Lithium battery diaphragm with hydrophobicity

Abstract

The invention discloses a hydrophobic lithium battery diaphragm, and relates to the technical field of lithium battery diaphragms, the hydrophobic lithium battery diaphragm comprises a diaphragm base layer and a functional layer, the diaphragm base layer is divided into an inner base layer and an outer base layer, and two sides of the diaphragm base layer are coated with filler layers. When the hydrophobic lithium battery diaphragm is used, the outer side of the whole diaphragm is coated with the filler layer, the filler layer mainly comprises the electrolyte affinity layer, the thermal stability layer and the hydrophobic layer, and the electrolyte absorption energy of the diaphragm can be increased through the electrolyte affinity layer, so that the conduction efficiency of lithium ions is improved; the stability of the diaphragm in a high-temperature environment can be improved through the thermal stability layer, so that the diaphragm cannot be melted and damaged in the high-temperature environment, the high-temperature-resistant effect of the diaphragm is improved, and finally the hydrophobic effect of the whole diaphragm can be improved through the hydrophobic layer; and moisture in the electrolyte is prevented from reacting with lithium ions to generate hydrogen or other harmful gases, and meanwhile, the effect of protecting an electrode material and the electrolyte can also be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of lithium battery separators, in particular to a hydrophobic lithium battery separator. Background Art

[0002] The lithium battery separator is one of the key components in lithium-ion batteries. It is located between the positive and negative electrodes. Its main function is to prevent the positive and negative electrodes inside the battery from directly contacting each other and causing a short circuit. At the same time, it allows lithium ions to pass freely to achieve ion transmission during the battery's charging and discharging process. Therefore, the design and manufacture of lithium battery separators are crucial to ensuring the safe and efficient operation of batteries.

[0003] When the existing lithium battery separator is in use, in order to enhance the wettability of the electrolyte, it needs a certain degree of hydrophilicity to ensure the uniform distribution of the electrolyte. Therefore, there is no hydrophobic material on the surface of the separator. However, excessive hydrophilicity will cause the electrolyte to be rapidly absorbed and even react with lithium ions to generate hydrogen or other harmful gases, thereby affecting the battery performance. Therefore, the existing lithium battery separator does not have a good hydrophobic effect. Summary of the invention

[0004] The object of the present invention is to provide a hydrophobic lithium battery separator to solve the problem that the existing lithium battery separator mentioned in the above background technology is not hydrophobic when in use.

[0005] To achieve the above object, the present invention provides the following technical solution: a hydrophobic lithium battery separator, comprising: a separator base layer and a functional layer, wherein the separator base layer is divided into an inner base layer and an outer base layer, both sides of the separator base layer are coated with a filler layer, and the functional layer is coated on the outer side of the filler layer;

[0006] The filler layer includes an electrolyte affinity layer, a thermal stability layer and a hydrophobic layer, and the functional layer includes a reinforcement layer, a conductive layer and a protective layer.

[0007] Preferably, the electrolyte affinity layer is evenly coated on both sides of the diaphragm base layer, and the main material of the electrolyte affinity layer is a mixture of inorganic particles and organic binders, the inorganic particles are any one of aluminum oxide and silicon dioxide, and the organic binder is polyvinyl pyrrolidone.

[0008] Preferably, the thermal stability layer is uniformly coated on the outer side of the electrolyte affinity layer, and the main material of the thermal stability layer is any one of aluminum oxide, silicon dioxide and titanium dioxide.

[0009] Preferably, the hydrophobic layer is evenly impregnated on the outside of the thermal stability layer, and the main material of the hydrophobic layer is any one of fluorine-containing polymer and siloxane.

[0010] Preferably, the reinforcing layer is evenly coated on both sides of the hydrophobic layer, and the main material of the reinforcing layer is any one of aramid fiber and polyimide.

