A lithium battery sealing material and preparation method thereof

Abstract

The present application relates to the field of batteries and specifically discloses a lithium battery sealing material and a preparation method thereof. The lithium battery sealing material comprises the following raw materials in parts by weight: 100-150 parts of nylon, 5-15 parts of maleic anhydride grafted polypropylene, 10-20 parts of rosin glycerol ester, 5-10 parts of poly(trimethylene terephthalate), 5-15 parts of filler, 0.5-1 part of antioxidant, and 0.2-0.5 parts of dispersant. The preparation method comprises the following steps: uniformly mixing nylon, poly(trimethylene terephthalate), and maleic anhydride grafted polypropylene to obtain a primary mixture; uniformly mixing the filler and rosin glycerol ester, and then uniformly mixing the filler and the rosin glycerol ester with the primary mixture to obtain a mixture; adding the antioxidant and the dispersant to the mixture, stirring evenly, and extruding to obtain a finished product. The hygroscopicity of a button battery sealing ring is reduced, and the sealing ring is ensured to have high mechanical strength, good sealing effect, and long service life, thereby extending the service life of the button battery.

Description

Technical Field

[0001] The present application relates to the field of batteries, and more specifically, to a lithium battery sealing material and a preparation method thereof. Background Art

[0002] Lithium batteries are batteries that use lithium metal or lithium alloy as the negative electrode material and a non-aqueous electrolyte solution. Button batteries are a type of lithium battery.

[0003] Button batteries, also known as button batteries, are batteries with an appearance similar to a small button. Generally speaking, they have a larger diameter and a thinner thickness. They can be used in electronic watches, electronic dictionaries, electronic scales, electric toys, cameras and other fields.

[0004] The interior of a button battery is composed of positive electrode material, negative electrode material and electrolyte, and the button battery shell is composed of positive electrode shell, negative electrode shell and sealing ring. The positive electrode shell, negative electrode shell and sealing ring constitute a closed sealed structure. Since the positive and negative electrode materials and the electrolyte are extremely sensitive to moisture, moisture will produce a chemical reaction that decomposes the positive and negative electrode materials, making the battery prone to gassing and high internal resistance problems, leading to battery failure. Therefore, a reliably sealed button battery shell plays an important role in the battery life, performance and quality.

[0005] Sealing rings are generally made of nylon. Although nylon has high mechanical strength, good insulation, toughness and wear resistance, it has a certain degree of hygroscopicity. After absorbing water, the mechanical strength of the nylon material will decrease, which will not only affect the sealing effect but also the service life of the battery.

[0006] When button batteries are used in electronic watches, people often come into contact with moisture when wearing electronic watches. For example, when washing hands, washing face, or getting wet by rain, it is easy for moisture to get between the arm and the electronic watch. Children, in particular, will not pay attention to whether moisture gets between the arm and the electronic watch. If the moisture is not wiped off and the contact point between the watch and the arm is left to dry naturally, then moisture and humidity will inevitably exist between the electronic watch and the arm. As the electronic watch is worn for a longer time, it is easy for moisture or humidity to gradually penetrate the electronic watch case and come into contact with the button battery, causing the button battery sealing ring to easily absorb moisture. After moisture absorption, it is easy to affect the service life of the button battery, thereby affecting the service life of the electronic watch.

[0007] Therefore, how to reduce the hygroscopicity of the button battery sealing ring and ensure that the sealing ring has high mechanical strength, good sealing effect and long service life, so that the button battery on the electronic watch has a longer service life, is a problem to be solved. Summary of the Invention

[0008] In order to reduce the hygroscopicity of the button battery sealing ring and ensure that the sealing ring has high mechanical strength, good sealing effect and long service life, so that the button battery on the electronic watch has a longer service life, the present application provides a lithium battery sealing material and a preparation method thereof.

[0009] This application provides a lithium battery sealing material, which adopts the following technical solution:

[0010] A lithium battery sealing material is made of the following raw materials in parts by weight: 100-150 parts of nylon, 5-15 parts of maleic anhydride grafted polypropylene, 10-20 parts of rosin glycerol ester, 5-10 parts of polytrimethylene terephthalate, 5-15 parts of filler, 0.5-1 part of antioxidant, and 0.2-0.5 part of dispersant.

