Modified sodium ion inorganic conductor and preparation method thereof, composite solid electrolyte and preparation method thereof, and solid-state battery

Abstract

The invention relates to the field of sodium ion batteries, and discloses a modified sodium ion inorganic conductor, a preparation method of the modified sodium ion inorganic conductor, a composite solid electrolyte, a preparation method of the composite solid electrolyte and a solid battery. The prepared modified sodium ion inorganic conductor can be subjected to a cross-linking polymerization reaction with a corresponding cross-linking agent containing unsaturated bonds in the presence of an initiator to form a compact structure in which inorganic filler and a cross-linking agent chain segment are directly chemically bonded; therefore, high ionic conductivity, high sodium ion transference number, low bulk phase impedance and low electrode-electrolyte interface impedance of the composite solid electrolyte are realized, and development of a sodium ion battery with high cycle stability and high use safety is facilitated.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion batteries, specifically to a modified sodium-ion inorganic conductor and its preparation method, a composite solid electrolyte and its preparation method, and a solid-state battery. Background Technology

[0002] Sodium-ion batteries are inexpensive and possess excellent high and low temperature performance as well as high rate performance, making them a promising replacement for currently commercially available lithium-ion batteries in large-scale battery applications such as energy storage. Current research on sodium-ion batteries is still limited to liquid battery systems. These liquid batteries pose safety hazards such as electrolyte leakage and spontaneous combustion during use, making them unsuitable for the development of high-safety battery systems. All-solid-state sodium-ion batteries use inorganic solid-state electrolytes or polymer solid-state electrolytes instead of the electrolyte in liquid battery systems, fundamentally solving the safety hazard of electrolyte leakage. Furthermore, all-solid-state electrolytes can better adapt to changes in ambient temperature, meeting the requirements for wide-temperature-range battery operation, which is of great significance for the development of high-safety, wide-temperature-range sodium-ion batteries.

[0003] Studies have shown that inorganic solid electrolytes possess a high Young's modulus, which can suppress the growth of sodium dendrites; however, their interface with the electrode is a solid-solid phase contact, resulting in generally high impedance at the electrode interface. Polymer solid electrolytes, on the other hand, exhibit good machinability due to their flexibility. However, the high crystallinity of polymer chains leads to low ionic conductivity, which fails to meet the application requirements of batteries. While composite all-solid electrolytes combining the advantages of both exhibit significantly improved mechanical and interfacial properties, their ionic conductivity still falls short of the required levels for practical applications.

[0004] The gel polymer electrolyte provided by this invention is a solid electrolyte, typically composed of cross-linked polymer segments binding the electrolyte. It is essentially non-flowable, solving the problem of electrolyte leakage in batteries. Furthermore, its charge carriers are mainly provided by the electrolyte, resulting in relatively high ionic conductivity. Adding an appropriate amount of inorganic solid electrolyte filler to the gel polymer electrolyte can further improve the ionic conductivity of the electrolyte. Simultaneously, the addition of inorganic solid electrolyte can significantly increase the sodium ion transport number of the battery, reduce side reactions at the negative electrode interface, and lower the mass transfer impedance of the battery, which is of great significance for the preparation of high-performance quasi-solid-state sodium-ion batteries. However, similar to composite all-solid-state electrolytes, the cross-linking network composed of cross-linking agents is usually incompatible with the inorganic solid electrolyte interface; simple doping cannot achieve good contact between the two, easily leading to a large interphase interfacial impedance. The composite quasi-solid-state electrolyte, prepared through chemical bonding between the cross-linking network and the surface of the inorganic solid electrolyte, and simultaneously using in-situ curing technology, can achieve good contact between the organic and inorganic phase interfaces and improve the affinity of the electrolyte-electrode interface, showing significant application potential. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of poor interfacial contact between the organic and inorganic phases and poor electrochemical performance in existing composite solid electrolytes. This invention provides a modified sodium ion inorganic conductor and its preparation method, a composite solid electrolyte and its preparation method, and a solid battery. The composite solid electrolyte has low interfacial impedance between the two phases (organic and inorganic) and excellent ionic conductivity, while the solid battery prepared by this invention has excellent electrochemical performance.

[0006] To achieve the above objectives, the present invention provides a modified sodium ion inorganic conductor, comprising a sodium ion inorganic conductor and silicon-containing groups grafted onto the surface of the sodium ion inorganic conductor; the silicon-containing groups are provided by a silane coupling agent with the structure shown in formula (A).

[0007] Formula (A):

[0008] Among them, R1, R2, and R3 are each independently selected from C0-C 10 Alkylenes; R4, R5, and R6 are each independently selected from C1-C6. 10 alkoxy or H;

[0009] R7 is selected from C2-C8 hydrocarbon groups containing carbon-carbon double bonds or -R8-OC(O)-R9; R8 is selected from C0-C 10 Alkylene; R9 is selected from C2-C containing a carbon-carbon double bond. 10 Hydrocarbon group.

[0010] A second aspect of the present invention provides a method for preparing the modified sodium ion inorganic conductor described in the first aspect of the present invention, wherein the method comprises:

[0011] A sodium ion inorganic conductor is reacted with a silane coupling agent of the structure shown in Formula (A) to graft silicon-containing groups provided by the silane coupling agent of the structure shown in Formula (A) onto the surface of the sodium ion inorganic conductor, thereby obtaining the modified sodium ion inorganic conductor.

