CN111029551A - Synthesis of in situ carbon coated FeF2Method for producing granules, and FeF2Particle and battery - Google Patents
Synthesis of in situ carbon coated FeF2Method for producing granules, and FeF2Particle and battery Download PDFInfo
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- CN111029551A CN111029551A CN201911335197.3A CN201911335197A CN111029551A CN 111029551 A CN111029551 A CN 111029551A CN 201911335197 A CN201911335197 A CN 201911335197A CN 111029551 A CN111029551 A CN 111029551A
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Abstract
The invention is suitable for the technical field of preparation of lithium ion battery anode materials, and provides a synthetic in-situ carbon-coated FeF2Method for producing granules, and FeF2A particle and a battery comprising the steps of: s1, drying the mixture of the iron source and the polyvinylidene fluoride in a vacuum drying oven; s2, performing ball milling on the dried mixture of the iron source and the polyvinylidene fluoride; s3, putting the mixture subjected to ball milling into a heating furnace for heating, and collecting C-FeF after cooling2Black powder. The embodiment of the invention utilizes a solid phase method to polymerize an iron sourceThe vinylidene fluoride mixture is dried in a vacuum environment, so that the drying effect of the mixture is good, the mixture is convenient to ball-mill, and the mixing effect of the mixture is better; heating the mixture after ball milling, and collecting C-FeF after cooling2Black powder of C-FeF2High purity, high capacity, high stability, high conductivity and low cost.
Description
Technical Field
The invention belongs to the technical field of preparation of lithium ion battery anode materials, and particularly relates to synthesis of in-situ carbon-coated FeF2Method for producing granules, and FeF2Particles and batteries.
Background
Lithium ion batteries are becoming the primary power source for portable electronic devices due to their higher energy density than other rechargeable systems. However, for new devices such as electric vehicles and large-scale power storage systems, the electrochemical performance of the battery needs to be further improved. While there are many factors that have an effect on the electrochemical performance of a battery, one of the most critical factors is related to how much energy the positive electrode material can store. Therefore, it is crucial to develop a novel positive electrode material satisfying the above requirements.
Metal fluoride electrodes based on the conversion reaction have been widely studied because of their high theoretical energy density, and are considered as positive electrode materials for next-generation lithium ion batteries. Among these metal fluorides, ferrous fluoride (FeF)2) It is of great interest because of its low cost and low toxicity. The high ionic property of several metal fluorides makes them have higher working potential, and are suitable for being used as anode materials. However, high ionicity generally results in a large band gap, and thus the metal fluoride exhibits insulating properties. The conversion reaction product LiF also has high insulating properties. The extremely strong ionization of fluoride can make its conductivity worsen, and the safety is low.
Disclosure of Invention
The invention provides a synthetic in-situ carbon-coated FeF2The preparation method of the particles aims to solve the problems of poor conductivity, high cost, poor safety and the like of the conventional lithium battery anode.
The invention is realized by providing a synthetic in-situ carbon-coated FeF2A method of making a particle comprising the steps of:
s1, drying the mixture of the iron source and the polyvinylidene fluoride in a vacuum environment;
s2, performing ball milling on the dried mixture of the iron source and the polyvinylidene fluoride;
s3, heating the mixture after ball milling, and collecting C FeF after cooling2Black powder.
Further, in the step S3, the mixture after ball milling is placed into a heating furnace for heating for 1-3h at 400-700 ℃.
Further, in the step S3, the mixture is heated to 600 ℃ at a speed of 2-4 ℃/min and is kept at 600 ℃ for 1-6 h.
Further, after the step S3, the method further comprises the step of subjecting the C-FeF to2Removing impurities from the black powder, wherein the step of removing the impurities specifically comprises the following steps:
cleaning the C-FeF by hydrogen fluoride2Collecting powder, vacuum drying at 40-80 deg.C for 12-24 hr, and collecting dried powder.
Further, in the step S1, the temperature in the vacuum environment is 50 to 140 ℃.
Further, in step S1, the drying time of the mixture of the iron source and the polyvinylidene fluoride in the vacuum environment is 12-24 h.
