Carbon material for sodium ion battery negative electrode, preparation method and application

Abstract

The invention discloses a carbon material for a negative electrode of a sodium-ion battery, a preparation method and application. The Raman spectrum of the carbon material meets the following characteristics (1) and (2): (1) 0.4 < = IG / ID < = 0.5; (2) ID3 + D4 / Iall is more than or equal to 0.35 and less than or equal to 0.42; and / or ID3 / IG + D2 + D3 > = 0.14; wherein IG is the area of a G peak in the Raman spectrum; iD is the area of a D peak in the Raman spectrum; iD3 + D4 is the total area of D3 and D4 peaks in the fitting Raman spectrum; iall is the total area of G, D1, D2, D3 and D4 peaks in the fitting Raman spectrum; iD3 is the area of the D3 peak in the fitting Raman spectrum; iG + D2 + D3 is the total area of G, D2 and D3 peaks in the fitting Raman spectrum. The carbon material structure for the negative electrode of the sodium-ion battery meets the requirements, and is beneficial to improvement of reversible capacity, first-circle discharge specific capacity and rate capability.

Description

Technical Field

[0001] The present invention relates to the technical field of anode materials for sodium-ion batteries, and more specifically, to carbon materials for sodium-ion battery anodes, preparation methods, and applications thereof. Background Art

[0002] In recent years, sodium-ion batteries are expected to be applied in the field of large-scale energy storage due to the advantages of abundant sodium resources and low cost. For sodium-ion batteries, their successful commercialization largely depends on the innovation of low-cost and high-performance electrode active materials. However, although graphite is widely used as the anode of lithium-ion batteries, due to the larger radius of Na ions (0.103 nm) than Li ions (0.071 nm), the small interlayer spacing of graphite anode materials seriously hinders the insertion and extraction of sodium ions, making the commonly used anode materials for existing lithium-ion batteries (such as graphite) not suitable for direct use in sodium-ion batteries. In 2000, Stevens, Dahn, and others found that hard carbon has a reversible sodium capacity of 300 mAhg -1 Thereafter, researchers turned their attention to the research of amorphous carbon anodes, especially hard carbon anode materials.

[0003] Generally, the precursors for preparing hard carbon are materials such as biomass, polymers, and coal. Among them, coal, as a fossil energy with rich reserves and wide distribution in China, has a higher carbon content and carbon density compared to small molecule substances and biomass carbon sources. It is the highest-quality carbon source with the highest carbon content in nature except for graphite and diamond. However, according to different metamorphic degrees of coal, there are different coal ranks, and different coal ranks show different structural characteristics, which make the performance of the anode materials prepared for sodium-ion battery anodes vary greatly. In view of this, it is particularly necessary to provide a high-capacity carbon material that can be prepared using coal as a precursor. Summary of the Invention

[0004] The purpose of the present invention is to provide carbon materials for sodium-ion battery anodes, preparation methods, and applications, and to provide a high-capacity carbon material that can use coal as a precursor.

[0005] The present invention is implemented as follows:

[0006] In a first aspect, the present invention provides a carbon material for a sodium-ion battery anode, and the Raman spectrum of the carbon material satisfies feature ① and feature ②:

[0007] Feature ① 0.4 ≤ I G / I D ≤ 0.5;

[0008] Feature ② 0.35 ≤ I D3+D4 / I All ≤ 0.42; and / or, I D3 / I Gˋ+D2+D3≥0.14;

[0009] wherein, I G is the area of the G peak in the Raman spectrum; I D is the area of the D peak in the Raman spectrum; I D3+D4 is the total area of the D3 and D4 peaks in the fitted Raman spectrum; I All is the total area of the Gˋ, D1, D2, D3 and D4 peaks in the fitted Raman spectrum; I D3 is the area of the D3 peak in the fitted Raman spectrum; I Gˋ+D2+D3 is the total area of the Gˋ, D2 and D3 peaks in the fitted Raman spectrum;

[0010] The fitted Raman spectrum is obtained by deconvolving the Raman spectrum; the peak value of the Gˋ peak is between 1560 cm -1 and 1600 cm -1 ; the peak value of the D1 peak is between 1330 cm -1 and 1370 cm -1 ; the peak value of the D2 peak is between 1480 cm -1 and 1520 cm -1 ; the peak value of the D3 peak is between 1610 cm -1 and 1640 cm -1 ; the peak value of the D4 peak is between 1180 cm -1 and 1220 cm -1 .

