A magnetoplumbite-type oxide, a method for preparing the same, and an application thereof

Abstract

This invention discloses a magnetolite-type oxide, its preparation method, and its application. The preparation method includes the following steps: S1, dissolving rare earth nitrates, transition metal nitrates, and Al(NO3)3 in deionized water to obtain a mixed nitrate solution; S2, adding citric acid monohydrate to the mixed nitrate solution, heating and stirring, and evaporating to obtain a transparent gel; S3, drying the gel to obtain a loose and porous dry gel; S4, subjecting the dry gel to a first high-temperature treatment in air at 650–950°C to obtain a precursor; S5, grinding and crushing the precursor, mixing it evenly with the dissolved salt, and then subjecting it to a second high-temperature treatment in air at 1500–2000°C to obtain the magnetolite-type oxide. The preparation method of this invention is low-cost, simple, easy to implement, and widely applicable. When the magnetolite-type oxide is applied to lithium-sulfur batteries, it helps to improve battery performance.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic materials technology, specifically relating to a magnetic lumpy oxide, its preparation method, and its application. Background Technology

[0002] The poor intrinsic conductivity and low utilization rate of elemental sulfur have significantly hampered the industrialization prospects of sulfur-based energy storage batteries. To overcome these challenges, developing advanced elemental sulfur carriers is key to improving battery performance (Nat. Nanotechnol. 2020, 15, 231).

[0003] Metal oxides, with their rich electronic structures and excellent mechanical properties, coupled strongly with elemental sulfur, possess abundant metal and oxygen vacancies, making them excellent potential as sulfur fixation sites to enhance battery stability. However, liquid polysulfides exhibit high affinity, which is detrimental to subsequent electrocatalytic conversion. Therefore, improving the intrinsic electrocatalytic activity of oxides is crucial (Energy Storage Mater. 2024, 67, 103315). Based on this, phase engineering is an effective strategy to improve the intrinsic electrocatalytic activity of materials. On the one hand, enriched heterogeneous phases and interfaces can serve as potential catalytic active sites, modulating the adsorption / desorption energies of intermediates (Chemical Reviews, 2024, 124, 1247). On the other hand, vacancy control and the implementation of topological ion exchange (TIE) can exhibit significant heterogeneous interactions and interfacial effects, further enhancing the catalytic activity of materials (Nat. Commun. 2023, 14, 5389).

[0004] Given the aforementioned problems in the multiphase / multistate / multi-electron reactions of sulfur-based electrodes, improving the overall performance of oxide sulfur storage batteries through phase engineering remains a challenge. This invention addresses these issues. Summary of the Invention

[0005] To address at least one of the aforementioned technical problems, this invention provides a magnetic plume oxide, its preparation method, and its application. The invention first prepares a precursor using a sol-gel method, then combines this with a molten salt method for high-temperature treatment, resulting in a powder with finer particles and a uniform particle size distribution. The magnetic plume oxide prepared by this invention exhibits excellent electrocatalytic performance during the reduction of elemental sulfur, providing theoretical support and technological breakthroughs for the practical application of magnetic plume oxides in sulfur reduction, thereby accelerating the practical application of sulfur-based batteries.

[0006] The technical solution of this invention is as follows:

[0007] This invention provides a method for preparing a magnetolite-type oxide, comprising the following steps:

[0008] S1. Dissolve rare earth nitrate Ln(NO3)3·6H2O, transition metal nitrate Me(NO3)2 and Al(NO3)3 in deionized water to obtain a mixed nitrate solution;

[0009] S2. Add citric acid monohydrate to the mixed nitrate solution obtained in step S1, heat and stir, and evaporate to obtain a transparent gel;

[0010] S3. Dry the gel obtained in step S2 to obtain a loose and porous dry gel.

[0011] The dry gels obtained in steps S4 and S3 are subjected to a first high-temperature treatment in air at 650–950°C to obtain the precursor.

[0012] S5. Grind and crush the precursor obtained in step S4, mix it evenly with the soluble salt, and then perform a second high-temperature treatment in air at 1500-2000℃ to obtain the magnetolite oxide.

