CN111333049B - Preparation method of lithium iron manganese phosphate - Google Patents

Preparation method of lithium iron manganese phosphate Download PDF

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CN111333049B
CN111333049B CN202010205831.8A CN202010205831A CN111333049B CN 111333049 B CN111333049 B CN 111333049B CN 202010205831 A CN202010205831 A CN 202010205831A CN 111333049 B CN111333049 B CN 111333049B
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蒋央芳
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Sichuan Langsheng New Energy Technology Co ltd
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Abstract

The invention discloses a preparation method of lithium iron manganese phosphate. Mixing a waste lithium iron phosphate material and a waste lithium manganate material together for leaching, adding a heavy metal trapping agent into filtrate for precipitation, filtering, extracting the filtrate by using a P204 extraction agent, and performing back extraction by using a phosphoric acid solution to obtain iron phosphate; filtering the extracted raffinate ammonium sulfide and ammonium fluoride, adding ammonium carbonate into the filtrate for reaction, and filtering to obtain a fourth filtrate and a fourth filter residue; adding water into the fourth filter residue, the iron phosphate, the battery-grade lithium carbonate and the titanium dioxide for slurrying, adding a phosphoric acid solution, stirring and dispersing to obtain a slurried material, adding a dispersing agent and a carbon source, and performing spray drying to obtain a dried material; and calcining the dried material, crushing, screening, removing iron and packaging to obtain the lithium manganese iron phosphate. The method has short flow, takes the waste as the raw material, can greatly reduce the cost, realizes the recovery of iron, lithium, phosphorus and manganese in the waste, and simultaneously obtains the lithium iron manganese phosphate with good electrical property and excellent cycle performance.

Description

Preparation method of lithium iron manganese phosphate
Technical Field
The invention relates to a preparation method of lithium iron manganese phosphate, belonging to the technical field of new energy anode materials.
Background
The lithium iron phosphate battery is a lithium ion battery using lithium iron phosphate as a positive electrode material. The anode material of the lithium ion battery mainly comprises lithium cobaltate, lithium manganate, lithium nickelate, ternary material, lithium iron phosphate and the like. Lithium cobaltate is a positive electrode material used by most lithium ion batteries at present.
In the metal market, cobalt (Co) is the most expensive and less abundant, nickel (Ni), manganese (Mn) are cheaper, and iron (Fe) is more abundant. The price of the positive electrode material is also in line with the price market for these metals. Therefore, the lithium ion battery made of the LiFePO4 anode material is very cheap and practical. It is also characterized by environmental protection and no pollution.
The requirements as a rechargeable battery are: high capacity, high output voltage, good charge-discharge cycle performance, stable output voltage, large current charge-discharge, electrochemical stability, safety in use (no combustion or explosion caused by overcharge, overdischarge, short circuit and other improper operations), wide working temperature range, no toxicity or little toxicity, and no pollution to environment. The lithium iron phosphate battery adopting LiFePO4 as the anode has good performance requirements, and is particularly the best in large discharge rate discharge (5-10C discharge), stable discharge voltage, safety (no combustion and no explosion), service life (cycle times) and no pollution to the environment, and is the best high-current output power battery at present.
LiFePO4 is used as the positive electrode of the battery and is connected with the positive electrode of the battery by aluminum foil, the middle part is a polymer diaphragm which separates the positive electrode from the negative electrode, but Li ions can pass through but e-can not pass through, the right part is the negative electrode of the battery which is composed of carbon (graphite) and is connected with the negative electrode of the battery by copper foil. The electrolyte of the battery is arranged between the upper end and the lower end of the battery, and the battery is hermetically packaged by a metal shell.
When the LiFePO4 battery is charged, lithium ions Li in the positive electrode migrate to the negative electrode through the polymer diaphragm; during discharge, lithium ions Li in the negative electrode migrate through the separator to the positive electrode. Lithium ion batteries are named for the fact that lithium ions migrate back and forth during charging and discharging.
The nominal voltage of the LiFePO4 cell was 3.2V, the end charge voltage was 3.6V, and the end discharge voltage was 2.0V. The positive and negative electrode materials and electrolyte materials adopted by various manufacturers have different qualities and processes, so that the performances of the positive and negative electrode materials and the electrolyte materials are different. For example, the capacity of the battery is greatly different (10-20%) in the same type (the same packaged standard battery).
At present, lithium iron phosphate is generally selected as a positive electrode material of a power type lithium ion battery at home, and the material is seen by market analysts such as governments, scientific research institutions, enterprises and even security companies, and is taken as a development direction of the power type lithium ion battery. The reason is analyzed, and the following two main points exist: firstly, under the influence of the research and development direction of the united states, the company Valence and a123 in the united states originally adopts lithium iron phosphate as the positive electrode material of the lithium ion battery. And secondly, a lithium manganate material with good high-temperature cycle and storage performance for power lithium ion batteries has not been prepared at home.
However, lithium iron phosphate has the disadvantages of low voltage, low capacity, and the like, and lithium iron manganese phosphate has high discharge voltage, obviously can improve energy density, but has high cost.
Disclosure of Invention
In view of the above, the invention provides a preparation method of lithium iron manganese phosphate, which has a short flow, takes waste as a raw material, can greatly reduce the cost, avoids the procedures of grinding and the like required in the conventional process, realizes the recovery of iron, lithium, phosphorus and manganese in the waste, and simultaneously obtains the lithium iron manganese phosphate with good electrical property and excellent cycle performance.
