CN110085904B - Flexible composite solid electrolyte, all-solid-state lithium ion battery and preparation method thereof - Google Patents
Flexible composite solid electrolyte, all-solid-state lithium ion battery and preparation method thereof Download PDFInfo
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- CN110085904B CN110085904B CN201910381850.3A CN201910381850A CN110085904B CN 110085904 B CN110085904 B CN 110085904B CN 201910381850 A CN201910381850 A CN 201910381850A CN 110085904 B CN110085904 B CN 110085904B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
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- 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
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- H—ELECTRICITY
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- 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
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
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Abstract
The invention provides a flexible composite solid electrolyte, an all-solid-state lithium ion battery and a preparation method thereof, wherein the sulfide solid electrolyte or a modifier thereof, a thermoplastic polymer or a modifier thereof and lithium salt are subjected to solid-phase mixing, so that the dispersion uniformity and effective contact of all components are improved, and the composite solid electrolyte has good flexibility. Particularly, before the compounding of the sulfide solid electrolyte and the polymer solid electrolyte is carried out, halide, phosphate and/or oxide are introduced into the sulfide material, a multi-dimensional channel for lithium ion transmission is provided, the disorder degree of lithium ion distribution is increased, and the lithium ion conductivity and the electrochemical stability of the composite solid electrolyte can be further improved. The flexible composite electrolyte has the advantages of high room temperature lithium conductivity, good electrochemical stability, easy processing and preparation, bending and cutting, and the like. The formed flexible all-solid-state battery has good mechanical property and bendability, and improved cycle service life and energy density.
Description
Technical Field
The invention belongs to the technical field of energy storage and conversion, and relates to a flexible composite solid electrolyte, an all-solid-state lithium ion battery and a preparation method thereof, in particular to application of the flexible composite solid electrolyte in the flexible all-solid-state battery.
Background
The traditional lithium ion battery usually uses liquid organic electrolyte and a diaphragm, but the organic electrolyte has the problems of easy volatilization, flammability, leakage and the like, so that the lithium ion battery has serious potential safety hazard. Currently, researchers are actively conducting research and development on all-solid-state batteries, that is, all-solid-state batteries are prepared by using solid electrolytes instead of organic electrolytes. The main scientific and technical problems to be solved by the all-solid-state battery include how to improve the lithium ion conductivity and electrochemical stability of the solid electrolyte material. Particularly, with the development of technologies such as flexible electronics and intelligent wearable technologies, the traditional lithium ion battery has serious safety problems such as easy liquid leakage and short circuit due to the presence of organic electrolyte during bending and folding, and the all-solid-state battery has obvious advantages in the development of flexible lithium ion batteries due to the advantages of high safety performance, excellent machining performance and the like. Therefore, next-generation flexible all-solid-state batteries require a solid electrolyte material having high lithium ion conductivity and excellent electrochemical stability, and further require a solid electrolyte material having flexible and foldable characteristics.
In the prior art, solid electrolyte materials include inorganic solid electrolyte materials, polymer electrolyte materials and composite electrolyte materials. In inorganic solid electrolyte materials, a general sulfide solid electrolyte has high lithium ion conductivity, but the sulfide solid electrolyte does not have flexibility, so that the sulfide solid electrolyte cannot be bent, and grain boundary resistance exists among particles of the sulfide solid electrolyte, so that the electrochemical stability is poor. The polymer electrolyte material has the advantages of simple preparation, strong plasticity and easy processing and forming, but has narrow use temperature range and low lithium ion conductivity. The composite electrolyte material is compounded by using more than two different solid electrolyte materials, wherein the sulfide solid electrolyte and the polymer electrolyte are compounded, and the polymer electrolyte can be used as a buffer layer between sulfide solid electrolyte particles to improve the effective contact and electrochemical stability between the particles; the sulfide solid electrolyte can be used as a lithium ion conduction accelerating layer of the polymer solid electrolyte to improve the ionic conductivity of the polymer solid electrolyte, and the composite solid electrolyte can improve the cycling stability of the all-solid battery to a certain extent. However, the composite solid electrolyte prepared by the method has relatively low ionic conductivity at room temperature, and the preparation process generally adopts a dry grinding mixing mode, so that the dispersion uniformity of the sulfide electrolyte and the polymer electrolyte is not utilized, the development of flexibility is restricted, and the flexible solid electrolyte cannot be formed.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
The first object of the present invention is to solve the above problems by providing a flexible composite solid electrolyte using a sulfide solid electrolyte or a modified product thereof (having a general molecular formula of [ (100-x) Li)2S-xP2S5]The material is obtained by solid-phase mixing of the yA-zB, the thermoplastic polymer and the modified substances thereof and the lithium salt, improves the dispersion uniformity and effective contact of the components, enables the composite solid electrolyte to have good flexibility, and particularly introduces halide, phosphate and/or oxide into the sulfide material before the sulfide solid electrolyte and the polymer solid electrolyte are compounded, provides a multi-dimensional channel for lithium ion transmission, and increases the lithium ion transmissionThe flexible composite electrolyte has the advantages of high room-temperature lithium conductivity, good electrochemical stability, easy processing and preparation, bending and cutting and the like.
