A low-hydrogen-evolution graphene material for lead-acid batteries and its preparation method

Abstract

This invention relates to the field of battery technology, specifically to a low-hydrogen evolution graphene material for lead-acid batteries and its preparation method. The method involves a multi-step synergistic modification: first, ethylenediamine is grafted onto the surface of graphene oxide using a carbodiimide / active ester method to obtain amine graphene; then, nitrogen doping is achieved through heat treatment under a nitrogen / ammonia atmosphere; next, it is composited with titanium dioxide and a stable structure is formed through a hydrothermal reaction; then, imidazolium silane and perfluorodecyl silane are sequentially grafted for hydrophobic modification; finally, it is stabilized by tetrabutoxytitanium and cured by low-temperature re-nitriding. The graphene material prepared by this method imparts excellent battery performance, exhibiting low DC internal resistance and high capacity retention.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a low-hydrogen-evolution graphene material for lead-acid batteries and its preparation method. Background Technology

[0002] Lead-acid batteries remain important in backup power, starting power, and energy storage due to their low cost, high reliability, and mature recycling technology. However, their inherent hydrogen evolution side reaction remains a key bottleneck restricting performance improvement. Under float charging or overcharging conditions, the negative electrode potential is negative than the hydrogen evolution potential, causing water to be electrolyzed to produce hydrogen gas. This not only leads to electrolyte loss and battery drying, but may also cause frequent opening of the safety valve and even battery swelling due to internal pressure buildup, significantly shortening service life.

[0003] To improve the high-current performance and active material utilization of batteries, the application of high-performance conductive additives has become an important technological direction. While traditional carbon black materials can construct conductive networks, their large specific surface area and numerous surface defect sites are precisely the most efficient catalysts for hydrogen evolution reactions, thus exacerbating the hydrogen evolution problem. In recent years, graphene has been considered an ideal alternative due to its excellent two-dimensional conductivity; however, the edges and surface defects of ordinary graphene sheets also exhibit high catalytic activity for hydrogen evolution. Direct application could even lead to a more severe hydrogen evolution problem than carbon black.

[0004] Existing technologies attempt to modify graphene to reduce its hydrogen evolution activity, such as through doping or surface coating. However, simple physical mixing or single functional group modification often fails to meet multiple requirements: excessive passivation of active sites sacrifices intrinsic conductivity; while single hydrophilic or hydrophobic modifications cannot effectively regulate ion and gas transport behavior at the electrode / electrolyte interface. If the surface modification layer becomes unstable in the long-term electrochemical environment of the battery and detaches or remodels, its protective effect will rapidly diminish, and the hydrogen evolution problem will reappear. Therefore, developing a negative electrode conductive material that can fundamentally and synergistically solve the problems of conductivity, hydrogen evolution inhibition, and interface stability is a pressing challenge in the field of lead-acid battery technology. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose a low-hydrogen-evolution graphene material for lead-acid batteries and its preparation method, so as to solve the problem that traditional lead-acid battery negative electrode conductive agents (such as carbon black or unmodified graphene) significantly catalyze hydrogen evolution side reactions while improving conductivity, leading to battery water loss, increased internal pressure, and increased risk of float charge thermal runaway, which seriously restricts the cycle life and safety of the battery.

[0006] To achieve the above objectives, the present invention provides a method for preparing low-hydrogen-evolution graphene material for lead-acid batteries, comprising the following steps:

[0007] S1: Ethylenediamine was grafted onto the surface of graphene oxide using the carbodiimide / active ester method to obtain amination graphene;

[0008] S2: The amination graphene is heat-treated under a nitrogen / ammonia atmosphere to achieve nitrogen doping, thereby obtaining nitrogen-doped graphene;

[0009] S3: The nitrogen-doped graphene is dispersed in a mixed solution of anhydrous ethanol and deionized water, and a tetrabutoxytitanium precursor solution with acetylacetone as a coordination stabilizer is added dropwise under acidic conditions. After hydrothermal reaction, a titanium dioxide-nitrogen-doped reduced graphene composite is obtained.

[0010] S4: In an alcohol-water system under acidic conditions, 1-methyl-3-(trimethoxysilylpropyl)imidazolium chloride was reacted with the complex to obtain an imidazolium silane grafted complex.

[0011] S5: React perfluorodecyltrimethoxysilane with the imidazolium silane grafted complex to obtain a hydrophobically modified imidazolium silane grafted complex.

[0012] S6: Add a dilute solution of tetrabutoxytitanium to the suspension of the hydrophobically modified imidazolium silane grafted composite and reflux under acidic conditions to obtain a titanium dioxide-stabilized composite.

