Separator, battery, and electric device

Abstract

The present application provides a separator, a battery, and an electric device. The separator comprises: a base membrane and a composite coating disposed on at least one side of the base membrane, the composite coating comprising a ceramic layer, the ceramic layer comprising a ceramic material and a polyacrylate layer directly bonded to one side of the ceramic layer, the polyacrylate layer comprising an acrylic acid alkali metal salt polymer, and the ceramic layer being disposed on the side close to the base membrane. The ceramic layer and the polyacrylate layer in the composite coating can form an active ion bridge high-speed channel, so that the separator can improve the transmission rate of active ions, so as to reduce the polarization of a battery during charge and discharge, thus improving the fast charging performance and cycle performance of the battery.

Description

Separator films, batteries and electrical equipment

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202311644063.6, filed on December 1, 2023, entitled “Isolation membrane, battery and electrical equipment,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to an isolation membrane, a battery, and an electrical device. Background Art

[0004] Battery cells, such as lithium-ion batteries, are widely used due to their reliable performance, pollution-free operation, and lack of memory effects. For example, with increasing attention to environmental protection and the growing popularity of new energy vehicles, demand for power battery cells is expected to surge. As battery applications expand, so too are the demands for faster charging performance. Consequently, improvements in fast charging performance are needed.

[0005] Summary of the Invention

[0006] The present application provides an isolation membrane, a battery and an electrical device, wherein the isolation membrane can improve the cycle performance of the battery.

[0007] In a first aspect, the present application provides an isolation membrane, comprising: a base membrane, and a composite coating arranged on at least one side of the base membrane, the composite coating comprising a ceramic layer, the ceramic layer comprising a ceramic material, and a polyacrylate layer directly bonded to one side of the ceramic layer, the polyacrylate layer comprising an alkali metal salt polymer of acrylic acid, and the ceramic layer being arranged close to one side of the base membrane.

[0008] According to the present application, by providing a composite coating on at least one side of the base membrane, the ceramic layer and the polyacrylate layer in the composite coating can form a high-speed path for active ion bridges, so that the isolation membrane can increase the transmission rate of active ions, reduce the polarization of the battery during the charging and discharging process, and thereby improve the fast charging performance and cycle performance of the battery.

[0009] In some embodiments, the mass percentage of alkali metal in the acrylic acid alkali metal salt polymer is 3% to 8.9%, preferably 5% to 7.5%. In this case, the separator has better ion transport performance, and the battery containing the separator has better fast charging performance and cycle performance.

[0010] In some embodiments, the number average molecular weight of the alkali metal salt of acrylic acid polymer is 3 kDa to 1000 kDa. Preferably, the number average molecular weight is 100 kDa to 500 kDa. In this case, the active ion bridge high-speed pathway formed by the composite coating has a higher ion transport rate, the separator has better ion transport performance, and the battery containing the separator has better fast charging performance and cycling performance.

[0011] In some embodiments, the alkali metal salt of acrylic acid polymer includes at least one of alkali metal salt of polyacrylic acid, alkali metal salt of polymethacrylic acid, and alkali metal salt of polyethacrylic acid.

[0012] In some embodiments, the alkali metal salt of polyacrylic acid includes at least one of lithium polyacrylate and sodium polyacrylate; and / or, the alkali metal salt of polymethacrylate includes at least one of lithium polymethacrylate and sodium polymethacrylate; and / or, the alkali metal salt of polyethylacrylate includes at least one of lithium polyethylacrylate and sodium polyethylacrylate. Alkali metal salts of polyacrylic acid, alkali metal salts of polymethacrylate and alkali metal salts of polyethylacrylate can be lithium salts or sodium salts or potassium salts, and can be respectively applied to lithium-ion batteries, sodium-ion batteries or potassium-ion batteries, and can improve their fast charging performance and cycle performance. In some embodiments, the isolation membrane meets at least one of the following conditions: 1) The thickness D of the ceramic layer c 0.3 μm to 5 μm; 2) the thickness D of the polyacrylate layer L Preferably, the isolation film satisfies at least one of the following conditions: 1) the thickness D of the ceramic layer is c 0.5 μm to 2 μm; 2) the thickness D of the polyacrylate layer L In this case, the separator has better ion transmission performance, and the battery containing the separator has better fast charging performance and cycle performance.

[0013] In some embodiments, the composite coating has a thickness of 0.5 μm to 8 μm. Preferably, the composite coating has a thickness of 1 μm to 4 μm. In this case, the use of the separator can better balance the fast charging performance and energy density of the battery.

[0014] In some embodiments, the ceramic material includes at least one of aluminum oxide, magnesium oxide, zirconium oxide, zinc oxide, titanium dioxide, silicon oxide, or calcium oxide.

[0015] In some embodiments, the mass percentage of the ceramic material is 80% to 95% based on the total mass of the ceramic layer. This allows the ceramic layer to have better wettability and electrolyte retention, and also provides a closer bond between the ceramic layer and the polyacrylate layer or base film, further improving the battery's fast-charging and cycling performance.

[0016] In some embodiments, the average particle size of the ceramic material is 0.1 μm to 1 μm. In this case, the ceramic layer has better wettability and liquid retention for the electrolyte, which can further improve the fast charging performance and cycle performance of the battery.

