A high-capacity, long-cycle sodium-ion battery anode material and its preparation method

Abstract

This invention relates to the field of electrochemical energy storage technology, specifically to a high-capacity, long-cycle sodium-ion battery anode material and its preparation method, addressing the problems of low capacity and low cycle capacity retention when using porous carbon as a sodium-ion battery anode material. This anode material uses phenolic resin microspheres as the carbon source, constructing a radially gradient porous carbon framework with increasing interlayer spacing from the inside to the outside through stepwise gradient impregnation and carbonization of zinc chloride and zinc acetate. A segmented vacuum impregnation method is used to gradient-load Sn-Bi precursors from the inside to the outside, followed by heat treatment to generate a sodium-loving alloy phase in situ within the closed pores. Plasma treatment is then used to introduce pyridine nitrogen onto the outer surface and weaken the sodium affinity. Finally, a NATP fast-ion conductor coating is applied to the particle surface using a sol-gel method. The material exhibits a gradient nucleation characteristic of strong sodium affinity inside the pores and weak sodium affinity outside the pores, guiding sodium to deposit uniformly within the closed pores, suppressing dendrite growth and interfacial side reactions, and possessing both high capacity and long-cycle performance.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, specifically to a high-capacity, long-cycle sodium-ion battery anode material and its preparation method. Background Technology

[0002] Sodium resources offer significant advantages, being abundant in the Earth's crust and available at low cost. Sodium-based batteries can reduce raw material costs and improve safety, making them competitive for large-scale applications in energy storage. Currently, in commercial applications of sodium-ion batteries, hard carbon materials are the mainstream choice for anode materials. However, these materials generally suffer from slow sodium-ion intercalation / deintercalation kinetics and high sodium metal nucleation overpotential. During battery service, sodium deposition easily occurs on the electrode surface, leading to frequent interfacial side reactions. Furthermore, the material structure is prone to pulverization and collapse during long-cycle periods, severely limiting battery cycle life and safety performance. Porous carbon materials, with their high specific surface area and tunable pore structure, have become a key research direction for sodium-ion battery anode materials.

[0003] However, existing porous carbon has strong surface chemical inertness, resulting in a large nucleation barrier for sodium metal, which easily induces sodium dendrite growth and deteriorates the stability of the electrode interface. Existing porous carbon anode materials also have the following problems, such as the intrinsic sodium-repellent properties: the closed-pore structure of the material cannot participate in the sodium ion storage reaction, resulting in low utilization of effective sodium storage sites; the open-pore structure easily causes the electrolyte to continuously decompose and corrode the electrode interface; at the same time, the sodium metal nucleation is in a random and disordered distribution state, resulting in excessively high local current density of the electrode, which further accelerates the battery capacity decay; in addition, the high specific surface area of ​​porous carbon will aggravate the interfacial side reactions, resulting in low coulombic efficiency in the first week of the material and low capacity retention in conventional systems, which makes it difficult to meet the needs of large-scale energy storage and power application scenarios.

[0004] Therefore, the high-capacity, long-cycle sodium-ion battery anode material and its preparation method of the present invention are of great significance in the field of electrochemical energy storage technology. Summary of the Invention

[0005] In order to overcome the above-mentioned technical problems, the purpose of this invention is to provide a high-capacity, long-cycle sodium-ion battery anode material and its preparation method, which solves the problems of low capacity and low cycle capacity retention of existing porous carbon as a sodium-ion battery anode material.

[0006] The objective of this invention can be achieved through the following technical solutions: In a first aspect, this application provides a high-capacity, long-cycle sodium-ion battery anode material, characterized in that it includes a radially gradient porous carbon framework, on which sodium-loving substances are loaded by vacuum impregnation and vapor deposition, and a sodium-loving phase of metal element or alloy is generated in situ within the pores; the outer surface of the material is treated by plasma, and the outermost layer is coated with a fast ion conductor coating. The specific surface area of ​​the radially gradient porous carbon framework is 1200-2800 m². 2 / g, with an average pore size of 3-20nm and an interlayer spacing of 0.37-0.42nm, and the proportion of closed pores ≥65%; the sodium-loving substance is one or more of Zn, Sn and Bi; the total loading of the sodium-loving substance accounts for 3-12% of the total mass of the loaded material; the particle size of the sodium-loving metal element or alloy phase generated in situ within the pores is 1-8nm.

[0007] In a preferred embodiment of the present invention, the specific surface area of ​​the radially gradient porous carbon framework is 1800-2400 m². 2 / g, with an average pore size of 5-12nm, an interlayer spacing of 0.385-0.405nm, and a closed-cell ratio of 70-85%.

[0008] In a preferred embodiment of the present invention, the vacuum impregnation process is as follows: impregnation for 2-6 hours under vacuum degree ≤10Pa and temperature of 60-90℃, followed by heat treatment for 1-3 hours at 300-450℃ in an argon atmosphere; the vapor deposition process is as follows: using SnCl4 and BiCl3 as precursors, deposition is carried out for 30-120 minutes at 350-500℃ and carrier gas flow rate of 50-120sccm, with the deposition pressure controlled at 100-500Pa.

[0009] In a preferred embodiment of the present invention, the natriuretic substance is a composite system of Sn and Bi, with a total loading of 5-9%, wherein the Sn content accounts for 40-70% of the total mass of the natriuretic substance, and the remainder is Bi.

