CN111816867A - Preparation method and application of mesoporous sea urchin-like NiCo2O4/stereostructured graphene microsphere composites - Google Patents

Abstract

A preparation method and application of a mesoporous structure sea urchin-like NiCo ₂ O ₄ / three-dimensionally constructed graphene microsphere composite material, comprising the following steps: (1) firstly treating the three-dimensionally constructed graphene with an oxidizing acid in a high pressure reaction kettle, After washing and drying, hydrophilic three-dimensional structured graphene is obtained; (2) the hydrophilic three-dimensional structured graphene is dispersed in water by ultrasonic method, and then cobalt salt, nickel salt, surfactant and precipitant are added to fully Stir to form a homogeneous solution; (3) hydrothermally react the mixed solution to obtain a nickel cobalt oxide precursor; (4) calcine the nickel cobalt oxide precursor in an air atmosphere to obtain a mesoporous NiCo ₂ O ₄ /stereostructured graphene microstructure. ball complex. The invention has the advantages of simple preparation process, environmental protection, wide source of raw materials and electrochemical performance of the product. The specific capacity of the lithium-ion battery anode material prepared by this material is as high as 1403 mA hg ^‑1 in the first discharge. When used as a negative electrode material for sodium-ion batteries, the first discharge specific capacity is as high as 818.4 mA hg ^‑1 .

Description

Preparation of mesoporous sea urchin-like NiCo2O4/stereostructured graphene microsphere composites Preparation method and application

technical field

The invention relates to a mesoporous structure NiCo ₂ O ₄ /stereo-structured graphene microsphere, in particular to a preparation method and application of a mesoporous structure sea urchin-like NiCo ₂ O ₄ /stereostructured graphene microsphere composite material.

Background technique

Graphite sheets with less than 10 layers are called graphene, a conductive material with a two-dimensional spatial structure of a hexagonal network. Because of its large specific surface area, good electrical conductivity, and ultra-high chemical stability, it has excellent application potential in the fields of supercapacitors and luminescent materials. However, when graphene with a two-dimensional spatial structure is used alone as the anode material for lithium-ion batteries or sodium-ion batteries, there are problems such as low discharge capacity and Coulombic efficiency, and rapid capacity decay. However, using graphene with two-dimensional spatial structure as the coating layer of the anode material or cathode material of lithium ion battery plays a positive role in improving the cycle stability of the battery (Hsu T H, Liu W R, Polymers, 2020, 12(5) : 1162; Yang X F, Qiu J Y et al, J. Alloys Compd., 2020, 824: 153945; Zhang J F, Ji G J et al, Appl. Surf. Sci., 2020, 513: 145854). However, due to the tendency of 2D graphene to agglomerate and agglomerate, there are still disadvantages such as being difficult to store and use. In addition, due to the small ion transport channel of 2D graphene, 2D graphene is not suitable as the anode material of Na-ion batteries or the coating layer of positive and negative electrode materials. Currently, constructing graphene with a three-dimensional (3D) structure has been shown to be an effective strategy to provide a self-supporting structure, prevent the aggregation of graphene nanosheets, and improve the energy storage performance of graphene-based materials with a unique 3D structure Provided a channel that can meet the transport of sodium ions (Li Y Y, Li Z S et al., Adv. Mater., 2013, 25(17): 2474–2480; Luo R, Ma Y T et al., ACS Appl.Mater.Inter., 2020, doi: 10.1021/acsami.0c04481; Chen W, Ning Y et al., Mater. Lett., 2019, 236:618–621).

