A CuFeS2 / poplar-based hard carbon composite material, its preparation method and application

Abstract

A CuFeS2 / poplar-based hard carbon composite material, its preparation method and application belong to the field of sodium-ion batteries. In this method, poplar is first carbonized into a hard carbon material with a high closed pore content under the self-foaming effect of polyvinylpyrrolidone, and then compounded with sulfur. Subsequently, iron salts, copper salts and glucose are compounded, and under the blocking effect of the high-temperature pyrolysis of glucose, a CuFeS2 nanocompound with a smaller particle size and uniform distribution and a poplar-based hard carbon composite material are obtained. Applying the prepared CuFeS2 / poplar-based hard carbon composite material to sodium-ion batteries can greatly improve the initial efficiency, battery polarization and cycle life of sodium-ion batteries, and the battery has good rate performance.

Description

Technical Field

[0001] The present invention belongs to the field of sodium-ion batteries, and particularly relates to a CuFeS2 / poplar-based hard carbon composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Compared with the fully commercialized lithium-ion batteries, sodium-ion batteries have the advantages of rich resources, low cost, and excellent high and low temperature performance, and are considered by researchers to be one of the ideal energy storage devices in the future. Nowadays, sodium-ion battery cathode materials such as layered metal oxides, Prussian blue / white materials, and polyanion compounds have been widely studied and applied, and excellent research results have been obtained. In terms of anode materials, since the sodium ion radius is much larger than the lithium ion radius, the graphite anode that can store lithium in lithium-ion batteries cannot be applied to sodium-ion batteries, while hard carbon materials have better sodium storage performance in sodium-ion batteries due to their wider lattice.

[0003] According to the different sources of precursors, hard carbon materials can be divided into resin-based, biomass-based, and pitch-based derived carbon materials. Due to the wide source, low price, self-doping elements, and high residual carbon rate of biomass, biomass has been widely used in the anodes of sodium-ion batteries and has achieved excellent electrochemical performance. One of the typical representatives is the Kuraray hard carbon material in Japan, which is derived from the carbonization of coconut shells and exhibits extremely high initial efficiency and reversible capacity in battery applications. However, the preparation process of the Kuraray hard carbon material is extremely strict, the raw material source is limited, and thus the selling price is extremely high, without cost advantages. Other hard carbon materials derived from biomass materials such as moso bamboo, peanut shells, and poplar still face problems such as low charge-discharge initial efficiency, low reversible capacity, short cycle life, and poor reversible specific capacity in sodium-ion battery applications.

[0004] To improve the initial efficiency of hard carbon materials in sodium-ion batteries, researchers have focused on improving the reversible capacity of the low-voltage platform to modify the materials. Through research, it has been found that some hard carbon materials with a high closed-pore content, when combined with some metal sulfides such as MoS2, CoS2, TiS2, etc., are prone to form sodium metal sulfides with sodium ions during the sodiation and desodiation processes, thus having a high sodium storage reversibility. Therefore, these compounds have a high initial efficiency and reversible specific capacity in the application of sodium-ion batteries. However, the material often undergoes a huge volume expansion during the sodiation and desodiation, resulting in material pulverization and greatly reducing the battery cycle life. Compared with single-metal sulfides, bimetal sulfides have more excellent electrical conductivity and higher sodium storage performance. The literature ACS Applied Materials & Interfaces 2021 13 (22), 26034-26045 first reported a chalcopyrite CuFeS2 used as the anode material for sodium-ion batteries. The authors synthesized polycrystalline CuFeS2 using a traditional high-temperature method. Its excellent electrical conductivity and high crystallinity enable it to exhibit excellent cycling performance in sodium-ion batteries, but the initial efficiency is only 73.1%, the charge-discharge polarization is large, and the reversible specific capacity is also lacking. The main reason is that the traditional method of directly calcining metal salts at high temperature easily causes metal agglomeration, resulting in a relatively large particle size of the compound. The uneven distribution of the compound in the carbon material ultimately leads to a reduction in sodium storage active sites and poor battery performance. Summary of the Invention

[0005] The object of the present invention is to provide a CuFeS2 / poplar-based hard carbon composite material, its preparation method and application. A hard carbon composite material is formed by combining CuFeS2 nanocompounds with a small particle size and uniform distribution with poplar-based materials. The preparation method is simple and the raw material cost is low, which can greatly improve the initial efficiency of sodium-ion batteries, improve the cycle life and reversible specific capacity, and can be used in sodium-ion batteries.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a preparation method of a CuFeS2 / poplar-based hard carbon composite material, including the following steps:

[0008] (1) Wash poplar successively with water, dry, pulverize, pickle with acid, and vacuum dry to obtain a pretreated material;

[0009] (2) Add zinc salt and polyvinylpyrrolidone to deionized water to prepare a mixed solution A, and add copper salt, iron salt, and glucose to deionized water to prepare a mixed solution B;

[0010] (3) Drop the mixed solution A onto the pretreated material obtained in step (1), grind it into a viscous state, and vacuum dry to obtain a poplar-based hard carbon precursor material;

[0011] (4) Under an argon protection atmosphere, the poplar-based hard carbon precursor material obtained in step (3) is calcined at high temperature, pickled, and vacuum dried to obtain a poplar-based hard carbon material;

[0012] (5) The poplar-based hard carbon material obtained in step (4) is ground and mixed with sulfur. The mixed solution B is added dropwise to the mixture of the poplar-based hard carbon material and sulfur, followed by vacuum drying and high-temperature calcination under an argon protection atmosphere to obtain a CuFeS2 / poplar-based hard carbon composite material.

[0013] Preferably, in step (2), the molar ratio of the zinc salt to polyvinylpyrrolidone is 1:1 to 2, and the zinc salt is one of zinc nitrate, zinc chloride, zinc sulfate, and zinc acetate; the molar ratio of the copper salt, iron salt, and glucose is 1:1:1 to 3; the copper salt is one of copper nitrate, copper chloride, copper sulfate, and copper acetate, and the iron salt is one of iron nitrate, iron chloride, iron sulfate, and iron acetate; the molar concentration of the zinc salt is 0.01 to 0.03 mol / L, and the molar concentration of the copper salt is 0.005 to 0.01 mol / L.

[0014] Preferably, in step (3), the vacuum drying temperature is 70 to 90 °C, and the time is 4 to 8 h.

[0015] Preferably, in step (4), the high-temperature calcination temperature is 1300 to 1500 °C, the heating rate is 3 to 10 °C / min, and the holding time is 1 to 3 h; the pickling conditions are 2M dilute acid, stirring for 8 to 12 h, the vacuum drying temperature is 80 to 100 °C, and the time is 10 to 24 h.

[0016] Preferably, in step (5), the mass ratio of the poplar-based hard carbon material to sulfur is 1:0.05 to 0.1; the vacuum drying temperature is 70 to 90 °C, the time is 4 to 8 h, the high-temperature calcination temperature is 600 to 800 °C, the heating rate is 2 to 5 °C / min, and the holding time is 2 to 4 h.

[0017] In a second aspect, the present invention provides a CuFeS2 / poplar-based hard carbon composite material prepared by the above method. The CuFeS2 / poplar-based hard carbon composite material includes a matrix and nanoparticles loaded on the matrix; the matrix is poplar-based hard carbon, and the nanoparticles are CuFeS2 nanocompounds; the closed pore content of the poplar-based hard carbon is 0.68 to 0.83 ml / g, and the particle size of the CuFeS2 particles is 10 to 60 nm.

[0018] In a third aspect, the present invention provides an application of the above CuFeS2 / poplar-based hard carbon composite material in a sodium-ion battery.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] (1) The preparation method of the CuFeS2 / poplar-based hard carbon composite provided by the present invention forms a hard carbon with a high closed-pore content through the combined action of spontaneous foaming of polyvinylpyrrolidone and carbonization of poplar during the pyrolysis process. The closed-pore capacity can reach 0.68 - 0.83 ml / g. During the formation of CuFeS2, glucose is used to prevent the aggregation of metal salts, reducing the particle size of CuFeS2. The particle size of CuFeS2 is 10 - 60 nm, and it is evenly distributed on the poplar-based hard carbon. The synergistic effect of the two provides more active sites for the sodium insertion / extraction reaction of the battery. This method is simple and easy to implement, facilitating the preparation of a hard carbon with a high closed-pore content and a composite material of a nano-metal or nano-metal compound with a small particle size and high uniformity.

