Diaphragms, batteries and electrical equipment

Abstract

The present application discloses a diaphragm, a battery and an electrical device. The diaphragm includes a diaphragm base layer, which has a first end and a second end along a first direction, and the first direction is the width direction of the diaphragm; a ceramic layer, which is arranged on at least one side of the diaphragm base layer along a second direction (i.e., the Z direction), and the second direction (i.e., the Z direction) is the thickness direction of the diaphragm, and the ceramic layer extends along the first direction, and the thickness of the ceramic layer decreases successively along the direction from the first end to the second end; a polymer layer, which is arranged on a side of the ceramic layer away from the diaphragm base layer or on a side of the diaphragm base layer away from the ceramic layer, and the polymer layer extends along the first direction, and the thickness of the polymer layer increases successively along the direction from the first end to the second end.

Description

Technical Field

[0001] The present application belongs to the field of battery technology, and specifically relates to a diaphragm, a battery and an electrical device. Background Art

[0002] Lithium-ion batteries consist of four parts: a positive electrode, a negative electrode, a separator, and an electrolyte. The separator separates the positive and negative electrodes, preventing short circuits between the positive and negative electrodes inside the battery, while also transmitting lithium ions. This requires the separator to have both low resistance and high conductivity, and good permeability to lithium ions. In order to improve the thermal shrinkage and wettability of the separator, various coatings are usually provided on the surface of the separator. However, after the battery cell has been running for a long time (especially 10,000 cycles), the existing separator still has the problem of being unable to adapt. Summary of the Invention

[0003] The present application aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the purpose of the present application is to propose a diaphragm, a battery and an electrical device. The present application can effectively adjust the problem of inconsistent ion transmission levels between the upper and lower parts of the battery cell by arranging a ceramic layer with a thickness that gradually decreases along the direction from the first end to the second end on at least one side of the diaphragm base layer. At the same time, the present application can effectively adjust the problem of inconsistent interfacial adhesion requirements of the upper and lower parts of the battery cell to the diaphragm by arranging a polymer layer with a thickness that gradually increases along the direction from the first end to the second end on the side of the ceramic layer away from the diaphragm base layer or on the side of the diaphragm base layer away from the ceramic layer.

[0004] In one aspect of the present application, the present application provides a diaphragm. According to an embodiment of the present application, the diaphragm includes:

[0005] a diaphragm base layer, the diaphragm base layer having a first end and a second end along a first direction, wherein the first direction is a width direction of the diaphragm;

[0006] a ceramic layer, the ceramic layer being disposed on at least one side of the diaphragm base layer along a second direction (i.e., the Z direction), the second direction (i.e., the Z direction) being the thickness direction of the diaphragm, the ceramic layer extending along the first direction, and the thickness of the ceramic layer decreasing successively along the direction from the first end to the second end;

[0007] A polymer layer is arranged on a side of the ceramic layer away from the diaphragm base layer or on a side of the diaphragm base layer away from the ceramic layer, the polymer layer extends along the first direction, and the thickness of the polymer layer increases successively along the direction from the first end to the second end.

[0008] According to the diaphragm of the embodiment of the present application, the present application can effectively adjust the problem of inconsistent ion transmission levels between the upper and lower parts of the battery cell by arranging a ceramic layer with a thickness that decreases gradually from the first end (located at the upper part of the battery) to the second end (the lower part of the battery) on at least one side of the diaphragm base layer, and at the same time adjusts the problem of inconsistent electrolyte infiltration in the late cycle, thereby improving the incremental permeability value of the diaphragm as a whole and improving the consistency of the battery cell operation. At the same time, the present application can effectively adjust the problem of inconsistent interface adhesion requirements of the upper and lower parts of the battery cell to the diaphragm by arranging a polymer layer with a thickness that increases gradually from the first end (located at the upper part of the battery) to the second end (the lower part of the battery) on the side of the ceramic layer away from the diaphragm base layer or on the side of the diaphragm base layer away from the ceramic layer, thereby improving the adhesion of the diaphragm to the electrode sheet as a whole and improving the consistency of the battery cell operation.

[0009] In addition, the diaphragm according to the above embodiment of the present application may also have the following additional technical features:

[0010] In some embodiments of the present application, the thickness of the ceramic layer decreases linearly along the direction from the first end to the second end; and / or the thickness of the polymer layer increases linearly along the direction from the first end to the second end.

[0011] In some embodiments of the present application, the thickness of the ceramic layer decreases linearly from the first end to the second end with a slope of 10 -6 ~10 -5 Alternatively, the thickness of the ceramic layer decreases linearly along the direction from the first end to the second end with a slope of 2*10 -6 ~5*10 -6 .

[0012] In some embodiments of the present application, the thickness of the polymer layer increases linearly from the first end to the second end with a slope of 10 -6 ~10 -5 Alternatively, the thickness of the polymer layer increases linearly along the direction from the first end to the second end with a slope of 2*10 -6 ~5*10 -6 .

[0013] In some embodiments of the present application, the absolute value of the slope of the linearly decreasing thickness of the ceramic layer along the direction from the first end to the second end is equal to the absolute value of the slope of the linearly increasing thickness of the polymer layer along the direction from the first end to the second end.

[0014] In some embodiments of the present application, the thickness of the ceramic layer corresponding to the first end is 2.2 μm to 4 μm; and / or the thickness of the ceramic layer corresponding to the second end is 1.8 μm to 2.2 μm.

[0015] In some embodiments of the present application, the thickness of the polymer layer corresponding to the first end is 0 μm to 0.8 μm; and / or the thickness of the polymer layer corresponding to the second end is 0.8 μm to 2.2 μm.

[0016] In some embodiments of the present application, the thickness of the diaphragm base layer is 7 μm to 20 μm; or the sum of the thicknesses of the ceramic layer and the polymer layer is 2 μm to 5 μm.

