CN114789998A - Negative electrode material, preparation method thereof and battery - Google Patents

Negative electrode material, preparation method thereof and battery Download PDF

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CN114789998A
CN114789998A CN202111285189.XA CN202111285189A CN114789998A CN 114789998 A CN114789998 A CN 114789998A CN 202111285189 A CN202111285189 A CN 202111285189A CN 114789998 A CN114789998 A CN 114789998A
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coal
graphene
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CN114789998B (en
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王建兴
曹礼洪
方波
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Guangdong Yina Technology Co ltd
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Abstract

The invention relates to a negative electrode material and a preparation method thereof, wherein the preparation method comprises the following steps: mixing a coal-based material and graphite, and adding the mixture into a solvent to obtain a mixed solution A; homogenizing the mixed solution A at high pressure to obtain a mixed solution B of the coal-based material and the graphene; and spray drying the mixed solution B to obtain the composite powder of the coal-based material and the graphene. According to the negative electrode material provided by the invention, the coal-based material and graphite are used as raw materials, in the high-pressure homogenization process, the graphite sheet is peeled to form graphene, and the coal is coated, so that the graphene-compounded coal-based material is finally obtained, and the coal-based material is stable in structure and has excellent conductivity and sodium storage performance. The invention also provides a battery.

Description

Negative electrode material, preparation method thereof and battery
Technical Field
The invention relates to the field of battery materials, in particular to a negative electrode material, a preparation method thereof and a battery.
Background
The carbon material has the advantages of rich source, environmental protection, good conductivity and the like, and is successfully applied to the commercial production of lithium batteries at present, and the graphite is the most common negative electrode material of the commercial lithium ion batteries because of having a long-range ordered stacking structure, good conductivity, high specific capacity and good cycle performance.
The compositions and working principles of lithium ion batteries and sodium ion batteries, including the charging and discharging processes, are also similar. Carbon materials are important negative electrode materials in lithium ion batteries and sodium ion batteries, but sodium ion batteries have been limited in development because no suitable negative electrode material has been found. The successful use of carbon materials in lithium ion batteries indicates that carbon materials are one of the most promising materials for the negative electrode of sodium ion batteries. The application of the carbon material in the sodium ion battery at present has the following problems:
1. the sodium ion battery cannot directly use a graphite cathode due to the large radius of sodium ions, the atomic radius of the sodium ions is larger than that of lithium atoms, the graphite interlayer spacing (0.34nm) is limited, and the sodium ions need larger energy when being embedded into the graphite interlayer, so the sodium storage capacity of the graphite and graphite materials is low;
2. the preparation method of the coal-based carbon material is simple, and has wide application prospects in the field of energy storage, but the conductivity of the coal-based carbon material is not high, and the conductivity of electrons or charges needs to be improved;
3. in the application of the sodium ion battery, coal is generally calcined at high temperature to generate hard carbon, the graphitization degree of the hard carbon is small, the disorder degree is high, the interlayer spacing is large, a large number of lattice defects are generated in the internal structure, the sodium storage capacity of the sodium ion battery is derived from sodium ions adsorbed on the lattice defects, but the structural stability of the sodium ion battery is reduced by the large number of lattice defects in the hard carbon.
Disclosure of Invention
In order to overcome the problems in the prior art, the invention provides a negative electrode material and a preparation method thereof, wherein the negative electrode material takes a coal-based material and graphite as raw materials, and the preparation method of the battery negative electrode material comprises the following steps: the method comprises the following steps of material mixing, high-pressure homogenization, spray drying and high-temperature calcination, wherein in the high-pressure homogenization process, graphite sheets are stripped to form graphene and coat coal, and finally the graphene-compounded coal-based material is obtained, and is stable in structure and excellent in conductivity and sodium storage performance.
