Dual-rare earth metal catalyzed nanomaterial, diaphragm and preparation method and application thereof

Abstract

The application discloses a double-rare earth metal catalyzed nanomaterial, a diaphragm and a preparation method and application thereof. A water solution containing a carbon source, a hard template, a graphene oxide dispersion solution, a nitrogen source, a phosphorus source, a cerium salt and a neodymium salt is subjected to a hydrothermal reaction; then, centrifugal separation is conducted to obtain a precipitate, thereby generating a Ce and Nd double-rare earth metal modified nitrogen and phosphorus doped graphene coated microsphere precursor; after the precipitate is subjected to heat treatment and chemical etching, a double-rare earth metal catalyzed nanomaterial (HCS@NPrGO / CeNd) is obtained. The HCS@NPrGO / CeNd can be used as a modification material for a lithium-sulfur battery diaphragm, can catalyze the conversion of polysulfides, can inhibit the shuttle effect of the polysulfides, and can make the lithium-sulfur battery have a higher capacity under high-rate charging and discharging and a lower capacity attenuation rate in a high-rate long cycle test.

Description

Technical Field

[0001] This invention relates to a functional nanomaterial, its preparation method, and its application, specifically a dual rare earth metal catalytic nanomaterial, a separator, its preparation method, and its application. Particularly, it relates to a cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon sphere and its preparation method and application; belonging to the technical field of battery separator materials. Background Technology

[0002] Lithium-sulfur batteries have a high theoretical energy density (1675 mAh g). -1 Lithium-sulfur batteries have attracted much attention due to their advantages such as low cost and high efficiency. The separator is a crucial component of lithium-sulfur batteries, and its performance directly affects the overall battery performance. During charging and discharging, lithium-sulfur batteries experience severe lithium polysulfide shuttle, which traditional polyolefin separators suffer from problems such as low suppression efficiency, low lithium-ion transference number, and slow conversion kinetics. Therefore, the development of high-performance separators has significant application value.

[0003] To address the aggregation and shuttle effect of polysulfides and achieve their physical adsorption, chemical anchoring, and catalytic conversion, thereby alleviating irreversible capacity decay and low capacity at high charge-discharge rates caused by the shuttle effect, researchers have successively prepared functional modification materials based on single-metal and bimetallic elements such as Fe, Co, Ni, Mn, and Ti, as well as their bimetallic and multimetallic components. However, current technologies primarily utilize transition metals, which suffer from poor catalytic performance due to their large size, low atom utilization, and insufficient catalytic active sites, thus limiting their overall battery performance improvement. Therefore, developing bimetallic catalytic nanomaterials and using them to prepare separators for lithium-sulfur batteries has significant application value. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a method for preparing and applying cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows.

[0006] A method for preparing dual rare earth metal catalytic nanomaterials includes the following steps:

[0007] (1) An aqueous solution containing a carbon source, a hard template, a graphene oxide dispersion, a nitrogen source, a phosphorus source, a cerium salt, and a neodymium salt was subjected to a hydrothermal reaction; then centrifuged to obtain a precipitate;

[0008] (2) The precipitate was heat-treated and then chemically etched to obtain dual rare earth metal catalytic nanomaterials.

[0009] In this invention, the carbon source includes dopamine hydrochloride, the hard template includes nano-silica, the nitrogen source includes urea, the phosphorus source includes ammonium dihydrogen phosphate, the cerium salt includes Ce(NO3)3•6H2O, and the neodymium salt includes Nd(NO3)3•6H2O; the weight ratio of the carbon source, hard template, graphene oxide, nitrogen source, phosphorus source, cerium salt, and neodymium salt is (1-3):(0.5-2):(0.01-0.1):(4-7):(2.5-6):(0.8-2):(2-4). Preferably, the weight ratio of carbon source, hard template, graphene oxide, nitrogen source, phosphorus source, cerium salt, and neodymium salt is (1.5-2.5):(0.6-1.5):(0.02-0.06):(5-6):(3-5):(1-1.5):(3-3.5); for example, 1.8:0.8:0.04:5.4:3.45:1.30:3.07.

[0010] In this invention, the hydrothermal reaction temperature is 150–200°C, and the reaction time is 5–20 h. Preferably, the hydrothermal reaction temperature is 160–190°C, and the reaction time is 10–15 h.

[0011] In this invention, the heat treatment is carried out under a N2 atmosphere; the heat treatment temperature is 750–950°C and the time is 3–6 hours; preferably, the heat treatment temperature is 800–900°C and the time is 4–5 hours.

[0012] In this invention, chemical etching is alkaline etching; preferably, the alkaline solution includes sodium hydroxide solution.

[0013] This invention discloses the preparation method of the above-mentioned dual rare earth metal catalytic nanomaterials.

[0014] This invention discloses a membrane comprising the above-mentioned dual rare earth metal catalytic nanomaterials.

[0015] The present invention discloses a method for preparing the above-mentioned separator, which includes the following steps: coating a slurry comprising the above-mentioned dual rare earth metal catalytic nanomaterials onto a polymer separator, and vacuum drying to obtain the separator.

[0016] Preferably, the polymer membrane includes one or more of the following: polyolefin membrane, polyester membrane, cellulose membrane, polyimide membrane, polyamide (PA) membrane, spandex membrane, and aramid membrane.

[0017] This invention discloses the application of the above-mentioned dual rare earth metal catalytic nanomaterials in the preparation of membranes.

[0018] This invention discloses the application of the above-mentioned dual rare earth metal catalytic nanomaterials or separators in the preparation of batteries.

[0019] The present invention discloses a battery comprising the above-described separator.

[0020] In this invention, the battery is a lithium-sulfur battery, and the separator is a separator for lithium-sulfur batteries.

[0021] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0022] 1. The cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres prepared in this invention combine rare earth dual metal catalysis with multiple effects such as physical adsorption and chemical anchoring, which makes it have good adsorption and catalytic effects on polysulfides, which is beneficial to suppress the shuttle effect of polysulfides in lithium-sulfur batteries and improve sulfur utilization.

[0023] 2. The present invention discloses a cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide coated hollow carbon sphere, which is used to prepare a bilayer composite membrane. The resulting composite membrane has an outstanding lithium-ion transference number (the lithium-ion transference number of the composite membrane obtained by combining with polypropylene is 0.839), providing a channel for lithium-ion migration and improving the conductivity of the functional material.