The invention solves the technical problems by the following technical means:
a preparation method of lithium iron manganese phosphate comprises the following steps:
1) mixing the waste lithium iron phosphate material and the waste lithium manganate material together, so that the molar ratio of ferromanganese in the mixture is 1: 1.52-1.55, then adding a hydrochloric acid solution, stirring and reacting for 2-3h at the temperature of 60-80 ℃, and filtering to obtain a first filtrate and a first filter residue;
2) adding an acid-base regulator into the first filtrate to regulate the pH value of the solution to be 1-1.5, then adding a heavy metal capture agent, reacting at the temperature of 40-50 ℃ for 30-45min, then filtering to obtain a second filtrate and a second filter residue, extracting the second filtrate by using a P204 extracting agent, washing the obtained extracted organic phase by using a washing solution, performing back extraction by using a phosphoric acid solution, and performing centrifugal separation to obtain iron phosphate and the P204 extracting agent;
3) adjusting the pH of the raffinate extracted in the step (2) to 2-2.5, adding an ammonium sulfide solution, reacting at the temperature of 40-55 ℃ for 1-2h, then adding ammonia water to adjust the pH of the solution to 4.5-5.5, then adding ammonium fluoride, heating to the temperature of 90-95 ℃, stirring for reacting for 2-4h, then filtering to obtain a third filtrate and a third filter residue,
4) adding ammonium carbonate into the third filtrate, reacting for 2-3h at 40-50 deg.C under stirring, heating to 80-90 deg.C, reacting for 15-30min under stirring, and filtering to obtain fourth filtrate and fourth residue;
5) adding water into the fourth filter residue and the iron phosphate, battery-grade lithium carbonate and titanium dioxide obtained in the step (2) for slurrying, adding a phosphoric acid solution, stirring and dispersing to obtain a slurried material, adding a dispersing agent and a carbon source, stirring and dispersing, removing iron through a 10-15-grade pipeline iron remover, removing iron through a 2-4-grade electromagnetic slurry iron remover, and spray-drying to obtain a dried material;
6) and calcining the dried material at high temperature under the protection of nitrogen to obtain a calcined material, and crushing, screening, deironing and packaging to obtain the lithium iron manganese phosphate.
The concentration of the hydrochloric acid solution in the step (1) is 2-4mol/L, and the ratio of the total mole number of ferromanganese in the added mixture to the mole number of the added hydrochloric acid is 1: 2.2-2.5, and returning the first filter residue to be leached again together with the mixture.
And (3) adding a heavy metal trapping agent into hydrochloric acid or ammonia water as an acid-base regulator in the step (2) to enable the total concentration of nickel, cobalt, zinc, lead, cadmium and copper in the second filtrate to be lower than 500 mg/L.
The second filtrate in the step (2) adopts a P204 extractant extraction process, the P204 extractant is firstly saponified and then extracted, countercurrent extraction is adopted, the number of extraction stages is 6-8, the mole ratio of the saponified P204 extractant added in the same time to the iron in the added second filtrate is 3-3.05:1, the obtained extracted organic phase adopts 0.5-0.75mol/L sulfuric acid solution in the washing process, the volume flow ratio of the extracted organic phase to the washing solution is 12-15:1, 6-8 stages of countercurrent washing is adopted for washing, the washed washing solution returns to be mixed with the second filtrate and then is extracted, the washed organic phase adopts phosphoric acid solution for back extraction, the concentration of the phosphoric acid solution is 0.5-1.5mol/L, the washed organic phase is added with phosphoric acid and stirred and mixed for 30-60min, the ratio of the mole number of the added phosphoric acid to the mole number of the iron in the washed organic phase is 1.02-1.05:1, the reacted materials are centrifugally separated to obtain iron phosphate and a P204 extracting agent, the iron phosphate is added with sulfonated kerosene for washing and then centrifugally separated, the separated liquid is returned to be mixed with the P204 extracting agent for use, the separated solid is added with hot water for washing, and then the solid is dried to obtain the battery-grade iron phosphate.
The ratio of the total mole number of nickel, cobalt, zinc, lead, cadmium and copper in the raffinate in the step (3) to the mole number of the added ammonium sulfide is 1:1.2-1.5, and the ratio of the mole number of the added ammonium fluoride to the total mole number of calcium and magnesium in the solution after the heavy metal is removed is 1.3-1.5: 1.
The ratio of the mole number of the ammonium carbonate added in the step (4) to the total mole number of the manganese and lithium in the third filtrate is 2.6-2.8: 3.
The molar ratio of lithium, manganese, iron, phosphorus and titanium in the slurry obtained in the step (5) is 1.03-1.05: 0.4-0.41: 0.6-0.61: 1.01-1.02: 0.01-0.015 percent, the mass fraction of solid in the slurry is 25-30 percent, the spray drying process, the air inlet temperature is 230-.
The total period of the calcination process is 25-28h, wherein the temperature rise time is 5-8h, the heat preservation time is 10-12h, the rest is the temperature reduction time, the heat preservation temperature is 770-800 ℃, nitrogen is continuously introduced in the calcination process, and the volume of the introduced nitrogen in the same time is 500 times of the volume of the furnace-entering spray drying material.
And stopping crushing when the particle size of the crushed material is 1.5-2.5 mu m, sieving by a sieve of 80-150 meshes, adopting nitrogen as a gas source in the crushing process, heating the nitrogen to the temperature of 120-150 ℃, and performing sieving, iron removal and packaging on the crushed material in a packaging room, wherein the constant temperature of the packaging room is 15-25 ℃, and the constant humidity is 5-10%.
The mass ratio of the dispersing agent and the carbon source added in the step (5) is 0.5-1:9-9.5, the dispersing agent is polyethylene glycol, the carbon source is at least one of glucose, sucrose and starch, and the dispersing agent and the carbon source are added to enable the carbon content in the finally obtained lithium manganese iron phosphate to be 1.5-2.0%.
