Composite material for preparing solid electrolyte and preparation method for composite material, preparation method for solid electrolyte, and lithium-ion battery

Abstract

The present application relates to the technical field of lithium-ion batteries, and discloses a composite material and a preparation method therefor, and a preparation method for a solid electrolyte. The composite material comprises 100 parts of solid electrolyte powder and 0.1 parts to 15 parts of an active monomer. An active monomer is added to the composite material, thereby improving the tensile strength of a green membrane. Moreover, the solid electrolyte obtained by sintering the green membrane has high density.

Description

Composite material for preparing solid-state electrolyte and preparation method, preparation method of solid-state electrolyte and lithium ion battery

[0001] This application claims priority to the Chinese patent application No. 202411321199.8 filed on September 20, 2024 to the Chinese Patent Office, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of batteries, in particular to a composite material for preparing a solid-state electrolyte and a preparation method thereof, a preparation method of the solid-state electrolyte and a lithium ion battery having the solid-state electrolyte. BACKGROUND

[0003] At present, lithium ion batteries have become one of the most important energy storage devices in people's daily life because of their long cycle life, high energy density and other advantages. In recent years, with the rapid development of electric vehicles, higher requirements have been put forward for the energy density and safety performance of batteries. All-solid-state lithium metal batteries replace flammable liquid electrolyte with solid-state electrolyte, and use metal lithium with higher theoretical specific capacity as the negative electrode, which has the advantages of high safety and high energy density, so it is of great significance to study all-solid-state lithium metal batteries.

[0004] Solid-state electrolyte is a core component of all-solid-state lithium metal batteries, which needs to meet the requirements of low preparation temperature, high ionic conductivity and high mechanical strength, and at the same time, inhibit lithium dendrites and maintain long-term stable cycling of the battery while ensuring the rapid migration of lithium ions between the positive and negative electrodes.

[0005] The common solid-state electrolytes at present include oxide solid-state electrolyte, sulfide solid-state electrolyte, composite solid-state electrolyte and emerging halide solid-state electrolyte, etc. Oxide solid-state electrolyte is widely studied as a material with high ionic conductivity, stable structure, simple synthesis process and no toxicity and pollution. Among many solid-state electrolytes, Li7La3Zr2O 12 (LLZO) with garnet structure has attracted much attention because of its high conductivity and good electrochemical stability.

[0006] The solid-state electrolyte film is generally prepared by tape casting. First, the powder (such as nano-LLZO powder) is mixed with an organic plasticizer solution in a proper ratio to form a slurry with a certain viscosity. The slurry flows from the container and is coated on a special base tape with a certain thickness by a scraper. After drying and solidification, the green tape is peeled off to form a green tape film. Then, according to the size and shape of the finished product, the green tape is processed by punching, laminating and other processing to form the sintered blank product.

[0007] However, the green body film prepared by the existing nano-LLZO powder has the problem of insufficient tensile strength, resulting in poor processability. In the related art, a high content of polymer binder is generally added to the slurry to improve the tensile strength of the green body film, but the addition of the polymer binder will cause the problem of poor density of the green body film after sintering, thereby causing poor cycle performance of the battery. Therefore, it is an urgent problem to be solved in the industry to improve the tensile strength of the ceramic electrolyte green body film while making the sintered solid-state electrolyte have high density. TECHNICAL PROBLEM TECHNICAL SOLUTION

[0008] Therefore, the first aspect of the present application provides a composite material for preparing a solid-state electrolyte. The green body film prepared from the composite material has high tensile strength, and the solid-state electrolyte obtained after sintering has high density.

[0009] In a first aspect, a composite material for preparing a solid-state electrolyte includes, by mass fraction:

[0010] 100 parts of solid-state electrolyte powder;

[0011] 0.1 to 15 parts of active monomer, the active monomer including at least one of methyl acrylate and methyl methacrylate;

[0012] The chemical formula of the solid-state electrolyte powder is Li 7-x La3Zr 2-x Ta x O 12 , 0≤x≤1, and the active monomer is at least partially dispersed on the surface of the solid-state electrolyte powder.

[0013] In some embodiments of the present application, the composite material further includes an organic solvent, and the mass fraction of the organic solvent is 100 to 200 parts;

[0014] And / or, the composite material further includes an initiator, and the mass ratio of the initiator to the active monomer is 0.1% to 2%;

[0015] And / or, the solid-state electrolyte powder includes at least one of LLZO and LLZTO;

[0016] And / or, the particle size of the solid-state electrolyte powder is 100 to 2000 nm.

[0017] In some embodiments of the present application, the mass fraction of the MMA is 3 to 8 parts;

[0018] And / or, the mass fraction of the organic solvent is 150 to 180 parts.

[0019] In some embodiments of the present application, the composite material further comprises a dispersant, the mass fraction of the dispersant being 0.5 parts to 10 parts; and / or

[0020] The mass fraction of the active monomer is 5 parts to 8 parts; and / or

[0021] The composite material further comprises a plasticizer, the mass fraction of the plasticizer being 3 parts to 15 parts.

[0022] In some embodiments of the present application, the dispersant comprises at least one of glyceryl trioleate, triethanolamine, and fish oil; and / or

[0023] The initiator comprises at least one of BPO and AIBN; and / or

[0024] The plasticizer comprises at least one of polyethylene glycol, butyl benzyl phthalate, and dioctyl terephthalate; and / or

[0025] The organic solvent comprises at least one of ethyl acetate, butyl acetate, dichloroethane, and ethanol; and / or

[0026] The mass fraction of the plasticizer is 3 parts to 8 parts.

