CN114132911B - Doped regenerated lithium iron phosphate material and preparation method and application thereof - Google Patents
Doped regenerated lithium iron phosphate material and preparation method and application thereof Download PDFInfo
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- CN114132911B CN114132911B CN202111433674.7A CN202111433674A CN114132911B CN 114132911 B CN114132911 B CN 114132911B CN 202111433674 A CN202111433674 A CN 202111433674A CN 114132911 B CN114132911 B CN 114132911B
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- C01B25/00—Phosphorus; Compounds thereof
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Abstract
The invention provides a doped regenerated lithium iron phosphate material, and a preparation method and application thereof, wherein the preparation method comprises the following steps: mixing waste lithium iron phosphate black powder with acid liquor, performing oxidation leaching, and performing solid-liquid separation on the obtained leached slurry to obtain primary filtrate and a filter cake; removing impurities from the primary filtrate, and performing solid-liquid separation to obtain secondary filtrate; mixing the acid liquor with the filter cake, and then carrying out solid-liquid separation to obtain a third filtrate; mixing the additive, the secondary filtrate and the tertiary filtrate, drying the obtained mixed solution to obtain a precursor, and sintering the precursor to obtain the doped regenerated lithium iron phosphate material. The invention makes the anode material of the waste lithium battery recycle, and uses the impurity element contained in the anode material as the doping element, thereby simplifying the preparation process of the lithium iron phosphate material, and obtaining the regenerated lithium iron phosphate material with even element doping and excellent electrochemical performance.
Description
Technical Field
The invention belongs to the field of lithium ion batteries, relates to a lithium iron phosphate material, and in particular relates to a doped regenerated lithium iron phosphate material, and a preparation method and application thereof.
Background
The lithium iron phosphate material has the advantages of wide raw material sources, low price, long cycle life, good safety performance and the like, and gradually becomes one of the lithium battery anode materials with the highest potential. However, due to the regular tetrahedra PO in the ferric lithium phosphate olivine structure 4 3- Not only prevents the diffusion of lithium ions, but also greatly reduces the electron conductivity, so that the energy attenuation of the lithium iron phosphate battery is fast and the cycling stability is poor in the heavy current discharging process.
Currently, the modification method aiming at the defects of the lithium iron phosphate material mainly comprises the following steps: (1) carbon coating: generating a carbon coating layer on the surface of the material through high-temperature pyrolysis so as to improve the conductivity of the lithium iron phosphate material; (2) nanocrystallization: reducing the particle size of the lithium iron phosphate material, thereby shortening the lithium ion diffusion path; (3) metal ion doping: defects or vacancies are formed inside the material structure, and the intrinsic conductivity of the lithium iron phosphate is improved. Among them, metal ion doping is a method for improving defects of lithium iron phosphate materials, which is currently being widely focused, because doping of metal ions can effectively widen a lithium ion transmission path while improving electron conductivity.
CN 112607725a discloses a nitrogen-doped carbon nanotube/rare earth metal ion-doped lithium iron phosphate composite positive electrode material and a preparation method thereof, the preparation method of the material is as follows: mixing hydrazine hydrate and the carbon nano tube, and then carrying out reflux, suction filtration and freeze drying to prepare the nitrogen-doped carbon nano tube; preparing rare earth metal ion doped lithium iron phosphate by taking lithium hydroxide, ferric phosphate, oxalic acid, glucose and rare earth metal oxide as raw materials; and finally, adding the nitrogen doped carbon nano tube and rare earth metal ion doped lithium iron phosphate into the dispersion liquid for dispersion and ball milling to prepare a final product. The disclosed method increases the diffusion channel of lithium ions to a certain extent, but has the disadvantages of complex preparation process and high raw material cost.
CN 111224103a discloses that an iron source, a phosphorus source, a lithium source, a doped metal ion source (one or more of Mg, co, zn, ni, ca, sr, cu, al, ti, V, mn or Ce), an organic ligand and a macromolecular template agent are mixed and dissolved in a solvent, and a sol-gel method is adopted to prepare a lithium iron phosphate material, wherein primary particles of the lithium iron phosphate material have smaller particle size, so that the diffusion rate of lithium ions is effectively improved; although the disclosed method omits the grinding procedure of particle size, the cost performance of the raw materials is low, the synthesis conditions are not easy to control, and industrial production is difficult to realize.
CN 110911680a discloses a preparation method of Ti and V element composite doped lithium iron phosphate, which comprises the following steps: fe is firstly added with 3+ Preparing a source and a phosphorus source into solutions with known concentrations respectively, slowly dripping the solutions into a phosphoric acid base solution according to a certain proportion, and then heating, stirring and precipitating to obtain ferric phosphate dihydrate; filtering, washing and drying the prepared ferric phosphate dihydrate, and calcining to obtain anhydrous ferric phosphate; the disclosed method has simpler production process, but the doped metal ions are in the ferric phosphateThe dispersion non-uniformity in the lithium material is mostly interparticle doping.