Further, in the step S2, the iron source and the polyvinylidene fluoride mixture are ball-milled in a planetary ball mill for 5-15 h.
Further, the iron source and the polyvinylidene fluoride mixture are alternately ball-milled in the planetary ball mill in the forward and reverse directions at 400-650 rpm.
The invention also provides a synthetic in-situ carbon-coated FeF2Granules prepared by any one of the above preparation methods.
The invention also provides a battery, and the FeF coated with the synthetic in-situ carbon adopts2The particles were used to prepare the positive electrode.
Compared with the prior art, the invention has the following beneficial effects: according to the invention, the mixture of the iron source and the polyvinylidene fluoride is dried in a vacuum environment by using a solid phase method, so that the drying effect of the mixture is good, the mixture is convenient to ball-mill, and the mixing effect of the mixture is better;heating the mixture after ball milling, and collecting C-FeF after cooling2Black powder of C-FeF2High purity, high capacity and good cycle stability, thereby improving the conductivity and safety of the cathode material.
The invention synthesizes FeF coated by in-situ carbon2The particles have the effects of high capacity, good stability, strong conductivity and low cost.
Drawings
FIG. 1 is a synthetic in-situ carbon-coated FeF provided in accordance with an embodiment of the present invention2A flow diagram of a method of making a particle;
FIG. 2 shows a synthetic in-situ carbon-coated FeF provided in example six of the present invention2A flow diagram of a method of making a particle;
FIG. 3 is a synthetic in-situ carbon-coated FeF provided in the seventh embodiment of the present invention2A flow diagram of a method of making a particle;
FIG. 4 is a composite in-situ carbon coated FeF provided in example eight of the present invention2A flow diagram of a method of making a particle;
FIG. 5 is a scanning electron micrograph of an electrode material obtained in an experiment according to an embodiment of the present invention;
FIG. 6 is a scanning electron micrograph of an electrode material obtained in an experiment according to an embodiment of the present invention;
FIG. 7 is a cyclic voltammogram of a working electrode of the electrode material obtained in experiment two of the present invention at different scan rates;
FIG. 8 is a constant current charge-discharge diagram of the working electrode of the electrode material obtained in experiment III of the present invention at different current densities;
FIG. 9 is a graph showing cycle performance of the electrode material obtained in experiment III of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
According to the invention, the mixture of ferric trifluoride and polyvinylidene fluoride is dried in a vacuum environment by using a solid phase method, so that the drying effect of the mixture is good, the mixture is convenient to ball-mill, and the mixing effect of the mixture is better; putting the mixture subjected to ball milling into a heating furnace for heating, and collecting C-FeF after cooling2Black powder of C-FeF2High purity, high capacity and good circulation stability, thereby improving the conductivity and safety of the lithium battery anode.
Example one
Referring to the attached drawing 1, FIG. 1 shows a FeF coated with synthetic in-situ carbon according to the present invention2A flow chart of a method for preparing particles. The invention provides a synthetic in-situ carbon-coated FeF2A method of making a particle comprising the steps of:
and S1, drying the mixture of the iron source and the polyvinylidene fluoride in a vacuum environment.
Wherein the iron source comprises ferric trifluoride, which is fully called FeF3。
The polyvinylidene fluoride is fully called PVDF, has the characteristics of fluororesin and general resin, and has special properties such as piezoelectric property, dielectric property, thermoelectric property and the like besides good chemical corrosion resistance, high temperature resistance, oxidation resistance, weather resistance and ray radiation resistance.
Wherein, the vacuum environment such as vacuum drying oven etc. is convenient for carry out the drying to iron source and polyvinylidene fluoride mixture, can not cause the pollution again.
