SnO2-loaded bi-sn alloy negative electrode material, preparation method and application thereof

Abstract

The application relates to the field of electrochemical electrode materials, and discloses a SnO2-loaded Bi-Sn alloy negative electrode material, which comprises Bi, Sn and SnO2, wherein the molar ratio of Bi to (Sn+SnO2) is 1:1; a preparation method of the SnO2-loaded Bi-Sn alloy negative electrode material, which comprises the following steps: S1, preparing a Bi2Sn2O7 precursor; S2, heating the Bi2Sn2O7 precursor prepared in S1 to 550-850 DEG C under a mixed atmosphere of inert gas and reducing gas, and keeping the temperature for 1-3 hours to obtain the SnO2-loaded Bi-Sn alloy negative electrode material; application of the SnO2-loaded Bi-Sn alloy negative electrode material, and the SnO2-loaded Bi-Sn alloy negative electrode material prepared in S2 is used for preparing a negative electrode active material of a secondary battery. The technical scheme can improve the diffusion speed of magnesium ions, prevent the formation of a passivation layer at an electrode / electrolyte interface, and realize reversible circulation of a magnesium battery.

Description

Technical Field

[0001] This invention relates to the field of electrochemical electrode materials, specifically to a Bi-Sn alloy anode material supported on SnO2, its preparation method, and its application. Background Technology

[0002] With the development of new energy vehicles, mobile phones, computers, and other technologies, batteries have become necessities in our lives. However, lithium batteries, as the main power source, suffer from problems such as resource shortages, high costs, serious environmental pollution, and poor safety. Developing alternative lithium batteries to ensure the stability and safety of energy storage is a future trend.

[0003] Among numerous candidates to replace lithium batteries, magnesium is abundant in the Earth's crust, a low-cost raw material, and readily and uniformly deposited with low dendrite growth, resulting in higher application safety and significant practical potential. Furthermore, compared to lithium, metallic magnesium is more stable under atmospheric conditions and easier to process and shape. Magnesium also has a low redox potential (-2.37V vs. H₂). + The characteristics of magnesium metal batteries, including H2 and divalent ions, give them a large theoretical volumetric capacity (3833 mAh / cm³). 3 Magnesium batteries, with their high charge density and high energy density, have potential advantages in cost, energy density, and safety. They are considered a very promising green secondary battery and have become an important research and development direction for new rechargeable batteries. However, the strong electrostatic interaction between magnesium ions with high charge density and the electrode substrate slows their diffusion in the cathode material. Most non-ether solvents and magnesium salt anions undergo reduction decomposition reactions on the surface of magnesium metal, and the resulting passivation layer at the electrode / electrolyte interface does not conduct magnesium ions, limiting the reversible cycling of magnesium batteries. This seriously hinders their commercial application. Summary of the Invention

[0004] The present invention aims to provide a Bi-Sn alloy anode material loaded with SnO2 to improve the diffusion rate of magnesium ions, prevent the formation of a passivation layer at the electrode / electrolyte interface, and realize reversible cycling of magnesium batteries.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a Bi-Sn alloy anode material loaded with SnO2, comprising Bi, Sn and SnO2, wherein the molar ratio of Bi and (Sn+SnO2) is 1:1.

[0006] The beneficial effects of this scheme are as follows: This technical scheme utilizes the high diffusion and migration ability of pure Bi to magnesium and the high theoretical capacity of pure Sn, while simultaneously compensating for the shortcomings of Bi's rapid decay and Sn's low activity, to obtain a high-capacity, cycle-stable Bi-Sn alloy anode material, thereby improving the kinetic performance of magnesium batteries and enabling faster diffusion of magnesium ions; due to the presence of the SnO2 particle layer loaded on the surface of the Bi-Sn alloy, the growth of alloy particles is limited, which can effectively prevent the formation of a passivation layer at the electrode / electrolyte interface, thereby improving the stability of reversible cycling of magnesium batteries, and the material has good repeatability, low cost, and is easy to mass-produce.

