Solid-state electrolyte membrane, preparation method thereof and solid-state battery

Abstract

The invention relates to a solid electrolyte membrane, a preparation method thereof and a solid-state battery. The preparation method of the solid electrolyte membrane comprises the following steps: stacking a first base material layer and a second base material layer; spraying solid electrolyte powder to the surface of the first base material layer to obtain an electrolyte membrane precursor; pressing the electrolyte membrane precursor to obtain an intermediate; and removing the second base material layer in the intermediate to obtain the solid electrolyte membrane, wherein the first base material layer is of a porous structure, and the porosity of the second base material layer is smaller than that of the first base material layer. According to the preparation method of the solid electrolyte membrane provided by the invention, the porosity of the second base material layer is smaller than that of the first base material layer, and the second base material layer blocks the solid electrolyte during pressing treatment, so that the density of the solid electrolyte membrane is improved, the ionic conductivity of the solid electrolyte membrane is improved, and the cycle performance of a battery is improved; by removing the second base material layer, the thickness of the solid electrolyte membrane is reduced, and the energy density of the battery is improved.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a solid electrolyte membrane and a preparation method thereof, and a solid-state battery. Background Art

[0002] In recent years, due to the increasing requirements for the safety performance of lithium-ion batteries, more methods have used solid electrolytes to replace liquid electrolytes.

[0003] In the traditional method, solid electrolyte powder is mixed with a binder to form a self-supporting electrolyte membrane, but the membrane has insufficient membrane strength, which causes processing problems. Therefore, the current electrolyte membrane preparation is to directly press the solid electrolyte powder into a single-layer macroporous base membrane, and finally obtain the target solid electrolyte membrane through multiple filling and pressing.

[0004] However, since both sides of the single-layer macroporous base membrane are porous structures, in the process of pressing the solid electrolyte powder onto the macroporous base membrane, the solid electrolyte powder is easy to leak out from the other side of the non-woven fabric, and more solid electrolyte is required, resulting in a thicker prepared solid electrolyte membrane, and the density of the solid electrolyte membrane is difficult to ensure, and it is not easy to form a continuous ion-conducting path in the pore structure of the non-woven fabric. It is necessary to repeatedly press to obtain a solid electrolyte membrane with a preset density, and to achieve a preset thickness, it is necessary to further increase the number of pressing times. However, when the number of pressing times is too many, the pore structure of the non-woven fabric is easily destroyed, resulting in a decrease in the mechanical properties of the solid electrolyte membrane and further escaping of the solid electrolyte powder, resulting in the solid electrolyte membrane prepared by the existing method not being able to meet the production requirements of composite batteries. Summary of the invention

[0005] Based on this, it is necessary to provide a solid electrolyte membrane and a preparation method thereof, and a solid-state battery. Compared with the solid electrolyte membrane prepared by the traditional method, the solid electrolyte membrane in the present application has higher density and lower thickness, and has both higher mechanical properties and ionic conductivity. The number of pressing times is reduced during the pressing process, the production efficiency is improved, and the battery has higher cycle performance.

[0006] The first aspect of the present application provides a method for preparing a solid electrolyte membrane, comprising the following steps: stacking a first substrate layer and a second substrate layer; wherein the first substrate layer and the second substrate layer are both porous structures, and the porosity of the second substrate layer is less than the porosity of the first substrate layer; or, the first substrate layer is a porous structure, and the second substrate layer is a non-porous structure; spraying a solid electrolyte powder onto the surface of the first substrate layer to obtain an electrolyte membrane precursor; pressing the electrolyte membrane precursor to obtain an intermediate; removing the second substrate layer in the intermediate to obtain a solid electrolyte membrane.

[0007] In some embodiments, in the step of stacking the first substrate layer and the second substrate layer, the porosity of the first substrate layer is satisfy: Porosity of the second substrate layer satisfy:

[0008] In some embodiments, the particle size of at least a portion of the solid electrolyte powder is smaller than or equal to the pore size of the porous structure of the first substrate layer and larger than the pore size of the porous structure of the second substrate layer.

[0009] In some preferred embodiments, the particle size D50 of the solid electrolyte is 3 μm to 20 μm.

[0010] In some embodiments, the step of pressing the electrolyte membrane precursor specifically includes: applying a pressing force to a surface of the first substrate layer on which the solid electrolyte powder is sprayed, to press the electrolyte membrane precursor.

[0011] In some embodiments, the pressure of the pressing treatment is 2t to 3t; and the time of the pressing treatment is 0.5min to 20min.

