A cold-pressed adhesive-coated diaphragm and its preparation method

Abstract

This invention provides a cold-pressed adhesive-coated separator and its preparation method, relating to the field of lithium battery technology. The cold-pressed adhesive-coated separator includes a separator substrate and an adhesive coating disposed on at least one surface of the separator substrate; the adhesive coating includes multiple discrete adhesive dots; each adhesive dot has a nested annular structure, including a central blank area, an inner ring area, and an outer ring area arranged sequentially from the inside out. The cold-pressed adhesive-coated separator, by setting an adhesive coating composed of multiple discrete nested annular adhesive dots on the substrate surface, perfectly balances high adhesion and low impedance. The central blank area directly constructs ion channels to significantly reduce internal resistance; the outer ring polyether component provides strong adhesion under room temperature cold pressing; and the inner ring polymer provides stable physical framework support. These three parts synergistically significantly improve overall performance.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and more specifically, to a cold-pressed adhesive-coated separator and its preparation method. Background Technology

[0002] Lithium-ion batteries, as a power technology with high energy density and long cycle life, have been widely used in modern electronic devices and new energy fields. A lithium-ion battery mainly consists of four core components: the positive electrode, the negative electrode, the separator, and the electrolyte. Among these, the separator, acting as a barrier between the positive and negative electrodes, must prevent direct contact between them, thus preventing short circuits, and must also ensure the smooth transport of lithium ions, playing a crucial role in the overall electrochemical and safety performance of the battery. Traditional separator substrates mostly use polyolefin materials, but their inherent characteristics are gradually revealing limitations in meeting the ever-increasing demands for higher-level battery performance.

[0003] To further improve the overall performance of separators, the industry commonly employs techniques such as adding functional coatings to the surface of the separator substrate, for example, introducing adhesive polymer coatings. These coatings aim to enhance the adhesion between the separator and the electrode, mitigating core deformation during charge-discharge cycles and thus extending battery life. Simultaneously, with the continuous iteration of battery manufacturing processes, in order to effectively reduce production energy consumption and improve manufacturing efficiency, the assembly and bonding methods between the separator and the electrode are gradually shifting from traditional high-temperature hot pressing to room-temperature cold pressing.

[0004] However, existing adhesive coating technologies face multiple challenges in addressing cold pressing processes and the demands for high ion conductivity. On one hand, conventional coating structures often exhibit high surface coverage; the large-area, dense coating inevitably clogs the original micropores of the separator, obstructing ion transport channels within the battery and leading to a sharp increase in internal resistance and a significant performance drop in later stages of cycling. On the other hand, conventional coating material systems struggle to simultaneously meet the dual requirements of mechanical framework support and room-temperature interfacial adhesion. Under room-temperature cold pressing conditions, the coating often fails to provide sufficient interfacial adhesion, resulting in poor adhesion between the separator and the electrode. Furthermore, conventional continuous coating or monolithic topcoat processes are insufficient in terms of coating uniformity, further deteriorating the consistency of separator permeability and impedance.

[0005] In summary, existing diaphragm coatings struggle to simultaneously achieve high interfacial adhesion and low impedance characteristics under cold-pressing assembly conditions, exhibiting inherent defects such as easy pore clogging, room-temperature adhesion failure, low ion conductivity, and poor coating uniformity. Achieving high-strength adhesion of the diaphragm during cold pressing without sacrificing permeability or increasing impedance is a pressing technical challenge in this field.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a cold-pressed adhesive-coated diaphragm and its preparation method. The cold-pressed adhesive-coated diaphragm utilizes a discrete ring-shaped nested morphology with a central blank space to reduce impedance, an outer ring of polyether to promote cold-pressing adhesion, and an inner ring of polymer to stabilize the skeleton, thus successfully achieving a perfect balance between high adhesion and low impedance characteristics under cold-pressing assembly.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a cold-pressed adhesive-coated diaphragm, comprising a diaphragm substrate and an adhesive coating disposed on at least one surface of the diaphragm substrate; the adhesive coating comprises a plurality of discrete adhesive dots. Each of the adhesive dots has a nested ring structure, which includes a central blank area, an inner ring area and an outer ring area arranged sequentially from the inside to the outside; The central blank area was not covered to expose the diaphragm substrate; The inner ring region contains PVDF-HFP type polymers and adhesive polymers; The outer ring region contains the adhesive polymer and the polyether compound.

[0009] In an optional implementation, the radius of the central blank area is 20 μm to 100 μm; and / or, The radius of the inner ring region is 50μm~200μm; and / or, The radius of the outer ring region is 60μm~250μm; and / or, The total radius of the adhesive dots is 60μm~400μm; and / or, The diameter of the central blank area accounts for 20% to 50% of the total diameter of the adhesive dots; and / or, The height of the inner ring region is 1μm~5μm; and / or, The height of the outer ring region is 0.2 μm to 2 μm; and / or, The height of the inner ring area is greater than the height of the outer ring area; and / or, The melting point of the PVDF-HFP polymer is 140℃~160℃; and / or, The glass transition temperature of the adhesive polymer is 0℃~80℃; and / or, The glass transition temperature of the polyether compound is 30℃~60℃; and / or, The PVDF-HFP polymer has a secondary particle size of 3 μm to 9 μm and a primary particle size of 150 nm to 500 nm; and / or, The adhesive polymer is composed of nano-sized particles.

[0010] In an optional embodiment, the PVDF-HFP polymer is selected from copolymers comprising VDF monomer units and HFP monomer units; optionally, the copolymer further comprises at least one of TrFE monomer units and CTFE monomer units; and / or, The adhesive polymer includes acrylate polymers and / or polyester polymers; preferably, the polyester polymer includes at least one of PBAT, PCL, PBS, and PLA; and / or, The polyether compound is selected from one or more of polyethylene glycol, polytetrahydrofuran, alkane polyether siloxane, and fatty alcohol polyoxyethylene ether.

[0011] In an optional embodiment, the inner and / or outer ring regions further contain additives; the additives include wetting agents and dispersants.

[0012] In an optional embodiment, the wetting agent comprises at least one selected from sodium dodecylbenzenesulfonate, fatty acid glycerides, alkane polyether siloxanes, and fatty alcohol polyoxyethylene ethers; and / or, The dispersant includes at least one of polyethylene glycol, polyvinylpyrrolidone, and polyvinyl alcohol; and / or, The coating film comprises 0.2 to 1 parts by weight of wetting agent and 0.1 to 2 parts by weight of dispersant, based on parts by weight.

[0013] In an optional embodiment, the cold-pressed adhesive-coated diaphragm satisfies at least one of the following properties: A. Cold pressing adhesion force ≥1N / m; B. Air permeability increase ≤30s / 100mL; C. Impedance ≤ 0.5Ω; D. Ionic conductivity ≥ 1 mS / cm.

[0014] In a second aspect, the present invention provides a method for preparing a cold-pressed adhesive-coated diaphragm as described in any of the foregoing embodiments, comprising: S1, mixing polymer powder, dispersant, adhesive, wetting agent and water to obtain a coating slurry; wherein, the polymer powder comprises PVDF-HFP type polymer; the adhesive comprises the adhesive polymer; the dispersant and / or wetting agent comprises polyether compound; S2, using a dot coating process, the coating slurry is uniformly arranged into multiple discrete adhesive dots on the surface of the diaphragm substrate; S3, the coated diaphragm substrate is dried in stages to separate and shape the components in the adhesive dots to form the central blank area, inner ring area and outer ring area; the staged drying includes first low temperature drying and then high temperature drying.

[0015] In an optional embodiment, step S1 specifically includes: mixing 60%~80% water, 10%~20% of the polymer powder, and 0.1%~2% of the dispersant by mass percentage until homogeneous, then adding 5%~15% of the adhesive and 0.1%~2% of the wetting agent and continuing mixing; and / or, The spacing between the adhesive dots is 200μm~800μm; and / or, The coating amount of the coating slurry is 0.2 g / m. 2 ~0.8g / m 2 ; and / or, The segmented drying specifically includes: first drying at 40℃~70℃ for 1s~3s, then drying at 80℃~100℃ for 1s~5s; and / or, The dot coating process specifically includes: transferring the coating slurry through a material box to an anilox roller, the anilox roller transferring the coating slurry to a flexographic roller with raised dots, and the flexographic roller regularly coating the coating slurry onto the diaphragm substrate through the raised dots on its surface.

