Diaphragm, battery comprising diaphragm, energy storage device and electric equipment

Abstract

The invention provides a diaphragm, a battery comprising the diaphragm, an energy storage device and electric equipment, the diaphragm comprises a base membrane and a point coating glue layer, the point coating glue layer is arranged on at least one side surface of the base membrane, the point coating glue layer comprises a plurality of glue points distributed in a dot matrix shape, the glue points have a first annular structure, and the first annular structure is arranged on the surface of at least one side of the base membrane. The distance between the outer edge of the first annular structure and the center of the glue point is R1, the distance between the inner edge of the first annular structure and the center of the glue point is R2, and 1-R2 / R1 is larger than or equal to 0.15 and smaller than or equal to 0.35; the point coating adhesive layer comprises a polymer binder and an auxiliary agent, and the auxiliary agent comprises at least one of a water-soluble coupling agent and a phosphate auxiliary agent.

Description

Technical Field

[0001] The present application relates to the technical field of energy storage, and particularly to a separator, a battery including the separator, an energy storage device, and an electrical device. Background Art

[0002] A secondary battery (such as a lithium-ion battery) generally consists of a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. The separator is located between the positive electrode sheet and the negative electrode sheet, and functions to separate the positive and negative electrodes to prevent the two electrodes from contacting and short-circuiting.

[0003] A PCS (Polymer Coating Separator) separator is a separator with a polymer coating added to the surface of a separator substrate. It has the advantage of improving the adhesion between the separator and the positive and negative electrode sheets without significantly reducing the energy efficiency and rate performance of the battery.

[0004] However, for the currently available PCS separators based on a dot coating process, they have a relatively high air permeability and a large increase in ionic resistance, resulting in wrinkles easily appearing at the negative electrode interface of the battery and a reduction in energy efficiency. Summary of the Invention

[0005] In order to solve the above technical problems, the present application discloses a separator, a battery including the separator, an energy storage device, and an electrical device, so as to improve the adhesion performance and air permeability of the PCS separator based on the dot coating process, and thereby improve the wrinkling condition and energy efficiency of the negative electrode sheet interface of the battery.

[0006] In a first aspect, the present application provides a separator, comprising: a base film and a dot coating layer, the dot coating layer being disposed on at least one surface of the base film, wherein,

[0007] the dot coating layer includes a plurality of glue dots distributed in a dot matrix pattern, the glue dots having a first ring structure, the distance between the outer edge of the first ring structure and the center of the glue dot being R1, and the distance between the inner edge of the first ring structure and the center of the glue dot being R2, where 0.15 ≤ 1 - R2 / R1 ≤ 0.35;

[0008] the dot coating layer includes a polymer binder and an auxiliary agent, and the auxiliary agent includes at least one of a water-soluble coupling agent and a phosphate-based auxiliary agent.

[0009] In some embodiments of the present application, the thickness compression ratio of the separator is K, where 5% ≤ K ≤ 15%.

[0010] In some embodiments of the present application, the average height of the first ring structure is H, where 5 μm ≤ H ≤ 15 μm.

[0011] In some embodiments of the present application, the air permeability increase of the separator is A, where 5 s / 100 cc ≤ A ≤ 20 s / 100 cc.

[0012] In some embodiments of the present application, the ionic conductivity of the separator is σ, where 1 mS / cm ≤ σ ≤ 1.7 mS / cm.

[0013] In some embodiments of the present application, the adhesion strength between the separator and the positive electrode sheet is 3 N / m to 8 N / m.

[0014] In some embodiments of the present application, the separator satisfies at least one of the following characteristics:

[0015] a) The diameter of the glue dots is d, where 200 μm ≤ d ≤ 800 μm;

[0016] b) Along the length direction of the dot-coated glue layer, the distance between the centers of adjacent glue dots is D1, where 200 μm ≤ D1 ≤ 1200 μm;

[0017] c) Along the width direction of the dot-coated glue layer, the distance between the centers of adjacent glue dots is D2, where 200 μm ≤ D2 ≤ 1200 μm;

[0018] d) The coverage rate of the dot-coated glue layer on the base film is C1, where 5% ≤ C1 ≤ 30%;

[0019] e) The single-sided areal density of the dot-coated glue layer is 0.3 g / m 2 ~0.8 g / m 2 .

[0020] In some embodiments of the present application, in the glue layer solution used to form the dot-coated glue layer, the mass percentage content of the auxiliary agent is a, where 0.1 wt% ≤ a ≤ 1 wt%.

[0021] In some embodiments of the present application, the water-soluble coupling agent includes at least one of polyvinyl alcohol, hydroxyethyl cellulose, fatty acid ester, carboxylic acid ester, lactate ester, and cellulose ester;

[0022] The phosphate-based auxiliary agent includes at least one of sodium tripolyphosphate, trisodium phosphate, sodium pyrophosphate, sodium phosphite, and sodium hexametaphosphate.

[0023] In a second aspect, the present application provides a battery, including a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator, where the separator is located between the positive electrode sheet and the negative electrode sheet, and the separator is the separator described in the first aspect.

[0024] In some embodiments of the present application, the surface of the positive electrode tab has a second annular structure, which is an annular imprint formed after the adhesive dots are peeled off from the surface of the positive electrode tab. The distance between the outer edge of the second annular structure and the center of the annular imprint is R3, and the distance between the inner edge of the second annular structure and the center of the annular imprint is R4, where 0.2 ≤ 1 - R4 / R3 ≤ 0.7.

[0025] In some embodiments of the present application, the effective bonding area coverage rate of the dot-coated adhesive layer on the positive electrode tab is C2, where 2% ≤ C2 ≤ 20%.

[0026] In some embodiments of the present application, 8% ≤ (C2 / C1) × 100% ≤ 50%.

[0027] In a third aspect, the present application provides an energy storage device, including a box body and at least one battery as described in the second aspect, and the battery is housed in the box body.

[0028] In a fourth aspect, the present application provides an electrical equipment, including the energy storage device as described in the third aspect, and the energy storage device supplies power to the electrical equipment.

[0029] Compared with the prior art, the present application has at least the following beneficial effects:

[0030] The present application provides a separator, a battery including the separator, an energy storage device, and an electrical equipment. The separator includes a base film and a dot-coated adhesive layer. The dot-coated adhesive layer includes a plurality of adhesive dots distributed in a dot matrix. The adhesive dots have a first annular structure. The distance between the outer edge of the first annular structure and the center of the adhesive dot is R1, and the distance between the inner edge of the first annular structure and the center of the adhesive dot is R2, where 0.15 ≤ 1 - R2 / R1 ≤ 0.35. The dot-coated adhesive layer includes a polymer binder and an additive. The additive includes at least one of a water-soluble coupling agent and a phosphate additive. This additive is more conducive to forming the first annular structure of the present application. Moreover, by adjusting R1 and R2 of the first annular structure to satisfy the above relationship, the bonding performance and air permeability of the separator can be balanced, the bonding property and ionic conductivity of the PCS separator based on the dot matrix coating process are improved, thereby improving the interface wrinkling situation and energy efficiency of the negative electrode tab of the lithium-ion battery. In addition, the dot-coated adhesive layer of the present application is formed based on the dot matrix coating process, which also improves the thickness uniformity of the separator. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1 Schematic cross-sectional view of a separator according to an embodiment of the present application;

