A method for preparing lithium manganese iron phosphate positive electrode material using ethyl cellulose as carbon source

Abstract

The invention discloses a method for preparing a lithium-iron manganese phosphate positive electrode material by employing ethyl cellulose as a carbon source. The method comprises the following steps of (1) weighing a manganese source compound, an iron source compound and a phosphorus source compound and then dissolving the manganese source compound, the iron source compound, the phosphorus source compound and a reducing agent into a solvent I to obtain a solution A, dissolving a lithium source into a solvent II to obtain a solution B, dropwise adding the solution B to a precursor solution of lithium manganese phosphate and putting the solution in a high-temperature and high-pressure reaction kettle for reaction for 1-20 hours to prepare a lithium-iron manganese phosphate precursor material; (2) carrying out ball-mill mixing on the precursor material obtained in the step (1) and the ethyl cellulose at the mass ratio of (1-30):1 to obtain a mixture; and (3) drying the mixture, then putting the mixture into a tube furnace for sintering and finally obtaining the carbon-coated lithium-iron manganese phosphate positive electrode material. The thickness of a carbon film on the surface of the positive electrode material obtained by the method is small, so that the electrochemical properties of the material are significantly improved.

Description

technical field

[0001] The invention relates to the field of preparation of positive electrode materials for lithium ion batteries, in particular to a method for preparing lithium manganese iron phosphate positive electrode materials by using ethyl cellulose as a carbon source. Background technique

[0002] Since Sony first launched commercial lithium-ion batteries in 1991, lithium-ion batteries have been widely used in people's work, All aspects of study and life. In recent years, with the increasing market demand for power batteries and large-scale power energy storage devices, power and energy storage power sources using lithium-ion batteries as carriers have emerged one after another.

[0003] Most of the cathode materials used in consumer batteries are LiCoO 2 , because of its high price, toxicity and other disadvantages, it is not suitable for power battery applications with higher energy density and safety. The vigorous development of pure electric vehicles and hyb...

Examples

Embodiment 1

[0037] ① Manganous sulfate (0.0384mol), ferrous sulfate (0.0096mol), phosphoric acid (0.048mol), ascorbic acid (0.014mol) (that is, according to LiMn X Fe 1-X PO 4 (X = 0.8) for weighing) dissolved in 160ml of water and ethylene glycol by volume ratio = 1:2 in the mixed solvent composition, called A liquid; dissolved lithium hydroxide (0.144mol) in 160ml of water and ethylene glycol Alcohol in the mixed solvent composed of volume ratio = 1:2 in solvent two, called B liquid. Then, liquid B was added dropwise to liquid A for 20 minutes to obtain a precursor solution of lithium manganese iron phosphate, wherein the total concentration of ascorbic acid in the precursor solution was 0.0438 mol / L, and the lithium ion concentration in the precursor solution was 0.45 mol / L. Place it in a high-temperature and high-pressure reactor, the volume of the precursor solution is 80% of the volume of the reactor, heat it to 240°C, and the reaction time is 4h. ℃, -0.1MPa vacuum drying to prep...

Embodiment 2

[0047] ① Manganous sulfate (0.0096mol), ferrous sulfate (0.0384mol), phosphoric acid (0.048mol), ascorbic acid (0.024mol), glucose (0.024mol) (that is, according to LiMn X Fe 1-X PO 4 (X = 0.2) for weighing) dissolved in 200ml of water and ethylene glycol by volume ratio = 1:1 mixed solvent, called A liquid; dissolved lithium hydroxide (0.1548mol) in 120ml of water and ethylene glycol Alcohol in the mixed solvent composed of volume ratio = 1:1 in solvent two, called B liquid. Then add liquid B dropwise to liquid A for 15 minutes to obtain a precursor solution of lithium manganese iron phosphate, wherein the total concentration of ascorbic acid and glucose in the precursor solution is 0.15mol / L, and the lithium ion concentration in the precursor solution is 0.4838mol / L . Place it in a high-temperature and high-pressure reactor, the volume of the precursor solution is 40% of the volume of the reactor, heat to 200°C, and the reaction time is 4h. ℃, -0.1MPa vacuum drying to pr...

