A negative electrode material, a preparation method therefor, and an application thereof

Abstract

The application relates to the technical field of electrochemical energy storage materials and devices, and particularly discloses a negative electrode material, a preparation method and application thereof. The negative electrode material comprises the following components by mass fraction: 8-10 parts of a three-dimensional heterojunction functional framework, 4-8 parts of an interface inducer, 1.5-2 parts of a composite precursor and 100 parts of an active material; wherein the three-dimensional heterojunction functional framework is a carbon nanotube and tin dioxide combined by a covalent bond; the interface inducer comprises sodium phytate, hydroxyethylidene diphosphonic acid and zirconium phosphate; and the composite precursor comprises polyvinylidene fluoride-hexafluoropropylene copolymer, silicon dioxide and perfluorosulfonic acid resin. The composition and the preparation method of the negative electrode material are optimized, the negative electrode material is applied to a battery, and the electrochemical performance and the corrosion resistance of the battery under a low-temperature condition can be obviously improved, and the hydrogen evolution potential is improved.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage materials and devices, and in particular to a negative electrode material, its preparation method, and its application. Background Technology

[0002] Lead-acid batteries are widely used in automotive start-stop systems and energy storage backup, but their severe performance degradation in low-temperature environments (especially below -20°C) restricts their application in new energy vehicles and high-altitude cold environments. In low-temperature environments, batteries face multiple coupled failure mechanisms: a surge in electrolyte viscosity leads to severe ion transport obstruction and a sharp increase in internal resistance; a sharp drop in the solubility and dissolution rate of lead sulfate makes it prone to Ostwald ripening, forming coarse, poorly conductive stable crystals, resulting in irreversible capacity loss; a decrease in the hydrogen evolution overpotential at the negative electrode exacerbates side reactions, leading to low charging efficiency and electrolyte drying; simultaneously, the volume changes of the active material during charging and discharging generate enormous stress, while traditional organic expanders and fiber reinforcing agents are prone to embrittlement and failure at low temperatures, leading to electrode pulverization.

[0003] To address these challenges, the current mainstream technical approach involves physically blending various functional additives into the negative electrode to form a "lead-carbon" composite system. However, this approach has fundamental limitations: relying on carbon materials such as carbon black and carbon nanotubes primarily improves electron conduction, but is ineffective in addressing the bottleneck of ion transport at low temperatures; adding nucleating agents such as barium carbonate only provides passive heterogeneous nucleation sites and cannot thermodynamically inhibit the ripening and growth of lead sulfate crystals, and the uniformity of dispersion is difficult to control; the use of interface modifiers such as imidazole ionic liquids relies mainly on physical adsorption, resulting in insufficient long-term cycle stability, and the problem of increased viscosity at low temperatures remains unresolved; structural additives such as sodium lignin sulfonate and polyester staple fibers are prone to failure at low temperatures, making it difficult to maintain the integrity of the electrode structure. More importantly, the simple blending of these additives based on different mechanisms lacks functional synergy and may even interfere with each other, failing to form a solution and unable to systematically address the complex degradation problem caused by multiple intertwined factors at low temperatures. Therefore, the upgrade of lead-acid battery technology urgently needs to shift from simple component superposition to mechanism-oriented innovation and systematic reconstruction. Summary of the Invention

[0004] In view of this, the present invention provides an anode material, its preparation method, and its application. The anode material and its preparation method provided by the present invention construct an innovative structure that integrates an acid-resistant heterojunction electrocatalytic system and an acid-resistant solid electrolyte protective layer formed by interfacial induction and in-situ polymerization of long-acting molecules. This aims to simultaneously overcome the comprehensive technical challenges of low-temperature lead-acid battery anodes, such as intensified sulfation, poor synergy of electronic or ion conduction, uncontrolled interfacial side reactions, and decreased electrode structural stability.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0006] The present invention provides a negative electrode material comprising the following raw material components in parts by mass: 8-10 parts of a three-dimensional heterojunction functional framework, 4-8 parts of an interface inducer, 1.5-2 parts of a composite precursor, and 100 parts of an active substance;

[0007] The three-dimensional heterostructure functional framework consists of carbon nanotubes and tin dioxide bonded together by covalent bonds.

[0008] The interface inducers include sodium phytate, hydroxyethylidene diphosphonic acid, and zirconium phosphate.

[0009] The composite precursor includes polyvinylidene fluoride-hexafluoropropylene copolymer, silica, and perfluorosulfonic acid resin.

[0010] Compared to existing technologies, the anode material provided by this invention features carbon nanotubes in a three-dimensional heterojunction functional framework that enhance electronic conductivity, tin dioxide that is resistant to concentrated sulfuric acid corrosion, and surface hydroxyl groups that can efficiently adsorb and transport H+. + It possesses the characteristic of interfacial catalytic activity. The two form a heterojunction through chemical bonds, constructing a three-functional integrated network that simultaneously realizes rapid electron transport, efficient ion conduction, and interfacial reaction catalysis. It is also resistant to the strong acidic environment of lead-acid batteries throughout the process, thereby significantly improving the low-temperature electrochemical performance and corrosion resistance of the negative electrode plate, and increasing the hydrogen evolution potential of the negative electrode plate.

