Isolating membrane, battery monomer, battery and electric device

Abstract

The present application discloses a separator, a battery cell, a battery, and an electric device, the separator comprising a porous substrate, the porous substrate satisfying at least one of the following conditions (1) to (3): (1) when t is 300 seconds, the compression creep compliance of the porous substrate is 0.05-0.24 MPa <-1 >, (2) when t is 1800 seconds, the compression creep compliance of the porous substrate is 0.12-0.36 MPa <-1 >, and (3) when t is 3600 seconds, the compression creep compliance of the porous substrate is 0.05-0.24 MPa <-1 >. And the compression creep compliance of the porous base material is 0.23 MPa <-1 > to 0.52 MPa <-1 >. The isolating membrane provided by the invention can enable the battery to have good cycle performance and rate capability.

Description

Technical Field

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

[0002] Compared with ion-type batteries, metal batteries can have higher energy density. However, unlike the negative electrode of ion-type batteries, the negative electrode of metal batteries has the problem of unlimited volume expansion. As the metal battery is cyclically charged and discharged, the separator and the positive electrode are squeezed by the expanded negative electrode, resulting in uneven stress inside the battery, which can easily lead to bending, damage, fracture, poor electrolyte wettability of the pole piece, thereby affecting the performance of the battery. The above statements are only used to provide background technical information related to this application and do not necessarily constitute prior art. Summary of the invention

[0003] The present application provides a separation membrane, a battery cell, a battery and an electrical device, which can enable the battery to have good cycle performance and rate performance.

[0004] In a first aspect, the present application provides an isolation membrane, comprising a porous substrate, characterized in that 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 .

[0005] 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.

[0006] 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. When 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 breaking of the electrode sheet, thereby facilitating the structural integrity of the electrode assembly. When the battery is discharged, 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, the metal battery using the separator containing the porous substrate that meets the above condition (1) has good cycle performance and rate performance when charged and discharged for 5 minutes, the metal battery using the separator containing the porous substrate that meets the above condition (2) has good cycle performance and rate performance when charged and discharged for 30 minutes, and the metal battery using the separator containing the porous substrate that meets the above condition (3) has good cycle performance and rate performance when charged and discharged for 1 hour.

[0007] 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 .

[0008] 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.

[0009] 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.

[0010] By adjusting the thickness and porosity of the porous substrate within the above range, sufficient compressible space can be provided when the metal battery is charged, and the compressed separator can still have a high porosity, which will not affect ion transmission and electrolyte infiltration, thereby enabling the battery to have good cycle performance and rate performance. In addition, the battery can also have a high volume energy density.

[0011] In some embodiments, the average pore size of the porous substrate is 10 nm to 200 nm, and optionally 20 nm to 60 nm.

[0012] 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.

[0013] In some embodiments, the total pore volume of pores with a pore size 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 less than 30 nm in the porous substrate accounts for more than 50% of the total pore volume of the porous substrate.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] In some embodiments, the porous substrate includes one or more of polyolefin, polyamide, polyester, polyacrylonitrile, and their respective derivatives, and may optionally include one or more of polyolefin and its derivatives.

[0018] In some embodiments, the weight average molecular weight of the porous substrate is 800,000-1.2 million, and can be 800,000-1.15 million.

[0019] In some embodiments, the tensile strength of the porous substrate in the TD direction is greater than or equal to 2000 kg / cm 2 .

[0020] In some embodiments, the tensile strength of the porous substrate in the MD direction is greater than or equal to 1500 kg / cm 2 .

[0021] In some embodiments, the elongation at break of the porous substrate in the TD direction is greater than or equal to 60%.

[0022] In some embodiments, the elongation at break of the porous substrate in the MD direction is greater than or equal to 60%.

[0023] In some embodiments, the porous substrate has a puncture strength of greater than or equal to 200 gf.

[0024] In some embodiments, the thermal shrinkage rate of the porous substrate in the TD direction at 105° C. for 1 h is less than or equal to 10%.

[0025] In some embodiments, the thermal shrinkage of the porous substrate in the MD direction at 105° C. for 1 h is less than or equal to 4%.

[0026] 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.

[0027] 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 wetting characteristics of the isolation membrane to 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] When the volume distribution particle size Dv50 of the dendrite reaction particles is within the above range, the coating slurry can have a suitable viscosity, which is convenient for coating, and is also beneficial to improving the uniformity of the coating and reducing the "powder falling" phenomenon; in addition, it can also reduce the pore blocking problem, thereby improving the air permeability and ion transmission characteristics of the isolation membrane, which is beneficial to improving the cycle performance and rate performance of the battery.

[0032] 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).

[0033] In some embodiments, 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 polymers and styrene-butadiene rubber.

[0034] In some embodiments, the coating has a thickness of 1 μm-10 μm, and optionally 1.5 μm-4.5 μm.

[0035] When the thickness of the coating is within the above range, the isolation membrane's resistance to dendrite penetration, heat resistance and electrolyte wettability can be improved, thereby helping to improve the reliability of the battery; the isolation membrane can also have a lower internal resistance and good ion transport properties, thereby helping the battery to have good cycle performance and / or rate performance.

[0036] In a second aspect, the present application provides a battery cell, which includes the isolation membrane of the first aspect of the present application.

[0037] 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.

[0038] In a third aspect, the present application provides a battery, which includes the battery cell of the second aspect of the present application.

[0039] In a fourth aspect, the present application provides an electrical device, comprising the battery of the third aspect of the present application, wherein the battery is used to provide electrical energy.

[0040] 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

[0041] In order 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 implementation methods of the present application, and for ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0042] Figure 1 A schematic diagram showing a battery cell provided by some embodiments of the present application.

