WO2021114747A1 - 废旧磷酸铁锂选择性氧化-还原再生的方法、再生磷酸铁锂和锂离子电池 - Google Patents

废旧磷酸铁锂选择性氧化-还原再生的方法、再生磷酸铁锂和锂离子电池 Download PDF

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WO2021114747A1
WO2021114747A1 PCT/CN2020/112973 CN2020112973W WO2021114747A1 WO 2021114747 A1 WO2021114747 A1 WO 2021114747A1 CN 2020112973 W CN2020112973 W CN 2020112973W WO 2021114747 A1 WO2021114747 A1 WO 2021114747A1
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iron phosphate
lithium iron
lithium
carbon
regenerated
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PCT/CN2020/112973
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English (en)
French (fr)
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岳海峰
贺雪琴
黄友元
杨才德
杨顺毅
席小兵
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贝特瑞（天津）纳米材料制造有限公司
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Priority to JP2021510453A priority Critical patent/JP7161606B2/ja
Priority to KR1020217011619A priority patent/KR20210076919A/ko
Priority to EP20870470.0A priority patent/EP3863106A4/en
Priority to US17/286,438 priority patent/US20220102773A1/en
Publication of WO2021114747A1 publication Critical patent/WO2021114747A1/zh

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    • 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
    • H01M10/54—Reclaiming serviceable parts of waste accumulators
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/45—Phosphates containing plural metal, or metal and ammonium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
    • C22B7/001—Dry processes
    • 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
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/90—Other properties not specified above
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling
    • 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

Definitions

  • This application relates to the field of lithium ion battery cathode materials, and relates to a method for selective oxidation-reduction regeneration of waste lithium iron phosphate, regenerated lithium iron phosphate and lithium ion batteries.
  • LiFePO 4 Since 2019, my country has gradually entered the decommissioning stage of large-scale lithium iron phosphate batteries. Improper disposal will cause serious pollution and cause new energy materials to change from "green” to "black”.
  • the structure of LiFePO 4 is relatively stable. After long-cycle decommissioning, it can restore its electrochemical performance to a considerable extent through appropriate lithium replenishment and coated carbon repair techniques, and has a high regeneration value. Although the energy density of recycled LFP is not high, it has the characteristics of low cost, long cycle performance, high thermal stability, and sufficient supply. It can be used in the field of energy storage on a large scale.
  • Material stripping is the most important technical link. From the macro perspective of composition control, it is equivalent to extracting higher purity LiFePO 4 from waste pole pieces. There are two key issues involved, one is how to achieve a higher stripping rate, and the other is how to avoid the introduction of foreign matter such as Al powder during the separation and extraction process.
  • relevant researchers have respectively developed a dry heat treatment route and a wet soaking route. Dry heat treatment is developed based on the difference between the melting point of the binder PVDF and aluminum foil. For example, when the temperature is between 360°C and 490°C, only PVDF melts and pyrolysis loses the effect of the binder. After cooling down, it is subjected to vibrating sieving, etc. You can peel off the LFP.
  • the purpose of this application is to provide a method for selective oxidation-reduction regeneration of waste lithium iron phosphate, a regenerated lithium iron phosphate and a lithium ion battery.
  • the regenerated lithium iron phosphate prepared by the method has the characteristics of low cost, excellent cycle performance, high compaction density and the like.
  • a method for selective oxidation-reduction regeneration of waste lithium iron phosphate comprising the following steps:
  • the lithium iron phosphate powder is subjected to lithium replenishment, carbon replenishment, and composition control by means of secondary sintering to obtain regenerated lithium iron phosphate;
  • the mild oxidizing gas is: water vapor, CO 2 gas, or a mixed gas of the two.
  • This application uses waste LiFePO 4 (LFP) battery pole pieces as raw materials, and sinters them in water vapor, CO 2 and other temperature and oxidizing gases at a time, so that the binder in the waste LFP is invalidated and the amorphous package is selectively oxidized and removed.
  • Carbon coating thereby increasing the degree of graphitization of the residual coated carbon. Because graphitized carbon has high conductivity, it can inhibit the growth of LFP crystal grains, thereby increasing the temperature during the secondary sintering of waste LFP without Make the crystal grains grow too much, so after proper lithium supplementation and secondary sintering, regenerated LFP with suitable grain size and higher crystallinity can be obtained.
  • the method has at least one of the following features (1) to (3):
  • the mild oxidizing gas a mixed gas of the CO 2 gas and water vapor, the water vapor and a CO 2 gas flow rate ratio of 1: 9 to 9: 1;
  • the water vapor is derived from at least one of deionized water and ultrapure water, and the resistance of the water vapor is ⁇ 18M ⁇ ;
  • the purity of the CO 2 gas is greater than or equal to 99.0%.
  • the waste lithium iron phosphate is derived from at least one of waste lithium iron phosphate battery pole pieces and waste lithium iron phosphate slurry;
  • the waste lithium iron phosphate battery pole pieces include: waste LFP pole pieces obtained from dismantling waste LFP batteries that are retired from service, waste LFP pole pieces scrapped from battery factory dismantling, waste LFP pole pieces scrapped from battery factory scrap LFP pole piece.
  • the method has at least one of the following features (1) to (3):
  • the mass ratio of the waste lithium iron phosphate to the mild oxidizing gas is 1: (0.1-10.0), and the flow rate of the mild oxidizing gas is constant;
  • the heating equipment used includes any one of tube furnace, box furnace, roller kiln or rotary kiln;
  • the primary sintering is holding at 300°C to 700°C for 0.5 hour to 15 hours, and optionally at 400°C to 600°C for 4 hours to 8 hours.
  • the step of separating the lithium iron phosphate powder from the material obtained by the primary sintering is specifically: first pulverizing the material obtained by the primary sintering, and then separating;
  • the material obtained from the primary sintering is crushed mechanically, and then sieved by a screen;
  • the mesh of the screen ranges from 10 mesh to 400 mesh, and can be selected from 100 mesh to 325 mesh.
  • the method has at least one of the following features (1) to (2):
  • the lithium source used for replenishing lithium includes any one or a combination of at least two of Li 2 CO 3 , LiOH ⁇ H 2 O, Li 3 PO 4 or LiNO 3;
  • the purity of the lithium source is industrial grade or battery grade.
  • the method has at least one of the following features (1) to (3):
  • the method of replenishing lithium includes wet method of replenishing lithium and dry method of replenishing lithium;
  • the median particle size of Li 2 CO 3 ranges from 0.2 ⁇ m to 10 ⁇ m, and can be selected from 0.5 ⁇ m to 3 ⁇ m;
  • the added amount of the lithium source is calculated according to the Li:Fe molar ratio, and the Li excess ranges from 0.1% to 10.0%, and can optionally be 2.0% to 5.0%.
  • the carbon source includes any one or a combination of at least two of glucose, sucrose, citric acid, acetylene black, polypropylene, or polyethylene glycol.
  • the method has at least one of the following features (1) to (3):
  • the carbon supplement methods include: wet carbon supplement and dry carbon supplement;
  • the amount of the carbon source added is calculated based on the carbon content of the obtained regenerated lithium iron phosphate being 1.0 wt% to 6.0 wt%;
  • a lithium source and a carbon source are used to perform lithium replenishment, carbon replenishment, and composition control on the lithium iron phosphate powder through secondary sintering, and the step of obtaining regenerated lithium iron phosphate is specifically :
  • the mixing method includes one of VC mixing, single-vertebral dry mixing, and double-vertical dry mixing;
  • the mixing time is 0.1 hour to 8 hours, optionally 1 hour to 3 hours.
  • the method has at least one of the following features (1) to (5):
  • the secondary sintering is performed under an inert gas, and the inert gas includes any one or a combination of at least two of nitrogen, argon, helium, neon, krypton, or xenon;
  • the mass ratio of the lithium iron phosphate powder to the inert gas is 1:(0.1 ⁇ 10.0), optionally 1:(0.8 ⁇ 3.0);
  • the secondary sintering is heat preservation at 700°C to 800°C for 2 hours to 20 hours, and optionally heat preservation at 730°C to 770°C for 6 hours to 16 hours;
  • the holding time of the secondary sintering is, optionally 6 hours to 16 hours;
  • the heating equipment used for the secondary sintering includes any one of a tube furnace, a box furnace, a roller kiln or a rotary kiln, and the roller kiln can be selected.
  • the method further includes: sieving and demagnetizing the regenerated lithium iron phosphate.
  • the method includes the following steps:
  • the flow rate ratio is 4:6 ⁇ 6:4, and the flow rate is constant.
  • the temperature is raised to 300°C at a heating rate of 2°C/min ⁇ 5°C/min. ⁇ 700°C, keep for 0.5 ⁇ 15 hours, and cool down with the furnace;
  • the mass ratio of the active ingredient waste lithium iron sulfate to the mixed gas in the waste pole piece is 1:(0.1 ⁇ 10.0);
  • the pole pieces After sintering, the pole pieces are mechanically crushed and passed through a 10-400 mesh sieve.
  • the powder under the sieve is analyzed by ICP and high frequency infrared carbon and sulfur to determine the content of Li, Fe and C;
  • the lithium is supplemented to an excess of 0.1% based on the Li:Fe molar ratio. 10.0%, the amount of carbon source added is calculated based on the carbon content of the regenerated lithium iron phosphate obtained from 1.0wt% to 6.0wt%, VC is mixed for 0.1 to 8 hours, nitrogen is introduced as a protective gas in the box furnace, and the second sintering , Regenerated LFP is obtained by cooling down the furnace;
  • the second sintering is: heating up to 700°C to 800°C at a heating rate of 2°C/min to 5°C/min, and holding for 2 to 20 hours.
  • the application also provides a regenerated lithium iron phosphate, which is prepared by the above-mentioned method.
  • the regenerated lithium iron phosphate has at least one of the following characteristics (1) to (3):
  • the median particle size of the regenerated lithium iron phosphate material is 0.1 ⁇ m to 10.0 ⁇ m, optionally 0.5 ⁇ m to 5.0 ⁇ m;
  • the specific surface area of the regenerated lithium iron phosphate material is 1.0m2/g-20.0m2/g, and can be selected as 10.0m2/g-15.0m2/g;
  • the powder compaction density of the regenerated lithium iron phosphate material is 1.0 g/cm3 to 2.8 g/cm3, optionally 2.0 g/cm3 to 2.5 g/cm3.
  • the pH of the regenerated lithium iron phosphate material is 6.0 to 12.0, optionally 8.0 to 10.0;
  • the carbon content of the regenerated lithium iron phosphate material is 1.0 wt% to 6.0 wt%, optionally 1.5 wt% to 2.5 wt%.
  • the present application also provides a lithium ion battery, including the lithium ion battery containing the above-mentioned regenerated lithium iron phosphate material.
  • FIG. 1 is a schematic diagram of the process flow of the LFP cathode material provided by the embodiment of the application;
  • Figure 2 is an electron microscope picture of the recycled LFP cathode material in Example 1 of this application;
  • Figure 3 is an XRD diagram of the recycled LFP cathode material in Example 1 of the application.
  • Example 4 is the first charge and discharge curve of the regenerated LFP cathode material in Example 1 of this application;
  • FIG. 5 is a cycle performance curve of the recycled LFP cathode material in Example 1 of the application.