[0011] The phosphate group in sodium phytate molecules can react with Pb on the surface of the negative electrode. 2+ Through strong coordination, hydroxyethylidene diphosphonic acid (HEDTA) exhibits resistance to oxidation and hydrolysis. It synergistically forms a dense interfacial layer with sodium phytate. Zirconium phosphate (ZPP) is embedded within this interfacial layer, further enhancing the mechanical strength of the negative electrode plate. Together, these three components construct a molecular-level organic-inorganic hybrid interfacial layer. This layer not only thermodynamically lowers the nucleation barrier of lead sulfate, guiding its uniform deposition in amorphous or ultrafine nanocrystal form and inhibiting the growth of coarse lead sulfate crystals at the molecular level, thus eliminating sulfation, but also, through its dense structure, isolates the acidic components in the electrolyte from direct contact with the surface of the negative electrode material, reducing H+. + Adsorption and reduction on the surface of the negative electrode plate effectively increase the hydrogen evolution potential while inhibiting oxidation corrosion and loss of active materials on the negative electrode surface; thus, it improves the electrochemical performance of the electrode plate under low temperature conditions in multiple dimensions and significantly enhances the long-term cycle stability of the negative electrode plate.

[0012] A specific composite precursor can solidify during charging to form a continuous, dense, and flexible acid-resistant solid electrolyte protective film. This film tightly coats the surface of the active material, forming an interfacial protective barrier that permanently isolates the acidic components in the electrolyte from direct contact with the active material. It effectively inhibits side reactions such as hydrogen evolution reaction, active material corrosion, and electrolyte decomposition. Furthermore, the polyvinylidene fluoride-hexafluoropropylene copolymer possesses intermolecular gaps, gaps between silica particles, and micro-regions formed by the spontaneous assembly of perfluorosulfonic acid resin, collectively constituting the initial micropores. During charging, the various components of the composite precursor... The in-situ crosslinking reaction fixes the pore structure, ultimately forming a continuous porous channel, which synergistically improves the electron / ion transport efficiency and enhances electrochemical performance. At the same time, the protective film formed by the in-situ polymerization of the composite precursor during charging can form an integrated anchoring structure with the framework structure, enhancing interfacial stability. The interfacial inducer bridges the active material and the protective film, improving interfacial compatibility and preventing the protective film from falling off under battery expansion conditions. The addition of specific composite precursors ensures the improvement of hydrogen evolution potential and inhibits negative electrode corrosion in the long term, improving the electrochemical performance of the battery under low temperature conditions.

[0013] This invention significantly improves the electrochemical performance and corrosion resistance of the negative electrode plate under low-temperature conditions and enhances the hydrogen evolution potential by optimizing the specific composition of the three-dimensional heterojunction functional framework, interface inducer, and composite precursor of the negative electrode material.

[0014] More preferably, the mass ratio of carbon nanotubes to tin dioxide in the three-dimensional heterostructure functional framework is 1:(3~8).

[0015] More preferably, the mass ratio of the carbon nanotubes to tin dioxide is 1:5.

[0016] More preferably, the interface inducer comprises sodium phytate, hydroxyethylidene diphosphonic acid and zirconium phosphate in a mass ratio of (4~6):(2~3):(2~3).

[0017] The optimal composition and ratio of the interface inducer are beneficial for further improving the performance of the anode material.

[0018] More preferably, the interface inducer comprises sodium phytate, hydroxyethylidene diphosphonic acid, and zirconium phosphate in a mass ratio of 5:3:2.

[0019] Preferably, the zirconium phosphate has a particle size of 10~100nm.

[0020] More preferably, the composite precursor comprises polyvinylidene fluoride-hexafluoropropylene copolymer, silica, and perfluorosulfonic acid resin in a mass ratio of (1~2):(0.2~0.6):(0.1~0.3).

[0021] More preferably, the composite precursor comprises polyvinylidene fluoride-hexafluoropropylene copolymer, silica, and perfluorosulfonic acid resin in a mass ratio of 1.4:0.4:0.2.

[0022] Preferably, the polyvinylidene fluoride-hexafluoropropylene copolymer contains 8% to 18% hexafluoropropylene by mass.

[0023] More preferably, the particle size of the silicon dioxide is 40~60nm.

[0024] For example, the silicon dioxide is hydrophilic silicon dioxide.

[0025] More preferably, the silicon dioxide is fumed silicon dioxide.

[0026] Preferably, the active material includes lead powder and lead oxide.

[0027] More preferably, the active material comprises lead powder and lead oxide in a mass ratio of (85~105):(15~25).

[0028] More preferably, the active material comprises lead powder and lead oxide in a mass ratio of 100:20.

[0029] More preferably, the method for preparing the three-dimensional heterostructure functional framework includes the following steps:

[0030] Step 1: Add carbon nanotubes and tin source to water to obtain a solid-liquid mixture;

[0031] Step 2: Adjust the pH of the solid-liquid mixture to 2.5-3.5, add urea and mix evenly, and react at 160-200℃ to obtain the three-dimensional heterojunction functional framework.

[0032] In the preparation method of the three-dimensional heterojunction functional framework provided by the present invention, by adjusting the pH value of the solid-liquid mixture to acidic conditions, active groups such as hydroxyl and carboxyl groups can be generated on the surface of carbon nanotubes. Furthermore, the urea decomposition control system is a weakly acidic environment, which promotes the decomposition of tin source into an intermediate containing Sn-OH. Heating at a specific temperature triggers the dehydration condensation of the two to generate CO-Sn covalent bonds, ensuring that carbon nanotubes and tin dioxide form stable covalent bonds. At the same time, the above reaction conditions can also control the morphology and dispersion of tin dioxide, thereby improving the performance of the negative electrode plate.

[0033] Preferably, in step 1, the tin source is tin tetrachloride.

[0034] Preferably, in step 1, the diameter of the carbon nanotube is 10~20nm.

[0035] Preferably, in step 1, the ratio of carbon nanotubes to water is 1g:(80~100)mL.

[0036] More preferably, in step 2, the pH of the solid-liquid mixture is adjusted to 3.

[0037] For example, in step 2, ammonia is used to adjust the pH.

[0038] Preferably, the mass ratio of the carbon nanotubes to urea is 1:(10~12).

