Solid-state electrolyte membrane and preparation method therefor, and lithium ion battery

Abstract

A solid-state electrolyte membrane and a preparation method therefor, and a lithium ion battery. The solid-state electrolyte membrane comprises a first membrane layer and a second membrane layer that are stacked, wherein the material of the first membrane layer comprises a first polymer and a lithium salt, the material of the second membrane layer comprises an inorganic ceramic filler, a second polymer, and cellulose, and the first polymer and the second polymer are each independently selected from one or more of PVDF and PVDF-HFP. The solid-state electrolyte membrane has high ionic conductivity.

Description

Solid-state electrolyte film, preparation method thereof and lithium ion battery

[0001] The present application claims priority to the Chinese patent application No. 202410724192.4, filed on June 5, 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 solid-state electrolyte film, a preparation method thereof and a lithium ion battery. BACKGROUND

[0003] In recent years, solid-state lithium ion batteries have gradually attracted attention due to the use of solid-state electrolytes instead of electrolytes and separators, which make the batteries thinner, smaller in volume and safer. As an important component in batteries, solid-state electrolyte films affect the cycle performance of the batteries, and therefore, it is necessary to develop solid-state electrolyte films with higher performance. TECHNICAL PROBLEM TECHNICAL SOLUTION

[0004] Embodiments of the present application provide a solid-state electrolyte film, a preparation method thereof and a lithium ion battery, aiming to provide a solid-state electrolyte film with high ionic conductivity.

[0005] In a first aspect, embodiments of the present application provide a solid-state electrolyte film, comprising a first film layer and a second film layer stacked together, wherein:

[0006] The material of the first film layer comprises a first polymer and a lithium salt;

[0007] The material of the second film layer comprises an inorganic ceramic filler, a second polymer and cellulose;

[0008] The cellulose comprises one or more of ethyl cellulose and propyl cellulose.

[0009] The first polymer and the second polymer are each independently selected from one or more of PVDF and PVDF-HFP.

[0010] Optionally, in some embodiments of the present application, the first polymer is selected from PVDF; and / or,

[0011] The second polymer is selected from PVDF-HFP; and / or,

[0012] The lithium salt comprises one or more of LiTFSI, LiFSI and LiClO4; and / or,

[0013] The inorganic ceramic filler comprises one or more of LLZTO and LLZGO.

[0014] Optionally, in some embodiments of the present application, the mass ratio of the first polymer to the lithium salt in the material of the first film layer is (6-8):(2-3); and / or,

[0015] the mass ratio of the inorganic ceramic filler to the second polymer in the material of the second film layer is (30-31):(0.62-2); and / or,

[0016] the mass ratio of the inorganic ceramic filler to the cellulose in the material of the second film layer is (30-31):(6-7).

[0017] Optionally, in some embodiments of the present application, the thickness of the first film layer is 10-20 μm; and / or,

[0018] the thickness of the second film layer is 30-45 μm.

[0019] In a second aspect, embodiments of the present application provide a method for preparing a solid-state electrolyte film, comprising the following steps:

[0020] providing a first substrate, a second substrate, a first slurry and a second slurry;

[0021] coating the first slurry on the first substrate to form a first film layer;

[0022] coating the second slurry on the second substrate to form a second film layer; and,

[0023] stacking the first film layer and the second film layer to form a solid-state electrolyte film;

[0024] wherein the first slurry comprises a first polymer, a lithium salt and a first solvent, the second slurry comprises an inorganic ceramic filler, a second polymer, cellulose and a second solvent, the cellulose comprises one or more of ethyl cellulose and propyl cellulose, and the first polymer and the second polymer are each independently selected from one or more of PVDF and PVDF-HFP.

[0025] Optionally, in some embodiments of the present application, the first solvent comprises one or more of DMF and tetrahydrofuran; and / or,

[0026] the second solvent comprises ethanol; and / or,

[0027] the first polymer is selected from PVDF; and / or,

[0028] the second polymer is selected from PVDF-HFP; and / or,

[0029] the lithium salt comprises one or more of LiTFSI, LiFSI and LiClO4; and / or,

[0030] The inorganic ceramic filler comprises one or more of LLZTO and LLZGO.

[0031] Optionally, in some embodiments of the present application, the first slurry comprises, by mass percentage, 6-8% first polymer, 2-3% lithium salt, and the balance being a first solvent; and / or,

[0032] The second slurry comprises, by mass percentage, 30-31% inorganic ceramic filler, 0.62-2% second polymer, 6-7% cellulose, and the balance being a second solvent.