NiCo ₂ O ₄ is a composite metal oxide with a spinel structure and a complex valence state, wherein nickel ions occupy octahedral sites in the spinel structure, and cobalt ions occupy tetrahedral sites. In the electrochemical reaction of solid NiCo ₂ O ₄ , there are two redox pairs, Ni ^{3 +} /Ni ²⁺ and Co ³⁺ /Co ²⁺ , which can provide two active centers for pseudocapacitance. Compared with the single _- component metal oxides _Co3O4 and NiO, the binary metal _{oxide NiCo2O4} has higher electrical conductivity, mechanical stability, theoretical capacity and lower cost. To improve the electrochemical performance of NiCo ₂ O ₄ , many efforts have been made, including surface modification, nano-ization of NiCo ₂ O ₄ , and mixing with various carbons to form composites (Wu Hongying, Wang Huanwen, Chinese Journal of Physical Chemistry, 2013, 29(7), 1501–1506). Using nickel nitrate hexahydrate, cobalt nitrate hexahydrate, NH ₄ F, urea and activated carbon fiber cloth as raw materials, by hydrothermal method and subsequent heat treatment, nickel cobalt oxide nanoflowers were successfully grown on activated carbon fiber scaffolds. (Fu F, Li JD, Yao YZ et al., ACS Appl.Mater.Interf., 2017, 9: ^{16194–16201} ) Synthesis of one _- dimensional porous _NiCo2O4 microrods by solvothermal method at a current of 100 mA g Under the density, when the microrod material is used as a lithium ion anode material, the discharge capacity after 50 cycles is about 1000mA hg ^-1 ; when used as a sodium ion battery anode material, the first charge capacity is 431.1mAh g ^-1 . (Li Fangfang, Wang Hongbin, Wang Runwei, et al., Journal of Chemistry of Universities, 2017, 38(11): 1913–1920) Rod-like NiCo ₂ O ₄ @C complexes were synthesized by a one-step hydrothermal method at a current density of 100 mA g ^-1 , the discharge capacities of NiCo ₂ O ₄ @C composite as anode material for Li-ion batteries for the first time and after 5 cycles are 767.2 mA hg ^-1 and 650.1 mA hg ^-1 , respectively. (Zhang Mingmei, Li Yuan, Xie Jimin, etc., Chinese patent CN 106169384 A discloses a preparation method of a three-dimensional mesoporous NiCo ₂ O ₄ / nitrogen-doped graphene composite electrode material, using graphene oxide as a carbon source and acetonitrile as a solvent Graphene oxide is first treated by hydrothermal method, then the obtained graphene is mixed with hexahydrate nickel nitrate, hexahydrate cobalt nitrate, hexamethylene tetramine to carry out a hydrothermal reaction, and finally the obtained precursor is in an air atmosphere. Three-dimensional mesoporous NiCo ₂ O ₄ /nitrogen-doped graphene composite electrode material is obtained by medium calcination. Chinese patent CN 104882298 A discloses a method for preparing NiCo ₂ O ₄ /graphene supercapacitor material by microwave method, and the natural stone is treated by Hummers method Graphene oxide obtained from graphene is the carbon source, nickel chloride and cobalt chloride are respectively used as nickel source and cobalt source, urea is used as precipitant, the precursor is synthesized by microwave heating method, and the precursor is calcined in air atmosphere to obtain porous Flake NiCo ₂ O ₄ /graphene supercapacitor material.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a preparation method of simple operation, preparation of sea urchin-like NiCo ₂ O ₄ /stereostructured graphene microsphere composite material with mesoporous structure, and the obtained material is respectively used as a lithium ion battery at a current density of 100mA g ^-1 and sodium ion battery anode materials, the first discharge specific capacity is 1403mA hg ^-1 and 818.4mA hg ^-1 , respectively, and the materials have good rate performance and cycle stability.

The present invention achieves the above object through the following technical solutions: a preparation method of a mesoporous structure sea urchin-shaped NiCo ₂ O ₄ / three-dimensionally structured graphene microsphere composite material, comprising the following steps:

(1) the three-dimensionally constructed graphene powder is placed in a hydrothermal kettle lined with polytetrafluoroethylene, 68wt% nitric acid is added, the hydrothermal kettle is heated at a constant temperature, and the hydrothermal kettle is naturally cooled to room temperature after the reaction, and filtered Collect the precipitation to obtain the hydrophilic three-dimensionally structured graphene powder, and when preparing the hydrophilic three-dimensionally structured graphene powder, the amount ratio of the three-dimensionally structured graphene to the nitric acid is 1 g: 25～70 mL, and the reaction temperature is 80～160 ℃, The reaction time is 10-36h, and the temperature of drying the three-dimensionally constructed graphene powder is 50-90°C;

(2) dispersing the hydrophilic three-dimensionally structured graphene powder obtained in step (1) into deionized water by ultrasonic waves to obtain a uniformly dispersed hydrophilic three-dimensionally structured graphene solution A, and the hydrophilic three-dimensional structured graphene The dosage ratio of powder and deionized water is 0.1g: 20～50mL, and the ultrasonic time is 5～40min;

(3) hexahydrate cobalt nitrate, hexahydrate nickel nitrate, urea and polyethylene glycol-400 are dissolved in deionized water, obtain solution B, when preparing mixed solution B, the hexahydrate nickel nitrate, hexahydrate cobalt nitrate used The dosage ratio of , urea and polyethylene glycol-400 is 0.003～0.009mol: 0.006～0.018mol: 0.036～0.108mol: 2～4ml;

