Asphalt-based hard carbon negative electrode material and preparation method and application thereof

Abstract

The invention provides an asphalt-based hard carbon negative electrode material as well as a preparation method and application thereof, belongs to the technical field of battery materials, and is used for solving the technical problems that a template is non-uniformly distributed in a carbon source and the size is difficult to control in hard carbon preparation. The preparation method of the asphalt-based hard carbon negative electrode material comprises the following steps: mixing asphalt and organic zinc salt, and then carrying out heat treatment to obtain high-softening-point asphalt; and pre-oxidizing and carbonizing the high-softening-point asphalt to obtain the asphalt-based hard carbon negative electrode material. Organic zinc salt and asphalt form a metal template in situ at a high temperature, the metal template can be uniformly distributed in the asphalt, meanwhile, the particle size of the template is controlled through process change, and the prepared asphalt-based hard carbon negative electrode material has high reversible specific capacity, high initial coulombic efficiency and good rate capability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery materials, and particularly relates to a pitch-based hard carbon negative material. BACKGROUND

[0002] With the continuous rise of energy storage demand, sodium-ion batteries rely on sodium resources in the earth's crust, which is cheaper than lithium, and are considered to be the most competitive alternative to lithium-ion batteries, but the lower energy density restricts its industrial application. At present, hard carbon has become the most promising negative material for sodium-ion batteries. However, the existing hard carbon has the problems of low initial coulombic efficiency (ICE), poor rate / cycle performance, low reversible capacity, high cost and the like to different extents. Therefore, it is urgent to develop a hard carbon negative material with high reversible capacity and high initial efficiency.

[0003] At present, the initial efficiency and reversible capacity of sodium-ion hard carbon are mainly regulated by controlling the microcrystalline sequence and micropore configuration of the hard carbon. The methods mainly include pore construction and oxidation cross-linking strategies, and the pore construction strategy mainly adopts a template method. For example, patent CN115353090A uses shell calcium carbonate as a template and uses food residue as a carbon source to prepare a hard carbon negative material. In this patent, the particle size and distribution of the template in the carbon source are not considered, and a strong acid solvent is used, which pollutes the environment and the preparation process is complicated and time-consuming. Patent CN119297223A considers environmental pollution and uses water-soluble templates such as NaCl, KCl and Na2SO4, but does not consider the distribution of the template in the pitch. At the same time, with the removal of the template, the specific surface area of the material increases, which leads to an increase in the irreversible capacity of the material and a decrease in the initial efficiency. For another example, patent CN119263259A discloses a pitch-based hard carbon microsphere, a preparation method thereof and a sodium-ion battery. The preparation method comprises the following steps: S1, stirring and reacting pitch and basic zinc carbonate microspheres in a solvent to obtain a pitch-based carbon microsphere precursor; S2, mixing the pitch-based carbon microsphere precursor with a metal salt modifier to obtain a modified pitch-based carbon microsphere precursor; the metal salt modifier is a zinc salt, a magnesium salt or a calcium salt; S3, annealing and carbonizing the modified pitch-based carbon microsphere precursor; and S4, performing acid washing, water washing and drying treatment on the carbonized product to obtain a pitch-based hard carbon microsphere. The patent adds a soluble zinc salt or carbonate as an exogenous template, and then removes the template by strong acid, which is destructive and easy to cause the structure of the carbon material to collapse or generate impurities. SUMMARY

[0004] In view of the technical problems that the template is unevenly distributed in the carbon source and the size is difficult to control in the preparation of the hard carbon, the application provides a pitch-based hard carbon negative material, a preparation method thereof and an application. An organic zinc salt and pitch form a metal template in situ at high temperature, which can be uniformly distributed in the pitch, and the size of the template is controlled through a process change.