The invention takes the lithium iron phosphate and the lithium manganate waste as raw materials, because the manganese exists in a high valence state and has certain oxidability in the lithium manganate, and the iron exists in a low valence state and exists in a divalent state and has certain reducibility, the two are mixed together, so that the redox reaction can be carried out, the reaction efficiency is improved, and simultaneously, the increase of the consumption of an oxidant in the process of preparing the iron phosphate is avoided, and the cost can be reduced by more than 800 yuan per ton of lithium iron phosphate through the step.
The precursor adopted by the invention has the advantages that iron exists in a trivalent state (namely iron phosphate), manganese exists in a divalent state (namely manganese carbonate is obtained), the trivalent iron phosphate has a stable structure, and the defects of easy oxidation of a ferrous precursor and the like are avoided.
The method comprises the steps of extracting oxidized ferric ions by a P204 extracting agent, wherein the ferric ions can be realized at a lower pH value, performing phosphoric acid back extraction to obtain granular iron phosphate, removing heavy metals, calcium and magnesium from raffinate by sulfide and fluoride, adding ammonium carbonate to coprecipitate manganese, lithium and the like, simultaneously precipitating a part of phosphate radical at a higher pH value, adding lithium carbonate, phosphoric acid and the like for blending, and performing spray drying and calcination to obtain the lithium manganese iron phosphate.
The invention has the beneficial effects that: the method has the advantages that the flow is short, the waste is used as the raw material, the cost can be greatly reduced, the procedures such as grinding and the like required in the conventional process are avoided, the recovery of iron, lithium, phosphorus and manganese in the waste is realized, and meanwhile, the obtained lithium manganese iron phosphate has good electrical property and excellent cycle performance.
Drawings
FIG. 1 is an SEM of the product obtained in example 1 of the present invention.
FIG. 2 is an SEM of the product obtained in example 2 of the present invention.
FIG. 3 is an SEM of the product obtained in example 3 of the present invention.
FIG. 4 is an SEM of a spray-dried material obtained in example 1 of the present invention.
Detailed Description
The invention will be described in detail with reference to the accompanying drawings and specific examples, wherein the preparation method of lithium iron manganese phosphate in the example comprises the following steps:
1) mixing the waste lithium iron phosphate material and the waste lithium manganate material together, so that the molar ratio of ferromanganese in the mixture is 1: 1.52-1.55, then adding a hydrochloric acid solution, stirring and reacting for 2-3h at the temperature of 60-80 ℃, and filtering to obtain a first filtrate and a first filter residue;
2) adding an acid-base regulator into the first filtrate to regulate the pH value of the solution to be 1-1.5, then adding a heavy metal capture agent, reacting at the temperature of 40-50 ℃ for 30-45min, then filtering to obtain a second filtrate and a second filter residue, extracting the second filtrate by using a P204 extracting agent, washing the obtained extracted organic phase by using a washing solution, performing back extraction by using a phosphoric acid solution, and performing centrifugal separation to obtain iron phosphate and the P204 extracting agent;
3) adjusting the pH of the raffinate extracted in the step (2) to 2-2.5, adding an ammonium sulfide solution, reacting at the temperature of 40-55 ℃ for 1-2h, then adding ammonia water to adjust the pH of the solution to 4.5-5.5, then adding ammonium fluoride, heating to the temperature of 90-95 ℃, stirring for reacting for 2-4h, then filtering to obtain a third filtrate and a third filter residue,
4) adding ammonium carbonate into the third filtrate, reacting for 2-3h at 40-50 deg.C under stirring, heating to 80-90 deg.C, reacting for 15-30min under stirring, and filtering to obtain fourth filtrate and fourth residue;
5) adding water into the fourth filter residue and the iron phosphate, battery-grade lithium carbonate and titanium dioxide obtained in the step (2) for slurrying, adding a phosphoric acid solution, stirring and dispersing to obtain a slurried material, adding a dispersing agent and a carbon source, stirring and dispersing, removing iron through a 10-15-grade pipeline iron remover, removing iron through a 2-4-grade electromagnetic slurry iron remover, and spray-drying to obtain a dried material;
6) and calcining the dried material at high temperature under the protection of nitrogen to obtain a calcined material, and crushing, screening, deironing and packaging to obtain the lithium iron manganese phosphate.
The concentration of the hydrochloric acid solution in the step (1) is 2-4mol/L, and the ratio of the total mole number of ferromanganese in the added mixture to the mole number of the added hydrochloric acid is 1: 2.2-2.5, and returning the first filter residue to be leached again together with the mixture.
And (3) adding a heavy metal trapping agent into hydrochloric acid or ammonia water as an acid-base regulator in the step (2) to enable the total concentration of nickel, cobalt, zinc, lead, cadmium and copper in the second filtrate to be lower than 500 mg/L.
The second filtrate in the step (2) adopts a P204 extractant extraction process, the P204 extractant is firstly saponified and then extracted, countercurrent extraction is adopted, the number of extraction stages is 6-8, the mole ratio of the saponified P204 extractant added in the same time to the iron in the added second filtrate is 3-3.05:1, the obtained extracted organic phase adopts 0.5-0.75mol/L sulfuric acid solution in the washing process, the volume flow ratio of the extracted organic phase to the washing solution is 12-15:1, 6-8 stages of countercurrent washing is adopted for washing, the washed washing solution returns to be mixed with the second filtrate and then is extracted, the washed organic phase adopts phosphoric acid solution for back extraction, the concentration of the phosphoric acid solution is 0.5-1.5mol/L, the washed organic phase is added with phosphoric acid and stirred and mixed for 30-60min, the ratio of the mole number of the added phosphoric acid to the mole number of the iron in the washed organic phase is 1.02-1.05:1, the reacted materials are centrifugally separated to obtain iron phosphate and a P204 extracting agent, the iron phosphate is added with sulfonated kerosene for washing and then centrifugally separated, the separated liquid is returned to be mixed with the P204 extracting agent for use, the separated solid is added with hot water for washing, and then the solid is dried to obtain the battery-grade iron phosphate.
