CN109775682B - Preparation method of lithium cobalt phosphate - Google Patents
Preparation method of lithium cobalt phosphate Download PDFInfo
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- CN109775682B CN109775682B CN201910092090.4A CN201910092090A CN109775682B CN 109775682 B CN109775682 B CN 109775682B CN 201910092090 A CN201910092090 A CN 201910092090A CN 109775682 B CN109775682 B CN 109775682B
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Abstract
The invention discloses a preparation method of lithium cobalt phosphate. Adding cobalt powder into phosphoric acid for dissolving, then carrying out precision filtration to obtain cobalt solution, slurrying lithium carbonate, and then introducing CO2Completely clarifying the lithium carbonate slurry to obtain a lithium solution, taking a polyethylene glycol solution as a base solution, adding the cobalt solution and the lithium solution into the base solution while stirring, and carrying out feeding reaction; spray drying the reacted material to obtain a spray dried material, putting the spray dried material into a roller furnace, introducing nitrogen, allowing the material to sequentially pass through a temperature rising section, a temperature preservation section and a temperature reduction section, and then cooling and discharging to obtain a calcined material; conveying the calcined material to a jet mill through a pipeline, crushing the calcined material through air flow, screening the calcined material after electromagnetic iron removal, and carrying out vacuum packaging to obtain the material. The method can realize the coprecipitation of lithium, phosphate radical and cobalt, and simultaneously adopts polyethylene glycol as a dispersing agent and a carbon source, so that the carbon-coated lithium cobalt phosphate with uniformly distributed particles can be obtained, and the carbon-coated lithium cobalt phosphate has good capacity and high compaction density.
Description
Technical Field
The invention relates to a preparation method of lithium cobalt phosphate, and belongs to the technical field of new energy lithium battery materials.
Background
The working voltage of the cobalt lithium phosphate material can reach 4.8V, the capacity reaches 170mAh/g, the cobalt lithium phosphate material has the same crystal structure as lithium iron phosphate, the cobalt lithium phosphate material has an ordered olivine structure, belongs to an orthorhombic system, the space group is Pmnb, the unit cell parameters are a-0.5922 nm, b-1.0202 nm and c-0.4699 nm. In the crystal, O atoms are in hexagonal close packing, P atoms occupy tetrahedral spaces, and Li atoms and Co atoms occupy octahedral spaces. Octahedral CoO with shared edges6Passing through PO in the C-axis direction4The tetrahedra are linked in a chain. Since the Co-O-P bond stabilizes the crystal structure, Li is present during charging and discharging+In the process of removing, the rearrangement of the crystal is very small, the crystal structure is very stable, and the good cycle performance of the lithium cobalt phosphate material is also ensured. Particularly in some fields needing long-term storage, such as distributed energy storage fields, the energy storage battery needs to carry out long-term low-current floating charge, which can cause Li+And excessive separation damages the structure of the anode material. And the phosphate material has stable structure, so that even if Li & lt + & gt is excessively extracted in the long-term low-current floating charge process, the phosphate material still has good stability and has good floating charge resistance. But due to CoO6The octahedrons are not directly connected but are linked through PO4 tetrahedrons, so that a continuous Co-O-Co structure cannot be formed like a lithium cobaltate material, and the cobalt lithium phosphate material has poor conductivity and influences the high-current discharge performance of the material.
The synthesis method of the lithium cobalt phosphate is similar to that of the lithium iron phosphate material, and comprises a solid phase method, a sol-gel method, a hydrothermal method, a microwave method and a spray drying pyrolysis method. The solid phase method is the simplest method, has low requirements on equipment and is suitable for large-scale industrial production. But the heat treatment temperature is higher, the energy consumption is high, the particle size distribution range of the material is wide, and the batch stability of the material is poor. The sol-gel method can ensure that the raw materials can reach the molecular level mixing, can effectively reduce the heat treatment temperature and time, and has small material particle size and uniform particle size distribution. However, the sol-gel method has high cost of raw materials, and the volume shrinkage of the precursor in the heat treatment process is high, so that the production efficiency is low. The hydrothermal method is a powerful means for synthesizing nano materials, and has the advantages of low reaction temperature, low energy consumption, high purity of the obtained materials, small particle size and the like. But the hydrothermal method has higher requirements on equipment and low production efficiency, and is not suitable for large-scale industrial production. The equipment required by the spray thermal decomposition method is simple, continuous production can be realized, and the production cost is low. However, because of the low crystallinity of the material, subsequent heat treatment is required to improve the properties of the material.
