Preparation method and application of oxidation-reduction medium intercalated LDH (layered double hydroxide) catalyst

Abstract

The invention belongs to the field of new energy materials, and relates to a preparation method and application of a redox medium intercalated LDH (layered double hydroxide) catalyst, the preparation method comprises the following steps: dispersing Co (NO3) 2.6 H2O in deionized water to obtain a solution A; dispersing 2-methylimidazole and CTAB (Cetyltrimethyl Ammonium Bromide) into deionized water to obtain a solution B; pouring the solution A into the solution B, stirring at room temperature, standing, washing the precipitate with absolute ethyl alcohol, and drying to obtain cubic ZIF-67; the cubic ZIF-67 is dispersed in absolute ethyl alcohol, and a solution C is obtained; dissolving nickel salt or iron salt in absolute ethyl alcohol to obtain a solution D; adding the solution D into the solution C to obtain a solution E, heating the solution E at a constant temperature, then washing a precipitate with absolute ethyl alcohol, and drying to obtain cobalt-based LDH; the preparation method comprises the following steps: dispersing cobalt-based LDH in absolute ethyl alcohol, adding an absolute ethyl alcohol solution containing a redox medium, stirring at room temperature, washing a precipitate with absolute ethyl alcohol, and drying to obtain the redox medium intercalated LDH catalyst.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials and relates to a method for preparing an LDH catalyst with redox media intercalation and its application. Background Technology

[0002] Driven by the demand for clean energy, electric vehicles (EVs) are gradually replacing traditional gasoline-powered vehicles as the preferred mode of transportation. While the EV market is experiencing rapid growth, the relatively low theoretical energy density of lithium-ion batteries, a core component, limits the driving range and further applications of EVs. Therefore, there is an urgent need to develop a new generation of high-energy-density rechargeable batteries with superior performance to meet the challenges of the future EV market. Among these, lithium-oxygen batteries with an organic electrolyte system boast a theoretical energy density as high as 11429 Wh / kg, almost comparable to that of gasoline. Therefore, lithium-oxygen batteries are considered one of the most promising technologies for future applications in EVs.

[0003] The performance of lithium-oxygen batteries primarily depends on the ORR and OER rates on the positive electrode side, both of which are limited by the catalytic activity of the positive electrode catalyst. While significant progress has been made in solid-state catalysts, their heterogeneous catalytic nature results in a solid-solid contact between the catalyst and the product Li₂O₂, thus limiting the effective contact area. Furthermore, as products accumulate, mass transfer channels may become blocked, leading to premature termination of the discharge process. During charging, although products in direct contact with the catalyst can be effectively decomposed, the remaining products are difficult to decompose completely due to poor contact with the catalyst, resulting in increased overpotential and battery failure.

[0004] Redox mediators (RMs), as liquid catalysts, essentially divide the original electrochemical process of Li₂O₂ into an electrochemical process of RM and a chemical process of Li₂O₂. This reduces overpotential and mitigates reaction instability, making it a highly sought-after kinetic optimization strategy. Unlike solid catalysts, RMs, as homogeneous catalysts, can be uniformly distributed in the electrolyte, thus ensuring good contact with all surfaces of the discharge products, effectively promoting Li₂O₂ growth and complete decomposition. However, this also means that after oxidation, the RM readily migrates to the lithium anode and reacts with it, leading to the continuous consumption of lithium and RM, ultimately causing its decomposition. Therefore, limiting the shuttle effect of RMs is one of the important research directions for promoting their further application. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for preparing an LDH catalyst with redox medium intercalation and its application in lithium-oxygen batteries, so as to solve the problems of negative electrode failure and reduced catalytic effect caused by the shuttle effect of existing liquid catalysts in lithium-oxygen batteries.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing an LDH catalyst intercalated with a redox medium includes the following steps: Step 1. Disperse Co(NO3)2·6H2O in deionized water to obtain solution A; Step 2. Disperse 2-methylimidazole and CTAB in deionized water to obtain solution B; Step 3. Pour solution A into solution B, stir at room temperature and let stand. Wash the precipitate with anhydrous ethanol and dry it to obtain cubic ZIF-67. Step 4. Disperse the cubic ZIF-67 obtained in Step 3 in anhydrous ethanol to obtain solution C; Step 5. Dissolve the nickel salt or iron salt in anhydrous ethanol to obtain solution D; Step 6. Add solution D to solution C to obtain solution E. Heat solution E at a constant temperature, then wash the precipitate with anhydrous ethanol and dry it to obtain cobalt-based LDH. Step 7. Disperse cobalt-based LDH in anhydrous ethanol, then add anhydrous ethanol solution containing redox media, stir at room temperature, wash the precipitate with anhydrous ethanol and dry it to obtain redox media-intercalated LDH catalyst.