[0027] The second aspect of the present application provides a preparation method of a composite material, the preparation method comprising:

[0028] configuring a first mixture comprising solid-state electrolyte powder and an organic solvent according to a preset proportion;

[0029] adding an active monomer to the first mixture to obtain the composite material

[0030] The active monomer comprises at least one of methyl acrylate and methyl methacrylate; the chemical formula of the solid-state electrolyte powder is Li 7-x La3Zr 2-x Ta x O 12 , 0≤x≤1.

[0031] In some embodiments of the present application, the step of preparing the first mixture comprises weighing the solid-state electrolyte powder, the organic solvent, and a dispersant according to a preset proportion, adding them into a ball mill tank for ball milling to obtain the first mixture; and / or

[0032] Before obtaining the composite material, the preparation method further comprises adding a plasticizer to the first mixture; and / or

[0033] Before obtaining the composite material, the preparation method further comprises adding an initiator to the first mixture.

[0034] The third aspect of the present application provides a preparation method of a solid-state electrolyte, comprising the following steps:

[0035] A composite material is provided, which comprises, in terms of mass fraction: 100 parts of solid-state electrolyte powder; 100-200 parts of organic solvent; 0.1-15 parts of active monomer; and initiator, the mass fraction of the initiator being 0.1%-5% of the active monomer; wherein the active monomer comprises at least one of methyl acrylate and methyl methacrylate; and the chemical formula of the solid-state electrolyte powder is Li 7-x La3Zr 2-x Ta x O 12 , 0≤x≤1;

[0036] The composite material is coated on a substrate to obtain a wet film with solvent;

[0037] The wet film is subjected to drying treatment to obtain a film piece after drying treatment;

[0038] The active monomer in the dried film piece is subjected to in-situ solidification under a saturated steam environment of the active monomer to obtain a green body;

[0039] The green body is heated to a preset temperature for degassing to obtain a pre-sintered body;

[0040] The pre-sintered body is sintered to obtain a solid-state electrolyte.

[0041] In some embodiments of the present application, the heating temperature in the degassing stage is 350-500 DEG C; and / or

[0042] The sintering temperature is 1000-1300 DEG C; and / or

[0043] The temperature in the drying treatment is 20-50 DEG C; and / or

[0044] The heating temperature in the in-situ solidification is 65-85 DEG C, and the time of the in-situ solidification is 1H-10H. Advantages

[0045] The embodiments of the present application add a specific content of methyl acrylate and / or methyl methacrylate in the composite material, thereby improving the tensile strength of the green body film, and the solid-state electrolyte obtained after sintering of the green body film has high density. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments will be briefly introduced. Obviously, the drawings in the following description only represent some of the embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort.

[0047] Fig. 1 is a scanning electron microscope image of the solid-state electrolyte prepared in Example 1 of the present application.

[0048] Fig. 2 is a scanning electron microscope image of the solid-state electrolyte prepared in Comparative Example 1 of the present application. Embodiments of the present application

[0049] The technical solutions in the embodiments of the present application will be described clearly and completely in the following description with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments only represent some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort fall within the scope of the present application. In addition, it should be understood that the specific embodiments described herein are only for the purpose of illustration and explanation of the present application, and are not intended to limit the present application.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0051] In the present application, the orientation words such as "upper" and "lower" refer to the upper and lower positions of the device in the actual use or working state, and specifically refer to the directions of the drawings in the drawings; and "inner" and "outer" refer to the outline of the device. In addition, in the description of the present application, the term "comprising" means "including but not limited to". The terms first, second, third, etc. are only used as labels and do not impose numerical requirements or establish sequences.

[0052] In the present application, "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B, which can represent the following cases: A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural.

[0053] In the present application, "at least one" means one or more, and "multiple" means two or more. "One or more", "at least one of the following (one)", or the like, means any combination of these items, including a single item or any combination of multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can mean a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, where a, b, and c can be a single item or multiple items.

[0054] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is merely for the sake of convenience and brevity, and should not be construed as a hard limit on the scope of the present application; therefore, it should be considered that the described range has been 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 range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fraction or integer) within the indicated range.

[0055] At present, lithium ion batteries have become one of the most important energy storage devices in people's daily life because of their long cycle life, high energy density and other advantages. In recent years, with the rapid development of electric vehicles, higher requirements for the energy density and safety performance of batteries have been put forward. The all-solid-state lithium metal battery replaces the flammable liquid electrolyte with a solid-state electrolyte, and uses metal lithium with higher theoretical specific capacity as the negative electrode, which has the advantages of high safety and high energy density, so it is of great significance to study the all-solid-state lithium metal battery.

[0056] Solid-state electrolyte is a core component of all-solid-state lithium metal battery, which needs to meet the requirements of low preparation temperature, high ionic conductivity and high mechanical strength, and at the same time, inhibit lithium dendrites and maintain long-term stable cycle of the battery while ensuring fast migration of lithium ions between positive and negative electrodes.

[0057] The common solid-state electrolytes at present include oxide solid-state electrolyte, sulfide solid-state electrolyte, composite solid-state electrolyte and emerging halide solid-state electrolyte, etc. Oxide solid-state electrolyte is widely studied as a material with high ionic conductivity, stable structure, simple synthesis process, non-toxic and non-polluting. Among many solid-state electrolytes, Li7La3Zr2O 12 (LLZO) with garnet structure has attracted much attention because of its high conductivity and good electrochemical stability.