[0043] Figure 2 A schematic diagram of an exploded view of a battery cell provided in some embodiments of the present application is shown.

[0044] Figure 3 A schematic diagram of a battery module provided in some embodiments of the present application is shown.

[0045] Figure 4 A schematic diagram of a battery pack provided in some embodiments of the present application is shown.

[0046] Figure 5 yes Figure 4 An exploded diagram of the battery pack is shown.

[0047] Figure 6 A schematic diagram of an electrical device provided in some embodiments of the present application is shown.

[0048] In the drawings, the drawings may not be drawn according to the actual scale. The reference numerals are as follows: 1 battery pack, 2 upper box, 3 lower box, 4 battery module, 5 battery, 51 housing, 52 electrode assembly, 53 cover plate. DETAILED DESCRIPTION

[0049] Hereinafter, the embodiments of the isolation membrane, battery cell, battery and electrical device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0050] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a 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 a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present 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 real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0051] If not otherwise specified, all embodiments and optional embodiments of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

[0052] Unless otherwise specified, all technical features and optional technical features of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

[0053] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), 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 also 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.

[0054] In the present application, the terms "plurality" and "multiple" refer to two or more.

[0055] 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”, or “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 higher in level than the second feature. A first feature being “below”, “below”, or “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 lower in level than the second feature.

[0056] Unless otherwise specified, the terms used in this application have the commonly understood meanings that are commonly understood by those skilled in the art.

[0057] Unless otherwise specified, the values ​​of the parameters mentioned in this application can be measured by 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 specified, the test temperature of each parameter is 25°C.

[0058] Unless otherwise specified, the test instruments mentioned in this application can be operated in accordance with the requirements of the product specifications.

[0059] 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.

[0060] A battery cell is the smallest unit of a battery, which can independently realize the functions of charging and discharging. The battery cell can be cylindrical, rectangular or in other shapes, etc., which is not limited in the embodiments of the present application. Figure 1 The battery cell 5 is a rectangular parallelepiped structure as an example.

[0061] When there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in mixed connection through 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 case and battery cells, and the battery cells or battery modules are accommodated in the case. In some embodiments, the case may serve as part of the chassis structure of the vehicle. For example, part of the case may become at least a part of the floor of the vehicle, or part of the case may become at least a part of the crossbeam and longitudinal beam of the vehicle.

[0062] In some embodiments, the battery may be an energy storage device, which includes an energy storage container, an energy storage cabinet, and the like.

[0063] A battery cell generally includes an electrode assembly and an electrolyte. The electrode assembly may be a wound structure or a laminated structure, which is not limited in the present application.

[0064] The battery cell may also include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte. The outer package may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).

[0065] In some embodiments, Figure 2 As shown, the outer package may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The electrode assembly 52 is encapsulated in the receiving cavity. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to demand.

[0066] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain multiple battery cells, and the specific number may be adjusted according to the application and capacity of the battery module. Figure 3 FIG. 4 is a schematic diagram of a battery module 4 as an example. Figure 3 As shown, in the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0067] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0068] 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.

[0069] Figure 4 and Figure 5 FIG. 1 is a schematic diagram of a battery pack 1 as an example. Figure 4 and Figure 5 As shown, the battery pack 1 may include a box body and a plurality of battery modules 4 disposed in the box body. The box body includes an upper box body 2 and a lower box body 3, and the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the box body in any manner.

[0070] 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.

[0071] A negative electrode-free battery cell generally refers to a battery cell that is formed by not actively setting a negative electrode active material layer on the negative electrode side during the manufacturing process of the battery cell, for example, in the manufacturing process of the battery cell, a layer is not set at the negative electrode through processes such as coating or deposition, or a negative electrode active material layer is formed by a carbonaceous active material layer. During the first charge, the ions obtain electrons on the negative electrode side and deposit on the surface of the negative electrode current collector to form a metal. During discharge, the metal can be converted into ions and return to the positive electrode to achieve cyclic charge and discharge. Compared with other battery cells, a negative electrode-free battery cell can obtain a higher energy density because it does not have a negative electrode active material layer. In some embodiments, in order to improve the performance of the battery cell, some conventional substances that can be used as negative electrode active materials, such as carbon materials, can also be set on the negative electrode side of the negative electrode-free battery cell. Although these substances have a certain capacity, due to their low content and not being used as the main negative electrode active material in the battery cell, the battery cell thus constructed can still be regarded as a negative electrode-free battery cell. The CB (Cell Balance) value of a battery cell without a negative electrode is usually very small. For example, in some embodiments, the CB value of a battery cell without a negative electrode may 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. Since the battery cell without a negative electrode does not contain or contains only a small amount of negative electrode active material, the unit area capacity of the negative electrode is small, and thus the CB value is very small, for example, usually less than or equal to 0.1.

[0072] 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.

[0073] 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) At t = 1800 seconds, the compressive creep compliance of the porous substrate is 0.12 MPa -1 -0.36MPa -1 , (3) At t = 3600 seconds, the compressive creep compliance of the porous substrate is 0.23 MPa -1 -0.52MPa -1 .

[0074] The compressive creep compliance of a porous substrate is the reciprocal of the compressive creep elastic modulus measured in accordance with GB / T 41061-2021 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. -1 The value is obtained by dividing the creep amount in time t seconds by the stress.

[0075] The testing instrument may be a Kappa SS-CF creep testing machine. During the test, the temperature is 25°C and the pressure is kept constant.