[0011] By adopting the above technical solution, nylon, maleic anhydride grafted polypropylene, poly(trimethylene terephthalate), rosin glycerol ester, filler, and dispersant are combined. When the sealing material is made into a button battery sealing ring, the low water absorption rate of the poly(trimethylene terephthalate), rosin glycerol ester, and filler in the sealing material, combined with the high structural density of the sealing material, reduces the hygroscopicity of the button battery sealing ring; the good compatibility and adhesion of the material raw materials, combined with the strength of the filler, ensure that the sealing ring has high mechanical strength and good sealing effect; that is, when the sealing material is used as a button battery sealing ring, even if it comes into contact with water, it is not easy to absorb water and moisture, thereby ensuring that the button battery in the electronic watch has a longer service life.

[0012] The combination of nylon and poly(trimethylene terephthalate) can reduce the water absorption of the sealing material, and the combination of maleic anhydride grafted polypropylene can improve the mechanical strength of the sealing material. In addition, the combination of rosin glycerol ester and filler can utilize the compatibility and adhesion of maleic anhydride grafted polypropylene and rosin glycerol ester to improve the compatibility of the filler in the sealing material. The combination of the strength of the filler itself and the high structural density of the sealing material can further improve the mechanical strength of the sealing material while reducing the water absorption of the sealing material. The combination of dispersant and maleic anhydride grafted polypropylene can improve the dispersion effect of the filler in the sealing material, so that the sealing material as a whole has higher mechanical strength.

[0013] Preferably, the filler is composed of silicon nitride particles, zirconium dioxide particles and hydrophobic silica particles in a weight ratio of 1:0.5-1:0.5-1.

[0014] By adopting the above technical solution, silicon nitride particles, zirconium dioxide particles and hydrophobic silica gel particles are combined, and the high mechanical strength and good insulation properties of silicon nitride particles and zirconium dioxide particles are utilized to make the sealing material have high mechanical strength and good insulation effect. In addition, nano silicon nitride and zirconium dioxide are acid and alkali resistant, which can improve the acid and alkali resistance of the sealing material and reduce the impact of the electrolyte on the service life of the sealing material.

[0015] Nylon, hydrophobic silica particles, and rosin glycerol ester are combined. The elasticity of nylon and hydrophobic silica particles is combined with the bonding stability of rosin glycerol ester. During the thermal expansion of the battery, the elastic buffering effect is used to reduce the impact of the thermal expansion of the battery on the sealing of the sealing material, thereby ensuring that the sealing material still has a long service life under cyclic overheating conditions.

[0016] Silicon nitride particles, zirconium dioxide particles, and hydrophobic silica particles are combined to make the finished sealing material have a lower moisture absorption rate by utilizing the non-water absorption of silicon nitride particles and zirconium dioxide particles, the hydrophobic effect of the hydrophobic silica particles, and the higher structural density of the sealing material.

[0017] Preferably, the silicon nitride particles are composed of nano-silicon nitride and polyvinyl alcohol in a weight ratio of 1:0.2-0.8, and the zirconium dioxide particles are composed of nano-zirconium dioxide and polyvinyl alcohol in a weight ratio of 1:0.2-0.8.

[0018] By adopting the above technical scheme, silicon nitride particles, zirconium dioxide particles and polyvinyl alcohol are matched, and the hydroxyl groups of polyvinyl alcohol are attracted and connected with the amide groups in nylon. On the one hand, it is possible to avoid the amide groups in the sealing material from absorbing moisture and affecting the mechanical strength and sealing effect of the sealing material, thereby reducing the moisture absorption rate of the sealing material and extending the service life of the sealing material; on the other hand, the viscosity of the hot melt of polyvinyl alcohol is utilized to improve the viscosity compatibility of silicon nitride particles, zirconium dioxide particles and raw materials such as nylon, thereby further improving the structural density of the sealing material, which can not only reduce the moisture absorption rate of the sealing material, but also improve the mechanical strength of the sealing material, thereby extending the service life of the sealing material.

[0019] Preferably, the polyvinyl alcohol is prepared by polyvinyl alcohol particles coated with EVA film.

