CN111785970A - Double-layer carbon-coated-metal selenide composite electrode material and preparation method thereof - Google Patents

Double-layer carbon-coated-metal selenide composite electrode material and preparation method thereof Download PDF

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CN111785970A
CN111785970A CN202010688602.6A CN202010688602A CN111785970A CN 111785970 A CN111785970 A CN 111785970A CN 202010688602 A CN202010688602 A CN 202010688602A CN 111785970 A CN111785970 A CN 111785970A
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electrode material
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metal selenide
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CN111785970B (en
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段军飞
曹晨浩
吴应泷
许嘉雄
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Changsha University of Science and Technology
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/581—Chalcogenides or intercalation compounds thereof
    • 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
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention relates to a double-layer carbon-coated-metal selenide composite electrode material and a preparation method thereof. The raw materials for preparing the composite electrode material are selenium powder and phthalocyanine salt, and the adding weight ratio of the selenium powder and the phthalocyanine salt is controlled, so that the prepared composite electrode material has high cycle stability and rate capability. In the preparation process, the raw materials are ground and mixed, then two-stage stepped heating heat treatment is carried out in a tubular furnace, and simultaneously chemical vapor deposition of an organic solvent is carried out, so that the prepared metal selenide composite electrode material forms carbon-coated metal selenide with double-layer and double-function, and the prepared composite electrode material has good comprehensive performance by controlling the reaction temperature, the loading rate of the organic solvent and other process parameters in the whole reaction process. The preparation process has the advantages of simple flow, short period, easy control and convenient industrial popularization and production.

Description

Double-layer carbon-coated-metal selenide composite electrode material and preparation method thereof
Technical Field
The invention belongs to the technical field of preparation of electrode materials for lithium ion batteries, and particularly relates to a double-layer carbon-coated metal selenide composite electrode material and a preparation method thereof.
Background
In the past decades, rechargeable lithium ion batteries have received much attention as power sources for various portable electronic devices and large-scale energy storage devices. Transition metal selenide (MSe)x) The material is considered to be one of the more potential lithium ion battery cathode materials due to higher theoretical capacity and abundant sources, however, similar to other high-capacity electrode materials with conversion reaction, MSe is generated in the process of charging and dischargingxThe electrode material is cracked and pulverized due to larger volume change, and further the formation of lithium and the separation of active materials from a current collector are caused, so that the problems of poor cycle stability, poor rate performance, short service life and the like of the battery are caused, and the wide application of the battery is greatly limited.
The research finds that MSe is going to bexLimited to nanometer scale and MSexThe metal selenide composite material prepared by the prior art still has the problems of poor cycle stability and rate capability, long preparation process period and relatively high cost, and the designed metal selenide composite material has very important significance in designing a simple preparation method, is convenient for industrial production, and has high cycle stability and high rate capability.
Disclosure of Invention
The invention aims to: aiming at the technical problems of poor cycling stability and rate capability, complex preparation process and long preparation period of the metal selenide composite material in the prior art, the invention provides a double-layer carbon-coated-metal selenide composite electrode material and a preparation method thereof; the double-layer carbon-coated-metal selenide composite electrode material has the advantages of high cycle stability and rate capability, simple preparation process, short preparation period and convenience for industrial popularization.
In order to achieve the purpose, the invention adopts the technical scheme that:
a double-layer carbon-coated-metal selenide composite electrode material is of a double-layer structure, the inner layer of the composite electrode material is a composite material consisting of nitrogen-doped carbon and metal selenide, the outer layer of the composite electrode material is an amorphous carbon material, and the outer layer of the composite electrode material is coated on the outer surface of the inner layer;
the composite material consisting of the nitrogen-doped carbon and the metal selenide is prepared from selenium powder and phthalocyanine salt serving as raw materials, wherein the weight ratio of the selenium powder to the phthalocyanine salt is 0.5-2: 1; the phthalocyanine salt is one or more of cobalt phthalocyanine, copper phthalocyanine, iron phthalocyanine and nickel phthalocyanine.
