Asphalt-based carbon material, preparation method and application thereof, sodium-ion battery negative electrode and sodium-ion battery

Abstract

The invention relates to the technical field of sodium-ion batteries, and discloses an asphalt-based carbon material, a preparation method and application thereof, a sodium-ion battery negative electrode and a sodium-ion battery, the average interlayer spacing d002 of the asphalt-based carbon material is 0.36-0.4 nm, and the proportion of a quasi-graphite microcrystalline phase is 30-80 wt%. The pitch-based carbon material provided by the invention is applied to the sodium ion battery and has relatively high reversible specific capacity and first coulombic efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a pitch-based carbon material and a preparation method and application thereof, a sodium ion battery negative electrode and a sodium ion battery. Background Art

[0002] As the demand for lithium-ion batteries grows, problems such as uneven distribution of lithium resources and increasing costs have become increasingly prominent, limiting the large-scale development and application of lithium-ion batteries. Compared with lithium, sodium is not only abundant in the earth's crust, but also evenly distributed. Therefore, sodium-ion batteries, as one of the potential alternative systems to lithium-ion batteries, have received extensive attention and research.

[0003] Due to the large size of sodium ions, graphite, the current commercial lithium-ion battery negative electrode material, is difficult to use as a sodium-ion battery negative electrode material. In contrast, amorphous carbon materials have disordered microcrystalline structures and large interlayer spacing, showing relatively excellent sodium storage performance. Although amorphous carbon materials can be prepared by direct pyrolysis of relatively easy-to-obtain organic precursors such as biomass and organic resins. However, the relatively low carbonization yield leads to a high preparation cost, which affects its application in sodium-ion batteries.

[0004] In order to solve the cost problem in the actual production process of amorphous carbon materials, researchers have gradually turned their attention to asphalt as a carbon precursor, which has a wide source, low cost and high carbon content. However, asphalt will melt during pyrolysis, the microcrystalline structure will rearrange at high temperature to form more regular graphite microcrystals with smaller interlayer spacing, resulting in fewer active sites for sodium storage, and the sodium storage performance needs to be improved. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems of insufficient sodium storage performance and low reversible specific capacity of asphalt-based carbon materials in the prior art, and to provide a asphalt-based carbon material and its preparation method and application, a sodium ion battery negative electrode and a sodium ion battery. The asphalt-based carbon material used in sodium ion batteries has a high reversible specific capacity and first coulombic efficiency.

[0006] In order to achieve the above-mentioned object, the first aspect of the present invention provides a pitch-based carbon material, wherein the average interlayer spacing d of the pitch-based carbon material is 002 The diameter of the nanostructured carbon fiber is 0.36-0.4 mm, and the proportion of the quasi-graphite microcrystalline phase is 30-80 wt%.

[0007] Preferably, the asphalt-based carbon material is obtained by high-temperature carbonization of sulfonated asphalt. Based on the total mass of the sulfonated asphalt, the content of element C is 75-89wt%, preferably 78-85wt%, the content of element O is 10-20wt%, preferably 12-18wt%, and the content of element S is 1-5wt%, preferably 2-4wt%.

[0008] The second aspect of the present invention provides a method for preparing the above pitch-based carbon material, comprising:

[0009] (1) mixing asphalt with sulfuric acid to react to obtain sulfonated asphalt;

[0010] (2) The sulfonated asphalt is carbonized at high temperature under an inert atmosphere.

[0011] Preferably, the reaction temperature in step (1) is 50-150°C, preferably 70-130°C, the heating rate is 0.1-10°C / min, preferably 2-8°C / min, and the reaction time is 4-24h, preferably 8-20h.

[0012] A third aspect of the present invention provides the use of the above-mentioned pitch-based carbon material in sodium ion batteries.

[0013] A fourth aspect of the present invention provides a negative electrode for a sodium ion battery, the negative electrode comprising a current collector and a negative electrode material composited on the current collector;

[0014] Wherein, the negative electrode material includes the asphalt-based carbon material described in the first aspect.

[0015] A fifth aspect of the present invention provides a sodium ion battery, comprising the sodium ion battery negative electrode described in the fourth aspect.

[0016] Generally speaking, carbon materials prepared from asphalt materials are soft carbons with low capacity and no platform capacity; hard carbons are usually obtained by high-temperature carbonization of organic polymers such as polyvinyl alcohol, polyvinyl chloride, polyvinylidene fluoride, polyacrylonitrile, or resins such as phenolic resins. Hard carbons have the characteristics of disordered structure and large interlayer spacing, which is conducive to the diffusion and transmission of sodium ions. However, the cost of such organic polymers or resin raw materials is high, resulting in high cost of hard carbon preparation, which affects its application in sodium-ion batteries.

