A flame retardant semi-solid gel electrolyte and preparation method thereof

Abstract

The invention discloses a flame retardant semi-solid gel electrolyte and a preparation method thereof. The flame retardant semi-solid gel electrolyte comprises the following raw materials in parts by weight: 100-120 parts of PVDF resin, 25-30 parts of PPC resin, 5-10 parts of modified hollow ceramic fiber, 3-5 parts of modified nano aluminum hydroxide, 15-20 parts of organic solvent, and 4-6 parts of conductive agent. The modified hollow ceramic fiber is Li-ion modified by grafting 3-aminopropyltrimethoxysilane on the surface. 0.5 La 0.5 TiO 3 Hollow ceramic fiber, modified nano aluminum hydroxide is an antioxidant flame retardant grafted modified nano aluminum hydroxide, the antioxidant flame retardant is a triazine derivative containing a hindered phenol structure and a DOPO structure. The present invention improves the gel strength of the flame retardant semi-solid gel electrolyte by adding the modified hollow ceramic fiber, and improves its ion conductivity at the same time. By adding the modified nano aluminum hydroxide, the flame retardant performance and thermal stability of the flame retardant semi-solid gel electrolyte are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of lead-acid batteries, and in particular relates to a flame-retardant semi-solid gel electrolyte and a preparation method thereof. Background Art

[0002] In order to solve the vehicle mileage anxiety, the demand for battery energy density in power batteries is getting higher and higher. In order to solve the safety problems brought about by the increase in high energy density, it is urgent to develop high energy density batteries. Solid electrolytes have the advantages of thermal stability, non-flammability, no leakage and no volatility, and they have a higher thermal runaway starting temperature, which greatly improves the stability and safety of the battery during use. Solid electrolytes are mainly divided into polymer solid electrolytes and inorganic solid electrolytes. Polymer electrolytes have the advantages of good flexibility and easy processing. However, the disadvantages of low conductivity, low electrochemical window and high operating temperature limit the application of polymer electrolytes in solid-state lithium batteries. Inorganic solid electrolytes, especially sulfide electrolytes, have high ionic conductivity, wide electrochemical window and good stability, and have received widespread attention. However, inorganic electrolytes have poor air stability and poor interface stability, and there are interface problems between the positive and negative electrodes, which limits the commercial application of solid-state batteries.

[0003] Gel electrolytes contain both liquid and solid components, and have the advantages of liquid electrolytes as well as the advantages of solid electrolytes. This system in which the polymer matrix is ​​covered with liquid electrolyte and has a network structure is also called a homogeneous electrolyte. Gel electrolytes also have ionic conductivity similar to that of liquid electrolytes, effectively solving the solid-solid interface contact and inhibiting the reduction of high-valent ions in the electrolyte by metallic lithium, which can greatly improve the interface performance of solid-state batteries. However, the conductivity of gel polymer electrolytes is still not ideal. At the same time, due to the presence of polymers and organic solvents in gel electrolytes, their flame retardancy is poor, which greatly limits their application. Summary of the invention

[0004] In order to solve the deficiencies mentioned in the above background technology, the purpose of the present invention is to provide a flame retardant semi-solid gel electrolyte and a preparation method thereof. By adding modified hollow ceramic fibers, the gel strength of the flame retardant semi-solid gel electrolyte is improved, and at the same time, its ionic conductivity is improved. By adding modified nano-aluminum hydroxide, the flame retardant properties and thermal stability of the flame retardant semi-solid gel electrolyte are improved.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] The invention provides a flame retardant semi-solid gel electrolyte, which comprises the following raw materials in parts by weight: 100-120 parts of PVDF resin, 25-30 parts of PPC resin, 5-10 parts of modified hollow ceramic fiber, 3-5 parts of modified nano aluminum hydroxide, 15-20 parts of organic solvent, and 4-6 parts of conductive agent;

[0007] The modified hollow ceramic fiber is Li-modified by 3-aminopropyltrimethoxysilane grafting 0.5 La 0.5 TiO 3 Hollow ceramic fiber;

[0008] The modified nano aluminum hydroxide is an antioxidant flame retardant grafted modified nano aluminum hydroxide, the antioxidant flame retardant is a triazine derivative containing a hindered phenol structure and a DOPO structure, and the structural formula of the antioxidant flame retardant is as follows:

[0009]

[0010] More preferably, the organic solvent is one of N,N-dimethylformamide, N-methylpyrrolidone and acetonitrile.

