CN115966838A - Method for preparing doped graphene-polyethylene glycol-based conversion film by vacuum adsorption method - Google Patents

Abstract

The invention discloses a method for preparing a doped graphene-polyethylene glycol based conversion membrane by a vacuum adsorption method, which comprises the steps of carrying out tape casting on a mixed solution prepared from a polyethylene glycol based polymer, a pore-forming agent, cyclodextrin group molecules, a terminated polymer and a doped graphene additive to form a membrane, carrying out ultrasonic treatment in water, ethanol or an ethanol aqueous solution, forming a conversion membrane, carrying out vacuum drying, removing the pore-forming agent, carrying out vacuum pumping, spraying electrolyte and the like to prepare a polymer electrolyte, namely the doped graphene-polyethylene glycol based conversion membrane. The invention can obviously improve the liquid absorption and retention capability, high temperature resistance, ionic conductivity, surface impedance and battery compatibility of the polymer film.

Description

Method for preparing doped graphene-polyethylene glycol-based conversion film by vacuum adsorption method

technical field

The invention belongs to the technical field of battery separators, and relates to a preparation method for solid-state battery electrolytes, in particular to a vacuum adsorption method that can be used for lithium batteries, lithium-ion batteries, sodium batteries, and sodium-ion batteries to prepare doped graphene-polyethylene glycol based conversion film method.

Background technique

At present, both at home and abroad, the development of solid-state batteries is regarded as an important method to improve the safety and energy density of lithium-ion batteries. In the field of solid-state batteries, polymer electrolytes are the key to the technology. The currently prepared solid electrolytes still have problems such as low ionic conductivity (10 ^-5 ~ 10 ^-10 S·cm ^-1 ), which hinders the real commercial application of solid-state batteries. Gel polymer electrolyte (GPE) for solid-state batteries has the advantages of good flexibility, good interfacial compatibility, and excellent electrochemical performance. A lot of research work has been carried out at home and abroad. Gel polymer electrolyte usually soaks the polymer-based membrane in the electrolyte to obtain a polymer membrane carrying lithium ions, which is a polymer electrolyte. In this polymer electrolyte, the polymer chain segment can move rapidly, which has the advantages of low glass transition temperature and wide electrochemical stability window. Polyethylene oxide (PEO) [Hassoun J. et al, Angew. Chem. Int. Ed., 2010, 49(13): 2371-2374.], polyvinylidene fluoride-hexa Fluoropropene (PVDF-HFP) [Wu N. et al., J. Power Sources, 2011, 196(22): 9751-9756; Zhang P. et al. , J. Membr. Sci., 2011, 379(1 -2): 80-85.], polymethyl methacrylate (PMMA), etc. In the gel polymer electrolyte, lithium ions can be transported with the chain segment movement of the polymer, so that the ion conduction of the polymer electrolyte is mainly carried out in the amorphous region. Adding plasticizer [Zhang D. et al., ACS Applied Materials & Interfaces, 2017, 9 (42): 36886-36896.], copolymerization [Singh M. et al., Macromolecules, 2007, 40(13): 4578 -4585.; Bouchet R. et al., Nature Materials, 2013, 12(5): 452.], adjusting polymer segments [Gadjourova Z. et al., Nature, 2001, 412:520], adding inorganic fillers [Yang T. et al., ACS Applied Materials & Interfaces, 2017, 9(26):21773.] and other methods to improve the ionic conductivity of polymer electrolytes. Incorporating nanomaterials into the polymer matrix can effectively improve the ionic conductivity, mechanical strength and stability to lithium metal of the polymer electrolyte [Croce F. et al., Electrochim. Acta, 2001, 46(16): 2457-2461 .]. The inorganic fillers used include inactive fillers and active fillers. Inactive fillers cannot transfer lithium ions, but can improve the performance of polymers, such as Al ₂ O ₃ , SiO ₂ and TiO ₂ . The active filler itself can deliver lithium salts, such as Li ₂ N, Li _0.33 La _0.57 TiO ₃ [Zhu P.et al., J. Mater. Chem. A,2018,6: 4279-4285] and Li _1.3 Al _0.3 Ti _0.7 (PO ₄ ) ₃ [Yang L. et al., Advanced Energy Materials, 2017, 7(22):1701437.] etc.