[0007] Furthermore, in step 1, the concentration of solution A is 0.05-0.2 mol / L.

[0008] Further, in step 2, the concentration of 2-methylimidazole in solution B is 0.5-1 mol / L, and the concentration of CTAB is 0.2-0.3 mmol / L.

[0009] Furthermore, in step 4, the concentration of solution C is 1-5 mg / mL.

[0010] Further, in step 5, the nickel salt is at least one of Ni(NO3)2·6H2O, NiCl2·6H2O, anhydrous Ni(NO3)2, and anhydrous NiCl2.

[0011] Further, in step 5, the iron salt is at least one of Fe(NO3)3·9H2O, FeCl3·6H2O, anhydrous Fe(NO3)3, and anhydrous FeCl3.

[0012] Furthermore, in step 5, the concentration of nickel salt or iron salt in solution D is 0.05-0.5 mol / L.

[0013] Furthermore, in step 6, the constant temperature heating is 60-100℃ and the time is 5-60 min.

[0014] In further step 7, the concentration of the cobalt-based LDH in anhydrous ethanol is 1-20 mg / mL.

[0015] In further step 7, the redox medium is at least one of sodium bromide, sodium iodide, potassium bromide, potassium iodide, sodium nitrate, and potassium nitrate.

[0016] On the other hand, the present invention also provides a redox medium intercalated LDH catalyst, wherein the redox medium intercalated LDH catalyst has redox medium anions intercalated between cobalt-based LDH layers.

[0017] Furthermore, the cobalt-based LDH has a hollow cubic structure with a cubic size of 100-500 nm.

[0018] Furthermore, the intercalated redox medium anion is a liquid catalyst in a lithium-oxygen battery, and its molecular radius is smaller than TFSI. - Anions.

[0019] On the other hand, the present invention also provides an application of an LDH catalyst with redox medium intercalation, wherein the catalyst is applied to the positive electrode of an organic electrolyte lithium-oxygen battery.

[0020] Furthermore, the lithium salt of the organic electrolyte is LiTFSI.

[0021] The beneficial effects of this invention are as follows: 1. The redox medium intercalated LDH catalyst prepared by this invention provides both liquid redox medium catalyst and solid catalyst in the lithium-oxygen battery reaction process through the synergistic effect of interlayer anions and layers, which promotes the formation and decomposition kinetics of reaction intermediates. Therefore, it can effectively reduce the charge and discharge overpotential and greatly improve the performance of lithium-oxygen batteries.

[0022] 2. The LDH catalyst with redox media intercalation prepared by the ZIF-67 template method in this invention has a larger specific surface area than the 2D layered structure of LDH obtained by the traditional coprecipitation method. This facilitates the exposure of more active sites and the adsorption of more redox media anions, thereby improving the OER (oxygen evolution reaction) performance of lithium-oxygen batteries.

[0023] 3. This invention utilizes the interlayer anion exchange characteristics of LDH, namely, smaller radius anions can more easily enter the interlayer, so that the redox media anions in the interlayer will not react with the larger radius TFSI in the electrolyte. - The exchange process anchors the redox medium in the positive electrode, suppressing the shuttle effect while improving the reaction efficiency of the reaction intermediates and the redox medium, thus accelerating the positive electrode reaction kinetics.