[0013] Preferably, in step S1, the molar ratio of rare earth nitrate Ln(NO3)3·6H2O, transition metal nitrate Me(NO3)2, and Al(NO3)3 is 1:1:11; the total concentration of the prepared mixed nitrate solution is 0.01 to 1 g / L, which is the total concentration of the three nitrates.

[0014] Preferably, in step S1, the rare earth nitrate Ln(NO3)3·6H2O is any one of Y(NO3)3·6H2O, La(NO3)3·6H2O, Pr(NO3)3·6H2O, Nd(NO3)3·6H2O, Sm(NO3)3·6H2O, Eu(NO3)3·6H2O, Gd(NO3)3·6H2O, Tm(NO3)3·6H2O, Ce(NO3)3·6H2O, and Yb(NO3)3·6H2O; and the transition metal nitrate Me(NO3)2 is any one of Mg(NO3)2, Fe(NO3)2, Co(NO3)2, Ni(NO3)2, Cu(NO3)2, Zr(NO3)2, and Zn(NO3)2.

[0015] Preferably, in step S2, the molar amount of citric acid monohydrate is 1 to 10 times the total molar amount of metal ions in the mixed nitrate solution;

[0016] Heating and stirring at 65–100°C, followed by evaporation, yields a transparent gel.

[0017] Preferably, in step S3, the drying conditions are: placing the gel in an oven at 50–200°C for 5–12 hours.

[0018] Preferably, in step S4, the first high-temperature treatment lasts for 1 to 5 hours.

[0019] Preferably, in step S5, the second high-temperature treatment takes 1 to 10 hours.

[0020] Preferably, in step S5, the dissolved salt is a mixture of NaCl and KCl, and the total mass of the dissolved salt is 2 to 20 times the mass of the precursor.

[0021] This invention also provides a magnetoplumbite-type oxide, prepared by the above-described method, which has a magnetoplumbite structure and has the chemical formula LnMeAl. 11 O 19 Ln is any one of the rare earth elements Y, La, Pr, Nd, Sm, Eu, Gd, Tm, Ce and Yb, and Me is any one of the transition metal elements Mg, Fe, Co, Ni, Cu, Zr and Zn.

[0022] The present invention also provides the application of the above-mentioned magnetic plume oxide as a catalyst material in sulfur reduction electrocatalysis. More preferably, the above-mentioned magnetic plume oxide can be used to prepare lithium-sulfur batteries and can be used as a catalyst material for lithium-sulfur batteries.

[0023] The beneficial effects of this invention are:

[0024] This invention combines the sol-gel method and the molten salt method to synergistically prepare the magnetoplumble oxide LnMeAl. 11 O 19 Compared with oxides prepared by other single methods (such as solid-state method, sol-gel method and molten salt method), the LnMeAl prepared in this invention has superior properties. 11 O 19 It exhibits stronger catalytic activity, which can significantly improve the reaction kinetics of sulfur-based batteries and is expected to fully realize the stable cycling performance of batteries at high rates. In addition, the preparation method of the present invention has the advantages of low cost, simplicity and ease of implementation, and wide applicability. Attached Figure Description

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0026] Figure 1 The XRD pattern of the magnetoplumble oxide material prepared in Example 1;

[0027] Figure 2 The SEM morphology of the magnetoplumble oxide material prepared in Example 2 is shown below.

[0028] Figure 3 The electrocatalytic performance of the magnetoplumble oxide material prepared in Example 3;

[0029] Figure 4 The electrocatalytic performance of the magnetoplumbleite-type oxide material prepared in Example 4;

[0030] Figure 5 The electrocatalytic performance of the magnetoplumbleite-type oxide material prepared in Example 5;

[0031] Figure 6 The electrocatalytic performance of the magnetoplumble oxide material prepared in Example 6;

[0032] Figure 7 Battery cycle performance of the magnetic plume oxide material prepared in Example 7;

[0033] Figure 8 The SEM morphology of the product prepared for Comparative Example 1 is shown.

