A segmented and spaced coated electrode and a bare battery cell

Abstract

The present invention relates to the technical field of batteries, and discloses a segmented and spaced coated electrode sheet and a bare battery cell. The segmented and spaced coated electrode sheet includes a current collector, and a material area and an empty foil area are provided on the front and back surfaces of the current collector. The material areas are arranged at intervals along the length direction of the current collector, and the empty foil areas are arranged around each material area. The interval length between two adjacent material areas increases in an arithmetic progression. The material area and the empty foil area are separated from each other to prevent material dropping when the electrode sheet is folded. The present invention also provides a bare battery cell, which includes the segmented and spaced coated electrode sheet and a separator. After the positive electrode sheet, the negative electrode sheet and the separator are stacked in layers and continuously wound in the same direction, a bare battery cell body is formed; the cross section of the bare battery cell body is rectangular, and the rectangular bare battery cell overcomes the defects of the arc ends of the bare battery cell in the prior art, ensures that the CB value of the bare battery cell does not deviate from the design value, the current density on both sides of the current collector is consistent, and voltage polarization causing voltage instability is prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a segmented and spaced-coated electrode sheet and a bare battery cell. Background Art

[0002] Lithium-ion batteries are a widely used type of rechargeable battery, which mainly includes: a positive electrode sheet, a negative electrode sheet, an electrolyte, a separator, and a structural member.

[0003] In the prior art, the positive and negative electrode pastes are usually continuously coated on the corresponding substrates, and then the substrates are cut into electrode sheets of the required size to produce the electrode sheets in lithium-ion batteries. Then, the positive electrode sheet, the negative electrode sheet, and the separator are made into a bare battery cell through a winding or stacking process, and the bare battery cell and the structural member are assembled into the battery cell of the lithium-ion battery. During charging, electrons enter the external circuit from the positive electrode paste area through the positive electrode current collector, and at the same time, electrons in the external circuit flow into the negative electrode through the negative electrode current collector, and lithium ions enter the electrolyte from the positive electrode paste area and pass through the separator to reach the negative electrode. The movement paths of electrons and lithium ions during the discharging process are opposite to those during the charging process.

[0004] For the bare battery cell made by the winding process, semi-circular arcs will be formed at both side edges. As the number of winding layers (the number of battery cell layers) increases, the radii of the arcs on both sides of the bare battery cell will also increase. This structure has the following several defects: 1. The curvature of the inner side of the winding is relatively large, and material dropping will occur during the folding process of the electrode sheet, posing a safety hazard. 2. The dressing states of the inner and outer sides of the arc formed by the side electrode sheet are different, resulting in the deviation of the CB value (the excess ratio of the negative electrode capacity per unit area relative to the positive electrode capacity) at this place from the designed value, making it prone to damage here. 3. During the charge and discharge process, the side arcs are prone to deformation and distortion, leading to a decline in the performance of the battery cell and even a safety hazard. 4. During the discharging process, the current densities on both sides of the current collector are different, the voltage polarization is relatively large, and the discharging voltage is unstable. 5. The commonly used structural member is a regular cuboid, and the arcs on both sides of the bare battery cell will cause waste of the internal space of the structural member and a low volume energy density. Summary of the Invention

[0005] Based on the above, the purpose of the present invention is to provide a segmented and spaced-coated electrode sheet and a bare battery cell to overcome the above defects.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A segmented and spaced-coated electrode sheet, which is divided into two types: a negative electrode sheet and a positive electrode sheet, and includes:

[0008] A paste area, which is provided on the front and back surfaces of the current collector and is arranged at intervals along the length direction of the current collector. The paste area is formed by coating the paste and is rectangular;

[0009] An empty foil area, which is provided around each paste area;

[0010] The sizes and directions of multiple material areas are exactly the same, and the interval length a between the nth material area and the (n - 1)th material area n = a1 + (n - 1) * b, where n is an integer greater than or equal to 2, and b is the common difference.

[0011] As an alternative for the segmented interval coated electrode sheet, when the segmented interval coated electrode sheet is made into a negative electrode sheet, the first term of the interval length in the negative electrode sheet is a′1, 0 < a′1 ≤ 5 mm;

[0012] When the segmented interval coated electrode sheet is made into a positive electrode sheet, the first term of the interval length in the positive electrode sheet is a″1, a″1 = a″1 + l1 * c + l2 * d + l3 * 2, where l1 is the cold pressing thickness of the negative electrode sheet, l2 is the cold pressing thickness of the positive electrode sheet, l3 is the thickness of the separator; c is the negative electrode expansion coefficient, 1.05 ≤ c ≤ 2; d is the positive electrode expansion coefficient, 1.02 ≤ d ≤ 1.8.

