A preparation method of a sodium-ion battery hard carbon negative electrode suitable for high initial efficiency and super-high specific capacity

Abstract

The application discloses a preparation method of a hard carbon negative electrode of a sodium ion battery suitable for high initial efficiency and super-high specific capacity. The method comprises the following steps: taking a carbon-containing material as a hard carbon precursor, and performing pre-oxidation treatment on the hard carbon precursor through a muffle furnace; adding a nitrogen-containing doping source into the hard carbon precursor, and placing the hard carbon precursor into a vacuum tube furnace containing a protective atmosphere to perform calcination pyrolysis and natural cooling. The application adopts the carbon-containing material as the precursor, adds the nitrogen-containing doping source to prepare nitrogen-doped hard carbon powder through high-temperature pyrolysis, and obtains a self-supporting structure electrode material by compounding the nitrogen-doped hard carbon powder with MXene, so that the space and mass energy densities of the electrode are greatly improved. The MXene on the surface is not only excellent in conductivity and electrochemical stability, but also can effectively block the destruction of electrolyte to the surface structure of the hard carbon, so that the initial charge-discharge efficiency and reversible specific capacity of the hard carbon negative electrode material are greatly improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of electrochemical energy sources, in particular to a preparation method of a hard carbon negative electrode of a sodium ion battery suitable for high initial efficiency and super-high specific capacity. BACKGROUND

[0002] Lithium ion batteries are widely used in portable electronic devices and power batteries and the like due to their high energy density, good cycle performance and environmental friendliness. However, the scarcity of lithium resources (0.0065% of the earth's crust) makes it increasingly difficult to meet the needs of the rapidly developing energy storage market, and the production cost is also high. It is worth noting that sodium resources are abundant (2.75% of the earth's crust) and widely distributed, and sodium ion batteries have similar working principles to lithium ion batteries and better low-temperature performance, excellent rate performance, cycle stability and higher safety, and are considered to be one of the most promising energy storage systems for large-scale application. The performance of sodium ion batteries mainly depends on the selection of electrode materials, electrolytes and the like. In particular, in the negative electrode material system, hard carbon has the advantages of high capacity, long cycle stability and easy preparation, and is the most promising type of sodium battery negative electrode for industrial application. However, compared with the commercialized graphite negative electrode of lithium ion batteries, hard carbon still faces the disadvantages of low initial coulomb efficiency and difficult to significantly improve the specific capacity, which to some extent restricts the commercial development process of high-energy-density sodium ion batteries.

[0003] Patent CN1422235A discloses preparing hard carbon materials by liquid-phase dehydration, washing and drying of resins and the like in an autoclave, high-temperature carbonization, which is a complicated process and difficult to realize industrial production. Patent CN103311519A discloses a composite hard carbon material prepared by crosslinking polymerization of pitch, crushing, grading and high-temperature carbonization, although the preparation process is simplified, there are still problems of low initial coulomb efficiency and limited capacity improvement. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of a hard carbon negative electrode of a sodium ion battery suitable for high initial efficiency and super-high specific capacity, to solve the technical problems proposed in the background.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0006] S1, taking a carbon-containing material as a hard carbon precursor, heating the hard carbon precursor to a preset heating temperature at a first preset heating rate by a muffle furnace, and heating to a preset heating time to perform pre-oxidation treatment on the hard carbon precursor;

[0007] S2, adding the pre-oxidized hard carbon precursor into a nitrogen-doped source and placing it into a vacuum tube furnace containing a protective atmosphere for multi-step calcination and pyrolysis, and naturally cooling to obtain a nitrogen-doped hard carbon powder;

[0008] S3, taking the MXene material as a precursor of a preparation solution, etching the MXene material by using an acid etching method, and preparing a MXene aqueous solution with a negative surface charge;

[0009] S4, treating the nitrogen-doped hard carbon powder by using a cationic surfactant solution to prepare a nitrogen-doped hard carbon powder aqueous solution with a positive surface charge;

[0010] S5, adding the nitrogen-doped hard carbon powder aqueous solution with a positive surface charge into the MXene aqueous solution with a negative surface charge, performing electrostatic self-assembly by using a probe to perform ultrasonic treatment for 5-10 min, performing filtration after the assembly is completed, and finally performing vacuum drying at 60°C to obtain a MXene-composite sodium-ion battery hard carbon negative electrode material.

[0011] Further, the specific steps of the step S2 are as follows:

[0012] S21, adding a hard carbon precursor into a nitrogen-doped source and placing it into a vacuum tube furnace containing a protective atmosphere;

[0013] S22, heating at a second preset heating rate to a first preset calcination temperature and calcining to a first preset calcination time;

[0014] S23, heating at a third preset heating rate to a second preset calcination temperature and calcining to a second preset calcination time, and then naturally cooling to room temperature to obtain the nitrogen-doped hard carbon powder.