[0017] In some embodiments, the base film has a thickness of 2 μm to 20 μm. Preferably, the base film has a thickness of 4 μm to 15 μm. In this case, the separator not only has good ion transport properties but also has better stability, which helps further improve the fast charging performance and cycle performance of the battery.

[0018] In some embodiments, the composite coating is provided on both sides of the base membrane. In this case, active ion bridges are formed on both sides of the separator, resulting in higher ion transport performance, further improving fast charging performance and battery cycle performance.

[0019] A second aspect of the present application provides a battery comprising the isolation membrane according to any embodiment of the first aspect.

[0020] According to the present application, the battery includes the isolation membrane described in any embodiment of the first aspect, so it can be understood that the battery has the beneficial effects of the first aspect.

[0021] A third aspect of the present application provides an electrical device comprising a battery according to any embodiment of the second aspect.

[0022] The present application provides an isolation membrane with good ion transport performance, thereby effectively improving the fast charging performance and cycle performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1 is a schematic diagram of an isolation membrane according to an embodiment of the present application.

[0024] FIG2 is a schematic diagram of an isolation membrane according to another embodiment of the present application.

[0025] FIG3 is a schematic structural diagram of a lithium-ion battery including the separator according to one embodiment of the present application shown in FIG2 .

[0026] FIG4 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0027] FIG. 5 is an exploded view of the battery cell shown in FIG. 4 according to an embodiment of the present application.

[0028] FIG6 is a schematic diagram of a battery module according to an embodiment of the present application.

[0029] FIG. 7 is a schematic diagram of a battery according to an embodiment of the present application.

[0030] FIG8 is an exploded view of the battery shown in FIG7 according to one embodiment of the present application.

[0031] FIG9 is a schematic diagram of an electrical device using a battery cell as a power source according to an embodiment of the present application.

[0032] Explanation of reference numerals: 10 composite coating; 11 polyacrylate layer; 12 ceramic layer; 20 base film; 30 positive electrode sheet; 40 negative electrode sheet; 50 electrolyte; 1 battery; 2 upper case; 3 lower case; 4 battery module; 5 battery cell; 51 housing; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0033] The following detailed description of the separator, battery, and electrical device disclosed herein will be described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid unnecessary length in the following description and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0034] The "ranges" disclosed herein are defined in terms of lower and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values ​​and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, the numerical range "a to b" is a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0035] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0036] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0037] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0038] As mentioned in the background technology above, with the widespread use of batteries, higher requirements have been placed on their fast charging performance. Batteries generally include a positive electrode sheet, a negative electrode sheet, and a separator. The separator is located between the positive and negative electrode sheets and serves to conduct ions and isolate electrons. The performance of the separator has a certain impact on the battery's cycle performance.

[0039] Currently, commonly used isolation membranes are generally polyolefin films, such as polyethylene films, polypropylene films, etc. The problem is that polyolefin isolation membranes have poor heat resistance and will shrink severely when heated, which may cause direct contact between the positive and negative electrodes, resulting in a short circuit and causing safety hazards.

[0040] To address the above issues, related technologies often use a ceramic coating on a polyolefin film to improve the heat resistance of the separator. The ceramic coating also has good liquid retention properties, which can increase the electrolyte content in the battery and improve battery performance. However, the problem is that the ceramic coating significantly increases the distance for ion transmission, resulting in a decrease in the ion transmission rate of the separator. This, to a certain extent, leads to increased polarization of the battery during charge and discharge, resulting in a decrease in the battery's fast-charging performance.

[0041] In view of the above technical problems, the present application provides an isolation membrane provided with a composite coating, which includes a directly bonded ceramic layer and a polyacrylate layer. The ceramic layer and the polyacrylate layer can synergistically form an ion bridge high-speed pathway, giving the isolation membrane good ion transport performance, reducing the polarization of the battery during the charge and discharge process, and thus improving the battery's fast charging performance. The isolation membrane, battery, and electrical equipment provided by this application are described in detail below.

[0042] Isolation film

[0043] The first aspect of the present application provides an isolation membrane, comprising: a base membrane, and a composite coating arranged on at least one side of the base membrane, the composite coating comprising a ceramic layer, the ceramic layer comprising a ceramic material, and a polyacrylate layer directly bonded to one side of the ceramic layer, the polyacrylate layer comprising an alkali metal salt polymer of acrylic acid, and the ceramic layer being arranged on one side close to the base membrane.

[0044] According to the present application, the composite coating includes a ceramic layer and a polyacrylate layer directly bonded to one side of the ceramic layer, and the ceramic layer is arranged on the side close to the base membrane. This is because in the battery, the electrolyte infiltration route is from the separator to the electrode plate. The ceramic layer located near the base membrane can effectively increase the electrolyte infiltration rate through capillary action, so that the electrolyte can fully penetrate the polyacrylate layer and enter the electrode plate, improving the battery's liquid retention performance. The acrylic acid alkali metal salt polymer in the polyacrylate layer can be ionized to form a large number of carboxylate ions under sufficient infiltration of the electrolyte, which can significantly increase the transmission rate of active ions in the electrolyte in the polyacrylate layer. It is understandable that during the charge and discharge process of the battery, the polyacrylate layer can quickly de- / intercalate active ions, and the ceramic layer with better liquid retention ability can also quickly replenish or receive active ions in the polyacrylate layer, so that the polyacrylate layer and the ceramic layer can form an ion bridge high-speed pathway, so that the separator has good ion transmission performance, reduces the polarization of the battery during the charge and discharge process, and improves the battery's fast charging performance and cycle performance.

