CN107093724B - Preparation method of lithium battery positive electrode material - Google Patents
Preparation method of lithium battery positive electrode material Download PDFInfo
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- CN107093724B CN107093724B CN201710288644.9A CN201710288644A CN107093724B CN 107093724 B CN107093724 B CN 107093724B CN 201710288644 A CN201710288644 A CN 201710288644A CN 107093724 B CN107093724 B CN 107093724B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/364—Composites as mixtures
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/626—Metals
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention discloses a preparation method of a lithium battery anode material, which comprises the following steps: a, dividing a positive active substance and a conductive agent into three equal parts respectively, dividing a binder into four parts and a dispersant into four parts, and mixing a first part of binder, a first part of dispersant, a first equal part of positive active substance and a first equal part of conductive agent to obtain a first mixed material; step B, preparing a second mixed material and a third mixed material; step C, mixing the first mixed material, the second mixed material and the third mixed material to obtain a core active material; and D, coating a layer of inorganic nano film outside the core active material to obtain the lithium battery cathode material. The lithium battery anode material prepared by the invention has good conductivity and high tap density, and the prepared battery has large capacity and can meet the requirement of large-scale production.
Description
Technical Field
The invention relates to the technical field of lithium battery anode materials. More specifically, the invention relates to a preparation method of a lithium iron phosphate lithium battery anode material.
Background
The development and construction of clean energy is one of the most important fields of development all over the world, and batteries are important media for reasonably and effectively utilizing the new energy. Lithium ion batteries have been widely applied and developed in the weak current industry, and the key technology for preparing lithium batteries is battery materials, especially positive electrode materials of lithium batteries. The currently commonly used positive electrode materials include a lithium cobaltate positive electrode material, a lithium nickel cobaltate positive electrode material, a lithium iron phosphate positive electrode material, a lithium manganese oxide positive electrode material and the like, wherein lithium iron phosphate is taken as a lithium ion battery positive electrode material which is widely concerned since the invention is self-evident, and compared with other lithium ion battery positive electrode materials, the lithium iron phosphate has higher energy density, more excellent high-temperature performance and better safety performance.
However, the preparation method of the lithium iron phosphate cathode material in the prior art has the following defects: 1) the active substance for preparing the lithium iron phosphate anode material has poor electrochemical performance, so that the prepared lithium battery anode material has poor low-temperature performance, and the production and the use of the lithium iron phosphate lithium battery are limited; 2) the ionic conductivity of the lithium iron phosphate is poor, the added conductive agent is not fully mixed with the active material, and the conductive agent is not uniformly dispersed in the active material, so that the charge and discharge performance of the battery is reduced, and the discharge capacity of the battery is reduced; 3) the preparation method is complicated, the preparation efficiency is low, the operation is not easy, and the raw material and production cost are high.
Therefore, a preparation method of the lithium battery cathode material which is simple, can obviously improve the conductivity, the thermal stability, the low-temperature discharge performance, the safety performance, the wide raw material source, the low price and the long service life of the lithium battery is urgently needed to be designed.
Disclosure of Invention
An object of the present invention is to solve at least the above problems and to provide at least the advantages described later.
The invention also aims to provide a preparation method of the lithium battery anode material, which comprises the steps of respectively dividing the active substance, the conductive agent and the binder of the anode material into a plurality of equal parts, respectively mixing the three equal parts, and finally uniformly mixing the three mixed materials, so that the phenomena of nonuniform mixing and easy agglomeration of the same substance caused by direct mixing of various materials in the anode material are avoided, the charge and discharge performance of the anode material is improved, and the charge and discharge capacity is increased; meanwhile, the outer surface of the core active material is coated with a layer of inorganic nano film, so that the dissolution of electrolyte to substances in the positive electrode material during charging and discharging is reduced, and the service life of the battery is prolonged.
