High capacity alloy negative material and sodium-ion secondary battery

Abstract

This invention provides a high-capacity alloy anode material and a sodium-ion secondary battery. Through the processes of melting the master alloy ingot, rapidly cooling and spinning to prepare a thin strip, electrochemical dealloying treatment, red phosphorus vapor deposition composite, and carbon layer coating, red phosphorus is innovatively deposited in a nanoporous bismuth framework with a continuous conductive network and buffer space. The resulting high-capacity alloy anode material has excellent interfacial charge transport performance. Compared with the traditional mechanical mixing method (simple grinding and mixing of red phosphorus and substrate), this directional filling process can avoid the agglomeration of red phosphorus particles, ensure that red phosphorus forms a tight interfacial bond with the inner wall of the bismuth framework pores, reduce the peeling of red phosphorus from the substrate during charging and discharging, and significantly improve the cycle stability of the composite material.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to high-capacity alloy anode materials and sodium-ion secondary batteries. Background Technology

[0002] In recent years, lithium-ion batteries (LIBs) have developed rapidly and are widely used, becoming one of the most important energy storage technologies. With the development of electric vehicles and large-scale new energy sources, the demand for rechargeable batteries is increasing daily. However, the small total reserves of lithium resources, their uneven global distribution, and poor availability make lithium resources very expensive. Limited lithium resources will inevitably face shortages; at the current rate of consumption, without considering recycling, they are expected to be depleted in over sixty years. Implementing LIBs for large-scale energy storage in the face of huge market demand is not a wise choice. On the other hand, the unsatisfactory cycle stability and low energy density of lead-acid batteries restrict their further development in more application scenarios. Developing new energy storage battery systems that are abundant in resources, inexpensive, have high specific capacity, high power, long cycle life, and are environmentally friendly, in line with energy development principles, is urgently needed. SIBs, due to their similar electrochemical properties to LIBs and abundant resource reserves, are expected to become the mainstream direction for future rechargeable battery development. Sodium-ion batteries, with their advantages of abundant resources and low cost, have shown broad application potential in many fields, such as large-scale energy storage systems, low-speed electric vehicles, and the construction of 5G communication base stations.

[0003] Red phosphorus, with its theoretical sodium storage capacity of up to 2596 mAh / g, is considered a highly promising anode material for sodium-ion batteries. However, its enormous volume expansion (>300%) and extremely low electronic conductivity lead to electrode pulverization and rapid capacity decay, severely hindering its practical application. In existing technologies, red phosphorus is typically combined with carbon materials (such as carbon nanotubes, graphene, and porous carbon) to alleviate these problems. However, carbon materials have limited mechanical modulus, insufficient ability to constrain the dramatic expansion of red phosphorus, and poor carbon / phosphorus interface stability. Bismuth (Bi) metal possesses excellent electrical conductivity (… It possesses high mechanical strength, and although its sodium storage volume expansion (~215%) exists, it is relatively controllable. If red phosphorus can be confined within a nanoporous bismuth framework with a continuous conductive network and buffer space, theoretically the following can be achieved: 1) porous bismuth as a highly conductive and high-strength three-dimensional current collector; 2) pores as reserved space for red phosphorus expansion; 3) close contact between bismuth and phosphorus to enhance interfacial charge transport.

[0004] CN119725434B discloses a phosphorus-based anode material with a solid electrolyte interface, its preparation method, and its application. The method includes the following steps: mixing phosphorus powder, carbon material, and metal fluoride and ball milling to obtain a composite anode material; sieving the composite anode material to obtain the phosphorus-based anode material. This application improves the cycle stability and rate performance of the battery by in-situ constructing a high-strength and high lithium-ion / electron transport solid electrolyte interface through the incorporation of metal fluoride. During lithium-ion battery discharge, the fluoride metal can pre-intercalate lithium onto the phosphorus-carbon particle surface to construct a solid electrolyte interface rich in high Young's modulus lithium fluoride and high ionic / electron conductivity lithium-metal alloy. This interface can be strengthened by the high Young's modulus lithium fluoride, thus suppressing the expansion of the phosphorus-carbon anode and improving cycle stability.

