Tin alloy negative electrode material and preparation method and application thereof

Abstract

The invention belongs to the technical field of synthesis and preparation of electrode materials, and particularly relates to a tin alloy negative electrode material and a preparation method and application thereof. The method comprises the following steps: mixing soluble tin salt, a chelating agent, fuel, transition metal salt and water, and adjusting the pH value to 5-6.5 to obtain a mixed solution; then heating the mixed solution to evaporate water, carrying out chelation reaction to form gel, continuously heating to a fuel ignition point, carrying out redox reaction to release gas, and forming a foamed precursor with a layered porous structure; and under a protective atmosphere, carrying out annealing treatment on the foamed precursor with the layered porous structure, so that a metal compound in the foamed precursor with the layered porous structure is decomposed and alloyed, and meanwhile, graphitizing residual fuel to form a carbon coating layer, so as to obtain the tin alloy negative electrode material with the layered porous structure. The tin alloy negative electrode material prepared by the invention shows excellent cycling stability and rate capability when being used as a lithium ion battery negative electrode material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrode material synthesis and preparation, and particularly relates to a tin alloy negative electrode material and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of the new energy automobile industry, as the core power source, the improvement of the energy density, safety and cycle life of lithium ion batteries has become the key to technological breakthrough. The graphite negative electrode material currently used in commercial applications has a low theoretical specific capacity of only ~372mAh·g -1 , and is prone to lithium dendrite deposition during the cycle process, which leads to rapid capacity decay and safety hazards, and is difficult to meet the needs of high energy density batteries.

[0003] Tin-based negative electrode materials have become a popular candidate to replace graphite due to their advantages of abundant resources, low cost and high electrical conductivity. Tin forms Li + Sn alloy through alloying with Li 4.4 , achieving a high theoretical specific capacity of ~994mAh·g -1 , and the working potential of tin is slightly higher than that of graphite, which helps to reduce the risk of lithium dendrite precipitation and improve battery safety. However, tin can expand by up to 300% in volume during charging and discharging, leading to material cracking, pulverization and shedding, which seriously restricts the cycle performance and commercial application of tin-based negative electrode materials.

[0004] Existing technologies mainly use nanocrystallization, buffer structure construction and metal composite strategies to improve the problem of structural failure caused by volume expansion of tin-based negative electrode materials. Among them, the metal composite strategy has been proven to be an effective way to inhibit volume expansion: by introducing non-active metal components such as cobalt, nickel and copper, the volume change of active tin can be inhibited by the rigid skeleton, and the stress can be buffered by the three-dimensional network structure to maintain the integrity of the electrode; in addition, the synergistic effect between double metals or multiple metals can further improve the reversible capacity and rate capability of the material.

[0005] Currently, the methods for preparing tin alloy negative electrode materials using the metal composite strategy mainly include electrochemical deposition, ball milling, precipitation and hydro / solvothermal methods; for example: CN101969124A uses an electrochemical deposition method to prepare a Cu6Sn5 alloy negative electrode material, which has improved cycle stability, but the specific capacity is only about 600mAh·g -1 , which is difficult to meet the demand for high capacity.

[0006] CN107516734B discloses a method for preparing a carbon-coated tin-nickel alloy negative electrode, which uses a solvothermal method to prepare a nickel-based metal organic framework precursor, then mixes and grinds with stannous oxalate, and obtains carbon-coated Ni3Sn2 nanospheres after calcination; the initial discharge capacity is only 536mAh·g-1 , the charge capacity 397mAh·g -1 , and the capacity of 197mAh·g -1 is maintained at 2000mA·g -1 The high-rate performance is still insufficient.

[0007] The prior art solves the volume expansion problem of the tin-based negative electrode material through the metal composite strategy, but the limitation of the preparation method causes the composite material to still have a low discharge capacity, which cannot meet the high performance requirement. SUMMARY

[0008] To solve the above technical problems, the application provides a tin alloy negative electrode material and a preparation method and application thereof.

[0009] The tin alloy negative electrode material of the application is used as an electrode material of a lithium ion battery, and the prepared lithium ion battery has excellent cycle stability and rate performance, solving the technical problem that the composite material prepared by the metal composite of the prior art still has a low discharge capacity and cannot meet the high performance requirement.