Based on the research, how to provide a doped regenerated lithium iron phosphate material, a preparation method and application thereof, wherein doped elements can be uniformly dispersed in the lithium iron phosphate material, the prepared lithium iron phosphate material has excellent performance, the preparation process can realize the recycling of the waste lithium battery anode material, the energy is saved, the environment is protected, the production process of the lithium iron phosphate material is simplified, the cost of raw materials is reduced, and the electrochemical performance is obviously improved, so that the problems which are urgently needed to be solved at present are solved.
Disclosure of Invention
The invention aims to provide a doped regenerated lithium iron phosphate material, a preparation method and application thereof, wherein the waste lithium battery anode material is recycled, so that doped elements are uniformly dispersed in the lithium iron phosphate material, the preparation method is simple, the raw material cost is reduced, the obtained lithium iron phosphate material has high electrochemical performance, and the problems of uneven element doping and higher cost of the lithium iron phosphate material are solved.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for preparing a doped regenerated lithium iron phosphate material, the method comprising the steps of:
(1) Mixing waste lithium iron phosphate black powder with acid liquor, carrying out oxidation leaching, and carrying out solid-liquid separation on the obtained leached slurry to obtain primary filtrate and a filter cake;
(2) Removing impurities from the primary filtrate obtained in the step (1), and performing solid-liquid separation to obtain secondary filtrate;
(3) Mixing the acid liquor with the filter cake in the step (1), and then carrying out solid-liquid separation to obtain a third filtrate;
(4) Mixing the additive, the secondary filtrate in the step (2) and the tertiary filtrate in the step (3), drying the obtained mixed solution to obtain a precursor, and sintering the precursor to obtain the doped regenerated lithium iron phosphate material;
step (2) and step (3) are not in sequence.
The invention adopts the waste lithium battery anode material with low cost as the raw material, and utilizes the impurity element contained in the material as the doping element, so that the doping element is uniformly dispersed in the lithium iron phosphate material; the preparation method of the invention enables the waste lithium battery anode material to be recycled, simplifies the preparation process of the lithium iron phosphate material, and obtains the doped regenerated lithium iron phosphate material with uniform doping elements and excellent electrochemical performance.
Preferably, the total content of impurities in the waste lithium iron phosphate black powder in the step (1) is 0.02-6wt%, for example, 0.02wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt% or 6wt%, but is not limited to the recited values, and other non-recited values in the numerical range are equally applicable.
Preferably, the acid solution of step (1) comprises any one or a combination of at least two of hydrochloric acid, nitric acid, acetic acid, oxalic acid, citric acid or malic acid, typically but not limited to a combination of hydrochloric acid and nitric acid, a combination of hydrochloric acid and acetic acid, or a combination of nitric acid and oxalic acid.
Preferably, the acid liquor of step (1) comprises citric acid and/or nitric acid.
Preferably, the concentration of the acid solution in the step (1) is 0.5 to 5mol/L, for example, 0.5mol/L, 1mol/L, 2mol/L, 3mol/L, 4mol/L or 5mol/L, but not limited to the values listed, and other values not listed in the numerical range are equally applicable, preferably 2 to 3mol/L.
Preferably, the oxidizing agent of the oxidative leaching in the step (1) includes any one or a combination of at least two of hydrogen peroxide, oxygen or air, and typically, but not limited to, a combination of hydrogen peroxide and oxygen, or a combination of hydrogen peroxide and air.
Preferably, the concentration of the hydrogen peroxide in the step (1) is 5-20%, for example, 5%, 10%, 15% or 20%, but not limited to the values listed, and other values not listed in the numerical range are equally applicable.
Preferably, the pH of the oxidative leaching in step (1) is 1 to 3, for example, but not limited to, 1, 1.5, 2, 2.5 or 3, and other non-enumerated values in the numerical range are equally applicable, preferably 1.9 to 2.1, more preferably 2.
Preferably, ammonia is used to regulate the pH of the oxidative leach of step (1).
Preferably, the solid to liquid ratio of the leach slurry in step (1) is in the range of 100 to 500g/L, for example 100g/L, 200g/L, 300g/L, 400g/L or 500g/L, but not limited to the values recited, other non-recited values within the range being equally applicable, preferably 250 to 300g/L.
Preferably, the mixing time in step (1) is 1 to 5 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours or 5 hours, but not limited to the recited values, and other non-recited values in the range of values are equally applicable, preferably 2 to 3 hours.
Preferably, the temperature of the mixing in the step (1) is 30 to 90 ℃, for example, 30 ℃, 40 ℃, 50 ℃,60 ℃, 70 ℃, 80 ℃ or 90 ℃, but not limited to the values listed, other non-listed values within the range of values are equally applicable, preferably 60 to 70 ℃.
The primary filtrate can be reused for cyclic leaching.
Preferably, the impurity removing agent for removing impurities in step (2) comprises a pH buffer.
Preferably, the pH buffer comprises aqueous ammonia.
Preferably, the pH of the secondary filtrate in step (2) is 6 to 10, and may be, for example, 6, 7, 8, 9 or 10, but is not limited to the values recited, and other values not recited in the range of values are equally applicable.