The second purpose of the invention is to provide a preparation method of the flexible composite solid electrolyte, which is convenient and simple, and the sulfide solid electrolyte and the modification thereof, the thermoplastic polymer and the modification thereof and the lithium salt are mixed in a solid phase under the condition of an organic solvent according to the molar ratio, so that the preparation method is suitable for batch production and industrial production.
The third purpose of the invention is to provide an all-solid-state lithium ion battery, which comprises an electrolyte layer formed by the flexible composite solid-state electrolyte, wherein the formed flexible all-solid-state battery has good mechanical property and bending property, and improved cycle service life and energy density.
The fourth purpose of the invention is to provide a preparation method of the all-solid-state lithium ion battery.
In order to achieve the above purpose of the present invention, the following technical solutions are adopted:
a flexible composite solid electrolyte is mainly prepared from a sulfide solid electrolyte and a modifier thereof, a thermoplastic polymer and a modifier thereof and lithium salt;
the general formula of the sulfide solid electrolyte and the modified substance thereof is [ (100-x) Li2S-xP2S5]-yA-zB, wherein 0<x is less than or equal to 50, y is less than or equal to 20 and z is less than or equal to 20 and is greater than or equal to 0, A comprises one or the combination of more of germanium sulfide, tin sulfide, silicon sulfide and aluminum sulfide, B comprises one or the combination of more of lithium halide, lithium phosphate, lithium silicate, lithium oxide, germanium oxide, silicon oxide, tin oxide, aluminum oxide and phosphorus oxide.
Preferably, the [ (100-x) Li2S-xP2S5]in-yA-zB, x is more than or equal to 10 and less than or equal to 30, y is more than or equal to 5 and less than or equal to 20, and 0<z≤10。
Preferably, the sulfide solid electrolyte and the modified product thereof are in a glassy state, a glass ceramic state, or a crystalline state, and more preferably, the sulfide solid electrolyte and the modified product thereof are in a crystalline state.
Preferably, the lithium halide is selected from one or a combination of LiF, LiCl, LiBr and LiI.
Preferably, the mass ratio of the sulfide solid electrolyte and the modifier thereof, the thermoplastic polymer and the modifier thereof to the lithium salt is 1-90: 5-80: 1-30, preferably 10-80: 10-75: 1 to 25.
Preferably, the thermoplastic polymer comprises one or a combination of more of polyethylene oxide and a modified product thereof, polyvinylidene fluoride and a modified product thereof, polytetrafluoroethylene and a modified product thereof, polyvinyl chloride and a modified product thereof, polyacrylonitrile and a modified product thereof, polymethyl methacrylate and a modified product thereof, polyphenyl ether and a modified product thereof, chlorohydrin rubber and a modified product thereof, and cellulose acetate and a modified product thereof; the molecular weight of the thermoplastic polymer is 103～107。
Preferably, the lithium salt comprises one or more of lithium perchlorate, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonylimide, lithium difluorophosphate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium dioxalate borate, lithium difluorooxalate borate, lithium tetrafluorooxalate phosphate, lithium bistrifluoromethanesulfonylimide and lithium bistrifluoromethanesulfonylimide.
