CN117326552B - Recovery method of waste graphite, purified graphite and application of purified graphite - Google Patents

Recovery method of waste graphite, purified graphite and application of purified graphite

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Publication number
CN117326552B
CN117326552B CN202311275704.5A CN202311275704A CN117326552B CN 117326552 B CN117326552 B CN 117326552B CN 202311275704 A CN202311275704 A CN 202311275704A CN 117326552 B CN117326552 B CN 117326552B
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graphite
acid
purified
graphite according
waste
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CN117326552A (en
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白文德
杜新伟
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Svolt Energy Technology Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/21—After-treatment
    • C01B32/215—Purification; Recovery or purification of graphite formed in iron making, e.g. kish graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/84—Recycling of batteries or fuel cells

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  • Inorganic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
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  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
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  • Manufacturing & Machinery (AREA)
  • Carbon And Carbon Compounds (AREA)

Abstract

The invention discloses a recovery method of waste graphite, purified graphite and application thereof. The recovery method comprises the following steps of 1) mixing a composition of acid and hydrogen peroxide with waste graphite, heating and curing to obtain cured graphite, 2) mixing the cured graphite with acid liquor, carrying out microwave treatment, mixing the mixed liquor after the microwave treatment with an accelerator, and carrying out high-pressure acid leaching treatment to obtain purified graphite, wherein the accelerator is a mixed organic solution, and the mixed organic solution comprises phosphate. According to the method, the curing and acid leaching are utilized, and the microwave and the accelerator are matched, so that the impurity content and the interlayer spacing can be effectively reduced, the conductivity of graphite is improved, and the prepared purified graphite is further subjected to high-temperature regeneration, so that the impurity content can be further reduced, the conductivity is improved, the graphitization degree is increased, and the electrochemical performance of the graphite applied to a battery is improved.

Description

Recovery method of waste graphite, purified graphite and application of purified graphite
Technical Field
The invention relates to the technical field of waste battery recovery, in particular to a recovery method of waste graphite, purified graphite and application thereof.
Background
With the development of economy, countries around the world are aware of the shortage of resources. The yield of lithium ion batteries is also increasing, and the average annual yield increase rate is kept above 32%. Generally, the service life of lithium ion batteries is about 5 years, and the problem of disposing of these waste batteries has now been paid attention to in various countries in the world. Graphite is used as the most common negative electrode material of commercial lithium ion batteries, and accounts for more than eighty percent of the negative electrode material. Graphite has good conductivity, ordered crystalline structure and reversible lithium ion storage performance. After long-time circulation, the anode graphite in the failed lithium ion battery still has a complete lattice structure, but due to the long-time reaction process, some lithium ions in the layered structure of the graphite cannot be removed after intercalation, so that the anode graphite remains in active sites of the graphite, namely commonly called dead lithium, and in addition, in the primary circulation process of the graphite, electrolyte and the graphite undergo side reaction to generate a solid electrolyte interface passivation film, so that the circulation performance of the graphite is failed.
At present, a complete and careful recovery process and an industrialized complete process are not established like the anode material, but the anode material in the lithium ion battery retired every year is gradually increased year by year, and huge pressure is brought to the environment and resource utilization, so that the establishment of a process standard and an industrialized process of anode recovery is urgently needed.
At present, the graphite is recovered by adopting a high-temperature burning and acid leaching method, but the former generates a large amount of toxic and harmful gas to pollute the environment, the latter can not effectively remove impurities in the graphite by acid leaching alone, and the binder, the metal oxide and lithium among graphite layers can not be removed as much as possible. The recycled graphite material has a larger interlayer spacing than commercial graphite and a tendency to delaminate, affecting the reuse of the recycled graphite and creating significant time costs.
Therefore, the recovery method of the waste graphite to obtain the high-performance regenerated graphite material is a technical problem to be solved urgently at present.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a recovery method of waste graphite, purified graphite and application thereof.
In order to achieve the above purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a method for recovering waste graphite, comprising the following steps:
(1) Mixing the acid and hydrogen peroxide composition with waste graphite, and heating to cure to obtain cured graphite;
(2) Mixing the cured graphite with acid liquor, carrying out microwave treatment, mixing the mixed liquor after the microwave treatment with an accelerator, and carrying out high-pressure acid leaching treatment to obtain purified graphite;
Wherein the accelerator is a mixed organic solution, and the mixed organic solution comprises phosphate.
In one embodiment, the waste graphite is powder after the current collector is removed from the graphite negative electrode disassembled from the waste lithium ion battery, or the powder after the current collector is removed from the graphite negative electrode in the cell which is disabled in the production process, and the waste graphite comprises a binder.
In the present invention, the graphite negative electrode means that graphite is included as an active material in the negative electrode, and in one embodiment, all of the active material in the negative electrode is graphite.
In the method, the composition of the acid (for example, mixed acid with oxidability) and the hydrogen peroxide is adopted to cure the waste graphite cathode, so that the oxidation to salt reaction of metal simple substance and oxide in the waste graphite can be accelerated, and meanwhile, the aging decomposition of the binder in the waste graphite cathode can be accelerated. The method has the advantages that the cured graphite is subjected to microwave treatment in the acid liquor, the microwave reaction can accelerate the dissolution and precipitation of impurities such as salt generated in the curing process, the interlayer spacing of the graphite is reduced, the graphite structure is recovered, and meanwhile, the mixed liquor after the microwave treatment is subjected to high-pressure acid leaching treatment under the action of the accelerator, so that the chemical and leaching dynamic reaction process can be accelerated, the impurity precipitation is accelerated, the impurities in the acid leaching process are reduced, and the interlayer spacing of the graphite is further reduced. XRD detection shows that the impurity peak is almost disappeared, the interlayer spacing is obviously reduced compared with that of waste graphite, and the purified graphite has good conductivity and good electrochemical performance when being applied to the negative electrode of a lithium ion battery.
