White carbon black for battery diaphragm as well as preparation method and application of white carbon black

Abstract

The invention provides white carbon black for a battery diaphragm as well as a preparation method and application of the white carbon black, and the preparation method comprises the following steps: mixing a first sodium silicate solution with N-acylamino acid salt, and then carrying out homogenization treatment; in an oxygen-containing atmosphere, adjusting the pH value of the homogenized first sodium silicate solution by using sulfuric acid, then adding sulfuric acid and the second sodium silicate solution in a parallel flow manner, and reacting under the condition that the pH value is kept stable to obtain a precursor suspension; (2) after the reaction is finished, sulfuric acid is added in an oxygen-containing atmosphere to adjust the pH value, and aging is carried out; and after aging is finished, carrying out spray drying to obtain the white carbon black for the battery diaphragm. According to the method, the white carbon black is prepared in the oxygen-containing atmosphere, the surface hydroxyl content of the obtained white carbon black can be reduced, the reaction is performed after homogenization treatment, the stability of a reaction system can be improved, and the performance of the obtained white carbon black used for the battery diaphragm is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and relates to a battery separator material, in particular to silica for battery separators, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium-ion batteries are widely used in portable products such as mobile phones and computers, and the development of electric vehicles has also driven a greater demand for lithium-ion batteries.

[0003] A lithium-ion battery mainly consists of electrodes, an electrolyte, a polymer separator, etc. As one of the main components of a lithium-ion battery, the polymer separator needs to have good electrical insulation, mechanical properties, and good wettability with the electrolyte. Its function is to allow ions to pass freely between the positive and negative electrodes, while isolating the positive and negative electrodes so that electrons cannot pass freely. Although the polymer separator does not participate in the electrochemical reaction during the use of the lithium-ion battery, it has an important impact on the power density, energy density, and safety of the lithium-ion battery. In addition, the polymer separator is also related to the cost of the lithium-ion battery. Currently, the cost of the lithium-ion battery separator accounts for about 1 / 3 - 2 / 5 of the production cost.

[0004] Polyethylene and polypropylene microporous membranes have a high porosity, low resistance, high tear strength, and good acid and alkali resistance. CN101051681A discloses a polymer lithium-ion battery separator and a processing method thereof, which is made of a polyolefin material as the main raw material to form a separator, adding 1 - 5% nano-SiO2 powder to the polyolefin material, and forming uniformly distributed through-holes on the membrane surface of the polymer lithium-ion battery separator after unidirectional stretching. It uses the addition of SiO2 to fill the gaps between the fibers in the separator, improving the long and narrow pore diameters, increasing the porosity without reducing the strength of the membrane. However, it is necessary to effectively disperse the silica in the polyolefin matrix to solve the problem of difficult micropore control caused by a large amount of inorganic particles added.

[0005] Using silica in the battery separator can improve the thermal stability of the separator, improve the affinity between the separator and the electrolyte, increase the mechanical strength of the separator, increase the porosity, prevent the growth of lithium dendrites, and also improve the rate performance and cycle stability of the lithium-ion battery. However, it is necessary to uniformly distribute the silica on the surface or inside of the separator to achieve the modification of the separator using silica. It is also necessary for the silica to have a high specific surface area and pore volume to provide more ion transport channels; it is also necessary to control the particle size and morphology of the silica to ensure uniform distribution and form an effective ion transport network.

[0006] Therefore, it is necessary to provide silica for battery separators with a high specific surface area, pore volume, and uniform particle size distribution, a preparation method thereof, and an application thereof. Summary of the Invention

[0007] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a silica for battery separator, its preparation method and application. The preparation method prepares silica in an oxygen-containing atmosphere, which can reduce the surface hydroxyl content of the obtained silica, and can improve the stability of the reaction system and the performance of the obtained silica when used in battery separators after homogenization treatment.