[0039] Preferably, in step 2, the condition for uniform mixing is: stirring with magnetic stirring for 30 minutes.

[0040] For example, the magnetic stirring speed is 300~500 rpm, preferably 400 rpm.

[0041] In a further preferred embodiment, step 2 involves a reaction at 180°C.

[0042] Preferably, in step 2, the reaction time is 10-14 hours.

[0043] More preferably, in step 2, the reaction time is 12 hours.

[0044] For example, the reaction is carried out in a reaction vessel lined with polytetrafluoroethylene.

[0045] It should be further explained that in step 2, after the reaction is completed, the cooled reaction product is centrifuged, washed with water and ethanol, and dried to obtain the three-dimensional heterostructure functional framework.

[0046] For example, the drying conditions are: vacuum drying at 50~70°C for 10~14 hours.

[0047] As a preferred embodiment, the drying conditions are: vacuum drying at 60°C for 12 hours.

[0048] This invention provides a method for preparing a negative electrode material, comprising the following steps:

[0049] S1. Weigh each component according to the mass ratio, add the three-dimensional heterostructure functional framework to water to obtain a slurry;

[0050] S2. The slurry is cooled to -50~-30℃ for directional growth, and then dried at 1~5Pa and -90~-70℃ to obtain a three-dimensional porous CNT-SnO2 self-supporting skeleton.

[0051] S3. Add the interface inducer to water, then add the active substance and mix to obtain a negative electrode paste;

[0052] S4. Under a vacuum of -0.098 to -0.085 MPa, the negative electrode paste is filled into the pores of the three-dimensional porous CNT-SnO2 self-supporting skeleton, and pressure is maintained at 45 to 55 kPa to obtain the treated skeleton.

[0053] S5. Add the composite precursor to a solvent to obtain a coating solution, and then coat the coating solution onto the surface of the treated skeleton to obtain a primary treated negative electrode material.

[0054] S6. Perform gradient drying treatment on the primary processed negative electrode material to obtain the negative electrode material.

[0055] Compared to existing technologies, the anode material preparation method provided by this invention utilizes an ice template method to enable the self-assembly of a three-dimensional porous CNT-SnO2 self-supporting framework into a three-dimensional structure with vertically arranged channels. This intrinsic structure provides strong mechanical support and serves as a channel for rapid electrolyte wetting and ion transport, eliminating the reliance on externally added short fibers. Subsequent vacuum filling and pressure holding processes ensure that the anode paste tightly fills the channels, reducing interfacial voids. The composite precursor coating combined with gradient drying precisely constructs a stable interfacial layer and avoids problems such as material structure cracking during the drying process. The preparation method provided by this invention has a coherent and controllable overall process, improving material forming quality, simplifying the preparation process, reducing the difficulty of industrial production, and providing a new approach to anode material preparation.

[0056] Preferably, in S1, the ratio of the three-dimensional heterojunction functional framework to water is 1g:(20~25)mL.

[0057] For example, in S1, the three-dimensional heterojunction functional framework is added to water using ultrasonic treatment, with an ultrasonic power of 300W and a duration of 30 minutes.

[0058] Preferably, in S2, the cooling rate is 1~3℃ / min.

[0059] Preferably, in step S2, the slurry is cooled to -40°C for directional growth.

[0060] Preferably, in S2, the directional growth time is 20-30 hours.

[0061] More preferably, in S2, the directional growth time is 24 hours.

[0062] For example, in S2, the slurry is injected into a polytetrafluoroethylene mold and placed in a precision low-temperature constant temperature bath to ensure that the ice crystals grow in a directional manner along the temperature gradient direction.

[0063] Preferably, in step S2, the drying time is 40-50 hours.

[0064] More preferably, in S2, the drying time is 48 hours.

[0065] Preferably, in S3, the ratio of the interface inducer to water is 1g:(10~30)mL.

[0066] Preferably, in S3, the mixing conditions are: mixing is carried out by ball milling, the mixing speed is 350~450 rpm, and the mixing time is 1.5~2.5 h.

[0067] For example, in S3, the mixing is carried out using a planetary ball mill, purchased from Nanjing University Instrument Factory, model QM-3SP2.

[0068] Preferably, in step S3, the density of the negative electrode paste is 4.1~4.3 g / cm³. 3 .

[0069] Preferably, in step S4, the pressure is maintained at 50 kPa.

[0070] Preferably, in step S4, the pressure holding time is 3 to 8 minutes.

[0071] More preferably, in S4, the pressure holding time is 5 minutes.

[0072] Preferably, in step S5, the solvent is acetonitrile.

[0073] Preferably, in S5, the ratio of the composite precursor to the solvent is 1g:(8~12)mL.

[0074] Preferably, in S5, the coating thickness is 80~120μm.

[0075] More preferably, in S5, the coating thickness is 100 μm.

[0076] Preferably, in step S5, the coating speed is 8~12 mm / s.

[0077] Preferably, in step S5, the coating speed is 10 mm / s.

[0078] For example, in S5, the coating is performed using an automatic coating machine purchased from Shenzhen Kejing Zhida Technology Co., Ltd., model MSK-AFA-III.

[0079] Preferably, in S5, the viscosity of the coating liquid at 25°C is 500 cP.

[0080] For example, in S5, when the composite precursor is dissolved in the solvent, magnetic stirring can be used to stir at 500 rpm at 50~70°C until a uniform, transparent and viscous coating liquid is formed.

[0081] Preferably, in S6, the gradient drying process includes a first-stage drying process, a second-stage drying process, and a third-stage drying process.

[0082] More preferably, the drying conditions for the first stage are: heat treatment at -0.095~-0.08MPa and 35~45℃ for 4~4.5h.

