A MOF-derived coS / feS heterostructure sodium-ion battery negative electrode material and a preparation method thereof

Abstract

The application relates to the technical field of sodium ion battery negative electrode materials, in particular to a MOF-derived CoS / FeS heterostructure sodium ion battery negative electrode material and a preparation method thereof, which comprises the following steps: placing a porcelain boat containing modified thioacetamide in the upstream of a tubular furnace, placing a porcelain boat containing a modified Co / Fe-MOF precursor in the downstream of the tubular furnace, raising the temperature in the tubular furnace to 500-520 DEG C, and keeping the inert gas environment for 2-2.5 hours, so as to obtain the MOF-derived CoS / FeS heterostructure sodium ion battery negative electrode material. + The application constructs the CoS / FeS heterostructure, shortens Na+ transmission path, reduces embedding / extraction energy barrier, perfectly matches the adaptation requirement of sodium ion batteries to large ionic radius, solves the core bottleneck of kinetic lag of traditional materials, and significantly enhances the electrode surface wettability and optimizes the electrolyte infiltration efficiency through the carbon layer and the phytic acid-derived functional group introduced in the modification step.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery anode material technology, specifically to a MOF-derived CoS / FeS heterostructure sodium-ion battery anode material and its preparation method. Background Technology

[0002] Lithium-ion batteries are currently the most widely used advanced rechargeable battery system. However, lithium resources are limited, making it difficult to meet the continuously growing market demand in the energy storage field. Sodium-ion batteries, due to the high abundance of sodium resources in the Earth's crust (2.74%, far exceeding lithium's 0.0065%), significant cost advantages, and outstanding inherent safety, are considered the most commercially promising alternative technology to lithium-ion batteries. However, compared with Li... + In comparison, Na + The larger mass and radius of the graphite anode make it suitable for LIBs but not for SIBs. + Radius may lead to Na + Diffusion in the host material slows down and may cause the crystal structure to collapse, making it difficult to achieve rapid and stable Na diffusion. + The insertion / extraction process makes the selection and design of electrode materials difficult, and developing electrode materials with excellent sodium storage performance is a key prerequisite for the practical application of SIBs.

[0003] In recent years, metal sulfides have shown advantages as anode materials for LIBs / SIBs. This is because their polycrystalline structure enhances ion diffusion and electrochemical performance. Among the many metal sulfides, transition metal sulfides (TMSs) can provide abundant active sites, which promotes improved electrochemical performance, thus becoming a strong candidate for new anode materials for sodium-ion batteries.

[0004] Therefore, in response to the problems mentioned above, this invention proposes a MOF-derived CoS / FeS heterostructure sodium-ion battery anode material and its preparation method. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a MOF-derived CoS / FeS heterostructure sodium-ion battery anode material and its preparation method, thereby solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a MOF-derived CoS / FeS heterostructure sodium-ion battery anode material includes the following steps: S1. Phytic acid is mixed with anhydrous ethanol, then thioacetamide is added and stirred at 60-65℃ until completely dissolved to obtain a mixture. The mixture is then subjected to rotary evaporation under reduced pressure to remove the ethanol, thereby obtaining modified thioacetamide. S2. Place a ceramic boat containing modified thioacetamide upstream of a tube furnace, and a ceramic boat containing modified Co / Fe-MOF precursor downstream of the tube furnace. Raise the temperature inside the tube furnace to 500-520℃ at a rate of 2-5℃ / min, and maintain it in an inert gas environment for 2-2.5h to obtain MOF-derived CoS / FeS heterostructure sodium-ion battery anode material. The modified Co / Fe-MOF precursor was prepared through the following steps; S21. Add melamine to deionized water and stir at 80-85℃ to form a suspension. Add phytic acid aqueous solution dropwise to the suspension. S22. After the addition is complete, stir for 20-25 minutes and then add the Co / Fe-MOF intermediate. Maintain the temperature and react for 4-5 hours. After the reaction is complete, cool naturally to room temperature and centrifuge to collect the precipitate. S23. Wash the precipitate 5-6 times with deionized water to remove unreacted melamine and phytic acid, and then vacuum dry to obtain the modified Co / Fe-MOF precursor.

