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

Abstract

The application provides a method for preparing a carbon-based negative electrode material for a lithium ion battery by using cyanamide waste residue and application, and the method comprises the following steps: dispersing and dissolving cyanamide waste residue and a carbon source in an ethanol solution in proportion and mixing thoroughly; then, the mixed solution is dried to remove ethanol, calcium carbonate in the cyanamide waste residue is used as a structure directing agent, the carbon source is used as a carbonization precursor, and carbonization is completed through calcination; finally, the calcination product is subjected to acid extraction treatment through a hydrochloric acid-hydrofluoric acid mixed acid solution, and is washed with water until neutral, so that a composite carbon material of waste residue carbon coupling nanometer ring-shaped microcrystalline carbon, i.e., a carbon-based negative electrode material for a lithium ion battery, is obtained. The application also provides application of the carbon-based negative electrode material in a lithium ion battery. The application realizes resourceization and high-value treatment of solid waste by efficiently utilizing cyanamide waste residue, and the obtained carbon-based negative electrode material has the advantages of high performance, low cost and the like, has environmental benefits and economic benefits, is suitable for a lithium ion battery negative electrode, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of resource utilization technology of cyanamide waste residue, and in particular to a method and application for preparing carbon-based anode materials for lithium-ion batteries using cyanamide waste residue. Background Technology

[0002] With the continuous expansion of the application fields and markets of cyanamide and its downstream products, the global demand for cyanamide has been growing at an annual rate of 8%-10%. Currently, the industrial production method of cyanamide in my country is mainly the calcium carbide process, which inevitably generates a large amount of industrial waste. Statistics show that the annual output of cyanamide waste in China is nearly 1.28 million tons, and the main components of the waste are calcium carbonate and carbon. For a long time, enterprises have typically chosen to directly dump or landfill the waste, resulting in serious resource waste and environmental pollution. Therefore, the resource utilization of cyanamide waste 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] In recent years, researchers have developed a series of methods for the resource utilization of cyanamide waste residue. For example, Chinese invention patents CN 112357917 B and CN 112479343 B propose obtaining graphite carbon from cyanamide waste residue after acid treatment, alkali treatment, and heat treatment, which is then applied to the treatment of phenol-containing wastewater. However, this method requires the consumption of large amounts of acid and alkali reagents, generates additional waste liquid, and can only effectively utilize the carbon component in the waste residue, resulting in low overall economic benefits. Another example is Chinese invention patent CN 111573706 A, which provides a resource utilization process for dicyandiamide black residue. First, the calcium carbonate content in the waste residue is increased through drying, sieving, and air classification. Then, modified binders and upgrading agents are used to form and carbonize the residue to obtain activated calcium oxide, which can be reused in the calcium carbide process for dicyandiamide production, achieving the goal of recycling. In addition, Chinese invention patents CN114539846 A, CN 110776331 A and CN 109319781 B respectively proposed methods for preparing pencil leads, lightweight ceramic particles and nitrogen-doped coal-based multi-level porous activated carbon using cyanamide waste residue. However, these methods all have problems such as complex raw materials, complicated process flow and low added value of products, which limit their large-scale promotion and application.

[0004] With the global energy structure shifting towards cleaner and lower-carbon energy sources, lithium-ion batteries have been widely used in 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) suffer from low theoretical specific capacity and poor cycle stability at high rates, making it difficult to meet the demands of high-energy-density batteries. Developing novel high-performance anode materials has become a current research hotspot. Meanwhile, the high-value utilization of cyanamide waste, as an industrial solid waste, still faces challenges.

[0005] Therefore, it is necessary to design a new method that is simple in process, low in cost, and can achieve efficient utilization of cyanamide waste residue, especially for its application in the field of lithium-ion battery anode materials, which has important research significance and application value. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method and application for preparing carbon-based anode materials for lithium-ion batteries using cyanamide waste residue. This invention utilizes calcium carbonate from cyanamide waste residue as a structure directing agent, while retaining the carbon component in the residue, and combines it with industrial and agricultural waste as a carbon source to successfully prepare a high-performance waste residue carbon-coupled nano-cyclic microcrystalline carbon composite material. This material, as a lithium-ion battery anode material, not only possesses high specific capacity and excellent cycle stability, but also achieves resource utilization and high-value-added utilization of waste, thus possessing both environmental and economic benefits.

[0007] The technical means employed in this invention are as follows:

[0008] A method for preparing carbon-based anode materials for lithium-ion batteries using cyanamide waste residue includes the following steps:

[0009] (1) Dissolve the cyanamide waste residue and carbon source in an ethanol solution at a certain mass ratio, and mix them thoroughly by ultrasonic or overnight impregnation.

