A CuS / C composite positive electrode material rich in carbon-sulfur heterojunction interfaces, and a preparation method and application thereof

Abstract

The application provides a CuS / C composite positive electrode material rich in carbon-sulfur heterojunctions and a preparation method thereof, a CuS nanoparticle is anchored on a carbon base material, and a rich carbon-sulfur (C-S) heterojunction is successfully constructed. The carbon-sulfur bond outside the plane effectively activates the Cu-S tetrahedral structure, and at the same time, the formation energy barrier of a disulfide bond (S-S) in CuS is reduced, so that the reversible phase change ability of Cu2S and CuS in the charging and discharging process is significantly improved. The composite positive electrode material provided by the application effectively alleviates the problem of copper ion dissolution caused by volume expansion, so that the cycle stability and electrochemical performance of the material are significantly improved, efficient magnesium ion transmission is realized, and a new direction is provided for developing conversion type positive electrode materials with fast ion kinetics and long cycle life.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nanomaterials and electrochemistry, and particularly relates to a CuS / C composite positive electrode material rich in carbon-sulfur heterojunctions, and a preparation method and application thereof. BACKGROUND

[0002] Lithium-ion batteries (LIBs) are one of the most advanced energy storage technologies, widely used in electric vehicles and portable electronic devices. However, the scarcity (only 0.0022 wt%) and uneven distribution of lithium resources in the earth's crust limit its sustainable development. Therefore, it is particularly important to develop new battery systems. Magnesium (Mg) is an element that is abundant in resources and has a small ionic radius (0.72 Å). Magnesium batteries not only have a higher energy density than LIBs, but also do not form dendrites during the cycling process, thereby having higher safety. However, the divalent Mg 2+ Strong electrostatic interaction with the host material leads to slow diffusion kinetics during intercalation / deintercalation, thereby affecting the cycling stability. Therefore, finding suitable positive electrode materials to achieve efficient and stable Mg 2+ storage has become the focus of current research.

[0003] In terms of magnesium ion storage, inorganic positive electrode materials are mainly divided into intercalation type and conversion type. Intercalation type positive electrode materials (such as V2O5, MoO3) are widely studied due to their high working voltage and small voltage hysteresis, but their capacity is relatively limited. In comparison, conversion type positive electrode materials utilize the multivalent state of elements, are not limited by fixed crystal structures, and exhibit higher theoretical capacity. CuS, as a typical conversion type material, has a theoretical capacity of about 560 mAhg -1 , and is low in cost, so it has attracted much attention. However, the poor phase transition reversibility of CuS during the cycling process limits its application. After comparing the crystal structures of Cu2S and CuS, we speculate that the formation of S-S bonds is a key step in phase transition.

[0004] In summary, reducing the formation energy of S-S bonds, promoting the conversion of Cu2S to CuS, and reducing copper ion dissolution to achieve fast diffusion of Mg 2+ , thereby improving the coulombic efficiency and cycling stability of magnesium batteries, is a problem that needs to be solved urgently. SUMMARY

[0005] The conversion type positive electrode becomes a promising positive electrode material in rechargeable magnesium batteries (RMBs) due to its multi-valence state transition and high energy density. However, its development is limited by poor phase transition reversibility and serious active material shuttling phenomenon. Therefore, the application provides a CuS / C composite positive electrode material rich in carbon-sulfur heterojunction and a preparation method thereof to solve the problems of low capacity, poor stability and low coulomb efficiency of the copper sulfide positive electrode in the existing magnesium battery. The C-S bond at the interface of the CuS positive electrode can activate the stable Cu-S tetrahedral structure and reduce the formation energy of the disulfide bond (S-S) in CuS, promoting the reversible phase transition of Cu2S to copper sulfide.

[0006] To achieve the above-mentioned purpose, the application provides a CuS / C composite positive electrode material rich in carbon-sulfur heterojunction, characterized in that the composite positive electrode material comprises a carbon base material and CuS nanoparticles distributed on the surface of the carbon base material, the CuS nanoparticles are in close contact with the carbon base, and a heterojunction containing a carbon-sulfur bond is formed at the interface between the CuS nanoparticles and the carbon base.

[0007] Further, the carbon base material is one or several of graphene, Ketjen black, porous carbon, acetylene black, carbon nanotubes and carbon fibers, preferably graphene.

[0008] Further, in the composite positive electrode material, the mass fraction of the carbon base material is 10% to 30%.

[0009] Further, the CuS nanoparticles have a hexagonal phase.

[0010] Further, the CuS nanoparticles have a hexagonal phase.

[0011] Further, the CuS nanoparticles have a hexagonal phase.