In a first aspect, the present invention provides a method for preparing an anode material, comprising the steps of:
s1, mixing the coal-based material and the graphite, and adding the mixture into a solvent to obtain a mixed solution A;
s2, homogenizing the mixed solution A at high pressure to obtain a mixed solution B of the coal-based material and graphene;
and S3, spray drying the mixed solution B to obtain the composite powder of the coal-based material and the graphene.
Further, in step S1, the coal-based material is obtained by subjecting coal to high temperature treatment, the coal is one or more of anthracite, coking coal and lignite, the particle size of the coal is D90 not more than 20 μm, the carbon content of the coal is greater than 90%, and the high temperature treatment satisfies: in the nitrogen or argon atmosphere, the temperature is 400-1200 ℃, the heating speed is 5-10 ℃/min, and the constant temperature is 6-12 hours.
Further, the preparation method also comprises the step of calcining the composite powder at high temperature.
Further, the high-temperature calcination is carried out in an inert atmosphere, the temperature is 400-1200 ℃, the temperature rise speed is 5-10 ℃/min, the constant temperature is 6-12 hours, and the inert gas is nitrogen or argon.
Further, the mass of the graphite is 1-10% of that of the coal-based material, the graphite is one or two of expanded graphite and flake graphite, and the particle size of the graphite is D50 which is not more than 100 mu m.
Further, the pressure of the high-pressure homogenization is 600-1200bar, and the high-pressure homogenization is finished when the homogeneous particle size of the mixed liquid B reaches D90 ≤ 7 μm. Preferably, the pressure for high-pressure homogenization is 800-1000 bar.
Further, the inlet temperature of the spray drying is 180-. Preferably, the spray drying has an inlet temperature of 190 ℃ and an outlet temperature of 130 ℃.
In a second aspect, the negative electrode material is prepared by the preparation method, the negative electrode material is a graphene-compounded coal-based material, the particle size D90 of the negative electrode material is not more than 7 μm, and the mass of graphene in the negative electrode material is 1-10% of the mass of the coal-based material.
In a third aspect, the invention provides a battery, the battery comprises the above negative electrode material, and the battery comprises a sodium ion battery.
Compared with the prior art, the invention has at least the following beneficial effects:
1. and the structural stability of the battery cathode material is improved. According to the invention, graphite and a coal-based material are used as raw materials, the raw materials are uniformly mixed through high-pressure homogenization and the graphite is peeled to be changed into graphene, the graphene is a two-dimensional material with thin sheets, the graphene shapes the coal-based material and coats the surface of the coal-based material under the high-pressure homogenization and spray drying processes, and the deformation or collapse caused by excessive defects is avoided when the coal-based carbon material is calcined at high temperature and applied to a battery, so that the structural stability of the coal-based carbon material is improved.
2. The conductivity of the battery negative electrode material is improved. Compared with graphene prepared by a chemical method, the graphene prepared by a physical method through high-pressure homogenization has excellent electronic conductivity, and the graphene is compounded with a coal-based material, so that the conductivity of the coal-based material is improved.
3. The sodium storage performance of the battery cathode material is improved. The sodium ions can be stored on two sides of the graphene sheet layer and can also be adsorbed at defect positions such as pores of the graphene material and the like and at the edge and the cavity position of the graphene sheet layer to reversibly de-embed the sodium ions.
4. In the prepared negative electrode material, the mass ratio of the graphene is 1-10%, the graphene not only improves the conductivity of the coal-based material, but also serves as a conductive agent, namely the negative electrode material is provided with the conductive agent, and the conductive agent is not required to be additionally added in the subsequent preparation of battery negative electrode slurry.
Drawings
Fig. 1 is a flowchart of a method for preparing an anode material according to an embodiment;
fig. 2 is a flowchart of a method for preparing an anode material according to another embodiment.
