CN113224311A - Multi-fluoride positive electrode material, preparation method thereof and lithium ion battery - Google Patents
Multi-fluoride positive electrode material, preparation method thereof and lithium ion battery Download PDFInfo
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Abstract
The invention discloses a multi-fluoride anode material, a preparation method thereof and a lithium ion battery. The chemical formula of the anode material is Fe1‑x‑yCoxAlyF3Wherein, 0<x≤0.1，0<y is less than or equal to 0.1. The method comprises the following steps: 1) preparing a mixed solution by adopting an iron source, a cobalt source, an aluminum source, a fluorine source, an acid and a solvent; 2) carrying out solvothermal reaction and solid-liquid separation on the mixed solution in a closed reactor; 3) and carrying out heat treatment on the solid-liquid separation product in the atmosphere of protective gas to obtain the multi-element fluoride cathode material. The lithium ion battery anode material provided by the invention has the advantages of high reversible specific capacity and good cycle stability.
Description
Technical Field
The invention belongs to the technical field of energy storage materials, relates to a lithium ion battery anode material, and particularly relates to a multi-fluoride anode material, a preparation method thereof and a lithium ion battery.
Background
With the rapid development of new energy automobiles, the lithium ion battery industry has entered a rapid development stage. The key materials influencing the performance of the lithium ion battery mainly comprise a positive electrode material, a negative electrode material, electrolyte and the like. The positive electrode material is a main factor which currently limits the performance of the battery and also a main factor which accounts for the higher cost of the lithium ion battery, and is close to 40%.
Iron fluoride has advantages of high specific capacity, high voltage, and abundant natural resources, and has gradually become one of the most interesting positive electrode materials in recent years. However, the ionic bonding property of metal fluoride causes poor electronic conductivity and ionic diffusion, and the electrochemical performance still needs to be further improved.
CN202010820328.3 discloses a composite ferric trifluoride anode material, a preparation method and application thereof. The synthesis method comprises the following steps: formed of carbon nanohorns and Fe (NO)3)3·9H2FeF synthesized by liquid phase synthesis of O3·0.33H2O-carbon nanohorn composite material for improving FeF3The conductivity is not good.
CN202010443374.6 discloses an iron-based fluoride particle, its preparation method and application. The obtained material comprises a porous octahedral carbon skeleton and ferric fluoride dispersed in the porous octahedral carbon skeleton, and the preparation method comprises the following steps: 1) respectively dispersing ferric salt and terephthalic acid in a solvent, and carrying out solvothermal reaction to obtain Fe-MOF; 2) mixing Fe-MOF and NH4And F is uniformly mixed and then placed in a protective atmosphere to carry out co-pyrolysis reaction, or Fe-MOF is added into a reaction kettle containing HF solution and placed above the liquid level, and heating is carried out to carry out fluorination reaction, so that the iron-based fluoride particles are obtained. The iron-based fluoride particles are porous octahedral and FeF3The carbon nano-particles are uniformly distributed in highly graphitized three-dimensional porous carbon, and the conductivity is high.
Jea Li et al fluorinate Fe by Using HF2O3Method of preparing/C precursor to obtain carbon-coated FeF3A material. The obtained material has a particle size of about 60nm, is beneficial to the full infiltration of electrolyte, and when used as the anode material of a lithium ion battery, the particle size is 20mA g-1The first discharge specific capacity is 166.4mAh g under the current density-1And the discharge capacity after 100 cycles was 126.3mAh g-1(Li J, Fu L, Xu Z, et al. Electrochimica Acta,2018,281: 88-98.).
However, the reversible specific capacity and the cycle performance of the electrode material obtained by the scheme are to be improved.