Preferably, the total content of impurities in the secondary filtrate in the step (2) is 0.02-2 wt%, for example, 0.02wt%, 0.05wt%, 0.1wt%, 0.2wt%, 1wt% or 2wt%, but is not limited to the recited values, and other non-recited values in the range of values are equally applicable.
Preferably, the acid solution of step (3) comprises any one or a combination of at least two of hydrochloric acid, nitric acid, acetic acid, oxalic acid, citric acid or malic acid, typically but not limited to a combination of hydrochloric acid and nitric acid, a combination of hydrochloric acid and acetic acid, or a combination of nitric acid and oxalic acid.
Preferably, the acid liquor of step (3) comprises citric acid and/or nitric acid.
Preferably, the concentration of the acid solution in the step (3) is 0.5 to 3mol/L, for example, 0.5mol/L, 1.5mol/L, 2mol/L, 2.5mol/L or 3mol/L, but not limited to the values listed, and other values not listed in the numerical range are equally applicable, preferably 1.5 to 2mol/L.
Preferably, the supplement of step (4) comprises any one or a combination of at least two of a lithium salt, an iron salt or a phosphorous-containing compound, typically but not limited to a combination comprising a lithium salt and an iron salt, a combination of a lithium salt and a phosphorous-containing compound, or a combination of an iron salt and a phosphorous-containing compound.
Preferably, in the mixed solution in the step (4), the molar ratio of lithium, iron and phosphorus is (1-1.1): 1, for example, may be 1:1:1, 1.05:1.05:1, 1.1:1.1:1, 1:1.1:1 or 1.1:1:1, but not limited to the recited values, and other non-recited values in the range of values are equally applicable, preferably 1.05:1:1.
Preferably, the lithium salt comprises any one or a combination of at least two of lithium hydroxide, lithium carbonate, lithium oxalate or lithium acetate, typically but not limited to a combination of lithium hydroxide and lithium carbonate, a combination of lithium hydroxide and lithium oxalate, or a combination of lithium carbonate and lithium acetate, preferably lithium carbonate.
Preferably, the iron salt comprises any one or a combination of at least two of ferric nitrate, ferric chloride or ferric acetate, typically but not limited to a combination of ferric nitrate and ferric chloride, a combination of ferric nitrate and ferric acetate, or a combination of ferric chloride and ferric acetate, preferably ferric nitrate.
Preferably, the phosphorus-containing compound comprises phosphoric acid and/or ammonium dihydrogen phosphate, preferably phosphoric acid.
Preferably, the mixing of step (4) further comprises mixing a carbon source and an additive.
Preferably, the content of the carbon source in the mixed solution in the step (4) is 1 to 10wt%, for example, 1wt%, 10wt%, 3wt%, 5wt%, 7wt%, 9wt% or 10wt%, but not limited to the values listed, and other values not listed in the numerical range are equally applicable, preferably 5 to 8wt%.
Preferably, the content of the additive in the mixed solution in the step (4) is 0.1 to 5wt%, for example, 0.1wt%, 1wt%, 2wt%, 3wt%, 4wt% or 5wt%, but not limited to the recited values, other non-recited values within the range of values are equally applicable, and preferably 1 to 2wt%.
Preferably, the pH of the mixture in step (4) is 1 to 3, for example, 1, 1.5, 2, 2.5 or 3, but not limited to the values listed, and other non-listed values within the range are equally applicable, preferably 1.9 to 2.1, more preferably 2.
The pH value of the mixed solution in the step (4) is regulated by ammonia water.
Preferably, the carbon source comprises glucose and/or sucrose, preferably glucose.
Preferably, the additive comprises any one or a combination of at least two of polyethylene glycol, polyvinyl alcohol, polyacrylamide or cetyltrimethylammonium bromide, typically but not limited to a combination of polyethylene glycol and polyvinyl alcohol, a combination of polyethylene glycol and polyacrylamide, or a combination of polyvinyl alcohol and polyacrylamide, preferably polyethylene glycol.
Preferably, the drying means of step (4) comprises spray drying.
Preferably, the sintering gas of step (4) comprises nitrogen and/or an inert gas, preferably nitrogen.
Preferably, the inert gas comprises any one or a combination of at least two of helium, argon, krypton or radon, typically but not limited to a combination of helium and argon, a combination of helium and krypton, or a combination of krypton and argon.
Preferably, the sintering temperature in step (4) is 600 to 900 ℃, for example 600 ℃, 700 ℃, 800 ℃ or 900 ℃, but not limited to the values listed, other values not listed in the range are equally applicable, preferably 750 to 800 ℃.
Preferably, the sintering time in step (4) is 5 to 15 hours, for example, 5 hours, 7 hours, 9 hours, 11 hours, 13 hours or 15 hours, but not limited to the recited values, and other non-recited values in the range of values are equally applicable, preferably 8 to 10 hours.
The solid-liquid separation mode comprises suction filtration and/or pressure filtration.