[0008] To achieve this purpose, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides a preparation method of silica for battery separator, and the preparation method includes the following steps:

[0010] (1) Mix the first sodium silicate solution with N-acyl amino acid salt, and then carry out homogenization treatment;

[0011] (2) In an oxygen-containing atmosphere, use sulfuric acid to adjust the pH value of the first sodium silicate solution after homogenization treatment, and then add sulfuric acid and the second sodium silicate solution in parallel flow, and carry out the reaction under the condition of maintaining the pH value stable to obtain a precursor suspension;

[0012] (3) After the reaction in step (2) is completed, add sulfuric acid to adjust the pH value in an oxygen-containing atmosphere for aging; after aging, carry out spray drying to obtain the silica for battery separator.

[0013] The preparation method provided by the present invention first carries out homogenization treatment, which can reduce the particle size non-uniformity of the obtained silica during subsequent reactions; moreover, it can improve the dispersibility of sodium silicate and make the specific surface area of the obtained silica larger. And the preparation in an oxygen-containing atmosphere has an obvious influence on the microstructure and surface hydroxyl content of the obtained silica. When preparing silica by the precipitation method, its surface hydroxyl content is relatively high. Preparing in an oxygen-containing atmosphere can reduce the hydroxyl content on the surface of silica and reduce its agglomeration degree, so that the obtained silica has uniform particle size, and at the same time has a relatively high specific surface area and pore volume, which is suitable for battery separators.

[0014] Preferably, the gas used in the oxygen-containing atmosphere includes air and / or oxygen, and oxygen is preferred.

[0015] Preferably, the concentration of the first sodium silicate solution in step (1) is 1-2 mol / L, for example, it can be 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L or 2 mol / L, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0016] Preferably, the modulus of sodium silicate in the first sodium silicate solution in step (1) is 2-3. For example, it can be 2, 2.5 or 3, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0017] Preferably, the composition of the second sodium silicate solution is the same as that of the first sodium silicate solution.

[0018] Preferably, the N-acyl amino acid salt in step (1) includes sodium N-acyl amino acid and / or potassium N-acyl amino acid.

[0019] Preferably, the dosage of the N-acyl amino acid salt in step (1) is 20-30% of the molar amount of sodium silicate in the first sodium silicate solution. For example, it can be 20%, 23%, 25%, 28% or 30%, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0020] Preferably, the temperature of the homogenization treatment in step (1) is 80-100 °C. For example, it can be 80 °C, 85 °C, 90 °C, 95 °C or 100 °C, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0021] Preferably, the absolute pressure of the homogenization treatment in step (1) is 10-12 MPa. For example, it can be 10 MPa, 10.5 MPa, 11 MPa, 11.5 MPa or 12 MPa, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0022] Preferably, the time of the homogenization treatment in step (1) is 2-5 h. For example, it can be 2 h, 3 h, 4 h or 5 h, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0023] Preferably, the pH value of the reaction in step (2) is 4-5. For example, it can be 4, 4.5 or 5, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0024] Preferably, the temperature of the reaction in step (2) is 50-60 °C. For example, it can be 50 °C, 52 °C, 55 °C, 58 °C or 60 °C, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0025] In the present invention, the temperature of the reaction in step (2) is lower than the temperature of the homogenization treatment, that is, after the homogenization treatment, the temperature is reduced to the temperature required for the reaction by natural reduction.

[0026] Preferably, the reaction time in step (2) is 90 - 100 min, for example, it can be 90 min, 92 min, 95 min, 98 min or 100 min, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0027] Preferably, adjusting the pH value in step (3) is to adjust the pH value to 3 - 4, for example, it can be 3, 3.5 or 4, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0028] Preferably, the aging temperature in step (3) is 70 - 80 °C, for example, it can be 70 °C, 72 °C, 75 °C, 78 °C or 80 °C, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0029] Preferably, the aging time in step (3) is 60 - 80 min, for example, it can be 60 min, 65 min, 70 min, 75 min or 80 min, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0030] Preferably, the spray drying temperature in step (3) is 200 - 240 °C, for example, it can be 200 °C, 210 °C, 220 °C, 230 °C or 240 °C, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0031] Preferably, the mass concentration of the sulfuric acid is above 80 wt%, for example, it can be 80 wt%, 85 wt%, 90 wt%, 95 wt% or 98 wt%, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0032] As a preferred technical solution of the preparation method provided by the present invention, the preparation method includes the following steps:

[0033] (1) Mix the first sodium silicate solution with the N-acyl amino acid salt, and then carry out homogenization treatment at 80 - 100 °C and 10 - 12 MPa for 2 - 5 h;