[0010] The self-propagating reaction characteristics of the solution combustion method are used, N2 and CO2 and other gases are released in the combustion process through the synergistic effect of the fuel and the chelating agent, and a layered porous structure is formed. + The structure not only provides a buffer space for the volume expansion of tin and disperses the cycle stress, but also significantly increases the contact area of the active material and the electrolyte, shortens the Li + and electron transport path, and improves the reaction kinetics. At the same time, the carbon elements produced by the decomposition of the excess fuel in the combustion process are partially reserved to form a carbon coating layer, which improves the electrode conductivity and enhances the structural stability. The transition metal is introduced to form an alloy with Sn, the rigid skeleton of the inactive metal is used to inhibit the volume change of Sn, the multi-metal synergistic effect is used to optimize the electronic structure, increase the active sites, and reduce the lithium ion embedding / extraction energy barrier.

[0011] The first object of the present application is to provide a preparation method of a tin alloy negative material, comprising the following steps: After mixing the soluble tin salt, the chelating agent, the fuel, the transition metal salt and water, the pH is adjusted to 5-6.5 to obtain a mixed solution; then the mixed solution is heated to evaporate the moisture and to form a gel through a chelation reaction; the temperature is continuously increased to the ignition point of the fuel, a redox reaction is occurred to release gas, and a foam-like precursor with a layered porous structure is formed; under a protective atmosphere, the foam-like precursor with a layered porous structure is annealed to decompose the metal compounds in the foam-like precursor with a layered porous structure and to form alloying, at the same time, the remaining fuel is graphitized to form a carbon coating layer, and a tin alloy negative material with a layered porous structure is obtained.

[0012] Preferably, the ratio of the total moles of the transition metal salt and the soluble tin salt to the moles of the fuel is 1-2.5:1. Insufficient fuel results in insufficient carbon content, thereby leading to poor electrical conductivity.

[0013] Preferably, the chelating agent is tartaric acid, ethylenediaminetetraacetic acid or ethylenediamine. The present application utilizes the functional groups in the chelating agent to form a coordination reaction with metal ions to form stable chelates, so that the metal ions are uniformly dispersed in the solution, ensuring the uniformity of the solution; and by adjusting the pH value of the mixed solution to 5-6.5, the solution is clear and transparent, ensuring that each substance can exist stably and react fully.

[0014] Preferably, the transition metal salt is at least one of a cobalt salt, a nickel salt, a copper salt and an iron salt. The present application introduces transition metals to form alloys with tin, uses the rigid skeleton of the inactive metal to inhibit the volume change of tin, and optimizes the electronic structure, increases the active sites and reduces the lithium ion insertion / extraction energy barrier through the synergistic effect of multiple metals.

[0015] Preferably, the fuel is glucose, sucrose, citric acid, urea or glycine. The fuel serves as both an energy source for the combustion reaction and a carbon source to provide electrical conductivity and structural support.

[0016] Preferably, the molar ratio of the transition metal salt to the soluble tin salt is 1:1-4; and the ratio of the total moles of the transition metal salt and the soluble tin salt to the moles of the chelating agent is 1:1.5-2. The soluble tin salt is the main source of specific capacity of the electrode material; and the ratio of the total moles of the transition metal salt and the soluble tin salt to the moles of the chelating agent directly affects the stability, solubility and reactivity of the metal ions. Excessive chelating agent enhances the chelation stability and inhibits precipitation, and insufficient chelating agent may lead to free metal ions or side reactions.

[0017] Preferably, the soluble tin salt is stannous chloride, stannous tetrachloride, stannous sulfate, or stannous sulfate; the transition metal salt is at least one of cobalt nitrate, cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt sulfate, nickel chloride, nickel nitrate, copper nitrate hexahydrate, copper chloride, ferrous chloride, ferric sulfate, and ferric nitrate nonahydrate.

[0018] Preferably, the soluble tin salt, chelating agent, fuel, transition metal salt and water are mixed at room temperature for 3 to 5 hours.

