Secondary battery isolating membrane and battery cell thereof

Abstract

The invention provides a secondary battery diaphragm and a battery cell thereof, and relates to the technical field of secondary batteries, the diaphragm body comprises a base layer, two hot melting layers and two infiltration layers, the hot melting layers and the infiltration layers are alternately overlapped, the base layer is arranged below the hot melting layers, the thickness of the hot melting layers is 0.02-1.5 [mu] m, and the thickness of the infiltration layers is 0.02-1.5 [mu] m. The porosity of the infiltration layer is 45-85%, the thickness of the infiltration layer is 0.1-6 [mu] m, the infiltration layer and the base layer are arranged on the two outer surfaces of the diaphragm body respectively, the thickness of the diaphragm body is 0.6-2.5 [mu] m, the hot melting layer is composed of hot melting resin fibers with the diameter of 30-750 nm, an overlapping part is subjected to hot melting through hot melting equipment, and the thickness of the hot melting layer is 0.1-6 [mu] m. The tail end of the diaphragm body and the inner-layer diaphragm body can be adhered into a whole after being heated, glue-free packaging is completed, and the tail end of the diaphragm body is positioned through hot melting of the diaphragm body.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary batteries, and more specifically, to a secondary battery separator and a battery cell thereof. Background Art

[0002] Secondary batteries, also known as rechargeable batteries or storage batteries, refer to batteries that can be used continuously by activating the active materials by charging after the battery is discharged. Secondary batteries include lithium batteries. The bare cell in lithium batteries is composed of a separator and a pole piece. The traditional assembly process usually forms a flat structure by winding or laminating the positive electrode, the negative electrode and the separator. The separator plays an isolating role in the bare cell. In the battery structure, the width of the separator is slightly larger than the positive and negative pole pieces, and the excess part is the extension of the separator. In order to ensure that the positive and negative electrodes in the bare battery cell do not separate, the diaphragm will finally wrap around the entire assembly structure, and then the ends of the diaphragm will be glued and fixed with tape. Traditional tape usually contains polyethylene terephthalate (PET). Under the high temperature in the battery, this plastic will decompose to form dimethyl terephthalate (DMT) molecules, causing the battery to self-discharge. Even if the battery is left there, the shuttling molecules are always moving, so the traditional method of fixing the diaphragm with tape will affect the stability of the entire battery cell.

[0003] In view of this, the present application provides a secondary battery bare cell to solve the above problems. Summary of the invention

[0004] The technical problem to be solved by the present invention is that cutting errors are inevitable during the working process, and the defective product rate increases. In view of the problems existing in the prior art, a secondary battery isolation membrane and a battery cell thereof are provided.

[0005] The purpose and effect of the present invention are achieved by the following specific technical means: A secondary battery separator, comprising: The diaphragm body includes a base layer, a hot-melt layer and a wetting layer. The hot-melt layer and the wetting layer are two layers. The hot-melt layer and the wetting layer overlap alternately, and the base layer is arranged below the hot-melt layer. The thickness of the hot melt layer is 0.02 to 1.5 μm; The porosity of the wetting layer is 45 to 85%, and the thickness of the wetting layer is 0.1 to 6 μm.

[0006] A further preferred solution is that the wetting layer and the base layer are respectively arranged on two outer surfaces of the diaphragm body.

[0007] A further preferred embodiment: the thickness of the diaphragm body is 0.6 to 2.5 μm.

[0008] A further preferred embodiment: the hot-melt layer is composed of hot-melt resin fibers with a diameter of 30 to 750 nm.

[0009] A further preferred embodiment: the resin fiber is a mixture of one or more of polyethylene wax, polystyrene, polyvinyl chloride, polyacrylate copolymer or polyethylene-vinyl acetate copolymer; The melting temperature of the resin fiber is 160-230°C.

[0010] A further preferred embodiment: the wetting layer is composed of polymer nanofibers with excellent electrolyte wettability and a diameter of 30 to 750 nm, selected from epoxy, polyethylene, polypropylene, ethylene-vinyl acetate, polyester, polyamide resin and their mixture resins.

[0011] A further preferred solution is that the base layer is composed of polyethylene, polypropylene and a mixture thereof, and the polyethylene is high-density polyethylene or ultra-high molecular weight polyethylene.

[0012] A further preferred embodiment is as follows: the viscosity of the hot melt layer is 200 to 700 CPs, and the electrical conductivity is 6.0 to 12.0 ms / cm; the viscosity of the wetting layer is 300 to 700 CPs, and the electrical conductivity is 15.0 to 30.0 ms.