[0083] More preferably, the drying conditions for the first stage are: heat treatment at -0.09 MPa and 40°C for 4 hours.

[0084] The first-stage drying process ensures that the acetonitrile solvent gradually evaporates, shaping the initial voids into interconnected channels and preventing pore collapse.

[0085] More preferably, the conditions for the second stage drying process are: heating to 60~70℃ and holding at that temperature for 6~10 hours.

[0086] More preferably, the conditions for the second stage drying process are: heating to 65°C at a rate of 1°C / min and holding at that temperature for 8 hours.

[0087] The second-stage drying process can deeply remove residual acetonitrile solvent from the coating solution, promote the initial cross-linking and curing of the composite precursor coating, strengthen the interfacial bonding between the active material and the three-dimensional porous CNT-SnO2 self-supporting framework, and lay the groundwork for the third-stage deep curing, avoiding the problem of coating cracks or structural damage caused by a sudden temperature rise.

[0088] More preferably, the conditions for the third stage drying process are: heating to 80~85℃ and holding at that temperature for 12~16 hours.

[0089] More preferably, the conditions for the third stage drying process are: heating to 80°C at a rate of 1°C / min and holding at that temperature for 14 hours.

[0090] The third-stage drying process promotes deep cross-linking and curing of the composite precursor coating, which not only strengthens the interfacial bonding between the coating and the skeleton and active materials, but also completely removes residual solvents and internal micro-defects; thus endowing the anode material with excellent structural stability, ion conduction efficiency and cycle life.

[0091] The present invention provides a negative electrode plate, comprising the above-mentioned negative electrode material and a grid.

[0092] Preferably, the thickness of the negative electrode material is 1~3mm.

[0093] Preferably, the thickness of the negative electrode material is 1.5~2mm.

[0094] Preferably, the thickness of the grid is 1~1.5mm.

[0095] More preferably, the thickness of the grid is 1.2 mm.

[0096] This invention constructs a structurally stable and interface-optimized anode material by limiting the specific ratio of a three-dimensional heterojunction functional framework, interface inducer, composite precursor and active material, combined with the ice template method to prepare a self-supporting framework, and limiting controllable processes such as vacuum filling and pressure holding, gradient drying, etc., effectively improving the hydrogen evolution potential, suppressing side reactions, and significantly improving low-temperature electrochemical performance and cycle life. The preparation process is easy to industrialize. Attached Figure Description

[0097] Figure 1 A comparison graph showing the cycle performance of batteries prepared using the embodiments and comparative examples of the present invention after 200 charge-discharge cycles at -20°C.

[0098] Figure 2 This is a comparison chart showing the rate performance of batteries prepared using the embodiments and comparative examples of the present invention at different discharge currents at -20°C. Detailed Implementation

[0099] 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 and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0100] In the embodiments and comparative examples of this invention, the carbon nanotubes had a purity ≥98%, a diameter of 10~20nm, and were purchased from Shenzhen Nanoport Co., Ltd.; sodium phytate was purchased from Tianjin Xiens Biochemical Technology Co., Ltd., with a purity ≥98%; hydroxyethylidene diphosphonic acid was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with a purity ≥99%; zirconium phosphate was purchased from Aladdin Biochemical Technology Co., Ltd., with a particle size ≤100nm; polyvinylidene fluoride-hexafluoropropylene copolymer was purchased from Arkema, with a hexafluoropropylene content of 12% by mass; fumed silica was purchased from Degussa, with a particle size of 50±10nm; perfluorosulfonic acid resin was purchased from DuPont; and the lead powder had a D... 50 The particle size is 3.5 μm.

[0101] Unless otherwise specified, the raw materials and reagents used in this invention are all conventional commercially available products; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0102] Example 1

[0103] This embodiment provides a negative electrode material, comprising the following raw material components in parts by mass: 10 parts of a three-dimensional heterojunction functional framework, 6 parts of an interface inducer, 2 parts of a composite precursor, and 100 parts of an active substance;

[0104] The interface inducers include sodium phytate, hydroxyethylidene diphosphonic acid, and zirconium phosphate in a mass ratio of 5:3:2;

[0105] The composite precursor comprises polyvinylidene fluoride-hexafluoropropylene copolymer, silica, and perfluorosulfonic acid resin in a mass ratio of 1.4:0.4:0.2;

[0106] The active materials consist of lead powder and lead oxide in a mass ratio of 100:20;

[0107] The three-dimensional heterostructure functional framework consists of carbon nanotubes and tin dioxide bonded by covalent bonds, with a mass ratio of carbon nanotubes to tin dioxide of 1:5.

[0108] The fabrication method of the three-dimensional heterostructure functional framework includes the following steps:

[0109] Step 1: Add carbon nanotubes and tin tetrachloride to water at a ratio of 1g:80mL to obtain a solid-liquid mixture.

[0110] Step 2: Adjust the pH of the solid-liquid mixture to 3 with ammonia. Add urea at a mass ratio of 1:10 for carbon nanotubes and urea. Stir at 400 rpm for 30 min with a magnetic stirrer. Then transfer the mixture to a polytetrafluoroethylene-lined reactor and react at 180°C for 12 h. After the reaction is complete, centrifuge the cooled reaction product and wash it three times each with water and ethanol. Place the precipitate in a vacuum drying oven and dry it at 60°C for 12 h to obtain a three-dimensional heterostructure functional framework.

[0111] This embodiment provides a method for preparing a negative electrode material, including the following steps:

[0112] S1. Weigh each component according to the mass ratio, control the ratio of the three-dimensional heterojunction functional framework to water to be 1g:20mL, add the three-dimensional heterojunction functional framework to water, and use an ultrasonic cell disruptor to sonicate for 30min, with the power controlled at 300W, working for 2s and pausing for 3s to obtain the slurry.