The preparation method of the flexible composite solid electrolyte comprises the following steps:
grinding a mixture of a sulfide solid electrolyte and a modifier thereof, a thermoplastic polymer and a modifier thereof and a lithium salt;
preferably, the grinding is wet grinding, including ball milling, sand milling or wet grinding mode of grinding;
preferably, the grinding solvent used for wet grinding comprises one or a combination of more of acetonitrile, N-methylpyrrolidone, dimethoxyethane, tetrahydrofuran, ethyl acetate, dimethyl carbonate, dimethylacetamide, ethyl propionate, N-methylformamide, dimethylformamide, acetone, ethanol and toluene;
preferably, the mass of the grinding solvent is 2-8 times of the sum of the mass of the sulfide solid electrolyte and the modifier thereof, the mass of the thermoplastic polymer and the modifier thereof, and the mass of the lithium salt.
Preferably, the [ (100-x) Li2S-xP2S5]The preparation method of the (E) -yA-zB specifically comprises the following steps:
when z ≠ 0, Li2S、P2S5A, B mixing the solid phase according to the molar ratio of (100-x) x: y: z, tabletting the mixed solid powder material, heat treating after tabletting, cooling and grinding to obtain the [ (100-x) Li2S-xP2S5]-yA-zB powder material; more preferably, the pressure of the pressed tablet is 100-360 MPa, and more preferably the pressure is 150-250 MPa; more preferably, the heat treatment is carried out at 400 to 600 ℃; more preferably, the solid phase mixing comprises a ball milling, sand milling or dry milling mode of grinding; more preferably, the solid phase mixing adopts a dry milling way of ball milling, the ball milling speed is 200-1500 rpm, and the ball milling time is 0.5-24 h.
An all-solid-state lithium ion battery comprises an electrolyte layer formed by the flexible composite solid electrolyte;
preferably, the all-solid-state lithium ion battery comprises a first PET film, a negative electrode layer, a thermoplastic polymer film, the electrolyte layer, a positive electrode layer and a second PET film which are connected in sequence.
The preparation method of the all-solid-state lithium ion battery comprises the following steps:
(a) flatly pressing a negative electrode on a smooth plane, coating the flexible composite solid electrolyte slurry on the negative electrode, and drying to obtain an electrolyte layer;
(b) coating the thermoplastic polymer film slurry on the electrolyte layer, and drying to obtain a layered object;
(c) sequentially stacking the first PET film, the layered object, the anode and the second PET film and then packaging to obtain the all-solid-state lithium ion battery;
preferably, in the step (b), the drying is drying, and the drying temperature is 45-55 ℃;
preferably, the temperature of the package is 140-160 ℃.
The preparation method of the all-solid-state lithium ion battery is operated under the condition of inert atmosphere, and the water oxygen content in the inert atmosphere is lower than 0.1 ppm.
Compared with the prior art, the invention has the beneficial effects that:
(1) the flexible composite solid electrolyte provided by the invention adopts sulfide solid electrolyte or modified substance thereof (the molecular general formula is [ (100-x) Li)2S-xP2S5]The material is obtained by solid-phase mixing of-yA-zB), a thermoplastic polymer and a modifier thereof, and a lithium salt, improves the dispersion uniformity and effective contact of each component, enables the composite solid electrolyte to have good flexibility, and particularly introduces halide, phosphate and/or oxide into a sulfide material before compounding the sulfide solid electrolyte and the polymer solid electrolyte, provides a multi-dimensional channel for lithium ion transmission, increases the disorder degree of lithium ion distribution, and can further improve the lithium ion conductivity and electrochemical stability of the composite solid electrolyte.
(2) The flexible composite solid electrolyte provided by the invention has the advantages of high lithium conductivity at room temperature, good electrochemical stability, easiness in processing and preparation, capability of being bent and cut and the like.
(3) The all-solid-state lithium ion battery provided by the invention comprises the electrolyte layer formed by the flexible composite solid electrolyte, and the formed flexible all-solid-state battery has good mechanical property and bending property, and improved cycle service life and energy density.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a photograph of a flexible composite solid electrolyte prepared in accordance with an example of the present invention compared to a polymer solid electrolyte PEO-LITFSI in terms of flexibility;
FIG. 2 is an AC impedance plot of a flexible composite solid electrolyte and a polymer solid electrolyte PEO-LITFSI according to an embodiment of the present invention.
