Solid electrolyte membrane, method for producing the same, battery, battery pack, power utilization device, and quality control method for solid electrolyte membrane

Abstract

This invention provides a solid electrolyte membrane and its preparation method, as well as a battery, battery pack, electrical device, and a quality control method for the solid electrolyte membrane. The solid electrolyte membrane includes a solid electrolyte material; the solid electrolyte material includes magnetic impurities; the solid electrolyte membrane satisfies: a = 0, b ≤ 5, c ≤ 10; where a is the number of magnetic impurities with a size greater than 200 μm in any direction, counted in particles; b is the number of magnetic impurities with a size of 100 μm to 200 μm in any direction, counted in particles; and c is the number of magnetic impurities with a size less than 100 μm in any direction, counted in particles. The solid electrolyte membrane of this invention enables the battery to have low self-discharge performance.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a solid electrolyte membrane and its preparation method, a battery, a battery pack, an electrical device, and a quality control method for the solid electrolyte membrane. Background Technology

[0002] Solid-state batteries have attracted widespread attention due to their safety and high energy density. As a key component of solid-state batteries, the solid electrolyte membrane must ensure good ion conductivity and stable interface performance.

[0003] To reduce the self-discharge performance of solid-state batteries, current technologies mainly focus on the design of material systems in solid-state batteries and the improvement of solid-solid interface impedance. However, the improvement effect has not met expectations.

[0004] Therefore, there is an urgent need for a solid electrolyte membrane that can reduce the self-discharge performance of batteries. Summary of the Invention

[0005] This invention provides a solid electrolyte membrane and its preparation method, as well as a battery, battery pack, electrical equipment, and a quality control method for the solid electrolyte membrane. By using the solid electrolyte membrane provided by this invention, the self-discharge performance of the battery can be reduced.

[0006] This invention provides a solid electrolyte membrane, which includes a solid electrolyte material; the solid electrolyte material includes magnetic impurities.

[0007] The solid electrolyte membrane satisfies: a = 0, b ≤ 5, c ≤ 10;

[0008] Wherein, a is the number of magnetic impurities with a size greater than 200 μm in any direction, expressed in particles;

[0009] b represents the number of magnetic impurities with a size of 100μm to 200μm in any direction, expressed in particles;

[0010] c represents the number of magnetic impurities whose size is less than 100 μm in any direction, expressed in particles.

[0011] In some embodiments of the present invention, the solid electrolyte material includes one or more of sulfide solid electrolyte materials, halide solid electrolyte materials, oxide solid electrolyte materials, and polymer solid electrolyte materials;

[0012] And / or, the magnetic impurities include one or more of elemental metals, metal oxides, and alloys;

[0013] The alloy comprises at least two elements selected from iron, chromium, nickel, manganese, copper, aluminum, and zinc.

[0014] In some embodiments of the present invention, the sulfide solid electrolyte material includes Li g M m / n P z A a S e D b Cl c X d ;

[0015] Wherein, M includes one or more of Na, Mg, Ca, Zn, and Al;

[0016] A includes one or more of Si, Sn, and Ge;

[0017] D includes one or more of O and Se;

[0018] X includes one or more of Br and I;

[0019] 0 < g ≤ 6;

[0020] 0≤z≤3;

[0021] 0≤m≤1;

[0022] 1≤n≤3;

[0023] 0≤a≤1;

[0024] 0 < e ≤ 5;

[0025] 0≤b≤2;

[0026] 0 ≤ c < 2;

[0027] 0 ≤ d < 2;

[0028] 1≤c+d<2.

[0029] In some embodiments of the present invention, the thickness of the solid electrolyte membrane is 20 μm to 100 μm;

[0030] And / or, the solid electrolyte material accounts for 90.0 wt% to 100.0 wt% of the mass of the solid electrolyte membrane.

[0031] This invention also provides a method for preparing the solid electrolyte membrane as described above, comprising the following steps:

[0032] A magnetic component is used to remove magnetic impurities from the solid electrolyte material to be treated, resulting in a solid electrolyte material. A slurry containing the solid electrolyte material is coated onto the surface of a substrate, and the substrate is then dried and rolled to obtain the solid electrolyte membrane. The solid electrolyte membrane satisfies the following conditions: a=0, b≤5, c≤10.

[0033] Wherein, a is the number of magnetic impurities with a size greater than 200 μm in any direction, expressed in particles;

[0034] b represents the number of magnetic impurities with a size of 100μm to 200μm in any direction, expressed in particles;

[0035] c represents the number of magnetic impurities whose size is less than 100 μm in any direction, expressed in particles.

[0036] The magnetic field strength of the magnetic component is 2000~20000 Gauss;

[0037] The impurity removal process includes: stirring the slurry containing the solid electrolyte material to be treated with a magnetic rod to obtain a slurry containing the solid electrolyte material; the stirring speed is 5 rpm to 100 rpm, and the stirring time is 10 h to 24 h; the diameter of the magnetic rod is 16 mm to 50 mm, and the length is 500 mm to 5000 mm.

[0038] Alternatively, the slurry containing the solid electrolyte material to be treated can be screened using a magnetic mesh to obtain a slurry containing the solid electrolyte material; the pore size of the magnetic mesh is 10 mesh to 500 mesh.

[0039] In some embodiments of the present invention, the impurity removal process is performed at least once;

[0040] And / or, the number of the magnetic components is at least one.

[0041] The present invention also provides a battery comprising a solid electrolyte membrane as described above, or a solid electrolyte membrane prepared by the method described above.

[0042] This invention also provides a battery pack comprising at least two batteries as described above.

[0043] This invention also provides an electrical device, including the battery described above, or the battery pack described above.

