A voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material, its preparation method and application

Abstract

This invention relates to the field of battery technology, specifically disclosing a voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material, its preparation method, and its applications. This invention constructs a three-dimensional nitrogen-doped carbon framework with hierarchical channels and utilizes in-situ polymerization to form a voltage-responsive copolymer layer on the carbon surface, doubly anchored by chemical and hydrogen bonds, achieving an effective synergy between material structural stability and dynamic regulation performance. This composite material not only possesses excellent electrolyte wettability and a high ion transport rate but also dynamically adjusts the ion channel state according to the operating voltage of the lead-acid battery, thereby achieving adaptive regulation within the battery. This invention effectively improves upon the limitations of traditional static separator structures, significantly suppressing problems such as increased internal resistance, dendrite growth, and electrolyte drying during battery cycling. It provides a practical material solution for significantly improving the cycle life, safety, and overall electrochemical performance of lead-acid batteries, with broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material, its preparation method, and its application. Background Technology

[0002] Lead-acid batteries occupy an irreplaceable position in fields such as new energy storage, transportation, and emergency backup power due to their advantages such as low cost, high safety, and stable charge and discharge performance. As one of the core components of lead-acid batteries, AGM (adsorbed glass fiber) separators play a crucial role in adsorbing electrolyte, isolating the positive and negative plates, and providing ion transport channels. Their performance directly determines the battery's internal resistance, capacity, cycle life, and safety stability.

[0003] Currently, traditional AGM separators generally use glass fiber wool as the substrate, relying on the porous structure of the glass fiber itself to adsorb and fix the electrolyte. However, traditional glass fiber substrates have poor ionic conductivity, limited electrolyte adsorption and retention capacity, and are prone to mechanical deformation during long-term charge-discharge cycles, leading to the collapse of the internal pore structure of the separator and obstruction of ion transport channels. This results in a continuous increase in battery internal resistance and accelerated capacity decay, which is severely mismatched with the lifespan of lead-acid batteries. This not only increases user costs but also limits the application of lead-acid batteries in scenarios requiring long lifespan.

[0004] To improve the performance defects of traditional AGM separators, current efforts mainly focus on two directions: carbon material composites and polymer coatings. However, these solutions still have significant limitations. While combining carbon materials with glass fibers can improve conductivity, it cannot solve problems such as current distribution, dendrite growth, and water decomposition within the battery. Furthermore, the electrolyte wetting speed is slow, making it difficult to meet the requirements for rapid battery activation and efficient charge / discharge. Polymer-coated glass fiber substrates are mainly coated through simple deposition, which easily leads to uneven polymer distribution on the fiber surface. The bonding force between the polymer and glass fibers is weak, relying only on physical adsorption or weak hydrogen bonding, making it prone to detachment under battery cycling vibration and electrolyte erosion. More importantly, this type of polymer coating lacks voltage response characteristics, making it unable to adapt to the charge / discharge voltage fluctuations in the 1.5~2.5V range of lead-acid batteries. It is difficult to dynamically control the ion transport channels according to the battery's operating state, and therefore cannot provide active dynamic safety protection for the battery.

[0005] Therefore, developing a novel AGM separator material with high ionic conductivity, excellent electrolyte retention capacity, stable structural performance, and voltage response characteristics is of great significance for breaking through the performance bottleneck of lead-acid batteries. Summary of the Invention

[0006] To address the shortcomings of traditional AGM separators in terms of conductivity, structural stability, and dynamic adaptability, this invention provides a voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material, its preparation method, and its applications.

[0007] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0008] In a first aspect, the present invention provides a method for preparing a voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material, comprising the following steps:

[0009] S1, disperse carbon source, nitrogen source and composite template in water to obtain precursor dispersion; heat the precursor dispersion to 150℃~250℃ for hydrothermal reaction; after the hydrothermal reaction is completed, separate solid and liquid; soak the obtained solid in a solution containing fluorine and freeze dry to obtain precursor.

[0010] The composite template includes nano-silica and cellulose nanofibers;

[0011] S2, Under an inert atmosphere, the precursor is carbonized at 600℃~900℃ to obtain a three-dimensional nitrogen-doped carbon material.

[0012] S3, the three-dimensional nitrogen-doped carbon material is dispersed in a polar solvent, a comonomer and an initiator are added, and a polymerization reaction is carried out at 0℃~5℃ to obtain a voltage-responsive copolymer coating the three-dimensional nitrogen-doped carbon material; wherein, the comonomer includes aniline, pyrrole and p-aminobenzenesulfonic acid.

