Diaphragm, single battery and energy storage device

Abstract

The application provides a diaphragm, a single battery and an energy storage device. The diaphragm comprises a base film, the base film has a first surface and a second surface arranged opposite to each other; a point coating glue layer, the point coating glue layer comprises a plurality of point coating parts, the plurality of point coating parts are arranged at intervals on the first surface; and a roller coating glue layer, the roller coating glue layer is arranged on the second surface.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a separator, a single cell, and an energy storage device. Background Technology

[0002] Due to the characteristics of the polyanionic positive electrode and the hard carbon negative electrode, sodium-ion batteries exhibit significant looseness in the bare cell openings after winding, severely impacting the wrapping of the Mylar membrane and the casing process. Therefore, the separator needs a double-sided adhesive structure, where the bare cell is formed into a "hard brick" shape after hot pressing. In related technologies, adhesive layers are sprayed onto both sides of the base film. However, the thickness uniformity of the sprayed adhesive layer is poor, easily causing misalignment of the tabs on the bare cell. While double-sided adhesive-coated separators offer significantly better thickness uniformity between bare cells, for sodium-ion batteries using a winding process, the thickness uniformity within the separator roll is crucial. Although the adhesive dots on both sides of the double-sided adhesive-coated separator are arranged in a regular matrix, the overlapping area is random, resulting in abrupt changes in thickness uniformity along the separator's length within the roll. This leads to irregular tab misalignment during winding. The hard carbon coating of sodium batteries is brittle and prone to powdering. The bare cells cannot be rubbed, and the accuracy requirements for the misalignment of the tabs are even higher, which seriously affects the winding yield. Summary of the Invention

[0003] This application provides a separator with good thickness uniformity, which can reduce the defect rate of misaligned tabs in single cells when applied to them.

[0004] In a first aspect, embodiments of this application provide a diaphragm, the diaphragm comprising: The base film has a first surface and a second surface disposed opposite to each other; The adhesive layer includes a plurality of dot-coating portions spaced apart on the first surface; and the adhesive layer is rolled onto the second surface.

[0005] Furthermore, the coverage of the dot-coated adhesive layer on the first surface is less than the coverage of the roll-coated adhesive layer on the second surface. The base film includes a substrate layer and a ceramic layer, with the ceramic layer disposed on the surface of the substrate layer and between the dot-coated adhesive layer and the substrate layer.

[0006] Furthermore, if the coverage rate of the dot-coated adhesive layer on the first surface is S1 and the coverage rate of the roller-coated adhesive layer on the second surface is S2, then 0.15≤S1 / S2≤0.5.

[0007] Furthermore, the coverage S1 of the dotted adhesive layer on the first surface is in the range of 10% ≤ S1 ≤ 35%; And / or, The coverage rate S2 of the roller-coated adhesive layer on the second surface is in the range of 60% ≤ S2 ≤ 90%.

[0008] Furthermore, the shape of the orthographic projection of the dotted part on the first surface is circular or near-circular, and the circularity K of the orthographic projection of the dotted part on the first surface is in the range of 0.85≤K≤1.

[0009] Furthermore, the dotting portion includes a connected central portion and an outer ring portion, the outer ring portion being disposed around the outer periphery of the central portion, and the thickness of the outer ring portion being greater than the thickness of the central portion.

[0010] Furthermore, along an extension plane parallel to the base film, the maximum width d of the orthographic projection of the dotted portion onto the first surface ranges from 200μm≤d≤800μm.

[0011] Furthermore, along the stacking direction of the dot-coated adhesive layer, the base film, and the roller-coated adhesive layer, the maximum thickness h1 of the dot-coated portion ranges from 3μm≤h1≤8μm; and / or, along the stacking direction of the base film and the roller-coated adhesive layer, the thickness h2 of the roller-coated adhesive layer ranges from 1μm≤h2≤5μm.

[0012] Secondly, embodiments of this application provide a single-cell battery, the single-cell battery including a positive electrode, a separator as described in embodiments of this application, a negative electrode and an electrolyte, wherein the separator is located between the positive electrode and the negative electrode.

[0013] Furthermore, the base film includes a substrate layer and a ceramic layer stacked together, the ceramic layer being disposed between the dot-coated adhesive layer and the substrate layer, the dot-coated adhesive layer facing the positive electrode sheet, and the roll-coated adhesive layer facing the negative electrode sheet.

[0014] Thirdly, embodiments of this application provide an energy storage device, which includes one or more single-cell batteries as described in embodiments of this application.

[0015] The separator described in this embodiment includes a base film, a dot-coated adhesive layer, and a roll-coated adhesive layer. The base film has a first surface and a second surface disposed opposite to each other. The dot-coated adhesive layer includes a plurality of dot-coated portions spaced apart on the first surface. The roll-coated adhesive layer is disposed on the second surface. The dot-coated adhesive layer is prepared by a dot-coating process, and the roll-coated adhesive layer is prepared by a roll-coating process. Only one surface of the separator is dot-coated, thus eliminating the random overlap of adhesive dots on the first surface 411 and the second surface 412, which greatly increases the consistency of the separator thickness. Furthermore, the high thickness consistency of the roll-coated adhesive layer results in a high overall thickness consistency of the separator, which effectively improves the problem of misalignment of the positive and / or negative tabs during the winding process of a single battery cell. In addition, when the base film includes a ceramic layer, the roll-coated adhesive layer is prone to clogging the ceramic layer, while the dot-coated adhesive layer is less likely to clog the ceramic layer. This allows the ceramic layer to be disposed between the base film and the dot-coated adhesive layer, thereby maintaining a high ionic conductivity of the separator. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of an energy storage system according to an embodiment of this application.

[0018] Figure 2 This is a schematic diagram of the structure of an energy storage system according to another embodiment of this application.

[0019] Figure 3 This is a schematic diagram of the structure of an energy storage system according to another embodiment of this application.

[0020] Figure 4 This is a schematic diagram of the structure of an electrical system according to an embodiment of this application.

[0021] Figure 5 This is a schematic diagram of the structure of an energy storage device according to an embodiment of this application.

[0022] Figure 6 This is a schematic diagram of the structure of a single battery cell according to an embodiment of this application.

[0023] Figure 7 For the application of an embodiment of the single cell battery Figure 6 A schematic diagram of the cross-sectional structure along the AA direction.

[0024] Figure 8This is a cross-sectional view of the positive electrode sheet according to an embodiment of this application.

[0025] Figure 9 This is a cross-sectional view of the negative electrode sheet according to an embodiment of this application.

[0026] Figure 10 This is a cross-sectional view of a diaphragm according to an embodiment of this application.

[0027] Figure 11 This is a cross-sectional view of the diaphragm according to another embodiment of this application.

[0028] Figure 12 This is a cross-sectional view of the diaphragm according to another embodiment of this application.

[0029] Figure 13 This is a cross-sectional view of the diaphragm according to another embodiment of this application.

[0030] Figure 14 This is a schematic diagram of the planar structure of a diaphragm according to an embodiment of this application.

[0031] Figure 15 This is a cross-sectional view of the diaphragm according to another embodiment of this application.

[0032] Figure 16 This is a scanning electron microscope image of the surface of the dotted adhesive layer of the diaphragm in Example 1.

[0033] Figure 17 This is a scanning electron microscope image of the surface of the dotted adhesive layer of the diaphragm in Example 2.

[0034] Figure 18 This is a scanning electron microscope image of the surface of the roller-coated adhesive layer of the diaphragm in Example 1.

[0035] Figure 19 This is a scanning electron microscope image of the surface of the roller-coated adhesive layer of the diaphragm in Example 2.

[0036] Explanation of reference numerals in the attached figures: 100 - Energy storage system; 110 - First power conversion device; 120 - First user load; 130 - Second user load; 140 - High-voltage cable; 150 - Second power conversion device; 160 - Photovoltaic-energy storage-charging station; 170 - Automobile; 200 - Energy storage device; 100' - Power consumption system; 110' - Electrical equipment; 300 - Single cell; 310 - Positive electrode sheet; 311 - Positive current collector; 312 - Positive active layer; 313 - Positive... Tab, 330-negative electrode sheet, 331-negative current collector, 332-negative active layer, 333-negative tab, 340-shell, 341-receiving cavity, 350-end cap assembly, 400-diaphragm, 410-base film, 411-first surface, 412-second surface, 413-substrate layer, 414-ceramic layer, 420-dot coating layer, 421-dot coating section, 4211-center section, 4212-outer ring section, 430-roll coating layer. Detailed Implementation

[0037] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0038] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0039] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0040] It should be noted that, for ease of explanation, the same reference numerals denote the same components in the embodiments of this application, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments.

[0041] Because the energy we need is highly time- and space-dependent, in order to utilize energy rationally and improve energy efficiency, it is necessary to store one form of energy in the same way or by converting it into another, and then release it in a specific energy form based on future application needs. Currently, the main way to generate green electricity is to develop green energy sources such as photovoltaics and wind power to replace fossil fuels.

[0042] Currently, the generation of green electricity generally relies on solar, wind, and hydropower. However, wind and solar power are generally characterized by strong intermittency and large fluctuations, which can cause grid instability, insufficient power during peak demand periods, and excessive power during off-peak periods. Unstable voltage can also damage the power grid. Therefore, insufficient electricity demand or insufficient grid capacity may lead to the problem of "wind and solar curtailment." Solving these problems requires energy storage. This involves converting electrical energy into other forms of energy through physical or chemical means and storing it. When needed, this energy can be converted back into electrical energy and released. Simply put, energy storage is like a large "power bank," storing electrical energy when solar and wind power are abundant and releasing the stored electricity when needed.

