A tin cobalt selenide@C heterostructure composite material, a preparation method thereof, and an application thereof

Abstract

The present invention discloses a tin cobalt selenide @C heterostructure composite material, a preparation method thereof and an application, comprising the following steps: A. preparing a precursor SnCo(OH)6 by a coprecipitation method; B. coating a carbon layer on the precursor SnCo(OH)6 to obtain a composite material; C. performing a selenization reaction on the above composite material to obtain a selenized composite material; D. performing a carbonization reaction on the selenized composite material to obtain a tin cobalt selenide @C heterostructure composite material. Compared with the single structure of traditional anode materials for sodium-ion batteries, the present invention enhances the adsorption of sodium ions by the material by introducing a heterostructure, thereby improving the rate performance of the sodium-ion battery. At the same time, the box-type buffer structure can effectively maintain the volume change of the material during long-term cycling, improving the cycle stability of the sodium-ion battery.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium-ion batteries, and particularly to a tin cobalt selenide @C heterostructure composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Among existing energy storage devices, since sodium and lithium are in adjacent positions in the periodic table and have similar physical and chemical properties, and sodium-ion batteries are similar to lithium-ion batteries in terms of energy storage mechanism, production equipment, and manufacturing process, sodium-ion batteries with advantages such as low cost, rich resources, and high safety performance are considered to have potential applications in fields such as 3C, new energy power tools, and new energy storage power stations. Sodium-ion batteries mainly work by the movement of sodium ions between the positive electrode and the negative electrode. The electrode materials used in sodium-ion batteries are mainly sodium salts, which are more abundant in reserves and lower in price compared to lithium salts. Since sodium ions are larger than lithium ions, sodium-ion batteries are a cost-effective alternative when the requirements for weight and energy density are not high.

[0003] The composition structure of sodium-ion batteries is exactly the same as that of lithium-ion batteries, mainly including a positive electrode, a negative electrode, an electrolyte, a separator, a current collector, etc. The positive electrode materials of sodium-ion batteries are mainly divided into five types: oxides, polyanions, Prussian blue compounds, fluorides, and organic compounds. Among them, the first three types have the highest maturity and have entered the initial stage of industrialization. The negative electrode material of sodium-ion batteries plays an important role in loading and releasing sodium ions, which directly affects the overall kinetic performance of the battery. The negative electrode materials of sodium-ion batteries are mainly divided into five types: carbon-based materials, titanium-based materials, alloy materials, organic compounds, and other systems. Among them, carbon-based materials have the highest technical maturity, rich resources, and metal compounds have advantages such as high theoretical capacity and a rich variety of materials, and are widely studied at home and abroad. Metal compounds are mainly certain transition metal oxides, sulfides, selenides, nitrides, and phosphides. These compounds have reversible sodium storage electrochemical activity and often accompany conversion reactions and alloying reactions at the same time. Therefore, their theoretical specific capacity can exceed that of corresponding alloy-based negative electrode materials, but there are also more technical problems. For example, during the process of sodium ion insertion and extraction, they have large volume changes and poor structural stability, and their electrochemical performance needs to be improved.

[0004] Chinese Patent CN114477106A discloses a CoSe2-SnSe@CNF composite material. This composite material is prepared by electrospinning to obtain a precursor, then through a selenization reaction to obtain a nanofiber material mixed with CoSe2 / SnSe, and finally coated with CNF to obtain the composite material. This composite material has stable electrochemical performance, but also shows obvious disadvantages, mainly in the following aspects: First, the preparation process of the material is too cumbersome, and electrospinning is required. This process requires the application of a high-voltage power supply, which is likely to cause safety hazards to operators; Second, the cycle capacity is not high. Even at a current density of 1Ag-1D, it only shows a specific capacity of about 200mAhg -1 or so; At the same time, its rate performance is not good. As the current density increases, the battery specific capacity drops rapidly, which reflects the problem of low capacity when the battery undergoes high-current discharge. Summary of the Invention

[0005] The object of the present invention is to provide a tin cobalt selenide@C heterostructure composite material, its preparation method and application. In view of the above problems, the present invention designs a cubic structure with a buffering function and introduces a heterostructure to maintain the structural stability of the composite material, while enhancing the electrochemical performance of the composite material, thereby alleviating the volume expansion problem caused by the insertion and extraction of sodium ions. The prepared composite material exhibits excellent rate performance and cycle stability.