[0016] Thirdly, the present invention provides a battery comprising a positive electrode, a negative electrode and an electrolyte, and a cold-pressed adhesive-coated separator as described in any of the foregoing embodiments disposed between the positive electrode and the negative electrode.

[0017] Fourthly, the present invention provides an electrical device including a battery as described in the foregoing embodiments.

[0018] Compared with existing technologies, the cold-pressed adhesive-coated separator provided by this invention effectively overcomes the inherent difficulty of simultaneously achieving high adhesion and low interfacial resistance at room temperature by setting an adhesive coating comprising multiple discrete adhesive dots on the substrate surface and utilizing the unique annular nested structure of the adhesive dots. The blank areas at the centers of each adhesive dot in the adhesive coating completely expose the original separator substrate; this unobstructed blank design directly constructs a wide lithium-ion direct channel. This spatial structure effectively avoids the micropore clogging problem caused by conventional large-area continuous coatings or solid dot coatings, significantly reducing interfacial ion transport resistance while maintaining the separator's excellent air permeability.

[0019] The outer and inner ring regions of the adhesive dots in the adhesive coating achieve synergistic optimization of physical morphology and chemical properties through differentiated component configuration. The outer ring region contains adhesive polymers and polyether compounds. Utilizing the physical properties of specific components, it can provide strong interfacial adhesion under room temperature cold pressing assembly conditions, effectively improving the initial bonding strength between the separator and the electrode, and greatly mitigating the deformation and misalignment of the electrode core during charge-discharge cycles.

[0020] The PVDF-HFP polymers and adhesive polymers contained in the inner ring region form a robust structural framework, ensuring the dimensional and morphological stability of the overall annular spots under pressure. The material differences from the inside out and the perfect coordination with the central ion channel achieve a comprehensive improvement in electrochemical performance, including high-strength adhesion under cold pressing, high air permeability, and extremely low internal resistance. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a top SEM view of the adhesive dots of the cold-pressed adhesive-coated diaphragm provided in Embodiment 1 of this application; Figure 2 This is a top SEM view of the adhesive dots of the cold-pressed adhesive-coated diaphragm provided in Embodiment 4 of this application; Figure 3 This is a SEM image of polymer particles anchored at the edge of micropores in the substrate, as shown in Example 1. Figure 4 An optical microscope image of the distribution of the adhesive dot array provided in Comparative Example 1 of this application; Figure 5 for Figure 4 The corresponding shape recognition contour map; Figure 6 This is a pseudo-color image of the three-dimensional morphology of a single adhesive dot provided in Embodiment 1 of this application; Figure 7 The height distribution curve of the adhesive dots along the radial section of Example 1 is shown in Figure A (Figure A is the height distribution curve of the adhesive dots along the radial section of Example 1, and Figure B is the height profile curve of the section). Detailed Implementation

[0023] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0024] This application provides a cold-pressed adhesive-coated diaphragm, including a diaphragm substrate and an adhesive coating disposed on at least one surface of the diaphragm substrate; the adhesive coating includes a plurality of discrete adhesive dots.

[0025] The cold-pressed adhesive-coated diaphragm provided in this application uses discretely distributed adhesive dots instead of the traditional continuous dense surface coating, which can effectively reduce the excessive coverage of micropores on the surface of the diaphragm substrate, thereby ensuring the excellent air permeability of the diaphragm on a macroscopic level.

[0026] Each adhesive dot exhibits a unique three-dimensional microstructure, namely a nested ring structure, comprising a central blank area, an inner ring area, and an outer ring area arranged sequentially from the inside out. The inner ring area contains PVDF-HFP type polymers and adhesive polymers; the outer ring area contains the adhesive polymers and polyether compounds.

[0027] Specifically, the phrase "the central blank area is not covered to expose the separator substrate" as described in this application refers to the fact that the central blank area is essentially not covered by a continuous polymer coating, thus exposing the original microporous structure of the separator substrate within this area. This central blank area, after the separator is bonded to the positive and negative electrodes, provides an unobstructed direct channel for lithium-ion transport. This structure significantly shortens the ion transport path, effectively avoiding the pore blockage problem easily caused by conventional coatings, thereby significantly reducing the battery's internal resistance and interface impedance. It should be noted that, due to the limitations of the actual fluid coating and drying physical process, the central blank area may contain scattered isolated polymer particles, mainly composed of PVDF-HFP type polymers; as long as these do not form a continuous obstruction, they fall within the protection scope of "not covered" as described in this application, and these scattered particles have no significant impact on the ion transport of the separator.

[0028] The inner ring region surrounds the central blank region, and the main components of the inner ring region include PVDF-HFP polymers and adhesive polymers. The PVDF-HFP polymers have high melting points and mechanical strength, and mainly play a role in providing a robust physical framework support in the coating structure. This ensures that the adhesive dots maintain their morphology and high stability when subjected to electrode assembly pressure, preventing the coating from being excessively crushed.

[0029] The outer ring region surrounds the inner ring region and is located at the outermost edge of the adhesive dot. The main components of the outer ring region include the adhesive polymer and polyether compounds. The polyether compounds have a low glass transition temperature, which endows the outer ring region with excellent flexibility and initial tack at room temperature. This allows the cold-pressed adhesive-coated separator to generate strong interfacial adhesion with the electrode under room temperature cold-press assembly conditions, effectively suppressing electrode core deformation during battery cycling.

[0030] The formation mechanism of the above-mentioned ring-shaped nested structure and its component distribution is as follows: After the coating slurry is dotted onto the surface of the diaphragm substrate to form droplets, it enters the drying and film-forming stage. Substances that reduce surface tension (such as surface-active polyether compounds) are added to the coating slurry, driving the droplets to spontaneously spread outwards at the solid-liquid interface of the diaphragm. During this process, significant Brownian motion occurs within the system. Due to the particle size differences within the slurry, PVDF-HFP polymer particles with larger aggregate sizes (e.g., micrometer-level) diffuse more slowly and have poorer flowability, mainly settling and aggregating in the inner ring region of the droplets, solidifying to form the inner ring region. Meanwhile, components composed of adhesive polymers and polyether compounds have extremely small particle sizes (e.g., nanometer-level), exhibiting intense Brownian motion and extremely rapid diffusion. They spread rapidly towards the outermost edge of the liquid and solidify after solvent evaporation, forming the outer ring region. Simultaneously, under the combined effects of surface tension and phase separation, the material in the center region of the droplets migrates and is evacuated, ultimately forming the central blank area that almost completely exposes the substrate. Through the synergistic effect of inner ring support, outer ring bonding, and central conduction, this embodiment perfectly solves the technical problem of balancing high bonding strength and low impedance at room temperature.

[0031] Because of the large physical gaps between the micron-sized PVDF-HFP polymer particles dispersed within the slurry, a loose microstructure is formed. This allows water, as well as nano-sized adhesive polymers and polyether compounds dissolved in water, to pass smoothly through the pores between the large particles. Based on this, the difference in Brownian motion rate caused by the particle size difference is used to achieve precise phase separation of the components.

[0032] The cold-pressed adhesive-coated separator overcomes the challenge of simultaneously achieving high adhesion and low impedance by constructing a discrete, nested annular structure on the substrate surface, comprising a central blank area, an inner ring area, and an outer ring area. The central blank area directly exposes the substrate, creating an unobstructed lithium-ion channel that effectively prevents pore blockage and significantly reduces internal resistance. The outer ring area utilizes polyether compounds to provide strong interfacial adhesion under room-temperature cold pressing, ensuring efficient bonding with the electrode. The PVDF-HFP polymer in the inner ring area provides robust skeletal support, maintaining structural stability. The synergistic combination of the structural morphology and specific materials in each region achieves excellent comprehensive electrochemical performance characterized by high adhesion, high permeability, and low impedance under cold pressing.

