Isolating membrane, battery monomer, battery and electric device

Abstract

The invention discloses an isolating membrane, a battery monomer, a battery and a power utilization device, the battery monomer comprises a positive pole piece, a negative pole piece and the isolating membrane, the isolating membrane comprises a porous base material, and a first coating and a second coating which are respectively positioned on two sides of the porous base material, the first coating comprises a first solid electrolyte material, the second coating comprises graphene oxide, and the first solid electrolyte material comprises a second solid electrolyte material. The first coating faces the positive pole piece, and the second coating faces the negative pole piece. According to the invention, the battery has good cycle performance and good 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] With the application and promotion of batteries, their reliability and service life have received more and more attention. During the battery charging and discharging process, the dendrite problem on the negative electrode is one of the important reasons affecting the reliability and service life of the battery. How to slow down the growth of dendrites without affecting the electrochemical performance and / or kinetic performance of the battery is a technical problem that needs to be solved urgently. Summary of the invention

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

[0004] In a first aspect, the present application provides a battery cell comprising a positive electrode sheet, a negative electrode sheet and a separator, wherein the separator comprises a porous substrate and a first coating and a second coating respectively located on both sides of the porous substrate, wherein the first coating comprises a first solid electrolyte material, and the second coating comprises graphene oxide, wherein the first coating faces the positive electrode sheet and the second coating faces the negative electrode sheet.

[0005] Starting from the structure of the isolation membrane, the present application provides a first coating including a first solid electrolyte material and a second coating including graphene oxide on both sides of a porous substrate, and makes the first coating face the positive electrode sheet and the second coating face the negative electrode sheet, so that the battery can have high reliability, good cycle performance and good rate performance.

[0006] In some embodiments, the weight content of the first solid electrolyte material in the first coating is greater than or equal to 80wt%, and can be optionally 90wt%-98wt%, based on the total weight of the first coating. By making the first coating mainly include the first solid electrolyte material, the ion concentration and ion conductivity on both sides of the separator can be better balanced, thereby further promoting balanced ion transmission, reducing the risk of dendrite formation at the negative electrode, and improving the reliability, cycle performance and rate performance of the battery.

[0007] In some embodiments, the weight content of the graphene oxide in the second coating is greater than or equal to 10wt%, and can be optionally 15wt%-22wt%, based on the total weight of the second coating. By making the content of graphene oxide within the above range, it is beneficial to improve the ionic conductivity of the isolation membrane, improve the ion conduction capacity of the isolation membrane, and better eliminate the dendrites grown on the negative electrode.

[0008] In some embodiments, the second coating further includes inorganic particles, and the weight content of the inorganic particles in the second coating is greater than or equal to 66 wt%, optionally 75 wt% - 82 wt%, based on the total weight of the second coating. By making the content of the inorganic particles within the above range, the air permeability of the separator can be better improved, the ion conduction ability of the separator can be improved, and the separator can also have better mechanical strength, puncture resistance and heat resistance.

[0009] In some embodiments, the inorganic particles include one or more of ceramics and a second solid electrolyte material.

[0010] In some embodiments, the volume distribution particle size Dv50 of the inorganic particles is 0.01 μm - 0.8 μm, optionally 0.03 μm - 0.5 μm. By adjusting the volume distribution particle size Dv50 of the inorganic particles in the second coating within the above range, the air permeability of the separator can be better improved, and the ion conduction ability of the separator can be improved.

[0011] In some embodiments, the graphene oxide is in a flake shape, the diameter of the flake graphene oxide is denoted as d1, the volume distribution particle size Dv50 of the inorganic particles is denoted as d2, with the unit being μm, and d1 / d2 is 0.5 - 2. By adjusting the diameter of the flake graphene oxide and the volume distribution particle size Dv50 of the inorganic particles in the second coating within the above range, the air permeability of the separator can be better improved, and the ion conduction ability of the separator can be improved.

[0012] In some embodiments, the second solid electrolyte material includes an inorganic solid electrolyte.

[0013] In some embodiments, the second solid electrolyte material includes an inorganic solid electrolyte, and the ionic conductivity of the inorganic solid electrolyte is greater than or equal to 10 -6 S / cm.

[0014] In some embodiments, the second solid electrolyte material includes an inorganic solid electrolyte, and the inorganic solid electrolyte includes one or more of oxide-based inorganic solid electrolytes, sulfide-based inorganic solid electrolytes or halide-based inorganic solid electrolytes.

[0015] In some embodiments, the graphene oxide is in a flake shape, and the diameter of the flake graphene oxide is 0.01 μm - 0.5 μm, optionally 0.05 μm - 0.4 μm. When the diameter of the flake graphene oxide is within the above range, it is beneficial to improve the ionic conductivity of the separator, improve the ion conduction ability of the separator, and can also better eliminate the dendrites growing on the negative electrode.

[0016] In some embodiments, the weight content of the O element in the graphene oxide is 20 wt% - 70 wt%, and may be optionally 30 wt% - 60 wt%. The higher the content of the O element in the graphene oxide, the higher its oxidation degree, and the content of hydrophilic oxygen-containing functional groups such as hydroxyl (-OH), carboxyl (-COOH), and aldehyde (-CHO) increases. Thereby, it is beneficial to improve the electrolyte wettability of the separator membrane. The higher the content of the O element in the graphene oxide, the better its electron insulation property, the risk of leakage current caused by electrons passing through the separator membrane is reduced, and in addition, the risk of side reactions occurring in the second coating through electron transfer is reduced, and the stability of the second coating is improved.

[0017] In some embodiments, the interlayer spacing of the graphene oxide is 0.1 nm - 10 nm, and may be optionally 0.4 nm - 3 nm.

[0018] In some embodiments, the number of layers of the graphene oxide is 1 - 10, and may be optionally 2 - 6.

[0019] In some embodiments, the ratio of the thickness of the first coating to the thickness of the second coating is (1 - 5):1, and may be optionally (1 - 3):1. Thereby, it is beneficial to further eliminate dendrites and reduce the risk of internal short circuit of the battery caused by dendrites piercing through the separator membrane and contacting the positive electrode.

[0020] In some embodiments, the sum of the thickness of the first coating and the thickness of the second coating is 2 μm - 8 μm, and may be optionally 3 μm - 5 μm. When the sum of the thickness of the first coating and the thickness of the second coating is within the above range, it is beneficial to improve the gas permeability of the separator membrane and reduce the battery impedance, thereby being beneficial to improving the cycle performance and rate performance of the battery.

[0021] In some embodiments, the thickness of the first coating is 0.5 μm - 5 μm, and may be optionally 1 μm - 3 μm. When the thickness of the first coating is within the above range, it can better play the role of eliminating dendrites and reducing the risk of internal short circuit of the battery caused by dendrites piercing through the separator membrane and contacting the positive electrode, and can also make the separator membrane have good gas permeability and the battery have a small impedance, thereby being beneficial to improving the cycle performance and rate performance of the battery.

[0022] In some embodiments, the thickness of the second coating is 0.1 μm - 3 μm, and may be optionally 0.5 μm - 2 μm. When the thickness of the second coating is within the above range, it can not only provide a high content of graphene oxide to eliminate dendrites growing on the negative electrode, but also avoid excessive consumption of active substances by too high a content of graphene oxide and reduce the battery capacity, and is also beneficial to improving the infiltration characteristics of the separator membrane for the electrolyte and reducing the ion transport impedance of the separator membrane, and further being beneficial to the battery having good cycle performance and rate performance.

[0023] In some embodiments, the first solid electrolyte material includes an inorganic solid electrolyte.

[0024] In some embodiments, the first solid electrolyte material includes an inorganic solid electrolyte, and the ionic conductivity of the inorganic solid electrolyte is greater than or equal to 10 -6 S / cm.

[0025] In some embodiments, the first solid electrolyte material includes an inorganic solid electrolyte, and the inorganic solid electrolyte includes one or more of an oxide-based inorganic solid electrolyte, a sulfide-based inorganic solid electrolyte, or a halide-based inorganic solid electrolyte.

[0026] In some embodiments, the volume distribution particle size Dv50 of the first solid electrolyte material is 0.02 μm - 2 μm. When the volume distribution particle size Dv50 of the first solid electrolyte material is within the above range, it is beneficial to balance the ion concentration and ionic conductivity on both sides of the separator, thereby promoting the balanced ion transport, reducing the risk of dendrite formation on the negative electrode, and also improving the reliability, cycle performance, and rate performance of the battery.

[0027] In some embodiments, the first coating further includes a first binder and / or a first dispersant.

[0028] In some embodiments, the second coating further includes a second binder and / or a second dispersant.

[0029] In some embodiments, the total thickness of the separator is 7 μm - 35 μm, and may be optionally 10 μm - 15 μm.

[0030] In some embodiments, the porosity of the separator is 25% - 50%, and may be optionally 30% - 45%.

[0031] When the total thickness and / or porosity of the separator is within the above range, the separator can have good ion conduction ability and low impedance.

[0032] In some embodiments, the thickness of the porous substrate is 5 μm - 25 μm, and may be optionally 5 μm - 12 μm.

[0033] In some embodiments, the porosity of the porous substrate is 25% - 60%, and may be optionally 30% - 50%.