[0007] The present invention also provides another technical solution, a method for preparing Bi-Sn alloy anode material supported on SnO2, comprising the following steps:

[0008] S1. Weigh out stannate and bismuth salt respectively, with a molar ratio of stannate to bismuth salt of (1-2):(1-2). First, dissolve the weighed stannate in 72-80 mL of pure water, then add the weighed bismuth salt and mix well. Add sodium hydroxide solution to adjust the pH value to 8-12. Transfer the solution to an autoclave, heat to 120-200℃, keep warm for 12-48 h, then centrifuge and wash the product, and dry the washed product to obtain Bi2Sn2O7 precursor.

[0009] S2, under a mixed atmosphere of inert gas and reducing gas, the Bi2Sn2O7 precursor prepared in S1 is heated to 550-850℃ and held for 1-3h to obtain Bi-Sn alloy anode material supported on SnO2.

[0010] The beneficial effects of this scheme are as follows: As can be seen from the Bi2Sn2O7 precursor, the molar ratio of stannate to bismuth salt is 1:1, while the molar ratio of stannate to bismuth salt in this technical scheme is (1-2):(1-2). The reaction rate is accelerated by adding excess stannate or bismuth salt, which shortens the reaction time and makes the Bi2Sn2O7 precursor generated faster. By washing the product, excess stannate or bismuth salt can be removed, resulting in higher purity of the generated Bi2Sn2O7 precursor. Furthermore, the impurity content of the prepared SnO2-loaded Bi-Sn alloy anode material is lower, preventing impurities from affecting the activity, capacity, and rate performance of the SnO2-loaded Bi-Sn alloy anode material.

[0011] In this technical solution, the Bi₂Sn₂O₇ precursor is heated in a mixed atmosphere of inert and reducing gases. This prevents the Bi₂Sn₂O₇ precursor from being oxidized by oxygen in the air, thus avoiding impurity formation. Furthermore, the reducing gas reduces the Bi₂Sn₂O₇ precursor, promoting the formation of the Bi-Sn alloy. The heating temperature is between 550-850℃, and the holding time is 1-3 hours. If the heating temperature is too low or the holding time is too short, the resulting SnO₂-loaded Bi-Sn alloy anode material will be doped with Bi. The incomplete decomposition of 2Sn2O7 intermediate products affects the performance of Bi-Sn alloy anode materials loaded with SnO2. If the heating temperature is too high or the holding time is too long, the prepared Bi-Sn alloy surface will not have a loaded SnO2 particle layer, the alloy particles will grow, the electrochemical activity will decrease, and a passivation layer will easily form at the electrode / electrolyte interface, which will limit the reversible cycling of magnesium batteries and hinder their commercial application. Therefore, it is necessary to strictly control the heating temperature and holding time of the Bi2Sn2O7 precursor to ensure that the Bi-Sn alloy surface is loaded with a SnO2 particle layer.

[0012] Furthermore, in S1, the stannate is sodium stannate trihydrate with a purity of 98%, and the bismuth salt is bismuth nitrate pentahydrate with a purity of 99%.

[0013] The beneficial effects of this scheme are as follows: using sodium stannate trihydrate with a purity of 98% as a stannate and bismuth nitrate pentahydrate with a purity of 99% as a bismuth salt to prepare the Bi2Sn2O7 precursor ensures that the Bi2Sn2O7 precursor is free of chloride ion doping, resulting in superior electrochemical performance of the prepared SnO2-loaded Bi-Sn alloy anode material.

[0014] Furthermore, in S1, the product is first washed by centrifugation with pure water, and then washed with ethanol.

[0015] The beneficial effects of this method are as follows: firstly, the product in S1 is centrifuged and washed with pure water, which can remove excess stannate or bismuth salt, resulting in a higher purity of the generated Bi2Sn2O7 precursor. Then, the product is washed with ethanol, which can accelerate the evaporation of water on the product surface and shorten the product drying time.

[0016] Furthermore, in S2, the volume ratio of inert gas to reducing gas is (90-95):(5-10).

[0017] The beneficial effects of this scheme are as follows: If no reducing gas is added, the Bi2Sn2O7 precursor will not undergo a redox reaction when heated under inert gas conditions, and no Bi-Sn alloy or SnO2 particle layer will be formed. This technical scheme sets the volume ratio of inert gas to reducing gas to (90-95):(5-10), which can ensure the amount of reducing gas so that the Bi2Sn2O7 precursor reacts with the reducing gas to generate a Bi-Sn alloy anode material loaded with SnO2, and can also prevent oxygen in the air from oxidizing the Bi2Sn2O7 precursor, thus reducing the doping of impurities.

