CN101264876B - Method for preparing ferric lithium phosphate precursor by comprehensive utilization of ilmenite - Google Patents

Abstract

The invention discloses a preparation method for lithium iron phosphate precursor by comprehensively utilizing ilmenite, comprising a plurality of steps: leach the ilmenite in acid and filtrate is obtained by filtering; dissolve a certain amount of other iron sources in the filtrate to make the Fe concentration in the mixed solution as 0.01-3mol/L and the molar ratio of Ti and Fe as 0.0005-0.5; add appropriate amount of oxidant to the mixed solution; use alkali aqueous solution to regulate the system pH as 4.0-14.0; react for 10min to 24h at 10-90 DEG Cin a stir reactor; filter, wash and dry the sedimentation at 50-159 DEG C; after drying, calcine the sedimentation in air at 300-800 DEG C for 1-24h; lithium iron phosphate precursor for the lithium-ion battery cathode material, which is also the ferric oxide of doped-metal elements, can be obtained. The preparation method has the advantages of wide material source, simple technological process, good and stable product quality and low cost.

Description

Method for preparing lithium iron phosphate precursor by comprehensive utilization of ilmenite

technical field

The invention relates to a preparation method of a lithium iron phosphate precursor for a positive electrode material of a lithium ion battery, in particular to a method for comprehensively utilizing ilmenite to prepare a lithium iron phosphate precursor for a positive electrode material of a lithium ion battery.

technical background

Lithium iron phosphate with an olivine structure has become one of the most promising cathode materials for lithium-ion batteries due to its high theoretical specific capacity (170mAh/g), good cycle performance, good thermal stability, low price, and environmental friendliness. . However, as the main raw material for the production of lithium iron phosphate-iron salt, the large-scale industrial production of lithium iron phosphate is seriously restricted due to shortcomings such as unstable product quality, low density, and low purity.

At present, most of the iron sources for preparing lithium iron phosphate are chemically pure or analytically pure iron salts, mainly including ferrous oxalate, ferrous acetate, ferrous sulfate, ferric sulfate, ferric nitrate, ferric phosphate, and ferric oxide. Most of these iron salts are made from ores. From natural ores to chemically pure or analytically pure iron salts, a series of impurity removal procedures are required, and chemically pure or analytically pure iron salts are used to prepare high-performance lithium iron phosphate. Add some doping elements that are beneficial to its electrochemical performance. Most of these doping elements exist in natural minerals, which leads to duplication of processes and greatly increases costs. Therefore, directly using minerals to prepare the precursor of lithium iron phosphate, the cathode material of lithium-ion batteries, is an effective method to reduce its production cost.

On the other hand, my country is rich in ilmenite resources, with a total reserve of about 30 million tons. At present, the titanium element is mainly used to produce titanium dioxide, sponge titanium and artificial rutile, while other elements such as iron, magnesium, aluminum, manganese, nickel , cobalt, etc. have not been well utilized, which not only wastes resources, but also causes serious pollution to the environment.

With the increasing shortage of resources and the increasingly prominent environmental problems, it has become an inevitable trend of mineral utilization to speed up the research and development of new technologies and new processes for comprehensive utilization of various elements in minerals. The present invention is with a kind of brand-new train of thought, directly take natural ilmenite as the precursor of the lithium iron phosphate lithium iron phosphate of raw material synthesis-the ferric oxide of doping type metal element, because metal doping element (titanium, aluminum , magnesium, manganese, nickel, cobalt, etc.) are evenly distributed in the precursor particles, so there is no need for doping when synthesizing lithium iron phosphate. These doping elements can greatly improve the conductivity of lithium iron phosphate, thereby greatly improving its electrical conductivity. chemical properties. Therefore, the present invention is particularly suitable for providing a high-quality iron source for the production of lithium iron phosphate, the cathode material of lithium-ion batteries. If large-scale production is formed, it will definitely bring huge economic and ecological benefits to the society. So far, there are no reports on the comprehensive utilization of ilmenite to prepare lithium iron phosphate precursors for lithium ion battery cathode materials.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for comprehensively utilizing ilmenite to prepare a lithium iron phosphate precursor with wide source of raw materials, simple process flow, good and stable product quality and low cost.

