Separator, battery cell, battery, and electric device

Abstract

A separator, a battery cell, a battery, and an electric device. The separator comprises a porous base material. The porous base material satisfies at least one of the following conditions (1) to (3): (1) when t is 300 seconds, the compressive creep compliance of the porous base material is 0.05 MPa-1 to 0.24 MPa-1; (2) when t is 1,800 seconds, the compressive creep compliance of the porous base material is 0.12 MPa-1 to 0.36 MPa-1; and (3) when t is 3,600 seconds, the compressive creep compliance of the porous base material is 0.23 MPa-1 to 0.52 MPa-1. The provided separator enables a battery to have good cycle performance and rate performance.

Description

Separator, battery cell, battery and electrical device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application 202311450894.X, filed on November 2, 2023, entitled “Separation membrane, battery cell, battery and electrical device,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to an isolation film, a battery cell, a battery and an electrical device. Background Art

[0004] Compared to ion-type batteries, metal batteries can have higher energy density. However, unlike the negative electrodes of ion-type batteries, metal battery negative electrodes are subject to unlimited volume expansion. As metal batteries cycle, the separator and positive electrode are squeezed by the expanding negative electrode, causing uneven stress within the battery. This can easily lead to bending, damage, and fracture of the electrode sheets, as well as reduced electrolyte wettability, thereby affecting battery performance. The above statements are intended only to provide background information related to this application and do not necessarily constitute prior art.

[0005] Summary of the Invention

[0006] The present application provides a separator, a battery cell, a battery and an electrical device, which can enable the battery to have good cycle performance and rate performance.

[0007] In a first aspect, the present application provides an isolation membrane comprising a porous substrate, wherein the porous substrate satisfies at least one of the following conditions (1) to (3): (1) when t is 300 seconds, the compressive creep compliance of the porous substrate is 0.05 MPa -1 -0.24MPa -1 , (2) When t is 1800 seconds, the compressive creep compliance of the porous substrate is 0.12 MPa - 1 -0.36MPa -1 , (3) When t is 3600 seconds, the compressive creep compliance of the porous substrate is 0.23 MPa -1 -0.52MPa -1 .

[0008] The compressive creep compliance of the porous substrate refers to the reciprocal of the compressive creep elastic modulus tested in accordance with GB / T41061-2021 under the conditions of a temperature of 25°C, a humidity of 10%, and a stress of 1 MPa applied to the porous substrate along its thickness direction, in MPa. -1The value obtained by dividing the creep amount in time t seconds by the stress is in units of t seconds.

[0009] The porous substrate provided in the embodiment of the present application that satisfies at least one of the above conditions (1) to (3) is actually applied to metal batteries. During charging, the porosity of the porous substrate decreases and the thickness becomes thinner under the expansion force of the large amount of metal deposited on the negative electrode side, but it does not affect ion transmission and electrolyte infiltration. At the same time, it can provide sufficient compressible space to reduce the probability of bending, breaking, and fracture of the electrode sheet, thereby facilitating the structural integrity of the electrode assembly. During battery discharge, the metal deposited on the negative electrode side dissolves, the pressure on the porous substrate disappears, and the porosity and thickness of the porous substrate can be restored. Therefore, a metal battery using a separator containing a porous substrate that satisfies the above condition (1) has good cycle performance and rate performance when charged and discharged for 5 minutes, a metal battery using a separator containing a porous substrate that satisfies the above condition (2) has good cycle performance and rate performance when charged and discharged for 30 minutes, and a metal battery using a separator containing a porous substrate that satisfies the above condition (3) has good cycle performance and rate performance when charged and discharged for 1 hour.

[0010] In some embodiments, the porous substrate satisfies all of the following conditions (1) to (3): (1) When t is 300 seconds, the compressive creep compliance of the porous substrate is 0.05 MPa -1 -0.24MPa -1 , (2) When t is 1800 seconds, the compressive creep compliance of the porous substrate is 0.12 MPa -1 -0.36MPa -1 , (3) When t is 3600 seconds, the compressive creep compliance of the porous substrate is 0.23 MPa -1 -0.52MPa -1 .

[0011] The compressive creep compliance generally increases with time t. Therefore, for a metal battery using an isolation membrane comprising a porous substrate that satisfies all of the above conditions (1) to (3), it has good cycle performance and rate performance when charged and discharged for 5 minutes to 1 hour.

[0012] In some embodiments, the porosity of the porous substrate is greater than or equal to 65%, and the thickness of the porous substrate is greater than or equal to 20 μm; optionally, the porosity of the porous substrate is 65%-95%, and the thickness of the porous substrate is 30 μm-70 μm; more optionally, the porosity of the porous substrate is 70%-85%, and the thickness of the porous substrate is 36 μm-50 μm.

[0013] By adjusting the thickness and porosity of the porous substrate within the above ranges, sufficient compressible space can be provided during charging of the metal battery, while maintaining a high porosity in the compressed separator. This does not affect ion transport and electrolyte infiltration, thereby enabling the battery to have good cycle performance and rate capability. Furthermore, the battery can also have a high volumetric energy density.

[0014] In some embodiments, the average pore size of the porous substrate is 10 nm to 200 nm, optionally 20 nm to 60 nm.

[0015] By adjusting the average pore size of the porous substrate within the above range, the compressed isolation membrane can still have a high porosity when the metal battery is charged, thereby not affecting ion transport and electrolyte infiltration, and thus enabling the battery to have good cycle performance and rate performance.

[0016] In some embodiments, the total pore volume of pores with a pore diameter of less than 70 nm in the porous substrate accounts for more than 90% of the total pore volume of the porous substrate, and the total pore volume of pores with a pore diameter of less than 30 nm in the porous substrate accounts for more than 50% of the total pore volume of the porous substrate.

[0017] By adjusting the pore size distribution of the porous substrate within the above range, the compressed isolation membrane can still have a high porosity when the metal battery is charged, thereby not affecting ion transport and electrolyte infiltration, and thus enabling the battery to have good cycle performance and rate performance.

[0018] In some embodiments, the porous substrate has an air permeability of 50 s / 100 mL to 300 s / 100 mL, and optionally 60 s / 100 mL to 150 s / 100 mL.

[0019] In some embodiments, the BET specific surface area of ​​the porous substrate is 30 m 2 / g-300m 2 / g, optional 50m 2 / g-200m 2 / g.

[0020] In some embodiments, the porous substrate comprises one or more of polyolefin, polyamide, polyester, polyacrylonitrile, and their respective derivatives, and may optionally comprise one or more of polyolefin and its derivatives.

[0021] In some embodiments, the porous substrate has a weight average molecular weight of 800,000 to 1.2 million, optionally 800,000 to 1.15 million.

[0022] In some embodiments, the tensile strength of the porous substrate in the TD direction is greater than or equal to 2000 kg / cm 2 .

[0023] In some embodiments, the tensile strength of the porous substrate in the MD direction is greater than or equal to 1500 kg / cm 2 .

[0024] In some embodiments, the elongation at break of the porous substrate in the TD direction is greater than or equal to 60%.

[0025] In some embodiments, the elongation at break of the porous substrate in the MD direction is greater than or equal to 60%.

[0026] In some embodiments, the porous substrate has a puncture strength greater than or equal to 200 gf.

[0027] In some embodiments, the thermal shrinkage rate of the porous substrate in the TD direction at 105° C. for 1 hour is less than or equal to 10%.

[0028] In some embodiments, the thermal shrinkage of the porous substrate in the MD direction at 105° C. for 1 hour is less than or equal to 4%.

[0029] In some embodiments, the isolation membrane further comprises a coating located on at least one surface of the porous substrate, wherein the coating comprises at least one of an organic coating, an inorganic coating, and an organic-inorganic composite coating.

[0030] By providing a coating on at least one surface of the porous substrate, the overall mechanical strength of the isolation membrane can be enhanced, the isolation membrane's resistance to dendrite puncture can be improved, the heat resistance of the isolation membrane can be enhanced, the degree of thermal shrinkage of the isolation membrane can be reduced, the compatibility of the isolation membrane with the electrolyte can be improved, the isolation membrane's wetting properties for the electrolyte can be improved, and the ion transfer impedance of the isolation membrane can be reduced, which is beneficial to further improve the reliability, cycle performance and rate performance of the battery.

[0031] In some embodiments, the coating comprises dendrite-reactive particles and a binder. Optionally, the dendrite-reactive particles comprise one or more of lithium-reactive particles and sodium-reactive particles.

[0032] When the coating includes dendrite-reactive particles, the coating can play a role in dissolving dendrites growing on the negative electrode side, thereby further reducing the probability of dendrites piercing the isolation membrane and causing internal short circuit of the battery, which is beneficial to further improve the reliability of the battery.