[0018] Furthermore, in S2, the inert gas is any one or a combination of two of argon and nitrogen, and the reducing gas is hydrogen.

[0019] The beneficial effects of this scheme are as follows: since the Bi2Sn2O7 precursor does not react in argon and nitrogen, it plays a protective role in preventing the Bi2Sn2O7 precursor from being oxidized and reducing the doping of impurities; using hydrogen as a reducing gas is because the product generated after hydrogen is oxidized is water, so that no other impurity elements are introduced into the generated Bi-Sn alloy anode material loaded with SnO2.

[0020] The present invention also provides another technical solution, the application of Bi-Sn alloy anode material loaded with SnO2, wherein the Bi-Sn alloy anode material loaded with SnO2 prepared in S2 is used to prepare anode active material for secondary batteries.

[0021] The beneficial effects of this scheme are: using Bi-Sn alloy anode material loaded with SnO2 to prepare the anode active material of secondary batteries can improve the activity, capacity and rate performance of secondary batteries.

[0022] Furthermore, the secondary electrode is a magnesium-ion battery.

[0023] The beneficial effects of this scheme are as follows: using Bi-Sn alloy anode material loaded with SnO2 to prepare the anode active material of magnesium-ion battery can improve the activity, capacity and rate performance of magnesium-ion battery. At the same time, the SnO2 particle layer loaded on the surface of Bi-Sn alloy can effectively prevent the formation of passivation layer at the electrode / electrolyte interface, thereby improving the stability of reversible cycling of magnesium-ion battery.

[0024] Furthermore, the negative electrode material of the magnesium-ion battery also includes a negative electrode conductive agent, a negative electrode binder, and a negative electrode binder solvent, wherein the mass ratio of the SnO2-loaded Bi-Sn alloy negative electrode material, the negative electrode conductive agent, and the negative electrode binder is (6-8):(1-3):1.

[0025] The beneficial effects of this solution are as follows: the magnesium-ion battery anode material made by using the negative electrode conductive agent, negative electrode binder, negative electrode binder solvent, and the Bi-Sn alloy anode material loaded with SnO2 prepared according to claim 2 can effectively prevent the formation of a passivation layer at the electrode / electrolyte interface, thereby improving the stability of the reversible cycle of the magnesium-ion battery. At the same time, it can improve the activity, capacity, and rate performance of the magnesium-ion battery. The reversible capacity of the magnesium-ion battery anode after 100 cycles at 50 mA / g can reach 314 mAh / g.

[0026] Furthermore, the negative electrode conductive agent is any one of acetylene black, carbon black, natural graphite, artificial graphite, Ketjen black, carbon fiber, copper, aluminum, silver, and nickel; the negative electrode binder is any one or a combination of several of polytetrafluoroethylene, polyvinylidene fluoride, polychlorotrifluoroethylene, polyvinyl fluoride PVF, and polyvinyl alcohol; and the negative electrode binder solvent is any one or a combination of several of N-methylpyrrolidone (NMP), styrene-butadiene ester (SBR), and carboxymethyl cellulose (CMC).

[0027] The beneficial effects of this scheme are as follows: using any one of acetylene black, carbon black, natural graphite, artificial graphite, Ketjen black, carbon fiber, copper, aluminum, silver, and nickel as a negative electrode conductive agent can ensure that the electrode has good charge and discharge performance; using any one or a combination of polytetrafluoroethylene, polyvinylidene fluoride, polychlorotrifluoroethylene, polyvinyl fluoride PVF, and polyvinyl alcohol as a negative electrode binder can ensure good adhesion strength between active materials and between active materials and current collectors during the use of the negative electrode; using any one or a combination of N-methylpyrrolidone (NMP), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) as a negative electrode binder solvent can dissolve the negative electrode binder powder and serve as the medium for mixing the slurry. Attached Figure Description

[0028] Figure 1 This is a scanning electron microscope image of the Bi-Sn alloy anode material loaded with SnO2 prepared in Example 1;

