CN114824546A - Method for recycling waste lithium iron phosphate - Google Patents

Method for recycling waste lithium iron phosphate Download PDF

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CN114824546A
CN114824546A CN202210478279.9A CN202210478279A CN114824546A CN 114824546 A CN114824546 A CN 114824546A CN 202210478279 A CN202210478279 A CN 202210478279A CN 114824546 A CN114824546 A CN 114824546A
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iron phosphate
lithium iron
lithium
carbon
sintering
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程冲
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Shanghai Xinyidan New Material Co ltd
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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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes

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Abstract

The invention belongs to the technical field of lithium ion battery anode materials, and particularly relates to a method for recycling waste lithium iron phosphate. The method comprises the steps of calcining waste high-carbon lithium iron phosphate powder or a lithium iron phosphate pole piece to obtain oxidized lithium iron phosphate; then, performing coating-sintering on the oxidized lithium iron phosphate and a carbon source substance for two times to obtain a regenerated lithium iron phosphate/carbon composite material; wherein, during the first coating-sintering, the carbon source substances comprise a lithium source, an iron source, a phosphorus source and a carbon source 1, and the carbon source substances during the second coating-sintering comprise a carbon source 2. The method disclosed by the invention has the advantages that waste materials do not need to be leached by acid, no waste water or waste acid is generated in the whole regeneration process, the method is more environment-friendly, does not need high temperature or high pressure, is low in cost and is suitable for large-scale production.

Description

Method for recycling waste lithium iron phosphate
Technical Field
The invention belongs to the technical field of lithium ion battery anode materials, and particularly relates to a method for recycling waste lithium iron phosphate.
Background
Because of the advantages of stable structure, low price, higher theoretical capacity (170mAh/g), stable working voltage, no toxicity, environmental protection, stable structure, safety, good thermal stability, long cycle life and the like, the lithium iron phosphate is directly favored by the power and energy storage market.
With the rapid development of electric automobiles and energy storage markets, the yield of lithium iron phosphate is also rapidly increased, however, a large amount of unqualified lithium iron phosphate waste materials (such as too high carbon content, unqualified electrochemical properties, too high specific surface area, too low compacted density and the like), unqualified waste pole pieces of lithium iron phosphate batteries (such as unqualified surface density, unqualified compacted density and the like) and a large amount of lithium iron phosphate waste batteries are also generated in the processes of producing lithium iron phosphate materials and preparing lithium iron phosphate batteries. How to reuse the lithium iron phosphate waste materials, the waste pole pieces and the waste batteries gradually becomes a research hotspot of people.
The traditional method for recycling the waste lithium iron phosphate material mainly adopts a roasting or acid leaching method, but has the disadvantages of complex recycling process, long flow, high equipment investment, easy brought new by-products in the acid leaching process, and the production of a large amount of waste acid and waste water, which is not beneficial to environmental protection. For example, chinese patent CN 108996484A discloses a method for preparing lithium iron phosphate by using a lithium iron phosphate positive plate. According to the method, firstly, an acid is used for dissolving a lithium iron phosphate positive plate, then ammonia water is added for regulating the pH value to obtain lithium and aluminum filtrate and iron phosphate filter residue, then ammonia water is added into the lithium and aluminum filtrate to separate out aluminum hydroxide, and then alkali and a phosphorus compound are added into a lithium solution to obtain lithium phosphate. And mixing the obtained lithium phosphate and iron phosphate with a phosphorus source and a carbon source to finally obtain the lithium iron phosphate material.
In order to avoid using a large amount of acid and alkali in the liquid phase recycling process, people improve the traditional roasting method (the roasting aim is to remove organic matters such as carbon, PVDF and the like in waste lithium iron phosphate, particularly high-carbon waste lithium iron phosphate, and the residual carbon can influence the coating effect of the later-period recycled carbon), and oxidized lithium iron phosphate (the oxidized product is mainly Li) is obtained by sintering the recycled lithium iron phosphate anode powder in the air 3 Fe2(PO4) 3 And Fe 2 O 3 ) Then, a small amount of lithium source, oxidized lithium iron phosphate and carbon source are mixed again, and the mixture is sintered for one time to obtain regenerated lithium iron phosphate, such as chinese patent applications CN 109346789 a and CN 112142029 a. But do notThe lithium iron phosphate prepared by the process has low compacted density and high impurity content, and the electrochemistry is improved compared with the performance of the recovered lithium iron phosphate, but the capacity only reaches 90-95% of the capacity of the newly-generated lithium iron phosphate, so the lithium iron phosphate prepared by the process is difficult to meet the requirements of a power market.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a method for recycling waste lithium iron phosphate, and the regenerated phosphate anode material sintered by the method has excellent performance, high compaction density, less impurity phase and high capacitance.
The purpose of the invention is realized by the following technical scheme:
a method for recycling waste lithium iron phosphate comprises the following steps:
(1) calcining waste high-carbon lithium iron phosphate powder or a lithium iron phosphate pole piece to obtain oxidized lithium iron phosphate;
(2) coating and sintering the oxidized lithium iron phosphate with carbon source substances for two times to obtain a regenerated lithium iron phosphate/carbon composite material;
the low-carbon lithium iron phosphate precursor is obtained through the first coating and sintering, wherein the carbon source substances comprise a lithium source, an iron source, a phosphorus source and a carbon source 1, and the carbon source substances comprise a carbon source 2 during the second coating and sintering.