The ratio of the total mole number of nickel, cobalt, zinc, lead, cadmium and copper in the raffinate in the step (3) to the mole number of the added ammonium sulfide is 1:1.2-1.5, and the ratio of the mole number of the added ammonium fluoride to the total mole number of calcium and magnesium in the solution after the heavy metal is removed is 1.3-1.5: 1.
The ratio of the mole number of the ammonium carbonate added in the step (4) to the total mole number of the manganese and lithium in the third filtrate is 2.6-2.8: 3.
The molar ratio of lithium, manganese, iron, phosphorus and titanium in the slurry obtained in the step (5) is 1.03-1.05: 0.4-0.41: 0.6-0.61: 1.01-1.02: 0.01-0.015 percent, the mass fraction of solid in the slurry is 25-30 percent, the spray drying process, the air inlet temperature is 230-.
The total period of the calcination process is 25-28h, wherein the temperature rise time is 5-8h, the heat preservation time is 10-12h, the rest is the temperature reduction time, the heat preservation temperature is 770-800 ℃, nitrogen is continuously introduced in the calcination process, and the volume of the introduced nitrogen in the same time is 500 times of the volume of the furnace-entering spray drying material.
And stopping crushing when the particle size of the crushed material is 1.5-2.5 mu m, sieving by a sieve of 80-150 meshes, adopting nitrogen as a gas source in the crushing process, heating the nitrogen to the temperature of 120-150 ℃, and performing sieving, iron removal and packaging on the crushed material in a packaging room, wherein the constant temperature of the packaging room is 15-25 ℃, and the constant humidity is 5-10%.
The mass ratio of the dispersing agent and the carbon source added in the step (5) is 0.5-1:9-9.5, the dispersing agent is polyethylene glycol, the carbon source is at least one of glucose, sucrose and starch, and the dispersing agent and the carbon source are added to enable the carbon content in the finally obtained lithium manganese iron phosphate to be 1.5-2.0%.
Example 1
A preparation method of lithium iron manganese phosphate comprises the following steps:
1) mixing the waste lithium iron phosphate material and the waste lithium manganate material together, so that the molar ratio of ferromanganese in the mixture is 1: 1.53, adding a hydrochloric acid solution, stirring and reacting at the temperature of 70 ℃ for 2.5 hours, and filtering to obtain a first filtrate and a first filter residue;
2) adding an acid-base regulator into the first filtrate to regulate the pH value of the solution to 1.3, then adding a heavy metal trapping agent, reacting at the temperature of 45 ℃ for 40min, filtering to obtain a second filtrate and second filter residue, extracting the second filtrate by using a P204 extracting agent, washing the obtained extracted organic phase by using a washing solution, performing back extraction by using a phosphoric acid solution, and performing centrifugal separation to obtain iron phosphate and the P204 extracting agent;
3) adjusting the pH of the raffinate extracted in the step (2) to 2.3, adding an ammonium sulfide solution, reacting at the temperature of 50 ℃ for 1.5h, then adding ammonia water to adjust the pH of the solution to 5, then adding ammonium fluoride, heating to the temperature of 93 ℃, stirring, reacting for 3h, filtering to obtain a third filtrate and a third filter residue,
4) adding ammonium carbonate into the third filtrate, stirring and reacting at the temperature of 45 ℃ for 3h, then heating to the temperature of 85 ℃, stirring and reacting at the temperature for 20min, and then filtering to obtain a fourth filtrate and a fourth filter residue;
5) adding water into the fourth filter residue and the iron phosphate, the battery-grade lithium carbonate and the titanium dioxide obtained in the step (2) for slurrying, adding a phosphoric acid solution, stirring and dispersing to obtain a slurried material, adding a dispersing agent and a carbon source, stirring and dispersing, removing iron through a 13-grade pipeline iron remover, removing iron through a 4-grade electromagnetic slurry iron remover, and performing spray drying to obtain a dried material;
6) and calcining the dried material at high temperature under the protection of nitrogen to obtain a calcined material, and crushing, screening, deironing and packaging to obtain the lithium iron manganese phosphate.
The concentration of the hydrochloric acid solution in the step (1) is 3mol/L, and the ratio of the total mole number of ferromanganese in the added mixture to the mole number of the added hydrochloric acid is 1: 2.4, returning the first filter residue to be leached again together with the mixture.
And (3) adding a heavy metal trapping agent into ammonia water serving as an acid-base regulator in the step (2) to enable the total concentration of nickel, cobalt, zinc, lead, cadmium and copper in the second filtrate to be lower than 500 mg/L.
The second filtrate in the step (2) adopts a P204 extractant extraction process, the P204 extractant is firstly saponified and then extracted, countercurrent extraction is adopted, the number of extraction stages is 8, the mole ratio of the saponified P204 extractant added in the same time to the iron in the added second filtrate is 3.02:1, the washing liquid adopted in the washing process of the obtained extracted organic phase is 0.65mol/L sulfuric acid solution, the volume flow ratio of the extracted organic phase to the washing liquid is 15:1, 8-stage countercurrent washing is adopted in washing, the washed washing liquid is returned to be mixed with the second filtrate and then extracted, the washed organic phase is subjected to back extraction by adopting phosphoric acid solution, the concentration of the phosphoric acid solution is 1mol/L, the washed organic phase is added with phosphoric acid, stirring and mixing are carried out for 50min, the mole ratio of the added phosphoric acid to the mole ratio of the washed organic phase iron is 1.03:1, and (3) centrifugally separating the reacted materials to obtain iron phosphate and a P204 extractant, adding sulfonated kerosene into the iron phosphate for washing, centrifugally separating, returning the separated liquid to be mixed with the P204 extractant for use, adding hot water into the separated solid for washing, and drying to obtain the battery-grade iron phosphate.