[0033] In some embodiments, the volume distribution particle size Dv50 of the dendrite reactive particles is 0.01 μm-10 μm, and can be optionally 0.05 μm-0.5 μm.

[0034] The volume distribution particle size Dv50 of the dendrite reaction particles is within the above range, which can make the coating slurry have a suitable viscosity, facilitate coating, and help improve the uniformity of the coating and reduce the "powder falling" phenomenon; in addition, it can also reduce the pore blocking problem, thereby improving the permeability and ion transmission characteristics of the isolation membrane, which is beneficial to improving the cycle performance and rate performance of the battery.

[0035] In some embodiments, the mass ratio of the dendrite reactive particles to the binder is 1:(0.005-0.05), and can be optionally 1:(0.01-0.03).

[0036] In some embodiments, the dendrite reaction type particles include one or more of solid electrolyte materials, metal oxides, non-metal oxides, metal sulfides, non-metal sulfides, metal nitrides, non-metal nitrides, and carbon-based materials; and / or, the binder includes one or more of vinyl fluoride-based polymers and styrene-butadiene rubber.

[0037] In some embodiments, the coating has a thickness of 1 μm-10 μm, optionally 1.5 μm-4.5 μm.

[0038] The thickness of the coating is within the above range, which can improve the isolation membrane's resistance to dendrite penetration, heat resistance and electrolyte wettability, thereby helping to improve the reliability of the battery; it can also make the isolation membrane have lower internal resistance and good ion transport properties, thereby helping the battery to have good cycle performance and / or rate performance.

[0039] In a second aspect, the present application provides a battery cell comprising the isolation membrane according to the first aspect of the present application.

[0040] Optionally, the battery cell includes at least one of a lithium metal battery cell, a negative electrode-free lithium metal battery cell, a sodium metal battery cell, and a negative electrode-free sodium metal battery cell.

[0041] In a third aspect, the present application provides a battery comprising the battery cell according to the second aspect of the present application.

[0042] In a fourth aspect, the present application provides an electrical device comprising the battery according to the third aspect of the present application, wherein the battery is used to provide electrical energy.

[0043] 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

[0044] 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.

[0045] FIG1 is a schematic diagram of a battery cell provided by some embodiments of the present application.

[0046] FIG2 shows an exploded schematic diagram of a battery cell provided in some embodiments of the present application.

[0047] FIG3 shows a schematic diagram of a battery module provided in some embodiments of the present application.

[0048] FIG4 shows a schematic diagram of a battery pack provided in some embodiments of the present application.

[0049] FIG5 is an exploded schematic diagram of the battery pack shown in FIG4 .

[0050] FIG6 shows a schematic diagram of an electrical device provided in some embodiments of the present application.

[0051] In the accompanying drawings, which are not necessarily drawn to scale, reference numerals are as follows: 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 battery, 51 housing, 52 electrode assembly, 53 cover plate. DETAILED DESCRIPTION

[0052] 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.

[0053] " 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.

[0054] 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.

[0055] 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.

[0056] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0057] In this application, the terms "plurality" and "multiple" refer to two or more.

[0058] In the description of the embodiments of the present application, unless otherwise specified, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," and "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is at a higher level than the second feature. A first feature being "below," "below," and "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0059] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0060] Unless otherwise stated, the numerical values ​​of the various 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 given in the examples of this application. Unless otherwise stated, the test temperature of each parameter is 25°C.

[0061] Unless otherwise specified, the test instruments mentioned in this application can be operated in accordance with the requirements of the product specifications.

[0062] The battery mentioned in the embodiments of the present application may be a single physical module including 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.

[0063] A battery cell is the smallest unit of a battery, independently capable of charging and discharging. A battery cell can be cylindrical, rectangular, or have other shapes, though this is not a limitation in the present invention. Figure 1 shows a battery cell 5 with a rectangular structure as an example.

[0064] When there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in mixed series via a busbar. In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery may be a battery pack, which includes a housing and battery cells, with the battery cells or battery modules housed in the housing. In some embodiments, the housing may serve as part of the vehicle's chassis structure. For example, a portion of the housing may form at least a portion of the vehicle's floor, or a portion of the housing may form at least a portion of the vehicle's crossbeam or longitudinal beam.

[0065] In some embodiments, the battery may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0066] A battery cell generally 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 present embodiment.

[0067] The battery cell may also include an outer packaging, which can be used to encapsulate the electrode assembly and electrolyte. The outer packaging can be a hard shell, such as a hard plastic shell, aluminum shell, steel shell, etc. The outer packaging can also be a soft package, such as a bag-type soft package. The soft package can be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0068] In some embodiments, as shown in Figure 2, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, which 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 the battery cell 5 can be one or more, and can be adjusted according to needs.

[0069] In some embodiments, battery cells can be assembled into a battery module. The number of battery cells contained in a battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. Figure 3 is a schematic diagram of a battery module 4 as an example. As shown in Figure 3, in the battery module 4, multiple battery cells 5 can be arranged in sequence 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 by fasteners.

[0070] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0071] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0072] Figures 4 and 5 are schematic diagrams of an exemplary battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a housing and multiple battery modules 4 disposed within the housing. The housing comprises an upper housing 2 and a lower housing 3. The upper housing 2 covers the lower housing 3 and forms an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 may be arranged in any manner within the housing.

[0073] The battery cells provided in the embodiments of the present application may be metal battery cells, for example, they may include lithium metal battery cells, negative electrode-free lithium metal battery cells, sodium metal battery cells, negative electrode-free sodium metal battery cells, etc.

[0074] A negative electrode-free battery cell generally refers to a battery cell constructed without the active negative electrode layer being applied during the manufacturing process. For example, a negative electrode active material layer is not applied to the negative electrode through coating or deposition, or a carbonaceous active material layer is used to form the negative electrode active material layer. During initial charging, ions on the negative electrode side gain electrons and deposit on the surface of the negative electrode current collector to form metal. During discharge, the metal can be converted back to ions and returned to the positive electrode, enabling cyclic charge and discharge. Compared to other battery cells, negative electrode-free battery cells can achieve higher energy density due to the lack of a negative electrode active material layer. In some embodiments, to improve battery cell performance, the negative electrode side of the negative electrode-free battery cell may also be provided with some conventional negative electrode active materials, such as carbon materials. Although these materials have a certain capacity, their content is relatively low and they are not used as the primary negative electrode active material in the battery cell. Therefore, the battery cell constructed in this manner can still be considered a negative electrode-free battery cell. The CB (Cell Balance) value of a battery cell without a negative electrode is typically very small. For example, in some embodiments, the CB value of a battery cell without a negative electrode can be less than or equal to 0.1. The CB value is the unit area capacity of the negative electrode in the battery cell divided by the unit area capacity of the positive electrode. Because a battery cell without a negative electrode contains no or only a small amount of negative electrode active material, the unit area capacity of the negative electrode is relatively small, and thus the CB value is very small, for example, typically less than or equal to 0.1.

[0075] An embodiment of the present application provides an isolation membrane, which is used in metal batteries, such as lithium metal batteries, negative electrode-free lithium metal batteries, sodium metal batteries, negative electrode-free sodium metal batteries, etc., and can enable the battery to have good cycle performance and rate performance.

[0076] The isolation membrane provided in the embodiment of the present application includes a porous substrate, and the porous substrate satisfies at least one of the following conditions (1) to (3): (1) when t is 300 seconds, the compressive creep compliance of the porous substrate is 0.05 MPa -1 -0.24MPa -1 , (2) When t is 1800 seconds, the compressive creep compliance of the porous substrate is 0.12 MPa -1 -0.36MPa -1 , (3) When t is 3600 seconds, the compressive creep compliance of the porous substrate is 0.23 MPa -1 -0.52MPa -1 .

[0077] The compressive creep compliance of a porous substrate is the reciprocal of the compressive creep elastic modulus measured in MPa at a temperature of 25°C and a humidity of 10% with a stress of 1 MPa applied to the porous substrate along its thickness direction according to GB / T 41061-2021. -1The value obtained by dividing the creep amount in time t seconds by the stress is in units of t seconds.

[0078] The testing instrument may be a Kappa SS-CF creep testing machine. The temperature during the test is 25°C and the pressure is kept constant.

[0079] As a key component of a battery, the performance of the separator is crucial. Located between the positive and negative electrodes, the separator primarily prevents short circuits. Currently, the separators commonly used in the battery field are relatively thin, typically less than 20 μm thick, which generally meets performance requirements in lithium-ion battery systems. However, in metal battery systems, due to the unlimited volume expansion of the negative electrode, as the metal battery cycles through charge and discharge, the separator and positive electrode are squeezed by the expanding negative electrode, resulting in uneven stress within the battery. This can easily lead to bending, damage, and breakage of the electrode sheets. This can also deteriorate the electrolyte wettability of the electrode assembly, impacting the battery's cycle and rate performance. Furthermore, a broken electrode sheet can puncture the separator, causing an internal short circuit.

