Sulfur-doped interconnected hollow porous composite carbon nano-microsphere, preparation method and application of sulfur-doped interconnected hollow porous composite carbon nano-microsphere

Abstract

The invention relates to the technical field of energy storage, in particular to a sulfur-doped interconnected hollow porous composite carbon nano-microsphere, a preparation method and application of the sulfur-doped interconnected hollow porous composite carbon nano-microsphere. According to the invention, resorcinol-formaldehyde resin and coal pitch are used as carbon sources, and sublimed sulfur is used as a sulfur source; the preparation method comprises the following steps: uniformly mixing resorcinol-formaldehyde resin, coal pitch and sublimed sulfur, putting the mixture into a carbonization furnace, and heating in an argon atmosphere to prepare the sulfur-doped interconnected hollow porous composite carbon nano-microspheres. The specific surface area of the hollow porous composite carbon nanospheres is 230-390 m < 2 > / g; the total pore volume is between 0.16 cm < 3 > / g and 0.38 cm < 3 > / g; as a negative electrode material of a potassium ion battery, in a 1.0 M potassium bis (fluorosulfonyl) imide (KFSI) electrolyte, when the current density is 0.1 C, the specific capacity reaches 394.6 mAh / g; and when the current density is 5C, the capacity is kept at 200.6 mAh / g after circulation is carried out for 1 to 500 times. When the current density is increased to 20C, the specific capacity can reach 140.4 mAh / g, and high capacity and good rate capability are shown.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage, in particular to a sulfur-doped interconnected hollow porous composite carbon nanomicrosphere, a preparation method and application thereof. BACKGROUND

[0002] With the rapid growth of global demand for renewable energy (such as solar energy, wind energy) and electric vehicles, efficient and low-cost energy storage technology has become a key. As a new energy storage technology, potassium ion batteries are considered as an important supplement or even alternative to lithium ion batteries due to their abundant resources, low cost and excellent electrochemical performance. Potassium is abundant in the earth's crust and widely distributed, and its cost is much lower than that of lithium, which makes potassium ion batteries have significant economic advantages in large-scale energy storage applications. However, the development of potassium ion batteries still faces many challenges, one of which is how to optimize the performance of carbon-based negative electrode materials. Carbon-based materials are an ideal choice for potassium ion battery negative electrode materials due to their good electrical conductivity, structural stability, low cost, and environmental friendliness. However, the larger radius of potassium ions can easily cause structural damage to the material during intercalation / deintercalation, thereby affecting the cycle stability and rate performance of the battery. Therefore, improving the performance of carbon-based negative electrode materials through material design and modification has become a key technology to promote the development of potassium ion battery technology.

[0003] Among carbon-based materials, the study of soft and hard carbon composite materials is particularly important. Soft carbon and hard carbon each have advantages and disadvantages: soft carbon has high electrical conductivity, but its potassium storage capacity is low; hard carbon has high structural stability, but its electrical conductivity is poor. By combining soft carbon and hard carbon, the advantages of both can be combined to make up for the shortcomings of single materials, thereby improving the overall performance of the negative electrode material. Optimizing the structure of soft and hard carbon composite materials can provide more active sites for potassium storage, thereby increasing the specific capacity; at the same time, the stable structure of hard carbon can effectively alleviate the volume expansion problem during potassium ion intercalation / deintercalation, thereby improving the cycle stability. In addition, through interface engineering, the transmission path of potassium ions in the soft and hard carbon composite material can be optimized, reducing the ion diffusion resistance, thereby improving the charge and discharge efficiency and energy density of the battery; at the same time, the interface synergistic effect of the composite material can further enhance the electrochemical performance of the material.

[0004] In view of the above-mentioned defects, the present inventors have finally obtained the present application after a long period of research and practice. SUMMARY

[0005] The present application aims to solve the problems of low capacity, poor rate performance and cycle stability of potassium ion batteries in application, and provides a sulfur-doped interconnected hollow porous composite carbon nanomicrosphere, a preparation method and application thereof.