[0011] In an optional embodiment, the carbon material satisfies at least one of the following characteristics a - e:

[0012] a. d 002 is 0.36 nm - 0.39 nm;

[0013] b. Lc is 1.20 nm - 1.4 nm;

[0014] c. Lc / d 002 is 3.35 - 3.65;

[0015] d. The closed - pore rate is 40% - 65%;

[0016] e. The carbon material includes amorphous carbon;

[0017] f. The reversible specific capacity > 300 mAh / g;

[0018] h. The discharge specific capacity in the first cycle > 320 mAh / g;

[0019] i. The first - cycle efficiency > 90%.

[0020] In a second aspect, the present invention provides a method for preparing a carbon material for the negative electrode of a sodium-ion battery as described in the foregoing embodiments, comprising:

[0021] Float a slurry containing raw coal powder to obtain a floating matter and a sinking matter;

[0022] Pickle the floating matter to obtain a deashed floating matter;

[0023] Subject the deashed floating matter to pre-oxidation, steam activation, and roasting in sequence to obtain the carbon material.

[0024] In an optional embodiment, the particle size of the raw coal powder is less than 200 mesh;

[0025] And / or, in the floating step, the ratio of the raw coal powder to water in the slurry is 1 g:(15 - 25) cm 3 ;

[0026] And / or, the slurry further comprises a collector and / or a foaming agent;

[0027] And / or, in the floating step, the enrichment rate of the floating matter is 60% - 80%, and the enrichment rate of the sinking matter is 10% - 40%.

[0028] In an optional embodiment, the collector is selected from at least one of oleic acid, cetyltrimethylammonium bromide, and sodium dodecyl sulfate;

[0029] And / or, the content of the collector in the slurry is 0.25 g / L - 0.3 g / L;

[0030] And / or, the foaming agent comprises one or more of n-octanol, sec-octanol, cyclohexanol, pine oil, industrial fusel oil, or methyl isobutyl carbinol;

[0031] And / or, the content of the foaming agent in the slurry is 0.08 g / L - 0.1 g / L.

[0032] In an optional embodiment, the pickling includes hydrochloric acid pickling and hydrofluoric acid pickling of the floating matter in sequence;

[0033] And / or, after the hydrochloric acid pickling and hydrofluoric acid pickling, the floating matter is washed with deionized water until neutral.

[0034] In an optional embodiment, the concentration of the hydrochloric acid solution used for hydrochloric acid pickling is 3 mol / L - 7 mol / L, and the amount of the hydrochloric acid solution corresponding to each gram of the floating matter in the hydrochloric acid pickling step is less than 10 mL;

[0035] And / or, the concentration of the hydrofluoric acid solution used for hydrofluoric acid pickling is 35 wt% - 45 wt%, and the amount of the hydrofluoric acid solution corresponding to each gram of the floating matter in the hydrofluoric acid pickling step is less than 10 mL.

[0036] In an alternative embodiment, the pre-oxidation temperature is 250°C - 300°C, the time is 3h - 6h, and the atmosphere is an oxidizing atmosphere;

[0037] and / or, the activation temperature is 900°C - 950°C, and the time is 2h - 5h;

[0038] and / or, the activation method is physical activation, the activation gas is water vapor and / or carbon dioxide, and the flow rate of the activation gas is 0.1L / min - 2L / min;

[0039] and / or, the activation method is chemical activation, the activator is selected from at least one of KOH, NaOH, phosphoric acid, and potassium bicarbonate, and the addition amount is 5wt% - 40wt% of the ash-free floating matter after pre-oxidation;

[0040] and / or, the calcination temperature is 1200°C - 1300°C, and the time is 2h - 4h.

[0041] In a third aspect, the present invention provides a negative electrode sheet, comprising the carbon material described in the foregoing embodiment.

[0042] In a fourth aspect, the present invention provides a sodium-ion battery, comprising the negative electrode sheet described in the foregoing embodiment.

[0043] The present invention has the following beneficial effects:

[0044] The structure of the carbon material for the negative electrode of the sodium-ion battery meets the above requirements, which is beneficial to the improvement of the reversible capacity, the first-cycle discharge specific capacity, and the rate performance.