[0017] The inventors of the present invention have found in their research that by sulfonation treatment, the asphalt molecular chains are cross-linked to form a network structure, thereby effectively inhibiting the melting and structural rearrangement of the asphalt during the carbonization process; at the same time, a large number of sulfonic acid groups and carboxyl groups are introduced, and these oxygen-containing groups will be partially retained in the hard carbon matrix during the high-temperature carbonization process. By controlling the sulfonation degree of the asphalt and controlling the appropriate sulfonic acid group content, an asphalt-based hard carbon negative electrode material with disordered structure and large interlayer spacing can be obtained. The asphalt-based carbon material provided by the present invention is applied to sodium ion batteries, and compared with untreated asphalt-based carbon negative electrode materials, the reversible specific capacity and the first coulomb efficiency are significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1is the XRD spectrum of the pitch-based carbon material prepared in Example 1 of the present invention;

[0019] Figure 2 is the XRD spectrum of the pitch-based carbon material prepared in Comparative Example 1 of the present invention;

[0020] Figure 3 is a TEM image of the pitch-based carbon material prepared in Example 1 of the present invention;

[0021] Figure 4 is a TEM image of the pitch-based carbon material prepared in Comparative Example 1 of the present invention;

[0022] Figure 5 The first three charge-discharge curves of the sodium ion battery prepared from the pitch-based carbon material prepared in Example 1 of the present invention;

[0023] Figure 6 The first three charge-discharge curves of the sodium ion battery prepared from the pitch-based carbon material prepared in Comparative Example 1 of the present invention;

[0024] Figure 7 It is a comparison chart of the first cycle charging curves of the sodium ion batteries prepared from the asphalt-based carbon materials obtained in Comparative Example 1 and Example 1, respectively. DETAILED DESCRIPTION

[0025] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0026] The first aspect of the present invention provides a pitch-based carbon material, wherein the average interlayer spacing d of the pitch-based carbon material is 002 The diameter of the nanostructured carbon fiber is 0.36-0.4 mm, and the proportion of the quasi-graphite microcrystalline phase is 30-80 wt%.

[0027] Specifically, in the present invention, the average interlayer spacing d of the asphalt-based material is 002 The XRD diffractometer used in the X-ray diffraction spectrum of the pitch-based carbon material is Ultima IV, and the XRD test conditions are: 3-90°, step length is 10° / min. The average interlayer spacing d of the pitch-based carbon material is 002 In the above range, it is confirmed that a hard carbon material is generated in the pitch-based carbon material.

[0028] In a further preferred embodiment, the average interlayer spacing d of the pitch-based carbon material is 002In the above preferred case, it is beneficial to further improve the reversible specific capacity and the first coulombic efficiency of the carbon material.

[0029] In the present invention, "quasi-graphite microcrystalline phase" refers to a carbon microcrystalline structure with an interlayer spacing of 0.36-0.4 nm. In the present invention, the proportion of the quasi-graphite microcrystalline phase is obtained by separating the (002) peak of the X-ray diffraction spectrum of the pitch-based carbon material and then calculating the peak area proportion.

[0030] It is understandable that the asphalt-based carbon material of the present invention also contains carbon microcrystalline phases with an interlayer spacing less than 0.36 nm or greater than 0.4 nm. The interlayer spacing and content of such carbon microcrystalline phases of the present invention are not particularly limited. As long as the above-mentioned average interlayer spacing and the proportion of quasi-graphite microcrystalline phases are met, the asphalt-based carbon material can have a higher reversible specific capacity and first coulombic efficiency.

[0031] According to some preferred embodiments of the present invention, in the pitch-based carbon material, the quasi-graphite microcrystalline phase accounts for 60-80wt%, for example, it can be 60wt%, 62wt%, 65wt%, 68wt%, 70wt%, 72wt%, 75wt%, 78wt%, 80wt% and other specific but non-limiting contents or a range between two points. Controlling the content of the quasi-graphite microcrystalline phase in the pitch-based carbon material within the above range is conducive to further improving the reversible specific capacity and the first coulombic efficiency of the carbon material.

[0032] According to some preferred embodiments of the present invention, the pitch-based carbon material contains C, O and S elements.

[0033] According to the present invention, the asphalt-based carbon material is prepared from asphalt as a raw material. Specifically, the asphalt-based carbon material is obtained by high-temperature carbonization of sulfonated asphalt. Preferably, based on the total mass of the sulfonated asphalt, the content of C element is 75-89wt%, preferably 78-85wt%, the content of O element is 10-20wt%, preferably 12-18wt%, and the content of S element is 1-5wt%, preferably 2-4wt%. It can be understood by those skilled in the art that due to the complex composition of asphalt, the sulfonated asphalt may also contain other metal or non-metal elements, such as N element, etc. The present invention has no special limitation on this, as long as the C, O and S elements in the sulfonated asphalt meet the above content range. When there are other metal or non-metal elements in the sulfonated asphalt, the sum of the contents of C, O and S elements may not meet 100.

