WO2024065151A1

WO2024065151A1 - Separator and preparation method therefor, secondary battery, battery module, battery pack, and electrical apparatus

Info

Publication number: WO2024065151A1
Application number: PCT/CN2022/121564
Authority: WO
Inventors: 朱翠翠; 张继君; 王少飞; 魏奕民; 李杨
Original assignee: 宁德时代新能源科技股份有限公司
Priority date: 2022-09-27
Filing date: 2022-09-27
Publication date: 2024-04-04

Abstract

The present application provides a separator and a preparation method therefor, a secondary battery, a battery module, a battery pack, and an electrical apparatus. The separator comprises a separator substrate layer and a solid electrolyte layer located on at least one surface of the separator substrate layer; and the solid electrolyte layer comprises a material having a chemical composition of LiaMXa+3, wherein 1≤a≤6; M is selected from cations containing one or more of the following elements: Al, Ga, In, Y, Zr, Nb, Sc, Ti, and Mn, as well as La series elements; and X is selected from anions containing one or more of the following elements: halogen, S, O, and P.

Description

Isolation film and preparation method thereof, secondary battery, battery module, battery pack and power-consuming device

Technical Field

The present application relates to the field of secondary batteries, and specifically to an isolation membrane and a preparation method thereof, a secondary battery, a battery module, a battery pack and an electrical device.

Background technique

With the continuous development of secondary battery technology, consumers have put forward higher requirements for the performance of secondary batteries. Among them, increasing the charging voltage of the battery is an effective way to increase the charging and discharging capacity of the battery. However, with the increase of charging voltage, traditional secondary batteries are difficult to maintain stable performance, and even high voltage may cause battery damage.

Summary of the invention

Based on the above problems, the present application provides an isolation film and a preparation method thereof, a secondary battery, a battery module, a battery pack and an electrical device, which can effectively improve the stability of the secondary battery during high voltage charging.

In order to achieve the above-mentioned purpose, the first aspect of the present application provides an isolation membrane, comprising an isolation membrane substrate layer and a solid electrolyte layer located on at least one surface of the isolation membrane substrate layer; the solid electrolyte layer comprises a material with a chemical composition of Li _a MX _a+3 , wherein 1≤a≤6; M is selected from cations of one or more of the following elements: Al, Ga, In, Y, Zr, Nb, Sc, Ti, Mn and La series elements; X is selected from anions containing one or more of the following elements: halogen, S, O and P.

In some embodiments, M is a +3 valent cation.

In some embodiments, M includes one or more of Al ³⁺ , Ga ³⁺ , In ³⁺ , Y ³⁺ , Zr ³⁺ , Nb ³⁺ , Sc ³⁺ , Ti ³⁺ , Mn ³⁺ , Er ³⁺ , Tb ³⁺ , Yb ³⁺ , Lu ³⁺ , La ³⁺ , and Ho ³⁺ .

In some embodiments, X includes one or more of F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , S ²⁻ , O ²⁻ , and PO ₄ ⁻ .

In some embodiments, the solid electrolyte layer includes at least one of Li ₃ InCl ₆ , Li ₃ MnCl ₆ , Li ₃ ScCl ₆ , Li ₃ ZrCl ₆ , Li ₃ YCl ₆ , and Li ₃ InF ₆ .

In some embodiments, the thickness of the solid electrolyte layer is 5 nm to 1000 nm; optionally, 50 nm to 100 nm;

In some embodiments, the electrochemical window of the solid electrolyte layer is ≥4.2V.

In some embodiments, the ionic conductivity of the solid electrolyte layer is ≥10 ^-3 S/cm.

In a second aspect, the present application also provides a method for preparing an isolation membrane, comprising the following steps:

Preparation of solid electrolyte targets;

The solid electrolyte target material is sputtered onto at least one surface of the isolation film substrate layer by magnetron sputtering to form an isolation film.

The isolation membrane includes an isolation membrane substrate layer and a solid electrolyte layer located on at least one surface of the isolation membrane substrate layer; the solid electrolyte layer includes a material with a chemical composition of Li _a MX _a+3 , wherein 1≤a≤6; M is selected from cations of one or more of the following elements: Al, Ga, In, Y, Zr, Nb, Sc, Ti, Mn and La series elements; X is selected from anions containing one or more of the following elements: halogen, S, O and P.

In some embodiments, the sputtering power is 150W-200W.

In some embodiments, the sputtering vacuum degree is 10 ^-1 Pa to 10 ^-2 Pa.

In some embodiments, during the sputtering, the temperature of the isolation film substrate layer is controlled to be ≤100°C.

In a third aspect, the present application further provides a secondary battery, comprising the isolation membrane of the first aspect or the isolation membrane prepared according to the preparation method of the second aspect.

In a fourth aspect, the present application further provides a battery module, comprising the secondary battery of the third aspect.