[0024] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 The images show the XRD and FT-IR comparisons of the iodide ion intercalated CoNi-LDH in Example 1 and the CoNi-LDH in Comparative Example 1, where (a) is the XRD comparison image and (b) is the FT-IR comparison image. Figure 2 The image shows a comparison of SEM-EDS images of iodide ion intercalated CoNi-LDH in Example 1 and CoNi-LDH in Comparative Example 1. Figure 3 The XRD patterns of the positive electrodes of the iodide-intercalated CoNi-LDH in Example 1, the CoNi-LDH in Comparative Example 1, and the Super P in Comparative Example 2 after discharging 1 mAh in a DME electrolyte of 1 mol / L LiTFSI are shown. Figure 4 Comparison of charge-discharge tests of iodide ion intercalated CoNi-LDH in Example 1, CoNi-LDH in Comparative Example 1, and Super P in Comparative Example 2 in 1 mol / L LiTFSI DME electrolyte; Figure 5 This is a comparison of the cycling stability of iodide ion intercalated CoNi-LDH in Example 1, CoNi-LDH in Comparative Example 1, and Super P in Comparative Example 2 in a 1 mol / L LiTFSI DME electrolyte. Figure 6 The image shows a comparison of the negative electrodes of Suoer P in Comparative Example 2 and CoNi-LDH intercalated with iodine ions in Example 1 after cycling tests in DME electrolyte with or without LiI in 1 mol / L LiTFSI. Detailed Implementation

[0026] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0027] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0028] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0029] In a specific embodiment of the present invention, a redox medium-intercalated LDH catalyst is provided, wherein redox medium anions are intercalated between cobalt-based LDH layers. The cobalt-based LDH has a hollow cubic structure with a cubic size of 100-500 nm. The intercalated redox medium anions are liquid catalysts used in lithium-oxygen batteries, and their molecular radius is smaller than TFSI. - (bis(trifluoromethanesulfonyl)imide) anion.

[0030] In a specific embodiment of the present invention, a method for preparing an LDH catalyst intercalated with a redox medium is also provided, comprising the following steps: Step 1: Prepare deionized water that has been boiled at 100℃ for more than 10 minutes. Then, disperse Co(NO3)2·6H2O in the deionized water to obtain solution A. Disperse 2-methylimidazole and CTAB (hexadecyltrimethylammonium bromide) in the deionized water to obtain solution B.

[0031] The concentration of solution A is 0.05-0.2 mol / L. In solution B, the concentration of 2-methylimidazole is 0.5-1 mol / L, and the concentration of CTAB is 0.2-0.3 mmol / L.

[0032] Step 2: Pour solution A into solution B, stir at 100-1000 rpm at room temperature for 1-20 min, let stand for 1-48 h, wash the precipitate three times with anhydrous ethanol, and dry at 40-70℃ to obtain cubic ZIF-67.

[0033] Step 3: Disperse the cubic ZIF-67 obtained in Step 2 in anhydrous ethanol to obtain solution C. Dissolve the nickel salt or iron salt in anhydrous ethanol to obtain solution D.

[0034] The concentration of solution C is 1-5 mg / mL. The concentration of nickel or iron salt in solution D is 0.05-0.5 mol / L.

[0035] The nickel salt is at least one selected from Ni(NO3)2·6H2O, NiCl2·6H2O, anhydrous Ni(NO3)2, and anhydrous NiCl2. The iron salt is at least one selected from Fe(NO3)3·9H2O, FeCl3·6H2O, anhydrous Fe(NO3)3, and anhydrous FeCl3.

[0036] Step 4: Add solution D to solution C to obtain solution E. Heat solution E at 60-100℃ for 5-60 minutes. Then wash the precipitate three times with anhydrous ethanol and dry it at 40-70℃ to obtain cobalt-based LDH.

[0037] Step 5: Disperse cobalt-based LDH in anhydrous ethanol, add a saturated anhydrous ethanol solution containing redox media under argon protection, stir at 200-400 rpm at room temperature for 12-48 h, wash the precipitate three times with anhydrous ethanol, and dry at 40-70℃ to obtain the redox media-intercalated LDH catalyst.

[0038] Specifically, the concentration of the cobalt-based LDH in anhydrous ethanol is 1-20 mg / mL.

[0039] The redox medium is at least one of sodium bromide, sodium iodide, potassium bromide, potassium iodide, sodium nitrate, and potassium nitrate.