(4) Mixing solution A and solution B to obtain solution C, when preparing mixed solution C, the dosage ratio of hydrophilic three-dimensional structured graphene and NiCo ₂ O ₄ is 0.1 g: 0.3-1.2 g;

(5) solution C is moved into the hydrothermal still of lining polytetrafluoroethylene, carries out constant temperature thermal reaction, obtains the nickel cobaltate precursor D of three-dimensional structure graphene coating after filter washing, prepares three-dimensional structure graphene coating In the case of the nickel cobaltate precursor D, the temperature of the constant temperature reaction is 85°C to 160°C, and the reaction time is 4 to 20h;

(6) The precursor D is calcined in a muffle furnace at a calcination temperature of 280°C to 360°C and a reaction time of 1 h to 4 h to obtain a mesoporous NiCo ₂ O ₄ /stereostructured graphene microsphere composite.

Further, the hydrothermal reaction temperature/time is 95～110°C/8～4h.

Further, the calcination temperature is controlled at 300-335°C.

The preparation method of the mesoporous NiCo ₂ O ₄ /stereostructured graphene microsphere composite comprises the following steps:

(1) the three-dimensionally constructed graphene powder is placed in a hydrothermal kettle lined with polytetrafluoroethylene, 68wt% nitric acid is added, the hydrothermal kettle is heated at a constant temperature, and the hydrothermal kettle is naturally cooled to room temperature after the reaction, and filtered Collect the precipitate to obtain hydrophilic three-dimensionally structured graphene powder. When preparing hydrophilic three-dimensionally structured graphene powder, the dosage ratio of three-dimensionally structured graphene to nitric acid is 1 g: 40 mL, the reaction temperature is 120 ° C, and the reaction time is 24 h , the temperature of drying the three-dimensionally constructed graphene powder is 60 °C;

(2) dispersing the hydrophilic three-dimensionally structured graphene powder obtained in step (1) into deionized water by ultrasonic waves to obtain a uniformly dispersed hydrophilic three-dimensionally structured graphene solution A, and the hydrophilic three-dimensional structured graphene The dosage ratio of powder to deionized water is 0.1g:30mL, and the ultrasonic time is 30min;

(3) hexahydrate cobalt nitrate, hexahydrate nickel nitrate, urea and polyethylene glycol-400 are dissolved in deionized water, obtain solution B, when preparing mixed solution B, the hexahydrate nickel nitrate, hexahydrate cobalt nitrate used , the dosage ratio of urea and polyethylene glycol-400 is 0.003mol:0.006mol:0.036mol:2ml;

(4) Mixing solution A and solution B to obtain solution C, when preparing mixed solution C, the dosage ratio of hydrophilic three-dimensional structured graphene and NiCo ₂ O ₄ is 0.1 g: 0.72 g;

(5) solution C is moved into the hydrothermal still of lining polytetrafluoroethylene, carries out constant temperature thermal reaction, obtains the nickel cobaltate precursor D of three-dimensional structure graphene coating after filter washing, prepares three-dimensional structure graphene coating In the case of nickel cobaltate precursor D, the temperature of the constant temperature reaction is 95°C, and the reaction time is 8h;

(6) The precursor D was calcined in a muffle furnace at a calcination temperature of 300 °C and a reaction time of 2 h to obtain a mesoporous NiCo ₂ O ₄ /stereostructured graphene microsphere composite.

Application of the prepared mesoporous NiCo ₂ O ₄ /stereostructured graphene microsphere composites in lithium-ion battery anode materials.

Application of the prepared mesoporous NiCo ₂ O ₄ /stereostructured graphene microsphere composites in the anode material of sodium ion batteries.

The materials were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), thermogravimetric analyzer (TG), nitrogen adsorption-desorption analyzer, X-ray photoelectron spectroscopy (XPS), by electrochemical workstation and battery The test system tests the electrochemical properties of the materials as anode materials for lithium/sodium batteries.

Unless otherwise stated, the percentages mentioned in the present invention are all mass percentages, and the sum of the percentages of the contents of each component is 100%. Beneficial effects of the present invention:

The mesoporous structure sea urchin-like NiCo ₂ O ₄ / three-dimensionally constructed graphene microsphere composite electrode material prepared by the invention has the controllable size of the microsphere and the size of the nanorods constituting the sea urchin-like microsphere. The diameter of the sea urchin-like microsphere is Between 1.9 and 4.5 μm, the diameter of the nanorods forming the sea urchin-like microspheres is about 60 nm, and the pore size and specific surface area of the material are 4.45 nm and 138.81 m ² g ⁻¹ , respectively. When the prepared materials are used as anode materials for lithium-ion batteries and sodium-ion batteries, the first discharge specific capacities are as high as 1403 mA hg ^-1 and 818.4 mA hg ^-1 at a current density of 100 mA g ^-1 , respectively. In addition, the material exhibits good rate performance and cycling stability. The preparation method has the advantages of simple operation, easy control of reaction conditions, low cost, and excellent lithium/sodium storage performance of the obtained material.