[0034] When the thickness and / or porosity of the porous substrate is within the above range, the separator can have good ion conduction ability and low impedance.

[0035] In some embodiments, the porous substrate includes one or more of polyolefin, polyamide, polyester, and their respective derivatives.

[0036] In some embodiments, the battery cell includes at least one of a lithium metal battery cell, a lithium metal battery cell without a negative electrode, a sodium metal battery cell, and a sodium metal battery cell without a negative electrode.

[0037] In a second aspect, the present application provides a separator, which includes a porous substrate, and a first coating and a second coating respectively located on both sides of the porous substrate. The first coating is the first coating of the first aspect of the present application, and the second coating is the second coating of the first aspect of the present application.

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

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

[0040] The electrical device of the present application includes the battery provided by the present application, and thus has at least the same advantages as the battery. Description of the Drawings

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and those of ordinary skill in the art can also obtain other drawings according to the drawings without creative efforts.

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

[0043] Figure 2 Exploded schematic diagram showing a battery cell provided by some embodiments of the present application.

[0044] Figure 3 Schematic diagram showing a battery module provided by some embodiments of the present application.

[0045] Figure 4 Schematic diagram showing a battery pack provided by some embodiments of the present application.

[0046] Figure 5 is Figure 4 Exploded schematic diagram of the battery pack shown.

[0047] Figure 6 Schematic diagram showing an electrical device provided by some embodiments of the present application.

[0048] In the drawings, the drawings are not necessarily drawn to actual scale.

[0049] The description of the reference numerals in the drawings is as follows: 1. Battery pack; 2. Upper box body; 3. Lower box body; 4. Battery module; 5. Battery cell; 51. Housing; 52. Electrode assembly; 53. Cover plate. Detailed implementation manners

[0050] Hereinafter, the implementation manners of the separator, battery cell, battery, and electrical device of the present application specifically disclosed will be described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where the detailed descriptions of well-known matters and the repeated descriptions of actually identical structures are omitted. This is to prevent 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 recited in the claims.

[0051] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The range defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when it is stated that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0052] If there is no special description, all the implementation manners and optional implementation manners of the present application can be combined with each other to form a new technical solution, and such a technical solution should be considered to be included in the disclosure content of the present application.

[0053] If there is no special description, all the technical features and optional technical features of the present application can be combined with each other to form a new technical solution, and such a technical solution should be considered to be included in the disclosure content of the present application.

[0054] Unless otherwise specified, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or steps (b) and (a) carried out sequentially. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0055] In this application, the terms "a plurality of" and "a variety of" mean two or more than two.

[0056] In the description of the embodiments of this application, unless otherwise specified, the first feature being "on" or "under" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may mean that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may mean that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0057] Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art.

[0058] Unless otherwise specified, the values of the various parameters mentioned in this application can be measured by various commonly used testing methods in the art. For example, they can be measured according to the testing methods given in the embodiments of this application. Unless otherwise specified, the test temperature for each parameter is 25 °C.

[0059] Unless otherwise specified, the testing instruments mentioned in this application can be operated according to the requirements of the product specification when in use.

[0060] The battery mentioned in the embodiments of this application can be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application can include battery cells, battery modules or battery packs, etc.

[0061] A battery cell is the smallest unit that makes up a battery and can independently perform the functions of charging and discharging. The battery cell can be in the shape of a cylinder, a cuboid or other shapes, etc., and the embodiments of this application do not limit this. For example, Figure 1 is a battery cell 5 in the shape of a cuboid as an example.

[0062] When there are multiple battery cells, the multiple battery cells are connected in series, parallel or in a hybrid connection through a busbar component. In some embodiments, the battery can 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 can be a battery pack, and the battery pack includes a box body and battery cells, and the battery cells or battery modules are accommodated in the box body. In some embodiments, the box body can be a part of the chassis structure of a vehicle. For example, a part of the box body can become at least a part of the vehicle floor, or a part of the box body can become at least a part of the cross beams and longitudinal beams of the vehicle.

[0063] In some embodiments, the battery can be an energy storage device. The energy storage device includes an energy storage container, an energy storage electrical cabinet, etc.

[0064] Generally, a battery cell includes an electrode assembly and an electrolyte. The electrode assembly can be a wound structure or a laminated structure, and the embodiments of the present application do not limit this.

[0065] The battery cell may further include an outer package, and the outer package can be used to encapsulate the electrode assembly and the electrolyte. The outer package can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).

[0066] In some embodiments, as Figure 2 shown, the outer package may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The electrode assembly 52 is encapsulated in the receiving cavity. The number of electrode assemblies 52 included in the battery cell 5 can be one or more, and can be adjusted according to requirements.

[0067] In some embodiments, battery cells can be assembled into a battery module, and the number of battery cells included in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. Figure 3 is a schematic diagram of a battery module 4 as an example. As Figure 3 shown, in the battery module 4, multiple battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other way. Further, the multiple battery cells 5 can be fixed by fasteners.

[0068] Optionally, the battery module 4 may further include a housing having a receiving space, and the multiple battery cells 5 are accommodated in the receiving space.

[0069] In some embodiments, the above battery modules can also be assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0070] Figure 4 and Figure 5 is a schematic diagram of a battery pack 1 as an example. As Figure 4 and Figure 5 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. 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 can be arranged in the box body in any manner.

[0071] The battery cell provided by the embodiment of the present application can be a metal battery cell. For example, it can include a lithium metal battery cell, a lithium metal battery cell without a negative electrode, a sodium metal battery cell, a sodium metal battery cell without a negative electrode, etc.

[0072] A battery cell without a negative electrode generally refers to a battery cell that does not actively provide a negative electrode active material layer on the negative electrode side during the manufacturing process of the battery cell. For example, during the manufacturing process of the battery cell, a layer is not provided on 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 charging, ions obtain electrons on the negative electrode side and deposit on the surface of the negative electrode current collector to form a metal. During discharging, 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 battery cell without a negative electrode 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 substances that can be used as conventional negative electrode active materials, such as carbon materials, can also be provided on the negative electrode side of the battery cell without a negative electrode. Although these substances have a certain capacity, due to their small content and not being used as the main negative electrode active material in the battery cell, the battery cell thus constituted can still be regarded as a battery cell without a negative electrode. 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 can be less than or equal to 0.1. The CB value is the unit area capacity of the negative electrode in the battery cell divided by the unit area capacity of the positive electrode. Since a battery cell without a negative electrode does not contain or only contains 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.

[0073] The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator, and the separator is located between the positive electrode plate and the negative electrode plate.

[0074] Embodiments of the present application provide a separator membrane, which is used in metal batteries, such as lithium metal batteries, lithium metal batteries without a negative electrode, sodium metal batteries, sodium metal batteries without a negative electrode, etc., and can enable the battery to have good cycle performance and good rate performance.

[0075] The separator membrane provided by the embodiments of the present application includes a porous substrate, and a first coating and a second coating respectively located on both sides of the porous substrate. The first coating includes a first solid electrolyte material, and the second coating includes graphene oxide.

[0076] In some embodiments, the first coating faces the positive electrode plate, and the second coating faces the negative electrode plate.

[0077] There are serious dendrite problems in the negative electrode of a battery, especially a metal battery. The existence of dendrites will shorten the life of the battery and affect the use of the battery. Especially after the battery is charged and discharged at a high rate for a long time, dendrites are more likely to grow on the negative electrode, resulting in a significant deterioration of the cycle performance and rate performance of the battery.

[0078] Starting from the structure of the separator membrane, the present application sets a first coating including a first solid electrolyte material and a second coating including graphene oxide on both sides of the porous substrate respectively, and makes the first coating face the positive electrode plate and the second coating face the negative electrode plate, so that the battery can have high reliability, good cycle performance and good rate performance.

[0079] The second coating includes graphene oxide (abbreviated as GO). Graphene oxide is rich in oxygen-containing functional groups such as hydroxyl (-OH), carboxyl (-COOH), aldehyde group (-CHO), etc. These oxygen-containing functional groups can react with metals such as Li and Na to generate metal oxides such as lithium oxide and sodium oxide, as well as reduced graphene oxide (rGO). Therefore, applying graphene oxide to the separator membrane can play a role in eliminating dendrites growing on the negative electrode. Taking lithium dendrites as an example, the reaction between graphene oxide and lithium dendrites is as follows: GO + Li → rGO + Li2O. The second coating is arranged facing the negative electrode plate. Therefore, the reduced graphene oxide rGO formed after the reaction between graphene oxide and dendrites can also cover the surface of the negative electrode to form a coating layer, which can also reduce the side reaction between the negative electrode and the electrolyte, and further help to improve the cycle performance of the battery.

[0080] Therefore, graphene oxide has high ionic conductivity. Applying graphene oxide to the separator membrane can improve the ionic conductivity of the separator membrane, improve the ionic conduction ability of the separator membrane, and can also eliminate dendrites growing on the negative electrode. However, when graphene oxide is arranged on one side of the porous substrate, it may cause a large difference in ionic conductivity on both sides of the separator membrane, resulting in an ionic concentration difference on both sides of the separator membrane, exacerbating the uneven ion transport, and further increasing the risk of dendrite formation on the negative electrode.