The invention provides a double-layer carbon-coated-metal selenide composite electrode material, which is microscopically divided into an inner layer and an outer layer, wherein the outer layer is an amorphous carbon material and can effectively inhibit the direct contact of an active material, namely metal selenide, and an electrolyte, so that the first coulomb efficiency and the cycle performance of a lithium ion battery assembled by the composite material are improved; meanwhile, the composite electrode material is prepared by taking selenium powder and phthalocyanine salt as raw materials, and the composite electrode material has good comprehensive performance by controlling the weight ratio of the selenium powder to the phthalocyanine salt.
Further, the weight ratio of the selenium powder to the phthalocyanine salt is 1-2: 1. Through a great deal of research by the inventor, the weight ratio of the selenium powder to the phthalocyanine salt raw material directly influences the performance of the final composite electrode material, and the performance of the composite electrode material is reduced when the ratio is too large or too small, and preferably, the weight ratio of the selenium powder to the phthalocyanine salt is 1-1.8: 1.
Furthermore, in the composite material consisting of the nitrogen-doped carbon and the metal selenide, the particle size of the metal selenide is 5 nm-10 nm. When the particle size of the metal selenide composite material in the inner layer is controlled to be the nanometer size, the volume change of the material in the charging and discharging process can be effectively inhibited, and the phenomena of the formation of dead lithium and the separation of an active material from a current collector caused by the cracking and the pulverization of an electrode material are prevented.
The invention also aims to provide a preparation method of the composite electrode material.
A preparation method of a double-layer carbon-coated-metal selenide composite electrode material comprises the following steps:
step 1, mixing selenium powder and phthalocyanine salt according to a proportion, and grinding for at least 20min to obtain a precursor material;
and 2, placing the precursor material obtained in the step 1 in a tubular furnace, controlling the furnace temperature at 260-300 ℃, heating the furnace to 500-800 ℃ after 10-30 min, taking protective gas as carrier gas to load an organic solvent into the tubular furnace, reacting for 4-8 h, cooling, washing and drying to obtain the double-layer carbon-coated-metal selenide composite electrode material.
According to the preparation method of the metal selenide composite electrode material, selenium powder and phthalocyanine salt are fully mixed in a grinding mode for at least 20min, then the mixture is subjected to high-temperature heat treatment for composite reaction, meanwhile, a two-stage step heating mode is adopted in the heat treatment process, firstly, in the first heating stage, the selenium powder is melted into hot fluid and fully diffused into the inner cavity of the phthalocyanine salt, so that the raw materials can be fully fused, a foundation is laid for the subsequent second stage heat treatment effect, and on the other hand, the electrochemical performance of the composite material can be effectively improved through the first stage heat treatment;
and then, in a second heating stage, along with the chemical vapor deposition of an organic solvent, the prepared metal selenide composite electrode material forms a double-layer structure, phthalocyanine salt in the inner layer provides a metal source, a nitrogen source and a carbon source, and volatile organic solvent sediment in the outer layer provides a carbon source, so that the composite electrode material obtained after the heat treatment composite reaction process forms a double-layer carbon-coated-metal selenide composite electrode material, and the prepared composite electrode material has good comprehensive performance by controlling the reaction temperature, the loading rate of the organic solvent and other process parameters in the whole reaction process. The preparation process disclosed by the invention is simple in flow, short in period, easy to control and convenient for industrial popularization and production, and meanwhile, the whole preparation process is compounded with the green and environment-friendly concept, and the raw material source is rich.
Further, in the step 2, the organic solvent is one or more of methanol, ethanol, isopropanol and acetone.
Further, in the step 2, the shielding gas is nitrogen or argon.
Further, in the step 2, after 10min to 30min, the temperature in the furnace is increased to 600 ℃ to 800 ℃. Through a great deal of experimental research, the inventor finds that the temperature in the tube furnace is closely related to the performance of the final composite electrode material, and the performance of the composite electrode material is reduced when the temperature in the tube furnace is lower than 500 ℃ or higher than 800 ℃, and preferably, the temperature in the tube furnace is increased to 600-800 ℃.