  • a method for selective oxidation-reduction regeneration of waste lithium iron phosphate includes the following steps S100 to S300:
  • Step S100 sintering the waste lithium iron phosphate once under the condition that mild oxidizing gas is passed through;
  • Step S200 separating lithium iron phosphate powder from the material obtained by the primary sintering
  • Step S300 using a lithium source and a carbon source to perform lithium replenishment, carbon replenishment, and composition control on the separated lithium iron phosphate powder through secondary sintering to obtain regenerated lithium iron phosphate;
  • the mild oxidizing gas is: water vapor, CO 2 gas, or a mixed gas of the two.
  • the waste lithium iron phosphate of the present application may be lithium iron phosphate without carbon coating, or lithium iron phosphate coated with carbon.
  • a lithium source is used for lithium supplementation
  • a carbon source is used for carbon supplementation and is used as a reducing agent.
  • Li is added into the LFP lattice
  • the carbon supplement plays the role of repairing the coated carbon.
  • the reducing agent can restore the trace Fe 3+ produced by the oxidation in step S100 to Fe 2+ , realize composition control, and finally maintain LiFePO 4 phase.
  • waste lithium iron phosphate LiFePO 4 (hereinafter referred to as LFP) is used as a raw material to sinter in a mild oxidizing gas of water vapor and/or CO 2 to make the binder in the waste LFP ineffective by means of gas-solid reaction.
  • LFP waste lithium iron phosphate LiFePO 4
  • the method of the present application also has the following advantages:
  • step S100 of the present application is sintered once under mild oxidizing gas conditions, it can react with the organic matter in the electrolyte and avoid the problem of corroding the aluminum foil; and if a relatively inert atmosphere such as nitrogen is used, it cannot react with the organic matter. , Resulting in possible corrosion of aluminum foil.
  • step S100 the method of the present application undergoes step S100 to perform a sintering under mild oxidizing gas conditions, which can make the binder (such as PVDF) ineffective and the oxidative removal of amorphous carbon (such as SP), if there is aluminum foreign matter Existence, through the above method, the reaction interface between lithium iron phosphate and aluminum powder can be loosened, thereby solving the problem that the aluminum powder cannot be removed in the prior art.
  • the mild oxidizing gas mixed gas of water vapor and a CO 2 gas, optionally steam and a CO 2 gas flow rate ratio of 1: 9 to 9: 1, e.g. 1: 9,2 :8, 3:7, 3.5:6.5, 4:6, 5:5, 6:4, 7:3, 8:2 or 9:1, etc. Further optional flow rate ratio is 4:6 ⁇ 6:4.
  • This application can choose to use a mixed gas of water vapor and CO 2 gas for the following reasons: using a mixed gas is better than a single gas, and a single type of water vapor is too oxidizable. Almost all of the lithium iron phosphate will be oxidized together. After the lithium is almost completely oxidized, it is difficult to completely reduce it when it is reduced again, and there will still be a small amount of Fe 3+ ; and the mixed gas has more suitable oxidizing properties. After oxidative decarburization, at most only a small amount of lithium iron phosphate is oxidized.
  • the water vapor is derived from at least one of deionized water and ultrapure water, and the resistance of the water vapor may be greater than or equal to 18M ⁇ , such as 18M ⁇ , 20M ⁇ , 30M ⁇ , 35M ⁇ , 40M ⁇ , or 50M ⁇ .
  • the CO 2 may be industrial grade CO 2 with a purity of ⁇ 99.0%.
  • waste lithium iron phosphate does not limit the source of the waste lithium iron phosphate, for example, it may be derived from waste lithium iron phosphate battery pole pieces and/or waste lithium iron phosphate slurry.
  • the waste lithium iron phosphate battery pole pieces include: waste LFP pole pieces obtained from the dismantling of waste LFP batteries that are decommissioned, and defective batteries scrapped by the battery factory (which can be products after injection, or non-injection products). Products) disassembled used LFP pole pieces, defective LFP pole pieces scrapped by the battery factory.
  • the mass ratio of waste lithium iron phosphate (here refers to the amount of active ingredient lithium iron phosphate in the pole piece or slurry) to the mild oxidizing gas is 1: (0.1 to 10.0), for example, 1:0.1, 1:0.5, 1:1, 1:2, 1:3, 1:3.5, 1:4, 1:5, 1:6, 1:7, 1:8 or 1:10, etc., but not limited to those listed Value, other unlisted values in this value range are also applicable, and it can be selected as 1:(0.8 ⁇ 3.0). If the concentration of the mild oxidizing gas is too low, the binder will not fully fail, and the amorphous coated carbon cannot be effectively oxidized. If the concentration of the mild oxidizing gas is too high, it will lead to excessive phosphoric acid. Lithium iron is oxidized, which affects the performance of the final regenerated lithium iron phosphate.
  • the gas flow rate can be calculated according to the total mass of the mild oxidizing gas and the total feed-out time.
  • the flow rate of the mild oxidizing gas is constant.
  • the heating equipment used in the primary sintering process includes any one of a tube furnace, a box furnace, a roller kiln or a rotary kiln, and a rotary kiln can be selected.
  • the holding temperature of the primary sintering is 300°C to 650°C, such as 300°C, 350°C, 400°C, 500°C, 550°C, 600°C, or 650°C; but not limited to the listed values, Other unlisted values within this value range are also applicable, and can be selected from 400°C to 600°C. If the temperature of the primary sintering is too low, the binder will not fully fail, and the amorphous coated carbon will not be effectively oxidized. If the temperature of the primary sintering is too high (such as 700°C), it will cause the aluminum foil to pulverize. The aluminum-containing powder is difficult to separate, and at the same time, too much lithium iron phosphate is oxidized, which affects the performance of the final regenerated lithium iron phosphate.
  • the holding time of the one-time sintering is 0.5 hour to 15 hours, such as 0.5 hour, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 10 hours , 11 hours, 13 hours or 14 hours, etc., but not limited to the listed values, other unlisted values within this range of values are also applicable; 4 hours to 8 hours can be selected.
  • step S200 includes but is not limited to: first pulverizing the material obtained from the primary sintering, and then separating.
  • step S200 of the present application include, but are not limited to, screen screening after mechanical crushing, and cyclone separation after jet crushing. Furthermore, it is optional to mechanically crush the material obtained from the primary sintering, and then sieve the material.
  • it is pulverized to a median particle size ranging from 0.2 ⁇ m to 10.0 ⁇ m, such as 0.2 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 1.5 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 6 ⁇ m, 8 ⁇ m, or 10 ⁇ m, etc., but not limited to those listed. Values, other unlisted values within this value range are also applicable; 0.5 ⁇ m ⁇ 3.0 ⁇ m can be selected.
  • the mesh size of the screen ranges from 10 mesh to 400 mesh, such as 10 mesh, 40 mesh, 80 mesh, 100 mesh, 125 mesh, 150 mesh, 200 mesh, 240 mesh, 300 mesh, or 325 mesh, etc. , but not limited to the listed values, other unlisted values within this range of values are also applicable; it can be selected from 100 mesh to 325 mesh.
  • the lithium source used for lithium supplementation in step S300 includes, but is not limited to, any one or a combination of at least two of Li 2 CO 3 , LiOH.H 2 O, Li 3 PO 4 or LiNO 3, Optional Li 2 CO 3 .
  • the purity of the lithium source described in this application can be industrial grade or battery grade, and can be battery grade.
  • the method for replenishing lithium in step S300 includes, but is not limited to, wet replenishment and dry replenishment, and may be dry replenishment.
  • Li 2 CO 3 is used as a lithium source for dry replenishment of lithium.
  • the median particle size of Li 2 CO 3 ranges from 0.2 ⁇ m to 10 ⁇ m, such as 0.2 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 3 ⁇ m, 5 ⁇ m. , 6 ⁇ m, 7 ⁇ m, 8 ⁇ m or 10 ⁇ m, etc., those skilled in the art can control the particle size of Li 2 CO 3 within the above range by crushing.
  • lithium carbonate is widely used as a raw material for the production of conventional lithium iron phosphate.
  • the Li in the lithium carbonate in this particle size range can be efficiently added to the regenerated lithium iron phosphate crystals.
  • the active Li content In the grid, supplement the active Li content.
  • More optional median particle size range is 0.5 ⁇ m ⁇ 3.0 ⁇ m.
  • the amount of lithium source added in step S300 is calculated according to the Li:Fe molar ratio, and the Li excess ranges from 0.1% to 10.0%, such as 0.1%, 0.5%, 1%, 2%, 3%, 5 %, 6%, 7%, 8% or 10%, etc., can be selected from 2% to 5%.
  • the carbon source in step S300 includes any one or a combination of at least two of glucose, sucrose, citric acid, acetylene black, polypropylene, or polyethylene glycol.
  • the combination is typical but non-limiting. Examples are: the combination of glucose and sucrose, the combination of glucose and citric acid, the combination of sucrose and acetylene black, the combination of sucrose and polypropylene, the combination of glucose, sucrose and acetylene black, the combination of glucose, sucrose, citric acid and ethylene glycol Combination etc.
  • the method of carbon supplementation includes, but is not limited to: wet carbon supplementation and dry carbon supplementation, and may be dry carbon supplementation.
  • the amount of the carbon source added is calculated based on the carbon content of the obtained regenerated lithium iron phosphate being 1.0wt% to 6.0wt%, for example, 1wt%, 2wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt% or 6wt%, etc., but not limited to the listed values, other unlisted values within this range of values are also applicable; optionally, the carbon content of the obtained regenerated lithium iron phosphate is 1.5wt% to 2.5wt%.
  • a mixed carbon source of glucose and polyethylene glycol is used for dry carbon supplementation, and the median particle size of the mixed carbon source ranges from 0.2 ⁇ m to 10.0 ⁇ m, such as 0.2 ⁇ m, 1 ⁇ m, 3 ⁇ m, 3 ⁇ m, 7 ⁇ m. , 8 ⁇ m or 10 ⁇ m, etc., those skilled in the art can control the particle size of the mixed carbon source within the above range by crushing.
  • the types of glucose and polyethylene glycol and the thermal pyrolysis temperature are better matched, and within a suitable median particle size range, it can achieve a better mixing effect with the powder, and can achieve synergistic optimization.
  • the median particle size can be selected in the range of 0.5 ⁇ m ⁇ 3.0 ⁇ m.
  • the mass ratio of glucose and polyethylene glycol ranges from 1:9 to 9:1, such as 1:9, 2:8, 3:7, 3.5:6.5, 4:6, 5:5, 6:4, 7:3, 8:2 or 9:1, etc., but not limited to the listed values, other unlisted values within this range of values are also applicable; 4:6 can be selected ⁇ 6:4.
  • step S300 includes: mixing the lithium source, the carbon source, and the lithium iron phosphate powder separated in step S200, and sintering for a second time to obtain regenerated lithium iron phosphate.
  • This is a method of dry replenishment of lithium and dry replenishment of carbon, which can simultaneously achieve the effects of Li replenishment into the lattice and carbon repair.
  • the mixing method includes, but is not limited to, any one of VC mixing, single-vertebral dry mixing, or double-vertical dry mixing.
  • the mixing time is from 0.1 hour to 8 hours, such as 0.1 hour, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 7 hours or 8 hours, etc., but is not limited to the listed values , Other unlisted values in this value range are also applicable; it can be 1 hour to 3 hours.