[0020] By adopting the above technical scheme, polyvinyl alcohol particles and EVA film are matched with each other, and the water-blocking effect of the EVA film is utilized to avoid the moisture absorption of the polyvinyl alcohol particles as much as possible. In addition, in the process of extrusion and hot melting of the sealing material, the fluidity of the EVA after hot melting is first utilized to gradually release the polyvinyl alcohol particles. As the temperature rises, the polyvinyl alcohol particles gradually melt, and their viscosity is utilized to cooperate with the hydroxyl groups in the polyvinyl alcohol to further improve the bonding effect of the zirconium dioxide particles and silicon nitride particles with nylon. Then, in the process of gradual cooling, since the melting point of polyvinyl alcohol is higher than that of EVA, the polyvinyl alcohol solidifies first. At this time, the EVA still has fluidity and can flow on the surface of the solidified polyvinyl alcohol film. As the EVA cools and solidifies, it can not only form a coating on the surface of the polyvinyl alcohol film, but also improve the bonding effect of the silicon nitride particles and zirconium dioxide particles with raw materials such as nylon, thereby improving the mechanical strength of the sealing material while reducing the water absorption rate of the sealing material.

[0021] When the sealing material is applied to the battery, if the battery temperature reaches above 60°C, the EVA will gradually melt, improving the internal bonding stability of the sealing material and avoiding the sealing effect affected by embrittlement and hardening of the sealing material.

[0022] Preferably, the hydrophobic silica gel particles are prepared by hydrophobically modifying nano silica gel particles with a silane coupling agent KH-570.

[0023] By adopting the above technical solution, the nano-silica gel particles are hydrophobically modified, which reduces the water absorption of the nano-silica gel particles, thereby making the sealing material less likely to absorb moisture and extending the service life of the sealing material; the combination of silane coupling agent KH-570 and nylon can further improve the bonding compatibility between the nano-silica gel particles and raw materials such as nylon, further improve the structural density of the sealing material, and make the sealing material have higher mechanical strength and better waterproof effect, thereby extending the service life of the sealing material.

[0024] Preferably, the antioxidant is antioxidant 1024.

[0025] By adopting the above technical solution, the anti-oxidation effect of the sealing material can be improved, thereby extending the service life.

[0026] Preferably, the dispersant is microcrystalline wax.

[0027] By adopting the above technical solution and utilizing the better dispersing effect of microcrystalline wax, maleic anhydride grafted polypropylene, filler, and rosin glycerol ester are evenly dispersed in nylon, ensuring the structural density of the sealing material and giving the sealing material higher mechanical strength.

[0028] In a second aspect, the present application provides a method for preparing a lithium battery sealing material, which adopts the following technical solution:

[0029] A method for preparing a lithium battery sealing material comprises the following steps:

[0030] S1. Mixing nylon, poly(trimethylene terephthalate), and maleic anhydride grafted polypropylene and stirring uniformly to prepare a primary mixture;

[0031] S2. Weigh the filler and rosin glycerol ester, mix and stir evenly, and then mix and stir evenly with the initial mixture to prepare a mixture;

[0032] S3. Weigh antioxidant and dispersant, add them to the mixture, stir evenly, and extrude to obtain a finished product.

[0033] By adopting the above technical solution, the finished sealing material has higher mechanical strength and lower water absorption, thereby extending the service life of the sealing material. When applied to button batteries in electronic watches, the service life of the button batteries can also be extended.

[0034] Preferably, in step S2, the particle size of the rosin glycerol ester is 20-80 μm.

[0035] By adopting the above technical solution, the particle size of rosin glycerol ester is limited, so that the rosin glycerol ester is evenly dispersed inside the sealing material, thereby improving the structural density of the sealing material, improving the mechanical strength of the sealing material and reducing the moisture absorption rate of the sealing material.

[0036] Preferably, in step S3, the extrusion molding temperature is 270-280°C.

[0037] By adopting the above technical solution, the extrusion molding temperature is limited, so that the resin and other raw materials are bonded to each other after being hot-melted, the structural density of the sealing material is improved, and the filler is promoted to be bonded more stably and evenly inside the sealing material, so that the sealing material has higher mechanical strength and lower water absorption.

[0038] In summary, this application has the following beneficial effects:

[0039] 1. When the sealing material is made of nylon, maleic anhydride grafted polypropylene, poly(trimethylene terephthalate), rosin glycerol ester, filler and dispersant to form a button battery sealing ring, the lower water absorption of poly(trimethylene terephthalate), rosin glycerol ester and filler in the sealing material is combined with the higher structural density of the sealing material to reduce the hygroscopicity of the button battery sealing ring; the better compatibility and adhesion of the material raw materials and the strength of the filler are combined to ensure that the sealing ring has higher mechanical strength and better sealing effect; that is, when the sealing material is used as a button battery sealing ring, it is not easy to absorb water and moisture even if it comes into contact with water, thereby making the button battery on the electronic watch have a longer service life.

