CN114348989A - Carbon-based negative electrode material, and preparation method and application thereof - Google Patents
Carbon-based negative electrode material, and preparation method and application thereof Download PDFInfo
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- CN114348989A CN114348989A CN202210266485.3A CN202210266485A CN114348989A CN 114348989 A CN114348989 A CN 114348989A CN 202210266485 A CN202210266485 A CN 202210266485A CN 114348989 A CN114348989 A CN 114348989A
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- C01B32/00—Carbon; Compounds thereof
- C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
- H01G11/32—Carbon-based
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- 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
- H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
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- H—ELECTRICITY
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- 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
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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- H—ELECTRICITY
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- 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
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- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/13—Energy storage using capacitors
Abstract
The invention discloses a carbon-based negative electrode material, and a preparation method and application thereof, and belongs to the technical field of carbon materials. The preparation method of the carbon-based negative electrode material comprises the following steps: step 1: respectively weighing the nitrogenous resin and the ingredients according to the mass ratio of 100 (0-20), and ball-milling the nitrogenous resin and the ingredients into powder to obtain a powdery condensate; step 2: pressing and molding the powdery condensate to obtain a resin pressed body; and step 3: putting the resin pressed body into a pressure-resistant high-temperature furnace, vacuumizing, replacing air in the pressure-resistant high-temperature furnace with inert gas for at least 1 time, and then heating for the first time under the protection of the inert gas and keeping the pressure in the pressure-resistant high-temperature furnace; and 4, step 4: and adjusting and maintaining the pressure in the pressure-resistant high-temperature furnace by using inert gas, heating for the second time, and naturally cooling to room temperature to obtain the carbon-based negative electrode material. The invention also discloses a carbon-based negative electrode material and application thereof. By adopting the method, the carbon-based negative electrode material with low specific surface area and high first coulombic efficiency can be prepared.
Description
Technical Field
The invention relates to a carbon-based negative electrode material, a preparation method and application thereof, and belongs to the technical field of carbon materials.
Background
At present, fossil fuels are still the main energy source and the supply is increasingly tense, the development of renewable energy sources such as solar energy, wind energy, tidal energy and the like is more and more important, and the energy supply proportion is higher and higher. However, due to the restriction of factors such as weather, place and time, the renewable energy has high volatility, and the large-scale application of the renewable energy is greatly limited. In order to solve this problem, large-scale energy storage technology has become an important research field. Among them, secondary batteries such as supercapacitors and lithium ion batteries are one of the selection paths for large-scale electricity storage.
Lithium ion batteries have the advantages of high operating voltage, high capacity, low self-discharge, good power performance, long cycle life, and the like, and have been widely used in various electronic products. Sodium and potassium elements have physicochemical properties similar to lithium, and sodium ion batteries and potassium ion batteries are also energy storage battery systems with great development potential, and more research and development are carried out recently.
Most of electrode materials commonly used in the super capacitor are activated carbon, the activated carbon has the characteristics of developed pores, high specific surface area, high pore volume, adjustable pore size in a certain range and the like, and can electrochemically adsorb positive ions and negative ions so as to store energy. However, activated carbon tends to produce a surface solid electrolyte membrane and consume lithium ions, sodium ions, and potassium ions when used as a negative electrode of lithium ion, sodium ion, and potassium ion batteries, mainly because of its high specific surface area and many active sites. The graphite can efficiently store lithium ions and becomes a negative electrode of a common lithium ion battery, but the lithium intercalation potential of the graphite material is close to the electroplating lithium potential, so that the graphite material has higher potential safety hazard, particularly during low-temperature charging. Compared with graphite, the hard carbon and the soft carbon have larger interlayer spacing, disordered structure and higher reversible specific capacity, particularly the lithium intercalation potential is higher than that of a graphite material, and the research on the negative electrode direction of lithium ion, sodium ion and potassium ion batteries is increasing day by day. However, the hard carbon and soft carbon materials still have the problems of low first coulombic efficiency, poor rate performance and the like when being used as the cathode materials of lithium ion batteries, sodium ion batteries and potassium ion batteries. The traditional hard carbon material precursor mainly comprises polymers such as saccharides, furan resin, phenolic resin and the like, and the cost for producing hard carbon is high due to the high price of the precursor materials.