In order to solve the above-mentioned technical problems, the comprehensive utilization of ilmenite provided by the invention prepares the method for lithium iron phosphate precursor, and its steps are:

(1), ilmenite is leached with acid, filtered to obtain filtrate, and a certain amount of other iron sources are dissolved in the filtrate, so that the concentration of Fe in the mixed solution is 0.01-3mol/L, and the molar ratio of Ti to Fe is 0.0005 -0.5;

(2) Add an appropriate amount of oxidant with a concentration of 0.01-6mol/L to the mixed solution, and adjust the pH of the system to 1.5-6.0 with an aqueous alkali solution with a concentration of 0.01-6mol/L, so that part of the iron and some impurity ions coprecipitation, filtration, to obtain the filtrate;

(3) Add a precipitant with a concentration of 0.01-6mol/L to the filtrate, adjust the pH of the system to 4.0-14.0 with an aqueous alkali solution with a concentration of 0.01-6mol/L, and place it in a stirred reactor at 10-90°C React for 10min-24h, filter, wash, dry the precipitate at 50-150°C, and then calcinate in air at 300-800°C for 1-24h to obtain the precursor of lithium iron phosphate, the positive electrode material of lithium ion battery-doped metal Elemental ferric oxide.

The acid described in the above step (1) is one of sulfuric acid and hydrochloric acid.

Other iron sources described in the above-mentioned steps (1) are magnetite, hematite, maghemite, limonite, siderite, metallic iron, ferric sulfate, ferrous sulfate, ferric chloride, ferrous chloride One or more of iron, ferric nitrate, and ferrous nitrate.

The alkali described in the above step (1) and step (3) is one or more of lithium hydroxide, sodium hydroxide, potassium hydroxide and ammonia water.

The oxidizing agent described in the above-mentioned step (2) is a kind of in sodium peroxide, hydrogen peroxide, potassium permanganate, sodium chlorate, sodium hypochlorite, potassium chlorate, potassium hypochlorite.

The precipitation agent described in the above-mentioned step (3) is one or more in lithium carbonate, lithium bicarbonate, ammonium carbonate, ammonium bicarbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate.

In order to overcome the disadvantages of poor electrical conductivity of lithium iron phosphate, the positive electrode material of lithium ion batteries, high cost of raw materials (iron source), and unstable product quality, the present invention provides a method for comprehensively utilizing ilmenite to prepare lithium iron phosphate precursors for lithium ion battery positive electrode materials , the method uses low-cost natural ilmenite as raw material, first leaching it, and adding a certain amount of other iron sources to the leaching solution to form a mixed solution, and by controlling the synthesis conditions, the electrochemical performance of lithium iron phosphate in the mixed solution can be improved. Beneficial elements (titanium, aluminum, magnesium, manganese, nickel, cobalt, etc.) selectively enter the precipitation, and the precipitate is dried and calcined in the air to obtain the precursor of lithium iron phosphate - ferric oxide of doped metal elements . The invention has wide sources of raw materials, simple process flow, good and stable product quality, and low cost, and is especially suitable for providing high-quality iron sources for large-scale production of lithium iron phosphate, and simultaneously enables comprehensive utilization of ilmenite resources.

Compared with other methods for preparing lithium iron phosphate precursors, the present invention has its advantages in the following aspects:

1) Using natural ilmenite as raw material, the cost is much lower than general chemically pure and analytically pure raw materials.

2) By controlling the synthesis conditions, elements in ilmenite that are beneficial to the electrochemical performance of lithium iron phosphate can be selectively precipitated, while elements that are harmful to the electrochemical performance of lithium iron phosphate do not enter the precipitation, and the process flow is simple.

3) The product (lithium iron phosphate precursor) is ferric oxide doped with metal elements, and the metal doping elements are evenly distributed in the precursor particles, which solves the problem that the doping elements are difficult to mix uniformly, and greatly improves the material quality. conductivity.

4) The synthesis time is short and easy to control, and the particle size of the product (lithium iron phosphate precursor) can be controlled through the synthesis time.