[0021] (2) The preparation method of the CuFeS2 / poplar-based hard carbon composite provided by the present invention forms a CuFeS2 / poplar-based hard carbon composite by treating poplar to form a poplar-based hard carbon with a high closed-pore content and a CuFeS2 nano-compound with a smaller particle size and uniform distribution loaded thereon. The poplar-based hard carbon containing closed pores increases the low-voltage platform capacity and reduces the volume expansion caused by the sodium insertion / extraction reaction of the CuFeS2 nano-compound, laying a foundation for obtaining a high initial efficiency of the battery. The smaller particle size and uniform distribution of the CuFeS2 nano-compound also increase the sodium storage active sites, and its high reversibility of sodium insertion / extraction also increases the initial efficiency of the battery from 62.5% to 94.5%. The synergistic effect of the two greatly improves the performance of the sodium-ion battery.

[0022] (3) The CuFeS2 / poplar-based hard carbon composite provided by the present invention is applied to a sodium-ion battery, and the battery has excellent electrochemical performance. At a current density of 0.2 A / g, the reversible specific capacity of the battery can reach 510.5 - 548.7 mAh / g, and the initial efficiency can reach 85.4 - 94.5%. At a high current density of 1 A / g, the capacity retention rate is still 83.2 - 90.5% after 300 cycles. Even at an ultra-high current density of 5 A / g, the reversible specific capacity of the battery can still reach 280.5 - 320.7 mAh / g. Description of the Drawings

[0023] Figure 1 Scanning electron microscope (SEM) image of the CuFeS2 / poplar-based hard carbon composite prepared in Example 1;

[0024] Figure 2 Transmission electron microscope (TEM) image of the CuFeS2 / poplar-based hard carbon composite prepared in Example 1;

[0025] Figure 3 X-ray diffraction (XRD) pattern of the CuFeS2 / poplar-based hard carbon composite prepared in Example 1;

[0026] Figure 4 TEM image of the CuFeS2 / poplar-based hard carbon composite prepared in Comparative Example 3;

[0027] Figure 5 First charge-discharge curves of the CuFeS2 / poplar-based hard carbon composites prepared in Example 1 and Comparative Examples 1-3;

[0028] Figure 6 Cycling performance graph of the CuFeS2 / poplar-based hard carbon composite prepared in Example 1 at a current density of 1 A / g;

[0029] Figure 7 Reversible specific capacity graphs of the CuFeS2 / poplar-based hard carbon composite prepared in Example 1 at different current densities. Detailed implementation manners

[0030] The present invention will be further described below through examples and accompanying drawings, but the protection scope of the present invention is not limited thereto. Example 1

[0031] (1) Poplar was successively washed with water, dried, pulverized, pickled with acid, and vacuum dried to obtain a pretreated material;

[0032] (2) 0.057 g of zinc nitrate and 0.067 g of polyvinylpyrrolidone were added to 10 ml of deionized water to prepare a mixed solution A. 0.019 g of copper nitrate, 0.024 g of iron nitrate, and 0.036 g of glucose were added to 10 ml of deionized water to prepare a mixed solution B. Both were reserved for later use;

[0033] (3) The mixed solution A was dropped onto 4 g of the pretreated material obtained in step (1), ground into a viscous state, vacuum dried at 80 °C for 8 h to obtain a poplar-based hard carbon precursor material. Subsequently, it was calcined at 1500 °C for 3 h in an argon atmosphere at a heating rate of 5 °C / min, cooled, continuously stirred in 2 M hydrochloric acid for 12 h, then filtered, washed with deionized water until neutral, and vacuum dried at 100 °C for 24 h to obtain a poplar-based hard carbon material;

[0034] (4) 0.8 g of the poplar-based hard carbon material obtained in step (3) was ground and mixed with 0.08 g of sulfur. The mixed solution B was dropped onto the mixture of poplar-based hard carbon and sulfur, vacuum dried at 80 °C for 8 h, and then heated to 700 °C at a heating rate of 5 °C / min in an argon atmosphere and held for 3 h to obtain a CuFeS2 / poplar-based hard carbon composite.

