Regenerated graphite material as well as preparation method and application thereof
By calcining waste graphite negative electrode materials at high temperature and quenching quickly, a submicro interface buffer layer is formed, which solves the problem of poor performance in recycling and utilization of waste graphite materials, and achieves efficient and low-cost graphite material repair, improving the electrochemical performance and resource utilization efficiency of lithium-ion batteries.
Patent Information
- Application Number
- CN202510513346.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-23
- Publication Date
- 2025-07-11
AI Technical Summary
The prior art is difficult to effectively recycle and utilize graphite negative electrode materials in waste lithium-ion batteries, resulting in waste of resources and poor performance, and the high-temperature calcination method has high energy consumption and low economic value.
By calcining the waste graphite negative electrode material at high temperature under a protective atmosphere, then quickly transfer it to a low-temperature cooling medium for quenching, a submicro-interface buffer layer is formed to repair graphite surface defects and improve its electrochemical properties.
The prepared recycled graphite material has excellent electrochemical properties and structural stability, significantly improving the capacity and rate performance of lithium-ion batteries, and is cheap and environmentally friendly.
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Abstract
Description
Technical Field
[0001] The present invention relates to a kind of graphite, in particular to a recycled graphite material, and also relates to its preparation method and application, belonging to the technical field of waste battery recycling. Background Art
[0002] The recycling of lithium-ion batteries is the last link to complete the new energy industry closed-loop, which is crucial for ensuring the healthy and orderly development of China's new energy industry. However, the service life of lithium-ion batteries is generally less than 10 years, and the wave of retired lithium-ion batteries is coming. Graphite is the main negative electrode material in the lithium-ion battery system and also an important strategic mineral resource in China. However, at present, effective recycling of the graphite negative electrode of waste lithium-ion batteries has not been achieved. At present, a large amount of waste graphite is used as fuel for incineration, resulting in a large amount of waste of resources. Waste graphite has many surface defects and large anisotropy. When directly used as the negative electrode material of lithium-ion batteries, its capacity is low and the rate performance is poor. Although the direct regeneration process by high-temperature calcination can restore the crystal phase of graphite materials, it is difficult to repair the surface characteristics of waste graphite, resulting in poor rate performance, high energy consumption and low economic value. Therefore, there is an urgent need to develop a low-cost and high-performance repair technology for waste graphite. Summary of the Invention
[0003] Aiming at the problems existing in the prior art, the first object of the present invention is to provide a recycled graphite material. This recycled graphite material has excellent electrochemical performance, high rate and stable structure.
[0004] The second object of the present invention is to provide a preparation method of a recycled graphite material. This method has easily available raw materials, low cost, simple method, low energy consumption and no secondary pollution.
[0005] The third object of the present invention is to provide an application of a recycled graphite material. When this graphite is used as the negative electrode material for lithium-ion batteries, the battery capacity can be greatly improved.
[0006] In order to achieve the above technical objects, the present invention provides a preparation method of a recycled graphite material, and this method is: calcining the waste graphite negative electrode material under a protective atmosphere and then immediately placing it in a cooling medium for quenching to obtain recycled graphite.
[0007] The present invention first conducts high-temperature degumming (removing substances such as binders) on the waste graphite negative electrode material to make the graphite in a highly dispersed state, and at the same time raises the temperature of the graphite itself. Then, during the process of quickly transferring the graphite in the high-temperature state to the cooling medium for quenching, the surface defects and void structures of the failed graphite are regulated to form a sub-micro interface buffer layer, improving the ion pumping ability, thereby improving the rate performance of the recycled graphite material.
[0008] As a preferred solution, the waste graphite anode material is obtained by manually disassembling or mechanically disassembling the anode sheet of the graphite-based waste lithium-ion battery, and then through ultrasonic aqueous phase separation.
[0009] As a preferred solution, the calcination temperature is 500~1800 °C, more preferably 600~1200 °C; the calcination time is 5~40 h, more preferably 5~15 h. Controlling the calcination temperature within a suitable range is beneficial to improving the performance of the graphite material. If the calcination temperature is too low, the degumming effect is not obvious, the particles are prone to agglomeration, and the temperature of the graphite particles themselves is relatively low, making it difficult to have an effective surface interface gasification reaction with water; if the calcination temperature is too high, the temperature of the graphite particles themselves is too high, and the reaction with water is too intense, resulting in a decrease in the carbon content of the graphite material.
