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

Abstract

The invention provides a solid electrolyte membrane, a preparation method thereof and a solid-state battery, and relates to the technical field of energy storage. The preparation method of the solid electrolyte membrane comprises the steps that a second base material layer is formed on a first base material layer, a composite base material layer is prepared, the porosity of the second base material layer is smaller than that of the first base material layer, first powder is sprayed on the side, opposite to the second base material layer, of the first base material layer, pressing treatment is conducted, and the solid electrolyte membrane is formed. According to the preparation method of the solid electrolyte membrane, the pressing frequency is reduced, the density of the solid electrolyte membrane is improved, the production efficiency is improved, and the damage to the solid electrolyte membrane base material in the pressing process is reduced.

Description

Technical Field

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

[0002] Solid-state batteries are energy storage elements that can store electrical energy and release it when needed. Compared with traditional liquid batteries, solid-state batteries use solid electrolytes instead of liquid electrolytes for ion transmission, which has higher safety, higher energy density, faster charging speed and longer cycle life. Solid-state electrolyte membranes play an important role in achieving the passage of lithium ions in solid-state batteries.

[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 that can avoid the problem of easy falling of the solid electrolyte in the solid electrolyte membrane, and to provide a solid electrolyte membrane with good density and a preparation method thereof, and a solid-state battery.

[0006] In one aspect of the present application, a method for preparing a solid electrolyte membrane is provided, comprising the following steps:

[0007] forming a second substrate layer on the first substrate layer to prepare a composite substrate layer;

[0008] Wherein, both the first substrate layer and the second substrate layer are porous structures, and the porosity of the second substrate layer is smaller than the porosity of the first substrate layer;

[0009] Spraying a first powder on a side of the first substrate layer facing away from the second substrate layer to form a solid electrolyte membrane precursor, wherein the first powder includes a solid electrolyte;

[0010] The solid electrolyte membrane precursor is pressed to form a solid electrolyte membrane.

[0011] In some embodiments, forming the second substrate layer on the first substrate layer includes: using the first substrate layer as a base, and forming the second substrate layer on the first substrate layer by electrospinning.

[0012] In some embodiments, the porosity of the first substrate layer is 70% to 95%;

[0013] In some embodiments, the porosity of the second substrate layer is 50% to 85%.

[0014] In some embodiments, forming the second substrate layer on the first substrate layer includes: forming a second substrate layer on the first substrate layer with a thickness less than that of the first substrate layer;

[0015] In some embodiments, the thickness ratio of the second substrate layer to the first substrate layer is 1:6 to 2:3.

[0016] In some embodiments, spraying the first powder on the side of the first substrate layer facing away from the second substrate layer comprises: 2 0.05 mg to 20 mg of the first powder is sprayed on the surface area of ​​the first substrate layer.

[0017] In some embodiments, the first powder is sprayed once or more times.

[0018] In some embodiments, at least a portion of the solid electrolyte has a particle size smaller than the pore size of the first substrate layer and at least a portion of the solid electrolyte has a particle size smaller than the pore size of the second substrate layer.

[0019] In some of the embodiments, the particle size of the solid electrolyte is 1 μm to 10 μm.

[0020] In some embodiments, the first powder further includes a binder, and the mass ratio of the binder to the halide solid electrolyte is 5:95 to 1:99.

[0021] In some of the embodiments, the electrolyte membrane precursor is further shaken before the pressing process.

[0022] In some embodiments, the electrolyte membrane precursor is oscillated once or more times.

[0023] In some embodiments, shaking the electrolyte membrane precursor includes shaking the electrolyte membrane precursor using a screen shaker.

[0024] In some embodiments, oscillating the electrolyte membrane precursor includes: the oscillation frequency of the mesh is 20 kHz-1000 kHz.

[0025] In some embodiments, the pressure of the pressing process is 2t~3t; the time of the pressing process is 0.5min~20min;

[0026] In some embodiments, the temperature of the pressing treatment is 60°C to 120°C;

[0027] In some embodiments, the pressing treatment includes applying a pressing force to a surface of a side of the first substrate layer sprayed with the first powder, thereby performing a pressing treatment on the electrolyte membrane precursor;

[0028] In some embodiments, the pressing process is performed once.

[0029] Another aspect of the present application provides a solid electrolyte membrane prepared by the above preparation method.

[0030] In some of the embodiments, the porosity of the solid electrolyte membrane is 0.1% to 10%.

