Preparation method and application of sulfide electrolyte and composite solid electrolyte

Abstract

The invention provides a preparation method and application of a sulfide electrolyte and a composite solid electrolyte. The invention provides a liquid-phase synthetic sulfide electrolyte, and a composite solid electrolyte is prepared on the basis of the electrolyte, and has good chemical stability, interface conductivity and thermal stability during application; the conductive polymer material can form polymer fibers under the action of high-speed shearing force, so that the processability of the electrolyte can be effectively improved; after the film is formed, a fiber net structure can be formed, a polymerization state with a non-localized pi-electron conjugated system is generated, and the transmission rate of electrons and ions can be effectively improved; by introducing the conductive polymer material, the stability of the electrolyte membrane can be effectively improved, and good conductivity and material stability can still be kept at high temperature; surfactants are introduced to the two sides of the solid electrolyte membrane, the affinity to the positive electrode material and the affinity to the negative electrode material are improved through acting force, and then the conductivity and the surface resistance are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a preparation method and application of a sulfide electrolyte and a composite solid electrolyte. Background Art

[0002] The electrolyte of traditional lithium-ion batteries is liquid electrolyte, which has a series of safety hazards such as easy leakage, poor thermal stability, and fire and explosion caused by internal short circuit of the battery. Compared with traditional liquid electrolytes, solid electrolytes have the advantages of high safety, high energy density, good cycle performance, wide operating temperature range, and convenient recycling. Solid electrolyte lithium-ion batteries are one of the research hotspots in the field of energy storage today. As the core component of solid-state secondary batteries, solid electrolytes have become the research and development focus of this field in recent years. Among them, argyrodite-type electrolytes have excellent mechanical ductility and high ionic conductivity, and at the same time avoid the use of precious metals, making them more cost-competitive. Considering the comprehensive thermal safety characteristics, cost, process maturity and other factors, they are the better technical route choice for sulfide all-solid-state batteries.

[0003] The traditional argyrodite electrolyte has the following problems: 1. Chemical stability problem: Sulfide electrolyte will react when in contact with trace amounts of water to produce toxic H 2 S gas and reduce the lithium ion conductivity. 2. Interface stability problem: The positive electrode-electrolyte interface (CEI) and solid electrolyte interface (SEI) are formed between the sulfide-based solid electrolyte and the electrode. These intermediate interfaces may hinder the Li + 3. Thermal stability issues: Composite cathodes composed of sulfide electrolytes and certain positive electrode materials (such as nickel-rich layered oxide cathode materials) may experience harmful thermal runaway when in a charged state.

[0004] Based on the problems existing in the current electrolytes, it is necessary to improve them. Summary of the invention

[0005] In view of this, the present invention provides a preparation method and application of a sulfide electrolyte and a composite solid electrolyte to solve or at least partially solve the defects in the prior art.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for preparing a sulfide electrolyte, comprising the following steps:

[0008] Sulfide, halide, lithium source, doping compound, defoamer and dispersant are added to a first organic solvent, mixed, and vacuum heated in a glove box to volatilize the first organic solvent to obtain a sulfide electrolyte.

[0009] Preferably, the heating temperature is 80-150° C. and the heating time is 2-12 h.

[0010] Preferably, the sulfide includes Li 2 S.P. 2 S 5 ,GeS 2 、SnS 2 At least one of;

[0011] The halides include LiCl, NaCl, LiClO 4 At least one of;

[0012] The lithium source Li 2 S, LiOH, Li 2 CO 3 At least one of;

[0013] The doping compound element includes at least one of Na, Se, Ge, Si, As, Sb, and In;

[0014] The defoaming agent includes at least one of polydimethylsiloxane, polyether defoaming agent and mineral oil defoaming agent;

[0015] The dispersant includes at least one of ε-caprolactam / acetamide low eutectic solvent, polyoxyethylene derivatives, polycarboxylic acid polymers, sodium oleate, polyethylene glycol, polyvinyl pyrrolidone, fatty acid dispersants, aliphatic amide dispersants, and ester dispersants;

[0016] The first organic solvent includes at least one of straight-chain alkanes, alicyclic hydrocarbons, branched alkanes, olefins, and aromatic hydrocarbons;

[0017] The straight-chain alkane includes at least one of n-hexane, cyclohexane, isooctane, 1-hexene and toluene. Preferably, the mass ratio of the sulfide, halide, lithium source, doping compound, defoamer and dispersant is (10-80):(10-40):(10-80):(10-80):(0.5-5):(0.5-5);

[0018] The mass of the first organic solvent is 1 to 4 times the sum of the mass of the sulfide, the halide, the lithium source, the doping compound, the defoaming agent and the dispersant.

