A hollow graphene microsphere-supported nanoparticles (Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 O and its preparation method

Abstract

This invention belongs to the field of electrochemical energy storage materials, specifically relating to a hollow graphene microsphere-supported nano-(Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The method for preparing hollow graphene microspheres (MgO) using metal nitrates and hollow graphene microspheres as raw materials involves preparing a high-entropy oxide precursor loaded with hollow graphene microspheres via a hydrothermal reaction. The precursor is then calcined at high temperature under an inert atmosphere to obtain hollow graphene microspheres loaded with nano-(MgO) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The high-entropy oxide composite material prepared has the following structural characteristics: (1) the particle size of the composite material is 2.5-4 micrometers; (2) the diameter of the internal cavity is 0.5-1 micrometer; (3) the particle size of the high-entropy oxide loaded on the graphene spherical shell is 100-200 nanometers. The synthesized composite material was tested with a coin cell and showed a yield of 1 A g. ‑1 The reversible specific capacity at current density is close to 500 mAh g. ‑1 ,2A g ‑1 At 412mAh g ‑1 Meanwhile, 1A g ‑1 After 800 cycles, the specific capacity is still higher than 500 mAh / g, demonstrating excellent structural stability.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage materials, specifically to a hollow graphene microsphere-supported nanoparticle (Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 O and its preparation method. Background Technology

[0002] The rapid development of electric vehicles has led to a continuous increase in demand for lithium-ion batteries with high energy density and long cycle life. Over the past two decades, researchers have devoted considerable effort to developing novel electrode materials with superior performance. Among various novel anode materials, conversion transition metal oxides (chemical formula M...) are... x O y Transition metal oxides (M = Fe, Co, Ni, Mn, V, etc.) have higher specific capacity than traditional intercalated layered oxides, showing great potential in high-energy lithium-ion battery applications. However, the large volume changes of transition metal oxides during cycling can cause particle pulverization, leading to rapid capacity decay, which is a key bottleneck restricting their practical application.

[0003] In recent years, the "high entropy" design concept has been applied in the research of positive and negative electrodes for lithium-ion batteries. Reaction-type metal oxide anodes have improved structural stability during electrochemical processes through entropy-stabilized structural strategies, leading to the development of high-entropy metal oxide (HEO) anode materials. HEOs are multi-principal solid solutions composed of five or more metal oxides. All metal cations have almost identical local chemical environments, and the metal elements are randomly distributed in the crystal lattice. The high and stable configurational entropy allows HEOs to exist as single-phase compounds. The earliest studied high-entropy oxide anode material (MgO) is an example. 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 Taking O as an example, Co, which is electrochemically active, 2+ Ni 2+ Cu 2+ Zn 2+ Metal ions provide capacity through conversion reactions, while inactive Mg... 2+ It acts as a buffer matrix to stabilize the structure, inhibiting the aggregation of active metal nanoparticles while allowing the ions involved in the reaction to easily diffuse back into the crystal structure during the subsequent oxidation process, thus achieving good cycle stability.

[0004] However, rock salt-type high-entropy oxides (Mg) 0.2 Co 0.2Ni 0.2 Cu 0.2 Zn 0.2 O has low electronic conductivity and slow ion diffusion, resulting in poor rate performance. GHIGNAP et al. reported (ACS Applied Materials & Interfaces, 2020, 12: 50344-50354) that when the current density is 0.09 A g... -1 At that time, (Mg 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The specific capacity of O is 600mAh g -1 Around, but if the current density is only increased to 0.1 A g -1 At that time, its reversible specific capacity was only 400mAh g. -1 Around. Kheradmandfard et al. synthesized rock-salt type high-entropy oxides (Mg). 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )O in 1Ag -1 At a current density of 325 mAh g, the reversible specific capacity is 325 mAh g. -1 (Materials Chemistry and Physics, 2021, 262). The rapid development of the electric vehicle sector requires that supporting lithium-ion batteries not only have high energy density but also a certain power density. Therefore, in order to achieve rock-salt type high-entropy oxide (Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 To improve the rate performance of O in high-energy lithium-ion batteries, it is necessary to study technical approaches.

