CN113120876B - Method for preparing lithium iron phosphate material by regenerating and recycling waste lithium iron phosphate pole pieces - Google Patents
Method for preparing lithium iron phosphate material by regenerating and recycling waste lithium iron phosphate pole pieces Download PDFInfo
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Abstract
The invention relates to the technical field of lithium battery recovery, and discloses a method for preparing a lithium iron phosphate material by regenerating and recovering waste lithium iron phosphate pole pieces. The method adopts a wet stripping technology, firstly, the lithium iron phosphate active substance is efficiently stripped from the waste lithium iron phosphate pole piece, and the lithium iron phosphate material is prepared by recovering and regenerating the lithium iron phosphate active substance. The method for recycling the waste lithium iron phosphate pole pieces can realize the recycling of all components of lithium, iron and phosphorus, so that the scrapped lithium iron phosphate battery can be well recycled.
Description
Technical Field
The invention relates to the technical field of lithium battery recovery, in particular to a method for preparing a lithium iron phosphate material by regenerating and recovering waste lithium iron phosphate pole pieces.
Background
The new energy automobile industry in China already advances to the motorway, and the new energy automobile output and sale volume in China leaps the first in the world in nearly 5 years. The service life of the power battery serving as the most core part of a new energy automobile is usually 3-5 years, the retired amount of the power battery is estimated to reach 20 ten thousand tons in 2020 and 130 ten thousand tons in 2030, wherein the lithium iron phosphate battery accounts for more than 60% of the total retired amount.
Some of the retired lithium iron phosphate batteries can be used for gradient utilization according to the performance of the retired lithium iron phosphate batteries, some of the retired lithium iron phosphate batteries directly enter scrapping regeneration, and no matter which recovery form power battery finally enters scrapping regeneration stage. And disassembling the scrapped lithium iron phosphate battery to obtain a positive plate, a negative plate, a diaphragm, a shell and the like.
The lithium iron phosphate positive plate is rich in valuable metal lithium with recovery value, and becomes an important circulation form in the battery recovery industry.
At present, the recovery technology of the scrapped lithium iron phosphate mainly focuses on recovering lithium from waste pole pieces or active materials, and the research technology of all-component recovery is relatively few. In the aspect of industrialization, most lithium iron phosphate recovery businesses mainly recover lithium to prepare lithium carbonate or a crude lithium salt product, and iron and phosphorus are usually discarded in the form of solid waste residues, so that environmental resource waste and environmental hazard are caused.
However, under the situation that the competition of the recycling market is increasingly severe, the waste lithium iron phosphate battery recycling enterprises can not realize profit only by recycling lithium metal, so that the enthusiasm of the waste lithium iron phosphate battery recycling enterprises is low, a lot of scrapped lithium iron phosphate batteries are not well recycled, and the healthy sustainable development of the new energy industry is hindered in the long term.
Therefore, a method capable of simultaneously recovering all components such as lithium, iron and phosphorus from the scrapped lithium iron phosphate battery has been developed.
Disclosure of Invention
The invention aims to solve the problem that the scrapped lithium iron phosphate battery in the prior art cannot simultaneously recover all components such as lithium, iron, phosphorus and the like.
In order to achieve the purpose, the invention provides a method for preparing a lithium iron phosphate material by regenerating and recycling waste lithium iron phosphate pole pieces, which comprises the following steps:
(1) carrying out contact reaction I on a waste battery pole piece containing lithium iron phosphate and an alkaline solvent I to obtain a mixed slurry I, and filtering the mixed slurry I to obtain a lithium iron phosphate active substance and a first solution;
(2) mixing and dissolving the lithium iron phosphate active material and a solvent A to obtain mixed slurry II; in the presence of oxidizing gas, carrying out contact reaction II on the mixed slurry II and an acidic solvent to obtain a mixed solution I, and filtering the mixed solution I to obtain leaching residues and a leaching mother liquor;
the conditions of the contact reaction II at least comprise: stirring at 10-60rpm under 0.1-1.0MPa for 0.5-5 hr;
(3) mixing the leaching mother liquor with an alkaline solvent II to adjust the pH value of the leaching mother liquor to 2.5-4.5 to obtain a mixed solution II, and filtering the mixed solution II to obtain an iron precipitation mother liquor and iron precipitation slag containing ferric phosphate;
(4) in the presence of an alkaline solvent III, carrying out contact reaction III on the iron precipitation mother liquor and a magnesium salt to obtain a mixed solution III, and filtering the mixed solution III to obtain a lithium-containing purification solution and phosphorus-magnesium slag; carrying out a contact reaction IV on the lithium-containing purified liquid and carbonate to obtain lithium carbonate;
(5) in the presence of a solvent B, the iron precipitation slag, the lithium carbonate and a carbon source are contacted and mixed to obtain a mixed slurry III, and the mixed slurry III is dried and roasted sequentially.