[0029] Figure 2 High-angle annular dark-field scanning transmission electron microscope image and corresponding elemental distribution map of the Bi-Sn alloy anode material loaded with SnO2 prepared in Example 1;

[0030] Figure 3 The XPS spectrum of the Bi-Sn alloy anode material loaded with SnO2 prepared in Example 1;

[0031] Figure 4 (a) is the XRD pattern of the Bi-Sn alloy anode material loaded with SnO2 prepared in Example 1;

[0032] Figure 4(b) is a cycle performance diagram of the Bi-Sn alloy anode material loaded with SnO2 prepared in Example 1;

[0033] Figure 5 (a) is the XRD pattern of the Bi-Sn alloy anode material loaded with SnO2 prepared in Example 2;

[0034] Figure 5 (b) is a cycle performance diagram of the Bi-Sn alloy anode material loaded with SnO2 prepared in Example 2;

[0035] Figure 6 Scanning electron microscope (SEM) image and XRD pattern of the product prepared in Comparative Example 1;

[0036] Figure 7 SEM and XRD patterns of the product prepared in Comparative Example 2;

[0037] Figure 8 SEM and XRD patterns of the product prepared in Comparative Example 3;

[0038] Figure 9 XRD patterns and electrochemical performance test results of the products prepared in Comparative Examples 4 and 5.

[0039] Figure 10 The XRD pattern and electrochemical performance test results are for the product prepared in Comparative Example 6. Detailed Implementation

[0040] The following detailed description illustrates the specific implementation method:

[0041] Example 1

[0042] Bi-Sn alloy anode material loaded with SnO2, comprising Bi, Sn and SnO2, wherein the molar ratio of Bi to (Sn+SnO2) is 1:1.

[0043] A method for preparing Bi-Sn alloy anode material supported on SnO2, characterized by comprising the following steps:

[0044] S1, 1.729g of sodium stannate trihydrate with a purity of 98% and 2.910g of bismuth nitrate pentahydrate with a purity of 99% were weighed out, with a molar ratio of sodium stannate trihydrate to bismuth nitrate pentahydrate of 6.5:6. The weighed sodium stannate trihydrate was first dissolved in 72mL of pure water, and then the weighed bismuth nitrate pentahydrate was added and mixed evenly. Sodium hydroxide solution was added to adjust the pH value to 8-12. The solution was transferred to an autoclave and heated to 120-200℃. After holding at this temperature for 12-48h, the product was first washed by centrifugation with pure water, and then washed with ethanol. Finally, the washed product was dried to obtain the Bi2Sn2O7 precursor. In this embodiment, sodium hydroxide solution was added to adjust the pH value to 12, the heating temperature was 180℃, and the holding time was 24h.

[0045] S2, under a mixed atmosphere of inert gas and reducing gas, the Bi2Sn2O7 precursor prepared in S1 is heated to 550-850℃ and held for 1-3 hours to obtain a Bi-Sn alloy anode material loaded with SnO2. The inert gas is either argon or nitrogen, the reducing gas is hydrogen, and the volume ratio of inert gas to reducing gas is (90-95):(5-10). In this embodiment, the inert gas is argon, the volume ratio of inert gas to reducing gas is 95:5, the heating temperature is 600℃, and the holding time is 3 hours.

[0046] Application of Bi-Sn alloy anode material loaded with SnO2: The Bi-Sn alloy anode material loaded with SnO2 prepared in S2 is used to prepare the anode active material of a secondary battery. The secondary electrode is a magnesium-ion battery. A magnesium-ion battery anode material includes an anode conductive agent, an anode binder, an anode binder solvent, and the Bi-Sn alloy anode material loaded with SnO2 prepared in S2. The mass ratio of the Bi-Sn alloy anode material loaded with SnO2, the anode conductive agent, and the anode binder is (6-8):(1-3):1. The negative electrode conductive agent is any one of acetylene black, carbon black, natural graphite, artificial graphite, Ketjen black, carbon fiber, copper, aluminum, silver, and nickel; the negative electrode binder is any one or a combination of several of polytetrafluoroethylene, polyvinylidene fluoride, polychlorotrifluoroethylene, polyvinyl fluoride PVF, and polyvinyl alcohol; the negative electrode binder solvent is any one or a combination of several of N-methylpyrrolidone (NMP), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC). In this embodiment, the negative electrode conductive agent is acetylene black, the negative electrode binder is polytetrafluoroethylene, the negative electrode binder solvent is N-methylpyrrolidone (NMP), and the mass ratio of the SnO2-loaded Bi-Sn alloy negative electrode material, acetylene black, and polytetrafluoroethylene is 7:2:1.

