A negative electrode composite structure, its preparation method and lithium battery

Abstract

This invention discloses a negative electrode composite structure, its preparation method, and a lithium battery. The negative electrode composite structure includes: an electrode body with a roughened surface on one side; a separator disposed on the roughened surface side of the electrode body and cold-pressed together with the electrode body; and an adhesive layer disposed on the separator and interlocked with the voids formed by the roughened surface. This invention, through the above configuration, utilizes the interlocking force between the adhesive layer and the electrode body to complete the composite of the separator and the electrode body under cold pressing conditions. This eliminates the need for preheating composite methods used in existing technologies, effectively saving preheating time and achieving composite completion without heating. This ensures that lithium plating does not occur at the cell corners while also increasing the composite rate between the separator and the electrode, thereby improving production capacity.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a negative electrode composite structure, its preparation method, and a lithium battery. Background Technology

[0002] Lithium-ion batteries (LIBs) possess advantages such as high energy density, high operating voltage, long cycle life, low environmental pollution, low self-discharge, and no memory effect, making them one of the most promising rechargeable batteries. They are currently widely used in mobile phones, laptops, cameras, portable tools, electric vehicles, and energy storage. With the rapid development of electric vehicles and energy storage, the demand for lithium-ion batteries is even stronger.

[0003] In the production of square-wound battery cells, to mitigate electrode wrinkling caused by stress during charging and discharging, single- or double-sided adhesive-coated separators are often used to provide adhesion and a stress-relieving buffer. However, hot pressing after winding only covers the larger surfaces of the cell, leaving the corners untouched. This results in excessively large gaps between the positive and negative electrodes at the corners during the later stages of cycling. Coupled with insufficient electrolyte causing bridging, this ultimately leads to lithium plating at the corners, thus affecting the cell's lifespan.

[0004] In the existing technology, in order to avoid the impact on the service life of the battery cell due to lithium plating at the corner position, the following two technical means are usually used to achieve the above function. Specifically, Method 1: Apply adhesive to the corner position to improve the liquid retention effect; Method 2: Pre-heat composite the separator and negative electrode sheet, and then wind the composite electrode sheet and positive electrode.

[0005] However, both of the above methods have certain drawbacks: Method 1 requires more steps in actual operation and it is difficult to ensure the uniformity of the adhesive coating, which makes it difficult to guarantee the quality control of the product; while Method 2 requires the electrode or diaphragm to be preheated and then hot roller lamination, which consumes a lot of energy, has low lamination efficiency, and is not conducive to improving production capacity.

[0006] Therefore, a negative electrode composite structure, its preparation method, and a lithium battery are proposed to solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to provide a negative electrode composite structure, its preparation method, and a lithium battery, so as to ensure that lithium does not deposit at the corner of the cell while increasing the composite rate of the separator and the electrode, thereby increasing the production capacity.

[0008] To solve the above technical problems, the present invention provides a negative electrode composite structure, comprising:

[0009] An electrode body, wherein one side of the electrode body has a rough surface;

[0010] A diaphragm is disposed on the side of the electrode body having the rough surface and is cold-pressed together with the electrode body;

[0011] An adhesive layer is disposed on the diaphragm and fits into the gaps formed by the rough surface.

[0012] Furthermore, the roughened surface includes multiple slots, and the adhesive layer includes multiple adhesive particles;

[0013] The negative electrode composite structure satisfies: 1.2≤L2 / L1≤2, 0.05≤H2 / H1≤0.2;

[0014] Wherein, L1 and H1 are the maximum inner diameter and depth of the slot, respectively, and L2 and H2 are the maximum outer diameter and thickness of the granules, respectively.

[0015] Furthermore, the maximum inner diameter L1 of the slot is 50μm-120μm.

[0016] Furthermore, the depth H1 of the slot is one-quarter to one-half of the thickness of the electrode body.

[0017] Furthermore, the distance D between two adjacent slots is 0.1mm-4mm.

[0018] Furthermore, the maximum outer diameter L2 of the colloidal particles is 60μm-240μm.