[0012] In some embodiments, the temperature of the press treatment is 60°C to 120°C.

[0013] In some embodiments, the pressing process is performed once.

[0014] In some embodiments, the step of spraying the solid electrolyte powder onto the surface of the first substrate layer specifically comprises: spraying the solid electrolyte powder onto the surface of the first substrate layer at every 1 cm 2 0.1 mg to 500 mg of solid electrolyte powder is sprayed on the surface of the first substrate layer.

[0015] In some embodiments, the solid electrolyte powder is sprayed onto the surface of the first substrate layer once or more times.

[0016] In some embodiments, before the step of pressing the electrolyte membrane precursor to obtain the intermediate, the step further includes: oscillating the electrolyte membrane precursor.

[0017] In some preferred embodiments, the electrolyte membrane precursor is oscillated once or more times.

[0018] In some preferred embodiments, the step of vibrating the electrolyte membrane precursor specifically includes: vibrating the electrolyte membrane precursor using a screen vibrator.

[0019] In some preferred embodiments, the oscillation frequency of the vibrating screen is 20 kHz to 1000 kHz.

[0020] The second aspect of the present application provides a solid electrolyte membrane, which is prepared by the preparation method provided by the first aspect.

[0021] In some embodiments, the porosity of the solid electrolyte membrane is 0.1% to 10%.

[0022] The third aspect of the present application provides a solid-state battery, which includes a positive electrode, a negative electrode, and a solid electrolyte membrane prepared by the preparation method provided in the first aspect or the solid electrolyte membrane provided in the second aspect.

[0023] Compared with the traditional technology, this application has at least the following beneficial effects:

[0024] The preparation method of the solid electrolyte membrane provided by the present application is to set a second substrate layer with a smaller porosity on one side of the first substrate layer. During the pressing process, the second substrate layer has a blocking effect on the solid electrolyte powder, reducing the probability of the solid electrolyte escaping from the first substrate layer; on the other hand, since the second substrate layer is stacked before the solid electrolyte powder is sprayed on the first substrate layer, even if a small part of the solid electrolyte powder is escaping from the first substrate layer, the second substrate layer will still support the solid electrolyte powder that has escaped, and under the combined action of pressure and the supporting force of the second substrate layer during pressing, the solid electrolyte powder that has escaped can be pressed together with the solid electrolyte in the first substrate again and pressed into the first substrate layer again. Therefore, the preparation method of the solid electrolyte membrane of the present application reduces the number of pressing times, improves the density of the solid electrolyte membrane, improves production efficiency, reduces the damage to the solid electrolyte membrane substrate during pressing, and after the pressing is completed, only the second substrate layer needs to be removed to prepare the solid electrolyte membrane, and the steps are simple and easy to implement. In addition, the increase in the density of the solid electrolyte membrane makes the structural arrangement of the solid electrolyte membrane more compact, takes into account the mechanical properties of the solid electrolyte membrane, reduces the thickness of the solid electrolyte membrane, and improves the energy density of the battery. In addition, the increased density of the solid electrolyte membrane also reduces internal defects, lowers the resistance to ion transmission, forms continuous ion channels during the pressing process, improves the ionic conductivity of the solid electrolyte membrane, reduces the capacity loss of the battery during the charge and discharge process, and thus improves the battery's cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of a process for preparing a solid electrolyte membrane in one embodiment of the present application. DETAILED DESCRIPTION

[0026] References to embodiments of the present application will now be provided in detail, one or more examples of which are described below. Each example is provided as an explanation rather than a limitation of the present application. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made to the present application without departing from the scope or spirit of the present application. For example, a feature described or described as part of one embodiment may be used in another embodiment to produce a further embodiment.

[0027] Therefore, it is intended that the present application covers such modifications and variations that fall within the scope of the appended claims and their equivalents. Other objects, features and aspects of the present application are disclosed in or are apparent from the following detailed description. It will be appreciated by those of ordinary skill in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the present application.

[0028] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0029] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0030] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0031] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0032] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, it is mentioned that the method may also include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0033] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0034] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0035] The first aspect of the present application provides a method for preparing a solid electrolyte membrane, such as Figure 1 As shown, the preparation method comprises the following steps:

[0036] S10, stacking the first substrate layer and the second substrate layer.

[0037] Wherein, both the first substrate layer and the second substrate layer are porous structures, and the porosity of the second substrate layer is less than that of the first substrate layer; or, the first substrate layer is a porous structure, and the second substrate layer is a non-porous structure;

[0038] S20, spraying solid electrolyte powder onto the surface of the first substrate layer to obtain an electrolyte membrane precursor.