[0040] 2. Silicon nitride particles, zirconium dioxide particles and hydrophobic silica particles are combined, and the high mechanical strength and good insulation of silicon nitride particles and zirconium dioxide particles are utilized to make the sealing material have high mechanical strength and good insulation effect. In addition, nano silicon nitride and zirconium dioxide are acid and alkali resistant, which can improve the acid and alkali resistance of the sealing material and reduce the impact of the electrolyte on the service life of the sealing material.

[0041] 3. Limiting the particle size of each raw material can improve the density of the sealing material, so that the sealing material has higher mechanical strength and lower hygroscopicity, thereby extending the service life of the sealing material. DETAILED DESCRIPTION

[0042] The present application is further described in detail below with reference to the embodiments.

[0043] Preparation Example of Polyvinyl Alcohol

[0044] Polyvinyl alcohol was purchased from Shandong Tianfeng Chemical Technology Co., Ltd. as polyvinyl alcohol 2099; other raw materials and equipment were commercially available.

[0045] Preparation Example 1: Polyvinyl alcohol was prepared by the following method:

[0046] Weigh EVA and heat it to 65°C to completely melt it to obtain EVA melt;

[0047] 0.8 kg of EVA melt was evenly sprayed on the surface of 1 kg of polyvinyl alcohol particles, the particle size of the polyvinyl alcohol particles was 5 μm, and the finished polyvinyl alcohol was obtained.

[0048] Preparation Example of Silicon Nitride Particles

[0049] Preparation Example 2: Silicon nitride particles are prepared by the following method:

[0050] 1 kg of nano-silicon nitride was evenly sprayed on the surface of 0.5 kg of polyvinyl alcohol prepared in Preparation Example 1. The particle size of the nano-silicon nitride was 100 nm. After drying and dispersion, finished silicon nitride particles were obtained. The particle size of the silicon nitride particles was 5-10 μm.

[0051] Preparation Example 3: This preparation example differs from Preparation Example 2 in that:

[0052] 1 kg of nano-silicon nitride was evenly sprayed on the surface of 0.2 kg of polyvinyl alcohol prepared in Preparation Example 1. The particle size of the nano-silicon nitride was 100 nm. After drying and dispersion, finished silicon nitride particles were obtained.

[0053] Preparation Example 4: This preparation example differs from Preparation Example 2 in that:

[0054] 1 kg of nano-silicon nitride was evenly sprayed on the surface of 0.8 kg of polyvinyl alcohol prepared in Preparation Example 1. The particle size of the nano-silicon nitride was 100 nm. After drying and dispersion, finished silicon nitride particles were obtained.

[0055] Preparation Example of Zirconium Dioxide Particles

[0056] Preparation Example 5: Zirconium dioxide particles were prepared by the following method:

[0057] 1 kg of nano zirconium dioxide was evenly sprayed on the surface of 0.5 kg of polyvinyl alcohol prepared in Preparation Example 1. The particle size of the nano zirconium dioxide was 100 nm. After drying and dispersion, finished zirconium dioxide particles were obtained. The particle size of the zirconium dioxide particles was 5-10 μm.

[0058] Preparation Example 6: This preparation example differs from Preparation Example 5 in that:

[0059] 1 kg of nano zirconium dioxide was evenly sprayed on the surface of 0.2 kg of polyvinyl alcohol prepared in Preparation Example 1. The particle size of the nano zirconium dioxide was 100 nm. After drying and dispersion, finished zirconium dioxide particles were obtained.

[0060] Preparation Example 7: This preparation example differs from Preparation Example 5 in that:

[0061] 1 kg of nano zirconium dioxide was evenly sprayed on the surface of 0.8 kg of polyvinyl alcohol prepared in Preparation Example 1. The particle size of the nano zirconium dioxide was 100 nm. After drying and dispersion, finished zirconium dioxide particles were obtained.

[0062] Preparation Example of Hydrophobic Silica Gel Particles

[0063] Nano-silica gel particles were purchased from Shandong Zhanze Biotechnology Co., Ltd.; other raw materials and equipment were commercially available.

[0064] Preparation Example 8: Hydrophobic silica gel particles were prepared by the following method:

[0065] The commercially available silica gel particles were crushed to obtain nano silica gel particles, the particle size of which was 500 nm.