In order to solve the problems of low first coulombic efficiency of hard carbon and soft carbon materials, many researches have been made, such as attempts to improve the problem of low first coulombic efficiency by coating the soft carbon with hard carbon, coating the hard carbon with soft carbon, and the like, but the reversible capacity and the cycling stability of the negative electrode material are generally influenced. Researchers prepare spherical hard carbon materials with regular shapes by a method of preparing hard carbon by hydrothermal sucrose and coating soft carbon at high temperature, the reversible capacity of the spherical hard carbon materials is 300mAh/g, and the first coulombic efficiency reaches more than 83 percent, but the method is complex in preparation process, high in cost and not suitable for large-scale production and application. Researchers also carry out high-temperature co-cracking on the hard carbon precursor and the soft carbon precursor to prepare hard carbon, and when the obtained hard carbon material is used as a negative electrode material of a sodium ion battery, the reversible capacity is only 250 mAh/g. The invention patent 2017101635284 in China adopts a multi-step pyrolysis and coating method, and the carbon cathode material of the raw materials such as phenolic resin and the like is prepared by coating hard carbon with soft carbon, so that the first coulomb efficiency is improved, but the pyrolysis is carried out for many times, the highest temperature reaches 1600 ℃, the preparation process is complex, and the cost is higher.
In view of this, it is necessary to provide a preparation method and application of a new carbon-based anode material to solve the deficiencies of the prior art.
Disclosure of Invention
The invention aims to provide a preparation method of a carbon-based negative electrode material.
The technical scheme for solving the technical problems is as follows: a preparation method of a carbon-based negative electrode material comprises the following steps:
step 1: respectively weighing the nitrogenous resin and the ingredients according to the mass ratio of 100 (0-20), and ball-milling the nitrogenous resin and the ingredients into powder to obtain a powdery condensate;
step 2: pressing and molding the powdery cured substance obtained in the step 1 to obtain a resin pressed body;
and step 3: putting the resin pressed body obtained in the step 2 into a pressure-resistant high-temperature furnace, vacuumizing, replacing air in the pressure-resistant high-temperature furnace with inert gas for at least 1 time, and then heating for the first time under the protection of the inert gas and keeping the pressure in the pressure-resistant high-temperature furnace to be 0.5-7 MPa;
and 4, step 4: adjusting and maintaining the pressure in the pressure-resistant high-temperature furnace to be 0.1-2 MPa by using inert gas, heating for the second time, and naturally cooling to room temperature to obtain the carbon-based negative electrode material.
The principle of the invention is as follows:
in step 1 of the invention, the nitrogenous resin, the ingredients and the like are mixed and ground into powder to obtain a powdery condensate.
In step 2 of the invention, the powdery solidified substance is pressed into a required shape, so that the powdery solidified substance is bonded and molded under the action of pressure and keeps a plurality of pores.
In step 3 of the invention, the resin pressed body is put into a pressure-resistant high-temperature furnace, and the air in the pressure-resistant high-temperature furnace is replaced by inert gas in modes of vacuumizing, injecting inert gas and the like, so as to ensure that the resin pressed body cannot be oxidized by air when thermally decomposed at 320-450 ℃, namely, the process of preoxidation at 200-450 ℃ when carbonized such as polyacrylonitrile fiber and the like is avoided; in the pre-oxidation process, oxygen-containing functional groups and the like are introduced, so that the first efficiency of the carbon-based negative electrode material is negatively affected, and the electronic conductivity of the finally obtained carbon-based negative electrode material is also affected. When the resin pressed body is thermally decomposed at 320-450 ℃, softening and melting are carried out, and pyrolysis gas is separated out along with the softening and melting, for example, polyacrylonitrile resin is pyrolyzed, gas decomposition products such as ammonia, hydrogen cyanide, methane and acrylonitrile are separated out, nitrogen-containing carbon residue solids are remained, and the nitrogen-containing carbon residue solids are foamed by the pyrolysis gas decomposition products under the condition of keeping the pressure resistance in a high-temperature furnace, so that porous solids with a plurality of macropores are formed and solidified. The pressure-resistant high-temperature furnace can be purchased commercially, for example, from the Federation Crystal Material technology Co., Ltd., and is a vertical high-temperature high-pressure tube furnace (OTF-1200X-II-HPV).
In the step 4 of the invention, the pressure in the pressure-resistant high-temperature furnace is properly reduced, the temperature is continuously raised to reach the carbonization temperature, the nitrogen-containing carbon residue solid is continuously decomposed, and the decomposed gas of the nitrogen-containing carbon residue solid is easily discharged out of pores and does not generate a plurality of micropores because the internal pressure is lower, the temperature raising speed is lower and the total amount of the pyrolysis gas is reduced (most of the pyrolysis gas is generated from 320 ℃ to 450 ℃), so that the specific surface area of the obtained carbon-based negative electrode material is low. Meanwhile, stress and the like are generated in the nitrogen-containing carbon residue solid due to the action force of internal pressure change, the discharge of decomposed gas from pores and the like, and the nitrogen-containing carbon residue solid is easy to break into small particles and is convenient to use as an electrode powdery active material. As the carbonization temperature is increased, the carbonization time is increased, and the like, the nitrogen element is partially volatilized, part of the nitrogen element and the carbon element form a conjugated cyclic structure, and a short-range ordered amorphous carbon structure is formed.