[0024] 3. A lithium-sulfur battery assembled using a bilayer composite membrane of cerium-neodymium dual rare-earth metal modified nitrogen-phosphorus doped reduced graphene oxide coated hollow carbon spheres, as disclosed in this invention, exhibits excellent electrochemical performance. Taking a polypropylene membrane as an example, the initial discharge capacity at 0.2C rate is 1353.3 mAh g⁻¹. -1 The discharge capacity reaches 868.8 mAh g at a 5C ultra-high rate. -1 This is because the synergistic effect of physical adsorption, chemical adsorption, and dual rare earth metal catalysis inhibits the dissolution and shuttle movement of lithium polysulfides in the electrolyte.

[0025] 4. Based on the cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres bilayer composite membrane disclosed in this invention, the lithium-sulfur battery exhibits stable long-cycle performance under high-rate charge-discharge conditions: taking the polypropylene membrane as an example, at a 1C high rate, the capacity decay rate per cycle of 500 cycles is only 0.082%. This is due to the different regulatory functions of the catalyst on the lithium polysulfide conversion reaction, separating them into different electron shell orbitals, thus efficiently accelerating the lithium polysulfide (LiPSs) conversion reaction. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the preparation process of the cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres (HCS@NPrGO / CeNd) of this invention.

[0027] Figure 2These are scanning electron microscope (SEM) images of the nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres (HCS@NPrGO) prepared in Example 1 and Comparative Example 1, and the reduced graphene oxide-coated hollow carbon spheres (HCS@rGO) prepared in Comparative Example 2.

[0028] Figure 3 These are X-ray diffraction (XRD) patterns of the three materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention.

[0029] Figure 4 These are the Raman spectra of the three materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention.

[0030] Figure 5 This is the elemental distribution mapping (EDS) diagram of the cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres (HCS@NPrGO / CeNd) prepared in Example 1 of this invention.

[0031] Figure 6 This is a transmission electron microscope (TEM) image of the cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres (HCS@NPrGO / CeNd) prepared in Example 1 of this invention.

[0032] Figure 7 These are the adsorption-desorption isotherms (BET) and particle size distribution diagrams of the cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres (HCS@NPrGO / CeNd) prepared in Example 1 of this invention.

[0033] Figure 8 This is the X-ray photoelectron spectroscopy (XPS) spectrum of the cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres (HCS@NPrGO / CeNd) prepared in Example 1 of this invention.

[0034] Figure 9 These are current-time (IT) curves and lithium-ion transport number graphs of the lithium-sulfur batteries assembled in Examples 8, 3, 4 and 5 of this invention.

[0035] Figure 10 These are rate performance graphs of lithium-sulfur batteries assembled in Examples 8, 3, 4 and 5 of the present invention at different current densities.

[0036] Figure 11 This is a charge / discharge curve (GCD) diagram of the lithium-sulfur battery assembled in Embodiment 8 of the present invention at different rates.

[0037] Figure 12 This is a graph showing the long-cycle performance of the lithium-sulfur battery assembled in Embodiment 8 of the present invention under 1C high-rate charge and discharge.

[0038] Figure 13 These are the electrochemical impedance (EIS) diagrams of the membrane-assembled batteries prepared in Examples 8, 3, 4 and 5 of this invention.

[0039] Figure 14 These are visualization experimental images of the adsorption of polysulfides by the materials prepared in Example 1 and the comparative example of this invention.

[0040] Figure 15 These are experimental images of the H-type electrolytic cell of the diaphragms prepared in Embodiment 1 and the comparative example of the present invention.

[0041] Figure 16 These are experimental images of the diaphragm prepared in the comparative example of this invention and the polypropylene (PP) diaphragm in an H-type electrolytic cell.

[0042] Figure 17 This is an X-ray photoelectron spectroscopy (XPS) image of the cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres (HCS@NPrGO / CeNd) prepared in Example 1 of this invention before and after adsorption of polysulfides. Detailed Implementation

[0043] In this invention, the dual rare earth metal catalytic nanomaterial is a hollow carbon sphere coated with cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide, and its preparation method includes the following steps:

[0044] (1) A Ce and Nd dual rare earth metal modified nitrogen and phosphorus doped graphene-coated microsphere precursor was synthesized by hydrothermal method;

[0045] (2) A hollow carbon nanosphere was obtained by heat treatment and chemical etching. It is a hollow carbon nanosphere coated with cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide.

[0046] Furthermore, in the above-mentioned method for preparing cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide coated hollow carbon spheres, the preparation method of the Ce and Nd dual rare earth metal modified nitrogen-phosphorus doped graphene coated microsphere precursor in step (1) is as follows: dopamine hydrochloride (PDA) and nano-SiO2 are added to deionized water and stirred in a conventional manner; then graphene oxide dispersion, urea, ammonium dihydrogen phosphate, Ce(NO3)3•6H2O, and Nd(NO3)3•6H2O are added. H2O was stirred at room temperature for 1–3 h, and then transferred to a hydrothermal reactor and reacted at 170–190 °C for 10–14 h under hydrothermal conditions. After the reaction was completed, the reaction product was centrifuged at a rate of 5000–20000 r / min to obtain a yellowish-brown precipitate. The precipitate was dried in a vacuum oven at 60–80 °C to obtain the cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped graphene oxide-coated hollow carbon sphere precursor SiO2@PDA / NPGO / CeNd.

[0047] Furthermore, in the above-mentioned method for preparing cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres, the heat treatment method in step (2) is to place SiO2@PDA / NPGO / CeNd in a tube furnace, and under N2 atmosphere, heat the temperature from room temperature to 800-900℃ at a rate of 1-5℃ / min for 4-5h to obtain cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated carbon spheres; add the obtained carbon spheres to a 1-3mol / L NaOH aqueous solution, and etch at 70-80℃ for 12-24h; then centrifuge at a rate of 5000-20000r / min to obtain a black precipitate, wash the precipitate with ethanol and deionized water, and dry it in a vacuum oven to obtain cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres HCS@NPrGO / CeNd.