Preferably, the calcination in step (1) is sintering under air or oxygen atmosphere, the calcination temperature is 300-450 ℃, and the calcination time is 3-6 h.
Preferably, the carbon content of the lithium iron phosphate in the waste lithium iron phosphate powder or the lithium iron phosphate pole piece in the step (1) is 2.6-6%.
Preferably, the lithium source is one or more of lithium carbonate, lithium hydroxide, lithium phosphate, lithium dihydrogen phosphate and lithium acetate.
Preferably, the iron source is one or more of iron phosphate, ferroferric oxide, ferric hydroxide, ferric oxide and ferric oxyhydroxide.
Preferably, the phosphorus source is one or more of ammonium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate and lithium phosphate.
Preferably, the carbon source 1 is selected from one or more of glucose, rock candy, sucrose, fructose, cyclodextrin and starch.
Preferably, the carbon source 2 is one or more selected from glucose, rock candy, sucrose, fructose, cyclodextrin, starch, polyethylene glycol, polyvinyl alcohol, ascorbic acid, citric acid and amino acid.
Preferably, the mass of the oxidized lithium iron phosphate is 30-60% of that of the low-carbon lithium iron phosphate precursor.
Preferably, the mass of the carbon source 1 accounts for 5-6% of the mass of the low-carbon lithium iron phosphate precursor.
Preferably, the first cladding-sintering process comprises: and mixing the oxidized lithium iron phosphate powder, a lithium source, an iron source, a phosphorus source and a carbon source 1, grinding, drying and sintering to obtain the low-carbon lithium iron phosphate precursor.
Preferably, the sintering temperature is 650-730 ℃, and the sintering time is 4-6 h.
Preferably, the mass fraction of carbon in the low-carbon lithium iron phosphate precursor is 0.1-0.4%.
Preferably, the second cladding-sintering process comprises: and mixing the low-carbon lithium iron phosphate precursor with the carbon source 2, grinding, drying and sintering to obtain the regenerated lithium iron phosphate/carbon composite material.
Preferably, the sintering temperature is 700-780 ℃, and the sintering time is 8-10 h.
Preferably, the first or second cladding-sintering further comprises adding an additive, wherein the additive is one or more of titanium dioxide, tetrabutyl titanate, magnesium acetate, magnesium hydroxide, magnesium oxide, zirconium hydroxide, niobium pentoxide, niobium hydroxide, nickel acetate, manganese acetate, aluminum oxide, molybdenum oxide and ammonium molybdate.
Preferably, the additive added during the first or second coating-sintering accounts for 0-0.5% of the mass of the lithium iron phosphate precursor.
Preferably, during the first or second coating-sintering, a solvent is added during the mixing process, wherein the solvent is one or more selected from water, methanol, ethanol, acetone and NMP.
Preferably, the grinding refers to the coarse grinding of the mixed slurry, when the coarse grinding is carried out until the particle size of the slurry is D 50 <And (3) when the particle size is 1um, then finely grinding until the particle size of the slurry is 350-500 nm.
Preferably, the drying is static drying or spray drying.
Preferably, the sintering is performed under an inert atmosphere.
Preferably, the inert atmosphere is one or more of nitrogen, argon, helium and carbon dioxide.
Preferably, the mass fraction of carbon in the regenerated lithium iron phosphate/carbon composite material is 1.5-3.5%.
Preferably, the molar ratio of lithium, iron and phosphorus elements in the regenerated lithium iron phosphate/carbon composite material is 1-1.1: 0.9-1.05: 1-1.08.
The invention further aims to provide application of the method in preparation of a lithium iron phosphate anode material or a preparation process for recycling waste lithium iron phosphate.
Compared with the prior art, the invention has the beneficial effects that:
(1) the method provided by the invention has the characteristics of low cost, simple process and capability of large-scale production, waste materials do not need acid leaching and high temperature and high pressure in the production process, no waste water and waste acid are generated in the whole regeneration process, and the method is environment-friendly, and particularly has a good recycling effect on high-carbon waste lithium iron phosphate.
(2) The invention is beneficial to the growth of the crystal form of the lithium iron phosphate and the uniformity of carbon coating and avoids the generation of ferric iron impurity phase in the preparation process of the regenerated lithium iron phosphate by two carbon coating and two sintering processes. The primary carbon coating is mainly used for completely reducing ferric iron in the oxidized lithium iron phosphate and ferric iron in the iron source raw material into ferrous iron through carbothermic reduction. And the primary sintering process is mainly used for preparing a low-carbon lithium iron phosphate precursor, so that Li/Fe/P elements are sintered and fused uniformly, and the growth of lithium iron phosphate particles, the surface smoothness and the attachment of a secondary carbon source in the later secondary sintering process are facilitated.
(3) The regenerated lithium iron phosphate/carbon composite electrode material is used for preparing power batteries and energy storage markets, and the obtained batteries are excellent in electrochemical performance, high in compaction density and good in processing performance.
