Solid solution positive electrode catalytic material for lithium oxygen battery as well as preparation method and application of solid solution positive electrode catalytic material

Abstract

The invention belongs to the technical field of battery positive electrodes, and particularly relates to a solid solution positive electrode catalytic material for a lithium oxygen battery and a preparation method and application thereof. Comprising the following steps: firstly, growing a nickel-cobalt bimetallic precursor nanoneedle array on carbon paper by using a 1-octyl-3-methylimidazole chloride salt assisted hydrothermal method; then preparing a selenylation sample through a NaHSe solution; and step 3, cleaning the selenylation sample for multiple times, roasting in an argon atmosphere to remove excessive selenium, and synthesizing the Ni-doped CoSe2 solid solution nanoneedle array. The reaction conditions are mild and easy to control; the selenized material completely inherits the morphology of the precursor; and in the application of the lithium oxygen battery, the lithium oxygen battery still has excellent stability after multiple cycles, and enough discharge depth can be realized.

Description

Technical Field

[0001] This invention belongs to the field of battery cathode technology, specifically relating to a solid solution cathode catalytic material for lithium-oxygen batteries, its preparation method, and its application. Background Technology

[0002] Non-aqueous lithium-oxygen batteries have a theoretical specific energy of up to 3500Wh / kg. -1 This technology demonstrates superior potential compared to traditional lithium-ion batteries and is expected to play a crucial role in future energy storage. However, during discharge, the Li₂O₂ generated by the oxygen reduction reaction is insulating and difficult to decompose on the electrode surface, resulting in a large charge / discharge overpotential and short cycle life. Therefore, developing efficient cathode electrocatalysts to regulate the nucleation and growth of Li₂O₂ and promote its reversibility during charge / discharge is an effective strategy to address this challenge.

[0003] Existing cathode electrocatalysts are typically porous carbon materials, transition metal oxides, noble metal catalysts, and conductive metal-organic frameworks. Application number "202311490072.4" discloses "Application of a Biochar Material in Lithium-Oxygen Batteries," which relates to the application of a biochar material as an oxygen cathode material. This involves selenizing an oxide using a solid-gas reaction, followed by high-temperature calcination of a mixture of oxide, carbon precursor, selenium powder, and sodium hypophosphite to prepare a phosphorus-doped transition metal selenide / carbon composite material. However, this method has significant shortcomings in practical applications: 1. Because the cathode can only be prepared using a coating method, it cannot fully utilize the advantages of biochar to achieve sufficient depth of discharge; 2. Due to the poor oxidation resistance of carbon materials at high voltages, the cycle stability is poor, especially at 0.02 mA cm⁻¹. -2 0.1mAh cm -2 Under certain conditions, it can only cycle 65 times. Summary of the Invention

[0004] This invention provides a solid solution cathode catalytic material for lithium-oxygen batteries, its preparation method, and its application, in order to solve the problems of insufficient depth of discharge and poor cycle stability in the prior art.

[0005] To achieve the above objectives, the technical solution of the present invention is: a method for preparing a solid solution cathode catalyst material for lithium-oxygen batteries, comprising the following steps:

[0006] Step 1: Growth of nickel-cobalt bimetallic precursor nanoneedle arrays on carbon paper using a solvothermal method;

[0007] Step 2: Prepare selenized samples using NaHSe solution;

[0008] Step 3: The selenized sample is washed multiple times, and Ni-doped CoSe2 solid solution nanoneedle array is synthesized in an argon atmosphere.

[0009] Furthermore, the specific steps of step one above are as follows:

[0010] 1.1 Dissolve 0.04 mmol of CoCl2, 0.02 mmol of NiCl2·6H2O and 24 mmol of urea in 40 mL of 0.5 M [OMIm]Cl to form a clear solution and stir.

[0011] 1.2 Pour the solution into a stainless steel autoclave lined with polytetrafluoroethylene, which contains a piece of pretreated carbon paper, and keep it at 120°C for 6 hours;

[0012] 1.3 After natural cooling, remove the carbon paper coated with the nickel-cobalt precursor and wash it repeatedly with deionized water and anhydrous ethanol.

[0013] 1.4 Drying yields a nickel-cobalt precursor nanoneedle array.

[0014] Furthermore, in step 1.2 above, the solution is kept at 120°C for 6 hours in a stainless steel autoclave.

[0015] Furthermore, in step 1.4 above, the product is dried under vacuum at 60°C for 12 hours.

[0016] Furthermore, the specific steps of step two above are as follows:

[0017] 2.1 Dissolve 14 mmol of NaBH4 in 10 mL of nitrogen-saturated deionized water, and quickly add 7 mmol of selenium powder to the solution under nitrogen protection.