[0019] and / or, adding sulfide, halide, lithium source, doping compound, defoaming agent and dispersant into the first organic solvent, stirring and mixing at a speed of 200 to 400 r / min for 10 to 40 hours;

[0020] And / or, the doping compound includes NaS, Na 2 S2 O 3 、PbSe、CdSe、ZnGeS 3 、PbGeS 3 、CdSiS 3 , CdAs 2 、ZnSb 2 、ZnIn 2 S 4 At least one of .

[0021] In a second aspect, the present invention further provides a method for preparing a composite solid electrolyte, comprising the following steps:

[0022] The sulfide electrolyte prepared by the preparation method, the conductive polymer material, the flame retardant, and the second organic solvent are mixed, and then stirred at a speed of 8000 to 25000 r / min for 5 to 40 hours to make the conductive polymer material draw into fibers to obtain an electrolyte slurry;

[0023] The electrolyte slurry is prepared by a solvent casting method or a hot pressing method to obtain a solid electrolyte membrane;

[0024] The surfactant is coated on both sides of the solid electrolyte membrane respectively, and after drying, a surfactant coating is formed to obtain a composite solid electrolyte.

[0025] Preferably, the conductive polymer material includes at least one of PEDOT:PSS, PEDOT:PDAS, PEDOT:PANI, PANI, PPy, and PT;

[0026] The flame retardant includes at least one of a phosphate flame retardant, an aluminate flame retardant, and a phosphazene flame retardant;

[0027] The second organic solvent includes at least one of N,N-dimethylformamide, acetonitrile, dimethyl sulfoxide, anisole, chloroform, dichloroethane, acetone, and tetrahydrofuran;

[0028] The surfactant includes at least one of a cationic surfactant, an anionic surfactant and a nonionic surfactant.

[0029] Preferably, the phosphate flame retardant includes at least one of ammonium phosphate, sodium tripolyphosphate, and ammonium polyphosphate;

[0030] The aluminate flame retardant includes at least one of aluminum trihydroxide and aluminum phosphate;

[0031] The phosphazene flame retardant includes at least one of hexafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene and pentafluorocyclotriphosphazene;

[0032] The cationic surfactant includes but is not limited to at least one of di(2-ethylhexyl) sodium sulfosuccinate, dodecyltrimethylammonium bromide, quaternary ammonium salt surfactants, amine oxide surfactants, imidazoline surfactants, quaternary phosphonium salt surfactants, and ammonium oxide surfactants;

[0033] The anionic surfactant includes but is not limited to at least one of hexadecyltrimethylammonium bromide, sodium dodecylbenzene sulfonate, sodium fatty alcohol polyoxyethylene ether sulfate, sodium fatty acid methyl ester sulfonate, sodium alkyl sulfonate, and phosphate type anionic surfactant;

[0034] The nonionic surfactant includes, but is not limited to, a nonionic surfactant containing polyoxyethylene.

[0035] Preferably, a surfactant is added to the third solvent to form a surfactant solution, and then the surfactant solution is sprayed on both sides of the solid electrolyte membrane, and after drying, a surfactant coating is formed to obtain a composite solid electrolyte;

[0036] The third solvent includes at least one of N,N-dimethylformamide, acetonitrile, dimethyl sulfoxide, anisole, chloroform, dichloroethane, acetone, and tetrahydrofuran;

[0037] The mass of the surfactant is 1 to 10% of the mass of the third solvent.

[0038] Preferably, the sulfide electrolyte, the conductive polymer material, the flame retardant, and the second organic solvent are stirred and mixed at a speed of 100 to 800 r / min, and then stirred at a speed of 8000 to 25000 r / min to draw the conductive polymer material into fibers to obtain an electrolyte slurry;

[0039] The electrolyte slurry is prepared by a solvent casting method to obtain a solid electrolyte membrane, which specifically includes:

[0040] The electrolyte slurry is heated to 25-200° C. and volatilized with a second organic solvent to obtain a solid electrolyte membrane;

[0041] The electrolyte slurry is prepared by hot pressing to obtain a solid electrolyte membrane, which specifically includes:

[0042] The electrolyte slurry is pressed at a temperature of 25 to 200° C. and a pressure of 0.1 to 500 MPa to volatilize the second organic solvent to obtain a solid electrolyte membrane;

[0043] The thickness of the solid electrolyte membrane is 0.01 to 1.5 mm

[0044] The surfactant coating has a thickness of 5 to 20 nm;

[0045] The mass ratio of the sulfide electrolyte, the conductive polymer material and the flame retardant is (10-90):(5-50):(0.01-10), and the mass of the second organic solvent is 1-4 times the sum of the masses of the sulfide electrolyte, the conductive polymer material and the flame retardant.