  • the secondary sintering is performed under an inert gas, and the inert gas includes any one or a combination of at least two of nitrogen, argon, helium, neon, krypton, or xenon.
  • the mass ratio of the lithium iron phosphate powder obtained by the separation in step S200 and the inert gas is 1:(0.1-10.0), for example, 1:0.1, 1:0.5, 1:1, 1:2, 1:3 , 1:3.5, 1:4, 1:5, 1:6, 1:7, 1:8 or 1:10, etc., can be 1:(0.8 ⁇ 3.0).
  • the flow rate of the inert gas is constant.
  • the holding temperature of the secondary sintering is 700°C to 800°C, such as 700°C, 725°C, 750°C, 765°C, 780°C or 800°C, etc., and the secondary sintering is performed within this range, It can better achieve the purpose of restoration, and the temperature can be selected from 730°C to 770°C.
  • the holding time of the secondary sintering is 2 hours to 20 hours, such as 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 13 hours, 15 hours, 18 hours or 20 hours. Hours, etc., can be selected from 6 hours to 16 hours.
  • the heating equipment used for the secondary sintering includes any one of a tube furnace, a box furnace, a roller kiln, or a rotary kiln, and may be a roller kiln.
  • the method includes the following steps:
  • the flow rate ratio is 4:6 ⁇ 6:4, and the flow rate is constant.
  • the temperature is increased to 300 ⁇ 700°C at a heating rate of 2 ⁇ 5°C/min. Keep the temperature for 0.5-15 hours, and cool down with the furnace;
  • the mass ratio of the active ingredient waste lithium iron sulfate to the mixed gas in the waste pole piece is 1:(0.1 ⁇ 10.0);
  • the pole pieces are mechanically crushed and passed through a 10-400 mesh sieve.
  • the powder under the sieve is analyzed by ICP and high-frequency infrared carbon and sulfur to determine the content of Li, Fe and C;
  • a mixed carbon source of Li 2 CO 3 with a median particle size of 0.2-10 ⁇ m, glucose and polyethylene glycol in a mass ratio of 1:9-9:1, and supplement lithium to an excess of 0.1-10.0 based on the Li:Fe molar ratio. %, the amount of carbon source added is calculated based on the carbon content of the obtained regenerated lithium iron phosphate being 1.0wt% to 6.0wt%, VC is mixed for 0.1 to 8 hours, nitrogen is introduced as a protective gas in the box furnace, and the second sintering is performed. Cool down with the furnace to obtain recycled LFP;
  • the secondary sintering is: heating up to 700-800°C at a heating rate of 2-5°C/min, and holding it for 2-20 hours.
  • the median particle size of the recycled LFP cathode material is 0.1 ⁇ m to 10.0 ⁇ m, for example, 0.1 ⁇ m, 0.5 ⁇ m, 1.5 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, or 10 ⁇ m, etc. , Can be 0.5 ⁇ m ⁇ 5.0 ⁇ m.
  • the specific surface area of the LFP Regeneration positive electrode material is 1.0m 2 /g ⁇ 20.0m 2 / g, optionally 10.0m 2 /g ⁇ 15.0m 2 / g, e.g. 10m 2 / g, 12m 2 /g, 14m 2 /g, 15m 2 /g, 17m 2 /g, 18m 2 /g, 20m 2 /g, etc.
  • the powder compaction density of the recycled LFP cathode material is 1.0 g/cm 3 ⁇ 2.8 g/cm 3 , optionally 2.0 g/cm 3 ⁇ 2.5 g/cm 3 , for example 2.0 g/cm 3 cm 3 , 2.1g/cm 3 , 2.2g/cm 3 , 2.3g/cm 3 , 2.4g/cm 3 or 2.5g/cm 3, etc.
  • the pH of the recycled LFP cathode material is 6.0 to 12.0, such as 6.0, 6.5, 7.0, 7.5, 8.0, 9.0, 9.5, 10.0, 11.0, or 12.0, etc., optionally 8.0 to 10.0.
  • the carbon content (that is, the total amount of residual carbon and carbon supplement) of the recycled LFP cathode material is 1.0 wt% to 6.0 wt%, for example, 1.0 wt%, 1.5 wt%, 2.0 wt%, 3.0 wt%, 4.0 wt%, 4.5 wt%, 5.0 wt%, 6.0 wt%, etc., can be 1.5 wt% to 2.5 wt%.
  • the present application provides a lithium ion battery, including the lithium ion battery including the regenerated lithium iron phosphate cathode material described in the second aspect.
  • lithium-ion battery may be a conventional aluminum shell, a steel shell, or a soft-packed lithium-ion battery.
  • the present application does not limit the method for assembling a battery using the regenerated lithium iron phosphate cathode material powder, and those skilled in the art can refer to the methods disclosed in the prior art for assembling.
  • This application also provides a method for preparing positive pole pieces by using the regenerated lithium iron phosphate, which includes:
  • the recycled LFP positive electrode material, conductive agent and binder are mixed in a solvent at a mass percentage of 95-96:1-2:2-4, coated on an aluminum foil current collector, and dried in a vacuum atmosphere.
  • the negative electrode active material used in the negative pole piece of the lithium ion battery includes any one or a combination of at least two of artificial graphite, natural graphite, silicon-carbon material, or silicon-oxygen material.
  • the conductive agent includes graphite powder and/or nano conductive liquid.
  • the nano conductive liquid is composed of 0.5 wt% to 20 wt% of nano carbon material and a dispersion solvent.
  • the nano-carbon material includes any one or a combination of at least two of graphene, carbon nanotube, nano-carbon fiber, fullerene, carbon black, or acetylene black.
  • the number of graphene sheets of the graphene is between 1-100.
  • the diameter of the carbon nanotubes and carbon nanofibers is between 0.2 nm and 500 nm.
  • the particle size of the fullerene, carbon black, and acetylene black is 1 nm-200 nm.
  • the binder includes polyvinylidene fluoride, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyacrylic acid, carboxylated chitosan, polymethyl methacrylate, polyvinyl acetate One or a combination of at least two of esters and acrylonitrile multi-element copolymers.
  • the specific surface area of the material was tested with the Tristar3000 automatic specific surface area and porosity analyzer from Mike Instruments.
  • Malvern laser particle size tester MS 2000 was used to test the particle size range of the material and the average particle size of the raw material particles.
  • a Hitachi S4800 scanning electron microscope was used to observe the surface morphology and particle size of the sample.
  • the charge and discharge test of the cylindrical battery was performed on the LAND battery test system of Wuhan Jinnuo Electronics Co., Ltd. Under normal temperature conditions, 0.1C constant current charge and discharge, and the charge and discharge voltage is limited to 2.5V ⁇ 3.7V.
  • Cylindrical battery's cycle performance is tested on the LAND battery test system of Wuhan Jinnuo Electronics Co., Ltd. Under normal temperature conditions, 1C/1C, the charging and discharging voltage is limited to 2.0 ⁇ 3.65V.
  • This embodiment provides a method for selective oxidation-reduction regeneration of waste lithium iron phosphate, using inferior LFP pole pieces scrapped by a battery factory as raw materials, using lithium carbonate as a lithium source, 50wt% glucose and 50wt% polyethylene glycol as raw materials Mixed carbon source.
  • Fig. 1 is a schematic diagram of the process flow of the LFP cathode material provided by the embodiment of the application. As shown in Fig. 1, the preparation method is as follows:
  • the waste pole piece is placed in the rotary kiln, and the mixed gas of water vapor and carbon dioxide is passed.
  • the flow rate of water vapor and carbon dioxide is 4:6, and the flow rate is constant. Increase the temperature to 500°C at a heating rate of 2°C/min, keep it for 6 hours, and then cool down with the furnace.
  • the pole piece After the first sintering, the pole piece is mechanically crushed, the median particle size reaches 3.0 ⁇ m, and it is passed through a 200-mesh sieve.
  • the powder under the sieve is determined by ICP and high frequency infrared carbon and sulfur analysis to determine the content of Li, Fe, and C.
  • the lithium is supplemented to a Li:Fe molar ratio of 1.05:1, the amount of residual carbon and the total amount of carbon supplement is 3wt%, and VC is mixed for 2 hours.
  • Nitrogen is introduced into the box furnace as a protective gas, the temperature is raised to 750°C at a heating rate of 2°C/min, and the temperature is kept for 8 hours. The temperature of the furnace is lowered to obtain the regenerated LFP.
  • Figure 2 is an electron microscope picture of the regenerated LFP positive electrode material in this embodiment. It can be seen from Figure 2 that the prepared material has a uniform particle size distribution.
  • Figure 3 is an XRD pattern of the regenerated LFP cathode material in this embodiment. It can be seen from Figure 3 that the material has only the diffraction peaks of lithium iron phosphate and no impurity peaks.
  • Figure 4 is the first charge and discharge curve of the regenerated LFP cathode material in this embodiment.
  • Fig. 5 is a cycle performance curve of the recycled LFP cathode material of this embodiment, in which the irregular thick line represents actual measured data, and the thinner straight line represents the attenuation trend of the thick line, which is used to predict the number of cycles when the attenuation reaches 80%.
  • This embodiment provides a method for selective oxidation-reduction regeneration of waste lithium iron phosphate
  • the preparation method is as follows:
  • the waste pole piece is placed in the rotary kiln, and the mixed gas of water vapor and carbon dioxide is passed.
  • the flow rate ratio of water vapor to carbon dioxide is 3:7, and the flow rate is constant.
  • the temperature is increased to 530°C at a heating rate of 2°C/min, kept for 7 hours, and the temperature is lowered with the furnace.
  • the pole piece After the first sintering, the pole piece is mechanically crushed, the median particle size reaches 3.5 ⁇ m, and it is passed through a 200-mesh sieve.
  • the powder under the sieve is determined by ICP and high frequency infrared carbon and sulfur analysis to determine the content of Li, Fe, and C.
  • the lithium is supplemented to a Li:Fe molar ratio of 1.02:1, the amount of residual carbon and the total amount of carbon supplement is 2.5wt%, and VC is mixed for 3 hours.
  • Nitrogen is introduced into the box furnace as a protective gas, the temperature is raised to 760°C at a heating rate of 2°C/min, and the temperature is kept for 8 hours. The temperature of the furnace is lowered to obtain the regenerated LFP.
  • This embodiment provides a method for selective oxidation-reduction regeneration of waste lithium iron phosphate
  • the preparation method is as follows:
  • the waste pole pieces are initially crushed and placed in a rotary kiln.
  • the mixed gas of water vapor and carbon dioxide is passed.
  • the flow rate ratio of water vapor to carbon dioxide is 3:7, and the flow rate is constant.
  • the pole pieces are finely ground and crushed, the median particle size reaches 2.0 ⁇ m, and they are passed through a 200 mesh sieve.
  • the powder under the sieve is determined by ICP and high frequency infrared carbon and sulfur analysis to determine the content of Li, Fe, and C.
  • the lithium is supplemented to a Li:Fe molar ratio of 1.08:1, the amount of residual carbon and the total amount of carbon supplement is 2.5wt%, and VC is mixed for 5 hours.
  • Nitrogen was introduced into the box furnace as a protective gas, the temperature was raised to 740°C at a heating rate of 2°C/min, and the temperature was kept for 12 hours. The temperature of the furnace was lowered to obtain the regenerated LFP.
