Diaphragm encapsulated negative electrode sheet and battery

Abstract

The utility model provides a kind of diaphragm encapsulation negative pole piece and battery, it is related to the technical field of negative pole piece, including the adhesive area of negative pole piece and its edge, and diaphragm covered on the negative pole piece;Wherein, adhesive area is equipped with force layer;Diaphragm is bonded with the force layer.The utility model in force layer can bind diaphragm contraction under high temperature condition, thus solved the problem that battery occurs internal short circuit due to diaphragm contraction under specific temperature, reached effectively reduce diaphragm contraction amplitude, delay positive and negative pole direct contact, improve the thermal stability of battery, to significantly improve the technical effect of battery security.

Description

Technical Field

[0001] This utility model relates to the technical field of negative electrode sheets, and in particular to a diaphragm-encapsulated negative electrode sheet and battery. Background Technology

[0002] The separator is a component that separates the positive and negative electrodes. Its material determines that it will shrink at high temperatures, which will cause the positive and negative electrodes of the battery to connect and induce thermal runaway in the cell.

[0003] In existing battery manufacturing processes, the negative electrode sheet and the separator are simply covered and encapsulated. Therefore, the separator lacks the corresponding restraining effect when it shrinks, resulting in severe separator shrinkage and causing direct contact between the positive and negative electrodes, which can lead to serious safety problems.

[0004] In view of the above, this utility model is hereby proposed. Utility Model Content

[0005] One of the objectives of this invention is to provide a separator-encapsulated negative electrode sheet, which uses the bonding area at the edge of the electrode sheet to form a force-applying layer to apply a binding force to the separator, thereby alleviating the shrinkage and deformation of the separator under high temperature conditions, delaying the direct contact between the positive and negative electrodes, and thus significantly improving battery safety.

[0006] The second objective of this invention is to provide a battery with good thermal stability and high safety.

[0007] In a first aspect, the present invention provides a diaphragm-encapsulated negative electrode sheet, including a negative electrode sheet and an adhesive area on its edge, and a diaphragm covering the negative electrode sheet;

[0008] The bonding area is provided with a force-applying layer;

[0009] The diaphragm is bonded to the force-applying layer.

[0010] Furthermore, the width of the force-applying layer is no greater than 0.2 times the width of the negative electrode sheet.

[0011] Furthermore, the width of the force-applying layer is less than 5 mm.

[0012] Furthermore, the thickness of the force-applying layer is no more than 0.5 times the thickness of the diaphragm.

[0013] Furthermore, the thickness of the applied layer is less than 10 μm.

[0014] Furthermore, the binder in the force-applying layer includes one or more combinations of polyvinylidene fluoride, polyacrylate, polycarbonate, polyvinyl alcohol, polyacrylamide, and styrene-butadiene rubber.

[0015] Furthermore, the diaphragm is a PP-based membrane or a PE-based membrane, or a multilayer diaphragm composed of a PP-based membrane, a PE-based membrane, and other coatings.

[0016] Furthermore, the thickness of the diaphragm is 5µm to 20µm.

[0017] Secondly, this utility model provides a battery comprising a separator-encapsulated negative electrode sheet as described in any of the above claims.

[0018] Furthermore, the separator in the diaphragm-encapsulated negative electrode separates the positive and negative electrodes.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] The diaphragm-encapsulated negative electrode sheet provided by this utility model has an adhesive area set at the edge of the negative electrode sheet, and a force-applying layer is coated in the adhesive area to form a force-applying layer. The force-applying layer contacts and adheres to the diaphragm, so that the diaphragm covers and encapsulates the negative electrode sheet. Since the force-applying layer formed by the adhesive area will provide a binding force in the opposite direction when the diaphragm shrinks, it can delay the shrinkage of the diaphragm and postpone the direct contact between the positive and negative electrodes, thereby achieving the purpose of significantly improving battery safety.

[0021] The battery provided by this invention has good thermal stability and high safety, and solves the problem of internal short circuit caused by diaphragm shrinkage in high-temperature environments. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 A cross-sectional view of a diaphragm-encapsulated negative electrode sheet provided in one embodiment of this utility model;

[0024] Figure 2 This is a schematic diagram of a diaphragm-encapsulated negative electrode sheet provided in one embodiment of the present invention.