Further, in the step 2, the volume flow of the organic solvent loaded into the tubular furnace is 50sccm to 80 sccm. The loading of the organic solvent can form a layer of amorphous carbon material on the outer layer of the prepared composite electrode material through chemical vapor deposition, and researches show that the performance of the composite electrode material also has an important relation with the loading rate of the organic solvent, when the rate is more than 80sccm, the capacity performance of the composite electrode material is obviously reduced probably because the thickness formed by the carbon layer is too large, and when the rate is less than 50sccm, the thickness formed by the carbon layer is too small, and the performance of the composite electrode material is attenuated too fast; preferably, the volume flow rate of the organic solvent loaded into the tubular furnace is 65sccm to 80 sccm.
Further, in the step 2, the temperature rise rate in the tube furnace is 3-5 ℃/min.
In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
1. the invention provides a double-layer carbon-coated-metal selenide composite electrode material, which is microscopically divided into an inner layer and an outer layer, wherein the outer layer is an amorphous carbon material and can effectively inhibit direct contact of active material metal selenide and electrolyte, the first coulomb efficiency and the cycle performance of a lithium ion battery assembled by the composite material are improved, the inner layer is nitrogen-doped carbon-coated metal selenide, the coating layer in the inner layer can further improve the conductivity, and the nitrogen-doped carbon-coated metal selenide formed in the inner layer can effectively improve the stability and the rate capability of the lithium ion battery assembled by the composite material; meanwhile, the composite electrode material is prepared by taking selenium powder and phthalocyanine salt as raw materials, the composite electrode material has good comprehensive performance by controlling the weight ratio of the selenium powder to the phthalocyanine salt, and the discharge specific capacity can reach more than 650mAh/g after four hundred cycles under the current density of 1000 mA/g.
2. According to the preparation method of the metal selenide composite electrode material, selenium powder and phthalocyanine salt are fully mixed in a grinding mode for at least 20min, then the mixture is subjected to high-temperature heat treatment for composite reaction, meanwhile, a two-stage step heating mode is adopted in the heat treatment process, firstly, in the first heating stage, the selenium powder is melted into hot fluid and fully diffused into the inner cavity of the phthalocyanine salt, so that the raw materials can be fully fused, a foundation is laid for the subsequent second stage heat treatment effect, and on the other hand, the electrochemical performance of the composite material can be effectively improved through the first stage heat treatment; and then, in a second heating stage, along with the chemical vapor deposition of an organic solvent, the prepared metal selenide composite electrode material forms a double-layer structure, phthalocyanine salt in the inner layer provides a metal source, a nitrogen source and a carbon source, and volatile organic solvent sediment in the outer layer provides a carbon source, so that the composite electrode material obtained after the heat treatment composite reaction process forms a double-layer carbon-coated-metal selenide composite electrode material, and the prepared composite electrode material has good comprehensive performance by controlling the reaction temperature, the loading rate of the organic solvent and other process parameters in the whole reaction process. The preparation process disclosed by the invention is simple in flow, short in period, easy to control and convenient for industrial popularization and production, and meanwhile, the whole preparation process is compounded with the green and environment-friendly concept, and the raw material source is rich.
Drawings
Fig. 1 is a schematic flow diagram of a two-layer carbon-coated-metal selenide composite electrode material prepared in example 1.
Fig. 2 is an XRD pattern of the double-layered carbon-coated-metal selenide composite electrode material prepared in example 1.
Fig. 3 is an SEM image of the double-layered carbon-coated-metal selenide composite electrode material prepared in example 1.
Fig. 4 is a graph of the cycling specific capacity of the double-layered carbon-coated-metal selenide composite electrode material prepared in example 1 at a current density of 100 mA/g.
FIG. 5 is a graph of the specific capacity of the double-layered carbon-coated-metal selenide composite electrode material prepared in example 1 under a current density of 1000 mA/g.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings.
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.
In the following embodiment, in the process of preparing the lithium ion button battery, the conductive agent is acetylene black, the adhesive is PVDF, and the mass ratio of the composite material, the acetylene black and the PVDF is 8: 1: 1.
example 1
The preparation flow of the C-coated-COSe/NC composite material is shown in figure 1.