[0005] CN116387477B discloses an MXene composite material, its preparation method, and its applications. This MXene composite material comprises a phosphorus-doped Bi₂Te₃ / MXene material. The phosphorus doping in this MXene composite material introduces tellurium vacancies into Bi₂Te₃, and the introduction of bismuth telluride effectively increases the specific surface area of ​​the material, increasing the active sites for potassium ions. The unique layered structure of the MXene material effectively alleviates the pressure of increased volume expansion of the negative electrode material caused by large potassium ions, thereby improving the electrochemical performance of potassium-ion batteries. This MXene composite material significantly reduces the negative electrode volume expansion phenomenon caused by potassium ion deintercalation and intercalation. When used as a negative electrode in potassium-ion batteries, it greatly improves the specific capacity and cycle stability of potassium-ion batteries.

[0006] CN118715624A discloses a lithium-ion battery comprising: a silicon anode containing a substantially pure amorphous porous silicon film deposited on a current collector and including more than one columnar structure; an electrolyte layer containing one or more solid components; and a cathode layer.

[0007] CN121172131A discloses a secondary battery, including a negative electrode sheet. The negative electrode sheet includes a negative current collector and a negative active layer stacked on at least one surface of the negative current collector. The negative active layer includes a negative active material and metal particles. At least a portion of the metal particles have a porous structure. The metal element in the metal particles includes at least one of group IVA metal elements and group VA metal elements.

[0008] No existing technologies disclose anode materials using bismuth-phosphorus composites. Therefore, how to construct such a stable, uniform, and tightly bonded nanoporous bismuth / phosphorus composite structure is of great value for future technological applications. Summary of the Invention

[0009] The technical problem to be solved by this invention is that there is no stable and uniform porous bismuth / phosphorus composite material, nor is there a mature and efficient preparation method. Therefore, there is a need to provide high-capacity alloy anode materials and sodium-ion secondary batteries.

[0010] To address the aforementioned technical problems, in a first aspect, the present invention provides a method for preparing a high-capacity alloy anode material, the method comprising: (1) Place the working electrode, counter electrode and reference electrode into an electrolytic cell, inject electrolyte into the electrolytic cell, and then apply a constant anodic potential to the working electrode for electrochemical treatment; the working electrode is a bismuth alloy sheet, the bismuth alloy sheet contains bismuth and metal M, the atomic percentage of metal M in the bismuth alloy sheet is 30%~70%, and metal M includes any one or at least two of Mg, Al, Zn or Mn; (2) The working electrode after electrochemical treatment in step (1) is washed with a solution to obtain a nanoporous bismuth framework material; (3) Place the nanoporous bismuth framework material obtained in step (2) and red phosphorus at both ends of the container. The nanoporous bismuth framework material is placed in the low-temperature region of the container, and the red phosphorus is placed in the high-temperature region of the container. The low-temperature region and the high-temperature region are heated to obtain a red phosphorus-filled nanoporous bismuth composite material. (4) The red phosphorus-filled nanoporous bismuth composite material obtained in step (3) is placed in a deposition furnace and a carbon source is introduced for chemical vapor deposition to obtain the high-capacity alloy anode material.

[0011] In this invention, the atomic percentage of metal M refers to the percentage of the number of metal M atoms relative to the total number of bismuth and metal M atoms, which can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%, etc.

[0012] In this invention, the content of metal M should not be too high or too low. Below 30%, the number of pores formed after the metal M dissolves is insufficient, resulting in a small specific surface area, which cannot provide enough space for subsequent red phosphorus loading. Above 70%, the bismuth content is too low, making it difficult to form a stable framework structure, which is prone to collapse during subsequent processing. The ratio set in this invention balances porosity and framework structure stability, ensuring that the formed nanoporous bismuth framework has both a high specific surface area and excellent structural support capabilities.

[0013] In this invention, the counter electrode can be a platinum sheet or a graphite rod, etc.; the reference electrode can be a g / AgCl electrode.

[0014] Preferably, the electrolyte in step (1) includes an acidic solution or a salt solution containing metal M ions.

[0015] A salt solution containing metal M ions can be a salt solution formed by the chloride of metal M, the sulfate of metal M, the nitrate of metal M, etc.

[0016] Preferably, the acidic solution includes hydrochloric acid and / or sulfuric acid, and the concentration of the acidic solution is 0.1~1 mol / L, for example, it can be 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.8 mol / L or 1 mol / L, etc.

[0017] Preferably, the concentration of the salt solution containing metal M ions is 0.05~0.5 mol / L, for example, it can be 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L, etc.

[0018] Preferably, the constant potential in step (1) is 0.1~0.3V relative to the reference electrode, for example, it can be 0.1V, 0.15V, 0.2V or 0.3V.

