Preparation method of metal sulfide modified porous carbon-based selenium positive electrode material

Abstract

The application provides a preparation method of a metal sulfide modified porous carbon selenium positive electrode material, and belongs to the technical field of lithium selenium battery positive electrode materials. The main purpose is to comprehensively improve the shuttle effect and the serious volume expansion in the lithium selenium battery. The main scheme comprises the following steps: high-temperature pyrolysis and etching of zeolite imidazolate framework coated with silicon dioxide SiO2@ZIF8 to obtain a porous carbon carrier; fully mixing the porous carbon carrier with a NiCl2.6H2O or FeCl3.6H2O or CoCl2.6H2O solution, and performing centrifugal drying and other steps to obtain a powder; mixing the obtained powder with sublimed sulfur according to a certain proportion, and then performing gas phase sulfuration at 350 DEG C for 3h in a tube furnace in an argon atmosphere to obtain a metal sulfide loaded three-dimensional porous carbon. The product is used as a battery positive electrode material.

Description

Technical Field

[0001] This invention belongs to the field of lithium selenium battery cathode material technology, specifically relating to a method for preparing a porous carbon-based selenium cathode material modified with metal sulfides. Background Technology

[0002] Due to the increasing demand for energy storage, extensive research has been conducted on the development of advanced rechargeable energy storage devices. Among various energy storage systems, lithium selenide batteries are considered one of the most promising next-generation energy storage systems due to their high energy density, low cost, and environmental friendliness. However, their slow electrochemical redox reaction, low utilization rate of active materials caused by the shuttle effect, and volume expansion during the reaction process have greatly hindered the development and application of lithium selenide batteries. To solve these problems, it is crucial to rationally construct the host material for the selenium cathode. An ideal host material should meet the following criteria: (1) high conductivity to accelerate electron transfer and improve the utilization rate of active materials; (2) high porosity to improve Se loading capacity and alleviate volume expansion during cycling; and (3) abundant chemisorption active sites to accelerate the catalytic conversion of lithium polyselenide.

[0003] Due to their high electrical conductivity, carbonaceous materials have been commonly chosen as host materials in previous studies. Various materials, such as carbon nanotubes, carbon nanofibers, carbon nanosheets, hollow porous carbon, and layered porous carbon, have been widely used in lithium selenide batteries. Despite significant progress in carbonaceous materials, the poor chemical affinity of nonpolar carbonaceous hosts for polar lithium polyselenide, coupled with insufficient adsorption sites, leads to slow kinetic conversion of lithium polyselenide, impacting battery performance and cycle life. Summary of the Invention

[0004] In view of the problems existing in the background technology, the purpose of this invention is to provide a preparation technology of selenium cathode host material based on metal sulfide modified hierarchical porous carbon, which can comprehensively improve the two problems of severe volume expansion and shuttle effect.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for preparing a porous carbon-based selenium cathode material modified with metal sulfides includes the following steps:

[0007] Step 1: Tetraethyl orthosilicate is added dropwise to a mixture of ammonia solution, ethanol, and deionized water. After continuous stirring, the mixture is centrifuged, washed, and vacuum dried overnight to obtain silica spheres.

[0008] Step 2: Add the silica spheres and Zn(NO3)2·6H2O to the methanol solution. Simultaneously, add dimethylimidazole to the methanol solution in another beaker. Then, quickly mix the two solutions and keep them warm in an oven.

[0009] Step 3: After centrifugation and drying, the solution is subjected to high-temperature heat treatment to obtain SiO2@ZIF8;

[0010] Step 4: After etching the prepared SiO2@ZIF8 with HF, centrifuge, filter, and dry to obtain porous carbon HPC;

[0011] Step 5: Disperse HPC powder in NiCl2·6H2O, FeCl3·6H2O, or CoCl2·6H2O solution, and continuously stir under oil bath to fully adsorb Ni. 2+ or Fe 3+ or Co 2+ ;

[0012] Step 6: Mix the dried powder with sublimed sulfur and treat it at high temperature to obtain MS2-HPC (M = Ni, Fe, Co);

[0013] Step 7: After grinding MS2-HPC (M = Ni, Fe, Co) and Se powder evenly in a mortar, transfer them to a sealed container and heat them in a muffle furnace to obtain MS2-HPC / Se (M = Ni, Fe, Co).