[0066] 1 kg of nano silica gel particles were weighed and uniformly dispersed in 5 kg of silane coupling agent KH-570, and then the nano silica gel particles were separated and dried to obtain hydrophobic silica gel particles.

[0067] Example

[0068] The nylon in the following raw materials is DuPont PA6 from the United States; maleic anhydride grafted polypropylene was purchased from Guangzhou Xichuan Plastic Raw Materials Co., Ltd. and SK of South Korea; rosin glycerol ester was purchased from Shandong Pingju Biotechnology Co., Ltd.; polytrimethylene terephthalate was purchased from Dongguan Jinshixiang Plastic Raw Materials Co., Ltd. to produce polytrimethylene terephthalate PTT resin chips, DuPont, 2261; other raw materials and equipment are commonly available on the market.

[0069] Example 1: A lithium battery sealing material:

[0070] 125kg of nylon, 10kg of maleic anhydride-grafted polypropylene, 15kg of rosin glycerol ester, 8kg of poly(trimethylene terephthalate), 10kg of filler, 0.8kg of antioxidant, and 0.3kg of dispersant; the rosin glycerol ester has a particle size of 50μm; the filler consists of silicon nitride particles, zirconium dioxide particles, and hydrophobic silica gel particles in a weight ratio of 1:1:0.5, the silicon nitride particles being those prepared in Preparation Example 2, the zirconium dioxide particles being those prepared in Preparation Example 5, and the hydrophobic silica gel particles being those prepared in Preparation Example 8; the antioxidant being antioxidant 1024, and the dispersant being microcrystalline wax;

[0071] The preparation method is as follows:

[0072] S1. Mixing nylon, poly(trimethylene terephthalate), and maleic anhydride grafted polypropylene and stirring uniformly to prepare a primary mixture;

[0073] S2. Weigh the nanofiller and rosin glycerol ester, mix and stir evenly, and then mix and stir evenly with the primary mixture to prepare a mixture;

[0074] S3. Weigh antioxidant and dispersant, add to the mixture, stir evenly, and extrude at 275° C. to obtain a finished product.

[0075] Example 2: This example differs from Example 1 in that:

[0076] 100 kg of nylon, 5 kg of maleic anhydride-grafted polypropylene, 10 kg of rosin glycerol ester, 5 kg of poly(trimethylene terephthalate), 5 kg of filler, 0.5 kg of antioxidant, and 0.2 kg of dispersant; the rosin glycerol ester has a particle size of 20 μm; the filler comprises silicon nitride particles, zirconium dioxide particles, and hydrophobic silica gel particles in a weight ratio of 1:0.5:0.5, the silicon nitride particles being those prepared in Preparation Example 3, and the zirconium dioxide particles being those prepared in Preparation Example 6;

[0077] During the preparation process:

[0078] S3. Weigh antioxidant and dispersant, add to the mixture, stir evenly, and extrude at 270° C. to obtain a finished product.

[0079] Example 3: This example differs from Example 1 in that:

[0080] 150kg of nylon, 15kg of maleic anhydride-grafted polypropylene, 20kg of rosin glycerol ester, 10kg of poly(trimethylene terephthalate), 15kg of filler, 1kg of antioxidant, and 0.5kg of dispersant; the rosin glycerol ester has a particle size of 80μm; the filler consists of silicon nitride particles, zirconium dioxide particles, and hydrophobic silica gel particles in a weight ratio of 1:1:1, the silicon nitride particles being those prepared in Preparation Example 4, and the zirconium dioxide particles being those prepared in Preparation Example 7;

[0081] During the preparation process:

[0082] S3. Weigh antioxidant and dispersant, add to the mixture, stir evenly, and extrude at 280° C. to obtain a finished product.

[0083] Example 4: This example differs from Example 1 in that:

[0084] The filler is silicon dioxide, and the particle size of silicon dioxide is 200 μm.

[0085] Example 5: This example differs from Example 1 in that:

[0086] The hydrophobic silica gel particles in the filler are replaced with silica gel particles of equal mass.

[0087] Example 6: This example differs from Example 1 in that:

[0088] There is no polyvinyl alcohol on the surfaces of silicon nitride particles and zirconium dioxide particles.

[0089] Example 7: This example differs from Example 1 in that:

[0090] During the preparation of silicon nitride particles, polyvinyl alcohol was replaced by polypropylene of equal mass and particle size. During the preparation of zirconium dioxide particles, polyvinyl alcohol was replaced by polypropylene of equal mass and particle size.