Description of drawings

Figure 1 is a SEM image of three-dimensionally constructed graphene.

Figure 2 is the XRD diffraction pattern of the mesoporous sea urchin-like NiCo ₂ O ₄ /stereo-structured graphene microsphere composite material, and characteristic diffraction peaks of graphene and nickel cobaltate appear in the figure.

Figure 3 is a SEM image of mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene.

Figure 4 is a graph of nitrogen adsorption-desorption curves of mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene.

Figure 5 shows the cycling performance of sea urchin-like (a) NiCo ₂ O ₄ and (b) NiCo ₂ O ₄ /stereostructured graphene microspheres as anode materials for Li-ion batteries at a current density of 0.1 A g ⁻¹ .

Figure 6 shows the cycling performance of sea urchin-like (a) NiCo ₂ O ₄ and (b) NiCo ₂ O ₄ /stereostructured graphene microspheres as anode materials for Na-ion batteries at a current density of 0.1 A g ⁻¹ .

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the implementation examples.

Example 1

Preparation of hydrophilic stereostructured graphene. Put 1 g of three-dimensionally structured graphene into an 80 mL hydrothermal reactor lined with PTFE, add 40 mL of nitric acid with a concentration of 68 wt%, and react at 120 °C for 24 h. After the reaction, it was naturally cooled to room temperature, and the obtained product was suction filtered with a No. 6 sand core funnel, washed alternately with deionized water and anhydrous ethanol for 6 times, and then dried in a vacuum drying oven at 60 ° C for 5 hours to obtain hydrophilic Three-dimensional structure of graphene powder. The SEM analysis of the product confirmed that its structure was a three-dimensional structure; the XPS analysis showed that it was confirmed that sp ² C existed in the obtained product; the water dispersibility test of the product showed that its hydrophilicity was lower than that of the product treated with 68wt% nitric acid. The previous three-dimensional structure of graphene has been significantly improved. It shows that the prepared product is hydrophilic three-dimensional structured graphene. As shown in Figure 1 and Figure 2.

Example 2

Preparation of mesoporous sea urchin-like NiCo ₂ O ₄ . 0.8724 g of 0.003 mol nickel nitrate hexahydrate, 1.7462 g of 0.006 mol cobalt nitrate hexahydrate, 2.1622 g of 0.036 mol urea and 2 mL of polyethylene glycol-400 were dissolved in 60 mL of deionized water. The resulting solution was transferred to a 100 mL polytetrafluoroethylene-lined hydrothermal reactor, and heated at 95° C. for 8 h. After cooling to room temperature, the precipitate was collected by suction filtration with a No. 6 sand core funnel, and washed 3 times alternately with deionized water and absolute ethanol. The precipitation was dried in a vacuum drying oven at a temperature of 60 °C for 4 h to obtain the NiCo ₂ O ₄ precursor. The NiCo ₂ O ₄ precursor was calcined in air at a temperature of 300 °C for 2 h at a heating rate of 2 min ^-1 to obtain a mesoporous sea urchin-like NiCo ₂ O ₄ . The pore size and specific surface area of the sea urchin-like NiCo ₂ O ₄ are 3.98nm and 125.71m ² g ^-1 . The as-prepared mesoporous sea urchin-like NiCo ₂ O ₄ was used as anode material for Li-ion batteries, and the first discharge capacity and the 50th cycle discharge capacity were 1409.6 mA hg ^-1 and 610.7 mA, respectively, at a current density of 0.1 A g ^-1 hg ^–1 , as shown in a in Figure 5. The prepared mesoporous sea urchin-like NiCo ₂ O ₄ was used as anode material for Na-ion batteries, and the first discharge capacity and the 50th cycle discharge capacity were 638 mA ^hg and ^214.6 mA hg, respectively, at a current density of 0.1 A g ^–1 , as shown in a in Figure 6.

