Diaphragm, design method of diaphragm, single battery and energy storage device

Abstract

The invention provides a diaphragm, a design method of the diaphragm, a single battery and an energy storage device. The diaphragm comprises a base film, wherein the base film is provided with a first surface and a second surface which are arranged oppositely; the first adhesive layer comprises a first adhesive point unit, and the first adhesive point unit comprises a plurality of first adhesive point parts which are arranged on the first surface in an array; the first adhesive layer comprises a first adhesive point unit, the second adhesive layer comprises a second adhesive point unit, the second adhesive point unit comprises a plurality of second adhesive point parts arranged on the second surface, and the distance between every two adjacent second adhesive point parts is at least partially unequal.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a separator, a separator design method, 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 exposed cell openings after winding, severely impacting the Mylar membrane wrapping and casing processes. Therefore, the separator needs a double-sided adhesive structure, where the exposed 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 resulting adhesive layer thickness is inconsistent, easily causing misalignment of the exposed cell's tabs. While double-sided adhesive-coated separators offer significantly better thickness consistency between exposed cells, the winding process for sodium-ion batteries requires high thickness consistency 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 is random, leading to abrupt changes in thickness consistency along the separator's length. This results in 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; A first adhesive layer, the first adhesive layer including a first adhesive dot unit, the first adhesive dot unit including a plurality of first adhesive dots arranged in an array on the first surface; and The second adhesive layer includes a second adhesive dot unit, which includes a plurality of second adhesive dots arranged on the second surface, wherein the spacing between two adjacent second adhesive dots is at least partially unequal.

[0005] Furthermore, the plurality of first adhesive dots in the first adhesive dot unit are arranged in P rows and Q columns, wherein each row extends along a first direction and each column extends along a second direction, wherein the first direction is perpendicular to the second direction; the plurality of second adhesive dots in the second adhesive dot unit are arranged in M ​​rows and N columns, wherein each row is parallel to the first direction and each column is parallel to the second direction; the length of each row in the first adhesive dot unit is equal to the length of each row in the second adhesive dot unit, and the length of each column in the first adhesive dot unit is equal to the length of each column in the second adhesive dot unit.

[0006] Furthermore, the second adhesive dot unit satisfies at least one of the following conditions: The second adhesive dot unit is centrally symmetrical; The second adhesive dot unit has a first axis of symmetry parallel to the first direction; and The second adhesive dot unit has a second axis of symmetry parallel to the second direction.

[0007] Furthermore, the diaphragm satisfies at least one of the following conditions: Along the first direction, the spacing between two adjacent second adhesive dots first gradually increases and then gradually decreases; Along the first direction, the spacing between two adjacent second adhesive dots first gradually decreases and then gradually increases; Along the second direction, the spacing between two adjacent second adhesive dots first gradually increases and then gradually decreases; and Along the second direction, the distance between two adjacent second adhesive dots first gradually decreases and then gradually increases.

[0008] Furthermore, the first adhesive dot is circular or nearly circular, and the first adhesive dot has a first center point. When the first adhesive dot is circular, the first center point is the center of the circle. When the first adhesive dot is nearly circular, the first center point is the center of the circumcircle of the first adhesive dot. The second adhesive dot is circular or nearly circular, and has a second center point. When the second adhesive dot is circular, the second center point is the center of the circle. When the second adhesive dot is nearly circular, the second center point is the center of the circumcircle of the second adhesive dot.

[0009] Furthermore, the diaphragm satisfies at least one of the following conditions: Along the first direction, the spacing between two adjacent second adhesive dots first gradually increases and then gradually decreases; Along the first direction, the spacing between two adjacent second adhesive dots first gradually decreases and then gradually increases; Along the second direction, the spacing between two adjacent second adhesive dots first gradually increases and then gradually decreases; and Along the second direction, the distance between two adjacent second adhesive dots first gradually decreases and then gradually increases.

[0010] Furthermore, along the first direction, the distance between the first center points of two adjacent first adhesive dots is T1, and the distance between the second center point of the i-th second adhesive dot and the second center point of the (i+1)-th second adhesive dot is T(i, i+1). Then, T(i, i+1) = T1 × a1 × b1 （i-1） , where i is the position of the second glue dot when counting from the first or Nth second glue dot in each row to the second axis of symmetry along the first direction, a1 is the initial starting coefficient, and b1 is the common ratio of the geometric sequence formed by the distances between two adjacent second glue dots along the first direction; When the number of second adhesive dots in each row along the first direction is greater than or equal to the number of first adhesive dots, 0.5≤a1<1, 0.9≤b1≤1.5, b≠1; When the number of second adhesive dots in each row along the first direction is less than the number of first adhesive dots, 0.9 ≤ a1 ≤ 1.5, 0.5 ≤ b1 < 1.

[0011] Furthermore, along the second direction, the distance between the first center points of two adjacent first adhesive dots is T2, and the distance between the second center point of the j-th second adhesive dot and the second center point of the (j+1)-th second adhesive dot is T(j, j+1). Then, T(j, j+1) = T2 × a2 × b2 （j-1） Where, j is the position of the second glue dot when counting from the first or Mth second glue dot in each column to the first axis of symmetry along the second direction, a2 is the initial starting coefficient, and b2 is the common ratio of the geometric sequence formed by the distances between two adjacent second glue dots along the second direction; When the number of the second adhesive dots in each column along the second direction is greater than or equal to the number of the first adhesive dots, 0.5 ≤ a2 < 1, 1 < b2 ≤ 1.5; When the number of second glue dots in each column along the first direction is less than the number of first glue dots, 1 < a2 ≤ 1.5, 0.5 ≤ b2 < 1.

[0012] Furthermore, the diaphragm satisfies: 5≤M≤12, 5≤N≤12, 5≤P≤12, 5≤Q≤12, where M, N, P, and Q are all integers; M equals P-1, P, or P+1; N equals Q-1, Q, or Q+1.

[0013] Furthermore, the diaphragm satisfies at least one of the following conditions: The equivalent circle diameter of the first adhesive dot ranges from 250 μm to 500 μm; The equivalent circle diameter of the second adhesive dot ranges from 250 μm to 500 μm; Along the first direction, the distance between the first center points of two adjacent first adhesive dots ranges from 250 μm to 3000 μm; Along the second direction, the distance between the first center points of two adjacent first adhesive dots ranges from 250 μm to 3000 μm; Along the first direction, the distance between the second center points of two adjacent second adhesive dots ranges from 250 μm to 3000 μm; and Along the second direction, the distance between the second center points of two adjacent second adhesive dots ranges from 250 μm to 3000 μm.

[0014] Furthermore, there are multiple first adhesive dot units, and multiple first adhesive dot unit arrays are arranged on the first surface. There are also multiple second adhesive dot units, and multiple second adhesive dot unit arrays are arranged on the second surface. One first adhesive dot unit corresponds to one second adhesive dot unit, and different first adhesive dot units correspond to different second adhesive dot units. The diaphragm satisfies at least one of the following conditions: The average overlap rate X between the first adhesive dot unit and the second adhesive dot unit ranges from 7% to X ≤ 26%. The range R of the overlap rate between the first adhesive dot unit and the second adhesive dot unit is 0% ≤ R ≤ 10%; and The standard deviation σ of the overlap rate between the first adhesive dot unit and the second adhesive dot unit is in the range of 0%≤σ≤3%.

[0015] Secondly, embodiments of this application also provide a method for designing a diaphragm, the method comprising: A base film is provided, the base film having a first surface and a second surface disposed opposite to each other; A first adhesive layer is designed on the first surface of the base film. The first adhesive layer includes a first adhesive dot unit. The first adhesive dot unit includes a plurality of first adhesive dot portions arranged in an array. The plurality of first adhesive dot portions are arranged in an array of P rows and Q columns. Each row extends along a first direction and each column extends along a second direction. The first direction is perpendicular to the second direction. Each first adhesive dot portion has a first center point. Along the first direction, the distance between the first center points of two adjacent first adhesive dot portions is T1. A second adhesive layer is designed on the second surface of the base film. The design of the second adhesive layer includes designing second adhesive dot units, such that each second adhesive dot unit comprises a plurality of second adhesive dot portions arranged in M ​​rows and N columns. Each row is parallel to the first direction, and each column is parallel to the second direction. Each second adhesive dot portion has a second center point. The length of each row in the first adhesive dot unit is equal to the length of each row in the second adhesive dot unit, and the length of each column in the first adhesive dot unit is equal to the length of each column in the second adhesive dot unit. The second adhesive dot unit has a first axis of symmetry parallel to the first direction and a second axis of symmetry parallel to the second direction. Along the first direction, the distance between the second center point of the i-th second adhesive dot portion and the second center point of the (i+1)-th second adhesive dot portion is T(i, i+1), then T(i, i+1) = T1 × a1 × b1. （i-1） Where i is the position of the second glue dot when counting along the first direction from the first or Nth second glue dot in each row to the second axis of symmetry, a1 is the initial starting coefficient, and b1 is the common ratio of the geometric sequence formed by the distances between two adjacent second glue dots along the first direction; wherein the first direction is perpendicular to the second direction; The values ​​of a1 and b1 are set, and the second adhesive layer is translated along at least four directions. The average overlap rate of the plurality of first adhesive dots of the first adhesive dot unit and the plurality of second adhesive dots of the second adhesive dot unit in each of the at least four directions is calculated after translation. The range of the overlap rate is calculated based on the average overlap rate in the at least four directions. The values ​​of a1 and b1 are adjusted multiple times, and the range of the overlap rate is calculated for different values ​​of a1 and b1. Wherein, the at least four directions are at least four different directions on the extension plane of the base film. The values ​​of a1 and b1 when the range of overlap rate is at its minimum are selected to determine the arrangement of the plurality of second adhesive dots in the second adhesive dot unit along the first direction.

[0016] Furthermore, along the second direction, the distance between the first center points of two adjacent first adhesive dots is T2. The design of the second adhesive layer on the second surface of the base film further includes: along the second direction, if the distance between the second center point of the j-th second adhesive dot and the second center point of the (j+1)-th second adhesive dot is T(j, j+1), then T(j, j+1) = T² × a² × b² （j-1） Where, j is the position of the second glue dot when counting from the first or Mth second glue dot in each column to the first axis of symmetry along the second direction, a2 is the initial starting coefficient, and b2 is the common ratio of the geometric sequence formed by the distances between two adjacent second glue dots along the second direction; The design method further includes: Set the values ​​of a2 and b2, translate the second adhesive layer along at least four directions, calculate the average overlap rate of multiple first adhesive dots of the first adhesive dot unit and multiple second adhesive dots of the second adhesive dot unit in each of the at least four directions after the second adhesive layer is translated in each direction, and calculate the range of the overlap rate based on the average overlap rate in the at least four directions; adjust the values ​​of a2 and b2 multiple times, and calculate the range of the overlap rate for different values ​​of a2 and b2; and The values ​​of a2 and b2 when the range of overlap rate is at its minimum are selected to determine the arrangement of the plurality of second adhesive dots in the second adhesive dot unit along the second direction.

[0017] Furthermore, the feature is that the values ​​of T(i, i+1) and T(j, j+1) are rounded to make T(i, i+1) and T(j, j+1) multiples of 10 μm.

[0018] Thirdly, embodiments of this application also 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.

[0019] Fourthly, embodiments of this application also provide an energy storage device, the energy storage device comprising: one or more single-cell batteries as described in embodiments of this application.