The method for recycling the waste lithium iron phosphate pole pieces can realize the recycling of all components of lithium, iron and phosphorus, so that the scrapped lithium iron phosphate battery can be well recycled.
The inventors have also found that lithium iron phosphate materials having excellent electrochemical properties can be prepared by using lithium carbonate and iron phosphate recovered by the method of the present invention as raw materials.
Drawings
FIG. 1 is a process flow diagram of a preferred embodiment of the process of the present invention;
fig. 2 is a scanning electron microscope image of the lithium iron phosphate material prepared in example 1 of the present invention;
fig. 3 is a scanning electron microscope image of the lithium iron phosphate material prepared in example 2 of the present invention;
fig. 4 is an X-ray diffraction pattern of the lithium iron phosphate material prepared in example 1 of the present invention;
fig. 5 is a voltammogram of the lithium iron phosphate material prepared in example 1 of the present invention.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
In the present invention, the pressures are gauge pressures unless otherwise specified.
In the present invention, the normal temperature is 25. + -. 2 ℃ unless otherwise stated.
In the present invention, unless otherwise specified, the average particle size of the mixed slurry III indicates a particle size corresponding to a cumulative percentage of particle size distribution of the mixed slurry III of 50%.
As mentioned above, the present invention provides a method for preparing a lithium iron phosphate material by regenerating and recycling a waste lithium iron phosphate pole piece, which comprises the following steps:
(1) carrying out contact reaction I on a waste battery pole piece containing lithium iron phosphate and an alkaline solvent I to obtain a mixed slurry I, and filtering the mixed slurry I to obtain a lithium iron phosphate active substance and a first solution;
(2) mixing and dissolving the lithium iron phosphate active material and a solvent A to obtain mixed slurry II; in the presence of oxidizing gas, carrying out contact reaction II on the mixed slurry II and an acidic solvent to obtain a mixed solution I, and filtering the mixed solution I to obtain leaching residues and a leaching mother liquor;
the conditions of the contact reaction II at least comprise: stirring at 10-60rpm under 0.1-1.0MPa for 0.5-5 hr;
(3) mixing the leaching mother liquor with an alkaline solvent II to adjust the pH value of the leaching mother liquor to 2.5-4.5 to obtain a mixed solution II, and filtering the mixed solution II to obtain an iron precipitation mother liquor and iron precipitation slag containing ferric phosphate;
(4) in the presence of an alkaline solvent III, carrying out contact reaction III on the iron precipitation mother liquor and a magnesium salt to obtain a mixed solution III, and filtering the mixed solution III to obtain a lithium-containing purification solution and phosphorus-magnesium slag; carrying out a contact reaction IV on the lithium-containing purified liquid and carbonate to obtain lithium carbonate;
(5) in the presence of a solvent B, the iron precipitation slag, the lithium carbonate and a carbon source are contacted and mixed to obtain a mixed slurry III, and the mixed slurry III is dried and roasted sequentially.
In the invention, the waste lithium iron phosphate pole pieces are positive pole pieces disassembled from waste lithium iron phosphate batteries without a reverse explanation. Preferably, the lithium content in the waste lithium iron phosphate pole piece is 3.5-4.0 wt%.
Preferably, in the step (1), the alkaline solvent I is at least one selected from sodium hydroxide and ammonia water.
Preferably, in step (1), the conditions of the contact reaction I at least include: the ultrasonic frequency is 20-40KHz, the temperature is 10-80 deg.C, and the time is 1-5 h. More preferably, in step (1), the conditions of the contact reaction I at least include: the ultrasonic frequency is 30-40KHz, the temperature is 40-80 deg.C, and the time is 1-3 h.
The method has no special requirement on the dosage of the alkaline solvent I in the step (1), and only needs to be capable of completely soaking the waste battery pole piece.
According to a particularly preferred embodiment, in step (1), the method further comprises: before the contact reaction I is carried out, shearing the waste pole piece of the battery containing the lithium iron phosphate to obtain fragments with the side length of 20-40mm, and cleaning the fragments.
The invention has no special requirements on the operation steps of cleaning and selection of cleaning solvent, and only needs to clean impurities such as aluminum scraps in the fragments. Illustratively, the pieces are washed with water at ambient temperature.
Preferably, in step (2), the oxidizing gas is selected from at least one of air, oxygen, ozone, and chlorine. The invention has no special requirement on the dosage of the oxidizing gas, and only needs to ensure that the pressure in the oxidation reaction process can reach 0.1-1.0 MPa.
Preferably, in the step (2), the acidic solvent is selected from at least one of hydrochloric acid, sulfuric acid, and nitric acid.
Preferably, in the step (2), the usage mass ratio of the lithium iron phosphate active material to the solvent a is 1: 1-6, preferably 1: 2-4.