[0033] In a preferred embodiment, the three-dimensional morphology and thermodynamic properties of multiple discrete adhesive dots distributed on the surface of the diaphragm substrate are precisely designed using physical and chemical methods to optimize the balance between air permeability and cold-pressing adhesion.

[0034] In some embodiments, the radius of the central blank area is 20 μm to 100 μm. For example, it can be 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, etc.

[0035] In some embodiments, the radius of the inner ring region is 50 μm to 200 μm. For example, it can be 50 μm, 60 μm, 80 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm, etc.

[0036] In some embodiments, the radius of the outer ring region is 60μm to 250μm. For example, it can be 60μm, 80μm, 100μm, 160μm, 180μm, 200μm, 220μm, 240μm, 250μm, etc.

[0037] In some embodiments, the total radius of the adhesive dots is 60 μm to 400 μm. For example, it can be 60 μm, 80 μm, 100 μm, 200 μm, 250 μm, 300 μm, 320 μm, 350 μm, 400 μm, etc.

[0038] In some implementations, the radius of the central blank area accounts for 20% to 50% of the total radius of the adhesive dots. For example, it can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.

[0039] From a microscopic planar perspective, the radius of the central blank area is controlled between 20 μm and 100 μm, the radius of the inner ring area is 50 μm to 200 μm, and the radius of the outer ring area is 60 μm to 250 μm. The total radius of the resulting adhesive dots falls within the range of 60 μm to 400 μm. In this structure, the radius of the central blank area accounts for 20% to 50% of the total radius of the adhesive dots. By maintaining this proportion, not only can sufficient unobstructed channels be provided for lithium-ion shuttle to effectively reduce impedance, but the annular coating also ensures a sufficiently large bottom area for contact with the electrode sheet, thereby maintaining high overall interfacial adhesion.

[0040] In some embodiments, the height of the inner ring region is 1 μm to 5 μm. For example, it can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc.

[0041] In some embodiments, the height of the outer ring region is 0.2 μm to 2 μm. For example, it can be 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, etc.

[0042] In some implementations, the height of the inner ring region is greater than the height of the outer ring region.

[0043] From a longitudinal three-dimensional perspective, the height of the inner ring region is 1μm to 5μm, while the height of the outer ring region is significantly lower than that of the inner ring region, ranging from 0.2μm to 2μm. This stepped height difference design allows the inner ring region to act as the main load-bearing framework during the battery cold-pressing assembly process, resisting external pressure to maintain the three-dimensional shape of the adhesive dots; the thinner outer ring region acts as a flexible interface, spreading outwards with slight deformation under pressure to tightly adhere to the microscopic unevenness of the electrode sheet.

[0044] In some embodiments, the melting point of the PVDF-HFP polymer is 140°C to 160°C. For example, it can be 140°C, 142°C, 145°C, 148°C, 150°C, 152°C, 155°C, 158°C, 160°C, etc.

[0045] In some embodiments, the glass transition temperature of the adhesive polymer is 0°C to 80°C. For example, it can be 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, etc.

[0046] In some embodiments, the glass transition temperature of the polyether compound is 30°C to 60°C. For example, it can be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, etc.

[0047] In some embodiments, the secondary particle size of the PVDF-HFP polymer is 3μm to 9μm, and its primary particle size is 150nm to 500nm. The secondary particle size can be 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, etc. The primary particle size can be 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, etc.

[0048] In the embodiments of this application, the PVDF-HFP polymer exhibits a specific multi-level morphology in the slurry system. Specifically, the PVDF-HFP polymer is formed by the agglomeration of primary particles with a particle size in the range of 150 nm to 500 nm to form secondary particles with a particle size in the range of 3 μm to 9 μm.

[0049] This multi-level structure makes a significant technological contribution to the formation of the morphology: on the one hand, the micron-sized secondary particles have a small diffusion coefficient in the slurry droplets and can be stably deposited in the off-center region during the drying process to build a tough inner ring framework; on the other hand, the nano-sized primary particles endow the inner ring region with an extremely high specific surface area, which is beneficial to enhancing the van der Waals forces between the inner ring and the substrate and adjacent components.

[0050] In contrast, the adhesive polymer exists as monodisperse nanoparticles. During the drying stage, the micron-sized PVDF-HFP secondary particles 'lag' and remain in the inner ring due to their slow Brownian motion, while the nanoscale adhesive polymer diffuses rapidly to the outer ring with the liquid flow. This significant rate difference between the 'micron-sized secondary particles' and the 'nanoscale monodisperse particles' is the underlying physical driving force behind the spontaneous generation of the central blank area and the double-ring nested structure.

[0051] In some embodiments, the adhesive polymer is nanoscale particles.

[0052] Regarding the selection of thermodynamic properties and material morphology, the PVDF-HFP polymers constituting the framework have melting points between 140℃ and 160℃ and exist in the form of micron-sized particles; the adhesive polymers providing bonding force have glass transition temperatures between 0℃ and 80℃ and are nano-sized particles; and the polyether compounds have glass transition temperatures between 30℃ and 60℃. On one hand, the combination of micron-sized and nano-sized particles utilizes the significant difference in their Brownian diffusion rates in fluids, driving the nanoparticles to rapidly spread outwards during the slurry drying stage, thus spontaneously forming the aforementioned unique morphology of inner and outer double-ring differentiation. On the other hand, the low glass transition temperature material endows the outer ring region with excellent room temperature flexibility and initial tack, meeting the requirements of advanced cold-pressing processes; while the high melting point inner ring material ensures that the separator does not experience thermal shrinkage failure during battery operation, exhibiting extremely high thermal dimensional stability.

[0053] In a preferred embodiment, in order to achieve high-strength adhesion of the cold-pressed adhesive-coated diaphragm at room temperature and structural stability under pressure, this application has carried out a specific compounding design for the polymer system in the adhesive dots.

[0054] In some embodiments, the PVDF-HFP polymer is selected from copolymers comprising VDF monomer units and HFP monomer units; optionally, the copolymer further comprises at least one of TrFE monomer units and CTFE monomer units.

[0055] Specifically, the PVDF-HFP polymer that constitutes the physical framework of the inner ring region is a copolymer composed of at least vinylidene fluoride (VDF) monomer units and hexafluoropropylene (HFP) monomer units. Optionally, the copolymer may further copolymerize monomer units such as trifluoroethylene (TrFE) and trifluorochloroethylene (CTFE).

[0056] In this application, the introduction of HFP monomer units makes a core contribution to achieving interfacial cold-press bonding. Pure polyvinylidene fluoride (PVDF), due to its high molecular chain regularity and crystallinity, exhibits high hardness and brittleness at room temperature, making it difficult to achieve sufficient wetting and adhesion with the electrode without heating. By copolymerizing HFP monomers, the regularity of the molecular chains can be effectively disrupted and the crystallinity reduced, endowing the polymer with excellent flexibility and initial tack under room-temperature cold-pressing conditions. This ensures that the diaphragm and electrode possess strong interfacial bonding strength immediately after assembly at room temperature.

[0057] In some embodiments, the adhesive polymer includes acrylate polymers and / or polyester polymers; preferably, the polyester polymer includes at least one of PBAT (polybutylene terephthalate), PCL (polycaprolactone), PBS (polybutylene succinate), and PLA (polylactic acid). The abundant polar groups such as ester groups in the molecular chains of these polymers not only firmly anchor the fluorinated polymer particles in the inner ring region to the surface of the membrane substrate, but also provide good basic adhesion at the interface.