[0020] During the roll coating or coating process of the diaphragm with the first and second adhesive layers, since the diaphragm is coated or coated in a whole roll (e.g., 4000m in length), the relative positions of the first adhesive dot units and the second adhesive dot units of the first adhesive layer are difficult to remain completely fixed at different positions on the diaphragm and will move and change. Once the process of the first and second adhesive layers fluctuates or becomes abnormal, it is necessary to cut off this section of the diaphragm, stop the machine for maintenance, or recoat. This application provides a diaphragm including a base film, a first adhesive layer, and a second adhesive layer. The base film has a first surface and a second surface disposed opposite to each other. The first adhesive layer includes a first adhesive dot unit, which includes a plurality of first adhesive dots arranged in an array on the first surface. The second adhesive layer includes a second adhesive dot unit, which includes a plurality of second adhesive dots arranged on the second surface, and the spacing between adjacent second adhesive dots is at least partially unequal. By employing an unequal spacing design between adjacent second adhesive dots in the second adhesive dot unit of the second adhesive layer on the second surface, the overlap rate between the first and second adhesive dot units of the separator can be reduced, resulting in a smaller difference in the overlap rate between the first and second adhesive dot units at different locations on the separator. This leads to better consistency in the separator thickness, effectively mitigating the problem of misalignment and abrupt changes in the positive and / or negative tabs during the winding process of a single cell when the separator is applied. Furthermore, the smaller difference in the overlap rate between the first and second adhesive dot units of the separator ensures higher consistency across different locations on the separator, preventing excessive differences in ionic conductivity at different locations due to large fluctuations in the overlap rate. Attached Figure Description

[0021] 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.

[0022] Figure 1 This is a schematic diagram of the structure of an energy storage system according to an embodiment of this application.

[0023] Figure 2 This is a schematic diagram of the structure of an energy storage system according to another embodiment of this application.

[0024] Figure 3 This is a schematic diagram of the structure of an energy storage system according to another embodiment of this application.

[0025] Figure 4 This is a schematic diagram of the structure of an electrical system according to an embodiment of this application.

[0026] Figure 5This is a schematic diagram of the structure of an energy storage device according to an embodiment of this application.

[0027] Figure 6 This is a schematic diagram of the structure of a single battery cell according to an embodiment of this application.

[0028] 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.

[0029] Figure 8 This is a cross-sectional view of the positive electrode sheet according to an embodiment of this application.

[0030] Figure 9 This is a cross-sectional view of the negative electrode sheet according to an embodiment of this application.

[0031] Figure 10 This is a partial perspective view of the diaphragm according to an embodiment of this application.

[0032] Figure 11 This is a schematic diagram of the structure of one surface of a diaphragm according to an embodiment of this application.

[0033] Figure 12 This is a schematic diagram of the structure of another surface of the diaphragm according to an embodiment of this application.

[0034] Figure 13 The diaphragm along the edge of an embodiment of this application Figure 10 A cross-sectional view of BB.

[0035] Figure 14 This is a schematic diagram of the structure of the first adhesive layer according to an embodiment of this application.

[0036] Figure 15 This is a schematic diagram of the structure of the second adhesive layer according to an embodiment of this application.

[0037] Figure 16 This is a cross-sectional view of the diaphragm according to another embodiment of this application.

[0038] Figure 17 This is a cross-sectional view of the diaphragm according to another embodiment of this application.

[0039] Figure 18 This is a cross-sectional view of the diaphragm according to another embodiment of this application.

[0040] Figure 19 This is a schematic flowchart illustrating a diaphragm design method according to an embodiment of this application.

[0041] Figure 20 This is a microscope image of the surface of the negative electrode sheet of the sodium battery core in Example 3 after disassembly.

[0042] Figure 21This is a microscope image of the second adhesive layer side of the separator after the core of the sodium battery in Example 3 has been disassembled.

[0043] Figure 22 This is a scanning electron microscope image of the negative electrode sheet of the sodium battery core of Example 3 after disassembly, showing the location of a second adhesive dot on the surface.

[0044] Figure 23 This is a scanning electron microscope image of the negative electrode sheet of the sodium battery core of Example 3 after disassembly, corresponding to the location of another second adhesive dot.

[0045] Figure 24 This is a scanning electron microscope image of the negative electrode sheet of the sodium battery core of Example 3 after disassembly, showing the location of another second adhesive dot on the surface.

[0046] 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. Electrode, 331-Negative current collector, 332-Negative active layer, 333-Negative tab, 340-Housing shell, 341-Receiving cavity, 350-End cap assembly, 400-Separator, 410-Base film, 411-First surface, 412-Second surface, 413-Substrate layer, 414-Ceramic layer, 420-First adhesive layer, 421-First adhesive dot unit, 4211-First adhesive dot portion, 430-Second adhesive layer, 431-Second adhesive dot unit, 4311-Second adhesive dot portion. Detailed Implementation

[0047] 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.

[0048] 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.

[0049] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] Figure 4 This is a schematic diagram of the structure of an electrical system 100' according to an embodiment of this application.

[0064] Please see Figure 4This 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.

[0065] 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.).

[0066] Optionally, the electrical equipment 110' and the energy storage device 200 can be electrically connected via a high-voltage cable 140.

[0067] 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.

[0068] Optionally, the energy storage device 200 includes one or more individual battery cells 300.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] Optionally, the single cell 300 can be, but is not limited to, at least one of cylindrical, square, prismatic, or other shaped cells.

[0074] 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.

[0075] 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.

[0076] Please see Figure 6 , Figure 6 This is a schematic diagram of the structure of a single cell battery 300 according to an 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.

[0077] 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.

[0078] 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.

[0079] Optionally, the positive electrode 310, the separator 400, and the negative electrode 330 are all at least partially immersed in the electrolyte.

[0080] Figure 8 This is a cross-sectional view of the positive electrode 310 according to an embodiment of this application.

[0081] 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.

[0082] Figure 9 This is a cross-sectional view of the negative electrode 330 according to an embodiment of this application.

[0083] Please see Figure 9 Optionally, 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.

[0084] 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.

[0085] 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.

[0086] Figure 10 This is a partial perspective view of a diaphragm 400 according to an embodiment of this application. Figure 11 This is a schematic diagram of the structure of one surface of a diaphragm 400 according to an embodiment of this application. Figure 12 This is a schematic diagram of the structure of another surface of the diaphragm 400 according to an embodiment of this application. Figure 13 The diaphragm 400 of one embodiment of this application is along Figure 10 A cross-sectional view of BB.

[0087] Please see Figures 10 to 13 This application provides a diaphragm 400, which includes a base film 410, a first adhesive layer 420, and a second adhesive layer 430. The base film 410 has a first surface 411 and a second surface 412 disposed opposite to each other. The first adhesive layer 420 includes a first adhesive dot unit 421, which includes a plurality of first adhesive dot portions 4211 arranged in an array on the first surface 411. The second adhesive layer 430 includes a second adhesive dot unit 431, which includes a plurality of second adhesive dot portions 4311 arranged on the second surface 412. The spacing between two adjacent second adhesive dot portions 4311 is at least partially unequal.

[0088] The term "multiple" refers to two or more. For example, the first adhesive dot unit 421 may include, but is not limited to, 10, 30, 50, 80, 100, 120, 150, 180, 200, etc. Similarly, the second adhesive dot unit 431 may include, but is not limited to, 10, 30, 50, 80, 100, 120, 150, 180, 200, etc.

[0089] It should be noted that the first surface 411 and the second surface 412 are arranged in the thickness direction of the base film 410 or the separator 400. The first adhesive layer 420, the base film 410 and the second adhesive layer 430 are stacked sequentially along the thickness direction of the separator 400.

[0090] "The spacing between two adjacent second adhesive dots 4311 is at least partially unequal" can be understood as meaning that the spacing between two adjacent second adhesive dots 4311 can be completely unequal, or partially equal and partially unequal.

[0091] Figure 14 This is a schematic diagram of the structure of the first adhesive layer 420 according to an embodiment of this application. Figure 15 This is a schematic diagram of the structure of the second adhesive layer 430 according to an embodiment of this application.

[0092] Please see Figure 14 and Figure 15 Optionally, there are multiple first adhesive dot units 421 arranged in an array on the first surface 411, and multiple second adhesive dot units 431 arranged in an array on the second surface 412. One first adhesive dot unit 421 corresponds to one second adhesive dot unit 431, and different first adhesive dot units 421 correspond to different second adhesive dot units 431. Understandably, the second surface 412 of the diaphragm 400 uses the second adhesive dot units 431 as repeating units, and multiple second adhesive dot units 431 are arranged in an array.

[0093] In some embodiments, the first adhesive layer 420 faces the positive electrode 310, and the second adhesive layer 430 faces the negative electrode 330. In other embodiments, the first adhesive layer 420 faces the negative electrode 330, and the second adhesive layer 430 faces the positive electrode 310.

[0094] During the roll coating or coating process of the diaphragm 400 with the first adhesive layer 420 and the second adhesive layer 430, since the diaphragm 400 is rolled or coated in a whole roll (e.g., 4000m in length), the relative positions of the first adhesive dot unit 421 and the second adhesive dot unit 431 of the first adhesive layer 420 are difficult to keep completely fixed at different positions on the diaphragm 400, and will move and change. Once there are process fluctuations or abnormalities in the first adhesive layer 420 and the second adhesive layer 430, it is necessary to cut off this section of the diaphragm 400, stop the machine for maintenance, or recoat. This application provides a diaphragm 400 including a base film 410, a first adhesive layer 420, and a second adhesive layer 430. The base film 410 has a first surface 411 and a second surface 412 disposed opposite to each other. The first adhesive layer 420 includes a first adhesive dot unit 421, which includes a plurality of first adhesive dot portions 4211 arranged in an array on the first surface 411. The second adhesive layer 430 includes a second adhesive dot unit 431, which includes a plurality of second adhesive dot portions 4311 arranged on the second surface 412. The spacing between two adjacent second adhesive dot portions 4311 is at least partially unequal. By employing an unequal spacing design for the distance between adjacent second adhesive dots 4311 in the second adhesive dot unit 431 of the second adhesive layer 430 on the second surface 412, the overlap rate fluctuation between the first adhesive dot unit 421 and the second adhesive dot unit 431 of the separator 400 can be reduced. The difference in the overlap rate between the first adhesive dot unit 421 and the second adhesive dot unit 431 at different positions of the separator 400 is also smaller, resulting in better consistency in the thickness of the separator 400. Consequently, when the separator 400 is applied to a single cell, it can effectively mitigate the problem of misalignment and abrupt changes in the positive electrode tab 313 and / or negative electrode tab 333 during the single cell winding process. Furthermore, the smaller difference in the overlap rate between the first adhesive dot unit 421 and the second adhesive dot unit 431 of the separator 400 ensures higher consistency at different positions of the separator 400, preventing excessive differences in ionic conductivity at different positions of the separator 400 due to large fluctuations in the overlap rate.

[0095] Please see again Figure 10 In some embodiments, the plurality of first adhesive dots 4211 of the first adhesive dot unit 421 are arranged in P rows and Q columns, wherein each row extends along a first direction and each column extends along a second direction, wherein the first direction is perpendicular to the second direction; the plurality of second adhesive dots 4311 of the second adhesive dot unit 431 are arranged in M ​​rows and N columns, wherein each row is parallel to the first direction and each column is parallel to the second direction; the length of each row in the first adhesive dot unit 421 is equal to the length of each row in the second adhesive dot unit 431, and the length of each column in the first adhesive dot unit 421 is equal to the length of each column in the second adhesive dot unit 431.

[0096] Understandably, rows P are arranged sequentially along the second direction, and columns Q are arranged sequentially along the first direction.

[0097] Understandably, the lengths of the first first glue dot 4211 to the Qth first glue dot 4211 in each row are equal to the lengths of the first second glue dot 4311 and the Nth second glue dot 4311 in each row. The lengths of the first first glue dot 4211 to the Pth first glue dot 4211 in each column are equal to the lengths of the first second glue dot 4311 and the Mth second glue dot 4311 in each column.

