Battery diaphragm and secondary battery

Abstract

The utility model belongs to the technical field of batteries, and particularly relates to a battery diaphragm and a secondary battery, the battery diaphragm comprises a base membrane and a safety coating arranged on at least one surface of the base membrane, the surface of the base membrane is also provided with a heat-resistant coating, and the internal resistance rise voltage of the safety coating is at least 5V. According to the utility model, the internal resistance is increased after the voltage is increased through the safety coating, so that the current is reduced, and the overcharge safety performance of the battery is improved by reducing the calorific value.

Description

Technical Field

[0001] This utility model belongs to the technical field of batteries, specifically relating to a battery separator and a secondary battery. Background Technology

[0002] The battery separator is a membrane material between the positive and negative electrodes of a battery. It is a very critical part of the battery and has a direct impact on battery safety and cost. Its main functions are to isolate the positive and negative electrodes and prevent electrons in the battery from passing through freely, while allowing ions in the electrolyte to pass freely between the positive and negative electrodes.

[0003] When a battery is overcharged, its voltage will increase significantly, which will accelerate the electrochemical reaction inside the battery and generate more heat. At the same time, if the current is not properly controlled, it may also lead to an abnormal increase in current, further aggravating the heat generation. When the heat accumulates to a certain level, it may cause the battery to catch fire.

[0004] Therefore, there is an urgent need to propose a new technical solution to address the above problems. Utility Model Content

[0005] One of the objectives of this invention is to provide a battery separator that addresses the shortcomings of existing technologies by increasing the internal resistance of its safety coating as the voltage increases, thereby reducing the current and thus reducing heat generation to improve the safety performance of the battery during overcharging.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A battery separator includes a base film and a safety coating disposed on at least one surface of the base film. The surface of the base film is further provided with a heat-resistant coating, and the internal resistance rise voltage of the safety coating is at least 5V.

[0008] Preferably, the heat-resistant coating has a heat resistance temperature ≥130℃.

[0009] Preferably, the safety coating is disposed on one surface of the base film, and the heat-resistant coating is disposed on the other surface of the base film.

[0010] Preferably, the heat-resistant coating is disposed around the safety coating, and the heat-resistant coating has a U-shaped structure.

[0011] Preferably, the heat-resistant coating is disposed on one surface of the base film, and the safety coating is disposed on one surface of the heat-resistant coating.

[0012] Preferably, the heat-resistant coating is a ceramic coating.

[0013] Preferably, the coating area of ​​the safety coating is not less than the coating area of ​​the heat-resistant coating.

[0014] Preferably, the coating thickness of the safety coating is 0.5 to 10 μm.

[0015] Preferably, the thickness of the heat-resistant coating is 0.5 to 10 μm.

[0016] The second objective of this utility model is to provide a secondary battery, including the battery separator as described above.

[0017] The beneficial effects of this invention are as follows: This invention includes a base film and a safety coating disposed on at least one surface of the base film. The surface of the base film is also provided with a heat-resistant coating. The internal resistance of the safety coating increases with voltage by at least 5V. The safety coating of this invention increases its internal resistance after voltage increases, thereby reducing current and thus reducing heat generation to improve the safety performance of the battery during overcharging. The heat-resistant coating has a heat resistance temperature greater than or equal to 130℃. When the battery undergoes a thermal reaction, it can prevent thermal shrinkage leading to misalignment and also prevent current collector burrs, further improving safety performance. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of this utility model.

[0019] Figure 2 This is a schematic diagram of the overall structure of Embodiment 2 of this utility model.

[0020] Figure 3 This is a schematic diagram of the overall structure of Embodiment 3 of this utility model.

[0021] Figure 4 This is a schematic diagram of the overall structure of Embodiment 4 of this utility model.

[0022] The components are: 1. base film; 2. safety coating; 3. heat-resistant coating. Detailed Implementation

[0023] If certain terms are used in the specification and claims to refer to specific components, those skilled in the art will understand that manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The term "comprising" as used throughout the specification and claims is an open-ended term and should be interpreted as "comprising but not limited to." In this utility model, unless otherwise explicitly specified and limited, terms such as "installed," "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two elements. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0024] The following is in conjunction with the appendix Figures 1-4 The present invention will be described in further detail, but this is not intended to limit the scope of the present invention.