[0048] Furthermore, in the above-mentioned method for preparing cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide coated hollow carbon spheres, the mass ratio of each reactant is: dopamine hydrochloride (PDA): nano-SiO2: graphene oxide: urea: ammonium dihydrogen phosphate: Ce(NO3)3•6H2O: Nd(NO3)3•6H2O = 1.80g: 0.80g: 40mg: 5.40g: 3.45g: 1.30g: 3.07g.

[0049] According to the above-mentioned method for preparing cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide coated hollow carbon spheres, a cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide coated hollow carbon sphere is prepared, which can be used in the preparation of lithium-sulfur battery composite separators.

[0050] This invention discloses the preparation of a composite separator for lithium-sulfur batteries, the preparation steps of which are as follows:

[0051] The above-mentioned cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide coated hollow carbon spheres, acetylene black, polyvinylidene fluoride, and N-methylpyrrolidone were mixed to obtain a slurry;

[0052] The slurry is coated onto an existing polymer separator and then vacuum dried to obtain a double-layer composite separator, which is a lithium-sulfur battery composite separator.

[0053] Existing polymer membranes include one or more of the following: polyolefin membranes, polyester membranes, cellulose membranes, polyimide membranes, polyamide (PA) membranes, spandex membranes, and aramid membranes.

[0054] In the preparation of the aforementioned lithium-sulfur battery composite separator, the mass ratio of cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide coated hollow carbon spheres, acetylene black, polyvinylidene fluoride (PVDF), and N-methylpyrrolidone is (6-8):(1.5-2.5):(0.8-1.2):(4-6). Preferably, the mass ratio of cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide coated hollow carbon spheres, acetylene black, PVDF, and N-methylpyrrolidone is 7:2:1:5. Acetylene black, PVDF, N-methylpyrrolidone, and the separator are all commercially available products. As is common knowledge, PVDF is in solution form with a mass concentration of 5 wt%.

[0055] In the preparation of the above-mentioned lithium-sulfur battery composite separator, the drying temperature is 60-70℃ and the drying time is 12-24h.

[0056] The thickness of the lithium-sulfur battery composite separator prepared by this invention is 15–40 μm.

[0057] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments; all raw materials are commercially available, and the specific preparation operations and testing methods involved are conventional methods in the art. The surface morphology of the nanofiller was observed using a scanning electron microscope (S-4700). The hollow structure of the nanomaterial was observed using a transmission electron microscope (HT7700). The phase structure of the material was tested using an X-ray diffractometer (D8 Advance). The elemental composition, content, and valence state of the nanofiller surface were tested using an X-ray photoelectron spectroscopy (XPS). The rate capability and cycle performance of the lithium-sulfur battery were tested using a battery testing system (CT3002A, Blue Battery). The reaction kinetics of the lithium-sulfur battery were analyzed using an electrochemical workstation (Zana).

[0058] Example 1

[0059] The preparation process of cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide coated hollow carbon spheres of this invention is described in [reference needed]. Figure 1 The specific steps are as follows:

[0060] (1) Dissolve dopamine hydrochloride (PDA) in deionized water (20 mL), stir at room temperature for 30 min, then add SiO2 nanoparticles (0.80 g, average particle size 30 nm), stir at room temperature for 1 h to obtain a silica (SiO2@PDA) solution coated with dopamine hydrochloride.

[0061] (2) Add the graphene oxide dispersion (20 mL, 2 mg / mL) to deionized water (10 mL), then add urea, ammonium dihydrogen phosphate, Ce(NO3)3•6H2O, and Nd(NO3)3•6H2O, stir to dissolve, and obtain a graphene oxide mixture containing nitrogen, phosphorus and rare earth elements.

[0062] The dosage ratio of dopamine hydrochloride (PDA), nano-SiO2, graphene oxide, urea, ammonium dihydrogen phosphate, Ce(NO3)3•6H2O, and Nd(NO3)3•6H2O is 1.80g:0.80g:40mg:5.40g:3.45g:1.30g:3.07g;

[0063] (3) The SiO2@PDA solution and the graphene oxide mixture containing nitrogen, phosphorus and rare earth elements were mixed and stirred at room temperature for 1 h, and then transferred to a hydrothermal reactor and reacted at 180℃ for 12 h under hydrothermal conditions. After the reaction was completed, the reaction product was centrifuged at 10000 r / min for 10 minutes to obtain a yellow-brown precipitate, which was then dried in a vacuum oven (80℃, 4 h) and ground to finally obtain the precursor, which is a precursor of nitrogen and phosphorus doped graphene coated microspheres containing cerium and neodymium rare earth bimetallic modification (SiO2@PDA / NPGO / CeNd).

[0064] (4) SiO2@PDA / NPGO / CeNd was placed in a tube furnace and heated from room temperature to 800℃ at a rate of 3℃ / min under N2 atmosphere for 4h to obtain cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide coated carbon spheres; the obtained carbon spheres were added to 2mol / L NaOH aqueous solution and etched at 70℃ for 12h; then centrifuged at 10000r / min to obtain black precipitate, washed with ethanol and deionized water, and dried in a vacuum oven (80℃, 4h) to obtain cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide coated hollow carbon spheres (HCS@NPrGO / CeNd).

[0065] The structure of HCS@NPrGO / CeNd was characterized using various methods. The surface morphology, surface elemental distribution, material structure, phase and crystal structure, defect degree, specific surface area and pore size distribution, elemental composition, and chemical bond energy state of HCS@NPrGO / CeNd are shown in the figures below. Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 .

[0066] Comparative Example 1

[0067] The preparation of nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres (HCS@NPrGO) is as follows:

[0068] (1) SiO2@PDA was obtained according to Example 1;

[0069] (2) Referring to Example 1, Ce(NO3)3•6H2O and Nd(NO3)3•6H2O were omitted to obtain the precursor SiO2@PDA / NPGO;

[0070] (3) Following step (4) of Example 1, calcination and etching with NaOH aqueous solution were performed, and a black precipitate was obtained by centrifugation at 10000 r / min. The precipitate was then washed alternately with ethanol and deionized water. Finally, the product was dried (80℃, 4h) to obtain HCS@NPrGO. The surface morphology, phase and crystal structure, and defect degree of HCS@NPrGO are shown in the figure. Figure 2 , Figure 3 , Figure 4 .