In summary, the present invention is a comprehensive utilization of ilmenite to prepare a lithium iron phosphate precursor with wide sources of raw materials, simple process flow, good and stable product quality, and low cost.

Description of drawings

Fig. 1 is the scanning electron microscope picture of the precursor of embodiment 1;

2 is a scanning electron microscope image of the precursor of Example 2.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Example 1:

Leach 1kg of ilmenite with sulfuric acid, filter to obtain filtrate, dissolve a certain amount of hematite and ferric sulfate in the filtrate, so that the concentration of Fe in the mixed solution is 0.1mol/L, and the molar ratio of Ti to Fe is 0.5; Add an appropriate amount of 0.01mol/L sodium peroxide solution to the mixed solution, adjust the pH of the system to about 1.5 with 0.5mol/L sodium hydroxide solution, stir for several minutes and filter to obtain the filtrate; add an appropriate amount of 1mol /L of ammonium carbonate solution, adjust the pH of the system to about 6.0 with 2mol/L ammonia water, react in a stirred reactor at 50°C for 10min, filter and wash, dry the precipitate at 100°C and place it in the air at 600°C Calcining at ℃ for 2 hours to obtain the precursor of lithium iron phosphate, the anode material of the lithium ion battery-ferric oxide of doped metal element.

Example 2:

Leach 1 kg of ilmenite with hydrochloric acid, filter to obtain the filtrate, dissolve a certain amount of ferric chloride in the filtrate, so that the concentration of Fe in the mixed solution is 1mol/L, and the molar ratio of Ti to Fe is 0.3; Add an appropriate amount of 3mol/L sodium hypochlorite solution, adjust the pH of the system to about 3.0 with a 2mol/L lithium hydroxide solution, and filter after stirring for several minutes to obtain a filtrate; add an appropriate amount of 2mol/L sodium carbonate solution in the filtrate, and use 0.1mol/L sodium hydroxide solution to adjust the pH of the system to about 4.0, react in a stirred reactor at 10°C for 4h, filter and wash, dry the precipitate at 50°C, and then calcinate at 800°C in air for 1h That is, the precursor of the positive electrode material lithium iron phosphate of the lithium ion battery-the ferric oxide of the doped metal element is obtained.

Example 3:

Leach 1 kg of ilmenite with sulfuric acid, filter to obtain the filtrate, dissolve a certain amount of ferrous sulfate and ferrous chloride in the filtrate, so that the concentration of Fe in the mixed solution is 2mol/L, and the molar ratio of Ti to Fe is 0.1 Add an appropriate amount of 1mol/L potassium chlorate solution to the mixed solution, adjust the pH of the system to about 6.0 with 3mol/L ammonia water, filter after stirring for several minutes, and obtain the filtrate; add an appropriate amount of 3mol/L potassium bicarbonate to the filtrate Solution, use 6mol/L potassium hydroxide solution to adjust the pH of the system to about 14.0, react in a stirred reactor at 70°C for 2h, filter and wash, dry the precipitate at 150°C, and then calcinate in air at 300°C After 24 hours, the precursor of lithium iron phosphate, the cathode material of the lithium ion battery, is obtained—the ferric oxide of the doped metal element.

Example 4:

Leach 1kg of ilmenite with hydrochloric acid, filter to obtain filtrate, dissolve a certain amount of siderite and ferric chloride in the filtrate, so that the concentration of Fe in the mixed solution is 0.01mol/L, and the molar ratio of Ti to Fe is 0.05 Add an appropriate amount of 1mol/L hydrogen peroxide to the mixed solution, adjust the pH of the system to about 4.0 with a 3mol/L sodium hydroxide solution, and filter after stirring for several minutes to obtain a filtrate; add an appropriate amount of 0.01mol/L hydrogen peroxide to the filtrate Ammonium bicarbonate solution, adjust the pH of the system to about 8.0 with 3mol/L ammonia water, react in a stirred reactor at 90°C for 1h, filter and wash, dry the precipitate at 120°C, and then dry it in the air at 500°C Calcined for 5 hours to obtain the precursor of lithium iron phosphate, the cathode material of the lithium ion battery-ferric oxide of the doped metal element.

