CN112897492B - Method for regenerating and recycling high-impurity lithium iron phosphate waste powder - Google Patents
Method for regenerating and recycling high-impurity lithium iron phosphate waste powder Download PDFInfo
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- CN112897492B CN112897492B CN202110097735.0A CN202110097735A CN112897492B CN 112897492 B CN112897492 B CN 112897492B CN 202110097735 A CN202110097735 A CN 202110097735A CN 112897492 B CN112897492 B CN 112897492B
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- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 98
- 239000002699 waste material Substances 0.000 title claims abstract description 54
- 239000012535 impurity Substances 0.000 title claims abstract description 52
- 238000000034 method Methods 0.000 title claims abstract description 47
- 239000000843 powder Substances 0.000 title claims abstract description 42
- 230000001172 regenerating effect Effects 0.000 title claims abstract description 8
- 238000004064 recycling Methods 0.000 title description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 132
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 96
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 95
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims abstract description 65
- 238000002386 leaching Methods 0.000 claims abstract description 62
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims abstract description 52
- 229910052742 iron Inorganic materials 0.000 claims abstract description 50
- 238000001354 calcination Methods 0.000 claims abstract description 41
- 239000007788 liquid Substances 0.000 claims abstract description 34
- 238000000926 separation method Methods 0.000 claims abstract description 30
- 238000000746 purification Methods 0.000 claims abstract description 27
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims abstract description 26
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims abstract description 26
- 238000002156 mixing Methods 0.000 claims abstract description 23
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 22
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 21
- 229910001386 lithium phosphate Inorganic materials 0.000 claims abstract description 18
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 claims abstract description 18
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 14
- 239000011230 binding agent Substances 0.000 claims abstract description 14
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 14
- 239000011574 phosphorus Substances 0.000 claims abstract description 14
- 229910000406 trisodium phosphate Inorganic materials 0.000 claims abstract description 13
- 238000000498 ball milling Methods 0.000 claims abstract description 11
- 239000003513 alkali Substances 0.000 claims abstract description 10
- 230000001502 supplementing effect Effects 0.000 claims abstract description 10
- 238000004090 dissolution Methods 0.000 claims abstract description 6
- 229910000399 iron(III) phosphate Inorganic materials 0.000 claims description 59
- 239000000047 product Substances 0.000 claims description 56
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 44
- 239000000706 filtrate Substances 0.000 claims description 42
- 229910019142 PO4 Inorganic materials 0.000 claims description 22
- 229910052799 carbon Inorganic materials 0.000 claims description 17
- 230000008569 process Effects 0.000 claims description 14
- 239000005955 Ferric phosphate Substances 0.000 claims description 12
- 229940032958 ferric phosphate Drugs 0.000 claims description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 10
- 229920002472 Starch Polymers 0.000 claims description 8
- 239000008107 starch Substances 0.000 claims description 8
- 235000019698 starch Nutrition 0.000 claims description 8
- 239000012298 atmosphere Substances 0.000 claims description 7
- 230000003647 oxidation Effects 0.000 claims description 6
- 238000007254 oxidation reaction Methods 0.000 claims description 6
- 229920000858 Cyclodextrin Polymers 0.000 claims description 5
- HFHDHCJBZVLPGP-UHFFFAOYSA-N schardinger α-dextrin Chemical compound O1C(C(C2O)O)C(CO)OC2OC(C(C2O)O)C(CO)OC2OC(C(C2O)O)C(CO)OC2OC(C(O)C2O)C(CO)OC2OC(C(C2O)O)C(CO)OC2OC2C(O)C(O)C1OC2CO HFHDHCJBZVLPGP-UHFFFAOYSA-N 0.000 claims description 5
- 238000003756 stirring Methods 0.000 claims description 5
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 claims description 4
- 239000003153 chemical reaction reagent Substances 0.000 claims description 4
- SZVJSHCCFOBDDC-UHFFFAOYSA-N ferrosoferric oxide Chemical compound O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 claims description 4
- 239000008103 glucose Substances 0.000 claims description 4
- 239000007774 positive electrode material Substances 0.000 claims description 4
- 239000002243 precursor Substances 0.000 claims description 4
- 239000013589 supplement Substances 0.000 claims description 4
- WQZGKKKJIJFFOK-VFUOTHLCSA-N beta-D-glucose Chemical compound OC[C@H]1O[C@@H](O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-VFUOTHLCSA-N 0.000 claims description 2
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 2
- 229910000398 iron phosphate Inorganic materials 0.000 abstract description 26
- 238000006243 chemical reaction Methods 0.000 abstract description 13
- 239000002893 slag Substances 0.000 abstract description 13
- TWQULNDIKKJZPH-UHFFFAOYSA-K trilithium;phosphate Chemical compound [Li+].[Li+].[Li+].[O-]P([O-])([O-])=O TWQULNDIKKJZPH-UHFFFAOYSA-K 0.000 abstract description 13
- 239000002253 acid Substances 0.000 abstract description 6
- AFSWOABZOLEQMR-UHFFFAOYSA-J iron(4+);hydroxide;phosphate Chemical compound [OH-].[Fe+4].[O-]P([O-])([O-])=O AFSWOABZOLEQMR-UHFFFAOYSA-J 0.000 abstract description 5
- WFGBXPXOFAFPTO-UHFFFAOYSA-N [P].[Fe].[Li] Chemical compound [P].[Fe].[Li] WFGBXPXOFAFPTO-UHFFFAOYSA-N 0.000 abstract 1
- 238000009776 industrial production Methods 0.000 abstract 1
- 238000005245 sintering Methods 0.000 abstract 1
- 239000002351 wastewater Substances 0.000 abstract 1
- 238000001914 filtration Methods 0.000 description 35
- 239000010949 copper Substances 0.000 description 31
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 27
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 21
- 229910021642 ultra pure water Inorganic materials 0.000 description 19
- 239000012498 ultrapure water Substances 0.000 description 19
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 16
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 16
- 238000001035 drying Methods 0.000 description 15
- 238000011084 recovery Methods 0.000 description 12
- 239000002033 PVDF binder Substances 0.000 description 11
- 229910001416 lithium ion Inorganic materials 0.000 description 11
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 10
- 239000012300 argon atmosphere Substances 0.000 description 9
- 229910000881 Cu alloy Inorganic materials 0.000 description 8
- 229910052786 argon Inorganic materials 0.000 description 8
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 8
- 229910052808 lithium carbonate Inorganic materials 0.000 description 8
- 238000002441 X-ray diffraction Methods 0.000 description 7
- 230000001276 controlling effect Effects 0.000 description 7
- 239000000203 mixture Substances 0.000 description 7
- 238000011056 performance test Methods 0.000 description 7
- 230000001105 regulatory effect Effects 0.000 description 6
- 239000007789 gas Substances 0.000 description 5
- 230000001590 oxidative effect Effects 0.000 description 5
- 238000011069 regeneration method Methods 0.000 description 5
- 230000008929 regeneration Effects 0.000 description 4
- QSNQXZYQEIKDPU-UHFFFAOYSA-N [Li].[Fe] Chemical compound [Li].[Fe] QSNQXZYQEIKDPU-UHFFFAOYSA-N 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000011888 foil Substances 0.000 description 3
- DPTATFGPDCLUTF-UHFFFAOYSA-N phosphanylidyneiron Chemical compound [Fe]#P DPTATFGPDCLUTF-UHFFFAOYSA-N 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- 238000013019 agitation Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000018109 developmental process Effects 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- 239000007790 solid phase Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- OEFNHCPKKJVIDJ-UHFFFAOYSA-L P(=O)(OO)([O-])[O-].[Fe+2] Chemical compound P(=O)(OO)([O-])[O-].[Fe+2] OEFNHCPKKJVIDJ-UHFFFAOYSA-L 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- JRBRVDCKNXZZGH-UHFFFAOYSA-N alumane;copper Chemical compound [AlH3].[Cu] JRBRVDCKNXZZGH-UHFFFAOYSA-N 0.000 description 1