[0006] In order to achieve the above object, the application discloses a preparation method of sulfur-doped interconnected hollow porous composite carbon nanomicro spheres, which comprises the following steps:

[0007] S1, uniformly mixing anhydrous ethanol, deionized water and ammonia water;

[0008] S2, pouring tetraethyl silicate into the solution obtained in step S1 and stirring for 15 min;

[0009] S3, adding a resorcinol and formaldehyde solution into the solution in step S2 and stirring for 24 h, and then obtaining silica@resorcinol-formaldehyde resin nanospheres through centrifugation, anhydrous ethanol washing and 60 DEG C vacuum drying for 12 h;

[0010] S4, pouring the material obtained in step S3 into a mortar, grinding into powder, and then adding sulfur sublimation and coal tar pitch, uniformly mixing the three to obtain a reactant;

[0011] S5, taking out the product obtained in step S5, grinding, washing with a sodium hydroxide solution, washing with deionized water and filtering, and drying to obtain sulfur-doped interconnected hollow porous composite carbon nanomicro spheres.

[0012] In step S1, the amount of the mixed anhydrous ethanol is 280 mL, the amount of the deionized water is 40 mL, and the amount of the ammonia water is 14 mL.

[0013] In step S2, the amount of the added tetraethyl silicate is 13.84 mL.

[0014] In step S3, the amount of the added resorcinol is 1.6 g, and the amount of the formaldehyde solution is 2.24 mL.

[0015] In step S4, the mass of the sulfur sublimation accounts for 1 / 2 of the total mass of the mixture of the silica@resorcinol-formaldehyde resin, the sulfur sublimation and the coal tar pitch, and the mass ratio of the sulfur sublimation to the coal tar pitch is 5 / 1.

[0016] In step S5, the inert gas is argon, the gas flow rate is 450 mL / min, the temperature is raised to 200 DEG C at a temperature raising rate of 2 DEG C / min, and then raised to 800 DEG C at a temperature raising rate of 5 DEG C / min, and carbonization is carried out for 2 h, and after the reaction is completed, the temperature is naturally lowered to room temperature.

[0017] In step S6, the concentration of the sodium hydroxide solution is 2 mol / L.

[0018] The application further discloses the sulfur-doped interconnected hollow porous composite carbon nanomicro spheres prepared by the above preparation method and application of the sulfur-doped interconnected hollow porous composite carbon nanomicro spheres in a potassium ion battery negative electrode.

[0019] The hollow structure provides more active sites, shortens the diffusion path of ions, the doping of sulfur introduces defects and active sites, and enhances the adsorption capacity of potassium ions. The combination of soft and hard carbon enhances the stability of the composite material, the hard carbon (resorcinol-formaldehyde resin derivative) improves the conductivity of the composite material, and the synergistic effect of the two improves the electrochemical performance of the composite material.

[0020] The beneficial effects of the present application compared with the prior art are:

[0021] 1. The present application provides a preparation method of sulfur-doped interconnected hollow porous composite carbon nanomicrospheres for potassium ion battery negative electrode. Under the in-situ silica template induction, resorcinol and formaldehyde solution can self-assemble on the spherical surface to generate spherical resorcinol-formaldehyde resin nanomicrospheres. By using a simple carbonization strategy, the sulfur-doped interconnected hollow porous composite carbon nanomicrospheres are realized by using resorcinol-formaldehyde resin nanomicrospheres and coal pitch as carbon sources and sublimed sulfur as a sulfur source after calcination. The method is simple, only a few processes such as synthesis, drying and carbonization are involved, and it is easy to mass produce;

[0022] 2. The material obtained by the preparation method has a high sulfur doping amount, a large porosity and a hollow structure, and can realize effective intercalation / adsorption of potassium ions.

[0023] 3. The sulfur-doped interconnected hollow porous composite carbon nanomicrospheres have a regular structure and many active sites, effectively improve the electrochemical performance, and have potential application potential as potassium ion battery negative electrode materials.

[0024] 4. The sulfur-doped interconnected hollow porous composite carbon nanomicrospheres obtained by the present application have a capacity of 394.6 mAh / g at a current density of 0.1C, a capacity of 140.4 mAh / g when the current density is increased to 20C, and a capacity of 200.6 mAh / g after 1,500 cycles at a current density of 5C. The material shows high capacity, excellent cycle performance and rate performance. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The XRD patterns of the materials obtained in Example 1, Example 2, Example 3, Example 4, Comparative Example 1 and Comparative Example 2 are shown in the following table:

[0026] Figure 2 The SEM images of the materials obtained in Examples 1-4 and Comparative Examples 1-2 are shown in the following table: (a) Example 1; (b) Example 2; (c) Example 3; (d) Example 4; (e) Comparative Example 1; (f) Comparative Example 2.

