Separator modified material and preparation method thereof, separator and sodium battery

Abstract

The application relates to the technical field of battery materials, and discloses a separator modification material, a preparation method thereof, a separator and a sodium battery. The disclosed preparation method comprises the following steps: gradually adding a first mixed solution into a second mixed solution to fully react to obtain a third mixed solution, the first mixed solution is an alcohol solution with a pH of 11-12.5, the second mixed solution comprises a monoalkyl silicate and nickel powder dispersed in the monoalkyl silicate; the third mixed solution is stirred at 60-90 DEG C to obtain a mixture in a colloidal state; the mixture in the colloidal state is freeze-dried to remove water in the mixture, and a porous silica composite material loaded with the nickel powder is obtained; the mass ratio of the monoalkyl silicate to the nickel powder is 2.5-9:1. The separator modification material prepared by the preparation method is coated on the surface of a base film as a modifier to prepare a separator, and compared with a conventional separator, the prepared separator can improve the volume expansion of a battery and prolong the service life of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery materials, in particular to a separator modification material, a preparation method thereof, a separator and a sodium battery. BACKGROUND

[0002] Sodium ion battery is a battery with layered oxide (such as nickel iron manganese oxide and copper iron manganese oxide) material, prussian blue analog (such as iron-based prussian white) material, polyanion (such as sodium iron sulfate, sodium iron phosphate, etc.) as the positive electrode, carbon material (such as hard carbon, soft carbon) as the negative electrode, mainly using ester and ether as the solvent, adding Na + Metal salt (such as sodium fluoride, sodium borate and perchlorate) electrolyte and various additives (such as film forming, flame retardant and overcharge protection, etc.), forming electrolyte. Although sodium ion battery and its negative electrode-free battery have the advantages of good low temperature performance, low cost, high safety and long cycle life, etc., but it still has serious gas problem, especially high temperature gas is more obvious. Especially the reversibility of CO and CO2 gas produced is poor, which not only accumulates in the cell, but also decomposes the electrolyte components, affecting the battery life. In addition, iron-based materials such as polyanion (such as sodium iron sulfate, sodium iron phosphate, etc.) have strong water absorption capacity, and H2O is also easy to decompose and produce gas.

[0003] In view of this, the present application is proposed. SUMMARY

[0004] The purpose of the present application is to provide a separator modification material, a preparation method thereof, a separator and a sodium battery, aiming at improving at least one problem mentioned in the background art.

[0005] The present application is realized as follows:

[0006] In a first aspect, the present application provides a preparation method of a separator modification material, comprising:

[0007] The first mixed solution is gradually added to the second mixed solution to obtain a third mixed solution, the first mixed solution is an alcohol solution with pH 11-12.5, and the second mixed solution comprises a monoalkyl silicate and nickel powder dispersed in the monoalkyl silicate;

[0008] The third mixed solution is stirred at 60-90℃ to obtain a colloidal mixture;

[0009] The colloidal mixture is freeze-dried to remove the water therein, and a porous silica composite material loaded with nickel powder is obtained;

[0010] The mass ratio of the monoalkyl silicate to the nickel powder is 2.5-9:1.

[0011] In an optional embodiment, the first mixed solution is prepared by:

[0012] Ammonia is added to the mixed solution of alcohol and water to adjust the pH to 11-12.5.

[0013] In an optional embodiment, at least one of the following features (1) and (2) is included:

[0014] (1) the alcohol is selected from at least one of methanol, ethanol, n-butanol and n-propanol;

[0015] (2) the mass ratio of the alcohol to water is 1.5-8:1.

[0016] In an optional embodiment, at least one of the following features (1)-(5) is included:

[0017] (1) the monoalkyl silicate is selected from at least one of tetraethyl orthosilicate and tetramethyl orthosilicate;

[0018] (2) the second mixed solution further disperses a hydroxide, and the mass ratio of the hydroxide to the monoalkyl silicate is 9-19:1;

[0019] (3) the hydroxide is selected from at least one of sodium hydroxide and calcium hydroxide;

[0020] (4) the particle size of the nickel powder is 80-120 nm;

[0021] (5) the third mixed solution is stirred at 60-90°C for 11-14 h to obtain a mixture in a colloidal state.