[0005] To achieve the above object, the technical scheme of the present application is as follows:

[0006] A preparation method of a pitch-based hard carbon negative electrode material and application thereof, comprising the following steps:

[0007] S1: mixing pitch and organic zinc salt at different mass ratios, then adding into a reaction kettle, and performing heat treatment under air atmosphere to obtain high-softening-point pitch;

[0008] S2: obtaining pitch-based hard carbon negative electrode material by pre-oxidation and carbonization of the high-softening-point pitch obtained in S1

[0009] The organic zinc salt in S1 is any one or combination of zinc oleate, zinc acetate, zinc hexanoate and zinc gluconate, and the pitch is coal pitch or petroleum pitch, including but not limited to any one or combination of medium-low temperature coal pitch, high temperature coal pitch, coal tar and petroleum pitch.

[0010] The organic zinc salt (such as zinc oleate, zinc acetate, zinc gluconate, etc.) has high solubility / melting degree with the pitch system, can participate in the softening and thermal reaction process, belongs to the system internal reaction type structure directing agent, is different from inert added particles such as zinc carbonate or inorganic zinc salt, does not react with the pitch, and can only be used as an "externally mixed mixed template", and needs to be washed out by a strong acid after carbonization.

[0011] The mass ratio of the pitch to the organic zinc salt in S1 is 1-36:6.

[0012] The reaction temperature of the reaction kettle in S1 is 250-360 DEG C, the reaction time is 2-8 h, and the heating rate is 2-5 DEG C / min.

[0013] The heat treatment in S1 decomposes the organic zinc salt to generate ZnO nanoparticles as metal nano-templates, and the metal nano-templates are uniformly embedded into the carbon skeleton, and the diameter of the in-situ generated metal nano-templates is 2-30 nm. The ZnO particle size can be controlled by the type, proportion and heating rate of the zinc salt,

[0014] The pre-oxidation temperature in S2 is 280-350 DEG C, the pre-oxidation time is 2-10 h, and the heating rate is 2-5 DEG C / min.

[0015] The carbonization in S2 is performed in an inert gas, the gas flow rate is 5-25 mL / min.g; the inert gas is high-purity nitrogen or high-purity argon, the carbonization temperature is 1100-1500 DEG C, the time is 1-5 h, and the heating rate is 2-5 DEG C / min.

[0016] The ZnO nano template is reduced to zinc and carbon monoxide gas in the carbonization process, the boiling point of zinc is about 907 DEG C, which will be converted into zinc vapor to escape at high temperature; or the local zinc concentration is too high, which may form zinc particles, and is naturally discharged with the airflow.

[0017] The particle size of the pitch-based hard carbon negative material is 5-50 mu m, and the specific surface area is less than or equal to 15 m 2 / g.

[0018] The pitch-based hard carbon negative material has a closed pore diameter range of 0.1-2.0 nm, and the closed pore volume ratio is 10-50%. ZnO as a structure template determines the degree of micropore closure, interlayer pore diameter and specific surface area.

[0019] The pitch-based hard carbon negative material has excellent reversible specific capacity and first coulombic efficiency in the application of sodium ion battery negative material.

[0020] The beneficial effects of the present application are:

[0021] (1) The pitch-based hard carbon negative material in the present application has simple and easy synthesis steps, and the particle size and distribution of metal nano-oxide can be controlled according to the process conditions, which has the advantages of simple and feasible process.

[0022] (2) The organic zinc salt is dissolved in pitch, and the metal nanoparticles are formed in situ at high temperature, and the metal oxide is uniformly distributed in the pitch as a template. This process solves the problem of uneven distribution of traditional templates in pitch, thereby avoiding the decline of electrochemical performance caused by uneven material structure. In this way, the reversible specific capacity and the first coulombic efficiency of the sodium battery hard carbon are significantly improved.

[0023] (3) The pitch-based hard carbon negative material in the present application is used in sodium ion battery negative material, and the in-situ formed template compared with the directly added template, the reversible capacity of the prepared negative material is obviously improved by 100-200 mAh / g, and the first coulombic efficiency is improved by 5-8%. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description, and obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of these drawings.

