Low-resistance hot melt adhesive material, preparation method thereof and application of low-resistance hot melt adhesive material in lithium battery pole piece bonding

Abstract

The invention discloses a low-resistance hot melt adhesive material, a preparation method and application in lithium battery pole piece bonding in the field of functional polymer bonding materials, and the method comprises the following steps: firstly, in a protective atmosphere, preparing a polyesteramide prepolymer from sebacic acid, hexamethylenediamine and butanediol through a copolycondensation reaction; then adding a silver modified silicon carbide core-shell structure and phenyltrimethoxysilane into the prepolymer, and dispersing at high temperature to obtain conductive paste; adding tackifying resin and a plasticizer to prepare a hot melt adhesive composition, and injecting the hot melt adhesive composition into a preheating mold; and finally cooling, pressurizing and shaping to obtain a finished product. According to the method, the specific polyesteramide matrix and the special conductive filler are compounded, and the process temperature is optimized, so that the obtained hot melt adhesive material has good thermoplastic processing performance and excellent conductivity, and is suitable for the fields needing conductive adhesion, such as lithium battery pole piece adhesion.

Description

Technical Field

[0001] This invention relates to the field of functional polymer adhesive materials technology, specifically to a low-resistance hot melt adhesive material and its preparation method, and its application in lithium battery electrode bonding. Background Technology

[0002] With the rapid development of the new energy industry, especially electric vehicles and portable electronic devices, lithium-ion batteries, as core energy storage units, have attracted much attention for performance improvement and safety assurance. In the manufacturing process of lithium-ion batteries, electrode preparation is one of the key steps, where a strong, low-resistance connection between the active material, conductive agent, and current collector (such as aluminum foil or copper foil) is crucial. Traditional electrode bonding typically uses organic solvent-based adhesives such as polyvinylidene fluoride (PVDF). This process suffers from problems such as solvent evaporation, environmental pollution, high production energy consumption, and insufficient electrode flexibility after drying. More importantly, these adhesives are themselves insulators. Although adding conductive carbon materials can partially improve this, it still introduces high contact resistance between the current collector and the active material layer, affecting the battery's rate performance and overall energy efficiency. Therefore, developing a novel electrode connection material that combines excellent bonding performance with high conductivity has become an important technological direction for improving battery performance.

[0003] To overcome these shortcomings, various conductive bonding solutions have been explored in the industry. Among them, hot melt adhesives have shown application potential due to their solvent-free nature, rapid curing, and clean processing. However, the matrices of ordinary hot melt adhesives (such as ethylene-vinyl acetate copolymers, polyolefins, etc.) are all insulating polymers, and achieving conductivity requires a large amount of conductive fillers, such as carbon black, carbon nanotubes, and silver powder. High filler content often severely deteriorates the melt flowability, bond strength, and flexibility of the material, leading to processing difficulties and electrode embrittlement. At the same time, the uniformity of filler dispersion is also a major challenge. Agglomerated fillers not only fail to form an effective conductive network but may also become stress concentration points, damaging the bonding interface. In addition, conventional conductive fillers have poor interfacial compatibility with the polymer matrix, and interfacial detachment is prone to occur during long-term use or thermal cycling, leading to a decline in conductivity. Although there have been attempts to improve this by using composite fillers or coupling agents in existing technologies, it is often difficult to maintain good thermoplastic processing properties, stable bond strength, and electrolyte erosion resistance that matches battery operating conditions while ensuring low resistance.

[0004] In summary, existing lithium-ion battery electrode bonding technologies, especially conductive bonding solutions designed for high-performance applications, have significant shortcomings in balancing conductivity, adhesion, processability, and long-term stability. Developing a novel low-resistance hot melt adhesive material hinges on designing an innovative polymer matrix and conductive filler system. An ideal matrix needs to exhibit good adhesion to both the current collector and the active material layer, and possess a suitable thermoplastic window for processing; while the conductive filler must be able to construct efficient and stable three-dimensional conductive pathways at low addition levels, and maintain a strong interface with the matrix. This requires molecular structure design and composite process innovation from the material synthesis stage, combining functional customization of the matrix resin with precise modification of the filler surface to fundamentally resolve the contradiction between conductivity and overall mechanical and process performance, thereby meeting the urgent needs of high-energy-density and high-power-density lithium-ion batteries for low-resistance and highly reliable electrode connections. Summary of the Invention

[0005] The purpose of this invention is to provide a low-resistivity hot melt adhesive material and its preparation method, as well as its application in the bonding of lithium battery electrodes. This invention solves the existing technical problems of simultaneously achieving low resistivity, high bonding strength, excellent hot melt processability, and long-term stability.