[0013] S7: Low-temperature re-nitriding and curing treatment is carried out under nitrogen / ammonia atmosphere, and after cooling, low hydrogen evolution graphene material for lead-acid batteries is obtained.

[0014] Preferably, step S1 is carried out in 0.1 mol / L MES buffer, first by adding 1-ethyl-3-dimethylaminopropylcarbodiimide hydrochloride and N-hydroxysuccinimide for activation, then by adding ethylenediamine, and reacting at 60°C for 12 h.

[0015] Preferably, the mass ratio of ethylenediamine to graphene oxide in step S1 is 4.8-7.2:50.

[0016] Preferably, in step S2, the temperature is increased to 320℃ at a rate of 2℃ / min and held for 45-75min, with a nitrogen flow rate of 180-220 sccm and an ammonia flow rate of 8-12 sccm.

[0017] Preferably, in step S3, the volume ratio of anhydrous ethanol to deionized water is 4:1, the pH of the system is 4.8-5.2, and the hydrothermal reaction is carried out at 180°C for 6 hours.

[0018] Preferably, in step S3, the weight ratio of nitrogen-doped graphene, acetylacetone, and tetrabutoxytitanium is 50:0.4-0.6:4-6.

[0019] Preferably, step S4 is carried out in an alcohol-water system with a pH of 4, and after stirring at 40°C for 6 hours, the temperature is increased to 65°C and aged for 2 hours.

[0020] Preferably, in step S4, the mass ratio of 1-methyl-3-(trimethoxysilylpropyl)imidazolium chloride to titanium dioxide-nitrogen-doped reduced graphene composite is 6-10:20.

[0021] Preferably, in step S5, the mass ratio of the perfluorodecyltrimethoxysilane and imidazolylsilane grafted composite is 3-5:20.

[0022] Preferably, in step S6, the mass ratio of the hydrophobically modified imidazolium silane grafted composite to tetrabutoxytitanium is 20:0.24-0.75.

[0023] Preferably, in step S7, the re-nitriding curing is carried out by heating to 220°C at a rate of 2°C / min and holding at that temperature for 45-75 min, with a nitrogen flow rate of 200 sccm and an ammonia flow rate of 15-25 sccm.

[0024] Furthermore, the present invention also provides a low-hydrogen-evolution graphene material for lead-acid batteries, which is obtained by the above preparation method.

[0025] The beneficial effects of this invention are:

[0026] This invention utilizes a multi-step synergistic modification process to construct a composite interface structure with low hydrogen evolution characteristics on a graphene substrate. This structure effectively passivates hydrogen evolution active sites at the edges and surfaces of graphene sheets, significantly reducing the exchange current density of the hydrogen evolution reaction, thereby suppressing hydrogen production at its source. This results in a substantial reduction in the side reaction current during float charging, reduced electrolyte loss, stable internal battery pressure, and significantly improved sealing reaction efficiency and safety of the battery.

[0027] This material effectively suppresses hydrogen evolution while perfectly preserving the excellent long-range conductive network of graphene. Its constructed electron transport channels are continuous and efficient, ensuring extremely low contact resistance and bulk resistance of the negative electrode active material. This results in excellent high-current discharge performance and high-rate capacity of the battery, while also enhancing its short-circuit current capability.

[0028] This composite material successfully introduces stable ionophilic microchannels and a hydrophobic skin layer onto the graphene surface. The ionophilic microchannels ensure the smooth migration of sulfate ions from the electrolyte to the surface of the active material, guaranteeing the successful electrochemical reaction; while the outer hydrophobic skin layer effectively blocks water molecules from forming continuous permeation channels and cuts off the adhesion and connectivity paths of microbubbles, further physically preventing the occurrence of aqueous side reactions. This synergistic effect optimizes the electrode / electrolyte interface environment.

[0029] Through the final low-temperature heat treatment step, the nitrogen-containing functional groups and silicon-oxygen network on the material surface are effectively solidified, forming a stable chemical bonding interface. This robust structure enables the material to withstand the harsh environment of strong acid, oxidation, and repeated charge-discharge cycles inside lead-acid batteries, preventing the degradation or peeling of the interface modification layer during long-term operation, ensuring the durability of low hydrogen evolution performance, and thus guaranteeing the performance stability of the battery throughout its entire life cycle.

[0030] In summary, the material provided by this invention ingeniously solves the contradiction between high conductivity and low hydrogen evolution activity, achieving a synergistic effect of suppressing side reactions, maintaining conductivity, ensuring ion transport, and improving interface stability. This provides a key material foundation for the preparation of advanced lead-acid batteries with long lifespan and high safety. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0032] Figure 1 The infrared spectra of the titanium dioxide-stabilized composite and the low-hydrogen-evolution graphene material for lead-acid batteries in Example 2 of this invention are shown.

