CN111816867B - Preparation method and application of mesoporous sea urchin-like NiCo2O4/three-dimensional structure graphene microsphere composite material - Google Patents

Abstract

Sea urchin-shaped NiCo with mesoporous structure ₂ O ₄ The preparation method and the application of the three-dimensional construction graphene microsphere composite material comprise the following steps: (1) Firstly, treating the three-dimensional constructed graphene with oxidizing acid in a high-pressure reaction kettle, washing with water, and drying to obtain hydrophilic three-dimensional constructed graphene; (2) Dispersing hydrophilic three-dimensional structure graphene in water by an ultrasonic method, then adding cobalt salt, nickel salt, a surfactant and a precipitator, and fully stirring to form a uniform solution; (3) Carrying out hydrothermal reaction on the mixed solution to obtain a nickel cobaltate precursor; (4) Calcining the nickel cobaltate precursor in air atmosphere to obtain the mesoporous NiCo ₂ O ₄ A three-dimensional structure graphene microsphere compound. The preparation method has the advantages of simple preparation process, environmental protection, wide raw material source and electrochemical performance of the product. The specific capacity of the lithium ion battery cathode material prepared by the material in the first discharge is up to 1403mA h g ^‑1 . When the material is used as the negative electrode material of a sodium ion battery, the first discharge specific capacity is as high as 818.4mA h g ^‑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 /stereoscopic graphene microsphere, in particular to a preparation method and application of a mesoporous structure sea urchin-like NiCo ₂ O ₄ /stereoscopic graphene microsphere composite material.

Background technique

Graphite sheets with less than 10 layers are called graphene, and graphene is a conductive material with a two-dimensional space structure of hexagonal network. Because of its large specific surface area, good electrical conductivity, and high chemical stability, it has excellent application potential in supercapacitors, luminescent materials, and other fields. However, when graphene with a two-dimensional space structure is used alone as the anode material of lithium-ion batteries or sodium-ion batteries, there are problems such as low discharge capacity and Coulombic efficiency, and fast capacity decay. However, using graphene with a two-dimensional spatial structure as the coating layer of the negative electrode material or positive electrode material of lithium-ion batteries 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, because two-dimensional graphene is easy to agglomerate and agglomerate, there are still disadvantages such as not easy to store and use. In addition, due to the small ion transport channel of two-dimensional graphene, two-dimensional graphene is not suitable as the negative electrode material of sodium ion battery or the coating layer of positive and negative electrode materials. Currently, constructing graphene with a three-dimensional (3D) structure has been proven to be a strategy that can effectively provide a self-supporting structure, prevent the aggregation of graphene nanosheets, and improve the energy storage performance of graphene-based materials. The unique 3D structure Provides a channel that can satisfy sodium ion transport (Li Y Y, Li Z S, etc., Adv.Mater., 2013, 25(17): 2474–2480; Luo R, Ma Y T, etc., 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 complex valence states, in which nickel ions occupy the octahedral sites in the spinel structure, while cobalt ions occupy the tetrahedral sites. In the electrochemical reaction of solid NiCo ₂ O ₄ , there are two redox pairs of Ni ^{3 +} /Ni ²⁺ and Co ³⁺ /Co ²⁺ , which can provide two active centers for pseudocapacitance. Compared with the single-component metal oxides Co ₃ O ₄ and NiO, the binary metal oxide NiCo ₂ O ₄ has higher electrical conductivity, mechanical stability, theoretical capacity, and lower cost. In order to improve the electrochemical performance of _NiCo2O4 , many efforts have been made, including surface modification of _NiCo2O4 , nanonization, and mixing _with various carbons to form composite materials (Wu _Hongying , Wang Huanwen, Acta Physicochemical Sinica, 2013, 29(7), 1501–1506). Using nickel nitrate hexahydrate, cobalt nitrate hexahydrate, NH ₄ F, urea and activated carbon fiber cloth as raw materials, nickel cobaltate nanoflowers were successfully grown on the activated carbon fiber support by hydrothermal method and subsequent heat treatment. (Fu F, Li JD, Yao YZ, et al., ACS Appl. Mater. Interf., 2017, 9:16194–16201) synthesized one-dimensional porous NiCo ₂ O ₄ microrods by solvothermal method at a current of 100 mA g ^-1 When the microrod material is used as the negative electrode material of lithium ion, the discharge capacity after 50 cycles is about 1000mA hg ^-1 ; when used as the negative electrode material of sodium ion battery, the initial charge capacity is 431.1mAh g ^-1 . (Li Fangfang, Wang Hongbin, Wang Runwei, et al., Chemical Journal of Chinese Universities, 2017, 38(11):1913–1920) synthesized rod-like NiCo ₂ O ₄ @C composites by a one-step hydrothermal method at a current density of 100mA g ^-1 , the discharge capacity of NiCo ₂ O ₄ @C composite as the anode material of Li-ion battery for the first time and after 5 cycles are 767.2mA hg ^-1 and 650.1mA hg ^-1 , respectively. (Zhang Mingmei, Li Yuan, Xie Jimin etc., Chinese patent CN _106169384 A discloses a kind of preparation method of three-dimensional mesoporous _NiCo2O4 /nitrogen-doped graphene composite electrode material, with graphene oxide as carbon source, acetonitrile as solvent , first treat graphene oxide by hydrothermal method, then mix the obtained graphene with nickel nitrate hexahydrate, cobalt nitrate hexahydrate, and hexamethylenetetramine for hydrothermal reaction, and finally prepare the obtained precursor in an air atmosphere The 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 natural stone is treated with Hummers method Graphene oxide obtained from graphene is used as carbon source, nickel chloride and cobalt chloride are used as nickel source and cobalt source respectively, urea is used as precipitant, the precursor is synthesized by microwave heating method, and then the precursor is calcined in air atmosphere to obtain porous Sheet-like NiCo ₂ O ₄ /graphene supercapacitor material.

