A sulfur and nitrogen co-doped MXene-3DPC anode material for sodium-ion batteries, its preparation method and application

Abstract

The present invention discloses a sulfur and nitrogen co-doped MXene-3DPC sodium ion battery anode material and a preparation method thereof, comprising the following steps: S1: adding dodecyl trimethyl ammonium chloride powder into a single-layer or few-layer MXene aqueous solution and stirring at room temperature until a uniform mixture is formed; S2: adding thiourea powder into a three-dimensional porous carbon aqueous solution and standing at room temperature until the thiourea is completely dissolved to form a uniform mixture; S3: mixing the mixtures obtained in step S1 and step S2, then carrying out a hydrothermal reaction at 115-130 °C for 5-7 h, and then freeze-drying the product to obtain the sulfur and nitrogen co-doped MXene-3DPC sodium ion battery anode material. The sulfur and nitrogen co-doped MXene / 3DPC sodium ion battery anode material prepared by the present invention has a large specific surface area, a high specific capacity and good cycle stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium-ion batteries, and particularly relates to a sulfur and nitrogen co-doped MXene-3DPC sodium-ion battery anode material, a preparation method thereof and an application thereof. Background Art

[0002] With the rapid development of society and the increasing improvement of people's living standards, people pay more and more attention to environmental protection and gradually realize the importance of clean energy. The emergence of pure electric and hybrid electric vehicles has replaced some traditional fuel vehicles. Therefore, the reversible storage of electricity has become a key technology in the field of new energy applications, fundamentally affecting the development of power applications. In recent years, lithium-ion batteries have been widely used in portable electronic products. However, due to factors such as their low energy density and the scarcity of lithium elements, the development of lithium-ion batteries in electric vehicles and large-scale energy storage applications has been severely restricted. Sodium ions, due to their rich resources and low price, bring great application prospects for sodium-ion batteries.

[0003] Conventional sodium-ion batteries mainly consist of a separator, an electrolyte, a current collector, positive and negative active materials, a conductive agent, a binder, etc. The energy storage mechanism of sodium-ion batteries is similar to the "rocking chair" ion storage mechanism of lithium-ion batteries. During the charge and discharge process of the battery, sodium ions in the electrolyte continuously intercalate and deintercalate between the positive and negative electrode materials to form a potential difference, and the external circuit is driven by the potential difference to generate current. This process mainly involves the conversion between chemical energy and electrical energy, and this mechanism can ensure the high reversibility and long cycle life of secondary batteries. However, due to the relatively large mass and radius of sodium ions, problems such as slow reaction kinetics and volume expansion of the active material occur during the charge and discharge process, severely restricting the reversible deintercalation process of sodium ions in the electrode material, and thus showing rapid decay of electrochemical activity. Therefore, there is an urgent need to develop new electrode materials to solve the existing problems.

[0004] In recent years, two-dimensional materials have shown broad application prospects in the fields of energy storage and conversion due to their high specific surface area and excellent physical properties. Graphene is a pioneer among two-dimensional materials, and its emergence has greatly promoted the development of energy storage technologies and devices. At the same time, other two-dimensional materials, including elemental substances, non-metal compounds, metal compounds, salts, organic substances, etc., also have the potential to become high-performance energy storage electrode materials. In 2011, a new two-dimensional transition metal carbide MXene material was synthesized for the first time. The precursor of Mxene is the MAX phase, which is a general term for a series of ternary layered compounds, where M represents a transition metal element, A represents a main group element, and X represents carbon and / or nitrogen. MXene is obtained by selectively etching the A atomic layer in the MAX phase. Usually, functional groups (-OH, -F, -O, etc.) are generated during the etching process, endowing MXene with good hydrophilicity, but having little obvious effect on its conductivity. This property of combining conductivity, hydrophilicity, and adjustable surface structure makes MXene show great potential in the fields of energy storage, catalysis, sensing, electromagnetic shielding, supercapacitors, and rechargeable secondary batteries. However, similar to other two-dimensional materials, severe re-stacking problems occur in layered MXene-based electrode materials during continuous charge / discharge processes, destroying the electrode structure, reducing the accessibility of electrolyte ion diffusion, and further leading to a rapid decay of battery capacity, especially for sodium ions with slow kinetics. Although some researchers have currently prepared three-dimensional structured MXene with rich active sites and excellent conductivity, the hydrogen bonds and van der Waals forces between adjacent MXene sheets will inevitably cause self-stacking of MXene, especially when used as the anode of sodium / potassium ion batteries with larger ionic radii, and the electrochemical performance is still satisfactory.