[0022] In a second aspect, an embodiment of the present application provides a separator modification material prepared by the preparation method provided by any of the embodiments of the present application.

[0023] In a third aspect, an embodiment of the present application provides a separator, which includes a base film and a modification coating layer coated on the surface of the base film, and the modification coating layer contains the separator modification material provided by the embodiment of the present application.

[0024] In an optional embodiment, the modification coating layer includes the separator modification material 9-19 parts and the adhesive 1 part by weight.

[0025] In an optional embodiment, at least one of the following features (1)-(4) is included:

[0026] (1) the material of the base film is polyethylene, polypropylene or glass fiber;

[0027] (2) the adhesive is selected from at least one of PVDF, CMC and SBR;

[0028] (3) the thickness of the modification coating layer is 2-4 μm;

[0029] (4) the face density of the modified coating is 2-4 mg / cm 2 .

[0030] In a fourth aspect, the embodiments of the present application provide a sodium battery, comprising the separator provided by any of the preceding embodiments.

[0031] In optional embodiments, the sodium battery comprises at least one of the following features (1)-(3):

[0032] (1) the sodium battery is a sodium ion battery or a sodium metal battery;

[0033] (2) the positive active material of the sodium battery is a polyanion material, a layered oxide or a Prussian blue analogue;

[0034] (3) the sodium battery is a sodium ion battery, and the sodium salt in the electrolyte is sodium hexafluorophosphate.

[0035] The present application has the following beneficial effects:

[0036] The preparation method provided by the present application prepares porous silica by a sol-gel method. Since the nickel powder is dispersed in the solution during the preparation process, the prepared product has the nickel powder loaded in the pores of the silica. The porous silica prepared by the sol-gel method has strong hydrophilicity and adsorption, and can well adsorb the water and gas generated in the battery. The nickel powder can be converted into a carbonyl nickel liquid by reacting with CO at room temperature (equation: CO + 4Ni = Ni(CO)4) and stored in the silica. Therefore, when the prepared separator modification material is applied to the separator of a sodium battery (such as a sodium ion battery or a negative electrode-free sodium metal battery), it can effectively absorb the water and gas generated during the charging and discharging process, greatly reduce the expansion of the volume of the sodium battery, and prolong the service life of the battery. In addition, the modification material based on silica coated on the surface of the separator can also improve the puncture strength, corrosion resistance, safety and uniformity of the electric field of the separator. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0038] Figure 1 SEM of the separator modification material prepared for Example 1. DETAILED DESCRIPTION

[0039] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. If the specific conditions are not indicated in the embodiments, the conventional conditions or the conditions suggested by the manufacturers are adopted. If the manufacturers of the reagents or instruments are not indicated, the conventional products that can be purchased in the market are adopted.

[0040] The separator modification material provided by the present application, the preparation method thereof, the separator and the sodium battery will be specifically described below.

[0041] The preparation method of the separator modification material provided by the embodiments of the present application comprises:

[0042] The first mixed solution is gradually added into the second mixed solution for sufficient reaction to obtain a third mixed solution, the first mixed solution is an alcohol solution with a pH of 11-12.5, and the second mixed solution comprises a monoalkyl silicate and nickel powder dispersed in the monoalkyl silicate;

[0043] The third mixed solution is stirred at 60-90℃ to obtain a mixture in a colloidal state;

[0044] The mixture in the colloidal state is freeze-dried to remove the water therein, and a porous silica composite material loaded with nickel powder is obtained;

[0045] The mass ratio of the monoalkyl silicate to the nickel powder is 2.5-9:1.