Contents of the invention

The object of the present invention is to provide a kind of preparation method that is simple to operate ^and prepare sea urchin-like NiCo ₂ O ₄ / three-dimensional structure graphene microsphere composite material with mesoporous structure. and sodium ion battery negative electrode materials, the first discharge specific capacity is 1403mA hg ^-1 and 818.4mA hg ^-1 respectively, the material has good rate performance and cycle stability.

The present invention achieves the above object through the following technical scheme: a method for preparing a mesoporous sea urchin-like NiCo ₂ O ₄ /three-dimensional structure graphene microsphere composite material, comprising the following steps:

(1) Place the three-dimensionally constructed graphene powder in a polytetrafluoroethylene-lined hydrothermal kettle, add 68wt% nitric acid, and heat the hydrothermal kettle at a constant temperature. After the reaction, the hydrothermal kettle is naturally cooled to room temperature, and the Collect the precipitate to obtain hydrophilic three-dimensional graphene powder. When preparing hydrophilic three-dimensional graphene powder, the ratio of three-dimensional graphene to nitric acid is 1g: 25-70mL, and the reaction temperature is 80-160°C. The reaction time is 10-36 hours, and the temperature for drying the three-dimensional structure graphene powder is 50-90°C;

(2) The hydrophilic three-dimensional structure graphene powder that step (1) obtains is dispersed in deionized water by ultrasonic waves, obtains the uniformly dispersed hydrophilic three-dimensional structure graphene solution A, and the hydrophilic three-dimensional structure graphene The dosage ratio of powder and deionized water is 0.1g: 20-50mL, and the ultrasonic time is 5-40min;

(3) Dissolve cobalt nitrate hexahydrate, nickel nitrate hexahydrate, urea and polyethylene glycol-400 with deionized water to obtain solution B. When preparing mixed solution B, nickel nitrate hexahydrate and cobalt nitrate hexahydrate 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) Mix solution A and solution B to obtain solution C. When preparing mixed solution C, the amount ratio of hydrophilic three-dimensional structure graphene and NiCo ₂ O ₄ is 0.1g:0.3～1.2g;

(5) Move solution C into a polytetrafluoroethylene-lined hydrothermal kettle, carry out constant temperature thermal reaction, obtain three-dimensional structure graphene-coated nickel cobaltate precursor D after filtration and washing, and prepare three-dimensional structure graphene-coated For nickel cobaltate precursor D, the temperature of the constant temperature reaction is 85°C-160°C, and the reaction time is 4-20h;

(6) Precursor D is calcined in a muffle furnace at a 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) Place the three-dimensionally constructed graphene powder in a polytetrafluoroethylene-lined hydrothermal kettle, add 68wt% nitric acid, and heat the hydrothermal kettle at a constant temperature. After the reaction, the hydrothermal kettle is naturally cooled to room temperature, and the Collect the precipitate to obtain hydrophilic three-dimensional graphene powder. When preparing hydrophilic three-dimensional graphene powder, the ratio of three-dimensional graphene to nitric acid is 1g:40mL, the reaction temperature is 120°C, and the reaction time is 24h , the temperature of drying the three-dimensional structured graphene powder is 60°C;