[0006] The technical solution adopted by the present invention is as follows: A preparation method of a tin cobalt selenide@C heterostructure composite material, comprising the following steps:

[0007] A. Prepare a precursor SnCo(OH)6 by coprecipitation method;

[0008] B. Coat a carbon layer on the precursor SnCo(OH)6 to obtain a composite material;

[0009] C. Perform a selenization reaction on the above composite material to obtain a selenized composite material;

[0010] D. Perform a carbonization reaction on the selenized composite material to obtain a tin cobalt selenide@C heterostructure composite material.

[0011] Further, the specific operation of step A is as follows:

[0012] A1. Dissolve a soluble salt of cobalt in a sodium salt solution (the sodium salt can be sodium citrate, sodium thiosulfate, sodium carbonate, sodium bicarbonate, sodium fluoride, sodium oxalate, sodium sulfite, etc., preferably sodium citrate), and stir to obtain solution A;

[0013] A2. Dissolve the soluble salt of tin in an alcohol solvent (the alcohol solvent can be ethanol, methanol, benzyl alcohol, ethylene glycol, etc., preferably ethanol), and obtain solution B after stirring;

[0014] A3. Mix solution A and solution B, and simultaneously add NaOH or / and KOH solution, and obtain the precursor SnCo(OH)6 after stirring and centrifuging.

[0015] Furthermore, in solution A and solution B, the molar ratio of cobalt to tin is 1:1; if the molar ratio of cobalt to tin is not 1:1, the purity of the formed substance is not high. When forming the target product SnCo(OH )6 at the same time, other impurity substances such as cobalt hydroxide and tin hydroxide will also be generated, resulting in the inability to carry out the subsequent preparation process.

[0016] Furthermore, the concentration of the NaOH or / and KOH solution is 1M - 2M, preferably 1.5M, and the molar ratio of OH - to cobalt ions or tin ions is 1.1 - 1.3:1.

[0017] Furthermore, the specific operation of step B is as follows: Prepare a HCl-Tris buffer solution (coating in the buffer solution can better control the coating thickness and uniformity, and the coating effect is good). Add the precursor SnCo(OH)6 into the HCl-Tris buffer solution, stir and disperse it, then add dopamine hydrochloride, and obtain the composite material after stirring and centrifuging. In the present invention, dopamine cannot be directly used for coating. Adding the precursor SnCo(OH)6 into the HCl-Tris buffer solution and stirring is mainly to make the Tris powder disperse more uniformly. After sufficient stirring for a long enough time, dopamine hydrochloride can be added; the purpose of using Tris is to stabilize the pH value of the solution and at the same time can be used as a surfactant to better promote the combination of the material surface and dopamine. Furthermore, the reason why other organic substances are not selected for coating in the present invention is that dopamine hydrochloride is extremely soluble in water and is a water-soluble substance. Adding dopamine hydrochloride to the Tris solution and stirring for 1 minute can completely dissolve it, while other organic substances such as free dopamine are unstable and are easily oxidized, so dopamine is not directly added.

[0018] Furthermore, the mass ratio of the precursor SnCo(OH)6, Tris, and dopamine hydrochloride is (3 - 5):(4 - 6):1 - 3. In the invention, the mass ratio of the precursor SnCo(OH)6, Tris, and dopamine hydrochloride needs to be in accordance with the above ratio. Beyond this range, various problems are likely to occur. For example, when Tris is in excess, it will affect the combination of dopamine hydrochloride and Tris in the buffer solution, thereby affecting the quality of the generated polydopamine, resulting in too high a concentration of the buffer solution and making it difficult to control the coating quality. In addition, the excessive Tris powder will also affect the pH value of the buffer solution, leading to a poor coating effect.