[0046] In a third aspect, the present invention also provides an application of the composite solid electrolyte prepared by the preparation method in the preparation of lithium-ion batteries.

[0047] The preparation method and application of a sulfide electrolyte and a composite solid electrolyte of the present invention have the following beneficial effects compared with the prior art:

[0048] 1. The present invention adopts liquid phase synthesis to obtain sulfide electrolyte, wherein the addition of defoaming agent can prevent the volatilization of the first organic solvent and the decomposition and escape of crystallization solvent molecules during the heat treatment process, which will produce a porous structure inside the electrolyte particles, thereby reducing the ionic conductivity; the addition of dispersant can increase the solubility of the raw materials and shorten the liquid phase reaction time, and at the same time, some dispersants can improve the thermal stability of the electrolyte;

[0049] 2. The present invention proposes a liquid-phase synthetic sulfide electrolyte, and prepares a composite solid electrolyte based on the electrolyte. The electrolyte has good chemical stability, interface conductivity and thermal stability when used; specifically, the added conductive polymer material can form polymer fibers under the action of high-speed shear force, which can effectively improve the processability of the electrolyte; after film formation, a fiber network structure can be formed to generate a polymerization state with a non-localized π-electron conjugated system, which can effectively improve the transmission rate of electrons and ions, and the fiber network structure can improve the processability of the electrolyte membrane; at the same time, the introduction of conductive polymer materials can effectively improve the stability of the electrolyte membrane, such as PEDOT has a very high stability in an oxidized state, and its conductivity remains basically unchanged even if it is kept at 120°C for 1000 hours, and it can still maintain good conductive properties and material stability at high temperatures; surfactants are introduced on both sides of the solid electrolyte membrane to respectively enhance the affinity for the positive electrode material and the negative electrode material through the action force, thereby improving the conductivity and surface resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0051] Figure 1 The structure of the composite solid electrolyte of the present invention;

[0052] Figure 2 is a stress curve of a composite solid electrolyte prepared according to the method in Example 2;

[0053] Figure 3 is the conductivity curve of the composite solid electrolyte prepared according to the method in Example 2;

[0054] Figure 4 is a physical picture of a composite solid electrolyte prepared according to the method in Example 2;

[0055] Figure 5 This is the TGA curve of the composite solid electrolyte prepared according to the method in Example 2. DETAILED DESCRIPTION

[0056] To make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them.

[0057] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. In addition, in the description of the present application, the term "including" means "including but not limited to". Various embodiments of the present invention may be in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single values ​​within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the numbered ranges, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated in this article, it is meant to include any quoted numbers (fractions or integers) within the indicated range.

[0059] The present invention provides a method for preparing a sulfide electrolyte, comprising the following steps:

[0060] Sulfide, halide, lithium source, doping compound, defoamer and dispersant are added to the first organic solvent, mixed, and heated under vacuum in a glove box to volatilize the organic solvent to obtain a sulfide electrolyte.

[0061] The present invention adopts liquid phase synthesis to obtain sulfide electrolyte, wherein the addition of defoaming agent can prevent the volatilization of the first organic solvent and the decomposition and escape of crystallization solvent molecules during the heat treatment process, and a porous structure will be generated inside the electrolyte particles, thereby reducing the ionic conductivity; the addition of dispersant can increase the solubility of the raw materials and shorten the liquid phase reaction time, and part of the dispersant can improve the thermal stability of the electrolyte.

[0062] In some embodiments, the heating temperature is 80-150° C. and the heating time is 2-12 hours.

[0063] In some embodiments, sulfides include but are not limited to lithium sulfide (Li 2 S), phosphorus sulfide (P 2 S 5 ), GeS 2 、SnS 2 Sulfides.

[0064] In some embodiments, halides include but are not limited to lithium chloride (LiCl), sodium chloride (NaCl), lithium perchlorate (LiClO 4 )wait.

[0065] In some embodiments, including but not limited to lithium sulfide (Li 2 S), lithium hydroxide (LiOH), lithium carbonate (Li 2 CO 3 ) at least one of.

[0066] In some embodiments, the doping compound element includes at least one of Na, Se, Ge, Si, As, Sb, and In.

[0067] In some embodiments, the defoaming agent includes at least one of polydimethylsiloxane, polyether defoaming agent, and mineral oil defoaming agent. These defoaming agents have good defoaming effects and do not react with the system.