[0010] (2) The mixture obtained in step (1) is placed in an oven to remove ethanol. The resulting material is placed in a tube furnace, and calcium carbonate in the cyanamide waste residue is used as a structure directing agent and carbon source is used as a carbonization precursor. The material is then roasted at a certain roasting temperature, roasting atmosphere and roasting time.

[0011] (3) The calcined sample was acid-extracted and washed with water until neutral by a mixed acid solution of hydrochloric acid and hydrofluoric acid. The resulting filter cake was a composite carbon material of waste carbon coupled with nano-ring microcrystalline carbon, i.e. carbon-based anode material.

[0012] Further, in step (1), the carbon source is one or more of petroleum asphalt, coal tar pitch, straw, and corn cob.

[0013] Further, in step (1), the mass ratio of the cyanamide waste residue to the carbon source is 0.5~7:1.

[0014] Further, in step (2), the mixture is placed in an oven at 40~80℃ to remove ethanol.

[0015] Further, in step (1), the calcination temperature is 600~1100℃, the calcination atmosphere is nitrogen or argon, and the calcination time is 1~4h.

[0016] Furthermore, in step (3), the waste acid filtrate obtained by vacuum filtration can be recycled for reuse in acid extraction.

[0017] Further, in step (3), the acid extraction conditions are as follows: prepare a mixed acid solution of hydrochloric acid and hydrofluoric acid with a volume ratio of 9:1, and stir the calcined sample in the mixed acid solution for 2 to 12 hours at 20 to 80°C.

[0018] The present invention also discloses a carbon-based anode material for lithium-ion batteries, which is prepared by the above-described method using cyanamide waste residue.

[0019] The present invention also discloses the application of the above-mentioned carbon-based anode material for lithium-ion batteries in lithium-ion batteries.

[0020] Furthermore, using carbon-based anode material as the active material, a slurry is prepared 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 sheets. The resulting electrode sheets are then placed in a glove box and assembled into lithium-ion batteries.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. This invention transforms cyanamide waste residue and industrial and agricultural waste carbon sources into high-performance carbon-based anode materials, making full use of calcium carbonate in the waste residue as a structure directing agent, while retaining the carbon components in the waste residue, and successfully preparing composite carbon materials of waste residue carbon coupled with nano-ring microcrystalline carbon, realizing the resource utilization and high-value utilization of solid waste, and effectively reducing environmental pollution;

[0023] 2. The carbon-based anode material provided by this invention has high specific capacity, excellent rate performance and cycle stability. Its unique cyclic microcrystalline carbon structure provides an efficient lithium-ion transport channel, which significantly improves the rate performance and long-cycle stability of the battery and can meet the application requirements of high energy density lithium-ion batteries.

[0024] 3. The carbon-based anode material provided by this invention is low in cost and has a simple preparation process. It can replace traditional anode materials, reduce the production cost of lithium-ion batteries, and enhance the economic value of the industrial chain.

[0025] In summary, this invention not only effectively solves the problem of treating solid wastes such as cyanamide residue, but also obtains high-performance, low-cost lithium-ion battery anode materials suitable for large-scale industrial production. It realizes high-value-added resource utilization of cyanamide 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. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a transmission electron microscope image of the composite carbon material obtained in Example 1 of the present invention.

[0028] Figure 2 This is a transmission electron microscope image of the composite carbon material obtained in Comparative Example 1 of the present invention.

[0029] Figure 3 This is a transmission electron microscope image of the composite carbon material obtained in Comparative Example 2 of the present invention.

[0030] Figure 4 The graph shows the rate performance of the composite carbon materials obtained in Example 1 and Comparative Examples 1-3 of this invention, tested at 0.01-3V.

[0031] Figure 5 The diagram shows the cycling stability of the composite carbon materials obtained in Example 1 and Comparative Examples 1-3 of this invention at 5C. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] This invention provides a method for preparing carbon-based anode materials for lithium-ion batteries using cyanamide waste residue, specifically including the following steps:

[0034] (1) Dissolve cyanamide waste residue and carbon source in ethanol at a mass ratio of 0.5 to 7:1, and mix them thoroughly by ultrasonic or overnight impregnation method. The carbon source is industrial and agricultural waste, specifically one or more of petroleum asphalt, coal tar pitch, straw, and corn cob.

[0035] (2) The mixture obtained in step (1) is placed in an oven at about 40~80℃ to remove the solvent ethanol. The resulting material is placed in a tube furnace, and calcium carbonate in the cyanamide waste residue is used as a structure directing agent and carbon source is used as a carbonization precursor. The roasting process is carried out at a roasting temperature of 600~1100℃, a roasting atmosphere of nitrogen or argon, and a roasting time of 1~4h.