[0039] S30, pressing the electrolyte membrane precursor to obtain an intermediate.

[0040] S40, removing the second substrate layer in the intermediate to obtain a solid electrolyte membrane.

[0041] The preparation method of the solid electrolyte membrane provided by the present application is to set a second substrate layer with a smaller porosity on one side of the first substrate layer. During the pressing process, the second substrate layer has a blocking effect on the solid electrolyte powder, reducing the probability of the solid electrolyte escaping from the first substrate layer; on the other hand, since the second substrate layer is stacked before the solid electrolyte powder is sprayed on the first substrate layer, even if a small part of the solid electrolyte powder is escaping from the first substrate layer, the second substrate layer will still support the solid electrolyte powder that has escaped, and under the combined action of pressure and the supporting force of the second substrate layer during pressing, the solid electrolyte powder that has escaped can be pressed together with the solid electrolyte in the first substrate again and pressed into the first substrate layer again. Therefore, the preparation method of the solid electrolyte membrane of the present application reduces the number of pressing times, improves the density of the solid electrolyte membrane, improves production efficiency, reduces the damage to the solid electrolyte membrane substrate during pressing, and after the pressing is completed, only the second substrate layer needs to be removed to prepare the solid electrolyte membrane, and the steps are simple and easy to implement. In addition, the increase in the density of the solid electrolyte membrane makes the structural arrangement of the solid electrolyte membrane more compact, takes into account the mechanical properties of the solid electrolyte membrane, reduces the thickness of the solid electrolyte membrane, and improves the energy density of the battery. In addition, the increased density of the solid electrolyte membrane also reduces internal defects, lowers the resistance to ion transmission, forms continuous ion channels during the pressing process, improves the ionic conductivity of the solid electrolyte membrane, reduces the capacity loss of the battery during the charge and discharge process, and thus improves the battery's cycle performance.

[0042] In some embodiments, in step S10, stacking the first substrate layer and the second substrate layer comprises: the porosity of the first substrate layer satisfy: Including but not limited to 70%, 75%, 80%, 85%, 90%, 95%, etc., further, the porosity of the first substrate layer is 85% to 95%.

[0043] Porosity of the second substrate layer satisfy: Including but not limited to 0, 1%, 3%, 7%, 11%, 13%, 15%, etc.

[0044] When the porosity of the second substrate layer When the second substrate layer is a non-porous structure.

[0045] In some embodiments, the first substrate layer includes one or more of aramid film, non-woven fabric, polyimide film, melt-blown fabric, cellulose film, glass fiber film, polyethylene, and polypropylene.

[0046] In some embodiments, the first substrate layer has a thickness of 10 μm to 120 μm.

[0047] In some embodiments, the second substrate layer includes one or more of an aramid film, a non-woven fabric, and a polyimide film.

[0048] In some embodiments, before step S20, the preparation method further includes: placing the solid electrolyte powder in a powder spraying mechanism; disposing the first substrate layer below the powder spraying mechanism, and disposing the second substrate layer on a side of the first substrate layer away from the powder spraying mechanism.

[0049] In some embodiments, the solid electrolyte powder further comprises a binder, and the binder comprises a fiberizable binder.

[0050] It can be understood that the fiberizable binder in the present application refers to a binder that can be transformed from a granular state to a fibrous state under the action of high shear force.

[0051] In some embodiments, the fiberizable binder includes one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene (PE), and polypropylene (PP).

[0052] In some embodiments, the weight proportion of the binder in the solid electrolyte powder is less than 5%. Too much binder will hinder the halide solid electrolyte powder from entering the pores of the first substrate layer.

[0053] In some embodiments, the particle size of the solid electrolyte powder is 3 μm to 20 μm, including but not limited to 3 μm, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm, 19 μm, 20 μm, etc. It should be noted that the particle sizes mentioned in this application are all D50 data.

[0054] Herein, the "particle size D50" refers to the particle size corresponding to when the cumulative volume distribution percentage reaches 50% from the small particle size side in the particle size distribution of the particles.

[0055] In this embodiment, the solid electrolyte powder is added with a binder or subjected to fiberization treatment, so the bonding force between the solid electrolyte powders is greater than the bonding force between the solid electrolyte powders and the second substrate layer, providing the possibility of pressing the solid electrolyte powder back into the first substrate layer.

[0056] In some implementation modes, in step S10, the first substrate layer and the second substrate layer are in a relatively static state.