Detailed Description
It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
As shown in fig. 1, an embodiment provides a preparation method of an anode material, including the following steps:
s101, mixing a coal-based material and graphite, and adding the mixture into a solvent to obtain a mixed solution A;
in this embodiment, the battery cathode material is made of anthracite and expanded graphite. The pretreatment of the anthracite coal comprises crushing and purification. Crushing smokeless coal: placing the bought blocky anthracite coal into a ball milling tank for 300r min -1 Grinding at the rotating speed until the anthracite is crushed to D90 which is less than or equal to 20 mu m; purification of anthracite: weighing a proper amount of anthracite powder, adding the anthracite powder into a mixed solution of 30 wt% of hydrochloric acid and 20 wt% of hydrofluoric acid, stirring and washing for 0.5-1 h at 90 ℃ to remove mineral substances in the coal powder, removing the solvent in a vacuum drying oven at 80 ℃ after suction filtration, and purifying to obtain the anthracite with carbon content>90%。
The inventor finds that when the particle size of the anthracite is D90 not more than 20 mu m through experiments, the particle size of the anthracite is reduced by a high-pressure homogenizing process more quickly, and the processing time of the materials in high-pressure homogenization can be effectively reduced, so that the energy consumption cost is reduced; the graphitization process is accelerated when the high-temperature calcination is directly carried out. The impurities in the anthracite not only influence the conductivity of the material, but also hinder the storage of sodium ions, when the carbon content of the anthracite is more than 90%, the lower the impurity content is, the better the conductivity of the coal material is, and meanwhile, when the anthracite is made into a negative electrode material and applied to a battery, the occurrence of side reactions in the battery is reduced, and the rate capability of the battery is improved.
Compared with flake graphite, the expanded graphite has larger interlayer spacing and higher conductivity, and is easier to strip through a high-pressure homogenization process to prepare graphene. When the particle size D50 of the expanded graphite is larger than 100 μm, the time for homogenizing the expanded graphite in the high-pressure homogenizer to the required particle size is long, which not only increases the energy consumption, but also increases the risk of damage to the homogenizer. And when the particle size D50 of the expanded graphite is less than or equal to 100 mu m, the particle size of the expanded graphite is reduced in the high-pressure homogenization process and the efficiency of converting the expanded graphite into graphene is higher, and the raw material purchasing cost is lower, so that the production and manufacturing cost is favorably reduced, and the method is suitable for industrial production.
In the mixing of the raw materials, the mass of the expanded graphite is 1-10% of that of the anthracite, and the inventor finds that when the addition amount of the expanded graphite is more than 10%, the mixed solution formed by adding the raw materials into the deionized water can not be subjected to the high-pressure homogenization process due to overlarge viscosity in the high-pressure homogenization process.
In both lithium batteries and sodium batteries, the amount of the conductive agent added to the negative electrode material was 10%. The mass of the expanded graphite is 1-10% of that of the anthracite, and the expanded graphite is converted into graphene after high-pressure homogenization treatment, namely the mass of the graphene is 1-10% of that of the anthracite. In addition, the inventor finds that the addition amount of the graphene is lower than 1%, the content of the graphene in the anthracite material is too low, the improvement of the conductivity of the anthracite material is not obvious, the addition amount of the graphene is higher than 10%, the migration of sodium ions is influenced by too much amount of the graphene, and the addition amount of the graphene has no competitive advantage compared with the addition amount of the existing conductive agent.
S102, homogenizing the mixed solution A at high pressure to obtain a mixed solution B of the coal-based material and the graphene;
in this embodiment, anthracite and expanded graphite are mixed and then added into deionized water to obtain a mixed solution, and the mixed solution is transferred to a high-pressure homogenizer for treatment. Anthracite, expanded graphite and graphite alkene are the powder, the mixing effect of powder in the liquid phase is superior to dry-mixing between the powder, deionized water provides the liquid environment for anthracite and expanded graphite so that dispersion and follow-up of both carry out high pressure homogeneity, the effect of misce bene and cladding between the powder can not be realized to conventional liquid phase mixing such as processes such as stirring, and in the high pressure homogeneity process, because the material can receive mechanical force effect such as high-speed shearing, high frequency oscillation, cavitation and convection current striking simultaneously, can make the misce bene of material and reduce the granularity size. The mixed liquid of anthracite and expanded graphite is at high-pressure homogeneity in-process, and the granularity of anthracite and expanded graphite all can reduce, and the material mixture that the granularity is little can be more even, and simultaneously, the lamella of expanded graphite can be peeled off and obtain graphite alkene, and graphite alkene can carry out the cladding to the anthracite surface because the lamella is thin, improves the structural stability of anthracite, and what the mixed liquid of anthracite and expanded graphite obtained through high-pressure homogeneity is the mixed liquid of anthracite and graphite alkene.