[0012] A third aspect of the present invention provides a composite solid electrolyte, wherein the solid electrolyte comprises a crosslinked copolymer containing structural units provided by a modified sodium ion inorganic conductor and crosslinked structural units provided by a crosslinking agent containing unsaturated bonds; the modified sodium ion inorganic conductor is the modified sodium ion inorganic conductor described in the first aspect of the present invention.

[0013] The fourth aspect of the present invention provides a method for preparing a composite solid electrolyte, wherein the method comprises: in the presence of an initiator, performing a polymerization reaction between the modified sodium ion inorganic conductor described in the first aspect of the present invention and a crosslinking agent containing unsaturated bonds to obtain the composite solid electrolyte.

[0014] The fifth aspect of the present invention provides a composite solid electrolyte prepared by the method for preparing the composite solid electrolyte described in the fourth aspect of the present invention.

[0015] A sixth aspect of the present invention provides a solid-state battery comprising the composite solid-state electrolyte described in the third or fifth aspect of the present invention.

[0016] By employing the technical solution described in this invention, the silicon-containing groups provided by the silane coupling agent with the structure shown in formula (A) are grafted onto the surface of the sodium ion inorganic conductor. The modified sodium ion inorganic conductor prepared can undergo cross-linking polymerization with the corresponding cross-linking agent containing unsaturated bonds in the presence of an initiator, forming a tight structure in which the inorganic filler and the cross-linking agent chain segments are directly chemically bonded. This achieves high ionic conductivity, high sodium ion transport number, low bulk impedance, and low electrode-electrolyte interface impedance of the composite solid electrolyte, which is beneficial for the development of sodium ion batteries with high cycle stability. Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] In one aspect, the present invention provides a modified sodium ion inorganic conductor, which includes a sodium ion inorganic conductor and silicon-containing groups grafted onto the surface of the sodium ion inorganic conductor; the silicon-containing groups are provided by a silane coupling agent with the structure shown in formula (A);

[0019] Formula (A):

[0020] Among them, R1, R2, and R3 are each independently selected from C0-C 10 Alkylenes; R4, R5, and R6 are each independently selected from C1-C6. 10 alkoxy or H;

[0021] R7 is selected from C2-C8 hydrocarbon groups containing carbon-carbon double bonds or -R8-OC(O)-R9; R8 is selected from C0-C 10 Alkylene; R9 is selected from C2-C containing a carbon-carbon double bond. 10 Hydrocarbon group.

[0022] In this invention, the silicon-containing groups provided by the silane coupling agent with the structure shown in formula (A) are grafted onto the surface of the sodium ion inorganic conductor, which can promote the cross-linking polymerization reaction between the modified sodium ion inorganic conductor and the corresponding cross-linking agent containing unsaturated bonds, thereby forming a tight structure in which the inorganic filler and the cross-linking agent chain segments are directly chemically bonded, so that the composite solid electrolyte has excellent electrochemical performance and safety performance.

[0023] In this invention, to improve the grafting effect of the silicon-containing group and the sodium ion inorganic conductor and prepare a composite solid electrolyte with excellent electrochemical performance, preferably, in the structure shown in formula (A), R1, R2, and R3 are each independently selected from C0-C6 alkylene groups; R4, R5, and R6 are each independently selected from C1-C6 alkoxy groups or H groups; R7 is selected from C2-C6 hydrocarbon groups containing carbon-carbon double bonds or -R8-OC(O)-R9; R8 is selected from C0-C6 alkylene groups; and R9 is selected from C2-C6 alkenyl groups (i.e., hydrocarbon groups containing 2-6 carbon atoms and one unsaturated double bond).

[0024] In this invention, to further improve the efficiency of the grafting reaction between the silicon-containing group and the sodium ion inorganic conductor, preferably, R1, R2, and R3 are each independently selected from C0 alkylene groups (C0 alkylene groups are those that do not exist and indicate that the groups at both ends of R1 / R2 / R3 are directly connected), -CH2-, -CH2-CH2-, -CH2-CH2-CH2-, -CH(CH3)-CH2-, -CH2-CH(CH3)-, -CH2-(CH2)2-CH2-, -C(CH3)2-CH2-, and -CH2-C(CH3)2-.

[0025] R4, R5, and R6 are each independently selected from methoxy, ethoxy, -O-CH2-CH2-CH3, -O-CH(CH3)2, -O-CH2-CH2-CH2-CH3, -O-CH(CH3)-CH2-CH3, -O-CH2-CH(CH3)2, -O-(CH 2)4 -CH3, -O-CH(CH3)-CH2-CH2-CH3, -O-CH2-CH(CH3)-CH2-CH3 or H;

[0026] R7 is selected from -CH=CH2, -CH=CH-CH3, -CH2-CH=CH2, -CH2-CH2-CH=CH2

[0027] Or -R8-CO-R9; R8 is selected from at least one of C0 alkylene, -CH2-, -CH2-CH2-, -CH2-CH2-CH2-, -CH(CH3)-CH2-, -CH2-CH(CH3)-, -CH2-(CH2)2-CH2-, -C(CH3)2-CH2- and -CH2-C(CH3)2-; R9 is selected from at least one of -CH=CH2, -CH=CH-CH3, -CH2-CH=CH2, -CH2-CH2-CH=CH2, -C(CH3)=CH2, -CH=C(CH3)-CH3, -CH2-C(CH3)=CH2, -CH(CH3)-CH2-CH=CH2 and -C(CH2CH3)=CH2, -CH=C(CH2CH3)-CH3, -CH2-C(CH2CH3)=CH2.

