CN111883747A - Method for preparing porous graphene coated lithium vanadium phosphate by recovering graphite cathode material from waste power battery - Google Patents

Method for preparing porous graphene coated lithium vanadium phosphate by recovering graphite cathode material from waste power battery Download PDF

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Publication number
CN111883747A
CN111883747A CN202010590457.8A CN202010590457A CN111883747A CN 111883747 A CN111883747 A CN 111883747A CN 202010590457 A CN202010590457 A CN 202010590457A CN 111883747 A CN111883747 A CN 111883747A
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porous graphene
vanadium phosphate
lithium vanadium
heating
waste power
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徐建铁
陆海英
赵思湸
肖峰
雷雨
黄春茂
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South China University of Technology SCUT
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South China University of Technology SCUT
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • 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
    • H01M10/54—Reclaiming serviceable parts of waste accumulators
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/84—Recycling of batteries or fuel cells

Abstract

The invention discloses a method for preparing porous graphene coated lithium vanadium phosphate by recovering graphite cathode materials from waste power batteries. The process method comprises the following steps: adding ammonium hydrogen phosphate and citric acid to water to form a solution; adding vanadium pentoxide, and stirring to form a clear orange solution; adding lithium carbonate into a beaker, placing the beaker into a water bath kettle, heating and stirring the beaker to form a dark green solution, and adding porous graphene prepared by recovering graphite from waste power batteries to form black sol; putting the beaker into an oven for drying; grinding the material into powder, and introducing mixed gas for heating to obtain a preparation material; grinding and rolling the prepared material into a sheet, and introducing mixed gas for heating to obtain the required material. The method is low in cost and high in yield, and the porous graphene-coated lithium vanadium phosphate is prepared. After the porous graphene is coated on the lithium vanadium phosphate, more active sites are provided for the lithium vanadium phosphate, and the pores on the porous graphene are beneficial to the transfer of electrons and the transmission of electrolyte, so that the performance of the lithium vanadium phosphate is improved.

Description

Method for preparing porous graphene coated lithium vanadium phosphate by recovering graphite cathode material from waste power battery
Technical Field
The invention belongs to the field of electrode material recycling, and particularly relates to a method for preparing porous graphene coated lithium vanadium phosphate by recycling a graphite cathode material from a waste power battery.
Background
The new energy technology is recognized as a high-tech technology in the 21 st century, and the battery industry becomes a new hotspot for the development of global economy as an important component of the new energy field. Currently, lithium ion batteries are widely used as an important energy source by people. In recent years, monoclinic structure Li3V2(PO4)3(LVP) cathode material theoretical capacity 197mAhg-1Has the advantages of good cyclicity, high charging and discharging voltage platform, low price and the like, and is considered to be secondary LiFePO4And then the other lithium ion battery anode material with great market application potential. But its electronic conductivity is low, limiting its development. The method for solving the problem mainly comprises the step of carrying out carbon coating on lithium vanadium phosphate, wherein the carbon coating not only can effectively reduce the particle size of the material, but also can improve the conductivity of the material, so that the lithium vanadium phosphate has better electrochemical performance, and glucose and citric acid are selected as conventional carbon sources which are commonly used at present. Among the two, the material coated by using glucose as a carbon source and the material coated by using citric acid as a carbon source are more excellent in the aspects of cycle performance and rate performance modification. However, carbonMost of the carbon sources selected for coating need to use a new material, and the carbon material plays a very important role in national economy and national defense safety, and the use of the carbon material requires a certain cost. Therefore, if the same or even better coating can be completed by using a low-cost carbon source, the preparation cost of the high-quality lithium vanadium phosphate is reduced, and the development prospect of improving the coating performance is improved.