(2) The hydrophilic three-dimensional structure graphene powder that step (1) obtains is dispersed in deionized water by ultrasonic waves, obtains the uniformly dispersed hydrophilic three-dimensional structure graphene solution A, and the hydrophilic three-dimensional structure graphene The dosage ratio of powder and deionized water is 0.1g: 30mL, and the ultrasonic time is 30min;

(3) Dissolve cobalt nitrate hexahydrate, nickel nitrate hexahydrate, urea and polyethylene glycol-400 with deionized water to obtain solution B. When preparing mixed solution B, nickel nitrate hexahydrate and cobalt nitrate hexahydrate used , The dosage ratio of urea and polyethylene glycol-400 is 0.003mol: 0.006mol: 0.036mol: 2ml;

(4) Solution A and solution B are mixed to obtain solution C. When preparing mixed solution C, the amount ratio of hydrophilic stereostructured graphene and NiCo ₂ O ₄ is 0.1g:0.72g;

(5) Move solution C into a polytetrafluoroethylene-lined hydrothermal kettle, carry out constant temperature thermal reaction, obtain three-dimensional structure graphene-coated nickel cobaltate precursor D after filtration and washing, and prepare three-dimensional structure graphene-coated For nickel cobaltate precursor D, the temperature of the constant temperature reaction is 95°C, and the reaction time is 8h;

(6) Precursor D was calcined in a muffle furnace at a 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 composite in lithium ion battery anode materials.

The application of the prepared mesoporous NiCo ₂ O ₄ /stereostructured graphene microsphere composite in the anode material of sodium ion battery.

Using X-ray diffractometer (XRD), scanning electron microscope (SEM), thermogravimetric analyzer (TG), nitrogen adsorption-desorption analyzer, X-ray photoelectron spectrometer (XPS) to characterize materials, through electrochemical workstation and battery The test system tests the electrochemical performance of the material as a negative electrode material for lithium/sodium batteries.

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

The mesoporous sea urchin-like NiCo ₂ O ₄ / three-dimensional structure graphene microsphere composite electrode material prepared by the present invention has controllable microsphere size, controllable size of the nanorods forming the sea urchin-like microsphere, and the diameter of the sea urchin-like microsphere is Between 1.9 and 4.5 μm, the diameter of the nanorods that make up the sea urchin-like microspheres is about 60nm, and the pore diameter and specific surface area of the material are 4.45nm and 138.81m ² g ^-1 , respectively. When the prepared material is used as the anode material of lithium ion battery and sodium ion battery, the first discharge specific capacity is as high as 1403mA hg ^-1 and 818.4mA hg ^-1 at the current density of 100mA g ^-1 respectively. In addition, the material exhibits good rate capability 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 structured graphene.

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

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

Fig. 4 is a nitrogen adsorption-desorption curve of mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene.

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

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

Detailed ways

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

Example 1

Preparation of hydrophilic stereostructured graphene. Put 1g of stereostructured graphene into 80mL polytetrafluoroethylene-lined hydrothermal reaction kettle, add 40mL of nitric acid with a concentration of 68wt%, and react at 120°C for 24h. After the reaction was finished, 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 absolute ethanol for 6 times, and then dried in a vacuum oven at 60°C for 5 hours to obtain a hydrophilic Unique three-dimensional structure of graphene powder. The product was analyzed by SEM, which confirmed that its structure was a three-dimensional structure; by XPS analysis, 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 that had not been treated with 68wt% nitric acid The previous three-dimensional structure of graphene has been significantly improved. It shows that the prepared product is a hydrophilic stereostructured graphene. As shown in Figure 1 and Figure 2.

Example 2

Preparation of sea urchin-like NiCo ₂ O ₄ with mesoporous structure. 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 three times alternately with deionized water and absolute ethanol. The precipitate was dried in a vacuum oven at 60° C. for 4 hours to obtain a NiCo ₂ O ₄ precursor. The NiCo ₂ O ₄ precursor was calcined in air at a temperature of 300°C for 2 hours at a heating rate of 2 min ^-1 to obtain mesoporous sea urchin-like NiCo ₂ O ₄ . The pore diameter and specific surface area of sea urchin-like NiCo ₂ O ₄ were respectively 3.98nm and 125.71m ² g ^–1 . The prepared mesoporous sea urchin-like NiCo ₂ O ₄ was used as the anode material for lithium-ion batteries. At a current density of 0.1A g ^-1 , the first discharge capacity and the 50th cycle discharge capacity were 1409.6mA hg ^-1 and 610.7mA, respectively. hg ^–1 , as shown in a in Figure 5. The prepared mesoporous sea urchin-like NiCo ₂ O ₄ was used as the anode material for sodium-ion batteries. At a current density of 0.1A g ^-1 , the first discharge capacity and the 50th cycle discharge capacity were 638mA hg ^-1 and 214.6mA hg, respectively. ^–1 , as shown in a in Figure 6.