[0014] In the above scheme, the amounts of tetraethyl orthosilicate, ammonia, ethanol, and deionized water used in step 1 are 15 ml, 5 ml, 225 ml, and 30 ml, respectively.

[0015] In the above scheme, the diameter of the silicon sphere in step 2 is 300nm, the temperature in the oven is 60℃, and the holding time is 24h.

[0016] In the above scheme, the high-temperature heat treatment in step 3 is at a temperature of 900℃, the heat treatment time is 2h, and the atmosphere is Ar gas.

[0017] In the above scheme, the concentration of HF in step 4 is 8%.

[0018] In the above scheme, the concentration of NiCl2·6H2O, FeCl3·6H2O, or CoCl2·6H2O in step 5 is 2 mol / L.

[0019] In the above scheme, the vulcanization temperature in step 6 is 350℃ and the time is 3h.

[0020] In the above scheme, in step 7, the ratio of MS2-HPC (M = Ni, Fe, Co) to Se powder is 1:1, the holding temperature is 260℃, and the time is 12h.

[0021] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0022] 1. In the process of synthesizing materials, this invention utilizes pore-forming agents including silica and Zn(NO3)2 to construct a three-dimensional layered porous structure with abundant micropores and mesopores and a high specific surface area, thereby increasing the loading capacity of the active material Se, alleviating the volume expansion during the cycling process, and accelerating the kinetics of electron and ion transfer.

[0023] 2. In the process of preparing the material, MS2 (M = Ni, Fe, Co) is introduced in this invention. The added metal sulfide mainly plays the following roles:

[0024] ① Introducing more active sites improves the adhesion of active substance Se to the carbon substrate, thereby increasing the utilization rate of Se;

[0025] ② It increases the polarity of the carbon support, which has a strong interaction with lithium polyselenide, a charge-discharge intermediate product that is also a polar material, thereby suppressing its "shuttle effect".

[0026] ③ It improves the charge transfer efficiency between lithium polyselenide and the carbon substrate, catalyzes the conversion reaction of lithium polyselenide, and thus accelerates the charging and discharging kinetics.

[0027] 3. The preparation method of this invention is simple and easy to operate, and is suitable for large-scale industrial production. Attached Figure Description

[0028] Figure 1 This is an electron microscope image of the porous carbon modified with metal sulfide according to Example 1 of the present invention.

[0029] Among them, (A) is the SEM image of porous carbon modified with metal sulfide, and (B) is the TEM image of porous carbon modified with metal sulfide.

[0030] Figure 2 The X-ray diffraction pattern of porous carbon modified with metal sulfides in Example 1 of this invention;

[0031] Figure 3 The N 1s X-ray photoelectron spectroscopy of porous carbon modified with metal sulfides is shown in Example 1 of this invention.

[0032] Figure 4 The X-ray photoelectron spectroscopy of S 2p porous carbon modified with metal sulfides is shown in Example 1 of this invention.

[0033] Figure 5 X-ray photoelectron spectroscopy of Ni 2p in porous carbon modified with metal sulfides, as described in Example 1 of this invention.

[0034] Figure 6 The theoretical calculation diagrams for the porous carbon composite material modified with metal sulfides in Example 1 of the present invention are shown in (A) the adsorption energy diagram and its optimized adsorption configuration, and (B) the density of states diagram.

[0035] Figure 7 This is a rate performance diagram of a lithium selenide battery with metal sulfide-modified porous carbon according to Embodiment 1 of the present invention.

[0036] Figure 8 This is a graph showing the long-cycle performance of a lithium selenium battery with porous carbon modified with metal sulfides, as described in Embodiment 1 of the present invention. Detailed Implementation

[0037] 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 embodiments and accompanying drawings.

[0038] This invention provides a method for preparing a porous carbon-based selenium cathode material modified with metal sulfides, comprising the following steps:

[0039] Step 1: Tetraethyl orthosilicate is added dropwise to a mixture of ammonia solution, ethanol, and deionized water. After continuous stirring, the mixture is centrifuged, washed, and vacuum dried overnight to obtain silica spheres.

