CN107845809B - Lithium ion battery adopting lithium iron phosphate cathode material and preparation method thereof - Google Patents
Lithium ion battery adopting lithium iron phosphate cathode material and preparation method thereof Download PDFInfo
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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
- 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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- 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 relates to a lithium ion battery adopting a lithium iron phosphate anode material and a preparation method thereof, belonging to the technical field of lithium batteries. The preparation material of the lithium iron phosphate anode material comprises, by weight, 20-40 parts of lithium hydroxide, 30-70 parts of microcrystalline cellulose, 30-40 parts of water and 90-150 parts of iron phosphate, and is prepared by the steps of raw material reaction, slurry preparation, drying and sintering. When the lithium iron phosphate material provided by the invention is applied to the anode material of a lithium ion battery, the lithium iron phosphate material has the advantages of large electric capacity, high discharge efficiency and more cycle discharge times.
Description
Technical Field
The invention relates to a lithium ion battery adopting a lithium iron phosphate anode material and a preparation method thereof, belonging to the technical field of lithium batteries.
Background
Compared with the secondary batteries such as the commonly used lead-acid battery, the chromium-nickel battery, the nickel-hydrogen battery and the like, the lithium ion battery has the following advantages: 1. high energy density: the mass ratio energy of the lithium ion battery reaches 150Wh/kg, which is 1.5 times of that of a Ni/MH battery and 3 times of that of a Cd/Ni battery; the weight of the lithium ion battery is half of that of a nickel-cadmium or nickel-hydrogen battery with the same capacity, and the volume of the lithium ion battery is 40-50% of that of the nickel-cadmium and 20-30% of that of the nickel-hydrogen battery. 2. No pollution: the lithium ion battery does not contain harmful metal substances such as cadmium, lead and mercury. 3. High voltage: the working voltage of the lithium ion battery monomer with different anode materials is between 3.2 and 4.5V, which is equivalent to three serial nickel-cadmium batteries or nickel-hydrogen batteries. 4. No metal treatment is carried out: the lithium ion battery does not contain metal lithium, so that the safety performance is greatly ensured. 5. The cycle performance is high: under normal circumstances, the charge-discharge cycle of a lithium ion battery may exceed 500 times. 6. No memory effect: the memory effect refers to the condition that the capacity of the nickel-cadmium battery is reduced in the charge-discharge cycle process. Lithium ion batteries do not have this memory effect. 7. The method can be used for quick charging: the lithium ion battery can be fully charged in one to two more hours.
The lithium ion battery completes charging and discharging through the back-and-forth movement of lithium ions between the positive electrode and the negative electrode, and in the process, the positive electrode and the negative electrode have small change along with the charging and discharging depth and good reversibility. Lithium ion batteries mostly adopt lithium composite oxides such as lithium iron phosphate as a positive electrode material, graphite as a negative electrode material, an organic solution of lithium hexafluorophosphate as an electrolyte, and a porous film as a diaphragm. When the battery is charged, lithium ions are extracted from the anode material and are embedded into the cathode material through the electrolyte and the diaphragm; during the discharge process of the battery, lithium ions are extracted from the negative electrode material of the battery, pass through the electrolyte and the diaphragm, and are re-inserted into the positive electrode material of the battery. Because the lithium ions have relatively fixed space and position in the positive electrode and the negative electrode, the reversibility of the charge-discharge reaction of the battery is good, thereby ensuring the long cycle life of the battery and the safety of the work.
The lithium iron phosphate takes iron and phosphorus as raw materials, has rich sources and low price, is considered as a preferred anode material lithium iron phosphate discharge platform of the power lithium ion battery with 3.2-3.3V, which is lower than 3.6-3.7V of lithium cobaltate and lithium manganate, but the discharge platform is more stable; the lithium iron phosphate has excellent heavy-current discharge characteristics, and can bear continuous discharge of 7C and instant discharge of more than 20C. LiFePO4The characteristics of the lithium ion battery in the aspects of price, safety, thermal stability, high-rate discharge performance and the like determine that the lithium ion battery has incomparable advantages in the field of power lithium ion batteries and has great market space.