[0033] Optionally, in some embodiments of the present application, the step of coating the second slurry on the second substrate to form a second film layer comprises: coating the second slurry on the first film layer, and then standing at 10-40℃ for 30-60min to obtain the second film layer.

[0034] Optionally, in some embodiments of the present application, the step of coating the first slurry on the first substrate to form a first film layer comprises: coating the first slurry on the first substrate, and then heating at 60-80℃ for 120-180min to obtain the first film layer.

[0035] In a third aspect, the embodiments of the present application provide a lithium ion battery, comprising oppositely arranged positive and negative electrodes, and a solid-state electrolyte film arranged between the positive electrode and the negative electrode, wherein the solid-state electrolyte film comprises the solid-state electrolyte film described above, or is prepared by the preparation method described above, and the first film layer of the solid-state electrolyte film is arranged towards the negative electrode. Advantages

[0036] In the technical scheme provided by the present application, a solid-state electrolyte film is provided, which has better ionic conductivity and can efficiently conduct lithium ions, and can greatly improve the cycle of the battery after being assembled into a battery. In addition, in the solid-state electrolyte film, the material of the second film layer can be well dispersed in ethanol, and the prepared slurry not only has better film-forming property and film-removing property, but also can effectively realize film formation at room temperature, which helps to reduce the energy consumption of film formation. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0038] Fig. 1 is a structural schematic diagram of a solid electrolyte membrane according to an embodiment of the present application;

[0039] Fig. 2 is a structural schematic diagram of a lithium ion battery according to an embodiment of the present application;

[0040] Fig. 3 is a flow schematic diagram of a method for preparing a solid electrolyte membrane according to an embodiment of the present application;

[0041] The following items are numbered: 100 - solid electrolyte membrane; 10 - first film layer; 20 - second film layer; 200 - lithium ion battery; 30 - negative electrode; 40 - positive electrode. Embodiments of the present application

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to one skilled in the art. The materials or reagents used in the embodiments and comparative examples of the present application are commercially available. In addition, any method and material similar or equivalent to those described can be used in the present application. The preferred implementation methods and materials described herein are only for demonstration, but cannot limit the content of the present application.

[0044] It should be noted that the description order of the following embodiments is not limited to the preferred order of the embodiments. Each embodiment of the present application can exist in a range of forms; it should be understood that the description in a range of forms is only for the convenience and brevity, and should not be understood as a hard limit to the scope of the present application; therefore, it should be considered that the range described 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 in this document, it refers to any cited number (fraction or integer) within the indicated range.

[0045] In the description of the present application, the term "comprising" means "including but not limited to".

[0046] The term "multiple", "multiple times" or similar expressions refers to two (times) or more than two (times), for example, can be two (times), three (times), four (times), five (times), six (times), etc.

[0047] The selection range of the term "and / or" includes any one of two or more related listed items, and also includes any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" includes three parallel schemes of A, B, and A+B. For another example, the technical scheme of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, a technical scheme connected by "logical or"), and also includes any and all combinations of A, B, C, and D, that is, includes a combination of any two or any three of A, B, C, and D, and also includes a four-item combination of A, B, C, and D (that is, a technical scheme connected by "logical and").

[0048] The term "solid content" refers to the proportion of the mass of solid in the slurry to the total mass of the slurry.

[0049] In a first aspect, an embodiment of the present application provides a solid-state electrolyte membrane 100, please refer to FIG. 1, the solid-state electrolyte membrane 100 includes a first film layer 10 and a second film layer 20 stacked. The material of the first film layer 10 includes a first polymer and a lithium salt; the material of the second film layer 20 includes an inorganic ceramic filler, a second polymer and cellulose; wherein the cellulose includes one or more of ethyl cellulose and propyl cellulose; the first polymer and the second polymer are each independently selected from one or more of PVDF (polyvinylidene fluoride) and PVDF-HFP (poly (vinylidene fluoride-co-hexafluoropropylene)).

[0050] In the related art, a ceramic sintering method is often used to prepare a solid-state electrolyte membrane 100. However, this method not only has high cost, time-consuming and high cost, but also has problems such as poor strength of pure ceramic oxide forming, poor interface performance contact with the positive electrode 40, etc. The solid-state electrolyte membrane 100 provided by the present application not only has good ionic conductivity and can efficiently conduct lithium ions, but also can greatly improve the cycle of the battery after being assembled into a battery, and has good flexibility, which can make up for the strength problem of pure ceramic electrolyte. In addition, since the material of the second film layer 20 in the solid-state electrolyte membrane 100 provided by the present application can be well dispersed in ethanol, and the prepared slurry not only has good film-forming property and film-removing property, but also can be formed at room temperature, the solid-state electrolyte membrane 100 proposed by the present application can be prepared by a wet process at a lower temperature, which helps to reduce the energy consumption and difficulty of film preparation.