[0040] Step 2: Add the silica spheres and Zn(NO3)2·6H2O to the methanol solution. Simultaneously, add dimethylimidazole to the methanol solution in another beaker. Then, quickly mix the two solutions and keep them warm in an oven.

[0041] Step 3: After centrifugation and drying, the solution is subjected to high-temperature heat treatment to obtain SiO2@ZIF8;

[0042] Step 4: After etching the prepared SiO2@ZIF8 with HF, centrifuge, filter, and dry to obtain porous carbon HPC;

[0043] Step 5: Disperse HPC powder in NiCl2·6H2O, FeCl3·6H2O, or CoCl2·6H2O solution, and continuously stir under oil bath to fully adsorb Ni. 2+ or Fe 3+ or Co 2+ ;

[0044] Step 6: Mix the dried powder with sublimed sulfur and treat it at high temperature to obtain MS2-HPC (M = Ni, Fe, Co);

[0045] Step 7: After grinding MS2-HPC (M = Ni, Fe, Co) and Se powder evenly in a mortar, transfer them to a sealed container and heat them in a muffle furnace to obtain MS2-HPC / Se (M = Ni, Fe, Co).

[0046] In the above scheme, the amounts of tetraethyl orthosilicate, ammonia, ethanol, and deionized water used in step 1 are 15ml, 5ml, 225ml, and 30ml, respectively.

[0047] In the above scheme, the diameter of the silicon sphere in step 2 is 300nm, the temperature in the oven is 60℃, and the holding time is 24h.

[0048] In the above scheme, the high-temperature heat treatment in step 3 is at a temperature of 900℃, the heat treatment time is 2h, and the atmosphere is Ar gas.

[0049] In the above scheme, the concentration of HF in step 4 is 8%.

[0050] In the above scheme, the concentration of NiCl2·6H2O, FeCl3·6H2O, or CoCl2·6H2O in step 5 is 2 mol / L.

[0051] In the above scheme, the vulcanization temperature in step 6 is 350℃ and the time is 3h.

[0052] In the above scheme, in step 7, the ratio of MS2-HPC (M = Ni, Fe, Co) to Se powder is 1:1, the holding temperature is 260℃, and the time is 12h.

[0053] Example 1

[0054] A method for preparing a porous carbon-based selenium cathode material modified with metal sulfides includes the following steps:

[0055] Step 1: Add 15 mL of tetraethyl orthosilicate dropwise to a mixture of ammonia solution (28-30%, 5 mL), ethanol (225 mL), and deionized water (30 mL). After stirring continuously for 2 hours, obtain silica spheres by centrifugation, washing, and vacuum drying overnight.

[0056] Step 2: Add silica nanospheres (0.5 g) and Zn(NO3)2-6H2O (0.87 g) to 20 ml of methanol solution. Simultaneously, add 2-methylimidazole (0.98 g) to another 20 ml of methanol solution in a separate beaker. Then, rapidly mix the two solutions and incubate at 60°C for 24 hours.

[0057] Step 3: The prepared SiO2@ZIF8 was etched with HF (8%, 40 mL) for 12 h, and the product was collected by centrifugation and filtration.

[0058] Step 4: Disperse 0.2g of HPC powder in 50ml of 0.1M NiCl2·6H2O solution and stir continuously at 45℃ for 6h to fully adsorb Ni. 2+ The dried product was then mixed with sublimed sulfur and calcined at 350°C for 3 hours under argon atmosphere to achieve in-situ formation of the corresponding metal sulfides. The sulfidation time and temperature were controlled to ensure that the formed sulfide particles were uniformly distributed on the porous carbon substrate while inhibiting their agglomeration and growth.

[0059] Step 5: Grind NiS2-HPC and Se powder in a mortar at a weight ratio of 1:1 to form a homogeneous mixture. Then, transfer the mixture to a sealed container and heat it in a muffle furnace at 260°C for 12 hours.