[0043] Taking electrochemical energy storage as an example, this solution provides an energy storage device for use in energy storage systems. The energy storage device is equipped with a set of chemical batteries, which mainly use the chemical elements in the batteries as energy storage media. The charging and discharging process is accompanied by the chemical reaction or change of the energy storage media. Simply put, the electrical energy generated by wind and solar energy is stored in the chemical batteries. When the use of external electrical energy reaches its peak, the stored electricity is released for use, or transferred to places with a shortage of electricity for use.

[0044] Current energy storage applications are quite widespread, including generation-side energy storage, grid-side energy storage, and consumption-side energy storage. The corresponding types of energy storage devices include: (1) Large-scale energy storage power stations (composed of multiple prefabricated energy storage modules) applied to wind power and photovoltaic power stations can help renewable energy power generation meet grid connection requirements and improve the utilization rate of renewable energy. As a high-quality active / reactive power regulation power source on the power supply side, the energy storage power station realizes the load matching of power in time and space, enhances the renewable energy absorption capacity, reduces instantaneous power changes, reduces the impact on the power grid, improves the problem of new energy power generation absorption, and is of great significance in power grid system backup, alleviating peak load power supply pressure and peak regulation and frequency regulation. (2) The energy storage prefabricated cabin applied on the grid side mainly functions as peak regulation, frequency regulation and grid congestion relief. In terms of peak regulation, it can realize peak shaving and valley filling of electricity load, that is, charging the energy storage battery when the electricity load is low and releasing the stored electricity during the peak electricity load period, thereby achieving a balance between power production and consumption. (3) Small energy storage cabinets applied to the electricity consumption side mainly function as self-consumption of electricity, peak-valley price arbitrage, capacity cost management, and improvement of power supply reliability. Depending on the application scenario, electricity consumption side energy storage can be divided into industrial and commercial energy storage cabinets, household energy storage devices, energy storage charging piles, etc., which are generally used in conjunction with distributed photovoltaics. Industrial and commercial users can use energy storage for peak-valley price arbitrage and capacity cost management. In the electricity market implementing peak-valley pricing, by charging the energy storage system when the electricity price is low and discharging the energy storage system when the electricity price is high, peak-valley price arbitrage can be achieved, reducing electricity costs. In addition, industrial enterprises subject to two-part tariffs can use energy storage systems to store energy during off-peak hours and discharge during peak loads, thereby reducing peak power and the maximum demand declared, achieving the goal of reducing capacity costs. Household photovoltaics with energy storage can improve the level of self-consumption of electricity. Due to high electricity prices and poor power supply stability, the demand for household photovoltaic installations is driven. Given that photovoltaic power generation occurs during the day, while user load is generally higher at night, configuring energy storage can better utilize photovoltaic power, improve self-consumption levels, and reduce electricity costs. Furthermore, energy storage is needed in areas such as communication base stations and data centers for backup power.

[0045] In some embodiments, see Figure 1 , Figure 1 This is a schematic diagram of the structure of an energy storage system 100 according to an embodiment of this application. Figure 1 The embodiments are illustrated using a home energy storage scenario in user-side energy storage as an example. The energy storage device 200 of this application is not limited to the home energy storage scenario.

[0046] This application provides an energy storage system 100, which includes a first power conversion device 110 (photovoltaic panel), a first user load 120 (household lighting fixture), a second user load 130 (e.g., household appliances such as air conditioners), and an energy storage device 200. The energy storage device 200 is a small energy storage box that can be wall-mounted on an outdoor wall. However, the energy storage device 200 is not limited to wall mounting and can also be placed in a user's residence in other ways. Specifically, the photovoltaic panel can convert solar energy into electrical energy during periods of low electricity prices, and the energy storage device 200 stores this electrical energy and supplies it to lighting fixtures and household appliances during peak electricity prices, or provides power during power outages / power interruptions.

[0047] In some embodiments, see Figure 2 , Figure 2 This is a schematic diagram of the structure of an energy storage system 100 according to another embodiment of this application, and this application Figure 2 The embodiments are illustrated using a shared energy storage scenario on the generation / distribution side as an example. The energy storage device 200 of this application is not limited to its generation / distribution side energy storage scenario.

[0048] This application provides an energy storage system 100, which includes: a high-voltage cable 140, a first power conversion device 110, a second power conversion device 150, and an energy storage device 200 provided in this application. In some embodiments of the power generation scenario, the second power conversion device 150 can be a wind power conversion device. Since the electricity generated by wind power conversion is volatile, random, and intermittent, the unstable electricity output by the wind power conversion device can be stored in the energy storage device 200 through grid connection. The energy storage device 200 is connected to the high-voltage cable 140 and outputs smooth electricity to the power consumption side of the distribution network, realizing peak shaving and frequency regulation, and stable grid operation; or, wind power conversion... The power conversion device is always connected to the high-voltage cable 140. Under normal power generation conditions, the power output of the wind power conversion device is supplied to the power consumption side of the distribution network through the high-voltage cable 140. When the current power load is low and the wind power conversion device generates excess power, the excess power is first stored in the energy storage device 200 to reduce wind and solar curtailment rates and improve the problem of new energy power generation consumption. When the power load is high, the power grid issues an instruction to transmit the power stored in the energy storage device 200 together with the high-voltage cable 140 in grid-connected mode to supply power to the power consumption side. This provides the power grid with various services such as peak shaving, frequency regulation, and backup, giving full play to the peak shaving role of the power grid, promoting peak shaving and valley filling, and alleviating the power supply pressure of the power grid.

[0049] In some embodiments on the distribution network side, the first power conversion device 110 can be a photovoltaic panel, and the energy storage device 200 is connected to the high-voltage cable 140 and installed downstream of the high-voltage cable 140 between the user load and the photovoltaic power conversion device. The electrical energy output by the photovoltaic power conversion device is stored in the energy storage device 200, which can respond in a timely manner to act as a backup power source when the power grid / distribution network fails; or, it can provide power supply support to alleviate line congestion when the high-voltage cable 140 transmission line is blocked, and to delay the economic pressure caused by the expansion of the power grid / distribution capacity when the power grid is planned to be expanded.

[0050] In some embodiments, see Figure 3 , Figure 3 This is a schematic diagram of the structure of an energy storage system 100 according to another embodiment of this application, and this application Figure 3 The embodiments are illustrated using an industrial and commercial energy storage scenario as an example. The energy storage device 200 of this application is not limited to industrial and commercial energy storage scenarios.

[0051] This application provides an energy storage system 100, which includes: an energy storage device 200, a high-voltage cable 140, a factory equipped with a first power conversion device 110, a photovoltaic-energy storage-charging station 160, and a vehicle 170. In some embodiments of industrial and commercial scenarios, the first power conversion device 110 can be a photovoltaic panel, which converts solar energy into electrical energy and stores it in the energy storage device 200 in the factory. In the event of a power grid failure, the energy storage device 200 provides power to ensure the safe and stable operation of the factory without interruption. Alternatively, when the factory's power load is high, the power grid issues an instruction to transmit the electricity stored in the energy storage device 200 in conjunction with the high-voltage cable 140 in a grid-connected mode to supply the factory with electricity, providing various services such as peak shaving / frequency regulation and backup for the power grid operation. In addition, the first power conversion device 110 can also convert solar energy into electrical energy and store it in the energy storage device 200 of the photovoltaic-energy storage-charging station 160, which can directly charge the vehicle 170, making it fast and convenient.

[0052] Optionally, the first power conversion device 110 may include, but is not limited to, a photovoltaic panel, and the second power conversion device 150 may include, but is not limited to, a wind power conversion device. The first power conversion device 110 and the second power conversion device 150 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy, and mechanical energy into electrical energy.

[0053] Figure 4 This is a schematic diagram of the structure of an electrical system 100' according to an embodiment of this application.

[0054] Please see Figure 4 This application embodiment also provides an electrical system 100', which includes an electrical device 110' and an energy storage device 200. The energy storage device 200 is electrically connected to the electrical device 110' and is used to supply power to the energy storage device 200.

[0055] Optionally, the electrical equipment 110' can be, but is not limited to, at least one of the following: power grid, base station, household appliances (such as air conditioner, refrigerator, washing machine, etc.).

[0056] Optionally, the electrical equipment 110' and the energy storage device 200 can be electrically connected via a high-voltage cable 140.

[0057] Please see Figure 5 , Figure 5 This is a schematic diagram of the structure of an energy storage device 200 according to an embodiment of this application.

[0058] Optionally, the energy storage device 200 includes one or more individual battery cells 300.

[0059] The term "multiple" refers to two or more, such as, but not limited to, 2, 5, 10, 30, 50, 100, 200, 300, 400, 800, 1000, etc.

[0060] It should be noted that the number of individual battery cells 300 included in the energy storage device 200 can be determined based on the rated capacity of the individual battery cells 300 and the rated capacity that the energy storage device 200 is to achieve.

[0061] Optionally, the energy storage device 200 can be used, but is not limited to, energy storage power stations, hydropower / thermal / wind power generation systems, solar power generation systems, mobile power systems, smart home systems, or temporary power supply systems, and is also applied in multiple fields such as data centers, military equipment, aerospace, charging piles, and electric vehicles.