[0113] S2. The slurry is injected into a polytetrafluoroethylene mold, and the mold is placed in a precision low temperature constant temperature bath. The temperature is lowered to -40℃ at a rate of 2℃ / min and directional growth is carried out for 24 hours to achieve unidirectional freezing from bottom to top and form directional ice crystals. Then, the completely frozen sample is transferred to a freeze dryer pre-cooled to -50℃, the vacuum pump is turned on to maintain the vacuum degree below 5Pa, and the sample is freeze-dried for 48 hours to obtain a three-dimensional porous CNT-SnO2 self-supporting skeleton.

[0114] S3. Add the interfacial inducing agent to water at a ratio of 1g:20mL, then add the active material. Place the mixture in the agate jar of a planetary ball mill, add agate balls, and ball mill at 400rpm for 2 hours to obtain a uniform and fine negative electrode paste with a density of 4.2g / cm³. 3 ;

[0115] S4. Fix the three-dimensional porous CNT-SnO2 self-supporting skeleton on the sample stage of the vacuum impregnation device, place the negative electrode paste on the storage tank above the three-dimensional porous CNT-SnO2 self-supporting skeleton, evacuate the entire system to a pressure of -0.095MPa, maintain for 10min, use the pressure difference to fill the negative electrode paste into the pores of the three-dimensional porous CNT-SnO2 self-supporting skeleton, ensure that the filling is dense, and then maintain the pressure at 50kPa for 5min to obtain the processed skeleton.

[0116] S5. Based on a composite precursor to acetonitrile ratio of 1g:10mL, the composite precursor is added to acetonitrile and stirred continuously at 500rpm under a 60℃ water bath until a uniform, semi-transparent coating solution with a viscosity of 500cP at 25℃ is formed. Using an automatic coating machine, the coating solution is uniformly coated onto the surface of the treatment skeleton at a coating speed of 10mm / s and a wet film thickness of 100μm to obtain a one-time treated negative electrode material.

[0117] S6. The primary processed negative electrode material is transferred into a programmable temperature-controlled vacuum drying oven and subjected to three gradient curing and drying processes. The first stage is to keep the material at -0.09 MPa and 40°C for 4 hours. The second stage is to raise the temperature to 65°C at a rate of 1°C / min and keep it at that temperature for 8 hours. The third stage is to raise the temperature to 80°C at a rate of 1°C / min and keep it at that temperature for 14 hours to obtain the negative electrode material.

[0118] Example 2

[0119] This embodiment provides a negative electrode material, comprising the following raw material components in parts by mass: 8 parts of a three-dimensional heterojunction functional framework, 4 parts of an interface inducer, 1.5 parts of a composite precursor, and 100 parts of an active substance;

[0120] The interface inducers include sodium phytate, hydroxyethylidene diphosphonic acid, and zirconium phosphate in a mass ratio of 4:2:3;

[0121] The composite precursor comprises polyvinylidene fluoride-hexafluoropropylene copolymer, silica, and perfluorosulfonic acid resin in a mass ratio of 2:0.6:0.1;

[0122] The active materials consist of lead powder and lead oxide in a mass ratio of 85:15;

[0123] The three-dimensional heterostructure functional framework consists of carbon nanotubes and tin dioxide bonded by covalent bonds, with a mass ratio of carbon nanotubes to tin dioxide of 1:7.

[0124] The fabrication method of the three-dimensional heterostructure functional framework includes the following steps:

[0125] Step 1: Add carbon nanotubes and tin tetrachloride to water at a ratio of 1g:100mL to obtain a solid-liquid mixture.

[0126] Step 2: Adjust the pH of the solid-liquid mixture to 3.5 with ammonia. Add urea at a mass ratio of 1:12 for carbon nanotubes and urea. Stir at 300 rpm for 30 min with a magnetic stirrer. Then transfer the mixture to a polytetrafluoroethylene-lined reactor and react at 160°C for 14 h. After the reaction is complete, centrifuge the cooled reaction product and wash it three times each with water and ethanol. Place the precipitate in a vacuum drying oven and dry it at 60°C for 12 h to obtain a three-dimensional heterostructure functional framework.

[0127] This embodiment provides a method for preparing a negative electrode material, including the following steps:

[0128] S1. Weigh each component according to the mass ratio, control the ratio of the three-dimensional heterojunction functional framework to water to be 1g:25mL, add the three-dimensional heterojunction functional framework to water, and use an ultrasonic cell disruptor to sonicate for 30min, with the power controlled at 300W, working for 2s and pausing for 3s, to obtain the slurry.

[0129] S2. Inject the slurry into a polytetrafluoroethylene mold, place the mold in a precision low-temperature constant temperature bath, and cool it to -50℃ at a rate of 3℃ / min for directional growth for 20h to achieve unidirectional freezing from bottom to top and form directional ice crystals. Then, transfer the completely frozen sample to a freeze dryer pre-cooled to -90℃, turn on the vacuum pump to maintain the vacuum degree below 5Pa, and freeze dry for 50h to obtain a three-dimensional porous CNT-SnO2 self-supporting skeleton.

[0130] S3. Add the interfacial inducing agent to water at a ratio of 1g:30mL, then add the active material. Place the mixture in the agate jar of a planetary ball mill, add agate balls, and ball mill at 450rpm for 1.5h to obtain a uniform and fine negative electrode paste with a density of 4.1g / cm³. 3 ;

[0131] S4. Fix the three-dimensional porous CNT-SnO2 self-supporting skeleton on the sample stage of the vacuum impregnation device, place the negative electrode paste on the storage tank above the three-dimensional porous CNT-SnO2 self-supporting skeleton, evacuate the entire system to a pressure of -0.098MPa, maintain for 10min, use the pressure difference to fill the negative electrode paste into the pores of the three-dimensional porous CNT-SnO2 self-supporting skeleton, ensure that the filling is dense, and then maintain the pressure at 55kPa for 8min to obtain the processed skeleton.