[0031] In some embodiments, the solid electrolyte membrane has a thickness of 10 μm to 100 μm.

[0032] In some embodiments, in the solid electrolyte membrane, in the first substrate layer, the mass m1 of the first solid electrolyte is greater than the mass m2 of the second solid electrolyte.

[0033] Another aspect of the present application provides a solid-state battery, which includes a positive electrode sheet, a negative electrode sheet and a solid electrolyte membrane.

[0034] The preparation method of the present application sets a second substrate layer with a smaller porosity on one side of the first substrate layer, and the second substrate layer supports the first powder. Since the second substrate layer is stacked with the first substrate layer before the solid electrolyte powder is sprayed on the first substrate layer, when the first powder escapes from the first substrate layer, under the combined action of pressure and the supporting force of the second substrate layer, the escaped first powder part returns to the first substrate layer, and the remaining escaped first powder enters the second substrate layer with higher density. 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, and reduces damage to the solid electrolyte membrane substrate during the pressing process.

[0035] Furthermore, by controlling the thickness ratio of the first substrate layer and the second substrate layer, and controlling the synergistic effect of the particle size of the solid electrolyte and the first substrate layer, the second substrate layer, etc., it is beneficial to further ensure the lithium ion transmission capacity of the solid electrolyte membrane.

[0036] In addition, the increase in the density of the solid electrolyte membrane makes the structure of the solid electrolyte membrane more compact, taking into account the mechanical properties of the solid electrolyte membrane while reducing the thickness of the solid electrolyte membrane and improving the energy density of the battery. In addition, the increase in the density of the solid electrolyte membrane also reduces internal defects, reduces the resistance to ion transmission, forms a continuous ion channel during the pressing process, improves the ion conductivity of the solid electrolyte membrane, reduces the capacity loss of the battery during the charge and discharge process, and thus improves the cycle performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic diagram of a method for preparing a solid electrolyte membrane according to one embodiment. DETAILED DESCRIPTION

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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).

[0046] In conventional technology, a solid electrolyte membrane is obtained by pressing solid electrolyte powder into a base membrane, wherein the solid electrolyte realizes the function of lithium ion transmission, and the base membrane realizes the improvement of the mechanical strength of the solid electrolyte membrane. However, it is difficult to achieve the matching of the particle size of the solid electrolyte powder and the pore size of the base membrane during pressing. When the particle size of the solid electrolyte powder is smaller than the pore size of the base membrane pore structure, it is not easy for the solid electrolyte powder to form a continuous ion-conducting path in the pore structure of the base membrane, and it is easy to escape from the pore structure of the base membrane. During the rolling process, it is necessary to sprinkle powder repeatedly. The rolling process is relatively complicated. During use, the solid electrolyte powder is also easy to escape, and the stability of the solid electrolyte membrane is poor. Moreover, a large amount of adhesive is required to combine the solid electrolyte powder with the base membrane, so that the prepared solid electrolyte membrane cannot have both the characteristics of thinness and density. When the particle size of the solid electrolyte powder is larger than the pore size of the base membrane pore structure, it is difficult to press the solid electrolyte powder into the base membrane. If the problem is solved by increasing the rolling pressure, it is easy to damage the pore structure of the base membrane, resulting in a decrease in the mechanical strength of the solid electrolyte membrane. Since the solid electrolyte powder is difficult to completely enter the pore structure of the base membrane, it is also easy to escape from the base membrane.

[0047] In order to solve the problem that the solid electrolyte membrane cannot be both thin and dense, the present application provides a method for preparing a solid electrolyte membrane, comprising the following steps:

[0048] S10, forming a second substrate layer on the first substrate layer to prepare a composite substrate layer;

[0049] Wherein, both the first substrate layer and the second substrate layer are porous structures, and the porosity of the second substrate layer is smaller than the porosity of the first substrate layer.

[0050] In some embodiments, forming the second substrate layer on the first substrate layer includes: using the first substrate layer as a base, and forming the second substrate layer on the first substrate layer by electrospinning. In this way, the porosity of the second substrate layer can be controlled by the electrospinning process.