[0013] Compared to existing technologies, the method for preparing voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon materials provided by this invention uses nano-silica and cellulose nanofibers as composite templates. Through etching and carbonization processes, an interconnected hierarchical porous structure is formed: after carbonization, macropores are formed in the gaps between the network skeleton of the cellulose nanofibers; after etching, the nano-SiO2 template forms abundant mesoporous channels; and during carbonization, the volatilization of small molecules inside generates a large number of micropores. This hierarchical structure with macropore-mesopore-micropore synergy greatly increases the specific surface area and electrolyte wettability of the material, and provides multidimensional and efficient channels for ion transport, effectively alleviating the ion transport polarization problem during charge and discharge processes.

[0014] The copolymer formed by copolymerizing aniline, pyrrole, and p-aminobenzenesulfonic acid exhibits unique voltage response properties, precisely adapting to the 1.5~2.5V charge-discharge voltage fluctuation range of lead-acid batteries. The copolymerization of aniline and pyrrole forms a denser and more stable conductive polymer network, which, through π-π conjugation and chemical interactions, forms a strong interfacial bond with the three-dimensional carbon skeleton, greatly improving the problems of weak bonding and easy detachment of traditional physical coatings. The sulfonate groups introduced in p-aminobenzenesulfonic acid not only enhance the polymer's hydrophilicity and ion exchange capacity in the electrolyte, but its negative charge also helps to homogenize the electric field distribution and suppress the disordered growth of lead dendrites.

[0015] By employing in-situ chemical polymerization in a polar solvent at low temperatures (0℃~5℃), copolymer monomers can be polymerized and deposited uniformly and densely on the surface and within the internal pores of three-dimensional nitrogen-doped carbon materials. This method avoids problems such as uneven coating and pore blockage caused by simple physical coating or deposition, maximizing the preservation of the porous structure of the carbon skeleton, and achieving complete coating of the polymer layer, thus ensuring the uniformity and stability of material properties.

[0016] Furthermore, in S1, the carbon source includes one or both of graphene oxide and chitosan.

[0017] Furthermore, in S1, the nitrogen source includes one or both of melamine or urea.

[0018] The preferred nitrogen source reacts with the carbon source at high temperature to generate a carbon matrix that is fully nitrogen-doped and has good electrical conductivity.

[0019] Further, in S1, the mass ratio of the carbon source, nitrogen source and composite template is 1:(2.5~4.0):(0.6~1.0).

[0020] By controlling the amount of composite template added within the above-mentioned range, it is possible to ensure that the template agent forms a rich mesoporous and macroporous structure, providing a guarantee for the rapid transport and storage of ions and electrolytes. This also avoids the problem of insufficient carbon material and excessive weakening of the conductive framework caused by excessive template agent, thus ensuring the conductivity and mechanical properties of the carbon framework.

[0021] Furthermore, in S1, the carbon source concentration in the precursor dispersion is 20 g / L to 25 g / L.

[0022] Furthermore, in S1, the mass ratio of the nano-silica to the cellulose nanofibers is 3:1 to 1:3.

[0023] Controlling the ratio of nano-silica to cellulose nanofibers within the above-mentioned range is beneficial for regulating the relative abundance and connectivity of mesopores and macropores in the final material, thereby simultaneously improving ion transport rate and electrolyte wettability.

[0024] Furthermore, in S1, the particle size of the nano-silica is 5nm~20nm; the diameter of the cellulose nanofibers is 2nm~5nm.

[0025] Furthermore, in S1, the hydrothermal reaction time is 6h~12h.

[0026] The optimized reaction time is conducive to the full reaction of carbon source, nitrogen source and composite template in hydrothermal environment to form precursor gel with stable three-dimensional network and preliminary multi-level pore structure.

[0027] Further, in S1, the fluoride solution is a hydrofluoric acid solution with a mass concentration of 2% to 5%.

[0028] Furthermore, in S1, the soaking time is 6h~12h.

[0029] Furthermore, in S1, the freeze-drying temperature is -50℃ to -40℃, and the freeze-drying time is 12h to 36h.

[0030] Furthermore, in S2, the carbonization time is 1h to 3h.

[0031] Furthermore, in S2, the temperature is raised to 600℃~900℃ using a programmed temperature rise method, with a heating rate of 5℃ / min~10℃ / min.

[0032] The optimal carbonization temperature, carbonization time, and heating rate can fully transform the precursor into a highly conductive and stable three-dimensional nitrogen-doped carbon framework, while maximizing the preservation of the integrity of the multi-level channel structure constructed by the template, achieving full graphitization.

