CN112366423A - Solid lithium ion battery composite diaphragm, preparation method and application thereof - Google Patents

Solid lithium ion battery composite diaphragm, preparation method and application thereof Download PDF

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Publication number
CN112366423A
CN112366423A CN202011205739.8A CN202011205739A CN112366423A CN 112366423 A CN112366423 A CN 112366423A CN 202011205739 A CN202011205739 A CN 202011205739A CN 112366423 A CN112366423 A CN 112366423A
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powder
solid
stirring
glue solution
lithium ion
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蒋易晟
王国光
王占洲
石程
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Hengdian Group DMEGC Magnetics Co Ltd
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Hengdian Group DMEGC Magnetics Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Secondary Cells (AREA)

Abstract

The invention discloses a solid-state lithium ion battery composite diaphragm, a preparation method and application thereof. The method comprises the following steps: (1) stirring and mixing oxide solid electrolyte powder with absolute ethyl alcohol, filtering until the pH value is neutral, and drying to obtain pretreated powder; 2) mixing the pretreated powder with a DMF (dimethyl formamide) glue solution of PVDF (polyvinylidene fluoride), and sealing and stirring to obtain a mixed slurry; 3) coating the mixed slurry on a base film, and drying to obtain a solid lithium ion battery composite diaphragm; the solid content of the DMF glue solution of the PVDF is less than or equal to 8 percent, and the mass of the pretreated powder accounts for no more than 15 percent based on 100 percent of the mass of the mixed glue solution. The solid-state lithium ion battery composite diaphragm prepared by the method has good flexibility and excellent ionic conductivity, and the thickness of the diaphragm can be dozens of microns or even millimeters, so that the good flexibility and the excellent ionic conductivity can be still maintained.

Description

Solid lithium ion battery composite diaphragm, preparation method and application thereof
Technical Field
The invention relates to the field of lithium ion batteries, in particular to a solid-state lithium ion battery composite diaphragm, and a preparation method and application thereof.
Background
With the rapid development of electronic devices and electric vehicles, batteries providing power sources for the electronic devices and the electric vehicles are researched more and more deeply, the safety of the batteries is especially important, for common diaphragms and electrolyte, safety problems exist in the charging and discharging processes of the batteries, the industry of new energy lithium ion batteries is developing towards all solid-state lithium batteries at present, and compared with the limitation and safety of the first generation electrolyte type lithium ion batteries, the solid electrolyte improves the safety and limitation of the electrolyte type lithium ion batteries and becomes the mainstream of new markets. The traditional solid oxide electrolyte sheet has the characteristics of high hardness, gaps among powder materials, incapability of achieving thickness of dozens of micrometers and the like, and is poor in applicability. Whereas polymer electrolytes are inferior to solid oxide electrolytes in electrical conductivity.
CN110336066A discloses a diaphragm containing a solid electrolyte coating, which comprises a diaphragm basal membrane and a solid electrolyte coating, wherein the thickness of the solid electrolyte coating is 5-20 μm, and the solid electrolyte coating uniformly covers the double surfaces or the double side surfaces of the diaphragm basal membrane; the solid electrolyte coating comprises the following raw materials, by weight, 0.5-2 parts of a dispersing agent, 10-40 parts of a solid electrolyte, 1-5 parts of a binder, 50-100 parts of a solvent A, and 50-100 parts of a solvent B. However, the powder is hard and easily broken after tabletting, and the thickness and shape are not easily changed, and the applicability is not strong.
CN109244547A discloses a preparation method of a composite solid electrolyte membrane, which comprises the following steps: 1) coating a metal oxide layer on the surface of the solid electrolyte powder by adopting an atomic layer deposition method; 2) and (3) hot-pressing the solid electrolyte powder coated with the metal oxide layer on the surface at 200-1400 ℃, and cooling to room temperature to obtain the composite solid electrolyte diaphragm. However, the method has high preparation cost, the powder is hard after tabletting and easy to crack, the thickness and the shape are not easy to change, and the applicability is not strong.
Therefore, there is a need to develop a solid oxide lithium ion battery composite separator, which has both good flexibility and high ionic conductivity, and improves the applicability of the separator.
