Bulk boron carbon nitride sodium storage material prepared based on alkali driving, preparation method and application in preparation of sodium ion capacitor

Abstract

The application discloses bulk boron-carbon-nitrogen sodium storage material prepared based on alkali driving, a preparation method and application in preparation of sodium ion capacitors, and belongs to the technical field of sodium ion capacitor materials. A boron source, a nitrogen source, a carbon source and a high-temperature activator are dissolved or dispersed in a solvent, and then drying is performed to obtain a solid precursor; the solid precursor is subjected to calcination treatment under an inert atmosphere, and after natural cooling, washing and drying, the bulk boron-carbon-nitrogen sodium storage material prepared based on alkali driving is obtained. The preparation method can directly obtain the bulk BCN material with layered and graded pores, orderly-disordered carbon domains and well-distributed hetero-elements, and the bulk BCN material can be used in sodium ion capacitors to significantly improve specific capacity and cycle stability. The material has an energy storage mechanism based on synergism of surface capacitance-diffusion mechanism, and can effectively optimize sodium ion storage kinetics.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion capacitor material technology, specifically relating to bulk boron-carbon-nitrogen sodium storage materials prepared based on alkali-driven processes, their preparation methods, and their application in the preparation of sodium-ion capacitors. Background Technology

[0002] The current over-reliance on fossil fuels necessitates the development of sustainable energy storage systems. Given the scarcity of lithium resources, sodium-ion storage systems are highly favored due to the abundance of sodium and its performance comparable to lithium. However, sodium... + The relatively large ionic radius (0.102 nm) hinders its storage in conventional graphite anodes. In contrast, hard carbon, with its larger interlayer spacing (>0.37 nm), can stably accommodate reversible Na+. + Intercalation / deintercalation makes it a promising anode candidate for sodium ion storage.

[0003] Typically, hard carbon consists of randomly stacked graphite domains and a porous structure containing both open and closed pores. This inherent structure gives it high specific capacity, low operating potential, and excellent structural stability for sodium storage applications. However, the amorphous structure lacks an ordered conductive network, and its randomly distributed pores hinder the formation of uninterrupted ion transport pathways. These structural limitations lead to high Na+... + The diffusion barrier and slow ion transport kinetics limit rate performance.

[0004] To address these challenges, various strategies have been developed to optimize the structure and chemical properties of hard carbon to improve sodium storage capacity and kinetic performance. Current strategies include heteroatom doping (N, B, O, S, P) to modulate electronic structure, high-temperature graphitization to introduce conductive graphitic domains, and hierarchical chemical activation to construct interconnected porous frameworks. However, traditional strategies often face trade-offs, where enhancing one property often comes at the expense of another. For example, heteroatom doping and hierarchical chemical activation tend to introduce sp... 3 Hybridization defects disrupt the π-conjugated network and impair the electrical conductivity of the carbon matrix. Subsequent high-temperature graphitization often leads to pore filling, thereby reducing the number of active sites and hindering Na+ absorption. + Ion transport.

[0005] Patent CN118352167A discloses a high-performance supercapacitor electrode material, boron, carbon, and nitrogen nanosheets, and its preparation method and application via a molten alkali method. However, this material is not suitable for use as a sodium storage material. The main reason is that the high specific surface area of ​​the carbon nanosheet structure will form an excessively thick solid electrolyte interphase (SEI) film during the first charge and discharge process, irreversibly consuming a large amount of sodium ions and electrolyte, resulting in a significant reduction in the first coulombic efficiency (ICE). At the same time, the high surface area and abundant defect sites will continuously trigger side reactions, destroying the stability of the SEI film and leading to poor cycle performance. In addition, this material mainly provides "slope capacity" through surface adsorption, but lacks the "plateau capacity" generated by ion intercalation / micropore filling, which is more critical for volumetric energy density, thus limiting the volumetric energy density.

[0006] Therefore, for current sodium storage systems, simultaneously adjusting the electronic structure, regulating the carbon domain architecture, and controlling pore evolution remains extremely challenging. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a bulk boron carbon nitrogen (BCN) sodium storage material prepared based on alkali-driven process, a preparation method, and its application in the preparation of sodium-ion capacitors. Through a one-step calcination strategy of adding a high-temperature activator to the precursor, a bulk boron carbon nitrogen (BCN) material with hierarchical pores, coordinated distribution of ordered and disordered carbon domains, and good dispersion of heterogeneous elements is directly obtained. When used in sodium-ion capacitors, it can achieve significantly improved specific capacitance and cycle stability.