[0017] In some embodiments of the present application, the ceramic layer includes: 20 to 50 parts by weight of ceramic material, 0.5 to 5 parts by weight of a first binder, 0.05 to 1 parts by weight of a thickener, 0.05 to 0.5 parts by weight of a dispersant, and 50 to 80 parts by weight of a first solvent; or, the ceramic layer includes: 27 to 38 parts by weight of ceramic material, 0.9 to 2 parts by weight of a first binder, 0.06 to 0.08 parts by weight of a thickener, 0.06 to 0.08 parts by weight of a dispersant, and 60 to 70 parts by weight of a first solvent.

[0018] In some embodiments of the present application, the polymer layer includes: 1 to 30 parts by weight of a polymer monomer, 0.1 to 5 parts by weight of a second binder, 0.1 to 1.5 parts by weight of an auxiliary agent, and 60 to 95 parts by weight of a second solvent; or, the polymer layer includes: 8.5 to 18 parts by weight of a polymer monomer, 1 to 3 parts by weight of a second binder, 0.5 to 0.8 parts by weight of an auxiliary agent, and 80 to 90 parts by weight of a second solvent.

[0019] In a second aspect of the present application, a battery is provided. According to an embodiment of the present application, the battery comprises the separator of the above embodiment, thereby effectively improving the cycle performance and safety performance of the battery.

[0020] In addition, the battery according to the above embodiment of the present application may also have the following additional technical features:

[0021] In some embodiments of the present application, the battery includes: a positive electrode sheet, a negative electrode sheet and the separator described in the above embodiments, the positive electrode sheet, the separator and the negative electrode sheet are stacked in sequence and wound along the length direction of the separator to form a core, the length direction of the separator is perpendicular to the width direction of the separator; and the first end of the separator base layer is located at the upper part of the battery, and the second end of the separator base layer is located at the lower part of the battery.

[0022] In a third aspect of the present application, an electrical device is provided. According to an embodiment of the present application, the electrical device comprises the battery described above. Thus, the electrical device has all the advantages of the battery, which will not be further elaborated here.

[0023] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0025] Figure 1 A schematic structural diagram of a battery according to an embodiment of the present application;

[0026] Figure 2 This is a structural schematic diagram of the unfolded state of the winding core according to an embodiment of the present application;

[0027] Figure 3 This is a schematic structural diagram of a diaphragm according to an embodiment of the present application;

[0028] Figure 4 This is a schematic structural diagram of a diaphragm according to another embodiment of the present application;

[0029] Figure 5 Schematic diagram of regional testing of the air permeability and adhesion performance of the diaphragm according to the embodiment of the present application.

[0030] Reference numerals:

[0031] 100 - battery, 110 - winding core, 120 - tab, 111 - separator, 111-1 - separator base layer, 111-2 - ceramic layer, 111-3 - polymer layer, A - first end, B - second end. DETAILED DESCRIPTION

[0032] The following describes in detail embodiments of the present application, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0033] The technical solution of this application was completed by the inventor based on the following findings:

[0034] In order to improve the thermal shrinkage and wettability of the diaphragm, a ceramic layer can be provided on the surface of the diaphragm base layer, thereby improving the safety performance and cycle performance of the battery. In order to improve the interface wrinkles caused by the expansion of the negative electrode and the gas production problem during the cycle, a polymer layer can be provided on the surface of the diaphragm base layer. The polymer layer can shorten the lithium ion transmission distance by bonding the positive electrode sheet and / or the negative electrode sheet, thereby achieving a balance between bonding and internal resistance. In the related art, the ceramic layer and the polymer layer provided on the surface of the diaphragm base layer are of the same thickness in the width direction of the diaphragm. However, studies have found that for high-capacity batteries (especially square batteries), after long-term operation (especially 10,000 turns), under the dual effects of electrolyte consumption and gravity, the electrolyte consumption at different positions of the battery roll (JR) is different, and there will be a problem of insufficient upper electrolyte, and the requirements for the transmission capacity of the diaphragm are also different. Generally speaking, after long-term operation, the amount of electrolyte in the upper part of the JR near the tab decreases, hindering ion transmission; while the electrolyte in the lower part of the JR is sufficient, and ion transmission is faster. This will cause inconsistency in the overall dynamics of the battery cell, affecting the electrical performance of the battery cell after long-term operation. At the same time, the upper and lower parts of the battery cell have different structures. There are tabs on the upper part of the JR. The welded tabs are welded to the top cover, which imposes a certain constraint on the upper part of the JR, while the lower part of the JR is only bound by blue glue, and its binding force is far less than the binding force of the tab on the battery cell. After long-term operation, the expansion of the negative electrode and the gas production caused by electrolyte consumption will impact the battery interface. The design of the battery cell makes the upper and lower parts of the JR have inconsistent requirements for bonding strength. The lower part of the JR requires a diaphragm with stronger bonding strength to avoid gaps between the electrode and the diaphragm, which leads to poor infiltration and purple lithium precipitation, affecting the safety and cycle performance of the battery.

[0035] In view of this, in one aspect of the present application, the present application proposes a diaphragm 111. According to an embodiment of the present application, referring to the attached Figure 3 and 4The diaphragm 111 includes: a diaphragm base layer 111-1, the diaphragm base layer 111-1 has a first end A and a second end B along a first direction (i.e., Y direction), and the first direction (i.e., Y direction) is the width direction of the diaphragm 111; a ceramic layer 111-2, the ceramic layer 111-2 is provided on at least one side of the diaphragm base layer 111-1 along a second direction (i.e., Z direction), and the second direction (i.e., Z direction) is the thickness direction of the diaphragm 111, and the ceramic layer 111-2 extends along the first direction (i.e., Y direction). , and the thickness of the ceramic layer 111-2 decreases gradually along the direction from the first end A to the second end B; the polymer layer 111-3, the polymer layer 111-3 is arranged on the side of the ceramic layer 111-2 away from the diaphragm base layer 111-1 or on the side of the diaphragm base layer 111-1 away from the ceramic layer 111-2, the polymer layer 111-3 extends along the first direction (i.e., the Y direction), and the thickness of the polymer layer 111-3 increases gradually along the direction from the first end A to the second end B. Therefore, the present application provides a ceramic layer 111-2 on at least one side of the diaphragm base layer 111-1, the thickness of which decreases successively from the first end A (located at the upper part of the battery 100, close to the end of the pole tab 120) to the second end B (located at the lower part of the battery 100, away from the end of the pole tab 120). This can effectively adjust the problem of inconsistent ion transmission levels in the upper and lower parts of the battery cell, and at the same time adjust the problem of inconsistent electrolyte infiltration in the late stage of the cycle, thereby improving the permeability value increment of the diaphragm 111 as a whole and improving the consistency of the battery cell operation. At the same time, the present application can effectively adjust the problem of inconsistent interface adhesion requirements of the upper and lower parts of the battery cell to the diaphragm 111 by arranging a polymer layer 111-3 with a thickness increasing successively along the direction from the first end A (located at the upper part of the battery) to the second end B (the lower part of the battery) on the side of the ceramic layer 111-2 away from the diaphragm base layer 111-1, thereby improving the overall adhesion of the diaphragm 111 to the electrode and improving the consistency of the battery cell operation.