[0051] The solid-state electrolyte film 100 provided by the embodiment has the first film layer 10 as a pure polymer film, which has strong flexibility and high compactness, can inhibit the further growth of lithium dendrites on the side of the lithium metal negative electrode 30, prevent short circuit caused by the lithium metal piercing the electrolyte film, and isolate the by-products on the side of the lithium metal from diffusing to the electrolyte film. The second film layer 20 is a composite ceramic electrolyte film, which has high ionic conductivity and can effectively conduct lithium ions. The composite film formed by the combination of the first film layer 10 and the second film layer 20 not only has high ionic conductivity and good transmission performance, but also can reduce the risk of short circuit caused by the lithium dendrites piercing the electrolyte film. When used as the electrolyte film of a lithium battery, the solid-state electrolyte film 100 can greatly improve the cycle performance of the battery.

[0052] In some embodiments, the battery prepared by using the solid-state electrolyte film 100 can be stably operated at 0.33C, and the assembled Li\NMC811 battery can be stably cycled for more than 100 cycles.

[0053] The first polymer film can isolate the lithium metal negative electrode 30 from the electrolyte film and prevent the lithium metal from piercing the electrolyte film to cause short circuit. In some embodiments, the first polymer is selected from PVDF. Compared with other materials, when the first polymer is selected from PVDF, the film can be better formed, the flexibility and compactness of the film layer can be improved, the lithium metal negative electrode 30 can be better isolated from the electrolyte film, and the cycle performance of the battery can be improved.

[0054] The second polymer helps to bond the ceramic particles to assist film formation and form an electrolyte film with high ionic conductivity. In some embodiments, the second polymer is selected from PVDF-HFP. Compared with other materials in the same layer, when the second polymer is selected from PVDF-HFP, the matching is better, the cycle performance of the battery can be further improved, and the second polymer is also more suitable for ethanol solvent, which is beneficial to the film formation of the film layer at room temperature.

[0055] In other embodiments, the first polymer is selected from PVDF, and the second polymer is selected from PVDF-HFP. In this way, the overall performance of the solid-state electrolyte film 100 can be greatly improved, and the cycle performance of the battery can be improved.

[0056] The cellulose in the film layer can play a role in bonding and supporting, which helps to improve the uniformity and compactness of the film layer. Compared with other materials in the same layer, ethyl cellulose and propyl cellulose have better matching, which is more conducive to the improvement of the film formation effect and the performance of the electrolyte film. In addition, the two materials have good solubility in ethanol, which is beneficial to the film formation of the film layer at room temperature. Furthermore, the arrangement of the first film layer 10 and the second film layer 20 in the solid-state electrolyte film 100 of the application is also conducive to increasing the proportion of cellulose, thereby helping to form the electrolyte film.

[0057] In some embodiments, the lithium salt includes one or more of LiTFSI (lithium bis-trifluoromethanesulfonimide), LiFSI (lithium bis-fluorosulfonimide), LiClO4 (lithium perchlorate), which helps to increase the lithium ion concentration in the film layer, improve the ion conductivity of the first film layer 10, and at the same time help to form a stable SEI layer (solid electrolyte interface layer).

[0058] In some embodiments, the inorganic ceramic filler includes one or more of LLZTO (tantalum-doped lithium lanthanum zirconium oxide) and LLZGO (gallium-doped lithium lanthanum zirconium oxide). In this way, the ion conductivity is more conducive to being improved.

[0059] In some embodiments, in the material of the first film layer 10, the mass ratio of the first polymer to the lithium salt is (6-8):(2-3); for example, it can be 6:2, 6:2.3, 6:2.5, 6:2.7, 6:3, 7:2, 7:2.1, 7:2.5, 7:2.8, 7:3, 8:2, 8:2.2, 8:2.5, 8:2.9, 8:3, etc. Controlling the mass ratio within this range helps to improve the strength of the film layer, improve the uniformity of film formation, and the detachability of the film layer, which is more conducive to improving the performance of the battery.

[0060] In some embodiments, in the material of the second film layer 20, the mass ratio of the inorganic ceramic filler to the second polymer is (30-31):(0.62-2); for example, it can be 30:0.62, 30:0.8, 30:1, 30:1.1, 30:1.3, 30:1.5, 30:1.8, 30:1.9, 30:2, 30.5:0.62, 30.5:1, 30.5:1.2, 30.5:1.5, 30.5:2, 30.8:1, 30.9:1.5, 30.3:2, 31:0.62, 31:1, 31:1.5, 31:1.8, 31:2, etc. Controlling the mass ratio within this range helps to improve the uniformity of film formation and the detachability of the film layer, which is more conducive to improving the performance of the battery.