[0068] In some embodiments, the dispersant includes at least one of ε-caprolactam / acetamide eutectic solvent, polyoxyethylene derivatives, polycarboxylic acid polymers, sodium oleate, polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP), fatty acid dispersants, aliphatic amide dispersants, and ester dispersants. Some dispersants, such as AEROSOL OT-70-PG (i.e., Solvay anionic surfactant AEROSOL OT-70-PG sodium diisooctyl sulfosuccinate), have a high flash point and exhibit extremely high flame retardancy when in contact with an open flame, which can improve the thermal stability of the electrolyte material.

[0069] In some embodiments, the first organic solvent includes at least one of straight-chain alkanes, alicyclic hydrocarbons, branched alkanes, olefins, and aromatic hydrocarbons; the first organic solvent does not contain oxygen atoms to avoid the generation of by-products.

[0070] In some embodiments, the linear alkane includes at least one of n-hexane, cyclohexane, isooctane, 1-hexene, and toluene.

[0071] In some embodiments, the mass ratio of sulfide, halide, lithium source, doping compound, defoaming agent, and dispersant is (10-80):(10-40):(10-80):(10-80):(0.5-5):(0.5-5);

[0072] The mass of the first organic solvent is 1 to 4 times the sum of the mass of the sulfide, the halide, the lithium source, the doping compound, the defoaming agent and the dispersant.

[0073] In some embodiments, sulfide, halide, lithium source, doping compound, defoaming agent, and dispersant are added to the first organic solvent and stirred and mixed at a speed of 200 to 400 r / min for 10 to 40 hours.

[0074] In some embodiments, the dopant compound includes NaS, Na 2 S 2 O 3 、PbSe、CdSe、ZnGeS 3 、PbGeS 3 、CdSiS 3 , CdAs 2 、ZnSb 2 、ZnIn 2 S 4 At least one of .

[0075] Based on the same inventive concept, the present invention also provides a method for preparing a composite solid electrolyte, comprising the following steps:

[0076] S1. Mix the sulfide electrolyte, conductive polymer material, flame retardant and second organic solvent prepared by the above preparation method, and stir at a speed of 8000-25000 r / min for 5-40 hours to make the conductive polymer material draw into fibers to obtain electrolyte slurry;

[0077] S2, preparing the electrolyte slurry by solvent casting method or hot pressing method to obtain a solid electrolyte membrane;

[0078] S3. Coating surfactants on both sides of the solid electrolyte membrane respectively, and after drying, forming a surfactant coating to obtain a composite solid electrolyte.

[0079] The present invention proposes a liquid-phase synthetic sulfide electrolyte, and prepares a composite solid electrolyte based on the electrolyte. The electrolyte has good chemical stability, interface conductivity and thermal stability when used. Specifically, the added conductive polymer material can form polymer fibers under the action of a high-speed shear force of 8000 to 25000 r / min, which can effectively improve the processability of the electrolyte. After film formation, a fiber mesh structure can be formed to generate a polymerization state with a non-localized π-electron conjugated system, which can effectively improve the transmission rate of electrons and ions, and the fiber mesh structure can improve the processability of the electrolyte membrane. At the same time, the introduction of the conductive polymer material can effectively improve the stability of the electrolyte membrane, such as PEDOT has high stability in an oxidized state, and its conductivity remains basically unchanged even if it is kept at 120° C. for 1000 hours, and it can still maintain good conductive properties and material stability at high temperatures. Surfactants are introduced on both sides of the solid electrolyte membrane to respectively enhance the affinity to the positive electrode material and the negative electrode material through the action force, thereby enhancing the conductivity and reducing the surface resistance.

[0080] In some embodiments, the electrolyte slurry is prepared by a solvent casting method to obtain a solid electrolyte membrane, specifically comprising:

[0081] The electrolyte slurry is heated to 25-200° C. and kept warm for 2-10 hours, and the second organic solvent is volatilized to obtain a solid electrolyte membrane.

[0082] In some embodiments, the electrolyte slurry is prepared by hot pressing to obtain a solid electrolyte membrane, specifically comprising:

[0083] The electrolyte slurry is kept at a temperature of 25 to 200° C. and a pressure of 0.1 to 500 MPa for 2 to 10 hours, and pressed to volatilize the second organic solvent to obtain a solid electrolyte membrane.