In the step, ferric trifluoride and polyvinylidene fluoride are mixed, so that the ferric trifluoride and the polyvinylidene fluoride become uniform mixture, and the mixing efficiency of the ferric trifluoride and the polyvinylidene fluoride is improved. Wherein, in the mixing process, the proportion of ferric trifluoride to polyvinylidene fluoride can be 1:2, 2:3, 3:5 and the like by weighing the ferric trifluoride powder and the polyvinylidene fluoride powder according to a certain proportion. For example, 1g of ferric trifluoride and 2g of polyvinylidene fluoride powder are respectively placed in a glass cup, and the glass cup is placed in a vacuum drying oven for drying treatment, so that the drying effect of the ferric trifluoride and polyvinylidene fluoride powder is good.
Because the ferric trifluoride and the polyvinylidene fluoride which are dried in the vacuum drying oven are placed in the same container or glass cup, the ferric trifluoride and the polyvinylidene fluoride form a uniform mixture by shaking or stirring, and the mixing effect between the ferric trifluoride and the polyvinylidene fluoride is improved.
Optionally, the ferric trifluoride is only one of iron sources, wherein the iron source further comprises one of ferrocene, iron acetylacetonate or iron oxalate.
Wherein, ferrocene, also called dicyclopentadiene iron, cyclopentadienyl iron, is a molecular formula of Fe (C)5H5)2An organometallic compound of (2).
Wherein the ferric acetylacetonate is a chemical substance with a molecular formula of C15H21FeO6The crystal is a reddish orange orthorhombic crystal.
Wherein the iron oxalate has a molecular formula of Fe2(C2O4)3·5H2O, decomposed when heated to 100 ℃, insoluble in water and acid, insoluble in ethanol, obtained by reacting a ferric salt solution with a suitable amount of ammonium oxalate.
And S2, performing ball milling on the mixture of the dried iron source and the polyvinylidene fluoride.
In the step, the dried mixture is subjected to ball milling, so that the mixture is uniformly mixed in the ball milling process, and the mixing rate of the iron source and the polyvinylidene fluoride powder is increased.
S3, heating the ball-milled mixture, cooling and collecting C-FeF2Black powder.
Wherein, through putting into the heating furnace with the mixture after the ball-milling and heating, because polyvinylidene fluoride pyrolysis temperature is low, along with the reaction environment temperature that polyvinylidene fluoride is in constantly rising, can make polyvinylidene fluoride pyrolysis become carbon and HF gas.
Because the ferric trifluoride and the polyvinylidene fluoride are subjected to ball milling, the ferric trifluoride and the polyvinylidene fluoride are fully and uniformly mixed. Reacting HF gas with ferric trifluoride to generate FeF2So that the carbon in situ wraps the generated FeF2Granules, thus effectively improving FeF2The conductivity of the particles. Cooling for a period of time, and cooling the cooled FeF2The particles are cooled and collected in a designated container to avoid FeF2The particles are oxidized, and FeF is improved2Collection effect of particles.
Wherein, C-FeF2FeF generated for carbon in-situ encapsulation2Granules of the FeF2The powder is typically a black powder.
Optionally, in the step of heating the ball-milled mixture by using the heating furnace, the ball-milled mixture may be heated by using a heating device corresponding to the heating furnace, as long as the heating temperature, the pressure and the like of the heating device are ensured.
Optionally, the heating device may also be a tube furnace or the like, and the heating effect of the mixture by the tube furnace is better.
In specific implementation, 1g of ferric trifluoride and 2g of polyvinylidene fluoride powder are weighed and respectively placed in a glass cup, and the glass cup is placed in a vacuum drying oven for drying. The moisture of ferric trifluoride and polyvinylidene fluoride is removed through the vacuum drying oven, so that the drying effect of the ferric trifluoride and polyvinylidene fluoride powder is good, and the ball milling effect is improved. The ferric trifluoride and the polyvinylidene fluoride are dried and then mixed, and the mixture of the ferric trifluoride and the polyvinylidene fluoride is subjected to ball milling, so that the refining efficiency of the mixture is improved, and the mixture is fully mixed. Heating the ball-milled mixture in a heating furnace to fully react the mixture, and cooling to obtain black C-FeF2And (3) powder. C-FeF with improved black color2The purity of the powder can be effectively improved, the volume change in the charging and discharging process can be buffered, the particle size can be reduced, the transport distance of electrons and ions can be reduced, and the electrochemical performance can be well improved.