[0010] As a preferred solution, the protective atmosphere is at least one of inert gas and nitrogen. The inert gas is argon.
[0011] As a preferred solution, the temperature of the cooling medium does not exceed -10 °C. The lower the temperature of the cooling medium, the more obvious the cold extraction effect and the better the surface regulation effect when the graphite contacts the cooling medium.
[0012] As a preferred solution, the cooling medium is a salt-containing solution. The salt-containing solution has a low freezing point, which meets the requirements of high-temperature graphite quenching. The lower the temperature of the salt-containing solution, the more capable it is of inducing cracks in the near-surface structure of high-temperature graphite during the rapid quenching process, thereby improving the ion rapid embedding ability.
[0013] As a preferred solution, the salt in the salt-containing solution includes at least one of metal nitrates, metal sulfates, metal chlorides, metal carbonates, and metal acetates.
[0014] As a preferred solution, the metal includes at least one of lithium, sodium, potassium, and magnesium.
[0015] As a preferred solution, the molar concentration of the salt in the salt-containing solution is the saturated molar concentration. Using a salt solution with a saturated concentration can prevent the aqueous solution from freezing at low temperatures, thereby ensuring quenching at lower temperatures and improving the surface interface regulation effect of the material.
[0016] As a preferred solution, the salt-containing solution also contains a dispersant.
[0017] As a preferred solution, the dispersant includes at least one of sodium carboxymethyl cellulose (CMC), polyacrylic acid, ethanol, sodium dodecyl sulfonate, and dodecyl trimethyl ammonium bromide.
[0018] As a preferred solution, the mass-volume ratio of the calcined graphite material to the cooling medium is 0.1~1 g:10 ml.
[0019] As a preferred solution, the quenching time is 0.5 - 5h. Controlling the quenching time within a suitable range is beneficial to improving the performance of the graphite material. If the quenching time is too short, the graphite material cannot be cooled rapidly enough, affecting the interface regulation effect; if the quenching time is too long, it will cause too high energy consumption and increase the cost.
[0020] As a preferred solution, the stirring speed during the quenching process is 200 - 3000rmp. Controlling the rotation speed within a suitable range during the quenching process can promote the quenching effect. If the stirring speed is too small, it is not conducive to the effective dispersion of graphite in the cooling medium, resulting in uneven reaction of single-particle graphite materials during the quenching process; if the stirring speed is too large, it may cause the graphite material to fly away and it is difficult to form a stable quenching process.
[0021] The present invention also provides a regenerated graphite material, which is prepared by the above method. The regenerated graphite material in the present invention has rich surface active sites, has certain near-surface interlayer fissures, and the formed holes have smooth edges, which is beneficial to the high-rate storage of lithium ions and improves the high-rate storage capacity of the material.
[0022] The present invention also provides an application of the regenerated graphite material, which is used as a negative electrode material for lithium-ion batteries. This material can significantly improve the capacity of lithium battery materials and has high stability.
[0023] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:
[0024] (1) The regenerated graphite material prepared by the present invention has excellent electrochemical performance and stable structure;
[0025] (2) Using waste graphite raw materials as raw materials, the cost is low. Through low-temperature quenching, the purpose of quickly eliminating and repairing the incomplete components and acetylene black on the graphite surface can be achieved. The repaired graphite surface is beneficial to the rapid storage of ions, and can improve the pumping ability near the surface of the material, effectively improving the rate performance of the regenerated graphite material. Moreover, this method is simple, has a short cycle, and high economic benefits. Description of the Drawings
[0026] Figure 1 It is the SEM diagram of the regenerated graphite material prepared in Example 1 of the present invention.
[0027] Figure 2 It is the charge-discharge curve diagram of the lithium battery prepared with the regenerated graphite material of Example 1.
[0028] Figure 3 It is the cyclic stability performance diagram of the lithium battery prepared with the regenerated graphite material of Example 1. Detailed Embodiments
[0029] The following examples are used to illustrate the content of the present invention, but not to limit the protection scope of the claims of the present invention.
[0030] The waste graphite used in the present invention is derived from waste negative electrode sheets obtained by manual disassembly or mechanical disassembly, and relatively pure negative electrode materials obtained after ultrasonic aqueous phase separation. The waste batteries are graphite-based waste lithium-ion batteries purchased on the market.