[0010] In a preferred embodiment of the present invention, the radial gradient porous carbon framework is prepared by using phenolic resin microspheres as the carbon source and activating them with a mixture of ZnCl2 and ZnAc2. The spacing between the inner and outer layers increases from the inside to the outside: 0.38-0.39 nm for the inner layer, 0.39-0.4 nm for the middle layer, and 0.4-0.415 nm for the outer layer. Sodium-loving substances are distributed and enriched in a gradient. The Sn / Bi loading is 8-10% for the inner layer, 5-7% for the middle layer, and 2-4% for the outer layer. The outer layer is then treated with plasma.

[0011] In a preferred embodiment of the present invention, the fast ion conductor coating is a NASICON-type fast ion conductor Na. 1.3 Al 0.3 Ti 1.7 The (PO4)3 coating is generated in situ using the sol-gel method, with a thickness of 3-20 nm.

[0012] Secondly, this application provides a method for preparing a high-capacity, long-cycle sodium-ion battery anode material, comprising the following steps: Step 1: Immerse the phenolic resin microspheres in the first solution at 60℃ and an absolute pressure of 2.13 × 10⁻⁶. 4 The mixture was stirred and impregnated at 200-300 r / min for 3 h under Pa conditions, filtered, and the filter cake was dried in an oven at 80 °C for 2 h to obtain the inner coating layer. The inner coating layer was then immersed in the second solution and impregnated for another 2 h under the above conditions, followed by drying for 2 h to obtain the middle coating layer. The middle coating layer was then immersed in solution C and impregnated for another 1.5 h under the above conditions, followed by drying for 2 h to obtain the outer coating layer. The outer coating layer was placed in a tube furnace and heated to 850 °C at a heating rate of 2 °C / min under nitrogen protection, carbonized at a constant temperature for 3 h, and then naturally cooled to 25 °C. The outer coating layer was washed 2-3 times with hydrochloric acid solution and distilled water, respectively, and then vacuum dried at 120 °C for 12 h to obtain a radially gradient porous carbon framework. Step 2: Place the radially gradient porous carbon framework in a tube furnace, introduce argon gas to a pressure of 200 Pa, and heat to 450 °C. Mix SnCl4 and BiCl3 and heat to 180-200 °C in an evaporator to vaporize them. The vaporized mixture is carried into the tube furnace by the argon carrier gas and deposited for 1 hour to obtain the precursor. Cool to 380 °C, maintaining the partial pressure of the precursor, and shorten the deposition time to 30 minutes. After naturally cooling to 25 °C, remove the precursor and immerse it in a SnCl2 / BiCl3 mixed ethanol solution. Immerse it under vacuum at 5 Pa and 65 °C for 1-2 hours, filter, dry at 150 °C for 1 hour, transfer to a tube furnace, and heat to 250 °C at 5 °C / min in an argon atmosphere. Hold for 1 hour, then continue heating to 400 °C and hold for 2 hours to obtain the gradient sodium-loving anode precursor. Spread the gradient sodium-loving anode precursor evenly on the sample stage of the remote plasma processing system, and evacuate the cavity to 1 × 10⁻⁶. -3 Pa, a mixed gas with a flow rate of 80 sccm was introduced, the chamber pressure was maintained at 60 Pa, and plasma treatment was carried out at 25 °C with a power of 200 W for 120 s to obtain functionalized gradient anode material. Step 3: Add tetrabutyl titanate and anhydrous ethanol to a beaker and mix and stir for 30 min. Then add aluminum nitrate, triethyl phosphate and sodium acetate in sequence, mix and stir for 10-15 min, then add deionized water and nitric acid solution. Hydrolyze at 25℃ with magnetic stirring at 400 r / min for 4 h. Add functionalized gradient anode material, continue stirring for 6 h, filter, dry in a rotary evaporator at 80℃ for 3-4 h, transfer to a tube furnace, heat to 600℃ at a heating rate of 3℃ / min under argon protection and sinter for 2 h. Cool naturally to 25℃ to obtain high-capacity long-cycle sodium-ion battery anode material.

[0013] In a preferred embodiment of the present invention, the ratio of the phenolic resin microspheres, the first solution, the second solution, and solution C in step one is 4-6g:25-30mL:20-25mL:15-20mL; the phenolic resin microspheres are of model 2123; the first solution is prepared by mixing zinc chloride, zinc acetate, and anhydrous ethanol in a ratio of 4.5g:1.5g:25mL; the second solution is prepared by mixing zinc chloride, zinc acetate, and anhydrous ethanol in a ratio of 1.8g:1.8g:20mL; solution C is prepared by mixing zinc chloride, zinc acetate, and anhydrous ethanol in a ratio of 0.6g:1.8g:15mL; and the concentration of the hydrochloric acid solution is 1mol / L.

[0014] In a preferred embodiment of the present invention, the ratio of the radial gradient porous carbon framework, SnCl4, BiCl3, and SnCl2 / BiCl3 mixed ethanol solution used in step two is 1-2g: 0.4-0.45g: 0.2-0.25g: 15-20mL; the argon carrier gas flow rate is 80sccm; and the SnCl2 / BiCl3 mixed ethanol solution contains Sn... 2+ and Bi 3+ The total molar concentration is 0.08 mol / L, wherein the mass ratio of Sn to Bi is 2:1; the mixed gas is composed of nitrogen and hydrogen mixed in a volume ratio of 9:1.