[0025] Figure 1 The SEM image of the pitch-based hard carbon negative material prepared in Example 1.

[0026] Figure 2HREM image of the pitch-based hard carbon anode material prepared in Example 1.

[0027] Figure 3 SAXS image of the pitch-based hard carbon anode material prepared in Example 1. DETAILED DESCRIPTION

[0028] 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 of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0029] Example 1

[0030] A pitch-based hard carbon anode material, and the preparation method steps thereof are as follows:

[0031] S1: After the pitch and zinc oleate are uniformly mixed according to a mass ratio of 1:3, the mixture is put into a reaction kettle, air is introduced, the temperature is raised to 300°C and kept for 6 hours, and then the temperature is naturally lowered to room temperature, and finally the zinc oxide with a particle size of about 5 nm is uniformly dispersed in the high softening point pitch.

[0032] S2: The sample in S1 is heated to 320°C at a heating rate of 3°C / min under an air gas atmosphere, and then lowered to room temperature after keeping for 6 hours. Then the sample is heated to 1300°C at a heating rate of 3°C / min under the protection of inert gas nitrogen, and then naturally lowered to room temperature after keeping for 2 hours, and finally the pitch-based hard carbon anode material is obtained.

[0033] Figure 1 SEM image of the pitch-based hard carbon anode material prepared in Example 1. It can be seen from the figure that the particle size of the hard carbon is uniform, and is between 10-30 μm.

[0034] Figure 2 HREM image of the pitch-based hard carbon anode material prepared in Example 1. It can be seen from the figure that the closed pore structure is uniformly distributed, and the closed pore diameter is less than 2 nm.

[0035] Figure 3 SAXS image of the pitch-based hard carbon anode material prepared in Example 1. A platform appears in the figure, indicating the existence of the closed pore structure, which is consistent with the result obtained by HRTEM.

[0036] Example 2

[0037] A pitch-based hard carbon anode material, and the preparation method steps thereof are as follows:

[0038] S1: the asphalt and zinc oleate are mixed uniformly at a mass ratio of 1:5, then put into a reaction kettle, air is introduced, the temperature is raised to 300 DEG C and kept for 6 hours, then naturally cooled to room temperature, finally the zinc oxide high softening point asphalt with particle size of about 10 nm is obtained.

[0039] S2: the sample in S1 is heated to 320 DEG C at a heating rate of 3 DEG C / min under air atmosphere, kept for 6 hours and then cooled to room temperature, then the sample is heated to 1300 DEG C at a heating rate of 3 DEG C / min under the protection of inert gas nitrogen, kept for 2 hours and then naturally cooled to room temperature, the asphalt-based hard carbon negative material is obtained.

[0040] Example 3

[0041] An asphalt-based hard carbon negative material, the preparation method steps are as follows:

[0042] S1: the asphalt and zinc oleate are mixed uniformly at a mass ratio of 1:5, then put into a reaction kettle, air is introduced, the temperature is raised to 320 DEG C and kept for 6 hours, then naturally cooled to room temperature, finally the zinc oxide high softening point asphalt with particle size of about 12 nm is obtained.

[0043] S2: the sample in S1 is heated to 340 DEG C at a heating rate of 3 DEG C / min under air atmosphere, kept for 4 hours and then cooled to room temperature, then the sample is heated to 1300 DEG C at a heating rate of 3 DEG C / min under the protection of inert gas nitrogen, kept for 4 hours and then naturally cooled to room temperature, the asphalt-based hard carbon negative material is obtained.

[0044] Example 4

[0045] An asphalt-based hard carbon negative material, the preparation method steps are as follows:

[0046] S1: the asphalt and zinc oleate are mixed uniformly at a mass ratio of 1:5, then put into a reaction kettle, air is introduced, the temperature is raised to 360 DEG C and kept for 4 hours, then naturally cooled to room temperature, finally the zinc oxide high softening point asphalt with particle size of about 15 nm is obtained.