[0031] Comparative Example 1
[0032] 1) Manually disassemble waste lithium-ion batteries to obtain waste negative electrode sheets, and through aqueous phase separation, quickly separate graphite from copper foil to obtain relatively pure graphite electrode materials; subsequently, dry 10 g of the graphite electrode materials and place them in a tube furnace. Under an argon atmosphere, calcine at a temperature of 1000 °C for 10 hours;
[0033] 2) Filter and dry the obtained turbid solution to obtain the regenerated graphite negative electrode material; subsequently, prepare electrode sheets from the obtained negative electrode material and assemble the batteries.
[0034] Comparative Example 2
[0035] 1) Manually disassemble waste lithium-ion batteries to obtain waste negative electrode sheets, and through aqueous phase separation, quickly separate graphite from copper foil to obtain relatively pure graphite electrode materials; subsequently, dry 10 g of the graphite electrode materials and place them in a tube furnace. Under an argon atmosphere, calcine at a temperature of 1000 °C for 10 hours;
[0036] 2) Without cooling, directly transfer the calcined graphite material to a normal temperature aqueous solution, stir for 2 h, and the rotation speed is 1000 rmp;
[0037] 3) Filter and dry the obtained turbid solution to obtain the regenerated graphite negative electrode material; subsequently, prepare electrode sheets from the obtained negative electrode material and assemble the batteries.
[0038] Example 1
[0039] 1) Manually disassemble waste lithium-ion batteries to obtain waste negative electrode sheets, and through aqueous phase separation, quickly separate graphite from copper foil to obtain relatively pure graphite electrode materials; subsequently, dry 10 g of the graphite electrode materials and place them in a tube furnace. Under an argon atmosphere, calcine at a temperature of 1000 °C for 10 hours;
[0040] 2) Without cooling, directly transfer the graphite material to a potassium chloride solution (cooling liquid) with a saturated concentration containing CMC dispersant, stir for 2 h, and the rotation speed is 1000 rmp; among them, the temperature of the cooling liquid is -15 °C, and the mass-volume ratio of the graphite material to the cooling liquid is 0.5 g : 10 ml;
[0041] 3) Filter and dry the obtained turbid solution to obtain the regenerated graphite anode material.
[0042] Example 2
[0043] The regenerated graphite material was prepared by the method of Example 1, except that the calcination temperature was 500 °C.
[0044] Example 3
[0045] The regenerated graphite material was prepared by the method of Example 1, except that the calcination temperature was 1800 °C. Due to the relatively high calcination temperature, the graphite produced by calcination reacted violently with water, C + H2O = CO + H2, causing a large amount of graphite to turn into gas and resulting in more graphite loss.
[0046] Example 4
[0047] The regenerated graphite material was prepared by the method of Example 1, except that the calcination time was 5 h.
[0048] Example 5
[0049] The regenerated graphite material was prepared by the method of Example 1, except that the calcination time was 40 h.
[0050] Example 6
[0051] The regenerated graphite material was prepared by the method of Example 1, except that the atmosphere during calcination was nitrogen.
[0052] Example 7
[0053] The regenerated graphite material was prepared by the method of Example 1, except that the cooling medium was a sodium chloride solution with a saturated concentration.
[0054] Example 8
[0055] The regenerated graphite material was prepared by the method of Example 1, except that the temperature of the cooling medium was controlled at -10 °C.
[0056] Example 9
[0057] The regenerated graphite material was prepared by the method of Example 1, except that the temperature of the cooling medium was controlled at -20 °C.
[0058] Example 10
[0059] The regenerated graphite material was prepared by the method of Example 1, except that the dispersant was ethanol.
[0060] Example 11
[0061] The regenerated graphite material was prepared by the method of Example 1, except that the mass-volume ratio of the graphite material to the coolant was 0.1 g : 10 ml.
[0062] Example 12
[0063] The regenerated graphite material was prepared by the method of Example 1, except that the mass-volume ratio of the graphite material to the coolant was 1 g : 10 ml.
[0064] Example 13
[0065] The regenerated graphite material was prepared by the method of Example 1, except that the stirring time of the graphite material in the cooling medium was 0.5 h.
[0066] Example 14
[0067] The regenerated graphite material was prepared by the method of Example 1, except that the stirring time of the graphite material in the cooling medium was 5 h.
[0068] Example 15
[0069] The regenerated graphite material was prepared by the method of Example 1, except that the stirring speed of the graphite material in the cooling medium was 200 rmp.