Example two
In this embodiment, the temperature in the vacuum environment is 50-140 ℃ in step S1 on the basis of the first embodiment.
The vacuum drying is mainly used for removing moisture of two materials in the ferric trifluoride and the polyvinylidene fluoride, so that the ferric trifluoride and the polyvinylidene fluoride are mixed more uniformly when being mixed. Because the pyrolysis temperature of the polyvinylidene fluoride is low, the polyvinylidene fluoride is pyrolyzed into carbon and hydrogen HF gas along with the increase of the temperature of the heating furnace. Therefore, in order to effectively remove the water in the ferric trifluoride and the polyvinylidene fluoride, the temperature in the vacuum drying oven should not be too high, so long as the water can be evaporated. Therefore, when the temperature in the vacuum drying oven is kept at 50-140 ℃, the moisture in the ferric trifluoride and the polyvinylidene fluoride can be conveniently removed, meanwhile, the polyvinylidene fluoride cannot be pyrolyzed, the safety is high, and the cost is saved.
Furthermore, when the temperature in the vacuum drying oven is kept at 80 ℃, the effect of removing water in ferric trifluoride and polyvinylidene fluoride is better, meanwhile, polyvinylidene fluoride is not pyrolyzed, the safety is high, and the cost is saved.
EXAMPLE III
In this embodiment, based on the first embodiment or the second embodiment, in step S1, the drying time of the mixture of the iron source and the polyvinylidene fluoride in the vacuum drying oven is 12-24 h.
Specifically, the mixture of the ferric trifluoride and the polyvinylidene fluoride is respectively placed in a glass cup, and the ferric trifluoride and the polyvinylidene fluoride in the glass cup are placed in a vacuum drying oven at 80 ℃ for drying for at least more than 12 hours, so that the moisture in the ferric trifluoride and the polyvinylidene fluoride powder can be conveniently removed, and the mixing effect of the ferric trifluoride and the polyvinylidene fluoride powder is improved.
Wherein, ferric trifluoride and polyvinylidene fluoride are in keeping the vacuum drying oven internal drying of 80 ℃, when guaranteeing to get rid of the moisture of ferric trifluoride and polyvinylidene fluoride, can also avoid polyvinylidene fluoride to take place the pyrolysis, and drying effect is good, and the security is high.
Because iron trifluoride and polyvinylidene fluoride are powdered materials, when iron trifluoride and polyvinylidene fluoride powder contain a large amount of water inside, the effect of bonding can be produced to iron trifluoride and polyvinylidene fluoride when mixing, the mixing efficiency of iron trifluoride and polyvinylidene fluoride powder has been reduced.
Example four
In this example, on the basis of the first example, in step S2, the iron source and the polyvinylidene fluoride mixture are ball-milled for 5-15h in a planetary ball mill.
The planetary ball mill is a necessary device for mixing, fine grinding, small sample preparation, nano material dispersion, new product development and small batch production of high and new technology materials, and the product has the advantages of small volume, complete functions and high efficiency.
Specifically, the mixture of the ferric trifluoride and the polyvinylidene fluoride is subjected to ball milling in a planetary ball mill, so that the mixing effect of the mixture of the ferric trifluoride and the polyvinylidene fluoride is good.
However, the mixture of the ferric trifluoride and the polyvinylidene fluoride has long ball milling time in a planetary ball mill, and the ball milling effect is better. However, the ball milling time is not longer, the production efficiency is affected by the longer ball milling time, the mixing effect of the mixture is not good and the production efficiency is also not good due to the shorter ball milling time. Therefore, the mixture is subjected to ball milling treatment for 8 hours in a planetary ball mill, so that the mixture is good in mixing effect, meanwhile, the ball milling time can be reduced, and the application range is wide.
EXAMPLE five
Based on the first embodiment, in this embodiment, the mixture of the iron source and the polyvinylidene fluoride is alternatively ball milled in the planetary ball mill at 400-.