To achieve these objects and other advantages in accordance with the present invention, there is provided a method for preparing a positive electrode material for a lithium battery, comprising the steps of:
step A, equally dividing the positive active substance into three equal parts, equally dividing the conductive agent into three equal parts, dividing the binder into four parts according to the weight ratio of 1:1:1:1.2, dividing the dispersant into four parts according to the weight ratio of 1:1:1:2, pouring the first part of the binder into a stirrer filled with a solvent, simultaneously adding a first equal part of conductive agent and a first equal part of positive active material into a stirrer while stirring, after the first equal part of conductive agent and the first equal part of positive active material are added, adding a first part of dispersing agent into the stirrer, stirring at a high speed for 1-2 h, vacuumizing, continuing to pump for 3min when the vacuum degree in the stirrer reaches 0.01MPa, stirring at a medium speed for 1.5-2.5 h in a vacuum state, closing the vacuum after stirring, adding absolute ethyl alcohol accounting for 0.2% of the weight of the solvent into the stirrer, vacuumizing again, and stirring at a low speed for 0.3-1.3 h; after stirring, closing the vacuum, and sieving the materials in the stirrer by a 100-mesh sieve to obtain a first mixture; wherein the weight of the solvent is 4 times of the weight of the first equal part of the positive electrode active material;
step B, respectively processing a second equal part of the positive electrode active substance, a second equal part of the conductive agent, a second part of the binder and a second part of the dispersant, and a third equal part of the positive electrode active substance, a third equal part of the conductive agent, a third part of the binder and a third part of the dispersant according to the operation of the step A to obtain a second mixture and a third mixture;
step C, mixing the first mixture, the second mixture, the third mixture and a fourth dispersant, fully stirring for 5-7 hours, storing in a vacuum drying oven at 160-200 ℃ for 2-4 hours, and then treating the dried mixture in inert gas at high temperature for 1-3 hours, wherein the treatment temperature is 450-600 ℃, so as to obtain a core active material;
step D, placing polypropylene and nano inorganic particles into an absolute ethyl alcohol solution to prepare a suspension, adding the suspension and a fourth binder into a stirrer filled with the core active material, stirring at a high speed for 40-50 min to enable the suspension to fully soak the core active material, starting a heating device of the stirrer to enable the temperature in the stirrer to rise to 60-70 ℃, keeping the temperature for 50-60 min to obtain a coating, placing the coating in an aerobic environment at the temperature of 750-1000 ℃ and calcining for 5-8 h at the temperature rising speed of 5-10 ℃/min to obtain the lithium battery anode material;
the positive electrode active material is modified lithium iron phosphate doped with 0.1 mass percent of titanium, 0.2 mass percent of magnesium and 0.1 mass percent of aluminum.
Preferably, in the preparation method of the lithium battery cathode material, the conductive agent is a composite formed by mixing carbon fibers and graphene in a weight ratio of 1: 2.
Preferably, the preparation method of the lithium battery cathode material comprises the following steps: respectively dissolving 30-40 parts by weight of lignin acetate and 20-28 parts by weight of alkaline lignin in 100 parts by weight of acetic acid solution to prepare a first solution and a second solution, and adding 0.01-0.03 part by weight of metallic nickel into the first solution to obtain a first spinning solution; adding 0.01-0.03 part of metal copper into the second solution to obtain a second spinning solution; and placing the first spinning solution and the second spinning solution in a high-voltage electrostatic spinning device, performing electrostatic spinning to obtain first nanofibers and second nanofibers, mixing the first nanofibers and the second nanofibers, placing the mixture into a muffle furnace for pre-oxidation, then placing the pre-oxidized nanofiber mixture in a nitrogen atmosphere, heating to 700 ℃, heating at a rate of 100 ℃/h, performing carbonization treatment for 1h, cooling to room temperature, and crushing to obtain the carbon fibers.
Preferably, in the preparation method of the lithium battery cathode material, the binder comprises styrene butadiene rubber, sodium carboxymethyl cellulose and polymethacrylic acid in a weight ratio of 3:1: 1.
