Preparation method and application of CuS / SnS2 composite heterogeneous negative electrode material

Abstract

A preparation method and application of a CuS / SnS2 composite heterogeneous negative electrode material, which relates to a preparation method and application of a negative electrode material. The purpose of the present invention is to solve the problems that the negative electrode materials of existing sodium ion batteries have poor conductivity, large volume expansion, low initial coulombic efficiency, slow sodium ion transmission speed, and when CuS is used as the negative electrode of lithium ion batteries, the capacity of the battery drops rapidly in the first few cycles due to the poor conductivity and severe volume expansion of the CuS material, and it is ultimately difficult to maintain a high specific capacity. Method: 1. Prepare CuS microspheres; 2. Prepare a CuS / SnS2 composite heterogeneous structure. A CuS / SnS2 composite heterogeneous negative electrode material is used as a negative electrode material for sodium ion batteries. The present invention provides a large specific surface area by constructing a CuS / SnS2 hollow heterogeneous structure, which is more conducive to the transmission of ions and improves the capacity. The method of the present invention is simple to operate and suitable for large-scale promotion and application.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a negative electrode material. Background Art

[0002] Energy is the material foundation that underpins the progress of human civilization. With the rapid development of society and the economy, human society's dependence on energy is increasing. Currently, traditional fossil fuels such as coal, oil, and natural gas provide the primary energy source for human society. These resources are becoming increasingly depleted and have significant environmental impacts. Therefore, changing the current irrational energy structure has become a primary challenge for sustainable development. Currently, wind, solar, tidal, and geothermal energy are all renewable and clean energy sources that are being vigorously developed. However, due to the randomness and intermittent nature of clean energy, directly feeding the generated electricity into the power grid can have a significant impact. In this context, developing efficient and convenient energy storage technologies to meet human energy needs has become a global research hotspot. In recent years, secondary batteries such as lithium-ion batteries, aluminum-ion batteries, and sodium-ion batteries (SIBs) have gradually come into focus. SIBs, due to their abundant reserves, low cost, and similar charge and discharge mechanisms to LIBs (as lithium and sodium are both in the first main group and share similar physical and chemical properties), are considered the most promising energy storage devices to replace LIBs.

[0003] Sodium-ion battery technology is developing rapidly, with some promising results, but several challenges remain. Metal sulfides, due to their diverse variety, high specific capacity, and high specific energy, are promising candidates for sodium-ion battery applications. However, due to a range of challenges, such as poor conductivity, large volume expansion, low initial coulombic efficiency, and slow sodium ion transport, systematic structural regulation and mechanism studies are needed to further enhance their electrochemical performance.

[0004] In recent years, research on copper sulfide (CuS) has intensified. As a negative electrode in lithium-ion batteries, CuS has been studied for its high theoretical specific capacity and flat lithium-deintercalation platform. However, the material's poor conductivity and severe volume expansion lead to a rapid capacity drop in the first few cycles, ultimately making it difficult to maintain a high specific capacity. This is the main obstacle to its further application. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems that the negative electrode materials of existing sodium ion batteries have poor conductivity, large volume expansion, low initial coulombic efficiency, slow sodium ion transmission speed, and when CuS is used as the negative electrode of lithium ion batteries, the capacity of the battery drops rapidly in the first few cycles due to the poor conductivity and severe volume expansion of the CuS material, and it is ultimately difficult to maintain a high specific capacity. A preparation method and application of a CuS / SnS2 composite heterogeneous negative electrode material are provided.

[0006] A method for preparing a CuS / SnS2 composite heterogeneous negative electrode material is specifically completed by the following steps:

[0007] 1. Preparation of CuS microspheres:

[0008] ① Dissolve Cu(NO3)2·3H2O and polyvinylpyrrolidone in ethylene glycol, then add thiourea and stir to obtain a clear solution;

[0009] ②. Place the clarified solution in a stainless steel reactor lined with polytetrafluoroethylene, then place the stainless steel reactor in an oven, conduct hydrothermal reaction at 150°C to 170°C for a period of time, and then naturally cool to room temperature to obtain reaction product I;

[0010] ③. Centrifuge the reaction product I, wash the solid product obtained after centrifugation, and vacuum dry it to obtain CuS microspheres;

