Method for preparing carbon-based negative electrode material for lithium ion battery by using cyanamide waste residue and application of carbon-based negative electrode material

Abstract

The invention provides a method for preparing a carbon-based negative electrode material for a lithium ion battery by using cyanamide waste residues and application. The method comprises the following steps: dispersing and dissolving the cyanamide waste residues and a carbon source in an ethanol solution in proportion, and fully mixing; then, drying the mixed solution to remove ethanol, and performing roasting treatment by taking calcium carbonate in the cyanamide waste residues as a structure-directing agent and a carbon source as a carbonization precursor to finish carbonization; and finally, carrying out acid extraction treatment on the roasted product by using a hydrochloric acid-hydrofluoric acid mixed acid solution, and washing to be neutral to obtain a composite carbon material of waste residue carbon coupled nano annular microcrystalline carbon, namely the carbon-based negative electrode material for the lithium ion battery. The invention also provides an application of the carbon-based negative electrode material in a lithium ion battery. According to the method, the cyanamide waste residues are efficiently utilized, recycling and high-value treatment of the solid wastes are achieved, and meanwhile the obtained carbon-based negative electrode material has the advantages of being high in performance, low in cost and the like, has environmental benefits and economic benefits, is suitable for lithium ion battery negative electrodes and has wide application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of resource utilization of cyanamide waste residue, and particularly to a method for preparing a carbon-based anode material for lithium-ion batteries by using cyanamide waste residue and its application. Background Art

[0002] With the continuous expansion of the application fields and markets of cyanamide and its downstream products, the annual growth rate of the global demand for cyanamide has reached as high as 8% - 10%. At present, the industrial method for producing cyanamide in China is mainly the calcium carbide method, and this process inevitably generates a large amount of industrial waste residue. According to statistics, the annual output of cyanamide waste residue in the country is nearly 1.28 million tons, and the main components of the waste residue are calcium carbonate and carbon. For a long time, enterprises usually choose to directly dump or landfill the waste residue, which has caused serious waste of resources and environmental pollution. Therefore, the resource utilization of cyanamide waste residue is not only an effective way to solve environmental problems but also an inevitable choice to promote the sustainable development of the cyanamide industry.

[0003] Regarding the resource utilization of cyanamide waste residue, a series of methods have been developed by researchers in recent years. For example: Chinese invention patents CN 112357917 B and CN 112479343 B propose to obtain graphite carbon after acid treatment, alkali treatment, and heat treatment of cyanamide waste residue, and the latter applies it to the treatment of phenolic wastewater. However, this method requires the consumption of a large amount of acid and alkali reagents, generates additional waste liquid, and can only effectively utilize the carbon component in the waste residue, with relatively low comprehensive economic benefits. Another example: Chinese invention patent CN 111573706 A provides a resource utilization treatment process for dicyandiamide black waste residue. First, the calcium carbonate content in the waste residue is increased through drying, screening, and air separation, and after forming and carbonizing with a modified binder and a quality improver, an active calcium oxide product is obtained, which can be recycled into the process of producing dicyandiamide by the calcium carbide method to achieve the purpose of circular utilization. In addition, Chinese invention patents CN114539846 A, CN 110776331 A, and CN 109319781 B respectively propose methods for preparing pencil cores, lightweight ceramsite, and nitrogen-doped coal-based hierarchical porous activated carbon by using cyanamide waste residue, but these methods all have problems such as complex raw materials, cumbersome process flows, and low product added value, which limit their large-scale popularization and application.

[0004] With the global energy structure transforming towards cleaner and lower-carbon, lithium-ion batteries have been widely used in fields such as electric vehicles, energy storage systems, and portable electronic devices due to their high energy density and excellent cycle life. However, traditional lithium-ion battery anode materials (such as graphite) have problems such as relatively low theoretical specific capacity and poor cycle stability at high rates, making it difficult to meet the requirements of high-energy-density batteries. Developing new high-performance anode materials has become a current research hotspot. At the same time, the high-value utilization of cyanamide waste residue, as industrial solid waste, still faces challenges.