[0028] According to a preferred embodiment, the silane coupling agent is selected from one or more compounds shown in the following formula;

[0029] Equation (A-1): Equation (A-2):

[0030] Equation (A-3): Equation (A-4):

[0031] Equation (A-5): Equation (A-6):

[0032] Formula (A-7): Equation (A-8):

[0033] In this invention, to further enable the composite solid electrolyte to possess high ionic conductivity and low bulk impedance, preferably, the sodium ion inorganic conductor is selected from Na3Zr2Si2PO4. 12 And / or Na3PS4. The sodium ion inorganic conductor can be prepared commercially or by conventional methods in the art.

[0034] A second aspect of the present invention provides a method for preparing the modified sodium ion inorganic conductor described in the first aspect of the present invention, wherein the method comprises:

[0035] A sodium ion inorganic conductor is reacted with a silane coupling agent of the structure shown in Formula (A) to graft silicon-containing groups provided by the silane coupling agent of the structure shown in Formula (A) onto the surface of the sodium ion inorganic conductor, thereby obtaining the modified sodium ion inorganic conductor.

[0036] In this invention, preferably, the method further includes: first hydrolyzing the silane coupling agent with the structure shown in formula (A), and then reacting it with a sodium ion inorganic conductor. More preferably, the conditions for the hydrolysis reaction include: a temperature of 20-80°C, preferably 40-60°C; and a time of 2-12 hours, preferably 2-5 hours.

[0037] In this invention, the sodium ion inorganic conductor undergoes a contact reaction with the silane coupling agent of formula (A), resulting in the grafting of silicon-containing groups provided by the silane coupling agent of formula (A) onto the surface of the sodium ion inorganic conductor, thereby facilitating the subsequent preparation of the composite solid electrolyte. To achieve a more suitable content of silicon-containing groups grafted onto the surface of the sodium ion inorganic conductor, preferably, the molar ratio of the sodium ion inorganic conductor (based on Na) to the silane coupling agent of formula (A) is 1:5-120. More preferably, the molar ratio of the sodium ion inorganic conductor (calculated as Na element) to the silane coupling agent with the structure shown in formula (A) is 1:10-100, for example, it can be 1:10, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, 1:120 and any other value between them.

[0038] In this invention, to improve the efficiency of the contact reaction, preferably, the contact reaction is carried out in the presence of a solvent selected from at least one of tetrahydrofuran, 1,3-dioxolane, and 1,4-dioxane. Preferably, based on the total mass of the sodium ion inorganic conductor and the silane coupling agent with the structure shown in formula (A), the amount of solvent used is 10wt%-70wt%, preferably 25wt%-65wt%, for example, it can be 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 60wt%, 65wt%, etc., and any range between these values.

[0039] In this invention, preferably, the conditions for the contact reaction include: a temperature of 10-100°C and a time of 0.5-8 hours. More preferably, the conditions for the contact reaction include: a temperature of 20-70°C, preferably 30-60°C; and a time of 1-6 hours, preferably 3-6 hours.

[0040] In this invention, the preparation method of the modified sodium ion inorganic conductor may specifically include the following process: first, the sodium ion inorganic conductor and the silane coupling agent with the structure shown in formula (A) are dispersed in solvents respectively to obtain a dispersion containing the sodium ion inorganic conductor and a solution containing the silane coupling agent with the structure shown in formula (A); then, the dispersion containing the sodium ion inorganic conductor and the solution containing the silane coupling agent with the structure shown in formula (A) are mixed and subjected to a contact reaction; subsequently, the product of the contact reaction is subjected to solid-liquid separation, and the separated precipitate is dried. The solvent used to disperse the modified sodium ion inorganic conductor and the silane coupling agent with the structure shown in formula (A) can be independently selected from one or more of the aforementioned solvents, which will not be elaborated here. The amount of solvent used to disperse the sodium ion inorganic conductor relative to the total weight of the dispersion can be 5-50 wt%. The amount of solvent used for the silane coupling agent with the structure shown in formula (A) can be 10-50 wt% relative to the total weight of the solution containing the silane coupling agent with the structure shown in formula (A).

[0041] In this invention, preferably, the method further includes grinding the dried product, rinsing it with a detergent, and then subjecting it to a second drying process to prepare the modified sodium ion inorganic conductor. The detergent is preferably selected from at least one of tetrahydrofuran, methanol, and chloroform, and the amount of detergent used can be 100-300 wt% based on the mass of the sodium ion inorganic conductor. More preferably, the drying conditions include: a temperature of 100-150°C, preferably 110-130°C, and a time of 2-12 hours, preferably 5-10 hours; the second drying conditions include: a temperature of 100-150°C, preferably 110-130°C, and a time of 2-12 hours, preferably 5-10 hours.