Disclosure of Invention
In view of the above, the invention provides a preparation method of lithium cobalt phosphate, which can realize co-precipitation of lithium, phosphate radical and cobalt, and can obtain carbon-coated lithium cobalt phosphate with uniformly distributed particles by using polyethylene glycol as a dispersant and a carbon source, and has the advantages of good capacity and high compaction density.
The invention solves the technical problems by the following technical means:
a preparation method of lithium cobalt phosphate comprises the following steps:
(1) dissolving cobalt powder in phosphoric acid, adjusting pH of the solution to 3.5-4.5, fine filtering to obtain cobalt solution, slurrying lithium carbonate, and introducing CO2Completely clarifying the lithium carbonate slurry to obtain a lithium solution, preparing a polyethylene glycol solution, taking the polyethylene glycol solution as a base solution, adding the cobalt solution and the lithium solution into the base solution while stirring, and continuously reacting for 30-60min after the addition is finished;
(2) spray drying the material reacted in the step (1) to obtain a spray drying material, putting the spray drying material into a roller furnace, introducing nitrogen gas to ensure that the oxygen content in the roller furnace is lower than 100ppm, sequentially passing the material through a temperature rising section, a heat preservation section and a temperature reduction section, wherein the temperature rising speed of the temperature rising section is 80-100 ℃/h, the temperature rises to 740 ℃ when the temperature is 720-;
(3) conveying the calcined material to a jet mill through a pipeline, crushing the calcined material through air flow, screening the crushed calcined material after electromagnetic iron removal, sieving the crushed calcined material through a 200-fold and 250-mesh sieve, and then carrying out vacuum packaging to obtain the catalyst.
The molar ratio of the cobalt powder, the phosphoric acid and the lithium carbonate added in the step (1) is 1: 1.01-1.02: 0.501-0.505 percent, the concentration of phosphoric acid is 5-6mol/L, the solid content of lithium carbonate slurry is 40-50 percent, the purity of lithium carbonate is battery grade, the concentration of polyethylene glycol solution is 0.3-0.5mol/L, polyethylene glycol adopts products with the polymerization degree of 2000, 4000 or 6000, the volume of the polyethylene glycol solution is 1/5-1/10 of the total volume of cobalt solution and lithium solution, the feeding time is 60-120min, and the temperature of the feeding process and the reaction process is 50-65 ℃.
The air inlet temperature of the spray drying in the step (2) is 200-.
And (3) when the roller furnace is calcined in the step (2), at least two air induction ports are arranged in the temperature rising section, the air induction ports are communicated with a negative pressure fan, the volume of the introduced nitrogen is 300-600 times of the volume of the added spray drying material, the furnace pressure in the roller furnace is maintained to be 50-80Pa, and the dew point of the gas in the roller furnace is maintained to be below 50 ℃.
In the step (3), a dry powder electromagnetic iron remover is adopted for electromagnetic iron removal, the magnetic induction intensity is 10000-15000 gauss, iron removal residues obtained by the electromagnetic iron removal are added into dilute sulfuric acid for dissolution, the reaction is carried out for 1-2h at the temperature of 50-60 ℃, then the filtration is carried out, the obtained filter residues are dried and then crushed by air flow, the obtained filter residues are screened after the electromagnetic iron removal, the obtained material and the conventional material are mixed for use, the concentration of the dilute sulfuric acid is 0.1-0.3mol/L, and the mass ratio of the iron removal residues to the dilute sulfuric acid is 1: 3-4.
And (3) the pipeline conveying in the step (3) adopts negative pressure conveying, an air source is heated to 120 ℃ for air flow crushing and then is contacted with the materials for crushing, the electromagnetic iron removal and the screening are carried out in a packaging room, the humidity of the packaging room is controlled to be less than 10%, and the temperature is maintained at 20-25 ℃.