[0033] Figure 2 Schematic structural view of a first annular structure according to an embodiment of the present application;

[0034] Figure 3 Schematic structural view of a separator according to an embodiment of the present application as observed along its thickness direction;

[0035] Figure 4 Schematic structural view of a second annular structure according to an embodiment of the present application;

[0036] Figure 5 Schematic structural view of a household energy storage system according to an embodiment of the present application;

[0037] Figure 6 Schematic structural view of a commercial energy storage system according to an embodiment of the present application;

[0038] Figure 7 Schematic diagram of the point selection of the height value of the outer ring of the glue dot measured by a super-depth-of-field three-dimensional stereomicroscope;

[0039] Figure 8a Schematic diagram of the coverage rate of the point-coated separator in Example 4 measured by a super-depth-of-field three-dimensional stereomicroscope;

[0040] Figure 8b Schematic diagram of the coverage rate of the point-coated separator in Comparative Example 1 measured by a super-depth-of-field three-dimensional stereomicroscope;

[0041] Figure 9 Scanning electron microscope (SEM) image of the glue dot in Example 4;

[0042] Figure 10 SEM image of the annular imprint formed by the glue dot in Example 4 on the surface of the positive electrode plate;

[0043] Figure 11 SEM image of the glue dot in Comparative Example 1;

[0044] Figure 12 SEM image of the annular imprint formed by the glue dot in Comparative Example 1 on the surface of the positive electrode plate;

[0045] Figure 13 Photo of the negative electrode plate after full charge of the negative electrode plate in Example 4;

[0046] Figure 14 Photo of the negative electrode plate after full charge of the negative electrode plate in Comparative Example 1.

[0047] Explanation of the accompanying drawings: 1-energy storage device, 2-electric energy conversion device, 3-first user load, 4-second user load, 10-base film, 20-dot-coated glue layer, 21-glue point, 211-first ring structure, 212-second ring structure, 400-commercial energy storage system, 410-high voltage cable, 420-first electric energy conversion device, 430-second electric energy conversion device. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0049] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0050] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0051] In addition, the terms "installed", "set", "provided with", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0052] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, "plurality" means two or more.

[0053] It should be noted that in the content of this application, a lithium-ion battery is used as an example of a secondary battery to explain this application. However, the secondary battery of this application is not limited to lithium-ion batteries.

[0054] This application provides a separator. As Figure 1 shown, the separator includes a base film 10 and a dot-coated adhesive layer 20, and the dot-coated adhesive layer 20 is disposed on at least one surface of the base film 10. In one embodiment, the dot-coated adhesive layer 20 is disposed on one surface of the base film 10; in another embodiment, the dot-coated adhesive layer 20 is disposed on both surfaces of the base film 10. The dot-coated adhesive layer 20 includes a plurality of adhesive dots 21 distributed in a dot matrix pattern. Referring to Figure 2 , the adhesive dot 21 has a first ring structure 211, the edge region of the adhesive dot bulges, and the central region is recessed, thus forming a morphology with a ring structure. The distance between the outer edge of the first ring structure 211 and the center O point of the adhesive dot is R1, and the distance between the inner edge of the first ring structure and the center of the adhesive dot is R2. The following relationship is satisfied between R1 and R2: 0.15 ≤ 1 - R2 / R1 ≤ 0.35. For example, 1 - R2 / R1 is 0.15, 0.2, 0.25, 0.3, or 0.35. In this application, 1 - R2 / R1 is defined as the average width ratio of the first ring structure.

[0055] The dot-coated adhesive layer of this application includes at least one of a water-soluble coupling agent and a phosphate-based auxiliary agent. This auxiliary agent can increase the surface tension and viscosity of the adhesive layer solution used to form the adhesive dots, which is more conducive to forming the first ring structure of this application. And the inventors have found through research that when 1 - R2 / R1 is too small (for example, less than 0.15), it indicates that the area ratio of the first ring structure in the adhesive dot is too small. Although the blockage of the pores of the positive electrode sheet is less affected, so that the influence of the dot-coated adhesive layer on the air permeability of the separator is smaller, the effective bonding area decreases, resulting in a decrease in the bonding performance of the separator; when 1 - R2 / R1 is too large (for example, greater than 0.35), it indicates that the area ratio of the first ring structure in the adhesive dot is too large. Although the bonding performance of the separator is improved, the increase in the air permeability of the separator by the dot-coated adhesive layer is relatively large, which is likely to increase the ionic impedance of the separator. Based on this, this application adjusts R1 and R2 of the first ring structure to satisfy the above relationship, balancing the two properties of the bonding performance and air permeability of the separator, improving the bonding property and ionic conductivity of the PCS separator based on the dot matrix coating process, thereby improving the interface wrinkling situation and energy efficiency of the negative electrode sheet of the lithium-ion battery; and, the dot-coated adhesive layer of this application is formed based on the dot matrix coating process, which also improves the thickness uniformity of the separator.

[0056] In an alternative embodiment, the thickness compression ratio of the separator is K, where 5% ≤ K ≤ 15%. For example, K is 5%, 8%, 10%, 12%, or 15%. When K is too small (e.g., less than 5%), the bonding area between the glue dots in the dot-coated glue layer and the positive electrode sheet is relatively small, resulting in low bonding strength; when K is too large (e.g., greater than 15%), the bonding area between the glue dots in the dot-coated glue layer and the positive electrode sheet is larger. Although the bonding strength between the separator and the positive electrode sheet is increased, a large amount of the glue material in the central area of the glue dots will be transferred and covered onto the positive electrode sheet in contact with the glue dots, affecting the air permeability and lithium-ion transmission effect in this area between the positive electrode sheets, easily causing excessive local impedance and uneven current density, and affecting the electrochemical performance of the lithium-ion battery. By controlling K within the above range, the electrochemical performance of the lithium-ion battery can be improved on the basis of meeting the bonding strength between the separator and the positive electrode sheet.

[0057] In an alternative embodiment, the average height of the first annular structure is H, where 5 μm ≤ H ≤ 15 μm. For example, H is 5 μm, 8 μm, 10 μm, 12 μm, or 15 μm. When H is too small (e.g., less than 5 μm), a very large pressure (e.g., greater than 9 MPa) is required to achieve a good bonding effect between the separator and the positive electrode sheet. Such a large pressure is likely to damage the internal pore structure of the positive electrode sheet and the separator, and even cause partial collapse of the pore structure; when H is too large (e.g., greater than 15 μm), on the one hand, the height of the first annular structure requires a relatively large glue dot diameter size d to support, which easily makes 1 - R2 / R too large, that is, the area coverage rate of the first annular structure is too large, resulting in an increase in the difficulty of the dot-coating process, and then making it difficult for the existing dot-coating process to reach such a high height; on the other hand, it will also affect the thickness consistency of the separator. By controlling H within the above range, a good bonding effect can be obtained with a moderate pressure, and the increase in the air permeability and the influence on the ion impedance of the separator are relatively small.

