CN118156491A - Ultralow-temperature phosphoric acid positive electrode material and preparation method thereof - Google Patents
Ultralow-temperature phosphoric acid positive electrode material and preparation method thereof Download PDFInfo
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Abstract
The invention provides an ultralow-temperature phosphoric acid positive electrode material and a preparation method thereof, and relates to the technical field of lithium batteries. The preparation method comprises the following steps: preparing solid-phase particles according to a solid-phase method, wherein the particle size of the solid-phase particles is 1000-3500 nm; preparing liquid phase particles according to a liquid phase method, wherein the particle size of the liquid phase particles is 50-500 nm; and mixing the solid phase particles and the liquid phase particles to obtain the ultralow-temperature phosphoric acid anode material, wherein the components of the solid phase particles and the liquid phase particles are one or more of lithium iron phosphate, lithium manganese phosphate and lithium iron manganese phosphate. Solid phase particles with larger particle size are obtained by a solid phase method, liquid phase particles with smaller particle size are obtained by a liquid phase method, and particles with different particle sizes are mixed, so that the phosphoric acid positive electrode material with excellent low-temperature performance is obtained by blending.
Description
Technical Field
The disclosure relates to the technical field of lithium batteries, and in particular relates to an ultralow-temperature phosphoric acid positive electrode material and a preparation method thereof.
Background
Along with the increasing prominence of energy problems and environmental protection problems, the lithium ion battery is widely applied to the fields of smart phones, digital cameras, electric vehicles and the like due to the excellent comprehensive performance and environmental protection. In the lithium ion battery, the lithium iron phosphate material has the advantages of low price, good safety performance, long service life and the like, and becomes the main lithium battery power material at present. The true density of lithium iron phosphate is 3.6g/mL, but because it contains carbon and voids, its compacted density is typically well below 3.6g/mL. The compacted density of lithium iron phosphate currently on the market is generally up to 2.5g/mL. In the prior art, a plurality of processes are adopted to improve the compaction density of the lithium iron phosphate material, the lithium iron phosphate material is synthesized by a solid phase method, and then the lithium iron phosphate material is ground to obtain large-particle and small-particle products. And filling the large particles and the small particles in a matched manner to obtain the high-compaction lithium iron phosphate material. However, the lithium iron phosphate material obtained by the method has the advantages that the filled small particles can provide the compacted density of the material to a certain extent, the electrochemical performance of the material is improved to a limited extent, and the crystal structure of the product is damaged to a certain extent in the grinding process, so that the cycle performance of the product is poor.
It should be noted that the information disclosed in the above background section is only for enhancing understanding of the background of the present disclosure and thus may include information that does not constitute prior art known to those of ordinary skill in the art.
Disclosure of Invention
In order to solve the technical problems, the disclosure provides an ultralow-temperature phosphoric acid positive electrode material and a preparation method thereof.
A first aspect of the present disclosure provides a method for preparing an ultralow-temperature phosphoric acid positive electrode material, including:
preparing solid-phase particles according to a solid-phase method, wherein the particle size of the solid-phase particles is 1000-3500 nm;
preparing liquid phase particles according to a liquid phase method, wherein the particle size of the liquid phase particles is 50-500 nm;
And mixing the solid phase particles and the liquid phase particles to obtain the ultralow-temperature phosphoric acid anode material, wherein the components of the solid phase particles and the liquid phase particles are one or more of lithium iron phosphate, lithium manganese phosphate and lithium iron manganese phosphate.
In one exemplary embodiment of the present disclosure, the solid phase particles have a particle size of 1000 to 2000nm and the liquid phase particles have a particle size of 100 to 400nm.
In one exemplary embodiment of the present disclosure, the particle size ratio of the solid phase particles to the liquid phase particles is 10:1 to 4.
In one exemplary embodiment of the present disclosure, the particle size ratio of the solid phase particles to the liquid phase particles is 10:1.5 to 3.
In one exemplary embodiment of the present disclosure, the preparing solid phase particles according to the solid phase method includes: adding metal phosphate, a lithium source and a carbon source into water to obtain a mixture, wherein the metal phosphate is selected from ferric phosphate and/or manganese phosphate; grinding the mixture to a particle size of 1000-3500 nm to obtain an abrasive; and (3) carrying out spray drying on the grinding material, and then sintering to obtain the solid-phase particles.
In an exemplary embodiment of the present disclosure, in the spray-drying the abrasive, the sintering process includes: sintering for 5-12 h at the first temperature under the inert atmosphere, cooling, and sintering for 5-12 h at the second temperature to obtain the solid phase particles.
In one exemplary embodiment of the present disclosure, the sintering is performed at the first temperature for 10 to 12 hours, the sintering is performed at the second temperature for 5 to 8 hours, and the second temperature is higher than the first temperature.
In one exemplary embodiment of the present disclosure, the sintering is performed at the first temperature for 10 to 12 hours, the sintering is performed at the second temperature for 5 to 8 hours, and the second temperature is higher than the first temperature.
