Disclosure of Invention
The invention aims to provide a preparation method of a lithium iron phosphate composite material, which has the effects of improving the conductivity, reducing the carbon content, improving the metal content and balancing the tap density and the electrochemical specific capacity of a lithium iron phosphate material.
The technical purpose of the invention is realized by the following technical scheme: a preparation method of a lithium iron phosphate composite material comprises the following steps:
preparing materials, namely weighing an iron source, a phosphorus source and an organic carbon source I, wherein the molar ratio of iron to phosphorus is 0.95-1:1, and the molar ratio of iron to carbon is 1: 0.1;
ball milling: taking the raw materials in the step (1), sequentially adding the raw materials into a ball mill for ball milling, adding a ball milling medium into the ball mill, and controlling ball milling: d50 of 0.5-2 μm, DmaxLess than 10 mu m to obtain ball milling slurry;
step (3), drying the double cones: taking the ball-milling slurry obtained in the step (2) to perform bipyramid drying at the temperature of 80-100 ℃;
and (4) sintering: sintering the material obtained after drying in the step (3) at high temperature of 400-700 ℃ in an inert gas protection furnace for 2-10h to prepare a precursor of the lithium iron phosphate composite material;
and (5) crushing: crushing the precursor of the lithium iron phosphate composite material, ball-milling in a dispersant medium after crushing, and controlling DmaxLess than 20 mu m to obtain precursor slurry of the lithium iron phosphate composite material;
step (6) material preparation and mixing: stirring and mixing the precursor slurry of the lithium iron phosphate composite material, lithium carbonate, a secondary organic carbon source, a nitrogen source, a metal source and a sanding medium uniformly, wherein Li: fe: p: x: the molar ratio of C is 0.98-1.03:0.95-1.0:1-1.05:0.01-0.05:1.5, X is a metal element, and C represents a carbon source;
sanding in step (7): putting the material obtained in the step (6) into a sand mill for sand milling, and controlling the sand milling granularity D50 to be 0.4-1 mu m;
step (8) spray drying: spray drying the sanded material at the temperature of 180 ℃ and 250 ℃, and controlling the drying granularity D50 to be 5-15 mu m and DmaxLess than 25 μm, and the water content is less than 4%;
and (9) sintering: sintering at the temperature of 700 ℃ and 800 ℃ for 4-15h, cooling and crushing to obtain the lithium iron phosphate material coated with the metal carbide or the metal carbonitride or the metal nitride.
The invention is further provided with: in the step (2), the feeding sequence is sequentially an iron source, a phosphorus source and an organic carbon source I.
The invention is further provided with: in the step (2), the ball-milling medium is one or more of alcohol, acetone, polyacrylonitrile and water, and the mass ratio of the raw materials and the ball-milling medium in the step (1) is 1: 2; in the step (6), the sanding medium is one or more of water, alcohol, acetone and polyacrylonitrile.
The invention is further provided with: in the step (2), the granularity of ball milling is controlled to be D50:1-4 mu m, DmaxLess than 10 μm, and in the step (7), the granularity of the sand grinding is controlled to be D50:0.4-1 μm, and D90 is less than 2 μm.
The invention is further provided with: in the step (4), the precursor of the lithium iron phosphate composite material is ferrous pyrophosphate.
The invention is further provided with: and (5) sequentially crushing the lithium iron phosphate composite material precursor by a jaw crusher and a mechanical crusher.
The invention is further provided with: in the step (2), the ball milling time is 4 h; in the step (7), the sanding time is 4 hours.
The invention is further provided with: the organic carbon source I is one or more of glucose, polypropylene, soluble starch and graphene, and the organic carbon source II is one or more of glucose, polypropylene, soluble starch and graphene; the iron source is one or more of ferrous oxalate, iron oxide red and iron powder, the phosphorus source is one or more of ammonium dihydrogen phosphate, iron phosphate and lithium dihydrogen phosphate, and the nitrogen source is one or more of urea, amino acid and nitrogen-containing organic matters; the metal source is one or more of vanadium pentoxide, nano tungsten oxide, nano chromium trioxide, nano magnesium oxide, nano magnesium hydroxide, ammonium metavanadate and vanadyl acetylacetonate.