In the high-pressure homogenizing process, the pressure is 600-1200bar, when the pressure is less than 600bar, the efficiency of the high-pressure homogenization is long, and when the pressure is more than 1200bar, the instrument is easy to damage, and when the pressure is more than 1200bar, the high-pressure homogenization pressure is less than 600bar or more than 1200bar, so that the production cost is increased, and the industrial production is not facilitated. After the high-pressure homogenization is finished, the grain diameter D90 of the mixed liquid of the anthracite and the graphene is less than or equal to 7 mu m. When the D90 is larger than 7 mu m, the subsequent preparation of the sodium ion battery hinders the extraction of sodium ions due to overlarge particle size, and is also not beneficial to the infiltration of electrolyte. Meanwhile, the inventor finds that when the particle size D90 of the mixed liquid of the anthracite and the graphene is less than or equal to 7 microns, the materials in the mixed liquid are uniformly dispersed, the graphene forms a stable lamellar structure in the mixed liquid, the stacking condition is avoided, namely the materials in the obtained mixed liquid are stable, and the wall sticking phenomenon and the material separation condition are effectively avoided in the subsequent spray drying process.
S103, spray drying the mixed solution B to obtain composite powder of the coal-based material and the graphene;
after the high-pressure homogenization is finished, the mixed solution is subjected to spray drying, the inlet temperature of the spray drying is 180-200 ℃, and the outlet temperature is 120-150 ℃. The solvent used in the invention is deionized water, the volatilization temperature of the deionized water is 100 ℃, and the arrangement of the inlet temperature and the outlet temperature is favorable for accelerating the drying efficiency of the material while ensuring the volatilization of the solvent. The mixed liquid of graphene and coal is converted into graphene composite coal material powder by spray drying, and the granulation function of the spray drying also enhances the effect of coating the coal material with the graphene, so that the structural stability of the coal material is enhanced.
The coal material with stable structure is obtained by spray drying, and the coal material avoids the powder leakage phenomenon caused by the over-fine powder particles in the subsequent high-temperature calcination process, thereby improving the yield of high-temperature calcination.
And S104, calcining the composite powder at high temperature to obtain the cathode material.
The calcination temperature and the heating rate in the heating process affect the interlayer spacing and the defect type and quantity of the prepared carbon material, and the interlayer spacing between carbon layers can be adjusted to an optimal value suitable for the deintercalation of lithium ions or sodium ions by adjusting the pyrolysis temperature. The high-temperature calcination parameters determined by the inventor after a plurality of tests are as follows: the high-temperature calcination is carried out in the inert atmosphere, the temperature is 400-1200 ℃, the temperature-rising speed is 5-10 ℃/min, and the constant temperature is 6-12 hours.
In another embodiment, the preparation process of the negative electrode material is shown in fig. 2, coal is processed at high temperature in an inert atmosphere to obtain a coal-based material; mixing a coal-based material and graphite, and adding the mixture into a solvent to obtain a mixed solution C; homogenizing the mixed solution C at high pressure to obtain a mixed solution D of the coal-based material and the graphene; and spray drying the mixed solution D to obtain composite powder of the coal-based material and the graphene, wherein the composite powder is a negative electrode material.
The parameters of the mixing, the high-pressure homogenization, the spray drying and the high-temperature calcination are the same in the two preparation processes, and the negative electrode materials obtained in the two preparation processes have similar effects in the application of the sodium-ion battery.