[0011] Preferably, the conductive layer is evenly impregnated on the outer side of the reinforcement layer, and the main material of the conductive layer is any one of carbon nanotubes or graphene.

[0012] Preferably, the protective layer is evenly coated on the outer side of the conductive layer, and the main material of the protective layer is polyimide.

[0013] Preferably, the surface of the inner base layer is provided with pores of equal size, and the diameter of the pores is microns.

[0014] Preferably, the pores are equidistantly distributed in the middle of the inner base layer, and the porosity of the pores is 50%.

[0015] Preferably, the main material of the outer base layer is a polymer coating, and the main material of the outer base layer is polyvinylidene fluoride.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: when the hydrophobic lithium battery separator is in use, the outer side of the entire separator is coated with a filler layer, and the filler layer mainly includes an electrolyte affinity layer, a thermal stability layer and a hydrophobic layer. The electrolyte affinity layer can increase the separator's absorption energy of the electrolyte, thereby improving the lithium ion conduction efficiency, while the thermal stability layer can increase the stability of the separator in a high temperature environment, so that the separator will not melt and be damaged in a high temperature environment, thereby increasing the high temperature resistance of the separator. Finally, the hydrophobic layer can improve the hydrophobic effect of the entire separator, preventing the moisture in the electrolyte from reacting with lithium ions to generate hydrogen or other harmful gases, and at the same time can also protect the electrode material and the electrolyte. This is the use feature of the hydrophobic lithium battery separator.

[0017] 1. The hydrophobic lithium battery separator is coated and impregnated with an electrolyte affinity layer, a thermal stability layer and a hydrophobic layer on the outer side of the separator base. The electrolyte affinity layer, the thermal stability layer and the hydrophobic layer can not only increase the lithium ion conduction efficiency and the stability of the separator in a high temperature environment, but also increase the hydrophobic effect of the separator, so that water will not react with lithium ions, reduce the side reactions caused by water, and thus play a role in protecting electrode materials and electrolytes;

[0018] 2. The hydrophobic lithium battery separator is coated and impregnated with a functional layer on the outside of the filler layer. The functional layer mainly includes a reinforcing layer, a conductive layer and a protective layer. The reinforcing layer, the conductive layer and the protective layer can increase the mechanical strength of the separator and improve the charging and discharging efficiency of the battery, reduce the contact resistance inside the battery, and protect the separator, thereby increasing the service life of the separator.

[0019] 3. The hydrophobic lithium battery separator has an entire separator base layer including an inner base layer and an outer base layer, and the surface of the inner base layer is provided with pores of the same size and evenly distributed. The pores of the same size will not affect the mechanical strength of the separator, nor will they affect the normal conduction of lithium ions. The inner base layer and the outer base layer can increase the mechanical strength of the entire separator, thereby making the entire separator less susceptible to damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention;

[0021] Figure 2 Schematic diagram of the three-dimensional structure of the diaphragm base layer of the present invention;

[0022] Figure 3 It is a schematic diagram of the three-dimensional structure of the packing layer of the present invention;

[0023] Figure 4 It is a schematic diagram of the three-dimensional structure of the functional layer of the present invention.

[0024] In the figure: 1. diaphragm base layer; 2. inner base layer; 3. outer base layer; 4. filler layer; 5. functional layer; 401. electrolyte affinity layer; 402. thermal stability layer; 403. hydrophobic layer; 501. reinforcement layer; 502. conductive layer; 503. protective layer; 6. pores. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] See also Figure 1 The present invention provides a technical solution: a hydrophobic lithium battery separator, comprising: a separator base layer 1 and a functional layer 5, the separator base layer 1 is divided into an inner base layer 2 and an outer base layer 3, both sides of the separator base layer 1 are coated with a filler layer 4, and the functional layer 5 is coated on the outer side of the filler layer 4;