[0015] Further, the ratio of the hard carbon precursor to the nitrogen-doped source is 9:1, the mass ratio of the MXene material to the nitrogen-doped hard carbon powder can be 1:0.05-20, the ratio of the MXene material to the acid is 1:6.57, and the ratio of the cationic surfactant solution to the nitrogen-doped hard carbon powder is 1:50.

[0016] Further, the first preset heating rate in the step S1 is preferably 1-5°C / min, the preset heating temperature is preferably 180-280°C, the heating time is preferably 0.1-10 h, and the carbon-containing material can be biomass-based, phenolic resin-based, or pitch-based.

[0017] Further, the biomass-based material can be glucose, sucrose, starch, lignin, or coconut shell, the phenolic resin-based material can be phenolic resin, epoxy resin, or polyfurfural alcohol, and the pitch-based material can be coal tar pitch, petroleum pitch, or natural pitch.

[0018] Further, the protective atmosphere in the step S2 is preferably nitrogen, argon, or a mixture of the two, the flow rate of the protective atmosphere gas in the vacuum tube furnace is 0.1-0.5 L / min, and the nitrogen-doped source can be urea, NH4Cl, melamine, or m-aminophenol.

[0019] Further, the second preset heating rate in the step S22 is preferably 0.5-10℃ / min, the first preset calcination temperature is preferably 600-1600℃, and the first preset calcination time is preferably 0.1-10h; the third preset heating rate in the step S23 is preferably 0.5-10℃ / min, the second preset calcination temperature is preferably 600-1600℃, and the second preset calcination time is preferably 0.1-10h.

[0020] Further, the acid in the acid etching method in the step S3 is preferably a mixture of LiF and HCL, wherein the mixing ratio of LiF and HCL is 1:6.57, the MXene material can be Ti3AlC2, Ti2AlC, the aqueous solution of MXene can be Ti3C2T x , Ti2CT x , TiNbCT x , Ti3CN x T x , Ta4C3T x , Nb2CT x , V2CT x , Nb4C3T x , Mo2CT x , (Nb 0.8 Ti 0.2 )4C3T x , (Nb 0.8 Zr 0.2 )4C3T x , Zr3C2T x and Hf3C2T x .

[0021] Further, the cationic surfactant in the step S4 is preferably hexadecyl trimethyl ammonium bromide (CTAB), octadecyl double ester quaternary ammonium salt, cetyl polyoxyethylene ether dimethyl octyl ammonium chloride, the concentration of the cationic surfactant solution is preferably 0.1-20mg / mL, and the treatment time of the surfactant solution is preferably 0.2-20h.

[0022] Further, the electrostatic self-assembly time in the step S5 is preferably 0.1-10h.

[0023] Beneficial effects:

[0024] 1、The application adopts carbon-containing material as hard carbon precursor to prepare nitrogen-doped hard carbon powder by adding nitrogen-containing doping source high-temperature pyrolysis, and is compounded with MXene to obtain a self-supporting structure electrode material, which avoids the use of current collector and greatly improves the space and mass energy density of the electrode. The MXene on the surface not only has excellent conductivity and electrochemical stability, but also can effectively block the destruction of the electrolyte to the surface structure of the hard carbon, especially benefiting from the suitable interlayer spacing of MXene, which can effectively screen the solvent molecules from co-embedding in the carbon layer, greatly improving the first charge-discharge efficiency and reversible specific capacity of the hard carbon negative electrode material.

[0025] 2、The preparation process of the application is simple, green and environmentally friendly without toxic solvents, the preparation method has high yield and low production cost, the product has stable properties, little difference between batches, good repeatability, is suitable for large-scale preparation, and the hard carbon precursor source is wide.

