CN113097591B - Method for recovering anode material of lithium iron phosphate battery - Google Patents
Method for recovering anode material of lithium iron phosphate battery Download PDFInfo
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- CN113097591B CN113097591B CN202110218976.6A CN202110218976A CN113097591B CN 113097591 B CN113097591 B CN 113097591B CN 202110218976 A CN202110218976 A CN 202110218976A CN 113097591 B CN113097591 B CN 113097591B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/54—Reclaiming serviceable parts of waste accumulators
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- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
- C01B25/37—Phosphates of heavy metals
- C01B25/375—Phosphates of heavy metals of iron
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- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
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- C01B25/26—Phosphates
- C01B25/45—Phosphates containing plural metal, or metal and ammonium
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- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
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Abstract
The invention relates to a method for recovering a positive electrode material of a lithium iron phosphate battery, which comprises the following steps: ultrasonically alkaline-washing waste positive pole pieces of the waste lithium iron phosphate batteries, and filtering to obtain a pole piece active material; dissolving the active material of the pole piece in first acid liquid, adding an oxidant, controlling the pH of a reaction liquid to be 2.0-2.3 at the end point of the reaction, and filtering and separating to obtain first filtrate to be recovered and ferrophosphorus slag; adjusting the pH value of the first filtrate to be recovered to be more than or equal to 5 by using alkali liquor, filtering to remove precipitates, adding phosphate to react, controlling the pH value of the reaction solution to be 10-11 at the end point of the reaction, filtering to remove the filtrate, drying, and recovering to obtain lithium phosphate; and dissolving the ferrophosphorus slag in a second acid solution, filtering to remove filter residues, adding a complexing agent, lithium hydroxide or lithium carbonate and a carbon source for reaction, separating to obtain colloidal precipitates, crushing and roasting, and recovering to obtain the lithium iron phosphate. By the mode, the recovery process is simplified, the process is short, the energy consumption is low, and the synthesized material is high in compaction density and good in electrical property.
Description
Technical Field
The invention relates to the technical field of recovery of waste lithium iron phosphate batteries, in particular to a method for recovering a positive electrode material of a lithium iron phosphate battery.
Background
With the promotion of a battery CTP technology and a blade battery technology, the volume energy density of lithium iron phosphate reaches the level of ternary 111, and the endurance mileage of an automobile carrying the lithium iron phosphate also reaches over 600 km. By virtue of the advantages of high safety and low cost, the market proportion of the lithium iron phosphate in the passenger vehicle is increased year by year. With the rapid increase of the market reserve, the scrappage of lithium iron phosphate batteries is bound to come after 4-5 years, so that a high-efficiency low-cost closed cycle process is urgently needed to be developed.
Firstly, the direct repair and reuse of lithium iron phosphate materials in waste lithium iron phosphate batteries have two problems: firstly, after long-term circulation, the anode material of the waste battery is lithium-deficient lithium iron phosphate. If the product performance is reduced too much by directly recycling, the requirements of the product can not be met. Secondly, the positive pole piece contains more than 6% of adhesive and conductive carbon, and if the positive pole piece is directly utilized, the processing performance of the product is poor, and the energy density is too low. And secondly, because the lithium iron phosphate battery does not contain precious heavy metals, if the traditional liquid phase recovery process is adopted, the cost is too high, so that the recovery industry cannot be sustained. Therefore, most manufacturers only recover high-price lithium by acid leaching to prepare related lithium salt products. The residual phosphorus-iron slag is directly used as waste, or iron is supplemented again or phosphorus is synthesized into iron phosphate again, then the iron phosphate is dried and dehydrated again, and then a lithium source is added for grinding, drying and roasting, so that the whole process is long, energy is consumed, and the recycling value is not high.
In view of the above, the present invention provides a new method for recovering a positive electrode material of a lithium iron phosphate battery to solve the existing defects.
Disclosure of Invention
Based on the method, the value of the whole recovery process is improved, and the synthesized material is high in compaction density and good in electrical property.