[0058] The solid electrolyte film is generally prepared by a casting method. First, the powder (e.g., nano-LLZO powder) is mixed with an organic plasticizer solution in a proper ratio to form a slurry with a certain viscosity. The slurry flows from a container and is coated on a special base strip by a doctor blade at a certain thickness. After drying and solidification, the green tape film is peeled off from the top. Then, according to the size and shape of the finished product, the green tape is processed by punching, lamination, etc. to form the sintered blank product.

[0059] However, the green film prepared from the existing nano-LLZO powder has the problem of insufficient tensile strength, resulting in poor processability. In the related art, a high content of polymer binder is generally added to the slurry to improve the tensile strength of the green film, but this will cause the sintered LLZO to have poor density, thereby causing poor cycle performance of the battery.

[0060] Therefore, the first aspect of the embodiments of the present application provides a composite material for preparing a solid electrolyte, which comprises, in terms of mass fraction:

[0061] 100 parts of solid electrolyte;

[0062] 0.1 to 15 parts of active monomer, wherein the active monomer comprises at least one of methyl acrylate and methyl methacrylate;

[0063] wherein the chemical formula of the solid electrolyte is Li 7-x La3Zr 2-x Ta x O 12 , 0≤x≤1, and the active monomer is at least partially dispersed on the surface of the solid electrolyte.

[0064] The embodiments of the present application add a certain amount of methyl acrylate and / or methyl methacrylate (i.e., MMA) to the composite material, thereby preparing a green film with high tensile strength, and the solid electrolyte obtained after sintering the green film has high density.

[0065] For example, the mass fraction of the active monomer in the composite material is 0.1 parts, 0.5 parts, 1 part, 1.5 parts, 2.0 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts, 10 parts, 10.5 parts, 11 parts, 11.5 parts, 12 parts, 12.5 parts, 13 parts, 13.5 parts, 14 parts, 14.5 parts, 15 parts, or any range value between any two of the above values.

[0066] It should be noted that if the mass fraction of the active monomer in the composite material is too low, for example, less than 0.1 part, the tensile strength of the prepared solid electrolyte green body is not obviously improved. If the mass fraction of the active monomer in the composite material is too high, for example, higher than 15 parts, the tensile strength of the prepared solid electrolyte green body is higher, but the density of the green body film after sintering will be correspondingly reduced.

[0067] In some embodiments of the present application, the solid electrolyte comprises at least one of LLZO and LLZTO (i.e., Ta-doped LLZO).

[0068] In some embodiments of the present application, the active monomer:solid electrolyte is (3 to 8):100, and further, the active monomer:solid electrolyte is (5 to 8):100. In this embodiment, by controlling the content of the active monomer in the composite material, the tensile strength of the green body film is above 6.5 MPa, and the density of the solid electrolyte obtained after sintering is above 96%. In some embodiments of the present application, x is 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.99, and any value between the aforementioned two values.

[0069] In some embodiments of the present application, the particle size (D50) of the solid electrolyte is 100 nm to 2000 nm. Further, the particle size (D50) of the solid electrolyte is 100 nm to 500 nm. Exemplarily, the particle size of the solid electrolyte is 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, 1600 nm, 1700 nm, 1800 nm, 1900 nm, 2000 nm. It can be understood that when the particle size of the solid electrolyte is lower, the tensile strength of the obtained green body film is better, and the density of the solid electrolyte obtained after sintering is higher.

[0070] In some embodiments of the present application, the composite material further comprises an organic solvent, and the mass fraction of the organic solvent is 100 parts to 200 parts.

[0071] It should be noted that the specific type of the organic solvent in the present application is not limited, and the organic solvent only needs to meet the requirements of powder stability and the ability to dissolve other components in the composite material. Exemplarily, the solvent comprises at least one of ethyl acetate, butyl acetate, dichloroethane, and ethanol. For example, in some embodiments of the present application, the solvent is ethyl acetate. For another example, in some other embodiments of the present application, the solvent is a mixed solvent of ethyl acetate and ethanol.

[0072] Exemplarily, the mass fraction of the organic solvent in the composite material is 100 parts, 110 parts, 120 parts, 130 parts, 140 parts, 150 parts, 160 parts, 170 parts, 180 parts, 190 parts, 200 parts, and any value between any two of the aforementioned values.

[0073] In some embodiments of the present application, the composite material further comprises an initiator, and the mass fraction of the organic solvent is 0.1 parts to 2 parts.

[0074] It should be noted that the specific type of initiator in the present application is not limited, and the initiator needs to meet the condition of being able to promote the polymerization reaction of the active monomer under certain conditions. Exemplarily, the initiator includes at least one of dibenzoyl peroxide (BPO) and AIBN.

[0075] In some embodiments of the present application, in the composite material, the mass ratio of the initiator to the active monomer is (0.1 to 2): 100, that is, the amount of the initiator is 0.1% to 2% of the amount of the active monomer. Exemplarily, the mass ratio of the initiator to the active monomer is 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.6%, 1.8%, 2%, and any value between any two of the aforementioned values.

[0076] In some embodiments of the present application, the composite material further comprises a dispersant, and the mass ratio of the dispersant to the solid-state electrolyte is (0.5 to 10): 100. Exemplarily, the mass ratio of the dispersant to the solid-state electrolyte is 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, and any value between any two of the aforementioned values.

[0077] It should be noted that the dispersant in the present application is used to improve the dispersibility and stability of the solid-state electrolyte in the solvent. Exemplarily, the dispersant includes but is not limited to at least one of glyceryl trioleate, triethanolamine, and fish oil (such as herring oil).