[0057] In some embodiments, the first substrate layer and the second substrate layer are both in a stationary state.

[0058] In some other specific embodiments, the first substrate layer and the second substrate layer both move in a horizontal direction away from the powder spraying mechanism, and the running speeds of the first substrate layer and the second substrate layer are kept consistent during the movement.

[0059] In some embodiments, in step S20, the particle size of at least part of the solid electrolyte powder is smaller than or equal to the pore size of the porous structure of the first substrate layer and larger than the pore size of the porous structure of the second substrate layer.

[0060] The present application further improves the barrier effect of the second substrate layer on the solid electrolyte during the pressing process by adjusting the particle size of the solid electrolyte powder and the pore size of the porous structure of the first substrate layer and the second substrate layer.

[0061] In some embodiments, the material of the solid electrolyte powder includes one or a combination of oxide solid electrolyte, sulfide solid electrolyte, and halide solid electrolyte.

[0062] It is understood that halide solid electrolyte is a known electrolyte material, which is considered to have the advantages of both oxide solid electrolyte and sulfide solid electrolyte. Halide solid electrolyte can usually use Li a MX b , where M is a metal element, which can be a mixture of multiple metal elements, the multiple metals can be of the same or different valences, and X is a halogen element. The structure of metal halide electrolytes depends on their ion radius and ion arrangement. There are generally three types of halide electrolytes commonly studied: Li a MX4, Li a MX6 and Li a MX8, etc. It can be understood that the present application does not specifically limit the type of halide solid electrolyte. On the basis of not violating the inventive concept of the present application, any known halide solid electrolyte can be used in the present application. It is only used as an illustrative example rather than a limitation on the scope of protection. The halide solid electrolyte can be Li2CdCl4, Li2MgCl4, Li2CdI4, Li2ZnI4, Li2ZrCl6, Li3InCl6, Li3YCl6, Li3ErCl6, Li3ScCl6, Li3HoCl6 and combinations thereof.

[0063] In some embodiments, the sulfide solid electrolyte includes Li 3.25 Ge 0.25 P 0.7 S4、Li7P3S 11 , Li6PS5X (X=Cl, Br, I), Li 10 GeP2S 12 , Li 6-x PS5-x Cl 1+x (x=0, 0.25, 0.375, 0.5, 0.55, 0.6), etc.

[0064] In some embodiments, the solid electrolyte is a halide solid electrolyte.

[0065] In some embodiments, step S20 specifically includes: 2 0.1 mg to 500 mg of solid electrolyte powder is sprayed on the surface of the first substrate layer.

[0066] In some embodiments, the solid electrolyte powder is sprayed onto the surface of the first substrate layer once or more times.

[0067] In some embodiments, before step S30, the step further includes: oscillating the electrolyte membrane precursor.

[0068] In some preferred embodiments, the electrolyte membrane precursor is oscillated once or more times.

[0069] In some preferred embodiments, the step of vibrating the electrolyte membrane precursor specifically includes: vibrating the electrolyte membrane precursor using a screen vibrator.

[0070] In some preferred embodiments, the oscillation frequency of the vibrating screen is 20-1000 kHz.

[0071] In some of the embodiments, step S30 specifically includes: applying a pressing force to a surface of the first substrate layer on which the solid electrolyte powder is sprayed, so as to perform a pressing treatment on the electrolyte membrane precursor.

[0072] In some embodiments, in step S30, the pressure of the pressing treatment is 2t to 3t, including but not limited to 2t, 2.2t, 2.4t, 2.6t, 2.8t, 3t, etc.

[0073] In some embodiments, in step S30, the pressing time is 0.5 min to 20 min, including but not limited to 1 min, 3 min, 5 min, 7 min, 9 min, 11 min, 13 min, 15 min, 18 min, 20 min, etc. Further, the pressing time is 3 min to 8 min.

[0074] In some embodiments, in step S30, the temperature of the pressing treatment is 60°C to 120°C.

[0075] In some embodiments, in step S30, the pressing process is performed once.

[0076] In some embodiments, in step S30, the pressing process is performed by flat plate pressing.

[0077] In some embodiments, in step S30, the pressing process is performed by roller pressing.

[0078] In some embodiments, in step S30, the pressing process is performed under an inert atmosphere.

[0079] In some embodiments, the inert atmosphere includes one or more of helium, neon, argon, krypton, or xenon.

[0080] In some embodiments, in step S40, the process for removing the second substrate layer in the intermediate is mechanical stripping.