Graphene is a zero-bandgap semiconductor. It has obvious advantages such as extremely low resistivity, high theoretical thermal conductivity (6000W m ^-1 K ^-1 ), and large specific surface area. However, the graphene surface is prone to defects, which can easily cause side reactions and stability issues in battery systems. Using doped graphene can significantly improve this problem.

Despite the above studies, the polymer electrolytes prepared so far still have the following problems. For example, the side reactions of the battery system are large, the conductivity is low, the interface impedance is large, the thermal shrinkage rate is too large, and the negative electrode is lithium-produced, etc., which make it difficult to apply polymer electrolytes in solid-state batteries.

Contents of the invention

The purpose of the present invention is to solve the above problems, and to provide a method for preparing doped graphene-polyethylene glycol-based conversion film by vacuum adsorption, which chemically bonds the doped graphene additive to the polymer system, improving the polymer The compatibility of the electrolyte in the battery system can avoid the side reaction of the polymer in the battery system and improve the ion conductivity. The application of the polymer electrolyte can reduce the interface impedance of the electrolyte, improve the thermal shrinkage performance of the polymer electrolyte, and significantly improve the application performance of the prepared solid-state battery.

In order to achieve the above object, the technical scheme adopted in the present invention is as follows:

The method for preparing doped graphene-polyethylene glycol based conversion film by vacuum adsorption method comprises the following steps:

1) Dissolving the mixture of polyethylene glycol-based polymer and pore-forming agent, cyclodextrin group molecules and end-capped polymer in liquid solvents respectively to prepare three kinds of liquid solutions;

2) Mix the three liquid solutions, stir for 12h-14, then add the doped graphene additive, continue heating and stirring for 5-48h, and prepare the mixed solution;

3) cast the mixed solution on a glass plate to form a film, and ultrasonically treat it in water, ethanol or an aqueous solution of ethanol at a temperature range of 40-70°C to form a conversion film; further ultrasonic treatment dissolves the pore-forming agent in the conversion film, Then vacuum-dry at a temperature range of 70-125°C to prepare a porous polymer;

4) In the temperature range of 70-125°C, continuously vacuumize the porous polymer in a vacuum drying oven to remove volatile substances, spray into the electrolyte solution containing lithium salt or sodium salt, and cool to room temperature to obtain a polymer electrolyte , which is the doped graphene-polyethylene glycol-based conversion film.

The pore forming agent is polyethylene glycol, polyvinyl alcohol or polypropylene glycol with molecular weight in the range of 200-800.

The weight ratio of the polyethylene glycol-based polymer to the pore-forming agent in the mixture of the polyethylene glycol-based polymer and the pore-forming agent is 1: (0.01～0.16).

The weight ratio of the end-capped polymer to the polyethylene glycol-based polymer is (0.05-1): 1.

The weight ratio of the doped graphene additive to the polyethylene glycol-based polymer is (0.001-0.10): 1.

The inclusion ratio of polyethylene glycol-based polymers and cyclodextrin-type group molecules in the polymer electrolyte is 1:5-27.

The doped graphene additive is graphene doped with nitrogen, titanium, chromium, iron, cobalt, nickel or copper.

The polyethylene glycol-based polymer is polyethylene glycol or a derivative of polyethylene glycol main chain polymer.

The cyclodextrin group molecule is α, β or γ type cyclodextrin, or the product of esterification and crosslinking reaction of some hydroxyl groups of cyclodextrin, or the chlorine or fluorine of some hydroxyl groups of cyclodextrin Substitutes.

The end-capped polymer is polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene or polymethyl methacrylate.

The liquid solvent is dimethylformamide, N-methylpyrrolidone, N,N-dimethylacetamide, cyclohexanone or butanone.

The lithium salt is lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate or lithium tetrafluoroborate.

The sodium salt is sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, sodium hexafluoroarsenate, sodium trifluoromethanesulfonate or sodium tetrafluoroborate.

The molecular weight of the polyethylene glycol-based polymer is in the range of 10,000 to 80,000.

The molecular weight of the end-capped polymer is in the range of 100,000 to 1.8 million.

The stated molecular weights are number average molecular weights.

The porous polymer meets the following requirements at the same time: the temperature at which the heat shrinkage rate is 5% is 180-230° C., the liquid absorption rate is 30-75%, and the tensile strength is 6-20 MPa.

The polymer electrolyte membrane, battery positive pole, negative pole and packaging materials can be made into battery cells.