[0058] In an alternative embodiment, the increase in the air permeability of the separator is A, where 5 s / 100 cc ≤ A ≤ 20 s / 100 cc. For example, A is 5 s / 100 cc, 10 s / 100 cc, 15 s / 100 cc, or 20 s / 100 cc. When the increase in the air permeability of the separator is within the above range, it indicates that the dot-coated glue layer has a relatively small influence on the air permeability of the separator, which is beneficial to improving the energy efficiency of the lithium-ion battery and has better low-temperature cycle performance.

[0059] In an alternative embodiment, the ionic conductivity of the separator is σ, where 1 mS / cm ≤ σ ≤ 1.7 mS / cm. For example, σ is 1 mS / cm, 1.3 mS / cm, 1.5 mS / cm, or 1.7 mS / cm. When the ionic conductivity of the separator is within the above range, it indicates that the ionic impedance of the separator is relatively small and has a relatively small influence on the energy efficiency of the lithium-ion battery.

[0060] In an alternative embodiment, the adhesion strength between the separator and the positive electrode sheet is 3 N / m to 8 N / m. For example, the adhesion strength between the separator and the positive electrode sheet is 3 N / m, 4 N / m, 5 N / m, 6 N / m, 7 N / m, or 8 N / m. When the adhesion strength between the separator and the positive electrode sheet is within the above range, it indicates that in the bare battery cell (i.e., the battery before injecting the electrolyte), the separator and the electrode sheet can resist the local bulging and deformation caused by the electrolyte infiltrating the separator and the electrode sheet during the liquid injection process; moreover, it can also alleviate the wrinkling phenomenon that occurs due to the repeated expansion caused by the lithium deintercalation from the negative electrode sheet during the cyclic charge and discharge process of the lithium-ion battery.

[0061] In an alternative embodiment, as Figure 2 shown, the diameter of the glue dot is d, and 200 μm ≤ d ≤ 800 μm. For example, d is 200 μm, 400 μm, 600 μm, or 800 μm. By controlling the diameter of the glue dot within the above range, it is beneficial to form a glue dot with a first annular structure that bulges in the edge region and depresses in the central region, and the increase in the air permeability of the separator is relatively small, thereby while improving the adhesion of the separator, reducing the influence on the ionic impedance of the separator.

[0062] In an alternative embodiment, as Figure 3 shown, along the length (MD) direction of the dot-coated glue layer, the distance between the centers of adjacent glue dots is D1, and 200 μm ≤ D1 ≤ 1200 μm. For example, D1 is 200 μm, 400 μm, 800 μm, or 1200 μm. By controlling the distance between the centers of adjacent glue dots within the above range, the coverage rate C1 of the dot-coated glue layer on the base film is within a suitable range, and it is beneficial to leave enough glue-free areas between the dot-coated glue dots, reducing the influence on the air permeability of the separator.

[0063] In an alternative embodiment, as Figure 3 shown, along the width (TD) direction of the dot-coated glue layer, the distance between the centers of adjacent glue dots is D2, and 200 μm ≤ D2 ≤ 1200 μm. For example, D2 is 200 μm, 400 μm, 800 μm, or 1200 μm. By controlling the distance between the centers of adjacent glue dots within the above range, the coverage rate C1 of the dot-coated glue layer on the base film is within a suitable range, and it is beneficial to leave enough glue-free areas between the dot-coated glue dots, reducing the influence on the air permeability of the separator.

[0064] In an alternative embodiment, the coverage rate of the dot-coated adhesive layer on the base film is C1, where 5% ≤ C1 ≤ 30%. For example, C1 is 5%, 10%, 15%, 20%, 25% or 30%. By controlling the coverage rate of the dot-coated adhesive layer within the above range, the separator and the positive electrode tab have a relatively high bonding area. At the same time, the increase in the air permeability of the separator caused by the dot-coated adhesive layer is small, and the impact on the ionic resistance of the separator is small.

[0065] In an alternative embodiment, the single-sided areal density of the dot-coated adhesive layer is 0.3 g / m 2 ~0.8 g / m 2 . For example, the single-sided areal density of the dot-coated adhesive layer is 0.3 g / m 2 , 0.5 g / m 2 , 0.7 g / m 2 or 0.8 g / m 2 . By controlling the single-sided areal density of the dot-coated adhesive layer within the above range, the ionic conductivity of the separator is not significantly reduced, and it is beneficial to the good bonding effect between the dot-coated layer and the positive electrode tab, alleviating the wrinkling phenomenon at the interface of the negative electrode tab during the cycling of the lithium-ion battery.

[0066] In an alternative embodiment, in the adhesive layer solution for forming the dot-coated adhesive layer, the mass percentage content of the auxiliary agent is a, where 0.1 wt% ≤ a ≤ 1 wt%. For example, a is 0.1 wt%, 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, 0.9 wt% or 1 wt%. By controlling the content of the auxiliary agent within the above range, the surface tension and viscosity of the adhesive layer solution for forming the dot-coated adhesive layer can be effectively increased, which is more conducive to forming the first annular structure with a sunken central region and a raised edge region.

[0067] In an alternative embodiment, the water-soluble coupling agent includes at least one of polyvinyl alcohol, hydroxyethyl cellulose, fatty acid ester, carboxylic acid ester, lactate ester and cellulose ester; the phosphate-based auxiliary agent includes at least one of sodium tripolyphosphate, trisodium phosphate, sodium pyrophosphate, sodium phosphite and sodium hexametaphosphate.

[0068] The present application has no particular limitation on the polymer binder, as long as the object of the present application can be achieved. For example, the polymer binder includes but is not limited to at least one of acrylate polymers, vinylidene fluoride polymers, and polyacrylic acid. The acrylate polymer and the vinylidene fluoride polymer are granular solids, and the polyacrylic acid is a liquid. Among them, the acrylate polymer can be selected from at least one of polymethacrylate, polymethyl methacrylate, polyethyl acrylate, polyacrylate, and polybutyl acrylate; among them, the vinylidene fluoride polymer can be a cross-linked polymer selected from homopolymers including only structural units derived from vinylidene fluoride monomers and copolymers including structural units derived from vinylidene fluoride and structural units derived from other monomers; the copolymer can include at least one of structural units derived from chlorotrifluoroethylene, trifluoroethylene, hexafluoropropylene, tetrafluoroethylene, and ethylene monomers and structural units derived from vinylidene fluoride, but is not limited thereto. For example, the copolymer can be a polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer including structural units derived from vinylidene fluoride monomers and structural units derived from hexafluoropropylene monomers.

[0069] The polymer binder can be granular solid binder particles with a Dv50 of 3 μm to 15 μm. In this way, it is beneficial to improve the dispersion uniformity of the polymer binder in the adhesive layer solution and is easier to control the thickness consistency of the adhesive layer.

[0070] In the present application, Dv50 represents the particle size value corresponding to the cumulative volume distribution percentage reaching 50% when measured from the small particle size in the particle size distribution based on volume.

[0071] The present application has no particular limitation on the preparation method of the separator. Exemplarily, it can be prepared according to the following steps:

[0072] Step A: Mix the binder and the auxiliary agent to prepare an adhesive layer solution;

[0073] Step B: Dot-coat the adhesive layer solution onto at least one side of the base film through a dot coating process, and form a separator based on the dot coating process after drying.