In the present invention, if no accelerator is used in the preparation method, or other types of additives are used instead of the accelerator of the present invention, the performance of the graphite material is reduced, and thus the electrochemical performance of the battery assembled using the same is reduced.
The following preferred technical solutions are used as the present invention, but not as limitations on the technical solutions provided by the present invention, and the technical objects and advantageous effects of the present invention can be better achieved and achieved by the following preferred technical solutions.
Preferably, the phosphate ester includes at least one of triethyl phosphate and dimethyl phosphate.
Preferably, the mixed organic solution further comprises at least one of ketone and azomethyl pyrrolidone;
preferably, the mixed organic solution is a mixture of triethyl phosphate and acetone in a volume ratio of (1-4): 1, e.g. 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or 4:1, etc.
Preferably, the ratio of the addition amount of the accelerator to the mass of the waste graphite is 1 (5-10), such as 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10.
In step (1), the acid in the combination of acid and hydrogen peroxide comprises at least two of nitric acid, acetic acid, hypochlorous acid, phosphoric acid, and citric acid.
Preferably, in step (1), the acid in the composition of acid and hydrogen peroxide is a mixed solution of 98wt% concentrated sulfuric acid and 90wt% concentrated hydrochloric acid, wherein the volume ratio of concentrated sulfuric acid to concentrated hydrochloric acid is 2:5-5:2, i.e. 0.4-2.5, such as 0.4, 0.6, 1, 1.3, 1.6, 2, 2.2 or 2.5, etc.
Preferably, in step (1), the ratio of the mass of the spent graphite to the mass of the combination of acid and hydrogen peroxide is 50 (20-100), i.e. 2.5-0.5, such as 2.5, 2.3, 2, 1.8, 1.5, 1.2, 1, 0.8 or 0.5, etc.
Preferably, in step (1), the concentration of hydrogen peroxide is 30wt%, and the mass ratio of hydrogen peroxide is 10-20%, for example 10%, 12%, 14%, 15%, 16%, 18% or 20%, etc., based on 100% of the total mass of the acid and the graphite anode.
Preferably, the mixing in step (1) is accompanied by stirring.
Preferably, the mixing time of step (1) is 20-60min, such as 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min or 60min, etc.
Preferably, in step (1), the temperature is raised to 80-180 ℃ for curing, and the temperature may be, for example, 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃ or the like.
Preferably, in step (1), the curing time is 4-32h, for example 4h, 6h, 8h, 10h, 12h, 15h, 18h, 20h, 22h, 24h, 26h, 28h, 30h or 32h, etc.
Preferably, the curing of step (1) is performed in a crucible.
Preferably, the acid solution in step (2) is a mixed solution of sulfuric acid solution with a concentration of 1-3mol L -1 (such as 1mol L -1、1.5mol L-1、mol L-1、2mol L-1、2.5mol L-1 or 3mol L -1, etc.) and hydrochloric acid solution with a concentration of 1-3mol L -1 (such as 1mol L -1、1.5mol L-1、mol L-1、2mol L-1、2.5mol L-1 or 3mol L -1, etc.), and the volume ratio of sulfuric acid solution to hydrochloric acid solution is (1-3): 1, such as 1:1, 1.5:1, 2:1, 2.5:1 or 3:1, etc.
Preferably, in step (2), the solid to liquid ratio of the mature graphite to the acid liquor is from 2:1 to 1:10, i.e. from 2:1 to 0.1:1, such as 2:1, 1.7:1, 1.5:1, 1.2:1, 1:1, 0.8:1, 0.5:1, 0.3:1 or 0.1:1, etc.
Preferably, in the step (2), after the cured graphite is mixed with the acid solution, the mixture is stirred for 20-40min and then subjected to microwave treatment, and the stirring time can be, for example, 20min, 25min, 30min, 35min or 40 min.
Preferably, the power of the microwave treatment in step (2) is 50-1500W, for example 50W, 100W, 200W, 300W, 400W, 500W, 600W, 700W, 800W, 900W, 1000W, 1100W, 1200W, 1300W, 1400W or 1500W, etc.
Preferably, the number of microwave treatments in step (2) is 9-12, such as 9, 10, 11 or 12, and the time of each microwave treatment is independently 8-15s, such as 8s, 9s, 10s, 11s, 12s, 13s or 15 s.
Preferably, the temperature of the high pressure acid leaching treatment of step (2) is 120-200 ℃, e.g. 120 ℃, 130 ℃, 140 ℃,150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃, 200 ℃, etc.
Preferably, the high pressure acid leaching treatment of step (2) is carried out for a period of time ranging from 18 to 33 hours, for example 18 hours, 20 hours, 21 hours, 23 hours, 25 hours, 28 hours, 30 hours or 32 hours, etc.
In the present invention, the high pressure acid leaching treatment is carried out in a closed vessel in which the reactants, when subjected to heating, generate high pressure.
Preferably, after the high pressure acid leaching treatment in step (2), the product is further subjected to washing and drying steps.
In a second aspect, the present invention provides purified graphite obtained by the recovery process of the first aspect.
In a third aspect, the present invention provides a reclaimed graphite prepared from the purified graphite of the second aspect.
In a fourth aspect, the present invention provides a method for preparing the regenerated graphite according to the third aspect, the method comprising the steps of:
mixing the purified graphite in the second aspect with borax, and roasting to obtain the regenerated graphite.