[0027] The filler layer 4 includes an electrolyte affinity layer 401, a thermal stability layer 402 and a hydrophobic layer 403, and the functional layer 5 includes a reinforcing layer 501, a conductive layer 502 and a protective layer 503. The electrolyte affinity layer 401 is evenly coated on both sides of the diaphragm base layer 1. The main material of the electrolyte affinity layer 401 is a mixture of inorganic particles and organic binders. The inorganic particles are any one of aluminum oxide and silicon dioxide. The organic binder is polyvinyl pyrrolidone. The thermal stability layer 402 is evenly coated on the outside of the electrolyte affinity layer 401. The main material of the thermal stability layer 402 is any one of aluminum oxide, silicon dioxide, and titanium dioxide. The hydrophobic layer 403 is evenly impregnated on the outside of the thermal stability layer 402. The main material of the hydrophobic layer 403 is any one of fluorine-containing polymers and siloxanes.

[0028] In a specific implementation, the hydrophobic lithium battery separator is coated with an electrolyte affinity layer 401 on both sides of the entire separator base layer 1. The electrolyte affinity layer 401 is a mixture of inorganic particles and organic binders, such as silicon dioxide, aluminum oxide, polyvinylidene fluoride, etc. Silicon dioxide or aluminum oxide is mixed with polyvinylidene fluoride in a ratio of 4:1. After mixing, a coating machine is used to evenly coat the mixed silicon dioxide or aluminum oxide on the separator base layer 1. The electrolyte affinity layer 401 can increase the absorption energy of the separator to the electrolyte, thereby ensuring sufficient electrolyte supply and improving the lithium ion conduction efficiency.

[0029] A thermal stability layer 402 is also coated on the outside of the electrolyte affinity layer 401. The thermal stability layer 402 is similar to the electrolyte affinity layer 401, and is also mixed with inorganic particles, but no organic binder is added. After mixing, it is evenly coated on the outside of the electrolyte affinity layer 401 until it cools. The thermal stability layer 402 can improve the stability of the diaphragm under high temperature conditions and prevent the diaphragm from melting when the battery is overheated, thereby avoiding internal short circuit of the battery;

[0030] After the thermal stability layer 402 on the outside of the diaphragm is cooled and formed, the dust and impurities on the surface of the diaphragm can be washed away. The fluorine-containing polymer can be selected from polytetrafluoroethylene, which has good hydrophobicity. Then the cleaned diaphragm is completely immersed in the polytetrafluoroethylene solution, and make sure that all areas are covered. Depending on the thickness of the coating, the diaphragm is immersed in the hydrophobic solution for a few seconds to a few minutes. After the immersion is completed, the diaphragm can be removed and the hydrophobic material on the surface can be dried. At this time, polytetrafluoroethylene will form a hydrophobic film on the surface of the diaphragm. Polytetrafluoroethylene can effectively increase the hydrophobic effect of the diaphragm, prevent moisture from entering the battery, and avoid the accumulation of hydrogen and oxygen produced by the decomposition of the electrolyte, thereby reducing the risk of explosion.

[0031] See also Figure 1 and Figure 2It can be seen that when in use, the electrolyte affinity layer 401, the thermal stability layer 402 and the hydrophobic layer 403 in the filler layer 4 can improve the conduction efficiency of lithium ions, while improving the stability of the diaphragm under high temperature conditions, while preventing moisture from entering the battery, reducing the risk of battery short circuit and explosion.

[0032] The reinforcing layer 501 is evenly coated on both sides of the hydrophobic layer 403, and the main material of the reinforcing layer 501 is either aramid fiber or polyimide. The conductive layer 502 is evenly impregnated on the outside of the reinforcing layer 501, and the main material of the conductive layer 502 is either carbon nanotube or graphene. The protective layer 503 is evenly coated on the outside of the conductive layer 502, and the main material of the protective layer 503 is polyimide.

