Pore-forming agent for lithium ion battery and preparation method and application thereof

Abstract

The application provides a pore-forming agent for lithium ion batteries and a preparation method thereof, which comprises a wall material preparation step, a core material preparation step, a W / O type initial milk preparation step and a pore-forming agent for lithium ion batteries preparation step. The pore-forming agent preparation method is a new pore-forming agent synthesis route, which has the advantages of simple reaction steps, mild reaction conditions, high yield, low cost and environmental protection. The technology can accurately construct a uniform multi-level pore network by introducing the pore-forming agent into the electrode, significantly reduces the charge transmission impedance, effectively improves the fast charging capacity and high-rate discharge performance of the battery, greatly improves the electrode-electrolyte interface contact, and ensures the full use of the active material. The application also provides an application of the pore-forming agent for lithium ion batteries to lithium ion batteries. The application of the pore-forming agent for lithium ion batteries to the lithium ion batteries can improve ion conduction and improve the rate performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery manufacturing technology, specifically to a pore-forming agent for lithium-ion batteries and its preparation method, and also to the application of the pore-forming agent for lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries, with their high efficiency, portability, and rechargeable characteristics, have become the energy link connecting the digital and physical worlds. Their applications have extended to every corner of modern society. In consumer electronics, they have enabled the thinner, lighter, and longer-lasting smartphones, laptops, and tablets. In transportation, the continuous decline in the cost of power batteries has directly spurred the large-scale use of electric vehicles. In the energy sector, with the increasing proportion of renewable energy, large-scale energy storage power stations have become key facilities for grid peak shaving. More cutting-edge applications have expanded to aerospace, deep-sea exploration, and medical implants. The working principle of a lithium-ion battery is that lithium ions and electrons shuttle back and forth simultaneously through internal and external circuits. During charging and discharging, the applied power source or load resistor causes reversible oxidation and reduction reactions at the positive and negative electrodes. The negative and positive electrode materials are spatially separated but connected by external circuits and electrolyte ions. For lithium-ion batteries, the transfer of electrons from the negative electrode to the positive electrode is accompanied by the extraction of lithium ions from the negative electrode material and their insertion into the positive electrode material to balance the charge.

[0003] The internal structure of a lithium-ion battery mainly consists of a positive electrode, a negative electrode, an electrolyte, and a separator. The stable development of lithium-ion batteries depends primarily on these four key systems, which together determine the quality of the battery. Among them, the electrode is a very important part of the lithium-ion battery.

[0004] Currently, lithium-ion battery electrode materials mainly consist of active materials, conductive agents, and binders, representing a mature industrial electrode. However, they still suffer from problems such as poor conductivity, low dispersibility, swelling, and high cost. Poor conductivity leads to increased electrode resistance, a rapid decline in battery rate performance, and a decrease in battery capacity over prolonged use. Swelling, on the other hand, damages the electrode structure and reduces the overall electrochemical performance of the battery. To address these issues, researchers are searching for materials to improve the overall performance of the electrode, thereby extending the lifespan of lithium-ion batteries. Summary of the Invention

[0005] In view of this, the present invention provides a pore-forming agent for lithium-ion batteries and a method for preparing the same. The present invention also relates to the application of the pore-forming agent for lithium-ion batteries to solve the problems of poor electrical performance and swelling phenomenon in existing electrodes.

[0006] In a first aspect, the present invention provides a method for preparing a pore-forming agent for lithium-ion batteries, comprising the following steps, by weight:

[0007] Preparation of wall material: Provide 2500-3500 parts of deionized water, 250-300 parts of cyanamide oligomer, 250-300 parts of urea compound, and 800-1200 parts of low-grade aliphatic aldehyde. Mix the deionized water, cyanamide oligomer, urea compound, and low-grade aliphatic aldehyde and transfer them to the first reaction vessel. Adjust the pH of the mixed solution in the first reaction vessel to 8.5-9. Then heat the first reaction vessel to 65-75℃ and maintain it for 0.5-1.5 h. After the reaction is completed, continue to add 10000-15000 parts of deionized water to the first reaction vessel and continue stirring for 0.5-2 h. Then let it stand for 0.5-1.5 h to obtain the wall material.

[0008] Preparation of core material: Provide 500-1000 parts of deionized water, 250-300 parts of polylactic acid and 10-30 parts of co-solvent. After mixing the deionized water, polylactic acid and co-solvent, filter the membrane to obtain the aqueous core material.

[0009] Preparation of W / O type primary emulsion: Provide 30-50 parts of oil phase additive, 1-10 parts of emulsifier and 1-5 parts of defoamer. Add the oil phase additive, emulsifier and defoamer to the second reaction vessel and mix well to obtain oil phase emulsifier. While stirring the oil phase emulsifier, add the aqueous phase core material dropwise to the second reaction vessel. Then add 150-200 parts of ionic strength regulator to the second reaction vessel and stir to obtain W / O type primary emulsion.

[0010] Preparation of pore-forming agent for lithium-ion batteries: Under the condition of stirring W / O type primary emulsion, wall material is added dropwise to W / O type primary emulsion. After the addition is completed, the pH value of the mixture is adjusted to 4-5, and stirring is continued for 0.1-0.5h. Then, the temperature of the second reaction vessel is raised to 70-80℃ and maintained for 1-5h to obtain emulsion. The emulsion is washed, dried and pulverized to obtain TM microcapsules, i.e., pore-forming agent for lithium-ion batteries.