[0034] According to some preferred embodiments of the present invention, based on the total mass of the sulfonated asphalt, the content of the C element is 78-82wt%, the content of the O element is 14-16wt%, and the content of the S element is 2-3.5wt%. The asphalt-based carbon material obtained by high-temperature carbonization of the sulfonated asphalt having the above preferred composition has a more excellent first charge capacity and coulombic efficiency.

[0035] In the present invention, the content of each element in the pitch-based carbon material is tested by X-ray photoelectron spectroscopy (XPS) method.

[0036] Preferably, the sulfonation yield of the sulfonated asphalt is 120-160wt%, more preferably 125-150wt%. The sulfonation yield refers to the mass percentage of the sulfonated asphalt obtained by the sulfonation reaction to the mass percentage of the asphalt. The inventors of the present invention have found in their research that by controlling the degree of sulfonation of the asphalt to obtain a sulfonated asphalt with a suitable C, O, and S content, and further high-temperature carbonization to obtain an asphalt-based carbon material having a high reversible specific capacity and first coulomb efficiency, the reason for this may be that appropriate oxygen-containing groups such as sulfonic acid groups in the sulfonated asphalt will be partially retained in the hard carbon matrix during the high-temperature carbonization process, thereby being able to obtain a disordered structure and a large interlayer spacing asphalt-based hard carbon negative electrode material, in addition, compared to conventional hard carbon raw materials (organic polymers or resin raw materials), etc., the carbon material prepared using asphalt as a raw material can greatly reduce the cost of raw materials.

[0037] The second aspect of the present invention provides a method for preparing the above pitch-based carbon material, comprising:

[0038] (1) mixing asphalt with sulfuric acid to react to obtain sulfonated asphalt;

[0039] (2) The sulfonated asphalt is carbonized at high temperature under an inert atmosphere.

[0040] In the present invention, after the asphalt is treated with sulfuric acid, the asphalt molecular chains are cross-linked to form a network structure, and a large number of functional groups such as sulfonic acid groups and carboxyl groups are introduced. These oxygen-containing groups will be partially retained in the hard carbon matrix during the high-temperature carbonization process, and an asphalt-based hard carbon negative electrode material with disordered structure and large interlayer spacing can be obtained, which is beneficial to further improve the reversible specific capacity and first coulombic efficiency of the prepared carbon material.

[0041] In the present invention, the temperature of the sulfonation reaction is controlled to further regulate the sulfonation degree of the asphalt to obtain a suitable sulfonic acid group content. Preferably, the temperature of the reaction in step (1) is 50-150°C, preferably 70-130°C, and more preferably 90-110°C; the heating rate is 0.1-10°C / min, preferably 2-8°C / min, and more preferably 4-6°C / min; the reaction time is 4-24h, preferably 8-20h, and more preferably 10-16h. The above preferred embodiment is conducive to controlling the appropriate sulfonation degree, improving the uniformity of asphalt sulfonation, and helping to further improve the reversible specific capacity and first coulombic efficiency of the carbon material.

[0042] According to the present invention, preferably, the reaction is carried out under stirring conditions, and the stirring rate is 500-1000 r / min, preferably 600-900 r / min, and further preferably 700-800 r / min.

[0043] The present invention has no particular limitation on the equipment used in the reaction of step (1), and those skilled in the art can adaptably select the equipment. For example, in a laboratory, the reaction can be carried out in a magnetic heating stirrer.

[0044] According to the present invention, preferably, the sulfuric acid is provided by an aqueous solution of sulfuric acid, and the concentration of the aqueous solution of sulfuric acid is 9-18 mol / L, for example, it can be 9 mol / L, 10 mol / L, 11 mol / L, 12 mol / L, 13 mol / L, 14 mol / L, 15 mol / L, 16 mol / L, 17 mol / L, 18 mol / L and other typical but non-limiting concentration values ​​or ranges therebetween. Preferably, the concentration of the aqueous solution of sulfuric acid is 12-17 mol / L, and more preferably 14-16 mol / L. The use of the above preferred embodiment is conducive to the moderate sulfonation reaction, the introduction of appropriate functional groups such as sulfonic acid and carboxyl groups, avoiding excessive or insufficient reaction, and is conducive to obtaining a disordered structure and an appropriate interlayer spacing asphalt-based hard carbon negative electrode material after carbonization.

[0045] Preferably, the volume dosage of the aqueous solution of sulfuric acid is 2-40mL relative to 1g of the asphalt, for example, it can be 2mL, 3mL, 5mL, 8mL, 10mL, 12mL, 15mL, 18mL, 20mL, 25mL, 30mL, 35mL, 40mL and other typical but non-limiting ratios or ranges therebetween. Preferably, the volume dosage of the aqueous solution of sulfuric acid is 3-30mL relative to 1g of the asphalt, and more preferably 5-20mL. The above preferred embodiment is conducive to the moderate sulfonation reaction and avoids over-reaction or under-reaction.