Detailed Description
The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and the detailed description, but those skilled in the art will understand that the following described embodiments are some, not all, of the embodiments of the present invention, and are only used for illustrating the present invention, and should not be construed as limiting the scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The invention provides a flexible composite solid electrolyte, which is mainly prepared from a sulfide solid electrolyte and a modifier thereof, a thermoplastic polymer and a modifier thereof and lithium salt;
the general formula of the sulfide solid electrolyte and the modified substance thereof is [ (100-x) Li2S-xP2S5]-yA-zB, wherein 0<x is less than or equal to 50, y is less than or equal to 0 and less than or equal to 20, z is less than or equal to 0 and less than or equal to 20, A comprises one or a combination of more of germanium sulfide, tin sulfide, silicon sulfide and aluminum sulfide, B comprises one or a combination of more of lithium halide, lithium phosphate, lithium silicate, lithium oxide, germanium oxide, silicon oxide, tin oxide, aluminum oxide and phosphorus oxide, and when z is 0, [ (100-x) Li2S-xP2S5]-yA-zB is the sulfide solid electrolyte which is disclosed in the prior art.
The flexible composite solid electrolyte provided by the invention adopts sulfide solid electrolyte or modified substance thereof (the molecular general formula is [ (100-x) Li)2S-xP2S5]-yA-zB), thermoplastic polymers and modifications thereof, andand lithium salt is obtained after solid phase mixing, the material improves the dispersion uniformity and effective contact of all components, simultaneously, the composite solid electrolyte has good flexibility, particularly, before the composite of the sulfide solid electrolyte and the polymer solid electrolyte is carried out, halide, phosphate and/or oxide are introduced into the sulfide material, a multi-dimensional channel for lithium ion transmission is provided, the disorder degree of lithium ion distribution is increased, the lithium ion conductivity and the electrochemical stability of the composite solid electrolyte can be further improved, and the flexible composite electrolyte has the advantages of high lithium conductivity at room temperature, good electrochemical stability, easiness in processing preparation, bending and cutting and the like.
In some preferred embodiments of the invention, the [ (100-x) Li2S-xP2S5]in-yA-zB, the ratio of x, y and z may be further preferably 10<x≤30，5≤y≤20，0<z≤10。
In some preferred embodiments of the present invention, the sulfide solid electrolyte and its modification are in a glassy state, a glass-ceramic state, or a crystalline state.
In some preferred embodiments of the present invention, the lithium halide is selected from one or a combination of LiF, LiCl, LiBr and LiI.
In some preferred embodiments of the present invention, the mass ratio of the sulfide solid electrolyte and its modification product, the thermoplastic polymer and its modification product, and the lithium salt is 1-90: 5-80: 1-30, and further the mass ratio is 10-80: 10-75: 1 to 25.
In some preferred embodiments of the present invention, the thermoplastic polymer comprises one or more of polyethylene oxide and its modified product, polyvinylidene fluoride and its modified product, polytetrafluoroethylene and its modified product, polyvinyl chloride and its modified product, polyacrylonitrile and its modified product, polymethyl methacrylate and its modified product, polyphenylene oxide and its modified product, chlorohydrin rubber and its modified product, and cellulose acetate and its modified product; further, the molecular weight of the thermoplastic polymer is 103～107The molecular weight can be adjusted depending on the type of thermoplastic polymer used.
In some preferred embodiments of the present invention, the lithium salt comprises one or more selected from the group consisting of lithium perchlorate, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonylimide, lithium difluorophosphate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium dioxalate, lithium difluorooxalato borate, lithium tetrafluorooxalato phosphate, lithium bistrifluoromethanesulfonylimide, and lithium bistrifluoromethanesulfonylimide.
The preparation method of the flexible composite solid electrolyte comprises the following steps:
and grinding the mixture of the sulfide solid electrolyte and the modifier thereof, the thermoplastic polymer and the modifier thereof and the lithium salt.
In some preferred embodiments of the present invention, the grinding is wet grinding, including ball milling, sand milling, or wet grinding of grinding.
In some preferred embodiments of the present invention, the grinding solvent used in the wet grinding includes one or more of acetonitrile, N-methylpyrrolidone, dimethoxyethane, tetrahydrofuran, ethyl acetate, dimethyl carbonate, dimethylacetamide, ethyl propionate, N-methylformamide, dimethylformamide, acetone, ethanol, and toluene.