As a preferable technical scheme of the invention, the preparation method comprises the following steps:
(1) Mixing waste lithium iron phosphate black powder, acid liquor and oxidant at the temperature of 30-90 ℃ for oxidation leaching for 1-5 h, and carrying out solid-liquid separation on the obtained leached slurry to obtain primary filtrate and a filter cake;
the total content of impurities in the waste lithium iron phosphate black powder is 0.02-6wt%; the concentration of the acid liquor is 0.5-5 mol/L; the pH value of the oxidation leaching is 1-3; the solid-liquid ratio of the leached slurry is 100-500 g/L;
(2) Removing impurities from the primary filtrate in the step (1) by adopting a pH buffer, and performing solid-liquid separation to obtain secondary filtrate with the pH of 6-10;
(3) Mixing the filter cake obtained in the step (1) with acid liquor with the concentration of 0.5-3 mol/L, and then carrying out solid-liquid separation to obtain a third filtrate;
(4) Mixing the supplement, the secondary filtrate in the step (2), the tertiary filtrate in the step (3), a carbon source and an additive, and performing spray drying on the obtained mixed solution with the pH value of 1-3 to obtain a precursor;
in the mixed solution, the mol ratio of lithium, iron and phosphorus is (1-1.1): 1, the content of carbon source is 1-10wt%, and the content of additive is 0.1-5wt%;
(5) Sintering the precursor in the step (4) for 5-15 hours at 600-900 ℃ under nitrogen and/or inert gas to obtain the doped regenerated lithium iron phosphate material;
step (2) and step (3) are not in sequence.
In a second aspect, the present invention provides a doped regenerated lithium iron phosphate material obtainable by a method of preparation as described in the first aspect.
Preferably, the chemical formula of the doped regenerated lithium iron phosphate material is Li a M b Fe c P d O 4 Wherein 0.A is more than or equal to 95 and less than or equal to 1.05,0.001, b is more than or equal to 0.1,0.95, c is more than or equal to 1.05,0.95, and d is more than or equal to 1.05; the M comprises any one or a combination of at least two of Al, cu, fe, ca, mg, zn, na, K or F.
The chemical formula of the doped regenerated lithium iron phosphate material is Li a M b Fe c P d O 4 Wherein 0.95.ltoreq.a.ltoreq.1.05, for example, 0.95, 0.98, 1.00, 1.02 or 1.05, but not limited to the values recited, other non-recited values within the numerical range are equally applicable.
The chemical formula of the doped regenerated lithium iron phosphate material is Li a M b Fe c P d O 4 Wherein, b is 0.001.ltoreq.b.ltoreq.0.1, which may be, for example, 0.001, 0.005, 0.01, 0.05 or 0.1, but is not limited to the values recited, and other non-recited values within the numerical range are equally applicable.
The chemical formula of the doped regenerated lithium iron phosphate material is Li a M b Fe c P d O 4 Wherein, c is more than or equal to 0.95 and less than or equal to 1.05, for example, 0.95, 0.98, 1.00, 1.02 or 1.05 can be adopted, but the numerical values are not limited to the listed numerical values, and other non-listed numerical values in the numerical range are also applicable.
The chemical formula of the doped regenerated lithium iron phosphate material is Li a M b Fe c P d O 4 Wherein d is 0.95.ltoreq.1.05, which may be, for example, 0.95, 0.98, 1.00, 1.02 or 1.05, but is not limited to the values recited, and other non-recited values within the range of values are equally applicable.
The chemical formula of the doped regenerated lithium iron phosphate material is Li a M b Fe c P d O 4 Wherein M comprises any one or a combination of at least two of Al, cu, fe, ca, mg, zn, na, K or F, typical but non-limiting combinations include a combination of Al and Cu, a combination of Al and F, or a combination of Cu and F.
In a third aspect, the present invention provides a lithium ion battery comprising a doped regenerated lithium iron phosphate material as described in the second aspect.
Compared with the prior art, the invention has the following beneficial effects:
the invention adopts the waste lithium battery anode material with low cost as the raw material, and utilizes the impurity element Al, cu, fe, ca, mg, zn, na, K or F contained in the material as the doping element to uniformly disperse the doping in the lithium iron phosphate material; the preparation method of the invention enables the waste lithium battery anode material to be recycled, simplifies the preparation process of the lithium iron phosphate material, and obtains the regenerated lithium iron phosphate material which is evenly doped and dispersed and has excellent electrochemical performance.
Drawings
Fig. 1 is a process flow diagram of the preparation of the doped regenerated lithium iron phosphate material of the present invention.
Fig. 2 is a topography of a doped regenerated lithium iron phosphate material as described in example 1.
Detailed Description
The technical scheme of the invention is further described by the following specific embodiments. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.