[0011] 2. Preparation of CuS / SnS2 composite heterostructure:

[0012] ① Add SnCl4·5H2O and thioacetamide to anhydrous ethanol, sonicate for a period of time, then add CuS microspheres and stir to obtain a mixture;

[0013] ②. Place the mixture in a stainless steel reactor lined with polytetrafluoroethylene, then place the stainless steel reactor in an oven, conduct hydrothermal reaction at 150°C to 170°C for a period of time, and then naturally cool to room temperature to obtain reaction product II;

[0014] ③. Centrifuge the reaction product II, wash the solid product obtained after centrifugation, and vacuum dry it to obtain a CuS / SnS2 composite heterogeneous negative electrode material.

[0015] A CuS / SnS2 composite heterogeneous negative electrode material is used as a negative electrode material for sodium ion batteries.

[0016] Principles and beneficial effects of the present invention:

[0017] 1. The present invention effectively shortens the charge transfer path in the battery by designing and constructing a heterogeneous structure, reducing the mechanical stress caused by volume fluctuations due to repeated charge and discharge. For other transition metal sulfides, Zhao et al. used kapok petal biomass to in situ grow MoS2 nanosheets through a simple one-step hydrothermal method, and further coated the surface with a conductive polypyrrole layer to construct a ternary sandwich structure PC / MoS2@PPy composite electrode, which also alleviated the volume effect of the material during the charge and discharge cycle. At 2Ag -1 Can reach 216.4mAhg -1 The present invention provides a large specific surface area by constructing a CuS / SnS2 hollow heterostructure, which is more conducive to ion transmission and improves capacity; its electrochemical performance is tested and the -1 The capacity can reach 379.5mAhg -1 , at 5A·g -1 After 350 cycles, it can reach 281.2 mAh g -1 This test result shows that the negative electrode material provided by the present invention still has a very considerable capacity even under high current, and the prepared composite material has good reversibility, making it very beneficial in the research of negative electrode materials for sodium ion batteries and other electrode materials in the field of energy storage.

[0018] 2. The present invention provides a method for preparing a CuS / SnS2 composite heterogeneous negative electrode material. The prepared CuS / SnS2 composite heterogeneous negative electrode material is used in sodium ion battery negative electrode materials. The preparation method of the present invention is simple to operate and is suitable for large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the process for preparing the CuS / SnS2 composite heterogeneous negative electrode material according to Example 1;

[0020] Figure 2 are scanning electron microscope images, in which ab are scanning electron microscope images of the CuS microspheres prepared in step 1 of Example 1, cd are scanning electron microscope images of the CuS / SnS2 composite heterogeneous negative electrode material prepared in step 2 of Example 2, and ef is a scanning electron microscope image of the CuS / SnS2 electrode grown on carbon cloth prepared in comparative example 1;

[0021] Figure 3 XRD spectra of CuS microspheres, SnS2, CuS / SnS2=2:1, CuS / SnS2=3:1, and CuS / SnS2=5:1 prepared in step 1 of Example 1;

[0022] Figure 4Raman spectra of CuS microspheres, SnS2, CuS / SnS2=2:1, CuS / SnS2=3:1, and CuS / SnS2=5:1 prepared in step 1 of Example 1;

[0023] Figure 5 The CuS microspheres prepared in step 1 of Example 1, SnS2, CC / CuS / SnS2, CuS / SnS2=2:1, CuS / SnS2=3:1, and CuS / SnS2=5:1 prepared in Comparative Example 1 were heated to a current density of 0.1 A g -1 Cycling performance under

[0024] Figure 6 CuS / SnS2=3:1 at 5A g -1 Cycling performance under

[0025] Figure 7 These are the magnification diagrams of CuS microspheres, SnS2, CuS / SnS2=2:1, CuS / SnS2=3:1, and CuS / SnS2=5:1 prepared in step 1 of Example 1. DETAILED DESCRIPTION

[0026] Specific embodiment 1: This embodiment is a method for preparing a CuS / SnS2 composite heterogeneous negative electrode material, which is specifically completed by the following steps:

[0027] 1. Preparation of CuS microspheres:

[0028] ① Dissolve Cu(NO3)2·3H2O and polyvinylpyrrolidone in ethylene glycol, then add thiourea and stir to obtain a clear solution;

[0029] ②. Place the clarified solution in a stainless steel reactor lined with polytetrafluoroethylene, then place the stainless steel reactor in an oven, conduct hydrothermal reaction at 150°C to 170°C for a period of time, and then naturally cool to room temperature to obtain reaction product I;

[0030] ③. Centrifuge the reaction product I, wash the solid product obtained after centrifugation, and vacuum dry it to obtain CuS microspheres;

[0031] 2. Preparation of CuS / SnS2 composite heterostructure:

[0032] ① Add SnCl4·5H2O and thioacetamide to anhydrous ethanol, sonicate for a period of time, then add CuS microspheres and stir to obtain a mixture;

[0033] ②. Place the mixture in a stainless steel reactor lined with polytetrafluoroethylene, then place the stainless steel reactor in an oven, conduct hydrothermal reaction at 150°C to 170°C for a period of time, and then naturally cool to room temperature to obtain reaction product II;

[0034] ③. Centrifuge the reaction product II, wash the solid product obtained after centrifugation, and vacuum dry it to obtain a CuS / SnS2 composite heterogeneous negative electrode material.

[0035] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the volume ratio of the amount of Cu(NO3)2·3H2O to ethylene glycol in step 1 (1) is (2 mmol to 4 mmol): 60 mL; and the volume ratio of the polyvinyl pyrrolidone to ethylene glycol in step 1 (1) is (0.3 g to 1 g): 60 mL. Other steps are the same as those in specific embodiment 1.

[0036] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that the volume ratio of the amount of thiourea and ethylene glycol in step 1 (1) is (7 mmol to 11 mmol): 60 mL. The other steps are the same as specific embodiment 1 or 2.

[0037] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the hydrothermal reaction time in step 1 ② is 10 to 14 hours. The other steps are the same as those in specific embodiments 1 to 3.

[0038] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that: the centrifugation speed in step 1 (3) is 10,000 rpm and the centrifugation time is 5 to 9 minutes; in step 1 (3), the solid product obtained after centrifugation is first washed 3 to 5 times with anhydrous ethanol and then 3 to 5 times with deionized water; the vacuum drying temperature in step 1 (3) is 60°C to 80°C and the vacuum drying time is 8 to 12 hours. The other steps are the same as those in specific embodiments 1 to 4.

[0039] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that the molar ratio of CuS microspheres to SnCl4·5H2O in step 2 (1) is (2-5):1; and the molar ratio of thioacetamide to SnCl4·5H2O in step 2 (1) is (3-5):1. The other steps are the same as specific embodiments 1 to 5.

[0040] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 6 in that the volume ratio of the CuS microspheres to anhydrous ethanol in step 2 (1) is (2 mol to 5 mol): (30 mL to 50 mL); the ultrasonication time in step 2 (1) is 20 min to 40 min; and the stirring time in step 2 (1) is 10 min to 20 min. The other steps are the same as those in specific embodiments 1 to 6.

[0041] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the hydrothermal reaction time in step 2 (2) is 10 to 14 hours; the centrifugation speed in step 2 (3) is 10,000 rpm, and the centrifugation time is 5 to 9 minutes. The other steps are the same as specific embodiments 1 to 7.

[0042] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that: in step 2 (3), the solid product obtained after centrifugation is first washed 3 to 5 times with anhydrous ethanol and then washed 3 to 5 times with deionized water; the vacuum drying temperature in step 2 (3) is 60°C to 80°C, and the vacuum drying time is 8 to 12 hours. The other steps are the same as specific embodiments 1 to 8.

[0043] Specific embodiment ten: This embodiment is a CuS / SnS2 composite heterogeneous negative electrode material used as a negative electrode material for sodium ion batteries.

