S-N co-doped porous carbon material and preparation method and application thereof

Abstract

The invention discloses an S-N co-doped porous carbon material as well as a preparation method and application thereof. The preparation method comprises the following steps: A1, synthesizing a porous carbon material GN; a2, preparation of an S-N co-doped material SNGN; weighing GN and an S-N doping source according to a certain mass ratio, grinding and mixing to be uniform; transferring the mixed powder into a calcining furnace, heating to 750-800 DEG C at a certain heating rate in a nitrogen atmosphere, and keeping the temperature; and naturally cooling, washing the product with a hydrochloric acid solution, washing with deionized water until the product is neutral, and carrying out vacuum drying to obtain the S-N co-doped porous carbon material marked as SNGN. Through an S-N co-doping strategy, a porous carbon material (SNGN-1) with a rich microporous structure and multiple active sites is constructed, the adsorption capacity of Na is remarkably enhanced, the specific capacity and the rate capability of a negative electrode material are improved, and then construction of the high-performance all-carbon sodium ion hybrid capacitor is achieved.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion hybrid capacitor (SIHC) anode material technology, and more particularly to an SN co-doped porous carbon material, its preparation method and application. Background Technology

[0002] Sodium-ion hybrid capacitors combine the high energy density of batteries with the long cycle life of capacitors, making them a research hotspot for next-generation energy storage devices. The sodium-ion storage performance of the anode material is key to determining the overall performance of SIHC.

[0003] Currently, sodium-ion hybrid capacitor (SIHC) anode materials generally suffer from problems such as weak sodium ion adsorption capacity, slow diffusion kinetics, and poor cycle stability, making it difficult to achieve both high energy density and high power density in the device. Traditional carbon materials have low specific surface area and insufficient active sites, making it impossible to achieve high-efficiency sodium adsorption. + Adsorption and rapid diffusion.

[0004] In the existing technology, sulfur or nitrogen-doped carbon materials have been studied for sodium ion storage, but their adsorption sites are singular and their conductivity is insufficient, making it impossible to achieve both high capacity and high power at the same time.

[0005] Therefore, existing technologies have shortcomings and need to be improved. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an SN co-doped porous carbon material, its preparation method and application, in order to overcome the shortcomings of the prior art.

[0007] The technical solution of the present invention is as follows: A method for preparing an SN co-doped porous carbon material includes the following steps: A1. Synthesis of porous carbon material GN The precursor is placed in a tube furnace and heated to 600-700℃ at a certain heating rate under a protective atmosphere, and then naturally cooled to room temperature. The carbonization product was soaked in an acidic solution (2.0 M hydrochloric acid solution), then washed with deionized water until neutral, and vacuum dried to obtain porous carbon material GN; A2. Preparation of SNGN co-doped material Weigh out GN and SN doped sources according to a certain mass ratio, and grind and mix them until uniform; The mixed powder is transferred to a calcining furnace and heated to 750-800℃ at a certain heating rate under a nitrogen atmosphere, and then held at that temperature. After natural cooling, the product was washed with hydrochloric acid solution, then washed with deionized water until neutral, and vacuum dried to obtain SN co-doped porous carbon material, denoted as SNGN.

[0008] The preparation method of sodium gallate is as follows: gallic acid is dissolved in deionized water by stirring, and sodium hydroxide is added and stirred until completely dissolved; the solution is transferred to a freeze dryer for freeze drying to obtain brown-green sodium gallate solid.

[0009] In the preparation method described above, the mass ratio of GN to thiourea is one of 1:1, 1:0.5, 1:2, or 1:3.

[0010] In the preparation method described above, the heating rate is 5℃ / min.

[0011] In the preparation method described above, the nitrogen atmosphere flow rate is 100 mL / min.

[0012] In the preparation method described above, the dopant source is one of thiourea, thioacetamide, or L-cysteine.

[0013] In the preparation method described above, the precursor is one of sodium gallate, sodium tannate, or sodium pyrogallol.

[0014] In the preparation method described above, the heat preservation time is 1-2 hours.

[0015] SN co-doped porous carbon materials prepared according to any of the preparation methods.