[0018] 2.2 After the selenium powder has completely dissolved, dilute the solution to 180 mL with deionized water;

[0019] 2.3 Transfer 40 mL of freshly prepared NaHSe solution to an autoclave containing nickel-cobalt precursor and seal it to obtain a selenized sample.

[0020] Furthermore, in step 2.3 above, the sample is sealed at 200°C for 24 hours.

[0021] Furthermore, in step three above, the treatment is carried out at 400°C for 2 hours in an argon atmosphere.

[0022] Furthermore, the above preparation method yields a solid solution cathode catalyst material for lithium-oxygen batteries.

[0023] Furthermore, the above-mentioned solid solution cathode catalyst materials are applied in lithium-oxygen batteries.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. This invention prepares the target product using a three-step method:

[0026] First, a nickel-cobalt bimetallic precursor nanoneedle array is grown on carbon paper using a 1-octyl-3-methylimidazolium chloride-assisted hydrothermal method. The nanoneedles are uniformly grown on the carbon fiber units of the carbon paper. With the assistance of 1-octyl-3-methylimidazolium chloride, each nanoneedle has a bottom diameter of approximately 250 nm, a top diameter of approximately 100 nm, and a length of 4–5 μm. Then, the array is selenized using a NaHSe solution. This invention uses a NaHSe solution for selenization, which provides mild and easily controllable reaction conditions. This invention uses a solution-phase ion exchange reaction for selenization instead of a solid-gas reaction, ensuring that the selenized material completely inherits the morphology of the precursor (parent material). Afterward, excess selenium is removed by calcination, and the material is completely transformed into a highly crystalline Ni-doped CoSe2 solid solution nanoneedle array.

[0027] 2. Due to the special solid solution crystal structure of this invention, Ni occupies some Co sites. At the same time, the self-supporting Ni-doped CoSe2 solid solution nanoneedle array constructed by this invention using carbon paper also effectively improves the structural stability during cycling. Therefore, the Ni-doped CoSe2 solid solution nanoneedle array prepared by this invention exhibits extremely high stability in lithium-oxygen battery applications. Tests have shown that it still has excellent stability after multiple cycles.

[0028] 3. The Ni and Co of this invention have a highly efficient synergistic catalytic effect, and the self-supporting three-dimensional electrode structure of this invention has the characteristics of being porous and having a large specific surface area. Therefore, in the application of lithium-oxygen batteries, sufficient discharge depth can be achieved. Attached Figure Description

[0029] Figure 1 XRD pattern of Embodiment 1 of the present invention ( (Representing the peaks on carbon paper);

[0030] Figure 2 This is a low-resolution SEM image of the Ni-doped CoSe2 solid solution nanoneedle array of the present invention;

[0031] Figure 3 This is a high-resolution SEM image of the Ni-doped CoSe2 solid solution nanoneedle array of the present invention.

[0032] Figure 4 This is a TEM elemental mapping image of the Ni-doped CoSe2 solid solution nanoneedle array of the present invention, wherein... Figure 4 (a) is the mapping region. Figure 4 (b) is the Ni element mapping diagram. Figure 4(c) is the Co element mapping diagram. Figure 4 (d) is the Se element mapping diagram;

[0033] Figure 5 This is the EDS image of the Ni-doped CoSe2 solid solution nanoneedle array of the present invention;

[0034] Figure 6 This is a TEM image of the Ni-doped CoSe2 solid solution nanoneedle array of the present invention;

[0035] Figure 7 The Ni-doped CoSe2 solid solution nanoneedle array cathode of this invention operates at 0.02 mA cm⁻¹. -2 0.1mAh cm -2 Cyclic performance diagram under certain conditions;

[0036] Figure 8 XRD pattern of a comparative CoSe2 nanoribbon array ( (Representing the peaks on carbon paper);

[0037] Figure 9 EDS plot of a comparative CoSe2 nanoribbon array;

[0038] Figure 10 Here are SEM images of a comparative CoSe2 nanoribbon array, where Figure 10 (a) is a low-resolution SEM image. Figure 10 (b) is a high-resolution SEM image;

[0039] Figure 11 The Ni-doped CoSe2 solid solution nanoneedle array cathode and the comparative CoSe2 nanoribbon array of the present invention are used at 0.02 mA cm⁻¹. -2 Initial discharge capacity diagram under the given conditions;

[0040] Figure 12 The comparative example of the present invention is a CoSe2 nanoribbon array at 0.02 mA cm⁻¹. -2 0.1mAh cm -2 Cyclic performance under certain conditions. Detailed Implementation

[0041] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0042] 1-Octyl-3-methylimidazolium chloride (IL, [OMIm]Cl) and carbon paper (CP, TGP-H-060) were both commercially available raw materials.