[0019] Apply a constant anodic potential for dealloying treatment, which can last from 0.5 to 5 hours. At this potential, the metallic M in the precursor bismuth alloy is selectively anoly dissolved into the electrolyte, while bismuth, as a framework element, is retained and reconstructed to form a nanoporous structure.

[0020] Preferably, the method for preparing the bismuth alloy sheet in step (1) is as follows: S1: Bismuth and metal M are smelted under an inert gas atmosphere to obtain a master alloy ingot; S2: After the master alloy ingot is crushed to form a liquid alloy, a copper roller is used as a rapid cooling substrate to spray the liquid alloy onto the surface of the rotating copper roller, and the liquid alloy solidifies to form a bismuth alloy sheet.

[0021] In this invention, the smelting in step S1 can be carried out in a water-cooled copper crucible within an electric arc melting furnace. During the smelting process, after the furnace is closed, a mechanical pump and a molecular pump assembly are used to evacuate the furnace cavity to a vacuum level not exceeding 5.0 × 10⁻⁶. -3 Pa. Then, high-purity argon gas (purity higher than 99.999%) is introduced into the furnace cavity to a slightly positive pressure (0.05~0.07 MPa). This vacuuming-argon purging process is repeated at least 2-3 times to maximize the removal of oxygen and nitrogen from the furnace. When starting the electric arc to melt the raw materials, the melting current should be gradually increased until the metal is fully melted to ensure uniform composition. During the melting process, electromagnetic stirring or repeated turning and remelting of the alloy ingot (at least 4-6 times) is used to ensure the formation of a homogeneous master alloy ingot.

[0022] In step S2, the master alloy ingot is broken into appropriately sized pieces and placed into a crucible with a quartz nozzle at the top. The equipment chamber is sealed, and a vacuuming and high-purity argon purging process similar to that in step S1 is performed to ensure the strip spinning process is carried out under an inert atmosphere. Simultaneously, a copper roller is selected as the quenching substrate. The rotation speed of the copper roller is adjusted to 2000-4000 rpm (the specific speed depends on the required strip thickness and cooling rate). The distance between the quartz nozzle and the surface of the copper roller is set to 0.2-0.5 mm. An argon injection system is prepared to blow the molten alloy from the nozzle. Under the protection of high-purity argon, a high-frequency induction coil or electric arc is used to rapidly melt the alloy material in the crucible. After the alloy is completely melted and superheated by 50-100°C, argon gas at a certain pressure (0.02-0.05 MPa) is applied to spray the molten bismuth alloy from the slit of the quartz nozzle, causing it to be sprayed at high speed onto the surface of the high-speed rotating copper roller. Under immense centrifugal force, the molten alloy rapidly spreads across the surface of the copper roller and solidifies extremely quickly (cooling rate can reach 10). 5 ~10 6 K / s), and then peeled off from the roller surface in the form of a continuous thin strip, thereby obtaining a uniform thin strip or foil with a thickness of 20~100 micrometers.

[0023] Preferably, the average ligament thickness of the nanoporous bismuth framework material in step (2) is 50~1000nm, for example, it can be 50nm, 100nm, 200nm, 600nm, 800nm, 1000nm, etc., and the porosity is 50%~80%, for example, it can be 50%, 60%, 70% or 80%, etc.

[0024] In step (2) of this invention, the solution can be water or ethanol, etc. The sample after electrochemical treatment is taken out of the electrolytic cell and subjected to repeated ultrasonic cleaning with deionized water and anhydrous ethanol to thoroughly remove residual electrolyte and dissolved products. Preferably, the temperature of the high-temperature region in step (3) is 350~550℃, for example, 350℃, 400℃, 450℃, 500℃ or 550℃.

[0025] The temperature of the low-temperature region mentioned in step (3) is 200~350℃, for example, it can be 200℃, 250℃, 300℃ or 350℃, etc.

[0026] The heating time for the high-temperature region and the low-temperature region in step (3) is 4~12h.

[0027] In step (3) of this invention, the container can be a vacuum-sealed quartz tube. Red phosphorus is in powder form. Before heating, the container is evacuated to a high vacuum (<10). -3After sealing (Pa), phosphorus vapor continuously permeates into the pores of the nanoporous bismuth under this high and low temperature gradient, and condenses, deposits, and crystallizes on the pore wall surface. The mixture is then kept at this temperature for 4-12 hours. Subsequently, it is cooled to room temperature to obtain the red phosphorus-filled nanoporous bismuth composite material.