Drawings
Fig. 1 is an SEM photograph of the lithium iron phosphate precursor prepared in example 1;
fig. 2 shows the electrochemical properties of the lithium iron phosphate/carbon composite material prepared in example 1.
Detailed Description
The present invention will be further described with reference to the following embodiments.
Example 1
The preparation method of the regenerated lithium iron phosphate/carbon composite material comprises the following steps:
(1) and (3) placing the waste lithium iron phosphate with the carbon content of 3.0 wt% into an atmosphere furnace for blowing air, heating for 4 hours at the constant temperature of 300 ℃ to obtain oxidized lithium iron phosphate powder, and crushing for later use.
(2) Preparation of lithium iron phosphate precursor
38.69g of lithium carbonate (99.5 wt%), 150g of iron phosphate, 150g of oxidized lithium iron phosphate and 16g of glucose are sequentially added into a 2L basket mill containing 1200mL of absolute ethyl alcohol to perform coarse grinding at the rotating speed of 2000r/min for several minutes until the granularity D of the slurry is reached 50 <1um is transferred into a sand mill for fine grinding, after the granularity of the slurry is controlled at 400nm, static drying is carried out, the obtained dry powder is placed into a tube furnace under the nitrogen atmosphere for sintering, the sintering temperature is 650 ℃, the constant temperature time is 4 hours, the material is taken out and crushed when the temperature of the tube furnace is naturally reduced to 80 ℃, and 300g of the lithium iron phosphate precursor with the carbon content of 0.2 wt% is obtained.
(3) Preparation of lithium iron phosphate/carbon composite material
Adding 300g of lithium iron phosphate precursor, 20g of glucose, 4g of cyclodextrin and 1.5g of titanium dioxide into a 2L basket mill containing 1200mL of absolute ethyl alcohol, starting to perform coarse grinding at the rotating speed of 2000r/min after the materials are added, and grinding for 35 minutes until the granularity D of the slurry is reached 50 <1um is transferred into a sand mill for fine grinding, and after the granularity of the slurry is controlled at 450nm, the slurry is subjected to static grindingAnd (3) drying in a state, placing the obtained dry powder in a tubular furnace in a nitrogen atmosphere for sintering, wherein the sintering temperature is 740 ℃, the constant temperature time is 10 hours, and taking out and crushing the material in a grading manner when the temperature of the tubular furnace is naturally reduced to 80 ℃ to obtain the regenerated lithium iron phosphate/carbon composite material with the carbon content of 1.5 wt%.
Through analysis, the lithium, iron and phosphorus molar ratio Li of the regenerated lithium iron phosphate to Fe to P is 1.05 to 1 to 1.03, and the powder is compacted to 2.58g/cm 3 。
The obtained regenerated lithium iron phosphate/carbon composite material was observed by scanning electron microscope, and the result is shown in fig. 1. As can be seen from FIG. 1, the size of the prepared primary particles is in the range of about 0.5-5um, and most of the particles are mainly concentrated in about 0.5 um.
The prepared lithium iron phosphate/carbon composite material for the lithium ion battery anode is taken as an anode material, acetylene black is taken as a conductive agent, polytetrafluoroethylene is taken as a binder, electrode plates are prepared, and metallic lithium is taken as a cathode to assemble the simulated button cell. Under the conditions of 2-3.75V and normal temperature, different charging and discharging current conditions are adopted for testing, the initial reversible capacity of charging and discharging at 0.1C is 159.5mAh/g, the initial reversible capacity of charging and discharging at 0.2C is 157.7mAh/g, and the initial reversible capacity of charging and discharging at 1C is 144.5mAh/g (see figure 2).
Example 2
The preparation method of the regenerated lithium iron phosphate/carbon composite material comprises the following steps:
(1) placing a certain amount of waste lithium iron phosphate pole pieces in an atmosphere furnace with oxygen blown in, heating for 4 hours at a constant temperature of 400 ℃ to obtain stripped aluminum sheets and oxidized lithium iron phosphate, and crushing the oxidized lithium iron phosphate for later use.
(2) Preparing a lithium iron phosphate precursor: 46.95g of lithium carbonate (99.5 wt%), 180g of iron phosphate, 120g of oxidized lithium iron phosphate and 16g of rock candy are added into a 2L basket mill containing 1200mL of absolute ethyl alcohol, coarse milling is started at the rotating speed of 2000r/min after the materials are added, and after the coarse milling is carried out for a plurality of minutes, the granularity D of the slurry is up to 50 <1um is transferred into a sand mill for fine grinding, after the granularity of the slurry is controlled to be 400nm, static drying is carried out, and the obtained dry powder is placed into a tube furnace under the nitrogen atmosphereSintering at 650 ℃ for 4h, naturally cooling the tube furnace to 80 ℃, taking out the material, and crushing to obtain 300g of a lithium iron phosphate precursor with the carbon content of 0.3 wt%.