[0015] In a preferred embodiment of the present invention, the ratio of tetrabutyl titanate, anhydrous ethanol, aluminum nitrate, triethyl phosphate, sodium acetate, deionized water, nitric acid solution, and functionalized gradient negative electrode material in step three is 4-5g: 20-25mL: 0.5-0.8g: 2.4-2.8g: 0.8-1g: 1-2mL: 0.5-1mL: 2-2.5g; and the concentration of the nitric acid solution is 2mol / L.

[0016] The beneficial effects of this invention are: This invention discloses a high-capacity, long-cycle sodium-ion battery anode material and its preparation method. Using phenolic resin microspheres as the carbon source, a radially gradient porous carbon framework with gradually increasing interlayer spacing is constructed through stepwise gradient impregnation with zinc chloride and zinc acetate followed by high-temperature carbonization. Then, a Sn-Bi precursor is gradient-loaded from the inside out using a segmented vacuum impregnation method, followed by heat treatment to generate a nano-sodium-loving alloy phase in situ within the closed pores. Subsequently, the outer surface is treated with a mixed gas plasma to weaken its sodium affinity. A NASICON-type NATP fast ion conductor coating is applied to the particle surface using a sol-gel method, and after sintering, a high-capacity, long-cycle sodium-ion battery anode material is obtained. The porous carbon framework exhibits a gradient increase in interlayer spacing from the inside to the outside, with a gradient enrichment of the sodium-loving phase. The outer layer is then subjected to low-temperature plasma nitrogen doping. The gradient interlayer spacing matches the kinetic requirements of different stages of sodium ion insertion / extraction, and the gradient sodium-loving phase distribution is combined with outer nitrogen doping passivation. Achieving a three-tiered synergy of "efficient nucleation in the inner layer, rapid transport in the middle layer, and stable interface in the outer layer" improves rate performance. The Sn-Bi nano-alloy phase, grown in a confined space within the closed pores, provides a lower sodium nucleation barrier, preferentially guiding sodium metal to deposit uniformly and orderly within the pores, improving the utilization rate of sodium storage space and achieving high first-cycle discharge capacity. The weak sodium affinity formed on the outer surface through plasma treatment effectively inhibits the continuous reduction and decomposition of the electrolyte on the outer surface. The NATP fast ion conductor coating on the surface further constructs a mechanically and chemically stable artificial SEI film. The synergistic effect of these two components reduces interfacial side reactions. On the one hand, the NATP coating physically blocks direct contact between the electrolyte and the carbon surface, inhibiting side reactions and improving high-temperature storage stability. On the other hand, it provides additional sodium ion transport channels, alleviating the pressure of sodium metal deposition during overcharging, allowing the battery to maintain structural integrity after constant-voltage overcharging and improving cycle stability. Attached Figure Description

[0017] The invention will now be further described with reference to the accompanying drawings.

[0018] Figure 1 This is an electron microscope image of the high-capacity, long-cycle sodium-ion battery anode material in Example 2 of this invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: This embodiment describes a method for preparing a high-capacity, long-cycle sodium-ion battery anode material, including the following steps: Step 1: Immerse 4g of phenolic resin microspheres 2123 into 25mL of the first solution, and heat at 60℃ and an absolute pressure of 2.13×10⁻⁶. 4 The mixture was stirred and impregnated at 200 rpm for 3 hours under Pa conditions, then filtered. The filter cake was dried in an oven at 80°C for 2 hours to obtain the inner coating layer. The inner coating layer was then immersed in 20 mL of [a solution / concentration solution]. In the second solution, the mixture was further immersed for 2 hours under the above conditions and dried for 2 hours to obtain the intermediate coating layer. The intermediate coating layer was then immersed in 15 mL of solution C and immersed for 1.5 hours under the above conditions and dried for 2 hours to obtain the outer coating layer. This outer coating layer was placed in a tube furnace and heated to 850°C at a heating rate of 2°C / min under nitrogen protection. It was then carbonized at this temperature for 3 hours and naturally cooled to 25°C. The outer coating layer was washed twice with 1 mol / L hydrochloric acid solution and distilled water, and then vacuum dried at 120°C for 12 hours to obtain a radially gradient porous carbon framework. The first solution was prepared by mixing zinc chloride, zinc acetate, and anhydrous ethanol in a ratio of 4.5 g: 1.5 g: 25 mL. The second solution was prepared by mixing zinc chloride, zinc acetate, and anhydrous ethanol in a ratio of 1.8 g: 1.8 g: 20 mL. Solution C was prepared by mixing zinc chloride, zinc acetate, and anhydrous ethanol in a ratio of 0.6 g: 1.8 g: 15 mL. Step 2: Place 1g of radially gradient porous carbon framework in a tube furnace, purge with argon gas to a pressure of 200Pa, heat to 450℃, and add 0.4g SnCl4 and 0.2g... BiCl3 mixture was heated to 180℃ in an evaporator to vaporize, and then carried into a tube furnace by argon gas at a flow rate of 80 sccm. Deposition was carried out for 1 h to obtain the precursor. The temperature was then lowered to 380℃, maintaining a constant partial pressure of the precursor, and the deposition time was shortened to 30 min. After natural cooling to 25℃, the precursor was removed and immersed in 15 mL of a SnCl2 / BiCl3 mixed ethanol solution at 65℃ under vacuum of 5 Pa for 1 h. After filtration, the precursor was dried at 150℃ for 1 h and transferred to a tube furnace. The furnace was heated to 250℃ at a rate of 5℃ / min under an argon atmosphere and held for 1 h, then further heated to 400℃ and held for 2 h to obtain a gradient sodium-philic anode precursor. This gradient sodium-philic anode precursor was then laid flat on the sample stage of a remote plasma processing system, and the cavity was evacuated to 1×10⁻⁶. -3 A mixed gas with a flow rate of 80 sccm was introduced to maintain a chamber pressure of 60 Pa. Plasma treatment was performed at 25°C and 200 W for 120 s to obtain a functionalized gradient anode material. The SnCl2 / BiCl3 mixed ethanol solution contained Sn... 2+ and Bi 3+ The total molar concentration is 0.08 mol / L, wherein the mass ratio of Sn to Bi is 2:1; the mixed gas is composed of nitrogen and hydrogen mixed in a volume ratio of 9:1. Step 3: Add 4g tetrabutyl titanate and 20mL anhydrous ethanol to a beaker and mix and stir for 30min. Then add 0.5g aluminum nitrate, 2.4g triethyl phosphate and 0.8g sodium acetate in sequence, mix and stir for 10min, then add 1mL deionized water and 0.5mL nitric acid solution with a concentration of 2mol / L. Hydrolyze at 25℃ with magnetic stirring at 400r / min for 4h. Add 2g functionalized gradient anode material and continue stirring for 6h. Filter and dry in a rotary evaporator at 80℃ for 3h. Transfer to a tube furnace and sinter at 600℃ for 2h under argon protection with a heating rate of 3℃ / min. Cool naturally to 25℃ to obtain high-capacity long-cycle sodium-ion battery anode material.