[0070] Example 16
[0071] The regenerated graphite material was prepared by the method of Example 1, except that the stirring speed of the graphite material in the cooling medium was 3000 rmp.
[0072] The graphite materials in each example and comparative example were respectively added with a quantitative aqueous solution according to the mass ratio of graphite material : acetylene black : sodium carboxymethyl cellulose (CMC) of 8 : 1 : 1 to prepare a uniform slurry. Each slurry was coated on a copper foil, and then placed in a vacuum oven at 800 °C for 12 h of drying. The obtained electrode sheets were then cut by a slicing machine into small round pieces with a diameter of 1 cm to obtain the negative electrode materials, where more than 1 mg of active substances were loaded on the copper foil.
[0073] The obtained positive electrode sheets, electrolyte, lithium sheets, battery cases, diaphragms, etc. were placed in an argon glove box for battery assembly. After sealing, the obtained batteries were the assembled button cells.
[0074] After standing the obtained button cells for 12 h, they were placed on a Blue-Energy test channel for electrochemical performance testing. The results are shown in Table 1, where the current density was set to 1.0 C and the voltage range was set to 0.01 - 2.5 V, etc.
[0075]
[0076] As can be seen from Table 1, the cooling medium has a significant impact on the electrochemical properties of graphite. The lower the temperature of the cooling medium and the greater the rotation speed during the cooling process, the more conducive it is to the rapid cold extraction of high-temperature graphite and the realization of uniform depth treatment on the graphite surface. When the graphite undergoes a cooling behavior in the cooling medium, an extended cooling time hardly has a significant impact on the graphite properties. In addition, the higher the calcination temperature of the graphite and the greater the temperature difference between the graphite and the cooling medium, the more conducive it is to the etching and energy storage activation of the graphite surface.
[0077] In addition, a morphological analysis was performed on the regenerated graphite material prepared in Example 1 of the present invention, as Figure 1 described. It can be seen that there are tiny holes and cracks on the surface of the graphite after the cooling treatment, which is conducive to the energy storage behavior.
[0078] Figure 2 Figure -1 is the charge-discharge curve of a lithium battery prepared using the regenerated graphite material of Example 1. Among them, at a current density of 1.0 C and a voltage of 0.01 - 2.5 V, its capacity was measured to be 316 mAh g
[0079] Figure 3 Figure is the cycle stability performance graph of a lithium battery prepared using the regenerated graphite material of Example 1. As can be seen from the figure, after 200 cycles, the capacity retention rate of the battery still remains nearly 100%.
Claims
1. A preparation method of a regenerated graphite material, characterized in that: The waste graphite anode material is calcined under a protective atmosphere and then immediately quenched in a cooling medium to obtain a regenerated graphite material.
2. The preparation method of a regenerated graphite material according to claim 1, characterized in that: The temperature of the calcination is 500 - 1800 °C, and the time of the calcination is 5 - 40 h.
3. The preparation method of a regenerated graphite material according to claim 1, characterized in that: The temperature of the cooling medium does not exceed -10 °C.
4. The preparation method of a regenerated graphite material according to claim 1 or 3, characterized in that: The cooling medium is a salt-containing solution.
5. The preparation method of a regenerated graphite material according to claim 4, characterized in that: The salt in the salt-containing solution includes at least one of metal nitrates, metal sulfates, metal chlorides, metal carbonates, and metal acetates; The metal includes at least one of lithium, sodium, potassium, and magnesium.
6. The preparation method of a regenerated graphite material according to claim 4, characterized in that: The molar concentration of the salt in the salt-containing solution is the saturated molar concentration.
7. The preparation method of a regenerated graphite material according to claim 4, characterized in that: The salt-containing solution further contains a dispersant; The dispersant includes at least one of sodium carboxymethyl cellulose, polyacrylic acid, ethanol, sodium dodecyl sulfonate, and dodecyl trimethyl ammonium bromide.
8. A method for preparing a regenerated graphite material according to claim 1 or 3, characterized in that: The mass-volume ratio of the calcined graphite material to the cooling medium is 0.1 - 1 g:10 ml; the time of the quenching is 0.5 - 5 h; the stirring speed during the quenching is 200 - 3000 rmp.
9. A regenerated graphite material, characterized in that: Prepared by the method according to any one of claims 1 - 8.
10. Use of a regenerated graphite material according to claim 9, characterized in that: Used as an anode material for lithium-ion batteries.