[0044] This invention also provides a quality control method for solid electrolyte membranes, comprising the following steps:

[0045] The current number of magnetic impurities in the solid electrolyte membrane is detected; it is determined whether the current number of magnetic impurities exceeds a preset threshold; wherein, the preset threshold is: a = 0, b ≤ 5, c ≤ 10; a is the number of magnetic impurities with a size greater than 200 μm in any direction, in units of particles; b is the number of magnetic impurities with a size of 100 μm to 200 μm in any direction, in units of particles; c is the number of magnetic impurities with a size less than 100 μm in any direction, in units of particles.

[0046] In some embodiments of the present invention, the detection includes the following steps:

[0047] A cross-section of the solid electrolyte membrane was obtained, and then the cross-section was photographed using a scanning electron microscope and an energy-dispersive X-ray spectrometer. The size and number of magnetic impurities in the field of view were counted.

[0048] The present invention provides a solid electrolyte membrane and its preparation method, a battery, a battery pack, an electrical device, and a quality control method for the solid electrolyte membrane. By controlling the number of magnetic impurities with dimensions greater than 200 μm, 100 μm to 200 μm, and less than 100 μm in any direction in the solid electrolyte membrane, the battery can have a lower self-discharge performance. Attached Figure Description

[0049] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0050] Figure 1 This is a SEM image of magnetic metal impurities in a solid electrolyte membrane provided in an embodiment of the present invention.

[0051] Figure 2 EDS diagram of Fe element in magnetic metal impurities in solid electrolyte membrane provided in this embodiment of the invention;

[0052] Figure 3 EDS diagram of S element in magnetic metal impurities in solid electrolyte membrane provided in this embodiment of the invention.

[0053] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0055] The design of the material system and the improvement of solid-solid interface impedance in solid-state batteries cannot effectively improve the self-discharge rate. The inventors analyzed that self-discharge causes irreversible capacity loss during storage, causing the battery to gradually lose charge even when not in use, thus requiring more frequent charging to maintain its operating state. At the same time, side reactions may occur during self-discharge, which may damage the electrode materials, electrolyte, and the stability of their interfaces, leading to increased internal resistance and reduced ion migration efficiency. This, in turn, will greatly affect the energy retention rate and storage performance of solid-state batteries, limiting their application.

[0056] The inventors further investigated the factors influencing the self-discharge problem in solid-state batteries. Through long-term research, they discovered that the self-discharge problem is caused by the reduced interface stability of solid-state batteries. When interface stability decreases, more side reactions occur at the solid-solid interface. The generated byproducts react with the electrolyte to form unstable intermediates, thereby accelerating the self-discharge process. At the same time, the reduced interface stability also causes the active metal of the negative electrode to precipitate and penetrate the solid electrolyte membrane, causing additional side reactions and increasing the self-discharge rate.

[0057] In the current solid-state battery manufacturing process, due to insufficient purity of raw materials or inadequate process environment control, various impurities are often introduced during the raw material production process when preparing solid electrolyte membranes. These impurities are prone to triggering interfacial side reactions during battery assembly and long-term operation, which reduces the interfacial stability of solid-state batteries and thus increases the battery self-discharge rate.

[0058] Based on the characteristics of impurities in solid electrolyte membranes, the inventors attempted to reduce the impurity content of solid electrolyte membranes in order to reduce the self-discharge rate of solid-state batteries.

[0059] Based on this, embodiments of the present invention provide a solid electrolyte membrane, the solid electrolyte membrane comprising a solid electrolyte material; the solid electrolyte material comprising magnetic impurities; the solid electrolyte membrane satisfying: a=0, b≤5, c≤10; wherein, a is the number of magnetic impurities with a size greater than 200μm in any direction, in units of particles; b is the number of magnetic impurities with a size of 100μm~200μm in any direction, in units of particles; c is the number of magnetic impurities with a size less than 100μm in any direction, in units of particles (μm).

[0060] When the solid electrolyte membrane of the present invention meets the above conditions, its impurity content is low, which can reduce the self-discharge rate of the solid battery.

[0061] Through careful analysis of impurities in the solid electrolyte membrane, the inventors discovered that most of these impurities are generated by metal equipment in the production line, and therefore, most are magnetic impurities. Effective removal of these magnetic impurities can significantly reduce the self-discharge rate of the solid-state battery. The inventors also found that magnetic impurities with a particle size larger than 200 μm have a significant impact on the battery's self-discharge rate. These magnetic impurities pose a risk of puncturing the solid electrolyte membrane, leading to a sharp increase in the battery's self-discharge rate. Magnetic impurities with a particle size of 100 μm to 200 μm and those smaller than 100 μm greatly affect the stability of the solid-solid interface in the solid-state battery. Therefore, when the number of magnetic impurities in the solid electrolyte membrane of this invention meets the above conditions, the magnetic impurities have a smaller impact on the solid-solid interface in the solid-state battery, resulting in a lower self-discharge rate.

[0062] It should be clarified that the number of magnetic impurities in the solid electrolyte membrane of the present invention refers to the number of magnetic impurities in a standard sheet with a size of 50mm × 30mm and a thickness of approximately 100μm.