[0021] Example 2: This embodiment describes a method for preparing a high-capacity, long-cycle sodium-ion battery anode material, including the following steps: Step 1: Immerse 5g of phenolic resin microspheres 2123 into 28mL of the first solution, and heat at 60℃ and an absolute pressure of 2.13×10⁻⁶. 4 The mixture was stirred and impregnated at 250 rpm for 3 hours under Pa conditions, then filtered. The filter cake was dried in an oven at 80°C for 2 hours to obtain the inner coating layer. The inner coating layer was then immersed in 23 mL of [a solution / concentration solution]. In the second solution, the mixture was further immersed for 2 hours under the above conditions and dried for 2 hours to obtain the intermediate coating layer. The intermediate coating layer was then immersed in 18 mL of solution C and immersed for 1.5 hours under the above conditions and dried for 2 hours to obtain the outer coating layer. This outer coating layer was placed in a tube furnace and heated to 850°C at a heating rate of 2°C / min under nitrogen protection. It was then carbonized at this temperature for 3 hours and naturally cooled to 25°C. The outer coating layer was washed three times with 1 mol / L hydrochloric acid solution and distilled water, and then vacuum dried at 120°C for 12 hours to obtain a radially gradient porous carbon framework. The first solution was prepared by mixing zinc chloride, zinc acetate, and anhydrous ethanol in a ratio of 4.5 g: 1.5 g: 25 mL. The second solution was prepared by mixing zinc chloride, zinc acetate, and anhydrous ethanol in a ratio of 1.8 g: 1.8 g: 20 mL. Solution C was prepared by mixing zinc chloride, zinc acetate, and anhydrous ethanol in a ratio of 0.6 g: 1.8 g: 15 mL. Step 2: Place 1.5g of radially gradient porous carbon framework in a tube furnace, introduce argon gas to a pressure of 200Pa, heat to 450℃, and add 0.43g of SnCl4 and 0.23g of... BiCl3 mixture was heated to 190℃ in an evaporator and vaporized. The vaporized precursor was carried into a tube furnace by argon gas at a flow rate of 80 sccm and deposited for 1 h to obtain the precursor. The temperature was then lowered to 380℃, maintaining the partial pressure of the precursor, and the deposition time was shortened to 30 min. After natural cooling to 25℃, the precursor was removed and immersed in 18 mL of a SnCl2 / BiCl3 mixed ethanol solution at 65℃ under vacuum of 5 Pa for 1.5 h. After filtration, the precursor was dried at 150℃ for 1 h and transferred to a tube furnace. The furnace was heated to 250℃ at 5℃ / min under an argon atmosphere and held for 1 h, then further heated to 400℃ and held for 2 h to obtain a gradient sodium-loving anode precursor. This gradient sodium-loving anode precursor was then laid flat on the sample stage of a remote plasma processing system, and the cavity was evacuated to 1×10⁻⁶. - 3 A mixed gas with a flow rate of 80 sccm was introduced to maintain a chamber pressure of 60 Pa. Plasma treatment was performed at 25°C and 200 W for 120 s to obtain a functionalized gradient anode material. The SnCl2 / BiCl3 mixed ethanol solution contained Sn... 2+ and Bi 3+ The total molar concentration is 0.08 mol / L, wherein the mass ratio of Sn to Bi is 2:1; the mixed gas is composed of nitrogen and hydrogen mixed in a volume ratio of 9:1. Step 3: Add 4.5g tetrabutyl titanate and 23mL anhydrous ethanol to a beaker and mix and stir for 30min. Then add 0.7g aluminum nitrate, 2.6g triethyl phosphate and 0.9g sodium acetate in sequence, mix and stir for 13min, then add 1.5mL deionized water and 0.8mL nitric acid solution with a concentration of 2mol / L. Hydrolyze at 25℃ with magnetic stirring at 400r / min for 4h. Add 2.3g functionalized gradient anode material, continue stirring for 6h, filter, dry in a rotary evaporator at 80℃ for 3.5h, transfer to a tube furnace, and sinter at 600℃ for 2h under argon protection with a heating rate of 3℃ / min. Cool naturally to 25℃ to obtain high-capacity long-cycle sodium-ion battery anode material.

