Design and manufacturing method of high-safety fast-charging lithium battery separator

Abstract

The application discloses a design and manufacturing method of a high-safety fast-charging type diaphragm for a lithium battery, and the preparation method of the diaphragm is as follows: mesogenic anatase TiO2, MX2 type semiconductor nanomaterial and PVDF are added into a polar solvent according to a molar ratio of 0.3-0.7:0.2-0.5:1.5-1.9, and normal-temperature stirring and ultrasonic treatment are sequentially performed; then the mixed solution is cast on an ITO conductive glass substrate, vacuum drying is performed at 60-80 DEG C, a TiO2-MX2-PVDF composite film is formed, gold spraying is then performed on the surface of the film, finally, polarization treatment is performed on the composite film after the gold spraying, a voltage range of 3V-9V is applied, and a frequency of 3mS-5mS is applied, so that a TiO2-MX2-PVDF composite diaphragm with a main beta phase is prepared. The mesogenic anatase TiO2 and MoS2 nanomaterial are used for modifying the PVDF diaphragm, the piezoelectric property of the PVDF film is significantly improved, the stress generated by the expansion of a silicon-based negative electrode is combined in a silicon-based lithium ion battery, a certain reverse overpotential is generated at the interface between the negative electrode and the diaphragm, the risk of lithium precipitation at the negative electrode interface under fast charging is effectively inhibited, and the safety and service life of the battery are significantly improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of lithium ion power batteries for electric aviation, in particular to a design and manufacturing method of a high-safety fast-charging type lithium battery separator. BACKGROUND

[0002] As a representative of new-quality productivity, the low-altitude economy is triggering fierce competition worldwide. The core of this strategic emerging industry lies in electric low-altitude aircraft, especially electric vertical take-off and landing aircraft (eVTOL). eVTOL has become the focus of attention at home and abroad due to its high safety, low cost, low noise and intelligent characteristics.

[0003] The development of eVTOL not only promotes the widespread application of lithium battery technology, but also provides a broad space for the development of next-generation battery technology. However, eVTOL has more stringent requirements for the performance of lithium batteries, especially in terms of high specific energy and high safety. High specific energy lithium ion power batteries have become the main power source for eVTOL due to their high energy density, small size and light weight.

[0004] However, during the rapid charging process, lithium deposition may occur on the surface of the negative electrode of the lithium ion power battery, which not only affects the performance of the battery, but also poses a serious threat to the safety and reliability of the battery. The use of piezoelectric materials to generate a reverse overpotential during the operation of the lithium battery to weaken the driving force of lithium ion nucleation and deposition diffusion has become an important technical method for inhibiting fast-charging lithium deposition due to its simple operation, low cost and good effect.

[0005] As disclosed in the invention patent application with application number 202311712605.9, a lithium ion battery separator and its preparation method and application are proposed. The flexible piezoelectric polyvinylidene fluoride (PVDF) is used as an innovative method for lithium ion battery separators. Through the application of this separator, the risk of lithium deposition on the surface of the metal lithium during charging is reduced, thereby improving the safety of the battery and the compatibility with the lithium metal battery system. However, the limitation of this technical solution lies in the fact that the piezoelectric ability of the PVDF separator is limited due to its single composition, which affects the performance of the separator in the battery. SUMMARY

[0006] The purpose of the present application is to provide a design and manufacturing method of a high-safety fast-charging type lithium battery separator. The mesogenic anatase TiO2 and MoS2 nanomaterials are used to modify the PVDF separator, which significantly improves the piezoelectric properties of the PVDF film. In silicon-based lithium ion batteries, the stress generated by the expansion of the silicon-based negative electrode produces a certain reverse overpotential at the interface between the negative electrode and the separator, effectively inhibiting the risk of lithium deposition at the negative electrode interface during fast charging, and significantly improving the safety and service life of the battery.

[0007] The application solves the above technical problems by adopting the technical scheme of

[0008] A manufacturing method of a high-safety fast-charging type lithium battery diaphragm, which comprises the following steps: adding mesogenic anatase titanium dioxide powder, MX2 type semiconductor nanomaterial and PVDF into a polar solvent according to a molar ratio of 0.3-0.7:0.2-0.5:1.5-1.9, sequentially performing normal-temperature stirring and ultrasonic treatment, pouring the mixed solution on an ITO conductive glass substrate, vacuum drying at 60-80 DEG C, forming a TiO2-MX2-PVDF composite film, then spraying gold on the surface of the film, and finally performing polarization treatment on the TiO2-MX2-PVDF composite film after gold spraying, with a voltage range of 3-9 V and a frequency of 3-5 mS, to prepare a TiO2-MX2-PVDF composite diaphragm with a main phase of beta.