CN101841021B discloses a lithium iron phosphate and lithium vanadium phosphate composite anode material and a manufacturing method thereof, the composite anode material is prepared by taking a nano vanadium source compound, a nano phosphorus source compound, a nano lithium source compound and a nano iron source compound as raw materials, and mixing the nano vanadium source compound, the nano phosphorus source compound, the nano lithium source compound and the nano iron source compound according to the molar ratio of vanadium, phosphorus, lithium and iron elements of 1: 1-1.5: 1-2: 1-1.5. CN103633321B discloses a preparation method of lithium iron phosphate, which comprises the following steps: the high-crystallinity and high-purity lithium iron phosphate material is prepared by a vapor phase method, reactants are divided into a solid phase and a liquid phase in a vapor phase reaction container, the solid phase comprises mixed powder or aqueous solution containing ferrous sulfate, lithium hydroxide, phosphoric acid and the like, the liquid phase is pure distilled water or aqueous solution containing acid or alkali, heat treatment is carried out at the temperature of 100-180 ℃, water in the liquid phase or mixed gas of the acid, the alkali and the water is continuously transferred into the solid phase, so that the solid phase reacts with the lithium hydroxide and the ferrous sulfate, and the vapor phase can simultaneously play a role in regulating the pH value during reaction, thereby realizing the controllable preparation of the lithium iron phosphate. CN100398434C discloses a method for preparing lithium iron phosphate as a high-performance lithium ion battery positive electrode material, which comprises mixing a self-made lithium dihydrogen phosphate containing doping elements, ferrous oxalate or ferrous acetate, and a conductive agent or a precursor of the conductive agent uniformly according to a certain proportion, then placing the mixture into a microwave reaction furnace protected by an inert atmosphere for calcination and heat treatment, and finally cooling to room temperature to obtain the lithium iron phosphate as the lithium ion battery positive electrode material.
However, the lithium iron phosphate positive electrode material has a problem of capacity loss after multiple cycle discharge.
Disclosure of Invention
The purpose of the invention is: the lithium iron phosphate material has the advantages of large electric capacity and high discharge efficiency when being applied to the anode material of the lithium ion battery.
The technical scheme is as follows:
a lithium ion battery adopting a lithium iron phosphate anode material adopts the lithium iron phosphate anode material, and the lithium iron phosphate anode material consists of the following components in parts by weight: the lithium iron phosphate anode material is prepared by the steps of raw material reaction, slurry preparation, drying and sintering, and comprises 20-40 parts of lithium hydroxide, 30-70 parts of microcrystalline cellulose, 30-40 parts of water and 90-150 parts of iron phosphate.
The microcrystalline cellulose refers to microcrystalline cellulose modified by polyethylene glycol.
The preparation method of the cathode material comprises the following steps:
step 1, mixing lithium hydroxide, water and 5-10 parts of ethanol, and adding microcrystalline cellulose for reaction;
step 2, preparing iron phosphate into an aqueous solution with a solid content of 30-50 wt.%, adding an anionic surfactant accounting for 1-4% of the weight of the iron phosphate, mixing at a high speed, adding the mixture into the reactant obtained in the step 1 after stirring by a rubber stirrer, and stirring uniformly to obtain a slurry;
and 3, carrying out spray drying and sintering on the slurry to obtain the lithium iron phosphate material.
In the step 1, the reaction temperature range is-15 to-5 ℃; the reaction time is 2-4 h.
The anionic surfactant is selected from fatty acids and their salts, such as oleic acid, palmitic acid, sodium oleate, potassium palmitate, and triethanolamine oleate; hydroxy-containing acids and their salts, such as glycolic acid, potassium glycolate, lactic acid and potassium lactate; more preferably oleic acid.
In the step 2, high-speed mixing means that the mixing and stirring speed is 1000-3000 rpm.
In the step 3, the spray drying temperature is 180-220 ℃; the sintering condition is that the sintering is carried out in an inert gas atmosphere, the sintering temperature is 760-850 ℃, and the sintering time is 8-12 hours.
Advantageous effects
The lithium ion adopting the lithium iron phosphate anode material provided by the invention has the advantages of large capacitance, high discharge efficiency and more cycle discharge times.
Detailed Description
The present invention will be described in further detail with reference to the following embodiments. It will be understood by those skilled in the art that the following examples are illustrative of the present invention only and should not be taken as limiting the scope of the invention. The examples do not specify particular techniques or conditions, and are performed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.