[0040] In a specific embodiment of the present invention, the application of the redox medium-intercalated LDH catalyst in the positive electrode of an organic electrolyte lithium-oxygen battery is also provided. The lithium salt of the organic electrolyte is LiTFSI.

[0041] The positive electrode of the lithium-oxygen battery can be prepared by the following method: (1) Preparation of LDH catalyst dispersion: The LDH catalyst intercalated with redox medium, Super P and 10wt% PTFE (polytetrafluoroethylene) suspension were thoroughly mixed in a mass ratio of 5:4:1. Then, 1.8 mL of isopropanol and 2.7 mL of N-methylpyrrolidone were added and ultrasonically homogenized at room temperature to obtain LDH catalyst dispersion.

[0042] (2) Preparation of LDH catalyst cathode: A piece of carbon paper with a diameter of 8-16 mm was immersed in the LDH catalyst dispersion obtained in step (1), and then the carbon paper was dried at room temperature for 10-20 min. The immersion-drying process was repeated to achieve an LDH catalyst loading of 0.3-0.7 mg / cm³. 2 Finally, it is dried in a vacuum at 80-110℃ for 10-24 h to obtain a lithium-oxygen battery cathode containing an LDH catalyst.

[0043] The assembly and testing methods for lithium-oxygen batteries are as follows: Under the protection of argon gas, the lithium-oxygen battery is assembled in sequence according to the following order: lithium sheet, glass fiber separator, positive electrode and stainless steel mesh. 40-60 μL of electrolyte is dropped onto the positive electrode and separator respectively. Finally, the performance of the lithium-oxygen battery is tested in a pure oxygen environment.

[0044] The electrolyte of the lithium-oxygen battery is a 1 mol / L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) solution in ethylene glycol dimethyl ether (DME), and the negative electrode is lithium metal.

[0045] The specific embodiments of the present invention will be further described in detail below through examples.

[0046] Example 1 This embodiment will prepare iodide ion-intercalated CoNi-LDH according to the following steps: Step 1: Prepare deionized water that has been boiled at 100℃ for more than 10 min. Then, disperse Co(NO3)2·6H2O in the deionized water to obtain a 0.1 mol / L solution A. Disperse 2-methylimidazole and 7 mg of CTAB (cetyltrimethylammonium bromide) in 70 mL of deionized water to obtain solution B, wherein the concentration of 2-methylimidazole is 0.8 mol / L.

[0047] Step 2: Pour solution A into solution B, stir at 600 rpm for 5 min at room temperature, let stand for 3 h, wash the precipitate 3 times with anhydrous ethanol, and dry at 40-70℃ to obtain cubic ZIF-67.

[0048] Step 3: Disperse 30 mg of cubic ZIF-67 in 15 mL of anhydrous ethanol to obtain solution C. Dissolve Ni(NO3)2·6H2O in anhydrous ethanol to obtain a 0.1 mol / L solution D.

[0049] Step 4: Add 2 mL of solution D to solution C to obtain solution E. Heat solution E at 80℃ for 20 min, then wash the precipitate three times with anhydrous ethanol, and dry it under vacuum at 60℃ to obtain CoNi-LDH.

[0050] Step 5: Disperse CoNi-LDH in anhydrous ethanol, add a saturated anhydrous ethanol solution of KI under argon protection, stir at 300 rpm at room temperature for 24 h, wash the precipitate three times with anhydrous ethanol, and dry it under vacuum at 60 °C to obtain iodide ion intercalated CoNi-LDH (i.e., redox medium intercalated LDH catalyst).

[0051] Furthermore, the catalyst (iodide-intercalated CoNi-LDH) obtained in this embodiment is prepared into an iodide-intercalated CoNi-LDH positive electrode according to the following steps: (1) Preparation of iodide-intercalated CoNi-LDH dispersion: Iodide-intercalated CoNi-LDH, Super P and 10wt% PTFE (polytetrafluoroethylene) suspension were thoroughly mixed in a mass ratio of 5:4:1, and then 1.8 mL of isopropanol and 2.7 mL of N-methylpyrrolidone were added. The mixture was ultrasonically homogenized at room temperature to obtain iodide-intercalated CoNi-LDH catalyst dispersion.