[0062] Optionally, the energy storage device 200 may include, but is not limited to, battery integrated systems comprising a single battery cell 300, or battery modules, battery packs, battery clusters, power banks, energy storage cabinets / prefabricated energy storage containers, etc., composed of single battery cells 300. In other words, when the energy storage device 200 includes a single battery cell 300, the energy storage device 200 may exist in the form of a single battery cell 300. When the energy storage device 200 includes multiple single battery cells 300, the multiple single battery cells 300 may be stacked, arranged, assembled, etc., to form battery integrated systems such as battery modules, battery packs, battery clusters, power banks, energy storage cabinets / energy storage containers, etc.; that is, the energy storage device 200 exists in the form of battery integrated systems such as battery modules, battery packs, battery clusters, power banks, energy storage cabinets / energy storage containers, etc. The actual application form of the energy storage device 200 provided in this application embodiment may be, but is not limited to, the listed products, and may also be other application forms. This application embodiment does not strictly limit the application form of the energy storage device 200. In the embodiments of this application, the energy storage device 200 is illustrated by taking a multi-cell battery (i.e., multiple single cells 300) as an example.

[0063] Optionally, the single cell 300 can be, but is not limited to, at least one of cylindrical, square, prismatic, or other shaped cells.

[0064] Optionally, the single cell 300 can be a rechargeable battery, which refers to a single cell 300 that can be recharged after discharge to activate the active materials and continue to be used. The single cell 300 can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and this application does not specifically limit it.

[0065] Understandably, the 300 single cell can be, but is not limited to, sodium batteries, lithium batteries, magnesium batteries, nickel-hydrogen batteries, nickel-cadmium batteries, lead-acid batteries, etc.

[0066] Please see Figure 6 , Figure 6 This is a schematic diagram of the structure of a single cell battery 300 according to another embodiment of this application. Figure 7 For an embodiment of the application, a single cell 300 is provided. Figure 6 A schematic diagram of the cross-sectional structure along the AA direction.

[0067] Please see Figure 6 This application provides a single-cell battery 300, which includes a positive electrode 310, a separator 400, a negative electrode 330, and an electrolyte. The separator 400 is located between the positive electrode 310 and the negative electrode 330.

[0068] Understandably, the positive electrode 310 and the negative electrode 330 are located on opposite sides of the separator 400, that is, the separator 400 is located between the positive electrode 310 and the negative electrode 330, separating them. The positive electrode 310, the separator 400, and the negative electrode 330 are sequentially stacked to obtain an electrode assembly, which is then wound to obtain a core (not shown). That is, the core includes the positive electrode 310, the separator 400, and the negative electrode 330.

[0069] Optionally, the positive electrode 310, the separator 400, and the negative electrode 330 are all at least partially immersed in the electrolyte.

[0070] Figure 8 This is a cross-sectional view of the positive electrode 310 according to an embodiment of this application.

[0071] Please see Figure 8 Optionally, the positive electrode 310 includes a positive current collector 311, a positive active layer 312, and a plurality of positive tabs 313. The positive active layer 312 is disposed on at least one of two opposite surfaces of the positive current collector 311, and the plurality of positive tabs 313 are disposed on the same side of the positive current collector 311 and are electrically connected to the positive current collector 311 respectively.

[0072] Figure 9 This is a cross-sectional view of the negative electrode 330 according to an embodiment of this application.

[0073] Please see Figure 9Optionally, the negative electrode 330 includes a negative electrode current collector 331, a negative electrode active layer 332, and a plurality of negative electrode tabs 333. The negative electrode active layer 332 is disposed on at least one of two opposing surfaces of the negative electrode current collector 331, and the plurality of negative electrode tabs 333 are disposed on the same side of the negative electrode current collector 331 and are electrically connected to the negative electrode current collector 331 respectively. The positive electrode tab 313 and the negative electrode tab 333 can be collectively referred to as electrode tabs.

[0074] Please see again Figure 6 and Figure 7 Optionally, the single-cell battery 300 further includes a housing 340 and an end cap assembly 350, the housing 340 and the end cap assembly 350 forming a closed receiving cavity 341 for housing the electrolyte, the positive electrode 310, the separator 400, and the negative electrode 330. Understandably, the end cap assembly 350 electrically connects the positive electrode 310 and the negative electrode 330, leading them out for electrical connection to external devices or other single-cell batteries 300.

[0075] Due to the characteristics of the positive electrode polyanionic material and the negative electrode hard carbon material, the electrode components of sodium batteries have obvious loose openings in the bare cells after winding, which seriously affects the process of wrapping the bare cells with Mylar film and inserting them into the casing. Therefore, the separator needs to adopt a double-sided adhesive structure, that is, after hot pressing, the bare cells form a shape similar to a "hard brick". In related technologies, the separator is coated with adhesive layers on both sides of the base film. However, the thickness uniformity of the adhesive layer produced by spraying is poor, which easily leads to misalignment of the tabs of the bare cells. Separators using double-sided adhesive application have significantly better thickness uniformity between bare cells than those using double-sided spraying. However, sodium batteries use a winding process, which also requires high thickness uniformity within the separator roll. Although the adhesive dots on both sides of the double-sided adhesive-coated separator are arranged in a regular matrix, the overlapping area of ​​the adhesive dots on the A / B sides is random. This results in abrupt changes in thickness uniformity within the roll along the separator's length, causing irregular tab misalignment during winding. The hard carbon coating of sodium batteries is brittle and prone to powdering, and the bare cells cannot be crumpled. This necessitates even higher precision in the amount of tab misalignment, which severely affects the winding yield and mass production schedule.

[0076] Figure 10 This is a cross-sectional view of a diaphragm 400 according to an embodiment of this application.

[0077] Please see Figure 10This application also provides a diaphragm 400, which includes a base film 410, a dot-coated adhesive layer 420, and a roll-coated adhesive layer 430. The base film 410 has a first surface 411 and a second surface 412 disposed opposite to each other. The dot-coated adhesive layer 420 includes a plurality of dot-coated portions 421, which are spaced apart on the first surface 411. The roll-coated adhesive layer 430 is disposed on the second surface 412.

[0078] Understandably, the dot-coated adhesive layer 420, the base film 410, and the roller-coated adhesive layer 430 are sequentially stacked along the thickness direction of the diaphragm 400.

[0079] It should be noted that the roller-coated adhesive layer 430 is a single film layer. However, due to the surface tension of the roller-coated adhesive after roller coating, the roller-coated adhesive will shrink on the base film 410. Therefore, after the roller-coated adhesive cures to form the roller-coated adhesive layer 430, there will be exposed portions on the second surface 412 of the base film 410. In addition, there will also be missed portions during the roller coating process.

[0080] It should be noted that the size, shape, and spacing between the multiple dot coating portions 421 can be equal, partially equal, partially unequal, or regularly distributed.

[0081] Optionally, the plurality of dot-coating portions 421 are arranged in an array.

[0082] It should be noted that the multiple dot-coated portions 421 of the dot-coated adhesive layer 420 are formed using a dot-coating process, such as contact dot-coating processes like single-point pipette dot-coating or roller dot-coating, or non-contact dot-coating processes like single-point piezoelectric jet dot-coating, array needle piezoelectric jet dot-coating, or array film piezoelectric jet dot-coating. The roller-coated adhesive layer 430 is formed using a roller coating process, such as gravure roller coating or microgravure roller coating.

[0083] In one specific example, the dot-coated adhesive layer 420 faces the positive electrode 310, and the roll-coated adhesive layer 430 faces the negative electrode 330. In other embodiments, the dot-coated adhesive layer 420 faces the negative electrode 330, and the roll-coated adhesive layer 430 faces the positive electrode 310.

[0084] The diaphragm 400 of this embodiment includes a base film 410, a dot-coated adhesive layer 420, and a roller-coated adhesive layer 430; the base film 410 has a first surface 411 and a second surface 412 disposed opposite to each other; the dot-coated adhesive layer 420 includes a plurality of dot-coated portions 421, which are spaced apart on the first surface 411; the roller-coated adhesive layer 430 is disposed on the second surface 412. The dot-coated adhesive layer 420 is obtained using a dot-coating process, while the roll-coated adhesive layer 430 is obtained using a roll-coating process. Since only one side of the separator 400 is dot-coated, there is no random overlap or interlacing of adhesive dots on the first surface 411 and the second surface 412, significantly increasing the thickness consistency of the separator 400. Furthermore, the high thickness consistency of the roll-coated adhesive layer 430 results in a high overall thickness consistency for the separator 400. This effectively mitigates the misalignment problem of the positive electrode tab 313 and / or negative electrode tab 333 during the winding process of the single-cell battery 300. Additionally, when the base film 410 includes a ceramic layer, the roll-coated adhesive layer 430 is prone to clogging the ceramic layer, while the dot-coated adhesive layer 420 is less likely to clog it. This allows the ceramic layer to be positioned between the base film 410 and the dot-coated adhesive layer 420, maintaining a high ionic conductivity for the separator 400.

[0085] Figure 11 This is a cross-sectional view of a diaphragm 400 according to another embodiment of this application.

[0086] Please see Figure 11 In some embodiments, the coverage of the dot-coated adhesive layer 420 on the first surface 411 is less than the coverage of the roll-coated adhesive layer 430 on the second surface 412. The base film 410 includes a substrate layer 413 and a ceramic layer 414. The ceramic layer 414 is disposed on the surface of the substrate layer 413 and is disposed between the dot-coated adhesive layer 420 and the substrate layer 413.

[0087] Optionally, the substrate layer 413 may be made of, but is not limited to, a polyethylene porous membrane (PE membrane) or a polypropylene porous membrane (PP membrane).