[0005] Currently, many researchers are committed to exploring the assembly techniques and strategies of two-dimensional MXene-based composites to solve the main scientific problems of MXene materials in sodium-ion battery applications. For example, Chinese Patent Publication No. CN115020680A discloses a hard carbon anode material for sodium-ion batteries coated with MXene, including heat-treating phenolic resin powder in an argon atmosphere to obtain phenolic resin-derived hard carbon; treating the phenolic resin-derived hard carbon with an aqueous solution of CTAB surfactant to make its surface positively charged, and using an acid etching method to prepare an aqueous solution of MXene with a negatively charged surface; electrostatic self-assembling the positively charged phenolic resin-derived hard carbon and the negatively charged MXene; after electrostatic self-assembly, filtering, drying, and baking to obtain the hard carbon anode material for sodium-ion batteries coated with MXene. Chinese Patent Publication No. CN113314705A discloses an in-situ oxidation-grown flower-like structure TiO 2Preparation method of / MXene / hard carbon sodium-ion battery anode material, including subjecting popcorn to thermal stabilization treatment with appropriate process under normal pressure to obtain pre-oxidized popcorn; subjecting the pre-oxidized popcorn to high-temperature carbonization in an atmosphere furnace, and obtaining popcorn-shaped hard carbon material after natural cooling; grinding and sieving the popcorn hard carbon to obtain popcorn hard carbon powder, mixing the sieved hard carbon powder with multi-layer MXene, and performing ball milling with water as a solvent in an air environment to obtain a flower-shaped structure of TiO 2 / MXene / hard carbon sodium-ion battery anode material.

[0006] The above invention has the advantages of simple and efficient preparation method, green environmental protection, low energy consumption, etc., and the prepared MXene-hard carbon composite material used as the anode material of sodium-ion battery shows high specific capacity and good electrochemical performance. Hard carbon is the most commonly used anode material in sodium-ion batteries, which has the advantages of rich sources, low cost, low sodium storage potential, non-toxic and environmental protection. However, there are still many performance problems with hard carbon anodes, such as low specific surface area and poor cycle stability, which affect the large-scale application of hard carbon anodes. Summary of the Invention

[0007] An object of the present invention is to provide a preparation method of a sulfur and nitrogen co-doped MXene-3DPC sodium-ion battery anode material with high specific capacity, high rate performance and excellent cycle performance for the above technical problems to be solved.

[0008] To achieve the above invention object, the present invention provides a preparation method of a sulfur and nitrogen co-doped MXene-3DPC sodium-ion battery anode material, including the following steps:

[0009] S1: Add dodecyltrimethylammonium chloride powder to the single-layer or few-layer MXene aqueous solution and stir at room temperature until a uniform mixture is formed;

[0010] S2: Add thiourea powder to the three-dimensional porous carbon aqueous solution and let it stand at room temperature until all the thiourea is dissolved to form a uniform mixture;

[0011] S3: Mix the mixtures obtained in step S1 and step S2, then carry out hydrothermal reaction at 115-130 °C for 5-7 h, and then freeze-dry the product to obtain the sulfur and nitrogen co-doped MXene-3DPC sodium-ion battery anode material.