The invention can significantly improve the liquid absorbing and holding capacity, high temperature resistance, ion conductivity, interface impedance and compatibility of the polymer. The prepared polymer electrolyte has good compatibility with many battery systems, and the capacity retention rate of the prepared battery is higher than 80% after being charged and discharged and stored for one month. The prepared polymer film remained stable above 180°C. Applied to the battery system, the internal resistance of the battery can be significantly reduced, and the electrochemical performance and safety performance of the battery can be improved.

The invention performs rapid wetting treatment on the polymer through the vacuum adsorption method, which can avoid the problems of long time, uneven distribution of electrolyte and the like in the wetting method of soaking and wetting the polymer. The electrolyte prepared by this method is evenly distributed on the surface of the polymer, the preparation speed is fast, and the batch consistency applied to the battery system is good.

Description of drawings

Fig. 1 is the infrared spectrogram of the porous polymer (PR conversion film) prepared in Example 1 of the present invention and the porous polymer (PR) prepared in Comparative Example 1 without nitrogen-doped graphene additive.

Fig. 2 is the infrared spectrum of the cyclodextrin of Example 1 of the present invention.

Fig. 3 is the polyethylene glycol infrared spectrum of the present invention.

Fig. 4 is the infrared spectrum of polyvinylidene fluoride-hexafluoropropylene of the present invention.

Detailed ways

The present invention will be further described below in conjunction with examples. The examples are only further supplements and descriptions of the present invention, rather than limiting the invention.

Example 1

1) Prepare a mixture of polyethylene glycol with a molecular weight of 20,000 and a polyethylene glycol pore-forming agent with a molecular weight of 350 at a weight ratio of 1:0.08. The mixture, α-type cyclodextrin molecules and polyvinylidene fluoride-hexafluoropropylene end polymer with a molecular weight of 1.5 million are respectively dissolved in N-methylpyrrolidone liquid solvent to prepare three liquid solutions. Wherein, the weight ratio of polyvinylidene fluoride-hexafluoropropylene end-capped polymer to polyethylene glycol is 0.1: 1.

2) Mix the three liquid solutions, stir for 12 hours, then add nitrogen-doped graphene (0.2 wt% nitrogen) additive, continue heating and stirring for 20 hours to prepare a mixed solution. In nitrogen-doped graphene, nitrogen acts as an electron donor and graphene acts as an electron acceptor. Electron transfer synergy enhances the effect of nitrogen doping. The weight ratio of described nitrogen-doped graphene additive and polyethylene glycol is 0.05: 1.

3) Cast the mixed solution on a glass plate to form a film, and ultrasonically treat it in ethanol at 60°C to form a conversion film; further ultrasonic treatment, so that the polyethylene glycol pore-forming agent with a molecular weight of 350 in the conversion film is dissolved in ethanol, and then in the Vacuum drying at 115°C to prepare a porous polymer.

4) Continuously evacuate the porous polymer at 115°C in a vacuum drying oven to remove volatile substances in the porous polymer, spray into the electrolyte containing bis(fluorosulfonyl)imide lithium, cool to room temperature, and prepare The obtained polymer electrolyte is a doped graphene-polyethylene glycol-based conversion membrane.

The inclusion ratio of polyethylene glycol (molecular weight: 20,000) and α-cyclodextrin molecules in the doped graphene-polyethylene glycol-based conversion film is 1:10.

The porous polymer meets the following requirements at the same time: a temperature of 200°C for a heat shrinkage rate of 5%, a liquid absorption rate of 30%, and a tensile strength of 20 MPa.

The doped graphene-polyethylene glycol-based conversion film, battery positive electrode, negative electrode and packaging materials are made into battery cells.

Comparative example 1

No nitrogen-doped graphene additive was added, and the remaining steps were the same as in Example 1 to prepare a polyethylene glycol-based conversion film without nitrogen-doped graphene additive.

Fig. 1 is the infrared spectrogram of the porous polymer (PR conversion film) prepared in Example 1 of the present invention and the porous polymer (PR) prepared in Comparative Example 1 without nitrogen-doped graphene additive. It can be seen from Figure 1 that after adding nitrogen-doped graphene, the infrared vibration of the CO group of polyethylene glycol in the prepared porous polymer moved from the original 944 cm ^-1 to 958 cm ^-1 , and the polysegmentation in the polymer The strong infrared absorption peak of CF ₃ originally located at 1073 cm ^-1 in vinyl fluoride-hexafluoropropylene is obviously weakened. It shows that the nitrogen-doped graphene makes the porous polymer form a stable hydrogen bond between polyvinylidene fluoride-hexafluoropropylene and polyethylene glycol. .