[0084] In some embodiments, the conductive polymer material includes at least one of PEDOT:PSS (poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)), PEDOT:PDAS (polydiphenylamine-4-sulfonic acid dispersed poly(3,4-ethylenedioxythiophene conductive composite), PEDOT:PANI (poly(3,4-ethylenedioxythiophene / polyaniline composite material), PANI (polyaniline), PPy (polypyrrole), PT (polythiophene), and composite conductive polymer materials; the purpose is to dissolve the conductive polymer and the electrolyte in a second organic solvent to obtain an electrolyte slurry, thereby increasing the conductivity of the electrolyte membrane by 10 to 100 times compared with the conductivity of the traditional electrolyte membrane, and realizing rapid electron and charge movement during battery operation.

[0085] In some embodiments, the flame retardant includes at least one of a phosphate flame retardant, an aluminate flame retardant, and a phosphazene flame retardant; the phosphate flame retardant has the characteristics of low toxicity, high stability, and non-volatility; the aluminate flame retardant can absorb heat, expand and release a large amount of water vapor to form a gas phase barrier.

[0086] In some embodiments, the phosphate flame retardant includes at least one of ammonium phosphate, sodium tripolyphosphate, and ammonium polyphosphate.

[0087] In some embodiments, the aluminate flame retardant includes at least one of aluminum trihydroxide and aluminum phosphate.

[0088] In some embodiments, the phosphazene flame retardant includes at least one of hexafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, and pentafluorocyclotriphosphazene.

[0089] In some embodiments, the second organic solvent includes at least one of N,N-dimethylformamide, acetonitrile, dimethyl sulfoxide, anisole, chloroform, dichloroethane, acetone, and tetrahydrofuran.

[0090] In some embodiments, the surfactant includes at least one of a cationic surfactant, an anionic surfactant, and a nonionic surfactant.

[0091] In some embodiments, the cationic surfactant includes but is not limited to at least one of sodium di(2-ethylhexyl)sulfosuccinate, dodecyltrimethylammonium bromide, quaternary ammonium salt surfactants, amine oxide surfactants, imidazoline surfactants, quaternary phosphonium salt surfactants, and ammonium oxide surfactants.

[0092] In some embodiments, the anionic surfactant includes but is not limited to at least one of CTAB (cetyltrimethylammonium bromide), sodium dodecylbenzene sulfonate, sodium fatty alcohol polyoxyethylene ether sulfate, sodium fatty acid methyl ester sulfonate, sodium alkyl sulfonate, and phosphate ester type anionic surfactant.

[0093] In some embodiments, nonionic surfactants include, but are not limited to, nonionic surfactants containing polyoxyethylene groups.

[0094] In some embodiments, a surfactant is added to a third solvent to form a surfactant solution, and then the surfactant solution is sprayed on both sides of the solid electrolyte membrane. After drying, a surfactant coating is formed to obtain a composite solid electrolyte. The surfactant solution is evenly distributed on both sides of the solid electrolyte membrane by spraying, and the surfactant types on both sides may be different. Introducing surfactants by spraying can reduce the surface tension and interfacial compatibility between the solid electrolyte membrane and the positive and negative battery materials, reduce the interfacial resistance, and promote the rapid transmission of ions at the interface; at the same time, the surface morphology and pore structure of the electrode material are optimized, the contact area between the electrode and the solid electrolyte membrane is increased, and the charge transfer rate is increased; some hydrophobic surfactants are distributed on the outside of the electrolyte membrane, which can effectively reduce the reaction between the sulfide electrolyte surface and water, and improve the stability and safety of the electrolyte membrane.

[0095] In some embodiments, surfactants are coated on both sides of the solid electrolyte membrane, and after drying, a surfactant coating is formed to obtain a composite solid electrolyte; wherein the drying method is vacuum drying or forced air drying to volatilize the third solvent to form a surfactant coating.

[0096] In some embodiments, the mass of the surfactant is 1-10% of the mass of the third solvent.

[0097] In some embodiments, the third solvent includes at least one of N,N-dimethylformamide, acetonitrile, dimethyl sulfoxide, anisole, chloroform, dichloroethane, acetone, and tetrahydrofuran.

[0098] In some embodiments, the sulfide electrolyte, the conductive polymer material, the flame retardant, and the second organic solvent are stirred and mixed at a speed of 100 to 800 r / min, and then stirred at a speed of 8000 to 25000 r / min for 5 to 40 hours to allow the conductive polymer material to be drawn into fibers to obtain an electrolyte slurry.

[0099] In some embodiments, the electrolyte slurry is heated to 25-200° C. to volatilize the second organic solvent to obtain a solid electrolyte.

[0100] In some embodiments, the solid electrolyte membrane has a thickness of 0.01 to 1.5 mm.