[0005] Therefore, it is necessary to design a new method with simple process, low cost and capable of realizing the efficient utilization of cyanamide waste residue. Especially when applied to the field of anode materials for lithium-ion batteries, it has important research significance and application value. Summary of the Invention

[0006] In view of the above-mentioned technical problems, a method for preparing a carbon-based anode material for lithium-ion batteries using cyanamide waste residue and its application are provided. In the present invention, calcium carbonate in the cyanamide waste residue is used as a structure-directing agent, while the carbon component in the waste residue is retained, and industrial and agricultural waste is combined as a carbon source to successfully prepare a high-performance waste residue carbon-coupled nano-ring-shaped microcrystalline carbon composite material. As an anode material for lithium-ion batteries, this material not only has a high specific capacity and excellent cycle stability, but also realizes the resource utilization and high-value utilization of waste, with both environmental and economic benefits.

[0007] The technical means adopted in the present invention are as follows: A method for preparing a carbon-based anode material for lithium-ion batteries using cyanamide waste residue, comprising the following steps: (1) Dispersing and dissolving the cyanamide waste residue and the carbon source in an ethanol solution according to a certain mass ratio, and fully mixing them by ultrasonic or overnight impregnation method; (2) Putting the mixed solution obtained in step (1) into an oven to remove ethanol, placing the obtained material in a tube furnace, using calcium carbonate in the cyanamide waste residue as a structure-directing agent and the carbon source as a carbonization precursor, and performing calcination treatment at a certain calcination temperature, calcination atmosphere and calcination time; (3) Acid-leaching the calcined sample with a hydrochloric acid-hydrofluoric acid mixed acid solution and washing it with water until neutral, and the obtained filter cake is a composite carbon material of waste residue carbon-coupled nano-ring-shaped microcrystalline carbon, that is, a carbon-based anode material.

[0008] Further, in step (1), the carbon source is one or more of petroleum asphalt, coal asphalt, straw, and corn cob.

[0009] Further, in step (1), the mass ratio of the cyanamide waste residue to the carbon source is 0.5-7:1.

[0010] Further, in step (2), the mixed solution is put into an oven at 40-80 °C to remove ethanol.

[0011] Further, in step (1), the calcination temperature is 600-1100 °C, the calcination atmosphere is nitrogen or argon, and the calcination time is 1-4 h.

[0012] Further, in step (3), the waste acid filtrate obtained by suction filtration can be recycled for repeated use in acid-leaching.

[0013] Further, in step (3), the conditions for acid leaching are as follows: prepare a hydrochloric acid-hydrofluoric acid mixed acid solution with a volume ratio of 9:1, and stir the calcined sample in the mixed acid solution at 20-80°C for 2-12 h.

[0014] The present invention also discloses a carbon-based negative electrode material for lithium-ion batteries, which is prepared by the above method for preparing from cyanamide waste residue.

[0015] The present invention also discloses an application of the above carbon-based negative electrode material for lithium-ion batteries in lithium-ion batteries.

[0016] Further, using the carbon-based negative electrode material as the active material, slurry is mixed in an N-methylpyrrolidone solvent according to the ratio of active material: conductive carbon black: polyvinylidene fluoride = 8:1:1. The slurry is coated on a copper foil, dried and cut into pieces. The obtained electrode sheets are put into a glove box to assemble a lithium-ion battery.

[0017] Compared with the prior art, the present invention has the following advantages: 1. The present invention converts cyanamide waste residue and industrial and agricultural waste carbon sources into high-performance carbon-based negative electrode materials, makes full use of calcium carbonate in the waste residue as a structure-directing agent, and retains the carbon component in the waste residue at the same time, successfully preparing a composite carbon material of waste residue carbon-coupled nano-ringed microcrystalline carbon, realizing the resource utilization and high-value utilization of solid waste, and effectively reducing environmental pollution; 2. The carbon-based negative electrode material provided by the present invention has a high specific capacity, excellent rate performance and cycle stability. Its unique ringed microcrystalline carbon structure provides an efficient lithium-ion transmission channel, significantly improving the rate performance and long-cycle stability of the battery, and can meet the application requirements of high-energy-density lithium-ion batteries; 3. The carbon-based negative electrode material provided by the present invention has a low cost and a simple preparation process, can replace traditional negative electrode materials, reduce the production cost of lithium-ion batteries, and improve the economic value of the industrial chain at the same time.