[0132] S5. Based on a composite precursor to acetonitrile ratio of 1g:8mL, the composite precursor is added to acetonitrile and stirred continuously at 500rpm under a 60℃ water bath until a uniform, semi-transparent coating solution with a viscosity of 500cP at 25℃ is formed. Using an automatic coating machine, the coating solution is uniformly coated onto the surface of the treatment skeleton at a coating speed of 12mm / s, and the wet film thickness is 120μm, thus obtaining the primary treated negative electrode material.

[0133] S6. The primary processed negative electrode material is transferred into a programmable temperature-controlled vacuum drying oven and subjected to three gradient curing and drying processes. The first stage is to keep the material at -0.095 MPa and 45°C for 4.5 hours. The second stage is to raise the temperature to 60°C at a rate of 1°C / min and keep it at that temperature for 10 hours. The third stage is to raise the temperature to 85°C at a rate of 1°C / min and keep it at that temperature for 16 hours to obtain the negative electrode material.

[0134] Example 3

[0135] This embodiment provides a negative electrode material, comprising the following raw material components in parts by mass: 10 parts of a three-dimensional heterojunction functional framework, 8 parts of an interface inducer, 1.5 parts of a composite precursor, and 100 parts of an active substance;

[0136] The interface inducers consist of sodium phytate, hydroxyethylidene diphosphonic acid, and zirconium phosphate in a mass ratio of 6:2:2.

[0137] The composite precursor comprises polyvinylidene fluoride-hexafluoropropylene copolymer, silica, and perfluorosulfonic acid resin in a mass ratio of 1:0.2:0.3;

[0138] The active materials consist of lead powder and lead oxide in a mass ratio of 105:25;

[0139] The three-dimensional heterostructure functional framework consists of carbon nanotubes and tin dioxide bonded by covalent bonds, with a mass ratio of carbon nanotubes to tin dioxide of 1:4.

[0140] The fabrication method of the three-dimensional heterostructure functional framework includes the following steps:

[0141] Step 1: Add carbon nanotubes and tin tetrachloride to water at a ratio of 1g:100mL to obtain a solid-liquid mixture.

[0142] Step 2: Adjust the pH of the solid-liquid mixture to 2.5 with ammonia. Add urea at a mass ratio of 1:12 for carbon nanotubes and urea. Stir at 500 rpm for 30 min with a magnetic stirrer. Then transfer the mixture to a polytetrafluoroethylene-lined reactor and react at 200°C for 10 h. After the reaction is complete, centrifuge the cooled reaction product and wash it three times each with water and ethanol. Place the precipitate in a vacuum drying oven and dry it at 60°C for 12 h to obtain a three-dimensional heterostructure functional framework.

[0143] This embodiment provides a method for preparing a negative electrode material, including the following steps:

[0144] S1. Weigh each component according to the mass ratio, control the ratio of the three-dimensional heterojunction functional framework to water to be 1g:25mL, add the three-dimensional heterojunction functional framework to water, and use an ultrasonic cell disruptor to sonicate for 30min, with the power controlled at 300W, working for 2s and pausing for 3s, to obtain the slurry.

[0145] S2. Inject the slurry into a polytetrafluoroethylene mold, place the mold in a precision low-temperature constant temperature bath, cool it to -30℃ at a rate of 1℃ / min, and grow it in a directional manner for 30h to achieve unidirectional freezing from bottom to top and form directional ice crystals. Then, transfer the completely frozen sample to a freeze dryer pre-cooled to -70℃, turn on the vacuum pump to maintain the vacuum degree below 5Pa, freeze dry for 40h, and obtain a three-dimensional porous CNT-SnO2 self-supporting skeleton.

[0146] S3. Add the interfacial inducing agent to water at a ratio of 1g:25mL, then add the active material. Place the mixture in the agate jar of a planetary ball mill, add agate balls, and ball mill at 350rpm for 2.5 hours to obtain a uniform and fine negative electrode paste with a density of 4.3g / cm³. 3 ;

[0147] S4. Fix the three-dimensional porous CNT-SnO2 self-supporting skeleton on the sample stage of the vacuum impregnation device, place the negative electrode paste on the storage tank above the three-dimensional porous CNT-SnO2 self-supporting skeleton, evacuate the entire system to a pressure of -0.085MPa, maintain for 10min, use the pressure difference to fill the negative electrode paste into the pores of the three-dimensional porous CNT-SnO2 self-supporting skeleton, ensure that the filling is dense, and then maintain the pressure at 45kPa for 3min to obtain the processed skeleton.

[0148] S5. Based on a composite precursor to acetonitrile ratio of 1g:12mL, the composite precursor is added to acetonitrile and stirred continuously at 500rpm under a 60℃ water bath until a uniform, semi-transparent coating solution with a viscosity of 500cP at 25℃ is formed. Using an automatic coating machine, the coating solution is uniformly coated onto the surface of the treated skeleton at a coating speed of 8mm / s, and the wet film thickness is 100μm, thus obtaining the primary treated negative electrode material.

[0149] S6. The primary processed negative electrode material is transferred into a programmable temperature-controlled vacuum drying oven and subjected to three gradient curing and drying processes. The first stage is to keep the material at -0.08 MPa and 35°C for 4 hours. The second stage is to raise the temperature to 70°C at a rate of 1°C / min and keep it at that temperature for 6 hours. The third stage is to raise the temperature to 80°C at a rate of 1°C / min and keep it at that temperature for 12 hours to obtain the negative electrode material.