On the other hand, the electrochemical cycle and the rate of lithium vanadium phosphate after carbon coating are improved, but the carbon layer is coated outside the lithium vanadium phosphate, the improvement of the charge and mass transfer performance is still a huge problem, and the current method for solving the problem is to coat the lithium vanadium phosphate by using graphene, so that the charge and mass transfer performance is obviously improved due to the obvious reduction of the number of layers. However, the van der waals forces present between graphene layers make graphene easily re-stacked, tending to graphitization. Therefore, in recent years, porous graphene attracts great attention, and the nano-pores are constructed on the graphene, so that not only is the rapid charge/ion shuttling realized, but also abundant edge active sites are provided. In addition to this, the presence of nanopores weakens the van der waals forces between graphene layers, so that the tendency of graphene graphitization is weakened. Therefore, the preparation of the porous graphene-coated lithium vanadium phosphate prepared by using the waste lithium ion battery cathode graphite material as the raw material has multiple meanings for recycling the waste battery material and coating a modification system.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide a method for preparing porous graphene coated lithium vanadium phosphate by utilizing a waste power battery to recover a graphite cathode material.
In order to solve the problems that the electronic conductivity of lithium vanadium phosphate is low and more cost is consumed by introducing a new material, the invention provides the porous graphene-coated lithium vanadium phosphate prepared by utilizing the graphite cathode material of the waste power battery, which is simple, efficient and low in cost. The invention aims to improve the performance and stability of lithium vanadium phosphate and coat the lithium vanadium phosphate. The porous graphene prepared from the graphite cathode material recovered from the waste power battery is selected for coating, so that the method is environment-friendly, low in cost and high in regeneration value. Third, the porous structure of the coated graphene has an effect of improving the conductivity of electrons, and further development of a recycling coating technology is promoted.
The purpose of the invention is realized by at least one of the following technical solutions.
The invention provides a method for preparing porous graphene coated lithium vanadium phosphate by recovering graphite cathode materials from waste power batteries, which comprises the following steps:
(1) adding citric acid and ammonium hydrogen phosphate into deionized water, and uniformly stirring to obtain a colorless transparent solution;
(2) adding vanadium pentoxide powder into the colorless transparent solution obtained in the step (1), and uniformly stirring to obtain a clear orange solution;
(3) adding lithium carbonate into the orange solution obtained in the step (2), and placing the solution in a water bath kettle to carry out water bath heating treatment under a stirring state to obtain a dark green solution;
(4) adding porous graphene prepared by recovering graphite from waste power batteries into the dark green solution obtained in the step (3), and heating and stirring to obtain a dark black solution;
(5) heating the dark black solution obtained in the step (4) to obtain sol; drying the sol, and grinding the sol in an agate mortar to obtain dark black powder;
(6) placing the dark black powder obtained in the step (5) in a reaction container, introducing mixed gas of argon and hydrogen, heating for heating treatment, and cooling to room temperature to obtain heated powder;
(7) and (4) pressing the heated powder in the step (6) into a sheet material, then placing the sheet material in a reaction container, introducing mixed gas of argon and hydrogen, heating, cooling to room temperature, and grinding into powder to obtain the porous graphene-coated lithium vanadium phosphate.
Further, the molar ratio of the citric acid to the ammonium hydrogen phosphate in the step (1) is 1:1-2: 1; the molar volume ratio of the citric acid to the water is 0.2-0.3: 1 mol/L. Preferably, the stirring time of step (1) is 5-10 min.
Further preferably, the stirring time of step (1) is 5 min.
Preferably, the molar ratio of citric acid to ammonium hydrogen phosphate in step (1) is 1: 3.
Further, the molar ratio of the citric acid in the step (1) to the vanadium pentoxide powder in the step (2) is 1:1-2: 1.
Preferably, the molar ratio of the vanadium pentoxide to the citric acid in the step (2) is 1: 1.
The vanadium pentoxide powder should be poured slowly into the system.
Preferably, the stirring time of the step (2) is 5-10 min. Preferably, the stirring is stirring with a glass rod.
Further preferably, the stirring time of the step (2) is 5-8 min.
Further preferably, the molar ratio of the lithium carbonate in step (3) to the citric acid in step (1) is from 1:1 to 2: 1. Further, the temperature of the water bath heating treatment in the step (3) is 50-70 ℃, and the time of the water bath heating treatment is 25-35 min.