[0081] The first coating includes a first solid electrolyte material. The first solid electrolyte material has a certain ionic conductivity and a relatively low electronic conductivity. Therefore, the first solid electrolyte material generally can have good ionic conduction ability and electronic insulation properties. When disposed on the porous substrate, it will not significantly increase the overall impedance of the separator, and at the same time can play a role in suppressing the transfer of electrons through the separator.

[0082] The first coating and the second coating are respectively located on both sides of the porous substrate. Oppositely arranging the first solid electrolyte material and graphene oxide can reduce the ion concentration difference and ion conductivity difference on both sides of the separator. Thereby, it can promote the balanced ion transport and reduce the risk of dendrite formation at the negative electrode. In addition, the first solid electrolyte material also has good reaction activity. After contacting with the dendrites piercing the porous substrate, a gradual lithiation (or sodiation) process will occur, accompanied by the change of the valence state of the transition metal element in the first solid electrolyte material. Thereby, it can play a role in further eliminating dendrites and reducing the risk of internal short circuit of the battery caused by the dendrites piercing the separator and contacting the positive electrode. Furthermore, the battery can have a long cycle life and can also have high-rate charging performance.

[0083] The separator provided by the embodiment of the present application has a multi-layer structure. The first solid electrolyte material and graphene oxide have high mechanical strength and good heat resistance, and can resist the thermal shrinkage of the porous substrate caused by dendrite puncture and the temperature rise inside the battery. Thereby, the separator can have high mechanical strength, good puncture resistance and good heat resistance.

[0084] By disposing a second coating containing graphene oxide and a first coating containing the first solid electrolyte material on both sides of the porous substrate, graphene oxide is rich in oxygen-containing functional groups such as hydroxyl (-OH), carboxyl (-COOH), aldehyde (-CHO), etc. Thereby, it can improve the compatibility of the separator with the electrolyte, enhance the wetting characteristics of the separator to the electrolyte, reduce the ionic transport impedance of the separator, and further contribute to improving the cycle performance and rate performance of the battery.

[0085] Therefore, the separator provided by the embodiment of the present application can eliminate dendrites and reduce the risk of internal short circuit of the battery caused by the dendrites piercing the separator and contacting the positive electrode. It also has good electrolyte wettability, high mechanical strength, good puncture resistance and good heat resistance. Furthermore, the battery can have high reliability, good cycle performance and good rate performance.

[0086] In some embodiments, the weight content of the first solid electrolyte material in the first coating may be greater than or equal to 80 wt%, optionally 82 wt% - 98 wt%, 85 wt% - 98 wt%, 88 wt% - 98 wt%, 90 wt% - 98 wt%, 92 wt% - 98 wt%, 94 wt% - 98 wt%, based on the total weight of the first coating.

[0087] By making the first coating mainly include the first solid electrolyte material, it can better balance the ion concentration and ionic conductivity on both sides of the separator, thereby further promoting the balanced ion transport, reducing the risk of dendrite formation on the negative electrode, and improving the reliability, cycle performance, and rate performance of the battery.

[0088] In some embodiments, the volume distribution particle size Dv50 of the first solid electrolyte material may be 0.02 μm - 2 μm, for example, it may be 0.02 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, or a range composed of any of the above values, optionally 0.1 μm - 2 μm, 0.1 μm - 1 μm, 0.2 μm - 0.8 μm.

[0089] When the volume distribution particle size Dv50 of the first solid electrolyte material is within the above range, it is beneficial to balance the ion concentration and ionic conductivity on both sides of the separator, thereby promoting the balanced ion transport, reducing the risk of dendrite formation on the negative electrode, and also improving the reliability, cycle performance, and rate performance of the battery.

[0090] When the volume distribution particle size Dv50 of the first solid electrolyte material is within the above range, it is also beneficial for the first coating slurry to have a suitable viscosity, which is convenient for coating, improves the coating effect, and can also make the first solid electrolyte material better adhere to the porous substrate, reducing the problem of powder falling off; it can also reduce the problem of pore blockage of the porous substrate.

[0091] In some embodiments, the first solid electrolyte material may include an inorganic solid electrolyte.

[0092] Optionally, the ionic conductivity of the inorganic solid electrolyte may be greater than or equal to 10 -6 S / cm, optionally greater than or equal to 10 -4 S / cm, more optionally 10 -4 S / cm - 10 S / cm.

[0093] Optionally, the inorganic solid electrolyte may include one or more of an oxide-based inorganic solid electrolyte, a sulfide-based inorganic solid electrolyte, and a halide-based inorganic solid electrolyte.

[0094] Optionally, the oxide-based inorganic solid electrolyte may include one or more of a NASICON-type solid electrolyte and a LISICON-type solid electrolyte. These solid electrolytes have the advantages of high ionic conductivity and a wide electrochemical window, and can better balance the ionic concentration and ionic conductivity on both sides of the separator, thereby further promoting the balanced ion transport, reducing the risk of dendrite formation on the negative electrode, and improving the reliability, cycle performance, and rate performance of the battery.

[0095] Optionally, the sulfide-based inorganic solid electrolyte may include one or more of a sulfide-based crystalline solid electrolyte and a sulfide glass-based solid electrolyte.

[0096] As an example, the inorganic solid electrolyte may include lithium titanium phosphate Li x Ti y (PO4)3 (0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate Li x Al y Ti z (PO4)3 (abbreviated as LATP, 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium aluminum germanium phosphate Li x Al y Ge z (PO4)3 (abbreviated as LAGP, 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium aluminum zirconium phosphate Li x Al y Zr z (PO4)3 (abbreviated as LAZP, 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium aluminum chromium phosphate Li x Al y Cr z (PO4)3 (abbreviated as LACP, 0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) x O y -type glass (0 < x < 4, 0 < y < 13), lithium thiargyrite electrolyte Li6PS5X (X includes one or more selected from Cl, Br, I), SiS2-type glass Li x Si y S z (0 < x < 3, 0 < y < 2, 0 < z < 4), P2S5-type glass Li x P y S z (0 < x < 3, 0 < y < 3, 0 < z < 7), lithium thiotriphosphate Li3PS4, Li7P3S11 , lithium germanium phosphorus sulfide Li 10 GeP2S 12 , and one or more of their respective doped compounds.

[0097] Optionally, the first solid electrolyte material may include lithium titanium phosphate Li x Ti y (PO4)3 (0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate Li x Al y Ti z (PO4)3 (abbreviated as LATP, 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium tetrathiophosphate Li3PS4, lithium germanium phosphorus sulfide Li 10 GeP2S 12 , Li6PS5Cl, Li6PS5Br, and one or more of their respective doped compounds.

[0098] Doped compounds are usually products obtained by doping other elements, such as metal elements, into a compound. The type of doped element is not particularly limited as long as it does not damage the gist of this application.

[0099] As an example, lithium titanium phosphate Li x Ti y (PO4)3 may include LiTi2(PO4)3. As an example, lithium aluminum titanium phosphate Li x Al y Ti z (PO4)3 may include Li 1.3 Al 0.3 Ti 1.7 (PO4)3. As an example, lithium aluminum germanium phosphate may include Li 1.5 A1 0.5 Ge 1.5 (PO4)3.

[0100] The above first solid electrolyte material has good ionic conduction ability and electron insulation, and also has high reactivity, thereby being able to better eliminate dendrites and reduce the risk of internal short circuit of the battery caused by dendrites piercing the separator and contacting the positive electrode.

[0101] In some embodiments, the first coating further includes a first binder.

[0102] Optionally, the first binder may include, but is not limited to, one or more of vinylidene fluoride-based polymers, sodium carboxymethyl cellulose, styrene-butadiene rubber, poly(meth)acrylic acid, pre-lithiated poly(meth)acrylic acid, and pre-sodiumated poly(meth)acrylic acid. The vinylidene fluoride-based polymer may include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, and vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer.

[0103] Optionally, based on 100 parts by weight of the first solid electrolyte material, the amount of the first binder may be 1-30 parts by weight, optionally 1.5-25 parts by weight, 1.5-22.5 parts by weight, 1.5-20 parts by weight, 1.5-17.5 parts by weight, 1.5-15 parts by weight, 1.5-12.5 parts by weight, 1.5-10 parts by weight, or 1.5-7.5 parts by weight.

[0104] An appropriate amount of the first binder can enable the first solid electrolyte material to better adhere to the porous substrate, reducing the problem of powder falling off; it is also beneficial for the preparation of the first coating slurry, facilitating coating and improving the coating effect.

[0105] The first coating of the separator provided by the embodiments of the present application is mainly composed of the first solid electrolyte material, and the amount of the first binder is relatively small. Thus, the performance of the first solid electrolyte material can be fully exerted, enabling the first coating to have high ion transport ability, good electrolyte wettability, and high mechanical strength, which is conducive to the battery having good cycle performance and rate performance.

[0106] In some embodiments, the first coating may further include a first dispersant.

[0107] Optionally, the first dispersant may include, but is not limited to, one or more of hydrolyzed polymaleic anhydride, acrylic block copolymer, polyester block copolymer, polyethylene glycol type polyol, polyethyleneimine, and their respective derivatives. Derivatives generally refer to products derived from the substitution of hydrogen atoms or atomic groups in the polymer by other atoms or atomic groups.

