A method for regenerating graphite electrode sheet scraps

Abstract

The present invention relates to the field of electrode material recycling and reuse technology, and in particular to a method for regenerating graphite electrode sheet scraps. The present invention provides a method for regenerating graphite electrode sheet scraps, comprising the steps of: soaking the graphite electrode sheet scraps in hot water to obtain a composite; the temperature of the hot water is above room temperature; and calcining the composite to obtain regenerated graphite containing a conductive agent. The regeneration method is simple, and the resulting regenerated graphite containing a conductive agent exhibits excellent electrochemical properties after reuse.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode material recycling and reuse, and in particular to a method for regenerating graphite electrode sheet scraps. Background Art

[0002] With the rapid development of the new energy industry in recent years, the demand for lithium-ion batteries has also increased dramatically, and the demand for negative electrode materials has also increased dramatically. Currently, commercial negative electrode materials are mainly graphite materials, with artificial graphite occupying a dominant position, followed by natural graphite and other materials. However, the synthesis of artificial graphite requires high temperatures exceeding 2500°C for graphitization, which consumes extremely high energy. However, in the preparation of lithium-ion batteries, especially in processes such as coating and slicing, approximately 10% of the graphite material is not actually utilized. If this material is recycled, the copper foil is extracted, and the solidified thickener and binder are removed, the graphene material can be effectively recycled and reused, which will help alleviate the energy and environmental pressures facing society.

[0003] Currently, the main methods for purifying graphite include acid-base, hydrofluoric acid, and high-temperature methods. The acid-base method is the most widely used industrially. A graphite purification method and application (Application No. 202011582934.2) discloses a method for purifying graphite. This method involves selecting a graphite raw material with a carbon content greater than 94%, adding hydrochloric acid, heating, and reacting, then washing to the center to obtain an intermediate material. This intermediate material is then added with a mixture of sodium hydroxide and boric acid for reaction, washed to neutrality, and dried to obtain a pretreated graphite powder raw material. Finally, the pretreated graphite powder raw material is irradiated to obtain graphite with a purity of 99.98%. This method is mature and versatile, but its drawbacks include high energy consumption, long reaction time, severe equipment corrosion, and significant water pollution. Furthermore, to improve graphite purity, graphite processing companies often use the hydrofluoric acid method. However, hydrofluoric acid is highly toxic and corrosive, placing stringent requirements on equipment and environmental protection.

[0004] These graphite purification methods primarily focus on purifying raw graphite and recycled graphite anode materials from used batteries. However, for the graphite anode scraps discarded during production, these processes are complex and costly. Therefore, finding a simple way to purify these graphite scraps and enable their reuse is an urgent challenge in this field. Summary of the Invention

[0005] The object of the present invention is to provide a method for regenerating graphite electrode sheet scraps. The regeneration method is simple, and the obtained regenerated graphite containing a conductive agent has excellent electrochemical properties after reuse.

[0006] In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions: The present invention provides a method for regenerating graphite electrode sheet scraps, comprising the following steps: soaking the graphite electrode sheet scraps in hot water to obtain a composite; the temperature of the hot water is higher than room temperature; and calcining the composite to obtain regenerated graphite containing a conductive agent.

[0007] Preferably, the temperature of the hot water is 40-90° C., and the soaking time is 0.5-2 h.

[0008] Preferably, the composite comprises graphite, a conductive agent and a binder; the mass ratio of the graphite, the conductive agent and the binder is 100:(1-10):(1-10).

[0009] Preferably, the conductive agent includes two or more of carbon black, carbon nanotubes and carbon nanofibers.

[0010] Preferably, the binder includes two or more of styrene-butadiene rubber, sodium carboxymethyl cellulose, sodium alginate and polyacrylic acid.

[0011] Preferably, the calcination temperature is 300-500° C. and the calcination time is 1-5 hours.

[0012] Preferably, after the soaking is completed, filtering and drying are further performed in sequence.

[0013] Preferably, the roasting further includes grinding and screening in sequence.

[0014] The present invention provides a method for regenerating graphite electrode scraps, comprising the following steps: soaking the graphite electrode scraps in hot water to obtain a composite; the hot water is kept at a temperature above room temperature; and calcining the composite to obtain regenerated graphite containing a conductive agent. The regeneration method comprises separating the copper foil from other electrode components (including the graphite composite) in the hot water, sintering the graphite scraps (including the graphite composite), and removing sodium carboxymethyl cellulose and styrene-butadiene rubber by oxidation. The resulting regenerated graphite containing a conductive agent, as a regenerated graphite negative electrode material, has a capacity close to that of the original commercial graphite raw material, with a voltage range of 0.005 to 1.5 V and an average discharge capacity of 362.4 mA·h / g at a current density of 0.1C. Furthermore, the regeneration method has the advantages of simple process, low equipment cost, low energy consumption, and is environmentally friendly and pollution-free. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the SEM image of the regenerated graphite containing the conductive agent described in Example 1.