Disclosure of Invention
In view of the above problems in the prior art, the present invention aims to provide a solid-state lithium ion battery composite separator, a preparation method and uses thereof.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for preparing a solid-state lithium ion battery composite separator, comprising the following steps:
(1) stirring and mixing oxide solid electrolyte powder with absolute ethyl alcohol, filtering until the pH value is neutral, and drying to obtain pretreated powder;
(2) mixing the pretreated powder with a DMF (dimethyl formamide) glue solution of PVDF (polyvinylidene fluoride), and sealing and stirring to obtain a mixed slurry;
(3) coating the mixed slurry on a base film, and drying to obtain a solid lithium ion battery composite diaphragm;
the solid content of the DMF glue solution of the PVDF is less than or equal to 8 percent, and the mass of the pretreated powder accounts for no more than 15 percent based on 100 percent of the mass of the mixed glue solution.
According to the method, the oxide solid electrolyte is pretreated by adopting absolute ethyl alcohol, then the oxide solid electrolyte and a DMF (dimethyl formamide) glue solution of PVDF (polyvinylidene fluoride) are sealed and stirred to prepare a mixed slurry, and the mixed slurry is coated to prepare the solid lithium ion battery composite diaphragm. The problems that a single solid oxide electrolyte is high in hardness, gaps exist among powder materials, and dozens of micrometers cannot be achieved are solved, the applicability is improved, and the problem that the conductivity of a polymer electrolyte is poor is also solved.
In the method, when the viscosity of the glue solution is not suitable to be too high, the viscosity of the glue solution is too high, the coating is not facilitated, and the curling is easy to occur during air drying, so that the consistency of the thickness of the diaphragm is not good, and the final performance is influenced; the mass ratio of the pretreatment powder is not too high, and if it exceeds 15%, the surface graininess of the film is very serious, the flexibility is poor, and the film is easy to break. In order to better balance good flexibility, uniform and smooth film forming property, uniformity and excellent conductivity, the solid content of the DMF glue solution of the PVDF is more preferably 3-8% (such as 3%, 4%, 5%, 6%, 7% or 8% and the like), and the mass proportion of the pretreatment powder is 5-15% based on 100% of the mass of the mixed glue solution.
The pH value of the neutral pH value means that the pH value is about 7, and the deviation of the pH value is +/-0.2.
The following is a preferred technical solution of the present invention, but not a limitation to the technical solution provided by the present invention, and the technical objects and advantageous effects of the present invention can be better achieved and achieved by the following preferred technical solution.
Preferably, the oxide solid electrolyte powder of step (1) includes Li7-xLa3Zr2-xTaxO12(LLZTO) and Li7La3Zr2O12(LLZO) wherein 0 is<x<2, e.g., 0.02, 0.05, 0.1, 0.2, 0.3, 0.5, 0.8, 1.0, 1.2, 1.5, 1.7, or 2, etc.
Preferably, the particle size of the oxide solid electrolyte powder of step (1) is 0.03mm or less, for example, 0.03mm, 0.02mm, 0.01mm, 0.005mm, 0.003mm, or the like. Under the condition of the particle size, the removal of alkaline substances in the step (1) and the composition in the step (2) are facilitated, the composition of the alkaline substances and the step (2) is improved, and the solid-state lithium ion battery composite diaphragm with high conductivity and good flexibility is obtained.
Preferably, the stirring and mixing speed of step (1) is 1000rpm or less, such as 1000rpm, 900rpm, 800rpm, 700rpm, 600rpm, 500rpm, 400rpm, 300rpm, 200rpm, 100rpm or 50rpm, etc., preferably 50rpm to 200 rpm.
Preferably, the total time of stirring and mixing in the step (1) is less than or equal to 6 hours, such as 6 hours, 5 hours, 4 hours, 3 hours, 2 hours, 1 hour or 0.5 hour, and the like, and preferably 1 hour to 3 hours.
Preferably, the stirring, mixing and filtering of step (1) are repeated 3 to 10 times, for example, 1, 2, 3, 5, 6, 8 or 10 times.
The invention preferably removes alkali at a lower rotating speed in a shorter time and according to the repeated mode, which has the advantages of reducing the risk of structural damage of the oxide solid electrolyte as much as possible and obtaining more thorough alkali removing effect.