[0033] In a specific implementation, the hydrophobic lithium battery separator can be evenly coated with a reinforcing layer 501 on the surface of the hydrophobic layer 403 after the hydrophobic layer 403 on the surface of the separator is cooled. The main material of the reinforcing layer 501 is any one of polyvinylidene fluoride, aramid fiber, and polyimide. After mixing them evenly, they can be evenly coated on the outside of the hydrophobic layer 403. After cooling, the mechanical strength of the separator can be improved, so that it is not easy to damage certain coating materials during battery assembly and use.

[0034] Then, a conductive layer 502 is impregnated on the outside of the reinforcement layer 501. The conductive layer 502 can be made of any material such as carbon nanotubes, graphene, and carbon black. The conductive layer 502 can improve the conductivity of the diaphragm, reduce the contact resistance inside the battery, and improve the charging and discharging efficiency of the battery.

[0035] Finally, a protective layer 503 is coated on the outermost side. The protective layer 503 can be made of polyimide or other high temperature resistant materials. The polyimide is dissolved in a suitable solvent, which can be N, N-dimethylformamide or dimethylacetamide. Then, it is evenly coated on the outside of the diaphragm and dried and cured. The protective layer 503 can provide good protection for the diaphragm, which can not only improve the mechanical strength of the diaphragm, but also improve the chemical stability of the diaphragm, thereby improving the overall performance and safety of the battery.

[0036] See also Figure 1 and Figure 3 It can be seen that when in use, the reinforcing layer 501, the conductive layer 502 and the protective layer 503 in the functional layer 5 can protect the diaphragm, and at the same time can increase the mechanical strength of the diaphragm, improve the charging and discharging efficiency of the battery, and increase the overall safety of the battery.

[0037] The surface of the inner base layer 2 is provided with pores 6 of equal size, the diameter of the pores 6 is 0.05 microns, the pores 6 are equidistantly distributed in the middle of the inner base layer 2, the porosity of the pores 6 is 50%, the main material of the outer base layer 3 is a polymer coating, the main material of the outer base layer 3 is polyvinylidene fluoride, and the material of the inner base layer 2 is a composite material of polyethylene and polypropylene.

[0038] In a specific implementation, the hydrophobic lithium battery separator, the separator base 1 includes an inner base 2 and an outer base 3, the surface of the inner base 2 is provided with pores 6 with a diameter of 0.05 microns, when the diameter of the pores 6 is too large, it will cause leakage of the electrolyte, and when the pores 6 are too small, it will hinder the transmission of lithium ions, and the pores 6 with a diameter of 0.05 microns will not affect the normal transmission of lithium ions, and will not cause leakage of the electrolyte, thereby ensuring the normal use of the entire separator, and the pores 6 are evenly distributed on the inner base 2, so that the conduction efficiency of lithium ions can be improved, and the The current distribution inside the battery is more uniform, and the uneven distribution of pores 6 can be avoided to cause local overheating or other adverse phenomena. At the same time, the overall porosity is 50%. The porosity refers to the proportion of the volume of pores 6 in the diaphragm to the total volume. When the porosity is high, the mechanical strength of the diaphragm will be reduced. When the porosity is too low, the normal conduction of lithium ions will be affected. Therefore, when the porosity is 50%, not only the conductivity is better, but also the mechanical strength of the diaphragm will not be affected. The pore 6 structure of the entire diaphragm is mainly formed by biaxially stretching the polyolefin film to form a uniformly distributed microporous structure, so that the overall performance of the diaphragm is better.

[0039] At the same time, the material of the inner base layer 2 is a composite material of polyethylene and polypropylene. By compounding polyethylene and polypropylene together, compared with a single polyethylene or polypropylene material, the mechanical strength and thermal stability of the entire inner base layer 2 are greatly improved, and the material of the outer base layer 3 is polyvinylidene fluoride. The entire diaphragm base layer 1 adopts a combination of an inner base layer 2 and an outer base layer 3, combining the advantages of different materials and adopting a multi-layer structure. While increasing the mechanical properties of the diaphragm, it can also increase the anti-leakage performance of the diaphragm.