[0108] Optionally, based on 100 parts by weight of the first solid electrolyte material, the amount of the first dispersant may be 1-3 parts by weight.

[0109] An appropriate amount of the first dispersant can make the first coating slurry disperse evenly, facilitating coating, and is also beneficial for improving the film layer quality of the first coating.

[0110] In some embodiments, the weight content of graphene oxide in the second coating may be greater than or equal to 10 wt%, optionally 15 wt%-25 wt%, 15 wt%-22 wt%, or 15 wt%-20 wt%, based on the total weight of the second coating.

[0111] By making the content of graphene oxide within the above range, it is beneficial to improve the ionic conductivity of the separator membrane, improve the ionic conduction ability of the separator membrane, and can also better eliminate the dendrites growing on the negative electrode.

[0112] In some embodiments, the graphene oxide is flaky, and the diameter of the flaky graphene oxide can be 0.01 μm - 0.5 μm, optionally 0.05 μm - 0.4 μm, 0.05 μm - 0.3 μm, 0.05 μm - 0.2 μm.

[0113] When the diameter of the flaky graphene oxide is within the above range, it is beneficial to improve the ionic conductivity of the separator membrane, improve the ionic conduction ability of the separator membrane, and can also better eliminate the dendrites growing on the negative electrode.

[0114] In some embodiments, the weight content of the O element in the graphene oxide can be 20 wt% - 70 wt%, optionally 30 wt% - 60 wt%, 35 wt% - 50 wt%.

[0115] The higher the content of the O element in the graphene oxide, the higher its oxidation degree, and the content of hydrophilic oxygen-containing functional groups such as hydroxyl (-OH), carboxyl (-COOH), and aldehyde (-CHO) increases. Thus, it is beneficial to improve the electrolyte wettability of the separator membrane.

[0116] The higher the content of the O element in the graphene oxide, the better its electron insulation property, the risk of leakage current caused by electrons passing through the separator membrane is reduced, and in addition, the risk of side reactions occurring in the second coating through the electron transfer method is reduced, and the stability of the second coating is improved.

[0117] The weight content of the O element in the graphene oxide can be tested by an energy dispersive spectrometer (EDS).

[0118] In some embodiments, the number of layers of the graphene oxide can be 1 - 10, optionally 2 - 6.

[0119] In some embodiments, the interlayer spacing of the graphene oxide can be 0.1 nm - 10 nm, optionally 0.4 nm - 3 nm.

[0120] When the graphene oxide has a multi-layer (i.e., the number of layers is greater than or equal to 2) structure, the interlayer spacing of the graphene oxide refers to the distance between two adjacent graphene oxide layers in the graphene oxide. The interlayer spacing of the graphene oxide can be tested by an atomic force microscope (AFM). For a multi-layer flaky material, the total thickness of the material is the sum of the thicknesses of several single layers and the interlayer spacing. Therefore, the interlayer spacing can also be calculated through the total thickness and the number of layers.

[0121] In some embodiments, the second coating may further include inorganic particles.

[0122] After the sheet-like graphene oxide is stacked, the air permeability of the overall separator will be reduced. By making the second coating include inorganic particles, it can play a role in spacing the graphene oxide, thereby improving the air permeability of the separator. At the same time, the gaps between the stacked graphene oxides can enable ions to pass through better, thus also improving the ion conduction ability of the separator. The inorganic particles can also play a role in eliminating dendrites and reducing the risk of internal short circuit of the battery caused by dendrites piercing the separator and contacting the positive electrode. In addition, the second coating includes both graphene oxide and inorganic particles, thereby enabling the separator to have better mechanical strength, puncture resistance and heat resistance.

[0123] Optionally, the weight content of the inorganic particles in the second coating can be greater than or equal to 66 wt%, and can be optionally 66 wt% - 85 wt%, 72 wt% - 82 wt%, 75 wt% - 82 wt%, based on the total weight of the second coating.

[0124] By making the content of the inorganic particles within the above range, the air permeability of the separator can be better improved, the ion conduction ability of the separator can be improved, and the separator can also have better mechanical strength, puncture resistance and heat resistance.

[0125] In some embodiments, the inorganic particles can include one or more of ceramics and a second solid electrolyte material.

[0126] In some embodiments, the ceramics can include, but are not limited to, one or more of boehmite, silicon oxide, titanium oxide, aluminum oxide, zinc oxide, zirconium oxide, barium oxide, calcium oxide, magnesium oxide, nickel oxide, tin oxide, cerium oxide, yttrium oxide, hafnium oxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, magnesium fluoride, calcium fluoride, barium fluoride, barium sulfate, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, mica stone, bentonite, hectorite, kaolin, talc.

[0127] In some embodiments, the second solid electrolyte material can include an inorganic solid electrolyte.

[0128] Optionally, the ionic conductivity of the inorganic solid electrolyte can be greater than or equal to 10 -6 S / cm, and can be optionally greater than or equal to 10 -4 S / cm, and more optionally 10 -4 S / cm - 10 S / cm.

[0129] Optionally, the inorganic solid electrolyte can include one or more of an oxide-type inorganic solid electrolyte, a sulfide-type inorganic solid electrolyte, and a halide-type inorganic solid electrolyte.

[0130] Optionally, the oxide-based inorganic solid electrolyte may include one or more of NASICON-type solid electrolytes and LISICON-type solid electrolytes.

[0131] Optionally, the sulfide-based inorganic solid electrolyte may include one or more of sulfide-based crystalline solid electrolytes and sulfide glass-based solid electrolytes.

[0132] As an example, the inorganic solid electrolyte may include lithium titanium phosphate Li x Ti y (PO4)3 (0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate Li x Al y Ti z (PO4)3 (abbreviated as LATP, 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium aluminum germanium phosphate Li x Al y Ge z (PO4)3 (abbreviated as LAGP, 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium aluminum zirconium phosphate Li x Al y Zr z (PO4)3 (abbreviated as LAZP, 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium aluminum chromium phosphate Li x Al y Cr z (PO4)3 (abbreviated as LACP, 0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) x O y -type glass (0 < x < 4, 0 < y < 13), lithium thiargyrite electrolyte Li6PS5X (X includes one or more selected from Cl, Br, I), SiS2-type glass Li x Si y S z (0 < x < 3, 0 < y < 2, 0 < z < 4), P2S5-type glass Li x P y S z (0 < x < 3, 0 < y < 3, 0 < z < 7), lithium thiotriphosphate Li3PS4, Li7P3S 11 , lithium germanium phosphorus sulfur sulfide Li 10 GeP2S 12 , and one or more of their respective doped compounds.

[0133] Optionally, the second solid electrolyte material may include lithium titanium phosphate Li x Ti y (PO4)3 (0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate Li xAl y Ti z (PO4)3 (abbreviated as LATP, 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium thiotetraphosphate Li3PS4, lithium germanium phosphorus sulfur sulfide Li 10 GeP2S 12 , Li6PS5Cl, Li6PS5Br, and one or more of their respective doped compounds.

[0134] Doped compounds are usually products obtained by doping other elements, such as metal elements, into the compound. The type of doped element is not particularly limited as long as it does not damage the gist of this application.

[0135] As an example, lithium titanium phosphate Li x Ti y (PO4)3 may include LiTi2(PO4)3. As an example, lithium aluminum titanium phosphate Li x Al y Ti z (PO4)3 may include Li 1.3 Al 0.3 Ti 1.7 (PO4)3. As an example, lithium aluminum germanium phosphate may include Li 1.5 A1 0.5 Ge 1.5 (PO4)3.

[0136] The above-mentioned second solid electrolyte material has good ion conduction ability and electron insulation, and also has high reactivity, which can eliminate dendrites.

[0137] In some embodiments, the volume distribution particle size Dv50 of the inorganic particles can be 0.01 μm - 0.8 μm, and can be optionally 0.03 μm - 0.5 μm.

[0138] By adjusting the volume distribution particle size Dv50 of the inorganic particles in the second coating within the above range, the air permeability of the separator can be better improved, and the ion conduction ability of the separator can be improved.

[0139] In some embodiments, graphene oxide is in sheet form. The diameter of the sheet-like graphene oxide is denoted as d1, and the volume distribution particle size Dv50 of the inorganic particles is denoted as d2, with the unit being μm. d1 / d2 can be 0.5 - 2.

[0140] By adjusting the diameter of the sheet-like graphene oxide and the volume distribution particle size Dv50 of the inorganic particles in the second coating within the above range, the air permeability of the separator can be better improved, and the ion conduction ability of the separator can be improved.

[0141] In some embodiments, the second coating further includes a second binder.

[0142] Optionally, the second binder may include, but is not limited to, one or more of vinylidene fluoride-based polymers, sodium carboxymethyl cellulose, styrene-butadiene rubber, poly(meth)acrylic acid, pre-lithiated poly(meth)acrylic acid, and pre-sodiumated poly(meth)acrylic acid. The vinylidene fluoride-based polymer may include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, and vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer.

[0143] Based on 100 parts by weight of the total weight of graphene oxide and inorganic particles, the content of the second binder may be 1-30 parts by weight, optionally 1.5-25 parts by weight, 1.5-22 parts by weight, 1.5-18 parts by weight, 1.5-15 parts by weight, 1.5-12 parts by weight, or 1.5-10 parts by weight.