[0063] This invention allows for the detection of magnetic impurities in solid electrolyte materials using conventional testing methods and instruments, such as a combination of SEM and EDS. Specifically, the testing of magnetic impurity data in a solid electrolyte membrane can include the following steps: Twenty rectangular samples (5mm × 5mm in size, approximately 1 / 3 the area of ​​the standard sheet) with a thickness of about 100μm are randomly cut from the solid electrolyte membrane. To ensure a smooth and undamaged cross-section, the samples are first cooled in liquid nitrogen for 2 minutes, and then cut along a predetermined plane using a precision cross-section cutting device. Next, the cut rectangular samples are fixed on a metal sample holder and polished in an argon ion polisher with a 2keV ion beam, a 20mA beam current, and a 5-minute scan time to remove mechanical damage from the cutting and obtain a smooth cross-section. The polished samples are then directly placed in a scanning electron microscope (SEM) in backscattered electron (BSE) mode. At an accelerating voltage of 2kV and a working distance of 10mm, the entire cross-sectional area is scanned at 1000x magnification to locate the areas where magnetic impurities exist. Suspected metallic impurity regions were identified in BSE mode and accurately characterized by EDS to confirm they were magnetic impurity particles. The number of magnetic impurities of different sizes (greater than 200 μm; 100 μm~200 μm; less than 100 μm) in the sample was counted. Then, the test results of 20 rectangular samples were summed and multiplied by 3 to obtain the metallic impurity content in the standard sheet. The experiment can be repeated on 3-10 standard sheets randomly selected, and the average value taken to improve the accuracy of the results. The size of the magnetic impurity is defined as the straight-line distance from one edge to another. When the shape of the magnetic impurity is irregular, the size is taken as the maximum straight-line distance between the two edges.

[0064] In some embodiments of the present invention, the solid electrolyte material includes one or more of sulfide solid electrolyte materials, halide solid electrolyte materials, oxide solid electrolyte materials, and polymer solid electrolyte materials, which can further reduce the self-discharge rate of the battery. Preferably, the solid electrolyte material includes a sulfide solid electrolyte material.

[0065] In some embodiments, the magnetic impurities include one or more of elemental metals and metal oxide alloys; the alloys include at least two elements selected from iron, chromium, nickel, manganese, copper, aluminum, and zinc. In the solid electrolyte membrane of this embodiment, the content of the above-mentioned magnetic impurities is relatively low. For example, the elemental metals are one or more of elemental iron, chromium, nickel, and manganese; the metal oxides are at least one of iron oxide, chromium oxide, manganese oxide, and nickel oxide; the alloys are one or more of stainless steel, iron-nickel alloys, nickel-cobalt alloys, copper-zinc alloys, aluminum-copper alloys, titanium-aluminum alloys, lead-tin alloys, magnesium-aluminum alloys, chromium-nickel-iron alloys, and tungsten-copper alloys.

[0066] In some embodiments of the present invention, the sulfide solid electrolyte material includes Li g M m / n P z A a S e D b Cl c X d M includes one or more of Na, Mg, Ca, Zn, and Al. By controlling the composition of the above-mentioned sulfide solid electrolyte material, the self-discharge rate of the battery can be further reduced in this embodiment of the invention.

[0067] In some embodiments, A includes one or more of Si, Sn, and Ge.

[0068] In some embodiments, D includes one or more of O and Se.

[0069] In some embodiments, X includes one or more of Br and I.

[0070] In some embodiments, 0 < g ≤ 6.

[0071] In some embodiments, 0 ≤ z ≤ 3.

[0072] In some embodiments, 0 ≤ m ≤ 1.

[0073] In some embodiments, 1 ≤ n ≤ 3.

[0074] In some embodiments, 0 ≤ a ≤ 1.

[0075] In some embodiments, 0 < e ≤ 5.

[0076] In some embodiments, 0 ≤ b ≤ 2.

[0077] In some embodiments, 0 ≤ c < 2.

[0078] In some embodiments, 0 ≤ d < 2.

[0079] In some embodiments, 1 ≤ c + d < 2.

[0080] Specifically, the sulfide solid electrolyte is, for example, Li 5.7 PS 4.7 Cl 1.3 Li6PS5Cl, Li7P3S 11 Li 5.3 PS 4.3 Br 1.7 Li 5.8 PS 4.8 Cl 0.6 Br0.6 At least one of them.

[0081] In some embodiments of the present invention, the thickness of the solid electrolyte membrane is 20 μm to 100 μm. When the thickness of the solid electrolyte membrane in the embodiments of the present invention is within the above range, it can further improve ionic conductivity and reduce self-discharge. In the embodiments of the present invention, the thickness of the solid electrolyte membrane can be detected by conventional testing methods and instruments in the art. For example, a cross-section of the solid electrolyte membrane can be obtained, and then the thickness of the solid electrolyte membrane can be tested using SEM. When the thickness of the solid electrolyte membrane is not uniform, its thickness is the average thickness of the solid electrolyte membrane.

[0082] Specifically, the size of the aforementioned magnetic impurities in the thickness direction of the solid electrolyte membrane is less than or equal to the thickness of the solid electrolyte membrane.

[0083] In this embodiment of the invention, the solid electrolyte material accounts for 90wt% to 100wt% of the mass of the solid electrolyte membrane, which can further improve ionic conductivity and address self-discharge issues. In some embodiments of the invention, the solid electrolyte membrane also includes a binder, which further enhances the mechanical properties of the solid electrolyte membrane. This embodiment of the invention does not impose a specific limit on the mass percentage of the binder in the solid electrolyte membrane; for example, the mass percentage of the binder in the solid electrolyte membrane can be 0wt% to 10wt%.