The words "include," "have," or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
The recitation of values by ranges is to be understood in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a concentration range of "about 0.1% to about 5%" should be interpreted to include not only the explicitly recited concentration of about 0.1% to about 5%, but also include individual concentrations (e.g., 1%, 2%, 3%, and 4%) and sub-ranges (e.g., 0.1% to 0.5%, 1% to 2.2%, 3.3% to 4.4%) within the indicated range. The percentages in the present invention refer to weight percentages unless otherwise specified.
The preparation material of the lithium iron phosphate anode material comprises, by weight, 20-40 parts of lithium hydroxide, 30-70 parts of microcrystalline cellulose, 30-40 parts of water and 90-150 parts of iron phosphate, and is prepared by the steps of raw material reaction, slurry preparation, drying and sintering.
The lithium iron phosphate anode material is prepared by reacting lithium hydroxide with cellulose at low temperature to fix lithium ions on microcrystalline cellulose, reacting with iron phosphate, and sintering.
The microcrystalline cellulose can be modified by polyethylene glycol, so that the dispersibility of the lithium hydroxide on the material can be effectively improved; the method adopted can be as follows: according to parts by weight, crushing 1-2 parts of plant fiber, mixing with 5-20 parts of an inorganic acid solution, heating to above 90 ℃ for hydrolysis reaction, filtering out residues after the reaction is finished, washing the residues with water until the pH is neutral, uniformly mixing the residues, 0.2-0.4 part of polyethylene glycol and 5-8 parts of water, heating to 80-90 ℃ for reaction to obtain white slurry, and spray-drying to obtain modified microcrystalline cellulose; the plant fiber is selected from one or more of cotton fiber, wood fiber, bamboo fiber and hemp fiber; the inorganic acid solution is hydrochloric acid, sulfuric acid or phosphoric acid solution, and the acid concentration is 0.1-1.0 mol/L.
The preparation method of the material can comprise the following steps:
step 1, mixing lithium hydroxide, water and 5-10 parts of ethanol, and adding microcrystalline cellulose for reaction;
step 2, preparing iron phosphate into an aqueous solution with a solid content of 30-50 wt.%, adding an anionic surfactant accounting for 1-4% of the weight of the iron phosphate, mixing at a high speed, adding the mixture into the reactant obtained in the step 1 after stirring by a rubber stirrer, and stirring uniformly to obtain a slurry;
and 3, carrying out spray drying and sintering on the slurry to obtain the lithium iron phosphate material.
In the step 1, the ethanol is used for improving the dispersibility of the lithium hydroxide; in the step 2, firstly, the iron phosphate is prepared into slurry and added with an anionic surfactant for high-speed dispersion, so that the surface of the iron phosphate is charged with negative charges, and the slurry obtained in the step 1 is stirred by a rubber rod, so that the surface of the slurry is charged with positive charges, and after mixing, the iron phosphate and a lithium source can be dispersed uniformly.
Suitable anionic surfactants for the above step include, for example, fatty acids and their salts, such as oleic acid, palmitic acid, sodium oleate, potassium palmitate, and triethanolamine oleate; hydroxy-containing acids and their salts, such as glycolic acid, potassium glycolate, lactic acid and potassium lactate; polyoxyalkylene alkyl ether acetic acids and their salts, such as polyoxyalkylene tridecyl ether acetic acid and its sodium salt; salts of carboxy-polysubstituted aromatic compounds, such as potassium trimellitate and potassium pyromellitate; alkyl benzene sulphonic acids and their salts, such as dodecyl benzene sulphonic acid and its sodium salt; polyoxyalkylene alkyl ether sulfonic acids and their salts, such as polyoxyethylene 2-ethylhexyl ether sulfonic acid and its potassium salt; higher fatty acid amide sulfonic acids and their salts, such as stearoyl methyl taurine and its sodium salt, lauroyl methyl taurine and its sodium salt, myristoyl methyl taurine and its sodium salt, and palmitoyl methyl taurine and its sodium salt; n-acyl sarcosines and their salts, such as lauroyl sarcosine and its sodium salt; alkyl phosphonic acids and their salts, such as octyl phosphonate and its potassium salts; aromatic phosphonic acids and their salts, such as phenylphosphonate and its potassium salts; alkylphosphonic acid alkylphosphonates and their salts, such as 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester and its potassium salt; nitrogen-containing alkyl phosphonic acids and their salts, such as aminoethylphosphonic acid and its diethanolamine salt; alkyl sulfates and their salts, such as 2-ethylhexyl sulfate and its sodium salt; polyoxyalkylene sulfates and their salts, such as polyoxyethylene 2-ethylhexyl ether sulfate and its sodium salt; alkyl phosphates and their salts, such as sulfosuccinates, e.g., sodium di-2-ethylhexyl sulfosuccinate and sodium dioctyl sulfosuccinate; and long chain N-acyl glutamates, such as monosodium N-lauroyl glutamate and disodium N-stearoyl-L-glutamate. Oleic acid is preferably used in view of improving the capacity properties of the battery.