[0011] Further preferably, the conductive agent is one of conductive carbon black, carbon nanotubes, carbon fibers and graphene.

[0012] Further preferably, the method for preparing the modified hollow ceramic fiber comprises the following steps:

[0013] (1) adding lithium nitrate and lanthanum nitrate to N,N-dimethylformamide solution and stirring evenly, then adding glacial acetic acid and stirring for 20 to 30 minutes, and then dropping tetrabutyl titanate and stirring evenly to obtain a precursor solution;

[0014] (2) immersing the pampas grass fiber in the obtained precursor solution to allow the salt in the solution to fully enter the template fiber, leaving it to stand and drain for 1 hour, then placing it in a drying oven at 80°C and vacuum drying it for 12 hours;

[0015] (3) placing the dried impregnated fiber in an alumina crucible, placing it in a muffle furnace, heating it to 1000°C at a rate of 5°C / min and keeping it for 6 hours, then cooling it to 300°C at a rate of 10°C / min and cooling it naturally to obtain a hollow ceramic fiber;

[0016] (4) The hollow ceramic fiber and hydrogen peroxide are vigorously stirred at 70° C. for 2 h, and then 3-aminopropyltrimethoxysilane is added and stirred for another 2 h. The fiber is washed with ethanol for 3 to 5 times, centrifuged and dried to obtain the modified hollow ceramic fiber.

[0017] Further preferably, in step (1), the molar ratio of lithium nitrate, lanthanum nitrate and tetrabutyl titanate is 1:1:2.

[0018] More preferably, in step (4), the mass of 3-aminopropyltrimethoxysilane relative to the mass of the hollow ceramic fiber is 5-10%.

[0019] Further preferably, the preparation method of modified nano aluminum hydroxide comprises the following steps:

[0020] A. Add cyanuric chloride to tetrahydrofuran and triethylamine under nitrogen atmosphere, stir to dissolve cyanuric chloride, then uniformly add 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl hydrazide, react in an ice bath for 3-4 hours after the addition is completed, then add 11-aminoundecyltriethoxysilane dropwise to the reaction system, then heat to 30°C and keep warm for 3-4 hours, finally add benzaldehyde to the reaction system, heat to 60°C and keep warm for 3-4 hours, after the reaction is completed, cool and filter to remove triethylamine hydrochloride, remove tetrahydrofuran by reduced pressure distillation, wash with deionized water 3-5 times, add ethyl acetate to the separated organic phase, dry and filter, distill the filtrate to obtain intermediate A, add intermediate A and DOPO to 1,4-dioxane, reflux for 24 hours, concentrate and add to ethanol, filter, wash and dry the precipitated solid to obtain an antioxidant flame retardant;

[0021] B. Add nano aluminum hydroxide powder to 95 Vol% ethanol aqueous solution, ultrasonically disperse for 10 to 15 minutes, adjust the solution pH to 4 with hydrochloric acid aqueous solution, then slowly add antioxidant flame retardant, continue ultrasonic dispersion for 5 to 10 minutes, heat to 80 ° C and keep the reaction for 3 to 5 hours, filter after cooling, wash and dry to obtain modified nano aluminum hydroxide.

[0022] More preferably, the molar ratio of cyanuric chloride, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionylhydrazide, 11-aminoundecyltriethoxysilane and benzaldehyde is 1:1:1:1, and the molar ratio of intermediate A and DOPO is 1:1-1.2.