In one exemplary embodiment of the present disclosure, the preparing liquid phase macroparticles according to the liquid phase method includes: mixing a lithium source, a metal source, a phosphorus source and water to obtain slurry, wherein the metal source is an iron source and/or a manganese source; carrying out high-pressure reaction on the slurry, and separating to obtain a reaction material; adding a carbon source into the reaction material, mixing, and then performing spray drying to obtain powder; sintering the powder to obtain the liquid phase particles.
In one exemplary embodiment of the present disclosure, the reaction temperature is 150 to 250 ℃ and the reaction time is 2 to 10 hours during the high pressure reaction.
In one exemplary embodiment of the present disclosure, the phosphorus source is phosphoric acid, and the amount of phosphoric acid in the slurry is controlled to generate liquid phase particles having a particle size of 50 to 500 nm.
In one exemplary embodiment of the present disclosure, the phosphoric acid is present in the slurry at a molar concentration of 0.3 to 0.9mol/L.
In one exemplary embodiment of the present disclosure, the solid phase particles and the liquid phase particles are further added with a dopant during the preparation process, wherein the dopant contains one or more metal elements of V, cr, nb, ti, la, W, Y, zr and Mg.
In an exemplary embodiment of the present disclosure, when the solid phase particles and the liquid phase particles are mixed, the stirring rate is 10 to 80Hz and the mixing time is 40 to 120min.
A second aspect of the present disclosure provides an ultralow-temperature phosphoric acid positive electrode material, which is prepared according to the preparation method of any one of the above.
The ultralow-temperature phosphoric acid positive electrode material and the preparation method thereof have the beneficial effects that: the ultralow-temperature phosphoric acid positive electrode material is prepared by mixing solid-phase particles and liquid-phase particles, wherein the solid-phase particles are prepared by a solid-phase method, the particle size is controlled between 1000 and 3500nm, the liquid-phase particles are prepared by a liquid-phase method, and the particle size is controlled between 50 and 500 nm. The discharge capacity of the solid phase particles in the micron level is stable, the solid phase particles become high-compaction frames, the nano level liquid phase particles are filled among the frames of the solid phase particles, and the obtained phosphoric acid positive electrode material has higher capacity, multiplying power, low temperature and cycle performance. The capacity retention rate of the product at the ultralow temperature of-20 ℃ for 500 circles in a 0.3C discharge cycle reaches more than 60%, and the product can be applied to the ultralow temperature environment, so that the application range of the product is greatly expanded.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present disclosure and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person of ordinary skill in the art.
FIG. 1 is a flow chart of a method for preparing an ultralow temperature phosphoric acid positive electrode material according to an embodiment of the disclosure;
fig. 2 is a scanning electron microscope image of lithium iron phosphate provided in example 1 of the present disclosure.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present disclosure more apparent, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
The ultralow-temperature phosphoric acid positive electrode material and the preparation method thereof in the embodiment of the disclosure are specifically described below.
The present disclosure provides a preparation method of an ultralow temperature phosphoric acid positive electrode material, including:
Step S1, preparing solid-phase particles according to a solid-phase method, wherein the particle size of the solid-phase particles is 1000-3500 nm;
s2, preparing liquid phase particles according to a liquid phase method, wherein the particle size of the liquid phase particles is 50-500 nm;
And step S3, mixing the solid-phase particles and the liquid-phase particles to obtain the ultralow-temperature phosphoric acid anode material, wherein the components of the solid-phase particles and the liquid-phase particles are one or more of lithium iron phosphate, lithium manganese phosphate and lithium iron manganese phosphate.
It is understood that the solid phase method according to the present application is a method of obtaining a product by mixing and calcining raw materials. The liquid phase method of the application is a method which adopts water solution or organic solvent solution as reaction stop in a specially-made closed reaction vessel (such as a reaction kettle) to create a high-temperature and high-pressure reaction environment, so that raw materials are redissolved and recrystallized to obtain a product.
In one embodiment, step S1 specifically includes:
s11, adding metal phosphate, a lithium source and a carbon source into water to obtain a mixture, wherein the metal phosphate is selected from ferric phosphate and/or manganese phosphate;
S12, grinding the mixture to the particle size of 1000-3500 nm to obtain an abrasive;
and S13, spray drying the grinding material, and sintering to obtain the solid-phase particles.
It is understood that in step S11, when the metal phosphate is iron phosphate, solid phase particles having a composition of lithium iron phosphate are obtained. When the metal phosphate is manganese phosphate, solid-phase particles with the components of lithium manganese phosphate are obtained. When the metal phosphate is ferric phosphate and manganese phosphate, solid-phase particles with the components of lithium ferric manganese phosphate are obtained.
In one embodiment, in step S11, the lithium source includes, but is not limited to, one or more of lithium hydroxide, lithium carbonate, lithium acetate, and lithium nitrate. Carbon sources include, but are not limited to, one or more of glucose, sucrose, starch, graphite, and polyvinyl alcohol.