[0012] S1, copper salt and tris(hydroxymethyl) aminomethane are added to a solution containing a carbon base material respectively, and a mixed solution A is obtained after sufficient stirring;

[0013] S2, ammonia solution is added to the mixed solution A, and a mixed solution B is obtained after sufficient stirring;

[0014] S3, NaOH solution is added to the mixed solution B, and a mixed solution C is obtained after sufficient stirring;

[0015] S4, thiourea solution is added to the mixed solution C, and a mixed solution D is obtained after sufficient stirring;

[0016] S6, the mixed solution E is heated in a water bath, and then the precipitate thereof is washed with deionized water and ethanol alternately for multiple times, and vacuum dried to obtain a CuS / C composite positive electrode material rich in carbon-sulfur heterojunction.

[0017] Further, the copper salt is one or more of chloride, sulfate, nitrate and acetate of copper.

[0018] Further, in step S1, the molar ratio of the copper salt to tris(hydroxymethyl)aminomethane is 1:1-5; preferably, the molar ratio is 1:1-3; and the concentration of the carbon-based material is 1 mg / mL.

[0019] Further, in step S2, the volume of the ammonia solution added is 5 mL-20 mL, and the concentration of the ammonia solution is 2M; in step S3, the volume of the NaOH solution added is 5 mL-20 mL, and the concentration of the NaOH solution is 1M; and in step S4, the volume of the thiourea solution added is 1 mL-10 mL, and the concentration of the thiourea solution is 1M.

[0020] Further, in step S5, the standing time is 1 h-5 h; the volume of the hydrazine hydrate solution added is 1 mL-20 mL, and the mass fraction of hydrazine hydrate in the hydrazine hydrate solution is 80%; in step S6, the water bath heating temperature is 50 ℃-80 ℃, and the time is 2 h-4 h; and the vacuum drying temperature is 50 ℃-80 ℃, and the time is 4 h-12 h.

[0021] Also provided is the use of the above-mentioned nanocomposite and the above-mentioned method for preparing the nanocomposite in a magnesium ion battery.

[0022] The present application has the following beneficial effects:

[0023] (1) In the customized copper sulfide positive electrode material structure rich in carbon-sulfur (C-S) heterojunction, the carbon-sulfur (C-S) bond at the interface effectively reduces the activation energy of the sulfur atom in the Cu-S tetrahedron, reduces the formation energy of the S-S bond, and promotes the conversion between Cu2S and CuS in the charging and discharging process.

[0024] (2) By realizing more reversible phase transition, the composite material in the present application effectively alleviates the volume expansion of the CuS positive electrode in the cycling process, inhibits the shuttle effect of copper ions, and thus improves the cycle stability and efficiency of the battery.

[0025] (3) The present application provides a feasible strategy for developing high-energy multi-valence ion batteries, which promotes reversible phase transition and inhibits the shuttle effect of conversion-type positive electrode active materials. In addition, the preparation method of the present application is simple, the raw materials are cheap and easy to obtain, and is suitable for large-scale production and has marketization promotion potential. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 This is a SEM image of the CuS / C composite cathode material rich in carbon-sulfur heterostructure as described in Example 1 of this invention;

[0027] Figure 2 These are TEM, HRTEM, and SAED images of the CuS / C composite cathode material rich in carbon-sulfur heterostructure as described in Example 1 of this invention.

[0028] Figure 3 This is a Raman comparison diagram of the CuS / C composite cathode material rich in carbon-sulfur heterostructure described in Example 1 of the present invention and copper sulfide.

[0029] Figure 4 This is a comparison of cyclic voltammetry between the CuS / C composite cathode material rich in carbon-sulfur heterostructure described in Example 1 of this invention and the copper sulfide cathode.

[0030] Figure 5 Comparison of cycle performance between CuS / C composite cathode material rich in carbon-sulfur heterostructure and copper sulfide cathode as described in Example 1 of this invention;

[0031] Figure 6 A comparison of the rate performance of the CuS / C composite cathode material rich in carbon-sulfur heterostructure and the copper sulfide cathode described in Example 1 of this invention. Detailed Implementation

[0032] To make the technical solution and advantages of the present invention clearer, the present invention and its beneficial effects will be described in further detail below with reference to specific embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0033] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0034] Example 1

[0035] This embodiment provides a method for preparing a CuS / C composite cathode material rich in carbon-sulfur heterostructure, including the following steps:

[0036] S1. CuCl2·H2O powder and tris(hydroxymethyl)aminomethane powder are added to graphene oxide solution and stirred thoroughly to obtain mixed solution A;