And 3, performing high-temperature sintering reaction on the obtained material to generate a solid lithium iron phosphate material.
Example 1
The preparation method of the cathode material comprises the following steps:
step 1, mixing 20 parts of lithium hydroxide, 30 parts of water and 5 parts of ethanol, and then adding 30 parts of microcrystalline cellulose modified by polyethylene glycol for reaction at the temperature of-15 ℃; the reaction time is 2 h;
step 2, preparing 90 parts of iron phosphate into an aqueous solution with a solid content of 30 wt.%, adding 1% oleic acid based on the weight of the iron phosphate, mixing at a high speed of 1000rpm for 10min, adding the mixture into the reactant obtained in the step 1 after stirring by a rubber stirrer, and stirring uniformly to obtain a slurry;
step 3, spray drying and sintering the slurry at 180 ℃ to obtain a lithium iron phosphate material; the sintering condition is that the sintering is carried out under the inert gas atmosphere, the sintering temperature is 760 ℃, and the sintering time is 8 hours.
The preparation method of the modified microcrystalline cellulose comprises the following steps:
according to parts by weight, 1 part of cotton fiber is crushed and then mixed with 5 parts of 1.0mol/L hydrochloric acid solution, the mixture is heated to above 90 ℃ for hydrolysis reaction, after the reaction is finished, residues are filtered out, the residues are washed by water until the pH is neutral, the residues, 0.2 part of polyethylene glycol and 5 parts of water are uniformly mixed, the mixture is heated to 80 ℃ for reaction, white slurry is obtained, and the modified microcrystalline cellulose is obtained after spray drying.
Example 2
The preparation method of the cathode material comprises the following steps:
step 1, mixing 40 parts of lithium hydroxide, 40 parts of water and 10 parts of ethanol, and then adding 70 parts of microcrystalline cellulose modified by polyethylene glycol for reaction at the temperature of-5 ℃; the reaction time is 4 h;
step 2, preparing 150 parts of iron phosphate into an aqueous solution with a solid content of 50 wt.%, adding 4% oleic acid based on the weight of the iron phosphate, mixing at 3000rpm for 10min at a high speed, adding the mixture into the reactant obtained in the step 1 after stirring by a rubber stirrer, and stirring uniformly to obtain a slurry;
step 3, spray drying and sintering the slurry at 220 ℃ to obtain a lithium iron phosphate material; the sintering condition is carried out in an inert gas atmosphere, the sintering temperature is 850 ℃, and the sintering time is 12 h.
The preparation method of the modified microcrystalline cellulose comprises the following steps:
according to parts by weight, 2 parts of cotton fiber are crushed and then mixed with 20 parts of 1.0mol/L hydrochloric acid solution, the mixture is heated to above 90 ℃ for hydrolysis reaction, after the reaction is finished, residues are filtered out, the residues are washed by water until the pH is neutral, the residues, 0.4 part of polyethylene glycol and 8 parts of water are uniformly mixed, the mixture is heated to 90 ℃ for reaction, white slurry is obtained, and the modified microcrystalline cellulose is obtained after spray drying.