In one embodiment, in step S11, the carbon source is controlled to be added in an amount of 5 to 20wt%, preferably 8 to 15wt%, of the total amount of the metal phosphate, the lithium source and the carbon source. The carbon content in the solid phase particles is regulated and controlled by controlling the addition amount of the carbon source. And a carbon source is added, so that a lithium iron phosphate particle coated carbon structure can be formed, and the charge and discharge capacity of the product can be improved.
In one embodiment, in step S11, a dopant is further added to the mixture, where the dopant contains one or more metal elements of V, cr, nb, ti, la, W, Y, zr and Mg. The dopant may be, for example, a high-valence metal oxide such as titanium dioxide, vanadium pentoxide, manganese oxide, zirconium oxide, niobium oxide, or the like.
In one embodiment, in step S12, the mixture may be ground, for example, by a sand mill, and solid phase particles of different particle sizes may be obtained by controlling the particle size of the grind. Further, the particle size of the abrasive is 1000 to 3500nm, for example, 1000nm, 1500nm, 2000nm, 2500nm, 3000nm, etc.
The particle diameters referred to in the present disclosure are all median particle diameters D50.
In one embodiment, in step S13, the spray-dried air inlet temperature is 200-250 ℃ and the air outlet temperature is 70-100 ℃. The air inlet temperature and the air outlet temperature of spray drying are controlled, so that the subsequent sintering process of the product is facilitated.
In one embodiment, in step S13, in said spray-drying and sintering of the abrasive, the sintering process includes: sintering for 5-12 h at the first temperature under inert atmosphere, cooling, and sintering for 5-12 h at the second temperature to obtain the solid phase particles. Specifically, the inert atmosphere may be, for example, a nitrogen atmosphere or a helium atmosphere. The first temperature and the second temperature may be, for example, 700 to 850 ℃, preferably 750 to 820 ℃. It will be appreciated that the first temperature and the second temperature may be the same or different.
In one embodiment, in step S13, the sintering process is: sintering at a first temperature for 10-12 h, sintering at a second temperature for 5-8 h, wherein the second temperature is higher than the first temperature. Preferably, the second temperature is 30-60 ℃ higher than the first temperature. For example, the mixture is sintered at 780℃for 12 hours, cooled and sintered at 820℃for 5 hours. Through the twice sintering process, the sintering is carried out at a lower temperature, and the sintering is carried out at a higher temperature after the cooling, so that the internal structure of grains can be effectively refined, and the cycle performance of the grains is improved.
In one embodiment, in step S13, the sintered product is crushed by a gas stream to obtain solid phase particles. The particle diameter of the solid phase particles is further preferably 1000 to 2000nm, for example 1000nm, 1200nm, 1500nm, 1800nm, 2000nm, etc.
In one embodiment, step S2 specifically includes:
step S21, mixing a lithium source, a metal source, a phosphorus source and water to obtain slurry, wherein the metal source is an iron source and/or a manganese source;
S22, carrying out high-pressure reaction on the slurry, and separating to obtain a reaction material;
s23, adding a carbon source into the reaction material, mixing, and then performing spray drying to obtain powder;
And S24, sintering the powder to obtain the liquid phase particles.
In one embodiment, in step S21, the lithium source includes, but is not limited to, one or more of lithium hydroxide, lithium carbonate, lithium acetate, and lithium nitrate. Phosphorus sources include, but are not limited to, phosphoric acid, monoammonium phosphate. Iron sources include, but are not limited to, one or more of iron phosphate, ferrous oxalate, iron oxide, and ferrous sulfate. Manganese sources include, but are not limited to, one or more of manganese carbonate, manganese acetate, and manganese oxide.
It is understood that when the metal source is an iron source, the composition of the liquid phase particles is lithium iron phosphate. When the metal source is a manganese source, the liquid phase particles are composed of lithium manganese phosphate. When the metal source is an iron source and a manganese source, the liquid phase particles comprise lithium iron manganese phosphate.
In one embodiment, in step S21, the molar ratio of lithium to metal (M) in the lithium source, the metal source is: li is M=2-5:0.5-1.5, and the addition of more lithium sources is helpful for compensating the loss in the reaction process and improving the cycle performance of the material.
In one embodiment, in step S21, the phosphorus source is phosphoric acid, and the amount of phosphoric acid used in the slurry is controlled to produce liquid phase particles having a particle size of 50 to 500 nm. And the pH value of the slurry is regulated by controlling the dosage of phosphoric acid, so that reaction materials with different particle sizes are obtained, and the reaction materials are sintered to obtain liquid phase particles with different particle sizes. The higher the content of phosphoric acid, the lower the pH of the slurry, and the smaller the particle size of the liquid phase particles.
It will be appreciated that in other embodiments, where the phosphorus source is other phosphorus-containing salts, the pH of the slurry may be adjusted by the addition of hydrochloric acid or the like.