[0035] For the CuFeS2 / poplar-based hard carbon composite obtained in this example, the particle size of the loaded CuFeS2 nanocompound particles is 10 - 25 nm. Example 2

[0036] (1) Wash poplar wood successively with water, dry, crush, pickle with acid, and dry under vacuum to obtain a pretreated material;

[0037] (2) Add 0.027 g of zinc chloride and 0.022 g of polyvinylpyrrolidone to 10 ml of deionized water to prepare a mixed solution A. Add 0.011 g of copper chloride, 0.013 g of iron chloride, and 0.014 g of glucose to 10 ml of deionized water to prepare a mixed solution B. Keep both for later use;

[0038] (3) Drop the mixed solution A into 4 g of the pretreated material obtained in step (1), grind it into a viscous state, dry it under vacuum at 90 °C for 4 h to obtain a poplar-based hard carbon precursor material. Then heat it to 1400 °C at a rate of 10 °C / min in an argon atmosphere and calcine for 2 h. After cooling, continuously stir it in 2 M nitric acid for 8 h, then filter and wash it with deionized water until neutral, and dry it under vacuum at 90 °C for 10 h to obtain a poplar-based hard carbon material;

[0039] (4) Take 0.8 g of the poplar-based hard carbon material obtained in step (3) and grind it with 0.064 g of sulfur for mixing. Drop the mixed solution B into the mixture of poplar-based hard carbon and sulfur, dry it under vacuum at 90 °C for 4 h, then heat it to 800 °C at a rate of 3 °C / min in an argon atmosphere and hold for 2 h to obtain a CuFeS2 / poplar-based hard carbon composite material.

[0040] The CuFeS2 / poplar-based hard carbon composite material obtained in this example has the particle size of the loaded CuFeS2 nanocompound particles ranging from 30 to 60 nm. Example 3

[0041] (1) Wash poplar wood successively with water, dry, crush, pickle with acid, and dry under vacuum to obtain a pretreated material;

[0042] (2) Add 0.016 g of zinc sulfate and 0.0167 g of polyvinylpyrrolidone to 10 ml of deionized water to prepare a mixed solution A. Add 0.008 g of copper sulfate, 0.020 g of iron sulfate, and 0.027 g of glucose to 10 ml of deionized water to prepare a mixed solution B. Keep both for later use;

[0043] (3) Drop the mixed solution A into 4 g of the pretreated material obtained in step (1), grind it into a viscous state, dry it under vacuum at 70 °C for 6 h to obtain a poplar-based hard carbon precursor material. Then heat it to 1300 °C at a rate of 3 °C / min in an argon atmosphere and calcine for 1 h. After cooling, continuously stir it in 2 M sulfuric acid for 10 h, then filter and wash it with deionized water until neutral, and dry it under vacuum at 80 °C for 12 h to obtain a poplar-based hard carbon material;

[0044] (4) Take 0.8 g of the poplar-based hard carbon material obtained in step (3) and grind it with 0.04 g of sulfur. Add the mixed solution B dropwise to the mixture of poplar-based hard carbon and sulfur. After vacuum drying at 70 °C for 6 h, heat it to 600 °C at a rate of 2 °C / min under an argon atmosphere and hold for 3 h to obtain the CuFeS2 / poplar-based hard carbon composite material.

[0045] For the CuFeS2 / poplar-based hard carbon composite material obtained in this example, the particle size of the loaded CuFeS2 nanocompound particles is 15 - 40 nm. Example 4

[0046] (1) Wash poplar wood successively with water, dry, crush, pickle with acid, and vacuum dry to obtain a pretreated material;

[0047] (2) Add 0.055 g of zinc acetate and 0.067 g of polyvinylpyrrolidone to 10 ml of deionized water to prepare a mixed solution A. Add 0.02 g of copper acetate, 0.021 g of iron acetate, and 0.036 g of glucose to 10 ml of deionized water to prepare a mixed solution B. Keep both for later use;

[0048] (3) Add the mixed solution A dropwise to 4 g of the pretreated material obtained in step (1), grind it into a viscous state, vacuum dry at 90 °C for 8 h to obtain a poplar-based hard carbon precursor material. Then heat it to 1500 °C at a rate of 5 °C / min under an argon atmosphere and calcine for 2 h. After cooling, stir continuously in 2 M hydrochloric acid for 12 h, then filter and wash with deionized water until neutral, and vacuum dry at 90 °C for 12 h to obtain the poplar-based hard carbon material;

[0049] (4) Take 0.8 g of the poplar-based hard carbon material obtained in step (3) and grind it with 0.08 g of sulfur. Add the mixed solution B dropwise to the mixture of poplar-based hard carbon and sulfur. After vacuum drying at 80 °C for 8 h, heat it to 700 °C at a rate of 5 °C / min under an argon atmosphere and hold for 3 h to obtain the CuFeS2 / poplar-based hard carbon composite material.