(3) Preparation of lithium iron phosphate/carbon composite material
Adding 300g of lithium iron phosphate precursor, 30g of glucose and 1.2g of magnesium hydroxide into a 2L basket mill containing 1200mL of absolute ethyl alcohol in sequence, after the materials are added, starting coarse milling at the rotating speed of 2000r/min, and after the materials are milled for several minutes, waiting for the granularity D of the slurry 50 <And (3) transferring the powder into a sand mill for fine grinding by 1um, performing static drying after the granularity of the slurry is controlled to be 400nm, sintering the obtained dry powder in a tube furnace under the nitrogen atmosphere, wherein the sintering temperature is 780 ℃, the constant temperature time is 10 hours, naturally cooling the tube furnace to 80 ℃, taking out the material, crushing the material, and sieving the crushed material by a 200-mesh sieve to obtain the regenerated lithium iron phosphate with the carbon content of 1.8 wt%.
Through analysis, the lithium and iron/phosphorus mol Li of the regenerated lithium iron phosphate is that the Fe and the P are 1.05 to 1 to 1.035, and the powder is compacted to 2.55g/cm 3 。
The prepared lithium iron phosphate/carbon composite material for the lithium ion battery anode is taken as an anode material, acetylene black is taken as a conductive agent, polytetrafluoroethylene is taken as a binder, electrode plates are prepared, and metallic lithium is taken as a cathode to assemble the simulated button cell. Under the conditions of 2-3.75V and normal temperature and different charging and discharging current tests, the initial reversible capacity of charging and discharging at 0.1C is 158.5mAh/g, the initial reversible capacity of charging and discharging at 0.2C is 156.5mAh/g, and the initial reversible capacity of charging and discharging at 1C is 143.2mAh/g (see table 1).
Example 3
The preparation method of the regenerated lithium iron phosphate/carbon composite material comprises the following steps:
(1) placing a certain amount of waste lithium iron phosphate with the carbon content of 3.0 wt% in an atmosphere furnace for blowing air, heating at the constant temperature of 350 ℃ for 4 hours to obtain oxidized lithium iron phosphate powder, and crushing for later use.
(2) Preparation of lithium iron phosphate precursor
39.72g of lithium carbonate (99.5 wt.%), 89.74g were successively added99 wt% of iron oxyhydroxide, 117.12g of diammonium hydrogen phosphate (99.5 wt%), 100g of oxidized lithium iron phosphate powder and 15g of glucose are added into a 2L basket mill containing 1200mL of absolute ethyl alcohol, coarse milling is started at 2000r/min after the materials are added, and after the materials are milled for a plurality of minutes, the granularity D of the slurry is obtained 50 <1um is transferred into a sand mill for fine grinding, after the granularity of slurry is controlled at 450nm, spray drying is carried out, the obtained dry powder is placed in a tube furnace under the nitrogen atmosphere for sintering, the sintering temperature is 700 ℃, the constant temperature time is 5 hours, the material is taken out and crushed when the temperature of the tube furnace is naturally reduced to 80 ℃, and 250g of lithium iron phosphate precursor with the carbon content of 0.3 wt% is obtained.
(3) Preparation of lithium iron phosphate/carbon composite material
Adding 250g of lithium iron phosphate precursor, 17.64g of rock sugar, 6g of polyethylene glycol 20000 and 1g of niobium pentoxide into a 2L basket mill containing 1200mL of deionized water in sequence, starting coarse milling at the rotating speed of 2000r/min after the materials are added, and after the materials are milled for several minutes, waiting for the granularity D of the slurry 50 <And (3) transferring the powder into a sand mill for fine grinding by 1um, performing spray drying after the granularity of the slurry is controlled to be 450nm, putting the obtained dried powder into a tube furnace under the argon atmosphere for sintering, wherein the sintering temperature is 760 ℃, the constant temperature time is 10 hours, naturally cooling the tube furnace to 80 ℃, taking out the material, and performing grading crushing to obtain the regenerated lithium iron phosphate with the carbon content of 1.6 wt%.
Through analysis, the lithium, iron and phosphorus molar ratio Li of the regenerated lithium iron phosphate is 1.045:1:1.03, and the powder is compacted to 2.58g/cm 3 。
The prepared lithium iron phosphate/carbon composite material for the lithium ion battery anode is taken as an anode material, acetylene black is taken as a conductive agent, polytetrafluoroethylene is taken as a binder, electrode plates are prepared, and metallic lithium is taken as a cathode to assemble the simulated button cell. Under the conditions of 2-3.75V and normal temperature and different charging and discharging current tests, the initial reversible capacity of charging and discharging at 0.1C is 157.8mAh/g, the initial reversible capacity of charging and discharging at 0.2C is 156.3mAh/g, and the initial reversible capacity of charging and discharging at 1C is 143.5mAh/g (see table 1).
Example 4
The preparation method of the regenerated lithium iron phosphate/carbon composite material comprises the following steps:
(1) placing a certain amount of waste lithium iron phosphate pole pieces in an atmosphere furnace with oxygen blown in, heating for 4 hours at a constant temperature of 400 ℃ to obtain peeled aluminum sheets and oxidized lithium iron phosphate, and crushing the oxidized lithium iron phosphate for later use.