[0044] The following examples are used to verify the beneficial effects of the present invention:

[0045] Example 1: A method for preparing a CuS / SnS2 composite heterogeneous negative electrode material is specifically completed by the following steps:

[0046] 1. Preparation of CuS microspheres:

[0047] ① Dissolve 3 mmol of Cu(NO3)2·3H2O and 0.5 g of polyvinylpyrrolidone in 60 mL of ethylene glycol, then add 9 mmol of thiourea and stir to obtain a clear solution;

[0048] ② Place the clarified solution in a stainless steel reactor lined with polytetrafluoroethylene, then place the stainless steel reactor in an oven and conduct a hydrothermal reaction at 160°C for 12 hours, then naturally cool to room temperature to obtain reaction product I;

[0049] ③. Centrifuge the reaction product I, then wash the solid product obtained after centrifugation 5 times with anhydrous ethanol, and then wash the solid product obtained after centrifugation 5 times with deionized water; finally, vacuum dry at 60°C for 10 hours to obtain CuS microspheres;

[0050] The centrifugal speed in step 1 (3) is 10,000 rpm and the centrifugal time is 7 min;

[0051] 2. Preparation of CuS / SnS2 composite heterostructure:

[0052] ① Add SnCl4·5H2O and thioacetamide to anhydrous ethanol, sonicate for 30 minutes, then add CuS microspheres and stir for 10 minutes to obtain a mixture;

[0053] The molar ratio of CuS microspheres to SnCl4·5H2O described in step 2① is 2:1;

[0054] The molar ratio of thioacetamide to SnCl4·5H2O described in step 2① is 4:1;

[0055] The volume ratio of the amount of CuS microspheres described in step 2① to anhydrous ethanol is 2 mol:40 mL;

[0056] ②. Place the mixture in a stainless steel reactor lined with polytetrafluoroethylene, then place the stainless steel reactor in an oven, conduct a hydrothermal reaction at 160°C for 12 hours, and then naturally cool to room temperature to obtain reaction product II;

[0057] ③. The reaction product II was centrifuged, and the solid product obtained after centrifugation was washed 5 times with anhydrous ethanol, and then washed 5 times with deionized water. Finally, the solid product obtained after centrifugation was vacuum dried at 60°C for 10 hours to obtain a CuS / SnS2 composite heterogeneous negative electrode material (CuS / SnS2=2:1);

[0058] The centrifugal speed described in step 2 (3) is 10000 rpm, and the centrifugal time is 7 min.

[0059] Example 2: This example differs from Example 1 in that the molar ratio of CuS microspheres to SnCl4·5H2O in step 2 (1) is 3:1; and step 2 (3) yields a CuS / SnS2 composite heterogeneous anode material (CuS / SnS2 = 3:1). All other steps and parameters are the same as in Example 1.

[0060] Example 3: This example differs from Example 1 in that the molar ratio of CuS microspheres to SnCl4·5H2O in step 2 (1) is 5:1; and step 2 (3) yields a CuS / SnS2 composite heterogeneous anode material (CuS / SnS2 = 5:1). Other steps and parameters are the same as in Example 1.

[0061] Comparative Example 1: A method for preparing a CuS / SnS2 electrode grown on carbon cloth is specifically completed by the following steps:

[0062] 1. Preparation of CuS microspheres:

[0063] ① Dissolve 3 mmol of Cu(NO3)2·3H2O and 0.5 g of polyvinylpyrrolidone in 60 mL of ethylene glycol, then add 9 mmol of thiourea and stir to obtain a clear solution;

[0064] ② Place the clarified solution in a stainless steel reactor lined with polytetrafluoroethylene, then place the stainless steel reactor in an oven and conduct a hydrothermal reaction at 160°C for 12 hours, then naturally cool to room temperature to obtain reaction product I;

[0065] ③. Centrifuge the reaction product I, then wash the solid product obtained after centrifugation 5 times with anhydrous ethanol, and then wash the solid product obtained after centrifugation 5 times with deionized water; finally, vacuum dry at 60°C for 10 hours to obtain CuS microspheres;

[0066] The centrifugal speed in step 1 (3) is 10,000 rpm and the centrifugal time is 7 min;

[0067] Second, CuS microspheres, carbon cloth, SnCl4·5H2O, thioacetamide, and anhydrous ethanol were placed in a stainless steel reactor for hydrothermal synthesis and heated at 160°C for 12 h. After the hydrothermal reaction, the mixture was allowed to cool naturally, washed five times with anhydrous ethanol and five times with deionized water, and then dried in vacuum at 60°C for 10 h to obtain a CuS / SnS2 electrode vertically grown on carbon cloth (CC / CuS / SnS2).