In conclusion, the carbon-based negative electrode material with low specific surface area and high initial coulombic efficiency is prepared by using nitrogen-containing resin to prepare the nitrogen-containing carbon material through inert gas protection foaming and carbonization. The whole preparation process strictly avoids the high-temperature effect of oxygen on the preparation of the carbon-based negative electrode material, retains the conjugated cyclization structure formed by nitrogen elements and carbon elements, is favorable for reducing the consumption of lithium ions caused by more solid electrolytes formed during lithium intercalation, and improves the initial coulomb efficiency; the conjugated cyclized nitrogen element has large electronegativity and is more hydrophilic to lithium ions, sodium ions and potassium ions, and the specific capacity of the lithium ions, the sodium ions and the potassium ions is favorably improved.
The preparation method of the carbon-based negative electrode material has the beneficial effects that:
1. by adopting the method, the carbon-based negative electrode material with low specific surface area and high first coulombic efficiency can be prepared.
2. The preparation method is simple, easy to operate, low in cost, wide in market prospect and suitable for large-scale popularization and application.
On the basis of the technical scheme, the invention can be further improved as follows.
Further, in step 1, the nitrogen-containing resin is any one or more of polyacrylonitrile resin, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, polyimide resin, polyurethane, and phthalonitrile resin.
The adoption of the further beneficial effects is as follows: the nitrogen source selected in the invention is a nitrogen-containing polymer instead of a nitrogen-containing micromolecular compound, and the main reason is that polyacrylonitrile resin, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, polyimide resin, polyurethane and phthalonitrile resin all contain polymerized nitrogen elements, so that not only can the carbon elements contained in the nitrogen source be carbonized into carbon materials and form a graphite-like structure, namely a short-range ordered amorphous carbon structure, but also part of nitrogen of the polymerized nitrogen elements can participate in the formation of the graphite-like structure, namely the nitrogen elements and the carbon elements form a conjugated cyclization structure and form the short-range ordered amorphous carbon structure during carbonization and decomposition, thereby improving the nitrogen content of the nitrogen-doped carbon-based negative electrode material and changing the surface property of the short-range ordered amorphous carbon structure. If the nitrogenous micromolecular compound is selected, most of the nitrogenous micromolecular compound is decomposed and gasified by heat during high-temperature carbonization, the residual quantity of carbon and nitrogen elements is extremely small and uncontrollable, and the method is not suitable for industrial development.
Further, the polyacrylonitrile resin has a weight average molecular weight of 50000-250000.
The further beneficial effects of the adoption are as follows: polyacrylonitrile is obtained by free radical polymerization of acrylonitrile monomer. The polyacrylonitrile resin adopting the parameters has better technical effect.
The polyacrylonitrile resin can be purchased from the market, such as the acrylonitrile resin can be purchased from the Aladdin, and the specification is P303198.
Furthermore, in the styrene-acrylonitrile copolymer, the weight percentages of styrene and acrylonitrile are 65-80% and 35-20%, respectively.
The further beneficial effects of the adoption are as follows: styrene-acrylonitrile resin (AS) is a general-purpose styrene resin, can be directly injected into plastic products, and can also be used AS a raw material of acrylonitrile-butadiene-styrene copolymer (ABS).
The styrene-acrylonitrile copolymer adopting the parameters has better technical effect.
The styrene-acrylonitrile copolymers described above are commercially available, for example from the merck biosciences official website, specification 182869.
Furthermore, in the acrylonitrile-butadiene-styrene copolymer, the mass percentage of butadiene is 5-50%.
The further beneficial effects of the adoption are as follows: acrylonitrile-butadiene-styrene copolymer (ABS) is copolymerized from three monomer components of acrylonitrile (a) -butadiene (B) -styrene (S), and is a two-phase structure having both a rubber dispersed phase and a matrix resin continuous phase, in which acrylonitrile provides chemical resistance and impact resistance, butadiene provides toughness and impact resistance, and styrene provides rigidity and easy processability.
The acrylonitrile-butadiene-styrene copolymer with the parameters has good toughness and impact resistance.
The above-mentioned acrylonitrile-butadiene-styrene copolymers are commercially available, for example from Pasteur, Germany, under the specification TERLURAN ABS KR2803G 3.
Furthermore, the density of the polyimide resin is more than or equal to 1.4g/cm3。
The further beneficial effects of the adoption are as follows: the polyimide resin adopting the parameters has better technical effect.
The polyimide resin can be purchased commercially, for example, from Shanghai Yegao Kogyo Co., Ltd, with specification P84 UHT.
Further, in the step 1, the ingredient is any one or a mixture of more than two of glucose, sucrose and starch.
Further, in step 1, the ingredients are mesophase pitch and/or needle coke.
Further, in step 1, the ingredient is any one or a mixture of two or more of polyvinyl alcohol, polyvinyl butyral, polyacrylic acid and carboxymethyl cellulose.