[0046] The preparation method provided by the present application prepares the porous silica with a porous structure by the sol-gel method. Since the nickel powder is dispersed in the solution in the preparation process, the nickel powder is loaded in the pores of the silica in the finished product. The porous silica prepared by the sol-gel method has strong hydrophilicity and adsorbability, and can well adsorb the water and gas generated in the battery. The nickel powder can be converted into a liquid of carbonyl nickel by reacting with CO at room temperature (equation: CO + 4Ni=Ni(CO)4). After the modification material is applied to the separator, the gas generated in the charging and discharging process of the battery is adsorbed into the pores of the silica, the liquid of carbonyl nickel generated by the reaction of the CO gas entering the pores with the nickel powder is stored in the pores of the silica, and the silica serves as both a collector of the gas and a storage of the carbonyl nickel, thereby reducing the contact of the gas and the carbonyl nickel with the original battery system and reducing unnecessary side reactions. Therefore, the porous silica and the nickel powder are synergistic in reducing the generation of gas. Therefore, when the separator modification material prepared by the present application is applied to the separator of a sodium battery (such as a sodium ion battery or a negative electrode-free sodium metal battery), the water and gas generated in the charging and discharging process can be effectively adsorbed, the expansion of the volume of the sodium battery is greatly reduced, and the service life of the battery is prolonged. In addition, the modification material mainly composed of silica coated on the surface of the separator can also improve the puncture strength, corrosion resistance, safety and uniformity of the electric field of the separator.

[0047] It is emphasized that the present discovery is that only by the sol-gel method can the nickel powder be loaded in the pores of the silicon dioxide, and other methods such as ball milling can only achieve simple mixing of the silicon dioxide and the nickel powder, and it is difficult to achieve loading of the nickel powder into the pores of the silicon dioxide.

[0048] It is noted that the mass ratio of the monoalkyl silicate to the nickel powder should be within the range defined in the present application. If the mass of the nickel powder is too small, the gas absorption effect is not significant, and if the mass of the nickel powder is too large, the proportion of the silicon dioxide is small, the gas adsorption capacity is reduced, and the cost is unnecessarily increased.

[0049] The preparation method is specifically as follows:

[0050] S1, providing a first mixed solution

[0051] The alcohol and water are mixed and stirred uniformly at a mass ratio of 1.5-8:1 (for example, 1.5:1, 3:1, 5:1, or 8:1), and then a pH adjuster is added to adjust the pH of the solution to 11-12.5 to obtain the first mixed solution.

[0052] Under alkaline conditions (such as adjusting the pH to alkaline by adding ammonia), the hydrolysis reaction rate is moderate, and the polycondensation reaction rate is accelerated. The alkaline environment provided by the ammonia can make the silanol groups (Si-OH) produced by the hydrolysis of tetraethyl orthosilicate more easily undergo polycondensation reaction to form Si-O-Si bonds, thereby promoting the transition of the sol to the gel. Under suitable alkaline conditions, the particle surface is negatively charged, and the electrostatic repulsion between particles can prevent excessive aggregation of particles, which is conducive to the formation of smaller and more uniform silica particles, thereby affecting the micro-morphology and specific surface area of the final product and other properties.

[0053] Optionally, the pH adjuster is ammonia.

[0054] Optionally, the alcohol is selected from at least one of methanol, ethanol, n-butanol, and n-propanol.

[0055] S2, providing a second mixed solution

[0056] The monoalkyl silicate and the high-purity nickel powder are mixed and stirred for 30-90 min (for example, 30 min, 60 min, or 90 min) to obtain the second mixed solution.

[0057] To ensure that the modified separator material has good performance, the mass ratio of the monoalkyl silicate to the high-purity nickel powder is 2.5-9:1 (for example, 2.5:1, 5:1, 7:1, or 9:1).

[0058] Optionally, to ensure that the nickel powder can be fully loaded in the pores of the silicon dioxide, the particle size of the nickel powder is 80-120 nm.

[0059] Optionally, the monoalkyl silicate is selected from at least one of ethyl orthosilicate and methyl orthosilicate.

[0060] Optionally, the second mixture further disperses a hydroxide, and a mass ratio of the hydroxide to the monoalkyl silicate is 9-19:1 (e.g., 9:1, 15:1, or 19:1).

[0061] Optionally, the hydroxide is selected from at least one of sodium hydroxide and calcium hydroxide.

[0062] When the second mixture disperses the hydroxide, the hydroxide is dispersed in the pores of the prepared porous silica, and the hydroxide has strong water absorption. The CO2 gas generated in the charging and discharging process of the battery can react with the wet sodium hydroxide to generate a carbonic acid compound or water, which can further alleviate the volume expansion of the battery.