[0045] It should be noted that although the polyacrylate layer has good ion transport performance, if it is not directly combined with the ceramic layer but directly combined with the base membrane, it cannot effectively improve the ion transport performance of the isolation membrane. This is because the wettability and liquid retention capacity of the base membrane and the polyacrylate layer are poorer than those of the ceramic layer. On the one hand, it may cause the electrolyte to be unable to completely infiltrate the polyacrylate layer, and the ion transport performance of the polyacrylate layer is reduced; on the other hand, during the battery cycle, although the polyacrylate layer can quickly de- / embed active ions, the active ions in the polyacrylate layer cannot be quickly replenished, thereby further reducing the ion transport performance of the polyacrylate layer, thereby failing to effectively reduce the polarization of the battery, and further failing to effectively improve the fast charging performance and cycle performance of the battery.

[0046] In some embodiments, the mass percentage of alkali metal in the acrylic acid alkali metal salt polymer is 3% to 8.9%. At this time, the active ion transmission rate in the polyacrylate layer is faster, and the high-speed ion bridge path formed by the composite coating thus obtained has a higher ion transmission efficiency, thereby further improving the ion transmission performance of the isolation membrane, and making the battery fast charging performance and cycle performance better. For example, the mass percentage of alkali metal in the acrylic acid alkali metal salt polymer can be 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 8.9%, or within the range composed of any of the above values. Preferably, the mass percentage of alkali metal in the acrylic acid alkali metal salt polymer is 5% to 7.5%. At this time, the isolation membrane has better ion transmission performance, and the battery containing the isolation membrane has better fast charging performance and cycle performance.

[0047] It should be noted that the mass percentage of alkali metal in alkali metal salt polymers of acrylic acid has a well-known meaning in the art and can be measured using methods and instruments known in the art. For example, the mass percentage of alkali metal in alkali metal salt polymers of acrylic acid can be measured using inductively coupled plasma emission spectrometry (ICP). Specifically, a polymer lithium salt sample of a certain mass M is taken and the mass m1 of the lithium element is measured using inductively coupled plasma emission spectrometry (ICP). Then, the average mass percentage of the lithium element in the polymer lithium salt = m1 / M×100%. Among them, the sample to be tested is prepared by the following method: weigh 0.2g of sample in a beaker, add 10mL of concentrated HNO3 solution, place it on a 180℃ hot plate and digest for 30min. After the sample is digested for 30min, cool it to room temperature, transfer the digestion solution to a 50mL volumetric flask through a funnel and make up the volume. Test according to the industry standard USEPA-6010D-2018, prepare the standard test solution, which is the multi-element standard solution of ICP analysis of the National Nonferrous Metals Testing Center. The curve concentration points are 0, 0.2, 0.5, 1.0, and 2.0mg / L respectively. Prepare the standard solution calibration curve through the instrument, input the sample mass and volume, and then test the digested solution. The solution outside the curve range needs to be diluted before testing. Finally, the element characteristic spectrum of atomic emission is used to identify the presence of the element (qualitative analysis), and the element content is determined according to the intensity of the spectral line (quantitative analysis).

[0048] In some embodiments, the number average molecular weight of the acrylic acid alkali metal salt polymer can be 3kDa to 1000kDa. At this time, the polyacrylate layer is more easily infiltrated by the electrolyte derived from the ceramic layer, and the polyacrylate layer can more quickly de- / embed active ions. The high-speed ion bridge path formed by the composite coating has a higher ion transmission efficiency, thereby further improving the ion transmission performance of the isolation membrane, and making the battery fast charging performance and cycle performance better. For example, the number average molecular weight of the acrylic acid alkali metal salt polymer can be 3kDa, 10kDa, 50kDa, 100kDa, 150kDa, 200kDa, 250kDa, 300kDa, 350kDa, 400kDa, 450kDa, 500kDa, 550kDa, 600kDa, 650kDa, 700kDa, 800kDa, 900kDa, 1000kDa, or within the range of any of the above values. Preferably, the number average molecular weight of the acrylic acid alkali metal salt polymer may be 200 kDa to 500 kDa, in which case the battery has better fast charging performance and cycle performance.

[0049] It should be noted that the number average molecular weight has a well-known meaning in the art and can be measured using methods and instruments known in the art. For example, gel permeation chromatography (GPC) can be used to detect the number average molecular weight of alkali metal salt polymers of acrylic acid.

[0050] In some embodiments, the alkali metal salt of acrylic acid polymer includes at least one of an alkali metal salt of polyacrylic acid, an alkali metal salt of polymethacrylic acid, and an alkali metal salt of polyethylacrylic acid. It is understood that the alkali metal salt of acrylic acid polymer is not limited to the aforementioned ones. Alkali metal salts of acrylic acid polymers known in the art that can form a coating and ionize in an electrolyte can be selected according to actual needs.