[0084] This invention also provides a method for preparing the above-mentioned solid electrolyte membrane, comprising the following steps: using a magnetic component to remove magnetic impurities from a slurry containing the solid electrolyte material to be treated, obtaining a slurry containing the solid electrolyte material; subsequently coating the slurry containing the solid electrolyte material onto a substrate surface, and then sequentially drying and rolling to obtain a solid electrolyte membrane; the solid electrolyte membrane satisfies: a=0, b≤5, c≤10; wherein, a is the number of magnetic impurities with a size greater than 200μm in any direction, in units of particles; b is the number of magnetic impurities with a size of 100μm~200μm in any direction, in units of particles; c is the number of magnetic impurities with a size of 100μm~200μm in any direction, in units of particles; and c is the number of magnetic impurities with a size greater than 200μm in any direction, in units of particles. The number of magnetic impurities with an upward dimension less than 100 μm, in units of particles; the magnetic field strength of the magnetic component is 2000~20000 Gauss (Gs); wherein, the impurity removal process includes: stirring the slurry containing the solid electrolyte material to be treated with a magnetic rod to obtain a slurry containing the solid electrolyte material; the stirring speed is 5 rpm~100 rpm, and the stirring time is 10h~24h; the diameter of the magnetic rod is 16mm~50mm, and the length is 500mm~5000mm; or, sieving the slurry containing the solid electrolyte material to be treated with a magnetic mesh to obtain a slurry containing the solid electrolyte material; the aperture of the magnetic mesh is 10 mesh~500 mesh.

[0085] The present invention provides an embodiment of a solid electrolyte membrane prepared by the above-described method. The solid electrolyte membrane comprises a solid electrolyte material, which includes magnetic impurities. The solid electrolyte membrane satisfies a=0, b≤5, and c≤10. Here, a represents the number of magnetic impurities with a size greater than 200 μm in any direction, expressed in particles; b represents the number of magnetic impurities with a size between 100 μm and 200 μm in any direction, expressed in particles; and c represents the number of magnetic impurities with a size less than 100 μm in any direction, expressed in particles.

[0086] The present invention provides a solid electrolyte membrane with low impurity content through the above-described method for preparing the solid electrolyte membrane, which enables the battery to have low self-discharge performance.

[0087] In detail, the inventors designed the above-mentioned method for preparing solid electrolyte membranes, taking into account the characteristic that most impurities in solid electrolyte materials are magnetic, which effectively reduces magnetic impurities in solid electrolyte membranes.

[0088] Specifically, the impurity removal process includes stirring a slurry containing the solid electrolyte material to be treated using a magnetic rod to obtain a slurry containing the solid electrolyte material; the stirring speed is 5 rpm to 100 rpm, and the stirring time is 10 h to 24 h. That is, the magnetic component in the above impurity removal process is a magnetic rod. Through the above impurity removal process, this embodiment of the invention can better remove magnetic impurities, thereby resulting in a battery with lower self-discharge performance. For example, the stirring speed is, for example, a range of 5 rpm, 10 rpm, 30 rpm, 60 rpm, 80 rpm, 100 rpm, or any combination thereof. The stirring time is, for example, a range of 1 h, 2 h, 4 h, 8 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, or any combination thereof. The number of stirring cycles can be, for example, three times.

[0089] In some embodiments, the impurity removal process includes: sieving a slurry containing the solid electrolyte material to be treated using a magnetic mesh to obtain a slurry containing the solid electrolyte material; the pore size of the magnetic mesh is 10 mesh to 500 mesh. That is, the magnetic component in the above impurity removal process is a magnetic mesh. Through the above impurity removal process, the embodiments of the present invention can better remove magnetic impurities, thereby resulting in a battery with lower self-discharge performance. For example, the pore size of the magnetic mesh is, for example, a range of 10 mesh, 50 mesh, 100 mesh, 200 mesh, 300 mesh, 400 mesh, 500 mesh, or any combination thereof.

[0090] In some embodiments of the present invention, the magnetic field strength of the magnetic component is 2000~20000 Gauss, which can better remove magnetic impurities, thereby giving the battery a lower self-discharge performance. For example, the magnetic strength of the magnetic component is in the range of 2000 Gauss, 5000 Gauss, 8000 Gauss, 10000 Gauss, 12000 Gauss, 15000 Gauss, 18000 Gauss, 20000 Gauss, or any combination thereof.

[0091] In detail, the number of magnetic impurities in the slurry containing the solid electrolyte material to be treated is relatively large. After the impurity removal treatment, the number of magnetic impurities in the slurry containing the solid electrolyte material is significantly reduced.

[0092] In some embodiments, the impurity removal process is performed at least once to better remove magnetic impurities, thereby resulting in a lower self-discharge performance of the battery.

[0093] In some embodiments, the number of magnetic components is at least one, which can better remove magnetic impurities, thereby giving the battery a lower self-discharge performance.

[0094] This invention also provides a battery comprising the above-described solid electrolyte membrane, or a solid electrolyte membrane prepared by the above-described method for preparing a solid electrolyte membrane. The battery provided by this invention has advantages corresponding to the above-described solid electrolyte membrane, which will not be elaborated upon here.

[0095] Generally, a battery includes a cell and a casing that encapsulates the cell. The electrolyte is located between the positive and negative electrodes and is assembled within the cell inside the casing. The negative electrode includes a negative electrode plate, and the positive electrode includes a positive electrode plate. The cell can be a stacked cell, meaning it is composed of alternating layers of positive electrode plates, electrolyte, and negative electrode plates; or it can be a wound cell, meaning it is composed of stacked positive electrode plates, electrolyte, and negative electrode plates, which are then wound together.

[0096] Specifically, the positive electrode sheet includes a positive current collector and a positive active material layer located on at least one side surface of the positive current collector. Specifically, the positive active material layer can be provided on one side surface in the thickness direction of the positive current collector, or positive active material layers can be provided on both opposite sides surface in the thickness direction of the positive current collector.

[0097] The positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder. In the positive electrode active material layer, the mass percentage of the positive electrode active material can be 70% to 99%, for example, 70%, 75%, 80%, 85%, 90%, 93%, 95%, 97%, 99%, or any combination thereof. The mass fraction of the conductive agent can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any combination thereof. The mass fraction of the binder can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any combination thereof.