[0005] For the transformation reaction mechanism (Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The main strategies for improving the rate performance of )O are particle nano-sizing, porous structure and coating with conductive materials, in order to reduce the polarization effect in the reaction process, improve kinetics, and ultimately achieve improved rate performance. Summary of the Invention

[0006] The purpose of this invention is to improve the performance of rock salt type (Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn0.2 To improve the rate performance of high-entropy oxide anode materials, a method for preparing high-entropy oxide nanoparticles supported on hollow graphene microspheres was designed.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides hollow graphene microspheres loaded with nano-(Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The preparation method of O specifically includes the following steps:

[0009] (1) After grinding the dry graphite oxide powder thoroughly, place it in an inert gas atmosphere, heat it to 650-800℃ at a rate of 5-15℃ / min, keep it at a constant temperature for 3-5 hours, and then cool it naturally to room temperature to obtain porous hollow graphene microsphere powder.

[0010] (2) Weigh cobalt(II), magnesium(II), copper(II), zinc(II), and nickel(II) nitrate according to the equimolar ratio of the metal elements, and add pure water to prepare a mixed solution A with a total metal ion concentration of 0.005-0.01 g / mL; prepare a suspension B with a concentration of 0.005-0.02 g / mL using anhydrous ethanol.

[0011] (3) According to the hollow graphene microspheres and (Mg 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The mass ratio of O is 0.1:1 to 1:1. Weigh A and B separately and add them to a hydrothermal reactor. Then add ammonia and urea. After the hydrothermal reactor is fully reacted at 130 to 150°C, it is naturally cooled to room temperature.

[0012] (4) Unscrew the hydrothermal reactor to release the gas, collect the solid obtained, wash it with pure water until the filtrate is neutral, dry the moisture and grind it to obtain powder, then place it in an inert gas atmosphere, raise the temperature from room temperature to 800-900℃ at a rate of 3-5℃ / min and hold it at that temperature for 1-3 hours, then cool it naturally to room temperature to obtain hollow graphene microspheres supported on nano-(Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 Powders of high-entropy oxides.

[0013] Preferably, in step (1), the dry graphite oxide powder is synthesized by the Hummers method.

[0014] Furthermore, after the graphite oxide powder is ball-milled at a speed of 200-450 rpm for 2 hours, the temperature is increased from room temperature to 750°C at a rate of 10°C / min, held at the temperature for 3-5 hours, and then naturally cooled to room temperature.

[0015] Preferably, in step (3), the concentration of ammonia in the mixture after addition is 0.2-1%; and the concentration of urea in the mixture after addition is 0.01-0.015 g / mL.

[0016] Preferably, in step (3), the mixture is added to a hydrothermal reactor with a volume of 100 mL, so that the volume of the mixed solution is in the range of 60 to 80 mL; the reaction time is 3 to 6 hours.

[0017] Preferably, the inert gas is argon.

[0018] Preferably, the cobalt nitrate, magnesium nitrate, copper nitrate, zinc nitrate, or nickel nitrate is replaced with other soluble salts of the same metal element.

[0019] Secondly, the present invention provides hollow graphene microspheres prepared by the method described in the first aspect, supported on rock salt (Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 O composite material.

[0020] Preferably, the hollow graphene microspheres are supported on rock salt type (Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The particle size of the O composite material is 2.5-4 micrometers, the internal cavity diameter is 0.5-1 micrometer, and the graphene spherical shell surface is in situ deposited with (Mg) particles of 100-200 nanometers in size. 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 O high-entropy oxide particles.

[0021] Thirdly, the present invention provides a hollow graphene microsphere supported on rock salt (Mg) as described in the second aspect. 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The application of O composite materials as a negative electrode in lithium batteries. Preferably, the hollow graphene microspheres are supported on nano-rock salt-type high-entropy oxides (MgO). 0.2 Co 0.2 Ni 0.2Cu 0.2 Zn 0.2 O powder, acetylene black, and polyvinylidene fluoride are mixed in a mass ratio of 7:2:1, and a slurry is prepared with N-methylpyrrolidone and coated onto copper foil. After drying, it is applied.