[0071] Comparative Example 2

[0072] The preparation of reduced graphene oxide-coated hollow carbon spheres (HCS@rGO) is as follows:

[0073] (1) SiO2@PDA was obtained according to Example 1;

[0074] (2) Referring to Example 1, urea, ammonium dihydrogen phosphate, Ce(NO3)3•6H2O and Nd(NO3)3•6H2O were omitted to obtain the precursor SiO2@PDA / GO;

[0075] (3) Following step (4) of Example 1, calcination and etching with NaOH aqueous solution were performed, and a black precipitate was obtained by centrifugation at 10000 r / min. The precipitate was then washed alternately with ethanol and deionized water. Finally, the product was dried (80℃, 4h) to obtain HCS@rGO. The surface morphology, phase and crystal structure, and defect degree of HCS@rGO are shown in the figure. Figure 2 , Figure 3 , Figure 4 .

[0076] Figure 2 Scanning electron microscope (SEM) images of HCS@NPrGO / CeNd (shown as Example 1), HCS@NPrGO (shown as Comparative Example 1), and HCS@rGO (shown as Comparative Example 2) prepared for this invention are shown. The images reveal that the prepared materials exhibit a relatively complete spherical structure with uniform size.

[0077] Figure 3X-ray diffraction (XRD) patterns of HCS@NPrGO / CeNd, HCS@NPrGO, and HCS@rGO were prepared for this invention. The XRD patterns show a broad diffraction peak at approximately 26° in all samples, corresponding to the (002) characteristic peak of graphitic carbon (PDF#41-1487). A smaller peak at approximately 44.3° was identified as the (101) characteristic peak of graphitic carbon. The (002) diffraction peak at 26° in HCS@NPrGO / CeNd (represented as Example 1), HCS@NPrGO (represented as Comparative Example 1), and HCS@rGO (represented as Comparative Example 2) gradually shifts towards smaller angles; this shift in diffraction angle can be attributed to the increased interplanar spacing induced by multi-atom doping. Specifically, the (002) peak of HCS@NPrGO / CeNd is the lowest among the three samples at (25.4°), indicating that it has the largest interplanar spacing. The spectrum of HCS@NPrGO / CeNd shows diffraction peaks at 21.3°, 28.8°, 31.2°, and 42.2°, corresponding to the diffraction peaks of (Nd, Ca, Ce)PO4 (PDF#46-1439), respectively. ), (120), (012) and ( The HCS@NPrGO / CeNd crystal planes were also observed. Furthermore, the HCS@NPrGO / CeNd spectrum exhibited characteristic diffraction peaks at 70.5° and 73.8°, confirming the successful synthesis of HCS@NPrGO / CeNd.

[0078] Figure 4 Raman spectra of HCS@NPrGO / CeNd, HCS@NPrGO, and HCS@rGO prepared for this invention are shown. From these spectra, it can be seen that HCS@NPrGO / CeNd has I D / I G The highest value (1.217) indicates a high degree of defect in the material and a low degree of graphitization. This is mainly due to the increased interplanar spacing induced by multi-atom doping.

[0079] Figure 5 This is an elemental distribution mapping (EDS) diagram of the cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres (HCS@NPrGO / CeNd) prepared in Example 1 of this invention. It can be seen that N, P, Ce, and Nd elements are uniformly distributed on the sample surface.

[0080] Figure 6This is a transmission electron microscope (TEM) image of the cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres (HCS@NPrGO / CeNd) prepared in Example 1 of this invention. It can be seen that the hollow carbon nanospheres have good dispersibility and do not exhibit significant agglomeration; the wall thickness of the carbon spheres is approximately 5 nm. Simultaneously, the transparent wrinkles and pores of graphene coating the sphere surface, with its layered structure, not only promote lithium-ion migration but also act as a physical barrier to inhibit polysulfide shuttle.

[0081] Figure 7 This document presents the adsorption-desorption isotherm (BET) and particle size distribution diagrams of the cerium-neodymium dual rare-earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres (HCS@NPrGO / CeNd) prepared in Example 1 of this invention. The diagrams show that HCS@NPrGO / CeNd exhibits a type IV isotherm, indicating a mesoporous structure with a specific surface area of ​​37.303 m². 2 g -1 The aperture is mainly concentrated at 23.73 nm.

[0082] Figure 8 This is the X-ray photoelectron spectroscopy (XPS) spectrum of the cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres (HCS@NPrGO / CeNd) prepared in Example 1 of this invention. The XPS test shows that N and P were successfully doped into the graphene, while Ce and Nd rare earth elements were introduced into the carbon material and modified its surface.

[0083] In summary, hollow carbon spheres coated with cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide were successfully prepared.

[0084] Example 2

[0085] The preparation of cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres is as follows:

[0086] (1) Dissolve 1.80 g of dopamine hydrochloride (PDA) in 20 mL of deionized water and stir at room temperature for 2 h. Add 0.80 g of SiO2 nanoparticles (average particle size 30 nm) and stir at room temperature for 1 h to obtain a solution of silica (SiO2@PDA) coated with dopamine hydrochloride.

[0087] (2) Graphene oxide dispersion (25 mL, 2 mg / mL) was added to deionized water (15 mL), followed by urea (6.0 g, 0.10 mol), ammonium dihydrogen phosphate (9.2 g, 0.08 mol), Ce(NO3)3•6H2O (0.87 g, 0.002 mol), and Nd(NO3)3•6H2O (3.07 g, 0.007 mol). After stirring and dissolving, SiO2@PDA solution was added. After stirring at room temperature for 2 h, the mixture was transferred to a hydrothermal reactor for reaction (180 °C, 12 h). The product prepared by hydrothermal reaction was centrifuged (10000 r / min, 10 min) to obtain a yellow-brown precipitate. Then, it was dried in a vacuum oven (80 °C, 4 h) to obtain the precursor SiO2@PDA / NPGO / CeNd.

[0088] (3) The precursor SiO2@PDA / NPGO / CeNd was placed in a tube furnace and heated to 800℃ at a rate of 4℃ / min under N2 atmosphere and kept at the temperature for 15h to obtain SiO2@CS / NPrGO / CeNd; the sintered material was added to NaOH solution (5mol / L, 60mL) and reacted for 12h, and then centrifuged at a rate of 10000r / min to obtain a black precipitate, which was washed alternately with ethanol and deionized water; finally, the product was dried (60℃, 6h) to obtain HCS@NPrGO / CeNd.