Preferably, the DMF solution of PVDF in step (2) is prepared under the conditions of 25-60 deg.C (such as 25 deg.C, 28 deg.C, 30 deg.C, 35 deg.C, 40 deg.C, 45 deg.C, 50 deg.C, 55 deg.C or 60 deg.C).
Preferably, the stirring under seal in step (2) is carried out at 55 ℃ to 65 ℃ (e.g., 55 ℃, 57 ℃, 60 ℃, 62 ℃, or 65 ℃, etc.).
Preferably, the rotation speed of the closed stirring in the step (2) is 400rpm to 1000rpm, such as 400rpm, 500rpm, 600rpm, 650rpm, 700rpm, 800rpm or 1000 rpm.
Preferably, the rotation speed is increased by 100rpm every 1 hour when the closed stirring is carried out in the step (2).
Preferably, the time for the closed stirring in the step (2) is 4h to 12h, such as 4h, 5h, 6h, 8h, 10h, 11h or 12 h.
Preferably, the coating of step (3) is a double-sided coating.
The present invention is not limited to the kind of the base film, and base films commonly used in the art for the preparation of separators are all suitable for the present invention, for example, PET films.
Preferably, the drying in step (3) is a hot air drying at 30 ℃ to 60 ℃ (e.g., 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, or 60 ℃, etc.).
Preferably, the coating formed by coating after drying in step (3) has a thickness of 10 μm to 2mm, for example 10 μm, 20 μm, 35 μm, 50 μm, 70 μm, 100 μm, 150 μm, 200 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, 550 μm, 600 μm, 700 μm, 800 μm, 1mm, 1.2mm, 1.5mm, 1.7mm, 2mm, etc., preferably 10 μm to 40 μm.
As a preferred technical scheme of the method, the method also comprises the step of sieving the mixed slurry through a 150-mesh sieve before coating.
As a further preferred technical solution of the method of the present invention, the method comprises the steps of:
(1) preparation of oxidationSolid electrolyte Li7-xLa3Zr2-xTaxO12，0<x<2
a) Mixing lithium source, lanthanum source and ZrO2、Ta2O5Performing primary ball milling according to the formula amount to obtain mixed powder;
b) putting the mixed powder into a muffle furnace, and pre-burning for 1-12 h (such as 1h, 2h, 3.5h, 4h, 5h, 6h, 7h, 8h, 9h, 10h or 12 h) under the condition of 800-1000 ℃ (such as 800 ℃, 825 ℃, 850 ℃, 900 ℃, 950 ℃ or 1000 ℃ and the like);
c) taking out the powder after cooling, carrying out secondary ball milling for 10-30 min, sieving the powder by a sieve of 300-500 meshes, and taking the powder under the sieve;
d) sintering the undersize powder obtained in the step c) at 1100-1380 ℃ for 10 min-12 h;
e) after cooling, taking out the powder, and repeating the steps of secondary ball milling for 10-30 min and sieving in the step c) to ensure that the particle size of the powder is below 0.03 mm;
adding the powder obtained in the step e) into absolute ethyl alcohol, stirring, mixing, filtering, repeating the step 3-10 times until the pH value is neutral, and drying to obtain pretreated Li7-xLa3Zr2-xTaxO12Powder material;
(2) adding PVDF polymer material into DMF solvent at 25-60 deg.c to obtain glue solution, and adding pretreated Li7-xLa3Zr2-xTaxO12Adding powder into the glue solution, wherein the mass ratio of the pretreated powder to PVDF in the glue solution is 10-15% based on 100% of the total amount of the pretreated powder and PVDF in the glue solution, hermetically stirring for 4-12 hours at the temperature of 55-65 ℃ at the rotating speed of 400-1000 rpm, and sieving with a 150-mesh sieve after the hermetically stirring is finished;
(3) and (3) taking the undersize obtained by sieving in the step (2), coating the undersize on a PET film, carrying out hot air drying at the temperature of 30-60 ℃ after coating, and obtaining a coating layer with the thickness of 10-40 mu m after air drying.