Therefore, the development of a lithium ion battery cathode material with better performance is of great significance to the field.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a multi-fluoride cathode material, a preparation method thereof and a lithium ion battery.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a multi-fluoride cathode material, wherein the chemical formula of the cathode material is Fe1-x- yCoxAlyF3Wherein, 0<x≤0.1，0<y≤0.1。
In the multi-component fluoride positive electrode material of the present invention, x is, for example, 0.005, 0.01, 0.02, 0.03, 0.05, 0.06, 0.07, 0.08 or 0.1, and y is, for example, 0.005, 0.008, 0.01, 0.02, 0.03, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1. The multi-element fluoride is a Co and Al doped ferric fluoride anode material, wherein the Co and Al have synergistic effect in the anode material, so that the anode material provided by the invention has excellent performance, and particularly, the Co and Al play a role in stabilizing the material structure in the electrode material and improving the electronic conductance of the material, thereby improving the specific capacity and the cycling stability of the material. Solves the problems of the lithium ion battery industry such as the shortage of nickel and cobalt element resources, high price and the like.
Preferably, 0.05. ltoreq. x.ltoreq.0.1, 0.05. ltoreq. y.ltoreq.0.1. In this preferred Co and Al doping range, better electrochemical performance can be obtained.
In a second aspect, the present invention provides a method for preparing a multi-fluoride positive electrode material as described in the first aspect, the method comprising the steps of:
(1) preparing a mixed solution by adopting an iron source, a cobalt source, an aluminum source, a fluorine source, an acid and a solvent;
(2) carrying out solvothermal reaction and solid-liquid separation on the mixed solution in a closed reactor;
(3) and carrying out heat treatment on the solid-liquid separation product in the atmosphere of protective gas to obtain the multi-element fluoride cathode material.
The method introduces a fluorine source, prepares the fluoride anode material by doping Co and Al ions, can realize atomic-level mixing in the preparation process, has high uniformity degree, provides an acid environment for acid, and ensures that the reaction process is milder, and has simple process and controllable process.
As a preferable technical scheme of the method, the iron source in the step (1) comprises any one of ferric nitrate, ferric chloride or ferrous oxalate or a combination of at least two of the ferric nitrate, the ferric chloride and the ferrous oxalate.
Preferably, the cobalt source in step (1) comprises any one of cobalt nitrate, cobalt chloride or cobalt oxalate or a combination of at least two of them.
Preferably, the aluminum source in step (1) comprises aluminum nitrate and/or sodium metaaluminate, and may be aluminum nitrate, sodium metaaluminate or a mixture of aluminum nitrate and sodium metaaluminate, for example.
Preferably, the fluorine source in step (1) comprises lithium fluoride and/or sodium fluoride, and may be lithium fluoride, sodium fluoride, or a mixture of aluminum fluoride and sodium fluoride.
Preferably, the acid of step (1) is hydrochloric acid.
Preferably, the mass fraction of hydrochloric acid is 40-50%, such as 40%, 42%, 43%, 45%, 47%, or 50%, etc.
In the invention, preferably, fluoride salt is used as a fluorine source, and hydrochloric acid is introduced to provide an acidic environment, so that the reaction process is milder, and the preparation of the high-performance multi-fluoride anode material is facilitated.
Preferably, the solvent in step (1) is an organic solvent, preferably an alcohol, and more preferably a mixed solvent of glycerol and ethanol;
preferably, the volume ratio of the glycerol to the ethanol in the mixed solvent of the glycerol and the ethanol is (0.1-2):1, such as 0.1:1, 0.5:1, 1.5:1, 1.7:1, 1.8:1 or 2: 1. The glycerol is used for adjusting the viscosity of the solvent, the ethanol is used for dispersing the particles, the particle size and the dispersity of the particles can be controlled by the mixed solvent of the glycerol and the ethanol, uniform nano particles are obtained, the volume change of the material in the circulating process is relieved, and the circulating stability of the material is improved.
Preferably, the iron source, the cobalt source, the aluminum source and the fluorine source in the step (1) are added in amounts satisfying: the molar ratio of Fe element, Co element, Al element and F element is (1-x-y) x: y:3, x is more than 0 and less than or equal to 0.1, and y is more than 0 and less than or equal to 0.1. Even if the amount of Fe element, Co element, Al element and F element in the material meets the molecular formula ratio of the lithium ion battery anode material.
Preferably, the molar ratio of F in the fluorine source and HCl in the hydrochloric acid is (0.5-2):1, e.g., 0.5:1, 0.8:1, 1:1, 1.5:1, 1.7:1, 1.8:1, or 2:1, etc.