[0063] Optionally, to ensure the purity of the nickel powder, before preparing the second mixture, the nickel powder is treated with hydrochloric acid to remove the oxide layer on the surface of the nickel powder, and then the nickel powder is washed with pure water multiple times to remove the acid on the surface of the nickel powder.

[0064] S3, mixing reaction

[0065] The first mixture is gradually added to the second mixture, and a third mixture is obtained after sufficient reaction.

[0066] Optionally, the specific way of gradual addition is slow dropwise addition with a burette.

[0067] In this step, the ethoxy group (-OC2H5) in the ethyl orthosilicate molecule is replaced by the hydroxyl group (-OH) in the water molecule, and the silanol group (Si-OH) produced by hydrolysis is more prone to condensation reaction.

[0068] S4, preparing a colloid

[0069] The third mixture is stirred at 60-90°C (e.g., 60°C, 70°C, 80°C, or 90°C) for 11-14 hours (e.g., 11 hours, 12 hours, or 14 hours) to obtain a mixture in the form of a colloid.

[0070] In this step, the silanol group (Si-OH) produced by hydrolysis is more prone to condensation reaction, and as the reaction proceeds, the viscosity of the system gradually increases, forming a sol, and further reaction forms a gel. This step needs to be carried out at 60-90°C (e.g., 60°C, 70°C, 80°C, or 90°C), and if the temperature is too high or too low, the colloid-like mixture cannot be generated.

[0071] S4, freeze-drying

[0072] The mixture in colloidal form is placed in a freezer at -12 to -8℃ (for example, -12℃, -10℃ or -8℃) for 4 to 8 hours (for example, 4 hours, 6 hours or 8 hours) to reduce the temperature, and then the water is sublimated in a freeze-drying device to obtain the porous silica membrane modified material loaded with nickel powder and hydroxide in the pores.

[0073] The porous silica membrane modified material is prepared by the preparation method provided in the embodiments of the present application.

[0074] The porous silica membrane modified material is applied to the battery membrane to improve the swelling of the battery and prolong the service life of the battery.

[0075] The porous membrane provided in the embodiments of the present application comprises a base membrane and a modified coating layer coated on the surface of the base membrane, and the modified coating layer contains the porous silica membrane modified material provided in the embodiments of the present application.

[0076] The porous membrane, because the modified coating layer contains the modified material improved in the present application, has better electrochemical performance when applied to the battery.

[0077] Optionally, the composition of the modified coating layer comprises 9 to 19 parts of the porous silica membrane modified material and 1 part of the adhesive by weight.

[0078] Optionally, the material of the base membrane is polyethylene, polypropylene or glass fiber.

[0079] Optionally, the adhesive is selected from at least one of PVDF, CMC and SBR.

[0080] Optionally, to make the porous membrane have better performance, the thickness of the modified coating layer is 2 to 4 μm (for example, 2 μm, 3 μm or 4 μm).

[0081] Optionally, to make the porous membrane have better performance, the areal density of the modified coating layer is 2 to 4 mg / cm 2 (for example, 2 mg / cm 2 , 3 mg / cm 2 or 4 mg / cm 2 ). Further, the preparation method of the porous membrane is as follows:

[0082] The porous silica membrane modified material, the adhesive and pure water are uniformly mixed to obtain a slurry with a solid content of 30 to 40% (for example, 30%, 35% or 40%).

[0083] The slurry is uniformly sprayed on the surface of the base membrane by using a membrane spraying / rolling instrument, then baked in a 95℃ oven for 2 hours, and finally rolled by a rolling machine to obtain the porous membrane.

[0084] The sodium battery provided in the embodiments of the present application comprises the porous membrane provided in the embodiments of the present application.

[0085] Optionally, the sodium battery is a sodium ion battery or a sodium metal battery.

[0086] Optionally, the positive active material of the sodium battery is a polyanion material, a layered oxide or a Prussian blue analogue.

[0087] Optionally, the sodium battery is a sodium ion battery, and the sodium salt in the electrolyte is sodium hexafluorophosphate. For example, 1M NaPF6+EC / DMC / VC (or 1M NaPF6+diethylene glycol dimethyl ether).

[0088] Optionally, the negative electrode is a hard carbon material coated negative electrode or an aluminum foil current collector serving as a negative electrode.

