Construction method of isomeric carbon negative electrode material based on coal blending process

Abstract

The invention discloses a construction method of an isomeric carbon negative electrode material based on a coal blending process, and belongs to the technical field of electrochemical energy storage materials. The method comprises the following steps: selection and pretreatment of coal types; matching coal types; coal mixing and pre-pyrolysis; carbonizing the mixed coal sample at high temperature; and post-processing and forming. According to the invention, anthracite and lignite are scientifically proportioned, and pretreatment, mixing pre-pyrolysis, high-temperature carbonization and post-treatment processes are combined, so that the microstructure of the hard carbon material is optimized, and the sodium storage performance is improved. The preparation method is simple in process, low in cost and suitable for large-scale industrial production, the prepared hard carbon negative electrode material shows excellent cycling stability and relatively high specific capacity, and the performance of the sodium ion battery is effectively improved. According to the invention, respective advantages of anthracite and lignite are fully utilized, a new path is opened up for research and development of the sodium ion battery negative electrode material, and the method has remarkable technical innovation and application value.

Description

Technical Field

[0001] The invention relates to a method for constructing a homogeneous carbon negative electrode material based on a coal blending process, and belongs to the technical field of electrochemical energy storage materials. Background Art

[0002] As a new generation of energy storage technology, sodium-ion batteries have received extensive attention and research in recent years. Among them, the selection of negative electrode materials has a crucial impact on the performance of sodium-ion batteries. Coal-based hard carbon materials are regarded as an important research direction for negative electrode materials of sodium-ion batteries because of their abundant resources, low preparation cost and high sodium storage capacity.

[0003] However, in practical applications, different types of coal have significant differences in structural evolution and carbonization product characteristics during pyrolysis, which has an important impact on the preparation and performance of hard carbon materials. Specifically:

[0004] Anthracite: This type of coal has a high fixed carbon content and low volatile matter, which enables it to form a relatively stable carbon structure during pyrolysis. However, the structure of anthracite is relatively dense, which is not conducive to the storage and diffusion of sodium ions, thus limiting its application in sodium ion battery negative electrode materials.

[0005] Lignite: Compared with anthracite, lignite has higher volatile matter and lower fixed carbon content. This makes lignite prone to structural changes during pyrolysis, forming looser carbonized products. These carbonized products usually show higher specific surface area and more active sites, which are conducive to the adsorption and storage of sodium ions. However, the carbonized products of lignite may have certain deficiencies in mechanical strength and stability.

[0006] In view of the above differences, how to prepare hard carbon materials with excellent sodium storage performance through scientific and reasonable coal blending and pyrolysis process optimization, fully combining the advantages of anthracite and lignite, has become an important topic in the current research on negative electrode materials for sodium ion batteries. Summary of the invention

[0007] In order to solve the problems existing in the background technology, the present invention provides a method for constructing isomeric carbon negative electrode materials based on a coal blending process.

[0008] To achieve the above object, the present invention adopts the following technical scheme: a method for constructing a homogeneous carbon negative electrode material based on a coal blending process, the method comprising the following steps:

[0009] S1: Selection and pretreatment of coal;

[0010] S101: selecting anthracite and lignite as raw materials;

[0011] S102: crushing the anthracite and lignite to less than 100 mesh;

[0012] S103: The pulverized anthracite and lignite are subjected to acid washing or alkali washing.

[0013] The acid washing or alkali washing in S103 uses an acid solution or an alkali solution with a concentration of 1% to 10%.

[0014] S2: coal type ratio;

[0015] The coal ratio in S2 is anthracite to lignite in a mass ratio of 1-3:1.

[0016] S3: coal mixing and pre-pyrolysis;

[0017] S301: Evenly mix the anthracite and the lignite according to a set ratio;

[0018] S302: Pre-pyrolyze the mixed coal sample at a temperature range of 300-400°C to remove part of the volatile matter and initially form a carbonized skeleton.

[0019] S4: high temperature carbonization of mixed coal samples;

[0020] The mixed coal sample after pre-pyrolysis is heated to 800-1200°C in an inert atmosphere for high-temperature carbonization, and the microstructure of the hard carbon material is regulated by controlling the heating rate (3-5°C / min) and the holding time (1-4 hours).

[0021] The purity of the inert atmosphere is not less than 99.9%.

[0022] S5: Post-processing and molding.

[0023] S501: performing physical activation treatment or chemical activation treatment on the product after high-temperature carbonization to adjust the pore structure of the hard carbon material;

[0024] S502: Pressing the activated hard carbon material into sheets for use as negative electrode materials for sodium ion batteries.

[0025] The physical activation treatment in S501 uses water vapor, CO2 or air as an activating agent.

[0026] The chemical activation treatment in S501 uses KOH or NaOH or ZnCl2 as an activating agent.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention optimizes the microstructure of hard carbon materials and improves sodium storage performance by scientifically proportioning anthracite and lignite, combined with pretreatment, mixed prepyrolysis, high-temperature carbonization and post-treatment processes. Not only is the process simple and low-cost, suitable for large-scale industrial production, but the prepared hard carbon negative electrode material also exhibits excellent cycle stability and high specific capacity, effectively improving the performance of sodium ion batteries. The present invention makes full use of the respective advantages of anthracite and lignite, opens up a new path for the research and development of negative electrode materials for sodium ion batteries, and has significant technical innovation and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of sodium storage performance of Example 1 of the present invention;

[0030] Figure 2 It is a schematic diagram of the sodium storage performance of Example 2 of the present invention. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] A method for constructing an isomeric carbon negative electrode material based on a coal blending process, wherein a high-performance coal-based hard carbon material is prepared by mixing anthracite and lignite, so as to significantly improve the sodium storage capacity and cycle stability of the hard carbon material, which can be applied to the negative electrode of a sodium ion battery. The method comprises the following steps:

[0033] S1: Selection and pretreatment of coal;

[0034] S101: selecting anthracite and lignite as raw materials;

[0035] S102: crushing the anthracite and lignite to less than 100 meshes by using a ball mill, a vibration mill or a jet mill or other crushing equipment;

[0036] S103: The pulverized anthracite and lignite are subjected to acid washing or alkali washing to remove inorganic impurities and improve the purity of the carbonized material.