[0080] Taking into account the limited compressible space of the positive and negative pole pieces, this application starts from the perspective of the isolation membrane and applies an isolation membrane including a porous substrate with a specific compressive creep compliance to the metal battery system, so that the battery can have good cycle performance and rate performance.

[0081] When a metal battery is charged, a large amount of metal (such as lithium, sodium, etc.) will be deposited on the negative electrode side and a large expansion force will be generated on the isolation membrane. The expansion force is usually around 0.5MPa-3MPa. That is, the compressive creep compliance of the porous substrate of the present application is the following indicator: when the isolation membrane containing the porous substrate is actually applied to a metal battery, the compressibility of the porous substrate is applied when a stress equal to the expansion force applied to the isolation membrane is applied.

[0082] Furthermore, when t is 300 seconds, it corresponds to a case where the metal battery containing the porous substrate is charged and discharged for 5 minutes. Similarly, when t is 1800 seconds and 3600 seconds, it corresponds to a case where the metal battery containing the porous substrate is charged and discharged for 30 minutes and 1 hour, respectively.

[0083] When the compressive creep compliance of the porous substrate is less than the lower limit of the range provided above, when the isolation membrane containing the porous substrate is actually applied to a metal battery, the isolation membrane cannot provide sufficient compressible space, and the electrode pieces are still prone to bending, breaking, and fracture during battery charging and discharging, thereby resulting in a higher risk of internal short circuit in the battery; at the same time, the electrolyte wettability of the electrode assembly deteriorates, which will also affect the cycle performance and rate performance of the battery.

[0084] On the other hand, when the compressive creep compliance of the porous substrate is greater than the upper limit of the range provided above, when the isolation membrane containing the porous substrate is actually applied to a metal battery, due to the excessive compressibility of the porous substrate, the porous substrate is easily squeezed under the expansion force of a large amount of metal deposited on the negative electrode side, resulting in excessive reduction in porosity, which in turn leads to poor electrolyte wettability of the isolation membrane and increased internal resistance of the battery, thereby affecting the cycle performance and rate performance of the battery; in addition, the difficulty of the preparation process of the porous substrate itself will also increase, and it is easy to cause warping, dislocation and other problems during the metal battery assembly process, resulting in increased difficulty in metal battery assembly and increased difficulty in industrial implementation.

[0085] Therefore, the porous substrate provided in the embodiment of the present application that satisfies at least one of the above conditions (1) to (3) is actually applied to metal batteries. During charging, the porosity of the porous substrate decreases and the thickness becomes thinner under the expansion force of the large amount of metal deposited on the negative electrode side, but it does not affect ion transmission and electrolyte infiltration. At the same time, it can provide sufficient compressible space to reduce the probability of bending, breaking, and other problems of the electrode sheet, thereby facilitating the structural integrity of the electrode assembly. During battery discharge, the metal deposited on the negative electrode side dissolves, the pressure on the porous substrate disappears, and the porosity and thickness of the porous substrate can be restored. Therefore, a metal battery using a separator containing a porous substrate that satisfies the above condition (1) has good cycle performance and rate performance when charged and discharged for 5 minutes, a metal battery using a separator containing a porous substrate that satisfies the above condition (2) has good cycle performance and rate performance when charged and discharged for 30 minutes, and a metal battery using a separator containing a porous substrate that satisfies the above condition (3) has good cycle performance and rate performance when charged and discharged for 1 hour.

[0086] Optionally, the porous substrate satisfies all of the following conditions (1) to (3): (1) When t is 300 seconds, the compressive creep compliance of the porous substrate is 0.05 MPa -1 -0.24MPa -1 , (2) When t is 1800 seconds, the compressive creep compliance of the porous substrate is 0.12 MPa -1 -0.36MPa -1 , (3) When t is 3600 seconds, the compressive creep compliance of the porous substrate is 0.23 MPa -1 -0.52MPa -1 .

[0087] The compressive creep compliance generally increases with time t. Therefore, for a metal battery using an isolation membrane comprising a porous substrate that satisfies all of the above conditions (1) to (3), it has good cycle performance and rate performance when charged and discharged for 5 minutes to 1 hour.

[0088] As a method of controlling the compressive creep compliance of the porous substrate, parameters such as the porosity, average pore size, pore size distribution, and thickness of the porous substrate may be adjusted.

[0089] In some embodiments, the porosity of the porous substrate may be greater than or equal to 65%, and the thickness of the porous substrate may be greater than or equal to 20 μm.

[0090] Optionally, the porosity of the porous substrate may be 65% to 95%, and the thickness of the porous substrate may be 30 μm to 70 μm.

[0091] More optionally, the porosity of the porous substrate may be 70% to 85%, and the thickness of the porous substrate may be 36 μm to 50 μm.

[0092] By adjusting the thickness and porosity of the porous substrate within the above ranges, sufficient compressible space can be provided during charging of the metal battery, while maintaining a high porosity in the compressed separator. This does not affect ion transport and electrolyte infiltration, thereby enabling the battery to have good cycle performance and rate capability. Furthermore, the battery can also have a high volumetric energy density.

[0093] The thickness of the porous substrate has a well-known meaning in the art and can be measured using methods known in the art, for example, referring to GB / T 6672-2001, Plastics film and sheeting - Determination of thickness - Mechanical measurement method.

[0094] The porosity of a porous substrate has a well-known meaning in the art and can be measured using methods known in the art. For example, the porosity can be measured with reference to GB / T 21650.2-2008, Determination of Pore Size Distribution and Porosity of Solid Materials by Mercury Intrusion Porosimetry and Gas Adsorption Methods - Part 2: Analysis of Mesopores and Macropores by Gas Adsorption Method.

[0095] In some embodiments, the average pore size of the porous substrate may be 10 nm to 200 nm, optionally 20 nm to 60 nm.

[0096] By adjusting the average pore size of the porous substrate within the above range, the compressed isolation membrane can still have a high porosity when the metal battery is charged, thereby not affecting ion transport and electrolyte infiltration, and thus enabling the battery to have good cycle performance and rate performance.

[0097] In some embodiments, the total pore volume of pores with a pore diameter of less than 70 nm in the porous substrate may account for more than 90% of the total pore volume of the porous substrate, and the total pore volume of pores with a pore diameter of less than 30 nm in the porous substrate may account for more than 50% of the total pore volume of the porous substrate.

[0098] By adjusting the pore size distribution of the porous substrate within the above range, the compressed isolation membrane can still have a high porosity when the metal battery is charged, thereby not affecting ion transport and electrolyte infiltration, and thus enabling the battery to have good cycle performance and rate performance.

[0099] The average pore size and pore size distribution of a porous substrate have meanings well known in the art and can be measured using methods known in the art. For example, the pore size can be measured using ASTM F316-03 (2019), Standard Test Method for Pore Size Characterization of Membrane Filters by Bubble Point and Mean Flow Pore Size Tests, and ASTM E1294-89 (1999).

[0100] In some embodiments, the porous substrate may have an air permeability of 50 s / 100 mL to 300 s / 100 mL, and optionally 60 s / 100 mL to 150 s / 100 mL.

[0101] The air permeability of a porous substrate has a well-known meaning in the art and can be measured using methods known in the art. For example, the following method can be used to measure the time required for 100 mL of air to pass through the porous substrate at 25°C. The test instrument can be a Kumagai KRK Wangken Air Permeability Tester.

[0102] In some embodiments, the BET specific surface area of ​​the porous substrate may be 30 m 2 / g-300m 2 / g, optional 50m 2 / g-200m 2 / g.

[0103] The BET specific surface area of ​​a porous substrate has a well-known meaning in the art and can be measured using methods known in the art. For example, it can be measured using the nitrogen adsorption specific surface area analysis method in accordance with GB / T 19587-2017 and calculated using the BET (Brunauer Emmett Teller) method. The test instrument can be a Micromeritics Tri-Star 3020 specific surface area pore size analyzer.

[0104] In some embodiments, the porous substrate may be made of one or more of polyolefins, polyamides, polyesters, polyacrylonitrile (PAN), and their derivatives. Derivatives generally refer to products derived from the substitution of hydrogen atoms or atomic groups in a polymer with other atoms or atomic groups.

[0105] Optionally, the polyester includes, but is not limited to, one or more of polyethylene terephthalate and polybutylene terephthalate.

[0106] Alternatively, the porous substrate may include one or more polyolefins and their derivatives. Alternatively, the monomers forming the polyolefin may include one or more of ethylene, propylene, tetrafluoroethylene, vinylidene fluoride, vinyl chloride, 1-butene, 4-methyl-1-pentene, and 1-hexene. Alternatively, the porous substrate may include polyethylene and its derivatives.