(1) Accurately weighing 0.2g of cobalt phthalocyanine and 0.4g of selenium powder, placing the mixture in a mortar, grinding for 20min to uniformly mix, and transferring the mixed powder to a quartz boat.
(2) And (2) putting the quartz boat into a tubular furnace, heating to 270 ℃ at a heating rate of 4 ℃/min, heating to 650 ℃ at a heating rate of 5 ℃/min after 15min, simultaneously blowing ethanol steam into the tubular furnace through nitrogen with a constant flow of 73sccm for sufficient reaction for 5 hours, cooling to room temperature, washing the obtained black powder with deionized water, and then putting into an oven for drying to obtain the COSe/NC/C composite material.
Carrying out X-ray diffraction characterization on the obtained COSe/NC/C composite material, wherein the result is shown in figure 2; scanning electron microscopy characterization (SEM) was performed, with the results shown in fig. 3; the prepared COSe/NC/C composite material is prepared into a button battery, the performance of the button battery is tested by a battery testing system, the first discharge specific capacity of the button battery reaches 1238mAh/g under the current density of 100mA/g, and 765mAh/g is obtained after two hundred cycles. The specific capacity of the catalyst at a current density of 100mA/g is shown in FIG. 4; under the current density of 1000mA/g, the first discharge specific capacity reaches 1251mAh/g, and 530mAh/g is obtained after four hundred cycles. The specific capacity at 1000mA/g current density is shown in FIG. 5.
The metal selenide prepared in the example 1 is made into the battery with the same model, and the performance test is carried out at the high temperature of 55 ℃, and the test shows that the capacity of the battery still has 458mAg/h after the battery is cycled for one hundred times under the current density of 1000 mA/g. Exhibits good high temperature performance.
Example 2
(1) 1.0g of iron phthalocyanine and 1.4g of selenium powder are accurately weighed and placed in a mortar, and the mixture is ground for 22min to be uniformly mixed, and then the mixed powder is transferred to a quartz boat.
(2) And (2) putting the quartz boat into a tubular furnace, heating to 280 ℃ at a heating rate of 5 ℃/min, heating to 800 ℃ at a heating rate of 5 ℃/min after 20min, simultaneously blowing ethanol steam into the tubular furnace through nitrogen with a constant flow of 75sccm for sufficient reaction for 4.5 hours, cooling to room temperature, washing the obtained black powder with deionized water, and then putting into an oven for drying to obtain the double-layer carbon-coated-metal selenide composite electrode material.
The prepared double-layer carbon-coated-metal selenide composite electrode material is prepared into a button battery, the performance of the button battery is tested by a battery testing system, and the specific discharge capacity of the button battery reaches 621mAh/g after four hundred cycles under the current density of 1000 mA/g.
Example 3
(1) 1.0g of nickel phthalocyanine and 1.5g of selenium powder are accurately weighed and placed in a mortar, and the mixture is ground for 30min to be uniformly mixed, and then the mixed powder is transferred to a quartz boat.
(2) And (2) putting the quartz boat into a tubular furnace, heating to 300 ℃ at a heating rate of 3 ℃/min, heating to 750 ℃ at a heating rate of 4 ℃/min after 20min, simultaneously blowing ethanol steam into the tubular furnace through nitrogen with a constant flow of 78sccm for sufficient reaction for 5 hours, cooling to room temperature, washing the obtained black powder with deionized water, and then putting into an oven for drying to obtain the double-layer carbon-coated-metal selenide composite electrode material.
The prepared double-layer carbon-coated-metal selenide composite electrode material is prepared into a button battery, the performance of the button battery is tested by a battery testing system, and the specific discharge capacity of the button battery reaches 678mAh/g after four hundred cycles under the current density of 1000 mA/g.
Example 4
(1) 1.0g of copper phthalocyanine and 1.3g of selenium powder are accurately weighed and placed in a mortar, and the mixture is ground for 25min to be uniformly mixed, and then the mixed powder is transferred to a quartz boat.