[0033] Figure 2 The infrared spectra of the titanium dioxide-nitrogen-doped reduced graphene composite, the imidazolium silane grafted composite, the hydrophobically modified imidazolium silane grafted composite, and the titanium dioxide-stabilized composite in Example 2 of this invention are shown. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0035] In a specific embodiment of the present invention, the graphene oxide powder has a sheet diameter of 1-5 μm and a thickness of 2-5 nm.

[0036] Example 1:

[0037] (1) 50g of graphene oxide powder was added to 1000mL of deionized water and ultrasonically dispersed for 60min. Then, 200mL of 0.1mol / L MES buffer was added, followed by 9.6g of 1-ethyl-3-dimethylaminopropylcarbodiimide hydrochloride and 5.8g of N-hydroxysuccinimide. The mixture was stirred at room temperature for 2h, and then 4.8g of ethylenediamine was added. The temperature was raised to 60℃ and stirred for 12h. The mixture was filtered and washed three times with deionized water and anhydrous ethanol. The mixture was then vacuum dried at 60℃ for 12h to obtain amine graphene.

[0038] (2) The ammoniated graphene was evenly spread in a quartz boat and pushed into a tube furnace. Nitrogen gas was introduced at 180 sccm and ammonia gas at 8 sccm. The temperature was increased to 320℃ at 2℃ / min, held for 45 min, and then naturally cooled to room temperature to obtain nitrogen-doped graphene.

[0039] (3) 50g of nitrogen-doped graphene was added to a mixed solution of 500mL of anhydrous ethanol and 125mL of deionized water and ultrasonically dispersed for 30min to obtain a dispersion. At the same time, 4g of tetrabutoxytitanium was dissolved in 50mL of anhydrous ethanol and 0.4g of acetylacetone was added as a coordination stabilizer to obtain a precursor solution. The precursor solution was added dropwise to the above dispersion solution. During this period, the pH was maintained between 4.8 and 5.2 with glacial acetic acid. After the dropwise addition was completed, the mixture was aged at room temperature for 60min and then hydrothermally reacted at 180℃ for 6h. The mixture was filtered and washed three times with anhydrous ethanol and deionized water. It was then vacuum dried at 60℃ for 8h to obtain a titanium dioxide-nitrogen-doped reduced graphene composite.

[0040] (4) Add 10g of 1-methylimidazolium and 25g of 3-chloropropyltrimethoxysilane to 100mL of anhydrous acetonitrile, heat to 80℃, stir and react for 8h under nitrogen protection, remove the solvent by rotary evaporation, crystallize with anhydrous diethyl ether, collect the precipitate, and dry under vacuum at 40℃ for 6h to obtain 1-methyl-3-(trimethoxysilylpropyl)imidazolium chloride;

[0041] (5) Mix 500 mL of anhydrous ethanol and 25 mL of deionized water and adjust the pH to 4 with glacial acetic acid. Add 20 g of titanium dioxide-nitrogen-doped reduced graphene complex, sonicate for 30 min, then add 6 g of 1-methyl-3-(trimethoxysilylpropyl)imidazolium chloride, heat to 40 °C, stir for 6 h, then heat to 65 °C, age for 2 h, filter, wash three times with anhydrous ethanol and deionized water, and vacuum dry at 60 °C for 6 h to obtain imidazolium silane grafted complex.

[0042] (6) Add 20g of imidazolium silane grafted composite to a mixed solution of 500mL anhydrous ethanol and 50mL deionized water, stir for 10min, then add 3g of perfluorodecyltrimethoxysilane, continue stirring at room temperature for 2h, raise the temperature to 120℃, age for 60min, filter, wash 3 times with anhydrous ethanol, and vacuum dry at 60℃ for 2h to obtain hydrophobic modified imidazolium silane grafted composite.

[0043] (7) 20g of hydrophobically modified imidazolium silane grafted complex was added to a mixed solution of 500mL anhydrous ethanol and 50mL deionized water and sonicated for 5min to obtain a suspension. Then, 0.25g of tetrabutoxytitanium was dissolved in 50mL anhydrous ethanol to obtain a dilute solution and added dropwise to the suspension. At the same time, the pH was adjusted to be stable between 4.8 and 5.2 with glacial acetic acid. The reaction was stirred under reflux for 2h, filtered, washed with anhydrous ethanol and deionized water in sequence, and dried under vacuum at 60℃ for 6h to obtain a titanium dioxide-stabilized complex.