[0019] This invention heats the mixed solution to evaporate the water, increasing the concentration of the mixture and promoting the complete chelation reaction between the chelating agent and metal ions, forming a viscous gel or foam precursor. As the temperature continues to rise, when the ignition temperature of the fuel is reached, the fuel undergoes a violent redox reaction with oxygen in the air, releasing a large amount of heat and gas, causing the system to expand and form a loose foam precursor. At the same time, the carbon produced by the combustion of the fuel is evenly distributed in the foam precursor.

[0020] Preferably, the annealing temperature is 550℃~750℃, and the time is 1h~6h. Annealing the foamed precursor causes the metal compounds in the precursor to decompose. Simultaneously, metal ions are reduced to elemental metals, which interdiffusion to form a tin alloy. Furthermore, excess fuel is further graphitized at high temperature, forming a carbon coating layer that facilitates electron conduction, improving the conductivity and structural stability of the tin alloy anode material. Furnace cooling prevents internal stress caused by rapid cooling. If the annealing temperature is too low, alloying will be incomplete; if the annealing temperature is too high, the carbon layer may be damaged.

[0021] The second objective of this invention is to provide a tin alloy anode material, which is prepared by the above-described method for preparing tin alloy anode materials.

[0022] The third objective of this invention is to provide an application of a tin alloy anode material as an anode material in lithium-ion batteries.

[0023] Compared with the prior art, the present invention has the following technical effects: This invention involves mixing soluble tin salts, chelating agents, fuel, transition metal salts, and water, followed by heating and combustion to form a foam-like precursor. Under a protective atmosphere, the foam-like precursor is annealed to obtain a tin alloy anode material with a layered porous structure. Utilizing the gas self-pore-forming mechanism of solution combustion to form a layered porous structure significantly increases the specific surface area, providing abundant electrochemical reaction active sites and shortening the Li... +The transmission distance of electrons and ions is reduced, thereby effectively improving the transmission efficiency of ions and electrons. After the pyrolysis of excess fuel, an amorphous carbon coating layer is formed, constructing a carbon network for electron conduction. At the same time, by introducing transition metals for alloying, the volume expansion of tin during charging and discharging is successfully suppressed, providing a buffer space for changes in material structure and ensuring the structural integrity of the electrode material during cycling. This solves the problem of volume expansion of tin-based anode materials while significantly improving the cycle stability and rate performance of composite materials.

[0024] The solution combustion method used in this invention is simple to synthesize, has a low reaction temperature, and a rapid reaction process, making it suitable for the preparation of various metal oxide system materials. Attached Figure Description

[0025] Figure 1 The X-ray diffraction pattern of the tin alloy anode material prepared in Example 1.

[0026] Figure 2 The X-ray diffraction pattern of the tin alloy anode material prepared in Example 2 is shown.

[0027] Figure 3 The X-ray diffraction pattern of the tin alloy anode material prepared in Example 3.

[0028] Figure 4 The X-ray diffraction pattern of the tin alloy anode material prepared in Example 4 is shown.

[0029] Figure 5 This is a scanning electron microscope image of the tin alloy anode material prepared in Example 2.

[0030] Figure 6 This is a scanning electron microscope image of the tin alloy anode material prepared in Example 3.

[0031] Figure 7 This is a scanning electron microscope image of the tin alloy anode material prepared in Example 4.

[0032] Figure 8 The graph shows the cycle performance of a lithium-ion battery prepared using the tin alloy anode material of Example 1.

[0033] Figure 9 The graph shows the cycle performance of a lithium-ion battery prepared using the tin alloy anode material of Example 2.

[0034] Figure 10 The graph shows the cycle performance of a lithium-ion battery prepared using the tin alloy anode material of Example 3.

[0035] Figure 11 The graph shows the cycle performance of a lithium-ion battery prepared using the tin alloy anode material of Example 4.

[0036] Figure 12 The graph shows a comparison of the cycle performance of lithium-ion batteries prepared using the tin alloy anode materials of Example 5 and Comparative Examples 1 to 2.