[0046] According to some preferred embodiments of the present invention, step (1) comprises: dispersing the asphalt in an aqueous solution of sulfuric acid under stirring conditions, and then heating to a reaction temperature to react. The present invention has no particular limitation on the dispersion process, and it can be carried out in a manner well known to those skilled in the art.

[0047] In the present invention, the "asphalt" has a conventional definition in the art. The present invention has no particular limitation on the source and composition of the asphalt. Preferably, the asphalt is selected from at least one of coal tar asphalt, petroleum asphalt and natural asphalt. When the asphalt is two or more of the above-mentioned selections, the present invention has no particular limitation on the ratio of the specific substances, and any ratio can be mixed. The asphalt can be commercially available or prepared by existing methods.

[0048] The present invention does not particularly limit the average particle size of the asphalt, and it can be a powder with uniform particle size distribution. Preferably, the average particle size of the asphalt is 30-50 μm, preferably 35-45 μm. Asphalt with an average particle size not within the above range can be ground and sieved to obtain asphalt powder with an average particle size that meets the above range, and the grinding and sieving methods are conventional methods in the field. The average particle size of the asphalt powder is measured by a laser particle size analyzer.

[0049] According to the present invention, the preparation method further comprises: cooling, diluting, solid-liquid separation, washing and drying the product of the reaction in step (1) to obtain the sulfonated asphalt. The present invention does not have any special limitation on the cooling process, and the process well known to those skilled in the art can be used and cooled to room temperature.

[0050] In the present invention, the diluent used for the dilution is preferably deionized water, and the dilution multiple is preferably 2-10 times. According to the present invention, the dilution process is preferably to slowly pour the product system obtained after the sulfonation treatment into deionized water under stirring; the present invention does not have any special restrictions on the stirring rate, and the conditions familiar to those skilled in the art can be used. The present invention does not have any special restrictions on the pouring speed of the product, and the process familiar to those skilled in the art can be used to ensure that no bumping occurs.

[0051] The present invention has no particular limitation on the solid-liquid separation method, and the solid-liquid separation can be carried out in a conventional manner in the art, such as vacuum filtration.

[0052] The washing and drying can be carried out in a conventional manner in the art, as long as the unreacted sulfuric acid is removed, and the present invention has no particular limitation thereto.

[0053] Preferably, the washing can be performed by washing while filtering until the pH of the filtrate becomes neutral. The washing is preferably performed alternately with deionized water and anhydrous ethanol in sequence; the present invention does not have any special limitation on the number of washings, and the number of times known to those skilled in the art can be used to make the object to be washed neutral.

[0054] In the present invention, the drying is preferably drying. The present invention does not have any special restrictions on the conditions of the drying, and the drying can be carried out using a process well known to those skilled in the art. In the present invention, the drying is preferably carried out in an oven. Preferably, the drying temperature is 60-100° C. and the drying time is 12-24 hours.

[0055] According to the present invention, the high temperature carbonization treatment is performed under an inert atmosphere, and the inert atmosphere can be provided by at least one of nitrogen, helium, argon, neon and xenon.

[0056] According to some preferred embodiments of the present invention, the conditions for high-temperature carbonization include: a temperature of 1000-1700°C, preferably 1100-1600°C, and further preferably 1200-1500°C; a heating rate of 1-10°C / min, 2-9°C / min, and further preferably 3-8°C / min; a time of 0.5-4h, preferably 1-3.5h, and further preferably 1.5-3h.

[0057] In the present invention, the equipment used for the high-temperature carbonization is not particularly limited, and those skilled in the art can select it adaptively. According to a specific embodiment of the present invention, the high-temperature carbonization is carried out in a tubular furnace.

[0058] In the present invention, preferably, the product is naturally cooled after high-temperature carbonization, which helps to obtain a stable pitch-based carbon material and avoids the danger of operating the equipment used for calcination at high temperature.

[0059] In another aspect, the present invention provides a method for preparing a pitch-based carbon material, comprising:

[0060] (1) mixing asphalt with sulfuric acid to react to obtain sulfonated asphalt;

[0061] The reaction temperature is 50-150°C, preferably 70-130°C, the heating rate is 0.1-10°C / min, preferably 2-8°C / min, and the reaction time is 4-24h, preferably 8-20h;

[0062] (2) in an inert atmosphere, subjecting the sulfonated asphalt to high-temperature carbonization to obtain an asphalt-based carbon material; the high-temperature carbonization conditions include: a temperature of 1000-1700° C., a heating rate of 1-10° C. / min, and a time of 0.5-4 h;

[0063] The average interlayer spacing d of the pitch-based carbon material 002 The particle size is 0.36-0.4 nm, and the proportion of the quasi-graphite microcrystalline phase is 30-80wt%.