[0081] The second aspect of the present application provides a solid electrolyte membrane, which is prepared by the preparation method provided by the first aspect.

[0082] In some embodiments, the solid electrolyte membrane has a thickness of 10 μm to 150 μm, including but not limited to 10 μm, 15 μm, 20 μm, 30 μm, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, etc.

[0083] In some embodiments, the porosity of the solid electrolyte membrane is 0.5% to 10%, including but not limited to 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.

[0084] The third aspect of the present application provides a solid-state battery, which includes a positive electrode, a negative electrode, and a solid electrolyte membrane prepared by the preparation method provided in the first aspect or the solid electrolyte membrane provided in the second aspect.

[0085] [positive electrode]:

[0086] In some embodiments, the secondary battery provided by the present invention includes a positive electrode, the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, the positive electrode active material layer having a thickness of greater than or equal to about 1 μm to less than or equal to about 1,000 μm. The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a compound that reversibly intercalates and deintercalates lithium ions.

[0087] In some embodiments, the positive electrode active material comprises one or more transition metal cations, such as manganese (Mn), nickel (Ni), cobalt (Co), chromium (Cr), iron (Fe), vanadium (V), and combinations thereof.

[0088] In some embodiments, the positive electrode active material is one of a layered oxide, a spinel, and a polyanion. For example, the layered oxide (e.g., a rock salt layered oxide) comprises one or more lithium-based positive electrode active materials selected from the group consisting of LiCoO2 (LCO), LiNi x Mn y Co 1-x-y O2 (where 0≤x≤1 and 0≤y≤1), LiNi 1-x-y Co x Al y O2 (where 0≤x≤1 and 0≤y≤1), LiNi x Mn 1-x O2 (where 0≤x≤1), and Li 1+x MO2 (wherein M is one of Mn, Ni, Co and Al and 0≤x≤1). The spinel comprises one or more lithium-based positive active materials selected from the group consisting of LiMn2O4 (LMO) and LiNi x Mn 1.5 O4. The olivine type contains one or more lithium-based positive electrode active materials LiMPO4 (wherein M is at least one of Fe, Ni, Co and Mn). The polyanion cation contains, for example, phosphates such as LiV2(PO4)3 and / or silicates such as LiFeSiO4.

[0089] In some embodiments, the positive electrode active material layer includes a binder, which improves the bonding between the positive electrode active material particles and also improves the bonding between the positive electrode active material layer and the positive electrode current collector.

[0090] In some embodiments, non-limiting examples of binders include polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like.

[0091] In some embodiments of the present invention, the mass of the binder accounts for 1%-20% of the mass of the positive electrode material layer.

[0092] In some embodiments of the present invention, the positive electrode active material layer includes a conductive agent to impart conductivity to the electrode. The conductive agent may include any conductive material as long as it does not cause chemical changes. Non-limiting examples of conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives) and mixtures thereof.

[0093] In some embodiments, the mass of the conductive agent accounts for 1%-20% of the mass of the positive electrode material layer.

[0094] In some embodiments, the positive electrode plate provided by the present invention further includes a fast ion conductor for improving the ionic conductivity of the positive electrode. The present invention does not limit the type of fast ion conductor, which can be an oxide solid electrolyte, a sulfide solid electrolyte, a halide solid electrolyte, a lithium salt, etc. Optionally, the mass of the fast ion conductor accounts for 1%-20% of the mass of the positive electrode plate; preferably 5%-20%.

[0095] In some embodiments, the positive electrode sheet includes a positive electrode current collector. For example, the positive electrode current collector may be aluminum (Al) or a composite aluminum foil, but is not limited thereto.

[0096] It is understood that the above examples of positive electrode active materials, binders, and conductive materials are only illustrative, and any known positive electrode active materials, binders, and conductive materials can be used in this application without violating the inventive concept of this application. And the addition of known additives based on actual use requirements should also be considered within the scope of protection of this application.

[0097] [negative electrode]:

[0098] In some embodiments of the present invention, the negative electrode sheet includes a current collector and a negative electrode active material layer disposed on the current collector.

[0099] In the present invention, the specific types of negative electrode active materials are not subject to specific restrictions and can be selected according to needs. Specifically, the negative electrode active material is selected from natural graphite, artificial graphite, mesophase microcarbon beads (MCMB for short), hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, spinel structured lithiated TiO2-Li4Ti5O 12 , Li-Al alloy. Non-limiting examples of carbon materials include crystalline carbon, amorphous carbon and mixtures thereof. Crystalline carbon can be amorphous or flake-shaped, platelet-shaped, spherical or fibrous natural graphite or artificial graphite. Amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbide, calcined coke, etc.