  • This embodiment provides a method for selective oxidation-reduction regeneration of waste lithium iron phosphate
  • the defective LFP pole pieces discarded from the battery factory are used as raw materials, lithium hydroxide is used as the lithium source, and 40% citric acid and 60% polypropylene are used as the mixed carbon source.
  • the preparation method is as follows:
  • the waste pole pieces are initially crushed and placed in a rotary kiln.
  • the mixed gas of water vapor and carbon dioxide is passed through.
  • the flow rate ratio of water vapor and carbon dioxide is 5:5, and the flow rate is constant.
  • the pole pieces are finely ground and crushed, the median particle size reaches 2.7 ⁇ m, and they are passed through a 200 mesh sieve.
  • the powder under the sieve is determined by ICP and high frequency infrared carbon and sulfur analysis to determine the content of Li, Fe, and C.
  • the lithium is supplemented to a Li:Fe molar ratio of 1.04:1, the amount of residual carbon and the total amount of carbon supplement is 2.8 wt%, and VC is mixed for 2 hours.
  • Nitrogen is introduced into the box furnace as a protective gas, the temperature is increased to 720°C at a heating rate of 2°C/min, and the temperature is kept for 14 hours. The temperature of the furnace is lowered to obtain the regenerated LFP.
  • This embodiment provides a method for selective oxidation-reduction regeneration of waste lithium iron phosphate
  • the preparation method is as follows:
  • the waste pole pieces are initially crushed and placed in a rotary kiln.
  • the mixed gas of water vapor and carbon dioxide is passed.
  • the flow rate ratio of water vapor to carbon dioxide is 3:7, and the flow rate is constant.
  • the pole pieces are finely ground and crushed, the median particle size reaches 2.0 ⁇ m, and they are passed through a 200 mesh sieve.
  • the powder under the sieve is determined by ICP and high frequency infrared carbon and sulfur analysis to determine the content of Li, Fe, and C.
  • the lithium is supplemented until the Li:Fe molar ratio is 1.01:1, the amount of residual carbon and the total amount of carbon supplement is 2.2wt%, and VC is mixed for 3 hours.
  • Nitrogen is introduced into the box furnace as a protective gas, the temperature is raised to 740°C at a heating rate of 2°C/min, and the temperature is kept for 10 hours. The temperature of the furnace is lowered to obtain the regenerated LFP.
  • This embodiment provides a method for selective oxidation-reduction regeneration of waste lithium iron phosphate, using inferior LFP pole pieces scrapped from a battery factory as a raw material, using LiNO 3 as a lithium source and sucrose as a carbon source.
  • the preparation method is as follows:
  • the waste pole piece is placed in a rotary kiln, and a mixed gas of water vapor and carbon dioxide is passed.
  • the flow rate ratio of water vapor and carbon dioxide is 8:2, and the flow rate is constant.
  • the temperature is increased to 400°C at a heating rate of 3°C/min, kept for 8 hours, and the temperature is lowered along with the furnace.
  • the pole piece After the first sintering, the pole piece is mechanically crushed, the median particle size reaches 2.5 ⁇ m, and it is passed through a 325-mesh sieve.
  • the powder under the sieve is determined by ICP and high frequency infrared carbon and sulfur analysis to determine the content of Li, Fe, and C.
  • the lithium is supplemented to a Li:Fe molar ratio of 1.08:1, the amount of residual carbon and the total amount of carbon supplement is 3.5 wt%, and VC is mixed for 7 hours.
  • Nitrogen was introduced into the box furnace as a protective gas, the temperature was raised to 770°C at a heating rate of 5°C/min, and the temperature was kept for 6 hours. The temperature of the furnace was lowered to obtain the regenerated LFP.
  • This embodiment provides a method for selective oxidation-reduction regeneration of waste lithium iron phosphate, using inferior LFP pole pieces scrapped from a battery factory as a raw material, Li 3 PO 4 as a lithium source, and polypropylene as a carbon source.
  • the preparation method is as follows:
  • the waste pole piece is placed in the rotary kiln, and the mixed gas of water vapor and carbon dioxide is passed.
  • the flow rate of water vapor and carbon dioxide is 7:3, and the flow rate is constant.
  • the temperature is increased to 450°C at a heating rate of 4°C/min, kept for 13 hours, and the temperature is lowered along with the furnace.
  • the pole piece After the first sintering, the pole piece is mechanically crushed, the median particle size reaches 3.0 ⁇ m, and it is passed through a 150-mesh sieve.
  • the powder under the sieve is determined by ICP and high frequency infrared carbon and sulfur analysis to determine the content of Li, Fe, and C.
  • the lithium is supplemented to a Li:Fe molar ratio of 1.02:1, the amount of residual carbon and the total amount of carbon supplement is 3.0wt%, and VC is mixed for 5.5 hours.
  • Nitrogen was introduced into the box furnace as a protective gas, the temperature was raised to 715°C at a heating rate of 5°C/min, and the temperature was kept for 16 hours. The temperature of the furnace was lowered to obtain the regenerated LFP.