- CNLWCVNCHLKFHK-UHFFFAOYSA-N aluminum;lithium;dioxido(oxo)silane Chemical compound [Li+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O CNLWCVNCHLKFHK-UHFFFAOYSA-N 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 238000010009 beating Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000005262 decarbonization Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 230000008676 import Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000011268 mixed slurry Substances 0.000 description 1
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical group O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000005588 protonation Effects 0.000 description 1
- 230000001698 pyrogenic effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 229910052642 spodumene Inorganic materials 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
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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
- 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
- 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
- C01B25/30—Alkali metal phosphates
- C01B25/308—Methods for converting an alkali metal orthophosphate into another one; Purification; Decolorasing; Dehydrating; Drying
-
- 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
- C01B25/37—Phosphates of heavy metals
- C01B25/375—Phosphates of heavy metals of iron
-
- 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
-
- 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
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- 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
- C01P2006/80—Compositional purity
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- 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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- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Crystallography & Structural Chemistry (AREA)
- Processing Of Solid Wastes (AREA)
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Abstract
The invention discloses a method for regenerating and circulating high-impurity lithium iron phosphate waste powder, which comprises the following steps of: 1) calcining the high-impurity lithium iron phosphate waste powder to remove the binder; 2) leaching by adopting potassium persulfate, and performing solid-liquid separation to obtain leachate and leaching slag; 3) carrying out alkali dissolution on the leached residues to remove aluminum, supplementing an iron source and hydrogen peroxide after removing the aluminum, carrying out hydrothermal purification by using phosphoric acid, and calcining to obtain an iron phosphate product; 4) adjusting pH of the leaching solution to remove impurities, and adding Na3PO4Extracting lithium to obtain a lithium phosphate product; 5) and adjusting the proportion of lithium iron phosphorus by using the iron phosphate and the lithium phosphate, then performing ball milling and mixing, sintering at a high temperature, and obtaining the lithium iron phosphate again. The method is simple and practical, generates less wastewater, uses less acid and alkali, can recycle the purified phosphoric acid solution, realizes the high-efficiency conversion from hydroxyl iron phosphate to iron phosphate and the comprehensive utilization of lithium, iron and phosphorus components of the waste lithium iron phosphate powder, has high lithium leaching rate, high iron phosphate crystallinity and low impurity content of lithium phosphate products, has excellent performance of regenerated lithium iron phosphate, and is suitable for industrial production.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a method for regenerating and recycling high-impurity lithium iron phosphate waste powder.
Background
The lithium iron phosphate battery occupies the half-wall Jiangshan of the electric automobile market firstly due to excellent stability and safety. Because of the higher safety performance of the lithium iron phosphate, the lithium iron phosphate battery in the passenger car accounts for 93 percent in the aspect that the lithium iron phosphate battery is mainly applied to public transportation in China. The lithium iron phosphate battery is applied earlier in China and faces to the problems of scrapping and the like earlier. Although the waste lithium iron phosphate power battery does not contain rare elements, the waste lithium iron phosphate power battery contains rich elements such as lithium, iron, copper, aluminum and the like, and the waste lithium iron phosphate power battery is short of lithium resources in China, low in spodumene grade and unstable in quality, and ores are mainly depended on and imported. The method has the advantages that the waste of resources can be reduced by recovering metal elements such as lithium resources in the waste lithium batteries, the import pressure of the lithium resources is relieved well, and the benign development of the lithium battery industry in China is promoted. However, in the face of increasingly severe market competition, it is also critical to improve the competitiveness of products, reduce the cost of raw materials and widen the source of raw materials, and as the early-service lithium iron phosphate battery enters a large-scale scrapping period, a large amount of lithium iron phosphate waste materials are generated, most of the lithium iron phosphate waste materials have high copper-aluminum content (high-impurity materials) and are difficult to directly regenerate, and lithium iron products are required to be prepared in advance and then prepared into lithium iron phosphate. Therefore, the development of an efficient selective separation technology and the reduction of cost and environmental load have important significance for the lithium iron phosphate recovery market in China.
At present, the main methods for recycling the lithium iron phosphate anode mainly comprise two methods: high-temperature solid-phase regeneration method and acid-base leaching method. In the former method, lithium iron phosphate is simply treated at high temperature to burn out PVDF, then lithium and carbon are supplemented, and solid phase regeneration is carried out after mixing, for example, CN 102280673A and CN 110828887A disclose the regeneration process conditions of waste lithium iron phosphate. Although the pyrogenic process regeneration is simple, the energy consumption is high, the impurities of the regenerated lithium iron phosphate are difficult to control, the recovery process is difficult to regulate and control, the electrochemical performance is easy to be unstable, and the processing performance is inconsistent. The wet recovery is to selectively leach iron and lithium into the solution by using acid or alkali, and then to precipitate lithium and iron. For example, CN 108110357 a discloses a method for treating lithium iron phosphate with dilute acid, which is not capable of treating waste lithium iron phosphate powder with high impurity content, although the flow is simple, the recovery rate is high, and the product purity is high. And in other methods for recovering lithium iron phosphate by wet method, the defects of too many impurity removal steps, too long flow, large acid and alkali consumption and the like exist.
In conclusion, most of the existing recovery technologies have the problems of complex process, high recovery cost, low lithium iron recovery rate, difficulty in wastewater treatment and the like.
Disclosure of Invention
Aiming at the problems of complex process, high recovery cost, low lithium iron recovery rate and impure recovered product iron phosphate in the existing waste lithium iron phosphate recovery technology, the invention provides a method for regenerating and recycling high-impurity waste lithium iron phosphate powder, which has the advantages of simple operation, common used reagents, low acid and alkali consumption of leaching agents, reusable phosphoric acid purification liquid, low cost, high lithium recovery rate, high purity of iron phosphate products, iron-phosphorus ratio meeting the requirement of battery-grade iron phosphate, and good performance of the prepared iron phosphate.