Further, according to dry weight, the mass of the porous graphene prepared by the waste power battery in the step (4) is 3-10% of that of the dark black solution; the temperature of the heating and stirring treatment is 50-70 ℃, and the time of the heating and stirring treatment is 3-4 h.
Preferably, the heating and stirring device in the step (4) is a water bath.
Preferably, the temperature of the heating and stirring treatment in the step (4) is 60 ℃.
Preferably, the method for preparing porous graphene by using the waste power batteries in the step (4) comprises the following steps:
discharging and disassembling the waste power battery to obtain a graphite negative plate; adding the graphite negative electrode sheet into water, uniformly mixing, then carrying out ultrasonic stripping treatment (ultrasonic dispersion is uniform, the time is preferably 0.5-4 h) to obtain a dispersion liquid, filtering to obtain a precipitate, and drying to obtain a graphite negative electrode material;
placing the graphite cathode material in the step I into a reaction container, sealing, vacuumizing, introducing inert gas and water vapor, heating and heating to obtain a porous graphite material;
mixing a sulfuric acid solution and a phosphoric acid solution, uniformly stirring, adding the porous graphite material and the potassium permanganate, and performing oil bath heating treatment (performing pre-oxidation treatment by an improved hummer method) under a stirring state to obtain a heated suspension;
fourthly, adding a hydrogen peroxide solution into the heated suspension obtained in the third step, uniformly dispersing the mixture by ultrasonic waves, then carrying out centrifugal treatment, removing supernate, taking precipitate, adding the precipitate into a hydrochloric acid solution, adding water, uniformly stirring the mixture to obtain a mixed solution, carrying out centrifugal washing until the pH value of the mixed solution is 6.0-7.0, and carrying out dialysis treatment to obtain a porous graphene oxide solution;
fifthly, freeze-drying the porous graphene oxide solution obtained in the step IV to obtain the dried porous graphene oxide;
further, the mass ratio of the graphite negative electrode sheet to water is 1:10-1: 50; the mass percentage concentration of the sulfuric acid solution is 95-98 wt%; the mass percentage concentration of the phosphoric acid solution is 85 wt%; the volume ratio of the sulfuric acid solution to the phosphoric acid solution is 9:1-9: 5; the mass ratio of the porous graphite material to the potassium permanganate is 1:2-1: 6; the mass volume ratio of the potassium permanganate to the sulfuric acid solution is 1:15-1:20 g/mL.
Fourthly, the mass percentage concentration of the hydrogen peroxide solution is 30 wt%; the volume ratio of the hydrogen peroxide solution to the phosphoric acid solution obtained in the third step is 1:2-1: 4; the mass percentage concentration of the hydrochloric acid solution is 35 to 38 weight percent; the volume ratio of the hydrochloric acid solution to the hydrogen peroxide solution is 10:1-20: 1; the volume ratio of the hydrochloric acid solution to the water is 2:1-2: 9.
Step two, the inert gas is argon, helium or nitrogen, and the flow rate of the inert gas is 10-200 mL/min; the flow rate of the water vapor is 0.2-1 mL/min; the rate of temperature rise is 5-20 ℃/min; the temperature of the heating treatment is 800-1000 ℃, and the time of the heating treatment is 0.5-2 h. Step four, a dialysis bag with the cut-off molecular weight of 80000-; the dialysis treatment time is 3-7 days. The freeze drying time is 48-96 h. The operation of the third step and the operation of the fourth step are carried out by adopting an improved hummer method.
The porous graphene can be prepared from waste power batteries or can be common porous graphene on the market.
The waste power batteries comprise waste lithium ion batteries with various shapes and various purposes; the waste lithium ion battery is a graphite system waste lithium ion battery; the shape of the waste lithium ion battery can be cylindrical, square or soft package; the waste lithium ion battery comprises a used lithium ion battery and does not comprise a lithium battery adopting silicon base, tin base, hard carbon and the like as negative electrode materials.
According to dry weight, the adding amount of the porous graphene accounts for 3-10% of the total mass ratio of all materials.
Further, the temperature of the heating treatment in the step (5) is 70-90 ℃, and the time of the heating treatment is 3-4 h; the drying time is 8-12 h.