  • This embodiment provides a method for selective oxidation-reduction regeneration of waste lithium iron phosphate, using lithium iron phosphate slurry scrapped from a battery factory as a raw material, lithium carbonate as a lithium source, and polyethylene glycol and sucrose as a carbon source.
  • the preparation method is as follows:
  • the pole piece After the first sintering, the pole piece is mechanically crushed, the median particle size reaches 2.0 ⁇ m, and it is passed through a 150-mesh sieve.
  • the powder under the sieve is determined by ICP and high frequency infrared carbon and sulfur analysis to determine the content of Li, Fe, and C.
  • the lithium is supplemented to a Li:Fe molar ratio of 1.02:1, the amount of residual carbon and the total amount of carbon supplement is 2.0 wt%, and VC is mixed for 5.5 hours.
  • Nitrogen was introduced into the box furnace as a protective gas, the temperature was raised to 745°C at a heating rate of 5°C/min, and the temperature was kept for 12 hours. The temperature of the furnace was lowered to obtain the regenerated LFP.
  • the regenerated LFP positive material was prepared in the same manner as in Example 1, except that nitrogen protection was used for the first sintering, and the carbon source was not used for carbon supplementation in step (3); the battery was fabricated in the same manner as in Example 1.
  • Table 1 shows the performance parameters and electrochemical test results of the positive electrode materials prepared in each embodiment and comparative example.
  • the electrochemical performance of the regenerated LFP positive electrode material prepared according to the method described in each embodiment is better than the positive electrode prepared by the method of the comparative example in terms of first reversible capacity, first coulombic efficiency, and cycle capacity retention rate.
  • the materials indicate that the selective oxidation-reduction method proposed in this application can prepare regenerated LFP with better electrochemical performance.
  • the first increase in reversible capacity is firstly due to the fact that the waste lithium iron phosphate has too high an electrochemically active carbon content due to the previous homogenization and other processes.
  • the present application removes the amorphous coating through selective oxidation.
  • Carbon reduces the carbon content and increases the proportion of electrochemically active LFP in the material; on the other hand, it can still significantly increase the conductivity of LFP without removing the coated carbon with a higher degree of graphitization.
  • the growth of LFP grains is suppressed, so that small grains with higher crystallinity are obtained, and the material has a longer cycle performance.

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Abstract

本申请公开了废旧磷酸铁锂选择性氧化-还原再生的方法、再生磷酸铁锂和锂离子电池。所述方法包括：在通有温和氧化性气体的条件下，对废旧磷酸铁锂进行一次烧结；分离出磷酸铁锂粉料；采用锂源和碳源，通过二次烧结的方式，对磷酸铁锂粉料进行补锂、补碳和组成调控，得到再生磷酸铁锂；其中，所述温和氧化性气体为：水蒸气、CO 2气体、或二者的混合气体。本申请的方法可以制备得到性能优异的磷酸铁锂，其电化学性能特征表现为具有极好的常温和高温循环性能、压实密度较高，同时该材料还具有成本低廉的优点。

Description

废旧磷酸铁锂选择性氧化-还原再生的方法、再生磷酸铁锂和锂离子电池
本申请要求于2019年12月9日提交中国专利局，申请号为2019112519214、发明名称为“废旧磷酸铁锂选择性氧化-还原再生的方法、再生磷酸铁锂和锂离子电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
【技术领域】
本申请涉及锂离子电池正极材料领域，涉及一种废旧磷酸铁锂选择性氧化-还原再生的方法、再生磷酸铁锂和锂离子电池。
【背景技术】
自2019年起我国已逐步进入大规模磷酸铁锂电池退役阶段，如处置不当，则会造成严重污染，导致新能源材料由“绿色”变为“黑色”。LiFePO 4自身结构较为稳定，长循环退役后通过适当的补锂、包覆碳修复等技术，可相当程度地恢复其电化学性能，具有较高的再生价值。再生LFP尽管能量密度不高，但其具有低成本、长循环性能、热稳定性高、货源充足等特点，可大规模用于储能领域。
目前废旧LFP直接再生利用已有大量的研究报道。主要工艺流程可总结归纳为：电池拆解、极片分拣→废旧LFP从极片剥离→成分及粒度调控→烧结修复。
材料剥离是最重要的技术环节，从成分调控的宏观角度看，相当于从废旧极片中提取较高纯度的LiFePO 4。这其中涉及2个关键问题，一是如何实现较高的剥离率，二是如何避免分离提取过程中Al粉等杂质异物的引入。针对以上问题，相关研究者们分别开发了干法热处理路线和湿法浸泡路线。干法热处理是依据粘结剂PVDF与铝箔的熔点不同而开发，如一种在360℃～490℃之间保温时只有PVDF熔融热解失去粘结剂效力，待冷却降温后经过振动筛分等方式即可剥离LFP。湿法浸泡则又分为无机碱性溶液溶解铝箔和有机溶剂溶解PVDF两类方法。然而，以上方法从实验室转化至中试量产时，尚存在若干问题。较为突出的问题有：火法路线中，少数极片因电解液未清理干净而致使铝箔粉化烧毁，不可避免地在后续剥离过程中引入了铝粉异物；而某些经过压实的极片，因材料颗粒已嵌入至铝箔中而无法完全剥离；同时具有共性的问题是经过匀浆添加的SP、PVDF在煅烧后会有残留碳，导致再生LFP碳含量明显过剩。这都带来了量产时剥离率和异物管控方面的问题。湿法路线中，碱性溶液湿法剥离路线则需消耗大量碱性试剂且剥离LFP需多次清洗产生大量废水；有机溶剂法的研究报道中液固比高达20:1，致使有机溶剂成本过高，若再加入蒸 馏回流工艺，则能耗成本又过高，依然难以实现产业化。
因此，开发一种能够使粘结剂充分失效实现高效剥离，同时能够选择性氧化脱除多余残留碳，最终实现废旧LFP短流程再生的技术，已成为该领域的攻关难点。
【申请内容】
基于此，本申请的目的在于提供一种废旧磷酸铁锂选择性氧化-还原再生的方法、再生磷酸铁锂和锂离子电池。采用该方法制备得到的再生磷酸铁锂具有成本低廉、循环性能优异、压实密度高等特点。
一种废旧磷酸铁锂选择性氧化-还原再生的方法，所述方法包括以下步骤：
在通有温和氧化性气体的条件下，对废旧磷酸铁锂进行一次烧结；
从所述一次烧结所得物料中分离出磷酸铁锂粉料；
采用锂源和碳源，通过二次烧结的方式，对所述磷酸铁锂粉料进行补锂、补碳和组成调控，得到再生磷酸铁锂；
所述温和氧化性气体为：水蒸气、CO 2气体、或二者的混合气体。
本申请以废旧LiFePO 4(LFP)电池极片为原料，在水蒸气、CO 2等温和氧化性气体中一次烧结，使废旧LFP中的粘结剂失效的同时实现选择性氧化脱除无定形包覆碳，由此提高了残留包覆碳的石墨化度，由于石墨化碳具有较高的导电性，能够抑制LFP晶粒的长大，进而可以提高废旧LFP二次烧结时的温度且不会使晶粒过度长大，因此经过适当补锂和二次烧结后可以获得晶粒尺寸适宜且结晶度更高的再生LFP，同时温和氧化一次烧结时微量被氧化至Fe 3+在更高温度下二次烧结时被还原为Fe 2+，最终保持LiFePO 4物相，其电化学性能特征表现为具有极好的常温和高温循环性能、压实密度较高，同时该材料还具有成本低廉的优点。
在一种可行的实施方式中，所述方法具备下述特征(1)～(3)中的至少一个：
(1)所述温和氧化性气体为：水蒸气和CO 2气体的混合气体，所述水蒸气和CO 2气体的流速比为1:9～9:1；
(2)所述水蒸气来源于去离子水及超纯水中的至少一种，所述水蒸气的电阻≥18MΩ；
(3)所述CO 2气体的纯度≥99.0％。
在一种可行的实施方式中，所述废旧磷酸铁锂来源于废旧磷酸铁锂电池极片和废旧磷酸铁锂浆料中的至少一种；
可选地，所述废旧磷酸铁锂电池极片包括：消费退役的废旧LFP电池拆解所得废旧LFP极片、电池厂报废的次品电池拆解所得废旧LFP极片、电池厂报废的次品LFP极片。
在一种可行的实施方式中，所述方法具备下述特征(1)～(3)中的至少一个：
(1)所述废旧磷酸铁锂与所述温和氧化性气体的质量比为1:(0.1～10.0)，所述温和氧化性气体的通入流速恒定；
(2)所述一次烧结过程中，采用的加热设备包括管式炉、箱式炉、辊道窑或回转窑中的任意一种；
(3)所述一次烧结为在300℃～700℃下保温0.5小时～15小时，可选为在400℃～600℃下保温4小时～8小时。
在一种可行的实施方式中，所述一次烧结所得物料中分离出磷酸铁锂粉料的步骤具体为：先将一次烧结所得物料进行粉碎，然后分离；
可选地，先将一次烧结所得物料机械粉碎，然后筛网筛分；
可选地，粉碎至中值粒径范围为0.2μm～10.0μm，可选为0.5μm～3.0μm；
可选地，筛网的目数范围为10目～400目，可选为100目～325目。