[0022] Example 3: This embodiment describes a method for preparing a high-capacity, long-cycle sodium-ion battery anode material, including the following steps: Step 1: Immerse 6g of phenolic resin microspheres 2123 into 30mL of the first solution, and heat at 60℃ and an absolute pressure of 2.13×10⁻⁶. 4The mixture was stirred and impregnated at 300 rpm for 3 hours under Pa conditions, then filtered. The filter cake was dried in an oven at 80°C for 2 hours to obtain the inner coating layer. The inner coating layer was then immersed in 25 mL of [a solution / concentration solution]. In the second solution, the mixture was further immersed for 2 hours under the above conditions and dried for 2 hours to obtain the intermediate coating layer. The intermediate coating layer was then immersed in 20 mL of solution C and immersed for 1.5 hours under the above conditions and dried for 2 hours to obtain the outer coating layer. The outer coating layer was placed in a tube furnace and heated to 850°C at a heating rate of 2°C / min under nitrogen protection. It was then carbonized at this temperature for 3 hours and naturally cooled to 25°C. The outer coating layer was washed three times with 1 mol / L hydrochloric acid solution and distilled water, and then vacuum dried at 120°C for 12 hours to obtain a radially gradient porous carbon framework. The first solution was prepared by mixing zinc chloride, zinc acetate, and anhydrous ethanol in a ratio of 4.5 g: 1.5 g: 25 mL. The second solution was prepared by mixing zinc chloride, zinc acetate, and anhydrous ethanol in a ratio of 1.8 g: 1.8 g: 20 mL. Solution C was prepared by mixing zinc chloride, zinc acetate, and anhydrous ethanol in a ratio of 0.6 g: 1.8 g: 15 mL. Step 2: Place 2g of radially gradient porous carbon framework in a tube furnace, introduce argon gas to a pressure of 200Pa, heat to 450℃, and add 0.45g SnCl4 and 0.25g... BiCl3 mixture was heated to 200℃ in an evaporator to vaporize, and then carried into a tube furnace by argon gas at a flow rate of 80 sccm. Deposition was carried out for 1 h to obtain the precursor. The temperature was then lowered to 380℃, maintaining a constant partial pressure of the precursor, and the deposition time was shortened to 30 min. After natural cooling to 25℃, the precursor was removed and immersed in 20 mL of a SnCl2 / BiCl3 mixed ethanol solution at 65℃ under vacuum of 5 Pa for 2 h. After filtration, the precursor was dried at 150℃ for 1 h and transferred to a tube furnace. The furnace was heated to 250℃ at a rate of 5℃ / min under an argon atmosphere and held for 1 h, then further heated to 400℃ and held for 2 h to obtain a gradient sodium-philic anode precursor. This gradient sodium-philic anode precursor was then laid flat on the sample stage of a remote plasma processing system, and the cavity was evacuated to 1×10⁻⁶. -3 A mixed gas with a flow rate of 80 sccm was introduced to maintain a chamber pressure of 60 Pa. Plasma treatment was performed at 25°C and 200 W for 120 s to obtain a functionalized gradient anode material. The SnCl2 / BiCl3 mixed ethanol solution contained Sn... 2+ and Bi 3+ The total molar concentration is 0.08 mol / L, wherein the mass ratio of Sn to Bi is 2:1; the mixed gas is composed of nitrogen and hydrogen mixed in a volume ratio of 9:1. Step 3: Add 5g tetrabutyl titanate and 25mL anhydrous ethanol to a beaker and mix and stir for 30min. Then add 0.8g aluminum nitrate, 2.8g triethyl phosphate and 1g sodium acetate in sequence. Mix and stir for 15min. Then add 2mL deionized water and 1mL nitric acid solution with a concentration of 2mol / L. Hydrolyze at 25℃ with magnetic stirring at 400r / min for 4h. Add 2.5g functionalized gradient anode material and continue stirring for 6h. Filter and dry in a rotary evaporator at 80℃ for 4h. Transfer to a tube furnace and sinter at 600℃ for 2h under argon protection with a heating rate of 3℃ / min. Cool naturally to 25℃ to obtain high-capacity long-cycle sodium-ion battery anode material.