[0028] Preferably, the carbon source in step (4) includes aliphatic hydrocarbon compounds.

[0029] In this invention, the carbon source can be an aliphatic hydrocarbon compound, such as alkanes, alkenes, alkynes, etc., specifically acetylene, methane, etc. The process in step (4) is chemical vapor deposition, which can improve interface stability and conductivity. The temperature of chemical vapor deposition can be 300~500℃. At this temperature, an amorphous carbon layer with a thickness of 2~10nm can be deposited on the surface of the red phosphorus-filled nanoporous bismuth composite material, resulting in a carbon-coated nanoporous bismuth / red phosphorus composite material, which is the high-capacity alloy anode material described in this invention.

[0030] On the other hand, the present invention provides a high-capacity alloy anode material prepared by the preparation method described above.

[0031] The high-capacity alloy anode material provided by this invention is a carbon-coated nanoporous bismuth / red phosphorus composite material. It innovatively deposits red phosphorus in a nanoporous bismuth framework with a continuous conductive network and buffer space, which has good interfacial charge transport performance.

[0032] The present invention also provides a sodium-ion secondary battery, wherein the sodium-ion secondary battery comprises the high-capacity alloy negative electrode material described above.

[0033] Implementing this invention has the following beneficial effects: (1) Porous bismuth is a three-dimensional current collector with high conductivity and high strength. Bismuth itself has good conductivity. The nanoporous structure further increases the contact area between the electrode and the electrolyte, shortens the diffusion path of sodium ions, and provides rich channels for electron transport, thereby improving the rate performance of the composite material.

[0034] (2) Pores serve as reserved space for the expansion of red phosphorus; the nanoporous bismuth framework has a certain degree of flexibility and buffer space, which can effectively prevent the electrode structure from cracking and falling off due to volume effect, and significantly enhance the structural stability of the electrode.

[0035] (3) The close contact between bismuth and phosphorus enhances the interfacial charge transport; compared with the traditional mechanical mixing method (simple grinding and mixing of red phosphorus and substrate), this directional filling process can avoid the agglomeration of red phosphorus particles, ensure that red phosphorus and the inner wall of the bismuth skeleton channel form a tight interfacial bond, reduce the peeling of red phosphorus and substrate during charging and discharging, and greatly improve the cycle stability of composite materials. Attached Figure Description

[0036] Figure 1 This is a flowchart of the preparation process of the high-capacity alloy anode material provided in Embodiment 1 of the present invention.

[0037] Figure 2 This is a charge-discharge curve of the material in Embodiment 1 of the present invention.

[0038] Figure 3 This is a graph showing the capacity retention rate of the full cells of Embodiment 1, Comparative Example 1, and Comparative Example 2 after 400 cycles of 1C / 1C cycling.

[0039] Figure 4 These are comparison charts of EIS before and after the cycle in Embodiment 1 and Comparative Example 1 of the present invention.

[0040] Figure 5 This is a comparison chart of the rate-discharge capacity retention rates of Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0042] Example 1

[0043] This embodiment provides a high-capacity alloy anode material, and the preparation flowchart is shown in Figure 1. Figure 2 It is a charge / discharge curve.

[0044] (1) Smelting of the master alloy ingot: Raw material weighing and preparation: Accurately weigh high-purity iridium (Bi, purity ≥99.99%) and high-purity magnesium (Mg, purity ≥99.99%) in bulk or shaving form according to an atomic percentage ratio of Bi:Mg = 50:50. Considering the slight volatilization of magnesium during the smelting process, pre-compensate for an excess of no more than 1% in the mass of magnesium.

[0045] The weighed raw materials were placed in a water-cooled copper crucible in the electric arc melting furnace. After the furnace was closed, a mechanical pump and a molecular pump assembly were used to evacuate the furnace cavity to a vacuum level of ≤5.0×10⁻⁶. -3 Pa. Subsequently, high-purity argon gas (purity ≥99.999%) is introduced into the furnace cavity to a slightly positive pressure (0.05 MPa). This vacuuming-argon purging process is repeated at least 2-3 times to maximize the removal of oxygen and nitrogen from the furnace.