[0034] Figure 9 The XRD pattern of the product prepared in Comparative Example 2;

[0035] Figure 10 The electrocatalytic performance of the product prepared in Comparative Example 2 is shown. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0037] Example 1

[0038] This embodiment provides a method for preparing magnetoplumbourine-type oxides based on a sol-gel precursor method:

[0039] Sm(NO3)3·6H2O, Mg(NO3)2, and Al(NO3)3 were weighed out in a molar ratio of 1:1:11 and dissolved separately in deionized water, resulting in a mixed nitrate solution with a total concentration of 0.1 g / L. After stirring for 10 minutes, citric acid monohydrate, five times the total molar amount of metal ions, was added to the nitrate solution. The mixture was heated and stirred at 80°C, and then rotary evaporated to obtain a transparent gel.

[0040] The gel was placed in an oven at 155°C for 7 hours until a loose and porous dry gel was obtained.

[0041] The above-mentioned dry gel was then placed into an alumina crucible and placed in a muffle furnace. It was heated at 850°C in an air atmosphere for 2 hours to obtain the precursor.

[0042] The above precursor was ground and crushed, then mixed evenly with molten salt at a weight ratio of 10 (molar ratio NaCl:KCl = 1:1). The mixture was then placed in an alumina crucible and heated in an air atmosphere at 1550°C for 1 hour to obtain SmMgAl. 11 O 19 Powder.

[0043] Analysis showed that the XRD pattern of the prepared magnetoplumble oxide was as follows: Figure 1 As shown in the figure, the prepared powder is SmMgAl. 11 O 19 There are no other metal compound impurities on the matrix.

[0044] Example 2

[0045] This embodiment provides a method for preparing magnetoplumbourine-type oxides based on a sol-gel precursor method:

[0046] Eu(NO3)3·6H2O, Co(NO3)2, and Al(NO3)3 were weighed out in a molar ratio of 1:1:11 and dissolved separately in deionized water, resulting in a mixed nitrate solution with a total concentration of 0.3 g / L. After stirring for 10 minutes, citric acid monohydrate, which was 6 times the total molar amount of metal ions, was added to the nitrate solution. The mixture was heated and stirred at 75°C, and then rotary evaporated to obtain a transparent gel.

[0047] The gel was placed in an oven at 135°C for 9 hours until a loose and porous dry gel was obtained.

[0048] The above-mentioned dry gel was then placed into an alumina crucible and placed in a muffle furnace. It was heated at 875°C in an air atmosphere for 2.5 hours to obtain the precursor.

[0049] The above precursor was ground and crushed, then mixed evenly with molten salt at a weight ratio of 12 (molar ratio NaCl:KCl = 1:1). The mixture was then placed in an alumina crucible and heated in an air atmosphere at 1575°C for 6 hours to obtain EuCoAl. 11 O 19 Powder.

[0050] Analysis revealed the following: the scanning electron microscope images of the prepared magnetoplumble oxide are shown below. Figure 2 As shown in the figure, the prepared powder particles appear to be fine and uniform under SEM observation, with individual particle sizes ranging from 600 to 800 nm.

[0051] Example 3

[0052] This embodiment provides a method for preparing magnetoplumbourine-type oxides based on a sol-gel precursor method:

[0053] Sm(NO3)3·6H2O, Mg(NO3)2, and Al(NO3)3 were weighed out in a molar ratio of 1:1:11 and dissolved separately in deionized water, resulting in a mixed nitrate solution with a total concentration of 0.25 g / L. After stirring for 10 minutes, 6.6 times the total molar amount of metal ions in citric acid monohydrate was added to the nitrate solution, and the mixture was heated and stirred at 90°C. The mixture was then rotary evaporated to obtain a transparent gel.

[0054] The gel was placed in an oven at 100°C for 7.5 hours until a loose and porous dry gel was obtained.

[0055] The above-mentioned dry gel was then placed into an alumina crucible and placed in a muffle furnace. It was heated at 820°C in an air atmosphere for 3 hours to obtain the precursor.

[0056] The above precursor was ground and crushed, and then mixed evenly with molten salt at a weight ratio of 11 (molar ratio NaCl:KCl = 1:1). The mixture was then placed in an alumina crucible and heated in an air atmosphere at 1610°C for 2 hours to obtain SmMgAl. 11 O 19 Powder.