[0016] According to the application of the aforementioned SN co-doped porous carbon material, it can be used as a negative electrode for sodium-ion batteries, a potassium-ion hybrid capacitor, or a sodium-ion hybrid capacitor. This invention constructs a porous carbon material (SNGN-1) with abundant microporous structure and multiple active sites through an SN co-doping strategy, significantly enhancing the adsorption capacity of Na⁺, improving the specific capacity and rate performance of the negative electrode material, and thus realizing the construction of a high-performance all-carbon sodium-ion hybrid capacitor.

[0017] This invention proposes to construct an S-N co-doped porous carbon material by using sodium gallate as a precursor and co-doping with thiourea through one-step carbonization. The synergistic effect of S and N is used to enhance Na+ adsorption, optimize the pore structure to promote ion diffusion, and achieve high-capacity, high-rate, and long-cycle sodium ion storage. Attached Figure Description

[0018] Figure 1 (a) SEM image of GN; (b) SEM image of SNGN-1; Figure 2 (a) SEM image of SNGN-0.5; (b) SEM image of SNGN-2; (c) SEM image of SNGN-3; Figure 3 shows the XRD patterns of GN and SNGN-1.

[0019] Figure 4XPS plots; (a) S 2p; (b) N 1s; Figure 5 The results are from a rate test of a sodium-ion half-cell. Figure 6 (a) Graphene nanosheets (GN); (b) Graphene oxide (SNGN-1) on a carbon surface with Na + First-principles calculations of adsorption behavior; (c) corresponding density of states; Figure 7 Rate performance of the assembled sodium-ion hybrid capacitor; Figure 8 The specific surface area of ​​traditional carbon materials and the carbon materials of this invention are compared; GN is 225 m² / g, SNGN-1 is 867 m² / g, SNGN-0.5 is 960 m² / g, SNGN-2 is 726 m² / g, and SNGN-3 is 680 m² / g. Figure 9 Electrochemical performance diagrams for N and S single doping (N doping at 0.1 A g). -1 The specific capacity at current density is 251 mAh g. -1 S doping in 0.1 A g -1 The specific capacity at current density is 298 mAh g. -1 ; Detailed Implementation

[0020] The present invention will be described in detail below with reference to specific embodiments.

[0021] Terminology Explanation: GN: Porous carbon material prepared from gallic acid through polymerization, cross-linking, and carbonization.

[0022] SNGN-X: SN co-doped porous carbon materials obtained by high-temperature calcination of GN and thiourea in different proportions, where X represents the mass ratio of GN to thiourea (e.g., SNGN-1 means GN:thiourea = 1:1).

[0023] SIHC: Sodium-ion mixed capacitor, constructed with SNGN-1 as the negative electrode.

[0024] Example 1: Preparation of SNGN-1, a co-doped porous carbon material A1. Synthesis of precursor GN Weigh 8.5 g of gallic acid (analytical grade) and place it in a 500 mL beaker; Add 200 mL of deionized water, stir to dissolve, then add 2.0 g of sodium hydroxide (analytical grade), and continue stirring until completely dissolved to form a pale yellow transparent solution; The solution was transferred to a freeze dryer and freeze-dried at -50°C for 48 hours to obtain a brownish-green sodium gallate solid. The solid was placed in a tube furnace and heated to 700°C at a rate of 5°C / min under a nitrogen atmosphere (flow rate 100 mL / min), held at that temperature for 2 hours, and then allowed to cool naturally to room temperature. The carbonized product was soaked in 2.0 M hydrochloric acid solution for 12 hours, then washed with deionized water until neutral, and vacuum dried at 80°C for 12 hours to obtain porous carbon material GN with a carbon yield of about 15%.

[0025] A2, Preparation of SNGN-1 co-doped material Weigh 1.0 g of GN and 1.0 g of thiourea (analytical grade), place them in an agate mortar and grind and mix for 30 minutes until homogeneous; The mixed powder was transferred to a ceramic boat and placed in a tube furnace. Under a nitrogen atmosphere (flow rate of 100 mL / min), the temperature was increased to 800°C at a rate of 5°C / min and held for 2 hours. After natural cooling, the product was washed three times with 2.0 M hydrochloric acid solution, then washed with deionized water until neutral, and vacuum dried at 80°C for 12 hours to obtain SN co-doped porous carbon material, denoted as SNGN-1.