The invention provides a method for recovering a positive electrode material of a lithium iron phosphate battery, which comprises the following steps of:
ultrasonically alkaline-washing waste positive pole pieces of the waste lithium iron phosphate batteries, and filtering to remove filtrate to obtain a pole piece active material;
dissolving the pole piece active material in a first acid solution, then adding an oxidant to carry out oxidation reaction, controlling the pH of a reaction solution to be 2.0-2.3 at the end point of the reaction, and filtering and separating to obtain a first filtrate to be recovered and ferrophosphorus slag;
adjusting the pH value of the first filtrate to be recovered to be more than or equal to 5 by using alkali liquor, and filtering to remove precipitates;
adding phosphate into the first filtrate to be recovered after removing the precipitate for lithium precipitation reaction, controlling the pH of the reaction solution to be 10-11 at the end point of the reaction, filtering to remove the filtrate, drying, and recovering to obtain lithium phosphate;
dissolving the ferrophosphorus slag in a second acid solution, and filtering to remove filter residues to obtain a second filtrate to be recovered;
and adding a complexing agent, lithium hydroxide or lithium carbonate and a carbon source into the second filtrate to be recovered to perform acid-base neutralization reaction to obtain colloidal precipitate, separating the colloidal precipitate, crushing and roasting, and recovering to obtain the lithium iron phosphate.
Preferably, the first acid solution comprises H2SO4、HCL、HNO3At least one of; the concentration of the first acid solution is 0.3-0.5mol/L, and the mass ratio of the pole piece active material to the first acid solution is 1: 10;
and/or, the oxidant comprises H2O2、NaClO3At least one of; the addition amount of the oxidant is more than 1.5 times of the theoretical dosage;
and/or, in the oxidation reaction process, controlling the reaction temperature at 30-60 ℃ and the reaction time at more than 20 min.
Preferably, the first acid liquid is H2SO4(ii) a The oxidant is H2O2。
Preferably, the alkali liquor comprises at least one of NaOH, KOH and LiOH;
and/or, the phosphate comprises Na3PO4、(NH4)2HPO4、Na2HPO4At least one of; the addition amount of the phosphate is more than 0.33 times of the mole number of lithium in the waste positive pole pieces;
and/or, controlling the reaction temperature to be 30-60 ℃ during the lithium precipitation reaction.
Preferably, the second acid solution comprises H2SO4、HCl、HNO3At least one of; the concentration of the second acid liquid is 0.5-2mol/L, and the mass ratio of the ferrophosphorus slag to the second acid liquid is 1: 10.
Preferably, the second acid solution is HNO3。
Preferably, the complexing agent comprises citric acid; the addition amount of the complexing agent is 1-3% of the mole number of phosphorus in the ferrophosphorus slag; the adding amount of the lithium hydroxide is 1 to 1.06 times of the mole number of the phosphorus in the phosphorus iron slag; or the addition amount of the lithium carbonate is 0.5 to 0.53 time of the mole number of the phosphorus in the ferrophosphorus slag.
Preferably, the carbon source comprises at least one of glucose, sucrose, starch, polyethylene glycol, polyvinyl alcohol and phenolic resin, and the addition amount of the carbon source is to ensure that the carbon content of the roasted product is 1.0-1.8%.
Preferably, the separation of the colloidal precipitate, the crushing and roasting, and the roasting conditions in the recovery of the lithium iron phosphate are as follows: baking at 700-800 deg.C for 4-16 h.
Preferably, the dissolving of the pole piece active material in the first acid solution comprises: drying the pole piece active material at the temperature of 100-150 ℃, and crushing the pole piece active material to pass through a 50-mesh screen.
The method has the beneficial effects that the pH is accurately controlled in the acid leaching stage, the leaching ratio of iron to phosphorus is controlled to be 1:1 under the condition that the lithium is completely leached, and the iron or phosphorus is prevented from being supplemented again in the subsequent material synthesis process. Meanwhile, the iron phosphate material is synthesized from the ferrophosphorus slag by a direct one-step method by utilizing the self-heat release of acid-base neutralization reaction, so that the value of the whole recovery process is greatly improved. The material synthesized by the method has high compaction density and good electrical property.