[0064] A third aspect of the present invention provides the use of the above-mentioned pitch-based carbon material in sodium ion batteries.

[0065] According to the present invention, preferably, the pitch-based carbon material is used in a negative electrode material for a sodium ion battery.

[0066] A fourth aspect of the present invention provides a negative electrode for a sodium ion battery, the negative electrode comprising a current collector and a negative electrode material composited on the current collector;

[0067] Wherein, the negative electrode material includes the asphalt-based carbon material described in the first aspect.

[0068] In the present invention, the negative electrode material prepared by using the above pitch-based carbon material is used in a sodium ion battery and has a high reversible capacity and first-cycle coulombic efficiency.

[0069] The present invention has no particular limitation on the current collector in the negative electrode of the sodium ion battery, and any material conventionally used for the negative electrode current collector of a sodium ion battery in the art may be used, such as copper foil.

[0070] The present invention has no particular limitation on the composition of the negative electrode material, as long as it contains the asphalt-based carbon material described in the first aspect. The negative electrode material may also contain additives such as adhesives, and those skilled in the art may select them according to actual needs. In the present invention, the amount and type of adhesive for the electrode material can be selected in a wide range, and the amount of adhesive can enable the asphalt-based carbon material to be prepared into a negative electrode material through the adhesive, and those skilled in the art may adjust it adaptively. Preferably, the adhesive is selected from sodium hydroxymethyl cellulose.

[0071] The present invention has no particular limitation on the preparation method of the negative electrode, and the preparation method may be carried out in a conventional manner in the art. For example, the preparation method may include: coating a slurry containing a negative electrode material on the current collector, and then drying the slurry.

[0072] A fifth aspect of the present invention provides a sodium ion battery, comprising the sodium ion battery negative electrode described in the fourth aspect.

[0073] The present invention has no particular limitation on the composition and structure of the sodium ion battery, as long as it contains the above-mentioned sodium ion battery negative electrode. Other compositions and structures can be selected conventionally in the art.

[0074] For example, the sodium ion battery includes an electrode group and a non-aqueous electrolyte, the electrode group and the non-aqueous electrolyte are sealed in a battery casing, the electrode group includes a positive electrode, a negative electrode and a diaphragm, the diaphragm is located between the positive electrode and the negative electrode, and the negative electrode is the negative electrode of the sodium ion battery described in the fourth aspect.

[0075] In the present invention, the non-aqueous electrolyte refers to an electrolyte solution whose solvent is not water. Those skilled in the art can select a suitable non-aqueous electrolyte according to the composition of the sodium ion battery, and no limitation is made here.

[0076] The present invention will be described in detail below through examples.

[0077] Unless otherwise specified, the raw materials used were purchased from commercial sources.

[0078] Example 1

[0079] (1) 4 g of petroleum asphalt with a particle size of 30-50 μm was dispersed in 40 mL of sulfuric acid (16 mol / L). In a magnetic heating stirrer, the mixture was heated to 110° C. at a heating rate of 5° C. / min. After stirring at a speed of 800 r / min for 12 h, the obtained product system was slowly poured into 400 mL of deionized water under stirring, filtered under reduced pressure, and washed alternately with deionized water and anhydrous ethanol until neutral. The mixture was dried in an oven at 80° C. for 10 h and weighed to obtain sulfonated asphalt (6.04 g, sulfonation yield 151.0%). Based on the total mass of the sulfonated asphalt, the content of C element was 79.20 wt%, the content of O element was 14.61 wt%, and the content of S element was 3.23 wt%.

[0080] (2) 1 g of the sulfonated asphalt was weighed and heated to 1300° C. at a heating rate of 5° C. / min in an argon atmosphere and kept at that temperature for 2 h for carbonization to obtain 0.564 g of asphalt-based carbon material A1.

[0081] The asphalt-based carbon material A1 was subjected to an X-ray diffraction test, and the obtained XRD pattern was as follows Figure 1 As shown, from Figure 1 It can be seen that the peak width of the (002) peak of the pitch-based carbon material obtained in this embodiment is relatively large, indicating that the degree of graphitization is low and the disorder is high. The average interlayer spacing d of the carbon material is calculated by the Bragg equation 002 The (002) peak is 0.378 nm, and the proportion of the quasi-graphite microcrystalline phase is calculated to be 72.38 wt % by peak fitting, indicating that the pitch-based carbon material has sufficient sodium storage sites.