[0007] Furthermore, the Co / Fe-MOF intermediate in step S22 is obtained through the following steps; S221. Add N,N-dimethylformamide to cobalt nitrate hexahydrate and ferric nitrate nonahydrate, stir for 25-30 minutes to form a transparent solution; S222. Add terephthalic acid to the transparent solution and continue stirring for 50-60 minutes to form a mixed solution. Heat the mixed solution to 110-120℃ at a rate of 5-7℃ / min and react for 20-24 hours. S223. After the reaction is complete, the mixture is naturally cooled to room temperature to obtain a suspension. The precipitate is collected by centrifugation, washed 3-4 times with N,N-dimethylformamide, then washed 2-3 times with anhydrous ethanol, and dried under vacuum to obtain Co / Fe-MOF prepolymer. S224. After activating the Co / Fe-MOF prepolymer, add it to anhydrous methanol and mix. Then, under nitrogen protection, add 1-butanethiol dropwise. After the addition is complete, continue stirring for 10-15 min. Then, add triethylamine dropwise and continue stirring at room temperature for 20-24 h to obtain the Co / Fe-MOF intermediate.

[0008] Furthermore, in step S1, the mass ratio of phytic acid, anhydrous ethanol, and thioacetamide is (0.18-0.22):(15-20):1.

[0009] Furthermore, in step S2, the mass ratio of modified thioacetamide to Co / Fe-MOF precursor is (2.8-3.2):1.

[0010] Furthermore, in step S21, the mass ratio of melamine, phytic acid aqueous solution, and deionized water is 1:(0.5-0.75):(4-6).

[0011] Furthermore, the mass ratio of the Co / Fe-MOF intermediate in step S22 to the melamine in step S21 is (4-5):1.

[0012] Furthermore, in step S221, the mass ratio of cobalt nitrate hexahydrate to ferric nitrate nonahydrate is 1:(0.95-1.05), and the mass ratio of the total amount of cobalt nitrate hexahydrate and ferric nitrate nonahydrate to N,N-dimethylformamide is 1:(65-75).

[0013] Furthermore, the total amount of cobalt nitrate hexahydrate and ferric nitrate nonhydrate in step S221 is in a mass ratio of 1:(0.55-0.65) to terephthalic acid in step S222.

[0014] Furthermore, in step S224, the mass ratio of Co / Fe-MOF prepolymer, anhydrous methanol, 1-butanethiol, and triethylamine is 1:(80-100):(1.8-2.2):(1.0-1.2).

[0015] Furthermore, a MOF-derived CoS / FeS heterostructure sodium-ion battery anode material is prepared according to the aforementioned preparation method.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention significantly shortens the Na₂S / FeS heterostructure by constructing a CoS / FeS heterostructure through lattice distortion and interfacial synergistic effects. + The modification process improves the transport path and lowers the insertion / extraction energy barrier, perfectly matching the adaptation requirements of sodium-ion batteries for large ion radii. It addresses the core bottleneck of kinetic lag in traditional materials. Phytic acid is introduced as a phosphorus and carbon source, and melamine as a nitrogen source, synergistically forming nitrogen- and phosphorus-doped amorphous carbon layers and phytic acid-derived functional groups. This significantly enhances electrode surface wettability, optimizes electrolyte wetting efficiency, and accelerates Na+ transport. + Migration within the electrode simultaneously suppresses electrolyte side reactions and stabilizes the SEI film structure, addressing common sodium-ion battery issues such as electrolyte decomposition and capacity decay at the interface level, thereby improving long-term compatibility and stability.

