A solid electrolyte thin film and its preparation method

Abstract

This invention relates to the field of solid electrolyte thin film preparation technology, and discloses a solid electrolyte thin film and its preparation method. The solid electrolyte thin film is composed of an oxide metal ion conductor filler, a polymer, and a metal salt. The oxide metal ion conductor filler includes: an oxide lithium ion conductor filler, an oxide sodium ion conductor filler, or an oxide potassium ion conductor filler; the metal salt includes: lithium salt, sodium salt, or potassium salt; by mass percentage, the oxide metal ion conductor filler accounts for 5-40%; the polymer accounts for 10-80%; and the metal salt accounts for 5-40%. This invention uses a blade coating method to prepare the solid electrolyte thin film, making the preparation of the film simpler and less costly, while possessing high ionic conductivity, strong thermodynamic stability, good density and uniformity, and good mechanical strength.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte thin film preparation technology, and in particular to a solid electrolyte thin film and its preparation method. Background Technology

[0002] Since 2000, lithium-ion battery technology has rapidly developed into a mature and widely used battery technology. However, this technology uses liquid electrolytes, composed of solvents, lithium salts, and additives, which function to transport ions and conduct current. In liquid electrolytes, organic solvents are flammable, highly corrosive, have poor oxidation resistance, and cannot solve the lithium dendrite problem, thus posing a high risk of thermal runaway. This also limits the use of high-voltage cathode materials and lithium metal anode materials, resulting in an energy density ceiling of only 300 Wh / kg. All-solid-state batteries can achieve an energy density of 500 Wh / kg. Existing solid-state electrolytes mainly focus on materials such as sulfides, polymers, and oxides, and solid-state electrolyte films are mainly prepared through methods such as magnetron sputtering, atomic layer deposition, dry pressing-heating-quenching-calcination, dip coating, or coating.

[0003] For example, patent publication number CN102931433A discloses "a method for preparing solid electrolyte films using radio frequency magnetron sputtering". The films prepared by this method have high ionic conductivity, good thermodynamic stability, and a wide electrochemical window, but the method is costly and the process is complex. Patent publication number CN109346752B discloses "a method for preparing solid electrolyte films through four steps: dry pressing, heating, quenching, and calcination". This method can accurately prepare electrolyte films of the required thickness according to the quality of electrolyte powder, and the films are dense and uniform, but the thermodynamic stability is poor. Patent publication number CN111653828A discloses "a method using a blade coating method". This method can obtain solid electrolyte films with high ionic conductivity, strong thermodynamic stability, and good contact with positive and negative electrodes, but it is time-consuming.

[0004] While the existing technologies disclosed above exhibit good density and high energy density, they suffer from poor uniformity, poor contact with the positive and negative electrodes, and high cost, hindering large-scale mass production. With the market's increasing demands for battery energy density, safety, and economy, the development of solid-state electrolyte films with higher energy density and safety is urgently needed. Therefore, it is necessary to provide a solid-state electrolyte film and its preparation method, making the preparation of solid-state electrolyte films more efficient and convenient, and exhibiting good adhesion and contact properties. Summary of the Invention

[0005] The purpose of this invention is to provide a solid electrolyte thin film and its preparation method, which can improve the thin film's high ionic conductivity, good uniformity, and high density, making it suitable for manufacturing all-solid-state ion batteries with high energy density, low expansion resistance, long lifespan, small size, and suitability for mass production. To achieve the above objective, this invention provides the following technical solution:

[0006] This invention provides a solid electrolyte film, characterized in that the solid electrolyte film is composed of an oxide metal ion conductor filler, a polymer, and a metal salt; wherein,

[0007] The oxide metal ion conductor type filler includes: oxide lithium ion conductor type filler, oxide sodium ion conductor type filler or oxide potassium ion conductor type filler;

[0008] The metal salts include: lithium salts, sodium salts, or potassium salts;

[0009] In terms of mass percentage,

[0010] The proportion of the oxide metal ion conductor type filler is 5-40%;

[0011] The polymer comprises 10-80%;

[0012] The metal salt accounts for 5-40%.