[0088] Figure 12 This is a cross-sectional view of a diaphragm 400 according to another embodiment of this application. Figure 13 This is a cross-sectional view of a diaphragm 400 according to another embodiment of this application. It should be noted that in other embodiments, the ceramic layer 414 may also be disposed between the roller-coated adhesive layer 430 and the substrate layer 413. In other words, the ceramic layer 414 may be one or two layers. It will be understood that, as Figure 11 As shown, in this embodiment, the diaphragm 400 includes a roller-coated adhesive layer 430, a substrate layer 413, a ceramic layer 414, and a dot-coated adhesive layer 420, which are sequentially stacked. Figure 12As shown, in other embodiments, the diaphragm 400 may further include a roll-coated adhesive layer 430, a ceramic layer 414, a substrate layer 413, and a dot-coated adhesive layer 420, which are sequentially stacked. Figure 13 As shown, in other embodiments, the diaphragm 400 may include a roller-coated adhesive layer 430, a ceramic layer 414, a substrate layer 413, a ceramic layer 414, and a dot-coated adhesive layer 420, which are stacked sequentially.

[0089] The ceramic layer 414 has relatively large pores, approximately 100 nm to 1000 nm. The roller-coated adhesive layer 430 has a high coverage on the second surface 412. If the ceramic layer 414 is disposed between the substrate layer 413 and the roller-coated adhesive layer 430, i.e., the roller-coated adhesive layer 430 is disposed on the surface of the ceramic layer 414, the roller-coated adhesive layer 430 easily blocks the pores of the ceramic, greatly increasing the air permeability of the diaphragm 400 and reducing the ionic conductivity of the diaphragm 400. In this embodiment, the dot-coated adhesive layer 420 has a low coverage on the first surface 411, and the substrate layer 413 has small pores, approximately 20 nm to 50 nm in diameter, making it difficult for adhesive to penetrate. The ceramic layer 414 is disposed between the dot-coated adhesive layer 420 and the substrate layer 413, which can better improve the ionic conductivity of the diaphragm 400.

[0090] In some embodiments, if the coverage of the dot-coated adhesive layer 420 on the first surface 411 is S1 and the coverage of the roll-coated adhesive layer 430 on the second surface 412 is S2, then 0.15≤S1 / S2≤0.5.

[0091] Understandably, the ratio S1 / S2 of the coverage S1 of the dot-coated adhesive layer 420 on the first surface 411 and the coverage S2 of the roll-coated adhesive layer 430 on the second surface 412 is in the range of 0.15 ≤ S1 / S2 ≤ 0.5.

[0092] Specifically, S1 / S2 can be, but is not limited to, 0.15, 0.18, 0.20, 0.23, 0.25, 0.28, 0.30, 0.33, 0.35, 0.38, 0.40, 0.43, 0.45, 0.48, 0.5, etc.

[0093] In this embodiment, if S1 / S2 is too small, then S1 is too small or S2 is too large. If S1 is too small, the adhesion of the adhesive layer 420 is insufficient, making it difficult to suppress the expansion and deformation of the positive electrode 310 and / or negative electrode 330 of the single cell 300 during charge and discharge cycles (i.e., the ability to suppress deformation deteriorates). In addition, it will also affect the interface flatness of the core, making the interface between the separator 400 and the positive electrode 310 or the interface between the separator 400 and the negative electrode 330 prone to wrinkling. If S2 is too large, it is easy to block the pores of the separator 400, which will cause the air permeability of the separator 400 to increase too much and reduce the ionic conductivity of the separator 400.

[0094] If S1 / S2 is too large, then S1 is too large or S2 is too small. If S1 is too large, it will easily clog the pores of the separator 400, reduce the ionic conductivity of the separator 400, and reduce the energy efficiency of the single cell 300. In addition, it will reduce the wettability of the electrolyte, making it difficult for the positive electrode 310 and the negative electrode 330 located in the center of the core to be fully wetted by the electrolyte, making the single cell 300 prone to purple spots and material shedding during cycling. If S2 is too small, it will reduce the adhesion of the roller-coated adhesive layer 430, and wrinkles will easily occur at the interface between the separator 400 and the positive electrode 310 or between the separator 400 and the negative electrode 330 during the charging and discharging of the single cell 300.

[0095] In some embodiments, the coverage S1 of the dotted adhesive layer 420 on the first surface 411 is in the range of 10% ≤ S1 ≤ 35%.

[0096] Understandably, the coverage of the plurality of dotted coating portions 421 on the first surface 411 is in the range of 10% ≤ S1 ≤ 35% for the period S1.

[0097] Specifically, the coverage S1 of the dot-coated adhesive layer 420 on the first surface 411 can be, but is not limited to, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 35%, etc.

[0098] In this embodiment, if the coverage S1 of the adhesive layer 420 on the first surface 411 is too small, the adhesive force of the adhesive layer 420 will be insufficient, making it difficult to suppress the expansion and deformation of the positive electrode 310 and / or negative electrode 330 of the single cell 300 during charge-discharge cycles. Furthermore, it will affect the interface flatness of the core, making the interface between the separator 400 and the positive electrode 310 or between the separator 400 and the negative electrode 330 prone to wrinkling. If the coverage S1 of the adhesive layer 420 on the first surface 411 is too large, it will easily clog the pores of the separator 400, reducing the ionic conductivity of the separator 400 and decreasing the energy efficiency of the single cell 300. In addition, it will reduce the wettability of the electrolyte, making it difficult for the portions of the positive electrode 310 and negative electrode 330 located at the center of the core to be fully wetted by the electrolyte, causing purple spots and material shedding in the single cell 300 during cycling.

[0099] In some embodiments, the coverage S2 of the roller-coated adhesive layer 430 on the second surface 412 is in the range of 60% ≤ S2 ≤ 90%.

[0100] Specifically, the coverage S2 of the roller-coated adhesive layer 430 on the second surface 412 can be, but is not limited to, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, etc.

[0101] In this embodiment, if the coverage S2 of the roller-coated adhesive layer 430 on the second surface 412 is too small, the adhesion of the roller-coated adhesive layer 430 is reduced, and wrinkles are easily formed at the interface between the separator 400 and the positive electrode 310 or between the separator 400 and the negative electrode 330 during the charging and discharging of the single cell 300. If the coverage S2 of the roller-coated adhesive layer 430 on the second surface 412 is too large, the air permeability of the separator 400 increases too much, which can easily clog the pores of the separator 400 and reduce the ionic conductivity of the separator 400.

[0102] The increase in air permeability of diaphragm 400 refers to the increase or percentage of air permeability of diaphragm 400 after treatment (such as roller coating of adhesive layer 430) relative to before treatment (base membrane 410).

[0103] In some embodiments, the shape of the orthographic projection of the dotting portion 421 onto the first surface 411 is circular or near-circular, and the circularity K of the orthographic projection of the dotting portion 421 onto the first surface 411 is in the range of 0.85≤K≤1.

[0104] Specifically, the circularity K of the orthographic projection of the dotted part 421 onto the first surface 411 can be, but is not limited to, 0.85, 0.86, 0.88, 0.90, 0.92, 0.94, 0.96, 0.98, 1.0, etc.

[0105] In this embodiment, with the material and coverage of the dot-coating portion 421 remaining constant, the higher the circularity K of the orthographic projection of the dot-coating portion 421 onto the first surface 411, the better the adhesion of the dot-coating portion 421. If the circularity K of the orthographic projection of the dot-coating portion 421 onto the first surface 411 is too small, the adhesion of the dot-coating portion 421 will be too low, requiring an increase in the coverage of the dot-coating adhesive layer 420 to meet the adhesion requirements of the single cell 300 for the dot-coating adhesive layer 420. This can easily clog the base film 410, reduce the ionic conductivity of the separator 400, and reduce the energy efficiency of the single cell 300. In addition, it will also reduce the wettability of the electrolyte, making it difficult for the positive electrode 310 and the negative electrode 330 located in the center of the core to be fully wetted by the electrolyte, making the single cell 300 prone to purple spots and material shedding during cycling.

[0106] Figure 14 This is a schematic diagram of the planar structure of a diaphragm 400 according to an embodiment of this application.

[0107] Please see Figure 14 In some embodiments, the maximum width d of the orthographic projection of the dotted portion 421 onto the first surface 411 along an extension plane parallel to the base film 410 ranges from 200 μm ≤ d ≤ 800 μm.

[0108] Specifically, the maximum width d of the orthographic projection of the dotted part 421 onto the first surface 411 can be, but is not limited to, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm, 500μm, 550μm, 600μm, 650μm, 700μm, 750μm, 800μm, etc.

[0109] In this embodiment, if the maximum width d of the orthographic projection of the dotted coating portion 421 onto the first surface 411 is too small, the adhesion strength of the dotted adhesive layer 420 will be too high if the coating amount remains unchanged, reducing the wettability of the electrolyte to the core. Furthermore, the central region of the crater-like morphology of the dotted coating portion 421 will be small, reducing ionic conductivity. Conversely, if the maximum width d of the orthographic projection of the dotted coating portion 421 onto the first surface 411 is too large, the adhesion strength of the dotted adhesive layer 420 will be too low if the coating amount remains unchanged. This will make the interface between the separator 400 and the positive electrode 310, or between the separator 400 and the negative electrode 330, prone to wrinkling during the charging and discharging of the single cell 300, increasing the risk of purple spots and lithium plating in the single cell 300.

[0110] Figure 15 This is a cross-sectional view of a diaphragm 400 according to another embodiment of this application.

[0111] Please see Figure 14 and Figure 15 In some embodiments, the dotting portion 421 includes a connected central portion 4211 and an outer ring portion 4212, the outer ring portion 4212 being disposed around the outer periphery of the central portion 4211, and the thickness of the outer ring portion 4212 being greater than the thickness of the central portion 4211.

