CN115650228A - Method for preparing coal-based hard carbon negative electrode material through alkali treatment modification and application - Google Patents
Method for preparing coal-based hard carbon negative electrode material through alkali treatment modification and application Download PDFInfo
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Abstract
The invention provides a preparation method of a coal-based hard carbon negative electrode material, which comprises the following steps of mixing coal powder and an alkali solution and then drying to obtain powder; sintering the powder obtained in the step under a protective atmosphere to obtain a carbon material; then, carrying out acid washing and deashing on the carbon material obtained in the step, and drying to obtain a material; and finally, mixing the material obtained in the step with asphalt, and carrying out heat treatment in a protective atmosphere to obtain the hard carbon negative electrode material. According to the invention, alkali reacts with a carbon substrate at high temperature to generate a large amount of microporous structures and enlarge interlayer spacing between graphite microcrystals, so that higher sodium storage specific capacity is obtained; and then the material is coated at high temperature by asphalt, so that the specific surface area of the material is reduced, the loss of irreversible capacity is reduced, the first-cycle charging and discharging coulombic efficiency is improved, the advantages of high yield and low sintering temperature are achieved, the high specific capacity value similar to that of biomass hard carbon is obtained, and the material is a cathode material with an industrial application prospect.
Description
Technical Field
The invention belongs to the technical field of alkali metal ion secondary battery cathodes, relates to a preparation method and application of a coal-based hard carbon cathode material, and particularly relates to a method for preparing the coal-based hard carbon cathode material through alkali treatment modification and application.
Background
In recent years, the electrochemical energy storage field is rapidly developed under the support of national policies, and lithium ion batteries as mainstream products are widely applied in many fields, namely toys and digital products and large-scale energy storage. The price of battery-grade lithium carbonate is high and high due to the shortage of lithium resources, the lithium resources in China are low in reserve and difficult to develop, most of the lithium resources depend on imports, and the strategic arrangement of the resources in China is very unfavorable. Compared with the shortage of lithium resources, sodium resources have absolute advantages in reserves and are relatively low in development and utilization cost, and the research time of sodium ion batteries is even earlier than that of lithium ion batteries, but the research time is limited by the bottleneck of the technology at that time and industrialization is not realized.
After 2020, many enterprises began to lay out sodium ion battery key materials and battery production lines. At present, the sodium ion battery cathode material with the most commercial application prospect is recognized to be a hard carbon material, which is different from a lithium storage mechanism of graphite, wherein the hard carbon sodium storage mechanism is complex and comprises two parts of slope adsorption and platform intercalation, and the interlayer spacing of graphite microcrystals in the hard carbon material is required to be more than 0.37nm, so that the hard carbon material is more favorable for the intercalation and deintercalation of sodium ions. The anthracite has low price, high carbonization degree, low content of volatile component and ash content, high content of fixed carbon and obvious advantage of comprehensive cost, and the cathode material of the Chinese sea sodium adopts the route. However, the carbon material obtained by high-temperature sintering of anthracite belongs to amorphous soft carbon, the interlayer spacing of graphite microcrystals is less than 0.37nm, and the sodium storage capacity and the first coulombic efficiency are both low.
Therefore, how to find a more suitable way to improve the sodium storage capacity of the carbon material of the coal-based carbon material has become one of the focuses of great concern of many prospective research and development type enterprises and research and development personnel in the industry.
Disclosure of Invention
In view of this, the technical problem to be solved by the present invention is to provide a preparation method and an application of a coal-based hard carbon negative electrode material, and in particular, to a method for preparing a coal-based hard carbon negative electrode material by alkali treatment modification. According to the invention, KOH high-temperature activation is adopted to optimize sodium storage sites and graphite microcrystal interlayer spacing, and high-temperature coating treatment is assisted, so that the sodium storage performance of the coal-based negative electrode material is improved, and higher sodium storage specific capacity and first-week charging and discharging coulombic efficiency are obtained; and the method has simple process, mild condition and strong controllability, and is more favorable for industrial popularization and application.
The invention provides a preparation method of a coal-based hard carbon negative electrode material, which comprises the following steps:
1) Mixing and drying coal powder and an alkali solution to obtain powder;
2) Sintering the powder obtained in the step 1) in a protective atmosphere to obtain a carbon material;
3) Pickling and deliming the carbon material obtained in the step 2), and drying to obtain a material;
4) Mixing the material obtained in the step 3) with asphalt, and carrying out heat treatment under a protective atmosphere to obtain the hard carbon negative electrode material.
Preferably, D of said coal dust 50 The grain diameter is 5-10 μm;
the pulverized coal comprises anthracite pulverized coal;
the hard carbon anode material includes a hard carbon anode material of a secondary ion battery.
Preferably, the base is an alkali metal hydroxide;
the alkali metal hydroxide comprises one or more of lithium hydroxide, sodium hydroxide and potassium hydroxide;
the adding mass of the alkali is 0.5-20% of the mass of the coal powder.
Preferably, the temperature rise rate of the sintering is 0.5-5 ℃/min;
the sintering temperature is 1000-1400 ℃;
the sintering heat preservation time is 2-6 h.