[0026] 3、The MXene used in the application is a two-dimensional material with excellent conductivity and electrochemical interface stability, and can effectively block the destruction of the electrolyte to the surface structure of the hard carbon, especially the suitable interlayer spacing which can effectively screen the solvent molecules from co-embedding in the carbon layer. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions implemented by the application, the following will briefly introduce the drawings needed to be used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0028] Figure 1 The scanning electron microscope graph of the electrode material Glu-1400 in the comparative example 1 of the application;

[0029] Figure 2 The scanning electron microscope graph of the electrode material NGlu-1400 in the comparative example 2 of the application;

[0030] Figure 3 The scanning electron microscope graph of the sodium ion battery hard carbon negative electrode material MNGlu-1400 of the application after the glucose precursor is treated by adding nitrogen-containing doping source and compounded with MXene;

[0031] Figure 4 The experimental data table of the comparative example 1 and the comparative example 2 of the application;

[0032] Figure 5 The first charge-discharge graph of the hard carbon negative electrode material of the comparative example 1, 2 of the application after being assembled into a button cell;

[0033] Figure 6The cycle performance diagram of the hard carbon negative electrode material of the embodiment 1, the comparative example 1 and the comparative example 2 after being assembled into a button cell is shown in the following figure. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0035] Please refer to Figures 1-6 The present application provides a preparation method of a hard carbon negative electrode for a sodium ion battery with high initial efficiency and super high specific capacity, and the specific steps are as follows:

[0036] Embodiment 1

[0037] S1, glucose is used as a hard carbon precursor, and the hard carbon precursor is pre-oxidized by heating to a preset heating temperature of 200℃ at a first preset heating rate of 2℃ / min in a muffle furnace and heating for a preset heating time of 10h.

[0038] S2, the pre-oxidized glucose precursor is added to urea and placed in a vacuum tube furnace containing argon for multi-step calcination and pyrolysis, and nitrogen-doped glucose-derived hard carbon powder is obtained by natural cooling; wherein the flow rate of the protective atmosphere gas in the vacuum tube furnace is 0.2L / min.

[0039] In order to further illustrate the implementation of step S2, the specific steps are as follows:

[0040] S21, 6.3g of glucose precursor is added to 0.7g of urea and placed in a vacuum tube furnace containing argon with a gas flow rate of 0.2L / min;

[0041] S22, heating to 600℃ at a rate of 5℃ / min and calcining for 2h;

[0042] S23, heating to 1400℃ at a rate of 2℃ / min and calcining for 0.5h, and then naturally cooling to room temperature to obtain nitrogen-doped glucose-derived hard carbon powder.

[0043] S3, 1g of Ti3AlC2 powder is used as a precursor for preparing a solution, and a mixture of 20ml of LiF and HCl is used to etch the Ti3AlC2 powder to prepare a Ti3C2T x aqueous solution with a mixing ratio of LiF to HCl of 1:6.57;

[0044] S4, prepare a surface positively charged nitrogen-doped glucose derivative hard carbon powder aqueous solution with a concentration of 5 mg / ml by treating nitrogen-doped glucose derivative hard carbon powder with 10 μl of 5 mg / ml cationic surfactant CTAB, and the CTAB treatment time is 2 h;

[0045] S5, add the nitrogen-doped glucose derivative hard carbon powder aqueous solution to 8.2 ml of Ti3C2T x aqueous solution, probe ultrasonic for 5-10 min, electrostatic self-assembly for 10 min, filter after assembly is completed, and finally vacuum drying at 60℃ to obtain a MXene composite sodium ion battery hard carbon negative electrode material, which is named as MNGlu-1400.

[0046] Example 2-4 is substantially the same as Example 1, and the specific differences are shown in the following table:

[0047]

[0048] Please refer to Figures 4-6 The present application has high initial coulombic efficiency, reversible capacity and excellent cycle performance. The glucose precursor is used as a hard carbon precursor, and the following comparative examples and experimental data are used to illustrate the application:

[0049] Comparative Example 1 is a hard carbon powder prepared from a glucose precursor without adding a nitrogen-doped source:

[0050] Put 6.3 g of glucose precursor into a vacuum tube furnace containing an argon protective atmosphere, the protective atmosphere gas flow in the vacuum tube furnace is 0.2 L / min, heat to 600℃ at a heating rate of 5℃ / min for 2 h, then heat to 1400℃ at a heating rate of 2℃ / min for 0.5 h, and naturally cool to room temperature to obtain a glucose derivative hard carbon powder, which is named as Glu-1400.

[0051] Comparative Example 2 is a hard carbon powder prepared from a glucose precursor with a nitrogen-doped source:

[0052] Put 6.3 g of glucose precursor into a vacuum tube furnace containing an argon protective atmosphere, the protective atmosphere gas flow in the vacuum tube furnace is 0.2 L / min, heat to 600℃ at a heating rate of 5℃ / min for 2 h, then heat to 1400℃ at a heating rate of 2℃ / min for 0.5 h, and naturally cool to room temperature to obtain a nitrogen-doped glucose derivative hard carbon powder, which is named as NGlu-1400.