(2) Putting a quartz boat into a tubular furnace, heating to 2900 ℃ at the heating rate of 3 ℃/min, heating to 700 ℃ at the heating rate of 4 ℃/min after 20min, simultaneously blowing ethanol steam into the tubular furnace through nitrogen with the constant flow of 80sccm for full reaction for 5 hours, cooling to room temperature, washing the obtained black powder with deionized water, and then putting into an oven for drying to obtain the double-layer carbon-coated-metal selenide composite electrode material.
The prepared double-layer carbon-coated-metal selenide composite electrode material is prepared into a button battery, the performance of the button battery is tested by a battery testing system, and the discharge specific capacity reaches 654mAh/g after four hundred cycles under the current density of 1000 mA/g.
Examples 5 to 13
Examples 5 to 13 have performed a series of research searches on the influence of the weight ratio of the selenium powder to the phthalocyanine salt on the performance of the final composite electrode material, in which examples 5 to 13 only change the weight ratio of the selenium powder to the phthalocyanine salt compared to example 1, other experimental procedures and process parameters are the same as example 1, and the total mass of the selenium powder and the phthalocyanine salt in examples 5 to 13 is the same as example 1, and is 0.6g, and the electrochemical performance test of the composite electrode material prepared in examples 5 to 13 is performed, and the first discharge specific capacity and the discharge specific capacity after four hundred cycles are recorded at a current density of 1000mA/g, and the recording results are shown in table 1.
Table 1 electrochemical performance test results of composite electrode materials
Figure BDA0002588512960000081
Figure BDA0002588512960000091
From the test results in table 1, through a great deal of research by the inventors, it is found that the weight ratio of the selenium powder to the phthalocyanine salt raw material directly affects the performance of the final composite electrode material, the performance of the composite electrode material is reduced when the ratio is too large and too small, the composite electrode material prepared under the synergistic effect of the proper ratio of the selenium powder to the phthalocyanine salt can only show excellent electrochemical performance, and when the weight ratio of the selenium powder to the phthalocyanine salt reaches 1.5:1, the prepared composite electrode material can have a specific discharge capacity of 635mAh/g after four hundred cycles under a current density of 1000mA/g, and shows good cycle performance and rate performance. Preferably, the weight ratio of the selenium powder to the phthalocyanine salt is 1-1.8: 1.
Examples 14 to 20
Examples 14 to 20 were a series of studies and researches on the influence of the temperature in the tube furnace on the performance of the final composite electrode material, in examples 14 to 20, compared with example 1, only the temperature in the tube furnace was changed, other experimental procedures, raw material ratios and process parameters were the same as those in example 1, the temperature set in the tube furnace in examples 14 to 20 was as shown in table 2, the electrochemical performance of the composite electrode material prepared in examples 14 to 20 was tested, the first discharge specific capacity and the discharge specific capacity after four hundred cycles at a current density of 1000mA/g were recorded, and the results were as shown in table 2.
Table 2 electrochemical performance test results of the composite electrode material
Figure BDA0002588512960000092
Figure BDA0002588512960000101
The test results in table 2 show that the temperature in the tube furnace is closely related to the performance of the final composite electrode material, the performance of the composite electrode material is reduced when the temperature in the tube furnace is lower than 500 ℃ or higher than 800 ℃, and the prepared composite electrode material has a specific discharge capacity of 568mAh/g after four hundred cycles at a current density of 1000mA/g and shows good cycle performance and rate performance when the temperature is 700 ℃. Preferably, the temperature in the tube furnace is 600-700 ℃.
Examples 21 to 27
Examples 21 to 27 were a series of studies and researches on the influence of the volume flow of the organic solvent loaded into the tube furnace on the performance of the final composite electrode material, in which examples 21 to 27 only changed the volume flow of the organic solvent loaded into the tube furnace compared to example 1, other experimental procedures, raw material ratios and process parameters were the same as in example 1, the volume flow of the organic solvent loaded into the tube furnace in examples 21 to 27 is shown in table 3, electrochemical performance tests were performed on the composite electrode materials prepared in examples 21 to 27, the first discharge specific capacity and the discharge specific capacity after four hundred cycles at a current density of 1000mA/g were recorded, and the results are shown in table 3.