Preferably, the temperature of the heat treatment in the step (5) is 75-85 ℃. The heat treatment may be performed in a water bath.
Preferably, the temperature for drying in the step (5) is 90-110 ℃. The drying may be performed in an oven.
Further preferably, the temperature of the heat treatment in the step (5) is 80 ℃.
Further preferably, the temperature of the drying in the step (5) is 100 ℃.
Preferably, the grinding time in the step (5) is 20-30 min.
Further preferably, the grinding time of step (5) is 25 min.
Further, in the mixed gas of argon and hydrogen in the step (6), the volume percentage concentration of hydrogen is 25-35%; the flow rate of the mixed gas of the argon and the hydrogen is 10-200 mL/min; the temperature of the heating treatment is 300-400 ℃, and the time of the heating treatment is 4-6 h.
Preferably, the heat treatment of step (6) is performed in a tube furnace.
Preferably, the temperature rising rate of the step (6) is 5-10 ℃/min.
Preferably, in the mixed gas of argon and hydrogen in the step (6), the volume percentage concentration of hydrogen is 30%, and the volume percentage concentration of argon is 70%.
Preferably, the temperature of the heating treatment in the step (6) is 350-400 ℃.
Further preferably, the temperature of the heat treatment in the step (6) is 350 ℃, and the time of the heat treatment is 5 h.
Preferably, the cooling time of the step (6) to the room temperature is 3 h.
Further, in the mixed gas of argon and hydrogen in the step (7), the volume percentage concentration of hydrogen is 25-35%; the flow rate of the mixed gas is 10-200 mL/min; the temperature of the heating treatment is 700-800 ℃, and the time of the heating treatment is 8-12 h.
Preferably, the grinding time in the step (7) is 20-40 min.
Further preferably, the grinding time in step (7) is 25-35 min.
Preferably, the sheet material of step (7) has a diameter of 10-20 mm.
Preferably, the tabletting instrument of step (7) is a tablet press.
Further, the reaction vessel of the heat treatment in the step (7) is a tube furnace.
Preferably, the temperature rising rate of the step (7) is 5-10 ℃/min.
Preferably, the cooling time of step (7) is 4-6 h.
Preferably, in the mixed gas of argon and hydrogen in the step (7), the concentration of argon is 70% by volume, and the concentration of hydrogen is 30% by volume.
Further preferably, the temperature of the heat treatment in the step (7) is 750 ℃.
Further preferably, the time of the heat treatment in the step (7) is 10 h.
Further preferably, the cooling time of step (7) is 5 h.
The invention provides porous graphene-coated lithium vanadium phosphate prepared by the preparation method.
Adding ammonium hydrogen phosphate and citric acid into a beaker together, and adding deionized water to form a solution; adding vanadium pentoxide and stirring; adding lithium carbonate into a beaker, placing the beaker into a water bath kettle, heating, stirring and dissolving the lithium carbonate, adding porous graphene prepared from graphite recovered from waste power batteries, heating and stirring the mixture to form black sol; putting the beaker into an oven for drying; taking out and grinding the mixture into powder, and introducing mixed gas for heating to obtain a preparation material; grinding and rolling the prepared material into sheets, and introducing mixed gas for heating to obtain the required material. The method is low in cost and high in yield, and the prepared graphene-coated lithium vanadium phosphate has high performance.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) according to the method, the porous graphene-coated lithium vanadium phosphate material prepared by recovering graphite from the waste power battery is low in cost and high in yield, and the prepared graphene-coated lithium vanadium phosphate has high performance; meanwhile, the method has wide application prospect and feasibility, can generate certain economic benefit and social benefit, can solve the problem of consumption of new carbon source materials in the coating process, and instead, the graphene prepared from the graphite recovered by the waste power battery is used for providing a carbon source, so that the materials are recycled, and the method is more environment-friendly;
(2) according to the method, the porous graphene-coated lithium vanadium phosphate material prepared by recovering graphite from the waste power battery is low in cost and high in yield, and the prepared graphene-coated lithium vanadium phosphate has high performance. The used porous graphene has hierarchical pores (micropores, mesopores and macropores) and micropores and mesopores of about 1-3nm, and after the porous graphene is coated, the pores existing in the graphene are more favorable for transferring electrons and transmitting electrolyte, and can provide more active sites, so that the cyclicity and the multiplying power of the vanadium phosphate lithium battery are improved.