In a fifth aspect, the present application also provides a battery pack, comprising the secondary battery of the third aspect or the battery module of the fourth aspect.

In a sixth aspect, the present application further provides an electrical device comprising at least one of the secondary battery of the third aspect, the battery module of the fourth aspect, and the battery pack of the fifth aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.

FIG. 2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. 1 .

FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.

FIG. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.

FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application.

FIG. 6 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.

FIG. 7 is a scanning electron microscope (SEM) image of the isolation film substrate layer in Example 1 of the present application.

FIG. 8 is a scanning electron microscope (SEM) image of the isolation film in Example 1 of the present application.

FIG. 9 is a graph showing the AC impedance test results of the symmetrical batteries assembled in Examples 1 to 3 and Comparative Examples 1 to 2 of the present application.

Description of reference numerals:

1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery module; 5. Secondary battery; 51. Shell; 52. Electrode assembly; 53. Cover plate; 6. Electrical device.

In order to better describe and illustrate the embodiments and/or examples of the inventions disclosed herein, reference may be made to one or more drawings. The additional details or examples used to describe the drawings should not be considered to limit the scope of the disclosed inventions, the embodiments and/or examples currently described, and any of the best modes of these inventions currently understood.

Detailed ways

In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and/or" used herein includes any and all combinations of one or more related listed items.

The "range" disclosed in this application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that the range of 60 to 110 and 80 to 120 is also expected. In addition, if the

minimum range values

1 and 2 are listed, and if the

maximum range values

3, 4 and 5 are listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" have been fully listed in this article, and "0 to 5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

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

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.

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, the method may further include step (c), which means that step (c) may 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.

If there is no special explanation, the "include" and "comprising" mentioned in this application represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent 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.

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).

Unless otherwise specified, the terms used in this application have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

With the continuous development of secondary battery technology, consumers have put forward higher requirements for the performance of secondary batteries. Among them, increasing the charging voltage of the battery is an effective way to increase the charging and discharging capacity of the battery. When charging the secondary battery at a higher voltage, the stability of the isolation membrane has an important influence on the stability of the battery during the charging process. Traditional isolation membranes are mostly made of polyolefin materials such as polyethylene and polypropylene. These materials have the advantages of low cost, excellent mechanical properties and good thermal closure performance. However, these materials are prone to oxidation denaturation under high voltage conditions, losing their ion conductivity and isolation of positive and negative electrodes.

The present application provides an isolation membrane and a preparation method thereof, a secondary battery, a battery module, a battery pack and an electric device. The isolation membrane includes an isolation membrane substrate layer and a solid electrolyte layer located on at least one surface of the isolation membrane substrate layer; the solid electrolyte layer includes a material with a chemical composition of Li _a MX _a+3 , wherein 1≤a≤6; M is selected from cations of one or more of the following elements: Al, Ga, In, Y, Zr, Nb, Sc, Ti, Mn and La series elements; X is selected from anions containing one or more of the following elements: halogen, S, O and P.

In the isolation membrane provided in the present application, by forming a solid electrolyte layer on at least one surface of the isolation membrane substrate layer, the stability of the isolation membrane can be improved, and the oxidation resistance of the isolation membrane during high voltage charging (for example, the charging voltage ≥ 4.5V) can be improved, thereby increasing the voltage window of the secondary battery, allowing the battery to maintain better stability during high voltage charging, and allowing the battery to still maintain good cycle performance under high voltage conditions.

In addition, since the high voltage stability of the isolation membrane in the present application is improved, when the battery is charged, the battery can be shown to have a higher voltage window, thereby increasing the charge and discharge capacity of the battery, providing a basis for the development of high-capacity batteries.

At the same time, during the charge and discharge process of the secondary battery, the positive electrode active material will inevitably produce a certain amount of transition metal ions, and the presence of transition metal ions will restrict the improvement of lithium ion conductivity. In the isolation membrane of the present application, the solid electrolyte layer can reduce the content of transition metal ions through chemical reactions or adsorption reactions, such as reducing the content of transition metal ions inside the battery through complexation with transition metal ions, thereby making the isolation membrane have good lithium ion conductivity and improving the capacity retention rate of the secondary battery. In addition, the isolation membrane of the present application has better wettability to the electrolyte, which can further improve the conductivity of lithium ions. Furthermore, the isolation membrane of the present application has better blocking ability for transition metal ions, which can effectively prevent the transition metal ions from transferring to the negative electrode surface and causing adverse effects on the battery.

In one embodiment, 2≤a≤4. Optionally, a＝3. In addition, a can represent an integer or a non-integer. As some optional examples of a, a can be 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, 5.2, 5.5, 5.8, 6, etc. It is understandable that a can also be selected in other values within the range of 2 to 6.