[0023] Comparative Example 1: This comparative example illustrates a method for preparing a high-capacity, long-cycle sodium-ion battery anode material, comprising the following steps: Step 1: Calculate the specific surface area of ​​2100 m². 2 One g of porous carbon with an average pore size of 8 nm, an interlayer spacing of 0.395 nm, and a closed-cell content of 78% was placed in a vacuum impregnation tank. 15 mL of an ethanol solution containing 0.085 g SnCl2·2H2O and 0.065 g BiCl3 was added. The mixture was vacuum impregnated at 80 °C and 5 Pa for 4 h. After filtration, the mixture was dried at 120 °C for 3 h and then heat-treated at 400 °C for 2 h in an argon atmosphere to obtain a high-capacity, long-cycle sodium-ion battery anode material.

[0024] Comparative Example 2: This comparative example illustrates a method for preparing a high-capacity, long-cycle sodium-ion battery anode material, comprising the following steps: Step 1: Calculate the specific surface area of ​​2100 m². 2 One g of porous carbon with an average pore size of 8 nm, an interlayer spacing of 0.395 nm, and a closed-cell content of 78% was placed in a vacuum impregnation tank. 15 mL of ethanol solution containing 0.085 g SnCl2·2H2O and 0.065 g BiCl3 was added. The mixture was vacuum impregnated at 80 °C and 5 Pa for 4 h. After filtration, the mixture was dried at 120 °C for 3 h and then heat-treated at 400 °C for 2 h in an argon atmosphere to obtain the negative electrode material. Step 2: Add 4.5g tetrabutyl titanate and 23mL anhydrous ethanol to a beaker and mix and stir for 30min. Then add 0.7g aluminum nitrate, 2.6g triethyl phosphate and 0.9g sodium acetate in sequence, mix and stir for 13min, then add 1.5mL deionized water and 0.8mL nitric acid solution with a concentration of 2mol / L. Hydrolyze at 25℃ with magnetic stirring at 400r / min for 4h. Add 2.3g of negative electrode material and continue stirring for 6h. Filter and dry in a rotary evaporator at 80℃ for 3.5h. Transfer to a tube furnace and sinter at 600℃ for 2h under argon protection with a heating rate of 3℃ / min. Cool naturally to 25℃ to obtain high-capacity long-cycle sodium-ion battery negative electrode material.

[0025] Comparative Example 3: This comparative example illustrates a method for preparing a high-capacity, long-cycle sodium-ion battery anode material, comprising the following steps: Step 1: Immerse 5g of phenolic resin microspheres 2123 into 28mL of the first solution, and heat at 60℃ and an absolute pressure of 2.13×10⁻⁶. 4 The mixture was stirred and impregnated at 250 rpm for 3 hours under Pa conditions, then filtered. The filter cake was dried in an oven at 80°C for 2 hours to obtain the inner coating layer. The inner coating layer was then immersed in 23 mL of [a solution / concentration solution]. In the second solution, the mixture was further immersed for 2 hours under the above conditions and dried for 2 hours to obtain the intermediate coating layer. The intermediate coating layer was then immersed in 18 mL of solution C and immersed for 1.5 hours under the above conditions and dried for 2 hours to obtain the outer coating layer. This outer coating layer was placed in a tube furnace and heated to 850°C at a heating rate of 2°C / min under nitrogen protection. It was then carbonized at this temperature for 3 hours and naturally cooled to 25°C. The outer coating layer was washed three times with 1 mol / L hydrochloric acid solution and distilled water, and then vacuum dried at 120°C for 12 hours to obtain a radially gradient porous carbon framework. The first solution was prepared by mixing zinc chloride, zinc acetate, and anhydrous ethanol in a ratio of 4.5 g: 1.5 g: 25 mL. The second solution was prepared by mixing zinc chloride, zinc acetate, and anhydrous ethanol in a ratio of 1.8 g: 1.8 g: 20 mL. Solution C was prepared by mixing zinc chloride, zinc acetate, and anhydrous ethanol in a ratio of 0.6 g: 1.8 g: 15 mL. Step 2: Place 1.5g of radially gradient porous carbon framework in a tube furnace, introduce argon gas to a pressure of 200Pa, heat to 450℃, and add 0.43g of SnCl4 and 0.23g of... BiCl3 mixture was heated to 190℃ in an evaporator and vaporized. The vaporized precursor was carried into a tube furnace by argon gas at a flow rate of 80 sccm and deposited for 1 h to obtain the precursor. The temperature was then lowered to 380℃, maintaining the partial pressure of the precursor, and the deposition time was shortened to 30 min. After natural cooling to 25℃, the precursor was removed and immersed in 18 mL of a SnCl2 / BiCl3 mixed ethanol solution at 65℃ under vacuum of 5 Pa for 1.5 h. After filtration, the precursor was dried at 150℃ for 1 h and transferred to a tube furnace. The furnace was heated to 250℃ at 5℃ / min under an argon atmosphere and held for 1 h, then further heated to 400℃ and held for 2 h to obtain a gradient sodium-loving anode precursor. This gradient sodium-loving anode precursor was then laid flat on the sample stage of a remote plasma processing system, and the cavity was evacuated to 1×10⁻⁶. - 3 A mixed gas with a flow rate of 80 sccm was introduced to maintain a chamber pressure of 60 Pa. Plasma treatment was performed at 25°C and 200 W for 120 s to obtain a high-capacity, long-cycle sodium-ion battery anode material. The SnCl2 / BiCl3 mixed ethanol solution contained Sn... 2+ and Bi 3+ The total molar concentration is 0.08 mol / L, wherein the mass ratio of Sn to Bi is 2:1; the mixed gas is composed of nitrogen and hydrogen mixed in a volume ratio of 9:1.