Drawings
FIG. 1 is a scanning electron microscope image of lithium vanadium phosphate prepared by comparative example 1 without adding waste power batteries to recover graphite cathode materials;
fig. 2 is a scanning electron micrograph of porous graphene-coated lithium vanadium phosphate obtained in step (8) of example 1;
fig. 3 is a transmission electron micrograph of porous graphene-coated lithium vanadium phosphate obtained in step (8) of example 1;
fig. 4 is a graph comparing the cycle performance of the porous graphene-coated lithium vanadium phosphate obtained in step (8) of example 1 with that of the uncoated graphene for waste power batteries prepared in comparative example 1.
Detailed Description
The following examples are presented to further illustrate the practice of the invention, but the practice and protection of the invention is not limited thereto. It is noted that the processes described below, if not specifically described in detail, are all realizable or understandable by those skilled in the art with reference to the prior art. The reagents or apparatus used are not indicated to the manufacturer, and are considered to be conventional products available by commercial purchase.
Example 1
A porous graphene-coated lithium vanadium phosphate prepared by recovering graphite cathode materials from waste power batteries comprises the following steps:
(1) taking a 100ml beaker, putting citric acid and ammonium hydrogen phosphate into the beaker according to the molar ratio of 1:3, adding 40ml of deionized water, wherein the molar volume ratio of the citric acid to the water is 0.28: 1mol/L, continuously stirring for 5min by using a glass rod, and uniformly stirring to form a colorless transparent solution;
(2) adding vanadium pentoxide powder into the colorless transparent solution in the step (1) according to the molar ratio of the vanadium pentoxide powder to the citric acid of 1:1, continuously stirring for 5min by using a glass rod, and uniformly stirring to obtain a clear orange solution;
(3) adding the lithium carbonate and the citric acid into the clear orange solution obtained in the step (2) according to the molar ratio of 3:2, heating the solution to 60 ℃ in a water bath kettle, continuously stirring the solution for 25min by using magnetons, and uniformly stirring the solution to obtain a dark green solution;
(4) adding porous graphene prepared by recovering graphite cathode materials from waste power batteries into the dark green solution obtained in the step (3) according to 3% of the total mass of all materials (except water), continuously stirring magnetic particles at 60 ℃ for 20min, and uniformly stirring to obtain a dark black solution;
(5) heating the dark black solution obtained in the step (4) to 80 ℃ for 3h until sol is formed, placing the beaker in a drying oven, heating to 90 ℃ for drying for 8h, taking out after drying, and grinding in an agate mortar for 20min to obtain dark black powder;
(6) placing the dark black powder obtained in the step (5) in a reaction vessel, introducing a mixed gas of 70% argon and 30% hydrogen, heating to 350 ℃ at the speed of 5 ℃/min, continuously heating for 5h, cooling for 3h to room temperature, and taking out to obtain the required powder;
(7) grinding the powder obtained in the step (6) in an agate mortar for 25min, and then putting the powder on a tablet press to be pressed into a sheet shape, wherein the pressure is 12Mpa, so as to obtain a sheet-shaped material;
(8) and (3) putting the sheet material obtained in the step (7) on a quartz boat, putting the quartz boat in a tubular furnace, introducing a mixed gas of 70% of argon and 30% of hydrogen, heating to 750 ℃ at the speed of 5 ℃/min, preserving the temperature for 10h, cooling for 5h to room temperature, taking out, putting the material on an agate mortar, and grinding the material into powder to obtain the porous graphene-coated lithium vanadium phosphate.
Comparative example 1
The comparative example 1 is basically the same as the example 1, except that the porous graphene prepared by recovering the graphite negative electrode material from the waste power battery is not added in the step (4), and the rest steps and operations are the same as the example 1, so that the lithium vanadium phosphate without the waste power battery graphene is obtained.