In one embodiment, in the step S22, the reaction temperature is 150 to 250 ℃ and the reaction time is 1 to 10 hours. After the high-pressure reaction, removing liquid by centrifugation or filter pressing to obtain filter residues, and washing the filter residues with pure water to obtain the reaction material. The washing water may be, for example, 10 to 30 times the mass of the filter residue. The number of washes may be one or more.
In one embodiment, in step S22, the particle size of the reaction material is 100 to 500nm, for example, 100nm, 150nm, 200nm, 300nm, 400nm, etc.
In one embodiment, in step S23, the carbon source includes, but is not limited to, one or more of glucose, sucrose, and polyvinyl alcohol.
In one embodiment, in step S23, the carbon source is controlled to be added in an amount of 5 to 20wt%, preferably 8 to 15wt%, of the reaction mass. The carbon content in the liquid phase particles is regulated and controlled by controlling the addition amount of the carbon source.
In one embodiment, in step S23, a dopant is further added to the reaction material, where the dopant contains one or more metal elements of V, cr, nb, ti, la, W, Y, zr and Mg. The dopant may be, for example, a high-valence metal oxide such as titanium dioxide, vanadium pentoxide, manganese oxide, zirconium oxide, niobium oxide, or the like.
In one embodiment, in step S23, the spray-dried air inlet temperature is 200-250 ℃ and the air outlet temperature is 70-100 ℃. The air inlet temperature and the air outlet temperature of spray drying are controlled, so that the subsequent sintering process of the product is facilitated.
In one embodiment, in step S24, the sintering temperature is 650-800 ℃ and the sintering time is 5-12 hours. And carrying out jet milling and demagnetizing on the sintered material to obtain liquid phase particles.
In one embodiment, step S3 specifically includes: and adding the solid phase particles and the liquid phase particles into mixing equipment according to a certain mass ratio for mixing to obtain the ultralow-temperature phosphoric acid anode material. Specifically, the stirring speed of the mixing equipment is 10-80 Hz, and the mixing time is 40-120 min. Further, the stirring speed is 30-50 Hz, and the mixing time is 40-60 min. And (3) obtaining a high-compaction product through high-energy mixing.
In one embodiment, the solid phase particles have a particle size of 1000 to 2000nm and the liquid phase particles have a particle size of 100 to 400nm. Further, the particle diameter ratio of the solid phase particles to the liquid phase particles is 10:1 to 4, more preferably 10:1.5 to 3. The particle size of the solid phase particles should not be too large, and the liquid phase particles should not be too small, otherwise, the two particles are difficult to form a proper level particle collocation effect. The solid phase particles were maintained at a particle size ratio of 10:1 to 4, can show better low-temperature performance and cycle performance.
In one embodiment. In the step S3, the mass ratio of the solid phase particles to the liquid phase particles is 4-0.25:1 during mixing. Further preferably, the mass ratio of the solid phase particles to the liquid phase particles is 4.5 to 2:3.
Under the condition that the mixing proportion of the solid phase particles and the liquid phase particles is kept unchanged, the particle sizes of the solid phase particles and the liquid phase particles are different, so that the product shows different performances, and when the particle sizes of the solid phase particles and the liquid phase particles are larger, the low-temperature performance is poorer. The particle diameters of the solid phase particles and the liquid phase particles are smaller, and the low-temperature performance is better.
The embodiment of the disclosure also provides an ultralow-temperature phosphoric acid positive electrode material, which is obtained according to the preparation method.
The features and capabilities of the present disclosure are described in further detail below in connection with the examples.
Example 1
The solid phase particles provided in this example were prepared according to the following steps:
100g of ferric phosphate, 24.87g of lithium carbonate, 12g of glucose, 0.18g of titanium dioxide and 200g of pure water are added into a stirring tank to be uniformly mixed, and the mixture is ground to 2000nm through a sand mill and discharged. And (3) spray drying, sintering in a sintering furnace at 780 ℃ for 12 hours in a nitrogen atmosphere, cooling, sintering at 820 ℃ for 5 hours, and crushing by airflow after sintering to obtain solid-phase particles.
Example 2
The solid phase particles provided in this example were prepared according to the following steps:
100g of ferric phosphate, 24.87g of lithium carbonate, 12g of glucose, 0.18g of titanium dioxide and 200g of pure water are added into a stirring tank to be uniformly mixed, and the mixture is ground to 1500nm through a sand mill and discharged. And (3) spray drying, sintering in a sintering furnace at 780 ℃ for 12 hours in a nitrogen atmosphere, cooling, sintering at 820 ℃ for 5 hours, and crushing by airflow after sintering to obtain solid-phase particles.
Example 3
The solid phase particles provided in this example were prepared according to the following steps:
100g of ferric phosphate, 24.87g of lithium carbonate, 12g of glucose, 0.18g of titanium dioxide and 200g of pure water are added into a stirring tank to be uniformly mixed, and the mixture is ground to 1000nm through a sand mill and discharged. And (3) spray drying, sintering in a sintering furnace at 780 ℃ for 12 hours in a nitrogen atmosphere, cooling, sintering at 820 ℃ for 5 hours, and crushing by airflow after sintering to obtain solid-phase particles.