[0107] In some embodiments, the weight average molecular weight of the porous substrate may be 800,000-1.2 million, and optionally 800,000-1.15 million.

[0108] In some embodiments, the porous substrate may be a single-layer membrane structure or a multi-layer membrane structure.

[0109] In some embodiments, the tensile strength of the porous substrate in the TD direction may be greater than or equal to 2000 kg / cm 2 .

[0110] In some embodiments, the tensile strength of the porous substrate in the MD direction can be greater than or equal to 1500 kg / cm 2 .

[0111] The tensile strength of a porous substrate 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 rate can be 50 mm / min. A universal tensile testing machine can be used as the testing instrument.

[0112] In some embodiments, the elongation at break of the porous substrate in the TD direction may be greater than or equal to 60%.

[0113] In some embodiments, the elongation at break of the porous substrate in the MD direction may be greater than or equal to 60%.

[0114] The elongation at break of a porous substrate has a meaning well known 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. During the test, the tensile rate can be 50 mm / min. The testing instrument can be a universal tensile testing machine.

[0115] In some embodiments, the porous substrate may have a puncture strength of 200 gf or greater.

[0116] The puncture strength of a porous substrate has a meaning well known in the art and can be measured using methods known in the art. For example, the test can be performed with reference to standard GB / T 36363-2018. For example, the porous substrate can be cut into samples with a width of 10 mm and a length of 150 mm, clamped with a fixture, and punctured with a steel needle at a rate of 50 mm / min (the puncture position can be near the geometric center of the sample), and the maximum load when the steel needle penetrates the porous substrate is read. The diameter of the steel needle can be 1 mm, the radius of the spherical top can be 0.5 mm, and the surface of the steel needle is smooth, free of rust, oxide layer and oil stains.

[0117] In some embodiments, the thermal shrinkage of the porous substrate in the TD direction at 105° C. for 1 hour may be less than or equal to 10%.

[0118] In some embodiments, the thermal shrinkage of the porous substrate in the MD direction at 105° C. for 1 hour may be less than or equal to 4%.

[0119] The thermal shrinkage of a porous substrate has a meaning well known in the art and can be measured using methods known in the art. For example, the test can be performed with reference to standard GB / T 36363-2018. During the test, the porous substrate can be punched into a sample with a width of 50 mm and a length of 100 mm using a punch press, placed on an A4 paper and fixed, and then the A4 paper with the sample is placed on a corrugated paper with a thickness of 1 mm to 5 mm; the temperature of the blast oven is set to 105°C, and after the temperature reaches the set temperature and stabilizes for 30 minutes, the A4 paper placed on the corrugated paper is placed and the timing is started. After the set time (1 hour in this application) is reached, the width a1 and length a2 of the porous substrate are measured. The transverse direction (TD) thermal shrinkage of the porous substrate at 105°C and 1 hour = [(50-a1) / 50]×100%, and the longitudinal direction (MD) thermal shrinkage of the porous substrate at 105°C and 1 hour = [(100-a2) / 100]×100%.

[0120] In some embodiments, the isolation membrane may further include a coating on at least one surface of the porous substrate. The coating may include at least one of an organic coating, an inorganic coating, and an organic-inorganic composite coating. The coating may include at least one of organic particles and inorganic particles.

[0121] Unlike the negative electrodes of ion-type batteries, metal battery negative electrodes also face a more serious dendrite problem. Porous substrates with high porosity may result in weaker resistance to dendrite penetration. Therefore, by providing a coating on at least one surface of the porous substrate, the overall mechanical strength of the separator can be enhanced, improving the separator's resistance to dendrite penetration and further improving battery reliability.

[0122] A porous substrate with a high porosity may also lead to a relatively high degree of thermal shrinkage. Therefore, by providing a coating on at least one surface of the porous substrate, the heat resistance of the separator can be enhanced, the thermal shrinkage degree of the separator can be reduced, and thus it is beneficial to further improve the reliability of the battery.

[0123] The porous substrate has strong hydrophobicity, while the electrolyte usually uses polar solvents, which will reduce the electrolyte wettability of the porous substrate and increase the ion transport impedance of the porous substrate. By providing a coating on at least one surface of the porous substrate, the compatibility between the separator and the electrolyte can also be improved, the wetting characteristics of the separator to the electrolyte can be improved, and the ion transport impedance of the separator can be reduced, and thus it is beneficial to further improve the cycle performance and rate performance of the battery.

[0124] In some embodiments, the coating may include dendrite reaction-type particles. When the coating includes dendrite reaction-type particles, the coating can play a role in eliminating the dendrites growing on the negative electrode side, and thus the probability of the dendrites piercing the separator and causing an internal short circuit of the battery can be further reduced, and thus it is beneficial to further improve the reliability of the battery.

[0125] In some embodiments, the dendrite reaction-type particles may include one or more of lithium reaction-type particles and sodium reaction-type particles.

[0126] In some embodiments, the dendrite reaction-type particles may include, but are not limited to, one or more of solid electrolyte materials, metal oxides, non-metal oxides, metal sulfides, non-metal sulfides, metal nitrides, non-metal nitrides, and carbon-based materials.

[0127] As an example, the dendrite reaction-type particles may include, but are not limited to, lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, LATP, 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum zirconium phosphate (Li x Al y Zr z (PO4)3, LAZP, 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium aluminum chromium phosphate (Li x Al y Cr z (PO4)3, LACP, 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), lithium lanthanum zirconium oxide (Li7La3Zr2O 12, LLZO), lithium thallium oxide (Li5La3Ta2O 12 , LLTA), lithium zinc germanium oxide (Li 14 ZnGe4O 16 ), lithium germanium phosphosulfide (Li 10 GeP2S 12 , LGPS), lithium tetrathiophosphate Li3PS4, Li6PS5Cl, Li6PS5Br, Li6PS5I, silicon oxide, silicon nitride, iron oxide, iron nitride, ferrite, tin oxide, titanium oxide, titanium nitride, copper oxide, copper nitride, manganese oxide, germanium oxide, ZrO2, ZnO, AlN, graphene oxide, and one or more of carbon fluoride.

[0128] In some embodiments, the volume distribution particle size Dv50 of the dendrite reactive particles may be 0.01 μm-10 μm, and optionally 0.05 μm-0.5 μm.

[0129] The volume distribution particle size Dv50 of the dendrite reaction particles is within the above range, which can make the coating slurry have a suitable viscosity, facilitate coating, and help improve the uniformity of the coating and reduce the "powder falling" phenomenon; in addition, it can also reduce the pore blocking problem, thereby improving the permeability and ion transmission characteristics of the isolation membrane, which is beneficial to improving the cycle performance and rate performance of the battery.

[0130] The Dv50 of a material is generally known in the art and can be measured using instruments and methods known in the art. For example, it can be conveniently measured using a laser particle size analyzer (such as the Malvern Mastersizer 3000) in accordance with GB / T 19077-2016. The physical definition of Dv50 is the particle size at which the cumulative volume distribution percentage of a material reaches 50%.

[0131] In some embodiments, the coating may include a binder.

[0132] In some embodiments, the binder may include one or more of a vinylidene fluoride polymer and styrene-butadiene rubber. The vinylidene fluoride polymer may include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, and a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer.

[0133] In some embodiments, the mass ratio of the dendrite reactive particles to the binder may be 1:(0.005-0.05), and may optionally be 1:(0.01-0.03).

[0134] In some embodiments, the coating may further include a dispersant.

[0135] Alternatively, the dispersant may include, but is not limited to, one or more of hydrolyzed polymaleic anhydride, polyacrylic acid, acrylic acid block copolymers, polyester block copolymers, polyethylene glycol-type polyols, polyethyleneimine, and their respective derivatives. Derivatives generally refer to products derived from the replacement of hydrogen atoms or atomic groups in a polymer with other atoms or atomic groups.

[0136] Optionally, the weight ratio of the dendrite reactive particles to the dispersant may be 1:(0.01-0.02), or optionally 1:(0.010-0.015).

[0137] An appropriate amount of dispersant can make the coating slurry dispersed evenly, facilitate coating, and also help to increase the film weight of the coating.

[0138] In some embodiments, the coating may also include a thickener.

[0139] Optionally, the thickener may include, but is not limited to, one or more of sodium hydroxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropyl methylcellulose, polyacrylate, polyurethane, and polyether.

[0140] Optionally, the weight ratio of the dendrite reactive particles to the thickener may be 1:(0.01-0.02), optionally 1:(0.010-0.015).

[0141] An appropriate amount of thickener can improve the stability of the slurry, facilitate coating, and help increase the film weight of the coating.

[0142] In some embodiments, the thickness of the coating layer may be 1 μm to 10 μm, and optionally 1.5 μm to 4.5 μm. The thickness of the coating layer refers to the thickness of the coating layer on a single side of the porous substrate.