Example 1
The embodiment provides a preparation method of a doped and regenerated lithium iron phosphate material, wherein the chemical formula of the doped and regenerated lithium iron phosphate material is Li a M b Fe c P d O 4 Wherein a is 1, b is 0.001, c is 1, d is 1, M comprises Al and F;
the preparation method adopts a flow chart shown in fig. 1, and specifically comprises the following steps:
(1) Mixing waste lithium iron phosphate black powder, citric acid with the concentration of 2.5mol/L, hydrogen peroxide with the concentration of 10% and ultrapure water at the temperature of 70 ℃, controlling the solid-to-liquid ratio of the mixed slurry to be 250g/L, carrying out oxidation leaching for 3h, adopting ammonia water to control the pH of the oxidation leaching to be 2, and carrying out suction filtration on the obtained leaching slurry to obtain primary filtrate and a filter cake;
the total content of impurities in the waste lithium iron phosphate black powder is 0.05wt%;
(2) Adjusting the pH value of the primary filtrate in the step (1) to 8 by adopting ammonia water, removing impurities and purifying the primary filtrate to reduce the impurity content to 0.02 weight percent, and obtaining secondary filtrate after solid-liquid separation;
(3) Mixing the filter cake in the step (1) with citric acid with the concentration of 2mol/L, and carrying out suction filtration to obtain a tertiary filtrate;
(4) Mixing lithium carbonate, ferric nitrate, phosphoric acid, the secondary filtrate in the step (2), the tertiary filtrate in the step (3), glucose, polyethylene glycol (PEG-200) and ammonia water, and performing spray drying on the obtained mixed solution with the pH of 2 to obtain a precursor;
in the mixed solution, the molar ratio of lithium, iron and phosphorus is 1.05:1:1, the content of glucose is 8wt%, and the content of polyethylene glycol is 2wt%;
(5) And (3) sintering the precursor in the step (4) for 10h at 750 ℃ under nitrogen gas to obtain the doped regenerated lithium iron phosphate material.
In this embodiment, the step (2) and the step (3) are not sequential.
The morphology diagram of the doped regenerated lithium iron phosphate material in this embodiment is shown in fig. 2.
Example 2
The embodiment provides a preparation method of a doped and regenerated lithium iron phosphate material, wherein the chemical formula of the doped and regenerated lithium iron phosphate material is Li a M b Fe c P d O 4 Wherein a is 1, b is 0.01, c is 1, d is 1, M comprises Al and F;
the preparation method adopts a flow chart shown in fig. 1, and specifically comprises the following steps:
(1) Mixing waste lithium iron phosphate black powder, hydrochloric acid with the concentration of 2.5mol/L, hydrogen peroxide with the concentration of 10% and ultrapure water at the temperature of 70 ℃, controlling the solid-to-liquid ratio of mixed slurry to be 250g/L, carrying out oxidation leaching for 3h, adopting ammonia water to control the pH of the oxidation leaching to be 2, and carrying out suction filtration on the obtained leaching slurry to obtain primary filtrate and a filter cake;
the total content of impurities in the waste lithium iron phosphate black powder is 0.5wt%;
(2) Adjusting the pH value of the primary filtrate in the step (1) to 9 by adopting ammonia water, removing impurities and purifying the primary filtrate to reduce the impurity content to 0.2 weight percent, and carrying out solid-liquid separation to obtain secondary filtrate;
(3) Mixing the filter cake in the step (1) with hydrochloric acid with the concentration of 0.5mol/L, and carrying out suction filtration to obtain a tertiary filtrate;
(4) Mixing lithium oxalate, ferric acetate, ammonium dihydrogen phosphate, the secondary filtrate in the step (2), the tertiary filtrate in the step (3), sucrose, polyethylene glycol (PEG-200) and ammonia water, and performing spray drying on the obtained mixed solution with the pH of 2 to obtain a precursor;
in the mixed solution, the molar ratio of lithium, iron and phosphorus is 1.05:1:1, the content of sucrose is 5wt%, and the content of polyethylene glycol is 1wt%;
(5) And (3) sintering the precursor in the step (4) for 10h at 750 ℃ under nitrogen gas to obtain the doped regenerated lithium iron phosphate material.
In this embodiment, the step (2) and the step (3) are not sequential.
Example 3
The embodiment provides a preparation method of a doped and regenerated lithium iron phosphate material, wherein the chemical formula of the doped and regenerated lithium iron phosphate material is Li a M b Fe c P d O 4 Wherein a is 1, b is 0.1, c is 1, d is 1, M comprises Al and F;
the preparation method adopts a flow chart shown in fig. 1, and specifically comprises the following steps:
(1) Mixing waste lithium iron phosphate black powder, nitric acid with the concentration of 2.5mol/L, hydrogen peroxide with the concentration of 20% and ultrapure water at the temperature of 70 ℃, controlling the solid-to-liquid ratio of mixed slurry to be 100g/L, carrying out oxidation leaching for 5h, adopting ammonia water to control the pH of the oxidation leaching to be 2, and carrying out suction filtration on the obtained leaching slurry to obtain primary filtrate and a filter cake;
the total content of impurities in the waste lithium iron phosphate black powder is 5wt%;
(2) Adjusting the pH value of the primary filtrate in the step (1) to 10 by adopting ammonia water, removing impurities and purifying the primary filtrate to reduce the impurity content to 2 weight percent, and carrying out solid-liquid separation to obtain secondary filtrate;
(3) Mixing the filter cake in the step (1) with nitric acid with the concentration of 0.5mol/L, and carrying out suction filtration to obtain a tertiary filtrate;
(4) Mixing lithium carbonate, ferric acetate, phosphoric acid, the secondary filtrate in the step (2), the tertiary filtrate in the step (3), sucrose, polyethylene glycol (PEG-200) and ammonia water, and performing spray drying on the obtained mixed solution with the pH of 2 to obtain a precursor;
in the mixed solution, the molar ratio of lithium, iron and phosphorus is 1.05:1:1, the content of sucrose is 5wt%, and the content of polyethylene glycol is 1wt%;
(5) And (3) sintering the precursor in the step (4) for 10h at 750 ℃ under nitrogen gas to obtain the doped regenerated lithium iron phosphate material.