[0091] Example 8: This example differs from Example 1 in that:

[0092] There is no EVA film on the surface of polyvinyl alcohol.

[0093] Example 9: This example differs from Example 1 in that:

[0094] During the preparation of polyvinyl alcohol, the melting point of EVA is 95°C.

[0095] Example 10: This example differs from Example 1 in that:

[0096] During the preparation of polyvinyl alcohol:

[0097] 1 kg of EVA melt was evenly sprayed on the surface of 1 kg of polyvinyl alcohol particles, the particle size of the polyvinyl alcohol particles was 5 μm, and the finished polyvinyl alcohol was obtained after drying.

[0098] Comparative Example

[0099] Comparative Example 1: The difference between this comparative example and Example 1 is that:

[0100] The raw materials are replaced by nylon of equal quality.

[0101] Comparative Example 2: This comparative example differs from Example 1 in that:

[0102] During the preparation of sealing materials:

[0103] The finished product is obtained by mixing nylon, poly(trimethylene terephthalate), maleic anhydride grafted polypropylene, filler, rosin glycerol ester, antioxidant and dispersant, stirring them uniformly, and extruding them.

[0104] Comparative Example 3: This comparative example differs from Example 1 in that:

[0105] The maleic anhydride grafted polypropylene is replaced by nylon of equal mass in the raw materials.

[0106] Comparative Example 4: This comparative example differs from Example 1 in that:

[0107] No dispersant was added to the raw materials.

[0108] Performance testing

[0109] 1. Tensile strength test

[0110] Sealing materials were prepared using the preparation methods of Examples 1-10 and Comparative Examples 1-4, respectively. The tensile strength was tested according to ASTM-D638, and the data were recorded.

[0111] 2. Notched impact strength test

[0112] Sealing materials were prepared using the preparation methods of Examples 1-10, respectively. Notched impact strength was tested according to ASTM-D256, and the data were recorded.

[0113] 3. Water absorption test

[0114] Sealing materials were prepared using the preparation methods of Examples 1-10 and Comparative Examples 1-4, respectively, and tested using a 1 / 10,000 moisture meter FBS-760A produced by FURBS.

[0115] 4. Sealing test

[0116] Sealing materials were prepared using the preparation methods of Examples 1-10 and Comparative Examples 1-4, respectively. A sealing ring made of the sealing material was installed on a simulated battery so that the internal and external pressure difference of the simulated battery was 2 MPa. The battery was heated to 60°C, maintained for 1 hour, cooled to room temperature, then heated to 60°C, maintained for 1 hour, cooled to room temperature, and the heating and insulation operations were repeated 10 times. The internal and external pressure difference was recorded. The smaller the pressure difference, the more pressure leakage there was and the worse the sealing effect.

[0117] Note: The relative humidity of the environment during the testing of tensile strength, notched impact strength and sealing is 80%; the relative humidity during the preparation of sealing materials is 50%.

[0118] Table 1 Performance test table

[0119]

[0120]

[0121] From Examples 1-3 and Table 1, it can be seen that the sealing material prepared in the present application has high tensile strength and high notched impact strength, and has low water absorption. After the battery is heated and heated in a cycle, it is not easy to affect the sealing effect of the sealing material due to expansion and contraction; thus, the sealing material has a long service life when used on button batteries of electronic watches or batteries of remote control cars.

[0122] Combining Example 1 and Examples 4-10 and Table 1, it can be seen that the filler in Example 4 is silica. Compared with Example 1, the sealing material prepared in Example 4 has lower tensile strength than Example 1, less notched impact strength than Example 1, greater water absorption than Example 1, and less pressure difference than Example 1. This shows that although silica also has higher strength than silicon nitride, zirconium dioxide, etc., the bonding effect between silica and other raw materials such as nylon depends solely on nylon and other hot-melt adhesive raw materials, and the bonding stability of larger particle size silica to the raw materials is lower than that of small particle size silicon nitride and zirconium dioxide. Moreover, polyvinyl alcohol and EVA are present on the surface of silicon nitride particles and zirconium dioxide particles in this application, which can not only further improve the bonding compatibility, but also block the amide group and reduce the water absorption rate, thereby ensuring that the finished sealing material has higher mechanical strength and lower water absorption rate, thereby extending the service life of the button battery on the electronic watch.

