阅读说明：本技术 一种硼酸铁锂的制备方法 (Preparation method of lithium iron borate ) 是由 蒋达金 于 2020-05-08 设计创作，主要内容包括：本发明公开一种硼酸铁锂的制备方法。将硼酸和醋酸溶解于甘油中,然后加入铁粉,搅拌反应至无气泡产生,再加入醋酸锂,搅拌溶解,得到浆料；将浆料放入到高压反应釜内反应得到反应料；将反应料冷却泄压,取出后经过过滤,得到,得到滤液和滤渣,将滤渣经过醋酸洗涤后,得到洗涤滤渣,洗涤滤渣烘干,得到烘干滤渣；将烘干滤渣经过加入钛酸丁酯,然后搅拌分散,得到的浆料加入纯水,继续搅拌反应,过滤,得到包覆滤渣；将包覆滤渣经过烘干后,得到烘干料,将烘干料在惰性气氛下煅烧,管道输送至恒温恒湿间,在恒温恒湿间筛分和真空包装,即得。本发明的一种硼酸铁锂的制备方法,可以得到一次颗粒小,BET大,分散性高的硼酸铁锂。(The invention discloses a preparation method of lithium iron borate. Dissolving boric acid and acetic acid in glycerol, adding iron powder, stirring to react until no bubbles are generated, adding lithium acetate, and stirring to dissolve to obtain slurry; putting the slurry into a high-pressure reaction kettle to react to obtain a reaction material; cooling and decompressing the reaction material, taking out the reaction material, and filtering the reaction material to obtain filtrate and filter residue, washing the filter residue with acetic acid to obtain washed filter residue, and drying the washed filter residue to obtain dried filter residue; adding butyl titanate into the dried filter residue, stirring and dispersing, adding pure water into the obtained slurry, continuously stirring for reaction, and filtering to obtain coated filter residue; and drying the coated filter residue to obtain a dried material, calcining the dried material in an inert atmosphere, conveying the calcined material to a constant temperature and constant humidity chamber through a pipeline, screening the calcined material in the constant temperature and constant humidity chamber, and carrying out vacuum packaging to obtain the coating. The preparation method of the lithium iron borate can obtain the lithium iron borate with small primary particles, large BET and high dispersibility.)

1. A preparation method of lithium iron borate is characterized by comprising the following steps:

(1) dissolving boric acid and acetic acid in glycerol, adding iron powder, heating to 50-70 ℃, stirring for reaction until no bubbles are generated, wherein the stirring speed is 100-300r/min, adding lithium acetate, and stirring for dissolution to obtain a slurry;

(2) putting the slurry obtained in the step (1) into a high-pressure reaction kettle, and stirring and reacting for 5-9h at the temperature of 250-350 ℃ and under the pressure of 3-5 atmospheric pressures to obtain a reaction material;

(3) cooling and decompressing the reaction material obtained in the step (2), taking out the reaction material, and filtering the reaction material to obtain filtrate and filter residue, washing the filter residue with acetic acid to obtain washed filter residue, and drying the washed filter residue to obtain dried filter residue;

(4) adding butyl titanate into the dried filter residue, stirring and dispersing, adding pure water into the obtained slurry, wherein the time for adding the pure water is 30-60min, continuing stirring and reacting for 10-30min, and filtering to obtain coated filter residue;

(5) and drying the coated filter residue to obtain a dried material, calcining the dried material at 400-500 ℃ for 5-8h in an inert atmosphere, cooling to the temperature of the material being less than or equal to 80 ℃, conveying the material to a constant temperature and humidity chamber through a pipeline, screening in the constant temperature and humidity chamber, and carrying out vacuum packaging to obtain the coating filter residue.

2. The method for preparing ferric lithium borate according to claim 1, wherein: the molar ratio of boric acid, acetic acid, glycerol, iron powder, lithium acetate and butyl titanate is 1: 0.98-1: 5-10: 0.99-1:1.01-1.03:0.02-0.05.