In one embodiment, M is a +3 valent cation. For example, M includes +3 valent cations of Al ³⁺ , Ga ³⁺ , In ³⁺ , Y ³⁺ , Zr ³⁺ , Nb ³⁺ , Sc ³⁺ , Ti ³⁺ , Mn ³⁺ , and La series elements. Optionally, M includes one or more of Al ³⁺ , Ga ³⁺ , In ³⁺ , Y ³⁺ , Zr ^{3+ , Nb 3+} ^, Sc ³⁺ , Ti ³⁺ , Mn ³⁺ , Er ³⁺ , Tb ³⁺ , Yb ³⁺ , Lu ³⁺ , La ³⁺ , and Ho ³⁺ . In addition, as an optional example of X, X includes one or more of F ^- , Cl ^- , Br ^- , I ^- , S ^2- , O ^2- , and PO ₄ ^- . Alternatively, Li _a MX _a+3 includes Li ₃ InCl ₆ , Li ₃ MnCl ₆ , Li ₃ ScCl ₆ , Li ₃ ZrCl ₆ , Li ₃ YCl ₆ , Li ₃ InF ₆ , Li ₃ YCl ₆ , and Li ₃ ScF ₆ .

In one embodiment, the solid electrolyte layer includes at least one of Li ₃ InCl ₆ , Li ₃ MnCl ₆ , Li ₃ ScCl ₆ , Li ₃ ZrCl ₆ , Li ₃ YCl ₆ , Li ₃ InF ₆ , Li ₃ YCl ₆ and Li ₃ ScF ₆ .

Some parameter examples about the solid electrolyte layer. The thickness of the solid electrolyte layer is 5nm to 1000nm. Within this thickness range, the solid electrolyte layer can make the separator have good high voltage stability and at the same time make the secondary battery have a lower ohmic impedance. Optionally, the thickness of the solid electrolyte layer can be but is not limited to 10nm, 15nm, 20nm, 50nm, 80nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm. It is understood that the thickness of the solid electrolyte layer can also be other choices within the range of 10nm to 1000nm. Further optionally, the thickness of the solid electrolyte layer is 50nm to 100nm.

Optionally, the electrochemical window of the solid electrolyte layer is ≥4.2V. The solid electrolyte layer has a higher electrochemical window, which can further improve the high voltage stability of the separator, so that the battery can maintain performance stability during high voltage charging, thereby increasing the capacity of the battery. Further optionally, the electrochemical window of the solid electrolyte layer is ≥4.4V.

It can be understood that the electrochemical window test is carried out using the linear voltammetric test module of the electrochemical workstation. The solid electrolyte and the binder PVDF are mixed in a mass ratio of 95:5 and drop-coated on the surface of the glassy carbon electrode as the working electrode. 1M _LiPF6 is used as the solution and the lithium sheet is used as the counter electrode to carry out the voltammetric curve test. The voltage range is 2.5-5V and the scan rate is 0.5mV/s. The oxidation potential recorded is the electrochemical window.

In one embodiment, the ion conductivity of the solid electrolyte layer is ≥10 ^-3 S/cm. In this case, the conductivity of lithium ions can be further increased, thereby improving the cycle performance of the battery.

It can be understood that the ionic conductivity measurement method: the AC impedance test uses the electrochemical workstation impedance test module, voltage perturbation mode PEIS, perturbation voltage 5mV, frequency range 200kHZ ~ 30mHZ, to perform impedance test on the solid electrolyte sheet and calculate the ionic conductivity of the electrolyte sheet.

Specifically, solid electrolytes are ion conductors and are not conductive to electrons. Therefore, before impedance testing, it is necessary to connect blocking Ag electrodes on both sides of the solid electrolyte sheet: polish both sides of the sintered solid electrolyte to a certain thickness, apply silver paste to lead out Ag wires, and sinter Ag in a muffle furnace to make the Ag electrode in close contact with the electrolyte surface. Measure the resistance R = h/(ρs) and solve for the ionic conductivity σ, where σ = 1/ρ.

It can be understood that the isolation membrane substrate layer has two surfaces opposite to each other in the thickness direction thereof, and the solid electrolyte layer is located on at least one surface of the isolation membrane substrate layer. In this case, the solid electrolyte layer can be located on both surfaces of the isolation membrane substrate layer, or the solid electrolyte layer can be located on any one surface of the isolation membrane substrate layer. Optionally, the solid electrolyte layer is located on one surface of the isolation membrane substrate layer, so that the small battery ohmic impedance can be better taken into account on the basis of improving the high voltage stability of the isolation membrane.

It can also be understood that, with respect to the isolation membrane substrate layer, the present application has no particular restrictions on its type, and any known porous structure isolation membrane substrate layer with good chemical stability and mechanical stability can be selected. Optionally, the material of the isolation membrane substrate layer can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film without particular restrictions. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different without particular restrictions.

The present application also provides a method for preparing an isolation membrane. The method for preparing the isolation membrane comprises the following steps: forming a solid electrolyte layer on at least one surface of the isolation membrane substrate layer. The isolation membrane with good high-voltage stability can be prepared by the method.