[0052] (2) Preparation of iodine ion intercalated CoNi-LDH cathode: A piece of carbon paper with a diameter of 16 mm was immersed in the catalyst dispersion obtained in step (1), and then the carbon paper was dried at room temperature for 10 min. The immersion-drying process was repeated to achieve a catalyst loading of 0.5 mg / cm³. 2 Finally, it was dried in a vacuum at 80°C for 12 h to obtain an iodine ion intercalated CoNi-LDH cathode (i.e., a lithium-oxygen battery cathode containing an LDH catalyst).

[0053] Comparative Example 1 This comparative example will prepare iodine ion intercalated CoNi-LDH according to the following steps: Step 1: Prepare deionized water that has been boiled at 100℃ for more than 10 min. Then, disperse Co(NO3)2·6H2O in the deionized water to obtain a 0.1 mol / L solution A. Disperse 2-methylimidazole and 7 mg of CTAB (cetyltrimethylammonium bromide) in 70 mL of deionized water to obtain solution B, wherein the concentration of 2-methylimidazole is 0.8 mol / L.

[0054] Step 2: Pour solution A into solution B, stir at 600 rpm for 5 min at room temperature, let stand for 3 h, wash the precipitate 3 times with anhydrous ethanol, and dry at 40-70℃ to obtain cubic ZIF-67.

[0055] Step 3: Disperse 30 mg of cubic ZIF-67 in 15 mL of anhydrous ethanol to obtain solution C. Dissolve Ni(NO3)2·6H2O in anhydrous ethanol to obtain a 0.1 mol / L solution D.

[0056] Step 4: Add 2 mL of solution D to solution C to obtain solution E. Heat solution E at 80℃ for 20 min, then wash the precipitate three times with anhydrous ethanol, and dry it under vacuum at 60℃ to obtain CoNi-LDH.

[0057] Furthermore, the CoNi-LDH obtained in this embodiment is fabricated into a positive electrode according to the following steps: (1) Preparation of CoNi-LDH dispersion: CoNi-LDH, Super P and 10wt% PTFE (polytetrafluoroethylene) suspension were thoroughly mixed in a mass ratio of 5:4:1, and then 1.8 mL of isopropanol and 2.7 mL of N-methylpyrrolidone were added. The mixture was ultrasonically homogenized at room temperature to obtain the catalyst dispersion.

[0058] (2) Preparation of CoNi-LDH cathode: A piece of carbon paper with a diameter of 16 mm was immersed in the catalyst dispersion obtained in step (1), and then the carbon paper was dried at room temperature for 10 min. The immersion-drying process was repeated to achieve a catalyst loading of 0.5 mg / cm³. 2 Finally, it was dried in a vacuum at 80°C for 12 h to obtain the CoNi-LDH cathode.

[0059] Comparative Example 2 This comparative example prepared the Super P cathode according to the following steps: (1) Preparation of Super P dispersion: Super P and 10wt% PTFE (polytetrafluoroethylene) suspension were thoroughly mixed at a mass ratio of 9:1, and then 1.8 mL of isopropanol and 2.7 mL of N-methylpyrrolidone were added. The mixture was ultrasonically homogenized at room temperature to obtain the catalyst dispersion.

[0060] (2) Preparation of Super P cathode: A piece of carbon paper with a diameter of 16 mm was immersed in the Super P dispersion obtained in step (1), and then the carbon paper was dried at room temperature for 10 min. The immersion-drying process was repeated to achieve a catalyst loading of 0.5 mg / cm³. 2Finally, it was dried in a vacuum at 80°C for 12 h to obtain the Super P cathode.