[0012] Compared with the prior art, the present invention combines MXene with three-dimensional porous carbon having a large specific surface area and a porous skeleton, and simultaneously performs sulfur and nitrogen co-doping to prepare a sulfur and nitrogen co-doped MXene / 3DPC anode material for a sodium-ion battery. The three-dimensional porous carbon is interposed between the MXene sheets, which can not only play a supporting role to prevent the MXene sheets from re-stacking due to hydrogen bonding and van der Waals forces, but also the porous skeleton structure of the three-dimensional porous carbon can provide more transfer paths for ions and charges, thereby improving the conductivity. In addition, sulfur and nitrogen heteroatoms are doped into MXene and three-dimensional porous carbon through the surfactant dodecyltrimethylammonium chloride and thiourea. Since dodecyltrimethylammonium chloride is a cationic surfactant, it can neutralize the negative charges on the surface of MXene, thus reducing the number of hydrogen bonds on the MXene sheets, and therefore can also slow down the re-stacking phenomenon between the MXene sheets. Moreover, sulfur and nitrogen co-doping can provide more active sites for the electrochemical reaction and improve the conductivity of the composite material. The conductivity, specific capacity, cycle stability, energy density and power density of the anode material for a sodium-ion battery prepared by the preparation method of the present invention are all greatly improved.

[0013] Preferably, in step S1, the mass ratio of MXene to dodecyltrimethylammonium chloride is (1.2 to 1.8):(1.8 to 2.5).

[0014] Preferably, in step S1, the concentration of the MXene aqueous solution is 32 - 35 mg / mL. -1 。

[0015] Preferably, in step S1, the stirring time is 1 - 3 h and the stirring rate is 500 - 800 rpm.

[0016] Preferably, in step S2, the mass ratio of three-dimensional porous carbon to thiourea is (1 to 1.5):(1.8 to 2.2).

[0017] Preferably, in step S2, the concentration of the three-dimensional porous carbon aqueous solution is (2.5 - 3.0) mg / mL. -1 。

[0018] Preferably, in step S2, the standing time is 2 - 5 h.

[0019] Preferably, in step S3, the freeze-drying temperature is -(30 - 45) °C and the time is 18 - 24 h.

[0020] The present invention also provides a sulfur and nitrogen co-doped MXene-3DPC anode material for a sodium-ion battery prepared by the above preparation method.

[0021] The present invention also provides an application of the above sulfur and nitrogen co-doped MXene-3DPC sodium ion battery anode material in a sodium ion battery.

[0022] The preparation method of the present invention has the characteristics of simplicity, high efficiency, low cost, environmental friendliness, etc. The sulfur and nitrogen co-doped MXene / 3DPC composite material prepared by the hydrothermal method has a high specific surface area and large pore size. When used as the anode of a sodium ion battery, it has a high capacitance, low internal resistance and excellent cycle stability. Description of the Drawings

[0023] Figure 1 SEM image of the sulfur and nitrogen co-doped MXene / 3DPC composite material prepared in Example 1;

[0024] Figure 2 Cyclic voltammogram of the sodium ion battery assembled with the sulfur and nitrogen co-doped MXene / 3DPC composite material prepared in Example 1 at 0.1 mV s -1 ;

[0025] Figure 3 Rate performance test chart of the sodium ion battery assembled with the sulfur and nitrogen co-doped MXene / 3DPC composite material prepared in Example 1. Detailed Embodiments

[0026] The following is a further description of the present invention in conjunction with specific embodiments. It should be understood that the implementation of the present invention is not limited to the following examples, and any formal modification or change based on the present invention will fall within the scope of the present invention.

[0027] In the present invention, the equipment and raw materials used can be purchased from the market or are commonly used in the art. The following are the main reagents used in the examples:

[0028] Table 1 Sources of Main Reagents

[0029]

[0030] The MXene aqueous solution used in the following examples was prepared by etching Ti with hydrofluoric acid 3 AlC 2 (200 mesh) and then ultrasonically dispersed; 3DPC was prepared using sodium chloride as a template and citric acid as a carbon source through dissolution, freeze-drying, high-temperature calcination, washing and drying.