3. The method for preparing ferric lithium borate according to claim 1, wherein: the stirring speed in the step (2) is 200-300 r/min.

4. The method for preparing ferric lithium borate according to claim 1, wherein: and (4) mixing the filtrate obtained in the step (3) with washing liquid obtained by washing filter residue, fractionating, collecting the fraction at the temperature of 110-120 ℃ to obtain acetic acid, returning the rest substance which is glycerol for use, drying by adopting vacuum drying, wherein the temperature of the vacuum drying is 40-70 ℃.

5. The method for preparing ferric lithium borate according to claim 1, wherein: and (4) after dissolving the butyl titanate in the glycerol, adding the dried filter residue, wherein the volume ratio of the butyl titanate to the added glycerol is 1:20-50, distilling the filtrate obtained by filtering and coating the filter residue, and collecting the fraction at the temperature of 110-120 ℃ to obtain n-butanol, wherein the substance after distillation is the glycerol.

6. The method for preparing ferric lithium borate according to claim 1, wherein: the stirring speed for stirring and dispersing in the step (4) is 250-350r/min, the molar ratio of the added butyl titanate to the added pure water is 1:4.05-4.1, and the temperature when the pure water is added is 40-60 ℃.

7. The method for preparing ferric lithium borate according to claim 1, wherein: and (5) drying the coated filter residue in vacuum at 40-70 ℃.

8. The method for preparing ferric lithium borate according to claim 1, wherein: and (3) introducing inert atmosphere of at least one of nitrogen, argon and carbon dioxide into the calcining furnace to ensure that the volume concentration of oxygen in the calcining furnace is lower than 10ppm, the temperature between constant temperature and constant humidity is less than or equal to 25 ℃, the humidity is less than or equal to 10%, and sieving by adopting a 200-mesh ultrasonic vibration sieve.

Technical Field

The invention relates to a preparation method of lithium iron borate, belonging to the field of new energy battery materials.

Background

Lithium iron borate (LiFeBO3) is used as a cathode material of a high-capacity lithium battery, the theoretical specific capacity is 220mAh/g, the theoretical specific capacity of the lithium iron phosphate is only 170mAh/g, the lithium iron phosphate is better in conductivity, and the change rate of the minimum volume is (-2%). Structurally, borate (BO3) is smaller in molar mass (58.8<95) than (PO4), and the lithium iron borate structure is capable of providing both lithium ion conduction and electron conduction. The preparation of this material requires great care because the electrochemical properties of this material deteriorate rapidly upon contact with moisture.

The product obtained by the conventional method has large specific surface area, and is easy to absorb moisture and oxygen to cause the performance reduction of the product.

Disclosure of Invention

In view of the above, the invention provides a method for preparing lithium iron borate, spherical particles with smooth surface and titanium-coated compound are prepared, and BET of the product is less than or equal to 8m²Per g, good product stability and excellent rate capability.

The invention solves the technical problems by the following technical means:

the invention relates to a preparation method of lithium iron borate, which comprises the following steps:

(1) dissolving boric acid and acetic acid in glycerol, adding iron powder, heating to 50-70 ℃, stirring for reaction until no bubbles are generated, wherein the stirring speed is 100-300r/min, adding lithium acetate, and stirring for dissolution to obtain a slurry;

(2) putting the slurry obtained in the step (1) into a high-pressure reaction kettle, and stirring and reacting for 5-9h at the temperature of 250-350 ℃ and under the pressure of 3-5 atmospheric pressures to obtain a reaction material;

(3) cooling and decompressing the reaction material obtained in the step (2), taking out the reaction material, and filtering the reaction material to obtain filtrate and filter residue, washing the filter residue with acetic acid to obtain washed filter residue, and drying the washed filter residue to obtain dried filter residue;

(4) adding butyl titanate into the dried filter residue, stirring and dispersing, adding pure water into the obtained slurry, wherein the time for adding the pure water is 30-60min, continuing stirring and reacting for 10-30min, and filtering to obtain coated filter residue;

(5) and drying the coated filter residue to obtain a dried material, calcining the dried material at 400-500 ℃ for 5-8h in an inert atmosphere, cooling to the temperature of the material being less than or equal to 80 ℃, conveying the material to a constant temperature and humidity chamber through a pipeline, screening in the constant temperature and humidity chamber, and carrying out vacuum packaging to obtain the coating filter residue.