The kind of the lithium source and the lanthanum source is not particularly limited in the present invention, and the lithium source may be, for example, LiOH and Li2CO3ToOne of them is less. The lanthanum source can be, for example, La2O3And La (OH)3At least one of (1).
Oxide solid electrolyte Li is carried out according to the method of the preferred technical scheme7-xLa3Zr2-xTaxO12(0<x<2) Can obtain a predetermined fine particle diameter while maintaining the oxide solid electrolyte Li7-xLa3Zr2-xTaxO12The structural stability of (2).
In a second aspect, the invention provides a solid-state lithium ion battery composite diaphragm, which is prepared by the method in the first aspect.
In a third aspect, the present invention provides a solid-state lithium ion battery, which includes a positive plate, a negative plate, and the solid-state lithium ion battery composite membrane of the second aspect located between the positive plate and the negative plate.
In a fourth aspect, the present invention provides a method for producing the solid-state battery of the third aspect, the method comprising: and combining the positive plate, the negative plate and the solid-state lithium ion battery composite diaphragm, and then carrying out hot pressing or cold pressing to obtain the solid-state battery.
Compared with the prior art, the invention has the following beneficial effects:
according to the method, the oxide solid electrolyte is pretreated by adopting absolute ethyl alcohol, then the oxide solid electrolyte and a DMF (dimethyl formamide) glue solution of PVDF (polyvinylidene fluoride) are sealed and stirred to prepare a mixed slurry, and the mixed slurry is coated to prepare the solid lithium ion battery composite diaphragm. The problems that a single solid oxide electrolyte is high in hardness, gaps exist among powder materials, and dozens of micrometers cannot be achieved are solved, the applicability is improved, and the problem that the conductivity of a polymer electrolyte is poor is also solved.
The thickness of the electrolyte layer manufactured by the invention can reach 10 mu m-2 mm, and the battery can be manufactured into various sizes and shapes, so that the adaptability is wide.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments.
It should be noted that the step of preparing the gel solution is not particularly limited as long as the preparation is completed before the step of mixing with the oxide solid electrolyte powder.
Example 1:
the embodiment provides a preparation method of a solid-state lithium ion battery composite diaphragm, which comprises the following steps:
1. adding LiOH and La2O3、ZrO2、Ta2O5Adding the mixture into a ball milling tank according to the molar ratio of 1.15:1:1:1 for ball milling, and carrying out ball milling alternately at the rotating speed of 300rpm for 12 hours in a clockwise and anticlockwise way for 15 minutes/time to prepare Li6.4La3Zr1.4Ta0.6O12。
2. And taking out the powder subjected to ball milling, transferring the powder into a muffle furnace for sintering, controlling the sintering temperature at 900 ℃ for sintering for 12 hours, and heating at 1.5 ℃/min.
3. And taking out the sintered powder, continuously performing ball milling and mixing at the ball milling rotation speed of 500rpm, sieving the powder with a 300-mesh sieve after 15 minutes, and continuously performing ball milling on the powder which is not sieved for a plurality of times until the powder is completely sieved.
4. And then putting the mixture into a muffle furnace for sintering again, wherein the sintering temperature is increased to 1120 ℃, the sintering is carried out for 12min, and the temperature is increased at 1.5 ℃/min.
5. And after sintering, taking out the powder, performing ball milling and crushing again at the rotating speed of 500rpm, sieving the powder with a 500-mesh sieve after 15 minutes, and continuously performing ball milling on the powder which is not sieved for a plurality of times until the powder is completely sieved.
6. Adding the sieved powder into absolute ethyl alcohol, stirring at 60rpm for 10 minutes, filtering, adding the powder into the absolute ethyl alcohol again, stirring at 60rpm for 10 minutes, filtering, repeating the steps for 5 times to ensure that the pH value is about 7.
7. And (3) drying the filtered powder in an oven at 60 ℃ for later use.
8. And (3) adding PVDF powder into a DMF solvent, wherein the mass ratio of the DMF solvent to the PVDF powder is 1:0.07, sealing to prevent the DMF solvent from volatilizing, putting the mixture into a 60 ℃ oven synchronously with the step (7), and accelerating the dissolution of PVDF at 60 ℃ to finally enable the solid content of the glue solution to be about 7%.