[0022] The beneficial effects achieved by this invention are as follows:

[0023] Button cell testing showed that the hollow graphene microspheres synthesized in this invention are supported on rock salt (Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 O high-entropy oxides in 1Ag -1 The reversible specific capacity at current density is close to 500 mAh g. -1 ,2A g -1 At 412mAh g -1 Correspondingly, (Mg) synthesized without using hollow graphene microspheres... 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )O, not only is it a solid, non-porous structure, but its rate performance is also worse, 1A g -1 The reversible specific capacity is less than 200mAh g. -1 ,2A g -1 At that time, there was almost no capacity. Moreover, hollow graphene microspheres supported on rock-salt type (Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The initial coulombic efficiency of the O composite material (current density 0.05 A g) -1 The content of MgO was 66.9%, which is higher than that of pure MgO without composite hollow graphene microspheres. 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )O 62%, while hollow graphene microspheres supported on rock salt type (Mg 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 )O in 1A g -1 After 700 cycles of current density cycling, its specific capacity is still greater than 400 mAh g. -1 Moreover, it also exhibits a significant capacity recovery effect.

[0024] The material preparation method of the present invention has the following characteristics: (1) the surface defects of hollow graphene spheres can promote the formation of nano high-entropy oxide particles; (2) the hollow graphene spheres can improve the electronic conductivity of composite materials; (3) the cavity of graphene microspheres can store electrolyte, reduce ion diffusion resistance, and thus improve rate performance; (4) the synthesis method is simple and highly reproducible. Attached Figure Description

[0025] Figure 1 SEM images of hollow graphene microspheres loaded with rock salt-type high-entropy oxides prepared by the method of this invention.

[0026] Figure 2 Cross-sectional FIB-SEM image of hollow graphene microspheres supported on rock salt-type high-entropy oxides prepared by the method of this invention.

[0027] Figure 3 The elemental EDS diagram of the hollow graphene microspheres supported on rock salt-type high-entropy oxides prepared by the method of this invention.

[0028] Figure 4 XRD pattern of hollow graphene microspheres loaded with rock salt-type high-entropy oxides prepared by the method of this invention.

[0029] In the figure: the vertical axis represents diffraction intensity, and the horizontal axis represents the diffraction angle 2θ, with units of °.

[0030] Figure 5 The charge-discharge curves of hollow graphene microspheres loaded with rock salt-type high-entropy oxides prepared by the method of this invention are shown at different current densities.

[0031] In the figure: the vertical axis represents voltage in V, and the horizontal axis represents specific capacity in mAh / g.

[0032] Figure 6 The results of 800 cycles at 1 A / g are shown for hollow graphene microspheres supported on rock salt-type high-entropy oxide prepared by the method of this invention.

[0033] In the figure: the vertical axis represents specific capacity in mAh / g, and the horizontal axis represents the number of cycles in cycles.

[0034] Figure 7 Comparative Example 1: Unmodified rock-salt type high-entropy oxide anode material (Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The initial charge-discharge curve of O;

[0035] (a) 0.05A g -1 (b)2A g -1 . Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0038] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0039] Example 1

[0040] (1) Weigh 1g of graphene oxide prepared by Hummers method, ball mill it at 250rpm for 2 hours, then place it in argon gas, raise it from room temperature to 750℃ at a rate of 10℃ / min, keep it at the temperature for 4 hours, and then cool it naturally to room temperature to obtain porous hollow graphene microsphere powder.

[0041] (2) Weigh 0.44g cobalt(II) nitrate hexahydrate, 0.38g magnesium(II) nitrate hexahydrate, 0.36g copper(II) nitrate trihydrate, 0.45g zinc(II) nitrate hexahydrate and 0.44g nickel(II) nitrate hexahydrate as raw materials for synthesis. Add pure water to prepare a solution A with a metal ion concentration of 0.006g / mL, totaling 67.8mL. Prepare a suspension B with a concentration of 0.01g / mL using anhydrous ethanol, totaling 5mL.