[0025] Figure 3 This is a schematic diagram of a negative electrode in the prior art;

[0026] Figure 4 This is a physical image of the initial state of the sample obtained from the experiment.

[0027] Figure 5 This is a photograph of the diaphragm shrinkage of the sample obtained in the test case after treatment at 170℃.

[0028] Icons: 1-Negative electrode sheet; 11-Current collector; 12-Negative electrode active coating; 13-Taper; 3-Binding area; 31-Force application layer; 4-Separator. Detailed Implementation

[0029] The technical solution of this utility model will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0030] According to a first aspect of the present invention, a diaphragm-encapsulated negative electrode sheet is provided, comprising a negative electrode sheet and an bonding area at its edge, and a diaphragm covering the negative electrode sheet.

[0031] The bonding area is provided with a force-applying layer;

[0032] The diaphragm is bonded to the force-applying layer.

[0033] It should be noted that a slurry is prepared by blending negative electrode active material, conductive agent, binder and solvent. The negative electrode active material includes, but is not limited to, carbon materials, silicon-based materials and lithium metal. The obtained slurry is coated on the current collector and then dried, rolled and slit to obtain the negative electrode sheet.

[0034] In this invention, an adhesive bonding area is provided at the edge of the negative electrode sheet. A coating liquid containing an adhesive is applied to the adhesive bonding area to form a force-applying layer, which is then dried and encapsulated with a separator. Hot pressing can be used to bring the force-applying layer into contact with and bond it to the separator. When the battery temperature rises, the force-applying layer formed by the adhesive bonding area of ​​the negative electrode sheet provides a binding force in the opposite direction to the separator as it contracts, effectively reducing the extent of separator contraction and delaying direct contact between the positive and negative electrodes, thereby significantly improving battery safety.

[0035] In a preferred embodiment, the width of the force-applying layer is no greater than 0.2 times the width of the negative electrode sheet, that is, the width W of the force-applying layer is 0. <W≤0.2W 负 It is further preferred to be below 5mm, which ensures sufficient membrane binding force while also helping to avoid excessive negative electrode capacity loss.

[0036] In a preferred embodiment, the thickness of the force-applying layer is no greater than 0.5 times the thickness of the diaphragm, i.e., the thickness H of the force-applying layer is 0. <H≤0.5H 隔膜 It is further preferred to be below 10um, which ensures sufficient membrane binding force while also helping to maintain cell flatness.

[0037] In this invention, the adhesive in the force-applying layer includes, but is not limited to, one or more combinations of polyvinylidene fluoride, polyacrylate, polycarbonate, polyvinyl alcohol, polyacrylamide, and styrene-butadiene rubber, which helps to improve the bonding effect between the bonding area and the diaphragm and provides sufficient reverse binding force when the diaphragm shrinks.

[0038] A method for preparing a separator-encapsulated negative electrode includes the following steps:

[0039] First, the adhesive and solvent are mixed to obtain a coating liquid. The adhesive can be one or more of polyvinylidene fluoride (PVDF), polyacrylate, polycarbonate, polyvinyl alcohol, polyacrylamide, and styrene-butadiene rubber, but is not limited to these. The solvent can be N-methylpyrrolidone (NMP), water, acetone, etc., but is not limited to these.

[0040] Next, the obtained coating solution is applied to the diced negative electrode sheet, that is, the coating solution is applied to the bonding area set on the edge of the negative electrode sheet, and then dried to form a force-applying layer;

[0041] The negative electrode is then encapsulated with a diaphragm. Through hot pressing, the force-applying layer comes into contact with and bonds to the diaphragm. The diaphragm and the force-applying layer are firmly bonded together, resulting in a diaphragm-encapsulated negative electrode.