[0037] Figure 13 The graph shows the rate performance of a lithium-ion battery prepared using the tin alloy anode material of Example 2.

[0038] Figure 14 The graph shows the rate performance of a lithium-ion battery prepared using the tin alloy anode material of Example 3. Detailed Implementation

[0039] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings.

[0040] Unless otherwise specified, all reagents used in this invention are commercially available, and all methods used are conventional techniques in the art.

[0041] Example 1 A method for preparing a tin alloy anode material includes the following steps: Weigh 0.075 mol of tartaric acid into a beaker, add 50 mL of ammonia water and stir until completely dissolved. Then add 0.05 mol of glucose, 0.025 mol of nickel chloride, 0.025 mol of tin tetrachloride pentahydrate and 250 mL of deionized water. Stir at room temperature for 5 hours until completely dissolved. Then add ammonia water and nitric acid dropwise to adjust the pH of the mixed solution to 5.8 so that the mixed solution is clear and transparent, thus obtaining the mixed solution.

[0042] The mixed solution is placed in a crucible and heated to 100°C using a heater to evaporate the water. The mixture undergoes a chelation reaction to form a viscous gel or foam precursor. The temperature is further increased until it reaches the ignition temperature of the fuel, at which point a violent redox reaction occurs, accompanied by a visible flame or spark, releasing a large amount of gas and heat, forming a loose, foamy precursor. All of the above processes must be carried out in a fume hood.

[0043] Under an argon atmosphere, the foamed precursor was heated to 650℃ at a heating rate of 10℃ / min and annealed, held at that temperature for 4 hours, and then cooled in the furnace to obtain the Sn / Ni / C alloy anode material.

[0044] Example 2 A method for preparing a tin alloy anode material includes the following steps: The difference from Example 1 is as follows: Ethylenediamine was used to replace tartaric acid, and citric acid was used to replace glucose; the annealing time was 2 hours.

[0045] Weigh 0.075 mol of ethylenediamine into a beaker, add 50 mL of ammonia water and stir until completely dissolved. Then add 0.05 mol of citric acid, 0.025 mol of nickel nitrate hexahydrate, 0.025 mol of tin tetrachloride pentahydrate and 250 mL of deionized water. Stir at room temperature for 5 hours until completely dissolved. Then add ammonia water and nitric acid dropwise to adjust the pH of the mixed solution to 5.8 so that the mixed solution is clear and transparent, thus obtaining the mixed solution.

[0046] The mixed solution is placed in a crucible and heated to 100°C using a heater to evaporate the water. The mixture undergoes a chelation reaction to form a viscous gel or foam precursor. The temperature is further increased until it reaches the ignition temperature of the fuel, at which point a violent redox reaction occurs, accompanied by a visible flame or spark, releasing a large amount of gas and heat, forming a loose, foamy precursor. All of the above processes must be carried out in a fume hood.

[0047] Under an argon atmosphere, the foamed precursor was heated to 650℃ at a heating rate of 10℃ / min and annealed for 2 hours, then cooled in the furnace to obtain the Sn / Ni / C alloy anode material.

[0048] Example 3 A method for preparing a tin alloy anode material includes the following steps: The difference from Example 1 is as follows: Ethylenediamine was used to replace tartaric acid, and glycine was used to replace glucose; the annealing time was 2 hours; and the molar ratio of nickel salt to tin salt was 1:1.5.

[0049] Weigh 0.075 mol of ethylenediamine into a beaker, add 50 mL of ammonia water and stir until completely dissolved. Then add 0.05 mol of glycine, 0.02 mol of nickel nitrate hexahydrate, 0.03 mol of tin tetrachloride pentahydrate and 250 mL of deionized water. Stir at room temperature for 5 hours until completely dissolved. Then add ammonia water and nitric acid dropwise to adjust the pH of the mixed solution to 6.0 to make the solution clear and transparent, thus obtaining the mixed solution.

[0050] The mixed solution is placed in a crucible and heated to 100°C using a heater to evaporate the water. The mixture undergoes a chelation reaction to form a viscous gel or foam precursor. The temperature is further increased until it reaches the ignition temperature of the fuel, at which point a violent redox reaction occurs, accompanied by a visible flame or spark, releasing a large amount of gas and heat, forming a loose, foamy precursor. All of the above processes must be carried out in a fume hood.

