Spherical iron phosphate and preparation method and application thereof

Abstract

The invention discloses spherical iron phosphate and a preparation method and application thereof. The preparation method comprises the following steps: adding a disperser into iron-phosphorus mixed liquor containing iron ion and phosphate anion, thus obtaining mixed liquor A; under a heating condition, adding urea into the mixed liquor A to regulate a pH value, and continuously heating to obtainmixed liquor B containing crystal-form iron phosphate; filtering the mixed liquor B, adding a filter cake into water to prepare mixed liquor C, atomizing the mixed liquor C by a spray gun, leading into a roasting furnace, and roasting at a temperature of 550 to 750 DEG C to obtain the spherical iron phosphate. The spherical iron phosphate is pure in crystalline phase, good in crystallinity, spherical in shape, uniform in grain fineness distribution and high in tap density, and can serve as a precursor for synthesizing spherical lithium iron phosphate with high tap density; the spherical iron phosphate can eliminate microscopic composition difference caused by different diffusion paths in a reaction, so as to generate the lithium iron phosphate with a uniform structure, and thus the performance of the lithium iron phosphate is improved.

Description

technical field

[0001] The invention relates to the technical field of lithium ion battery materials, in particular to a spherical iron phosphate and its preparation method and application. Background technique

[0002] Olivine-structured lithium iron phosphate (LiFePO 4 ) has the advantages of abundant raw materials, stable discharge platform, good thermal stability, high safety, and environmental friendliness. It has attracted much attention in the fields of electric vehicles, power tools, and large-scale energy storage. However, LiFePO 4 It has the disadvantages of poor conductivity and low tap density. Poor electrical conductivity can be improved by coating conductive carbon material on its surface, doping high-valent metal ions in the bulk, or refining particles, etc., but the shortcoming of low tap density has not been effectively solved.

[0003] After research, it is found that the preparation of high-density spherical precursors is one of the effective ways to obt...

Examples

preparation example Construction

[0034] The preparation method of spherical iron phosphate of the present invention comprises the following steps:

[0035] (1) Add a dispersant to the iron-phosphorus mixed solution containing iron ions and phosphate ions to obtain mixed solution A;

[0036] (2) Under heating conditions, add urea to the mixed solution A obtained in step (1) to adjust the pH value, and continue heating to obtain mixed solution B comprising crystalline ferric phosphate;

[0037] (3) Filter the mixed solution B prepared in step (2), add the filter cake into water to prepare mixed solution C, atomize the mixed solution C with a spray gun and introduce it into a roasting furnace, and heat it at a temperature of 550-750°C Roasting to obtain spherical iron phosphate.

[0038] In the above preparation method of spherical ferric phosphate, the application of the dispersant as the crystal form control agent in step (1) can weaken the molecular force between particles, reduce the tendency of primary par...

Embodiment 1

[0057] (1) The iron-phosphorus mixed solution obtained by mixing the ferric sulfate solution with an iron ion concentration of 1mol / L and the ammonium dihydrogen phosphate solution with a phosphate ion concentration of 1mol / L according to the iron-phosphorus molar ratio of 1:1, at 55°C, Under the condition of rotating speed of 180r / min, polyvinyl alcohol with a fraction of 10% of iron-phosphorus mixed liquid was added, stirred for 5 minutes, and mixed liquid A was obtained;

[0058] (2) Under the conditions of heating at 60°C and a stirring rate of 360r / min, add urea with a concentration of 0.2mol / L to the mixed solution A obtained in step (1) to adjust the pH value to 2.0, continue heating to 85°C, and keep warm 120min, obtain the mixed solution B that comprises crystalline ferric phosphate, i.e. ferric phosphate slurry;

[0059] (3) The mixed solution B obtained in step (2) is repeatedly washed with pure water and press-filtered until the conductivity of the filtrate is less...

