Isolating membrane, battery monomer, battery and electric device

Abstract

The invention provides an isolating membrane, a battery monomer, a battery and a power utilization device, the isolating membrane comprises a first porous base material, a second porous base material and a first functional layer located between the first porous base material and the second porous base material, the first functional layer comprises graphene oxide, and the first functional layer is provided with a through hole arranged along the thickness direction of the first functional layer.

Description

Separator, battery cell, battery and electrical device Technical Field

[0001] The present application relates to an isolation film, a battery cell, a battery and an electrical device. Background Art

[0002] In recent years, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in consumer electronics, power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. With the application and promotion of batteries, their reliability has received more and more attention. During the battery charging and discharging process, the dendrite problem on the negative electrode is one of the important reasons affecting the reliability of the battery. How to slow down the growth of dendrites without affecting the normal use of the battery is a technical problem that needs to be solved urgently. The above statements are only used to provide background technical information related to this application and do not necessarily constitute prior art.

[0003] Summary of the Invention

[0004] The present application provides an isolation membrane, a battery cell, a battery and an electrical device, which can enable the battery to have good cycle performance.

[0005] In a first aspect, the present application provides an isolation membrane comprising a first porous substrate, a second porous substrate, and a first functional layer located between the first porous substrate and the second porous substrate, wherein the first functional layer comprises graphene oxide and has through holes extending through the first functional layer along its thickness direction.

[0006] The isolation membrane provided in the embodiments of the present application has a multi-layer structure, wherein the first functional layer is located between the first porous substrate and the second porous substrate, and the first functional layer includes graphene oxide. The graphene oxide can react with the dendrites that pierce the porous substrate on the negative electrode side to slow down the growth of the dendrites, thereby reducing the probability of the dendrites piercing the porous substrate on the positive electrode side and causing an internal short circuit in the battery. The isolation membrane provided in the embodiments of the present application has good high temperature resistance, high mechanical strength, and good electrolyte infiltration and retention characteristics. The isolation membrane provided in the embodiments of the present application has a stable structure and is not prone to problems such as powder loss.

[0007] The first functional layer of the isolation membrane provided in the embodiment of the present application also has through holes arranged along its own thickness direction, thereby fully utilizing the role of graphene oxide in improving the high temperature resistance, mechanical strength, electrolyte wetting characteristics and retention characteristics of the isolation membrane and slowing down dendrite growth, and also enabling the isolation membrane to have good air permeability and high ion transmission capacity. Therefore, the isolation membrane provided in the embodiment of the present application can reduce the probability of internal short circuit of the battery and enable the battery to have good cycle performance.

[0008] In any embodiment of the present application, the thickness of the first functional layer is less than or equal to 10 μm, and can be optionally 0.5-5 μm. When the thickness of the first functional layer is within the above range, the graphene oxide can fully exert its role in improving the high temperature resistance, mechanical strength, electrolyte wetting and retention properties of the separator, and slowing down dendrite growth, while also avoiding excessive increase in the weight of the separator and affecting the energy density of the battery. In addition, when the thickness of the first functional layer is within the above range, the separator can also have good air permeability and high ion transport capacity, thereby helping to improve the cycle performance of the battery.

[0009] In any embodiment of the present application, the ratio of the total area of ​​the through holes to the total area of ​​the first functional layer is (0.50-0.85):1, and can optionally be (0.60-0.82):1. When the ratio of the total area of ​​the through holes to the total area of ​​the first functional layer is within the above range, the graphene oxide can fully exert its effect of improving the high temperature resistance, mechanical strength, electrolyte wetting and retention properties of the separator, and slowing down dendrite growth, while also providing the separator with good air permeability and high ion transport capacity. As a result, the separator provided by the embodiments of the present application can reduce the probability of internal short circuits in the battery and improve the battery's cycle performance.

[0010] In any embodiment of the present application, the through hole is a continuous pattern. Optionally, the continuous pattern is a reciprocating bending pattern.

[0011] In any embodiment of the present application, the number of the through holes is multiple and discretely distributed. Optionally, the multiple through holes are distributed in a discrete array.

[0012] In any embodiment of the present application, the pore spacing between two adjacent through holes is 0.5-10 μm, and optionally 0.7-5 μm. When the pore spacing between two adjacent through holes is within the above range, on the one hand, the separator can have good air permeability and high ion transport capacity, thereby further reducing the internal resistance of the battery and improving the cycle performance of the battery. On the other hand, it can also reduce the problem of pore blockage caused by the first functional layer breaking into powder or particles.

[0013] In any embodiment of the present application, the through-hole has an equivalent circular diameter of 5-25 μm, optionally 8-17 μm. When the through-hole has an equivalent circular diameter within the above range, the separator can have good air permeability and high ion transport capacity, thereby further reducing the internal resistance of the battery and improving the battery's cycle performance. Furthermore, the separator can be better able to slow down dendrite growth, thereby further reducing the probability of internal short circuits in the battery.

[0014] In any embodiment of the present application, the through hole pattern includes one or more of a circle, an ellipse, an oblong, a polygon, a sector, a straight line, and a pattern.

[0015] In any embodiment of the present application, the volume distribution particle size Dv50 of the graphene oxide is 0.01-5 μm, and can be optionally 0.05-3 μm.

[0016] In any embodiment of the present application, the graphene oxide has a layered structure.

[0017] In any embodiment of the present application, the graphene oxide sheet thickness is less than or equal to 4 nm, and can be 1-2 nm. When the volume distribution particle size Dv50 of the graphene oxide is within the above range, the slurry viscosity is moderate, which helps to form a uniform first functional layer, reduces powder loss during the coating process, and reduces the probability of pore blockage. This can further enable the separator to have good air permeability and high ion transport capacity, thereby improving the battery's cycle performance.

[0018] In any embodiment of the present application, the ratio of the thickness of the first porous substrate to the thickness of the first functional layer is 1:(0.1-0.9), and can be optionally 1:(0.1-0.5).

[0019] In any embodiment of the present application, the ratio of the thickness of the second porous substrate to the thickness of the first functional layer is 1:(0.1-0.9), and can be optionally 1:(0.1-0.5).

[0020] In any embodiment of the present application, the thickness of the first porous substrate is 2-15 μm, and optionally 3-10 μm.

[0021] In any embodiment of the present application, the thickness of the second porous substrate is 2-15 μm, and optionally 3-10 μm.

[0022] In any embodiment of the present application, the ratio of the thickness of the first porous substrate to that of the second porous substrate is (0.8-1.05):(0.8-1.06), and can be optionally (0.9-1.03):(0.9-1.04).

[0023] Further adjusting the thickness of the first porous substrate and / or the second porous substrate can help the separator to have both high mechanical strength and high bonding strength, and also help the separator to have good air permeability and high ion transmission capacity.

[0024] In any embodiment of the present application, the total thickness of the isolation membrane is 5-25 μm, and optionally 8-18 μm, thereby helping the isolation membrane to have high mechanical strength, good air permeability, and high ion transmission capability.

[0025] In any embodiment of the present application, the first functional layer further comprises a non-particulate binder. Optionally, the non-particulate binder comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinyl alcohol, polyacrylic acid, polyurethane, carboxymethyl cellulose, and styrene-butadiene rubber emulsion.

[0026] In any embodiment of the present application, the content of the non-particulate binder in the first functional layer is 2%-15%, optionally 3%-10%, based on the total weight of the first functional layer.

[0027] In any embodiment of the present application, the first functional layer further comprises first inorganic particles. The first inorganic particles can reduce the degree of overlap between graphene oxide microsheets, thereby helping to further improve the air permeability and ion transmission capability of the isolation membrane.

[0028] In any embodiment of the present application, the first inorganic particles include one or more of inorganic particles having the ability to transport active ions and inorganic particles having a dielectric constant of 5 or greater.

[0029] In any embodiment of the present application, the volume distribution particle size Dv50 of the first inorganic particles is 0.2-5 μm, and more preferably 1-3 μm. When the volume distribution particle size Dv50 of the first inorganic particles is within this range, it helps further reduce the degree of overlap between graphene oxide microplatelets, thereby further improving the air permeability and ion transport capacity of the separator. Furthermore, it can also reduce the probability of pore blockage caused by powder loss during the coating process, thereby improving the battery's cycle performance.

[0030] In any embodiment of the present application, the content of the first inorganic particles in the first functional layer is 2%-15%, optionally 5%-10%, based on the total weight of the first functional layer.

[0031] In any embodiment of the present application, the through hole is obtained by one or more of a phase separation process, a photolithography process, and a plasma etching process.

[0032] In any embodiment of the present application, the through hole is obtained by a laser etching process.

[0033] In any embodiment of the present application, the laser wavelength is 100-2000 nm, and can be optionally 300-1500 nm.

[0034] In any embodiment of the present application, the power of the laser is 1-15W, and can be optionally 2-10W.

[0035] In any embodiment of the present application, the cutting speed of the laser spot is 20-70 mm / s, and can be optionally 40-60 mm / s.

