Composite solid electrolyte, preparation method, application and solid-state battery

Abstract

The invention provides a composite solid electrolyte, a preparation method, application and a solid-state battery. The composite solid electrolyte comprises: a rigid molecular sieve skeleton; the cross-linked polyalkali metal acrylate derivative polymer matrix and the molecular sieve framework form a multistage interpenetrating network structure; wherein one part of the cross-linked polyalkali metal acrylate derivative polymer matrix is confined in a pore channel of the molecular sieve through in-situ polymerization, and the other part of the cross-linked polyalkali metal acrylate derivative polymer matrix forms a continuous three-dimensional network coating and connecting the molecular sieve particles. The composite solid electrolyte provided by the invention has high ionic conductivity, excellent mechanical strength and good interface compatibility, and shows excellent electrochemical performance when being applied to a solid-state battery; and the preparation process is simple and has a remarkable cost advantage.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid-state batteries, and particularly relates to a composite solid-state electrolyte, a preparation method, application and a solid-state battery. BACKGROUND

[0002] Solid-state electrolytes are the core materials of the next generation of high-safety and high-energy-density batteries. The current mainstream systems include polymer, oxide and sulfide electrolytes, but they all have their own bottlenecks: (1) polymer electrolytes (such as PEO-based): low room-temperature ionic conductivity, weak mechanical strength, and unable to effectively inhibit lithium dendrites; (2) inorganic ceramic / glass electrolytes (such as LLZO, LATP): high rigidity, poor interface contact with electrodes, high interface impedance, and easy to crack; (3) simple composite electrolytes: usually inorganic fillers are simply mixed into a polymer matrix, the fillers are easy to agglomerate, and a continuous and efficient ion transport channel cannot be formed, and the interface problem is still prominent.

[0003] Chinese patent document CN120749220A solves the interface problem by designing a double-layer electrolyte structure to adapt to the positive and negative electrodes respectively, but does not fundamentally design the microstructure of the electrolyte.

[0004] Therefore, there is an urgent need in the art for a new electrolyte structure that can simultaneously take into account high ionic conductivity, excellent mechanical strength and good interface compatibility, and a preparation method thereof. SUMMARY

[0005] The purpose of the present application is to overcome the deficiencies of the prior art and provide a composite solid-state electrolyte, a preparation method, application and a solid-state battery. The composite solid-state electrolyte provided by the present application has high ionic conductivity, excellent mechanical strength and good interface compatibility, and exhibits excellent electrochemical performance when applied in a solid-state battery; and the preparation process is simple, and has a significant cost advantage.

[0006] The present application solves the above technical problems by the following technical solutions:

[0007] The present application provides a composite solid-state electrolyte, which comprises:

[0008] (a) a rigid molecular sieve framework; and

[0009] (b) a cross-linked polyalkali metal acrylate derivative polymer matrix forming a multi-level interpenetrating network structure with the molecular sieve framework; wherein a part of the cross-linked polyalkali metal acrylate derivative polymer matrix is confined inside the pores of the molecular sieve by in-situ polymerization, and the other part forms a continuous three-dimensional network that coats and connects the molecular sieve particles.

[0010] In the present application, the pore size of the molecular sieve should generally be greater than the kinetic diameter of the monomer corresponding to the polyalkali metal acrylate derivative, preferably greater than 2 nm, more preferably 2-50 nm, such as 3 nm, 3.8 nm, 4 nm, 4.3 nm, 5 nm, 6 nm or 10 nm, to ensure the smooth diffusion of the monomer. When the monomer corresponding to the polyalkali metal acrylate derivative is lithium acrylate, the kinetic diameter is about 0.5 nm.

[0011] In the present application, the silica-alumina ratio of the molecular sieve can be 10-50, such as 15, 20, 25, 28, 29, 30 or 35, and the silica-alumina ratio refers to the molar ratio of SiO2 / Al2O3.