[0057] To test the electrocatalytic activity of sulfur-based batteries, 80 wt.% sulfur-containing electrode material (30% SmMgAl) was first used. 11 O 19 Powder (70% elemental sulfur), 10 wt.% Super P and 10 wt.% polyvinylidene fluoride (PVDF) were thoroughly mixed in a mortar, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) (Aldrich, 99% battery grade) solvent was added dropwise. After stirring for 8 hours, a uniform slurry was obtained. The slurry was then uniformly coated onto the positive electrode current collector and dried in a vacuum oven at 60°C for approximately 10 hours. After cooling to room temperature, it was cut into standard circular electrode sheets using a punching machine, weighed, and set aside. The coin-type CR2016 half-cell was prepared in a glove box filled with inert gas Ar (H2O and O2, <10 ppm). -5 The battery is assembled in a 100% (%), with a polypropylene (PP) separator of model Celgard 2400. High-purity Li sheets are used as the negative electrode. The electrolyte contains 1M LiTFSI and 1 wt.% LiNO3, with a mixed solution of DOL and DME (volume ratio 1:1) as the solvent. Cyclic voltammetry (CV, voltage range: 1.7-2.8V) was performed using a CHI760E electrochemical workstation.

[0058] Analysis showed that the electrocatalytic performance of the prepared magnetoplumble oxide was as follows: Figure 3As shown, two distinct reduction peaks appear in the discharge plateau of the reduction reaction, reaching their maximum peak current values ​​at 2.289 V and 1.981 V, respectively. This corresponds to the stepwise lithiation reaction of the sulfur cathode, where elemental sulfur is transformed into long-chain lithium polysulfides: S8 → Li2S x (4≤x≤8) and the transformation of long-chain lithium polysulfides into short-chain lithium polysulfides: Li₂S x (4≤x≤8)→Li2S x (1≤x≤3). It can be seen that the prepared SmMgAl... 11 O 19 It exhibits good performance as an electrocatalyst for sulfur-based batteries.

[0059] Example 4

[0060] This embodiment provides a method for preparing magnetoplumbourine-type oxides based on a sol-gel precursor method:

[0061] Ce(NO3)3·6H2O, Ni(NO3)2, and Al(NO3)3 were weighed out in a molar ratio of 1:1:11 and dissolved separately in deionized water, resulting in a mixed nitrate solution with a total concentration of 0.45 g / L. After stirring for 10 minutes, citric acid monohydrate, which was 9 times the total molar amount of metal ions, was added to the nitrate solution. The mixture was heated and stirred at 95°C, and then rotary evaporated to obtain a transparent gel.

[0062] The gel was placed in an oven at 175°C for 8 hours until a loose and porous dry gel was obtained.

[0063] The above-mentioned dry gel was then placed into an alumina crucible and placed in a muffle furnace. It was heated at 870°C in an air atmosphere for 2 hours to obtain the precursor.

[0064] The above precursor was ground and crushed, and then mixed evenly with molten salt at a weight ratio of 12 (molar ratio NaCl:KCl = 1:1). The mixture was then placed in an alumina crucible and placed in a muffle furnace. Heating was carried out at 1600°C in air for 2 hours to obtain CeNiAl. 11 O 19 Powder.

[0065] A sulfur-based battery was prepared according to the method in Example 3, except that the magnetoplumble oxide was replaced with CeNiAl as in this example. 11 O 19 Powder. Cyclic voltammetry (CV, voltage range: 1.7-2.8V) tests were conducted using a CHI760E electrochemical workstation.

[0066] Analysis showed that the electrocatalytic performance of the prepared magnetoplumble oxide was as follows: Figure 4As shown, two distinct reduction peaks appear in the discharge plateau of the reduction reaction, reaching their maximum peak current values ​​at 2.283 V and 1.976 V, respectively. This corresponds to the stepwise lithiation reaction of the sulfur cathode, where elemental sulfur is transformed into long-chain lithium polysulfides: S8 → Li2S x (4≤x≤8) and the transformation of long-chain lithium polysulfides into short-chain lithium polysulfides: Li₂S x (4≤x≤8)→Li2S x (1≤x≤3). It can be seen that the prepared CeNiAl... 11 O 19 It exhibits good performance as an electrocatalyst for sulfur-based batteries.