This patent utilizes cobalt powder and phosphoric acid reaction, and under lower pH, phosphate radical and cobalt ion do not produce the sediment, then pulpify lithium carbonate, then let in CO2The lithium carbonate is thus converted into lithium bicarbonate, which is dissolved in water, and then a polyethylene glycol solution is prepared as a base solution, and the lithium solution is added into the base solution towards the cobalt solution, the following reactions take place:
HPO4 2-+HCO3 --------H2O+CO2+PO4 3-
PO4 3-+3Li+-----Li3PO4
3Co2++2PO4 3------Co3(PO4)2
thereby forming mixed precipitation of lithium phosphate and cobalt phosphate, the mixed precipitation realizes the mixing of the two precipitation molecular levels by forming the mixing in the precipitation particles, compared with mechanical mixing, the mixing degree is higher, the step of mixing materials is omitted, the operation cost is lower, the recovery rate of the product is improved, the mixing degree is better, meanwhile, the bottom liquid is polyethylene glycol (PEG), the particle size distribution of the precipitation particles is more uniform, meanwhile, the existence of the polyethylene glycol can avoid the mutual adhesion between the solid particles, in the spray drying process, as the spray can form fog drops firstly, because of the surface tension of the liquid, the structure of the fog drops is that the solid particles are cores, and the structure of the liquid shell is used, in the instant drying process, moisture is evaporated, the PEG in the solution can be crystallized and separated out, thereby forming a structure that the PEG is coated outside the mixed precipitation, due to the coating of PEG, the adhesion between two adjacent particles is avoided, thereby avoiding the agglomeration of the particles.
In the high-temperature calcination process, the temperature rise section and the inert atmosphere are firstly carried out, the PEG can carry out the thermal cracking reaction, hydrogen in the PEG and oxygen react to obtain water vapor, carbon elements are converted into carbon, the carbon is coated on the surfaces of particles, the carbon coating also prevents the fusion of adjacent solid particles from growing, so that the cobalt lithium phosphate with uniform particle size is formed, the generation of too large particles is avoided, the electrical property of a product is improved, and the generation of too small particles is also avoided, so that the compaction density and the processing performance of the product are influenced (the particle size is too small, the dispersion and suspension of the cobalt lithium phosphate in a solvent are not facilitated, and the processing performance of the product is influenced when the battery is prepared), therefore, the electrical property and the compaction density of the cobalt lithium phosphate prepared by the process are good, and the processing performance is good.
Because this patent is in precursor preparation process earlier, the cobalt deposit has realized the mixing of molecular level with lithium deposit resynthesis process, compare with cobalt salt and lithium salt mechanical mixing, the mixed effect is better, because solid phase reaction, the migration speed of ion is the factor that can influence solid phase reaction most, so because the two kinds of deposits resynthesis processes of this patent form the mixing of molecular level promptly, so adopt lower temperature and shorter calcination time can realize synthesizing, because realize synthesizing at lower temperature and shorter time, thereby make the cobalt lithium phosphate cyclicity that this patent obtained also better.
And the conductivity of the lithium cobalt phosphate is also greatly improved due to the formation of carbon coating.
Simultaneously this patent is at precursor synthetic process, can not produce waste water, only at the spray drying process, can evaporate out vapor, because vapor is discharged outward behind the sack dust collection, also can not discharge sewage outward, has realized clean production, and low in manufacturing cost has also, has not had the step that cobalt salt and lithium salt mix simultaneously, has reduced equipment investment, operating cost and manufacturing cost, further the cost is reduced.
The indexes of the finally obtained lithium cobalt phosphate are as follows:
the invention has the beneficial effects that: the coprecipitation of lithium, phosphate radical and cobalt can be realized, and the carbon-coated lithium cobalt phosphate with uniformly distributed particles can be obtained by using polyethylene glycol as a dispersing agent and a carbon source, and has the advantages of good capacity and high compaction density.
Drawings
FIG. 1 is an SEM of the product of example 1 of the invention.
FIG. 2 is an SEM of the product of example 2 of the invention.
FIG. 3 is an SEM of a product of example 3 of the invention.