[0013] A further preferred solution: comprising the aluminum-plastic film described in claims 1-8, and also comprising pole pieces, wherein the diaphragm body is assembled with pole pieces by winding or Z-shaped folding, the pole pieces are located between the diaphragm body layer structures, and the diaphragm body at the end of the battery cell is wound around the inner diaphragm body for at least one week to form an overlapping portion.

[0014] A further preferred solution is that the overlapping portion is formed with a hot melting point by hot melting the double-layer diaphragm body through hot melting equipment.

[0015] Beneficial effects of the present invention: 1. The diaphragm body at the end of the battery cell is wound around the inner diaphragm body for at least one week, and the overlapping part is melted by hot-melt equipment. The end of the diaphragm body and the inner diaphragm body will be adhered together after heating to complete the glue-free packaging. The end of the diaphragm body is positioned by hot-melting the diaphragm body, which effectively reduces the self-discharge of the battery caused by the decomposition of plastic substances in traditional tapes to form dimethyl terephthalate (DMT) molecules.

[0016] 2. When the hot melt equipment is hot-melting the diaphragm body, it can be a full pressure type or a point pressure type. The hot melt head of the hot melt equipment is used to apply high temperature to the diaphragm body, and the hot-melt resin fiber will melt, while the impregnation layer and the base layer will be adhered. The thickness of the hot melt layer is preferably 1μm, which is relatively thick and is not easy to penetrate after hot melting, thereby protecting the integrity of the surface of the diaphragm body and improving the battery efficiency. The viscosity between the hot melt layer and the impregnation layer is strong, which can improve the overall structural strength of the diaphragm body. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below in conjunction with the accompanying drawings.

[0018] Figure 1 It is a schematic diagram of the overall structure assembly of the present invention (laminated battery core); Figure 2 It is a schematic diagram of the overall structure assembly of the present invention; Figure 3 It is a schematic diagram of the overall structural assembly plan of the present invention (wound battery cell); Figure 4 It is a schematic diagram of the overall structure assembly of the present invention; Figure 5 It is a schematic diagram of the overall structure assembly of the present invention; Figure 6 It is a schematic diagram of the overall structure assembly of the present invention; Figure 7 It is a partial schematic diagram of the overlapping portion structure of the present invention; Figure 8 It is a schematic diagram of the diaphragm structure of the present invention.

[0019] Figure 1-Figure 8 Middle: pole piece (1), diaphragm body (2), base layer (201), hot melt layer (202), wetting layer (203), overlapping portion (3), hot melt point (4). Implementation

[0020] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, Figure 1-Figure 8 The present invention is further described in detail with specific embodiments. The following embodiments are only examples for implementing the present invention. It must be pointed out that the disclosed embodiments do not limit the scope of the present invention. On the contrary, changes and modifications made without departing from the scope of the present invention are all within the scope of patent protection of the present invention.

[0021] See also Figure 1-Figure 8A battery cell comprises a diaphragm body 2 and a pole piece 1, wherein the diaphragm body 2 is wound or folded in a Z-shape to assemble the pole piece 1, the pole piece 1 comprises a positive pole piece 1 and a negative pole piece 1, the positive pole piece 1 and the negative pole piece 1 are respectively distributed on both sides of the diaphragm body 2, and the diaphragm body 2 separates the two, and the width of the diaphragm body 2 is slightly larger than the width of the pole piece 1, so as to avoid contact between the positive pole piece 1 and the negative pole piece 1, such as Figure 1 The battery cell shown is a laminated battery cell. Figure 3 The cell shown is a wound cell; Furthermore, the diaphragm body 2 at the end of the cell is wound around the inner diaphragm body 2 for at least one cycle to form an overlapping portion 3 (such as Figure 3 and Figure 7 As shown), the bare battery core is wrapped around by the overlapping portion 3; The diaphragm body 2 includes a base layer 201, a hot melt layer 202 and a wetting layer 203. The hot melt layer 202 and the wetting layer 203 are both two layers. The hot melt layer 202 and the wetting layer 203 overlap alternately, and the base layer 201 is arranged under the hot melt layer 202. After the battery cell is assembled, the diaphragm body 2 is positioned. The overlapping part 3 is a double-layer diaphragm. The overlapping part 3 is hot-melted by a hot-melt device. The end of the diaphragm body 2 and the inner diaphragm body 2 will adhere to each other after being heated to complete the glue-free packaging. The end of the diaphragm body 2 is positioned by hot-melting the diaphragm body 2, which effectively reduces the self-discharge of the battery caused by the decomposition of plastic substances in traditional tapes to form dimethyl terephthalate DMT molecules.

