Diaphragm of battery cell, battery cell and battery pack

Abstract

The utility model relates to the technical field of batteries, and discloses a diaphragm of a battery cell, the battery cell and a battery pack. The separator includes a base film and a hybrid coating. The mixed coating is coated on a single surface or double surfaces of the base film; the mixed coating comprises a heat-resistant material and polymer particles, the particle size of the polymer particles is larger than that of the heat-resistant material, the polymer particles at least partially protrude out of the heat-resistant material to form supporting protrusions, and the supporting protrusions are suitable for forming a gap between the diaphragm and the pole piece after the diaphragm and the pole piece are laminated. According to the diaphragm of the battery cell provided by the utility model, the electrolyte infiltration effect of the pole piece can be improved. And meanwhile, the polymer particles have relatively strong electrolyte absorption performance, can absorb and store part of electrolyte, are beneficial to infiltration of a battery cell pole piece, and continuously release the electrolyte in the cycle process of the lithium battery cell for supplementing the electrolyte consumed by the pole piece, so that the cycle life of the battery cell is prolonged.

Description

TECHNICAL FIELD

[0001] The utility model relates to battery technology field, concretely relates to the diaphragm of electric core, electric core and battery package. BACKGROUND

[0002] Lithium ion battery has the advantages of high specific energy, low self-discharge, good cycle performance, no memory effect and green environmental protection, is the most promising high-efficiency secondary battery and the fastest developing chemical energy storage power source at present. In recent years, lithium ion battery is widely used in various fields.

[0003] Because the large cylindrical electric core adopts the winding structure, the winding core is composed of the positive plate, the negative plate and the diaphragm. The tab processing mode of the positive and negative poles has two modes of full tab rubbing and die cutting into multiple tabs. The infiltration path of the electrolyte after injection is mainly from the tab of the positive and negative poles to the middle of the plate. Due to the electrolyte infiltration path and the high assembly ratio of the large cylindrical electric core, the middle of the positive and negative plates of the large cylindrical electric core often forms a color difference stripe of insufficient infiltration, especially the positive plate. SUMMARY

[0004] Therefore, the utility model provides a kind of diaphragm of electric core, electric core and battery package to solve the problem of uneven infiltration of electric core plate.

[0005] In a first aspect, the utility model provides a kind of diaphragm of electric core, including base film and mixed coating. Mixed coating is coated on one side or both sides of base film. Mixed coating is formed by mixed slurry coating and solidification. Mixed slurry includes heat-resistant material and polymer particles. Heat-resistant material solidification forms heat-resistant material layer. Polymer particles are embedded in heat-resistant material layer. The particle size of polymer particles is larger than the thickness of heat-resistant material layer. Polymer particles at least partially protrude from heat-resistant material layer to form support protrusions. Support protrusions are suitable for forming a gap between diaphragm and plate after diaphragm and plate are stacked.

[0006] Beneficial effects: the diaphragm of electric core provided by the utility model has mixed coating on the surface of base film. Mixed coating contains heat-resistant material and polymer particles. Because the particle size of polymer particles is large, polymer particles are not completely embedded in heat-resistant material layer after mixed coating with heat-resistant material. Part of polymer particles is exposed from heat-resistant material layer. Mixed coating presents several support protrusions. A gap is formed between diaphragm and plate after diaphragm and plate are stacked due to the existence of support protrusions. The gap can store electrolyte. The electrolyte infiltration effect of plate is improved. Polymer particles have strong electrolyte absorption performance. Polymer particles can absorb and store part of electrolyte. It is beneficial to the infiltration of electric core plate. Polymer particles continuously release electrolyte during the cycle of lithium electric core to supplement the consumption of electrolyte by plate, thereby improving the cycle life of electric core.

[0007] In an alternative embodiment, the particle size of the polymer particles is D, 2 μm≤D≤5 μm.

[0008] In an alternative embodiment, the electrolyte swelling rate of the polymer particles is 50% to 70%.

[0009] In an alternative embodiment, the polymer particles comprise one or a combination of polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyethylene oxide, and polymethyl methacrylate.

[0010] In an alternative embodiment, the heat-resistant material comprises alumina, and the particle size is in the range of 0.3 μm to 1.5 μm;

[0011] Alternatively, the heat-resistant material comprises boehmite, and the particle size is in the range of 0.3 μm to 2.0 μm;

[0012] Alternatively, the heat-resistant material comprises magnesium hydroxide, and the particle size is in the range of 0.5 μm to 5.0 μm;

[0013] Alternatively, the heat-resistant material comprises nanofibers, and the diameter is in the range of 4 nm to 20 nm, and the length is in the range of 100 nm to 500 nm;

[0014] Alternatively, the heat-resistant material comprises aramid fibers, and the aramid fibers comprise para-aramid and meta-aramid, and the diameter is in the range of 0.01 μm to 20 μm, and the length is in the range of 0.1 μm to 2000 μm.

