Method for synthesizing boron-doped wrinkled nanospheres carbon material by in-situ template method and application

Abstract

The application belongs to the field of hybrid ion capacitors and ion batteries, and discloses a method for synthesizing boron-doped wrinkled nanospherical carbon material by an in-situ template method and application of the boron-doped wrinkled nanospherical carbon material. The method is as follows: first, carbon-containing salt and boric acid are mixed in hot deionized water at a molar ratio of carbon element to boron element of 1:5-5:1, and then a solid mixture is obtained by evaporation and drying; then, the solid mixture is calcined under a protective atmosphere, and the calcined product is neutralized with an alkali and washed to obtain the boron-doped wrinkled nanospherical carbon material. The boron-doped wrinkled nanospherical carbon material prepared by the method has a special wrinkled nanospherical morphology and very good electrochemical performance, and is a high-performance boron-doped wrinkled nanospherical carbon material, which can be particularly applied to alkali metal hybrid ion capacitors and alkali metal batteries as a negative active material.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of hybrid ion capacitors and ion batteries, and more particularly relates to a method for synthesizing boron-doped wrinkled nanospherical carbon material by an in-situ template method and application, and boron-doped wrinkled nanospherical carbon material obtained accordingly. By means of boron doping and changing the interlayer spacing of the carbon material, the boron-doped wrinkled nanospherical carbon material can be used as an alkali metal hybrid ion capacitor and an alkali metal battery negative electrode material, and the discharge capacity can be effectively improved. BACKGROUND

[0002] Effective energy storage systems have a huge impact on modern society and are widely used in electric vehicles and electronic devices. At present, the development of hybrid ion capacitors is mainly based on their high energy density and excellent cycle performance. However, due to high cost and uneven distribution, the further development of hybrid ion capacitor energy storage devices is essentially hindered. However, it is generally believed that the low power density and poor cycle stability of non-boron-doped carbon materials hinder the practical application of hybrid ion capacitors. In this case, boron-doped modified carbon materials are one of the most promising material candidates, especially for future large-scale energy storage, which has attracted great attention for large-scale application.

[0003] Recently, the above problems have been significantly alleviated by doping heteroatoms (B) and morphology regulation into carbon-based anodes, aiming to expand the interlayer spacing and promote reversible ion diffusion. For example, morphology-regulated structures alleviate volume expansion and achieve excellent ion storage performance. Boron-doped carbon materials, in which boron doping ensures fast ion diffusion kinetics and excellent rate performance of the anode. The three valence electrons of boron move the Fermi level to the valence band, resulting in a higher carrier concentration and state density of the Fermi level, and together enhancing the supercapacitor performance. In addition, boron heteroatoms have similar atomic radii to carbon, making them easily enter the carbon lattice. Boron-doped carbon as a typical anode has become a research hotspot, although some progress has been made in the field of boron doping so far, but the reported synthesis routes, such as chemical vapor deposition and hydrothermal reaction, are too complex to meet the actual needs. Therefore, the design of an advanced preparation method for boron-doped carbon anodes for practical hybrid ion capacitors is still a daunting challenge. SUMMARY

[0004] In view of the above defects or improvement needs of the prior art, the present application aims to provide a method for synthesizing boron-doped wrinkled nanospheres carbon material by in-situ template method and application, wherein the overall process design of the preparation method is improved, boric acid is used as the boron source and in-situ template for boron doping, the precursor is pretreated by mixing, and the amount of carbon-containing salt and boric acid is controlled to make the molar ratio of carbon element to boron element be 1:5-5:1, and then a calcination reaction is used to generate the boron-doped wrinkled nanospheres carbon material, which has a special wrinkled nanospheres morphology and very good electrochemical performance, and is a high-performance boron-doped wrinkled nanospheres carbon material.

[0005] To achieve the above-mentioned purpose, according to one aspect of the present application, a method for synthesizing boron-doped wrinkled nanospheres carbon material by in-situ template method is provided, characterized in that the method is to use boric acid as the boron source and template, first mix the carbon-containing salt and boric acid in hot deionized water according to the molar ratio of carbon element to boron element being 1:5-5:1, then evaporate and dry to obtain a solid mixture; then, the solid mixture is subjected to calcination treatment under a protective atmosphere, and the calcination product is neutralized with an alkali and washed to obtain the boron-doped wrinkled nanospheres carbon material.

[0006] As a further preferred embodiment of the present application, the temperature of the hot deionized water is not less than 80℃.

[0007] Preferably, the boric acid and carbon-containing salt used in the mixing are matched according to the molar ratio of boron element to carbon element being 1:1-1:3.

[0008] As a further preferred embodiment of the present application, the carbon-containing salt is at least one of citrate, gluconate, tartrate, rhodanic acid salt, benzoate, and ethylenediaminetetraacetate; and preferably at least one of lithium citrate, sodium citrate, and potassium citrate.

[0009] As a further preferred embodiment of the present application, the calcination temperature of the calcination is 500-900℃.

[0010] As a further preferred embodiment of the present application, the protective atmosphere is an inert atmosphere of argon or nitrogen.

[0011] According to another aspect of the present application, the present application provides the boron-doped wrinkled nanospheres carbon material obtained by the above-mentioned method.