[0058] Furthermore, the core component endowing the outer ring region with excellent room-temperature cold-pressing adhesion performance—the polyether compound—is specifically selected from one or more of polyethylene glycol, polytetrahydrofuran, alkane polyether siloxane, and fatty alcohol polyoxyethylene ether. On one hand, these compounds contain a large number of flexible ether bonds or highly active polar groups such as hydroxyl groups, and their molecular chains have extremely high degrees of freedom of movement at room temperature, enabling them to quickly wet the electrode surface and form a dense hydrogen bond network, thereby achieving extremely high initial interfacial adhesion during the cold-pressing process. On the other hand, these compounds also exhibit excellent surface wetting activity in the coating slurry, significantly reducing the surface tension of droplets. In the initial stage of drying and film formation, they drive the internal nanoscale adhesive resin particles to rapidly diffuse and spread outwards, thus spontaneously promoting the smooth formation of the central blank area and the outer ring region. Through the synergistic combination of the rigid fluorinated skeleton, polar adhesive matrix, and highly active polyether material, the coated diaphragm of this embodiment achieves the best balance between cold-pressing assembly and low interfacial impedance in terms of physicochemical properties.

[0059] To ensure that the aforementioned discretely distributed annular nested adhesive dots can spontaneously and accurately form, the inner and / or outer ring regions of this embodiment also specifically contain trace amounts of functional additives, which consist of wetting agents and dispersants.

[0060] In some embodiments, the wetting agent includes at least one of sodium dodecylbenzenesulfonate, fatty acid glycerides, alkane polyether siloxanes, and fatty alcohol polyoxyethylene ethers.

[0061] In the microscopic physical process of slurry drying and film formation, these surface-active substances significantly reduce the surface tension of the liquid through directional adsorption at the liquid-solid interface. This change in tension gradient provides a strong spontaneous spreading force for the droplets, driving the slurry to spread outward. It is the core macroscopic driving force that promotes the migration and evacuation of material in the central region (to form a central blank area) and pulls nanoscale components to the outermost edge (to form an outer ring region).

[0062] In some embodiments, the dispersant includes at least one of polyethylene glycol, polyvinylpyrrolidone, and polyvinyl alcohol.

[0063] These compounds, rich in polar groups, can be firmly adsorbed onto the surface of various polymer microparticles, preventing the aggregation of micron-sized and nano-sized particles through steric hindrance. They maintain excellent suspension stability within the slurry, ensuring that microparticles of different sizes remain independent, thus achieving perfect spontaneous phase separation under Brownian motion, strictly following the rule that "the smaller the particle size, the faster the diffusion."

[0064] In some embodiments, the adhesive dots comprise, by weight, 0.2 to 1 part of a wetting agent (e.g., 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, 1, etc.) and 0.1 to 2 parts of a dispersant (e.g., 0.1, 0.3, 0.5, 0.7, 1, 1.2, 1.5, 1.7, 1.9, 2, etc.).

[0065] By limiting the amount of wetting agent and dispersant to the above-mentioned trace range, sufficient spreading power and suspension stability can be provided to form a perfect inner and outer double-ring nested structure, while avoiding the shielding effect of excessive additive residue on cold pressing adhesion or the introduction of impurities to the internal electrochemical environment of the battery, thus achieving a perfect synergy between three-dimensional morphology control and interfacial electrochemical performance.

[0066] Based on the above-mentioned special annular nested adhesive dot morphology and composition design, the cold-pressed adhesive-coated diaphragm provided in this embodiment achieves an excellent balance between macroscopic physical and mechanical properties and microscopic electrochemical properties, successfully overcoming the inherent technical defect that traditional continuous coating or solid dot coating structures inevitably lead to impedance increase when improving adhesion.

[0067] In some embodiments, the cold-pressed adhesive-coated diaphragm satisfies at least one of the following properties: A. Cold pressing adhesion force ≥1N / m; B. Air permeability increase ≤30s / 100mL; C. Impedance ≤ 0.5Ω; D. Ionic conductivity ≥ 1 mS / cm.

[0068] Specifically, the cold-pressed adhesive-coated diaphragm exhibits excellent interfacial affinity under room temperature assembly conditions, with a cold-pressing adhesion strength ≥1 N / m. This high-strength adhesion is mainly attributed to the low glass transition temperature materials (such as polyether compounds and nanoscale adhesive resins) enriched in the outer ring region of the adhesive dots. These materials can rapidly generate strong intermolecular forces with the electrode surface during room temperature cold pressing without the need for additional heat sources, ensuring the structural stability of the electrode core during long-cycle processes and preventing deformation and misalignment.

[0069] Meanwhile, thanks to the discrete distribution pattern and the design of blank areas not covered at the center of the adhesive dots, the original micropores of the substrate are preserved to the maximum extent, and the increase in gas permeability is strictly controlled within the range of ≤30s / 100mL. This design of unobstructed ion-passing channels minimizes the physical steric hindrance faced by lithium ions during their penetration of the separator interface. Reflected in electrochemical indicators, the interface impedance of this coated separator is ≤0.5Ω, and the ionic conductivity reaches ≥1mS / cm. The extremely low impedance and high ion transport rate significantly reduce internal resistance polarization and heat accumulation during battery operation, which not only greatly improves the high-rate charge and discharge capability of the battery, but also effectively improves the performance degradation problem at the end of the battery cycle, achieving a perfect synergy between high-strength adhesion and low-resistance conduction.

[0070] This embodiment also provides a method for preparing the above-mentioned cold-pressed adhesive-coated separator. This method aims to induce the spontaneous formation of a microscopic double-ring nested structure in the polymer through a single coating and a specific thermodynamic drying field. Specifically, the preparation method includes the following steps: S1, Prepare an aqueous coating slurry: Mix polymer powder, dispersant, adhesive, wetting agent and water to obtain a coating slurry; wherein, the polymer powder contains PVDF-HFP type polymer (as a source of the inner ring skeleton); the adhesive contains the adhesive polymer (as a source of the basic bonding matrix); the dispersant and / or wetting agent contains polyether compound (as a source of the outer ring highly active initial tack component).

[0071] During the mixing process, the dispersant adsorbs onto the surface of each solid particle, providing steric hindrance and preventing component agglomeration; the wetting agent dissolves in the aqueous phase, significantly reducing the surface tension of the coating slurry system, providing a hydrodynamic basis for the subsequent spontaneous spreading of the slurry on the diaphragm substrate.

[0072] S2, Discrete dot coating of adhesive dots: The coating slurry is uniformly arranged into multiple discrete adhesive dots on the surface of the diaphragm substrate using a dot coating process.

[0073] In this step, a point-to-point, quantitative discontinuous transfer coating process ensures that the slurry droplets are arrayed on the separator surface, maintaining sufficient safety spacing between adjacent droplets to prevent cross-linking and fusion. This process preserves a large number of exposed micropores on the separator substrate from a physical source, which is crucial to avoiding a sharp increase in battery internal resistance caused by conventional surface coating processes. In actual production implementation, the point coating process can achieve efficient and uniform droplet transfer using a flexographic roller with a regularly convex dot structure.

[0074] S3, Segmented gradient drying and shaping: The coated diaphragm substrate is dried in segments to separate and shape the components in the adhesive dots, thereby forming the central blank area, inner ring area and outer ring area; the segmented drying includes first low-temperature drying and then high-temperature drying.

[0075] This step is the core of achieving a specific three-dimensional morphology. The segmented drying must strictly follow the temperature gradient rule of "drying at low temperature first, then drying at high temperature".

[0076] The microscopic mechanism is as follows: In the initial low-temperature drying stage, due to the moderate ambient temperature, the water in the slurry droplets does not undergo instantaneous boiling and evaporation, thus providing sufficient time for the Brownian motion of the particles within the system. Within this time window, the surface tension within the system is broken by the wetting agent, causing the droplets to spontaneously spread outward at the solid-liquid interface. Large gaps exist between the micron-sized PVDF-HFP polymer particles dispersed within the slurry, allowing the liquid and nanoparticles to move relatively easily through these gaps. Therefore, based on the physical law of Brownian motion that 'the smaller the particle size, the faster the diffusion rate,' the nano-sized adhesive polymers and polyether compounds in the slurry can smoothly pass through the gaps between the large particles and rapidly spread towards the outermost edge with the liquid flow; while the micron-sized PVDF-HFP polymer powder moves slowly, mainly settling towards the outer edge of the center; simultaneously, the material at the geometric center of the droplet is pulled outward by surface tension. Thus, the initial phase separation of the inner and outer rings is achieved in the low-temperature stage, leaving a central void.