In order to achieve the purpose, the invention provides the following technical scheme:
a method for regenerating and circulating high-impurity lithium iron phosphate waste powder comprises the following steps:
step (1): calcining the high-impurity lithium iron phosphate waste powder to remove the binder in an inert atmosphere to obtain waste lithium iron phosphate waste powder;
step (2): stirring and leaching the waste lithium iron phosphate powder obtained in the step (1) by using a potassium persulfate solution, and performing solid-liquid separation to obtain a leachate and leaching residues;
and (3): carrying out alkali dissolution on the leaching residue obtained in the step (2) to remove aluminum, and carrying out solid-liquid separation to obtain aluminum-removed filter residue;
and (4): supplementing an iron source and hydrogen peroxide to the aluminum-removed filter residue obtained in the step (3), performing hydrothermal purification by using phosphoric acid, and performing solid-liquid separation to obtain purified filter residue;
and (5): calcining the purified filter residue obtained in the step (4) in an air atmosphere to obtain battery-grade FePO4A product;
and (6): removing impurities from the leachate obtained in the step (2), and performing solid-liquid separation to obtain a lithium-rich filtrate;
and (7): extracting lithium from the lithium-rich filtrate obtained in the step (6), and performing solid-liquid separation to obtain battery grade Li3PO4A product;
and (8): respectively adopting the recovered battery grade FePO4Products and battery grade Li3PO4The product is used as an iron source and a lithium source, and the molar ratio of lithium, iron and phosphorus in the system is adjusted to be 1 to1.1:1:1, supplementing an organic carbon source, and performing ball milling and mixing to obtain a lithium iron phosphate precursor;
and (9): and (5) calcining the lithium iron phosphate precursor obtained in the step (8) in an inert atmosphere to obtain the lithium iron phosphate positive active material.
In the invention, the high-impurity lithium iron phosphate waste powder is waste powder obtained by disassembling and sorting the anode and the cathode of a retired lithium iron phosphate battery, and the main impurities and the contents of the waste powder are 0.5-3.5 wt% of Al, 0.3-2 wt% of Cu and 5-15 wt% of graphite.
Preferably, in the step (1), the calcining temperature is 500-550 ℃, and the calcining time is 4-6 h.
Preferably, in the step (2), the solid-liquid ratio in the agitation leaching process is 1: 3-1: 5g/mL, the leaching time is 1-3 h, the temperature is 40-60 ℃, and the agitation speed is 300-500 r/min.
Preferably, in the step (2), the molar weight of the potassium persulfate added is the Fe in the waste lithium iron phosphate powder2+And oxidation of Cu to Fe3+And Cu2+1.05 to 1.2 times the theoretical molar amount of (b).
In the invention, no extra reagent is needed to be added in the stirring leaching process to regulate and control the pH, the pH is stabilized at 2-3, and the FePO is satisfied4The extent of precipitation.
Preferably, in the step (3), the reagent for the alkali dissolution aluminum removal process is LiOH, the solid-to-liquid ratio is 1: 3-1: 6g/mL, and the molar weight of the LiOH is that Al in the leaching residue is converted into AlO2 -1.05 to 1.2 times of the theoretical molar weight and 0.5 to 1 hour.
Preferably, in the step (4), the iron source is at least one of iron powder or ferroferric oxide, the supplement amount of the iron source is 1-5% of the molar amount of ferric phosphate in the aluminum removal filter residue, and the addition amount of the hydrogen peroxide is capable of oxidizing the iron source into Fe3+1.2 to 2 times the theoretical molar amount of (A).
Preferably, in the step (4), the adding amount of the phosphoric acid in the purification process is such that the molar ratio of the ferric phosphate to the phosphoric acid in the hydrothermal reaction kettle is 1: 0.8-1: 2, the temperature of the hydrothermal purification is 95-100 ℃, and the time is 1-4 h.
In the oxidation leaching of the potassium persulfate solution in the step (2), the pH value is stabilized at 2-3, so that hydroxyl iron phosphate is formed under the protonation action of a solvent, the hydroxyl iron phosphate is extremely unstable at high temperature and is easy to form iron oxide in the calcination decarbonization process in the step (5), and a battery-grade iron phosphate product cannot be obtained.
Preferably, in the step (5), the calcining temperature is 650-700 ℃ and the time is 4-7 h.
Preferably, in the step (6), the pH value is adjusted to 8-10 in the impurity removal process.
Preferably, in the step (7), Na is added during the lithium extraction process3PO4，Na3PO4The amount of (b) is 1.5 to 2 times of the molar amount of lithium in the filtrate.
Preferably, in the step (8), the molar ratio of lithium, iron and phosphorus in the system is adjusted to be 1.02-1.05: 1: 1; the adding amount of the organic carbon source is 10-15 wt% of the quality of the target lithium iron phosphate product, and the organic carbon source is selected from at least one of starch, cyclodextrin and glucose.
Preferably, the calcining temperature in the step (9) is 600-900 ℃, and the calcining time is 6-18 h.
The invention has the beneficial effects that:
according to the invention, waste lithium iron phosphate powder is calcined in an inert atmosphere to remove a binder, potassium persulfate is adopted for oxidation leaching, copper and lithium are leached by using acidity and strong oxidizing property provided by potassium persulfate in a solution, and the leachate is used for adjusting pH to remove Cu2+Then adding Na3PO4Extracting lithium to obtain battery grade Li3PO4. Meanwhile, the iron source and hydrogen peroxide are supplemented to the leached residues after the aluminum is removed by alkali dissolution to adjust the iron-phosphorus ratio of the ferric phosphate in the residues, and then hydrothermal purification is carried out under high acid and high pressure, so that FePO can be greatly improved4To obtain battery grade FePO4. Finally, the prepared battery grade Li is respectively adopted3PO4And battery grade FePO4As an iron source and a lithium source, adjusting the molar ratio of lithium, iron and phosphorus in the system, supplementing an organic carbon source,and calcining to obtain the lithium iron phosphate positive active material.
The invention realizes the regeneration of the high-impurity lithium iron phosphate waste material, realizes the conversion from hydroxyl iron phosphate to iron phosphate through high-temperature purification, and overcomes the problem that the iron phosphate product is impure due to the hydroxyl iron phosphate formed in the oxidation leaching process because of insufficient acidity. And iron is supplemented in the purification process, the iron-phosphorus ratio of the prepared iron phosphate meets the requirements of battery-grade iron phosphate, the obtained iron phosphate has high crystallinity and low impurity content of lithium phosphate products, and the regenerated lithium iron phosphate has excellent performance, so that the high-efficiency recovery of lithium, iron and lithium in the high-impurity lithium iron phosphate waste powder is really realized, and a direction is provided for industrialization.