Specifically, 1g of ferric trifluoride and 2g of polyvinylidene fluoride powder were weighed, placed in a glass cup, and dried in a vacuum oven at 80 ℃ for 12 hours. The moisture of ferric trifluoride and polyvinylidene fluoride is removed through the vacuum drying oven, so that the drying effect of the ferric trifluoride and polyvinylidene fluoride powder is good, and the ball milling effect is improved. Drying and mixing ferric trifluoride and polyvinylidene fluoride, ball-milling the mixture of the ferric trifluoride and the polyvinylidene fluoride in a planetary ball mill for 8 hours, and keeping the mixture to be alternately ball-milled in the forward and reverse directions of 500rpm in the planetary ball mill, so that the refining efficiency of the mixture is improved, and the mixture is fully mixed. Because the ball milling time in the planet ball mill is long, the mixture is more refined and can be fully mixed, and the mixing effect of the ferric trifluoride and the polyvinylidene fluoride is improved.
EXAMPLE six
Referring to FIG. 2, in the present embodiment, on the basis of the first embodiment, in the step S3, S301, the ball-milled mixture is placed in a heating furnace for heating at 400-700 ℃ for 1-3 h.
Specifically, the ball-milled mixture was placed in a heating furnace and heated to 600 ℃ and heated at 600 ℃ for 1h to allow the mixture to react well. After cooling the mixture to room temperature, a black powder was collected. Cleaning black powder with hydrofluoric acid (HF), collecting, drying in a vacuum drying oven at 60 deg.C for 12h to obtain powder labeled C-FeF2. By mixing C-FeF2The carbon is used for coating the surfaces of the particles, so that the conductivity can be effectively improved, the volume change in the charging and discharging process is buffered, the particle size is reduced, the transport distance of electrons and ions is reduced, the electrochemical performance can be well improved, and the carbon-coated carbon material is widely used.
EXAMPLE seven
Referring to FIG. 3, in the present embodiment, based on the first embodiment or the second embodiment, in step S3, S302, C-FeF2Heating to 600 deg.C at a speed of 2-4 deg.C/min and maintaining at 600 deg.C for 1-6 h.
Specifically, the ball-milled mixture is placed into a heating furnace to be heated to 600 ℃ at the temperature of 4 ℃/min, and the temperature is kept at 600 ℃ for 1h, so that the mixture is fully reacted. After cooling the mixture to room temperature, a black powder was collected. Cleaning black powder with hydrofluoric acid (HF), collecting, drying in a vacuum drying oven at 60 deg.C for 12h to obtain powder labeled C-FeF2. By mixing C-FeF2The carbon is used for coating the surfaces of the particles, so that the conductivity can be effectively improved, the volume change in the charging and discharging process is buffered, the particle size is reduced, the transport distance of electrons and ions is reduced, the electrochemical performance can be well improved, and the carbon-coated carbon material is widely used.
Example eight
With reference to fig. 4, on the basis of the first embodiment, in this embodiment, after step S3, a step of removing impurities from the C-FeF2 black powder is further included;
s4, the step of removing impurities specifically comprises the following steps: cleaning the C-FeF by hydrogen fluoride2Collecting powder, vacuum drying at 40-80 deg.C for 12-24 hr, and collecting dried powder.
Specifically, the pyrolysis temperature of the polyvinylidene fluoride is low, and the polyvinylidene fluoride is pyrolyzed into carbon and HF gas along with the increase of the temperature of the heating furnace. And putting the uniformly mixed ferric trifluoride and the polyvinylidene fluoride after the high-energy ball milling into a heating furnace for heating, so that the pyrolysis efficiency of the polyvinylidene fluoride is improved. Because the ferric trifluoride and the polyvinylidene fluoride are fully and uniformly mixed, the HF gas and the ferric trifluoride react to generate FeF2In situ carbon encapsulation of the resulting FeF2And (3) granules. The purpose of adding hydrofluoric acid (which can be replaced by other acid) in the invention is to clean impurities, so as to obtain purer C-FeF2The powder does not function as a fluorinate. In the prior art, purchased HF gas needs to be introduced, the invention generates the HF gas through the pyrolysis of polyvinylidene fluoride, and the HF gas generated through the reaction is used for cleaning the C-FeF2Collecting powder, vacuum drying at 80 deg.C for 12 hr, and collecting dried powder. The method has the advantages of low cost, low risk coefficient and high operability.