[0034] The concentration of the first sodium silicate solution is 1 - 2 mol / L, and the modulus is 2 - 3;

[0035] The dosage of the N-acyl amino acid salt is 20 - 30% of the molar amount of sodium silicate in the first sodium silicate solution;

[0036] (2) In an oxygen atmosphere, use sulfuric acid to adjust the pH value of the first sodium silicate solution after homogenization treatment to 4 - 5, and then add sulfuric acid and the second sodium silicate solution in a co-current manner, and carry out the reaction under the condition of maintaining the pH value stable at 4 - 5 to obtain a precursor suspension;

[0037] The temperature of the reaction is 50 - 60 °C, and the time is 90 - 100 min;

[0038] (3) After the reaction described in step (2) ends, sulfuric acid is added to adjust the pH value to 3 - 4 in an oxygen atmosphere, and aging is carried out for 60 - 80 min under the condition of 70 - 80 °C; after aging ends, spray drying is carried out under the condition of 200 - 240 °C to obtain the silica white for battery separator.

[0039] In a second aspect, the present invention provides a silica white for battery separator, which is prepared by the preparation method described in the first aspect.

[0040] In a third aspect, the present invention provides a battery separator, which includes the silica white for battery separator obtained by the preparation method described in the first aspect, or includes the silica white for battery separator described in the second aspect.

[0041] The numerical ranges described in the present invention not only include the point values exemplified above, but also include any point values between the above numerical ranges not exemplified. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the ranges.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] The preparation method provided by the present invention first performs homogenization treatment. The homogenization treatment can reduce the particle size non-uniformity of the silica white obtained in the subsequent reaction; moreover, it can improve the dispersibility of sodium silicate, making the specific surface area of the obtained silica white larger. And preparing in an oxygen-containing atmosphere has an obvious influence on the microstructure and surface hydroxyl content of the obtained silica white. When preparing silica white by the precipitation method, its surface hydroxyl content is relatively high. Preparing in an oxygen-containing atmosphere can reduce the hydroxyl content on the surface of silica white and reduce its agglomeration degree, so that the obtained silica white has uniform particle size, and at the same time has a relatively high specific surface area and pore volume, which is suitable for battery separators. Specific Embodiments

[0044] The technical solutions of the present invention will be further described below through specific embodiments.

[0045] Example 1

[0046] This example provides a preparation method of silica white for battery separator, and the preparation method includes the following steps:

[0047] (1) Mix the first sodium silicate solution with N-acyl amino acid sodium, and then carry out homogenization treatment at 90 °C and 11 MPa for 4 h;

[0048] The concentration of the first sodium silicate solution is 1.5 mol / L and the modulus is 2.5;

[0049] The dosage of sodium N-acyl amino acid is 25% of the molar amount of sodium silicate in the first sodium silicate solution;

[0050] (2) In an oxygen atmosphere, use 98 wt% sulfuric acid to adjust the pH value of the first sodium silicate solution after homogenization treatment to 4.5, and then add 98 wt% sulfuric acid and the second sodium silicate solution in a co-current manner. React under the condition of maintaining the pH value stable at 4.5 to obtain a precursor suspension;

[0051] The concentration of the second sodium silicate solution is 1.5 mol / L and the modulus is 2.5;

[0052] The temperature of the reaction is 55 °C and the time is 95 min;

[0053] (3) After the reaction in step (2) is completed, add 98 wt% sulfuric acid in an oxygen atmosphere to adjust the pH value to 3.5, and age at 75 °C for 70 min; after aging, perform spray drying at 220 °C to obtain the white carbon black for battery separator.