[0044] (8) The titanium dioxide-stabilized composite was evenly spread on a quartz boat and placed in a tube furnace. Nitrogen gas of 200 sccm and ammonia gas of 15 sccm were introduced, and the temperature was raised to 220°C at 2°C / min. The temperature was held for 45 min and then naturally cooled to room temperature to obtain low hydrogen evolution graphene material for lead-acid batteries.

[0045] Example 2:

[0046] (1) 50g of graphene oxide powder was added to 1000mL of deionized water and ultrasonically dispersed for 60min. Then, 200mL of 0.1mol / L MES buffer was added, followed by 12g of 1-ethyl-3-dimethylaminopropylcarbodiimide hydrochloride and 7.2g of N-hydroxysuccinimide. The mixture was stirred at room temperature for 2h, and then 6g of ethylenediamine was added. The temperature was raised to 60℃ and stirred for 12h. The mixture was filtered and washed three times with deionized water and anhydrous ethanol. The mixture was then vacuum dried at 60℃ for 12h to obtain amine graphene.

[0047] (2) The ammoniated graphene was evenly spread in a quartz boat and pushed into a tube furnace. Nitrogen gas of 200 sccm and ammonia gas of 10 sccm were introduced. The temperature was raised to 320℃ at 2℃ / min and held for 60 min. The graphene was then naturally cooled to room temperature and removed to obtain nitrogen-doped graphene.

[0048] (3) 50g of nitrogen-doped graphene was added to a mixed solution of 500mL of anhydrous ethanol and 125mL of deionized water and ultrasonically dispersed for 30min to obtain a dispersion. At the same time, 5g of tetrabutoxytitanium was dissolved in 50mL of anhydrous ethanol and 0.5g of acetylacetone was added as a coordination stabilizer to obtain a precursor solution. The precursor solution was added dropwise to the above dispersion solution. During this period, the pH was maintained between 4.8 and 5.2 with glacial acetic acid. After the dropwise addition was completed, the solution was aged at room temperature for 60min and then hydrothermally reacted at 180℃ for 6h. The solution was filtered and washed three times with anhydrous ethanol and deionized water. The solution was vacuum dried at 60℃ for 8h to obtain a titanium dioxide-nitrogen-doped reduced graphene composite.

[0049] (4) Add 10g of 1-methylimidazolium and 25g of 3-chloropropyltrimethoxysilane to 100mL of anhydrous acetonitrile, heat to 80℃, stir and react for 8h under nitrogen protection, remove the solvent by rotary evaporation, crystallize with anhydrous diethyl ether, collect the precipitate, and dry under vacuum at 40℃ for 6h to obtain 1-methyl-3-(trimethoxysilylpropyl)imidazolium chloride;

[0050] (5) Mix 500 mL of anhydrous ethanol and 25 mL of deionized water and adjust the pH to 4 with glacial acetic acid. Add 20 g of titanium dioxide-nitrogen-doped reduced graphene complex, sonicate for 30 min, then add 8 g of 1-methyl-3-(trimethoxysilylpropyl)imidazolium chloride, heat to 40 °C, stir for 6 h, then heat to 65 °C, age for 2 h, filter, wash with anhydrous ethanol and deionized water 3 times in sequence, and vacuum dry at 60 °C for 6 h to obtain imidazolium silane grafted complex.

[0051] (6) Add 20g of imidazolium silane grafted composite to a mixed solution of 500mL anhydrous ethanol and 50mL deionized water, stir for 10min, then add 4g of perfluorodecyltrimethoxysilane, continue stirring at room temperature for 2h, raise the temperature to 120℃, age for 60min, filter, wash 3 times with anhydrous ethanol, and vacuum dry at 60℃ for 2h to obtain hydrophobic modified imidazolium silane grafted composite.

[0052] (7) 20g of hydrophobically modified imidazolium silane grafted complex was added to a mixed solution of 500mL anhydrous ethanol and 50mL deionized water and sonicated for 5min to obtain a suspension. Then, 0.5g of tetrabutoxytitanium was dissolved in 50mL anhydrous ethanol to obtain a dilute solution and added dropwise to the suspension. At the same time, the pH was adjusted to be stable between 4.8 and 5.2 with glacial acetic acid. The reaction was stirred under reflux for 2h, filtered, washed with anhydrous ethanol and deionized water in sequence, and dried under vacuum at 60℃ for 6h to obtain a titanium dioxide-stabilized complex.

[0053] (8) The titanium dioxide-stabilized composite was evenly spread on a quartz boat and placed in a tube furnace. Nitrogen gas of 200 sccm and ammonia gas of 20 sccm were introduced, and the temperature was increased to 220°C at 2°C / min. The temperature was held for 60 min and then naturally cooled to room temperature to obtain low hydrogen evolution graphene material for lead-acid batteries.