[0009] Preferably, M in the MX2 type semiconductor nanomaterial is a transition metal element W or Mo, and X is one of Te, Se and S.

[0010] Preferably, the thickness of the TiO2-MX2-PVDF composite film after vacuum drying is 1-15 μm, and the thickness of the sprayed gold is 5-10 nm.

[0011] Preferably, the polar solvent comprises one of dimethylformamide DMF, dimethylacetamide DMA, hexamethylphosphoramide, trifluoroacetic acid, tetramethyl ethylenediamine, pyridine and dimethyl sulfoxide.

[0012] Preferably, the mesogenic anatase titanium dioxide powder is prepared by the following method: dissolving a titanium source in a 1-3 mol / L hydrochloric acid solution, with a volume ratio of the titanium source to the hydrochloric acid solution being 1-3:4-10, stirring at 40-100 DEG C for 40-60 h, centrifugally treating to obtain a white product, washing the white product with deionized water to remove residual ions, vacuum drying the white product at 80-120 DEG C for 12-36 h, and finally calcining in air at 400-500 DEG C for 12-24 h to obtain the mesogenic anatase titanium dioxide powder.

[0013] Preferably, the titanium source comprises at least one of dichlorobis-titanocene, titanium tetraisopropoxide, tetrabutyl titanate, titanium citrate and titanium tetrachloride.

[0014] As preferred, the MX2 type semiconductor nanomaterial is MoS2 nanomaterial, which is prepared by solvothermal method: ammonium molybdate or ammonium heptamolybdate tetrahydrate, organic acid are added into deionized water according to the molar ratio of 0.5-1.5:4-7, and magnetic stirring is carried out at room temperature until dissolution, then continuous stirring and refluxing is carried out at 110-140℃, and ammonia water is added to adjust the pH value to 3.5-4.5, then one of polysulfide ammonium, thiourea and ammonium sulfide is added dropwise into the solution, finally the solution is transferred into a stainless steel autoclave, the autoclave is kept at 185-200℃ for a period of time, and then naturally cooled to room temperature, and the black precipitate MoS2 is obtained by centrifugal treatment of the solution, and then the residual is removed by washing with acetone and deionized water in turn.

[0015] As preferred, the molar ratio of ammonium molybdate to polysulfide ammonium is 0.5-1.5:0.7-1.9.

[0016] As preferred, the organic acid is one of gluconic acid, citric acid, malic acid and lactic acid.

[0017] A high-safety fast-charging type lithium battery comprises the diaphragm prepared by the method.

[0018] Compared with the prior art, the application has the advantages that:

[0019] 1. The application significantly enhances the piezoelectric properties of the PVDF diaphragm by introducing TiO2-MoS2 dual-component nucleation additives, and the reverse overpotential is generated by the expansion stress of the silicon-based negative electrode, which weakens the lithium precipitation probability at the negative electrode and diaphragm interface, and the lithium precipitation inflection point appears later, compared with the conventional diaphragm, the fast-charging cycle life of the lithium ion battery is improved by more than 200%, and the safety risk of the lithium ion battery under fast charging is significantly reduced. At the same time, the mesocrystal anatase titanium dioxide material provides more lithium storage sites, further improving the cycle life of the battery. The method of the application is also applicable to the performance improvement of high-specific-energy metal lithium batteries, and provides a technical reference for the development of fast-charging lithium ion power batteries in the field of electric aviation.

[0020] 2. By intermolecular interaction and the use of nanofillers, the formation of the beta phase structure with special properties of PVDF can be effectively promoted. The intermolecular bonding from different molecules or surface functional groups promotes the beta phase formation of PVDF and its copolymer, the polar interaction between PVDF and polar solvent dimethylformamide leads to the formation of beta phase by crystallization during solvent evaporation, and the mesocrystal anatase TiO2 and MoS2 nanofillers further optimize the interface and promote the preferential orientation of CH2 / –CF2 dipole in the direction perpendicular to the PVDF chain axis, thereby generating more beta phase-PVDF.