In some preferred embodiments of the present invention, the mass of the grinding solvent is 2 to 8 times the sum of the mass of the sulfide solid electrolyte and its modification, the mass of the thermoplastic polymer and its modification, and the mass of the lithium salt.
In some preferred embodiments of the invention, the [ (100-x) Li2S-xP2S5]The preparation method of the (E) -yA-zB specifically comprises the following steps:
when z is 0, the preparation method of the sulfide solid electrolyte is a preparation method of a sulfide solid electrolyte which is disclosed in the prior art, and the application is not particularly limited.
When z ≠ 0, Li2S、P2S5A, B mixing the solid phase according to the molar ratio of (100-x) x: y: z, tabletting the mixed solid powder material, heat treating after tabletting, cooling and grinding to obtain the [ (100-x) Li2S-xP2S5]-yA-zB powder material; further, the pressure of the pressed tablets is 100-360 MPa, and further the pressure is 150-250 MPa; further, carrying out the heat treatment at 400-600 ℃; further, the solid phase mixing comprises a dry grinding mode of ball milling, sand milling or grinding; further, the solid phase mixing adopts a dry milling mode of ball milling, the ball milling speed is 200-1500 rpm, and the ball milling time is 0.5-24 h.
An all-solid-state lithium ion battery comprises an electrolyte layer formed by the flexible composite solid electrolyte;
in some preferred embodiments of the present invention, the all solid-state lithium ion battery includes a first PET film, a negative electrode layer, a thermoplastic polymer film, the electrolyte layer, a positive electrode layer, and a second PET film, which are connected in sequence.
The preparation method of the all-solid-state lithium ion battery comprises the following steps:
(a) flatly pressing a negative electrode on a smooth plane, coating the flexible composite solid electrolyte slurry on the negative electrode, and drying to obtain an electrolyte layer;
(b) coating the thermoplastic polymer film slurry on the electrolyte layer, and drying to obtain a layered object;
(c) sequentially stacking the first PET film, the layered object, the anode and the second PET film and then packaging to obtain the all-solid-state lithium ion battery;
further, in the step (b), the drying is drying, and the drying temperature is 45-55 ℃;
further, the temperature of the package is 140-160 ℃.
In some preferred embodiments of the present invention, the method for preparing the all-solid-state lithium ion battery is operated under an inert atmosphere, and the oxygen content of water in the inert atmosphere is less than 0.1 ppm.
Embodiments of the present invention will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.
FIG. 1 is a photograph of a flexible composite solid electrolyte prepared in accordance with an example of the present invention compared to a polymer solid electrolyte PEO-LITFSI in terms of flexibility: (a, b) a polymer solid electrolyte PEO-LiTFSI; (c, d) a flexible composite solid electrolyte PEO-LiTFSI-10 wt% LGPS; (e, f) a flexible composite solid electrolyte PEO-LiTFSI-80 wt% LGPS; (g, h) Flexible composite solid electrolyte (PEO-LiTFSI-80 wt% LGPS) -0.7 LiBr.
Example 1
As a specific aspect of the present invention, the flexible composite solid electrolyte of the present embodiment includes crystalline Li10GeP2S12A thermoplastic polymer PEO (molecular weight 60 ten thousand) and a lithium salt LiTFSI. The sulfide solid electrolyte adopts crystalline 5Li2S-P2S5-GeS2I.e. Li10GeP2S12(ii) a The thermoplastic polymer is PEO; the lithium salt is LiTFSI; and the organic solvent is ACN.
The preparation process of the flexible composite solid electrolyte in the embodiment is as follows:
crystalline Li10GeP2S12PEO (molecular weight 60 ten thousand) and LiTFSI, adding into ACN solvent, and ball milling. Wherein Li10GeP2S12The solid electrolyte accounts for 80 wt%, and the PEO polymer and the LiTFSI lithium salt account for 20 wt%; the molar ratio of the polymer monomer to the lithium ions in the lithium salt is 18: 1; the mass of the ACN organic solvent is 2.2 times of that of the added solid mixture. The ball milling speed is 1200rpm, the ball milling time is 2 hours, and the flexible composite solid electrolyte slurry is obtained for standby.