[0098] Optionally, the first first adhesive dot 4211 in the first row of the first adhesive dot unit 421 coincides with the first second adhesive dot 4311 in the first row of the second adhesive dot unit 431; the Qth first adhesive dot 4211 in the first row of the first adhesive dot unit 421 coincides with the Nth second adhesive dot 4311 in the first row of the second adhesive dot unit 431; the first first adhesive dot 4211 in the Pth row of the first adhesive dot unit 421 coincides with the first second adhesive dot 4311 in the Mth row of the second adhesive dot unit 431; and the Qth first adhesive dot 4211 in the Pth row of the first adhesive dot unit 421 coincides with the Nth second adhesive dot 4311 in the Mth row of the second adhesive dot unit 431. Understandably, the plurality of first adhesive dot portions 4211 of the first adhesive dot unit 421 are arranged in a rectangular array. The plurality of second adhesive dot portions 4311 of the second adhesive dot unit 431 are arranged in a rectangular array with unequal spacing. The first adhesive dots 4211 at the four corners of the rectangular structure of the first adhesive dot unit 421 overlap with the second adhesive dots 4311 at the four corners of the rectangular structure of the second adhesive dot unit 431.

[0099] In this embodiment, the length of each row in the first adhesive dot unit 421 is equal to the length of each row in the second adhesive dot unit 431, and the length of each column in the first adhesive dot unit 421 is equal to the length of each column in the second adhesive dot unit 431. This ensures that the size of the rectangular structure formed by the first adhesive dot units 421 and the rectangular structure formed by the second adhesive dot units 431 are the same. This results in smaller fluctuations in the overlap rate between the first adhesive dot units 421 and the second adhesive dot units 431 at different positions of the separator 400, and a smaller difference in the overlap rate between the first adhesive dot units 421 and the second adhesive dot units 431. Consequently, the thickness of the separator 400 exhibits better consistency. Therefore, when the separator 400 is applied to a single battery cell, it can effectively improve the problem of misalignment and abrupt changes in the positive electrode tab 313 and / or negative electrode tab 333 during the single battery cell winding process.

[0100] Please see again Figure 15In some embodiments, the second adhesive dot unit 431 satisfies at least one of the following conditions: The second adhesive dot unit 431 is centrally symmetrical (e.g., Figure 15 (O) The second adhesive dot unit 431 has a direction parallel to the first direction (e.g., Figure 15 The first axis of symmetry of the double arrow X (e.g.) Figure 15 (E); and The second adhesive dot unit 431 has a direction parallel to the second direction (e.g., Figure 15 The second axis of symmetry of the double arrow Y (as shown in the image) Figure 15 (Middle F).

[0101] Understandably, the second adhesive dot unit 431 has a center of symmetry, and after rotating 180° around the center of symmetry, the second adhesive dot unit 431 coincides with the original second adhesive dot unit 431.

[0102] Understandably, the second adhesive dot unit 431 is symmetrical about the first axis of symmetry. The first axis of symmetry is parallel to the first direction.

[0103] Understandably, the second adhesive dot unit 431 is symmetrical about the second axis of symmetry. The second axis of symmetry is parallel to the second direction.

[0104] In this embodiment, by making the second adhesive dot unit 431 centrally symmetrical, and / or having a first axis of symmetry parallel to the first direction, and / or having a second axis of symmetry parallel to the second direction, multiple first adhesive dot units 421 are arranged in an array on the first surface 411, and multiple second adhesive dot units 431 are arranged in an array on the second surface 412. This results in smaller fluctuations in the overlap rate between the first adhesive dot units 421 and the second adhesive dot units 431 at different positions on the separator 400, and a smaller difference in the overlap rate between the first adhesive dot units 421 and the second adhesive dot units 431. Consequently, the thickness of the separator 400 has better consistency. Therefore, when the separator 400 is applied to a single battery cell, it can effectively improve the problem of misalignment and abrupt changes in the positive electrode tab 313 and / or the negative electrode tab 333 during the single battery cell winding process.

[0105] Please see again Figure 15 In some embodiments, along the first direction, the spacing between two adjacent second adhesive dots 4311 gradually increases and then gradually decreases, or gradually decreases and then gradually increases.

[0106] In some examples, along the first direction, the spacing between two adjacent second adhesive dots 4311 first gradually increases and then gradually decreases. Understandably, along the first direction from both sides towards the middle, the spacing between two adjacent second adhesive dots 4311 gradually increases.

[0107] In other examples, along the first direction, the spacing between two adjacent second adhesive dots 4311 first gradually decreases and then gradually increases. Understandably, along the first direction from both sides towards the middle, the spacing between two adjacent second adhesive dots 4311 gradually decreases.

[0108] In this embodiment, along the first direction, the spacing between two adjacent second adhesive dots 4311 gradually increases and then gradually decreases, or gradually decreases and then gradually increases. This is beneficial because when multiple first adhesive dot units 421 are arrayed on the first surface 411 and multiple second adhesive dot units 431 are arrayed on the second surface 412, the overlap rate of the first adhesive dot units 421 and the second adhesive dot units 431 fluctuates less at different positions of the separator 400, and the difference in the overlap rate of the first adhesive dot units 421 and the second adhesive dot units 431 is smaller. This results in better consistency in the thickness of the separator 400, and when the separator 400 is applied to a single cell, it can effectively improve the problem of misalignment and abrupt changes of the positive tab 313 and / or negative tab 333 during the winding process of the single cell.

[0109] In some embodiments, the first adhesive dot portion 4211 is circular or near-circular, and the first adhesive dot portion 4211 has a first center point (not shown). When the first adhesive dot portion 4211 is circular, the first center point is the center of the circle. When the first adhesive dot portion 4211 is near-circular, the first center point is the center of the smallest circumcircle of the first adhesive dot portion 4211. The second adhesive dot portion 4311 is circular or nearly circular, and the second adhesive dot portion 4311 has a second center point (not shown in the figure). When the second adhesive dot portion 4311 is circular, the second center point is the center of the circle. When the second adhesive dot portion 4311 is nearly circular, the second center point is the center of the smallest circumcircle of the second adhesive dot portion 4311.

[0110] The first adhesive dot portion 4211 and the second adhesive dot portion 4311 are circular or near-circular structures. In this way, the first center point of the first adhesive dot portion 4211 and the second center point of the second adhesive dot portion 4311 can be better positioned and designed, which helps to reduce the fluctuation of the overlap rate between the first adhesive dot unit 421 and the second adhesive dot unit 431.

[0111] Please see again Figure 15 In some embodiments, along the first direction, the distance between the second center points of two adjacent second adhesive dots 4311 increases proportionally and then decreases proportionally, or decreases proportionally and then increases proportionally.

[0112] In some examples, along the first direction, the distance between the second center points of two adjacent second adhesive dots 4311 first increases proportionally and then decreases proportionally. Understandably, along the first direction from both sides towards the middle, the distance between the second center points of two adjacent second adhesive dots 4311 follows a proportionally increasing sequence.

[0113] In other examples, along the first direction, the distance between the second center points of two adjacent second adhesive dots 4311 decreases proportionally first and then increases proportionally. Understandably, along the first direction from both sides towards the center, the distance between the second center points of two adjacent second adhesive dots 4311 follows a proportionally decreasing sequence.

[0114] In this embodiment, by making the distance between the second center points of two adjacent second adhesive dots 4311 in a proportionally increasing or decreasing sequence along the first direction from both sides towards the middle, multiple first adhesive dot units 421 are arranged in an array on the first surface 411, and multiple second adhesive dot units 431 are arranged in an array on the second surface 412. This results in smaller fluctuations in the overlap rate between the first adhesive dot units 421 and the second adhesive dot units 431 at different positions on the separator 400, and a smaller range of overlap rates between them. This leads to better consistency in the thickness of the separator 400, and consequently, when the separator 400 is applied to a single battery cell, it effectively improves the problem of misalignment and abrupt changes in the positive electrode tab 313 and / or negative electrode tab 333 during the single battery cell winding process.

[0115] In some embodiments, along the first direction, the distance between the first center points of two adjacent first adhesive dots 4211 is T1, and the distance between the second center point of the i-th second adhesive dot 4311 and the second center point of the (i+1)-th second adhesive dot 4311 is T(i, i+1). Then, T(i, i+1) = T1 × a1 × b1 （i-1） Where i is the position of the second glue dot 4311 when counting along the first direction from the first or Nth second glue dot 4311 in each row to the second axis of symmetry, a1 is the initial starting coefficient, and b1 is the common ratio (also known as the iteration coefficient) of the geometric sequence formed by the distances between two adjacent second glue dots 4311 along the first direction. When the number of the second adhesive dots 4311 in each row along the first direction is greater than or equal to the number of the first adhesive dots 4211, 0.5≤a1<1, 1<b1≤1.5; When the number of second adhesive dots 4311 in each row along the first direction is less than the number of first adhesive dots 4211, 1 < a1 ≤ 1.5, 0.5 ≤ b1 < 1.

[0116] Specifically, when the number of the second adhesive dots 4311 in each row along the first direction is greater than or equal to the number of the first adhesive dots 4211, a1 can be, but is not limited to, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.97, 0.99, etc.; b1 can be, but is not limited to, 1.01, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, etc.

[0117] Specifically, when the number of second adhesive dots 4311 in each row along the first direction is less than the number of first adhesive dots 4211, a1 can be, but is not limited to, 1.01, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, etc.; b1 can be, but is not limited to, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.97, 0.99, etc.

[0118] Understandably, the distance between the first center points of two adjacent first adhesive dots 4211 along the first direction is equal.

[0119] In this embodiment, the distance T(i, i+1) between the second center point of the i-th second adhesive dot 4311 and the second center point of the (i+1)-th second adhesive dot 4311 is designed to be related to the distance T1 between the first center points of two adjacent first adhesive dots 4211, such that T(i, i+1) satisfies the geometric sequence T1×a1×b1. （i-1） The values ​​of a1 and b1 are designed so that when multiple first adhesive dot units 421 are arrayed on the first surface 411 and multiple second adhesive dot units 431 are arrayed on the second surface 412, the overlap rate of the first adhesive dot units 421 and the second adhesive dot units 431 at different positions of the separator 400 fluctuates less and the difference in the overlap rate of the first adhesive dot units 421 and the second adhesive dot units 431 is smaller. This results in better consistency in the thickness of the separator 400. Consequently, when the separator 400 is applied to a single cell, it can effectively improve the problem of misalignment and abrupt changes in the positive electrode tab 313 and / or negative electrode tab 333 during the winding process of the single cell.

[0120] Please see again Figure 15 In some embodiments, along the second direction, the spacing between two adjacent second adhesive dots 4311 gradually increases and then gradually decreases, or gradually decreases and then gradually increases.

[0121] In some examples, along the second direction, the spacing between two adjacent second adhesive dots 4311 first gradually increases and then gradually decreases. Understandably, along the second direction from both sides towards the middle, the spacing between two adjacent second adhesive dots 4311 gradually increases.

[0122] In other examples, along the second direction, the spacing between two adjacent second adhesive dots 4311 first gradually decreases and then gradually increases. Understandably, along the second direction from both sides towards the middle, the spacing between two adjacent second adhesive dots 4311 gradually decreases.

[0123] In this embodiment, along the second direction, the spacing between two adjacent second adhesive dots 4311 gradually increases and then gradually decreases, or gradually decreases and then gradually increases. This is beneficial because when multiple first adhesive dot units 421 are arrayed on the first surface 411 and multiple second adhesive dot units 431 are arrayed on the second surface 412, the overlap rate of the first adhesive dot units 421 and the second adhesive dot units 431 fluctuates less at different positions of the separator 400, and the difference in the overlap rate of the first adhesive dot units 421 and the second adhesive dot units 431 is smaller. This results in better consistency in the thickness of the separator 400, and when the separator 400 is applied to a single cell, it can effectively improve the problem of misalignment and abrupt changes in the positive tab 313 and / or negative tab 333 during the winding process of the single cell.