[0077] The system then enters a high-temperature drying stage. The high temperature field causes the residual moisture in the system to evaporate rapidly and instantly, interrupting the Brownian motion trajectory of the particles and instantly "freezing" the morphology formed in the low-temperature stage. At the same time, the high temperature promotes the physical cross-linking and curing of the PVDF-HFP polymer deposited in the inner ring, forming a ring-shaped load-bearing skeleton with excellent mechanical strength. Through the above two-step thermodynamic control of low-temperature empowered diffusion followed by high-temperature locking and molding, a perfect nested structure with rigid inner ring support, flexible outer ring bonding, and direct central ion flow is spontaneously constructed within a single adhesive dot.

[0078] In order to achieve the aforementioned special annular nested adhesive dot morphology, this embodiment has carried out a precise and coordinated design of the coating slurry preparation process, mechanical transfer method, and thermodynamic drying parameters.

[0079] In some embodiments, step S1 specifically includes: mixing 60% to 80% water, 10% to 20% of the polymer powder and 0.1% to 2% of the dispersant by mass percentage, and then adding 5% to 15% of the adhesive and 0.1% to 2% of the wetting agent and continuing to mix.

[0080] For "60%~80% water", for example, it can be 60%, 62%, 65%, 68%, 70%, 72%, 75%, 77%, 78%, 80%, etc. For "10%~20% polymer powder", for example, it can be 10%, 11%, 12%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc. For "0.1%~2% dispersant", for example, it can be 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.7%, 1.9%, 2%, etc. For "5%~15% adhesive", for example, it can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 15%, etc. For "0.1%~2% wetting agent", for example, it can be 0.1%, 0.2%, 0.5%, 0.7%, 1%, 1.2%, 1.5%, 1.7%, 1.9%, 2%, etc.

[0081] In the preparation stage of the coating slurry (step S1), this embodiment employs a two-step mixing process to ensure the microscopic stability of the multiphase suspension system. Specifically, by mass percentage, water, the polymer powder, and the dispersant are first added to a stirring device for premixing and slurrying. During this stage, trace amounts of dispersant can fully adsorb onto the surface of the micron-sized polymer powder, forming a steric hindrance protective layer to prevent sedimentation and agglomeration. After the system is uniformly mixed, the adhesive and the wetting agent are added and mixing continues. Adding the surface-active wetting agent in the second stage effectively avoids excessive bubble formation during initial high-shear dispersion and also prevents abnormal encapsulation of undispersed powder by nano-sized adhesive macromolecules.

[0082] In some embodiments, the spacing between the adhesive dots is 200μm to 800μm. For example, it can be 200μm, 250μm, 300μm, 400μm, 500μm, 600μm, 650μm, 700μm, 750μm, 800μm, etc.

[0083] In some embodiments, the coating amount of the coating slurry is 0.2 g / m³. 2 ~0.8g / m 2 For example, it could be 0.2 g / m³. 2 0.25g / m2 0.3g / m 2 0.4g / m 2 0.5g / m 2 0.6g / m 2 0.65g / m 2 0.7g / m 2 0.75g / m 2 0.8g / m 2 etc.

[0084] In the transfer stage of the slurry to the diaphragm surface (step S2), to precisely control the macroscopic distribution and microscopic amount of adhesive dots, this embodiment employs a precision printing process using an anilox roller and a flexographic roller. The operation path is as follows: First, the prepared coating slurry is injected into the material box. A fixed volume of slurry is drawn from the material box by the regular cells on the surface of the rotating anilox roller and metered by a doctor blade. Subsequently, the anilox roller precisely transfers the slurry from the cells to the flexographic roller with raised dots in contact with it. Finally, the elastic flexographic roller, through its array of raised dots, regularly presses and coats the tiny droplets onto the diaphragm substrate. Through this specific mechanical transfer structure, this embodiment strictly controls the single-sided coating amount of the coating slurry to 0.2 g / m². 2 ~0.8g / m 2 The center-to-center spacing of each adhesive dot was set between 200μm and 800μm. This ensures that there is sufficient uncoated area on a macroscopic scale to maintain high air permeability, while also preventing the droplets from merging and connecting due to excessively close spacing on a microscopic scale.

[0085] In some embodiments, the segmented drying specifically includes: first drying at 40℃~70℃ for 1s~3s, and then drying at 80℃~100℃ for 1s~5s.

[0086] For "drying at 40℃~70℃", for example, it could be 40℃, 42℃, 45℃, 50℃, 55℃, 60℃, 62℃, 65℃, 68℃, 70℃, etc. For "drying for 1s~3s", for example, it could be 1s, 1.2s, 1.5s, 1.8s, 2s, 2.2s, 2.5s, 2.7s, 2.9s, 3s, etc. For "further drying at 80℃~100℃", for example, it could be 80℃, 82℃, 85℃, 88℃, 90℃, 92℃, 95℃, 97℃, 99℃, 100℃, etc. For "drying for 1s~5s", for example, it could be 1s, 1.5s, 2s, 2.5s, 3s, 3.5s, 4s, 4.5s, 4.8s, 5s, etc.

[0087] In the segmented drying stage (step S3) that determines the microstructure, this embodiment constructs a continuous non-isothermal drying field with a clear gradient. Specifically, the segmented drying includes first performing low-temperature drying at 40℃~70℃ for 1s~3s, followed by high-temperature drying at 80℃~100℃ for 1s~5s. In this process design, the low-temperature thermal field in the first stage provides a mild evaporation environment for the slurry system, allowing the internal nano-sized particles (adhesives and polyether wetting agents) and micron-sized large particles (polymer powders) to spontaneously complete phase separation and migration towards the inner and outer edges within the time window before the droplets completely lose their fluidity, thanks to the significant difference in their Brownian motion rates, accompanied by the contraction and evacuation of the liquid in the central region; the high-temperature thermal field in the second stage is responsible for instantly evaporating the remaining moisture to stop molecular motion, instantly freezing the formed double-ring nested morphology, and promoting the micro-melting and solidification of the inner skeleton polymer. The perfect combination of the above coating and drying processes ultimately endows the diaphragm product with both excellent air permeability and high adhesion during cold pressing.

[0088] In some embodiments, the dot coating process specifically includes: transferring the coating slurry through a hopper to an anilox roller, the anilox roller transferring the coating slurry to a flexographic roller with raised dots, and the flexographic roller regularly coating the coating slurry onto the diaphragm substrate through the raised dots on its surface.

[0089] This application also provides a battery comprising a positive electrode, a negative electrode, and an electrolyte, and a cold-pressed adhesive-coated separator as described in any of the foregoing embodiments, disposed between the positive electrode and the negative electrode.

[0090] The battery provided in this application mainly consists of four core components: a positive electrode, a negative electrode, an electrolyte, and a cold-pressed adhesive-coated separator placed between the positive and negative electrodes. The positive and negative electrodes serve as active carriers for the electrochemical reaction, the electrolyte is responsible for conducting ions between the two electrodes, and the aforementioned coated separator with a discrete double-ring nested morphology not only physically isolates the positive and negative electrodes to prevent internal short circuits, but also ensures unimpeded ion transport and effectively suppresses core deformation and misalignment during long charge-discharge cycles due to its extremely low interfacial impedance and excellent room-temperature cold-pressing adhesion. Depending on the internal chemical system and packaging form, the specific type of this battery can be very broad, including but not limited to conventional liquid lithium-ion batteries, lithium polymer batteries, sodium-ion batteries, potassium-ion batteries, semi-solid-state batteries, and any other rechargeable batteries that rely on the cold-pressing bonding of the separator and electrodes.

[0091] This application also provides an electrical device, including the battery as described in the foregoing embodiments.