The application of the flexible composite solid electrolyte in the all-solid battery of the embodiment relates to the preparation and assembly of the all-solid battery as follows:
the positive electrode is prepared from lithium iron phosphate, a conductive agent super P, a binder PVDF and a lithium salt LiTFSI according to a mass ratio of 50: 10: 5: and 35, magnetically stirring in an NMP solution for 12 hours to obtain positive electrode slurry, coating the positive electrode slurry on an aluminum foil with the thickness of 20 microns, airing at room temperature, and placing the dried positive electrode slurry in a vacuum drying oven for later use.
The negative electrode adopts lithium indium alloy, the mass ratio of the lithium foil to the indium foil is 1:100, and the thickness of the lithium indium alloy is about 50 mu m.
Flatly pressing the negative electrode on a smooth glass plate, coating the flexible composite solid electrolyte slurry on the negative electrode, naturally airing, coating the thermoplastic polymer slurry on the flexible composite solid electrolyte film, and naturally airing. The glass plate was dried in a muffle furnace at 50 ℃ and the above layered product was removed from the glass plate. The above thermoplastic polymer slurry was prepared by adding 0.5g of PEO (molecular weight: 60 ten thousand) and 0.18g of LiTFSI to 5g of ACN solvent, and magnetically stirring for 12 hours.
And then sequentially stacking and packaging the PET film, the layered object, the anode and the PET film, wherein the film sealing temperature is 150 ℃, and thus obtaining the flexible all-solid-state lithium ion battery.
Experimental example 1 Flexible display and ion conductivity test of Flexible composite solid electrolyte
The flexible composite solid electrolyte slurry is coated on a glass plate, the glass plate is naturally aired, then the glass plate is placed in a muffle furnace to be dried at 50 ℃, and then the prepared flexible composite solid electrolyte is taken down from the glass plate to obtain the flexible composite solid electrolyte PEO-LiTFSI-80 wt% LGPS (LGPS is the abbreviation of flexible composite solid electrolyte) (see e and f in figure 1). The flexible composite solid electrolyte can also be bent and folded in the same way as the comparative polymer solid electrolyte PEO-LiTFSI (see a and b in fig. 1).
Using a slicer to obtain a disc-shaped flexible composite solid electrolyte PEO-LiTFSI-80 wt% LGPS with the diameter of 12mm and the thickness of 164 mu m, adding a stainless steel sheet on each of two sides of the disc-shaped flexible composite solid electrolyte, placing the disc-shaped flexible composite solid electrolyte in a self-assembled testing grinding tool, and testing after compaction. The AC impedance method was tested using a BiologicVMP3 electrochemical workstation, setting the sweep frequency to 106Hz-0.1 Hz, and 10mV of amplitude. The test results are shown in FIG. 2, which shows that the room temperature lithium ion conductivity is 4.13X 10-5S/cm, comparisonThe room temperature lithium ion conductivity of the polymer electrolyte without sulfide addition, namely PEO-LiTFSI, is improved by 330%, so that the prepared flexible composite solid electrolyte is suitable for assembling and preparing flexible all-solid batteries.
Example 2
A flexible composite solid electrolyte was prepared in the same manner as in example 1 using the same components except that a sulfide solid electrolyte or a modified product thereof, Li10GeP2S12The mass ratio of (A) to (B) is 10 wt%; and the mass of the ACN organic solvent is 4.6 times of that of the added solid mixture.
The flexible composite solid electrolyte of the present embodiment includes crystalline Li10GeP2S12PEO (molecular weight 60 ten thousand) and LiTFSI, whose ionic conductivity was tested in the same procedure as in example 1, except that the flexible solid electrolyte had a thickness of 70 μm. The test result shows that the room temperature lithium ion conductivity is 1.36 multiplied by 10 < -5 > S/cm. In comparative example 1, it was found that the lithium ion conductivity of the flexible composite solid electrolyte was reduced when the sulfide solid electrolyte content was reduced to 10 wt%.
Example 3
A flexible composite solid electrolyte was prepared in the same manner as in example 1, except that the sulfide solid electrolyte or its modified substance was selected from crystalline 5Li2S-P2S5-GeS2-0.7LiBr。
Crystalline 5Li2S-P2S5-GeS2The preparation method of-0.7 LiBr comprises the following steps: mixing Li2S, P2S5, GeS2 and LiBr in a glove box under inert atmosphere according to a molar ratio, placing the mixture in a ball milling tank, ball milling at 1200rpm for 0.5h, dry milling, pressing the mixed powder into tablets under the action of 360MPa of a tablet press, heating to 550 ℃ at a heating rate of 10 ℃/min for sintering, keeping the temperature for 8h, reducing the temperature to the furnace temperature at a cooling rate of 1 ℃/min, and finally grinding the powder in an agate mortar to obtain 5Li2S-P2S5-GeS2-0.7LiBr solid electrolyte powder for use.