[0047] The prepared Bi-Sn alloy anode material loaded with SnO2 was used as the anode of a magnesium-ion battery, and its performance was tested.

[0048] The prepared SnO2-loaded Bi-Sn alloy anode material was uniformly mixed with acetylene black and polytetrafluoroethylene at a mass ratio of 7:2:1. A slurry was prepared using N-methylpyrrolidone as a solvent and then coated onto stainless steel foil to form an electrode sheet. The sheet was vacuum dried at 80°C for 12 hours and then stamped into 12mm diameter electrode discs. These discs were stored in a glove box filled with high-purity argon gas. Using 0.4M (MgPhCl)2-AlCl3 as the electrolyte, glass fiber (GF / D) as the separator, and magnesium sheets as the counter and reference electrodes, a CR2032 coin cell was assembled in the argon-filled glove box. The battery underwent constant current charge-discharge testing at a current density of 50mA / g, a charge-discharge cutoff voltage range of 0-1.0V, and room temperature.

[0049] Test results: The microstructure of the prepared SnO2-loaded Bi-Sn alloy anode material is as follows: Figure 1 As shown, particles with a diameter of 2-5 μm can be seen loaded on the alloy spheres. Further analysis of the high-angle annular dark-field scanning transmission electron microscopy (STEM) images and their corresponding elemental distributions reveals further details. Figure 2 As shown, the supported particles were SnO2, and the alloy spheres were a fused Bi-Sn alloy. XPS analysis of the SnO2-supported Bi-Sn alloy is shown below. Figure 3 As shown, the alloy surface is mainly composed of Bi, Sn, and O elements, and the alloy particle surface contains SnO2 and metallic bismuth; the XRD analysis of the Bi-Sn alloy anode material supported on SnO2 is as follows. Figure 4 As shown in Figure a, it can be seen that the prepared SnO2-loaded Bi-Sn alloy anode material is mainly composed of Bi, Sn, and SnO2, which verifies the composition of the alloy. The cycle performance of the prepared SnO2-loaded Bi-Sn alloy anode material is as follows: Figure 4 As shown in b, at a current density of 50 mA / g, the initial discharge capacity is 279 mAh / g, and after 100 cycles, the reversible capacity can reach 314 mAh / g.

[0050] Example 2

[0051] Unlike Example 1, in the preparation method of Bi-Sn alloy anode material supported on SnO2, 1.867 g of sodium stannate trihydrate and 3.15 g of bismuth nitrate pentahydrate were weighed in S1, and the molar ratio of sodium stannate trihydrate to bismuth nitrate pentahydrate was 7:6.5; the heating temperature in S2 was 800℃ and the holding time was 2 h.

[0052] The prepared SnO2-loaded Bi-Sn alloy anode material was used to fabricate the anode of a magnesium-ion battery, and its performance was tested. The battery assembly method and performance testing method were the same as in Example 1. The XRD test results of the prepared SnO2-loaded Bi-Sn alloy anode material are as follows: Figure 5 As shown in Figure a, the phase composition is consistent with that of Example 1, and the electrochemical test results are as follows. Figure 7 As shown in b, the initial discharge capacity is 14 mAh / g during the electrode activation process, the second discharge capacity is 264 mAh / g, and the reversible capacity after 100 cycles at a current density of 50 mA / g is 298 mAh / g.

[0053] Comparative Example 1

[0054] Unlike Example 1, in the preparation method of Bi-Sn alloy anode material loaded with SnO2, the heating temperature in S2 is 600℃ and the holding time is 4h.