[0037] S2. Add the ammonia solution to the mixed solution A, and stir thoroughly to obtain the mixed solution B;

[0038] S3. Add NaOH solution to mixed solution B and stir thoroughly to obtain mixed solution C;

[0039] S4. Add thiourea solution to mixed solution C, and stir thoroughly to obtain mixed solution D;

[0040] S5. After letting the mixed solution D stand, pour off the supernatant, then add the hydrazine hydrate solution to the mixed solution D, and stir thoroughly to obtain the mixed solution E;

[0041] S6. After heating the mixed solution E in a water bath, the precipitate was washed repeatedly with deionized water and ethanol, and then dried under vacuum to obtain a copper sulfide cathode material rich in carbon-sulfur (CS) heterostructure.

[0042] 1) Under normal temperature conditions, take 60 ml of graphene oxide (1 mg / ml) and place it in a beaker. Then weigh 0.85 g of CuCl2·H2O powder and 1.75 g of tris(hydroxymethyl)aminomethane powder and pour them into the beaker. Stir magnetically for ten minutes to obtain a uniform mixed solution A.

[0043] 2) Add another 10 ml of ammonia solution to mixed solution A, and stir magnetically for ten minutes to obtain a homogeneous mixed solution B;

[0044] 3) Weigh another 10 ml of NaOH solution and pour it into mixed solution B. Stir magnetically for ten minutes to obtain a homogeneous mixed solution C.

[0045] 4) Add another 6 ml of thiourea solution to mixed solution C, and stir magnetically for ten minutes to obtain a homogeneous mixed solution D;

[0046] 5) After letting the mixed solution D stand for 3 hours, pour off the supernatant, then dilute 5 ml of hydrazine hydrate solution with deionized water to 50 ml, add it to the mixed solution D, and stir thoroughly to obtain a homogeneous mixed solution E;

[0047] 6) The mixed solution E was heated in a water bath for 3 hours, and then the precipitate was washed repeatedly with deionized water and ethanol alternately. It was then dried in a vacuum drying oven at 60 °C for 6 hours to obtain a CuS / C composite cathode material rich in carbon-sulfur heterostructure.

[0048] The performance of the CuS / C composite cathode material rich in carbon-sulfur heterostructure prepared in Example 1 was tested, and the results are as follows: Figures 1-3 As shown.

[0049] Figure 1 This is a scanning electron microscope (SEM) image of a CuS / C composite cathode material rich in carbon-sulfur heterostructures. The image shows that CuS nanoparticles are uniformly dispersed on a graphene substrate, in close contact with the graphene, forming numerous carbon-sulfur (CS) heterostructures.

[0050] Figure 2 Transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) images of CuS nanoparticles are shown. The TEM images reveal the partial dispersion and encapsulation of CuS nanoparticles on the surface of graphene sheets, validating the SEM observations. HRTEM analysis shows two distinct lattice patterns in the CuS-graphene composite structure. The clear lattice spacing of 3.23 Å ​​corresponds to the (101) crystal plane of hexagonal CuS, while the blurred green area indicates an amorphous graphene structure. Furthermore, the lattice patterns gradually transition to an amorphous phase without clear domain boundaries, indicating an interaction between the CuS nanoparticles and graphene. The SAED images further confirm this interaction, showing the diffraction points corresponding to the (110) and (102) crystal planes of polycrystalline CuS and the (002) crystal plane of graphene.

[0051] Figure 3 This is a comparison of the Raman spectra of CuS / C composite cathode material rich in carbon-sulfur heterostructures and pure CuS. As can be seen from the figure, the Raman spectrum of pure CuS is at 455 cm⁻¹. -1 There is a significant peak at 1349 cm⁻¹, corresponding to the SS bond vibration mode in the crystal structure. In contrast, the Raman spectrum of the CuS@G composite material exhibits characteristic peaks of graphene, with peaks at 1349 cm⁻¹. -1 (D belt) and 1595 cm -1 (G-band). Additionally, 601 cm -1 and 1054 cm -1 The new peak at this point is attributed to the vibrational mode of the CS bond, indicating the existence of abundant CS heterointerfaces between CuS and graphene.

[0052] The CuS / C composite cathode material rich in carbon-sulfur heterostructure prepared in Example 1 was directly used as the cathode, a magnesium sheet as the anode, Mg(MPFB)₂ as the electrolyte, and GF / D glass fiber as the separator to assemble a CR2016 coin cell. The coin cell was tested, and the results are as follows: Figures 4-6 As shown.