[0015] In an alternative embodiment, the thickness of the heat-resistant material layer is T1, and 0.5 μm≤T1≤5 μm.

[0016] In an alternative embodiment, the base film is a PP film or a PE film, and the base film is prepared by a dry method or a wet method;

[0017] Alternatively, the base film is a composite film composed of PP, PE, and a PP three-layer film.

[0018] Alternatively, the base film is a non-woven fabric film.

[0019] In an alternative embodiment, the thickness of the base film is T2, and 5 μm≤T2≤20 μm, and the porosity of the base film is in the range of 30% to 80%.

[0020] In a second aspect, the utility model also provides a kind of electric core, including shell, roll core and electrolyte. Roll core is located in shell;Roll core includes positive plate, negative plate and the diaphragm of the electric core of any one of above technical solutions, and diaphragm is located between positive plate and negative plate;Electrolyte is located in shell, and infiltrates roll core.

[0021] Beneficial effects: because the battery cell includes the diaphragm of the battery cell, has the same effect with the diaphragm of the battery cell, and here is not repeated.

[0022] In a third aspect, the utility model also provides a battery pack, including the battery cell in above technical scheme.

[0023] Beneficial effects: because the battery pack includes the battery cell, has the same effect with the battery cell, and here is not repeated. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the specific embodiment of the utility model or the technical scheme in prior art, the following will briefly introduce the drawing needed to be used in the specific embodiment or prior art description, and obviously, the drawing in the following description is some embodiments of the utility model, and for those skilled in the art, other drawings can also be obtained according to these drawings without creative labor.

[0025] Fig. 1 It is the real picture of the pole piece of poor infiltration;

[0026] Fig. 2 It is the real picture of the pole piece of sufficient infiltration;

[0027] Fig. 3 It is the structure schematic diagram of the section of the diaphragm of the battery cell provided by the utility model embodiment.

[0028] EXPLANATION OF REFERENCE NUMERALS:

[0029] 1, base film;2, mixed coating;21, heat-resistant material layer;22, polymer particles. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantage of the utility model embodiment more clear, the following will combine the drawing in the utility model embodiment, and the technical scheme in the utility model embodiment is clearly and completely described, obviously, the described embodiment is a part of the embodiment of the utility model, not all the embodiment.Based on the embodiment in the utility model, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the utility model.

[0031] The following will combine Figs. 1-3 , and describe the embodiment of the utility model.

[0032] According to the embodiment of the utility model, first, a diaphragm of an electric core is provided, which comprises a base film 1 and a mixed coating 2. The mixed coating 2 is coated on one side or both sides of the base film 1. The mixed coating 2 is formed by coating and curing a mixed slurry, which comprises heat-resistant material and polymer particles 22. The heat-resistant material is cured to form a heat-resistant material layer 21, and the polymer particles 22 are embedded in the heat-resistant material layer 21. The particle size of the polymer particles 22 is greater than the thickness of the heat-resistant material layer 21. The polymer particles 22 at least partially protrude from the heat-resistant material layer 21 to form support protrusions. The support protrusions are suitable for forming a gap between the diaphragm and the electrode plate after the diaphragm is stacked with the electrode plate.

[0033] The diaphragm of the electric core provided by the utility model has the mixed coating 2 on the surface of the base film 1, and the mixed coating 2 contains heat-resistant material and polymer particles 22. Because the particle size of the polymer particles 22 is large, the polymer particles 22 are not completely embedded in the heat-resistant material layer 21 after being mixed and coated with the heat-resistant material. Part of the polymer particles 22 is exposed from the heat-resistant material layer 21. Therefore, the mixed coating 2 has several support protrusions. After the diaphragm is stacked with the electrode plate, a gap is formed between the diaphragm and the electrode plate due to the presence of the support protrusions. The gap can store electrolyte, thereby improving the electrolyte infiltration effect of the electrode plate.

[0034] Meanwhile, the polymer particles 22 themselves have strong electrolyte absorption performance. The polymer particles 22 can absorb and store part of the electrolyte, which is conducive to the infiltration of the electrode plate of the electric core and continuously releases the electrolyte during the cycle of the lithium electric core to supplement the consumption of the electrolyte by the electrode plate, thereby improving the cycle life of the electric core.

