CN106898771B - Lithium-iron disulfide lithium battery cathode material - Google Patents

Abstract

The invention discloses a lithium-iron disulfide lithium battery positive electrode material, which comprises a modified iron disulfide positive electrode active material, the positive electrode active material is doped with 2% by mass of titanium oxide, 4% by mass Magnesium oxide and 6% copper oxide iron disulfide, the method for preparing the positive active material is specifically: a) preparing the first heat-treated iron disulfide, the second heat-treated iron disulfide and the third heat-treated iron disulfide; b) preparing the first coated iron disulfide, the second coated iron disulfide and the third coated iron disulfide; c) the first coated iron disulfide, the second coated iron disulfide and the third coated iron disulfide The iron disulfide is uniformly mixed to obtain a positive electrode material for a lithium-iron disulfide lithium battery. The invention can reduce the open circuit voltage of the battery, so that the voltage platform is more stable; in addition, a composite conductive agent is added to the positive electrode material, which can greatly improve the conductivity, reduce the polarization of the battery, improve the high and low temperature performance of the battery, and prolong the life of the battery. .

Description

Lithium-iron disulfide lithium battery cathode material

technical field

The invention relates to the technical field of lithium battery materials. More specifically, the present invention relates to a lithium-iron disulfide lithium battery positive electrode material obtained by adding modified iron disulfide.

Background technique

The lithium-iron disulfide battery is a high-energy and environmentally friendly primary battery with iron disulfide as the positive active material and lithium ion as the negative active material. It has many advantages that traditional primary batteries cannot match: high and stable discharge voltage; large discharge capacity; High specific power and large discharge current; the lightest weight among the same type of battery products; wide operating temperature range; good high temperature storage performance; good leak-proof performance; long storage life; no mercury, no cadmium, no battery Lead is a green, safe and reliable new energy storage device. Because of its excellent performance, lithium-iron disulfide is widely used in daily life. At present, it is mainly used in digital cameras, MP3, handheld game consoles, portable CD players, handheld computers, digital display instruments, medical equipment, and various electric meters. It also has potential application prospects in military fields such as weapons and equipment, aerospace and so on.

With the advancement of science and technology, the demand for lithium-iron disulfide batteries is increasing, and the performance requirements are also getting higher and higher. The improvement and upgrading of electrode materials have become a breakthrough point in the performance development and research of lithium-iron disulfide batteries. Especially the cathode material becomes one of the most important components in research. The cathode material iron disulfide of lithium-iron disulfide battery is usually separated and purified from pyrite. The battery assembled with the initially obtained iron disulfide as a material has high open circuit voltage, poor voltage platform and high current discharge performance. , in order to improve the voltage platform and discharge performance, it is necessary to modify the active material iron disulfide. In the existing technology, the treatment of iron disulfide has problems such as single method, insignificant effect and complex and tedious process; in addition, as a positive electrode The performance of the conductive agent, one of the components of the material, also has an extremely important influence on the discharge performance of the battery.

SUMMARY OF THE INVENTION

An object of the present invention is to solve at least the above-mentioned problems and to provide at least the advantages which will be explained later.

Another object of the present invention is to provide a positive electrode material for a lithium-iron disulfide lithium battery. In the present invention, the iron disulfide obtained by preliminary separation is divided into batches, and different batches of iron disulfide are subjected to heat treatment and introduction at different temperatures. From different metal oxides, three modified iron disulfides with different crystal phase structures, particle sizes and surface structures were obtained, and the three modified iron disulfides were mixed uniformly, and the active material of the prepared iron disulfide was used as lithium- The material of iron disulfide can reduce the open circuit voltage of the battery and make the voltage platform more stable; in addition, a composite conductive agent is added to the positive electrode material, which can greatly improve the conductivity, reduce the polarization of the battery, and improve the high and low temperature performance of the battery. Extend battery life.

In order to achieve these objects and other advantages according to the present invention, a lithium-iron disulfide lithium battery positive electrode material is provided, which comprises a modified iron disulfide positive electrode active material, the positive electrode active material is doped with a mass percentage of It is 2% titanium oxide, 4% magnesium oxide and 6% copper oxide iron disulfide, and the preparation method of the positive electrode active material is as follows:

a) The iron disulfide obtained by separating and purifying the pyrite is divided into three equal parts, and the three equal parts iron disulfide are put into the electric heating constant temperature blast drying oven with the temperature of 250 ℃, 300 ℃ and 380 ℃ respectively , take out and cool to room temperature after storage for 24h to obtain the first heat-treated iron disulfide, the second heat-treated iron disulfide and the third heat-treated iron disulfide, during which nitrogen is fed into the three drying ovens;