[0008] This invention is achieved through the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing a bulk boron-carbon-nitrogen sodium storage material based on alkali-driven preparation, characterized by comprising the following steps:

[0010] (1) Dissolve or disperse boron source, nitrogen source, carbon source and high temperature activator in solvent, and then dry to obtain solid precursor;

[0011] (2) Step (1) The solid precursor is calcined in an inert atmosphere, and after natural cooling, it is washed and dried to obtain bulk boron carbon nitrogen sodium storage material based on alkali-driven preparation.

[0012] Furthermore, the boron source is one or more of boric acid, boron oxide, and ammonium borate; the nitrogen source is one or more of urea, ammonium bicarbonate, and dicyandiamide; and the carbon source is one or more of glucose, expanded graphite, and worm graphite.

[0013] Furthermore, the high-temperature activator is one or more of potassium hydroxide, sodium hydroxide, and barium hydroxide.

[0014] Furthermore, the mass ratio of the boron source, nitrogen source, carbon source and high-temperature activator is 1-10:1-10:1-10:1-10.

[0015] Furthermore, the calcination treatment in step (2) is carried out at a temperature of 800~1000℃ for 1~4h, and the heating rate is 3-10℃ / min.

[0016] Further, the solvent mentioned in step (1) is water, and the mixture is stirred at 80~120℃ for 0.5~2h to dissolve or disperse the boron source, nitrogen source, carbon source and high temperature activator in water.

[0017] In a second aspect, the present invention provides a bulk boron-carbon-nitrogen sodium storage material prepared by the above-described preparation method.

[0018] In a third aspect, the present invention provides the application of the aforementioned bulk boron-carbon-nitrogen sodium storage material prepared based on alkali-driven processes in the preparation of sodium-ion capacitors.

[0019] Furthermore, bulk boron-carbon-nitrogen sodium storage materials prepared based on alkali-driven processes are used as the negative electrode active material for sodium-ion capacitors.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0021] This invention utilizes a one-step calcination strategy involving the addition of a high-temperature activator to the precursor to directly obtain bulk boron, carbon, and nitrogen sodium storage materials with hierarchical pores, coordinated distribution of ordered and disordered carbon domains, and good dispersion of impurities. When used in sodium-ion capacitors, these materials can achieve significantly improved specific capacitance and cycle stability. This method is simple to operate, highly efficient and convenient, and has the potential for industrial-scale production. Attached Figure Description

[0022] Figure 1 SEM image of the bulk boron-carbon-nitrogen sodium storage material prepared based on alkali-driven process in Example 1;

[0023] Figure 2 TEM image of the bulk boron carbon nitrogen sodium storage material prepared based on alkali-driven process in Example 1;

[0024] Figure 3 The image shows an HRTEM image of the boron carbon nitride material based on carbon lattice doped silicon nitride prepared in Example 1.

[0025] Figure 4 HRTEM image of the boron carbon nitride material prepared in Comparative Example 1;

[0026] Figure 5 Here is an HRTEM image of the boron carbon nitride material prepared in Comparative Example 2;

[0027] Figure 6 XPS spectra of the boron carbon nitride materials prepared in Example 1, Comparative Example 1, and Comparative Example 2;

[0028] Figure 7 The charge-discharge performance diagrams are shown for the boron carbon nitride materials prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0029] Figure 8 The charge-discharge performance diagrams are shown for the boron carbon-nitrogen materials based on carbon lattice doped silicon-nitrogen elements prepared in Examples 2-3.

[0030] Figure 9 An image showing the sodium-ion capacitor assembled in Application Example 1 powering a light-emitting diode (LED) screen;

[0031] Figure 10 The graph shows the long-cycle performance of the sodium-ion capacitor assembled in Application Example 1. Detailed Implementation

[0032] The present invention is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods not specifically described in the following examples are generally performed under conventional conditions or as recommended by the manufacturer.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. All reagents and materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods in the art or as per the product instructions.

[0034] Example 1

[0035] (1) Add 5 g glucose, 2 g urea, 2 g boric acid and 2 g KOH to 30 mL deionized water, stir vigorously at 80℃ for 1 h to obtain a clear solution, transfer to an air-purge constant temperature oven, keep warm at 105℃ for 8 h to remove water, and obtain a solid precursor.

[0036] (2) The solid precursor in step (1) is transferred to a vacuum tube furnace and heated to 900°C at a rate of 5°C / min under a nitrogen atmosphere and kept at that temperature for 2 hours. It is then naturally cooled to room temperature. The product is ultrasonically washed three times with deionized water and dried overnight at 80°C to obtain a bulk boron carbon nitrogen sodium storage material prepared based on alkali drive.