[0051] In some embodiments, forming a second substrate layer on the first substrate layer includes: using the first substrate layer as a substrate, preparing the second substrate layer by a melt-blown spinning process. Unlike electrospinning, the raw materials prepared by melt-blown spinning need to pass through a nozzle that melts the polymer, and high-temperature air is used to promote the deposition of spinning droplets on a cooled substrate at high speed. Compared with electrospinning, the whole process does not require an external electric field and does not require additional solvents. The thickness and density of the second substrate layer can be controlled within a reasonable range through the melt-blown spinning process.

[0052] 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.

[0053] In some embodiments, the porosity of the first substrate layer is 70% to 95%. Optionally, the porosity of the first substrate layer may be, but is not limited to, 70%, 75%, 80%, 85%, 90% or 95%, etc. Further, the porosity of the first substrate layer is 80% to 90%.

[0054] In some embodiments, the porosity of the second substrate layer is 50% to 85%. Alternatively, the porosity of the second substrate layer may be, but is not limited to, 50%, 55%, 60%, 65%, 70%, 75%, 80% or 85%. Further, the porosity of the second substrate layer may be 60% to 70%.

[0055] In some embodiments, forming the second substrate layer on the first substrate layer includes: forming a second substrate layer on the first substrate layer with a thickness less than that of the first substrate layer;

[0056] In some embodiments, the thickness ratio of the second substrate layer to the first substrate layer is 1:6 to 2:3. Alternatively, the thickness ratio of the second substrate layer to the first substrate layer may be, but is not limited to, 1:6, 1:5, 1:4, 1:3, 2:5, 1:2, 2:3.

[0057] S20, spraying a first powder on a side of the first substrate layer facing away from the second substrate layer to form a solid electrolyte membrane precursor.

[0058] In some embodiments, spraying the first powder on the side of the first substrate layer facing away from the second substrate layer comprises: 2 0.05-20 mg of the first powder is sprayed on the surface area of ​​the first substrate layer. By controlling the mass of the first powder, the particle size of the solid electrolyte, and the thickness ratio of the first substrate layer to the second substrate layer, the first powder is ensured to be contained in both the first substrate layer and the second substrate layer, which is conducive to ensuring the good lithium ion conductivity of the prepared solid electrolyte membrane.

[0059] In some embodiments, the first powder is sprayed once or more times.

[0060] Wherein, the first powder includes a solid electrolyte.

[0061] In some embodiments, the solid electrolyte 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 PS 5−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, at least a portion of the solid electrolyte has a particle size smaller than the pore size of the first substrate layer and at least a portion of the solid electrolyte has a particle size smaller than the pore size of the second substrate layer.

[0066] In some embodiments, the particle size of the solid electrolyte is 1 μm to 10 μm, including but not limited to 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, 10 μm, etc. It should be noted that the particle sizes mentioned in this application are all D50 data.

[0067] In some embodiments, the solid electrolyte further comprises a binder, and the binder comprises a fiberizable binder.

[0068] It can be understood that the fiberizable binder of 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.

[0069] 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).

[0070] In some embodiments, the weight proportion of the binder in the solid electrolyte is less than 5%. Too much binder will hinder the solid electrolyte powder from entering the pores of the first substrate layer.

[0071] S30, pressing the solid electrolyte membrane precursor to form a solid electrolyte membrane.

[0072] In some embodiments, before the pressing process, the electrolyte membrane precursor is further vibrated. By vibrating the electrolyte membrane precursor, the first powder is evenly distributed on the surface of the first substrate layer, which is beneficial to the uniformity of the thickness of the prepared solid electrolyte membrane and prevents the battery prepared by the solid electrolyte membrane from having irregular lithium deposition.

[0073] In some embodiments, the electrolyte membrane precursor is oscillated once or more times.

[0074] In some embodiments, shaking the electrolyte membrane precursor includes shaking the electrolyte membrane precursor using a screen shaker.

[0075] In some embodiments, oscillating the electrolyte membrane precursor includes: the oscillation frequency of the mesh is 20 kHz-1000 kHz.

[0076] In some embodiments, the process of spraying the first powder and shaking the electrolyte membrane precursor is repeated 2-5 times.

[0077] In some embodiments, the pressure of the pressing process is 2t~3t; the time of the pressing process is 0.5min~20min;

[0078] In some embodiments, the temperature of the pressing treatment is 60°C to 120°C;

[0079] In some embodiments, the pressing treatment includes applying a pressing force to a surface of a side of the first substrate layer sprayed with the first powder, thereby performing a pressing treatment on the electrolyte membrane precursor;

[0080] In some embodiments, the pressing process is performed once.