[0042] (3) Add the prepared solution A and suspension B to a 100mL hydrothermal reactor, then add 2mL of concentrated ammonia and 1g of urea. After tightening the reactor lid, place it in a 140℃ constant temperature oven for 5 hours, and then let it cool naturally to room temperature.

[0043] (4) Open the hydrothermal reactor to release the gas, collect the obtained solid, wash with pure water until the filtrate is neutral, dry in an 80℃ oven for 5 hours, grind to obtain powder, then place in argon gas and heat from room temperature to 850℃ at a rate of 4℃ / min, hold at the temperature for 2 hours, continuously introduce argon gas and cool to room temperature to obtain hollow graphene microspheres supported on nano-rock salt type high-entropy oxide (Mg). 0.2 Co 0.2 Ni 0.2 Cu 0.2Zn 0.2 O powder.

[0044] Test results:

[0045] The prepared hollow graphene microspheres supported nano-rock salt type high-entropy oxide (Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The morphology of O is shown in the appendix. Figure 1 -Appendix Figure 3 Phase analysis is attached. Figure 4 This demonstrates that its structural characteristics are: the main particle size is 3-4 micrometers, and the loaded high-entropy oxide (Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The size of the )O is 100-200 nanometers, and the diameter of the internal cavity is 0.5-1 micrometer.

[0046] The prepared hollow graphene microspheres were loaded with nano-rock salt-type high-entropy oxide (Mg). 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 O powder, acetylene black, and polyvinylidene fluoride were mixed in a mass ratio of 7:2:1, and a slurry was prepared with N-methylpyrrolidone and coated onto copper foil. After drying at 80°C for 24 hours, the mixture was cut into 16mm diameter discs. The discs were then dried in a vacuum at 120°C for 4 hours and transferred to an argon glove box. They were then assembled into button cells with lithium metal sheets and 1M LiPF6EC / DEC (volume ratio 1:1) electrolyte. Finally, the cells were tested using a LANHE CT3004A at 0.05A g. -1 -2A g -1 The current range was tested;

[0047] The prepared hollow graphene microspheres support 0.05Ag of nano-rock salt-type high-entropy oxide. -1 -2A g -1 The charge / discharge curves and cycle life are shown in the appendix. Figure 5 -Appendix Figure 6 It shows 2Ag -1 The reversible specific capacity is 412 mAh g. -1 It is 0.05Ag. -1 51% of the specific capacity, 1Ag -1 The reversible specific capacity during the next 800 cycles was consistently around 500 mAh g. -1 The above, along with an enhancement effect, resulted in a reversible specific capacity exceeding 1200 mAh g after 800 cycles.-1 .

[0048] Comparative Example 1

[0049] Unmodified rock salt type high entropy oxide (Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 Anode material, acetylene black, and polyvinylidene fluoride were mixed in a mass ratio of 7:2:1. A slurry was prepared with N-methylpyrrolidone and coated onto copper foil. After drying at 80°C for 24 hours, the mixture was cut into 16mm diameter discs. The discs were then dried in a vacuum at 120°C for 4 hours and transferred to an argon glove box. They were then assembled into button cells with lithium metal sheets and 1M LiPF6 EC / DEC (volume ratio 1:1) electrolyte. Finally, LANHE CT3004A was used to heat the electrolyte at 0.05-2Ag. -1 The current range was tested;

[0050] Unmodified rock-salt type high-entropy oxide anode material at 0.05A g -1 The first charge-discharge curve and 2Ag -1 The charge and discharge curves are as follows: Figure 7 As shown. At 0.05Ag -1 During the first charge and discharge process, its initial coulombic efficiency was 62.07% and its initial reversible specific capacity was 497.3 mAh g. -1 ; in 2Ag -1 At that time, its reversible specific capacity was 103.4 mAh g. -1 .