[0043] Example 1: A method for preparing a solid solution cathode catalyst material for lithium-oxygen batteries, comprising the following steps:

[0044] Step 1: Growth of nickel-cobalt bimetallic precursor nanoneedle arrays on carbon paper using a solvothermal method:

[0045] 1.1 Dissolve 0.04 mmol of CoCl2, 0.02 mmol of NiCl2·6H2O and 24 mmol of urea in 40 mL of 0.5 M [OMIm]Cl to form a clear solution and stir.

[0046] 1.2 Pour the solution into a 50 mL stainless steel autoclave lined with polytetrafluoroethylene, containing a piece of pretreated carbon paper, and keep it at 120 °C for 6 hours.

[0047] 1.3 After natural cooling, remove the carbon paper coated with the nickel-cobalt precursor and wash it repeatedly with deionized water and anhydrous ethanol.

[0048] 1.4 Nickel-cobalt precursor nanoneedle arrays were obtained by drying under vacuum at 60°C for 12 hours.

[0049] Step 2: Synthesize Ni-doped CoSe2 solid solution nanoneedle arrays on carbon paper:

[0050] 2.1 Dissolve 14 mmol of NaBH4 in 10 mL of nitrogen-saturated deionized water, and then quickly add 7 mmol of selenium powder to the solution under nitrogen protection.

[0051] 2.2 After the selenium powder has completely dissolved, dilute the solution to 180 mL with deionized water.

[0052] 2.3 Transfer 40 mL of freshly prepared NaHSe solution to a 50 mL autoclave containing a nickel-cobalt precursor and seal it for treatment. Treat at 200 °C for 24 hours to obtain a selenized sample.

[0053] 2.4 The selenized sample was washed multiple times, using deionized water and ethanol in sequence.

[0054] 2.5 Ni-doped CoSe2 solid solution nanoneedle arrays were obtained by treating the nanoneedle array at 400℃ for 2 hours in an argon atmosphere.

[0055] Comparative example: CoSe2 nanoribbon array without Ni doping, which was prepared in the same way as in Example 1, except that NiCl2·6H2O and 1-octyl-3-methylimidazolium chloride were not added in step 1.1.

[0056] See Figure 1 As can be seen, after selenization treatment, all diffraction peaks of the sample are classified as cubic pyrite-structured CoSe2 (JCPDS No. 09-0234), and no nickel-containing phase was observed, indicating that a nickel-doped CoSe2 type solid solution was formed.

[0057] See Figure 2 In Example 1 of this invention, 1-octyl-3-methylimidazolium chloride was added. Compared with the comparative example, 1-octyl-3-methylimidazolium chloride has a significant impact on the precursor structure, thus enabling the final preparation of Ni-doped CoSe2 solid solution nanoneedles with a bottom diameter of approximately 250 nm, a top diameter of approximately 100 nm, and a length of 4–5 μm. The Ni-doped CoSe2 solid solution cathode catalyst grows on carbon paper in the form of upright 1D nanoneedles, and all these nanoneedles have a uniform morphology and distribution.

[0058] See Figure 3 The Ni-doped CoSe2 solid solution nanoneedles have a top diameter of about 100 nm and a length of 4–5 μm.

[0059] See Figure 4 TEM elemental mapping of Ni-doped CoSe2 solid solution shows that, see [references to be inserted here] Figure 4 (b) Figure 4 (c) Figure 4 (d) Ni, Co, and Se elements are uniformly distributed within the nanoneedles, further confirming the formation of a nickel-doped CoSe2 type solid solution.

[0060] See Figure 5 EDS analysis of Ni-doped CoSe2 solid solutions showed the presence of Ni, Co, Se, C, and O elements. The atomic ratios of Ni and Co were close to the stoichiometric ratio of CoCl2 and NiCl2·6H2O, and the atomic ratios of Co and Se were close to 1:2, further confirming the formation of a nickel-doped CoSe2 solid solution.

[0061] See Figure 6 TEM images of the Ni-doped CoSe2 solid solution nanoneedle array show that the nanoneedles have a bottom diameter of about 250 nm, a top diameter of about 100 nm, and a length of 4–5 μm, which is consistent with the SEM results.

[0062] See Figure 7 A lithium-oxygen battery using a Ni-doped CoSe2 solid solution nanoneedle array as the positive electrode operates at a current density of 0.02 mA cm⁻¹. -2 Surface capacity 0.1mAh cm -2 Under certain conditions, it can be stably cycled for 960 hours, or 100 cycles.