The method uses borax as a regeneration promoter, and further removes impurities on the surface of graphite by utilizing the characteristics of sublimation and reduction of borax at high temperature, reduces the oxygen content and the impurity content of the graphite, improves the graphitization degree of the graphite, and promotes the recovery and regeneration of the graphite to the commercial graphite performance.
Preferably, the mass ratio of the purified graphite to the borax is 5:1-20:1, such as 5:1, 7:1, 8:1, 10:1, 12:1, 15:1, 17:1, 18:1, or 20:1, etc.
Preferably, the mixing mode of the purified graphite and the borax is grinding mixing.
Preferably, the calcination is performed under the protection of a protective gas.
Preferably, the protective gas comprises at least one of nitrogen, helium and argon.
Preferably, the firing temperature is 1600-2000 ℃, e.g., 1600 ℃, 1650 ℃, 1700 ℃, 1750 ℃, 1800 ℃, 1900 ℃, 1950 ℃, 2000 ℃, or the like.
Preferably, the calcination time is 2-4 hours, such as 2 hours, 2.2 hours, 2.5 hours, 3 hours, 3.3 hours, 3.6 hours, 4 hours, etc.
The interlayer spacing of the regenerated graphite is basically the same as that of commercial graphite, the interlayer spacing is obviously reduced compared with that of purified graphite, and the graphitization degree of the regenerated graphite is improved, the conductivity is improved and the impurity content is reduced compared with that of purified graphite. Therefore, the electrochemical performance of the regenerated graphite applied to the battery is further improved compared with that of the purified graphite.
In a fifth aspect, the present invention provides a negative electrode comprising the regenerated graphite according to the third aspect.
In a sixth aspect, the present invention provides a lithium ion battery, where the lithium ion battery includes the negative electrode according to the fifth aspect.
The numerical ranges recited herein include not only the recited point values, but also any point values between the recited numerical ranges that are not recited, and are limited to, and for the sake of brevity, the invention is not intended to be exhaustive of the specific point values that the recited range includes.
Compared with the prior art, the invention has the following beneficial effects:
(1) In the method, the composition of the acid (for example, mixed acid with oxidability) and the hydrogen peroxide is adopted to cure the waste graphite cathode, so that the oxidation to salt reaction of metal simple substance and oxide in the waste graphite can be accelerated, and meanwhile, the aging decomposition of the binder in the waste graphite cathode can be accelerated. The method has the advantages that the cured graphite is subjected to microwave treatment in the acid liquor, the microwave reaction can accelerate the dissolution and precipitation of impurities such as salt generated in the curing process, the interlayer spacing of the graphite is reduced, the graphite structure is recovered, and meanwhile, the mixed liquor after the microwave treatment is subjected to high-pressure acid leaching treatment under the action of the accelerator, so that the chemical and leaching dynamic reaction process can be accelerated, the impurity precipitation is accelerated, the impurities in the acid leaching process are reduced, and the interlayer spacing of the graphite is further reduced. XRD detection shows that the impurity peak is almost disappeared, the interlayer spacing is obviously reduced compared with that of waste graphite, and the purified graphite has good conductivity and good electrochemical performance when being applied to the negative electrode of a lithium ion battery.
(2) The interlayer spacing of the regenerated graphite is basically the same as that of commercial graphite, the interlayer spacing is obviously reduced compared with that of purified graphite, and the graphitization degree of the regenerated graphite is improved, the conductivity is improved and the impurity content is reduced compared with that of purified graphite. Therefore, the electrochemical performance of the regenerated graphite applied to the battery is further improved compared with that of the purified graphite.
Drawings
Fig. 1 is an SEM image of spent graphite.
FIG. 2 is a graph showing the effect of different volume ratios of acids in a mixed acid on impurity removal in the aging step.
FIG. 3 is a graph showing the effect of different mass ratios (i.e., solid to liquid ratios) of waste graphite and mixed acid on impurity removal.
FIG. 4 is a graph showing the effect of different H 2O2 solution ratios on impurity removal.
FIG. 5 is a graph showing the comparison of the element contents in graphite before and after the microwave reaction in example 1.
FIG. 6 is a graph showing the effect of different pickling times on the removal of impurities.
FIG. 7 is a graph showing the effect of different pickling temperatures on the removal of impurities.
FIG. 8 is an SEM image of purified graphite prepared in example 1
Fig. 9 is an XRD pattern of the purified graphite and the regenerated graphite prepared in example 1.
Fig. 10 is a raman spectrum of the waste graphite, purified graphite and regenerated graphite in example 1.
FIG. 11 is a cycle performance curve of application example 1-A, application example 1-B, application comparative example 1and application comparative example 2, wherein the negative electrode material in application example 1-A is purified graphite in example 1, the negative electrode material in application example 1-B is regenerated graphite in example 1, the negative electrode material in application comparative example 1 is waste graphite, and the negative electrode material in application comparative example 2 is commercial graphite.
Detailed Description
The technical scheme of the invention is further described below by the specific embodiments with reference to the accompanying drawings.
In the embodiment of the invention, the ternary waste battery core refers to a ternary material of an anode active substance in the battery core.
In the embodiment of the invention, the solid-liquid mixture in the step (1) refers to a mixture of mixed acid and the negative electrode plate in the step (1).