[0012] In the present application, the type of the molecular sieve can be reasonably selected according to the type of the battery to be used later. When used in a lithium battery, the type of the molecular sieve is preferably H + type molecular sieve and / or Li + type molecular sieve, more preferably one or more of SBA-15, MCM-41 and KIT-6; when used in a lithium battery, if the type of the molecular sieve is Na + type molecular sieve or K + type molecular sieve, the Na + type molecular sieve or K + type molecular sieve can be ion exchanged into H + type molecular sieve and / or Li + type molecular sieve, and then used again. When used in a sodium battery, the type of the molecular sieve is preferably Na + type molecular sieve; when used in a potassium battery, the type of the molecular sieve is preferably K + type molecular sieve. Accordingly, the alkali metal ion in the polyalkali metal acrylate derivative can also be reasonably selected according to the type of the battery to be used, i.e. when used in a lithium battery, the alkali metal ion is lithium ion; when used in a sodium battery, the alkali metal ion is sodium ion; when used in a potassium battery, the alkali metal ion is potassium ion.

[0013] In the present application, the polyalkali metal acrylate derivative generally refers to a polymer formed by in-situ copolymerization and crosslinking reaction of an alkali metal acrylate derivative monomer and a crosslinking agent.

[0014] The alkali metal acrylate derivative monomer refers to an organic salt compound generated after neutralization reaction of acrylic acid and its hydrocarbon derivatives with alkali metals. The hydrocarbon derivatives refer to derivatives obtained by substituting the alpha and beta positions of acrylic acid with hydrocarbon groups. The general formula of the alkali metal acrylate derivative monomer is preferably CHR1=CR2-COOM, wherein R1 and R2 are independently H atom, methyl or ethyl group, and M is an alkali metal ion. The M is preferably lithium ion, sodium ion or potassium ion.

[0015] When applied to lithium batteries, the molecular sieve is preferably mesoporous H + type molecular sieve and / or mesoporous Li + type molecular sieve.

[0016] When applied to lithium batteries, the alkali metal acrylate derivative monomer is preferably one or more of lithium acrylate, lithium methacrylate and lithium ethyl acrylate; and the polyalkali metal acrylate derivative is preferably one or more of poly-lithium acrylate, poly-lithium methacrylate and poly-lithium ethyl acrylate.

[0017] In the present application, the mass percentage of the molecular sieve in the composite solid-state electrolyte membrane can be 10% to 60%, for example, 15%, 16%, 18%, 20%, 25%, 30%, 31%, 32%, 35%, 40% or 50%.

[0018] In the present application, the structure of the composite solid-state electrolyte preferably comprises: a rigid molecular sieve framework; and a multi-level interpenetrating network structure formed with the molecular sieve framework.

[0019] The multi-level interpenetrating network structure comprises: (1) a primary interpenetrating network: polyalkali metal acrylate derivative polymer chains grown by in-situ polymerization confinement in the internal channels of the molecular sieve; and (2) a secondary interpenetrating network: a three-dimensional continuous polyalkali metal acrylate derivative polymer matrix formed by cross-linking between the particles of the molecular sieve.

[0020] In the present application, the structure of the composite solid-state electrolyte realizes perfect combination of rigidity and flexibility through the “framework-matrix” dual interpenetration structure, thereby creating multi-dimensional fast transmission channels for conductive ions (such as lithium ions or sodium ions).

[0021] In the present application, the composite solid-state electrolyte can be prepared into a film or a block according to actual application needs.

[0022] The present application also provides a preparation method of the composite solid-state electrolyte as described above, which comprises the following steps: in-situ polymerization of a slurry containing a molecular sieve and an alkali metal acrylate derivative monomer.

[0023] In the present application, the pore size and type of the molecular sieve are as previously described. The water content of the molecular sieve is preferably less than 1%.

[0024] In the present application, the molecular sieve is preferably further subjected to an activation treatment before use. The moisture and impurities of the molecular sieve are removed by the activation treatment.

[0025] In the present application, the activation treatment preferably comprises the following process: calcining the molecular sieve.