[0060] Example 2

[0061] Following the steps of Example 1, only step 4 was omitted, while the other steps remained unchanged. The resulting sample was a three-dimensional porous carbon without metal sulfides. Compared with the material obtained in Example 1, its morphology was not significantly different, but its electrochemical performance was worse than that of Example 1.

[0062] The three-dimensional hierarchical porous carbon modified with NiS2 nanoparticles prepared by this technology, used as the host material for the selenium cathode in lithium selenium batteries, can simultaneously alleviate volume expansion and shuttle effects during the reaction process. This highly ordered porous structure provides high loading and efficient utilization of active selenium, and its conductive network enables rapid electron transport. Furthermore, the embedded NiS2 nanoparticles increase the number of active sites and the ability to adsorb polyselenoside intermediates, thereby mitigating the shuttle effect during the reaction. Therefore, the battery using the prepared NiS2-HPC / Se as the cathode exhibits an initial discharge capacity as high as 569 mA hg. -1 After 200 cycles at 0.5C, the capacity retention was 93.7%, and the coulombic efficiency was approximately 100%. First-principles calculations showed that the anchored NiS2 nanoparticles not only enhanced the adsorption energy for different polyselenides but also improved the charge transfer characteristics of the composite material. This work demonstrates the effectiveness of porous, hierarchical, three-dimensional conductive carbon embedded with NiS2 nanoparticles as a highly efficient host material for lithium-selenium batteries, providing a promising approach for designing electrocatalysts for high-performance energy storage devices.

[0063] Figure 1 The scanning electron microscope image shown in Embodiment 1 of this invention reveals that NiS2-HPC exhibits a highly ordered porous structure with a pore size of approximately 200 nanometers. Figure 1 (A) This is consistent with the particle size of the SiO2 template. Furthermore, TEM observations show (...) Figure 1In the middle (B), NiS2 particles are uniformly distributed in porous carbon, with an average particle size of about 60 nanometers.

[0064] Figure 2 The X-ray diffraction results of the NiS2-modified three-dimensional porous carbon prepared in Example 1 of this invention are shown in the figure. The obvious diffraction peaks of cubic NiS2 (JCPDS card 65-3325) can be seen. The diffraction peaks at 31.4°, 35.3°, 38.8°, 45.1°, and 53.4° correspond to the (200), (210), (211), (220), and (311) crystal planes, respectively, and no impurity phases are formed.

[0065] Figure 3 This is the X-ray photoelectron spectrum of the NiS2-modified three-dimensional porous carbon electrode material N 1s prepared in Example 1 of this invention. The high-resolution N 1s spectrum can be decomposed into five peaks: graphitized N (401.0 eV), pyrrole N (399.9 eV), pyridine N (398.2 eV), Ni-N (399.1 eV), and N oxide (402.1 eV). These N-containing functional groups present in the carbon matrix can improve electronic conductivity and surface polarity, thereby enhancing the catalytic performance of the material.

[0066] Figure 4 This is the X-ray photoelectron spectrum of the NiS2-modified three-dimensional porous carbon electrode material S 2p prepared in Example 1 of this invention. Figure 4 As shown, the S 2p spectrum reveals the S 2p 3 / 2 (163.4 eV) and S 2p 1 / 2 The peak value is 164.7 eV. In addition, the peak value at 168.2 eV is due to SO bonds on the sulfide surface.

[0067] Figure 5 This is the X-ray photoelectron spectrum of Ni 2p in the NiS2-modified three-dimensional porous carbon electrode material prepared in Example 1 of this invention. In NiS2-HPC, Ni 2p can be decomposed into several peaks, specifically located at 855.0 eV, 856.8 eV, 872.7 eV, and 874.9 eV, corresponding to Ni 2p and Ni 2p, respectively. 2+ Ni 3+ , Ni 2p 3 / 2 and Ni 2p 1 / 2 Peaks located near 859.5 eV, 862.7 eV, and 879.7 eV can be classified as satellite peaks.

[0068] Figure 6 DFT calculations were performed on the prepared NiS2-modified three-dimensional porous carbon electrode material. Figure 6 (A) shows the selected and optimized planar adsorption configuration of NiS2(001) and the adsorption energy of the intermediate product. Figure 6 (B) shows the density of states (DOS) of NiS2-HPC. NiS2-HPC exhibits a high charge density near the Fermi level, indicating that it has higher conductivity, which is conducive to electron transport.