[0045] The carbon material for the negative electrode of the sodium-ion battery in the present application can be prepared using coal as a precursor, which is beneficial to cost reduction and large-scale industrial production.

[0046] The preparation process flow in the present application is simple, the process conditions are relatively mild, excessive corrosive activation (such as alkaline solution) is avoided, and it is environmentally friendly. At the same time, it provides a new direction for the high-value utilization of low-rank coal. Description of the Drawings

[0047] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0048] Figure 1 Microscopic morphology diagrams of raw coal SY, vitrinite-rich component SY-RV1, and inertinite component SY-RI1 in Example 1;

[0049] Figure 2 XRD diffraction pattern and fitting peak separation pattern of SY-RVC-H1;

[0050] Figure 3 Raman spectra of SY-RVC-H1 and SY-RIC-H1;

[0051] Figure 4 Raman fitting peak of SY-RVC-H1;

[0052] Figure 5 Electrochemical performance diagrams of some hard carbon materials;

[0053] Figure 6 Rate cycling performance of some hard carbon materials. Detailed implementation manners

[0054] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are followed. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0055] The embodiments of the present invention provide a carbon material for the negative electrode of a sodium-ion battery, and the Raman spectrum of the carbon material satisfies feature ① and feature ②:

[0056] Feature ① 0.4 ≤ I G / I D ≤ 0.5;

[0057] Feature ② 0.35 ≤ I D3+D4 / I All ≤ 0.42; and / or, I D3 / I Gˋ+D2+D3 ≥ 0.14;

[0058] Wherein, I G is the area of the G peak in the Raman spectrum; I D is the area of the D peak in the Raman spectrum; I D3+D4 is the total area of the D3 and D4 peaks in the fitted Raman spectrum; I All is the total area of the Gˋ, D1, D2, D3 and D4 peaks in the fitted Raman spectrum; I D3 is the area of the D3 peak in the fitted Raman spectrum; I Gˋ+D2+D3 is the total area of the Gˋ, D2 and D3 peaks in the fitted Raman spectrum;

[0059] The fitted Raman spectrum is obtained by deconvolution of the Raman spectrum; the peak value of the Gˋ peak is at 1560 cm -1 ~1600 cm -1between; the peak value of the D1 peak is at 1330 cm -1 ~1370 cm -1 between; the peak value of the D2 peak is at 1480 cm -1 ~1520 cm -1 between; the peak value of the D3 peak is at 1610 cm -1 ~1640 cm -1 between; the peak value of the D4 peak is at 1180 cm -1 ~1220 cm -1 between.

[0060] I G / I D is related to the degree of order of the carbon structure in the Raman spectrum. In this application, I G / I D is used to characterize the degree of order of the carbon structure. Specifically, I G / I D satisfies 0.4 ≤ I G / I D ≤ 0.5. For example, I G / I D can be 0.4, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5.

[0061] I D3+D4 / I All is related to the defects of the carbon structure. In this application, I D3+D4 / I All is used to characterize the degree of defects of the carbon structure. Specifically, I D3+D4 / I All satisfies 0.35 ≤ I D3+D4 / I All ≤ 0.42. For example, I D3+D4 / I All can be 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42.

[0062] I D3 / I Gˋ+D2+D3 is related to the degree of disorder of the carbon structure. In this application, I D3 / I Gˋ+D2+D3 is used to characterize the degree of disorder of the carbon structure. Specifically, I D3 / I Gˋ+D2+D3 satisfies I D3 / I Gˋ+D2+D3 ≥ 0.14. For example, I D3 / I Gˋ+D2+D3It can be 0.141, 0.142, 0.143, 0.144, 0.145, 0.146, 0.147, 0.148, 0.149, 0.150, 0.160, 0.170, 0.180, preferably 0.18 ≥ I D3 / I Gˋ+D2+D3 ≥ 0.14

[0063] The carbon material structure for the negative electrode of the sodium-ion battery meets the above requirements, which is beneficial to the improvement of reversible capacity, first-cycle discharge specific capacity and rate performance.

[0064] In this application, the peak of the G peak is usually between 1580 cm and 1620 cm, and the peak of the D peak is usually between 1300 cm and 1400 cm. The Gˋ peak is obtained by deconvoluting the G peak.