[0076] As an important component of the battery, the performance of the separator is crucial to the performance of the battery. The separator is located between the positive and negative electrodes of the battery and mainly plays the role of preventing short circuits. At present, the separators commonly used in the battery field are relatively thin, for example, the thickness is usually less than 20μm, which can usually meet the performance requirements in lithium-ion battery systems. However, in metal battery systems, due to the problem of infinite volume expansion of the negative electrode, as the metal battery is cycled and discharged, the separator and the positive electrode are squeezed by the expanded negative electrode, which will cause uneven stress inside the battery, which can easily lead to bending, damage, and fracture of the pole piece. At the same time, it will also cause the electrolyte wettability of the electrode assembly to deteriorate, affecting the cycle performance and rate performance of the battery; in addition, the broken pole piece may pierce the separator, causing a short circuit inside the battery.

[0077] 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, by applying an isolation membrane comprising a porous substrate with a specific compressive creep compliance to a metal battery system, can enable the battery to have good cycle performance and rate performance.

[0078] 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 when a stress equal to the expansion force applied to the isolation membrane is applied.

[0079] In addition, when t is 300 seconds, it is equivalent to the 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 is equivalent to the case where the metal battery containing the porous substrate is charged and discharged for 30 minutes and 1 hour, respectively.

[0080] When the compressive creep compliance of the porous substrate is less than the lower limit of the range provided above, when the isolation membrane comprising the porous substrate is actually applied to a metal battery, the isolation membrane cannot provide sufficient compressible space, and the electrode piece is still prone to bending, breaking, and fracture when the battery is charged and discharged, thereby resulting in a high risk of internal short circuit in the battery; at the same time, the electrolyte wettability of the electrode assembly deteriorates, thereby also affecting the cycle performance and rate performance of the battery.

[0081] 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 comprising 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 also 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.

[0082] 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. When 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 breaking of the electrode sheet, thereby facilitating the structural integrity of the electrode assembly. When the battery is discharged, 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, the metal battery using the separator containing the porous substrate satisfying the above condition (1) has good cycle performance and rate performance when charged and discharged for 5 minutes, the metal battery using the separator containing the porous substrate satisfying the above condition (2) has good cycle performance and rate performance when charged and discharged for 30 minutes, and the metal battery using the separator containing the porous substrate satisfying the above condition (3) has good cycle performance and rate performance when charged and discharged for 1 hour.

[0083] 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) At t = 1800 seconds, the compressive creep compliance of the porous substrate is 0.12 MPa -1 -0.36MPa -1 , (3) At t = 3600 seconds, the compressive creep compliance of the porous substrate is 0.23 MPa-1 -0.52MPa -1 .

[0084] 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.

[0085] 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.

[0086] 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.

[0087] Optionally, the porosity of the porous substrate may be 65%-95%, and the thickness of the porous substrate may be 30 μm-70 μm.

[0088] 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.

[0089] By adjusting the thickness and porosity of the porous substrate within the above range, sufficient compressible space can be provided when the metal battery is charged, and the compressed separator can still have a high porosity, which will not affect ion transmission and electrolyte infiltration, thereby enabling the battery to have good cycle performance and rate performance. In addition, the battery can also have a high volume energy density.

[0090] The thickness of the porous substrate has a well-known meaning in the art and can be measured by methods known in the art, for example, by referring to GB / T 6672-2001, Mechanical measurement method for thickness of plastic films and sheets.

[0091] The porosity of a porous substrate has a well-known meaning in the art and can be measured by methods known in the art. For example, the test can be performed with reference to GB / T 21650.2-2008, Determination of pore size distribution and porosity of solid materials by mercury intrusion and gas adsorption method Part 2: Analysis of mesopores and macropores by gas adsorption method.

[0092] In some embodiments, the average pore size of the porous substrate may be 10 nm to 200 nm, and optionally 20 nm to 60 nm.

[0093] 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.

[0094] In some embodiments, the total pore volume of pores with a pore size 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 size less than 30 nm in the porous substrate may account for more than 50% of the total pore volume of the porous substrate.

[0095] 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.

[0096] The average pore size and pore size distribution of a porous substrate have meanings known in the art and can be measured using methods known in the art. For example, the test can be performed with reference to ASTM F316-03 (2019), Standard Test Method for Characterizing Pore Size of Membrane Filters by Bubble Point and Mean Flow Pore Tests, and ASTM E1294-89 (1999).

[0097] 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.

[0098] The air permeability of a porous substrate has a well-known meaning in the art and can be measured by methods known in the art. For example, the test can be performed as follows: at 25° C., the time required for 100 mL of air to pass through the porous substrate is measured. The test instrument can be a Kumagai KRK Wangyan air permeability tester.

[0099] 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.

[0100] The BET specific surface area of ​​the porous substrate has a well-known meaning in the art and can be measured by methods known in the art. For example, it can be measured by nitrogen adsorption specific surface area analysis test method according to GB / T 19587-2017 and calculated by BET (Brunauer Emmett Teller) method. The test instrument can be the Tri-Star 3020 specific surface area pore size analysis tester of Micromeritics, USA.

[0101] In some embodiments, the porous substrate may be made of one or more of polyolefin, polyamide, polyester, polyacrylonitrile (PAN), and their derivatives. Derivatives generally refer to products derived from the substitution of hydrogen atoms or atomic groups in a polymer by other atoms or atomic groups.

[0102] Optionally, the polyester includes, but is not limited to, one or more of polyethylene terephthalate and polybutylene terephthalate.

[0103] Alternatively, the porous substrate may include one or more of polyolefins and their derivatives. Alternatively, the monomers used to form 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.

[0104] In some embodiments, the weight average molecular weight of the porous substrate may be 800,000 to 1.2 million, and may be 800,000 to 1.15 million.

[0105] In some embodiments, the porous substrate may be a single-layer film structure or a multi-layer film structure.

[0106] 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 .

[0107] In some embodiments, the tensile strength of the porous substrate in the MD direction may be greater than or equal to 1500 kg / cm 2 .