[0036] The following is a detailed description of the principle by which the diaphragm 111 proposed in this application can achieve the above beneficial effects:

[0037] After a long period of operation (especially 10,000 cycles), under the dual effects of electrolyte consumption and gravity, there will be a problem of insufficient upper electrolyte inside the battery cell. At the same time, due to the expansion of the negative electrode and the increase in gas production, the demand for adhesion at the bottom of JR increases. The reduction of the upper electrolyte leads to the obstruction of lithium ion transmission in the upper layer of JR, and it is necessary to match the coating of thick ceramic and thin polymer to achieve the effect of accelerating ion transmission. At the same time, the high-porosity diaphragm 111 can bring higher liquid retention performance, which can alleviate the problem of insufficient upper electrolyte after long-term circulation to the greatest extent. The electrolyte in the lower part of JR is sufficient, and the ion transmission is unobstructed. In order to match the transmission capacity of the upper part and meet the higher adhesion requirements caused by gas production and expansion, the overall transmission capacity of the battery cell is consistent and the interface is consistent. A thin ceramic and thick polymer coating is used at the bottom. Thus, the present application provides a ceramic layer 111-2 whose thickness decreases in the direction from the first end A (located at the upper part of the battery) to the second end B (the lower part of the battery) on at least one side of the diaphragm base layer 111-1, which can effectively adjust the problem of inconsistent ion transmission levels between the upper and lower parts of the battery cell, and at the same time adjust the problem of inconsistent electrolyte infiltration in the late cycle, thereby improving the permeability increment of the diaphragm 111 as a whole and improving the consistency of the battery cell operation. At the same time, the present application provides a polymer layer 111-3 whose thickness increases in the direction from the first end A (located at the upper part of the battery) to the second end B (the lower part of the battery) on the side of the ceramic layer 111-2 away from the diaphragm base layer 111-1 or on the side of the diaphragm base layer 111-1 away from the ceramic layer 111-2, which can effectively adjust the problem of inconsistent interface adhesion requirements of the upper and lower parts of the battery cell to the diaphragm 111, thereby improving the adhesion of the diaphragm 111 to the electrode as a whole and improving the consistency of the battery cell operation.

[0038] In the embodiment of the present application, the diaphragm 111 includes two structures. The first structure is: the ceramic layer 111-2 is arranged on one side of the diaphragm base layer 111-1 along the second direction (i.e., the Z direction), and the polymer layer 111-3 is arranged on the side of the diaphragm base layer 111-1 away from the ceramic layer 111-2, as shown in the attached figure. Figure 3 The second structure is as follows: the ceramic layer 111-2 is arranged on at least one side of the diaphragm base layer 111-1 along the second direction (ie, the Z direction), and the polymer layer 111-3 is arranged on the side of the ceramic layer 111-2 away from the diaphragm base layer 111-1, as shown in the attached figure. Figure 4 shown.

[0039] According to some specific embodiments of the present application, the thickness of the ceramic layer decreases linearly along the direction from the first end to the second end. Further, the thickness of the ceramic layer 111-2 decreases linearly along the direction from the first end A to the second end B at a slope of 10 -6 ~10 -5 , for example, it can be 1*10 -6 , 2*10 -6, 4*10 -6 , 5*10 -6 , 6*10 -6 、8*10 -6 , 10 -5 Etc., by limiting the slope of the linear decrease in the thickness of the ceramic layer 111-2 to the above range, it is possible to further effectively ensure that the problem of inconsistent ion transmission levels between the upper and lower parts of the battery cell is regulated, and at the same time, the problem of inconsistent electrolyte infiltration in the late cycle can be further effectively regulated. The inventors found that if the slope of the linear decrease in the thickness of the ceramic layer 111-2 is too large, it will cause the dynamic differences of the various parts of the diaphragm 111 to be too large, which is not conducive to improving the consistency of the battery cell operation; if the slope of the linear decrease in the thickness of the ceramic layer 111-2 is too small, it will lead to the failure to achieve the purpose of regulating the dynamics of the various parts of the diaphragm 111, and it will be difficult to achieve in manufacturing. Preferably, the slope of the linear decrease in the thickness of the ceramic layer 111-2 along the direction from the first end A to the second end B can be 2*10 -6 ~5*10 -6 .

[0040] According to some further specific embodiments of the present application, the thickness of the polymer layer increases linearly along the direction from the first end to the second end. Further, the thickness of the polymer layer 111-3 increases linearly along the direction from the first end A to the second end B at a slope of 10 -6 ~10 -5 , for example, it can be 1*10 -6 , 2*10 -6 , 4*10 -6 , 5*10 -6 , 6*10 -6 、8*10 -6 , 10 -5 Etc., by limiting the slope of the linear increase in the thickness of the polymer layer 111-3 to the above range, it is possible to further effectively ensure that the problem of inconsistent requirements for the interfacial adhesion force of the upper and lower parts of the battery cell to the diaphragm 111 is regulated. The inventors have found that if the slope of the linear increase in the thickness of the polymer layer 111-3 is too large, it will cause the adhesion force of each part of the diaphragm 111 to be too different, and local stratification may occur in the later stage of the cycle; if the slope of the linear increase in the thickness of the polymer layer 111-3 is too small, it will lead to the failure to achieve the purpose of regulating the adhesion force of each part of the diaphragm 111, thereby failing to meet the different requirements of different parts of the battery cell for the interfacial adhesion force, and it is difficult to achieve in manufacturing. Preferably, the slope of the linear increase in the thickness of the polymer layer 111-3 along the direction from the first end A to the second end B can be 2*10 -6 ~5*10 -6 .