[0026] The high-capacity, long-cycle sodium-ion battery anode materials prepared in Examples 1-3 and Comparative Examples 1-3 were used as anode active materials. The anode active material, conductive carbon black ENSACO 250G, sodium carboxymethyl cellulose, and N-methylpyrrolidone were mixed in a mass ratio of 7:2:1:8, coated onto the surface of copper foil, vacuum dried at 80°C for 24 hours, and cut to obtain the anode sheet. Sodium metal was used as the counter electrode, and a glass fiber membrane was used. Using GF / C as the separator and a mixture of ethylene carbonate and diethyl carbonate (volume ratio 1:1) containing sodium hexafluorophosphate as the electrolyte, with a sodium hexafluorophosphate concentration of 1 mol / L, a 2032 type button cell was assembled. The first-cycle discharge capacity at 0.1C was measured. Cycle life tests were performed using an electrochemical performance tester, measuring the capacity retention after 1000 charge-discharge cycles at 25℃ and 1C, as well as the charge-discharge capacity at 10C, 20C, and 30C. The test results are shown in Table 1. Table 1 Test results for each embodiment and comparative example

[0027] Comparing Examples 1-3 with Comparative Examples 1-3: Example 2 uses phenolic resin microspheres with a suitable liquid-to-solid ratio and ZnCl2 / ZnAc2 mixture for activation to prepare radial gradient porous carbon, resulting in more thorough gradient penetration. The radial gradient interlayer spacing after carbonization is moderate, the closed-pore structure is complete, and the interlayer spacing gradient transition is smooth. The gradient impregnation amount of the sodium-loving substance solution corresponding to the carbon skeleton ensures a better gradient and uniform distribution of the Sn-Bi sodium-loving phase in the pores. The ratio of NATP precursor to carbon material is moderate, forming a uniform and fully covered fast ion conductor coating. In Example 1, due to the smaller amount of phenolic resin microspheres and the relatively larger amount of solution used in each step, overactivation and higher sodium-loving phase loading occurred, and some pores were filled, affecting the ion transport efficiency at high rates. In Example 3, the increased feed amount made it more difficult to control the gradient penetration depth of the ZnCl2 / ZnAc2 mixture, and the reduced differentiation between the inner and middle layers resulted in lower capacity and rate performance than Example 2. Comparing Example 1, it can be seen that: Comparative Example 1 uses ordinary porous carbon, which cannot effectively participate in sodium storage. The lack of sodium-loving sites on the open surface leads to a high overpotential for sodium metal nucleation, random and disordered nucleation, easy formation of dendrites, and continuous decomposition of the electrolyte, resulting in rapid capacity decay. Comparing Example 2 with Comparative Example 2, it can be seen that: Comparative Example 2 uses ordinary porous carbon with an added NATP coating. The closed-pore structure of ordinary porous carbon cannot be effectively utilized, resulting in wasted sodium storage space. The NATP coating only serves to stabilize the outer surface interface and cannot improve the intrinsic pore structure and sodium-loving phase distribution defects of the carbon material. Comparing Example 2 with Comparative Example 3, it can be seen that: Comparative Example 3 uses a radial gradient porous carbon framework, a gradient Sn-Bi sodium-loving phase distribution, and a weak sodium-loving outer surface formed by plasma treatment. Lacking the protection of the NATP fast ion conductor coating, although its outer surface is plasma passivated, it will undergo slow side reactions with the electrolyte during long-term cycling. The SEI film continues to thicken and consumes active sodium, resulting in a gradual increase in interfacial impedance and a decrease in capacity retention.

[0028] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0029] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in this application, they should all fall within the protection scope of the present invention.

Claims

1. A high-capacity, long-cycle sodium-ion battery anode material, characterized in that, It includes a radially gradient porous carbon framework, on which sodium-loving materials are loaded by vacuum impregnation and vapor deposition, and sodium-loving metal elements or alloys are generated in situ within the pores; the outer surface of the material is treated with plasma and the outermost layer is coated with a fast ion conductor coating. The specific surface area of ​​the radially gradient porous carbon framework is 1200-2800 m². 2 / g, with an average pore size of 3-20nm and an interlayer spacing of 0.37-0.42nm, and the proportion of closed pores ≥65%; the sodium-loving substance is one or more of Zn, Sn and Bi; the total loading of the sodium-loving substance accounts for 3-12% of the total mass of the loaded material; the particle size of the sodium-loving metal element or alloy phase generated in situ within the pores is 1-8nm.

2. The high-capacity, long-cycle sodium-ion battery anode material according to claim 1, characterized in that, The specific surface area of ​​the radially gradient porous carbon framework is 1800-2400 m². 2 / g, with an average pore size of 5-12nm, an interlayer spacing of 0.385-0.405nm, and a closed-cell ratio of 70-85%.

3. The high-capacity, long-cycle sodium-ion battery anode material according to claim 1, characterized in that, The vacuum impregnation process is as follows: impregnation for 2-6 hours under vacuum degree ≤10Pa and temperature of 60-90℃, followed by heat treatment at 300-450℃ for 1-3 hours in an argon atmosphere; the vapor deposition process is as follows: using SnCl4 and BiCl3 as precursors, deposition is carried out for 30-120 minutes at 350-500℃ and carrier gas flow rate of 50-120sccm, with the deposition pressure controlled at 100-500Pa.