Example 1
A method for recycling waste graphite comprises the following steps:
(1) Curing of waste graphite
Taking a negative electrode plate which is disassembled from a 0% SOH ternary waste battery cell, scraping an active layer from a current collector from the negative electrode plate to obtain 50g of waste graphite powder, placing waste graphite into a polytetrafluoroethylene container, mixing and stirring 100g of mixed acid (the volume ratio of the mixed acid is V Sulfuric acid ：V Hydrochloric acid = 1.2:1) and H 2O2 solution (the mass concentration is 30 wt%) accounting for 20% of the mass of a solid-liquid mixture by using a mixed solution of concentrated sulfuric acid with the mass concentration of 98wt% and concentrated hydrochloric acid with the mass concentration of 90wt%, and placing the graphite mixture into a corundum crucible for curing for 25H at 150 ℃ to enable metal and metal oxide in the graphite to fully react and dissolve, thus obtaining cured graphite.
In step (1) of this example, the ratio of the mass of the waste graphite to the mass of the mixed acid (i.e., the solid-liquid ratio) was 0.5.
(2) Preparation of purified graphite
Mixing cured graphite with acid liquor (mixed solution of H 2SO4 solution with concentration of 2mol L -1 and HCl solution with concentration of 1mol L -1, wherein the volume ratio of the H 2SO4 solution to the HCl solution is V Sulfuric acid ：V Hydrochloric acid =2:1) according to the solid-liquid ratio of 1:1 to obtain a solid-liquid mixture, stirring the solid-liquid mixture for 30min, carrying out microwave reaction on the mixture by using a microwave reactor, setting the power to be 1000W, carrying out microwave reaction for 10 times, each time of reaction time for 10s, placing the mixture after the microwave reaction in a high-pressure reaction kettle, adding 6.25g of accelerator (mixed organic solution with the volume ratio of triethyl phosphate to acetone of 2:1), carrying out acid leaching for 24H in a 140 ℃ environment, taking out graphite, washing to be neutral by deionized water, and drying in a vacuum oven at 80 ℃ to obtain purified graphite.
In this example, V Sulfuric acid ：V Hydrochloric acid = 1.2:1 in the mixed acid used in step (1).
Fig. 1 is an SEM image of waste graphite, and fig. 8 is an SEM image of purified graphite, and SEM analysis shows that the binder and metal impurities in the material are effectively removed through curing and acid leaching, and the purified graphite material basically presents a purified graphite state, and the surface of the purified graphite is smoother than that of the waste graphite.
ICP detection is carried out on graphite before and after microwave reaction, so that the content of Li, al, co, cu, ni, fe and Mn element in the graphite is obtained, and the result is shown in FIG. 5. The figure shows that the microwave reaction has a remarkable influence on the impurity removal effect, and the microwave reaction is beneficial to the impurity removal.
ICP detection is carried out on the purified graphite to obtain the content of Li, al, co, cu, ni, fe and Mn element in the purified graphite, and the result is shown in figure 2.
The preparation method of the regenerated graphite comprises the following steps:
Sampling the purified graphite and borax according to the mass ratio of 10:1, fully grinding and mixing in an agate mortar to obtain a graphite and borax mixture, placing the mixture in a corundum crucible, placing the corundum crucible containing the mixture in a high-temperature tube furnace, and roasting for 3 hours at 1800 ℃ in an argon atmosphere to obtain the regenerated graphite.
Fig. 9 is an XRD pattern of the purified graphite and the regenerated graphite prepared in this example. XRD analysis and Bragg equation (nλ= dsin θ) show that the interlayer spacing of the purified graphite is obviously reduced compared with waste graphite and the impurity peak almost disappears, but the interlayer spacing is higher than that of commercial graphite, so that graphite impurities are basically removed through two processes of curing and acid leaching, meanwhile, the effect of reducing the impurity content and reducing the interlayer spacing by using an accelerator and microwave reaction is obvious, the interlayer spacing of regenerated graphite is basically the same as that of commercial graphite and obviously reduced compared with the purified graphite, and the method of regenerating borax and high temperature is adopted to reduce graphite impurities, improve the graphitization degree of graphite and promote graphite normalization.
Fig. 10 is a raman spectrum of the waste graphite, purified graphite and regenerated graphite in this example. The result shows that the graphitization degree of the graphite is further improved through purification and regeneration, which shows that the curing, acid leaching and high-temperature regeneration play a key role in promoting the graphite regeneration.
Example 2
A method for recycling waste graphite comprises the following steps:
(1) Curing of waste graphite
Taking a negative electrode plate which is disassembled from a 0% SOH ternary waste battery cell, scraping an active layer from a current collector from the negative electrode plate to obtain 50g of waste graphite powder, placing waste graphite into a polytetrafluoroethylene container, mixing and stirring 70g of mixed acid (a mixed solution of concentrated sulfuric acid with the mass concentration of 98wt% and concentrated hydrochloric acid with the mass concentration of 90wt%, wherein the volume ratio of the mixed acid to the mixed solution is V Sulfuric acid ：V Hydrochloric acid = 2:1) and H 2O2 solution (the mass concentration of 30 wt%) accounting for 15% of the mass of a solid-liquid mixture for 50min, placing the graphite mixture into a corundum crucible, curing for 10H at 110 ℃, and fully reacting and dissolving metal and metal oxide in the graphite to obtain cured graphite;
(2) Preparation of purified graphite
Mixing cured graphite with acid liquor (a mixed solution of H 2SO4 solution with the concentration of 1mol L -1 and HCl solution with the concentration of 1.5mol L -1, wherein the volume ratio of the H 2SO4 solution to the HCl solution is V Sulfuric acid ：V Hydrochloric acid =1:1) according to the solid-liquid ratio of 1:5 to obtain a solid-liquid mixture, stirring the solid-liquid mixture for 20min, carrying out microwave reaction on the mixture by using a microwave reactor, setting the power to be 700W, carrying out microwave reaction for 12 times, each time for 8s, placing the mixture after microwave reaction in a high-pressure reaction kettle, adding 5g of accelerator (a mixed organic solution with the volume ratio of triethyl phosphate to acetone of 3:1), carrying out acid leaching for 18H in a 130 ℃ environment, taking out graphite, washing to be neutral by using deionized water, and drying in a vacuum oven at 90 ℃ to obtain purified graphite.