[0124] Please see again Figure 15 In some embodiments, along the second direction, the distance between the second center points of two adjacent second adhesive dots 4311 increases proportionally and then decreases proportionally, or decreases proportionally and then increases proportionally.

[0125] In some examples, along the second direction, the distance between the second center points of two adjacent second adhesive dots 4311 first increases proportionally and then decreases proportionally. Understandably, along the second direction from both sides towards the middle, the distance between the second center points of two adjacent second adhesive dots 4311 follows a proportionally increasing sequence.

[0126] In other examples, along the second direction, the distance between the second center points of two adjacent second adhesive dots 4311 decreases proportionally first and then increases proportionally. Understandably, along the second direction from both sides towards the middle, the distance between the second center points of two adjacent second adhesive dots 4311 follows a proportionally decreasing sequence.

[0127] In this embodiment, the distances between the second center points of two adjacent second adhesive dots 4311 are arranged in a proportionally increasing or decreasing sequence along the second direction from both sides towards the middle. This allows multiple first adhesive dot units 421 to be arrayed on the first surface 411 and multiple second adhesive dot units 431 to be arrayed on the second surface 412. At different positions on the separator 400, the overlap rate of the first adhesive dot units 421 and the second adhesive dot units 431 fluctuates less, and the difference in the overlap rate of the first adhesive dot units 421 and the second adhesive dot units 431 is smaller. This results in better consistency in the thickness of the separator 400. Consequently, when the separator 400 is applied to a single cell, it can effectively improve the problem of misalignment and abrupt changes in the positive electrode tab 313 and / or negative electrode tab 333 during the winding process of the single cell.

[0128] Please see again Figure 15 In some embodiments, along the second direction, the distance between the first center points of two adjacent first adhesive dots 4211 is T2, and the distance between the second center point of the j-th second adhesive dot 4311 and the second center point of the (j+1)-th second adhesive dot 4311 is T(j, j+1). Then, T(j, j+1) = T2 × a2 × b2 （j-1） Where, j is the position of the second glue dot 4311 when counting along the second direction from the first or Mth second glue dot 4311 of each column to the first axis of symmetry, a2 is the initial starting coefficient, and b2 is the common ratio (also known as the iteration coefficient) of the geometric sequence formed by the distances between two adjacent second glue dots 4311 along the second direction. When the number of the second adhesive dots 4311 in each column along the second direction is greater than or equal to the number of the first adhesive dots 4211, 0.5≤a2<1, 1<b2≤1.5; When the number of second adhesive dots 4311 in each column along the first direction is less than the number of first adhesive dots 4211, 1 < a2 ≤ 1.5, 0.5 ≤ b2 < 1.

[0129] Understandably, the distance between the first center points of two adjacent first adhesive dots 4211 along the second direction is equal.

[0130] Optionally, T1=T2, that is, the distance between the first center points of two adjacent first adhesive dots 4211 along the first direction is equal to the distance between the first center points of two adjacent first adhesive dots 4211 along the second direction.

[0131] Specifically, when the number of the second adhesive dots 4311 in each row along the second direction is greater than or equal to the number of the first adhesive dots 4211, a2 can be, but is not limited to, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.97, 0.99, etc.; b2 can be, but is not limited to, 1.01, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, etc.

[0132] Specifically, when the number of second adhesive dots 4311 in each row along the second direction is less than the number of first adhesive dots 4211, a2 can be, but is not limited to, 1.01, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, etc.; b2 can be, but is not limited to, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.97, 0.99, etc.

[0133] In this embodiment, the distance T(j, j+1) between the second center point of the j-th second adhesive dot 4311 and the second center point of the (j+1)-th second adhesive dot 4311 is designed to be related to the distance T2 between the first center points of two adjacent first adhesive dots 4211, such that T(j, j+1) satisfies the geometric sequence T2×a2×b2. （j-1） The values ​​of a2 and b2 are designed so that when multiple first adhesive dot units 421 are arrayed on the first surface 411 and multiple second adhesive dot units 431 are arrayed on the second surface 412, the overlap rate of the first adhesive dot units 421 and the second adhesive dot units 431 at different positions of the separator 400 fluctuates less and the difference in the overlap rate of the first adhesive dot units 421 and the second adhesive dot units 431 is smaller. This results in better consistency in the thickness of the separator 400. Consequently, when the separator 400 is applied to a single cell, it can effectively improve the problem of misalignment and abrupt changes in the positive electrode tab 313 and / or negative electrode tab 333 during the winding process of the single cell.

[0134] In some embodiments, the diaphragm 400 satisfies: 5≤M≤12, 5≤N≤12, 5≤P≤12, 5≤Q≤12, where M, N, P, and Q are all integers; M equals P-1, P, or P+1; N equals Q-1, Q, or Q+1.

[0135] Specifically, M can be, but is not limited to, 5, 6, 7, 8, 9, 10, 11, or 12.

[0136] Specifically, N can be, but is not limited to, 5, 6, 7, 8, 9, 10, 11, or 12.

[0137] Specifically, P can be, but is not limited to, 5, 6, 7, 8, 9, 10, 11, or 12.

[0138] Specifically, Q can be, but is not limited to, 5, 6, 7, 8, 9, 10, 11, or 12.

[0139] In this embodiment, the number of first adhesive dots 4211 in the first adhesive dot unit 421 and the number of second adhesive dots 4311 in the second adhesive dot unit 431 are designed. This allows multiple first adhesive dot units 421 to be arrayed on the first surface 411 and multiple second adhesive dot units 431 to be arrayed on the second surface 412. At different positions on the separator 400, the overlap rate of the first adhesive dot units 421 and the second adhesive dot units 431 fluctuates less, and the difference in the overlap rate of the first adhesive dot units 421 and the second adhesive dot units 431 is smaller. This results in better consistency in the thickness of the separator 400. Consequently, when the separator 400 is applied to a single battery cell, it can effectively improve the problem of misalignment and abrupt changes in the positive electrode tab 313 and / or negative electrode tab 333 during the winding process of the single battery cell.

[0140] In some embodiments, the diaphragm 400 satisfies at least one of the following conditions: The equivalent circle diameter of the first adhesive dot portion 4211 ranges from 250 μm to 500 μm; The equivalent circle diameter of the second adhesive dot portion 4311 ranges from 250 μm to 500 μm; Along the first direction, the distance between the first center points of two adjacent first adhesive dots 4211 ranges from 250 μm to 3000 μm; Along the second direction, the distance between the first center points of two adjacent first adhesive dots 4211 ranges from 250 μm to 3000 μm; Along the first direction, the distance between the second center points of two adjacent second adhesive dots 4311 ranges from 250 μm to 3000 μm; and Along the second direction, the distance between the second center points of two adjacent second adhesive dots 4311 ranges from 250 μm to 3000 μm.

[0141] "Equivalent circle diameter" refers to the diameter of a circle when the area of ​​an irregularly shaped two-dimensional figure is equivalent to the area of ​​a circle of the same area.

[0142] It should be noted that the equivalent circle diameter of the first glue dot portion 4211 and the equivalent circle diameter of the second glue dot portion 4311 can be the same or different.

[0143] Specifically, the equivalent circle diameter of the first adhesive dot portion 4211 can be, but is not limited to, 250μm, 300μm, 350μm, 400μm, 450μm, 500μm, etc. If the equivalent circle diameter of the first adhesive dot portion 4211 is too small, the coverage of the first adhesive layer 420 will be too low and the adhesion of the first adhesive layer 420 will be too low when the center point distance between adjacent first adhesive dots 4211 remains unchanged. This reduces the adhesion between the separator 400 and the positive electrode 310 or negative electrode 330, making the cross-section of the positive electrode 310 or negative electrode 330 prone to wrinkling, increasing the risk of purple spots and lithium plating in the single cell. If the equivalent circle diameter of the first adhesive dot portion 4211 is too large, the coverage of the first adhesive layer 420 will be too high when the center point distance between adjacent first adhesive dots 4211 remains unchanged. This can easily clog the pores of the separator 400 and reduce the ionic conductivity of the separator 400.

[0144] Specifically, the equivalent circle diameter of the second adhesive dot portion 4311 can be, but is not limited to, 250μm, 300μm, 350μm, 400μm, 450μm, 500μm, etc. If the equivalent circle diameter of the second adhesive dot portion 4311 is too small, the coverage of the second adhesive layer 430 will be too low and the adhesion of the second adhesive layer 430 will be too low when the center point distance between adjacent second adhesive dots 4311 remains unchanged. This reduces the adhesion between the separator 400 and the positive electrode 310 or negative electrode 330, making the cross-section of the positive electrode 310 or negative electrode 330 prone to wrinkling, increasing the risk of purple spots and lithium plating in the single cell. If the equivalent circle diameter of the second adhesive dot portion 4311 is too large, the coverage of the second adhesive layer 430 will be too high when the center point distance between adjacent second adhesive dots 4311 remains unchanged. This can easily clog the pores of the separator 400 and reduce the ionic conductivity of the separator 400.

[0145] Specifically, along the first direction, the distance between the first center points of two adjacent first adhesive dots 4211 can be, but is not limited to, 250μm, 300μm, 400μm, 500μm, 600μm, 800μm, 1000μm, 1300μm, 1500μm, 1800μm, 2000μm, 2300μm, 2500μm, 2800μm, 3000μm, etc. If the distance between the first center points of two adjacent first adhesive dots 4211 is too small along the first direction, the coverage of the first adhesive layer 420 will be too high, which will easily block the pores of the separator 400 and reduce the ionic conductivity of the separator 400. If the distance between the first center points of two adjacent first adhesive dots 4211 is too large along the first direction, the coverage of the first adhesive layer 420 will be too low, and the adhesion of the first adhesive layer 420 will be too low, which will reduce the adhesion between the separator 400 and the positive electrode 310 or the negative electrode 330, making the cross-section of the positive electrode 310 or the negative electrode 330 prone to wrinkling, increasing the risk of purple spots and lithium plating in the single cell.

[0146] Specifically, along the second direction, the distance between the first center points of two adjacent first adhesive dots 4211 can be, but is not limited to, 250μm, 300μm, 400μm, 500μm, 600μm, 800μm, 1000μm, 1300μm, 1500μm, 1800μm, 2000μm, 2300μm, 2500μm, 2800μm, 3000μm, etc. If the distance between the first center points of two adjacent first adhesive dots 4211 is too small along the second direction, the coverage of the first adhesive layer 420 will be too high, which will easily block the pores of the separator 400 and reduce the ionic conductivity of the separator 400. If the distance between the first center points of two adjacent first adhesive dots 4211 is too large along the second direction, the coverage of the first adhesive layer 420 will be too low, and the adhesion of the first adhesive layer 420 will be too low, which will reduce the adhesion between the separator 400 and the positive electrode 310 or the negative electrode 330, making the cross-section of the positive electrode 310 or the negative electrode 330 prone to wrinkling, increasing the risk of purple spots and lithium plating in the single cell.

[0147] Specifically, along the first direction, the distance between the second center points of two adjacent second adhesive dots 4311 can be, but is not limited to, 250μm, 300μm, 400μm, 500μm, 600μm, 800μm, 1000μm, 1300μm, 1500μm, 1800μm, 2000μm, 2300μm, 2500μm, 2800μm, 3000μm, etc. If the distance between the second center points of two adjacent second adhesive dots 4311 is too small along the first direction, the coverage of the second adhesive layer 430 will be too high, which will easily block the pores of the separator 400 and reduce the ionic conductivity of the separator 400. If the distance between the second center points of two adjacent second adhesive dots 4311 is too large along the first direction, the coverage of the second adhesive layer 430 will be too low, and the adhesion of the second adhesive layer 430 will be too low, which will reduce the adhesion between the separator 400 and the positive electrode 310 or the negative electrode 330, making the cross-section of the positive electrode 310 or the negative electrode 330 prone to wrinkling, increasing the risk of purple spots and lithium plating in the single cell.