The ratio of the total mole number of nickel, cobalt, zinc, lead, cadmium and copper in the raffinate in the step (3) to the mole number of the added ammonium sulfide is 1:1.45, and the ratio of the mole number of the added ammonium fluoride to the total mole number of calcium and magnesium in the solution after the heavy metals are removed is 1.4: 1.
The ratio of the mole number of the ammonium carbonate added in the step (4) to the total mole number of the manganese and lithium in the third filtrate is 2.75: 3.
The molar ratio of lithium, manganese, iron, phosphorus and titanium in the slurry obtained in the step (5) is 1.045: 0.405: 0.605: 1.015: 0.013 percent, the mass fraction of solid in the slurry is 28 percent, in the spray drying process, the air inlet temperature is 245 ℃, the discharging temperature is less than or equal to 80 ℃, and a centrifugal spray drying mode is adopted, so that the particle size of the fog drops is 1-20 microns, and the mass fraction of the discharged water is less than 1 percent.
The total period of the calcination process is 27h, wherein the temperature rise time is 7h, the heat preservation time is 11h, the rest is the temperature reduction time, the heat preservation temperature is 780 ℃, nitrogen is continuously introduced in the calcination process, and the volume of the introduced nitrogen in the same time is 450 times of the volume of the furnace-entering spray drying material.
And stopping crushing when the particle size of the crushed material is 1.8 mu m, sieving the crushed material by a 120-mesh sieve, adopting nitrogen as a gas source in the crushing process, heating the nitrogen to the temperature of 140 ℃, and performing the processes of sieving, deironing and packaging the crushed material in a packaging room, wherein the constant temperature of the packaging room is 15 ℃ and the constant humidity is 8%.
The mass ratio of the dispersing agent and the carbon source added in the step (5) is 0.8:9.2, the dispersing agent is polyethylene glycol, the carbon source is glucose, and the dispersing agent and the carbon source are added so that the carbon content in the finally obtained lithium manganese iron phosphate is 1.85%.
Example 2
A preparation method of lithium iron manganese phosphate comprises the following steps:
1) mixing the waste lithium iron phosphate material and the waste lithium manganate material together, so that the molar ratio of ferromanganese in the mixture is 1: 1.53, adding a hydrochloric acid solution, stirring and reacting at the temperature of 70 ℃ for 2.5 hours, and filtering to obtain a first filtrate and a first filter residue;
2) adding an acid-base regulator into the first filtrate to regulate the pH value of the solution to 1.3, then adding a heavy metal trapping agent, reacting at the temperature of 45 ℃ for 40min, filtering to obtain a second filtrate and second filter residue, extracting the second filtrate by using a P204 extracting agent, washing the obtained extracted organic phase by using a washing solution, performing back extraction by using a phosphoric acid solution, and performing centrifugal separation to obtain iron phosphate and the P204 extracting agent;
3) adjusting the pH of the raffinate extracted in the step (2) to 2.3, adding an ammonium sulfide solution, reacting at the temperature of 50 ℃ for 1.5h, then adding ammonia water to adjust the pH of the solution to 5, then adding ammonium fluoride, heating to the temperature of 93 ℃, stirring, reacting for 3h, filtering to obtain a third filtrate and a third filter residue,
4) adding ammonium carbonate into the third filtrate, stirring and reacting at the temperature of 45 ℃ for 3h, then heating to the temperature of 85 ℃, stirring and reacting at the temperature for 20min, and then filtering to obtain a fourth filtrate and a fourth filter residue;
5) adding water into the fourth filter residue and the iron phosphate, the battery-grade lithium carbonate and the titanium dioxide obtained in the step (2) for slurrying, adding a phosphoric acid solution, stirring and dispersing to obtain a slurried material, adding a dispersing agent and a carbon source, stirring and dispersing, removing iron through a 13-grade pipeline iron remover, removing iron through a 4-grade electromagnetic slurry iron remover, and performing spray drying to obtain a dried material;
6) and calcining the dried material at high temperature under the protection of nitrogen to obtain a calcined material, and crushing, screening, deironing and packaging to obtain the lithium iron manganese phosphate.
The concentration of the hydrochloric acid solution in the step (1) is 3mol/L, and the ratio of the total mole number of ferromanganese in the added mixture to the mole number of the added hydrochloric acid is 1: 2.5, returning the first filter residue to be leached again together with the mixture.
And (3) adding a heavy metal trapping agent into ammonia water serving as an acid-base regulator in the step (2) to enable the total concentration of nickel, cobalt, zinc, lead, cadmium and copper in the second filtrate to be lower than 500 mg/L.
The second filtrate in the step (2) adopts a P204 extractant extraction process, the P204 extractant is firstly saponified and then extracted, countercurrent extraction is adopted, the number of extraction stages is 7, the mole ratio of the saponified P204 extractant added in the same time to the iron in the added second filtrate is 3.05:1, the washing liquid adopted in the washing process of the obtained extracted organic phase is 0.75mol/L sulfuric acid solution, the volume flow ratio of the extracted organic phase to the washing liquid is 13:1, 8-stage countercurrent washing is adopted for washing, the washed washing liquid is returned to be mixed with the second filtrate and then extracted, the washed organic phase is subjected to back extraction by adopting phosphoric acid solution, the concentration of the phosphoric acid solution is 1.2mol/L, the washed organic phase is added with phosphoric acid, stirring and mixing are carried out for 50min, the mole ratio of the added phosphoric acid to the mole ratio of the iron in the washed organic phase is 1.03:1, and (3) centrifugally separating the reacted materials to obtain iron phosphate and a P204 extractant, adding sulfonated kerosene into the iron phosphate for washing, centrifugally separating, returning the separated liquid to be mixed with the P204 extractant for use, adding hot water into the separated solid for washing, and drying to obtain the battery-grade iron phosphate.