As a method of forming a solid electrolyte layer on at least one surface of the separator substrate layer, coating, lamination, etc. can be used. Alternatively, the material of the solid electrolyte layer can be prepared into a solid electrolyte slurry, and then the solid electrolyte slurry can be coated on at least one surface of the separator substrate layer by coating. The solid electrolyte layer can also be formed on at least one surface of the separator substrate layer by bonding between the solid electrolyte layer and the separator substrate layer.

In one embodiment, a solid electrolyte containing a material having a chemical composition of Li _a MX _a+3 is transferred to at least one surface of the isolation membrane substrate layer to form a solid electrolyte layer. Wherein, as described above with respect to the chemical composition of Li _a MX _a+3 , 1≤a≤6; M is selected from cations of one or more of the following elements: Al, Ga, In, Y, Zr, Nb, Sc, Ti, Mn, and La series elements; X is selected from anions containing one or more of the following elements: halogen, S, O, and P. Wherein, a, M, and X can be arbitrarily selected from the corresponding values, elements, and ions listed above.

Optionally, when the solid electrolyte containing a material having a chemical composition of Li _a MX _a+3 is transferred to at least one surface of the isolation membrane substrate layer, the transfer method may be a deposition method. Further optionally, the transfer method is a physical vapor deposition method. Still further optionally, the transfer method is a sputtering method. Still further optionally, the transfer method is a magnetron sputtering method.

In one embodiment, the preparation method of the isolation membrane includes the following steps: preparing a solid electrolyte target; using a magnetron sputtering method to sputter the solid electrolyte target on at least one surface of the isolation membrane substrate layer to form an isolation membrane, the isolation membrane includes an isolation membrane substrate layer and a solid electrolyte layer located on at least one surface of the isolation membrane substrate layer; the solid electrolyte layer includes a material with a chemical composition of Li _a MX _a+3 , wherein 1≤a≤6; M is selected from cations of one or more of the following elements: Al, Ga, In, Y, Zr, Nb, Sc, Ti, Mn and La series elements; X is selected from anions containing one or more of the following elements: halogen, S, O and P. Compared with the traditional coating method, by preparing a solid electrolyte target and sputtering, a solid electrolyte layer with a smaller thickness can be prepared on at least one surface of the isolation membrane substrate layer, and it is also convenient to accurately control the thickness of the solid electrolyte layer. The solid electrolyte layer with a smaller thickness is beneficial to the improvement of lithium ion conductivity and the reduction of battery impedance, so the performance of the isolation membrane can be further improved. For example, the traditional coating method can usually obtain a solid electrolyte layer with a thickness of micrometer level. However, the sputtering method can obtain a solid electrolyte layer with a thickness of nanometer level. Specifically, a solid electrolyte layer with a thickness of 5 nm to 1000 nm can be obtained by sputtering. In addition, a solid electrolyte layer with better uniformity can be obtained by sputtering, and a solid electrolyte layer with better uniformity can further improve the stability of the isolation membrane.

It is understood that sputtering refers to the ionization of electrons under the action of an electric field to generate Ar positive ions and bombard the target surface with high energy. In the sputtered particles, the target atoms or molecules are deposited on the substrate to form a thin film, forming a deposition layer of several atoms thick to achieve uniform coating. In the present application, sputtering is used to form a solid electrolyte layer with a small thickness, easy to control thickness and uniform thickness on at least one surface of the diaphragm substrate layer.

As an example of preparing a solid electrolyte target material, the preparation of the solid electrolyte target material includes the following steps: mixing a solid electrolyte with a binder to prepare a mixture; compacting the mixture to prepare a compact; and calcining the compact.

Optionally, the binder includes at least one of polyvinyl alcohol and polyvinylidene fluoride. The mass ratio of the solid electrolyte to the binder is (45-50):1. Further optionally, the mass ratio of the solid electrolyte to the binder is (48-49):1. For example, the mass ratio of the solid electrolyte to the binder can be but is not limited to 45:1, 46:1, 47:1, 48:1, 49:1, 50:1, etc.

In one embodiment, mixing the solid electrolyte with the binder comprises the following steps: mixing the solid electrolyte and the binder in a dispersion medium, and then removing the dispersion medium. At this time, a solid electrolyte and a binder with better mixing uniformity can be obtained, that is, a mixture with better uniformity can be prepared. Optionally, the dispersion medium is at least one of ethanol and ethylene glycol. Optionally, the dispersion medium can be removed by drying. Specifically, the drying temperature is 85°C to 95°C. It is understandable that in order to improve the removal effect of the dispersion medium, a blast drying method can be used during drying.

In one of the embodiments, when the mixture is compacted, the particle size of the mixture is controlled to be 0.1 μm to 100 μm. Within this particle size range, a better compaction effect can be obtained. Optionally, when the mixture is compacted, the particle size of the mixture can be controlled by grinding. Optionally, when the mixture is compacted, the particle size of the mixture can be controlled to be 0.5 μm, 1 μm, 2 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, etc.