Preferably, the total concentration of metal ions in the mixed solution in step (1) is 0.01-2mol/L, such as 0.01mol/L, 0.05mol/L, 0.1mol/L, 0.3mol/L, 0.5mol/L, 1mol/L, 1.2mol/L, 1.5mol/L or 2 mol/L.
As a preferred technical scheme of the method, the mixed solution in the step (1) is prepared according to the following modes: firstly dissolving an iron source, a cobalt source and an aluminum source in a solvent according to the formula amount, and then adding a fluorine source and hydrochloric acid according to the formula amount.
Preferably, the temperature of the solvothermal reaction in step (2) is 95-130 ℃, such as 95 ℃, 100 ℃, 110 ℃, 120 ℃ or 130 ℃, and the like.
Preferably, the solvothermal reaction of step (2) is carried out for 6-12h, such as 6h, 8h, 9h, 10h, 11h or 12 h.
Preferably, the protective gas in step (3) comprises any one or a combination of at least two of nitrogen, helium or argon.
Preferably, the temperature of the heat treatment in step (3) is 250-450 ℃, such as 250-450 ℃, e.g., 250 ℃, 270 ℃, 300 ℃, 325 ℃, 350 ℃, 375 ℃, 400 ℃ or 450 ℃, etc.
Preferably, the heating rate of the heat treatment in step (3) is 1 ℃/min-30 ℃/min, such as 1 ℃/min, 3 ℃/min, 5 ℃/min, 8 ℃/min, 10 ℃/min, 15 ℃/min, 20 ℃/min, 25 ℃/min or 30 ℃/min, and the like.
Preferably, the heat treatment in step (3) has a holding time of 1h to 10h, such as 1.5h, 2h, 3h, 4h, 5h, 6h, 8h, 9h or 10 h.
Preferably, after the solid-liquid separation in the step (2) and before the heat treatment in the step (3), the solid-liquid separation product is washed and dried.
As a further preferred technical solution of the method of the present invention, the method comprises the steps of:
(1) iron source, cobalt source and aluminum source are mixed according to the molecular formula of Fe1-x-yCoxAlyF3Dissolving the mixture in a mixed solvent of glycerol and ethanol according to the molar ratio, stirring, and adding a fluorine source and hydrochloric acid to obtain a mixed solution;
wherein, in the mixed solvent of glycerol and ethanol, the volume ratio of the glycerol to the ethanol is (0.1-2) to 1;
the molar ratio of F in the fluorine source to HCl in the hydrochloric acid is (0.5-2) to 1;
in the mixed solution, the total concentration of metal ions is 0.01-2 mol/L;
(2) transferring the obtained mixed solution into a closed reaction kettle, carrying out solvent heat treatment reaction for 6-12h at the temperature of 95-130 ℃, carrying out solid-liquid separation after the reaction is finished, washing and drying;
(3) carrying out heat treatment on the obtained powder under the protective atmosphere, raising the temperature to 250-450 ℃ at the speed of 1-30 ℃/min, preserving the heat for 1-10h, and cooling to obtain Fe1-x-yCoxAlyF3A multi-component fluoride positive electrode material.
In a third aspect, the present invention provides a lithium ion battery comprising the multi-fluoride positive electrode material of the first aspect.
Compared with the prior art, the invention has the following beneficial effects:
(1) the anode material of the lithium ion battery provided by the invention is a Co and Al doped ferric fluoride anode material. Wherein, Co and Al play a role in stabilizing the material structure and improving the electronic conductance of the material in the electrode material. The obtained material has the advantages of high reversible specific capacity, good cycling stability and the like. Under the voltage window of 1.5-4.5V and the current density of 50mA, the first cyclic discharge specific capacity is more than 200mAh/g, and the capacity retention rate of 200 cycles is more than 90%. Solves the problems of the lithium ion battery industry such as the shortage of nickel and cobalt element resources, high price and the like.
(2) The preparation method provided by the invention realizes atomic-level mixing of the materials in the preparation process, has high uniformity, introduces fluorine salt as a fluorine source, provides an acidic environment with hydrochloric acid, and makes the reaction process milder. Moreover, the preparation method has simple process and controllable process.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments.