[0012] As a further preferred embodiment of the present application, the discharge capacity is 250-450 mAh g -1 ; the interlayer spacing is 0.38-0.42 nm; and the boron content is 0.5wt%-10wt%;

[0013] Preferably, the boron-doped wrinkled nanospheres carbon material is a high-boron-doped wrinkled nanospheres carbon material, with a discharge capacity of 350-450 mAh g -1 ; an interlayer spacing of 0.39-0.42 nm; and a boron content of 5wt%-10wt%.

[0014] According to another aspect of the present application, the present application provides the use of the above-mentioned boron-doped wrinkled nanospheres carbon material as a negative electrode active material in an alkali metal hybrid ion capacitor or an alkali metal battery.

[0015] Compared with the prior art, the method of the present application uses a carbon-containing salt as a carbon source and boric acid as a boron-doped boron source and an in-situ template for wrinkled nanospheres, mixes and pretreats the carbon-containing salt and boric acid by dissolving them in hot deionized water, uses a precursor premixing strategy to achieve ion dispersion, and obtains an ion system liquid precursor with good mixing and dispersion. Since boric acid is used as a boron-doped in-situ template for wrinkled nanospheres, a boron-doped wrinkled nanospheres carbon material with a special wrinkled micro-morphology can be obtained. The commonly used boric acid raw material in industry is generally a white crystalline powder, which is a spherical crystal particle in micro-morphology, has a smooth surface, and does not have a micro-wrinkled morphology. In the synthesis reaction process of the present application, C atoms can enter the template and replace B atoms in-situ, so that the electron-deficient B in the carbon-boron composite material formed in this way can act as an electron acceptor to accept other electrons in alkali metal ions, ultimately leading to an increase in the charge storage properties of the material. In addition, the boron doping also constructs a wrinkled spherical structure (it is speculated that the structure decomposition of boric acid and the volatilization of the organic components in the in-situ doping process of the carbon-containing salt led to the wrinkled structure). Furthermore, the boron-containing functional groups can provide more active sites, so that the material has better electrochemical activity. The comprehensive effects of these aspects make the boron-doped wrinkled nanospheres carbon material obtained by the method of the present application have excellent long cycle performance and good rate performance, and compared with other boron-doped carbon materials in the prior art, the boron-doped wrinkled nanospheres carbon material obtained by the method of the present application will have better performance when applied to an alkali metal hybrid ion capacitor. Of course, the boron-doped wrinkled nanospheres carbon material obtained by the method of the present application can also be used as a negative electrode active material and applied to the field of alkali metal hybrid ion capacitors and batteries.

[0016] In the mixing pretreatment of the preparation method of the present application, the molar ratio of carbon and boron elements of the carbon-containing salt and boric acid needs to be strictly controlled to be 1:5-5:1, because if the ratio deviates from this interval, for example, if the proportion of the carbon-containing salt is too high and the proportion of boric acid is too low, too few templates cannot allow the morphology of the wrinkled nanospheres to be successfully synthesized; for another example, if the proportion of boric acid is too high and the proportion of the carbon-containing salt is too low, too few carbon-containing precursors cause the boron element doping amount to be saturated, and the boric acid template is wasted in large quantities.

[0017] There is no better unified method in the prior art for the selection of synthesis method, the selection of boron source and the microstructure regulation of composite material; for example, although the prior art has used boric acid as a reaction participant, most of these synthesis methods obtain nanosheet products or amorphous porous carbon. The present application uses boric acid as a template and a boron source to achieve boron doping while obtaining a micro-creased spherical structure and realizing the directional regulation of the morphology. The present application has two outstanding advantages: one is that it can obtain a product with a micro-creased spherical structure, and the other is that it can further improve the capacity in cooperation with boron doping (especially high boron doping with a boron content of greater than or equal to 5wt%).

[0018] The boron-doped creased nanospherical carbon material obtained by the method of the present application has a creased spherical structure that improves the conductivity of the material. Moreover, the boron-doped carbon material is obtained by reacting carbon atoms with the boric acid template to incorporate boron atoms into the carbon skeleton, which changes the structure of carbon, expands the interlayer spacing, improves the discharge capacity and can improve the capacitor capacity characteristics. Since boron is a covalent heteroatom, it can release high-activity boron atoms in the form of covalence, which can improve the storage capacity of alkali metal hybrid ion capacitors by enhancing the alkali metal ion adsorption capacity and electronic conductivity. Moreover, the method of the present application can especially obtain a high-boron-doped product with a boron content of greater than or equal to 5wt%, which further improves the specific discharge capacity.

[0019] Among numerous carbon materials, the modification of the creased spherical material structure is very conducive to the transmission of alkali metal ions. The creased spherical material has a large surface area and high atomic utilization, which is more suitable for the infiltration of alkali metal ion electrolyte. The creased spherical material can act as an ion transmission channel to further transmit alkali metal ions.

[0020] The introduction of boron doping in the present application expands the carbon interlayer spacing and acts as an active site, which greatly improves the performance of hybrid ion capacitors. When used as the negative electrode of an alkali metal hybrid ion capacitor, the present application exhibits very good electrochemical performance and can achieve very high discharge capacity.