[0074] In step A, during the preparation of the adhesive layer solution, control the temperature to 25°C to 50°C and the pH to 5 to 9, which is beneficial to the full dissolution of the binder and the auxiliary agent and to improve the dispersion effect, and is beneficial to extend the sedimentation time of the adhesive layer solution. The viscosity of the adhesive layer solution is 200 mPa·s to 600 mPa·s, the solid content is 10% to 18%, and the surface tension is 90 mN / m to 150 mN / m. The adhesive layer solution satisfying the above viscosity, solid content, and surface tension parameters is more suitable for the dot coating process.

[0075] In step B, in one embodiment, the adhesive layer solution is dot-coated onto one side of the base film facing the positive electrode plate; in another embodiment, the adhesive layer solution is dot-coated onto both sides of the base film; in another embodiment, the adhesive layer solution is dot-coated onto one side of the base film facing the negative electrode plate.

[0076] The present application places no particular limitation on the dot matrix coating process. For example, it may include contact type plate roll dot coating, non-contact jet dot coating, etc.

[0077] In the present application, the formation mechanism of the first annular structure is as follows: after the adhesive layer solution forms droplet-shaped adhesive dots through the dot coating process, the evaporation rate at the edge of the droplet is higher than that at the center, resulting in an outward capillary flow inside the droplet, which carries the suspended solid particles to the edge of the droplet and deposits to form a ring after drying. When drying begins, factors such as the porous structure on the surface of the separator and the additional frictional resistance caused by the chemical composition differences between the liquid phase and solid particles of the droplet generate resistance, which hinders the shrinkage of the droplet. The height at the center of the droplet is greater than that at the edge. When the water at the edge of the droplet evaporates, some water molecules will flow from the center of the droplet to the edge. The volume of the droplet continuously decreases, but the diameter of the droplet remains roughly unchanged. Therefore, the solid binder particles (such as PVDF-HFP solid particles) or other liquid adhesive phases in the droplet will continuously flow from the center of the droplet to the edge along with the water phase. And since the surface tension is also a force that causes the liquid surface area to shrink, during the drying process, the adhesive binder with a large surface tension will entrain the solid binder particles and accelerate their movement towards the edge, resulting in an increasing accumulation of solid particles precipitated at the edge of the adhesive dot, while the solid binder particles remaining in the center become fewer and fewer. When the adhesive dot is completely dry, the vast majority of the solid binder particles remain at the edge of the droplet, naturally forming an annular structure.

[0078] The present application also provides a battery, including a positive electrode plate, a negative electrode plate, an electrolyte, and a separator, where the separator is located between the positive electrode plate and the negative electrode plate, and the separator is the separator described in any of the above embodiments.

[0079] In an optional implementation manner, refer to Figure 4, the surface of the positive electrode plate has a second annular structure 212. The distance between the outer edge of the second annular structure and its center O is R3, and the distance between the inner edge of the second annular structure and its center O is R4, where 0.2 ≤ 1 - R4 / R3 ≤ 0.7. For example, 1 - R4 / R3 is 0.2, 0.4, 0.5, 0.6, or 0.7. The annular imprint formed after the second annular structure adhesive dots are peeled off from the surface of the positive electrode plate is the adhesive dot residue on the positive electrode plate after peeling. By controlling 1 - R4 / R3 within the above range, it indicates that there is an appropriate bonding effect between the separator adhesive dots and the positive electrode plate, and the coverage of the adhesive layer on the surface of the positive electrode plate does not significantly affect the insertion and extraction and migration of lithium ions, enabling good interfacial contact between the separator and the positive electrode plate in the lithium-ion battery, and improving the energy efficiency and cycle performance of the lithium-ion battery.

[0080] In an alternative embodiment, the effective bonding area coverage rate of the dot-coated adhesive layer on the positive electrode plate is C2, where 3% ≤ C2 ≤ 20%. For example, C2 is 3%, 10%, 15%, or 20%. By controlling the effective bonding area coverage rate of the dot-coated adhesive layer on the positive electrode plate within the above range, it indicates that there is an appropriate bonding effect between the separator dot-coated adhesive layer and the positive electrode plate, and it does not significantly affect the insertion and extraction and migration of lithium ions.

[0081] In an alternative embodiment, 20% ≤ (C2 / C1)×100% ≤ 50%. For example, (C2 / C1)×100% is 20%, 30%, 40%, or 50%. By controlling (C2 / C1)×100% within the above range, it indicates that the dot-coated adhesive layer has an appropriate transfer rate on the surface of the positive electrode plate, resulting in a good bonding effect between the separator and the surface of the positive electrode plate.

[0082] This application has no special restrictions on the positive electrode plate, as long as the purpose of this application can be achieved. For example, the positive electrode plate generally includes a positive current collector and a positive electrode material layer. The positive electrode material layer can be disposed on one surface in the thickness direction of the positive current collector, or on both surfaces in the thickness direction of the positive current collector. In this application, the positive electrode material layer is disposed on the surface of the positive current collector, that is, the positive electrode material layer can be disposed in a partial area or the entire area of one surface of the positive current collector. In this application, there are no special restrictions on the positive current collector, as long as the purpose of this application can be achieved. For example, it can include, but is not limited to, aluminum foil, aluminum alloy foil, or composite current collector, etc. In this application, there are no special restrictions on the thickness of the positive current collector, as long as the purpose of this application can be achieved. For example, the thickness is 5 μm to 13 μm. The single-sided thickness of the positive electrode material layer in this application can be 75 μm to 120 μm.

[0083] In the present application, the positive electrode active material layer includes a positive electrode active material. There is no particular limitation on the positive electrode active material in the present application, as long as the object of the present application can be achieved. For example, it may include at least one of lithium iron phosphate, lithium-rich manganese-based material, lithium cobaltate, lithium manganate, and lithium manganese iron phosphate.

[0084] In the present application, the positive electrode active material layer may further include a positive electrode binder. There is no particular limitation on the positive electrode binder in the present application, as long as the object of the present application can be achieved. For example, it may include, but is not limited to, at least one of fluororesin, polypropylene resin, fiber-type binder, rubber-type binder, or polyimide-type binder.

[0085] The lithium-ion battery of the present application further includes a negative electrode tab. There is no particular limitation on the negative electrode tab in the present application, as long as the object of the present application can be achieved. For example, the negative electrode tab generally includes a negative electrode current collector and a negative electrode material layer. The negative electrode material layer may be disposed on one surface or two surfaces in the thickness direction of the negative electrode current collector. In the present application, the negative electrode material layer is disposed on the surface of the negative electrode current collector, that is, the negative electrode material layer may be disposed on a partial area of one surface of the negative electrode current collector or on the entire area of one surface of the negative electrode current collector. There is no particular limitation on the negative electrode current collector in the present application, as long as the object of the present application can be achieved. For example, it may include, but is not limited to, copper foil, copper alloy foil, nickel foil, or composite current collector, etc. In the present application, there is no particular limitation on the thickness of the negative electrode current collector, as long as the object of the present application can be achieved. For example, the thickness is 4 μm to 12 μm. The single-sided thickness of the negative electrode material layer of the present application may be 50 μm to 80 μm.

[0086] In the present application, the negative electrode material layer includes a negative electrode material. Among them, there is no particular limitation on the negative electrode material, as long as the object of the present application can be achieved. For example, it may include at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, hard carbon, silicon, and silicon carbon.