[0054] Example 2

[0055] This example provides a preparation method of white carbon black for battery separator. The preparation method includes the following steps:

[0056] (1) Mix the first sodium silicate solution with sodium N-acyl amino acid, and then perform homogenization treatment at 80 °C and 10 MPa for 5 h;

[0057] The concentration of the first sodium silicate solution is 1 mol / L and the modulus is 2;

[0058] The dosage of sodium N-acyl amino acid is 20% of the molar amount of sodium silicate in the first sodium silicate solution;

[0059] (2) In an oxygen atmosphere, use 98 wt% sulfuric acid to adjust the pH value of the first sodium silicate solution after homogenization treatment to 4, and then add 98 wt% sulfuric acid and the second sodium silicate solution in a co-current manner. React under the condition of maintaining the pH value stable at 4 to obtain a precursor suspension;

[0060] The concentration of the second sodium silicate solution is 1 mol / L and the modulus is 2;

[0061] The temperature of the reaction is 50 °C and the time is 100 min;

[0062] (3) After the reaction described in step (2) is completed, 98 wt% sulfuric acid is added in an oxygen atmosphere to adjust the pH value to 3, and aging is carried out at 70 °C for 80 min; after the aging is completed, spray drying is carried out at 200 °C to obtain the silica white for battery separator.

[0063] Example 3

[0064] This example provides a preparation method of silica white for battery separator, and the preparation method includes the following steps:

[0065] (1) The first sodium silicate solution is mixed with sodium N-acylamino acid, and then homogenization treatment is carried out at 100 °C and 12 MPa for 2 h;

[0066] The concentration of the first sodium silicate solution is 2 mol / L and the modulus is 3;

[0067] The dosage of sodium N-acylamino acid is 30% of the molar amount of sodium silicate in the first sodium silicate solution;

[0068] (2) In an oxygen atmosphere, 98 wt% sulfuric acid is used to adjust the pH value of the first sodium silicate solution after homogenization treatment to 5, and then 98 wt% sulfuric acid and the second sodium silicate solution are added in a co-current manner, and the reaction is carried out under the condition of maintaining the pH value stable at 5 to obtain a precursor suspension;

[0069] The concentration of the second sodium silicate solution is 2 mol / L and the modulus is 3;

[0070] The temperature of the reaction is 60 °C and the time is 90 min;

[0071] (3) After the reaction described in step (2) is completed, 98 wt% sulfuric acid is added in an oxygen atmosphere to adjust the pH value to 4, and aging is carried out at 80 °C for 60 min; after the aging is completed, spray drying is carried out at 240 °C to obtain the silica white for battery separator.

[0072] Example 4

[0073] This example provides a preparation method of silica white for battery separator. Except that the oxygen atmosphere in the preparation method is replaced by an air atmosphere, the rest are the same as in Example 1.

[0074] Example 5

[0075] This example provides a preparation method of silica white for battery separator, and the preparation method includes the following steps:

[0076] (1) The first sodium silicate solution is mixed with sodium N-acylamino acid, and then homogenization treatment is carried out at 90 °C and 11 MPa for 4 h;

[0077] The concentration of the first sodium silicate solution is 1.5 mol / L and the modulus is 2.5;

[0078] The dosage of sodium N-acyl amino acid is 25% of the molar amount of sodium silicate in the first sodium silicate solution;

[0079] (2) In an oxygen atmosphere, use 98 wt% sulfuric acid to adjust the pH value of the first sodium silicate solution after homogenization treatment to 3.5, and then add 98 wt% sulfuric acid and the second sodium silicate solution in a co-current manner. React under the condition of maintaining the pH value stable at 3.5 to obtain a precursor suspension;

[0080] The concentration of the second sodium silicate solution is 1.5 mol / L and the modulus is 2.5;

[0081] The temperature of the reaction is 55 °C and the time is 95 min;

[0082] (3) After the reaction in step (2) is completed, in an oxygen atmosphere, maintain the pH value at 3.5 (adjusted by 98 wt% sulfuric acid), and age at 75 °C for 70 min; after aging, perform spray drying at 220 °C to obtain the white carbon black for battery separator.