[0089] The features and performances of the present application are further described in detail below in combination with examples.

[0090] Example 1

[0091] Ethanol and pure water were mixed in a mass ratio of 6:1 to obtain an alcohol solution, and 0.1M ammonia water was added dropwise to the alcohol solution as a pH regulator to adjust the pH value to 12 to obtain a first mixed solution;

[0092] Tetraethyl orthosilicate, nickel powder with a particle size of 80-120nm and calcium hydroxide were mixed uniformly to obtain a second mixed solution, wherein the mass ratio of tetraethyl orthosilicate to nickel powder was 8:2, and the mass ratio of tetraethyl orthosilicate to calcium hydroxide was 9:1;

[0093] The first mixed solution was added dropwise to the second mixed solution and reacted sufficiently to obtain a third mixed solution;

[0094] The third mixed solution was stirred at a temperature of 60℃ for 14h to obtain a colloidal mixture;

[0095] The colloidal mixture was placed in a freezer at-10℃ for 6h, and then freeze-dried to obtain a porous silica diaphragm modified material loaded with nickel powder and calcium hydroxide, the SEM image of which is shown in Figure 1 As can be seen from the figure, the spherical silica particles are coated with nickel powder and hydroxide on the structure.

[0096] The prepared diaphragm modified material, PVDF and pure water were mixed uniformly to obtain a slurry with a solid content of 30%, wherein the mass ratio of the diaphragm modified material to PVDF was 15:1.

[0097] The slurry was sprayed onto the surface of a polyethylene-based film, placed in an oven at 95℃ for 2h, and then rolled to obtain a diaphragm with a coating area density of 3mg / cm 2 and a modified coating thickness of 3μm.

[0098] Example 2

[0099] Mix methanol and pure water according to the mass ratio of 8:1 to obtain an alcohol solution, and then drop 0.06M ammonia water as a pH regulator into the alcohol solution to adjust the pH value to 11 to obtain a first mixed solution;

[0100] Mix tetraethyl orthosilicate, nickel powder with a particle size of 80-120nm and sodium hydroxide uniformly to obtain a second mixed solution, wherein the mass ratio of tetraethyl orthosilicate to nickel powder is 7:3, and the mass ratio of tetraethyl orthosilicate to calcium hydroxide is 9:1;

[0101] Drop the first mixed solution into the second mixed solution to fully react to obtain a third mixed solution;

[0102] Put the third mixed solution in a 90℃ temperature for 10h stirring to obtain a colloidal mixture;

[0103] Put the colloidal mixture in a freezer at-10℃ for 6h, and then freeze-dry to obtain a porous silica diaphragm modified material loaded with nickel powder and sodium hydroxide.

[0104] Mix the prepared diaphragm modified material, PVDF and pure water uniformly to obtain a slurry with a solid content of 25%, wherein the mass ratio of the diaphragm modified material to PVDF is 19:1.

[0105] Spray the slurry onto the surface of a polyethylene-based film, place it in an oven at 95℃ for 2h, and then roll it to obtain a diaphragm with a coating area density of 2mg / cm 2 and a modified coating thickness of 2μm.

[0106] Example 3

[0107] Mix n-propyl alcohol and pure water according to the mass ratio of 4:1 to obtain an alcohol solution, and then drop 1.2M ammonia water as a pH regulator into the alcohol solution to adjust the pH value to 12.5 to obtain a first mixed solution;

[0108] Mix tetraethyl orthosilicate, nickel powder with a particle size of 80-120nm and sodium hydroxide uniformly to obtain a second mixed solution, wherein the mass ratio of tetraethyl orthosilicate to nickel powder is 9:1, and the mass ratio of tetraethyl orthosilicate to calcium hydroxide is 9:1;

[0109] Drop the first mixed solution into the second mixed solution to fully react to obtain a third mixed solution;

[0110] Put the third mixed solution in a 75℃ temperature for 12h stirring to obtain a colloidal mixture;

[0111] Put the colloidal mixture in a freezer at-10℃ for 6h, and then freeze-dry to obtain a porous silica diaphragm modified material loaded with nickel powder and sodium hydroxide.