Example 3

Preparation of 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 three-dimensional graphene, 2mL of polyethylene glycol-400 ultrasonically dispersed in 60mL to 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 precipitate was dried in a vacuum oven at 60° C. for 4 hours to obtain a precursor of NiCo ₂ O ₄ /stereostructured graphene. The precursor of NiCo ₂ O ₄ /stereostructured graphene was calcined in an air atmosphere at a temperature of 300°C for 2 hours at a heating rate of 2min ^-1 to obtain mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene microspheres , _as shown in Figure 2 and Figure 3, the pore diameter and specific surface area of the composite material are 4.45nm and 138.81m ² g ^–1 , respectively, as shown in Figure ₄ , the pore diameter and specific surface area of the composite material are both larger Samples have improved. The prepared mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured 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 1403mA hg ^-1 and 1027mA hg ^-1 , as shown in b in Fig. 5 . The prepared mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene was used as the anode material for sodium ion batteries. At a current density of 0.1A g ^-1 , the first discharge capacity and the 50th cycle discharge capacity were 819mA hg ^{- 1} and 314mAh g ^–1 , as shown in b in Fig. 6. It shows that the lithium/sodium storage performance of NiCo ₂ O ₄ /stereostructured graphene composite obtained after _{NiCo 2} O ₄ is coated with stereostructured graphene is significantly higher 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.

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 three-dimensional graphene, 3mL of polyethylene glycol-400 ultrasonic dispersion in 60 mL 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 precipitate was dried in a vacuum oven at 60° C. for 4 hours to obtain a precursor of NiCo ₂ O ₄ /stereostructured graphene. The precursor of NiCo ₂ O ₄ /stereostructured graphene was calcined in air atmosphere at a temperature of 300 ℃ with a heating rate of 2min ^-1 for 2h to obtain mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene microspheres , the pore diameter and specific surface area of the composite material are 4.40nm and 129.03m ² g ^-1 , respectively, and the pore diameter and specific surface area of the composite material are slightly smaller than those obtained under the technical conditions of Example 3. The prepared mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured 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 1370 mA hg ^-1 and 1001 mA hg ^-1 . The prepared mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene was used as the anode material for sodium-ion batteries. At a current density of 0.1A g ^-1 , the first discharge capacity and the 50th cycle discharge capacity were 810mA hg ^{- 1} and 310mA hg ^–1 . It shows that the lithium/sodium storage performance of the obtained NiCo ₂ O ₄ /stereostructured graphene composite is lower than that of the sample obtained in Example 3.

Example 5

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

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 three-dimensional graphene, 6mL of polyethylene glycol-400 ultrasonically dispersed in 60 mL 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 precipitate was dried in a vacuum oven at 60° C. for 4 hours to obtain a precursor of NiCo ₂ O ₄ /stereostructured graphene. The precursor of NiCo ₂ O ₄ /stereostructured graphene was calcined in air atmosphere at a temperature of 300 ℃ with a heating rate of 2min ^-1 for 2h to obtain mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene microspheres , the pore diameter and specific surface area of the composite material are 4.25nm and 126.7m ² g ^–1 , respectively, and the pore diameter and specific surface area of the composite material are 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 /stereostructured 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 1365mA hg ^-1 and 995mA hg ^-1 . The prepared mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene was used as the anode material for sodium ion batteries. At a current density of 0.1A g ^-1 , the first discharge capacity and the 50th cycle discharge capacity were 800mA hg ^{- 1} and 300.4mA hg ^–1 . It shows that the NiCo ₂ O ₄ /stereo-structured graphene composite lithium/sodium storage performance obtained after NiCo ₂ O ₄ is coated with three-dimensional structure graphene surface is significantly improved than that of single NiCo ₂ O ₄ , but less than that of Example 3 and the implementation Sample from Example 4.

Example 6

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 three-dimensional graphene, and 2mL of polyethylene glycol-400 ultrasonically dispersed in 60 mL 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 precipitate was dried in a vacuum oven at 60° C. for 4 hours to obtain a 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, and the mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene microstructure was obtained. Ball, the pore diameter and specific surface area of the composite material are 3.80nm and 110.6m ² g ^-1 , respectively, and the pore diameter and specific surface area of the composite material are smaller than those of Examples 2-5. The prepared mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene microspheres were used as anode materials for lithium-ion batteries. At a current density of 0.1Ag ^-1 , the first discharge capacity and the 50th cycle discharge capacity were 1350mA hg ^-1 and 990mA hg ^–1 . The prepared mesoporous sea urchin-like NiCo ₂ O ₄ /stereostructured graphene was used as the anode material for sodium ion batteries. At a current density of 0.1A g ^-1 , the first discharge capacity and the 50th cycle discharge capacity were 798mA hg ^{- 1} and 285mA hg ^–1 . It shows 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 3-5.