[0023] Further preferably, the nano aluminum hydroxide powder is added to the ethanol aqueous solution at a solid-liquid ratio of 1:15-20, and the mass ratio of the nano aluminum hydroxide to the antioxidant flame retardant is 3-4:1.

[0024] A method for preparing a flame retardant semi-solid gel electrolyte comprises the following steps:

[0025] S1. Mix PVDF resin and PPC resin in proportion and add them to an organic solvent. Then stir on a magnetic stirring table at 50°C until they are uniformly dissolved. Add modified hollow ceramic fiber, modified nano aluminum hydroxide and conductive agent to the uniform polymer solution and continue stirring for 6 hours until the solution is completely uniform.

[0026] S2. The solution was placed in a vacuum oven at 60° C. for degassing for 30 minutes. After degassing, the solution was allowed to stand for 30 minutes to obtain a flame retardant semi-solid gel electrolyte.

[0027] Beneficial effects of the present invention:

[0028] The addition of the modified hollow ceramic fiber of the present invention can make the three-dimensional network structure of the electrolyte more stable, improve the gel strength test of the electrolyte, and prevent the hydration stratification phenomenon of the colloidal electrolyte, which leads to poor battery performance and reduces the life of the battery. At the same time, the modified hollow ceramic fiber of the present invention is evenly dispersed in the polymer matrix and has a high electrolyte absorption rate. The liquid electrolyte area absorbed by the polymer network, the interface area between the nanorods with high specific surface area and large aspect ratio and the polymer, and the uniform and tight interface formed by hydrogen bonds between the modified hollow ceramic fibers, as well as the large number of fast lithium ion transport channels constructed by the modified hollow ceramic fibers. Hydrogen bonds can promote the interaction between the polymer and the polar groups, while increasing the irregular area of ​​the polymer, thereby increasing the free Li in the entire electrolyte. + concentration, thereby improving the ionic conductivity of the colloidal electrolyte.

[0029] The modified nano aluminum hydroxide of the present invention adopts an antioxidant flame retardant to graft the modified nano aluminum hydroxide. The antioxidant flame retardant is a triazine derivative containing a hindered phenol structure and a DOPO structure. The rich N, P, and Si elements promote the dehydration and carbonization of the polymer during thermal cracking, and form a carbonaceous protective layer of Si-O and Si-C. At the same time, the DOPO group also has a good gas phase flame retardant effect. At the same time, aluminum hydroxide itself is also an excellent inorganic flame retardant. Several effects promote each other and can give the material good flame retardant properties. In addition, the hindered phenol structure of the antioxidant flame retardant can also improve the thermal stability of the flame retardant semi-solid gel electrolyte. DETAILED DESCRIPTION

[0030] 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.

[0031] Example 1

[0032] A modified hollow ceramic fiber, wherein the modified hollow ceramic fiber is Li-modified by grafting 3-aminopropyltrimethoxysilane on the surface 0.5 La 0.5 TiO 3 The hollow ceramic fiber, the preparation method thereof comprises the following steps:

[0033] (1) 0.7 g of lithium nitrate and 4.3 g of lanthanum nitrate were added to 20 ml of N,N-dimethylformamide solution and stirred evenly, then 5 ml of glacial acetic acid was added and stirred for 25 min, and then 6.8 g of tetrabutyl titanate was added dropwise and stirred evenly to obtain a precursor solution;

[0034] (2) 10.0 g of pampas grass fiber was immersed in the obtained precursor solution to allow the salt in the solution to fully enter the template fiber. After standing and draining for 1 h, it was placed in a drying oven at 80 ° C and vacuum dried for 12 h;

[0035] (3) placing the dried impregnated fiber in an alumina crucible, placing it in a muffle furnace, heating it to 1000°C at a rate of 5°C / min and keeping it for 6 hours, then cooling it to 300°C at a rate of 10°C / min and cooling it naturally to obtain a hollow ceramic fiber;

[0036] (4) 5.6 g of the hollow ceramic fiber and 20 ml of hydrogen peroxide were vigorously stirred at 70° C. for 2 h, and then 0.4 g of 3-aminopropyltrimethoxysilane was added and stirred for another 2 h. The fiber was washed with ethanol for 3 to 5 times, centrifuged and dried to obtain the modified hollow ceramic fiber.