[0019] Furthermore, the number of the colloidal particles, d, is 4000–20000 particles / cm². 2 .

[0020] Furthermore, the ratio of the maximum outer diameter L2 of the adhesive particle to the maximum inner diameter L1 of the slot is 15:8, and the ratio of the thickness H2 of the adhesive particle to the depth H1 of the slot is 1:10.

[0021] In another aspect, the present invention also proposes a method for preparing a negative electrode composite structure, comprising the following steps:

[0022] The surface of the electrode body is roughened to form a rough surface;

[0023] Apply an adhesive layer to the diaphragm;

[0024] The adhesive layer and the rough surface are fitted together under cold pressing conditions to complete the composite of the electrode body and the diaphragm.

[0025] Furthermore, the method for forming the rough surface includes laser etching and / or needle roller pressing.

[0026] Furthermore, the adhesive layer is applied to the diaphragm by spraying.

[0027] Furthermore, the cold pressing condition embedding includes a double-roll cold pressing composite process.

[0028] In another aspect, the present invention also proposes a lithium battery comprising the negative electrode composite structure described in the above embodiments, or the negative electrode composite structure obtained by the preparation method described in the above embodiments.

[0029] Compared with the prior art, the present invention has at least the following beneficial effects:

[0030] By setting an electrode body with a rough surface and a coating layer that interlocks with the gap formed by the rough surface on one side of the separator, the interlocking force between the coating layer and the electrode body allows the separator and electrode body to be composited under cold pressing conditions. This eliminates the need for preheating composite as in existing technologies, effectively saving the time required for preheating and achieving composite without heating. Furthermore, by pre-compositing the separator and electrode body, the lifespan of the battery cell can be effectively avoided due to lithium plating at the corners. Therefore, while ensuring that lithium plating does not occur at the corners of the battery cell, the composite rate of the separator and electrode body can also be increased, thereby improving production capacity. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the negative electrode composite structure in one embodiment of the present invention.

[0032] Figure 2 This is a flowchart illustrating the preparation method of the negative electrode composite structure in another embodiment of the present invention.

[0033] Reference numerals: 1. Electrode body; 11. Groove; 2. Diaphragm; 3. Coating layer. Detailed Implementation

[0034] The negative electrode composite structure, its preparation method, and lithium battery of the present invention will be described in more detail below with reference to the schematic diagrams, which illustrate preferred embodiments of the present invention. It should be understood that those skilled in the art can modify the present invention described herein while still achieving the advantageous effects of the present invention. Therefore, the following description should be understood as being of general knowledge to those skilled in the art and is not intended to limit the present invention.

[0035] The invention is described more specifically by way of example in the following paragraphs with reference to the accompanying drawings. The advantages and features of the invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0036] Example 1

[0037] like Figure 1 As shown, an embodiment of the present invention proposes a negative electrode composite structure, comprising:

[0038] The electrode body 1 has a rough surface on one side. By setting the rough surface, the diaphragm 2 can achieve initial bonding with the interlocking force between the adhesive layer 3 and the rough surface. Then, in the subsequent composite process, the two can be composited under cold pressing conditions. Therefore, compared with the hot pressing composite method in the prior art, the time required for preheating can be saved, thereby achieving the purpose of increasing production capacity.

[0039] It should be noted that in this embodiment, the electrode body 1 refers to the cathode sheet.

[0040] The diaphragm 2 is disposed on the side of the electrode body 1 having the rough surface and is cold-pressed together with the electrode body 1.

[0041] The adhesive layer 3 is disposed on the diaphragm 2 and fits into the gap formed by the rough surface. The positioning of the diaphragm 2 and the electrode body 1 is achieved by the interlocking force between the adhesive layer 3 and the rough surface, thereby ensuring the normal progress of subsequent cold pressing and lamination.