Preferably, in the preparation method of the lithium battery cathode material, the dispersant comprises polyethylene glycol and polyvinyl alcohol in a weight ratio of 2: 1; the solvent is N-methyl pyrrolidone.
Preferably, in the preparation method of the lithium battery positive electrode material, the mass ratio of the positive electrode active substance, the conductive agent, the binder and the dispersing agent is 90.8: 3.1-4.5: 0.9-1.5, and the mass ratio of the solvent to the positive electrode active substance is 2.5: 1.
Preferably, in the preparation method of the lithium battery cathode material, the high-speed stirring speed is 40-50 Hz in revolution and 30-40 Hz in rotation, and the medium-speed stirring speed is 20-30 Hz in revolution and 20-30 Hz in rotation; the low-speed stirring speed is 10Hz in revolution and 0Hz in rotation.
The invention at least comprises the following beneficial effects:
1. according to the invention, the active substance, the conductive agent and the binder of the anode material are respectively uniformly divided into a plurality of equal parts, the three equal parts of the active substance, the conductive agent and the binder are respectively mixed, and finally the three mixed materials are uniformly mixed, so that the phenomena of nonuniform mixing and easy agglomeration of the same substance caused by direct mixing of various materials in the anode material are avoided, the charge and discharge performance of the anode material is improved, and the charge and discharge capacity is increased; meanwhile, the outer surface of the core active material is coated with a layer of inorganic nano film, so that the dissolution of electrolyte to substances in the positive electrode material during charging and discharging is reduced, and the service life of the battery is prolonged;
2. the nano carbon fiber is prepared by utilizing the acetic acid lignin and the alkaline lignin through electrospinning and carbonization, has good conductivity and flexibility, and the conductivity of the carbon fiber is increased by introducing the additive of the metal simple substance in the electrospinning process, so that the conductivity of the conductive agent is further increased.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Detailed Description
The present invention is further described in detail below with reference to examples so that those skilled in the art can practice the invention with reference to the description.
It will be understood that terms such as "having," "including," and "comprising," as used herein, do not preclude the presence or addition of one or more other elements or groups thereof.
It is to be noted that the experimental methods described in the following embodiments are all conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified.
< example 1>
A preparation method of a lithium battery positive electrode material comprises the following steps:
step A, equally dividing the positive active substance into three equal parts, equally dividing the conductive agent into three equal parts, dividing the binder into four parts according to the weight ratio of 1:1:1:1.2, dividing the dispersing agent into four parts according to the weight ratio of 1:1:1:2, pouring the first part of the binder into a stirrer with a solvent, simultaneously adding the first equal part of the conductive agent and the first equal part of the positive active substance into the stirrer while stirring, adding the first part of the dispersing agent into the stirrer after the first equal part of the conductive agent and the first equal part of the positive active substance are added, stirring at a high speed for 1h, vacuumizing, continuing to pump for 3min when the vacuum degree in the stirrer reaches 0.01MPa, stirring at a medium speed for 1.5h in a vacuum state, closing the vacuum after the stirring is finished, adding absolute ethyl alcohol of 0.2% of the weight of the solvent into the stirrer, vacuumizing again and stirring at a low speed for 0.3 h; after stirring, closing the vacuum, and sieving the materials in the stirrer by a 100-mesh sieve to obtain a first mixture; wherein the weight of the solvent is 4 times of the weight of the first equal part of the positive electrode active material;
step B, respectively processing a second equal part of the positive electrode active substance, a second equal part of the conductive agent, a second part of the binder and a second part of the dispersant, and a third equal part of the positive electrode active substance, a third equal part of the conductive agent, a third part of the binder and a third part of the dispersant according to the operation of the step A to obtain a second mixture and a third mixture;