[0011] The present invention provides a method for preparing a pore-forming agent for lithium-ion batteries, comprising steps for preparing a wall material, preparing a core material, preparing a W / O type primary emulsion, and preparing a pore-forming agent for lithium-ion batteries. In the wall material preparation step, urea compounds react with aldehydes to form urea-formaldehyde resin, which is the main film-forming substance, providing adhesion while reducing costs. Cyanoamine oligomers can undergo condensation polymerization with aldehydes, improving the polymer's heat resistance and water resistance. In the wall material preparation step, the reactants are first uniformly mixed before the reaction. Cyanoamine oligomers, urea compounds, and aldehydes undergo hydroxymethylation under weakly alkaline conditions. The resulting intermediates further condense to form a prepolymer linked by methylene bonds (-CH2-) and ether bonds (-CH2-O-CH2-). Further heating accelerates the reaction, and the prepolymer forms a three-dimensional network structure. In the core material preparation step, aliphatic polyesters, due to their excellent biocompatibility and biodegradability, are known as "green plastics" and are currently widely used in various industries. In this application, the primary function of the aliphatic polyester is pore formation, while an appropriate amount of co-solvent acts as a "lubricant," increasing the free space between polymer chains and making the chain segments easier to move and rotate under stress. In the preparation steps, by introducing co-solvents and deionized water during the processing of the aliphatic polyester, chemical reactions or strong interactions occur with the end groups of the aliphatic polyester, disrupting the rigid intermolecular forces of the aliphatic polyester itself, increasing the chain segment mobility, thereby significantly improving its brittleness and obtaining a soft, tough material, forming a weak cross-linked or branched network. In the preparation of the W / O type primary emulsion, the addition of an oil phase provides the main framework of the emulsion, while the compounded emulsifier acts as the main force, providing basic W / O emulsification capability and also as a "reinforcement," filling and thickening the interfacial film with its multi-long chain structure, thus improving mechanical strength. The addition of an antifoaming agent can reduce the elasticity of the liquid film and may also change the properties of interfacial flow, reducing the surface tension of the liquid. In the emulsifier preparation step, this compounding process enables the production of fine, uniformly distributed, and long-term stable W / O emulsions in this unique and challenging oil phase. The addition of an ionic strength modifier enhances the ionic layer of the solution, improving conductivity and making the electric field distribution and ion migration more uniform and controllable. In the pore-forming agent preparation step for lithium-ion batteries, the wall material is dropped into the W / O primary emulsion, the pH is adjusted, and the reaction is initiated. The surface of the aqueous core material is treated, forming a wall material polymer coating layer, thereby creating a microcapsule structure. Adjusting the pH allows for the regulation and control of the acidity of the aqueous core material surface, promoting the formation of the coating layer. Finally, TM microcapsules are obtained through filtration, washing, drying, and pulverization.

[0012] This invention presents a novel synthetic route for preparing pore-forming agents, offering advantages such as simple reaction steps, mild reaction conditions, high yield, low cost, and environmental friendliness. This technology, by introducing pore-forming agents into the electrode, can precisely construct a uniform multi-level pore network. This microstructure design brings several synergistic benefits: First, it significantly shortens the solid-state diffusion path of lithium ions within the electrode, substantially reducing charge transport impedance, thereby effectively improving the battery's fast-charging capability and high-rate discharge performance. Second, the abundant and interconnected pore channels allow the electrolyte to quickly and uniformly wet the entire electrode, greatly improving the electrode-electrolyte interface contact and ensuring the full utilization of active materials. This not only helps to increase the battery's initial specific capacity but also enhances the reaction uniformity during cycling. Furthermore, this internal pore structure provides valuable buffer space for materials with significant volume expansion, such as silicon anodes, helping to maintain the mechanical integrity of the electrode structure and extend battery cycle life. In summary, this technical solution cleverly optimizes the ion transport environment inside the electrode without adding extra mass through a "subtraction" process, successfully achieving a synergistic improvement in battery rate performance, initial capacity, and long-term cycle stability.

[0013] Preferably, in the wall material preparation step, the cyanamide oligomer is at least one selected from melamine, dimelamine, and thiodicyandiamide; the urea compound is at least one selected from urea, thiourea, methylurea, and 1,1-dimethylurea; and the lower aliphatic aldehyde is at least one selected from formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, and pentanal. Selecting suitable cyanamide oligomers, urea compounds, and lower aliphatic aldehydes ensures the heat resistance, water resistance, and flexibility of the prepared polymer.

[0014] Preferably, in the wall material preparation step, the specific operation of adjusting the pH value of the mixed solution in the first reaction vessel to 8.5-9 is as follows: while stirring the mixed solution, an alkalinity adjuster is added until the pH value reaches 8.5-9;

[0015] The alkalinity regulator is at least one of triethanolamine solution, ethanolamine solution, sodium bicarbonate solution, and sodium hydroxide solution. By precisely controlling the pH value of the mixed solution in the first reaction vessel, the degree of polymer polymerization can be effectively controlled, which is beneficial for the subsequent preparation of TM microcapsules.

[0016] Preferably, in the core material preparation step, the aliphatic polyester is any one of polylactic acid, polyglycolic acid, polydextral polylactic acid and polycaprolactone, and the cosolvent is at least one of glycerol, butanediol and pentanediol.

[0017] The filter membrane has a pore size of 0.45 micrometers. Selecting appropriate amounts of aliphatic polyester, co-solvent, and reaction steps can significantly improve the reaction rate, enhance the uniformity of the core material, and reduce the reaction time.

[0018] Preferably, in the step of preparing the W / O type primary emulsion, the oil phase additive is at least one of dimethyl silicone oil, phenyl silicone oil, and amino silicone oil; the emulsifier is at least two of Span-40, Span-60, Span-65, and Span-80; and the defoamer is at least one of isopropanol, n-butanol, 1-octanol, and ethanol. Selecting suitable oil phase additives, emulsifiers, and defoamers helps to fully participate in the formation of the primary emulsion and eliminate bubbles generated during the reaction, resulting in a W / O type emulsion with fine droplets, uniform distribution, and long-term stability.