[0082] The pitch-based carbon material obtained in Example 1 was tested by transmission electron microscopy. The HRTEM image obtained is as follows: Figure 3 As shown, from Figure 3It can be seen that the lattice stripes of the asphalt-based hard carbon material obtained in this embodiment have a high degree of disorder and a larger interlayer spacing of the crystallites, which is conducive to the interlayer embedding reaction of sodium ions and improves the platform sodium storage capacity at low potential.

[0083] Comparative Example 1

[0084] 1 g of petroleum asphalt with a particle size of 30-50 μm was carbonized in an argon atmosphere at a heating rate of 5°C / min to 1300°C and kept at this temperature for 2 hours to obtain 0.491 g of asphalt-based carbon material DA1.

[0085] The asphalt-based carbon material DA1 was subjected to an X-ray diffraction test, and the obtained XRD pattern was as follows Figure 2 As shown, from Figure 2 It can be seen that the peak width of the (002) peak of the pitch-based carbon material is small, indicating that the carbon material has a high degree of crystallite order. The average interlayer spacing d of the carbon material is calculated by the Bragg equation. 002 The diameter of the nanostructured carbon nanotubes is 0.349 nm, indicating that there are not enough sodium storage sites. The proportion of the quasi-graphite microcrystalline phase is calculated to be 14.53 wt%.

[0086] The pitch-based carbon material obtained in Comparative Example 1 was tested by transmission electron microscopy. The HRTEM image obtained is as follows: Figure 4 As shown, from Figure 4 It can be seen that the lattice fringes of the pitch-based carbon material obtained in Comparative Example 1 are orderly and regular, which is not conducive to the interlayer embedding reaction of sodium ions.

[0087] Example 2

[0088] (1) 4 g of petroleum asphalt with a particle size of 30-50 μm was dispersed in 40 mL of sulfuric acid (16 mol / L). In a magnetic heating stirrer, the mixture was heated to 100° C. at a heating rate of 5° C. / min. After stirring for 12 h at a speed of 750 r / min at the temperature, the obtained product system was slowly poured into 400 mL of deionized water under stirring, filtered under reduced pressure, and washed alternately with deionized water and anhydrous ethanol in sequence until neutral, dried in an oven at 80° C. for 10 h, and weighed to obtain sulfonated asphalt (6 g, sulfonation yield 150.0%). Based on the total mass of the sulfonated asphalt, the content of C element was 78.93 wt%, the content of O element was 14.63 wt%, and the content of S element was 3.34 wt%.

[0089] (2) 1 g of the sulfonated asphalt was weighed and heated to 1500° C. at a heating rate of 5° C. / min in an argon atmosphere and kept at that temperature for 2 h for carbonization to obtain 0.526 g of asphalt-based carbon material A2.

[0090] The asphalt-based carbon material A2 was subjected to X-ray diffraction test, and the obtained XRD pattern was similar to Figure 1The average interlayer spacing d of the carbon material is calculated by the Bragg equation: 002 It is 0.372nm, and the proportion of the quasi-graphite microcrystalline phase is 63.22wt%.

[0091] Example 3

[0092] (1) 4 g of petroleum asphalt with a particle size of 30-50 μm was dispersed in 30 mL of sulfuric acid (14 mol / L). In a magnetic heating stirrer, the mixture was heated to 110° C. at a heating rate of 5° C. / min. After stirring at a speed of 700 r / min for 12 h, the obtained product system was slowly poured into 400 mL of deionized water under stirring, filtered under reduced pressure, and washed alternately with deionized water and anhydrous ethanol to neutrality, dried in an oven at 80° C. for 10 h, and weighed to obtain sulfonated asphalt (5.04 g, sulfonation yield 126%). Based on the total mass of the sulfonated asphalt, the content of C element was 80.71 wt%, the content of O element was 14.34 wt%, and the content of S element was 2.84 wt%.

[0093] (2) 1 g of the sulfonated asphalt was weighed and heated to 1400° C. at a heating rate of 5° C. / min in an argon atmosphere and kept at that temperature for 2 h for carbonization to obtain 0.541 g of asphalt-based carbon material A3.

[0094] The asphalt-based carbon material A3 was subjected to X-ray diffraction test, and the obtained XRD pattern was similar to Figure 1 The average interlayer spacing d of the carbon material is calculated by the Bragg equation: 002 It is 0.376nm, and the proportion of the quasi-graphite microcrystalline phase is 66.82wt%.

[0095] Example 4

[0096] (1) 4 g of petroleum asphalt with a particle size of 30-50 μm was dispersed in 40 mL of sulfuric acid (18 mol / L). In a magnetic heating stirrer, the mixture was heated to 110° C. at a heating rate of 5° C. / min. After stirring at a speed of 800 r / min for 12 h, the obtained product system was slowly poured into 400 mL of deionized water under stirring, filtered under reduced pressure, and washed alternately with deionized water and anhydrous ethanol to neutrality, dried in an oven at 80° C. for 10 h, and weighed to obtain sulfonated asphalt (6.2 g, sulfonation yield 155%). Based on the total mass of the sulfonated asphalt, the content of C element was 77.04 wt%, the content of O element was 16.85 wt%, and the content of S element was 3.89 wt%.