Drawings
FIG. 1 shows FePO prepared in example 14XRD pattern of (a).
FIG. 2 shows Li obtained in example 13PO4XRD pattern of (a).
Fig. 3 is an XRD spectrum of lithium iron phosphate prepared in example 1.
Fig. 4 is an electrochemical performance chart of lithium iron phosphate prepared in example 1.
Fig. 5 is a graph of the cyclic coulombic efficiency of the lithium iron phosphate prepared in example 1.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
Example 1
Step (1): placing the high-impurity lithium iron phosphate waste powder in an argon atmosphere at 550 ℃ for calcining for 6h to fully decompose the binder PVDF;
step (2): mixing the PVDF-removed waste powder obtained in the step (1) with ultrapure water according to the solid-to-liquid ratio of 1:3g/mL, and adding theoretical Fe oxide2+Leaching the copper alloy with potassium persulfate of which the molar weight is 1.2 times that of the Cu for 2 hours, and filtering and separating to obtain leachate and leaching slag; the leachate mainly comprises: li+、Cu2+(ii) a The leaching residue mainly contains FePO4、Al、C；
And (3): mixing the leaching residue obtained in the step (2) with ultrapure water according to the proportion of 1:3g/mL, and converting Al into AlO2 -Removing aluminum by LiOH with the molar weight 1.05 times of the theoretical molar weight, controlling the concentration of LiOH in the system to be 0.6mol/L, reacting for 0.5h, and filtering to obtain aluminum-removed filter residue after the reaction is finished; the main component of the aluminum-removing filter residue is FePO4、C；
And (4): drying the aluminum-removed filter residue obtained in the step (3), measuring the iron content, and determining the FePO content in the aluminum-removed filter residue4Supplementing iron powder with 3 percent of molar weight, wherein the iron powder can be completely oxidized into Fe by supplementing3+Hydrogen peroxide with the theoretical molar weight of 1.5 times, regulating the molar ratio of the ferric phosphate to the phosphoric acid in a system to be 1:0.8 by using phosphoric acid with the concentration of 85%, placing the system in a high-pressure kettle, performing hydrothermal purification for 3 hours at the temperature of 95 ℃, and filtering and separating to obtain purified filter residue after purification; the main component in the purified filter residue is purified FePO4、C；
And (5): calcining the purified filter residue obtained in the step (4) in air at 700 ℃ for 4h to obtain battery-grade FePO4A product;
and (6): adjusting the pH obtained in step (2) to 8 with NaOH so that Cu2+With Cu (OH)2Precipitating in a form, and performing solid-liquid separation to obtain a lithium-rich filtrate; the lithium-rich filtrate mainly contains Li+；
And (7): adding Na into the lithium-rich filtrate obtained in the step (6)3PO4Extracting lithium and Na3PO4The input amount is 1.8 times of the molar weight of lithium in the filtrate, and the battery grade Li is obtained after filtration and separation3PO4And (3) obtaining the product.
Battery grade FePO4The XRD pattern of the product is shown in figure 1, and the battery grade Li3PO4The XRD pattern of the product is shown in figure 2. The detection proves that the content of Cu impurities of the ferric phosphate is lower than 50ppm, and the content of Al impurities is lower than 100 ppm.
The prepared iron phosphate and lithium phosphate are used as an iron source and a lithium source, iron oxide and lithium carbonate are supplemented to adjust the molar ratio of lithium to iron to phosphorus in the system to be 1.02:1:1, starch with the mass being 12% of that of a target lithium iron phosphate product is supplemented, ethanol is used as a medium to perform ball milling, the mixture is dried and calcined for 6 hours at 750 ℃ under the protection of argon gas to obtain battery-grade lithium iron phosphate, and an XRD (X-ray diffraction) spectrum is shown in figure 3.
And (3) electrochemical performance testing:
the lithium iron phosphate positive electrode material prepared in example 1, acetylene black and a binder (PVDF) were uniformly mixed in a mass ratio of 8:1:1, and then manually ground using NMP as a solvent to obtain a uniformly mixed slurry. Coating the obtained slurry on an aluminum foil, drying the aluminum foil in a vacuum oven at 120 ℃ for 12 hours, and then beating the aluminum foil into a disk-shaped pole piece with the diameter of 10 mm. The pole piece is assembled into a CR2025 button cell. And carrying out constant-current charge and discharge tests at room temperature (25 ℃) and with the limiting voltage of 2.5-4.1V. After 100 cycles, the lithium iron phosphate still maintains the specific capacity of 145mAh/g, as shown in figure 4, and the coulombic efficiency map is shown in figure 5.
Example 2
Step (1): placing the high-impurity lithium iron phosphate waste powder in an argon atmosphere and calcining at 500 ℃ for 4h to fully decompose the binder PVDF;
step (2): mixing the PVDF-removed waste powder obtained in the step (1) with ultrapure water according to the solid-to-liquid ratio of 1:3g/mL, and adding theoretical Fe oxide2+Leaching the copper alloy with potassium persulfate of which the molar weight is 1.05 times that of the Cu for 3 hours, and filtering and separating to obtain leachate and leaching slag; the leachate mainly comprises: li+、Cu2+(ii) a The leaching residue mainly contains FePO4、Al、C；
And (3): mixing the leaching residue obtained in the step (2) and ultrapure water according to the proportion of 1:3g/mL, and converting Al into AlO2 -Removing aluminum from LiOH with the molar weight being 1.05 times of the theoretical molar weight, wherein the concentration of LiOH in the system is 0.6mol/L, the reaction time is 0.5h, and filtering to obtain aluminum-removed filter residues after the reaction is finished; the main component of the aluminum-removing filter residue is FePO4、C；
And (4): drying the aluminum-removed filter residue obtained in the step (3), measuring the iron content, and determining the FePO content in the aluminum-removed filter residue4Supplementing ferroferric oxide with 1.5 percent of molar weight, and completely oxidizing the ferroferric oxide into Fe by supplementing the ferroferric oxide3+Hydrogen peroxide with the theoretical molar weight of 2 times, regulating the molar ratio of the iron phosphate to the phosphoric acid in the system to be 1:1 by using phosphoric acid with the concentration of 85%, placing the mixture in a high-pressure kettle, performing hydrothermal purification for 1 hour at the temperature of 100 ℃, and filtering and separating the purified mixture to obtain purified filter residue; purifying filterThe main component in the slag is purified FePO4、C；
And (5): calcining the purified filter residue obtained in the step (4) in air at 700 ℃ for 6h to obtain battery-grade FePO4A product; detected battery grade FePO4The Cu impurity content in the product is lower than 50ppm, and the Al impurity content is lower than 100 ppm;
and (6): adjusting the pH obtained in step (2) to 9 with NaOH so that Cu2+With Cu (OH)2Precipitating in a form, and performing solid-liquid separation to obtain a lithium-rich filtrate; the lithium-rich filtrate mainly contains Li+；
And (7): adding Na into the lithium-rich filtrate obtained in the step (6)3PO4Extracting lithium and Na3PO4The input amount is 1.7 times of the molar weight of lithium in the filtrate, and battery grade Li is obtained after filtration and separation3PO4And (3) obtaining the product.