[0098] In some embodiments of the present invention, the positive electrode active material layer further includes the aforementioned solid electrolyte material, and the mass ratio of the solid electrolyte material in the positive electrode active material layer can be selected according to the actual situation.

[0099] In some embodiments, the battery is a sodium-ion battery, and the positive electrode active material includes, but is not limited to, one or a combination of transition metal oxides, polyanionic compounds, organic compounds, and Prussian blue materials. The transition metal oxides may be, but are not limited to, NaMO2 (M may be Fe, Co, Ni, Mn, etc.); the polyanionic compounds may be, but are not limited to, Na3V2(PO4)3, NaFePO4, Na2FePO4F, etc.; the Prussian blue materials may be, but are not limited to, Na2Fe(CN)6, etc.; and the organic compounds may be, but are not limited to, sodium terephthalic acid salts, etc.

[0100] In some embodiments, the battery is a lithium-ion battery, and the positive electrode active material may include LiCoO2, LiNiO2, or LiCo. x Ni 1-x O2 (0≤x≤1), LiCo x Ni 1-x-y Al y O2 (0≤x≤1, 0≤y≤1), LiMn2O4, LiFe x Mn y M z O4 (M is one or more of Al, Mg, Ga, Cr, Co, Ni, Cu, Zn or Mo, 0≤x≤1, 0≤y≤1, 0≤z≤1, x+y+z=1), Li 1＋ x L 1－y－z M y N zO2 (L, M, N are one or more of Li, Co, Mn, Ni, Fe, Al, Mg, Ga, Ti, Cr, Cu, Zn, Mo, F, I, S, B, -0.1≤x≤0.2, 0≤y≤1, 0≤z≤1, 0≤y+z≤1), LiFePO4, Li3V2(PO4)3, Li3V3(PO4)3, LiVPO4F, Li2CuO2, Li5FeO4, and metal sulfides and oxides (such as TiS2, V2S3, FeS, FeS2, LiMS) x (M is at least one of the transition metal elements such as Ti, Fe, Ni, Cu, Mo, etc., 1≤x≤2.5), TiO2, Cr3O8, V2O5, MnO2, etc.

[0101] In some embodiments, the battery is a potassium-ion battery, and the positive electrode active material includes, but is not limited to, one or more of the following: Prussian blue analogues, layered transition metal oxides, polyanionic compounds (such as KFeSO4F, KVPO4F), organic compounds (such as potassium terephthalate), sulfides (such as K2FeS2), phosphates (such as K3V2(PO4)3), potassium manganese oxides (such as KMnO4 derivatives), potassium cobalt oxides (such as KCoO2), and potassium nickel oxides (such as KNiO2).

[0102] In this embodiment of the invention, the conductive agent in the positive electrode active material layer can be a conventional conductive material in the art. For example, the conductive agent in the positive electrode active material layer may include one or more of conductive carbon black, conductive graphite, carbon nanotubes (CNTs), carbon fibers, graphene, acetylene black, and Ketjen black.

[0103] In this embodiment of the invention, the binder in the positive electrode active material layer can be a conventional binder in the art. For example, the binder in the positive electrode active material layer may include one or more of the following: polyvinylidene fluoride (PVDF), polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, etc.

[0104] The embodiments of the present invention may employ conventional positive current collectors in the art, for example, positive current collectors may include aluminum foil.

[0105] In this embodiment of the invention, the positive electrode sheet can be prepared by conventional methods in the art, such as by coating. Specifically, the components used to form the positive electrode active material layer, such as the positive electrode active material, conductive agent, and binder, can be dispersed in a solvent, such as N-methylpyrrolidone (NMP), to prepare a positive electrode slurry. This slurry is then coated onto the surface of the positive electrode current collector, and after drying, rolling, and other processes, the positive electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing positive electrode sheets using the coating method, and are not particularly limited thereto.

[0106] In practice, a slurry containing positive electrode active material (positive electrode slurry) can be prepared at a temperature of 20℃~45℃; the slurry containing positive electrode active material can be coated onto the surface of the positive electrode current collector using conventional coating equipment in the field, such as continuous coating equipment.

[0107] Specifically, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on at least one side surface of the negative electrode current collector. Specifically, the negative electrode active material layer can be provided on one side surface of the negative electrode current collector, or negative electrode active material layers can be provided on both opposite sides of the negative electrode current collector in the thickness direction.

[0108] Specifically, the negative electrode active material layer may include a negative electrode active material, a conductive agent, and a binder, all of which can be conventional materials in the art. For example, the negative electrode active material may include graphite; the conductive agent may include one or more of conductive carbon black, carbon nanotubes (CNT), acetylene black, graphene, Ketjen black, and carbon fiber; and the binder may include one or more of sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol, and sodium polyacrylate.

[0109] In some embodiments of the present invention, the negative electrode active material layer further includes the aforementioned solid electrolyte material, and the mass ratio of the solid electrolyte material in the negative electrode active material layer can be selected according to the actual situation.

[0110] The embodiments of the present invention may employ conventional negative electrode current collectors in the art, for example, negative electrode current collectors include copper foil.

[0111] In this embodiment of the invention, the negative electrode sheet can be prepared by conventional methods in the art, such as by coating. Specifically, the components used to form the negative electrode active material layer, solid electrolyte material, conductive agent, binder, etc., can be dispersed in a solvent, such as water, to prepare a negative electrode slurry. This slurry is then coated onto the surface of the negative electrode current collector, and after drying, rolling, and other processes, the negative electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing negative electrode sheets using the coating method, and are not particularly limited thereto.