[0100] In some embodiments, metal elements and metal compounds can also be selected as negative electrode active materials, such as compounds containing metals or metalloids such as Li, Ag, Al, Bi, Cu, Ga, Ge, In, Ni, Pb, Sb, Si, Sn, Sr, and Zn.

[0101] In some embodiments, the mass percentage of the negative electrode active material contained in the negative electrode active material layer may be 80%-99%, for example, 80%, 85%, 90%, 95%, 97%, 99%, etc., preferably 95%-97%.

[0102] In some embodiments, the negative electrode material layer may include a binder; the binder improves bonding of negative electrode active material particles to each other and bonding of the negative electrode active material to the current collector.

[0103] In some embodiments, non-limiting examples of binders include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy resin, nylon, and the like.

[0104] In some embodiments, the negative electrode active material layer can be obtained by coating a negative electrode slurry on a negative electrode current collector and then drying the negative electrode slurry, wherein the negative electrode slurry includes at least a negative electrode active material and a negative electrode binder. When an aqueous solvent is used as a liquid medium for forming the negative electrode slurry, a thickener is preferably used for slurrying, and the thickener can generally be used to adjust the viscosity of the slurry.

[0105] In some embodiments, the aforementioned viscosity enhancer may be one or more of the following: carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof.

[0106] In some embodiments, the mass proportion of the thickener in the negative electrode slurry can be 0.1%-5%, for example, 0.1%, 0.2%, 0.5%, 0.6%, 1%, 2%, 3%, 4%, 5%, etc., preferably 0.5%-3%, and more preferably 0.6%-2%.

[0107] In some embodiments, the negative electrode active material layer includes a conductive material so that the electrode has conductivity. The conductive material may include any conductive material as long as it does not cause chemical changes. Non-limiting examples of conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., such as copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives) and mixtures thereof.

[0108] In some embodiments of the present invention, the negative electrode current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0109] Solid-state batteries:

[0110] In some embodiments, the solid-state battery of the present invention comprises the above-mentioned positive electrode sheet, negative electrode sheet and solid electrolyte membrane.

[0111] In some embodiments, the secondary battery according to the present invention is made by stacking the above-mentioned positive and negative electrode sheets.

[0112] In some embodiments, the secondary battery of the present invention may include an outer package, which may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0113] The following are specific embodiments.

[0114] Example 1

[0115] Solid electrolyte membrane:

[0116] (1) The solid electrolyte powder Li3InCl6 is placed in a powder spraying mechanism, wherein the particle size D50 of the Li3InCl6 powder is 10 μm.

[0117] (2) The first substrate layer is arranged below the powder spraying mechanism, and the second substrate layer is arranged on the side of the first substrate layer away from the powder spraying mechanism. The first substrate layer is a polyolefin film with a porosity of 90%, and the second substrate layer is a non-woven fabric with a porosity of 5%. The thickness of the first substrate layer is 60 μm.

[0118] (3) Spraying Li3InCl6 powder into the porous structure of the first substrate layer to obtain an electrolyte membrane precursor.

[0119] (4) The electrolyte membrane precursor and the second substrate layer are laminated and pressed to obtain an intermediate, wherein the pressing pressure is 3 tons, the pressing time is 15 minutes, the pressing number is 1, and the pressing method is roller pressing.

[0120] (5) The second substrate layer in the intermediate is removed to obtain a solid electrolyte membrane.

[0121] Solid-state batteries:

[0122] The solid electrolyte membrane is aligned and stacked with the positive electrode sheet, and after rolling, the negative electrode sheet is attached, and after assembling with the shell, a solid-state battery is obtained. The positive electrode composition is 95wt% NCM622, 3wt% PTFE and 2wt% super-P; the negative electrode composition is 95wt% graphite, 3wt% (CMC+SBR) and 2wt% super-P.

[0123] Example 2

[0124] The preparation method of the solid electrolyte membrane and the solid-state battery in this embodiment is basically the same as the preparation method in Example 1, except that:

[0125] The porosity of the second substrate layer in step (2) is 0.

[0126] Example 3

[0127] The preparation method of the solid electrolyte membrane and the solid-state battery in this embodiment is basically the same as the preparation method in Example 1, except that:

[0128] The porosity of the second substrate layer in step (2) is 15%.

[0129] Example 4

[0130] The preparation method of the solid electrolyte membrane and the solid-state battery in this embodiment is basically the same as the preparation method in Example 1, except that:

[0131] The particle size D50 of the Li3InCl6 powder in step (1) is 3 μm.