[0087] In the present application, the negative electrode material layer may further include a negative electrode binder. There is no particular limitation on the negative electrode binder in the present application, as long as the object of the present application can be achieved. For example, it may include, but is not limited to, at least one of acrylate, polyamide, polyimide, polyamideimide, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, sodium carboxymethylcellulose, and potassium carboxymethylcellulose.

[0088] There is no particular limitation on the base film of the separator in this application. Those skilled in the art can select it according to actual needs as long as the purpose of this application can be achieved. For example, the base film is a non-woven fabric, film or composite film with a porous structure, and the material of the base film is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film can be selected.

[0089] The battery of this application also includes an electrolyte. There is no particular limitation on the electrolyte in this application. Those skilled in the art can select it according to actual needs as long as the purpose of this application can be achieved. For example, after mixing at least one of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl propionate (EP), propyl propionate (PP), ethylene methyl carbonate (EMC), dimethyl carbonate (DMC), vinylene carbonate (VC) or fluoroethylene carbonate (FEC) etc. in a certain mass ratio or volume ratio to obtain a non-aqueous organic solvent, a lithium salt is added and dissolved and mixed evenly. There is no limitation on the type of lithium salt in this application as long as the purpose of this application can be achieved. For example, the lithium salt can include at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, lithium bis(oxalato)borate (LiBOB) or lithium difluoroborate.

[0090] There is no particular limitation on the concentration of the lithium salt in the electrolyte in this application as long as the purpose of this application can be achieved. Taking LiPF6 as an example, the concentration of LiPF6 in the electrolyte is 5wt% to 25wt%. For example, the concentration of LiPF6 is 5wt%, 10wt%, 11wt%, 12wt%, 12.5wt%, 15wt%, 20wt% or 25wt%.

[0091] The battery of this application also includes a housing. There is no particular limitation on the housing in this application. Those skilled in the art can select it according to actual needs as long as the purpose of this application can be achieved. For example, the housing can include an aluminum-plastic film.

[0092] There is no particular limitation on the preparation method of the battery in this application. A preparation method well-known in the art can be selected as long as the purpose of this application can be achieved. For example, the preparation method of the battery includes but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in sequence, and winding, laminating, etc. as needed to obtain a bare battery cell, and putting the bare battery cell into an aluminum alloy square shell, and obtaining a lithium-ion battery through processes such as vacuum baking, liquid injection, formation, etc.

[0093] The present application also provides an energy storage device, which includes a box body and at least one battery in any of the above embodiments, and the battery is housed in the box body. The energy storage device with such a battery has excellent performance, which is beneficial to the use of the energy storage device. By housing the battery in the box body, the fixing and protecting effects on the battery can be increased, and the service life of the energy storage device can be improved. It can be understood that the energy storage device may have one or more batteries. When the energy storage device contains multiple batteries, the multiple batteries can be connected by at least one of parallel connection and series connection.

[0094] The present application also provides an electrical equipment, which includes the energy storage device in the above embodiment, which is beneficial to improving the product competitiveness and service performance of the electrical equipment. In an optional embodiment, the electrical equipment includes an electrical equipment body, and the energy storage device is used to supply power to the electrical equipment body. In an optional embodiment, the electrical equipment body includes a device positive electrode and a device negative electrode. The positive electrode plate of the battery in the energy storage device is used for electrically connecting to the device positive electrode of the electrical equipment body, and the negative electrode plate of the battery in the energy storage device is used for electrically connecting to the device negative electrode of the electrical equipment body to supply power to the electrical equipment.

[0095] The electrical equipment of the present application may include, but is not limited to: containers, household energy storage systems, battery cars, electric vehicles, ships, spacecrafts, electric toys, and electric tools, etc. Among them, spacecrafts such as airplanes, rockets, space shuttles, and spaceships, etc., electric toys include, for example, fixed or mobile electric toys, specifically, for example, electric vehicle toys, electric ship toys, and electric airplane toys, etc., and electric tools include, for example, metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, specifically, for example, electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact electric drills, concrete vibrators, and electric planers.

[0096] Please refer to Figure 5 , Figure 5 which is a schematic structural diagram of a household energy storage system according to an embodiment of the present application, and the embodiment of the present application Figure 5 takes the household energy storage scenario in user-side energy storage as an example for illustration, and the energy storage device of the present application is not limited to the household energy storage scenario.

[0097] The present application provides a household energy storage system, which includes an electric energy conversion device 2 (photovoltaic panel), a first user load 3 (street lamp), a second user load 4 (such as household appliances like air conditioners), etc., and an energy storage device 1. The energy storage device 1 is a small energy storage box, which can be installed on an outdoor wall in a wall-mounted manner. Specifically, the photovoltaic panel can convert solar energy into electric energy during the low electricity price period, and the energy storage device 1 is used to store the electric energy and supply it to the street lamp and household appliances for use during the high electricity price period, or supply power when the power grid is powered off / out of power.

[0098] Please refer toFigure 6 , Figure 6 is a schematic structural diagram of a commercial energy storage system 400 according to an embodiment of the present application, and the embodiment of the present application Figure 6 takes the shared energy storage scenario on the power generation / distribution side as an example for illustration, and the energy storage device 1 of the present application is not limited to its energy storage scenario on the power generation / distribution side.

[0099] The present application provides a commercial energy storage system 400. The commercial energy storage system 400 includes: a high-voltage cable 410, a first power conversion device 420, a second power conversion device 430, and the energy storage device 1 provided by the present application. In the case of power generation, the first power conversion device 420 and the second power conversion device 430 are used to convert other forms of energy into electric energy, connect with the high-voltage cable 410 and supply it for use on the power grid's power consumption side. When the power consumption load is low and the first power conversion device 420 and the second power conversion device 430 generate excess power, the excess power is stored in the energy storage device 1 to reduce the curtailment rate of wind and light and improve the problem of new energy power generation accommodation; when the power consumption load is high, the power grid issues an instruction to transmit the electric energy stored in the energy storage device 1 in parallel connection mode with the high-voltage cable 410 to supply the power consumption side for use, providing various services such as peak shaving, frequency modulation, and standby for the power grid operation, giving full play to the role of the power grid's peak shaving, promoting the power grid to cut peaks and fill valleys, and alleviating the power supply pressure of the power grid.

[0100] Optionally, the first power conversion device 420 and the second power conversion device 430 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy, and mechanical energy into electric energy.

[0101] The number of the energy storage devices 1 can be multiple. The multiple energy storage devices 1 are connected in series or in parallel with each other, and the multiple energy storage devices 1 are supported and electrically connected by a separator (not shown in the figure). In this embodiment, "multiple" means two or more. An energy storage box can also be provided outside the energy storage device 1 for accommodating the energy storage device 1.

[0102] Optionally, the energy storage device 1 can include, but is not limited to, battery modules, battery packs, battery systems, etc. Among them, the battery module can be a battery module formed by connecting multiple batteries of the present application in series / parallel, the battery pack can include multiple batteries of the present application, and the battery system can be a charge and discharge system including the batteries or battery packs of the present application.