[0013] As an alternative for the segmented interval coated electrode sheet, the common difference of the interval length is b, b = l1 * c + l2 * d + l3 * 2, where l1 is the cold pressing thickness of the negative electrode sheet, l2 is the cold pressing thickness of the positive electrode sheet, l3 is the thickness of the separator; c is the negative electrode expansion coefficient, 1.05 ≤ c ≤ 2; d is the positive electrode expansion coefficient, 1.02 ≤ d ≤ 1.8.

[0014] As an alternative for the segmented interval coated electrode sheet, the outer sides of the first side, the second side, and the third side of each material area are all empty foil areas, the first side and the second side are perpendicular to the length direction of the current collector, and the third side is parallel to the length direction of the current collector.

[0015] As an alternative for the segmented interval coated electrode sheet, the material areas of the negative electrode sheet are configured to be able to completely cover the material areas of the positive electrode sheet.

[0016] As an alternative for the segmented interval coated electrode sheet, two material areas located at symmetrical positions on the front and back sides of the current collector form a material area group, and each material area group is provided with 1 pole tab.

[0017] A bare battery cell includes the segmented interval coated electrode sheet and the separator according to any one of the above solutions. The segmented interval coated electrode sheet includes two types: a positive electrode sheet and a negative electrode sheet; after the positive electrode sheet, the negative electrode sheet, and the separator are stacked layer by layer and continuously wound in the same direction, a bare battery cell body is formed; the cross-section of the bare battery cell body is rectangular, including empty foil parts located at opposite ends and another group of material area parts located at opposite ends, and the material areas are located in the material area parts of the bare battery cell body.

[0018] As an alternative for the bare battery cell, the positive electrode sheet is provided with a positive pole tab, the negative electrode sheet is provided with a negative pole tab, and the positive pole tab and the negative pole tab do not overlap.

[0019] As an alternative to a bare battery cell, after winding, the misalignment range of the positive electrode tab or the negative electrode tab is ±10 mm.

[0020] The beneficial effects of the present invention are as follows:

[0021] The present invention provides a segmented and spaced coating electrode sheet, including material regions which are arranged on the front and back surfaces of the current collector and are spaced along the length direction of the current collector. The material regions are formed by coating a dressing and are rectangular in shape. An empty foil region is arranged around each material region; the sizes and directions of the multiple material regions are exactly the same, and the interval length a between the nth material region and the (n - 1)th material region n = a1 + (n - 1) * b, where n is an integer greater than or equal to 2 and b is the common difference. Such a setting separates the material regions and the empty foil regions of the segmented and spaced coating electrode sheet, preventing material loss during the folding of the electrode sheet. Compared with the traditional continuously coated electrode sheet, the transmission path of electrons is optimized. In the segmented and spaced coating electrode sheet, electrons are transmitted to the tab through the spaced empty foil regions, reducing the internal resistance of the battery cell and optimizing the high-rate charge and discharge performance of the battery cell.

[0022] The present invention also provides a bare battery cell, including a segmented and spaced coating electrode sheet and a separator. The segmented and spaced coating electrode sheet includes the positive electrode sheet and the negative electrode sheet; after laminating the positive electrode sheet, the negative electrode sheet and the separator and continuously winding them in the same direction, a bare battery cell body is formed; the cross-section of the bare battery cell body is rectangular, including empty foil portions at opposite ends and material region portions at the other pair of opposite ends, and the material regions are located in the material region portions of the bare battery cell body. The rectangular bare battery cell overcomes the defects of the arc ends of the bare battery cell in the prior art, ensures that the CB value of the bare battery cell does not deviate from the design value, and during the discharging process, the current densities on both sides of the current collector are consistent, preventing voltage instability caused by voltage polarization. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments of the present invention. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the content of the embodiments of the present invention and these drawings.

[0024] Figure 1 is a schematic diagram of the segmented and spaced coating electrode sheet provided by the specific embodiment of the present invention;

[0025] Figure 2 is a cross-sectional view of the bare battery cell provided by the specific embodiment of the present invention;

[0026] Figure 3 is a schematic diagram of the tabs arranged on the same side of the bare battery cell provided by the specific embodiment of the present invention;

[0027] Figure 4 It is a schematic diagram of arranging tabs on opposite sides of a bare battery cell provided by the specific embodiment of the present invention.

[0028] In the figure:

[0029] 1. Current collector; 11. Coating area; 111. First side; 112. Second side; 113. Third side; 12. Empty foil area; 13. Tab

[0030] 2. Separator

[0031] 110. Negative electrode plate; 120. Positive electrode plate. Specific embodiment

[0032] To make the technical problems solved by the present invention, the technical solutions adopted, and the achieved technical effects clearer, the technical solutions of the embodiments of the present invention will be further described in detail below with reference to the drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention.