[0089] Example 3

[0090] The preparation of cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres is as follows:

[0091] (1) Dissolve 1.52 g of dopamine hydrochloride (PDA) in 15 mL of deionized water and stir at room temperature for 1 h. Add 0.6 g of SiO2 nanoparticles (average particle size 30 nm) and stir at room temperature for 2 h to obtain a solution of silica (SiO2@PDA) coated with dopamine hydrochloride.

[0092] (2) Graphene oxide dispersion (15 mL, 2 mg / mL) was added to deionized water (8 mL), followed by urea (3.00 g, 0.05 mol), ammonium dihydrogen phosphate (3.45 g, 0.03 mol), Ce(NO3)3•6H2O (1.30 g, 0.003 mol) and Nd(NO3)3•6H2O (3.51 g, 0.008 mol). After stirring and dissolving, SiO2@PDA solution was added. After stirring at room temperature for 2 h, the mixture was transferred to a hydrothermal reactor for reaction (180 °C, 12 h). The product prepared by hydrothermal reaction was centrifuged (10000 r / min, 10 min) to obtain a yellow-brown precipitate. Then, it was dried in a vacuum oven (80 °C, 4 h) to obtain the precursor SiO2@PDA / NPGO / CeNd.

[0093] (3) The precursor SiO2@PDA / NPGO / CeNd was placed in a tube furnace and heated to 800℃ at a rate of 4℃ / min under N2 atmosphere and kept at the temperature for 10h to obtain SiO2@CS / NPrGO / CeNd; the sintered material was added to NaOH solution (5mol / L, 60mL) and reacted for 10h; then the black precipitate was obtained by centrifugation at a rate of 10000r / min and washed alternately with ethanol and deionized water; finally the product was dried (60℃, 6h) to obtain HCS@NPrGO / CeNd.

[0094] Example 4

[0095] The preparation of cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres is as follows:

[0096] (1) Dissolve 1.80 g of dopamine hydrochloride (PDA) in 20 mL of deionized water and stir at room temperature for 1 h. Add 0.80 g of SiO2 nanoparticles (average particle size 30 nm) and stir at room temperature for 1 h to obtain a solution of silica (SiO2@PDA) coated with dopamine hydrochloride.

[0097] (2) Graphene oxide dispersion (18 mL, 2 mg / mL) was added to deionized water (10 mL), followed by urea (4.80 g, 0.08 mol), ammonium dihydrogen phosphate (4.60 g, 0.04 mol), Ce(NO3)3•6H2O (1.30 g, 0.003 mol) and Nd(NO3)3•6H2O (2.63 g, 0.006 mol). After stirring and dissolving, SiO2@PDA solution was added. After stirring at room temperature for 1 h, the mixture was transferred to a hydrothermal reactor for reaction (180 °C, 16 h). The product prepared by hydrothermal reaction was centrifuged (10000 r / min, 10 min) to obtain a yellow-brown precipitate. Then, it was dried in a vacuum oven (80 °C, 4 h) to obtain the precursor SiO2@PDA / NPGO / CeNd.

[0098] (3) The precursor SiO2@PDA / NPGO / CeNd was placed in a tube furnace and heated to 800℃ at a rate of 4℃ / min under N2 atmosphere and kept at the temperature for 6h to obtain SiO2@CS / NPrGO / CeNd; the sintered material was added to NaOH solution (3mol / L, 50mL) and reacted for 12h; then the black precipitate was obtained by centrifugation at a rate of 10000r / min and washed alternately with ethanol and deionized water; finally the product was dried (80℃, 4h) to obtain HCS@NPrGO / CeNd.

[0099] Example 5

[0100] The preparation of cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres is as follows:

[0101] (1) Dissolve 1.80 g of dopamine hydrochloride (PDA) in 20 mL of deionized water and stir at room temperature for 1 h. Add 0.80 g of SiO2 nanoparticles (average particle size 30 nm) and stir at room temperature for 1.5 h to obtain a silica (SiO2@PDA) solution coated with dopamine hydrochloride.

[0102] (2) Graphene oxide dispersion (20 mL, 2 mg / mL) was added to deionized water (10 mL), followed by urea (3.00 g, 0.05 mol), ammonium dihydrogen phosphate (2.30 g, 0.02 mol), Ce(NO3)3•6H2O (1.74 g, 0.004 mol) and Nd(NO3)3•6H2O (3.95 g, 0.009 mol). After stirring and dissolving, SiO2@PDA solution was added. After stirring at room temperature for 2 h, the mixture was transferred to a hydrothermal reactor for reaction (180 °C, 20 h). The product prepared by hydrothermal reaction was centrifuged (10000 r / min, 10 min) to obtain a yellow-brown precipitate. Then, it was dried in a vacuum oven (80 °C, 4 h) to obtain the precursor SiO2@PDA / NPGO / CeNd.

[0103] (3) The precursor SiO2@PDA / NPGO / CeNd was placed in a tube furnace and heated to 800℃ at a rate of 4℃ / min under N2 atmosphere and kept at the temperature for 10h to obtain SiO2@CS / NPrGO / CeNd; the sintered material was added to NaOH solution (3mol / L, 60mL) and reacted for 24h; then the black precipitate was obtained by centrifugation at a rate of 10000r / min and washed alternately with ethanol and deionized water; finally the product was dried (60℃, 6h) to obtain HCS@NPrGO / CeNd.

[0104] Example 6

[0105] The preparation of cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres is as follows:

[0106] (1) Dissolve dopamine hydrochloride (PDA) (3.60 g) in deionized water (25 mL), stir at room temperature for 2 h, add SiO2 nanoparticles (1.20 g, average particle size 30 nm), stir at room temperature for 1 h; to obtain a silica (SiO2@PDA) solution coated with dopamine hydrochloride.

[0107] (2) Graphene oxide dispersion (25 mL, 2 mg / mL) was added to deionized water (18 mL), followed by urea (4.20 g, 0.07 mol), ammonium dihydrogen phosphate (2.30 g, 0.02 mol), Ce(NO3)3•6H2O (1.30 g, 0.003 mol), and Nd(NO3)3•6H2O (3.95 g, 0.009 mol). After stirring and dissolving, SiO2@PDA solution was added. After stirring at room temperature for 2 h, the mixture was transferred to a hydrothermal reactor for reaction (180 °C, 24 h). The product prepared by hydrothermal reaction was centrifuged (10000 r / min, 10 min) to obtain a yellow-brown precipitate. Then, it was dried in a vacuum oven (80 °C, 4 h) to obtain the precursor SiO2@PDA / NPGO / CeNd.