[0103] The actual application form of the energy storage device 1 provided by the embodiment of the present application can be, but is not limited to, the listed products, and can also be other application forms. The embodiment of the present application does not strictly limit the application form of the energy storage device 1. The embodiment of the present application only takes the energy storage device 1 as a multi-core battery as an example for illustration. When the energy storage device 1 includes single cells, the single cells can be at least one of cylindrical batteries, square batteries, etc.

[0104] Examples

[0105] Hereinafter, preparation examples, examples and comparative examples are given to illustrate the embodiments of the present application more specifically. Various tests and evaluations are carried out according to the following methods.

[0106] Example 1

[0107] <Preparation of separator>

[0108] <Preparation of adhesive layer solution>

[0109] Weigh PVDF-HFP powder (Dv50 is 7 μm), polyacrylic acid (PAA), methyl acrylate emulsion and the auxiliary sodium tripolyphosphate according to the mass ratio of 72.7∶5∶22∶0.3; first add deionized water as a solvent into a stirrer, then add the weighed PAA, stir evenly at 1000 rpm / 15 min (that is, stir at a speed of 1000 rpm for 15 minutes), then add sodium tripolyphosphate, stir evenly at 1000 rpm / 15 min, control the temperature at about 40 °C, and control the pH at about 7; then add PVDF-HFP powder, stir evenly at 2500 rpm / 90 min, then add methyl acrylate emulsion, stir evenly at 1000 rpm / 15 min, and then slowly stir at 500 rpm / 15 min to remove bubbles, and obtain an adhesive layer solution.

[0110] <Preparation of dot-coated adhesive layer>

[0111] Use a plate roller dot coating device to dot coat the adhesive layer solution on both sides of a base film. The base film is a base film with a ceramic coating on the surface. The thickness of the ceramic coating is 2 μm. The base film is a polyethylene (PE) porous film with a thickness of 7 μm. After drying at 65 °C, a separator with a dot-coated adhesive layer is obtained and cut into pieces for use. Among them, the areal density of the single-sided dot-coated adhesive layer is 0.5 g / m 2 , the diameter (d) of a single adhesive dot is about 452 μm, the distance (D1) between the centers of adjacent adhesive dots in the MD direction is 675 μm, the distance (D2) between the centers of adjacent adhesive dots in the TD direction is 800 μm, the coverage rate of the dot-coated adhesive layer is 29.70%, and the running speed of the separator is 100 m / min.

[0112] <Preparation of positive electrode sheet>

[0113] Mix the cathode active material lithium iron phosphate (LiFePO4), conductive carbon black (Super-P), and binder PVDF in a mass ratio of 97:1:2; then add N-methylpyrrolidone (NMP) as a solvent and stir evenly to prepare a cathode slurry with a solid content of 60 wt%. Then, evenly coat the cathode slurry on one surface of a 11-μm-thick cathode current collector aluminum foil, dry it at 85 °C, and then repeat the above steps on the other surface of the cathode plate. After rolling, a cathode plate with a cathode material layer coated on both sides is obtained. The single-sided thickness of the cathode material layer is 90 μm.

[0114] <Preparation of the negative electrode plate>

[0115] Mix the negative electrode material artificial graphite, conductive carbon black (Super-P), sodium carboxymethyl cellulose (CMC-Na), and styrene-butadiene rubber (SBR) in a mass ratio of 97:1:1.5:0.5, add deionized water, and stir evenly to prepare a negative electrode slurry with a solid content of 55 wt%. Then, evenly coat the negative electrode slurry on one surface of a 6-μm-thick negative electrode current collector copper foil, dry it at 105 °C, and then repeat the above steps on the other surface of the negative electrode plate. After rolling, a negative electrode plate with a negative electrode material layer coated on both sides is obtained, and the single-sided thickness of the negative electrode material layer is 70 μm.

[0116] <Preparation of the electrolyte>

[0117] Mix ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) in a volume ratio of 1:1:1, dissolve and stir well, then place it in an environment of less than or equal to 5 °C for 12 h, and then add lithium hexafluorophosphate (LiPF6). After mixing evenly, an electrolyte is obtained. Among them, the molar concentration of LiPF6 in the electrolyte is 1.0 mol / L.

[0118] <Preparation of the lithium-ion battery>

[0119] Stack the above-prepared cathode plate, separator, and negative electrode plate in sequence, with the separator in the middle of the cathode and the negative electrode to play a role in isolation, and wind it to obtain a bare battery cell. Place the bare battery cell in an aluminum alloy square shell, inject the electrolyte after vacuum drying, and obtain a lithium-ion battery through processes such as vacuum packaging, standing, and formation.

[0120] Examples 2 to 4

[0121] Except in the <Preparation of the adhesive layer solution>, adjust the addition amount of the auxiliary agent according to Table 1, and the rest is the same as in Example 1.

[0122] Examples 5 to 8

[0123] Except in the <Preparation of Adhesive Layer Solution>, where the types of additives were adjusted according to Table 5, the rest was the same as in Example 2.

[0124] Comparative Example 1

[0125] Except in the <Preparation of Adhesive Layer Solution>, where the additive sodium tripolyphosphate was not added, the rest was the same as in Example 1.

[0126] Comparative Examples 2 - 3

[0127] Except in the <Preparation of Adhesive Layer Solution>, where the addition amount of the additive sodium tripolyphosphate was adjusted to change 1 - R2 / R1, the rest was the same as in the Examples.

[0128] Table 1: Preparation Parameters of Examples 1 - 4 and Comparative Examples 1 - 3

[0129]

[0130] Table 2: Diaphragm - Related Parameters of Examples 1 - 4 and Comparative Examples 1 - 3

[0131]

[0132]

[0133] Table 3: Parameters Related to the First Ring Structure and the Second Ring Structure of Examples 1 - 4 and Comparative Examples 1 - 3

[0134]

[0135] In Table 3, " / " indicates the non - existence of relevant parameters.

[0136] Table 4: Glue Point Coverage of Examples 1 - 4 and Comparative Examples 1 - 3

[0137]

[0138] Table 5: Preparation Parameters of Examples 2 and 5 - 8

[0139]

[0140]

[0141] Testing Methods and Equipment

[0142] Particle Size Test of Solid Binder Particles:

[0143] According to the test method of the reference standard "GB / T 19077-2016 Laser Diffraction Method for Particle Size Distribution", a laser particle size analyzer is used to test the particle size of the solid binder particles, and the Dv50 data is obtained.

[0144] Testing of separator thickness and thickness compression ratio:

[0145] According to the thickness test method in 6.4.1 of the reference standard "GB / T 36363-2018 Polyolefin Separators for Lithium-Ion Batteries", a thickness gauge (model: Mahr C1202 from Germany) is used to test the thickness of the single-layer separator. The flat probe has a probe diameter φ = 8 mm, and the test pressure is 0.25 N. The thickness of the original state separator (i.e., the separator before cold pressing) is measured using the Mahr thickness gauge, denoted as d1; after cutting and stacking 10 layers of the original state separator with a size of 100 mm × 100 mm and compressing it under cold pressing conditions (25 °C, 6 MPa, 40 s), the thickness is measured and then divided by 10 layers to obtain the thickness d2 of the single-layer separator after compression. The thickness compression ratio of the separator is: (1 - d2 / d1) × 100%.