[0108] The tensile strength of the porous substrate has a well-known meaning in the art and can be measured by methods known in the art. For example, the test can be performed with reference to the standard GB / T 36363-2018. During the test, the tensile rate can be 50 mm / min. The test instrument can be a universal tensile testing machine.

[0109] In some embodiments, the elongation at break of the porous substrate in the TD direction may be greater than or equal to 60%.

[0110] In some embodiments, the elongation at break of the porous substrate in the MD direction may be greater than or equal to 60%.

[0111] The elongation at break of the porous substrate has a well-known meaning in the art and can be measured by methods known in the art. For example, the test can be performed with reference to the standard GB / T 36363-2018. During the test, the tensile rate can be 50 mm / min. The test instrument can be a universal tensile testing machine.

[0112] In some embodiments, the porous substrate may have a puncture strength of 200 gf or greater.

[0113] The puncture strength of a porous substrate has a meaning known in the art and can be measured by 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, and then clamped with a clamp 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.

[0114] In some embodiments, the thermal shrinkage of the porous substrate in the TD direction at 105° C. for 1 h may be less than or equal to 10%.

[0115] In some embodiments, the thermal shrinkage of the porous substrate in the MD direction at 105° C. for 1 h may be less than or equal to 4%.

[0116] The thermal shrinkage of the porous substrate has a well-known meaning in the art and can be measured by 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 by a punching machine, 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 reaching the set time (1h in this application), the width a1 and length a2 of the porous substrate are measured. The transverse (TD) thermal shrinkage of the porous substrate at 105°C and 1h = [(50-a1) / 50]×100%, and the longitudinal (MD) thermal shrinkage of the porous substrate at 105°C and 1h = [(100-a2) / 100]×100%.

[0117] In some embodiments, the separator 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.

[0118] Different from the negative electrode of an ionic battery, the negative electrode of a metal battery also has a more serious dendrite problem. And a porous substrate with a high porosity may lead to a weak dendrite puncture resistance. Therefore, by providing a coating on at least one surface of the porous substrate, the overall mechanical strength of the separator membrane can be enhanced, the dendrite puncture resistance of the separator membrane can be improved, and thus it is beneficial to further improve the reliability of the battery.

[0119] 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 membrane can also be enhanced, the thermal shrinkage degree of the separator membrane can be reduced, and thus it is beneficial to further improve the reliability of the battery.

[0120] 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 of the separator membrane with the electrolyte can also be improved, the wetting characteristics of the separator membrane to the electrolyte can be enhanced, and the ion transport impedance of the separator membrane can be reduced, and thus it is beneficial to further improve the cycle performance and rate performance of the battery.

[0121] 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 decomposing the dendrites growing on the negative electrode side, thereby further reducing the probability of the battery internal short circuit caused by the dendrites piercing the separator membrane, and thus it is beneficial to further improve the reliability of the battery.

[0122] In some embodiments, the dendrite reaction type particles may include one or more of lithium reaction type particles and sodium reaction type particles.

[0123] In some embodiments, the dendrite reaction type particles may include, but are not limited to, one or more of a solid electrolyte material, a metal oxide, a non-metal oxide, a metal sulfide, a non-metal sulfide, a metal nitride, a non-metal nitride, and a carbon-based material.

[0124] 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, where 0 < x < 2, 0 < y < 3), lithium aluminum zirconium phosphate (Li x Al y Zr z (PO4)3, LAZP, where 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium aluminum chromium phosphate (Li x Al y Cr z (PO4)3, LACP, where 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium lanthanum titanate (Li x La y TiO3, where 0 < x < 2, 0 < y < 3), lithium lanthanum zirconium oxide (Li7La3Zr2O 12 , LLZO), lithium lanthanum tantalum oxide (Li5La3Ta2O 12 , LLTA), lithium zinc germanium oxide (Li 14 ZnGe4O 16 ), lithium germanium phosphorus sulfide (Li 10 GeP2S 12 , LGPS), lithium thiotetraphosphate 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, carbon fluoride, or one or more of them.

[0125] In some embodiments, the volume - distribution particle size Dv50 of the dendritic reaction - type particles can be 0.01 μm - 10 μm, and can be optionally 0.05 μm - 0.5 μm.

[0126] When the volume - distribution particle size Dv50 of the dendritic reaction - type particles is within the above range, it can make the coating slurry have an appropriate viscosity, which is convenient for coating, and is also beneficial to improving the uniformity of the coating and reducing the "powder dropping" phenomenon; in addition, it can also reduce the problem of pore blockage, thereby improving the gas permeability and ion - transport characteristics of the separator, and further being beneficial to improving the cycle performance and rate performance of the battery.

[0127] The meaning of Dv50 of the material is well - known in the art and can be measured by instruments and methods known in the art. For example, it can be conveniently measured by a laser particle size analyzer (such as Malvern Mastersizer 3000) with reference to GB / T 19077 - 2016. The physical definition of Dv50 is the particle size corresponding to when the cumulative volume - distribution percentage of the material reaches 50%.

[0128] In some embodiments, the coating can include a binder.

[0129] In some embodiments, the binder may include one or more of a vinyl fluoride polymer and styrene-butadiene rubber. The vinyl 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.

[0130] In some embodiments, the mass ratio of the dendrite reactive particles to the binder may be 1:(0.005-0.05), and may be optionally 1:(0.01-0.03).

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

[0132] 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, polyethylene imine, and their respective derivatives. Derivatives generally refer to products derived from the substitution of hydrogen atoms or atomic groups in a polymer by other atoms or atomic groups.

[0133] Optionally, the weight ratio of the dendrite reactive particles to the dispersant may be 1:(0.01-0.02), and may be 1:(0.010-0.015).