In this embodiment, the step (2) and the step (3) are not sequential.
Example 4
The embodiment provides a preparation method of a doped and regenerated lithium iron phosphate material, wherein the chemical formula of the doped and regenerated lithium iron phosphate material is Li a M b Fe c P d O 4 Wherein a is 1, b is 0.0001, c is 1, d is 1, M includes Al and F;
the preparation method is the same as in example 1 except that the total content of impurities in the waste lithium iron phosphate black powder in step (1) is 0.01wt%, the pH value of the primary filtrate in step (1) is adjusted to 8 by adopting ammonia water, and the primary filtrate is subjected to impurity removal and purification, so that the impurity content in step (2) is 0.002 wt%.
Example 5
The embodiment provides a preparation method of a doped and regenerated lithium iron phosphate material, wherein the chemical formula of the doped and regenerated lithium iron phosphate material is Li a M b Fe c P d O 4 Wherein a is 1, b is 0.0005, c is 1, d is 1, M comprises Al and F;
the preparation method was the same as in example 1 except that ammonia water was used in step (2) to adjust the pH of the primary filtrate in step (1) to 12 so that the impurity content in step (2) was 0.01 wt%.
Example 6
The embodiment provides a preparation method of a doped and regenerated lithium iron phosphate material, wherein the chemical formula of the doped and regenerated lithium iron phosphate material is Li a M b Fe c P d O 4 Wherein a is 1, b is 0.002, c is 1, d is 1, M includes Al and F;
the preparation method was the same as in example 1, except that the leaching temperature in step (1) was 95 ℃.
Example 7
The embodiment provides a preparation method of a doped and regenerated lithium iron phosphate material, wherein the chemical formula of the doped and regenerated lithium iron phosphate material is Li a M b Fe c P d O 4 Wherein a is 1, b is 0.0005, c is 1, d is 1, M comprises Al and F;
the preparation method was the same as in example 1, except that the pH of the oxidative leaching in step (1) was 3.5.
Example 8
The embodiment provides a preparation method of a doped and regenerated lithium iron phosphate material, wherein the chemical formula of the doped and regenerated lithium iron phosphate material is Li a M b Fe c P d O 4 Wherein a is 1, b is 0.005, c is 1, d is 1, M comprises Al and F;
the preparation method is the same as in example 1 except that the solid-to-liquid ratio of the slurry mixture in step (1) is 50 g/L.
Example 9
The embodiment provides a preparation method of a doped and regenerated lithium iron phosphate material, wherein the chemical formula of the doped and regenerated lithium iron phosphate material is Li a M b Fe c P d O 4 Wherein a is 0.97, b is 0.001, c is 1, d is 1, M comprises Al and F;
the preparation method is the same as in example 1 except that in the mixed solution in step (4), the molar ratio of lithium, iron and phosphorus is 1:1:1.
Example 10
The embodiment provides a preparation method of a doped and regenerated lithium iron phosphate material, wherein the chemical formula of the doped and regenerated lithium iron phosphate material is Li a M b Fe c P d O 4 Wherein a is 1, b is 0.001, c is 1, d is 1, M comprises Al and F;
the preparation method was the same as in example 1 except that the content of glucose in the mixed solution in step (4) was 2wt%.
Example 11
The embodiment provides a preparation method of a doped and regenerated lithium iron phosphate material, wherein the chemical formula of the doped and regenerated lithium iron phosphate material is Li a M b Fe c P d O 4 Wherein a is 0.98, b is 0.001, c is 1, d is 1, M comprises Al and F;
the preparation method was the same as in example 1 except that the sintering temperature in step (5) was 900 ℃.