[0022] See also Figure 7-Figure 8 , the wetting layer 203 and the base layer 201 are respectively arranged on the two outer surfaces of the diaphragm body 2; The thickness of the diaphragm body 2 is preferably 2 μm, and the hot melt layer 202 is composed of hot melt resin fibers with a diameter of 600 nm. The resin fibers are preferably a 1:1 mixture of polyacrylate copolymer and polyethylene-vinyl acetate copolymer. The melting temperature of the resin fibers is 200°C. When the hot melt device is hot-melting the diaphragm body 2, it can be a full pressure type or a point pressure type. The hot melt head of the hot melt device is used to heat the diaphragm body 2. The hot melt resin fibers will melt, and the impregnation layer 203 and the base layer 2 will be melted. 01 sticking, the thickness of the hot melt layer 202 is preferably 1 μm, which is relatively thick and not easy to penetrate after hot melting, protecting the integrity of the surface of the diaphragm body 2 and improving the battery quality. The viscosity of the hot melt layer 202 is 200 to 700 CPs, and the conductivity is 6.0 to 12.0 ms / cm. The viscosity of the wetting layer 203 is 300 to 700 CPs, and the conductivity is 15.0 to 30.0 ms. The viscosity between the hot melt layer 202 and the wetting layer 203 is strong, which can improve the overall structural strength of the diaphragm body 2; like Figure 4-Figure 6 The hot melt layer 202 can be in the shape of strips, dots, or circles.

[0023] like Figure 7 and Figure 8 The porosity of the wetting layer 203 is 45 to 85%, the thickness of the wetting layer 203 is 0.1 to 6 μm, and the wetting layer 203 is composed of polymer nanofibers with excellent electrolyte wettability and a diameter of 30 to 750 nm, selected from epoxy, polyethylene, polypropylene, ethylene-vinyl acetate, polyester, polyamide resin and their mixture resins. The electrolyte can penetrate well from the diaphragm body 2, thereby improving the wetting rate of the battery cell and enhancing the quality of the battery cell.

[0024] The base layer 201 is preferably made of polypropylene material, and the polyethylene is high-density polyethylene or ultra-high molecular weight polyethylene, which has strong toughness and is not easily scratched by the pole piece 1 or the aluminum-plastic film during the processing process.

Claims

1. A secondary battery separator, characterized in that: include The diaphragm body includes a base layer, a hot-melt layer and a wetting layer. The hot-melt layer and the wetting layer are two layers. The hot-melt layer and the wetting layer overlap alternately, and the base layer is arranged below the hot-melt layer. The thickness of the hot melt layer is 0.02 to 1.5 μm; The porosity of the wetting layer is 45 to 85%, and the thickness of the wetting layer is 0.1 to 6 μm.

2. A secondary battery separator according to claim 1, characterized in that: The wetting layer and the base layer are respectively arranged on two outer surfaces of the diaphragm body.

3. A secondary battery separator according to claim 1, characterized in that: The thickness of the diaphragm body is 0.6 to 2.5 μm.

4. A secondary battery separator according to claim 1, characterized in that: The heat-fusible layer is composed of heat-fusible resin fibers with a diameter of 30 to 750 nm.

5. A secondary battery separator according to claim 4, characterized in that: The resin fiber is a mixture of one or more of polyethylene wax, polystyrene, polyvinyl chloride, polyacrylate copolymer or polyethylene-vinyl acetate copolymer; The melting temperature of the resin fiber is 160-230°C.

6. A secondary battery separator according to claim 1, characterized in that: The wetting layer is composed of polymer nanofibers with excellent electrolyte wettability and a diameter of 30 to 750 nm, and is selected from epoxy, polyethylene, polypropylene, ethylene-vinyl acetate, polyester, polyamide resin and their mixture resins.

7. A secondary battery separator according to claim 1, characterized in that: The base layer is composed of polyethylene, polypropylene and a mixture thereof, and the polyethylene is high-density polyethylene or ultra-high molecular weight polyethylene.

8. A secondary battery separator according to claim 1, characterized in that: The viscosity of the hot melt layer is 200 to 700 CPs, and the electrical conductivity is 6.0 to 12.0 ms / cm. The viscosity of the wetting layer is 300 to 700 CPs, and the electrical conductivity is 15.0 to 30.0 ms.

9. A battery cell, characterized in that: The invention comprises the aluminum-plastic film as described in claims 1 to 8, and also comprises a pole piece, wherein the diaphragm body is assembled with the pole piece by winding or Z-shaped folding, the pole piece is located between the diaphragm body layer structure, and the diaphragm body at the end of the battery cell is wound around the inner diaphragm body for at least one week to form an overlapping portion.

10. A battery cell according to claim 9, characterized in that: The overlapping portion is formed with a hot melting point by hot melting the double-layer diaphragm body through hot melting equipment.

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