[0013] Furthermore, the oxide lithium-ion conductor type filler is one or more of aluminum-doped lithium titanium phosphate, germanium-doped lithium titanium phosphate, lithium lanthanum titanium oxide, lithium lanthanum zirconium oxide, and lithium titanium aluminum phosphate; the oxide sodium-ion conductor type filler is one or more of aluminum-doped sodium titanium phosphate, germanium-doped sodium titanium phosphate, sodium lanthanum titanium oxide, sodium lanthanum zirconium oxide, and sodium titanium aluminum phosphate; the oxide potassium-ion conductor type filler is one or more of aluminum-doped potassium titanium phosphate, germanium-doped potassium titanium phosphate, potassium lanthanum titanium oxide, potassium lanthanum zirconium oxide, and potassium titanium aluminum phosphate.

[0014] Furthermore, the polymer is one or more selected from polyacrylonitrile, polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyvinylidene chloride, polyethylene carbonate, and polypropylene carbonate.

[0015] Furthermore, the lithium salt is one or more selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalate)borate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium bis(oxalate)borate.

[0016] The sodium salt is one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bis(oxalate)borate, sodium trifluoromethylsulfonylimide, sodium bis(fluorosulfonylimide), and sodium bis(oxalate)borate.

[0017] The potassium salt is one or more of potassium hexafluorophosphate, potassium tetrafluoroborate, potassium bis(oxalate)borate, potassium bis(trifluoromethylsulfonyl)imide, potassium bis(fluorosulfonyl)imide, and potassium bis(oxalate)borate.

[0018] Furthermore, the thickness of the solid electrolyte film is 10-200 μm.

[0019] The present invention also provides a method for preparing a solid electrolyte thin film, the method comprising the following steps:

[0020] Preparation of solid electrolyte precursor liquid;

[0021] The solid electrolyte precursor liquid is coated onto the substrate using a heated substrate and a doctor blade to form a uniform solid electrolyte precursor film.

[0022] Vacuum flash evaporation process is used to assist in the film formation of solid electrolyte precursor films;

[0023] The solid electrolyte precursor film, after vacuum flash evaporation, is then annealed to obtain the solid electrolyte film.

[0024] Furthermore, the preparation of the solid electrolyte precursor liquid includes:

[0025] The oxide metal ion conductor filler and the first solvent were added to a container, then the surface treatment agent was added and stirred to obtain a dispersion. The dispersion was then subjected to centrifugation, washing and sonication in sequence. Finally, the solid phase was separated by centrifugation and vacuum drying to obtain the coated ion conductor filler.

[0026] The polymer, metal salt, and the obtained coated ion conductor filler are sequentially dissolved in a second solvent and stirred until homogeneous to obtain a solid electrolyte precursor liquid.

[0027] Furthermore, the surface treatment agent is one or more of polymethyl methacrylate, polyethyl methacrylate, and polyvinyl acetate;

[0028] The first solvent is one or more of deionized water, anhydrous ethanol, or acetone;

[0029] The second solvent is one or more of N,N-dimethylformamide, acetonitrile, tetrahydrofuran, and N-methylpyrrolidone.

[0030] Furthermore, the pressure range of the vacuum flash evaporation process is 120-150 Pa, and the pressure holding time is 240-360 s.

[0031] Furthermore, the annealing conditions include: a temperature of 200-300℃ and a time of 90-120 minutes.

[0032] The technical effects and advantages of this invention are as follows:

[0033] The purpose of this patent is to overcome the shortcomings and deficiencies described in the background technology and to provide a solid electrolyte film and its preparation method. The film is prepared by a blade coating method. During the coating process, a mesophase film is formed by uniform heating of the substrate. Then, the residual solvent in the film is quickly evaporated and removed by a vacuum flash evaporation device. After annealing, a high-quality solid electrolyte film is obtained. This makes the preparation of the film simpler and cheaper, and at the same time, it has high ionic conductivity, strong thermodynamic stability, good density and uniformity, and good mechanical strength.

[0034] This invention employs a blade coating method to uniformly coat a solid electrolyte precursor liquid onto a substrate. The bottom of the substrate is heated via a platform to assist film formation and accelerate solvent evaporation. The solvent is then rapidly removed using a vacuum flash evaporation method, followed by annealing to obtain a high-quality solid electrolyte film. This method extends the preparation window for solid electrolyte films, effectively reducing the difficulty of their fabrication. The resulting solid electrolyte films exhibit stable spatial structures, high ionic conductivity, good uniformity, and good mechanical strength.