b) Disperse the first heat-treated iron disulfide in absolute ethanol for 2 to 4 hours, then put it into a vacuum drying oven at 70 to 80°C for drying, then disperse the dried product in deionized water, and add it to the Add the mixed solution of metal salt titanium tetrachloride solution and ammonia water, fully stir for 4 to 6 hours and then filter, collect the first filter residue and wash it with absolute ethanol for 1 to 3 times, and put the washed first filter residue into a vacuum of 70 to 80 ° C. Dry in a drying oven, then treat in a high temperature inert gas at 180-240°C for 1-3 hours to obtain the first coated iron disulfide; disperse the second heat-treated iron disulfide in acetone for ball milling for 2-4 hours, and then put Dry in a vacuum drying oven at 70-80 °C, then disperse the dried product in deionized water, add a mixed solution of metal salt magnesium chloride solution and ammonia water to it, stir well for 4-6 hours, filter, collect the second filter residue and use Wash with acetone for 1 to 3 times, put the washed second filter residue into a vacuum drying oven at 70 to 80 ° C for drying, and then treat it in a high temperature inert gas at 240 to 280 ° C for 1 to 3 hours to obtain a second coating Iron sulfide; disperse the third heat-treated iron disulfide in dimethylformamide and ball mill for 2-4 hours, then put it into a vacuum drying oven at 170-220°C for drying, and then disperse the dried product in deionized water, Add metal salt copper sulfate solution and ammonia water to it, fully stir for 4-6 hours, filter, collect the third filter residue and wash it with absolute ethanol for 1-3 times, put the washed third filter residue into vacuum drying at 170-220°C Dry in a box, and then treat in a high temperature inert gas at 300-340°C for 1-3 hours to obtain the third coated iron disulfide;

c) Putting the first coated iron disulfide, the second coated iron disulfide and the third coated iron disulfide into a ball milling jar of polytetrafluoroethylene, into which the first coated iron disulfide was added The anhydrous ethanol coated iron disulfide 3.2 times the weight is ball-milled for 3-5 hours, then the material in the ball-milling jar is placed in a vacuum drying box, and the temperature is kept at 70-80 ° C for 2-4 hours. powder, that is.

Preferably, the positive electrode material of the lithium-iron disulfide battery further includes a conductive agent, which is a composite formed by carbon fibers, carbon nanotubes and carbon black in a weight ratio of 1:2:3; The preparation method is specifically as follows: the carbon black is divided into a first part and a second part with a weight ratio of 2:1, the first part of the carbon black and the carbon nanotubes are placed in a ball milling tank equipped with anhydrous ethanol, and after ball milling for 2 hours. Take it out, put it into a vacuum drying oven at 100 °C for 10 hours to get the first conductive material; put the second part of carbon black and carbon fiber into a ball milling jar filled with absolute ethanol, and take it out after ball milling for 2 hours and put it in a 100 °C Dry in a vacuum drying box for 10 hours to obtain the second conductive material; pour the first conductive material and the second conductive material into the dimethyl sulfoxide solution dissolved with gelatin, stir at a high speed for 40-60 minutes and then filter, and use the filtrate separately for The conductive agent is obtained by washing with acetone and ethanol for 1 to 3 times, and then putting it into a vacuum drying oven at 100° C. to dry for 4 to 6 hours.

Preferably, the lithium-iron disulfide lithium battery cathode material further includes a binder, which includes styrene-butadiene rubber, sodium carboxymethyl cellulose and polymethacrylic acid in a weight ratio of 3:1:1.

Preferably, the lithium-iron disulfide positive electrode material further includes a dispersant, and the dispersant includes polyethylene glycol and polyvinyl alcohol in a weight ratio of 2:1.

Preferably, the positive electrode material of the lithium-iron disulfide battery further includes a solvent, and the solvent is N-methylpyrrolidone.

Preferably, in the positive electrode material of the lithium-iron disulfide battery, the mass ratio of the positive electrode active material, the conductive agent, the binder and the dispersant is 90.8:3.1-4.5:3.1-4.5 : 0.9 to 1.5, and the mass ratio of the solvent to the positive electrode active material is 2.5:1.