[0027] Figure 3 TEM image of the sulfur-doped interconnected hollow porous composite carbon nanomicrospheres obtained in Example 1;

[0028] Figure 4 Nitrogen adsorption / desorption curve of the material obtained in Example 1;

[0029] Figure 5 Rate performance of the materials obtained in Example 1, Example 2, Example 3, Example 4 applied to the negative electrode of potassium ion battery;

[0030] Figure 6 Cycle performance at 5C of the materials obtained in Example 1, Example 2, Example 3, Example 4 as the negative electrode of potassium ion battery. DETAILED DESCRIPTION

[0031] The above and other technical features and advantages of the present application will be more apparent from the following detailed description of the application, taken in conjunction with the accompanying drawings.

[0032] Example 1

[0033] Sulfur-doped interconnected hollow porous composite carbon nanomicrospheres PCRC 14 The specific preparation process is as follows:

[0034] (1) Synthesis of silica@resorcinol-formaldehyde resin nanospheres: uniformly mix 280 mL of anhydrous ethanol, 40 mL of deionized water and 14 mL of ammonia water; pour 13.84 mL of tetraethyl orthosilicate into the above solution and stir for 15 min; weigh 1.6 g of resorcinol and add it to the above solution, then add 2.24 mL of formaldehyde solution, and stir at room temperature for 24 h; centrifuge the above solution, wash with anhydrous ethanol, and transfer to a blast drying oven at 60℃ for 12 h to collect the reaction product.

[0035] (2) Sulfur-doped interconnected hollow porous composite carbon nanomicrospheres: weigh 0.8 g of silica@resorcinol-formaldehyde resin nanospheres and 0.2 g of coal tar, and uniformly mix them with 1 g of sulfur sublimation; transfer the mixture to a tube furnace, heat to 200℃ at a heating rate of 2℃ / min under an argon atmosphere, then heat to 800℃ at a heating rate of 5℃ / min and keep the temperature constant for 2 h; put the carbonized product into a 2M NaOH solution, heat and stir at 80℃ for 48 h, then wash with a large amount of deionized water until the filtrate is neutral. Dry the washed product in a blast drying oven at 80℃ for 12 h to obtain sulfur-doped interconnected hollow porous composite carbon nanomicrospheres, denoted as PCRC 14 .

[0036] Example 2

[0037] Sulfur-doped interconnected hollow porous composite carbon nanomicrospheres PCRC 23The specific preparation process is as follows:

[0038] (1) Synthesis of silica@resorcinol-formaldehyde resin nanospheres: the same method as step (1) in Example 1 was used.

[0039] (2) Sulfur-doped interconnected hollow porous composite carbon nanospheres: 0.6 g of silica@resorcinol-formaldehyde resin nanospheres and 0.4 g of coal pitch were weighed and uniformly mixed with 1 g of sulfur; the mixture was transferred to a tube furnace and heated to 200°C at a heating rate of 2°C / min under an argon atmosphere, then heated to 800°C at a heating rate of 5°C / min and kept at this temperature for 2 h; the carbonized product was then placed in a 2M NaOH solution and heated and stirred at 80°C for 48 h, and then washed with a large amount of deionized water until the filtrate was neutral. The washed product was transferred to a 80°C air drying oven and dried for 12 h to obtain sulfur-doped interconnected hollow porous composite carbon nanospheres, denoted as PCRC 23 .

[0040] Example 3

[0041] Sulfur-doped interconnected hollow porous composite carbon nanospheres PCRC 32 The specific preparation process is as follows:

[0042] (1) Synthesis of silica@resorcinol-formaldehyde resin nanospheres: the same method as step (1) in Example 1 was used.