[0053] Please refer to Figures 1-2 , Figure 1 is a scanning electron microscope image of the electrode material Glu-1400 in Comparative Example 1,Figure 2 For the scanning electron microscope graph of the electrode material NGlu-1400 in the comparative example 2, the electrode material Glu-1400 obtained in the comparative example 1 and the electrode material NGlu-1400 obtained in the comparative example 2 are respectively taken as the negative electrode material of the button cell, and the button cell is assembled. The first charge-discharge test is carried out under the current density of 0.1C and the voltage window of 0-3V, and the cycle performance is tested under the current density of 1C discharge and 5C charge, and the test results are as shown in Figure 4 The application adopts the method of adding the hard carbon precursor into the nitrogen-doped source and then pyrolyzing at high temperature to prepare the negative electrode material, and has high initial coulombic efficiency, reversible capacity and excellent cycle performance.

[0054] Figure 3 For the scanning electron microscope graph of the MXene-composite sodium ion battery hard carbon negative electrode material (MNGlu-1400), the electrode material (MNGlu-1400) obtained in the embodiment 1 is taken as the negative electrode material of the button cell, and the button cell is assembled. The first charge-discharge test is carried out under the current density of 0.1C and the voltage window of 0-3V, and the cycle performance is tested under the current density of 1C discharge and 5C charge, and the MXene-composite sodium ion battery hard carbon negative electrode material prepared by the application has high initial coulombic efficiency, reversible capacity and excellent cycle performance, as shown in Figure 4 The application has high initial coulombic efficiency, reversible capacity and excellent cycle performance, solves the core scientific problems of low first charge-discharge efficiency and low capacity of the sodium ion battery hard carbon negative electrode material, and is expected to lay a solid foundation for the wide application of the sodium ion battery. Figure 5 and Figure 6 The MXene-composite sodium ion battery hard carbon negative electrode material obtained by the preparation method provided by the application has high initial coulombic efficiency, reversible capacity and excellent cycle performance, solves the core scientific problems of low first charge-discharge efficiency and low capacity of the sodium ion battery hard carbon negative electrode material, and is expected to lay a solid foundation for the wide application of the sodium ion battery.

[0055] The application discloses a preparation method of a sodium ion battery hard carbon negative electrode suitable for high initial efficiency and super-high specific capacity. The MXene is a two-dimensional material, has excellent conductivity and electrochemical interface stability, and can effectively block the damage of the electrolyte to the surface structure of the hard carbon. In particular, the suitable interlayer spacing can effectively screen the solvent molecules from being co-embedded in the carbon layer. The application adopts the carbon-containing material as the hard carbon precursor, adds the nitrogen-doped source to pyrolyze at high temperature to prepare the nitrogen-doped hard carbon powder, and is combined with the MXene to obtain the three-dimensional MXene coating structure, which can effectively relieve the Na +The volume expansion caused by the insertion greatly improves the cycle stability of the electrode, and the structure is a self-supporting electrode material, avoiding the use of a current collector, greatly improving the space and mass energy density of the electrode, and the MXene on the surface is not only excellent in conductivity and electrochemical stability, but also can effectively block the destruction of the electrolyte to the surface structure of the hard carbon, especially benefiting from the suitable interlayer spacing of MXene, which can effectively screen the solvent molecules from co-embedding in the carbon layer, greatly improving the first charge and discharge efficiency and reversible specific capacity of the hard carbon negative electrode material.

[0056] Therefore, the MXene composite sodium ion battery hard carbon negative electrode material can effectively improve the electrode electrochemical stability and sodium storage capacity, while saving the use of negative electrode current collector, which is extremely beneficial to the design of high space and high mass energy density battery. The preparation process of the present application is simple, non-toxic solvent green and environmentally friendly, the preparation method has high yield and low production cost, the product properties are stable, there is little difference between batches, the repeatability is good, it is suitable for large-scale preparation, and the hard carbon precursor source is wide.

[0057] It is apparent to those skilled in the art that the present application is not limited to the details of the foregoing exemplary embodiments, and that the present application can be implemented in other particular forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, and the scope of the present application is defined by the appended claims rather than the foregoing description, and it is intended to encompass all changes falling within the meaning and range of equivalents of the essential elements of the claims. Any reference signs in the claims should not be considered as limiting the claims to which they relate.