Preferably, in the lithium-iron disulfide positive electrode material for the lithium-iron disulfide battery, the carbon fiber is prepared as follows: in parts by weight, 30-40 parts of acetic acid lignin and 20-28 parts of alkaline lignin are taken, respectively. Dissolve in 100 parts of acetic acid solution, configure a first solution and a second solution, add 0.01-0.03 parts of metallic nickel to the first solution to obtain a first spinning solution; add 0.01-0.01 to the second solution 0.03 parts of metallic copper to obtain the second spinning solution; the first spinning solution and the second spinning solution are placed in a high-voltage electrospinning device, and electrospinning is performed to obtain the first nanofiber and the second spinning solution. Two nanofibers, the first nanofiber and the second nanofiber are mixed and put into a muffle furnace for pre-oxidation, and then the pre-oxidized nanofiber mixture is heated to 700 ℃ under nitrogen protection, and the heating rate is 100 ℃/h , carbonized for 1 h, cooled to room temperature, and pulverized to obtain the carbon fiber.

The present invention includes at least the following beneficial effects:

1. Heat treatment can increase the content of iron disulfide in minerals by removing the moisture in iron disulfide, and can also increase the specific surface area of iron disulfide. The increase in specific surface area can improve the positive electrode of lithium-iron disulfide lithium battery. The absorption rate of the material to the electrolyte, the increase of the iron disulfide content and the increase of the absorption rate of the electrolyte can increase the discharge capacity of the battery and improve the performance of the lithium battery, but the heat treatment will increase the packing density of the iron disulfide. , the higher the temperature, the greater the bulk density, and the excessive bulk density will lead to the problem of uneven mixing of the active material with the conductive agent and the binder; the present invention divides the iron disulfide obtained by separation and purification into three equal parts, and the three equal parts are carried out Heat treatment at different temperatures, and three equal parts of iron disulfide after heat treatment are coated with different metal oxides, and the advantages and disadvantages of three different modified iron disulfides are complemented, so that the active material can reduce the open circuit of the battery. The voltage makes the voltage platform more stable, which greatly increases the discharge capacity of the battery and improves the discharge efficiency;

2. Carbon fibers, carbon nanotubes and other materials are commonly used as conductive agents for lithium batteries. The particle size of carbon black is small, the conduction distance is small, and the conductivity is good. The tubes have excellent axial one-dimensional conductivity, but their particle size is large, and the required conduction distance is large; carbon fibers and carbon nanotubes are mixed with carbon black, so that the carbon black with small particle size and good conductivity enters the carbon fiber In the pore size and voids of carbon nanotubes, the mutual contact of active materials is increased, the conductivity of the overall electrode is improved, and the stress caused by the volume change during the charging and discharging process can be relieved, and the battery life can be improved. A layer of gelatin reduces the dissolving effect of the electrolyte on the conductive agent and further prolongs the service life of the battery;

3. Nano-carbon fibers are prepared by electrospinning and carbonization using acetic acid lignin and alkaline lignin, which have good electrical conductivity and flexibility, and the addition of metal elements is introduced in the electrospinning process to increase the electrical conductivity of carbon fibers. , to further increase the conductivity of the conductive agent.

Other advantages, objects, and features of the present invention will appear in part from the description that follows, and in part will be appreciated by those skilled in the art from the study and practice of the invention.

Detailed ways

The present invention will be further described in detail below with reference to the embodiments, so that those skilled in the art can implement according to the description.

It should be understood that terms such as "having", "comprising" and "including" as used herein do not assign the presence or addition of one or more other elements or combinations thereof.

It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial sources unless otherwise specified.

<Example 1>

A lithium-iron disulfide lithium battery positive electrode material, comprising:

Positive electrode active material, the positive electrode active material is iron disulfide doped with 2% by mass of titanium oxide, 4% of magnesium oxide and 6% of copper oxide, and the preparation method of the positive electrode active material is as follows:

a) The iron disulfide obtained by separating and purifying the pyrite is divided into three equal parts, and the three equal parts iron disulfide are put into the electric heating constant temperature blast drying oven with the temperature of 250 ℃, 300 ℃ and 380 ℃ respectively , take out and cool to room temperature after storage for 24h to obtain the first heat-treated iron disulfide, the second heat-treated iron disulfide and the third heat-treated iron disulfide, during which nitrogen is fed into the three drying ovens;