TABLE 3 electrochemical test results of composite electrode materials
Figure BDA0002588512960000102
Figure BDA0002588512960000111
The loading of the organic solvent can form a layer of amorphous carbon material on the outer layer of the prepared composite electrode material through chemical vapor deposition, and researches show that the performance of the composite electrode material also has an important relation with the loading rate of the organic solvent, when the rate is more than 80sccm, the capacity performance of the composite electrode material is obviously reduced probably because the thickness formed by the carbon layer is too large, and when the rate is less than 50sccm, the thickness formed by the carbon layer is too small, and the performance of the composite electrode material is attenuated too fast; preferably, the volume flow rate of the organic solvent loaded into the tubular furnace is 65sccm to 80 sccm.
Comparative example 1
(1) Accurately weighing 0.2g of cobalt phthalocyanine and 0.4g of selenium powder, placing the mixture in a mortar, grinding for 20min to uniformly mix, and transferring the mixed powder to a quartz boat.
(2) And (3) putting the quartz boat into a tube furnace, heating to 650 ℃ at the heating rate of 5 ℃/min, fully reacting for 5 hours by using nitrogen with the constant flow of 73sccm, cooling to room temperature, washing the obtained black powder with deionized water, and drying in an oven to obtain the double-layer carbon-coated-metal selenide composite electrode material. The obtained double-layer carbon-coated-metal selenide composite electrode material is made into button batteries with the same model, and the performance of the button batteries is tested by a battery testing system with the same model. Under the current density of 1000mA/g, the discharge specific capacity of the material after four hundred cycles is 334 mAh/g.
Comparative example 1 only introduces shielding gas and does not load organic solvent into the tube furnace, and the outer surface of the double-layer carbon-coated-metal selenide composite electrode material is not coated with amorphous carbon material, so that the cycle performance and rate capability of the finally prepared composite electrode material are greatly reduced.
Comparative example 2
(1) Accurately weighing 0.4g of cobalt phthalocyanine, placing the cobalt phthalocyanine in a mortar, grinding for 20min to uniformly mix, and transferring the mixed powder to a quartz boat.
(2) And (2) putting the quartz boat into a tubular furnace, heating to 650 ℃ at the heating rate of 5 ℃/min, simultaneously blowing ethanol steam into the tubular furnace through nitrogen with the constant flow of 80sccm for sufficient reaction for 4-5 hours, cooling to room temperature, washing the obtained black powder with deionized water, and then putting the black powder into an oven for drying to obtain the NC composite material.
And (4) preparing the prepared NC composite material into button batteries with the same model, and testing by using a battery testing system with the same model. Under the current density of 1000mAh/g, the discharge specific capacity of the lithium ion battery is 325mAh/g after four hundred cycles.
Comparative example 3
(1) Accurately weighing 0.2g of cobalt phthalocyanine and 0.4g of selenium powder, placing the mixture in a mortar, grinding for 10min to uniformly mix the mixture, and transferring the mixed powder to a quartz boat.
(2) And (2) putting the quartz boat into a tubular furnace, heating to 650 ℃ at the heating rate of 5 ℃/min, simultaneously blowing ethanol steam into the tubular furnace through nitrogen with the constant flow of 73sccm for full reaction for 5 hours, cooling to room temperature, washing the obtained black powder with deionized water, and then putting the black powder into an oven for drying to obtain the COSe/NC/C composite material.
The prepared COSe/NC/C composite material is prepared into a button battery, the performance of the button battery is tested by a battery testing system, and the specific discharge capacity of the button battery is 370mAh/g after four hundred cycles under the current density of 1000 mA/g. Researches find that the raw material grinding time is too short, the selenium powder and the phthalocyanine salt cannot be fully mixed, and the electrochemical performance of the finally prepared composite electrode material is reduced.