[0035] In a conventional large cylindrical electric core, the diaphragm adopts a ceramic coating, and the positive electrode plate and the negative electrode plate may have a problem of poor electrolyte infiltration, as shown in FIG. 1. Fig. 1 The diaphragm of the electric core provided by the utility model replaces the original ceramic coating diaphragm and can solve the problem of poor infiltration of the positive electrode plate and the negative electrode plate. The infiltration effect is good, the poor electrolyte infiltration of the electrode plate is improved, and the result is shown in FIG. 2. There are no color difference stripes in the middle of the electrode plate. Fig. 2

[0036] In the utility model, the diaphragm is stacked between the positive electrode plate and the negative electrode plate. If the infiltration effect of the positive electrode plate is poor, the mixed coating 2 can be arranged on the surface of the diaphragm close to the positive electrode plate. Alternatively, in some embodiments, the mixed coating 2 is arranged on both surfaces of the diaphragm. In this way, the infiltration effects of the positive electrode plate and the negative electrode plate can be improved.

[0037] In some embodiments, the particle size of the polymer particles 22 is D, and 2 μm≤D≤5 μm.

[0038] ​In some embodiments, the electrolyte swelling rate of the polymer particles 22 is 50% to 70%.

[0039] In the traditional large cylindrical cell, the surface of the base film 1 is provided with a ceramic coating through the adhesive polyvinyl fluoride (PVDF), and the electrolyte swelling rate of the polyvinyl fluoride is 25% to 35%. The utility model adds polymer particles 22 in the mixed coating 2, and the electrolyte swelling rate of the polymer particles 22 is 50% to 70%, which is obviously improved. After the lithium cell is charged, the negative plate expands, and the gap between the diaphragm and the plate of the utility model and the electrolyte absorbed by the polymer particles 22 can be extruded to supplement the electrolyte infiltration of the positive and negative plates.

[0040] In some embodiments, the polymer particles 22 include one or a combination of polytetrafluoroethylene, polyvinyl fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyethylene oxide, and polymethyl methacrylate.

[0041] These materials are added to the heat-resistant material and coated on the surface of the base film 1 to form the mixed coating 2, which can achieve the above-mentioned effects of the utility model.

[0042] In some embodiments, the heat-resistant material includes alumina with a particle size in the range of 0.3 to 1.5 microns;

[0043] Alternatively, the heat-resistant material includes boehmite with a particle size in the range of 0.3 to 2.0 microns;

[0044] Alternatively, the heat-resistant material includes magnesium hydroxide with a particle size in the range of 0.5 to 5.0 microns;

[0045] Alternatively, the heat-resistant material includes nanofibers with a diameter in the range of 4 to 20 nanometers and a length in the range of 100 to 500 nanometers;

[0046] Alternatively, the heat-resistant material includes aramid fibers, which include para-aramid and meta-aramid fibers, with a diameter in the range of 0.01 to 20 microns and a length in the range of 0.1 to 2000 microns.

[0047] These materials are mixed with the polymer particles 22 and coated on the surface of the base film 1 to form the mixed coating 2, which can achieve the above-mentioned effects of the utility model.

[0048] In some embodiments, the thickness of the heat-resistant material layer 21 is T1, and 0.5 microns ≤ T1 ≤ 5 microns.

[0049] In some embodiments, the base film 1 is a PP film or a PE film, and the base film 1 is prepared by dry or wet method;

[0050] Alternatively, the base film 1 is a composite film composed of PP, PE, and PP three-layer film;

[0051] Or, the base film 1 is a non-woven fabric film.

[0052] The above three forms of structures can be used as the base film 1 of the separator.

[0053] In some embodiments, the thickness of the base film 1 is T2, 5 μm≤T2≤20 μm, and the porosity of the base film 1 is in the range of 30% to 80%.

[0054] The following provides specific experimental examples one to five, and comparative examples one to four, to verify the effect of the present application, and the specific results are shown in Table 1.

[0055] Table 1:

[0056]

[0057] Wherein, SOH is the abbreviation of state of health, that is, the health degree of the battery.

[0058] From Table 1, it can be seen that using the separator provided by the present application can significantly improve the infiltration effect of the pole piece, the surface of the pole piece has no color difference stripe, and sufficient infiltration is obtained. At the same time, the cycle life of the battery cell is also significantly improved compared with the comparative examples.

[0059] In the present embodiment, the preparation method of the separator is as follows:

[0060] The mixed slurry of the polymer particles 22 and the heat-resistant material is coated on the base film 1, and after drying, a mixed coating layer 2 is obtained. According to the weight fraction, the mixed slurry includes: 30-90 parts of heat-resistant material, 5-50 parts of polymer particles, 0.5-10 parts of dispersing agent, 0.5-10 parts of wetting agent, 3-10 parts of adhesive, and 0.1-8 parts of thickening agent.

[0061] Deionized water, a dispersing agent and a thickening agent are added to the blender, and low-speed stirring is performed until complete dissolution to obtain a first mixed slurry;

[0062] Polymer particles 22 are added to the first mixed slurry, and after stirring and dispersing, a second mixed slurry is obtained;

[0063] A wetting agent is added to the second mixed slurry, and after stirring evenly, an adhesive is added, and a third mixed slurry is obtained after sieving;

[0064] A heat-resistant material is added to the third mixed slurry, and after stirring, a mixed coating slurry is obtained;

[0065] The mixed coating slurry is coated on the separator, and after drying, a separator with a mixed coating layer 2 is obtained.