Example 3

Preparation of mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene microspheres. Disperse 0.8724g of 0.003mol nickel nitrate hexahydrate, 1.7462g of 0.006mol cobalt nitrate hexahydrate, 2.1622g of 0.036mol urea, 100mg of hydrophilic stereostructured graphene, 2mL of polyethylene glycol-400 ultrasonically dispersed in 60mL of ionized water. The resulting mixture was transferred to a 100 mL polytetrafluoroethylene-lined hydrothermal reactor, and heated at 95 °C for 8 h. After cooling to room temperature, the precipitate was collected by suction filtration with a No. 6 sand core funnel, and washed three times alternately with deionized water and absolute ethanol. The precipitation was dried in a vacuum drying oven at a temperature of 60° C. for 4 h to obtain the precursor of NiCo ₂ O ₄ /stereostructured graphene. The precursor of NiCo ₂ O ₄ /stereostructured graphene was calcined at 300 °C for 2h at a heating rate of 2min ^-1 in air atmosphere to obtain mesoporous sea urchin-like NiCo _{2 O4} /stereostructured graphene microspheres , as shown in Figures 2 and 3, the pore size and specific surface area of the composite are 4.45 nm and 138.81 m ² g ^–1 , respectively. As shown in Figure 4, the pore size and specific surface area of the composite are higher than those of single NiCo ₂ O ₄ Samples have improved. The prepared mesoporous sea urchin-like NiCo ₂ O ₄ / three-dimensionally constructed graphene microspheres were used as anode materials for lithium ion batteries, and the first discharge capacity and the 50th cycle discharge capacity were 1403 mA at a current density of 0.1 A g ^-1 , respectively. hg ^-1 and 1027 mA hg ^-1 , as shown in b in Fig. 5 . The prepared mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene was used as anode material for sodium-ion batteries, and the first discharge capacity and the 50th cycle discharge capacity were 819 mA hg at a current density of 0.1 A g ⁻¹ , respectively ^{. 1} and 314mAh g ⁻¹ , as shown in b in Fig. 6 . It is shown that the lithium/sodium storage performance of NiCo ₂ O ₄ /stereo-structured graphene composites obtained after NiCo ₂ O ₄ is coated on the surface of stereo-structured graphene is significantly improved than that of single NiCo ₂ O ₄ prepared under the same technical conditions.

Example 4

Preparation of mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene microspheres.

Disperse 1.7448g of 0.006mol nickel nitrate hexahydrate, 3.4924g of 0.012mol cobalt nitrate hexahydrate, 4.3244g of 0.072mol urea, 200mg of hydrophilic stereostructured graphene, and 3mL of polyethylene glycol-400 ultrasonically dispersed in 60mL deionized water. The resulting mixture was transferred to a 100 mL polytetrafluoroethylene-lined hydrothermal reactor, and heated at 95 °C for 8 h. After cooling to room temperature, the precipitate was collected by suction filtration with a No. 6 sand core funnel, and washed three times alternately with deionized water and absolute ethanol. The precipitation was dried in a vacuum drying oven at a temperature of 60° C. for 4 h to obtain the precursor of NiCo ₂ O ₄ /stereostructured graphene. The precursor of NiCo ₂ O ₄ /stereostructured graphene was calcined at 300 ℃ for 2h at a heating rate of _2min ^-1 in air atmosphere to obtain mesoporous sea urchin-like _NiCo2O4 /stereostructured graphene microspheres , the pore size and specific surface area of the composite are 4.40 nm and 129.03 m ² g ⁻¹ , respectively, and the pore size and specific surface area of the composite are slightly smaller than those of the sample obtained under the technical conditions of Example 3. The prepared mesoporous sea urchin-like NiCo ₂ O ₄ / three-dimensionally constructed graphene microspheres were used as anode materials for lithium-ion batteries. At a current density of 0.1 A g ^-1 , the first discharge capacity and the 50th cycle discharge capacity were 1370 mA hg ^-1 and 1001 mA hg ^-1 . The prepared mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene was used as anode material for sodium-ion batteries, and the first discharge capacity and the 50th cycle discharge capacity were 810 mA hg at 0.1 A g ⁻¹ current density, respectively ^{. 1} and 310mA hg ^–1 . It is shown that the lithium/sodium storage properties of the obtained NiCo ₂ O ₄ /stereostructured graphene composites are all lower than those of the samples obtained in Example 3.

Example 5

The prepared mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene microspheres.