As can be seen from fig. 1, 2, 3, and 4, in example 1, porous graphene is put in when lithium vanadium phosphate is prepared, and lithium vanadium phosphate coated with porous graphene is obtained by a sol-gel method and high-temperature treatment. Since the graphene is porous, after the graphene is coated on the lithium vanadium phosphate, more active sites are provided for the lithium vanadium phosphate, and the pores on the graphene are beneficial to the transfer of electrons and the transmission of electrolyte, so that the performance of the lithium vanadium phosphate is improved, and the cost is saved. Meanwhile, the method is more environment-friendly, has wide application prospect and feasibility, and can generate certain economic benefit and social benefit.
As can be seen from fig. 1, 2 and 3, the porous graphene-coated lithium vanadium phosphate obtained in step (8) of example 1 is clearly seen to have a coating layer compared to the material of comparative example 1.
In FIG. 4, LVP represents the lithium vanadium phosphate of the uncoated waste power battery graphene prepared in comparative example 1, and LVP @ h-rsG represents the porous graphene coated lithium vanadium phosphate prepared in example 1. As can be seen from fig. 4, compared with comparative example 1, the battery assembled by the porous graphene coated lithium vanadium phosphate prepared in example 1 has the advantages that not only the initial specific capacity is improved, but also the cycle performance of the battery is significantly improved.
Example 2
A porous graphene-coated lithium vanadium phosphate prepared by recovering graphite cathode materials from waste power batteries comprises the following steps:
(1) taking a 100ml beaker, putting citric acid and ammonium hydrogen phosphate into the beaker according to the molar ratio of 1:3, adding 50ml of deionized water, wherein the molar volume ratio of the citric acid to the water is 0.22: 1mol/L, continuously stirring for 8min by using a glass rod, and uniformly stirring to form a colorless transparent solution;
(2) adding vanadium pentoxide powder into the colorless transparent solution in the step (1) according to the molar ratio of the vanadium pentoxide powder to the citric acid of 1:1, continuously stirring for 8min by using a glass rod, and uniformly stirring to obtain a clear orange solution;
(3) adding lithium carbonate into the clear orange solution obtained in the step (2) according to the molar ratio of 3:2 to citric acid, heating the solution to 60 ℃ in a water bath kettle, continuously stirring the solution for 30min by using magnetons, and uniformly stirring the solution to obtain a dark green solution;
(4) adding oxidized porous graphene prepared from waste power batteries into the dark green solution obtained in the step (3) according to 8% of the total mass of all materials, keeping the temperature at 60 ℃, continuously stirring for 25min, and uniformly stirring to obtain a dark black solution;
(5) heating the dark black solution obtained in the step (4) to 80 ℃ for 3.5h until sol is formed, placing the beaker in a drying oven, continuously heating to 100 ℃ for drying for 10h, taking out the beaker after drying, and grinding the beaker in an agate mortar for 30min to obtain dark black powder;
(6) placing the dark black powder obtained in the step (5) in a reaction vessel, introducing a mixed gas of 70% argon and 30% hydrogen, heating to 380 ℃ at the speed of 5 ℃/min, continuously heating for 5h, cooling for 3h to room temperature, and taking out to obtain the required powder;
(7) grinding the powder obtained in the step (6) in an agate mortar for 30min, and then putting the powder on a tablet press to be pressed into a sheet shape, wherein the pressure is 12Mpa, so as to obtain a sheet-shaped material;
(8) and (3) putting the sheet material obtained in the step (7) on a quartz boat, putting the quartz boat in a tube furnace, introducing a mixed gas of 70% argon and 30% hydrogen, heating to 750 ℃ at a speed of 5 ℃/min, keeping the temperature for 10h, cooling for 5h to room temperature, taking out, putting the material on an agate mortar, and grinding for 30min to obtain the porous graphene-coated lithium vanadium phosphate.