[0036] (3) The calcined sample was acid-extracted and washed with water until neutral by a mixed acid solution of hydrochloric acid and hydrofluoric acid with a volume ratio of 9:1. During acid extraction, the sample was stirred at 20~80℃ for 2~12h and then allowed to stand. The waste acid filtrate obtained by vacuum filtration can be recycled for reuse in acid extraction. The final filter cake is a composite carbon material of waste carbon coupled with nano-ring microcrystalline carbon, i.e. carbon-based anode material.

[0037] Furthermore, the composite carbon material of carbon from waste residue coupled with nano-ring microcrystalline carbon was used as the active material. The active material, conductive carbon black and polyvinylidene fluoride were mixed in N-methylpyrrolidone solvent in a ratio of 8:1:1. The slurry was coated on copper foil, dried and cut into sheets. Finally, the electrode sheets were placed in a glove box and assembled into a lithium-ion battery.

[0038] Example 1

[0039] The method for preparing carbon-based anode materials for lithium-ion batteries using cyanamide waste residue provided by the present invention specifically includes the following steps:

[0040] Cyanamine waste residue and coal tar pitch were dispersed and dissolved in ethanol at a mass ratio of 1.25:1. The mixture was thoroughly mixed using ultrasound, and then placed in an oven at approximately 60°C to remove the ethanol solvent. The resulting material was placed in a tube furnace and calcined at 1100°C under an argon atmosphere for 2 hours, using calcium carbonate from the cyanamine waste residue as a structure-directing agent and coal tar pitch as a carbonization precursor. The calcined sample was then subjected to acid extraction with a hydrochloric acid-hydrofluoric acid mixed acid solution and washed with water until neutral. The waste acid filtrate obtained by vacuum filtration could be recycled for reuse in the acid extraction process. The final filter cake was the composite carbon material of carbon coupled with nano-cyclic microcrystalline carbon from the waste residue. The transmission electron microscopy results of the obtained composite carbon material are shown below. Figure 1 As shown. The composite material of carbon-coupled waste residue and nano-ring microcrystalline carbon was used as the active material. The active material, conductive carbon black and polyvinylidene fluoride were mixed in N-methylpyrrolidone solvent in a ratio of 8:1:1. The slurry was coated on copper foil, dried and cut into sheets. Finally, the electrode sheets were placed in a glove box and assembled into a lithium-ion battery.

[0041] Example 2

[0042] Based on Example 1, cyanamide waste residue and coal tar pitch were dispersed and dissolved in ethanol at a mass ratio of 3.75:1. The mixture was then thoroughly mixed using ultrasound, and the solvent ethanol was removed by placing the mixture in an oven at approximately 60°C. The resulting material was placed in a tubular furnace, using calcium carbonate from the cyanamide waste residue as a structure-directing agent and coal tar pitch as a carbonization precursor, and calcined at 900°C under an argon atmosphere for 2 hours. Subsequent steps were the same as in Example 1.

[0043] Example 3

[0044] Based on Example 1, cyanamide waste residue and coal tar pitch were dispersed and dissolved in ethanol at a mass ratio of 6.25:1. The mixture was thoroughly mixed using ultrasound, and the solvent ethanol was removed by placing the mixture in an oven at approximately 60°C. The resulting material was placed in a tubular furnace, using calcium carbonate from the cyanamide waste residue as a structure-directing agent and coal tar pitch as a carbonization precursor, and calcined at 1000°C under a nitrogen atmosphere for 2 hours. Subsequent steps were the same as in Example 1.

[0045] Example 4

[0046] Based on Example 1, cyanamide waste residue and straw were dispersed and dissolved in ethanol at a mass ratio of 6.25:1. The mixture was thoroughly mixed using ultrasound, and the solvent ethanol was removed by placing the mixture in an oven at approximately 60°C. The resulting material was placed in a tubular furnace, using calcium carbonate from the cyanamide waste residue as a structure-directing agent and straw as a carbonization precursor, and calcined at 900°C under a nitrogen atmosphere for 2 hours. Subsequent steps were the same as in Example 1.

[0047] Comparative Example 1

[0048] First, cyanamide waste residue was acid-extracted using a hydrochloric acid-hydrofluoric acid mixed acid solution, followed by filtration and water washing to obtain waste residue carbon. The waste acid filtrate could be recycled for reuse in the acid extraction process. Then, the waste residue carbon and coal tar pitch were dispersed and dissolved in ethanol in a specific ratio, maintaining the same carbon content ratio as in Example 1. The mixture was thoroughly mixed using ultrasound, and the ethanol solvent was removed from the mixture in an oven at approximately 60°C. The resulting material was placed in a tubular furnace, where calcium carbonate from the waste residue was no longer used as a structure-directing agent, and coal tar pitch served as the carbonization precursor. The material was calcined at 1100°C under an argon atmosphere for 2 hours. After calcination, a composite carbon material was obtained, consisting of directly acid-extracted waste residue carbon coupled with coal tar pitch carbon. The transmission electron microscopy results are shown below. Figure 2 As shown. Using the obtained composite carbon material as the active material, the active material: conductive carbon black: polyvinylidene fluoride = 8:1:1 was mixed in N-methylpyrrolidone solvent to form a slurry. The slurry was coated on copper foil, dried, and cut into sheets. Finally, the electrode sheets were placed in a glove box and assembled into a lithium-ion battery.