Detailed Description
The present invention will be described in detail with reference to specific examples, in which the preparation method of lithium cobalt phosphate of this example comprises the following steps:
(1) dissolving cobalt powder in phosphoric acid, adjusting pH of the solution to 3.5-4.5, fine filtering to obtain cobalt solution, slurrying lithium carbonate, and introducing CO2Completely clarifying the lithium carbonate slurry to obtain a lithium solution, preparing a polyethylene glycol solution, taking the polyethylene glycol solution as a base solution, adding the cobalt solution and the lithium solution into the base solution while stirring, and continuously reacting for 30-60min after the addition is finished;
(2) spray drying the material reacted in the step (1) to obtain a spray drying material, putting the spray drying material into a roller furnace, introducing nitrogen gas to ensure that the oxygen content in the roller furnace is lower than 100ppm, sequentially passing the material through a temperature rising section, a heat preservation section and a temperature reduction section, wherein the temperature rising speed of the temperature rising section is 80-100 ℃/h, the temperature rises to 740 ℃ when the temperature is 720-;
(3) conveying the calcined material to a jet mill through a pipeline, crushing the calcined material through air flow, screening the crushed calcined material after electromagnetic iron removal, sieving the crushed calcined material through a 200-fold and 250-mesh sieve, and then carrying out vacuum packaging to obtain the catalyst.
The molar ratio of the cobalt powder, the phosphoric acid and the lithium carbonate added in the step (1) is 1: 1.01-1.02: 0.501-0.505 percent, the concentration of phosphoric acid is 5-6mol/L, the solid content of lithium carbonate slurry is 40-50 percent, the purity of lithium carbonate is battery grade, the concentration of polyethylene glycol solution is 0.3-0.5mol/L, polyethylene glycol adopts products with the polymerization degree of 2000, 4000 or 6000, the volume of the polyethylene glycol solution is 1/5-1/10 of the total volume of cobalt solution and lithium solution, the feeding time is 60-120min, and the temperature of the feeding process and the reaction process is 50-65 ℃.
The air inlet temperature of the spray drying in the step (2) is 200-.
And (3) when the roller furnace is calcined in the step (2), at least two air induction ports are arranged in the temperature rising section, the air induction ports are communicated with a negative pressure fan, the volume of the introduced nitrogen is 300-600 times of the volume of the added spray drying material, the furnace pressure in the roller furnace is maintained to be 50-80Pa, and the dew point of the gas in the roller furnace is maintained to be below 50 ℃.
In the step (3), a dry powder electromagnetic iron remover is adopted for electromagnetic iron removal, the magnetic induction intensity is 10000-15000 gauss, iron removal residues obtained by the electromagnetic iron removal are added into dilute sulfuric acid for dissolution, the reaction is carried out for 1-2h at the temperature of 50-60 ℃, then the filtration is carried out, the obtained filter residues are dried and then crushed by air flow, the obtained filter residues are screened after the electromagnetic iron removal, the obtained material and the conventional material are mixed for use, the concentration of the dilute sulfuric acid is 0.1-0.3mol/L, and the mass ratio of the iron removal residues to the dilute sulfuric acid is 1: 3-4.
And (3) the pipeline conveying in the step (3) adopts negative pressure conveying, an air source is heated to 120 ℃ for air flow crushing and then is contacted with the materials for crushing, the electromagnetic iron removal and the screening are carried out in a packaging room, the humidity of the packaging room is controlled to be less than 10%, and the temperature is maintained at 20-25 ℃.