[0143] The thickness of the coating is within the above range, which can improve the isolation membrane's resistance to dendrite penetration, heat resistance and electrolyte wettability, thereby helping to improve the reliability of the battery; it can also make the isolation membrane have lower internal resistance and good ion transport properties, thereby helping the battery to have good cycle performance and / or rate performance.

[0144] In some embodiments, the surface density of the isolation film can be 5 g / m 2 -15g / m 2 , optional 7g / m 2 -10g / m 2 .

[0145] [Method for preparing isolation film]

[0146] The present application also provides a method for preparing a separator, comprising the following steps of preparing a porous substrate: providing a polymer resin raw material and a pore-forming agent, pressing the polymer resin raw material and the pore-forming agent into a film, and removing the pore-forming agent with a solvent to obtain a porous substrate. The method utilizes the solid-liquid phase separation or liquid-liquid phase separation that occurs during the cooling of a molten mixture of the polymer resin raw material and the pore-forming agent, pressing the film into a film, and then extracting the pore-forming agent from the film with a solvent to obtain the porous substrate.

[0147] In some embodiments, the steps of preparing a porous substrate may include the following steps: providing a polymer resin raw material and a pore-forming agent; pressing the polymer resin raw material and the pore-forming agent into a membrane; removing the pore-forming agent from the membrane; stretching the membrane after removing the pore-forming agent; and heat-setting the stretched membrane to obtain a porous substrate.

[0148] In some embodiments, the steps of preparing a porous substrate may include the following steps: providing a polymer resin raw material and a pore-forming agent; pressing the polymer resin raw material and the pore-forming agent into a membrane; stretching the membrane; removing the pore-forming agent from the stretched membrane; and heat-setting the membrane after removing the pore-forming agent to obtain a porous substrate.

[0149] Methods for adjusting the porosity, average pore size, and pore size distribution of the porous substrate may include at least one of the following: adjusting parameters such as the weight-average molecular weight of the polymer resin raw material for preparing the porous substrate, the melt flow index of the polymer resin raw material, the amount of pore-forming agent, and the stretching ratio.

[0150] As a method for adjusting the porosity, average pore size, pore size distribution and compression creep compliance of the porous substrate, the overall weight average molecular weight of the polymer resin raw material can be 800,000-1.2 million, optionally 800,000-1.15 million.

[0151] By adjusting the weight average molecular weight of the entire polymer resin raw material within the above range, the mechanical properties and electrochemical properties of the porous substrate can be improved, and the processing properties of the porous substrate can also be improved.

[0152] As a method for adjusting the porosity, average pore size, pore size distribution, and compression creep compliance of the porous substrate, the melt flow index (DIN 53 735) of the polymer resin raw material can be 0.5 g / 10 min or more, optionally 3 g / 10 min or more, and more preferably 5 g / 10 min or more; in addition, the melt flow index of the polymer resin raw material can be 30 g / 10 min or less, and more preferably 10 g / 10 min or less. Alternatively, the melt flow index of the polymer resin raw material is 3 g / 10 min to 10 g / 10 min, or 3.5 g / 10 min to 7.5 g / 10 min.

[0153] As a method for adjusting the porosity, average pore size, pore size distribution and compression creep compliance of the porous substrate, the amount of the pore-forming agent used can be more than 30 parts by weight relative to 100 parts by weight of the polymer resin raw material and the pore-forming agent in total, and can be optionally 40 parts by weight to 58 parts by weight, and more optionally 42 parts by weight to 55 parts by weight.

[0154] As a method for adjusting the porosity, average pore size, pore size distribution and compression creep compliance of the porous substrate, the heat setting temperature may be 100°C-150°C, optionally 120°C-140°C.

[0155] As a method for adjusting the porosity, average pore size, pore size distribution and compressive creep compliance of the porous substrate, the transverse direction (TD) stretching ratio of the diaphragm can be greater than 4.5 times, and can be optionally 4.5 times-8 times, 4.5 times-6 times, and the longitudinal direction (MD) stretching ratio of the diaphragm can be greater than 6.5 times, and can be optionally 6.5 times-10 times, 6.5 times-8 times.

[0156] By adjusting the stretching ratio of the diaphragm within the above range, the micropores inside the diaphragm can be effectively stretched, the shape of the pores can be made more uniform and regular, the number of closed or irregular pores can be reduced, and the air permeability of the porous substrate can be improved; the thickness of the diaphragm in the longitudinal and transverse directions can also be made more uniform.

[0157] As an example, the pore-forming agent may include one or more of white oil, paraffin oil, phthalates, aliphatic dibasic acid esters, and phosphates. Optionally, the pore-forming agent has a molecular weight of less than 10,000.

[0158] The solvent for removing the pore former may include one or more of dichloromethane and trichloroethylene.

[0159] Methods for adjusting the thickness of the porous substrate may include at least one of the following: adjusting parameters such as the thickness of the film after pressing, and the stretching ratio.

[0160] In some embodiments, when preparing the porous substrate, some additives, such as antioxidants, may be added to the raw materials.

[0161] In some embodiments, the method for preparing the isolation membrane may further include the following steps: providing a coating slurry, coating the coating slurry on at least one surface of the porous substrate, and drying to obtain the isolation membrane.

[0162] In some embodiments, the drying temperature of the coating slurry may be 60°C-80°C.

[0163] In some embodiments, the coating slurry may be applied by methods including, but not limited to, gravure transfer coating, spin spray coating, dip coating, and blade coating.

[0164] In some embodiments, the solvent in the coating slurry may include, but is not limited to, one or more of deionized water, N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAC), and tetrahydrofuran (THF).

[0165] In some embodiments, the solid content of the coating slurry may be 25%-45%, and optionally 30%-40%, thereby facilitating coating.

[0166] In some embodiments, the coating slurry may include dendrite-reactive particles, a binder, and a solvent.

[0167] In some embodiments, the coating slurry may further include a dispersant and / or a thickener.

[0168] In some embodiments, the step of providing a coating slurry may include the following steps: dispersing the dendrite reaction particles, dispersant and solvent once to obtain a primary dispersion solution; adding a binder and a thickener to the obtained primary dispersion solution for secondary dispersion to obtain a coating slurry.

[0169] Optionally, the primary dispersion process may be ultrasonic dispersion, and stirring may be performed during the ultrasonic dispersion process. Optionally, the stirring speed during the ultrasonic dispersion process may be 700 rpm-1200 rpm, and the ultrasonic dispersion time may be 30 min-60 min.

[0170] Optionally, the secondary dispersion process may be ultrasonic dispersion, and stirring may be performed during the ultrasonic dispersion process. Optionally, the stirring speed during the ultrasonic dispersion process may be 1000 rpm-1600 rpm, and the ultrasonic dispersion time may be 30 min-90 min.

[0171] Some parameters such as raw materials and their contents used in the preparation method of the isolation membrane provided in the embodiments of the present application can refer to the isolation membrane provided in the embodiments of the present application, and will not be repeated here.

[0172] Unless otherwise specified, all raw materials used in the preparation method of the separator can be obtained commercially.

[0173] [Positive electrode]

[0174] The battery cell includes a positive electrode plate.

[0175] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and comprising a positive electrode active material. For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposing surfaces of the positive electrode current collector.

[0176] In some embodiments, the positive electrode active material includes a material capable of extracting and inserting lithium.

[0177] As an example, the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, metal chalcogenides, lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of 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. Lithium transition metal oxides may include, but are not limited to, layered structures and spinel structures. 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.

[0178] 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 may include but is not limited to one or more of Ge, Mo, Sn, Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and D may include but is not limited to one or more of N, F, S and Cl.

[0179] In some embodiments, the positive electrode active material may include both a lithium transition metal oxide and a lithium-containing phosphate, thereby facilitating the production of a battery with both high capacity and high reliability.

[0180] As an example, the positive electrode active material may include but is not limited to LiCoO2, LiNiO2, LiMnO2, LiNi 1 / 2 Mn 1 / 2 O2、LiMn2O4、Li 4 / 3 Ti 5 / 3 O4、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), LiNi0.6 Co 0.2 Mn 0.2 O2(NCM622),LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.80 Co 0.15 Al 0.05 O2, LiFePO4, LiMnPO4, Li 1.13 Ti 0.57 Fe 0.3 One or more of S2.

[0181] In some embodiments, the positive electrode active material includes a material capable of extracting and inserting sodium. For example, the positive electrode active material may include, but is not limited to, one or more of layered transition metal oxides (including but not limited to P2 type, O3 type, etc.), polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian materials.