The molar ratio of boric acid, acetic acid, glycerol, iron powder, lithium acetate and butyl titanate is 1: 0.98-1: 5-10: 0.99-1:1.01-1.03:0.02-0.05.

The stirring speed in the step (2) is 200-300 r/min.

And (4) mixing the filtrate obtained in the step (3) with washing liquid obtained by washing filter residue, fractionating, collecting the fraction at the temperature of 110-120 ℃ to obtain acetic acid, returning the rest substance which is glycerol for use, drying by adopting vacuum drying, wherein the temperature of the vacuum drying is 40-70 ℃.

And (4) after dissolving the butyl titanate in the glycerol, adding the dried filter residue, wherein the volume ratio of the butyl titanate to the added glycerol is 1:20-50, distilling the filtrate obtained by filtering and coating the filter residue, and collecting the fraction at the temperature of 110-120 ℃ to obtain n-butanol, wherein the substance after distillation is the glycerol.

The stirring speed for stirring and dispersing in the step (4) is 250-350r/min, the molar ratio of the added butyl titanate to the added pure water is 1:4.05-4.1, and the temperature when the pure water is added is 40-60 ℃.

And (5) drying the coated filter residue in vacuum at 40-70 ℃.

And (3) introducing inert atmosphere of at least one of nitrogen, argon and carbon dioxide into the calcining furnace to ensure that the volume concentration of oxygen in the calcining furnace is lower than 10ppm, the temperature between constant temperature and constant humidity is less than or equal to 25 ℃, the humidity is less than or equal to 10%, and sieving by adopting a 200-mesh ultrasonic vibration sieve.

The method is similar to hydrothermal reaction, but the lithium iron borate is obtained by high-temperature high-pressure liquid phase reaction in an organic system, spherical particles with better dispersibility can be obtained in the organic system due to the dispersion effect (glycerol) of an organic phase, and the polarity of an organic matter is smaller than that of a water phase, and the organic system can realize high temperature under lower pressure, and because the boiling point of water is 100 ℃ and the boiling point of glycerol is 290 ℃, the generation of waste water is avoided, the glycerol and reaction products can be recycled, and the recycling cost is reduced.

According to the invention, spherical particles and lithium iron borate with good dispersibility are obtained through reaction in an organic phase, but the crystallinity is low, then butyl titanate is added, titanium hydroxide is obtained through hydrolysis, the titanium hydroxide is coated on the lithium iron borate, and then the lithium iron borate is calcined in an inert atmosphere, so that the crystallinity is improved, meanwhile, the surface of the lithium iron borate is smoother at high temperature, the BET of the product is further reduced, and the product has better stability and higher capacity.

According to the invention, through the coating of the lithium iron phosphate/C/iron boride, the conductivity can be improved, the internal resistance of powder can be reduced, the BET can be reduced, and the stability of the product can be improved.

The 0.1C discharge capacity of the lithium iron borate prepared by the invention is more than or equal to 195mAh/g, reaches the level of NCM622, but the price is lower than 60 percent of the price of NCM622, and the invention has obvious advantages.

Meanwhile, the product prepared by the method has good stability and very good industrialization prospect.

Meanwhile, the invention is a product with high sphericity, the processing performance is particularly excellent, the solid content can be greatly improved in the homogenate process in the battery preparation process, the solid content can reach more than 80%, and the efficiency can be greatly improved compared with the 60% solid content of the conventional lithium iron phosphate material.

The product of the invention has strip-shaped primary particle size and particularly excellent rate capability.

The method has no waste water, the obtained organic matters can be recovered through simple distillation to obtain acetic acid, n-butanol, glycerol and the like, the recovery value is high, and the equipment is simple.