[0043] (2) Sulfur-doped interconnected hollow porous composite carbon nanospheres: 0.6 g of silica@resorcinol-formaldehyde resin nanospheres and 0.4 g of coal pitch were weighed and uniformly mixed with 1 g of sulfur; the mixture was transferred to a tube furnace and heated to 200°C at a heating rate of 2°C / min under an argon atmosphere, then heated to 800°C at a heating rate of 5°C / min and kept at this temperature for 2 h; the carbonized product was then placed in a 2M NaOH solution and heated and stirred at 80°C for 48 h, and then washed with a large amount of deionized water until the filtrate was neutral. The washed product was transferred to a 80°C air drying oven and dried for 12 h to obtain sulfur-doped interconnected hollow porous composite carbon nanospheres, denoted as PCRC 32 .

[0044] Example 4

[0045] Sulfur-doped interconnected hollow porous composite carbon nanospheres PCRC 41 The specific preparation process is as follows:

[0046] (1) Synthesis of silica@resorcinol-formaldehyde resin nanospheres: the same method as step (1) in Example 1 was used.

[0047] (2) Sulfur-doped interconnected hollow porous composite carbon nanomicrospheres: 0.2 g of silica@resorcinol-formaldehyde resin nanospheres and 0.8 g of coal pitch were weighed and mixed uniformly with 1 g of sulfur; the mixture was transferred into a tube furnace, heated to 200 °C at a heating rate of 2 °C / min under an argon atmosphere, then heated to 800 °C at a heating rate of 5 °C / min and kept for 2 h, and the carbonized product was put into a 2M NaOH solution and heated and stirred at 80 °C for 48 h, and then washed with a large amount of deionized water until the filtrate was neutral. The washed product was transferred to a 80 °C air drying oven and dried for 12 h to obtain sulfur-doped interconnected hollow porous composite carbon nanomicrospheres, denoted as PCRC. 41 .

[0048] Comparative Example 1

[0049] The specific preparation process of the sulfur-doped hollow porous carbon nanomicrospheres PCR is as follows:

[0050] (1) Synthesis of silica@resorcinol-formaldehyde resin nanospheres: the same method as in step (1) of Example 1 was used.

[0051] (2) Sulfur-doped hollow porous carbon nanomicrospheres: 1 g of silica@resorcinol-formaldehyde resin nanospheres was weighed and mixed uniformly with 1 g of sulfur; the mixture was transferred into a tube furnace, heated to 200 °C at a heating rate of 2 °C / min under an argon atmosphere, then heated to 800 °C at a heating rate of 5 °C / min and kept for 2 h, and the carbonized product was put into a 2M NaOH solution and heated and stirred at 80 °C for 48 h, and then washed with a large amount of deionized water until the filtrate was neutral. The washed product was transferred to a 80 °C air drying oven and dried for 12 h to obtain sulfur-doped hollow porous carbon nanomicrospheres, denoted as PCR.

[0052] Comparative Example 2

[0053] The specific preparation process of the sulfur-doped carbon material PCC is as follows:

[0054] (1) Sulfur-doped carbon material: 1 g of coal pitch was weighed and mixed uniformly with 1 g of sulfur; the mixture was transferred into a tube furnace, heated to 200 °C at a heating rate of 2 °C / min under an argon atmosphere, then heated to 800 °C at a heating rate of 5 °C / min and kept for 2 h, and the carbonized product was put into a 2M NaOH solution and heated and stirred at 80 °C for 48 h, and then washed with a large amount of deionized water until the filtrate was neutral. The washed product was transferred to a 80 °C air drying oven and dried for 12 h to obtain sulfur-doped carbon material, denoted as PCC.

[0055] The XRD spectrum of the prepared material is as shown in Figure 1As shown, the material of Example 1 is a carbon material according to the test results. As can be seen from the SEM images (Fig. 1), Example 1 and Comparative Example 1 present a uniform spherical structure. With the gradual addition of coal pitch, Example 2, Example 3 and Example 4 gradually change from a spherical structure to a honeycomb structure. Comparative Example 2 presents a massive structure with a large particle size. As can be more clearly seen from the TEM images (Fig. 2), Example 1 is a hollow carbon nanomicrosphere with a thin layer of soft carbon on the surface. As can be seen from the N2 adsorption-desorption isotherm (Fig. 3), the material of Example 1 has a typical type II adsorption-desorption curve, indicating that there are no mesopores in the material. Figure 2 Figure 3 Figure 4

[0056] The above examples and comparative examples were assembled into potassium ion batteries to test the electrochemical performance. Figure 5 As can be seen, Example 1 has good rate characteristics, and when the current density is 0.1C, the specific capacity can reach 394.6mAh / g; when the current density is increased to 20C, the specific capacity is 140.4mAh / g.