The ratio of the total mole number of nickel, cobalt, zinc, lead, cadmium and copper in the raffinate in the step (3) to the mole number of the added ammonium sulfide is 1:1.4, and the ratio of the mole number of the added ammonium fluoride to the total mole number of calcium and magnesium in the solution after the heavy metals are removed is 1.4: 1.
The ratio of the mole number of the ammonium carbonate added in the step (4) to the total mole number of the manganese and lithium in the third filtrate is 2.7: 3.
The molar ratio of lithium, manganese, iron, phosphorus and titanium in the slurry in the step (5) is 1.035: 0.405: 0.6: 1.015: 0.012 percent of solid mass in the slurry, spray drying, wherein the air inlet temperature is 245 ℃ and the discharging temperature is less than or equal to 80 ℃, and a centrifugal spray drying mode is adopted to ensure that the particle size of the fog drops is 1-20 microns and the mass fraction of the discharged water is less than 1 percent.
The total period of the calcination process is 26h, wherein the temperature rise time is 7h, the heat preservation time is 12h, the rest is the temperature reduction time, the heat preservation temperature is 785 ℃, nitrogen is continuously introduced in the calcination process, and the volume of the introduced nitrogen in the same time is 350 times of the volume of the spray-dried material entering the furnace.
And stopping crushing when the particle size of the crushed material is 2 mu m, sieving the crushed material by a 100-mesh sieve, adopting nitrogen as a gas source in the crushing process, heating the nitrogen to the temperature of 135 ℃, performing screening, iron removal and packaging on the crushed material in a packaging room, and keeping the temperature of the packaging room at 18 ℃ and the constant humidity at 9%.
The mass ratio of the dispersing agent and the carbon source added in the step (5) is 0.6:9.4, the dispersing agent is polyethylene glycol, the carbon source is starch, and the dispersing agent and the carbon source are added so that the carbon content in the finally obtained lithium manganese iron phosphate is 1.86%.
Example 3
A preparation method of lithium iron manganese phosphate comprises the following steps:
1) mixing the waste lithium iron phosphate material and the waste lithium manganate material together, so that the molar ratio of ferromanganese in the mixture is 1: 1.535, then adding a hydrochloric acid solution, stirring and reacting for 2.5 hours at the temperature of 75 ℃, and filtering to obtain a first filtrate and a first filter residue;
2) adding an acid-base regulator into the first filtrate to regulate the pH value of the solution to 1.5, then adding a heavy metal trapping agent, reacting at the temperature of 45 ℃ for 40min, filtering to obtain a second filtrate and second filter residue, extracting the second filtrate by using a P204 extracting agent, washing the obtained extracted organic phase by using a washing solution, performing back extraction by using a phosphoric acid solution, and performing centrifugal separation to obtain iron phosphate and the P204 extracting agent;
3) adjusting the pH of the raffinate extracted in the step (2) to 2.25, adding an ammonium sulfide solution, reacting at the temperature of 50 ℃ for 1.5h, then adding ammonia water to adjust the pH of the solution to 5.2, then adding ammonium fluoride, heating to the temperature of 93 ℃, stirring to react for 4h, then filtering to obtain a third filtrate and a third filter residue,
4) adding ammonium carbonate into the third filtrate, stirring and reacting at the temperature of 45 ℃ for 2.5h, then heating to the temperature of 85 ℃, stirring and reacting at the temperature for 25min, and then filtering to obtain a fourth filtrate and a fourth filter residue;
5) adding water into the fourth filter residue and the iron phosphate, the battery-grade lithium carbonate and the titanium dioxide obtained in the step (2) for slurrying, adding a phosphoric acid solution, stirring and dispersing to obtain a slurried material, adding a dispersing agent and a carbon source, stirring and dispersing, removing iron through a 15-grade pipeline iron remover, removing iron through a 4-grade electromagnetic slurry iron remover, and performing spray drying to obtain a dried material;
6) and calcining the dried material at high temperature under the protection of nitrogen to obtain a calcined material, and crushing, screening, deironing and packaging to obtain the lithium iron manganese phosphate.
The concentration of the hydrochloric acid solution in the step (1) is 4mol/L, and the ratio of the total mole number of ferromanganese in the added mixture to the mole number of the added hydrochloric acid is 1: 2.35, and returning the first filter residue to be leached again together with the mixture.
And (3) adding a heavy metal trapping agent into ammonia water serving as an acid-base regulator in the step (2) to enable the total concentration of nickel, cobalt, zinc, lead, cadmium and copper in the second filtrate to be lower than 500 mg/L.
The second filtrate in the step (2) adopts a P204 extractant extraction process, the P204 extractant is firstly saponified and then extracted, countercurrent extraction is adopted, the number of extraction stages is 7, the mole ratio of the saponified P204 extractant added in the same time to the iron in the added second filtrate is 3.02:1, the washing liquid adopted in the washing process of the obtained extracted organic phase is 0.65mol/L sulfuric acid solution, the volume flow ratio of the extracted organic phase to the washing liquid is 13:1, 8-stage countercurrent washing is adopted for washing, the washing liquid after washing is returned to be mixed with the second filtrate and then extracted, the washed organic phase is subjected to back extraction by adopting phosphoric acid solution, the concentration of the phosphoric acid solution is 1.2mol/L, the washed organic phase is added with phosphoric acid, stirring and mixing are carried out for 50min, the mole ratio of the added phosphoric acid to the mole ratio of the iron in the washed organic phase is 1.035:1, and (3) centrifugally separating the reacted materials to obtain iron phosphate and a P204 extractant, adding sulfonated kerosene into the iron phosphate for washing, centrifugally separating, returning the separated liquid to be mixed with the P204 extractant for use, adding hot water into the separated solid for washing, and drying to obtain the battery-grade iron phosphate.