[0033] Furthermore, in S3, the polar solvent is N,N-dimethylformamide.

[0034] Furthermore, in S3, the mass ratio of the three-dimensional nitrogen-doped carbon material to the polar solvent is 1:10 to 1:30.

[0035] Further, in S3, the initiator is a mixed solution of ammonium persulfate and concentrated hydrochloric acid, wherein the mass ratio of ammonium persulfate to concentrated hydrochloric acid is 1:1 to 1:3, and the mass fraction of concentrated hydrochloric acid is 36% to 38%.

[0036] Furthermore, in S3, the amount of initiator added is 2% to 8% of the total mass of the comonomer.

[0037] Further, in S3, the molar ratio of aniline, pyrrole and p-aminobenzenesulfonic acid is (4~6):(2~4):(1~3).

[0038] The copolymer at this ratio can precisely adapt to the charge / discharge voltage fluctuation range of lead-acid batteries from 1.5 to 2.5V. Under different battery operating conditions, it dynamically regulates the ion transport channels by adjusting its own chemical structure. When the battery is overcharged at high voltage, the copolymer is oxidized, the molecular chains expand and become positively charged, the hydrophilicity is enhanced, and the ion channels are dynamically widened, alleviating ion congestion and polarization. When the battery is discharged to low voltage, the copolymer is reduced, the molecular chains contract, the ion channels are dynamically tightened, effectively binding the electrolyte and preventing electrolyte loss that could lead to dry short circuits, thus providing active and intelligent dynamic safety protection for the battery.

[0039] Furthermore, in S3, the mass ratio of the total amount of the comonomer to the three-dimensional nitrogen-doped carbon material is 0.5:1 to 1.5:1.

[0040] By controlling the amount of comonomer added within the above range, it is possible not only to ensure the formation of a complete and dense electroresponsive polymer functional layer on the surface of carbon materials, allowing functions such as voltage response and dendrite suppression to be fully utilized, but also to avoid excessive coating and blockage of multi-level channels. Thus, while endowing the material with intelligent responsive performance, the high ion transport capability of the carbon skeleton is preserved to the greatest extent.

[0041] Furthermore, in S3, the polymerization reaction takes 2 to 8 hours.

[0042] Aniline, pyrrole, and p-aminobenzenesulfonic acid copolymers can form a strong chemically anchored interface with a three-dimensional nitrogen-doped carbon backbone. The amino groups (-NH2) on the carbon backbone surface undergo dehydration condensation with the imine groups (-N=CH-) on the polymer chain, forming stable amide bonds (-NH-N=CH-); simultaneously, strong hydrogen bonds (-NH2...HO-SO2-) are formed between the amino groups and the sulfonic acid groups (-SO3H) on the polymer side chains. This dual anchoring of chemical bonds and hydrogen bonds effectively improves the interfacial bonding strength between the polymer and the carbon backbone, ensuring that the polymer coating does not detach under long-term charge-discharge cycles and electrolyte scouring, thus improving the stability of the material's performance during long-term charge-discharge processes.

[0043] In a second aspect, the present invention provides a voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material, which is prepared by the preparation method of the voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material described in any one of the above claims.

[0044] This invention utilizes a unique process design to prepare a novel composite material that combines excellent conductivity, high electrolyte affinity, stable interfacial bonding, and dynamic voltage response. When used in AGM separators for lead-acid batteries, this material can simultaneously address core issues such as increased internal resistance, short cycle life, and insufficient safety, significantly improving the overall performance of the battery and laying the material foundation for the practical application of high-performance intelligent AGM separators.

[0045] Thirdly, the present invention also provides the application of the above-mentioned voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material in AGM separators for lead-acid batteries.

[0046] Fourthly, the present invention provides an AGM separator for lead-acid batteries, comprising a glass fiber cotton substrate and a three-dimensional nitrogen-doped carbon material coated with the aforementioned voltage-responsive copolymer loaded on the glass fiber cotton substrate.

[0047] Specifically, the voltage-responsive copolymer prepared in this invention is coated with a three-dimensional nitrogen-doped carbon material, a dispersant, and a binder to form a slurry. This slurry is then loaded onto one or both sides of a glass fiber cotton substrate using a dipping-coating, spraying, or roller coating process, with the loading amount controlled at 40 g / m². 2 ~45g / m 2 Then, after drying and curing, AGM partitions are obtained.