[0055] Depend on Figure 6 It can be seen that most of the particles have a diameter of 50-100 μm, and small particles tend to aggregate and grow. The alloy particles contain only Bi and Sn. Under these conditions, SnO2 is reduced more thoroughly. Without the protection of SnO2 particles, the alloy particles aggregate and grow, reducing the specific surface area. Compared with Example 1, it can be seen that extending the holding time can increase the particle size, thereby reducing the specific surface area of ​​the Bi-Sn alloy and thus reducing the capacity of the Bi-Sn alloy. At the same time, after the SnO2 particles are completely reduced, the electrode / electrolyte interface is more likely to form a passivation layer, thereby reducing the stability of the magnesium battery's reversible cycle.

[0056] Comparative Example 2

[0057] Unlike Example 1, in the preparation method of Bi-Sn alloy anode material loaded with SnO2, in S2, the Bi2Sn2O7 precursor prepared in S1 is heated to 600°C and held for 3 hours under an argon atmosphere to obtain Bi-Sn alloy anode material loaded with SnO2.

[0058] Depend on Figure 7 It can be seen that the product prepared in Comparative Example 2 is basically the same as the Bi2Sn2O7 precursor. Therefore, hydrogen is essential for reducing Bi2Sn2O7 to obtain Bi-Sn alloy anode material loaded with SnO2.

[0059] Comparative Example 3

[0060] Unlike Example 2, in the preparation method of Bi-Sn alloy anode material loaded with SnO2, in S2, the Bi2Sn2O7 precursor prepared in S1 is heated to 800°C and held for 2 hours under an argon atmosphere to obtain Bi-Sn alloy anode material loaded with SnO2.

[0061] Depend on Figure 8 As can be seen from the SEM microstructure observation, Bi2Sn2O7 showed slight growth. Further XRD analysis of the product showed that although the characteristic peaks narrowed, indicating that the particle size of Bi2Sn2O7 increased, no phase change occurred. This indicates that Bi2Sn2O7 has high thermal stability and also proves that hydrogen is an essential reducing agent for the reduction of Bi2Sn2O7 to obtain Bi-Sn alloy anode material supported on SnO2.

[0062] Comparative Example 4

[0063] Weigh 1g of bismuth powder with a purity of 99.99%, place it in a zirconia ball mill jar under an argon atmosphere, add stainless steel grinding balls at a ball / material ratio of 5:1, and ball mill for 5 hours to obtain micron-sized Bi powder.

[0064] The collected micron-sized Bi powder was used to prepare the negative electrode of a magnesium-ion battery, and its performance was tested. The preparation method and performance testing method of the magnesium-ion battery negative electrode were the same as those in Example 1.

[0065] The obtained product was analyzed by XRD. Figure 9 The result shows that the pure Bi phase has an initial discharge capacity of 292 mAh / g, but after 80 cycles at a current density of 50 mA / g, the capacity drops to only 196 mAh / g, representing a capacity decay of 33%. This indicates that while using pure Bi to prepare the anode for a magnesium-ion battery exhibits good magnesium ion migration kinetics, the significant volume change during charge-discharge processes as magnesium intercalates and deintercalates within the bismuth makes the bismuth anode prone to pulverization and detachment, leading to capacity decay and poor cycle stability.

[0066] Comparative Example 5

[0067] Weigh 1g of tin powder with a purity of 99.99%, place it in a zirconia ball mill jar under an argon atmosphere, add stainless steel grinding balls at a ball / material ratio of 5:1, and ball mill for 5 hours to obtain micron-sized Sn powder.

[0068] The collected micron-sized Sn powder was used to prepare the negative electrode of a magnesium-ion battery, and its performance was tested. The preparation method and performance testing method of the magnesium-ion battery negative electrode were the same as those in Example 1.

[0069] The obtained product was analyzed by XRD. Figure 9It can be seen that the result is a pure Sn phase, which has no electrochemical activity and almost no capacity at a current density of 50 mA / g. Therefore, it can be concluded that although pure Sn has a high theoretical capacity (903 mAh / g), magnesium is difficult to diffuse and migrate in the Sn anode, so the pure Sn anode exhibits almost no electrochemical activity.

[0070] Comparative Example 6

[0071] 0.5g of bismuth powder with a purity of 99.99% and 0.5g of tin powder with a purity of 99.99% were weighed separately and placed in a zirconia ball mill jar under an argon atmosphere. Stainless steel grinding balls were added at a ball / material ratio of 5:1 and the mixture was ball-milled at high energy for 5 hours. Micron-sized Bi-Sn blocks were then collected.