Preferably, the acid washing and deashing are carried out firstly to remove impurities by water washing and then to carry out acid washing and deashing;
the concentration of the acid for acid washing is 0.1-5 mol/L;
the acid comprises one or more of hydrochloric acid, nitric acid, sulfuric acid and hydrofluoric acid;
the pickling temperature is 20-80 ℃.
Preferably, the solid-liquid mass ratio of the acid washing is 1: (2-20);
the pickling time is 1-6 h;
the specific process of acid washing and deashing comprises washing, filtering and washing for many times until the filtrate is nearly neutral.
Preferably, the process of mixing the material and the asphalt is specifically a process of compounding the asphalt on the surface of the material;
the compounding is specifically coating;
the adding mass of the asphalt accounts for 0.5-20% of the mass of the material.
Preferably, the heating rate of the heat treatment is 0.5-5 ℃/min;
the temperature of the heat treatment is 600-1200 ℃;
the heat preservation time of the heat treatment is 2-6 h.
Preferably, the hard carbon negative electrode material is obtained by performing coal-alkali activated pore-forming, plugging partial pores with asphalt, and performing heat treatment;
the surface of the hard carbon negative electrode material is provided with a coated carbon film coating layer;
the specific surface area of the material is 50-300 m 2 /g；
The specific surface area of the hard carbon negative electrode material is 2-25 m 2 /g。
The invention also provides application of the coal-based hard carbon negative electrode material prepared by any one of the preparation methods in the technical scheme in an alkali metal ion secondary battery.
The invention provides a preparation method of a coal-based hard carbon negative electrode material, which comprises the following steps of mixing coal powder and an alkali solution and then drying to obtain powder; sintering the powder obtained in the step under a protective atmosphere to obtain a carbon material; then, carrying out acid washing and deliming on the carbon material obtained in the step, and drying to obtain a material; and finally, mixing the material obtained in the step with asphalt, and carrying out heat treatment in a protective atmosphere to obtain the hard carbon negative electrode material. Compared with the prior art, the invention aims at the limitation of the existing hard carbon material of the cathode of the alkali metal ion secondary battery in the aspects of industrialization and commercialization, and the anthracite is considered to have more advantages as a raw material. The invention also aims at the defect that the anthracite sintered at high temperature belongs to amorphous soft carbon and has low sodium storage capacity, although the document also indicates that KOH is partially reduced into simple substance potassium at high temperature and enters between graphite sheets in the form of potassium steam to increase the interlayer spacing on the report that the potassium ions improve the interlayer spacing of hard carbon materials. However, the research of the invention considers that excessive KOH can consume a large amount of carbon and reduce the yield, and although the activation pore-forming effect and the potassium ion doping effect of the KOH are fully utilized, better sodium storage active sites and interlayer spacing are obtained, and the sodium storage capacity of the hard carbon material is improved, the larger specific surface area promotes the surface side reaction to generate more SEI films, the irreversible capacity loss is larger, and the processing performance of the material is not facilitated, so the method is difficult to be applied to the negative electrode of the battery.
Based on the above, the invention particularly designs a preparation method of the coal-based hard carbon negative electrode material, which adopts KOH high-temperature activation to optimize sodium storage sites and graphite microcrystal interlayer spacing, is assisted with high-temperature coating treatment, and forms the coated hard carbon negative electrode material with a specific structure through specific steps and parameters, thereby improving the sodium storage performance of the coal-based carbon negative electrode material, and having higher sodium storage specific capacity and first-week charging and discharging coulombic efficiency. The present invention adopts a method combining the manufacture of microporous active sites and the enlargement of the graphite crystallite interlayer spacing. The potassium hydroxide has the best effect in the application of the carbon material as the activating pore-forming agent, and can react with the carbon material at high temperature to generate a large number of micropores, so that the specific surface area of the material is effectively improved. The invention also adopts the asphalt coating method to reduce the specific surface area and reduce the contact between the naked microporous structure and the electrolyte, thereby reducing the side reaction and the loss of irreversible sodium storage capacity and improving the first-cycle coulomb charging and discharging efficiency of the material.
The invention discloses a method for preparing a coal-based hard carbon negative electrode material by alkali treatment modification, which utilizes the reaction of alkali and a carbon substrate at high temperature to generate a large amount of microporous structures and enlarge the interlayer spacing between graphite microcrystals to obtain higher sodium storage specific capacity; and then the material is coated by asphalt at high temperature, so that the specific surface area of the material is reduced, the loss of irreversible capacity is reduced, and the first cycle coulomb charging and discharging efficiency is improved. The method for activating at high temperature by alkali treatment provided by the invention obviously improves the sodium storage performance of the coal-based hard carbon negative electrode material by a comprehensive method of activating and pore-forming, doping to increase the graphite microcrystal interlayer spacing and coating to improve the surface structure, effectively improves the sodium storage capacity and the first-week charging and discharging coulombic efficiency, and breaks through the bottleneck that the sodium storage performance of the carbon material prepared by using anthracite as a raw material is poor. The method belongs to a chemical modification method, is simple in preparation method and high in cost performance, can eliminate the difference of the same coal types due to different regions to a certain extent, and can be used for large-scale production. The coal-based hard carbon material produced by the preparation method is used as a negative electrode material of a sodium ion battery, shows excellent electrochemical sodium storage performance, is stable in cycle performance, simple in process, mild in condition and strong in controllability, is more beneficial to industrial popularization and application, and is a negative electrode material with application prospect.