[0036] In any embodiment of the present application, the pulse width of the laser generator is 2-20 ps, ​​and can be optionally 5-15 ps.

[0037] In any embodiment of the present application, the laser light emission time is 2-6 ms / via.

[0038] By adjusting one or more of the aforementioned laser parameters, the first functional layer can be provided with through-holes extending through its thickness. Parameters such as the total area and pattern of the through-holes can also be adjusted. Furthermore, by adjusting one or more of the aforementioned laser parameters, damage to the first and second porous substrates by the high-energy laser can be minimized.

[0039] In any embodiment of the present application, the first porous substrate includes one or more of polyolefins, halogenated polyolefins, polyamides, polyesters, and derivatives thereof.

[0040] In any embodiment of the present application, the second porous substrate includes one or more of polyolefins, halogenated polyolefins, polyamides, polyesters, and derivatives thereof.

[0041] In any embodiment of the present application, the separator further includes a second functional layer located on a surface of the first porous substrate and / or the second porous substrate facing away from the first functional layer, wherein the second functional layer includes one or more of second inorganic particles and organic particles. This can improve at least one of the high temperature resistance and bonding strength of the separator.

[0042] In any embodiment of the present application, the second inorganic particles include one or more of inorganic particles having the ability to transport active ions and inorganic particles having a dielectric constant of 5 or greater.

[0043] In any embodiment of the present application, the organic particles include one or more of polyvinylidene fluoride particles, polytetrafluoroethylene particles, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer particles, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer particles, and tetrafluoroethylene-hexafluoropropylene copolymer particles.

[0044] In any embodiment of the present application, the ionic conductivity of the isolation membrane at 25° C. is 0.8-2.8 mS·cm -1 , optional 1.0-2.5mS·cm -1 The separator has high ionic conductivity, which can improve the cycle performance of the battery.

[0045] In any embodiment of the present application, the air permeability of the separator is 100-400s / 100ml, and can be optionally 120-200s / 100ml. The separator has good air permeability, thereby improving the cycle performance of the battery.

[0046] In any embodiment of the present application, the transverse tensile strength of the isolation film is greater than or equal to 1000 kgf / cm 2 , optional 1100-1600kgf / cm 2 .

[0047] In any embodiment of the present application, the longitudinal tensile strength of the isolation film is greater than or equal to 900 kgf / cm 2 , optional 1000-1600kgf / cm 2 .

[0048] The separator has high tensile strength in both the transverse and longitudinal directions, thereby improving the reliability of the battery.

[0049] In any embodiment of the present application, the puncture strength of the isolation film is 9.0-15N·μm -1 , optional 9.5-12N·μm -1 The separator has high puncture strength, which can improve the reliability of the battery.

[0050] In any embodiment of the present application, the porosity of the isolation membrane is 40%-80%, and optionally 45%-76%, which helps the isolation membrane to have good air permeability and high ion transmission capacity.

[0051] A second aspect of the present application provides a battery cell comprising the isolation membrane of the first aspect of the present application.

[0052] In any embodiment of the present application, the battery cell includes at least one of a lithium-ion battery cell, a sodium-ion battery cell, a lithium metal battery cell, a sodium metal battery cell, a lithium-sulfur battery cell, a sodium-sulfur battery cell, a lithium-air battery cell, and a sodium-air battery cell.

[0053] A third aspect of the present application provides a battery, comprising the battery cell of the second aspect of the present application and a box for accommodating the battery cell.

[0054] A fourth aspect of the present application provides an electrical device comprising the battery of the third aspect of the present application.

[0055] The electric device of the present application includes the battery provided by the present application, and thus has at least the same advantages as the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] To more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive effort.

[0057] FIG1 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0058] FIG2 is an exploded schematic diagram of an embodiment of a battery cell of the present application.

[0059] FIG3 is a schematic diagram of an embodiment of a battery module of the present application.

[0060] FIG4 is a schematic diagram of an embodiment of a battery pack of the present application.

[0061] FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4 .

[0062] FIG6 is a schematic diagram of an isolation film according to an embodiment of the present application.

[0063] FIG. 7 is a schematic diagram of an embodiment of the first functional layer of the isolation film of the present application.

[0064] FIG8 is a schematic diagram of another embodiment of the first functional layer of the isolation film of the present application.

[0065] FIG9 is a schematic diagram of an embodiment of an electric device including the battery of the present application as a power source.

[0066] In the accompanying drawings, which are not necessarily drawn to scale, the reference numerals are as follows: 1, battery pack; 2, upper housing; 3, lower housing; 4, battery module; 5, battery cell; 51, housing; 52, electrode assembly; 53, cover plate; 10, separator; 101, first porous substrate; 102, second porous substrate; 103, first functional layer; 1031, through-hole. DETAILED DESCRIPTION

[0067] Below, the embodiments of the separator, battery cell, battery, and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0068] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this 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.

[0069] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0070] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0071] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (1) and (2), which means that the method may include steps (1) and (2) performed sequentially, or may include steps (2) and (1) performed sequentially. For example, the method may further include step (3), which means that step (3) may be added to the method in any order, for example, the method may include steps (1), (2) and (3), or may include steps (1), (3) and (2), or may include steps (3), (1) and (2), etc.

[0072] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0073] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: 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).

[0074] Unless otherwise specified, in this application, the terms "first", "second", etc. are used to distinguish different objects rather than to describe a specific order or a primary-secondary relationship.

[0075] Unless otherwise specified, all ratio parameters involved in this application are compared in the same unit. For example, the area ratio of A to B is 0.75:1, in which case the area units of A and B are the same.

[0076] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0077] Unless otherwise noted, the values ​​of the parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods provided in this application. Unless otherwise noted, the test temperature of the parameters is 25°C and the test pressure is standard atmospheric pressure.

[0078] The battery mentioned in the embodiments of the present application refers to a single physical module that includes one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery cell, a battery module or a battery pack, etc. A battery cell is the smallest unit that makes up a battery, which can realize the function of charging and discharging alone. The present application has no special restrictions on the shape of the battery cell, which can be a cylinder, a rectangular parallelepiped or any other shape. Figure 1 is an example of a battery cell 5 with a rectangular parallelepiped structure. Multiple battery cells can be connected in series, in parallel or in mixed connection, and mixed connection refers to a mixture of series and parallel connection. In the embodiments of the present application, multiple battery cells can directly form a battery pack, or they can first form a battery module, and the battery modules can then form a battery pack.

[0079] A battery generally includes a casing for encapsulating one or more battery cells. The casing can prevent liquids or other foreign matter from affecting the charging or discharging of the battery cells. The casing can be a simple three-dimensional structure such as a single cuboid, cylinder, or sphere, or a complex three-dimensional structure composed of a combination of simple three-dimensional structures such as cuboids, cylinders, or spheres, and the embodiments of the present application do not limit this. The material of the casing can be an alloy material such as aluminum alloy, iron alloy, or a polymer material such as polycarbonate, polyisocyanurate foam plastic, or a composite material such as glass fiber and epoxy resin, and the embodiments of the present application do not limit this.

[0080] The battery cells mentioned in the embodiments of the present application may be at least one of lithium-ion battery cells, sodium-ion battery cells, lithium metal battery cells, sodium metal battery cells, lithium-sulfur battery cells, sodium-sulfur battery cells, lithium-air battery cells, sodium-air battery cells, etc., and the embodiments of the present application are not limited to this.

[0081] The dendrites mentioned in the embodiments of the present application may be lithium dendrites, sodium dendrites, and the like.

[0082] The battery cell provided in the embodiments of the present application includes an electrode assembly and an electrolyte. The electrode assembly can be a wound structure or a laminated structure, which is not limited in the embodiments of the present application.

[0083] The battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte. The outer packaging can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging can also be a soft shell, such as a bag-type soft shell. The soft shell can be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0084] As shown in Figure 2, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate. The base plate and side plates together form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening, thereby sealing the receiving cavity. The electrode assembly 52 is enclosed in the receiving cavity. The number of electrode assemblies 52 contained in a battery cell 5 can be one or more, and can be adjusted according to needs.

[0085] Battery cells can be assembled into battery modules, which can contain multiple battery cells. The specific number can be adjusted according to the application and capacity of the battery module. Figure 3 is a schematic diagram of an example battery module 4. As shown in Figure 3, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. The multiple battery cells 5 can further be fixed using fasteners.

[0086] The battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 may be accommodated in the accommodation space.

[0087] The above-mentioned battery modules can also be assembled into a battery pack. The number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack. Figures 4 and 5 are schematic diagrams of a battery pack 1 as an example. As shown in Figures 4 and 5, the battery pack 1 may include a box and multiple battery modules 4 disposed in the box. The box includes an upper box 2 and a lower box 3. The upper box 2 is used to cover the lower box 3 and form an enclosed space for accommodating the battery modules 4. Multiple battery modules 4 can be arranged in the box in any manner.