(2) Preparation of lithium iron phosphate precursor
59.03g of lithium carbonate (99.5 wt%), 122.45g of iron oxide (98 wt%), 180g of diammonium hydrogen phosphate (99.5 wt%), 100g of oxidized lithium iron phosphate powder, 18g of sucrose and 0.6g of magnesium oxide were sequentially added into a 2L basket mill containing 1200mL of absolute ethyl alcohol, coarse milling was started at 2000r/min after the addition of the materials, and after several minutes of milling, the slurry particle size D was obtained 50 <1um is transferred into a sand mill for fine grinding, spray drying is carried out after the granularity of slurry is controlled to be about 400nm, the obtained dry powder is placed into a tube furnace under the nitrogen atmosphere for sintering, the sintering temperature is 700 ℃, the constant temperature time is 4 hours, the material is taken out and crushed after the tube furnace is naturally cooled to 80 ℃, and 330g of lithium iron phosphate precursor with the carbon content of 0.25 wt% is obtained.
(3) Preparation of lithium iron phosphate/carbon composite material
Sequentially adding 330g of lithium iron phosphate precursor, 30g of fructose, 5g of polyethylene glycol 20000, 1.2g of titanium dioxide and 0.3g of niobium pentoxide into a 2L basket mill containing 1200mL of deionized water, starting coarse milling at the rotating speed of 2000r/min after the materials are added, and after the materials are milled for several minutes, waiting for the granularity D of the slurry 50 <1um is transferred into a sand mill for fine grinding, spray drying is carried out when the granularity of slurry is controlled to be about 350nm, the obtained dry powder is placed into a tube furnace under the argon atmosphere for sintering, the sintering temperature is 780 ℃, the constant temperature time is 8 hours, the material is taken out when the tube furnace is naturally cooled to 80 ℃, and the material is crushed in a grading way, so that regenerated lithium iron phosphate with the carbon content of 1.6 wt% is obtained, through analysis, the molar ratio of lithium, iron and phosphorus of the regenerated lithium iron phosphate is Li, Fe, P is 1.055:1:1.036, and the powder is compacted to be 2.54g/cm 3 。
The prepared lithium iron phosphate/carbon composite material for the lithium ion battery anode is taken as an anode material, acetylene black is taken as a conductive agent, polytetrafluoroethylene is taken as a binder, electrode plates are prepared, and metallic lithium is taken as a cathode to assemble the simulated button cell. Under the conditions of 2-3.75V and normal temperature and different charging and discharging current tests, the initial reversible capacity of charging and discharging at 0.1C is 158.9mAh/g, the initial reversible capacity of charging and discharging at 0.2C is 157.5mAh/g, and the initial reversible capacity of charging and discharging at 1C is 144.1mAh/g (see table 1).
Comparative example 1
The difference between the comparative example and the example 1 is that the preparation method adopts carbon source substances to carry out primary coating-sintering, and the specific preparation method is as follows:
placing waste lithium iron phosphate with the carbon content of 3.0 wt% in an atmosphere furnace with air blown, heating at the constant temperature of 300 ℃ for 4 hours to obtain oxidized lithium iron phosphate powder, and crushing for later use.
38.69g of lithium carbonate (99.5 wt%), 150g of iron phosphate, 150g of oxidized lithium iron phosphate, 36g of glucose, 4g of cyclodextrin and 1.5g of titanium dioxide are sequentially added into a 2L basket mill containing 1200mL of absolute ethyl alcohol, coarse milling is started at the rotating speed of 2000r/min after the materials are added, and after the materials are milled for a plurality of minutes, the particle size D of the slurry is obtained 50 <1um is transferred into a sand mill for fine grinding, after the granularity of slurry is controlled at 450nm, static drying is carried out, the obtained dry powder is placed into a tube furnace under the nitrogen atmosphere for sintering, the sintering temperature is 740 ℃, the constant temperature time is 10 hours, when the temperature of the tube furnace is naturally reduced to 80 ℃, the material is taken out and graded and crushed, the carbon content is 1.5 wt%, and the powder compaction is 2.40g/cm 3 The regenerated lithium iron phosphate/carbon composite material.
The prepared lithium iron phosphate/carbon composite material for the lithium ion battery anode is taken as an anode material, acetylene black is taken as a conductive agent, polytetrafluoroethylene is taken as a binder, electrode plates are prepared, and metallic lithium is taken as a cathode to assemble the simulated button cell. Under the conditions of 2-3.75V and normal temperature and different charging and discharging current tests, the initial reversible capacity of charging and discharging at 0.1C is 154.6mAh/g, the initial reversible capacity of charging and discharging at 0.2C is 153.1mAh/g, and the initial reversible capacity of charging and discharging at 1C is 139.5mAh/g (see table 1).
Comparative example 2
The difference between the comparative example and the example 2 is that the preparation method adopts carbon source substances to carry out primary coating-sintering, and the specific preparation method is as follows:
placing a certain amount of waste lithium iron phosphate pole pieces in an atmosphere furnace with oxygen blown in, heating for 4 hours at a constant temperature of 400 ℃ to obtain peeled aluminum sheets and oxidized lithium iron phosphate, and crushing the oxidized lithium iron phosphate for later use.