[0016] Figure 2 This is the TEM image of the composite powder described in Comparative Example 1.

[0017] Figure 3 This is the TEM image of the regenerated graphite containing the conductive agent described in Example 1.

[0018] Figure 4 The cycle performance curves of button batteries prepared from the regenerated graphite containing a conductive agent obtained in Example 1 and the composite powder obtained in Comparative Example 1 are shown. DETAILED DESCRIPTION

[0019] The invention provides a method for regenerating graphite electrode sheet scraps, comprising the following steps: soaking the graphite electrode sheet scraps in hot water to obtain a composite; the temperature of the hot water is higher than room temperature; and calcining the composite to obtain regenerated graphite containing a conductive agent.

[0020] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well known to those skilled in the art.

[0021] The present invention soaks the scraps of graphite electrode sheets in hot water to obtain a composite; the temperature of the hot water is higher than room temperature.

[0022] In the present invention, the source of the graphite electrode sheet scraps is preferably the negative electrode sheet scraps of power batteries.

[0023] In the present invention, the temperature of the hot water is preferably 40-90° C., more preferably 60-80° C.; the soaking time is preferably 0.5-2 h, more preferably 1.0-1.5 h.

[0024] In the present invention, the purpose of soaking is to separate the current collector from the scraps.

[0025] After the soaking is completed, the present invention also preferably includes filtering and drying in sequence. The present invention does not have any particular limitation on the filtering process, and can be carried out using a process well known to those skilled in the art. In the present invention, the drying temperature is preferably 110° C. and the drying time is preferably 5 hours.

[0026] In the present invention, the composite preferably includes graphite, a conductive agent and a binder; the mass ratio of the graphite, the conductive agent and the binder is preferably 100:(1-10):(1-10), more preferably 100:(3-8):(3-8), and most preferably 100:(4-6):(4-6).

[0027] In the present invention, the conductive agent preferably includes two or more of carbon black, carbon nanotubes and carbon nanofibers; the binder includes two or more of styrene-butadiene rubber, sodium carboxymethyl cellulose, sodium alginate and polyacrylic acid.

[0028] After obtaining the composite, the present invention bakes the composite to obtain regenerated graphite containing a conductive agent.

[0029] Before roasting, the present invention further preferably includes sequential grinding and sieving. The present invention does not have any special limitation on the grinding and sieving process, and the grinding and sieving process may be performed using a process well known to those skilled in the art.

[0030] In the present invention, the calcination temperature is preferably 300-500° C., more preferably 350-450° C., and most preferably 380-420° C.; the calcination time is preferably 1-5 h, more preferably 2-4 h.

[0031] The following describes in detail the method for regenerating graphite electrode sheet scraps provided by the present invention in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0032] Example 1

[0033] Graphite electrode sheet scraps generated during the production of artificial graphite negative electrode sheets for power batteries were soaked in hot water (the temperature of the hot water was 80°C) for 1 hour to separate the copper foil fragments. The remaining slurry was then filtered and dried at 110°C for 5 hours to obtain a composite powder (including graphite, a conductive agent, and a binder in a mass ratio of 95:2:3, with acetylene black as the conductive agent and carboxymethyl cellulose and styrene-butadiene rubber as the binder).

[0034] The composite powder was ground and sieved in sequence, and then calcined in an oxidation furnace at 450°C for 1 hour to obtain regenerated graphite containing a conductive agent (such as Figure 1 As shown by Figure 1 It can be seen that the product after calcination is spherical graphite, and the morphology remains intact after calcination; Figure 3 is the TEM image of the regenerated graphite containing the conductive agent, Figure 3 It can be seen that the regenerated graphite containing the conductive agent can clearly see the layered structure of graphite, which is a highly crystalline graphite material. There is no amorphous binder at the edge, indicating that the binder layer on the surface has disappeared).

[0035] Example 2

[0036] Graphite electrode sheet scraps generated during the production of artificial graphite negative electrode sheets for power batteries were soaked in hot water (the temperature of the hot water was 70°C) for 1.25 hours to separate the copper foil fragments. The remaining slurry was then filtered and dried at 115°C for 4 hours to obtain a composite powder (including graphite, a conductive agent, and a binder in a mass ratio of 95:2:3, with the conductive agent being acetylene black and the binder being carboxymethyl cellulose and styrene-butadiene rubber).

[0037] The composite powder is ground and sieved in sequence, and then calcined in an oxidation furnace at 400° C. for 1.5 hours to obtain regenerated graphite containing a conductive agent.