Example 4
The liquid phase particles provided in this example were prepared according to the following steps:
80g of lithium hydroxide monohydrate, 45g of phosphoric acid, 176g of ferrous sulfate heptahydrate and 1000g of pure water. Adding into a stirring tank, and uniformly mixing by high-intensity stirring to obtain slurry. Transferring the slurry to a high-pressure reaction kettle, heating to 200 ℃, keeping the temperature for 6 hours, cooling, discharging, centrifuging to remove mother liquor, washing with pure water, and obtaining the reaction material (the test granularity is 400 nm) after washing. 100g of glucose and 0.5g of vanadium pentoxide are added into the reaction material, stirred and mixed uniformly, and then spray-dried to form powder, and sintered in a sintering furnace at 700 ℃ for 12 hours. And carrying out jet milling and demagnetizing on the sintered material to obtain liquid phase particles.
Example 5
The liquid phase particles provided in this example were prepared according to the following steps:
80g of lithium hydroxide monohydrate, 56g of phosphoric acid, 176g of ferrous sulfate heptahydrate and 1000g of pure water. Adding into a stirring tank, and uniformly mixing by high-intensity stirring to obtain slurry. Transferring the slurry to a high-pressure reaction kettle, heating to 200 ℃, keeping the temperature for 6 hours, cooling, discharging, centrifuging to remove mother liquor, washing with pure water, and obtaining the reaction material (the test granularity is 300 nm) after washing. 100g of glucose and 0.5g of vanadium pentoxide are added into the reaction material, stirred and mixed uniformly, and then spray-dried to form powder, and sintered in a sintering furnace at 700 ℃ for 12 hours. And carrying out jet milling and demagnetizing on the sintered material to obtain liquid phase particles.
Example 6
The liquid phase particles provided in this example were prepared according to the following steps:
80g of lithium hydroxide monohydrate, 73g of phosphoric acid, 176g of ferrous sulfate heptahydrate and 1000g of pure water. Adding into a stirring tank, and uniformly mixing by high-intensity stirring to obtain slurry. Transferring the slurry to a high-pressure reaction kettle, heating to 200 ℃, keeping the temperature for 6 hours, cooling, discharging, centrifuging to remove mother liquor, washing with pure water, and obtaining the reaction material (the test granularity is 200 nm) after washing. 100g of glucose and 0.5g of vanadium pentoxide are added into the reaction material, stirred and mixed uniformly, and then spray-dried to form powder, and sintered in a sintering furnace at 700 ℃ for 12 hours. And carrying out jet milling and demagnetizing on the sintered material to obtain liquid phase particles.
Example 7
The liquid phase particles provided in this example were prepared according to the following steps:
80g of lithium hydroxide monohydrate, 80g of phosphoric acid, 176g of ferrous sulfate heptahydrate and 1000g of pure water. Adding into a stirring tank, and uniformly mixing by high-intensity stirring to obtain slurry. Transferring the slurry to a high-pressure reaction kettle, heating to 200 ℃, keeping the temperature for 6 hours, cooling, discharging, centrifuging to remove mother liquor, washing with pure water, and obtaining the reaction material (the test granularity is 150 nm) after washing. 100g of glucose and 0.5g of vanadium pentoxide are added into the reaction material, stirred and mixed uniformly, and then spray-dried to form powder, and sintered in a sintering furnace at 700 ℃ for 12 hours. And carrying out jet milling and demagnetizing on the sintered material to obtain liquid phase particles.
Comparative example 1
The solid phase particles provided in this comparative example were prepared according to the following steps:
100g of ferric phosphate, 24.87g of lithium carbonate, 12g of glucose, 0.18g of titanium dioxide and 200g of pure water are added into a stirring tank to be uniformly mixed, and the mixture is ground to 400nm through a sand mill and discharged. And (3) spray drying, sintering in a sintering furnace at 780 ℃ for 12 hours in a nitrogen atmosphere, cooling, sintering at 820 ℃ for 5 hours, and crushing by airflow after sintering to obtain solid-phase particles.
Comparative example 2
The solid phase particles provided in this comparative example were prepared according to the following steps:
100g of ferric phosphate, 24.87g of lithium carbonate, 12g of glucose, 0.18g of titanium dioxide and 200g of pure water are added into a stirring tank to be uniformly mixed, and the mixture is ground to 300nm through a sand mill and discharged. And (3) spray drying, sintering in a sintering furnace at 780 ℃ for 12 hours in a nitrogen atmosphere, cooling, sintering at 820 ℃ for 5 hours, and crushing by airflow after sintering to obtain solid-phase particles.
