along the second direction Y corresponding to the third part 113.

[0045] The difference from the specific embodiments described above is that the protective layer 14 is disposed on the surface of the first coating 12 and / or the second coating 13, and the protective layer 14 and the second portion 112 of the base film layer 11 are arranged opposite each other along the second direction Y. The first coating 12 and the second coating 13 are both mixed coatings of adhesive and ceramic, and the protective layer 14 is a thickened portion of the mixed coating of adhesive and ceramic. By thickening the mixed coating, the strength of key parts of the diaphragm can be specifically enhanced, effectively resisting the puncture force generated by the sharp bends of the electrode sheets, and improving the local puncture resistance of the diaphragm in the second portion 112.

[0046] As a further preferred embodiment, the base film layer 11 also has a first portion 111. The first portion 111, the second portion 112, and the third portion 113 are sequentially arranged along the first direction X. The surface of the first coating 12 forms a first vacancy area 121 along the second direction Y corresponding to the first portion 111. The surface of the second coating 13 forms a third vacancy area 131 along the second direction Y corresponding to the first portion 111. The length of the first vacancy area 121 and the second and third vacancy areas 131 along the first direction X is L1, and the length of the protective layer 14 along the first direction X is L2, satisfying that L2>L1. The thickness of the base film layer 11 in the second direction Y is T1, the thickness of the first coating 12 in the second direction Y is T2, the thickness of the second coating 13 in the second direction Y is T3, and the thickness of the protective layer 14 in the second direction Y is T4, satisfying that T1 = 2μm~10μm, T2 = 0.3μm~3μm, T3 = 0.3μm~3μm, and T4 = 0.5*T2~2*T2.

[0047] like Figure 3 As shown in the figure, a battery cell according to an embodiment of the present invention includes a separator 1, an anode plate 2, and a cathode plate 3. The separator 1 is the same as the separator in the various specific embodiments of the above-described embodiments, and will not be described again here. The separator 1 is stacked between the anode plate 2 and the cathode plate 3 along the second direction Y, and the anode plate 2, the separator 1, and the cathode plate 3 are wound together along the first direction X.

[0048] As a further preferred embodiment, the battery cell has a bending region a and a straight region b along its width direction. The end of the cathode sheet 3 located inside the battery cell is the winding start end. The cathode sheet 3 is wound along the first direction X. Along the winding direction of the battery cell, the cathode sheet 3 has a plurality of bending portions 30. The plurality of bending portions 30 are located in the bending region a. The bending portion 30 connected to the winding start end is the first bending portion 31. The second portion 112 is arranged at least opposite to the first bending portion 31 of the cathode sheet 3 along the second direction Y.

[0049] To verify the coverage ratio between the protective layer 14 and the bent portion 30 of the cathode sheet 3, the thickness of the ceramic coating (i.e., the protective layer 14) was selected as 1 μm. The following verification was conducted with the cathode sheet not covered by the ceramic coating, and with the ceramic coating covering the first bent portion, the first two bent portions, the first three bent portions, the first four bent portions, the first five bent portions, the first six bent portions, and the first seven bent portions of the cathode sheet 3:

[0050] Ceramic coating coverage K-value yield Comparative Example The cathode plate was not covered with a ceramic coating. 96.2％ Experimental Example 1 The first bend of the cathode plate 97.6％ Experiment Example 2 The first two bends of the cathode plate 98.2％ Experimental Example 3 The first three bends of the cathode plate 98.7 Experiment Example 4 The first four bends of the cathode plate 99.0％ Experimental Example 5 The first five bends of the cathode plate 99.2％ Experimental Example 6 The first six bends of the cathode plate 99.25％ Experimental Example 7 The first seven bends of the cathode plate 99.3％

[0051] As can be seen from the comparative examples and experimental examples 1 to 7 above, the more the ceramic coating (i.e., protective layer 14) covers the bending portion 30 of the cathode sheet 3, the higher the yield of the cell's K-value and the lower the risk of short circuit. However, after experimental example 6, the gain effect on the yield of the cell's K-value is significantly reduced. In order to balance the energy density of the battery, covering the first five bending portions 30 of the cathode sheet 3 with the ceramic coating is the optimal approach.

[0052] It should be noted that the K-value test method and equipment are as follows: After the cell completes the capacity test, it is placed in a 45℃ environment for two days, then placed in a 25℃ environment for two days to test voltage ①, and then placed in a 25℃ environment for three days to test voltage ②. K-value = (voltage ① - voltage ②) / (test interval between voltage ② and voltage ①), and the K-value specification is 0~0.04mv / h.