[0018] In summary, the present invention not only effectively solves the problem of treating solid waste such as cyanamide waste residue, but also obtains a high-performance and low-cost negative electrode material for lithium-ion batteries, is suitable for large-scale industrial production, realizes the high-value resource utilization of cyanamide waste residue and industrial and agricultural waste, solves the problem of waste treatment, and has important technical value and promotion prospects in the fields of environmental protection and new energy. Description of the Drawings

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 It is the transmission electron microscope image of the composite carbon material obtained in Example 1 of the present invention.

[0021] Figure 2 It is the transmission electron microscope image of the composite carbon material obtained in Comparative Example 1 of the present invention.

[0022] Figure 3 It is the transmission electron microscope image of the composite carbon material obtained in Comparative Example 2 of the present invention.

[0023] Figure 4 It is the rate performance graph of the composite carbon materials obtained in Example 1 of the present invention and Comparative Examples 1 - 3 tested at 0.01 - 3V.

[0024] Figure 5 It is the cycle stability performance graph of the composite carbon materials obtained in Example 1 of the present invention and Comparative Examples 1 - 3 at 5C. Detailed Embodiments

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0026] The present invention provides a method for preparing a carbon - based anode material for lithium - ion batteries using cyanamide waste residue, which specifically includes the following steps: (1) Disperse and dissolve the cyanamide waste residue and the carbon source in ethanol according to a mass ratio of 0.5 - 7:1, and make them fully mixed by ultrasonic or overnight impregnation method. Among them, the carbon source is industrial and agricultural waste, specifically one or more mixtures of petroleum pitch, coal pitch, straw, and corn cob.

[0027] (2) Put the mixed solution obtained in step (1) into an oven at about 40 - 80°C to remove the solvent ethanol. The obtained material is placed in a tube furnace, using calcium carbonate in the cyanamide waste residue as a structure - guiding agent and the carbon source as a carbonization precursor, and carry out roasting treatment under the conditions of a roasting temperature of 600 - 1100°C, a roasting atmosphere of nitrogen or argon, and a roasting time of 1 - 4h.

[0028] (3) The roasted sample is subjected to acid extraction and washed with water to neutrality using a hydrochloric acid - hydrofluoric acid mixed acid solution with a volume ratio of 9:1. During acid extraction, it is stirred at 20 - 80 °C for 2 - 12 h and then left to stand; the waste acid filtrate obtained by suction filtration can be recycled for repeated use in acid extraction, and the final filter cake is a composite carbon material of waste residue carbon - coupled nano - ring - shaped microcrystalline carbon, that is, the carbon - based anode material.

[0029] Furthermore, the obtained composite carbon material of waste residue carbon - coupled nano - ring - shaped microcrystalline carbon is used as the active material, and a slurry is mixed in an N - methyl - 2 - pyrrolidone solvent according to the ratio of active material: conductive carbon black: polyvinylidene fluoride = 8:1:1. The slurry is coated on a copper foil, dried, and cut into pieces. Finally, the electrode pieces are put into a glove box to assemble into a lithium - ion battery.

[0030] Example 1 The method for preparing a carbon - based anode material for lithium - ion batteries using cyanamide waste residue provided by the present invention specifically includes the following steps: The cyanamide waste residue and coal tar pitch are dispersed and dissolved in ethanol according to a mass ratio of 1.25:1, and are fully mixed by ultrasonic method. The mixed solution is placed in an oven at about 60 °C to remove the solvent ethanol. The obtained material is placed in a tubular furnace, with calcium carbonate in the cyanamide waste residue as the structure - guiding agent and coal tar pitch as the carbonization precursor, and is calcined in an argon atmosphere at 1100 °C for 2 h. The roasted sample is subjected to acid extraction and washed with water to neutrality using a hydrochloric acid - hydrofluoric acid mixed acid solution. The waste acid filtrate obtained by suction filtration can be recycled for repeated use in acid extraction, and the final filter cake is the composite carbon material of waste residue carbon - coupled nano - ring - shaped microcrystalline carbon. The transmission electron microscope results of the obtained composite carbon material are as Figure 1 shown. Using the obtained composite material of waste residue carbon - coupled nano - ring - shaped microcrystalline carbon as the active material, a slurry is mixed in an N - methyl - 2 - pyrrolidone solvent according to the ratio of active material: conductive carbon black: polyvinylidene fluoride = 8:1:1. The slurry is coated on a copper foil, dried, and cut into pieces. Finally, the electrode pieces are put into a glove box to assemble into a lithium - ion battery.