[0054] Example 3:

[0055] (1) 50g of graphene oxide powder was added to 1000mL of deionized water and ultrasonically dispersed for 60min. Then, 200mL of 0.1mol / L MES buffer was added, followed by 14.4g of 1-ethyl-3-dimethylaminopropylcarbodiimide hydrochloride and 8.6g of N-hydroxysuccinimide. The mixture was stirred at room temperature for 2h, and then 7.2g of ethylenediamine was added. The temperature was raised to 60℃ and stirred for 12h. The mixture was filtered and washed three times with deionized water and anhydrous ethanol. The mixture was then vacuum dried at 60℃ for 12h to obtain amine graphene.

[0056] (2) The ammoniated graphene was evenly spread in a quartz boat and pushed into a tube furnace. Nitrogen gas 220 sccm and ammonia gas 12 sccm were introduced. The temperature was raised to 320℃ at 2℃ / min and held for 75 min. The graphene was then naturally cooled to room temperature and removed to obtain nitrogen-doped graphene.

[0057] (3) 50g of nitrogen-doped graphene was added to a mixed solution of 500mL of anhydrous ethanol and 125mL of deionized water and ultrasonically dispersed for 30min to obtain a dispersion. At the same time, 6g of tetrabutoxytitanium was dissolved in 50mL of anhydrous ethanol and 0.6g of acetylacetone was added as a coordination stabilizer to obtain a precursor solution. The precursor solution was added dropwise to the above dispersion solution. During this period, the pH was maintained between 4.8 and 5.2 with glacial acetic acid. After the dropwise addition was completed, the solution was aged at room temperature for 60min and then hydrothermally reacted at 180℃ for 6h. The solution was filtered and washed three times with anhydrous ethanol and deionized water. The solution was vacuum dried at 60℃ for 8h to obtain a titanium dioxide-nitrogen-doped reduced graphene composite.

[0058] (4) Add 10g of 1-methylimidazolium and 25g of 3-chloropropyltrimethoxysilane to 100mL of anhydrous acetonitrile, heat to 80℃, stir and react for 8h under nitrogen protection, remove the solvent by rotary evaporation, crystallize with anhydrous diethyl ether, collect the precipitate, and dry under vacuum at 40℃ for 6h to obtain 1-methyl-3-(trimethoxysilylpropyl)imidazolium chloride;

[0059] (5) Mix 500 mL of anhydrous ethanol and 25 mL of deionized water and adjust the pH to 4 with glacial acetic acid. Add 20 g of titanium dioxide-nitrogen-doped reduced graphene complex, sonicate for 30 min, then add 10 g of 1-methyl-3-(trimethoxysilylpropyl)imidazolium chloride, heat to 40 °C, stir for 6 h, then heat to 65 °C, age for 2 h, filter, wash three times with anhydrous ethanol and deionized water, and vacuum dry at 60 °C for 6 h to obtain imidazolium silane grafted complex.

[0060] (6) Add 20g of imidazolium silane grafted composite to a mixed solution of 500mL anhydrous ethanol and 50mL deionized water, stir for 10min, then add 5g of perfluorodecyltrimethoxysilane, continue stirring at room temperature for 2h, raise the temperature to 120℃, age for 60min, filter, wash 3 times with anhydrous ethanol, and vacuum dry at 60℃ for 2h to obtain hydrophobic modified imidazolium silane grafted composite.

[0061] (7) 20g of hydrophobically modified imidazolium silane grafted complex was added to a mixed solution of 500mL anhydrous ethanol and 50mL deionized water and sonicated for 5min to obtain a suspension. Then, 0.75g of tetrabutoxytitanium was dissolved in 50mL anhydrous ethanol to obtain a dilute solution and added dropwise to the suspension. At the same time, the pH was adjusted to be stable between 4.8 and 5.2 with glacial acetic acid. The reaction was stirred under reflux for 2h, filtered, washed with anhydrous ethanol and deionized water in sequence, and dried under vacuum at 60℃ for 6h to obtain a titanium dioxide-stabilized complex.

[0062] (8) The titanium dioxide-stabilized composite was evenly spread on a quartz boat and placed in a tube furnace. Nitrogen gas of 200 sccm and ammonia gas of 25 sccm were introduced, and the temperature was raised to 220°C at 2°C / min. The temperature was held for 75 min and then naturally cooled to room temperature to obtain low hydrogen evolution graphene material for lead-acid batteries.

[0063] Comparative Example 1:

[0064] The difference between Comparative Example 1 and Example 2 is that the addition of tetrabutoxytitanium in step (7) is not performed; the other conditions are the same as in Example 2.