The flexible composite solid electrolyte of the present embodiment includes a crystalline state5Li2S-P2S5-GeS20.7LiBr, PEO (molecular weight 60 ten thousand) and LiTFSI, the ionic conductivity of which was tested in the same manner as in example 1, except that the thickness of the flexible solid electrolyte was 305 μm. The test result shows that the room temperature lithium ion conductivity is 6.05 multiplied by 10-5S/cm. In comparison with example 1, it was found that the lithium ion conductivity of the flexible composite solid electrolyte can be further improved by introducing LiBr into the sulfide material.
In summary, the lithium ion conductivities of the flexible composite solid electrolyte and the polymer solid electrolyte PEO-LITFSI at room temperature are shown in table 1.
TABLE 1 conductivity test results
| Sample (I) | Conductivity of lithium ion |
| PEO-LiTFSI | 9.59×10-6S/cm |
| PEO-LiTFSI-10wt％LGPS | 1.36×10-5S/cm |
| PEO-LiTFSI-80wt％LGPS | 4.13×10-5S/cm |
| (PEO-LiTFSI-80wt％LGPS)-0.7LiBr | 6.05×10-5S/cm |
Experimental example 2 all-solid-state battery charge and discharge performance test
The all-solid-state lithium ion battery obtained in example 1 was subjected to charge and discharge tests while being flat and bent. Setting the charging and discharging voltage range to be 1.4-3.6V, the charging and discharging multiplying power to be 0.1C and the testing temperature to be room temperature, and respectively carrying out charging and discharging tests in a flat state and a bent state.
Table 2 shows the specific discharge capacity of the battery according to the cycle number when the flexible composite solid electrolyte of example 1 of the present invention is applied to an all-solid battery, the battery is flat and curved.
TABLE 2
Test results show that the discharge specific capacity of the battery in the initial cycle under the flat state can reach 142.8mAh/g, the cycle capacity retention rate for 10 times can reach 100%, and the cycle capacity retention rate for 20 times is 81.6%. And the discharge specific capacity of the battery in the initial cycle under the bending state can reach 146.1mAh/g, the capacity retention rate of 10 cycles is 95.6%, and the capacity retention rate of 20 cycles still reaches 79.8%, which is not obviously different from the discharge performance of a flat battery.
While particular embodiments of the present invention have been illustrated and described, it will be appreciated that the above embodiments are merely illustrative of the technical solution of the present invention and are not restrictive; those of ordinary skill in the art will understand that: modifications may be made to the above-described embodiments, or equivalents may be substituted for some or all of the features thereof without departing from the spirit and scope of the present invention; the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention; it is therefore intended to cover in the appended claims all such alternatives and modifications that are within the scope of the invention.
Claims (21)
1. A flexible composite solid electrolyte is characterized in that the flexible composite solid electrolyte is mainly prepared from a sulfide solid electrolyte and a modifier thereof, a thermoplastic polymer and a modifier thereof and lithium salt;
the above-mentionedThe general formula of the sulfide solid electrolyte and the modified substance thereof is [ (100-x) Li2S-xP2S5]-yA-zB, wherein x is more than or equal to 10 and less than or equal to 30, y is more than or equal to 5 and less than or equal to 20, and 0<z is less than or equal to 10, A is selected from one of germanium sulfide, tin sulfide, silicon sulfide and aluminum sulfide, B is selected from one of lithium phosphate, lithium silicate, lithium oxide, germanium oxide, silicon oxide, tin oxide and aluminum oxide;
the mass ratio of the sulfide solid electrolyte and the modifier thereof to the thermoplastic polymer and the modifier thereof to the lithium salt is 10-80: 10-75: 1-25;
the thermoplastic polymer is polyoxyethylene and a modified product thereof; the molecular weight of the thermoplastic polymer is 103～107。
2. The flexible composite solid electrolyte of claim 1, wherein the sulfide solid electrolyte and its modifications are in a glassy, glass-ceramic, or crystalline state.