4. The high-capacity, long-cycle sodium-ion battery anode material according to claim 1, characterized in that, The natriuretic substance is a composite system of Sn and Bi, with a total loading of 5-9%, wherein the Sn content accounts for 40-70% of the total mass of the natriuretic substance, and the balance is Bi.

5. The high-capacity, long-cycle sodium-ion battery anode material according to claim 1, characterized in that, The radial gradient porous carbon framework is prepared using phenolic resin microspheres as the carbon source and activated by a ZnCl2 / ZnAc2 mixture. The spacing between the inner and outer layers increases from the inside to the outside: 0.38-0.39 nm for the inner layer, 0.39-0.4 nm for the middle layer, and 0.4-0.415 nm for the outer layer. Sodium-loving substances are distributed and enriched in a gradient manner. The Sn / Bi loading is 8-10% for the inner layer, 5-7% for the middle layer, and 2-4% for the outer layer. The outer layer is then treated with plasma.

6. The high-capacity, long-cycle sodium-ion battery anode material according to claim 1, characterized in that, The fast ion conductor coating is a NASICON-type fast ion conductor Na. 1.3 Al 0.3 Ti 1.7 The (PO4)3 coating is generated in situ using the sol-gel method, with a thickness of 3-20 nm.

7. A method for preparing a high-capacity, long-cycle sodium-ion battery anode material, used to prepare the high-capacity, long-cycle sodium-ion battery anode material as described in any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Immerse the phenolic resin microspheres in the first solution and stir to impregnate them. Filter the solution and dry the filter cake to obtain the inner coating layer. Immerse the inner coating layer in the second solution and continue to impregnate it. Dry the solution to obtain the middle coating layer. Immerse the middle coating layer in solution C and dry it to obtain the outer coating layer. Place the outer coating layer in a tube furnace for carbonization, cool it, wash it with hydrochloric acid solution and distilled water respectively, and dry it to obtain a radially gradient porous carbon framework. Step 2: Place the radially gradient porous carbon framework in a tube furnace, introduce argon gas, and heat. Mix SnCl4 and BiCl3 and heat them in an evaporator to vaporize them. The vaporized mixture is then carried by the argon carrier gas into the tube furnace for deposition, yielding the precursor. Cool the precursor while maintaining its partial pressure, shorten the deposition time, cool it, and immerse it in a SnCl2 / BiCl3 mixed ethanol solution. Filter, dry, and transfer it to a tube furnace for vacuum impregnation, yielding a gradient sodium-loving anode precursor. Spread the gradient sodium-loving anode precursor on the sample stage of a remote plasma processing system, evacuate, and introduce a mixed gas for plasma treatment to obtain the functionalized gradient anode material. Step 3: Tetrabutyl titanate and anhydrous ethanol are mixed, aluminum nitrate, triethyl phosphate and sodium acetate are added and stirred, then deionized water and nitric acid solution are added and stirred for hydrolysis. Functionalized gradient anode material is added, stirred and filtered, dried, transferred to a tube furnace for sintering, and cooled to obtain high-capacity long-cycle sodium-ion battery anode material.

8. The method for preparing a high-capacity, long-cycle sodium-ion battery anode material according to claim 7, characterized in that, In step one, the volume ratio of the phenolic resin microspheres, the first solution, the second solution, and solution C is 4-6g: 25-30mL: 20-25mL: 15-20mL; the first solution is prepared by mixing zinc chloride, zinc acetate, and anhydrous ethanol in a volume ratio of 4.5g: 1.5g: 25mL; the second solution is prepared by mixing zinc chloride, zinc acetate, and anhydrous ethanol in a volume ratio of 1.8g: 1.8g: 20mL; solution C is prepared by mixing zinc chloride, zinc acetate, and anhydrous ethanol in a volume ratio of 0.6g: 1.8g: 15mL; and the concentration of the hydrochloric acid solution is 1mol / L.

9. The method for preparing a high-capacity, long-cycle sodium-ion battery anode material according to claim 7, characterized in that, In step two, the ratio of the radial gradient porous carbon framework, SnCl4, BiCl3, and the SnCl2 / BiCl3 mixed ethanol solution is 1-2 g : 0.4-0.45 g : 0.2-0.25 g : 15-20 mL; the argon carrier gas flow rate is 80 sccm; the SnCl2 / BiCl3 mixed ethanol solution contains Sn 2+ and Bi 3+ The total molar concentration is 0.08 mol / L, wherein the mass ratio of Sn to Bi is 2:1; the mixed gas is composed of nitrogen and hydrogen mixed in a volume ratio of 9:

1.

10. The method for preparing a high-capacity, long-cycle sodium-ion battery anode material according to claim 7, characterized in that, In step three, the ratio of tetrabutyl titanate, anhydrous ethanol, aluminum nitrate, triethyl phosphate, sodium acetate, deionized water, nitric acid solution, and functionalized gradient anode material is 4-5g: 20-25mL: 0.5-0.8g: 2.4-2.8g: 0.8-1g: 1-2mL: 0.5-1mL: 2-2.5g; the concentration of the nitric acid solution is 2mol / L.

Images