As an example of some parameter selections for compaction treatment, the pressure of compaction treatment is 150MPa to 250MPa. For example, the pressure of compaction treatment can be but not limited to 150MPa, 180MPa, 200MPa, 220MPa, 250MPa, etc. During compaction treatment, a suitable compaction treatment time can be selected based on the compaction effect. For example, the holding time of compaction treatment is 1h to 5h. Optionally, the holding time of compaction treatment can be but not limited to 1.5h, 2h, 3h or 4h, etc. It is understandable that, as a specific method of compaction treatment, compaction treatment is cold pressing treatment.

In one embodiment, when the compacted material is calcined, the calcination temperature is 700°C to 800°C. Optionally, the calcination temperature is 700°C, 720°C, 750°C, 780°C, 800°C, etc. During the calcination, the calcination time is 5h to 15h. For example, the calcination time is 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h or 14h, etc.

In one embodiment, before mixing the solid electrolyte with the binder, the solid electrolyte is also pre-calcined. Optionally, when the solid electrolyte is pre-calcined, the temperature of the pre-calcination is 700°C to 800°C. For example, the temperature of the pre-calcination is 700°C, 720°C, 750°C, 780°C, 800°C, etc. During the pre-calcination, the pre-calcination time is 1h to 4h. Optionally, the pre-calcination time can be but is not limited to 1h, 2h, 2.5h, 3h, 3.5h, etc.

In one embodiment, when the solid electrolyte target is sputtered on at least one surface of the isolation membrane substrate layer to form the isolation membrane, the sputtering power is 150W to 200W. Optionally, the sputtering power is 150W, 160W, 170W, 180W, 190W, 200W, etc. The vacuum degree of sputtering is 10 ^-1 Pa to 10 ^-2 Pa. Optionally, during sputtering, the voltage is 1000V to 1500V and the current is 300mA to 500mA. For example, the voltage can be 1100V, 1200V, 1300V, 1400V, etc. The current can be 350mA, 400mA, 450mA, 500mA, etc.

In one embodiment, during sputtering, the temperature of the isolation film substrate layer is controlled to be ≤100°C. This can prevent the isolation film substrate from being damaged due to excessive temperature during the sputtering process. Optionally, as an example of a method for controlling the temperature of the isolation film substrate layer, a sample stage carrying the isolation film substrate layer can be connected to a cooling medium pipeline, and the sample stage can be cooled by the cooling medium in the cooling medium pipeline, thereby controlling the temperature of the isolation film substrate layer to be ≤100°C. Optionally, the cooling medium includes water.

The present application also provides a secondary battery, which includes the isolation membrane provided in the present application or the isolation membrane prepared according to the preparation method provided in the present application.

The present application also provides a battery module, which includes the secondary battery provided by the present application.

The present application also provides a battery pack, which includes the secondary battery or battery module provided in the present application.

The present application also provides an electrical device. The electrical device includes at least one of the secondary battery, battery module and battery pack provided in the present application. Among them, the secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. Electrical devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these. As the electrical device, a secondary battery, battery module or battery pack can be selected according to its usage requirements.

The secondary battery, battery module, battery pack, and electric device of the present application are described below with reference to the accompanying drawings as appropriate.

Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

In one embodiment, the isolation film is selected from the isolation films provided in the present application.

Positive electrode

The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two facing surfaces of the positive electrode current collector.

In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

As an example, the positive electrode active material may include a positive electrode active material for a battery known in the art. As an example, the positive electrode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to _, lithium cobalt oxide (such as _LiCoO2 ), lithium nickel oxide (such as _LiNiO2 ), lithium manganese oxide (such as _LiMnO2 , _LiMn2O4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel _cobalt manganese oxide (such as LiNi1 _/ 3Co1 _/ _3Mn1 _/ _3O2 (also referred to as _NCM333 ), _{LiNi0.5Co0.2Mn0.3O2} (also referred _to _as _NCM523 ₎ _, _{LiNi0.5Co0.25Mn0.25O2} (also referred _to as _NCM211 ₎ , _{LiNi0.6Co0.2Mn0.2O2} (also referred to as _NCM622 ), _{LiNi0.8Co0.1Mn0.1O2} (also referred to _as _NCM811 ), lithium _nickel _cobalt aluminum oxide ( _such as LiNi _0.85 Co _0.15 Al _0.05 O ₂ ) and at least one of its modified compounds. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO ₄ (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO ₄ ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. The weight ratio of the positive electrode active material in the positive electrode film layer is 80 to 100 weight %, based on the total weight of the positive electrode film layer.

In some embodiments, the positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin. The weight ratio of the binder in the positive electrode film layer is 0 to 20% by weight, based on the total weight of the positive electrode film layer.