[0019] Preferably, in the step of preparing the W / O type primary emulsion, the ionic strength regulator is at least one of sodium chloride solution, potassium chloride solution, and calcium chloride solution. Selecting a suitable ionic strength regulator helps to improve the conductivity of the pore-forming agent, making the electric field distribution and ion migration more uniform and controllable.

[0020] Preferably, in the step of preparing the pore-forming agent for lithium-ion batteries, the stirring speed is 200-500 r / min, and the stirring reaction continues for 0.1-0.5 h after the dropwise addition is completed;

[0021] The specific operation for adjusting the pH value of the mixing system is as follows: An acidity regulator is added to the mixing system until the pH value is 4-5. The acidity regulator is at least one of hydrochloric acid-sodium citrate buffer, acetic acid-sodium acetate buffer, disodium hydrogen phosphate-sodium dihydrogen phosphate buffer, and sodium citrate solution. The wall material is slowly added dropwise to the primary emulsion under slow stirring. Adjusting the pH value initiates the polymerization reaction, ensuring uniform mixing of the wall material and the primary emulsion, while simultaneously promoting the coating of the core material by the wall material to form a microcapsule structure.

[0022] Preferably, in the step of preparing the pore-forming agent for lithium-ion batteries, the washing, drying, and pulverizing operations are as follows: the emulsion is washed with an ethanol-water solution and the solid product is collected by filtration; the solid product is then vacuum dried; and finally, the solid product is pulverized and passed through a 100-mesh sieve to obtain TM microcapsules. Using ethanol-water solution to wash the emulsion and vacuum drying oven ensures the maximum production of the final product while effectively avoiding raw material waste and reducing the difficulty of subsequent purification.

[0023] In a second aspect, the present invention provides a pore-forming agent for lithium-ion batteries, which is prepared by any of the methods for preparing pore-forming agents for lithium-ion batteries in the first aspect.

[0024] The pore-forming agent for lithium-ion batteries of this invention is biodegradable, does not occupy the final mass or effective volume of the electrode, and can be uniformly dispersed in the electrode slurry, forming a stable structure with the active material and conductive agent. After the electrode dries, it leaves interconnected micron / nanoscale channels. These channels greatly shorten the solid-state diffusion distance of lithium ions and provide a wetting path for the electrolyte, allowing the electrolyte to quickly and uniformly penetrate deep into the electrode, thereby significantly reducing the interfacial impedance and internal ion transport resistance of the battery. Its direct technical effect is that even with increased electrode thickness or the use of high-energy-density active materials, the electrode's kinetic performance remains excellent, manifested in a significant improvement in battery rate performance and a reduction in polarization voltage during charge and discharge. Simultaneously, rapid and sufficient electrolyte wetting ensures the utilization rate of the active material, thereby effectively improving the initial specific capacity of the battery and achieving synergistic optimization of energy density and power density.

[0025] Thirdly, the present invention provides an application of a pore-forming agent for lithium-ion batteries in lithium-ion batteries.

[0026] Applying the pore-forming agent for lithium-ion batteries of this invention to lithium-ion batteries can improve ion conduction and rate performance; the in-situ generated conductive network reduces interface resistance, improves conductivity, and inhibits swelling; the unique structural support effect enhances electrode mechanical integrity and extends cycle life. This invention provides a method for preparing the pore-forming agent for lithium-ion batteries, which features mild reaction conditions, simple preparation process, low cost, and environmental friendliness throughout the preparation process.

[0027] The advantages of the present invention will be set forth in part in the description which follows, and in part will be obvious from the description or may be learned by practice of the embodiments thereof. Attached Figure Description

[0028] To more clearly illustrate the content of this invention, it will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Figure 1 The TG-DSC image provided in Embodiment 1 of the present invention;

[0030] Figure 2 The electrode compaction and liquid absorption test results provided in Example 2 of the present invention are shown in the figure ("0" indicates the electrode group without the pore-forming agent of this application, and "0.5" indicates the electrode group containing 0.5% pore-forming agent).

[0031] Figure 3 The physical rebound test results provided in Example 3 of the present invention (“0” represents the electrode group without the pore-forming agent of this application, and “0.5” represents the electrode group containing 0.5% pore-forming agent);

[0032] Figure 4 DCIR results provided in Example 4 of the present invention (“0” indicates the electrode group without the pore-forming agent of this application, and “0.5” indicates the electrode group containing 0.5% pore-forming agent);

[0033] Figure 5 The electrode internal resistance test result diagram provided in Example 5 of the present invention ("0" represents the electrode group without the pore-forming agent of this application, and "0.5" represents the electrode group containing 0.5% pore-forming agent);

[0034] Figure 6 The rate discharge test results provided in Example 6 of the present invention (“0” represents a lithium battery pack without the pore-forming agent of this application, and “0.5” represents a lithium battery pack containing 0.5% pore-forming agent);

[0035] Figure 7 The high and low temperature discharge test results provided in Example 7 of the present invention (“0” represents a lithium battery pack without the pore-forming agent of this application, and “0.5” represents a lithium battery pack containing 0.5% pore-forming agent). Detailed Implementation

[0036] The following describes preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

[0037] The following detailed embodiments illustrate the preparation process of the pore-forming agent for lithium-ion batteries and the performance of the prepared pore-forming agent. Example 1

[0038] A method for preparing a pore-forming agent for lithium-ion batteries includes the following steps:

[0039] Preparation steps of the wall material: A 20 L reactor was provided. Under stirring (stirring at 400 r / min), 3000 g of deionized water, 254 g of melamine, 251 g of urea, and 1100 g of propionaldehyde solution were added to the reactor. Stirring continued to promote dissolution. After homogeneous mixing, 100 mL of triethanolamine solution was added to the reactor, resulting in a pH of 8.5. The reactor was then heated to 65℃ and stirred for 1.5 h. After the reaction was complete, 12100 g of deionized water was added to the reactor, and the temperature was adjusted to 25℃. Stirring continued for 0.5 h. After the reaction was complete, the mixture was allowed to stand for 0.5 h to obtain the wall material, which was then transferred to a storage tank.