[0037] Example 2

[0038] A modified nano aluminum hydroxide, wherein the modified nano aluminum hydroxide is a nano aluminum hydroxide grafted with an antioxidant flame retardant, wherein the antioxidant flame retardant is a triazine derivative containing a hindered phenol structure and a DOPO structure, and the structural formula of the antioxidant flame retardant is as follows:

[0039]

[0040] The preparation method of the modified nano aluminum hydroxide comprises the following steps:

[0041] A. Add 3.7g of cyanuric chloride to 50ml of tetrahydrofuran and 30ml of triethylamine under nitrogen atmosphere, stir to dissolve the cyanuric chloride, then uniformly add 5.8g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionohydrazide, react in an ice bath for 3.5h after the addition is complete, then add 6.6g of 11-aminoundecyltriethoxysilane dropwise to the reaction system, then heat to 30℃ and keep warm for 3.5h, finally add 2.1g of benzaldehyde to the reaction system, heat to 60℃ and keep warm for 3.5h, after the reaction is completed, cool and filter to remove triethylamine hydrochloride, remove tetrahydrofuran by reduced pressure distillation, wash with deionized water 3 to 5 times, add ethyl acetate to the separated organic phase, dry and filter, distill the filtrate under reduced pressure to obtain intermediate A, add 8.1g of intermediate A and 2.2g of DOPO to 50ml 1,4-dioxane, reflux reaction for 24 hours, then concentrate and add ethanol, filter, wash and dry the precipitated solid to obtain the antioxidant flame retardant;

[0042] B. Add 4.4 g of nano aluminum hydroxide powder into 80 ml of 95 Vol% ethanol aqueous solution, ultrasonically disperse for 12 min, adjust the solution pH to 4 with hydrochloric acid aqueous solution, then slowly add 1.2 g of antioxidant flame retardant, continue ultrasonic dispersion for 8 min, heat to 80 ° C and keep the reaction for 4 h, filter after cooling, wash and dry to obtain the modified nano aluminum hydroxide.

[0043] Example 3

[0044] A flame retardant semi-solid gel electrolyte, the flame retardant semi-solid gel electrolyte comprising the following raw materials in parts by weight: 100 parts of PVDF resin, 30 parts of PPC resin, 5 parts of modified hollow ceramic fiber, 5 parts of modified nano aluminum hydroxide, 15 parts of acetonitrile, and 6 parts of conductive carbon black; the modified hollow ceramic fiber is Li 2O3 prepared in Example 1 and surface-grafted with 3-aminopropyltrimethoxysilane. 0.5 La 0.5 TiO 3 The hollow ceramic fiber, the modified nano aluminum hydroxide is the antioxidant flame retardant grafted modified nano aluminum hydroxide prepared in Example 2.

[0045] The method for preparing the flame retardant semi-solid gel electrolyte comprises the following steps:

[0046] S1. Mix PVDF resin and PPC resin in proportion and add them to acetonitrile, then stir on a magnetic stirring table at 50°C until they are uniformly dissolved, add modified hollow ceramic fiber, modified nano aluminum hydroxide and conductive carbon black to the uniform polymer solution and continue stirring for 6 hours until they are completely uniform;

[0047] S2. The solution was placed in a vacuum oven at 60° C. for degassing for 30 min. After degassing, the solution was allowed to stand for 30 min to obtain a flame retardant semi-solid gel electrolyte.