[0053] Figure 4 The cyclic voltammetry (CV) curves of the CuS / C composite cathode material rich in carbon-sulfur (CS) heterointerfaces are compared with those of the pure CuS cathode. The comparison shows that the introduction of graphene significantly affects the morphology of the CV curves. In the first three cycles, the reduction peak intensity of the pure CuS cathode decreases progressively, while the peak intensity of the copper sulfide cathode rich in CS heterointerfaces remains relatively stable. After the first 10 cycles, the CV curve of the pure CuS cathode shows two distinct reduction peaks at 1.75 V and 1.90 V. In contrast, the copper sulfide cathode rich in CS heterointerfaces shows three clear reduction peaks at 1.54 V, 1.80 V, and 1.90 V in the third cycle, indicating a more reversible phase transition process during charging.

[0054] Figure 5 This is a comparison of the cycle performance of the CuS / C composite cathode material rich in carbon-sulfur heterostructures and the pure CuS cathode. The specific capacity of the pure CuS cathode decays rapidly, while the specific capacity of the copper sulfide cathode rich in carbon-sulfur heterostructures remains constant at 100 mA g. -1 After 100 cycles at the current density, it exhibits a stable specific capacity of 212 mAh g⁻¹. -1 And maintain 83.2% of the initial capacity.

[0055] Figure 6 This chart compares the rate performance of the CuS / C composite cathode material rich in carbon-sulfur heterointerfaces with that of pure CuS cathodes. The copper sulfide cathode rich in carbon-sulfur heterointerfaces achieves a significant improvement in rate performance. (At 50 mA g...) -1 At current density, its specific capacity exceeds 280 mAh g. -1 Even if the current density is increased to 1 A g -1 The copper sulfide cathode rich in carbon-sulfur heterostructure still maintains 160.5 mAh g⁻¹. -1 The specific capacity is equivalent to 57.3% of the initial specific capacity, demonstrating excellent rate performance.

[0056] In summary, the test results show that CuS / C composite cathode materials rich in carbon-sulfur heterostructures have excellent electrochemical performance and can be used in highly reversible magnesium batteries.

[0057] Example 2

[0058] The difference between this embodiment and Embodiment 1 is that:

[0059] At room temperature, 60 ml of graphene oxide (0.5 mg / ml) was placed in a beaker, and then 0.85 g of CuCl2·H2O powder and 1.75 g of tris(hydroxymethyl)aminomethane powder were weighed and poured into the beaker. After stirring magnetically for ten minutes, a homogeneous mixed solution A was obtained.

[0060] The remaining steps and parameters are the same as in Example 1.

[0061] Using the CuS / C composite cathode material rich in carbon-sulfur heterostructure obtained in Example 2 as the cathode assembly electrode, coin cells were assembled and tested according to the above method. The test results showed that at 0.1 A g... -1 At the given current density, the discharge capacity of the electrode is 197 mAh g. -1 The capacity retention rate was only 68%. Analysis showed that the electrochemical performance of the material was poor when the graphene content was low (10%). Further analysis suggested that when the graphene content was low (10%), fewer CS bonds were formed between the copper sulfide nanoparticles and graphene, which limited the promoting effect on the reversible phase transformation of copper sulfide, resulting in poor performance.

[0062] Example 3

[0063] The difference between this embodiment and Embodiment 1 is that:

[0064] At room temperature, 60 ml of graphene oxide (1.5 mg / ml) was placed in a beaker, and 0.85 g of CuCl2·H2O powder and 1.75 g of tris(hydroxymethyl)aminomethane powder were weighed and poured into the beaker. After stirring magnetically for ten minutes, a homogeneous mixed solution A was obtained.

[0065] The remaining steps and parameters are the same as in Example 1.

[0066] Using the CuS / C composite cathode material rich in carbon-sulfur heterostructure obtained in Example 3 as the cathode assembly electrode, coin cells were assembled and tested according to the above method. The test results showed that at 0.1 A g... -1 At the current density, the discharge capacity of the electrode is 228 mAh g. -1 The capacity retention rate was only 80%. Analysis showed that the electrochemical performance of the material decreased when the graphene content was high (30%). Further analysis suggested that when the graphene content was high (30%), copper sulfide only formed CS bonds with graphene at the interface, while graphene at greater distances could not participate, thus failing to promote the reversible phase transition and contributing little to the capacity, leading to the performance degradation.

[0067] Example 4

[0068] The difference between this embodiment and Embodiment 1 is that:

[0069] At room temperature, 60 g of Ketjen black (1 mg / ml) was placed in a beaker, and then 0.85 g of CuCl2·H2O powder and 1.75 g of tris(hydroxymethyl)aminomethane powder were weighed and poured into the beaker. After stirring magnetically for ten minutes, a homogeneous mixed solution A was obtained.