[0037] The acid washing or alkali washing in S103 uses an acid solution or an alkali solution with a concentration of 1% to 10%.

[0038] S2: coal type ratio;

[0039] According to the pyrolysis characteristics of the coal types, the coal type ratio in S2 is anthracite to lignite with a mass ratio of 1-3:1.

[0040] S3: coal mixing and pre-pyrolysis;

[0041] S301: Evenly mix the anthracite and the lignite according to a set ratio;

[0042] S302: Pre-pyrolyze the mixed coal sample at a temperature range of 300-400°C for 1-3h to remove part of the volatile matter and initially form a carbonized skeleton.

[0043] S4: high temperature carbonization of mixed coal samples;

[0044] The pre-pyrolyzed mixed coal sample is heated to 800-1200°C in an inert atmosphere (such as argon, nitrogen or helium) for high-temperature carbonization, and the microstructure of the hard carbon material is regulated by controlling the heating rate (3-5°C / min) and the holding time (1-4 hours).

[0045] The purity of the inert atmosphere is not less than 99.9%.

[0046] S5: Post-processing and molding.

[0047] S501: performing physical activation treatment or chemical activation treatment on the product after high-temperature carbonization to adjust the pore structure of the hard carbon material;

[0048] The physical activation treatment in S501 uses water vapor, CO2 or air as an activating agent.

[0049] The chemical activation treatment in S501 uses KOH or NaOH or ZnCl2 as an activating agent.

[0050] S502: Pressing the activated hard carbon material into sheets for use as negative electrode materials for sodium ion batteries.

[0051] Embodiment 1:

[0052] Anthracite and lignite were mixed in a mass ratio of 3:1, the mixed coal sample was pre-pyrolyzed at 350°C for 2 hours, and then carbonized at 1000°C for 3 hours. The obtained hard carbon material had a specific capacity of 140 mAh / g in sodium ion batteries.

[0053] Embodiment 2:

[0054] The difference between this embodiment and embodiment 1 is that:

[0055] By mixing anthracite and lignite in a mass ratio of 1:1 and regulating the pore structure through an activation process, the prepared hard carbon material has a specific capacity of 320mAh / g at a low current density and exhibits a first coulombic efficiency of 79%.

[0056] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and range of equivalents of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0057] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for constructing a homogeneous carbon negative electrode material based on a coal blending process, characterized in that: The method comprises the following steps: S1: Selection and pretreatment of coal; S2: coal type ratio; S3: coal mixing and pre-pyrolysis; S4: high temperature carbonization of mixed coal samples; S5: Post-processing and molding.

2. The method for constructing a homogeneous carbon negative electrode material based on a coal blending process according to claim 1, characterized in that: The S1 comprises the following steps: S101: selecting anthracite and lignite as raw materials; S102: crushing the anthracite and lignite to less than 100 mesh; S103: The pulverized anthracite and lignite are subjected to acid washing or alkali washing.

3. The method for constructing a homogeneous carbon negative electrode material based on a coal blending process according to claim 2, characterized in that: The acid washing or alkali washing in S103 uses an acid solution or an alkali solution with a concentration of 1% to 10%.

4. The method for constructing a homogeneous carbon negative electrode material based on a coal blending process according to claim 2, characterized in that: The coal ratio in S2 is anthracite to lignite in a mass ratio of 1-3:

1.

5. The method for constructing a homogeneous carbon negative electrode material based on a coal blending process according to claim 3, characterized in that: The S3 comprises the following steps: S301: Evenly mix the anthracite and the lignite according to a set ratio; S302: Pre-pyrolyze the mixed coal sample at a temperature range of 300-400°C to remove part of the volatile matter and initially form a carbonized skeleton.

6. The method for constructing a homogeneous carbon negative electrode material based on a coal blending process according to claim 4, characterized in that: The S4 comprises the following steps: The mixed coal sample after pre-pyrolysis is heated to 800-1200°C in an inert atmosphere for high-temperature carbonization, and the microstructure of the hard carbon material is regulated by controlling the heating rate and holding time.

7. The method for constructing a homogeneous carbon negative electrode material based on a coal blending process according to claim 6, characterized in that: The purity of the inert atmosphere is not less than 99.9%.

8. The method for constructing a homogeneous carbon negative electrode material based on a coal blending process according to claim 5, characterized in that: The S5 comprises the following steps: S501: performing physical activation treatment or chemical activation treatment on the product after high-temperature carbonization to adjust the pore structure of the hard carbon material; S502: Pressing the activated hard carbon material into sheets for use as negative electrode materials for sodium ion batteries.

9. The method for constructing a homogeneous carbon negative electrode material based on a coal blending process according to claim 7, characterized in that: The physical activation treatment in S501 uses water vapor, CO2 or air as an activating agent.

10. The method for constructing a homogeneous carbon negative electrode material based on a coal blending process according to claim 7, characterized in that: The chemical activation treatment in S501 uses KOH or NaOH or ZnCl2 as an activating agent.

Images