b) Disperse the first heat-treated iron disulfide in absolute ethanol for 2 hours, then put it into a vacuum drying oven at 70°C for drying, then disperse the dried product in deionized water, and add metal salt four Titanium chloride solution and ammonia water mixed solution, fully stirred for 4 hours, filtered, collected the first filter residue and washed with absolute ethanol once, put the washed first filter residue into a vacuum drying box at 70°C for drying, and then dried at 180°C Treated in high temperature inert gas for 1h to obtain the first coated iron disulfide; disperse the second heat-treated iron disulfide in acetone and ball mill for 2h, then put it into a vacuum drying oven at 70 °C for drying, and then dry the dried product Disperse in deionized water, add a mixed solution of metal salt magnesium chloride solution and ammonia water to it, stir well for 4 hours, filter, collect the second filter residue and wash it with acetone once, put the washed second filter residue into a vacuum drying oven at 70°C Dry in medium, and then treat in a high temperature inert gas at 240 °C for 1 h to obtain the second coated iron disulfide; disperse the third heat-treated iron disulfide in dimethylformamide for 2 h, and then put it in a 170 °C Dry in a vacuum drying oven, then disperse the dried product in deionized water, add metal salt copper sulfate solution and ammonia water to it, stir well for 4 hours, filter, collect the third filter residue and wash with absolute ethanol once, the washing The third filter residue was dried in a vacuum drying oven at 170°C, and then treated in a high-temperature inert gas at 300°C for 1 hour to obtain the third coated iron disulfide;

c) Putting the first coated iron disulfide, the second coated iron disulfide and the third coated iron disulfide into a ball milling jar of polytetrafluoroethylene, into which the first coated iron disulfide was added 3.2 times the weight of iron disulfide coated with anhydrous ethanol ball mill for 3 hours, then place the material in the ball mill in a vacuum drying oven, and keep the temperature at 70 °C for 2 hours.

A conductive agent, which is a composite formed by carbon fibers, carbon nanotubes and carbon black in a weight ratio of 1:2:3; the preparation method of the conductive agent is specifically as follows: the carbon black is divided into a first one with a weight ratio of 2:1 Place the first part of carbon black and carbon nanotubes in a ball-milling jar with anhydrous ethanol, take them out after ball-milling for 2 hours, and put them into a vacuum drying oven at 100°C for 10 hours to dry to obtain the first conductive material. ; Put the second part of carbon black and carbon fiber into a ball-milling jar with absolute ethanol, take it out after ball milling for 2 hours, and put it into a vacuum drying oven at 100 °C for 10 hours to dry to obtain a second conductive material; the first conductive material and The second conductive material was poured into the gelatin-dissolved dimethyl sulfoxide solution, stirred at a high speed for 40 min, and filtered. The filtrate was washed once with acetone and ethanol, and then placed in a vacuum drying oven at 100 °C for 4 h. to obtain the conductive agent;

The preparation method of the carbon fiber is as follows: in parts by weight, 30 parts of acetic acid lignin and 20 parts of alkaline lignin are respectively dissolved in 100 parts of acetic acid solution, a first solution and a second solution are prepared, and a first solution and a second solution are prepared. Add 0.01 part of metallic nickel to the first solution to obtain the first spinning solution; add 0.01 part of metallic copper to the second solution to obtain the second spinning solution; combine the first spinning solution and the second spinning solution. The second spinning solution is placed in a high-voltage electrospinning device, and electrospinning is performed to obtain the first nanofiber and the second nanofiber. The first nanofiber and the second nanofiber are mixed and placed in a muffle furnace for pre-oxidation, Then, the pre-oxidized nanofiber mixture was heated to 700°C under nitrogen protection at a heating rate of 100°C/h, carbonized for 1 h, cooled to room temperature, and crushed to obtain the carbon fibers.

A binder comprising styrene-butadiene rubber, sodium carboxymethyl cellulose and polymethacrylic acid in a weight ratio of 3:1:1;

a dispersant, the dispersant comprising polyethylene glycol and polyvinyl alcohol in a weight ratio of 2:1;

solvent, the solvent is N-methylpyrrolidone.

In another technical solution, in the cathode material of the lithium-iron disulfide battery, the mass ratio of the cathode active material, the conductive agent, the binder and the dispersant is 90.8:3.1:3.1 : 0.9, and the mass ratio of the solvent to the positive active material is 2.5:1.

<Example 2>

A lithium-iron disulfide lithium battery positive electrode material, comprising:

Positive electrode active material, the positive electrode active material is iron disulfide doped with 2% by mass of titanium oxide, 4% of magnesium oxide and 6% of copper oxide, and the preparation method of the positive electrode active material is as follows:

a) The iron disulfide obtained by separating and purifying the pyrite is divided into three equal parts, and the three equal parts iron disulfide are put into the electric heating constant temperature blast drying oven with the temperature of 250 ℃, 300 ℃ and 380 ℃ respectively , take out and cool to room temperature after storage for 24h to obtain the first heat-treated iron disulfide, the second heat-treated iron disulfide and the third heat-treated iron disulfide, during which nitrogen is fed into the three drying ovens;