The technical scheme adopted by the invention is as follows: 1. the anthracite and the expanded graphite are screened and the proportion is determined, the raw materials are mixed and added into the solvent, the liquid phase provides conditions for uniformly mixing and coating the raw materials, and the selection and the proportion of the raw materials ensure that the raw material mixed solution can efficiently carry out a high-pressure homogenization process on one hand, and on the other hand, the conductivity of the cathode material is improved, and the transmission of sodium ions cannot be hindered due to overlarge proportion in the raw materials; 2. the high-pressure homogenization is subjected to parameter adjustment according to the proportion of the raw materials, so that not only is the graphene prepared in the high-pressure homogenization process, but also the graphene coats the coal-based material, a mixed solution with uniformly mixed materials and proper granularity is obtained, and the electric conductivity and the structural stability of the coal-based material are improved by coating the coal-based material with the graphene; 3. the spray drying process is subjected to parameter adjustment according to the high-pressure homogenized material, so that the mixed solution is changed into composite powder, the coating effect can be enhanced by the granulation function of spray drying, and the structural stability of the composite material is further improved; 4. the composite powder is calcined at high temperature to generate the cathode material, and simultaneously, the graphene is combined with the cathode more tightly, the graphene provides a sodium storage site, and the sodium storage performance of the coal-based material is enhanced. The synergistic effects of uniform mixing, high-pressure homogenization, spray drying and high-temperature calcination ensure that the cathode material disclosed by the invention is stable in structure and has excellent conductivity and sodium storage performance. In addition, the inventor also unexpectedly finds that the graphene prepared by the invention not only improves the conductivity of the coal-based material, but also has the function of a conductive agent, namely the negative electrode material is provided with the conductive agent, and the conductive agent is not required to be additionally added in the subsequent preparation of the battery negative electrode slurry.
Example 1
Weighing 100g of pretreated anthracite (carbon content is more than 90 percent, D90 is less than 20 mu m) and 10g of expanded graphite (D50 is less than 100 mu m) in a 1L beaker, and adding 500g of deionized water to prepare a mixed solution; placing the mixed solution in a feeding cup of a high-pressure homogenizer, circularly homogenizing at 1000bar homogenizing pressure, sampling every hour during homogenizing to perform granularity test on the slurry, performing the granularity test in a laser particle sizer, and ending the high-pressure homogenizing until the granularity of the slurry reaches D90<7 mu m; obtaining composite slurry of graphene and anthracite after high-pressure homogenization, and performing spray drying on the slurry under the conditions that the inlet temperature is 190 ℃ and the outlet temperature is 130 ℃; and (3) placing the composite powder obtained by spray drying in a tubular furnace, introducing inert gas nitrogen, heating to 600 ℃ at the speed of 5 ℃/min, keeping the temperature for 8 hours, stopping heating, naturally cooling to normal temperature, and calcining at high temperature to obtain about 100g of the composite battery cathode material of graphene and anthracite.
Example 2
Weighing 100g of pretreated anthracite (carbon content is more than 90 percent, D90 is less than 20 mu m) and 1g of expanded graphite (D50 is less than 100 mu m) in a 1L beaker, and adding 500g of deionized water to prepare a mixed solution; placing the mixed solution in a feeding cup of a high-pressure homogenizer, circularly homogenizing at the homogenizing pressure of 800bar, sampling every hour during homogenizing to perform granularity test on the slurry, performing the granularity test in a laser particle sizer, and ending the high-pressure homogenizing until the granularity of the slurry reaches D90<5 mu m; carrying out high-pressure homogenization to obtain composite slurry of graphene and anthracite, and carrying out spray drying on the slurry under the conditions that the inlet temperature is 190 ℃ and the outlet temperature is 130 ℃; and (3) placing the composite powder obtained by spray drying in a tubular furnace, introducing inert gas nitrogen, heating to 1000 ℃ at the heating speed of 5 ℃/min, keeping the temperature for 8 hours, stopping heating, naturally cooling to normal temperature, and calcining at high temperature to obtain about 100g of the graphene and anthracite composite battery negative electrode material.