[0051] In some embodiments, the alkali metal salt of polyacrylate includes at least one of lithium polyacrylate, sodium polyacrylate, and potassium polyacrylate; and / or, the alkali metal salt of polymethacrylate includes at least one of lithium polymethacrylate, sodium polymethacrylate, and potassium polymethacrylate; and / or, the alkali metal salt of polyethylacrylate includes at least one of lithium polyethylacrylate, sodium polyethylacrylate, and potassium polyethylacrylate. Alkali metal salts of polyacrylate, alkali metal salts of polymethacrylate, and alkali metal salts of polyethylacrylate can be lithium salts or sodium salts or potassium salts, and can be used in lithium-ion batteries, sodium-ion batteries, and potassium-ion batteries, respectively, to improve their cycle performance. In addition, lithium salts, sodium salts, and potassium salts are ionized after the polyacrylate layer is infiltrated by the electrolyte, which can increase the content of active ions in the battery, thereby improving the first efficiency of the battery.

[0052] In some embodiments, the polyacrylate layer may further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose).

[0053] In some embodiments, the mass percentage of the alkali metal salt of acrylic acid polymer in the polyacrylate layer may be 80% to 100%.

[0054] In some embodiments, the thickness D of the ceramic layer c It can be 0.3μm to 5μm. In this case, the ceramic layer can have better liquid retention ability, and the ion bridge high-speed path formed with the polyacrylate layer is more stable, and it is not easy to stop the ion bridge high-speed path due to the inability to quickly replenish the active ions in the polyacrylate layer, thereby further improving the ion transmission performance of the isolation membrane and making the battery fast charging performance and cycle performance better. For example, the thickness of the ceramic layer D c Can be 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1 .5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2.0μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3.0μm, 3.1μm, 3.2μm, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4.0μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 4.6μm, 4.7μm, 4.8μm, 4.9μm, 5.0μm or any range thereof. Preferably, the thickness D of the ceramic layer is within the range of c It can be 0.5 μm to 2 μm, in which case the battery containing the isolation film has better fast charging performance and cycle performance.

[0055] In some embodiments, the thickness D of the polyacrylate layer is L It can be 0.2μm to 5μm. In this case, the polyacrylate layer is more easily infiltrated by the electrolyte and can provide sufficient active ions for deintercalation / embedding, thereby having better ion transmission performance, forming a more stable ion bridge high-speed path with the ceramic layer, and is less likely to be interrupted by the ion bridge high-speed path due to the excessive deintercalation / embedding of active ions in the polyacrylate layer, thereby further improving the ion transmission performance of the separator and making the battery fast-charging performance and cycle performance better. For example, the thickness D of the polyacrylate layer is LIt can be 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2.0μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2. 7 μm, 2.8 μm, 2.9 μm, 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4.0 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, 4.6 μm, 4.7 μm, 4.8 μm, 4.9 μm, 5.0 μm or any range thereof. Preferably, the thickness D of the polyacrylate layer is 2.8 μm, 2.9 μm, 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4.0 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, 4.6 μm, 4.7 μm, 4.8 μm, 4.9 μm, 5.0 μm or any range thereof. L It can be 0.5 μm to 2 μm, in which case the battery containing the isolation film has better fast charging performance and cycle performance.

[0056] In some embodiments, the thickness of the composite coating can be 0.5 μm to 8 μm. In this case, the ion bridge formed by the polyacrylate layer and the ceramic layer in the composite coating is more stable, and the resulting separator has better ion transport performance, improving the battery's fast charging performance and cycle performance. At the same time, the energy density of the separator can be better balanced. For example, the thickness of the composite coating can be 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, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm , 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4.0μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 4.6μm, 4.7μm, 4.8μm, 4.9μm, 5.0μm , 5.1μm, 5.2μm, 5.3μm, 5.4μm, 5.5μm, 5.6μm, 5.7μm, 5.8μm, 5.9μm, 6.0μm, 6.1μm, 6.2μm, 6.3μm, 6.4μm, 6.5μm, 6.6μm, 6.7μm, 6.8μm, 6.9μm, 7.0μm, 7.1μm, 7.2μm, 7.3μm, 7.4μm, 7.5μm, 7.6μm, 7.7μm, 7.8μm, 7.9μm, 8.0μm or any of the above values. Preferably, the thickness of the composite coating can be 1μm to 4μm. In this case, the use of the separator can better balance the fast charging performance and energy density of the battery.

[0057] It should be noted that the thicknesses of the composite coating, ceramic layer, and polyacrylate layer refer to the thickness ranges of the composite coating, ceramic layer, and polyacrylate layer on one side of the base film. When the composite coating is provided on both sides of the base film, the thickness of the composite coating, ceramic layer, and polyacrylate layer on either side falls within the aforementioned ranges and falls within the scope of protection of this application. The thicknesses of the composite coating, ceramic layer, polyacrylate layer, and base film can all be directly measured using a micrometer, but are not limited to the aforementioned measurement method. Other thickness measurement methods in the art can also be used for measurement.

[0058] In some embodiments, the ceramic material may include at least one of aluminum oxide, magnesium oxide, zirconium oxide, zinc oxide, titanium dioxide, silicon oxide, or calcium oxide. The ceramic material includes but is not limited to the above substances, and other ceramic materials available in the art may also be selected as the ceramic layer.