b) Disperse the first heat-treated iron disulfide in anhydrous ethanol for ball milling for 4 hours, then put it into a vacuum drying oven at 80°C for drying, then disperse the dried product in deionized water, and add metal salt four Titanium chloride solution and ammonia water mixed solution, fully stirred for 6 hours, filtered, collected the first filter residue and washed with absolute ethanol 3 times, put the washed first filter residue into a vacuum drying box at 80 °C for drying, and then dried at 240 °C The second part of heat-treated iron disulfide was dispersed in acetone and ball-milled for 4 hours, and then put into a vacuum drying oven at 80 °C for drying, and then the dried product was dried. Disperse in deionized water, add a mixed solution of metal salt magnesium chloride solution and ammonia water to it, stir well for 6 hours, filter, collect the second filter residue and wash it with acetone 3 times, put the washed second filter residue into a vacuum drying oven at 80 °C Dry in medium, and then treat in a high temperature inert gas at 280°C for 3h to obtain the second coated iron disulfide; disperse the third heat-treated iron disulfide in dimethylformamide for 4h ball milling, and then put it in a 220°C Dry in a vacuum drying box, then disperse the dried product in deionized water, add metal salt copper sulfate solution and ammonia water to it, stir well for 6h, filter, collect the third filter residue and wash with absolute ethanol 3 times, the washing The third filter residue was dried in a vacuum drying oven at 220°C, and then treated in a high-temperature inert gas at 340°C for 3 hours to obtain the third coated iron disulfide;

c) Putting the first coated iron disulfide, the second coated iron disulfide and the third coated iron disulfide into a ball milling jar of polytetrafluoroethylene, into which the first coated iron disulfide was added Ball-milling with anhydrous ethanol coated with iron disulfide 3.2 times the weight is carried out for 5 hours, and then the material in the ball-milling jar is placed in a vacuum drying oven, kept at a constant temperature of 80 °C for 4 hours, and the dried material is taken out and placed in a grinding bowl and ground into powder.

A conductive agent, which is a composite formed by carbon fibers, carbon nanotubes and carbon black in a weight ratio of 1:2:3; the preparation method of the conductive agent is specifically as follows: the carbon black is divided into a first one with a weight ratio of 2:1 Place the first part of carbon black and carbon nanotubes in a ball-milling jar with anhydrous ethanol, take them out after ball-milling for 2 hours, and put them into a vacuum drying oven at 100°C for 10 hours to dry to obtain the first conductive material. ; Put the second part of carbon black and carbon fiber into a ball-milling jar with absolute ethanol, take it out after ball milling for 2 hours, and put it into a vacuum drying oven at 100 °C for 10 hours to dry to obtain a second conductive material; the first conductive material and The second conductive material was poured into the gelatin-dissolved dimethyl sulfoxide solution, stirred at a high speed for 60 min, and filtered. The filtrate was washed with acetone and ethanol for 3 times, and then placed in a vacuum drying oven at 100 °C for 6 h. to obtain the conductive agent;

The preparation method of the carbon fiber is as follows: in parts by weight, 40 parts of acetic acid lignin and 28 parts of alkaline lignin are respectively dissolved in 100 parts of acetic acid solution, a first solution and a second solution are prepared, and a first solution and a second solution are prepared. Add 0.03 parts of metallic nickel to the first solution to obtain the first spinning solution; add 0.03 parts of metallic copper to the second solution to obtain the second spinning solution; combine the first spinning solution and the second spinning solution. The second spinning solution is placed in a high-voltage electrospinning device, and electrospinning is performed to obtain the first nanofiber and the second nanofiber. The first nanofiber and the second nanofiber are mixed and placed in a muffle furnace for pre-oxidation, Then, the pre-oxidized nanofiber mixture was heated to 700°C under nitrogen protection at a heating rate of 100°C/h, carbonized for 1 h, cooled to room temperature, and crushed to obtain the carbon fibers.

A binder comprising styrene-butadiene rubber, sodium carboxymethyl cellulose and polymethacrylic acid in a weight ratio of 3:1:1;

a dispersant, the dispersant comprising polyethylene glycol and polyvinyl alcohol in a weight ratio of 2:1;

solvent, the solvent is N-methylpyrrolidone.

In another technical solution, in the positive electrode material of the lithium-iron disulfide battery, the mass ratio of the positive electrode active material, the conductive agent, the binder and the dispersant is 90.8:4.5:4.5 : 1.5, and the mass ratio of the solvent to the positive active material is 2.5:1.