The invention is further provided with: in the step (9), the particle size of the obtained lithium iron phosphate composite material is controlled to be D10 more than 1.0 mu m, D50:1.5-4 mu m, D90 less than 10 mu m, and DmaxLess than 30 μm and water content less than 1000 ppm.
The invention is further provided with: and (4) coating the surface of the lithium iron phosphate composite material obtained in the step (9) with a metal carbide or a metal carbonitride, wherein the C element content in the surface coating material is lower than 1%.
The invention has the beneficial effects that:
1. the lithium iron phosphate composite material prepared by the method is coated with the metal carbide and the metal carbonitride, so that the tap density and the conductivity of the lithium iron phosphate composite material are improved, and meanwhile, the lithium iron phosphate composite material has the characteristics of low carbon content and high metal content, the content of C element in the coating material is about 0.5 percent and is far lower than 1.0-1.5 percent of the content of C element in the coating material of the railway phosphate composite material in the prior art, and the prepared lithium iron phosphate composite material can well balance between tap density and electrochemical specific capacity.
2. The lithium iron phosphate composite material prepared by the invention has excellent conductivity, tap density and electrochemical performance, and is low in carbon content, common and easily available in used raw materials, low in price, simple in process, suitable for large-scale production, high in raw material utilization rate, small in emission, environment-friendly, low in pollution and low in cost, and has a better application prospect.
Detailed Description
The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.
Example 1
A preparation method of a lithium iron phosphate composite material, namely VC coated with lithium iron phosphate, comprises the following steps
Step (1) preparation of materials: mixing a phosphorus source, an iron source and a carbon source according to a molar ratio of 1:1: 0.1.
Ball milling: adding the raw materials weighed in the step (1) into a ball mill, sequentially adding an iron source, a phosphorus source and an organic carbon source I, finally adding alcohol serving as a ball milling medium, wherein the mass ratio of the raw materials to the alcohol is 1:3, the rotating speed of the ball mill is 60rpm, ball milling is carried out for 4 hours, and the ball milling particle size is controlled: d50 of 0.5-2 μm, DmaxLess than 10 mu m to obtain ball milling slurry.
Step (3), drying the double cones: and (3) taking the ball-milling slurry obtained in the step (2) to perform bipyramid drying at the temperature of 95 ℃.
And (4) sintering: and (4) putting the dried material obtained in the step (3) into a nitrogen protection furnace, heating to 500 ℃ at a speed of 5 ℃/min, preserving the temperature for 2 hours, and naturally cooling to room temperature to obtain a precursor of the lithium iron phosphate composite material, namely ferrous pyrophosphate.
And (5) crushing: carrying out jaw crushing and mechanical crushing treatment on ferrous pyrophosphate, carrying out ball milling in secondary reverse osmosis pure water, and controlling DmaxLess than 20 mu m to obtain the ferrous pyrophosphate slurry.
Step (6) material preparation and mixing: mixing ferrous pyrophosphate slurry, a carbon source, a lithium source and a metal vanadium source according to the molar ratio: fe: P: Li: V: c is 0.98:1:1.01:0.02, the molar ratio of Li to C is 1:1.5, secondary reverse osmosis pure water is added as a sanding medium and is uniformly mixed by a homogenizing pump.
Sanding in step (7): squeeze into the material that step (6) obtained in the sand mill and sand, control sanding granularity D50: 0.5-1.0 μm, D90 less than 2 μm, sanding for 4 hours;
step (8) spray drying: spray drying at 220 deg.C, controlling the drying particle size D50:10 μm, DmaxLess than 25 μm, and the water content is less than 4%;
and (9) sintering: taking the material obtained in the step (8), and putting the material into nitrogen for protectionHeating to 450 deg.C at 5 deg.C/min, keeping the temperature for 2 hr, directly heating to 750 deg.C, keeping the temperature for 10 hr, cooling, crushing, and pulverizing to particle size D10 > 1.0 μm, D50:1.5-4 μm, D90 < 10 μm, and DmaxLess than 30 mu m and less than 1000ppm of water content to obtain LiFePO4Sample 1 of the/VC composite material.