The invention has no special limitation on the mixing and dissolving conditions, and only needs to completely dissolve the iron precipitation slag. Preferably, in step (2), the conditions of the mixed dissolution at least include: the stirring speed is 10-60rpm, and the temperature is 20-100 ℃. More preferably, in step (2), the conditions of the mixed dissolution at least include: the stirring speed is 10-30rpm, and the temperature is 20-60 ℃.
Preferably, in step (2), the conditions of the contact reaction II include at least: the stirring speed is 20-40rpm, the pressure is 0.1-0.25MPa, and the time is 1-3 h. In this preferable case, the leaching rate of lithium ions can be increased, and further, a larger amount of lithium carbonate product can be recovered.
In step (2) of the present invention, the temperature of the contact reaction II is not particularly required, and is typically normal temperature.
Preferably, in the step (3), the operation step of mixing the leaching mother liquor with the alkaline solvent II comprises: adding the alkaline solvent II into the leaching mother liquor at a speed of 10-15mL/min at a temperature of 60-80 ℃ for every 2L of the leaching mother liquor so as to adjust the pH value of the leaching mother liquor to 2.5-4.5. The inventors found that in this preferable case, the leaching rate of lithium element is made higher.
Preferably, in the step (4), the magnesium salt is selected from at least one of magnesium chloride, magnesium sulfate and magnesium nitrate.
In order to avoid more impurities in the system, the type of the magnesium salt in the invention corresponds to the type of the three-acid solvent, and when the acid solvent is sulfuric acid, the magnesium salt is magnesium sulfate; when the acid solvent is hydrochloric acid and nitric acid respectively, the magnesium salt is magnesium chloride and magnesium nitrate respectively correspondingly.
Preferably, in the step (4), the mass ratio of the iron precipitation mother liquor to the magnesium salt is 150-200: 1.
Preferably, in step (4), the conditions of the contact reaction III include at least: the temperature is 80-100 ℃ and the time is 0.5-5 h. More preferably, in step (4), the conditions of the contact reaction III include at least: the temperature is 80-90 ℃ and the time is 1-3 h.
Preferably, in step (4), the conditions of the contact reaction IV include at least: the temperature is 80-95 ℃ and the time is 0.5-2 h. More preferably, in step (4), the conditions of the contact reaction IV include at least: the temperature is 80-90 ℃ and the time is 1-2 h.
Preferably, in step (5), the carbon source is selected from at least one of sucrose, glucose and polyvinyl alcohol.
In the invention, the iron precipitation slag is used as a phosphorus source and an iron source, and the lithium carbonate is used as a lithium source. According to the invention, additional lithium carbonate can be introduced as a lithium source according to the requirement, and additional iron phosphate is introduced as a phosphorus source and an iron source. The invention has no special requirement on the introduced additional quantities of lithium carbonate and iron phosphate, and only needs to ensure that the molar ratio of the total quantity of lithium carbonate calculated by lithium element to the total quantity of iron phosphate calculated by iron element in a reaction system is 1-1.5: 1.
preferably, in the step (5), the carbon source is used in an amount of 0.45 to 1.2 wt% based on the total amount of lithium carbonate.
According to a particularly preferred embodiment, in step (5), the drying treatment is spray drying.
Preferably, in step (5), the conditions of the drying treatment include at least: the temperature is 150 ℃ and 250 ℃.
More preferably, in step (5), the conditions of the drying treatment include at least: the temperature is 200-250 ℃. With the preferred embodiment, a lithium iron phosphate material having more excellent electrochemical performance can be obtained.
The invention has no special requirement on the drying time, and only needs to dry the mixed slurry III into a powder form.
Preferably, in the step (5), the roasting conditions at least include: the temperature is 600 ℃ and 850 ℃, and the time is 2-10 h. More preferably, in step (5), the roasting conditions at least include: the temperature is 750 ℃ and 850 ℃ and the time is 5-8 h.
According to a particularly preferred embodiment, in step (5), the method further comprises: and grinding the materials obtained after the iron precipitation slag, the lithium carbonate and the carbon source are contacted and mixed to obtain the mixed slurry III with the average particle size of 50-500 nm.
Preferably, the solvent a is the same as the solvent B and is water. Illustratively, the solvent a and the solvent B are both deionized water.
Preferably, the basic solvent I, the basic solvent II and the basic solvent III are the same, and the basic solvent I is selected from at least one of sodium hydroxide and ammonia water.
In the present invention, "I", "II", "III" and "IV" in the contact reaction I, II, III, IV and the like are used only to indicate that four contact reactions are involved, and not the same contact reaction, but they do not represent the order unless otherwise specified.
The invention has no special requirements on the specific operation of the filtration, and only needs to realize solid-liquid separation.