[0037] Example 2

[0038] Unlike Example 1, in Example 2, 1 g of KOH was added in step (1), and the other steps were the same as in Example 1, thus preparing a bulk boron carbon nitrogen sodium storage material based on alkali-driven preparation.

[0039] Example 3

[0040] Unlike Example 1, in Example 3, 3 g of KOH was added in step (1), and the other steps were the same as in Example 1, thus preparing a bulk boron carbon nitrogen sodium storage material based on alkali-driven preparation.

[0041] Example 4

[0042] Unlike Example 1, the high-temperature activator added in step (1) of Example 4 is NaOH, and the other steps are the same as in Example 1, thus preparing a bulk boron carbon nitrogen sodium storage material based on alkali-driven preparation.

[0043] Example 5

[0044] (1) Add 2 g potassium borohydride, 2 g melamine, 5 g sodium citrate and 2 g KOH to 30 mL deionized water, stir vigorously at 80 °C for 1 h to obtain a clear solution, transfer to an air-purge constant temperature oven, keep warm at 105 °C for 8 h to remove moisture, and obtain a solid precursor.

[0045] (2) The solid precursor in step (1) is transferred to a vacuum tube furnace and heated to 900°C at a rate of 5°C / min under a nitrogen atmosphere and kept at that temperature for 2 hours. It is then naturally cooled to room temperature. The product is ultrasonically washed three times with deionized water and dried overnight at 80°C to obtain a bulk boron carbon nitrogen sodium storage material prepared based on alkali drive.

[0046] Example 6

[0047] (1) Add 2 g ammonium borate, 2 g dicyandiamide, 5 g sodium citrate and 2 g KOH to 30 mL deionized water, stir vigorously at 80 °C for 1 h to obtain a clear solution, transfer to an air-purge constant temperature oven, keep warm at 105 °C for 8 h to remove water, and obtain a solid precursor.

[0048] (2) The solid precursor in step (1) is transferred to a vacuum tube furnace and heated to 900°C at a rate of 5°C / min under a nitrogen atmosphere and kept at that temperature for 2 hours. It is then naturally cooled to room temperature. The product is ultrasonically washed three times with deionized water and dried overnight at 80°C to obtain a bulk boron carbon nitrogen sodium storage material prepared based on alkali drive.

[0049] Example 7

[0050] Unlike Example 1, the calcination temperature in step (2) of Example 7 is 800°C, and the other steps are the same as in Example 1, thus preparing a bulk boron carbon nitrogen sodium storage material based on alkali-driven preparation.

[0051] Example 8

[0052] Unlike Example 1, the calcination temperature in step (2) of Example 8 is 1100℃, and the other steps are the same as in Example 1, thus preparing a bulk boron carbon nitrogen sodium storage material based on alkali-driven preparation.

[0053] Comparative Example 1

[0054] Unlike Example 1, KOH was not added in step (1) of Comparative Example 1, but the other steps were the same as in Example 1, and boron carbon nitride material was prepared.

[0055] Comparative Example 2

[0056] (1) Add 5 g glucose, 2 g urea and 2 g boric acid to 30 mL deionized water and stir vigorously at 80 °C for 1 h to obtain a clear solution. Transfer the solution to an air-purge constant temperature oven and keep it at 105 °C for 8 h to remove moisture and obtain a solid precursor.

[0057] (2) The above solid precursor was transferred to a vacuum tube furnace and heated to 900°C at a rate of 5°C / min under a nitrogen atmosphere, and held at that temperature for 2 hours, and then cooled to room temperature naturally.

[0058] (3) After the product is mixed evenly with 2g KOH, it is transferred to a vacuum tube furnace and heated to 900℃ at a rate of 5℃ / min under a nitrogen atmosphere, and held at that temperature for 2h. Then it is naturally cooled to room temperature. The product is dispersed in deionized water, ultrasonically cleaned, and filtered to remove impurities. This process is repeated three times. The washed product is dried overnight at 80℃ to obtain boron carbon nitride material.

[0059] Application Example 1

[0060] Preparation of sodium-ion capacitors

[0061] BCN and AC electrodes were prepared using the bulk boron-carbon-nitrogen sodium storage material prepared based on alkali-driven process and activated carbon (AC) as raw materials. The BCN electrode was prepared by mixing 80 wt% BCN material (bulk boron-carbon-nitrogen sodium storage material prepared based on alkali-driven process), 10 wt% conductive carbon black SP (which can be replaced with other conductive agents), and 10 wt% binder PVDF (which can also be replaced with other binders) in NMP solvent (which can also be replaced with other solvents) to form a homogeneous slurry, which was then coated onto aluminum foil. The preparation method of AC electrode is the same as that of BCN electrode, but the slurry is coated on copper foil; after the above electrode sheet is fully dried in an oven, it is cut into appropriately sized round pieces for later use; assemble sodium ion capacitor (BCN / / AC full cell) in a glove box filled with argon gas: with BCN electrode as negative electrode, AC electrode as positive electrode, electrolyte as appropriate solution containing sodium ions (1 M NaPF6 dissolved in a mixed solution of diethyl carbonate DEC and ethylene carbonate EC), and separator as appropriate porous polymer material (glass fiber membrane).