[0050] For the CuFeS2 / poplar-based hard carbon composite material obtained in this example, the particle size of the loaded CuFeS2 nanocompound particles is 10 - 30 nm. Comparative Example 1

[0051] The difference from Example 1 is that polyvinylpyrrolidone is not added to the mixed solution A in step (2), and other steps remain unchanged. Comparative Example 2

[0052] The difference from Example 1 is that glucose is not added to the mixed solution B in step (2), and other steps remain unchanged. Comparative Example 3

[0053] The difference from Example 1 is that polyvinylpyrrolidone is not added to the mixed solution A in step (2), and glucose is not added to the mixed solution B, and other steps remain unchanged. Comparative Example 4

[0054] The electrode materials obtained in Examples 1-4 and Comparative Examples 1-3 were mixed with Super P conductive carbon black and polyvinylidene fluoride in a mass ratio of 8:1:1 in N-methylpyrrolidone to form a slurry with appropriate viscosity, and then coated on aluminum foil. After drying and compaction, it was cut into appropriate sizes to obtain the negative electrode sheets of sodium ion batteries. Then, it was assembled with Whatman GF / A glass fiber membrane, an electrolyte of ethylene carbonate - diethyl carbonate - ethyl methyl carbonate (volume ratio of 1:2:2) containing 1.5 M sodium hexafluorophosphate, and a sodium metal sheet to form a button cell for electrochemical performance testing. The test results are shown in Table 1.

[0055]

[0056] As can be seen from the above table, Examples 1-4 have a relatively high closed pore capacity. Combining with the TEM image of Example 1 ( Figure 2 ), the CuFeS2 nanocompound particles are evenly distributed and have a relatively small particle size. The relatively high closed pore capacity not only increases the low voltage platform capacity of the battery, but also alleviates the volume expansion caused by the sodiation / desodiation of CuFeS2. In addition, the inherent properties of the CuFeS2 nanocompound particles also increase the sodium storage active sites. At a current density of 0.2 A / g, the reversible specific capacity of the battery can reach 510.5~548.7 mAh / g, and the initial efficiency can reach 85.4~94.5%. At a high current density of 1 A / g, the capacity retention rate is still 83.2~90.5% after 300 cycles. Even at an ultra-high current density of 5 A / g, the reversible specific capacity of the battery can still reach 280.5~320.7 mAh / g. Therefore, Examples 1-4 exhibit relatively high initial efficiency, relatively high cycle retention rate and excellent reversible specific capacity.

[0057] Figure 1 SEM image of the CuFeS2 / poplar-based hard carbon composite prepared in Example 1, Figure 2 corresponding TEM image, Figure 3 XRD pattern. It can be seen from the SEM and TEM images that the CuFeS2 / poplar-based hard carbon composite is a blocky and irregular material, composed of a hard carbon matrix and uniformly loaded CuFeS2 nanocompound particles with a size of 10-25 nm. The relatively small particle size and uniform distribution of the CuFeS2 nanocompound particles can increase the sodium storage active sites, and its high reversibility of sodiation / desodiation can also improve the initial efficiency of the battery. The XRD pattern shows that the main diffraction peaks (112), (220), (204), etc. of CuFeS2 are consistent with the standard PDF card numbers, and the diffraction peak at about 22.6° is the peak of poplar-based hard carbon.

[0058] Figure 5 It is the first charge-discharge curve graph of Example 1. Figure 6 It is the cycle performance graph of Example 1 at a current density of 1 A / g. Figure 7 It is the reversible specific capacity graph of Example 1 at different current densities. Example 1 shows a high first efficiency of 94.5%. After activation at a lower current density of 0.2 A / g, at a high current density of 1 A / g, the capacity retention rate is still 90.5% after 300 cycles. Compared with Example 1-4, Comparative Example 1 lacks the closed pore capacity, so the capacity of the low voltage platform is reduced. Compared with Example 1-4, although Comparative Example 2 also has a high content of closed pore capacity, without the hindrance of glucose pyrolytic carbon, CuFeS2 will be dispersed disorderly, and the particle size will become larger due to the agglomeration of metals. Compared with Example 1-4, Comparative Example 3 contains less closed pore capacity, and the disorder degree and particle size of CuFeS2 are further increased ( Figure 4 ). Through the above analysis, Comparative Example 3 shows the worst electrochemical performance. Due to the lack of closed pore capacity and uniform, smaller-sized CuFeS2, too much sodium salt is consumed during the first charge process to obtain a high irreversible capacity, and there is almost no low voltage platform capacity, resulting in too low charge capacity, that is, the first efficiency is extremely low, only 62.5%, and there is almost no capacity at high current densities of 2 A / g and 5 A / g.