Experimental results show that the hard carbon material prepared by the invention has the advantages of high anthracite yield and low sintering temperature, obtains a high specific capacity value similar to biomass hard carbon, has a first-week coulombic efficiency of over 85 percent, and is a cathode material with an industrial application prospect.
Drawings
Fig. 1 is XRD diffractograms of the coal-based negative electrode materials prepared in comparative example 1 and example 1 of the present invention;
fig. 2 is a scanning electron microscope image of the coal-based hard carbon negative electrode material 1 and the coal-based hard carbon negative electrode material 2 prepared in example 1 of the present invention;
fig. 3 is a data chart of a first loop of a power-off test of the coal-based hard carbon anode material 1 and the coal-based hard carbon anode material 2 prepared in example 1 of the present invention.
Detailed Description
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.
All of the starting materials of the present invention, without particular limitation as to their source, may be purchased commercially or prepared according to conventional methods well known to those skilled in the art.
All the raw materials of the invention are not particularly limited in purity, and the invention preferably adopts the purity of the conventional raw materials used in the field of preparation of analytically pure or sodium-ion battery cathode materials.
The invention provides a preparation method of a coal-based hard carbon negative electrode material, which comprises the following steps:
1) Mixing the coal powder and the aqueous alkali and then drying to obtain powder;
2) Sintering the powder obtained in the step 1) in a protective atmosphere to obtain a carbon material;
3) Pickling and deashing the carbon material obtained in the step 2), and drying to obtain a material;
4) Mixing the material obtained in the step 3) with asphalt, and carrying out heat treatment under a protective atmosphere to obtain the hard carbon negative electrode material.
The invention firstly mixes the coal powder and the alkali solution and then dries the mixture to obtain the powder.
In the present invention, D of the pulverized coal 50 The particle size is preferably 5 to 10 μm, more preferably 5 to 9 μm, and still more preferably 6 to 8 μm.
In the present invention, the pulverized coal preferably includes pulverized anthracite.
In the present invention, the hard carbon anode material preferably includes a hard carbon anode material of a secondary ion battery.
In the present invention, the base is preferably an alkali metal hydroxide, more preferably includes one or more of lithium hydroxide, sodium hydroxide and potassium hydroxide, and more preferably lithium hydroxide, sodium hydroxide or potassium hydroxide.
In the present invention, the addition mass of the alkali is preferably 0.5% to 20%, more preferably 5% to 17%, and still more preferably 8% to 12% of the mass of the pulverized coal.
Sintering the powder obtained in the step 1) in a protective atmosphere to obtain the carbon material.
In the present invention, the heating rate of the sintering is preferably 0.5 to 5 ℃/min, more preferably 1 to 4 ℃/min, and still more preferably 2 to 3 ℃/min.
In the present invention, the sintering temperature is preferably 1000 to 1400 ℃, more preferably 1050 to 1350 ℃, more preferably 1100 to 1300 ℃, more preferably 1150 to 1250 ℃.
In the present invention, the holding time for the sintering is preferably 2 to 6 hours, more preferably 2.5 to 5.5 hours, more preferably 3 to 5 hours, and more preferably 3.5 to 4.5 hours.
The carbon material obtained in the step 2) is subjected to acid washing and deashing, and then is dried to obtain the material.
In the invention, the acid washing and deashing are particularly preferably carried out by firstly removing impurities by water washing and then carrying out acid washing and deashing.
In the present invention, the concentration of the acid for acid washing is preferably 0.1 to 5mol/L, more preferably 0.5 to 4 mol/L, and still more preferably 1 to 3mol/L.
In the present invention, the acid preferably includes one or more of hydrochloric acid, nitric acid, sulfuric acid, and hydrofluoric acid, and more preferably hydrochloric acid.
In the present invention, the temperature of the acid washing is preferably 20 to 80 ℃, more preferably 25 to 65 ℃, and more preferably 40 to 60 ℃.
In the present invention, the solid-liquid mass ratio of the acid washing is preferably 1: (2 to 20), more preferably 1: (4 to 15), more preferably 1: (5-10).
In the present invention, the time for the acid washing is preferably 1 to 6 hours, more preferably 2 to 5 hours, and still more preferably 3 to 4 hours.
In the invention, the specific process of acid washing and deashing is preferably washing, filtering and washing for multiple times until the filtrate is nearly neutral.
Finally, mixing the material obtained in the step 3) with asphalt, and carrying out heat treatment in a protective atmosphere to obtain the hard carbon negative electrode material.
In the invention, the process of mixing the material and the asphalt is particularly preferably a process of compounding the asphalt on the surface of the material.