[0006] The present invention achieves the above objectives through the following technical solutions: A method for preparing a low-resistance hot melt adhesive material includes the following steps: S1, in a dry argon-protected reactor, sebacic acid, 1,4-butanediol and hexamethylenediamine are added; tetrabutyl titanate and sodium hypophosphite are added; under stirring, the temperature is raised to 180-220℃ to react and obtain polyesteramide prepolymer; S2, add silver-modified silicon carbide core-shell structure and phenyltrimethoxysilane to the polyesteramide prepolymer to obtain a mixture; transfer the mixture to a mixer and disperse it at a temperature of 170-210°C to obtain a conductive slurry; S3, adjust the temperature of the conductive paste to 160-200℃, add tackifying resin and plasticizer, stir to obtain hot melt adhesive composition, and inject the hot melt adhesive composition into a mold preheated to 170-190℃; S4. Cool the mold to room temperature to set and then demold.

[0007] In this invention, the core of the preparation reaction mechanism of the low-resistance hot melt adhesive material lies in the gradual chemical synthesis and physical compounding to construct a stable composite system with a polymer of a specific structure as the continuous phase and a surface-modified high-efficiency conductive filler as the dispersed phase. First, under argon protection, sebacic acid, hexamethylenediamine, and butanediol monomers undergo a melt co-condensation reaction in the presence of a composite catalyst. During this process, the carboxyl groups of sebacic acid preferentially react with the amino groups of hexamethylenediamine to form amide bonds, while the carboxyl groups also undergo esterification with the hydroxyl groups of butanediol to form ester bonds, thereby generating a polyesteramide prepolymer containing both amide and ester bonds in its molecular chain. This prepolymer combines the strong polar adhesive force of amide bonds with the flexibility of ester bonds, providing the material with basic adhesive properties and a thermoplastic processing window. Subsequently, a silver-modified silicon carbide core-shell structure filler, prepared beforehand through chemical silver plating and heat treatment, is added to the prepolymer melt along with phenyltrimethoxysilane. Phenylacetyltrimethoxysilane plays a crucial dual coupling role here: its methoxy group, after hydrolysis, forms siloxane bonds with the silver layer on the filler surface or the hydroxyl groups on the silicon carbide surface, while its phenyl group tightly binds with the polyesteramide prepolymer through physical entanglement and compatibility, thus constructing a strong chemical bridging interface between the inorganic filler and the organic matrix, greatly improving the dispersibility of the filler and enhancing interfacial conductivity. While maintaining the molten state, tackifying resins and plasticizers are added for physical blending to further adjust the system's adhesion, flexibility, and melt rheological properties. Finally, through a physical molding process of hot injection molding and pressurized cooling, the conductive filler is fixed in the matrix to form a highly efficient three-dimensional conductive network, while the polymer matrix crystallizes or vitrifies, resulting in a dense, durable, low-resistance, and excellent mechanically strong hot melt adhesive solid material. The entire mechanism embodies a systematic innovation from molecular structure design and interfacial chemical modification to microscopic physical composites, ultimately achieving macroscopic performance.

[0008] According to a preferred embodiment of the present invention, in step S1, the temperature is raised to 180-220°C and the reaction time is 3-6 hours.

[0009] According to a preferred embodiment of the present invention, in step S2, the dispersion treatment is carried out at a temperature of 170-210°C for 1-2 hours.

[0010] According to a preferred embodiment of the present invention, the tackifying resin is selected from at least one of hydrogenated petroleum resin, terpene resin and rosin resin; the plasticizer is selected from dicyclohexyl phthalate.

[0011] According to a preferred embodiment of the present invention, in step S4, the cooling to room temperature for shaping includes: placing the mold in a press, applying a pressure of 0.5-2 MPa, and cooling to 25-28°C.