Embodiment 3

[0051] The reaction equation in the present embodiment hydrothermal process is:

[0052] 3LiOH+XMn(NO 3 ) 2 +(1-X)Fe(NO 3 ) 2 +H 3 PO 4 →LiMn x Fe 1-x PO 4 +2LiNO 3 +3H 2 o

[0053] where X=0.1-0.9;

[0054] The specific experiment is:

[0055] ① Manganous nitrate (0.0336mol), ferrous nitrate (0.0144mol), phosphoric acid (0.048mol), ascorbic acid (0.0096mol) (that is, according to LiMn X Fe 1-X PO 4 (X = 0.7) for weighing) dissolved in 160ml of water and ethylene glycol by volume ratio = 1:2 in the mixed solvent, called A liquid; dissolved lithium hydroxide (0.144mol) in 120ml of water and ethylene glycol Alcohol in the mixed solvent composed of volume ratio = 1:2 in solvent two, called B liquid. Then, liquid B was added dropwise to liquid A for 20 minutes to obtain a precursor solution of lithium manganese iron phosphate, wherein the total concentration of ascorbic acid in the precursor solution was 0.0343 mol / L, and the lithium ion concentration in the precur...

technical field

[0001] The invention relates to the field of preparation of positive electrode materials for lithium ion batteries, in particular to a method for preparing lithium manganese iron phosphate positive electrode materials by using ethyl cellulose as a carbon source. Background technique

[0002] Since Sony first launched commercial lithium-ion batteries in 1991, lithium-ion batteries have been widely used in people's work, All aspects of study and life. In recent years, with the increasing market demand for power batteries and large-scale power energy storage devices, power and energy storage power sources using lithium-ion batteries as carriers have emerged one after another.

[0003] Most of the cathode materials used in consumer batteries are LiCoO 2 , because of its high price, toxicity and other disadvantages, it is not suitable for power battery applications with higher energy density and safety. The vigorous development of pure electric vehicles and hyb...

Examples

Embodiment 1

[0037] ① Manganous sulfate (0.0384mol), ferrous sulfate (0.0096mol), phosphoric acid (0.048mol), ascorbic acid (0.014mol) (that is, according to LiMn X Fe 1-X PO 4 (X = 0.8) for weighing) dissolved in 160ml of water and ethylene glycol by volume ratio = 1:2 in the mixed solvent composition, called A liquid; dissolved lithium hydroxide (0.144mol) in 160ml of water and ethylene glycol Alcohol in the mixed solvent composed of volume ratio = 1:2 in solvent two, called B liquid. Then, liquid B was added dropwise to liquid A for 20 minutes to obtain a precursor solution of lithium manganese iron phosphate, wherein the total concentration of ascorbic acid in the precursor solution was 0.0438 mol / L, and the lithium ion concentration in the precursor solution was 0.45 mol / L. Place it in a high-temperature and high-pressure reactor, the volume of the precursor solution is 80% of the volume of the reactor, heat it to 240°C, and the reaction time is 4h. ℃, -0.1MPa vacuum drying to prep...

Embodiment 2

[0047] ① Manganous sulfate (0.0096mol), ferrous sulfate (0.0384mol), phosphoric acid (0.048mol), ascorbic acid (0.024mol), glucose (0.024mol) (that is, according to LiMn X Fe 1-X PO 4 (X = 0.2) for weighing) dissolved in 200ml of water and ethylene glycol by volume ratio = 1:1 mixed solvent, called A liquid; dissolved lithium hydroxide (0.1548mol) in 120ml of water and ethylene glycol Alcohol in the mixed solvent composed of volume ratio = 1:1 in solvent two, called B liquid. Then add liquid B dropwise to liquid A for 15 minutes to obtain a precursor solution of lithium manganese iron phosphate, wherein the total concentration of ascorbic acid and glucose in the precursor solution is 0.15mol / L, and the lithium ion concentration in the precursor solution is 0.4838mol / L . Place it in a high-temperature and high-pressure reactor, the volume of the precursor solution is 40% of the volume of the reactor, heat to 200°C, and the reaction time is 4h. ℃, -0.1MPa vacuum drying to pr...

Embodiment 3

[0051] The reaction equation in the present embodiment hydrothermal process is:

[0052] 3LiOH+XMn(NO 3 ) 2 +(1-X)Fe(NO 3 ) 2 +H 3 PO 4 →LiMn x Fe 1-x PO 4 +2LiNO 3 +3H 2 o

[0053] where X=0.1-0.9;

[0054] The specific experiment is:

[0055] ① Manganous nitrate (0.0336mol), ferrous nitrate (0.0144mol), phosphoric acid (0.048mol), ascorbic acid (0.0096mol) (that is, according to LiMn X Fe 1-X PO 4 (X = 0.7) for weighing) dissolved in 160ml of water and ethylene glycol by volume ratio = 1:2 in the mixed solvent, called A liquid; dissolved lithium hydroxide (0.144mol) in 120ml of water and ethylene glycol Alcohol in the mixed solvent composed of volume ratio = 1:2 in solvent two, called B liquid. Then, liquid B was added dropwise to liquid A for 20 minutes to obtain a precursor solution of lithium manganese iron phosphate, wherein the total concentration of ascorbic acid in the precursor solution was 0.0343 mol / L, and the lithium ion concentration in the precur...

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