[0072] The collected micron-sized Bi-Sn blocks were used to prepare the negative electrode of a magnesium-ion battery, and its performance was tested. The preparation method and performance testing method of the magnesium-ion battery negative electrode were the same as those in Example 1.

[0073] The obtained product was analyzed by XRD. Figure 10 The results show that the Bi-Sn phase exhibits an initial discharge capacity of 50 mAh / g at a current density of 50 mA / g. A prolonged activation process follows, with the discharge specific capacity gradually increasing, reaching a maximum of 230 mAh / g after 30 cycles. However, the capacity drops to only 192 mAh / g after 80 cycles. This indicates that the Bi-Sn alloy, as a negative electrode in a magnesium battery, is not stable. The initial activation process results in a lower capacity, possibly due to the relatively large size of the ball-milled alloy particles, requiring a gradual activation of electrochemical activity.

[0074] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A Bi-Sn alloy anode material supported on SnO2, characterized in that: The mixture comprises Bi, Sn, and SnO2, wherein the molar ratio of Bi to (Sn + SnO2) is 1:1; the preparation method includes the following steps: S1. Weigh out stannate and bismuth salt respectively, with a molar ratio of stannate to bismuth salt of (1-2):(1-2). First, dissolve the weighed stannate in 72-80 mL of pure water, then add the weighed bismuth salt and mix well. Add sodium hydroxide solution to adjust the pH value to 8-12. Transfer the solution to an autoclave, heat to 120-200℃, keep warm for 12-48 h, then centrifuge and wash the product, and dry the washed product to obtain Bi2Sn2O7 precursor. S2, under a mixed atmosphere of inert gas and reducing gas, the Bi2Sn2O7 precursor prepared in S1 is heated to 550-850℃ and held for 1-3h to obtain Bi-Sn alloy anode material supported on SnO2.

2. The Bi-Sn alloy anode material supported on SnO2 according to claim 1, characterized in that: In S1, the stannate is sodium stannate trihydrate with a purity of 98%, and the bismuth salt is bismuth nitrate pentahydrate with a purity of 99%.

3. The Bi-Sn alloy anode material supported on SnO2 according to claim 1, characterized in that: In S1, the product is first washed by centrifugation with pure water, and then washed with ethanol.

4. The Bi-Sn alloy anode material supported on SnO2 according to claim 1, characterized in that: In S2, the volume ratio of inert gas to reducing gas is (90-95):(5-10).

5. The Bi-Sn alloy anode material supported on SnO2 according to claim 1, characterized in that: In S2, the inert gas is any one or a combination of two of argon and nitrogen, and the reducing gas is hydrogen.

6. The application of the Bi-Sn alloy anode material supported on SnO2 according to any one of claims 2-5, characterized in that: The Bi-Sn alloy anode material loaded with SnO2 prepared in S2 is used to prepare the anode active material for secondary batteries.

7. The application of the Bi-Sn alloy anode material supported on SnO2 according to claim 6, characterized in that: The secondary battery is a magnesium-ion battery.

8. The application of the Bi-Sn alloy anode material supported on SnO2 according to claim 7, characterized in that: The negative electrode material of magnesium-ion batteries also includes a negative electrode conductive agent, a negative electrode binder and a negative electrode binder solvent. The mass ratio of the SnO2-loaded Bi-Sn alloy negative electrode material, the negative electrode conductive agent and the negative electrode binder is (6-8):(1-3):

1.

9. The application of the Bi-Sn alloy anode material supported on SnO2 according to claim 8, characterized in that: The negative electrode conductive agent is any one of acetylene black, carbon black, natural graphite, artificial graphite, Ketjen black, carbon fiber, copper, aluminum, silver and nickel; the negative electrode binder is any one or a combination of several of polytetrafluoroethylene, polyvinylidene fluoride, polychlorotrifluoroethylene, polyvinyl fluoride PVF, and polyvinyl alcohol; the negative electrode binder solvent is any one or a combination of several of N-methylpyrrolidone (NMP), styrene-butadiene ester (SBR) and carboxymethyl cellulose (CMC).

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