[0092] The electrical device provided in this application is equipped with the aforementioned battery, which possesses high safety and low internal resistance characteristics, and uses this battery as the core power source, working power supply, or backup energy storage unit. Thanks to the high stability of the internal cell structure and excellent ion conduction efficiency, the device as a whole achieves superior, safer, and longer electrochemical operating life and battery life performance. The specific form and application field of this electrical device are not particularly limited, and it can include, but is not limited to, portable consumer electronic devices such as smartphones, tablets, laptops, smartwatches, and digital cameras; it can also cover new energy transportation power tools such as electric bicycles, electric scooters, battery electric vehicles (BEVs), and plug-in hybrid electric vehicles (PHEVs); furthermore, it can be widely used in large or small-to-medium-sized energy storage electrical equipment such as drones, handheld power tools, smart home cleaning equipment, and wind and solar power peak-shaving base stations and portable outdoor power supplies for homes.

[0093] The present invention will be further illustrated below with specific embodiments. However, it should be understood that these embodiments are merely for the purpose of more detailed illustration and should not be construed as limiting the present invention in any way.

[0094] Example 1 This embodiment provides a cold-pressed adhesive-coated diaphragm prepared using a dot coating process and a specific segmented drying process, which serves as the preferred option for evaluating various parameters in this application.

[0095] Preparation method: (1) Slurry preparation: By mass percentage, first add 74% water, 15% PVDF powder (micron-sized PVDF-HFP copolymer, melting point between 148~154℃, primary particle size D50 of 200nm, secondary particle size of 3-9 microns) and 0.5% dispersant (polyvinylpyrrolidone) for the first mixing; after stirring evenly, add 10% adhesive (water-based nano-sized acrylic emulsion adhesive) and 0.5% wetting agent (alkane polyether siloxane type) for the second mixing to obtain the coating slurry.

[0096] (2) Spot coating: Control the coating amount of the coating slurry to be 0.2±0.1g / m 2 The process employs a dot coating technique (applying slurry to the base film via a flexographic roller with regularly arranged raised dots, transferring the slurry through a material box to an anilox roller, and then to a flexographic roller with raised dots for printing), forming adhesive dots on the surface of the diaphragm substrate. The center-to-center spacing of the adhesive dots is controlled at 400μm.

[0097] (3) Segmented drying: The drying process of first low temperature and then high temperature is adopted. Specifically, the drying is first at 40℃ for 3s and then at 80℃ for 2s, so that the components in the glue dots are separated and shaped to form a three-dimensional structured coating with a central blank area, an inner ring area and an outer ring area.

[0098] Examples 2 to 7: Investigation of wetting agent dosage This example group mainly investigated the effects of different wetting agent dosages in the coating slurry on the micro-size of the adhesive dots (especially the degree of outer ring diffusion) and macroscopic electrochemical performance.

[0099] Preparation method: The preparation methods of Examples 2 to 7 are basically the same as those of Example 1, except that the mass percentage of wetting agent added during the second mixing in step (1) is different.

[0100] Specifically: In Example 2, the wetting agent dosage was 0.1%, and the water dosage was 74.4%. In Example 3, the wetting agent dosage was 0.3%, and the water dosage was 74.2%. In Example 4, the wetting agent dosage was 0.7%, and the water dosage was 73.8%. In Example 5, the wetting agent dosage was 1.0%, and the water dosage was 73.5%. In Example 6, the wetting agent dosage was 1.5%, and the water dosage was 73%. In Example 7, the amount of wetting agent was 2.0% and the amount of water was 72.5%.

[0101] All other conditions remain completely consistent with those in Example 1.

[0102] Examples 8 to 10: Investigation of drying temperature curves This example group mainly investigated the effects of different thermodynamic drying processes on the microstructure (inner and outer ring widths) and final properties of the adhesive dots.

[0103] Preparation method: The preparation methods of Examples 8 to 10 are basically the same as those of Example 1. The slurry formulation and coating process are consistent. The only difference is the drying temperature and time curve of step (3).

[0104] Specifically: Example 8: Change the baking temperature curve to "high temperature first, then low temperature", that is, first dry at 80℃ for 3 seconds, then dry at 40℃ for 2 seconds.

[0105] Example 9: Change the baking temperature to "single-stage high temperature throughout", that is, dry directly at 80°C for 5 seconds.

[0106] Example 10: Change the baking temperature to "single-stage low temperature throughout", that is, dry directly at 40°C for 5 seconds.

[0107] Examples 11 to 12: Boundary Investigation of Polymer Powder to Adhesive Ratio This example group mainly investigated the influence of the ratio of polymer powder (main skeleton material) and adhesive (bonding matrix) in the coating slurry on the morphology and final macroscopic properties of the coating under the upper and lower limits of the protection range.

[0108] Preparation method: The preparation methods of Examples 11 and 12 are basically the same as those of Example 1, the only difference being the different mass percentages of polymer powder and adhesive added in step (1).

[0109] Specifically: Example 11 (Testing the lower limit of polymer powder + the upper limit of adhesive): The amount of polymer powder is 10%, and the amount of adhesive is 15% (the slurry composition is: 74% water, 10% PVDF powder, 0.5% dispersant, 15% adhesive and 0.5% wetting agent).

[0110] Example 12 (Testing the upper limit of polymer powder + lower limit of adhesive): The amount of polymer powder is 20%, and the amount of adhesive is 5% (the slurry composition is: 74% water, 20% PVDF powder, 0.5% dispersant, 5% adhesive and 0.5% wetting agent).

[0111] The remaining coating and drying conditions were exactly the same as in Example 1.

[0112] Comparative Examples 1 to 2: Investigation of Coating Process This comparative group mainly investigated the impact of non-dot coating process on the macroscopic properties of the diaphragm.

[0113] Preparation method: The slurry preparation methods of Comparative Examples 1 and 2 are completely consistent with those of Example 1, with the main difference being the coating process.

[0114] Comparative Example 1: Coating was performed by spraying (using the centrifugal force generated by a high-speed rotating turntable to atomize the slurry and throw it onto the surface of the base film), and the remaining drying conditions were the same as in Example 1.

[0115] Comparative Example 2: Full-coverage coating was performed using a traditional continuous roller coating method, with the remaining drying conditions the same as in Example 1.

[0116] Comparative Example 3: The preparation method is basically the same as that of Example 1, except that no wetting agent is added during the second mixing in step (1) (the components are 74.5% water, 15% PVDF powder, 0.5% dispersant and 10% adhesive).

[0117] Comparative Example 4: The preparation method is basically the same as that of Example 1, except that PVDF (components are 74% water, 0.5% dispersant, 0.5% wetting agent and 25% adhesive) is not added during the first mixing in step (1).

[0118] Comparative Example 5: The preparation method is basically the same as that of Example 1, except that in step (1) slurry preparation, "PVDF powder (micron-sized PVDF-HFP copolymer)" is replaced with "pure PVDF powder (without hexafluoropropylene HFP monomer units)" in equal amounts. The melting point (approximately 165~172℃), primary particle size, and secondary particle size of the pure PVDF powder are all consistent with those of the PVDF powder described in Example 1. The remaining coating amount, dot coating process, and segmented drying conditions are exactly the same as those in Example 1.

[0119] Test Experiment 1. Testing method: (1) For the cold-pressed adhesive-coated diaphragms prepared in each embodiment and comparative example, the coated diaphragm and the positive and negative electrode sheets were pressed for 10-120s at 25°C and 3MPa, and then their cold-pressed peel strength (adhesion) was tested; at the same time, the increase in air permeability (Gurley value increase), interfacial impedance and ionic conductivity relative to the base membrane before and after the diaphragm coating were tested and recorded.

[0120] (2) Microstructure and component distribution test: The coating surface was observed using a scanning electron microscope (SEM). The component classification was identified by utilizing the particle size differences of different components (micron-sized PVDF and nano-sized adhesive polymer).

[0121] (3) Three-dimensional morphology and height test: The dried glue dots are scanned using a super depth-of-field microscope or white light interferometer to obtain a three-dimensional morphology image, and the height distribution curve of the radial section is extracted using the supporting software to measure the height of the inner ring, the outer ring and the radius of the central blank area.

[0122] (4) Battery cycle performance test: Assemble the separator into a full battery and conduct a long cycle test at a 1C charge-discharge rate. Record the number of cycles when the battery capacity retention rate drops to 80%.