Drawings
FIG. 1 is a flow chart of a method for recovering a positive electrode material of a lithium iron phosphate battery according to an embodiment of the present invention;
fig. 2 is an SEM image of finished lithium iron phosphate 1 in example 1 of the present invention.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The invention provides a method for recovering a positive electrode material of a lithium iron phosphate battery, and the method is shown in figure 1 and specifically comprises the following steps:
and S100, ultrasonically washing the waste positive electrode sheets of the waste lithium iron phosphate batteries with alkali, and filtering to remove filtrate to obtain the active material of the electrode sheet.
Specifically, the waste lithium iron phosphate battery is discharged to below 2.0V; then cutting the shell of the structural part of the battery, and pouring out the electrolyte; and finally, disassembling the battery cell, and separating the anode, the cathode and the diaphragm to obtain the anode waste sheet.
In addition, in the ultrasonic alkali washing process, the positive electrode waste sheet is soaked in alkali liquor with the concentration of 0.3mol/LNaOH for 20min, the mass ratio of the alkali liquor to the positive electrode waste sheet is 1:10, and ultrasonic treatment is carried out by adopting the frequency of 50Khz in the soaking process so as to separate aluminum foil and active materials in the positive electrode waste sheet.
And S200, dissolving the pole piece active material in a first acid solution, adding an oxidant to perform oxidation reaction, controlling the pH of a reaction solution to be 2.0-2.3 at the end point of the reaction, and filtering and separating to obtain a first filtrate to be recovered and the ferrophosphorus slag.
Optionally, before the pole piece active material is dissolved in the first acid solution, the solid pole piece active material is dried at 100-150 ℃ and then crushed through a 50-mesh screen, so that the pole piece active material can be fully dissolved in the first acid solution, the contact area with an oxidant in the first acid solution is increased, and the oxidation reaction is fully performed.
Optionally, the first acid solution comprises H2SO4、HCL、HNO3Preferably H2SO4(ii) a The concentration of the first acid solution is 0.3-0.5mol/L, and the mass ratio of the pole piece active material to the first acid solution is 1: 10; the oxidizing agent comprises H2O2、NaClO3Preferably H2O2(ii) a When the oxidant is H2O2, the theoretical addition amount is 0.5 times of the mole number of iron in the waste positive electrode piece, when the oxidant is NaCLO3, the theoretical addition amount is 0.17 times of the mole number of iron in the waste positive electrode piece, and the actual addition amount of the oxidant is more than 1.5 times of the theoretical addition amount; preferably 2 times or more. In the oxidation reaction process, the reaction temperature is controlled to be 30-60 ℃, and the reaction time is controlled to be more than 20 min.
And step S300, adjusting the pH value of the first filtrate to be recovered to be more than or equal to 5 by using alkali liquor, and filtering to remove precipitates.
Optionally, the alkali solution comprises at least one of NaOH, KOH and LiOH; when the PH value of the first filtrate to be recovered is adjusted to be more than or equal to 5 by using the alkaline solution, impurities Al and Fe in the first filtrate to be recovered are Al (OH)3And Fe (OH)3And precipitating.
And S400, adding phosphate into the first to-be-recovered filtrate after the precipitate is removed for lithium precipitation reaction, controlling the pH of the reaction solution to be 10-11 at the end point of the reaction, filtering to remove the filtrate, drying, and recovering to obtain lithium phosphate.
Alternatively, the phosphate comprises Na3PO4、(NH4)2HPO4、Na2HPO4At least one of; the adding amount of the phosphate is more than 0.33 times of the mole number of the lithium in the waste positive pole pieces. And in the process of lithium deposition reaction, the reaction temperature is controlled at 30-60 ℃.
And S500, dissolving the ferrophosphorus slag in a second acid solution, and filtering to remove filter residues to obtain a second filtrate to be recovered.
Specifically, the phosphorus-iron slag also contains impurities such as a conductive agent, an adhesive and the like, phosphorus and iron in the phosphorus-iron slag are dissolved by acid liquor, and conductive carbon and an adhesive in the phosphorus-iron slag can be removed by filtering filter residues. The second acid solution comprises H2SO4、HCl、HNO3Preferably HNO3(ii) a The concentration of the second acid liquid is 0.5-2mol/L, and the mass ratio of the ferrophosphorus slag to the second acid liquid is 1: 10.