Comparative example 1
The comparative example provides a preparation method of a lithium iron phosphate material, wherein the chemical formula of the lithium iron phosphate material is Li a M b Fe c P d O 4 Wherein a is 1, b is 0.2, c is 1, d is 1, M comprises Al and F;
the preparation method comprises the following steps:
(1) Mixing waste lithium iron phosphate black powder, citric acid with the concentration of 2.5mol/L, hydrogen peroxide with the concentration of 10% and ultrapure water at the temperature of 70 ℃, controlling the solid-to-liquid ratio of the mixed slurry to be 250g/L, carrying out oxidation leaching for 3h, adopting ammonia water to control the pH of the oxidation leaching to be 2, and carrying out suction filtration on the obtained leaching slurry to obtain filtrate and a filter cake;
the total content of impurities in the waste lithium iron phosphate black powder is 4wt%;
(2) Mixing lithium carbonate, ferric nitrate, phosphoric acid, the filtrate obtained in the step (1), glucose, polyethylene glycol and ammonia water, and performing spray drying on the obtained mixed solution with the pH value of 2 to obtain a precursor;
in the mixed solution, the molar ratio of lithium, iron and phosphorus is 1.05:1:1, the content of glucose is 8wt%, and the content of polyethylene glycol is 2wt%;
(3) And (3) sintering the precursor in the step (2) for 10h at 750 ℃ under nitrogen gas to obtain the doped regenerated lithium iron phosphate material.
Comparative example 2
This comparative example provides a commercially conventional commercially available lithium iron phosphate material (LIB-LFPO-S13).
The doped regenerated lithium iron phosphate material provided in the above example and the lithium iron phosphate material provided in the comparative example are mixed with a conductive agent (conductive carbon black) and a binder (polyvinylidene fluoride) according to a ratio of 8:1:1, and then dissolved in N-methyl pyrrolidone to obtain slurry, the slurry is spread on an aluminum foil, and a cut piece is used as an anode after drying;
lithium sheet as negative electrode, polyethylene film as separator, liPF with solute of 1M 6 And a solvent (the solvent is a mixture of ethylene carbonate, dimethyl carbonate and diethyl carbonate with the volume ratio of 1:1:1) is used as electrolyte, and is sequentially stacked and pressed according to the sequence of a negative electrode shell, a negative electrode, electrolyte, a diaphragm, electrolyte, a positive electrode and a current collector positive electrode shell, so as to assemble a CR2016 button type lithium ion battery, and battery performance test is carried out;
the battery performance conditions are: the test voltage is 2.5-4.1V, the nominal specific capacity is 1 C=170 mAh/g, the first charge-discharge capacity and efficiency are measured at 0.1C, and the cycling stability is measured at 1C.
The test results are shown in table 1:
TABLE 1
The following points can be seen from table 1:
(1) According to the embodiment 1 and the embodiments 2-5, doping of impurities with different contents can be achieved by regulating and controlling the total content of impurities in the waste lithium iron phosphate black powder in the step (1) and the pH value of the secondary filtrate in the step (2), so that the doped regenerated lithium iron phosphate material with excellent performance is obtained.
(2) As is clear from examples 1 and 6 to 8, the oxidation leaching conditions in step (1) are within a preferable range, which is favorable for improving the oxidation leaching efficiency of the raw material, thereby obtaining the doped regenerated lithium iron phosphate material with excellent performance.
(3) From examples 1 and 9-11, it is understood that the material reconstruction process parameters (molar ratio of lithium, iron to phosphorus, carbon source content and material sintering temperature) in step (4) are within the preferred ranges, which is advantageous for obtaining the doped regenerated lithium iron phosphate material with excellent performance.
(4) As is clear from example 1 and comparative example 1, the preparation method provided in comparative example 1 has too high impurity content of the raw material and does not perform effective impurity content control, and the performance of the lithium iron phosphate material obtained in comparative example 1 is significantly reduced compared with that of example 1.
(5) As can be seen from examples 1 and 2, the commercial lithium iron phosphate material provided in comparative example 2 has an electrochemical performance reduced compared to example 1 due to the undoped element, and thus the element-uniformly doped lithium iron phosphate material obtained in the present invention has excellent electrochemical performance.
In summary, the invention provides a doped regenerated lithium iron phosphate material, a preparation method and application thereof, and the invention adopts a waste lithium battery anode material with low cost as a raw material, and the waste lithium battery anode material contains impurity elements, such as Al, cu, fe, ca, mg, zn, na, K or F, so that the impurity elements can be used as doping elements to obtain the doped regenerated lithium iron phosphate material; meanwhile, by regulating and controlling the reaction conditions in the preparation process, the lithium iron phosphate material can be uniformly dispersed in different doping amounts; the preparation method of the invention enables the waste lithium battery anode material to be recycled, simplifies the preparation process of the lithium iron phosphate material, and obtains the doped regenerated lithium iron phosphate material with excellent electrochemical performance.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and it should be apparent to those skilled in the art that any changes or substitutions that fall within the technical scope of the present invention disclosed herein are within the scope of the present invention.