[0042] A third aspect of the present invention provides a composite solid electrolyte, wherein the solid electrolyte comprises a crosslinked copolymer containing structural units provided by a modified sodium ion inorganic conductor and crosslinked structural units provided by a crosslinking agent containing unsaturated bonds; the modified sodium ion inorganic conductor is the modified sodium ion inorganic conductor described in the first aspect of the present invention.

[0043] In this invention, preferably, the crosslinking agent containing unsaturated bonds is selected from one or more of polyalkylene glycol diC3-C6 acrylate, diC3-C6 alkylene acrylate, and dipentaerythritol pent- / hexyl-acrylate. Specifically, polyalkylene glycol diC3-C6 acrylate refers to an alkylene glycol polymer with 3-6 carbon atoms attached to each end, and diC3-C6 alkylene acrylate refers to an alkylene glycol with 3-6 carbon atoms attached to each end. More preferably, the crosslinking agent containing unsaturated bonds is one or more of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, and dipentaerythritol pent- / hexyl-acrylate.

[0044] In this invention, preferably, the content of cross-linking structural units provided by the cross-linking agent containing unsaturated bonds is 20-60 wt% relative to the total weight of the cross-linked copolymer, preferably 30-50 wt%, for example, it can be 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, etc., and any range between these values.

[0045] The fourth aspect of the present invention provides a method for preparing a composite solid electrolyte, wherein the method comprises: in the presence of an initiator, performing a polymerization reaction between a modified sodium ion inorganic conductor as described in the first aspect of the present invention and a crosslinking agent containing unsaturated bonds to obtain the composite quasi-solid electrolyte.

[0046] In this invention, to enhance the synergistic effect between the modified sodium ion inorganic conductor and the crosslinking agent containing unsaturated bonds, preferably, the weight ratio of the modified sodium ion inorganic conductor to the crosslinking agent containing unsaturated bonds is 100:5-300, more preferably 100:10-250, for example, values ​​such as 100:5, 100:10, 100:30, 100:50, 100:150, 100:200, 100:250, 100:300, etc., and any range between these values.

[0047] In this invention, to improve the initiation effect of the initiator in the polymerization reaction, preferably, the initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, dodecyl peroxide, and diisopropyl peroxide dicarbonate.

[0048] In this invention, preferably, the amount of the initiator is 1-10 wt%, preferably 2-8 wt%, based on the total mass of the modified sodium ion inorganic conductor and the crosslinking agent containing unsaturated bonds. For example, it can be 2 wt%, 4 wt%, 6 wt%, 8 wt%, or any value between these values.

[0049] In this invention, preferably, the polymerization reaction conditions include a temperature of 60-90°C and a time of 6-30 hours; more preferably, the polymerization reaction conditions include a temperature of 50-75°C and a time of 8-24 hours.

[0050] In this invention, the polymerization reaction between the modified sodium ion inorganic conductor and the crosslinking agent containing unsaturated bonds can be carried out in a base electrolyte comprising a solvent, a sodium salt, and an additive. Preferably, the organic solvent is selected from at least one of ethylene carbonate, propylene carbonate, and dimethyl carbonate, more preferably from ethylene carbonate and / or propylene carbonate, particularly ethylene carbonate and propylene carbonate in a volume ratio of 1:1-3, for example, ethylene carbonate and propylene carbonate in volume ratios of 1:1, 1.1.1, 1.1.2, or 1:1.5. The sodium salt is selected from at least one of sodium hexafluorophosphate, sodium perchlorate, and sodium bis(trifluoromethanesulfonyl)imide; the additive is selected from at least one of fluoroethylene carbonate, sodium nitrate, and sodium iodide. Preferably, based on the total mass of the modified sodium ion inorganic conductor and the crosslinking agent containing unsaturated bonds, the amount of sodium salt is 20-75 wt%, and the amount of additive is 10-40 wt%. The amount of organic solvent used can be adjusted within a wide range. For example, the amount of organic solvent used is such that the amount of sodium salt in the resulting base electrolyte is 0.5-5 wt% and the amount of additive is 1-10 wt%. Therefore, the resulting solid electrolyte may also contain the above-mentioned sodium salt and additive.

[0051] The fifth aspect of the present invention provides a composite solid electrolyte prepared by the method for preparing the composite solid electrolyte described in the fourth aspect of the present invention.

[0052] A sixth aspect of the present invention provides a solid-state battery comprising the composite solid-state electrolyte described in the third or fifth aspect of the present invention.

[0053] In this invention, the solid-state battery includes a positive electrode, a separator, a negative electrode, and the composite solid-state electrolyte. This invention does not impose any particular limitations on the positive electrode, negative electrode, and separator of the battery; various types of positive electrodes, negative electrodes, and separators used in battery manufacturing can be used, as long as the electrolyte used in the battery is the composite solid-state electrolyte described in this invention.

[0054] In this invention, the preparation method of the positive electrode can adopt various methods commonly used in the art. For example, it can include mixing the positive electrode active material, the positive electrode conductive agent and the positive electrode binder with the negative electrode solvent, coating and / or filling them on the positive electrode current collector, drying, and rolling or not rolling to obtain the positive electrode.