[0047] S2: the sample in S1 is heated to 360 DEG C at a heating rate of 5 DEG C / min under air atmosphere, kept for 2 hours and then cooled to room temperature, then the sample is heated to 1500 DEG C at a heating rate of 5 DEG C / min under the protection of inert gas nitrogen, kept for 2 hours and then naturally cooled to room temperature, the asphalt-based hard carbon negative material is obtained.

[0048] Example 5

[0049] An asphalt-based hard carbon negative material, the preparation method steps are as follows:

[0050] S1: The asphalt and zinc acetate are mixed uniformly at a mass ratio of 1:5, then put into a reaction kettle, air is introduced, the temperature is raised to 280°C and kept for 6 hours, then naturally cooled to room temperature, finally the zinc oxide high softening point asphalt with particle size of about 9 nm is obtained.

[0051] S2: The sample in S1 is heated to 290°C at a heating rate of 5°C / min under air gas atmosphere, kept for 4h and then cooled to room temperature, then the sample is heated to 1400°C at a heating rate of 2°C / min under the protection of inert gas nitrogen, kept for 4h and then naturally cooled to room temperature, to obtain the asphalt-based hard carbon negative electrode material.

[0052] Example 6

[0053] An asphalt-based hard carbon negative electrode material, the preparation method steps are as follows:

[0054] S1: The asphalt and zinc acetate are mixed uniformly at a mass ratio of 1:5, then put into a reaction kettle, air is introduced, the temperature is raised to 280°C and kept for 6 hours, then naturally cooled to room temperature, finally the zinc oxide high softening point asphalt with particle size of about 9 nm is obtained.

[0055] S2: The sample in S1 is heated to 290°C at a heating rate of 5°C / min under air gas atmosphere, kept for 4h and then cooled to room temperature, then the sample is heated to 1400°C at a heating rate of 2°C / min under the protection of inert gas nitrogen, kept for 4h and then naturally cooled to room temperature, to obtain the asphalt-based hard carbon negative electrode material.

[0056] Table 1 Performance test results

[0057] Item Initial discharge capacity (mAh / g) Initial coulombic efficiency (%) Example 1 480 92.3 Example 2 467 90.1 Example 3 450 91.4 Example 4 470 88.9 Example 5 426 87.8 Example 6 397 89.3

[0058] Example 7

[0059] An asphalt-based hard carbon negative electrode material, the preparation method steps are as follows:

[0060] S1: The asphalt and zinc acetate are mixed uniformly at a mass ratio of 1:5, then put into a reaction kettle, air is introduced, the temperature is raised to 280°C and kept for 6 hours, then naturally cooled to room temperature, finally the zinc oxide high softening point asphalt with particle size of about 9 nm is obtained.

[0061] S2: The sample in S1 is heated to 290°C at a heating rate of 5°C / min under air gas atmosphere, kept for 4h and then cooled to room temperature, then the sample is heated to 1400°C at a heating rate of 2°C / min under the protection of inert gas nitrogen, kept for 4h and then naturally cooled to room temperature, to obtain the asphalt-based hard carbon negative electrode material.

[0062] Example 8

[0063] A pitch-based hard carbon negative electrode material, the preparation method steps of which are as follows:

[0064] S1: After the pitch and zinc oleate are uniformly mixed at a mass ratio of 1:1, the mixture is placed in a reaction kettle, air is introduced, the temperature is raised to 360 DEG C and kept for 6 hours, and then the temperature is naturally lowered to room temperature, finally obtaining high-softening-point pitch.