[0182] In some embodiments, as examples, the positive electrode active material may include but is not limited to NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, Na 0.67 MO2 (M includes at least two of Fe, Co, Cr, Mn, Ni, V, Ti, Mo), NaMO2 (M includes at least two of Fe, Co, Ni, V, Ti, Mo), NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, Prussian white, and one or more of their respective modified compounds.

[0183] 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.

[0184] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0185] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene oxide, fluorinated acrylic resin, 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 one or more of carboxymethyl chitosan (CMCS).

[0186] 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 but is not limited to 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 but is not limited to one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0187] The positive electrode film layer is typically formed by coating a positive electrode slurry onto a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, optional positive electrode conductive agent, optional positive electrode binder, and any other components in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0188] [Negative electrode]

[0189] The battery cell includes a negative electrode plate.

[0190] In some embodiments, the negative electrode plate may include a negative electrode current collector and a metal layer disposed on at least one surface of the negative electrode current collector. The metal material in the metal layer may include but is not limited to one or more of lithium, lithium alloy, sodium, and sodium alloy.

[0191] A lithium alloy may be an alloy of metallic lithium and other metallic elements or non-metallic elements. For example, the other metallic elements in the lithium alloy may include one or more of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, and platinum, and the non-metallic elements in the lithium alloy may include one or more of boron, carbon, and silicon.

[0192] The sodium alloy may be an alloy of metallic sodium and other metallic elements or non-metallic elements. For example, the other metallic elements in the sodium alloy may include one or more of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, and platinum, and the non-metallic elements in the sodium alloy may include one or more of boron, carbon, and silicon.

[0193] In some embodiments, the negative electrode sheet may include a negative electrode current collector but not a metal layer, so as to be assembled into a negative electrode metal-free battery cell.

[0194] In some embodiments, to improve battery performance, the negative electrode side of a negative electrode metal-free battery may also be provided with some conventional negative electrode active materials, such as carbon materials. Although these materials have a certain capacity, their content is relatively small and they are not used as the primary negative electrode active material in the battery cell. Therefore, the battery cell thus constructed can still be considered a negative electrode metal-free battery cell.

[0195] In some embodiments, the negative electrode current collector may include a metal foil, a three-dimensional porous current collector, or a composite current collector. As examples of metal foils, copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, and aluminum alloy foil may be used. As examples of three-dimensional porous current collectors, copper mesh, nickel mesh, aluminum mesh, foam copper, foam nickel, and foam aluminum 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, but is not limited to, 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, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0196] [Electrolytes]

[0197] The battery cells include an electrolyte.

[0198] In some embodiments, the electrolyte is an electrolyte solution including an electrolyte salt and an organic solvent.

[0199] In some embodiments, the electrolyte includes anions, which may include bis(fluorosulfonyl)imide anions (FSI - ), bis(trifluoromethanesulfonyl)imide anion (TFSI - ), dioxalatoborate anion (BOB - ), difluorooxalatoborate anion (DFOB - ), difluorobis(oxaloyl)phosphate anion (DFOP - ), tetrafluorooxalophosphate anion (TFOP -), difluorophosphate anion (PO2F2 - ), hexafluorophosphate anion (PF6 - ), tetrafluoroborate anion (BF4 - ), hexafluoroarsenate anion (AsF6 - ), trifluoromethanesulfonate anion (CF3SO3 - )

[0200] In some embodiments, the electrolyte includes cations, which may include one or more of lithium ions and sodium ions.

[0201] In some embodiments, the concentration of the electrolyte salt may be greater than 0.3 mol / L, and may be greater than 0.7 mol / L. The concentration of the electrolyte salt may further be less than 4 mol / L, and may be less than 2.5 mol / L or less than 1.7 mol / L. When the concentration of the electrolyte salt is within the above range, the electrolyte solution can have suitable ionic conductivity.

[0202] Organic solvent can include but not limited to one or more in esters, ethers, sulfones, nitrile etc.Ester can include but not limited to one or more in carbonate, phosphate, carboxylate, sulfate, sulfonate etc.Carbonate can comprise cyclic carbonate and / or chain carbonate, alternatively, carbonate can comprise cyclic carbonate and chain carbonate simultaneously.Chain carbonate can comprise low-viscosity polar chain carbonate, aliphatic branched-chain carbonate etc.

[0203] As an example, the organic solvent may include, but is not limited to, 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, 3-methoxypropionitrile, H(CF2)2OCH3, C4F9O CH3, H(CF2)2OCH2CH3, H(CF2)2OCH2CF3, H(CF2)2CH2O(CF2)2H, CF3CHFCF2OCH3, CF3CHFCF2OCH2CH3, 2-trifluoromethylhexafluoropropyl methyl ether, 2-trifluoromethylhexafluoropropyl ethyl ether, 2-trifluoromethylhexafluoropropyl propyl ether, 3-trifluoromethyloctafluorobutyl methyl ether, 3-trifluoromethyloctafluorobutyl ethyl ether, 3-trifluoromethyloctafluorobutyl propyl ether, 4-trifluoromethyl One or more of 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 hexafluorooctyl ethyl ether, and 7-trifluoromethyl hexafluorooctyl propyl ether.

[0204] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0205] The preparation method of battery cells is well known. In some embodiments, the positive electrode sheet, separator, negative electrode sheet and electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, separator, and negative electrode sheet can be formed into an electrode assembly through a winding process and / or a lamination process, and the electrode assembly is placed in an outer package, dried and injected with the above-mentioned electrolyte, and then vacuum packaged, allowed to stand, formed and other processes to obtain a battery cell. Multiple battery cells can also be further connected in series, in parallel or in a mixed connection to form a battery module. Multiple battery modules can also be connected in series, in parallel or in a mixed connection to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.

[0206] The present application also provides an electrical device, which includes a battery provided in 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 tablet computer, 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.

[0207] The electrical device can select the type of battery according to its usage requirements, such as a battery cell, a battery module or a battery pack.

[0208] Figure 6 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.

[0209] 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.

[0210] Example

[0211] The following examples describe the present disclosure in more detail and 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 indicated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further processing, and all instruments used in the examples are commercially available.

[0212] Example 1

[0213] Preparation of porous substrates

[0214] The following raw materials were weighed and mixed uniformly: 60 parts by weight of ultra-high molecular weight polyethylene with a weight-average molecular weight of 1.1 million and 40 parts by weight of white oil with a weight-average molecular weight of 1000.

[0215] The above two substances were mixed to make 100 parts by weight, and 3 parts by weight of butylated hydroxytoluene and 3 parts by weight of phosphite were added thereto as antioxidants.

[0216] The raw materials were extruded through a twin-screw extruder at 210°C to produce a high-temperature melt. The high-temperature melt was accurately metered by a melt pump and fed into a die. The high-temperature melt flowed out through a slit in the die. The high-temperature melt was then extruded through a chilled roller at 30°C to produce a film. The melt flow index (DIN 53 735) of the high-temperature melt at 230°C and a load of 2.16 kg was 5.5 g / 10 min.

[0217] The extruded film was fed into a biaxial asynchronous stretching machine and stretched 6.5 times in the longitudinal direction (MD) and 4.5 times in the transverse direction (TD) to obtain a film containing a pore-forming agent.

[0218] The film containing the pore-forming agent was fully soaked in dichloromethane for 20 minutes to remove the pore-forming agent, and then the dichloromethane was volatilized through a drying process at 40° C. to obtain a microporous film.

[0219] The microporous film was kept in a high-temperature setting device at 130° C. for 6 hours to fully remove the membrane stress, thereby obtaining a porous substrate having a thickness of 55 μm and a porosity of 65%.

[0220] Preparation of isolation membrane

[0221] Li 1.3 Al 0.3 Ti 1.7 (PO4)3 powder is evenly dispersed in NMP, and hydrolyzed polymaleic anhydride is added for ultrasonic dispersion. After ultrasonic dispersion for 2 hours, sodium hydroxymethyl cellulose is added for secondary dispersion, and then PVDF is added for mixing to obtain a coating slurry with a solid content of about 35%. 1.3 Al 0.3 Ti 1.7 The volume distribution particle size Dv50 of (PO4)3 powder is 500nm-1000nm. 1.3 Al 0.3 Ti 1.7 The weight ratio of (PO4)3, hydrolyzed polymaleic anhydride, sodium hydroxymethyl cellulose and PVDF is 1:0.01:0.01:0.03.

[0222] The obtained coating slurry was coated on one surface of the porous substrate by gravure transfer coating, and vacuum dried at 60° C. to obtain an isolation film with a coating thickness of 3 μm.

[0223] Example 2

[0224] The preparation method of the isolation membrane is similar to that of Example 1, except that the preparation process of the porous substrate is different.