46.95g of lithium carbonate (99.5 wt%), 180g of iron phosphate, 120g of oxidized lithium iron phosphate, 16g of rock candy, 30g of glucose and 1.2g of magnesium hydroxide are added into a 2L basket mill containing 1200mL of absolute ethyl alcohol, coarse milling is started at the rotating speed of 2000r/min after the materials are added, and after the materials are milled for a plurality of minutes, the granularity D of the slurry is up to 50 <1um is transferred into a sand mill for fine grinding, after the granularity of the slurry is controlled to be 400nm, static drying is carried out, the obtained dry powder is placed into a tube furnace under the nitrogen atmosphere for sintering, the sintering temperature is 780 ℃, the constant temperature time is 10 hours, when the temperature of the tube furnace is naturally reduced to 80 ℃, the material is taken out and is crushed in a grading way, the carbon content is 1.8 wt%, and the powder compaction is 2.42g/cm 3 The regenerated lithium iron phosphate/carbon composite material.
The prepared lithium iron phosphate/carbon composite material for the lithium ion battery anode is taken as an anode material, acetylene black is taken as a conductive agent, polytetrafluoroethylene is taken as a binder, electrode plates are prepared, and metallic lithium is taken as a cathode to assemble the simulated button cell. Under the conditions of 2-3.75V and normal temperature and different charging and discharging current tests, the initial reversible capacity of charging and discharging at 0.1C is 153.3mAh/g, the initial reversible capacity of charging and discharging at 0.2C is 152.5mAh/g, and the initial reversible capacity of charging and discharging at 1C is 138.2mAh/g (see table 1).
Comparative example 3
The difference between the comparative example and the example 3 is that the preparation method adopts carbon source substances to carry out primary coating-sintering, and the specific preparation method is as follows:
placing a certain amount of waste lithium iron phosphate pole pieces in an atmosphere furnace with oxygen blown in, heating for 4 hours at a constant temperature of 400 ℃ to obtain peeled aluminum sheets and oxidized lithium iron phosphate, and crushing the oxidized lithium iron phosphate for later use.
59.03g of lithium carbonate (99.5 wt%), 122.45g of iron oxide (98 wt%), 180g of diammonium hydrogen phosphate (99.5 wt%), 100g of oxidized lithium iron phosphate powder, 18g of sucrose 30g of fructose, 5g of polyethylene glycol 20000, 1.2g of titanium dioxide and 0.3g of niobium oxide are sequentially added into a 2L basket mill containing 1200mL of deionized water, coarse milling is started at 2000r/min after the addition of the materials, and after several minutes of milling, the slurry is milled until the particle size D of the slurry is reached 50 <1um is transferred into a sand mill for fine grinding, spray drying is carried out when the granularity of slurry is controlled to be about 350nm, the obtained dry powder is placed into a tube furnace under the argon atmosphere for sintering, the sintering temperature is 780 ℃, the constant temperature time is 8 hours, the material is taken out when the tube furnace is naturally cooled to 80 ℃, and grading crushing is carried out to obtain the carbon content of 1.6 wt%, and the powder is compacted to be 2.36g/cm 3 The regenerated lithium iron phosphate/carbon composite material.
The prepared lithium iron phosphate/carbon composite material for the lithium ion battery anode is taken as an anode material, acetylene black is taken as a conductive agent, polytetrafluoroethylene is taken as a binder, electrode plates are prepared, and metallic lithium is taken as a cathode to assemble the simulated button cell. Under the conditions of 2-3.75V and normal temperature and different charging and discharging current tests, the initial reversible capacity of charging and discharging at 0.1C is 153.1mAh/g, the initial reversible capacity of charging and discharging at 0.2C is 151.8mAh/g, and the initial reversible capacity of charging and discharging at 1C is 137.5mAh/g (see table 1).
Comparative example 4
The comparative example is different from example 1 in that the amounts of carbon sources added in the first and second coating-sintering steps are different from each other, but the total carbon source mass is the same, and the comparative example is identical to example 1.
(1) Placing waste lithium iron phosphate with the carbon content of 3.0 wt% in an atmosphere furnace with air blown, heating at the constant temperature of 300 ℃ for 4 hours to obtain oxidized lithium iron phosphate powder, and crushing for later use.
(2) Preparation of lithium iron phosphate precursor
38.69g of lithium carbonate (99.5 wt%), 150g of iron phosphate and 150g of oxidized lithium carbonate were sequentially mixedAdding the lithium iron phosphate and 28g of glucose into a 2L basket mill containing 1200mL of absolute ethyl alcohol, performing coarse grinding at the rotating speed of 2000r/min for several minutes until the granularity D of the slurry is reached 50 <1um is transferred into a sand mill for fine grinding, after the granularity of the slurry is controlled at 400nm, static drying is carried out, the obtained dry powder is placed into a tube furnace under the nitrogen atmosphere for sintering, the sintering temperature is 600 ℃, the constant temperature time is 4 hours, the material is taken out and crushed when the temperature of the tube furnace is naturally reduced to 80 ℃, and 300g of the lithium iron phosphate precursor with the carbon content of 0.7 wt% is obtained.