[0081] Another aspect of the present application provides a solid electrolyte membrane prepared by the above preparation method.

[0082] In some embodiments, the porosity of the solid electrolyte membrane is 0.1% to 10%. Optionally, the porosity of the solid electrolyte membrane can be, but is not limited to, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%. After the first substrate layer is filled with the first powder, the overall porosity of the solid electrolyte membrane decreases. Within the above porosity range, the solid electrolyte membrane has good mechanical strength and good lithium ion pass rate, thereby improving the cycle performance of the solid-state battery.

[0083] In some embodiments, the solid electrolyte membrane has a thickness of 10 μm to 100 μm.

[0084] In some embodiments, in the solid electrolyte membrane, the mass of the first powder in the first substrate layer after pressing is greater than the mass of the first powder in the second substrate layer after pressing.

[0085] The present application also provides a solid-state battery, which includes a positive electrode sheet, a negative electrode sheet and a solid electrolyte membrane. The solid-state battery can be a full solid-state battery or a semi-solid-state battery.

[0086] Positive electrode:

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] In some of these 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.

[0092] 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.

[0093] 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.

[0094] In some embodiments, the mass of the conductive agent accounts for 1%-20% of the mass of the positive electrode material layer.

[0095] 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%.

[0096] In some embodiments, the positive electrode sheet includes a positive electrode current collector. For example, the positive electrode current collector may be aluminum (Al), but is not limited thereto.

[0097] 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.

[0098] Negative electrode:

[0099] 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.

[0100] 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.

[0101] In some of the 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.

[0102] 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%.

[0103] In some embodiments, the negative electrode material layer may include a binder; the binder improves the bonding between negative electrode active material particles and the bonding between the negative electrode active material and the current collector.

[0104] In some of these 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.

[0105] 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.

[0106] In some embodiments, the aforementioned thickener 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.

[0107] 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 further preferably 0.6%-2%.

[0108] 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.

[0109] 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.

[0110] Secondary battery:

[0111] In some embodiments, the secondary battery of the present invention comprises the above-mentioned positive electrode sheet, negative electrode sheet, separator, electrolyte, etc., but is not limited thereto.

[0112] In some embodiments, the secondary battery according to the present invention is made by stacking the above-mentioned positive and negative electrode sheets.

[0113] 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.

[0114] The following are specific embodiments.

[0115] Example 1

[0116] Preparation of solid electrolyte membrane:

[0117] (1) A second substrate layer is formed on a first substrate layer to prepare a composite substrate layer.

[0118] Wherein, the first substrate layer and the second substrate layer are both porous structures, the first substrate layer is a non-woven fabric, and its porosity is 85%. The second substrate layer is formed on the first substrate layer by an electrostatic spinning process. Wherein, the second substrate layer is a polypropylene porous membrane, and its porosity is 70%, and the thickness ratio of the second substrate layer to the first substrate layer is 5:12.

[0119] (2) Spraying a first powder on a side of the first substrate layer facing away from the second substrate layer to form a solid electrolyte membrane precursor, and oscillating the electrolyte membrane precursor using a vibrating screen so that the first powder is evenly spread on the first substrate layer.

[0120] The first powder material includes solid electrolyte powder Li2ZrCl6, and the particle size D50 is 5 μm;

[0121] Every 1cm 2 Spray 6 mg of the first powder on the surface area of ​​the first substrate layer;

[0122] The vibration frequency of the vibrating screen is 30 kHz.

[0123] (3) A pressing force is applied to the surface of the first substrate layer on which the first powder is sprayed, so as to press the electrolyte membrane precursor and form a solid electrolyte membrane.

[0124] The pressing pressure was 2.5 t, the pressing time was 15 min, the pressing times was 1, the pressing method was flat plate pressing, and the pressing temperature was 70°C.

[0125] The solid-state battery is a lithium-ion battery, and the preparation method of the lithium-ion battery is:

[0126] The positive electrode sheets are aligned and stacked on one side of the first substrate layer in the solid electrolyte membrane, and after rolling, the negative electrode sheets are attached to the second substrate layer in the solid electrolyte membrane. 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.

[0127] Example 2

[0128] The preparation method of the solid electrolyte membrane and the preparation method of the lithium ion battery in this embodiment are basically the same as those in Embodiment 1, except that:

[0129] In step (1), the porosity of the first substrate layer is 70%, and the porosity of the second substrate layer is 50%.