[0017] 2. This invention constructs a continuous conductive network through a composite design combining bimetallic heterogeneous synergy and MOF-derived carbon coating, thereby improving the material's conductivity by more than two orders of magnitude, achieving 10 A·g. -1 It still maintains 498 mA·h·g under ultra-high current. -1High capacity completely solves the core defect of poor rate performance of monometallic sulfides. By utilizing the flexible buffering effect of MOF-derived carbon and the stress regulation effect of heterogeneous interfaces, the volume expansion is suppressed to below 50%. After 1200 long cycles, the capacity retention rate is still over 75%, solving the fatal defects of short cycle life and easy structural collapse of monometallic sulfides. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the preparation method of the MOF-derived CoS / FeS heterostructure sodium-ion battery anode material of the present invention. Figure 2 This is a schematic diagram of the preparation method of the modified Co / Fe-MOF precursor of the present invention; Figure 3 This is a schematic diagram of the preparation method of the Co / Fe-MOF intermediate of the present invention; Figure 4 The Fourier transform infrared spectrum (a) and scanning electron microscope image (b) of the modified Co / Fe-MOF precursor prepared in Example 1 of this invention are shown. Figure 5 The images show scanning electron microscope (SEM) images (a), transmission electron microscope (TEM) images (b), high-resolution transmission electron microscope (HTEM) images (c), and scanning transmission electron microscope (STEM) images (d) of the MOF-derived CoS / FeS heterostructure sodium-ion battery anode material prepared in Example 1 of this invention, along with the corresponding elemental distribution diagrams of Co, Fe, S, and C. Figure 6 The images show the X-ray diffraction pattern (a), Raman spectrum (b), and X-ray photoelectron spectrum (c) of the MOF-derived CoS / FeS heterostructure sodium-ion battery anode material prepared in Example 1 of this invention. Figure 7 The graph shows the cycle performance of the MOF-derived CoS / FeS heterostructure sodium-ion battery anode material prepared in Example 1 of this invention. Figure 8 The rate performance diagrams of the negative electrode materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention are shown. Figure 9 The GCD curves of the negative electrode materials prepared in Example 1(a), Comparative Example 1(b), and Comparative Example 2(c) of this invention are shown below. Figure 10 The MOF-derived CoS / FeS heterostructure sodium-ion battery anode material prepared in Example 1 of this invention operates at 0.1 mV·s. -1 Cyclic voltammetry curves after 5 cycles at a scan rate of [missing value]. Detailed Implementation

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

[0020] Please see Figures 1-10 The present invention provides a technical solution: Example 1: A method for preparing a MOF-derived CoS / FeS heterostructure sodium-ion battery anode material includes the following steps: I. Preparation of Co / Fe-MOF intermediates: S221. Take 100g of cobalt nitrate hexahydrate and 95g of ferric nitrate nonahydrate, add 12675g of DMF, and stir for 25 minutes to form a transparent solution.

[0021] S222. Add 107.25g of terephthalic acid to the transparent solution, continue stirring for 50min, increase the temperature to 110℃ at 5℃ / min, and react for 20h.

[0022] S223, cooled, centrifuged, washed 3 times with DMF, washed 2 times with ethanol, and vacuum dried to obtain Co / Fe-MOF prepolymer.

[0023] S224. Take 100g of Co / Fe-MOF prepolymer and activate it by treating it under vacuum at 150℃ for 3h. Add 8000g of anhydrous methanol to disperse it. Add 180g of 1-butanethiol dropwise under nitrogen protection and stir for 10min. Add 100g of triethylamine dropwise and stir at room temperature for 20h to obtain Co / Fe-MOF intermediate.

[0024] II. Preparation of modified Co / Fe-MOF precursors: S21. Add 25g of melamine to 100g of deionized water, stir at 80℃ to form a suspension, and add 12.5g of phytic acid dropwise.

[0025] S22. Stir for 20 min, add 100 g of Co / Fe-MOF intermediate, react at 80℃ for 4 h, cool naturally to room temperature, and collect the precipitate by centrifugation.

[0026] S23. The precipitate was washed five times with deionized water and then vacuum dried to obtain the modified Co / Fe-MOF precursor.

[0027] III. Preparation of MOF-derived CoS / FeS heterostructure sodium-ion battery anode materials: S1. Add 18g of phytic acid to 1500g of anhydrous ethanol and stir to dissolve at 60℃. Add 100g of thioacetamide and dissolve. Place the solution in a rotary evaporator and evaporate at 35℃ and 120 rpm to remove the low-boiling-point ethanol solvent, thereby obtaining modified thioacetamide.

[0028] S2. 280g of modified thioacetamide was loaded onto an upstream ceramic boat in a tubular furnace, and 100g of Co / Fe-MOF precursor was loaded onto a downstream ceramic boat. The furnace was heated to 500℃ at a rate of 2℃ / min under an argon atmosphere and held for 2 hours to obtain a MOF-derived CoS / FeS heterostructure, which was named CoS / FeS@C.