[0144] An appropriate amount of the second binder can enable graphene oxide and inorganic particles to better adhere to the porous substrate, reducing the problem of powder falling off; it is also beneficial for the preparation of the second coating slurry, facilitating coating, and improving the coating effect.

[0145] The second coating of the separator provided by the embodiments of the present application is mainly composed of graphene oxide and inorganic particles, and the amount of the second binder used is relatively small. Therefore, the performance of graphene oxide and inorganic particles can be fully exerted, enabling the second coating to have high ion transport ability and good electrolyte wettability, and thus being beneficial for the battery to have good cycle performance and rate performance.

[0146] In some embodiments, the second coating may further include a second dispersant.

[0147] Optionally, the second dispersant may include, but is not limited to, one or more of hydrolyzed polymaleic anhydride, acrylic block copolymer, polyester block copolymer, polyethylene glycol-based polyol, polyethyleneimine, and their respective derivatives. Derivatives generally refer to products derived from the substitution of hydrogen atoms or atomic groups in the polymer by other atoms or atomic groups.

[0148] Based on 100 parts by weight of the total weight of graphene oxide and inorganic particles, the content of the second dispersant may be 1-3 parts by weight.

[0149] An appropriate amount of the second dispersant can make the second coating slurry disperse uniformly, facilitate coating, and is also beneficial for improving the film layer quality of the second coating.

[0150] In some embodiments, the ratio of the thickness of the first coating to the thickness of the second coating may be (1-5):1, optionally (1-3):1.

[0151] The first coating faces the positive electrode plate, and the second coating faces the negative electrode plate. The thickness of the first coating is greater than or equal to the thickness of the second coating, which is beneficial to further eliminate dendrites and reduce the risk of internal short circuit of the battery caused by dendrites piercing the separator and contacting the positive electrode.

[0152] In some embodiments, the sum of the thickness of the first coating and the thickness of the second coating can be 2μm - 8μm, and can be optionally 3μm - 5μm.

[0153] When the sum of the thickness of the first coating and the thickness of the second coating is within the above range, it is beneficial to improve the air permeability of the separator and reduce the battery impedance, thereby being beneficial to improving the cycle performance and rate performance of the battery.

[0154] In some embodiments, the thickness of the first coating can be 0.5μm - 5μm, and can be optionally 1μm - 3μm.

[0155] When the thickness of the first coating is within the above range, it can better play the role of eliminating dendrites and reducing the risk of internal short circuit of the battery caused by dendrites piercing the separator and contacting the positive electrode. It can also make the separator have good air permeability and the battery have a small impedance, thereby being beneficial to improving the cycle performance and rate performance of the battery.

[0156] In some embodiments, the thickness of the second coating can be 0.1μm - 3μm, and can be optionally 0.5μm - 2μm.

[0157] When the battery is charged and discharged, graphene oxide can eliminate the dendrites growing on the negative electrode and also consume a part of the active substances. When the thickness of the second coating is within the above range, it can not only provide a high content of graphene oxide to eliminate the dendrites growing on the negative electrode, but also avoid excessive consumption of active substances by too high a content of graphene oxide and reduce the battery capacity. In addition, graphene oxide is rich in oxygen-containing functional groups such as hydroxyl (-OH), carboxyl (-COOH), aldehyde (-CHO), etc., which can improve the compatibility between the separator and the electrolyte. When the thickness of the second coating is within the above range, it is also beneficial to improve the wetting characteristics of the separator for the electrolyte and reduce the ion transport impedance of the separator, and thus is beneficial to the battery having good cycle performance and rate performance.

[0158] In some embodiments, the thickness of the porous substrate can be 5μm - 25μm, and can be optionally 5μm - 12μm.

[0159] In some embodiments, the porosity of the porous substrate can be 25% - 60%, and can be optionally 30% - 50%.

[0160] When the thickness and / or porosity of the porous substrate is within the above range, the separator can have good ion conduction ability and low impedance.

[0161] In some embodiments, the porous substrate may include one or more of polyolefins, polyamides, polyesters, and their respective derivatives. Derivatives generally refer to products derived from the substitution of hydrogen atoms or atomic groups in polymers by other atoms or atomic groups.

[0162] Optionally, the polyester may include, but is not limited to, one or more of polyethylene terephthalate and polybutylene terephthalate.

[0163] Optionally, the porous substrate may include one or more of polyolefins and their derivatives. Optionally, the monomers for forming polyolefins may include, but are not limited to, one or more of ethylene, propylene, tetrafluoroethylene, vinylidene fluoride, and vinyl chloride. Optionally, the porous substrate may include polyethylene.

[0164] In some embodiments, the porous substrate may be a single-layer film structure, a multi-layer film structure, or a non-woven fabric structure.

[0165] In some embodiments, the total thickness of the separator membrane may be 7 μm - 35 μm, optionally 10 μm - 15 μm.

[0166] In some embodiments, the porosity of the separator membrane may be 25% - 50%, optionally 30% - 45%.

[0167] When the total thickness and / or porosity of the separator membrane are within the above ranges, the separator membrane can have good ion conduction ability and low impedance.

[0168] The thicknesses of the porous substrate, the first coating, the second coating, and the separator membrane have meanings well-known in the art and can be measured by methods known in the art. For example, reference can be made to GB / T 6672-2001, Determination of thickness of plastic films and sheets - Mechanical measurement method, for measurement.

[0169] The porosities of the porous substrate and the separator membrane have meanings well-known in the art and can be measured by methods known in the art. For example, reference can be made to GB / T 21650.2-2008, Determination of pore size distribution and porosity of solid materials by mercury intrusion porosimetry and gas adsorption - Part 2: Gas adsorption method for analysis of mesopores and macropores, for testing.

[0170] The Dv50 of the material has a meaning well-known in the art and can be determined by instruments and methods known in the art. For example, it can be conveniently determined 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%.

[0171] [Preparation method of separator membrane]

[0172] The embodiment of the present application also provides a method for preparing a separator membrane, which can prepare the separator membrane provided by the embodiment of the present application.

[0173] The preparation method includes the following steps: providing a porous substrate, a first coating slurry and a second coating slurry, the first coating slurry includes a solid electrolyte, and the second coating slurry includes graphene oxide; coating the first coating slurry and the second coating slurry on both sides of the porous substrate respectively, and after drying, a separator membrane is obtained.

[0174] In some embodiments, the solvent in the first 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).

[0175] In some embodiments, the solid content of the first coating slurry may be 30%-60%, and optionally 35%-45%. This facilitates coating.

[0176] In some embodiments, the first coating slurry may further include a first binder and / or a first dispersant.

[0177] In some embodiments, the step of providing the first coating slurry may include the following steps: performing a primary dispersion on the solid electrolyte and the solvent to obtain a primary dispersion solution; adding a first binder and / or a first dispersant to the obtained primary dispersion solution for secondary dispersion to obtain the first coating slurry.

[0178] Optionally, the secondary dispersion process may be ultrasonic dispersion, and stirring may be performed during the ultrasonic dispersion. Optionally, the stirring speed during the ultrasonic dispersion may be 1000 rpm - 1600 rpm, and the ultrasonic dispersion time may be 0.5 h - 3 h.

[0179] In some embodiments, the solvent in the second 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).

[0180] In some embodiments, the solid content of the second coating slurry may be 30%-60%, and optionally 35%-45%. This facilitates coating.

[0181] In some embodiments, the second coating slurry may further include inorganic particles.

[0182] In some embodiments, the second coating slurry may further include a second binder and / or a second dispersant.

[0183] In some embodiments, the step of providing the second coating slurry may include the following steps: graphene oxide and optional inorganic particles are dispersed once with a solvent to obtain a primary dispersion solution; a second binder and / or a second dispersant are added to the obtained primary dispersion solution for secondary dispersion to obtain the second coating slurry.

[0184] Optionally, the secondary dispersion process may be ultrasonic dispersion, and stirring may be carried out during the ultrasonic dispersion. Optionally, the stirring speed during the ultrasonic dispersion may be 1000 rpm - 1600 rpm, and the ultrasonic dispersion time may be 0.5 h - 3 h.

[0185] In some embodiments, the drying temperature of the first coating slurry may be 60°C - 80°C, and the drying time may be 5 h - 8 h.

[0186] In some embodiments, the drying temperature of the second coating slurry may be 60°C - 80°C, and the drying time may be 5 min - 10 min.

[0187] In some embodiments, the coating method of the first coating slurry may include, but is not limited to, gravure transfer coating, rotary spraying, dip coating, knife coating, etc.

[0188] In some embodiments, the coating method of the second coating slurry may include, but is not limited to, gravure transfer coating, rotary spraying, dip coating, knife coating, etc.

[0189] For some raw materials used in the method for preparing the separator provided in the embodiments of the present application and parameters such as their contents, reference may be made to the separator provided in the embodiments of the present application, and details are not described herein again.

[0190] If there is no special instruction, each raw material used in the method for preparing the separator can be obtained through commercial purchase.

[0191] [Positive electrode plate]

[0192] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided 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 own thickness direction, and the positive electrode film layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector.