The process flow of a preferred embodiment of the method for preparing battery-grade lithium carbonate from lithium iron phosphate waste material according to the present invention is provided below with reference to fig. 1:
(1) shearing the waste battery pole pieces to obtain fragments with the side length of 20-40mm, cleaning the fragments, carrying out contact reaction I on the cleaned fragments and an alkaline solvent I to obtain a mixed slurry I, and filtering the mixed slurry I to obtain a lithium iron phosphate active substance and a first solution;
(2) mixing and dissolving the lithium iron phosphate active material and water to obtain mixed slurry II; in the presence of oxidizing gas, carrying out contact reaction II on the mixed slurry II and an acidic solvent to obtain a mixed solution I, and filtering the mixed solution I to obtain leaching residues and a leaching mother liquor; the conditions of the contact reaction II at least comprise: stirring at 10-60rpm under 0.1-1.0MPa for 0.5-5 hr;
(3) mixing the leaching mother liquor with an alkaline solvent II to adjust the pH value of the leaching mother liquor to 2.5-4.5 to obtain a mixed solution II, and filtering the mixed solution II to obtain an iron precipitation mother liquor and iron precipitation slag containing ferric phosphate;
(4) in the presence of an alkaline solvent III, carrying out contact reaction III on the iron precipitation mother liquor and a magnesium salt to obtain a mixed solution III, and filtering the mixed solution III to obtain a lithium-containing purification solution and phosphorus-magnesium slag; carrying out a contact reaction IV on the lithium-containing purified liquid and carbonate to obtain lithium carbonate;
(5) in the presence of a solvent B, mixing the iron precipitation slag, the lithium carbonate and additionally added lithium carbonate and iron phosphate to obtain slurry, grinding the slurry after the slurry is contacted and mixed with a carbon source to obtain mixed slurry III, and sequentially carrying out spray drying and roasting on the mixed slurry III.
The present invention will be described in detail below by way of examples.
In the following examples, various raw materials and instruments used are commercially available unless otherwise specified.
Battery waste pole piece: purchased from Jiangxi Jianfeng cycle science and technology Co., Ltd, wherein the content of lithium element, iron element and phosphorus element in the waste battery materials is 3.7 wt%, 29.8 wt% and 16.5 wt% based on the total mass of the waste battery pole pieces; the contents of lithium element, iron element and phosphorus element are all measured by an Inductively Coupled Plasma (ICP);
magnesium chloride hexahydrate: purchased from west longs chemical gmbh;
magnesium sulfate heptahydrate: purchased from west longs chemical gmbh;
sodium hydroxide: purchased from west longs chemical gmbh;
hydrochloric acid: 36 wt% concentration, purchased from Shigaku chemical Co., Ltd;
concentrated sulfuric acid: 98 wt% concentration, purchased from Wuhanxin China pine chemical Co., Ltd;
carbonate salt: anhydrous sodium carbonate, available from west longe chemical gmbh;
carbon source: polyvinyl alcohol, brand 2488, purchased from Shanghai minister and promoter chemical science and technology Co., Ltd;
a reaction tank: type GSH-10L, purchased from Kalia Ensifera Usta chemical machinery Co., Ltd;
ultrasonic cleaning tank: model BNX-S80, available from Changzhou pioneer drying engineering Co., Ltd, Toguan Mingfeng environmental protection and purification equipment Co., Ltd;
a peristaltic pump: model BT102S, available from Cinderson fluid technology, Inc.;
a spray dryer: model LPG-5, available from Changzhou pioneer Dry engineering, Inc.;
nitrogen atmosphere furnace: model SK-G08163, available from Zhonghuan electric furnace, Inc. of Tianjin;
in the following examples, the solids content is calculated as: { (total mass of lithium carbonate in slurry + total mass of iron phosphate in slurry)/(total mass of lithium carbonate in slurry + total mass of iron phosphate in slurry + added amount of deionized water) } × 100%.