[0021] The method of the present application can especially synthesize high-boron-doped creased nanospherical carbon material with a boron doping amount of greater than or equal to 5wt%. The electronegativity of boron atoms is relatively low, and it is difficult for boron atoms to be doped into the carbon skeleton in general preparation methods. Moreover, because the atomic radius of boron atoms is smaller than that of carbon atoms, it is difficult for boron atoms to change the interlayer spacing of carbon materials, so it is difficult to synthesize high-boron-doped carbon materials. The method of the present application overcomes the difficulty in synthesizing high-boron-doped carbon materials. The method of the present application uses boric acid as a template to simultaneously regulate the morphology and doping, which can achieve a very high boron doping ratio of up to 10wt%.

[0022] Boric acid is slightly soluble in water at room temperature and normal pressure, so the mixing of two precursors by using the conventional solution co-mixing method usually does not have the mixing effect. However, by using hot deionized water (for example, the deionized water can be heated by using an oil bath method or other hot field heating method), the boric acid slightly soluble in water at room temperature and the organic salt are successfully dissolved into the deionized water, and then the water is evaporated, and the precipitated precursor is the successfully mixed precursor, the mixing is more sufficient, the ion dispersion can be realized, and the mixing and dispersion are good.

[0023] In summary, the application can achieve the following beneficial effects:

[0024] 1. The synthesis method of the application uses carbon-containing salt and boric acid as raw materials, which are widely available, have strong adaptability, good compatibility, and high economic value.

[0025] 2. The ion environment premixing method is used to construct the high-boron-doped wrinkled nanospherical carbon material, the original boron-containing characteristics of the template are not damaged, and the high-boron-doped wrinkled nanospherical carbon material can improve the electrochemical performance.

[0026] 3. The in-situ template method is used to ensure the intrinsic advantages of boron doping during the preparation of the wrinkled nanospherical carbon material, and the structure of the constructed wrinkled nanospherical carbon material can improve the conductivity.

[0027] 4. The process of the application is simple, short in cycle, and low in cost, and meets the requirements of industrial production.

[0028] 5. The accurate selection of the precursors can significantly improve the rate performance and conductivity of the boron-doped wrinkled nanospherical carbon material, and can also adjust the interlayer spacing of the wrinkled nanospherical carbon material to increase the negative electrode capacity of the alkali metal hybrid ion capacitor.

[0029] 6. The method of the application uses the in-situ boron-doped template method to control the boron doping of the wrinkled nanospherical carbon, which is suitable for various heteroatom doping including boron element, and the corresponding wrinkled nanospherical carbon negative electrode material can meet the various actual needs of the alkali metal hybrid ion capacitor electrode.

[0030] The preparation method of the application is simple, the raw materials are cheap and abundant, and the in-situ reaction of one-step synthesis has the characteristics of rapidness and high efficiency. The boron-doped wrinkled nanospherical carbon material obtained by the method is an excellent negative electrode material for alkali metal hybrid ion capacitors, which can promote the practical application of alkali metal hybrid ion capacitors to a certain extent, is easy to expand production, has actual application advantages, and is worth popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1The image shows a scanning electron microscope (SEM) image of the morphology of boron-doped wrinkled carbon nanospheres provided in Example 1 of this invention.

[0032] Figure 2 Transmission electron microscope (TEM) image of the boron-doped wrinkled carbon nanosphere morphology provided in Example 1 of the present invention (the scale bar in the image represents 500 nm).

[0033] Figure 3 This is a scanning electron microscope image of the morphology of the undoped and unstructured carbon material provided in Comparative Example 1 of the present invention.

[0034] Figure 4 This is a scanning electron microscope image of the morphology of boron-doped wrinkled carbon nanospheres provided in Example 2 of the present invention.

[0035] Figure 5 This is a scanning electron microscope image of the morphology of boron-doped wrinkled carbon nanospheres provided in Example 3 of the present invention.

[0036] Figure 6 This is a scanning electron microscope image of the morphology of boron-doped wrinkled carbon nanospheres provided in Example 6 of the present invention.

[0037] Figure 7 The boron X-ray photoelectron spectroscopy of boron-doped wrinkled carbon nanospheres provided in Example 1 of the present invention.

[0038] Figure 8 The charge-discharge curves of boron-doped wrinkled carbon nanospheres provided in Example 1 of this invention are used as negative electrode materials for ion capacitors.

[0039] Figure 9 The materials provided in Embodiment 1 and Comparative Embodiment 1 of this invention are used for the rate performance of the negative electrode material of a potassium-ion hybrid capacitor.

[0040] Figure 10 The materials provided in Embodiment 1 and Comparative Embodiment 1 of this invention are used for the cycling performance of the negative electrode material of a potassium ion hybrid capacitor.

[0041] Figure 11 The materials provided in Examples 1-3 of this invention are used for the cycling performance of the negative electrode material of potassium ion hybrid capacitors.