[0065] In an alternative embodiment, the carbon material satisfies at least one of the following characteristics a-i:

[0066] a.d 002 is 0.36 nm - 0.39 nm, for example, it can be 0.36 nm, 0.365 nm, 0.37 nm, 0.375 nm, 0.38 nm, 0.385 nm, 0.39 nm; moderately increasing d 002 is beneficial to reducing the sodium ion diffusion resistance and providing more active sites, which is beneficial to the insertion and extraction of sodium ions, and thus helps to improve the sodium storage capacity, but d 002 being too large will lead to a decrease in structural stability, electronic conductivity and cycle stability.

[0067] b. Lc is 1.20 nm - 1.4 nm, for example, it can be 1.20 nm, 1.25 nm, 1.30 nm, 1.35 nm, 1.40 nm; Lc is related to the crystallinity of the material. When Lc is within a reasonable range, it is beneficial to balance the electronic conductivity while providing sufficient sodium storage sites.

[0068] c. Lc / d 002 is 3.35 - 3.65, for example, it can be 3.35, 3.40, 3.45, 3.50, 3.55, 3.60, 3.65; the decrease of Lc / d 002 is beneficial to improving the sodium storage capacity, but at the same time it will also lead to a decrease in electronic conductivity and rate performance.

[0069] d. The closed pore rate is 40% - 65%, for example, it can be 40%, 45%, 50%, 55%, 60%, 65%; the decrease of the closed pore rate is beneficial to increasing the number of effective sodium storage sites, and thus increasing the sodium storage capacity, but too low closed pore rate will lead to a decrease in cycle performance.

[0070] e. The carbon material includes amorphous carbon;

[0071] f. Reversible specific capacity > 300 mAh / g, for example, it can be 300 mAh / g, 305 mAh / g, 310 mAh / g, 315 mAh / g, 320 mAh / g;

[0072] h. Specific discharge capacity in the first cycle > 320 mAh / g, for example, it can be 320 mAh / g, 330 mAh / g, 340 mAh / g, 350 mAh / g, 360 mAh / g;

[0073] i. Initial efficiency > 90%, for example, it can be 90%, 91%, 92%, 93%, 94%.

[0074] The embodiment of the present invention also provides a preparation method of the carbon material for the negative electrode of a sodium ion battery described in the foregoing embodiment, including:

[0075] Float the slurry containing raw coal powder to obtain the floating matter and the sinking matter;

[0076] Pickle the floating matter to obtain the ash - removed floating matter;

[0077] Successively subject the ash - removed floating matter to pre - oxidation, steam activation and roasting to obtain the carbon material.

[0078] In this application, the main components in the floating matter are vitrinite and a small amount of exinite. Vitrinite and exinite have a high volatile content and adhesiveness, and their chemical reaction activity is high, which is called the active component; the main component in the sinking matter is inertinite, which has high thermal stability and aromatization degree, and is called the inert component. The I G / I D 、I D3+D4 / I All and I D3 / I Gˋ+D2+D3 of the carbon material obtained by pickling, pre - oxidizing, steam - activating and roasting the floating matter meet the foregoing requirements, which is beneficial to the improvement of the capacity.

[0079] The raw coal powder in this application can be selected as low - rank coal, which is obtained by screening the low - rank coal according to the national standard GB / T477 - 2008 "Coal Screening Test Method", and then subjected to flotation.

[0080] In an alternative embodiment, the particle size of the raw coal powder is less than 200 mesh;

[0081] and / or, in the flotation step, the ratio of the raw coal powder to water in the slurry is 1 g:(15 - 25) cm 3 ;

[0082] and / or, the slurry further includes a collector and / or a foaming agent;

[0083] And / or, in the flotation step, the enrichment rate of the floating matter is 60%-80%, and the enrichment rate of the sinking matter is 10%-40%.

[0084] The enrichment content can be determined according to the heavy liquid separation method, that is, according to the configuration specific gravity liquid standard in the "Compilation of Coal Industry Standards", the ZnCl2 solution is configured, and the enrichment rate is determined using solutions with different specific gravities. The enrichment rate of the floating material, i.e., the vitrinite group, is 60-80%, and the enrichment rate of the sinking material, i.e., the inert group, is 10-40%. Vitrinite-based hard carbon has a richer graphite microcrystalline structure and C=O content, and the prepared carbon materials show better reversible capacity, ICE and rate performance. The impurities contained in the vitrinite intermediate product are the inert group and the exinite group that are not completely separated. The exinite group has a low content and decomposes into visible oil-like liquid and gas volatilization during the carbonization process, which has little effect on the negative electrode material; the inert group is difficult to graphitize, needs to be heated to a higher temperature to achieve sodium storage performance, and has a relatively large specific surface area, so its content needs to be reduced as much as possible.