[0048] Example 4

[0049] A flame retardant semi-solid gel electrolyte, the flame retardant semi-solid gel electrolyte comprising the following raw materials in parts by weight: 120 parts of PVDF resin, 25 parts of PPC resin, 10 parts of modified hollow ceramic fiber, 3 parts of modified nano aluminum hydroxide, 20 parts of N-methylpyrrolidone, and 4 parts of carbon nanotubes; the modified hollow ceramic fiber is Li 200 surface-grafted modified with 3-aminopropyltrimethoxysilane prepared in Example 1. 0.5 La 0.5 TiO 3 The hollow ceramic fiber, the modified nano aluminum hydroxide is the antioxidant flame retardant grafted modified nano aluminum hydroxide prepared in Example 2.

[0050] The method for preparing the flame retardant semi-solid gel electrolyte comprises the following steps:

[0051] S1. Mix PVDF resin and PPC resin in proportion and add them to N-methylpyrrolidone, then stir on a magnetic stirring table at 50°C until they are uniformly dissolved, add modified hollow ceramic fiber, modified nano aluminum hydroxide and carbon nanotubes to the uniform polymer solution and continue stirring for 6 hours until they are completely uniform;

[0052] S2. The solution was placed in a vacuum oven at 60° C. for degassing for 30 min. After degassing, the solution was allowed to stand for 30 min to obtain a flame retardant semi-solid gel electrolyte.

[0053] Example 5

[0054] A flame retardant semi-solid gel electrolyte, the flame retardant semi-solid gel electrolyte comprising the following raw materials in parts by weight: 110 parts of PVDF resin, 18 parts of PPC resin, 8 parts of modified hollow ceramic fiber, 4 parts of modified nano aluminum hydroxide, 17 parts of N,N-dimethylformamide, and 5 parts of graphene; the modified hollow ceramic fiber is Li 200 surface-modified by 3-aminopropyltrimethoxysilane prepared in Example 1. 0.5 La 0.5 TiO 3 The hollow ceramic fiber, the modified nano aluminum hydroxide is the antioxidant flame retardant grafted modified nano aluminum hydroxide prepared in Example 2.

[0055] The method for preparing the flame retardant semi-solid gel electrolyte comprises the following steps:

[0056] S1. Mix PVDF resin and PPC resin in proportion and add them to N,N-dimethylformamide, then stir on a magnetic stirring table at 50°C until they are uniformly dissolved, add modified hollow ceramic fiber, modified nano aluminum hydroxide and graphene to the uniform polymer solution and continue stirring for 6 hours until they are completely uniform;

[0057] S2. The solution was placed in a vacuum oven at 60° C. for degassing for 30 min. After degassing, the solution was allowed to stand for 30 min to obtain a flame retardant semi-solid gel electrolyte.

[0058] Comparative Example 1

[0059] A flame retardant semi-solid gel electrolyte comprises the following raw materials in parts by weight: 110 parts of PVDF resin, 18 parts of PPC resin, 4 parts of modified nano aluminum hydroxide, 17 parts of N,N-dimethylformamide, and 5 parts of graphene; the modified nano aluminum hydroxide is the antioxidant flame retardant grafted modified nano aluminum hydroxide prepared in Example 2.

[0060] The method for preparing the flame retardant semi-solid gel electrolyte comprises the following steps:

[0061] S1. Mix PVDF resin and PPC resin in proportion and add them to N,N-dimethylformamide, then stir on a magnetic stirring table at 50°C until they are uniformly dissolved, add modified nano aluminum hydroxide and graphene to the uniform polymer solution and continue stirring for 6 hours until they are completely uniform;

[0062] S2. The solution was placed in a vacuum oven at 60° C. for degassing for 30 min. After degassing, the solution was allowed to stand for 30 min to obtain a flame retardant semi-solid gel electrolyte.

[0063] Comparative Example 2

[0064] A flame retardant semi-solid gel electrolyte, the flame retardant semi-solid gel electrolyte comprising the following raw materials in parts by weight: 110 parts of PVDF resin, 18 parts of PPC resin, 8 parts of modified hollow ceramic fiber, 17 parts of N,N-dimethylformamide, and 5 parts of graphene; the modified hollow ceramic fiber is Li 20 prepared in Example 1 and surface-grafted with 3-aminopropyltrimethoxysilane. 0.5 La 0.5 TiO 3 Hollow ceramic fiber.