[0065] Comparative Example 2:

[0066] The difference between Comparative Example 2 and Example 2 is that the grafting treatment of perfluorodecyltrimethoxysilane in step (6) is not performed; the other conditions are the same as those in Example 2.

[0067] Comparative Example 3:

[0068] The difference between Comparative Example 3 and Example 2 is that the low-temperature re-nitriding and curing treatment with ammonia and nitrogen at 220°C in step (8) is not performed; the other conditions are the same as in Example 2.

[0069] Comparative Example 4:

[0070] The difference between Comparative Example 4 and Example 2 is that acetylacetone is not added in step (3); the other conditions are the same as in Example 2.

[0071] Comparative Example 5:

[0072] The difference between Comparative Example 5 and Example 2 is that 1-methyl-3-(trimethoxysilylpropyl)imidazolium chloride is not added in step (5); the other conditions are the same as in Example 2.

[0073] Performance testing:

[0074] Sample preparation: The materials obtained in the examples and comparative examples were used as conductive agents for the negative electrode active material, respectively. Lead paste (lead powder: dilute sulfuric acid solution, density 1.40 g / cm³) was added at a mass fraction of 0.20%. 3 The mixture consisted of deionized water (100:13.5:6.0, with lignin phosphonate and barium sulfate added according to industry standard ratios), double-sided coated onto a lead-calcium-tin alloy negative electrode grid (grid size 100mm × 50mm × 1.2mm). After curing (25℃, 95% relative humidity, 24h) and forming, it was assembled with commercial positive electrode plates and microporous glass fiber separators to form a small 2V valve-regulated sealed lead-acid battery cell (rated capacity 2.0Ah). After formation, it was left to stand at 25℃ for 24h before testing. All electrical tests were conducted at 25±1℃ and 50%±5% relative humidity, using sulfuric acid as the electrolyte.

[0075] Infrared spectroscopy: scanning range 4000-500 cm⁻¹ -1 4cm resolution -1 .

[0076] Hydrogen evolution rate: The hydrogen evolution rate test and sealed reaction efficiency test procedures in industry standard MT 658-2011 were followed. The hydrogen collection device adopted the gas collection hood and gas storage bottle volume method to calculate the hydrogen evolution rate per unit capacity per unit time (mL / (Ah·h)) converted to standard state volume, and the sealed reaction efficiency % was calculated simultaneously. Batteries that passed the capacity test were used for this test. Each sample was measured twice and the average value was taken. The results are shown in Table 1.

[0077] Float current: According to the relevant items of the technical conditions for stationary valve-regulated lead-acid batteries in GB / T 19638.1-2014, the steady-state float current mA / Ah was recorded for 30 minutes after constant voltage stabilization at 25℃ and a float voltage of 2.27V / cell. The results are shown in Table 1.

[0078] DC internal resistance and short-circuit current: According to the requirements of GB / T 19638.1-2014, the DC internal resistance (mΩ) was tested at 25℃ using the specified method and fixture, and the short-circuit current was calculated. Each sample was measured 3 times, and the average value was reported. The results are shown in Table 1.

[0079] 20-hour rate capacity and charge acceptance: Capacity testing was conducted according to GB / T 19638.1-2014, discharging to a termination voltage of 1.80V / cell at I = 0.05C (0.10A). The 20-hour rate capacity (Ah) and capacity retention (relative to the nominal 2.0Ah) were reported. Charge acceptance was conducted at 25℃ under constant voltage of 2.35V / cell and current limiting of 0.2C. The average charging current for the first 15 minutes was recorded and normalized to A / Ah. The results are shown in Table 1.

[0080] Table 1 Performance Test Results

[0081]

[0082] Data Analysis:

[0083] As can be seen from the data in Examples 1-3 of Table 1, the low-hydrogen evolution graphene material for lead-acid batteries prepared in this invention exhibits synergistic benefits in three dimensions: suppressing side reactions, maintaining continuous conductivity, and ensuring capacity. Site-guided in-situ nucleation of titanium dioxide, combined with secondary micro-replenishment, preferentially covers edges and defective active sites, reducing the exchange current density related to hydrogen evolution. The sequential grafting, first ionophilic and then hydrophobic, constructs imidazolium silane ion microchannels on the surface to ensure ion transport in the electrolyte. Simultaneously, the hydrophobic skin formed by perfluorodecyltrimethoxysilane segregates the connection path between the continuous water film and microbubbles. Low-temperature re-nitriding further stabilizes the nitrogen-containing functional groups and the silicon-oxygen network, maintaining the interfacial chemistry in a steady state during float charging and cycling. This coupling reduces the steady-state side reaction current during float charging without excessively damaging the DC conductivity network, resulting in a lower float charging current, less hydrogen evolution, and stable capacity output.