Example 1
A preparation method of lithium cobalt phosphate comprises the following steps:
(1) adding phosphoric acid into cobalt powder for dissolving, adjusting the pH value of the solution to 3.9, then carrying out precision filtration to obtain a cobalt solution, slurrying lithium carbonate, and then introducing CO2Completely clarifying the lithium carbonate slurry to obtain a lithium solution, preparing a polyethylene glycol solution, taking the polyethylene glycol solution as a base solution, adding the cobalt solution and the lithium solution into the base solution while stirring, and continuously reacting for 50min after the addition is finished;
(2) spray drying the material reacted in the step (1) to obtain a spray dried material, putting the spray dried material into a roller furnace, introducing nitrogen gas to ensure that the oxygen content in the roller furnace is lower than 100ppm, sequentially passing the material through a heating section, a heat preservation section and a cooling section, wherein the heating speed of the heating section is 90 ℃/h, the temperature is increased to 735 ℃, the heat preservation section is subjected to heat preservation for 6.5h at the temperature, then cooling to the temperature lower than 80 ℃, and discharging to obtain a calcined material;
(3) conveying the calcined material to a jet mill through a pipeline, crushing the calcined material through air flow, screening the crushed calcined material after electromagnetic iron removal, sieving the crushed calcined material through a 225-mesh sieve, and then carrying out vacuum packaging to obtain the catalyst.
The molar ratio of the cobalt powder, the phosphoric acid and the lithium carbonate added in the step (1) is 1: 1.015: 0.503, the concentration of phosphoric acid is 5.4mol/L, the solid content of the lithium carbonate slurry is 45%, the purity of lithium carbonate is battery grade, the concentration of the polyethylene glycol solution is 0.4mol/L, the polyethylene glycol adopts a product with the polymerization degree of 2000, the volume of the polyethylene glycol solution is 1/8 of the total volume of the cobalt solution and the lithium solution, the feeding time is 80min, and the temperature in the feeding process and the reaction process is 55 ℃.
The air inlet temperature of the spray drying in the step (2) is 230 ℃, the discharging temperature is less than 100 ℃, the particle size of the spray drying material is 4 mu m, and the water content is less than 0.5%.
And (3) when the roller furnace is calcined in the step (2), at least two air inducing ports are arranged in the temperature rising section, the air inducing ports are communicated with a negative pressure fan, the volume of introduced nitrogen is 500 times of the volume of the added spray drying material, the furnace pressure in the roller furnace is maintained to be 70Pa, and the dew point of the gas in the roller furnace is maintained to be below minus 50 ℃.
In the step (3), a dry powder electromagnetic iron remover is adopted for electromagnetic iron removal, the magnetic induction intensity is 13000 gauss, iron removal residues obtained by the electromagnetic iron removal are added into dilute sulfuric acid for dissolution, the reaction is carried out for 1.5h at the temperature of 55 ℃, then the filtration is carried out, the obtained filter residue is dried, then airflow is crushed, the obtained filter residue is screened after the electromagnetic iron removal, the obtained material is mixed with conventional materials for use, the concentration of the dilute sulfuric acid is 0.15mol/L, and the mass ratio of the iron removal residues to the dilute sulfuric acid is 1: 3.5.
And (3) the pipeline conveying in the step (3) adopts negative pressure conveying, an air source is heated to 115 ℃ during air flow crushing and then is in contact with the materials for crushing, the electromagnetic iron removal and the screening are carried out in a packaging room, the humidity of the packaging room is controlled to be less than 10%, and the temperature is maintained at 20-25 ℃.
The indexes of the finally obtained lithium cobalt phosphate are as follows:
| index (I) | Li | Co | Cd | Na | Ni |
| Numerical value | 3.98％ | 32.8％ | 2ppm | 20ppm | 5ppm |
| Mn | Zn | Cu | P | Al | Ca |
| 34ppm | 12ppm | 3ppm | 19.4％ | 23ppm | 26ppm |
| Sulfate radical | Chloride ion | Fe | Bulk density | D10 | D50 |
| 18ppm | 6ppm | 5ppm | 0.53g/mL | 0.45 micron | 1.23 micron |
| D90 | Specific surface area | Tap density | Density of compaction | Magnetic foreign matter | C |
| 3.54 micron | 12.1m2/g | 1.1g/mL | 2.43g/mL | 0.03ppm | 0.64％ |
Example 2
A preparation method of lithium cobalt phosphate comprises the following steps:
(1) adding phosphoric acid into cobalt powder for dissolving, adjusting the pH value of the solution to 3.9, then carrying out precision filtration to obtain a cobalt solution, slurrying lithium carbonate, and then introducing CO2Completely clarifying the lithium carbonate slurry to obtain a lithium solution, preparing a polyethylene glycol solution, taking the polyethylene glycol solution as a base solution, adding the cobalt solution and the lithium solution into the base solution while stirring, and continuously reacting for 45min after the addition is finished;
(2) spray drying the material reacted in the step (1) to obtain a spray dried material, putting the spray dried material into a roller furnace, introducing nitrogen gas to ensure that the oxygen content in the roller furnace is lower than 100ppm, sequentially passing the material through a heating section, a heat preservation section and a cooling section, wherein the heating speed of the heating section is 95 ℃/h, the temperature is increased to 735 ℃, the heat preservation section is subjected to heat preservation for 6.5h at the temperature, then cooling to the temperature lower than 80 ℃, and discharging to obtain a calcined material;
(3) conveying the calcined material to a jet mill through a pipeline, crushing the calcined material through air flow, screening the crushed calcined material after electromagnetic iron removal, sieving the crushed calcined material through a 200-mesh sieve, and then carrying out vacuum packaging to obtain the catalyst.