[0070] The remaining steps and parameters are the same as in Example 1.

[0071] Using the copper sulfide material rich in carbon-sulfur heterostructure obtained in Example 4 as the positive electrode, coin cells were assembled and tested according to the above method. Test results showed that at 0.1 A g... -1 At the current density, the discharge capacity of the electrode is 201 mAh g. -1 The capacity retention was only 76%. Analysis revealed that the two-dimensional structure of graphene (rGO) can anchor more CuS nanoparticles, and the CuS nanoparticles can be better dispersed on the carbon material surface, successfully constructing abundant carbon-sulfur (CS) heterointerfaces. Ordinary carbon materials cannot adequately anchor CuS nanoparticles; therefore, the content of materials capable of forming carbon-sulfur (CS) heterointerfaces is relatively low, limiting the promoting effect on the reversible phase transformation of copper sulfide, resulting in limited capacity contribution and performance degradation.

[0072] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A CuS / C composite cathode material rich in carbon-sulfur heterostructure, characterized in that, The composite cathode material includes a carbon substrate and CuS nanoparticles distributed on the surface of the carbon substrate. The CuS nanoparticles are in close contact with the carbon substrate, and a heterogeneous interface containing carbon-sulfur bonds is formed at the interface between the CuS nanoparticles and the carbon substrate. The preparation method of the CuS / C composite cathode material includes the following steps: S1. Add copper salt and tris(hydroxymethyl)aminomethane to a solution containing carbon substrate material respectively, and stir thoroughly to obtain mixed solution A; S2. Add the ammonia solution to the mixed solution A, and stir thoroughly to obtain the mixed solution B; S3. Add NaOH solution to mixed solution B and stir thoroughly to obtain mixed solution C; S4. Add thiourea solution to mixed solution C, and stir thoroughly to obtain mixed solution D; S5. After letting the mixed solution D stand, pour off the supernatant, then add the hydrazine hydrate solution to the mixed solution D, and stir thoroughly to obtain the mixed solution E. S6. The mixed solution E is heated in a water bath, and then its precipitate is washed repeatedly with deionized water and ethanol alternately, and then dried under vacuum to obtain a CuS / C composite cathode material rich in carbon-sulfur heterostructure.

2. The CuS / C composite cathode material rich in carbon-sulfur heterostructure according to claim 1, characterized in that, The carbon substrate material is one or more of graphene, Ketjen black, porous carbon, acetylene black, carbon nanotubes, and carbon fiber.

3. The CuS / C composite cathode material rich in carbon-sulfur heterostructure according to claim 2, characterized in that, The carbon substrate material is graphene.

4. The CuS / C composite cathode material rich in carbon-sulfur heterostructure according to claim 1, characterized in that, In the composite cathode material, the mass fraction of carbon substrate material is 10% to 30%.

5. The CuS / C composite cathode material rich in carbon-sulfur heterostructure according to claim 1, characterized in that, The CuS nanoparticles have a hexagonal phase.

6. The CuS / C composite cathode material rich in carbon-sulfur heterostructure according to claim 1, characterized in that, Copper salts are one or more of the following: copper chloride, sulfate, nitrate, and acetate.

7. The CuS / C composite cathode material rich in carbon-sulfur heterostructure according to claim 1, characterized in that, In step S1, the molar ratio of copper salt to tris(hydroxymethyl)aminomethane is 1:1-5.

8. The CuS / C composite cathode material rich in carbon-sulfur heterostructure according to claim 7, characterized in that, In step S1, the molar ratio of copper salt to tris(hydroxymethyl)aminomethane is 1:1-3.

9. The CuS / C composite cathode material rich in carbon-sulfur heterostructure according to claim 1, characterized in that, In step S2, the volume of the ammonia solution added is 5 mL to 20 mL; in step S3, the volume of the NaOH solution added is 5 mL to 20 mL; in step S4, the volume of the thiourea solution added is 1 mL to 10 mL.

10. The CuS / C composite cathode material rich in carbon-sulfur heterostructure according to claim 1, characterized in that, In step S5, the standing time is 1 h-5 h; the volume of hydrazine hydrate solution added is 1 mL-20 mL; in step S6, the water bath heating temperature is 50 ℃-80 ℃ and the time is 2 h-4 h; the vacuum drying temperature is 50 ℃-80 ℃ and the time is 4 h-12 h.

11. The use of the CuS / C composite cathode material rich in carbon-sulfur heterostructure as described in any one of claims 1-10 in magnesium-ion batteries.

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