[0055] According to the present invention, the positive electrode active material may be sodium nickel iron manganese oxide (NaNi). 0.33 Fe 0.33 Mn 0.33 At least one of O2, sodium iron phosphate (NaFePO4), and Prussian blue Fe4[Fe(CN)6]3. Preferably, the content of the positive electrode active material in the positive electrode material layer of the battery is 95-98 wt%.

[0056] According to the present invention, the positive electrode conductive agent may be selected from one or more of conductive carbon black, carbon fiber, acetylene black, Ketjen black, graphene, or carbon nanotubes. Preferably, based on the positive electrode active material, the amount of the positive electrode conductive agent may be 1-5 wt%.

[0057] According to the present invention, the positive electrode binder may be selected from one or more of polyvinylidene fluoride, polypropylene, polyethylene, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene, polytetrafluoroethylene, or polyhexafluoropropylene. Preferably, based on the positive electrode active material, the amount of the positive electrode binder may be 1-5 wt%.

[0058] In this invention, the negative electrode can be prepared by various methods commonly used in the art. For example, it may include mixing negative electrode active material, negative electrode binder and negative electrode solvent, coating and / or filling it on the negative electrode current collector, forming a negative electrode material layer on the surface of the negative electrode current collector, drying, and calendering or not calendering to obtain the negative electrode.

[0059] According to the present invention, the negative electrode active material may be selected from one or more of biomass hard carbon, resin-based hard carbon, and fossil fuel-based hard carbon materials. Preferably, the content of the negative electrode active material in the negative electrode material layer of the battery is 93-98 wt%.

[0060] According to the present invention, the negative electrode conductive agent may be selected from one or more of conductive carbon black, carbon fiber, acetylene black, Ketjen black, graphene, or carbon nanotubes. Preferably, based on the negative electrode active material, the amount of the negative electrode conductive agent may be 1-5 wt%.

[0061] According to the present invention, the negative electrode binder may be selected from one or more of carboxymethyl cellulose, styrene-butadiene rubber, polypropylene, polyethylene, polyvinylidene fluoride, vinyl chloride-hexafluoropropylene, polytetrafluoroethylene, or polyhexafluoropropylene. Preferably, based on the negative electrode active material, the amount of the negative electrode binder may be 1-5 wt%.

[0062] According to the present invention, the current collectors in the positive and negative electrodes are respectively current collectors commonly used in the art, for example, aluminum foil.

[0063] According to the present invention, the separator is disposed between the positive electrode and the negative electrode and has electrical insulation properties and liquid retention properties. The separator can be at least one selected from various separators used in sodium-ion batteries, such as glass fiber, polyethylene membrane, or polypropylene membrane.

[0064] The composite all-solid electrolyte prepared by this invention possesses both high ionic conductivity and good interfacial contact performance, further enabling the prepared solid-state battery to exhibit excellent cycle performance. According to some preferred embodiments of this invention, the ionic conductivity of the composite solid electrolyte prepared by this invention is not less than 7 × 10⁻⁶. -5 S cm -1 The prepared solid-state battery has an initial coulombic efficiency of no less than 80% and a capacity retention of no less than 80% after 90 cycles. In particular, the composite solid electrolyte prepared in Examples 1-3 has an ionic conductivity of no less than 3 × 10⁻⁶. -3 S cm -1 Furthermore, the solid-state battery prepared has an initial coulombic efficiency of no less than 90% and a capacity retention rate of no less than 85% after 90 cycles.

[0065] The present invention will be described in detail below through examples. In the following examples, γ-methacryloyloxypropyltrimethoxysilane coupling agent was purchased from Aladdin Company, brand name G107576; polyethylene glycol diacrylate was purchased from Aladdin Company, brand name P131592; dipentaerythritol pentyl / hexyl acrylic acid was purchased from Aladdin Company, brand name D137290; Na3Zr2Si2PO4 12 Purchased from Hefei Kejing Materials Technology Co., Ltd., grade Na3Zr2Si2PO 12 95% D50.

[0066] The following preparation examples illustrate the preparation of modified sodium ion inorganic conductors:

[0067] Preparation Example 1

[0068] (1) At room temperature, 0.18 mol Na3Zr2Si2PO 12 The powder was added to 200 mL of tetrahydrofuran and mixed and stirred for 1 h to obtain a sodium ion conductor dispersion; 2 mol of γ-methacryloxypropyltrimethoxysilane coupling agent of formula (A-1) was added to 800 mL of aqueous tetrahydrofuran and hydrolyzed at 50 °C for 2 h to prepare a silane coupling agent dilution solution.

[0069] (2) The sodium ion conductor dispersion in step (1) was reacted with the silane coupling agent dilution at 50°C for 6 hours. The product of the reaction was then separated into solid and liquid phases and the precipitate was retained. The precipitate was washed with 200 wt% tetrahydrofuran (based on the mass of the sodium ion inorganic conductor) and then dried at 120°C for 8 hours to prepare the modified sodium ion inorganic conductor a1.