[0148] Specifically, along the second direction, the distance between the second center points of two adjacent second adhesive dots 4311 can be, but is not limited to, 250μm, 300μm, 400μm, 500μm, 600μm, 800μm, 1000μm, 1300μm, 1500μm, 1800μm, 2000μm, 2300μm, 2500μm, 2800μm, 3000μm, etc. If the distance between the second center points of two adjacent second adhesive dots 4311 is too small along the second direction, the coverage of the second adhesive layer 430 will be too high, which will easily block the pores of the separator 400 and reduce the ionic conductivity of the separator 400. If the distance between the second center points of two adjacent second adhesive dots 4311 is too large along the second direction, the coverage of the second adhesive layer 430 will be too low, and the adhesion of the second adhesive layer 430 will be too low, which will reduce the adhesion between the separator 400 and the positive electrode 310 or the negative electrode 330, making the cross-section of the positive electrode 310 or the negative electrode 330 prone to wrinkling, increasing the risk of purple spots and lithium plating in the single cell.

[0149] In some embodiments, there are multiple first adhesive dot units 421, and multiple first adhesive dot units 421 are arranged in an array on the first surface 411. There are multiple second adhesive dot units 431, and multiple second adhesive dot units 431 are arranged in an array on the second surface 412. One first adhesive dot unit 421 corresponds to one second adhesive dot unit 431, and different first adhesive dot units 421 correspond to different second adhesive dot units 431. The diaphragm 400 satisfies at least one of the following conditions: The average overlap rate X between the first adhesive dot unit 421 and the second adhesive dot unit 431 ranges from 7% to X ≤ 26%. The range R of the overlap rate between the first adhesive dot unit 421 and the second adhesive dot unit 431 is 0% ≤ R ≤ 10%; and The standard deviation σ of the overlap rate between the first adhesive dot unit 421 and the second adhesive dot unit 431 is in the range of 0%≤σ≤3%.

[0150] It should be noted that since there are multiple first adhesive dot units 421 and multiple second adhesive dot units 431, the overlap rate between each first adhesive dot unit 421 and each second adhesive dot unit 431 will vary during the fabrication of the diaphragm 400 and will not be exactly the same. Therefore, the average overlap rate between the first adhesive dot unit 421 and the second adhesive dot unit 431 is the average of the overlap rates between multiple first adhesive dot units 421 and multiple second adhesive dot units 431.

[0151] Specifically, the average overlap rate X of the first adhesive dot unit 421 and the second adhesive dot unit 431 can be, but is not limited to, 7%, 8%, 9%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, etc. If the average overlap rate X of the first adhesive dot unit 421 and the second adhesive dot unit 431 is lower, it is less likely to clog the pores of the separator 400, which is beneficial to improving the ionic conductivity of the separator 400. However, this increases the difficulty of preparing the separator 400 and is difficult to achieve in terms of process. If the average overlap rate X of the first adhesive dot unit 421 and the second adhesive dot unit 431 is too large, the pores of the separator 400 are more easily clogged in the overlapping portion of the first adhesive dot unit 421 and the second adhesive dot unit 431, reducing the ionic conductivity of the separator 400.

[0152] Specifically, the range R of the overlap rate between the first adhesive dot unit 421 and the second adhesive dot unit 431 can be, but is not limited to, 0%, 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0%, etc. If the range R of the overlap rate between the first adhesive dot unit 421 and the second adhesive dot unit 431 is too large, the difference in ionic conductivity at different positions of the separator 400 will be too large, reducing the consistency of the separator 400.

[0153] Specifically, the standard deviation σ of the overlap rate between the first adhesive dot unit 421 and the second adhesive dot unit 431 can be, but is not limited to, 0%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, etc. If the standard deviation σ of the overlap rate between the first adhesive dot unit 421 and the second adhesive dot unit 431 is too large, the difference in ionic conductivity at different positions of the diaphragm 400 will be too large, reducing the consistency of the diaphragm 400.

[0154] Optionally, the first adhesive layer 420 is obtained by applying a first adhesive using a dot coating method or a dot coating roller. The second adhesive layer 430 is obtained by applying a second adhesive using a dot coating method or a dot coating roller.

[0155] Optionally, the viscosity of the first adhesive ranges from 150 mPa•s to 600 mPa•s. Specifically, the viscosity of the first 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 first adhesive is too low, the water content in the first adhesive will be too high, and the solid content of the first 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 first adhesive is too high, it is easy to form strings during dot coating, resulting in an irregular shape of the first adhesive layer 420, which is prone to deformation and affects the adhesion of the first adhesive layer 420.

[0156] Optionally, the surface tension γ1 of the first adhesive is in the range of 80mN / m ≤ γ1 ≤ 150mN / m. Specifically, the surface tension γ1 of the first adhesive can be, but is not limited to, 80mN / m, 90mN / m, 100mN / m, 110mN / m, 120mN / m, 130mN / m, 140mN / m, 150mN / m, etc. If the surface tension γ1 of the first 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 γ1 of the first adhesive is too small, due to the coffee ring effect, it will be difficult to form a ring-shaped crater morphology, reducing the adhesion of the first adhesive layer 420.

[0157] Optionally, the first 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 first adhesive is P1, and the range of P1 is 4μm ≤ P1 ≤ 8μm. Specifically, the D50 particle size of the first binder particles in the first 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 first 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 first adhesive dot 4211 is too low, the compression ratio is too small, and the adhesive force of the first adhesive dot 4211 is reduced. If the D50 particle size of the first adhesive particles in the first adhesive is too large, the height of the first adhesive dot 4211 formed will be too high, the compression ratio will be too large, and the thickness uniformity will be poor. In addition, the adhesion of the first adhesive dot 4211 to the base film 410 will be reduced, making the first adhesive dot 4211 easy to fall off or shed powder.

[0158] "D50" refers to the particle size value corresponding to a sample when the cumulative volume distribution reaches 50%.

[0159] It should be noted that the D50 particle size of this application is determined by referring to the standard GB / T 19077-2016 Particle Size Distribution by Laser Diffraction Method to test the laser particle size of the first adhesive particles in the first adhesive or the second adhesive particles in the second adhesive. A Better size laser particle size analyzer system (model: Better size 2600) was used, and the average value of D50 was taken from three tests.

[0160] Optionally, the first binder particles may be, but are not limited to, at least one of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF), polymethyl methacrylate (PMMA), polystyrene (PS), etc.

[0161] Optionally, the areal density of the first adhesive layer 420 is 0.3 g / m³. 2 Up to 0.8g / m 2 Specifically, the areal density of the first adhesive layer 420 can be, but is not limited to, 0.3 g / m³. 2 0.4g / m 2 0.5g / m 2 0.6g / m 2 0.7g / m 2 0.8g / m 2If the areal density of the first adhesive layer 420 is too low, the adhesion will be too weak, and wrinkles will easily occur between the first adhesive layer 420 and the negative electrode 330 or the first adhesive layer 420 and the positive electrode 310 during the charging and discharging process of the single cell 300. If the areal density of the first 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.

[0162] 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 Using a grammage sampler, five pieces each of base film 410 and separator 400 were cut and weighed to obtain their mass. The areal density of each was obtained by dividing the mass by the sampling area. The difference between the two is the areal density of the adhesive coating amount. The average value was taken after five tests.

[0163] Optionally, the coverage S1 of the first adhesive layer 420 on the first surface 411 is in the range of 10% ≤ S1 ≤ 35%. Specifically, the coverage S1 of the first 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.

[0164] In this embodiment, if the coverage S1 of the first adhesive layer 420 on the first surface 411 is too small, the adhesive force of the first 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. 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 between the separator 400 and the negative electrode 330 prone to wrinkling. If the coverage S1 of the first adhesive layer 420 on the first surface 411 is too large, it will easily block 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, material shedding, etc. during cycling.

[0165] In some embodiments, the shape of the orthographic projection of the first adhesive dot portion 4211 onto the first surface 411 is circular or near-circular, and the circularity K1 of the orthographic projection of the first adhesive dot portion 4211 onto the first surface 411 is in the range of 0.85≤K1≤1.

[0166] Specifically, the circularity K1 of the orthographic projection of the first adhesive dot 4211 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.

[0167] In this embodiment, with the material and coverage of the first adhesive dot 4211 remaining unchanged, the higher the circularity K1 of the orthographic projection of the first adhesive dot 4211 onto the first surface 411, the better the adhesion of the first adhesive dot 4211. If the circularity K1 of the orthographic projection of the first adhesive dot 4211 onto the first surface 411 is too small, the adhesion of the first adhesive dot 4211 is too low, and the coverage of the first adhesive dot 4211 needs to be increased to meet the adhesion requirements of the single cell 300 to the first adhesive dot 4211. 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, material shedding, etc. during cycling.

[0168] In some embodiments, the separator 400 is stacked with the positive electrode 310, with the first adhesive layer 420 facing the positive electrode 310, and pressed at room temperature for 40 seconds (s). The average peel strength Q1 between the first adhesive layer 420 and the positive electrode 310 ranges from 1 N / m ≤ Q1 ≤ 8 N / m. Specifically, the average peel strength Q1 between the first 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 first 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 first 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.

[0169] Peel strength test: The peel strength of the separator 400 and positive electrode 310 with a first adhesive layer 420 and a second adhesive layer 430 was tested according to the standard GB / T 2792-2014 "Test Method for Peel Strength of Adhesive Tapes". After pressing, the sample size was cut to 20mm × 100mm and fixed in the middle of the clamp of the tensile testing machine. Then, the tensile testing machine peeled the separator 400 and positive electrode 310 along a 180° direction at a speed of 50mm / min, with a test distance of 80mm. Five samples were tested, and the average value was taken. The adhesive force was then used as the average peel strength. The pressing method for the separator 400 and positive electrode 310 was as follows: 100mm × 100mm positive electrode 310 and separator 400 were cut, naturally stacked, and placed in a flatbed press for pressing. The room temperature pressing temperature was 25℃, the holding time was 40s, and the unit area pressure was 4.8MPa.

[0170] Optionally, the viscosity of the second adhesive ranges from 150 mPa•s to 600 mPa•s. Specifically, the viscosity of the second 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 second adhesive is too low, the water content in the second adhesive will be too high, and the solid content of the second 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 second adhesive is too high, it is easy to form strings during dot coating, resulting in an irregular shape of the second adhesive layer 430, which is prone to deformation and affects the adhesion of the second adhesive layer 430.

[0171] Optionally, the surface tension γ2 of the second adhesive is in the range of 80 mN / m ≤ γ2 ≤ 150 mN / m. Specifically, the surface tension γ2 of the second 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 γ2 of the second 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 γ2 of the second adhesive is too small, due to the coffee ring effect, it will be difficult to form a ring-shaped crater morphology, reducing the adhesion of the second adhesive layer 430.

[0172] Optionally, the second 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 second adhesive is P2, and the range of P2 is 4μm ≤ P2 ≤ 8μm. Specifically, the D50 particle size of the second binder particles in the second 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 second binder particles in the second adhesive is too small, the second 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 second adhesive dot portion 4311 is too low, the compression ratio is too small, and the adhesive force of the second adhesive dot portion 4311 is reduced. If the D50 particle size of the second adhesive particles in the second adhesive is too large, the height of the formed second adhesive dot 4311 will be too high, the compression ratio will be too large, and the thickness uniformity will be poor. In addition, the adhesion of the second adhesive dot 4311 to the base film 410 will be reduced, making the second adhesive dot 4311 easy to fall off or shed powder.