[0065] S2: The sample in S1 is heated to 250 DEG C at a heating rate of 3 DEG C / min under an air gas atmosphere, kept for 5 hours, and then lowered to room temperature, and then the sample is heated to 1200 DEG C at a heating rate of 3 DEG C / min under the protection of inert gas nitrogen, kept for 2 hours, and then naturally lowered to room temperature, obtaining a pitch-based hard carbon negative electrode material.

[0066] Example 9

[0067] A pitch-based hard carbon negative electrode material, the preparation method steps of which are as follows:

[0068] S1: After the pitch and zinc acetate are uniformly mixed at a mass ratio of 1:1, the mixture is placed in a reaction kettle, air is introduced, the temperature is raised to 360 DEG C and kept for 6 hours, and then the temperature is naturally lowered to room temperature, finally obtaining high-softening-point pitch.

[0069] S2: The sample in S1 is heated to 250 DEG C at a heating rate of 3 DEG C / min under an air gas atmosphere, kept for 5 hours, and then lowered to room temperature, and then the sample is heated to 1200 DEG C at a heating rate of 3 DEG C / min under the protection of inert gas nitrogen, kept for 2 hours, and then naturally lowered to room temperature, obtaining a pitch-based hard carbon negative electrode material.

[0070] Example 10

[0071] A pitch-based hard carbon negative electrode material, the preparation method steps of which are as follows:

[0072] S1: After the pitch and zinc gluconate are uniformly mixed at a mass ratio of 1:4, the mixture is placed in a reaction kettle, air is introduced, the temperature is raised to 300 DEG C and kept for 5 hours, and then the temperature is naturally lowered to room temperature, finally obtaining high-softening-point pitch.

[0073] S2: The sample in S1 is heated to 280 DEG C at a heating rate of 3 DEG C / min under an air gas atmosphere, kept for 10 hours, and then lowered to room temperature, and then the sample is heated to 1500 DEG C at a heating rate of 3 DEG C / min under the protection of inert gas nitrogen, kept for 1 hour, and then naturally lowered to room temperature, obtaining a pitch-based hard carbon negative electrode material.

[0074] The above merely provides the preferred embodiment of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a pitch-based hard carbon negative electrode material, characterized by, The method comprises the following steps: (1) mixing pitch with organic zinc salt and then performing heat treatment to obtain high softening point pitch; (2) performing pre-oxidation and carbonization on the high softening point pitch to obtain pitch-based hard carbon negative electrode material.

2. The method for preparing the pitch-based hard carbon anode material according to claim 1, characterized in that, The organic zinc salt is any one or more than two of zinc oleate, zinc acetate, zinc hexanoate and zinc gluconate.

3. The method for preparing the pitch-based hard carbon anode material according to claim 1, characterized in that, The pitch is coal pitch or petroleum pitch.

4. The method for preparing the pitch-based hard carbon anode material according to claim 2, characterized in that, The mass ratio of the pitch to the organic zinc salt is 1-36:

6.

5. The method for preparing the pitch-based hard carbon anode material according to claim 3, characterized in that, The heat treatment is performed in air atmosphere at a temperature of 250-360 DEG C for 2-8 h.

6. The process for the preparation of pitch-based hard carbon negative material according to any one of claims 1-4, characterized in that, The pre-oxidation is performed at a temperature of 280-350 DEG C for 2-10 h.

7. The method for preparing the pitch-based hard carbon anode material according to claim 5, characterized in that, The carbonization is performed at a temperature of 1100-1500 DEG C for 1-5 h.

8. The pitch-based hard carbon negative electrode material prepared by the method of any one of claims 1-6.

9. The pitch-based hard carbon negative electrode material according to claim 8, characterized in that, The particle size of the pitch-based hard carbon electrode material is 5-50 μm, the specific surface area is ≤15 m 2 / g, the pitch-based hard carbon electrode material has a closed pore diameter ranging from 0.1-2 nm, and the closed pore volume accounts for 10-50%.

10. Application of the pitch-based hard carbon negative electrode material of claim 8 or 9 in sodium ion battery.

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