step C, mixing the first mixture, the second mixture, the third mixture and a fourth dispersant, fully stirring for 5 hours, storing for 2 hours in a vacuum drying box at 160 ℃, and then treating the dried mixture in inert gas at high temperature for 1 hour, wherein the treatment temperature is 450 ℃ to obtain a core active material;
step D, placing polypropylene and nano inorganic particles into an absolute ethyl alcohol solution to prepare a suspension, adding the suspension and a fourth binder into a stirrer filled with the core active material, stirring at a high speed for 40min to enable the suspension to fully soak the core active material, starting a heating device of the stirrer to enable the temperature in the stirrer to rise to 60 ℃, keeping the temperature for 50min to obtain a coating, placing the coating in an aerobic environment at 750 ℃ and calcining for 5hh at the temperature rising speed of 5 ℃/min to obtain the lithium battery anode material;
the cathode active material is modified lithium iron phosphate doped with 0.1 mass percent of titanium, 0.2 mass percent of magnesium and 0.1 mass percent of aluminum;
the conductive agent is a composite formed by mixing carbon fibers and graphene in a weight ratio of 1: 2; the preparation method of the carbon fiber comprises the following steps: respectively dissolving 30 parts of acetic acid lignin and 20 parts of alkaline lignin in 100 parts of acetic acid solution according to parts by weight, preparing a first solution and a second solution, and adding 0.01 part of metallic nickel into the first solution to obtain a first spinning solution; adding 0.01 part of metal copper into the second solution to obtain a second spinning solution; placing the first spinning solution and the second spinning solution in a high-voltage electrostatic spinning device, performing electrostatic spinning to obtain first nanofibers and second nanofibers, mixing the first nanofibers and the second nanofibers, placing the mixture into a muffle furnace for pre-oxidation, then placing the pre-oxidized nanofiber mixture under the protection of nitrogen, heating to 700 ℃, the heating rate is 100 ℃/h, performing carbonization treatment for 1h, cooling to room temperature, and crushing to obtain the carbon fibers;
the binder comprises styrene butadiene rubber, sodium carboxymethylcellulose and polymethacrylic acid in a weight ratio of 3:1: 1; the dispersing agent comprises polyethylene glycol and polyvinyl alcohol in a weight ratio of 2: 1; the solvent is N-methyl pyrrolidone;
the mass ratio of the positive electrode active material to the conductive agent to the binder to the dispersing agent is 90.8:3.1:3.1:0.9, and the mass ratio of the solvent to the positive electrode active material is 2.5: 1;
the high-speed stirring speed is 40Hz in revolution, the rotation speed is 30Hz, and the medium-speed stirring speed is 20Hz in revolution and 20Hz in rotation; the low-speed stirring speed is 10Hz in revolution and 0Hz in rotation.
< example 2>
A preparation method of a lithium battery positive electrode material comprises the following steps:
step A, equally dividing the positive active substance into three equal parts, equally dividing the conductive agent into three equal parts, dividing the binder into four parts according to the weight ratio of 1:1:1:1.2, dividing the dispersing agent into four parts according to the weight ratio of 1:1:1:2, pouring the first part of the binder into a stirrer with a solvent, simultaneously adding the first equal part of the conductive agent and the first equal part of the positive active substance into the stirrer while stirring, adding the first part of the dispersing agent into the stirrer after the first equal part of the conductive agent and the first equal part of the positive active substance are added, stirring at a high speed for 2 hours, vacuumizing, continuing to pump for 3 minutes when the vacuum degree in the stirrer reaches 0.01MPa, stirring at a medium speed for 2.5 hours in a vacuum state, closing the vacuum after the stirring is finished, adding absolute ethyl alcohol of 0.2% of the weight of the solvent into the stirrer, vacuumizing again and stirring at a low speed for 1.3 hours; after stirring, closing the vacuum, and sieving the materials in the stirrer by a 100-mesh sieve to obtain a first mixture; wherein the weight of the solvent is 4 times of the weight of the first equal part of the positive electrode active material;