The ratio of the total mole number of nickel, cobalt, zinc, lead, cadmium and copper in the raffinate in the step (3) to the mole number of the added ammonium sulfide is 1:1.35, and the ratio of the mole number of the added ammonium fluoride to the total mole number of calcium and magnesium in the solution after the heavy metals are removed is 1.5: 1.
The ratio of the mole number of the ammonium carbonate added in the step (4) to the total mole number of the manganese and lithium in the third filtrate is 2.65: 3.
The molar ratio of lithium, manganese, iron, phosphorus and titanium in the slurry obtained in the step (5) is 1.05: 0.405: 0.61: 1.015: 0.013 percent, the mass fraction of solid in the slurry is 26 percent, in the spray drying process, the air inlet temperature is 245 ℃, the discharging temperature is less than or equal to 80 ℃, and a centrifugal spray drying mode is adopted, so that the particle size of the fog drops is 1-20 microns, and the mass fraction of the discharged water is less than 1 percent.
The total period of the calcination process is 28h, wherein the temperature rise time is 8h, the heat preservation time is 12h, the rest is the temperature reduction time, the heat preservation temperature is 790 ℃, nitrogen is continuously introduced in the calcination process, and the volume of the introduced nitrogen in the same time is 480 times of the volume of the furnace-entering spray drying material.
And stopping crushing when the particle size of the crushed material is 1.9 mu m, sieving the crushed material by a 120-mesh sieve, adopting nitrogen as a gas source in the crushing process, heating the nitrogen to 145 ℃ at the same time, and performing the processes of sieving, deironing and packaging on the crushed material in a packaging room, wherein the constant temperature of the packaging room is 22 ℃ and the constant humidity is 8%.
The mass ratio of the dispersing agent and the carbon source added in the step (5) is 0.8:9.2, the dispersing agent is polyethylene glycol, the carbon source is sucrose, and the dispersing agent and the carbon source are added so that the carbon content in the finally obtained lithium manganese iron phosphate is 1.9%.
The materials obtained in examples 1/2 and 3 were tested and the data are as follows:
Figure BDA0002421040450000101
Figure BDA0002421040450000111
the measurement method of the compacted density comprises the following steps: weighing a certain weight of crushed material (2g), putting into a compaction density tester, and pressing under the pressure of 4T until the volume of the powder is not changed, wherein the mass/volume is the compaction density of the powder.
The SEM of the lithium iron phosphate obtained in examples 1, 2, and 3 of the present invention is shown in fig. 1/2 and 3, and the particles are spheroidal particles and the size of the single crystal particles is 50 to 500nm as seen from the scanning electron microscope.
As can be seen from fig. 4, the spray-dried material obtained in example 1 was an agglomerate composed of particles having a primary particle size of about 50nm, and such particles were more likely to undergo a solid-phase reaction because the particles in the agglomerate were in close contact with each other during the sintering process. The lithium iron phosphate materials obtained in examples 1/2 and 3 were assembled into a power button in the following specific manner:
mixing a positive electrode material, conductive graphite and PVDF according to a mass ratio of 90:5:5, adding NMP for homogenizing, coating on an aluminum foil, drying, compacting the positive electrode plate material to 2.2g/mL, then taking metal lithium as a negative electrode, taking a diaphragm as a 2400 type polypropylene film of Celgard company, taking 1mo/L lithium hexafluorophosphate as electrolyte, taking EC/DMC with a volume ratio of 1:1 as solvent, assembling into a CR2032 power-on glove box under the protection of argon, testing by using a battery testing system at 25 ℃, and measuring the charging and discharging voltage to be 2.0-4.5V;
the final test data is as follows:
example 1 Example 2 Example 3
0.1C first charge capacity (mAh/g) 162.3 162.2 161.9
0.1C first discharge capacity (mAh/g) 156.9 156.2 156.7
0.5C first discharge capacity (mAh/g) 152.3 152.4 152.3
1C first discharge capacity (mAh/g) 148.4 149.3 148.7
Constant temperature of 25 ℃ and capacity retention rate after 100 cycles of 1C 95.1% 95.1% 95.2%
Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered in the claims of the present invention.

Claims (10)

1. The preparation method of the lithium iron manganese phosphate is characterized by comprising the following steps of:
1) mixing the waste lithium iron phosphate material and the waste lithium manganate material together, so that the molar ratio of ferromanganese in the mixture is 1: 1.52-1.55, then adding a hydrochloric acid solution, stirring and reacting for 2-3h at the temperature of 60-80 ℃, and filtering to obtain a first filtrate and a first filter residue;
2) adding an acid-base regulator into the first filtrate to regulate the pH value of the solution to be 1-1.5, then adding a heavy metal capture agent, reacting at the temperature of 40-50 ℃ for 30-45min, then filtering to obtain a second filtrate and a second filter residue, extracting the second filtrate by using a P204 extracting agent, washing the obtained extracted organic phase by using a washing solution, performing back extraction by using a phosphoric acid solution, and performing centrifugal separation to obtain iron phosphate and the P204 extracting agent;
3) adjusting the pH of the raffinate extracted in the step (2) to 2-2.5, adding an ammonium sulfide solution, reacting at the temperature of 40-55 ℃ for 1-2h, then adding ammonia water to adjust the pH of the solution to 4.5-5.5, then adding ammonium fluoride, heating to the temperature of 90-95 ℃, stirring for reacting for 2-4h, then filtering to obtain a third filtrate and a third filter residue,
4) adding ammonium carbonate into the third filtrate, reacting for 2-3h at 40-50 deg.C under stirring, heating to 80-90 deg.C, reacting for 15-30min under stirring, and filtering to obtain fourth filtrate and fourth residue;
5) adding water into the fourth filter residue and the iron phosphate, battery-grade lithium carbonate and titanium dioxide obtained in the step (2) for slurrying, adding a phosphoric acid solution, stirring and dispersing to obtain a slurried material, adding a dispersing agent and a carbon source, stirring and dispersing, removing iron through a 10-15-grade pipeline iron remover, removing iron through a 2-4-grade electromagnetic slurry iron remover, and spray-drying to obtain a dried material;
6) and calcining the dried material at high temperature under the protection of nitrogen to obtain a calcined material, and crushing, screening, deironing and packaging to obtain the lithium iron manganese phosphate.