[0026] Example 2: Preparation of materials SNGN-0.5, SNGN-2, and SNGN-3 with different doping ratios The preparation method is the same as in Example 1, except that the mass ratio of GN to thiourea is adjusted to 1:0.5, 1:2, and 1:3, respectively. The resulting materials are denoted as SNGN-0.5, SNGN-2, and SNGN-3, respectively.

[0027] Comparative Example 1: Pure GN material The preparation steps of GN in Example 1 were performed only, without thiourea doping.

[0028] (II) Examples of Electrode Fabrication and Battery Assembly Example 3: Preparation of SNGN-1 negative electrode and half-cell testing Electrode preparation Mix SNGN-1, conductive carbon black Super P, and binder sodium alginate in a mass ratio of 8:1:1; Add an appropriate amount of deionized water and grind to form a uniform slurry; The slurry is applied to the copper foil, with a coating thickness of approximately 80 μm. Vacuum dried at 100℃ for 12 hours, then cut into discs with a diameter of 12 mm, with an active substance loading of approximately 2.0 mg / cm².

[0029] Half-cell assembly Assemble CR2032 button cells in an argon glove box (H2O < 0.1 ppm, O2 < 0.1 ppm); Sodium metal sheet was used as the counter electrode, glass fiber membrane was used as the diaphragm, and the electrolyte was 1 M NaClO4 in EC / DEC (1:1) containing 2% FEC; The SNGN-1 electrode is the working electrode.

[0030] Electrochemical test results GCD test: At a current density of 0.2 A / g, the initial discharge specific capacity is 500 mAh / g; Cycling performance: 92% capacity retention after 1000 cycles at 1 A / g; Rate performance: The capacities at 0.1, 0.2, 0.5, 1, 2, and 5 A / g are 520, 500, 480, 460, 430, and 380 mAh / g, respectively.

[0031] Example 4: Assembly and Testing of a Sodium-Carbon Hybrid Capacitor (SIHC) Anode preparation SNGN-1, Super P, and PVDF were mixed in a ratio of 8:1:1 and pulped using N-methylpyrrolidone as a solvent. Coated onto aluminum foil, dried, and then cut, with a loading of approximately 3.0 mg / cm².

[0032] All-battery assembly Negative electrode: SNGN-1 (pre-sodium treated); The mass ratio of positive to negative electrode active materials is 1:1; The electrolyte and diaphragm are the same as in Example 3.

[0033] Electrochemical performance Energy / Power Density: At 0.2 A / g, the energy density is 165.2 Wh / kg and the power density is 218.6 W / kg; Cycle life: 85% capacity retention after 5000 cycles at 1 A / g; Self-discharge rate: Voltage retention rate >95% after 24 hours of rest.

[0034] Figure 3 shows the XRD patterns of GN and SNGN-1. The amorphous state of the two samples was confirmed by the broadened (002) and (101) diffraction peaks at 22° and 43°, which is consistent with the results of high-resolution transmission electron microscopy (HRTEM). Due to the corrosive effect of sulfur, the intensity of the (002) peak of SNGN-1 is significantly reduced compared with GN, indicating that SNGN-1 has a more disordered carbon structure.

[0035] like Figure 4 As shown, sulfur and nitrogen have formed covalent bonds with the carbon skeleton. Figure 4 The peaks at 164.2 eV and 165.4 eV in peak a are attributed to the 2p1 / 2 and 2p3 / 2 orbitals of sulfur atoms in the C−S−C structure, respectively, while the peak at 168.7 eV corresponds to sulfur oxide in C-SOX-C. The covalent incorporation of sulfur atoms leads to an increase in interlayer spacing, and the dominant C−S−C 2p3 / 2 component provides additional electrochemically active sites, thus contributing to improved capacitance performance. Figure 4 As shown in b, three distinct peaks were detected at 398.6 eV, 400.4 eV, and 402.1 eV, respectively. Specifically, the peaks at 398.6 eV and 400.4 eV are attributed to pyridine nitrogen (N−6, 22.10%) and pyrrole nitrogen (N−5, 53.40%), respectively. The predominant N−5 group, as an electrochemically active group, can undergo a Faraday reaction with Na⁺, providing additional capacity. Furthermore, the characteristic peak at ~402.1 eV is attributed to graphitic nitrogen (N−Q, 24.49%), which is rich in lone pair electrons and can effectively improve the conductivity of the material.