[0061] In some embodiments, in the material of the second film layer 20, the mass ratio of the inorganic ceramic filler to the cellulose is (30-31):(6-7); for example, it can be 30:6, 30:6.2, 30:6.4, 30:6.5, 30:6.8, 30:6.9, 30:7, 30.5:6, 30.5:6.5, 30.5:6.7, 30.5:7, 30.4:6, 30.9:6.5, 30.8:7, 31:6, 31:6.5, 31:6.8, 31:7, etc. Controlling the mass ratio within this range helps to improve the uniformity of film formation and the detachability of the film layer, which is more conducive to improving the performance of the battery.

[0062] In some embodiments, the thickness of the first film layer 10 is 10-20 μm; for example, it can be 10 μm, 12 μm, 14 μm, 15 μm, 16 μm, 18 μm, 20 μm, and a value between any two of the above values.

[0063] In some embodiments, the thickness of the second film layer 20 is 30-45 μm; for example, it can be 30 μm, 32 μm, 34 μm, 35 μm, 36 μm, 37 μm, 40 μm, 42 μm, 45 μm, and a value between any two of the above values.

[0064] In a second aspect, the embodiments of the present application further provide a preparation method of the solid-state electrolyte film 100, please refer to FIG. 3, the preparation method comprises the following steps:

[0065] S10, providing a first substrate, a second substrate, a first slurry, and a second slurry;

[0066] S20, coating the first slurry on the first substrate to form a first film layer 10;

[0067] S30, coating the second slurry on the second substrate to form a second film layer 20;

[0068] S40, laminating the first film layer 10 and the second film layer 20 to form a solid-state electrolyte film 100;

[0069] The first slurry comprises a first polymer, a lithium salt, and a first solvent, the second slurry comprises an inorganic ceramic filler, a second polymer, cellulose, and a second solvent, the cellulose comprises one or more of ethyl cellulose and propyl cellulose, and the first polymer and the second polymer are each independently selected from one or more of PVDF and PVDF-HFP.

[0070] The preparation method provided by the present application uses a wet process to prepare the solid-state electrolyte film 100, which is simple and easy to implement, and the formation process of the second film layer 20 can be carried out at room temperature, greatly reducing the difficulty and energy consumption of film preparation and reducing the cost. The solid-state electrolyte film 100 prepared by the preparation method has a good ionic conductivity and can efficiently conduct lithium ions, and can greatly improve the cycle of the battery after being assembled into a battery.

[0071] The first substrate and the second substrate are respectively used for preparing and carrying the first film layer 10 and the second film layer 20, and can be any plate material having a plane for film formation, such as a PET substrate, an aluminum foil, a glass substrate, and the like. The first substrate and the second substrate can be the same or different. In some embodiments, the first substrate and the second substrate can also be any prepared film layer, such as the first film layer 10, the second film layer 20, the positive electrode 40, the negative electrode 30, and the like. In some embodiments, the first film layer 10 can be prepared first, and then the second film layer 20 is prepared on the surface of the first film layer 10 to obtain the solid-state electrolyte film 100 with a laminated structure; or the second film layer 20 can be prepared first, and then the first film layer 10 is prepared on the surface of the second film layer 20 to obtain the solid-state electrolyte film 100 with a laminated structure.

[0072] In the embodiments of the present application, the first film layer 10 and the second film layer 20 can also be prepared on different substrates respectively, and then laminated to form the solid-state electrolyte film 100 after being removed from the substrates, which helps to improve the film formation quality of each film layer.

[0073] In some embodiments, the second solvent includes ethanol. Ethanol can not only well disperse other components of the second slurry, but also volatilize at room temperature, and the slurry prepared therefrom has suitable film formation and removability, so that the second film layer 20 with good removability and uniform film formation can be prepared.

[0074] In some embodiments, the second polymer is selected from PVDF-HFP. PVDF-HFP not only has good matching with other materials in the same layer, which is beneficial to improving the cycle performance of the battery, but also can be well dissolved in ethanol, which helps to form a film at room temperature and improve the film formation effect.

[0075] In some embodiments, the inorganic ceramic filler includes one or more of LLZTO and LLZGO.

[0076] In some embodiments, the first solvent includes one or more of DMF and tetrahydrofuran.

[0077] In some embodiments, the first polymer is selected from PVDF.

[0078] In some embodiments, the lithium salt includes one or more of LiTFSI, LiFSI, and LiClO4.