Example 2

1) A mixture of fluorinated polyethylene glycol with a molecular weight of 100,000 (fluorine content of 0.15%) and a polyethylene glycol pore-forming agent with a molecular weight of 400 at a weight ratio of 1:0.01. The mixture, γ-type cyclodextrin and polyvinylidene fluoride-terminated polymer with a molecular weight of 800,000 are heated and stirred respectively, and dissolved in dimethylformamide liquid solvent to prepare three kinds of liquid solutions. The weight ratio of the polyvinylidene fluoride-terminated polymer to the fluoropolyethylene glycol polymer is 0.05: 1.

2) Mix the three liquid solutions, stir for 12 hours, then add titanium-doped graphene (titanium content 0.2 wt%) additive, and continue heating and stirring for 5 hours to prepare a mixed solution. In titanium-doped graphene, Ti acts as an electron donor and graphene acts as an electron acceptor, and the synergistic effect of electron transfer strengthens the effect of Ti doping. The weight ratio of described titanium-doped graphene additive and fluoropolyethylene glycol is 0.10: 1.

3) casting the mixed solution on a glass plate to form a film, and ultrasonically treating it in water at 70° C. to form a conversion film. Further ultrasonic treatment, the polyethylene glycol pore-forming agent with a molecular weight of 400 in the conversion film was dissolved in water to prepare a porous polymer, and then vacuum-dried at 70° C. to prepare a porous polymer.

4) At 125°C, continuously evacuate the porous polymer in a vacuum drying oven to remove volatile substances, spray into the electrolyte solution containing sodium bis(fluorosulfonyl)imide, and cool to room temperature to obtain a polymer electrolyte , which is the doped graphene-polyethylene glycol-based conversion film.

The inclusion ratio of polyethylene glycol (molecular weight: 20,000) and α-cyclodextrin group molecules in the polymer electrolyte is 1:27.

The polymer electrolyte also meets the following requirements: a thermal shrinkage rate of 5% at a temperature of 200° C., a liquid absorption rate of 30%, and a tensile strength of 6 MPa.

The polymer electrolyte, battery positive electrode, negative electrode and packaging materials are made into battery cells.

Example 3

1) Prepare a mixture of 1-polyethylene glycol acetate with a molecular weight of 30,000 and a polyethylene glycol pore-forming agent with a molecular weight of 800 at a weight ratio of 1:0.16. The mixture, α-cyclodextrin and polymethylmethacrylate end-capped polymer with a molecular weight of 1 million were heated and stirred respectively, and dissolved in dimethylformamide liquid solvent to prepare three kinds of liquid solutions. The weight ratio of described polymethyl methacrylate end-capped polymer and 1-polyethylene glycol acetate is 1: 1.

2) Mix the three liquid solutions, stir for 12 hours, then add cobalt-doped graphene (cobalt content 0.3 wt%) additives, continue heating and stirring for 48 hours to prepare a mixed solution. In cobalt-doped graphene, cobalt ions act as electron donors and graphene acts as electron acceptor, and the synergistic effect of electron transfer strengthens the effect of cobalt doping. The weight ratio of described cobalt-doped graphene additive and 1-polyethylene glycol acetate is 0.10: 1.

3) Cast the mixed solution on a glass plate to form a film, and ultrasonically treat it in an ethanol aqueous solution (70 vol.% ethanol) at 68°C to form a conversion film, and continue the ultrasonic treatment to make polyethylene glycol with a molecular weight of 800 in the conversion film The pore agent is dissolved in ethanol aqueous solution to form a porous polymer, and then vacuum-dried at 70° C. to prepare a porous polymer film.

4) At 70°C, continuously evacuate the porous polymer film in a vacuum drying oven to remove volatile substances, spray into the electrolyte solution containing sodium hexafluoroarsenate, and cool to room temperature to obtain a polymer electrolyte, namely It is a doped graphene-polyethylene glycol based conversion film.

The inclusion ratio of 1-acetic acid polyethylene glycol and α-type cyclodextrin group molecules in the doped graphene-polyethylene glycol-based conversion film is 1:5.