[0038] Example 3

[0039] Graphite electrode sheet scraps generated during the production of natural graphite negative electrode sheets for portable electronic device batteries were soaked in hot water (the temperature of the hot water was 60°C) for 1.5 hours to separate the copper foil fragments. The remaining slurry was then filtered and dried at 105°C for 6 hours to obtain a composite powder (including graphite, a conductive agent, and a binder in a mass ratio of 95:2:3, with the conductive agent being carbon black and the binder being carboxymethyl cellulose and styrene-butadiene rubber).

[0040] The composite powder is ground and sieved in sequence, and then calcined in an oxidation furnace at 350° C. for 2 hours to obtain regenerated graphite containing a conductive agent.

[0041] Comparative Example 1

[0042] The recycled graphite electrode scraps were soaked in hot water (the temperature of the hot water was 80°C) for 1 hour to separate the copper foil fragments. The remaining slurry was then filtered and dried at 110°C for 5 hours to obtain a composite powder (including graphite, a conductive agent and a binder in a mass ratio of 95:2:3, with the conductive agent being acetylene black and the binder being carboxymethyl cellulose and styrene-butadiene rubber).

[0043] Figure 2 is the TEM image of the composite powder, Figure 2 It can be seen that the interior of the composite powder is a layered structure of graphite, and the surface is coated with a layer of binder (carboxymethyl cellulose and styrene-butadiene rubber).

[0044] Test Case

[0045] The regenerated graphite containing the conductive agent obtained in Example 1 and the composite powder obtained in Comparative Example 1 were used as negative electrode materials to prepare button batteries. Specifically:

[0046] Electrode preparation

[0047] The regenerated graphite containing a conductive agent obtained in Example 1 and the composite powder obtained in Comparative Example 1 were used as the negative electrode active materials. Sodium carboxymethyl cellulose and styrene-butadiene rubber were used as the binder, and deionized water was used as the solvent. The mixture was mixed in a mass ratio of 96.5:1.5:2 and stirred evenly to form a slurry. The slurry was then applied to a smooth, clean copper foil using an automatic coating machine, with a scraper adjusting the coating thickness to 60 μm. After coating, the electrode sheet was placed in an 80°C oven for at least 12 hours to dry out the moisture. The dried electrode sheet was removed and cut into small discs with a 14 mm diameter using a die punch. These were the electrode sheets required for button cell assembly. To calculate parameters such as the specific capacity of the electrode material, the electrode sheets were accurately weighed using a 1 / 10,000th analytical balance, with the mass of the electrode sheets used in the assembled battery remaining within 0.5 mg. The accurately weighed electrode sheets were placed in a battery bag and placed in a vacuum drying oven at 80°C for at least 12 hours to remove adsorbed moisture from the electrode material. Before adding the active substance during slurry preparation, the active substance material needs to be ground into powder and sieved with a 200-mesh sample sieve to ensure uniform particles of the active substance material.

[0048] Battery assembly

[0049] The vacuum-dried electrode sheet is taken out and quickly placed in the glove box. The battery is assembled in the order of negative electrode shell - spring - gasket - metal lithium sheet - electrolyte - diaphragm - electrolyte - electrode sheet - gasket - positive electrode shell. Then, it is packaged using a button battery packaging machine to successfully assemble a button-type lithium-ion half-cell.

[0050] During battery assembly, all gaskets and lithium metal sheets must face the separator with their smooth sides to prevent burrs from piercing the separator and causing a short circuit. The diameter of the lithium metal sheet is 15.6 mm, and the diameter of the separator is 16 mm. The amount of electrolyte added twice is 50 μL.

[0051] Figure 4 The cycle performance curve of the button battery prepared from the regenerated graphite containing the conductive agent obtained in Example 1 and the composite powder obtained in Comparative Example 1 is shown in FIG. Figure 4 It can be seen that the regenerated graphite containing a conductive agent described in Example 1 still has a discharge specific capacity of 312.9 mA·h / g after 50 cycles at a current density of 0.1C, and the first discharge capacity and the first coulombic efficiency are 362.4 mA·h / g and 87.4%, respectively; the composite powder obtained in Comparative Example 1 has a discharge specific capacity of 79.4 mA·h / g after 50 cycles at a current density of 0.1C, and the first discharge capacity and the first coulombic efficiency are 3.4 mA·h / g and 2.1%, respectively.

[0052] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for regenerating graphite electrode sheet scraps, characterized in that: It consists of the following steps: Graphite electrode scraps were soaked in hot water for 1 hour to separate copper foil fragments, and the remaining slurry was filtered and dried at 110°C for 5 hours to obtain a composite powder; the temperature of the hot water was 80°C; the composite powder comprised graphite, a conductive agent, and a binder in a mass ratio of 95:2:3, wherein the conductive agent was acetylene black and the binder was carboxymethyl cellulose and styrene-butadiene rubber; The composite powder is ground and sieved in sequence, and then calcined in an oxidation furnace at 450° C. for 1 hour to obtain regenerated graphite containing a conductive agent.

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