Embodiment 2

[0063] (1) The iron-phosphorus mixed solution obtained by mixing the ferric sulfate solution with the iron ion concentration of 0.5mol / L and the ammonium dihydrogen phosphate solution with the phosphate ion concentration of 0.5mol / L according to the iron-phosphorus molar ratio of 1: 1.15, at 55 ℃, under the condition of rotating speed of 360r / min, add polyvinyl alcohol with a fraction of 5% of the iron-phosphorus mixed liquid, and stir for 10 minutes to obtain the mixed liquid A;

[0064] (2) Under the conditions of heating at 70°C and a stirring rate of 600r / min, add urea with a concentration of 0.2mol / L to the mixed solution A obtained in step (1) to adjust the pH value to 1.0, continue heating to 95°C, and keep warm 50min, obtain the mixed solution B that comprises crystalline ferric phosphate, i.e. ferric phosphate slurry;

[0065] (3) The mixed solution B obtained in step (2) is repeatedly washed with pure water and press-filtered until the conductivity of the filtrate is...

technical field

[0001] The invention relates to the technical field of lithium ion battery materials, in particular to a spherical iron phosphate and its preparation method and application. Background technique

[0002] Olivine-structured lithium iron phosphate (LiFePO 4 ) has the advantages of abundant raw materials, stable discharge platform, good thermal stability, high safety, and environmental friendliness. It has attracted much attention in the fields of electric vehicles, power tools, and large-scale energy storage. However, LiFePO 4 It has the disadvantages of poor conductivity and low tap density. Poor electrical conductivity can be improved by coating conductive carbon material on its surface, doping high-valent metal ions in the bulk, or refining particles, etc., but the shortcoming of low tap density has not been effectively solved.

[0003] After research, it is found that the preparation of high-density spherical precursors is one of the effective ways to obt...

Examples

preparation example Construction

[0034] The preparation method of spherical iron phosphate of the present invention comprises the following steps:

[0035] (1) Add a dispersant to the iron-phosphorus mixed solution containing iron ions and phosphate ions to obtain mixed solution A;

[0036] (2) Under heating conditions, add urea to the mixed solution A obtained in step (1) to adjust the pH value, and continue heating to obtain mixed solution B comprising crystalline ferric phosphate;

[0037] (3) Filter the mixed solution B prepared in step (2), add the filter cake into water to prepare mixed solution C, atomize the mixed solution C with a spray gun and introduce it into a roasting furnace, and heat it at a temperature of 550-750°C Roasting to obtain spherical iron phosphate.

[0038] In the above preparation method of spherical ferric phosphate, the application of the dispersant as the crystal form control agent in step (1) can weaken the molecular force between particles, reduce the tendency of primary par...

Embodiment 1

[0057] (1) The iron-phosphorus mixed solution obtained by mixing the ferric sulfate solution with an iron ion concentration of 1mol / L and the ammonium dihydrogen phosphate solution with a phosphate ion concentration of 1mol / L according to the iron-phosphorus molar ratio of 1:1, at 55°C, Under the condition of rotating speed of 180r / min, polyvinyl alcohol with a fraction of 10% of iron-phosphorus mixed liquid was added, stirred for 5 minutes, and mixed liquid A was obtained;

[0058] (2) Under the conditions of heating at 60°C and a stirring rate of 360r / min, add urea with a concentration of 0.2mol / L to the mixed solution A obtained in step (1) to adjust the pH value to 2.0, continue heating to 85°C, and keep warm 120min, obtain the mixed solution B that comprises crystalline ferric phosphate, i.e. ferric phosphate slurry;

[0059] (3) The mixed solution B obtained in step (2) is repeatedly washed with pure water and press-filtered until the conductivity of the filtrate is less...

Embodiment 2

[0063] (1) The iron-phosphorus mixed solution obtained by mixing the ferric sulfate solution with the iron ion concentration of 0.5mol / L and the ammonium dihydrogen phosphate solution with the phosphate ion concentration of 0.5mol / L according to the iron-phosphorus molar ratio of 1: 1.15, at 55 ℃, under the condition of rotating speed of 360r / min, add polyvinyl alcohol with a fraction of 5% of the iron-phosphorus mixed liquid, and stir for 10 minutes to obtain the mixed liquid A;

[0064] (2) Under the conditions of heating at 70°C and a stirring rate of 600r / min, add urea with a concentration of 0.2mol / L to the mixed solution A obtained in step (1) to adjust the pH value to 1.0, continue heating to 95°C, and keep warm 50min, obtain the mixed solution B that comprises crystalline ferric phosphate, i.e. ferric phosphate slurry;

[0065] (3) The mixed solution B obtained in step (2) is repeatedly washed with pure water and press-filtered until the conductivity of the filtrate is...

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