[0041] In the embodiments of the present application, the thickness of the diaphragm 111 must be consistent across the width. Inconsistent thickness can lead to significant differences in the mechanical properties and insulation withstand voltage capabilities of various parts of the diaphragm 111. Furthermore, in manufacturing, inconsistent thickness of the diaphragm 111 can cause tab misalignment during winding, seriously impacting manufacturing. To ensure consistent thickness across the width of the diaphragm 111, the absolute value of the linearly decreasing slope of the thickness of the ceramic layer 111-2 along the direction from the first end A to the second end B is equal to the absolute value of the linearly increasing slope of the thickness of the polymer layer 111-3 along the direction from the first end A to the second end B. Furthermore, the ceramic layer 111-2 and the polymer layer 111-3 appear in pairs. This ensures consistent thickness across the width of the diaphragm 111, avoiding significant differences in the mechanical properties and insulation withstand voltage capabilities of various parts of the diaphragm 111.

[0042] According to some other specific embodiments of the present application, the thickness (thickest part) of the ceramic layer 111-2 corresponding to the first end A can be 2.2μm to 4μm, for example, it can be 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 3μm, 3.5μm, 4μm, etc. By limiting the thickness (thickest part) of the ceramic layer 111-2 corresponding to the first end A to the above range, the thermal shrinkage and wettability of the diaphragm 111 can be significantly improved, thereby improving the safety performance and cycle performance of the battery, and the excessive thickness of the ceramic layer 111-2 can be avoided, which affects the air permeability of the diaphragm 111 and thus affects the energy efficiency of the battery.

[0043] According to some other specific embodiments of the present application, the thickness (thinnest part) of the ceramic layer 111-2 corresponding to the second end B can be 1.8μm to 2.2μm, for example, it can be 1.8μm, 1.9μm, 2.0μm, 2.1μm, 2.2μm, etc. By limiting the thickness (thinnest part) of the ceramic layer 111-2 corresponding to the second end B within the above range, the thermal shrinkage and wettability of the diaphragm 111 can be effectively improved, thereby improving the battery safety performance and cycle performance.

[0044] According to some other specific embodiments of the present application, the thickness (thinnest part) of the polymer layer 111-3 corresponding to the first end A is 0 μm to 0.8 μm, for example, it can be 0 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, etc. By limiting the thickness (thinnest part) of the polymer layer 111-3 corresponding to the first end A to within the above range, it can be effectively ensured that the adhesion force of the polymer layer 111-3 corresponding to the first end A is sufficient, thereby effectively improving the interface and internal resistance of the diaphragm 111 and effectively improving the battery cycle.

[0045] According to some other specific embodiments of the present application, the thickness (thickest part) of the polymer layer 111-3 corresponding to the second end B can be 0.8μm to 2.2μm, for example, it can be 0.8μm, 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.5μm, 2μm, 2.2μm, etc. Therefore, by limiting the thickness (thickest part) of the polymer layer 111-3 corresponding to the second end B to the above range, it can not only ensure that the interface and internal resistance of the diaphragm 111 are effectively improved, but also avoid the increase in the resistance of the diaphragm 111 due to the excessive thickness of the polymer layer 111-3, which is not conducive to the transmission of lithium ions and thus affects the energy efficiency of the battery, thereby achieving a balance between adhesion and internal resistance.

[0046] According to some further specific embodiments of the present application, the thickness of the diaphragm base layer 111 - 1 may be 7 μm to 20 μm, for example, 7 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, etc.

[0047] According to some further specific embodiments of the present application, the sum of the thicknesses of the ceramic layer 111 - 2 and the polymer layer 111 - 3 is 2 μm to 5 μm, for example, 2 μm, 3 μm, 4 μm, 5 μm, etc.

[0048] According to some other specific embodiments of the present application, the ceramic layer includes: 20 to 50 parts by weight of ceramic material, 0.5 to 5 parts by weight of a first binder, 0.05 to 1 part by weight of a thickener, 0.05 to 0.5 parts by weight of a dispersant, and 50 to 80 parts by weight of a first solvent. By limiting the content of each component of the ceramic layer to the above range, the thermal shrinkage and wettability of the diaphragm can be further effectively improved, thereby improving the safety and cycle performance of the battery. At the same time, by combining the linear decrease in the thickness of the ceramic layer with the limitation of the content of each component of the ceramic layer, it is possible to further effectively ensure that the problem of inconsistent ion transmission levels between the upper and lower parts of the battery cell is regulated, and at the same time, the problem of inconsistent electrolyte wetting in the late stage of the cycle is regulated. Preferably, the ceramic layer includes: 27 to 38 parts by weight of ceramic material, 0.9 to 2 parts by weight of a first binder, 0.06 to 0.08 parts by weight of a thickener, 0.06 to 0.08 parts by weight of a dispersant, and 60 to 70 parts by weight of a first solvent.

[0049] According to some further specific embodiments of the present application, the particle size of the ceramic material may be 200 nm to 1500 nm, preferably 400 nm to 900 nm.

[0050] In the embodiments of the present application, the specific types of the above-mentioned ceramic materials are not particularly limited, and those skilled in the art can select them according to actual needs. As some preferred options, the above-mentioned ceramic materials include at least one of aluminum oxide, boehmite, titanium oxide and zirconium oxide.

[0051] In the embodiments of the present application, the specific type of the above-mentioned first adhesive is not particularly limited, and those skilled in the art can select it according to actual needs. As some preferred options, the first adhesive includes at least one of lithium acrylate copolymer, polyacrylate copolymer, polyvinylidene fluoride-hexafluoropropylene and fluorine-containing polypropylene.