[0132] Example 5

[0133] The preparation method of the solid electrolyte membrane and the solid-state battery in this embodiment is basically the same as the preparation method in Example 1, except that:

[0134] The particle size D50 of the Li3InCl6 powder in step (4) is 20 μm.

[0135] Example 6

[0136] The preparation method of the solid electrolyte membrane and the solid-state battery in this embodiment is basically the same as the preparation method in Example 1, except that:

[0137] The thickness of the first substrate layer in step (2) is 10 μm.

[0138] Example 7

[0139] The preparation method of the solid electrolyte membrane and the solid-state battery in this embodiment is basically the same as the preparation method in Example 1, except that:

[0140] The thickness of the first substrate layer in step (2) is 120 μm.

[0141] Example 8

[0142] The preparation method of the solid electrolyte membrane and the solid-state battery in this embodiment is basically the same as the preparation method in Example 1, except that:

[0143] In step (2), the first substrate layer is a non-woven fabric with a porosity of 95%.

[0144] Example 9

[0145] The preparation method of the solid electrolyte membrane and the solid-state battery in this embodiment is basically the same as the preparation method in Example 1, except that:

[0146] In step (2), the first substrate layer is a non-woven fabric with a porosity of 70%.

[0147] Example 10

[0148] The preparation method of the solid electrolyte membrane and the lithium ion battery in this embodiment is basically the same as the preparation method in Example 1, except that:

[0149] In step (1), the solid electrolyte powder is replaced with Li2ZrCl6 powder.

[0150] Comparative Example 1

[0151] Solid electrolyte membrane:

[0152] (1) Place Li3InCl6 powder in the powder spraying mechanism.

[0153] (2) The first substrate layer is arranged below the powder spraying mechanism, wherein the first substrate layer is a non-woven fabric with a porosity of 90%.

[0154] (3) Spraying Li3InCl6 powder into the porous structure of the first substrate layer and performing a pressing process to obtain a solid electrolyte membrane. The pressing process pressure is 3t, the pressing process time is 15min, the pressing number of the pressing process is 1, and the pressing process method is roller pressing.

[0155] Solid-state batteries:

[0156] The solid electrolyte membrane is aligned and stacked with the positive electrode sheet, and after rolling, the negative electrode sheet is attached, and after assembling with the shell, a button-type lithium-ion battery is obtained. The positive electrode composition is 95wt% NCM622, 3wt% PTFE and 2wt% super-P; the negative electrode composition is 95wt% graphite, 3wt% (CMC+SBR) and 2wt% super-P.

[0157] The data of the above embodiments and comparative examples are sorted out as shown in Table 1.

[0158] Table 1

[0159]

[0160] Test Case

[0161] (1) Porosity test

[0162] The porosity of the solid electrolyte membranes in the above embodiments and comparative examples was tested using an SSA-4200 pore size and specific surface area analyzer. The test results are shown in Table 2.

[0163] (2) Thickness test

[0164] According to the provisions of GB / T 6672-2001ISO 4593:1993, the thickness of the solid electrolyte membrane in the above embodiment and comparative example was tested using a Mahr thickness gauge. The test results are shown in Table 2.

[0165] (3) Tensile strength test

[0166] Tensile strength refers to the ratio of the maximum tensile force to the cross section of the sample during the tensile test. The tensile strength test was performed on the solid electrolyte membranes in the above embodiments and comparative examples, specifically in accordance with the provisions of GB / T1040.3-2006. The test results are shown in Table 2.

[0167] (4) Ionic conductivity test

[0168] At 25°C, the solid electrolyte membrane obtained in the above embodiments and comparative examples adopts a test structure of stainless steel sheet / solid electrolyte membrane / stainless steel sheet, the frequency range is 0.1 Hz-7 MHz, and the AC signal amplitude Z is 10 -2 The AC impedance test was carried out under the condition of 100 V, and the calculation was performed according to the ionic conductivity calculation formula σ=L / (S*R), where L is the thickness of the solid electrolyte membrane, S is the cross-sectional area of ​​the solid electrolyte membrane, and R represents the charge transfer resistance. The test results are shown in Table 2.

[0169] (5) Cyclic performance test

[0170] The solid-state batteries of the above embodiments and comparative examples were subjected to cycle tests. At a temperature of 25°C ± 2°C, the first step was to charge at 0.1C or a specified current to the final voltage, the cut-off current was 0.01C, and the battery was left standing for 30 minutes; the second step was to discharge at 0.1C to the final discharge voltage (2.75V), record the discharge capacity, and leave the battery standing for 30 minutes; the first and second steps were repeated to test the cycle performance of the solid-state battery for 300 cycles. The test results are shown in Table 2.