[0029] Example 2: A method for preparing a MOF-derived CoS / FeS heterostructure sodium-ion battery anode material includes the following steps: I. Preparation of Co / Fe-MOF intermediates: S221. Take 100g of cobalt nitrate hexahydrate and 100g of ferric nitrate nonahydrate, add 14000g of DMF, and stir for 28 minutes to form a transparent solution.

[0030] S222. Add 120g of terephthalic acid to the transparent solution, continue stirring for 55min, increase the temperature to 115℃ at 6℃ / min, and react for 22h.

[0031] S223, cooled, centrifuged, washed 3 times with DMF, washed 2 times with ethanol, and vacuum dried to obtain Co / Fe-MOF prepolymer.

[0032] S224. Take 100g of Co / Fe-MOF prepolymer and activate it under vacuum at 150℃ for 3h. Add 9000g of anhydrous methanol to disperse it. Add 200g of 1-butanethiol dropwise under nitrogen protection and stir for 13min. Add 110g of triethylamine dropwise and stir at room temperature for 22h to obtain Co / Fe-MOF intermediate.

[0033] II. Preparation of modified Co / Fe-MOF precursors: S21. Add 25g of melamine to 125g of deionized water, stir at 83℃ to form a suspension, and add 15g of phytic acid dropwise.

[0034] S22, stir for 23 min, add 112.5 g Co / Fe-MOF intermediate, react at 83℃ for 4 h, cool naturally to room temperature, and collect the precipitate by centrifugation.

[0035] S23. The precipitate was washed five times with deionized water and then vacuum dried to obtain the modified Co / Fe-MOF precursor.

[0036] III. Preparation of MOF-derived CoS / FeS heterostructure sodium-ion battery anode materials: S1. Add 20g of phytic acid to 1800g of anhydrous ethanol and stir to dissolve at 63℃. Add 100g of thioacetamide and dissolve. Place the solution in a rotary evaporator and evaporate at 35℃ and 120 rpm to remove the low-boiling-point ethanol solvent, thereby obtaining modified thioacetamide.

[0037] S2. In a tube furnace, 300g of modified thioacetamide was placed in an upstream ceramic boat, and 100g of Co / Fe-MOF precursor was placed in a downstream ceramic boat. The furnace was heated to 510℃ at a rate of 4℃ / min under an argon atmosphere and held for 2.3h to obtain a MOF-derived CoS / FeS heterostructure.

[0038] Example 3: A method for preparing a MOF-derived CoS / FeS heterostructure sodium-ion battery anode material includes the following steps: I. Preparation of Co / Fe-MOF intermediates: S221. Take 100g of cobalt nitrate hexahydrate and 105g of ferric nitrate nonahydrate, add 15375g of DMF, and stir for 30 minutes to form a transparent solution.

[0039] S222. Add 133.25g of terephthalic acid to the transparent solution, continue stirring for 60min, increase the temperature to 120℃ at 7℃ / min, and react for 24h.

[0040] S223, cooled, centrifuged, washed 4 times with DMF, washed 3 times with ethanol, and vacuum dried to obtain Co / Fe-MOF prepolymer.

[0041] S224. Take 100g of Co / Fe-MOF prepolymer and activate it by treating it under vacuum at 150℃ for 3h. Add 10000g of anhydrous methanol to disperse it. Add 220g of 1-butanethiol dropwise under nitrogen protection and stir for 15min. Add 120g of triethylamine dropwise and stir at room temperature for 24h to obtain Co / Fe-MOF intermediate.

[0042] II. Preparation of modified Co / Fe-MOF precursors: S21. Add 25g of melamine to 150g of deionized water, stir at 85℃ to form a suspension, and add 18.75g of phytic acid dropwise.

[0043] S22. Stir for 25 min, add 125 g of Co / Fe-MOF intermediate, react at 85℃ for 5 h, cool naturally to room temperature, and collect the precipitate by centrifugation.

[0044] S23. The precipitate was washed 6 times with deionized water and then vacuum dried to obtain the modified Co / Fe-MOF precursor.