The prepared iron phosphate and lithium phosphate are used as an iron source and a lithium source, the molar ratio of lithium to iron to phosphorus in the system is adjusted to 1.05:1:1 by supplementing iron oxide and lithium carbonate, 5% of cyclodextrin and 5% of starch in the mass of a target lithium iron phosphate product are supplemented, ethanol is used as a medium for ball milling, and after drying, the lithium iron phosphate product is calcined for 6 hours at 700 ℃ under the protection of argon gas to obtain the battery-grade lithium iron phosphate.
Electrochemical performance tests are the same as example 1, and after 100 cycles, the specific capacity of the lithium iron phosphate battery is 141 mAh/g.
Example 3
Step (1): placing the high-impurity lithium iron phosphate waste powder in an argon atmosphere at 550 ℃ for calcining for 4h to fully decompose the binder PVDF;
step (2): mixing the PVDF-removed waste powder obtained in the step (1) with ultrapure water according to the solid-to-liquid ratio of 1:4g/mL, and adding theoretical Fe oxide2+Leaching the copper alloy with potassium persulfate of which the molar weight is 1.2 times that of the Cu for 2 hours, and filtering and separating to obtain leachate and leaching slag; the leachate mainly comprises: li+、Cu2+(ii) a The main component of the leaching residue is FePO4、Al、C；
And (3): mixing the leaching residue obtained in the step (2) and ultrapure water according to the proportion of 1:3g/mL, and converting Al into AlO2 -1.05 of theoretical molar weightRemoving aluminum by multiplying LiOH, wherein the concentration of LiOH in the system is 0.6mol/L, the reaction time is 0.5h, and filtering to obtain aluminum-removed filter residue after the reaction is finished; the main component of the aluminum-removing filter residue is FePO4、C；
And (4): drying the aluminum-removed filter residue obtained in the step (3), measuring the iron content, and determining the FePO content in the aluminum-removed filter residue4Supplementing iron powder with 5 percent of molar weight, wherein the iron powder can be completely oxidized into Fe by supplementing3+Hydrogen peroxide with 2 times of theoretical molar weight, adjusting the molar ratio of the ferric phosphate to the phosphoric acid in a system to be 1:1.2 by using phosphoric acid with the concentration of 85%, placing the mixture in a high-pressure kettle, performing hydrothermal purification for 1h at the temperature of 100 ℃, and filtering and separating the purified mixture to obtain purified filter residue; the main component in the purified filter residue is purified FePO4、C；
And (5): calcining the purified filter residue obtained in the step (4) in air at 700 ℃ for 6h to obtain battery-grade FePO4A product; detected battery grade FePO4The Cu impurity content in the product is lower than 50ppm, and the Al impurity content is lower than 100 ppm;
and (6): adjusting the pH obtained in step (2) to 10 with NaOH so that Cu2+With Cu (OH)2Precipitating in a form, and performing solid-liquid separation to obtain a lithium-rich filtrate; the lithium-rich filtrate mainly contains Li+；
And (7): adding Na into the lithium-rich filtrate obtained in the step (6)3PO4Extracting lithium and Na3PO4The input amount is 1.9 times of the molar weight of lithium in the filtrate, and the battery grade Li is obtained after filtration and separation3PO4And (3) obtaining the product.
The prepared iron phosphate and lithium phosphate are used as an iron source and a lithium source, the molar ratio of lithium to iron to phosphorus in the system is adjusted to 1.03:1:1 by supplementing iron oxide and lithium carbonate, cyclodextrin accounting for 8% of the mass of the target lithium iron phosphate product and starch accounting for 4% of the mass of the target lithium iron phosphate product are supplemented, ethanol is used as a medium for ball milling, and the battery-grade lithium iron phosphate is obtained by calcining for 6 hours at 750 ℃ under the protection of argon after drying.
Electrochemical performance tests are the same as example 1, and after 100 cycles, the specific capacity of the lithium iron phosphate battery is 143 mAh/g.
Example 4
Step (1): placing the high-impurity lithium iron phosphate waste powder in an argon atmosphere and calcining at 500 ℃ for 4h to fully decompose the binder PVDF;
step (2): mixing the PVDF-removed waste powder obtained in the step (1) with ultrapure water according to the solid-to-liquid ratio of 1:4g/mL, and adding theoretical Fe oxide2+Leaching the copper alloy with potassium persulfate of which the molar weight is 1.2 times that of the Cu for 2 hours, and filtering and separating to obtain leachate and leaching slag; the leachate mainly comprises: li+、Cu2+(ii) a The leaching residue mainly contains FePO4、Al、C；
And (3): mixing the leaching residue obtained in the step (2) with ultrapure water according to the proportion of 1:3g/mL, and converting Al into AlO2 -Removing aluminum by LiOH with the molar weight 1.05 times of the theoretical molar weight, controlling the concentration of LiOH in the system to be 0.6mol/L, reacting for 0.5h, and filtering to obtain aluminum-removed filter residue after the reaction is finished; the main component of the aluminum-removing filter residue is FePO4、C；
And (4): drying the aluminum-removed filter residue obtained in the step (3), measuring the iron content, and determining the FePO content in the aluminum-removed filter residue4Supplementing iron powder with 3.5 percent of molar weight, and completely oxidizing the iron powder into Fe by the supplement3+Hydrogen peroxide with the theoretical molar weight of 1.5 times, regulating the molar ratio of the ferric phosphate to the phosphoric acid in a system to be 1:1 by using phosphoric acid with the concentration of 85%, placing the system in a high-pressure kettle, performing hydrothermal purification for 3 hours at the temperature of 100 ℃, and filtering and separating to obtain purified filter residue after purification; the main component in the purified filter residue is purified FePO4、C；
And (5): calcining the purified filter residue obtained in the step (4) in air at 700 ℃ for 6h to obtain battery-grade FePO4A product; detected battery grade FePO4The Cu impurity content in the product is lower than 50ppm, and the Al impurity content is lower than 100 ppm;
and (6): adjusting the pH obtained in step (2) to 10 with NaOH so that Cu2+With Cu (OH)2Precipitating in a form, and performing solid-liquid separation to obtain a lithium-rich filtrate; the lithium-rich filtrate mainly contains Li+；
And (7): adding Na into the lithium-rich filtrate obtained in the step (6)3PO4Extracting lithium and Na3PO4The input amount is 2 times of the molar weight of lithium in the filtrate, and the battery grade Li is obtained after filtration and separation3PO4And (4) obtaining a product.