And S600, adding a complexing agent, lithium hydroxide or lithium carbonate and a carbon source into the second filtrate to be recovered to perform acid-base neutralization reaction to obtain colloidal precipitate, separating the colloidal precipitate, crushing and roasting, and recovering to obtain the lithium iron phosphate.
Optionally, the complexing agent comprises citric acid; the addition amount of the complexing agent is 1-3% of the mole number of phosphorus in the ferrophosphorus slag; the adding amount of the lithium hydroxide is 1 to 1.06 times of the mole number of the phosphorus in the ferrophosphorus slag; or the addition amount of the lithium carbonate is 0.5 to 0.53 time of the mole number of the phosphorus in the ferrophosphorus slag. Optionally, the carbon source comprises at least one of glucose, sucrose, starch, polyethylene glycol, polyvinyl alcohol and phenolic resin, and the addition amount of the carbon source is to ensure that the carbon content of the roasted product is 1.0-1.8%. Optionally, separating the colloidal precipitate, crushing and roasting, and recovering to obtain the lithium iron phosphate under the roasting conditions: baking at 700-800 deg.C for 4-16 h.
According to the method for recovering the positive electrode material of the lithium iron phosphate battery, provided by the embodiment of the invention, the positive electrode material and the aluminum foil are separated more thoroughly by adding the ultrasonic wave into the alkali liquor, and compared with the traditional high-temperature roasting and organic solvent soaking, the method is low in energy consumption, small in pollution, safe and high in recovery rate; by controlling the acid liquor concentration, the mass ratio and the pH value, the Li leaching rate is over 96 percent, and meanwhile, the Fe and P equal proportion leaching is ensured, the leaching rates of the two are below 2 percent, and the Fe and P equal proportion leaching can avoid additional iron supplement or phosphorus supplement during the subsequent synthesis of lithium iron phosphate; the phosphate is used for precipitating lithium, the lithium precipitation rate is higher, the lithium recovery rate is more than 96%, the value is higher, and the preparation process is simplified; the iron phosphate lithium is directly synthesized by one step through complexation and acid-base neutralization reaction, and compared with the traditional method of firstly preparing iron phosphate and then preparing the iron phosphate lithium, the method has the advantages of short process, low energy consumption and high value.
Reference will now be made in detail to the embodiments.
Example 1
1 index of the anode material of the waste lithium iron phosphate battery:
the method for recovering the positive electrode material 1 of the lithium iron phosphate battery specifically comprises the following steps:
firstly, discharging an old lithium iron phosphate battery to below 2.0V; cutting the shell of the structural part of the battery, and pouring out the electrolyte; thirdly, disassembling the battery core, separating the anode, the cathode and the diaphragm, fourthly, under the ultrasonic frequency of 50Khz, using the waste lithium iron phosphate anode with the concentration of 0.3 mol/mlSoaking the L NaOH aqueous alkali for 20min to separate aluminum foil from the pole piece active material in the waste positive pole piece; drying the pole piece active material at 100 ℃, and crushing the pole piece active material through a 50-mesh screen; sixthly, adding the crushed and sieved pole piece active material into H with the concentration of 0.3mol/L according to the mass ratio of 1:102SO4Soaking, and simultaneously adding H with the mole number of iron being 1 time in the pole piece active material2O2Carrying out oxidation reaction for 20min at the temperature of 60 ℃, controlling the pH value at the end point of the reaction to be 2.2, and filtering and separating to obtain a first filtrate to be recovered and ferrophosphorus slag; seventhly, adjusting the pH of the first filtrate to be recovered to 6 by using NaOH, and filtering to remove Al (OH)3And Fe (OH)3After precipitation, adding Na with the mole number 0.33 times of that of lithium in the pole piece active material into the filtrate3PO4Controlling the temperature at 60 ℃ to carry out lithium precipitation reaction, controlling the pH value at the end point of the reaction to be 10.5, filtering, drying and recovering to obtain a finished product lithium phosphate 1; dissolving the phosphorus iron slag with HNO3 with the mass ratio of 1:10 and the concentration of 1mol/L, and filtering out conductive carbon and a binder to obtain a second filtrate to be recovered; ninthly, adding citric acid with the mole number of 1% of phosphorus in the phosphorus iron slag, adding lithium hydroxide with the mole number of 1.03 times of the mole number of phosphorus in the phosphorus iron slag and adding a certain amount of dextrose monohydrate into the second filtrate to be recovered, wherein the addition amount of the dextrose monohydrate is 1.2% of the carbon content of a roasting product, the acid-base neutralization reaction generates heat to produce a gelatinous lithium, iron and phosphorus mixture, the mixture is roasted after being crushed and in a furnace, roasting is carried out at 790 ℃ for 8h, and a finished product of lithium iron phosphate 1 is obtained through recovery. Fig. 2 is a structural diagram of a finished product of lithium iron phosphate 1 under a scanning electron microscope.