[0021] 3. Strain concentration phenomenon will occur at the interface of mesocrystal anatase TiO2 and MoS2 nanofiller, the synergistic control of the surface and interface between the two will not only promote the generation of local beta phase in the matrix, but also effectively improve the strain transmission effect of the nanofiller with high voltage electric sensitivity, significantly enhancing the piezoelectric performance of the TiO2-MoS2-PVDF composite film.

[0022] 4. Compared with other crystal forms, mesocrystal anatase titanium dioxide has more lithium storage sites, which is conducive to improving the lithium ion transmission performance in the PVDF composite separator and improving the fast charging performance of the lithium ion battery. DETAILED DESCRIPTION

[0023] The technical solutions of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments.

[0024] Embodiment 1,

[0025] A high-safety fast-charging type lithium battery comprises a positive electrode sheet, a negative electrode sheet and a separator.

[0026] The separator is prepared by the following method: mesocrystal anatase titanium dioxide, MoS2 nanomaterial and PVDF are added to dimethylformamide DMF in a molar ratio of 0.5:0.4:1.6, and magnetic stirring is performed at room temperature for 1.5 hours, followed by ultrasonic (55KHZ) treatment for 35 minutes. The mixed solution is cast on an ITO conductive glass substrate, and then placed in an oven at 75℃ under a vacuum degree of 0.07 standard atmosphere for 30 hours to form a TiO2-MoS2-PVDF composite film. Then, gold is sprayed on the surface of the film. The thickness of the TiO2-MoS2-PVDF composite film is 2μm, and the thickness of the sprayed gold is 9nm. Finally, the TiO2-MoS2-PVDF composite film after gold spraying is polarized, and the applied voltage is in the range of 5V, and the frequency is 4mS. A TiO2-MoS2-PVDF composite film with a main beta phase is prepared.

[0027] The dimethylformamide DMF in this embodiment can be replaced by one of dimethylacetamide DMA, hexamethylphosphoramide, trifluoroacetic acid, tetramethyl ethylenediamine, pyridine, dimethyl sulfoxide and other polar solvents.

[0028] Preparation of mesocrystal anatase titanium dioxide powder: first, a certain amount of titanium isopropoxide is added dropwise into 1.5mol / L hydrochloric acid, and the volume ratio of titanium isopropoxide to hydrochloric acid is 1:3. Then, stirring is continuously performed at 70℃ for 52 hours, and after centrifugal treatment, the white product is washed with deionized water for 5 times to remove residual ions. The white product is vacuum dried at 110℃ for 26 hours, and then sintered in air at 450℃ for 20 hours to obtain mesocrystal anatase titanium dioxide powder.

[0029] MoS2nanomaterials are prepared by a simple and easy-to-operate solvothermal method: ammonium heptamolybdate tetrahydrate and gluconic acid are added to deionized water in a molar ratio of 1:5, and magnetic stirring is performed at room temperature until dissolution. Then, the white suspension is continuously stirred and refluxed at 130°C for 45 minutes, and ammonia water is added to adjust the pH value to 3.6. Then, ammonium polysulfide is added dropwise to the solution, and the molar ratio of ammonium molybdate to ammonium polysulfide is 1:1.2. Finally, the solution is transferred to a stainless steel autoclave, and the autoclave is kept at 190°C for 14 hours. The solution is naturally cooled to room temperature, and the black precipitate MoS2is obtained by centrifugal treatment. The residue is removed by washing with acetone and deionized water for 3 times, respectively.

[0030] The preparation method of the positive electrode sheet is as follows:

[0031] The positive active material layer of high-nickel ternary material (NCM811), the conductive agent single-walled carbon nanotube, the binder PVDF, and N-methyl pyrrolidone (NMP) are put into a ball jar in a mass ratio of 96:1.2:2.5:145, and the ball-to-material ratio is 1.3:1. The grinding time is 55 minutes. The mixed slurry is uniformly coated on the aluminum current collector by using the doctor blade method or the transfer coating method, and the coating thickness is 110 μm. After drying, rolling, and punching, the positive electrode sheet is obtained.