[0040] Core material preparation steps: Provide a 5 L beaker and add 500 g of deionized water, 270 g of polylactic acid and 10 g of butanediol. Stir at 200 r / min for 0.2 h and then filter with a 0.45 μm filter membrane to obtain the aqueous core material, which is then transferred to the liquid feed tank of the reaction vessel.

[0041] Preparation of W / O type primary emulsion: A reaction vessel is provided, and 50 g of dimethyl silicone oil, 5 g of Span-40, 5 g of Span-80, and 4.9 g of ethanol are added to it. The mixture is stirred at 500 r / min for 0.5 h to form a homogeneous oil phase emulsifier. The aqueous phase core material prepared above is then transferred dropwise at a rate of 5 ml / min to a reaction vessel containing oil phase additives, emulsifiers, and defoamers. 150 mL of a 4% sodium chloride solution is added, and the reaction vessel is stirred at 500 r / min for another 0.5 h to form a stable W / O type primary emulsion.

[0042] The preparation steps of the pore-forming agent for lithium-ion batteries are as follows: While stirring a W / O type primary emulsion at 400 r / min, the wall material is added dropwise to the W / O type primary emulsion at a rate of 3 ml / min. After the addition is complete, while continuing to stir the W / O type primary emulsion, 200 mL of hydrochloric acid-sodium citrate buffer solution is added to the W / O type primary emulsion at a rate of 5 ml / min. At this point, the pH of the mixture is 4.1. After adding the buffer solution, stirring is continued for 0.5 h. The reactor is then heated to 70℃ and maintained for 5 h to obtain the primary emulsion. Finally, the obtained primary emulsion is cooled to room temperature, filtered, washed with 30% ethanol-water solution, and the solid product is collected. This process is repeated once. Subsequently, the solid product is washed with deionized water and collected, and this process is repeated once. Finally, the solid product is transferred to a vacuum drying oven at 60℃ and dried for 12 h. The solid product is then pulverized and passed through a 100-mesh sieve to obtain TM microcapsules, i.e., the pore-forming agent for lithium-ion batteries. Example 2

[0043] A method for preparing a pore-forming agent for lithium-ion batteries includes the following steps:

[0044] Preparation steps of the wall material: A 20 L reactor was provided. Under stirring (stirring at 300 r / min), 2500 g of deionized water, 274 g of melamine, 261 g of thiourea, and 900 g of acetaldehyde solution were added to the reactor. Stirring continued to promote dissolution. After homogeneous mixing, 125 mL of sodium bicarbonate solution was added to the reactor, resulting in a pH of 9.0. The reactor was then heated to 70℃ and stirred for 0.5 h. After the reaction was complete, 15000 g of deionized water was added to the reactor. The reactor temperature was cooled to room temperature, and stirring continued for 1 h. After the reaction was complete, the mixture was allowed to stand for 1 h to obtain the wall material, which was then transferred to a storage tank.

[0045] Core material preparation steps: Provide a 5 L beaker and add 1000 g deionized water, 300 g polyglycolic acid and 15 g glycerol. Stir at 300 r / min for 0.5 h and then filter with a 0.45 μm filter membrane to obtain the aqueous core material, which is then transferred to the liquid feeding tank of the reaction vessel.

[0046] Preparation of W / O type primary emulsion: A reaction vessel was provided, and 40 g of phenyl silicone oil, 2.5 g of Span-60, 2.5 g of Span-65, and 4 g of isopropanol were added to it. The mixture was stirred at 400 r / min for 0.2 h to form a homogeneous oil phase emulsifier. The aqueous core material prepared above was then transferred dropwise at a rate of 5 ml / min to a reaction vessel containing oil phase additives, emulsifiers, and defoamers. 200 mL of a 4% potassium chloride solution was added, and the reaction vessel was stirred at 250 r / min for 0.3 h to form a stable W / O type primary emulsion.

[0047] The preparation steps of the pore-forming agent for lithium-ion batteries are as follows: While stirring the W / O type primary emulsion at 300 r / min, the wall material is added dropwise to the W / O type primary emulsion at a rate of 5 ml / min. After the addition is complete, while continuing to stir the W / O type primary emulsion, 400 mL of disodium hydrogen phosphate-sodium dihydrogen phosphate buffer solution is added to the W / O type primary emulsion at a rate of 5 ml / min. At this point, the pH of the mixture is 4.9. After adding the buffer solution, stirring is continued for 0.4 h. The reactor is then heated to 65℃ and maintained for 3 h to obtain the primary emulsion. Finally, the obtained primary emulsion is cooled to room temperature, filtered, washed with 30% ethanol-water solution, and the solid product is collected. This process is repeated once. Subsequently, the solid product is washed with deionized water and collected, and this process is repeated once. Finally, the solid product is transferred to a vacuum drying oven at 60℃ and dried for 12 h. The solid product is then pulverized and passed through a 100-mesh sieve to obtain TM microcapsules, i.e., the pore-forming agent for lithium-ion batteries. Example 3

[0048] A method for preparing a pore-forming agent for lithium-ion batteries includes the following steps:

[0049] Preparation steps of the wall material: A 20 L reactor was provided. Under stirring (stirring at 400 r / min), 3000 g of deionized water, 284 g of melamine, 271 g of urea, and 1100 g of formaldehyde solution were added to the reactor. Stirring continued to promote dissolution. After homogeneous mixing, 125 mL of triethanolamine solution was added to the reactor, resulting in a mixed solution with a pH of 8.8. The reactor was then heated to 65℃ and stirred for 1 h. After the reaction was complete, 12100 g of deionized water was added to the reactor. The reactor temperature was cooled to room temperature, and stirring continued for 0.5 h. After the reaction was complete, the mixture was allowed to stand for 0.5 h to obtain the wall material, which was then transferred to a storage tank.