[0051] Under an argon atmosphere, the foamed precursor was heated to 650℃ at a heating rate of 10℃ / min and annealed for 2 hours, then cooled in the furnace to obtain the Sn / Ni / C alloy anode material.

[0052] Example 4 A method for preparing a tin alloy anode material includes the following steps: The difference from Example 1 is as follows: Tartaric acid was replaced with ethylenediaminetetraacetic acid, and glucose was replaced with citric acid; the annealing time was 2 hours; the molar ratio of nickel salt to tin salt was 1:2.3.

[0053] Weigh 0.075 mol of ethylenediaminetetraacetic acid into a beaker, add 50 mL of ammonia water and stir until completely dissolved. Then add 0.05 mol of citric acid, 0.015 mol of nickel nitrate hexahydrate, 0.035 mol of stannous chloride and 250 mL of deionized water. Stir at room temperature for 5 hours until completely dissolved. Then add ammonia water and nitric acid dropwise to adjust the pH of the mixed solution to 5.8 to make the solution clear and transparent, thus obtaining the mixed solution.

[0054] The mixed solution is placed in a crucible and heated to 100°C using a heater to evaporate the water. The mixture undergoes a chelation reaction to form a viscous gel or foam precursor. The temperature is further increased until it reaches the ignition temperature of the fuel, at which point a violent redox reaction occurs, accompanied by a visible flame or spark, releasing a large amount of gas and heat, forming a loose, foamy precursor. All of the above processes must be carried out in a fume hood.

[0055] Under an argon atmosphere, the foamed precursor was heated to 650℃ at a heating rate of 10℃ / min and annealed for 2 hours, then cooled in the furnace to obtain the Sn / Ni / C alloy anode material.

[0056] Example 5 A method for preparing a tin alloy anode material includes the following steps: The difference from Example 1 is as follows: Tartaric acid was replaced with ethylenediaminetetraacetic acid, glucose was replaced with glycine, and nickel chloride was replaced with copper nitrate. The molar ratio of copper salt to tin salt was 1:1.2.

[0057] Weigh 0.075 mol of ethylenediaminetetraacetic acid into a beaker, add 50 mL of ammonia water and stir until completely dissolved. Then add 0.05 mol of glycine, 0.0227 mol of copper nitrate, 0.0273 mol of stannous chloride and 250 mL of deionized water. Stir at room temperature for 5 hours until completely dissolved. Then add ammonia water and nitric acid dropwise to adjust the pH of the mixed solution to 6.0 so that the solution is clear and transparent, thus obtaining the mixed solution.

[0058] The mixed solution is placed in a crucible and heated to 100°C using a heater to evaporate the water. The mixture undergoes a chelation reaction to form a viscous gel or foam precursor. The temperature is further increased until it reaches the ignition temperature of the fuel, at which point a violent redox reaction occurs, accompanied by a visible flame or spark, releasing a large amount of gas and heat, forming a loose, foamy precursor. All of the above processes must be carried out in a fume hood.

[0059] Under an argon atmosphere, the foam precursor was heated to 600℃ at a heating rate of 5℃ / min and annealed for 2 hours, then cooled in the furnace to obtain the Sn / Cu / C alloy anode material.

[0060] Comparative Example 1 A method for preparing a tin alloy anode material includes the following steps: According to the molar ratio of tin dioxide to copper oxide of 1:1.2, tin dioxide and copper oxide were weighed and placed in a ball milling jar containing zirconium oxide balls. 15 mL of ethanol was added to form a paste. The ball milling jar was placed in a planetary ball mill and ball milled at 300 rpm for 12 hours. Then, the particles were threshed and dried to obtain the precursor. Under argon atmosphere, the precursor was heated to 600℃ at a heating rate of 10℃ / min and annealed for 2 hours. It was then cooled in the furnace to obtain the Sn / Cu alloy composite material.

[0061] Comparative Example 2 A method for preparing a tin alloy anode material includes the following steps: The difference from Comparative Example 1 is as follows: The annealing temperature is 650℃.