[0026] The calcination is generally performed in an air atmosphere; the equipment for the calcination can be conventional in the art, such as a muffle furnace; the temperature for the calcination can be 350-700℃, such as 400℃, 500℃, 550℃ or 600℃; the time for the calcination can be 2-12h, such as 4h, 6h or 8h.

[0027] In the present application, the chemical formula of the alkali metal acrylate derivative monomer is as previously described.

[0028] In some embodiments, the alkali metal acrylate derivative monomer can be one or more of lithium acrylate, lithium methacrylate and lithium ethyl acrylate.

[0029] In the present application, the mass ratio of the molecular sieve to the alkali metal acrylate derivative monomer can be 1: (0.5-10), such as 1:1.3, 1:1.5, 1:2, 1:3, 1:4 or 1:6.

[0030] In the present application, the solvent in the slurry can be conventional in the art, and is preferably one or more of deionized water, methanol and ethanol.

[0031] In the present application, the mass of the alkali metal acrylate derivative monomer to the volume of the solvent in the slurry can be (0.1-5) g / mL, such as 0.2 g / mL, 0.4 g / mL, 0.5 g / mL, 0.8 g / mL, 1 g / mL, 1.25 g / mL, 1.5 g / mL or 2 g / mL.

[0032] In the present application, the slurry preferably further comprises a crosslinking agent and an initiator.

[0033] In the present application, the crosslinking agent undergoes in-situ copolymerization and crosslinking reaction with the alkali metal acrylate derivative monomer to form a three-dimensional polymer network. The crosslinking agent is preferably an acrylate compound, and is more preferably selected from one or more of poly(ethylene glycol) diacrylate (PEGDA), trimethylolpropane triacrylate and pentaerythritol tetraacrylate.

[0034] In the present application, the mass ratio of the crosslinking agent to the alkali metal acrylate derivative monomer can be 1:(5-50), for example 1:10, 1:15, 1:20 or 1:30.

[0035] In the present application, the initiator refers to a substance capable of initiating the polymerization reaction of the alkali metal acrylate derivative monomer.

[0036] In the present application, the type of the initiator can be conventional in the art. When the in-situ polymerization is ultraviolet polymerization, the initiator is preferably a photoinitiator, more preferably a water-soluble radical photoinitiator (for initiating UV polymerization), for example Irgacure 2959. When the in-situ polymerization is thermal polymerization, the initiator is, for example, azobisisobutyronitrile (AIBN).

[0037] In the present application, the mass ratio of the crosslinking agent to the initiator can be (1-20):1, for example 2:1, 2.5:1, 3:1, 5:1 or 8:1.

[0038] In the present application, the mass of the molecular sieve per the sum of the masses of the molecular sieve, the alkali metal acrylate derivative monomer, the crosslinking agent and the initiator can be 10% to 60%, for example 15%, 16%, 18%, 20%, 25%, 30%, 31%, 32%, 35%, 40% or 50%.

[0039] In the present application, the preparation method of the slurry preferably comprises the following steps: mixing the raw materials uniformly; more preferably comprises the following steps: dissolving the remaining substances except the molecular sieve in a solvent, and then adding the molecular sieve and mixing uniformly.

[0040] The mixing method can be conventional in the art, for example stirring and / or ultrasonication.

[0041] In the present application, the in-situ polymerization can be ultraviolet polymerization or thermal polymerization.

[0042] The ultraviolet polymerization is generally carried out in a glove box; the ultraviolet polymerization is generally carried out under the protection of an inert atmosphere (for example argon); in the process of the ultraviolet polymerization, the wavelength of the ultraviolet light irradiation can be 300-400 nm, for example 365 nm; the light intensity can be 10-50 mW / cm², for example 15 mW / cm², 20 mW / cm², 25 mW / cm² or 30 mW / cm²; the time of the ultraviolet light irradiation can be 1-10 min, for example 2 min, 3 min or 5 min. In the process of the ultraviolet polymerization, the ultraviolet light irradiation initiates the polymerization and crosslinking reaction of the monomer, causing the slurry to rapidly solidify from a liquid state.

