CN1837033A - Synthetic method of lithium iron phosphate lithium ion battery cathode material - Google Patents

Abstract

The invention discloses a Synthesis of lithium ferrous phosphate which is anode material of lithium ion battery. The material synthesis is as follows: geeting lithium salt, malysite and mammonium dihydrogen phosphate, according to the mole ratio of lithium ion: iron ion: phosphate radical ion is (0.8-1.2):(0.8-1.2):(0.8-1.2), getting compound A of equal proportion, joining some compound A in aqueous solution B which contains soluble salt and soluble organic species, putting it in high temperature furnace, then cooling naturely, compounding ferrous phosphate powder containing carbon and adulterating metal ion, milling the synthetical aqueous lithium solution powder, controllong the grain diameter between 1-50 mum. The synthetical material of this invention distribute equally, using this material as positive material can improve batteries' charging capacity effectively.

Description

Synthetic method of lithium iron phosphate lithium ion battery cathode material

technical field

The invention relates to a cathode material of a lithium ion battery, in particular to a synthesis method of lithium iron phosphate, an anode material of a lithium ion battery.

Background technique

As a green high-energy power source, lithium-ion batteries have been widely valued for more than ten years. It has the characteristics of high energy density, good cycle performance and low self-discharge rate. In recent years, the battery industry generally believes that lithium iron phosphate (molecular formula: LiFePO ₄ ) is one of the best new cathode materials for high-energy power batteries. In order to improve the capacity of lithium iron phosphate, carbon and metal doping are generally adopted during the synthesis process. ion. Chinese Patent Publication No. (Patent No.: 200410039176.4) discloses a preparation method of lithium ferrous phosphate, a positive electrode material for lithium ion batteries. It is to mix lithium salt, ferrous salt, phosphate and additives uniformly in proportion and put them into heat treatment equipment , heated in sections under the protection of an inert gas flow with a flow rate of 0.01-50 liters/minute, with a heating rate of 1-20°C/mi. 30 hours, then continue to heat up, carry out high-temperature treatment, keep the temperature at 500-850° C. for 10-48 hours, and then cool down to room temperature to prepare lithium iron phosphate cathode material. This preparation method is simple to operate and easy to control, and the prepared product has excellent electrical conductivity. The disadvantage is: because the added carbon is added in the form of solid, the amount of adulteration is relatively small, so it is not easy to mix, and the mixing is not easy. Thoroughly, so that the positive electrode material in the synthesized ferrous phosphate is not uniform, and the capacity of the material cannot be effectively improved.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, and provide a method for synthesizing a high-capacity lithium ferrous phosphate battery cathode material with short synthesis time and uniform synthetic materials.

The technical scheme of the present invention is

1. Take lithium salt, iron salt and ammonium dihydrogen phosphate, and mix them uniformly in the ratio of lithium ion: iron ion: phosphate ion molar ratio (0.8-1.2): (0.8-1.2): (0.8-1.2) to obtain a mixture A, where:

The lithium salt is one of lithium carbonate, lithium hydroxide, dilithium phosphate, lithium sulfate, lithium acetate, lithium nitrate and lithium oxalate.

The iron salt is ferrous acetate or ferrous oxalate.

2. Put a certain amount of mixture A above into a certain amount of aqueous solution B containing soluble salts and soluble organics, stir evenly, put it into a high-temperature furnace, and in a non-air or non-oxidizing atmosphere, use 1- Heating at a heating rate of 30°C/min, when the temperature rises to about 50-200°C, keep it warm for 0-100h, the higher the temperature, the shorter the time, and then perform high-temperature treatment according to the existing one-stage or stage-by-stage heating method, and then cool naturally. Synthesize ferrous phosphate powder (represented by Li _x Fe _y M _z PO ₄ ) containing carbon simple substance (represented by C) and doped metal ions (represented by M), the values of x, y and z in the formula are based on the corresponding substances It depends on the dosage under the following conditions;

(1) The mass ratio of the aqueous solution B to the mixture A is = (0.1-10): 1;