Example 3
Weighing 100g of pretreated anthracite (carbon content is more than 90 percent, D90 is less than 20 mu m) and 6g of expanded graphite (D50 is less than 100 mu m) in a 1L beaker, and adding 500g of deionized water to prepare a mixed solution; placing the mixed solution in a feeding cup of a high-pressure homogenizer, circularly homogenizing at 1000bar homogenizing pressure, sampling every hour during homogenizing to perform granularity test on the slurry, performing the granularity test in a laser particle sizer, and ending the high-pressure homogenizing until the granularity of the slurry reaches D90<7 mu m; carrying out high-pressure homogenization to obtain composite slurry of graphene and anthracite, and carrying out spray drying on the slurry under the conditions that the inlet temperature is 190 ℃ and the outlet temperature is 130 ℃; and (3) placing the composite powder obtained by spray drying in a tubular furnace, introducing inert gas nitrogen, heating to 1000 ℃ at a speed of 5 ℃/min, keeping the temperature for 8 hours, stopping heating, naturally cooling to normal temperature, and calcining at high temperature to obtain about 100g of the composite battery cathode material of graphene and anthracite.
Example 4
Weighing 100g of pretreated anthracite (carbon content is more than 90%, D90 is less than 20 mu m), placing the anthracite in a tube furnace, introducing inert gas nitrogen, raising the temperature at a speed of 5 ℃/min to 600 ℃, keeping the temperature for 8 hours, stopping raising the temperature, and naturally cooling to the normal temperature to obtain about 100g of coal-based material; 100g of the coal-based material after high-temperature calcination and 10g of expanded graphite (D50 is less than 100 mu m) are weighed and added into 500g of deionized water to prepare a mixed solution; placing the mixed solution in a feeding cup of a high-pressure homogenizer, circularly homogenizing at 1000bar homogenizing pressure, sampling every hour during homogenizing, and performing particle size test on the slurry in a laser particle size analyzer until the particle size of the slurry reaches D90<7 μm, wherein the high-pressure homogenizing is finished; and (3) obtaining composite slurry of graphene and coal-based materials after high-pressure homogenization, and performing spray drying on the slurry under the conditions that the inlet temperature is 190 ℃ and the outlet temperature is 130 ℃ to obtain the composite battery cathode material of graphene and anthracite.
Example 5
Weighing 100g of pretreated anthracite (carbon content is more than 90%, D90 is less than 20 mu m), placing the anthracite in a tube furnace, introducing inert gas nitrogen, heating to 1000 ℃ at a speed of 5 ℃/min, keeping the temperature for 8 hours, stopping heating, and naturally cooling to normal temperature to obtain about 100g of coal-based material; weighing 100g of the coal-based material after high-temperature calcination and 1g of expanded graphite (D50 is less than 100 mu m), and adding the materials into 500g of deionized water to prepare a mixed solution; placing the mixed solution in a feeding cup of a high-pressure homogenizer, circularly homogenizing at the homogenizing pressure of 800bar, sampling every hour during homogenizing to perform granularity test on the slurry, performing the granularity test in a laser particle sizer, and ending the high-pressure homogenizing until the granularity of the slurry reaches D90<5 mu m; and (3) obtaining composite slurry of graphene and a coal-based material after high-pressure homogenization, and performing spray drying on the slurry under the conditions that the inlet temperature is 190 ℃ and the outlet temperature is 130 ℃ to obtain the composite battery negative electrode material of graphene and anthracite.