[0059] In some embodiments, based on the total mass of the ceramic layer, the mass percentage of the ceramic material is 80% to 95%, and the ceramic layer also includes a binder. The ceramic material is ceramic particles, and the ceramic particles may include at least one of aluminum oxide particles, magnesium oxide particles, zirconium oxide particles, zinc oxide particles, titanium dioxide particles, silicon oxide particles or calcium oxide particles, and the binder may be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin. At this time, the ceramic layer has better wettability and liquid retention ability for the electrolyte, and the ceramic layer is more tightly bonded to the polyacrylate layer or base film, which can further improve the fast charging performance and cycle performance of the battery.

[0060] In some embodiments, the average particle size of the ceramic material can be 0.1 μm to 1 μm. In this case, the ceramic layer has better wettability and liquid retention for the electrolyte, which can further improve the fast charging performance and cycle performance of the battery. For example, the average particle size of the ceramic material can be 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 μm, or any range consisting of the above values.

[0061] The average particle size of a ceramic material has a well-known meaning in the art and can be determined by known methods. For example, the particle size distribution can be measured using a laser diffraction particle size distribution analyzer (Malvern Mastersizer 3000) in accordance with the particle size distribution laser diffraction method (GB / T 19077-2016). The particle size Dv50 corresponding to the cumulative particle size distribution on a volume basis reaching 50% is obtained, which is the average particle size of the ceramic material.

[0062] In some embodiments, the ceramic layer may further include other additives, such as dispersants (e.g., organic acids). It should be noted that the ceramic layer is not limited to the above components, and those skilled in the art may select other components for preparing the ceramic layer in the prior art for use in separators according to actual needs.

[0063] In some embodiments, the thickness of the base film may be 2μm to 20μm. At this time, the base film has a higher strength to support the composite coating, and the isolation membrane has better stability. In addition, the isolation membrane has better ion transmission performance, which is conducive to further improving the fast charging performance and cycle performance of the battery. For example, the thickness of the base film may be 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm or within the range of any of the above values. Preferably, the thickness of the base film may be 4μm to 15μm, at which time the fast charging performance and cycle performance of the battery containing the isolation membrane are better.

[0064] In some embodiments, the ceramic layer is directly bonded to the base membrane. Because the ceramic layer not only has excellent wettability and electrolyte retention but also excellent thermal stability, its direct bonding to the base membrane can enhance the thermal stability of the separator and improve battery reliability. For example, Figure 1 shows an exemplary separator. The composite coating 10 includes a directly bonded polyacrylate layer 11 and a ceramic layer 12. In the composite coating 10, the ceramic layer 12 is directly bonded to one side of the base membrane 20.

[0065] In some embodiments, the base film can be made of at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The base film can be a single-layer film or a multi-layer composite film, without particular limitation. When the base film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0066] In some embodiments, a composite coating is provided on both sides of the base membrane. At this time, active ion bridge high-speed pathways are formed on both sides of the isolation membrane, and the ion transmission performance is higher, further improving the fast charging performance and cycle performance of the battery. For example, Figure 2 is an isolation membrane as an example, and a composite coating 10 is directly bonded to both sides of the base membrane 20. The composite coating 10 includes a directly bonded polyacrylate layer 11 and a ceramic layer 12. The ceramic layer 12 in the composite coating 1 is directly bonded to one side of the base membrane 20. In addition, since the polyacrylate layer 11 is provided in the outermost layer and has good adhesion, it can be well integrated with the positive electrode sheet and the negative electrode sheet, which can improve the flatness of the battery, and can form a passivation layer to reduce the side reactions between the active material and the electrolyte, thereby further improving the fast charging performance and cycle performance of the battery.

[0067] In some embodiments, the isolation membrane can be prepared by the following method: the components for preparing the ceramic layer, such as ceramic particles, binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a ceramic layer slurry; the ceramic layer slurry is coated on the base membrane and dried to form a ceramic layer; the components for preparing the polyacrylate layer, such as an alkali metal salt polymer of acrylic acid, are dispersed in a solvent (such as water) to form a polyacrylate layer slurry; the polyacrylate layer slurry is coated on the ceramic layer and dried to form a composite coating to obtain an isolation membrane. It is understood that the method for preparing the isolation membrane is not limited to the above embodiment, and can also be prepared by other embodiments, such as casting the ceramic layer slurry on a separate carrier to form a ceramic layer; casting the polyacrylate layer slurry on the ceramic layer to form a composite coating; and pressing the composite coating on the base membrane to obtain the isolation membrane. In addition, the solid content of the ceramic layer slurry and the polyacrylate layer slurry can be selected according to actual needs to obtain a slurry with an appropriate viscosity for easy coating.

[0068] Battery

[0069] A second aspect of the present application provides a battery comprising an isolation membrane according to any embodiment of the first aspect.

[0070] According to the present application, the battery includes the isolation membrane of any embodiment of the first aspect, so it can be understood that the battery has the beneficial effects of the first aspect.

[0071] Typically, a battery consists of a positive electrode, a negative electrode, and an electrolyte. During the battery's charge and discharge processes, active ions are embedded in and released from the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes.

[0072] In some embodiments, the separator composite coating is disposed on the negative electrode side. Because the ionic conductivity of the negative electrode side of a battery is poorer than that of the positive electrode side, which is a limiting factor in improving battery cycle performance, disposing the separator composite coating on the negative electrode side can further improve battery cycle performance.