[0042] Figure 12 The materials provided in Examples 1-3 and Comparative Example 1 of this invention are used for the conductivity of the negative electrode material of a potassium ion hybrid capacitor. Detailed Implementation

[0043] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0044] The synthesis method of the boron-doped wrinkled nanospherical carbon material of the present application can include the following steps during actual synthesis:

[0045] (1) Put the carbon-containing salt and boric acid into hot deionized water (the temperature may be, for example, not lower than 80°C) to mix, and mix the two components according to the ionic system (the temperature of the hot deionized water used in the examples below is all 80°C);

[0046] (2) Then put the solution mixed with the two components into an oil bath pot to evaporate dry, and the boric acid acts as an in-situ template for boron doping and wrinkled nanospheres;

[0047] (3) After evaporation is completed, the material precursor obtained thereafter is then put into a tube furnace to calcine, and the boron-doped wrinkled nanospherical carbon material is obtained.

[0048] The following are specific examples:

[0049] Example 1

[0050] In-situ boron-doped template method for preparing carbon-containing potassium salt / boric acid system to control wrinkled nanocarbon spheres:

[0051] (1) Ionic system and mixing: 0.612g of potassium citrate and 0.061g of boric acid (at this time, the molar ratio is C:B=2:1) are added to a beaker containing 60ml of hot deionized water, and stirred until the two materials are fully dissolved and mixed to form a clear solution.

[0052] (2) Template combination: The beaker is placed in an oil bath constant temperature stirrer, set to 80°C constant temperature heating, and the stirring speed is 200rpm. After 12h, the solid after stirring is taken out and placed in a quartz boat.

[0053] (3) Calcination: The material is calcined at high temperature under argon atmosphere, heated to 700°C, and kept for 3 hours. Then the boron-doped carbonized product is neutralized with KOH and repeatedly washed with deionized water to obtain the product.

[0054] (4) Electrode performance test: The boron-doped template method for preparing wrinkled nanocarbon spheres of Example 1 is applied to a potassium ion hybrid capacitor negative electrode, as follows:

[0055] The boron-doped template method obtained in Example 1 was used to prepare the wrinkled nanocarbon balls as negative active materials. Polyvinylidene fluoride (PVDF), conductive carbon black were mixed in a mass ratio of 8:1:1, and a proper amount of NMP was added to prepare a slurry, which was then coated on a copper foil with a diameter of 13 mm. After the solvent was evaporated, the coated copper foil was dried in a vacuum drying oven at 120°C for 10 h. Then, the prepared active material-coated copper foil was used as the working electrode, and an organic electrolyte (0.8 M KPF6 in EC / DEC 1:1) was used to assemble a coin-type potassium ion hybrid capacitor for charge and discharge tests, with a voltage range of 0.005-3 V.

[0056] The high-boron-doped wrinkled nanocarbon balls prepared in step (3) of Example 1 were characterized by scanning electron microscopy and transmission electron microscopy, and the results are shown in Figure 1 and Figure 2 As can be seen from the above, the morphology of the material shows the unique characteristics of wrinkled nanoballs.

[0057] X-ray photoelectron spectroscopy is shown in Figure 7 As can be seen from the above, the boron-doped wrinkled nanocarbon balls prepared in step (3) of Example 1 successfully achieved boron doping.

[0058] The charge and discharge curve is shown in Figure 8 As can be seen from the above, the high-boron-doped wrinkled nanocarbon balls prepared in step (3) of Example 1 have good potassium storage performance in the potassium ion hybrid capacitor device.

[0059] The rate performance is shown in Figure 9 As can be seen from the above, the high-boron-doped wrinkled nanocarbon balls prepared in step (3) of Example 1 have good rate performance in the potassium ion hybrid capacitor device compared with the material without boron doping (i.e., the product obtained in Comparative Example 1 hereinafter).

[0060] The cycle performance is shown in Figure 10 As can be seen from the above, the high-boron-doped wrinkled nanocarbon balls prepared in step (3) of Example 1 have good cycle performance in the potassium ion hybrid capacitor device compared with the material without boron doping (i.e., the product obtained in Comparative Example 1 hereinafter).

[0061] The conductive performance is shown in Figure 12 As can be seen from the above, the high-boron-doped wrinkled nanocarbon balls prepared in step (3) of Example 1 have good conductivity in the potassium ion hybrid capacitor device compared with the material without boron doping (i.e., the product obtained in Comparative Example 1 hereinafter).

[0062] Example 2

[0063] In-situ boron-doped template method for preparing wrinkled nanocarbon balls using carbon-containing potassium salt / boric acid system:

[0064] (1) Ion system and mixing: 0.153 g of potassium citrate and 0.061 g of boric acid (at this time, the molar ratio is C:B = 1:2) are added to a beaker containing 60 ml of hot deionized water, and the two materials are stirred until they are fully dissolved and mixed to form a clear solution.

[0065] (2) Template combination: The beaker is placed in an oil bath constant temperature heater stirrer, set to 80°C constant temperature heating, and the stirring speed is 200 rpm. After 12 h, the stirred solid is removed and placed in a quartz boat.

[0066] (3) Calcination: The material is calcined at high temperature under an argon atmosphere, heated to 700°C, and held for 3 hours. Then the boron-doped carbonized product is neutralized with KOH and repeatedly filtered with deionized water to obtain the product.