2. The method for preparing lithium iron manganese phosphate according to claim 1, wherein the method comprises the following steps: the concentration of the hydrochloric acid solution in the step (1) is 2-4mol/L, and the ratio of the total mole number of ferromanganese in the added mixture to the mole number of the added hydrochloric acid is 1: 2.2-2.5, and returning the first filter residue to be leached again together with the mixture.
3. The method for preparing lithium iron manganese phosphate according to claim 1, wherein the method comprises the following steps: and (3) adding a heavy metal trapping agent into hydrochloric acid or ammonia water as an acid-base regulator in the step (2) to enable the total concentration of nickel, cobalt, zinc, lead, cadmium and copper in the second filtrate to be lower than 500 mg/L.
4. The method for preparing lithium iron manganese phosphate according to claim 1, wherein the method comprises the following steps: the second filtrate in the step (2) adopts a P204 extractant extraction process, the P204 extractant is firstly saponified and then extracted, countercurrent extraction is adopted, the number of extraction stages is 6-8, the mole ratio of the saponified P204 extractant added in the same time to the iron in the added second filtrate is 3-3.05:1, the obtained extracted organic phase adopts 0.5-0.75mol/L sulfuric acid solution in the washing process, the volume flow ratio of the extracted organic phase to the washing solution is 12-15:1, 6-8 stages of countercurrent washing is adopted for washing, the washed washing solution returns to be mixed with the second filtrate and then is extracted, the washed organic phase adopts phosphoric acid solution for back extraction, the concentration of the phosphoric acid solution is 0.5-1.5mol/L, the washed organic phase is added with phosphoric acid and stirred and mixed for 30-60min, the ratio of the mole number of the added phosphoric acid to the mole number of the iron in the washed organic phase is 1.02-1.05:1, the reacted materials are centrifugally separated to obtain iron phosphate and a P204 extracting agent, the iron phosphate is added with sulfonated kerosene for washing and then centrifugally separated, the separated liquid is returned to be mixed with the P204 extracting agent for use, the separated solid is added with hot water for washing, and then the solid is dried to obtain the battery-grade iron phosphate.
5. The method for preparing lithium iron manganese phosphate according to claim 1, wherein the method comprises the following steps: the ratio of the total mole number of nickel, cobalt, zinc, lead, cadmium and copper in the raffinate in the step (3) to the mole number of the added ammonium sulfide is 1:1.2-1.5, and the ratio of the mole number of the added ammonium fluoride to the total mole number of calcium and magnesium in the solution after the heavy metal is removed is 1.3-1.5: 1.
6. The method for preparing lithium iron manganese phosphate according to claim 1, wherein the method comprises the following steps: the ratio of the mole number of the ammonium carbonate added in the step (4) to the total mole number of the manganese and lithium in the third filtrate is 2.6-2.8: 3.
7. The method for preparing lithium iron manganese phosphate according to claim 1, wherein the method comprises the following steps: the molar ratio of lithium, manganese, iron, phosphorus and titanium in the slurry obtained in the step (5) is 1.03-1.05: 0.4-0.41: 0.6-0.61: 1.01-1.02: 0.01-0.015 percent, the mass fraction of solid in the slurry is 25-30 percent, the spray drying process, the air inlet temperature is 230-.
8. The method for preparing lithium iron manganese phosphate according to claim 1, wherein the method comprises the following steps: the total period of the calcination process is 25-28h, wherein the temperature rise time is 5-8h, the heat preservation time is 10-12h, the rest is the temperature reduction time, the heat preservation temperature is 770-800 ℃, nitrogen is continuously introduced in the calcination process, and the volume of the introduced nitrogen in the same time is 500 times of the volume of the furnace-entering spray drying material.
9. The method for preparing lithium iron manganese phosphate according to claim 1, wherein the method comprises the following steps: and stopping crushing when the particle size of the crushed material is 1.5-2.5 mu m, sieving by a sieve of 80-150 meshes, adopting nitrogen as a gas source in the crushing process, heating the nitrogen to the temperature of 120-150 ℃, and performing sieving, iron removal and packaging on the crushed material in a packaging room, wherein the constant temperature of the packaging room is 15-25 ℃, and the constant humidity is 5-10%.
10. The method for preparing lithium iron manganese phosphate according to claim 1, wherein the method comprises the following steps: the mass ratio of the dispersing agent and the carbon source added in the step (5) is 0.5-1:9-9.5, the dispersing agent is polyethylene glycol, the carbon source is at least one of glucose, sucrose and starch, and the dispersing agent and the carbon source are added to enable the carbon content in the finally obtained lithium manganese iron phosphate to be 1.5-2.0%.
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