[0046] Under a protective atmosphere of high-purity argon, an electric arc is initiated to melt the raw materials. To ensure uniform composition, the melting current should be gradually increased until the metal is fully melted. During the melting process, electromagnetic stirring or repeated turning and remelting of the alloy ingot (at least 4-6 times) is employed to ensure the formation of a uniformly composed Bi alloy. 50 Mg 50 Master alloy ingot.

[0047] Preparation of thin strips by rapid cooling and spinning: A single-roller rapid cooling and spinning equipment was used. The master alloy ingot prepared in step one was broken into blocks of appropriate size and placed into a crucible with a quartz nozzle at the top. The equipment chamber was sealed, and a vacuuming and high-purity argon purging process similar to that in step one was performed to ensure that the spinning process was carried out under an inert atmosphere.

[0048] Select a copper roller as the quenching substrate. Adjust the copper roller speed to 2000 rpm. Set the distance between the quartz nozzle and the copper roller surface to 0.2 mm. Prepare an argon injection system to blow the molten alloy from the nozzle.

[0049] Under the protection of high-purity argon gas, the alloy material in the crucible is rapidly melted using a high-frequency induction coil or electric arc. After the alloy is completely melted and superheated to 50°C, argon gas at a certain pressure (0.02 MPa) is applied, and the molten Bi is then... 50 Mg 50 The molten alloy is ejected from the slit of the quartz nozzle, causing it to be sprayed at high speed onto the surface of the high-speed rotating copper roller.

[0050] Under immense centrifugal force, the molten alloy rapidly spreads across the surface of the copper roller and solidifies extremely quickly (cooling rate can reach 10). 5 ~10 6 (K / s), and then peeled off from the roll surface in the form of a continuous thin strip, thus obtaining a Bi with a uniform thickness of approximately 30 micrometers. 50 Mg 50 Alloy strip.

[0051] Electrochemical dealloying: Bi 50 Mg 50 An alloy strip serves as the working electrode, a platinum sheet inert electrode as the counter electrode, and an Ag / AgCl electrode as the reference electrode. An electrolyte solution of 0.05 mol / L hydrochloric acid and 0.1 mol / L magnesium chloride is injected into the electrolytic cell.

[0052] Under the control of an electrochemical workstation, a constant potential of 0.10 V was applied to the working electrode for 20 min. At this potential, metallic magnesium in the precursor alloy was selectively anolyzed into the electrolyte, while bismuth, as a framework element, was retained and reconstructed to form a nanoporous structure.

[0053] (2) The sample after electrochemical treatment was taken out of the electrolytic cell and ultrasonically cleaned repeatedly with deionized water and anhydrous ethanol to completely remove the residual electrolyte and dissolution products. Then it was dried to obtain the final nanoporous bismuth skeleton material with an average ligament thickness of 600 nm and a porosity of 60%.

[0054] (3) Red phosphorus vapor deposition composite: The nanoporous bismuth framework material obtained in step (2) and red phosphorus powder (purity > 99.9%) were placed at both ends of a vacuum-sealed quartz tube, with the red phosphorus placed in the high-temperature zone and the porous bismuth placed in the low-temperature zone. The quartz tube was then evacuated to a high vacuum (< 10). -3 After sealing (Pa),

[0055] The high-temperature zone was slowly heated to 350°C to sublimate red phosphorus and generate phosphorus vapor, while the low-temperature zone was controlled at 200°C. Under this temperature gradient, the phosphorus vapor continuously permeated into the pores of the nanoporous bismuth, where it condensed, deposited, and crystallized on the pore wall surface. This process was maintained at this temperature for 4 hours. Subsequently, the mixture was cooled to room temperature to obtain the red phosphorus-filled nanoporous bismuth composite material.

[0056] (4) Carbon coating: To further improve the interface stability and conductivity, the composite material obtained in step (3) was placed in a chemical vapor deposition furnace, and methane was introduced under an inert atmosphere. An amorphous carbon layer with a thickness of 2 nm was deposited at 300 °C, and finally carbon-coated nanoporous bismuth / red phosphorus composite material was obtained.

[0057] Example 2

[0058] The Bi:Mg ratio of the master alloy ingot in step (1) was 70:30. All other steps were the same, and the final preparation of a nanoporous bismuth framework material with an average ligament thickness of 800 nm and a porosity of 50% was obtained.

[0059] Example 3

[0060] In step (1), the Bi:Mg:Al ratio of the smelting of the master alloy ingot is 70:20:10. 0.03 mol / L aluminum chloride solution is added during electrochemical dealloying. All other steps are the same, resulting in the final preparation of a nanoporous bismuth framework material with an average ligament thickness of 200 nm and a porosity of 80%.