[0045] III. Preparation of MOF-derived CoS / FeS heterostructure sodium-ion battery anode materials: S1. Add 22g of phytic acid to 2000g of anhydrous ethanol and stir to dissolve at 65℃. Add 100g of thioacetamide and dissolve. Place the solution in a rotary evaporator and evaporate at 35℃ and 120 rpm to remove the low-boiling-point ethanol solvent, thereby obtaining modified thioacetamide.

[0046] S2. 320g of modified thioacetamide was loaded onto an upstream ceramic boat in a tubular furnace, and 100g of Co / Fe-MOF precursor was loaded onto a downstream ceramic boat. The furnace was heated to 520℃ at a rate of 5℃ / min under an argon atmosphere and held for 2.5h to obtain a MOF-derived CoS / FeS heterostructure.

[0047] Comparative Example 1 Compared to Example 1, Comparative Example 1 omits the process of ferric nitrate nonahydrate in step S221. In step S224, a Co-MOF intermediate is finally obtained. The Co-MOF intermediate is added directly to step S2 without modification to replace the original modified Co / Fe-MOF precursor. The remaining steps are exactly the same as steps S1 and S2 in Example 1. Finally, a black powder product is obtained, named CoS@C.

[0048] Comparative Example 2 Compared to Example 1, Comparative Example 2 omits cobalt nitrate hexahydrate in step S221. In step S224, Fe-MOF intermediate is finally obtained. The Fe-MOF intermediate is added directly to step S2 without modification to replace the original modified Co / Fe-MOF precursor. The remaining steps are exactly the same as steps S1 and S2 in Example 1. Finally, a black powder product is obtained, named FeS@C.

[0049] Sodium-ion battery assembly: The negative electrode materials prepared in Examples 1-3 and Comparative Examples 1-2, namely conductive carbon black and polyvinylidene fluoride binder, were mixed and ground evenly in a mass ratio of 8:1:1 and then coated onto a 1.539 cm thick substrate. 2 The negative electrode was made of carbon-coated copper foil, and the positive electrode was metallic sodium. The electrolyte was a 1.0M NaPF6 solution in ethylene glycol dimethyl ether. The battery was assembled in a glove box under argon protection.

[0050] Performance testing The Co / FeMOF precursor obtained in Example 1 of this invention was characterized and tested, see [reference needed]. Figure 4 As shown in Figure (a), the Fourier transform infrared (FTIR) spectrum of the precursor is located at 1576 cm⁻¹. -1 and 1389cm -1 The peak at 1508 cm⁻¹ is attributed to the carboxylate group after deprotonation of the terephthalic acid ligand. -1 The peak at 750 cm⁻¹ is attributed to the C=C skeletal vibration of the benzene ring. -1 and 710cm-1 The peak at the position is attributed to the out-of-plane bending vibration of CH. The above analysis indicates that the precursor is a complex formed by the coordination of metal ions and carboxylic acid. Figure (b) shows that the modified Co / Fe-MOF precursor exhibits a rhombohedral polyhedral structure.

[0051] See Figure 5 Figure 1 shows the scanning electron microscope (SEM) image (a), transmission electron microscope (TEM) image (b), high-resolution transmission electron microscope (HTEM) image (c), and scanning transmission electron microscope (STEM) image (d) of CoS / FeS@C prepared in Example 1, along with the corresponding elemental distribution diagram. As shown in Figure 1a, the composite material exhibits a micron-sized microsphere morphology. As shown in Figure 1b, the CoS / FeS particles are successfully embedded in the carbon layer. The clear heterostructure interface in Figure 1c confirms the successful construction of the CoS / FeS heterostructure. Figure 1c and the corresponding elemental distribution diagram show that the composite material contains four elements: Co, Fe, S, and C, confirming the synchronous formation of CoS and FeS.

[0052] See Figure 6 Figure 1 shows the XRD pattern (a), Raman spectrum (b), and X-ray photoelectron spectrum (c) of the CoS / FeS@C prepared in Example 1. As shown in Figure 1a, the prepared MOF-derived CoS / FeS heterostructure sodium-ion battery anode material contains crystalline CoS and FeS. As shown in Figure 1b, the ratio of the D band intensity to the G band intensity in the Raman spectrum of this material is 0.83, indicating that the carbon matrix in the MOF-derived CoS / FeS heterostructure sodium-ion battery anode material has a high defect degree. As shown in Figure 1c, the MOF-derived CoS / FeS heterostructure sodium-ion battery anode material contains five elements: C, O, S, Co, and Fe, indicating that CoS / FeS@C was successfully synthesized.