[0193] In some embodiments, the positive electrode active material includes a material capable of deintercalating and intercalating lithium.

[0194] 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.

[0195] 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.

[0196] 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.

[0197] 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 0.2O2 (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.

[0198] In some embodiments, the positive electrode active material includes materials capable of deintercalating and intercalating 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.), polyanion materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian materials.

[0199] In some embodiments, by way of example, the positive electrode active material may include, but is not limited to, NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, Na 0.67 MO2 (M includes at least two of Fe, Co, Cr, Mn, Ni, V, Ti, Mo), NaMO2 (M includes at least two of Fe, Co, Ni, V, Ti, Mo), NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, Prussian white, and one or more of their respective modified compounds.

[0200] The modified compounds of the above positive electrode active materials may be doping modification and / or surface coating modification of the positive electrode active materials.

[0201] In some embodiments, the positive electrode film layer may also optionally include a positive electrode conductive agent. By way of 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.

[0202] In some embodiments, the positive electrode film layer may optionally further 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 acrylate 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), or one or more of them.

[0203] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of the 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, 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), polyethylene (PE).

[0204] The positive electrode film layer is usually formed by coating a positive electrode paste on a positive electrode current collector and then drying and cold pressing. The positive electrode paste is usually formed by dispersing a positive electrode active material, an optional positive electrode conductive agent, an optional positive electrode binder, and any other components in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.

[0205] [Negative electrode tab]

[0206] The structure and composition of the negative electrode tab can be adjusted according to the type of battery cell.

[0207] In some embodiments, the negative electrode tab may include a negative electrode current collector and a metal layer provided on at least one surface of the negative electrode current collector. The metal material in the metal layer may include, but is not limited to, one or more of lithium metal, lithium alloy, sodium, sodium alloy.

[0208] The lithium alloy may be an alloy formed by lithium metal and other metal elements or non-metal elements. As an example, the other metal elements in the lithium alloy may include one or more elements of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, platinum, and the non-metal elements in the lithium alloy may include one or more elements of boron, carbon, silicon.

[0209] The sodium alloy can 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 can include one or more elements among tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, platinum, and the non-metallic elements in the sodium alloy can include one or more elements among boron, carbon, silicon.

[0210] In some embodiments, the negative electrode tab can include a negative electrode current collector and does not include a metal layer to assemble and form a non-negative electrode metal battery cell.

[0211] In some embodiments, in order to improve the battery performance, some substances that can be used as negative electrode active materials conventionally, such as carbon materials, etc., can also be provided on the negative electrode side of the non-negative electrode metal battery cell. Although these substances have a certain capacity, due to their small content and not being used as the main negative electrode active material in the battery cell, the battery cell thus constituted can still be regarded as a non-negative electrode metal battery cell.

[0212] In some embodiments, the negative electrode current collector can include a metal foil, a three-dimensional porous current collector, or a composite current collector. As an example of the metal foil, copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, aluminum alloy foil can be used. As an example of the three-dimensional porous current collector, copper mesh, nickel mesh, aluminum mesh, copper foam, nickel foam, aluminum foam can be used. The composite current collector can 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 can 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 can include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0213] [Electrolyte]

[0214] In some embodiments, the electrolyte uses an electrolytic solution, and the electrolytic solution includes an electrolyte salt and an organic solvent.

[0215] In some embodiments, the electrolytic solution includes anions, and the anions can include bis(fluorosulfonyl)imide anion (FSI - ), bis(trifluoromethylsulfonyl)imide anion (TFSI - ), bis(oxalato)borate anion (BOB - ), difluoro(oxalato)borate anion (DFOB - ), difluoro bis(oxalato)phosphate anion (DFOP - ), tetrafluoro(oxalato)phosphate anion (TFOP - ), difluorophosphate anion (PO2F2 -) One or more of hexafluorophosphate anions (PF6 - ) tetrafluoroborate anions (BF4 - ) hexafluoroarsenate anions (AsF6 - ) trifluoromethanesulfonate anions (CF3SO3 - ).

[0216] In some embodiments, the electrolyte includes cations, which may include one or more of lithium ions and sodium ions.

[0217] In some embodiments, the concentration of the electrolyte salt can be 0.3 mol / L or more, optionally 0.7 mol / L or more, and further can be 4 mol / L or less, optionally 2.5 mol / L or less, 1.7 mol / L or less. When the concentration of the electrolyte salt is within the above range, the electrolyte can have appropriate ionic conductivity.

[0218] The organic solvent can include, but is not limited to, one or more of esters, ethers, sulfones, nitriles, etc. Esters can include, but are not limited to, one or more of carbonates, phosphates, carboxylates, sulfates, sulfonates, etc. Carbonates can include cyclic carbonates and / or chain carbonates. Optionally, carbonates can include both cyclic carbonates and chain carbonates at the same time. Chain carbonates can include low-viscosity polar chain carbonates, aliphatic branched carbonates, etc.

[0219] 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), ethyl methyl 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, C4F9OCH3, H(CF2)2OCH2CH3, H(CF2)2OCH2CF3, H(CF2)2CH2O(CF2)2H, CF3CHFCF2OCH3, CF3CHFCF2OCH2CH3, 2-trifluoromethylhexafluoropropyl methyl ether, 2-trifluoromethylhexafluoropropyl ethyl ether, 2-trifluoromethylhexafluoropropyl propyl ether, 3-trifluoromethyl octafluorobutyl methyl ether, 3-trifluoromethyl octafluorobutyl ethyl ether, 3-trifluoromethyl octafluorobutyl propyl ether, 4-trifluoromethyl decafluoropentyl methyl ether, 4-trifluoromethyl decafluoropentyl ethyl ether, 4-trifluoromethyl decafluoropentyl propyl ether, 5-trifluoromethyl dodecafluorohexyl methyl ether, 5-trifluoromethyl dodecafluorohexyl ethyl ether, 5-trifluoromethyl dodecafluorohexyl propyl ether, 6-trifluoromethyl tetrafluoroheptyl methyl ether, 6-trifluoromethyl tetrafluoroheptyl ethyl ether, 6-trifluoromethyl tetrafluoroheptyl propyl ether, 7-trifluoromethyl hexafluoroctyl methyl ether, 7-trifluoromethyl hexafluoroctyl ethyl ether, 7-trifluoromethyl hexafluoroctyl propyl ether, or one or more of them.

[0220] In some embodiments, the electrolyte may optionally further include additives. For example, the additives may include negative electrode film-forming additives, may also include positive electrode film-forming additives, and may further include additives that can improve certain battery performance, such as additives that improve the overcharge performance of the battery, additives that improve the high-temperature performance of the battery, additives that improve the low-temperature power performance of the battery, and the like.

[0221] The preparation method of battery cells is well-known. In some embodiments, a battery cell can be assembled by combining a positive electrode plate, a separator, a negative electrode plate, and an electrolyte. As an example, the positive electrode plate, the separator, and the negative electrode plate can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly is placed in an outer package, dried, and then the above-mentioned electrolyte is injected. After processes such as vacuum packaging, standing, and formation, a battery cell is obtained. Multiple battery cells can further form a battery module through series connection, parallel connection, or a combination of both. Multiple battery modules can also form a battery pack through series connection, parallel connection, or a combination of both. In some embodiments, multiple battery cells can also directly form a battery pack.

[0222] An embodiment of the present application also provides an electrical device, which includes the battery provided by the embodiment of the present application. The battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0223] The electrical device can select the type of battery according to its usage requirements, such as a battery cell, a battery module, or a battery pack.

[0224] Figure 6 It is a schematic diagram of an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the requirements of the electrical device for high power and high energy density, a battery pack or a battery module can be used.

[0225] Another example of an electrical device can be a mobile phone, a tablet computer, a laptop computer, etc. This type of electrical device usually requires a thin and light design, and a battery cell can be used as the power source.

[0226] Example

[0227] The following embodiments more specifically describe the content disclosed in the present application. These embodiments are only for illustrative purposes, because various modifications and changes within the scope of the content disclosed in the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and all instruments used in the embodiments are commercially available.

[0228] Embodiment 1

[0229] Preparation of the first coating slurry

[0230] Disperse the first solid electrolyte material Li 1.3 Al 0.3 Ti 1.7 (PO4)3 uniformly into N-methylpyrrolidone (NMP). Then add the first binder polyvinylidene fluoride (PVDF) and the first dispersant hydrolyzed polymaleic anhydride to the solution, and ultrasonically disperse it at 1100 rpm for 2 h to obtain the first coating slurry with a solid content of about 40%. The volume distribution particle size Dv50 of the first solid electrolyte material is 0.5 μm, and the weight ratio of the first solid electrolyte material, the first binder, and the first dispersant is 100:1.5:1.5.

[0231] Preparation of the second coating slurry

[0232] Disperse graphene oxide powder and inorganic particle silica SiO2 uniformly into N-methylpyrrolidone (NMP). Then add the second binder polyvinylidene fluoride (PVDF) and the second dispersant hydrolyzed polymaleic anhydride to the solution, and ultrasonically disperse it at 1100 rpm for 2 h to obtain the second coating slurry with a solid content of about 40%. The graphene oxide is flaky, the diameter of the flaky graphene oxide is 0.3 μm, the number of layers is 2, and the layer spacing is 1 nm - 2 nm. The weight ratio of graphene oxide, inorganic particles, the second binder, and the second dispersant is 18:82:2:1. The graphene oxide is purchased from Jiangsu Xianfeng Nano Materials Technology Co., Ltd.