Disperse 2.6172g of 0.009mol nickel nitrate hexahydrate, 5.2386g of 0.018mol cobalt nitrate hexahydrate, 6.4866g of 0.108mol urea, 300mg of hydrophilic stereostructured graphene, and 6mL of polyethylene glycol-400 ultrasonically dispersed in 60mL deionized water. The resulting mixture was transferred to a 100 mL polytetrafluoroethylene-lined hydrothermal reactor, and heated at 95 °C for 8 h. After cooling to room temperature, the precipitate was collected by suction filtration with a No. 6 sand core funnel, and washed three times alternately with deionized water and absolute ethanol. The precipitation was dried in a vacuum drying oven at a temperature of 60° C. for 4 h to obtain the precursor of NiCo ₂ O ₄ /stereostructured graphene. The precursor of NiCo ₂ O ₄ /stereostructured graphene was calcined at 300 ℃ for 2h at a heating rate of _2min ^-1 in air atmosphere to obtain mesoporous sea urchin-like _NiCo2O4 /stereostructured graphene microspheres , the pore size and specific surface area of the composite are 4.25 nm and 126.7 m ² g ⁻¹ , respectively. The pore size and specific surface area of the composite are both higher than those of the single NiCo ₂ O ₄ sample, but smaller than those of Example 3 and Example 4. sample. The prepared mesoporous sea urchin-like NiCo ₂ O ₄ / three-dimensionally constructed graphene microspheres were used as anode materials for lithium-ion batteries, and the first discharge capacity and the 50th cycle discharge capacity were 1365mA at a current density of 0.1A g ^-1 , respectively. hg ^-1 and 995mA hg ^-1 . The prepared mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene was used as anode material for sodium-ion batteries, and the first discharge capacity and the 50th cycle discharge capacity were 800 mA hg at 0.1 A g ⁻¹ current density, respectively ^{. 1} and 300.4mA hg ^–1 . It is shown that the lithium/sodium storage performance of the NiCo ₂ O ₄ /stereo-structured graphene composite obtained after NiCo ₂ O ₄ is coated on the surface of three-dimensional structured graphene is significantly improved than that of single NiCo ₂ O ₄ , but it is smaller than that of Example 3 and the implementation of Sample of Example 4.

Example 6

The prepared mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene microspheres.

Disperse 0.8724g of 0.003mol nickel nitrate hexahydrate, 1.7462g of 0.006mol cobalt nitrate hexahydrate, 2.1622g of 0.036mol urea, 100mg of hydrophilic stereostructured graphene, and 2mL of polyethylene glycol-400 ultrasonically dispersed in 60mL deionized water. The resulting mixture was transferred to a 100 mL polytetrafluoroethylene-lined hydrothermal reactor, and heated at 110 °C for 8 h. After cooling to room temperature, the precipitate was collected by suction filtration with a No. 6 sand core funnel, and washed three times alternately with deionized water and absolute ethanol. The precipitation was dried in a vacuum drying oven at a temperature of 60° C. for 4 h to obtain the precursor of NiCo ₂ O ₄ /stereostructured graphene. The precursor of NiCo ₂ O ₄ /stereostructured graphene was calcined at 350℃ for 1.5h at a heating rate of _2min ^-1 in air atmosphere to obtain mesoporous sea urchin-like _NiCo2O4 /stereostructured graphene microstructures. The pore size and specific surface area of the composite material are 3.80 nm and 110.6 m ² g ⁻¹ respectively, and the pore size and specific surface area of the composite material are both smaller than those of Examples 2 to 5. The prepared mesoporous sea urchin-like NiCo ₂ O ₄ / three-dimensionally constructed graphene microspheres were used as anode materials for lithium ion batteries. At a current density of 0.1A g ^-1 , the first discharge capacity and the 50th cycle discharge capacity were 1350mA, respectively. hg ^-1 and 990mA hg ^-1 . The prepared mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene was used as anode material for Na-ion batteries, and the first discharge capacity and the 50th cycle discharge capacity were 798 mA hg at 0.1 A g ⁻¹ current density, respectively ^{. 1} and 285mA hg ^–1 . It is shown that the lithium/sodium storage performance of the NiCo ₂ O ₄ /stereostructured graphene composite obtained under this technical condition is lower than that of Examples 3 to 5.

Example 7

The prepared mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene microspheres.