step B, respectively processing a second equal part of the positive electrode active substance, a second equal part of the conductive agent, a second part of the binder and a second part of the dispersant, and a third equal part of the positive electrode active substance, a third equal part of the conductive agent, a third part of the binder and a third part of the dispersant according to the operation of the step A to obtain a second mixture and a third mixture;
step C, mixing the first mixture, the second mixture, the third mixture and a fourth dispersant, fully stirring for 7 hours, storing for 4 hours in a vacuum drying oven at 200 ℃, and then treating the dried mixture in inert gas at high temperature for 3 hours at 600 ℃ to obtain a core active material;
step D, placing polypropylene and nano inorganic particles into an absolute ethyl alcohol solution to prepare a suspension, adding the suspension and a fourth binder into a stirrer filled with the core active material, stirring at a high speed for 50min to enable the suspension to fully soak the core active material, starting a heating device of the stirrer to enable the temperature in the stirrer to rise to 70 ℃, keeping the temperature for 60min to obtain a coating, and placing the coating in an aerobic environment at the temperature of 1000 ℃ for calcining for 8h at the temperature rising speed of 10 ℃/min to obtain the lithium battery anode material;
the cathode active material is modified lithium iron phosphate doped with 0.1 mass percent of titanium, 0.2 mass percent of magnesium and 0.1 mass percent of aluminum;
the conductive agent is a composite formed by mixing carbon fibers and graphene in a weight ratio of 1: 2; the preparation method of the carbon fiber comprises the following steps: respectively dissolving 40 parts of acetic acid lignin and 28 parts of alkaline lignin in 100 parts of acetic acid solution according to parts by weight, preparing a first solution and a second solution, and adding 0.03 part of metallic nickel into the first solution to obtain a first spinning solution; adding 0.03 part of metal copper into the second solution to obtain a second spinning solution; placing the first spinning solution and the second spinning solution in a high-voltage electrostatic spinning device, performing electrostatic spinning to obtain first nanofibers and second nanofibers, mixing the first nanofibers and the second nanofibers, placing the mixture into a muffle furnace for pre-oxidation, then placing the pre-oxidized nanofiber mixture under the protection of nitrogen, heating to 700 ℃, the heating rate is 100 ℃/h, performing carbonization treatment for 1h, cooling to room temperature, and crushing to obtain the carbon fibers;
the binder comprises styrene butadiene rubber, sodium carboxymethylcellulose and polymethacrylic acid in a weight ratio of 3:1: 1; the dispersing agent comprises polyethylene glycol and polyvinyl alcohol in a weight ratio of 2: 1; the solvent is N-methyl pyrrolidone;
the mass ratio of the positive electrode active material to the conductive agent to the binder to the dispersing agent is 90.8:4.5:4.5:1.5, and the mass ratio of the solvent to the positive electrode active material is 2.5: 1;
the high-speed stirring speed is 50Hz in revolution and 40Hz in rotation, and the medium-speed stirring speed is 30Hz in revolution and 30Hz in rotation; the low-speed stirring speed is 10Hz of revolution and 0Hz of rotation
< example 3>
A preparation method of a lithium battery positive electrode material comprises the following steps:
step A, equally dividing the positive active substance into three equal parts, equally dividing the conductive agent into three equal parts, dividing the binder into four parts according to the weight ratio of 1:1:1:1.2, dividing the dispersing agent into four parts according to the weight ratio of 1:1:1:2, pouring the first part of the binder into a stirrer with a solvent, simultaneously adding the first equal part of the conductive agent and the first equal part of the positive active substance into the stirrer while stirring, adding the first part of the dispersing agent into the stirrer after the first equal part of the conductive agent and the first equal part of the positive active substance are added, stirring at a high speed for 1.5h, vacuumizing, continuing to pump for 3min when the vacuum degree in the stirrer reaches 0.01MPa, stirring at a medium speed for 2h in a vacuum state, closing the vacuum after the stirring is finished, adding absolute ethyl alcohol of 0.2% of the weight of the solvent into the stirrer, vacuumizing again and stirring at a low speed for 0.8 h; after stirring, closing the vacuum, and sieving the materials in the stirrer by a 100-mesh sieve to obtain a first mixture; wherein the weight of the solvent is 4 times of the weight of the first equal part of the positive electrode active material;