The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.
Example 1
(1) According to the weight ratio of Fe: co: al element molar ratio of 0.8: 0.1: 0.1, weighing ferric nitrate, cobalt nitrate and aluminum nitrate, mixing, dissolving in a mixed solvent of glycerol and ethanol (the volume ratio of glycerol to ethanol in the mixed solvent is 0.5: 1), and stirring to obtain a mixed solution I;
(2) adding lithium fluoride and hydrochloric acid (the mass fraction is 40%) into the mixed solution I to obtain a mixed solution II; the molar ratio of F in lithium fluoride to HCl in hydrochloric acid in the mixed solution II is 1: 1; the total concentration of metal ions in the mixed solution II is 1 mol/L;
(3) transferring the obtained mixed solution II into a closed reaction kettle, carrying out solvothermal reaction for 10 hours at the temperature of 95 ℃, carrying out solid-liquid separation after the reaction is finished, washing and drying;
(4) carrying out heat treatment on the obtained powder in an argon atmosphere, heating to 250 ℃ at the speed of 10 ℃/min for heat treatment for 4h, and cooling to obtain Fe0.8Co0.1Al0.1F3And (3) a positive electrode material.
The obtained anode material is used as the anode material of the lithium ion battery for electrochemical performance test, and the pole piece ratio is that the anode material: acetylene black: PVDF (mass ratio) 90:5: 5. And preparing the CR2025 button cell by taking a lithium sheet as a reference electrode. Under the voltage window of 1.5-4.5V and the current density of 50mA/g, the first cyclic discharge specific capacity is 202mAh/g, and the capacity retention rate of 200 cycles is 94%.
Example 2
(1) According to the weight ratio of Fe: co: molar ratio of Al element 0.9: 0.05: 0.05 weighing ferric chloride, cobalt chloride and sodium metaaluminate, mixing and dissolving in a mixed solvent of glycerol and ethanol (the volume ratio of the glycerol to the ethanol in the mixed solvent is 0.1: 1), and stirring to obtain a mixed solution I;
(2) adding sodium fluoride and hydrochloric acid (the mass fraction is 40%) into the mixed solution I to obtain a mixed solution II; the molar ratio of F in sodium fluoride to HCl in hydrochloric acid in the mixed solution II is 2: 1; the total concentration of the metal ions in the mixed solution II is 0.01 mol/L;
(3) transferring the obtained mixed solution II into a closed reaction kettle, carrying out solvothermal reaction for 6 hours at the temperature of 130 ℃, carrying out solid-liquid separation after the reaction is finished, washing and drying;
(4) carrying out heat treatment on the obtained powder in a nitrogen atmosphere, heating to 450 ℃ at the speed of 1 ℃/min for heat treatment for 1h, and cooling to obtain Fe0.9Co0.05Al0.05F3And (3) a positive electrode material.
The obtained anode material is used as the anode material of the lithium ion battery for electrochemical performance test, and the pole piece ratio is that the anode material: acetylene black: PVDF (mass ratio) 90:5: 5. And preparing the CR2025 button cell by taking a lithium sheet as a reference electrode. Under the voltage window of 1.5-4.5V and the current density of 50mA/g, the first cyclic discharge specific capacity is 213mAh/g, and the capacity retention rate of 200 cycles is 91%.
Example 3
(1) According to the weight ratio of Fe: co: molar ratio of Al element 0.97: 0.01: 0.02 weighing ferrous oxalate, cobalt nitrate, cobalt chloride and sodium metaaluminate, mixing and dissolving in a mixed solvent of glycerol and ethanol (the volume ratio of the glycerol to the ethanol in the mixed solvent is 2: 1), and stirring to obtain a mixed solution I;
(2) adding lithium fluoride and hydrochloric acid (the mass fraction is 40%) into the mixed solution I to obtain a mixed solution II; the molar ratio of F in lithium fluoride to HCl in hydrochloric acid in the mixed solution II is 0.5: 1; the total concentration of metal ions in the mixed solution II is 2 mol/L;
(3) transferring the obtained mixed solution II into a closed reaction kettle, carrying out solvothermal reaction for 12 hours at the temperature of 110 ℃, carrying out solid-liquid separation after the reaction is finished, washing and drying;
(4) carrying out heat treatment on the obtained powder in helium atmosphere, heating to 300 ℃ at the speed of 30 ℃/min for heat treatment for 10h, and cooling to obtain Fe0.97Co0.01Al0.02F3And (3) a positive electrode material.