[0042] In this utility model, the negative electrode sheet is encapsulated with a diaphragm. Figure 1 and Figure 2 The negative electrode 1 is composed of a current collector 11, a negative electrode active coating 12, and a tab 13. At the same time, a bonding area 3 is provided at the edge of the negative electrode 1, and a force-applying layer 31 is provided on the bonding area 3. The diaphragm 4 is firmly bonded to the force-applying layer 31.

[0043] In summary, the separator-encapsulated negative electrode sheet of this invention provides a binding force in the opposite direction when the separator contracts due to the force-applying layer formed in the bonding area. This delays the separator contraction, postpones the direct contact between the positive and negative electrodes, and thus significantly improves battery safety.

[0044] In a preferred embodiment, the diaphragm can be a PP-based membrane or a PE-based membrane, or a multilayer diaphragm composed of a PP-based membrane, a PE-based membrane, and other coatings, and the thickness of the diaphragm can be 5µm to 20µm.

[0045] According to a second aspect of the present invention, a battery is provided, comprising a separator-encapsulated negative electrode sheet as described in any of the preceding claims.

[0046] In this invention, the diaphragm in the diaphragm-encapsulated negative electrode sheet can achieve physical isolation between the positive and negative electrodes.

[0047] The battery provided by this invention has good thermal stability and high safety, and solves the problem of internal short circuit caused by diaphragm shrinkage in high-temperature environments.

[0048] Example 1

[0049] A separator-encapsulated negative electrode includes a negative electrode and an bonding area at its edge, and a separator covering the negative electrode.

[0050] The diaphragm is selected from PE diaphragms with ceramic coating, with a thickness of 11µm, of which the base film thickness is 7µm;

[0051] The bonding area is provided with a force-applying layer, which has a width of 2mm and a thickness of 5um.

[0052] The diaphragm is bonded to the force-applying layer;

[0053] Specifically, the diaphragm-encapsulated negative electrode sheet in this embodiment is shown below. Figure 1 and Figure 2 The negative electrode 1 is composed of a current collector 11, a negative electrode active coating 12, and a tab 13. At the same time, a bonding area 3 is provided at the edge of the negative electrode 1, and a force-applying layer 31 is provided on the bonding area 3. The diaphragm 4 is firmly bonded to the force-applying layer 31.

[0054] The method for preparing the diaphragm-encapsulated negative electrode includes the following steps:

[0055] (1) First, the adhesive and solvent are mixed at a weight ratio of 3:17 to prepare an adhesive solution, which is used as a coating liquid;

[0056] The binder is selected from polyvinylidene fluoride (PVDF), and the solvent is selected from N-methylpyrrolidone (NMP).

[0057] (2) Apply the obtained coating liquid to the diced negative electrode sheet (W*L=58*88mm), that is, apply the coating liquid to the bonding area set on the edge of the negative electrode sheet, and dry it at 80℃ to form a force-applying layer;

[0058] (3) The negative electrode is encapsulated with a diaphragm. The force layer is brought into contact with and bonded to the diaphragm by hot pressing. The diaphragm and the force layer are firmly bonded to obtain the diaphragm-encapsulated negative electrode, which is denoted as sample 1.

[0059] Example 2

[0060] This embodiment provides a diaphragm-encapsulated negative electrode sheet, which differs from Embodiment 1 only in that the width of the force-applying layer is 0.5 mm;

[0061] The remaining structure and parameters are the same as in Example 1.

[0062] Example 3

[0063] This embodiment provides a diaphragm-encapsulated negative electrode sheet, which differs from Embodiment 1 only in that the width of the force-applying layer is 3.5 mm;

[0064] The remaining structure and parameters are the same as in Example 1.

[0065] Example 4

[0066] This embodiment provides a diaphragm-encapsulated negative electrode sheet, which differs from Embodiment 1 only in that the width of the force-applying layer is 5mm;

[0067] The remaining structure and parameters are the same as in Example 1.

[0068] Example 5

[0069] This embodiment provides a diaphragm-encapsulated negative electrode sheet, which differs from Embodiment 1 only in that the width of the force-applying layer is 15mm;

[0070] The remaining structure and parameters are the same as in Example 1.

[0071] Compared with Example 1, the drawback of this example is that the wider the force-applying layer, the higher the capacity loss of the negative electrode.