[0134] 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.

[0135] In some embodiments, the coating may also include a thickener.

[0136] Optionally, the thickener may include, but is not limited to, one or more of sodium hydroxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, polyacrylate, polyurethane, and polyether.

[0137] 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).

[0138] An appropriate amount of thickener can improve the stability of the slurry, facilitate coating, and help increase the film weight of the coating.

[0139] In some embodiments, the thickness of the coating layer may be 1 μm-10 μm, and may be 1.5 μm-4.5 μm. The thickness of the coating layer refers to the thickness of the coating layer on one side of the porous substrate.

[0140] When the thickness of the coating is within the above range, the isolation membrane's resistance to dendrite penetration, heat resistance and electrolyte wettability can be improved, thereby helping to improve the reliability of the battery; the isolation membrane can also have a lower internal resistance and good ion transport properties, thereby helping the battery to have good cycle performance and / or rate performance.

[0141] 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 .

[0142] [Method for preparing isolation film]

[0143] The present application also provides a method for preparing a separator, which includes 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, removing the pore-forming agent with a solvent, and obtaining a porous substrate. The molten mixture of the polymer resin raw material and the pore-forming agent is pressed into a film by utilizing the solid-liquid phase separation or liquid-liquid phase separation during the cooling process, and then the pore-forming agent is extracted from the film with a solvent to prepare a porous substrate.

[0144] In some embodiments, the step 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.

[0145] In some embodiments, the step 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.

[0146] The method for adjusting the porosity, average pore size, and pore size distribution of the porous substrate may include at least one of the following: adjusting 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, the stretching ratio, and other parameters.

[0147] 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, and can be optionally 800,000-1.15 million.

[0148] 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.

[0149] 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 optionally 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 optionally 10 g / 10 min or less. Optionally, the melt flow index of the polymer resin raw material is 3 g / 10mi-10 g / 10min, 3.5 g / 10mi-7.5 g / 10min.

[0150] As a method for adjusting the porosity, average pore size, pore size distribution and compression creep compliance of the porous substrate, the amount of pore former used can be more than 30 parts by weight, and can be optionally 40 parts by weight to 58 parts by weight, and can be more optionally 42 parts by weight to 55 parts by weight, relative to 100 parts by weight of the polymer resin raw material and the pore former.

[0151] 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, and may be optionally 120°C-140°C.

[0152] As a method for adjusting the porosity, average pore size, pore size distribution and compressive creep compliance of the porous substrate, the stretching ratio of the diaphragm in the transverse direction (TD) can be greater than 4.5 times, and can be optionally 4.5 times-8 times, 4.5 times-6 times, and the stretching ratio of the diaphragm in the longitudinal direction (MD) can be greater than 6.5 times, and can be optionally 6.5 times-10 times, 6.5 times-8 times.

[0153] 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.

[0154] As an example, the pore-forming agent may include one or more of white oil, paraffin oil, phthalates, aliphatic dibasic acid esters, and phosphate esters. Optionally, the molecular weight of the pore-forming agent is less than 10,000.

[0155] The solvent for removing the pore former may include one or more of dichloromethane and trichloroethylene.

[0156] The method 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, the stretching ratio, etc.

[0157] In some embodiments, when preparing the porous substrate, some additives, such as antioxidants, etc., may be added to the raw materials.

[0158] 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 obtaining the isolation membrane after drying.

[0159] In some embodiments, the drying temperature of the coating slurry may be 60°C-80°C.

[0160] In some embodiments, the coating slurry may be coated by methods including, but not limited to, gravure transfer coating, spin spray coating, dip coating, blade coating, and the like.

[0161] 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).

[0162] In some embodiments, the solid content of the coating slurry may be 25%-45%, and optionally 30%-40%, thereby facilitating coating.

[0163] In some embodiments, the coating slurry may include dendrite-reactive particles, a binder, and a solvent.

[0164] In some embodiments, the coating slurry may further include a dispersant and / or a thickener.

[0165] In some embodiments, the step of providing a coating slurry may include the following steps: dispersing the dendrite reactive 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.

[0166] 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.

[0167] 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.

[0168] Some parameters such as raw materials and their contents used in the preparation method of the isolation film provided in the embodiments of the present application can refer to the isolation film provided in the embodiments of the present application, and will not be repeated here.

[0169] Unless otherwise specified, all raw materials used in the method for preparing the isolation membrane can be obtained commercially.

[0170] [Positive electrode]

[0171] The battery cell includes a positive electrode plate.

[0172] 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 including a positive electrode active material. For example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0173] In some embodiments, the positive electrode active material includes a material capable of extracting and inserting lithium.

[0174] 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.

[0175] 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 of 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.

[0176] In some embodiments, the positive electrode active material may include both lithium transition metal oxide and lithium-containing phosphate, thereby facilitating obtaining a battery having both large capacity and high reliability.

[0177] As an example, the positive electrode active material may include but is not limited to LiCoO2, LiNiO2, LiMnO2, LiNi 1 / 2 Mn 1 / 2O2, 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), LiNi 0.6 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.

[0178] In some embodiments, the positive electrode active material includes a material capable of extracting and embedding 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.

[0179] 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, and Mo), NaMO2 (M includes at least two of Fe, Co, Ni, V, Ti, and 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.

[0180] The modified compounds of the above-mentioned positive electrode active materials may be the ones that undergo doping modification and / or surface coating modification on the positive electrode active materials.

[0181] In some embodiments, the positive electrode film layer may also 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.

[0182] In some embodiments, the positive electrode film layer may also 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), carboxymethyl chitosan (CMCS) One or more.

[0183] 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).