[0042] By setting an electrode body 1 with a rough surface and a coating layer 3 on one side of the separator 2 that fits into the gap formed by the rough surface, the intercalation force between the coating layer 3 and the electrode body 1 allows the separator 2 and the electrode body 1 to be composited under cold pressing conditions. This eliminates the need for preheating composite as in existing technologies, effectively saving the time required for preheating and achieving the function of composite without heating. Furthermore, by pre-compositing the separator 2 and the electrode body 1, the lifespan of the battery cell can be effectively avoided due to lithium plating at the corner of the cell. Therefore, while ensuring that lithium plating does not occur at the corner of the battery cell, the composite rate of the separator 2 and the electrode body 1 can also be increased to improve production capacity.

[0043] In a further embodiment, the rough surface and the adhesive layer 3 are further defined to improve the composite effect of the separator 2 and the electrode body 1, and correspondingly improve the production quality of the battery cell made from the negative electrode composite structure, that is, to ensure that the battery cell will not have lithium plating and that the electrode body 1 will not have wrinkles.

[0044] Specifically, the rough surface includes multiple slots 11, and the adhesive layer 3 includes multiple adhesive particles.

[0045] The negative electrode composite structure satisfies: 1.2≤L2 / L1≤2, 0.05≤H2 / H1≤0.2, where L1 and H1 are the maximum inner diameter and depth of the slot 11, respectively, and L2 and H2 are the maximum outer diameter and thickness of the adhesive particles, respectively. By limiting the maximum inner diameter and depth of the slot 11 and the maximum outer diameter and thickness of the adhesive particles, the air permeability of the separator 2 of the negative electrode composite structure is kept within a predetermined threshold, thereby improving the quality of the battery cell subsequently made from the negative electrode composite structure.

[0046] It should be noted that the air permeability of separator 2 represents the effect of the negative electrode composite structure preparation on the porosity of separator 2. The air permeability of separator 2 is measured by the time required for 100cc of gas to pass through a unit area sample, with the unit being s / 100cc. The air permeability of separator 2 is closely related to the quality of the battery cell. Specifically, when the air permeability of separator 2 exceeds a predetermined threshold, it will affect lithium-ion transport during subsequent charging and discharging processes, and the smaller interlayer spacing will also cause a certain degree of lithium plating. Conversely, when the air permeability of separator 2 is less than the predetermined threshold, the adhesion between separator 2 and the electrode body 1 is weak, failing to effectively improve the interface, thus leading to excessive cell thickness and affecting production quality.

[0047] Therefore, by limiting the size of the slot 11 and the adhesive particles, when the separator 2 and the electrode body 1 are combined, the air permeability of the separator 2 can be kept within a predetermined threshold, thereby improving the quality of the battery cell.

[0048] The maximum inner diameter L1 of the slot 11 is 50μm-120μm.

[0049] It should also be noted that the cross-section of the slot 11 is an inverted trapezoidal structure, which effectively increases the contact area between the slot 11 and the adhesive particles, thereby increasing the interlocking force between the two, which is beneficial to the subsequent cold pressing composite between the diaphragm 2 and the electrode body 1.

[0050] Furthermore, the depth H1 of the slot 11 is one-quarter to one-half of the thickness of the electrode body 1.

[0051] In a further embodiment, the distance D between two adjacent slots 11 is 0.1mm-4mm.

[0052] In other embodiments, the maximum outer diameter L2 of the colloidal particles is 60 μm-240 μm, and the distribution number d of the colloidal particles is 4000-20000 particles / cm. 2 .

[0053] It should be noted that the number of colloidal particles, d, is linearly related to the maximum outer diameter L2 of the colloidal particles. For example, when the maximum outer diameter L2 of the colloidal particles is 150 μm, the number of colloidal particles, d, is 8000 particles / cm.2 Therefore, I will not elaborate further here.

[0054] The granules can be made of materials such as acrylic, acrylate, polyvinylidene fluoride, and polytetrafluoroethylene.

[0055] In this embodiment, a specific example is also provided to better ensure that the battery cell will not experience lithium plating and that the electrode body 1 will not develop wrinkles.