[0173] Optionally, the second binder particles may be, but are not limited to, at least one of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF), polymethyl methacrylate (PMMA), polystyrene (PS), etc.

[0174] Optionally, the areal density of the second adhesive layer 430 is 0.3 g / m³. 2 Up to 0.8g / m 2 Specifically, the areal density of the second adhesive layer 430 can be, but is not limited to, 0.3 g / m³. 2 0.4g / m 2 0.5g / m 2 0.6g / m 2 0.7g / m 2 0.8g / m 2 If the areal density of the second adhesive layer 430 is too low, the adhesion will be too weak, and wrinkles will easily occur between the second adhesive layer 430 and the negative electrode 330 or the second 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 second 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.

[0175] Optionally, the coverage rate S2 of the second adhesive layer 430 on the second surface 412 is in the range of 10% ≤ S2 ≤ 35%. Specifically, the coverage rate S2 of the second adhesive layer 430 on the second surface 412 can be, but is not limited to, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 35%, etc.

[0176] In this embodiment, if the coverage S2 of the second adhesive layer 430 on the second surface 412 is too small, the adhesive force of the second adhesive layer 430 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. 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 between the separator 400 and the negative electrode 330 prone to wrinkling. If the coverage S2 of the second adhesive layer 430 on the second surface 412 is too large, it will easily block 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, material shedding, etc. during cycling.

[0177] In some embodiments, the shape of the orthographic projection of the second adhesive dot portion 4311 onto the second surface 412 is circular or near-circular, and the circularity K2 of the orthographic projection of the second adhesive dot portion 4311 onto the second surface 412 is in the range of 0.85≤K2≤1.

[0178] Specifically, the circularity K2 of the orthographic projection of the second adhesive dot 4311 onto the second surface 412 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.

[0179] In this embodiment, with the material and coverage of the second adhesive dot portion 4311 remaining unchanged, the higher the circularity K2 of the orthogonal projection of the second adhesive dot portion 4311 onto the second surface 412, the better the adhesion of the second adhesive dot portion 4311. If the circularity K2 of the orthogonal projection of the second adhesive dot portion 4311 onto the second surface 412 is too small, the adhesion of the second adhesive dot portion 4311 is too low, and the coverage of the second adhesive dot portion 4311 needs to be increased to meet the adhesion requirements of the single cell 300 to the second adhesive dot portion 4311. 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, material shedding, etc. during cycling.

[0180] In some embodiments, the separator 400 is stacked with the negative electrode 330, with the second adhesive layer 430 facing the negative electrode 330, and pressed at room temperature for 40 seconds (s). The average peel strength Q1 between the second adhesive layer 430 and the negative electrode 330 ranges from 1 N / m to 8 N / m. Specifically, the average peel strength Q1 between the second 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 Q1 between the second 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 negative electrode 330 during cycling. If the average peel strength Q1 between the second 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.

[0181] Figure 16 This is a cross-sectional view of a diaphragm 400 according to another embodiment of this application. Figure 17 This is a cross-sectional view of a diaphragm 400 according to another embodiment of this application. Figure 18 This is a cross-sectional view of a diaphragm 400 according to another embodiment of this application.

[0182] Please see Figures 16 to 18 In some embodiments, the base film 410 includes a substrate layer 413 and a ceramic layer 414, the ceramic layer 414 being disposed on the surface of the substrate layer 413 facing the positive electrode 310. In other embodiments, the ceramic layer 414 is disposed on the surface of the substrate layer 413 facing the negative electrode 330. In still other embodiments, the ceramic layer 414 is disposed on both the surface of the substrate layer 413 facing the positive electrode 310 and the surface of the substrate layer 413 facing the negative electrode 330.

[0183] 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).

[0184] Figure 19 This is a schematic flowchart illustrating the design method of a diaphragm 400 according to an embodiment of this application.

[0185] Please see Figure 19 This application also provides a design method for a diaphragm 400, the design method comprising: S201, a base film 410 is provided, the base film 410 having a first surface 411 and a second surface 412 disposed opposite to each other; For a detailed description of other aspects of the base film 410, please refer to the description in the corresponding section of the above embodiments.

[0186] S202, a first adhesive layer 420 is designed on the first surface 411 of the base film 410. The first adhesive layer 420 includes a first adhesive dot unit 421. The first adhesive dot unit 421 includes a plurality of first adhesive dot portions 4211 arranged in an array. The plurality of first adhesive dot portions 4211 are arranged in an array of P rows and Q columns. Each row extends along a first direction and each column extends along a second direction. The first direction is perpendicular to the second direction. The first adhesive dot portion 4211 has a first center point. Along the first direction, the distance between the first center points of two adjacent first adhesive dot portions 4211 is T1. For further detailed descriptions of the first adhesive layer 420, the first adhesive dot unit 421, and the first adhesive dot portion 4211, please refer to the descriptions of the corresponding parts of the above embodiments.

[0187] S203, a second adhesive layer 430 is designed on the second surface 412 of the base film 410. The design of the second adhesive layer 430 includes designing second adhesive dot units 431, such that each second adhesive dot unit 431 includes a plurality of second adhesive dot portions 4311. These plurality of second adhesive dot portions 4311 are arranged in M ​​rows and N columns, wherein each row is parallel to the first direction and each column is parallel to the second direction. Each second adhesive dot portion 4311 has a second center point. The length of each row in the first adhesive dot unit 421 is equal to the length of each row in the second adhesive dot unit 431. In the first adhesive dot unit 421, each... The length of the column is equal to the length of each column in the second glue dot unit 431; the first glue dot portion 4211 in the P-th row and Q-th column of the first glue dot unit 421 coincides with the second glue dot portion 4311 in the M-th row and N-th column of the second glue dot unit 431; the second glue dot unit 431 has a first axis of symmetry parallel to the first direction and a second axis of symmetry parallel to the second direction; along the first direction, the distance between the second center point of the i-th second glue dot portion 4311 and the second center point of the (i+1)-th second glue dot portion 4311 is T(i, i+1), then T(i, i+1) = T1 × a1 × b1 （i-1） Where i is the position of the second adhesive dot 4311 when counting along the first direction from the first or Nth second adhesive dot 4311 in each row to the second axis of symmetry, a1 is the initial starting coefficient, and b1 is the common ratio of the geometric sequence formed by the distances between two adjacent second adhesive dots 4311 along the first direction; wherein the first direction is perpendicular to the second direction. Optionally, the first first adhesive dot 4211 in the first row of the first adhesive dot unit 421 coincides with the first second adhesive dot 4311 in the first row of the second adhesive dot unit 431; the Qth first adhesive dot 4211 in the first row of the first adhesive dot unit 421 coincides with the Nth second adhesive dot 4311 in the first row of the second adhesive dot unit 431; the first first adhesive dot 4211 in the Pth row of the first adhesive dot unit 421 coincides with the first second adhesive dot 4311 in the Mth row of the second adhesive dot unit 431.

[0188] For further detailed descriptions of the second adhesive layer 430, the second adhesive dot unit 431, and the second adhesive dot portion 4311, please refer to the descriptions of the corresponding parts of the above embodiments.

[0189] S204, set the values ​​of a1 and b1, translate the second adhesive layer 430 along at least four directions, calculate the average overlap rate of the plurality of first adhesive dots 4211 of the first adhesive dot unit 421 and the plurality of second adhesive dots 4311 of the second adhesive dot unit 431 in at least four directions after the second adhesive layer 430 is translated in each direction, and calculate the range of the overlap rate based on the average overlap rate in at least four directions; adjust the values ​​of a1 and b1 multiple times, and calculate the range of the overlap rate for different values ​​of a1 and b1; wherein, the at least four directions are at least four different directions on the extension plane of the base film 410; and Optionally, the at least four directions can be, but are not limited to, four, five, six, seven, eight, ten, twelve, sixteen, etc.

[0190] For example, at least four directions are eight directions. In the initial position, the first first adhesive dot 4211 in the first row of the first adhesive dot unit 421 coincides with the first second adhesive dot 4311 in the first row of the second adhesive dot unit 431; the Qth first adhesive dot 4211 in the first row of the first adhesive dot unit 421 coincides with the Nth second adhesive dot 4311 in the first row of the second adhesive dot unit 431; the first first adhesive dot 4211 in the Pth row of the first adhesive dot unit 421 coincides with the first second adhesive dot 4311 in the Mth row of the second adhesive dot unit 431. The components are translated along the positive direction of the first direction, the negative direction of the first direction, the positive direction of the second direction, the negative direction of the second direction, the angle bisector of the positive and positive directions of the first and second directions, the angle bisector of the positive and negative directions of the first and second directions, and the angle bisector of the negative and positive directions of the first and second directions, respectively. The average overlap rate of the first adhesive dot unit 421 and the second adhesive dot unit 431 after each translation is calculated, and the range of the overlap rate is calculated. The values ​​of a1 and b1 are adjusted multiple times, and the range of the overlap rate for different values ​​of a1 and b1 is calculated.

[0191] S205, select the values ​​of a1 and b1 when the difference in overlap rate is the minimum value, so as to determine the arrangement of the plurality of second adhesive dots 4311 of the second adhesive dot unit 431 along the first direction.

[0192] It should be noted that the settings of a1 and b1, as well as the calculation of overlap rate and overlap rate range, can be adjusted and calculated automatically by computer software through iterative calculations.

[0193] The design method of the diaphragm 400 in this application involves arranging a plurality of first adhesive dots 4211 of the first adhesive dot unit 421 of the first adhesive layer 420 in an array, and arranging a plurality of second adhesive dots 4311 of the second adhesive dot unit 431 of the second adhesive layer 430 at unequal intervals. Furthermore, along the first direction, from both ends towards the middle, the distance between the second center points of two adjacent second adhesive dots 4311 forms a geometric sequence. The method adjusts a1 to adjust the first term T1×a1 of the geometric sequence (i.e., i=1, the distance between the second center points of the first and second second adhesive dots 4311 in each row of the first direction, or the distance between the second center points of the first and second second adhesive dots 4311 in each row of the first direction), and adjusts the value of the common ratio b1 of the geometric sequence, thereby making the diaphragm 400... When the relative positions of the first adhesive dot unit 421 and the second adhesive dot unit 431 at different positions of the separator 400 move, the worst overlap of the first adhesive dot unit 421 and the second adhesive dot unit 431 is minimized. Therefore, the values ​​of a1 and b1 when the minimum difference is used are used to determine the arrangement of the plurality of second adhesive dot portions 4311 of the second adhesive dot unit 431 along the first direction. This makes the fluctuation of the overlap rate of the first adhesive dot unit 421 and the second adhesive dot unit 431 at different positions of the separator 400 smaller, and the difference in the overlap rate of the first adhesive dot unit 421 and the second adhesive dot unit 431 smaller. This makes the thickness of the separator 400 more consistent. As a result, when the separator 400 is applied to a single cell, it can effectively improve the problem of misalignment and abrupt change of the positive tab 313 and / or negative tab 333 during the winding process of the single cell.