[0062] Data representation

[0063] SEM images of the bulk boron-carbon-nitrogen sodium storage material prepared in Example 1 based on alkali-driven synthesis are shown below. Figure 1 As shown, the TEM image is as follows Figure 2 As shown; by Figure 1 and Figure 2 As can be seen, the bulk boron-carbon-nitrogen sodium storage material prepared in Example 1 exhibits a bulk structure with a porous surface. During the carbonization process, the etching of KOH and the escape of gas together form a continuous channel structure, which is Na + This created the conditions for rapid storage.

[0064] HRTEM image of the bulk boron-carbon-nitrogen sodium storage material prepared in Example 1 based on alkali-driven preparation is shown below. Figure 3 As shown, the HRTEM image of the boron carbon nitride material prepared in Comparative Example 1 is as follows. Figure 4 As shown, the HRTEM image of the boron carbon nitride material prepared in Comparative Example 2 is as follows. Figure 5 As shown; by Figures 3-5 It can be seen that the bulk boron-carbon-nitrogen sodium storage material prepared in Example 1, based on alkali-driven fabrication, exhibits a hierarchical porous structure, with both ordered and disordered carbon regions present in its HRTEM image. This short-range graphite stacking domain with interconnected pores has a Na+ energy level. + This provides more migration channels and effectively shortens the diffusion distance, thereby significantly improving sodium storage kinetics. The boron carbon nitride material prepared in Comparative Example 1 exhibits a bulk structure, and no clear lattice fringes were observed in the HRTEM image, confirming that it is an amorphous carbon structure. The boron carbon nitride material prepared in Comparative Example 2 shows a thin-layer morphology, and its HRTEM image confirms the existence of an amorphous carbon structure similar to that of Comparative Example 1.

[0065] XPS spectra of the bulk boron-carbon-nitrogen sodium storage material prepared in Example 1 based on alkali-driven preparation, and the boron-carbon-nitrogen materials prepared in Comparative Examples 1 and 2 are shown below. Figure 6 As shown, the B1s spectrum can be deconvolved to obtain fitting peaks at 190.5 eV, 191.3 eV, and 192.3 eV, corresponding to BC, BN, and BO bonds, respectively. Due to the enhanced synergistic effect of BC bonds, the B1s peak of the bulk boron carbon nitrogen sodium storage material prepared in Example 1 based on alkali-driven preparation shows a significant blue shift, and the integrated area of ​​its BC bonds increases to 28.9% (compared to 14.9% in Comparative Example 1). The C1s spectrum reveals that the CB bonds (19.9%) and ordered sp bonds in the BCN sample prepared in Example 1 are closely related to the BC bonds. 2The increased proportion of C-C bonds (37.5%) (compared to 15.6% and 28.4% in the BCN sample of Comparative Example 1) reveals enhanced B-bonding and an increase in ordered carbon domains. In the N 1s spectrum, the BCN sample prepared in Example 1 showed a higher proportion of pyridine nitrogen, demonstrating that the KOH-assisted method achieved efficient electronic rearrangement and increased active sites. The increased proportion of B and N bonded to carbon indicates that the one-step activation process altered the configurational tendency of the aforementioned heteroatoms in the BCN material, promoting their uniform doping within the carbon framework. These trends play a crucial role in regulating the electronic structure, thereby promoting conductive network optimization and enhancing Na... + Adsorption capacity.