The porous polymer film meets the following requirements at the same time: a temperature of 200° C. for a heat shrinkage rate of 5%, a liquid absorption rate of 75%, and a tensile strength of 6 MPa.

The doped graphene-polyethylene glycol-based conversion film, battery positive electrode, negative electrode and packaging materials are made into battery cells.

Example 4

1) Prepare a mixture of polyethylene glycol 1-formate with a molecular weight of 80,000 and polyvinyl alcohol pore-forming agent with a molecular weight of 500 at a weight ratio of 1:0.10. The mixture, α-cyclodextrin 1-formate and polyvinylidene fluoride-terminated polymer with a molecular weight of 1.8 million were heated and stirred separately, and dissolved in N,N-dimethylacetamide liquid solvent to prepare three kinds of liquid solutions . The weight ratio of described polyvinylidene fluoride-terminated polymer and 1-formic acid polyethylene glycol ester polymer is 1: 1.

2) Mix the three liquid solutions, stir for 12 hours, then add nickel-doped graphene (nickel content 1 wt%) additive, continue heating and stirring for 5 hours, and prepare a mixed solution. In nickel-doped graphene, nickel ions act as electron donors, graphene acts as electron acceptor, and the synergistic effect of electron transfer strengthens the nickel doping effect. The weight ratio of described nickel-doped graphene additive and 1-polyethylene glycol formate is 0.10: 1.

3) Cast the mixed solution on a glass plate to form a film, and ultrasonically treat it at 65°C in an aqueous ethanol solution (30 vol.% ethanol content) to form a conversion film. Continue ultrasonic treatment to dissolve the polyvinyl alcohol pore-forming agent with a molecular weight of 500 in the conversion film in an aqueous ethanol solution, and then vacuum-dry at 125° C. to prepare a porous polymer.

4) At 125°C, continuously evacuate the porous polymer in a vacuum drying oven to remove volatile substances, spray into an electrolyte solution containing lithium tetrafluoroborate, and cool to room temperature to obtain a polymer electrolyte, which is a doped Heterographene-polyethylene glycol-based conversion film.

The inclusion ratio of polyethylene glycol 1-formate and α-cyclodextrin 1-formate in the doped graphene-polyethylene glycol-based conversion film is 1:27.

The porous polymer film also meets the following requirements: a temperature of 210° C. at which the heat shrinkage rate is higher than 5%, a liquid absorption rate of 30%, and a tensile strength of 10 MPa.

The doped graphene-polyethylene glycol-based conversion film, battery positive electrode, negative electrode and packaging materials are made into battery cells.

Example 5

1) A mixture prepared with 1-methyl polyethylene glycol with a molecular weight of 10,000 and a polyvinyl alcohol pore-forming agent with a molecular weight of 200 at a weight ratio of 1:0.05. The mixture, α-cyclodextrin 1-formate molecules and polyvinylidene fluoride end-capped polymer with a molecular weight of 100,000 were heated and stirred respectively, and dissolved in a liquid cyclohexanone solvent to prepare three liquid solutions. The weight ratio of the polyvinylidene fluoride-terminated polymer to 1-methyl polyethylene glycol is 0.12: 1.

2) Mix the three liquid solutions, stir for 12 hours, then add nickel-doped graphene (nickel content 1.5 wt.%) additive, continue heating and stirring for 40 hours to prepare a mixed solution. In nickel-doped graphene, nickel acts as an electron donor and graphene acts as an electron acceptor, and the synergistic effect of electron transfer strengthens the effect of nickel doping. The weight ratio of described nickel-doped graphene additive and 1-methyl polyethylene glycol is 0.055: 1.

3) Casting the mixed solution on a glass plate to form a film, and ultrasonically treating it in ethanol at 40° C. to form a conversion film. Continue ultrasonic treatment to dissolve the polyvinyl alcohol pore-forming agent with a molecular weight of 200 in the conversion film in ethanol, and then vacuum-dry at 90° C. to prepare a porous polymer.

4) At 125°C, continuously evacuate the porous polymer in a vacuum drying oven to remove volatile substances, spray into an electrolyte solution containing sodium trifluoromethanesulfonate, and cool to room temperature to obtain a polymer electrolyte. It is doped graphene-polyethylene glycol based conversion film.

The inclusion ratio of 1-methyl polyethylene glycol and 1-formic acid α-cyclodextrin ester molecules in the doped graphene-polyethylene glycol-based conversion film is 1:5.