[0194] In some embodiments, the distance between the first center points of two adjacent first adhesive dots 4211 along the second direction is T2. The design of the second adhesive layer 430 on the second surface 412 of the base film 410 further includes: along the second direction, the distance between the second center point of the j-th second adhesive dot 4311 and the second center point of the (j+1)-th second adhesive dot 4311 is T(j, j+1), then T(j, j+1) = T2 × a2 × b2. （j-1） , where j is the position of the second glue dot 4311 when counting along the second direction from the first or Mth second glue dot 4311 of each column to the first axis of symmetry, a2 is the initial starting coefficient, and b2 is the common ratio of the geometric sequence formed by the distances between two adjacent second glue dots 4311 along the second direction. The design method further includes: S204', set the values ​​of a2 and b2, translate the second adhesive layer 430 along at least four directions, calculate the average overlap rate of the plurality of first adhesive dots 4211 of the first adhesive dot unit 421 and the plurality of second adhesive dots 4311 of the second adhesive dot unit 431 in at least four directions after the second adhesive layer 430 is translated in each direction, calculate the range of the overlap rate based on the average overlap rate in at least four directions; adjust the values ​​of a2 and b2 multiple times, and calculate the range of the overlap rate for different values ​​of a2 and b2; and S205', select the values ​​of a2 and b2 when the difference in overlap rate is the minimum value, so as to determine the arrangement of the plurality of second adhesive dots 4311 of the second adhesive dot unit 431 along the second direction.

[0195] It should be noted that the settings of a2 and b2, as well as the calculation of overlap rate and overlap rate range, can be adjusted and calculated automatically by computer software through iterative calculations.

[0196] It should be noted that S204' and S204 can be performed simultaneously, and S205' and S205 can be performed simultaneously.

[0197] In some embodiments, the values ​​of T(i, i+1) and T(j, j+1) are rounded to make them multiples of 10 μm. Since the preparation accuracy (such as the processing accuracy of the dot coating roller) of the first adhesive dot portion 4211 and the second adhesive dot portion 4311 is approximately 10 μm during preparation (e.g., roll coating using a dot coating roller), the distance T(i, i+1) between the second center points of two adjacent second adhesive dot portions 4311 in the first direction and the distance T(j, j+1) between the second center points of two adjacent second adhesive dot portions 4311 in the second direction are rounded to make their values ​​multiples of 10 μm. This simplifies the design of the second adhesive dot portion 4311.

[0198] The diaphragm 400 and the single cell 300 of this application will be further described below through specific embodiments.

[0199] Examples 1 to 48, Comparative Examples 1 to 4 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 first glue / second glue: Weigh polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP powder), polyacrylic acid (PAA), acrylic resin emulsion and water-soluble additive 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 1000 rpm / 15 min, then add glycerol, stir evenly at 1000 rpm / 15 min, control the temperature at about 40℃, control the pH at about 7; then add PVDF-HFP powder, stir evenly at 2500 rpm / 90 min, then add acrylic resin emulsion, stir evenly at 1000 rpm / 15 min. 1) Mix evenly, then slowly stir at 500 rpm for 15 minutes to eliminate air bubbles, to obtain the first adhesive / second adhesive; 2) Formation of the first adhesive layer 420 and the second adhesive layer 430: Provide a base film 410, which includes a substrate layer 413 and a ceramic layer 414 stacked together. The substrate layer 413 is a 9 μm thick polyethylene (PE) porous film, and the ceramic layer 414 is 2 μm thick. Apply the first adhesive to the surface of the base film 410 using a contact roller coating device, and dry at 65°C to obtain the first adhesive layer 420; apply the second adhesive to the other surface of the base film 410, and dry at 65°C to obtain the second adhesive layer 430, thereby obtaining the diaphragm 400; the single-sided surface density of the first adhesive layer 420 and the second adhesive layer 430 is 0.5 g / m³. 2 In each embodiment, the diameter of the first adhesive dot 4211 is 400 μm, the distance between two adjacent first adhesive dots 4211 is 680 μm (i.e., T1=T2=680 μm), and the diameter of the second adhesive dot 4311 in each embodiment is 400 μm.

[0200] (2) Preparation of positive electrode 310: The positive electrode active material is polyanionic sulfate Na 2.4 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.

[0201] (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.

[0202] (4) 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.

[0203] (5) 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 between the positive electrode 310 and the negative electrode 330 to play a role in isolation (and the first adhesive layer 420 faces the positive electrode 310 and the second adhesive layer 430 faces the negative electrode 330) to obtain the electrode assembly. The electrode assembly is wound to obtain the 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 and formation processes, the sodium battery is obtained.

[0204] 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.

[0205] The following performance tests were conducted on the separator 400 and sodium battery of each embodiment and comparative example: (1) Single-sided areal density test of the first adhesive layer 420 / second adhesive layer 430: The test was conducted in accordance with the standard GB / T 20220-2006 Determination of average thickness, average thickness and unit mass area of ​​plastic films and sheets by weighing method, using a 100cm... 2Five pieces of base film 410 and five pieces of separator 400 with first adhesive layer 420 or second adhesive layer 430 are cut using a gram sampler. The mass of each is weighed and then divided by the sampling area to obtain the areal density of each. The difference between the two is the areal density of the first adhesive layer 420 or the second adhesive layer 430. The average value is taken after five tests.

[0206] (2) Coverage S1 test of the first adhesive layer 420 / second adhesive layer 430: The diameter and area of ​​the first adhesive dot 4211 / second adhesive dot 4311 on the surface of the diaphragm 400 are identified and calculated using a super depth-of-field three-dimensional stereo microscope (model: Keyence VHX-7000). The magnification is 50X. Within the target area (e.g., a rectangular area of ​​17mm×13mm), 10 first adhesive dots 4211 / second adhesive dots 4311 are selected, their diameters are measured and averaged, and the average area of ​​a single first adhesive dot 4211 / second adhesive dot 4311 is calculated. Then, the average area is divided by the area of ​​the square formed by connecting the centers of four first adhesive dots 4211 / second adhesive dots 4311, which is the coverage.

[0207] (3) Air permeability test of separator 400: Referring to the air permeability test method in 6.5.4 of the standard "GB / T 36363-2018 Polyolefin separator 400 for lithium-ion batteries", an air permeability tester (model: Wang Yan EG01-55-1MR) was used to test the time required for 100 mL of air to pass through 1 square inch of separator 400 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 separator 400. The increase in air permeability of separator 400 refers to the increase or percentage of its air permeability value after treatment (such as coating the first adhesive layer 420 / second adhesive layer 430, etc.) relative to before treatment (base membrane 410).

[0208] (4) Ionic conductivity test of membrane 400: The ionic conductivity of membrane 400 was tested and calculated in accordance with the ionic conductivity test method in 6.6.2 of the standard GB / T 36363 2018 Polyolefin Separator for Lithium-ion Batteries.

[0209] (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.

[0210] The calculation method for the tab misalignment defect rate is as follows: 300 cores are wound in each group, and the number of misaligned cores is calculated separately. The defect rate for 1 misalignment is 1 / 300 × 100% = 0.33%, and the defect rate for 2 misalignments is 2 / 300 × 100% = 0.67%. Under normal circumstances, the lower the tab misalignment defect rate, the better; for normal mass production, it should be ≤1%.

[0211] (6) 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%.

[0212] (7) 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.

[0213] The performance parameters of the separator 400 and sodium battery in each embodiment and comparative example are shown in Tables 1 to 3 below.

[0214] Table 1 Performance parameters of diaphragm 400 in Examples 1 to 12

[0215] Table 2 Performance parameters of the separator 400 and sodium battery in Examples 1 to 12

[0216] Table 3 Performance parameters of diaphragm 400 in Examples 13 to 48

[0217] The test results from Examples 1 to 12 show that the first adhesive dot unit 421 and the second adhesive dot unit 431 of the separator 400 of this application have a low overlap rate. When the separator 400 is applied to the core of a single battery cell, the defect rate of the electrode tab misalignment of the core is low. The separator 400 has high ionic conductivity, which, when applied to a sodium battery, results in high energy efficiency. After the sodium battery is fully charged, the negative electrode sheet 330 is less prone to wrinkling. The test results from Examples 1 to 12 show that the lower the overlap rate between the first adhesive dot unit 421 and the second adhesive dot unit 431, the lower the defect rate of the electrode tab misalignment of the core. As can be seen from the test results of Example 3, by adopting the design scheme of the diaphragm 400 of this application, the overlap difference between the first adhesive layer 420 and the second adhesive layer 430 of the diaphragm 400 can be as low as 0.49%, thereby making the thickness of the diaphragm 400 have good uniformity. When the diaphragm 400 is applied to the core, the misalignment defect rate of the tabs can be reduced to 0.53%.

[0218] The test results from Examples 1 to 48 show that when 5≤M≤12, 5≤N≤12, 5≤P≤12, and 5≤Q≤12, as the values ​​of M, N, P, and Q increase (i.e., as the number of first adhesive dots 4211 in the first adhesive dot unit 421 increases, and the number of second adhesive dots 4311 in the second adhesive dot unit 431 increases), the range of overlap between the first adhesive dot unit 421 and the second adhesive dot unit 431 generally decreases. When the values ​​of M, N, P, and Q are between 10 and 12, the range of overlap between the first adhesive dot unit 421 and the second adhesive dot unit 431 is even smaller, which can result in a lower defect rate of misaligned tabs in the core.

[0219] The test results from Examples 1 to 48 and Comparative Examples 1 to 4 show that in Comparative Examples 1 to 4, the first adhesive dot units 421 of the first adhesive layer 420 of the diaphragm 400 of the first adhesive layer 420 are arranged in an array, and the second adhesive dot units 431 of the second adhesive layer 430 are also arranged in an array. During the preparation of the diaphragm 400, as the first adhesive layer 420 and the second adhesive layer 430 are applied, the first adhesive dot units 421 and the second adhesive dot units 431 will move or misalign relative to each other. Therefore, the overlap rate of the first adhesive dot units 421 and the second adhesive dot units 431 will change. The overlap rate of the first adhesive dot units 421 and the second adhesive dot units 431 in Comparative Examples 1 to 4 fluctuates greatly, with a range of 44.06%. When the diaphragm 400 is applied to the core, it results in a high misalignment rate of the core's tabs. In Examples 1 to 48, the arrangement of the second adhesive dots 4311 of the second adhesive dot unit 431 of the diaphragm 400 is centrally symmetrical, laterally axially symmetrical, and longitudinally axially symmetrical. In both the lateral and longitudinal directions, the second adhesive dots are arranged from both sides toward the middle. The spacing between the second center points of adjacent second adhesive dots 4311 is increased or decreased proportionally. This can greatly reduce the fluctuation of the overlap rate between the first adhesive dot unit 421 and the second adhesive dot unit 431 at different positions of the diaphragm 400, reduce the extreme difference in the overlap rate between the first adhesive dot unit 421 and the second adhesive dot unit 431 at different positions of the diaphragm 400, and thus reduce the defect rate of the core's tab misalignment.

[0220] Figure 20 This is a microscope image of the surface of the negative electrode 330 of the sodium battery core after disassembly in Example 3. Figure 21 This is a microscope image of the second adhesive layer 430 side of the separator 400 after the core of the sodium battery in Example 3 has been disassembled.

[0221] Figure 22 This is a scanning electron microscope image of the negative electrode sheet 330 of the sodium battery core of Example 3 after disassembly, corresponding to a second adhesive dot 4311 on its surface. Figure 23 This is a scanning electron microscope image of the negative electrode sheet 330 of the sodium battery core after disassembly, corresponding to the position of another second adhesive dot 4311. Figure 24 This is a scanning electron microscope image of the negative electrode sheet 330 of the sodium battery core of Example 3 after disassembly, corresponding to the position of another second adhesive dot 4311.

[0222] Figure 22 The position of the dashed box is the position of a second adhesive dot 4311 on the negative electrode sheet 330. The second adhesive dot 4311 does not overlap with the first adhesive dot 4211 on the other side (i.e., it is completely offset). At this time, after the core is disassembled, the second adhesive dot 4311 will be transferred to the negative electrode sheet 330.