[0031] Example 1:

[0032] Prepare the sulfur and nitrogen co-doped MXene / 3DPC sodium ion battery anode material according to the following steps:

[0033] S1: Add 4 mL of a solution with a concentration of 33 mg mL-1 Add 200 mg of dodecyltrimethylammonium chloride powder to the single-layer or few-layer MXene aqueous solution and stir at room temperature for 2 h at a stirring rate of 650 rpm.

[0034] S2: Add 200 mg of thiourea powder to 40 mL of 3DPC aqueous solution with a concentration of 2.6 mg mL -1 and let it stand at room temperature for 2.5 h.

[0035] S3: Mix the mixtures obtained in steps S1 and S2, then carry out a hydrothermal reaction at 120 °C for 6 h, and finally freeze-dry at -40 °C for 24 h to obtain the sulfur and nitrogen co-doped MXene / 3DPC anode material for sodium-ion batteries.

[0036] Example 2:

[0037] Prepare the sulfur and nitrogen co-doped MXene / 3DPC anode material for sodium-ion batteries according to the following steps:

[0038] S1: Add 250 mg of dodecyltrimethylammonium chloride powder to 4 mL of single-layer or few-layer MXene aqueous solution with a concentration of 35 mg mL -1 and stir at room temperature for 3 h at a stirring rate of 800 rpm.

[0039] S2: Add 180 mg of thiourea powder to 40 mL of 3DPC aqueous solution with a concentration of 2.5 mg mL -1 and let it stand at room temperature for 2 h.

[0040] S3: Mix the mixtures obtained in steps S1 and S2, then carry out a hydrothermal reaction at 125 °C for 6 h, and finally freeze-dry at -40 °C for 24 h to obtain the sulfur and nitrogen co-doped MXene / 3DPC anode material for sodium-ion batteries.

[0041] Example 3:

[0042] Prepare the sulfur and nitrogen co-doped MXene / 3DPC anode material for sodium-ion batteries according to the following steps:

[0043] S1: Add 250 mg of dodecyltrimethylammonium chloride powder to 5 mL of single-layer or few-layer MXene aqueous solution with a concentration of 32 mg mL -1 and stir at room temperature for 1 h at a stirring rate of 500 rpm.

[0044] S2: Add 220 mg of thiourea powder to 50 mL of 3DPC aqueous solution with a concentration of 3.0 mg mL -1 and let it stand at room temperature for 4 h.

[0045] S3: Mix the mixtures obtained in Steps S1 and S2, then conduct a hydrothermal reaction at 115 °C for 5 h, and finally conduct freeze-drying at -45 °C for 18 h to obtain the sulfur and nitrogen co-doped MXene / 3DPC sodium-ion battery anode material.

[0046] Example 4:

[0047] Prepare the sulfur and nitrogen co-doped MXene / 3DPC sodium-ion battery anode material according to the following steps:

[0048] S1: Add 200 mg of dodecyltrimethylammonium chloride powder to 4 mL of monolayer or few-layer MXene aqueous solution with a concentration of 33 mg mL -1 and stir at room temperature for 2 h at a stirring rate of 650 rpm.

[0049] S2: Add 220 mg of thiourea powder to 50 mL of 3DPC aqueous solution with a concentration of 2.6 mg mL -1 and let it stand at room temperature for 5 h.

[0050] S3: Mix the mixtures described in Steps S1 and S2, then conduct a hydrothermal reaction at 130 °C for 6 h, and finally conduct freeze-drying at -30 °C for 24 h to obtain the sulfur and nitrogen co-doped MXene / 3DPC sodium-ion battery anode material.