Example 2
2 indexes of the anode material of the waste lithium iron phosphate battery:
the method for recovering the positive electrode material 2 of the lithium iron phosphate battery specifically comprises the following steps:
(ii) old phosphorusFirstly discharging the iron lithium battery to be below 2.0V; cutting the shell of the structural part of the battery, and pouring out the electrolyte; thirdly, disassembling the battery core, separating the anode, the cathode and the diaphragm, and soaking the waste lithium iron phosphate anode slices in NaOH aqueous alkali with the concentration of 0.3mol/L for 20min at the ultrasonic frequency of 50Khz according to the mass ratio of 1:10 so as to separate aluminum foils and active materials of the pole pieces in the waste anode slices; drying the pole piece active material at 100 ℃, and crushing the pole piece active material through a 50-mesh screen; sixthly, adding the crushed and sieved pole piece active material into H with the concentration of 0.3mol/L according to the mass ratio of 1:102SO4Soaking, and simultaneously adding H with the mole number of iron being 1 time in the pole piece active material2O2Carrying out oxidation reaction for 20min at the temperature of 60 ℃, controlling the pH value at the end point of the reaction to be 2.3, and filtering and separating to obtain a first filtrate to be recovered and ferrophosphorus slag; seventhly, adjusting the pH of the first filtrate to be recovered to 6 by using NaOH, and filtering to remove Al (OH)3And Fe (OH)3After precipitation, adding Na with the mole number 0.33 times of that of lithium in the pole piece active material into the filtrate3PO4Controlling the temperature at 60 ℃ to carry out lithium precipitation reaction, controlling the pH value at the end point of the reaction to be 10.5, filtering, drying and recovering to obtain a finished product lithium phosphate 2; dissolving the phosphorus iron slag with HNO3 with the mass ratio of 1:10 and the concentration of 1mol/L, and filtering out conductive carbon and a binder to obtain a second filtrate to be recovered; ninthly, adding citric acid with the mole number of 1% of phosphorus in the phosphorus iron slag, adding lithium hydroxide with the mole number of 1.0 time of phosphorus in the phosphorus iron slag and adding a certain amount of dextrose monohydrate into the second filtrate to be recovered, wherein the addition amount of the dextrose monohydrate is 1.2% of the carbon content of a roasting product, the acid-base neutralization reaction generates heat to produce a gelatinous lithium, iron and phosphorus mixture, the mixture is roasted after being crushed and fed into a furnace, and the mixture is roasted at 795 ℃ for 8 hours and recovered to obtain a finished product of lithium iron phosphate 2.