The molar ratio of the cobalt powder, the phosphoric acid and the lithium carbonate added in the step (1) is 1: 1.018: 0.504, the concentration of phosphoric acid is 6mol/L, the solid content of the lithium carbonate slurry is 45%, the purity of lithium carbonate is battery grade, the concentration of the polyethylene glycol solution is 0.45mol/L, the polyethylene glycol adopts a product with the polymerization degree of 4000, the volume of the polyethylene glycol solution is 1/7 of the total volume of the cobalt solution and the lithium solution, the feeding time is 110min, and the temperature in the feeding process and the reaction process is 60 ℃.
The air inlet temperature of the spray drying in the step (2) is 245 ℃, the discharging temperature is less than 100 ℃, the particle size of the spray drying material is 5.5 mu m, and the water content is less than 0.5%.
And (3) when the roller furnace is calcined in the step (2), at least two air inducing ports are arranged in the temperature rising section, the air inducing ports are communicated with a negative pressure fan, the volume of introduced nitrogen is 400 times of the volume of the added spray drying material, the furnace pressure in the roller furnace is maintained to be 75Pa, and the dew point of the gas in the roller furnace is maintained to be below minus 50 ℃.
And (3) electromagnetically removing iron by using a dry powder electromagnetic iron remover, wherein the magnetic induction intensity is 15000 gauss, iron removal residues obtained by electromagnetically removing iron are dissolved by adding dilute sulfuric acid, the reaction is carried out for 1.2h at the temperature of 55 ℃, then, the filtering is carried out, the obtained filter residues are dried, then, airflow is crushed, the obtained filter residues are screened after being electromagnetically removed, the obtained material is mixed with conventional materials for use, the concentration of the dilute sulfuric acid is 0.2mol/L, and the mass ratio of the iron removal residues to the dilute sulfuric acid is 1: 3.5.
And (3) the pipeline conveying in the step (3) adopts negative pressure conveying, an air source is heated to 115 ℃ during air flow crushing and then is in contact with the materials for crushing, the electromagnetic iron removal and the screening are carried out in a packaging room, the humidity of the packaging room is controlled to be less than 10%, and the temperature is maintained at 20-25 ℃.