step B, respectively processing a second equal part of the positive electrode active substance, a second equal part of the conductive agent, a second part of the binder and a second part of the dispersant, and a third equal part of the positive electrode active substance, a third equal part of the conductive agent, a third part of the binder and a third part of the dispersant according to the operation of the step A to obtain a second mixture and a third mixture;
step C, mixing the first mixture, the second mixture, the third mixture and a fourth dispersant, fully stirring for 6 hours, storing for 3 hours in a vacuum drying box at 180 ℃, and then treating the dried mixture in inert gas at high temperature for 2 hours at 500 ℃ to obtain a core active material;
step D, placing polypropylene and nano inorganic particles into an absolute ethyl alcohol solution to prepare a suspension, adding the suspension and a fourth binder into a stirrer filled with the core active material, stirring at a high speed for 45min to enable the suspension to fully soak the core active material, starting a heating device of the stirrer to enable the temperature in the stirrer to rise to 65 ℃, keeping the temperature for 55min to obtain a coating, and placing the coating in an aerobic environment at 900 ℃ for calcining for 7h at the temperature rising speed of 8 ℃/min to obtain the lithium battery anode material;
the cathode active material is modified lithium iron phosphate doped with 0.1 mass percent of titanium, 0.2 mass percent of magnesium and 0.1 mass percent of aluminum;
the conductive agent is a composite formed by mixing carbon fibers and graphene in a weight ratio of 1: 2; the preparation method of the carbon fiber comprises the following steps: respectively dissolving 35 parts of acetic acid lignin and 24 parts of alkaline lignin in 100 parts of acetic acid solution according to parts by weight to prepare a first solution and a second solution, and adding 0.02 part of metallic nickel into the first solution to obtain a first spinning solution; adding 0.02 part of metal copper into the second solution to obtain a second spinning solution; placing the first spinning solution and the second spinning solution in a high-voltage electrostatic spinning device, performing electrostatic spinning to obtain first nanofibers and second nanofibers, mixing the first nanofibers and the second nanofibers, placing the mixture into a muffle furnace for pre-oxidation, then placing the pre-oxidized nanofiber mixture under the protection of nitrogen, heating to 700 ℃, the heating rate is 100 ℃/h, performing carbonization treatment for 1h, cooling to room temperature, and crushing to obtain the carbon fibers;
the binder comprises styrene butadiene rubber, sodium carboxymethylcellulose and polymethacrylic acid in a weight ratio of 3:1: 1; the dispersing agent comprises polyethylene glycol and polyvinyl alcohol in a weight ratio of 2: 1; the solvent is N-methyl pyrrolidone;
the mass ratio of the positive electrode active material to the conductive agent to the binder to the dispersing agent is 90.8:3.8:3.8:1.2, and the mass ratio of the solvent to the positive electrode active material is 2.5: 1;
the high-speed stirring speed is 45Hz in revolution and 35Hz in rotation, and the medium-speed stirring speed is 25Hz in revolution and 25Hz in rotation; the low-speed stirring speed is 10Hz in revolution and 0Hz in rotation.
< example 4>
A method for preparing a positive electrode material for a lithium battery, which is different from example 3 in that a positive electrode active material, a conductive agent, a binder and a dispersant are directly mixed in a solvent according to a conventional method. The remaining conditions and parameters were the same as in example 3.
< example 5>
The difference between the preparation method of the lithium battery positive electrode material and the embodiment 3 is that the core active material obtained in the step C is the lithium battery positive electrode material, namely the step D coating operation is not performed. The remaining conditions and parameters were the same as in example 3.