[0112] In practice, a slurry containing negative electrode active material (negative electrode slurry) can be prepared at a temperature of 20℃~45℃; the slurry containing negative electrode active material can be coated onto the surface of the negative electrode current collector using conventional coating equipment in the field, such as continuous coating equipment.

[0113] The battery in this embodiment of the invention can be a solid-state battery. Generally, the solid-state battery includes a cell and a casing for encapsulating the cell. A solid electrolyte membrane is located between the positive and negative electrodes of the solid-state battery and assembled within the cell in the casing. The negative electrode includes a negative electrode sheet, and the positive electrode includes a positive electrode sheet. The solid electrolyte membrane can be any of the aforementioned solid electrolyte membranes. The cell can be a stacked cell, i.e., the cell is formed by alternating layers of a positive electrode sheet, a separator, and a negative electrode sheet; or, the cell can be a wound cell, i.e., the cell is formed by stacking and winding a positive electrode sheet, a solid electrolyte membrane, and a negative electrode sheet.

[0114] The battery in this embodiment of the invention can be a lithium-ion battery (such as a lithium-ion power battery), a potassium-ion battery, a sodium-ion battery, or other novel energy storage batteries, preferably a lithium-ion battery.

[0115] In this embodiment of the invention, the battery cell can be packaged using conventional housing materials in the art, such as flexible packaging materials like aluminum-plastic film, but is not limited thereto.

[0116] This invention also provides a battery pack comprising at least two of the above-described batteries, which has advantages corresponding to the above-described negative electrode sheet, and will not be described in detail here.

[0117] Generally, a battery pack includes multiple batteries as individual cells, which are connected to form the battery pack. These batteries can be electrically connected using methods conventional in the art, such as series connection, parallel connection, or a combination of these connection methods, without any particular limitation.

[0118] This invention also provides an electrical device, including the battery or battery pack described above. This electrical device has advantages corresponding to the negative electrode sheet described above, which will not be elaborated further.

[0119] The electrical equipment used in the embodiments of the present invention can be conventional electrical equipment in the art, such as power equipment (e.g., electric vehicles, electric cars), electronic equipment (e.g., mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (e.g., watches, bracelets, VR glasses, etc.), energy storage power stations, etc., and there are no particular limitations on this.

[0120] This invention also provides a quality control method for solid electrolyte membranes, comprising the following steps:

[0121] The current number of magnetic impurities in the solid electrolyte membrane is detected; it is then determined whether the current number of magnetic impurities exceeds a preset threshold. The preset threshold is: a = 0, b ≤ 5, c ≤ 10; a is the number of magnetic impurities with a size greater than 200 μm in any direction, counted in particles; b is the number of magnetic impurities with a size between 100 μm and 200 μm in any direction, counted in particles; c is the number of magnetic impurities with a size less than 100 μm in any direction, counted in particles.

[0122] When the solid electrolyte membrane of this invention meets the above-mentioned preset threshold, it can enable the battery to have low self-discharge performance.

[0123] In some embodiments, detecting the current number of magnetic impurities in a solid electrolyte membrane includes the following steps: obtaining a cross-section of the solid electrolyte membrane, then taking pictures of the cross-section using a scanning electron microscope energy-dispersive X-ray spectrometer, and counting the size and number of magnetic impurities in the field of view. The present invention can better count the number of magnetic impurities through the above method.

[0124] In one specific embodiment, the quality control method for solid electrolyte membranes includes the following steps: Twenty rectangular samples with dimensions of 5mm × 5mm are randomly cut from the solid electrolyte membrane (the total area of ​​the 20 rectangular samples accounts for approximately 1 / 3 of the area of ​​the standard sheet), with a thickness of approximately 100μm. To ensure a smooth and undamaged cross-section, the samples are first cooled in liquid nitrogen for 2 minutes, and then cut along a predetermined plane using a precision cross-section cutting device. Next, the cut rectangular samples are fixed on a metal sample holder and surface polished in an argon ion polisher using a 2keV ion beam, a 20mA beam current, and a 5-minute scanning time to remove mechanical damage caused by cutting and obtain a smooth cross-section. After polishing, the rectangular samples are directly placed in a scanning electron microscope. Using backscattered electron (BSE) mode, under conditions of 2kV accelerating voltage and a 10mm working distance, a high-resolution scan of the entire cross-sectional area is performed at 1000x magnification to locate areas where magnetic impurities exist. Suspected metallic impurity regions were identified in BSE mode and accurately characterized by EDS to be magnetic impurity particles. The number of magnetic impurities of different sizes (greater than 200 μm; 100 μm~200 μm; less than 100 μm) in the sample was counted. The size of a magnetic impurity was defined as the straight-line distance from one edge to another. When the shape of the magnetic impurity was irregular, the size was taken as the maximum straight-line distance between the two edges.

[0125] If multiple solid electrolyte membranes are prepared using the same batch of the above-mentioned solid electrolyte materials, multiple (e.g., 30) solid electrolyte membranes can be randomly selected to perform the above-mentioned solid electrolyte membrane quality inspection method, and the values ​​of a, b, and c are the average values ​​of multiple solid electrolyte membranes.

[0126] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0127] Example 1

[0128] The solid electrolyte membrane in this embodiment is prepared by the following method:

[0129] 1) In a -50℃ dew point environment, Li 5.7 PS 4.7 Cl 1.3(LPSCl) type sulfide solid electrolyte (the solid electrolyte material to be treated) and binder (containing butadiene rubber with a solid content of 5% wt) are dissolved in xylene solvent at a weight ratio of 20:1. The mixture is thoroughly stirred to prepare a slurry containing the solid electrolyte material. Then, a rotating magnetic rod device (magnetic strength of 10000 Gauss, diameter range of 30 mm, and length range of 3000 mm) is added to remove magnetic metal particles (impurity removal treatment). The magnetic rod rotates at 75 rpm for 12 hours, yielding the slurry containing the solid electrolyte material. Finally, the slurry containing the solid electrolyte material is sieved and coated onto an aluminum foil substrate, then dried at 100℃ to obtain a 100 μm thick electrolyte membrane. The prepared solid electrolyte membrane is cut into multiple sets of 50 mm × 30 mm standard sheets for subsequent metal impurity detection and solid-state battery assembly.