[0056] Specifically, the ratio of the maximum outer diameter L2 of the adhesive particle to the maximum inner diameter L1 of the slot 11 is 15:8, and the ratio of the thickness H2 of the adhesive particle to the depth H1 of the slot 11 is 1:10.

[0057] The maximum outer diameter L2 of the adhesive particles is 50µm, the maximum inner diameter L1 of the slot 11 is 80µm, the depth H1 of the slot 11 is 20µm, the thickness H2 of the adhesive particles is 2µm, the distance D between two adjacent slots 11 is 2mm, and the distribution number d of the adhesive particles is 8000 particles / cm. 2 .

[0058] As an example, the method for manufacturing a battery cell includes the following steps:

[0059] Positive electrode preparation: LiFePO4, SP and PVDF are uniformly dispersed in NMP at a mass ratio of 96.5%:1.5%:2% to form a positive electrode slurry, which is then coated, dried, rolled, slit, die-cut, and made into a positive electrode sheet to be wound.

[0060] Negative electrode preparation: Artificial graphite, SP, CMC, and SBR are uniformly dispersed in deionized water at a mass ratio of 96%:1.2%:1%:1.8% to form a negative electrode slurry. This slurry is then coated, dried, rolled, slit, surface-drilled or grooved, die-cut, and cold-pressed with a separator 2 to form a composite negative electrode structure. The dimensions are: L1=80µm, H1=20µm, L2=150µm, H2=2µm, D=2mm, and d=8000 particles / cm. 2 .

[0061] The composite structure of positive and negative electrode sheets to be wound is wound into a battery cell, and then the finished battery cell is obtained through processes such as assembly, liquid injection and formation.

[0062] It should also be noted that the preparation process of the positive electrode sheet and the preparation process of the battery cell are existing technologies, so they will not be described in detail here. The difference between the negative electrode sheet preparation process and the traditional preparation process is that the separator 2 can be combined with the negative electrode sheet by cold pressing. The remaining steps are the same as the traditional negative electrode sheet preparation, so they will not be described in detail here.

[0063] In addition, the following comparative examples are provided to demonstrate the application of the battery cell when different sizes of granules and different sizes of slots 11 are combined.

[0064] Comparative Example 1: L2 is 80µm, and the rest is the same as the example above.

[0065] Comparative Example 2: L2 is 280µm, and the rest is the same as the example above.

[0066] Comparative Example 3: H2 is 0.4µm, and the rest is the same as the example above.

[0067] Comparative Example 4: H2 is 5µm, and the rest is the same as the example above.

[0068] The specific test data is shown in Table 1 below:

[0069] Table 1

[0070]

[0071] As can be clearly observed from Table 1 above, when different adhesive particles are fitted with slots 11 of different sizes, the air permeability of the separator 2 is significantly affected, which in turn affects the quality of the finished battery cell. Therefore, this product limits the relative relationship between the size of the adhesive particles and the slots 11 (i.e., 1.2≤L2 / L1≤2, 0.05≤H2 / H1≤0.2) so that the air permeability of the separator 2 can be kept within a predetermined threshold. This can effectively prevent lithium plating in the finished battery cell and wrinkles in the electrode body 1. Thus, while ensuring that lithium plating does not occur at the corners of the battery cell, it can also increase the composite rate of the separator 2 and the electrode body 1, thereby increasing the production capacity.

[0072] Example 2

[0073] like Figure 2 As shown, this embodiment, based on Embodiment 1, also proposes a method for preparing a negative electrode composite structure, including the following steps:

[0074] The surface of electrode body 1 is roughened to form a rough surface;

[0075] Apply an adhesive layer 3 to the diaphragm 2;

[0076] The adhesive layer 3 is then fitted to the rough surface under cold pressing conditions to complete the composite of the electrode body 1 and the diaphragm 2.