[0033] As Figure 1 shown, this embodiment provides a segmented and spaced-coated electrode plate, which can generally be made into a negative electrode plate 110 or a positive electrode plate 120. The segmented and spaced-coated electrode plate includes a coating material and a current collector 1, and the coating material is coated on the current collector 1 to form a coating area 11. The coating area 11 of the negative electrode plate 110 is configured to be able to completely cover the coating area 11 of the positive electrode plate 120 to ensure the effective transmission of current. In this embodiment, the coating area 11 is rectangular. The area on the surface of the current collector 1 that is not coated with the coating material forms an empty foil area 12.

[0034] Both the front and back sides of the current collector 1 are coated with a plurality of coating areas 11 at intervals along the length direction of the current collector 1. The coating areas 11 located on the front side of the current collector 1 and the coating areas 11 located on the back side of the current collector 1 are symmetrically distributed with respect to the current collector 1. The sizes and directions of the multiple coating areas are exactly the same, and the interval length a n between the nth coating area and the (n - 1)th coating area = a1 + (n - 1) * b, where n is an integer greater than or equal to 2, and b is the tolerance. Such a setting makes the coating areas and the empty foil areas of the segmented and spaced-coated electrode plate separated from each other, preventing the coating material from falling off during the folding process of the electrode plate. Compared with the traditional continuously coated electrode plate, the transmission path of electrons is optimized. In the segmented and spaced-coated electrode plate, electrons are transmitted to the tabs through the spaced empty foil areas, reducing the internal resistance of the battery cell and optimizing the high-rate charge and discharge performance of the battery cell.

[0035] Specifically, when the segmented and spaced coated electrode sheet is made into the negative electrode sheet 110, the current collector 1 is made of aluminum foil. When the segmented and spaced coated electrode sheet is made into the positive electrode sheet 120, the current collector 1 is made of copper foil.

[0036] When the segmented and spaced coated electrode sheet is made into the negative electrode sheet 110, the first term of the interval length in the negative electrode sheet 110 is a′1, and 0 < a′1 ≤ 5 mm.

[0037] When the segmented and spaced coated electrode sheet is made into the positive electrode sheet 120, the first term of the interval length in the positive electrode sheet 120 is a″1, and a″1 = a′1 + l1*c + l2*d + l3*2, where l1 is the cold pressing thickness of the negative electrode sheet 110, usually 50 μm to 200 μm. l2 is the cold pressing thickness of the positive electrode sheet 120, usually 100 μm to 300 μm. l3 is the thickness of the separator; c is the negative electrode expansion coefficient, 1.05 ≤ c ≤ 2; d is the positive electrode expansion coefficient, 1.02 ≤ d ≤ 1.8.

[0038] The tolerance of the interval length is b, and b = l1*c + l2*d + l3*2, where l1 is the cold pressing thickness of the negative electrode sheet 110, l2 is the cold pressing thickness of the positive electrode sheet 120, l3 is the thickness of the separator; c is the negative electrode expansion coefficient, 1.05 ≤ c ≤ 2; d is the positive electrode expansion coefficient, 1.02 ≤ d ≤ 1.8.

[0039] Each rectangular material area 11 includes four sides, the first side 111, the second side 112, the third side 113 and the fourth side. The first side 111 and the second side 112 are perpendicular to the length direction of the current collector 1, and the third side 113 and the fourth side are parallel to the length direction of the current collector 1. The outer sides of the first side 111, the second side 112 and the third side 113 of each material area 11 are all empty foil areas 12. The empty foil areas 12 on the outer sides of the first side 111 and the second side 112 are used for winding forming, and the empty foil area 12 on the outer side of the third side 113 is used for making the tab.

[0040] Two material areas 11 located at symmetrical positions on the front and back sides of the current collector 1 form a material area group, and each material area group is provided with 1 tab 13. When the segmented and spaced coated electrode sheet is made into the negative electrode sheet 110, this tab is the negative electrode tab; when the segmented and spaced coated electrode sheet is made into the positive electrode sheet 120, this tab is the positive electrode tab.