[0025] According to a first aspect of this utility model, a battery separator is provided, comprising a base film 1 and a safety coating 2 disposed on at least one surface of the base film 1. A heat-resistant coating 3 is also disposed on the surface of the base film 1. The internal resistance of the safety coating 2 increases with voltage by at least 5V, for example, it can be 5V, 6V, 7V, 8V, 9V, or 10V. The internal resistance of the safety coating 2 increases when the battery voltage increases, thereby reducing the current and thus reducing heat generation to improve the safety performance of the battery during overcharging. The safety coating 2 is a low-pore coating; when the battery is at a high voltage, the pores close, increasing the internal resistance and thus reducing the current. The increased internal resistance of the safety coating 2 after voltage increase reduces the current and thus reduces heat generation, improving the safety performance of the battery during overcharging. The heat-resistant coating 3 has a heat resistance temperature greater than or equal to 130℃. When the battery undergoes a thermal reaction, it can prevent thermal shrinkage leading to misalignment and also prevent current collector burrs, improving safety performance. The heat-resistant coating 3 and the safety coating 2 can be composited by gravure printing, spraying, or impregnation. Safety coating 2 includes polyaniline (PANI), polypyrrole (PPy), polythiophene (PTh) and their derivatives, or conductive polymer composites. The conductive polymer composites can be polyaniline / carbon nanotube composites, polypyrrole / graphene composites, etc. Polyaniline is a common conductive polymer material. At lower voltages, it can exhibit good conductivity through doping and other methods. However, when the voltage increases to a certain level, the polyaniline molecular chain may undergo structural changes, such as excessive oxidation or conformational alteration. This disrupts the internal conductive pathways, hinders carrier transport, and increases internal resistance. The internal resistance of polyaniline increases with increasing voltage because during charging and discharging, the electrode material undergoes a transition between a fully doped state and a fully dedoped state. In both states, the conductivity of polyaniline is very low, leading to increased internal resistance. Polypyrrole is also an important conductive polymer. Under increased voltage, polypyrrole may undergo overdoping or molecular structure disruption. Overdoping alters the crystal structure, affecting carrier transport; while molecular structure disruption leads to incomplete conductive networks, both increasing internal resistance. The resistance of polypyrrole increases with voltage because it experiences an "overpotential" phenomenon, which increases the ionic conductivity and capacitance of the polypyrrole film, thus increasing its electrochemical impedance. Polythiophene materials have wide applications in organic electronics. With increased voltage, polythiophene molecules may undergo oxidation or enhanced intermolecular interactions, affecting carrier mobility and leading to increased internal resistance. For example, at higher voltages, the side chains of polythiophene molecules may react, affecting the overall conductivity of the material.Conductive polymer composites are materials composed of conductive polymers and other materials, such as polyaniline / carbon nanotube composites and polypyrrole / graphene composites. When the voltage increases, the interaction between the components in the composite material may change, leading to an increase in interfacial resistance. At the same time, the conductive polymer part in the composite material may also be affected by the voltage, resulting in changes in its structure or properties, thereby increasing the overall internal resistance.

[0026] In some embodiments, the heat-resistant coating 3 has a heat resistance temperature ≥130°C, such as 130°C, 135°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C or 200°C, which can avoid the problem of misalignment caused by thermal shrinkage of the diaphragm.

[0027] In some embodiments, a safety coating 2 is disposed on one surface of a base film 1, a heat-resistant coating 3 is disposed on the other surface of a base film 1, and the base film 1 is disposed between the safety coating 2 and the heat-resistant coating 3.

[0028] In some embodiments, the heat-resistant coating 3 surrounds the safety coating 2, and the heat-resistant coating 3 and the safety coating 2 together form a U-shaped structure. Applying the heat-resistant coating 3 to the edges effectively prevents displacement problems caused by thermal shrinkage. In the U-shaped structure, the proportion of the heat-resistant coating 3 is less than 50%, for example, it can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, or 45%; the proportion of the safety coating 2 is more than 50%, for example, it can be 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%.

[0029] In some embodiments, a heat-resistant coating 3 is disposed on one surface of a base film 1, a safety coating 2 is disposed on one surface of a heat-resistant coating 3, and the heat-resistant coating 3 is disposed between the base film 1 and the safety coating 2.

[0030] In some embodiments, the heat-resistant coating 3 is a ceramic coating. The ceramic can be at least one of alumina, zirconium dioxide, silicon carbide, silicon nitride, boehmite, silicon dioxide, titanium dioxide, magnesium dioxide, barium sulfate, zirconium oxide, and calcium oxide, which improves the high-temperature resistance of the battery.

[0031] In some embodiments, the coating area of ​​the safety coating 2 is not less than the coating area of ​​the heat-resistant coating 3.

[0032] In some embodiments, the coating thickness of the safety coating 2 is 0.5 to 10 μm, for example, it can be 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm.

[0033] In some embodiments, the coating thickness of the heat-resistant coating 3 is 0.5 to 10 μm, for example, it can be 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm.

[0034] According to a second aspect of the present invention, the present invention also provides a secondary battery, comprising a battery separator, a positive electrode, a negative electrode, and an electrolyte as described above.

[0035] The positive or negative electrode includes a current collector, and a positive or negative active material layer is disposed on the surface of the current collector. The areal density of the positive or negative active material layer is 10–15 mg / cm³. 2 For example, it could be: 10mg / cm 2 11mg / cm 2 12mg / cm 2 13mg / cm 2 14mg / cm 2 Or 15mg / cm 2 .