[0088] The electrode assembly consists of a positive electrode sheet, a negative electrode sheet, and a separator. The separator is positioned between the positive and negative electrodes and primarily serves to prevent internal short circuits. As a crucial component of the battery, the performance of the separator is crucial to its performance. Currently, the separators used in commercial batteries are typically polyolefin porous membranes. However, these membranes have poor electrolyte wetting and retention properties, as well as poor thermal stability. Furthermore, as the battery's charge and discharge cycles increase, dendrites form on the negative electrode. Continued dendrite growth can pierce the polyolefin porous membrane, causing internal short circuits and, in severe cases, even fires, explosions, and other safety hazards.

[0089] Modifying the separator is an effective way to improve battery reliability and reduce the probability of internal short circuits. Currently, the commonly used strategy is to layer an inorganic ceramic layer on the separator surface. However, this inorganic ceramic layer presents several issues: first, poor adhesion between the inorganic ceramic layer and the polyolefin porous membrane, making the coating prone to detachment; and second, the inorganic ceramic layer has limited effectiveness in suppressing dendrite formation.

[0090] In view of this, the inventors improved the structure of the isolation membrane.

[0091] Figure 6 is a schematic diagram of an embodiment of the isolation membrane of the present application. Figure 7 is a schematic diagram of an embodiment of the first functional layer of the isolation membrane of the present application. Figure 8 is a schematic diagram of another embodiment of the first functional layer of the isolation membrane of the present application.

[0092] As shown in Figures 6 to 8, the isolation membrane 10 includes a first porous substrate 101, a second porous substrate 102, and a first functional layer 103 located between the first porous substrate 101 and the second porous substrate 102. The first functional layer 103 includes graphene oxide, and the first functional layer 103 has through holes 1031 arranged along the thickness direction of the first functional layer 103.

[0093] The first functional layer is located between the first porous substrate and the second porous substrate, thereby preventing the graphene oxide from directly contacting the positive and negative electrodes, thereby reducing the occurrence of side reactions. In particular, when graphene oxide contacts the negative electrode, it will continuously consume metal (such as lithium metal, etc.), thereby reducing the battery capacity and cycle life. In addition, compared with traditional polyolefin separators, the separator provided by the embodiments of the present application has good high temperature resistance and high mechanical strength; compared with traditional separators coated with inorganic ceramic layers, the separator provided by the embodiments of the present application has a stable structure and is not prone to problems such as powder loss.

[0094] After multiple charge and discharge cycles of a battery cell, dendrites will form on the negative electrode. The continued growth of dendrites will pierce the isolation membrane, causing an internal short circuit. In severe cases, safety accidents such as combustion and explosion may even occur. The first functional layer of the isolation membrane provided in the embodiment of the present application includes graphene oxide (abbreviated as GO). Graphene oxide is an oxide of graphene, and its surface has a large number of oxygen-containing functional groups, such as hydroxyl, carboxyl, aldehyde, etc. During the research process, the inventors discovered that graphene oxide can react with dendrites that pierce the porous substrate on the negative electrode side to slow down the growth of dendrites, thereby effectively reducing the probability of dendrites piercing the porous substrate on the positive electrode side and causing an internal short circuit in the battery. Therefore, the first functional layer of the isolation membrane provided in the embodiment of the present application can act as a barrier layer, reducing or even preventing dendrites from piercing the isolation membrane, thereby reducing the probability of internal short circuits in the battery.

[0095] Taking lithium dendrites as an example, the reaction between graphene oxide (GO) and lithium dendrites can be:

[0096] Graphene oxide (GO) + Li → reduced graphene oxide (r-GO) + Li + .

[0097] Taking sodium dendrites as an example, the reaction between graphene oxide (GO) and sodium dendrites can be:

[0098] Graphene oxide (GO) + Na → reduced graphene oxide (r-GO) + Na + .

[0099] The porous substrate of the isolation membrane is typically highly hydrophobic and has poor affinity for highly polar electrolytes, resulting in the isolation membrane's poor wetting and retention properties for the electrolyte. The first functional layer of the isolation membrane provided in the embodiments of the present application includes graphene oxide. Graphene oxide has a large number of oxygen-containing functional groups that are highly hydrophilic, thereby increasing the isolation membrane's wetting and retention properties for the electrolyte and improving the battery's cycling performance. Furthermore, the graphene oxide obtained through micro-oxidation treatment can be composited with the isolation membrane's porous substrate through van der Waals forces, thereby reducing the amount of binder used and improving the battery's cycling performance.

[0100] During their research, the inventors discovered that graphene oxide readily swells and spreads in a slurry, forming graphene oxide microsheets when coated on a porous substrate. These microsheets stack on top of each other, reducing the permeability and porosity of the separator and the number of ion channels. This, in turn, leads to a decrease in ionic conductivity and an increase in internal resistance, impacting the battery's cycle performance and service life. The first functional layer of the separator provided in the embodiments of the present application has through-holes extending through its thickness, resulting in excellent permeability and high ion transport capacity, and thus, excellent battery cycle performance.

[0101] Therefore, the isolation membrane provided in the embodiment of the present application has a multi-layer structure, wherein the first functional layer is located between the first porous substrate and the second porous substrate, and the first functional layer includes graphene oxide. The graphene oxide can react with the dendrites that pierce the porous substrate on the negative electrode side to slow down the growth of the dendrites, thereby reducing the probability of the dendrites piercing the porous substrate on the positive electrode side and causing an internal short circuit in the battery. The isolation membrane provided in the embodiment of the present application has good high temperature resistance, high mechanical strength, and good electrolyte infiltration and retention characteristics. The isolation membrane provided in the embodiment of the present application has a stable structure and is not prone to problems such as powder loss.

[0102] The first functional layer of the isolation membrane provided in the embodiment of the present application also has through holes arranged along its own thickness direction, thereby fully utilizing the role of graphene oxide in improving the high temperature resistance, mechanical strength, electrolyte wetting characteristics and retention characteristics of the isolation membrane and slowing down dendrite growth, and also enabling the isolation membrane to have good air permeability and high ion transmission capacity. Therefore, the isolation membrane provided in the embodiment of the present application can reduce the probability of internal short circuit of the battery and enable the battery to have good cycle performance.

[0103] In some embodiments, the thickness of the first functional layer may be less than or equal to 10 μm. For example, the thickness of the first functional layer may be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.5 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or any range thereof.

[0104] When the thickness of the first functional layer is within the above range, graphene oxide can fully utilize its effects of improving the separator's high-temperature resistance, mechanical strength, electrolyte wetting and retention properties, and mitigating dendrite growth, while also preventing excessive weight increase that could affect the battery's energy density. Furthermore, when the thickness of the first functional layer is within the above range, the separator also possesses good air permeability and high ion transport capacity, thereby contributing to improved battery cycle performance.

[0105] Optionally, the thickness of the first functional layer may be 0.5-10 μm, 0.5-9 μm, 0.5-8 μm, 0.5-7 μm, 0.5-6 μm, 0.5-5 μm, 0.7-10 μm, 0.7-9 μm, 0.7-8 μm, 0.7-7 μm, 0.7-6 μm, 0.7-5 μm, 0.9-10 μm, 0.9-9 μm , 0.9-8μm, 0.9-7μm, 0.9-6μm, 0.9-5μm, 1-10μm, 1-9μm, 1-8μm, 1-7μm, 1-6μm, 1-5μm, 1.1-10μm, 1.1-9μm, 1.1-8μm, 1.1-7μm, 1.1-6μm, 1.1-5μm, 1.1-3.5μm.

[0106] In some embodiments, the ratio of the total area of ​​the through holes to the total area of ​​the first functional layer may be (0.50-0.85): 1. For example, the ratio of the total area of ​​the through holes to the total area of ​​the first functional layer may be 0.50:1, 0.52:1, 0.55:1, 0.58:1, 0.60:1, 0.62:1, 0.65:1, 0.68:1, 0.70:1, 0.72:1, 0.75:1, 0.78:1, 0.80:1, 0.82:1, 0.85:1 or any range thereof.

[0107] When the ratio of the total area of ​​the through holes to the total area of ​​the first functional layer is within the above range, the graphene oxide can fully exert its role in improving the high temperature resistance, mechanical strength, electrolyte wetting characteristics and retention characteristics of the isolation membrane and slowing down the growth of dendrites, and can also make the isolation membrane have good air permeability and high ion transmission capacity. Therefore, the isolation membrane provided by the embodiment of the present application can not only reduce the probability of internal short circuit of the battery, but also make the battery have better cycle performance.

[0108] Optionally, the ratio of the total area of ​​the through holes to the total area of ​​the first functional layer may be (0.52-0.82):1, (0.52-0.80):1, (0.52-0.78):1, (0.55-0.82):1, (0.55-0.80):1, (0.55-0.78):1, (0.60-0.82):1, (0.60-0.80):1, (0.60-0.78):1, (0.62-0.82):1, (0.62-0.80):1, (0.62-0.78):1, (0.62-0.75):1, (0.65-0.82):1, (0.65-0.80):1, (0.65-0.78):1, (0.65-0.75):1.