[0123] In Example 5, the hydrophobic silica gel particles are replaced with silica gel particles of equal mass in the filler. Compared with Example 1, the sealing material prepared in Example 5 has lower tensile strength than Example 1, less notched impact strength than Example 1, greater water absorption than Example 1, and less pressure difference than Example 1. This shows that the silica gel particles are hydrophilic. If they are not hydrophobicized, it is easy for the sealing material to absorb moisture, affecting the mechanical strength and service life.

[0124] In Example 6, there is no polyvinyl alcohol on the surface of the silicon nitride particles and the zirconium dioxide particles. Compared with Example 1, the sealing material prepared in Example 6 has lower tensile strength than Example 1, less notched impact strength than Example 1, greater water absorption than Example 1, and less pressure difference than Example 1; this indicates that the hydroxyl group in polyvinyl alcohol can cooperate with the amide group in nylon to attract and connect, which can reduce the amide group in the sealing material and reduce the water absorption of the sealing material; and polyvinyl alcohol and EVA have a bonding effect after hot melting, which can further improve the density of the sealing material, so that the sealing material has higher mechanical strength and better sealing effect, thereby extending the service life of the sealing material, thereby extending the service life of the button battery in the electronic watch.

[0125] In the preparation process of silicon nitride particles in Example 7, polyvinyl alcohol is replaced by polypropylene of equal mass and particle size. In the preparation process of zirconium dioxide particles, polyvinyl alcohol is replaced by polypropylene of equal mass and particle size. Compared with Example 1, the tensile strength of the sealing material prepared in Example 7 is lower than that in Example 1, the notched impact strength is lower than that in Example 1, the water absorption rate is higher than that in Example 1, and the pressure difference is lower than that in Example 1. This indicates that polypropylene does not contain hydroxyl groups and cannot combine with amide groups, thereby affecting the hygroscopicity of the sealing material. Sealing materials that easily absorb moisture will affect the mechanical strength and sealing effect.

[0126] There is no EVA film on the surface of polyvinyl alcohol in Example 8. Compared with Example 1, the tensile strength of the sealing material prepared in Example 8 is lower than that in Example 1, the notched impact strength is less than that in Example 1, the water absorption rate is greater than that in Example 1, and the pressure difference is less than that in Example 1; this indicates that the addition of the EVA film with a melting point of 60°C, after the battery is heated, the EVA is hot-melted, which can further stabilize the internal structure of the sealing material, thereby ensuring the mechanical strength of the sealing material while ensuring the sealing effect of the sealing material.

[0127] During the preparation of polyvinyl alcohol in Example 9, the melting point of EVA is 95°C. Compared with Example 1, the tensile strength of the sealing material prepared in Example 9 is lower than that in Example 1, the notched impact strength is less than that in Example 1, the water absorption rate is greater than that in Example 1, and the pressure difference is less than that in Example 1; this indicates that the normal temperature for battery use is around 60°C, and the maximum should not exceed 80°C. Therefore, the high-melting-point EVA cannot play a role in bonding stability during the use of the battery, thereby easily affecting the sealing effect of the finished sealing material.

[0128] In the preparation process of polyvinyl alcohol in Example 10, 1 kg of EVA melt is evenly sprayed on the surface of 1 kg of polyvinyl alcohol particles, and the particle size of the polyvinyl alcohol particles is 5 μm. After drying, a finished polyvinyl alcohol is obtained, that is, the EVA melt on the surface of the finished polyvinyl alcohol has been dried. Compared with Example 1, the sealing material prepared in Example 10 has a lower tensile strength than Example 1, a smaller notched impact strength than Example 1, a higher water absorption rate than Example 1, and a smaller pressure difference than Example 1; this indicates that after drying, polyvinyl alcohol is mixed with nano-silicon nitride and nano-zirconium dioxide, and bonding cannot be achieved. Instead, the mixture is in a mixed state, which easily causes a situation in which there is no polyvinyl alcohol near some nano-silicon nitride and nano-zirconium dioxide in the sealing material, affecting the bonding compatibility of nano-silicon nitride, nano-zirconium dioxide with nylon and other raw materials, thereby affecting the mechanical strength and service life.