[0108] (3) The precursor SiO2@PDA / NPGO / CeNd was placed in a tube furnace and heated to 800℃ at a rate of 4℃ / min under N2 atmosphere and kept at the temperature for 15h to obtain SiO2@CS / NPrGO / CeNd; the sintered material was added to NaOH solution (5mol / L, 60mL) and reacted for 12h; then the black precipitate was obtained by centrifugation at a rate of 10000r / min and washed alternately with ethanol and deionized water; finally the product was dried (60℃, 6h) to obtain HCS@NPrGO / CeNd.

[0109] Example 7

[0110] The preparation of cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres is as follows:

[0111] (1) Dissolve 2.70 g of dopamine hydrochloride (PDA) in 25 mL of deionized water and stir at room temperature for 1 h. Add 1.20 g of SiO2 nanoparticles (average particle size 30 nm) and stir at room temperature for 1.5 h to obtain a silica (SiO2@PDA) solution coated with dopamine hydrochloride.

[0112] (2) Graphene oxide dispersion (25 mL, 2 mg / mL) was added to deionized water (25 mL), followed by urea (4.80 g, 0.08 mol), ammonium dihydrogen phosphate (2.30 g, 0.02 mol), Ce(NO3)3•6H2O (1.74 g, 0.004 mol) and Nd(NO3)3•6H2O (4.38 g, 0.010 mol). After stirring and dissolving, SiO2@PDA solution was added. After stirring at room temperature for 2 h, the mixture was transferred to a hydrothermal reactor for reaction (180 °C, 16 h). The product prepared by hydrothermal reaction was centrifuged (10000 r / min, 10 min) to obtain a yellow-brown precipitate. Then, it was dried in a vacuum oven (80 °C, 4 h) to obtain the precursor SiO2@PDA / NPGO / CeNd.

[0113] (3) The precursor SiO2@PDA / NPGO / CeNd was placed in a tube furnace and heated to 800℃ at a rate of 5℃ / min under N2 atmosphere and kept at the temperature for 8h to obtain SiO2@CS / NPrGO / CeNd; the sintered material was added to NaOH solution (3mol / L, 60mL) and reacted for 24h; then the black precipitate was obtained by centrifugation at a rate of 10000r / min and washed alternately with ethanol and deionized water; finally the product was dried (80℃, 4h) to obtain HCS@NPrGO / CeNd.

[0114] Example 8 Application Example

[0115] The preparation of the bilayer composite separator and battery assembly follow conventional methods, with the following steps:

[0116] (1) Weigh 0.14g of the cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres (HCS@NPrGO / CeNd) prepared in Example 1, 0.04g of acetylene black (AB), and 0.40g (5wt%) of polyvinylidene fluoride (PVDF) in a mortar and grind them to obtain mixture A;

[0117] (2) Add 2 mL of N-methylpyrrolidone (NMP) to the above mixture A, stir on a slurry mixer (8000 r / min, 30 min) to make a black slurry, use a scraper to evenly coat the slurry onto a commercially available polyolefin membrane with a coating thickness of 80 μm, coating one side to obtain an undried double-layer composite membrane;

[0118] (3) The undried double-layer separator prepared in step (2) is dried in a vacuum oven (60°C, 24h) to obtain a double-layer composite separator; it is cut into round pieces with a diameter of 16mm using a slicer to obtain a separator for battery assembly, denoted as HCS@NPrGO / CeNd‖PP.

[0119] The HCS@NPrGO / CeNd‖PP prepared above was used to assemble button cells. The specific steps are as follows:

[0120] (4) Assemble lithium-sulfur batteries in a glove box under an argon atmosphere: a standard CR2032 coin cell is composed of a lithium metal anode, a sulfur cathode, an HCS@NPrGO / CeNd‖PP separator (HCS@NPrGO / CeNd coating side facing the sulfur cathode) and an electrolyte; wherein the electrolyte composition is dioxolane (DOL): ethylene glycol dimethyl ether (DME) = 1:1 (v / v), 2wt% LiNO3, and 1M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI);

[0121] (5) Place the assembled coin cells in a 28°C constant temperature chamber and perform electrochemical performance tests on the assembled cells using a battery testing system and an electrochemical workstation. The lithium-ion transference number, rate performance, charge / discharge characteristics, and long-cycle stability of the HCS@NPrGO / CeNd‖PP assembled cells are shown in the figures below. Figure 9 , Figure 10 , Figure 11 , Figure 12 ;

[0122] (6) Analysis of lithium polysulfide adsorption on the prepared nanomaterials and composite membranes was performed; reaction kinetics analysis of the assembled battery was conducted using an electrochemical workstation. The electrochemical impedance of the HCS@NPrGO / CeNd‖PP assembled battery, the adsorption of polysulfides by the HCS@NPrGO / CeNd functional material, the experimental images of the H-type electrolyzer of HCS@NPrGO / CeNd‖PP, and the X-ray photoelectron spectra of HCS@NPrGO / CeNd before and after polysulfide adsorption are shown in the figures. Figure 13 , Figure 14 , Figure 15 , Figure 16 .

[0123] Comparative Example 3: Comparative Application Examples

[0124] Referring to the application examples, the cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres (HCS@NPrGO / CeNd) prepared in Example 1 were replaced with HCS@NPrGO in Comparative Example 1, with the rest remaining the same, to obtain an HCS@NPrGO‖PP separator; and further assembled into a standard CR2032 coin cell.

[0125] Comparative Example 4: Comparative Application Examples

[0126] Referring to the application examples, the cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres (HCS@NPrGO / CeNd) prepared in Example 1 was replaced with HCS@rGO in Comparative Example 2, with the rest remaining the same, to obtain an HCS@rGO‖PP separator; and further assembled into a standard CR2032 coin cell.

[0127] Comparative Example 5: Controlled Application Examples

[0128] Commercially available polypropylene (PP) separators are cut into discs with a diameter of 16 mm using a slicer.