< example 6>
A method for preparing a positive electrode material for a lithium battery, which is different from embodiment 3 in that the conductive agent is carbon fiber. The remaining conditions and parameters were the same as in example 3.
< example 7>
A method for preparing a positive electrode material for a lithium battery, which is different from embodiment 3 in that the conductive agent is graphene. The remaining conditions and parameters were the same as in example 3.
< example 8>
A method for preparing a positive electrode material for a lithium battery, which is different from example 3 in that the carbon fiber is a commercially available product. The remaining conditions and parameters were the same as in example 3.
< comparative example 1>
2025 button cells were assembled from the lithium battery positive electrode materials prepared in examples 3 to 8 of the present invention by the same method, and the discharge capacity and cycle performance were measured in a voltage range of 2.5 to 4.2V, and the results are shown in table 1.
As can be seen from table 1, when the lithium battery positive electrode material is obtained by using the preparation method of the lithium battery positive electrode material provided in embodiment 3 of the present invention, the specific discharge capacity and specific capacity retention rate of the assembled battery are much higher than those of the batteries assembled by the lithium battery positive electrode materials provided in embodiments 4 to 8.
Comparing the experimental data of the embodiment 3 and the embodiment 4, it is demonstrated that the positive active material, the conductive agent, the binder and the dispersant are primarily mixed in batches by dividing into a plurality of parts, and then the several mixed materials are uniformly mixed again, so that the problem of uneven mixing of effective components caused by the fact that the plurality of materials of the positive material are directly mixed and the same material with small particle size is easy to agglomerate can be solved, the charge and discharge performance of the positive material is improved, and the discharge specific capacity and specific capacity retention rate of the battery are increased; comparing the experimental data of example 3 and example 5, it is shown that the performance of the positive electrode material can be improved by coating a layer of inorganic nano-film on the outer surface of the core active material, thereby improving the performance of the battery; the experimental data comparison of the embodiment 3, the embodiment 6, the embodiment 7 and the embodiment 8 shows that the performance of the battery can be improved by using the combination of the carbon fiber and the graphene independently, the conductivity of the positive electrode material can be improved by electrospinning and introducing the additive of the nickel and the copper into the process, and the discharge specific capacity and the specific capacity retention rate of the battery can be greatly improved.
The number of apparatuses and the scale of the process described herein are intended to simplify the description of the present invention. Applications, modifications and variations of the present invention will be apparent to those skilled in the art.
While embodiments of the invention have been disclosed above, it is not limited to the applications listed in the description and the embodiments, which are fully applicable in all kinds of fields of application of the invention, and further modifications may readily be effected by those skilled in the art, so that the invention is not limited to the specific details without departing from the general concept defined by the claims and the scope of equivalents.
Claims (5)
1. The preparation method of the lithium battery positive electrode material is characterized by comprising the following steps of:
step A, equally dividing the positive active substance into three equal parts, equally dividing the conductive agent into three equal parts, dividing the binder into four parts according to the weight ratio of 1:1:1:1.2, dividing the dispersant into four parts according to the weight ratio of 1:1:1:2, pouring the first part of the binder into a stirrer filled with a solvent, simultaneously adding a first equal part of conductive agent and a first equal part of positive active material into a stirrer while stirring, after the first equal part of conductive agent and the first equal part of positive active material are added, adding a first part of dispersing agent into the stirrer, stirring at a high speed for 1-2 h, vacuumizing, continuing to pump for 3min when the vacuum degree in the stirrer reaches 0.01MPa, stirring at a medium speed for 1.5-2.5 h in a vacuum state, closing the vacuum after stirring, adding absolute ethyl alcohol accounting for 0.2% of the weight of the solvent into the stirrer, vacuumizing again, and stirring at a low speed for 0.3-1.3 h; after stirring, closing the vacuum, and sieving the materials in the stirrer by a 100-mesh sieve to obtain a first mixture; wherein the weight of the solvent is 4 times of the weight of the first equal part of the positive electrode active material;