[0079] In some embodiments, the first slurry comprises, by mass percentage, 6-8% first polymer, 2-3% lithium salt, and the balance first solvent. For example, the first slurry can comprise 6% first polymer, 2% lithium salt, and 92% first solvent, 6.5% first polymer, 3% lithium salt, and 90.5% first solvent, 7% first polymer, 2.5% lithium salt, and 90.5% first solvent, or 6.2% first polymer, 2.6% lithium salt, and 91.2% first solvent, etc. The first polymer, lithium salt, and first solvent are mixed in appropriate proportions to obtain the first slurry, which, after coating, can form the first film layer 10. In some embodiments, the mass ratio of the first polymer to the lithium salt in the first film layer 10 is (6-8):(2-3).

[0080] The second slurry comprises, by mass percentage, 30-31% inorganic ceramic filler, 0.62-2% second polymer, 6-7% cellulose, and the balance second solvent. For example, the second slurry can comprise 30% inorganic ceramic filler, 2% second polymer, 6% cellulose, and 62% second solvent, 30.5% inorganic ceramic filler, 1.8% second polymer, 6.5% cellulose, and 61.2% second solvent, 31% inorganic ceramic filler, 1.5% second polymer, 6.7% cellulose, and 60.8% second solvent, 30.8% inorganic ceramic filler, 1.2% second polymer, 7% cellulose, and 61% second solvent, etc. The inorganic ceramic filler, second polymer, cellulose, and second solvent are mixed in appropriate proportions to obtain the second slurry, which, after coating, can form the second film layer 20. In some embodiments, the mass ratio of the inorganic ceramic filler to the second polymer in the second film layer 20 is (30-31):(0.62-2); the mass ratio of the inorganic ceramic filler to the cellulose is (30-31):(6-7).

[0081] In some embodiments, the step of coating the second slurry on the first film layer 10 to form the second film layer 20 comprises coating the second slurry on the first film layer 10 and then standing at 10-40°C for 30-60 min to obtain the second film layer 20. The second slurry has good film-forming and demoulding properties, can be stood to form a film at a lower temperature, and has good film-forming effect, thereby reducing the energy consumption for film formation.

[0082] In some embodiments, the step of coating the first slurry on the first substrate to form the first film layer 10 comprises coating the first slurry on the first substrate and then heating at 60-80°C for 120-180 min to obtain the first film layer 10.

[0083] In step S40, the first film layer 10 and the second film layer 20 are stacked, for example, the first film layer 10 can be stacked on the second film layer 20, or the second film layer 20 can be stacked on the first film layer 10, and the two film layers are pressed under the action of an external force to obtain the solid-state electrolyte film 100. Alternatively, the two film layers can be stacked and assembled in sequence with the positive electrode 40 and the negative electrode 30 when the lithium ion battery 200 is prepared, and then pressed or wound into a battery cell.

[0084] In a third aspect, the embodiments of the present application also provide a lithium ion battery 200, including but not limited to a button cell, a soft pack battery, a square lithium ion battery 200, a cylindrical lithium ion battery 200, etc. Please refer to FIG. 2, the lithium ion battery 200 includes oppositely arranged positive electrode 40 and negative electrode 30, and solid-state electrolyte film 100 arranged between the positive electrode 40 and the negative electrode 30, the solid-state electrolyte film 100 includes the solid-state electrolyte film 100 as described in any of the preceding embodiments, or the solid-state electrolyte film 100 is prepared by the preparation method as described in any of the preceding embodiments, wherein the first film layer 10 of the solid-state electrolyte film 100 is arranged towards the negative electrode 30, and the second film layer 20 is arranged close to the positive electrode 40.

[0085] The technical solutions and technical effects of the present application will be described in detail through specific embodiments below. The following embodiments are only part of the embodiments of the present application and do not specifically limit the present application.

[0086] Embodiment 1

[0087] The structure of the solid-state electrolyte film provided in this embodiment is as follows:

[0088] The material of the first film layer is PVDF and LiTFSI, and the mass ratio of PVDF and LiTFSI is 6.6:2.2. The solvent used in preparation is DMF, and the proportion of each component in the prepared slurry is: PVDF 7.4wt%, LiTFSI 2.48wt%, and DMF 90.09wt%.

[0089] The material of the second film layer is Ga-LLZO ceramic, PVDF-HFP and ethyl cellulose, and the mass ratio of the three is 5:0.1:1. The solvent used in preparation is ethanol, and the proportion of each component in the prepared slurry is about: Ga-LLZO ceramic 31.06wt%, PVDF-HFP 0.62wt%, ethyl cellulose 6.21wt%, and ethanol 62.11wt%.