The porous polymer film meets the following requirements at the same time: a temperature of 180° C. for a heat shrinkage rate of 5%, a liquid absorption rate of 60%, and a tensile strength of 15 MPa.

The doped graphene-polyethylene glycol-based conversion film, battery positive electrode, negative electrode and packaging materials are made into battery cells.

Example 6

1) Prepare a mixture of polyethylene glycol with a molecular weight of 30,000 and a polypropylene glycol pore-forming agent with a molecular weight of 400 at a weight ratio of 1:0.05. The mixture, β-type cyclodextrin molecules and polymethyl methacrylate end-capped polymer with a molecular weight of 1.8 million are heated and stirred respectively, and dissolved in a liquid cyclohexanone solvent to prepare three kinds of liquid solutions. The weight ratio of the polymethyl methacrylate end-capped polymer to Polyethylene Glycol is 0.2: 1.

2) Mix the three liquid solutions, stir for 12 hours, then add nickel-doped graphene (nickel content 2 wt%) additives, continue heating and stirring for 20 hours to prepare a mixed solution. In nickel-doped graphene, nickel acts as an electron donor and graphene acts as an electron acceptor, and the synergistic effect of electron transfer strengthens the nickel doping effect. The weight ratio of described nickel-doped graphene additive to polyethylene glycol is 0.05:1.

3) Casting the mixed solution on a glass plate to form a film, and ultrasonically treating it in water at 65° C. to form a conversion film. Continue the ultrasonic treatment, dissolve the polypropylene glycol pore-forming agent with a molecular weight of 400 in the conversion film in water, and dry it in vacuum at 125°C again to prepare a porous polymer.

4) At 90°C, continuously evacuate the porous polymer in a vacuum drying oven to remove volatile substances, spray into the electrolyte solution containing sodium bis(fluorosulfonyl)imide, and cool to room temperature to obtain a polymer The electrolyte is a doped graphene-polyethylene glycol-based conversion film.

The inclusion ratio of polyethylene glycol with a molecular weight of 30,000 to β-cyclodextrin in the doped graphene-polyethylene glycol-based conversion film is 1:27.

The porous polymer film also meets the following requirements: the temperature at which the heat shrinkage rate is higher than 5% is 230°C, the liquid absorption rate is 30%, and the tensile strength is 20 MPa.

The doped graphene-polyethylene glycol-based conversion film, battery positive electrode, negative electrode and packaging materials are made into battery cells.

Example 7

1) Prepare a mixture of 1-fluoropolyethylene glycol with a molecular weight of 85,000 and a polyethylene glycol pore-forming agent with a molecular weight of 600 at a weight ratio of 1:0.10. The mixture, gamma cyclodextrin molecules and polyvinylidene fluoride-hexafluoropropylene capped polymer with a molecular weight of 100,000 are heated and stirred respectively, and dissolved in N-methylpyrrolidone liquid solvent to prepare three kinds of liquid solutions. The weight ratio of the polyvinylidene fluoride-hexafluoropropylene end-capped polymer to the 1-fluoropolyethylene glycol polymer is 0.2: 1.

2) Mix the three liquid solutions, stir for 12 hours, then add cobalt-doped graphene additive (cobalt content 1.2 wt%), continue heating and stirring for 10 hours to prepare a mixed solution. In cobalt-doped graphene, cobalt acts as an electron donor and graphene acts as an electron acceptor, and the synergistic effect of electron transfer strengthens the effect of cobalt doping. The weight ratio of described cobalt-doped graphene additive and 1-fluoropolyethylene glycol is 0.002: 1.

3) Cast the mixed solution on a glass plate to form a film, and ultrasonically treat it in ethanol at 40°C to obtain a conversion film. Continue to ultrasonically treat the conversion film to dissolve the polyethylene glycol pore-forming agent with a molecular weight of 600 in the conversion film in ethanol, and then dry it in vacuum at 100° C. to prepare a porous polymer.

4) At 122°C, continuously evacuate the porous polymer in a vacuum drying oven to remove volatile substances, spray into an electrolyte containing lithium trifluoromethanesulfonate, and cool to room temperature to obtain a polymer electrolyte. It is doped graphene-polyethylene glycol based conversion film.

The inclusion ratio of 1-fluoropolyethylene glycol to γ-type cyclodextrin molecules in the doped graphene-polyethylene glycol-based conversion film is 1:19.