And (10) uniformly mixing the prepared sample 1, acetylene black and PVDF in a mass ratio of 90:5:5, dispersing in a proper amount of NMP, continuously stirring uniformly to obtain anode slurry, coating the anode slurry on an aluminum foil, drying at 60 ℃, flattening by using a press to prepare a lithium iron phosphate anode, preparing a button cell CR2025 model, and carrying out electrochemical detection.
Example 2
A preparation method of a lithium iron phosphate composite material, namely VCN coated with lithium iron phosphate, comprises the following steps
Step (1) preparation of materials: mixing a phosphorus source, an iron source and a carbon source according to a molar ratio of 1:1: 0.1.
Ball milling: adding the raw materials weighed in the step (1) into a ball mill, sequentially adding an iron source, a phosphorus source and a carbon source, finally adding alcohol serving as a ball milling medium, wherein the mass ratio of the raw materials to the alcohol is 1:3, the rotating speed of the ball mill is 60rpm, ball milling is carried out for 4 hours, and the ball milling particle size is controlled: d50 of 0.5-2 μm, DmaxLess than 10 mu m to obtain ball milling slurry.
Step (3), drying the double cones: taking the ball-milling slurry obtained in the step (2), carrying out bipyramid drying at the temperature of 95 ℃,
and (4) sintering: and (4) putting the dried material obtained in the step (3) into a nitrogen protection furnace, heating to 500 ℃ at a speed of 5 ℃/min, preserving the temperature for 2 hours, and naturally cooling to room temperature to obtain a precursor of the lithium iron phosphate composite material, namely ferrous pyrophosphate.
And (5) crushing: carrying out jaw crushing and mechanical crushing treatment on ferrous pyrophosphate, carrying out ball milling in secondary reverse osmosis pure water, and controlling DmaxLess than 20 mu m to obtain the ferrous pyrophosphate slurry.
Step (6) material preparation and mixing: mixing the crushed ferrous pyrophosphate, a carbon source, a lithium source, a vanadium source and a nitrogen source according to the molar ratio: and adding secondary reverse osmosis pure water as a sanding medium into the mixture, and uniformly mixing the mixture by using a homogenizing pump.
Sanding in step (7): squeeze into the material that step (6) obtained in the sand mill and sand, control sanding granularity D50: 0.5-1.0 μm, D90 < 2 μm, and sanding time 4 hr.
Step (8) spray drying: spray drying at 220 deg.C, controlling the drying particle size D50:10 μm, DmaxLess than 25 μm, and the water content is less than 4%;
and (9) sintering: putting the material obtained in the step (8) into a fluidized bed reactor heated by ammonia plasma for carrying out a reaction in a maintenance way, heating the material by a heating system assisted by a plasma main heating source and a thermal resistance wire, heating the material to 450 ℃ at a speed of 5 ℃/min, keeping the temperature for 2 hours, directly heating the material to 750 ℃, keeping the temperature for 10 hours, cooling the material, crushing and crushing the material, controlling the granularity to be D10 more than 1.0 mu m, D50:1.5-4 mu m, D90 less than 10 mu m, and controlling the granularity to be D10 more than 1.0 mu mmaxLess than 30 mu m and less than 1000ppm of water content to obtain LiFePO4Sample 2 of the/VCN composite.
And (10) uniformly mixing the prepared sample 2, acetylene black and PVDF in a mass ratio of 90:5:5, dispersing in a proper amount of NMP, continuously stirring uniformly to obtain anode slurry, coating the anode slurry on an aluminum foil, drying at 60 ℃, flattening by using a press to prepare a lithium iron phosphate anode, preparing a button cell CR2025 model, and carrying out electrochemical detection.