[0031] Example 2 On the basis of Example 1, the cyanamide waste residue and coal tar pitch are dispersed and dissolved in ethanol according to a mass ratio of 3.75:1, and are fully mixed by ultrasonic method. The mixed solution is placed in an oven at about 60 °C to remove the solvent ethanol. The obtained material is placed in a tubular furnace, with calcium carbonate in the cyanamide waste residue as the structure - guiding agent and coal tar pitch as the carbonization precursor, and is calcined in an argon atmosphere at 900 °C for 2 h. The subsequent steps are the same as those in Example 1.

[0032] Example 3 On the basis of Example 1, cyanamide waste residue and coal tar pitch are dispersed and dissolved in ethanol at a mass ratio of 6.25:1, and are fully mixed by ultrasonic method. The mixed solution is placed in an oven at about 60 °C to remove the solvent ethanol. The obtained material is placed in a tubular furnace. Using calcium carbonate in the cyanamide waste residue as a structure guiding agent and coal tar pitch as a carbonization precursor, it is calcined in a nitrogen atmosphere at 1000 °C for 2 h, and the subsequent steps are the same as those in Example 1.

[0033] Example 4 On the basis of Example 1, cyanamide waste residue and straw are dispersed and dissolved in ethanol at a mass ratio of 6.25:1, and are fully mixed by ultrasonic method. The mixed solution is placed in an oven at about 60 °C to remove the solvent ethanol. The obtained material is placed in a tubular furnace. Using calcium carbonate in the cyanamide waste residue as a structure guiding agent and straw as a carbonization precursor, it is calcined in a nitrogen atmosphere at 900 °C for 2 h, and the subsequent steps are the same as those in Example 1.

[0034] Comparative Example 1 First, the cyanamide waste residue is acid-leached with a hydrochloric acid-hydrofluoric acid mixed acid solution, filtered by suction and washed with water to obtain waste residue carbon. The waste acid filtrate can be recycled for reuse in acid leaching. Then, the waste residue carbon and coal tar pitch are dispersed and dissolved in ethanol in a certain proportion. The carbon content ratio of the waste residue carbon to the coal tar pitch is kept the same as that in Example 1, and they are fully mixed by ultrasonic method. The mixed solution is placed in an oven at about 60 °C to remove the solvent ethanol. The obtained material is placed in a tubular furnace. At this time, there is no calcium carbonate in the waste residue as a structure guiding agent, and coal tar pitch is used as a carbonization precursor. It is calcined in an argon atmosphere at 1100 °C for 2 h. After calcination, a composite carbon material of directly acid-leached waste residue carbon coupled with pitch carbon is obtained. The transmission electron microscope results are as Figure 2 shown. Using the obtained composite carbon material as the active material, it is mixed into a slurry in N-methylpyrrolidone solvent according to the ratio of active material: conductive carbon black: polyvinylidene fluoride = 8:1:1. The slurry is coated on a copper foil, dried and cut into pieces. Finally, the electrode pieces are put into a glove box to assemble into a lithium-ion battery.

[0035] Comparative Example 2 The cyanamide waste residue is directly acid-leached with a hydrochloric acid-hydrofluoric acid mixed acid solution, filtered by suction and washed with water to obtain waste residue carbon. The waste acid filtrate can be recycled for reuse in acid leaching. The transmission electron microscope results are as Figure 3 shown. Using the obtained waste residue carbon as the active material, it is mixed into a slurry in N-methylpyrrolidone solvent according to the ratio of active material: conductive carbon black: polyvinylidene fluoride = 8:1:1. The slurry is coated on a copper foil, dried and cut into pieces. Finally, the electrode pieces are put into a glove box to assemble into a lithium-ion battery.