The solid phase particles obtained in examples 1 to 7 and comparative examples 1 to 2 were mixed with the solid phase particles according to 70% solid phase particles+30% liquid phase particles, and the mixture was mixed at high speed in a high-energy mixer for 50 minutes to obtain a lithium iron phosphate finished product. The mixing proportion of different lithium iron phosphate finished products is as follows:
lithium iron phosphate finished product A: example 1 solid phase particles + example 4 liquid phase particles;
lithium iron phosphate finished product B: example 1 solid phase particles + example 5 liquid phase particles;
Lithium iron phosphate finished product C: example 1 solid phase particles + example 6 liquid phase particles;
lithium iron phosphate finished product D: example 2 solid phase particles + example 4 liquid phase particles;
Lithium iron phosphate finished product E: example 2 solid phase particles + example 5 liquid phase particles;
lithium iron phosphate finished product F: example 3 solid phase particles + example 6 liquid phase particles;
Lithium iron phosphate finished product G: example 3 solid phase particles + example 7 liquid phase particles;
lithium iron phosphate finished product H: comparative example 1 solid phase particles + example 4 liquid phase particles;
lithium iron phosphate finished product I: example 1 solid phase particles + comparative example 1 solid phase particles;
Lithium iron phosphate finished product J: example 1 solid phase particles + comparative example 2 solid phase particles.
And (3) performing performance measurement on the lithium iron phosphate finished products A-J:
(1) The compaction density was measured using an internal resistance tester for a test area of 16mm and the measurement parameters are shown in Table 1.
TABLE 1
(2) Full cell assay:
mixing a lithium iron phosphate finished product, acetylene black and an adhesive PVDF according to a mass ratio of 90:4:6 to prepare a positive electrode material, taking a mesocarbon microbead MCMB as a negative electrode material, taking 1.0M LiPF 6, EC (ethylene carbonate) and EMC (ethylmethyl carbonate) as electrolyte, assembling to obtain a 18650 type battery, and testing the discharge capacity and the cycle performance.
The testing method comprises the following steps: at normal temperature of 25 ℃, the battery is charged and discharged at 0.3 ℃, and the charge-discharge cut-off voltage is 2.5-3.8V. Discharge capacity was recorded at 0.3C to 2.5V.
After the battery is placed for 12 hours at the temperature of minus 20 ℃, discharging to 2.0V at constant current of 0.3 ℃ and circulating for 500 circles, and recording the ratio of 0.3C discharge capacity at minus 20 ℃ to normal temperature 0.3C discharge capacity, namely, the capacity retention rate percent of 500 circles circulating at minus 20 ℃.
The results of the compacted density measurement and the full cell measurement are shown in table 2.
TABLE 2
Example 8
The ultralow-temperature lithium iron phosphate provided by the embodiment is prepared according to the following steps:
(1) 100g of ferric phosphate, 24.87g of lithium carbonate, 12g of glucose and 200g of pure water are added into a stirring tank to be uniformly mixed, and the mixture is ground to 1500nm through a sand mill and discharged. And (3) spray drying, sintering in a sintering furnace at 780 ℃ for 12 hours in a nitrogen atmosphere, cooling, sintering at 820 ℃ for 5 hours, and crushing by airflow after sintering to obtain solid-phase particles.
(2) 80G of lithium hydroxide monohydrate, 45g of phosphoric acid, 176g of ferrous sulfate heptahydrate and 1000g of pure water. Adding into a stirring tank, and uniformly mixing by high-intensity stirring to obtain slurry. Transferring the slurry to a high-pressure reaction kettle, heating to 200 ℃, keeping the temperature for 6 hours, cooling, discharging, centrifuging to remove mother liquor, washing with pure water, and obtaining the reaction material (the test granularity is 400 nm) after washing. And adding 100g of glucose into the reaction materials, stirring and mixing uniformly, then forming powder by spray drying, and sintering in a sintering furnace at 700 ℃ for 12 hours. And carrying out jet milling and demagnetizing on the sintered material to obtain liquid phase particles.
(3) According to the mass ratio of 7: and 3, placing the solid-phase large particles and the liquid-phase small particles into a high-energy mixer, and mixing at a high speed for 50 minutes to obtain a lithium iron phosphate finished product.
According to the test method, the capacity retention rate of the finished lithium iron phosphate product of the embodiment is 60.22% after 500 cycles of circulation at-20 ℃.
Example 9
The ultralow-temperature lithium iron phosphate provided by the embodiment is prepared according to the following steps:
(1) 100g of ferric phosphate, 24.87g of lithium carbonate, 12g of glucose, 0.18g of titanium dioxide and 200g of pure water are added into a stirring tank to be uniformly mixed, and the mixture is ground to 2000nm through a sand mill and discharged. And (3) spray drying, sintering in a sintering furnace at 780 ℃ for 12 hours in a nitrogen atmosphere, cooling, sintering at 820 ℃ for 5 hours, and crushing by airflow after sintering to obtain solid-phase particles.