[0062] According to the molar ratio of tin dioxide to copper oxide of 1:1.2, tin dioxide and copper oxide were weighed and placed in a ball milling jar containing zirconium oxide balls. 15 mL of ethanol was added to form a paste. The ball milling jar was placed in a planetary ball mill and ball milled at 300 rpm for 12 hours. Then, the particles were threshed and dried to obtain the precursor. Under argon atmosphere, the precursor was heated to 650℃ at a heating rate of 10℃ / min and annealed for 2 hours. It was then cooled in the furnace to obtain the Sn / Cu alloy composite material.

[0063] Application Examples Electrochemical tests were performed on the tin alloy anode materials prepared in Examples 1-5 and Comparative Examples 1-2, respectively. The specific test methods are as follows: Taking the tin alloy anode material prepared in Example 1 as an example, the tin alloy anode material prepared in Example 1, acetylene black, and polyvinylidene fluoride were mixed, and NMP was added to form a uniform slurry; wherein, the mass ratio of the tin alloy anode material, acetylene black, and polyvinylidene fluoride prepared in Example 1 was 6:2:2; the slurry was coated on copper foil, dried, and an active material layer was formed on the copper foil to obtain a negative electrode sheet, which was then cut into 14mm diameter pieces for later use; in a glove box with oxygen and water content both below 0.01ppm, lithium sheets as positive electrode sheets, Celgard 2400 separator material, electrolyte with LiFP6 as the main component, and negative electrode sheets were sequentially assembled to obtain a lithium-ion battery.

[0064] Experimental test: 1. X-ray diffraction test.

[0065] like Figures 1-4 As shown, the prepared tin alloy anode material was compared with the standard card. The results showed that the characteristic peaks of the tin alloy anode material were similar to those of Ni. 2.67 Sn2 (JCPDS No. 03-065-9456) and Ni3Sn2 (JCPDS No. 006-0414) are consistent. Furthermore, with the increase of the molar ratio of soluble tin salt to transition metal salt, the peak intensity of amorphous carbon corresponding to the diffraction peak near 25° increases. This is because the increased amount of soluble tin salt reduces carbon decomposition in the fuel during combustion, thereby increasing the carbon content in the formed tin alloy anode material.

[0066] 2. Surface morphology characterization.

[0067] like Figures 5-7 As shown, the tin alloy anode materials prepared in Examples 2-4 exhibit a significant layered hierarchical porous structure. Numerous uniformly precipitated tin alloy nanoparticles can be observed on the surface of the layers and at the edges of the pores. This unique composite morphology of "layered hierarchical porous matrix + surface nanoparticles" not only provides abundant ion migration channels and sufficient buffer space but also effectively increases the active specific surface area of ​​the material, which is beneficial for electrolyte wetting and charge transport, thereby significantly improving the rate performance and structural stability of the material.

[0068] 3. Electrochemical performance testing.

[0069] This invention evaluates the cycle stability, rate performance, and efficiency changes of lithium-ion batteries by analyzing charge-discharge curves, thereby assessing battery performance.

[0070] In the cyclic charge-discharge test, the cyclic test current density is 0.2 A·g. -1 The rate test current density is 0.2 A·g. -1 ~2.0A·g-1 The voltage range is 0.05V to 3.0V. The battery operates at 0.2A·g. -1 The battery underwent 200 cycles of constant current charging and discharging. In the rate test, the battery was subjected to [temperature range missing]. -1 0.4A·g -1 0.8A·g -1 1.2A·g -1 2.0A·g -1 and 0.2A·g -1 The battery was tested at various charge / discharge rates, and its specific capacity was recorded at different rates. All tests were conducted at room temperature.