[0068] The molar ratio of the CuS microspheres to SnCl4·5H2O is 2:1;

[0069] The molar ratio of thioacetamide to SnCl4·5H2O is 4:1;

[0070] The volume ratio of the amount of the CuS microspheres to anhydrous ethanol is 2 mol:40 mL.

[0071] Figure 2 are scanning electron microscope images, in which ab are scanning electron microscope images of the CuS microspheres prepared in step 1 of Example 1, cd are scanning electron microscope images of the CuS / SnS2 composite heterogeneous negative electrode material prepared in step 2 of Example 2, and ef is a scanning electron microscope image of the CuS / SnS2 electrode grown on carbon cloth prepared in comparative example 1;

[0072] from Figure 2 It can be seen that: during the composite process, the CuS / SnS2 composite heterostructure is gradually transformed into a hollow sheet, the gaps between the nanosheets are gradually connected, and the sheet thickness becomes thinner. This morphology greatly increases the specific surface area of the entire structure, which will provide more sodium ion attachment sites, allowing the material to maintain a more stable structure, which helps to stabilize the material's structure and is conducive to maintaining the cycle stability of the electrode material.

[0073] Figure 3XRD spectra of CuS microspheres, SnS2, CuS / SnS2=2:1, CuS / SnS2=3:1, and CuS / SnS2=5:1 prepared in step 1 of Example 1;

[0074] from Figure 3 It can be seen that the main diffraction peaks of the CuS / SnS2=3:1 composite heterogeneous electrode material all correspond to the standard spectrum of CuS. Compared with the results of pure CuS microspheres, the intensity of each diffraction peak of the CuS / SnS2=3:1 sample prepared in Example 2 is significantly reduced, and the half-peak width is also widened.

[0075] Figure 4 Raman spectra of CuS microspheres, SnS2, CuS / SnS2=2:1, CuS / SnS2=3:1, and CuS / SnS2=5:1 prepared in step 1 of Example 1;

[0076] from Figure 4 It can be seen that the Raman spectrum of the CuS / SnS2=3:1 composite heterogeneous electrode material prepared in Example 2 is at 461 cm -1 The characteristic peak of Cu-S bond in copper sulfide is shown at 314 cm -1 There is a strong peak at the SnS2, which is the S stretching vibration (A 1g mode). Raman test results confirmed the existence of CuS / SnS2 in the composite heterostructure.

[0077] Figure 5 The CuS microspheres prepared in step 1 of Example 1, SnS2, CC / CuS / SnS2, CuS / SnS2=2:1, CuS / SnS2=3:1, and CuS / SnS2=5:1 prepared in Comparative Example 1 were heated to a current density of 0.1 A g -1 Cycling performance under

[0078] Figure 5 The test results show that the discharge capacity of the CuS / SnS2=3:1 composite heterogeneous electrode material prepared in Example 2 reaches the highest, and the first discharge capacity of the pure CuS electrode is 423.7 mAh g -1 and 565.5mAh g -1 The results show that the cycle performance is significantly improved after modification. The discharge capacity of the composite heteroelectrode of CuS / SnS2=3:1 can reach 376.1 mAh g after 50 cycles. -1 By comparison, it can be found that the initial capacity of the CC / CuS / SnS2 heterogeneous electrode material prepared in Comparative Example 1 is 325.8 mAh g -1 After 50 cycles, the capacity is 55.5 mAh g -1The above test results show that the formation of the CuS / SnS2=3:1 heterostructure prepared in Example 2 enhances its reaction kinetics, thereby greatly improving the rate performance of the electrode.

[0079] Figure 6 CuS / SnS2=3:1 at 5A g -1 Cycling performance under

[0080] Figure 6 The CuS / SnS2=3:1 composite heterogeneous electrode material prepared in Example 2 is -1 Cycling performance test under high current density shows that it can still maintain 281.2mAhg after 350 cycles. -1 The discharge specific capacity (the first 30 cycles are activation cycles) and the capacity attenuation rate is low.