[0078] In some embodiments of the present application, the composite material further comprises a plasticizer, and the mass ratio of the plasticizer to the solid-state electrolyte is (3 to 15): 100. Exemplarily, the mass ratio of the plasticizer to the solid-state electrolyte is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, and any value between any two of the aforementioned values.

[0079] It should be noted that the plasticizer in the present application is used to improve the flexibility of the green film, and the specific type is not limited. Exemplarily, the plasticizer includes but is not limited to at least one of polyethylene glycol (such as PEG300), butyl benzyl phthalate, dioctyl terephthalate.

[0080] In some embodiments of the present application, the composite material includes a solid-state electrolyte, a solvent, an active monomer, an initiator, a dispersant and a plasticizer, and the mass ratio of the solid-state electrolyte powder: the organic solvent: the dispersant: the active monomer: the plasticizer is 100:(100-200):(0.5-10):(2-15):(3-15), and the mass ratio of the initiator to the active monomer is 0.1%-0.5%.

[0081] In some embodiments of the present application, the composite material is composed of a solid-state electrolyte, an organic solvent, an active monomer, an initiator, a dispersant and a plasticizer.

[0082] The second aspect of the present application provides a preparation method of a composite material for preparing a solid-state electrolyte, including the following steps:

[0083] S10 configures a first mixture including a solid-state electrolyte and an organic solvent according to a preset ratio.

[0084] Specifically, the LLZO or LLZTO powder, the organic solvent and the dispersant are weighed according to a preset ratio and added into a ball mill tank for ball milling to obtain the first mixture. In the first mixture, the mass ratio of the LLZO powder: the solvent: the dispersant is 100:(100-200):(2-10).

[0085] Further, before the ball milling treatment, the ball mill tank is sealed.

[0086] Further, the ball milling process includes a first ball milling treatment and a second ball milling treatment. The ball milling speed of the first ball milling treatment is 450 rpm-550 rpm, and exemplarily, the ball milling speed is 450 rpm, 460 rpm, 470 rpm, 480 rpm, 490 rpm, 500 rpm, 510 rpm, 520 rpm, 530 rpm, 540 rpm, 550 rpm and any value between any two of the foregoing values.

[0087] Further, the ball milling time of the first ball milling treatment is 1.5H-3H. Exemplarily, the ball milling time is 1.5H, 2H, 2.5H, 3H and any value between any two of the foregoing values.

[0088] Further, the ball milling speed of the second ball milling treatment is 200 rpm to 350 rpm. Illustratively, the ball milling speed is 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, 250 rpm, 260 rpm, 270 rpm, 280 rpm, 290 rpm, 300 rpm, 310 rpm, 320 rpm, 330 rpm, 340 rpm, 350 rpm, and any value between any two of the aforementioned values.

[0089] Further, the ball milling time of the second ball milling treatment is 5H to 15H. Illustratively, the ball milling time is 5H, 6H, 7H, 8H, 9H, 10H, 11H, 12H, 13H, 14H, 15H, and any value between any two of the aforementioned values.

[0090] S20 adding a certain amount of active monomer to the first mixture to obtain a second mixture.

[0091] Specifically, the active monomer and the plasticizer are added to the first mixture, and the second mixture is obtained by a third ball milling treatment. Illustratively, 0.1 to 15 parts of the active monomer and 3 to 15 parts of the plasticizer are added by mass ratio. It can be understood that the ball milling tank needs to be opened before adding MMA to the first mixture, and the ball milling tank is sealed before the third ball milling treatment after the addition is completed.

[0092] Further, the ball milling speed of the third ball milling treatment is 200 rpm to 350 rpm. Illustratively, the ball milling speed is 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, 250 rpm, 260 rpm, 270 rpm, 280 rpm, 290 rpm, 300 rpm, 310 rpm, 320 rpm, 330 rpm, 340 rpm, 350 rpm, and any value between any two of the aforementioned values.

[0093] Further, the ball milling time of the third ball milling treatment is 0.5H to 5H. Illustratively, the ball milling time is 0.5H, 1H, 1.5H, 2H, 2.5H, 3H, 3.5H, 4H, 4.5H, 5H, and any value between any two of the aforementioned values.

[0094] S30 adding a certain amount of initiator to the second mixture to obtain the composite material.

[0095] Specifically, the initiator is added to the second mixture, and the composite material is obtained by a fourth ball milling treatment.

[0096] Further, the amount of the initiator added is 0.01 part to 0.75 part. Further, the mass ratio of the amount of the initiator added to the active monomer is 0.1% to 5%.

[0097] Further, the ball milling speed of the fourth ball milling treatment is 200 rpm to 300 rpm. Illustratively, the ball milling speed is 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, 250 rpm, 260 rpm, 270 rpm, 280 rpm, 290 rpm, 300 rpm, and any value between any two of the aforementioned values.

[0098] Further, the ball milling time of the third ball milling treatment is 0.5H to 2H. Illustratively, the ball milling time is 0.5H, 1H, 1.5H, 2H, and any value between any two of the aforementioned values.

[0099] Specifically, the preparation of the composite material described above is performed at room temperature.

[0100] It should be noted that the LLZO powder in the present application includes doped or undoped LLZO powder. Illustratively, the doped LLZO powder includes nano LLZTO powder (i.e., Ta-doped LLZO). Specifically, the chemical formula of the nano LLZTO powder is Li 7-x La3Zr 2-x Ta x O 12 , wherein 0 < x < 1.

[0101] In some embodiments of the present application, x is 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.99, and any value between any two of the aforementioned values.

[0102] In some embodiments of the present application, the particle size (D50) of the solid-state electrolyte is 100 nm to 2000 nm.