[0035] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a flowchart illustrating the preparation method of the solid electrolyte thin film provided by the present invention. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] The flowchart shown in the attached diagram is merely an illustrative example and does not necessarily include all steps. For example, some steps may be broken down, while others may be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0040] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0041] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion, such that a process, method, system, product, or device that includes a series of steps or sub-modules is not necessarily limited to those steps or sub-modules that are explicitly listed, but may include other steps or sub-modules that are not explicitly listed or that are inherent to such process, method, product, or device.

[0042] To address the shortcomings of existing technologies, this invention discloses a solid electrolyte film, which is composed of lithium oxide (or sodium, potassium) ion conductor filler, polymer, and lithium salt (or sodium salt, potassium salt); wherein, by mass percentage, the lithium oxide (or sodium, potassium) ion conductor filler accounts for 5-40%, the polymer accounts for 10%-80%, and the lithium salt accounts for 5%-40%.

[0043] The oxide lithium (or sodium, potassium) ion conductor filler in the solid electrolyte film is one or more of the following: aluminum-doped lithium titanium phosphate, germanium-doped lithium titanium phosphate (or sodium, potassium), lithium lanthanum titanium oxide (also called lithium lanthanum titanate) (or sodium, potassium), lithium lanthanum zirconium oxide (also called lithium lanthanum zirconate) (or sodium, potassium), and lithium titanium aluminum phosphate (or sodium, potassium).

[0044] The surface treatment agent in the solid electrolyte film is one or more of polymethyl methacrylate, polyethyl methacrylate, and polyvinyl acetate.

[0045] The polymer in the solid electrolyte membrane is one or more of polyacrylonitrile, polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyvinylidene chloride, polyvinyl carbonate, and polypropylene carbonate.

[0046] The lithium salt in the solid electrolyte film is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium bis(fluorooxalato)borate; the sodium salt is one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bis(oxalato)borate, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, and sodium bis(fluorooxalato)borate; and the potassium salt is one or more of potassium hexafluorophosphate, potassium tetrafluoroborate, potassium bis(oxalato)borate, potassium bis(trifluoromethanesulfonyl)imide, potassium bis(fluorosulfonyl)imide, and potassium bis(fluorooxalato)borate.

[0047] The solvent used in the preparation of solid electrolyte films is one or more of N,N-dimethylformamide, deionized water, anhydrous ethanol, acetone, acetonitrile, tetrahydrofuran, and N-methylpyrrolidone.

[0048] The thickness of the solid electrolyte film can be between 10-200 μm, and can be adjusted accordingly based on the scraper running speed.

[0049] This invention also provides a method for preparing a solid electrolyte thin film. Figure 1 The flowchart of the preparation method of the solid electrolyte thin film provided by the present invention is as follows: Figure 1 As shown, the preparation method of the above-mentioned solid electrolyte thin film is carried out according to the following steps:

[0050] Step S1: Preparation of solid electrolyte precursor liquid;

[0051] Step S11: Add a certain amount of lithium oxide (or sodium, potassium) ion conductor filler and solvent (deionized water, anhydrous ethanol or acetone) to a container, then add a certain amount of surface treatment agent, stir for 10-24 hours to obtain a dispersion, and then centrifuge, wash and sonicate the dispersion in sequence, repeating 3-5 times. Finally, separate the solid phase by centrifugation and vacuum dry at 60-80℃ for 10-24 hours to obtain a coated ion conductor filler.

[0052] Step S12: Dissolve the polymer, lithium salt and the coated ion conductor filler obtained in step S11 in the solvent (one or more of N,N-dimethylformamide, acetonitrile, tetrahydrofuran, and N-methylpyrrolidone) in sequence and stir until homogeneous to obtain a solid electrolyte precursor liquid.

[0053] Step S2: Prepare a solid electrolyte precursor film by heating the substrate and coating it with a doctor blade;

[0054] In step S2 of the present invention, the distance between the blade used for coating and the substrate is 250-500 μm.

[0055] The base heating temperature is 50-300℃, and the heating accuracy is ≤±1℃.

[0056] During the coating process, the doctor blade moves at a constant linear speed relative to the substrate, with a blade speed of 10-20 mm / s. The substrate is adsorbed onto the substrate, and the precursor liquid is placed on the edge of the substrate. As the doctor blade moves at a constant speed across the substrate, a layer of solid electrolyte wet film is coated. Then, the bottom of the substrate is heated to evaporate part of the solvent in the wet film, removing some of the liquid solvent and initially forming a uniform solid electrolyte precursor film.