[0171] Table 2

[0172]

[0173]

[0174] As shown in Table 2, by comparing Examples 1 to 10 and Comparative Example 1, it can be seen that the use of the solid electrolyte membrane provided by the present application reduces the porosity of the solid electrolyte membrane, improves the tensile strength and ionic conductivity of the solid electrolyte membrane while ensuring that the thickness of the solid electrolyte membrane is relatively thin, and improves the energy density cycle capacity retention rate.

[0175] As shown in Table 2, by comparing Example 1 and Example 2, the porosity of the second substrate layer is When the second substrate layer is formed, it is denser and has a stronger barrier effect on the solid electrolyte powder during the pressing process, which further reduces the porosity of the composite solid electrolyte membrane, reduces the thickness of the solid electrolyte membrane, improves the tensile strength and ionic conductivity of the solid electrolyte membrane, and improves the cycle capacity retention rate.

[0176] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0177] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the technical concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for preparing a solid electrolyte membrane, characterized in that: The following steps are involved: Laying a first substrate layer and a second substrate layer in a stacked manner; Wherein, both the first substrate layer and the second substrate layer are porous structures, and the porosity of the second substrate layer is less than that of the first substrate layer; or, the first substrate layer is a porous structure, and the second substrate layer is a non-porous structure; Spraying solid electrolyte powder onto the surface of the first substrate layer to obtain an electrolyte membrane precursor; Performing a pressing process on the electrolyte membrane precursor to obtain an intermediate; The second substrate layer in the intermediate is removed to obtain a solid electrolyte membrane.

2. The method for preparing a solid electrolyte membrane according to claim 1, characterized in that: In the step of stacking the first substrate layer and the second substrate layer, the porosity φ1 of the first substrate layer satisfies: 70%≤φ1≤95%, and the porosity φ2 of the second substrate layer satisfies: φ2<15%.

3. The method for preparing a solid electrolyte membrane according to claim 2, characterized in that: The particle size of at least part of the solid electrolyte powder is smaller than or equal to the pore size of the porous structure of the first substrate layer and larger than the pore size of the porous structure of the second substrate layer; Preferably, the particle size D50 of the solid electrolyte powder is 3 μm to 20 μm.

4. The method for preparing a solid electrolyte membrane according to claim 1, characterized in that: The step of pressing the electrolyte membrane precursor specifically comprises: A pressing force is applied to the surface of the first substrate layer on one side of which the solid electrolyte powder is sprayed, so as to perform a pressing treatment on the electrolyte membrane precursor.

5. The method for preparing a solid electrolyte membrane according to claim 1, characterized in that: The pressure of the pressing treatment is 2t to 3t; the time of the pressing treatment is 0.5min to 20min; Preferably, the temperature of the pressing treatment is 60°C to 120°C; Preferably, the pressing process is performed once.

6. The method for preparing a solid electrolyte membrane according to claim 1, characterized in that: The step of spraying the solid electrolyte powder onto the surface of the first substrate layer specifically includes: In every 1cm 2 Spraying 0.1 mg to 500 mg of solid electrolyte powder on the surface of the first substrate layer; Preferably, the solid electrolyte powder is sprayed onto the surface of the first substrate layer once or more times.

7. The method for preparing a solid electrolyte membrane according to any one of claims 1 to 6, characterized in that: Before the step of pressing the electrolyte membrane precursor to obtain an intermediate, the method further comprises: oscillating the electrolyte membrane precursor; Preferably, the number of oscillating the electrolyte membrane precursor is 1 time or more; Preferably, the step of oscillating the electrolyte membrane precursor specifically comprises: oscillating the electrolyte membrane precursor using a vibrating screen; Preferably, the vibration frequency of the vibrating screen is 20kHz to 1000kHz.

8. A solid electrolyte membrane, characterized in that: The solid electrolyte membrane is prepared by the preparation method according to any one of claims 1 to 7.

9. The solid electrolyte membrane according to claim 8, characterized in that The porosity of the solid electrolyte membrane is 0.1% to 10%.

10. A solid-state battery, characterized in that: The invention comprises a positive electrode, a negative electrode and a solid electrolyte membrane prepared by the preparation method according to any one of claims 1 to 7 or a solid electrolyte membrane according to claim 8 or 9.

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