In the porous graphene-coated lithium vanadium phosphate prepared by using graphite recovered from waste power batteries provided in embodiment 2, when preparing lithium vanadium phosphate, porous graphene is put in, and the lithium vanadium phosphate coated with porous graphene is obtained by a sol-gel method and high-temperature treatment. Since the graphene is porous, after the graphene is coated on the lithium vanadium phosphate, more active sites are provided for the lithium vanadium phosphate, and the pores are beneficial to the transfer of electrons and the transmission of electrolyte, so that the performance of the lithium vanadium phosphate is improved, and the cost is saved. Meanwhile, the method is more environment-friendly, has wide application prospect and feasibility, can generate certain economic benefit and social benefit, and can refer to fig. 2, fig. 3 and fig. 4.
Example 3
A porous graphene-coated lithium vanadium phosphate prepared by recovering graphite cathode materials from waste power batteries comprises the following steps:
(1) taking a 100ml beaker, putting citric acid and ammonium hydrogen phosphate into the beaker according to the molar ratio of 1:3, adding 55ml of deionized water, wherein the molar volume ratio of the citric acid to the water is 0.20: 1mol/L, continuously stirring for 10min by using a glass rod, and uniformly stirring to form a colorless transparent solution;
(2) adding vanadium pentoxide powder into the colorless transparent solution in the step (1) according to the molar ratio of the vanadium pentoxide powder to the citric acid of 1:1, continuously stirring for 10min by using a glass rod, and uniformly stirring to obtain a clear orange solution;
(3) adding lithium carbonate into the clear orange solution obtained in the step (2) according to the molar ratio of 3:2 to citric acid, heating the solution to 60 ℃ in a water bath kettle, continuously stirring the solution for 30min by using magnetons, and uniformly stirring the solution to obtain a dark green solution;
(4) adding oxidized porous graphene prepared from waste power batteries into the dark green solution obtained in the step (3) according to 10% of the total mass of all materials, and heating to 70 ℃ for 30min to obtain a dark black solution;
(5) heating the dark black solution obtained in the step (4) to 85 ℃ for 4h until sol is formed, placing the beaker in a drying oven, heating to 110 ℃ for drying for 12h, taking out after drying, placing the beaker in an agate mortar, and grinding for 30min to obtain dark black powder;
(6) placing the dark black powder obtained in the step (5) in a reaction vessel, introducing a mixed gas of 70% argon and 30% hydrogen, heating to 400 ℃ at a speed of 10 ℃/min, continuously heating for 6h, cooling for 3h to room temperature, and taking out to obtain the required powder;
(7) grinding the powder obtained in the step (6) in an agate mortar for 35min, and then putting the powder on a tablet press to be pressed into a sheet shape, wherein the pressure is 12Mpa, so as to obtain a sheet-shaped material;
(8) and (3) putting the sheet material obtained in the step (7) on a quartz boat, putting the quartz boat in a tube furnace, introducing a mixed gas of 70% of argon and 30% of hydrogen, heating to 800 ℃ at a speed of 10 ℃/min, keeping the temperature for 12h, cooling for 5h to room temperature, taking out, putting the material on an agate mortar, and grinding the material into powder to obtain the porous graphene-coated lithium vanadium phosphate.
In the porous graphene-coated lithium vanadium phosphate prepared by using graphite recovered from waste power batteries provided in embodiment 3, when the lithium vanadium phosphate is prepared, the porous graphene is put in, and the lithium vanadium phosphate coated with the porous graphene is obtained by a sol-gel method and high-temperature treatment. Since the graphene is porous, after the graphene is coated on the lithium vanadium phosphate, more active sites are provided for the lithium vanadium phosphate, and the pores are beneficial to the transfer of electrons and the transmission of electrolyte, so that the performance of the lithium vanadium phosphate is improved, and the cost is saved. Meanwhile, the method is more environment-friendly, has wide application prospect and feasibility, can generate certain economic benefit and social benefit, and can refer to fig. 2, fig. 3 and fig. 4.
The above examples are only preferred embodiments of the present invention, which are intended to be illustrative and not limiting, and those skilled in the art should understand that they can make various changes, substitutions and alterations without departing from the spirit and scope of the invention.