[0067] (4) Electrode performance test: The boron-doped template method prepared in Example 2 is used to control the folding nanocarbon balls as the negative electrode of the potassium ion hybrid capacitor, as follows:

[0068] The boron-doped template method prepared in Example 2 is used to control the folding nanocarbon balls as the negative electrode active material, and polyvinylidene fluoride (PVDF) and conductive carbon black are mixed in a mass ratio of 8:1:1, and an appropriate amount of NMP is added to form a slurry, and coated on a copper foil with a diameter of 13 mm, and then placed in a vacuum drying oven at 120°C for 10 h after the solvent is evaporated. The copper foil coated with the active material is used as the working electrode, and an organic electrolyte (0.8 M KPF6 in EC / DEC 1:1) is used to assemble a coin-type potassium ion hybrid capacitor for charge and discharge testing, with a voltage range of 0.005-3 V.

[0069] The boron-doped folding nanocarbon balls prepared in step (3) of Example 2 are characterized by scanning electron microscopy, and the results are shown in Figure 4 The content of boric acid has a very obvious effect on the control of the morphology of the material, and when the content of boric acid increases, the folding nanoballs further agglomerate unevenly, causing the material structure to crack.

[0070] Example 3

[0071] Carbon-containing potassium salt / boric acid system for preparing in-situ boron-doped template-controlled folding nanocarbon balls:

[0072] (1) Ion system and mixing: 0.918 g of potassium citrate and 0.061 g of boric acid (at this time, the molar ratio is C:B = 3:1) are added to a beaker containing 60 ml of hot deionized water, and the two materials are stirred until they are fully dissolved and mixed to form a clear solution.

[0073] (2) Template combination: The beaker was placed in an oil bath constant temperature heater stirrer, set at 80°C constant temperature heating, and the stirring speed was 200 rpm. After 12 h, the stirred solid was removed and placed in a quartz boat.

[0074] (3) Calcination: The material was subjected to high-temperature calcination under an argon atmosphere, heated to 700°C, and held for 3 hours. Then the boron-doped carbonized product was neutralized with KOH and repeatedly washed with deionized water to obtain the product.

[0075] (4) Electrode performance test: The boron-doped template method prepared in Example 3 was used to control the wrinkled nanocarbon spheres as the negative electrode of the potassium ion hybrid capacitor, as follows:

[0076] The boron-doped template method prepared in Example 3 was used to control the wrinkled nanocarbon spheres as the negative electrode active material, and polyvinylidene fluoride (PVDF) and conductive carbon black were mixed in a mass ratio of 8:1:1, and an appropriate amount of NMP was added to form a slurry, which was coated on a copper foil with a diameter of 13 mm. After the solvent was evaporated, it was placed in a vacuum drying oven at 120°C for 10 h. Then the prepared copper foil coated with active material was used as the working electrode, and an organic electrolyte (0.8M KPF6 in EC / DEC 1:1) was used to assemble a coin-type potassium ion hybrid capacitor for charge and discharge test, with a voltage range of 0.005-3V.

[0077] The boron-doped wrinkled nanocarbon spheres prepared in step (3) of Example 3 were characterized by scanning electron microscopy, and the results are shown in Figure 5 The content of boric acid has a very obvious effect on the morphology control of the material. When the content of boric acid decreases, the morphology of the material obviously shows the initial formation process of the wrinkled nanospheres.

[0078] Comparative Example 1

[0079] Carbon material prepared without in-situ boron-doped template from carbon-containing potassium salt:

[0080] (1) Ion system and mixing: 0.306 g of sodium citrate was added to a beaker containing 60 ml of deionized water, and the material was stirred until it was fully dissolved and mixed to form a clear solution.

[0081] (2) No template combination: The beaker was placed in an oil bath constant temperature heater stirrer, set at 80°C constant temperature heating, and the stirring speed was 200 rpm. After 12 h, the stirred solid was removed and placed in a quartz boat.

[0082] (3) Calcination: The material was subjected to high-temperature calcination under an argon atmosphere, heated to 700°C, and held for 3 hours. Then the boron-doped carbonized product was neutralized with KOH and repeatedly washed with deionized water to obtain the product.

[0083] (4) Electrode performance test: the undoped material prepared in Comparative Example 1 was applied to a potassium ion hybrid capacitor negative electrode, as follows:

[0084] The undoped material obtained in Comparative Example 1 was used as a negative active material, and polyvinylidene fluoride (PVDF), conductive carbon black were mixed in a mass ratio of 8:1:1, and an appropriate amount of NMP was added to prepare a slurry, which was coated on a copper foil with a diameter of 13 mm. After the solvent was volatilized, the coated copper foil was placed in a vacuum drying oven at 120°C for 10h. Then, the prepared active material-coated copper foil was used as a working electrode, and an organic electrolyte (0.8M KPF6 in EC / DEC 1:1) was assembled into a coin-type potassium ion hybrid capacitor for charge-discharge test, with a voltage range of 0.005-3V.

[0085] The carbon material prepared in step (3) of Comparative Example 1 without boron doping and morphology control was characterized by scanning electron microscopy, and the results are shown in Figure 3 The content of boric acid has a very obvious effect on the morphology control of the material. When there is no boric acid, the morphology of the material exhibits a nanosheet morphology.