[0061] The morphology and properties of the samples obtained in the above embodiments and comparative examples were characterized as follows: 1. XRD characterization The iodine ion intercalated CoNi-LDH obtained in Example 1 and the CoNi-LDH obtained in Comparative Example 1 were characterized by XRD, and the results are as follows: Figure 1 As shown in (a), it can be seen that all peaks of the prepared ZIF-67 are consistent with the theoretical characteristic peaks; the diffraction peaks of CoNi-LDH appear at 2θ at 10.32°, 21.52° and 33.73°, corresponding to the (003), (006) and (012) crystal planes respectively, exhibiting diffraction peaks unique to hydrotalcite, indicating that CoNi-LDH was successfully prepared; compared with CoNi-LDH, the interlayer spacing of iodide ion intercalated CoNi-LDH changed, and the diffraction peaks of the (003) crystal plane in XRD shifted significantly to lower angles, indicating that I - Successfully intercalated into CoNi-LDH.

[0062] 2. FT-IR characterization The iodine ion intercalated CoNi-LDH obtained in Example 1 and the CoNi-LDH obtained in Comparative Example 1 were characterized by FT-IR, and the results are as follows: Figure 1 As shown in (b), it can be seen that in the iodine ion intercalated CoNi-LDH, the CoNi-LDH was originally located at 1384 cm⁻¹. -1 and, 1360cm -1 NO3 - CO3 2- The vibration peak disappeared, and a new I appeared. - The vibration peak is located at 1635 cm⁻¹. -1 The vibrational peak of interlayer water molecules at this point is weakened because I - The absence of hydrogen bonding results in a reduction of interlayer water, demonstrating the successful preparation of iodine ion intercalated CoNi-LDH.

[0063] 3. SEM-EDS characterization The iodine ion intercalated CoNi-LDH obtained in Example 1 and the CoNi-LDH obtained in Comparative Example 1 were characterized by SEM-EDS, and the results are as follows: Figure 2 As shown, hollow cubic CoNi-LDH was synthesized by etching cubic ZIF-67 at 100-200 nm with nickel; further, by etching with I... - By intercalation, hollow cubic iodide-intercalated CoNi-LDH was prepared. EDS results showed the presence of I, proving that iodide-intercalated CoNi-LDH was successfully prepared.

[0064] 4. Battery performance test The iodine-intercalated CoNi-LDH cathode from Example 1 was selected as the experimental group, while the CoNi-LDH cathode from Comparative Example 1 and the Super P cathode from Comparative Example 2 were used as control groups. Lithium-oxygen batteries were assembled using these methods. The electrolyte composition was a 1 mol / L LiTFSI DME solution. Constant current discharge tests, constant current charge-discharge tests, and cycle stability tests were performed on the lithium-oxygen batteries. The cathode after discharge was characterized by XRD.

[0065] The XRD characterization results of the positive electrode after discharge are as follows: Figure 3 As shown, it can be seen that the products obtained from the iodine ion intercalation CoNi-LDH in Example 1, the CoNi-LDH in Comparative Example 1, and the Super P cathode in Comparative Example 2 are all Li2O2.

[0066] Charge and discharge test results are as follows Figure 4 As shown, it can be seen that the lithium-oxygen battery of the iodine ion intercalated CoNi-LDH in Example 1 has an overpotential that is 0.19 V lower than that of CoNi-LDH in Comparative Example 1 and 0.46 V lower than that of Super P in Comparative Example 2, proving that the iodine ion intercalated CoNi-LDH has the best catalytic effect.

[0067] Cyclic stability test results are as follows Figure 5 As shown, it can be seen that the lithium-oxygen battery with iodine ion intercalation CoNi-LDH in Example 1 has the lowest overpotential and the best cycle stability.

[0068] 5. Observe the negative electrode after circulation. The iodide-intercalated CoNi-LDH cathode from Example 1 was selected as the experimental group, and the Super P cathode from Comparative Example 2 was selected as the control group. Lithium-oxygen batteries were assembled in both groups. The electrolyte composition for Example 1 was a 1 mol / L LiTFSI DME solution, and the electrolyte composition for Comparative Example 2 was a 1 mol / L LiTFSI DME solution containing 10 mmol LiI. Cyclic tests were performed on the lithium-oxygen batteries, and the negative electrode was observed after the cycle tests.

[0069] Negative electrode photograph after cyclic testing, as shown Figure 6 As shown, it can be seen that the negative electrode of the lithium-oxygen battery with iodine ion intercalation CoNi-LDH in Example 1 is brighter after cycling.