[0066] BCN electrodes were prepared according to the method in Application Example 1, and BCN / / Na half-cells were assembled in an argon-filled glove box: assembly was performed using a sodium sheet as the reference electrode and counter electrode, and the BCN electrode as the working electrode; the charge-discharge performance of the half-cells was tested using constant current charge-discharge (GCD). The charge-discharge performance graphs of the bulk boron-carbon-nitrogen sodium storage material prepared in Example 1 based on alkali-driven synthesis, and the boron-carbon-nitrogen materials prepared in Comparative Examples 1 and 2 are shown below. Figure 7 As shown; by Figure 7 It can be seen that the half-cell prepared based on the bulk boron carbon nitrogen sodium storage material prepared in Example 1, with current densities of 0.05, 0.1, 0.2, 0.5, 1, and 2 A·g -1 At that time, 371, 312, 265, 215, 166 and 112 mAh·g were obtained respectively. -1 The capacity, where the current density recovers to 0.1 A·g -1 It still maintains 318 mAh·g -1 The capacities of Comparative Example 1 at the corresponding rate of increase were 230.6, 191.4, 147.3, 108.4, 77.2, and 36.5 mAh·g, respectively. -1 The current density recovered to 0.1 A·g -1 Maintaining 195.6 mAh·g -1 The capacity of the first example was [not specified]; the capacities of the second example at the corresponding rate were 150.9, 114.4, 78.8, 57.7, 38.3 and 18.1 mAh·g, respectively. -1 The current density recovered to 0.1 A·g -1 Maintaining 135.1 mAh·g -1 The increased capacity and excellent rate performance of BCN demonstrate that abundant boron / nitrogen active sites, hierarchical porous structure, and regulated amorphous-graphite microregions can effectively enhance Na+ capacity. + Storage activity and reaction kinetics.

[0067] The charge-discharge performance diagrams of the bulk boron-carbon-nitrogen sodium storage materials prepared in Examples 2-3 based on alkali-driven processes are shown below. Figure 8 As shown. Example 2: A half-cell prepared based on a bulk boron-carbon-nitrogen sodium storage material prepared by alkali-driven process was used at current densities of 0.1 and 2 A·g. -1 At that time, 219.3 and 91.5 mAh·g were obtained respectively. -1 The capacity, where the current density recovers to 0.1 A·g -1 It can maintain 197.8 mAh·g -1 The capacity. Example 3: A half-cell prepared based on a bulk boron-carbon-nitrogen sodium storage material prepared by alkali-driven process was used at current densities of 0.1 and 2 A·g. -1 At that time, 242.7 and 147.6 mAh·g were obtained respectively. -1 The capacity, where the current density recovers to 0.1 A·g -1 It can maintain 236.1 mAh·g -1 The capacity.

[0068] Figure 9 An image showing the sodium-ion capacitor assembled in Application Example 1 powering a light-emitting diode (LED) screen. Figure 10 The graph shows the long-cycle performance of the sodium-ion capacitor assembled in Example 1 at 1 A·g. -1 It can provide 158 mAh·g at a current density. -1 High reversible capacity, achieving 128.4 Wh·kg -1 The energy density is high. Furthermore, after 300 cycles, its capacity retention is 90.5%, demonstrating excellent cycling stability.

Claims

1. A method for preparing bulk boron-carbon-nitrogen sodium storage materials based on alkali-driven preparation, characterized in that, Includes the following steps: (1) Dissolve boron source, nitrogen source, carbon source and high temperature activator in solvent, and then dry to obtain solid precursor; (2) Step (1) The solid precursor is calcined in an inert atmosphere, and after natural cooling, it is washed and dried to obtain bulk boron carbon nitrogen sodium storage material based on alkali-driven preparation. The boron source is one of boric acid, ammonium borate, and potassium borohydride; the nitrogen source is one of urea, melamine, and dicyandiamide; the carbon source is glucose or sodium citrate; and the high-temperature activator is potassium hydroxide or sodium hydroxide.

2. The method for preparing bulk boron-carbon-nitrogen sodium storage material based on alkali-driven preparation according to claim 1, characterized in that, The mass ratio of the boron source, nitrogen source, carbon source and high-temperature activator is 1-10:1-10:1-10:1-10.

3. The method for preparing bulk boron-carbon-nitrogen sodium storage material based on alkali-driven preparation according to claim 1, characterized in that, The calcination treatment in step (2) is carried out at a temperature of 800~1000℃ for 1~4h, with a heating rate of 3-10℃ / min.

4. The method for preparing bulk boron-carbon-nitrogen sodium storage material based on alkali-driven preparation according to claim 1, characterized in that, The solvent mentioned in step (1) is water. Stir at 80°C for 0.5~2h to dissolve the boron source, nitrogen source, carbon source and high temperature activator in water.

5. A bulk boron-carbon-nitrogen sodium storage material prepared by the preparation method according to any one of claims 1 to 4.

6. The application of the bulk boron-carbon-nitrogen sodium storage material prepared based on alkali-driven process as described in claim 5 in the preparation of sodium-ion capacitors.

7. The application according to claim 6, characterized in that, Bulk boron-carbon-nitrogen sodium storage materials prepared based on alkali-driven processes are used as negative electrode active materials for sodium-ion capacitors.

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