<Example 3>

A lithium-iron disulfide lithium battery positive electrode material, comprising:

Positive electrode active material, the positive electrode active material is iron disulfide doped with 2% by mass of titanium oxide, 4% of magnesium oxide and 6% of copper oxide, and the preparation method of the positive electrode active material is as follows:

a) The iron disulfide obtained by separating and purifying the pyrite is divided into three equal parts, and the three equal parts iron disulfide are put into the electric heating constant temperature blast drying oven with the temperature of 250 ℃, 300 ℃ and 380 ℃ respectively , take out and cool to room temperature after storage for 24h to obtain the first heat-treated iron disulfide, the second heat-treated iron disulfide and the third heat-treated iron disulfide, during which nitrogen is fed into the three drying ovens;

b) Disperse the first heat-treated iron disulfide in absolute ethanol for 3 hours, then put it into a vacuum drying oven at 75°C for drying, then disperse the dried product in deionized water, and add metal salt four to it. Titanium chloride solution and ammonia water mixed solution, fully stirred for 5 hours, filtered, collected the first filter residue and washed twice with absolute ethanol, put the washed first filter residue into a vacuum drying box at 75°C for drying, and then dried at 210°C The second part of heat-treated iron disulfide was dispersed in acetone and ball-milled for 3 hours, and then dried in a vacuum drying oven at 75 °C, and then the dried product was dried. Disperse in deionized water, add a mixed solution of metal salt magnesium chloride solution and ammonia water to it, stir well for 5 hours, filter, collect the second filter residue and wash it twice with acetone, put the washed second filter residue into a vacuum drying oven at 75°C Dry in medium, and then treat it in a high temperature inert gas at 260 °C for 2 hours to obtain the second coated iron disulfide; disperse the third heat-treated iron disulfide in dimethylformamide for 3 hours, and then put it in a 195 °C Dry in a vacuum drying box, then disperse the dried product in deionized water, add metal salt copper sulfate solution and ammonia water to it, stir well for 5h, filter, collect the third filter residue and wash with absolute ethanol twice, the washing The third filter residue was dried in a vacuum drying oven at 195°C, and then treated in a high-temperature inert gas at 320°C for 2 hours to obtain the third coated iron disulfide;

c) Putting the first coated iron disulfide, the second coated iron disulfide and the third coated iron disulfide into a ball milling jar of polytetrafluoroethylene, into which the first coated iron disulfide was added 3.2 times the weight of iron disulfide coated with anhydrous ethanol ball milled for 4 hours, then put the material in the ball mill in a vacuum drying box, and kept the temperature at 75 °C for 3 hours.

A conductive agent, which is a composite formed by carbon fibers, carbon nanotubes and carbon black in a weight ratio of 1:2:3; the preparation method of the conductive agent is specifically as follows: the carbon black is divided into a first one with a weight ratio of 2:1 Place the first part of carbon black and carbon nanotubes in a ball-milling jar with anhydrous ethanol, take them out after ball-milling for 2 hours, and put them into a vacuum drying oven at 100°C for 10 hours to dry to obtain the first conductive material. ; Put the second part of carbon black and carbon fiber into a ball-milling jar with absolute ethanol, take it out after ball milling for 2 hours, and put it into a vacuum drying oven at 100 °C for 10 hours to dry to obtain a second conductive material; the first conductive material and The second conductive material was poured into the gelatin-dissolved dimethyl sulfoxide solution, stirred at a high speed for 50 min, and filtered. The filtrate was washed twice with acetone and ethanol, respectively, and then placed in a vacuum drying oven at 100 °C for 5 h. to obtain the conductive agent;

The preparation method of the carbon fiber is as follows: in parts by weight, 35 parts of acetic acid lignin and 24 parts of alkaline lignin are respectively dissolved in 100 parts of acetic acid solution, a first solution and a second solution are prepared, and a first solution and a second solution are prepared. Add 0.02 part of metallic nickel to the first solution to obtain the first spinning solution; add 0.02 part of metallic copper to the second solution to obtain the second spinning solution; combine the first spinning solution and the second spinning solution. The second spinning solution is placed in a high-voltage electrospinning device, and electrospinning is performed to obtain the first nanofiber and the second nanofiber. The first nanofiber and the second nanofiber are mixed and placed in a muffle furnace for pre-oxidation, Then, the pre-oxidized nanofiber mixture was heated to 700°C under nitrogen protection at a heating rate of 100°C/h, carbonized for 1 h, cooled to room temperature, and crushed to obtain the carbon fibers.

A binder comprising styrene-butadiene rubber, sodium carboxymethyl cellulose and polymethacrylic acid in a weight ratio of 3:1:1;

a dispersant, the dispersant comprising polyethylene glycol and polyvinyl alcohol in a weight ratio of 2:1;

solvent, the solvent is N-methylpyrrolidone.

In another technical solution, in the cathode material of the lithium-iron disulfide battery, the mass ratio of the cathode active material, the conductive agent, the binder and the dispersant is 90.8:3.8:3.8 : 1.2, and the mass ratio of the solvent to the positive active material is 2.5:1.