Example 3
The preparation method of the cathode material comprises the following steps:
step 1, mixing 30 parts of lithium hydroxide, 35 parts of water and 8 parts of ethanol, and then adding 50 parts of microcrystalline cellulose modified by polyethylene glycol for reaction at the temperature of-10 ℃; the reaction time is 3 h;
step 2, preparing 120 parts of iron phosphate into an aqueous solution with a solid content of 40 wt.%, adding oleic acid accounting for 3% of the weight of the iron phosphate, mixing at a high speed of 2000rpm for 10min, adding the mixture into the reactant obtained in the step 1 after stirring by a stirrer made of rubber, and stirring uniformly to obtain a slurry;
step 3, spray drying and sintering the slurry at 200 ℃ to obtain a lithium iron phosphate material; the sintering condition is that the sintering is carried out in an inert gas atmosphere, the sintering temperature is 800 ℃, and the sintering time is 10 hours.
The preparation method of the modified microcrystalline cellulose comprises the following steps:
according to parts by weight, 2 parts of cotton fiber are crushed and then mixed with 10 parts of 1.0mol/L hydrochloric acid solution, the mixture is heated to above 90 ℃ for hydrolysis reaction, after the reaction is finished, residues are filtered out, the residues are washed by water until the pH is neutral, the residues, 0.3 part of polyethylene glycol and 6 parts of water are uniformly mixed, the mixture is heated to 85 ℃ for reaction, white slurry is obtained, and the modified microcrystalline cellulose is obtained after spray drying.
Comparative example 1
The difference from example 3 is that: microcrystalline cellulose was not modified with polyethylene glycol.
The preparation method of the cathode material comprises the following steps:
step 1, mixing 30 parts of lithium hydroxide, 35 parts of water and 8 parts of ethanol, and then adding 50 parts of microcrystalline cellulose for reaction at the temperature of-10 ℃; the reaction time is 3 h;
step 2, preparing 120 parts of iron phosphate into an aqueous solution with a solid content of 40 wt.%, adding oleic acid accounting for 3% of the weight of the iron phosphate, mixing at a high speed of 2000rpm for 10min, adding the mixture into the reactant obtained in the step 1 after stirring by a stirrer made of rubber, and stirring uniformly to obtain a slurry;
step 3, spray drying and sintering the slurry at 200 ℃ to obtain a lithium iron phosphate material; the sintering condition is that the sintering is carried out in an inert gas atmosphere, the sintering temperature is 800 ℃, and the sintering time is 10 hours.
The preparation method of the microcrystalline cellulose comprises the following steps:
according to parts by weight, 2 parts of cotton fiber are crushed and then mixed with 10 parts of 1.0mol/L hydrochloric acid solution, the mixture is heated to above 90 ℃ for hydrolysis reaction, after the reaction is finished, residues are filtered out, the residues are washed by water until the pH is neutral, the residues and 6 parts of water are uniformly mixed, the temperature is raised to 85 ℃ for reaction, slurry is obtained, and the microcrystalline cellulose is obtained after spray drying.
Comparative example 2
The difference from example 3 is that: preparation step 2, the reactants were not stirred by a rubber stirrer.
The preparation method of the cathode material comprises the following steps:
step 1, mixing 30 parts of lithium hydroxide, 35 parts of water and 8 parts of ethanol, and then adding 50 parts of microcrystalline cellulose modified by polyethylene glycol for reaction at the temperature of-10 ℃; the reaction time is 3 h;
step 2, preparing 120 parts of iron phosphate into an aqueous solution with a solid content of 40 wt.%, adding oleic acid accounting for 3% of the weight of the iron phosphate, mixing at 2000rpm for 10min at a high speed, adding the mixture into the reactant obtained in the step 1, and stirring uniformly to obtain a slurry;
step 3, spray drying and sintering the slurry at 200 ℃ to obtain a lithium iron phosphate material; the sintering condition is that the sintering is carried out in an inert gas atmosphere, the sintering temperature is 800 ℃, and the sintering time is 10 hours.
The preparation method of the modified microcrystalline cellulose comprises the following steps:
according to parts by weight, 2 parts of cotton fiber are crushed and then mixed with 10 parts of 1.0mol/L hydrochloric acid solution, the mixture is heated to above 90 ℃ for hydrolysis reaction, after the reaction is finished, residues are filtered out, the residues are washed by water until the pH is neutral, the residues, 0.3 part of polyethylene glycol and 6 parts of water are uniformly mixed, the mixture is heated to 85 ℃ for reaction, white slurry is obtained, and the modified microcrystalline cellulose is obtained after spray drying.