[0085] In an optional embodiment, the collector is selected from at least one of oleic acid, hexadecyltrimethylammonium bromide and sodium dodecyl sulfate; but not limited to the above, any substance that can play the same role can be used;

[0086] And / or, the content of the collector in the slurry is 0.25 g / L-0.3 g / L;

[0087] And / or, the foaming agent includes one or more of n-octanol, sec-octanol, cyclohexanol, pine oil, industrial fusel alcohol or methyl isobutyl carbinol; but not limited thereto, any substance that can play the same role can be used.

[0088] And / or, the content of the foaming agent in the slurry is 0.08g / L-0.1g / L.

[0089] Reasonable setting of the types and dosage of collectors and frothers is beneficial to improving flotation efficiency and reducing flotation costs while obtaining the target floated objects.

[0090] In an optional embodiment, the pickling comprises sequentially performing hydrochloric acid pickling and hydrofluoric acid pickling on the floating matter;

[0091] And / or, after the hydrochloric acid washing and the hydrofluoric acid washing, the floating matter is washed with deionized water to neutrality.

[0092] The hydrochloric acid washing and hydrofluoric acid washing of the floating matter can remove the minerals contained in the floating matter and reduce the influence of the mineral residues on the performance of the negative electrode material.

[0093] In an alternative embodiment, the concentration of the hydrochloric acid solution used in the hydrochloric acid washing is 3 mol / L - 7 mol / L, for example, it can be 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L; the amount of the hydrochloric acid solution corresponding to each gram of the floating matter in the hydrochloric acid washing step is less than 10 mL, for example, it can be 10 mL, 9 mL, 8 mL, 7 mL, 6 mL, 5 mL, 4 mL, 3 mL, 2 mL, 1 mL;

[0094] and / or, the concentration of the hydrofluoric acid solution used in the hydrofluoric acid washing is 35 wt% - 45 wt%, for example, it can be 35 wt%, 37 wt%, 39 wt%, 40 wt%, 42 wt%, 44 wt%, 45 wt%; the amount of the hydrofluoric acid solution corresponding to each gram of the floating matter in the hydrofluoric acid washing step is less than 10 mL, for example, it can be 10 mL, 9 mL, 8 mL, 7 mL, 6 mL, 5 mL, 4 mL, 3 mL, 2 mL, 1 mL.

[0095] Reasonably adjusting the acid concentration and dosage is beneficial to improving the removal effect of minerals. It should be noted that, if necessary, in order to improve the removal efficiency of minerals, the pickling times and the acid dosage can also be increased, but it will cause a decrease in efficiency or an increase in acid loss.

[0096] In an alternative embodiment, the pre-oxidation temperature is 250°C - 300°C, for example, it can be 250°C, 260°C, 270°C, 280°C, 290°C, 300°C; the time is 3 h - 6 h, for example, it can be 3 h, 4 h, 5 h, 6 h; the atmosphere is an oxidizing atmosphere, such as at least one of air and oxygen; some impurities such as organic matters can be removed in the pre-oxidation step.

[0097] and / or, the activation temperature is 900°C - 950°C, for example, it can be 900°C, 910°C, 920°C, 930°C, 940°C, 950°C; the time is 2 h - 6 h, for example, it can be 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h.

[0098] The activation method can be one or more of physical activation and chemical activation. Among them, the activation gas used in physical activation can be at least one of water vapor and carbon dioxide, and the flow rate of the activation gas is 0.1 L / min - 2 L / min. For example, it can be 0.1 L / min, 0.3 L / min, 0.5 L / min, 1 L / min, 1.5 L / min, 2 L / min; the activator used in chemical activation is selected from at least one of KOH, NaOH, phosphoric acid, and potassium bicarbonate, and the addition amount of the activator is 5 wt% - 40 wt% of the deashed floating matter after pre-oxidation. For example, it can be 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%. During the activation step, it is necessary to control the activation temperature, time, and gas flow rate to adjust the carbon material structure while controlling the closed pore rate and avoiding too low a closed pore rate caused by ineffective closure of excessive open pores generated during the activation process.