The prepared iron phosphate and lithium phosphate are used as an iron source and a lithium source, iron oxide and lithium carbonate are supplemented, the molar ratio of lithium to iron to phosphorus in the system is adjusted to 1.05:1:1, glucose accounting for 15% of the mass of the target lithium iron phosphate product is supplemented, ethanol is used as a medium for ball milling, and after drying, the battery-grade lithium iron phosphate is obtained by calcining for 8 hours at 800 ℃ under the protection of argon.
Electrochemical performance tests are the same as example 1, and after 100 cycles, the specific capacity of the lithium iron phosphate battery is 136 mAh/g.
Comparative example 1
Step (1): placing the high-impurity lithium iron phosphate waste powder in an argon atmosphere at 550 ℃ for calcining for 6h to fully decompose the binder PVDF;
step (2): mixing the PVDF-removed waste powder obtained in the step (1) with ultrapure water according to the solid-to-liquid ratio of 1:3g/mL, and adding theoretical Fe oxide2+Leaching the copper alloy with potassium persulfate of which the molar weight is 1.2 times that of the Cu for 2 hours, and filtering and separating to obtain leachate and leaching slag; the leachate mainly comprises: li+、Cu2+(ii) a The leaching residue mainly contains FePO4、Al、C；
And (3): mixing the leaching residue obtained in the step (2) with ultrapure water according to the proportion of 1:3g/mL, and converting Al into AlO2 -Removing aluminum by LiOH with the molar weight 1.05 times of the theoretical molar weight, controlling the concentration of LiOH in the system to be 0.6mol/L, reacting for 0.5h, and filtering to obtain aluminum-removed filter residue after the reaction is finished; the main component of the aluminum-removing filter residue is FePO4、C；
And (4): directly regulating the molar ratio of the ferric phosphate to the phosphoric acid in the system to be 1:0.8 by using phosphoric acid with the concentration of 85% without supplementing an iron source, placing the residue obtained in the step (2) into a high-pressure kettle, performing hydrothermal purification for 3 hours at 95 ℃, and filtering and separating the purified residue after purification; the main component in the purified filter residue is purified FePO4、C；
And (5): calcining the purified filter residue obtained in the step (4) in air at 700 ℃ for 4h to obtain FePO with partial ash4A product; detected FePO4The Cu impurity content in the product is lower than 50ppm, and the Al impurity content is lower than 100 ppm;
and (6): adjusting the pH obtained in step (2) to 8 with NaOH so that Cu2+With Cu (OH)2Precipitating in a form, and performing solid-liquid separation to obtain a lithium-rich filtrate; the lithium-rich filtrate mainly contains Li+；
And (7): adding Na into the lithium-rich filtrate obtained in the step (6)3PO4Extracting lithium and Na3PO4The input amount is 1.8 times of the molar weight of lithium in the filtrate, and battery grade Li is obtained after filtration and separation3PO4And (3) obtaining the product.
The prepared iron phosphate and lithium phosphate are used as an iron source and a lithium source, iron oxide and lithium carbonate are supplemented, the molar ratio of lithium to iron to phosphorus in the system is adjusted to 1.02:1:1, starch with the mass being 12% of that of a target lithium iron phosphate product is supplemented, ethanol is used as a medium for ball milling, and after drying, the lithium iron phosphate is calcined for 6 hours at 750 ℃ under the protection of argon gas to obtain the lithium iron phosphate.
In this comparative example, the iron phosphate was produced as gray with an excessive amount of P, since the iron source was not supplemented.
Electrochemical performance tests are the same as example 1, and after 100 cycles, the specific capacity of the lithium iron phosphate battery is 122 mAh/g.
Comparative example 2
Step (1): placing the high-impurity lithium iron phosphate waste powder in an argon atmosphere and calcining at 500 ℃ for 4h to fully decompose the binder PVDF;
step (2): mixing the PVDF-removed waste powder obtained in the step (1) with ultrapure water according to the solid-to-liquid ratio of 1:3g/mL, and adding theoretical Fe oxide2+Leaching the copper alloy with potassium persulfate of which the molar weight is 1.05 times that of the Cu for 3 hours, and filtering and separating to obtain leachate and leaching slag; the leachate mainly comprises: li+、Cu2+(ii) a The leaching residue mainly contains FePO4、Al、C；
And (3): mixing the leaching residue obtained in the step (2) and ultrapure water according to the proportion of 1:3g/mL, and converting Al into AlO2 -Removing aluminum by LiOH with the molar weight 1.05 times of the theoretical molar weight, controlling the concentration of LiOH in the system to be 0.6mol/L, reacting for 0.5h, and filtering to obtain aluminum-removed filter residue after the reaction is finished; the main component of the aluminum-removing filter residue is FePO4、C；
And (4): calcining the aluminum-removed filter residue obtained in the step (3) in air at 700 ℃ for 6h to obtain a reddish-brown product; the main product is ferric oxide through detection;
and (5): adjusting the pH obtained in step (2) to 9 with NaOH so that Cu2+With Cu (OH)2Precipitating in a form, and performing solid-liquid separation to obtain a lithium-rich filtrate; the lithium-rich filtrate mainly contains Li+；
And (6): adding Na into the lithium-rich filtrate obtained in the step (6)3PO4Extracting lithium and Na3PO4The input amount is 1.7 times of the molar weight of lithium in the filtrate, and battery grade Li is obtained after filtration and separation3PO4And (3) obtaining the product.
In this comparative example, the iron hydroxyl phosphate produced was directly oxidized to iron oxide in air, since no purification was performed.