[0048] Specifically, the binder and dispersant can be substances commonly used in the art, such as polytetrafluoroethylene as the binder and sodium dodecylbenzene sulfonate as the dispersant. The mass content of the binder in the slurry is 0.2% to 0.5%, and the mass content of the dispersant is 3% to 7%.

[0049] In summary, this invention achieves a synergistic effect between material structural stability and dynamic regulation performance by constructing a three-dimensional nitrogen-doped carbon framework with hierarchical channels and forming a voltage-responsive copolymer layer on the carbon surface through in-situ polymerization, anchored by both chemical and hydrogen bonds. This composite material not only possesses excellent electrolyte wettability and a high ion transport rate but also dynamically adjusts the ion channel state according to the operating voltage of the lead-acid battery, thereby achieving adaptive regulation within the battery. This invention effectively improves the limitations of traditional static separator structures, significantly suppressing problems such as increased internal resistance, dendrite growth, and electrolyte drying during battery cycling. It provides a practical material solution for significantly improving the cycle life, safety, and overall electrochemical performance of lead-acid batteries, with broad application prospects. Attached Figure Description

[0050] Figure 1 The nitrogen adsorption-desorption isotherm of the voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material prepared in Example 1 of this invention;

[0051] Figure 2 The image shows the pore size distribution of the voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material prepared in Example 1 of this invention. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0053] To better illustrate the present invention, further examples are provided below.

[0054] The polytetrafluoroethylene (PTFE) emulsion used in the following examples has a solid content of 60%. The glass fiber wool substrate has a thickness of 1.5 mm and an areal density of 300 g / m³. 2 The particle size of nano-silica is 5nm~20nm; the diameter of cellulose nanofibers is 2nm~5nm. The mass concentration of concentrated hydrochloric acid is 36%~38%.

[0055] Example 1

[0056] This invention provides a method for preparing a voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material, specifically including the following steps:

[0057] S1, 10g of graphene oxide, 30g of melamine, 2g of nano-silica and 6g of cellulose nanofibers were dispersed in 500mL of deionized water and ultrasonically dispersed for 30min. The mixture was then transferred to a hydrothermal reactor, heated to 200℃ and kept at that temperature for 8h. After filtration, the resulting solid was added to a 4wt% hydrofluoric acid solution at a material-to-liquid ratio of 1:15 and soaked at room temperature for 8h. Then, it was freeze-dried at -40℃ for 24h and placed in a nitrogen atmosphere furnace for carbonization at 800℃ for 2h to obtain a three-dimensional nitrogen-doped carbon material.

[0058] S2, 10g of the three-dimensional nitrogen-doped carbon material prepared above was dispersed in 200mL of N,N-dimethylformamide, and 50mmol aniline, 30mmol pyrrole, 20mmol p-aminobenzenesulfonic acid, 0.17g ammonium persulfate and 0.34g concentrated hydrochloric acid were added. The mixture was stirred and polymerized at 0℃ for 4h to obtain a reaction solution of voltage-responsive copolymer coated with three-dimensional nitrogen-doped carbon material.

[0059] Add 0.6g of sodium dodecylbenzenesulfonate and 5g of polytetrafluoroethylene emulsion to the above reaction solution, and stir for 30 minutes to obtain a composite slurry. Spray the composite slurry onto a layer of a glass fiber cotton substrate with a loading of 40g / m². 2 Then, it is dried at 100℃ for 30 minutes to obtain AGM separator.

[0060] The nitrogen adsorption-desorption isotherm of the voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material prepared in this embodiment is as follows: Figure 1 As shown, this curve is a typical type IV isotherm, exhibiting typical capillary condensation characteristics of mesoporous materials, with the adsorption capacity ultimately reaching 650 cm⁻¹. 3 / g(STP), corresponding to its high specific surface area of ​​1242m² 2 / g.

[0061] The pore size distribution curve of the voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material prepared in this embodiment is shown in the figure below. Figure 2 As shown in the figure, the pore volume change rate (dV / dr) reaches its peak near a pore radius of 10 Å (1 nm, micropore range), indicating that micropores (<2 nm) are the core source of pore volume. Within a pore radius of 20–50 Å (2–5 nm, mesopore range), dV / dr continuously contributes, corresponding to the proportion of mesopore volume. After the pore radius exceeds 50 Å, dV / dr begins to decrease to a lower level, indicating a low proportion of macropores. This demonstrates that the overall pore structure of the voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material prepared in this embodiment exhibits a multi-level distribution structure of micropores (<2 nm) – mesopores (2–50 nm) – macropores (>50 nm).