[0066] The dispersant is one or a combination of several of sodium tripolyphosphate, polyacrylic acid (PAA), polyethylene glycol (PEG), sodium polyacrylate (PAA-Na), potassium polyacrylate (PAA-K), sodium polymetaphosphate, sodium silicate, and sodium dodecyl sulfate.

[0067] The wetting agent is one or a combination of several of fluorinated alkyl methoxy ether alcohol, fluorinated alkyl ethoxy ether alcohol, alkyl phenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and fatty acid polyoxyethylene ether.

[0068] The adhesive is one or a combination of several of butyl benzene latex, pure benzene latex, benzene propylene latex, polymethyl acrylate, polybutyl methacrylate, polyethyl acrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, and polyurethane.

[0069] The thickening agent is one or a combination of several of hydroxymethyl cellulose, methylhydroxyethyl cellulose, sodium carboxymethyl cellulose (CMC-Na), polyacrylamide (PAM), and sodium alginate.

[0070] According to the embodiments of the utility model, the second aspect further provides an electric core, including shell, roll core and electrolyte. Roll core is located in the shell, roll core includes positive plate, negative plate and the diaphragm of any one of the electric core in above technical scheme, diaphragm is located between positive plate and negative plate, electrolyte is located in the shell, infiltrates roll core.

[0071] Because the electric core includes the diaphragm of the electric core, has the same effect with the diaphragm of the electric core, and here will not repeat.

[0072] According to the embodiments of the utility model, the third aspect further provides a battery pack, including the electric core in above technical scheme.

[0073] Because the battery pack includes the electric core, has the same effect with the electric core, and here will not repeat.

[0074] Although the embodiments of the utility model have been described in conjunction with the drawings, various modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the utility model, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A separator for an electric cell, characterized by, include: basement membrane; A mixed coating applied to one or both sides of the base film; The mixed coating is formed by coating and curing a mixed slurry, wherein the mixed slurry includes a heat-resistant material and polymer particles. The heat-resistant material is cured to form a heat-resistant material layer, and the polymer particles are embedded in the heat-resistant material layer. The particle size of the polymer particles is greater than the thickness of the heat-resistant material layer, and the polymer particles at least partially protrude from the heat-resistant material layer to form a supporting protrusion. The supporting protrusion is suitable for forming a gap between the diaphragm and the pole piece after the diaphragm and the pole piece are stacked.

2. The separator of the battery cell according to claim 1, characterized by, The particle size of the polymer particles is D, 2 μm≤D≤5 μm.

3. The separator of the battery cell according to claim 1 or 2, characterized in that, The electrolyte swelling rate of the polymer particles is 50% to 70%.

4. The separator of the battery cell according to claim 1 or 2, characterized in that, The polymer particles include one of polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyethylene oxide, and polymethyl methacrylate.

5. The separator of the battery cell according to claim 1 or 2, characterized in that: The heat-resistant material includes aluminum oxide, and the particle size is in the range of 0.3 μm to 1.5 μm; Alternatively, the heat-resistant material comprises boehmite, and the particle size thereof is in the range of 0.3 μm to 2.0 μm; Alternatively, the heat-resistant material comprises magnesium hydroxide, and the particle size thereof is in the range of 0.5 μm to 5.0 μm; or the heat-resistant material comprises nanofibers having a diameter in the range of 4 nm to 20 nm and a length in the range of 100 nm to 500 nm; Or the heat-resistant material includes aramid fiber with a diameter ranging from 0.01 μm to 20 μm and a length ranging from 0.1 μm to 2000 μm.

6. The separator of the battery cell according to claim 1 or 2, characterized by, The thickness of the heat-resistant material layer is T1, 0.5 μm≤T1≤5 μm.

7. The separator of the battery cell according to claim 1 or 2, characterized in that, The base film is a PP film or a PE film, and the base film is prepared by a dry process or a wet process; Alternatively, the base film is a composite film consisting of three layers of PP, PE, and PP; Alternatively, the base film is a non-woven fabric film.

8. The separator of the battery cell according to claim 1 or 2, characterized by, The thickness of the base film is T2, 5 μm≤T2≤20 μm, and the porosity of the base film is in the range of 30% to 80%.

9. An electric cell characterized by include: case; A winding core is provided in the shell; the winding core comprises a positive electrode sheet, a negative electrode sheet and a separator of the battery cell according to any one of claims 1 to 8, wherein the separator is provided between the positive electrode sheet and the negative electrode sheet; An electrolyte is disposed in the shell and soaks the winding core.

10. A battery pack, characterized by, Including the battery cell according to claim 9.

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