0.8724g of 0.003mol nickel nitrate hexahydrate, 1.7462g of 0.006mol cobalt nitrate hexahydrate, 2.1622g of 0.036mol urea, 100mg of hydrophilic stereo-structured graphene, 2mL of polyethylene glycol-400 ultrasonically dispersed in 60mL of deionized water. The resulting mixture was transferred to a 100 mL polytetrafluoroethylene-lined hydrothermal reactor, and heated at 105 °C for 6 h. After cooling to room temperature, the precipitate was collected by suction filtration with a No. 6 sand core funnel, and washed three times alternately with deionized water and absolute ethanol. The precipitation was dried in a vacuum drying oven at a temperature of 60° C. for 4 hours to obtain the precursor of NiCo ₂ O ₄ /stereostructured graphene. The precursor of NiCo ₂ O ₄ /stereostructured graphene was calcined at 330℃ for 1h at a heating rate of _2min ^-1 in air to obtain mesoporous sea urchin-like _NiCo2O4 /stereostructured graphene microspheres. The prepared mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene microspheres were used as anode materials for lithium-ion batteries, and the first discharge capacity and the 10th cycle discharge capacity were 1300mA at a current density of 0.5A g ^-1 , respectively. hg ^-1 and 900mA hg ^-1 . When the material is used as a negative electrode material for sodium-ion batteries, the first discharge capacity and the 10th cycle discharge capacity are 645mAh g ^-1 and 450mA hg ^-1 at a current density of 0.5A g ^-1 , respectively.

Example 8

The prepared mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene microspheres.

Disperse 0.8724g of 0.003mol nickel nitrate hexahydrate, 1.7462g of 0.006mol cobalt nitrate hexahydrate, 2.1622g of 0.036mol urea, 100mg of hydrophilic stereostructured graphene, and 2mL of polyethylene glycol-400 ultrasonically dispersed in 60mL deionized water. The resulting mixture was transferred to a 100 mL polytetrafluoroethylene-lined hydrothermal reactor, and heated at 110 °C for 4 h. After cooling to room temperature, the precipitate was collected by suction filtration with a No. 6 sand core funnel, and washed three times alternately with deionized water and absolute ethanol. The precipitation was dried in a vacuum drying oven at 60° C. for 4 hours to obtain the precursor of NiCo ₂ O ₄ /hydrophilic stereostructured graphene. The precursor of NiCo ₂ O ₄ /hydrophilic stereostructured graphene was calcined in air at a temperature of 335 °C for 1 h at a heating rate of 2 min ^-1 to obtain mesoporous sea urchin-like NiCo _{2 O4} /stereostructured graphene Microspheres. The prepared mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene microspheres were used as anode materials for lithium ion batteries, and the first discharge capacity and the 200th cycle discharge capacity were 1308 mA hg at a current density of 1 A g ^-1 , respectively. ^-1 and 500mA hg ^-1 . When the material was used as a negative electrode material for sodium ion batteries, the first discharge capacity and the 10th cycle discharge capacity were 638 mA hg ^-1 and 372 mA hg ^-1 at a current density of 1 A g ^-1 , respectively.

Table 1 Li/Na storage properties of the prepared products under different experimental control conditions

From the lithium/sodium storage properties of the products prepared under different experimental control conditions in Table 1, it can be seen that the sea urchin-like NiCo ₂ O ₄ /stereostructured graphene microspheres prepared after adding stereostructured graphene are higher than those without the addition of stereostructures. Graphene-like sea urchin _- like _NiCo2O4 microspheres exhibit higher discharge capacity and cycling stability. This is because the three-dimensionally structured graphene coated on the surface of the sea urchin-like NiCo ₂ O ₄ microspheres has a three-dimensional conductive network that can improve the electronic conductivity of the material, and at the same time, the three-dimensional structured graphene can also relieve the charging/discharging process of NiCo ₂ O ₄ volume change in . In addition, in order to obtain NiCo ₂ O ₄ / three-dimensionally structured graphene microspheres with large specific surface area and high electrochemical performance, the calcination temperature should be controlled at 300-335 °C.

Claims (6)

1. Sea urchin-shaped NiCo with mesoporous structure₂O₄The preparation method of the three-dimensional construction graphene microsphere composite material is characterized by comprising the following steps:

(1) placing the three-dimensional structure graphene powder into a hydrothermal kettle lined with polytetrafluoroethylene, adding 68 wt% of nitric acid, heating the hydrothermal kettle at a constant temperature, naturally cooling the hydrothermal kettle to room temperature after the reaction is finished, filtering, collecting and precipitating to obtain hydrophilic three-dimensional structure graphene powder, wherein when the hydrophilic three-dimensional structure graphene powder is prepared, the dosage ratio of the three-dimensional structure graphene to the nitric acid is 1 g: 25-70 mL of the graphene powder, the reaction temperature of 80-160 ℃, the reaction time of 10-36 h, and the temperature for drying the three-dimensional structure graphene powder of 50-90 ℃;

(2) ultrasonically dispersing the hydrophilic three-dimensional structure graphene powder obtained in the step (1) into deionized water to obtain a uniformly dispersed hydrophilic three-dimensional structure graphene solution A, wherein the dosage ratio of the hydrophilic three-dimensional structure graphene powder to the deionized water is 0.1 g: 20-50 mL, and 5-40 min of ultrasonic time;