The obtained anode material is used as the anode material of the lithium ion battery for electrochemical performance test, and the pole piece ratio is that the anode material: acetylene black: PVDF (mass ratio) 90:5: 5. And preparing the CR2025 button cell by taking a lithium sheet as a reference electrode. Under the voltage window of 1.5-4.5V and the current density of 50mA/g, the first cyclic discharge specific capacity is 209mAh/g, and the capacity retention rate of 200 cycles is 90%.
Example 4
(1) According to the weight ratio of Fe: co: molar ratio of Al element 0.9: 0.05: 0.05 weighing ferric nitrate, cobalt nitrate and aluminum nitrate, mixing and dissolving in a mixed solvent of glycerol and ethanol (the volume ratio of glycerol to ethanol in the mixed solvent is 0.8: 1), and stirring to obtain a mixed solution I;
(2) adding sodium fluoride and hydrochloric acid (the mass fraction is 40%) into the mixed solution I to obtain a mixed solution II; the molar ratio of F in sodium fluoride to HCl in hydrochloric acid in the mixed solution II is 1.2: 1; the total concentration of the metal ions in the mixed solution II is 0.5 mol/L;
(3) transferring the obtained mixed solution II into a closed reaction kettle, carrying out solvothermal reaction for 8 hours at the temperature of 100 ℃, carrying out solid-liquid separation after the reaction is finished, washing and drying;
(4) carrying out heat treatment on the obtained powder in an argon atmosphere, heating to 350 ℃ at the speed of 5 ℃/min for heat treatment for 2h, and cooling to obtain Fe0.8Co0.05Al0.05F3And (3) a positive electrode material.
The obtained anode material is used as the anode material of the lithium ion battery for electrochemical performance test, and the pole piece ratio is that the anode material: acetylene black: PVDF (mass ratio) 90:5: 5. And preparing the CR2025 button cell by taking a lithium sheet as a reference electrode. Under the voltage window of 1.5-4.5V and the current density of 50mA/g, the first cyclic discharge specific capacity is 215mAh/g, and the capacity retention rate of 200 cycles is 92%.
Example 5
(1) According to the weight ratio of Fe: co: molar ratio of Al element 0.98: 0.01: 0.01 weighing ferric chloride, cobalt oxalate and sodium metaaluminate, mixing and dissolving in a mixed solvent of glycerol and ethanol (the volume ratio of glycerol to ethanol in the mixed solvent is 1.5: 1), and stirring to obtain a mixed solution I;
(2) adding lithium fluoride and hydrochloric acid (the mass fraction is 40%) into the mixed solution I to obtain a mixed solution II; the molar ratio of F in lithium fluoride to HCl in hydrochloric acid in the mixed solution II is 1.2: 1; the total concentration of the metal ions in the mixed solution II is 0.08 mol/L;
(3) transferring the obtained mixed solution II into a closed reaction kettle, carrying out solvothermal reaction for 8 hours at the temperature of 115 ℃, carrying out solid-liquid separation after the reaction is finished, washing and drying;
(4) carrying out heat treatment on the obtained powder in an argon atmosphere, heating to 320 ℃ at the speed of 15 ℃/min for heat treatment for 4h, and cooling to obtain Fe0.98Co0.01Al0.01F3And (3) a positive electrode material.
The obtained anode material is used as the anode material of the lithium ion battery for electrochemical performance test, and the pole piece ratio is that the anode material: acetylene black: PVDF (mass ratio) 90:5: 5. And preparing the CR2025 button cell by taking a lithium sheet as a reference electrode. Under the voltage window of 1.5-4.5V and the current density of 50mA/g, the first cyclic discharge specific capacity is 220mAh/g, and the capacity retention rate of 200 cycles is 90%.