[0052] In the embodiments of the present application, the specific type of the above-mentioned thickener is not particularly limited, and those skilled in the art can select it according to actual needs. As some preferred options, the thickener includes at least one of lithium carboxymethyl cellulose, ammonium carboxymethyl cellulose, sodium carboxymethyl cellulose, and lithium polyacrylate.

[0053] In the embodiments of the present application, the specific types of the above-mentioned dispersants are not particularly limited, and those skilled in the art can select them according to actual needs. As some preferred options, the dispersants include at least one of ammonium acrylate, lithium polyacrylate, sodium polyacrylate, polyvinyl alcohol, and polyvinyl pyrrolidone.

[0054] In the embodiments of the present application, the specific type of the first solvent is not particularly limited, and may be water, for example.

[0055] According to some other specific embodiments of the present application, the polymer layer includes: 1 to 30 parts by weight of polymer monomer, 0.1 to 5 parts by weight of a second binder, 0.1 to 1.5 parts by weight of an auxiliary agent, and 60 to 95 parts by weight of a second solvent. By limiting the content of each component of the polymer layer to the above range, it is possible to further ensure that the interfacial adhesion and internal resistance of the diaphragm are effectively improved, and the battery cycle is effectively improved; at the same time, by combining the linear increase in the thickness of the polymer layer with the limitation of the content of each component of the polymer layer, it is possible to further ensure that the inconsistent interfacial adhesion requirements of the upper and lower parts of the battery cell to the diaphragm are effectively adjusted, thereby improving the consistency of the battery cell during operation. Preferably, the polymer layer includes: 8.5 to 18 parts by weight of polymer monomer, 1 to 3 parts by weight of a second binder, 0.5 to 0.8 parts by weight of an auxiliary agent, and 80 to 90 parts by weight of a second solvent.

[0056] In the embodiments of the present application, the specific types of the above-mentioned polymer monomers are not particularly limited, and those skilled in the art can select them according to actual needs. As some preferred options, the polymer monomers include at least one of polyvinylidene fluoride (PVDF) and polymethyl methacrylate (PMMA).

[0057] In the embodiments of the present application, the specific type of the above-mentioned second adhesive is not particularly limited, and those skilled in the art can select it according to actual needs. As some preferred options, the second adhesive includes at least one of styrene-butadiene latex, styrene-acrylic latex, pure styrene latex, polymethyl methacrylate, polybutyl methacrylate, polyethyl acrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, and polyurethane.

[0058] In the embodiments of the present application, the specific types of the above-mentioned auxiliary agents are not particularly limited, and those skilled in the art can select them according to actual needs. As some preferred schemes, the auxiliary agents include at least one of fluoroalkyl methoxy ether alcohol, fluoroalkyl ethoxy ether alcohol, polyoxyethylene alkyl amide, and fatty alcohol polyoxyethylene ether.

[0059] In the embodiments of the present application, the specific type of the second solvent is not particularly limited, and may be water, for example.

[0060] In order to achieve coating of a ceramic layer with a decreasing design in μm scale and / or a polymer layer with an increasing design on the diaphragm base layer, the coating methods mainly include micro-concave coating and slit coating.

[0061] Among them, micro-concave coating is a semi-quantitative coating. The coating thickness can be designed to decrease or increase in sequence by changing the number of lines of the micro-concave roller, or by changing the distance between the scraper and the micro-concave roller. The coating thickness can also be designed to decrease or increase in sequence by changing the number of lines of the micro-concave roller and the distance between the scraper and the micro-concave roller at the same time.

[0062] The number of lines on a micro-concave roller is generally fixed; a higher number of lines corresponds to a thinner coating thickness. Micro-concave rollers with a diameter of 150-240 lins / in are commonly used for diaphragm coating. This application can design a micro-concave roller with a decreasing or increasing number of lines, based on the coating thickness, to achieve a gradual arrangement of the lines.

[0063] The present application can also be designed according to the sequential decreasing or sequential increasing design of the coating thickness, and the distance between the scraper and the micro-concave roller can be changed so that the distance between the upper and lower scrapers and the roller is gradually reduced.

[0064] Slit coating is a pre-metered coating method where the coating thickness can be set in advance using a metering pump to match extruders with different slot widths. Typically, diaphragm coating requires multiple extruders operating simultaneously. In this application, by designing extruders with different slot widths and arranging them from small to large, we can achieve a coating thickness that decreases or increases sequentially.

[0065] In a second aspect of the present application, a battery 100 is provided. According to an embodiment of the present application, the battery 100 includes the separator 111 of the above embodiment, thereby effectively improving the cycle performance and safety performance of the battery.

[0066] According to some specific embodiments of this application, refer to the attached Figure 1 and 2 The above-mentioned battery 100 includes: a positive electrode sheet, a negative electrode sheet and the separator 111 described in the above embodiment, the positive electrode sheet, the separator and the negative electrode sheet are stacked in sequence and wound along the length direction of the separator (i.e., the X direction) to form a winding core 110, and the length direction of the separator (i.e., the X direction) is perpendicular to the width direction of the separator (i.e., the Y direction); and the first end A of the separator base layer 111-1 is located at the upper part of the battery 100 (i.e., the side close to the tab 120), and the second end B of the separator base layer 111-1 is located at the lower part of the battery 100 (i.e., the side away from the tab 120).