[0112] The prepared separator modification material, PVDF and pure water were mixed uniformly to prepare a slurry with a solid content of 35%, wherein the mass ratio of the separator modification material and PVDF was 9:1.

[0113] The slurry was sprayed onto the surface of a polyethylene-based film, placed in an oven at 95°C for 2h, and then rolled to obtain a separator with a coating area density of 4mg / cm 2 and a modified coating thickness of 4μm.

[0114] Example 4

[0115] This example was basically the same as Example 3, except that no hydroxide was added in the second mixed solution, and the prepared modified separator material was a composite material in which nickel powder was loaded in the pores of porous silica.

[0116] Comparative Example 1

[0117] This comparative example provided a base film as a separator as in Example 4.

[0118] Comparative Example 2

[0119] This comparative example was basically the same as Example 4, except that:

[0120] The mixed powder obtained by fully ball-milling nickel powder and conventional non-porous silica powder with a particle size of 200-250nm was used to replace the modified separator material, wherein the ratio of nickel powder to silica was the same as that in the modified separator material prepared in Example 4.

[0121] Comparative Example 3

[0122] This comparative example was basically the same as Example 4, except that no nickel powder was added in the second mixed solution.

[0123] Comparative Example 4

[0124] This comparative example was basically the same as Example 4, except that an equal amount of nickel powder was used to replace the modified separator material to prepare a separator.

[0125] Comparative Example 5

[0126] This comparative example was basically the same as Example 4, except that the ratio of nickel powder to tetraethyl orthosilicate was 7:3.

[0127] Experimental Example

[0128] The separators prepared in each of the examples and the comparative examples were made into sodium ion batteries. The preparation method of the positive electrode was as follows: sodium iron phosphate pyrophosphate, conductive carbon black, PVDF, and PAA were uniformly mixed in a ratio of 95:2:2:1 and added into a solvent (NMP) to obtain a positive electrode slurry, and the positive electrode slurry was coated on the surface of a carbon-coated aluminum foil to obtain a positive electrode sheet. The preparation method of the negative electrode current collector was as follows: conductive carbon black, SBR, and CMC were uniformly mixed in a ratio of 95:3:2 and added into a solvent (deionized water) to obtain a carbon coating slurry, and the slurry was coated on the surface of an aluminum foil to obtain a negative electrode current collector. The electrolyte was 1M NaPF6+diethylene glycol dimethyl ether.

[0129] The electrochemical performance of the prepared sodium ion batteries was tested, and the exhaust volume was measured. The test method was the drainage method, and the specific method was as follows: a water tank was placed on an electronic balance, and the soft package battery was placed in the water, which was just immersed in the water. Principle: Archimedes, F 浮 =G 排 =ρ 水 gV 排 , ρ 水 g = 10. V 排 =1 / 10 F 浮 = the weight (g) displayed on the electronic balance.

[0130] The test results were recorded in Table 1.

[0131] Table 1: Test results of each example and the comparative example

[0132]

[0133] As can be seen from Table 1, the sodium ion batteries assembled with the separators prepared in each of the examples of the application have better performance than the sodium ion battery assembled with the separator of the comparative example 1;

[0134] Comparing the comparative example 2 with the example 4, it can be seen that the gas inhibition of the comparative example 2 is obviously poorer than that of the example 4, indicating that the effect of replacing the porous silica coated nickel powder with the conventional silica mixed nickel powder on improving the cycle performance of the separator is poor;

[0135] Comparing the comparative example 3 with the example 4, it can be seen that the gas inhibition of the comparative example 3 is obviously poorer than that of the example 4, indicating that without the loading of nickel powder in the porous silica, the improvement effect of the volume expansion of the battery is poor, and the extension effect of the service life of the battery is poor;

[0136] Comparing the comparative example 4 with the example 4, it can be seen that the capacity retention rate and the gas inhibition of the comparative example 4 are obviously poorer than those of the example 4, indicating that only the nickel powder is used as the modification material coated on the surface of the separator, and compared with the joint action of the nickel powder and the porous silica, the capacity retention rate is poorer due to the increase of self-discharge, resulting in poorer cycle life;

[0137] Comparative Example 5 and Example 4 can be seen that the capacity retention and gas inhibition of Comparative Example 5 is significantly worse than Example 4, indicating that if the amount of nickel powder is too much, the capacity retention will be worse due to the increase in self-discharge, resulting in a worse cycle life.