[0090] The preparation steps of the solid-state electrolyte film are as follows:

[0091] 1. Using wet forming process, 0.66g PVDF, 0.22g LiTFSI, dissolved in 8g DMF, stirred at room temperature (about 20℃) for 8h, to obtain a uniform solution; take the above uniform solution, use a 150μm doctor blade, through solution casting-drying method on the glass plate for scraping, then dried at 80℃ for 180min, to obtain a first film layer with a thickness of about 15μm;

[0092] 2. Dissolve 0.5g ethyl cellulose and 5g ethanol in a homogenizer, then add 2.5g Ga-LLZO ceramic and 0.05g PVDF-HFP polymer to the homogenizer and mix uniformly to form a uniform slurry. Use a 150μm doctor blade to scrape the slurry onto a PET film, and wait for it to dry and release the film at room temperature (about 20℃), to obtain a second film layer with a thickness of about 35μm.

[0093] 3. Directly stack the above two layers of film, and when assembling the battery, contact the first film layer with the lithium metal negative electrode, and contact the second film layer with the positive electrode.

[0094] Example 2

[0095] This example is basically the same as Example 1, the only difference being that in this example: the thickness of the second film layer is about 45μm.

[0096] Example 3

[0097] This example is basically the same as Example 1, the only difference being that in this example: the proportion of each component in the slurry of the second film layer is about 30wt% Ga-LLZO ceramic, 2wt% PVDF-HFP, 6wt% ethyl cellulose and 62wt% ethanol.

[0098] Example 4

[0099] This example is basically the same as Example 1, the only difference being that in this example, the cellulose in the second film layer is replaced by propyl cellulose, and the preparation step 2 is adjusted accordingly.

[0100] Except for this, other parameters and steps remain unchanged.

[0101] Example 5

[0102] This example is basically the same as Example 1, the only difference being that in this example, the proportion of each component in the slurry of the second film layer is adjusted to Ga-LLZO ceramic 31.06wt%, PVDF-HFP 0.62wt%, ethyl cellulose 6wt%, ethanol 62.32wt%, and the preparation step 2 is adjusted accordingly.

[0103] Except for this, other parameters and steps remain unchanged.

[0104] Example 6

[0105] This example is basically the same as Example 1, except that in this example, the proportion of each component in the second membrane layer slurry is adjusted to Ga-LLZO ceramic 31.06wt%, PVDF-HFP 0.62wt%, ethyl cellulose 7wt%, ethanol 61.32wt%, and the corresponding adjustment is made in Step 2 of the preparation.

[0106] Except for this, other parameters and steps remain unchanged.

[0107] Example 7

[0108] This example is basically the same as Example 1, except that in this example, the proportion of each component in the second membrane layer slurry is adjusted to Ga-LLZO ceramic 31.06wt%, PVDF-HFP 0.62wt%, ethyl cellulose 5wt%, ethanol 63.32wt%, and the corresponding adjustment is made in Step 2 of the preparation.

[0109] Except for this, other parameters and steps remain unchanged.

[0110] Example 8

[0111] This example is basically the same as Example 1, except that in this example, the proportion of each component in the second membrane layer slurry is adjusted to Ga-LLZO ceramic 31.06wt%, PVDF-HFP 0.62wt%, ethyl cellulose 8wt%, ethanol 60.32wt%, and the corresponding adjustment is made in Step 2 of the preparation.

[0112] Except for this, other parameters and steps remain unchanged.

[0113] Example 9

[0114] This example is basically the same as Example 1, except that in this example, the polymer in the first membrane layer of the solid-state electrolyte membrane provided is changed to PVDF-HFP, and the corresponding adjustment is made in Step 1 of the preparation.

[0115] Except for this, other parameters and steps remain unchanged.

[0116] Example 10

[0117] This example is basically the same as Example 1, except that in this example, the polymer in the second membrane layer of the solid-state electrolyte membrane provided is changed to PVDF, and the corresponding adjustment is made in Step 2 of the preparation.

[0118] Except for this, other parameters and steps remain unchanged.

[0119] Comparative Example 1

[0120] The comparative example is basically the same as example 1, the only difference is that the solid-state electrolyte film provided by the comparative example only has the first film layer, and correspondingly, step 2 is omitted in the preparation steps of the comparative example. Except for this, other parameters and steps remain unchanged.

[0121] Comparative example 2

[0122] The comparative example is basically the same as example 1, the only difference is that the solid-state electrolyte film provided by the comparative example only has the second film layer, and correspondingly, step 1 is omitted in the preparation steps of the comparative example. Except for this, other parameters and steps remain unchanged.