[0019] Furthermore, the specific operation of step C is as follows: Place the composite material and selenium powder in two magnetic boats. The mass ratio of the composite material to selenium powder is 1:2 - 10. Then, heat it to 300°C - 400°C in a hydrogen-containing atmosphere and keep it warm for 2h - 6h to obtain the selenized composite material. The doping amount of selenium powder should be controlled within a certain ratio and should not be too much or too little. Too little selenium powder will lead to insufficient reaction time, resulting in the product not meeting the target requirements; too much selenium powder will cause too long a selenization time, which may affect the material purity of the final product. At the same time, the selenium component in the selenide is not stable at high temperatures, and continuous heating will cause the selenium in the material to re-form into gas and escape. Therefore, the doping amount of selenium powder should be within the above range.

[0020] Furthermore, the hydrogen-containing atmosphere is a mixed atmosphere of hydrogen and an inert gas (hydrogen reacts with vaporized selenium vapor to generate H2Se). The flow rate ratio of hydrogen to the inert gas is 4 - 6:94 - 96 (the concentration of hydrogen should not be too high, as too high a hydrogen concentration poses a safety hazard in a heating environment). The flow rate of the mixed atmosphere is 4m 3 / h - 6m 3 / h.

[0021] Furthermore, the specific operation of step D is as follows: Sinter the selenized composite material in an inert gas atmosphere at 400°C - 600°C for 0.5h - 2h, and then cool it to obtain the product.

[0022] Furthermore, the present invention also includes a tin cobalt selenide@C heterostructure composite material, and the tin cobalt selenide@C heterostructure composite material is prepared by the above preparation method.

[0023] Furthermore, the present invention also includes an application of the tin cobalt selenide@C heterostructure composite material in a sodium-ion battery, using the above tin cobalt selenide@C heterostructure composite material as the negative electrode material of the sodium-ion battery.

[0024] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows:

[0025] 1. The SnCoSe@C heterostructure composite material prepared by the present invention has a particle size between 300 nm and 500 nm and is a core-shell box structure. Its inner core is a pure SnCoSe with a heterostructure, that is, a pure body with both CoSe and SnSe lattice structures, and its outer shell is a carbon coating layer with a thickness between 19 nm and 35 nm. This crystal structure can alleviate the volume expansion problem caused by the insertion and extraction of sodium ions, showing excellent rate performance and cycle stability.

[0026] 2. Compared with the single structure of traditional anode materials for sodium-ion batteries, the present invention can enhance the adsorption of sodium ions by the material through the introduced heterostructure, thereby improving the rate performance of sodium-ion batteries. At the same time, the box-type buffer structure can effectively maintain the volume change of the material during long-term cycling, improving the cycle stability of sodium-ion batteries.

[0027] 3. The preparation method of the present invention has few steps, is simple, has a wide range of raw material sources, and has strong industrial practicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is the morphology diagram of the precursor SnCo(OH prepared in Example 1 )6 ;

[0029] Figure 2 is the XRD diagram of the precursor SnCo(OH prepared in Example 1 )6 ;

[0030] Figure 3 is the graph of the graphitization morphology of the carbon coating layer of the SnCoSe@C heterostructure composite material prepared in Example 1;

[0031] Figure 4 is the morphology diagram of the SnCoSe@C heterostructure composite material prepared in Example 1;

[0032] Figure 5 is the XRD diagram of the SnCoSe@C heterostructure composite material prepared in Example 1;

[0033] Figure 6 is the TEM diagram of the SnCoSe@C heterostructure composite material prepared in Example 1;

[0034] Figures 7 - 10 is the XPS diagram of the SnCoSe@C heterostructure composite material prepared in Example 1;

[0035] Figure 11 is the cycle performance diagram of the sodium-ion battery formed by the SnCoSe@C heterostructure composite material prepared in Example 1;

[0036] Figure 12It is the rate performance graph of the sodium-ion battery formed by the tin cobalt selenide@C heterostructure composite material of Example 1;

[0037] Figures 13 - 18 It is the morphology graph of the composite materials obtained under different carbon coating times (6h, 8h, 10h, 12h, 14h, 16h) in Example 2 (the composite materials after the carbonization reaction). Specific embodiments

[0038] The present invention will be described in detail below with reference to the accompanying drawings.