[0061] Example 4

[0062] The high and low temperatures differ from those in step (3) of Example 1. Specifically, the high-temperature zone is slowly heated to 400°C to sublimate red phosphorus and generate phosphorus vapor, while the low-temperature zone is controlled at 300°C. Under this temperature gradient, phosphorus vapor continuously penetrates into the pores of the nanoporous bismuth and condenses, deposits, and crystallizes on the pore wall surface. The temperature is maintained for 5 hours. Subsequently, the mixture is cooled to room temperature to obtain the red phosphorus-filled nanoporous bismuth composite material.

[0063] Comparative Example 1 The difference from Example 1 is that commercially available hard carbon material is used as the negative electrode material.

[0064] Comparative Example 2 The difference from Example 1 is that a commercially available phosphorus-carbon composite material was selected as the negative electrode material.

[0065] Comparative Example 3 The difference between this comparative example and Example 1 is that Bi:Mg = 80:20 in this comparative example, while the rest are the same as in Example 1.

[0066] Comparative Example 4 The difference between this comparative example and Example 1 is that Bi:Mg = 20:80 in this comparative example, while the rest are the same as in Example 1.

[0067] Comparative Example 5 The difference between this comparative example and Example 1 is that Mg is not added in this comparative example, while everything else is the same as in Example 1.

[0068] Button cell specific capacity test: The negative electrode material samples obtained in the above examples and comparative examples were assembled with sodium sheets into button cells for testing. The negative electrode material served as the positive electrode in the button cell, and the sodium sheet served as the negative electrode. The electrodes were discharged at 0.1C to 0V and left to stand for 10 minutes. They were then charged at 0.1C to 2V and left to stand for 10 minutes. The specific results are shown in Table 1 below: All-electric performance test: Preparation of the positive electrode sheet: 95 wt% of positive electrode material, 2 wt% of conductive agent acetylene black, and 3 wt% of binder PVDF are mixed and stirred at 1200 rpm for 20 min using a low-speed mixer. Then, a certain amount of solvent NMP is added, wherein NMP:positive electrode material = 1:1 (mass ratio), and the mixture is stirred at 2400 rpm for 60 min using a low-speed mixer. The prepared positive electrode slurry is then uniformly coated onto a 14 μm thick aluminum foil (positive electrode current collector). After drying (baking), rolling, slitting, and die-cutting, the positive electrode sheet is obtained. The electrode sheet is baked after coating at 150℃ for 10 hours.

[0069] Preparation of the negative electrode sheet: 93 wt% of the negative electrode material, 1.2 wt% of the binder CMC adhesive, and 2 wt% of the conductive agent acetylene black were mixed and stirred at 1200 r / min for 20 min using a low-speed mixer. The CMC adhesive was prepared from deionized water and CMC (carboxymethyl cellulose), with a CMC content of 1.2 wt%. Then, 40% solids content styrene-butadiene rubber latex binder was added at a rate of 3.8 wt%, and the mixture was stirred at 300 r / min for 1 hour. The prepared negative electrode slurry was then uniformly rolled onto a 14 μm thick aluminum foil (negative electrode current collector), and after drying (baking), slitting, and die-cutting, the negative electrode sheet was obtained.

[0070] The obtained positive electrode, negative electrode, and 16μm thick polypropylene separator are stacked sequentially in the order of separator / negative electrode / separator / positive electrode, with 10 positive electrode sheets and 11 negative electrode sheets. The obtained sodium-ion core is sealed in an aluminum-plastic film to obtain a sodium-ion battery with a designed capacity of 2Ah.

[0071] The electrolyte consists of sodium hexafluorophosphate and a solvent. The concentration of sodium hexafluorophosphate is 1 mol / L, and the solvent is ethylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC) = 1:1:1 (mass ratio). The obtained sodium-ion full battery is baked in a high-temperature vacuum chamber for 24 hours. After electrolyte injection, it undergoes formation, aging, and capacity testing to prepare a lithium-ion battery. The battery undergoes a degassing process after formation and before aging.

[0072] The capacity retention rate of the full battery after 400 cycles at 1C / 1C is as follows: Figure 3 EIS data before and after the loop are as follows Figure 4 The curve of rate discharge capacity retention is as follows: Figure 5 .