[0086] Example 4

[0087] In-situ boron-doped template method to control the wrinkled nanocarbon spheres in a carbon-containing lithium salt / boric acid system:

[0088] (1) Ion system and mixing: 0.161 g of lithium tartrate and 0.061 g of boric acid (at this time, the molar ratio is C:B=1:1) were added to a beaker containing 60 ml of hot deionized water, and stirred until the two materials were fully dissolved and mixed to form a clear solution.

[0089] (2) Template combination: the beaker was placed in an oil bath constant temperature stirrer, set to 80°C constant temperature heating, and the stirring speed was 200 rpm. After 12h, the stirred solid was taken out and placed in a quartz boat.

[0090] (3) Calcination: the material was calcined at a high temperature in argon gas, heated to 500°C, and kept for 3 hours. Then the boron-doped carbonized product was repeatedly washed with KOH and deionized water by filtration, and the product was obtained.

[0091] (4) Electrode performance test: the boron-doped template method to control the wrinkled nanocarbon spheres prepared in Example 4 was applied to a potassium ion hybrid capacitor negative electrode, as follows:

[0092] The boron-doped template method prepared folded nanocarbon spheres obtained in Example 4 were used as negative active materials, and polyvinylidene fluoride (PVDF), conductive carbon black were mixed in a mass ratio of 8:1:1, and a proper amount of NMP was added to prepare a slurry, which was coated on a copper foil with a diameter of 13 mm. After the solvent was volatilized, the coated copper foil was dried in a vacuum drying oven at 120°C for 10h. Then, the prepared active material coated copper foil was used as the working electrode, and an organic electrolyte (0.8MKPF6in EC / DEC 1:1) was used to assemble a coin-type potassium ion hybrid capacitor for charge and discharge test, and the voltage range was 0.005-3V.

[0093] The boron-doped folded nanocarbon spheres prepared in step (3) of Example 4 were analyzed for interlayer spacing, discharge capacity, and doping amount, and the results are shown in Tables 1, 2, and 3. Tartarate as a precursor can synthesize high boron-doped folded nanosphere materials with large interlayer spacing, high capacity, and high doping amount.

[0094] Example 5

[0095] In-situ boron-doped template method for preparing folded nanocarbon spheres using carbon-containing sodium salt / boric acid system:

[0096] (1) Ion system and mixing: 0.428g of sodium rose bengal and 0.061g of boric acid (at this time, the molar ratio is C:B=2:1) were added to a beaker containing 60ml of hot deionized water, and stirred until the two materials were fully dissolved and mixed to form a clear solution.

[0097] (2) Template combination: The beaker was placed in an oil bath constant temperature stirrer, set to 80°C constant temperature heating, and the stirring speed was 200rpm. After 12h, the stirred solid was taken out and placed in a quartz boat.

[0098] (3) Calcination: The material was calcined at a high temperature in an argon atmosphere, heated to 600°C, and kept for 3 hours. Then the boron-doped carbonized product was repeatedly washed with KOH and deionized water by filtration to obtain the product.

[0099] (4) Electrode performance test: The boron-doped template method prepared folded nanocarbon spheres obtained in Example 5 were used as the negative electrode of the potassium ion hybrid capacitor, as follows:

[0100] The boron-doped template method prepared folded nanocarbon spheres obtained in Example 5 were used as negative active materials, and polyvinylidene fluoride (PVDF), conductive carbon black were mixed in a mass ratio of 8:1:1, and a proper amount of NMP was added to prepare a slurry, which was coated on a copper foil with a diameter of 13 mm. After the solvent was volatilized, the coated copper foil was dried in a vacuum drying oven at 120°C for 10h. Then, the prepared active material coated copper foil was used as the working electrode, and an organic electrolyte (0.8MKPF6in EC / DEC 1:1) was used to assemble a button-type potassium ion hybrid capacitor for charge and discharge test, and the voltage range was 0.005-3V.

[0101] The boron-doped folded nanocarbon spheres prepared in step (3) of Example 5 were analyzed for interlayer spacing, discharge capacity, and doping amount, and the results are shown in Tables 1, 2, and 3. Rose Bengal as a precursor can synthesize high-boron-doped folded nanosphere materials with large interlayer spacing, high capacity, and high doping amount.

[0102] Example 6

[0103] In-situ boron-doped template method for preparing folded nanocarbon spheres from carbon-containing potassium salt / boric acid system:

[0104] (1) Ion system and mixing: 1.17g of potassium gluconate and 0.061g of boric acid (at this time, the molar ratio is C:B=5:1) were added to a beaker containing 60ml of hot deionized water, and stirred until the two materials were fully dissolved and mixed to form a clear solution.

[0105] (2) Template combination: The beaker was placed in an oil bath constant temperature stirrer, set to 80°C constant temperature heating, and the stirring speed was 200rpm. After 12h, the stirred solid was taken out and placed in a quartz boat.

[0106] (3) Calcination: The material was calcined at a high temperature in an argon atmosphere, heated to 600°C, and kept for 3 hours. Then the boron-doped carbonized product was repeatedly washed with KOH and deionized water by filtration to obtain the product.