step B, respectively processing a second equal part of the positive electrode active substance, a second equal part of the conductive agent, a second part of the binder and a second part of the dispersant, and a third equal part of the positive electrode active substance, a third equal part of the conductive agent, a third part of the binder and a third part of the dispersant according to the operation of the step A to obtain a second mixture and a third mixture;
step C, mixing the first mixture, the second mixture, the third mixture and a fourth dispersant, fully stirring for 5-7 hours, storing in a vacuum drying oven at 160-200 ℃ for 2-4 hours, and then treating the dried mixture in inert gas at high temperature for 1-3 hours, wherein the treatment temperature is 450-600 ℃, so as to obtain a core active material;
step D, placing polypropylene and nano inorganic particles into an absolute ethyl alcohol solution to prepare a suspension, adding the suspension and a fourth binder into a stirrer filled with the core active material, stirring at a high speed for 40-50 min to enable the suspension to fully soak the core active material, starting a heating device of the stirrer to enable the temperature in the stirrer to rise to 60-70 ℃, keeping the temperature for 50-60 min to obtain a coating, placing the coating in an aerobic environment at the temperature of 750-1000 ℃ and calcining for 5-8 h at the temperature rising speed of 5-10 ℃/min to obtain the lithium battery anode material;
the cathode active material is modified lithium iron phosphate doped with 0.1 mass percent of titanium, 0.2 mass percent of magnesium and 0.1 mass percent of aluminum;
the conductive agent is a composite formed by mixing carbon fibers and graphene in a weight ratio of 1: 2;
the preparation method of the carbon fiber comprises the following steps: respectively dissolving 30-40 parts by weight of lignin acetate and 20-28 parts by weight of alkaline lignin in 100 parts by weight of acetic acid solution to prepare a first solution and a second solution, and adding 0.01-0.03 part by weight of metallic nickel into the first solution to obtain a first spinning solution; adding 0.01-0.03 part of metal copper into the second solution to obtain a second spinning solution; and placing the first spinning solution and the second spinning solution in a high-voltage electrostatic spinning device, performing electrostatic spinning to obtain first nanofibers and second nanofibers, mixing the first nanofibers and the second nanofibers, placing the mixture into a muffle furnace for pre-oxidation, then placing the pre-oxidized nanofiber mixture in a nitrogen atmosphere, heating to 700 ℃, heating at a rate of 100 ℃/h, performing carbonization treatment for 1h, cooling to room temperature, and crushing to obtain the carbon fibers.
2. The method of preparing a positive electrode material for a lithium battery as claimed in claim 1, wherein the binder comprises styrene-butadiene rubber, sodium carboxymethyl cellulose and polymethacrylic acid in a weight ratio of 3:1: 1.
3. The method for preparing a positive electrode material for a lithium battery as claimed in claim 2, wherein the dispersant comprises polyethylene glycol and polyvinyl alcohol in a weight ratio of 2: 1; the solvent is N-methyl pyrrolidone.
4. The method for producing a positive electrode material for a lithium battery according to claim 3, wherein a mass ratio of the positive electrode active material, the conductive agent, the binder, and the dispersant is 90.8:3.1 to 4.5:0.9 to 1.5, and a mass ratio of the solvent to the positive electrode active material is 2.5: 1.
5. The method for preparing the positive electrode material for a lithium battery according to claim 4, wherein the high-speed stirring speed is 40 to 50Hz in revolution and 30 to 40Hz in rotation, and the medium-speed stirring speed is 20 to 30Hz in revolution and 20 to 30Hz in rotation; the low-speed stirring speed is 10Hz in revolution and 0Hz in rotation.
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| KR101468018B1 (en) * | 2013-05-21 | 2014-12-02 | 한국생산기술연구원 | EMI Shield sheet comprising carbon complex fiber manufactured by electrospinning and a preparation method thereof |
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