Claims (10)

1. A method for preparing porous graphene coated lithium vanadium phosphate by recovering graphite cathode materials from waste power batteries is characterized by comprising the following steps:
(1) adding citric acid and ammonium hydrogen phosphate into water, and uniformly stirring to obtain a colorless transparent solution;
(2) adding vanadium pentoxide powder into the colorless transparent solution obtained in the step (1), and uniformly stirring to obtain an orange solution;
(3) adding lithium carbonate into the orange solution obtained in the step (2), and carrying out water bath heating treatment under a stirring state to obtain a dark green solution;
(4) adding porous graphene prepared by recovering graphite from waste power batteries into the dark green solution obtained in the step (3), and heating and stirring to obtain a dark black solution;
(5) heating the dark black solution obtained in the step (4) to obtain sol; drying the sol, and grinding to obtain dark black powder;
(6) placing the dark black powder obtained in the step (5) in a reaction container, introducing mixed gas of argon and hydrogen, heating for heating treatment, and cooling to room temperature to obtain heated powder;
(7) and (4) pressing the heated powder in the step (6) into a sheet material, then placing the sheet material in a reaction container, introducing mixed gas of argon and hydrogen, heating, cooling to room temperature, and grinding into powder to obtain the porous graphene-coated lithium vanadium phosphate.
2. The method for preparing porous graphene coated lithium vanadium phosphate by using the waste power battery recycled graphite cathode material as claimed in claim 1, wherein the molar ratio of citric acid to ammonium hydrogen phosphate in the step (1) is 1:1-2: 1; the molar volume ratio of the citric acid to the water is 0.2-0.3: 1 mol/L.
3. The method for preparing porous graphene coated lithium vanadium phosphate by using the waste power battery recycled graphite anode material according to claim 1, wherein the molar ratio of the citric acid in the step (1) to the vanadium pentoxide powder in the step (2) is 1:1-2: 1.
4. The method for preparing porous graphene coated lithium vanadium phosphate by using the waste power battery recycled graphite cathode material as claimed in claim 1, wherein the molar ratio of the lithium carbonate in the step (3) to the citric acid in the step (1) is 1:1-2: 1.
5. The method for preparing porous graphene coated lithium vanadium phosphate by using the waste power battery recycled graphite cathode material according to claim 1, wherein the temperature of the water bath heating treatment in the step (3) is 50-70 ℃, and the time of the water bath heating treatment is 25-35 min.
6. The method for preparing porous graphene coated lithium vanadium phosphate by using the waste power battery recycled graphite cathode material according to claim 1, wherein the mass of the porous graphene prepared by the waste power battery in the step (4) is 3-10% of the mass of the dark black solution according to dry weight; the temperature of the heating and stirring treatment is 50-70 ℃, and the time of the heating and stirring treatment is 20-40 min.
7. The method for preparing porous graphene coated lithium vanadium phosphate by utilizing the waste power battery recycled graphite cathode material according to claim 1, wherein the heating treatment temperature in the step (5) is 70-90 ℃, and the heating treatment time is 3-4 h; the drying temperature is 90-110 ℃, and the drying time is 8-12 h.
8. The method for preparing porous graphene coated lithium vanadium phosphate by using the waste power batteries to recover the graphite cathode material according to claim 1, wherein in the mixed gas of argon and hydrogen in the step (6), the volume percentage concentration of hydrogen is 25-35%; the flow rate of the mixed gas of the argon and the hydrogen is 10-200 mL/min; the temperature of the heating treatment is 300-400 ℃, and the time of the heating treatment is 4-6 h.
9. The method for preparing porous graphene coated lithium vanadium phosphate by using the waste power batteries to recover the graphite cathode material according to claim 1, wherein in the mixed gas of argon and hydrogen in the step (7), the volume percentage concentration of hydrogen is 25-35%; the flow rate of the mixed gas of the argon and the hydrogen is 10-200 mL/min; the temperature of the heating treatment is 700-800 ℃, and the time of the heating treatment is 8-12 h.
10. A porous graphene-coated lithium vanadium phosphate prepared by the preparation method according to any one of claims 1 to 9.
CN202010590457.8A 2020-06-24 2020-06-24 Method for preparing porous graphene coated lithium vanadium phosphate by recovering graphite cathode material from waste power battery Pending CN111883747A (en)

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