[0084] As can be seen from the data in Example 2 and Comparative Example 1 in Table 1, omitting the second addition of tetrabutoxytitanium resulted in insufficient coverage of edges and defect sites, leaving scattered active sites at the interface, leading to increased side reactions and decreased float-charge stability. The main reason for this is that the initial nucleation load was too low, resulting in a thinner coating and failing to completely passivate highly active sites. During oxygen reduction coupling, hydrogen was shunted from the negative electrode. However, the conductive framework was not filled with additional particles, and the DC internal resistance did not increase significantly. Therefore, although the amount of micro-addition is extremely low, it can achieve precise secondary sealing at key sites, exhibiting a hydrogen suppression effect exceeding linear superposition.

[0085] As can be seen from the data in Example 2 and Comparative Example 2 in Table 1, without the grafting of perfluorodecyltrimethoxysilane, the interface maintained a high wettability for a long time, making it easier for a continuous water film to form and connect microbubbles, thus increasing the side reaction current. The main reason is that only the ionophilic channels of imidazolium silane promote ion transport but are difficult to sever the water-water connections, limiting the oxygen recombination efficiency. Simultaneously, the increased wettability can slightly improve the electrode surface contact in the short term, resulting in a seemingly contradictory phenomenon of a slight decrease in internal resistance. It is evident that the ionophilic and hydrophobic skins are not simply substitutes but rather work in parallel and synergistically, with the latter being crucial for long-term hydrogen suppression.

[0086] As can be seen from the data in Example 2 and Comparative Example 3 in Table 1, without re-nitriding and curing with ammonia / nitrogen at 220°C, the stability of the surface amine / imidazolium and silicon-oxygen network is insufficient. During float charging, interfacial chemistry is prone to rearrangement, leading to side reactions and resistance fluctuations. The main reason is that uncured nitrogen-containing functional groups and silicon-oxygen bonds are easily hydrolyzed or migrated, resulting in decreased integrity of the hydrophobic layer and instability of oxygen recombination channels. Therefore, re-nitriding is not only an aging step but also a crucial step in interface structure shaping, possessing an unexpectedly amplifying effect on durability and hydrogen suppression.

[0087] As can be seen from the data in Table 1 for Example 2 and Comparative Example 4, the hydrolysis of tetrabutoxytitanium was more intense without the addition of acetylacetone. Larger, unevenly distributed particles of titanium dioxide formed on the flake surface, partially obscuring ion channels and reducing acceptor capacity. The main reason for this is that the precursor tends to rapidly condense in the absence of a ligand, leading to particle aggregation and uneven distribution. Larger particles in some areas undergo hardening and passivation at a few edge sites, providing a slight short-term relief for hydrogen evolution, resulting in a slightly better hydrogen suppression but poorer overall electrochemical performance.

[0088] As can be seen from the data in Example 2 and Comparative Example 5 in Table 1, without imidazolium silane grafting, the interface lacks positively charged ion channels and silicon-oxygen bridging, making it difficult to stably anchor the hydrophobic modification. This results in a discontinuous conductive network, poor interfacial contact, and a greater likelihood of side reactions. The main reason is the absence of an imidazolium layer, leading to insufficient anchoring density of hydrophobic molecules on the graphene and titanium dioxide surfaces. This results in surface breakage, micro-area desorption, and simultaneous damage to both hydrogen suppression and conductivity.

[0089] from Figure 1 It can be seen that the titanium dioxide stabilizes the composite at 1100 cm⁻¹. -1 (Si-O-Si), 955cm -1 (Si-O-Ti) and 650cm -1 The peak intensity at (Ti-O-Ti) is obvious, indicating that the inorganic network has been stabilized; while the sample after low-temperature ammoniation shows a peak intensity at 3300 cm⁻¹. -1 (NH stretching), 1545cm -1 (NH bending) and 1235cm -1The newly added characteristic peak at (CN redshift) indicates the introduction of nitrogen and the formation of a stable nitrogen coordination structure. Meanwhile, at 3120 cm⁻¹... -1 With 1575cm -1 The imidazolium ring CH and C=N vibrational peaks at 1240 cm⁻¹ remain unchanged. -1 With 1145cm -1 CF2, 1335cm -1 The CF3 absorption peak also maintained its intensity, indicating that the ammoniation treatment did not destroy the imidazolium structure and hydrophobic layer. Combined with the fact that the Ti-O-Ti and Si-O-Si frameworks did not decay, it can be confirmed that the ammoniation process achieved nitrogen-containing functionalization and defect passivation, while maintaining the integrity of the organic-inorganic and hydrophobic interfaces, thus achieving low hydrogen evolution and high interface stability in lead-acid batteries.