[0083] Example 6

[0084] This example provides a preparation method of white carbon black for battery separator, and the preparation method includes the following steps:

[0085] (1) Mix the first sodium silicate solution with sodium N-acyl amino acid, and then perform homogenization treatment at 90 °C and 11 MPa for 4 h;

[0086] The concentration of the first sodium silicate solution is 1.5 mol / L and the modulus is 2.5;

[0087] The dosage of sodium N-acyl amino acid is 25% of the molar amount of sodium silicate in the first sodium silicate solution;

[0088] (2) In an oxygen atmosphere, use 98 wt% sulfuric acid to adjust the pH value of the first sodium silicate solution after homogenization treatment to 5.5, and then add 98 wt% sulfuric acid and the second sodium silicate solution in a co-current manner. React under the condition of maintaining the pH value stable at 5.5 to obtain a precursor suspension;

[0089] The concentration of the second sodium silicate solution is 1.5 mol / L and the modulus is 2.5;

[0090] The temperature of the reaction is 55 °C and the time is 95 min;

[0091] (3) After the reaction described in step (2) is completed, 98 wt% sulfuric acid is added in an oxygen atmosphere to adjust the pH value to 3.5, and aging is carried out at 75 °C for 70 min; after the aging is completed, spray drying is carried out at 220 °C to obtain the silica white for battery separator.

[0092] Example 7

[0093] This example provides a preparation method of silica white for battery separator, and the preparation method includes the following steps:

[0094] (1) The first sodium silicate solution is mixed with sodium N-acyl amino acid, and then homogenization treatment is carried out at 90 °C and 11 MPa for 4 h;

[0095] The concentration of the first sodium silicate solution is 1.5 mol / L and the modulus is 2.5;

[0096] The dosage of sodium N-acyl amino acid is 25% of the molar amount of sodium silicate in the first sodium silicate solution;

[0097] (2) In an oxygen atmosphere, 98 wt% sulfuric acid is used to adjust the pH value of the first sodium silicate solution after homogenization treatment to 4.5, and then 98 wt% sulfuric acid and the second sodium silicate solution are added in a co-current manner, and the reaction is carried out under the condition of maintaining the pH value stable at 4.5 to obtain a precursor suspension;

[0098] The concentration of the second sodium silicate solution is 1.5 mol / L and the modulus is 2.5;

[0099] The temperature of the reaction is 55 °C and the time is 95 min;

[0100] (3) After the reaction described in step (2) is completed, 98 wt% sulfuric acid is added in an oxygen atmosphere to adjust the pH value to 2.5, and aging is carried out at 75 °C for 70 min; after the aging is completed, spray drying is carried out at 220 °C to obtain the silica white for battery separator.

[0101] Example 8

[0102] This example provides a preparation method of silica white for battery separator, and the preparation method includes the following steps:

[0103] (1) The first sodium silicate solution is mixed with sodium N-acyl amino acid, and then homogenization treatment is carried out at 90 °C and 11 MPa for 4 h;

[0104] The concentration of the first sodium silicate solution is 1.5 mol / L and the modulus is 2.5;

[0105] The dosage of sodium N-acyl amino acid is 25% of the molar amount of sodium silicate in the first sodium silicate solution;

[0106] (2) In an oxygen atmosphere, the pH value of the first sodium silicate solution after homogenization treatment is adjusted to 4.5 using 98 wt% sulfuric acid, and then 98 wt% sulfuric acid and the second sodium silicate solution are added in a co-current manner, and the reaction is carried out under the condition of maintaining the pH value stable at 4.5 to obtain a precursor suspension;

[0107] The concentration of the second sodium silicate solution is 1.5 mol / L, and the modulus is 2.5;

[0108] The temperature of the reaction is 55 °C, and the time is 95 min;

[0109] (3) After the reaction in step (2) is completed, in an oxygen atmosphere, the pH value is maintained at 4.5 (adjusted by 98 wt% sulfuric acid), and aging is carried out at 75 °C for 70 min; after aging, spray drying is carried out at 220 °C to obtain the white carbon black for battery separator.

[0110] Comparative Example 1

[0111] This comparative example provides a preparation method of white carbon black for battery separator. Except that the oxygen atmosphere in the preparation method is replaced with a carbon dioxide atmosphere, the rest are the same as in Example 1.