[0069] Figure 7 To assess the rate performance of the prepared NiS2-modified three-dimensional porous carbon electrode material in lithium selenide batteries, this material exhibits high reversible capacity: specific capacities of 591, 494, 457, 431, 405, 350, and 188 mAh g⁻¹ at current densities ranging from 0.1C to 10C. -1 Furthermore, when the current density returns to 0.1C, its specific capacity is almost the same as its initial capacity.

[0070] Figure 8 The lithium selenium battery using the NiS2-modified three-dimensional porous carbon electrode material prepared in Example 1 exhibits long-cycle performance, with a specific capacity of 549 mAh g at 2C rate. -1 After 1000 cycles, the capacity can still reach 289mAh g. -1 This indicates that it has good cycle performance.

Claims

1. A method for preparing a porous carbon-based selenium cathode material modified with metal sulfides, characterized in that, Includes the following steps: Step 1: Add tetraethyl orthosilicate dropwise to a mixture of ammonia, ethanol and deionized water, stir continuously, and then centrifuge, wash and vacuum dry overnight to obtain silicon spheres; Step 2: Add the silica balls and Zn(NO3)2·6H2O to the methanol solution to obtain solution A. At the same time, take another methanol solution and add dimethylimidazole to obtain solution B. Then, quickly mix solution A and solution B and keep warm in an oven. Step 3: After centrifugation and drying, the solution is subjected to high-temperature heat treatment to obtain SiO2@ZIF8; Step 4: After etching the prepared SiO2@ZIF8 with HF, centrifuge, filter, and dry to obtain porous carbon HPC; Step 5: Disperse HPC powder in NiCl2·6H2O, FeCl3·6H2O, or CoCl2·6H2O solution, and continuously stir under oil bath to fully adsorb Ni. 2+ or Fe 3+ or Co 2+ The powder was then centrifuged and dried to obtain the dried powder. Step 6: Mix the dried powder with sublimed sulfur and treat it at high temperature to obtain MS2-HPC (M=Ni, Fe, Co). Step 7: Grind MS2-HPC (M=Ni, Fe, Co) and Se powder evenly in a mortar, transfer to a sealed container, and keep warm in a muffle furnace to obtain MS2-HPC / Se (M=Ni, Fe, Co).

2. The method for preparing a porous carbon-based selenium cathode material modified with metal sulfide according to claim 1, characterized in that, In step 1, the amounts of tetraethyl orthosilicate, ammonia, ethanol, and deionized water used are 15 ml, 5 ml, 225 ml, and 30 ml, respectively.

3. The method for preparing a porous carbon-based selenium cathode material modified with metal sulfide according to claim 1, characterized in that, In step 2, the diameter of the silicon spheres is 300 nm, the temperature in the oven is 60 °C, and the holding time is 24 h.

4. The method for preparing a porous carbon-based selenium cathode material modified with metal sulfide according to claim 1, characterized in that, In step 3, the high-temperature heat treatment temperature is 900 ℃, the heat treatment time is 2 h, and the atmosphere is Ar.

5. The method for preparing a porous carbon-based selenium cathode material modified with metal sulfide according to claim 1, characterized in that, The concentration of HF mentioned in step 4 is 8%.

6. The method for preparing a porous carbon-based selenium cathode material modified with metal sulfide according to claim 1, characterized in that, The concentration of NiCl2·6H2O, FeCl3·6H2O, or CoCl2·6H2O mentioned in step 5 is 2 mol / L.

7. The method for preparing a porous carbon-based selenium cathode material modified with metal sulfide according to claim 1, characterized in that, In step 6, the vulcanization temperature is 350 °C and the time is 3 h.

8. A method for preparing a porous carbon-based selenium cathode material modified with metal sulfide according to claim 1, characterized in that, In step 7, the ratio of MS2-HPC (M=Ni, Fe, Co) to Se powder is 1:1, the holding temperature is 260 ℃, and the time is 12 h.

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