(2) The soluble salts in aqueous solution B include at least: nitrates, acetates, and sulfates of metal elements such as aluminum, titanium, magnesium, zirconium, vanadium, manganese, nickel, cobalt, niobium, rhodium, barium, and chromium One of hydrochloride and hydrochloride, its dosage must meet the following conditions: the molar ratio of metal ions (M) in soluble salts to lithium ions in lithium salts is ≤0.3;

(3) The soluble organic substances in the aqueous solution B include at least one of: sucrose, glucose, and one of the soluble high molecular compounds that can be decomposed into carbon substances with excellent conductivity by pyrolysis, and the dosing amount must meet the following conditions: The mass ratio of simple carbon to Li _x Fe _y M _z PO ₄ in the final composition is ≤10;

3. Grinding the lithium iron phosphate powder synthesized above, the particle size is controlled between 1-50um.

Because the present invention adopts the above-mentioned solution mixing method, it is easy to mix and thoroughly mixed, so that the material after synthesis is distributed evenly. When the material is used as the positive electrode material of lithium ion battery, the charging capacity of the battery can be effectively improved.

Detailed ways

In order to illustrate the present invention more clearly, the following examples are cited, but they do not limit the present invention in any way.

Embodiment one:

(1) First, lithium oxalate, ferrous oxalate and ammonium dihydrogen phosphate are uniformly mixed in a ratio of lithium ion: iron ion: phosphate ion molar ratio of 1:1:1 to obtain mixture A

(2) Take 1 kg of mixture A and put it into 1 kg of aqueous solution B containing glucose and zirconium nitrate, stir evenly, heat at a heating rate of 20°C/min under a nitrogen atmosphere, keep it warm for 5 hours when the temperature reaches about 100°C, and then continue to heat up , kept at 700°C for 10 hours, cooled naturally, and synthesized lithium ferrous phosphate powder containing carbon simple substance and doped metal zirconium ions, wherein:

It is required that 1 kg of aqueous solution B contains 10 g of glucose and 1 g of zirconium nitrate (Zr(NO ₃ ) ₄ ) (about 0.003 mol);

According to step (1), it can be seen that 1 kg of mixture A contains 1.62 moles of lithium oxalate (Li ₂ C ₂ O ₄ molecular weight 102), 3.24 moles of ferrous oxalate (FeC ₂ O ₄ molecular weight: 143) and 3.24 moles of ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ molecular weight: 115), so the finally synthesized lithium ferrous phosphate positive electrode material containing carbon simple substance and doped metal zirconium ions is represented by LiFeZr _0.0009 PO ₄ ;

(3) The synthesized lithium iron phosphate powder is finely ground, and the particle size is controlled between 1-50um.

Embodiment two:

(1) First, lithium carbonate, ferrous oxalate and ammonium dihydrogen phosphate are uniformly mixed in a ratio of lithium ion: iron ion: phosphate ion molar ratio of 1:1:1 to obtain mixture A

(2) Take 1 kg of mixture A and put it into 1 kg of aqueous solution B containing polyvinyl alcohol and magnesium nitrate and stir evenly. Under nitrogen atmosphere, heat at a heating rate of 30°C/min. When the temperature rises to about 110°C, keep it warm for 4 hours. Continue to heat up, when the temperature reaches 300 ° C, keep the temperature for 5 hours, then continue to heat up to 700 ° C, keep the temperature for 5 hours, cool naturally, and synthesize lithium ferrous phosphate powder containing carbon element and doped metal magnesium ions, wherein:

It is required that 1 kg of aqueous solution B contains 10 g of polyvinyl alcohol and 1 g of magnesium nitrate (about 0.004 moles);

According to step (1), it can be seen that 1 kg of mixture A contains 1.70 moles of lithium carbonate (Li ₂ CO ₃ molecular weight 74), 3.48 moles of ferrous oxalate (FeC ₂ O ₄ molecular weight: 143) and 3.4 moles of ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ molecular weight: 115), so the finally synthesized lithium iron phosphate cathode material containing simple carbon and doped metal magnesium ions can be represented by LiFeMg _0.0013 PO ₄ ;

(3) Grinding the synthesized lithium iron phosphate powder, and controlling the particle size between 1-50um.