[0109] The total area of ​​the first functional layer refers to the product of the length and the width of the first functional layer, and the total area of ​​the through-holes refers to the sum of the areas of one or more through-holes in the first functional layer.

[0110] In some embodiments, the through-holes may be obtained by one or more of a phase separation process, a photolithography process, and a plasma etching process.

[0111] In some embodiments, the through-holes can be obtained by a laser etching process. The laser etching process has advantages such as high yield, high stability, good flexibility, and easy automated control. For example, during laser etching, the scanning path can be set according to the set pattern shape, so that the desired pattern shape is obtained after the laser etching is completed. In addition, the first functional layer is usually brown-black and can absorb laser light, while the first porous substrate and the second porous substrate are usually white and do not absorb laser light. Therefore, during laser etching, the high-energy laser comes into contact with the graphene oxide and generates a large amount of heat, which can ablate and remove part of the graphene oxide, so that the first functional layer has through-holes set along its thickness direction, thereby giving the separator good air permeability and high ion transmission capacity, thereby reducing the internal resistance of the battery and improving the battery's cycle performance. At the same time, during laser etching, the high-energy laser does not damage or substantially damage the first porous substrate and the second porous substrate, thereby minimizing the problem of the first porous substrate and / or the second porous substrate being punctured due to laser etching and accelerating internal short circuits.

[0112] In some embodiments, the laser wavelength may be 100-2000 nm, optionally 300-1500 nm.

[0113] In some embodiments, the power of the laser may be 1-15 W, optionally 2-10 W.

[0114] In some embodiments, the cutting speed of the laser spot may be 20-70 mm / s, optionally 40-60 mm / s.

[0115] In some embodiments, the pulse width of the laser generator may be 2-20 ps, ​​optionally 5-15 ps.

[0116] In some embodiments, the laser light emission time may be 2-6 ms / via.

[0117] By adjusting one or more of the aforementioned laser parameters, the first functional layer can be provided with through-holes extending through its thickness. Parameters such as the total area and pattern of the through-holes can also be adjusted. Furthermore, by adjusting one or more of the aforementioned laser parameters, damage to the first and second porous substrates by the high-energy laser can be minimized.

[0118] The through holes may be in various regular or irregular patterns, which are not limited in the present embodiment. The through holes may be in a continuous or discontinuous pattern, which are not limited in the present embodiment.

[0119] Continuing with Figure 7, in some embodiments, the through-holes may be a continuous pattern. Alternatively, the continuous pattern may be a reciprocating zigzag pattern, for example, a bow-shaped or S-shaped zigzag pattern. As shown in Figure 7, the zigzag pattern is bow-shaped. By making the continuous pattern a reciprocating zigzag pattern, the separator can have good air permeability and high ion transport capacity, thereby further reducing the battery's internal resistance and improving the battery's cycle performance. Furthermore, the pattern can also slow down dendrite growth, thereby reducing the probability of internal short circuits in the battery.

[0120] Continuing to refer to FIG. 8 , in some embodiments, the number of through holes may be multiple and discretely distributed.

[0121] In some embodiments, the number of through holes can be multiple, and the multiple through holes can be distributed in a discrete array. For example, the multiple through holes can be arranged in a straight row or staggered, and the staggered arrangement can further be 45° staggered, 60° staggered, Z-shaped staggered, or K-shaped staggered, etc., which is not limited in the embodiments of the present application. By distributing the multiple through holes in a discrete array, on the one hand, the isolation membrane can have good air permeability and high ion transmission capacity, thereby further reducing the internal resistance of the battery and improving the cycle performance of the battery. On the other hand, it can also slow down the growth of dendrites, thereby reducing the probability of internal short circuits in the battery.

[0122] The discretely distributed through-holes may be arranged in various regular or irregular patterns, which are not limited in the present embodiment. For example, the through-holes may be one or more of circular, elliptical, oblong, polygonal, fan-shaped, straight, or patterned. Alternatively, the polygonal shape may include one or more of rectangular, square, diamond, hexagonal, and the like.

[0123] In some embodiments, the spacing between two adjacent through holes may be 0.5-10 μm. For example, the spacing between two adjacent through holes may be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.5 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or any range thereof.

[0124] When the spacing between two adjacent through-holes is within the above range, the separator can, on the one hand, have good air permeability and high ion transport capacity, thereby further reducing the internal resistance of the battery and improving the battery's cycle performance. On the other hand, it can also reduce the problem of pore blockage caused by the first functional layer breaking into powder or particles. In addition, the inventors found that the first functional layer breaking into powder or particles also affects its effectiveness in eliminating dendrites and slowing their growth.

[0125] Optionally, the hole spacing between two adjacent through holes may be 0.6-8μm, 0.6-5μm, 0.6-4μm, 0.6-3μm, 0.7-8μm, 0.7-5μm, 0.7-4μm, 0.7-3μm, 0.8-8μm, 0.8-5μm, 0.8-4μm, 0.8-3μm, 1-5μm, 1-4μm, 1-3μm.

[0126] Please continue to refer to FIG. 8 . The hole spacing S between two adjacent through holes 1031 refers to the hole spacing between the two adjacent through holes 1031 in the direction of the geometric centers.

[0127] In some embodiments, the equivalent circular diameter of the through hole may be 5-25 μm. For example, the equivalent circular diameter of the through hole may be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 22 μm, 25 μm, or any range thereof.

[0128] When the equivalent circle diameter of the through hole is within the above range, on the one hand, the isolation membrane can have good air permeability and high ion transmission capacity, thereby further reducing the internal resistance of the battery and improving the cycle performance of the battery. On the other hand, it can also better slow down the growth of dendrites, thereby further reducing the probability of internal short circuit of the battery.

[0129] Optionally, the equivalent circular diameter of the through hole may be 6-22 μm, 7-20 μm, or 8-17 μm.

[0130] The “equivalent circular diameter of the through hole” refers to the diameter of a circle having the same area as the through hole when the through hole is non-circular. When the through hole is circular, the equivalent circular diameter of the through hole is the diameter of the circle.

[0131] In some embodiments, the volume distribution particle size Dv50 of the graphene oxide may be 0.01-5 μm. When the volume distribution particle size Dv50 of the graphene oxide is within the above range, the slurry viscosity is moderate, which helps to form a uniform first functional layer, reduces powder loss during the coating process, and reduces the probability of pore blockage. This can further enable the separator to have good air permeability and high ion transport capacity, and thus provide the battery with better cycle performance. Optionally, the volume distribution particle size Dv50 of the graphene oxide may be 0.02-4 μm, 0.05-3 μm, 0.1-3 μm, 0.2-3 μm, 0.5-3 μm, 0.1-2 μm, 0.2-2 μm, or 0.5-2 μm.

[0132] In some embodiments, the graphene oxide has a layer structure, and the layer can be one or more layers, for example, 2-6 layers, which is not limited in the embodiments of the present application.

[0133] In some embodiments, the thickness of the graphene oxide sheet may be less than or equal to 4 nm, and may be 1-2 nm.

[0134] In some embodiments, the first functional layer may further include a non-particulate binder. The present application does not particularly limit the type of the non-particulate binder. As an example, the non-particulate binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyurethane (PU), carboxymethyl cellulose (CMC), and styrene-butadiene rubber emulsion (SBR).

[0135] In some embodiments, the content of the non-particulate binder in the first functional layer may be less than or equal to 15%, optionally 2%-15%, and more optionally 3%-10%, based on the total weight of the first functional layer.

[0136] In some embodiments, the first functional layer may further include first inorganic particles. The first inorganic particles can reduce the degree of overlap between graphene oxide microplatelets, thereby helping to further improve the air permeability of the isolation membrane and further enhance the ion transmission capability of the isolation membrane.

[0137] Alternatively, the first inorganic particles may include one or more of inorganic particles capable of transporting active ions and inorganic particles having a dielectric constant greater than 5. As an example, the inorganic particles capable of transporting active ions may include lithium phosphate, lithium titanium phosphate (Li x Ti y (PO4)3, 0<x<2, 0<y<3), lithium aluminum titanium phosphate (Li x Al y Tiz (PO4)3, 0<x<2, 0<y<1, 0<z<3), (LiAlTiP) x O y Glass-like (0<x<4, 0<y<13), lithium lanthanum titanate (Li x La y TiO3, 0<x<2, 0<y<3), lithium germanium thiophosphate (Li x Ge y P z S w , 0<x<4, 0<y<1, 0<z<1, 0<w<5), lithium nitride (Li x N y , 0<x<4, 0<y<2), SiS2 type glass (Li x Si y S z , 0<x<3, 0<y<2, 0<z<4), P2S5 type glass (Li x P y S z , 0<x<3, 0<y<3, 0<z<7). As an example, the inorganic particles having a dielectric constant of 5 or more may include one or more of boehmite, aluminum oxide, magnesium oxide, magnesium hydroxide, silicon oxide, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, and barium titanate.