Comparative example 3
The difference from example 3 is that: oleic acid was not added in step 2.
The preparation method of the cathode material comprises the following steps:
step 1, mixing 30 parts of lithium hydroxide, 35 parts of water and 8 parts of ethanol, and then adding 50 parts of microcrystalline cellulose modified by polyethylene glycol for reaction at the temperature of-10 ℃; the reaction time is 3 h;
step 2, preparing 120 parts of iron phosphate into an aqueous solution with a solid content of 40 wt.%, mixing at a high speed of 2000rpm for 10min, adding the mixture into the reactant obtained in the step 1 after stirring by a rubber stirrer, and stirring uniformly to obtain a slurry;
step 3, spray drying and sintering the slurry at 200 ℃ to obtain a lithium iron phosphate material; the sintering condition is that the sintering is carried out in an inert gas atmosphere, the sintering temperature is 800 ℃, and the sintering time is 10 hours.
The preparation method of the modified microcrystalline cellulose comprises the following steps:
according to parts by weight, 2 parts of cotton fiber are crushed and then mixed with 10 parts of 1.0mol/L hydrochloric acid solution, the mixture is heated to above 90 ℃ for hydrolysis reaction, after the reaction is finished, residues are filtered out, the residues are washed by water until the pH is neutral, the residues, 0.3 part of polyethylene glycol and 6 parts of water are uniformly mixed, the mixture is heated to 85 ℃ for reaction, white slurry is obtained, and the modified microcrystalline cellulose is obtained after spray drying.
Testing performance
1. Preparation of test cells:
(1) preparing a positive plate: respectively taking the lithium iron phosphate materials prepared in the examples and the comparative examples as positive electrode active materials, and mixing the positive electrode material, acetylene black and PVDF in a weight ratio of 100: 4: 5 dissolving in N-methyl pyrrolidone, stirring, coating on aluminum foil, baking at 100 + -5 deg.C, rolling to a certain thickness with a tablet machine, and rolling to obtain positive plate;
(2) preparing a negative plate: graphite, acetylene black and PVDF are mixed in a weight ratio of 100: 3: 6, dissolving in N-methyl pyrrolidone, uniformly stirring, coating on a copper foil, baking at the temperature of 100 +/-5 ℃, rolling to a certain thickness by using a tablet press, and rolling and cutting into a negative plate;
(3) winding the positive and negative plates and the polypropylene diaphragm into a square shapeThe lithium ion battery core is received in the battery shell and welded, and then 1.0mol/L LiPF is injected6And (3) adding an electrolyte of/EC + EMC + DMC (wherein the mass ratio of EC, EMC and DMC is 1: 1: 1), sealing, and preparing the test battery.
2.1, specific capacity test:
at room temperature, the test cell is placed for 5min, and is charged at a constant current of 0.8mA, the voltage is cut off to 3.8V, the constant voltage charging is carried out at 3.8V, the current is cut off to 0.1mA, the test cell is placed for 5min, and is discharged at a constant current of 0.8mA, and the voltage is limited to 2.5V. The specific capacity was calculated and the results are shown in the table below.
2.2 testing of cycle Performance
At room temperature, the test cell is charged at constant current of 0.8mA, the voltage is limited to 3.8V, the cell is charged at constant voltage of 3.8V, the current is cut off to 0.1mA, the cell is placed for 5min, and the cell is discharged at constant current of 0.8 mA. The capacity retention was calculated 500 times by repeating 500 times, and the results are shown in the following table.
The lithium iron phosphate material prepared by the preparation method provided by the embodiment of the invention has large specific capacity and longer cyclic discharge life; example 3 compared to comparative example 1, the discharge efficiency can be effectively improved by modifying microcrystalline cellulose; compared with the comparative example 2, in the embodiment 3, the reaction is stirred by adopting a rubber stirrer to enable the reaction to have positive charges, so that the reaction can be better mixed with the ferric phosphate, and the electric quantity retention rate of the cyclic discharge of the lithium ion battery is further improved; example 3 also contributes to improvement in capacitance and capacity retention rate in cyclic discharge by negatively charging iron phosphate with oleic acid as compared with comparative example 3.