The preparation method of the regenerated graphite comprises the following steps:
Sampling the purified graphite and borax after acid leaching, cleaning and drying according to the mass ratio of 15:1, fully grinding and mixing in an agate mortar to obtain a graphite and borax mixture, placing the mixture in a corundum crucible, placing the corundum crucible containing the mixture in a high-temperature tube furnace, and roasting for 2 hours at 2000 ℃ in an argon atmosphere to obtain the regenerated graphite.
Example 3
A method for recycling waste graphite comprises the following steps:
(1) Curing of waste graphite
Taking a negative electrode plate which is disassembled from a 0% SOH ternary waste battery cell, scraping an active layer from a current collector from the negative electrode plate to obtain 50g of waste graphite powder, placing waste graphite into a polytetrafluoroethylene container, mixing and stirring 30g of mixed acid (a mixed solution of concentrated sulfuric acid with the mass concentration of 98wt% and concentrated hydrochloric acid with the mass concentration of 90wt%, wherein the volume ratio of the mixed acid to the mixed solution is V Sulfuric acid ：V Hydrochloric acid = 2.5:1) and H 2O2 solution (the mass concentration of 30 wt%) accounting for 10% of the mass of a solid-liquid mixture for 20min, placing the graphite mixture into a corundum crucible, curing for 6H at 170 ℃ to enable metal and metal oxide in the graphite to fully react and dissolve, and obtaining cured graphite;
(2) Preparation of purified graphite
Mixing cured graphite with acid liquor (mixed solution of H 2SO4 solution with concentration of 3mol L -1 and HCl solution with concentration of 2mol L -1, wherein the volume ratio of the H 2SO4 solution to the HCl solution is V Sulfuric acid ：V Hydrochloric acid =2.5:1) according to a solid-liquid ratio of 1:7 to obtain a solid-liquid mixture, stirring the solid-liquid mixture for 40min, carrying out microwave reaction on the mixture by using a microwave reactor, setting the power to 1250W, carrying out microwave reaction for 9 times, each time of reaction time for 15s, placing the mixture after microwave reaction in a high-pressure reaction kettle, adding 10g of accelerator (mixed organic solution with the volume ratio of triethyl phosphate to acetone of 2.5:1), carrying out acid leaching for 30H in a 180 ℃ environment, taking out graphite, washing the graphite to be neutral by deionized water, and drying the graphite in a vacuum oven at 80 ℃ to obtain purified graphite.
The preparation method of the regenerated graphite comprises the following steps:
Sampling the purified graphite and borax according to the mass ratio of 7:1, fully grinding and mixing in an agate mortar to obtain a graphite and borax mixture, placing the mixture in a corundum crucible, placing the corundum crucible containing the mixture in a high-temperature tube furnace, and roasting at 1650 ℃ for 4 hours in an argon atmosphere to obtain the regenerated graphite.
Examples 4 to 7
A method for recycling waste graphite is different from the method in the embodiment 1 in that in the mixed acid adopted in the step (1), V Sulfuric acid ：V Hydrochloric acid is respectively 0.4, 0.8, 2 and 2.5 in sequence.
The process for preparing regenerated graphite differs from example 1 in that the purified graphite prepared in example 1 is replaced by the purified graphite prepared in examples 4 to 7, respectively.
ICP detection was performed on the purified graphite prepared in examples 4 to 7 in the same manner as in example 1 to obtain the contents of Li, al, co, cu, ni, fe and Mn element therein, and the results are shown in FIG. 2.
As can be seen from FIG. 2, when V Sulfuric acid ：V Hydrochloric acid is within the range of 0.4-2.5, a good impurity removal effect can be achieved, the effect of V Sulfuric acid ：V Hydrochloric acid on removing cobalt ions is large, and when V Sulfuric acid ：V Hydrochloric acid is within the range of 0.8-2, the comprehensive impurity removal effect of multiple elements is better.
Examples 8 to 11
A method for recovering waste graphite is different from example 1 in that in step (1), the ratio of the mass of waste graphite to the mass of mixed acid (i.e., solid-to-liquid ratio) is 1, 1.5, 2 and 2.5, respectively.
The process for preparing regenerated graphite differs from example 1 in that the purified graphite prepared in example 1 is replaced by the purified graphite prepared in examples 4 to 7, respectively.
ICP detection was performed on the purified graphite prepared in examples 8 to 11 in the same manner as in example 1 to obtain the contents of Li, al, co, cu, ni, fe and Mn element therein, and the results are shown in FIG. 3.
As can be seen from fig. 3, in the curing process, the ratio of the mass of the waste graphite to the mass of the mixed acid (i.e., solid-liquid) is in the range of 2.5-0.5, the overall trend of the impurity removal effect becomes better as the solid-liquid ratio is reduced, the cobalt element is greatly affected by the solid-liquid ratio, and the comprehensive impurity removal effect on a plurality of elements is better when the solid-liquid ratio is in the range of 1.5-0.5.
Examples 12 to 15
A method for recycling waste graphite is different from example 1 in that in the step (1), the mass ratio of H 2O2 solution is 10%, 15%, 25% and 30%.