In some embodiments, the positive electrode film layer may further include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. The weight ratio of the conductive agent in the positive electrode film layer is 0 to 20 weight %, based on the total weight of the positive electrode film layer.

In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry, wherein the positive electrode slurry has a solid content of 40 to 80 wt%, and the viscosity at room temperature is adjusted to 5000 to 25000 mPa·s, the positive electrode slurry is coated on the surface of the positive current collector, and after drying, the positive electrode sheet is formed after cold pressing by a cold rolling mill; the positive electrode powder coating unit area density is 150-350 mg/m ² , and the positive electrode sheet compaction density is 3.0-3.6 g/cm ³ , and can be optionally 3.3-3.5 g/cm ³ . The compaction density is calculated as follows: compaction density = coating area density/(thickness of the sheet after extrusion-thickness of the current collector).

Negative electrode

The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the negative electrode active material may adopt the negative electrode active material for the battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material and lithium titanate. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more. The weight ratio of the negative electrode active material in the negative electrode film layer is 70 to 100% by weight, based on the total weight of the negative electrode film layer.

In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS). The weight ratio of the binder in the negative electrode film layer is 0 to 30% by weight, based on the total weight of the negative electrode film layer.

In some embodiments, the negative electrode film layer may further include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. The weight ratio of the conductive agent in the negative electrode film layer is 0 to 20 weight %, based on the total weight of the negative electrode film layer.

In some embodiments, the negative electrode film layer may further include other additives, such as a thickener (such as sodium carboxymethyl cellulose (CMC-Na)), etc. The weight ratio of the other additives in the negative electrode film layer is 0 to 15 weight %, based on the total weight of the negative electrode film layer.

In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30-70wt%, and the viscosity at room temperature is adjusted to 2000-10000mPa·s; the obtained negative electrode slurry is coated on the negative electrode collector, and after a drying process, cold pressing such as rolling, a negative electrode sheet is obtained. The negative electrode powder coating unit area density is 75-220mg/ ^m2 , and the negative electrode sheet compaction density is 1.2-2.0g/ ^m3 .

Electrolytes

The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

In some embodiments, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO ₂ F ₂ ), lithium difluorobis(oxalatophosphate) (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP). The concentration of the electrolyte salt is generally 0.5 to 5 mol/L.

In some embodiments, the solvent can be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, and polybutylene succinate can be listed. The present application has no particular restrictions on the shape of the secondary battery, which can be cylindrical, square, or other arbitrary shapes. For example, FIG. 1 is a secondary battery 5 of a square structure as an example.

In some embodiments, referring to FIG. 2 , the outer package may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

In some embodiments, secondary batteries may be assembled into a battery module. The number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

FIG3 is a battery module 4 as an example. Referring to FIG3 , in the battery module 4, a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.

Optionally, the battery module 4 may further include a housing having a housing space, and the plurality of secondary batteries 5 are housed in the housing space.

In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

FIG4 and FIG5 are battery packs 1 as an example. Referring to FIG4 and FIG5, the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

In addition, the present application also provides an electrical device, the electrical device includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to this. This secondary battery is suitable for various electrical devices using batteries, such as mobile phones, portable devices, laptops, battery cars, electric toys, electric tools, electric cars, ships and spacecraft, etc. For example, spacecraft include airplanes, rockets, space shuttles and spacecraft, etc.

As the electrical device, a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.

Fig. 6 is an example of an electric device. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the electric device's requirements for high power and high energy density of secondary batteries, a battery pack or a battery module may be used.

Another example of a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.

Example

In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the present application will be further described in detail below in conjunction with the embodiments and drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its applications. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

Embodiment 1:

Preparation of isolation membrane:

The Li ₃ InCl ₆ solid electrolyte was pre-calcined at a temperature of 780°C for 2 hours. The calcined Li ₃ InCl ₆ solid electrolyte and polyvinyl alcohol binder were mixed in ethanol, wherein the mass ratio of Li ₃ InCl ₆ solid electrolyte to binder was 49:1. After mixing, the mixture was dried overnight at 90°C to remove ethanol to prepare a mixture. The mixture was ground to a particle size of 10μm, and then cold pressed at 200MPa for 1 hour to prepare a compact. The compact was calcined at a temperature of 780°C for 10 hours. After calcination, a solid electrolyte target was obtained.

The solid electrolyte target material is sputtered on a sputtering device with a cooling function. A solid electrolyte layer is deposited on one surface of the polypropylene isolation membrane substrate layer. The sputtering conditions are: sputtering power of 180W, vacuum degree of ^10-1 ~ ^10-2 Pa, sputtering time of 30min, voltage of 1200V, and current of 400mA. During the sputtering process, the temperature of the polypropylene isolation membrane substrate is controlled to be ≤100°C. Through the sputtering treatment, a solid electrolyte layer with a thickness of 50nm is formed on one surface of the polypropylene isolation membrane substrate layer. The specific cooling method is: the sample stage carrying the isolation membrane substrate layer is connected to the cooling medium pipeline, and the sample stage is cooled by cooling in the cooling medium pipeline, thereby controlling the temperature of the isolation membrane substrate layer to be ≤100°C. The cooling medium is water.