[0103] It should be noted that the specific type of solvent in the present application is not limited, and the solvent needs to meet the requirements of powder stability and the ability to dissolve other components in the composite material. Illustratively, the solvent includes at least one of ethyl acetate, butyl acetate, dichloroethane, and ethanol. For example, in some embodiments of the present application, the solvent is ethyl acetate. For another example, in some other embodiments of the present application, the solvent is a mixed solvent of ethyl acetate and ethanol.

[0104] Illustratively, the mass fraction of the solvent in the composite material is 100 parts, 110 parts, 120 parts, 130 parts, 140 parts, 150 parts, 160 parts, 170 parts, 180 parts, 190 parts, 200 parts, and any value between any two of the aforementioned values.

[0105] It should be noted that the specific type of initiator in the present application is not limited, and the initiator needs to meet the condition of being able to promote the polymerization reaction of the active monomer under certain conditions. Illustratively, the initiator includes dibenzoyl peroxide (BPO). The mass fraction of the initiator in the composite material is 0.01 parts, 0.05 parts, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts, 0.5 parts, 0.55 parts, 0.6 parts, 0.65 parts, 0.7 parts, 0.75 parts, and any value between the aforementioned two values.

[0106] It should be noted that the dispersant in the present application is used to improve the dispersibility and stability of the solid-state electrolyte in the solvent. The type of dispersant in the present application is not specifically limited, and illustratively, the dispersant includes but is not limited to at least one of glyceryl trioleate, triethanolamine, and herring oil.

[0107] It should be noted that the plasticizer in the present application is used to improve the flexibility of the green membrane, and its specific type is not limited. Illustratively, the plasticizer includes but is not limited to at least one of polyethylene glycol (such as PEG300), butyl benzyl phthalate, and dioctyl terephthalate.

[0108] In some embodiments of the present application, the composite material includes a solid-state electrolyte, a solvent, an active monomer, an initiator, a dispersant, and a plasticizer. In terms of mass ratio, the solid-state electrolyte: the solvent: the dispersant: the active monomer: the plasticizer is 100:(100 to 200):(0.1 to 10):(2 to 15):(3 to 15), and the mass ratio of the initiator to the active monomer is 0.1% to 0.5%.

[0109] In some embodiments of the present application, the dispersant is fish oil, and the plasticizer is PEG. This embodiment can complete the degassing at a lower temperature.

[0110] The third aspect of the embodiments of the present application provides a preparation method of a solid-state electrolyte, including the following steps:

[0111] S100 provides a composite material.

[0112] Specifically, the composite material includes 100 parts of solid-state electrolyte powder, 100 to 200 parts of solvent, 0.1 to 15 parts of active monomer, and 0.1% to 2% of the active monomer in terms of mass fraction. The specific composition and preparation of the composite material can be referred to the foregoing, and will not be repeated here.

[0113] S200 coats the composite material on a substrate to prepare a wet film with solvent.

[0114] Specifically, the wet film is prepared by a casting machine. The casting thickness is 1000-2000 μm, and the casting speed is 0.2 m / min. It should be noted that the preparation of the composite material by the casting machine to prepare the wet film is not the main improvement point of the present application, and will not be further described herein.

[0115] Exemplarily, the substrate is a PET film.

[0116] S300 carries out drying treatment on the wet film to obtain a dried film.

[0117] Specifically, the wet film can be dried at a low temperature to obtain a dry film. The drying temperature is 40-50 °C, and the drying time is 5-15 min.

[0118] S400 causes in-situ curing of the active monomer in the dried film in a saturated vapor environment of the active monomer to obtain a green body.

[0119] Specifically, a small amount of active monomer liquid is first placed in an oven to make the oven reach the saturated vapor pressure of the active monomer. Then, the dried film is placed in the oven and heated at 70-85 °C for 2-4 h to cause in-situ thermal polymerization of the active monomer in the film.

[0120] S500 heats the green body to a preset temperature to perform degassing to obtain a pre-sintered body.

[0121] It should be noted that the step is used to remove the organic components in the green body. The degassing can be performed in air or a protective gas.

[0122] Specifically, the degassing temperature is 350-500 °C, and further 350-450 °C. The degassing temperature needs to be determined according to the types of the dispersant, the binder, and the plasticizer.

[0123] Taking the dispersant as fish oil and the plasticizer as PEG as an example, the degassing process can be as follows: heating from room temperature to 450 °C at a rate of 0.5 °C / min, then maintaining the temperature for 2 h, and then naturally cooling to room temperature.

[0124] S600 sintering the pre-sintered body to obtain a solid-state electrolyte.

[0125] Specifically, the pre-sintered body (i.e., the body after degassing) can be sintered at 1000-1300 °C to obtain a solid-state electrolyte.

[0126] Exemplarily, the body after degassing is placed in a tube furnace, heated to 1200 °C at a rate of 10 °C / min, maintained at 1200 °C for 2 h, cooled to 500 °C at a rate of 5 °C / min, and then naturally cooled. The whole process is performed under argon protection.

[0127] For the sake of better understanding, the application will be further described below in connection with specific examples.

[0128] Example 1

[0129] (1) Preparation of composite material

[0130] The nano-LLZTO powder, solvent and dispersant were weighed according to the mass ratio of 100:150:1. The solvent was ethyl acetate, and the dispersant was glyceryl trioleate. The weighed powder, solvent and dispersant were added to the ball mill tank, and the ball mill tank was sealed. First, the ball mill was carried out at a speed of 500 rpm for 2H, and then the ball mill speed was reduced to 300 rpm for 10H to obtain the first composite material (i.e., the first mixture).