[0130] Examples 2-8 are basically the same as Example 1, except that the type of solid electrolyte material, the speed of stirring, the time of stirring, and the magnetic properties of the magnetic components are different, as detailed in Table 1.

[0131] Example 9

[0132] This embodiment is basically the same as Embodiment 1, except that the magnetic component in this embodiment is a magnetic mesh, and the impurity removal process is as follows: 1 kg of Li 5.7 PS 4.7 Cl 1.3 The dry powder raw material of sulfide solid electrolyte material is poured into a material tank, and the environment is sealed to prevent moisture and isolate external metal dust. A magnetic mesh with a 200-mesh aperture is added in the middle of the material tank for sieving. The raw material is sieved three times in a cycle, and then the magnetic mesh device is removed to obtain the solid electrolyte material.

[0133] The difference between Comparative Example 1 and Example 1 is that the solid electrolyte material in Comparative Example 1 is the solid electrolyte material to be treated in Example 1.

[0134] The difference between Comparative Examples 2-4 and Example 1 is that the solid electrolyte material in Comparative Examples 2-4 is the same as the solid electrolyte material to be treated in Example 1, and the type of solid electrolyte material is different from that in Example 1, as shown in Table 1.

[0135] The difference between Comparative Examples 5-7 and Example 1 lies in the different parameters of the stirring speed, stirring time, and magnetic properties of the magnetic components in Comparative Examples 5-7, as detailed in Table 1.

[0136] In the examples and comparative examples, the number of magnetic impurities of different particle sizes obtained by the magnetic impurity content detection is shown in Table 2. In the table, a represents the number of magnetic impurities in the solid electrolyte membrane with a size greater than 200 μm in any direction; b represents the number of magnetic impurities in the solid electrolyte membrane with a size of 100 μm to 200 μm in any direction; and c represents the number of magnetic impurities in the solid electrolyte membrane with a size less than 100 μm in any direction.

[0137] Test case

[0138] 1. Detection of Magnetic Impurities in Solid Electrolyte Membranes: Twenty rectangular samples (5mm × 5mm in size, approximately 1 / 3 the area of ​​the standard sheet) with a thickness of about 100μm were cut from the solid electrolyte membranes of the above examples and comparative examples. To ensure a flat and undamaged cross-section, the samples were first cooled in liquid nitrogen for 2 minutes and then cut along a predetermined plane using a precision cross-section cutting device. The cut rectangular samples were then fixed on a metal sample holder and polished in an argon ion polisher with a 2keV ion beam, a 20mA beam current, and a 5-minute scanning time to remove mechanical damage caused by cutting and obtain a flat cross-section. After polishing, the samples were directly placed in a scanning electron microscope. Using backscattered electron (BSE) mode, the entire cross-sectional area was scanned at 1000x magnification under a 2kV accelerating voltage and a 10mm working distance to locate the areas where magnetic impurities were present. Suspected metallic impurity regions were identified in BSE mode and accurately characterized by EDS to be magnetic impurity particles. The number of magnetic impurities of different sizes (greater than 200 μm; 100 μm~200 μm; less than 100 μm) in the sample was counted. Then, the test results of 20 rectangular samples were summed, multiplied by 3, and the metallic impurity content in the standard sheet was obtained. The size of the magnetic impurity was the straight-line distance from one edge of the magnetic impurity to another. When the shape of the magnetic impurity was irregular, the size was taken as the maximum straight-line distance between the two edges. The results are shown in Table 1. Figure 1 , Figure 2 , Figure 3 As shown, where, Figure 1 , Figure 2 and Figure 3 The material within the middle circle represents three magnetic impurities in the solid electrolyte membrane. As shown in the figure, the size of the magnetic impurity in the solid electrolyte membrane of this embodiment is less than 200 μm (approximately 20 μm). The magnetic impurity mainly includes Fe element (S element is used to distinguish metal impurities from sulfide electrolytes).

[0139] 2. Solid-state battery preparation: 1) Preparation of positive electrode: In a -50℃ dew point environment, the ternary active material NCM811 of nickel cobalt manganese oxide and Li...5.7 PS 4.7 Cl 1.3 The sulfide solid electrolyte material and the binder (including butadiene rubber with a solid content of 5% wt) are mixed thoroughly in xylene solvent at a mass ratio of 60:40:1 to obtain a positive electrode slurry. The positive electrode slurry is then sieved, coated onto a carbon-coated aluminum foil substrate, cold-pressed, dried at 100°C, and cut to obtain a positive electrode sheet.

[0140] 2) Preparation of the negative electrode: In a -50℃ dew point environment, silicon-carbon and Li 5.7 PS 4.7 Cl 1.3 The sulfide solid electrolyte material, binder (including butadiene rubber with a solid content of 5% wt), and conductive carbon black CB are thoroughly mixed in xylene solvent at a mass ratio of 60:40:1 to obtain a negative electrode slurry. The negative electrode slurry is then sieved, coated onto a carbon-coated copper foil substrate, cold-pressed, dried at 100°C, and cut to obtain a negative electrode sheet.