Embodiment three:

(1) At first three kinds of materials dilithium hydrogen phosphate, ferrous oxalate and ammonium dihydrogen phosphate are uniformly mixed in the ratio of lithium ion: iron ion: phosphate ion molar ratio is 1: 1: 1 to obtain mixture A;

(2) Take 1 kg of mixture A and put it into 1 kg of aqueous solution B containing sucrose and magnesium nitrate and stir evenly. Under a nitrogen atmosphere, heat at a heating rate of 5°C/min. When the temperature reaches about 90°C, keep it warm for 6 hours, and continue heating. When the temperature reaches 300°C, keep the temperature for 5 hours, then continue to heat up to 700°C, keep the temperature for 5 hours, cool naturally, and synthesize lithium ferrous phosphate powder containing carbon element and doped metal magnesium ions, wherein:

It is required to contain 10 g of sucrose and 1 g of magnesium nitrate (about 0.004 mole) in 1 kg of aqueous solution B;

According to step (1), it can be known that 1 kg of mixture A contains 1.6 moles of dilithium hydrogen phosphate (Li ₂ HPO ₄ molecular weight 110), 3.2 moles of ferrous oxalate (FeC ₂ O ₄ molecular weight: 143) and 3.2 moles of ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ molecular weight: 115), so the finally synthesized lithium iron phosphate positive electrode material containing carbon simple substance and doped metal magnesium ions can be represented by LiFeMg _0.0011 PO ₄ ;

(3) Grinding the synthesized lithium iron phosphate powder, and controlling the particle size between 1-50um.

For ease of calculation, lithium salt, iron salt, and ammonium dihydrogen phosphate in the examples of the present invention are all mixed according to the ratio of lithium ion: iron ion: phosphate ion molar ratio is 1: 1: 1, so that The values of X, Y, and Z in the finally synthesized lithium ferrous phosphate powder molecular formula LiFeMg _0.0013 PO ₄ are equal, but this should not be used as a limitation to the technical solution of the present invention.

Claims (1)

1, a kind of synthetic method of lithium ferrous phosphate as anode material of lithium ion battery, its concrete synthetic method is as follows:

(1) get lithium salts, molysite, primary ammonium phosphate, in lithium ion: iron ion: the phosphate anion mol ratio is (0.8-1.2): (0.8-1.2): ratio uniform mixing (0.8-1.2), obtain mixture A, wherein:

Lithium salts is wherein a kind of of Quilonum Retard, lithium hydroxide, phosphoric acid hydrogen two lithiums, Lithium Sulphate, Lithium Acetate, lithium nitrate and lithium oxalate,

Molysite is ferrous acetate or Ferrox;

(2) above-mentioned a certain amount of mixture A is put into a certain amount of aqueous solution B that contains solubility salt and the organic class of solubility, after evenly stirring, put into High Temperature Furnaces Heating Apparatus, in non-air or non-oxidizing atmosphere, temperature rise rate heating with 1-30 ℃/min, the insulation 0-100h time when temperature rises to the 50-200 ℃ of left and right sides, the high more time of temperature is short more, carry out pyroprocessing according to existing heating means then, naturally cooling, the synthetic ferrous phosphate lithium powder that contains carbon simple substance (representing with C) and doped metal ion (representing with M) (is used Li _xFe _yM _zPO ₄Expression), the x in the formula, y, z value are decided according to respective substance addition content under the following conditions;

1. the mass ratio of aqueous solution B and mixture A is (0.1-10): 1;

2. comprise at least in the solubility salt among the aqueous solution B: a kind of in nitrate, acetate, vitriol and the hydrochloride of aluminium, titanium, magnesium, zirconium, vanadium, manganese, nickel, cobalt, niobium, rhodium, barium, chromium metallic element, its addition content must meet following condition: molar ratio≤0.3 of lithium ion in the metal ion in the solubility salt (M) and the lithium salts;

3. the organic class material of the solubility among the aqueous solution B comprises at least: sucrose, glucose and can be decomposed into a kind of in the soluble high-molecular compound with good electric conductivity carbon class material through pyrolysis, its addition content must meet following condition: carbon simple substance and Li in the final synthetics _xFe _yM _zPO ₄Quality ratio≤10;

(3) above synthetic ferrous phosphate lithium powder is levigate, particle diameter is controlled between the 1-50um.