[0057] Step S3: Vacuum flash evaporation process is used to assist in the formation of solid electrolyte precursor films;

[0058] In step S3 of the present invention, the pressure range of the vacuum flash evaporation process is 120-150 Pa, and the pressure holding time is 240-360 s.

[0059] The vacuum flash evaporation apparatus described above can rapidly remove volatile solvents, achieving rapid drying of the wet film. The specific principle is as follows: The vacuum flash evaporation apparatus provides a high vacuum environment under the action of a vacuum pump, lowering the boiling point of the solvent. Most of the solvent in the solid electrolyte precursor film is rapidly removed by the vacuum pump. Since the solid electrolyte precursor film has already formed a uniform, pore-free mesophase film after being heated on the substrate, no defects such as shrinkage cavities or cracks will be left on the film during vacuum flash evaporation due to excessively rapid solvent evaporation. Vacuum flash evaporation avoids the fractionation of mixed solvents in the solid electrolyte precursor liquid, allowing the mixed solvents to be removed simultaneously and rapidly in the same space. The combination of substrate heating and vacuum flash evaporation improves the quality of the solid electrolyte film, thereby achieving the preparation of high-quality solid electrolyte films.

[0060] Step S4: Anneal the solid electrolyte precursor film again to obtain the solid electrolyte film;

[0061] In step S4 of the present invention, the precursor film after vacuum flash evaporation is annealed at 200-300°C for 90-120 minutes.

[0062] It is worth noting that, in preparing solid electrolyte films using the blade coating method, in addition to the uniform heating of the substrate of the blade coater, film formation can also be assisted by the hot airflow of an air knife. That is, in addition to the substrate heating assisting the vacuum flash evaporation process, substrate heating can also be combined with air knife and vacuum flash evaporation processes.

[0063] The technical solution of this application will be further described below with reference to specific embodiments.

[0064] Example:

[0065] This invention provides a method for preparing a solid electrolyte thin film, as detailed below:

[0066] Step S1: Preparation of solid electrolyte precursor liquid;

[0067] Step S11: Add 2g of aluminum-doped lithium titanium phosphate to 10mL of deionized water, then add 2.5g of polyethyl methacrylate surface treatment agent, stir at room temperature for 12h to obtain a dispersion, and then centrifuge, wash and sonicate the dispersion in sequence, repeating 3 times. Finally, separate the solid phase by centrifugation, and vacuum dry the solid phase at 80℃ for 12h to obtain polyethyl methacrylate-coated aluminum-doped lithium titanium phosphate ion conductor filler.

[0068] Step S12: Dissolve 1g of polyvinylidene chloride, 1g of polyvinylidene fluoride, and 1g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 10mL of N,N-dimethylformamide solvent and stir for 2h. Then add the aluminum-doped lithium titanium phosphate ion conductor filler coated with polymethyl methacrylate prepared in step S11 and continue stirring at 60℃ for 20h to obtain a solid electrolyte precursor liquid.

[0069] Step S2: Prepare a solid electrolyte precursor film using a substrate heating method combined with slit coating; specifically, the distance between the blade used for the coating and the substrate is 300 μm; the substrate heating temperature is 100℃, and the heating accuracy is ≤±1℃; during the coating process, the blade moves in a uniform linear motion relative to the substrate at a speed of 10 mm / s. The substrate is adsorbed onto the substrate, and the precursor liquid is placed on the edge of the substrate. A layer of solid electrolyte wet film is coated by the blade passing uniformly through the substrate. Then, the solvent in the wet film is partially evaporated by heating at the bottom of the substrate, removing some of the liquid solvent and initially forming a uniform solid electrolyte precursor film.

[0070] Step S3: Vacuum flash evaporation process is used to assist in the formation of solid electrolyte precursor films; specifically, the pressure of the vacuum flash evaporation process is 120 Pa, and the pressure holding time is 300 s.

[0071] Step S4: Anneal the solid electrolyte precursor film again to obtain a solid electrolyte film; specifically, anneal the precursor film after vacuum flash evaporation at 200°C for 100 min.

[0072] In summary, Example 1 of this invention uses a blade coating method to prepare a solid electrolyte film. During the coating process, a mesophase film is formed by uniform heating on a substrate. Subsequently, residual solvent in the film is rapidly evaporated and removed using a vacuum flash evaporation device. After annealing, a high-quality solid electrolyte film is obtained. Testing shows an average film thickness of 162 μm, a film thickness uniformity of ±4.5%, and an ionic conductivity of 1.3 × 10⁻⁶. -3 The membrane exhibits stable spatial structure, high ionic conductivity, strong thermodynamic stability, good uniformity, and density.