[0012] According to a preferred embodiment of the present invention, the preparation steps of the silver-modified silicon carbide core-shell structure include: A1. SiC micro powder is placed in a sensitizing solution containing stannous chloride and hydrochloric acid to obtain treated SiC micro powder. The treated SiC micro powder is washed with deionized water and then transferred to an activation solution containing palladium chloride and hydrochloric acid to obtain activated SiC particles. A2, the activated SiC particles are dispersed in an alkaline solution of glucose, silver nitrate solution is added, and the reaction is carried out at 60-80℃; after the reaction is completed, the solid product is separated and heat-treated at 250-300℃ in an argon atmosphere.

[0013] In this invention, the preparation mechanism of the silver-modified silicon carbide core-shell structure involves a precise process of surface catalysis and chemical reduction. First, silicon carbide micropowder is treated in an acidic sensitizing solution containing stannous chloride. The key lies in the adsorption of stannous ions onto the surface of the silicon carbide particles, forming a layer of reducing activation sites. Subsequently, the thoroughly cleaned particles are transferred to an activation solution containing palladium chloride. The previously adsorbed stannous ions reduce palladium ions in the solution to highly catalytically active palladium atoms. These palladium atoms are firmly anchored on the silicon carbide surface in the form of nanoclusters, becoming the catalytic centers for subsequent electroless silver plating. The subsequent electroless silver plating step is carried out in an alkaline environment, using glucose as a reducing agent and silver nitrate as the silver source. Under the excitation of the palladium catalytic centers, silver ions in the solution are preferentially reduced on the surface of the silicon carbide particles and gradually grow using these as nuclei, ultimately forming a continuous and dense nanosilver shell layer that completely encapsulates the silicon carbide core. The final heat treatment step, carried out in an inert atmosphere, plays a crucial role: on the one hand, the heat promotes the diffusion and rearrangement of silver atoms, eliminating coating defects, making it denser, and significantly improving conductivity; on the other hand, the high temperature enhances the physical bonding force between the silver layer and the silicon carbide core, ensuring the long-term stability of the core-shell structure. The resulting composite material combines the mechanical strength and thermal stability of silicon carbide with the extremely high electrical conductivity of silver, making it an ideal filler for constructing conductive networks.

[0014] According to a preferred embodiment of the present invention, in step A1, the particle size of the SiC micro powder is 2-5 μm.

[0015] According to a preferred embodiment of the present invention, in step A2, the heat treatment time is 1-2 hours.

[0016] The present invention also provides a low-resistance hot melt adhesive material prepared according to the preparation method of the low-resistance hot melt adhesive material.

[0017] The present invention also provides an application of the low-resistance hot melt adhesive material described above in the bonding of lithium battery electrodes.

[0018] The beneficial effects of this invention are as follows: The low-resistance hot melt adhesive material and its preparation method provided by this invention achieve several technical effects that are significantly superior to existing technologies through innovative material system design and precise composite process, comprehensively solving the multiple requirements for conductivity, adhesion, processability and stability in lithium battery electrode bonding.

[0019] First, this invention achieves a fundamental breakthrough in material design and final performance. The core technological effect is manifested in the extremely low volume resistivity achieved with a relatively low amount of conductive filler. This is mainly attributed to the synergistic effect of the unique "silver-modified silicon carbide core-shell structure" filler and the "polyesteramide" matrix. Specifically, the continuous silver layer constructed on the silicon carbide surface through chemical silver plating greatly improves the conductivity of a single filler; while the high hardness and thermal stability of the silicon carbide core itself provide a solid support for the silver layer, preventing it from shrinking or being damaged during processing and use, thereby ensuring the durability and stability of the conductive path. At the same time, the self-synthesized polyesteramide prepolymer serves as the matrix, and its molecular chain contains both polar amide bonds and flexible ester bonds. It not only exhibits excellent inherent adhesion to the surfaces of metal current collectors and electrode active materials, but also forms a strong chemical bond interface with the filler surface through the coupling bridging effect of phenyltrimethoxysilane. This strong interfacial bonding effectively avoids the degradation of conductivity caused by interfacial debonding and significantly improves the mechanical strength and toughness of the composite material. The resulting hot melt adhesive has excellent bonding strength and impact and bending resistance while possessing high conductivity, perfectly overcoming the shortcomings of traditional conductive adhesives with high filler content that are prone to brittleness.