[0032] The preparation method of the negative electrode sheet is as follows:

[0033] The silicon carbon, artificial graphite, single-walled carbon nanotube, binder PAA, and deionized water are put into a ball mill jar in a mass ratio of 55:45:2:6:380, and the ball-to-material ratio is 1.3:1. The grinding time is 65 minutes. The mixed slurry is uniformly coated on the copper current collector by using the doctor blade method or the transfer coating method, and the coating thickness is 85 μm. After drying, rolling, punching, the negative electrode sheet is obtained.

[0034] The β-phase-based TiO2-MoS2-PVDF composite film prepared above is stacked with a conventional PP separator, and the positive electrode sheet and the negative electrode sheet are stacked, welded, packaged, injected, and formed to obtain a lithium ion battery.

[0035] Example 2,

[0036] A high-safety fast-charging lithium battery, which is different from example 1 in that the separator in the application is prepared by the following method: mesocrystal anatase titanium dioxide, MoS2 nanomaterial and PVDF are added to dimethylacetamide DMA according to a molar ratio of 0.7:0.2:1.9, magnetic stirring at room temperature for 2 hours, followed by ultrasonic (60KHZ) treatment for 20 minutes, the mixed solution is cast on an ITO conductive glass substrate, then placed in an oven at 80℃, vacuum degree is 0.05 standard atmosphere for 35 hours, to form a TiO2-MoS2-PVDF composite film, then spray gold on the surface of the film. Among them, the thickness of the TiO2-MoS2-PVDF composite film is 1μm, and the thickness of the sprayed gold is 5nm. Finally, the TiO2-MoS2-PVDF composite film after spraying gold is polarized, the voltage applied is 9V, the frequency is 5mS, and a TiO2-MoS2-PVDF composite film with mainly β phase is prepared.

[0037] Example 3,

[0038] A high-safety fast-charging lithium battery, which is different from example 1 in that mesocrystal anatase titanium dioxide, MoS2 nanomaterial and PVDF are added to hexamethylphosphoramide according to a molar ratio of 0.3:0.5:1.5, magnetic stirring at room temperature for 1 hour, followed by ultrasonic (40KHZ) treatment for 40 minutes, the mixed solution is cast on an ITO conductive glass substrate, then placed in an oven at 60℃, vacuum degree is 0.2 standard atmosphere for 25 hours, to form a TiO2-MoS2-PVDF composite film, then spray gold on the surface of the film. Among them, the thickness of the TiO2-MoS2-PVDF composite film is 15μm, and the thickness of the sprayed gold is 10nm. Finally, the TiO2-MoS2-PVDF composite film after spraying gold is polarized, the voltage applied is 3V, the frequency is 3mS, and a TiO2-MoS2-PVDF composite film with mainly β phase is prepared.

[0039] Example 4,

[0040] A high-safety fast-charging lithium battery, which is different from example 1 in that in the preparation process of MoS2 nanomaterial: ammonium molybdate and citric acid are added to deionized water according to a molar ratio of 0.5:7, magnetic stirring at room temperature until dissolved, then continue to stir at 110℃ for 60 minutes, continuously stir and reflux the white suspension, and add ammonia water to adjust the pH value to 3.5, then add ammonium polysulfide dropwise into the solution, the molar ratio of ammonium molybdate to ammonium polysulfide is 1.5:0.7, finally transfer the solution to a stainless steel autoclave, keep the autoclave at 200℃ for 12 hours, naturally cool to room temperature, and centrifuge the solution to obtain black precipitate MoS2, then wash with acetone and deionized water for 3 times respectively to remove residues.

[0041] Example 5,

[0042] A high-safety fast-charging lithium battery, which differs from Example 1 in that WS2 nanomaterials are used in the preparation of the separator.

[0043] Example 6,

[0044] A high-safety fast-charging lithium battery, which differs from Example 1 in that WSe2 nanomaterials are used in the preparation of the separator.

[0045] Comparative Example 1,

[0046] Compared with Example 1, mesogenic rutile titanium dioxide powder is used, and the specific preparation method of the mesogenic rutile titanium dioxide powder is as follows: a certain amount of titanium isopropoxide is added dropwise into 1.5 mol / L hydrochloric acid, and the volume ratio of titanium isopropoxide to hydrochloric acid is 1:3. Then, stirring is continued at 70°C for 52 hours, and after centrifugal treatment, the white product is washed with deionized water for 5 times to remove residual ions. After the white product is vacuum dried at 110°C for 26 hours, mesogenic rutile titanium dioxide powder is obtained by calcining at 550°C in air for 20 hours.