[0138] In some embodiments, the volume distribution particle size Dv50 of the first inorganic particles may be 0.2-5 μm, optionally 1-3 μm. When the volume distribution particle size Dv50 of the first inorganic particles is within this range, it helps further reduce the degree of overlap between graphene oxide microplatelets, thereby further improving the air permeability and ion transport capacity of the separator. Furthermore, it can also reduce the probability of pore blockage caused by powder loss during the coating process, thereby improving the battery's cycle performance.

[0139] In some embodiments, the content of the first inorganic particles in the first functional layer may be less than or equal to 15%, optionally 2%-15%, and more optionally 5%-10%, based on the total weight of the first functional layer.

[0140] In some embodiments, the ratio of the thickness of the first porous substrate to the thickness of the first functional layer may be 1:(0.1-0.9), and may optionally be 1:(0.1-0.5).

[0141] In some embodiments, the thickness of the first porous substrate may be 2-15 μm, and optionally 3-10 μm.

[0142] In some embodiments, the ratio of the thickness of the second porous substrate to the thickness of the first functional layer is 1:(0.1-0.9), and can be optionally 1:(0.1-0.5).

[0143] In some embodiments, the second porous substrate has a thickness of 2-15 μm, optionally 3-10 μm.

[0144] In some embodiments, the ratio of the thickness of the first porous substrate to the thickness of the second porous substrate may be (0.8-1.05):(0.8-1.06), or optionally (0.9-1.03):(0.9-1.04).

[0145] Further adjusting the thickness of the first porous substrate and / or the second porous substrate can help the separator to have both high mechanical strength and high bonding strength, and also help the separator to have good air permeability and high ion transmission capacity.

[0146] In some embodiments, the separator may further include a second functional layer located on a surface of the first porous substrate and / or the second porous substrate facing away from the first functional layer. The second functional layer may include one or more of second inorganic particles and organic particles. This may improve at least one of the high temperature resistance and bonding strength of the separator.

[0147] Alternatively, the second inorganic particles may include one or more of inorganic particles capable of transporting active ions and inorganic particles having a dielectric constant of 5 or more. As an example, the inorganic particles capable of transporting active ions may include lithium phosphate, lithium titanium phosphate (Li x Ti y (PO4)3, 0<x<2, 0<y<3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0<x<2, 0<y<1, 0<z<3), (LiAlTiP) x O y Glass-like (0<x<4, 0<y<13), lithium lanthanum titanate (Li x La y TiO3, 0<x<2, 0<y<3), lithium germanium thiophosphate (Li x Ge y P z S w , 0<x<4, 0<y<1, 0<z<1, 0<w<5), lithium nitride (Li x N y , 0<x<4, 0<y<2), SiS2 type glass (Li x Si y S z, 0<x<3, 0<y<2, 0<z<4), P2S5 type glass (Li x P y S z , 0<x<3, 0<y<3, 0<z<7). As an example, the inorganic particles having a dielectric constant of 5 or more may include one or more of boehmite, aluminum oxide, magnesium oxide, magnesium hydroxide, silicon oxide, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, and barium titanate.

[0148] Alternatively, the organic particles may include one or more of polyvinylidene fluoride (PVDF) particles, polytetrafluoroethylene (PTFE) particles, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer particles, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer particles, and tetrafluoroethylene-hexafluoropropylene copolymer particles.

[0149] In some embodiments, the material of the first porous substrate may include, but is not limited to, one or more of polyolefins (e.g., polyethylene, polypropylene), halogenated polyolefins (e.g., polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride), polyamides, polyesters (e.g., polyethylene terephthalate), and their respective derivatives.

[0150] In some embodiments, the material of the second porous substrate may include, but is not limited to, one or more of polyolefins (e.g., polyethylene, polypropylene), halogenated polyolefins (e.g., polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride), polyamides, polyesters (e.g., polyethylene terephthalate), and their respective derivatives.

[0151] Derivatives usually refer to products derived from the replacement of hydrogen atoms or atomic groups in polymers by other atoms or atomic groups.

[0152] In some embodiments, the first porous substrate may have a weight average molecular weight of 100,000 to 1,000,000.

[0153] In some embodiments, the second porous substrate may have a weight average molecular weight of 100,000 to 1,000,000.

[0154] The weight average molecular weights of the first porous substrate and the second porous substrate have well-known meanings in the art and can be measured using methods known in the art, for example, gel permeation chromatography.

[0155] In some embodiments, the total thickness of the isolation membrane may be 5-25 μm, and optionally 8-18 μm, thereby helping the isolation membrane to have high mechanical strength, good air permeability, and high ion transmission capability.

[0156] In some embodiments, the porosity of the isolation membrane may be 40%-80%, and optionally 45%-76%, thereby helping the isolation membrane to have good air permeability and high ion transmission capacity.

[0157] The porosity of the separator has a well-known meaning in the art and can be measured using methods known in the art, for example, according to the standard GB / T 36363-2018.

[0158] In some embodiments, the ionic conductivity of the isolation membrane at 25°C may be 0.8-2.8 mS·cm -1 , optional 1.0-2.5mS·cm -1 .

[0159] The separator has high ionic conductivity, which can improve the cycle performance of the battery.

[0160] The ionic conductivity of the isolation membrane can be obtained through electrochemical impedance spectroscopy experiments. For example, the isolation membrane can be cut into discs of a certain area, dried, and placed between two stainless steel electrodes. After absorbing a sufficient amount of electrolyte, it is sealed to form a button battery and an electrochemical impedance spectroscopy experiment is performed. The resistance Rs of different isolation membrane layers n is measured using the confined symmetric battery electrochemical impedance spectroscopy method as the isolation membrane resistance. The slope k (corresponding to the resistance of a single-layer isolation membrane) is obtained by plotting Rs and n. The ionic conductivity of the isolation membrane is calculated based on the resistance of the single-layer isolation membrane, the area of ​​the isolation membrane, and the thickness of the isolation membrane (single-layer thickness).

[0161] In some embodiments, the air permeability of the isolation membrane may be 100-400 s / 100 ml, and optionally 120-200 s / 100 ml.

[0162] The separator has good air permeability, which can improve the cycle performance of the battery.

[0163] The air permeability of a separator has a well-known meaning in the art and can be measured using methods known in the art. For example, the test can be performed in accordance with the standard GB / T 36363-2018.

[0164] In some embodiments, the transverse direction (TD) tensile strength of the separator may be greater than or equal to 1000 kgf / cm 2 , optional 1100-1600kgf / cm 2 .

[0165] In some embodiments, the longitudinal tensile strength of the separator may be greater than or equal to 900 kgf / cm 2 , optional 1000-1600kgf / cm 2 .

[0166] The separator has high tensile strength in both the transverse and longitudinal directions, thereby improving the reliability of the battery.

[0167] The tensile strength of a separator has a meaning generally known in the art and can be measured using methods known in the art. For example, the test can be performed in accordance with standard GB / T 36363-2018. During the test, the tensile strength can be measured at a rate of 50 mm / min.

[0168] In some embodiments, the puncture strength of the isolation film can be 9.0-15N·μm -1 , optional 9.5-12N·μm -1 .

[0169] The separator has high puncture strength, thereby improving the reliability of the battery.

[0170] The puncture strength of a barrier film has a meaning well known in the art and can be measured using methods known in the art. For example, testing can be performed with reference to the standard GB / T 36363-2018. For example, the barrier film can be cut into samples with a width of 10 mm and a length of 150 mm. The samples are punctured with a steel needle at a rate of 50 mm / min, and the maximum load at which the needle penetrates the barrier film is measured. The diameter of the steel needle can be 1 mm, and the radius of the spherical tip can be 0.5 mm. The surface of the steel needle must be smooth and free of rust, oxide layers, and oil stains.

[0171] In this application, the volume distribution particle size Dv50 of a material has a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be measured using a laser particle size analyzer (e.g., Master Size 3000) with reference to standard GB / T 19077-2016.

[0172] [Preparation method]

[0173] The embodiments of the present application also provide a method for preparing an isolation membrane, which can prepare the isolation membrane described above in the present application.

[0174] In some embodiments, the preparation method includes the steps of: providing a slurry including graphene oxide; coating the slurry including graphene oxide on the surface of a first porous substrate and / or a second multilayer substrate layer, and then obtaining an isolation membrane through lamination, hot pressing, drying, and etching processes, wherein the isolation membrane includes a first porous substrate, a second porous substrate, and a first functional layer located between the first porous substrate and the second porous substrate, the first functional layer includes graphene oxide, and the first functional layer has through holes arranged along its own thickness direction.

[0175] In some embodiments, the slurry including graphene oxide may further include a binder, first inorganic particles, and the like.