[0070] Preparation Example 2

[0071] (1) At room temperature, 0.36 mol Na3Zr2Si2PO 12 The powder was added to 300 mL of tetrahydrofuran and mixed and stirred for 1.5 h to obtain a sodium ion conductor dispersion; 5 mol of γ-methacryloxypropyltrimethoxysilane coupling agent of formula (A-1) was added to 1500 mL of aqueous tetrahydrofuran and hydrolyzed at 60 °C for 2 h to prepare a diluted silane coupling agent solution;

[0072] (2) The sodium ion conductor dispersion in step (1) was reacted with the silane coupling agent dilution at 60°C for 5.5 h. The product of the reaction was then separated into solid and liquid phases and the precipitate was retained. The precipitate was washed with 150 wt% tetrahydrofuran (based on the mass of the sodium ion inorganic conductor) and then dried at 130°C for 8 h to prepare the modified sodium ion inorganic conductor a2.

[0073] Preparation Example 3

[0074] (1) At room temperature, 0.25 mol Na3Zr2Si2PO 12 The powder was added to 200 mL of tetrahydrofuran and stirred for 1.5 h to obtain a sodium ion conductor dispersion; 5 mol of γ-methacryloxypropyltrimethoxysilane coupling agent of formula (A-1) was added to 1500 mL of aqueous tetrahydrofuran and hydrolyzed at 55 °C for 2.5 h to prepare a diluted silane coupling agent solution;

[0075] (2) The sodium ion conductor dispersion in step (1) was reacted with the silane coupling agent dilution at 55°C for 5 hours. The product of the reaction was then separated into solid and liquid phases and the precipitate was retained. The precipitate was washed with 250 wt% tetrahydrofuran (based on the mass of the sodium ion inorganic conductor) and then dried at 125°C for 9 hours to prepare the modified sodium ion inorganic conductor a3.

[0076] Preparation Example 4

[0077] The method is similar to that in Example 1, except that step (1) is as follows:

[0078] At room temperature (25℃, the same below), 0.15 mol Na3Zr2Si2PO4 was added. 12 The powder was added to 150 mL of tetrahydrofuran and stirred for 1 h to obtain a sodium ion conductor dispersion; 0.25 mol of γ-methacryloxypropyltrimethoxysilane coupling agent of formula (A-1) was added to 100 mL of aqueous tetrahydrofuran and hydrolyzed at 50 °C for 2 h to obtain a diluted silane coupling agent solution.

[0079] The remaining steps are consistent with those in Example 1, and the modified sodium ion inorganic conductor a4 is prepared.

[0080] Preparation Example 5

[0081] The method is similar to that in Example 1, except that step (1) is as follows:

[0082] At room temperature (25℃, the same below), 0.15 mol Na3Zr2Si2PO4 was added. 12 The powder was added to 150 mL of tetrahydrofuran and stirred for 1 h to obtain a sodium ion conductor dispersion; 6 mol of γ-methacryloxypropyltrimethoxysilane coupling agent of formula (A-1) was added to 1500 mL of aqueous tetrahydrofuran and hydrolyzed at 50 °C for 2 h to obtain a diluted silane coupling agent solution.

[0083] The remaining steps are consistent with those in Example 1, and the modified sodium ion inorganic conductor a5 is prepared.

[0084] Preparation Example 6

[0085] The method was similar to that used in Example 1, except that the same molar amount of Na3PS4 was used instead of Na3Zr2Si2PO4. 12 Modified sodium ion inorganic conductor a6 was prepared.

[0086] The following examples illustrate the preparation of composite solid electrolytes:

[0087] Example 1

[0088] (1) At room temperature (25℃, the same below), 125g of sodium perchlorate and 50g of fluoroethylene carbonate were added to 1000ml of ethylene carbonate / propylene carbonate solution (volume ratio of 1:1) to prepare the basic electrolyte.

[0089] (2) At room temperature, 75g of modified sodium ion inorganic conductor a1 and 100g of polyethylene glycol diacrylate were placed in the above basic electrolyte and stirred for 1h. Then, 10g of azobisisobutyronitrile (solid) was added and heated to 70℃ for polymerization reaction. The reaction time was 10h to prepare composite solid electrolyte A1.

[0090] Example 2

[0091] (1) At room temperature, 120g of sodium perchlorate and 55g of fluoroethylene carbonate were added to 1000ml of ethylene carbonate / propylene carbonate solution (volume ratio 1:1.2) to prepare the basic electrolyte.

[0092] (2) At room temperature, 200g of modified sodium ion inorganic conductor a2 and 100g of polyethylene glycol diacrylate were placed in the above basic electrolyte and stirred for 2h. Then, 8g of azobisisobutyronitrile was added and heated to 65℃ for polymerization reaction. The reaction time was 12h to prepare composite solid electrolyte A2.

[0093] Example 3

[0094] (1) At room temperature, 125g of sodium perchlorate and 50g of fluoroethylene carbonate were added to 1000ml of ethylene carbonate / propylene carbonate solution (volume ratio 1:1.5) to prepare the basic electrolyte.

[0095] (2) At room temperature, 250g of modified sodium ion inorganic conductor a3 and 200g of polyethylene glycol diacrylate were placed in the above basic electrolyte and mixed and stirred for 1.5h. Then, 12g of azobisisobutyronitrile (solid) was added and heated to 75℃ for polymerization reaction. The reaction time was 10h to prepare composite solid electrolyte A3.