[0150] Comparative Example 1

[0151] This comparative example provides a negative electrode material that differs from Example 1 in that the three-dimensional functional framework is a physical mixture of carbon nanotubes and tin dioxide; the mass ratio of carbon nanotubes to tin dioxide is 1:5.

[0152] Other operations and components are the same as in Example 1, and will not be repeated here.

[0153] Comparative Example 2

[0154] This comparative example provides a negative electrode material that differs from Example 1 in that no interface inducer is added;

[0155] The preparation method of the negative electrode material was adapted, while other operations and components were the same as in Example 1, and will not be repeated here.

[0156] Comparative Example 3

[0157] This comparative example provides a negative electrode material, which differs from Example 1 in that no composite precursor is added and S5 is omitted;

[0158] Other operations and components are the same as in Example 1, and will not be repeated here.

[0159] Comparative Example 4

[0160] This comparative example provides a negative electrode material that differs from Example 1 in that hydroxyethylidene diphosphonic acid is replaced with an equal amount of aminotrimethylene phosphonic acid with a purity of ≥99%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0161] Other operations and components are the same as in Example 1, and will not be repeated here.

[0162] Comparative Example 5

[0163] This comparative example provides a negative electrode material that differs from Example 1 in that the perfluorosulfonic acid resin is replaced with an equal amount of sulfonated polystyrene-divinylbenzene copolymer with a sulfonation degree of 40%, a particle size of 3~8μm, soluble in acetonitrile, and a purity of ≥99%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0164] Other operations and components are the same as in Example 1, and will not be repeated here.

[0165] Example of effect

[0166] The negative electrode materials provided in Examples 1-3 and Comparative Examples 1-5 were composited and fixed with a lead-calcium-tin alloy grid (thickness 1.2 mm, 1-1.5 mm; grid spacing 2 mm, aperture 3.0 mm, purity ≥99.5%) to obtain a negative electrode plate. The specific bonding method is as follows:

[0167] The lead-calcium-tin alloy grid was immersed in a 5wt% dilute sulfuric acid solution for 30 seconds to remove the surface oxide film. Then it was rinsed with deionized water until neutral and vacuum dried at 60℃ for 1 hour to improve the interfacial conductivity and bonding force between the grid and the electrode.

[0168] Anode material and grid composite: A mechanical pressing + low-temperature curing process is used to attach the anode material to both sides of the pre-treated grid (the size of the anode material matches the grid, and the thickness of the electrode sheet on one side is 0.8~1mm). A pressure of 80~100kPa is applied by a flatbed press and held for 5 minutes to make the anode material and the grid form a physical interlock. Then, the composite grid-anode material assembly is placed in a 60℃ vacuum drying oven for 2 hours to further enhance the interface contact and prevent the electrode sheet from falling off during charge and discharge cycles.

[0169] Negative electrode plate forming: After composite curing, excess electrode sheets at the edge of the grid are trimmed to obtain a complete negative electrode plate (total thickness 3.0~3.5mm, electrode sheet peel strength ≥1.5N / cm, contact resistance ≤5mΩ).

[0170] Using the prepared negative electrode plate as the negative electrode, a commercially available lead dioxide positive electrode plate (PbO2 content ≥85%) was paired with it. An AGM separator (Germany, Enos, 1.5mm thickness, liquid absorption rate ≥180%) was used to assemble a standard 2V / 5Ah (2V / 3~10Ah) lead-acid battery cell with an injection density of 1.28±0.01g / cm³. 3 The battery was prepared by allowing the sulfuric acid electrolyte (prepared with analytical grade sulfuric acid) to stand for 12 hours (10-14 hours) to complete the preparation of the battery.

[0171] Batteries made from the negative electrode materials provided in Examples 1-3 and Comparative Examples 1-5 were activated by constant current charging to 2.45V at 0.1C and constant voltage float charging for 12 hours, and the following indicators were tested at -20℃:

[0172] 1. Initial capacity (mAh / g)

[0173] Conditions: Discharge at 0.2C to 1.75V, and allow the battery to rest for 4 hours;

[0174] Step: Weigh out the active substance by mass m 活性 Record the discharge current I and time t;

[0175] Formula: Initial capacity = (I × t × 1000) / m 活性 .

[0176] 2.5C discharge time (min)

[0177] Conditions: 5C constant current discharge to 1.75V;

[0178] Steps: Discharge time until the voltage reaches the target, and record the duration.

[0179] 3. Capacity retention rate after 200 cycles (%)

[0180] Conditions: 200 cycles of 0.1C charge / 0.5C discharge;

[0181] Steps: Measure the initial capacity C0 before the loop and the capacity C after the loop. 200 ;

[0182] Formula: Cyclic capacity retention rate = (C 200 / C0)×100%.

[0183] 4. Hydrogen evolution overpotential (mV)

[0184] Conditions: Three-electrode system, LSV scan (-1.2~-0.6V, 5mV / s);

[0185] Steps: Measure the hydrogen precipitation initiation potential EHER and the lead equilibrium potential E0;

[0186] Formula: Hydrogen evolution overpotential = E0 - EHER.

[0187] 5. Electrode corrosion rate (%)

[0188] Conditions: Synchronized with 200 cycles, the sample was washed and dried with dilute sulfuric acid;

[0189] Steps: Weigh the sample m1 before the loop, m2 after the loop, and the blank sample m0;

[0190] Formula: Electrode corrosion rate = (m0-m2) / m1×100%.