Example 3
A preparation method of a lithium iron phosphate composite material, namely WC coated by lithium iron phosphate comprises the following steps
Step (1) preparation of materials: mixing a phosphorus source, an iron source and a carbon source according to a molar ratio of 1:1: 0.1.
Ball milling: adding the raw materials weighed in the step (1) into a ball mill, sequentially adding an iron source, a phosphorus source and a carbon source, finally adding alcohol serving as a ball milling medium, wherein the mass ratio of the raw materials to the alcohol is 1:3, the rotating speed of the ball mill is 60rpm, ball milling is carried out for 4 hours, and the ball milling particle size is controlled: d50 of 0.5-2 μm, DmaxLess than 10 mu m to obtain ball milling slurry.
Step (3), drying the double cones: and (3) taking the ball-milling slurry obtained in the step (2) to perform bipyramid drying at the temperature of 95 ℃.
And (4) sintering: and (4) putting the dried material obtained in the step (3) into a nitrogen protection furnace, heating to 500 ℃ at a speed of 5 ℃/min, preserving the temperature for 2 hours, and naturally cooling to room temperature to obtain a precursor of the lithium iron phosphate composite material, namely ferrous pyrophosphate.
And (5) crushing: carrying out jaw crushing and mechanical crushing treatment on ferrous pyrophosphate, carrying out ball milling in secondary reverse osmosis pure water, and controlling DmaxLess than 20 mu m to obtain the ferrous pyrophosphate slurry.
Step (6) material preparation and mixing: mixing the crushed ferrous pyrophosphate, a carbon source, a lithium source and a metal tungsten source according to the molar ratio: and (3) adding secondary reverse osmosis pure water serving as a sanding medium into the mixture, and uniformly mixing the mixture by using a homogenizing pump.
Sanding in step (7): squeeze into the material that step (6) obtained in the sand mill and sand, control sanding granularity D50: 0.5-1.0 μm, D90 less than 2 μm, sanding for 4 hours;
step (8) spray drying: spray drying at 220 deg.C, controlling the drying particle size D50:10 μm, DmaxLess than 25 μm, and the water content is less than 4%;
and (9) sintering: putting the material obtained in the step (8) into a nitrogen protection furnace, heating to 450 ℃ at a speed of 5 ℃/min, preserving heat for 2 hours, directly heating to 750 ℃, preserving heat for 10 hours, cooling, crushing and crushing, wherein the granularity is controlled to be D10 more than 1.0 mu m, D50 is 1.5-4 mu m, D90 is less than 10 mu m, and DmaxLess than 30 mu m and less than 1000ppm of water content to obtain LiFePO4the/WC composite sample 3.
And (10) uniformly mixing the prepared sample 2, acetylene black and PVDF in a mass ratio of 90:5:5, dispersing in a proper amount of NMP, continuously stirring uniformly to obtain anode slurry, coating the anode slurry on an aluminum foil, drying at 60 ℃, flattening by using a press to prepare a lithium iron phosphate anode, preparing a button cell CR2025 model, and carrying out electrochemical detection.
Example 4
A preparation method of a lithium iron phosphate composite material, namely a lithium iron phosphate coated WCN, comprises the following steps
Step (1) preparation of materials: mixing a phosphorus source, an iron source and a carbon source according to a molar ratio of 1:1: 0.1.
Ball milling: adding the raw materials weighed in the step (1) into a ball mill, sequentially adding an iron source, a phosphorus source and a carbon source, finally adding alcohol serving as a ball milling medium, wherein the mass ratio of the raw materials to the alcohol is 1:3, the rotating speed of the ball mill is 60rpm, ball milling is carried out for 4 hours, and the ball milling particle size is controlled: d50 of 0.5-2 μm, DmaxLess than 10 mu m to obtain ball milling slurry.
Step (3), drying the double cones: and (3) taking the ball-milling slurry obtained in the step (2) to perform bipyramid drying at the temperature of 95 ℃.