(3) Preparation of lithium iron phosphate/carbon composite material
Adding 300g of lithium iron phosphate precursor, 8g of glucose, 4g of cyclodextrin and 1.5g of titanium dioxide into a 2L basket mill containing 1200mL of absolute ethyl alcohol, starting to perform coarse grinding at the rotating speed of 2000r/min after the materials are added, and grinding for several minutes until the granularity D of the slurry is reached 50 <1um is transferred into a sand mill for fine grinding, after the granularity of slurry is controlled at 450nm, static drying is carried out, the obtained dry powder is placed into a tube furnace under the nitrogen atmosphere for sintering, the sintering temperature is 740 ℃, the constant temperature time is 10 hours, when the temperature of the tube furnace is naturally reduced to 80 ℃, the material is taken out and graded and crushed, the carbon content is 1.5 wt%, and the powder compaction is 2.38g/cm 3 . The regenerated lithium iron phosphate/carbon composite material.
The prepared lithium iron phosphate/carbon composite material for the lithium ion battery anode is taken as an anode material, acetylene black is taken as a conductive agent, polytetrafluoroethylene is taken as a binder, electrode plates are prepared, and metal lithium is taken as a cathode to assemble the simulated button cell. Under the normal temperature of 2-3.75V and by adopting different charging and discharging current conditions for testing, the initial reversible capacity of charging and discharging at 0.1C is 154.3mAh/g, the initial reversible capacity of charging and discharging at 0.2C is 150.2mAh/g, and the initial reversible capacity of charging and discharging at 1C is 138.7 mAh/g.
Comparative example 5
The present comparative example is different from example 1 in that the sintering temperatures at the first and second cladding-sintering are different. The method specifically comprises the following steps: the first was 500 ℃ and the second 790 ℃. The rest corresponds to example 1.
1) Placing waste lithium iron phosphate with the carbon content of 3.0 wt% in an atmosphere furnace with air blown, heating at the constant temperature of 300 ℃ for 4 hours to obtain oxidized lithium iron phosphate powder, and crushing for later use.
(2) Preparation of lithium iron phosphate precursor
38.69g of lithium carbonate (99.5 wt%), 150g of iron phosphate, 150g of oxidized lithium iron phosphate and 16g of glucose are sequentially added into a 2L basket mill containing 1200mL of absolute ethyl alcohol to perform coarse grinding at the rotating speed of 2000r/min for several minutes until the granularity D of the slurry is reached 50 <1um is transferred into a sand mill for fine grinding, after the granularity of the slurry is controlled to be 400nm, static drying is carried out, the obtained dry powder is placed into a tube furnace under the nitrogen atmosphere for sintering, the sintering temperature is 500 ℃, the constant temperature time is 4 hours, when the temperature of the tube furnace is naturally reduced to 80 ℃, the material is taken out and crushed, and 300g of the lithium iron phosphate precursor with the carbon content of 0.1 wt% is obtained.
(3) Preparation of lithium iron phosphate/carbon composite material
Adding 300g of lithium iron phosphate precursor, 20g of glucose, 4g of cyclodextrin and 1.5g of titanium dioxide into a 2L basket mill containing 1200mL of absolute ethyl alcohol, starting to perform coarse grinding at the rotating speed of 2000r/min after the materials are added, and grinding for several minutes until the granularity D of the slurry is reached 50 <1um is transferred into a sand mill for fine grinding, after the granularity of slurry is controlled at 450nm, static drying is carried out, the obtained dry powder is placed into a tube furnace under the nitrogen atmosphere for sintering, the sintering temperature is 790 ℃, the constant temperature time is 10 hours, when the temperature of the tube furnace is naturally reduced to 80 ℃, the material is taken out and graded and crushed, the carbon content is 1.5 wt%, and the powder compaction is 2.45g/cm 3 . The regenerated lithium iron phosphate/carbon composite material.
The prepared lithium iron phosphate/carbon composite material for the lithium ion battery anode is taken as an anode material, acetylene black is taken as a conductive agent, polytetrafluoroethylene is taken as a binder, electrode plates are prepared, and metallic lithium is taken as a cathode to assemble the simulated button cell. Under the normal temperature of 2-3.75V and by adopting different charging and discharging current conditions for testing, the initial reversible capacity of charging and discharging at 0.1C is 151.2mAh/g, the initial reversible capacity of charging and discharging at 0.2C is 148.5mAh/g, and the initial reversible capacity of charging and discharging at 1C is 133.2 mAh/g.
TABLE 1 comparison of chemical Properties of examples and comparative examples with powder compaction
Figure BDA0003623870770000101
The above detailed description is specific to one possible embodiment of the present invention, and the embodiment is not intended to limit the scope of the present invention, and all equivalent implementations or modifications without departing from the scope of the present invention should be included in the technical scope of the present invention.

Claims (10)

1. A method for recycling waste lithium iron phosphate is characterized by comprising the following steps:
(1) calcining waste high-carbon lithium iron phosphate powder or a lithium iron phosphate pole piece to obtain oxidized lithium iron phosphate;
(2) coating and sintering the oxidized lithium iron phosphate with carbon source substances for two times to obtain a regenerated lithium iron phosphate/carbon composite material;
the low-carbon lithium iron phosphate precursor is obtained through the first coating and sintering, wherein the carbon source substances comprise a lithium source, an iron source, a phosphorus source and a carbon source 1, and the carbon source substances comprise a carbon source 2 during the second coating and sintering.