[0112] Understandably, the dotting portion 421 is shaped like a volcano crater. Understandably, the outer ring portion 4212 of the dotting portion 421 is thicker, while the central portion 4211 is thinner. This is beneficial for improving the adhesion of the dotting portion 421 and increasing the ionic conductivity of the diaphragm 400.

[0113] Please see again Figure 15In some embodiments, along the stacking direction of the dot-coated adhesive layer 420, the base film 410, and the roller-coated adhesive layer 430, the maximum thickness h1 of the dot-coated portion 421 ranges from 3μm ≤ h1 ≤ 8μm. Specifically, the maximum thickness h1 of the dot-coated portion 421 can be, but is not limited to, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, etc. If the maximum thickness h1 of the dot-coated portion 421 is too small, the compression ratio of the dot-coated portion 421 will be too small, reducing the bonding strength of the dot-coated portion 421. If the maximum thickness h1 of the dot-coated portion 421 is too large, it increases the difficulty of process implementation. In addition, the dot-coated portion 421 is prone to stringing during the dot-coating process, causing the shape of the dot-coated portion 421 to deform, reducing the bonding effect of the dot-coated portion 421.

[0114] "Compression ratio" refers to the thickness before compression divided by the thickness after compression.

[0115] In some embodiments, in the stacking direction of the base film 410 and the roll-coated adhesive layer 430, the thickness h2 of the roll-coated adhesive layer 430 is in the range of 1μm≤h2≤5μm. Specifically, the thickness h2 of the roll-coated adhesive layer 430 can be, but is not limited to, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, etc. If the thickness h2 of the roll-coated adhesive layer 430 is too small, the bonding strength of the roll-coated adhesive layer 430 will be too small, and wrinkles will easily occur at the interface between the separator 400 and the positive electrode 310 or between the separator 400 and the negative electrode 330 during the charging and discharging of the single cell 300. If the thickness h2 of the roll-coated adhesive layer 430 is too large, it will easily block the pores of the separator 400, reduce the ionic conductivity of the flow channel separator 400, and reduce the energy efficiency of the single cell 300.

[0116] In some embodiments, the base film 410 includes a substrate layer 413 and a ceramic layer 414 stacked together. The ceramic layer 414 is disposed between the dot-coated adhesive layer 420 and the substrate layer 413. The dot-coated adhesive layer 420 faces the positive electrode 310, and the roll-coated adhesive layer 430 faces the negative electrode 330.

[0117] The positive electrode active material of sodium batteries is under high voltage when charged and has strong oxidizing properties. Therefore, when the single cell 300 is a sodium battery, the ceramic layer 414 is disposed between the adhesive layer 420 and the substrate layer 413, with the adhesive layer 420 facing the positive electrode 310. Since the ceramic layer 414 has high oxidation resistance, it can better improve the oxidation resistance of the separator 400. Furthermore, when the single cell 300 experiences thermal runaway, heat is often generated intensely first on the positive electrode 310 side. Therefore, the ceramic layer 414 is disposed between the adhesive layer 420 and the substrate layer 413, with the adhesive layer 420 facing the positive electrode 310, which can better improve the thermal stability of the separator 400. Moreover, the reaction kinetics of the positive electrode 310 are generally slower than those of the negative electrode 330 and involve multiple electron transfers. The surface of the separator 400 facing the positive electrode 310 requires excellent electrolyte wettability to form a low-resistance interface and promote Na+ reaction. + Rapid transmission and the high electrolyte wettability of the ceramic layer 414 can better reduce interfacial impedance, improving the rate performance and low-temperature performance of the single cell 300. When the single cell 300 is a sodium battery, sodium metal is prone to forming dendrites when deposited on the surface of the negative electrode 330 (especially under conditions such as fast charging or low temperature). These dendrites may penetrate the separator 400, causing an internal short circuit. Therefore, the surface of the separator 400 facing the negative electrode 330 needs higher mechanical strength / toughness (to physically block dendrite penetration); smaller pore size and more uniform pore structure (to increase the difficulty of dendrite penetration), while the substrate layer 413 has high toughness. The substrate layer 413 and the roll-coated adhesive layer 430 do not have a ceramic layer 414, which can better increase the difficulty of dendrite penetration into the separator 400. In addition, the challenges faced by the negative electrode 330 side are more about the requirements of interface stability during the sodium deposition / dissolution process, and the need to adapt to the large volume changes of the negative electrode 330 (especially hard carbon). The negative electrode active material of sodium battery (such as hard carbon) usually has significant volume expansion / contraction during charge and discharge. The surface of the separator 400 facing the negative electrode 330 needs better flexibility and adhesive elasticity to adapt to this volume change and avoid coating peeling or poor contact between the separator 400 and the negative electrode 330 due to repeated expansion during charge and discharge cycles. Furthermore, the roller-coated adhesive layer 430 with an ultra-high coverage (≥60%) can effectively bond loose hard carbon particles at the inner corners of the negative electrode 330, greatly reducing the risk of hard carbon particles spreading to the larger surface area and forming foreign matter that punctures the separator. Therefore, for cost considerations, the ceramic layer 414 may not be coated on the negative electrode 330 side, but for higher adhesion performance requirements, the high-adhesion roller-coated adhesive layer 430 is preferred.

[0118] In other embodiments, the ceramic layer 414 is disposed between the dot-coated adhesive layer 420 and the substrate layer 413, with the dot-coated adhesive layer 420 facing the negative electrode 330 and the roll-coated adhesive layer 430 facing the positive electrode 310. This can improve the problem of misalignment of the tabs (positive tab 313 and / or negative tab 333) of the core; however, the ceramic layer 414 is prone to clogging, reducing the ionic conductivity of the separator 400.

[0119] In some embodiments, the dot-coated adhesive layer 420 is obtained by dot-coating adhesive and then curing it.

[0120] Optionally, the viscosity of the dispensing adhesive ranges from 1500 mPa•s to 6000 mPa•s. Specifically, the viscosity of the dispensing adhesive can be, but is not limited to, 150 mPa•s, 200 mPa•s, 250 mPa•s, 300 mPa•s, 350 mPa•s, 400 mPa•s, 450 mPa•s, 500 mPa•s, 550 mPa•s, 600 mPa•s, etc. If the viscosity of the dispensing adhesive is too low, the water content in the dispensing adhesive will be too high, and the solid content of the dispensing adhesive will be too low, requiring a longer drying time, reducing baking efficiency, and increasing the preparation cost of the diaphragm 400. If the viscosity of the dispensing adhesive is too high, it is easy to form strings during dispensing, resulting in an irregular shape of the dotted part 421, which is prone to deformation and affects the adhesion of the dispensing adhesive layer 420.

[0121] Optionally, the surface tension γ of the dot-applied adhesive is in the range of 80 mN / m ≤ γ ≤ 150 mN / m. Specifically, the surface tension γ of the dot-applied adhesive can be, but is not limited to, 80 mN / m, 90 mN / m, 100 mN / m, 110 mN / m, 120 mN / m, 130 mN / m, 140 mN / m, 150 mN / m, etc. If the surface tension γ of the dot-applied adhesive is too large, the contact angle will be too large, making it difficult to wet the base film 410 of the separator 400; if the surface tension γ of the dot-applied adhesive is too small, due to the coffee ring effect, it will be difficult to form a ring-shaped crater morphology, i.e., a concave center and a convex outer ring, resulting in poor adhesion.

[0122] Optionally, the areal density of the dot-coated adhesive layer 420 is 0.3 g / m³. 2 Up to 0.6g / m 2 Specifically, the areal density of the dot-coated adhesive layer 420 can be, but is not limited to, 0.3 g / m². 2 0.4g / m 2 0.5g / m 2 0.6g / m 2If the areal density of the adhesive layer 420 is too low, the adhesion will be too weak, and wrinkles will easily occur between the adhesive layer 420 and the negative electrode 330 or between the adhesive layer 420 and the positive electrode 310 during the charging and discharging of the single cell 300. If the areal density of the adhesive layer 420 is too high, it will easily clog the pores, reduce the ionic conductivity of the separator 400, and reduce the energy efficiency of the single cell 300.

[0123] Areal density test of the adhesive layer: The test was conducted according to the standard GB / T 20220-2006 "Determination of average thickness, average thickness of roll and area per unit mass of plastic films and sheets - Weighing method", using a 100cm... 2 Five pieces of base film 410 and five pieces of diaphragm 400 with dot-coated or roller-coated adhesive layer 430 were cut using a gram sampler. The mass of each diaphragm was measured and then divided by the sampling area to obtain the areal density of each diaphragm. The difference between the two is the areal density of the adhesive layer coating amount. The average value was taken after five tests.

[0124] In some embodiments, the separator 400 is stacked with the positive electrode 310, with the adhesive layer 420 facing the positive electrode 310, and pressed at room temperature for 40 seconds (s). The average peel strength Q1 between the adhesive layer 420 and the positive electrode 310 ranges from 1 N / m to 8 N / m. Specifically, the average peel strength Q1 between the adhesive layer 420 and the positive electrode 310 can be, but is not limited to, 1 N / m, 2 N / m, 3 N / m, 4 N / m, 5 N / m, 6 N / m, 7 N / m, 8 N / m, etc. If the average peel strength Q1 between the adhesive layer 420 and the positive electrode 310 is too small, the adhesion between the separator 400 and the positive electrode 310 will be weak, making it difficult to suppress the expansion and deformation of the positive electrode 310 and the negative electrode 330 during cycling. If the average peel strength Q1 between the adhesive layer 420 and the positive electrode 310 is too large, it will easily clog the pores and affect the energy efficiency of the single cell 300.