And (4) sintering: and (4) putting the dried material obtained in the step (3) into a nitrogen protection furnace, heating to 500 ℃ at a speed of 5 ℃/min, preserving the temperature for 2 hours, and naturally cooling to room temperature to obtain a precursor of the lithium iron phosphate composite material, namely ferrous pyrophosphate.
And (5) crushing: carrying out jaw crushing and mechanical crushing treatment on ferrous pyrophosphate, carrying out ball milling in secondary reverse osmosis pure water, and controlling DmaxLess than 20 mu m to obtain the ferrous pyrophosphate slurry.
Step (6) material preparation and mixing: ferrous pyrophosphate slurry, a carbon source, a lithium source and a tungsten source are mixed, wherein the molar ratio of a nitrogen source is as follows: and adding secondary reverse osmosis pure water as a sanding medium, and uniformly mixing the materials by using a homogenizing pump.
Sanding in step (7): squeeze into the material that step (6) obtained in the sand mill and sand, control sanding granularity D50: 0.5-1.0 μm, D90 less than 2 μm, sanding for 4 hours;
step (8) spray drying: spray drying at 220 deg.C, controlling drying particle size D50 at 10 μm, and water content less than 4%;
and (9) sintering: putting the material obtained in the step (8) into a fluidized bed reactor heated by ammonia plasma for carrying out a reaction in a maintenance way, heating the material by a heating system assisted by a plasma main heating source and a thermal resistance wire, heating the material to 450 ℃ at a speed of 5 ℃/min, keeping the temperature for 2 hours, directly heating the material to 750 ℃, keeping the temperature for 10 hours, cooling the material, crushing and crushing the material, controlling the granularity to be D10 more than 1.0 mu m, D50:1.5-4 mu m, D90 less than 10 mu m, and controlling the granularity to be D10 more than 1.0 mu mmaxLess than 30 mu m, the water content is controlled to be less than 1000ppm, and L is obtainediFePO4the/WCN composite sample 4 was,
and (10) uniformly mixing the prepared sample 4, acetylene black and PVDF in a mass ratio of 90:5:5, dispersing in a proper amount of NMP, continuously stirring uniformly to obtain anode slurry, coating the anode slurry on an aluminum foil, drying at 60 ℃, flattening by using a press to prepare a lithium iron phosphate anode, preparing a button cell CR2025 model, and carrying out electrochemical detection.
Example 5
Preparation method of lithium iron phosphate composite material, lithium iron phosphate coats Mg3N2Comprises the following steps
Step (1) preparation of materials: mixing a phosphorus source, an iron source and a carbon source according to a molar ratio of 1:1: 0.1.
Ball milling: adding the raw materials weighed in the step (1) into a ball mill, sequentially adding an iron source, a phosphorus source and a carbon source, finally adding alcohol serving as a ball milling medium, wherein the mass ratio of the raw materials to the alcohol is 1:3, the rotating speed of the ball mill is 60rpm, ball milling is carried out for 4 hours, and the ball milling particle size is controlled: d50 of 0.5-2 μm, DmaxLess than 10 mu m to obtain ball milling slurry.
Step (3), drying the double cones: and (3) taking the ball-milling slurry obtained in the step (2) to perform bipyramid drying at the temperature of 95 ℃.
And (4) sintering: and (4) putting the dried material obtained in the step (3) into a nitrogen protection furnace, heating to 500 ℃ at a speed of 5 ℃/min, preserving the temperature for 2 hours, and naturally cooling to room temperature to obtain a precursor of the lithium iron phosphate composite material, namely ferrous pyrophosphate.
And (5) crushing: carrying out jaw crushing and mechanical crushing treatment on ferrous pyrophosphate, carrying out ball milling in secondary reverse osmosis pure water, and controlling DmaxLess than 20 mu m to obtain the ferrous pyrophosphate slurry.
Step (6) material preparation and mixing: the molar ratio of ferrous pyrophosphate slurry to carbon source, lithium source, metal magnesium source and nitrogen source is as follows: and adding secondary reverse osmosis pure water as a sanding medium, and uniformly mixing the materials by using a homogenizing pump.