[0072] Example 6

[0073] This embodiment provides a diaphragm-encapsulated negative electrode sheet, which differs from Embodiment 1 only in that the thickness of the force-applying layer is 4µm;

[0074] The remaining structure and parameters are the same as in Example 1.

[0075] Example 7

[0076] This embodiment provides a membrane-encapsulated negative electrode sheet, which differs from Embodiment 1 only in that the thickness of the force-applying layer is 3µm;

[0077] The remaining structure and parameters are the same as in Example 1.

[0078] Example 8

[0079] This embodiment provides a diaphragm-encapsulated negative electrode sheet, which differs from Embodiment 1 only in that the thickness of the force-applying layer is 20 μm;

[0080] The remaining structure and parameters are the same as in Example 1.

[0081] Compared with Example 1, the drawback of this example is that the thickness of the force-applying layer is too large, which will affect the flatness of the battery.

[0082] Comparative Example 1

[0083] The difference between this comparative example and Example 1 is that the negative electrode containing the force-applying layer is removed, and only the separator is retained, which is referred to as Sample 2.

[0084] Comparative Example 2

[0085] The difference between this comparative example and Example 1 is that although there is a force-applying layer on the negative electrode sheet, it is not hot-pressed, so the separator and the force-applying layer do not adhere.

[0086] The rest were the same as in Example 1, and a membrane-encapsulated negative electrode sheet was obtained, which was designated as Sample 3.

[0087] Test case

[0088] The initial states of samples 1, 2, and 3 are shown in the figure. Figure 4 The figures show the initial states of sample 1, sample 2, and sample 3 from left to right.

[0089] Samples 1, 2, and 3 were placed in a heating chamber and heated to 170°C for 1 hour. The samples were then cooled and their condition was checked. Figure 5 The figures show the shrinkage of the diaphragms of samples 1, 2, and 3 after treatment at 170°C, from left to right. It can be seen that the diaphragm-encapsulated negative electrode sheet of Sample 1 in Example 1 has a significantly better shrinkage amplitude than the samples of Comparative Examples 1-2 because the force layer formed in the bonding area provides a reverse force when the diaphragm shrinks.

[0090] In summary, this invention solves the problem of internal short circuits caused by separator shrinkage in batteries under high-temperature environments, achieving the technical effect of effectively reducing the degree of separator shrinkage, delaying direct contact between positive and negative electrodes, and improving the thermal stability of the battery, thereby significantly improving battery safety.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A diaphragm-encapsulated negative electrode sheet, characterized in that, Includes the bonding area of ​​the negative electrode sheet and its edges, and the separator covering the negative electrode sheet; The bonding area is provided with a force-applying layer; The diaphragm is bonded to the force-applying layer.

2. The diaphragm-encapsulated negative electrode sheet according to claim 1, characterized in that, The width of the force-applying layer is no greater than 0.2 times the width of the negative electrode sheet.

3. The diaphragm-encapsulated negative electrode sheet according to claim 2, characterized in that, The width of the force-applying layer is less than 5 mm.

4. The diaphragm-encapsulated negative electrode sheet according to claim 1, characterized in that, The thickness of the force-applying layer is no more than 0.5 times the thickness of the diaphragm.

5. The diaphragm-encapsulated negative electrode sheet according to claim 4, characterized in that, The thickness of the force-applying layer is less than 10 μm.

6. The diaphragm-encapsulated negative electrode sheet according to any one of claims 1-5, characterized in that, The diaphragm is a PP-based membrane or a PE-based membrane, or a multilayer diaphragm composed of a PP-based membrane, a PE-based membrane, and other coatings.

7. The diaphragm-encapsulated negative electrode sheet according to claim 6, characterized in that, The thickness of the diaphragm is 5µm to 20µm.

8. A battery, characterized in that, Includes the diaphragm-encapsulated negative electrode sheet as described in any one of claims 1-7.

9. The battery according to claim 8, characterized in that, The diaphragm in the diaphragm-encapsulated negative electrode separates the positive and negative electrodes.

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