[0039] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0040] It should be noted that the present invention relates to a tin cobalt selenide@C heterostructure composite material for sodium-ion batteries and is applied to the negative electrode of sodium-ion batteries. The technical and technological preparation schemes in the embodiments of the present invention will be described in detail and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Among them, the raw materials used in the following embodiments are all commercially available or self-made.

[0041] Example 1

[0042] A precursor SnCo(OH )6 , and its preparation method includes the following steps:

[0043] S1. Add 4 mmol of sodium citrate and cobalt chloride into a beaker containing deionized water, and stir at room temperature for 10 min to form solution A;

[0044] S2. Dissolve stannous chloride in 20 mL of absolute ethanol and stir for 10 minutes to form solution B;

[0045] S3. Quickly mix solutions B and A, where the molar ratio of cobalt to tin is 1:1, and then slowly add 30 mL of NaOH solution (concentration 1.5 M), control the dropping rate, and finish dropping within 10 min;

[0046] S4. Then continue to stir and react at room temperature for 10 h, and finally centrifuge to obtain a pink solid powder, which is the precursor SnCo(OH)6.

[0047] As Figure 1 and Figure 2 shown, inFigure 1 In the morphology diagram, we can see that the prepared precursor material presents a very uniform cubic structure, and the size of the particles is roughly the same. Figure 2 From the XRD diagram, it can be obtained that there are no characteristic peaks of impurities, which proves the high purity of the material. Moreover, the peak height and peak width of the characteristic peaks of the precursor indicate its good crystallinity.

[0048] Using the above-prepared precursor SnCo(OH )6 , prepare the composite material of PDA-coated SnCo(OH )6 . The preparation method includes the following steps:

[0049] S1. Add 605.7 mg of Tris to 400 mL of deionized water and stir for 3 minutes, then add 150 μL of HCl (concentration: 98%) dropwise to the above solution and stir for 6 hours to form an HCl-Tris buffer solution;

[0050] S2. Add the prepared SnCo(OH)6 powder to a beaker containing 90 mL of HCl-Tris buffer solution and stir for 30 minutes to disperse it fully;

[0051] S3. Add dopamine hydrochloride to the solution and stir vigorously for 12 h. The mass ratio of SnCo(OH)6 powder, Tris, and dopamine hydrochloride is 4:5:2;

[0052] S4. After the coating is completed, wash with deionized water and absolute ethanol to obtain a grass blue solid powder, which is the SnCo(OH)6@PDA composite material.

[0053] Furthermore, using the above-prepared SnCo(OH)6@PDA composite material as the raw material, prepare the tin cobalt selenide@C heterostructure composite material. The preparation method includes the following steps:

[0054] S1. Place the SnCo(OH)6@PDA composite material and selenium powder in a mass ratio of 1:5 in two magnetic boats. In a mixed atmosphere of hydrogen and argon (the volume ratio of H2 to Ar is 5:95, and the flow rate of the mixed gas is 5 m 3 / h), heat from room temperature to 350 °C at a heating rate of 2 °C / min, and then keep it at a constant temperature for 4 h for the selenization reaction. During the selenization reaction, the selenium powder should be placed near the inlet end, and the SnCo(OH)6@PDA composite material should be placed near the outlet end. Finally, obtain the tin cobalt selenide@PDA material;

[0055] S2. In an argon atmosphere, heat from room temperature to 500 °C at a heating rate of 2 °C / min and hold for 1 h to carry out the carbonization reaction on the cobalt tin selenide@PDA material, and finally obtain the cobalt tin selenide@C heterostructure composite material.