[0176] In some embodiments, a slurry comprising graphene oxide can be prepared according to the following steps: soaking the graphene oxide in a first solvent for a period of time, then centrifuging it, and taking the precipitate obtained by centrifugation and soaking it in the first solvent again, repeating several times, and finally taking the precipitate obtained by centrifugation and letting it stand for a period of time to obtain purified graphene oxide; mixing the purified graphene oxide with a second solvent, stirring evenly, and letting it stand for a period of time to obtain a mixture; adding a binder to the obtained mixture, stirring evenly, and obtaining a slurry comprising graphene oxide.

[0177] In some embodiments, when preparing a slurry including graphene oxide, the first solvent may be ethanol or isopropyl alcohol.

[0178] In some embodiments, when the graphene oxide is immersed in the first solvent, the immersion time may be 1-5 hours each time, and the number of immersions may be 2-5 times.

[0179] In some embodiments, when preparing a slurry comprising graphene oxide, the precipitate obtained by centrifugation can be allowed to stand for 5-10 hours to obtain purified graphene oxide.

[0180] In some embodiments, when preparing a slurry including graphene oxide, the second solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.

[0181] In some embodiments, the purified graphene oxide is mixed with the second solvent, stirred evenly, and then allowed to stand for 8-16 hours to obtain a mixture.

[0182] In some embodiments, when preparing a slurry comprising graphene oxide, a pore-forming agent may be added to the resulting mixture to enhance the air permeability of the separator. For example, the pore-forming agent may include one or more of polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG), polyvinyl alcohol (PVA), mineral oil, kerosene, decalin, sodium chloride, potassium carbonate, lithium chloride, ADC foaming agent, and water.

[0183] In some embodiments, after adding a binder to the obtained mixture, the mixture may be stirred at a rotation speed of 700-1200 rpm for 5-50 minutes to obtain a slurry including graphene oxide.

[0184] In some embodiments, when preparing the isolation film, the etching process may include one or more of a photolithography process and a plasma etching process.

[0185] In some embodiments, when preparing the isolation film, the etching process may be a laser etching process.

[0186] In some embodiments, the laser wavelength may be 100-2000 nm, optionally 300-1500 nm.

[0187] In some embodiments, the power of the laser may be 1-15 W, optionally 2-10 W.

[0188] In some embodiments, the cutting speed of the laser spot may be 20-70 mm / s, optionally 40-60 mm / s.

[0189] In some embodiments, the pulse width of the laser generator may be 2-20 ps, ​​optionally 5-15 ps.

[0190] In some embodiments, the laser light emission time may be 2-6 ms / via.

[0191] In some embodiments, when preparing the isolation film, the hot pressing temperature may be 100-130°C.

[0192] In some embodiments, when preparing the isolation film, the hot pressing pressure may be 2-6 MPa.

[0193] In some embodiments, when preparing the isolation film, drying can be performed in a vacuum oven. Optionally, the drying temperature can be 60-120° C. Optionally, the drying time can be 5-10 hours.

[0194] In some embodiments, when preparing the isolation membrane, the slurry including graphene oxide may be coated on one of the first porous substrate and the second multi-layer substrate layer, and then laminated to the other of the first porous substrate and the second multi-layer substrate layer.

[0195] In some embodiments, when preparing the isolation membrane, a slurry including graphene oxide can be simultaneously coated on one surface of the first porous substrate and one surface of the second multi-layer substrate layer, and then the coated sides of the first porous substrate and the second porous substrate are laminated.

[0196] In some embodiments, the method for preparing an isolation membrane may further include the step of providing a second functional layer on the surface of the first porous substrate and / or the second porous substrate of the isolation membrane obtained above, facing away from the first functional layer. The second functional layer may include one or more of second inorganic particles and organic particles.

[0197] The parameters of some raw materials and their contents used in the preparation method of the isolation membrane provided in the embodiments of this application can be referred to the isolation membrane described above in this application and will not be repeated here. Unless otherwise specified, the raw materials used in the preparation method of the isolation membrane of this application can be obtained commercially.

[0198] [Positive electrode]

[0199] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two surfaces opposite to each other in the thickness direction of itself, and the positive electrode film layer is arranged on any one or both of the two opposite surfaces of the positive electrode current collector.

[0200] The positive electrode film layer includes a positive electrode active material. The present application has no particular limitation on the type of the positive electrode active material, and a suitable positive electrode active material can be selected according to the type of battery cell.

[0201] For example, when the battery cell is a lithium-ion battery cell or a lithium metal battery cell, the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, lithium-containing phosphates, layered metal chalcogenides, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium titanium oxide, and their respective modified compounds. Examples of lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and their respective modified compounds.

[0202] In some embodiments, in order to further improve the energy density of the battery, the positive electrode active material may include a general formula of Li a Ni b Co c M d O e D f One or more lithium transition metal oxides and modified compounds thereof. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M includes one or more of Ge, Mo, Sn, Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and D includes one or more of N, F, S and Cl.

[0203] As an example, the positive electrode active material may include LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 2 Mn 1 / 2 O2、LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333),LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co0.2 Mn 0.2 O2(NCM622),LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.85 Co 0.15 Al 0.05 One or more of O2, LiFePO4, LiMnPO4.

[0204] The modified compounds of the above-mentioned positive electrode active materials may be used to perform doping modification and / or surface coating modification on the positive electrode active materials.

[0205] When the battery cell is a sodium ion battery cell or a sodium metal battery cell, the positive electrode active material may include but is not limited to one or more of sodium transition metal oxides, polyanion materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian blue materials. As an example, the positive electrode active material may include NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, NaNi 1 / 2 Ti 1 / 2 O2、NaNi 1 / 2 Mn 1 / 2 O2、Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2、NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, NaFePO4, NaMnPO4, NaCoPO4, Prussian blue materials, general formula X p M' q (PO4) r O x Y 3-x One or more materials. p M' q (PO4) r O z Y 3-z , 0<p≤4, 0<q≤2, 1≤r≤3, 0≤z≤2, X includes H + 、Li + 、Na + , K + and NH4 + One or more of, M' comprises a transition metal, optionally comprising one or more of V, Ti, Mn, Fe, Co, Ni, Cu and Zn, and Y comprises a halogen atom, optionally comprising one or more of F, Cl and Br.

[0206] The modified compounds of the above-mentioned positive electrode active materials may be used to perform doping modification and / or surface coating modification on the positive electrode active materials.

[0207] When the battery cell is a lithium-sulfur battery or a sodium-sulfur battery, the positive electrode active material may include, but is not limited to, one or more of elemental sulfur, sulfur-carbon composite materials, sulfur-conductive polymer composite materials, and sulfur-metal oxide composite materials.

[0208] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. The present application does not particularly limit the type of the positive electrode conductive agent. As examples, the positive electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0209] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. This application does not particularly limit the type of positive electrode binder. As an example, the positive electrode binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylic resin, and polyethylene oxide.

[0210] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0211] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0212] [Negative electrode]

[0213] The present application has no particular restriction on the type of negative electrode sheet, and a suitable negative electrode sheet can be selected according to the type of battery cell.

[0214] For example, when the battery cell is a lithium-ion battery cell or a sodium-ion battery cell, the negative electrode plate may include 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. For example, the negative electrode current collector has two surfaces that oppose each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposing surfaces of the negative electrode current collector.

[0215] The negative electrode active material may be any negative electrode active material known in the art. As an example, the negative electrode active material may include, but is not limited to, one or more of carbon-based materials, silicon-based materials, tin-based materials, and lithium titanate. Carbon-based materials may include one or more of natural graphite, artificial graphite, soft carbon, hard carbon, pyrolytic carbon, coke, glassy carbon, a sintered product of an organic polymer compound, and mesophase carbon microbeads. Silicon-based materials may include one or more of elemental silicon, silicon oxide, a silicon-carbon complex, a silicon-nitrogen complex, and a silicon alloy. Tin-based materials may include one or more of elemental tin, tin oxide, and a tin alloy.

[0216] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The present application does not particularly limit the type of the negative electrode conductive agent. For example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0217] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. The present application does not particularly limit the type of the negative electrode binder. As examples, the negative electrode binder may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0218] In some embodiments, the negative electrode film layer may further include other additives, such as thickeners, sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

[0219] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0220] The negative electrode film layer is typically formed by coating the negative electrode slurry onto the negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0221] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate of the present application further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode plate of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0222] For example, when the battery cell is a lithium metal battery cell, a sodium metal battery cell, a lithium-sulfur battery cell, a sodium-sulfur battery cell, a lithium-air battery cell, or a sodium-air battery cell, the negative electrode plate may not include a material capable of extracting and inserting active ions, such as graphite. For example, in some embodiments, the negative electrode plate may include a negative electrode current collector and a lithium sheet, a lithium alloy sheet, a sodium sheet, a sodium alloy sheet, or the like disposed on at least one surface of the negative electrode current collector.