Sanding in step (7): and (3) sanding the sand mill obtained in the step (6), and controlling the sanding granularity D50: 0.5-1.0 μm, sanding for 4 hours;
step (8) spray drying: spray drying at 220 deg.C, controlling the drying particle size D50:10 μm, DmaxLess than 25 μm, and the water content is less than 4%;
and (9) sintering: putting the material obtained in the step (8) into a fluidized bed reactor heated by ammonia plasma for carrying out a reaction in a maintenance way, heating the material by a heating system assisted by a plasma main heating source and a thermal resistance wire, heating the material to 450 ℃ at a speed of 5 ℃/min, keeping the temperature for 2 hours, directly heating the material to 750 ℃, keeping the temperature for 10 hours, cooling the material, crushing and crushing the material, controlling the granularity to be D10 more than 1.0 mu m, D50:1.5-4 mu m, D90 less than 10 mu m, and controlling the granularity to be D10 more than 1.0 mu mmaxLess than 30 mu m and less than 1000ppm of water content to obtain LiFePO4/Mg3N2Sample 5.
And (10) uniformly mixing the prepared sample 5, acetylene black and PVDF in a mass ratio of 90:5:5, dispersing in a proper amount of NMP, continuously stirring uniformly to obtain anode slurry, coating the anode slurry on an aluminum foil, drying at 60 ℃, flattening by using a press to prepare a lithium iron phosphate anode, preparing a button cell CR2025 model, and carrying out electrochemical detection.
Example 6
Preparation method of lithium iron phosphate composite material, lithium iron phosphate is coated with Cr2C3Comprises the following steps
Step (1) preparation of materials: mixing a phosphorus source, an iron source and a carbon source according to a molar ratio of 1:1: 0.1.
Ball milling: adding the raw materials weighed in the step (1) into a ball mill, sequentially adding an iron source, a phosphorus source and a carbon source, finally adding alcohol serving as a ball milling medium, wherein the mass ratio of the raw materials to the alcohol is 1:3, the rotating speed of the ball mill is 60rpm, ball milling is carried out for 4 hours, and the ball milling particle size is controlled: d50 of 0.5-2 μm, DmaxLess than 10 mu m to obtain ball milling slurry.
Step (3), drying the double cones: and (3) taking the ball-milling slurry obtained in the step (2) to perform bipyramid drying at the temperature of 95 ℃.
And (4) sintering: and (4) putting the dried material obtained in the step (3) into a nitrogen protection furnace, heating to 500 ℃ at a speed of 5 ℃/min, preserving the temperature for 2 hours, and naturally cooling to room temperature to obtain a precursor of the lithium iron phosphate composite material, namely ferrous pyrophosphate.
And (5) crushing: carrying out jaw crushing and mechanical crushing treatment on ferrous pyrophosphate, carrying out ball milling in secondary reverse osmosis pure water, and controlling DmaxLess than 20 mu m to obtain the ferrous pyrophosphate slurry.
Step (6) material preparation and mixing: the mol ratio of the ferrous pyrophosphate slurry to the carbon source to the lithium source to the chromium source is as follows: and (3) adding secondary reverse osmosis pure water serving as a sanding medium into the mixture, and uniformly mixing the mixture by using a homogenizing pump.
Sanding in step (7): squeeze into the material that step (6) obtained in the sand mill and sand, control sanding granularity D50: 0.5-1.0 μm, sanding for 4 hours;
step (8) spray drying: spray drying at 220 deg.C, controlling the drying particle size D50:10 μm, DmaxLess than 25 μm, and the water content is less than 4%;
and (9) sintering: heating to 450 ℃ at the speed of 5 ℃/min, preserving heat for 2 hours, directly heating to 750 ℃, preserving heat for 10 hours, cooling, crushing and crushing to obtain LiFePO4/Cr2C3The composite material of sample 6 was prepared by the method,
and (10) uniformly mixing the prepared sample 2, acetylene black and PVDF in a mass ratio of 90:5:5, dispersing in a proper amount of NMP, continuously stirring uniformly to obtain anode slurry, coating the anode slurry on an aluminum foil, drying at 60 ℃, flattening by using a press to prepare a lithium iron phosphate anode, preparing a button cell CR2025 model, and carrying out electrochemical detection.