[0125] In some embodiments, the roller-coated adhesive layer 430 is obtained by roller coating and curing of roller-coated adhesive.

[0126] Optionally, the viscosity of the roller-coating adhesive ranges from 100 mPa•s to 300 mPa•s. Specifically, the viscosity of the roller-coating adhesive can be, but is not limited to, 100 mPa•s, 150 mPa•s, 200 mPa•s, 250 mPa•s, 300 mPa•s, etc. If the viscosity of the roller-coating adhesive is too low, the water content in the roller-coating adhesive will be too high, the solid content of the roller-coating adhesive will be too low, a longer drying time will be required, the baking efficiency will be reduced, and the preparation cost of the diaphragm 400 will be increased; if the viscosity of the roller-coating adhesive is too high, it will affect the uniformity of the roller coating.

[0127] Optionally, the areal density of the roller-coated adhesive layer 430 is 0.2 g / m³.2 Up to 0.6g / m 2 Specifically, the areal density of the roller-coated adhesive layer 430 can be, but is not limited to, 0.2 g / m³. 2 0.3g / m 2 0.4g / m 2 0.5g / m 2 0.6g / m 2 If the areal density of the roller-coated adhesive layer 430 is too low, the adhesion will be too weak, and wrinkles will easily occur between the roller-coated adhesive layer 430 and the negative electrode 330 or between the roller-coated adhesive layer 430 and the positive electrode 310 during the charging and discharging process of the single cell 300. If the areal density of the roller-coated adhesive layer 430 is too high, it will easily clog the pores, reduce the ionic conductivity of the separator 400, and reduce the energy efficiency of the single cell 300.

[0128] Optionally, the air permeability increase of the roller-coated adhesive layer 430 ranges from 5s / 100cc to 20s / 100cc. Specifically, the air permeability increase of the roller-coated adhesive layer 430 can be, but is not limited to, 5s / 100cc, 8s / 100cc, 10s / 100cc, 13s / 100cc, 15s / 100cc, 18s / 100cc, 20s / 100cc, etc.

[0129] "The increase in air permeability of the roller-coated adhesive layer 430" refers to the increase in air permeability after the roller-coated adhesive layer 430 is applied to the base membrane 410, compared to the base membrane 410. A smaller increase in air permeability of the roller-coated adhesive layer 430 is better. Excessive increase in air permeability can easily clog the pores of the diaphragm 400, reducing the ionic conductivity of the diaphragm 400.

[0130] In some embodiments, the separator 400 is stacked with the negative electrode 330, with the roller-coated adhesive layer 430 facing the negative electrode 330, and pressed at room temperature for 40 seconds (s). The average peel strength Q2 between the roller-coated adhesive layer 430 and the negative electrode 330 ranges from 1 N / m to 8 N / m. Specifically, the average peel strength Q2 between the roller-coated adhesive layer 430 and the negative electrode 330 can be, but is not limited to, 1 N / m, 2 N / m, 3 N / m, 4 N / m, 5 N / m, 6 N / m, 7 N / m, 8 N / m, etc. If the average peel strength Q2 between the roller-coated adhesive layer 430 and the negative electrode 330 is too small, the adhesion between the separator 400 and the negative electrode 330 will be weak, making it difficult to suppress the expansion and deformation of the positive electrode 310 and the negative electrode 330 during cycling. If the average peel strength Q2 between the roller-coated adhesive layer 430 and the negative electrode 330 is too large, it will easily clog the pores and affect the energy efficiency of the single cell 300.

[0131] Optionally, the dispensing adhesive includes a first solvent and first binder particles. The D50 particle size (also known as the median particle size) of the first binder particles in the dispensing adhesive is P1, and the range of P1 is 4μm ≤ P1 ≤ 8μm. Specifically, the D50 particle size of the first binder particles in the dispensing adhesive can be, but is not limited to, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, etc. If the D50 particle size of the first binder particles in the dispensing adhesive is too small, the first binder particles are difficult to disperse and are prone to agglomeration, which increases the impedance of the obtained diaphragm 400, and the height of the obtained dispensing portion 421 is too low, the compression ratio is too small, and the adhesion of the dispensing portion 421 is reduced. If the D50 particle size of the first adhesive particles in the dot-coating adhesive is too large, the height of the formed dot-coating portion 421 will be too high, the compression ratio will be too large, and the thickness uniformity will be poor. In addition, the adhesion of the dot-coating portion 421 to the base film 410 will be reduced, making the dot-coating portion 421 easy to fall off or shed powder.

[0132] "D50" refers to the particle size value corresponding to a sample when the cumulative volume distribution reaches 50%.

[0133] Optionally, the dotting section 421 includes primary particles with a particle size ranging from 200 nm to 300 nm (e.g., 200 nm, 230 nm, 250 nm, 280 nm, 300 nm, etc.). If the primary particle size is too large, it will affect the formation of secondary particles and the adhesion between the secondary particle agglomerates and the dotting section 421 and the base film 410; if the primary particle size is too small, i.e., the specific surface area is too large, the powder is very easy to absorb moisture and agglomerate, and the secondary particles will be difficult to disperse.

[0134] Optionally, the roller-coating adhesive includes a second solvent and second binder particles. The D50 particle size (also known as the median particle size) of the second binder particles in the roller-coating adhesive is P2, and the range of P2 is 0.3μm ≤ P2 ≤ 5μm. Specifically, the D50 particle size of the second binder particles in the roller-coating adhesive can be, but is not limited to, 0.3μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, etc. If the D50 particle size of the second binder particles in the roller coating adhesive is too small, the bulk density of the second binder particles in the resulting roller coating layer 430 will be very high, increasing the impedance of ion transport. In addition, the slurry of the roller coating adhesive is difficult to disperse evenly and has a high risk of clogging after compaction, resulting in a large increase in the air permeability and ion impedance of the diaphragm 400. Furthermore, if the particle size of the second binder particles in the roller coating layer 430 is too small, the leveling time will be too short, making it impossible for the roller coating layer 430 to flow and level sufficiently before curing, which can easily lead to unevenness in the roller coating layer 430 and affect the consistency of thickness. Moreover, a large number of fine second binder particles have a large specific surface area, making them prone to moisture absorption and clumping during storage, reducing material utilization and affecting the performance and storage stability of the roller coating layer 430. If the D50 particle size of the second binder particles in the roller coating adhesive is too large, the gaps between the second binder particles in the roller coating adhesive layer 430 will be larger. The larger pore size results in a smaller capillary force, making it difficult for the liquid adhesive to be locked between the second binder particles to a large extent. The second binder particles will have weak adhesion, and the liquid will flow into the base, causing a risk of pore blockage. The air permeability and ion resistance of the diaphragm 400 will also increase significantly. Furthermore, the surface of the roller coating adhesive layer 430 is prone to forming protrusions or depressions, reducing the adhesion between the roller coating adhesive layer 430 and the base film 410, making the roller coating adhesive layer 430 easy to fall off or shed powder.

[0135] Optionally, the first adhesive particles may be, but are not limited to, at least one of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polymethyl methacrylate (PMMA), polystyrene (PS), etc.

[0136] Optionally, the first solvent may be, but is not limited to, water. The second solvent may be, but is not limited to, water.

[0137] In some embodiments, 0.8 ≤ P1 / P2 ≤ 10. Specifically, P1 / P2 can be, but is not limited to, 0.8, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc.

[0138] If P1 / P2 is too small, then P1 is too small, or P2 is too large. If P1 is too small, the first binder particles are not easily dispersed and tend to agglomerate, increasing the impedance of the resulting diaphragm 400. The height of the resulting dot-coated portion 421 is also too low, resulting in a smaller compression ratio and reduced adhesion of the dot-coated portion 421. If P2 is too large, the gaps between the second binder particles in the roll-coated adhesive layer 430 are larger. The larger pore size results in a smaller capillary force, making it difficult for the liquid adhesive to be locked between the second binder particles. The second binder particles have weak adhesion, and the liquid flows into the base, causing a risk of pore blockage. The air permeability of the diaphragm 400 increases significantly, and the ionic impedance is also greater. Furthermore, the surface of the roll-coated adhesive layer 430 is prone to forming protrusions or depressions, reducing the adhesion between the roll-coated adhesive layer 430 and the base film 410, making the roll-coated adhesive layer 430 prone to peeling off or shedding powder.

[0139] If P1 / P2 is too large, then P1 is too large or P2 is too small; if P1 is too large, then the height of the formed dotted part 421 is too high, the compression ratio is too large, and the thickness uniformity is poor; in addition, it reduces the adhesion of the dotted part 421 to the base film 410, making the dotted part 421 easy to fall off or shed powder. If P2 is too small, the bulk density of the second binder particles in the resulting roller-coated adhesive layer 430 will be very high, increasing the impedance of ion transport. In addition, the roller-coated adhesive slurry will be difficult to disperse evenly and will have a high risk of clogging after compaction. The air permeability of the diaphragm 400 will increase significantly, and the ion impedance will also be large. Furthermore, if the particle size of the second binder particles in the roller-coated adhesive layer 430 is too small, the leveling time will be too short, making it impossible for the roller-coated adhesive layer 430 to flow and level sufficiently before curing. This will easily lead to unevenness in the roller-coated adhesive layer 430, affecting the consistency of thickness. Moreover, a large number of fine second binder particles have a large specific surface area, making them prone to moisture absorption and clumping during storage, reducing material utilization and affecting the performance and storage stability of the roller-coated adhesive layer 430.