[0050] Core material preparation steps: Provide a 5 L beaker and add 750 g of deionized water, 287 g of polylactic acid and 19 g of glycerol. Stir at 500 r / min for 0.5 h and then filter with a 0.45 μm filter membrane to obtain the aqueous core material, which is then transferred to the liquid feed tank of the reaction vessel.

[0051] Preparation of W / O type primary emulsion: A reaction vessel was provided, and 47 g of dimethyl silicone oil, 6.6 g of Span-80, 2.8 g of Span-65, and 3.1 g of 1-octanol were added to it. The mixture was stirred at 450 r / min for 0.5 h to form a homogeneous oil phase emulsifier. The aqueous core material prepared above was then transferred dropwise at a rate of 5 ml / min to a reaction vessel containing oil phase additives, emulsifiers, and defoamers. 187 mL of a 4% sodium chloride solution was added, and the reaction vessel was stirred at 450 r / min for another 0.5 h to form a stable W / O type primary emulsion.

[0052] The preparation steps of the pore-forming agent for lithium-ion batteries are as follows: While stirring the W / O type primary emulsion at 500 r / min, the wall material is added dropwise to the W / O type primary emulsion at a rate of 2 ml / min. After the addition is complete, while continuing to stir the W / O type primary emulsion, 450 mL of acetate-sodium acetate buffer solution is added to the W / O type primary emulsion at a rate of 5 ml / min. At this point, the pH of the mixture is 4.5. After adding the buffer solution, stirring is continued for 0.2 h. The reactor is then heated to 80℃ and maintained for 2 h to obtain the primary emulsion. Finally, the obtained primary emulsion is cooled to room temperature, filtered, washed with 30% ethanol-water solution, and the solid product is collected. This process is repeated once. Subsequently, the solid product is washed with deionized water and collected, and this process is repeated once. Finally, the solid product is transferred to a vacuum drying oven at 40℃ and dried for 12 h. The solid product is then pulverized and passed through a 100-mesh sieve to obtain TM microcapsules, i.e., the pore-forming agent for lithium-ion batteries. Example 4

[0053] A method for preparing a pore-forming agent for lithium-ion batteries includes the following steps:

[0054] Preparation steps of the wall material: A 20 L reactor was provided. Under stirring (controlled at 300 r / min), 3500 g of deionized water, 300 g of thiodicyandiamide, 300 g of methylurea, and 800 g of pentanal solution were added to the reactor. Stirring continued to promote dissolution. After homogeneous mixing, 100 mL of dilute sodium hydroxide solution was added to the reactor, resulting in a pH of 8.9. The reactor was then heated to 75℃ and stirred for 0.5 h. After the reaction was complete, 10000 g of deionized water was added to the reactor. The reactor temperature was cooled to 20℃, and stirring continued for 1 h. After the reaction was complete, the mixture was allowed to stand for 1.5 h to obtain the wall material, which was then transferred to a storage tank.

[0055] Core material preparation steps: Provide a 5 L beaker and add 600 g of deionized water, 250 g of poly(D-lactic acid) and 25 g of hexanediol. Stir at 400 r / min for 0.5 h and then filter with a 0.45 μm filter membrane to obtain the aqueous core material, which is then transferred to the liquid feed tank of the reaction vessel.

[0056] Preparation of W / O type primary emulsion: A reaction vessel is provided, and 35 g of amino silicone oil, 0.5 g of Span-60, 0.5 g of Span-80, and 1 g of n-butanol are added to it. The mixture is stirred at 500 r / min for 2 h to form a homogeneous oil phase emulsifier. The aqueous core material prepared above is then transferred dropwise at a rate of 5 ml / min to a reaction vessel containing oil phase additives, emulsifiers, and defoamers. 175 mL of a 4% potassium chloride solution is added, and the reaction vessel is stirred at 200 r / min for 2 h to form a stable W / O type primary emulsion.

[0057] The preparation steps of the pore-forming agent for lithium-ion batteries are as follows: While stirring the W / O type primary emulsion at a rate of 200 r / min, the wall material is added dropwise to the W / O type primary emulsion at a rate of 4 ml / min. After the addition is complete, while continuing to stir the W / O type primary emulsion, 100 mL of hydrochloric acid-sodium citrate buffer solution is added to the W / O type primary emulsion at a rate of 3 ml / min. At this point, the pH of the mixture is 4.2. After adding the buffer solution, stirring is continued for 0.2 h. The reactor is then heated to 65℃ and maintained for 3 h to obtain the primary emulsion. Finally, the obtained primary emulsion is cooled to room temperature, filtered, washed with 30% ethanol-water solution, and the solid product is collected. This process is repeated once. Subsequently, the solid product is washed with deionized water and collected, and this process is repeated once. Finally, the solid product is transferred to a vacuum drying oven at 50℃ and dried for 12 h. The solid product is then pulverized and passed through a 100-mesh sieve to obtain TM microcapsules, i.e., the pore-forming agent for lithium-ion batteries. Example 5

[0058] A method for preparing a pore-forming agent for lithium-ion batteries includes the following steps:

[0059] Preparation steps of the wall material: A 20 L reactor was provided. Under stirring (controlled at 200 r / min), 3500 g of deionized water, 294 g of melamine, 281 g of 1,1-dimethylurea, and 1200 g of butyraldehyde solution were added to the reactor. Stirring continued to promote dissolution. After homogeneous mixing, 150 mL of ethanolamine solution was added to the reactor, resulting in a mixed solution with a pH of 8.6. The reactor was then heated to 70℃ and stirred for 1 h. After the reaction was complete, 15000 g of deionized water was added to the reactor. The reactor temperature was cooled to room temperature, and stirring continued for 2 h. After the reaction was complete, the mixture was allowed to stand for 1 h to obtain the wall material, which was then transferred to a storage tank.