[0191] The specific testing methods are shown in Table 1:

[0192] Table 1

[0193]

[0194] As shown in Table 1, the overall electrochemical performance of the batteries prepared with the negative electrode materials provided in Examples 1-3 is significantly better than that of the batteries prepared with the negative electrode materials provided in Comparative Examples 1-5, specifically as follows:

[0195] The initial capacity (122.5~129.8mAh / g) and 5C high-rate discharge time (58~66min) of Examples 1~3 are better than those of Comparative Examples 1~5, indicating that the synergistic system of the negative electrode material provided in the embodiments of the present invention can effectively improve the utilization rate of active material and the high-rate charge transport efficiency.

[0196] Compared with Comparative Examples 1-5, Examples 1-3 exhibited higher capacity retention (90.1%-93.2%) after 200 cycles, higher hydrogen evolution overpotential (455-478 mV), and lower electrode corrosion rate (3.2%-4.0%). This indicates that the components in the negative electrode materials prepared in Examples 1-3 of this invention can synergistically suppress sulfation, hydrogen evolution side reactions, and electrode corrosion, significantly improving the cycle stability of the battery. In contrast, Comparative Examples 1-5, lacking core functional components, showed significant shortcomings in high-rate performance, cycle stability, or interface stability, directly verifying the necessity and synergistic effect of the core components of this invention.

[0197] Figures 1-2It is evident that the negative electrode plate made using the negative electrode material provided in the embodiments of the present invention, when applied to lead-acid batteries, can significantly reduce the capacity decay of the battery under negative temperature conditions, and the capacity retention rate is still greater than 90% after 200 cycles. Furthermore, the negative electrode plate made using the negative electrode material provided in the embodiments of the present invention, when applied to lead-acid batteries, exhibits the highest discharge capacity at 0.2C, 1C, 3C, and 5C full discharge rates; reaching a maximum of 130.0 mAh / g at 0.2C, 125.0 mAh / g at 1C, 115.0 mAh / g at 3C, and still reaching a maximum of 105.0 mAh / g at 5C ultra-high rate, significantly outperforming the comparative examples. This further proves that the negative electrode material provided by the present invention has excellent high power output and fast discharge capability.

[0198] 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 negative electrode material, characterized in that, The raw material components include the following parts by weight: 8-10 parts of three-dimensional heterostructure functional framework, 4-8 parts of interface inducer, 1.5-2 parts of composite precursor and 100 parts of active substance; The three-dimensional heterostructure functional framework consists of carbon nanotubes and tin dioxide bonded together by covalent bonds. The interface inducers include sodium phytate, hydroxyethylidene diphosphonic acid, and zirconium phosphate. The composite precursor includes polyvinylidene fluoride-hexafluoropropylene copolymer, silica, and perfluorosulfonic acid resin; The method for preparing the three-dimensional heterostructure functional framework includes the following steps: Step 1: Add carbon nanotubes and tin source to water to obtain a solid-liquid mixture; Step 2: Adjust the pH of the solid-liquid mixture to 2.5-3.5, add urea and mix evenly, and react at 160-200℃ to obtain the three-dimensional heterojunction functional framework.

2. The negative electrode material as described in claim 1, characterized in that, The mass ratio of carbon nanotubes to tin dioxide in the three-dimensional heterojunction functional framework is 1:(3~8).

3. The negative electrode material as described in claim 1, characterized in that, The mass ratio of sodium phytate, hydroxyethylidene diphosphonic acid and zirconium phosphate is (4~6):(2~3):(2~3).

4. The negative electrode material as described in claim 1, characterized in that, The mass ratio of the polyvinylidene fluoride-hexafluoropropylene copolymer, silica, and perfluorosulfonic acid resin is (1~2):(0.2~0.6):(0.1~0.3).

5. A method for preparing the negative electrode material according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Weigh each component according to the mass ratio, add the three-dimensional heterostructure functional framework to water, and obtain a slurry. S2. The slurry is cooled to -50~-30℃ for directional growth, and then dried at 1~5Pa and -90~-70℃ to obtain a three-dimensional porous CNT-SnO2 self-supporting skeleton. S3. Add the interface inducer to water, then add the active substance and mix to obtain a negative electrode paste; S4. Under a vacuum of -0.098 to -0.085 MPa, the negative electrode paste is filled into the pores of the three-dimensional porous CNT-SnO2 self-supporting skeleton, and pressure is maintained at 45 to 55 kPa to obtain the treated skeleton. S5. Add the composite precursor to a solvent to obtain a coating solution, and then coat the coating solution onto the surface of the treatment framework to obtain a primary treated negative electrode material. S6. Perform gradient drying treatment on the primary processed negative electrode material to obtain the negative electrode material.

6. The method for preparing the negative electrode material as described in claim 5, characterized in that, In S1, the ratio of the three-dimensional heterojunction functional framework to water is 1 g: (20~25) mL; and / or In S2, the cooling rate is 1~3℃ / min; and / or In S2, the directional growth time is 20~30h.

7. The method for preparing the negative electrode material as described in claim 5, characterized in that, In S2, the drying time is 40-50 hours; and / or In S3, the ratio of the interface inducer to water is 1 g: (10~30) mL; and / or In S3, the density of the negative electrode paste is 4.1~4.3 g / cm³. 3 ; and / or In S4, the pressure holding time is 3~8 minutes; and / or In S5, the ratio of the composite precursor to the solvent is 1 g: (8~12) mL.

8. The method for preparing the negative electrode material as described in claim 5, characterized in that, In S6, the gradient drying process includes a first-stage drying process, a second-stage drying process, and a third-stage drying process; The drying conditions for the first stage are: heat treatment at -0.095~-0.08MPa and 35~45℃ for 4~4.5h; The conditions for the second stage of drying are: heating to 60~70℃ and holding at that temperature for 6~10 hours; The conditions for the third stage of drying are: heating to 80~85℃ and holding at that temperature for 12~16 hours.

9. A negative electrode plate, comprising the negative electrode material and grid as described in any one of claims 1 to 4.

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