[0184] The positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, the optional positive electrode conductive agent, the optional positive electrode binder and any other components in a solvent and stirring them uniformly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0185] [Negative electrode]

[0186] The battery cell includes a negative electrode plate.

[0187] 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, and 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.

[0188] The lithium alloy may be an alloy formed by metallic lithium and other metallic elements or non-metallic elements. As an 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.

[0189] The sodium alloy may be an alloy formed by metallic sodium and other metallic elements or non-metallic elements. As an 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.

[0190] In some embodiments, the negative electrode sheet may include a negative electrode current collector but not a metal layer to be assembled into a negative electrode metal-free battery cell.

[0191] In some embodiments, in order to improve battery performance, the negative electrode side of the negative electrode metal-free battery may also be provided with some conventional substances that can be used as negative electrode active materials, such as carbon materials, etc. Although these substances have a certain capacity, due to their low content and not being used as the main negative electrode active material in the battery cell, the battery cell thus constructed can still be regarded as a negative electrode metal-free battery cell.

[0192] 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 an example of a metal foil, copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, and aluminum alloy foil may be used. As an example of a three-dimensional porous current collector, 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).

[0193] [Electrolytes]

[0194] The battery cells include an electrolyte.

[0195] In some embodiments, the electrolyte is an electrolyte solution including an electrolyte salt and an organic solvent.

[0196] In some embodiments, the electrolyte includes anions, which may include bis(fluorosulfonyl)imide anions (FSI - ), bis(trifluoromethanesulfonyl)imide anion (TFSI - ), borate oxalate anion (BOB - ), difluorooxalatoborate anion (DFOB - ), difluorobis(oxalate)phosphate anion (DFOP - ), tetrafluorooxalophosphate anion (TFOP - ), difluorophosphate anion (PO2F2 - ), hexafluorophosphate anion (PF6 - ), tetrafluoroborate anion (BF4 - ), hexafluoroarsenate anion (AsF6 - ), trifluoromethanesulfonate anion (CF3SO3 - )

[0197] In some embodiments, the electrolyte includes cations, and the cations may include one or more of lithium ions and sodium ions.

[0198] In some embodiments, the concentration of the electrolyte salt may be 0.3 mol / L or more, and may be 0.7 mol / L or more, and the concentration of the electrolyte salt may be 4 mol / L or less, and may be 2.5 mol / L or less, or 1.7 mol / L or less. When the concentration of the electrolyte salt is within the above range, the electrolyte solution may have a suitable ionic conductivity.

[0199] Organic solvents may include, but are not limited to, one or more of esters, ethers, sulfones, nitriles, etc. Esters may include, but are not limited to, one or more of carbonates, phosphates, carboxylates, sulfates, sulfonates, etc. Carbonates may include cyclic carbonates and / or linear carbonates, and optionally, carbonates may include cyclic carbonates and linear carbonates simultaneously. Linear carbonates may include low-viscosity polar linear carbonates, aliphatic branched-chain carbonates, etc.

[0200] 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-trifluoromethylhexafluoropropylmethyl ether, 2-trifluoromethylhexafluoropropylethyl ether, 2-trifluoromethylhexafluoropropylpropyl ether, 3-trifluoromethyloctafluorobutylmethyl ether, 3-trifluoromethyloctafluorobutylethyl ether, 4-trifluoromethyl The invention further comprises 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 hexadecafluorooctyl methyl ether, 7-trifluoromethyl hexadecafluorooctyl ethyl ether, and 7-trifluoromethyl hexadecafluorooctyl propyl ether.

[0201] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, and additives that improve battery low temperature power performance.

[0202] The preparation method of battery cells is well known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, the separator, and the 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, and the above-mentioned electrolyte is injected after drying. After vacuum packaging, standing, formation and other processes, a battery cell is obtained. Multiple battery cells can also be further connected in series, in parallel or in mixed connection to form a battery module. Multiple battery modules can also be connected in series, in parallel or in mixed connection to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.

[0203] 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 and a satellite, an energy storage system, etc.

[0204] The electric device can select the type of battery according to its usage requirements, such as a battery cell, a battery module or a battery pack.

[0205] Figure 6 Schematic diagram of an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the requirements of the electric device for high power and high energy density, a battery pack or a battery module may be used.

[0206] As another example, the electric device may be a mobile phone, a tablet computer, a notebook computer, etc. The electric device is usually required to be light and thin, and a battery cell may be used as a power source.

[0207] Example

[0208] The following examples describe the disclosure of the present application in more detail, and these examples are intended for illustrative purposes only, as various modifications and variations within the scope of the disclosure of the present application are apparent to those skilled in the art. Unless otherwise stated, 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 can be used directly without further processing, and the instruments used in the examples are commercially available.

[0209] Example 1

[0210] Preparation of porous substrates

[0211] The raw materials were weighed and mixed uniformly according to the following weight proportions: 60 weight proportions of ultra-high molecular weight polyethylene with a weight average molecular weight of 1.1 million and 40 weight proportions of white oil with a weight average molecular weight of 1000.

[0212] The above two substances were mixed and recorded as 100 parts by weight, and 3 parts by weight of butylated hydroxytoluene and 3 parts by weight of phosphite were added thereto as antioxidants.

[0213] The above raw materials are passed through a twin-screw extruder at 210°C to obtain a high-temperature melt, which is accurately metered by a melt pump and fed into a die head, and the high-temperature melt fed into the die head flows out from the die head slit, and the high-temperature melt flowing out from the die head slit is extruded through a 30°C chilled roller to obtain a film. The melt flow index (DIN 53 735) of the high-temperature melt at 230°C and a load of 2.16kg is 5.5g / 10min.

[0214] 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.