Further, in the step 1, the particle size of the powdery condensate is less than or equal to 180 mu m.
Further, in the step 2, the shape of the press forming is any one of a circle, an ellipse, a polygon and a rectangle, and the thickness is 0.8mm-10 mm.
The adoption of the further beneficial effects is as follows: in practical application, customers can make various shapes according to actual requirements.
Further, in the step 3 and the step 4, the inert gas is any one or more than two of nitrogen, helium and argon.
The adoption of the further beneficial effects is as follows: the inert gas is used for replacing air in a pressure-resistant high-temperature furnace, and is used for ensuring that a resin pressed body cannot be oxidized by air when thermally decomposed at 320-450 ℃, namely, the process of preoxidation at 200-450 ℃ when carbonized such as polyacrylonitrile fiber is avoided.
Further, in step 3, the first heating refers to heating to 320-450 ℃ at a rate of 5-20 ℃/min and keeping the temperature for 30-180 min.
The adoption of the further beneficial effects is as follows: the powdery solidified material formed by pressing is partially melted and thermally decomposed in this temperature range, gas is generated and foaming is caused, and the internal pressure is increased; the heating rate and the constant temperature can adjust the thermal decomposition rate, and the discharge of pyrolysis gas can be blocked by pressurizing inert gas and maintaining the internal pressure, so that a solidified body containing macropores is formed.
Furthermore, the first heating refers to heating to 350-430 ℃ at a rate of 10-15 ℃/min and keeping the temperature for 30-180 min.
The further beneficial effects of the adoption are as follows: by adopting the parameters, the thermal decomposition speed can be adjusted, and the pyrolysis gas can be blocked to form a solidified body containing macropores.
Further, in the step 3, the pressure in the pressure-resistant high-temperature furnace is 2MPa-7 MPa.
Further, in the step 4, the temperature is raised to 750-1100 ℃ at the rate of 1-10 ℃/min for the second time, and the second time is carbonized for 30-180 min at constant temperature.
Furthermore, the second heating is carried out at the speed of 1-8 ℃/min until the temperature reaches 780-1050 ℃, and the second heating is carbonized at constant temperature for 30-180 min.
Further, in the step 4, the pressure in the pressure-resistant high-temperature furnace is 0.5MPa-2 MPa.
The second objective of the present invention is to provide a carbon-based negative electrode material.
The technical scheme for solving the technical problems is as follows: the carbon-based negative electrode material prepared by the preparation method.
The carbon-based negative electrode material has the beneficial effects that:
the carbon-based negative electrode material has a low specific surface area (2 m)2/g-15m2(g), high first coulombic efficiency>80%) of the product.
The third purpose of the invention is to provide the application of the carbon-based negative electrode material prepared by the preparation method.
The technical scheme for solving the technical problems is as follows: the carbon-based negative electrode material prepared by the preparation method is applied to lithium ion batteries, sodium ion batteries or super capacitors.
The application of the carbon-based negative electrode material has the beneficial effects that:
the carbon-based negative electrode material can be used in the fields of lithium ion batteries, sodium ion batteries or super capacitors, has a wide market prospect, and is suitable for large-scale popularization and application.
Drawings
FIG. 1 is a scanning electron microscope photograph of a carbon-based negative electrode material prepared in example 1 of the present invention;
FIG. 2 is a thermogravimetric curve of polyacrylonitrile resin when polyacrylonitrile resin is used as the nitrogen-containing resin in example 1 of the present invention;
fig. 3 is an X-ray diffraction pattern of the carbon-based negative electrode material prepared in example 1 of the present invention.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.
Example 1
The preparation method of the carbon-based anode material of the embodiment includes the following steps:
step 1: weighing polyacrylonitrile resin as nitrogen-containing resin, and ball-milling to obtain powdery condensate with particle size less than or equal to 180 μm from Mitsui chemical corporation.
Step 2: pressing the powdery condensate obtained in the step 1 into a circle with the diameter of 50mm and the thickness of 2mm to obtain a resin pressed body.
And step 3: and (3) putting the resin pressed body obtained in the step (2) into a pressure-resistant high-temperature furnace (the inner diameter is slightly larger than 50 mm), filling the volume of the pressure-resistant high-temperature furnace is about 2/3 times, vacuumizing, replacing air in the pressure-resistant high-temperature furnace with nitrogen for at least 2 times, heating to 350 ℃ for the first time at a speed of 15 ℃/min under the protection of nitrogen, keeping the temperature for 180min, and keeping the pressure in the pressure-resistant high-temperature furnace at 0.5 MPa.
And 4, step 4: and adjusting and maintaining the pressure in the pressure-resistant high-temperature furnace to be 2MPa by using nitrogen, raising the temperature to 1100 ℃ for the second time at the speed of 10 ℃/min, carbonizing at the constant temperature for 30min, and naturally cooling to room temperature to obtain the carbon-based negative electrode material.