Comparative example 1
The indexes of the anode material of the waste lithium iron phosphate battery are as follows:
the method for recovering the positive electrode material 3 of the lithium iron phosphate battery specifically comprises the following steps:
firstly, the old lithium iron phosphate battery is firstlyDischarging to below 2.0V; cutting the shell of the structural part of the battery, and pouring out the electrolyte; thirdly, disassembling the battery core, separating the anode, the cathode and the diaphragm, and soaking the waste lithium iron phosphate anode slices in NaOH aqueous alkali with the concentration of 0.3mol/L for 20min at the ultrasonic frequency of 50Khz according to the mass ratio of 1:10 so as to separate aluminum foils and active materials of the pole pieces in the waste anode slices; drying the pole piece active material at 100 ℃, and crushing the pole piece active material through a 50-mesh screen; sixthly, adding the crushed and sieved pole piece active material into H with the concentration of 0.3mol/L according to the mass ratio of 1:102SO4Soaking, and simultaneously adding H with the mole number of iron being 1 time in the pole piece active material2O2Carrying out oxidation reaction for 20min at the temperature of 60 ℃, controlling the pH value at the end point of the reaction to be 2.5, and filtering and separating to obtain a first filtrate to be recovered and ferrophosphorus slag; seventhly, adjusting the pH of the first filtrate to be recovered to 6 by using NaOH, and filtering to remove Al (OH)3And Fe (OH)3After precipitation, adding Na with the mole number 0.33 times of that of lithium in the pole piece active material into the filtrate3PO4Controlling the temperature at 60 ℃ to carry out lithium precipitation reaction, controlling the pH value at the end point of the reaction to be 10.5, filtering, drying and recovering to obtain a finished product lithium phosphate 3; dissolving the phosphorus iron slag with HNO3 with the mass ratio of 1:10 and the concentration of 1mol/L, and filtering out conductive carbon and a binder to obtain a second filtrate to be recovered; ninthly, adding citric acid with the mole number of phosphorus of 1 percent in the phosphorus-iron slag, adding lithium hydroxide with the mole number of iron of 1.0 time in the phosphorus-iron slag and adding H with the mole number of phosphorus of 0.02 time in the phosphorus-iron slag into the second filtrate to be recovered3PO4And adding a certain amount of dextrose monohydrate, wherein the adding amount of the dextrose monohydrate is ensured to ensure that the carbon content of the roasted product is 1.2%, generating heat by acid-base neutralization reaction to produce a gelatinous lithium, iron and phosphorus mixture, crushing the mixture, roasting the crushed mixture in a furnace, roasting the crushed mixture at 790 ℃ for 8 hours, and recovering to obtain the finished product of the lithium iron phosphate 3.
Comparative example 2
The positive electrode material of the waste lithium iron phosphate battery has 4 indexes:
the method for recovering the positive electrode material 4 of the lithium iron phosphate battery specifically comprises the following steps:
firstly, discharging an old lithium iron phosphate battery to below 2.0V; cutting the shell of the structural part of the battery, and pouring out the electrolyte; thirdly, disassembling the battery core, separating the anode, the cathode and the diaphragm, and soaking the waste lithium iron phosphate anode slices in NaOH aqueous alkali with the concentration of 0.3mol/L for 20min at the ultrasonic frequency of 50Khz according to the mass ratio of 1:10 so as to separate aluminum foils and active materials of the pole pieces in the waste anode slices; drying the pole piece active material at 100 ℃, and crushing the pole piece active material through a 50-mesh screen; sixthly, adding the crushed and sieved pole piece active material into H with the concentration of 0.3mol/L according to the mass ratio of 1:102SO4Soaking, and simultaneously adding H with the mole number of iron being 1 time in the pole piece active material2O2Carrying out oxidation reaction for 20min at the temperature of 60 ℃, controlling the pH value at the end point of the reaction to be 1.5, and filtering and separating to obtain a first filtrate to be recovered and ferrophosphorus slag; seventhly, adjusting the pH of the first filtrate to be recovered to 6 by using NaOH, and filtering to remove Al (OH)3And Fe (OH)3After precipitation, adding Na with the mole number 0.33 times of that of lithium in the pole piece active material into the filtrate3PO4Controlling the temperature at 60 ℃ to carry out lithium precipitation reaction, controlling the pH value at the end point of the reaction to be 10.5, filtering, drying and recovering to obtain a finished product lithium phosphate 4; dissolving the phosphorus iron slag with the mass ratio of 1:10 and the concentration of 1mol/LHNO3, and filtering conductive carbon and binder to obtain a second filtrate to be recovered; ninthly, adding citric acid with the phosphorus mole number of 1 percent in the phosphorus iron slag, lithium hydroxide with the phosphorus mole number of 1.03 times that of the phosphorus iron slag and Fe (NO) with the iron mole number of 0.2 in the phosphorus iron slag into the second filtrate to be recovered3)3And adding a certain amount of dextrose monohydrate, wherein the adding amount of the dextrose monohydrate is ensured to ensure that the carbon content of the roasted product is 1.2%, generating heat by acid-base neutralization reaction to produce a gelatinous lithium, iron and phosphorus mixture, crushing the mixture, roasting the crushed mixture in a furnace, roasting the crushed mixture at 790 ℃ for 8 hours, and recovering to obtain a finished product of the lithium iron phosphate 4.