[0096] Example 4

[0097] Following a similar method to Example 1, except that the same weight of modified sodium ion inorganic conductor a4 was used to replace the modified sodium ion inorganic conductor a1 to prepare the composite solid electrolyte A4.

[0098] Example 5

[0099] Following a similar method to Example 1, except that the modified sodium ion inorganic conductor a1 was replaced with the same weight of modified sodium ion inorganic conductor a5, a composite solid electrolyte A5 was prepared.

[0100] Example 6

[0101] Following a similar method to Example 1, except that the same weight of modified sodium ion inorganic conductor a6 was used to replace the modified sodium ion inorganic conductor a1 to prepare the composite solid electrolyte A6.

[0102] Example 7

[0103] The composite solid electrolyte A7 was prepared by following a similar method to Example 1, except that 6.5g of polyethylene glycol diacrylate was used instead of 100g of polyethylene glycol diacrylate.

[0104] Example 8

[0105] Following a similar method to Example 1, except that 230g of polyethylene glycol diacrylate was used instead of 100g of polyethylene glycol diacrylate, composite solid electrolyte A8 was prepared.

[0106] Example 9

[0107] Following a similar method to Example 1, except that the same weight of dipentaerythritol pentyl / hexyl acrylic acid was used to replace polyethylene glycol diacrylate to prepare the composite solid electrolyte A9.

[0108] Example 10

[0109] Following a similar method to Example 1, except that benzoyl peroxide was used instead of azobisisobutyronitrile in the same weight proportions, a composite solid electrolyte A10 was prepared.

[0110] Comparative Example 1

[0111] The method is similar to that in Example 1, except that the same weight parts of sodium ion inorganic conductor Na3Zr2Si2PO are used. 12 A composite solid electrolyte B1 was prepared by replacing the modified sodium ion inorganic conductor a1.

[0112] Test Example 1

[0113] The ionic conductivity of the composite solid electrolytes A1-A10 and B1 prepared in Examples 1-10 and Comparative Example 1 was tested, and the test results are shown in Table 1.

[0114] Test Example 2

[0115] With NaNi 0.33 Fe 0.33 Mn 0.33 O2 is the positive electrode material, hard carbon is the negative electrode, and polypropylene membrane is the separator. After slurry preparation, coating, winding, and baking at 100°C for 10 hours, it is assembled with the composite solid electrolytes A1-A10 and B1 prepared in Examples 1-10 and Comparative Example 1 to prepare sodium-ion batteries S1-S10 and DS1. Cyclic tests were then performed on them, and the test results are shown in Table 2.

[0116] The positive electrode consists of: 95 wt% positive electrode material; 2 wt% positive electrode binder PVDF (polyvinylidene fluoride); and 3 wt% positive electrode conductive agent conductive carbon black. The negative electrode consists of: 97 wt% hard carbon; 1 wt% negative electrode binder SBR (styrene-butadiene rubber); and 2 wt% negative electrode conductive agent conductive carbon black.

[0117] Test method:

[0118] 1. Ionic conductivity: The bulk resistance of the solid electrolyte is measured using the electrochemical impedance spectroscopy method, and then the ionic conductivity is calculated according to the formula: Ionic conductivity = Solid electrolyte thickness / (Bulk resistance × Solid electrolyte area);

[0119] 2. Cyclic performance: After assembling the aforementioned battery, it is cycled once at a rate of 0.1C, and then the battery is cycled at a constant rate of 0.2C.

[0120] Table 1

[0121]

[0122]

[0123] Table 2

[0124]

[0125] As can be seen from the results in Table 1, compared with Comparative Example 1, the composite solid electrolytes prepared in Examples 1-10 of this application have an ionic conductivity of not less than 7 × 10⁻⁶. -5 S cm -1 The solid-state batteries prepared have an initial coulombic efficiency of no less than 80% and a capacity retention of no less than 80% after 100 cycles. In particular, the composite solid electrolytes and solid-state batteries prepared in Examples 1-3 have excellent ionic conductivity and cycle performance.

[0126] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A modified sodium ion inorganic conductor, characterized in that, It includes a sodium ion inorganic conductor and silicon-containing groups grafted onto the surface of the sodium ion inorganic conductor; the silicon-containing groups are provided by a silane coupling agent with the structure shown in formula (A); Formula (A): Among them, R1, R2, and R3 are each independently selected from C0-C 10 Alkylenes; R4, R5, and R6 are each independently selected from C1-C6. 10 alkoxy or H; R7 is selected from C2-C8 hydrocarbon groups containing carbon-carbon double bonds or -R8-OC(O)-R9; R8 is selected from C0-C 10 Alkylene; R9 is selected from C2-C containing a carbon-carbon double bond. 10 Hydrocarbon group.