[0129] The specific steps for using the above-mentioned PP separator to assemble button batteries are as follows:

[0130] (1) Assemble lithium-sulfur batteries in a glove box under an argon atmosphere: standard CR2032 button batteries are composed of lithium metal anode, sulfur cathode, PP separator and electrolyte; wherein the electrolyte composition is dioxolane (DOL): ethylene glycol dimethyl ether (DME) = 1:1 (v / v), 2wt% LiNO3, 1M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI);

[0131] (2) The assembled button cells were placed in a 28°C constant temperature chamber, and their electrochemical performance was tested using a battery testing system and an electrochemical workstation. The lithium-ion transference number and rate performance of the PP separator assembled cells are shown in the figures below. Figure 9 , Figure 10 .

[0132] Figure 9 The figures show the current-time (IT) curves and lithium-ion transport number plots of the batteries assembled with HCS@NPrGO / CeNd‖PP (shown as Example 8), HCS@NPrGO‖PP (shown as Comparative Example 3), HCS@rGO‖PP (shown as Comparative Example 4), and PP separators (shown as Comparative Example 5) prepared in this invention. The tests were performed using the chronoamperometry method at a constant potential of 10 mV. The formula t... Li+ =I s / I o (t) Li+ Indicates the lithium-ion transfer number; I s Indicates the steady-state current value; I o Calculated from (representing the initial current value), by Figure 9 It can be seen that the lithium-sulfur battery assembled with HCS@NPrGO / CeNd‖PP has the highest lithium-ion transference number (0.839).

[0133] Figure 10The figure shows the rate performance of the HCS@NPrGO / CeNd‖PP (represented as Example 8), HCS@NPrGO‖PP (represented as Comparative Example 3), HCS@rGO‖PP (represented as Comparative Example 4), and PP separator (represented as Comparative Example 5) assembled batteries at different current densities. Figure 10 The results show that the lithium-sulfur battery prepared in Example 8, with a cerium-neodymium dual rare-earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon sphere modified separator, has a capacity of 1353.3 mAh g at a 0.2C rate. -1 High specific capacity; even at an ultra-high rate of 5C, the discharge capacity reaches 868.8 mAh g. -1 This is higher than that of Comparative Example 3 (579.2 mAh g). -1 Comparative Example 4 (528.9 mAh g) -1 ) and Comparative Example 5 (205.6 mAh g) -1 This is because HCS@NPrGO / CeNd materials are beneficial for Li + It can also act as a physical barrier to effectively block the transport and diffusion of polysulfides, and can also achieve efficient anchoring of lithium polysulfides (LiPSs) through chemical adsorption. More importantly, the unique electronic structure and highly active sites of Ce and Nd rare earth bimetals can rapidly catalyze the conversion of adsorbed LiPSs, thereby achieving higher sulfur utilization and enabling the assembled lithium-sulfur battery to have superior rate performance.

[0134] Figure 11 This is the charge / discharge curve (GCD) of the HCS@NPrGO / CeNd‖PP assembled battery prepared in Example 8 of this invention. It can be seen that even under the high-rate charge and discharge conditions of 5C, the battery still maintains the typical charge / discharge plateau of lithium-sulfur batteries, indicating that the HCS@NPrGO / CeNd‖PP composite separator material has little effect on the polarization of the battery.

[0135] Figure 12 This is a long-cycle performance diagram of the HCS@NPrGO / CeNd‖PP separator assembled battery prepared in Example 8 of this invention. Figure 12 It can be seen that after three cycles of activation at 0.1C, the initial discharge specific capacity at 1C is as high as 1137.8 mAh g. -1 After 500 cycles at 1C high rate, the capacity remained at 670.2mAh g. -1The capacity decay rate is only 0.082% per cycle. This is because the cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped graphene-coated hollow carbon spheres combine physical adsorption, chemical anchoring and rare earth bimetallic catalysis to effectively suppress polysulfide shuttle and catalyze the conversion of lithium polysulfides. Therefore, the lithium-sulfur battery assembled with the modified separator has excellent long-cycle stability.

[0136] Figure 13 The figures show the electrochemical impedance spectroscopy (EIS) diagrams of the HCS@NPrGO / CeNd‖PP (Example 8), HCS@NPrGO‖PP (Comparative Example 3), HCS@rGO‖PP (Comparative Example 4), and PP separator (Comparative Example 5) assembled batteries prepared according to this invention. It can be seen that the lithium-sulfur battery assembled with HCS@NPrGO / CeNd‖PP has the lowest impedance value (27.4Ω), indicating that its separator has the highest ion transport efficiency. This is mainly due to the layered graphene coated on the nanosphere surface and the hollow Li... + The migration provides multiple pathways.

[0137] Comparative Example 6

[0138] Referring to Example 1, Nd(NO3)3•6H2O was omitted, and everything else remained the same, cerium single rare earth metal modified nitrogen and phosphorus doped reduced graphene oxide coated hollow carbon spheres HCS@NPrGO / Ce were prepared.

[0139] Comparative Example 7

[0140] Referring to Example 1, Ce(NO3)3•6H2O was omitted, and everything else remained the same, neodymium single rare earth metal modified nitrogen and phosphorus doped reduced graphene oxide coated hollow carbon spheres HCS@NPrGO / Nd were prepared.

[0141] Comparative Example 8

[0142] Referring to Example 1, urea and ammonium dihydrogen phosphate were omitted, while the rest remained the same, to prepare cerium-neodymium dual rare earth metal modified reduced graphene oxide-coated hollow carbon spheres HCS@rGO / CeNd.

[0143] Comparative Example 9

[0144] Referring to Example 1, Nd(NO3)3•6H2O and Ce(NO3)3•6H2O were replaced with FeCl3•6H2O (0.01 mol), while the rest remained the same, to prepare iron transition monometallic modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres HCS@NPrGO / Fe.

[0145] Figure 14Visualization images of the adsorption of polysulfides by HCS@NPrGO / CeNd and the hollow carbon spheres prepared in comparison for this invention are shown. In an argon-filled glove box, 0.30 g of Li₂S and 1.04 g of S were dissolved in 130 mL of dimethyl ethylene glycol (DME) solution and stirred at 60 °C for 24 h to prepare a Li₂S₆ solution. 0.18 g of sample and 13 mL of Li₂S₆ solution were added to each sample vial. As shown in the figures, the characteristic peak intensity of the HCS@NPrGO / CeNd solution is significantly lower in the 400-450 nm wavelength range, indicating that HCS@NPrGO / CeNd has excellent adsorption capacity for Li₂S₆.