Recycled product performance test
1. Pole piece compaction Density test
The finished lithium iron phosphate 1-4 prepared in the above examples and comparative examples, a conductive agent (CNT: graphene: 5), and PVDF added with a certain amount of NMP were mixed uniformly in a mass ratio of 100:1:2.55, and the prepared slurry was uniformly coated on an Al foil with a 250 μm slit die, one side was coated, dried, and then the other side was coated. After drying, rolling the pole piece under 10Mpa, cutting a phi 15mm wafer in the middle area, weighing and measuring the thickness, and calculating the compaction density, wherein the specific parameters refer to Table 1.
2. Specific capacity test
The finished lithium iron phosphate 1-4 prepared in the above examples and comparative examples is used for preparing a positive plate as a positive electrode, a metal lithium plate as a negative electrode, a Celgard2300 microporous membrane as a diaphragm and 1.0mol/LLIPF6Ethylene Carbonate (EC): and (3) taking a solution of dimethyl carbonate (DMC) in a volume ratio of 1: 1-5 as an electrolyte, and assembling the solution into the R2025 button cell in a glove box. Electrochemical performance tests were performed as follows using the nover 3008 cell test system.
Specific capacity test: firstly, the battery is charged and discharged once at the normal temperature of 25 ℃ at 0.1C, and the charge and discharge cut-off voltage is 2.5-3.8V (vs. Li/Li +). The mass of the active material lithium iron phosphate in the positive plate is converted into specific capacity data, and the specific charge-discharge capacity and the discharge efficiency are shown in table 1.
TABLE 1
As can be seen from the above preparation methods of example 1, example 2, comparative example 1 and comparative example 2, additional phosphorus or iron is not required in the preparation of the materials of examples 1 and 2, and step ninthly of the preparation methods of comparative examples 1 and 2 is additionally supplemented with phosphorus or iron. Therefore, the preparation methods of the embodiment 1 and the embodiment 2 have short process, low energy consumption and higher value.
As shown by the data in Table 1, the material prepared after supplementing phosphorus in comparative example 1 can have a compacted density of more than 2.55, but has a discharge capacity of 2-3mAh/g lower than that of examples 1 and 2; comparative example 2 discharge capacity after iron supplement was possible, but the compacted density was less than 2.50g/cm3The high compaction density was not achieved, but the compaction densities of comparative documents 1 and 2 were both greater than 2.50g/cm3And then the corresponding lithium iron phosphate 1 and 2 materials are both high compaction materials. As can be seen from the above, the preparation methods of examples 1 and 2 not only can prepare highly compacted materials, but also the discharge capacity of the materials is good, and the materials are integrally formedThe performance is better.
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above examples only express preferred embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A method for recovering a positive electrode material of a lithium iron phosphate battery is characterized by comprising the following steps of:
ultrasonically alkaline-washing waste positive pole pieces of the waste lithium iron phosphate batteries, and filtering to remove filtrate to obtain a pole piece active material;
dissolving the pole piece active material in a first acid solution, then adding an oxidant to carry out oxidation reaction, controlling the pH of a reaction solution to be 2.0-2.3 at the end point of the reaction, and filtering and separating to obtain a first filtrate to be recovered and ferrophosphorus slag;
adjusting the pH value of the first filtrate to be recovered to be more than or equal to 5 by using alkali liquor, and filtering to remove precipitates;
adding phosphate into the first filtrate to be recovered after removing the precipitate for lithium precipitation reaction, controlling the pH of the reaction solution to be 10-11 at the end point of the reaction, filtering to remove the filtrate, drying, and recovering to obtain lithium phosphate;
dissolving the ferrophosphorus slag in a second acid solution, and filtering to remove filter residues to obtain a second filtrate to be recovered;
and adding a complexing agent, lithium hydroxide or lithium carbonate and a carbon source into the second filtrate to be recovered to perform acid-base neutralization reaction to obtain colloidal precipitate, separating the colloidal precipitate, crushing and roasting, and recovering to obtain the lithium iron phosphate.