Example 5:

Leach 1 kg of ilmenite with hydrochloric acid, filter to obtain a filtrate, dissolve a certain amount of limonite and metallic iron powder in the filtrate, so that the concentration of Fe in the mixed solution is 3mol/L, and the molar ratio of Ti to Fe is 0.0005; Add an appropriate amount of 6mol/L potassium permanganate solution to the mixed solution, adjust the pH of the system to about 5.0 with a 6mol/L sodium hydroxide solution, stir for several minutes and filter to obtain the filtrate; add an appropriate amount of 6mol/L to the filtrate L of sodium bicarbonate solution, adjust the pH of the system to about 6.0 with 0.01mol/L sodium hydroxide solution, react in a stirred reactor at 30°C for 24h, filter, wash, and dry the precipitate at 80°C Calcining at 500° C. for 10 h in the air to obtain the precursor of lithium iron phosphate, the cathode material of the lithium ion battery, and the ferric oxide of the doped metal element.

Although the present invention has been described in various preferred embodiments, those skilled in the art can easily understand that the present invention is not limited to the above description, and it can be changed or improved in various other ways without departing from the claims of the present invention The spirit and scope set forth in. For example, other iron sources may also be one or more of magnetite, maghemite, ferric nitrate, and ferrous nitrate. The oxidizing agent can also be sodium chlorate or potassium hypochlorite. Precipitating agent can also be one or more in lithium carbonate, lithium bicarbonate, potassium carbonate.

Claims (6)

1. A method for comprehensively utilizing ilmenite to prepare lithium iron phosphate precursor is characterized in that: its steps are: (1), ilmenite is leached with acid, filtered to obtain filtrate, and a certain amount of other iron sources are dissolved in the filtrate, so that the concentration of Fe in the mixed solution is 0.01-3mol/L, and the molar ratio of Ti to Fe is 0.0005 -0.5; (2) Add an appropriate amount of oxidant with a concentration of 0.01-6mol/L to the mixed solution, and adjust the pH of the system to 1.5-6.0 with an aqueous alkali solution with a concentration of 0.01-6mol/L, so that part of the iron and some impurity ions coprecipitation, filtration, to obtain the filtrate; (3) Add a precipitant with a concentration of 0.01-6mol/L to the filtrate, adjust the pH of the system to 4.0-14.0 with an aqueous alkali solution with a concentration of 0.01-6mol/L, and place it in a stirred reactor at 10-90°C React for 10min-24h, filter, wash, dry the precipitate at 50-150°C, and then calcinate in air at 300-800°C for 1-24h to obtain the precursor of lithium iron phosphate, the positive electrode material of lithium ion battery. 2. The method for comprehensively utilizing ilmenite to prepare a lithium iron phosphate precursor according to claim 1, characterized in that: the acid described in the above step (1) is one of sulfuric acid and hydrochloric acid. 3. the comprehensive utilization of ilmenite according to claim 1 prepares the method for lithium iron phosphate precursor, it is characterized in that: other iron sources described in the above-mentioned steps (1) are magnetite, hematite, maghemite One or more of ore, limonite, siderite, metallic iron, ferric sulfate, ferrous sulfate, ferric chloride, ferrous chloride, ferric nitrate, ferrous nitrate. 4. the comprehensive utilization of ilmenite according to claim 1 prepares the method for lithium iron phosphate precursor, it is characterized in that: the alkali described in above-mentioned steps (1) and step (3) is lithium hydroxide, sodium hydroxide, One or more of potassium hydroxide and ammonia water. 5. the comprehensive utilization of ilmenite according to claim 1 prepares the method for lithium iron phosphate precursor, it is characterized in that: described in above-mentioned step (2) oxygenant is sodium peroxide, hydrogen peroxide, potassium permanganate, chloric acid One of sodium, sodium hypochlorite, potassium chlorate, and potassium hypochlorite. 6. the comprehensive utilization ilmenite according to claim 1 prepares the method for lithium iron phosphate precursor, it is characterized in that: the precipitation agent described in the above-mentioned step (3) is lithium carbonate, lithium bicarbonate, ammonium carbonate, bicarbonate One or more of ammonium, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate.

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