[0070] As can be seen, compared with carbon materials and LDH (layered bimetallic hydroxide) catalysts without redox media intercalation, the redox media intercalated LDH catalyst prepared in this invention not only has the synergistic effect of liquid and solid catalysts, but also anchors the redox media in the positive electrode, thereby effectively accelerating the positive electrode reaction kinetics of lithium-oxygen batteries, reducing the charge-discharge overpotential, improving electrochemical performance, solving the problems of negative electrode failure and reduced catalytic effect caused by the shuttle effect of existing liquid catalysts in lithium-oxygen batteries, and the preparation method is simple.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing an LDH catalyst intercalated with a redox medium, characterized in that, Includes the following steps: Step 1. Disperse Co(NO3)2·6H2O in deionized water to obtain solution A; Step 2. Disperse 2-methylimidazole and CTAB in deionized water to obtain solution B; Step 3. Pour solution A into solution B, stir at room temperature and let stand. Wash the precipitate with anhydrous ethanol and dry it to obtain cubic ZIF-67. Step 4. Disperse the cubic ZIF-67 obtained in Step 3 in anhydrous ethanol to obtain solution C; Step 5. Dissolve the nickel salt or iron salt in anhydrous ethanol to obtain solution D; Step 6. Add solution D to solution C to obtain solution E. Heat solution E at a constant temperature, then wash the precipitate with anhydrous ethanol and dry it to obtain cobalt-based LDH. Step 7. Disperse cobalt-based LDH in anhydrous ethanol, then add anhydrous ethanol solution containing redox media, stir at room temperature, wash the precipitate with anhydrous ethanol and dry it to obtain redox media-intercalated LDH catalyst.

2. The preparation method according to claim 1, characterized in that: In step 1, the concentration of solution A is 0.05-0.2 mol / L.

3. The preparation method according to claim 1, characterized in that: In step 2, the concentration of 2-methylimidazole in solution B is 0.5-1 mol / L, and the concentration of CTAB is 0.2-0.3 mmol / L.

4. The preparation method according to claim 1, characterized in that: In step 4, the concentration of solution C is 1-5 mg / mL.

5. The preparation method according to claim 1, characterized in that: In step 5, the nickel salt is at least one of Ni(NO3)2·6H2O, NiCl2·6H2O, anhydrous Ni(NO3)2, and anhydrous NiCl2.

6. The preparation method according to claim 1, characterized in that: In step 5, the iron salt is at least one of Fe(NO3)3·9H2O, FeCl3·6H2O, anhydrous Fe(NO3)3, and anhydrous FeCl3.

7. The preparation method according to claim 1, characterized in that: In step 5, the concentration of nickel salt or iron salt in solution D is 0.05-0.5 mol / L.

8. The preparation method according to claim 1, characterized in that: In step 6, the constant temperature heating is 60-100℃ and the time is 5-60 min.

9. The preparation method according to claim 1, characterized in that: In step 7, the concentration of the cobalt-based LDH in anhydrous ethanol is 1-20 mg / mL.

10. The preparation method according to claim 1, characterized in that: In step 7, the redox medium is at least one of sodium bromide, sodium iodide, potassium bromide, potassium iodide, sodium nitrate, and potassium nitrate.

11. An LDH catalyst with redox media intercalation prepared by the preparation method according to any one of claims 1 to 10, characterized in that: The redox medium intercalated LDH catalyst is a cobalt-based LDH layer intercalated with redox medium anions.

12. The LDH catalyst with redox media intercalation according to claim 11, characterized in that: The cobalt-based LDH has a hollow cubic structure with a cubic size of 100-500 nm.

13. The LDH catalyst with redox media intercalation according to claim 11, characterized in that: The intercalated redox medium anion is a liquid catalyst in lithium-oxygen batteries, and its molecular radius is smaller than TFSI. - Anions.

14. The application of an LDH catalyst with redox media intercalation as described in any one of claims 11-13, characterized in that: The catalyst is used in the positive electrode of an organic electrolyte lithium-oxygen battery.

15. The application according to claim 14, characterized in that: The lithium salt of the organic electrolyte is LiTFSI.

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