[0225] The following raw materials were weighed and mixed uniformly: 57 parts by weight of ultra-high molecular weight polyethylene (UHMWPE) with a weight-average molecular weight of 1,000, and 43 parts by weight of white oil with a weight-average molecular weight of 1,000. The total weight of these two materials was recorded as 100 parts by weight. Three parts by weight of butylated hydroxytoluene and three parts by weight of a phosphite ester were then added as antioxidants.

[0226] The raw materials were extruded through a twin-screw extruder at 210°C to produce a high-temperature melt. The high-temperature melt was accurately metered by a melt pump and fed into a die. The high-temperature melt flowed out through a slit in the die. The melt was then extruded through a chilled roller at 30°C to produce a film. The melt flow index (DIN 53 735) of the high-temperature melt at 230°C and a load of 2.16 kg was 5.2 g / 10 min.

[0227] The extruded film was fed into a biaxial asynchronous stretching machine and stretched 6.8 times in the longitudinal direction (MD) and 4.8 times in the transverse direction (TD) to obtain a film containing a pore-forming agent.

[0228] The film containing the pore-forming agent was fully soaked in dichloromethane for 20 minutes to remove the pore-forming agent, and then the dichloromethane was volatilized through a drying process at 40° C. to obtain a microporous film.

[0229] The microporous film was kept in a high-temperature setting device at 130° C. for 6 hours to fully remove the membrane stress, thereby obtaining a porous substrate having a thickness of 50 μm and a porosity of 72%.

[0230] Example 3

[0231] The preparation method of the isolation membrane is similar to that of Example 1, except that the preparation process of the porous substrate is different.

[0232] The following raw materials were weighed and mixed uniformly: 55 parts by weight of ultra-high molecular weight polyethylene (UHMWPE) with a weight-average molecular weight of 950,000 and 45 parts by weight of white oil with a weight-average molecular weight of 1000. The resulting mixture was recorded as 100 parts by weight. Three parts by weight of butylated hydroxytoluene and three parts by weight of a phosphite ester were then added as antioxidants.

[0233] The raw materials were extruded through a twin-screw extruder at 210°C to produce a high-temperature melt. The high-temperature melt was accurately metered by a melt pump and fed into a die. The high-temperature melt flowed out through a slit in the die. The high-temperature melt was then extruded through a chilled roller at 30°C to produce a film. The melt flow index (DIN 53 735) of the high-temperature melt at 230°C and a load of 2.16 kg was 5.5 g / 10 min.

[0234] The extruded film was fed into a biaxial asynchronous stretching machine and stretched 7.4 times in the longitudinal direction (MD) and 5.2 times in the transverse direction (TD) to obtain a film containing a pore-forming agent.

[0235] The film containing the pore-forming agent was fully soaked in dichloromethane for 20 minutes to remove the pore-forming agent, and then the dichloromethane was volatilized through a drying process at 40° C. to obtain a microporous film.

[0236] The microporous film was kept in a high-temperature setting device at 130° C. for 6 hours to fully remove the membrane stress, thereby obtaining a porous substrate having a thickness of 45 μm and a porosity of 75%.

[0237] Example 4

[0238] The preparation method of the isolation membrane is similar to that of Example 1, except that the preparation process of the porous substrate is different.

[0239] The following raw materials were weighed and mixed uniformly: 50 parts by weight of ultra-high molecular weight polyethylene (UHMWPE) with a weight-average molecular weight of 850,000 and 50 parts by weight of white oil with a weight-average molecular weight of 1,000. The combined volume was recorded as 100 parts by weight. Three parts by weight of butylated hydroxytoluene and three parts by weight of a phosphite ester were then added as antioxidants.

[0240] The raw materials were extruded through a twin-screw extruder at 210°C to produce a high-temperature melt. The high-temperature melt was accurately metered by a melt pump and fed into a die. The high-temperature melt flowed out through a slit in the die. The high-temperature melt was then extruded through a chilled roller at 30°C to produce a film. The melt flow index (DIN 53 735) of the high-temperature melt at 230°C and a load of 2.16 kg was 6.4 g / 10 min.

[0241] The extruded film was fed into a biaxial asynchronous stretching machine and stretched 7.5 times in the longitudinal direction (MD) and 5.5 times in the transverse direction (TD) to obtain a film containing a pore-forming agent.

[0242] The film containing the pore-forming agent was fully soaked in dichloromethane for 20 minutes to remove the pore-forming agent, and then the dichloromethane was volatilized through a drying process at 40° C. to obtain a microporous film.

[0243] The microporous film was kept in a high-temperature setting device at 130° C. for 6 hours to fully remove the membrane stress, thereby obtaining a porous substrate having a thickness of 40 μm and a porosity of 80%.

[0244] Example 5

[0245] The preparation method of the isolation membrane is similar to that of Example 1, except that the preparation process of the porous substrate is different.

[0246] The following raw materials were weighed and mixed uniformly: 45 parts by weight of ultra-high molecular weight polyethylene (UHMWPE) with a weight-average molecular weight of 830,000 and 55 parts by weight of white oil with a weight-average molecular weight of 1000. The resulting mixture was recorded as 100 parts by weight. Three parts by weight of butylated hydroxytoluene and three parts by weight of a phosphite ester were then added as antioxidants.

[0247] The raw materials were extruded through a twin-screw extruder at 210°C to produce a high-temperature melt. The high-temperature melt was accurately metered by a melt pump and fed into a die. The high-temperature melt flowed out through a slit in the die. The melt was then extruded through a chilled roller at 30°C to produce a film. The melt flow index (DIN 53 735) of the high-temperature melt at 230°C and a load of 2.16 kg was 7.5 g / 10 min.

[0248] The extruded film was fed into a biaxial asynchronous stretching machine and stretched 8.0 times in the longitudinal direction (MD) and 6.0 times in the transverse direction (TD) to obtain a film containing a pore-forming agent.

[0249] The film containing the pore-forming agent was fully soaked in dichloromethane for 20 minutes to remove the pore-forming agent, and then the dichloromethane was volatilized through a drying process at 40° C. to obtain a microporous film.

[0250] The microporous film was kept in a high-temperature setting device at 130° C. for 6 hours to fully remove the membrane stress, thereby obtaining a porous substrate having a thickness of 36 μm and a porosity of 82%.

[0251] Comparative Example 1

[0252] The preparation method of the isolation membrane is similar to that of Example 1, except that the preparation process of the porous substrate is different.

[0253] Weigh and mix the following raw materials: 55 parts by weight of high-density polyethylene (HDPE) with a weight-average molecular weight of 300,000 and 45 parts by weight of white oil (1,000). Combine these two materials to create 100 parts by weight. Add 3 parts by weight of butylated hydroxytoluene and 3 parts by weight of a phosphite ester as an antioxidant.

[0254] The raw materials were extruded through a twin-screw extruder at 210°C to produce a high-temperature melt. The high-temperature melt was accurately metered by a melt pump and fed into a die. The high-temperature melt flowed out through a slit in the die. The melt was then extruded through a chilled roller at 30°C to produce a film. The melt flow index (DIN 53 735) of the high-temperature melt at 230°C and a load of 2.16 kg was 32 g / 10 min.

[0255] The extruded film is fed into a biaxial asynchronous stretching machine and stretched 12 times in the longitudinal direction (MD) and 10 times in the transverse direction (TD) to obtain a film containing a pore-forming agent.

[0256] The film containing the pore-forming agent was fully soaked in dichloromethane for 20 minutes to remove the pore-forming agent, and then the dichloromethane was volatilized through a drying process at 40° C. to obtain a microporous film.

[0257] The microporous film was kept in a high-temperature setting device at 130° C. for 6 hours to fully remove the membrane stress, thereby obtaining a porous substrate having a thickness of 12 μm and a porosity of 40%.

[0258] Comparative Example 2

[0259] The preparation method of the isolation membrane is similar to that of Example 1, except that the preparation process of the porous substrate is different.

[0260] The following raw materials were weighed and mixed uniformly: 40 parts by weight of ultra-high molecular weight polyethylene (UHMWPE) with a weight-average molecular weight of 1.2 million and 60 parts by weight of white oil (WM 1000). The combined weight was recorded as 100 parts by weight. Three parts by weight of butylated hydroxytoluene and three parts by weight of a phosphite ester were then added as antioxidants.

[0261] The raw materials were extruded through a twin-screw extruder at 210°C to produce a high-temperature melt. The high-temperature melt was accurately metered by a melt pump and fed into a die. The high-temperature melt flowed out through a slit in the die. The high-temperature melt was then extruded through a chilled roller at 30°C to produce a film. The melt flow index (DIN 53 735) of the high-temperature melt at 230°C and a load of 2.16 kg was 12 g / 10 min.

[0262] The extruded film was fed into a biaxial asynchronous stretching machine and stretched 6.0 times in the longitudinal direction (MD) and 4.0 times in the transverse direction (TD) to obtain a film containing a pore-forming agent.