[0051] Test result analysis:

[0052] The summary of the discharge capacity and cycle life data of each example is shown in Table 2:

[0053] Table 2 Discharge capacity and cycle life data table of each example

[0054] Name Discharge Capacity (Current Density) Cycle Life (Current Density, Number of Cycles) Example 1 <![CDATA[309.7mAh g -1 (0.2Ag -1 )]]> <![CDATA[240mAh g -1 (2Ag -1 , 1000 turns)]]> Example 2 <![CDATA[303.5mAh g -1 (0.2A g -1 )]]> <![CDATA[235.9mAh g -1 (2A g -1 , 200 turns)]]> Example 3 <![CDATA[303.5mAh g -1 (0.2A g -1 )]]> <![CDATA[238.8mAh g -1 (2A g -1 , 200 turns)]]> Example 4 <![CDATA[307.8mAh g -1 (0.2Ag -1 )]]> <![CDATA[238mAh g -1 (2Ag -1 , 200 turns)]]>

[0055] In the above examples, Example 1 is the best example. The sulfur and nitrogen co-doped MXene / 3DPC sodium-ion battery anode material prepared in Example 1 is tested and analyzed. From Figure 1 the SEM images, it can be observed that 3DPC plays a supporting role, and the sulfur and nitrogen co-doped MXene / 3DPC has a three-dimensional interconnected porous structure, which is helpful for the transfer and storage of ions and charges.

[0056] Using the sulfur and nitrogen co-doped MXene / 3DPC sodium-ion battery anode material prepared in Example 1 as the anode to assemble a sodium-ion battery, and conducting cyclic voltammetry tests at 0.1 mV s -1 , the cyclic voltammetry curve as shown in Figure 2 is obtained. From Figure 2 it can be seen that the shapes of the cyclic voltammetry curves of each cycle basically remain unchanged, indicating that the electrode material has good rate performance.

[0057] From Figure 3 the rate performance test chart of the sodium-ion battery, it can be seen that in the first 50 cycles, the specific capacity of the sulfur and nitrogen co-doped MXene / 3DPC sodium-ion battery anode material decreases with the increase of the current density. At the 51st cycle, the current density returns to 0.2 Ag -1 , and the specific capacity of sulfur and nitrogen co-doped MXene / 3DPC is 94% of the capacity at the 10th cycle, indicating that this material has good rate performance and cycle stability.

[0058] The above performance data show that 3DPC with a porous framework structure plays a supporting role for MXene, thus alleviating the phenomenon of MXene re-agglomeration during the cyclic charge and discharge process. The three-dimensional porous structure of the porous carbon provides more paths for the transfer of ions and charges, increasing the conductivity of the electrode material. In addition, sulfur and nitrogen co-doping also provides more reaction sites for the electrochemical reaction, improving the electrochemical performance. Therefore, it can be proved from the test results that the sulfur and nitrogen co-doped MXene / 3DPC sodium-ion battery anode material prepared in Example 1 has a large specific surface area, a high specific capacity (at a current density of 0.2 Ag -1 , the first discharge capacity is as high as 787 mAh g -1 ) and good cycle stability (after 1000 cycles of charge and discharge at a current density of 2 Ag -1 , the capacity retention rate is about 75%).

[0059] Performance comparison:

[0060] The sulfur and nitrogen co-doped MXene / 3DPC sodium-ion battery anode material prepared in this application is compared with the existing sodium-ion battery anode materials in terms of performance, as shown in Table 3:

[0061] Table 3 Performance comparison of sodium-ion battery anode materials

[0062]

[0063] Note: References:

[0064] (1) Yuting Wu, Ping Nie, Jiang Wang, Hui Dou, Xiaogang Zhang*, Few-Layer MXenes

[0065] Delaminated via High-Energy Mechanical Milling for Enhanced Sodium-Ion Batteries

[0066] Performance, ACS Appl. Mater. Interfaces 2017, 9, 45, 39610–39617.

[0067] (2) Feng Wu, Ying Jiang, Zhengqing Ye, Yongxin Huang, Ziheng Wang, Shuaijie Li, Yang

[0068] Mei, Man Xie, Renjie Chen, A 3D flowe-like VO 2 / MXene hybrid architecture with

[0069] superior anode performance for sodium ion batteries, J. Mater. Chem. A, 2019, 7, 1315 - 1322.