[0223] For example, when the battery cell is a lithium metal battery cell or a sodium metal battery cell, the negative electrode plate may include a mesh or foam-like three-dimensional skeleton layer, such as foamed copper (or copper alloy), foamed nickel (or nickel alloy), foamed aluminum (or aluminum alloy), copper (or copper alloy) mesh, nickel (or nickel alloy) mesh, aluminum (or aluminum alloy) mesh, etc. The pore structure of the three-dimensional skeleton layer can serve as a storage space for lithium metal or sodium metal, etc.

[0224] [Electrolytes]

[0225] The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can include one or more selected from solid electrolytes and liquid electrolytes (ie, electrolytes).

[0226] In some embodiments, the electrolyte may be an electrolyte solution, which may include an electrolyte salt and a solvent. The types of the electrolyte salt and the solvent are not particularly limited and may be selected according to actual needs.

[0227] As an example, when the battery cell is a lithium ion battery cell, a lithium metal battery cell, a lithium sulfur battery cell, or a lithium air battery cell, the electrolyte salt may include, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium hexafluoroantimonate (LiSbF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), LiCF3CO2, lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0228] As an example, when the battery cell is a sodium ion battery cell, a sodium metal battery cell, a sodium-sulfur battery cell, or a sodium-air battery cell, the electrolyte salt may include, but is not limited to, one or more of sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium bisfluorosulfonyl imide (NaFSI), sodium bistrifluoromethanesulfonyl imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalatoborate (NaDFOB), sodium dioxalatoborate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorobisoxalatophosphate (NaDFOP), and sodium tetrafluorooxalatophosphate (NaTFOP).

[0229] In some embodiments, the concentration of the electrolyte salt may be 0.3 mol / L or more, and may be 0.7 mol / L or more. The concentration of the electrolyte salt may be 4 mol / L or less, and may be 2.5 mol / L or less.

[0230] The solvent may include one or more of esters (eg, carbonates, phosphates, carboxylates, sulfates, sulfonates, etc.), ethers, fluoroethers, sulfones, nitriles, and the like.

[0231] As an example, the solvent may include, but is not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), 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), methyl ethyl sulfone (EMS), diethyl sulfone (ESE), tetraethylene glycol dimethyl ether (TEGDME), ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL), trimethyl phosphate, and 3-methoxypropionitrile.

[0232] In some embodiments, when the battery cell is a lithium metal battery cell or a sodium metal battery cell, the solvent may include an ether solvent and / or a fluoroether solvent, for example, dimethyl ether tetraglycol (TEGDME), ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL), H(CF2)2OCH3, C4F9OCH3, H(CF2)2OCH2CH3, H(CF2)2OCH2CF3, H(CF2)2CH2O(CF2)2H(TTE), CF3CHFCF2OCH3, CF3CHFCF2OCH2CH3, 2-trifluoromethylhexafluoropropyl methyl ether, 2-trifluoromethylhexafluoropropyl ethyl ether, 2-trifluoromethyl hexafluoropropyl propyl ether, 3-trifluoromethyl octafluorobutyl methyl ether, 3-trifluoromethyl octafluorobutyl ethyl ether, 3-trifluoromethyl octafluorobutyl propyl ether, 4-trifluoromethyl decafluoropentyl methyl ether, 4-trifluoromethyl decafluoropentyl ethyl ether, 4-trifluoromethyl decafluoropentyl propyl ether, 5-trifluoromethyl dodecafluorohexyl methyl ether, 5-trifluoromethyl dodecafluorohexyl ethyl ether, 5-trifluoromethyl dodecafluorohexyl propyl ether, 6-trifluoromethyl tetradecafluoroheptyl methyl ether, 6-trifluoromethyl tetradecafluoroheptyl ethyl ether, 6-trifluoromethyl tetradecafluoroheptyl propyl ether, 7-trifluoromethyl hexafluorooctyl methyl ether, 7-trifluoromethyl hexadecafluorooctyl ethyl ether, and one or more of the group consisting of trifluoromethyl hexafluorooctyl propyl ether and trifluoromethyl hexadecafluorooctyl propyl ether.

[0233] In some embodiments, the electrolyte may further include various additives that can improve battery performance, which is not limited in the embodiments of the present application.

[0234] The present application also provides an electrical device, which includes the battery of the present application. The battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0235] The electrical device can select the type of battery according to its usage requirements, for example, a battery cell, a battery module or a battery pack.

[0236] Figure 9 is a schematic diagram of an exemplary electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of this device, a battery pack or battery module may be used.

[0237] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0238] An Shili

[0239] The following examples describe the present disclosure in more detail. These examples are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing. The instruments used in the examples are commercially available.

[0240] The isolation films of Examples 1-30 were all prepared according to the following method, with the differences shown in Table 1.

[0241] Two polyethylene porous membranes with a thickness of 7 μm were taken as the first porous substrate and the second porous substrate respectively. They were washed with ethanol or acetone, dried at 60-70° C. and flattened, and then plasma treated for 4 minutes for use.

[0242] Commercially available graphene oxide was soaked in anhydrous ethanol for 3 hours, followed by centrifugal purification. The precipitate obtained by centrifugation was soaked in anhydrous ethanol again, and this process was repeated three times. The precipitate obtained by centrifugation was then allowed to stand for 8 hours and air-dried.

[0243] A pore-forming agent PVP and a solvent NMP were added to the obtained graphene oxide and mixed, with the mass of PVP being 1% of the mass of the graphene oxide. After being fully stirred and dispersed, the mixture was allowed to stand for 12 hours to obtain a mixture.

[0244] To the obtained mixture, a binder PVDF was added, with the mass of PVDF being 5% of the mass of graphene oxide, and the mixture was stirred at 1000 rpm for 20 minutes to form a slurry.

[0245] The slurry was coated on one side of the above-mentioned polyethylene porous membrane by wire rod coating to obtain two polyethylene porous membranes with coatings. The coated sides of the two polyethylene porous membranes were overlapped and bonded together by hot pressing. They were then dried in a vacuum oven at 60°C for 8 hours. After that, the isolation membrane was etched with a laser to form through holes in the coating (first functional layer).

[0246] In Examples 1-30, the laser wavelength can be 355-1061 nm, the power can be 3-5 W, the laser spot cutting speed can be 40-60 mm / s, the pulse width of the generator can be 5-15 ps, and the light emission time can be 2-6 ms / via. By adjusting one or more of the above-mentioned laser parameters, the total area and / or depth of the through-holes can be adjusted. The depth of the through-holes is equal to the thickness of the coating to form a through-hole.

[0247] The through-hole patterns formed by laser etching in Examples 1-30 are shown in Table 1. The ratio of the total area of ​​the through-holes to the area of ​​the first functional layer can be obtained by adjusting one or more of the parameters such as the pattern of the through-holes, the arrangement of the through-hole pattern, the diameter of the through-holes, and the through-hole spacing.

[0248] The thickness of the first functional layer of Examples 1-30 can be adjusted by adjusting one or more of the parameters such as the solid content of the slurry, the coating weight, or the number of coating times.

[0249] Comparative Example 1

[0250] The preparation method of the isolation film is similar to that of Example 1, except that the isolation film is not subjected to laser etching.

[0251] Test section

[0252] (1) Thickness test of isolation film

[0253] The test is conducted in accordance with the national standard GB / T 36363-2018. During the test, the number of isolation membrane samples can be more than 6, and 3 points are taken for each isolation membrane sample, and the test results are averaged.

[0254] (2) Tensile strength test of isolation film

[0255] Test the tensile strength of the separator film in the machine direction (MD) and transverse direction (TD) according to GB / T 36363-2018. Cut the separator film into samples with a width of 10 mm and a length of 150 mm for testing. The number of separator film samples can be 12, with the long sides of 6 samples parallel to the longitudinal direction of the separator film and the long sides of 6 samples parallel to the transverse direction. The test results are averaged. The testing instrument can be a universal tensile testing machine. During testing, the tensile rate can be 50 mm / min.

[0256] (3) Isolation membrane air permeability test

[0257] The test is conducted in accordance with the national standard GB / T 36363-2018. Six or more barrier film samples may be used, and the test results are averaged. The testing instrument can be a fully automatic air permeability tester. The time required for 100 mL of air to pass through the sample is used as the barrier film's air permeability. The lower the barrier film's air permeability, the better its air permeability.

[0258] (4) Ionic conductivity test of isolation membrane

[0259] The ionic conductivity of the isolation membrane is obtained by electrochemical impedance spectroscopy. Specifically, the isolation membrane is cut into a disc of a certain area (for example, a diameter of 22 mm), dried, and placed between two stainless steel electrodes. After absorbing a sufficient amount of electrolyte, it is sealed to form a button battery, and an electrochemical impedance spectroscopy experiment is performed using an electrochemical workstation. The electrolyte uses a mixed system of LiFSI, ethylene glycol dimethyl ether (DME) and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (H(CF2)2CH2O(CF2)2H, abbreviated as TTE) with a molar ratio of 1:1.2:3. The resistance Rs of different isolation membrane layers n is measured as the isolation membrane resistance using confined symmetric cell electrochemical impedance spectroscopy. The slope k (corresponding to the resistance of a single-layer isolation membrane) is obtained by plotting Rs and n. The ionic conductivity of the isolation membrane is calculated based on the resistance of the single-layer isolation membrane, the area of ​​the isolation membrane, and the thickness of the isolation membrane (single-layer thickness).