Fig. 1 is a scanning electron microscope photograph of the carbon-based negative electrode material prepared in this example after being crushed into powder, and it can be seen that the material has an irregular particle shape and an average particle size of about 20 μm.
Fig. 2 shows a thermogravimetric curve of polyacrylonitrile resin in nitrogen atmosphere, and it can be known from the thermogravimetric curve that polyacrylonitrile resin loses weight by about 20% at about 300-450 ℃, and at this time, ammonia gas, hydrocyanic acid gas, methane, acrylonitrile and other gases are generated by melting and pyrolysis, and in the temperature section, the gases and factors such as furnace internal pressure and the like cause the polyacrylonitrile resin to pyrolyze to form nitrogen-containing carbon residue solids with a large number of macropores. The thermal weight loss curve of 450-900 ℃ shows that the polyacrylonitrile resin is continuously pyrolyzed and the weight loss becomes gentle, and the total weight loss of the polyacrylonitrile resin is about 45% when the temperature reaches 900 ℃. Polyacrylonitrile resin melts at about 300 c to 450 c and adheres to the walls of the container, and if the fibers lose their shape, it is common to use air oxidation to stabilize the powder or fibers in shape (so-called pre-oxidation or stabilization). The experiment of the application shows that the initial coulomb efficiency of the final material is greatly reduced when the final material is used for the cathode of the battery due to the pre-oxidation and other treatments.
FIG. 3 is an X-ray diffraction pattern of the carbon-based anode material prepared in this example, and two relatively broad diffraction peaks exist near about 22 ° and 43 ° corresponding to the (002) and (100) crystal planes of the carbon material, indicating that the material has typical amorphous carbon characteristics, and the calculation results show that the material has the characteristic of amorphous carbonThe carbon layer spacing for the carbon-based anode material is about 0.39 nm. The specific surface area of the obtained carbon-based negative electrode material is about 6m through specific surface area test2(ii) in terms of/g. Elemental analysis of a sample of the carbon-based negative electrode material after being crushed into powder shows that the atomic ratio of N/C is about 0.03, which indicates that the nitrogen element is still partially remained in the conjugated cyclic structure.
The carbon-based negative electrode material prepared in the embodiment is used as a working electrode, and the electrode preparation method comprises the steps of adding 10wt% of PVDF, mixing with NMP, coating the mixture on a copper foil, drying, cutting, weighing and the like to prepare the electrode slice. The button cell is assembled by taking metal lithium as a counter electrode, and the electrolyte adopts 1M LiPF6(EC + DME) (volume ratio of EC: DME is 1:1), charging and discharging are carried out at 0-2.5V under the current density of 50mA/g, the first coulombic efficiency is 88.2%, the first reversible specific capacity is 495mAh/g, and the specific capacity of 466mAh/g can be still maintained after 100 weeks of circulation.
Therefore, the carbon-based negative electrode material prepared by the embodiment has the advantages of low specific surface area and high first coulombic efficiency, can be used in the field of lithium ion batteries, sodium ion batteries or super capacitors, has wide market prospect, and is suitable for large-scale popularization and application.
Example 2
The preparation method of the carbon-based anode material of the embodiment includes the following steps:
step 1: weighing polyacrylonitrile resin and phthalonitrile resin as nitrogen-containing resins according to the mass ratio of 1:1, and performing ball milling to obtain powdery cured substances with the particle size of less than or equal to 150 mu m. Wherein the polyacrylonitrile resin is purchased from Aladdin and has the specification of P303198; phthalonitrile resin was purchased from maverick, usa and specified as MVK-3.
Step 2: pressing the powdery condensate obtained in the step 1 into a circle with the diameter of 50mm and the thickness of 2mm to obtain a resin pressed body.
And step 3: and (3) putting the resin pressed body obtained in the step (2) into a pressure-resistant high-temperature furnace (the inner diameter is slightly larger than 50 mm), filling the volume of the pressure-resistant high-temperature furnace is about 2/3 times, vacuumizing, replacing air in the pressure-resistant high-temperature furnace with helium for at least 2 times, heating to 380 ℃ for the first time at the speed of 12 ℃/min under the protection of the helium, keeping the temperature for 30min, and keeping the pressure in the pressure-resistant high-temperature furnace at 7 MPa.
And 4, step 4: and regulating and maintaining the pressure in the pressure-resistant high-temperature furnace to be 2MPa by using helium, raising the temperature to 800 ℃ for the second time at the speed of 5 ℃/min, carbonizing at the constant temperature for 30min, and naturally cooling to room temperature to obtain the carbon-based negative electrode material.