[0097] (2) 1 g of the sulfonated asphalt was weighed and heated to 1300° C. at a heating rate of 5° C. / min in an argon atmosphere and kept at that temperature for 2 h for carbonization to obtain 0.561 g of asphalt-based carbon material A4.

[0098] The asphalt-based carbon material A4 was subjected to X-ray diffraction test, and the obtained XRD pattern was similar to Figure 1 The average interlayer spacing d of the carbon material is calculated by the Bragg equation: 002 The particle size is 0.368 nm, and the proportion of the quasi-graphite microcrystalline phase is 50.6 wt %.

[0099] Example 5

[0100] (1) 4 g of petroleum asphalt with a particle size of 30-50 μm was dispersed in 40 mL of sulfuric acid (14 mol / L). In a magnetic heating stirrer, the mixture was heated to 50°C at a rate of 5°C / min, and stirred at 800 r / min for 12 h at the temperature. Under stirring, the obtained product system was slowly poured into 400 mL of deionized water, filtered under reduced pressure, and washed alternately with deionized water and anhydrous ethanol until neutral, dried in an oven at 80°C for 10 h, and weighed to obtain sulfonated asphalt (4.31 g, sulfonation yield 107.8%). Based on the total mass of the asphalt-based carbon material, the content of C element was 82.13 wt%, the content of O element was 12.53 wt%, and the content of S element was 2.79 wt%.

[0101] (2) 1 g of the sulfonated asphalt was weighed and heated to 1400° C. at a heating rate of 5° C. / min in an argon atmosphere and kept at that temperature for 2 h for carbonization to obtain 0.538 g of asphalt-based carbon material A5.

[0102] The asphalt-based carbon material A5 was subjected to X-ray diffraction test, and the obtained XRD pattern was similar to Figure 1 The average interlayer spacing d of the carbon material is calculated by the Bragg equation: 002 It is 0.367nm, and the proportion of the quasi-graphite microcrystalline phase is 53.1wt%.

[0103] Example 6

[0104] (1) 4 g of petroleum asphalt with a particle size of 30-50 μm was dispersed in 40 mL of sulfuric acid (14 mol / L). In a magnetic heating stirrer, the mixture was heated to 80°C at a rate of 5°C / min, stirred at 800 r / min for 12 h at the temperature, and then the obtained product system was slowly poured into 400 mL of deionized water under stirring, filtered under reduced pressure, and washed alternately with deionized water and anhydrous ethanol to neutrality, dried in an oven at 80°C for 10 h, and weighed to obtain sulfonated asphalt (4.84 g, sulfonation yield 121%). Based on the total mass of the sulfonated asphalt, the content of C element was 82.54 wt%, the content of O element was 12.68 wt%, and the content of S element was 2.81 wt%.

[0105] (2) 1 g of the sulfonated asphalt was weighed and heated to 1300° C. at a heating rate of 5° C. / min in an argon atmosphere and kept at that temperature for 2 h for carbonization to obtain 0.556 g of asphalt-based carbon material A6.

[0106] The asphalt-based carbon material A6 was subjected to X-ray diffraction test, and the obtained XRD pattern was similar to Figure 1 The average interlayer spacing d of the carbon material is calculated by the Bragg equation: 002 It is 0.369nm, and the proportion of the quasi-graphite microcrystalline phase is 53.31wt%.

[0107] Performance Testing

[0108] The electrochemical performance of the pitch-based carbon materials prepared in the above examples and comparative examples was tested;

[0109] Specifically include:

[0110] The prepared asphalt-based carbon material was mixed with sodium carboxymethyl cellulose in a mass ratio of 95:5, and ground into slurry by adding appropriate amount of water. The obtained slurry was evenly scraped on the current collector copper foil, dried, and cut into a circular electrode with a diameter of 10 mm; the circular electrode was dried under vacuum conditions at 120°C for 10 h and then transferred to a glove box; in an Ar atmosphere, sodium metal was used as a counter electrode, and 1 mol of NaClO4 was dissolved in 1L of ethylene carbonate and diethyl carbonate solution with a volume ratio of 1:1 was used as an electrolyte to assemble the battery to obtain a CR2025 button battery;

[0111] The battery was charged and discharged using a LAND CT2001A charge and discharge instrument from Wuhan Rambo Electronics Co., Ltd. The test conditions were: charge and discharge rate was 0.1C, discharge cut-off voltage was 0.001V, and charge cut-off voltage was 2.5V. The test results are shown in Table 1.