The indexes of the finally obtained lithium cobalt phosphate are as follows:
| index (I) | Li | Co | Cd | Na | Ni |
| Numerical value | 4.11％ | 33.1％ | 3ppm | 29ppm | 6ppm |
| Mn | Zn | Cu | P | Al | Ca |
| 38ppm | 13ppm | 1ppm | 19.1％ | 45ppm | 28ppm |
| Sulfate radical | Chloride ion | Fe | Bulk density | D10 | D50 |
| 18ppm | 17ppm | 3ppm | 0.56g/mL | 0.52 micron | 1.34 micron |
| D90 | Specific surface area | Tap density | Density of compaction | Magnetic foreign matter | C |
| 4.2 micron | 11.2m2/g | 1.12g/mL | 2.46g/mL | 0.05ppm | 0.65％ |
Example 3
A preparation method of lithium cobalt phosphate comprises the following steps:
(1) adding phosphoric acid into cobalt powder for dissolving, adjusting the pH value of the solution to 4.3, then carrying out precision filtration to obtain a cobalt solution, slurrying lithium carbonate, and then introducing CO2Completely clarifying the lithium carbonate slurry to obtain a lithium solution, preparing a polyethylene glycol solution, taking the polyethylene glycol solution as a base solution, adding the cobalt solution and the lithium solution into the base solution while stirring, and continuously reacting for 40min after the addition is finished;
(2) spray drying the material reacted in the step (1) to obtain a spray dried material, putting the spray dried material into a roller furnace, introducing nitrogen gas to ensure that the oxygen content in the roller furnace is lower than 100ppm, sequentially passing the material through a heating section, a heat preservation section and a cooling section, wherein the heating speed of the heating section is 90 ℃/h, the temperature is increased to 735 ℃, the heat preservation section is subjected to heat preservation for 6.5h at the temperature, then cooling to the temperature lower than 80 ℃, and discharging to obtain a calcined material;
(3) conveying the calcined material to a jet mill through a pipeline, crushing the calcined material through air flow, screening the crushed calcined material after electromagnetic iron removal, sieving the crushed calcined material through a 250-mesh sieve, and then carrying out vacuum packaging to obtain the catalyst.
The molar ratio of the cobalt powder, the phosphoric acid and the lithium carbonate added in the step (1) is 1: 1.018: 0.504, the concentration of phosphoric acid is 6mol/L, the solid content of the lithium carbonate slurry is 48%, the purity of lithium carbonate is battery grade, the concentration of the polyethylene glycol solution is 0.43mol/L, the polyethylene glycol adopts a product with the polymerization degree of 6000, the volume of the polyethylene glycol solution is 1/9 of the total volume of the cobalt solution and the lithium solution, the feeding time is 100min, and the temperature in the feeding process and the reaction process is 65 ℃.
The air inlet temperature of the spray drying in the step (2) is 235 ℃, the discharging temperature is less than 100 ℃, the particle size of the spray drying material is 4.5 mu m, and the water content is less than 0.5 percent.
And (3) when the roller furnace is calcined in the step (2), at least two air inducing ports are arranged in the temperature rising section, the air inducing ports are communicated with a negative pressure fan, the volume of introduced nitrogen is 500 times of the volume of the added spray drying material, the furnace pressure in the roller furnace is maintained to be 75Pa, and the dew point of the gas in the roller furnace is maintained to be below minus 50 ℃.
And (3) electromagnetically removing iron by using a dry powder electromagnetic iron remover, wherein the magnetic induction intensity is 15000 gauss, iron removal residues obtained by electromagnetically removing iron are dissolved by adding dilute sulfuric acid, the reaction is carried out for 1.5h at the temperature of 55 ℃, then, the filtering is carried out, the obtained filter residues are dried, then, airflow is crushed, the obtained filter residues are screened after being electromagnetically removed, the obtained material is mixed with conventional materials for use, the concentration of the dilute sulfuric acid is 0.2mol/L, and the mass ratio of the iron removal residues to the dilute sulfuric acid is 1: 3.5.
And (3) the pipeline conveying in the step (3) adopts negative pressure conveying, an air source is heated to 110 ℃ during air flow crushing and then is in contact with the materials for crushing, the electromagnetic iron removal and the screening are carried out in a packaging room, the humidity of the packaging room is controlled to be less than 10%, and the temperature is maintained at 20-25 ℃.
The indexes of the finally obtained lithium cobalt phosphate are as follows:
as shown in FIGS. 1, 2 and 3, according to SEM, the obtained lithium cobalt phosphate is coated with fibrous carbon particles and spherical particles are obtained, and the size of the primary particles is basically between 100-400 nm.