Comparative example 4
(1) Accurately weighing 0.2g of cobalt phthalocyanine and 0.4g of selenium powder, placing the mixture in a mortar, grinding for 20min to uniformly mix, and transferring the mixed powder to a quartz boat.
(2) And (2) putting the quartz boat into a tubular furnace, heating to 650 ℃ at the heating rate of 5 ℃/min, simultaneously blowing ethanol steam into the tubular furnace through nitrogen with the constant flow of 73sccm for full reaction for 5 hours, cooling to room temperature, washing the obtained black powder with deionized water, and then putting the black powder into an oven for drying to obtain the COSe/NC/C composite material. Under the current density of 1000mA/g, the first discharge specific capacity reaches 1151mAh/g, and 413mAh/g is obtained after four hundred cycles.
The preparation process of comparative example 4 eliminates the first-stage heating heat treatment process compared with example 1, and directly heats the temperature in the tube furnace to 650 ℃ to perform the chemical vapor deposition reaction of the organic solvent, so that the rate and the cycle stability of the composite material are reduced compared with the composite material prepared by the two-stage heating method in example 1.
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. The double-layer carbon-coated metal selenide composite electrode material is characterized in that the composite electrode material is of a double-layer structure, the inner layer of the composite electrode material is a composite material consisting of nitrogen-doped carbon and metal selenide, the outer layer of the composite electrode material is an amorphous carbon material, and the outer layer of the composite electrode material is coated on the outer surface of the inner layer;
the composite material consisting of the nitrogen-doped carbon and the metal selenide is prepared from selenium powder and phthalocyanine salt serving as raw materials, wherein the weight ratio of the selenium powder to the phthalocyanine salt is 0.5-2: 1; the phthalocyanine salt is one or more of cobalt phthalocyanine, copper phthalocyanine, iron phthalocyanine and nickel phthalocyanine.
2. The double-layer carbon-coated-metal selenide composite electrode material according to claim 1, wherein the weight ratio of the selenium powder to the phthalocyanine salt is 1-2: 1.
3. The double-layer carbon-coated metal selenide composite electrode material according to claim 2, wherein the weight ratio of the selenium powder to the phthalocyanine salt is 1-1.8: 1.
4. The double-layered carbon-coated-metal selenide composite electrode material according to claim 1, wherein the metal selenide in the composite material consisting of the nitrogen-doped carbon and the metal selenide has a particle size of 5nm to 10 nm.
5. A method for preparing the double-layer carbon-coated-metal selenide composite electrode material as claimed in any one of claims 1 to 4, comprising the steps of:
step 1, mixing selenium powder and phthalocyanine salt according to a proportion, and grinding for at least 20min to obtain a precursor material;
and 2, placing the precursor material obtained in the step 1 in a tubular furnace, controlling the furnace temperature at 260-300 ℃, heating the furnace to 500-800 ℃ after 10-30 min, taking protective gas as carrier gas to load an organic solvent into the tubular furnace, reacting for 4-8 h, cooling, washing and drying to obtain the double-layer carbon-coated-metal selenide composite electrode material.
6. The method for preparing a double-layered carbon-coated-metal selenide composite electrode material according to claim 5, wherein in the step 2, after 10-30 min, the temperature in the furnace is raised to 600-800 ℃.
7. The method for preparing a double-layered carbon-coated-metal selenide composite electrode material according to claim 5, wherein in the step 2, the volume flow of the organic solvent loaded into the tubular furnace is 50sccm to 80 sccm.
8. The method for preparing a double-layered carbon-coated-metal selenide composite electrode material according to claim 7, wherein in the step 2, the volume flow of the organic solvent loaded into the tubular furnace is 65sccm to 80 sccm.
9. The method for preparing a double-layered carbon-coated-metal selenide composite electrode material according to claim 5, wherein in the step 2, the temperature rise rate in the tube furnace is 3-5 ℃/min.
10. The method for preparing the double-layered carbon-coated-metal selenide composite electrode material according to claim 5, wherein in the step 2, the organic solvent is one or more of methanol, ethanol, isopropanol and acetone; the shielding gas is nitrogen or argon.
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