In the present invention, the compounding is particularly preferably coating.
In the present invention, the added mass of the asphalt is preferably 0.5% to 20%, more preferably 1% to 15%, and still more preferably 2% to 10% of the mass of the material.
In the present invention, the rate of temperature rise in the heat treatment is preferably 0.5 to 5 ℃/min, more preferably 1 to 4 ℃/min, and still more preferably 2 to 3 ℃/min.
In the present invention, the temperature of the heat treatment is preferably 600 to 1200 ℃, more preferably 750 to 1100 ℃, and more preferably 800 to 1050 ℃.
In the present invention, the heat treatment is preferably carried out for a holding time of 2 to 6 hours, more preferably 2.5 to 5.5 hours, more preferably 3 to 5 hours, and more preferably 3.5 to 4.5 hours.
In the invention, the hard carbon negative electrode material is preferably obtained by performing coal alkali activation pore forming, plugging partial pores by using asphalt and performing heat treatment.
In the present invention, the hard carbon anode material surface preferably has a coated carbon film coating layer.
In the present invention, the specific surface area of the material is preferably 50 to 300m 2 Per g, more preferably 100 to 250 m 2 (ii) g, more preferably 100 to 200m 2 /g。
In the present invention, the hard carbon negative electrode material preferably has a specific surface area of 2 to 25m 2 (ii) g, more preferably 5 to 23m 2 A ratio of (i)/g, more preferably 8 to 20m 2 (ii) g, more preferably 10 to 18m 2 /g。
The invention is a complete and refined integral technical scheme, better ensures the structure, the composition and the parameters of the coal-based hard carbon negative electrode material, and further improves the sodium storage performance of the coal-based hard carbon negative electrode material, and the preparation method of the coal-based hard carbon negative electrode material specifically comprises the following steps:
the invention provides a preparation method for preparing a coal-based hard carbon negative electrode material by KOH high-temperature activation modification, which comprises the following steps:
1) Crushing anthracite coal to D 50 5-10 μm to obtain coal powder;
2) Dissolving alkali in a certain amount of water to prepare a steeping fluid, adding coal powder, uniformly mixing under stirring, and drying at 105 ℃ for later use; wherein the alkali is sodium hydroxide or potassium hydroxide, and the addition amount of the alkali is 0.5-20% of that of the coal powder; more preferably potassium hydroxide.
3) Sintering the material obtained in the step 2) at a high temperature, heating to 1000-1400 ℃ at a heating rate of 0.5-5 ℃/min under the protection of inert atmosphere such as nitrogen or argon, and keeping the temperature for 2-6 h;
4) Performing acid washing and deashing on the carbon material prepared in the step 3), firstly washing with water to remove water-soluble impurities, then washing with 0.1-5 mol/L hydrochloric acid under stirring at the temperature of room temperature-80 ℃ and the solid-liquid mass ratio of 1:2-1 for 1-6 h to remove ash and impurities, filtering for many times, washing until the filtrate is nearly neutral, and drying at 150 ℃ for later use;
5) Coating the material obtained in the step 4) with high-temperature asphalt, wherein the addition amount of the asphalt is 0.5-20%, the temperature is increased to 800-1200 ℃ at the heating rate of 0.5-5 ℃/min under the protection of inert atmosphere such as nitrogen or argon, and the heat preservation time is 2-6 h;
6) Crushing and screening the crushed coal-based hard carbon negative electrode material with a 400-mesh screen to obtain the coal-based hard carbon negative electrode material.
In order to improve the sodium storage performance of the coal-based carbon negative electrode material, the invention adopts a method of combining manufacturing microporous active sites and increasing the interlayer spacing of graphite microcrystals. The potassium hydroxide has the best effect in the application of the carbon material as the activating pore-forming agent, and can react with the carbon material at high temperature to generate a large number of micropores, so that the specific surface area of the material is effectively improved. Although the literature also reports about the improvement of the spacing between hard carbon material layers by potassium ions, KOH is partially reduced to elemental potassium at high temperature and enters between graphite sheets in the form of potassium vapor, so that the spacing between the graphite sheets is increased, but excessive KOH consumes a large amount of carbon and reduces the yield. The activation pore-forming effect of KOH and the potassium ion doping effect are fully utilized, better sodium storage active sites and interlayer spacing are obtained, and the sodium storage capacity of the hard carbon material is improved. But the larger specific surface area promotes more SEI films generated by surface side reactions, the irreversible capacity loss is larger, and the processing performance of the material is not favorable, so the method is less applied to the battery cathode. The invention adopts the asphalt coating method to reduce the specific surface area and reduce the contact between the naked microporous structure and the electrolyte, thereby reducing the side reaction and the loss of irreversible sodium storage capacity and improving the first-cycle coulomb charging and discharging efficiency of the material.
The invention provides application of the coal-based hard carbon negative electrode material prepared by any one of the preparation methods in the technical scheme in an alkali metal ion secondary battery. Specifically, the alkali metal ion secondary battery is more preferably a sodium ion secondary battery.