在一种可行的实施方式中，所述方法具备下述特征(1)～(2)中的至少一个：
(1)所述补锂采用的锂源包括Li 2CO 3、LiOH·H 2O、Li 3PO 4或LiNO 3中的任意一种或至少两种的组合；
(2)所述锂源的纯度为工业级或电池级。
在一种可行的实施方式中，所述方法具备下述特征(1)～(3)中的至少一个：
(1)所述补锂的方式包括湿法补锂和干法补锂；
(2)以Li 2CO 3为锂源进行干法补锂，Li 2CO 3的中值粒径范围为0.2μm～10μm，可选为0.5μm～3μm；
(3)所述锂源的加入量按照Li:Fe摩尔比计算，Li过量范围为0.1％～10.0％，可选为2.0％～5.0％。
在一种可行的实施方式中，所述碳源包括葡萄糖、蔗糖、柠檬酸、乙炔黑、聚丙烯或聚乙二醇中的任意一种或至少两种的组合。
在一种可行的实施方式中，所述方法具备下述特征(1)～(3)中的至少一个：
(1)所述补碳的方式包括：湿法补碳和干法补碳；
(2)所述碳源的加入量按照使所得再生磷酸铁锂的碳含量为1.0wt％～6.0wt％计算；
(3)以葡萄糖和聚乙二醇的混合碳源进行干法补碳，所述混合碳源的中值粒径范围为0.2μm～10.0μm；可选地，所述混合碳源中，葡萄糖和聚乙二醇的质量配比范围为1:9～9:1。
在一种可行的实施方式中，采用锂源和碳源，通过二次烧结的方式，对所述磷酸铁锂粉料进行补锂、补碳和组成调控，得到再生磷酸铁锂的步骤具体为：
将锂源、碳源与所述磷酸铁锂粉料混合，二次烧结，得到再生磷酸铁锂；
可选地，所述混合的方式包括VC混合、单椎干燥混合及双椎干燥混合中的一种；
可选地，所述混合的时间为0.1小时～8小时，可选为1小时～3小时。
在一种可行的实施方式中，所述方法具备下述特征(1)～(5)中的至少一个：
(1)所述二次烧结在惰性气体下进行，所述惰性气体包括氮气、氩气、氦气、氖气、氪气或氙气中的任意一种或至少两种的组合；
(2)所述磷酸铁锂粉料和所述惰性气体的质量比为1:(0.1～10.0)，可选为1:(0.8～3.0)；
(3)所述二次烧结的过程中，所述惰性气体的通入流速恒定；
(4)所述二次烧结为在700℃～800℃下保温2小时～20小时，可选为在730℃～770℃下保温6小时～16小时；
所述二次烧结的保温时间为，可选为6小时～16小时；
(5)所述二次烧结采用的加热设备包括管式炉、箱式炉、辊道窑或回转窑中的任意一种，可选为辊道窑。
在一种可行的实施方式中，在得到再生磷酸铁锂之后，所述方法还包括：对再生磷酸铁锂进行过筛并除磁。
在一种可行的实施方式中，所述方法包括以下步骤：
将废旧极片置于回转窑中，通水蒸气与二氧化碳的混合气体，流速比4:6～6:4，且流速恒定，以2℃/min～5℃/min的升温速率升温至300℃～700℃，保温0.5～15小时，随炉降温；
废旧极片中的有效成分废旧硫酸铁锂与混合气体的质量比为1:(0.1～10.0)；
一次烧结后极片经机械破碎，过10～400目筛，筛下粉料经ICP、高频红外碳硫分析确定Li、Fe和C含量；
采用中值粒径0.2～10μm的Li 2CO 3、葡萄糖和聚乙二醇按质量比1:9～9:1的混合碳源，补锂至以Li:Fe摩尔比计Li过量0.1％～10.0％，碳源的加入量按照使所得再生磷酸铁锂的碳含量为1.0wt％～6.0wt％计算，VC混合0.1～8小时，在箱式炉中通入氮气作为保护气，二次烧结，随炉降温获得再生LFP；
二次烧结为：以2℃/min～5℃/min升温速率升温至700℃～800℃，保温2～20小时。
本申请还提供一种再生磷酸铁锂，所述再生磷酸铁锂通过上述的方法制备得到。
在一种可行的实施方式中，所述再生磷酸铁锂具备下述特征(1)～(3)中的至少一个：
(1)所述再生磷酸铁锂材料的中值粒径为0.1μm～10.0μm，可选为0.5μm～5.0μm；
(2)所述再生磷酸铁锂材料的比表面积为1.0m2/g～20.0m2/g，可 选为10.0m2/g～15.0m2/g；
(3)所述再生磷酸铁锂材料的粉体压实密度为1.0g/cm3～2.8g/cm3，可选为2.0g/cm3～2.5g/cm3。
(4)所述再生磷酸铁锂材料的pH为6.0～12.0，可选为8.0～10.0；
(5)所述再生磷酸铁锂材料的碳含量为1.0wt％～6.0wt％，可选为1.5wt％～2.5wt％。
本申请还提供一种锂离子电池，包括锂离子电池包含上述的再生磷酸铁锂材料。
【附图说明】
图1为本申请实施例所提供的LFP正极材料的工艺流程示意图；
图2为本申请实施例1中再生LFP正极材料的电镜图片；
图3为本申请实施例1中再生LFP正极材料的XRD图；
图4为本申请实施例1中再生LFP正极材料的首次充放电曲线；
图5为本申请实施例1的再生LFP正极材料循环性能曲线。
【具体实施方式】
下面结合附图并通过具体实施方式来进一步说明本申请的技术方案。
为达上述目的，本申请采用以下技术方案：
第一方面，一实施方式的一种废旧磷酸铁锂选择性氧化-还原再生的方法，包括以下步骤S100～S300：
步骤S100:在通有温和氧化性气体的条件下，对废旧磷酸铁锂进行一次烧结；
步骤S200:从一次烧结所得物料中分离出磷酸铁锂粉料；
步骤S300:采用锂源和碳源，通过二次烧结的方式，对分离所得磷酸铁锂粉料进行补锂、补碳和组成调控，得到再生磷酸铁锂；
所述温和氧化性气体为：水蒸气、CO 2气体、或二者的混合气体。
本申请的废弃磷酸铁锂既可以是未进行碳包覆的磷酸铁锂，也可以是碳包覆的磷酸铁锂。
本申请的方法经过步骤S300中，使用锂源进行补锂，使用碳源进行补碳并作为还原剂。经过引入锂源和碳源实现调质，二次烧结，Li补入LFP晶格中，补碳起到修补包覆碳的作用，还原剂可以将步骤S100氧化产生的微量Fe 3+重新还原为Fe 2+，实现组成调控，最终保持LiFePO 4物相。
本申请以废旧磷酸铁锂LiFePO 4(以下简称LFP)原料，在水蒸气和/或CO 2的温和氧化性气体中一次烧结，以气固反应的方式使废旧LFP中的粘结剂失效的同时实现选择性氧化脱除残留包覆碳中的无定形包覆碳，而未脱除石墨化碳，由此提高了残留包覆碳的石墨化度，由于石墨化碳具有较高的导电性，能够抑制LFP晶粒的长大，进而可以提高废旧LFP在 步骤S300补锂、补碳和组成调控时二次烧结的温度且不会使晶粒过度长大，因此，经过适当补锂和二次烧结后最终可以获得晶粒尺寸适宜且结晶度更高的再生LFP，其电化学性能特征表现为具有极好的常温和高温循环性能、压实密度较高且成本低廉。
本申请的方法相对于现有技术还具有如下优势：
第一、由于本申请步骤S100在温和氧化性气体条件下一次烧结，从而可以与电解液中的有机物反应，避免产生侵蚀铝箔的问题；而若采用氮气等相对惰性的气氛，则无法与有机物反应，导致可能产生侵蚀铝箔的问题。
第二、本申请的方法经过步骤S100在温和氧化性气体的条件下进行一次烧结，可以使粘结剂(例如PVDF)失效以及无定型碳(例如SP)的氧化性脱除，若有铝异物存在，通过上述方法可以使磷酸铁锂和铝粉的反应界面松动，从而解决现有技术中无法脱除铝粉异物的问题。
以下作为本申请可选的技术方案，但不作为对本申请提供的技术方案的限制，通过以下可选的技术方案，可以更好的达到和实现本申请的技术目的和有益效果。
在一些实施方式中，所述温和氧化性气体为：水蒸气和CO 2气体的混合气体，可选水蒸气和CO 2气体的流速比为1:9～9:1，例如1:9、2:8、3:7、3.5:6.5、4:6、5:5、6:4、7:3、8:2或9:1等，进一步可选流速比为4:6～6:4。
本申请可选采用水蒸气和CO 2气体的混合气体的原因如下：使用混合气体比单一气体效果好，单一种类的水蒸气氧化性过高，几乎全部磷酸铁锂会被一同氧化，当磷酸铁锂几乎全被氧化后，再经还原时很难完全还原，仍会有微量的Fe 3+；而混合气体氧化性更合适，氧化脱碳后最多只有微量的磷酸铁锂被氧化，在二次烧结时易于被彻底还原修复；单一种类的二氧化碳在中低温(比如300～600℃)下氧化性不够，效果甚微，如果温度升至700℃左右则铝箔会粉化，后续难以分离。采用水蒸气和二氧化碳混合气体可以调控出合适的氧势，使其在目标温度范围内实现无定形碳组分的氧化脱除同时磷酸铁锂不被氧化(虽然有微量的Fe 2+被氧化为Fe 3+，由于含量微小，其可在步骤(3)碳修复的过程中被还原)。由此获得的再生LFP可以严格控制Fe 3+/Fe 2+，表现出更好的比容量和循环性能。
在一些实施方式中，所述水蒸气来源于去离子水及超纯水中的至少一种，可选所述水蒸气的电阻≥18MΩ，例如18MΩ、20MΩ、30MΩ、35MΩ、40MΩ或50MΩ等。
在一些实施方式中，所述CO 2可以是工业级的CO 2，纯度≥99.0％。
本申请对所述废旧磷酸铁锂来源不作限定，例如可以是来源于废旧磷酸铁锂电池极片和/或废旧磷酸铁锂浆料。
具体地，所述废旧磷酸铁锂电池极片包括：消费退役的废旧LFP电池拆解所得废旧LFP极片、电池厂报废的次品电池(可以是注液后的产品，也可以是未注液的产品)拆解所得废旧LFP极片、电池厂报废的次 品LFP极片。
在一些实施方式中，废旧磷酸铁锂(此处指极片或者浆料中有效成分磷酸铁锂的量)与温和氧化性气体的质量比为1:(0.1～10.0)，例如1:0.1、1:0.5、1:1、1:2、1:3、1:3.5、1:4、1:5、1:6、1:7、1:8或1:10等，但不仅限于所列举数值，该数值范围内其他未列举的数值同样适用，可选为1:(0.8～3.0)。若温和氧化性气体的使用浓度过低，会导致无法使粘结剂充分失效，也无法有效氧化脱除无定形包覆碳；若温和氧化性气体的使用浓度过高，会导致过多的磷酸铁锂被氧化，影响最终再生磷酸铁锂的性能。
本申请中，根据温和氧化性气体的用气总质量、进料-出料总时间，可以换算出气体流速。
在一些实施方式中，所述一次烧结的过程中，温和氧化性气体的通入流速恒定。
在一些实施方式中，所述一次烧结过程中，采用的加热设备包括管式炉、箱式炉、辊道窑或回转窑中的任意一种，可选为回转窑。
在一些实施方式中，所述一次烧结的保温温度为300℃～650℃，例如300℃、350℃、400℃、500℃、550℃、600℃或650℃等；但不仅限于所列举数值，该数值范围内其他未列举的数值同样适用，可选为400℃～600℃。若一次烧结的温度过低，会导致无法使粘结剂充分失效，也无法有效氧化脱除无定形包覆碳；若一次烧结的温度过高(比如700℃)，会导致铝箔粉化，导致含铝粉末难以分离，同时也会导致过多的磷酸铁锂被氧化，影响最终再生磷酸铁锂的性能。
在一些实施方式中，所述一次烧结的保温时间为0.5小时～15小时，例如0.5小时、1小时、2小时、3小时、4小时、5小时、6小时、7小时、8小时、10小时、11小时、13小时或14小时等，但不仅限于所列举数值，该数值范围内其他未列举的数值同样适用；可选为4小时～8小时。
在一些实施方式中，步骤S200包括但不限于：先将一次烧结所得物料进行粉碎，然后分离。
本申请步骤S200可采用的方案包括但不限于机械破碎后筛网筛分、气流粉碎后旋风分离。进一步可选先将一次烧结所得物料机械粉碎，然后筛网筛分。
在一些实施方式中，粉碎至中值粒径范围为0.2μm～10.0μm，例如0.2μm、0.5μm、1μm、1.5μm、2μm、3μm、4μm、6μm、8μm或10μm等，但不仅限于所列举数值，该数值范围内其他未列举的数值同样适用；可选为0.5μm～3.0μm。
在一些实施方式中，筛网的目数范围为10目～400目，例如10目、40目、80目、100目、125目、150目、200目、240目、300目或325目等，但不仅限于所列举数值，该数值范围内其他未列举的数值同样适用；可选为100目～325目。
在一些实施方式中，步骤S300所述补锂采用的锂源包括但不限于 Li 2CO 3、LiOH.H 2O、Li 3PO 4或LiNO 3中的任意一种或至少两种的组合，可选为Li 2CO 3。
本申请中所述锂源的纯度可以是工业级或电池级，可选为电池级。
在一些实施方式中，步骤S300所述补锂的方法包括但不限于湿法补锂和干法补锂，可选为干法补锂。
在一些实施方式中，步骤S300以Li 2CO 3为锂源进行干法补锂，Li 2CO 3的中值粒径范围为0.2μm～10μm，例如0.2μm、0.5μm、1μm、3μm、5μm、6μm、7μm、8μm或10μm等，本领域技术人员可以通过破碎的方式使Li 2CO 3的粒度控制在上述范围内。此可选技术方案中，碳酸锂作为常规磷酸铁锂生产广泛采用的原料，在再生磷酸铁锂二次烧结温度下，此粒度范围的碳酸锂中的Li可以高效地补入再生磷酸铁锂晶格中，补充活性Li含量。更可选中值粒径范围为0.5μm～3.0μm。