The process for producing regenerated graphite differs from example 1 in that the purified graphite produced in example 1 is replaced with the purified graphite produced in examples 12 to 15, respectively.
ICP detection was performed on the purified graphite prepared in examples 8 to 11 in the same manner as in example 1 to obtain the contents of Li, al, co, cu, ni, fe and Mn element therein, and the results are shown in FIG. 4.
As can be seen from fig. 4, the effect of removing impurities is good when the hydrogen peroxide is in the range of 10 to 25%, and the effect of removing impurities is rather unfavorable when the hydrogen peroxide is increased to 30%.
Examples 16 to 20
The recovery method of waste graphite is different from example 1 in that the acid leaching time in the step (2) is 18h, 21h, 27h, 30h and 33h respectively.
The process for producing regenerated graphite differs from example 1 in that the purified graphite produced in example 1 is replaced with the purified graphite produced in examples 16 to 20, respectively.
ICP detection was performed on the purified graphite prepared in examples 16 to 20 in the same manner as in example 1 to obtain the contents of Li, al, co, cu, ni, fe and Mn element therein, and the results are shown in FIG. 6.
As can be seen from FIG. 6, the acid leaching time is prolonged, which is favorable for removing impurities, and the impurity removing effect is better at 24-33 h.
Examples 21 to 23
The difference between the recovery method of waste graphite and the embodiment 1 is that the acid leaching temperature in the step (2) is 120 ℃, 180 ℃ and 200 ℃ respectively.
The process for producing regenerated graphite differs from example 1 in that the purified graphite produced in example 1 is replaced with the purified graphite produced in examples 16 to 20, respectively.
ICP detection was performed on the purified graphite prepared in examples 21 to 23 in the same manner as in example 1 to obtain the contents of Li, al, co, cu, ni, fe and Mn element therein, and the results are shown in FIG. 7.
As can be seen from fig. 7, the acid leaching temperature is 120-200 ℃ to facilitate the impurity removal, and preferably, the impurity removal effect is better at 130-200 ℃.
Application example 1-A
A battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, the method of making the battery comprising the steps of:
(1) Preparing a positive electrode, namely mixing LiFePO 4, PVDF, SP, carbon Nanotubes (CNTs) and NMP according to the mass ratio of 96:1.5:1.5:1:40 to prepare slurry, coating the slurry on an aluminum foil, and drying to prepare the positive electrode plate.
(2) Preparing a negative electrode, namely mixing a negative electrode material (such as waste graphite, purified graphite or regenerated graphite), CMC, SBR, SP and H 2 O according to a mass ratio of 95:2.5:1.5:1:150 to prepare the negative electrode plate.
(3) The electrolyte adopts LiPF 6/EC+DEC,(LiPF6 as electrolyte, the mixture of EC and DEC with volume ratio of 1:1 as solvent, the electrolyte concentration is 1.3 mol/L), and the diaphragm adopts a composite film of polyethylene PE, polypropylene PP and polyethylene propylene PEP. The assembly of the coin cell was performed in an argon filled glove box.
And assembling the anode, the cathode, the diaphragm and the electrolyte to obtain the battery.
In this application example 1, the negative electrode material was purified graphite in example 1.
Application example 1-B
A battery differing from application example 1-A only in that the regenerated graphite in example 1 was used as the negative electrode material in the preparation of the battery, instead of the purified graphite in example 1.
Application examples 2 to 23
A battery differing from application example 1-A only in that the negative electrode material used the regenerated graphite of examples 2-23 instead of the purified graphite of example 1 in the production process of the battery.
Comparative example 1 was used
A battery differing from application example 1-A only in that the negative electrode material used the waste graphite of example 1 instead of the purified graphite of example 1 in the preparation process of the battery.
Comparative example 2 was used
A battery was different from application example 1-a only in that commercial graphite was used as the negative electrode material instead of the purified graphite in example 1 in the production process of the battery.
Performance test:
The batteries of application example 1-a, application example 1-B, application example 2-23, application comparative example 1 and application comparative example 2 were subjected to cycle performance test, both of the charge rate and the discharge rate were 1/3C, the cycle number was 50, and the first coulombic efficiency, the cycle 50 discharge capacity and the cycle capacity retention were recorded. The results are shown in Table 1.
The cycle performance curves of application example 1-A, application example 1-B, application comparative example 1 and application comparative example 2 are shown in figure 11, and the cycle performance of the lithium ion battery assembled by the purified graphite prepared by the curing method and the acid leaching method is greatly improved compared with that of waste graphite, the cycle performance of the lithium ion battery assembled by the regenerated graphite prepared by the high-temperature regeneration method is further improved on the basis, the cycle performance of the lithium ion battery assembled by the regenerated graphite is equivalent to that of the lithium ion battery assembled by commercial graphite, the specific capacity of the lithium ion battery assembled by the regenerated graphite is 349mAh g -1 after the lithium ion battery is cycled for 50 circles at 0.1C, and the initial coulombic efficiency is 91.3%. It can be demonstrated that the graphitization degree of the material and the cycling stability of the material are greatly improved after borax is removed and regenerated at high temperature.
TABLE 1
As can be seen from table 1, the lithium ion battery assembled by the purified graphite prepared by the method of the present invention has good electrochemical performance, the electrochemical performance of the lithium ion battery assembled by the regenerated graphite obtained by further high-temperature regeneration of the purified graphite is further improved, the level of commercial graphite can be reached, the first coulomb efficiency of the batteries of application example 1-B and application examples 2 and 3 is more than 91%, the cycle capacity retention rate is more than 93.5%, and the remaining batteries of application examples 2-23 have slightly reduced impurity content compared with application example 1-B due to graphite, and still have good electrochemical performance. However, the electrochemical performance of the lithium ion battery assembled by adopting the waste graphite is poor, and the practical application requirements cannot be met.