[0049] Comparative Example 2

[0050] The cyanamide waste residue was directly acid-extracted with a hydrochloric acid-hydrofluoric acid mixed acid solution, followed by filtration and water washing to obtain waste carbon. The waste acid filtrate could be recycled for reuse in acid extraction. The transmission electron microscopy results are as follows: Figure 3 As shown. Using the obtained waste carbon as the active material, the active material, conductive carbon black, and polyvinylidene fluoride were mixed in N-methylpyrrolidone solvent at a ratio of 8:1:1. The slurry was coated on copper foil, dried, and cut into sheets. Finally, the electrode sheets were placed in a glove box and assembled into a lithium-ion battery.

[0051] Comparative Example 3

[0052] Commercial graphite was used as the active material. The active material, conductive carbon black, and polyvinylidene fluoride were mixed in N-methylpyrrolidone solvent at a ratio of 8:1:1. The slurry was coated on copper foil, dried, and cut into sheets. Finally, the electrode sheets were placed in a glove box and assembled into a lithium-ion battery.

[0053] The lithium-ion batteries assembled in Examples 1-3 and Comparative Examples 1-3 were allowed to stand for 10 hours before being connected to a battery tester. Rate performance was tested within a voltage range of 0.01-3V, and cycle stability was tested at 5C. The test results are summarized in Table 1.

[0054] Table 1 Battery performance test results

[0055]

[0056] Table 1 shows the battery performance test results. Compared with Comparative Examples 1-3, the carbon-based anode materials formed by coupling carbon sources with calcium carbonate from cyanamide waste residue as a structure directing agent all exhibit higher discharge specific capacity (especially at high rates above 3C) and excellent cycle stability. The performance test data of Example 1, which shows superior performance, and the comparative examples are illustrated in the following figures. Figure 4 , Figure 5 As shown. From Figures 1-3 Microstructural analysis reveals that both direct acid-extracted waste carbon and commercial graphite possess long-range ordered graphite lattice fringes. In the absence of a structure directing agent, the carbon material formed by coupling carbon source with the waste carbon from direct acid extraction exhibits both long-range and short-range ordered microcrystalline structures. In contrast, the carbon material formed by coupling carbon source with calcium carbonate from cyanamide waste as a structure directing agent possesses both the long-range ordered lattice fringes of the waste carbon and a ring-shaped nanocrystalline structure attached to the structure directing agent. This unique structure provides more sites and channels for lithium-ion storage and transport, thus exhibiting high discharge specific capacity and excellent cycle stability, especially at high rates.

[0057] The above embodiments are merely 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 skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing carbon-based anode materials for lithium-ion batteries using cyanamide waste residue, characterized in that, The process includes the following steps: (1) Disperse and dissolve cyanamide waste residue and carbon source in ethanol solution at a certain mass ratio, and mix them thoroughly by ultrasonic or overnight impregnation method; (2) Place the mixture obtained in step (1) into an oven to remove ethanol, and place the obtained material in a tube furnace, using calcium carbonate in cyanamide waste residue as a structure guiding agent and carbon source as a carbonization precursor, and perform roasting treatment under a certain roasting temperature, roasting atmosphere and roasting time; (3) The calcined sample was acid-extracted and washed with water until neutral by a mixed acid solution of hydrochloric acid and hydrofluoric acid. The resulting filter cake was a composite carbon material of waste carbon coupled with nano-ring microcrystalline carbon, i.e. carbon-based anode material.

2. The method according to claim 1, characterized in that, In step (1), the carbon source is one or more of petroleum asphalt, coal tar pitch, straw, and corn cob.

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 mixture is placed in an oven at 40~80℃ to remove ethanol.

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

6. The method according to claim 1, characterized in that, In step (3), the waste acid filtrate obtained by vacuum filtration can be recycled for reuse in acid extraction.

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

8. A carbon-based anode material for lithium-ion batteries, characterized in that, It is prepared by the method of using cyanamide waste residue as described in any one of claims 1 to 7.

9. The application of the carbon-based anode material for lithium-ion batteries as described in claim 8 in lithium-ion batteries.

10. The application according to claim 9, characterized in that, Using carbon-based anode material as the active material, the active material, conductive carbon black, and polyvinylidene fluoride were mixed in N-methylpyrrolidone solvent at a ratio of 8:1:

1. The slurry was coated on copper foil, dried, and cut into sheets. The resulting electrode sheets were then placed in a glove box and assembled into lithium-ion batteries.

Images