[0020] Secondly, in terms of processing technology and applicability, this invention demonstrates high feasibility and superiority. The entire preparation method is streamlined, with scientifically and rationally set temperatures for each step. From the melt co-condensation of monomers to the high-temperature dispersion of fillers, and finally to injection molding, the entire temperature chain is meticulously designed to ensure that the polymer matrix is ​​always in a suitable melt flow state, guaranteeing uniform dispersion of conductive fillers. The process is solvent-free and environmentally friendly. The final material exhibits typical thermoplastic behavior and can be repeatedly processed by heating and melting, then cooling and shaping, greatly facilitating the integration and application of battery electrode coating, hot-pressing lamination, and other production processes. Furthermore, by adjusting the components, such as selecting tackifying resins like hydrogenated petroleum resins and specific plasticizers, the melt viscosity, open time, and flexibility of the hot melt adhesive can be flexibly adjusted to meet the production requirements of electrodes of different thicknesses or different process speeds. The pressure-cooling shaping step further enhances the material's density and dimensional stability, providing a reliable guarantee for subsequent battery winding or stacking processes.

[0021] Finally, the material provided by this invention demonstrates outstanding performance in battery applications and long-term reliability. When applied to lithium battery electrode bonding, it establishes a robust and highly conductive interface between the current collector and the active material layer, significantly reducing the internal resistance of the electrode and thus improving the battery's rate discharge performance and energy efficiency. The excellent chemical resistance of the polyesteramide matrix, combined with the stability of the filler core-shell structure, allows this hot melt adhesive to maintain stable performance in the battery electrolyte environment for a long time, with no significant increase in impedance, effectively extending the battery's lifespan. In summary, this invention successfully creates a hot melt adhesive material that combines low resistance, high adhesion, easy processing, and good stability, providing an ideal electrode bonding solution for high-performance lithium-ion batteries, especially power batteries and energy storage batteries with stringent requirements for high power and long cycle life, and has broad prospects for industrial application. Detailed Implementation

[0022] The following detailed embodiments are only used to further illustrate this application and should not be construed as limiting the scope of protection of this application. Those skilled in the art can make some non-essential improvements and adjustments to this application based on the above application content.

[0023] Example 1 50.00 g of silicon carbide micropowder with a particle size of 3 μm was weighed and placed in a sensitization solution consisting of 5.00 g of stannous chloride dissolved in 200 mL of 10% hydrochloric acid solution. The solution was magnetically stirred at 25 °C for 30 min. After treatment, the solid was vacuum filtered using a Buchner funnel, and washed three times with 500 mL of deionized water. The washed solid was then transferred to an activation solution consisting of 1.00 g of palladium chloride dissolved in 200 mL of 10% hydrochloric acid solution, and magnetically stirred at 25 °C for 30 min. Vacuum filtration was performed again, and the solid was washed three times with 500 mL of deionized water to obtain activated silicon carbide particles. Activated silicon carbide particles were dispersed in an alkaline solution consisting of 20.00 g glucose and 200 mL of 5% sodium hydroxide solution. The solution was placed in a 70°C constant-temperature water bath and, under mechanical stirring (300 rpm), a solution prepared by dissolving 10.00 g silver nitrate in 100 mL of deionized water was slowly added dropwise over 30 min. After the addition was complete, the reaction was continued at 70°C for 60 min. After the reaction, the product was subjected to vacuum hot filtration (the filtrate temperature was maintained above 60°C). The solid product was washed three times each with 200 mL of hot deionized water (60°C) and 200 mL of anhydrous ethanol. The washed solid was placed in an alumina crucible and then placed in a tube furnace. Under an argon atmosphere with a flow rate of 100 mL / min, the temperature was increased from room temperature to 280°C at a rate of 5°C / min, and then heat-treated at 280°C for 90 min. After the process is completed, the furnace is allowed to cool naturally to below 50°C. After removal, it is ground to obtain silver-modified silicon carbide core-shell structure powder.