[0043] The thermal polymerization is generally performed in an oven; the thermal polymerization is generally performed under protection of inert atmosphere (e.g. nitrogen); the thermal polymerization can be performed at a temperature of 50-100°C, e.g. 65°C, 70°C, 80°C or 90°C; the thermal polymerization can be performed for a time period of 4-12h, e.g. 6h, 8h or 10h.

[0044] In the present application, before the in-situ polymerization, the slurry is preferably cast on a substrate to form a wet film, and then the in-situ polymerization is performed to solidify the slurry into a film. The substrate can be any substrate known in the art, e.g. a glass plate or a PET film. The thickness of the wet film can be 50-500μm, e.g. 100μm. After the slurry is cast on the substrate, a tool such as a doctor blade can be used to spread the slurry to form a wet film. After the in-situ polymerization, the solid film can be peeled off from the substrate.

[0045] When the in-situ polymerization is thermal polymerization, before the thermal polymerization, the slurry is preferably cast on a substrate to form a wet film, and then the wet film is preheated to form a wet gel film, and then the thermal polymerization is performed. The preheating can be performed at a temperature of 40-70°C, e.g. 50°C, 55°C or 60°C; the preheating can be performed for a time period of 10-30min, e.g. 20min. The preheating can slightly shape the wet film, which is convenient for transferring to the environment of the next step.

[0046] In the present application, after the in-situ polymerization, a drying process is generally performed to remove residual solvent. The drying process is generally performed under vacuum; the drying can be performed at a temperature of 40°C-80°C, e.g. 60°C; the drying can be performed for a time period of 12-48h, e.g. 24h.

[0047] In some embodiments, the method for preparing the composite solid electrolyte comprises the following steps:

[0048] (1) casting a slurry comprising molecular sieve, alkali metal acrylate derivative monomer, crosslinking agent and initiator on a substrate to form a wet film;

[0049] (2) irradiating the wet film with ultraviolet light or heating the wet film under inert atmosphere, thereby forming a solid film.

[0050] In some preferred embodiments, the method for preparing the composite solid electrolyte comprises the following steps:

[0051] (1) calcining molecular sieve to obtain activated molecular sieve;

[0052] (2) mixing alkali metal acrylate derivative monomer, crosslinking agent, initiator and solvent uniformly, then adding molecular sieve and mixing uniformly to obtain a slurry, and casting the slurry on a substrate to form a wet film.

[0053] (3) irradiating the wet film with ultraviolet light or heating the wet film under an inert atmosphere to form a solid-state film.

[0054] In some embodiments, the method for preparing the composite solid-state electrolyte comprises the following steps:

[0055] (1) calcining a molecular sieve to obtain an activated molecular sieve;

[0056] (2) mixing an alkali metal acrylic salt derivative monomer, a crosslinking agent, an initiator and a solvent uniformly, then adding the activated molecular sieve and mixing uniformly to obtain a slurry, and casting the slurry on a substrate to form a wet film;

[0057] (3) irradiating the wet film with ultraviolet light or heating the wet film under an inert atmosphere to form a solid-state film;

[0058] (4) drying the solid-state film to obtain the composite solid-state electrolyte.

[0059] The application also provides a use of the composite solid-state electrolyte as described above in a solid-state battery.

[0060] In the application, the solid-state battery is generally a solid-state lithium battery, a solid-state sodium battery or a solid-state potassium battery.

[0061] The application also provides a solid-state battery comprising a positive electrode, a negative electrode and the composite solid-state electrolyte as described above; wherein the composite solid-state electrolyte is arranged between the positive electrode and the negative electrode.

[0062] In the application, when the solid-state battery is a solid-state lithium battery, the positive electrode active material on the positive electrode can comprise one or more of lithium cobaltate, high-nickel positive electrode, lithium iron phosphate and polyanion positive electrode material.

[0063] In the application, the positive electrode can comprise a positive electrode current collector and a positive electrode active material on the surface of the positive electrode current collector.