[0090] from Figure 2 It can be seen that the key signals for the four intermediates are established sequentially as the steps progress: 3120, 1575, and 1170 cm⁻¹ appear after the introduction of imidazolium silane into the titanium dioxide-nitrogen-doped reduced graphene. -1 Accompanied by 1100 / 960cm -1 Si-O-Si / Si-O-Ti; further hydrophobic modification resulted in the addition of 1335, 1240, and 1145 cm⁻¹. -1 The fluorine-containing peak; after micro-addition of tetrabutoxytitanium and reflux stabilization, ≈955 cm⁻¹ -1 Ti-O-Si bridge with 650 / 525cm -1 The Ti-O-Ti sequence was significantly enhanced, indicating site-selective recovering and inorganic network reinforcement. This sequence change corresponds one-to-one with the synthesis steps of the manuscript.

[0091] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A method for preparing a low-hydrogen-evolution graphene material for lead-acid batteries, characterized in that, Includes the following steps: S1: Ethylenediamine was grafted onto the surface of graphene oxide using the carbodiimide / active ester method to obtain amination graphene; S2: The amination graphene is heat-treated under a nitrogen / ammonia atmosphere to achieve nitrogen doping, thereby obtaining nitrogen-doped graphene; S3: The nitrogen-doped graphene is dispersed in a mixed solution of anhydrous ethanol and deionized water, and a tetrabutoxytitanium precursor solution with acetylacetone as a coordination stabilizer is added dropwise under acidic conditions. After hydrothermal reaction, a titanium dioxide-nitrogen-doped reduced graphene composite is obtained. S4: In an alcohol-water system under acidic conditions, 1-methyl-3-(trimethoxysilylpropyl)imidazolium chloride was reacted with the complex to obtain an imidazolium silane grafted complex. S5: React perfluorodecyltrimethoxysilane with the imidazolium silane grafted complex to obtain a hydrophobically modified imidazolium silane grafted complex. S6: Add a dilute solution of tetrabutoxytitanium to the suspension of the hydrophobically modified imidazolium silane grafted composite and reflux under acidic conditions to obtain a titanium dioxide-stabilized composite. S7: Low-temperature re-nitriding and curing treatment is carried out under nitrogen / ammonia atmosphere, and after cooling, low hydrogen evolution graphene material for lead-acid batteries is obtained; In step S2, the temperature is increased to 320℃ at a rate of 2℃ / min and held for 45-75 minutes, with a nitrogen flow rate of 180-220 sccm and an ammonia flow rate of 8-12 sccm. In step S7, the re-nitriding and curing process involves increasing the temperature to 220℃ at a rate of 2℃ / min and holding for 45-75 minutes, with a nitrogen flow rate of 200 sccm and an ammonia flow rate of 15-25 sccm.

2. The method for preparing low-hydrogen-evolution graphene material for lead-acid batteries according to claim 1, characterized in that, Step S1 is carried out in 0.1 mol / L MES buffer. First, 1-ethyl-3-dimethylaminopropylcarbodiimide hydrochloride and N-hydroxysuccinimide are added for activation, and then ethylenediamine is added. The reaction is carried out at 60°C for 12 h.

3. The method for preparing low-hydrogen-evolution graphene material for lead-acid batteries according to claim 1, characterized in that, In step S1, the mass ratio of ethylenediamine to graphene oxide is 4.8-7.2:

50.

4. The method for preparing low-hydrogen-evolution graphene material for lead-acid batteries according to claim 1, characterized in that, In step S3, the weight ratio of nitrogen-doped graphene, acetylacetone, and tetrabutoxytitanium is 50:0.4-0.6:4-6.

5. The method for preparing low-hydrogen-evolution graphene material for lead-acid batteries according to claim 1, characterized in that, In step S4, the mass ratio of 1-methyl-3-(trimethoxysilylpropyl)imidazolium chloride to titanium dioxide-nitrogen-doped reduced graphene composite is 6-10:

20.

6. The method for preparing low-hydrogen-evolution graphene material for lead-acid batteries according to claim 1, characterized in that, In step S5, the mass ratio of the perfluorodecyltrimethoxysilane and imidazolylsilane grafted composite is 3-5:

20.

7. The method for preparing low-hydrogen-evolution graphene material for lead-acid batteries according to claim 1, characterized in that, In step S6, the mass ratio of the hydrophobically modified imidazolium silane grafted composite to tetrabutoxytitanium is 20:0.24-0.

75.

8. A low-hydrogen-evolution graphene material for lead-acid batteries, characterized in that, It is obtained by the preparation method of low hydrogen evolution graphene material for lead-acid batteries according to any one of claims 1-7.

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