[0067] After a long period of operation (especially 10,000 cycles), conventional batteries will have a problem of insufficient upper electrolyte inside the battery cell under the dual effects of electrolyte consumption and gravity. At the same time, due to the expansion of the negative electrode and the increase in gas production, the demand for adhesion at the bottom of JR increases. The reduction of the upper electrolyte leads to the obstruction of lithium ion transmission in the upper layer of JR. It is necessary to match the coating of thick ceramic and thin polymer to achieve the effect of accelerating ion transmission. At the same time, the high-porosity diaphragm can bring higher liquid retention performance, which can alleviate the problem of insufficient upper electrolyte after long-term circulation to the greatest extent. The electrolyte in the lower part of JR is sufficient and the ion transmission is unobstructed. In order to match the transmission capacity of the upper part and meet the higher adhesion requirements brought about by gas production and expansion, the overall transmission capacity and interface of the battery cell are consistent, and a thin ceramic and thick polymer coating is used at the bottom. Therefore, the present application can effectively adjust the problem of inconsistent ion transmission levels in the upper and lower parts of the battery cell by setting a ceramic layer whose thickness decreases in the direction from the upper part of the battery to the lower part of the battery, and at the same time adjust the problem of inconsistent electrolyte infiltration in the late stage of the cycle, thereby improving the consistency of the battery cell operation. At the same time, the present application can effectively adjust the problem of inconsistent interface adhesion force requirements of the upper and lower parts of the battery cell to the diaphragm by setting a polymer layer with a thickness increasing successively from the upper part to the lower part of the battery, thereby improving the consistency of the battery cell operation.

[0068] The type of battery in the present application is not particularly limited, and may be, for example, a lithium-ion battery or a sodium-ion battery.

[0069] The batteries of the present application may include battery cells, battery modules, and battery packs. In some embodiments, battery cells may be assembled into a battery module, which may contain one or more battery cells, with the specific number selected by those skilled in the art based on the application and capacity of the battery module. In some embodiments, battery modules may also be assembled into a battery pack, which may contain one or more battery modules, with the specific number selected by those skilled in the art based on the application and capacity of the battery pack.

[0070] In a third aspect of the present application, an electrical device is provided. According to an embodiment of the present application, the electrical device includes a battery as described above. Thus, the electrical device has all the advantages of a battery, which will not be further elaborated here.

[0071] Specifically, the electrical devices may include, but are not limited to, mobile phones, tablets, laptop computers, electric toys, electric tools, battery-powered vehicles, electric cars, ships, spacecraft, etc. Electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0072] The following examples of the present application are described in detail. It should be noted that the following examples are illustrative and are intended only to explain the present application and are not to be construed as limiting the present application. In addition, unless otherwise expressly stated, all reagents used in the following examples are commercially available or can be synthesized according to methods described herein or known methods. Reaction conditions not listed are also readily available to those skilled in the art.

[0073] Example 1

[0074] This embodiment provides a diaphragm, and the preparation method thereof includes:

[0075] Alumina powder (D50 is 600 nm), polyacrylate copolymer, thickener CMC1140, lithium polyacrylate and deionized water are evenly mixed in a mass ratio of 32:1.5:0.07:0.07:65, and stirred thoroughly to obtain a ceramic slurry.

[0076] PVDF monomer, binder styrene-butadiene latex, additive fluoroalkyl methoxy ether alcohol and deionized water were mixed in a mass ratio of 13:2:0.6:85 to obtain a polymer slurry.

[0077] A polyethylene diaphragm base layer with a thickness of 12 μm and a width of 200 mm was selected.

[0078] Select a 180 lines / in micro-concave roller and change its line number arrangement so that the line number arrangement gradually becomes denser from one end to the other end of the roller surface. First, apply the ceramic slurry on one side of the polyethylene diaphragm base to obtain a ceramic layer with a thickness that decreases linearly along the width of the diaphragm. The slope of the linear decrease is 1*10 -6 The thickness of the thinnest part of the ceramic layer is 2μm, and the thickness of the thickest part of the ceramic layer is 2.2μm.

[0079] Adjust the direction of the diaphragm so that the thick ceramic side corresponds to the roller side with more lines. Apply polymer slurry on the surface of the ceramic layer away from the polyethylene diaphragm base to obtain a polymer layer with a linear thickness matching the ceramic layer. That is, the thickness of the polymer layer increases linearly along the width direction of the diaphragm, and the slope of the linear decrease is 1*10 -6 The thickness of the thinnest part of the polymer layer is 0.8 μm, and the thickness of the thickest part of the polymer layer is 1 μm.

[0080] Example 2

[0081] The preparation method of Example 2 is similar to that of Example 1, except that:

[0082] Select a 180 lines / in micro-concave roller and change its line number arrangement so that the line number arrangement gradually becomes denser from one end to the other end of the roller surface. First, apply the ceramic slurry on one side of the polyethylene diaphragm base to obtain a ceramic layer with a thickness that decreases linearly along the width of the diaphragm. The slope of the linear decrease is 2*10 -6 The thickness of the thinnest part of the ceramic layer is 2μm, and the thickness of the thickest part of the ceramic layer is 2.4μm.

[0083] Adjust the direction of the diaphragm so that the thick ceramic side corresponds to the roller side with more lines, and apply the polymer slurry to obtain a polymer layer with a linear thickness matching the ceramic layer. That is, the thickness of the polymer layer increases linearly along the width direction of the diaphragm, and the slope of the linear decrease is 2*10 -6 The thickness of the thinnest part of the polymer layer is 0.6 μm, and the thickness of the thickest part of the polymer layer is 1 μm.

[0084] Example 3

[0085] The preparation method of Example 3 is similar to that of Example 1, except that:

[0086] Select a 180 lines / in micro-concave roller and change its line number arrangement so that the line number arrangement gradually becomes denser from one end to the other end of the roller surface. First, apply the ceramic slurry on one side of the polyethylene diaphragm base to obtain a ceramic layer with a thickness that decreases linearly along the width of the diaphragm. The slope of the linear decrease is 3*10 -6 The thickness of the thinnest part of the ceramic layer is 2μm, and the thickness of the thickest part of the ceramic layer is 2.6μm.

[0087] Adjust the direction of the diaphragm so that the thick ceramic side corresponds to the roller side with more lines, and apply the polymer slurry to obtain a polymer layer with a linear thickness matching the ceramic layer. That is, the thickness of the polymer layer increases linearly along the width direction of the diaphragm, and the slope of the linear decrease is 3*10 -6 The thickness of the thinnest part of the polymer layer is 0.4 μm, and the thickness of the thickest part of the polymer layer is 1 μm.

[0088] The rest of the contents are the same as those in Example 1.