[0060] Core material preparation steps: Provide a 5 L beaker and add 900 g of deionized water, 260 g of polycaprolactone and 30 g of pentanediol. Stir at 250 r / min for 0.1 h and then filter with a 0.45 μm filter membrane to obtain the aqueous core material, which is then transferred to the liquid feed tank of the reaction vessel.

[0061] Preparation of W / O type primary emulsion: A reaction vessel is provided, and 30 g of phenyl silicone oil, 3 g of Span-40, 1 g of Span-65, and 2 g of isopropanol are added to it. The mixture is stirred at 300 r / min for 0.4 h to form a homogeneous oil phase emulsifier. The aqueous core material prepared above is then transferred dropwise at a rate of 5 ml / min to a reaction vessel containing oil phase additives, emulsifiers, and defoamers. 150 mL of 4% calcium chloride solution is added, and the reaction vessel is stirred at 300 r / min for 1 h to form a stable W / O type primary emulsion.

[0062] The preparation steps of the pore-forming agent for lithium-ion batteries are as follows: While stirring the W / O type primary emulsion at 300 r / min, the wall material is added dropwise to the W / O type primary emulsion at a rate of 2 ml / min. After the addition is complete, while continuing to stir the W / O type primary emulsion, 300 mL of acetate-sodium acetate buffer solution is added to the W / O type primary emulsion at a rate of 3 ml / min. At this point, the pH of the mixture is 4.7. After adding the buffer solution, stirring is continued for 0.1 h. The reactor is then heated to 60℃ and maintained for 5 h to obtain the primary emulsion. Finally, the obtained primary emulsion is cooled to room temperature, filtered, washed with 30% ethanol-water solution, and the solid product is collected. This process is repeated once. Subsequently, the solid product is washed with deionized water and collected, and this process is repeated once. Finally, the solid product is transferred to a vacuum drying oven at 40℃ and dried for 12 h. The solid product is then pulverized and passed through a 100-mesh sieve to obtain TM microcapsules, i.e., the pore-forming agent for lithium-ion batteries. Example 6

[0063] An electrode sheet is made by a conventional pulping, coating, rolling and cutting process, which is special in that: the pore-forming agent for lithium-ion batteries prepared in Example 3 is added in the pulping step, and the amount of the pore-forming agent for lithium-ion batteries added is 0.5% of the total weight.

[0064] Comparative Example 1

[0065] An electrode sheet that differs from the electrode sheet in Example 6 in that it omits the addition of a pore-forming agent for lithium-ion batteries.

[0066] Example 1: Low-Temperature Decomposition Performance Test

[0067] The pore-forming agent for lithium-ion batteries prepared in Example 3 above was used for decomposition performance testing. The specific testing method was as follows: a small amount of sample was placed in a thermobalance crucible, and under a set gas atmosphere (nitrogen), the temperature was increased from room temperature to the target temperature (600℃) at a constant rate (10℃ / min). The thermobalance continuously and in real-time measured and recorded the change in sample mass with temperature / time (TG) and the rate of mass change (DTG). The test results are shown in the appendix. Figure 1 .

[0068] like Figure 1 As shown, the TG curve of the pore-forming agent for lithium-ion batteries prepared in Example 3 begins to decline at lower temperatures, mainly due to water evaporation. When the temperature rises to 120°C, the wall material begins to degrade, with the main degradation stage occurring between 120°C and 170°C. Within this temperature range, the mass decreases sharply, indicating a significant thermal decomposition reaction, which is the main weight loss stage. After 170°C, the DTG curve quickly returns to near zero, indicating that the degradation of the remaining wall material is mainly complete, and the overall thermal decomposition process is essentially finished. This demonstrates that the pore-forming agent for lithium-ion batteries prepared in this application possesses excellent degradation and dispersion properties.

[0069] Example 2: Electrode Compaction and Liquid Absorption Test

[0070] Electrode sheets prepared in Example 6 (containing 0.5% pore-forming agent) and those in Comparative Example 1 (containing 0% pore-forming agent) were used for testing electrode compaction and liquid absorption properties. The specific testing method was as follows: the electrode sheets were compacted to different compaction densities (1.45–1.80 g / cm³). 3 Then, using a pipette, PC (polycarbonate) was added dropwise to electrodes with different compaction densities. The time it took for the electrodes to absorb PC was measured using a stopwatch. The test results are shown in the appendix. Figure 2 .

[0071] like Figure 2As shown, the electrolyte absorption time of the electrode gradually increases with increasing compaction density. This is because under high compaction density, the electrode pores become smaller and fewer, making it difficult for the electrolyte to penetrate quickly. When the compaction density is 1.75 mg / cm³... 3 When near the electrode, compared to the electrode without a pore-forming agent, the electrode corresponding to Example 3 has a shorter liquid absorption time at the same compaction density. A shorter absorption time indicates better electrolyte wettability. This shows that the battery corresponding to the electrode assembled using a pore-forming agent for lithium-ion batteries prepared in this application has superior initial coulombic efficiency, higher rate performance, and greater stability over long cycles.