[0073] [Positive electrode]

[0074] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

[0075] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0076] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0077] In some embodiments, the positive electrode active material may adopt the positive electrode active material for batteries that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0078] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0079] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0080] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0081] [Negative electrode]

[0082] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0083] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0084] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0085] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0086] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0087] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0089] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0090] [Electrolyte]

[0091] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. This application has no specific restrictions on the type of electrolyte, and it can be selected according to needs.

[0092] In some embodiments, the electrolyte includes an electrolyte salt and a solvent.

[0093] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0094] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0095] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0096] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0097] In some embodiments, the battery may be a lithium-ion battery or a sodium-ion battery.

[0098] Figure 3 is a schematic structural diagram of a lithium-ion battery including an isolation membrane according to an embodiment of the present application shown in Figure 2. The positive electrode sheet 30, the isolation membrane and the positive electrode sheet are stacked. The direction of the arrow in the figure indicates the diffusion direction of the electrolyte in the lithium-ion battery. The electrolyte 50 expands from the isolation membrane to the electrode sheets on both sides. The capillary action of the ceramic layer 12 in the composite coating 10 increases the infiltration rate of the electrolyte 50, so that the electrolyte 50 fully penetrates the polyacrylate layer 11 and enters the positive electrode sheet 30 and the negative electrode sheet 40 respectively, forming a lithium ion bridge high-speed passage on both sides of the base membrane, thereby increasing the transmission rate of lithium ions in the battery, thereby reducing polarization during charging and discharging, and improving the cycle performance of the lithium-ion battery.

[0099] In some embodiments, a battery may include a battery cell including the above-described electrode assembly.

[0100] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0101] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0102] The present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square, or any other shape. For example, FIG4 shows a battery cell 5 with a square structure as an example.

[0103] In some embodiments, referring to Figure 5, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0104] In some embodiments, the battery may further include a case; the battery cells are housed in the case.

[0105] The battery may include one or more battery cells, and those skilled in the art may select the specific number based on the application and capacity of the battery.

[0106] Furthermore, in the above-described battery, multiple battery cells are assembled to form a battery module. Figure 6 shows an example battery module 4. Referring to Figure 6, within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple battery cells 5 may be secured using fasteners.

[0107] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0108] Figures 7 and 8 illustrate an example battery 1. Referring to Figures 7 and 8 , the battery 1 may include a battery box and multiple battery modules 4 disposed within the box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be positioned over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0109] In some embodiments, the battery may be a secondary battery.

[0110] Electrical devices

[0111] In a third aspect, the present application further provides an electrical device comprising a battery according to any embodiment of the second aspect.

[0112] The battery can be used as a power source or an energy storage unit for the electrical devices. The electrical devices may include, but are not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, and energy storage systems.

[0113] As the electrical device, the above-mentioned battery can be selected according to its usage requirements.

[0114] FIG9 shows an example of an electric device, which may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

[0115] As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery consisting of only battery cells as a power source.

[0116] Example

[0117] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0118] Example 1

[0119] (1) Preparation of isolation membrane

[0120] A commercially available 7μm-thick PE polymer microporous film (from Zhuogao Electronic Technology Co., Ltd.) was used as the base membrane. Ceramic particles and polyvinylidene fluoride (PVDF) were dispersed in N-methylpyrrolidone at a mass ratio of 95:5 to form a ceramic layer slurry with a viscosity of 10 mPa·s. This ceramic layer slurry was coated on both sides of the base membrane and dried to form ceramic layers. An alkali metal salt of acrylic acid polymer was dispersed in water to form a polyacrylate layer slurry with a mass fraction of 20 wt%. The polyacrylate layer slurry was then coated on both sides of the ceramic layers and dried to form a composite coating on both sides of the base membrane to form a separator. The ceramic particles were alumina ceramic particles with a Dv50 of 0.1μm, and the ceramic layer was 0.3μm thick. The alkali metal salt of acrylic acid polymer was lithium polyacrylate with a number-average molecular weight of 300 kDa and a lithium content (lithium by mass) of 6.5%. The polyacrylate layer was 1μm thick, and the composite coating was 1.3μm thick.

[0121] (2) Preparation of positive electrode sheet

[0122] Polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), conductive carbon black, and N-methylpyrrolidone (NMP) were mixed in a mass ratio of 1.2:58.38:0.42:40 and stirred thoroughly to prepare a positive electrode slurry. 2 The loading amount is evenly coated on both sides of the positive electrode current collector aluminum foil, and then dried, cold pressed and cut to obtain the positive electrode sheet.

[0123] (3) Preparation of negative electrode sheet

[0124] Artificial graphite, conductive agent acetylene black, binder styrene butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC-Na) were added into deionized water in a mass ratio of 96.2:1.0:1.6:1.2, and stirred thoroughly to prepare a negative electrode slurry (solid content of 63%). 2 The negative electrode sheet is obtained by coating the negative electrode current collector copper foil with a loading amount of 200 nm on both sides, and then drying, cold pressing and cutting.

[0125] (4) Preparation of electrolyte

[0126] At 25°C, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain a mixed solvent, and then LiPF6 is dissolved in the above mixed solvent to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0127] (5) Preparation of lithium-ion batteries

[0128] The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, wound, and cold-pressed (during which the separator and the electrode sheet are bonded) to obtain a battery cell; the battery cell is placed in an outer package, and the above-prepared electrolyte is added. After packaging, standing, formation, aging and other processes, a lithium-ion battery is obtained.