The invention provides a method for preparing a coal-based hard carbon negative electrode material through alkali treatment modification and application. According to the invention, the sodium storage sites and the graphite microcrystal interlayer spacing are optimized by adopting KOH high-temperature activation, and then high-temperature coating treatment is assisted, so that the coated hard carbon negative electrode material with a specific structure is formed through specific steps and parameters, and thus the sodium storage performance of the coal-based carbon negative electrode material is improved, and the coated hard carbon negative electrode material has higher sodium storage specific capacity and first-week charging and discharging coulombic efficiency. The present invention adopts a method combining the manufacture of microporous active sites and the enlargement of the graphite crystallite interlayer spacing. The potassium hydroxide has the best effect in the application of the carbon material as the activating pore-forming agent, and can react with the carbon material at high temperature to generate a large number of micropores, so that the specific surface area of the material is effectively improved. The invention also adopts the asphalt coating method to reduce the specific surface area and reduce the contact between the naked microporous structure and the electrolyte, thereby reducing the side reaction and the loss of irreversible sodium storage capacity and improving the first-cycle coulomb charging and discharging efficiency of the material.
The invention discloses a method for preparing a coal-based hard carbon negative electrode material by alkali treatment modification, which utilizes the reaction of alkali and a carbon substrate at high temperature to generate a large amount of microporous structures and enlarge the interlayer spacing between graphite microcrystals to obtain higher sodium storage specific capacity; and then the material is coated by asphalt at high temperature, so that the specific surface area of the material is reduced, the loss of irreversible capacity is reduced, and the first-cycle charging and discharging coulomb efficiency is improved. The method for activating at high temperature by alkali treatment provided by the invention obviously improves the sodium storage performance of the coal-based hard carbon negative electrode material by a comprehensive method of activating and pore-forming, doping to increase the graphite microcrystal interlayer spacing and coating to improve the surface structure, effectively improves the sodium storage capacity and the first-week charging and discharging coulombic efficiency, and breaks through the bottleneck that the sodium storage performance of the carbon material prepared by using anthracite as a raw material is poor. The method belongs to a chemical modification method, is simple in preparation method and high in cost performance, can eliminate the difference of the same coal types due to different regions to a certain extent, and can realize large-scale production. The coal-based hard carbon material produced by the preparation method is used as the cathode material of the sodium ion battery, has excellent electrochemical sodium storage performance, stable cycle performance, simple process, mild conditions and strong controllability, is more beneficial to industrial popularization and application, and is a cathode material with application prospect.
Experimental results show that the hard carbon material prepared by the invention has the advantages of high anthracite yield and low sintering temperature, obtains a high specific capacity value similar to biomass hard carbon, has a first-week coulombic efficiency of over 85 percent, and is a cathode material with an industrial application prospect.
For further illustration of the present invention, the following will describe in detail the preparation method and application of a coal-based hard carbon negative electrode material provided by the present invention with reference to the following examples, but it should be understood that these examples are implemented on the premise of the technical solution of the present invention, and the detailed embodiments and specific operation procedures are given, only for further illustration of the features and advantages of the present invention, and not for limitation of the claims of the present invention, and the scope of protection of the present invention is not limited to the following examples.
The sodium storage performance of the coal-based hard carbon negative electrode material prepared by the invention is evaluated by a button cell, and the preparation proportion of the electrode slurry is as follows: conductive agent SP: and (3) adding a proper amount of NMP into the binder PVDF =92 6 The PC/DEC/EC (1.
Comparative example 1
The preparation method of the negative electrode material of the sodium-ion battery comprises the following steps: 1) Crushing anthracite coal to D 50 5-10 μm to obtain coal powder; 2) Sintering at high temperature under the protection of nitrogen, wherein the oxygen content is less than 50ppm, the heating rate of 2 ℃/min is up to 1200 ℃, the heat preservation time is 4h, cooling to below 50 ℃ along with the furnace, and discharging; crushing, sieving with a 400-mesh sieve, carrying out acid washing and impurity removal under the conditions of 1mol/L hydrochloric acid, 60 ℃, a solid-liquid mass ratio of 1.
The electricity deduction test data show that the reversible specific capacity is 205.4mAh/g, and the first-week charging and discharging coulombic efficiency is 80.55%.
Comparative example 2
The preparation method of the negative electrode material of the sodium-ion battery comprises the following steps:1) Crushing anthracite coal to D 50 5-10 μm to obtain coal powder; 2) Mixing the coal powder with 20% of sodium hydroxide or potassium hydroxide, and drying; 3) Sintering at high temperature under the protection of nitrogen, wherein the oxygen content is less than 50ppm, the heating rate of 2 ℃/min is up to 800 ℃, the heat preservation time is 4h, cooling to below 50 ℃ along with the furnace, and discharging; 4) Washing with water until the filtrate is neutral, then carrying out acid washing impurity removal under the conditions of 1mol/L hydrochloric acid, 80 ℃, a solid-liquid mass ratio of 1:5, and a heat preservation time of 4h, filtering, washing for multiple times until the filtrate is close to neutral, and drying at 150 ℃; 5) Mixing 10% asphalt, coating at high temperature, heating to 1200 ℃ at a heating rate of 2 ℃/min under the protection of nitrogen atmosphere, keeping the temperature for 6h, cooling to below 50 ℃ along with the furnace, and discharging; crushing and sieving with a 400-mesh sieve to obtain the coal-based hard carbon negative electrode material.