[0223] Figure 23 The position of the dashed box in the middle is the position of another second adhesive dot 4311 on the negative electrode sheet 330. The second adhesive dot 4311 partially overlaps with the first adhesive dot 4211 on the other side. At this time, after the core is disassembled, the area where the second adhesive dot 4311 and the first adhesive dot 4211 overlap will take away the negative electrode active material on the negative electrode sheet 330, and the adhesive in the part where the second adhesive dot 4311 and the first adhesive dot 4211 do not overlap will be transferred to the negative electrode sheet 330.

[0224] Figure 24 The dashed box indicates the location of another second adhesive dot 4311 on the negative electrode 330. This second adhesive dot 4311 completely overlaps with the first adhesive dot 4211 on the other side. When the core is disassembled, the second adhesive dot 4311 will carry away the entire area of ​​the negative electrode active material corresponding to the second adhesive dot 4311 on the negative electrode 330. Therefore, by disassembling the core and analyzing the scanning electron microscope morphology of the location corresponding to the second adhesive dot 4311 on the negative electrode 330, the overlap between the first adhesive dot 4211 and the second adhesive dot 4311 of the separator 400 can be deduced.

[0225] 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.

[0226] 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 first adhesive layer, the first adhesive layer including a first adhesive dot unit, the first adhesive dot unit including a plurality of first adhesive dots arranged in an array on the first surface; and The second adhesive layer includes a second adhesive dot unit, which includes a plurality of second adhesive dots arranged on the second surface, wherein the spacing between two adjacent second adhesive dots is at least partially unequal.

2. The diaphragm according to claim 1, characterized in that, The plurality of first adhesive dots in the first adhesive dot unit are arranged in P rows and Q columns, wherein each row extends along a first direction and each column extends along a second direction, wherein the first direction is perpendicular to the second direction; the plurality of second adhesive dots in the second adhesive dot unit are arranged in M ​​rows and N columns, wherein each row is parallel to the first direction and each column is parallel to the second direction; the length of each row in the first adhesive dot unit is equal to the length of each row in the second adhesive dot unit, and the length of each column in the first adhesive dot unit is equal to the length of each column in the second adhesive dot unit.

3. The diaphragm according to claim 2, characterized in that, The second adhesive dot unit satisfies at least one of the following conditions: The second adhesive dot unit is centrally symmetrical; The second adhesive dot unit has a first axis of symmetry parallel to the first direction; and The second adhesive dot unit has a second axis of symmetry parallel to the second direction.

4. The diaphragm according to claim 2, characterized in that, The diaphragm satisfies at least one of the following conditions: Along the first direction, the spacing between two adjacent second adhesive dots first gradually increases and then gradually decreases; Along the first direction, the spacing between two adjacent second adhesive dots first gradually decreases and then gradually increases; Along the second direction, the spacing between two adjacent second adhesive dots first gradually increases and then gradually decreases; and Along the second direction, the distance between two adjacent second adhesive dots first gradually decreases and then gradually increases.

5. The diaphragm according to claim 2, characterized in that, The first adhesive dot is circular or nearly circular, and has a first center point. When the first adhesive dot is circular, the first center point is the center of the circle. When the first adhesive dot is nearly circular, the first center point is the center of the smallest circumcircle of the first adhesive dot. The second adhesive dot is circular or nearly circular, and has a second center point. When the second adhesive dot is circular, the second center point is the center of the circle. When the second adhesive dot is nearly circular, the second center point is the center of the smallest circumcircle of the second adhesive dot.

6. The diaphragm according to claim 5, characterized in that, The diaphragm satisfies at least one of the following conditions: Along the first direction, the distance between the second center points of two adjacent second adhesive dots first increases proportionally and then decreases proportionally. Along the first direction, the distance between the second center points of two adjacent second adhesive dots first decreases proportionally and then increases proportionally. Along the second direction, the distance between the second center points of two adjacent second adhesive dots first increases proportionally and then decreases proportionally; and Along the second direction, the distance between the second center points of two adjacent second adhesive dots decreases proportionally first and then increases proportionally.

7. The diaphragm according to claim 5, characterized in that, Along the first direction, the distance between the first center points of two adjacent first adhesive dots is T1, and the distance between the second center point of the i-th second adhesive dot and the second center point of the (i+1)-th second adhesive dot is T(i, i+1). Then, T(i, i+1) = T1 × a1 × b1 （i-1） , where i is the position of the second glue dot when counting from the first or Nth second glue dot in each row to the second axis of symmetry along the first direction, a1 is the initial starting coefficient, and b1 is the common ratio of the geometric sequence formed by the distances between two adjacent second glue dots along the first direction; When the number of the second adhesive dots in each row along the first direction is greater than or equal to the number of the first adhesive dots, 0.5 ≤ a1 < 1, 1 < b1 ≤ 1.5; When the number of second adhesive dots in each row along the first direction is less than the number of first adhesive dots, 1 < a1 ≤ 1.5, 0.5 ≤ b1 < 1.

8. The diaphragm according to claim 5, characterized in that, Along the second direction, the distance between the first center points of two adjacent first adhesive dots is T2, and the distance between the second center point of the j-th second adhesive dot and the second center point of the (j+1)-th second adhesive dot is T(j, j+1). Then, T(j, j+1) = T2 × a2 × b2 （j-1） Where, j is the position of the second glue dot when counting from the first or Mth second glue dot in each column to the first axis of symmetry along the second direction, a2 is the initial starting coefficient, and b2 is the common ratio of the geometric sequence formed by the distances between two adjacent second glue dots along the second direction; When the number of the second adhesive dots in each column along the second direction is greater than or equal to the number of the first adhesive dots, 0.5 ≤ a2 < 1, 1 < b2 ≤ 1.5; When the number of second glue dots in each column along the first direction is less than the number of first glue dots, 1 < a2 ≤ 1.5, 0.5 ≤ b2 < 1.

9. The diaphragm according to claim 2, characterized in that, The diaphragm satisfies: 5≤M≤12, 5≤N≤12, 5≤P≤12, 5≤Q≤12, where M, N, P, and Q are all integers; M equals P-1, P, or P+1; N equals Q-1, Q, or Q+1.

10. The diaphragm according to claim 5, characterized in that, The diaphragm satisfies at least one of the following conditions: The equivalent circle diameter of the first adhesive dot ranges from 250 μm to 500 μm; The equivalent circle diameter of the second adhesive dot ranges from 250 μm to 500 μm; Along the first direction, the distance between the first center points of two adjacent first adhesive dots ranges from 250 μm to 3000 μm; Along the second direction, the distance between the first center points of two adjacent first adhesive dots ranges from 250 μm to 3000 μm; Along the first direction, the distance between the second center points of two adjacent second adhesive dots ranges from 250 μm to 3000 μm; as well as Along the second direction, the distance between the second center points of two adjacent second adhesive dots ranges from 250 μm to 3000 μm.

11. The diaphragm according to any one of claims 1-10, characterized in that, The number of first adhesive dot units is multiple, and multiple first adhesive dot units are arranged in an array on the first surface. The number of second adhesive dot units is multiple, and multiple second adhesive dot units are arranged in an array on the second surface. One first adhesive dot unit corresponds to one second adhesive dot unit, and different first adhesive dot units correspond to different second adhesive dot units. The diaphragm satisfies at least one of the following conditions: The average overlap rate X between the first adhesive dot unit and the second adhesive dot unit ranges from 7% to X ≤ 26%. The range R of the overlap rate between the first adhesive dot unit and the second adhesive dot unit is 0% ≤ R ≤ 10%; and The standard deviation σ of the overlap rate between the first adhesive dot unit and the second adhesive dot unit is in the range of 0%≤σ≤3%.

12. A method for designing a diaphragm, characterized in that, The design method includes: A base film is provided, the base film having a first surface and a second surface disposed opposite to each other; A first adhesive layer is designed on the first surface of the base film. The first adhesive layer includes a first adhesive dot unit. The first adhesive dot unit includes a plurality of first adhesive dot portions arranged in an array. The plurality of first adhesive dot portions are arranged in an array of P rows and Q columns. Each row extends along a first direction and each column extends along a second direction. The first direction is perpendicular to the second direction. Each first adhesive dot portion has a first center point. Along the first direction, the distance between the first center points of two adjacent first adhesive dot portions is T1. A second adhesive layer is designed on the second surface of the base film. The design of the second adhesive layer includes designing second adhesive dot units, such that each second adhesive dot unit comprises a plurality of second adhesive dot portions arranged in M ​​rows and N columns. Each row is parallel to the first direction, and each column is parallel to the second direction. Each second adhesive dot portion has a second center point. The length of each row in the first adhesive dot unit is equal to the length of each row in the second adhesive dot unit, and the length of each column in the first adhesive dot unit is equal to the length of each column in the second adhesive dot unit. The second adhesive dot unit has a first axis of symmetry parallel to the first direction and a second axis of symmetry parallel to the second direction. Along the first direction, the distance between the second center point of the i-th second adhesive dot portion and the second center point of the (i+1)-th second adhesive dot portion is T(i, i+1), then T(i, i+1) = T1 × a1 × b1. （i-1） Where i is the position of the second glue dot when counting along the first direction from the first or Nth second glue dot in each row to the second axis of symmetry, a1 is the initial starting coefficient, and b1 is the common ratio of the geometric sequence formed by the distances between two adjacent second glue dots along the first direction; wherein the first direction is perpendicular to the second direction; The values ​​of a1 and b1 are set, and the second adhesive layer is translated along at least four directions. The average overlap rate of the plurality of first adhesive dots of the first adhesive dot unit and the plurality of second adhesive dots of the second adhesive dot unit in each of the at least four directions is calculated after translation. The range of the overlap rate is calculated based on the average overlap rate in the at least four directions. The values ​​of a1 and b1 are adjusted multiple times, and the range of the overlap rate is calculated for different values ​​of a1 and b1. Wherein, the at least four directions are at least four different directions on the extension plane of the base film. The values ​​of a1 and b1 when the range of overlap rate is at its minimum are selected to determine the arrangement of the plurality of second adhesive dots in the second adhesive dot unit along the first direction.

13. The diaphragm design method according to claim 12, characterized in that, Along the second direction, the distance between the first center points of two adjacent first adhesive dots is T2. The design of the second adhesive layer on the second surface of the base film further includes: along the second direction, if the distance between the second center point of the j-th second adhesive dot and the second center point of the (j+1)-th second adhesive dot is T(j, j+1), then T(j, j+1) = T² × a² × b² （j-1） Where, j is the position of the second glue dot when counting from the first or Mth second glue dot in each column to the first axis of symmetry along the second direction, a2 is the initial starting coefficient, and b2 is the common ratio of the geometric sequence formed by the distances between two adjacent second glue dots along the second direction; The design method further includes: Set the values ​​of a2 and b2, translate the second adhesive layer along at least four directions, calculate the average overlap rate of multiple first adhesive dots of the first adhesive dot unit and multiple second adhesive dots of the second adhesive dot unit in each of the at least four directions after the second adhesive layer is translated in each direction, and calculate the range of the overlap rate based on the average overlap rate in the at least four directions; adjust the values ​​of a2 and b2 multiple times, and calculate the range of the overlap rate for different values ​​of a2 and b2; and The values ​​of a2 and b2 when the range of overlap rate is at its minimum are selected to determine the arrangement of the plurality of second adhesive dots in the second adhesive dot unit along the second direction.

14. The diaphragm design method according to claim 13, characterized in that, The values ​​of T(i, i+1) and T(j, j+1) are rounded to make them multiples of 10 μm.

15. A single-cell battery, characterized in that, The single cell includes a positive electrode, a separator as described in any one of claims 1-11, a negative electrode, and an electrolyte, wherein the separator is located between the positive electrode and the negative electrode.

16. An energy storage device, characterized in that, The energy storage device includes one or more single-cell batteries as described in claim 15.

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