Example 6
This example differs from example 1 in that the molar ratio of F in lithium fluoride and HCl in hydrochloric acid in the mixed solution ii was 0.3: 1.
the obtained anode material is used as the anode material of the lithium ion battery for electrochemical performance test, and the pole piece ratio is that the anode material: acetylene black: PVDF (mass ratio) 90:5: 5. And preparing the CR2025 button cell by taking a lithium sheet as a reference electrode. Under the voltage window of 1.5-4.5V and the current density of 50mA/g, the first cycle discharge specific capacity is 189mAh/g, and the capacity retention rate of 200 cycles is 81%.
Example 7
This example differs from example 1 in that the molar ratio of F in lithium fluoride and HCl in hydrochloric acid in the mixed solution ii was 2.5: 1.
the obtained anode material is used as the anode material of the lithium ion battery for electrochemical performance test, and the pole piece ratio is that the anode material: acetylene black: PVDF (mass ratio) 90:5: 5. And preparing the CR2025 button cell by taking a lithium sheet as a reference electrode. Under the voltage window of 1.5-4.5V and the current density of 50mA/g, the first cyclic discharge specific capacity is 183mAh/g, and the capacity retention rate is 79% after 200 cycles.
Example 8
This example is different from example 1 in that step (1) the mixed solvent of glycerin and ethanol is replaced with an ethanol solvent.
The obtained anode material is used as the anode material of the lithium ion battery for electrochemical performance test, and the pole piece ratio is that the anode material: acetylene black: PVDF (mass ratio) 90:5: 5. And preparing the CR2025 button cell by taking a lithium sheet as a reference electrode. Under the voltage window of 1.5-4.5V and the current density of 50mA/g, the first cyclic discharge specific capacity is 190mAh/g, and the capacity retention rate of 200 cycles is 83%.
Comparative example 1
(1) According to the weight ratio of Fe: molar ratio of Co element 0.9: 0.1, weighing ferric nitrate and cobalt nitrate, mixing and dissolving in a mixed solvent of glycerol and ethanol (the volume ratio of the glycerol to the ethanol in the mixed solvent is 0.5: 1), and stirring to obtain a mixed solution I;
(2) adding lithium fluoride and hydrochloric acid (the mass fraction is 40%) into the mixed solution I to obtain a mixed solution II; the molar ratio of F in lithium fluoride to HCl in hydrochloric acid in the mixed solution II is 1: 1; the total concentration of metal ions in the mixed solution II is 1 mol/L;
(3) transferring the obtained mixed solution II into a closed reaction kettle, carrying out solvothermal reaction for 10 hours at the temperature of 95 ℃, carrying out solid-liquid separation after the reaction is finished, washing and drying;
(4) carrying out heat treatment on the obtained powder in an argon atmosphere, heating to 250 ℃ at the speed of 10 ℃/min for heat treatment for 4h, and cooling to obtain Fe0.9Co0.1F3And (3) a positive electrode material.
The obtained anode material is used as the anode material of the lithium ion battery for electrochemical performance test, and the pole piece ratio is that the anode material: acetylene black: PVDF (mass ratio) 90:5: 5. And preparing the CR2025 button cell by taking a lithium sheet as a reference electrode. Under the voltage window of 1.5-4.5V and the current density of 50mA/g, the first cyclic discharge specific capacity is 184mAh/g, and the capacity retention rate of 200 cycles is 72%.
Comparative example 2
(1) According to the weight ratio of Fe: molar ratio of Al element 0.9: 0.1, weighing ferric nitrate and aluminum nitrate, mixing and dissolving the ferric nitrate and the aluminum nitrate in a mixed solvent of glycerol and ethanol (the volume ratio of the glycerol to the ethanol in the mixed solvent is 0.5: 1), and stirring to obtain a mixed solution I;
(2) adding lithium fluoride and hydrochloric acid (the mass fraction is 40%) into the mixed solution I to obtain a mixed solution II; the molar ratio of F in lithium fluoride to HCl in hydrochloric acid in the mixed solution II is 1: 1; the total concentration of metal ions in the mixed solution II is 1 mol/L;
(3) transferring the obtained mixed solution II into a closed reaction kettle, carrying out solvothermal reaction for 10 hours at the temperature of 95 ℃, carrying out solid-liquid separation after the reaction is finished, washing and drying;
(4) carrying out heat treatment on the obtained powder in an argon atmosphere, heating to 250 ℃ at the speed of 10 ℃/min for heat treatment for 4h, and cooling to obtain Fe0.9Al0.1F3And (3) a positive electrode material.