[0040] See also Figure 1 and Figure 2 It can be seen that when in use, the diaphragm base layer 1 mainly adopts a structure combining an inner base layer 2 and an outer base layer 3, which can increase the mechanical strength and anti-leakage effect of the entire diaphragm. At the same time, combined with the equal-sized and equally spaced pores 6 opened on the surface of the inner base layer 2, the anti-leakage and mechanical strength of the entire diaphragm can be improved, thereby increasing the overall performance of the diaphragm.

[0041] To sum up, when the hydrophobic lithium battery separator is used, the polyethylene and polypropylene to be processed are first mixed and melted, then extruded into a film through an extruder at high temperature, and then quickly cooled. After cooling, it is stretched to form a pore structure, and finally the corresponding filler layer and functional layer 5 can be dip-coated on its surface to ensure that the mechanical strength and overall performance of the entire separator can be improved. This is the use feature of the hydrophobic lithium battery separator. The content not described in detail in this description belongs to the existing technology known to professional and technical personnel in this field.

[0042] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A hydrophobic lithium battery separator, comprising: A diaphragm base layer (1) and a functional layer (5), characterized in that: the diaphragm base layer (1) is divided into an inner base layer (2) and an outer base layer (3), both sides of the diaphragm base layer (1) are coated with a filler layer (4), and the functional layer (5) is coated on the outer side of the filler layer (4); The filler layer (4) comprises an electrolyte affinity layer (401), a thermal stability layer (402) and a hydrophobic layer (403), and the functional layer (5) comprises a reinforcement layer (501), a conductive layer (502) and a protective layer (503).

2. The hydrophobic lithium battery separator according to claim 1, characterized in that: The electrolyte affinity layer (401) is evenly coated on both sides of the diaphragm base layer (1), and the main material of the electrolyte affinity layer (401) is a mixture of inorganic particles and an organic binder, the inorganic particles are any one of aluminum oxide and silicon dioxide, and the organic binder is a polyvinyl pyrrolidone material.

3. The hydrophobic lithium battery separator according to claim 1, characterized in that: The thermal stability layer (402) is evenly coated on the outside of the electrolyte affinity layer (401), and the main material of the thermal stability layer (402) is any one of aluminum oxide, silicon dioxide, and titanium dioxide.

4. The hydrophobic lithium battery separator according to claim 1, characterized in that: The hydrophobic layer (403) is evenly impregnated on the outside of the thermal stability layer (402), and the main material of the hydrophobic layer (403) is any one of fluorine-containing polymer and silicone.

5. The hydrophobic lithium battery separator according to claim 1, characterized in that: The reinforcing layer (501) is evenly coated on both sides of the hydrophobic layer (403), and the main material of the reinforcing layer (501) is any one of aramid fiber and polyimide.

6. The hydrophobic lithium battery separator according to claim 1, characterized in that: The conductive layer (502) is uniformly impregnated on the outside of the reinforcement layer (501), and the main material of the conductive layer (502) is any one of carbon nanotubes or graphene.

7. The hydrophobic lithium battery separator according to claim 1, characterized in that: The protective layer (503) is evenly coated on the outer side of the conductive layer (502), and the main material of the protective layer (503) is polyimide.

8. The hydrophobic lithium battery separator according to claim 1, characterized in that: The surface of the inner base layer (2) is provided with pores (6) of equal size, and the diameter of the pores (6) is 0.05 micrometers.

9. The hydrophobic lithium battery separator according to claim 8, characterized in that: The pores (6) are evenly distributed in the middle of the inner base layer (2), and the porosity of the pores (6) is 50%.

10. The hydrophobic lithium battery separator according to claim 1, characterized in that: The main material of the outer base layer (3) is a polymer coating, and the main material of the outer base layer (3) is polyvinylidene fluoride.

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