[0215] The film containing the pore-forming agent is fully soaked in dichloromethane for 20 minutes to remove the pore-forming agent, and then the dichloromethane is volatilized by a drying process at 40° C. to obtain a microporous film.

[0216] 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%.

[0217] Preparation of isolation membrane

[0218] Li 1.3 Al 0.3 Ti 1.7 (PO4)3 powder was evenly dispersed in NMP, and hydrolyzed polymaleic anhydride was added for ultrasonic dispersion. After ultrasonic dispersion for 2 hours, sodium hydroxymethyl cellulose was added for secondary dispersion, and then PVDF was 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.

[0219] 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.

[0220] Example 2

[0221] The method for preparing the isolation membrane is similar to that of Example 1, except that the preparation process of the porous substrate is different.

[0222] The following raw materials were weighed and mixed evenly: 57 parts by weight of ultra-high molecular weight polyethylene with a weight average molecular weight of 1,000,000, and 43 parts by weight of white oil with a weight average molecular weight of 1,000. The above two materials were mixed and recorded as 100 parts by weight, and 3 parts by weight of butylated hydroxytoluene and 3 parts by weight of phosphite were added thereto as antioxidants.

[0223] The above raw materials are passed through a twin-screw extruder at 210°C to obtain a high-temperature melt, which is accurately metered by a melt pump and fed into a die head, and the high-temperature melt fed into the die head flows out from the die head slit, and the high-temperature melt flowing out from the die head slit is extruded through a 30°C chilled roller to obtain a film. The melt flow index (DIN 53 735) of the high-temperature melt at 230°C and a load of 2.16kg is 5.2g / 10min.

[0224] 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.

[0225] The film containing the pore-forming agent is fully soaked in dichloromethane for 20 minutes to remove the pore-forming agent, and then the dichloromethane is volatilized by a drying process at 40° C. to obtain a microporous film.

[0226] 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%.

[0227] Example 3

[0228] 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.

[0229] The following raw materials were weighed and mixed evenly: 55 parts by weight of ultra-high molecular weight polyethylene 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 above two materials were mixed and recorded as 100 parts by weight, and 3 parts by weight of butylated hydroxytoluene and 3 parts by weight of phosphite were added thereto as antioxidants.

[0230] The above raw materials are passed through a twin-screw extruder at 210°C to obtain a high-temperature melt, which is accurately metered by a melt pump and fed into a die head, and the high-temperature melt fed into the die head flows out from the die head slit, and the high-temperature melt flowing out from the die head slit is extruded through a 30°C chilled roller to obtain a film. The melt flow index (DIN 53 735) of the high-temperature melt at 230°C and a load of 2.16kg is 5.5g / 10min.

[0231] 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.

[0232] The film containing the pore-forming agent is fully soaked in dichloromethane for 20 minutes to remove the pore-forming agent, and then the dichloromethane is volatilized by a drying process at 40° C. to obtain a microporous film.

[0233] 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%.

[0234] Example 4

[0235] 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.

[0236] The following raw materials were weighed and mixed evenly: 50 parts by weight of ultra-high molecular weight polyethylene with a weight average molecular weight of 850,000 and 50 parts by weight of white oil with a weight average molecular weight of 1000. The above two materials were mixed and recorded as 100 parts by weight, and 3 parts by weight of butylated hydroxytoluene and 3 parts by weight of phosphite were added thereto as antioxidants.

[0237] The above raw materials are passed through a twin-screw extruder at 210°C to obtain a high-temperature melt, which is accurately metered by a melt pump and fed into a die head, and the high-temperature melt fed into the die head flows out from the die head slit, and the high-temperature melt flowing out from the die head slit is extruded through a 30°C chilled roller to obtain a film. The melt flow index (DIN 53 735) of the high-temperature melt at 230°C and a load of 2.16kg is 6.4g / 10min.

[0238] 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.

[0239] The film containing the pore-forming agent is fully soaked in dichloromethane for 20 minutes to remove the pore-forming agent, and then the dichloromethane is volatilized by a drying process at 40° C. to obtain a microporous film.

[0240] 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%.

[0241] Example 5

[0242] 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.

[0243] The following raw materials were weighed and mixed evenly: 45 parts by weight of ultra-high molecular weight polyethylene 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 above two materials were mixed and recorded as 100 parts by weight, and 3 parts by weight of butylated hydroxytoluene and 3 parts by weight of phosphite were added thereto as antioxidants.

[0244] The above raw materials are passed through a twin-screw extruder at 210°C to obtain a high-temperature melt, which is accurately metered by a melt pump and fed into a die head, and the high-temperature melt fed into the die head flows out from the die head slit, and the high-temperature melt flowing out from the die head slit is extruded through a 30°C chilled roller to obtain a film. The melt flow index (DIN 53 735) of the high-temperature melt at 230°C and a load of 2.16kg is 7.5g / 10min.

[0245] The extruded film sheet 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 former.

[0246] The film containing the pore-forming agent is fully soaked in dichloromethane for 20 minutes to remove the pore-forming agent, and then the dichloromethane is volatilized by a drying process at 40° C. to obtain a microporous film.

[0247] 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%.

[0248] Comparative Example 1

[0249] 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.

[0250] The following raw materials were weighed and mixed evenly: 55 parts by weight of high-density polyethylene with a weight average molecular weight of 300,000 and 45 parts by weight of white oil with a weight average molecular weight of 1000. The above two materials were mixed and recorded as 100 parts by weight, and 3 parts by weight of butylated hydroxytoluene and 3 parts by weight of phosphite were added thereto as antioxidants.