[0062] Example 2

[0063] This invention provides a method for preparing a voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material, specifically including the following steps:

[0064] S1, 12g chitosan, 30g melamine, 5.4g nano silica and 1.8g cellulose nanofibers were dispersed in 500mL deionized water and ultrasonically dispersed for 30min. The mixture was then transferred to a hydrothermal reactor, heated to 250℃ and kept at that temperature for 6h. After filtration, the resulting solid was added to a 2wt% hydrofluoric acid solution at a material-to-liquid ratio of 1:15 and soaked at room temperature for 12h. Then, it was freeze-dried at -40℃ for 24h and placed in a nitrogen atmosphere furnace for carbonization at 900℃ for 1h to obtain a three-dimensional nitrogen-doped carbon material.

[0065] S2, 10g of the three-dimensional nitrogen-doped carbon material prepared above was dispersed in 300mL of N,N-dimethylformamide, and 40mmol aniline, 20mmol pyrrole, 10mmol p-aminobenzenesulfonic acid, 0.1g ammonium persulfate and 0.1g concentrated hydrochloric acid were added. The mixture was stirred and polymerized at 2℃ for 2h to obtain a reaction solution of voltage-responsive copolymer coated with three-dimensional nitrogen-doped carbon material.

[0066] Add 0.6g of sodium dodecylbenzenesulfonate and 5g of polytetrafluoroethylene emulsion to the above reaction solution, and stir for 30 minutes to obtain a composite slurry. Spray the composite slurry onto a layer of a glass fiber cotton substrate with a loading of 40g / m². 2 Then, it is dried at 100℃ for 30 minutes to obtain AGM separator.

[0067] Example 3

[0068] This invention provides a method for preparing a voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material, specifically including the following steps:

[0069] S1, 11g of graphene oxide, 44g of urea, 4g of nano-silica and 7g of cellulose nanofibers were dispersed in 500mL of deionized water and ultrasonically dispersed for 30min. The mixture was then transferred to a hydrothermal reactor, heated to 150℃ and kept at that temperature for 12h. After filtration, the resulting solid was added to a 5wt% hydrofluoric acid solution at a material-to-liquid ratio of 1:15 and soaked at room temperature for 6h. Then, it was freeze-dried at -40℃ for 24h and placed in a nitrogen atmosphere furnace for carbonization at 600℃ for 3h to obtain a three-dimensional nitrogen-doped carbon material.

[0070] S2, 10g of the three-dimensional nitrogen-doped carbon material prepared above was dispersed in 100mL of N,N-dimethylformamide, and 60mmol of aniline, 40mmol of pyrrole, 30mmol of p-aminobenzenesulfonic acid, 0.2g of ammonium persulfate and 0.6g of concentrated hydrochloric acid were added. The mixture was stirred and polymerized at 5°C for 2h to obtain a reaction solution of voltage-responsive copolymer coated with three-dimensional nitrogen-doped carbon material.

[0071] Add 0.6g of sodium dodecylbenzenesulfonate and 5g of polytetrafluoroethylene emulsion to the above reaction solution, and stir for 30 minutes to obtain a composite slurry. Spray the composite slurry onto a layer of a glass fiber cotton substrate with a loading of 40g / m². 2 Then, it is dried at 100℃ for 30 minutes to obtain AGM separator.

[0072] Comparative Example 1

[0073] This comparative example provides an AGM separator, which differs from Example 1 only in that when preparing the copolymer-coated three-dimensional nitrogen-doped carbon material, only nano-silica is used as a template. The specific steps are as follows:

[0074] S1, 10g of graphene oxide, 30g of melamine, and 8g of nano-silica were dispersed in 500mL of deionized water and ultrasonically dispersed for 30min. The mixture was then transferred to a hydrothermal reactor, heated to 200℃ and kept at that temperature for 8h. After filtration, the resulting solid was added to a 4wt% hydrofluoric acid solution at a material-to-liquid ratio of 1:15 and soaked at room temperature for 8h. Then, it was freeze-dried at -40℃ for 24h and placed in a nitrogen atmosphere furnace for carbonization at 800℃ for 2h to obtain a three-dimensional nitrogen-doped carbon material.

[0075] S2, 10g of the three-dimensional nitrogen-doped carbon material prepared above is dispersed in 200mL of N,N-dimethylformamide, 50mmol aniline, 30mmol pyrrole, 20mmol p-aminobenzenesulfonic acid, 0.17g ammonium persulfate and 0.34g concentrated hydrochloric acid are added, and the mixture is stirred and polymerized at 0℃ for 4h to obtain a copolymer-coated reaction solution of the three-dimensional nitrogen-doped carbon material.