[0047] Comparative Example 2,

[0048] Compared with Example 1, the PVDF composite separator in Comparative Example 2 does not add mesogenic anatase titanium dioxide, and the other conditions are the same as those in Example 1.

[0049] Comparative Example 3,

[0050] Compared with Example 1, the PVDF composite separator in Comparative Example 3 does not add MoS2 nanomaterials, and the other conditions are the same as those in Example 1.

[0051] Comparative Example 4,

[0052] Compared with Example 1, the PVDF composite separator in Comparative Example 4 does not add MoS2 and titanium dioxide nanomaterials, and the other conditions are the same as those in Example 1.

[0053] Comparative Example 5,

[0054] Compared with Example 1, the lithium ion battery in Comparative Example 5 only uses a conventional PP separator without a PVDF composite separator, and the other conditions are the same as those in Example 1.

[0055] Measurement of piezoelectric coefficient: The piezoelectric coefficient of the composite separator obtained in the above examples and the separator obtained in the comparative examples is accurately measured using a DH-1 type digital charge meter by a static method.

[0056] The lithium ion battery prepared from the examples and comparative examples was subjected to 4-6C charge-discharge cycle test at 25°C in the range of 20-80% SOC until the inflection point appeared in the discharge capacity attenuation curve, at which point lithium precipitation occurred in the negative electrode, indicating that the lithium ion battery was invalid.

[0057] Table 1. Comparison of piezoelectric properties of PVDF separators in different groups and cycle life of lithium ion batteries

[0058]

[0059] The specific results are shown in Table 1, and it can be seen from Examples 1-6 that within the scope of the technical requirements of the present application, the piezoelectric properties of the PVDF composite separator and the fast-charging cycle life of the lithium ion battery have been significantly improved, and the technical effect of Example 1 is the best. In combination with Example 1 and Comparative Examples 1-5, it is shown that the addition of mesocrystalline anatase titanium dioxide powder and MoS2 nanomaterials significantly improves the piezoelectric properties of the PVDF film. Compared with conventional separators, the PVDF composite separator with high piezoelectric properties in the silicon-based system battery weakens the probability of lithium precipitation at the negative electrode and separator interface by using the expansion stress of the silicon-based negative electrode to generate a reverse overpotential, the inflection point of lithium precipitation occurs later, the cycle life of the lithium ion battery under fast charging is improved, and the safety risk of the lithium ion battery under fast charging is significantly reduced. At the same time, the mesocrystalline anatase titanium dioxide material provides more lithium storage sites, further improving the cycle life of the battery. The method of the present application is also applicable to the performance improvement of high-specific-energy metal lithium batteries, and provides a technical reference for the development of fast-charging lithium ion power batteries in the field of electric aviation.

[0060] It should be noted that the preparation of mesocrystalline anatase titanium dioxide powder needs to strictly control the parameters as follows: first, a certain amount of titanium source is added dropwise into 1-3 mol / L hydrochloric acid, wherein the volume ratio of titanium source to hydrochloric acid is 1-3:4-10, and the titanium source includes but is not limited to dichlorobis-cyclopentadienyl titanium, tetraisopropoxy titanium, tetrabutyl titanate, titanium citrate, titanium tetrachloride, etc. Then continuously stir at 40-100°C for 40-60 hours, centrifuge to obtain white product, wash with deionized water for 3-6 times to remove residual ions. The white product is vacuum dried at 80-120°C for 12-36 hours, and then calcined at 400-500°C in air for 12-24 hours to obtain mesocrystalline anatase titanium dioxide powder. Compared with conventional nanometer and micrometer titanium dioxide materials, the mutual synergy of the inherent fast diffusion network between the grains in the mesocrystalline anatase TiO2 makes its lithium ion diffusion rate higher, and can significantly improve the cycle stability of the material. The mesocrystalline anatase TiO2 prepared by the present application includes but is not limited to pure titanium dioxide and its doped modified derivatives (including nitrogen-doped, carbon-doped, sulfur-doped, various metal and oxide modified, etc.).