[0123] 2. Test Results: Table 1. Performance Test Results

[0124] In the representation of this application embodiment, the radius of the blank area at the center of the adhesive dot is defined as R1, the outer radius of the inner ring area is R2, and the outer radius of the outer ring area is R3. Then the width of one side of the inner ring area is (R2-R1), and the width of one side of the outer ring area is (R3-R2).

[0125] Based on the experimental data in Table 1 above and the multi-dimensional observation results in the accompanying figures, the technical mechanism and beneficial effects of this application are analyzed in detail as follows: (1) Regarding the macroscopic distribution of discrete dot coating, this application uses a specific dot coating process instead of the traditional continuous topcoat. The coating slurry forms a uniformly arranged, non-adhesive array of discrete adhesive dots on the surface of the diaphragm substrate. This macroscopic array distribution avoids excessive obstruction of the original micropores of the base film by the large-area coating from the physical source, laying the macroscopic structural foundation for achieving the extremely low gas permeability increase (such as 9.53s / 100mL in Example 1) and low impedance in this application.

[0126] (2) Regarding the microstructure and spontaneous formation mechanism of the “double-ring nested” structure, the core of this application, the “central blank area + inner ring + outer ring” double-ring nested structure, is mainly formed by the synergy between the particle size difference of the components and the fluid dynamics (Brownian motion).

[0127] like Figures 1 to 3 As shown, during the pulping process, since only physical mixing occurs, the morphology of micron-sized PVDF particles remains unchanged (in... Figure 3 Larger fluorinated particles and fine nanoscale adhesive resin particles can be clearly distinguished in the image. When the slurry droplets contact the base film, the droplets spread outwards due to the reduction of surface tension by the wetting agent. In the initial stage of low-temperature drying, based on Brownian motion (the smaller the particle size, the faster the diffusion), the nanoscale particles composed of adhesive and wetting agent rapidly diffuse towards the outermost edge with the liquid, forming a gently sloping outer ring region (mainly providing adhesion for cold pressing at room temperature); while the diffusion of larger micron-sized PVDF particles is hindered, and they mainly settle and aggregate in the off-center region to form an inner ring region (serving as a physical support framework); at the same time, the material in the center of the droplet is pulled outwards by surface tension, exposing the micropores of the substrate (such as... Figure 3 As shown in the figure, a central blank area is formed.

[0128] refer to Figure 4 An optical microscope image of the glue dot array distribution provided for Comparative Example 1; Figure 5 for Figure 4 The corresponding shape recognition contour map.

[0129] (3) Three-dimensional step height shaping mechanism: In addition to the double ring structure on the plane, this application also constructs a special three-dimensional step shape through instantaneous high temperature shaping.

[0130] refer to Figure 6 (3D pseudo-color image of topography) and Figure 7 (Cross-section height distribution curve), where Figure 7 The measurement data are shown in Table 2.

[0131] Table 2. Statistical Table of Measurement Data

[0132] Combination Figure 6 and Figure 7It can be seen that after drying at low temperature followed by high temperature, the peak height of the inner ring area is significantly greater than the skirt height of the outer ring area (resembling a crater). The design of a thick inner ring and a thin outer ring balances the high-strength physical support in the middle with the flexible, large-area bonding at the edges.

[0133] It should be noted that although the planar spreading width (R3-R2) of the outer ring region was changed by adjusting the amount of wetting agent in Examples 2-7, the overall coating amount was controlled at 0.2 g / m² in this application. 2 ~0.8g / m 2 The precise micro-range of the aqueous slurry, with a fixed solid content ratio between the nano-sized adhesive resin and solid particles, combined with a segmented drying gradient of low temperature followed by high temperature, ensures that the macroscopic fluid laminar thickness is supported by the solid-liquid interfacial tension due to spontaneous phase separation as the slurry migrates outward. Multi-point sampling of the microstructure shows that the discrete adhesive dots constructed in Examples 1 to 12 consistently maintain a peak height in the inner ring region between 1 μm and 5 μm, and a stable skirt height in the outer ring region between 0.2 μm and 2 μm. Furthermore, all exhibit a crater-like three-dimensional step morphology, with the inner ring significantly larger than the outer ring.

[0134] (4) Effect of wetting agent dosage on dot size and performance (Comparative Examples 1-7): The wetting agent mainly controls the surface tension of the liquid, which in turn affects the spreading size of the outer ring (R3-R2). As can be seen from the data of Examples 2 to 7, with the increase of wetting agent dosage (0.1% to 2%), the outer ring size (R3-R2) increased significantly from 0.1 μm to 10.2 μm.

[0135] Improved adhesion: The outer ring size is increased, the effective bonding contact area between the coating and the electrode is increased, and the cold pressing adhesion is significantly improved from 0.93 N / m to 2.35 N / m (2.50 N / m in some embodiments).

[0136] Impedance and Cycle Performance Constraints: However, when excessive wetting agent leads to an overly large outer ring size (as in Examples 6 and 7), the excessively wide outer ring coating adheres extensively to the base film, thus blocking lithium-ion channels. This results in a significant increase in permeability (to 27.80 s / 100 mL) and a rise in impedance (to 0.598 Ω), ultimately leading to increased polarization at the end of the battery cycle and a decrease in the number of cycles (from 213 cycles to 186 cycles). Example 1 (0.5% dosage) achieved the optimal balance between cold-pressed adhesion and low impedance.

[0137] (5) Effect of drying process on morphology (comparative examples 1, 8, 9, 10): The final shape of the inner and outer rings of the glue dots is highly dependent on the temperature field control during the drying stage.

[0138] When high temperature is used throughout or high temperature followed by low temperature (Examples 8 and 9), the moisture is dried rapidly, causing a significant and instantaneous reduction in droplet fluidity. Before Brownian motion can fully develop, the adhesive dots are "frozen" and fixed. This results in a small overall spreading size (inner rings R2-R1 are only 60 μm and 20 μm, respectively). Although air permeability and resistance are good, the cold-pressing adhesion is significantly reduced (to 1.23 N / m and 1.05 N / m, respectively) due to the severely insufficient contact area of ​​the adhesive dots.

[0139] The preferred method of this application is to perform a staged drying process, first at low temperature and then at high temperature (Example 1). The first stage uses low temperature to give the fluid sufficient time for Brownian motion to achieve sufficient phase separation and spreading. Then, the high temperature is used to instantly remove moisture and lock in the above-mentioned three-dimensional step morphology, thereby taking into account both structural integrity and excellent adhesion.

[0140] (6) Effect of the polymer powder to adhesive ratio boundary on performance (comparative examples 1, 11, and 12): Examples 11 and 12 verified the effectiveness of the slurry ratio range boundary. When the polymer powder was reduced to the lower limit of 10% and the adhesive was increased to the upper limit of 15% (Example 11), the outer ring spread was slightly wider due to the increase in the proportion of flexible adhesive resin in the system, and the cold pressing adhesive force increased to 2.25 N / m. However, due to the relatively weakened support of the fluorinated rigid skeleton, the air permeability value increased slightly. When the polymer powder was increased to the upper limit of 20% and the adhesive was reduced to the lower limit of 5% (Example 12), the rigid skeleton deposited in the inner ring thickened, the air permeability value decreased to 8.15 s / 100 mL, and the number of cycles reached 215. However, due to the relatively small amount of adhesive matrix and the narrower outer ring, the adhesive force decreased to 1.55 N / m. Test results show that both can spontaneously form a clear double-ring morphology, and within a limited range, both maintain a cold-pressing adhesive force greater than 1 N / m and extremely low impedance, proving the rationality and high implementation value of this ratio boundary range.

[0141] (7) Coating process comparison (comparative example 1 and comparative examples 1 and 2): Compared with continuous roller coating (comparative example 2), the dot coating process of example 1 uses the above-mentioned special "center blank" structure to avoid full coverage, which makes the air permeability increase significantly reduced from 18.96s / 100mL to 9.53s / 100mL, and the impedance is significantly reduced, thereby improving the ionic conductivity and the long cycle life of the full cell (213 cycles vs 190 cycles).