[0130] Example 3

[0131] The preparation method of the solid electrolyte membrane and the preparation method of the lithium ion battery in this embodiment are basically the same as those in Embodiment 1, except that:

[0132] In step (1), the porosity of the first substrate layer is 95%, and the porosity of the second substrate layer is 70%.

[0133] Example 4

[0134] The preparation method of the solid electrolyte membrane and the preparation method of the lithium ion battery in this embodiment are basically the same as those in Embodiment 1, except that:

[0135] In step (1), the porosity of the first substrate layer is 85%, and the porosity of the second substrate layer is 50%.

[0136] Example 5

[0137] The preparation method of the solid electrolyte membrane and the preparation method of the lithium ion battery in this embodiment are basically the same as those in Embodiment 1, except that:

[0138] In step (1), the porosity of the first substrate layer is 95%, and the porosity of the second substrate layer is 85%.

[0139] Example 6

[0140] The preparation method of the solid electrolyte membrane and the preparation method of the lithium ion battery in this embodiment are basically the same as those in Embodiment 1, except that:

[0141] In step (2), the particle size D50 of the first solid electrolyte is 1 μm.

[0142] Example 7

[0143] The preparation method of the solid electrolyte membrane and the preparation method of the lithium ion battery in this embodiment are basically the same as those in Embodiment 1, except that:

[0144] In step (2), the particle size D50 of the first solid electrolyte is 10 μm.

[0145] Example 8

[0146] The preparation method of the solid electrolyte membrane and the preparation method of the lithium ion battery in this embodiment are basically the same as those in Embodiment 1, except that:

[0147] In step (1), the thickness ratio of the second substrate layer to the first substrate layer is 1:6.

[0148] Example 9

[0149] The preparation method of the solid electrolyte membrane and the preparation method of the lithium ion battery in this embodiment are basically the same as those in Embodiment 1, except that:

[0150] In step (1), the thickness ratio of the second substrate layer to the first substrate layer is 2:3.

[0151] Example 10

[0152] The preparation method of the solid electrolyte membrane and the preparation method of the lithium ion battery in this embodiment are basically the same as those in Embodiment 1, except that:

[0153] In step (1), the initial porosity of the first substrate layer is 65%, and the initial porosity of the second substrate layer is 45%.

[0154] In step (2), the thickness ratio of the second substrate layer to the first substrate layer is 1:8. The particle size D50 of the first solid electrolyte is 12 μm.

[0155] In step (2), no oscillation is performed.

[0156] Embodiment 11

[0157] The preparation method of the solid electrolyte membrane and the preparation method of the lithium ion battery in this embodiment are basically the same as those in Embodiment 1, except that: in step 1), the second substrate layer is prepared by melt-blowing spinning process with the first substrate layer as the base.

[0158] Comparative Example 1

[0159] The preparation method of the solid electrolyte membrane and the preparation method of the lithium ion battery in this comparative example are basically the same as those in Example 1, except that:

[0160] The porosity of the first substrate layer of the solid electrolyte membrane is less than that of the second substrate layer, the porosity of the first substrate layer is 70%, and the porosity of the second substrate layer is 85%.

[0161] Comparative Example 2

[0162] The preparation method of the solid electrolyte membrane and the preparation method of the lithium ion battery in this comparative example are basically the same as those in Example 1, except that:

[0163] The solid electrolyte membrane includes only the first substrate layer and has a thickness of 40 μm.

[0164] Comparative Example 3

[0165] The preparation method of the solid electrolyte membrane and the preparation method of the lithium ion battery in this comparative example are basically the same as those in Example 1, except that:

[0166] In step (2), the solid electrolyte powder Li2ZrCl6 is first mixed with the binder PTFE, and then hot-pressed after fiberization to form a solid electrolyte layer. The solid electrolyte layer is then stacked on the side of the first substrate layer facing away from the second substrate layer, and then pressed to form a solid electrolyte membrane.

[0167] The process parameters of Examples 1 to 11 and Comparative Examples 1 to 3 are listed in Table 1.

[0168] Table 1

[0169]

[0170] The test results are shown in Table 2 below, where the test conditions or test standards for each performance test item are:

[0171] (1) Porosity test

[0172] The prepared halide solid electrolyte membrane was stacked into 5 layers, pressed tightly, and the air therein was removed. The porosity was tested by mercury intrusion method (GBT 21650.1).