[0036] like Figure 5 As shown, the rate performance of the SNGN-1 anode exhibits significant stability at different current densities. When the current density increases from 0.1 A g⁻¹ to 5 A g⁻¹, its reversible charging capacity decreases from 585 mA hg⁻¹ to 160.6 mA hg⁻¹. More importantly, once the current density is reduced back to 1 A g⁻¹, the reversible capacity recovers to 245.9 mA hg⁻¹. This phenomenon clearly demonstrates the excellent rate capability and reversibility of the SNGN-1 anode, which is mainly attributed to its structural stability and hierarchical porous architecture. In addition to rate performance, the cycling stability of the SNGN-1 anode was further investigated at two typical current densities: specifically, at 0.1 A g⁻¹, its reversible storage capacity remained stable at 500.88 mA hg⁻¹ after 10 cycles, with a coulombic efficiency close to 74.6%; in contrast, the GN sample showed significantly lower reversible capacity after the same 10 cycles (only 153.3 mA hg⁻¹ at 0.1 A g⁻¹ and only 40.8 mA hg⁻¹ at 5 A g⁻¹), further highlighting the excellent electrochemical performance of the SNGN-1 anode.

[0037] like Figure 6As shown, the adsorption energy of sodium ions (Na⁺) on the material surface and the density of states (DOS) of the system were systematically evaluated using first-principles calculations. Among these parameters, adsorption energy is a key indicator of the adsorption stability of Na⁺ on the material surface, while the density of states can effectively characterize the charge transfer capability within the material. The calculation results show that the adsorption energy (Ead) of sodium ions on nitrogen / sulfur co-doped porous carbon (SNGN-1) material is -1.936 eV. In contrast, the adsorption energy of undoped porous carbon (GN) material is -0.709 eV.

[0038] Figure 7 The rate performance shown indicates that SNGN-1 exhibits an impressive reversible specific capacity of 110.1 mA hg⁻¹ at 0.1 A g⁻¹ and maintains 45.7 mA hg⁻¹ even at 5 A g⁻¹, achieving a power density of 165.2 W kg⁻¹ at a storage density of 218.6 Wh kg⁻¹.

[0039] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing an SN co-doped porous carbon material, characterized in that, Includes the following steps: A1. Synthesis of porous carbon material GN The precursor is placed in a tube furnace and heated to 600-700℃ at a certain heating rate under a protective atmosphere, and then naturally cooled to room temperature. The carbonization product was soaked in an acidic solution, then washed with deionized water until neutral, and vacuum dried to obtain porous carbon material GN. A2. Preparation of SNGN co-doped material Weigh out GN and SN doped sources according to a certain mass ratio, and grind and mix them until uniform; The mixed powder is transferred to a calcining furnace and heated to 750-800℃ at a certain heating rate under a nitrogen atmosphere, and then held at that temperature. After natural cooling, the product was washed with hydrochloric acid solution, then washed with deionized water until neutral, and vacuum dried to obtain SN co-doped porous carbon material.

2. The preparation method according to claim 1, characterized in that, The preparation method of sodium gallate is as follows: gallic acid is dissolved in deionized water by stirring, and sodium hydroxide is added and stirred until completely dissolved; the solution is transferred to a freeze dryer and freeze-dried to obtain brown-green sodium gallate solid.

3. The preparation method according to claim 1, characterized in that, The mass ratio of GN to thiourea is one of 1:1, 1:0.5, 1:2, or 1:

3.

4. The preparation method according to claim 1, characterized in that, The heating rate is 5°C / min.

5. The preparation method according to claim 1, characterized in that, The nitrogen atmosphere flow rate is 100 mL / min.

6. The preparation method according to claim 1, characterized in that, The dopant source is one of thiourea, thioacetamide, or L-cysteine.

7. The preparation method according to claim 1, characterized in that, The precursor is one of sodium gallate, sodium tannate, or sodium pyrogallol.

8. The preparation method according to claim 1, characterized in that, The heat preservation time is 1-2 hours.

9. SN co-doped porous carbon materials prepared by any one of the preparation methods according to claims 1-8.

10. The application of the SN co-doped porous carbon material according to claim 9, used as a sodium-ion battery anode, potassium-ion hybrid capacitor, or sodium-ion hybrid capacitor.

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