[0129] Examples 2 to 19 are substantially the same as Example 1, and some of the different parameters are detailed in Table 1.

[0130] Example 20 is substantially the same as Example 3, except that the mass ratio of ceramic particles to polyvinylidene fluoride in the ceramic layer slurry is 80:20.

[0131] Example 21

[0132] (1) The preparation method of the isolation film is substantially the same as that of Example 3, except that the composite coating is prepared only on one side of the base film.

[0133] (2-4) The preparation of the positive electrode sheet, negative electrode sheet and electrolyte is the same as that in Example 1.

[0134] (5) Preparation of lithium-ion batteries: The positive electrode sheets, separators, and negative electrode sheets are stacked in sequence, wound, and cold-pressed (during which the separators are bonded to the sheets) to obtain a battery cell; wherein the composite coating of the separator is provided on the side close to the negative electrode sheet; the battery cell is placed in an outer package, and the electrolyte prepared above is added, and after packaging, standing, formation, aging, and other processes, a lithium-ion battery is obtained.

[0135] Comparative Example 1

[0136] The process is substantially the same as Example 1, except that a commercially available PE polymer microporous film with a thickness of 7 μm is directly used as the separator of the secondary battery.

[0137] Comparative Example 2

[0138] (1) Preparation of isolation membrane

[0139] A commercially available 7μm-thick PE polymer microporous film (from Zhuogao Electronic Technology Co., Ltd.) was used as the base membrane. Ceramic particles and polyvinylidene fluoride (PVDF) were dispersed in N-methylpyrrolidone at a mass ratio of 95:5 to form a ceramic layer slurry with a viscosity of 10 mPa·s. This ceramic layer slurry was applied to one side of the base membrane and dried to form a ceramic layer. An alkali metal salt of acrylic acid polymer was dispersed in water to form a polyacrylate layer slurry with a mass fraction of 20 wt%. This polyacrylate layer slurry was applied to the other side of the base membrane and dried to form a polyacrylate layer. The separator membrane was obtained. The ceramic particles were alumina ceramic particles with a Dv50 of 0.1μm, and the ceramic layer was 2μm thick. The alkali metal salt of acrylic acid polymer was lithium polyacrylate with a number-average molecular weight of 300 kDa and a lithium metal content of 6.5%, and the polyacrylate layer was 1μm thick.

[0140] (2-4) The preparation of the positive electrode sheet, negative electrode sheet and electrolyte is the same as that in Example 1.

[0141] (5) Preparation of lithium-ion batteries: The positive electrode sheets, separators, and negative electrode sheets are stacked in sequence, wound, and cold-pressed (during which the separators are bonded to the sheets) to obtain a battery cell; wherein the ceramic layer of the separator is arranged on the side close to the negative electrode sheet; the battery cell is placed in an outer package, and the electrolyte prepared above is added, and after packaging, standing, formation, aging, and other processes, a lithium-ion battery is obtained.

[0142] Comparative Example 3

[0143] (1-4) The preparation of the separator, positive electrode sheet, negative electrode sheet and electrolyte is the same as that of Comparative Example 2.

[0144] (5) Preparation of lithium-ion batteries: The positive electrode sheets, separators, and negative electrode sheets are stacked and wound in order, and cold-pressed (during which the separators are bonded to the sheets) to obtain a battery cell; wherein the ceramic layer of the separator is arranged on the side close to the positive electrode sheet; the battery cell is placed in an outer package, and the electrolyte prepared above is added, and after packaging, standing, formation, aging, and other processes, a lithium-ion battery is obtained.

[0145] The lithium-ion batteries obtained in Examples 1 to 21 and Comparative Examples 1 to 3 were subjected to the following performance tests. The test results are shown in Table 1 below.

[0146] (1) Lithium-ion battery cycle capacity retention test at different temperatures:

[0147] Place the battery cell in a fixed temperature (25℃ / 35℃ / 60℃) incubator for 2 hours;

[0148] Charge the battery at a constant current rate of 1C to 100% SOC.

[0149] Set aside for 30 minutes;

[0150] Discharge at a constant current rate of 1C until the cell reaches 0% SOC;

[0151] Completing the above ①②③④ process tests is one cycle, recorded as 1Cycle, and the capacity discharged by the battery cell is Cap;

[0152] Cycle ①②③④ 1500 times to complete the test. The capacity of the battery discharged in the first cycle is recorded as Cap1, and the capacity of the battery discharged in the 1500th cycle is recorded as Cap 1500 , the retention rate of the battery cell cycle capacity is Cap 1500 / Cap1×100%.

[0153] (2) Lithium-ion battery fast charging performance test:

[0154] Using Cu wire as the three electrodes, charge at a 5C charge rate until the anode potential drops to 0mV, then jump to low-rate charging, and charge at low rates of 4C, 3C, 2C, and 1C in sequence to obtain the maximum charging capacity Map of the battery cell.

[0155] Starting from 0% SOC, perform step charging with the maximum capacity charging map of the battery cell until the battery cell cut-off voltage reaches 3.8V. The time required to charge from 0% SOC to 3.8V is recorded as the fast charging time of the battery.