[0057] Figure 6 As can be seen, the material obtained in Example 1 has excellent cycle stability, and after 1,500 cycles at 5C, the average capacity attenuation of each cycle is less than 0.016%. As can be seen from the charge-discharge curves (Fig. 4), the rate and cycle performance of Example 1 are better than those of Example 2, Example 3 and Example 4. Figure 5 Figure 6

[0058] The synthesis parameters and electrochemical performance of each sample obtained in Examples 1-4 and Comparative Examples 1 and 2 are shown in Table 1 below:

[0059] Table 1 Synthesis parameters and electrochemical performance of each example and comparative example

[0060]

[0061] As can be seen from Table 1, the present application can realize the control of the morphology and structure of the material by controlling the raw material ratio, and ultimately obtain a carbon-based negative electrode material suitable for a potassium ion battery, which exhibits high specific capacity and good cycle stability.

[0062] The above description is merely preferred embodiments of the present application, merely illustrative, but not restrictive. Those skilled in the art understand that many changes, modifications and even equivalents can be made to the present application within the spirit and scope defined by the claims of the present application, but all will fall within the protection scope of the present application.​​​​​

Claims

1. A method for preparing sulfur-doped interconnected hollow porous composite carbon nanomicrospheres, characterized in that, The method comprises the following steps: S1, mixing anhydrous ethanol, deionized water and ammonia water uniformly; S2, pouring tetraethyl silicate into the solution obtained in step S1 and stirring for 15 min; S3, adding resorcinol and formaldehyde solution into the solution in step S2 and stirring for 24 h, then obtaining silica@resorcinol-formaldehyde resin nanospheres by centrifugation, anhydrous ethanol washing and 60℃ vacuum drying box for 12 h; S4, pouring the material obtained in step S3 into a mortar, grinding into powder, then adding sulfur and coal tar, and mixing the three uniformly to obtain a reactant; S5, taking out the product obtained in step S5, grinding, washing with sodium hydroxide solution, washing with deionized water and filtering, and drying to obtain sulfur-doped interconnected hollow porous composite carbon nanospheres.

2. The method for preparing sulfur-doped interconnected hollow porous composite carbon nanospheres as described in claim 1, characterized in that, In the step S1, the amount of mixed anhydrous ethanol is 280 mL, the amount of deionized water is 40 mL, and the amount of ammonia water is 14 mL.

3. The method for preparing sulfur-doped interconnected hollow porous composite carbon nanospheres as described in claim 1, characterized in that, In the step S2, the amount of added tetraethyl silicate is 13.84 mL.

4. The method for preparing sulfur-doped interconnected hollow porous composite carbon nanospheres as described in claim 1, characterized in that, In the step S3, the amount of added resorcinol is 1.6 g, and the amount of formaldehyde solution is 2.24 mL.

5. The method for preparing sulfur-doped interconnected hollow porous composite carbon nanospheres as described in claim 1, characterized in that, In the step S4, the mass of sulfur accounts for 1 / 2 of the total mass of the mixture of silica@resorcinol-formaldehyde resin, sulfur and coal tar, and the mass ratio of sulfur to coal tar is 5 / 1.

6. The method for preparing sulfur-doped interconnected hollow porous composite carbon nanospheres as described in claim 1, characterized in that, In the step S5, the inert gas is argon, the gas flow rate is 450 mL / min, the temperature is raised to 200℃ at a rate of 2℃ / min, then raised to 800℃ at a rate of 5℃ / min, and carbonized for 2 h, after the reaction is completed, the temperature is naturally lowered to room temperature.

7. The method for preparing sulfur-doped interconnected hollow porous composite carbon nanospheres as described in claim 1, characterized in that, In the step S6, the concentration of sodium hydroxide solution is 2 mol / L.

8. A sulfur-doped interconnected hollow porous composite carbon nanosphere prepared by the method of any one of claims 1-7.

9. Use of the sulfur-doped interconnected hollow porous composite carbon nanosphere of claim 8 in a potassium ion battery negative electrode.

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