[0036] The positive electrode active material layer includes a positive electrode active substance, which may be, but is not limited to, a chemical formula such as Li. a Ni x Co y M z O 2-b N b (where 0.95≤a≤1.2, x>0, y≥0, z≥0, and x+y+z=1, 0≤b≤1, M is selected from one or more combinations of Mn and Al, and N is selected from one or more of F, P, and S) The positive electrode active material may also be, but is not limited to, LiCoO2, LiNiO2, LiVO2, LiCrO2, LiMn2O4, LiCoMnO4, Li2NiMn3O8, LiNi 0.5 Mn 1.5One or more of O4, LiCoPO4, LiMnPO4, LiFePO4, and LiNiPO4 are used. The positive electrode active material can also be modified. Methods for modifying the positive electrode active material are known to those skilled in the art. For example, coating, doping, and other methods can be used to modify the positive electrode active material. The materials used for modification can be one or more combinations of Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce, and W, including but not limited to. The negative electrode active material layer includes a negative electrode active material, which can be one or more of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon-based materials, tin-based materials, lithium titanate, or other metals that can form alloys with lithium. The graphite can be selected from one or more of artificial graphite, natural graphite, and modified graphite; the silicon-based material can be selected from one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, and silicon alloys; the tin-based material can be selected from one or more of elemental tin, tin oxide compounds, and tin alloys.

[0037] The electrolyte comprises an organic solvent, a lithium electrolyte salt, and additives. The lithium electrolyte salt can be LiPF6 and / or LiBOB used in high-temperature electrolytes; it can also be at least one of LiBF4, LiBOB, and LiPF6 used in low-temperature electrolytes; it can also be at least one of LiBF4, LiBOB, LiPF6, and LiTFSI used in overcharge-resistant electrolytes; or it can be at least one of LiClO4, LiAsF6, LiCF3SO3, and LiN(CF3SO2)2. The organic solvent can be a cyclic carbonate, including PC and EC; it can also be a chain carbonate, including DFC, DMC, or EMC; or it can be a carboxylic acid ester, including MF, MA, EA, and MP. The additives include, but are not limited to, at least one of the following: film-forming additives, conductive additives, flame-retardant additives, overcharge-resistant additives, additives for controlling H2O and HF content in the electrolyte, additives for improving low-temperature performance, and multifunctional additives.

[0038] This secondary battery can be used in vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, among others. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc.

[0039] Obviously, this utility model includes a base film and a safety coating disposed on at least one surface of the base film. A heat-resistant coating is also disposed on the surface of the base film. The internal resistance of the safety coating increases with voltage by at least 5V. The safety coating of this utility model increases its internal resistance with increasing voltage, thereby reducing current and thus reducing heat generation to improve the safety performance of the battery during overcharging. The heat-resistant coating has a heat resistance temperature greater than or equal to 130℃. When the battery undergoes a thermal reaction, it can prevent thermal shrinkage leading to misalignment and also prevent current collector burrs, further improving safety performance.

[0040] Based on the disclosure and teachings of the above specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the utility model is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on the utility model are within the protection scope of the utility model. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the utility model.

Claims

1. A battery separator, characterized by, It includes a base film (1) and a safety coating (2) disposed on at least one surface of the base film (1), the surface of the base film (1) is further provided with a heat-resistant coating (3), and the internal resistance rise voltage of the safety coating (2) is at least 5V.

2. The battery separator of claim 1, wherein The heat-resistant coating (3) has a heat resistance temperature ≥130℃.

3. The battery separator of claim 1 wherein, The safety coating (2) is disposed on one surface of the base film (1), and the heat-resistant coating (3) is disposed on the other surface of the base film (1).

4. The battery separator of claim 1 wherein, The heat-resistant coating (3) is disposed around the safety coating (2), and the heat-resistant coating (3) has a U-shaped structure.

5. The battery separator of claim 1 wherein the polymeric material is a polyolefin. The heat-resistant coating (3) is disposed on one surface of the base film (1), and the safety coating (2) is disposed on one surface of the heat-resistant coating (3).

6. The battery separator of claim 1 wherein, The safety coating (2) is selected from one of polyaniline, polypyrrole, and polythiophene.

7. The battery separator of claim 1 wherein, The area of ​​the safety coating (2) is not less than the area of ​​the heat-resistant coating (3).

8. The battery separator of claim 1 wherein, The coating thickness of the safety coating (2) is 0.5 to 10 μm.

9. The battery separator of claim 1 wherein, The coating thickness of the heat-resistant coating (3) is 0.5 to 10 μm.

10. A secondary battery characterized by comprising: Includes the battery separator as claimed in any one of claims 1 to 9.

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