[0061] The preparation of MoS2 nanomaterials requires strict control of parameters as follows: ammonium molybdate, gluconic acid are added to deionized water in a molar ratio of 0.5-1.5:4-7, and magnetic stirring is carried out at room temperature until dissolution, then stirring is continued at 110-140℃ for 40-60 minutes, the white suspension is continuously stirred and refluxed, and ammonia water is added to adjust the pH value to 3.5-4.5, then ammonium polysulfide is added dropwise into the solution, the molar ratio of ammonium molybdate to ammonium polysulfide is 0.5-1.5:0.7-1.9, finally the solution is transferred to a stainless steel autoclave, the autoclave is kept at 185-200℃ for 12-16 hours, and then naturally cooled to room temperature, the solution is subjected to centrifugal treatment to obtain black precipitate MoS2, and then washed with acetone and deionized water for 3 times respectively to remove residues. In the present application, ammonium molybdate can be replaced by ammonium heptamolybdate tetrahydrate, gluconic acid can be replaced by organic acids such as citric acid, malic acid, lactic acid, and ammonium polysulfide can be replaced by thiourea, ammonium sulfide, etc. The MoS2 nanomaterial prepared in the present application can be replaced by one or more of other MX2 type semiconductor materials (M is a transition metal element W or Mo, and S is Te, Se or S).

[0062] It should be understood by those skilled in the art that the positive active material, conductive agent, binder PVDF and N-methyl pyrrolidone (NMP) used in the preparation of the positive electrode sheet are put into a ball mill jar in a mass ratio of 90-97:0.5-3:1-3:130-160, the ball-to-material ratio is 1.2-1.7:0.9-1.1, and the grinding time is 40min-60min. The mixed slurry is uniformly coated on the aluminum current collector by using a doctor blade method or a transfer coating method, the coating thickness is 50-300μm, and the positive electrode sheet is obtained after drying, rolling and punching.

[0063] The positive active material in the present embodiment includes but is not limited to lithium iron phosphate, layered nickel cobalt manganese ternary material, lithium cobaltate, lithium manganate, lithium manganese iron phosphate, and lithium-rich manganese-based layered material, etc. which are currently available in lithium ion batteries. The positive electrode conductive agent includes but is not limited to conductive carbon black, conductive graphite, carbon nanotubes, ketchen black, graphene, etc. which are used in lithium ion batteries. The positive electrode binder includes but is not limited to polyvinylidene fluoride PVDF, sulfated polysaccharide, polytetrafluoroethylene PTFE, polyvinyl alcohol PVA, polyolefin (PP, PE and other copolymers), etc. The positive electrode slurry process includes but is not limited to ball milling, dry mixing, wet slurry, etc. which are all applied in lithium ion positive electrode slurry process. The positive electrode coating process in the present application includes but is not limited to transfer coating, doctor blade method, extrusion coating, dry electrode, etc. which are all lithium ion battery coating processes. The aluminum current collector can be replaced by one of composite current collector, carbon-coated aluminum foil, conductive polymer film, etc.

[0064] The skilled in the art should understand that the silicon-based material, graphite, conductive agent, binder and deionized water used in the preparation of the negative electrode sheet are put into a ball mill tank in a mass ratio of 50-100:0-50:1-10:2-10:300-500, the ball-to-material ratio is 1.2-1.7:0.9-1.1, the grinding time is 50-80 minutes, the mixed slurry is uniformly coated on the copper current collector by the doctor blade method or the transfer coating method, the coating thickness is 50-300 μm, and the negative electrode sheet is obtained after drying, rolling and punching. The silicon-based material includes but is not limited to silicon oxide, silicon-carbon or silicon alloy, etc. The graphite includes but is not limited to natural graphite, artificial graphite, hard carbon, soft carbon, mesocarbon microbeads, etc. The negative electrode conductive agent includes but is not limited to conductive carbon black, conductive graphite, carbon nanotubes, Ketjen black, graphene and other conductive agents for lithium ion batteries. The negative electrode binder includes but is not limited to butyl rubber SBR, carboxymethyl cellulose and its derivatives, polyacrylic acid PAA, polyacrylonitrile PAN and other negative electrode binders for lithium ion batteries. The negative electrode slurry process includes but is not limited to ball milling, dry mixing, wet slurry mixing and all other slurry processes applied to lithium ion negative electrodes. The negative electrode coating process includes but is not limited to transfer coating, doctor blade method, extrusion coating, dry electrode and all other lithium ion battery coating processes. The copper current collector can be replaced by one of the composite current collector, carbon-coated copper foil and conductive polymer film.