Example 6
Weighing 100g of pretreated anthracite (carbon content is more than 90%, D90 is less than 20 mu m), placing the anthracite in a tube furnace, introducing inert gas nitrogen, heating to 1000 ℃ at a speed of 5 ℃/min, keeping the temperature for 8 hours, stopping heating, and naturally cooling to normal temperature to obtain about 100g of coal-based material; weighing 100g of the coal-based material after high-temperature calcination and 6g of expanded graphite (D50 is less than 100 mu m), and adding the materials into 500g of deionized water to prepare a mixed solution; placing the mixed solution in a feeding cup of a high-pressure homogenizer, circularly homogenizing at 1000bar homogenizing pressure, sampling every hour during homogenizing to perform granularity test on the slurry, performing the granularity test in a laser particle sizer, and ending the high-pressure homogenizing until the granularity of the slurry reaches D90<7 mu m; and (3) obtaining composite slurry of graphene and a coal-based material after high-pressure homogenization, and performing spray drying on the slurry under the conditions that the inlet temperature is 190 ℃ and the outlet temperature is 130 ℃ to obtain the composite battery negative electrode material of graphene and anthracite.
Comparative example 1
This example differs from example 3 in that no expanded graphite was added and the other parameters and conditions were exactly the same as in example 3.
Comparative example 2
This example is different from example 6 in that no expanded graphite was added, and other parameters and conditions were exactly the same as example 6.
Mixing the negative electrode materials in the examples and the comparative examples with polyvinylidene fluoride respectively according to the mass ratio of 9:1, adding deionized water, uniformly stirring to prepare slurry, coating the prepared slurry on a copper foil current collector through a coating machine, drying the copper foil coated with the slurry in a vacuum drying oven at 100 ℃ for 12 hours, and cutting the electrode plate into a wafer with the diameter of 12mm by using a slicing machine after the drying is finished. 1mol L of glass fiber membrane as a diaphragm -1 Lithium hexafluorophosphate is dissolved in 1L of mixed solution of ethylene carbonate and dimethyl carbonate (volume ratio is 1:1) as electrolyte, and the electrolyte is assembled into a CR2025 type button cell in a glove box in argon atmosphere. The electrochemical performance of the battery is tested on a Land 2001A type battery test system, a metal sodium sheet is used as a counter electrode, and the charge-discharge voltage range is 0.01-3V. The constant current charging and discharging test is carried out under the current density of 0.1C, and the test data of the CR2025 type button cell assembled by the negative electrode material in the embodiment are shown in the table 1.
TABLE 1 electrochemical Properties of the different anode materials in the examples
Figure BDA0003332591680000111
As can be seen from table 1, when the addition amount of the graphite is 6% of the mass of the anthracite, that is, the mass ratio of the graphene in the coal-based material is 6%, the electrochemical performance of the negative electrode material is the best, and in example 3, the reversible specific capacity is 237mAh g -1 The initial coulombic efficiency was 75%, the capacity retention rate after 50-week cycle was 92.7%, and the reversible specific capacity in example 6 was 240mAh g -1 The first coulombic efficiency was 74% and the capacity retention after 50 weeks cycling was 94.5%. Fruit of Chinese wolfberryThe electrochemical performance of the negative electrode materials in examples 1-6 is better than that of comparative examples 1 and 2.
The graphene material has a unique sodium storage mechanism, and sodium ions can be stored on two sides of a graphene sheet layer and also can be adsorbed at defect positions such as pores of the graphene material and the like and at the edge and hole positions of the graphene sheet layer to reversibly de-intercalate the sodium ions. According to the invention, the added graphite is peeled into graphene through high-pressure homogenization, and the graphene and the coal-based material are compounded to obtain the negative electrode material, so that the sodium storage points are increased, and the condition that the sodium storage points are lost due to secondary stacking of single-layer graphene in the charging and discharging processes is avoided; the graphene is a two-dimensional material with a thin sheet layer, can be adsorbed on the surface of a coal-based material to be coated in the processes of high-pressure homogenization and spray drying, and can be used for adjusting the structure of the coal-based material to realize the shaping of the coal-based material; compared with a single coal-based material, the cathode material provided by the invention has higher cathode capacity, more stable structure and high capacity retention rate after 50-week circulation.