[0041] Such as Figure 2As shown in the figure, this embodiment also provides a bare battery cell, which includes a segmented and spaced coated electrode sheet and a separator 2. The segmented and spaced coated electrode sheet includes two types: a positive electrode sheet 120 and a negative electrode sheet 110. The positive electrode sheet 120, the negative electrode sheet 110, and the separator 2 are stacked layer by layer. Exemplarily, the stacking method can be five layers: separator 2, positive electrode sheet 120, separator 2, negative electrode sheet 110, and separator 2. After stacking, it is continuously wound in the same direction to form a bare battery cell body. The cross-section of the bare battery cell body is rectangular, including empty foil parts at opposite ends and material area parts at the other pair of opposite ends. The material area 11 is entirely located in the material area part of the bare battery cell body. Among them, the positive electrode tab and the negative electrode tab do not overlap. Exemplarily, as Figure 3 shown, the positive electrode tab and the negative electrode tab can be located on the same side of the bare battery cell. Or as Figure 4 shown, the positive electrode tab and the negative electrode tab can also be located on opposite sides of the bare battery cell.

[0042] This bare battery cell overcomes the defects of the arc ends of the bare battery cell in the prior art, ensures that the CB value of the bare battery cell does not deviate from the design value, and during the discharge process, the current density on both sides of the current collector is consistent, preventing voltage polarization from causing voltage instability. In addition, the structural member for accommodating the bare battery cell is usually a regular cuboid. Making the bare battery cell into a cube can better fit the aluminum shell and improve the energy density.

[0043] Furthermore, continuing to refer to Figure 1 , when the segmented and spaced coated electrode sheet is wound into a bare battery cell, the misalignment range between multiple positive electrode tabs distributed vertically in the cross-section is ±10 mm, and the misalignment range between multiple negative electrode tabs is also ±10 mm.

[0044] Note that the above is only a preferred embodiment of the present invention and the applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described here. Various obvious changes, re-adjustments, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, it can also include more other equivalent embodiments, and the scope of the present invention is determined by the scope of the appended claims.

[0045] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is 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 thus should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions.

[0046] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

Claims

1. A segmented and spaced coated electrode, characterized in that, Comprising: The material regions (11) are provided on the front and back surfaces of the current collector (1) and are spaced apart along the length direction of the current collector (1). The material regions (11) are formed by coating a dressing and are formed into rectangles. The empty foil regions (12) are provided around each of the material regions (11). The sizes and directions of multiple said material areas (11) are exactly the same, and the interval length between the nth said material area (11) and the (n - 1)th said material area (11) , where is an integer greater than or equal to 2, and b is the common difference; When the segmented spaced coating electrode sheet is made into a negative electrode sheet (110), the first term of the spaced length in the negative electrode sheet (110) is , 0 < ≤ 5 mm; When the segmented spaced coating electrode sheet is made into a positive electrode sheet (120), the first term of the spaced length in the positive electrode sheet (120) is , , where is the cold pressing thickness of the negative electrode sheet (110), is the cold pressing thickness of the positive electrode sheet (120), is the separator thickness; is the negative electrode expansion coefficient, ; is the positive electrode expansion coefficient, ; The tolerance of the interval length is , , where is the cold-pressed thickness of the negative electrode plate (110), is the cold-pressed thickness of the positive electrode plate (120), is the separator thickness; is the expansion coefficient of the negative electrode, ; is the expansion coefficient of the positive electrode, ; The material region (11) of the negative electrode tab (110) is configured to be able to completely cover the material region (11) of the positive electrode tab (120).

2. The segmented and spaced coating electrode sheet according to claim 1, wherein, On the outer sides of the first side (111), the second side (112), and the third side (113) of each of the material regions (11) are the empty foil regions (12). The first side (111) and the second side (112) are perpendicular to the length direction of the current collector (1), and the third side (113) is parallel to the length direction of the current collector (1).

3. The segmented spaced coating electrode sheet according to claim 1, wherein, Two of the material regions (11) located at symmetric positions on the front and back surfaces of the current collector (1) form a material region group, and one tab (13) is provided for each of the material region groups.

4. A bare battery cell, characterized in that, Comprising the segmented and spaced coating electrode tab as described in any one of claims 1-3 and a separator (2). The segmented and spaced coating electrode tab includes two types: a positive electrode tab (120) and a negative electrode tab (110). After laminating the positive electrode tab (120), the negative electrode tab (110), and the separator (2) in layers and continuously winding them in the same direction, a bare battery cell body is formed. The cross-section of the bare battery cell body is rectangular, including empty foil portions at opposite ends and material region portions at the other pair of opposite ends. The material region (11) is located in the material region portion of the bare battery cell body.

5. The bare battery cell according to claim 4, wherein The positive electrode tab (120) is provided with a positive electrode tab, and the negative electrode tab (110) is provided with a negative electrode tab. The positive electrode tab and the negative electrode tab do not overlap.

6. The bare battery cell according to claim 5, characterized in that, After winding, the misalignment range of the positive electrode tab or the negative electrode tab is ±10 mm.

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