Example 7

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 of deionized in the 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 precipitate was dried in a vacuum oven at 60° C. for 4 hours to obtain a precursor of NiCo ₂ O ₄ /stereostructured graphene. The precursor of NiCo ₂ O ₄ /stereostructured graphene was calcined in air at 330°C for 1 hour at a heating rate of 2min ^-1 to obtain mesoporous sea urchin-like NiCo ₂ O ₄ /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. At a current density of 0.5A g ^-1 , the first discharge capacity and the 10th cycle discharge capacity were 1300mA hg ^-1 and 900mA hg ^-1 . When this material is used as the anode material of Na-ion battery, the first discharge capacity and the 10th cycle discharge ^capacity are 645mAh g ^-1 and 450mA hg ^-1 respectively at a current density of 0.5A g -1 .

Example 8

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 three-dimensional graphene, and 2mL of polyethylene glycol-400 ultrasonically dispersed in 60 mL 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 precipitate was dried in a vacuum oven at 60° C. for 4 hours to obtain a precursor of NiCo ₂ O ₄ /hydrophilic stereostructured graphene. The precursor of NiCo ₂ O ₄ /hydrophilic stereostructured graphene was calcined in air at 335°C for 1 h at a heating rate of 2 min ^-1 to obtain mesoporous sea urchin-like NiCo ₂ O ₄ /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. At a current density of 1A g ^-1 , the first discharge capacity and the 200th cycle discharge capacity were 1308mA hg, respectively. ^-1 and 500mA hg ^–1 . When this material is used as the anode material of Na-ion battery, the first discharge ^capacity and the 10th cycle discharge capacity are 638mA hg ^-1 and 372mA hg ^-1 respectively at a current density of 1A g -1 .

Table 1 Lithium/sodium storage properties of products prepared under different experimental control technical conditions

From the lithium/sodium storage properties of the products prepared under different experimental control technical 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 were much higher than those prepared without adding stereostructured graphene. Graphene-based sea urchin-like _NiCo2O4 microspheres exhibit higher discharge capacity and cycle _stability . This is because the three-dimensional 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 graphene can also relieve the NiCo ₂ O ₄ during the charge/discharge process. volume change in . In addition, in order to obtain NiCo ₂ O ₄ /stereostructured 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 structure ₂ O ₄ The 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 68wt% 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 1g: 25-70 mL of graphene powder, the reaction temperature is 80-160 ℃, the reaction time is 10-36 h, and the temperature for drying the three-dimensional structure graphene powder is 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 0.1g: 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 to 4ml;

(4) Mixing the solution A and the solution B to obtain a solution C, and preparing the mixed solution C by using hydrophilic three-dimensional construction graphene and NiCo ₂ O ₄ The dosage ratio of the components is 0.1g: 0.3E1.2g；

(5) Transferring the solution C into a hydrothermal kettle lined with polytetrafluoroethylene for 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 NiCo ₂ O ₄ A three-dimensional structure graphene microsphere compound.

2. The mesoporous NiCo of claim 1 ₂ O ₄ The preparation method of the three-dimensional structure graphene microsphere compound is characterized in that the hydrothermal reaction temperature/time is 95-110 ℃/8-4 h.

3. The mesoporous NiCo of claim 1 ₂ O ₄ The 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 1 ₂ O ₄ The 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 68wt% 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 1g:40mL, the reaction temperature is 120 ℃, the reaction time is 24 hours, and the temperature for drying and stereostructuring the 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 use amount ratio of the hydrophilic three-dimensional structure graphene powder to the deionized water is 0.1g:30mL, and the ultrasonic time is 30min;

(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 0.003mol:0.006mol:0.036mol:2ml;

(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 NiCo ₂ O ₄ The dosage ratio of the components is 0.1g:0.72g;

(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) Calcining the precursor D in a muffle furnace at the calcining temperature of 300 ℃ for 2 hours to obtain the mesoporous NiCo ₂ O ₄ A three-dimensional structure graphene microsphere compound.

5. The mesoporous NiCo prepared in claim 1 ₂ O ₄ Application of the three-dimensional structure graphene microsphere compound in a lithium ion battery cathode material.

6. The mesoporous NiCo prepared in claim 1 ₂ O ₄ Application of the three-dimensional structure graphene microsphere compound in a sodium ion battery cathode material.

Images