[0065] The method for preparing the flame retardant semi-solid gel electrolyte comprises the following steps:

[0066] S1. Mix PVDF resin and PPC resin in proportion and add them to N,N-dimethylformamide, then stir on a magnetic stirring table at 50°C until they are uniformly dissolved, add modified hollow ceramic fiber and graphene to the uniform polymer solution and continue stirring for 6 hours until they are completely uniform;

[0067] S2. The solution was placed in a vacuum oven at 60° C. for degassing for 30 min. After degassing, the solution was allowed to stand for 30 min to obtain a flame retardant semi-solid gel electrolyte.

[0068] Performance Testing

[0069] (1) Gel strength test: The colloidal electrolytes prepared in Examples 3-4 and Comparative Examples 1-2 were placed in a test tube with a diameter of 3 cm and placed in a water bath at 25°C for 24 hours. A self-made instrument was used to drop a ruler with a length of 15 cm, a rectangular end face (length 16 mm, width 1 mm), and a weight of 14 g from a height of 10 cm from the surface of the colloidal electrolyte. The gel strength was reflected by the depth of the ruler inserted into the colloidal electrolyte. The experiment was performed H times (the error was required to be ≤3%), and the average value was calculated. The data obtained are shown in Table 1 below.

[0070] Table 1 Colloidal electrolyte gel strength test results

[0071] Group Average depth (mm) Example 3 30.7 Example 4 35.6 Example 5 32.4 Comparative Example 1 48.3 Comparative Example 2 31.9

[0072] It can be seen from the data in Table 1 that in Comparative Document 1, no modified hollow ceramic fiber is added, and the gel strength is significantly lower than that of Examples 3 to 5 and Comparative Example 2, indicating that the addition of modified hollow ceramic fibers can make the three-dimensional network structure of the electrolyte more stable, improve the gel strength test of the electrolyte, and prevent the hydration stratification phenomenon of the colloidal electrolyte, resulting in poor battery performance and reduced battery life.

[0073] (2) Ion conductivity test: Three negative plates and two positive plates were arranged alternately, and the negative plates were wrapped with AGM separators and placed together in a rectangular organic glass battery case, wherein the total amount of active material on the negative plates was the same as that on the positive plates. The colloidal electrolyte prepared in Examples 3 to 5 and Comparative Examples 1 to 2 was injected into the battery case, and the colloidal electrolyte ion conductivity test was performed after the colloidal solidification:

[0074] The test was completed using an electrochemical workstation using the AC resistance method. The AC voltage amplitude was set to 5mV and the frequency was between 105 or 106Hz and 0.1Hz. After the test, the membrane thickness was measured using a thickness gauge. The bulk impedance R of the electrolyte membrane b , obtained from data measurement. According to the formula, the ionic conductivity of the electrolyte can be calculated as σ = L / R b ×S, L here refers to the thickness of the electrolyte membrane, S here refers to the contact area between the steel sheet and the electrolyte membrane, R b Here it refers to the bulk impedance of the electrolyte. The results are shown in Table 2.

[0075] Table 2 Test results of ionic conductivity of colloidal electrolyte

[0076] Group Room temperature ionic conductivity (S / cm) Example 3 <![CDATA[1.02×10 -3 ]]> Example 4 <![CDATA[1.25×10 -3 ]]> Example 5 <![CDATA[1.16×10 -3 ]]> Comparative Example 1 <![CDATA[5.75×10 -4 ]]> Comparative Example 2 <![CDATA[1.13×10 -3 ]]>