[0064] In the process of preparing the positive electrode, preferably, the positive electrode active material, the binder and the conductive agent are mixed to form a slurry, and then coated on the surface of the positive electrode current collector.

[0065] The binder can be conventional in the art, for example, PVDF. The conductive agent can be conventional in the art, for example, conductive carbon black (SP). The solvent in the slurry can be conventional in the art, for example, NMP. The mass ratio of the positive electrode active material, the binder and the conductive agent can be (70-90):(5-20):(5-20), for example, 80:10:10.

[0066] The positive electrode current collector can be conventional in the art, such as an aluminum foil.

[0067] In the present application, the negative electrode can be a metal lithium negative electrode, a silicon-carbon negative electrode, a graphite negative electrode, or a titanate negative electrode.

[0068] On the basis of common knowledge in the art, the above-mentioned preferred conditions can be combined arbitrarily, thereby obtaining preferred examples of the present application.

[0069] The reagents and raw materials used in the present application are commercially available.

[0070] The positive progress of the present application is that:

[0071] (1) The composite solid-state electrolyte prepared in the present application has an innovative structure and excellent performance: the "multistage interpenetrating network" structure enables the material to have good interface contact of the polymer and high mechanical strength of the inorganic material, thereby effectively inhibiting lithium dendrites; the regular pore channels of the molecular sieve can also promote the transmission of lithium ions.

[0072] (2) The process is simple and suitable for mass production: the one-step in-situ preparation has a short process and low energy consumption, and is highly compatible with the existing battery production process, thereby having the potential for large-scale application.

[0073] (3) Low interface impedance: the in-situ polymerization process enables the electrolyte membrane to form a close interface contact with the electrode, thereby significantly reducing the interface impedance.

[0074] (4) High safety: the all-solid-state system completely eliminates the risk of leakage and combustion of liquid electrolytes. BRIEF DESCRIPTION OF DRAWINGS

[0075] Figure 1 SEM image of the composite solid-state electrolyte membrane prepared in Example 1. DETAILED DESCRIPTION

[0076] The present application will be further described below by way of examples, but the present application is not limited to the scope of the examples. In the following examples, the experimental methods not specified in the specific conditions are selected according to the conventional methods and conditions or according to the product instructions.

[0077] The relevant raw material information used in the examples and comparative examples is shown in Table 1:

[0078] Table 1

[0079]

[0080] Example 1

[0081] Activated molecular sieve: 1 gram of SBA-15 molecular sieve (water content ~ 10%) was calcined at 550°C for 6 hours in a muffle furnace to obtain activated molecular sieve (water content < 1%).

[0082] Preparation of slurry: 2 g of lithium acrylate, 0.2 g of PEGDA crosslinker, 0.04 g of Irgacure 2959 photoinitiator were weighed and dissolved in 4 ml of deionized water, stirred until completely dissolved. The activated SBA-15 molecular sieve was added, first stirred at 200 rpm for 2 hours, then ultrasonically treated for 30 minutes to obtain a uniform slurry.

[0083] Casting and polymerization: the slurry was cast onto a glass plate, and the thickness was controlled to be 100 μm with a doctor blade. Subsequently, the glass plate was transferred to an argon-filled glove box, and irradiated with a UV lamp of 365 nm wavelength (light intensity 20 mW / cm²) for 3 minutes, and the slurry was cured into a film.

[0084] Post-treatment: the cured film was peeled off and placed in a vacuum drying oven at 60°C for 24 hours to obtain the final composite solid electrolyte film.

[0085] Example 2

[0086] Compared with Example 1, except that the amount of crosslinker was adjusted to 0.1 g, the rest of the operation and conditions were the same as Example 1.

[0087] Example 3

[0088] Compared with Example 1, except that the amount of molecular sieve was increased to 1.5 g, the rest of the operation and conditions were the same as Example 1.

[0089] Example 4

[0090] Compared with Example 1, except that the SBA-15 molecular sieve was replaced by MCM-41 molecular sieve, the rest of the operation and conditions were the same as Example 1.