[0056] As Figures 3 - 6 shown, Figure 3 is the transmission morphology diagram of the composite material obtained after carbonization. It can be seen that obvious lattice fringes exist, proving that the graphitization degree of the coated PDA has been significantly improved after high-temperature sintering; Figure 4 is the morphology diagram of the product after selenization and carbonization. As can be obtained from Figure 4 , the morphology of the product has not changed compared with the precursor, but only the size uniformity has changed. It is speculated that the structure of the material may be affected during high-temperature selenization and carbonization; Figure 5 The XRD of Figure 6 describes the crystal structure information of the target product cobalt tin selenide@C, proving the high-purity characteristics of the material.

[0057] Furthermore, Figure 7 , Figure 8 , Figure 9 and Figure 10 are the XPS valence state analyses of C1s, Sn3d, Se3d, and Co2p of the constituent elements in the composite material respectively. Figure 7 shows that the peak positions at approximately 287.51, 285.71, and 284.61 eV correspond to carbon-oxygen, carbon-nitrogen, and carbon-carbon chemical bonds respectively. From Figure 8 , two peaks at 494.55 and 486.00 eV can be observed, which correspond to Sn 3d3 / 2 and Sn 3d5 / 2, confirming the presence of Sn in SnSe2. 4+ In Figure 9 , the 3d3 / 2 and 3d5 / 2 of Se 3d correspond to peaks at approximately 55.38 eV and 54.48 eV respectively. The valence state analysis of Co is shown in Figure 10 . Co 2p1 / 2 and 2p3 / 2 correspond to two relatively strong peaks located at 793.55 and 778.3 eV respectively.

[0058] Sodium-ion battery assembly and electrochemical performance test:

[0059] The cobalt tin selenide@C heterostructure composite material, conductive carbon black, and polyvinylidene fluoride (PVDF) binder are uniformly mixed in a mass ratio of 8:1:1 by the coating method, ground to obtain the negative electrode slurry, and then coated on the copper foil current collector and dried and cut into pieces to prepare the negative electrode of the sodium-ion battery.

[0060] Next, in a glove box under an argon atmosphere, using sodium flakes as the counter electrode and reference electrode, the positive electrode case, negative electrode case, glass fiber separator, sodium flakes, and electrolyte were assembled together into a CR2032-type button battery. The electrolyte was a diglyme solvent dissolved with 1 M of NaPF6.

[0061] The assembled sodium-ion battery was subjected to constant current charge-discharge tests in a BlueTEC test system. At current densities of 0.1 Ag -1 , 0.2 Ag -1 , 0.5 Ag -1 , 1.0 Ag -1 , 2.0 Ag -1 , 5.0 Ag -1 , within a voltage range of 0.01 V - 3 V, its rate performance and cycling performance were tested.

[0062] Test results

[0063] As Figure 11 shown, it can be found from Figure 11 that as the current density continuously increases, the battery capacity does not show an obvious decline. Among them, when the current density is 0.1 Ag -1 , the capacity can reach 400 mAh g -1 . When the current density continues to increase to 5.0 Ag -1 , the capacity reaches 380 mAh g -1 , which confirms that cobalt tin selenide@C has good rate performance; at the same time, when the current density returns to the initial value of 0.1 Ag -1 , the capacity increases to a certain extent, reaching a specific capacity of 420 mAh g -1 , which is due to the activation of the battery with a small current. Figure 12 shows that the battery can still exhibit a specific capacity close to 320 mAh g -1 after continuous charge and discharge at a high current density of 2.0 Ag -1 for 500 cycles, and the capacity retention rate is close to 100%, and the capacity is well maintained, with almost no attenuation.

[0064] Example 2

[0065] Example 2 was the same as Example 1, except that when performing PDA coating on the precursor SnCo(OH)6, the influence of stirring time on the coating effect was investigated. Among them, the stirring time was set to 6 h, 8 h, 10 h, 12 h, 14 h, and 16 h.