[0131] The active monomer MMA and the plasticizer polyethylene glycol (PEG300) were added to the first composite material, and the mass of MMA was 5% of the mass of the LLZTO powder, and the mass of PEG300 was 5% of the mass of the LLZTO powder. The ball mill tank was sealed, and the ball mill speed was 300 rpm for 2H to obtain the second composite material (i.e., the second mixture).

[0132] The initiator (dibenzoyl peroxide (BPO)) was added to the second composite material, and the mass of BPO was 0.5% of the mass of MMA. After sealing the ball mill tank, the ball mill was continued at a speed of 250 rpm for 1H to obtain the target composite material.

[0133] The target composite material is a composite material for flow casting, and in the target composite material, the mass ratio of LLZTO powder: solvent: dispersant: binder: plasticizer: initiator is 100:150:1:5:5:0.025.

[0134] (2) Preparation of green body

[0135] The prepared target composite material was placed in a flow casting machine for flow casting to obtain a wet film. The flow casting parameters were: flow casting thickness 1000 μm, flow casting speed 0.2 m / min. The flow casting substrate was a PET film. Then, drying treatment was carried out at 50°C for 10 min to remove the solvent in the wet film, and a film piece after drying treatment was obtained. Then, the film piece after drying treatment was placed in a saturated steam environment with MMA and heated at 80°C for 3H for in-situ curing to obtain a green body.

[0136] (3) Preparation of solid electrolyte

[0137] The prepared green body was degreased, and the degreasing process was carried out in an air atmosphere, specifically: 0.5°C / min from room temperature to 450°C, then 2h, then natural cooling to room temperature. The degreased embryo was placed in a tube furnace, heated to 1200°C at 10°C / min, kept for 2h, cooled to 500°C at 5°C / min, and then naturally cooled to obtain a solid-state electrolyte.

[0138] Example 2

[0139] The difference from Example 1 is that the mass ratio of MMA to LLZTO powder in the composite material is 2%.

[0140] Example 3

[0141] The difference from Example 1 is that the mass ratio of MMA to LLZTO powder in the composite material is 3%.

[0142] Example 4

[0143] The difference from Example 1 is that the mass ratio of MMA to LLZTO powder in the composite material is 4%.

[0144] Example 5

[0145] The difference from Example 1 is that the mass ratio of MMA to LLZTO powder in the composite material is 6%.

[0146] Example 6

[0147] The difference from Example 1 is that the mass ratio of MMA to LLZTO powder in the composite material is 7%.

[0148] Example 7

[0149] The difference from Example 1 is that the mass ratio of MMA to LLZTO powder in the composite material is 8%.

[0150] Example 8

[0151] The difference from Example 1 is that the mass ratio of MMA to LLZTO powder in the composite material is 10%.

[0152] Example 9

[0153] The difference from Example 1 is that the mass ratio of MMA to LLZTO powder in the composite material is 12%.

[0154] Example 10

[0155] The difference from Example 1 is that the mass ratio of MMA to LLZTO powder in the composite material is 15%.

[0156] Example 11

[0157] The difference from Example 1 is that the amount of solvent added in the composite material is 100 parts, that is, LLZTO powder: solvent = 100: 100.

[0158] Example 12

[0159] The difference from Example 1 is that the amount of solvent added in the composite material is 100 parts, that is, LLZTO powder: solvent = 100: 200.

[0160] Example 13

[0161] The difference from Example 1 is that the amount of solvent added in the composite material is 100 parts, that is, LLZTO powder: solvent = 100: 120.

[0162] Example 14

[0163] The difference from Example 1 is that the amount of solvent added in the composite material is 100 parts, that is, LLZTO powder: solvent = 100: 180.

[0164] Example 15

[0165] The difference from Example 1 is that the mass ratio of plasticizer to LLZTO powder in the composite material is 3%.

[0166] Example 16

[0167] The difference from Example 1 is that the mass ratio of plasticizer to LLZTO powder in the composite material is 8%.

[0168] Example 17

[0169] The difference from Example 1 is that the mass ratio of plasticizer to LLZTO powder in the composite material is 15%.

[0170] Example 18

[0171] The difference from Example 1 is that the initiator in the composite material is AIBN.

[0172] Example 19

[0173] The difference from Example 1 is that the mass ratio of dispersant to LLZTO powder in the composite material is 0.5%.

[0174] Example 20

[0175] The difference from Example 1 is that the mass ratio of dispersant to LLZTO powder in the composite material is 5%.

[0176] Example 21

[0177] The difference from Example 1 is that both the glue removal process and the sintering process are completed under an inert atmosphere (argon).

[0178] Comparative Example 1

[0179] The difference from Example 1 is that the adhesive in the composite is PMMA, and BPO is cancelled.

[0180] Comparative Example 2

[0181] The difference from Example 2 is that the adhesive in the composite is PMMA, and BPO is cancelled.

[0182] Comparative Example 3

[0183] The difference from Example 3 is that the adhesive in the composite is PMMA, and BPO is cancelled.

[0184] Comparative Example 4

[0185] The difference from Example 4 is that the adhesive in the composite is PMMA, and BPO is cancelled.

[0186] Comparative Example 5

[0187] The difference from Example 5 is that the adhesive in the composite is PMMA, and BPO is cancelled.

[0188] Comparative Example 6

[0189] The difference from Example 6 is that the adhesive in the composite is PMMA, and BPO is cancelled.

[0190] Comparative Example 7

[0191] The difference from Example 7 is that the adhesive in the composite is PMMA, and BPO is cancelled.