[0024] In a 500mL four-necked flask equipped with a mechanical stirrer, thermometer, dual nitrogen / argon inlets, and a distillation outlet, the vacuum-argon purging process was repeated three times to ensure the reaction system was under an inert atmosphere. 100.00g of sebacic acid, 50.00g of 1,4-butanediol, and 60.00g of hexamethylenediamine were added to the flask. Stirring was started at 150rpm, and heating was initiated simultaneously. When the materials melted and the internal temperature reached 160℃, a mixture of 0.50g of tetrabutyl titanate and 0.30g of sodium hypophosphite was rapidly added via syringe. The temperature was further increased to 200℃, at which point distilled water began to distill off. The reaction temperature was maintained at 200±2℃ for 240min. During the reaction, the distilled water was collected and measured using a water separator. After the reaction was complete, heating was stopped, yielding a pale yellow, highly viscous polyesteramide prepolymer melt.

[0025] The entire melt of the aforementioned polyesteramide prepolymer was transferred to a Hacker internal mixer (equivalent model, 60mL chamber capacity) set at 190℃. Immediately, 30.00g of the previously prepared silver-modified silicon carbide core-shell structure powder and 3.00g of phenyltrimethoxysilane were added. The mixer chamber was closed, and the mixture was stirred for 90 minutes at 190℃ and a rotor speed of 60rpm until the torque value stabilized, resulting in a uniform conductive slurry. The conductive slurry was transferred to a mold (mold cavity size: 100mm×100mm×2mm) in a flat vulcanizing machine preheated to 180℃. The mold was quickly closed, and a pressure of 1.0MPa was immediately applied. Simultaneously, the mold's circulating cooling water (water temperature 10℃) was turned on, allowing the mold temperature to uniformly decrease from 180℃ to 26℃ within 30 minutes. After holding the pressure and cooling to 26℃, the pressure was released, and the mold was demolded to obtain a smooth, uniformly thick, dark gray, low-resistance hot melt adhesive sheet.

[0026] Example 2 The specific implementation method is the same as in Example 1, except that 60.00 g of silicon carbide micropowder with a particle size of 4 μm was weighed and processed according to the exact same sensitization and activation steps described in Example 1 to obtain activated silicon carbide particles. The activated silicon carbide particles were dispersed in an alkaline solution composed of 25.00 g of glucose and 250 mL of 5% sodium hydroxide solution. Under constant temperature water bath at 65°C and mechanical stirring at 300 rpm, a solution prepared by dissolving 12.00 g of silver nitrate in 120 mL of deionized water was added dropwise over a period of 30 min, followed by a further reaction at 65°C for 72 min. The subsequent hot filtration and washing steps were the same as in Example 1. The washed solid was then heated to 270°C at a rate of 5°C / min under an argon atmosphere and kept at that temperature for 120 min to obtain silver-modified silicon carbide core-shell structure powder.

[0027] In an argon-protected reactor, 110.00 g of sebacic acid, 55.00 g of 1,4-butanediol, and 65.00 g of hexamethylenediamine were added. 0.60 g of tetrabutyl titanate and 0.35 g of sodium hypophosphite were also added. The mixture was heated to 190 °C with stirring and reacted for 300 min to obtain a polyesteramide prepolymer. The prepolymer was then mixed at 180 °C with 35.00 g of the aforementioned silver-modified silicon carbide powder and 3.50 g of phenyltrimethoxysilane in a mixer at 60 rpm for 72 min. The temperature of the resulting conductive slurry was adjusted to 170 °C, and 25.00 g of terpene resin and 12.00 g of dicyclohexyl phthalate were added. The mixture was mechanically stirred for 60 min. The hot melt adhesive composition was injected into a mold preheated to 175 °C, and a pressure of 0.8 MPa was applied in a press. After cooling to 27 °C, the mixture was demolded.