[0073] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A solid electrolyte thin film, characterized in that, The solid electrolyte film is composed of an oxide-metal ion conductor filler, a polymer, and a metal salt; wherein, The oxide metal ion conductor type filler includes: oxide lithium ion conductor type filler, oxide sodium ion conductor type filler or oxide potassium ion conductor type filler; The metal salts include: lithium salts, sodium salts, or potassium salts; In terms of mass percentage, The proportion of the oxide metal ion conductor type filler is 5-40%; The polymer comprises 10-80%; The metal salt accounts for 5-40%.

2. The solid electrolyte thin film according to claim 1, characterized in that, The oxide lithium-ion conductor type filler is one or more of aluminum-doped lithium titanium phosphate, germanium-doped lithium titanium phosphate, lithium lanthanum titanium oxide, lithium lanthanum zirconium oxide, and lithium titanium aluminum phosphate; the oxide sodium-ion conductor type filler is one or more of aluminum-doped sodium titanium phosphate, germanium-doped sodium titanium phosphate, sodium lanthanum titanium oxide, sodium lanthanum zirconium oxide, and sodium titanium aluminum phosphate; the oxide potassium-ion conductor type filler is one or more of aluminum-doped potassium titanium phosphate, germanium-doped potassium titanium phosphate, potassium lanthanum titanium oxide, potassium lanthanum zirconium oxide, and potassium titanium aluminum phosphate.

3. The solid electrolyte film according to claim 1, characterized in that, The polymer is one or more of polyacrylonitrile, polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyvinylidene chloride, polyethylene carbonate, and polypropylene carbonate.

4. The solid electrolyte film according to claim 1, characterized in that, The lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalate)borate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium bis(oxalate)borate. The sodium salt is one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bis(oxalate)borate, sodium trifluoromethylsulfonylimide, sodium bis(fluorosulfonylimide), and sodium bis(oxalate)borate. The potassium salt is one or more of potassium hexafluorophosphate, potassium tetrafluoroborate, potassium bis(oxalate)borate, potassium bis(trifluoromethylsulfonyl)imide, potassium bis(fluorosulfonyl)imide, and potassium bis(oxalate)borate.

5. The solid electrolyte film according to claim 1, characterized in that, The thickness of the solid electrolyte film is 10-200 μm.

6. A method for preparing a solid electrolyte thin film, used to prepare the solid electrolyte thin film as described in any one of claims 1-5, characterized in that, The method includes the following steps: Preparation of solid electrolyte precursor liquid; The solid electrolyte precursor liquid is coated onto the substrate using a heated substrate and a doctor blade to form a uniform solid electrolyte precursor film. Vacuum flash evaporation process was used to assist in the film formation of solid electrolyte precursor films. The solid electrolyte precursor film, after vacuum flash evaporation, is then annealed to obtain the solid electrolyte film.

7. The method for preparing a solid electrolyte thin film according to claim 6, characterized in that, The preparation of the solid electrolyte precursor fluid includes: The oxide metal ion conductor filler and the first solvent were added to a container, then the surface treatment agent was added and stirred to obtain a dispersion. The dispersion was then subjected to centrifugation, washing and sonication in sequence. Finally, the solid phase was separated by centrifugation and vacuum drying to obtain the coated ion conductor filler. The polymer, metal salt, and the obtained coated ion conductor filler are sequentially dissolved in a second solvent and stirred until homogeneous to obtain a solid electrolyte precursor liquid.

8. The method for preparing a solid electrolyte thin film according to claim 7, characterized in that, The surface treatment agent is one or more of polymethyl methacrylate, polyethyl methacrylate, and polyvinyl acetate; The first solvent is one or more of deionized water, anhydrous ethanol, or acetone; The second solvent is one or more of N,N-dimethylformamide, acetonitrile, tetrahydrofuran, and N-methylpyrrolidone.

9. The method for preparing a solid electrolyte thin film according to claim 6, characterized in that, The pressure range of the vacuum flash evaporation process is 120-150 Pa, and the pressure holding time is 240-360 s.

10. The method for preparing a solid electrolyte thin film according to claim 6, characterized in that, The annealing conditions include a temperature of 200-300℃ and a time of 90-120 minutes.

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