[0091] Example 5

[0092] Compared with Example 1, except that the SBA-15 molecular sieve was replaced by KIT-6 molecular sieve, the rest of the operation and conditions were the same as Example 1.

[0093] Example 6

[0094] Compared with Example 1, except that the amount of SBA-15 molecular sieve was adjusted to 0.5 g, the rest of the operation and conditions were the same as Example 1.

[0095] Example 7

[0096] Compared with Example 1, except that lithium acrylate was replaced by lithium methacrylate, the rest of the operation and conditions were the same as Example 1.

[0097] Example 8

[0098] The operations and conditions were the same as those in Example 1, except that the amount of lithium acrylate was adjusted to 5 g.

[0099] Example 9

[0100] Activated molecular sieve: Take 1 g of SBA-15 molecular sieve (water content 10%), calcine in a muffle furnace at 550°C for 6 hours to obtain an activated molecular sieve (water content <1%).

[0101] Preparation of slurry: First, 2.0 g of lithium acrylate, 0.04 g of thermal initiator azobisisobutyronitrile (AIBN), and 0.2 g of crosslinking agent polyethylene glycol diacrylate (PEGDA) were completely dissolved in 4 ml of deionized water, then 1.0 g of SBA-15 molecular sieve activated at 550°C was added, first stirred at a speed of 200 rpm for 2 hours, then ultrasonically treated for 30 minutes to form a uniform slurry.

[0102] Casting and polymerization: The slurry was cast on a substrate with a thickness of 100 μm controlled by a doctor blade, preheated at 50°C for 20 minutes to form a wet gel film; then it was transferred to a nitrogen-filled glove box and placed in a 70°C oven for thermal initiation in situ polymerization reaction for 8 hours, and the slurry was solidified into a film.

[0103] Post-processing: After the reaction was completed, the film was peeled off, and finally dried in a vacuum drying oven at 60°C for 24 hours to obtain a self-supporting composite solid electrolyte film.

[0104] Comparative Example 1

[0105] No molecular sieve was added, and the other operations and conditions were the same as those in Example 1.

[0106] Comparative Example 2

[0107] No crosslinking agent was added, and the other operations and conditions were the same as those in Example 1.

[0108] Comparative Example 3

[0109] Activated molecular sieve: Take 1 g of SBA-15 molecular sieve (water content 10%), calcine in a muffle furnace at 550°C for 6 hours to obtain an activated molecular sieve (water content <1%).

[0110] Preparation of slurry: Weigh 2 g of lithium acrylate, 0.2 g of PEGDA crosslinking agent, and 0.04 g of Irgacure 2959 photoinitiator, dissolve in 4 ml of deionized water, stir until completely dissolved, and obtain a uniform slurry.

[0111] Casting and polymerization: The slurry was cast onto a glass plate with a doctor blade to control the thickness to be 100 pm. Subsequently, the glass plate was transferred into an argon-filled glove box and irradiated with a UV lamp of 365 nm wavelength (light intensity 20 mW / cm2) for 3 min, and the slurry was cured into a film.

[0112] Post-processing: The cured film was peeled off and dried in a vacuum drying oven at 60 °C for 24 h, then physically mixed with activated molecular sieves in a ball mill, and finally hot-pressed into a film to obtain the final composite solid electrolyte film.

[0113] Effect example

[0114] The composite solid electrolyte films obtained in Examples 1-10 and Comparative Examples 1-3 were characterized and performance tested.

[0115] (1) According to the SEM image of Figure 1 , no obvious molecular sieve particles were observed, indicating that the two were closely combined.

[0116] (2) According to the test results of BET: the specific surface area and pore volume of the composite solid electrolyte film prepared in Example 1 were greatly reduced compared with pure SBA-15 molecular sieve, the specific surface area of the composite film prepared in Example 1 was 120 m 2 / g, the pore volume was 0.15 cm 3 / g; the specific surface area of pure SBA-15 molecular sieve was 850 m 2 / g, the pore volume was 1.1 cm 3 / g; it was proved that the polymer successfully filled the molecular sieve channels.