Example 1
The embodiment provides a method for preparing a lithium iron phosphate material by regenerating and recycling waste lithium iron phosphate pole pieces, which specifically comprises the following steps:
(1) cutting waste pole pieces of a battery containing lithium iron phosphate into fragments with the size of 20mm multiplied by 20mm, soaking the fragments in water for 5min, adding 1500g of the soaked fragments into an ultrasonic cleaning tank (the ultrasonic frequency is 30KHz and the temperature is 40 ℃) containing a sodium hydroxide solution (the concentration is 5 wt%) to soak for 2h to obtain mixed slurry I, and filtering the mixed slurry I to obtain a lithium iron phosphate active substance and a first solution; the first solution is circulated in the system as sodium hydroxide solution;
(2) adding 1000g of the obtained lithium iron phosphate active substance and 4000g of deionized water into a reaction tank at normal temperature, adding 700g of hydrochloric acid with the concentration of 31 wt%, sealing, filling chlorine gas until the pressure in the reaction tank reaches 0.2MPa, stirring at 40rpm, maintaining for 2 hours, then releasing pressure to obtain a mixed solution I, and filtering the mixed solution I to obtain leaching residues and a leaching mother solution;
(3) adding all the obtained leaching mother liquor into a 2L three-neck flask under the condition of 60 ℃ water bath, pumping a 5 wt% sodium hydroxide solution at the speed of 10mL/min by using a peristaltic pump, monitoring the pH value of the liquid in the system on line, pumping the sodium hydroxide solution until the pH value of the liquid in the system reaches 3.5 to obtain a mixed solution II, and filtering the mixed solution II to obtain 1066g of iron precipitation mother liquor and iron precipitation slag containing ferric phosphate;
(4) adding 24g of magnesium chloride hexahydrate into all the obtained iron precipitation mother liquor at 80 ℃, adding a sodium hydroxide solution with the concentration of 5 wt%, simultaneously monitoring the pH value of the liquid in the system on line, introducing the sodium hydroxide solution until the pH value of the liquid in the system reaches 12 to obtain a mixed solution III, and filtering the mixed solution III to obtain a lithium-containing purified liquid and 13.5g of phosphorus-magnesium slag;
(5) adding sodium carbonate into all the obtained lithium-containing purified liquid at the temperature of 80 ℃, and reacting for 2 hours to obtain 145g of lithium carbonate;
(6) 1066g of the iron phosphate obtained previously and 145g of lithium carbonate were mixed, and additional 87.1g of lithium carbonate and 51.2g of iron phosphate were added, so that the molar ratio of the total amount of lithium carbonate in terms of lithium element to the total amount of iron phosphate in terms of iron element was 1.05: 1, adding deionized water to obtain slurry with the solid content of 15%, adding 50g of polyvinyl alcohol, mixing, and grinding to obtain mixed slurry III with the average particle size of 55 nm;
(7) and introducing all the obtained mixed slurry III into a spray dryer at the temperature of 200 ℃ to obtain a lithium iron phosphate precursor, and roasting the lithium iron phosphate precursor in a nitrogen atmosphere furnace at the temperature of 750 ℃ for 5 hours to obtain 944g of the lithium iron phosphate material.
Example 2
The embodiment provides a method for preparing a lithium iron phosphate material by regenerating and recycling waste lithium iron phosphate pole pieces, which specifically comprises the following steps:
(1) cutting waste pole pieces of a battery containing lithium iron phosphate into fragments with the size of 20mm multiplied by 40mm, soaking the fragments in water for 5min, adding 1500g of the soaked fragments into an ultrasonic cleaning tank (the ultrasonic frequency is 30KHz and the temperature is 40 ℃) containing a sodium hydroxide solution (the concentration is 5 wt%) to soak for 2h to obtain mixed slurry I, and filtering the mixed slurry I to obtain a lithium iron phosphate active substance and a first solution; the first solution is circulated in the system as sodium hydroxide solution;
(2) at normal temperature, adding 1000g of the obtained lithium iron phosphate active substance and 4000g of deionized water into a reaction tank, adding 626g of concentrated sulfuric acid with the concentration of 98 wt%, sealing, filling chlorine gas until the pressure in the reaction tank reaches 0.25MPa, stirring at 40rpm, maintaining for 2 hours, then releasing pressure to obtain a mixed solution I, and filtering the mixed solution I to obtain leaching residues and a leaching mother solution;
(3) adding all the obtained leaching mother liquor into a 2L three-neck flask under the condition of water bath at 60 ℃, pumping a sodium hydroxide solution with the concentration of 5 wt% by using a peristaltic pump at the speed of 10mL/min, simultaneously monitoring the pH value of liquid in a system on line, pumping the sodium hydroxide solution until the pH value of the liquid in the system reaches 2.5 to obtain a mixed solution II, and filtering the mixed solution II to obtain an iron precipitation mother liquor and 1125g of iron precipitation slag containing ferric phosphate;
(4) adding 30g of magnesium sulfate heptahydrate into the obtained total iron precipitation mother liquor at 90 ℃, then adding a 5 wt% sodium hydroxide solution, simultaneously monitoring the pH value of the liquid in the system on line, introducing the sodium hydroxide solution until the pH value of the liquid in the system reaches 13 to obtain a mixed solution III, and filtering the mixed solution III to obtain a lithium-containing purified liquid and 15g of phosphorus-magnesium slag;
(5) adding sodium carbonate into all the obtained lithium-containing purified liquid at the temperature of 80 ℃, and reacting for 2 hours to obtain 142g of lithium carbonate;
(6) 1125g of the iron phosphate obtained previously and 142g of lithium carbonate, as well as additional lithium carbonate and iron phosphate were added and mixed so that the molar ratio of the total amount of lithium carbonate in terms of lithium element to the total amount of iron phosphate in terms of iron element was 1.05: 1, adding deionized water to obtain slurry with the solid content of 15%, adding 40g of polyvinyl alcohol, mixing, and grinding to obtain mixed slurry III with the average particle size of 150 nm;
(7) and introducing all the obtained mixed slurry III into a spray dryer at the temperature of 200 ℃ to obtain a lithium iron phosphate precursor, and roasting the lithium iron phosphate precursor in a nitrogen atmosphere furnace at the temperature of 820 ℃ for 8 hours to obtain 984g of a lithium iron phosphate material.