[0260] The electrochemical workstation used was a Shanghai Chenhua CHI 660C electrochemical workstation with an AC signal frequency range of 0.01 Hz to 1 MHz and a sine wave potential amplitude of 5 mV. For accuracy, the average value of six parallel samples was taken as the test result.

[0261] (5) Cyclic performance test

[0262] Lithium iron phosphate, conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were mixed in an appropriate amount of N-methylpyrrolidone (NMP) solvent at a mass ratio of 8:1:1 to form a positive electrode slurry. The slurry was coated onto aluminum foil, the cathode current collector, and dried to form a positive electrode sheet. In an argon-protected glove box, the positive electrode sheet, separator, and lithium sheet were assembled into a CR2430 button cell. The electrolyte salt was LiDFOB at a concentration of 1.2 mol / L, and the solvent was a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a mass ratio of 30:70.

[0263] At 25°C, charge the button cell at a constant current of 0.1C to 3.65V, then charge it at a constant voltage of 3.65V to 0.02C. After allowing the button cell to rest for 10 minutes, discharge it at a constant current of 0.1C to 2.5V. After cycling the button cell twice using the above method, perform the following cycling performance test.

[0264] First, the button cell was charged at a constant current of 0.33C to 3.65V, then charged at a constant voltage of 3.65V to 0.02C, fully charging the cell. The cell was then allowed to rest for 10 minutes before being discharged at a constant current of 0.33C to 2.5V. This constituted one charge-discharge cycle, and the discharge capacity at this point was recorded as the discharge capacity for cycle 1. The cell was then subjected to cyclic charge-discharge testing as described above, with the discharge capacity recorded after each cycle until the discharge capacity decayed to 70% of the discharge capacity for cycle 1. The number of cycles at this point was used to characterize the battery's cycling performance.

[0265] From the test results in Table 1, it can be seen that the isolation membrane provided in the embodiment of the present application can fully utilize the effect of graphene oxide in slowing down dendrite growth and reducing the probability of internal short circuit in the battery, so that the isolation membrane has high mechanical strength, good air permeability and high ion transmission capacity, and thus the battery using the isolation membrane can also have good cycle performance.

[0266] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present application, embodiments having substantially the same structure as the technical idea and exerting the same effects are all included in the technical scope of the present application. In addition, within the scope of the subject matter of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other methods constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A separation film, wherein: The isolation membrane includes a first porous substrate, a second porous substrate, and a first functional layer located between the first porous substrate and the second porous substrate. The first functional layer includes graphene oxide, and the first functional layer has through holes arranged along the thickness direction thereof.

2. The isolation film according to claim 1, wherein: The thickness of the first functional layer is less than or equal to 10 μm, and can be optionally 0.5-5 μm.

3. The isolation film according to claim 1 or 2, wherein: The ratio of the total area of ​​the through holes to the total area of ​​the first functional layer is (0.50-0.85):1, and can be optionally (0.60-0.82):

1.

4. The isolation film according to any one of claims 1 to 3, wherein: The through holes are in a continuous pattern. Optionally, the continuous pattern is a reciprocating bending pattern.

5. The isolation film according to any one of claims 1 to 3, wherein: The number of the through holes is multiple and distributed in a discrete manner. Optionally, the multiple through holes are distributed in a discrete array.

6. The isolation film according to claim 5, wherein: The hole spacing between two adjacent through holes is 0.5-10 μm, and can be 0.7-5 μm; and / or, The equivalent circular diameter of the through hole is 5-25 μm, and can be 8-17 μm; and / or, The through hole pattern includes one or more of a circle, an ellipse, an oblong, a polygon, a sector, a straight line, and a pattern.

7. The isolation film according to any one of claims 1 to 6, wherein: The volume distribution particle size Dv50 of the graphene oxide is 0.01-5 μm, and can be 0.05-3 μm; and / or, The graphene oxide has a lamellar structure; and / or, The thickness of the graphene oxide layer is less than or equal to 4 nm, and can be 1-2 nm.

8. The isolation film according to any one of claims 1 to 7, wherein: The thickness ratio of the first porous substrate to the first functional layer is 1:(0.1-0.9), and can be optionally 1:(0.1-0.5); and / or, The thickness ratio of the second porous substrate to the first functional layer is 1:(0.1-0.9), and can be optionally 1:(0.1-0.5).

9. The isolation film according to any one of claims 1 to 8, wherein: The thickness of the first porous substrate is 2-15 μm, and optionally 3-10 μm; and / or, The thickness of the second porous substrate is 2-15 μm, and optionally 3-10 μm; and / or, The thickness ratio of the first porous substrate to the second porous substrate is (0.8-1.05):(0.8-1.06), and may be (0.9-1.03):(0.9-1.04); and / or, The total thickness of the isolation film is 5-25 μm, and can be 8-18 μm.

10. The isolation film according to any one of claims 1 to 9, wherein: The first functional layer further comprises a non-particulate binder; Optionally, the non-granular binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinyl alcohol, polyacrylic acid, polyurethane, carboxymethyl cellulose, and styrene-butadiene rubber emulsion; Optionally, the content of the non-particulate binder in the first functional layer is 2%-15%, more preferably 3%-10%, based on the total weight of the first functional layer.

11. The isolation film according to any one of claims 1 to 10, wherein: The first functional layer further includes first inorganic particles; Optionally, the first inorganic particles include one or more of inorganic particles having the ability to transport active ions and inorganic particles having a dielectric constant of 5 or more; Optionally, the volume distribution particle size Dv50 of the first inorganic particles is 0.2-5 μm, more preferably 1-3 μm; Optionally, the content of the first inorganic particles in the first functional layer is 2%-15%, more preferably 5%-10%, based on the total weight of the first functional layer.

12. The isolation film according to any one of claims 1 to 11, wherein: The through hole is obtained by one or more of a phase separation process, a photolithography process, and a plasma etching process.

13. The isolation film according to any one of claims 1 to 12, wherein: The through hole is obtained by laser etching process; Optionally, the laser wavelength is 100-2000nm, more preferably 300-1500nm; and / or, Optionally, the power of the laser is 1-15W, more preferably 2-10W; and / or, Optionally, the cutting speed of the laser spot is 20-70 mm / s, more preferably 40-60 mm / s; and / or, Optionally, the pulse width of the laser generator is 2-20 ps, ​​more preferably 5-15 ps; and / or, Optionally, the laser emission time is 2-6ms / via.

14. The isolation film according to any one of claims 1 to 13, wherein: The first porous substrate comprises one or more of polyolefins, halogenated polyolefins, polyamides, polyesters, and their respective derivatives; and / or, The second porous substrate includes one or more of polyolefins, halogenated polyolefins, polyamides, polyesters, and derivatives thereof.

15. The isolation film according to any one of claims 1 to 14, wherein: The isolation film further comprises a second functional layer located on the surface of the first porous substrate and / or the second porous substrate away from the first functional layer, wherein the second functional layer comprises one or more of second inorganic particles and organic particles; Optionally, the second inorganic particles include one or more of inorganic particles having the ability to transport active ions and inorganic particles having a dielectric constant of 5 or more; and / or, Optionally, the organic particles include one or more of polyvinylidene fluoride particles, polytetrafluoroethylene particles, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer particles, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer particles, and tetrafluoroethylene-hexafluoropropylene copolymer particles.

16. The isolation film according to any one of claims 1 to 15, wherein: The isolation film satisfies at least one of the following conditions (1) to (6): (1) The ionic conductivity of the isolation membrane at 25°C is 0.8-2.8 mS·cm -1 , optional 1.0-2.5mS·cm -1 ; (2) The air permeability of the isolation film is 100-400s / 100ml, and can be 120-200s / 100ml; (3) The transverse tensile strength of the isolation film is greater than or equal to 1000 kgf / cm 2 , optional 1100-1600kgf / cm 2 ; (4) The longitudinal tensile strength of the isolation film is greater than or equal to 900 kgf / cm 2 , optional 1000-1600kgf / cm 2 ; (5) The puncture strength of the isolation film is 9.0-15N·μm -1 , optional 9.5-12N·μm -1 ; (6) The porosity of the isolation membrane is 40%-80%, and can be optionally 45%-76%.

17. A battery cell comprising the separator according to any one of claims 1 to 16.

18. The battery cell according to claim 17, wherein: The battery cell includes at least one of a lithium ion battery cell, a sodium ion battery cell, a lithium metal battery cell, a sodium metal battery cell, a lithium sulfur battery cell, a sodium sulfur battery cell, a lithium air battery cell, and a sodium air battery cell.

19. A battery comprising the battery cell according to claim 17 or 18 and a box for accommodating the battery cell.

20. An electrical device comprising the battery according to claim 19.

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