[0070] (3) Chengkui Lv, Linlin Tai, Xiao Li, Xiaowei Miao, Huaixin Wei, Jun Yang, Hongbo Geng, Interfacial covalent bonding of the MXene-stabilized Sb2Se3 nanotube hybrid with fast

[0071] ion transport for enhance sodium-ion half / full batteries, Chem. Commun. 2023.

[0072] (4) Guoxia Lv, Jing Wang, Zhiqiang Shi, Liping Fan, Intercalation and delamination of two

[0073] dimensional MXene(Ti 3 C 2 T x ) and application in sodium-ion batteries, Matter Letters, 2018, 219, 45 - 50.

[0074] (5)Xin Guo,Jinqiang Zhang,Jianjun Song,Wenjian Wu,Hao Liu,GuoxiuWang,MXene

[0075] encapsulated titanium oxide nanospheres for ultra-stable and fastsodium storage,Energy

[0076] Storage Materials,2018,14,306-313.

[0077] From the performance comparison of each negative electrode material of the sodium-ion battery in the above table, it can be seen that compared with other negative electrode materials of the sodium-ion battery, the sulfur and nitrogen co-doped MXene / 3DPC sodium-ion battery negative electrode material prepared in this application has a higher specific capacity and good cycle stability. The addition of three-dimensional porous carbon can provide a supporting effect for MXene to relieve the re-stacking of MXene during the charge and discharge process, improve the conductivity and cycle stability of the electrode material. In addition, sulfur and nitrogen co-doping can provide more reaction sites for the electrochemical reaction, increasing the capacity of the electrode material.

[0078] The present invention is not limited to the applications listed in the specification and embodiments, and it can be fully applied to various fields suitable for the present invention. Without departing from the spirit and essence of the present invention, for those familiar with the field, additional modifications and deformations can be easily achieved, but these corresponding modifications and deformations should all fall within the protection scope required by the present invention.

[0079] The above are only partial embodiments of the present invention, and thus do not limit the implementation manners and protection scope of the present invention. For those skilled in the art, it should be realized that the equivalent replacements and obvious changes made by using the content of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. Preparation method of sulfur and nitrogen co-doped MXene-3DPC sodium ion battery anode material, Characterized in that: It includes the following steps: S1: Add dodecyl trimethyl ammonium chloride powder to the single-layer or few-layer MXene aqueous solution and stir at room temperature until a uniform mixture is formed; S2: Add thiourea powder to the three-dimensional porous carbon aqueous solution and let it stand at room temperature until all the thiourea is dissolved to form a uniform mixture; S3: Mix the mixtures obtained in steps S1 and S2, then carry out hydrothermal reaction at 115-130 °C for 5-7 h, and then freeze-dry the product to obtain the sulfur and nitrogen co-doped MXene-3DPC sodium ion battery anode material.

2. The preparation method according to claim 1, Characterized in that: In step S1, the mass ratio of MXene to dodecyl trimethyl ammonium chloride is (1.2-1.8):(1.8-2.5).

3. The preparation method according to claim 1, Characterized in that: In step S1, the concentration of the MXene aqueous solution is 32 to 35 mg / mL -1 .

4. The preparation method according to claim 1, Characterized in that: In step S1, the stirring time is 1-3 h and the stirring rate is 500-800 rpm.

5. The preparation method according to claim 1, Characterized in that: In step S2, the mass ratio of three-dimensional porous carbon to thiourea is (1-1.5):(1.8-2.2).

6. The preparation method according to claim 1, Characterized in that: In step S2, the concentration of the three-dimensional porous carbohydrate solution is (2.5 - 3.0) mg / mL -1 .

7. The preparation method according to claim 1, Characterized in that: In step S2, the standing time is 2-5 h.

8. The preparation method according to claim 1, Characterized in that: In step S3, the freeze-drying temperature is -(30-45) °C and the time is 18-24 h.

9. A sulfur and nitrogen co-doped MXene-3DPC sodium ion battery anode material, Characterized in that: It is prepared by using the preparation method described in any one of claims 1-8.

10. A sodium ion battery, Characterized in that: Its anode material is prepared by using the preparation method described in any one of claims 1-8.

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