Example 3
The embodiment provides a method for preparing a lithium iron phosphate material by regenerating and recycling waste lithium iron phosphate pole pieces, which specifically comprises the following steps:
(1) cutting waste pole pieces of a battery containing lithium iron phosphate into fragments with the size of 20mm multiplied by 40mm, soaking the fragments in water for 5min, adding 1500g of the soaked fragments into an ultrasonic cleaning tank (the ultrasonic frequency is 30KHz and the temperature is 40 ℃) containing a sodium hydroxide solution (the concentration is 5 wt%) to soak for 2h to obtain mixed slurry I, and filtering the mixed slurry I to obtain a lithium iron phosphate active substance and a first solution; the first solution is circulated in the system as sodium hydroxide solution;
(2) at normal temperature, adding 1000g of the obtained lithium iron phosphate active substance and 4000g of deionized water into a reaction tank, then adding 690g of hydrochloric acid with the concentration of 31 wt%, sealing, filling chlorine gas until the pressure in the reaction tank reaches 0.1MPa, stirring at 30rpm, maintaining for 3 hours, then releasing pressure to obtain a mixed solution I, and filtering the mixed solution I to obtain leaching residues and a leaching mother solution;
(3) adding all the obtained leaching mother liquor into a 2L three-neck flask under the condition of water bath at 60 ℃, pumping a sodium hydroxide solution with the concentration of 5 wt% by using a peristaltic pump at the speed of 10mL/min, simultaneously monitoring the pH value of liquid in a system on line, pumping the sodium hydroxide solution until the pH value of the liquid in the system reaches 2.5 to obtain a mixed solution II, and filtering the mixed solution II to obtain 1109g of precipitated iron mother liquor and precipitated iron slag containing ferric phosphate;
(4) adding 24g of magnesium chloride hexahydrate into all the obtained iron precipitation mother liquor at 90 ℃, adding a 5 wt% sodium hydroxide solution, monitoring the pH value of the liquid in the system on line, introducing the sodium hydroxide solution until the pH value of the liquid in the system reaches 14 to obtain a mixed solution III, and filtering the mixed solution III to obtain lithium-containing purified liquid and 17.5g of phosphorus-magnesium slag;
(5) adding sodium carbonate into all the obtained lithium-containing purified liquid at 90 ℃, and reacting for 3 hours to obtain 139g of lithium carbonate;
(6) 1109g of the iron phosphate and 139g of lithium carbonate obtained in the previous step, and 96.3g of additional lithium carbonate and 23.6g of iron phosphate were added and mixed, so that the molar ratio of the total lithium carbonate usage in terms of lithium element to the total iron phosphate usage in terms of iron element was 1.05: 1, adding deionized water to obtain slurry with the solid content of 15%, adding 40g of polyvinyl alcohol, mixing, and grinding to obtain mixed slurry III with the average particle size of 350 nm;
(7) and introducing all the obtained mixed slurry III into a spray dryer at the temperature of 200 ℃ to obtain a lithium iron phosphate precursor, and roasting the lithium iron phosphate precursor in a nitrogen atmosphere furnace at the temperature of 790 ℃ for 6 hours to obtain 957g of a lithium iron phosphate material.
Example 4
The embodiment provides a method for preparing a lithium iron phosphate material by regenerating and recycling waste lithium iron phosphate pole pieces, which specifically comprises the following steps:
(1) cutting waste pole pieces of a battery containing lithium iron phosphate into fragments with the size of 20mm multiplied by 40mm, soaking the fragments in water for 5min, adding 1500g of the soaked fragments into an ultrasonic cleaning tank (the ultrasonic frequency is 30KHz and the temperature is 40 ℃) containing a sodium hydroxide solution (the concentration is 5 wt%) to soak for 2h to obtain mixed slurry I, and filtering the mixed slurry I to obtain a lithium iron phosphate active substance and a first solution; the first solution is circulated in the system as sodium hydroxide solution;
(2) adding 1000g of the obtained lithium iron phosphate active substance and 4000g of deionized water into a reaction tank at normal temperature, adding 675g of hydrochloric acid with the concentration of 31 wt%, sealing, filling chlorine gas until the pressure in the reaction tank reaches 0.2MPa, stirring at 30rpm, maintaining for 3 hours, then releasing pressure to obtain a mixed solution I, and filtering the mixed solution I to obtain leaching residues and a leaching mother solution;
(3) adding all the obtained leaching mother liquor into a 2L three-neck flask under the condition of water bath at 60 ℃, pumping a 5 wt% sodium hydroxide solution at the speed of 10mL/min by using a peristaltic pump, simultaneously monitoring the pH value of liquid in the system on line, pumping the sodium hydroxide solution until the pH value of the liquid in the system reaches 2.5 to obtain a mixed solution II, and filtering the mixed solution II to obtain an iron precipitation mother liquor and 1072g of iron precipitation slag containing ferric phosphate;