[0173] (2) Ionic conductivity test

[0174] At 25°C, a test structure of stainless steel sheet / solid electrolyte membrane / stainless steel sheet was used, the frequency range was 0.1Hz~7MHz, and the AC signal amplitude Z was 10 -2 The AC impedance test was carried out under the condition of V, and the ionic conductivity was calculated according to the 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.

[0175] (3) Battery capacity test

[0176] The solid-state batteries in the embodiments and comparative examples were subjected to capacity tests, left to stand for 1 min, and discharged at a discharge current of 0.1 C to a cut-off voltage of 2.75 V, and the first discharge capacity was recorded.

[0177] (4) Cyclic performance test

[0178] At a temperature of 25℃±2℃, in the first step, charge at 0.1C or specified current to the termination voltage, with a cutoff current of 0.01C, and let stand for 30 minutes; in the second step, discharge at 0.1C to the discharge final voltage (2.75V), record the discharge capacity, and let stand for 30 minutes; cycle the first and second steps to test the cycle performance of the lithium-ion battery for 300 cycles.

[0179] Table 2

[0180]

[0181] As shown in Table 2, by comparing Examples 1 to 11 and Comparative Examples 1 to 3, it can be seen that the solid electrolyte membrane provided by the present application improves the cycle capacity retention rate, can improve the cycle stability of the battery, and extend the battery life.

[0182] 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.

[0183] 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 construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A method for preparing a solid electrolyte membrane, characterized in that: The steps include: forming a second substrate layer on the first substrate layer to prepare a composite substrate layer; Wherein, both the first substrate layer and the second substrate layer have porous structures, and the porosity of the second substrate layer is smaller than the porosity of the first substrate layer; Spraying a first powder on a side of the first substrate layer facing away from the second substrate layer to form a solid electrolyte membrane precursor; Wherein, the first powder material comprises a solid electrolyte; The solid electrolyte membrane precursor is pressed to form a solid electrolyte membrane.

2. The preparation method according to claim 1, characterized in that: Forming the second substrate layer on the first substrate layer comprises: using the first substrate layer as a base, and forming the second substrate layer on the first substrate layer by electrospinning; Preferably, the porosity of the first substrate layer is 70% to 95%; Preferably, the porosity of the second substrate layer is 50% to 85%.

3. The preparation method according to claim 1, characterized in that: Forming a second substrate layer on the first substrate layer includes: forming the second substrate layer on the first substrate layer, the thickness of which is less than the thickness of the first substrate layer; Preferably, the thickness ratio of the second substrate layer to the first substrate layer is 1:6 to 2:

3.

4. The preparation method according to claim 1, characterized in that: Spraying the first powder on the side of the first substrate layer facing away from the second substrate layer comprises: 2 Spray 0.05 mg to 20 mg of the first powder on the surface area of ​​the first substrate layer; Preferably, the first powder is sprayed once or more times.

5. The preparation method according to claim 1, characterized in that: The particle size of at least part of the solid electrolyte is smaller than the pore size of the first substrate layer and the particle size of at least part of the solid electrolyte is smaller than the pore size of the second substrate layer; Preferably, the particle size of the solid electrolyte is 1 μm to 10 μm.

6. The preparation method according to claim 1, characterized in that: Before the pressing process, the electrolyte membrane precursor is vibrated; Preferably, the electrolyte membrane precursor is oscillated once or more times.

7. The preparation method according to claim 6, characterized in that: The oscillating the electrolyte membrane precursor comprises: oscillating the electrolyte membrane precursor using a vibrating screen; Preferably, the oscillating electrolyte membrane precursor comprises: an oscillation frequency of the vibrating screen is 20 kHz-1000 kHz.

8. The preparation method according to claim 1, characterized in that: The pressure of the pressing treatment is 2t~3t; the time of the pressing treatment is 0.5min~20min; Preferably, the temperature of the pressing treatment is 60°C to 120°C; Preferably, the pressing treatment comprises applying a pressing force to a surface of one side of the first substrate layer sprayed with the first powder, so as to perform a pressing treatment on the electrolyte membrane precursor; Preferably, the pressing process is performed once.

9. A solid electrolyte membrane, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

10. A solid-state battery, characterized in that: The solid-state battery comprises a positive electrode sheet, a negative electrode sheet and the solid electrolyte membrane according to claim 9.

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