[0123] Comparative example 3

[0124] The comparative example is basically the same as example 1, the only difference is that the solid-state electrolyte film provided by the comparative example has the first film layer and the second film layer, and the stacking order of the first film layer and the second film layer is exchanged, that is, the first film layer is arranged close to the positive electrode sheet. Except for this, other parameters and steps remain unchanged.

[0125] Comparative example 4

[0126] The comparative example is basically the same as example 1, the only difference is that the solid-state electrolyte film provided by the comparative example has LiTFSI in the second film layer, and the proportion of lithium salt in the slurry is 2.0wt%, and the proportion of ethanol solvent is changed to 60.11wt%, and the proportions of other components remain unchanged, and the preparation step 2 of the comparative example is adjusted accordingly. Except for this, other parameters and steps remain unchanged.

[0127] Comparative example 5

[0128] The comparative example is basically the same as example 1, the only difference is that in step 2 of the comparative example, cellulose is replaced by methyl cellulose. Except for this, other parameters and steps remain unchanged.

[0129] Comparative example 6

[0130] The comparative example is basically the same as example 1, the only difference is that in step 2 of the comparative example, ethanol is replaced by methanol. Except for this, other parameters and steps remain unchanged.

[0131] Comparative example 7

[0132] The comparative example is basically the same as example 1, the only difference is that in step 2 of the comparative example, PVDF-HFP is replaced by polyethylene oxide. Except for this, other parameters and steps remain unchanged.

[0133] Experimental example

[0134] The solid-state electrolyte films prepared in the above examples and comparative examples are subjected to the following tests, and the results are recorded in Tables 1 and 2.

[0135] Peeling condition: visually observe the peeling condition when dry peeling is performed in step 1 and / or 2;

[0136] Film forming uniformity: visually observe the second film layer prepared, and observe the dispersion uniformity of particles on the film layer;

[0137] Ion conductivity detection method: the bulk impedance R of the lithium battery is tested, and the ion conductivity σ is calculated according to the formula σ = l / RS, wherein l is the thickness of the film, R is the bulk impedance value, and S is the area of the film;

[0138] Symmetrical battery detection method: assemble a battery with the structure of Li|solid-state electrolyte film|Li, and clamp the solid-state symmetrical battery with steel sheets on both sides, place it on the new Wei software, set the current density, and test after waiting for the cycle.

[0139] Cycle number detection method: assemble a button cell, place it on the new Wei test software, set the charge and discharge rate, cutoff voltage and other test conditions, and then start testing after waiting for the cycle.

[0140] The specific assembly steps of the battery are as follows:

[0141] The positive electrode is a commercial mass-produced NCM811 positive electrode sheet, and the load is 15 mg / cm 2 The negative electrode is a 50-micron-thick metal lithium foil. Two layers of solid-state electrolyte films are cut into 16-mm round sheets, the first film layer is close to the negative electrode, and the second film layer is close to the positive electrode, forming a sandwich structure, which is then packaged in a CR2032 button cell, and a lithium metal battery can be obtained after standing at room temperature for about 6 hours.

[0142] Table 1

[0143] Table 2

[0144] From the above table, it can be seen that:

[0145] The batteries of embodiments 1 to 10 all exhibit ion conductivity, electrochemical window and cycle number far higher than those of comparative examples 1 to 3, indicating that the solid-state electrolyte film with a composite structure provided by the application has high ion conductivity, strong high-pressure resistance and electrochemical stability, and when the solid-state electrolyte film is used in a battery, it helps to improve the cycle performance of the battery; further, the ion conductivity, electrochemical window and cycle number of embodiment 1 are far higher than those of comparative examples 1 to 3, also indicating that in the solid-state electrolyte film provided by the application, the first film layer and the second film layer cooperate with each other to better improve the ion conductivity, transmission performance and stability, which can greatly improve the cycle of the battery, at the same time, the first film layer faces the negative electrode, and the second film layer faces the positive electrode, which can make the solid-state electrolyte film have good contact with the positive electrode and the negative electrode respectively, and help to improve the battery cycle.

[0146] The first film layer and the second film layer of embodiments 1 to 10 can be completely detached, and the second film layer has good film forming uniformity, while in comparative examples 1 to 7, the second film layer of comparative example 4 is adhered to the PET substrate, and the film forming is not uniform, and the second film layer of comparative examples 5 to 7 cannot be detached, and the film forming of the second film layer itself is also not uniform, which indicates that the application optimizes the types of components, and using ethyl cellulose and propyl cellulose as the cellulose component and using ethanol as the solvent of the second film layer slurry helps to improve the film forming effect and detachability of the second film layer slurry.