Claims (34)
1. The preparation method of the doped regenerated lithium iron phosphate material is characterized by comprising the following steps of:
(1) Mixing waste lithium iron phosphate black powder, acid liquor and oxidant at the temperature of 30-90 ℃ for oxidation leaching for 1-5 h, and carrying out solid-liquid separation on the obtained leached slurry to obtain primary filtrate and a filter cake;
the total content of impurities in the waste lithium iron phosphate black powder is 0.02-6wt%; the concentration of the acid liquor is 0.5-5 mol/L; the pH of the oxidation leaching is 1-3; the solid-liquid ratio of the leached slurry is 100-500 g/L;
(2) Removing impurities from the primary filtrate in the step (1) by adopting a pH buffer, and performing solid-liquid separation to obtain a secondary filtrate with the pH of 6-10; the total content of impurities in the secondary filtrate is 0.02-2wt%;
(3) Mixing the filter cake in the step (1) with acid liquor with the concentration of 0.5-3 mol/L, and then carrying out solid-liquid separation to obtain a third filtrate;
(4) Mixing the supplement, the secondary filtrate in the step (2), the tertiary filtrate in the step (3), a carbon source and an additive, and performing spray drying on the obtained mixed solution with the pH value of 1-3 to obtain a precursor;
in the mixed solution, the molar ratio of lithium, iron and phosphorus is (1-1.1): 1, the content of a carbon source is 1-10wt%, and the content of an additive is 0.1-5wt%;
(5) Sintering the precursor in the step (4) for 5-15 hours at 600-900 ℃ under nitrogen and/or inert gas to obtain a regenerated lithium iron phosphate material taking impurity elements contained in waste lithium iron phosphate as doping elements;
step (2) and step (3) are not in sequence.
2. The method of claim 1, wherein the acid solution of step (1) comprises any one or a combination of at least two of hydrochloric acid, nitric acid, acetic acid, oxalic acid, citric acid, and malic acid.
3. The method of claim 1, wherein the acid solution of step (1) comprises citric acid and/or nitric acid.
4. The preparation method of claim 1, wherein the concentration of the acid solution in the step (1) is 2-3 mol/L.
5. The method of claim 1, wherein the oxidizing agent of the oxidative leaching of step (1) comprises any one or a combination of at least two of hydrogen peroxide, oxygen, or air.
6. The preparation method of claim 5, wherein the concentration of the hydrogen peroxide in the step (1) is 5-20%.
7. The method according to claim 1, wherein the pH of the oxidative leaching in step (1) is 1.9 to 2.1.
8. The method according to claim 1, wherein the leaching slurry in step (1) has a solid-to-liquid ratio of 250 to 300g/L.
9. The method of claim 1, wherein the mixing time in step (1) is 2-3 hours.
10. The method according to claim 1, wherein the temperature of the mixing in the step (1) is 60-70 ℃.
11. The method of claim 1, wherein the pH buffer comprises aqueous ammonia.
12. The method of claim 1, wherein the acid solution in step (3) comprises any one or a combination of at least two of hydrochloric acid, nitric acid, acetic acid, oxalic acid, citric acid, and malic acid.
13. The method of claim 12, wherein the acid solution of step (3) comprises citric acid and/or nitric acid.
14. The preparation method of claim 1, wherein the concentration of the acid solution in the step (3) is 1.5-2 mol/L.
15. The method of claim 1, wherein the supplement of step (4) comprises any one or a combination of at least two of a lithium salt, an iron salt, or a phosphorous compound.
16. The method of claim 15, wherein the lithium salt comprises any one or a combination of at least two of lithium hydroxide, lithium carbonate, lithium oxalate, or lithium acetate.
17. The method of claim 16, wherein the lithium salt is lithium carbonate.
18. The method of claim 15, wherein the iron salt comprises any one or a combination of at least two of ferric nitrate, ferric chloride, or ferric acetate.
19. The method of claim 18, wherein the iron salt is ferric nitrate.
20. The method of claim 15, wherein the phosphorus-containing compound comprises phosphoric acid and/or monoammonium phosphate.
21. The method of claim 20, wherein the phosphorus-containing compound is phosphoric acid.
22. The method according to claim 1, wherein the content of the carbon source in the mixed solution in the step (4) is 5-8wt%.
23. The method according to claim 1, wherein the content of the additive in the mixed solution in the step (4) is 1-2wt%.
24. The method according to claim 1, wherein the pH of the mixed solution in the step (4) is 1.9 to 2.1.
25. The method of claim 1, wherein the carbon source comprises glucose and/or sucrose.
26. The method of claim 25, wherein the carbon source is glucose.
27. The method of claim 1, wherein the additive comprises any one or a combination of at least two of polyethylene glycol, polyvinyl alcohol, polyacrylamide, or cetyltrimethylammonium bromide.
28. The method of claim 27, wherein the additive is polyethylene glycol.
29. The method of claim 1, wherein the sintering gas of step (4) is nitrogen.
30. The method of claim 1, wherein the inert gas comprises any one or a combination of at least two of helium, argon, krypton, or radon.
31. The method according to claim 1, wherein the sintering temperature in step (4) is 750-800 ℃.
32. The method according to claim 1, wherein the sintering time in the step (4) is 8-10 hours.
33. A doped regenerated lithium iron phosphate material, characterized in that the doped regenerated lithium iron phosphate material is obtained by the preparation method according to any one of claims 1-32.
34. A lithium ion battery comprising the doped regenerated lithium iron phosphate material of claim 33.
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