<Example 4>

A positive electrode material for a lithium-iron disulfide lithium battery, the difference from Example 3 is that the positive electrode active material is modified iron disulfide, and the positive electrode active material is titanium oxide doped with a mass percentage of 2%. Described positive active material is obtained by separating and purifying the iron disulfide obtained from pyrite, according to the heat treatment of the first equal part of iron disulfide, metal oxidation coating, drying, grinding into powder to obtain in Example 3, the remaining conditions and parameters Same as Example 3.

<Example 5>

A positive electrode material for a lithium-iron disulfide lithium battery, the difference from Example 3 is that the positive electrode active material is modified iron disulfide, and the positive electrode active material is magnesium oxide doped with a mass percentage of 4%. Described positive active material is obtained by separating and purifying the iron disulfide obtained from pyrite, according to the heat treatment of second equal parts iron disulfide, metal oxidation coating, drying, grinding into powder in Example 3, and the remaining conditions and parameters are obtained. Same as Example 3.

<Example 6>

A positive electrode material for a lithium-iron disulfide lithium battery, the difference from Example 3 is that the positive electrode active material is modified iron disulfide, and the positive electrode active material is copper oxide doped with a mass percentage of 6%. Described positive active material is obtained by separating and purifying the iron disulfide obtained from pyrite, according to the heat treatment, metal oxidation coating, drying, grinding into powder of the third equal part of iron disulfide in Example 3, and the remaining conditions and parameters are obtained. Same as Example 3.

<Example 7>

A lithium-iron disulfide lithium battery cathode material, the difference from Example 3 is that the conductive agent is a composite formed by ordinary mixing of carbon fibers, carbon nanotubes and carbon black, and other conditions and parameters are the same as those of Example 3.

<Example 8>

A positive electrode material for a lithium-iron disulfide battery, the difference from Example 3 is that the carbon fiber is a commercially available common carbon fiber, and other conditions and parameters are the same as those of Example 3.

<Comparative Example 1>

The positive electrode materials provided in Examples 3 to 8 of the present invention were used to assemble batteries by the same method, and the discharge capacities of 6 kinds of batteries under 45mA constant current discharge were tested, and the maximum compaction densities of 6 kinds of positive electrode materials were tested. The results are shown in Table 1 shown:

Numbering Discharge capacity (Ah) Maximum compaction density (g/cm³) Example 3 2.67 3.89 Example 4 2.12 3.74 Example 5 2.09 3.73 Example 6 2.18 3.75 Example 7 2.35 3.25 Example 8 2.36 3.28

As can be seen from Table 1, the lithium-iron disulfide lithium battery cathode material provided in Example 3 of the present invention has higher discharge capacity and higher compaction density than Examples 4 to 8; it is explained that the present invention is obtained by preliminary separation. different batches of iron disulfide were heat-treated at different temperatures and introduced into different metal oxides to obtain three modified iron disulfides with different crystal phase structures, particle sizes and surface structures, and the The three modified iron disulfides are evenly mixed, and the active material of the prepared iron disulfide is used as the material of lithium-iron disulfide. At the same time, a composite conductive agent is also added to the positive electrode material, which can greatly increase the compaction density of the positive electrode material. Conductive properties.

The number of apparatuses and processing scales described here are intended to simplify the description of the present invention. Applications, modifications and variations to the present invention will be apparent to those skilled in the art.

Although the embodiment of the present invention has been disclosed as above, it is not limited to the application listed in the description and the embodiment, and it can be applied to various fields suitable for the present invention. For those skilled in the art, it can be easily Therefore, the invention is not limited to the specific details without departing from the general concept defined by the appended claims and the scope of equivalents.

Claims (1)