[0138] In summary, the porous silica prepared by the sol-gel method has strong hydrophilicity and adsorbability, and can well adsorb the water and gas generated in the battery. The nickel powder can be converted into carbonyl nickel liquid at room temperature by reacting with CO (equation: CO + 4Ni = Ni(CO)4) and stored in the silica. Therefore, when the separator modification material prepared by the present application is applied to the separator of a sodium battery (such as a sodium ion battery or a negative electrode-free sodium metal battery), it can effectively absorb the water and gas generated during charging and discharging, greatly reducing the expansion of the volume of the sodium battery and prolonging the service life of the battery. In addition, the modified material based on silica coated on the surface of the separator can also improve the puncture strength, corrosion resistance, safety and uniformity of the electric field of the separator.

[0139] In a preferred embodiment, the addition of hydroxide in the second mixed solution enables the prepared porous silica to also load hydroxide, which can further improve the moisture absorption and gas absorption of the material.

[0140] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a membrane modified material, characterized in that: include: gradually adding the first mixed solution to the second mixed solution to fully react to obtain a third mixed solution, wherein the first mixed solution is an alcohol solution with a pH of 11 to 12.5, and the second mixed solution includes a monoalkyl silicate and nickel powder dispersed in the monoalkyl silicate; Stirring the third mixed solution at 60-90° C. until a colloidal mixture is obtained; freeze-drying the colloidal mixture to remove water therein, thereby obtaining a porous silica composite material loaded with nickel powder; The mass ratio of the monoalkyl silicate to the nickel powder is 2.5-9:

1.

2. The preparation method according to claim 1, characterized in that The preparation method of the first mixed solution is: Ammonia water was added to the mixture of alcohol and water to adjust the pH to 11-12.

5.

3. The preparation method according to claim 2, characterized in that Include at least one of the following features (1) and (2): (1) The alcohol is selected from at least one of methanol, ethanol, n-butanol and n-propanol; (2) The mass ratio of the alcohol to water is 1.5 to 8:

1.

4. The preparation method according to claim 1, characterized in that The monoalkyl silicate is selected from at least one of ethyl orthosilicate and methyl orthosilicate.

5. The preparation method according to claim 1, characterized in that The second mixed liquid further contains hydroxide, and the mass ratio of the hydroxide to the monoalkyl silicate is 9-19:

1.

6. The preparation method according to claim 5, characterized in that The hydroxide is selected from at least one of sodium hydroxide and calcium hydroxide.

7. The preparation method according to claim 1, characterized in that The particle size of the nickel powder is 80-120 nm.

8. The preparation method according to claim 1, characterized in that The third mixed solution is stirred at 60-90° C. for 11-14 hours to obtain the colloidal mixture.

9. A membrane modified material, characterized in that: The method is as described in any one of claims 1 to 8.

10. A diaphragm, characterized in that: It comprises a base film and a modified coating layer coated on the surface of the base film, wherein the modified coating layer contains the diaphragm modified material according to claim 9.

11. The diaphragm according to claim 10, characterized in that The components of the modified coating include 9 to 19 parts of the diaphragm modification material and 1 part of the adhesive in parts by weight.

12. The diaphragm according to claim 11, characterized in that Include at least one of the following features (1) to (4): (1) The base film is made of polyethylene, polypropylene or glass fiber; (2) The adhesive is selected from at least one of PVDF, CMC and SBR; (3) The thickness of the modified coating is 2-4 μm; (4) The surface density of the modified coating is 2~4 mg / cm 2 .

13. A sodium battery, characterized in that: The invention comprises the diaphragm according to any one of claims 10 to 12.

14. The sodium battery according to claim 13, characterized in that Include at least one of the following features (1) to (3): (1) The sodium battery is a sodium ion battery or a sodium metal battery; (2) The positive electrode active material of the sodium battery is a polyanion material, a layered oxide or a Prussian blue analogue; (3) The sodium battery is a sodium ion battery, and the sodium salt in its electrolyte is sodium hexafluorophosphate.

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