[0067] Example 5

[0068] This embodiment provides a method for preparing magnetoplumbourine-type oxides based on a sol-gel precursor method:

[0069] Weigh out La(NO3)3·6H2O, Mg(NO3)2, and Al(NO3)3 in a molar ratio of 1:1:11 and dissolve them separately in deionized water to obtain a mixed nitrate solution with a total concentration of 0.1 g / L. After stirring for 10 minutes, add citric acid monohydrate, which is three times the total molar amount of metal ions, to the nitrate solution obtained above. Heat and stir at 70°C, and then rotary evaporate to obtain a transparent gel.

[0070] The gel was placed in an oven at 80°C for 5 hours until a loose and porous dry gel was obtained.

[0071] The above-mentioned dry gel was then placed into an alumina crucible and placed in a muffle furnace. It was heated at 750°C in an air atmosphere for 2 hours to obtain the precursor.

[0072] The above precursor was ground and crushed, then mixed evenly with molten salt (NaCl:KCl = 1:1) at a weight ratio of 8. The mixture was then placed in an alumina crucible and heated in an air atmosphere at 1600°C for 3.5 hours to obtain LaMgAl. 11 O 19 Powder.

[0073] A sulfur-based battery was prepared according to the method in Example 3, except that the magnetoplumble oxide was replaced with LaMgAl from this example. 11 O 19 Powder. Cyclic voltammetry (CV, voltage range: 1.7-2.8V) tests were conducted using a CHI760E electrochemical workstation.

[0074] Analysis showed that the electrocatalytic performance of the prepared magnetoplumble oxide was as follows: Figure 5As shown, two distinct reduction peaks appear in the discharge plateau of the reduction reaction, reaching their maximum peak current values ​​at 2.213 V and 1.856 V, respectively. This corresponds to the stepwise lithiation reaction of the sulfur cathode, where elemental sulfur is transformed into long-chain lithium polysulfides: S8 → Li2S x (4≤x≤8) and the transformation of long-chain lithium polysulfides into short-chain lithium polysulfides: Li₂S x (4≤x≤8)→Li2S x (1≤x≤3). It can be seen that the prepared LaMgAl... 11 O 19 It exhibits good performance as an electrocatalyst for sulfur-based batteries.

[0075] Example 6

[0076] This embodiment provides a method for preparing magnetoplumble-type oxides based on a sol-gel precursor method:

[0077] Gd(NO3)3·6H2O, Zn(NO3)2, and Al(NO3)3 were weighed out in a molar ratio of 1:1:11 and dissolved separately in deionized water, resulting in a mixed nitrate solution with a total concentration of 0.5 g / L. After stirring for 10 minutes, citric acid monohydrate, at a molar ratio of 5.5 times the total number of metal ions, was added to the nitrate solution. The mixture was heated and stirred at 80°C, and then rotary evaporated to obtain a transparent gel.

[0078] The gel was placed in an oven at 165°C for 6 hours until a loose and porous dry gel was obtained.

[0079] The above-mentioned dry gel was then placed into an alumina crucible and placed in a muffle furnace. It was heated at 900°C in an air atmosphere for 2 hours to obtain the precursor.

[0080] The above precursor was ground and crushed, and then mixed evenly with molten salt at a weight ratio of 10 (molar ratio NaCl:KCl = 1:1). The mixture was then placed in an alumina crucible and heated in an air atmosphere at 1500°C for 2.5 hours to obtain GdZnAl. 11 O 19 Powder.

[0081] A sulfur-based battery was prepared according to the method in Example 3, except that the magnetoplumble oxide was replaced with GdZnAl from this example. 11 O 19 Powder. Cyclic voltammetry (CV, voltage range: 1.7-2.8V) tests were conducted using a CHI760E electrochemical workstation.

[0082] Analysis showed that the electrocatalytic performance of the prepared magnetoplumble oxide was as follows: Figure 6As shown, two distinct reduction peaks appear in the discharge plateau of the reduction reaction, reaching their maximum peak current values ​​at 2.246 V and 1.952 V, respectively. This corresponds to the stepwise lithiation reaction of the sulfur cathode, where elemental sulfur is transformed into long-chain lithium polysulfides: S8 → Li2S x (4≤x≤8) and the transformation of long-chain lithium polysulfides into short-chain lithium polysulfides: Li₂S x (4≤x≤8)→Li2S x (1≤x≤3). It can be seen that the prepared GdZnAl 11 O 19 It exhibits good performance as an electrocatalyst for sulfur-based batteries.