1. a lithium-iron disulfide lithium battery positive electrode material, is characterized in that, it comprises the positive electrode active material of modified iron disulfide, and described positive electrode active material is to be doped with the titanium oxide that mass percentage is 2%, 4 % magnesium oxide and 6% copper oxide iron disulfide, the preparation method of the positive active material is as follows: a) The iron disulfide obtained by separating and purifying the pyrite is divided into three equal parts, and the three equal parts iron disulfide are put into the electric heating constant temperature blast drying oven with the temperature of 250 ℃, 300 ℃ and 380 ℃ respectively , take out and cool to room temperature after storage for 24h to obtain the first heat-treated iron disulfide, the second heat-treated iron disulfide and the third heat-treated iron disulfide, during which nitrogen is fed into the three drying ovens; b) Disperse the first heat-treated iron disulfide in absolute ethanol for 2 to 4 hours, then put it into a vacuum drying oven at 70 to 80°C for drying, then disperse the dried product in deionized water, and add it to the Add the mixed solution of metal salt titanium tetrachloride solution and ammonia water, fully stir for 4 to 6 hours and then filter, collect the first filter residue and wash it with absolute ethanol for 1 to 3 times, and put the washed first filter residue into a vacuum of 70 to 80 ° C. Dry in a drying oven, then treat in a high temperature inert gas at 180-240°C for 1-3 hours to obtain the first coated iron disulfide; disperse the second heat-treated iron disulfide in acetone for ball milling for 2-4 hours, and then put Dry in a vacuum drying oven at 70-80 °C, then disperse the dried product in deionized water, add a mixed solution of metal salt magnesium chloride solution and ammonia water to it, stir well for 4-6 hours, filter, collect the second filter residue and use Wash with acetone for 1 to 3 times, put the washed second filter residue into a vacuum drying oven at 70 to 80 ° C for drying, and then treat it in a high temperature inert gas at 240 to 280 ° C for 1 to 3 hours to obtain a second coating Iron sulfide; disperse the third heat-treated iron disulfide in dimethylformamide and ball mill for 2-4 hours, then put it into a vacuum drying oven at 170-220°C for drying, and then disperse the dried product in deionized water, Add metal salt copper sulfate solution and ammonia water to it, fully stir for 4-6 hours, filter, collect the third filter residue and wash it with absolute ethanol for 1-3 times, put the washed third filter residue into vacuum drying at 170-220°C Dry in a box, and then treat in a high temperature inert gas at 300-340°C for 1-3 hours to obtain the third coated iron disulfide; c) Putting the first coated iron disulfide, the second coated iron disulfide and the third coated iron disulfide into a ball milling jar of polytetrafluoroethylene, into which the first coated iron disulfide was added The anhydrous ethanol coated iron disulfide 3.2 times the weight is ball-milled for 3-5 hours, then the material in the ball-milling jar is placed in a vacuum drying box, and the temperature is kept at 70-80 ° C for 2-4 hours. powder, that is; It also includes a conductive agent, which is a composite formed by carbon fibers, carbon nanotubes and carbon black in a weight ratio of 1:2:3; the preparation method of the conductive agent is specifically: the carbon black is divided into a weight ratio of 2:1. The first part and the second part, put the first part of carbon black and carbon nanotubes in a ball-milling jar filled with absolute ethanol, take them out after ball-milling for 2 hours, and put them in a vacuum drying oven at 100°C for 10 hours to obtain the first part. Conductive material; put the second part of carbon black and carbon fiber into a ball milling jar filled with absolute ethanol, take it out after ball milling for 2 hours, and put it into a vacuum drying box at 100 ° C for drying for 10 hours to obtain a second conductive material; put the first conductive material The material and the second conductive material are poured into the gelatin-dissolved dimethyl sulfoxide solution, stirred at a high speed for 40 to 60 minutes, and then filtered. The filtrate was washed with acetone and ethanol for 1 to 3 times, and then put into a vacuum drying at 100 ° C. The conductive agent is obtained by drying in the box for 4-6 hours; The preparation method of the carbon fiber is as follows: in parts by weight, 30-40 parts of acetic acid lignin and 20-28 parts of alkaline lignin are respectively dissolved in 100 parts of acetic acid solution, and the first solution and the second solution are prepared. , adding 0.01-0.03 parts of metallic nickel to the first solution to obtain a first spinning solution; adding 0.01-0.03 parts of metallic copper to the second solution to obtain a second spinning solution; A spinning solution and the second spinning solution are placed in a high-voltage electrospinning device, and electrospinning is performed to obtain a first nanofiber and a second nanofiber, and the first nanofiber and the second nanofiber are mixed and put into Pre-oxidation is carried out in a muffle furnace, and then the pre-oxidized nanofiber mixture is heated to 700°C under nitrogen protection at a heating rate of 100°C/h, carbonized for 1 hour, cooled to room temperature, and pulverized to obtain the carbon fiber; Also includes a binder, which includes styrene-butadiene rubber, sodium carboxymethyl cellulose and polymethacrylic acid in a weight ratio of 3:1:1; Also includes a dispersant, the dispersant includes polyethylene glycol and polyvinyl alcohol in a weight ratio of 2:1; Also includes a solvent, the solvent is N-methylpyrrolidone; The mass ratio of the positive electrode active material, the conductive agent, the binder and the dispersant is 90.8:3.1-4.5:3.1-4.5:0.9-1.5, and the mass ratio of the solvent to the positive electrode active material 2.5:1.