The applicant states that the detailed method of the present invention is illustrated by the above examples, but the present invention is not limited to the detailed method described above, i.e. it does not mean that the present invention must be practiced in dependence upon the detailed method described above. It should be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of raw materials for the product of the present invention, addition of auxiliary components, selection of specific modes, etc., falls within the scope of the present invention and the scope of disclosure.

Claims (30)

1.一种废旧石墨的回收方法，其特征在于，所述回收方法包括以下步骤：1. A method for recycling waste graphite, characterized in that the recycling method comprises the following steps: (1)将酸和过氧化氢的组合物与废旧石墨混合后，升温进行熟化，得到熟化石墨；(1) mixing a composition of an acid and hydrogen peroxide with waste graphite, and heating the mixture to ripen the mixture to obtain ripened graphite; (2)将所述的熟化石墨与酸液混合并进行微波处理后，将微波处理后的混合液与促进剂混合，并进行高压酸浸处理，得到纯化石墨；(2) mixing the aged graphite with an acid solution and subjecting the mixture to microwave treatment, mixing the microwave-treated mixture with a promoter, and subjecting the mixture to high-pressure acid leaching to obtain purified graphite; 将所述的熟化石墨与酸液混合后，搅拌20-40min再进行微波处理；The matured graphite is mixed with the acid solution, stirred for 20-40 minutes and then subjected to microwave treatment; 所述微波处理的次数为9-12次，每次微波处理的时间独立地为8-15s；The number of microwave treatments is 9-12 times, and the duration of each microwave treatment is independently 8-15 seconds; 所述促进剂的加入量与废旧石墨的质量之比为1:(5-10)；The mass ratio of the added amount of the promoter to the waste graphite is 1:(5-10); 其中，所述促进剂为混合有机溶液，所述混合有机溶液中包括磷酸酯。Wherein, the accelerator is a mixed organic solution, and the mixed organic solution includes phosphate. 2.根据权利要求1所述的废旧石墨的回收方法，其特征在于，所述磷酸酯包括磷酸三乙酯和磷酸二甲酯中的至少一种。2. The method for recycling waste graphite according to claim 1, wherein the phosphate ester comprises at least one of triethyl phosphate and dimethyl phosphate. 3.根据权利要求1所述的废旧石墨的回收方法，其特征在于，所述混合有机溶液中还包括酮和氮甲基吡咯烷酮中的至少一种。3. The method for recycling waste graphite according to claim 1, wherein the mixed organic solution further comprises at least one of ketone and nitrogen-methyl pyrrolidone. 4.根据权利要求1所述的废旧石墨的回收方法，其特征在于，所述混合有机溶液为磷酸三乙酯和丙酮的混合物，磷酸三乙酯和丙酮的体积比为(1-4):1。4. The recovery method of waste graphite according to claim 1, wherein the mixed organic solution is a mixture of triethyl phosphate and acetone, and the volume ratio of triethyl phosphate and acetone is (1-4): 1. 5.根据权利要求1所述的废旧石墨的回收方法，其特征在于，步骤(1)中，所述酸和过氧化氢的组合物中的酸包括硝酸、醋酸、次氯酸、磷酸和柠檬酸中的至少两种。5. The method for recycling waste graphite according to claim 1, characterized in that, in step (1), the acid in the composition of acid and hydrogen peroxide comprises at least two of nitric acid, acetic acid, hypochlorous acid, phosphoric acid and citric acid. 6.根据权利要求1所述的废旧石墨的回收方法，其特征在于，步骤(1)中，所述酸和过氧化氢的组合物中的酸为98wt％的浓硫酸和90wt％的浓盐酸的混合溶液，其中，浓硫酸和浓盐酸的体积比为2:5-5:2。6. The method for recycling waste graphite according to claim 1, characterized in that, in step (1), the acid in the composition of acid and hydrogen peroxide is a mixed solution of 98wt% concentrated sulfuric acid and 90wt% concentrated hydrochloric acid, wherein the volume ratio of concentrated sulfuric acid to concentrated hydrochloric acid is 2:5-5:2. 7.根据权利要求1所述的废旧石墨的回收方法，其特征在于，步骤(1)中，所述废旧石墨的质量和所述酸和过氧化氢的组合物的质量之比为50:(20-100)。7. The method for recovering waste graphite according to claim 1, characterized in that, in step (1), the ratio of the mass of the waste graphite to the mass of the composition of the acid and hydrogen peroxide is 50:(20-100). 8.根据权利要求1所述的废旧石墨的回收方法，其特征在于，步骤(1)中，所述过氧化氢的浓度为30wt％，以酸和废旧石墨的总质量为100％计，过氧化氢的质量占比为10-20％。8. The method for recycling waste graphite according to claim 1, characterized in that in step (1), the concentration of hydrogen peroxide is 30wt%, and the mass proportion of hydrogen peroxide is 10-20% based on the total mass of the acid and the waste graphite as 100%. 9.根据权利要求1所述的废旧石墨的回收方法，其特征在于，步骤(1)所述混合的过程中伴有搅拌。9. The method for recycling waste graphite according to claim 1, characterized in that the mixing process in step (1) is accompanied by stirring. 10.根据权利要求1所述的废旧石墨的回收方法，其特征在于，步骤(1)所述混合的时间为20-60min。10. The method for recycling waste graphite according to claim 1, characterized in that the mixing time in step (1) is 20-60 min. 11.根据权利要求1所述的废旧石墨的回收方法，其特征在于，步骤(1)中，升温至80-180℃进行熟化。