[0028] Example 3 The specific implementation method is the same as in Example 1, except that 55.00 g of silicon carbide micropowder with a particle size of 2.5 μm was weighed and processed according to the same sensitization and activation steps as described in Example 1 to obtain activated silicon carbide particles. The activated silicon carbide particles were dispersed in an alkaline solution composed of 22.00 g of glucose and 220 mL of 5% sodium hydroxide solution. Under constant temperature water bath at 75°C and mechanical stirring at 300 rpm, a solution prepared by dissolving 11.00 g of silver nitrate in 110 mL of deionized water was added dropwise over a period of 30 min, followed by a reaction at 75°C for another 60 min. The subsequent hot filtration and washing steps were the same as in Example 1. The washed solid was then heated to 260°C at a rate of 5°C / min under an argon atmosphere and kept at that temperature for 60 min to obtain silver-modified silicon carbide core-shell structure powder.

[0029] In an argon-protected reactor, 105.00 g of sebacic acid, 52.00 g of 1,4-butanediol, and 62.00 g of hexamethylenediamine were added. 0.55 g of tetrabutyl titanate and 0.32 g of sodium hypophosphite were also added. The mixture was heated to 210 °C with stirring and reacted for 210 min to obtain a polyesteramide prepolymer. The prepolymer was then mixed at 200 °C with 32.00 g of the aforementioned silver-modified silicon carbide powder and 3.20 g of phenyltrimethoxysilane in a mixer at 60 rpm for 108 min. The temperature of the resulting conductive slurry was adjusted to 190 °C, and 18.00 g of rosin resin and 18.00 g of dicyclohexyl phthalate were added. The mixture was mechanically stirred for 60 min. The hot melt adhesive composition was injected into a mold preheated to 185 °C, and a pressure of 1.5 MPa was applied in a press. After cooling to 25 °C, the mixture was demolded.

[0030] Comparative Example 1 The specific implementation method is the same as in Example 1, except that no chemical silver plating reaction is performed in the step of preparing the silver-modified silicon carbide core-shell structure. Specifically, the activated silicon carbide particles from Example 1 are filtered, washed, and then placed directly in a tube furnace for treatment under the same argon atmosphere and heat treatment procedure (280°C, 90 min) as in Example 1, to obtain unmodified pure silicon carbide powder. In the subsequent preparation of the polyesteramide prepolymer and composite steps, 30.00 g of this unmodified silicon carbide powder is used, and all other material types, amounts, and process conditions are exactly the same as in Example 1.

[0031] Comparative Example 2 The specific implementation method is the same as in Example 1, except that phenyltrimethoxysilane coupling agent is not added in step S2. The specific preparation process is as follows: after obtaining the polyesteramide prepolymer, the temperature is maintained at 190°C, and only 30.00g of the silver-modified silicon carbide core-shell structure powder prepared in Example 1 is added. Phenyltrimethoxysilane is not added. The amount of other materials and all subsequent process conditions are exactly the same as in Example 1.

[0032] Comparative Example 3 The specific implementation method is the same as in Example 1, except that sebacic acid, 1,4-butanediol, and hexamethylenediamine are not used in step S1 to synthesize the polyesteramide prepolymer. Specifically, 100.00g of general-purpose polyamide 6 resin is directly added to a dry argon-protected reactor and heated to 200°C to melt it, obtaining a polyamide 6 melt base. In subsequent steps, 30.00g of silver-modified silicon carbide core-shell structure powder and 3.00g of phenyltrimethoxysilane prepared in Example 1 are added to this melt base, and the mixture is kneaded at 190°C and 60 rpm for 90 min. Subsequent steps, such as adding 20.00g of hydrogenated petroleum resin and 15.00g of dicyclohexyl phthalate, and all process conditions are the same as in Example 1.

[0033] Performance testing According to relevant national and industry standards, the performance of Examples 1-3 and Comparative Examples 1-3 above was tested according to the following method, which included the following steps: all prepared samples were conditioned in a standard constant temperature and humidity chamber at a temperature of 23±2℃ and a relative humidity of 50±5% for 24 hours before testing.

[0034] Volume resistivity was measured using the four-probe method, employing a digital four-probe testing system equipped with four tungsten carbide probes and a DC power source meter. Before testing, the sample was cut and polished into a square block with a flat surface and dimensions of 10.0 mm × 10.0 mm × 2.0 mm. A special fixture was used to ensure good contact between the four probes and the sample surface with equal spacing of 1.0 mm. Measurements were taken in four different regions, and the average value was recorded. The current source output was set to 10.0 mA.