[0146] Comparative Example 10: Comparative Application Examples

[0147] Referring to the application examples, the cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon spheres (HCS@NPrGO / CeNd) prepared in Example 1 were replaced with hollow carbon spheres from Comparative Examples 6 to 9, with the rest remaining the same, to obtain a separator.

[0148] Figure 15 as well as Figure 16 The images show H-type electrolytic cell experiments of the HCS@NPrGO / CeNd‖PP membrane prepared in this invention, the PP composite membrane prepared with hollow carbon spheres as a comparative example, and the simple PP membrane. The left side shows a clear DME solution (ethylene glycol dimethyl ether), and the right side shows a 4.0 mM Li₂S₆ solution. It can be seen that with increasing diffusion time, the solution on the left side of the HCS@NPrGO / CeNd‖PP membrane is the clearest, indicating that it has the best effect in inhibiting the migration of polysulfides.

[0149] Figure 17 This is an X-ray photoelectron spectrum of HCS@NPrGO / CeNd prepared in Example 1 of this invention before and after polysulfide adsorption. It can be seen that, compared with before adsorption, the Ce 3d fitting peak in HCS@NPrGO / CeNd after Li2S6 adsorption shifts towards higher binding energies, while the Nd 3d fitting peak belongs to Nd 3d... 3 / 2 The fitted peaks at binding energies of 1001.9 eV and 1005.8 eV shifted towards higher binding energies by 0.95 eV and 0.31 eV, respectively, belonging to Nd3d 5 / 2 The 980.1 eV value shifted by 0.51 eV towards lower binding energies, confirming the interaction between Ce and Nd atoms and Li₂S₆. These results demonstrate that HCS@NPrGO / CeNd possesses a strong adsorption capacity for LiPSs, effectively anchoring them and suppressing their shuttle behavior.

[0150] Referring to the application examples, a composite separator was prepared by coating hollow carbon spheres with cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide (HCS@NPrGO / CeNd) using Examples 2 to 7; and further assembled into a standard CR2032 coin cell.

[0151] Example 9

[0152] Referring to the application examples, a cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide-coated hollow carbon sphere (HCS@NPrGO / CeNd) prepared in Examples 1 to 7 was used as a catalyst and coated on the surface of other commercially available polyester membranes, cellulose membranes, and polyimide membranes to obtain a composite separator; and further assembled into a standard CR2032 coin cell.

[0153] This invention involves a hydrothermal reaction of an aqueous solution containing a carbon source, a hard template, a graphene oxide dispersion, a nitrogen source, a phosphorus source, a cerium salt, and a neodymium salt; followed by centrifugation to obtain a precipitate, generating a precursor containing Ce and Nd rare-earth bimetallic modified nitrogen-phosphorus doped graphene-coated microspheres; the precipitate is then heat-treated and chemically etched to obtain a dual rare-earth metal catalytic nanomaterial (HCS@NPrGO / CeNd). HCS@NPrGO / CeNd can be used as a modification material for lithium-sulfur battery separators, not only catalyzing the conversion of polysulfides but also suppressing the shuttle effect of polysulfides, resulting in high capacity of lithium-sulfur batteries under high-rate charge-discharge conditions and low capacity decay rate in high-rate long-cycle testing.

Claims

1. A method for preparing dual rare earth metal catalytic nanomaterials, characterized in that, Includes the following steps: (1) Add dopamine hydrochloride and nano-SiO2 to water; then add graphene oxide dispersion, urea, ammonium dihydrogen phosphate, Ce(NO3)3•6H2O, and Nd(NO3)3•6H2O. Stir at room temperature for 1-3 hours, then transfer to a hydrothermal reactor and react at 170-190℃ for 10-14 hours. After the reaction is completed, centrifuge the reaction product at a rate of 5000-20000 r / min to obtain a yellow-brown precipitate. Dry the precipitate in a vacuum oven at 60-80℃ to obtain cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped graphene oxide-coated hollow carbon sphere precursor SiO2@PDA / NPGO / CeNd. (2) SiO2@PDA / NPGO / CeNd was placed in a tube furnace and heated from room temperature to 800-900℃ at a rate of 1-5℃ / min under N2 atmosphere for 4-5h to obtain cerium-neodymium dual rare earth metal modified nitrogen-phosphorus doped reduced graphene oxide coated carbon spheres; the obtained carbon spheres were added to a 1-3mol / L NaOH aqueous solution and etched at 70-80℃ for 12-24h; then centrifuged at a rate of 5000-20000r / min to obtain a black precipitate, which was washed with ethanol and water and dried in a vacuum oven to obtain dual rare earth metal catalytic nanomaterials.

2. The preparation method of the dual rare earth metal catalytic nanomaterial according to claim 1, characterized in that, The weight ratio of dopamine hydrochloride, nano-SiO2, graphene oxide, urea, ammonium dihydrogen phosphate, Ce(NO3)3•6H2O, and Nd(NO3)3•6H2O is (1-3):(0.5-2):(0.01-0.1):(4-7):(2.5-6):(0.8-2):(2-4).

3. The dual rare earth metal catalytic nanomaterial prepared by the method described in claim 1.

4. A diaphragm, characterized in that, Includes the dual rare earth metal catalytic nanomaterials as described in claim 3.

5. The method for preparing the diaphragm according to claim 4, characterized in that, The process includes the following steps: coating a slurry containing the dual rare earth metal catalytic nanomaterials of claim 3 onto a polymer membrane, followed by vacuum drying to obtain the membrane.

6. The method for preparing the diaphragm according to claim 5, characterized in that, The polymer membrane includes one or more of the following: polyolefin membrane, polyester membrane, cellulose membrane, polyimide membrane, polyamide membrane, spandex membrane, and aramid membrane.

7. The application of the dual rare earth metal catalytic nanomaterials of claim 3 in the preparation of membranes.

8. The application of the dual rare earth metal catalytic nanomaterial of claim 3 or the separator of claim 4 in the preparation of batteries.

9. A battery, characterized in that, Includes the diaphragm as described in claim 4.

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