[0141] 3) The solid electrolyte membrane from the above embodiments and comparative examples is transferred to both sides of the negative electrode sheet and rolled together. The positive electrode sheet and the transferred negative electrode sheet are stacked in a layered manner to form a stacked cell. The cell is first packaged and subjected to isostatic pressing at 1000MPa to ensure tight contact at the interface. After unpacking, tabs are welded and the cell is repackaged. After standing, formation, and capacity testing at 100MPa pressure and 45°C, a solid-state battery is obtained.

[0142] 3. Battery self-discharge rate test: The solid-state batteries prepared in the examples and comparative examples were charged to 4.3V and placed in a room temperature environment (25℃±5℃) for a 14-day static test. Then, the open-circuit voltage (OCV) of the battery was measured daily, the voltage change was recorded, and the voltage drop rate (K value) was calculated: K = (initial OCV - OCV after 14 days) / 14, in mV / days. The results (self-discharge rate) are shown in Table 1.

[0143]

[0144] As shown in the table, compared with the comparative example, the embodiments of the present invention use magnetic components to remove magnetic impurities from the solid electrolyte material to be treated, so that the number of magnetic impurities in the solid electrolyte film reaches a preset threshold, thereby reducing the self-discharge rate of the battery.

[0145] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A solid electrolyte membrane, characterized in that, The solid electrolyte membrane comprises a solid electrolyte material; the solid electrolyte material includes magnetic impurities; The solid electrolyte membrane satisfies: a = 0, b ≤ 5, c ≤ 10; Wherein, a is the number of magnetic impurities with a size greater than 200 μm in any direction, expressed in particles; b represents the number of magnetic impurities with a size of 100μm to 200μm in any direction, expressed in particles. c represents the number of magnetic impurities whose size is less than 100 μm in any direction, expressed in particles.

2. The solid electrolyte membrane according to claim 1, characterized in that, The solid electrolyte material includes one or more of the following: sulfide solid electrolyte material, halide solid electrolyte material, oxide solid electrolyte material, and polymer solid electrolyte material; And / or, the magnetic impurities include one or more of elemental metals, metal oxides, and alloys; The alloy comprises at least two elements selected from iron, chromium, nickel, manganese, copper, aluminum, and zinc.

3. The solid electrolyte membrane according to claim 2, characterized in that, The sulfide solid electrolyte material includes Li g M m / n P z A a S e D b Cl c X d ; Wherein, M includes one or more of Na, Mg, Ca, Zn, and Al; A includes one or more of Si, Sn, and Ge; D includes one or more of O and Se; X includes one or more of Br and I; 0＜g≤6； 0≤z≤3； 0≤m≤1； 1≤n≤3； 0≤a≤1； 0＜e≤5； 0≤b≤2； 0≤c＜2； 0≤d＜2； 1≤c+d<2.

4. The solid electrolyte membrane according to any one of claims 1-3, characterized in that, The thickness of the solid electrolyte membrane is 20μm~100μm; And / or, the solid electrolyte material accounts for 90.0 wt% to 100.0 wt% of the mass of the solid electrolyte membrane.

5. A method for preparing a solid electrolyte membrane according to any one of claims 1-4, characterized in that, Includes the following steps: A magnetic component is used to remove magnetic impurities from a slurry containing the solid electrolyte material to be treated, resulting in a slurry containing the solid electrolyte material. The slurry containing the solid electrolyte material is then coated onto the surface of a substrate, and after drying and rolling, the solid electrolyte membrane is obtained. The solid electrolyte membrane satisfies the following conditions: a=0, b≤5, c≤10. Wherein, a is the number of magnetic impurities with a size greater than 200 μm in any direction, expressed in particles; b represents the number of magnetic impurities with a size of 100μm to 200μm in any direction, expressed in particles; c represents the number of magnetic impurities whose size is less than 100 μm in any direction, expressed in particles. The magnetic field strength of the magnetic component is 2000~20000 Gauss; The impurity removal process includes: stirring the slurry containing the solid electrolyte material to be treated with a magnetic rod to obtain a slurry containing the solid electrolyte material; the stirring speed is 5 rpm to 100 rpm and the stirring time is 10 h to 24 h. Alternatively, the slurry containing the solid electrolyte material to be treated can be screened using a magnetic mesh to obtain a slurry containing the solid electrolyte material; the pore size of the magnetic mesh is 10 mesh to 500 mesh.

6. The method for preparing a solid electrolyte membrane according to claim 5, characterized in that, The impurity removal process is performed at least once. And / or, the number of the magnetic components is at least one.

7. A battery, characterized in that, This includes the solid electrolyte membrane according to any one of claims 1-4, or the solid electrolyte membrane prepared by the method of preparing the solid electrolyte membrane according to claim 5 or 6.

8. A battery pack, characterized in that, It includes at least two batteries as described in claim 7.

9. An electrical appliance, characterized in that, Includes the battery as described in claim 7, or the battery pack as described in claim 8.

10. A quality control method for a solid electrolyte membrane, characterized in that, Includes the following steps: The current number of magnetic impurities in the solid electrolyte membrane is detected; it is determined whether the current number of magnetic impurities exceeds a preset threshold; wherein, the preset threshold is: a = 0, b ≤ 5, c ≤ 10; a is the number of magnetic impurities with a size greater than 200 μm in any direction, in units of particles; b is the number of magnetic impurities with a size of 100 μm to 200 μm in any direction, in units of particles; c is the number of magnetic impurities with a size less than 100 μm in any direction, in units of particles.

11. The quality control method for solid electrolyte membranes according to claim 10, characterized in that, The detection includes the following steps: A cross-section of the solid electrolyte membrane was obtained, and then the cross-section was photographed using a scanning electron microscope and an energy-dispersive X-ray spectrometer. The size and number of magnetic impurities in the field of view were counted.

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