[0083] Example 7

[0084] This embodiment provides a method for preparing magnetoplumbourine-type oxides based on a sol-gel precursor method:

[0085] Eu(NO3)3·6H2O, Mg(NO3)2, and Al(NO3)3 were weighed out in a molar ratio of 1:1:11 and dissolved separately in deionized water, resulting in a mixed nitrate solution with a total concentration of 0.6 g / L. After stirring for 10 minutes, citric acid monohydrate, at a molar ratio of 7 times the total number of metal ions, was added to the nitrate solution. The mixture was heated and stirred at 90°C, and then rotary evaporated to obtain a transparent gel.

[0086] The gel was placed in an oven at 160°C for 7 hours until a loose and porous dry gel was obtained.

[0087] The above-mentioned dry gel was then placed into an alumina crucible and placed in a muffle furnace. It was heated at 850°C in an air atmosphere for 2 hours to obtain the precursor.

[0088] The above precursor was ground and crushed, then mixed evenly with molten salt in a weight ratio of 9 (molar ratio NaCl:KCl = 1:1). The mixture was then placed in an alumina crucible and heated in an air atmosphere at 1550°C for 3.5 hours to obtain EuMgAl. 11 O 19 Powder.

[0089] Analysis revealed that the prepared magnetoplumble oxide, after being melt-infiltrated with sulfur at 155℃, yielded the sulfur-storing cathode material EuMgAl. 11 O 19 / S, the long-cycle performance of the assembled coin cells is as follows Figure 7 As shown. When the current is increased and the cycle period is extended, EuMgAl 11 O 19 The / S composite electrodes all exhibited more stable high-rate performance, 3.7 mg / cm 2Under high areal load, the 2C current density charge-discharge cycle can be stably maintained for at least 560 cycles.

[0090] Comparative Example 1

[0091] Eu(NO3)3·6H2O, Co(NO3)2, and Al(NO3)3 were weighed out in a molar ratio of 1:1:11 and dissolved separately in deionized water, resulting in a mixed nitrate solution with a total concentration of 0.3 g / L. After stirring for 10 minutes, citric acid monohydrate, which was 6 times the total molar amount of metal ions, was added to the nitrate solution obtained above. The mixture was heated and stirred at 75°C, and then rotary evaporated to obtain a transparent gel.

[0092] The gel was placed in an oven at 135°C for 9 hours until a loose and porous dry gel was obtained.

[0093] The above-mentioned dry gel was then placed into an alumina crucible and placed in a muffle furnace. It was heated at 875°C in an air atmosphere for 2.5 hours to obtain the precursor.

[0094] The above precursor was ground and crushed, and then placed in a muffle furnace and heated at 1575°C in air for 6 hours to obtain EuCoAl. 11 O 19 Powder.

[0095] Analysis revealed the following SEM images of the prepared product: Figure 8 As shown, the magnetoplumble oxide sintered using a single solid-state method exhibits a large amount of agglomeration and is not a fine, uniform nanoscale particle. Compared to Example 2, when the synthesis conditions do not include the relevant treatment operation of molten salt grinding and mixing, the prepared powder morphology is not a fine, uniform particle.

[0096] Comparative Example 2

[0097] Metal oxides Sm2O3, FeO, and Al2O3 powders were weighed out in a molar ratio of 1:2:22. The powders were mixed in a planetary ball mill. The resulting mixed powder was placed in an alumina crucible and then placed in a muffle furnace. The mixture was heated at 1600°C in an air atmosphere for 4 hours to obtain the powder.

[0098] Analysis showed that the XRD pattern of the prepared product was as follows: Figure 9 As shown in the figure, the prepared powder cannot yield pure phase SmFeAl. 11 O 19 It also contains other metal compound impurities, such as Al2O3 and FeAl2O4.

[0099] A sulfur-based battery was prepared according to the method in Example 3, except that the magnetoplumble oxide was replaced with the powder prepared in this comparative example. Cyclic voltammetry (CV, voltage range: 1.7-2.8V) was studied using a CHI760E electrochemical workstation.