[0192] Comparative Example 8

[0193] The difference from Example 8 is that the adhesive in the composite is PMMA, and BPO is cancelled.

[0194] Comparative Example 9

[0195] The difference from Example 9 is that the adhesive in the composite is PMMA, and BPO is cancelled.

[0196] Comparative Example 10

[0197] The difference from Example 10 is that the adhesive in the composite is PMMA, and BPO is cancelled.

[0198] Comparative Example 11

[0199] The difference between it and Example 1 is that after drying the film, it is placed in an inert atmosphere and heated at 80°C for 3H to cure in situ to obtain the green body.

[0200] Application Examples 1 to 21 and Comparative Examples 1 to 11

[0201] The sintered solid-state electrolyte is polished to be smooth, with a thickness of 90-100 μm, then soaked in dilute hydrochloric acid for 30 seconds to remove surface impurities (such as Li2CO3, LiOH, etc.), then put into a glove box for standby. The polished LLZTO is assembled with a lithium foil negative electrode and a NCM811 positive electrode to form a battery, and a charge-discharge cycle test is performed.

[0202] Experimental test

[0203] Tensile strength test: The green body without the substrate (PET film) is made into a long strip sample with a length of 15 cm and a width of 1 cm, and the two ends of the strip are fixed on a tensile testing machine. The tensile force is applied by the jaws until it breaks. By testing the maximum tensile force during the breaking process, the tensile strength of the material can be obtained.

[0204] Sulfur carbon test: The working principle of the carbon sulfur analyzer is to oxidize the organic matter in the sample into CO, CO2, SO2, etc. at high temperature, and then use infrared or ultraviolet spectroscopy technology to detect and analyze it, and calculate the carbon and sulfur element content in the sample.

[0205] Density test: electronic balance drainage method, using Archimedes principle, through the deduction and transformation of buoyancy and density calculation formula to form the equation, first use high-precision electronic analytical balance to calculate the weight of the sample in air (W1) and in water (W2), and calculate the value of W1-W2, the density of water is defaulted as ρ = 1 g / cm 3 , through the equation Vsample = Vdrainage, the density value of the sample can be calculated: ρ = W1 / (W1-W2)*ρwater, which is the solid calculation formula.

[0206] Cycling performance test: the solid-state electrolyte after cooling was polished to make its surface flat. The LLZTO negative electrode side was evaporated with nano-silver (thickness 300 nm) under the condition of 50 A, 50 s. The LLZTO and lithium foil after evaporation were put into an atmosphere furnace for hot pressing, the temperature was 250℃, the pressure was 10 MPa, and the pressure was maintained for 10 minutes to ensure that the lithium foil and the LLZTO were tightly attached. The LLZTO with single-sided silver-plated nickel and lithium foil was assembled into a battery with NCM811 positive electrode for charge-discharge cycling test. The test conditions were: positive electrode load 17.2 mg / cm 2 After activation, the first specific capacity was 183.5 mAh / g, the charge was 0.33 C, the discharge was 0.5 C, and the charge-discharge interval was 3V-4.2V. The cycle number when the capacity decreased to 80% of the first cycle capacity was recorded to characterize the cycling performance of the battery.

[0207] The green body, solid-state electrolyte and battery prepared by the examples and comparative examples were tested, and the test results are shown in FIG. 1, FIG. 2 and Table 1.

[0208] Table 1

[0209] FIG. 1 is a scanning electron microscope image of the cross section of the ceramic film prepared in Example 1, and FIG. 2 is a scanning electron microscope image of the cross section of the ceramic film prepared in Comparative Example 1. It can be seen that compared with FIG. 2, FIG. 1 has fewer gaps and uniform distribution, and higher density.

[0210] From the test results of Examples 1 to 10 and corresponding Comparative Examples 1 to 10, it can be seen that the green body prepared by adding MMA in the composite material has higher tensile strength, and after degassing, the carbon content is less, and after sintering, the ceramic film has higher density, and the prepared battery has better cycling performance.

[0211] From Examples 1 to 10 and the table, it can be seen that the content of MMA in the composite material has a great influence on the tensile strength of the green body. The more the content of MMA, the greater the tensile strength of the green body. However, the density of the ceramic film generally shows a trend of first increasing and then decreasing. When the mass ratio of the content of MMA in the composite material to the mass of the LLZO powder is 3% to 8%, the tensile strength of the obtained green body is above 6 MPa, and the minimum density of the ceramic film is close to 97%, and at the same time, the green body has high tensile strength and density, and the comprehensive performance is better.

[0212] As can be seen from Example 1, Example 11 to Example 14 and Table 1, the content of the solvent in the composite material also affects the tensile strength and density of the green body prepared, when the mass ratio of the solvent to the LLZTO powder in the composite material is greater than 150, the dispersion of the powder, the uniformity of the combination of the powder and the MMA, the tensile strength and the density of the green body prepared are improved, when the mass ratio of the solvent to the LLZTO powder in the composite material is greater than 180, the density of the ceramic film obtained is significantly reduced, when the mass ratio of the solvent to the LLZTO powder in the composite material is (150 to 180): 100, the tensile strength and the density of the green body are both high.

[0213] As can be seen from Example 1, Example 15 to Example 17 and Table 1, the content of the plasticizer in the composite material also affects the tensile strength and density of the green body prepared, when the content of the plasticizer in the composite material increases, the tensile strength and the density of the green body prepared are both first increased and then decreased, when the mass ratio of the plasticizer to the LLZTO powder in the composite material is 3% to 8%, the tensile strength of the green body is high, and the density of the ceramic film obtained is high.