11. The method for recycling waste graphite according to claim 1, characterized in that in step (1), the temperature is raised to 80-180°C for aging. 12.根据权利要求1所述的废旧石墨的回收方法，其特征在于，步骤(1)中，所述熟化的时间为4-32h。12. The method for recycling waste graphite according to claim 1, characterized in that in step (1), the aging time is 4-32 hours. 13.根据权利要求1所述的废旧石墨的回收方法，其特征在于，步骤(1)所述熟化在坩埚中进行。13. The method for recycling waste graphite according to claim 1, characterized in that the aging in step (1) is carried out in a crucible. 14.根据权利要求1所述的废旧石墨的回收方法，其特征在于，步骤(2)所述酸液为浓度为1-3mol L-1的硫酸溶液和浓度为1-3mol L-1的盐酸溶液的混合溶液，硫酸溶液和盐酸溶液的体积比为(1-3):1。14. The method for recovering waste graphite according to claim 1, characterized in that the acid solution in step (2) is a mixed solution of a sulfuric acid solution with a concentration of 1-3 mol L -1 and a hydrochloric acid solution with a concentration of 1-3 mol L -1 , and the volume ratio of the sulfuric acid solution to the hydrochloric acid solution is (1-3):1. 15.根据权利要求1所述的废旧石墨的回收方法，其特征在于，步骤(2)中，所述熟化石墨和所述酸液的固液比为2:1-1:10。15. The method for recycling waste graphite according to claim 1, characterized in that in step (2), the solid-liquid ratio of the matured graphite to the acid solution is 2:1-1:10. 16.根据权利要求1所述的废旧石墨的回收方法，其特征在于，步骤(2)所述微波处理的功率为50-1500W。16. The method for recycling waste graphite according to claim 1, characterized in that the power of the microwave treatment in step (2) is 50-1500W. 17.根据权利要求1所述的废旧石墨的回收方法，其特征在于，步骤(2)所述高压酸浸处理的温度为120-200℃。17. The method for recycling waste graphite according to claim 1, characterized in that the temperature of the high-pressure acid leaching treatment in step (2) is 120-200°C. 18.根据权利要求1所述的废旧石墨的回收方法，其特征在于，步骤(2)所述高压酸浸处理的时间为18-33h。18. The method for recycling waste graphite according to claim 1, characterized in that the time of the high-pressure acid leaching treatment in step (2) is 18-33 hours. 19.根据权利要求1所述的废旧石墨的回收方法，其特征在于，步骤(2)所述高压酸浸处理后，还对产物进行洗涤和干燥的步骤。19. The method for recycling waste graphite according to claim 1, characterized in that after the high-pressure acid leaching treatment in step (2), the product is further washed and dried. 20.一种纯化石墨，其特征在于，所述纯化石墨由权利要求1-19任一项所述的回收方法得到。20. Purified graphite, characterized in that the purified graphite is obtained by the recovery method according to any one of claims 1 to 19. 21.一种再生石墨，其特征在于，所述再生石墨采用权利要求20所述的纯化石墨制备得到。21. A regenerated graphite, characterized in that the regenerated graphite is prepared using the purified graphite according to claim 20. 22.一种如权利要求21所述的再生石墨的制备方法，其特征在于，所述再生石墨的制备方法包括以下步骤：22. A method for preparing regenerated graphite according to claim 21, characterized in that the method for preparing regenerated graphite comprises the following steps: 将权利要求20所述的纯化石墨和硼砂混合，焙烧，得到所述的再生石墨。The purified graphite described in claim 20 is mixed with borax and roasted to obtain the regenerated graphite. 23.根据权利要求22所述的再生石墨的制备方法，其特征在于，所述纯化石墨和所述硼砂的质量比为5:1-20:1。23. The method for preparing regenerated graphite according to claim 22, characterized in that the mass ratio of the purified graphite to the borax is 5:1-20:1. 24.根据权利要求22所述的再生石墨的制备方法，其特征在于，所述纯化石墨和所述硼砂的混合方式为研磨混合。24. The method for preparing regenerated graphite according to claim 22, characterized in that the purified graphite and the borax are mixed by grinding. 25.根据权利要求22所述的再生石墨的制备方法，其特征在于，所述焙烧在保护性气体的保护下进行。25. The method for preparing regenerated graphite according to claim 22, characterized in that the calcination is carried out under the protection of a protective gas. 26.根据权利要求25所述的再生石墨的制备方法，其特征在于，所述保护性气体包括氮气、氦气和氩气中的至少一种。26. The method for preparing regenerated graphite according to claim 25, characterized in that the protective gas comprises at least one of nitrogen, helium and argon. 27.根据权利要求22所述的再生石墨的制备方法，其特征在于，所述焙烧的温度为1600-2000℃。27. The method for preparing regenerated graphite according to claim 22, characterized in that the calcination temperature is 1600-2000°C. 28.根据权利要求22所述的再生石墨的制备方法，其特征在于，所述焙烧的时间为2-4h。28. The method for preparing regenerated graphite according to claim 22, characterized in that the calcination time is 2-4 hours. 29.一种负极，其特征在于，所述负极中包括权利要求21所述的再生石墨。29. A negative electrode, characterized in that it comprises the regenerated graphite according to claim 21. 30.一种锂离子电池，其特征在于，所述锂离子电池中包括权利要求29所述的负极。30. A lithium ion battery, characterized in that it comprises the negative electrode according to claim 29.
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