[0053] See Figure 7 The figure shows the CoS / FeS@C prepared in Example 1 at 10 A·g -1 The cycling performance diagram at ultra-high current density shows that the discharge specific capacity remains at 498.1 mA·h·g after 1200 cycles. -l .

[0054] See Figure 8 The results show that the negative electrode materials prepared in Examples 1, 1, and 2 have a range of 0.1 to 10 A·g. -1 The rate performance is shown in Table 1 below: Table 1: Anode materials in the range of 0.1 to 10 Ag -1 Ratio performance test table The data in Table 1 show that CoS / FeS@C operates at low currents (0.1 A·g). -1At this initial specific capacity, it is 828.6 mA·h·g. -1 The current density is significantly higher than that of the two single-metal materials, increasing progressively with increasing current density (0.2→0.5→1→2→5→8→10 A·g). -1 The capacity decays very slowly, at 10 A·g -1 Even under extremely high currents, it can still maintain 470.2 mA·h·g -1 High specific capacity, current density recovery (10→8→5→2→1→0.5→0.2→0.1A·g) -1 After that, the capacity was almost fully recovered, eventually returning to 0.1 A·g. -1 At that time, the specific capacity was still as high as 750 mA·h·g -1 With a capacity retention rate exceeding 90%, the material structure is highly stable and free from irreversible damage. Comparative Examples 1 (CoS@C) and 2 (FeS@C) lacked Fe and Co elements respectively during preparation, and the MOF intermediates were not modified. This single-metal and unmodified system lacked the lattice mismatch and interfacial synergistic effect necessary for heterostructure, resulting in the inability to form an effective interfacial built-in electric field during charging and discharging. At the same time, the lack of carbon layer and phytic acid-derived functional group modification on the material surface resulted in poor wettability at the electrode / electrolyte interface. Therefore, the poor performance of Comparative Examples 1 and 2 not only stemmed from the inherent defects of the single-metal sulfide, but also reflected the coupling failure between the lack of bimetallic synergy and the lack of interfacial modification. Both are indispensable and together lead to a significant deterioration in kinetic performance.

[0055] Figure 9 The negative electrode materials prepared in Example 1(a), Comparative Example 1(b), and Comparative Example 2(c) are shown in 1.0 A·g -1 The GCD curves below show that constructing a heterostructure improved the initial discharge and charge specific capacity of CoS / FeS@C, reaching 890.7 and 728.7 mA·h·g, respectively. -1 It is higher than CoS@C (768.1 / 447.8 mA·h·g). -1 ) and FeS@C (713.9 / 529.2 mA·h·g) -1 ).

[0056] Figure 10 The MOF-derived CoS / FeS heterostructure sodium-ion battery anode material prepared in Example 1 is shown to operate at 0.1 mV·s. -1 The cyclic voltammetry curves show: a broad peak at 0.661 / 1.731 V in the first cycle, attributed to the conversion of the alkalization product Co and Na2S and the dealkalization to form CoS; at discharge 0.937 V, there is sodium formation of FeS nanoparticles to generate Na2FeS2 and an SEI film; at 1.013 V, there is a reduction peak and Na...2-x FeS2 reduction correlation: the cathode peak at 1.22–1.34V during charging is a small amount of dissolved polysulfides. Except for the first cycle, the CV overlaps well in the latter two cycles, indicating good reversibility.

[0057] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a MOF-derived CoS / FeS heterostructure sodium-ion battery anode material, characterized in that, Includes the following steps: S1. Phytic acid is mixed with anhydrous ethanol, then thioacetamide is added and stirred at 60-65℃ until completely dissolved to obtain a mixture. The mixture is then subjected to rotary evaporation under reduced pressure to remove the ethanol, thereby obtaining modified thioacetamide. S2. Place a ceramic boat containing modified thioacetamide upstream of a tube furnace, and a ceramic boat containing modified Co / Fe-MOF precursor downstream of the tube furnace. Raise the temperature inside the tube furnace to 500-520℃ at a rate of 2-5℃ / min, and maintain it in an inert gas environment for 2-2.5h to obtain MOF-derived CoS / FeS heterostructure sodium-ion battery anode material. The modified Co / Fe-MOF precursor was prepared through the following steps; S21. Add melamine to deionized water and stir at 80-85℃ to form a suspension. Add phytic acid aqueous solution dropwise to the suspension. S22. After the addition is complete, stir for 20-25 minutes and then add the Co / Fe-MOF intermediate. Maintain the temperature and react for 4-5 hours. After the reaction is complete, cool naturally to room temperature and centrifuge to collect the precipitate. S23. Wash the precipitate 5-6 times with deionized water to remove unreacted melamine and phytic acid, and then vacuum dry to obtain the modified Co / Fe-MOF precursor.