[0035] Tensile shear strength was tested using a universal testing machine with a range of 5 kN. The bonding substrate was a 6061 aluminum alloy plate with dimensions of 100.0 mm × 25.0 mm × 1.5 mm. Before bonding, the surface of the substrate was successively sanded with 400-grit sandpaper, ultrasonically cleaned with acetone for 10 minutes, and dried. The molten hot melt adhesive sample to be tested was evenly applied to the bonding area (25.0 mm × 12.5 mm) of one substrate, quickly stacked with another substrate, and placed on a press preheated to 180°C. A pressure of 0.5 MPa was applied and held for 120 seconds, then removed and cooled for 24 hours under standard conditions to complete curing. During testing, the bonded sample was clamped on the testing machine, and the tensile speed of the crossbeam was set to 10.0 mm / min until the sample failed. The maximum load was recorded, and each set of data was the average of five parallel samples.

[0036] Melt viscosity was measured using a rotational rheometer with a parallel plate fixture of 25.0 mm diameter and a plate spacing of 1.0 mm. Before testing, a suitable amount of sample was preheated and melted at 190 °C and loaded into the fixture. After amplitude scanning to determine the linear viscoelastic region, the sample was held at 190 °C with a shear rate of 10.0 s⁻¹. -1 Under stable conditions, the viscosity was tested for 180 seconds, and the average viscosity value in the last 30 seconds was taken as the result.

[0037] The thermal decomposition temperature was determined using a thermogravimetric analyzer. Approximately 10.0 mg of sample was weighed and placed in an alumina crucible. Under the protection of high-purity nitrogen at a flow rate of 50.0 mL / min, the sample was heated from 50 °C to 600 °C at a heating rate of 10.0 °C / min. The change curve of sample mass with temperature was recorded, and the temperature at which the mass loss reached 5% was taken as the thermal decomposition temperature (Td5%).

[0038] For the electrolyte immersion resistivity test, the sample was completely immersed in a sealed glass bottle containing commercial lithium-ion battery electrolyte (composed of 1 mol / L lithium hexafluorophosphate, with ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate mixed in a 1:1:1 volume ratio as solvent), and the bottle was placed in a 60.0°C drying oven for 168 hours. After removal, the sample surface was thoroughly cleaned with anhydrous ethanol and dried in an 80°C vacuum oven for 12 hours until constant weight. Subsequently, the volume resistivity was measured again according to the aforementioned method, and the percentage change in resistivity before and after immersion was calculated.

[0039] Test results: Table 1: Test results of each embodiment and comparative example ; As can be seen from Table 1, the test data of Examples 1 to 3, compared with those of Comparative Examples 1 to 3, comprehensively and powerfully demonstrate that the present invention has successfully solved the key problems that are difficult to address in the prior art.

[0040] First, regarding the core conductivity, the resistivity of this embodiment is as low as approximately 8.5 × 10⁻⁶. -3 Ω·cm, while Comparative Example 1 (unmodified silver) is as high as 5.6 × 10⁻⁶. 1 The resistivity of silver is Ω·cm, a difference of more than four orders of magnitude, confirming its indispensability for constructing highly efficient conductive networks; Comparative Example 2 (without coupling agent) has a resistivity of 2.4 × 10⁻⁶ Ω·cm. -1 The resistivity of Ω·cm was significantly higher than that of the examples, indicating that phenyltrimethoxysilane is crucial for achieving uniform dispersion of the filler and preventing agglomeration to form a stable conductive pathway; the resistivity of Comparative Example 3 (general matrix) was 1.8 × 10⁻⁶ Ω·cm. -2 The Ω·cm reading, while acceptable, is still an order of magnitude higher than that of the example, indicating that the specially formulated polyesteramide prepolymer is more conducive to the formation and stability of conductive pathways.

[0041] Secondly, regarding mechanical properties, the tensile shear strength of the embodiments is all above 14.8 MPa, reaching a maximum of 15.5 MPa, while the comparative examples are all at or below 11.7 MPa. This fully verifies the strong inherent adhesion provided by the specific polyesteramide matrix, and the decisive contribution of the filler-matrix interface strengthened by the coupling agent to the overall adhesive strength. In terms of processability, the embodiments exhibit moderate and stable melt viscosity (1180-1420 Pa·s) at 190°C, while Comparative Example 2 suffers from unstable processing viscosity due to uneven filler dispersion, and Comparative Example 3 has a viscosity as high as 2850 Pa·s due to matrix characteristics, making processing difficult. This highlights the superiority of the system of this invention in terms of the hot melt processing window.