[0129] Combining Example 1 and Comparative Examples 1-4 with Table 1, it can be seen that in Comparative Example 1, rosin glycerol ester is replaced with nylon of equal mass in the raw materials. Compared with Example 1, the sealing material prepared in Comparative Example 1 has lower tensile strength than Example 1, lower notched impact strength than Example 1, higher water absorption than Example 1, and lower pressure difference than Example 1. This indicates that the combination of rosin glycerol ester and nylon, and the bonding compatibility of rosin glycerol ester after hot melting, can improve the structural density of the sealing material, and improve the bonding stability between the filler and raw materials such as nylon, so that the sealing material has higher mechanical strength. At the same time, rosin glycerol ester does not absorb water, reduces the hygroscopicity of the sealing material, and thus extends the service life of the sealing material.

[0130] During the preparation of the sealing material of Comparative Example 2, all raw materials were mixed at one time. Compared with Example 1, the tensile strength of the sealing material prepared in Comparative Example 2 was lower than that of Example 1, the notched impact strength was lower than that of Example 1, the water absorption rate was higher than that of Example 1, and the pressure difference was lower than that of Example 1. This indicates that one-time mixing can easily affect the dispersion and contact effect of the filler and rosin glycerol ester, thereby affecting the mechanical strength and sealing effect of the finished sealing material.

[0131] In Comparative Example 3, the maleic anhydride grafted polypropylene is replaced with nylon of equal mass in the raw materials. Compared with Example 1, the sealing material prepared in Comparative Example 3 has lower tensile strength than Example 1, less notched impact strength than Example 1, greater water absorption than Example 1, and less pressure difference than Example 1; this indicates that the combination of maleic anhydride grafted polypropylene and rosin glycerol ester utilizes their compatible adhesion after hot melting to improve the higher structural density of the sealing material, further improve the mechanical strength of the sealing material while reducing the water absorption of the sealing material.

[0132] No dispersant was added to the raw materials of Comparative Example 4. Compared with Example 1, the sealing material prepared in Comparative Example 4 had lower tensile strength than that of Example 1, less notched impact strength than that of Example 1, greater water absorption than that of Example 1, and less pressure difference than that of Example 1. This indicates that microcrystalline wax can promote the uniform dispersion of fillers, i.e., other raw materials, in the sealing material, so that the sealing material has the advantages of high mechanical strength and low water absorption.

[0133] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A lithium battery sealing material, characterized in that: The invention is prepared from the following raw materials in parts by weight: 100-150 parts of nylon, 5-15 parts of maleic anhydride grafted polypropylene, 10-20 parts of rosin glycerol ester, 5-10 parts of poly(trimethylene terephthalate), 5-15 parts of filler, 0.5-1 part of antioxidant, and 0.2-0.5 part of dispersant; the filler comprises silicon nitride particles, zirconium dioxide particles, and hydrophobic silica particles in a weight ratio of 1:0.5-1:0.5-1; the silicon nitride particles comprise nano-silicon nitride and polyvinyl alcohol particles coated with EVA film in a weight ratio of 1:0.2-0.8; the zirconium dioxide particles comprise nano-zirconium dioxide and polyvinyl alcohol particles coated with EVA film in a weight ratio of 1:0.2-0.8; the dispersant is microcrystalline wax; and the hydrophobic silica particles are prepared by hydrophobically modifying nano-silicon particles with a silane coupling agent KH-570. The polyvinyl alcohol microparticles coated with EVA film were prepared by the following method: Weigh EVA and heat it to 65°C to completely melt it to obtain EVA melt; 0.8 kg of EVA melt was evenly sprayed on the surface of 1 kg of polyvinyl alcohol particles, the particle size of the polyvinyl alcohol particles was 5 μm, and the finished polyvinyl alcohol was obtained; The preparation of lithium battery sealing material includes the following steps: S1. Mixing nylon, poly(trimethylene terephthalate), and maleic anhydride grafted polypropylene and stirring uniformly to prepare a primary mixture; S2. Weigh the filler and rosin glycerol ester, mix and stir evenly, and then mix and stir evenly with the initial mixture to prepare a mixture; S3. Weigh antioxidant and dispersant, add to the mixture, stir evenly, and extrude to obtain a finished product.

2. A lithium battery sealing material according to claim 1, characterized in that: The antioxidant is antioxidant 1024.

3. A lithium battery sealing material according to claim 1, characterized in that: In step S2, the particle size of rosin glycerol ester is 20-80 μm.

4. A lithium battery sealing material according to claim 1, characterized in that: In step S3, the extrusion molding temperature is 270-280°C.

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