9. And (3) mixing the LLZTO powder dried in the step (7) according to the ratio of LLZTO powder: adding the glue solution (mass ratio) of 1:9 into the glue solution prepared in the step 8, sealing and stirring at the temperature of 60 ℃, increasing the rotation speed by 100rpm every 1 hour from 400rpm, and finally stirring for 2 hours at 1000 rpm.
10. The resulting slurry was passed through a 150 mesh sieve and coated on a PET film.
11. And after the coating is finished, transferring the film into a hot oven to carry out hot air drying at 60 ℃, wherein the film obtained after air drying is the solid lithium ion battery composite diaphragm.
The embodiment also provides a solid-state lithium ion battery, which is prepared by the following method, wherein the method comprises the following steps:
12. taking off the air-dried film, combining with a positive electrode (thickness of 150 μm) and a negative electrode (thickness of 100 μm), and hot-pressing to obtain an electrode layer, wherein the temperature of the hot press is 80 ℃ and the pressure of the hot press is 20 MPa.
The test shows that the thickness of the electrode layer is 300 mu m, and the test conductivity of the assembled battery is 10-4S/cm。
Example 2:
the difference from example 1 is that the composite film obtained in step 11 of example 1 was combined with a positive electrode and a negative electrode and then cold-pressed by a roll press at a pressure of 90T.
The thickness of the electrode layer is 300 mu m, and the test conductivity of the assembled battery is 10-4S/cm。
Example 3:
the embodiment provides a preparation method of a solid-state lithium ion battery composite diaphragm, which comprises the following steps:
1. adding LiOH and La2O3、ZrO2、Ta2O5Adding the mixture into a ball milling tank according to the molar ratio of 1.15:1:1:1 for ball milling, wherein the rotating speed is 450rpm, and the clockwise and anticlockwise speeds are 15 minutes/timeAlternative ball milling for 12 hours to prepare Li6.4La3Zr1.4Ta0.6O12。
2. And taking out the powder subjected to ball milling, transferring the powder into a muffle furnace for sintering, controlling the sintering temperature at 950 ℃ for sintering for 10 hours, and raising the temperature at 2.5 ℃/min.
3. And taking out the sintered powder, continuously performing ball milling and mixing at the ball milling rotation speed of 700rpm, sieving the powder with a 300-mesh sieve after 10 minutes, and continuously performing ball milling on the powder which is not sieved for a plurality of times until the powder is completely sieved.
4. And then putting the mixture into a muffle furnace for sintering again, wherein the sintering temperature is increased to 1150 ℃, the sintering is carried out for 10min, and the temperature is increased by 2 ℃/min.
5. And after sintering, taking out the powder, performing ball milling and crushing again at the rotation speed of 550rpm for 15 minutes, sieving the powder with a 600-mesh sieve, and continuously performing ball milling on the powder which is not sieved for a plurality of times until the powder is completely sieved.
6. Adding the sieved powder into absolute ethyl alcohol, stirring at 60rpm for 10 minutes, filtering, adding the powder into the absolute ethyl alcohol again, stirring at 60rpm for 10 minutes, filtering, repeating the steps for 5 times to ensure that the pH value is about 7.
7. And (3) drying the filtered powder in an oven at 60 ℃ for later use.
8. And (3) adding PVDF powder into a DMF solvent, wherein the mass ratio of the DMF solvent to the PVDF powder is 1:0.05, sealing to prevent the DMF solvent from volatilizing, putting the mixture into a 60 ℃ oven synchronously with the step (7), and accelerating the dissolution of PVDF at 60 ℃ to finally enable the solid content of the glue solution to be about 5%.
9. And (3) mixing the LLZTO powder dried in the step (7) according to the ratio of LLZTO powder: adding the glue solution (mass ratio) of 0.8:9.2 into the glue solution prepared in the step 8, sealing and stirring at the temperature of 60 ℃, increasing the rotating speed by 100rpm from 400rpm every 1 hour, and finally stirring at 1000rpm for 2 hours.