[0117] (3) Ion conductivity test: at room temperature 25 °C, the solid electrolyte films prepared in Examples 1-10 and Comparative Examples 1-3 were placed in a mold, and the two ends of the mold were connected to Autolab for electrochemical impedance test, and the test results are shown in Table 2.

[0118] (4) Young's modulus test

[0119] Test method: atomic force microscope was used for Young's modulus test (the test process was a routine operation in the art), an optical image was first scanned, then a point was selected to obtain a mechanical-displacement curve, and then Young's modulus was fitted by IA-trunk software, and the test results are shown in Table 2.

[0120] Table 2

[0121]

[0122] (5) Linear sweep voltammetry: In an argon-filled glove box, a stainless steel (SS) electrode was used as the working electrode, a lithium metal sheet was used as the counter electrode and reference electrode, and the to-be-tested solid electrolyte film was sandwiched in the middle to assemble a SS|electrolyte film|Li symmetric button cell. An electrochemical workstation was used, and the scan rate (such as 0.5 mV / s) and scan voltage range (such as 0 V to 6.0 V (vs. Li + / Li)) were set. Testing and recording were performed; the test was started, and the instrument recorded the curve of the current change with the voltage. The measured electrochemical stability window was 0-4.6 V (vs. Li + / Li).

[0123] (6) Battery cycle test:

[0124] Test equipment: Wuhan Land battery test system (Land CT2001A)

[0125] The composite solid electrolyte films obtained in Examples 1-9 and Comparative Examples 1-3 above were used as solid electrolytes to assemble batteries for electrochemical performance testing, and the specific steps were as follows:

[0126] (a) LiFePO4, PVDF, and SP were mixed in a mass ratio of 80:10:10, NMP was added for stirring until uniform, and a slurry was prepared; the above slurry was coated on an aluminum foil, and baked at 100°C in a vacuum drying oven for 24 h, then rolled by a roll mill, and finally punched into a positive electrode sheet (the electrode slurry loading was 2 mg / cm 2 );

[0127] (b) The above positive electrode sheet was assembled into a Li|composite solid electrolyte film|LiFePO4 button cell with lithium metal as the counter electrode, and the assembly process was carried out in a vacuum glove box filled with high-purity argon;

[0128] (c) After assembly, electrochemical performance testing was performed:

[0129] After cycling at 0.5C rate, the capacity retention rate, discharge capacity, initial efficiency, and rate performance were tested under the following conditions: 0.2-20C constant current charge and discharge at room temperature, and the voltage range was 3-4.5 V; the test results are shown in Table 3.

[0130] Table 3

[0131]

[0132] According to the test results in Tables 2 and 3, the composite solid-state electrolyte prepared in the application has high ionic conductivity and Young's modulus, and when applied to a solid-state lithium battery, it exhibits excellent electrochemical performance. In Comparative Example 1, the composite solid-state electrolyte has a low Young's modulus because no molecular sieve is added, and the capacity retention rate after 0.5C cycling for 100 cycles is even less than 70%; in Comparative Example 2, the lithium acrylate fails to polymerize because no crosslinking agent is added during preparation, resulting in the prepared electrolyte failing to form a film; in Comparative Example 3, the lithium acrylate fails to form a crosslinked lithium acrylate polymer matrix with a multi-level interpenetrating network structure with the molecular sieve skeleton because the molecular sieve is added after polymerization, and when applied to a solid-state lithium battery as a solid-state electrolyte, not only is the first-cycle specific discharge capacity low, but the cycle performance is also poor.

[0133] Although the specific embodiments of the application are described above, those skilled in the art should understand that this is only an example, and the protection scope of the application is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the application, and such changes and modifications fall within the protection scope of the application.

Claims

1. A composite solid electrolyte, characterized in that, include: (a) Rigid molecular sieve framework; as well as (b) A cross-linked polyalkali metal acrylate derivative polymer matrix that forms a multi-level interpenetrating network structure with the molecular sieve framework; wherein a portion of the cross-linked polyalkali metal acrylate derivative polymer matrix is ​​confined inside the pores of the molecular sieve by in-situ polymerization, and another portion forms a continuous three-dimensional network that coats and connects the molecular sieve particles.