[0251] The above raw materials are passed through a twin-screw extruder at 210°C to obtain a high-temperature melt, which is accurately metered by a melt pump and fed into a die head, and the high-temperature melt fed into the die head flows out from the die head slit, and the high-temperature melt flowing out from the die head slit is extruded through a 30°C chilled roller to obtain a film. The melt flow index (DIN 53 735) of the high-temperature melt at 230°C and a load of 2.16kg is 32g / 10min.

[0252] The extruded film sheet was 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.

[0253] The film containing the pore-forming agent is fully soaked in dichloromethane for 20 minutes to remove the pore-forming agent, and then the dichloromethane is volatilized by a drying process at 40° C. to obtain a microporous film.

[0254] 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%.

[0255] Comparative Example 2

[0256] 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.

[0257] The following raw materials were weighed and mixed evenly: 40 parts by weight of ultra-high molecular weight polyethylene with a weight average molecular weight of 1.2 million and 60 parts by weight of white oil with a weight average molecular weight of 1000. The above two materials were mixed and recorded as 100 parts by weight, and 3 parts by weight of butylated hydroxytoluene and 3 parts by weight of phosphite were added thereto as antioxidants.

[0258] The above raw materials are passed through a twin-screw extruder at 210°C to obtain a high-temperature melt, which is accurately metered by a melt pump and fed into a die head, and the high-temperature melt fed into the die head flows out from the die head slit, and the high-temperature melt flowing out from the die head slit is extruded through a 30°C chilled roller to obtain a film. The melt flow index (DIN 53 735) of the high-temperature melt at 230°C and a load of 2.16kg is 12g / 10min.

[0259] 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 former.

[0260] The film containing the pore-forming agent is fully soaked in dichloromethane for 20 minutes to remove the pore-forming agent, and then the dichloromethane is volatilized by a drying process at 40° C. to obtain a microporous film.

[0261] 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%.

[0262] Testing of porous substrates

[0263] The thickness of the porous substrate is measured with reference to GB / T 6672-2001, Mechanical measurement method for thickness of plastic films and sheets.

[0264] The porosity of the porous substrate is tested with reference to GB / T 21650.2-2008, Determination of pore size distribution and porosity of solid materials by mercury intrusion and gas adsorption method Part 2: Analysis of mesopores and macropores by gas adsorption method.

[0265] The average pore size and pore size distribution of the porous substrate are tested according to ASTM F316-03 (2019), Standard Test Method for Characterizing the Pore Size of Membrane Filters by Bubble Point and Mean Flow Pore Tests, and ASTM E1294-89 (1999).

[0266] The compressive creep compliance of the porous substrate is tested using a Kappa SS-CF creep tester. The temperature during the test is 25°C and the pressure is kept constant. The compressive creep compliance of the porous substrate refers to the reciprocal of the compressive creep elastic modulus tested in accordance with GB / T 41061-2021 under the conditions of a temperature of 25°C, a humidity of 10%, and a stress of 1MPa 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.

[0267] Next, the above-mentioned isolation membranes were assembled into button-type batteries, and the cycle performance and rate performance were tested.

[0268] The button cell can be prepared as follows.

[0269] Lithium iron phosphate, conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are mixed evenly in an appropriate amount of solvent N-methylpyrrolidone (NMP) at a weight ratio of 8:1:1 to obtain a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector aluminum foil and dried to obtain a positive electrode plate. In an argon-protected glove box, the positive electrode plate, the above-mentioned isolation film and the lithium sheet are assembled into a CR2430 button battery. The electrolyte salt of the electrolyte is LiFSI with a concentration of 1 mol / L, and the solvent of the electrolyte is ethylene glycol dimethyl ether.

[0270] The coating layers of the separators of Examples 1 to 5 and Comparative Examples 1 to 2 all faced the lithium sheet.

[0271] At 25°C, the button cell was charged to 3.65V at 0.1C constant current, and then charged to 0.05C at 3.65V constant voltage; after the button cell was left to stand for 10 minutes, it was discharged to 2.5V at 0.1C constant current. After the button cell was cycled twice according to the above method, the following cycle performance test was performed.

[0272] The button cell was charged to 3.65V at 0.5C, 1C, and 2C rates respectively, and then charged to 0.05C at 3.65V; after the button cell was left to stand for 10 minutes, it was discharged to 2.5V at 0.2C constant current to obtain. The button cell was cycled 100 times according to the above method to obtain the charging capacity of the 100th cycle and the discharge capacity of the 100th cycle. The coulomb efficiency of the button cell cycled 100 times = the discharge capacity of the 100th cycle / the charging capacity of the 100th cycle.

[0273] During the test, the number of button cell samples may be more than 6, and the test results shall be averaged.

[0274] The test results are shown in Table 1.

[0275] Table 1

[0276]

[0277] It can be seen from the test results of Examples 1 to 5 and Comparative Examples 1 to 2 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.

[0278] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of 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, characterized in that: 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, characterized in that: 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, characterized in that: 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 membrane according to any one of claims 1 to 3, characterized in that: 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, characterized in that: 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, characterized in that: 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 membrane according to any one of claims 1 to 6, characterized in that: 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 membrane according to any one of claims 1 to 7, characterized in that: 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, characterized in that: 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, characterized in that: The coating includes 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, characterized in that: 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 membrane according to any one of claims 10 to 11, characterized in that: 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 membrane according to any one of claims 10 to 12, characterized in that: 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 membrane according to any one of claims 9 to 13, characterized in that: The thickness of the coating is 1 μm-10 μm, and can be optionally 1.5 μm-4.5 μm.

15. A battery cell, characterized in that: The isolation film comprises the isolation film according to any one of claims 1 to 14, and 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, characterized in that: Comprising the battery cell according to claim 15.

17. An electrical device, characterized in that: The battery according to claim 16 is used to provide electrical energy.

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