The specific surface area of the carbon-based negative electrode material obtained in the embodiment after being crushed into powder is about 4m2Elemental analysis indicated an N/C atomic ratio of about 0.10, indicating that the nitrogen element remains partially in the conjugated cyclized structure. The carbon-based negative electrode material prepared in the embodiment is used as a working electrode, the preparation method is the same as that of embodiment 1, metal sodium is used as a counter electrode to assemble a button cell, and 1M NaClO is used as electrolyte4(EC + PC) (volume ratio of EC: DME is 1:1), charging and discharging are carried out at 0-3.0V under the current density of 50mA/g, the first coulombic efficiency is 84.5%, the first reversible specific capacity is 341mAh/g, and after the circulation is carried out for 100 weeks, the specific capacity of 320mAh/g can still be kept.
Therefore, the carbon-based negative electrode material prepared by the embodiment has the advantages of low specific surface area and high first coulombic efficiency, can be used in the field of lithium ion batteries, sodium ion batteries or super capacitors, has wide market prospect, and is suitable for large-scale popularization and application.
Example 3
The preparation method of the carbon-based anode material of the embodiment includes the following steps:
step 1: respectively weighing polyacrylonitrile resin and polyimide resin as nitrogen-containing resin according to the mass ratio of 70:30, adding needle coke accounting for 20% of the mass of the nitrogen-containing resin, and performing ball milling to obtain powdery cured substances with the particle size of less than or equal to 150 mu m. Wherein the polyacrylonitrile resin is purchased from Aladdin and has the specification of P303198; the polyimide resin is available from Shanghai Yehe Industrial and trade Co., Ltd, and has a specification of P84 UHT.
Step 2: pressing the powdery condensate obtained in the step 1 into a circle with the diameter of 50mm and the thickness of 2mm to obtain a resin pressed body.
And step 3: and (3) putting the resin pressed body obtained in the step (2) into a pressure-resistant high-temperature furnace (the inner diameter is slightly larger than 50 mm), filling the volume of the pressure-resistant high-temperature furnace is about 2/3 times, vacuumizing, replacing air in the pressure-resistant high-temperature furnace with argon for at least 2 times, heating to 400 ℃ for the first time at a speed of 10 ℃/min under the protection of argon, keeping the temperature for 90min, and keeping the pressure in the pressure-resistant high-temperature furnace at 3 MPa.
And 4, step 4: adjusting and maintaining the pressure in the pressure-resistant high-temperature furnace to be 0.5MPa by using argon, raising the temperature to 900 ℃ for the second time at the speed of 5 ℃/min, carbonizing at the constant temperature for 60min, and naturally cooling to room temperature to obtain the carbon-based negative electrode material.
The specific surface area of the carbon-based negative electrode material obtained in the embodiment after being crushed into powder is about 5m2The elemental analysis showed that the N/C atomic ratio was about 0.07, indicating that the nitrogen element remained partially in the conjugated cyclized structure. The carbon-based negative electrode material prepared in the embodiment is used as a working electrode, the preparation method is the same as that of the embodiment 1, the metal potassium is used as a counter electrode to assemble a button cell, and the electrolyte adopts 0.5M KPF6(EC + DEC) (EC: DME volume ratio 1:1), charging and discharging at 0-2.5V under the current density of 50mA/g, the first coulombic efficiency is 83.8%, the first reversible specific capacity is 235mAh/g, and after 100 cycles, the specific capacity of 215mAh/g can be still maintained.
Therefore, the carbon-based negative electrode material prepared by the embodiment has the advantages of low specific surface area and high first coulombic efficiency, can be used in the field of lithium ion batteries, sodium ion batteries or super capacitors, has wide market prospect, and is suitable for large-scale popularization and application.
Example 4
Step 1: respectively weighing polyacrylonitrile resin and polyurethane resin as nitrogen-containing resin according to a mass ratio of 80:20, adding mesophase pitch accounting for 20% of the mass of the nitrogen-containing resin, and performing ball milling to obtain powdery condensate with the particle size of less than or equal to 150 mu m. Wherein the polyacrylonitrile resin is purchased from Aladdin and has the specification of P303198; the polyurethane resin was purchased from basf, germany and was designated as S74D 50.
Step 2: pressing the powdery condensate obtained in the step 1 into a circle with the diameter of 50mm and the thickness of 2mm to obtain a resin pressed body.
And step 3: and (3) putting the resin pressed body obtained in the step (2) into a pressure-resistant high-temperature furnace (the inner diameter is slightly larger than 50 mm), filling the volume of the pressure-resistant high-temperature furnace is about 2/3 times, vacuumizing, replacing air in the pressure-resistant high-temperature furnace with argon for at least 2 times, heating to 380 ℃ for the first time at a speed of 15 ℃/min under the protection of argon, keeping the temperature for 90min, and keeping the pressure in the pressure-resistant high-temperature furnace at 2 MPa.