[0071] like Figures 8-12 As shown, lithium-ion batteries prepared using tin alloy anode materials from Examples 1 to 5 were tested at 0.2 A·g -1 Constant current charge-discharge tests were conducted at current density, and the reversible specific capacity decreased during the first 10 cycles, subsequently increasing. The initial decrease was attributed to some Li... + The electrolyte is consumed to form a solid electrolyte interfacial film. Because the active material is porous, the electrolyte gradually permeates into the pores during cycling, gradually activating the material and forming a stable solid electrolyte interfacial film. Simultaneously, some irreversible Li₂ is consumed. + The released energy participates in subsequent electrochemical reactions, gradually increasing the battery's reversible specific capacity. Furthermore, the battery exhibits extremely high efficiency throughout the entire cycle, with coulombic efficiency consistently remaining above 99%.

[0072] like Figure 12 As shown, compared to the lithium-ion battery prepared using the tin alloy anode material of Example 5, the lithium-ion battery prepared using the tin alloy anode material of Comparative Examples 1 to 2 exhibits a rapid decrease in reversible specific capacity during cycling. However, when the number of cycles reaches approximately 80, the capacity remains stable and even increases to some extent.

[0073] like Figure 13 As shown, the lithium-ion battery prepared using the tin alloy anode material of Example 2 operates at 0.2 A·g -1 0.4A·g -1 0.8A·g -1 1.2A·g -1 and 2.0A·g -1 The reversible specific capacity at current density is stable at 473 mAh·g -1 387mAh·g -1 320mAh·g -1 283mAh·g -1 and 229mAh·g -1 When the current density changes from 2.0 A·g-1 Restored to 0.2 A·g -1 At that time, its capacity quickly rebounded to 503 mAh·g -1 The capacity retention rate was 106.3%.

[0074] like Figure 14 As shown, the lithium-ion battery prepared using the tin alloy anode material of Example 3 achieves a flux density of 0.2 A·g. -1 0.4A·g -1 0.8A·g -1 1.2A·g -1 and 2.0A·g -1 The reversible specific capacity at current density was stabilized at 682 mAh·g -1 521mAh·g -1 393mAh·g -1 325mAh·g -1 and 248mAh·g -1 When the current density changes from 2.0 A·g -1 Restored to 0.2 A·g -1 Its capacity quickly rebounded to 665mAh·g -1 The capacity retention rate was 97.5%. This indicates that the electrode structure did not suffer irreversible damage during high-rate charge and discharge, demonstrating good structural stability and rapid ion / electron transport capabilities, fully proving its excellent rate performance and reaction kinetics.

[0075] Table 1 Electrochemical test data of lithium-ion batteries prepared using tin alloy anode materials from Examples 1-5 and Comparative Examples 1-2 As shown in Table 1, in Example 2, ethylenediamine was used instead of tartaric acid as the chelating agent in Example 1, and citric acid was used instead of glucose as the fuel. This change significantly affects the synthesis route and final performance of the tin alloy anode material. The electrochemical performance of the tin alloy anode material prepared in the tartaric acid-glucose system of Example 1 is inferior to that prepared in the ethylenediamine-citric acid system of Example 2. The main reasons are the relatively weak chelating ability of tartaric acid and the mild combustion characteristics of glucose. The O-coordination mode of tartaric acid in an acidic environment cannot effectively inhibit the ion migration and aggregation of the foam-like precursor during heating, resulting in larger and unevenly distributed active metal particles in the final product. At the same time, the mild combustion process of glucose may generate a carbon coating layer with low graphitization and poor conductivity, which cannot adequately buffer the volumetric strain during cycling. In contrast, in the ethylenediamine-citric acid system of Example 2, the strong N-chelation of ethylenediamine and the polydentate coordination of citric acid form a synergistic effect, which can fix metal ions more uniformly at the molecular level. After vigorous combustion, finer nanoparticles are generated and embedded in a carbon matrix with better conductivity, thereby giving the electrode superior structural stability and electrochemical performance.

[0076] In Example 3, ethylenediamine replaced tartaric acid in Example 1, and glycine replaced glucose; the molar ratio of nickel salt to tin salt was 1:1.5. Glycine has similar chelating ability to citric acid, and the reaction of glycine is more vigorous during combustion, which helps to form a porous structure. Furthermore, compared to the 1:1 molar ratio of nickel salt to tin salt in Example 1, the increased amount of tin salt in Example 3 significantly enhanced the overall reversible specific capacity of the material.