(3) dissolving cobalt nitrate hexahydrate, nickel nitrate hexahydrate, urea and polyethylene glycol-400 by using deionized water to obtain a solution B, wherein the dosage ratio of the nickel nitrate hexahydrate, the cobalt nitrate hexahydrate, the urea and the polyethylene glycol-400 is 0.003-0.009 mol: 0.006-0.018 mol: 0.036-0.108 mol: 2-4 ml;

(4) mixing solution A and solution B to obtainSolution C, when preparing mixed solution C, hydrophilic three-dimensional structure graphene and NiCo₂O₄The dosage ratio of the components is 0.1 g: 0.3-1.2 g;

(5) transferring the solution C into a hydrothermal kettle lined with polytetrafluoroethylene, carrying out constant-temperature thermal reaction, filtering and washing to obtain a three-dimensional constructed graphene-coated nickel cobaltate precursor D, wherein the constant-temperature reaction temperature is 85-160 ℃ and the reaction time is 4-20 h when the three-dimensional constructed graphene-coated nickel cobaltate precursor D is prepared;

(6) placing the precursor D in a muffle furnace for calcining at the temperature of 280-360 ℃ for 1-4 h to obtain the mesoporous NiCo₂O₄A three-dimensional structure graphene microsphere compound.

2. The mesoporous NiCo of claim 1₂O₄The preparation method of the three-dimensional construction graphene microsphere compound is characterized in that the hydrothermal reaction temperature/time is 95-110 ℃/8-4 h.

3. The mesoporous NiCo of claim 1₂O₄The preparation method of the three-dimensional structure graphene microsphere compound is characterized in that the calcining temperature is controlled to be 300-335 ℃.

4. The mesoporous NiCo of claim 1₂O₄The preparation method of the three-dimensional structure graphene microsphere compound is characterized by comprising the following steps:

(1) placing the three-dimensional structure graphene powder into a hydrothermal kettle lined with polytetrafluoroethylene, adding 68 wt% of nitric acid, heating the hydrothermal kettle at a constant temperature, naturally cooling the hydrothermal kettle to room temperature after the reaction is finished, filtering, collecting and precipitating to obtain hydrophilic three-dimensional structure graphene powder, wherein when the hydrophilic three-dimensional structure graphene powder is prepared, the dosage ratio of the three-dimensional structure graphene to the nitric acid is 1 g: 40mL, the reaction temperature is 120 ℃, the reaction time is 24 hours, and the temperature for drying the three-dimensional graphene powder is 60 ℃;

(2) ultrasonically dispersing the hydrophilic three-dimensional structure graphene powder obtained in the step (1) into deionized water to obtain a uniformly dispersed hydrophilic three-dimensional structure graphene solution A, wherein the dosage ratio of the hydrophilic three-dimensional structure graphene powder to the deionized water is 0.1 g: 30mL, and the ultrasonic time is 30 min;

(3) dissolving cobalt nitrate hexahydrate, nickel nitrate hexahydrate, urea and polyethylene glycol-400 by using deionized water to obtain a solution B, wherein when a mixed solution B is prepared, the dosage ratio of the nickel nitrate hexahydrate, the cobalt nitrate hexahydrate, the urea and the polyethylene glycol-400 is 0.003 mol: 0.006 mol: 0.036 mol: 2 ml;

(4) mixing the solution A and the solution B to obtain a solution C, and preparing the mixed solution C by using the hydrophilic three-dimensional structure graphene and NiCo₂O₄The dosage ratio of the components is 0.1 g: 0.72 g;

(5) transferring the solution C into a hydrothermal kettle lined with polytetrafluoroethylene, carrying out constant-temperature thermal reaction, filtering and washing to obtain a three-dimensional constructed graphene-coated nickel cobaltate precursor D, wherein the constant-temperature reaction temperature is 95 ℃ and the reaction time is 8 hours when the three-dimensional constructed graphene-coated nickel cobaltate precursor D is prepared;

(6) placing the precursor D in a muffle furnace for calcining at the calcining temperature of 300 ℃ for 2h to obtain the mesoporous NiCo₂O₄A three-dimensional structure graphene microsphere compound.

5. The mesoporous NiCo prepared in claim 1₂O₄Application of the three-dimensional structure graphene microsphere compound in a lithium ion battery cathode material.

6. The mesoporous NiCo prepared in claim 1₂O₄Application of the three-dimensional structure graphene microsphere compound in a sodium ion battery cathode material.

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