The obtained anode material is used as the anode material of the lithium ion battery for electrochemical performance test, and the pole piece ratio is that the anode material: acetylene black: PVDF (mass ratio) 90:5: 5. And preparing the CR2025 button cell by taking a lithium sheet as a reference electrode. Under the voltage window of 1.5-4.5V and the current density of 50mA/g, the first cyclic discharge specific capacity is 175mAh/g, and the capacity retention rate of 200 cycles is 81%.
Comparative example 3
(1) Weighing ferric nitrate, dissolving the ferric nitrate in a mixed solvent of glycerol and ethanol (the volume ratio of the glycerol to the ethanol in the mixed solvent is 0.5: 1), and stirring to obtain a mixed solution I;
(2) adding lithium fluoride and hydrochloric acid (the mass fraction is 40%) into the mixed solution I to obtain a mixed solution II; the molar ratio of F in lithium fluoride to HCl in hydrochloric acid in the mixed solution II is 1: 1; the total concentration of metal ions in the mixed solution II is 1 mol/L;
(3) transferring the obtained mixed solution II into a closed reaction kettle, carrying out solvothermal reaction for 10 hours at the temperature of 95 ℃, carrying out solid-liquid separation after the reaction is finished, washing and drying;
(4) carrying out heat treatment on the obtained powder in an argon atmosphere, heating to 250 ℃ at the speed of 10 ℃/min for heat treatment for 4h, and cooling to obtain FeF3And (3) a positive electrode material.
The obtained anode material is used as the anode material of the lithium ion battery for electrochemical performance test, and the pole piece ratio is that the anode material: acetylene black: PVDF (mass ratio) 90:5: 5. And preparing the CR2025 button cell by taking a lithium sheet as a reference electrode. Under the voltage window of 1.5-4.5V and the current density of 50mA/g, the first cyclic discharge specific capacity is 161mAh/g, and the capacity retention rate of 200 cycles is 64%.
Comparative example 4
This comparative example differs from example 1 in that no hydrochloric acid was added in step (2).
The obtained anode material is used as the anode material of the lithium ion battery for electrochemical performance test, and the pole piece ratio is that the anode material: acetylene black: PVDF (mass ratio) 90:5: 5. And preparing the CR2025 button cell by taking a lithium sheet as a reference electrode. Under the voltage window of 1.5-4.5V and the current density of 50mA/g, the first cyclic discharge specific capacity is 158mAh/g, and the capacity retention rate is 66% after 200 cycles.
The Co and Al doped ferric fluoride cathode material provided by the invention can be known by combining the examples and the comparative examples. Wherein, Co and Al play a role in stabilizing the material structure and improving the electronic conductance of the material in the electrode material. The obtained material has the advantages of high reversible specific capacity, good cycling stability and the like. The comparative example did not adopt the scheme of the present invention, and thus the effects of the present invention could not be obtained.
As can be seen from the comparison between example 1 and examples 6-7, the addition amount of HCl is in a preferred range, and the addition amount of HCl is less or more, which is not beneficial to improving the electrochemical performance of the cathode material.
As can be seen from a comparison between example 1 and example 8, the use of the mixed solvent of glycerol and ethanol is advantageous for improving the electrochemical performance of the positive electrode material.