[0089] Example 4

[0090] The preparation method of Example 4 is similar to that of Example 1, except that:

[0091] Select a 180 lines / in micro-concave roller and change its line number arrangement so that the line number arrangement gradually becomes denser from one end to the other end of the roller surface. First, apply the ceramic slurry on one side of the polyethylene diaphragm base to obtain a ceramic layer with a thickness that decreases linearly along the width of the diaphragm. The slope of the linear decrease is 5*10 -6 The thickness of the thinnest part of the ceramic layer is 2μm, and the thickness of the thickest part of the ceramic layer is 3μm.

[0092] Adjust the direction of the diaphragm so that the thick ceramic side corresponds to the roller side with more lines, and apply the polymer slurry to obtain a polymer layer with a linear thickness matching the ceramic layer. That is, the thickness of the polymer layer increases linearly along the width direction of the diaphragm, and the slope of the linear decrease is 5*10 -6 , the thickness of the thinnest part of the polymer layer is 0 μm, and the thickness of the thickest part of the polymer layer is 1 μm.

[0093] Example 5

[0094] The preparation method of Example 5 is similar to that of Example 1, except that:

[0095] Select a 180 lines / in micro-concave roller and change its line number arrangement, so that the line number arrangement gradually becomes denser from one end to the other end of the roller surface. First, apply the ceramic slurry on one side of the polyethylene diaphragm base to obtain a ceramic layer with a linear thickness decreasing along the width direction of the diaphragm. The slope of the linear decrease is 8*10 -6 The thickness of the thinnest part of the ceramic layer is 1.8μm, and the thickness of the thickest part of the ceramic layer is 3.4μm.

[0096] Adjust the direction of the diaphragm so that the thick ceramic side corresponds to the roller side with more lines, and apply the polymer slurry to obtain a polymer layer with a linear thickness matching the ceramic layer. That is, the thickness of the polymer layer increases linearly along the width direction of the diaphragm, and the slope of the linear decrease is 8*10 -6 The thickness of the polymer layer at its thinnest point is 0.6 μm, and the thickness of the polymer layer at its thickest point is 2.2 μm.

[0097] Example 6

[0098] The preparation method of Example 6 is similar to that of Example 1, except that:

[0099] Select a 180 lines / in micro-concave roller and change its line number arrangement so that the line number arrangement gradually becomes denser from one end to the other end of the roller surface. First, apply the ceramic slurry on one side of the polyethylene diaphragm base to obtain a ceramic layer with a thickness that decreases linearly along the width of the diaphragm. The slope of the linear decrease is 1*10 -5 The thickness of the thinnest part of the ceramic layer is 2μm, and the thickness of the thickest part of the ceramic layer is 4μm.

[0100] Adjust the direction of the diaphragm so that the thick ceramic side corresponds to the roller side with more lines, and apply the polymer slurry to obtain a polymer layer with a linear thickness matching the ceramic layer. That is, the thickness of the polymer layer increases linearly along the width direction of the diaphragm, and the slope of the linear decrease is 1*10 -5 The thickness of the thinnest part of the polymer layer is 0 μm, and the thickness of the thickest part of the polymer layer is 2 μm.

[0101] Example 7

[0102] The preparation method of Example 7 is similar to that of Example 3, except that:

[0103] Alumina powder (D50 is 600 nm), polyacrylate copolymer, thickener CMC1140, lithium polyacrylate and deionized water are prepared in a mass ratio of 27:2:0.06:0.08:60.

[0104] Example 8

[0105] The preparation method of Example 8 is similar to that of Example 3, except that:

[0106] Alumina powder (D50 is 600 nm), polyacrylate copolymer, thickener CMC1140, lithium polyacrylate and deionized water are prepared in a mass ratio of 38:0.9:0.08:0.06:70.

[0107] Example 9

[0108] The preparation method of Example 9 is similar to that of Example 3, except that:

[0109] Alumina powder (D50 is 600 nm), polyacrylate copolymer, thickener CMC1140, lithium polyacrylate and deionized water are prepared in a mass ratio of 20:0.5:0.05:0.05:50.

[0110] Example 10

[0111] The preparation method of Example 10 is similar to that of Example 3, except that:

[0112] Alumina powder (D50 is 600 nm), polyacrylate copolymer, thickener CMC1140, lithium polyacrylate and deionized water are prepared in a mass ratio of 50:5:1:0.5:80.

[0113] Example 11

[0114] The preparation method of Example 11 is similar to that of Example 3, except that:

[0115] PVDF monomer, binder styrene-butadiene latex, additive fluoroalkyl methoxy ether alcohol and deionized water were mixed in a mass ratio of 8.5:3:0.6:90.

[0116] Example 12

[0117] The preparation method of Example 12 is similar to that of Example 3, except that:

[0118] PVDF monomer, binder styrene-butadiene latex, additive fluoroalkyl methoxy ether alcohol and deionized water were mixed in a mass ratio of 18:1:0.8:80.

[0119] Example 13

[0120] The preparation method of Example 13 is similar to that of Example 3, except that:

[0121] PVDF monomer, binder styrene-butadiene latex, additive fluoroalkyl methoxy ether alcohol and deionized water were mixed in a mass ratio of 1:0.1:0.1:60.

[0122] Example 14

[0123] The preparation method of Example 14 is similar to that of Example 3, except that:

[0124] PVDF monomer, binder styrene-butadiene latex, additive fluoroalkyl methoxy ether alcohol and deionized water were mixed in a mass ratio of 30:5:1.5:95.

[0125] Comparative Example 1

[0126] The difference between Comparative Example 1 and Example 3 is only that:

[0127] The ceramic layer has a uniform thickness of 2 μm along the width direction of the diaphragm.

[0128] The polymer layer had a uniform thickness of 1 μm along the width direction of the separator.

[0129] The air permeability and adhesion of the diaphragms of Examples 1-14 and Comparative Example 1 were tested in different regions. Three test areas ①, ② and ③ were taken along the width direction of the diaphragm. Figure 5As shown, test area ① is sampling point 1, test area ② is sampling point 2, and test area ③ is sampling point 3. The test results are shown in Table 1. The Wangyan type air permeability instrument is used to test the air permeability of the diaphragm.