[0099] It should be noted that when physical activation is used in the activation step, the activation gas reacts with carbon in the coal: C + H2O = CO + H2 or CO2 + C = 2CO. While affecting the material structure, it can also generate a developed pore structure. After calcination, the carbon layer is distorted to form a closed pore structure, which can add more active sites for the storage of Na + and is beneficial to the intercalation and deintercalation of Na + and thus is beneficial to improving the capacity.

[0100] And / or, the calcination temperature is 1200 °C - 1300 °C. For example, it can be 1200 °C, 1220 °C, 1240 °C, 1260 °C, 1280 °C, 1300 °C; the time is 2 h - 4 h. For example, it can be 2 h, 3 h, 4 h. The calcination process affects the degree of carbonization. Generally, the higher the carbonization temperature and the longer the time, the more beneficial it is to improve the degree of carbonization.

[0101] It should be noted that starting from the perspective of organic microscopic composition, this application uses the method of heavy liquid centrifugal separation to separate and enrich the components of coal rock, and uses pre-oxidation and non-alkali activation methods to obtain a high-capacity and low-impurity coal-based hard carbon anode material. Moreover, the preparation process flow is simple, the process conditions are relatively mild, excessive corrosive activation (such as alkaline solution) is avoided, it is environmentally friendly, and it is suitable for large-scale promotion.

[0102] The embodiment of the present invention also provides a negative electrode plate, including the carbon material described in the foregoing embodiment.

[0103] The embodiment of the present invention also provides a sodium-ion battery, including the negative electrode plate described in the foregoing embodiment.

[0104] The features and performance of the present invention will be further described in detail below in conjunction with the embodiments.

[0105] Explanation of Terms

[0106] Mad refers to moisture (air-dried basis), Ad refers to ash (dry ash-free basis), Vdaf refers to volatile matter (dry ash-free basis), and FCad refers to fixed carbon (dry ash-free basis). The above various bases are based on the proportions of moisture, ash, volatile matter, and fixed carbon in different states of the material, which can better measure the quality of the material in industry; in elemental analysis, d refers to the mass fraction of elements in the dry basis.

[0107] Explanation of Test Methods

[0108] 1. Pore characteristic parameters: The specific surface area and pore volume of the material were measured by the low-temperature nitrogen adsorption method using a MICROMERITICS ASAP2020 fully automatic physical sorption analyzer in the United States. The test conditions were: adsorption temperature of -195.8 °C (77.35 K), degassing temperature of 150 °C, degassing time of 6 h, BET method for specific surface area analysis, and BJH model for pore size analysis model.

[0109] 2. XRD and Raman tests: The XRD instrument used was a Beijing Purkinje General MSALXD-3 X-ray powder diffractometer. The test scanning range was: 12 - 65°; the scanning speed was: 2° / min; the step size was: 0.02°, and the incident wavelength λ = 1.5406. The sample was ground and sieved to less than 100 mesh, immediately sent to the laboratory, placed on a glass carrier and pressed into a tablet, placed on the sample holder, and then sent to the X-ray diffractometer for XRD experiments. The laser Raman spectroscopy (LRS) characterization of the sample was carried out on an In-Via Qontor laser confocal Raman spectrometer (Renishaw, UK). The laser wavelength used for testing was 532 nm. It was equipped with a 532 nm laser, laser power of 5 mW, integration time of 2 s, and accumulation times of 10 times.