[0101] In some embodiments, the surfactant coating has a thickness of 5 to 20 nm.

[0102] In some embodiments, the mass ratio of the sulfide electrolyte, the conductive polymer material, and the flame retardant is (10-90):(5-50):(0.01-10), and the mass of the second organic solvent is 1-4 times the sum of the masses of the sulfide electrolyte, the conductive polymer material, and the flame retardant.

[0103] For further reference, Figure 1 As shown, it shows the structure of the composite solid electrolyte of the present invention; specifically, the conductive polymer material forms polymer fibers (i.e. Figure 1 Conductive polymer fiber structure), and in sulfide electrolyte (i.e. Figure 1 A fiber network structure is formed in a sulfide solid electrolyte) and then a surfactant is coated on both sides of the solid electrolyte membrane to obtain a composite solid electrolyte.

[0104] Based on the same inventive concept, the present invention also provides an application of the composite solid electrolyte prepared by the above-mentioned preparation method in the preparation of lithium-ion batteries.

[0105] The following further illustrates the preparation method and application of the sulfide electrolyte and composite solid electrolyte of the present application with specific examples. This section further illustrates the content of the present invention in conjunction with specific examples, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0106] Example 1

[0107] This embodiment provides a method for preparing a sulfide electrolyte, comprising the following steps:

[0108] 0.022 mol of Li 2 S, 0.005 mol P 2 S 5 , 0.013 mol of LiCl was placed in a liquid phase reactor, polydimethylsiloxane was added as a defoaming agent, polyvinyl pyrrolidone (PVP) was added as a dispersant, and a first organic solvent, tetrahydrofuran (THF), was added, and mixed and stirred at a speed of 300 r / min for 20 hours, and then placed in a glove box heating chamber for vacuum heating at a heating temperature of 100 ° C. for a heating time of 8 hours to remove the first organic solvent, and finally a sulfide electrolyte was obtained; wherein the mass of the defoaming agent is Li 2 S.P. 2 S 5 , LiCl, the mass of the dispersant is 0.01% of the sum of the masses of Li 2 S.P. 2 S 5The mass of the first organic solvent tetrahydrofuran (THF) is 0.05% of the sum of the masses of Li 2 S.P. 2 S 5 , 4 times the sum of the mass of LiCl, defoamer and dispersant.

[0109] Example 2

[0110] This embodiment provides a method for preparing a composite solid electrolyte, comprising the following steps:

[0111] S1. The sulfide electrolyte, PANI (polyaniline), hexafluorocyclotriphosphazene and N,N-dimethylformamide prepared in Example 1 were stirred and mixed at a speed of 200 r / min for 20 h, and then stirred at a speed of 15000 r / min for 30 h to draw the conductive polymer material into fibers to obtain an electrolyte slurry; wherein the mass ratio of the sulfide electrolyte, PANI (polyaniline) and hexadecyltrimethylammonium bromide is 90:5:5; the mass of N,N-dimethylformamide is twice the sum of the masses of the sulfide electrolyte, PANI and hexadecyltrimethylammonium bromide;

[0112] S2, pressing the electrolyte slurry at a temperature of 50° C. and a pressure of 1 MPa to volatilize N,N-dimethylformamide to obtain a solid electrolyte membrane with a thickness of 0.2 mm;

[0113] S3. Add hexadecyltrimethylammonium bromide to N,N-dimethylformamide to form a surfactant solution, and then spray the surfactant solution on both sides of the solid electrolyte membrane, dry it, and form a surfactant coating with a thickness of 15 nm to obtain a composite solid electrolyte; the mass of hexadecyltrimethylammonium bromide is 1% of the mass of N,N-dimethylformamide.

[0114] Example 3

[0115] The preparation method of the composite solid electrolyte provided in this embodiment is the same as that in Embodiment 2, except that the mass ratio of the sulfide electrolyte, PANI (polyaniline), and hexadecyltrimethylammonium bromide is 80:15:5, and the rest is the same as that in Embodiment 2.

[0116] Example 4

[0117] The preparation method of the composite solid electrolyte provided in this embodiment is the same as that in Embodiment 2, except that the mass ratio of the sulfide electrolyte, PANI (polyaniline), and hexadecyltrimethylammonium bromide is 75:20:5, and the rest is the same as that in Embodiment 2.

[0118] Example 5

[0119] The preparation method of the composite solid electrolyte provided in this embodiment is the same as that in Embodiment 2, except that the mass ratio of the sulfide electrolyte, PANI (polyaniline), and hexadecyltrimethylammonium bromide is 70:25:5, and the rest is the same as that in Embodiment 2.