[0077] It can be seen from the data in Table 2 that no modified hollow ceramic fiber was added to Comparative Example 1, and the ionic conductivity of Comparative Example 1 was significantly lower than that of other groups. The modified hollow ceramic fiber of the present invention is evenly dispersed between the polymer matrix and has a high electrolyte absorption rate. The liquid electrolyte area absorbed by the polymer network, the interface area between the nanorods with high specific surface area and large aspect ratio and the polymer, and the uniform and tight interface formed by hydrogen bonds between the modified hollow ceramic fibers, as well as the large number of fast lithium ion transport channels constructed by the modified hollow ceramic fibers. Hydrogen bonds can promote the interaction between the polymer and the polar groups, while increasing the irregular area of ​​the polymer, thereby increasing the free Li in the entire electrolyte. + concentration, thereby improving the ionic conductivity of the colloidal electrolyte.

[0078] (3) Flame retardant performance test

[0079] Flame retardant performance test The flame retardant semi-solid gel electrolytes in Examples 3 to 5 and Comparative Examples 1 to 2 were made into standard specimens of 127×12.7×3.2 mm, and horizontal and vertical (UL-94) combustion tests were performed according to ASTM D3801-1996 standard. At the same time, an oxygen index test (LOI) was performed according to ASTM D2863-70 standard to obtain the data shown in Table 3 below.

[0080] Table 3 Flame retardant properties test results of flame retardant semi-solid gel electrolyte

[0081]

[0082]

[0083] It can be seen from the data in Table 3 that the flame retardant semi-solid gel electrolyte of the present invention has good flame retardant properties. In Comparative Example 2, no modified nano aluminum hydroxide is added, and its flame retardant properties are significantly lower than those of other groups. The modified nano aluminum hydroxide of the present invention adopts an antioxidant flame retardant to graft modified nano aluminum hydroxide. The antioxidant flame retardant is a triazine derivative containing a hindered phenol structure and a DOPO structure, rich in N, P, and Si elements, which promotes polymer dehydration and carbonization during thermal cracking, and forms a carbonaceous protective layer of Si-O and Si-C. At the same time, the DOPO group also has a good gas phase flame retardant effect, and aluminum hydroxide itself is also an excellent inorganic flame retardant. Several effects promote each other and can give the material good flame retardant properties. In addition, the hindered phenol structure of the antioxidant flame retardant can also improve the thermal stability of the flame retardant semi-solid gel electrolyte.

[0084] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0085] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A flame retardant semi-solid gel electrolyte, characterized in that: The flame retardant semi-solid gel electrolyte comprises the following raw materials in parts by weight: 100-120 parts of PVDF resin, 25-30 parts of PPC resin, 5-10 parts of modified hollow ceramic fiber, 3-5 parts of modified nano aluminum hydroxide, 15-20 parts of organic solvent, and 4-6 parts of conductive agent; The modified hollow ceramic fiber is Li-2O3 modified by 3-aminopropyltrimethoxysilane surface grafting. 0.5 La 0.5 TiO3 hollow ceramic fiber; The modified nano aluminum hydroxide is an antioxidant flame retardant grafted modified nano aluminum hydroxide, the antioxidant flame retardant is a triazine derivative containing a hindered phenol structure and a DOPO structure, and the structural formula of the antioxidant flame retardant is as follows:

2. The flame retardant semi-solid gel electrolyte according to claim 1, characterized in that: The organic solvent is one of N,N-dimethylformamide, N-methylpyrrolidone and acetonitrile.

3. The flame retardant semi-solid gel electrolyte according to claim 1, characterized in that: The conductive agent is one of conductive carbon black, carbon nanotubes, carbon fibers and graphene.