[0112] Comparative Example 2

[0113] This comparative example provides a preparation method of white carbon black for battery separator. The preparation method includes the following steps:

[0114] (1) The first sodium silicate solution is mixed with sodium N-acyl amino acid;

[0115] The concentration of the first sodium silicate solution is 1.5 mol / L, and the modulus is 2.5;

[0116] The dosage of sodium N-acyl amino acid is 25% of the molar amount of sodium silicate in the first sodium silicate solution;

[0117] (2) In an oxygen atmosphere, the pH value of the first sodium silicate solution after homogenization treatment is adjusted to 4.5 using 98 wt% sulfuric acid, and then 98 wt% sulfuric acid and the second sodium silicate solution are added in a co-current manner, and the reaction is carried out under the condition of maintaining the pH value stable at 4.5 to obtain a precursor suspension;

[0118] The concentration of the second sodium silicate solution is 1.5 mol / L, and the modulus is 2.5;

[0119] The temperature of the reaction is 55 °C, and the time is 95 min;

[0120] (3) After the reaction described in step (2) is completed, 98 wt% sulfuric acid is added in an oxygen atmosphere to adjust the pH value to 3.5, and aging is carried out at 75 °C for 70 min; after aging is completed, spray drying is carried out at 220 °C to obtain the silica white for battery separator.

[0121] Performance characterization

[0122] For the silica white for battery separator prepared in the above examples and comparative examples, the particle size distribution D50, the full width at half maximum (FWHM) of the particle size distribution, the pore volume and the pore diameter were measured. The narrower the full width at half maximum, the more uniform the particle size distribution. The obtained results are shown in Table 1.

[0123] Among them, the particle size D50 was measured according to GB / T 32698-2016 "Determination of particle size distribution of precipitated hydrated silica for rubber compounding agents - Laser diffraction method"; the pore volume and pore diameter analysis were carried out in accordance with ISO 15901-1:2005 "Determination of pore size distribution and porosity of solid materials by mercury porosimetry and gas adsorption - Part 1: Mercury porosimetry".

[0124] Table 1

[0125] Particle size D50 (μm) Full width at half maximum (μm) <![CDATA[Pore volume (cm 3 / g)]]> Most probable pore size (nm) Example 1 11.2 1.3 2.82 18.97 Example 2 12.5 1.5 2.60 20.34 Example 3 11.8 1.6 2.68 19.51 Example 4 13.4 2.8 2.44 21.83 Example 5 15.2 5.7 2.32 17.02 Example 6 16.1 5.6 2.38 19.35 Example 7 14.9 4.2 2.39 17.96 Example 8 14.5 4.8 2.41 19.64 Comparative Example 1 20.4 7.2 2.15 16.28 Comparative Example 2 22.6 9.6 1.98 21.54

[0126] The silica white for battery separator obtained in the above examples and comparative examples was mixed with polypropylene (intrinsic viscosity in decalin at 135 °C is 15 dL / g) at a mass ratio of 1:6, and then blended and pelletized with a conventional polypropylene resin (the mass ratio of silica white for battery separator to conventional polypropylene resin is 1:43) to obtain masterbatch; the masterbatch with a mass ratio of 1:9 was melt-blended and extruded with a conventional polypropylene resin at a temperature of 200 °C and a draw ratio of 200 times to obtain a film sheet; the film sheet was continuously drawn using a unidirectional drawing machine with a draw ratio of 3 times and a draw temperature of 100 °C, and after drawing, it was shaped at 145 °C for 10 min to obtain a polyolefin microporous separator.

[0127] The film porosity of the obtained polyolefin microporous separator was tested, and the obtained results are shown in Table 2, where:

[0128] For the film porosity, the weighed polyolefin microporous separator was immersed in cetane for 2 hours, and the volume (V1) of the polyolefin microporous separator and the volume (V2) of the absorbed cetane were measured. Then the film porosity is:

[0129] Film porosity = (V2 / (V1 + V2)) × 100%.

[0130] Table 2

[0131] Membrane porosity (%) Example 1 85.3 Example 2 82.4 Example 3 83.6 Example 4 79.2 Example 5 77.6 Example 6 78.4 Example 7 78.3 Example 8 80.7 Comparative Example 1 59.5 Comparative Example 2 67.1

[0132] In summary, the preparation method provided by the present invention first performs homogenization treatment, which can reduce the particle size non-uniformity of the precipitated silica obtained during subsequent reactions; moreover, it can improve the dispersibility of sodium silicate, resulting in a larger specific surface area of the obtained precipitated silica. Preparation in an oxygen-containing atmosphere has an obvious influence on the microstructure and surface hydroxyl content of the obtained precipitated silica. When precipitated silica is prepared by the precipitation method, its surface hydroxyl content is relatively high. Preparation in an oxygen-containing atmosphere can reduce the surface hydroxyl content of precipitated silica and reduce its degree of agglomeration, thereby making the particle size of the obtained precipitated silica uniform, and at the same time having a relatively high specific surface area and pore volume, which is suitable for battery separators.