[0065] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for part or all of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for manufacturing a high-safety, fast-charging lithium battery separator, characterized in that: Mesocrystalline anatase titanium dioxide powder, MX2-type semiconductor nanomaterial, and PVDF are added to a polar solvent in a molar ratio of 0.3-0.7: 0.2-0.5: 1.5-1.9, stirred at room temperature, and ultrasonically treated. The mixture is then cast on an ITO conductive glass substrate and vacuum-dried at 60°C-80°C to form a TiO2-MX2-PVDF composite film. The film surface is then sprayed with gold, and the gold-sprayed TiO2-MX2-PVDF composite film is polarized at a voltage range of 3V-9V and a frequency of 3mS-5mS to prepare a TiO2-MX2-PVDF composite membrane mainly composed of a β phase. In the MX2 type semiconductor nanomaterial, M is a transition metal element W or Mo, and X is one of Te, Se, and S.

2. The method for manufacturing a high-safety, fast-charging lithium battery separator according to claim 1, characterized in that: The thickness of the TiO2-MX2-PVDF composite film after vacuum drying is 1μm-15μm, and the thickness of the gold spraying is 5nm-10nm.

3. The method for manufacturing a high-safety, fast-charging lithium battery separator according to claim 1, characterized in that: The polar solvent includes one of dimethylformamide (DMF), dimethylacetamide (DMA), hexamethylphosphoramide, trifluoroacetic acid, tetramethylethylenediamine, pyridine, and dimethyl sulfoxide.

4. The method for manufacturing a high-safety, fast-charging lithium battery separator according to claim 1, characterized in that: The mesocrystalline anatase titanium dioxide powder is prepared by the following method: a titanium source is dissolved in a 1 mol / L-3 mol / L hydrochloric acid solution, the volume ratio of the titanium source to the hydrochloric acid solution is 1-3: 4-10, the mixture is stirred at 40°C-100°C for 40h-60h, and centrifuged to obtain a white product. The white product is washed with deionized water to remove residual inorganic ions, and the white product is vacuum dried at 80°C-120°C for 12h-36h. Finally, the product is calcined in air at 400°C-500°C for 12h-24h to obtain the mesocrystalline anatase titanium dioxide powder.

5. The method for manufacturing a high-safety, fast-charging lithium battery separator according to claim 4, characterized in that: The titanium source includes at least one of titanocene dichloride, tetraisopropoxytitanium, tetrabutyl titanate, titanium citrate, and titanium tetrachloride.

6. The method for manufacturing a high-safety, fast-charging lithium battery separator according to claim 1, characterized in that: The MX2-type semiconductor nanomaterial is a MoS2 nanomaterial, which is prepared by a solvothermal method: ammonium molybdate or ammonium heptamolybdate tetrahydrate and an organic acid are added to deionized water in a molar ratio of 0.5-1.5:4-7, and magnetic stirring is performed at room temperature until dissolved. Stirring is continued at 110-140°C, and the white suspension is continuously stirred and refluxed, and ammonia water is added to adjust the pH value to 3.5-4.

5. Then, one of ammonium polysulfide, thiourea, and ammonium sulfide is added dropwise to the solution. Finally, the solution is transferred to a stainless steel autoclave, and the autoclave is maintained at 185°C-200°C for a period of time, naturally cooled to room temperature, and the solution is centrifuged to obtain a black precipitate MoS2, which is then rinsed with acetone and deionized water in sequence to remove residues.

7. The method for manufacturing a high-safety, fast-charging lithium battery separator according to claim 6, characterized in that: The molar ratio of the ammonium molybdate to the ammonium polysulfide is 0.5-1.5:0.7-1.

9.

8. The method for manufacturing a high-safety, fast-charging lithium battery separator according to claim 6, wherein: The organic acid is one of gluconic acid, citric acid, malic acid and lactic acid.

9. A high-safety fast-charging lithium battery, characterized in that: The invention comprises a diaphragm prepared by the method according to any one of claims 1 to 8.

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