[0233] Preparation of the separator membrane

[0234] Coat the second coating slurry on one side of a wet-process PE porous substrate with a porosity of 45% and a thickness of 9 μm by gravure transfer coating, and bake it at 60°C - 65°C for about 10 min; then coat the first coating slurry on the other side of the PE porous substrate in the same way, and bake it at 60°C - 65°C for about 5 h to obtain a separator with a three-layer structure. The thickness of the first coating is 2 μm, and the thickness of the second coating is 2 μm.

[0235] Comparative Example 1

[0236] Use a wet-process PE porous membrane with a porosity of 45% and a thickness of 9 μm as the separator.

[0237] Comparative Example 2

[0238] The graphene oxide powder is uniformly dispersed in N-methylpyrrolidone (NMP). Then, the binder polyvinylidene fluoride (PVDF) and the dispersant hydrolyzed polymaleic anhydride are added to the solution, and ultrasonic dispersion is carried out at 1100 rpm for 2 h to obtain a coating slurry with a solid content of about 40%. The graphene oxide is flaky, the diameter of the flaky graphene oxide is 0.3 μm, the number of layers is 2, and the layer spacing is 1 nm - 2 nm. The weight ratio of graphene oxide, binder, and dispersant is 100:2:1.

[0239] The coating slurry is coated on one side of a wet PE porous substrate with a porosity of 45% and a thickness of 9 μm by gravure transfer coating, and baked at 60°C - 65°C for about 10 min to obtain a separator membrane with a two-layer structure. The thickness of the coating is 2 μm.

[0240] Comparative Example 3

[0241] The graphene oxide powder is uniformly dispersed in N-methylpyrrolidone (NMP). Then, the binder polyvinylidene fluoride (PVDF) and the dispersant hydrolyzed polymaleic anhydride are added to the solution, and ultrasonic dispersion is carried out at 1100 rpm for 2 h to obtain a coating slurry with a solid content of about 40%. The graphene oxide is flaky, the diameter of the flaky graphene oxide is 0.3 μm, the number of layers is 2, and the layer spacing is 1 nm - 2 nm. The weight ratio of graphene oxide, binder, and dispersant is 100:2:1.

[0242] The coating slurry is coated on both sides of a wet PE porous substrate with a porosity of 45% and a thickness of 9 μm by gravure transfer coating, and baked at 60°C - 65°C for about 10 min to obtain a separator membrane with a three-layer structure. The thickness of each coating is 2 μm.

[0243] Comparative Example 4

[0244] The solid electrolyte material Li 1.3 Al 0.3 Ti 1.7 (PO4)3 is uniformly dispersed in N-methylpyrrolidone (NMP). Then, the binder polyvinylidene fluoride (PVDF) and the dispersant hydrolyzed polymaleic anhydride are added to the solution, and ultrasonic dispersion is carried out at 1100 rpm for 2 h to obtain a coating slurry with a solid content of about 40%. The volume distribution particle size Dv50 of the solid electrolyte material is 0.5 μm, and the weight ratio of the solid electrolyte material, binder, and dispersant is 100:1.5:1.5.

[0245] The coating slurry is coated on one side of a wet PE porous substrate with a porosity of 45% and a thickness of 9 μm by gravure transfer coating, and baked at 60°C - 65°C for about 5 h to obtain a separator membrane with a two-layer structure. The thickness of the coating is 2 μm.

[0246] Comparative Example 5

[0247] Disperse the solid electrolyte material Li 1.3 Al 0.3 Ti 1.7 (PO4)3 uniformly into N-methylpyrrolidone (NMP), and then add the binder polyvinylidene fluoride (PVDF) and the dispersant hydrolyzed polymaleic anhydride to the solution, and disperse it ultrasonically at 1100 rpm for 2 h to obtain a coating slurry with a solid content of about 40%. The volume distribution particle size Dv50 of the solid electrolyte material is 0.5 μm, and the weight ratio of the solid electrolyte material, the binder, and the dispersant is 100:1.5:1.5.

[0248] Coat the coating slurry on both sides of a wet PE porous substrate with a porosity of 45% and a thickness of 9 μm by gravure transfer coating, and bake it at 60 °C - 65 °C for about 5 h to obtain a separator with a two-layer structure. The thickness of the coating is 2 μm for both layers.

[0249] Performance test of the separator membrane

[0250] (1) Puncture strength test of the separator

[0251] Test the puncture strength of the separator according to GB / T36363-2018. Cut the separator into samples with a width of 10 mm and a length of 150 mm, then lay it flat in the fixture and clamp it, and perform a puncture test with a steel needle at a rate of 100 mm / min. After the test, take out the sample, and perform a 4-point thickness test around the pinhole according to GB / T6672-2001, take the average value and calculate the puncture strength. The diameter of the steel needle is 1 mm, the radius of the spherical tip is 0.5 mm, and the surface of the steel needle is smooth, free of rust, oxide layer and oil stain. During the test, the number of separator samples can be more than 6, and the test results are averaged.

[0252] (2) Tensile strength test of the separator

[0253] Test the tensile strength of the separator in the transverse direction (TD) and the longitudinal direction (MD) according to GB / T36363-2018.

[0254] Cut the separator into samples with a width of 10 mm and a length of 150 mm (the length direction is parallel to the transverse direction of the separator) for testing to obtain the tensile strength of the separator in the transverse direction (TD). The test instrument can be a universal tensile machine, and the tensile rate is 50 mm / min. During the test, the number of separator samples can be more than 6, and the test results are averaged.

[0255] Cut the separator into samples with a width of 10 mm and a length of 150 mm (the length direction is parallel to the longitudinal direction of the separator) for testing to obtain the tensile strength in the longitudinal direction (MD) of the separator. The testing instrument can be a universal tensile machine, and the tensile rate is 50 mm / min. During testing, the number of separator samples can be more than 6, and the test results are averaged.

[0256] (3) Thermal shrinkage rate test of the separator

[0257] According to GB / T36363-2018, test the thermal shrinkage rate in the transverse direction (TD) and longitudinal direction (MD) of the separator. The separator sample has a width of 50 mm and a length of 100 mm. The temperature of the hot box is 105 °C and the heat treatment time is 1 h. After completion, measure the length and width of the separator, and the values are marked as a and b respectively. The thermal shrinkage rate in the longitudinal direction (MD) = [(100 - a) / 100] × 100%, and the thermal shrinkage rate in the transverse direction (TD) = [(50 - b) / 50] × 100%. During testing, the number of separator samples can be more than 6, and the test results are averaged.

[0258] (4) Permeability test of the separator

[0259] According to GB / T36363-2018, test the permeability of the separator. The time (seconds) required for 100 mL of air to pass through the separator is used as the permeability of the separator. The greater the permeability of the separator, the worse the gas permeability of the separator. During testing, the number of separator samples can be more than 6, and the test results are averaged. The testing instrument can use the Kumagai KRK Wang research type permeability tester.

[0260] Next, after assembling the above-mentioned separator into a coin cell, perform the following performance tests.

[0261] The coin cell can be prepared as follows. Mix lithium iron phosphate, conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) in a weight ratio of 8:1:1 in an appropriate amount of solvent N-methylpyrrolidone (NMP) to obtain a positive electrode paste; coat the positive electrode paste on the positive electrode current collector aluminum foil, and after drying, obtain a positive electrode plate. In a glove box under argon protection, assemble the positive electrode plate, the above-mentioned separator, and a lithium sheet into a CR2430 type coin cell. The electrolyte salt of the electrolyte is LiFSI, with a concentration of 1 mol / L, and the solvent of the electrolyte uses ethylene glycol dimethyl ether (DME). The second coating of the separator in Example 1 faces the lithium sheet, and the coatings of the separators in Comparative Example 2 and Comparative Example 4 face the lithium sheet.

[0262] At 25 °C, the coin cell was charged at a constant current of 0.1C to 3.65V, and then charged at a constant voltage of 3.65V to 0.05C; after the coin cell was left standing for 10 min, it was discharged at a constant current of 0.1C to 2.5V. After the coin cell was cycled twice according to the above method, the following performance tests were carried out.

[0263] The coin cell was charged at a constant current of 0.5C, 1C, and 2C to 3.65V respectively, and then charged at a constant voltage of 3.65V to 0.05C; after the coin cell was left standing for 10 min, it was discharged at a constant current of 0.2C to 2.5V. The coin cell was cycled 100 times according to the above method to obtain the charging capacity of the 100th cycle and the discharging capacity of the 100th cycle. The Coulombic efficiency of the coin cell cycled 100 times = the discharging capacity of the 100th cycle / the charging capacity of the 100th cycle.

[0264] The coin cell was charged at a constant current of 1C to 3.65V, and then charged at a constant voltage of 3.65V to 0.05C; after the coin cell was left standing for 10 min, it was discharged at a constant current of 0.2C to 2.5V to obtain the discharging capacity of the first cycle. The coin cell was cycled 100 times according to the above method to obtain the discharging capacity of the 100th cycle. The capacity retention rate of the coin cell cycled 100 times = the discharging capacity of the 100th cycle / the discharging capacity of the first cycle.