[0112] Table 1

[0113] <![CDATA[Initial charge capacity / mAh·g -1 > First coulombic efficiency / % Example 1 278.7 79.3 Comparative Example 1 85.6 62.5 Example 2 250.1 68.3 Example 3 261.4 82.7 Example 4 206.1 64.8 Example 5 231.3 65.9 Example 6 226.5 66.1

[0114] It can be seen from Table 1 that when the asphalt-based carbon material provided by the present invention is used as the negative electrode of the sodium ion battery, the first charge capacity, platform capacity and first cycle coulombic efficiency are significantly improved compared with the unmodified asphalt-based carbon.

[0115] The charge-discharge curves of the first three cycles of a sodium ion battery prepared by using the pitch-based carbon material obtained in Example 1 as the negative electrode material are as follows: Figure 5 As shown. Figure 5 It can be seen that the asphalt-based hard carbon negative electrode material provided by the present invention exhibits a higher reversible capacity when used as a negative electrode of a sodium ion battery, and the platform capacity accounts for a high proportion.

[0116] The charge-discharge curves of the first three cycles of a sodium ion battery prepared by using the pitch-based carbon material obtained in Comparative Example 1 as the negative electrode material are as follows: Figure 6 As shown, from Figure 6 It can be seen that when the unmodified asphalt-based carbon material is used as the negative electrode material of the sodium ion battery, typical soft carbon behavior occurs, with low capacity and no platform capacity.

[0117] The first cycle charging curves of the sodium ion batteries prepared using the pitch-based carbon materials obtained in Comparative Example 1 and Example 1 as electrode materials are shown in FIG. Figure 7 As shown, from Figure 7 It can be seen that compared with the unsulfonated asphalt-based carbon negative electrode material, the prepared sulfonated asphalt-based carbon negative electrode material has a low potential platform and a significantly improved capacity.

[0118] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A pitch-based carbon material, characterized in that: The average interlayer spacing d of the pitch-based carbon material 002 The particle size is 0.36-0.4 nm, and the proportion of the quasi-graphite microcrystalline phase is 30-80wt%.

2. The pitch-based carbon material according to claim 1, wherein The average interlayer spacing d of the pitch-based carbon material 002 0.37-0.39nm; Preferably, in the pitch-based carbon material, the quasi-graphite microcrystalline phase accounts for 60-80wt%; Preferably, the pitch-based carbon material contains C, O and S elements.

3. The carbon material according to claim 1 or 2, wherein The asphalt-based carbon material is obtained by high-temperature carbonization of sulfonated asphalt. Based on the total mass of the sulfonated asphalt, the content of C element is 75-89wt%, preferably 78-85wt%, the content of O element is 10-20wt%, preferably 12-18wt%, and the content of S element is 1-5wt%, preferably 2-4wt%.

4. The method for preparing the pitch-based carbon material according to any one of claims 1 to 3, comprising: (1) mixing asphalt with sulfuric acid to react to obtain sulfonated asphalt; (2) The sulfonated asphalt is carbonized at high temperature under an inert atmosphere.

5. The preparation method according to claim 4, wherein: The reaction temperature of step (1) is 50-150°C, preferably 70-130°C, the heating rate is 0.1-10°C / min, preferably 2-8°C / min, and the reaction time is 4-24h, preferably 8-20h; Preferably, the reaction is carried out under stirring at a rate of 500-1000 r / min.

6. The preparation method according to claim 4 or 5, wherein: The sulfuric acid is provided by an aqueous solution of sulfuric acid, and the concentration of the aqueous solution of sulfuric acid is 9-18 mol / L, preferably 12-17 mol / L; Preferably, the volume usage of the aqueous solution of sulfuric acid is 2-40 mL relative to 1 g of the asphalt; Preferably, the asphalt is selected from at least one of coal tar asphalt, petroleum asphalt and natural asphalt; Preferably, the average particle size of the asphalt is 30-50 μm.

7. The preparation method according to any one of claims 4 to 6, wherein: The inert atmosphere is provided by at least one of nitrogen, helium, argon, neon and xenon; Preferably, the conditions for high temperature carbonization include: temperature of 1000-1700°C, preferably 1100-1600°C, heating rate of 1-10°C / min, preferably 2-9°C / min, time of 0.5-4h, preferably 1-3.5h.

8. Use of the pitch-based carbon material according to any one of claims 1 to 3 in sodium ion batteries; Preferably, the asphalt-based carbon material is used in a negative electrode material for a sodium ion battery.

9. A sodium ion battery negative electrode, characterized in that: The negative electrode includes a current collector and a negative electrode material composited on the current collector; Wherein, the negative electrode material comprises the asphalt-based carbon material according to any one of claims 1-3.

10. A sodium ion battery, comprising the sodium ion battery negative electrode according to claim 9.

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