[0076] Add 0.6g of sodium dodecylbenzenesulfonate and 5g of polytetrafluoroethylene emulsion to the above reaction solution, and stir for 30 minutes to obtain a composite slurry. Spray the composite slurry onto a layer of a glass fiber cotton substrate with a loading of 40g / m². 2 Then, it is dried at 100℃ for 30 minutes to obtain AGM separator.

[0077] Comparative Example 2

[0078] This comparative example provides an AGM separator, which differs from Example 1 only in that the comonomer used is aniline. The specific steps are as follows:

[0079] S1, 10g of graphene oxide, 30g of melamine, 2g of nano-silica and 6g of cellulose nanofibers were dispersed in 500mL of deionized water and ultrasonically dispersed for 30min. The mixture was then transferred to a hydrothermal reactor, heated to 200℃ and kept at that temperature for 8h. After filtration, the resulting solid was added to a 4wt% hydrofluoric acid solution at a material-to-liquid ratio of 1:15 and soaked at room temperature for 8h. Then, it was freeze-dried at -40℃ for 24h and placed in a nitrogen atmosphere furnace for carbonization at 800℃ for 2h to obtain a three-dimensional nitrogen-doped carbon material.

[0080] S2, 10g of the three-dimensional nitrogen-doped carbon material prepared above was dispersed in 200mL of N,N-dimethylformamide, 100mmol of aniline, 0.17g of ammonium persulfate and 0.34g of concentrated hydrochloric acid were added, and the mixture was stirred and polymerized at 0℃ for 4h to obtain a reaction solution of voltage-responsive copolymer coated with three-dimensional nitrogen-doped carbon material.

[0081] Add 0.6g of sodium dodecylbenzenesulfonate and 5g of polytetrafluoroethylene emulsion to the above reaction solution, and stir for 30 minutes to obtain a composite slurry. Spray the composite slurry onto a layer of a glass fiber cotton substrate with a loading of 40g / m². 2 Then, it is dried at 100℃ for 30 minutes to obtain AGM separator.

[0082] Comparative Example 3

[0083] This comparative example provides an AGM separator, which differs from Example 1 only in that it does not contain p-aminobenzenesulfonic acid. The specific steps are as follows:

[0084] S1, 10g of graphene oxide, 30g of melamine, 2g of nano-silica and 6g of cellulose nanofibers were dispersed in 500mL of deionized water and ultrasonically dispersed for 30min. The mixture was then transferred to a hydrothermal reactor, heated to 200℃ and kept at that temperature for 8h. After filtration, the resulting solid was added to a 4wt% hydrofluoric acid solution at a material-to-liquid ratio of 1:15 and soaked at room temperature for 8h. Then, it was freeze-dried at -40℃ for 24h and placed in a nitrogen atmosphere furnace for carbonization at 800℃ for 2h to obtain a three-dimensional nitrogen-doped carbon material.

[0085] S2, 10g of the three-dimensional nitrogen-doped carbon material prepared above was dispersed in 200mL of N,N-dimethylformamide, 70mmol aniline, 30mmol pyrrole, 0.17g ammonium persulfate and 0.34g concentrated hydrochloric acid were added, and the mixture was stirred and polymerized at 0℃ for 4h to obtain a reaction solution of voltage-responsive copolymer coated with three-dimensional nitrogen-doped carbon material.

[0086] Add 0.6g of sodium dodecylbenzenesulfonate and 5g of polytetrafluoroethylene emulsion to the above reaction solution, and stir for 30 minutes to obtain a composite slurry. Spray the composite slurry onto a layer of a glass fiber cotton substrate with a loading of 40g / m². 2 Then, it is dried at 100℃ for 30 minutes to obtain AGM separator.

[0087] Comparative Example 4

[0088] This comparative example provides an AGM separator, which differs from Example 1 only in that p-aminobenzenesulfonic acid is replaced with an equal amount of p-aminobenzenesulfonamide. The specific steps are as follows:

[0089] S1, 10g of graphene oxide, 30g of melamine, 2g of nano-silica and 6g of cellulose nanofibers were dispersed in 500mL of deionized water and ultrasonically dispersed for 30min. The mixture was then transferred to a hydrothermal reactor, heated to 200℃ and kept at that temperature for 8h. After filtration, the resulting solid was added to a 4wt% hydrofluoric acid solution at a material-to-liquid ratio of 1:15 and soaked at room temperature for 8h. Then, it was freeze-dried at -40℃ for 24h and placed in a nitrogen atmosphere furnace for carbonization at 800℃ for 2h to obtain a three-dimensional nitrogen-doped carbon material.