[0107] (4) Electrode performance test: The boron-doped template method prepared folded nanocarbon spheres obtained in Example 6 were used as negative active materials for sodium ion hybrid capacitor, as follows:

[0108] The boron-doped template method prepared in Example 6 was used to prepare the wrinkled nanocarbon spheres as the negative active material. Polyvinylidene fluoride (PVDF), conductive carbon black were mixed in a mass ratio of 8:1:1, and a proper amount of NMP was added to prepare a slurry, which was coated on a copper foil with a diameter of 13 mm. After the solvent was evaporated, the coated copper foil was dried in a vacuum drying oven at 120°C for 10 h. Then, the prepared active material coated copper foil was used as the working electrode, and an organic electrolyte (1M NaClO4 in DMC:EC:EMC = 1:1:1 Vol%) was used to assemble a coin-type sodium-ion hybrid capacitor for charge and discharge tests, with a voltage range of 0.01-3V.

[0109] The boron-doped wrinkled nanocarbon spheres prepared in step (3) of Example 6 were characterized by scanning electron microscopy, and the results are shown in FIG. 2. As can be seen from the figure, the morphology of the material shows the unique characteristics of wrinkled nanospheres. Figure 6

[0110] The boron-doped wrinkled nanocarbon spheres prepared in step (3) of Example 6 were analyzed for interlayer spacing, discharge capacity, and doping amount, and the results are shown in Tables 1, 2, and 3. Gluconate as a precursor can be used to synthesize high-boron-doped wrinkled nanosphere materials with large interlayer spacing, high capacity, and high doping amount.

[0111] Example 7

[0112] Preparation of in-situ boron-doped template method to control wrinkled nanocarbon spheres using a carbon-containing lithium salt / boric acid system:

[0113] (1) Ion system and mixing: 0.128 g of lithium benzoate and 0.305 g of boric acid (at this time, the molar ratio is C:B = 1:5) were added to a beaker containing 60 ml of hot deionized water, and stirred until the two materials were fully dissolved and mixed to form a clear solution.

[0114] (2) Template combination: The beaker was placed in an oil bath constant temperature stirrer, set to 80°C constant temperature heating, and the stirring speed was 200 rpm. After 12 h, the stirred solid was removed and placed in a quartz boat.

[0115] (3) Calcination: The material was calcined at a high temperature in an argon atmosphere, heated to 600°C, and kept for 3 hours. Then, the boron-doped carbonized product was repeatedly filtered and washed with KOH and deionized water to obtain the product.

[0116] (4) Electrode performance test: The boron-doped template method to control wrinkled nanocarbon spheres prepared in Example 7 were used as the negative electrode of a sodium-ion hybrid capacitor, as follows:

[0117] ​The boron-doped template method prepared in Example 7 was used to prepare the wrinkled nanocarbon spheres as the negative active material. Polyvinylidene fluoride (PVDF), conductive carbon black were mixed in a mass ratio of 8:1:1, and a proper amount of NMP was added to form a slurry, which was coated on a copper foil with a diameter of 13 mm. After the solvent was evaporated, the coated copper foil was dried in a vacuum drying oven at 120°C for 10 h. Then, the prepared active material coated copper foil was used as the working electrode, and an organic electrolyte (1M NaClO4 in DMC:EC:EMC = 1:1:1 Vol%) was used to assemble a coin-type sodium ion hybrid capacitor for charge and discharge test, with a voltage range of 0.01-3V.

[0118] The boron-doped wrinkled nanocarbon spheres prepared in step (3) of Example 7 were analyzed for interlayer spacing, discharge capacity, and doping amount, and the results are shown in Tables 1, 2, and 3. Benzoate as the precursor can be used to synthesize high boron-doped wrinkled nanosphere materials with large interlayer spacing, high capacity, and high doping amount.

[0119] Example 8

[0120] In-situ boron-doped template method for preparing carbon-containing sodium salt / boric acid system to control wrinkled nanocarbon spheres:

[0121] (1) Ion system and mixing: 0.452 g of sodium ethylenediaminetetraacetate tetrahydrate and 0.122 g of boric acid (at this time, the molar ratio is C:B = 1:2) were added to a beaker containing 60 ml of hot deionized water, and stirred until the two materials were fully dissolved and mixed to form a clear solution.

[0122] (2) Template combination: The beaker was placed in an oil bath constant temperature stirrer, set to 80°C constant temperature heating, and the stirring speed was 200 rpm. After 12 h, the stirred solid was removed and placed in a quartz boat.

[0123] (3) Calcination: The material was calcined at a high temperature in an argon atmosphere, heated to 600°C, and kept for 3 hours. Then, the boron-doped carbonized product was repeatedly filtered and washed with KOH and deionized water, respectively, to obtain the product.