[0058] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A method for preparing a sodium-ion battery hard carbon anode suitable for high initial efficiency and ultrahigh specific capacity, characterized in that, The method comprises the following steps: S1, the carbon-containing material is used as a hard carbon precursor, and the hard carbon precursor is pre-oxidized by a muffle furnace at a first preset heating rate to a preset heating temperature and heated for a preset heating time; S2, the pre-oxidized hard carbon precursor is added into a nitrogen-doped source and placed in a vacuum tube furnace containing a protective atmosphere for multi-step calcination pyrolysis, and a nitrogen-doped hard carbon powder is obtained by natural cooling; S3, the MXene material is used as a precursor of a preparation solution, and the MXene material is etched by an acid etching method to prepare a MXene aqueous solution with a negative surface charge; S4, the nitrogen-doped hard carbon powder is treated by a cationic surfactant solution to prepare a nitrogen-doped hard carbon powder aqueous solution with a positive surface charge; S5, the nitrogen-doped hard carbon powder aqueous solution with a positive surface charge is added into the MXene aqueous solution with a negative surface charge, and electrostatic self-assembly is performed by probe ultrasonic for 5-10 min, and then the assembly is filtered and vacuum dried at 60°C to obtain a MXene-composite sodium-ion battery hard carbon negative electrode material.

2. The method for preparing a hard carbon anode for a sodium-ion battery according to claim 1, characterized in that, The specific steps of step S2 are as follows: S21, the hard carbon precursor is added into a nitrogen-doped source and placed in a vacuum tube furnace containing a protective atmosphere; S22, a second preset heating rate is used to heat to a first preset calcination temperature, and the first preset calcination temperature is calcined for a first preset calcination time; S23, a third preset heating rate is used to heat to a second preset calcination temperature, and the second preset calcination temperature is calcined for a second preset calcination time, and the nitrogen-doped hard carbon powder is obtained by natural cooling to room temperature.

3. The method for preparing a hard carbon anode for a sodium-ion battery according to claim 1, characterized in that: The ratio of the hard carbon precursor to the nitrogen-doped source is 9:1, the mass ratio of the MXene material to the nitrogen-doped hard carbon powder is 1:0.05-20, the ratio of the MXene material to the acid is 1:6.57, and the ratio of the cationic surfactant solution to the nitrogen-doped hard carbon powder is 1:

50.

4. The method for preparing a hard carbon anode for a sodium-ion battery according to claim 1, characterized in that: The first preset heating rate in step S1 is 1-5°C / min, the preset heating temperature is 180-280°C, the heating time is 0.1-10 h, and the carbon-containing material is biomass-based, phenolic resin-based, or pitch-based.

5. The method for preparing a hard carbon anode for a sodium-ion battery according to claim 4, characterized in that: The biomass-based material is glucose, sucrose, starch, lignin, or coconut shell, the phenolic resin-based material is phenolic resin, epoxy resin, or polyfurfural alcohol, and the pitch-based material is coal tar pitch, petroleum pitch, or natural pitch.

6. The method for preparing a hard carbon anode for a sodium-ion battery according to claim 1, characterized in that: The protective atmosphere in step S2 is nitrogen, argon, or a mixture of the two, the protective atmosphere gas flow in the vacuum tube furnace is 0.1-0.5 L / min, and the nitrogen-doped source is urea, NH4Cl, melamine, or m-aminophenol.

7. The method for preparing a hard carbon anode for a sodium-ion battery according to claim 2, characterized in that: The second preset heating rate in step S22 is 0.5-10°C / min, the first preset calcination temperature is 600-1600°C, and the first preset calcination time is 0.1-10 h. The third preset heating rate in step S23 is 0.5-10°C / min, the second preset calcination temperature is 600-1600°C, and the second preset calcination time is 0.1-10 h.

8. The method for preparing a hard carbon anode for a sodium-ion battery according to claim 1, characterized in that: The acid in the acid etching method in the step S3 is a mixture of LiF and HCL, wherein the mixing ratio of LiF and HCL is 1:6.57, the MXene material is Ti3AlC2, Ti2AlC, the aqueous solution of MXene is Ti3C2T x , Ti2CT x , TiNbCT x , Ti3CN x T x , Ta4C3T x , Nb2CT x , V2CT x , Nb4C3T x , Mo2CT x , (Nb 0.8 Ti 0.2 )4C3T x , (Nb 0.8 Zr 0.2 )4C3T x , Zr3C2T x and Hf3C2T x .

9. The method for preparing a hard carbon anode for a sodium-ion battery according to claim 1, characterized in that: The cationic surfactant in the step S4 is cetyl trimethyl ammonium bromide (CTAB), octadecyl double ester quaternary ammonium salt, cetyl alcohol polyoxyethylene ether dimethyl octyl ammonium chloride, and the concentration of the cationic surfactant solution is 0.1-20 mg / mL, and the time for treating the active agent solution is 0.2-20 h.

10. The method for preparing a hard carbon anode for a sodium-ion battery according to claim 1, characterized in that: The electrostatic self-assembly time in the step S5 is 0.1-10 h.

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