[0120] Example 6

[0121] The preparation method of the composite solid electrolyte provided in this embodiment is the same as that in Embodiment 2, except that the mass ratio of the sulfide electrolyte, PANI (polyaniline), and hexadecyltrimethylammonium bromide is 65:30:5, and the rest is the same as that in Embodiment 2.

[0122] Example 7

[0123] The preparation method of the composite solid electrolyte provided in this embodiment is the same as that in Embodiment 2, except that the mass ratio of the sulfide electrolyte, PANI (polyaniline), and hexadecyltrimethylammonium bromide is 60:35:5, and the rest is the same as that in Embodiment 2.

[0124] Performance Characterization

[0125] Figure 2 This is the stress curve of the composite solid electrolyte prepared according to the method in Example 2.

[0126] from Figure 2 It can be seen that the composite solid electrolyte in Example 2 has good ductility and can improve the performance of battery special-shaped processing.

[0127] Figure 3 The conductivity curve of the composite solid electrolyte prepared according to the method in Example 2.

[0128] from Figure 3 It can be seen that the composite solid electrolyte can increase the conduction rate of electrons by adding conductive polymer materials and surfactants.

[0129] Figure 4 This is a physical picture of the composite solid electrolyte prepared according to the method in Example 2.

[0130] Figure 5 This is the TGA curve of the composite solid electrolyte prepared according to the method in Example 2.

[0131] from Figure 5 It can be seen that the composite solid electrolyte will only lose weight at a high temperature of 330°C, and will experience a significant weight loss change after exceeding 350 degrees, so it has excellent high temperature resistance.

[0132] Table 1 shows the ionic conductivity and tensile strength of the composite solid electrolytes prepared in Examples 2 to 7.

[0133] Table 1 - Ionic conductivity and tensile strength of composite solid electrolytes in different embodiments

[0134] Example Ionic conductivity (S / m) Tensile strength(MPa) Example 2 0.44 42.3 Example 3 0.37 47.6 Example 4 0.52 51.7 Example 5 0.52 50.4 Example 6 0.45 49.9 Example 7 0.31 49.1

[0135] As can be seen from Table 1, the ionic conductivity of the composite solid electrolyte prepared by the present invention is 0.31-0.52 S / m, and the tensile strength is 42.3-51.7 MPa. As the amount of PANI added increases within a certain range, the conductivity and tensile strength can be improved, but a negative effect will be shown after exceeding a certain range.

[0136] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a sulfide electrolyte, characterized in that: The following steps are involved: Sulfide, halide, lithium source, doping compound, defoamer and dispersant are added to a first organic solvent, mixed, and vacuum heated in a glove box to volatilize the first organic solvent to obtain a sulfide electrolyte.

2. The method for preparing a sulfide electrolyte according to claim 1, characterized in that: The heating temperature is 80-150°C and the time is 2-12h.

3. The method for preparing a sulfide electrolyte according to claim 1, characterized in that: The sulfide includes at least one of Li2S, P2S5, GeS2, and SnS2; The halide includes at least one of LiCl, NaCl, and LiClO4; At least one of the lithium sources Li2S, LiOH, and Li2CO3; The doping compound element includes at least one of Na, Se, Ge, Si, As, Sb, and In; The defoaming agent includes at least one of polydimethylsiloxane, polyether defoaming agent and mineral oil defoaming agent; The dispersant includes at least one of ε-caprolactam / acetamide low eutectic solvent, polyoxyethylene derivatives, polycarboxylic acid polymers, sodium oleate, polyethylene glycol, polyvinyl pyrrolidone, fatty acid dispersants, aliphatic amide dispersants, and ester dispersants; The first organic solvent includes at least one of straight-chain alkanes, alicyclic hydrocarbons, branched alkanes, olefins, and aromatic hydrocarbons; The straight-chain alkane includes at least one of n-hexane, cyclohexane, isooctane, 1-hexene and toluene.

4. The method for preparing a sulfide electrolyte according to claim 1, characterized in that: The mass ratio of the sulfide, halide, lithium source, doping compound, defoamer and dispersant is (10-80):(10-40):(10-80):(10-80):(0.5-5):(0.5-5); The mass of the first organic solvent is 1 to 4 times the sum of the mass of the sulfide, the halide, the lithium source, the doping compound, the defoaming agent, and the dispersant; and / or, adding sulfide, halide, lithium source, doping compound, defoaming agent and dispersant into the first organic solvent, stirring and mixing at a speed of 200 to 400 r / min for 10 to 40 hours; And / or, the doping compound includes at least one of NaS, Na2S2O3, PbSe, CdSe, ZnGeS3, PbGeS3, CdSiS3, CdAs2, ZnSb2, and ZnIn2S4.