2. The method for recycling the positive electrode material of the lithium iron phosphate battery as claimed in claim 1, wherein the first acid solution comprises H2SO4、HCL、HNO3At least one of; the concentration of the first acid solution is 0.3-0.5mol/L, and the mass ratio of the pole piece active material to the first acid solution is 1: 10;
and/or, the oxidant comprises H2O2、NaClO3At least one of; the addition amount of the oxidant is more than 1.5 times of the theoretical dosage;
and/or, in the oxidation reaction process, controlling the reaction temperature at 30-60 ℃ and the reaction time at more than 20 min.
3. The method for recovering a positive electrode material for a lithium iron phosphate battery according to claim 1 or 2,
the first acid liquid is H2SO4(ii) a The oxidant is H2O2。
4. The method for recycling a positive electrode material for a lithium iron phosphate battery according to claim 1,
the alkali liquor comprises at least one of NaOH, KOH and LiOH;
and/or, the phosphate comprises Na3PO4、(NH4)2HPO4、Na2HPO4At least one of; the addition amount of the phosphate is more than 0.33 times of the mole number of lithium in the waste positive pole pieces;
and/or, controlling the reaction temperature to be 30-60 ℃ during the lithium precipitation reaction.
5. The method for recycling a positive electrode material for a lithium iron phosphate battery according to claim 1,
the second acid solution comprises H2SO4、HCl、HNO3At least one of; the concentration of the second acid solution is 0.5-2mol/L, and the mass ratio of the ferrophosphorus slag to the second acid solution is 1:10。
6. The method for recycling a positive electrode material for a lithium iron phosphate battery according to claim 1 or 5,
the second acid solution is HNO3。
7. The method for recycling a positive electrode material for a lithium iron phosphate battery according to claim 1,
the complexing agent comprises citric acid; the addition amount of the complexing agent is 1-3% of the mole number of phosphorus in the ferrophosphorus slag; the adding amount of the lithium hydroxide is 1 to 1.06 times of the mole number of the phosphorus in the phosphorus iron slag; or the addition amount of the lithium carbonate is 0.5 to 0.53 time of the mole number of the phosphorus in the ferrophosphorus slag.
8. The method for recycling a positive electrode material for a lithium iron phosphate battery according to claim 1,
the carbon source comprises at least one of glucose, sucrose, starch, polyethylene glycol, polyvinyl alcohol and phenolic resin, and the addition amount of the carbon source is to ensure that the carbon content of the roasted product is 1.0-1.8%.
9. The method for recycling a positive electrode material for a lithium iron phosphate battery according to claim 1,
separating the colloidal precipitate, crushing and roasting, and recovering to obtain the lithium iron phosphate under the roasting conditions that: baking at 700-800 deg.C for 4-16 h.
10. The method for recycling a positive electrode material for a lithium iron phosphate battery according to claim 1,
dissolving the pole piece active material in a first acid solution, wherein the method comprises the following steps: drying the pole piece active material at the temperature of 100-150 ℃, and crushing the pole piece active material to pass through a 50-mesh screen.
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| CN114180545B (en) * | 2021-12-10 | 2023-05-23 | 合肥国轩电池材料有限公司 | Copper removal method and method for preparing iron phosphate from waste lithium iron phosphate battery cell powder |
| CN114702017B (en) * | 2022-04-29 | 2023-11-17 | 武汉工程大学 | Method for preparing ferric phosphate from lithium extraction slag |
| CN115676792A (en) * | 2022-07-06 | 2023-02-03 | 宜宾天原锂电新材有限公司 | Method for preparing iron-based phosphate lithium battery material by using phosphorus iron slag as raw material |
| CN116177512B (en) * | 2023-04-23 | 2023-07-04 | 赣州市力道新能源有限公司 | Method for preparing iron phosphate material from scrapped lithium battery iron phosphate slag |
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