Testing the electronic conductivity of the cathode material by a four-probe method: mixing the negative electrode material and polyvinylidene fluoride according to the mass ratio of 9:1, adding N-methyl pyrrolidone, uniformly stirring to prepare slurry, coating the prepared slurry on a PET film through a coating machine, drying the PET film coated with the slurry in a vacuum drying oven at 100 ℃ for 4 hours, taking out, and cutting a small wafer with the diameter of 19mm by using a slicing machine. The film resistivity test was performed on a ST2258C multifunctional digital four-probe tester. The test data are shown in Table 2.
TABLE 2 film resistivity of pole pieces made of different materials in the examples
Figure BDA0003332591680000121
Figure BDA0003332591680000131
As can be seen from the data in table 2, in the two processes, when the mass percentage of graphene in the coal-based material is 6% and 10%, the resistivity of the negative electrode material is the lowest, the conductivity is better, and the difference is not large, which indicates that a good conductive network is achieved when the percentage is 6%, and based on the cost, the graphene is preferably 6%, and the conductivity of the negative electrode material in examples 1 to 6 is better than that in comparative examples 1 and 2. The graphene is compounded with the coal-based material, so that the conductivity of the coal-based material is improved.
All possible combinations of the technical features of the above embodiments may not be described for the sake of brevity, but should be considered as within the scope of the present disclosure as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is specific and detailed, but not to be understood as limiting the scope of the invention. It should be noted that various changes and modifications can be made by those skilled in the art without departing from the spirit of the invention, and these changes and modifications are all within the scope of the invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (10)

1. The preparation method of the anode material is characterized by comprising the following steps of:
s1, mixing the coal-based material and the graphite, and adding the mixture into a solvent to obtain a mixed solution A;
s2, homogenizing the mixed solution A at high pressure to obtain a mixed solution B of the coal-based material and graphene;
and S3, spray drying the mixed solution B to obtain the composite powder of the coal-based material and the graphene.
2. The preparation method according to claim 1, wherein in the step S1, the coal-based material is obtained by subjecting coal to high temperature treatment, the coal is one or more of anthracite, coking coal and lignite, the particle size of the coal is D90 ≤ 20 μm, the carbon content of the coal is greater than 90%, and the high temperature treatment satisfies: in the nitrogen or argon atmosphere, the temperature is 400-1200 ℃, the heating speed is 5-10 ℃/min, and the constant temperature is 6-12 hours.
3. The preparation method according to claim 1, further comprising subjecting the composite powder to high-temperature calcination.
4. The preparation method according to claim 1, characterized in that the mass of the graphite is 1-10% of the mass of the coal-based material, the graphite is one or two of expanded graphite and flake graphite, and the particle size of the graphite is D50 ≤ 100 μm.
5. The preparation method as claimed in claim 1, wherein the pressure for the high-pressure homogenization is 600-1200bar, and the high-pressure homogenization is completed when the homogeneity particle size of the mixed liquid B reaches D90 ≦ 7 μm.
6. The method as claimed in claim 1, wherein the inlet temperature of the spray drying is 180-200 ℃ and the outlet temperature is 120-150 ℃.
7. The preparation method as claimed in claim 3, wherein the high temperature calcination is carried out in an inert atmosphere at 400-1200 ℃, the temperature rise rate is 5-10 ℃/min, the constant temperature is 6-12 hours, and the inert gas is nitrogen or argon.
8. The negative electrode material is prepared by the preparation method of any one of claims 1 to 7, the negative electrode material is a graphene-compounded coal-based material, the particle size D90 of the negative electrode material is less than or equal to 7 μm, and the mass of the graphene in the negative electrode material is 1-10% of the mass of the coal-based material.
9. A battery comprising the negative electrode material for battery of claim 8.
10. The battery of claim 9, wherein the battery comprises a sodium ion battery.
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