[0072] Example 3: Electrode Physical Rebound Test

[0073] Electrode sheets prepared in Example 6 (containing 0.5% pore-forming agent) and those in Comparative Example 1 (containing 0% pore-forming agent) were used for physical rebound testing. The specific testing method was as follows: the thickness of different electrode sheets was measured with calipers, and then the entire electrode sheet was placed in an oven at 60°C for 24 hours. During storage, the electrode thickness was measured periodically, and the thickness expansion rate was calculated before and after storage. The test results are shown in the appendix. Figure 3 .

[0074] like Figure 3 As shown, when the storage time is 24 h, compared with the electrode sheet without pore-forming agent, the electrode sheet corresponding to Example 6 has a lower electrode thickness expansion rate under the same conditions, indicating that the pore-forming agent prepared by this application has lower physical expansion at higher temperatures, and the corresponding electrode sheet has more stable performance when working at higher temperatures.

[0075] Example 4: DC Internal Resistance Test

[0076] Electrode sheets prepared in Example 6 (containing 0.5% pore-forming agent) and those prepared in the comparative example (containing 0% pore-forming agent) were assembled into batteries. Different SOC states (remaining battery capacity 100%, 80%, 60%, 40%, 20%) were adjusted, and their 1 C & 30 s DC impedance DCIR was measured using a DC resistance meter. 30s -V 0s ) / I1C. See the appendix for test results. Figure 4 .

[0077] like Figure 4As shown, the DC internal resistance of the battery exhibits a strong "smile curve" relationship with the SOC state. When the remaining battery capacity decreases from 40% to 20%, the increase in internal resistance is very steep, indicating that the battery's performance drops sharply at low charge levels. Furthermore, at all SOC states (remaining battery capacity of 100%, 80%, 60%, 40%, and 20%), compared to the DC resistance of electrodes assembled without the addition of a pore-forming agent, the electrodes assembled using the pore-forming agent for lithium-ion batteries prepared in this application have a lower DC internal resistance. This demonstrates that the electrode sheet prepared in Example 6 has superior conductivity, resulting in better electrical performance for the corresponding lithium battery.

[0078] Example 5: Electrode Internal Resistance Test

[0079] The electrode sheet prepared in Example 6 (containing 0.5% pore-forming agent) and the electrode sheet in Comparative Example 1 (containing 0% pore-forming agent) were cut into pieces 200 mm wide and 220 mm long, and the thickness of the sheets was tested. The test sample was placed on the sample holder, and the height handwheel was adjusted to ensure good contact between the probe and its surface. The power was turned on and preheated for 1 hour. The resistivity was measured three times according to the operating procedure of the four-probe tester, and the average value was taken. The test results are shown in the appendix. Figure 5 .

[0080] like Figure 5 As shown in the results of the three tests, the internal resistance of the electrode without the pore-forming agent was higher than that of the electrode prepared in Example 6. This indicates that the electrode assembled based on the pore-forming agent for lithium-ion batteries prepared in Example 3 has a lower internal resistance, which helps to reduce the capacity loss of lithium batteries and also improves the rate performance and cycle life of lithium-ion batteries.

[0081] Example 6: Ratio Performance Test

[0082] The electrode sheet prepared in Example 6 (containing 0.5% pore-forming agent) and the electrode sheet prepared in Comparative Example 1 (containing 0% pore-forming agent) were assembled into a lithium-ion battery for rate performance testing. The specific testing method was as follows: (1) The test battery was prepared according to the battery preparation process and marked. (2) Charging method: constant current and constant voltage charging at 0.5 C to 4.2 V, with a cutoff current of 0.01 C; Discharging method: constant current discharge at 0.2 C, 0.5 C, 1.0 C, 2.0 C, and 3.0 C to a voltage of 2.75 V. (3) The discharge capacity at 0.2 C / 0.2 C, 0.2 C / 0.5 C, 0.2 C / 1.0 C, 0.2 C / 2.0 C, and 0.2 C / 3.0 C was calculated. The test results are shown in Appendix. Figure 6 .

[0083] like Figure 6As shown, compared to the battery without the pore-forming agent, the lithium-ion battery prepared based on the electrode sheet in Example 6 exhibits higher discharge capacity under different current intensities. This indicates that the battery assembled with the pore-forming agent prepared in this application has a higher specific capacity under different current intensities. This may be related to the fact that the pore-forming agent prepared in this application optimizes the electrode conductivity, thereby resulting in the prepared electrode sheet having greater energy storage performance and rate performance stability.

[0084] Example 7: High and Low Temperature Discharge Performance Test

[0085] The electrode sheet prepared in Example 6 (containing 0.5% pore-forming agent) and the electrode sheet in Comparative Example 1 (containing 0% pore-forming agent) were assembled into a lithium-ion battery for high and low temperature discharge performance testing. The specific testing method was as follows: (1) The test battery was prepared according to the battery preparation process and marked. (2) The battery was charged: it was charged to 4.2 V with a constant current and constant voltage of 0.5 C and the cut-off current was 0.01 C. (3) The battery was placed in a biochemical incubator at different temperatures (-20℃, -10℃, 0℃, 45℃, 60℃) and left to stand for 72 h. Then it was discharged to 2.75 V with a constant current of 1.0 C. (4) The battery capacity was tested. The test results are shown in Appendix. Figure 7 .