在一些实施方式中，步骤S300所述锂源的加入量按照Li:Fe摩尔比计算，Li过量范围为0.1％～10.0％，例如0.1％、0.5％、1％、2％、3％、5％、6％、7％、8％或10％等，可选为2％～5％。
在一些实施方式中，步骤S300所述碳源包括葡萄糖、蔗糖、柠檬酸、乙炔黑、聚丙烯或聚乙二醇中的任意一种或至少两种的组合，所述组合典型但非限制性实例有：葡萄糖和蔗糖的组合，葡萄糖和柠檬酸的组合，蔗糖和乙炔黑的组合，蔗糖和聚丙烯的组合，葡萄糖、蔗糖和乙炔黑的组合，葡萄糖、蔗糖、柠檬酸和乙二醇的组合等。
在一些实施方式中，所述补碳的方法包括但不限于：湿法补碳和干法补碳，可选为干法补碳。
在一些实施方式中，所述碳源的加入量按照使所得再生磷酸铁锂的碳含量为1.0wt％～6.0wt％计算，例如1wt％、2wt％、3wt％、3.5wt％、4wt％、4.5wt％、5wt％或6wt％等，但不仅限于所列举数值，该数值范围内其他未列举的数值同样适用；可选使所得再生磷酸铁锂的碳含量为1.5wt％～2.5wt％。
在一些实施方式中，以葡萄糖和聚乙二醇的混合碳源进行干法补碳，混合碳源的中值粒径范围为0.2μm～10.0μm，例如0.2μm、1μm、3μm、3μm、7μm、8μm或10μm等，本领域技术人员可以通过破碎的方式使混合碳源的粒度控制在上述范围内。此可选技术方案中，葡萄糖和聚乙二醇的种类、热裂解温度匹配度更好，在合适的中值粒径范围内，与粉料实现较好的混匀效果，可以实现协同优化的效果，更可选中值粒径范围为0.5μm～3.0μm。
在一些实施方式中，所述混合碳源中，葡萄糖和聚乙二醇的质量配比范围为1:9～9:1，例如1:9、2:8、3:7、3.5:6.5、4:6、5:5、6:4、7:3、8:2或9:1等，但不仅限于所列举数值，该数值范围内其他未列举的数值同样适用；可选为4:6～6:4。
在一些实施方式中，步骤S300包括：将锂源、碳源与步骤S200分离 所得磷酸铁锂粉料混合，二次烧结，得到再生磷酸铁锂。这是一种干法补锂和干法补碳的方法，可以同时实现Li补入晶格以及碳修复的效果。
在一些实施方式中，所述混合的方式包括但不限于VC混合、单椎干燥混合或双椎干燥混合中的任意一种。
在一些实施方式中，所述混合的时间为0.1小时～8小时，例如0.1小时、1小时、2小时、3小时、4小时、5小时、7小时或8小时等，但不仅限于所列举数值，该数值范围内其他未列举的数值同样适用；可选为1小时～3小时。
在一些实施方式中，所述二次烧结在惰性气体下进行，所述惰性气体包括氮气、氩气、氦气、氖气、氪气或氙气中的任意一种或至少两种的组合。
在一些实施方式中，步骤S200分离所得磷酸铁锂粉料和惰性气体的质量比为1:(0.1～10.0)，例如1:0.1、1:0.5、1:1、1:2、1:3、1:3.5、1:4、1:5、1:6、1:7、1:8或1:10等，可选为1:(0.8～3.0)。
在一些实施方式中，所述二次烧结的过程中，惰性气体的通入流速恒定。
在一些实施方式中，所述二次烧结的保温温度为700℃～800℃，例如700℃、725℃、750℃、765℃、780℃或800℃等，在此范围内进行二次烧结，可以更好地达到修复的目的，可选为730℃～770℃。
在一些实施方式中，所述二次烧结的保温时间为2小时～20小时，例如2小时、4小时、6小时、8小时、10小时、12小时、13小时、15小时、18小时或20小时等，可选为6小时～16小时。
在一些实施方式中，所述二次烧结采用的加热设备包括管式炉、箱式炉、辊道窑或回转窑中的任意一种，可选为辊道窑。
作为本申请所述方法的进一步可选技术方案，所述方法包括以下步骤：
将废旧极片置于回转窑中，通水蒸气与二氧化碳的混合气体，流速比4:6～6:4，且流速恒定，以2～5℃/min的升温速率升温至300～700℃，保温0.5～15小时，随炉降温；
废旧极片中的有效成分废旧硫酸铁锂与混合气体的质量比为1:(0.1～10.0)；
一次烧结后极片经机械破碎，过10～400目筛，筛下粉料经ICP、高频红外碳硫分析确定Li、Fe和C含量；
采用中值粒径0.2～10μm的Li 2CO 3、葡萄糖和聚乙二醇按质量比1:9～9:1的混合碳源，补锂至以Li:Fe摩尔比计Li过量0.1～10.0％，碳源的加入量按照使所得再生磷酸铁锂的碳含量为1.0wt％～6.0wt％计算，VC混合0.1～8小时，在箱式炉中通入氮气作为保护气，二次烧结，随炉降温获得再生LFP；
二次烧结为：以2～5℃/min升温速率升温至700～800℃，保温2～20小时。
第二方面，另一实施方式的一种再生磷酸铁锂，所述再生磷酸铁锂通过上述实施方式的方法制备得到。
在一些实施方式中，所述再生LFP正极材料的中值粒径为0.1μm～10.0μm，例如0.1μm、0.5μm、1.5μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm或10μm等，可选为0.5μm～5.0μm。
在一些实施方式中，所述再生LFP正极材料的比表面积为1.0m 2/g～20.0m 2/g，可选为10.0m 2/g～15.0m 2/g，例如10m 2/g、12m 2/g、14m 2/g、15m 2/g、17m 2/g、18m 2/g或20m 2/g等。
在一些实施方式中，所述再生LFP正极材料的粉体压实密度为1.0g/cm 3～2.8g/cm 3，可选为2.0g/cm 3～2.5g/cm 3，例如2.0g/cm 3、2.1g/cm 3、2.2g/cm 3、2.3g/cm 3、2.4g/cm 3或2.5g/cm 3等。
在一些实施方式中，所述再生LFP正极材料的pH为6.0～12.0，例如6.0、6.5、7.0、7.5、8.0、9.0、9.5、10.0、11.0或12.0等，可选为8.0～10.0。
在一些实施方式中，所述再生LFP正极材料的碳含量(也即残碳和补碳的总量)为1.0wt％～6.0wt％，例如1.0wt％、1.5wt％、2.0wt％、3.0wt％、4.0wt％、4.5wt％、5.0wt％或6.0wt％等，可选为1.5wt％～2.5wt％。
第三方面，本申请提供一种锂离子电池，包括锂离子电池包含第二方面所述的再生磷酸铁锂正极材料。
本申请对锂离子电池的种类不作限定，例如可以是常规铝壳、钢壳、或软包锂离子电池。
本申请对采用所述再生磷酸铁锂正极材料粉料装配成电池的方法不作限定，本领域技术人员可以参照现有技术公开的方法进行装配。
本申请还提供了采用所述的再生磷酸铁锂制备正极极片的方法，包括：
将再生LFP正极材料、导电剂和粘结剂按质量百分比95～96:1～2:2～4在溶剂中混合、涂覆于铝箔集流体上，真空氛围下烘干制得。
在一些实施方式中，所述锂离子电池的负极极片采用的负极活性材料包括人造石墨、天然石墨、硅碳材料或硅氧材料中的任意一种或至少两种的组合。
在一些实施方式中，所述导电剂包括石墨粉和/或纳米导电液。
在一些实施方式中，所述纳米导电液由0.5wt％-20wt％的纳米碳材料与分散溶剂组成。
在一些实施方式中，所述纳米碳材料包括石墨烯、碳纳米管、纳米碳纤维、富勒烯、炭黑或乙炔黑中的任意一种或至少两种的组合。
在一些实施方式中，所述石墨烯的石墨片层数在1-100之间。
在一些实施方式中，所述碳纳米管和纳米碳纤维的直径在0.2nm-500nm。
在一些实施方式中，所述富勒烯、炭黑和乙炔黑的粒径为1nm-200nm。
在一些实施方式中，所述粘结剂包括聚偏氟乙烯、羧甲基纤维素钠、羧甲基纤维素锂、聚丙烯酸、羧化壳聚糖、聚甲基丙烯酸甲酯、聚醋酸乙 烯酯、丙烯晴多元共聚物的1种或至少2种的组合。
采用以下方法对实施例1～8和对比例1～3的正极材料进行测试：
本申请所述的粉体压实密度采用CARVER粉体压实机测试，其中，粉体压实密度＝测试样品的质量/测试样品的体积；极片压实密度＝(正极片质量-铝箔质量)/(极片面积×极片压实后的厚度)。
采用美国麦克仪器公司的Tristar3000全自动比表面积和孔隙度分析仪测试材料的比表面积。
采用马尔文激光粒度测试仪MS 2000测试材料粒径范围以及原料颗粒的平均粒径。
采用X射线衍射仪X’Pert Pro，PANalytical测试材料的结构。
采用日立公司S4800扫描电子显微镜观察样品的表面形貌、颗粒大小等。
采用以下方法测试电化学循环性能：将正极材料、导电剂和粘结剂按质量百分比95:2:3将他们溶解在溶剂中混合，控制固含量在50％，涂覆于铝箔集流体上，真空烘干、制得正极极片；然后将传统成熟工艺制备的人造石墨负极极片、1mol/L的LiPF 6/EC+DMC+EMC(v/v＝1:1:1)电解液、Celgard2400隔膜、外壳采用常规生产工艺装配18650圆柱单体电池。
圆柱电池的充放电测试在武汉金诺电子有限公司LAND电池测试系统上，在常温条件，0.1C恒流充放电，充放电电压限制在2.5V～3.7V。
圆柱电池的循环性能测试在武汉金诺电子有限公司LAND电池测试系统上，在常温条件，1C/1C，充放电电压限制在2.0～3.65V。
实施例1
本实施例提供一种废旧磷酸铁锂选择性氧化-还原再生的方法，以电池厂报废的次品LFP极片为原料，以碳酸锂为锂源、50wt％葡萄糖与50wt％聚乙二醇为混合碳源。
图1为本申请实施例所提供的LFP正极材料的工艺流程示意图，如图1所示，制备方法如下：
(1)废旧极片置于回转窑中，通水蒸气与二氧化碳的混合气体，水蒸气与二氧化碳的流速比4:6，且流速恒定。以2℃/min的升温速率升温至500℃，保温6小时，随炉降温。
(2)一次烧结后极片经机械破碎，中值粒径达到3.0μm，过200目筛。筛下粉料经ICP、高频红外碳硫分析确定Li、Fe、C含量。
(3)采用中值粒径2.0μm的锂源、混合碳源，补锂至Li:Fe摩尔比为1.05:1，残炭量和补碳总量为3wt％，VC混合2小时。在箱式炉中通入氮气作为保护气，以2℃/min升温速率升温至750℃，保温8小时，随炉降温获得再生LFP。
图2为本实施例中再生LFP正极材料的电镜图片，从图2中可以看出，制得的材料具有均匀的粒径分布。
图3为本实施例中再生LFP正极材料的XRD图，从图3中可以看出材料只有磷酸铁锂的衍射峰且无杂质峰。
图4为本实施例中再生LFP正极材料的首次充放电曲线。
图5为本实施例的再生LFP正极材料循环性能曲线，其中，不规则的粗线代表实测数据，较细的直线代表粗线的衰减趋势，用于预判衰减至80％时的循环次数。
图4和图5中可以看出材料具有接近常规磷酸铁锂放电比容量并且具有优异的循环性能。
实施例2
本实施例提供一种废旧磷酸铁锂选择性氧化-还原再生的方法，
以电池厂次品电池拆解LFP极片为原料，以碳酸锂为锂源、60wt％蔗糖与40wt％聚乙二醇为混合碳源。
制备方法如下：
(1)废旧极片置于回转窑中，通水蒸气与二氧化碳的混合气体，水蒸气与二氧化碳的流速比3:7，且流速恒定。以2℃/min的升温速率升温至530℃，保温7小时，随炉降温。
(2)一次烧结后极片经机械破碎，中值粒径达到3.5μm，过200目筛。筛下粉料经ICP、高频红外碳硫分析确定Li、Fe、C含量。
(3)采用中值粒径2.2μm的锂源、混合碳源，补锂至Li:Fe摩尔比为1.02:1，残炭量和补碳总量为2.5wt％，VC混合3小时。在箱式炉中通入氮气作为保护气，以2℃/min升温速率升温至760℃，保温8小时，随炉降温获得再生LFP。
实施例3
本实施例提供一种废旧磷酸铁锂选择性氧化-还原再生的方法，
以消费淘汰电池拆解LFP极片为原料，以氢氧化锂为锂源、50％蔗糖与50％聚丙烯为混合碳源。
制备方法如下：
(1)废旧极片初步破碎后置于回转窑中，通水蒸气与二氧化碳的混合气体，水蒸气与二氧化碳的流速比3:7，且流速恒定。以2℃/min的升温速率升温至550℃，保温5小时，随炉降温。
(2)一次烧结后极片经细磨破碎，中值粒径达到2.0μm，过200目筛。筛下粉料经ICP、高频红外碳硫分析确定Li、Fe、C含量。
(3)采用中值粒径1.8μm的锂源、混合碳源，补锂至Li:Fe摩尔比为1.08:1，残炭量和补碳总量为2.5wt％，VC混合5小时。在箱式炉中通入氮气作为保护气，以2℃/min升温速率升温至740℃，保温12小时，随炉降温获得再生LFP。
实施例4
本实施例提供一种废旧磷酸铁锂选择性氧化-还原再生的方法，
以电池厂报废的次品LFP极片为原料，以氢氧化锂为锂源、40％柠檬 酸与60％聚丙烯为混合碳源。
制备方法如下：
(1)废旧极片初步破碎后置于回转窑中，通水蒸气与二氧化碳的混合气体，水蒸气与二氧化碳的流速比5:5，且流速恒定。以2℃/min的升温速率升温至570℃，保温1小时，随炉降温。