(4) adding 24g of magnesium chloride hexahydrate into the obtained total iron precipitation mother liquor at 85 ℃, adding a 5 wt% sodium hydroxide solution, monitoring the pH value of the liquid in the system on line, introducing the sodium hydroxide solution until the pH value of the liquid in the system reaches 13 to obtain a mixed solution III, and filtering the mixed solution III to obtain a lithium-containing purified liquid and 15.2g of phosphorus-magnesium slag;
(5) adding sodium carbonate into all the obtained lithium-containing purified liquid at 85 ℃ to react for 1h to obtain 153g of lithium carbonate;
(6) 1072g of the iron phosphate and 153g of lithium carbonate obtained previously, and additional lithium carbonate and iron phosphate were added and mixed so that the molar ratio of the total amount of lithium carbonate in terms of lithium element to the total amount of iron phosphate in terms of iron element was 1.05: 1, adding deionized water to obtain slurry with the solid content of 15%, adding 50g of polyvinyl alcohol, mixing, and grinding to obtain mixed slurry III with the average particle size of 150 nm;
(7) and introducing all the obtained mixed slurry III into a spray dryer at the temperature of 200 ℃ to obtain a lithium iron phosphate precursor, and roasting the lithium iron phosphate precursor in a nitrogen atmosphere furnace at the temperature of 790 ℃ for 6 hours to obtain 985g of the lithium iron phosphate material.
Example 5
The lithium iron phosphate material was prepared by regeneration and recovery according to the method of example 3, except that in the step (2), the pressure in the reaction tank was 0.5 MPa.
Example 6
A lithium iron phosphate material was prepared by regeneration and recovery in the same manner as in example 3, except that in step (7), the temperature in the spray dryer was 180 ℃.
Example 7
The difference of preparing the lithium iron phosphate material by regenerating and recycling according to the method of the embodiment 3 is that in the step (3), a sodium hydroxide solution with the concentration of 5 wt% is slowly dripped, the pH value of the liquid in the system is monitored on line, and the sodium hydroxide solution is introduced until the pH value of the liquid in the system reaches 3.5.
Comparative example 1
The lithium iron phosphate material is prepared by regeneration and recovery according to the method of example 3, except that in the step (2), 1000g of the obtained lithium iron phosphate active material and 4000g of deionized water are added into a reaction tank at normal temperature and normal pressure, 675g of hydrochloric acid with the concentration of 31 wt% is added, then chlorine gas is introduced for bubbling, and stirring reaction is carried out for 3 hours at 30 rpm.
Test example 1
The lithium iron carbonate materials prepared in the examples and the comparative examples are used as a positive electrode, a metal lithium sheet is used as a negative electrode, a lithium hexafluorophosphate solution is used as an electrolyte, polyethylene is used as a diaphragm, and a CR2032 battery is sequentially assembled, is kept stand for 12 hours, and is subjected to charge and discharge tests.
Charging and discharging test conditions: under the condition of 25 ℃, in a voltage interval of 2.7-4.3V, the battery is activated for three times at a multiplying power of 0.1C, then the battery is subjected to charge-discharge circulation for 200 times at a multiplying power of 1C, a Wuhan blue point tester (CT3002A) is adopted to detect the specific discharge capacity of the battery, and the capacity retention rate is calculated.
Wherein, the calculation formula of the capacity retention rate is as follows: (200 times of circulation 1C specific discharge capacity/1C specific discharge capacity) x 100%. The specific test results are shown in table 1.
TABLE 1
The results in table 1 show that the method for recycling the waste lithium iron phosphate pole pieces can not only realize the recycling of all lithium, phosphorus and iron components, but also ensure that the regenerated and recycled lithium iron phosphate material has excellent electrochemical properties.
In addition, the present invention exemplarily provides scanning electron micrographs of the lithium iron phosphate materials prepared in examples 1 and 2, and an X-ray diffraction pattern and a voltammogram of the lithium iron phosphate material prepared in example 1, which are respectively shown in fig. 2 to fig. 5.
The voltammogram was obtained by an electrochemical workstation (model number CHI760E) at a scanning speed of 0.1 mV/min.
Fig. 2 is a scanning electron microscope image of the lithium iron phosphate material prepared in example 1, and in fig. 2, (2a) and (2b) are electron microscope images of the lithium iron phosphate material prepared in example 1 at a magnification of 5000 and a magnification of 10000, respectively.
Fig. 3 is a scanning electron microscope image of the lithium iron phosphate material prepared in example 2, and in fig. 3, (3a) and (3b) are electron microscope images of the lithium iron phosphate material prepared in example 2 at a magnification of 5000 and a magnification of 10000, respectively.
As can be seen from fig. 2 and 3, the lithium iron phosphate material can be prepared by the method of the present invention.