Example 7
A preparation method of a lithium iron phosphate composite material, namely a lithium iron phosphate coated CrCN, comprises the following steps
Step (1) preparation of materials: mixing a phosphorus source, an iron source and a carbon source according to a molar ratio of 1:1: 0.1.
Ball milling: adding the raw materials weighed in the step (1) into a ball mill, sequentially adding an iron source, a phosphorus source and a carbon source, finally adding alcohol serving as a ball milling medium, wherein the mass ratio of the raw materials to the alcohol is 1:3, the rotating speed of the ball mill is 60rpm, ball milling is carried out for 4 hours, and the ball milling particle size is controlled: d50 of 0.5-2 μm, Dmax<10μAnd m, obtaining the ball milling slurry.
Step (3), drying the double cones: and (3) taking the ball-milling slurry obtained in the step (2) to perform bipyramid drying at the temperature of 95 ℃.
And (4) sintering: and (4) putting the dried material obtained in the step (3) into a nitrogen protection furnace, heating to 500 ℃ at a speed of 5 ℃/min, preserving the temperature for 2 hours, and naturally cooling to room temperature to obtain a precursor of the lithium iron phosphate composite material, namely ferrous pyrophosphate.
And (5) crushing: carrying out jaw crushing and mechanical crushing treatment on ferrous pyrophosphate, carrying out ball milling in secondary reverse osmosis pure water, and controlling DmaxLess than 20 mu m to obtain the ferrous pyrophosphate slurry.
Step (6) material preparation and mixing: the molar ratio of ferrous pyrophosphate slurry to carbon source, lithium source, chromium source and nitrogen source is as follows: and adding secondary reverse osmosis pure water as a sanding medium, and uniformly mixing the materials by using a homogenizing pump.
Sanding in step (7): squeeze into the material that step (6) obtained in the sand mill and sand, control sanding granularity D50: 0.5-1.0 μm, sanding for 4 hours;
step (8) spray drying: spray drying at 220 deg.C, controlling the drying particle size D50:10 μm, DmaxLess than 25 μm, and the water content is less than 4%;
and (9) sintering: taking the material obtained in the step (8), putting the material into an ammonia plasma heating fluidized bed reactor for carrying out a centering reaction, heating the material by a heating system through a plasma main heating source and a thermal resistance wire in an auxiliary manner, directly heating the material to 750 ℃ after heating the material to 450 ℃ at a speed of 5 ℃/min and preserving the temperature for 2 hours, continuously preserving the temperature for 10 hours and cooling the material, and crushing the material to obtain LiFePO4the/CrN composite sample 7 was,
and (10) uniformly mixing the prepared sample 2, acetylene black and PVDF in a mass ratio of 90:5:5, dispersing in a proper amount of NMP, continuously stirring uniformly to obtain anode slurry, coating the anode slurry on an aluminum foil, drying at 60 ℃, flattening by using a press to prepare a lithium iron phosphate anode, preparing a button cell CR2025 model, and carrying out electrochemical detection.
Table 1 shows the electrochemical properties of examples 1 to 7.
Name (R)
|
O.1C/mAh/g
|
O.2C/mAh/g
|
1.0C/mAh/g
|
Capacity retention/% for 80 weeks of cycles
|
Example 1
|
158.2
|
154.2
|
145.7
|
98.19
|
Example 2
|
160.1
|
156.5
|
145.8
|
99.2
|
Example 3
|
159.2
|
154.9
|
143.8
|
97.8
|
Example 4
|
158.1
|
155.2
|
145.9
|
98.1
|
Example 5
|
161.5
|
157.6
|
146.8
|
98.2
|
Example 6
|
159.8
|
156.3
|
145.6
|
98.5
|
Example 7
|
157.9
|
153.7
|
142.5
|
99.1 |
Table 2 is a table of tap densities for examples 1 to 7