[0142] Compared to conventional spraying (Comparative Example 1), although spraying can also form discontinuous coatings, the shape of the atomized droplets is uncontrollable, making it difficult to spontaneously form a regular and uniform "central blank + double ring" specific morphology. This results in its cold-pressing adhesion (1.01 N / m) being much lower than that of Example 1 (2.05 N / m), further demonstrating the irreplaceable nature of the specific anilox roller / flexographic roller dotting process of this application, combined with specific slurry components, in resolving the "adhesion and resistance contradiction" under the cold-pressing process.

[0143] (8) Regarding the core technological contribution of the comonomer HFP to cold-press bonding performance, based on the test data of Example 1 and Comparative Example 5, it can be seen that after replacing the micron-sized PVDF-HFP copolymer with pure PVDF powder of the same particle size distribution, Comparative Example 5, thanks to the same multi-level particle size gradient and the segmented drying process of low temperature followed by high temperature, can still spontaneously separate phases and construct a clear double-ring nested morphology in both planar and longitudinal three-dimensional structures. Therefore, the air permeability increase (9.85s / 100mL) and interfacial impedance (0.435Ω) of Comparative Example 5 are basically equivalent to those of Example 1 (9.53s / 100mL, 0.421Ω), indicating that the construction of the physical morphology is mainly controlled by hydrodynamic diffusion and temperature field.

[0144] However, in terms of macroscopic mechanical properties, the room-temperature cold-pressing adhesion of Comparative Example 5 dropped sharply from 2.05 N / m in Example 1 to 0.42 N / m, exhibiting a precipitous decline, completely failing to meet the industrial-grade strength requirement of ≥1 N / m for cell assembly at room temperature. This stark performance contrast reveals the underlying chemical mechanism of this application: pure PVDF, due to its overly regular molecular chains and extremely high crystallinity, exhibits extremely high physical hardness and microscopic brittleness at room temperature. In the cold-pressing process without applying additional heat sources (i.e., without introducing high-temperature hot-pressing activation), the molecular chain segments of pure PVDF particles are in a 'frozen' state, unable to generate sufficient microscopic wetting, spreading, and intermolecular van der Waals anchoring with the surface of the adjacent electrode active material at the moment of pressure.

[0145] Conversely, in Example 1 of this application, a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) was specifically selected. Due to the forceful intrusion of the larger HFP monomer units, the regularity of the PVDF backbone is effectively disrupted at the microscopic level, significantly reducing its overall crystallinity. This change in chemical structure endows the rigid inner ring skeleton material with unique molecular chain flexibility and initial adhesion activity under room temperature cold pressing, enabling the skeleton particles to form an excellent chemical bonding synergistic effect with the flexible polyether material and nanoscale adhesive resin of the outer ring when subjected to compression. The counter-evidence of Comparative Example 5 strongly demonstrates that the PVDF-HFP polymer in this application is an irreplaceable underlying chemical basis for the diaphragm coating, achieving both high-strength cold pressing adhesion at room temperature and extremely low interfacial resistance.

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cold-pressed adhesive-coated diaphragm, characterized in that, It includes a diaphragm substrate and an adhesive coating disposed on at least one surface of the diaphragm substrate; The adhesive coating comprises multiple discrete adhesive dots; Each of the adhesive dots has a nested ring structure, which includes a central blank area, an inner ring area and an outer ring area arranged sequentially from the inside to the outside; The central blank area was not covered to expose the diaphragm substrate; The inner ring region contains PVDF-HFP type polymers and adhesive polymers; The outer ring region contains the adhesive polymer and the polyether compound.

2. The cold-pressed adhesive-coated diaphragm as described in claim 1, characterized in that, The radius of the central blank area is 20μm~100μm; and / or, The radius of the inner ring region is 50μm~200μm; and / or, The radius of the outer ring region is 60μm~250μm; and / or, The total radius of the adhesive dots is 60μm~400μm; and / or, The diameter of the central blank area accounts for 20% to 50% of the total diameter of the adhesive dots; and / or, The height of the inner ring region is 1μm~5μm; and / or, The height of the outer ring region is 0.2 μm to 2 μm; and / or, The height of the inner ring area is greater than the height of the outer ring area; and / or, The melting point of the PVDF-HFP polymer is 140℃~160℃; and / or, The glass transition temperature of the adhesive polymer is 0℃~80℃; and / or, The glass transition temperature of the polyether compound is 30℃~60℃; and / or, The PVDF-HFP polymer has a secondary particle size of 3 μm to 9 μm and a primary particle size of 150 nm to 500 nm; and / or, The adhesive polymer is composed of nano-sized particles.

3. The cold-pressed adhesive-coated diaphragm as described in claim 1, characterized in that, The PVDF-HFP polymers are selected from copolymers comprising VDF monomer units and HFP monomer units; optionally, the copolymers further comprise at least one of TrFE monomer units and CTFE monomer units; and / or, The adhesive polymer includes acrylate polymers and / or polyester polymers; preferably, the polyester polymer includes at least one of PBAT, PCL, PBS, and PLA; and / or, The polyether compound is selected from one or more of polyethylene glycol, polytetrahydrofuran, alkane polyether siloxane, and fatty alcohol polyoxyethylene ether.

4. The cold-pressed adhesive-coated diaphragm as described in claim 1, characterized in that, The inner and / or outer ring regions also contain additives; the additives include wetting agents and dispersants.

5. The cold-pressed adhesive-coated diaphragm as described in claim 4, characterized in that, The wetting agent comprises at least one of sodium dodecylbenzenesulfonate, fatty acid glycerides, alkane polyether siloxanes, and fatty alcohol polyoxyethylene ethers; and / or, The dispersant includes at least one of polyethylene glycol, polyvinylpyrrolidone, and polyvinyl alcohol; and / or, The adhesive dots comprise 0.2 to 1 parts by weight of wetting agent and 0.1 to 2 parts by weight of dispersant, based on parts by weight.

6. The cold-pressed adhesive-coated diaphragm as described in claim 1, characterized in that, The cold-pressed adhesive-coated diaphragm meets at least one of the following properties: A. Cold pressing adhesion force ≥1N / m; B. Air permeability increase ≤30s / 100mL; C. Impedance ≤ 0.5Ω; D. Ionic conductivity ≥ 1 mS / cm.

7. A method for preparing a cold-pressed adhesive-coated diaphragm as described in any one of claims 1-6, characterized in that, include: S1, mixing polymer powder, dispersant, adhesive, wetting agent and water to obtain a coating slurry; wherein, the polymer powder comprises PVDF-HFP type polymer; the adhesive comprises the adhesive polymer; the dispersant and / or wetting agent comprises polyether compound; S2, using a dot coating process, the coating slurry is uniformly arranged into multiple discrete adhesive dots on the surface of the diaphragm substrate; S3, the coated diaphragm substrate is dried in stages to separate and shape the components in the adhesive dots to form the central blank area, inner ring area and outer ring area; the staged drying includes first low temperature drying and then high temperature drying.

8. The preparation method according to claim 7, characterized in that, Step S1 specifically includes: mixing 60%~80% water, 10%~20% of the polymer powder, and 0.1%~2% of the dispersant by mass percentage until homogeneous, then adding 5%~15% of the adhesive and 0.1%~2% of the wetting agent and continuing mixing; and / or, The spacing between the adhesive dots is 200μm~800μm; and / or, The coating amount of the coating slurry is 0.2 g / m. 2 ~0.8g / m 2 ; and / or, The segmented drying specifically includes: first drying at 40℃~70℃ for 1s~3s, then drying at 80℃~100℃ for 1s~5s; and / or, The dot coating process specifically includes: transferring the coating slurry through a material box to an anilox roller, the anilox roller transferring the coating slurry to a flexographic roller with raised dots, and the flexographic roller regularly coating the coating slurry onto the diaphragm substrate through the raised dots on its surface.

9. A battery, characterized in that, It includes a positive electrode, a negative electrode, and an electrolyte, as well as a cold-pressed adhesive-coated separator as described in any one of claims 1-6, disposed between the positive electrode and the negative electrode.

10. An electrical appliance, characterized in that, Includes the battery as described in claim 9.

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