2. The modified sodium ion inorganic conductor according to claim 1, wherein, In the structure shown in formula (A), R1, R2, and R3 are each independently selected from C0-C6 alkylene groups; R4, R5, and R6 are each independently selected from C1-C6 alkoxy groups or H groups; R7 is selected from C2-C6 hydrocarbon groups containing carbon-carbon double bonds or -R8-OC(O)-R9; R8 is selected from C0-C6 alkylene groups; and R9 is selected from C2-C6 alkenyl groups. Preferably, R1, R2, and R3 are each independently selected from C0 alkylene groups, -CH2-, -CH2-CH2-, -CH2-CH2-CH2-, -CH(CH3)-CH2-, -CH2-CH(CH3)-, -CH2-(CH2)2-CH2-, -C(CH3)2-CH2-, and -CH2-C(CH3)2-. R4, R5, and R6 are each independently selected from methoxy, ethoxy, -O-CH2-CH2-CH3, -O-CH(CH3)2, -O-CH2-CH2-CH2-CH3, -O-CH(CH3)-CH2-CH3, -O-CH2-CH(CH3)2, -O-(CH 2)4 -CH3, -O-CH(CH3)-CH2-CH2-CH3, -O-CH2-CH(CH3)-CH2-CH3 or H; R7 is selected from -CH=CH2, -CH=CH-CH3, -CH2-CH=CH2, -CH2-CH2-CH=CH2 Or -R8-CO-R9; R8 is selected from at least one of C0 alkylene, -CH2-, -CH2-CH2-, -CH2-CH2-CH2-, -CH(CH3)-CH2-, -CH2-CH(CH3)-, -CH2-(CH2)2-CH2-, -C(CH3)2-CH2- and -CH2-C(CH3)2-; R9 is selected from at least one of -CH=CH2, -CH=CH-CH3, -CH2-CH=CH2, -CH2-CH2-CH=CH2, -C(CH3)=CH2, -CH=C(CH3)-CH3, -CH2-C(CH3)=CH2, -CH(CH3)-CH2-CH=CH2 and -C(CH2CH3)=CH2, -CH=C(CH2CH3)-CH3, -CH2-C(CH2CH3)=CH2.

3. The modified sodium ion inorganic conductor according to claim 1 or 2, wherein, The silane coupling agent is selected from one or more compounds shown in the following formula; Equation (A-1): Equation (A-2): Equation (A-3): Equation (A-4): Equation (A-5): Equation (A-6): Formula (A-7): Equation (A-8):

4. The modified sodium ion inorganic conductor according to any one of claims 1-3, wherein, The sodium ion inorganic conductor is selected from Na3Zr2Si2PO4. 12 And / or Na3PS4.

5. A method for preparing a modified sodium-ion inorganic conductor according to any one of claims 1-4, wherein, The method includes: A sodium ion inorganic conductor is reacted with a silane coupling agent of the structure shown in Formula (A) to graft silicon-containing groups provided by the silane coupling agent of the structure shown in Formula (A) onto the surface of the sodium ion inorganic conductor, thereby obtaining the modified sodium ion inorganic conductor.

6. The preparation method according to claim 5, wherein, The molar ratio of the sodium ion inorganic conductor (based on Na element) to the silane coupling agent with the structure shown in formula (A) is 1:5-120, preferably 1:10-100.

7. The preparation method according to claim 5 or 6, wherein, The contact reaction is carried out in the presence of a solvent selected from at least one of tetrahydrofuran, 1,3-dioxolane, and 1,4-dioxane; Preferably, the amount of solvent used is 10wt%-70wt%, based on the total mass of the sodium ion inorganic conductor and the silane coupling agent with the structure shown in formula (A); Preferably, the conditions for the contact reaction include: a temperature of 10-100℃ and a time of 0.5-8h.

8. A composite solid electrolyte, wherein, The solid electrolyte comprises a crosslinked copolymer containing structural units provided by a modified sodium ion inorganic conductor and crosslinked structural units provided by a crosslinking agent containing unsaturated bonds; the modified sodium ion inorganic conductor is the modified sodium ion inorganic conductor as described in any one of claims 1-4.

9. The composite solid electrolyte according to claim 8, wherein, The crosslinking agent containing unsaturated bonds is selected from one or more of polyalkylene glycol diC3-C6 acrylate, diC3-C6 alkylene glycol diacrylate, and dipentaerythritol pent- / hexyl acrylate, preferably one or more of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, and dipentaerythritol pent- / hexyl acrylate; And / or, relative to the total weight of the crosslinking copolymer, the crosslinking agent containing unsaturated bonds provides 20-60 wt% of crosslinking structural units.

10. A method for preparing a composite solid electrolyte, wherein, The method includes: in the presence of an initiator, polymerizing the modified sodium ion inorganic conductor according to any one of claims 1-4 with a crosslinking agent containing unsaturated bonds to obtain the composite solid electrolyte.

11. The preparation method according to claim 10, wherein, The weight ratio of the modified sodium ion inorganic conductor to the crosslinking agent containing unsaturated bonds is 100:5-300, preferably 100:10-250; And / or, the initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, dodecyl peroxide and diisopropyl peroxide; And / or, based on the total mass of the modified sodium ion inorganic conductor and the crosslinking agent containing unsaturated bonds, the amount of the initiator is 1-10 wt%, preferably 2-8 wt%; And / or, the conditions for the polymerization reaction include: a temperature of 60-90°C and a time of 6-30 h.

12. A composite solid electrolyte prepared by the preparation method according to claim 10 or 11.

13. A solid-state battery, wherein, The battery includes the composite solid electrolyte as described in any one of claims 8-9 and 12.

Images