2. The method for preparing a MOF-derived CoS / FeS heterostructure sodium-ion battery anode material according to claim 1, characterized in that, The Co / Fe-MOF intermediate in step S22 is prepared through the following steps; S221. Add N,N-dimethylformamide to cobalt nitrate hexahydrate and ferric nitrate nonahydrate, stir for 25-30 minutes to form a transparent solution; S222. Add terephthalic acid to the transparent solution and continue stirring for 50-60 minutes to form a mixed solution. Heat the mixed solution to 110-120℃ at a rate of 5-7℃ / min and react for 20-24 hours. S223. After the reaction is complete, the mixture is naturally cooled to room temperature to obtain a suspension. The precipitate is collected by centrifugation, washed 3-4 times with N,N-dimethylformamide, then washed 2-3 times with anhydrous ethanol, and dried under vacuum to obtain Co / Fe-MOF prepolymer. S224. After activating the Co / Fe-MOF prepolymer, add it to anhydrous methanol and mix. Then, under nitrogen protection, add 1-butanethiol dropwise. After the addition is complete, continue stirring for 10-15 min. Then, add triethylamine dropwise and continue stirring at room temperature for 20-24 h to obtain the Co / Fe-MOF intermediate.

3. The method for preparing a MOF-derived CoS / FeS heterostructure sodium-ion battery anode material according to claim 1, characterized in that, In step S1, the mass ratio of phytic acid, anhydrous ethanol, and thioacetamide is (0.18-0.22):(15-20):

1.

4. The method for preparing a MOF-derived CoS / FeS heterostructure sodium-ion battery anode material according to claim 1, characterized in that, In step S2, the mass ratio of modified thioacetamide to Co / Fe-MOF precursor is (2.8-3.2):

1.

5. The method for preparing a MOF-derived CoS / FeS heterostructure sodium-ion battery anode material according to claim 1, characterized in that, In step S21, the mass ratio of melamine, phytic acid aqueous solution, and deionized water is 1:(0.5-0.75):(4-6).

6. The method for preparing a MOF-derived CoS / FeS heterostructure sodium-ion battery anode material according to claim 1, characterized in that, In step S22, the mass ratio of the Co / Fe-MOF intermediate to the melamine in step S21 is (4-5):

1.

7. The method for preparing a MOF-derived CoS / FeS heterostructure sodium-ion battery anode material according to claim 2, characterized in that, In step S221, the mass ratio of cobalt nitrate hexahydrate to ferric nitrate nonahydrate is 1:(0.95-1.05), and the mass ratio of the total amount of cobalt nitrate hexahydrate and ferric nitrate nonahydrate to N,N-dimethylformamide is 1:(65-75).

8. The method for preparing a MOF-derived CoS / FeS heterostructure sodium-ion battery anode material according to claim 2, characterized in that, The total mass ratio of cobalt nitrate hexahydrate and ferric nitrate nonhydrate in step S221 to the mass fraction of terephthalic acid in step S222 is 1:(0.55-0.65).

9. The method for preparing a MOF-derived CoS / FeS heterostructure sodium-ion battery anode material according to claim 2, characterized in that, In step S224, the mass ratio of Co / Fe-MOF prepolymer, anhydrous methanol, 1-butanethiol, and triethylamine is 1:(80-100):(1.8-2.2):(1.0-1.2).

10. A MOF-derived CoS / FeS heterostructure sodium-ion battery anode material, characterized in that, The MOF-derived CoS / FeS heterostructure sodium-ion battery anode material is prepared by the method described in any one of claims 1-9.

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