The electricity deduction test data show that the reversible specific capacity is 223.4mAh/g, and the first-week charging and discharging coulombic efficiency is 82.44%. The preparation method has a certain promotion effect on the performance improvement of the hard carbon cathode material, but the improvement effect is poor.
Example 1
Obviously, the sodium storage capacity of the coal-based negative electrode material cannot be obviously improved by alkali treatment activation at a relatively low temperature, and the invention adopts a higher activation temperature and also considers the optimal temperature for high-temperature sintering of the anthracite. The preparation method of the coal-based hard carbon negative electrode material comprises the following steps:
1) Crushing anthracite coal to D 50 Is 6 mu m to obtain coal powder;
2) Dissolving potassium hydroxide accounting for 15% of the mass of the coal powder into a certain amount of pure water, adding the coal powder, stirring and mixing uniformly at a high speed, and drying at 105 ℃ for later use;
3) Sintering at high temperature under the protection of nitrogen, wherein the oxygen content is less than 50ppm, the heating rate of 2 ℃/min is up to 1200 ℃, the heat preservation time is 4h, cooling to below 50 ℃ along with the furnace, and discharging;
4) Washing with pure water to remove soluble salt, and washing until the filtrate is neutral; then washing with hydrochloric acid to remove metal element impurities, carrying out acid washing and impurity removal under the conditions of 1mol/L hydrochloric acid, 60 ℃, a solid-liquid mass ratio of 1 to 10 and a heat preservation time of 2h, filtering, washing for multiple times until the filtrate is nearly neutral, and drying at 150 ℃; crushing and sieving with a 400-mesh sieve to obtain the coal-based hard carbon negative electrode material 1.
5) Crushing the asphalt to micron level in advance, and sieving for later use; weighing 5-20% of asphalt by mass fraction, stirring and mixing with the carbon material obtained in the step 4) at a high speed, then heating to 850 ℃ at a heating rate of 1 ℃/min under the protection of nitrogen, keeping the temperature for 2h, cooling to below 50 ℃ along with a furnace, and discharging;
6) Crushing and sieving by a 400-mesh sieve to obtain the coal-based hard carbon cathode material 2.
The hard carbon cathode material 1 is obtained by KOH high-temperature activation treatment, has higher specific surface area and is tested to be about 278.39m 2 The data of the electricity deduction test show that the reversible specific capacity is 258.9mAh/g, and the first coulombic efficiency is 74.28%.
The hard carbon cathode material 2 is subjected to asphalt coating treatment on the basis of the hard carbon cathode material 1, the specific surface area is reduced, and the test shows that the specific surface area is about 21.19m 2 The/g, the data of the electricity-saving test show that the reversible specific capacity is 297.7mAh/g, and the first-week charging and discharging coulombic efficiency is 86.47%.
Compared with a comparative example, the method provided by the embodiment of the invention has the advantages that the sodium storage performance of the coal-based hard carbon negative electrode material is remarkably improved, the reversible specific capacity is improved by more than 33%, the first-week charging and discharging coulombic efficiency is more than 86%, and the negative electrode material has an industrial application prospect.
Referring to fig. 1, fig. 1 is an XRD diffractogram of the coal-based negative electrode materials prepared in comparative example 1 and example 1 of the present invention.
As can be seen from FIG. 1, when the XRD pattern of the coal-based hard carbon negative electrode material prepared by KOH high-temperature activation treatment is compared with that of the untreated hard carbon negative electrode material, the (002) peak position is shifted to the direction of a low diffraction angle, and the spacing between graphite microcrystalline layers is obviously increased.
As can be seen from fig. 1, compared with the effect of the KOH high-temperature activation treatment on the interlayer spacing of the coal-based hard carbon negative electrode material, the interlayer spacing is obviously increased due to the action of the potassium vapor.
Referring to fig. 2, fig. 2 is a scanning electron microscope image of the coal-based hard carbon negative electrode material 1 and the coal-based hard carbon negative electrode material 2 prepared in example 1 of the present invention. The upper figure is a coal-based hard carbon negative electrode material 1, and the lower figure is a coal-based hard carbon negative electrode material 2.
As can be seen from fig. 2, by comparing the surface morphologies of the hard carbon negative electrode material before and after the pitch coating treatment, it can be seen that a carbon film coating layer was formed on the particle surface.
Referring to fig. 3, fig. 3 is a first data chart of the power-off test of the coal-based hard carbon anode material 1 and the coal-based hard carbon anode material 2 prepared in example 1 of the present invention.