4. The flame retardant semi-solid gel electrolyte according to claim 1, characterized in that: The preparation method of the modified hollow ceramic fiber comprises the following steps: (1) adding lithium nitrate and lanthanum nitrate to N,N-dimethylformamide solution and stirring evenly, then adding glacial acetic acid and stirring for 20 to 30 minutes, and then dropping tetrabutyl titanate and stirring evenly to obtain a precursor solution; (2) immersing the pampas grass fiber in the obtained precursor solution to allow the salt in the solution to fully enter the template fiber, leaving it to stand and drain for 1 hour, then placing it in a drying oven at 80°C and vacuum drying it for 12 hours; (3) placing the dried impregnated fiber in an alumina crucible, placing it in a muffle furnace, heating it to 1000°C at a rate of 5°C / min and keeping it for 6 hours, then cooling it to 300°C at a rate of 10°C / min and cooling it naturally to obtain a hollow ceramic fiber; (4) The hollow ceramic fiber and hydrogen peroxide are vigorously stirred at 70° C. for 2 h, and then 3-aminopropyltrimethoxysilane is added and stirred for another 2 h. The fiber is washed with ethanol for 3 to 5 times, centrifuged and dried to obtain the modified hollow ceramic fiber.

5. The flame retardant semi-solid gel electrolyte according to claim 4, characterized in that: In the step (1), the molar ratio of lithium nitrate, lanthanum nitrate and tetrabutyl titanate is 1:1:

2.

6. The flame retardant semi-solid gel electrolyte according to claim 4, characterized in that: In the step (4), the mass of 3-aminopropyltrimethoxysilane relative to the mass of the hollow ceramic fiber is 5-10%.

7. The flame retardant semi-solid gel electrolyte according to claim 1, characterized in that: The preparation method of the modified nano aluminum hydroxide comprises the following steps: A. Add cyanuric chloride to tetrahydrofuran and triethylamine under nitrogen atmosphere, stir to dissolve cyanuric chloride, then uniformly add 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl hydrazide, react in an ice bath for 3-4 hours after the addition is completed, then add 11-aminoundecyltriethoxysilane dropwise to the reaction system, then heat to 30°C and keep warm for 3-4 hours, finally add benzaldehyde to the reaction system, heat to 60°C and keep warm for 3-4 hours, after the reaction is completed, cool and filter to remove triethylamine hydrochloride, remove tetrahydrofuran by reduced pressure distillation, wash with deionized water 3-5 times, add ethyl acetate to the separated organic phase, dry and filter, distill the filtrate under reduced pressure to obtain intermediate A, add intermediate A and DOPO to 1,4-dioxane, reflux for 24 hours, concentrate and add to ethanol, filter, wash and dry the precipitated solid to obtain the antioxidant flame retardant; B. Add nano aluminum hydroxide powder to 95 Vol% ethanol aqueous solution, ultrasonically disperse for 10 to 15 minutes, adjust the solution pH to 4 with hydrochloric acid aqueous solution, then slowly add antioxidant flame retardant, continue ultrasonic dispersion for 5 to 10 minutes, heat to 80°C and keep warm for 3 to 5 hours, filter after cooling, wash and dry to obtain the modified nano aluminum hydroxide.

8. The flame retardant semi-solid gel electrolyte according to claim 7, characterized in that: The molar ratio of cyanuric chloride, 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl hydrazide, 11-aminoundecyltriethoxysilane and benzaldehyde is 1:1:1:1, and the molar ratio of the intermediate A and DOPO is 1:1-1.

2.

9. The flame retardant semi-solid gel electrolyte according to claim 7, characterized in that: The nano aluminum hydroxide powder is added to the ethanol aqueous solution at a solid-liquid ratio of 1:15-20, and the mass ratio of the nano aluminum hydroxide to the antioxidant flame retardant is 3-4:

1.

10. The method for preparing a flame retardant semi-solid gel electrolyte according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Mix PVDF resin and PPC resin in proportion and add them to an organic solvent. Then stir on a magnetic stirring table at 50°C until they are uniformly dissolved. Add modified hollow ceramic fiber, modified nano aluminum hydroxide and conductive agent to the uniform polymer solution and continue stirring for 6 hours until the solution is completely uniform. S2. The solution was placed in a vacuum oven at 60° C. for degassing for 30 minutes. After degassing, the solution was allowed to stand for 30 minutes to obtain a flame retardant semi-solid gel electrolyte.

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