[0063] See Figure 8 As can be seen, all the diffraction peaks of the prepared sample are attributed to the cubic pyrite structure of CoSe2 (JCPDS No. 09-0234), indicating that CoSe2 was successfully prepared.

[0064] See Figure 9 In the comparative example, no NiCl2·6H2O or 1-octyl-3-methylimidazolium chloride was added, and the ratio of elemental Co to elemental Se was 1:2, indicating that pure phase CoSe2 was prepared.

[0065] See Figure 10 In the comparative example, without the addition of NiCl2·6H2O and 1-octyl-3-methylimidazolium chloride, the CoSe2 cathode catalyst was grown on carbon paper in the form of nanoribbons. (See [link to relevant documentation]). Figure 10 (a) The nanometer bandwidth is approximately 500 nm, and the length is approximately several micrometers. See [reference needed]. Figure 10 (b)

[0066] See Figure 11 Ni-doped CoSe2 solid solution nanoneedle array at 0.02 mA cm⁻¹ -2 The initial discharge capacity under certain conditions is as high as 1.23 mAh cm⁻¹. -2 The discharge capacity of the comparative CoSe2 nanobelt array under the same conditions was 0.28 mAh cm⁻¹. -2 Due to the catalytic effect of Ni and Co elements and the characteristics of being porous and having a large specific surface area, Ni-doped CoSe2 solid solution nanoneedle arrays have achieved higher discharge capacity.

[0067] See Figure 12 The comparative example of a lithium-oxygen battery using CoSe2 nanoribbons as the positive electrode at a current density of 0.02 mA cm⁻¹ -2 Surface capacity 0.1mAh cm -2 Under certain conditions, it can only maintain a stable cycle for 529 hours, or 57 cycles.

[0068] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a solid solution cathode catalyst material for lithium-oxygen batteries, characterized in that: Includes the following steps: Step 1: Growth of nickel-cobalt bimetallic precursor nanoneedle arrays on carbon paper using a solvothermal method; Step 2: Prepare selenized samples using NaHSe solution; Step 3: The selenized sample is washed multiple times, and Ni-doped CoSe2 solid solution nanoneedle array is synthesized in an argon atmosphere.

2. The method for preparing a solid solution cathode catalyst material for lithium-oxygen batteries according to claim 1, characterized in that: The specific steps of step one are as follows: 1.1 Dissolve 0.04 mmol of CoCl2, 0.02 mmol of NiCl2∙6H2O and 24 mmol of urea in 40 mL of 0.5 M [OMIm]Cl to form a clear solution and stir. 1.2 Pour the solution into a stainless steel autoclave lined with polytetrafluoroethylene, which contains a piece of pretreated carbon paper, and keep it at 120°C for 6 hours; 1.3 After natural cooling, remove the carbon paper coated with the nickel-cobalt precursor and wash it repeatedly with deionized water and anhydrous ethanol. 1.4 Drying yields a nickel-cobalt precursor nanoneedle array.

3. The method for preparing a solid solution cathode catalyst material for lithium-oxygen batteries according to claim 2, characterized in that: In step 1.2, the solution is kept at 120°C for 6 hours in a stainless steel autoclave.

4. The method for preparing a solid solution cathode catalyst material for lithium-oxygen batteries according to claim 2, characterized in that: In step 1.4, the product is dried under vacuum at 60°C for 12 hours.

5. The method for preparing a solid solution cathode catalyst material for lithium-oxygen batteries according to claim 1, characterized in that: The specific steps of step two are as follows: 2.1 Dissolve 14 mmol of NaBH4 in 10 mL of deionized water saturated with nitrogen, and quickly add 7 mmol of selenium powder to the solution under nitrogen protection. 2.2 After the selenium powder has completely dissolved, dilute the solution to 180 mL with deionized water; 2.3 Transfer 40 mL of freshly prepared NaHSe solution to an autoclave containing nickel-cobalt precursor and seal it to obtain a selenized sample.

6. The method for preparing a solid solution cathode catalyst material for lithium-oxygen batteries according to claim 5, characterized in that: In step 2.3, the sample is sealed at 200°C for 24 hours.

7. The method for preparing a solid solution cathode catalyst material for lithium-oxygen batteries according to claim 1, characterized in that: In step three, the treatment is carried out at 400°C for 2 hours in an argon atmosphere.

8. A solid solution cathode catalyst material for lithium-oxygen batteries prepared by the method according to claim 1.

9. The application of the solid solution cathode catalyst material according to claim 8 in lithium-oxygen batteries.

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