[0147] The above describes the embodiments of the application in detail, and the principles and implementation modes of the application are described by applying specific examples; the above description of the embodiments is only used to help understand the method of the application and its core idea; at the same time, for those skilled in the art, according to the idea of the application, the specific implementation mode and application range will be changed, and the above description of the content of the specification should not be understood as a limitation of the application.

Claims

1. A solid-state electrolyte membrane comprising a first membrane layer and a second membrane layer stacked together, wherein: a material of the first membrane layer comprises a first polymer and a lithium salt; a material of the second membrane layer comprises an inorganic ceramic filler, a second polymer and cellulose; the cellulose comprises one or more of ethyl cellulose and propyl cellulose; the first polymer and the second polymer are each independently selected from one or more of PVDF and PVDF-HFP.

2. The solid-state electrolyte film of claim 1, wherein, the first polymer is selected from PVDF.

3. The solid-state electrolyte film of claim 1, wherein, the second polymer is selected from PVDF-HFP.

4. The solid-state electrolyte film of claim 1, wherein, the lithium salt comprises one or more of LiTFSI, LiFSI, LiClO4.

5. The solid-state electrolyte film of claim 1, wherein, the inorganic ceramic filler comprises one or more of LLZTO and LLZGO.

6. The solid-state electrolyte film of any one of claims 1 to 5, wherein, a mass ratio of the first polymer to the lithium salt in the material of the first membrane layer is (6-8):(2-3).

7. The solid-state electrolyte film of any one of claims 1 to 5, wherein, a mass ratio of the inorganic ceramic filler to the second polymer in the material of the second membrane layer is (30-31):(0.62-2).

8. The solid-state electrolyte membrane of any one of claims 1 to 5, wherein a mass ratio of the inorganic ceramic filler to the cellulose in the material of the second membrane layer is (30-31):(6-7).

9. The solid-state electrolyte film of claim 1, wherein, a thickness of the first membrane layer is 10-20 pm.

10. The solid-state electrolyte film of claim 1, wherein, a thickness of the second membrane layer is 30-45 pm.

11. A method of preparing a solid-state electrolyte membrane, comprising the steps of: providing a first substrate, a second substrate, a first slurry and a second slurry; coating the first slurry on the first substrate to form a first membrane layer; coating the second slurry on the second substrate to form a second membrane layer; and, stacking the first membrane layer and the second membrane layer to form a solid-state electrolyte membrane; wherein the first slurry comprises a first polymer, a lithium salt and a first solvent, and the second slurry comprises an inorganic ceramic filler, a second polymer, cellulose and a second solvent, the cellulose comprises one or more of ethyl cellulose and propyl cellulose, and the first polymer and the second polymer are each independently selected from one or more of PVDF and PVDF-HFP.

12. The production method according to claim 11, wherein the first solvent comprises one or more of DMF and tetrahydrofuran; and / or, the second solvent comprises ethanol.

13. The method of making according to claim 11, wherein, the first polymer is selected from PVDF.

14. The method of making according to claim 11, wherein, the second polymer is selected from PVDF-HFP.

15. The method of making according to claim 11, wherein, the lithium salt comprises one or more of LiTFSI, LiFSI, LiClO4; and / or, the inorganic ceramic filler comprises one or more of LLZTO and LLZGO.

16. The method of making according to claim 11, wherein, the first slurry comprises, by mass percentage, 6-8% of the first polymer, 2-3% of the lithium salt, and a remainder of the first solvent.

17. The method of making according to claim 11, wherein, the second slurry comprises, by mass percentage, 30-31% of the inorganic ceramic filler, 0.62-2% of the second polymer, 6-7% of the cellulose, and a remainder of the second solvent.

18. The method of making according to claim 11, wherein, The step of coating the second slurry on the second substrate to form a second film layer comprises: coating the second slurry on the second substrate, and then standing for 30 min to 60 min at 10 ℃ to 40 ℃ to obtain the second film layer.

19. The method of making according to claim 11, wherein, The step of coating the first slurry on the first substrate to form a first film layer comprises: coating the first slurry on the first substrate, and then heating for 120 min to 180 min at 60 ℃ to 80 ℃ to obtain the first film layer.

20. A lithium-ion battery, wherein, The all-solid-state battery comprises oppositely arranged positive and negative electrodes, and a solid electrolyte membrane arranged between the positive and negative electrodes, wherein the solid electrolyte membrane comprises the solid electrolyte membrane according to any one of claims 1 to 10, or is prepared by the preparation method according to any one of claims 11 to 19, and the first film layer of the solid electrolyte membrane is arranged towards the negative electrode.

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