3. The flexible composite solid electrolyte according to claim 2, wherein the sulfide solid electrolyte and its modification are crystalline.
4. The flexible composite solid electrolyte of claim 1, wherein the lithium salt comprises one or a combination of lithium salts selected from the group consisting of lithium perchlorate, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonylimide, lithium difluorophosphate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium dioxalate, lithium difluorooxalato borate, lithium tetrafluorooxalato phosphate, lithium difluorosulfonimide, and lithium bistrifluoromethanesulfonylimide.
5. The method of preparing a flexible composite solid-state electrolyte according to any one of claims 1 to 4, comprising the steps of:
and grinding the mixture of the sulfide solid electrolyte and the modifier thereof, the thermoplastic polymer and the modifier thereof and the lithium salt.
6. The method of claim 5, wherein the milling is wet milling, including ball milling, sand milling, or wet milling of milling.
7. The method for preparing a flexible composite solid electrolyte according to claim 6, wherein the grinding solvent used in the wet grinding comprises one or more of acetonitrile, N-methylpyrrolidone, dimethoxyethane, tetrahydrofuran, ethyl acetate, dimethyl carbonate, dimethylacetamide, ethyl propionate, N-methylformamide, dimethylformamide, acetone, ethanol and toluene.
8. The method according to claim 6, wherein the mass of the grinding solvent is 2 to 8 times the sum of the mass of the sulfide solid electrolyte and its modification, the mass of the thermoplastic polymer and its modification, and the mass of the lithium salt.
9. The method of claim 5, wherein the [ (100-x) Li ] is2S-xP2S5]The preparation method of the (E) -yA-zB specifically comprises the following steps:
when z ≠ 0, Li2S、P2S5A, B according to the molar ratio of (100-x) x: y: z, tabletting the solid powder material, heat treating, cooling and grinding to obtain the [ (100-x) Li2S-xP2S5]-yA-zB powder material.
10. The method for preparing a flexible composite solid electrolyte according to claim 9, wherein the pressure of the pressed sheet is 100 to 360 MPa.
11. The method of claim 9, wherein the pressure of the pressed sheet is 150 to 250 MPa.
12. The method for preparing a flexible composite solid electrolyte according to claim 9, wherein the heat treatment is performed at 400 to 600 ℃.
13. The method of claim 9, wherein the solid phase mixing comprises ball milling, sand milling, or dry milling of the milling.
14. The preparation method of the flexible composite solid electrolyte according to claim 9, wherein the solid phase mixing is performed by a dry milling method of ball milling, the ball milling speed is 200-1500 rpm, and the ball milling time is 0.5-24 h.
15. An all-solid-state lithium ion battery comprising an electrolyte layer formed of the flexible composite solid-state electrolyte according to any one of claims 1 to 4.
16. The all-solid lithium ion battery according to claim 15, wherein the all-solid lithium ion battery comprises a first PET film, a negative electrode layer, a thermoplastic polymer film, the electrolyte layer, a positive electrode layer and a second PET film connected in this order.
17. The method for manufacturing an all-solid-state lithium ion battery according to claim 16, comprising the steps of:
(a) flatly pressing a negative electrode on a smooth plane, coating the flexible composite solid electrolyte slurry on the negative electrode, and drying to obtain an electrolyte layer;
(b) coating the thermoplastic polymer film slurry on the electrolyte layer, and drying to obtain a layered object;
(c) and sequentially stacking and packaging the first PET film, the layered object, the anode and the second PET film to obtain the all-solid-state lithium ion battery.
18. The method for preparing an all-solid-state lithium ion battery according to claim 17, wherein in the step (b), the drying is baking, and the temperature of the baking is 45 to 55 ℃.
19. The method for preparing an all-solid-state lithium ion battery according to claim 17, wherein in the step (c), the temperature of the package is 140 to 160 ℃.
20. The method of manufacturing an all-solid-state lithium ion battery according to claim 17, wherein the method of manufacturing an all-solid-state lithium ion battery is operated under inert atmosphere conditions.
21. The method of manufacturing an all-solid lithium ion battery according to claim 20, wherein in step (b), the water oxygen content in the inert atmosphere is less than 0.1 ppm.
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