And 4, step 4: adjusting and maintaining the pressure in the pressure-resistant high-temperature furnace to be 0.5MPa by using argon, raising the temperature to 750 ℃ for the second time at the speed of 1 ℃/min, carbonizing at the constant temperature for 180min, and naturally cooling to room temperature to obtain the carbon-based negative electrode material.
The specific surface area of the carbon-based negative electrode material obtained in the embodiment after being crushed into powder is about 6m2(ii) in terms of/g. Elemental analysis of a sample of the carbon-based negative electrode material after being crushed into powder shows that the atomic ratio of N/C is about 0.12, which indicates that the nitrogen element is still partially remained in the conjugated cyclic structure. The carbon-based negative electrode material prepared in the embodiment is used as a working electrode, the electrode preparation method comprises the steps of adding 10wt% of PVDF, mixing with NMP, coating the NMP on a copper foil in a slurry mode, drying, cutting, weighing and the like to prepare an electrode plate, the lithium metal is used as a counter electrode to assemble a button cell, and 1M LiPF is used as electrolyte6(EC + DME) (volume ratio of EC: DME is 1:1), charging and discharging are carried out at 0-2.5V under the current density of 50mA/g, the first coulombic efficiency is 86.4%, the first reversible specific capacity is 585mAh/g, and the specific capacity of 545mAh/g can be still maintained after 100 cycles.
Therefore, the carbon-based negative electrode material prepared by the embodiment has the advantages of low specific surface area and high first coulombic efficiency, can be used in the field of lithium ion batteries, sodium ion batteries or super capacitors, has wide market prospect, and is suitable for large-scale popularization and application.
Example 5
Preparing an electrode from the carbon-based negative electrode material obtained in the example 1 as a negative electrode, preparing the electrode from commercial activated carbon in the same manner as the example 1, adding 10wt% of PVDF into the electrode, mixing with NMP, coating the mixture on an aluminum foil, drying, cutting, weighing and the like to prepare an electrode plate as a positive electrode, and adopting 1M LiPF as electrolyte6And (EC + DMC) (EC: DMC volume ratio 1:1) to form a button supercapacitor, wherein lithium is supplemented by lithium foil for a negative electrode, the specific energy based on an electrode material is about 80Wh/kg when the charging and discharging voltage is 1.8-3.9V, and the capacity is still higher than the initial 80% after 10C charging and discharging for 10000 times.
Comparative example 1
The difference between this comparative example 1 and example 1 is that there is no step of preparing a resin compact, there is no step of evacuating and replacing inert gas and inert gas protection in the first stage heat treatment, and air pre-oxidation is used instead, and there is no inert gas pressurization (inert gas protection at normal pressure) in the second stage heat treatment, and the rest are the same. Specifically, comparative example 1 includes the following steps:
step 1: the same as in example 1.
Step 2: and (3) putting the powdery condensate obtained in the step (1) into a tube furnace, heating to 280 ℃ at the speed of 1 ℃/min, and keeping the temperature for 120min, wherein the atmosphere is air so as to preoxidize or stabilize the powdery condensate.
And step 3: and (3) putting the pre-oxidized powdery condensate obtained in the step (2) into a high-temperature tube furnace, taking nitrogen as protective gas, heating to 1100 ℃ at the speed of 3 ℃/min, carbonizing at constant temperature for 30min, and naturally cooling to room temperature to obtain the carbon-based negative electrode material.
The carbon-based negative electrode material prepared by the comparative example is used as a working electrode, and the electrode preparation method comprises the steps of adding 10wt% of PVDF, mixing with NMP, coating on a copper foil, drying, cutting, weighing and the like to prepare the electrode slice. The button cell is assembled by taking metal lithium as a counter electrode, and the electrolyte adopts 1M LiPF6(EC + DME) (volume ratio of EC: DME is 1:1), the charging and discharging are carried out at 0-2.5V under the current density of 50mA/g, the first coulombic efficiency is 71.4%, the first reversible specific capacity is 374mAh/g, and the specific capacity of 296mAh/g can be still maintained after the circulation for 100 weeks. The first coulomb efficiency can be improved to a certain extent by increasing the constant-temperature carbonization temperature, but the specific discharge capacity is reduced, for example, the first coulomb efficiency of the material which is carbonized at constant temperature to 1250 ℃ for 30min is 80.2 percent, and the first reversible specific capacity is 338 mAh/g; the first coulomb efficiency is lower when the constant temperature carbonization temperature is reduced. Although the preoxidation process in the air atmosphere reduces the melt adhesion and the decomposition rate of the polyacrylonitrile resin in the subsequent treatment, the introduced oxygen-containing functional group also causes the high-temperature activated pore-forming to increase the specific surface area, and the residual oxygen-containing functional group and the high specific surface area of the final product are reasons for reducing the coulombic efficiency for the first time.