[0042] Finally, in terms of long-term stability, the examples exhibited higher thermal decomposition temperatures (above 380°C) and extremely low resistivity change rates (approximately +4.5%) after electrolyte immersion, far superior to all comparative examples (all with change rates exceeding +15%). This comprehensively demonstrates the durability of the silver-modified silicon carbide core-shell structure and the excellent heat resistance and electrolyte erosion resistance of the polyesteramide matrix, ensuring the long-lasting performance of the material in harsh battery environments.

[0043] In summary, this invention achieves a systematic balance of low resistance, high adhesion, good processability, and excellent long-term stability through the synergistic innovation of polyesteramide matrix synthesis, silver-modified core-shell filler, and silane coupling agent interface bridging, effectively solving the technical defects of existing conductive adhesive materials pointed out in the background art.

[0044] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a low-resistance hot melt adhesive material, characterized in that, Includes the following steps: S1, in a dry argon-protected reactor, sebacic acid, 1,4-butanediol and hexamethylenediamine are added; tetrabutyl titanate and sodium hypophosphite are added; under stirring, the temperature is raised to 180-220℃ to react and obtain polyesteramide prepolymer; S2, add silver-modified silicon carbide core-shell structure and phenyltrimethoxysilane to the polyesteramide prepolymer to obtain a mixture; transfer the mixture to a mixer and disperse it at a temperature of 170-210°C to obtain a conductive slurry; S3, adjust the temperature of the conductive paste to 160-200℃, add tackifying resin and plasticizer, stir to obtain hot melt adhesive composition, and inject the hot melt adhesive composition into a mold preheated to 170-190℃; S4. Cool the mold to room temperature to set and then demold.

2. The method for preparing the low-resistance hot melt adhesive material according to claim 1, characterized in that, In step S1, the temperature is raised to 180-220℃ and the reaction time is 3-6 hours.

3. The method for preparing the low-resistance hot melt adhesive material according to claim 1, characterized in that, In step S2, the dispersion treatment is carried out at a temperature of 170-210℃ for 1-2 hours.

4. The method for preparing the low-resistance hot melt adhesive material according to claim 1, characterized in that, In step S3, the tackifying resin is selected from at least one of hydrogenated petroleum resin, terpene resin and rosin resin; the plasticizer is selected from dicyclohexyl phthalate.

5. The method for preparing the low-resistance hot melt adhesive material according to claim 1, characterized in that, In step S4, the cooling to room temperature for shaping includes: placing the mold in a press, applying a pressure of 0.5-2 MPa, and cooling to 25-28°C.

6. The method for preparing the low-resistivity hot melt adhesive material according to any one of claims 1-5, characterized in that, The preparation steps of the silver-modified silicon carbide core-shell structure include: A1. SiC micro powder is placed in a sensitizing solution containing stannous chloride and hydrochloric acid to obtain treated SiC micro powder. The treated SiC micro powder is washed with deionized water and then transferred to an activation solution containing palladium chloride and hydrochloric acid to obtain activated SiC particles. A2, the activated SiC particles are dispersed in an alkaline solution of glucose, silver nitrate solution is added, and the reaction is carried out at 60-80℃; after the reaction is completed, the solid product is separated and heat-treated at 250-300℃ in an argon atmosphere.

7. The method for preparing the low-resistance hot melt adhesive material according to claim 6, characterized in that, In step A1, the particle size of SiC micro powder is 2-5 μm.

8. The method for preparing the low-resistance hot melt adhesive material according to claim 6, characterized in that, In step A2, the heat treatment time is 1-2 hours.

9. A low-resistance hot melt adhesive material, characterized in that, The low-resistance hot melt adhesive material is prepared by the method of preparing the low-resistance hot melt adhesive material according to any one of claims 1-8.

10. An application of the low-resistance hot melt adhesive material according to claim 9, characterized in that, Application of the low-resistance hot melt adhesive material in lithium battery electrode bonding.