(2) 80G of lithium hydroxide monohydrate, 73g of phosphoric acid, 176g of ferrous sulfate heptahydrate and 1000g of pure water. Adding into a stirring tank, and uniformly mixing by high-intensity stirring to obtain slurry. Transferring the slurry to a high-pressure reaction kettle, heating to 200 ℃, keeping the temperature for 6 hours, cooling, discharging, centrifuging to remove mother liquor, washing with pure water, and obtaining the reaction material (the test granularity is 200 nm) after washing. 100g of glucose and 0.5g of vanadium pentoxide are added into the reaction material, stirred and mixed uniformly, and then spray-dried to form powder, and sintered in a sintering furnace at 700 ℃ for 12 hours. And carrying out jet milling and demagnetizing on the sintered material to obtain liquid phase particles.
(3) Weighing 70g of solid phase particles and 30g of liquid phase particles, and placing the solid phase particles and the liquid phase particles in a high-energy mixer, and mixing at a high speed for 50 minutes to obtain a lithium iron phosphate finished product.
According to the test method, the capacity retention rate of the finished lithium iron phosphate product of the embodiment is 59.30% after 500 cycles of circulation at-20 ℃.
Example 10
The ultralow-temperature lithium manganese phosphate provided by the embodiment is prepared according to the following steps:
(1) 100g of manganese phosphate, 24.87g of lithium carbonate, 12g of glucose, 0.18g of titanium dioxide and 200g of pure water are added into a stirring tank to be uniformly mixed, and the mixture is ground to 2000nm through a sand mill and discharged. And (3) spray drying, sintering in a sintering furnace at 780 ℃ for 12 hours in a nitrogen atmosphere, cooling, sintering at 820 ℃ for 5 hours, and crushing by airflow after sintering to obtain solid-phase particles.
(2) 80G of lithium hydroxide monohydrate, 56g of phosphoric acid, 107g of manganese sulfate and 1000g of pure water. Adding into a stirring tank, and uniformly mixing by high-intensity stirring to obtain slurry. Transferring the slurry to a high-pressure reaction kettle, heating to 200 ℃, keeping the temperature for 6 hours, cooling, discharging, centrifuging to remove mother liquor, washing with pure water, and obtaining the reaction material (the test granularity is 200 nm) after washing. 100g of glucose and 0.5g of vanadium pentoxide are added into the reaction material, stirred and mixed uniformly, and then spray-dried to form powder, and sintered in a sintering furnace at 700 ℃ for 12 hours. And carrying out jet milling and demagnetizing on the sintered material to obtain liquid phase particles.
(3) Weighing 70g of solid phase particles and 30g of liquid phase particles, and placing the solid phase particles and the liquid phase particles in a high-energy mixer, and mixing at a high speed for 50 minutes to obtain a lithium iron phosphate finished product.
According to the test method, the capacity retention rate of the finished lithium manganese phosphate product of the embodiment is 60.02 percent after 500 circles of circulation at the temperature of minus 20 ℃.
Example 9
The ultralow-temperature lithium iron manganese phosphate provided by the embodiment is prepared according to the following steps:
(1) 50g of ferric phosphate, 50g of manganese phosphate, 24.87g of lithium carbonate, 12g of glucose, 0.18g of titanium dioxide and 200g of pure water are added into a stirring tank to be uniformly mixed, and the mixture is ground to 2000nm through a sand mill and discharged. And (3) spray drying, sintering in a sintering furnace in nitrogen atmosphere at 780 ℃ for 17 hours, and crushing by airflow after sintering to obtain solid-phase particles.
(2) 80G of lithium hydroxide monohydrate, 56g of phosphoric acid, 88g of ferrous sulfate heptahydrate, 53.5g of manganese sulfate and 1000g of pure water. Adding into a stirring tank, and uniformly mixing by high-intensity stirring to obtain slurry. Transferring the slurry to a high-pressure reaction kettle, heating to 200 ℃, keeping the temperature for 6 hours, cooling, discharging, centrifuging to remove mother liquor, washing with pure water, and obtaining the reaction material (the test granularity is 200 nm) after washing. 100g of glucose and 0.5g of vanadium pentoxide are added into the reaction material, stirred and mixed uniformly, and then spray-dried to form powder, and sintered in a sintering furnace at 700 ℃ for 12 hours. And carrying out jet milling and demagnetizing on the sintered material to obtain liquid phase particles.
(3) Weighing 70g of solid phase particles and 30g of liquid phase particles, and placing the solid phase particles and the liquid phase particles in a high-energy mixer, and mixing at a high speed for 50 minutes to obtain a finished product of the lithium iron manganese phosphate.
According to the test method, the capacity retention rate of the finished product of the lithium iron manganese phosphate of the embodiment is 62.48% after 500 circles of circulation at the temperature of minus 20 ℃.
In summary, the ultralow-temperature phosphoric acid positive electrode material disclosed by the invention is prepared by solid-phase sintering to obtain solid-phase large particles with the particle size of 1000-3500 nm, and liquid-phase sintering to obtain liquid-phase small particles with the particle size of 50-500 nm. The solid phase large particles serve as a high-compaction frame, the liquid phase small particles are filled, as shown in fig. 2, the strip-shaped liquid phase small particles are filled among the solid phase large particles, and good low-temperature circulation performance is shown. Compared with the mixing of solid-phase particles with two particle sizes, the product obtained by the embodiment of the disclosure has better retention rate at the low temperature of-20 ℃. And the particle size of the solid phase particles needs to reach the micron level, and when the particle sizes of the solid phase particles and the liquid phase particles are consistent, the compaction effect is poor, and the low-temperature performance is reduced.