[0140] The diaphragm 400 of this application will be further described below through specific embodiments.

[0141] Examples 1, 2, and Comparative Examples 1 to 6 The separator 400 and the single cell 300 of each embodiment and comparative example are prepared by the following steps: (1) Preparation of diaphragm 400: 1) Preparation of adhesive for dotting: Weigh polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP powder, first adhesive particles), polyacrylic acid (PAA), acrylic resin emulsion and water-soluble glycerol according to the mass ratio of 70:5:24.6:0.4; first add deionized water as solvent in the stirrer, then add the weighed PAA, stir evenly at 1000rpm / 15min, then add glycerol, stir evenly at 1000rpm / 15min, control the temperature at about 40℃, and control the pH at 7. Add PVDF-HFP powder and stir evenly at 2500 rpm for 90 minutes. Then add acrylic resin emulsion and stir evenly at 1000 rpm for 15 minutes. Finally, stir slowly at 500 rpm for 15 minutes to eliminate air bubbles, resulting in dot-coating adhesive. 2) Roller coating adhesive preparation: Weigh polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP powder, second binder granules), polyacrylic acid (PAA), acrylic resin emulsion, and wetting agent (propylene glycol) according to a mass ratio of 70:5:24.6:0.4. First, stir... Add deionized water as a solvent to the container, then add the weighed PAA, and stir evenly at 1000 rpm / 15 min. Next, add the acrylic resin emulsion and stir evenly at 1000 rpm / 15 min, controlling the temperature at approximately 40℃ and the pH at approximately 7. Then add PVDF-HFP powder and stir evenly at 2500 rpm / 90 min. Next, add the wetting agent (propylene glycol) and stir evenly at 1000 rpm / 15 min. Finally, slowly stir at 500 rpm / 15 min to eliminate air bubbles, obtaining the roller coating adhesive. 3) Apply... Forming of the adhesive coating layer 420: A base film 410 is provided, comprising a substrate layer 413 and a ceramic layer 414 stacked together. The substrate layer 413 is a porous polyethylene (PE) film with a thickness of 9 μm, and the ceramic layer 414 has a thickness of 2 μm. The adhesive is applied to the surface of the base film 410 using a contact roller coating device. After drying at only 65°C, the adhesive coating layer 420 is obtained. The adhesive coating layer 420 includes multiple dotted portions 421 arranged in an array. The dotted portions 421 are circular and cut for later use. The single-sided surface density of the adhesive coating layer 420 is 0.5 g / m². 2 4) Formation of roller-coated adhesive layer 430: Roller-coated adhesive is applied to the surface of the base film 410 using a gravure roller coating machine. After drying at 65°C, a diaphragm 400 is obtained, which is then slit and ready for use. The areal density of the roller-coated adhesive layer 430 is 0.5 g / m³. 2 The laminated structure of the diaphragm 400 in each embodiment and comparative example, the diameter of the dot coating portion 421, the coverage of the dot coating adhesive layer 420, and the coverage of the roller coating adhesive layer 430 are shown in Tables 1 and 2 below.

[0142] (2) Preparation of positive electrode 310: The positive electrode active material is polyanionic sulfate Na2.4 Fe 1.8 (SO4)3, conductive carbon black (Super-P), and binder PVDF are mixed at a mass ratio of 97:1:2; then N-methylpyrrolidone (NMP) is added as a solvent and stirred evenly to prepare a positive electrode slurry with a solid content of 60wt%. The positive electrode slurry is then uniformly coated on one surface of a 11μm thick positive electrode current collector 311 aluminum foil and dried at 85℃. The above steps are then repeated on the other surface of the positive electrode 310. After rolling, a positive electrode 310 with a positive active layer 312 coated on both sides is obtained; the single-sided thickness of the positive active layer 312 is 80μm.

[0143] (3) Preparation of negative electrode sheet 330: The negative electrode active material hard carbon, conductive carbon black (Super-P) and sodium carboxymethyl cellulose (CMC-Na) and styrene-butadiene rubber (SBR) are mixed in a mass ratio of 97:1:1.5:0.5, deionized water is added, and the mixture is stirred evenly to prepare a negative electrode slurry with a solid content of 55wt%. Then, the negative electrode slurry is uniformly coated on one surface of a negative electrode current collector 331 aluminum foil with a thickness of 11μm, and dried at 105℃. Then, the above steps are repeated on the other surface of the negative electrode sheet 330. After rolling, a negative electrode sheet 330 with a negative electrode active layer 332 coated on both sides is obtained. The single-sided thickness of the negative electrode active layer 332 is 70μm.

[0144] (5) Preparation of electrolyte: Ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 1:1:1, dissolved, and stirred thoroughly. The mixture was then placed at 5°C or lower for 12 hours. Sodium hexafluorophosphate (NaPF6) was then added and mixed thoroughly to obtain the electrolyte. The molar concentration of NaPF6 in the electrolyte was 1.0 mol / L.

[0145] (6) Preparation of sodium battery (single cell 300): The positive electrode 310, separator 400 and negative electrode 330 prepared above are arranged in order, so that the separator 400 is placed between the positive electrode 310 and the negative electrode 330 to play a role in isolation, and an electrode assembly is obtained. The electrode assembly is wound to obtain a core. The core is pressed at room temperature, and the unit area pressure is controlled to be 4.8 MPa and the holding time is 40 s. Finally, the core is placed in an aluminum alloy square shell, vacuum dried and injected with electrolyte. After vacuum sealing, standing, formation and other processes, a sodium battery is obtained.

[0146] In the specific embodiments of this application, the single cell 300 is illustrated using a sodium battery as an example, and should not be construed as a limitation on the single cell 300 and the separator 400 of the embodiments of this application.

[0147] The following performance tests were conducted on the separator 400 and sodium battery of each embodiment and comparative example: (1) Laser particle size test: The laser particle size of the first adhesive particles in the dot-coated adhesive or the second adhesive particles in the roller-coated adhesive was tested according to the standard GB / T 19077-2016 Particle size distribution laser diffraction method. The Better size laser particle size analyzer system (model: Better size 2600) was used, and the average value of D50 was taken after 3 tests.

[0148] (2) Coverage S1 test of dot-coated adhesive layer 420: The dot-coated parts 421 on the surface of the diaphragm 400 with dot-coated adhesive layer 420 are identified and calculated using a super depth-of-field three-dimensional stereo microscope. The magnification is 50X. Within the target area (e.g., a rectangular area of ​​17mm×13mm), 10 dot-coated parts 421 are selected, their diameters are measured and averaged, and the average area of ​​a single dot-coated part 421 is calculated. Then, the average area is divided by the area of ​​the square formed by connecting the centers of four adjacent dot-coated parts 421, which is the coverage S1 of the dot-coated coating.

[0149] (3) Coverage test of roller coating layer 430: The surface of the diaphragm 400 with roller coating layer 430 is identified and calculated using a scanning electron microscope with a magnification of 500X. Five areas are randomly selected for testing. The coverage of roller coating layer 430 is identified and calculated using Image Pro Plus software. The average value is the coverage of roller coating layer 430.

[0150] (4) Air permeability test of 400 membrane: Referring to the air permeability test method in 6.5.4 of the standard GB / T 36363-2018 Polyolefin membrane 400 for lithium-ion batteries, an air permeability tester (model: Wangyan EG01-55-1MR) was used to test the time required for 100 mL of air to pass through 1 square inch of 400 membrane under a pressure of 1.22 kPa. This time is the air permeability value. Five tests were performed and the average value was taken. The smaller the air permeability value, the better the air permeability of the 400 membrane.

[0151] (5) Specifications and measurement methods for misalignment of the core tabs (positive tab 313 and / or negative tab 333): Tab misalignment refers to tab alignment. If the tab misalignment specification exceeds the standard, it will increase the scrap loss of the core on the one hand; on the other hand, poor alignment will have an adverse effect on the tab welding (some tabs cannot be welded or the welding area is small, which will cause some positive tabs 310 / negative tabs 330 to be unable to conduct electricity, resulting in invalid positive tabs 310 / negative tabs 330 and increasing the difficulty of ultrasonic welding). The tab misalignment specification of the core must meet the following 4 conditions at the same time: ① Distance from the first positive tab 313 to the edge of the core: A±4mm; ② Distance from the first negative tab 333 to the edge of the core: B±4mm; ③ Distance from the innermost tab to the edge of the core: ≤[(A+B) / 2+54]mm; ④ Distance from the outermost tab to the edge of the core: ≥[(A+B) / 2-7.5]mm. Where A and B are both natural numbers, and 15≤A≤35, 15≤B≤35.

[0152] The calculation method for the tab misalignment defect rate is as follows: 300 bare cells are wound in each group, and the number of misaligned bare cells is calculated separately. The defect rate for 1 misaligned cell is 1 / 300 × 100% = 0.33%; the defect rate for 2 misaligned cells is 2 / 300 × 100% = 0.67%; and the defect rate for 35 misaligned cells is 20 / 300 × 100% = 6.67%. Under normal circumstances, the lower the tab misalignment defect rate, the better; for normal mass production, it should be ≤1%.