In the step, the reaction efficiency is improved by heating the ball-milled mixture of the ferric trifluoride and the polyvinylidene fluoride through the heating furnace, so that the polyvinylidene fluoride can be rapidly pyrolyzed under the conditions of high temperature and high pressure to generate the gas of pyrolytic carbon and HF. FeF formation by reaction of HF gas with ferric trifluoride2So that the carbon in situ wraps the generated FeF2Particles of increased C-FeF2Rate of black powder formation.
However, the C-FeF produced as described above2The reaction of the black powder did not reach a reaction rate of 100%, so C-FeF was formed2Impurities may be present in the black powder. By the pair C-FeF2Removing impurities from the black powder to obtain the final C-FeF2The black powder is better pure and has low impurity content. Simultaneously improve C-FeF2Black powder containerQuantity, conductivity and good cycle stability.
Example nine
The invention also provides a synthetic in-situ carbon-coated FeF2The particles are prepared by the preparation method of any one of the first embodiment to the eighth embodiment. Synthesis of in situ carbon coated FeF2The product has high capacity and good circulation stability.
Example ten
The invention also provides a battery, which adopts the FeF coated with the synthetic in-situ carbon of the ninth embodiment2The particles were used to prepare the positive electrode. By in situ carbon-coated FeF synthesis2The particles are used as the anode material of the lithium battery, so that the conductivity can be effectively improved, the volume change in the charging and discharging process can be buffered, and the particle size can be reduced, so that the transport distance of electrons and ions can be reduced, and the electrochemical performance can be well improved.
To further illustrate the beneficial effects of the method for synthesizing the composition of the lithium ion battery cathode material by the solid phase method provided by the embodiment of the present invention, the following detailed description is further provided in conjunction with specific test examples:
experiment one:
weigh 1gFeF3And 2g of PVDF powder, which are respectively placed in a glass cup and dried in a vacuum drying oven at 80 ℃ for 12 hours, wherein the drying purpose is to remove water and obtain better ball milling effect.
The mixture of ferric trifluoride and polyvinylidene fluoride was ball milled on a planetary ball mill for 8h with alternating forward and reverse ball milling at 500rpm to refine and thoroughly mix the mixture.
And putting the ball-milled mixture into a heating furnace, heating to 600 ℃ at the speed of 4 ℃/min, preserving the heat at 600 ℃ for 1h, cooling to room temperature, and collecting black powder.
Cleaning black powder with HF acid, collecting, drying in a vacuum drying oven at 60 deg.C for 12h to obtain powder labeled C-FeF2。
Subjecting the obtained C-FeF to field emission scanning electron microscopy2Powder preparationScanning, the scanning electron micrographs obtained are shown in FIGS. 5 and 6, from which FeF can be seen2The diameter of the particle structure is about 300nm, and the carbon layer wraps FeF2The particles and the carbon layer play a role in conducting electricity and limiting volume expansion.
Experiment two:
weigh 1gFeF3And 2g of PVDF powder, which are respectively placed in a glass cup and dried in a vacuum drying oven at 80 ℃ for 12 hours, wherein the drying purpose is to remove water and obtain better ball milling effect.
The mixture of ferric trifluoride and polyvinylidene fluoride was ball milled on a planetary ball mill for 8h with alternating forward and reverse ball milling at 500rpm to refine and thoroughly mix the mixture.
And putting the ball-milled mixture into a heating furnace, heating to 600 ℃ at the speed of 4 ℃/min, preserving the heat at 600 ℃ for 1h, cooling to room temperature, and collecting black powder.