10. The resulting slurry was passed through a 150 mesh sieve and coated on a PET film.
11. And after the coating is finished, transferring the film into a hot oven to carry out hot air drying at 60 ℃, wherein the film obtained after air drying is the solid lithium ion battery composite diaphragm.
The embodiment also provides a solid-state lithium ion battery, which is prepared by the following method, wherein the method comprises the following steps:
12. taking off the air-dried film, combining with a positive electrode (thickness of 150 μm) and a negative electrode (thickness of 100 μm), and hot-pressing to obtain an electrode layer, wherein the temperature of the hot press is 80 ℃ and the pressure of the hot press is 25 MPa.
The test shows that the thickness of the electrode layer is 500 mu m, and the test conductivity of the assembled battery is 4 multiplied by 10-4S/cm。
Example 3
The difference from example 1 is that step 5 was passed through a 300 mesh screen.
The test shows that the thickness of the electrode layer is 300 mu m, and the test conductivity of the assembled battery is 10-5S/cm。
In conclusion, the granularity of the composite diaphragm of the solid-state lithium ion battery has important influence on the product performance.
Example 4
The difference from example 1 is that step 6 is carried out in the following manner: adding the sieved powder into absolute ethyl alcohol for ball milling at 1500rpm for 10 minutes, filtering, adding the powder into the absolute ethyl alcohol again for ball milling at 1500rpm for 10 minutes, and repeating the steps for 5 times to ensure that the pH value is about 7.
The test shows that the thickness of the electrode layer is 300 mu m, and the test conductivity of the assembled battery is 5 multiplied by 10-6S/cm。
In conclusion, when step 6 is carried out by high-speed ball milling, the structure of the oxide solid electrolyte is damaged to a certain extent, and the conductivity of the product is influenced.
Comparative example 1:
the difference from example 1 is that the mass ratio of DMF solvent to PVDF powder in step 8 is 1: 0.1.
Tests show that the thickness consistency of the composite diaphragm of the solid-state lithium ion battery is poor.
In conclusion, when the viscosity of the glue solution is too high, the coating is not facilitated, and the edge curling is easy to occur during air drying, so that the consistency of the thickness of the diaphragm is not good, and the final performance is affected.
Comparative example 2:
the difference from example 1 is that LLZTO powder in step 9: the glue solution (mass ratio) is 2: 8.
Through tests, the surface granular sensation of the solid-state lithium ion battery composite diaphragm is very serious, the flexibility is very poor, and the solid-state lithium ion battery composite diaphragm is easy to crack.
In conclusion, when the LLZTO powder is added in an amount of more than 15 wt% based on the mixed slurry, the grainy feeling of the surface of the film-formed film is very severe, and the flexibility is poor and the breakage is easy. The applicability is not strong.
Comparative example 3:
the difference from example 1 is that step 6 was not performed.
This comparative example shows gelation in the step of mixing the LLZTO powder and the gum solution and stirring them in a sealed state. Subsequent screen coating steps cannot be performed.
In conclusion, when the LLZTO powder is not neutralized by pH, the LLZTO powder becomes alkaline and participates in the decomposition of DMF solvent, and a gel phenomenon occurs. Subsequent steps cannot be performed.
The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims (10)

1. A preparation method of a solid-state lithium ion battery composite diaphragm is characterized by comprising the following steps:
(1) stirring and mixing oxide solid electrolyte powder with absolute ethyl alcohol, filtering until the pH value is neutral, and drying to obtain pretreated powder;
(2) mixing the pretreated powder with a DMF (dimethyl formamide) glue solution of PVDF (polyvinylidene fluoride), and sealing and stirring to obtain a mixed slurry;
(3) coating the mixed slurry on a base film, and drying to obtain a solid lithium ion battery composite diaphragm;
the solid content of the DMF glue solution of the PVDF is less than or equal to 8 percent, and the mass of the pretreated powder accounts for no more than 15 percent based on 100 percent of the mass of the mixed glue solution.