[0090] S2, 10g of the three-dimensional nitrogen-doped carbon material prepared above was dispersed in 200mL of N,N-dimethylformamide, and 50mmol aniline, 30mmol pyrrole, 20mmol p-aminobenzenesulfonamide, 0.17g ammonium persulfate and 0.34g concentrated hydrochloric acid were added. The mixture was stirred and polymerized at 0℃ for 4h to obtain a reaction solution of voltage-responsive copolymer coated with three-dimensional nitrogen-doped carbon material.

[0091] Add 0.6g of sodium dodecylbenzenesulfonate and 5g of polytetrafluoroethylene emulsion to the above reaction solution, and stir for 30 minutes to obtain a composite slurry. Spray the composite slurry onto a layer of a glass fiber cotton substrate with a loading of 40g / m². 2 Then, it is dried at 100℃ for 30 minutes to obtain AGM separator.

[0092] Performance testing

[0093] Lead-acid full cells are assembled using existing mature lead-acid battery assembly technology.

[0094] The negative electrode plate uses lead (Pb) as the main active material. The specific preparation method is as follows: lead powder, carbon black, short fibers, deionized water, and dilute sulfuric acid are mixed in a mass ratio of 80:1:0.5:9:9.5 to prepare a negative electrode slurry. Subsequently, this negative electrode slurry is uniformly coated onto the grid of the negative electrode plate to form a 2.5 mm thick electrode plate. The coated electrode plate is then dried at approximately 150°C to thoroughly remove moisture and solvent, resulting in a structurally stable negative electrode plate.

[0095] The positive electrode plate is prepared using existing mature lead-acid battery technology, with lead oxide powder (PbO2 / PbO mixture) as the main active material. The specific steps are as follows: lead oxide powder, carbon black, short fibers, deionized water and dilute sulfuric acid are mixed in the same mass ratio of 80:1:0.5:9:9.5 to prepare a positive electrode slurry, which is then coated onto the positive electrode grid to form a coating of about 2.5 mm thickness. After drying at 150°C, the positive electrode plate is obtained.

[0096] During battery assembly, a 1.28M sulfuric acid solution is used as the electrolyte, and the smart AGM separator prepared in the above embodiment is placed between the positive and negative plates to form a full battery.

[0097] The electrolyte adsorption capacity, electrolyte wetting rate, volume resistivity, cycle capacity retention, 24-hour self-discharge rate, coating peeling rate, and cycle charging efficiency were tested according to the following methods. The results are shown in Table 1.

[0098] 1. Electrolyte adsorption capacity: Weigh a dry AGM separator (m1), immerse it completely in 1.25M sulfuric acid electrolyte for 2 hours, remove it and drain the surface electrolyte (no dripping), weigh the mass (m2), electrolyte adsorption capacity = (m2-m1) / m1.

[0099] 2. Electrolyte wetting rate: The separator material to be tested was cut into standard 1cm×1cm samples and vacuum dried at 60℃ for 2 hours to remove any adsorbed moisture. 1mL of electrolyte was accurately measured using a pipette and slowly dripped into a petri dish. The time taken for the 1cm×1cm separator sample to be completely wetted from contact with the 1.28M sulfuric acid electrolyte surface was recorded using a stopwatch. The wetting rate (mL / min) was calculated based on the electrolyte volume (1mL).

[0100] 3. Volume resistivity: The volume resistivity of the partition sample was tested using a four-probe resistivity meter at 25℃.

[0101] 4. Cyclic Capacity Retention Rate: Using the Blue Electric test system, under 25℃ environment, the battery is charged to 2.5V with a constant current of 10mA, and then discharged to 1.5V with a constant current. This cycle is repeated 200 times. The capacity retention rate is obtained by dividing the capacity of the 200th cycle by the capacity of the first cycle.

[0102] 5. 24h self-discharge rate: After charging the battery to 2.5V with constant current and letting it stand for 24 hours, discharge it to 1.5V with constant current and record the discharge capacity (C_discharge); compare it with the full charge capacity before standing (C_full), the self-discharge rate = (C_full - C_discharge) / C_full × 100%. The more severe the dendrite growth, the higher the self-discharge rate.