[0077] In Example 4, ethylenediamine replaced tartaric acid in Example 1, and citric acid replaced glucose; the molar ratio of nickel salt to tin salt was 1:2.3. Tin, as a key active material, directly increased its content, leading to a greater number of active sites per unit mass or volume capable of participating in alloying-dealloying reactions, thus significantly improving the lithium storage capacity of the tin alloy anode material as an electrode material. As can be seen from the electrochemical test data of Examples 2-3 in Table 1, with the increase of the tin salt ratio, the reversible specific capacity of the tin alloy anode material as an electrode material at different current densities increases accordingly. Furthermore, sufficient tin content constitutes a more continuous conductive network, promoting electron transport and further improving the rate performance of the tin alloy anode material.

[0078] Under the same molar ratio of copper salt and tin salt in Example 5, Comparative Example 1 and Comparative Example 2, the synthesis method of Comparative Example 1 and Comparative Example 2 was ball milling. Since the tin alloy anode material prepared by ball milling can usually only obtain a regular spherical morphology and lacks the microstructure unique to the solution combustion method, the material is difficult to effectively buffer the violent volume expansion of the tin anode during charge-discharge cycle, which ultimately leads to a significant reduction in its cycle stability.

[0079] It should be noted that when numerical ranges are involved in this invention, it should be understood that the two endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described in this invention to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments, and all such changes and modifications fall within the scope of this invention.

[0080] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. If these modifications and variations fall within the scope of equivalents of this invention, then this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a tin alloy anode material, characterized in that, Includes the following steps: Soluble tin salt, chelating agent, fuel, transition metal salt and water are mixed and the pH is adjusted to 5-6.5 to obtain a mixed solution; then the mixed solution is heated to evaporate the water and a chelation reaction occurs to form a gel. The temperature is continued to rise to the ignition point of the fuel, a redox reaction occurs to release gas and form a layered porous foam precursor. Under a protective atmosphere, the layered porous foam precursor is annealed to decompose and alloy the metal compounds in the layered porous foam precursor. At the same time, the remaining fuel is graphitized to form a carbon coating layer, resulting in a tin alloy anode material with a layered porous structure.

2. The method for preparing the tin alloy anode material according to claim 1, characterized in that, The ratio of the total molar amount of transition metal salts and soluble tin salts to the molar amount of fuel is 1 to 2.5:

1.

3. The method for preparing the tin alloy anode material according to claim 1, characterized in that, The molar ratio of transition metal salt to soluble tin salt is 1:1 to 4.

4. The method for preparing the tin alloy negative electrode material according to claim 1, characterized in that, The ratio of the total molar amount of transition metal salts and soluble tin salts to the molar amount of chelating agent is 1:1.5 to 2.

5. The method for preparing the tin alloy anode material according to claim 1, characterized in that, The chelating agent is tartaric acid, ethylenediaminetetraacetic acid, or ethylenediamine; The transition metal salt is at least one of cobalt, nickel, copper, and iron salts; The fuel is glucose, sucrose, citric acid, urea, or glycine.

6. The method for preparing the tin alloy anode material according to claim 1, characterized in that, The annealing temperature is 550℃~750℃.

7. The method for preparing the tin alloy anode material according to claim 1, characterized in that, Soluble tin salts include stannous chloride, stannous tetrachloride, stannous sulfate, or stannous sulfate; The transition metal salt is at least one of cobalt nitrate, cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt sulfate, nickel chloride, nickel nitrate, copper nitrate hexahydrate, copper chloride, ferrous chloride, ferric sulfate, and ferric nitrate nonahydrate.

8. The method for preparing the tin alloy negative electrode material according to claim 1, characterized in that, The soluble tin salt, chelating agent, fuel, transition metal salt and water are mixed at room temperature for 3 to 5 hours.

9. A tin alloy anode material, characterized in that, The tin alloy anode material is prepared by the method for preparing the tin alloy anode material according to any one of claims 1 to 8.

10. The application of a tin alloy anode material as an anode material in lithium-ion batteries, characterized in that, The tin alloy anode material is the tin alloy anode material as described in claim 9.

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