[0146] Testing of separator air permeability:

[0147] According to the air permeability test method in 6.5.4 of the reference standard "GB / T 36363-2018 Polyolefin Separators for Lithium-Ion Batteries", an air permeability tester (model: Wangyan EG01-55-1MR) is used to measure the time required for 100 mL of air to pass through 1 square inch of the separator at a pressure of 1.22 kPa, which is the air permeability value. The smaller the air permeability value, the better the air permeability of the separator.

[0148] Testing of the single-sided areal density of the dot-coated adhesive layer:

[0149] The test is carried out according to the reference standard "GB / T 20220-2006 Determination of Average Thickness, Roll Average Thickness and Areal Mass of Plastic Film and Sheet Samples - Gravimetric Method". Using a 100 cm 2 gram weight sampler, cut 5 pieces of the base film and the separator with the dot-coated adhesive layer respectively, weigh them to obtain the mass, and then divide the mass by the sampling area to obtain their respective areal densities. The difference between the two is the areal density of the dot-coated adhesive layer coating amount, and the average value is taken after testing 5 times.

[0150] Testing of the coverage rate of the dot-coated adhesive layer on the base film:

[0151] The surface glue dot area of the separator was identified and calculated using a super-depth-of-field three-dimensional microscope (Keyence VHX-7000). The magnification was 50X. In the target area (e.g., a rectangular area of 17 mm × 13 mm), the area of the glue dots was denoted as S1, and the area of the separator was denoted as S2. Then, the coverage rate of the dot-coated glue layer on the base film = (S1 / S2) × 100%. Three target areas were randomly selected for testing and the average value was calculated.

[0152] Test of the average height of the first annular structure:

[0153] The height values of the first annular structure of the glue dots on the surface of the original separator were identified and measured using a super-depth-of-field three-dimensional microscope (Keyence VHX-7000). Refer to Figure 7 For each glue dot, the height of the first annular structure was measured at 10 position points. Three glue dots were randomly selected for testing, and 30 values were obtained. The average value of these 30 values was calculated.

[0154] Test of the bonding strength between the separator and the positive electrode tab:

[0155] Refer to the standard "GB / T 2792-2014 Test Method for Peel Strength of Adhesive Tapes" to conduct a peel strength test on the separator-positive electrode tab with a glue layer. After pressing, the sample size was cut to 20 mm × 100 mm and fixed in the middle of the fixture of the tensile machine. Then, the tensile machine peeled the separator and the positive electrode tab along the 180° direction at a speed of 50 mm / min until the test distance reached 80 mm. Five tests were conducted and the average value was taken. The bonding force was the average value of the peel strength. The pressing method for the separator and the positive electrode tab was as follows: Cut the positive electrode tab and the separator into 100 mm × 100 mm, stack them naturally and then put them into a flat press for pressing. The pressing temperature at room temperature was 25 °C, the pressure holding time was 40 s, and the pressure per unit area was 4 - 7 MPa.

[0156] Test of the coverage rate of the effective bonding area of the dot-coated glue layer on the positive electrode tab:

[0157] Refer to Figure 8a or Figure 8b After the peel strength test was conducted on the separator-positive electrode tab with a dot-coated glue layer, the percentage of the area of the raised annular pattern and the raised irregular pattern transferred from the separator to the positive electrode tab by the dot-coated glue layer in the area of the positive electrode tab was called the coverage rate of the effective bonding area. In the target area (e.g., a rectangular area of 17 mm × 13 mm), the raised area (i.e., the area of the raised annular pattern and the raised irregular pattern) on the surface of the peeled positive electrode tab was identified and calculated using a super-depth-of-field three-dimensional microscope with a magnification of 50X. Three target areas were randomly selected for testing and the average value was calculated.

[0158] Test of the average width ratio of the first annular structure:

[0159] The radius of the glue dot on the surface of the pristine separator is R1, which is equivalent to the distance between the outer edge of the first annular structure and the center of the glue dot; the radius of the part without protrusion in the core of the glue dot is R2, which is equivalent to the distance between the inner edge of the first annular structure and the center of the glue dot. The diameter d of the glue dot (i.e., 2R1) is measured by SEM. Five glue dots are randomly selected, and 2R1 and 2R2 of each glue dot are measured 3 times respectively, and then the average values of R1 and R2 are taken, and 1 - R2 / R1 is calculated accordingly.

[0160] Test of the average width ratio of the second annular structure:

[0161] After the positive electrode sheet and the PCS separator are peeled off under dry pressing at room temperature (cold pressing conditions: 25°C, 6 MPa, 40 s), the radius of the annular imprint on the surface of the positive electrode sheet after peeling is R3, which is equivalent to the distance between the outer edge of the second annular structure and the center of the annular imprint; the radius of the blank area inside the annular imprint is R2, which is equivalent to the distance between the inner edge of the second annular structure and the center of the annular imprint. Five glue dots are randomly selected, and 2R3 and 2R4 of each glue dot are measured 3 times respectively, and then the average values of R3 and R4 are taken, and 1 - R4 / R3 is calculated accordingly.

[0162] Test of the ionic conductivity of the separator:

[0163] Refer to the ionic conductivity test method in 6.6.2 of the standard "GB / T 36363-2018 Polyolefin Separators for Lithium-Ion Batteries" to test and calculate the ionic conductivity of the separator.

[0164] Test of the energy efficiency of lithium-ion batteries:

[0165] Under the condition of 25°C, the lithium-ion battery is charged and discharged in a charge-discharge cycle by 0.5C charge and 0.5C discharge, where the charge cut-off voltage is 3.7V and the discharge cut-off voltage is 2.45V, and the charge-discharge cycle stops until the capacity of the lithium-ion battery reaches 60% of the initial capacity. At the same time, the energy efficiency of the lithium-ion battery after 500 cycles is tested by the constant current method, and the energy efficiency = the discharge energy of the 500th cycle / the charge energy of the 500th cycle × 100%.

[0166] Test of the interface condition of the negative electrode sheet after full charge:

[0167] Disassemble the fully charged lithium-ion battery according to the operation specification requirements. The humidity in the disassembly room is ≤5%RH, and the temperature is 25±3°C. Take pictures to record the wrinkling situation of the interface of the negative electrode sheet. If the number of wrinkles of the negative electrode sheet is 0, it is judged as no wrinkle; if the number of wrinkles of the negative electrode sheet is 1 - 3, it is judged as extremely slight wrinkle; if the number of wrinkles of the negative electrode sheet is 4 - 6, it is judged as slight wrinkle; if the number of wrinkles of the negative electrode sheet is 7 or more, it is judged that obvious wrinkles appear.

[0168] Table 6: Performance data of Examples 1 to 8 and Comparative Example 1

[0169]

[0170] It can be seen from Examples 1 to 4 and Comparative Example 1 that the bonding strength between the separator of Comparative Example 1 and the positive electrode sheet is low, the ionic conductivity of the separator is low, the energy efficiency at room temperature is low, and obvious wrinkles appear on the negative electrode sheet after full charge. This may be because the auxiliary agent of the present application is not added to the adhesive layer solution of Comparative Example 1, resulting in difficulty in forming the first ring structure of the present application, thus affecting the bonding performance and air permeability of the separator, leading to a decrease in the energy efficiency of the lithium-ion battery and making wrinkles more likely to appear; while the separator of the present application has a higher bonding strength with the positive electrode sheet, a higher ionic conductivity of the separator, a higher energy efficiency at room temperature, and no wrinkles at the interface of the negative electrode sheet after full charge.