[0051] Based on the experimental data from Example 1 and Comparative Example 1, the hollow graphene microspheres supported on rock salt-type high-entropy oxide anode material (Mg) prepared by this method... 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 O possesses excellent rate performance and cycle stability, reaching the advanced level of similar materials.

Claims

1. A hollow graphene microsphere-supported nanoparticle (Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The preparation method of O is characterized in that, Specifically, the steps include the following: (1) After grinding the dry graphite oxide powder thoroughly, place it in an inert gas atmosphere, heat it to 650-800℃ at a rate of 5-15℃ / min, keep it at a constant temperature for 3-5 hours, and then cool it naturally to room temperature to obtain porous hollow graphene microsphere powder. (2) Weigh cobalt nitrate, magnesium nitrate, copper nitrate, zinc nitrate and nickel nitrate according to the equimolar ratio of the metal elements, add pure water to prepare a mixed solution A with a total metal ion concentration of 0.005~0.01g / mL; prepare a suspension B with a concentration of 0.005~0.02g / mL using anhydrous ethanol. (3) According to the hollow graphene microspheres and (Mg 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The mass ratio of O is 0.1:1 to 1:

1. Weigh A and B separately and add them to a hydrothermal reactor. Then add ammonia and urea. After the hydrothermal reactor is fully reacted at 130-150°C, it is naturally cooled to room temperature. (4) Unscrew the hydrothermal reactor to release the gas, collect the solid, wash with pure water until the filtrate is neutral, dry the water and grind to obtain powder, then place it in an inert gas atmosphere, raise the temperature from room temperature to 800-900℃ at a rate of 3-5℃ / min and hold for 1-3 hours, then cool naturally to room temperature to obtain hollow graphene microspheres supported on nano-(Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 Powders of high-entropy oxides.

2. The hollow graphene microspheres supported on nano-(Mg) according to claim 1 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The preparation method of O is characterized in that, In step (1), the dry graphite oxide powder is synthesized by the Hummers method.

3. The hollow graphene microspheres supported on nano-(Mg) nanoparticles according to claim 2. 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The preparation method of O is characterized in that, The graphite oxide powder was ball-milled at 200-450 rpm for 2 hours, then heated from room temperature to 750°C at a rate of 10°C / min, held at that temperature for 3-5 hours, and then naturally cooled to room temperature.

4. The hollow graphene microspheres supported on nano-(Mg) according to claim 1 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The preparation method of O is characterized in that, In step (3), the concentration of ammonia in the mixture after addition is 0.2-1%; the concentration of urea in the mixture after addition is 0.01-0.015 g / mL.

5. The hollow graphene microspheres supported on nano-(Mg) according to claim 1 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The preparation method of O is characterized in that, In step (3), the mixture is added to a hydrothermal reactor with a volume of 100 mL, so that the volume of the mixed solution is in the range of 60~80 mL.

6. The hollow graphene microspheres supported on nano-(Mg) according to claim 1 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The preparation method of O is characterized in that, The inert gas is argon.

7. The hollow graphene microspheres supported on nano-(Mg) according to claim 1 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The preparation method of O is characterized in that, The cobalt nitrate, magnesium nitrate, copper nitrate, zinc nitrate, or nickel nitrate are replaced with other soluble salts of the same metal element.

8. A hollow graphene microsphere supported on rock salt (Mg) prepared by the method according to any one of claims 1 to 7. 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 O composite material.

9. A hollow graphene microsphere supported on rock salt (Mg) as described in claim 8 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 Application of O composite materials as negative electrodes for lithium-ion batteries.

10. Hollow graphene microspheres supported on rock salt (Mg) prepared by the method according to any one of claims 1 to 7 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 O composite material, characterized in that, The hollow graphene microspheres are loaded with rock salt type (Mg) 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 The composite material particles have a size of 2.5-4 micrometers, with internal cavity diameters of 0.5-1 micrometers. In-situ deposition of 100-200 nanometer-sized (Mg) particles on the graphene spherical shell surface further enhances the composite material's properties. 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 O high-entropy oxide particles.

Images