[0153] (6) Pressing and sampling of diaphragm 400 and positive electrode 310 / negative electrode 330 and bonding strength test: According to the standard GB / T 2792-2014 Test method for peel strength of adhesive tape, the peel strength of diaphragm 400 with dot-coated adhesive layer 420 / roll-coated adhesive layer 430 is tested. After pressing, the sample size is cut to 20mm×100mm and fixed in the middle of the clamp of the tensile testing machine. Then the tensile testing machine peels the diaphragm 400 and positive electrode 310 / negative electrode 330 along the 180° direction at a speed of 50mm / min. The test distance is up to 80mm. Five tests are taken and the average value is taken. The bonding force is the average value of the peel strength. The pressing method for the diaphragm 400 and the positive electrode 310 / negative electrode 330 is as follows: cut 100mm×100mm positive electrode 310 / negative electrode 330 and diaphragm 400, stack them naturally and put them into a flat plate press for pressing. The room temperature pressing temperature is 25℃, the holding time is 40s, and the unit area pressure is 4.8MPa.

[0154] (7) Energy efficiency test of sodium battery at room temperature (25℃): Under 25℃ conditions, the sodium-ion battery was charged and discharged using 1P charging and 1P discharging cycles, with the charging cut-off voltage at 3.3V and the discharging cut-off voltage at 1.5V, until the sodium battery capacity reached 60% of the initial capacity. At the same time, the energy efficiency of the sodium battery after 2 cycles was tested using the constant power method. The energy efficiency of the sodium battery = discharge energy of the second cycle / charging energy of the second cycle × 100%.

[0155] (8) Test on the interface condition of the negative electrode 330 after full charge: Disassemble the sodium battery after full charge according to the operating specifications. The humidity of the disassembly room is ≤5%RH and the temperature is 25±3℃. Take pictures to record the interface wrinkles of the negative electrode 330. Start counting from the inner circle of the core. If the number of wrinkles of the negative electrode 330 is 0, it is judged as no wrinkles; if the number of wrinkles of the negative electrode 330 is 1 to 3, it is judged as very slight wrinkles; if the number of wrinkles of the negative electrode 330 is 4 to 6, it is judged as slight wrinkles; if the number of wrinkles of the negative electrode 330 is 7 or more, it is judged as obvious wrinkles.

[0156] The performance parameters of the separator 400 and sodium battery in each embodiment and comparative example are shown in Tables 1 to 3 below.

[0157] Table 1 Performance parameters of dot-coated and roller-coated adhesives in each embodiment and comparative example

[0158] Table 2 Performance parameters of diaphragm 400 in each embodiment and comparative example

[0159] Table 3: Performance data of each embodiment and comparative example

[0160] Figure 16 This is a scanning electron microscope image of the surface of the dotted adhesive layer 420 of the diaphragm 400 in Example 1. Figure 17 This is a scanning electron microscope image of the surface of the dotted adhesive layer 420 of the diaphragm 400 in Example 2. Figure 18 This is a scanning electron microscope image of the surface of the roller-coated adhesive layer 430 of the diaphragm 400 in Example 1. Figure 19 This is a scanning electron microscope image of the surface of the roller-coated adhesive layer 430 of the diaphragm 400 in Example 2.

[0161] As can be seen from the test data of Examples 1 and 2 in Tables 1 to 3, compared with Example 2 where the roll-coated adhesive layer 430 faces the positive electrode 310 and the dot-coated adhesive layer 420 faces the negative electrode 330, the scheme in Example 1 where the dot-coated layer faces the positive electrode 310 and the roll-coated adhesive layer 430 faces the negative electrode 330 can better reduce the increase in air permeability of the separator 400, and the core has a lower defect rate of electrode tab misalignment, higher ionic conductivity of the separator 400, and higher energy efficiency of the sodium battery at 25°C.

[0162] The test results of Example 1, Comparative Example 1 and Comparative Example 2 show that the coverage S1 of the dot-coated adhesive layer 420 in Comparative Example 1 is too small, and the ratio S1 / S2 of the coverage S1 of the dot-coated adhesive layer 420 to the coverage S2 of the roll-coated adhesive layer 430 is too small. This can result in a lower increase in the air permeability of the separator 400, but the peel strength Q1 between the separator 400 and the positive electrode 310 is too low. After the sodium battery is fully charged, the negative electrode 330 will have obvious wrinkles. In Comparative Example 2, the coverage S1 of the dot-coated adhesive layer 420 is too large, and the ratio S1 / S2 of the coverage S1 of the dot-coated adhesive layer 420 to the coverage S2 of the roll-coated adhesive layer 430 is too large. This can result in a significant increase in the air permeability of the separator 400, an excessively large peel strength Q1 between the separator 400 and the positive electrode 310, a decrease in the ionic conductivity of the separator 400, a decrease in the energy efficiency of the sodium battery, and the appearance of purple spots on the negative electrode 330 after the sodium battery is fully charged.

[0163] The test results of Examples 2, 3, and 4 show that if the laser particle size D50 of the roller-coated adhesive is too small (i.e., P2 is too small, as in Comparative Example 3), the packing density of the second binder particles in the roller-coated adhesive layer 430 is very high, making it difficult to disperse the slurry evenly and increasing the risk of pore blockage after compaction. The permeability and ion resistance of the separator 400 increase significantly, and the negative electrode 330 shows obvious wrinkles after the sodium battery is fully charged. If the laser particle size D50 of the roller-coated adhesive is too small (i.e., P2 is too small, as in Comparative Example 4), the gaps between the second binder particles in the roller-coated adhesive layer 430 are larger. The larger pore size results in a smaller capillary force, making it difficult for the liquid adhesive to be locked between the second binder particles. The bonding effect between the second binder particles is weak, and the liquid adhesive easily flows into the substrate, causing the risk of pore blockage. The permeability and ion resistance of the separator 400 also increase significantly, and the bonding strength is low. The negative electrode 330 shows obvious wrinkles after the sodium battery is fully charged.

[0164] The test results from Examples 1, 5, and 6 show that in Comparative Example 5, both sides of the base film 410 of the separator 400 are dot-coated adhesive layers 420. This increases the air permeability and reduces the ion resistance of the separator 400, thus increasing the energy efficiency of the sodium battery. However, the random distribution and overlap of the dot-coated adhesive dots in conventional double-sided coatings make it easy for the thickness of the separator 400 roll to be coated, resulting in a high rate of electrode misalignment defects. In Comparative Example 6, both sides of the base film 410 of the separator 400 are roll-coated adhesive layers 430. Although the thickness consistency of the separator 400 is the highest and the rate of electrode misalignment defects is the lowest, the large coverage of the roll-coated adhesive layer 430 easily clogs the pores, greatly increasing the air permeability and ion resistance of the separator 400, thus reducing the energy efficiency of the sodium battery.

[0165] In this application, the terms "embodiment" and "implementation" mean that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of these phrases in various locations throughout the specification does not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this application can be combined with other embodiments. Furthermore, it should be understood that the features, structures, or characteristics described in the various embodiments of this application can be arbitrarily combined to form another embodiment that does not depart from the spirit and scope of the technical solution of this application, provided there is no contradiction between them.

[0166] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A diaphragm, characterized in that, The diaphragm includes: The base film has a first surface and a second surface disposed opposite to each other; A dotted adhesive layer, comprising a plurality of dotted portions spaced apart on the first surface; and A roller-coated adhesive layer is disposed on the second surface.

2. The diaphragm according to claim 1, characterized in that, The coverage of the dot-coated adhesive layer on the first surface is less than the coverage of the roll-coated adhesive layer on the second surface. The base film includes a substrate layer and a ceramic layer. The ceramic layer is disposed on the surface of the substrate layer and between the dot-coated adhesive layer and the substrate layer.

3. The diaphragm according to claim 1, characterized in that, If the coverage of the dot-coated adhesive layer on the first surface is S1, and the coverage of the roller-coated adhesive layer on the second surface is S2, then 0.15 ≤ S1 / S2 ≤ 0.

5.

4. The diaphragm according to claim 3, characterized in that, The coverage rate S1 of the dot-coated adhesive layer on the first surface is in the range of 10% ≤ S1 ≤ 35%; And / or, The coverage rate S2 of the roller-coated adhesive layer on the second surface is in the range of 60% ≤ S2 ≤ 90%.

5. The diaphragm according to claim 1, characterized in that, The shape of the orthographic projection of the dotted part onto the first surface is circular or near-circular, and the circularity K of the orthographic projection of the dotted part onto the first surface is in the range of 0.85≤K≤1.

6. The diaphragm according to claim 1, characterized in that, The dotting portion includes a connected central portion and an outer ring portion, the outer ring portion is disposed around the outer periphery of the central portion, and the thickness of the outer ring portion is greater than the thickness of the central portion.

7. The diaphragm according to claim 1, characterized in that, Along an extension plane parallel to the base film, the maximum width d of the orthographic projection of the dotted portion onto the first surface ranges from 200μm≤d≤800μm.

8. The diaphragm according to any one of claims 1-7, characterized in that, Along the stacking direction of the dot-coated adhesive layer, the base film, and the roller-coated adhesive layer, the maximum thickness h1 of the dot-coated portion ranges from 3μm≤h1≤8μm; and / or, along the stacking direction of the base film and the roller-coated adhesive layer, the thickness h2 of the roller-coated adhesive layer ranges from 1μm≤h2≤5μm.

9. A single-cell battery, characterized in that, The single cell includes a positive electrode, a separator as described in any one of claims 1-8, a negative electrode, and an electrolyte, wherein the separator is located between the positive electrode and the negative electrode.

10. The single-cell battery according to claim 9, characterized in that, The base film includes a substrate layer and a ceramic layer stacked together. The ceramic layer is disposed between the dot-coated adhesive layer and the substrate layer. The dot-coated adhesive layer faces the positive electrode sheet, and the roll-coated adhesive layer faces the negative electrode sheet.

11. An energy storage device, characterized in that, The energy storage device includes one or more single-cell batteries as described in claim 9 or 10.

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