After the sputtering process, the isolation film in this embodiment is obtained.

The SEM image of the polypropylene separator substrate layer is shown in Figure 7, and the SEM image of the separator obtained after sputtering is shown in Figure 8. It can be seen from Figures 7 and 8 that after sputtering, a solid electrolyte layer with uniform thickness is formed on the surface of the separator substrate layer.

Preparation of positive electrode:

Nickel-cobalt-manganese (NCM) ternary material, conductive agent carbon black, binder polyvinylidene fluoride (PVDF), and N-methylpyrrolidone (NMP) are stirred and mixed evenly in a weight ratio of 97.34:28.86:2.7:1.1 to obtain a positive electrode slurry; the positive electrode slurry is then evenly coated on the positive electrode collector, and then dried, cold pressed, and cut to obtain a positive electrode sheet.

Preparation of negative electrode sheet:

The active material artificial graphite, the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) are dissolved in the solvent deionized water in a weight ratio of 96.0:2.0:2.0, and the mixture is evenly mixed to prepare a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode collector copper foil once or multiple times, and the negative electrode sheet is obtained after drying, cold pressing, and slitting.

Preparation of electrolyte:

In an argon atmosphere glove box (H ₂ O<0.1ppm, O ₂ <0.1ppm), organic solvents ethylene carbonate (EC)/ethyl methyl carbonate (EMC) were mixed uniformly in a volume ratio of 3/7, 12.5% LiPF6 lithium salt was added and dispersed, and stirred uniformly to obtain an electrolyte.

Preparation of secondary batteries:

Assemble the positive electrode sheet, isolation membrane, and negative electrode sheet, inject 120 μL of electrolyte, compact and let stand for 2 hours.

Example 2

Compared with Example 1, the present example is different in that a solid electrolyte layer having a thickness of 10 nm is formed on one surface of the polypropylene separator substrate layer by sputtering.

Example 3

Compared with Example 1, the present example is different in that a solid electrolyte layer having a thickness of 1000 nm is formed on one surface of the polypropylene separator substrate layer by sputtering.

Example 4

Compared with Example 1, the difference of this embodiment is that the sputtering power is 150W.

Example 5

Compared with Example 1, the difference of this embodiment is that the sputtering power is 200W.

Example 6

Compared with Example 1, the present example is different in that a solid electrolyte layer having a thickness of 100 nm is formed on one surface of the polypropylene separator substrate layer by sputtering.

Example 7

Compared with Example 1, the present example is different in that a solid electrolyte layer having a thickness of 5 nm is formed on one surface of the polypropylene separator substrate layer by sputtering.

Example 8

Compared with Example 1, the difference of this example is that the solid electrolyte is Li ₃ MnCl ₆ .

Example 9

Compared with Example 1, the difference of this example is that the solid electrolyte is Li ₃ ScCl ₆ .

Example 10

Compared with Example 1, the difference of this example is that the solid electrolyte is Li ₃ ZrCl ₆ .

Embodiment 11

Compared with Example 1, the difference of this example is that the solid electrolyte is Li ₃ YCl ₆ .

Example 12

Compared with Example 1, the difference of this example is that the solid electrolyte is Li ₃ InF ₆ .

Example 13

Compared with Example 1, the difference of this example is that the solid electrolyte layer is deposited on both surfaces of the polypropylene separator substrate layer, and the thickness of the solid electrolyte layer on each surface is 25 nm.

Comparative Example 1

Compared with Example 1, the difference of this comparative example is that the separator is a polypropylene separator, and no solid electrolyte layer is formed on both surfaces of the polypropylene separator.

Comparative Example 2

Compared with Example 1, the difference of this comparative example is that the temperature of the polypropylene separator substrate is not controlled during the sputtering process.

Comparative Example 3

Compared with Example 1, the difference of this comparative example is that the solid electrolyte is made into slurry, and a solid electrolyte layer is formed on one surface of the polypropylene separator substrate layer by coating. The thickness of the solid electrolyte layer is 2000 nm.

Test Case

Battery capacity retention rate test: At 25°C, the batteries corresponding to the embodiment and the comparative example were charged to 4.5V at a constant current of 1/3C, then charged to a current of 0.05C at a constant voltage of 4.5V, left for 5 minutes, and then discharged to 2.8V at 1/3C. The obtained capacity was recorded as the initial capacity C ₀ . The above steps were repeated, and the discharge capacity C _n of the battery after the nth cycle was recorded at the same time. The battery capacity retention rate after each cycle was P _n =C _n /C ₀ *100%. The capacity retention rate of the battery after 50 cycles was tested, that is, the value of P _50. The test results are shown in Table 1.