As can be seen from fig. 3, comparison of the electricity consumption test data of the hard carbon negative electrode material before and after the asphalt coating treatment shows the influence of the sodium storage performance of the hard carbon negative electrode material before and after the asphalt coating treatment, the asphalt coating on the surface of the hard carbon negative electrode material forms a carbon coating film, the contact between the material surface and the electrolyte is reduced, the irreversible capacity loss is reduced, and the first cycle charging and discharging efficiency is significantly improved. Therefore, the asphalt-coated hard carbon negative electrode material has higher first coulombic efficiency, higher sodium storage specific capacity, obviously reduced specific surface area of the material due to the coating layer, and reduced irreversible capacity loss caused by side reaction and SEI.
Example 2
The preparation method of the coal-based hard carbon negative electrode material comprises the following steps:
1) Crushing anthracite coal to D 50 8 μm to obtain coal powder;
2) Dissolving potassium hydroxide with the mass of 2 percent of that of the coal powder into a certain amount of pure water, adding the coal powder, stirring and mixing uniformly at a high speed, and drying at 105 ℃ for later use;
3) Sintering at high temperature under the protection of nitrogen, wherein the oxygen content is less than 50ppm, the heating rate of 2 ℃/min is 1250 ℃, the heat preservation time is 2 hours, cooling to below 50 ℃ along with the furnace, and discharging;
4) Washing with pure water to remove soluble salt, and washing until the filtrate is neutral; then washing with hydrochloric acid-hydrofluoric acid to remove metal element impurities, carrying out acid washing impurity removal under the conditions of 2mol/L hydrochloric acid, 80 ℃, a solid-liquid mass ratio of 1:5, and a heat preservation time of 4h, filtering, washing for multiple times until the filtrate is nearly neutral, and drying at 150 ℃; crushing and sieving with a 400-mesh sieve to obtain the coal-based hard carbon negative electrode material 1.
5) Crushing the asphalt to micron level in advance, and sieving for later use; weighing 5% of asphalt by mass fraction, stirring and mixing with the carbon material obtained in the step 4) at a high speed, then heating to 800 ℃ at a heating rate of 2 ℃/min under the protection of nitrogen, keeping the temperature for 2 hours, cooling to below 50 ℃ along with a furnace, and discharging;
6) Crushing and sieving by a 400-mesh sieve to obtain the coal-based hard carbon cathode material 2.
The specific surface area of the hard carbon anode material 1 is about 98.52m 2 The specific reversible capacity is 235.5mAh/g, and the first coulombic efficiency is 71.2%. The specific surface area of the hard carbon negative electrode material 2 is about 8.75m 2 The/g, the electricity deduction test data shows that the reversible specific capacity is 231.4mAh/g, and the first-week charging and discharging coulombic efficiency is 82.3%.
Example 3
The preparation method of the coal-based hard carbon negative electrode material comprises the following steps:
1) Crushing anthracite coal to D 50 Is 6 mu m to obtain coal powder;
2) Dissolving sodium hydroxide with the mass of 10 percent of that of the coal powder into a certain amount of pure water, adding the coal powder, stirring and mixing uniformly at a high speed, and drying at 105 ℃ for later use;
3) Sintering at high temperature under the protection of nitrogen, wherein the oxygen content is less than 50ppm, the heating rate of 2 ℃/min is up to 1200 ℃, the heat preservation time is 4h, cooling to below 50 ℃ along with the furnace, and discharging;
4) Washing with pure water to remove soluble salt, and washing until the filtrate is neutral; then washing with hydrochloric acid to remove metal element impurities, carrying out acid washing and impurity removal under the conditions of 2mol/L hydrochloric acid, 50 ℃, a solid-liquid mass ratio of 1:5, and a heat preservation time of 4h, filtering, washing for multiple times until the filtrate is nearly neutral, and drying at 150 ℃; crushing and sieving with a 400-mesh sieve to obtain the coal-based hard carbon negative electrode material 1.
5) Crushing the asphalt to micron level in advance, and sieving for later use; weighing 8% of asphalt by mass fraction, stirring and mixing with the carbon material obtained in the step 4) at a high speed, then heating to 1050 ℃ at a heating rate of 2 ℃/min under the protection of nitrogen, keeping the temperature for 2 hours, cooling to below 50 ℃ along with a furnace, and discharging;
6) Crushing and sieving with a 400-mesh sieve to obtain the coal-based hard carbon negative electrode material 2.
The specific surface area of the hard carbon negative electrode material 1 was about 65.8m 2 /g, reversible specific capacity of 246.6mAhg, first coulombic efficiency 75.3%. The specific surface area of the hard carbon negative electrode material 2 was about 4.72m 2 The/g, the electricity deduction test data shows that the reversible specific capacity is 250.9mAh/g, and the first-week charging and discharging coulombic efficiency is 84.3%.
The above detailed description of the method and application of the alkali treatment modified coal-based hard carbon anode material provided by the present invention, and the principle and embodiments of the present invention are illustrated herein by using specific examples, the above description of the examples is only for assisting understanding of the method and the core concept of the present invention, including the best mode, and also for enabling any person skilled in the art to practice the present invention, including making and using any devices or systems and performing any combination of the methods. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
Claims (10)
1. The preparation method of the coal-based hard carbon negative electrode material is characterized by comprising the following steps of:
1) Mixing the coal powder and the aqueous alkali and then drying to obtain powder;
2) Sintering the powder obtained in the step 1) in a protective atmosphere to obtain a carbon material;
3) Pickling and deliming the carbon material obtained in the step 2), and drying to obtain a material;
4) Mixing the material obtained in the step 3) with asphalt, and carrying out heat treatment under a protective atmosphere to obtain the hard carbon negative electrode material.