[0110] 3. XRD microcrystalline parameters: There are two relatively large "bun-shaped" cell diffraction peaks in the range of 15 - 55°, corresponding to the 002 peak and 100 peak respectively. (The 002 peak of natural graphite is located at 26.6°). In order to compare the microcrystalline structures of the carbon residue materials, the 002 peak and 100 peak in the wavelength bands of 12 - 35° and 35 - 50° of the diffraction angle were fitted by Origin. For more accurate comparison and less error, first, the baseline of the 12 - 65° data was subtracted, and then the 002 peak and 100 peak were fitted by peak fitting. The specific microcrystalline structure information of the sample was calculated according to Bragg's law and Scherrer's law:

[0111] The calculation formula is as follows:

[0112] La = k1λ / (β 100 cosθ 100 )

[0113] Lc = k2λ / (β 002 cosθ 002 )

[0114] d 002 = λ2sinθ 002

[0115] where: d 002 is the monolayer distance of the microcrystalline structure; Lc is the microcrystalline stacking height perpendicular to the layer; La is the microcrystalline diameter size; θ 002 , θ 100 are the Bragg diffraction angles; β 002 , β 100 are the full width at half maximum; λ is the X-ray wavelength, nm; k is the shape factor, k1 = 1.84, k2 = 0.94.

[0116] 4. Raman microcrystalline parameters: In the first-order region (800 - 2000 cm -1 ) of the Raman spectrum of the carbonaceous material, there are two distinct overlapping bands, respectively called the D and G bands. Due to the overlap of the D and G bands, using only the D and G bands in the Raman spectrum will result in the loss or unknown of the characteristic information of highly disordered carbonaceous materials. Therefore, it is necessary to further deconvolute (peak fitting) the Raman spectrum of coal to obtain the hidden information of the skeletal carbon structure in the overlapping region. Among various methods, the Raman spectrum of the carbonaceous material has first-order and second-order spectral bands. The first-order spectral band can usually be further analyzed and divided into D1 - D4 and G band characteristic peaks. Applying Origin2016 to fit the peaks between 800 - 2000 cm -1 of the Raman spectrum and deconvoluting the Raman spectrum into 4 Lorentz peaks (D1, D2, D4, G) and 1 D3 Gaussian peak is the best fit, as specifically described in Table 1.

[0117] Table 1 Raman deconvolution peak / band assignment definition

[0118]

[0119]

[0120] 5. Material electrochemical performance testing:

[0121] According to the mass ratio of negative electrode material: SP: CMC: SBR = 94: 2: 1.5: 2.5, weigh the negative electrode material, SP, CMC, SBR respectively and mix them evenly in deionized water to form a slurry; apply the mixed slurry on the aluminum foil current collector, bake in an oven at 80°C for 1h, and take it out and cool it to room temperature. Adjust the rolling spacing to roll the pole piece. Cut the rolled pole piece into a small disc with a diameter of 14mm and weigh it as m1. Similarly, cut the aluminum foil current collector into an aluminum foil disc with a diameter of 14mm and weigh it as m2. Among them, (m1-m2)*0.94 is the mass of the active material, recorded as m3. The weighed small discs were then placed in an 80°C oven under vacuum for 12 hours and then transferred to a glove box. The sodium sheet was used as the counter electrode and auxiliary electrode (electrolyte 1MNaPF6 / EC:DMC:DEC=3:2:2) and the fiber diaphragm was used as the diaphragm to assemble a sodium ion button cell in a glove box with oxygen and water content less than 0.01ppm. After standing for 12 hours, the electrochemical performance was tested at a constant current on the Wuhan Blue Electric Battery Test System.

[0122] The test method adopts the first-effect test system: stand for 2 hours, discharge to 0.000V at 0.1C, discharge to 0.000V at 0.08C, discharge to 0.000V at 0.05C, discharge to 0.000V at 0.02C, stand for 5 minutes, charge to 2.0V at 0.1C, and stand for 5 minutes. The cycle rate performance test mainly adopts different discharge test methods. At 25°C, each battery is charged to 2.0V at 0.1C rate and discharged to 0V at 0.1C rate, and fully charged and discharged 3 times, and then 0.2C, 0.5C, 0.2C, and 0.1C are carried out in sequence, and the number of cycles and the capacity of the corresponding battery are recorded.

[0123] Example 1

[0124] This embodiment provides a carbon negative electrode material, which specifically includes the following steps:

[0125] S1: The raw coal SY is naturally dried and then coarsely crushed and ground. Then, the raw coal is screened according to the national standard GB / T477-2008 "Coal Screening Test Method" and passed through a 200-mesh sieve to obtain the flotation sample.