Comparative example 3
Step (1): placing the high-impurity lithium iron phosphate waste powder in an argon atmosphere at 550 ℃ for calcining for 4h to fully decompose the binder PVDF;
step (2): mixing the PVDF-removed waste powder obtained in the step (1) with ultrapure water according to the solid-to-liquid ratio of 1:4g/mL, and adding theoretical Fe oxide2+Leaching the copper alloy with potassium persulfate of which the molar weight is 1.2 times that of the Cu for 2 hours, and filtering and separating to obtain leachate and leaching slag; the leachate mainly comprises: li+、Cu2+(ii) a The leaching residue mainly contains FePO4、Al、C；
And (3): mixing the leaching residue obtained in the step (2) and ultrapure water according to the proportion of 1:3g/mL, and converting Al into AlO2 -Removing aluminum by LiOH with the molar weight 1.05 times of the theoretical molar weight, controlling the concentration of LiOH in the system to be 0.6mol/L, reacting for 0.5h, and filtering to obtain aluminum-removed filter residue after the reaction is finished; the main component of the aluminum-removing filter residue is FePO4、C；
And (4): drying the aluminum-removed filter residue obtained in the step (3), measuring the iron content, and determining the FePO content in the aluminum-removed filter residue4Supplementing iron powder with 5 percent of molar weight, wherein the iron powder can be completely oxidized into Fe by supplementing3+Hydrogen peroxide with 2 times of theoretical molar weight, adjusting the molar ratio of the ferric phosphate to the phosphoric acid in a system to be 1:1.2 by using phosphoric acid with the concentration of 85%, placing the mixture in a high-pressure kettle, performing hydrothermal purification for 2 hours at the temperature of 80 ℃, and filtering and separating the purified mixture to obtain purified filter residue; the main component in the purified filter residue is purified FePO4、C；
And (5): calcining the purified filter residue obtained in the step (4) in air at 700 ℃ for 6h to obtain the partial yellow FePO4A product; detected FePO4The Cu impurity content in the product is lower than 50ppm, and the Al impurity content is lower than 100 ppm;
and (6): adjusting the pH obtained in step (2) to 10 with NaOH so that Cu2+With Cu (OH)2Precipitating in a form, and performing solid-liquid separation to obtain a lithium-rich filtrate; the lithium-rich filtrate mainly contains Li+；
And (7): adding Na into the lithium-rich filtrate obtained in the step (6)3PO4Extracting lithium and Na3PO4The input amount is 1.9 times of the molar weight of lithium in the filtrate, and the battery grade Li is obtained after filtration and separation3PO4And (3) obtaining the product.
The prepared iron phosphate and lithium phosphate are used as an iron source and a lithium source, the molar ratio of lithium to iron to phosphorus in the system is adjusted to 1.03:1:1 by supplementing iron oxide and lithium carbonate, cyclodextrin with the mass of 8% and starch with the mass of 4% of that of a target lithium iron phosphate product are supplemented, ethanol is used as a medium for ball milling, and the lithium iron phosphate is obtained by drying and calcining for 6 hours at 750 ℃ under the protection of argon.
In this comparative example, the iron phosphate conversion was incomplete due to too low a hydrothermal purification temperature.
Electrochemical performance tests are the same as example 1, and after 100 cycles, the specific capacity of the lithium iron phosphate battery is 123 mAh/g.
Comparative example 4
Step (1): placing the high-impurity lithium iron phosphate waste powder in an argon atmosphere and calcining at 500 ℃ for 4h to fully decompose the binder PVDF;
step (2): mixing the PVDF-removed waste powder obtained in the step (1) with ultrapure water according to the solid-to-liquid ratio of 1:4g/mL, and adding theoretical Fe oxide2+Leaching the copper alloy with potassium persulfate of which the molar weight is 1.2 times that of the Cu for 2 hours, and filtering and separating to obtain leachate and leaching slag; the leachate mainly comprises: li+、Cu2+(ii) a The leaching residue mainly contains FePO4、Al、C；
And (3): mixing the leaching slag obtained in the step (2) and ultrapure water according to the proportion of 1:3g/mL, and mixing the leaching slag and the ultrapure water according to the proportion ofConversion of Al to AlO2 -Removing aluminum by LiOH with the molar weight 1.05 times of the theoretical molar weight, controlling the concentration of LiOH in the system to be 0.6mol/L, reacting for 0.5h, and filtering to obtain aluminum-removed filter residue after the reaction is finished; the main component of the aluminum-removing filter residue is FePO4、C；
And (4): drying the aluminum-removed filter residue obtained in the step (3), measuring the iron content, and determining the FePO content in the aluminum-removed filter residue4Supplementing iron powder with 3.5 percent of molar weight, and completely oxidizing the iron powder into Fe by the supplement3+Hydrogen peroxide with the theoretical molar weight of 1.5 times, regulating the molar ratio of the ferric phosphate to the phosphoric acid in a system to be 1:1 by using phosphoric acid with the concentration of 85%, placing the system in a high-pressure kettle, performing hydrothermal purification for 0.5h at the temperature of 100 ℃, and filtering and separating to obtain purified filter residue after purification; the main component in the purified filter residue is purified FePO4、C；
And (5): calcining the purified filter residue obtained in the step (4) in air at 700 ℃ for 6h to obtain pink FePO4A product; detected FePO4The Cu impurity content in the product is lower than 50ppm, and the Al impurity content is lower than 100 ppm;
and (6): adjusting the pH obtained in step (2) to 10 with NaOH so that Cu2+With Cu (OH)2Precipitating in a form, and performing solid-liquid separation to obtain a lithium-rich filtrate; the lithium-rich filtrate mainly contains Li+；
And (7): adding Na into the lithium-rich filtrate obtained in the step (6)3PO4Extracting lithium and Na3PO4The input amount is 2 times of the molar weight of lithium in the filtrate, and the battery grade Li is obtained after filtration and separation3PO4And (3) obtaining the product.
The prepared iron phosphate and lithium phosphate are used as an iron source and a lithium source, iron oxide and lithium carbonate are supplemented, the molar ratio of lithium to iron to phosphorus in the system is adjusted to 1.05:1:1, glucose accounting for 15% of the mass of the target lithium iron phosphate product is supplemented, ethanol is used as a medium for ball milling, and after drying, the lithium iron phosphate is calcined for 8 hours at 800 ℃ under the protection of argon gas to obtain the lithium iron phosphate.
In this comparative example, the iron phosphate conversion was incomplete due to too short hydrothermal purification time.
Electrochemical performance tests are the same as example 1, and after 100 cycles, the specific capacity of the lithium iron phosphate battery is 121 mAh/g.