[0124] (4) Electrode performance test: The boron-doped template method prepared in Example 8 was used to prepare the wrinkled nanocarbon spheres as the negative active material for potassium ion batteries, as follows:

[0125] The boron-doped template method obtained in Example 8 was used to prepare the wrinkled nanocarbon sphere as a negative active material. A slurry was prepared by mixing the wrinkled nanocarbon sphere, polyvinylidene fluoride (PVDF), and conductive carbon black in a mass ratio of 8:1:1, adding an appropriate amount of NMP, and coating on a copper foil with a diameter of 13 mm. After the solvent was evaporated, the coated copper foil was dried in a vacuum drying oven at 120°C for 10 h. Then, the coated copper foil was used as a working electrode to assemble a coin-type potassium ion battery with an organic electrolyte (0.8 M KPF6 in EC / DEC 1:1) and perform charge-discharge tests in a voltage range of 0.005-3 V.

[0126] The boron-doped wrinkled nanocarbon sphere prepared in step (3) of Example 8 was analyzed for interlayer spacing, discharge capacity, and doping amount, and the results are shown in Tables 1, 2, and 3. The ethylenediaminetetraacetate salt as a precursor can be used to synthesize a high-boron-doped wrinkled nanosphere material with a large interlayer spacing, high capacity, and high doping amount.

[0127] In addition, the boron-doped wrinkled nanocarbon sphere obtained in step (3) of each example and the non-boron-doped carbon material prepared in step (3) of Comparative Example 1 were characterized by XRD. After conversion, the interlayer spacing results are shown in Table 1. The discharge capacity performance is shown in Table 2. The boron content and oxygen content are shown in Table 3.

[0128] Table 1 Interlayer spacing of the carbon-based material product prepared in each of Examples 1-8 and Comparative Example 1

[0129]

[0130]

[0131] Table 2 Discharge capacity of the carbon-based material product prepared in each of Examples 1-8 and Comparative Example 1

[0132] Name Capacity (mAh g -1 ) Example 1 351 Example 2 306 Example 3 224 Comparative Example 1 220 Example 4 417 Example 5 450 Example 6 335 Example 7 298 Example 8 250

[0133] Table 3 Boron content of the carbon-based material product prepared in each of Examples 1-8 and Comparative Example 1

[0134]

[0135]

[0136] As can be seen from Tables 1, 2, and 3, boron doping expands the carbon interlayer spacing, acts as an active site, and greatly improves the capacity of the negative electrode. By controlling the amount of boric acid and carbon-containing salt to make the molar ratio of boron to carbon satisfy 1:1-1:3, and in combination with a specific carbon-containing salt material, a high-boron-doped wrinkled nanosphere carbon material with a boron doping amount greater than or equal to 5 wt% can be synthesized.

[0137] In addition, Figure 11 The cycle performance of different doping amounts is compared, and the results show that the more boron doping amount of the wrinkled carbon sphere material has better cycle performance, better cycle stability, and lower attenuation amplitude.

[0138] Meanwhile, Figure 12 The conductive performance of different doping amounts is also compared, and the results show that the more boron doping amount of the wrinkled carbon sphere material has lower impedance and better conductive performance.

[0139] Those skilled in the art will easily understand that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for synthesizing boron-doped wrinkled nanosphere carbon materials using an in-situ template method, characterized in that, This method uses boric acid as the boron source and template. First, carbon-containing salts and boric acid are mixed in hot deionized water at a carbon to boron molar ratio of 1:5 to 5:1, and then evaporated and dried to obtain a solid mixture. Next, the solid mixture is calcined under a protective atmosphere, and the calcined product is neutralized with alkali and washed to obtain boron-doped wrinkled nanosphere carbon material. The boron element in the boron-doped wrinkled nanosphere carbon material includes both BCO2 and BC2O states. The carbon-containing salt is at least one of citrate, gluconate, tartrate, rose sulfite, benzoate, and ethylenediaminetetraacetate; the calcination temperature is 500-900℃.

2. The method as described in claim 1, characterized in that, The temperature of the hot deionized water is not lower than 80°C.

3. The method as described in claim 1, characterized in that, The boric acid and carbon salt used in the mixture are mixed in a molar ratio of boron to carbon of 1:1 to 1:

3.

4. The method as described in claim 1, characterized in that, The carbon-containing salt is at least one of lithium citrate, sodium citrate, and potassium citrate.

5. The method as described in claim 1, characterized in that, The protective atmosphere is an inert atmosphere, such as argon or nitrogen.

6. Boron-doped wrinkled nanosphere carbon material obtained by the method described in any one of claims 1-5.

7. The boron-doped wrinkled nanosphere carbon material as described in claim 6, characterized in that, Discharge capacity: 250 ~ 450 mAhg -1 ; Interlayer spacing: 0.38 ~ 0.42 nm; Boron content: 0.5 wt% ~ 10 wt%.

8. The boron-doped wrinkled nanosphere carbon material as described in claim 6, characterized in that, The boron-doped wrinkled nanosphere carbon material is a highly boron-doped wrinkled nanosphere carbon material with a discharge capacity of 350 ~ 450 mAh g. -1 ; Interlayer spacing: 0.39 ~ 0.42 nm; Boron content: 5 wt% ~ 10 wt%.

9. The application of the boron-doped wrinkled nanosphere carbon material as described in any one of claims 6-8 as a negative electrode active material in alkali metal mixed-ion capacitors or alkali metal batteries.

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