[0086] like Figure 7 As shown, the discharge capacity of batteries assembled based on the electrodes in Example 6 and Comparative Example 1 increases with increasing temperature. Compared to lithium batteries without pore-forming agents, lithium batteries with pore-forming agents prepared in the examples have higher discharge capacities at different temperatures. Especially when the temperature reaches above 0°C, the difference between the discharge capacity of lithium batteries with pore-forming agents prepared in Example 3 and those without pore-forming agents is greater, indicating that the lithium-ion batteries assembled with pore-forming agents prepared in this application can adapt to different temperature operating environments and maintain high discharge capacity.

[0087] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are 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. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a pore-forming agent for lithium-ion batteries, characterized in that, By weight, the following steps are included: Preparation of wall material: Provide 2500-3500 parts of deionized water, 250-300 parts of cyanamide oligomer, 250-300 parts of urea compound, and 800-1200 parts of low-grade aliphatic aldehyde. Mix the deionized water, cyanamide oligomer, urea compound, and low-grade aliphatic aldehyde and transfer them to the first reaction vessel. Adjust the pH of the mixed solution in the first reaction vessel to 8.5-9. Then heat the first reaction vessel to 65-75℃ and maintain it for 0.5-1.5 h. After the reaction is completed, continue to add 10000-15000 parts of deionized water to the first reaction vessel and continue stirring for 0.5-2 h. Then let it stand for 0.5-1.5 h to obtain the wall material. Preparation of core material: Provide 500-1000 parts of deionized water, 250-300 parts of aliphatic polyester and 10-30 parts of co-solvent. Mix the deionized water, aliphatic polyester and co-solvent and pass them through a filter membrane to obtain an aqueous core material. Preparation of W / O type primary emulsion: Provide 30-50 parts of oil phase additive, 1-10 parts of emulsifier and 1-5 parts of defoamer. Add the oil phase additive, emulsifier and defoamer to the second reaction vessel and mix well to obtain oil phase emulsifier. While stirring the oil phase emulsifier, add the aqueous phase core material dropwise to the second reaction vessel. Then add 150-200 parts of ionic strength regulator to the second reaction vessel and stir to obtain W / O type primary emulsion. Preparation of pore-forming agent for lithium-ion batteries: Under the condition of stirring W / O type primary emulsion, wall material is added dropwise to W / O type primary emulsion. After the addition is completed, the pH value of the mixture is adjusted to 4-5, and stirring is continued for 0.1-0.5 h. Then the temperature of the second reaction vessel is raised to 70-80℃ and maintained for 1-5 h to obtain emulsion. The emulsion is washed, dried and pulverized to obtain TM microcapsules, which are pore-forming agents for lithium-ion batteries.

2. The method for preparing the pore-forming agent for lithium-ion batteries as described in claim 1, characterized in that, In the wall material preparation step, the cyanamide oligomer is at least one of melamine, dicyandiamide and thiodicyandiamide, the urea compound is at least one of urea, thiourea, methylurea and 1,1-dimethylurea, and the lower aliphatic aldehyde is at least one of formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde and pentanal.

3. The method for preparing the pore-forming agent for lithium-ion batteries as described in claim 1, characterized in that, In the wall material preparation step, the specific operation of adjusting the pH value of the mixed solution in the first reaction vessel to 8.5-9 is as follows: while stirring the mixed solution, add an alkalinity adjuster until the pH value reaches 8.5-9; The alkalinity adjuster is at least one of triethanolamine solution, ethanolamine solution, sodium bicarbonate solution, and sodium hydroxide solution.

4. The method for preparing the pore-forming agent for lithium-ion batteries as described in claim 1, characterized in that, In the core material preparation step, the aliphatic polyester is any one of polylactic acid, polyglycolic acid, polydextral polylactic acid and polycaprolactone, and the cosolvent is at least one of glycerol, butanediol, pentanediol and hexanediol. The filter membrane has a pore size of 0.45 micrometers.

5. The method for preparing the pore-forming agent for lithium-ion batteries as described in claim 1, characterized in that, In the step of preparing W / O type primary emulsion, the oil phase additive is at least one of dimethyl silicone oil, phenyl silicone oil and amino silicone oil, the emulsifier is at least two of Span-40, Span-60, Span-65 and Span-80, and the defoamer is at least one of isopropanol, n-butanol and 1-octanol and ethanol.

6. The method for preparing the pore-forming agent for lithium-ion batteries as described in claim 1, characterized in that, In the preparation of W / O type colostrum, the ionic strength regulator is at least one of sodium chloride solution, potassium chloride solution and calcium chloride solution.

7. The method for preparing the pore-forming agent for lithium-ion batteries as described in claim 1, characterized in that, In the step of preparing the pore-forming agent for lithium-ion batteries, the stirring speed is 200-500 r / min, and the stirring reaction continues for 0.1-0.5 h after the dropwise addition is completed; The specific operation for adjusting the pH value of the mixture is as follows: add an acidity regulator to the mixture until the pH value is 4-5. The acidity regulator is at least one of hydrochloric acid-sodium citrate buffer, acetic acid-sodium acetate buffer, disodium hydrogen phosphate-sodium dihydrogen phosphate buffer, and sodium citrate solution.

8. The method for preparing the pore-forming agent for lithium-ion batteries as described in claim 1, characterized in that, In the step of preparing the pore-forming agent for lithium-ion batteries, the washing, drying, and pulverizing operations are as follows: the emulsion is washed with an ethanol-water solution and the solid product is collected by filtration, the solid product is then vacuum dried, and finally the solid product is pulverized and passed through a 100-mesh sieve to obtain TM microcapsules.

9. A pore-forming agent for lithium-ion batteries, characterized in that, It is prepared by the method for preparing the pore-forming agent for lithium-ion batteries according to any one of claims 1-8.

10. An application of the pore-forming agent for lithium-ion batteries as described in claim 9, characterized in that, The application is in lithium-ion batteries.

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