Cleaning black powder with HF acid, collecting, drying in a vacuum drying oven at 60 deg.C for 12h to obtain powder labeled C-FeF2。
And (3) electrochemical performance testing:
the cyclic voltammetry is characterized in that triangular pulse voltage is applied to a working electrode, a testing instrument is used for testing the initial potential of a button type half cell, then the initial potential is scanned from the initial potential to the low potential at a certain scanning speed, then the low potential is scanned from the high potential, then the high potential is scanned from the low potential to the high potential, then the high potential is scanned from the low potential in a reverse direction, and a voltage-current curve graph obtained by scanning can be used for researching the relation of the current of an electrode plate along with the change of the potential and researching the oxygen reduction process of the electrode plate in the charging and discharging process. And 2 sections are scanned for one circle during testing, and testing parameters can be set as required.
The test apparatus used was an electrochemical workstation model CHI660D, with the following parameters, as shown in FIG. 7: scan rate (0.2mV s-1), high potential (4.5V), low potential (1.0V), number of stages (10 stages). The results of the inventive material show that a conversion reaction occurs at around 1.7V and a lithium intercalation reaction occurs at around 1V.
Experiment three
Weigh 1gFeF3And 2g of PVDF powder, which are respectively placed in a glass cup and dried in a vacuum drying oven at 80 ℃ for 12 hours, wherein the drying purpose is to remove water and obtain better ball milling effect.
The mixture of ferric trifluoride and polyvinylidene fluoride was ball milled on a planetary ball mill for 8h with alternating forward and reverse ball milling at 500rpm to refine and thoroughly mix the mixture.
And putting the ball-milled mixture into a heating furnace, heating to 600 ℃ at the speed of 4 ℃/min, preserving the heat at 600 ℃ for 1h, cooling to room temperature, and collecting black powder.
Cleaning black powder with HF acid, collecting, drying in a vacuum drying oven at 60 deg.C for 12h to obtain powder labeled C-FeF2。
And (3) electrochemical performance testing:
the resulting active material was conventionally formed into an electrode material for lithium ion batteries and tested for electrochemical properties in a three-electrode system and a novyi battery test system. FIGS. 7, 8 and 9 are C-FeF based on the active material of the present invention2Electrochemical performance diagram, Cyclic Voltammogram (CV), charge-discharge curve diagram and cyclic performance diagram. As can be seen, the first-cycle discharge capacity of the electrode can reach 110mAhg < -1 > under the action of the current density of 30mAg < -1 >. And as shown in figure 6, the current density is 30mAg < -1 > and the current density is kept about 100 percent after being circulated for 140 circles, so that good circulation stability is shown.
And (3) electrochemical performance testing: respectively weighing 80% of FeF by using an electronic balance2Active substance, 10% conductive carbon black, 10% PVDF, each weighed substance was placed in a dry glass beaker, which was put in a vacuum drying oven (80 ℃, 12 hours) to remove water.
Putting the active material, graphite and carbon black which are subjected to vacuum drying at 80 ℃ into a dry and clean ball milling tank, simultaneously putting 3 large ball milling beads and 4 small ball milling beads into the ball milling tank, fixing the ball milling tank on a planetary ball mill, and carrying out ball milling for 2 hours at the speed of 450 r.min < -1 > to uniformly mix all the substances; then adding NMP (N-methyl pyrrolidone) solution dissolved with the binder (PVDF) into the uniformly mixed substances, and continuing ball milling for 2h to obtain uniform slurry with moderate viscosity.
During the process of ball-milling the slurry, a flat glass plate is cleaned and then placed in an oven for drying, the aluminum foil is cut into a shape slightly smaller than the glass plate, and then the front side and the back side of the aluminum foil are respectively wiped for three times by alcohol cotton so that the surface of the aluminum foil is clean.
Then pouring the uniform slurry with moderate viscosity obtained by ball milling on the rough surface (dark surface) of the clean aluminum foil, and adjusting the coating size of the coating machine according to the requirement to coat the uniformly mixed slurry on the aluminum foil. And (3) putting the aluminum foil coated with the slurry into a forced air drying oven for pre-drying (35 ℃ for 3h), and adjusting the temperature of the forced air drying machine to 60 ℃ to continuously dry for 8h after the surface of the slurry on the aluminum foil is basically solidified.