The porous polymer also meets the following requirements: a temperature of 180° C. for a heat shrinkage rate of 5%, a liquid absorption rate of 75%, and a tensile strength of 8 MPa.

The doped graphene-polyethylene glycol-based conversion film, battery positive electrode, negative electrode and packaging materials are made into battery cells.

Claims (10)

1. The method for preparing the doped graphene-polyethylene glycol based conversion membrane by using the vacuum adsorption method is characterized by comprising the following steps of:

1) Respectively dissolving a mixture of a polyethylene glycol-based polymer and a pore-forming agent, cyclodextrin group molecules and a terminated polymer in a liquid solvent to prepare 3 liquid solutions;

2) Mixing 3 liquid solutions, stirring for 12-14 h, adding the doped graphene additive, and continuously heating and stirring for 5-48 h to obtain a mixed solution;

3) Casting the mixed solution on a glass plate to form a film, and carrying out ultrasonic treatment in water, ethanol or an ethanol aqueous solution at the temperature of 40-70 ℃ to form a conversion film; further ultrasonic treatment is carried out to dissolve the pore-forming agent in the conversion film, and then vacuum drying is carried out at the temperature of 70-125 ℃ to prepare a porous polymer;

4) Continuously vacuumizing the porous polymer in a vacuum drying oven at the temperature of 70-125 ℃, removing volatile substances, spraying electrolyte containing lithium salt or sodium salt, and cooling to room temperature to obtain the polymer electrolyte, namely the doped graphene-polyethylene glycol conversion film.

2. The method for preparing the doped graphene-polyethylene glycol-based conversion film by the vacuum adsorption method according to claim 1, wherein the weight ratio of the polyethylene glycol-based polymer to the pore-forming agent in the mixture of the polyethylene glycol-based polymer and the pore-forming agent is 1 (0.01-0.16); the weight ratio of the end-capping polymer to the polyethylene glycol-based polymer is (0.05-1) to 1; the weight ratio of the doped graphene additive to the polyethylene glycol-based polymer is (0.001-0.10) to 1; the inclusion ratio of the polyethylene glycol-based polymer to the cyclodextrin type group molecules in the doped graphene-polyethylene glycol-based conversion film is 1: 5-27.

3. The method for preparing the doped graphene-polyethylene glycol-based conversion film according to claim 1, wherein the doped graphene additive is graphene doped with nitrogen, titanium, chromium, iron, cobalt, nickel or copper.

4. The method for preparing a graphene-polyethylene glycol-based doped conversion film according to claim 1, wherein the pore-forming agent is polyethylene glycol, polyvinyl alcohol or polypropylene glycol having a molecular weight of 200 to 800.

5. The method for preparing a graphene-polyethylene glycol-based doped conversion film according to claim 1, wherein the lithium salt is lithium hexafluorophosphate, lithium bis (fluorosulfonyl) imide, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate or lithium tetrafluoroborate.

6. The method for preparing a doped graphene-polyethylene glycol-based conversion film according to claim 1, wherein the sodium salt is sodium hexafluorophosphate, sodium bis (fluorosulfonyl) imide, sodium hexafluoroarsenate, sodium trifluoromethanesulfonate or sodium tetrafluoroborate.

7. The method for preparing a doped graphene-polyethylene glycol-based conversion coating by vacuum adsorption according to claim 1, wherein the polyethylene glycol-based polymer is polyethylene glycol or a derivative of a polyethylene glycol backbone polymer.

8. The method for preparing the graphene-polyethylene glycol-based doped conversion film according to claim 1, wherein the cyclodextrin group molecule is alpha, beta or gamma cyclodextrin, or is a product of esterification and cross-linking reaction of a part of hydroxyl groups of cyclodextrin, or is a chlorine or fluorine substitute of a part of hydroxyl groups of cyclodextrin.

9. The method for preparing the doped graphene-polyethylene glycol-based conversion film according to claim 1, wherein the end-capping polymer is polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene or polymethyl methacrylate; the liquid solvent is dimethylformamide, N-methylpyrrolidone, N-dimethylacetamide, cyclohexanone or butanone.

10. The method for preparing the doped graphene-polyethylene glycol-based conversion film according to claim 1, wherein the molecular weight of the polyethylene glycol-based polymer is 1 ten thousand to 8 ten thousand, and the molecular weight of the end-capped polymer is 10 ten thousand to 180 ten thousand.

Images