2. The method as claimed in claim 1, wherein the calcination in step (1) is sintering under air or oxygen atmosphere, the calcination temperature is 300-450 ℃, and the calcination time is 3-6 h.
3. The method according to claim 1, wherein the carbon content of the lithium iron phosphate in the waste lithium iron phosphate powder or the lithium iron phosphate pole piece in the step (1) is 2.6-6%.
4. The method according to claim 1, wherein the lithium source is one or more of lithium carbonate, lithium hydroxide, lithium phosphate, lithium dihydrogen phosphate and lithium acetate, the iron source is one or more of iron phosphate, ferroferric oxide, iron hydroxide, iron oxide and ferric iron oxyhydroxide, and the phosphorus source is one or more of ammonium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate and lithium phosphate; the carbon source 1 is selected from one or more of glucose, rock candy, cane sugar, fructose, cyclodextrin and starch; the carbon source 2 is selected from one or more of glucose, rock candy, sucrose, fructose, cyclodextrin, starch, polyethylene glycol, polyvinyl alcohol, ascorbic acid, citric acid and amino acid; preferably, the mass of the oxidized lithium iron phosphate is 30-60% of the mass of the low-carbon lithium iron phosphate precursor, and the mass of the carbon source 1 accounts for 5-6% of the mass of the low-carbon lithium iron phosphate precursor.
5. The method of claim 1, wherein the first cladding-sintering process comprises: mixing the oxidized lithium iron phosphate powder, a lithium source, an iron source, a phosphorus source and a carbon source 1, grinding, drying and sintering to obtain a low-carbon lithium iron phosphate precursor; preferably, the sintering temperature is 650-730 ℃, and the sintering time is 4-6 h; the mass fraction of carbon in the low-carbon lithium iron phosphate precursor is 0.1-0.4%.
6. The method of claim 1, wherein the second cladding-sintering process comprises: mixing a low-carbon lithium iron phosphate precursor with a carbon source 2, grinding, drying and sintering to obtain a regenerated lithium iron phosphate/carbon composite material; preferably, the sintering temperature is 700-780 ℃, and the sintering time is 8-10 h.
7. The method of claim 1, further comprising adding an additive during the first or second cladding-sintering, wherein the additive is one or more of titanium dioxide, tetrabutyl titanate, magnesium acetate, magnesium hydroxide, magnesium oxide, zirconium hydroxide, niobium pentoxide, niobium hydroxide, nickel acetate, manganese acetate, aluminum oxide, molybdenum oxide, and ammonium molybdate, and the additive added during the first or second cladding-sintering accounts for 0-0.5% of the mass of the lithium iron phosphate precursor.
8. The method according to claim 5 or 6, wherein a solvent is added during the mixing process, the solvent is selected from one or more of water, methanol, ethanol, acetone and NMP, the grinding is performed by coarse grinding of the mixed slurry, and when the mixed slurry is coarse ground until the particle size of the slurry is D 50 <And (3) when the particle size is 1um, then finely grinding until the particle size of the slurry is 350-500 nm.
9. The method according to any one of claims 1 to 7, wherein the mass fraction of the regenerated lithium iron phosphate/carbon composite carbon is 1.5 to 3.5%; the molar ratio of lithium, iron and phosphorus elements in the regenerated lithium iron phosphate/carbon composite material is 1-1.1: 0.9-1.05: 1-1.08.
10. The method of any one of claims 1 to 9, applied to a preparation process of a lithium iron phosphate positive electrode material or a recycling preparation process of waste lithium iron phosphate.
CN202210478279.9A 2022-04-29 2022-04-29 Method for recycling waste lithium iron phosphate Pending CN114824546A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116239092A (en) * 2023-02-03 2023-06-09 河南师范大学 Repairing and regenerating method for waste lithium iron phosphate anode material
CN116525819A (en) * 2023-07-03 2023-08-01 国网浙江省电力有限公司湖州供电公司 Preparation method for regenerating waste lithium iron phosphate positive electrode material based on nitrogen doping
EP4335818A1 (en) * 2022-09-08 2024-03-13 Advanced Lithium Electrochemistry Co., Ltd. Recycling and reworking method of lithium iron phosphate cathode material

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4335818A1 (en) * 2022-09-08 2024-03-13 Advanced Lithium Electrochemistry Co., Ltd. Recycling and reworking method of lithium iron phosphate cathode material
CN116239092A (en) * 2023-02-03 2023-06-09 河南师范大学 Repairing and regenerating method for waste lithium iron phosphate anode material
CN116525819A (en) * 2023-07-03 2023-08-01 国网浙江省电力有限公司湖州供电公司 Preparation method for regenerating waste lithium iron phosphate positive electrode material based on nitrogen doping
CN116525819B (en) * 2023-07-03 2023-09-29 国网浙江省电力有限公司湖州供电公司 Preparation method for regenerating waste lithium iron phosphate positive electrode material based on nitrogen doping

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