2. The method of claim 1, wherein the oxide solid electrolyte powder of step (1) comprises Li7-xLa3Zr2-xTaxO12And Li7La3Zr2O12At least one of (1), wherein 0<x<2；
Preferably, the particle size of the oxide solid electrolyte powder in the step (1) is below 0.03 mm;
preferably, the stirring and mixing speed of the step (1) is less than or equal to 1000rpm, preferably 50rpm to 200 rpm;
preferably, the total time of stirring and mixing in the step (1) is less than or equal to 6 hours, and preferably 1 to 3 hours;
preferably, the stirring, mixing and filtering of step (1) are repeated for 3 to 10 times.
3. The method according to claim 1 or 2, characterized in that the PVDF DMF glue solution has a solid content of 3-8%, and the mass ratio of the pretreatment powder material is 5-15% based on 100% of the mixed glue solution;
preferably, the PVDF DMF glue solution obtained in the step (2) is prepared at the temperature of 25-60 ℃;
preferably, the closed stirring in the step (2) is carried out at the temperature of 55-65 ℃;
preferably, the rotation speed of the closed stirring in the step (2) is 400 rpm-1000 rpm;
preferably, the rotation speed is increased by 100rpm every 1 hour when the closed stirring is carried out in the step (2);
preferably, the time of the closed stirring in the step (2) is 4-12 h.
4. The method according to any one of claims 1 to 3, wherein the coating of step (3) is a double-sided coating;
preferably, the base film of step (3) is a PET film.
5. The method according to any one of claims 1 to 4, wherein the drying in step (3) is a hot air drying at 30 ℃ to 60 ℃;
preferably, the thickness of the coating formed by coating after drying in step (3) is 10 μm to 2mm, preferably 10 μm to 40 μm.
6. The method of any one of claims 1-5, further comprising passing the mixed slurry through a 150 mesh screen prior to coating.
7. Method according to any of claims 1-6, characterized in that the method comprises the steps of:
(1) preparation of oxide solid electrolyte Li7-xLa3Zr2-xTaxO12，0<x<2
a) Mixing lithium source, lanthanum source and ZrO2、Ta2O5Performing primary ball milling according to the formula amount to obtain mixed powder;
b) putting the mixed powder into a muffle furnace, and presintering for 1-12 h at 800-1000 ℃;
c) taking out the powder after cooling, carrying out secondary ball milling for 10-30 min, sieving the powder by a sieve of 300-500 meshes, and taking the powder under the sieve;
d) sintering the undersize powder obtained in the step c) at 1100-1380 ℃ for 10 min-12 h;
e) after cooling, taking out the powder, and repeating the steps of secondary ball milling for 10-30 min and sieving in the step c) to ensure that the particle size of the powder is below 0.03 mm;
adding the powder obtained in the step e) into absolute ethyl alcohol, stirring, mixing, filtering, repeating the step 3-10 times until the pH value is neutral, and drying to obtain pretreated Li7-xLa3Zr2-xTaxO12Powder material;
(2) adding PVDF polymer material into DMF solvent at 25-60 deg.c to obtain glue solution, and adding pretreated Li7-xLa3Zr2-xTaxO12Adding powder into the glue solution, wherein the mass ratio of the pretreated powder to PVDF in the glue solution is 10-15% based on 100% of the total amount of the pretreated powder and PVDF in the glue solution, hermetically stirring for 4-12 hours at the temperature of 55-65 ℃ at the rotating speed of 400-1000 rpm, and sieving with a 150-mesh sieve after the hermetically stirring is finished;
(3) and (3) taking the undersize obtained by sieving in the step (2), coating the undersize on a PET film, carrying out hot air drying at the temperature of 30-60 ℃ after coating, and obtaining a coating layer with the thickness of 10-40 mu m after air drying.
8. A solid-state lithium ion battery composite separator, characterized in that it is prepared by the method of any one of claims 1 to 7.
9. The solid-state lithium ion battery is characterized by comprising a positive plate, a negative plate and a solid-state lithium ion battery composite diaphragm positioned between the positive plate and the negative plate.
10. A method for producing a solid-state battery according to claim 9, characterized in that the method comprises: and combining the positive plate, the negative plate and the solid-state lithium ion battery composite diaphragm, and then carrying out hot pressing or cold pressing to obtain the solid-state battery.
CN202011205739.8A 2020-11-02 2020-11-02 Solid lithium ion battery composite diaphragm, preparation method and application thereof Pending CN112366423A (en)

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