[0100] The electrocatalytic performance of the prepared product is as follows: Figure 10 As shown, only one reduction peak appears in the discharge plateau of the reduction reaction, reaching its maximum peak current at 2.165V, corresponding to the lithiation reaction of the sulfur cathode, where elemental sulfur is transformed into lithium polysulfides: S8 → Li2S x (1≤x≤8). It is evident that when the synthesis conditions are not strictly in accordance with the claims (sol-gel method + molten salt), the prepared powder morphology is not that of fine, uniform particles. SmFeAl 11 O 19 It did not exhibit good electrocatalytic performance.

[0101] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for preparing a magnetoplumbleite-type oxide, characterized in that, Includes the following steps: S1. Dissolve rare earth nitrate Ln(NO3)3·6H2O, metal nitrate Me(NO3)2, and Al(NO3)3 in deionized water to obtain a mixed nitrate solution; wherein, Me(NO3)2 is any one of Mg(NO3)2, Fe(NO3)2, Co(NO3)2, Ni(NO3)2, Cu(NO3)2, Zr(NO3)2, and Zn(NO3)2; S2. Add citric acid monohydrate to the mixed nitrate solution obtained in step S1, heat and stir, and evaporate to obtain a transparent gel; S3. Dry the gel obtained in step S2 to obtain a loose and porous dry gel. The dry gels obtained in steps S4 and S3 are subjected to a first high-temperature treatment in air at 650~950℃ to obtain the precursor. S5. Grind and crush the precursor obtained in step S4, and grind and mix it evenly with the soluble salt. Then, perform a second high-temperature treatment in air at 1500~2000℃ to obtain the magnetolite oxide. The soluble salt is a mixture of NaCl and KCl, and the total mass of the soluble salt is 2 to 20 times the mass of the precursor. When magnetoplumble oxide is used as a catalyst in lithium-sulfur batteries, a stepwise lithiation reaction occurs at the sulfur cathode, transforming elemental sulfur into long-chain lithium polysulfides: S8 → Li2S x Transformation of long-chain lithium polysulfides into short-chain lithium polysulfides: Li₂S x →Li2S x Li2S x In Li2S, x satisfies 4 ≤ x ≤ 8. x x in the equation satisfies 1 ≤ x ≤ 3.

2. The preparation method according to claim 1, characterized in that, In step S1, the molar ratio of rare earth nitrate Ln(NO3)3·6H2O, metal nitrate Me(NO3)2, and Al(NO3)3 is 1:1:11; the total concentration of the prepared mixed nitrate solution is 0.01~1g / L.

3. The preparation method according to claim 1, characterized in that, In step S1, the rare earth nitrate Ln(NO3)3·6H2O is any one of Y(NO3)3·6H2O, La(NO3)3·6H2O, Pr(NO3)3·6H2O, Nd(NO3)3·6H2O, Sm(NO3)3·6H2O, Eu(NO3)3·6H2O, Gd(NO3)3·6H2O, Tm(NO3)3·6H2O, Ce(NO3)3·6H2O, and Yb(NO3)3·6H2O.

4. The preparation method according to claim 1, characterized in that, In step S2, the molar amount of citric acid monohydrate is 1 to 10 times the total molar amount of metal ions in the mixed nitrate solution; Heating and stirring at 65~100℃, followed by evaporation, yields a transparent gel.

5. The preparation method according to claim 1, characterized in that, In step S3, the drying conditions are as follows: place the gel in an oven at 50~200℃ and keep it at that temperature for 5~12 hours.

6. The preparation method according to claim 1, characterized in that, In step S4, the first high-temperature treatment takes 1 to 5 hours.

7. The preparation method according to claim 1, characterized in that, In step S5, the second high-temperature treatment takes 1 to 10 hours.

8. A magnetoplumbago-type oxide, characterized in that, The magnetic lead oxide with the chemical formula LnMeAl is prepared by the preparation method according to any one of claims 1-7. 11 O 19 Ln is any one of the rare earth elements Y, La, Pr, Nd, Sm, Eu, Gd, Tm, Ce and Yb, and Me is any one of the metallic elements Mg, Fe, Co, Ni, Cu, Zr and Zn.

9. The application of the magnetic lead oxide as a catalyst material according to claim 8 in lithium-sulfur batteries.

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