[0066] The test results are as Figures 13 - 18 shown. It can be obtained from Figures 13 - 18 that the material morphology and structure were fragmented to varying degrees, especially at 6 h of stirringFigure 13 Among them, the fragmentation of the material is relatively obvious because the coating is too thin due to insufficient stirring time, while Figure 17 and Figure 18 showed the phenomenon of excessive dopamine aggregation on the material surface due to too long stirring time. Especially in Figure 18 this phenomenon is more obvious, while Figure 16 The morphology diagram shown is after 12 hours of stirring time. It can be seen that the material morphology is maintained, and the surface is relatively smooth without excessive dopamine aggregation. Therefore, it is more appropriate to control the stirring time at 12 hours.

[0067] Example 3

[0068] Example 3 is the same as Example 1, except that cobalt chloride is replaced by cobalt sulfate and stannous dichloride is replaced by tin sulfate, and other conditions are the same.

[0069] Implementation result: The same cobalt stannous selenide@C heterostructure composite material as in Example 1 was obtained.

[0070] Electrochemical performance test: At a current density of 0.1 Ag -1 the specific capacity is stable at about 370 mAhg -1 and at a current density of 5.0 Ag -1 the specific capacity is stable at about 350 mAhg -1 ; meanwhile, after 500 charge-discharge cycles at a current density of 2.0 Ag -1 the specific capacity remains at about 305 mAhg -1 . Example 4

[0071] Example 4 is the same as Example 1, except that cobalt chloride is replaced by cobalt carbonate and stannous dichloride is replaced by tin carbonate, and other conditions are the same.

[0072] Implementation result: The same cobalt stannous selenide@C heterostructure composite material as in Example 1 cannot be obtained.

[0073] Example 5

[0074] Example 5 is the same as Example 1, except that the mass ratio of SnCo(OH)6@PDA composite material to selenium powder is 1:10, and other conditions are the same.

[0075] Implementation result: The same cobalt stannous selenide@C heterostructure composite material as in Example 1 can be obtained, but too much selenium powder forms too much selenium vapor during heating, posing a safety hazard to the experimental personnel.

[0076] Electrochemical performance test results: At a current density of 0.1 Ag -1 the specific capacity is stable at 375 mAhg-1 or so, at 5.0 Ag -1 current density, the specific capacity is stable at about 355 mAh g -1 or so; meanwhile, at 2.0 Ag -1 after 500 charge-discharge cycles at current density, the specific capacity remains at about 300 mAh g -1 or so. Example 6

[0077] Example 6 is the same as Example 1, except that the molar ratio of cobalt to tin is 2:1 and other conditions are the same.

[0078] Implementation result: The same box material structure as that in Example 1 cannot be obtained. Among them, about half of the cobalt ions co-precipitate with tin metal ions to form a cubic material structure, but about half of the cobalt ions will react with hydroxide ions in the solution to form cobalt hydroxide precipitate, resulting in low purity of the obtained product and inconsistent morphology. In the subsequent carbon coating process, due to the uneven morphology of the material, dopamine covers the surface of the material, and the material is not coated comprehensively.

[0079] Example 7

[0080] Example 7 is the same as Example 1, except that HCl-Tris solution is not used and other conditions are the same.

[0081] Implementation result: Cobalt tin selenide heterostructure material can be obtained, but the same box material structure as that in Example 1 cannot be obtained. Although the cubic morphology of the box of the material can be partially maintained, due to the lack of HCl-Tris solution to protect the pH stability of the reaction system, uneven coating is caused during the stirring coating process, and even some parts cannot be coated. These parts will break during the selenization process.

[0082] Electrochemical performance test results: At 0.1 Ag -1 current density, the specific capacity is stable at about 350 mAh g -1 or so, at 5.0 Ag -1 current density, the specific capacity is stable at about 330 mAh g -1 or so; meanwhile, at 2.0 Ag -1 continuous charge-discharge is carried out at current density. At the beginning, the specific capacity can reach about 330 mAh g -1 or so, but as the cycle progresses, the stability of the material shows serious damage. After 500 cycles, the specific capacity decays severely, and at this time the capacity only remains at about 260 mAh g -1 or so.