FIG. 4 is an X-ray diffraction pattern of the lithium iron phosphate material prepared in example 1, and in FIG. 4, the lithium iron phosphate powder is the lithium iron phosphate material prepared in example 1, PDF #40-1799LiFePO4For the standard map of lithium iron phosphate, it can be seen from fig. 4 that the method of the present invention can regenerate and recover the waste lithium iron phosphate pole pieces and prepare the lithium iron phosphate material.
Fig. 5 is a voltammogram of the lithium iron phosphate material prepared in example 1, and it can be seen from the voltammogram that the lithium iron phosphate material prepared by the method of the present invention has excellent electrochemical properties.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including various technical features being combined in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (8)
1. A method for preparing a lithium iron phosphate material by regenerating and recycling waste lithium iron phosphate pole pieces is characterized by comprising the following steps:
(1) carrying out contact reaction I on a waste battery pole piece containing lithium iron phosphate soaked in water and an alkaline solvent I to obtain a mixed slurry I, and filtering the mixed slurry I to obtain a lithium iron phosphate active substance and a first solution; the contact reaction I is carried out in an ultrasonic environment, and the conditions of the contact reaction I at least comprise: the ultrasonic frequency is 20-40KHz, the temperature is 10-80 ℃, and the time is 1-5 h;
(2) mixing and dissolving the lithium iron phosphate active material and water to obtain mixed slurry II; in the presence of chlorine, carrying out contact reaction II on the mixed slurry II and an acidic solvent to obtain a mixed solution I, and filtering the mixed solution I to obtain leaching residues and a leaching mother liquor; the conditions of the contact reaction II at least comprise: stirring at 20-40rpm under 0.1-0.25MPa for 1-3 hr; the mass ratio of the lithium iron phosphate active material to water is 1: 2-4; the acidic solvent is at least one selected from hydrochloric acid, sulfuric acid and nitric acid;
(3) mixing the leaching mother liquor with an alkaline solvent II to adjust the pH value of the leaching mother liquor to 2.5-4.5 to obtain a mixed solution II, and filtering the mixed solution II to obtain an iron precipitation mother liquor and iron precipitation slag containing ferric phosphate;
wherein the operation step of mixing the leaching mother liquor with the alkaline solvent II comprises the following steps: adding the alkaline solvent II into the leaching mother liquor at the speed of 10-15mL/min at the temperature of 60-80 ℃ relative to every 2L of the leaching mother liquor;
(4) in the presence of an alkaline solvent III, carrying out contact reaction III on the iron precipitation mother liquor and a magnesium salt to obtain a mixed solution III, and filtering the mixed solution III to obtain a lithium-containing purification solution and phosphorus-magnesium slag; carrying out a contact reaction IV on the lithium-containing purified liquid and carbonate to obtain lithium carbonate; the magnesium salt is selected from at least one of magnesium chloride, magnesium sulfate and magnesium nitrate; the conditions of the contact reaction III at least comprise: the temperature is 80-100 ℃, and the time is 0.5-5 h;
(5) in the presence of water, the iron precipitation slag, the lithium carbonate and a carbon source are contacted and mixed to obtain mixed slurry III, and the mixed slurry III is sequentially dried and roasted;
the drying treatment is spray drying, and the conditions of the drying treatment at least comprise: the temperature is 150 ℃ and 250 ℃.
2. The method according to claim 1, wherein in step (1), the basic solvent I is at least one selected from sodium hydroxide and ammonia water.
3. The process of claim 1 or 2, wherein in step (4), the conditions of the contact reaction IV comprise at least: the temperature is 80-95 ℃ and the time is 0.5-2 h.
4. The method according to claim 1 or 2, wherein in step (5), the carbon source is selected from at least one of sucrose, glucose, polyvinyl alcohol.
5. The process according to claim 1 or 2, wherein in step (5), the molar ratio of the total amount of lithium carbonate, expressed as lithium element, to the total amount of iron phosphate, expressed as iron element, is from 1 to 1.5: 1.
6. the method according to claim 1 or 2, wherein, in step (5), the carbon source is used in an amount of 0.45-1.2 wt% based on the total amount of lithium carbonate.
7. The method of claim 1 or 2, wherein, in step (5), the roasting conditions at least comprise: the temperature is 600 ℃ and 850 ℃, and the time is 2-10 h.
8. The method according to claim 1 or 2, wherein the basic solvent I, the basic solvent II and the basic solvent III are the same, and the basic solvent I is selected from at least one of sodium hydroxide and ammonia water.
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| KR101377139B1 (en) * | 2010-04-21 | 2014-03-21 | 주식회사 엘지화학 | Process for preparation of lithium iron phosphate having olivine crystal structure |
| KR101178769B1 (en) * | 2010-09-27 | 2012-09-07 | 주식회사 세화엔스텍 | Method of recovery of lithium from cathodic active material of phosphorus oxide lithium battery |
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