[0156]

[0157]

[0158] According to the results in Table 1, the fast charging performance and the cycle capacity retention rate at different temperatures of each embodiment are significantly improved compared with the comparative examples. This shows that the composite coating prepared on the surface of the base membrane can form an ion bridge high-speed passage, which can effectively improve the ion transmission performance of the isolation membrane, thereby improving the fast charging performance and cycle performance of the battery. In Comparative Examples 2 to 3, the ceramic layer and the polyacrylate layer are respectively arranged on both sides of the base membrane, and the two play a role on both sides of the base membrane, so that the two cannot cooperate to form an ion bridge high-speed passage in the obtained isolation membrane, and compared with Comparative Example 1, it cannot effectively improve the fast charging performance of the battery and the cycle capacity retention rate at different temperatures.

[0159] Comparing Examples 1 to 8, it can be seen that the thickness of the ceramic layer and the polyacrylate layer in the composite coating have a certain impact on the fast charging performance and cycle performance of the battery. When the ceramic layer thickness is 0.3μm to 5μm, the battery has good fast charging performance and cycle performance, and more preferably 0.5μm to 2μm. When the polyacrylate layer thickness is 0.2μm to 5μm, the battery has good fast charging performance and cycle performance, and more preferably 0.5μm to 2μm.

[0160] Comparison of Examples 3 and 9-12 shows that the alkali metal content of the acrylic acid alkali metal salt polymer in the polyacrylate layer has a certain impact on the fast-charging and cycling performance of the battery. When the alkali metal content is 3% to 8%, the battery has good fast-charging and cycling performance, and more preferably, it is 5% to 7.5%.

[0161] Comparison of Example 3 with Examples 13-16 shows that the number average molecular weight of the alkali metal salt of acrylic acid polymer in the polyacrylate layer has a certain impact on the fast-charging and cycling performance of the battery. When the number average molecular weight is between 3 kDa and 800 kDa, the battery has good fast-charging and cycling performance, and a number average molecular weight of 500-700 kDa is more preferred.

[0162] By comparing Examples 5, 17, and 18, it can be seen that different types of ceramics and polyacrylates have little effect on the fast charging performance and cycle performance of the battery, and can all effectively improve the fast charging performance and cycle performance of the battery.

[0163] By comparing Examples 5 and 19, it can be seen that the ceramic layers formed by ceramic particles of different particle sizes can effectively improve the fast charging performance and cycle performance of the battery.

[0164] By comparing Examples 5 and 20, it can be seen that when the mass percentage of ceramic particles in the ceramic layer is 80% to 95%, the fast charging performance and cycle performance of the battery can be effectively improved.

[0165] According to Example 21, the isolation membrane coated with a composite coating on one side can effectively improve the fast charging performance and cycle performance of the battery.

[0166] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A separation film, comprising: A base film, and a composite coating disposed on at least one side of the base film, The composite coating comprises a ceramic layer, wherein the ceramic layer comprises a ceramic material, and a polyacrylate layer directly bonded to one side of the ceramic layer, the polyacrylate layer comprising an alkali metal salt polymer of acrylic acid, The ceramic layer is arranged on a side close to the base film.

2. The isolation film according to claim 1, wherein: The mass percentage of alkali metal in the acrylic acid alkali metal salt polymer is 3% to 8.9%.

3. The isolation film according to claim 1 or 2, wherein: The number average molecular weight of the acrylic acid alkali metal salt polymer is 3 kDa to 1000 kDa.

4. The isolation film according to any one of claims 1 to 3, wherein: The acrylic acid alkali metal salt polymer includes at least one of polyacrylic acid alkali metal salt, polymethacrylic acid alkali metal salt or polyethylacrylic acid alkali metal salt.

5. The isolation film according to claim 4, wherein: The polyacrylic acid alkali metal salt includes at least one of lithium polyacrylate, sodium polyacrylate and potassium polyacrylate; And / or, the polymethacrylate alkali metal salt includes at least one of lithium polymethacrylate, sodium polymethacrylate, and potassium polymethacrylate; And / or, the alkali metal salt of polyethylacrylate includes at least one of lithium polyethylacrylate, sodium polyethylacrylate and potassium polyethylacrylate.

6. The isolation film according to any one of claims 1 to 5, wherein: The isolation film satisfies at least one of the following conditions: 1) The thickness D of the ceramic layer c 0.3μm~5μm; 2) Thickness D of the polyacrylate layer L 0.2μm~5μm.

7. The isolation film according to any one of claims 1 to 6, wherein: The thickness of the composite coating is 0.5 μm to 8 μm.

8. The isolation film according to any one of claims 1 to 7, wherein: The ceramic material includes at least one of aluminum oxide, magnesium oxide, zirconium oxide, zinc oxide, titanium dioxide, silicon oxide or calcium oxide.

9. The isolation film according to claim 8, wherein: Based on the total mass of the ceramic layer, the mass percentage of the ceramic material is 80% to 95%.

10. The isolation film according to claim 9, wherein: The average particle size of the ceramic material is 0.1 μm to 1 μm.

11. The isolation film according to claim 1, wherein: The base film has a thickness of 2 μm to 20 μm.

12. The separator according to any one of claims 1 to 11, wherein: Composite coatings are arranged on both sides of the base film.

13. A battery comprising the separator according to any one of claims 1 to 12.

14. An electrical device comprising the battery according to claim 13.

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