[0130] The adhesion test method is as follows: stack the diaphragm in the order of electrode-diaphragm-electrode, then press it in a hot press at 85℃-9.5MPa for 1 minute, then cut it into sections, and use a tensile testing machine to test the 180° peel force of the diaphragm to the electrode.

[0131] Table 1

[0132]

[0133] As can be seen from Table 1, the air permeability of Examples 1-14 increases sequentially from sampling point 1 to sampling point 3, meaning that the ion transmission capacity decreases sequentially. This effectively addresses the problem of inconsistent ion transmission levels between the upper and lower parts of the cell, as well as the problem of inconsistent electrolyte wetting in the later stages of the cycle. This overall improves the incremental air permeability of the separator and enhances the consistency of cell operation. However, the air permeability of Comparative Example 1 does not show a sequentially increasing pattern from sampling point 1 to sampling point 3, and therefore fails to achieve the technical effects of the present application.

[0134] Table 1 also shows that the cathode adhesion of Examples 1-14 increases sequentially from sampling point 1 to sampling point 3, effectively addressing the inconsistent interfacial adhesion requirements between the upper and lower portions of the cell and the separator, thereby improving the overall adhesion of the separator to the electrode sheet and enhancing the consistency of the cell during operation. However, the cathode adhesion of Comparative Example 1 does not exhibit a sequentially increasing pattern from sampling point 1 to sampling point 3, and therefore cannot achieve the technical effects of the present application.

[0135] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0136] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A diaphragm, the diaphragm being used for a battery comprising a positive electrode sheet and a negative electrode sheet, characterized in that: The diaphragm comprises: a diaphragm base layer, the diaphragm base layer having a first end and a second end along a first direction, the first direction being the width direction of the diaphragm; the first end being located at an upper portion of the battery, the upper portion of the battery being a side close to the battery tab, and the second end being located at a lower portion of the battery, the lower portion of the battery being a side away from the battery tab; a ceramic layer, the ceramic layer being disposed on at least one side of the diaphragm base layer along a second direction, the second direction being a thickness direction of the diaphragm, the ceramic layer extending along the first direction, and the thickness of the ceramic layer decreasing successively along a direction from the first end to the second end; A polymer layer, the polymer layer is used to bond the positive electrode sheet and / or the negative electrode sheet, the polymer layer is arranged on the side of the ceramic layer away from the diaphragm base layer or on the side of the diaphragm base layer away from the ceramic layer, the polymer layer extends along the first direction, and the thickness of the polymer layer increases successively along the direction from the first end to the second end.

2. The diaphragm according to claim 1, characterized in that The thickness of the ceramic layer decreases linearly along the direction from the first end to the second end; And / or, the thickness of the polymer layer increases linearly along the direction from the first end to the second end.

3. The diaphragm according to claim 2, characterized in that The thickness of the ceramic layer decreases linearly from the first end to the second end with a slope of 10 -6 ~10 -5 ; Alternatively, the thickness of the ceramic layer decreases linearly along the direction from the first end to the second end with a slope of .

4. The diaphragm according to claim 2, characterized in that The thickness of the polymer layer increases linearly from the first end to the second end with a slope of 10 -6 ~10 -5 ; Alternatively, the thickness of the polymer layer increases linearly along the direction from the first end to the second end with a slope of .

5. The diaphragm according to claim 2, characterized in that An absolute value of a slope at which the thickness of the ceramic layer decreases linearly from the first end to the second end is equal to an absolute value of a slope at which the thickness of the polymer layer increases linearly from the first end to the second end.

6. The diaphragm according to claim 2, characterized in that The thickness of the ceramic layer corresponding to the first end is 2.2µm to 4µm; And / or, the thickness of the ceramic layer corresponding to the second end is 1.8µm~2.2µm.

7. The diaphragm according to claim 2, characterized in that The thickness of the polymer layer corresponding to the first end is 0µm to 0.8µm; And / or, the thickness of the polymer layer corresponding to the second end is 0.8µm~2.2µm.

8. The diaphragm according to any one of claims 1 to 7, characterized in that The thickness of the diaphragm base layer is 7µm~20µm; Alternatively, the sum of the thicknesses of the ceramic layer and the polymer layer is 2µm to 5µm.

9. The diaphragm according to any one of claims 1 to 7, characterized in that The ceramic layer comprises: 20 to 50 parts by weight of a ceramic material, 0.5 to 5 parts by weight of a first binder, 0.05 to 1 part by weight of a thickener, 0.05 to 0.5 parts by weight of a dispersant, and 50 to 80 parts by weight of a first solvent; Alternatively, the ceramic layer includes: 27 to 38 parts by weight of ceramic material, 0.9 to 2 parts by weight of a first binder, 0.06 to 0.08 parts by weight of a thickener, 0.06 to 0.08 parts by weight of a dispersant, and 60 to 70 parts by weight of a first solvent.

10. The diaphragm according to any one of claims 1 to 7, characterized in that The polymer layer comprises: 1 to 30 parts by weight of a polymer monomer, 0.1 to 5 parts by weight of a second binder, 0.1 to 1.5 parts by weight of an auxiliary agent, and 60 to 95 parts by weight of a second solvent; Alternatively, the polymer layer includes: 8.5 to 18 parts by weight of a polymer monomer, 1 to 3 parts by weight of a second binder, 0.5 to 0.8 parts by weight of an auxiliary agent, and 80 to 90 parts by weight of a second solvent.

11. A battery, characterized in that: The invention comprises the diaphragm according to any one of claims 1 to 10.

12. The battery according to claim 11, characterized in that include: A positive electrode sheet, a negative electrode sheet, and the separator according to any one of claims 1 to 10, wherein the positive electrode sheet, the separator, and the negative electrode sheet are stacked in sequence and wound along the length direction of the separator to form a winding core, and the length direction of the separator is perpendicular to the width direction of the separator.

13. An electrical device, characterized in that: A battery according to claim 11 or 12.

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