The products of example 1, example 2 and example 3 were tested for their electrochemical performance and the results were as follows:
| example 1 | Example 2 | Example 3 | |
| 0.1C charging capacity (mAh/g) | 162.1 | 161.2 | 163 |
| 0.1C discharge capacity (mAh/g) | 158.7 | 158.1 | 157.9 |
| Efficiency of discharge | 97.9％ | 98.1％ | 96.9％ |
| Cycle performance (25 ℃ C.) | 89.2％ | 88.7％ | 88.9％ |
| Cycle performance (55 ℃ C.) | 84.8％ | 84.1％ | 83.9％ |
The cycle performance (25 ℃) refers to the ratio of the discharge capacity after 2000 times of charge-discharge cycles to the first cycle discharge capacity under the condition of the rate of 1.0C at 25 ℃; the cycle performance (55 ℃) is the ratio of the discharge capacity after 2000 times of charge-discharge cycles to the first cycle discharge capacity under the conditions of 55 ℃ and 1.0C rate.
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 (4)
1. The preparation method of lithium cobalt phosphate is characterized by comprising the following steps:
(1) dissolving cobalt powder in phosphoric acid, adjusting pH of the solution to 3.5-4.5, fine filtering to obtain cobalt solution, slurrying lithium carbonate, and introducing CO2Completely clarifying the lithium carbonate slurry to obtain a lithium solution, preparing a polyethylene glycol solution, taking the polyethylene glycol solution as a base solution, adding the cobalt solution and the lithium solution into the base solution while stirring, and continuously reacting for 30-60min after the addition is finished; the molar ratio of the added cobalt powder to the added phosphoric acid to the added lithium carbonate is 1: 1.01-1.02: 0.501-0.505, the concentration of phosphoric acid is 5-6mol/L, the solid content of the lithium carbonate slurry is 40-50%, the purity of lithium carbonate is battery grade, the concentration of polyethylene glycol solution is 0.3-0.5mol/L, and the polymerization degree of polyethylene glycol is 2000. 4000 or 6000, wherein the volume of the polyethylene glycol solution is 1/5-1/10 of the total volume of the cobalt solution and the lithium solution, the feeding time is 60-120min, and the temperature in the feeding process and the reaction process is 50-65 ℃;
(2) spray drying the material reacted in the step (1) to obtain a spray drying material, putting the spray drying material into a roller furnace, introducing nitrogen gas to ensure that the oxygen content in the roller furnace is lower than 100ppm, sequentially passing the material through a temperature rising section, a heat preservation section and a temperature reduction section, wherein the temperature rising speed of the temperature rising section is 80-100 ℃/h, the temperature rises to 740 ℃ when the temperature is 720-; when the material is calcined in the roller furnace, at least two air induction ports are arranged in the temperature rising section and are communicated with a negative pressure fan, the volume of the introduced nitrogen is 600 times of the volume of the added spray drying material, the furnace pressure in the roller furnace is maintained to be 50-80Pa, and the dew point of the gas in the furnace is maintained to be below 50 ℃ below zero;
(3) conveying the calcined material to a jet mill through a pipeline, crushing the calcined material through air flow, screening the crushed calcined material after electromagnetic iron removal, sieving the crushed calcined material through a 200-fold and 250-mesh sieve, and then carrying out vacuum packaging to obtain the catalyst.
2. The method for preparing lithium cobalt phosphate according to claim 1, wherein: the air inlet temperature of the spray drying in the step (2) is 200-.
3. The method for preparing lithium cobalt phosphate according to claim 1, wherein: in the step (3), a dry powder electromagnetic iron remover is adopted for electromagnetic iron removal, the magnetic induction intensity is 10000-15000 gauss, iron removal residues obtained by the electromagnetic iron removal are added into dilute sulfuric acid for dissolution, the reaction is carried out for 1-2h at the temperature of 50-60 ℃, then the filtration is carried out, the obtained filter residues are dried and then crushed by air flow, the obtained filter residues are screened after the electromagnetic iron removal, the obtained material and the conventional material are mixed for use, the concentration of the dilute sulfuric acid is 0.1-0.3mol/L, and the mass ratio of the iron removal residues to the dilute sulfuric acid is 1: 3-4.
4. The method for preparing lithium cobalt phosphate according to claim 1, wherein: and (3) the pipeline conveying in the step (3) adopts negative pressure conveying, an air source is heated to 120 ℃ for air flow crushing and then is contacted with the materials for crushing, the electromagnetic iron removal and the screening are carried out in a packaging room, the humidity of the packaging room is controlled to be less than 10%, and the temperature is maintained at 20-25 ℃.
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