(2)一次烧结后极片经细磨破碎，中值粒径达到2.7μm，过200目筛。筛下粉料经ICP、高频红外碳硫分析确定Li、Fe、C含量。
(3)采用中值粒径2.7μm的锂源、混合碳源，补锂至Li:Fe摩尔比为1.04:1，残炭量和补碳总量为2.8wt％，VC混合2小时。在箱式炉中通入氮气作为保护气，以2℃/min升温速率升温至720℃，保温14小时，随炉降温获得再生LFP。
实施例5
本实施例提供一种废旧磷酸铁锂选择性氧化-还原再生的方法，
以电池厂次品电池拆解LFP极片为原料，以碳酸锂为锂源、60％乙炔黑与40％蔗糖为混合碳源。
制备方法如下：
(1)废旧极片初步破碎后置于回转窑中，通水蒸气与二氧化碳的混合气体，水蒸气与二氧化碳的流速比3:7，且流速恒定。以2℃/min的升温速率升温至510℃，保温6小时，随炉降温。
(2)一次烧结后极片经细磨破碎，中值粒径达到2.0μm，过200目筛。筛下粉料经ICP、高频红外碳硫分析确定Li、Fe、C含量。
(3)采用中值粒径2.2μm的锂源、混合碳源，补锂至Li:Fe摩尔比为1.01:1，残炭量和补碳总量为2.2wt％，VC混合3小时。在箱式炉中通入氮气作为保护气，以2℃/min升温速率升温至740℃，保温10小时，随炉降温获得再生LFP。
实施例6
本实施例提供一种废旧磷酸铁锂选择性氧化-还原再生的方法，以电池厂报废的次品LFP极片为原料，以LiNO 3为锂源、蔗糖为碳源。
制备方法如下：
(1)废旧极片置于回转窑中，通水蒸气与二氧化碳的混合气体，水蒸气与二氧化碳的流速比8:2，且流速恒定。以3℃/min的升温速率升温至400℃，保温8小时，随炉降温。
(2)一次烧结后极片经机械破碎，中值粒径达到2.5μm，过325目筛。筛下粉料经ICP、高频红外碳硫分析确定Li、Fe、C含量。
(3)采用中值粒径4.0μm的锂源、混合碳源，补锂至Li:Fe摩尔比为1.08:1，残炭量和补碳总量为3.5wt％，VC混合7小时。在箱式炉中通入氮气作为保护气，以5℃/min升温速率升温至770℃，保温6小时，随炉降温获得再生LFP。
实施例7
本实施例提供一种废旧磷酸铁锂选择性氧化-还原再生的方法，以电池厂报废的次品LFP极片为原料，以Li 3PO 4为锂源、聚丙烯为碳源。
制备方法如下：
(1)废旧极片置于回转窑中，通水蒸气与二氧化碳的混合气体，水蒸气与二氧化碳的流速比7:3，且流速恒定。以4℃/min的升温速率升温至450℃，保温13小时，随炉降温。
(2)一次烧结后极片经机械破碎，中值粒径达到3.0μm，过150目筛。筛下粉料经ICP、高频红外碳硫分析确定Li、Fe、C含量。
(3)采用中值粒径1.3μm的锂源、混合碳源，补锂至Li:Fe摩尔比为1.02:1，残炭量和补碳总量为3.0wt％，VC混合5.5小时。在箱式炉中通入氮气作为保护气，以5℃/min升温速率升温至715℃，保温16小时，随炉降温获得再生LFP。
实施例8
本实施例提供一种废旧磷酸铁锂选择性氧化-还原再生的方法，以电池厂报废的磷酸铁锂浆料为原料，以碳酸锂为锂源、聚乙二醇和蔗糖为碳源。
制备方法如下：
(1)废旧浆料经离心、烘干后，得到黑色粉末，置于回转窑中，通水蒸气与二氧化碳的混合气体，水蒸气与二氧化碳的流速比7:3，且流速恒定。以4℃/min的升温速率升温至450℃，保温10小时，随炉降温。
(2)一次烧结后极片经机械破碎，中值粒径达到2.0μm，过150目筛。筛下粉料经ICP、高频红外碳硫分析确定Li、Fe、C含量。
(3)采用中值粒径1.0μm的锂源、混合碳源，补锂至Li:Fe摩尔比为1.02:1，残炭量和补碳总量为2.0wt％，VC混合5.5小时。在箱式炉中通入氮气作为保护气，以5℃/min升温速率升温至745℃，保温12小时，随炉降温获得再生LFP。
对比例1
按照与实施例1基本相同的方法制备再生LFP正材料，区别在于：一次烧结时采用氮气保护，步骤(3)不使用碳源进行补碳；按与实施例1相同的方法制作电池。
对比例2
除了将水蒸气与二氧化碳的混合气体替换为水蒸气，且保持气体流量与原混合气体总流量相同，其他内容与实施例1相同。
对比例3
除了将水蒸气与二氧化碳的混合气体替换为二氧化碳气体，且保持气体流量与原混合气体总流量相同，其他内容与实施例1相同。
各实施例及对比例所制备的正极材料的性能参数及电化学测试结果如表1所示。
表1
Figure PCTCN2020112973-appb-000001
由以上表格中数据可以看出，根据各实施例所述方法制备的再生LFP正极材料首次可逆容量、首次库伦效率、循环容量保持率等方面电化学性能均优于对比例所述方法制备的正极材料，说明本申请提出的选择性氧化-还原的方法可以制备出电化学性能更好的再生LFP。首次可逆容量的提升首先是得益于：废旧磷酸铁锂由于经过前期匀浆等工序导致其不具有电化学活性的碳的含量过高，本申请通过选择性氧化脱除其中的无定型包覆碳，一方面使碳含量下降，使材料中具有电化学活性的LFP占比提高；另一方面使较高石墨化度的包覆碳未被脱除依然能显著提高LFP的电导率，同时可在更高的二次烧结温度下抑制LFP晶粒长大，从而获得结晶度更高的小晶粒，使材料具有更长的循环性能。
由实施例1、对比例1和对比例2的对比可知，采用水蒸气与二氧化碳的混合气体可以使获得的再生LFP可以严格控制Fe 3+/Fe 2+，表现出更好的比容量和循环性能。
申请人声明，本申请通过上述实施例来说明本申请的详细方法，但本申请并不局限于上述详细方法，即不意味着本申请必须依赖上述详细方法才能实施。所属技术领域的技术人员应该明了，对本申请的任何改进，对本申请产品各原料的等效替换及辅助成分的添加、具体方式的选择等，均落在本申请的保护范围和公开范围之内。

Claims (16)

  1. 一种废旧磷酸铁锂选择性氧化-还原再生的方法，其特征在于，所述方法包括以下步骤：
    在通有温和氧化性气体的条件下，对废旧磷酸铁锂进行一次烧结；
    从所述一次烧结所得物料中分离出磷酸铁锂粉料；
    采用锂源和碳源，通过二次烧结的方式，对所述磷酸铁锂粉料进行补锂、补碳和组成调控，得到再生磷酸铁锂；
    所述温和氧化性气体为：水蒸气、CO 2气体、或二者的混合气体。
  2. 根据权利要求1所述的方法，其特征在于，具备下述特征(1)～(3)中的至少一个：
    (1)所述温和氧化性气体为：水蒸气和CO 2气体的混合气体，所述水蒸气和CO 2气体的流速比为1:9～9:1；
    (2)所述水蒸气来源于去离子水及超纯水中的至少一种，所述水蒸气的电阻≥18MΩ；
    (3)所述CO 2气体的纯度≥99.0％。
  3. 根据权利要求1或2所述的方法，其特征在于，具备下述特征(1)～(2)中的至少一个：
    (1)所述废旧磷酸铁锂来源于废旧磷酸铁锂电池极片和废旧磷酸铁锂浆料中的至少一种；
    (2)所述废旧磷酸铁锂电池极片包括：消费退役的废旧LFP电池拆解所得废旧LFP极片、电池厂报废的次品电池拆解所得废旧LFP极片、电池厂报废的次品LFP极片。
  4. 根据权利要求3所述的方法，其特征在于，具备下述特征(1)～(3)中的至少一个：
    (1)所述废旧磷酸铁锂与所述温和氧化性气体的质量比为1:(0.1～10.0)，所述温和氧化性气体的通入流速恒定；
    (2)所述一次烧结过程中，采用的加热设备包括管式炉、箱式炉、辊道窑及回转窑中的一种；
    (3)所述一次烧结为在300℃～700℃下保温0.5小时～15小时。
  5. 根据权利要求1-4任一项所述的方法，其特征在于，所述一次烧结所得物料中分离出磷酸铁锂粉料的步骤具体为：先将一次烧结所得物料进行粉碎，然后分离；
    可选地，先将一次烧结所得物料机械粉碎，然后筛网筛分；
    可选地，粉碎至中值粒径范围为0.2μm～10.0μm；
    可选地，筛网的目数范围为10目～400目。
  6. 根据权利要求1-5任一项所述的方法，其特征在于，具备下述特征(1)～(2)中的至少一个：
    (1)所述补锂采用的锂源包括Li 2CO 3、LiOH·H 2O、Li 3PO 4或LiNO 3 中的任意一种或至少两种的组合；
    (2)所述锂源的纯度为工业级或电池级。
  7. 根据权利要求6所述的方法，其特征在于，具备下述特征(1)～(3)中的至少一个：
    (1)所述补锂的方式包括湿法补锂和干法补锂；
    (2)以所述Li 2CO 3为锂源进行干法补锂，所述Li 2CO 3的中值粒径范围为0.2μm～10μm；
    (3)所述锂源的加入量按照Li:Fe摩尔比计算，Li过量范围为0.1％～10.0％。
  8. 根据权利要求1-7任一项所述的方法，其特征在于，所述碳源包括葡萄糖、蔗糖、柠檬酸、乙炔黑、聚丙烯或聚乙二醇中的任意一种或至少两种的组合。
  9. 根据权利要求8所述的方法，其特征在于，具备下述特征(1)～(3)中的至少一个：
    (1)所述补碳的方式包括：湿法补碳和干法补碳；
    (2)所述碳源的加入量按照使所得再生磷酸铁锂的碳含量为1.0wt％～6.0wt％计算；
    (3)以葡萄糖和聚乙二醇的混合碳源进行干法补碳，所述混合碳源的中值粒径范围为0.2μm～10.0μm；可选地，所述混合碳源中，葡萄糖和聚乙二醇的质量配比范围为1:9～9:1。
  10. 根据权利要求8所述的方法，其特征在于，所述采用锂源和碳源，通过二次烧结的方式，对所述磷酸铁锂粉料进行补锂、补碳和组成调控，得到再生磷酸铁锂的步骤具体为：
    将锂源、碳源与所述磷酸铁锂粉料混合，二次烧结，得到再生磷酸铁锂；
    可选地，所述混合的方式包括VC混合、单椎干燥混合或双椎干燥混合；
    可选地，所述混合的时间为0.1小时～8小时。
  11. 根据权利要求10所述的方法，其特征在于，具备下述特征(1)～(5)中的至少一个：
    (1)所述二次烧结在惰性气体下进行，所述惰性气体包括氮气、氩气、氦气、氖气、氪气或氙气中的任意一种或至少两种的组合；
    (2)所述磷酸铁锂粉料和所述惰性气体的质量比为1:(0.1～10.0)；
    (3)所述二次烧结的过程中，所述惰性气体的通入流速恒定；
    (4)所述二次烧结为在700℃～800℃下保温2小时～20小时；
    (5)所述二次烧结采用的加热设备包括管式炉、箱式炉、辊道窑或回转窑中的任意一种。
  12. 根据权利要求1-11任一项所述的方法，其特征在于，在得到再生磷酸铁锂之后，所述方法还包括：对再生磷酸铁锂进行过筛并除磁。
  13. 根据权利要求1-12任一项所述的方法，其特征在于，所述方法包括以下步骤：
    将废旧极片置于回转窑中，通水蒸气与二氧化碳的混合气体，流速比4:6～6:4，且流速恒定，以2℃/min～5℃/min的升温速率升温至300℃～700℃，保温0.5小时～15小时，随炉降温；
    废旧极片中的有效成分废旧硫酸铁锂与混合气体的质量比为1:(0.1～10.0)；
    一次烧结后极片经机械破碎，过10～400目筛，筛下粉料经ICP、高频红外碳硫分析确定Li、Fe和C含量；
    采用中值粒径0.2～10μm的Li 2CO 3、葡萄糖和聚乙二醇按质量比1:9～9:1的混合碳源，补锂至以Li:Fe摩尔比计Li过量0.1％～10.0％，碳源的加入量按照使所得再生磷酸铁锂的碳含量为1.0wt％～6.0wt％计算，VC混合0.1～8小时，在箱式炉中通入氮气作为保护气，二次烧结，随炉降温获得再生磷酸铁锂；
    二次烧结为：以2℃/min～5℃/min升温速率升温至700℃～800℃，保温2～20小时。
  14. 一种再生磷酸铁锂，其特征在于，所述再生磷酸铁锂通过权利要求1-13任一项所述的方法制备得到。
  15. 根据权利要求14所述的再生磷酸铁锂，其特征在于，具备下述特征(1)～(5)中的至少一个：
    (1)所述再生磷酸铁锂材料的中值粒径为0.1μm～10.0μm，可选为0.5μm～5.0μm；
    (2)所述再生磷酸铁锂材料的比表面积为1.0m 2/g～20.0m 2/g，可选为10.0m 2/g～15.0m 2/g；
    (3)所述再生磷酸铁锂材料的粉体压实密度为1.0g/cm 3～2.8g/cm 3，可选为2.0g/cm 3～2.5g/cm 3；
    (4)所述再生磷酸铁锂材料的pH为6.0～12.0；
    (5)所述再生磷酸铁锂材料的碳含量为1.0wt％～6.0wt％。
  16. 一种锂离子电池，其特征在于，包括锂离子电池包含权利要求14～15任一项所述的再生磷酸铁锂。
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