Comparative example 2
The difference between this comparative example 2 and example 1 is that there is no step of preparing a resin compact, there is no step of evacuating and replacing inert gas and inert gas protection in the first stage heat treatment, and air pre-oxidation is used instead, and there is no inert gas pressurization (inert gas protection at normal pressure) in the second stage heat treatment, and the rest are the same. Specifically, comparative example 1 includes the following steps:
step 1: the same as in example 1.
Step 2: and (3) putting the powdery condensate obtained in the step (1) into a tube furnace, heating to 280 ℃ at the speed of 1 ℃/min, and keeping the temperature for 120min, wherein the atmosphere is air so as to preoxidize or stabilize the powdery condensate.
And step 3: and (3) putting the pre-oxidized powdery condensate obtained in the step (2) into a high-temperature tube furnace, taking nitrogen as protective gas, heating to 1250 ℃ at the speed of 3 ℃/min, carbonizing at constant temperature for 30min, and naturally cooling to room temperature to obtain the carbon-based negative electrode material.
The carbon-based negative electrode material prepared by the comparative example is used as a working electrode, and the electrode preparation method comprises the steps of adding 10wt% of PVDF, mixing with NMP, coating on a copper foil, drying, cutting, weighing and the like to prepare the electrode slice. The electrolyte adopts 1M NaClO4(EC + PC) (volume ratio of EC: DME is 1:1), charging and discharging are carried out at 0-3.0V under the current density of 50mA/g, the first coulombic efficiency is 73.5%, the first reversible specific capacity is 179mAh/g, and after the circulation is carried out for 100 weeks, the specific capacity of 144mAh/g can still be maintained. The first coulomb efficiency can be improved to a certain extent by increasing the constant temperature carbonization temperature, but the discharge specific capacity is reduced; the first coulomb efficiency is lower when the constant temperature carbonization temperature is reduced.
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, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A preparation method of a carbon-based negative electrode material is characterized by comprising the following steps:
step 1: respectively weighing the nitrogenous resin and the ingredients according to the mass ratio of 100 (0-20), and ball-milling the nitrogenous resin and the ingredients into powder to obtain a powdery condensate;
step 2: pressing and molding the powdery cured substance obtained in the step 1 to obtain a resin pressed body;
and step 3: putting the resin pressed body obtained in the step 2 into a pressure-resistant high-temperature furnace, vacuumizing, replacing air in the pressure-resistant high-temperature furnace with inert gas for at least 1 time, and then heating for the first time under the protection of the inert gas and keeping the pressure in the pressure-resistant high-temperature furnace to be 0.5-7 MPa;
and 4, step 4: adjusting and maintaining the pressure in the pressure-resistant high-temperature furnace to be 0.1-2 MPa by using inert gas, heating for the second time, and naturally cooling to room temperature to obtain the carbon-based negative electrode material.
2. The method for preparing the carbon-based negative electrode material according to claim 1, wherein in the step 1, the nitrogen-containing resin is any one or more of polyacrylonitrile resin, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, polyimide resin, polyurethane and phthalonitrile resin; the particle size of the powdery condensate is less than or equal to 180 mu m.
3. The method for preparing the carbon-based anode material according to claim 1, wherein in the step 1, the ingredient is any one or a mixture of two or more of glucose, sucrose and starch.
4. The method for preparing the carbon-based anode material according to claim 1, wherein in the step 1, the ingredients are mesophase pitch and/or needle coke.
5. The method for preparing the carbon-based negative electrode material as claimed in claim 1, wherein in the step 1, the ingredient is any one or a mixture of two or more of polyvinyl alcohol, polyvinyl butyral, polyacrylic acid and carboxymethyl cellulose.
6. The method for preparing a carbon-based anode material according to claim 1, wherein in the step 2, the press-molded shape is any one of a circle, an ellipse, a polygon and a rectangle, and the thickness is 0.8mm to 10 mm.
7. The method for preparing the carbon-based anode material according to claim 1, wherein in the step 3, the inert gas is any one or more of nitrogen, helium and argon; the first heating refers to heating to 320-450 ℃ at the speed of 5-20 ℃/min and keeping the temperature for 30-180 min; in the step 3, the pressure in the pressure-resistant high-temperature furnace is 2MPa-7 MPa.
8. The method for preparing the carbon-based anode material according to claim 1, wherein in the step 4, the inert gas is any one or more of nitrogen, helium and argon; the second heating is carried out at the speed of 1-10 ℃/min until the temperature is 750-1100 ℃ and the second heating is carbonized for 30-180 min at constant temperature; the pressure in the pressure-resistant high-temperature furnace is 0.5MPa-2 MPa.
9. A carbon-based negative electrode material produced by the production method according to any one of claims 1 to 8.
10. The application of the carbon-based negative electrode material prepared by the preparation method of any one of claims 1 to 8 in lithium ion batteries, sodium ion batteries or super capacitors.
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