The invention has the beneficial effects that: the prepared spherical particles are smooth in surface, are coated with titanium compounds, and have the advantages of BET (BET) of less than or equal to 8m2/g, good product stability and excellent rate capability.

Drawings

FIG. 1 is an SEM of the product obtained in example 1 of the present invention.

FIG. 2 is an SEM of the product obtained in example 2 of the present invention.

FIG. 3 is an SEM of the product obtained in example 3 of the present invention.

FIG. 4 is an SEM of an intermediate product obtained by high temperature synthesis of an organic system in example 1 of the present invention.

FIG. 5 is an SEM of an intermediate product obtained by high temperature synthesis of an organic system in example 2 of the present invention.

FIG. 6 is an SEM of an intermediate product obtained by high temperature synthesis of an organic system in example 3 of the present invention.

Detailed Description

The present invention will be described in detail below with reference to specific examples and accompanying drawings, in which the preparation method of lithium iron borate of the present embodiment includes the following steps:

(1) dissolving boric acid and acetic acid in glycerol, adding iron powder, heating to 50-70 ℃, stirring for reaction until no bubbles are generated, wherein the stirring speed is 100-300r/min, adding lithium acetate, and stirring for dissolution to obtain a slurry;

(2) putting the slurry obtained in the step (1) into a high-pressure reaction kettle, and stirring and reacting for 5-9h at the temperature of 250-350 ℃ and under the pressure of 3-5 atmospheric pressures to obtain a reaction material;

(3) cooling and decompressing the reaction material obtained in the step (2), taking out the reaction material, and filtering the reaction material to obtain filtrate and filter residue, washing the filter residue with acetic acid to obtain washed filter residue, and drying the washed filter residue to obtain dried filter residue;

(4) adding butyl titanate into the dried filter residue, stirring and dispersing, adding pure water into the obtained slurry, wherein the time for adding the pure water is 30-60min, continuing stirring and reacting for 10-30min, and filtering to obtain coated filter residue;

(5) and drying the coated filter residue to obtain a dried material, calcining the dried material at 400-500 ℃ for 5-8h in an inert atmosphere, cooling to the temperature of the material being less than or equal to 80 ℃, conveying the material to a constant temperature and humidity chamber through a pipeline, screening in the constant temperature and humidity chamber, and carrying out vacuum packaging to obtain the coating filter residue.

The molar ratio of boric acid, acetic acid, glycerol, iron powder, lithium acetate and butyl titanate is 1: 0.98-1: 5-10: 0.99-1:1.01-1.03:0.02-0.05.

The stirring speed in the step (2) is 200-300 r/min.

And (4) mixing the filtrate obtained in the step (3) with washing liquid obtained by washing filter residue, fractionating, collecting the fraction at the temperature of 110-120 ℃ to obtain acetic acid, returning the rest substance which is glycerol for use, drying by adopting vacuum drying, wherein the temperature of the vacuum drying is 40-70 ℃.

And (4) after dissolving the butyl titanate in the glycerol, adding the dried filter residue, wherein the volume ratio of the butyl titanate to the added glycerol is 1:20-50, distilling the filtrate obtained by filtering and coating the filter residue, and collecting the fraction at the temperature of 110-120 ℃ to obtain n-butanol, wherein the substance after distillation is the glycerol.

The stirring speed for stirring and dispersing in the step (4) is 250-350r/min, the molar ratio of the added butyl titanate to the added pure water is 1:4.05-4.1, and the temperature when the pure water is added is 40-60 ℃.

And (5) drying the coated filter residue in vacuum at 40-70 ℃.

And (3) introducing inert atmosphere of at least one of nitrogen, argon and carbon dioxide into the calcining furnace to ensure that the volume concentration of oxygen in the calcining furnace is lower than 10ppm, the temperature between constant temperature and constant humidity is less than or equal to 25 ℃, the humidity is less than or equal to 10%, and sieving by adopting a 200-mesh ultrasonic vibration sieve.