2. According toThe method according to claim 1, wherein D is the amount of the pulverized coal 50 The grain diameter is 5-10 mu m;
the pulverized coal comprises pulverized anthracite;
the hard carbon anode material includes a hard carbon anode material of a secondary ion battery.
3. The production method according to claim 1, wherein the base is an alkali metal hydroxide;
the alkali metal hydroxide comprises one or more of lithium hydroxide, sodium hydroxide and potassium hydroxide;
the adding mass of the alkali is 0.5-20% of the mass of the coal powder.
4. The production method according to claim 1, wherein the temperature increase rate of the sintering is 0.5 to 5 ℃/min;
the sintering temperature is 1000-1400 ℃;
the sintering heat preservation time is 2-6 h.
5. The preparation method according to claim 1, wherein the acid washing deashing comprises removing impurities by water washing, and then performing acid washing deashing;
the concentration of the acid for acid washing is 0.1-5 mol/L;
the acid comprises one or more of hydrochloric acid, nitric acid, sulfuric acid and hydrofluoric acid;
the pickling temperature is 20-80 ℃.
6. The method according to claim 5, wherein the solid-liquid mass ratio of the acid washing is 1: (2-20);
the pickling time is 1-6 h;
the specific process of acid washing and ash removal comprises washing, filtering and washing for many times until the filtrate is nearly neutral.
7. The preparation method according to claim 1, wherein the process of mixing the material and the asphalt is specifically a process of compounding asphalt on the surface of the material;
the compounding is specifically coating;
the adding mass of the asphalt accounts for 0.5-20% of the mass of the material.
8. The production method according to claim 1, wherein the temperature increase rate of the heat treatment is 0.5 to 5 ℃/min;
the temperature of the heat treatment is 600-1200 ℃;
the heat preservation time of the heat treatment is 2-6 h.
9. The preparation method of the anode material according to claim 1, wherein the hard carbon anode material is obtained by performing coal-base activation pore-forming, plugging partial pores with pitch, and performing heat treatment;
the surface of the hard carbon negative electrode material is provided with a coated carbon film coating layer;
the specific surface area of the material is 50-300 m 2 /g；
The specific surface area of the hard carbon negative electrode material is 2-25 m 2 /g。
10. The use of the coal-based hard carbon negative electrode material prepared by the preparation method of any one of claims 1 to 9 in an alkali metal ion secondary battery.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116553547A (en) * | 2023-07-12 | 2023-08-08 | 玖贰伍碳源科技（天津）有限公司 | High-energy high-power carbon material, preparation method and sodium ion battery |
| CN116613300A (en) * | 2023-07-18 | 2023-08-18 | 成都锂能科技有限公司 | Coal-based carbonized sodium battery anode material, preparation method thereof and sodium ion battery comprising coal-based carbonized sodium battery anode material |
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| JP2017183080A (en) * | 2016-03-30 | 2017-10-05 | 株式会社クレハ | Carbonaceous material for nonaqueous electrolyte secondary battery negative electrode, and method for manufacturing the same |
| CN112645305A (en) * | 2021-01-22 | 2021-04-13 | 哈尔滨工业大学 | Preparation method of pre-activated pore-forming and high-temperature carbonization combined anthracite-based hard carbon material |
| CN115207320A (en) * | 2022-08-11 | 2022-10-18 | 多氟多新材料股份有限公司 | Preparation method of lithium/sodium ion battery negative electrode material |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2017183080A (en) * | 2016-03-30 | 2017-10-05 | 株式会社クレハ | Carbonaceous material for nonaqueous electrolyte secondary battery negative electrode, and method for manufacturing the same |
| CN112645305A (en) * | 2021-01-22 | 2021-04-13 | 哈尔滨工业大学 | Preparation method of pre-activated pore-forming and high-temperature carbonization combined anthracite-based hard carbon material |
| CN115207320A (en) * | 2022-08-11 | 2022-10-18 | 多氟多新材料股份有限公司 | Preparation method of lithium/sodium ion battery negative electrode material |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116553547A (en) * | 2023-07-12 | 2023-08-08 | 玖贰伍碳源科技（天津）有限公司 | High-energy high-power carbon material, preparation method and sodium ion battery |
| CN116613300A (en) * | 2023-07-18 | 2023-08-18 | 成都锂能科技有限公司 | Coal-based carbonized sodium battery anode material, preparation method thereof and sodium ion battery comprising coal-based carbonized sodium battery anode material |
| CN116613300B (en) * | 2023-07-18 | 2023-09-22 | 成都锂能科技有限公司 | Coal-based carbonized sodium battery anode material, preparation method thereof and sodium ion battery comprising coal-based carbonized sodium battery anode material |
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