5. A method for preparing a composite solid electrolyte, characterized in that: The following steps are involved: The sulfide electrolyte prepared by the preparation method of any one of claims 1 to 4, the conductive polymer material, the flame retardant, and the second organic solvent are mixed, and then stirred at a speed of 8000 to 25000 r / min for 5 to 40 hours to draw the conductive polymer material into fibers to obtain an electrolyte slurry; The electrolyte slurry is prepared by a solvent casting method or a hot pressing method to obtain a solid electrolyte membrane; The surfactant is coated on both sides of the solid electrolyte membrane respectively, and after drying, a surfactant coating is formed to obtain a composite solid electrolyte.

6. The method for preparing the composite solid electrolyte according to claim 5, characterized in that: The conductive polymer material includes at least one of PEDOT:PSS, PEDOT:PDAS, PEDOT:PANI, PANI, PPy, and PT; The flame retardant includes at least one of a phosphate flame retardant, an aluminate flame retardant, and a phosphazene flame retardant; The second organic solvent includes at least one of N,N-dimethylformamide, acetonitrile, dimethyl sulfoxide, anisole, chloroform, dichloroethane, acetone, and tetrahydrofuran; The surfactant includes at least one of a cationic surfactant, an anionic surfactant and a nonionic surfactant.

7. The method for preparing a composite solid electrolyte according to claim 6, characterized in that: The phosphate flame retardant includes at least one of ammonium phosphate, sodium tripolyphosphate, and ammonium polyphosphate; The aluminate flame retardant includes at least one of aluminum trihydroxide and aluminum phosphate; The phosphazene flame retardant includes at least one of hexafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene and pentafluorocyclotriphosphazene; The cationic surfactant includes but is not limited to at least one of di(2-ethylhexyl) sodium sulfosuccinate, dodecyltrimethylammonium bromide, quaternary ammonium salt surfactants, amine oxide surfactants, imidazoline surfactants, quaternary phosphonium salt surfactants, and ammonium oxide surfactants; The anionic surfactant includes but is not limited to at least one of hexadecyltrimethylammonium bromide, sodium dodecylbenzene sulfonate, sodium fatty alcohol polyoxyethylene ether sulfate, sodium fatty acid methyl ester sulfonate, sodium alkyl sulfonate, and phosphate type anionic surfactant; The nonionic surfactant includes, but is not limited to, a nonionic surfactant containing polyoxyethylene.

8. The method for preparing a composite solid electrolyte according to claim 5, characterized in that: adding a surfactant to a third solvent to form a surfactant solution, spraying the surfactant solution on both sides of the solid electrolyte membrane, and after drying, forming a surfactant coating to obtain a composite solid electrolyte; The third solvent includes at least one of N,N-dimethylformamide, acetonitrile, dimethyl sulfoxide, anisole, chloroform, dichloroethane, acetone, and tetrahydrofuran; The mass of the surfactant is 1 to 10% of the mass of the third solvent.

9. The method for preparing a composite solid electrolyte according to claim 5, characterized in that: The sulfide electrolyte, the conductive polymer material, the flame retardant, and the second organic solvent are stirred and mixed at a speed of 100 to 800 r / min, and then stirred at a speed of 8000 to 25000 r / min to draw the conductive polymer material into fibers to obtain an electrolyte slurry; The electrolyte slurry is prepared by a solvent casting method to obtain a solid electrolyte membrane, which specifically includes: The electrolyte slurry is heated to 25-200° C. and volatilized with a second organic solvent to obtain a solid electrolyte membrane; The electrolyte slurry is prepared by hot pressing to obtain a solid electrolyte membrane, which specifically includes: The electrolyte slurry is pressed at a temperature of 25 to 200° C. and a pressure of 0.1 to 500 MPa to volatilize the second organic solvent to obtain a solid electrolyte membrane; The thickness of the solid electrolyte membrane is 0.01 to 1.5 mm The surfactant coating has a thickness of 5 to 20 nm; The mass ratio of the sulfide electrolyte, the conductive polymer material and the flame retardant is (10-90):(5-50):(0.01-10), and the mass of the second organic solvent is 1-4 times the sum of the masses of the sulfide electrolyte, the conductive polymer material and the flame retardant.

10. Use of the composite solid electrolyte prepared by the preparation method according to any one of claims 5 to 9 in preparing lithium-ion batteries.

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