[0053] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present utility model, and these improvements and substitutions should also be considered within the protection scope of the present utility model.

Claims

1. A diaphragm having a first direction (X) and a second direction (Y) that are perpendicular to each other, characterized in that, include: The base film layer (11) has a first side surface (11a) and a second side surface (11b) arranged opposite to each other along the second direction (Y), and the base film layer (11) has a second portion (112) and a third portion (113) disposed along the first direction (X); A first coating (12) is disposed on the first side surface (11a), and the surface of the first coating (12) forms a second vacant area (122) corresponding to the third part (113) along the second direction (Y); A second coating (13) is disposed on the second side (11b), and the surface of the second coating (13) forms a fourth vacant area (132) corresponding to the third part (113) along the second direction (Y); A protective layer (14) is disposed on the surface of the first coating (12) and / or the second coating (13), and the protective layer (14) is arranged opposite to the second portion (112) of the base film layer (11) along the second direction (Y); the protective layer (14) corresponds at least to a curved portion of the starting section of the anode sheet (2) or cathode sheet (3) being wound.

2. The diaphragm according to claim 1, characterized in that, The base film layer (11) further has a first part (111), the first part (111), the second part (112) and the third part (113) are arranged sequentially along the first direction (X), the surface of the first coating (12) forms a first vacancy area (121) along the second direction (Y) corresponding to the first part (111), the surface of the second coating (13) forms a third vacancy area (131) along the second direction (Y) corresponding to the first part (111), the length of the first vacancy area (121) and the third vacancy area (131) along the first direction (X) is L1, and the length of the protective layer (14) along the first direction (X) is L2, satisfying: L2 > L1.

3. The diaphragm according to claim 1, characterized in that, The first coating (12) and the second coating (13) are both adhesive coatings, and the protective layer (14) is a ceramic coating.

4. The diaphragm according to claim 3, characterized in that, The thickness of the base film layer (11) in the second direction (Y) is T1, the thickness of the first coating layer (12) in the second direction (Y) is T2, the thickness of the second coating layer (13) in the second direction (Y) is T3, and the thickness of the protective layer (14) in the second direction (Y) is T4, satisfying: T1 = 2μm ~ 10μm, T2 = 0.3μm ~ 3μm, T3 = 0.3μm ~ 3μm, T4 = 0.5μm ~ 2μm.

5. The diaphragm according to claim 1, characterized in that, The first coating (12) and the second coating (13) are both mixed coatings of adhesive and ceramic, and the protective layer (14) is a thickened portion of the mixed coating of adhesive and ceramic.

6. The diaphragm according to claim 5, characterized in that, The thickness of the base film layer (11) in the second direction (Y) is T1, the thickness of the first coating layer (12) in the second direction (Y) is T2, the thickness of the second coating layer (13) in the second direction (Y) is T3, and the thickness of the protective layer (14) in the second direction (Y) is T4, satisfying: T1 = 2μm ~ 10μm, T2 = 0.3μm ~ 3μm, T3 = 0.3μm ~ 3μm, T4 = 0.5*T2 ~ 2*T2.

7. A battery cell, characterized in that, Includes the diaphragm as described in any one of claims 1 to 6.

8. The battery cell according to claim 7, characterized in that, The battery cell also includes an anode plate (2) and a cathode plate (3). The diaphragm is stacked between the anode plate (2) and the cathode plate (3) along the second direction (Y), and the anode plate (2), the diaphragm and the cathode plate (3) are wound along the first direction (X).

9. The battery cell according to claim 8, characterized in that, The battery cell has a bending region (a) and a straight region (b) along its width direction. The end of the cathode sheet (3) located inside the battery cell is the winding start end. The cathode sheet (3) is wound along the first direction (X). Along the winding direction of the battery cell, the cathode sheet (3) has a plurality of bending portions (30). The plurality of bending portions (30) are located in the bending region (a). The bending portion (30) connected to the winding start end is the first bending portion (31). The second portion (112) is arranged at least opposite to the first bending portion (31) of the cathode sheet (3) along the second direction (Y).

10. The battery cell according to claim 9, characterized in that, The second part (112) is arranged opposite to the first five bends of the cathode sheet (3) along the second direction (Y).

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