And taking out the dried electrode slice in the vacuum drying oven, pressing the electrode slice with the required size on a manual slicer, pressing the pressed electrode slice with the proper size on a tablet press to improve the binding force of the active material and the current collector, and maintaining the pressure for 2min under the pressure of 12MP to obtain the flat and smooth electrode slice.
And (3) placing the pressed electrode slice in a glass dish, and finally drying in a vacuum drying oven at 120 ℃ for 12 hours. And (5) preparing the lithium ion battery electrode slice. The electrochemical performance was tested in a three-electrode system test. The electrode plate is used as a working electrode, and the lithium plate is used as a reference electrode. The electrolyte was a 1.0mol L-1LiPF6-EC: DEC: DMC (1:1:1) solution. Both cyclic voltammetry and galvanostatic charge-discharge tests were performed in an electrochemical workstation (CHI 660E).
Example nine
The invention also provides a synthetic in-situ carbon-coated FeF2The particles are prepared by any preparation method. So that the synthesized in-situ carbon-coated FeF2The particles have excellent supercapacitor performance and good cycling stability (about 100% retained after 5000 cycles). The FeF2 particle coated with carbon in situ is obtained by a solid phase method, and has high capacity and good cycling stability (the efficiency is close to 100 percent after 140 circles).
Example ten
The invention also provides a synthetic in-situ carbon-coated FeF2Method of using particles for making lithium battery anodes, wherein the FeF is carbon coated in situ2The particles are example nine FeF2And (3) granules.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. Synthetic in-situ carbon-coated FeF2A method of making particles, comprising the steps of:
s1, drying the mixture of the iron source and the polyvinylidene fluoride in a vacuum environment;
s2, performing ball milling on the dried mixture of the iron source and the polyvinylidene fluoride;
s3, heating the mixture after ball milling, and collecting C-FeF after cooling2Black powder.
2. The synthetic in situ carbon coated FeF of claim 12The preparation method of the particles is characterized in that in the step S3, the mixture after ball milling is placed into a heating furnace for heating for 1-3h at 400-700 ℃.
3. The synthetic in situ carbon coated FeF of claim 22A method for preparing granules, wherein in the step S3, the mixture is heated to 600 ℃ at a rate of 2-4 ℃/min and is maintained at 600 ℃ for 1-6 hours.
4. The synthetic in situ carbon coated FeF of any one of claims 1-32The method for producing granules, characterized in that after the step S3, the method further comprises subjecting the C-FeF to2Removing impurities from the black powder, wherein the step of removing the impurities specifically comprises the following steps:
cleaning the C-F with hydrogen fluorideeF2Collecting powder, vacuum drying at 40-80 deg.C for 12-24 hr, and collecting dried powder.
5. The synthetic in situ carbon coated FeF of any one of claims 1-32A method for producing granules, wherein in step S1, the temperature in the vacuum atmosphere is 50 to 140 ℃.
6. The synthetic in situ carbon coated FeF of claim 52The preparation method of the particles is characterized in that in the step S1, the drying time of the mixture of the iron source and the polyvinylidene fluoride in the vacuum environment is 12-24 h.
7. The synthetic in-situ carbon coated FeF of any one of claims 1-3, 62The preparation method of the particles is characterized in that in the step S2, the iron source and the polyvinylidene fluoride mixture are subjected to ball milling in a planetary ball mill for 5-15 h.
8. The synthetic in situ carbon coated FeF of claim 72The preparation method of the particles is characterized in that the mixture of the iron source and the polyvinylidene fluoride is alternately ball-milled in the planetary ball mill in the positive and negative directions of 400-650 rpm.
9. Synthetic in-situ carbon-coated FeF2Granules, characterized in that they are obtained by a process according to any one of claims 1 to 8.
10. A battery using the synthetic in-situ carbon coated FeF of claim 92The particles were used to prepare the positive electrode.
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