[0214] As can be seen from Example 1, Comparative Example 11 and Table 1, the de-gassing and sintering process is carried out in a protective atmosphere, which is beneficial to improve the density of the ceramic film.

[0215] As can be seen from Example 1, Comparative Example 11 and Table 1, during the preparation of the green body, the reaction conditions of the in-situ curing greatly affect the tensile strength of the green body prepared and the density of the ceramic film. The possible reason is that, in the inert atmosphere environment, a large amount of MMA volatilizes during the in-situ curing reaction, so that the polymerized MMA in the green body is too little. In the inert atmosphere environment, the in-situ curing reaction in a small closed environment can improve the problem of the significant reduction of the tensile strength and the density of the ceramic film to a certain extent.

[0216] The technical solutions provided by the embodiments of the present application are described in detail above, and the principles and implementation modes of the present application are described by applying specific examples; the above description of the embodiments is only used to help understand the method and the core idea of the present application; meanwhile, according to the idea of the present application, the specific implementation modes and application ranges can be changed by those skilled in the art; in conclusion, the content of the description should not be understood as a limitation of the present application.

Claims

1. A composite material for preparing a solid-state electrolyte, comprising, in parts by mass: 100 parts of a solid-state electrolyte powder; 0.1 to 15 parts of an active monomer, the active monomer comprising at least one of methyl acrylate and methyl methacrylate; The chemical formula of the solid-state electrolyte powder is Li 7-x La3Zr 2-x Ta x O 12 , 0≤x≤1, and the active monomer is at least partially dispersed on the surface of the solid-state electrolyte powder.

2. The composite material of claim 1, wherein, the composite material further comprising an organic solvent, the organic solvent being in a mass fraction of 100 to 200 parts.

3. The composite material of claim 1, wherein, the composite material further comprising an initiator, the mass ratio of the initiator to the active monomer being 0.1% to 2%.

4. The composite material of claim 1, wherein, the solid-state electrolyte powder comprising at least one of LLZO and LLZTO.

5. The composite material of claim 1, wherein, the solid-state electrolyte powder having a particle size of 100 nm to 2000 nm.

6. The composite material of claim 1, wherein, the active monomer being in a mass fraction of 3 to 8 parts.

7. The composite material of claim 2, wherein, the organic solvent being in a mass fraction of 150 to 180 parts.

8. The composite material of claim 1, wherein, the composite material further comprising a dispersant, the dispersant being in a mass fraction of 0.5 to 10 parts.

9. The composite material of claim 1, wherein, the active monomer being in a mass fraction of 5 to 8 parts.

10. The composite material of claim 1, wherein, the composite material further comprising a plasticizer, the plasticizer being in a mass fraction of 3 to 15 parts.

11. The composite material of claim 8, wherein, the dispersant comprising at least one of glyceryl trioleate, triethanolamine, and fish oil.

12. The composite material of claim 3, wherein, the initiator comprising at least one of BPO and AIBN.

13. The composite material of claim 10, wherein, the plasticizer comprising at least one of polyethylene glycol, butyl benzyl phthalate, and dioctyl terephthalate.

14. The composite material of claim 2, wherein, the organic solvent comprising at least one of ethyl acetate, butyl acetate, dichloroethane, and ethanol.

15. The composite material of claim 10, wherein, the plasticizer being in a mass fraction of 3 to 8 parts.

16. A method of making a composite material, wherein, the preparation method comprising: configuring a first mixture comprising the solid-state electrolyte powder and the organic solvent according to a preset ratio; adding the active monomer to the first mixture to obtain the composite material The active monomer includes at least one of methyl acrylate and methyl methacrylate; the chemical formula of the solid-state electrolyte powder is Li 7-x La3Zr 2-x Ta x O 12 , 0<=x<=1.

17. The method of making a composite material of claim 16, wherein, the step of preparing the first mixture comprises weighing the solid-state electrolyte powder, the organic solvent, and the dispersant according to a preset ratio and adding them into a ball mill tank for ball milling to obtain the first mixture.

18. The method of making a composite material of claim 16, wherein, before obtaining the composite material, the preparation method further comprises adding the plasticizer to the first mixture; and / or before obtaining the composite material, the preparation method further comprises adding the initiator to the first mixture.

19. A method of making a solid state electrolyte, wherein, the preparation method of the solid-state electrolyte comprises the following steps: A composite material is provided, comprising, in parts by mass: a solid electrolyte powder 100 parts; an organic solvent 100 to 200 parts; an active monomer 0.1 to 15 parts; an initiator, the mass fraction of which is 0.1% to 5% of the active monomer; wherein the active monomer comprises at least one of methyl acrylate, methyl methacrylate; the chemical formula of the solid electrolyte powder is Li 7-x La3Zr 2-x Ta x O 12 , 0≤x≤1; coating the composite material on a substrate to prepare a wet film with solvent; drying the wet film to obtain a film piece after drying treatment; in a saturated steam environment of the active monomer, the active monomer in the dried film piece is cured in situ to obtain a green body; heating the green body to a preset temperature for degassing to obtain a pre-sintered body; sintering the pre-sintered body to obtain the solid-state electrolyte.

20. The production method according to claim 19, wherein the heating temperature of the degassing stage is 350°C to 500°C; and / or the sintering temperature is 1000°C to 1300°C; and / or the temperature of the drying treatment is 20°C to 50°C; and / or the heating temperature of the in-situ curing is 65°C to 85°C, and the time of the in-situ curing is 1H to 10H.

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