[0036] Comparative Example 3 Using commercial graphite as the active material, slurry is mixed in N-methylpyrrolidone solvent according to the ratio of active material: conductive carbon black: polyvinylidene fluoride = 8:1:1. The slurry is coated on copper foil, dried and cut into pieces. Finally, the electrode pieces are put into a glove box to assemble into a lithium-ion battery.

[0037] After standing for 10 h, the assembled lithium-ion batteries of Examples 1-3 and Comparative Examples 1-3 are connected to a battery tester to test the rate performance in the voltage range of 0.01-3 V and the cycle stability at 5C. The test results are summarized in Table 1.

[0038] Table 1 Test Results of Battery Performance From the test results of battery performance in Table 1, compared with Comparative Examples 1-3, the carbon-based anode materials formed by coupling carbon sources with calcium carbonate in cyanamide waste residue as the structure guiding agent all have higher discharge specific capacity (especially at high rates above 3C) and excellent cycle stability. The performance test data graphs of Example 1 with better performance and each comparative example are as Figure 4 、 Figure 5 shown. From Figures 1 to 3 the microstructure analysis, it can be seen that both directly acid-leached waste residue carbon and commercial graphite have long-range ordered graphite lattice stripes. When there is no structure guiding agent, the carbon material formed by coupling carbon sources with directly acid-leached waste residue carbon coexists with long-range ordered and short-range ordered microcrystalline structures. However, in the carbon material formed by coupling carbon sources with calcium carbonate in cyanamide waste residue as the structure guiding agent, there are both long-range ordered lattice stripe structures of waste residue carbon and ring-shaped nanocrystalline structures attached to the structure guiding agent. This special structure provides more sites and channels for the storage and transmission of lithium ions, and thus exhibits high discharge specific capacity and excellent cycle stability especially at high rates.

[0039] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the present invention; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a carbon-based anode material for lithium-ion batteries using cyanamide waste residue, characterized in that, It includes the following steps: (1) Disperse and dissolve cyanamide waste residue and carbon source in an ethanol solution according to a certain mass ratio, and fully mix them by ultrasonic or overnight impregnation method; (2) Put the mixed solution obtained in step (1) into an oven to remove ethanol, place the obtained material in a tubular furnace, use calcium carbonate in the cyanamide waste residue as a structure guiding agent and the carbon source as a carbonization precursor, and carry out calcination treatment at a certain calcination temperature, calcination atmosphere and calcination time; (3) Acid-extract the calcined sample with a hydrochloric acid-hydrofluoric acid mixed acid solution and wash it with water until neutral. The obtained filter cake is a composite carbon material of waste residue-carbon coupled nano-ring-shaped microcrystalline carbon, that is, a carbon-based anode material.

2. The method according to claim 1, wherein In step (1), the carbon source is one or more mixtures of petroleum asphalt, coal tar pitch, straw, and corncob.

3. The method according to claim 2, characterized in that In step (1), the mass ratio of the cyanamide waste residue to the carbon source is 0.5-7:

1.

4. The method according to claim 1, characterized in that In step (2), the mixed solution is put into an oven at 40-80°C to remove ethanol.

5. The method according to claim 4, characterized in that, In step (1), the calcination temperature is 600-1100°C, the calcination atmosphere is nitrogen or argon, and the calcination time is 1-4h.

6. The method according to claim 1, wherein In step (3), the waste acid filtrate obtained by suction filtration can be recycled and reused for acid extraction.

7. The method according to claim 6, characterized in that, In step (3), the conditions for acid extraction are: prepare a hydrochloric acid-hydrofluoric acid mixed acid solution with a volume ratio of 9:1, and stir the calcined sample in the mixed acid solution at 20-80°C for 2-12h.

8. A carbon-based anode material for a lithium-ion battery, characterized in that, Prepared by the method for preparing using cyanamide waste residue according to any one of claims 1-7.

9. Application of the carbon-based anode material for a lithium-ion battery as described in claim 8 in a lithium-ion battery.

10. The application according to claim 9, wherein Using the carbon-based anode material as the active material, mix the slurry in an N-methylpyrrolidone solvent according to the ratio of active material: conductive carbon black: polyvinylidene fluoride = 8:1:1, coat the slurry on a copper foil, dry it and cut it into pieces, and put the obtained electrode sheet into a glove box to assemble a lithium-ion battery.

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