Battery AC impedance test: Assemble the positive electrode plates, isolation membranes, and 120uL of electrolyte in Examples 1 to 3 and Comparative Examples 1 to 2 into a symmetrical battery with a positive electrode, and place it in a 25°C constant temperature box for 2 hours to ensure the infiltration of the electrolyte. The AC impedance test uses an electrochemical workstation impedance test module, voltage perturbation mode PEIS, perturbation voltage 5mV, frequency range 200kHZ~30mHZ, 0~5V voltage range, 0~5V voltage protection, and the test data is plotted with the negative number (-Z") of the imaginary part of the impedance as the ordinate and the real part Z as the abscissa to obtain the impedance spectrum in Figure 9.

Impedance test data fitting processing: The impedance data of Examples 1 to 3 and Comparative Examples 1 to 2 were fitted using Z-fit software, and the fitting circuit was selected as R _s +C ₁ /R _SEI +C ₂ /R _ct +W, where R _s is ohmic impedance, which is mainly related to the conductivity of the positive electrode material, and R _ct is charge transfer impedance, which mainly reflects the deintercalation rate of lithium ions in the positive electrode material. The judgment basis for fitting is required: the error is less than 5%, and the intersection with the real part should have a deviation of <5% from the R _s obtained by fitting. Only the fitting results that meet the above requirements can be selected to be accepted, and R _ct and R _s are extracted from the fitting results and recorded in Table 1.

Table 1

It can be seen from Table 1 that the battery obtained in the embodiment has better performance in cycle retention rate than the comparative example.

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.

The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. 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 of the present application shall be subject to the attached claims.

Claims

A separation membrane, characterized in that it comprises a separation membrane substrate layer and a solid electrolyte layer located on at least one surface of the separation membrane substrate layer; the solid electrolyte layer comprises a material with a chemical composition of Li a MX a+3 , wherein 1≤a≤6; M is selected from cations of one or more of the following elements: Al, Ga, In, Y, Zr, Nb, Sc, Ti, Mn and La series elements; X is selected from anions containing one or more of the following elements: halogen, S, O and P.
The isolation membrane according to claim 1 is characterized in that M is a +3 valent cation.
The isolation film according to any one of claims 1 to 2 is characterized in that M includes one or more of Al 3+ , Ga 3+ , In 3+ , Y 3+ , Zr 3+ , Nb 3+ , Sc 3+ , Ti 3+ , Mn 3+ , Er 3+ , Tb 3+ , Yb 3+ , Lu 3+ , La 3+ and Ho 3+ .
The isolation film according to any one of claims 1 to 3, characterized in that X comprises one or more of F - , Cl - , Br - , I - , S 2 - , O 2 - and PO 4 - .
The separator according to any one of claims 1 to 4, characterized in that the solid electrolyte layer comprises at least one of Li 3 InCl 6 , Li 3 MnCl 6 , Li 3 ScCl 6 , Li 3 ZrCl 6 , Li 3 YCl 6 , Li 3 InF 6 , Li 3 YCl 6 and Li 3 ScF 6 .
The separator according to any one of claims 1 to 5, characterized in that the solid electrolyte layer satisfies at least one of the following characteristics:

(1) The thickness of the solid electrolyte layer is 5 nm to 1000 nm; optionally, 50 nm to 100 nm;

(2) The electrochemical window of the solid electrolyte layer is ≥4.2V;

(3) The ionic conductivity of the solid electrolyte layer is ≥10 -3 S/cm.
A method for preparing an isolation film, characterized in that it comprises the following steps:

Preparation of solid electrolyte targets;

The solid electrolyte target material is sputtered onto at least one surface of the isolation film substrate layer by magnetron sputtering to form an isolation film.

The isolation membrane includes an isolation membrane substrate layer and a solid electrolyte layer located on at least one surface of the isolation membrane substrate layer; the solid electrolyte layer includes a material with a chemical composition of Li a MX a+3 , wherein 1≤a≤6; M is selected from cations of one or more of the following elements: Al, Ga, In, Y, Zr, Nb, Sc, Ti, Mn and La series elements; X is selected from anions containing one or more of the following elements: halogen, S, O and P.
The method for preparing an isolation film according to claim 7, wherein the sputtering satisfies at least one of the following characteristics:

(1) The sputtering power is 150W to 200W;

(2) The vacuum degree of the sputtering is 10 -1 Pa to 10 -2 Pa;

(3) During the sputtering, the temperature of the isolation film substrate layer is controlled to be ≤100°C.
A secondary battery, characterized by comprising the separator according to any one of claims 1 to 6 or the separator prepared by the preparation method according to any one of claims 7 to 8.
A battery module, characterized by comprising the secondary battery according to claim 9.
A battery pack, characterized by comprising the secondary battery according to claim 9 or the battery module according to claim 10.
An electrical device, characterized in that it comprises at least one of the secondary battery according to claim 9, the battery module according to claim 10, and the battery pack according to claim 11.