[0059] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Those of ordinary skill in the art should understand that the present invention can still be modified or equivalently replaced to achieve the same technical effect; as long as it meets the use requirements, it is within the protection scope of the present invention.

Claims

1. A preparation method of a CuFeS2 / poplar-based hard carbon composite material, characterized in that, It includes the following steps: (1) Wash poplar wood successively with water, dry, pulverize, pickle with acid, and vacuum dry to obtain a pretreated material; (2) Add zinc salt and polyvinylpyrrolidone to deionized water to prepare a mixed solution A, and add copper salt, iron salt, and glucose to deionized water to prepare a mixed solution B; (3) Drop the mixed solution A onto the pretreated material obtained in step (1), grind it into a viscous state, and vacuum dry to obtain a poplar-based hard carbon precursor material; (4) Under an argon protection atmosphere, calcine the poplar-based hard carbon precursor material obtained in step (3) at a high temperature, pickle it with acid, and vacuum dry to obtain a poplar-based hard carbon material; (5) Grind and mix the poplar-based hard carbon material obtained in step (4) with sulfur, drop the mixed solution B onto the mixture of the poplar-based hard carbon material and sulfur, vacuum dry, and calcine at a high temperature under an argon protection atmosphere to obtain a CuFeS2 / poplar-based hard carbon composite material.

2. The preparation method of the CuFeS2 / poplar-based hard carbon composite material according to claim 1, characterized in that In the step (2), the molar ratio of the zinc salt to polyvinylpyrrolidone is 1:1 to 2, and the zinc salt is one of zinc nitrate, zinc chloride, zinc sulfate, and zinc acetate; the molar ratio of the copper salt, iron salt, and glucose is 1:1:1 to 3; the copper salt is one of copper nitrate, copper chloride, copper sulfate, and copper acetate, and the iron salt is one of iron nitrate, iron chloride, iron sulfate, and iron acetate; the molar concentration of the zinc salt is 0.01 to 0.03 mol / L, and the molar concentration of the copper salt is 0.005 to 0.01 mol / L.

3. The preparation method of the CuFeS2 / poplar-based hard carbon composite material according to claim 1, wherein, In the step (3), the vacuum drying temperature is 70 to 90 °C, and the time is 4 to 8 h.

4. The preparation method of the CuFeS2 / poplar-based hard carbon composite material according to claim 1, characterized in that, In the step (4), the high-temperature calcination temperature is 1300 to 1500 °C, the heating rate is 3 to 10 °C / min, and the holding time is 1 to 3 h; the pickling condition is 2M dilute acid, stirring for 8 to 12 h, the vacuum drying temperature is 80 to 100 °C, and the time is 10 to 24 h.

5. The preparation method of the CuFeS2 / poplar-based hard carbon composite material according to claim 1, characterized in that, In the step (5), the mass ratio of the poplar-based hard carbon material to sulfur is 1:0.05 to 0.1; the vacuum drying temperature is 70 to 90 °C, the time is 4 to 8 h, the high-temperature calcination temperature is 600 to 800 °C, the heating rate is 2 to 5 °C / min, and the holding time is 2 to 4 h.

6. A CuFeS2 / poplar-based hard carbon composite material prepared by the preparation method according to any one of claims 1-5, characterized in that, The CuFeS2 / poplar-based hard carbon composite material includes a matrix and nanoparticles loaded on the matrix; the matrix is poplar-based hard carbon, and the nanoparticles are CuFeS2 nanocompounds; the closed pore content of the poplar-based hard carbon is 0.68 to 0.83 ml / g, and the particle size of the CuFeS2 particles is 10 to 60 nm.

7. Use of the CuFeS2 / poplar-based hard carbon composite material as described in claim 6, characterized in that, Apply the CuFeS2 / poplar-based hard carbon composite material to a sodium-ion battery.

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