The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. The multi-fluoride cathode material is characterized in that the chemical formula of the cathode material is Fe1-x-yCoxAlyF3Wherein, 0<x≤0.1，0<y≤0.1。
2. A method of preparing the multi-fluoride positive electrode material of claim 1, comprising the steps of:
(1) preparing a mixed solution by adopting an iron source, a cobalt source, an aluminum source, a fluorine source, an acid and a solvent;
(2) carrying out solvothermal reaction and solid-liquid separation on the mixed solution in a closed reactor;
(3) and carrying out heat treatment on the solid-liquid separation product in the atmosphere of protective gas to obtain the multi-element fluoride cathode material.
3. The method of claim 2, wherein the iron source of step (1) comprises any one of ferric nitrate, ferric chloride or ferrous oxalate or a combination of at least two thereof;
preferably, the cobalt source in step (1) comprises any one of cobalt nitrate, cobalt chloride or cobalt oxalate or a combination of at least two of the above;
preferably, the aluminium source of step (1) comprises aluminium nitrate and/or sodium metaaluminate;
preferably, the fluorine source of step (1) comprises lithium fluoride and/or sodium fluoride;
preferably, the acid of step (1) is hydrochloric acid;
preferably, the mass fraction of the acid is 40-50%;
preferably, the solvent in step (1) is an organic solvent, preferably an alcohol, and more preferably a mixed solvent of glycerol and ethanol;
preferably, in the mixed solvent of glycerol and ethanol, the volume ratio of glycerol to ethanol is (0.1-2): 1.
4. The method according to claim 2 or 3, wherein the iron source, the cobalt source, the aluminum source and the fluorine source are added in the step (1) in amounts such that: the mol ratio of Fe element, Co element, Al element and F element is (1-x-y), x is y:3, x is more than 0 and less than or equal to 0.1, y is more than 0 and less than or equal to 0.1;
preferably, the molar ratio of F in the fluorine source and HCl in hydrochloric acid is (0.5-2): 1;
preferably, the total concentration of the metal ions in the mixed solution in the step (1) is 0.01-2 mol/L.
5. The method according to any one of claims 2 to 4, wherein the mixed solution of step (1) is prepared in the following manner: firstly dissolving an iron source, a cobalt source and an aluminum source in a solvent according to the formula amount, and then adding a fluorine source and hydrochloric acid according to the formula amount.
6. The process according to any one of claims 2 to 5, wherein the temperature of the solvothermal reaction of step (2) is 95 to 130 ℃;
preferably, the solvothermal reaction time of the step (2) is 6-12 h.
7. The method of any one of claims 2-6, wherein the shielding gas of step (3) comprises any one of nitrogen, helium, or argon, or a combination of at least two thereof;
preferably, the temperature of the heat treatment in the step (3) is 250-450 ℃;
preferably, the heating rate of the heat treatment in the step (3) is 1-30 ℃/min;
preferably, the heat treatment in the step (3) has the heat preservation time of 1h-10 h.
8. The process according to any one of claims 2 to 7, wherein after the solid-liquid separation in step (2) and before the heat treatment in step (3), the solid-liquid separation product is washed and dried.
9. Method according to any of claims 2-8, characterized in that the method comprises the steps of:
(1) iron source, cobalt source and aluminum source are mixed according to the molecular formula of Fe1-x-yCoxAlyF3Dissolving the mixture in a mixed solvent of glycerol and ethanol according to the molar ratio, stirring, and adding a fluorine source and hydrochloric acid to obtain a mixed solution;
wherein, in the mixed solvent of glycerol and ethanol, the volume ratio of the glycerol to the ethanol is (0.1-2) to 1;
the molar ratio of F in the fluorine source to HCl in the hydrochloric acid is (0.5-2) to 1;
in the mixed solution, the total concentration of metal ions is 0.01-2 mol/L;
(2) transferring the obtained mixed solution into a closed reaction kettle, carrying out solvent heat treatment reaction for 6-12h at the temperature of 95-130 ℃, carrying out solid-liquid separation after the reaction is finished, washing and drying;
(3) the obtained powder is subjected to heat treatment under the protective atmosphere, the temperature is raised to 250-450 ℃ at the speed of 1-30 ℃/min and is kept for 1-10h,cooling to obtain Fe1-x-yCoxAlyF3A multi-component fluoride positive electrode material.
10. A lithium ion battery comprising the positive electrode material according to claim 1.
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