[0081] Figure 7 Magnification diagrams of CuS microspheres, SnS2, CuS / SnS2=2:1, CuS / SnS2=3:1, and CuS / SnS2=5:1 prepared in step 1 of Example 1;

[0082] from Figure 7 It can be seen that the composite material of CuS / SnS2=3:1 has a -1 Still has 281.8mAh g -1 The discharge capacity is restored to 100mA g -1 The capacity can reach 379.5mAh g -1 This test result shows that the prepared composite material has good reversibility.

Claims

1. A method for preparing a CuS / SnS2 composite heterogeneous negative electrode material, characterized in that The preparation method is specifically completed according to the following steps:

1. Preparation of CuS microspheres: ① Dissolve Cu(NO3)2·3H2O and polyvinylpyrrolidone in ethylene glycol, then add thiourea and stir to obtain a clear solution; The volume ratio of the amount of Cu(NO3)2·3H2O described in step 1① to ethylene glycol is (2mmol~4mmol):60mL; The mass ratio of polyvinyl pyrrolidone described in step 1① to ethylene glycol is (0.3g~1g):60mL; The volume ratio of the amount of thiourea described in step 1① to ethylene glycol is (7mmol~11mmol):60mL; ②. Place the clarified solution in a stainless steel reactor lined with polytetrafluoroethylene, then place the stainless steel reactor in an oven, conduct a hydrothermal reaction at 150°C to 170°C for 10 hours to 14 hours, and then naturally cool to room temperature to obtain reaction product I; ③. Centrifuge the reaction product I, wash the solid product obtained after centrifugation, and vacuum dry it to obtain CuS microspheres; 2. Preparation of CuS / SnS2 composite heterostructure: ① Add SnCl4·5H2O and thioacetamide to anhydrous ethanol, sonicate for a period of time, then add CuS microspheres and stir to obtain a mixture; The molar ratio of CuS microspheres to SnCl4·5H2O described in step 2① is 3:1; The molar ratio of thioacetamide to SnCl4·5H2O described in step 2① is 4:1; ②. Place the mixture in a stainless steel reactor lined with polytetrafluoroethylene, then place the stainless steel reactor in an oven, conduct a hydrothermal reaction at 150°C to 170°C for 10 hours to 14 hours, and then naturally cool to room temperature to obtain reaction product II; ③. Centrifuge the reaction product II, wash the solid product obtained after centrifugation, and vacuum dry it to obtain a CuS / SnS2 composite heterogeneous negative electrode material.

2. The method for preparing a CuS / SnS2 composite heterogeneous negative electrode material according to claim 1, characterized in that The centrifugal speed described in step 1③ is 10000rpm, and the centrifugation time is 5min to 9min; in step 1③, the solid product obtained after centrifugation is first washed 3 to 5 times with anhydrous ethanol, and then the solid product obtained after centrifugation is washed 3 to 5 times with deionized water; the vacuum drying temperature described in step 1③ is 60℃ to 80℃, and the vacuum drying time is 8h to 12h.

3. The method for preparing a CuS / SnS2 composite heterogeneous negative electrode material according to claim 1, characterized in that The volume ratio of the amount of CuS microspheres described in step 2① to anhydrous ethanol is (2mol~5mol):(30mL~50mL); the ultrasonic time described in step 2① is 20min~40min; the stirring time described in step 2① is 10min~20min.

4. The method for preparing a CuS / SnS2 composite heterogeneous negative electrode material according to claim 1, characterized in that The centrifugal speed in step 2 (3) is 10,000 rpm, and the centrifugal time is 5 to 9 minutes.

5. The method for preparing a CuS / SnS2 composite heterogeneous negative electrode material according to claim 1, characterized in that In step 2③, the solid product obtained after centrifugation is first washed 3 to 5 times with anhydrous ethanol, and then washed 3 to 5 times with deionized water; the vacuum drying temperature in step 2③ is 60°C to 80°C, and the vacuum drying time is 8h to 12h.

6. Application of a CuS / SnS2 composite heterogeneous negative electrode material prepared by the preparation method according to claim 1, characterized in that A CuS / SnS2 composite heterogeneous negative electrode material is used as a negative electrode material for sodium ion batteries.

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