[0073] Table 1 sample Button capacity (Ah / g) Capacity retention after 400 full-electric cycles at 1C Example 1 527 97% Example 2 500 95% Example 3 482 96% Example 4 460 94% Comparative Example 1 300 94.8% Comparative Example 2 450 92% Comparative Example 3 445 53% Comparative Example 4 440 75% Comparative Example 5 380 55% Through Table 1, Figure 3 The data shows that the red phosphorus in Example 1 can be uniformly and stably deposited in the nanoporous bismuth framework with a continuous conductive network and buffer space, and has a high specific capacity and capacity retention rate.

[0074] By adjusting the metal element content ratio in Example 1, materials with different nanoporous bismuth ligament thicknesses and porosities can be prepared. However, the specific capacity and capacity retention are lower than those in Example 1, but are superior to currently commercially available hard carbon and phosphorus carbon composite materials.

[0075] The material prepared by adjusting the red phosphorus vapor deposition temperature in Example 4 has low composite strength with nanoporous bismuth, so its capacity retention rate is lower than that in Examples 1, 2, and 3.

[0076] Figure 4 The data shows that, compared with the commercial anode material used in Comparative Example 1, the impedance of Example 1 is smaller before and after cycling, and the impedance change of Example 1 before and after cycling is smaller, indicating that the material structure is more stable. Figure 5 and Figure 4 The data are consistent, indicating that the impedance and internal resistance of Example 1 are relatively small.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high-capacity alloy anode material, characterized in that, The preparation method includes: (1) Place the working electrode, counter electrode and reference electrode into an electrolytic cell, inject electrolyte into the electrolytic cell, and then apply a constant anodic potential to the working electrode for electrochemical treatment; the working electrode is a bismuth alloy sheet, the bismuth alloy sheet contains bismuth and metal M, the atomic percentage of metal M in the bismuth alloy sheet is 30%~70%, and metal M includes any one or at least two of Mg, Al, Zn or Mn; (2) The working electrode after electrochemical treatment in step (1) is washed with a solution to obtain a nanoporous bismuth framework material; (3) Place the nanoporous bismuth framework material obtained in step (2) and red phosphorus at both ends of the container. The nanoporous bismuth framework material is placed in the low-temperature region of the container, and the red phosphorus is placed in the high-temperature region of the container. The low-temperature region and the high-temperature region are heated to obtain a red phosphorus-filled nanoporous bismuth composite material. (4) The red phosphorus-filled nanoporous bismuth composite material obtained in step (3) is placed in a deposition furnace and a carbon source is introduced for chemical vapor deposition to obtain the high-capacity alloy anode material.

2. The preparation method according to claim 1, characterized in that, The electrolyte in step (1) includes an acidic solution or a salt solution containing metal M ions.

3. The preparation method according to claim 2, characterized in that, The acidic solution includes hydrochloric acid and / or sulfuric acid, and the concentration of the acidic solution is 0.1~1 mol / L.

4. The preparation method according to claim 2, characterized in that, The concentration of the salt solution containing metal M ions is 0.05~0.5 mol / L.

5. The preparation method according to claim 1, characterized in that, The constant potential in step (1) is 0.1~0.3V relative to the reference electrode.

6. The preparation method according to claim 1, characterized in that, The method for preparing the bismuth alloy sheet in step (1) is as follows: S1: Bismuth and metal M are smelted under an inert gas atmosphere to obtain a master alloy ingot; S2: After the master alloy ingot is crushed to form a liquid alloy, a copper roller is used as a rapid cooling substrate to spray the liquid alloy onto the surface of the rotating copper roller, and the liquid alloy solidifies to form a bismuth alloy sheet.

7. The preparation method according to claim 1, characterized in that, The average ligament thickness of the nanoporous bismuth framework material in step (2) is 50~1000nm, and the porosity is 50%~80%.

8. The preparation method according to claim 1, characterized in that, The temperature of the high-temperature zone mentioned in step (3) is 350~550℃; The temperature of the low-temperature region mentioned in step (3) is 200~350℃; The heating time for the high-temperature region and the low-temperature region in step (3) is 4~12 hours; The carbon source mentioned in step (4) includes aliphatic hydrocarbon compounds.

9. The high-capacity alloy anode material prepared by the preparation method according to any one of claims 1 to 8.

10. A sodium-ion secondary battery, characterized in that, The sodium-ion secondary battery includes the high-capacity alloy anode material as described in claim 9.

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