[0077] By utilizing the intercalation force between the rough surface and the adhesive layer 3, the separator 2 and the electrode body 1 can be initially positioned, allowing for direct cold pressing during the subsequent lamination process. Therefore, compared to the hot pressing lamination method in the prior art, this effectively shortens the time required to preheat the separator 2 and the electrode body 1. Furthermore, by pre-laminating the separator 2 and the electrode body 1 (i.e., the cathode sheet), the lithium plating at the corner of the cell can be effectively avoided, thus preventing the cell's lifespan from being affected. This achieves the goal of ensuring that lithium plating does not occur at the corner of the cell while also increasing the lamination rate between the separator 2 and the electrode body 1, thereby improving production capacity.

[0078] The method for forming the rough surface includes laser etching and / or needle roller pressing. That is, only a slot 11 for fitting with the adhesive layer 3 needs to be formed on the electrode body 1. The positioning work before cold pressing the diaphragm 2 and the electrode body 1 can be completed by the interlocking force between the adhesive layer 3 and the slot 11. This can solve the problems of long preparation time and high energy consumption caused by hot pressing in the prior art.

[0079] Furthermore, the cold pressing condition fitting includes a double-roll cold pressing composite process.

[0080] Example 3

[0081] This embodiment proposes a lithium battery, including the negative electrode composite structure described in Embodiment 1, or the negative electrode composite structure obtained by the preparation method described in Embodiment 2.

[0082] By setting up lithium batteries with a negative electrode composite structure, it is possible to increase the recombination rate between the separator and the electrode body while ensuring that lithium does not deposit at the corners of the cell, thereby increasing production capacity.

[0083] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A composite structure for a negative electrode sheet, characterized in that, include: An electrode body, wherein one side of the electrode body has a rough surface; A diaphragm is disposed on the side of the electrode body having the rough surface and is cold-pressed together with the electrode body; An adhesive layer is disposed on the diaphragm and fits into the gaps formed by the rough surface; The rough surface includes multiple slots, and the adhesive layer includes multiple adhesive particles; The negative electrode composite structure satisfies: 1.2≤L2 / L1≤2, 0.05≤H2 / H1≤0.2; Wherein, L1 and H1 are the maximum inner diameter and depth of the slot, respectively, and L2 and H2 are the maximum outer diameter and thickness of the granules, respectively.

2. The negative electrode composite structure as described in claim 1, characterized in that, The maximum inner diameter L1 of the slot is 50μm-120μm.

3. The negative electrode composite structure as described in claim 1, characterized in that, The depth H1 of the slot is one-quarter to one-half of the thickness of the electrode body.

4. The negative electrode composite structure as described in claim 1, characterized in that, The distance D between two adjacent slots is 0.1mm-4mm.

5. The negative electrode composite structure as described in claim 1, characterized in that, The maximum outer diameter L2 of the colloidal particles is 60μm-240μm.

6. The negative electrode composite structure as described in claim 1, characterized in that, The number of the colloidal particles, d, is 4000–20000 particles / cm². 2 .

7. The negative electrode composite structure as described in claim 1, characterized in that, The ratio of the maximum outer diameter L2 of the adhesive particle to the maximum inner diameter L1 of the slot is 15:8, and the ratio of the thickness H2 of the adhesive particle to the depth H1 of the slot is 1:

10.

8. A method for preparing a negative electrode composite structure as described in any one of claims 1-7, characterized in that, Includes the following steps: The surface of the electrode body is roughened to form a rough surface; Apply an adhesive layer to the diaphragm; The adhesive layer and the rough surface are fitted together under cold pressing conditions to complete the composite of the electrode body and the diaphragm.

9. The preparation method according to claim 8, characterized in that, The method for forming the rough surface includes laser etching and / or needle roller pressing.

10. The preparation method according to claim 8, characterized in that, The adhesive layer is applied to the diaphragm by spraying.

11. The preparation method according to claim 8, characterized in that, The cold pressing condition embedding includes a double-roll cold pressing composite process.

12. A lithium battery, characterized in that, It includes the negative electrode composite structure as described in any one of claims 1-7, or the negative electrode composite structure obtained by the preparation method as described in any one of claims 8-11.

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