[0103] 6. Coating peeling rate: Immerse a 1cm×1cm partition sample in 1.25M sulfuric acid electrolyte and stir at 50℃ (300r / min) for 24h. After removal and drying, weigh the coating mass (m3, m4) before and after immersion. Peeling rate = (m3-m4) / m3×100%.

[0104] 7. Cyclic charging efficiency: The Blue Electric test system charges the battery to 2.5V at 25℃ and 10mA constant current, then discharges it to 1.5V at constant current, and repeats this cycle 50 times. The charging efficiency is calculated as (discharge capacity per cycle / corresponding charge capacity) × 100%, and the average value of the 50 cycles is taken. The less water decomposition, the higher the charging efficiency.

[0105] Table 1

[0106]

[0107] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material, characterized in that, Includes the following steps: S1, disperse carbon source, nitrogen source and composite template in water to obtain precursor dispersion; heat the precursor dispersion to 150℃~250℃ for hydrothermal reaction; after the hydrothermal reaction is completed, separate solid and liquid; soak the obtained solid in a solution containing fluorine and freeze dry to obtain precursor. The composite template includes nano-silica and cellulose nanofibers; S2, Under an inert atmosphere, the precursor is carbonized at 600℃~900℃ to obtain a three-dimensional nitrogen-doped carbon material. S3, the three-dimensional nitrogen-doped carbon material is dispersed in a polar solvent, a comonomer and an initiator are added, and a polymerization reaction is carried out at 0℃~5℃ to obtain a voltage-responsive copolymer coating the three-dimensional nitrogen-doped carbon material; wherein, the comonomer includes aniline, pyrrole and p-aminobenzenesulfonic acid.

2. The method for preparing voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material as described in claim 1, characterized in that, In S1, the carbon source includes one or both of graphene oxide and chitosan; and / or In S1, the nitrogen source includes one or both of melamine or urea.

3. The method for preparing voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material as described in claim 1, characterized in that, In S1, the mass ratio of the carbon source, nitrogen source, and composite template is 1:(2.5~4.0):(0.6~1.0); and / or In S1, the carbon source concentration in the precursor dispersion is 20 g / L to 25 g / L; and / or In S1, the mass ratio of nano-silica to cellulose nanofibers is 3:1 to 1:

3.

4. The method for preparing a voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material as described in claim 1, characterized in that, In S1, the particle size of the nano-silica is 5nm~20nm; the diameter of the cellulose nanofibers is 2nm~5nm; and / or In S1, the hydrothermal reaction time is 6h~12h; and / or In S1, the fluorinated acid solution is a hydrofluoric acid solution with a mass concentration of 2% to 5%; and / or In S1, the soaking time is 6h~12h; and / or In S1, the freeze-drying temperature is -50℃ to -40℃, and the freeze-drying time is 12h to 36h.

5. The method for preparing a voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material as described in claim 1, characterized in that, In S2, the carbonization time is 1h to 3h; and / or In S2, the temperature is raised to 600℃~900℃ using a programmed temperature rise method, with a heating rate of 5℃ / min~10℃ / min.

6. The method for preparing a voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material as described in claim 1, characterized in that, In S3, the polar solvent is N,N-dimethylformamide; and / or In S3, the mass ratio of the three-dimensional nitrogen-doped carbon material to the polar solvent is 1:10 to 1:30; and / or In S3, the initiator is a mixed solution of ammonium persulfate and concentrated hydrochloric acid, wherein the mass ratio of ammonium persulfate to concentrated hydrochloric acid is 1:1 to 1:3, and the mass fraction of concentrated hydrochloric acid is 36% to 38%; and / or In S3, the amount of initiator added is 2% to 8% of the total mass of the comonomer.

7. The method for preparing a voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material as described in claim 1, characterized in that, In S3, the molar ratio of aniline, pyrrole, and p-aminobenzenesulfonic acid is (4~6):(2~4):(1~3); and / or In S3, the mass ratio of the total amount of the comonomer to the three-dimensional nitrogen-doped carbon material is 0.5:1 to 1.5:1; and / or In S3, the polymerization reaction takes 2 to 8 hours.

8. A voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material, characterized in that, It is prepared by the method for preparing voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material according to any one of claims 1 to 7.

9. The application of the voltage-responsive copolymer-coated three-dimensional nitrogen-doped carbon material as described in claim 8 in AGM separators for lead-acid batteries.

10. An AGM separator for lead-acid batteries, characterized in that, The invention comprises a glass fiber cotton substrate and a voltage-responsive copolymer of claim 8 coated with a three-dimensional nitrogen-doped carbon material loaded on the glass fiber cotton substrate.

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