[0263] The film containing the pore-forming agent was fully soaked in dichloromethane for 20 minutes to remove the pore-forming agent, and then the dichloromethane was volatilized through a drying process at 40° C. to obtain a microporous film.

[0264] The microporous film was kept in a high-temperature setting device at 125° C. for 6 hours to fully remove the membrane stress, thereby obtaining a porous substrate having a thickness of 58 μm and a porosity of 88%.

[0265] Testing of porous substrates

[0266] The thickness of the porous substrate is measured according to GB / T 6672-2001, Plastic film and sheeting - Determination of thickness - Mechanical measurement method.

[0267] The porosity of the porous substrate was tested with reference to GB / T 21650.2-2008, Determination of pore size distribution and porosity of solid materials by mercury intrusion porosimetry and gas adsorption method - Part 2: Analysis of mesopores and macropores by gas adsorption method.

[0268] The average pore size and pore size distribution of the porous substrate were tested according to ASTM F316-03 (2019), Standard Test Method for Pore Size Characteristics of Membrane Filters by Bubble Point and Mean Flow Pore Tests, and ASTM E1294-89 (1999).

[0269] The compressive creep compliance of porous substrates is tested using a Kappa SS-CF creep tester. The test temperature is 25°C and the pressure is kept constant. The compressive creep compliance of porous substrates is the reciprocal of the compressive creep elastic modulus (MPa) measured in accordance with GB / T 41061-2021 at a temperature of 25°C, a humidity of 10%, and a stress of 1 MPa applied to the porous substrate along its thickness. -1 The value obtained by dividing the creep amount in time t seconds by the stress is in units of t seconds.

[0270] Next, the above-mentioned isolation membrane was assembled into a button-type battery, and the cycle performance and rate performance were tested.

[0271] The button cell can be prepared as follows.

[0272] 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 weight ratio of 8:1:1 to form a positive electrode slurry. The slurry was applied to the positive electrode current collector aluminum foil and dried to form a positive electrode sheet. In an argon-protected glove box, the positive electrode sheet, the separator, and the lithium sheet were assembled into a CR2430 button cell. The electrolyte salt was LiFSI at a concentration of 1 mol / L, and the solvent was ethylene glycol dimethyl ether.

[0273] The coating layers of the separators of Examples 1 to 5 and Comparative Examples 1 to 2 all faced the lithium sheet.

[0274] 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 0.05C. 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.

[0275] A button cell was charged at constant current rates of 0.5C, 1C, and 2C to 3.65V, followed by constant voltage charge at 3.65V to 0.05C. After standing for 10 minutes, the cell was discharged at a constant current of 0.2C to 2.5V. The cell was cycled 100 times using this method to determine the charge capacity and discharge capacity at the 100th cycle. The coulombic efficiency of the cell after 100 cycles is calculated as: discharge capacity at the 100th cycle / charge capacity at the 100th cycle.

[0276] During the test, the number of button battery samples can be more than 6, and the test results are averaged.

[0277] The test results are shown in Table 1.

[0278] Table 1

[0279] From the test results of Examples 1 to 5 and Comparative Examples 1 to 2, it can be seen that the use of a separator having a porous substrate with a specific compressive creep compliance of the present application can enable the metal battery to have good cycle performance at both low and high rates.

[0280] 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 concept 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 separator comprising a porous substrate, wherein: The porous substrate satisfies at least one of the following conditions (1) to (3): (1) When t is 300 seconds, the compressive creep compliance of the porous substrate is 0.05 MPa -1 -0.24MPa -1 , (2) When t is 1800 seconds, the compressive creep compliance of the porous substrate is 0.12 MPa -1 -0.36MPa -1 , (3) When t is 3600 seconds, the compressive creep compliance of the porous substrate is 0.23 MPa -1 -0.52MPa -1 , The compressive creep compliance of the porous substrate refers to the reciprocal of the compressive creep elastic modulus tested in accordance with GB / T41061-2021 under the conditions of a temperature of 25°C, a humidity of 10%, and a stress of 1 MPa applied to the porous substrate along its thickness direction, expressed in MPa. -1 The value is obtained by dividing the creep amount in time t seconds by the stress.

2. The isolation film according to claim 1, wherein: The porous substrate satisfies all of the following conditions (1) to (3): (1) When t is 300 seconds, the compressive creep compliance of the porous substrate is 0.05 MPa -1 -0.24MPa -1 , (2) When t is 1800 seconds, the compressive creep compliance of the porous substrate is 0.12 MPa -1 -0.36MPa -1 , (3) When t is 3600 seconds, the compressive creep compliance of the porous substrate is 0.23 MPa -1 -0.52MPa -1 .

3. The isolation film according to any one of claims 1 to 2, wherein: The porosity of the porous substrate is greater than or equal to 65%, and the thickness of the porous substrate is greater than or equal to 20 μm; Optionally, the porosity of the porous substrate is 65%-95%, and the thickness of the porous substrate is 30 μm-70 μm; More optionally, the porosity of the porous substrate is 70%-85%, and the thickness of the porous substrate is 36 μm-50 μm.

4. The isolation film according to any one of claims 1 to 3, wherein: The average pore size of the porous substrate is 10 nm-200 nm, and can be 20 nm-60 nm. Optionally, the total pore volume of pores with a pore size of less than 70 nm in the porous substrate accounts for more than 90% of the total pore volume of the porous substrate, and the total pore volume of pores with a pore size of less than 30 nm in the porous substrate accounts for more than 50% of the total pore volume of the porous substrate.

5. The isolation film according to any one of claims 1 to 4, wherein: The air permeability of the porous substrate is 50s / 100mL-300s / 100mL, and can be optionally 60s / 100mL-150s / 100mL.

6. The isolation film according to any one of claims 1 to 5, wherein: The BET specific surface area of ​​the porous substrate is 30 m 2 / g-300m 2 / g, optional 50m 2 / g-200m 2 / g.

7. The isolation film according to any one of claims 1 to 6, wherein: The porous substrate comprises one or more of polyolefin, polyamide, polyester, polyacrylonitrile, and their respective derivatives, and may optionally comprise one or more of polyolefin and its derivatives; and / or, The weight average molecular weight of the porous substrate is 800,000-1.2 million, and can be 800,000-1.15 million.

8. The isolation film according to any one of claims 1 to 7, wherein: The porous substrate satisfies at least one of the following conditions (1) to (7): (1) The tensile strength of the porous substrate in the TD direction is greater than or equal to 2000 kg / cm 2 ; (2) The tensile strength of the porous substrate in the MD direction is greater than or equal to 1500 kg / cm 2 ; (3) The elongation at break of the porous substrate in the TD direction is greater than or equal to 60%; (4) the elongation at break of the porous substrate in the MD direction is greater than or equal to 60%; (5) The puncture strength of the porous substrate is greater than or equal to 200 gf; (6) The thermal shrinkage of the porous substrate in the TD direction at 105° C. for 1 hour is less than or equal to 10%; (7) The thermal shrinkage of the porous substrate in the MD direction at 105° C. for 1 h is less than or equal to 4%.

9. The isolation film according to any one of claims 1 to 8, wherein: The isolation membrane further comprises a coating located on at least one surface of the porous substrate, wherein the coating comprises at least one of an organic coating, an inorganic coating, and an organic-inorganic composite coating.

10. The isolation film according to claim 9, wherein: The coating comprises dendrite reactive particles and a binder; Optionally, the dendrite reactive particles include one or more of lithium reactive particles and sodium reactive particles.

11. The isolation film according to claim 10, wherein: The volume distribution particle size Dv50 of the dendrite reaction type particles is 0.01 μm-10 μm, and can be optionally 0.05 μm-0.5 μm.

12. The isolation film according to any one of claims 10 to 11, wherein: The mass ratio of the dendrite reactive particles to the binder is 1:(0.005-0.05), and can be optionally 1:(0.01-0.03).

13. The isolation film according to any one of claims 10 to 12, wherein: The dendrite reactive particles include one or more of solid electrolyte materials, metal oxides, non-metal oxides, metal sulfides, non-metal sulfides, metal nitrides, non-metal nitrides, and carbon-based materials; and / or, The binder includes one or more of vinyl fluoride-based polymer and styrene-butadiene rubber.

14. The isolation film according to any one of claims 9 to 13, wherein: The thickness of the coating is 1 μm-10 μm, and can be optionally 1.5 μm-4.5 μm.

15. A battery cell, comprising the isolation membrane according to any one of claims 1 to 14, optionally, the battery cell comprises at least one of a lithium metal battery cell, a negative electrode-free lithium metal battery cell, a sodium metal battery cell, and a negative electrode-free sodium metal battery cell.

16. A battery comprising the battery cell according to claim 15.

17. An electrical device comprising the battery according to claim 16, wherein the battery is used to provide electrical energy.

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