2. The composite solid electrolyte as described in claim 1, characterized in that, The pore size of the molecular sieve is larger than the kinetic diameter of the corresponding monomer of the polyalkali metal acrylate derivative, preferably larger than 2 nm, and more preferably 2-50 nm. And / or, the silica-alumina ratio of the molecular sieve is 10-50, for example 15, 20, 25, 28, 29, 30 or 35.

3. The composite solid electrolyte as described in claim 1, characterized in that, When applied to lithium batteries, the molecular sieve is of type H. + Type I molecular sieves and / or Li + The molecular sieve is preferably one or more of SBA-15, MCM-41 and KIT-6; When applied to sodium batteries, the molecular sieve is of the Na type. + Type molecular sieve; When applied to potassium batteries, the molecular sieve is of type K. + Type of molecular sieve.

4. The composite solid electrolyte as described in claim 1, characterized in that, The general formula of the polyalkali metal acrylate derivative monomer is: ,in , Each of the atoms is independently a H atom, a methyl atom, or an ethyl atom, and M is an alkali metal ion; preferably, M is a lithium ion, a sodium ion, or a potassium ion; And / or, the molecular sieve accounts for 10% to 60% of the mass percentage of the composite solid electrolyte membrane.

5. A method for preparing a composite solid electrolyte as described in any one of claims 1-4, characterized in that, The process includes the following steps: in-situ polymerization of a slurry containing molecular sieves and alkali metal acrylate derivative monomers.

6. The method for preparing the composite solid electrolyte as described in claim 5, characterized in that, The preparation method satisfies one or more of the following conditions: (1) The water content of the molecular sieve is less than 1%; (2) The alkali metal acrylate derivative monomer is one or more of lithium acrylate, lithium methacrylate and lithium ethyl acrylate; (3) The mass ratio of the molecular sieve to the alkali metal acrylate derivative monomer is 1:(0.5-10), for example 1:1.3, 1:1.5, 1:2, 1:3, 1:4 or 1:6; (4) The solvent in the slurry is one or more of deionized water, methanol and ethanol; (5) The ratio of the mass of the alkali metal acrylate derivative monomer to the volume of the solvent in the slurry is (0.1-5) g / mL; (6) The slurry also contains a crosslinking agent and an initiator; The crosslinking agent is preferably an acrylate compound, and more preferably selected from one or more of poly(ethylene glycol) diacrylate, trimethylolpropane triacrylate, and pentaerythritol tetraacrylate; The mass ratio of the crosslinking agent to the alkali metal acrylate derivative monomer is preferably 1:(5-50), for example 1:10, 1:15, 1:20 or 1:

30.

7. The method for preparing the composite solid electrolyte as described in claim 5, characterized in that, The method for preparing the slurry includes the following steps: mixing all raw materials evenly; preferably, it includes the following steps: dissolving the other substances except the molecular sieve in a solvent first, and then adding the molecular sieve and mixing evenly. And / or, the in-situ polymerization method is ultraviolet polymerization or thermal polymerization.

8. The method for preparing the composite solid electrolyte as described in claim 7, characterized in that, The preparation method satisfies one or more of the following conditions: (1) During the ultraviolet polymerization process, the wavelength of ultraviolet light irradiation is 300-400nm; (2) During the ultraviolet polymerization process, the light intensity is 10-50 mW / cm²; (3) During the ultraviolet polymerization process, the ultraviolet light irradiation time is 1-10 min; (4) The temperature of the thermal polymerization is 50-100℃; (5) The time for thermal polymerization is 4-12 hours.

9. The application of a composite solid electrolyte as described in any one of claims 1-4 in a solid-state battery.

10. A solid-state battery, comprising a positive electrode, a negative electrode, and a composite solid-state electrolyte as described in any one of claims 1-4; wherein, The composite solid electrolyte is disposed between the positive electrode and the negative electrode.

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