[0265] During the test, the number of coin cell samples can be more than 6, and the test results are averaged.

[0266] Table 1

[0267]

[0268] As can be seen from the test results in Table 1, by respectively arranging a first coating including a first solid electrolyte material and a second coating including graphene oxide on both sides of the porous substrate, and making the first coating face the positive electrode plate and the second coating face the negative electrode plate, the battery can have good cycle performance and good rate performance, and in particular, the Coulombic efficiency under high-rate current cycling can be significantly improved.

[0269] Examples 2 to 4

[0270] The preparation method of the separator is similar to that of Example 1, except that the composition of the first coating is different, and the specific parameters are shown in Table 2. LATP represents Li 1.3 Al 0.3 Ti 1.7 (PO4)3. The test results of the separator and the battery are shown in Table 3.

[0271] Table 2

[0272]

[0273] Table 3

[0274]

[0275] It can also be seen from the test results in Table 3 that by further adjusting the weight content of the first solid electrolyte material in the first coating, the performance of the battery can be further improved.

[0276] Examples 5 to 12

[0277] The preparation method of the separator is similar to that of Example 1, except that the composition of the second coating is different. The specific parameters are shown in Table 4. The test results of the separator and the battery are shown in Table 5.

[0278] Table 4

[0279]

[0280] Table 5

[0281]

[0282] It can also be seen from the test results in Table 5 that by further adjusting the weight content of graphene oxide and / or inorganic particles in the second coating, the performance of the battery can be further improved.

[0283] Examples 13 to 18

[0284] The preparation method of the separator is similar to that of Example 1, except that the thickness of the first coating and / or the second coating is different. The specific parameters are shown in Table 6. The test results of the separator and the battery are shown in Table 7.

[0285] Table 6

[0286] Serial number Thickness of the first coating (μm) Thickness of the second coating (μm) Example 13 3 2 Example 14 5 2 Example 15 0.5 2 Example 16 2 3 Example 17 2 0.5 Example 18 2 0.1

[0287] Table 7

[0288]

[0289] It can also be seen from the test results in Table 7 that by further adjusting the thickness of the first coating and / or the second coating, the performance of the battery can be further improved.

[0290] Examples 19 to 22

[0291] The preparation method of the separator is similar to that of Example 1, except that the weight content of the O element of graphene oxide in the second coating is different. The specific parameters are shown in Table 8.

[0292] Table 8

[0293]

[0294] It can also be seen from the test results in Table 8 that by further adjusting the weight content of the O element of graphene oxide in the second coating, the performance of the battery can be further improved.

[0295] Examples 23 to 25

[0296] The preparation method of the separator is similar to that of Example 1, except that the type of the first solid electrolyte material in the first coating and / or the type of the inorganic particles in the second coating are different. The specific parameters are shown in Table 9. In Table 9, Li 1.3 Al 0.3 Ti 1.7 (PO4)3 is abbreviated as LATP, and LiTi2(PO4)3 is abbreviated as LTP.

[0297] Table 9

[0298]

[0299] It can also be seen from the test results in Table 9 that when the type of the first solid electrolyte and / or the type of the inorganic particles are different, the improvement effect on the battery performance is slightly different.

[0300] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same structure and the same function and effect as the technical idea within the technical solution scope of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various deformations that can be thought of by those skilled in the art on the embodiments and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of this application.

Claims

1. A battery cell, comprising a positive electrode plate, a negative electrode plate and a separator, characterized in that, The separator membrane includes a porous substrate, and a first coating and a second coating respectively located on both sides of the porous substrate. The first coating includes a first solid electrolyte material, the second coating includes graphene oxide, the first coating faces the positive electrode plate, and the second coating faces the negative electrode plate.

2. The battery cell according to claim 1, wherein the weight content of the first solid electrolyte material in the first coating is greater than or equal to 80 wt%, and can be selected from 90 wt% - 98 wt%, based on the total weight of the first coating; and / or the weight content of the graphene oxide in the second coating is greater than or equal to 10 wt%, and can be selected from 15 wt% - 22 wt%, based on the total weight of the second coating.

3. The battery cell according to any one of claims 1-2, characterized in that, The second coating further includes inorganic particles, and the weight content of the inorganic particles in the second coating is greater than or equal to 66 wt%, and can be selected from 75 wt% - 82 wt%, based on the total weight of the second coating.

4. The battery cell according to claim 3, wherein, The second coating satisfies at least one of the following conditions (1) to (3): (1) The inorganic particles include one or more of ceramics and a second solid electrolyte material; (2) The volume distribution particle size Dv50 of the inorganic particles is 0.01 μm - 0.8 μm, and can be selected from 0.03 μm - 0.5 μm; (3) The graphene oxide is in a sheet shape. The diameter of the sheet-shaped graphene oxide is denoted as d1, and the volume distribution particle size Dv50 of the inorganic particles is denoted as d2, with the unit of both being μm, and d1 / d2 is 0.5 - 2.

5. The battery cell according to claim 4, characterized in that The second solid electrolyte material satisfies at least one of the following conditions (1) to (3): (1) The second solid electrolyte material includes an inorganic solid electrolyte; (2) The second solid electrolyte material includes an inorganic solid electrolyte, and the ionic conductivity of the inorganic solid electrolyte is greater than or equal to 10 -6 S / cm; (3) The second solid electrolyte material includes an inorganic solid electrolyte, and the inorganic solid electrolyte includes one or more of an oxide-type inorganic solid electrolyte, a sulfide-type inorganic solid electrolyte, or a halide-type inorganic solid electrolyte.

6. The battery cell according to any one of claims 1-5, characterized in that, The graphene oxide satisfies at least one of the following conditions (1) to (4): (1) The graphene oxide is in a sheet shape, and the diameter of the sheet-shaped graphene oxide is 0.01 μm - 0.5 μm, and can be selected from 0.05 μm - 0.4 μm; (2) The weight content of O element in the graphene oxide is 20 wt% - 70 wt%, and can be selected from 30 wt% - 60 wt%; (3) The interlayer spacing of the graphene oxide is 0.1 nm - 10 nm, and can be selected from 0.4 nm - 3 nm; (4) The number of layers of the graphene oxide is 1 - 10, and can be selected from 2 - 6.

7. The battery cell according to any one of claims 1 - 6, wherein the ratio of the thickness of the first coating to the thickness of the second coating is (1 - 5):1, and can be selected from (1 - 3):1; and / or the sum of the thickness of the first coating and the thickness of the second coating is 2 μm - 8 μm, and can be selected from 3 μm - 5 μm.

8. The battery cell according to any one of claims 1 - 7, wherein the thickness of the first coating is 0.5 μm - 5 μm, and can be selected from 1 μm - 3 μm; and / or The thickness of the second coating is 0.1 μm - 3 μm, and can be optionally 0.5 μm - 2 μm.

9. The battery cell according to any one of claims 1-8, characterized in that, The first solid electrolyte material satisfies at least one of the following conditions (1) to (4): (1) The first solid electrolyte material includes an inorganic solid electrolyte; (2) The first solid electrolyte material includes an inorganic solid electrolyte, and the ionic conductivity of the inorganic solid electrolyte is greater than or equal to 10 -6 S / cm; (3) The first solid electrolyte material includes an inorganic solid electrolyte, and the inorganic solid electrolyte includes one or more of an oxide-based inorganic solid electrolyte, a sulfide-based inorganic solid electrolyte, or a halide-based inorganic solid electrolyte; (4) The volume distribution particle size Dv50 of the first solid electrolyte material is 0.02 μm - 2 μm.

10. The battery cell according to any one of claims 1 - 9, characterized in that The first coating further includes a first binder and / or a first dispersant; and / or, The second coating further includes a second binder and / or a second dispersant.

11. The battery cell according to any one of claims 1-10, characterized in that, The separator satisfies at least one of the following conditions (1) to (5): (1) The total thickness of the separator is 7 μm - 35 μm, and can be optionally 10 μm - 15 μm; (2) The porosity of the separator is 25% - 50%, and can be optionally 30% - 45%; (3) The thickness of the porous substrate is 5 μm - 25 μm, and can be optionally 5 μm - 12 μm; (4) The porosity of the porous substrate is 25% - 60%, and can be optionally 30% - 50%; (5) The porous substrate includes one or more of polyolefin, polyamide, polyester, and their respective derivatives.

12. The battery cell according to any one of claims 1-11, characterized in that, The battery cell includes at least one of a lithium metal battery cell, a lithium metal battery cell without a negative electrode, a sodium metal battery cell, and a sodium metal battery cell without a negative electrode.

13. An isolation film, comprising a porous substrate and a first coating and a second coating respectively located on both sides of the porous substrate, characterized in that, The first coating is the first coating according to any one of claims 1 - 12, and the second coating is the second coating according to any one of claims 1 - 12.

14. A battery, characterized in that, Includes the battery cell according to any one of claims 1 - 12.

15. An electrical device, characterized in that, Includes the battery according to claim 14, and the battery is used to provide electrical energy.

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