The embodiments described above are some, but not all, embodiments of the present disclosure. The detailed description of the embodiments of the present disclosure is not intended to limit the scope of the disclosure, as claimed, but is merely representative of selected embodiments of the disclosure. All other embodiments, which can be made by one of ordinary skill in the art without inventive effort, based on the embodiments in this disclosure are intended to be within the scope of this disclosure.
Claims (15)
1. The preparation method of the ultralow-temperature phosphoric acid positive electrode material is characterized by comprising the following steps of:
preparing solid-phase particles according to a solid-phase method, wherein the particle size of the solid-phase particles is 1000-3500 nm;
preparing liquid phase particles according to a liquid phase method, wherein the particle size of the liquid phase particles is 50-500 nm;
And mixing the solid phase particles and the liquid phase particles to obtain the ultralow-temperature phosphoric acid anode material, wherein the components of the solid phase particles and the liquid phase particles are one or more of lithium iron phosphate, lithium manganese phosphate and lithium iron manganese phosphate.
2. The method for producing an ultralow-temperature phosphoric acid positive electrode material according to claim 1, wherein the particle size of the solid phase particles is 1000 to 2000nm and the particle size of the liquid phase particles is 100 to 400nm.
3. The method for producing an ultralow-temperature phosphoric acid positive electrode material according to claim 1, wherein the ratio of the particle diameters of the solid phase particles and the liquid phase particles is 10:1 to 4.
4. The method for producing an ultralow-temperature phosphoric acid positive electrode material according to claim 1, wherein the ratio of the particle diameters of the solid phase particles and the liquid phase particles is 10:1.5 to 3.
5. The method for preparing ultralow temperature phosphoric acid positive electrode material according to claim 1, wherein the preparing solid phase particles according to the solid phase method comprises: adding metal phosphate, a lithium source and a carbon source into water to obtain a mixture, wherein the metal phosphate is selected from ferric phosphate and/or manganese phosphate; grinding the mixture to a particle size of 1000-3500 nm to obtain an abrasive; and (3) carrying out spray drying on the grinding material, and then sintering to obtain the solid-phase particles.
6. The method for producing an ultralow-temperature phosphoric acid positive electrode material according to claim 5, wherein in the step of spray-drying the abrasive, the sintering step comprises: sintering for 5-12 h at the first temperature under the inert atmosphere, cooling, and sintering for 5-12 h at the second temperature to obtain the solid phase particles.
7. The method for producing a high-pressure and low-temperature positive electrode material according to claim 6, wherein the sintering is performed at the first temperature for 10 to 12 hours and at the second temperature for 5 to 8 hours, and wherein the second temperature is higher than the first temperature.
8. The method for producing a high-compaction low-temperature cathode material according to claim 7, wherein the sintering is performed at the first temperature for 10 to 12 hours, the sintering is performed at the second temperature for 5 to 8 hours, and the second temperature is higher than the first temperature.
9. The method for preparing ultralow temperature phosphoric acid positive electrode material according to claim 1, wherein the preparing the liquid phase large particles according to the liquid phase method comprises: mixing a lithium source, a metal source, a phosphorus source and water to obtain slurry, wherein the metal source is an iron source and/or a manganese source; carrying out high-pressure reaction on the slurry, and separating to obtain a reaction material; adding a carbon source into the reaction material, mixing, and then performing spray drying to obtain powder; sintering the powder to obtain the liquid phase particles.
10. The method for preparing an ultralow temperature phosphoric acid positive electrode material according to claim 9, wherein the reaction temperature is 150-250 ℃ and the reaction time is 2-10 h in the high pressure reaction process.
11. The method for producing an ultralow-temperature phosphoric acid positive electrode material according to claim 9, wherein the phosphorus source is phosphoric acid, and the amount of phosphoric acid used in the slurry is controlled so as to produce liquid-phase particles having a particle size of 50 to 500 nm.
12. The method for producing an ultralow-temperature phosphoric acid positive electrode material according to claim 11, wherein the molar concentration of the phosphoric acid in the slurry is 0.3 to 0.9mol/L.
13. The method for preparing an ultralow-temperature phosphoric acid positive electrode material according to claim 1, wherein a dopant is further added into the solid-phase particles and the liquid-phase particles in the preparation process, and the dopant contains one or more metal elements of V, cr, nb, ti, la, W, Y, zr and Mg.
14. The method for preparing an ultralow-temperature phosphoric acid positive electrode material according to claim 1, wherein the stirring rate is 10-80 Hz and the mixing time is 40-120 min when the solid-phase particles and the liquid-phase particles are mixed.
15. An ultralow-temperature phosphoric acid positive electrode material, characterized by being prepared according to the preparation method of any one of claims 1 to 14.
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