[0171] It can be seen from Examples 1 to 4 and Comparative Examples 2 to 3 that if the addition amount of the auxiliary agent is too small (such as Comparative Example 2), the area ratio of the first ring structure in the glue dots is too small, and the effective bonding area between the first ring structure and the positive electrode sheet is small. Although the energy efficiency of the lithium-ion battery is high, the ability to resist wrinkles on the electrode sheet is weak, and slight wrinkles appear at the interface of the negative electrode sheet after full charge; if the addition amount of the auxiliary agent is too large (such as Comparative Example 3), the area ratio of the first ring structure in the glue dots is too large, and the effective bonding area between the first ring structure and the positive electrode sheet is large. Although the ability to resist wrinkles on the electrode sheet is strong and there are no wrinkles at the interface of the negative electrode sheet after full charge, the energy efficiency of the lithium-ion battery is low.

[0172] The type of the auxiliary agent usually also affects the performance of the separator. It can be seen from Example 2 and Examples 5 to 8 that by selecting the auxiliary agent of the present application, it is beneficial to obtain a separator with good bonding performance and good air permeability, thereby being beneficial to the improvement of the performance of the lithium-ion battery.

[0173] Figure 9 SEM image of the glue dot of Example 4, from Figure 9 It can be seen that the PVDF-HFP solid particle aggregates in the outer ring area of the original state dot-coated glue dot of Example 4 are dense, while the PVDF-HFP solid particles in the core position of the dot-coated glue dot are relatively sparse, forming an obvious first ring structure, and this first ring structure has a morphology with a raised edge area and a sunken central area.

[0174] Figure 10 SEM image of the ring-shaped imprint formed by the glue dot of Example 4 on the surface of the positive electrode sheet, from Figure 10 It can be seen that the glue dots remaining on the surface of the positive electrode sheet present a circular ring-like morphology, and there is no obvious glue dot residue in the core, indicating that the main bonding part is the outer ring area of the glue dots.

[0175] Figure 11 SEM image of the glue dots of Comparative Example 1. From Figure 11 it can be seen that in the overall area of the original state dot-coated glue dots of Comparative Example 1, the agglomerates of PVDF-HFP solid particles are densely distributed. The core and outer ring of the circular glue dots are relatively flat, without the morphology of raised edge regions and sunken central regions. This is because the surface tension of the conventional glue layer solution is small, the repulsive force between the agglomerates of PVDF-HFP solid particles decreases, and they are prone to coagulation and precipitate under the action of gravity during the drying process. Therefore, the surface of the glue dots is overall flat after drying.

[0176] Figure 12 SEM image of the circular imprint formed by the glue dots of Comparative Example 1 on the surface of the positive electrode plate. From Figure 12 it can be seen that the morphology of the glue dots remaining on the surface of the positive electrode plate has no obvious circular ring structure, the residues are irregular and have a small area, indicating that the bonding strength of the glue dots is small, and it is difficult to form a high-strength bonding effect between the flat surface of the glue dots and the flat surface of the positive electrode plate.

[0177] From Figure 13 and Figure 14 it can be seen that there are no wrinkles at the interface of the negative electrode plate of the lithium-ion battery in Example 4 of the present application after full charge, while obvious wrinkles appear at the interface of the negative electrode plate of the lithium-ion battery of Comparative Example 1 after full charge.

[0178] The above has introduced in detail a separator, a battery, an energy storage device, and an electrical equipment including the separator disclosed in the present application. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the technical solution and the core inventive point of the embodiments of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A diaphragm, characterized in that: include: A base film and a dot-coated adhesive layer, wherein the dot-coated adhesive layer is disposed on at least one side surface of the base film, wherein: The glue dot layer includes a plurality of glue dots distributed in a dot matrix, the glue dots have a first annular structure, the distance between the outer edge of the first annular structure and the center of the glue dots is R1, the distance between the inner edge of the first annular structure and the center of the glue dots is R2, 0.15≤1-R2 / R1≤0.35; The dot-coated glue layer includes a polymer binder and an auxiliary agent, and the auxiliary agent includes at least one of a water-soluble coupling agent and a phosphate auxiliary agent.

2. The diaphragm according to claim 1, characterized in that The thickness compression ratio of the diaphragm is K, 5%≤K≤15%.

3. The diaphragm according to claim 1, characterized in that The average height of the first ring structure is H, 5 μm≤H≤15 μm.

4. The diaphragm according to claim 1, characterized in that The air permeability increase of the diaphragm is A, 5s / 100cc≤A≤20s / 100cc.

5. The diaphragm according to claim 1, characterized in that The ionic conductivity of the separator is σ, 1 mS / cm≤σ≤1.7 mS / cm.

6. The diaphragm according to claim 1, characterized in that The bonding strength between the separator and the positive electrode plate is 3N / m to 8N / m.

7. The diaphragm according to claim 1, characterized in that The diaphragm satisfies at least one of the following characteristics: a) the diameter of the glue dot is d, 200 μm≤d≤800 μm; b) Along the length direction of the glue layer, the distance between the centers of adjacent glue dots is D1, 200μm≤D1≤1200μm; c) Along the width direction of the glue layer, the distance between the centers of adjacent glue dots is D2, 200μm≤D2≤1200μm; d) the coverage of the point-coated glue layer on the base film is C1, 5%≤C1≤30%; e) The single-sided surface density of the point-coated glue layer is 0.3 g / m 2 ~0.8g / m 2 .

8. The diaphragm according to claim 1, characterized in that In the adhesive layer solution used to form the spot-coated adhesive layer, the mass percentage of the auxiliary agent is a, 0.1wt%≤a≤1wt%.

9. The diaphragm according to claim 1, characterized in that The water-soluble coupling agent includes at least one of polyvinyl alcohol, hydroxyethyl cellulose, fatty acid esters, carboxylates, lactates and cellulose esters; The phosphate additive includes at least one of sodium tripolyphosphate, trisodium phosphate, sodium pyrophosphate, sodium phosphite and sodium hexametaphosphate.

10. A battery, characterized in that: The invention comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator, wherein the separator is located between the positive electrode sheet and the negative electrode sheet, and the separator is the separator according to any one of claims 1 to 9.

11. The battery according to claim 10, characterized in that The surface of the positive electrode plate has a second annular structure, which is an annular mark formed after the glue spot is peeled off from the surface of the positive electrode plate, the distance between the outer edge of the second annular structure and the center of the annular mark is R3, and the distance between the inner edge of the second annular structure and the center of the annular mark is R4, 0.2≤1-R4 / R3≤0.

7.

12. The battery according to claim 10, characterized in that The effective bonding area coverage of the spot-coated glue layer on the positive electrode plate is C2, 2%≤C2≤20%.

13. The battery according to claim 12, characterized in that 8%≤(C2 / C1)×100%≤50%.

14. An energy storage device, characterized in that: The invention comprises a box and at least one battery according to any one of claims 10 to 13, wherein the battery is accommodated in the box.

15. An electrical equipment, characterized in that: It includes the energy storage device as described in claim 14, and the energy storage device supplies power to the electrical equipment.

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