Comparative example 5
Step (1): placing the high-impurity lithium iron phosphate waste powder in an argon atmosphere at 550 ℃ for calcining for 6h to fully decompose the binder PVDF;
step (2): mixing the PVDF-removed waste powder obtained in the step (1) with ultrapure water according to the solid-to-liquid ratio of 1:3g/mL, and adding theoretical Fe oxide2+Leaching for 2 hours with potassium persulfate of which the molar weight is 1.01 times that of Cu, and filtering and separating to obtain leachate and leaching slag; the leachate mainly comprises: li+、Cu2+(ii) a The leaching residue mainly contains FePO4、Al、C；
And (3): mixing the leaching residue obtained in the step (2) and ultrapure water according to the proportion of 1:3g/mL, and converting Al into AlO2 -Removing aluminum by LiOH with the molar weight 1.05 times of the theoretical molar weight, controlling the concentration of LiOH in the system to be 0.6mol/L, reacting for 0.5h, and filtering to obtain aluminum-removed filter residue after the reaction is finished; the main component of the aluminum-removing filter residue is FePO4、C；
And (4): drying the aluminum-removed filter residue obtained in the step (3), measuring the iron content, and determining the FePO content in the aluminum-removed filter residue4Supplementing iron powder with 3 percent of molar weight, wherein the iron powder can be completely oxidized into Fe by supplementing3+Hydrogen peroxide with the theoretical molar weight of 1.5 times, regulating the molar ratio of the ferric phosphate to the phosphoric acid in a system to be 1:0.8 by using phosphoric acid with the concentration of 85%, placing the system in a high-pressure kettle, performing hydrothermal purification for 3 hours at the temperature of 95 ℃, and filtering and separating to obtain purified filter residue after purification; the main component in the purified filter residue is purified FePO4、C；
And (5): calcining the purified filter residue obtained in the step (4) in air at 700 ℃ for 4h to obtain FePO4A product; detected FePO4The Cu impurity content in the product is higher than 1500ppm, and the Al impurity content is higher than 1000 ppm;
and (6): adjusting the pH obtained in step (2) to 8 with NaOH so that Cu2+With Cu (OH)2Precipitating in a form, and performing solid-liquid separation to obtain a lithium-rich filtrate; the lithium-rich filtrate mainly contains Li+；
And (7): adding Na into the lithium-rich filtrate obtained in the step (6)3PO4Extracting lithium and Na3PO4Is thrown inThe amount of the lithium ion is 1.8 times of the molar amount of the lithium in the filtrate, and the Li is obtained after filtration and separation3PO4And (3) obtaining the product.
The prepared iron phosphate and lithium phosphate are used as an iron source and a lithium source, iron oxide and lithium carbonate are supplemented, the molar ratio of lithium to iron to phosphorus in the system is adjusted to 1.02:1:1, starch with the mass being 12% of that of a target lithium iron phosphate product is supplemented, ethanol is used as a medium for ball milling, and after drying, the lithium iron phosphate is calcined for 6 hours at 750 ℃ under the protection of argon gas to obtain the lithium iron phosphate.
In this comparative example, the amount of impurities of Cu and Al was too high due to incomplete leaching caused by too low an amount of potassium persulfate added in the oxidation leaching.
Electrochemical performance tests are the same as example 1, and after 100 cycles, the specific capacity of the lithium iron phosphate battery is 116 mAh/g.
Claims (10)
1. A method for regenerating and circulating high-impurity lithium iron phosphate waste powder is characterized by comprising the following steps:
step (1): calcining the high-impurity lithium iron phosphate waste powder to remove the binder in an inert atmosphere to obtain waste lithium iron phosphate waste powder;
step (2): stirring and leaching the waste lithium iron phosphate powder obtained in the step (1) by using a potassium persulfate solution, and performing solid-liquid separation to obtain a leaching solution and leaching residues;
and (3): carrying out alkali dissolution on the leaching residue obtained in the step (2) to remove aluminum, and carrying out solid-liquid separation to obtain aluminum-removed filter residue;
and (4): supplementing an iron source and hydrogen peroxide to the aluminum-removed filter residue obtained in the step (3), performing hydrothermal purification by using phosphoric acid, and performing solid-liquid separation to obtain purified filter residue;
and (5): calcining the purified filter residue obtained in the step (4) in an air atmosphere to obtain battery-grade FePO4A product;
and (6): removing impurities from the leachate obtained in the step (2), and performing solid-liquid separation to obtain a lithium-rich filtrate;
and (7): extracting lithium from the lithium-rich filtrate obtained in the step (6), and performing solid-liquid separation to obtain battery grade Li3PO4A product;
and (8): respectively adopting the recovered batteriesGrade FePO4Products and battery grade Li3PO4The product is used as an iron source and a lithium source, the molar ratio of lithium to iron to phosphorus in the system is adjusted to 1-1.1: 1:1, an organic carbon source is supplemented, and a lithium iron phosphate precursor is prepared by ball milling and mixing;
and (9): and (5) calcining the lithium iron phosphate precursor obtained in the step (8) in an inert atmosphere to obtain the lithium iron phosphate positive active material.
2. The method of claim 1, wherein the method comprises the following steps: in the step (1), the calcining temperature is 500-550 ℃, and the calcining time is 4-6 h.
3. The method of claim 1, wherein the method comprises the following steps: in the step (2), the solid-liquid ratio in the stirring and leaching process is 1: 3-1: 5g/mL, the leaching time is 1-3 h, the temperature is 40-60 ℃, and the stirring speed is 300-500 r/min.
4. The method of claim 1, wherein the method comprises the following steps: in the step (2), the molar weight of the potassium persulfate added is the Fe in the waste lithium iron phosphate powder2+And oxidation of Cu to Fe3+And Cu2+1.05 to 1.2 times the theoretical molar amount of (A).
5. The method of claim 1, wherein the method comprises the following steps: in the step (3), a reagent used in the process of removing aluminum by alkali dissolution is LiOH, the solid-to-liquid ratio is 1: 3-1: 6g/mL, and the molar weight of the LiOH is that Al in leaching residues is converted into AlO2 -1.05 to 1.2 times of the theoretical molar weight and 0.5 to 1 hour.
6. The method of claim 1, wherein the method comprises the following steps: in the step (4), the iron source is at least one of iron powder or ferroferric oxide, and the supplement amount of the iron source is phosphoric acid in the aluminum-removing filter residue1-5% of the molar weight of iron, and the addition amount of hydrogen peroxide is that the iron source can be oxidized into Fe3+1.2 to 2 times the theoretical molar amount of (A).
7. The method of claim 1, wherein the method comprises the following steps: in the step (4), the adding amount of phosphoric acid in the purification process is such that the molar ratio of ferric phosphate to phosphoric acid in the hydrothermal reaction kettle is 1: 0.8-1: 2, the temperature of hydrothermal purification is 95-100 ℃, and the time is 1-4 hours.
8. The method for regenerating and circulating the high-impurity lithium iron phosphate waste powder according to claim 1, characterized in that: in the step (5), the calcining temperature is 650-700 ℃, and the time is 4-7 h;
and (6) adjusting the pH to 8-10 in the impurity removal process.
9. The method of claim 1, wherein the method comprises the following steps: in the step (7), Na is added in the process of extracting lithium3PO4，Na3PO4The amount of (b) added is 1.5 to 2 times the molar amount of lithium in the filtrate.
10. The method of claim 1, wherein the method comprises the following steps: in the step (8), the molar ratio of lithium, iron and phosphorus in the system is adjusted to 1.02-1.05: 1: 1; the adding amount of the organic carbon source is 10-15 wt% of the quality of the target lithium iron phosphate product, and the organic carbon source is selected from at least one of starch, cyclodextrin and glucose;
in the step (9), the calcining temperature is 600-900 ℃, and the calcining time is 6-18 h.
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| CN115044780A (en) * | 2022-06-06 | 2022-09-13 | 安徽大学绿色产业创新研究院 | Method for recovering lithium from lithium iron phosphate battery positive electrode material |
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