Claims (2)
1. The lithium ion battery adopting the lithium iron phosphate anode material is characterized in that the lithium iron phosphate anode material is adopted, and the lithium iron phosphate anode material consists of the following components in parts by weight: the lithium iron phosphate anode material is prepared by the steps of raw material reaction, slurry preparation, drying and sintering, wherein the microcrystalline cellulose is microcrystalline cellulose modified by polyethylene glycol, and the preparation method of the microcrystalline cellulose comprises the following steps:
according to parts by weight, crushing 1-2 parts of plant fiber, mixing with 5-20 parts of an inorganic acid solution, heating to above 90 ℃ for hydrolysis reaction, filtering out residues after the reaction is finished, washing the residues with water until the pH is neutral, uniformly mixing the residues, 0.2-0.4 part of polyethylene glycol and 5-8 parts of water, heating to 80-90 ℃ for reaction to obtain white slurry, and spray-drying to obtain modified microcrystalline cellulose;
the preparation method of the lithium iron phosphate anode material comprises the following steps:
step 1, mixing lithium hydroxide with 5-10 parts of water and ethanol, and then adding microcrystalline cellulose for reaction, wherein in the step 1, the reaction temperature is in the range of-15 to-5 ℃; the reaction time is 2-4 h;
step 2, preparing iron phosphate into an aqueous solution with a solid content of 30-50 wt.%, adding an anionic surfactant accounting for 1-4% of the weight of the iron phosphate, mixing at a high speed, adding the mixture into the reactant obtained in the step 1 after stirring by a rubber stirrer, and stirring uniformly to obtain a slurry, wherein in the step 2, the high-speed mixing means that the mixing and stirring speed is 1000-3000 rpm; step 3, spray drying and sintering the slurry to obtain a lithium iron phosphate material, wherein in the step 3, the spray drying temperature is 180-220 ℃; the sintering condition is that the sintering is carried out in an inert gas atmosphere, the sintering temperature is 760-850 ℃, and the sintering time is 8-12 hours.
2. The lithium ion battery using a lithium iron phosphate positive electrode material according to claim 1, wherein the anionic surfactant is selected from the group consisting of fatty acids and salts thereof including oleic acid, palmitic acid, sodium oleate, potassium palmitate and triethanolamine oleate; the hydroxycarboxylic acids and their salts include glycolic acid, potassium glycolate, lactic acid and potassium lactate.
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| CN101070352B (en) * | 2007-03-27 | 2011-05-11 | 鲁东大学 | Method for preparing sheet-like microcrystal cellulose and modification processing method |
| CN102544448A (en) * | 2010-12-30 | 2012-07-04 | 北京当升材料科技股份有限公司 | Method for preparing lithium battery positive electrode material |
| CN103022425B (en) * | 2011-09-26 | 2015-06-24 | 比亚迪股份有限公司 | Preparation method of lithium iron phosphate material and lithium-ion battery |
| CN102649847B (en) * | 2012-05-17 | 2014-02-12 | 钟春燕 | Polyethylene glycol modified biological cellulose gel |
| CN103400982A (en) * | 2013-07-26 | 2013-11-20 | 烟台卓能电池材料有限公司 | Nanometer lithium zirconate modified lithium iron phosphate composite material and preparation method thereof |
| CN104505493B (en) * | 2014-12-05 | 2017-01-04 | 东莞新能源科技有限公司 | A kind of preparation method and application of anode material for lithium-ion batteries |
| CN105295063B (en) * | 2015-10-15 | 2019-01-11 | 安徽山河药用辅料股份有限公司 | A kind of surface modification of microcrystalline cellulose and preparation method thereof |
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Address after: 225603 Gaoyou Battery Industrial Park, Gaoyou Economic Development Zone, Yangzhou City, Jiangsu Province Patentee after: JIANGSU HUAFU STORAGE NEW TECHNOLOGY DEVELOPMENT Co.,Ltd. Address before: 225603 Jiangsu Huafu storage energy new technology Limited by Share Ltd of Gaoyou City Battery Industrial Park, Gaoyou City, Zhenjiang City, Jiangsu Province Patentee before: JIANGSU HUAFU STORAGE NEW TECHNOLOGY DEVELOPMENT Co.,Ltd. |