[0133] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only for the specific embodiments of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of silica for battery separator, characterized in that, The preparation method comprises the following steps: (1) Mix the first sodium silicate solution with the N-acyl amino acid salt, and then carry out homogenization treatment; (2) In an oxygen-containing atmosphere, use sulfuric acid to adjust the pH value of the first sodium silicate solution after homogenization treatment, and then add sulfuric acid and the second sodium silicate solution in parallel flow, and carry out the reaction under the condition of maintaining a stable pH value to obtain a precursor suspension; (3) After the reaction in step (2) is completed, add sulfuric acid in an oxygen-containing atmosphere to adjust the pH value and carry out aging; after aging is completed, carry out spray drying to obtain the silica white for battery separator.

2. The preparation method according to claim 1, wherein The gas used in the oxygen-containing atmosphere includes air and / or oxygen, and preferably oxygen.

3. The preparation method according to claim 1 or 2, characterized in that, The concentration of the first sodium silicate solution in step (1) is 1-2 mol / L; Preferably, the modulus of sodium silicate in the first sodium silicate solution in step (1) is 2-3; Preferably, the N-acyl amino acid salt in step (1) includes sodium N-acyl amino acid and / or potassium N-acyl amino acid; Preferably, the dosage of the N-acyl amino acid salt in step (1) is 20-30% of the molar amount of sodium silicate in the first sodium silicate solution.

4. The preparation method according to any one of claims 1-3, characterized in that, The temperature of the homogenization treatment in step (1) is 80-100 °C; Preferably, the absolute pressure of the homogenization treatment in step (1) is 10-12 MPa; Preferably, the time of the homogenization treatment in step (1) is 2-5 h.

5. The preparation method according to any one of claims 1-4, characterized in that, The pH value of the reaction in step (2) is 4-5; Preferably, the temperature of the reaction in step (2) is 50-60 °C; Preferably, the time of the reaction in step (2) is 90-100 min.

6. The preparation method according to any one of claims 1-5, characterized in that, Adjusting the pH value in step (3) means adjusting the pH value to 3-4; Preferably, the temperature of the aging in step (3) is 70-80 °C; Preferably, the time of the aging in step (3) is 60-80 min.

7. The preparation method according to any one of claims 1-6, characterized in that, The temperature of the spray drying in step (3) is 200-240 °C.

8. The preparation method according to claim 1, wherein, The preparation method comprises the following steps: (1) Mix the first sodium silicate solution with the N-acyl amino acid salt, and then carry out homogenization treatment at a temperature of 80-100 °C and an absolute pressure of 10-12 MPa for 2-5 h; The concentration of the first sodium silicate solution is 1-2 mol / L and the modulus is 2-3; The dosage of the N-acyl amino acid salt is 20-30% of the molar amount of sodium silicate in the first sodium silicate solution; (2) In an oxygen atmosphere, use sulfuric acid to adjust the pH value of the first sodium silicate solution after homogenization treatment to 4-5, and then add sulfuric acid and the second sodium silicate solution in parallel flow, and carry out the reaction under the condition of maintaining a stable pH value of 4-5 to obtain a precursor suspension; The temperature of the reaction is 50-60 °C and the time is 90-100 min; (3) After the reaction in step (2) is completed, add sulfuric acid in an oxygen atmosphere to adjust the pH value to 3-4, and carry out aging at 70-80 °C for 60-80 min; after aging is completed, carry out spray drying at 200-240 °C to obtain the silica white for battery separator.

9. Fumed silica for battery separator, characterized in that, The silica white for battery separator is prepared by the preparation method according to any one of claims 1-8.

10. A battery separator, characterized in that The battery separator includes the silica for battery separator obtained by the preparation method according to any one of claims 1-8, or includes the silica for battery separator according to claim 9.