[0083] Example 8

[0084] Example 8 is the same as Example 1, except that carbon coating is not carried out. After obtaining the precursor SnCo(OH )6 , the selenization reaction is directly carried out, and other conditions are the same.

[0085] Implementation result: A tin cobalt selenide heterostructure material can be obtained, and the same box material structure as in Example 1 cannot be obtained. Due to the lack of protection of porous carbon with stretching effect, the cubic morphology of the material is damaged during the selenization process, and the material morphology shows a large degree of aggregation.

[0086] Electrochemical performance test results: At a current density of 0.1 Ag -1 , the specific capacity is stable at about 320 mAh g -1 . At a current density of 5.0 Ag -1 , the specific capacity is stable at about 300 mAh g -1 . At the same time, when charging and discharging are continuously carried out at a current density of 2.0 Ag -1 , the specific capacity can reach about 300 mAh g -1 at the beginning. However, with the progress of the cycle, the stability of the material is severely damaged. After 500 cycles, the specific capacity decays severely, and the capacity only remains at about 220 mAh g -1 at this time. The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a tin cobalt selenide @C heterostructure composite material, characterized in that, It includes the following steps: A. Prepare the precursor SnCo(OH)6 by the coprecipitation method; B. Coating a carbon layer on the precursor SnCo(OH)6 to obtain a composite material. The specific operation is as follows: Prepare an HCl-Tris buffer solution, add the precursor SnCo(OH)6 into the HCl-Tris buffer solution, after stirring and dispersing, add dopamine hydrochloride, stir and then centrifuge to obtain the composite material. The mass ratio of the precursor SnCo(OH)6, Tris, and dopamine hydrochloride is 3-5:4-6:1-3; C. Carry out a selenization reaction on the above composite material to obtain the selenized composite material. The specific operation is as follows: Place the composite material and selenium powder in two magnetic boats, the mass ratio of the composite material to selenium powder is 1:2-10, then heat up to 300°C - 400°C in a hydrogen-containing atmosphere, keep warm for 2h - 6h, and then obtain the selenized composite material; D. Carry out a carbonization reaction on the selenized composite material to obtain the tin cobalt selenide@C heterostructure composite material. The specific operation is as follows: Sinter the selenized composite material in an inert gas atmosphere at 400°C - 600°C for 0.5h - 2h, and then obtain it after cooling.

2. The preparation method according to claim 1, characterized in that, The specific operation of step A is as follows: A1. Dissolve the soluble salt of cobalt in the sodium salt solution, and stir to obtain solution A; A2. Dissolve the soluble salt of tin in the alcohol solvent, and stir to obtain solution B; A3. Mix solution A and solution B, and at the same time add NaOH or / and KOH solution, stir and then centrifuge to obtain the precursor SnCo(OH)6.

3. The preparation method according to claim 2, characterized in that, In solution A and solution B, the molar ratio of cobalt to tin is 1:1; the concentration of the NaOH or / and KOH solution is 1 M - 2 M, and the molar ratio of OH - to cobalt ions or tin ions is 1.1 - 1.3:

1.

4. The preparation method according to claim 1, characterized in that, The hydrogen-containing atmosphere is a mixed atmosphere of hydrogen and an inert gas, and the flow rate ratio of hydrogen to the inert gas is 4-6:94-96. The flow rate of the mixed atmosphere is 4 m 3 / h - 6 m 3 / h.

5. A cobalt tin selenide @C heterostructure composite material, characterized in that, The tin cobalt selenide@C heterostructure composite material is prepared by the preparation method described in any one of claims 1-4 above.

6. Application of a tin cobalt selenide@C heterostructure composite material in a sodium ion battery, characterized in that, Use the tin cobalt selenide@C heterostructure composite material described in claim 5 as the negative electrode material of the sodium ion battery.

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