[0126] S2: Mix the original flotation sample with water at a rate of 50g:1000cm 3 The mixture was mixed in proportion, and a certain amount of collector was added during flotation and stirred for 1 minute, and then a certain amount of frother was added. The floating foam and the sinking material were collected, filtered and dried to obtain the vitrinite enriched product SY-RV1 and the inertinite enriched product SY-RI1 (wherein the collector was oleic acid and the frother was n-octanol, and the amounts thereof were 0.3 g / L and 0.1 g / L, respectively). The SEM images of the raw coal SY, the vitrinite enriched product SY-RV1 and the inertinite enriched product SY-RI1 are shown in FIG.Figure 1 As shown, the basic data is shown in Table 2.

[0127] S3: Place the obtained vitrinite concentrate SY-RV1 in a 5 mol / L HCl solution (ratio: 1 g solid sample : 10 mL acid solution, the same below), keep stirring at 80 °C for 6 h, after suction filtration, wash with deionized water until neutral, then place it in 40 wt% HF and keep stirring at 80 °C for 6 h, after suction filtration, wash with deionized water until neutral, and dry at 70 °C after suction filtration. After drying is completed, cool to room temperature and then dry to obtain the deashed sample SY-RVRC1.

[0128] S4: Place the prepared deashed sample in a tube furnace, heat up to 275 °C and pre-oxidize with air for 3 h, then pass steam at 0.5 L / min in a small rotary furnace for activation at 915 °C for 4 h, and finally roast at 1250 °C in an inert atmosphere of nitrogen for 3 h to obtain the carbon negative electrode material SY-RVC-H1. The XRD diffraction pattern and the fitting peak splitting pattern are as Figure 2 shown, the Raman spectrum is as Figure 3 shown, the Raman fitting peaks are as Figure 4 shown.

[0129] Table 2

[0130]

[0131] Example 2

[0132] This example provides a carbon negative electrode material, which specifically includes the following steps:

[0133] S1: After the raw coal SY is naturally air-dried, it is coarsely broken, ground, and then screened according to the national standard GB / T477-2008 "Coal Screening Test Method" to obtain the flotation original sample through a 200-mesh sieve.

[0134] S2: Mix the flotation original sample with water at a ratio of 40 g : 1000 cm 3 proportion, add a certain amount of collector and stir for 1 min during flotation, then add a certain amount of frother, collect the floating foam and the sinking matter, perform suction filtration and drying to obtain the vitrinite concentrate SY-RV2 and the inertinite concentrate SY-RI2 (wherein, the collector is oleic acid, the frother is n-octanol, and their dosages are 0.3 g / L and 0.1 g / L respectively).

[0135] S3: Place the obtained vitrinite concentrate SY-RV2 in a 5.5 mol / L HCl solution (ratio: 1 g solid sample : 10 mL acid solution, the same below), keep stirring at 80 °C for 6 h, after suction filtration, wash with deionized water until neutral, then place it in 40 wt% HF, keep stirring at 80 °C for 6 h, after suction filtration, wash with deionized water until neutral, and then dry at 70 °C. After drying, cool to room temperature and then dry to obtain the deashed sample SY-RVRC2.

[0136] S4: Place the prepared deashed sample in a tubular furnace, heat up to 290 °C, introduce air for pre-oxidation for 4 h, then introduce steam at 1 L / min in a small rotary furnace for activation at 950 °C for 2.5 h, and finally roast in an inert atmosphere of nitrogen at 1280 °C for 2.5 h to obtain the carbon negative electrode material SY-RVC-H2.

[0137] Example 3:

[0138] This example provides a carbon negative electrode material, which specifically includes the following steps:

[0139] S1: After the raw coal SY is naturally air-dried, it is roughly broken and then ground. Then, according to the national standard GB / T477-2008 "Coal Screening Test Method", the raw coal is screened, and the flotation original sample is obtained by passing through a 200-mesh sieve.

[0140] S2: Mix the flotation original sample with water at a ratio of 40 g : 1000 cm 3 proportion. During the flotation process, add a certain amount of collector and stir for 1 min, then add a certain amount of foaming agent. Collect the floating foam and the sinking matter, carry out suction filtration and drying to obtain the vitrinite concentrate SY-RV3 and the inertinite concentrate SY-RI3 (wherein, the collector is oleic acid, the foaming agent is n-octanol, and their dosages are 0.25 g / L and 0.08 g / L respectively).

[0141] S3: Place the obtained vitrinite concentrate SY-RV3 in a 4 mol / L HCl solution (ratio: 1 g solid sample : 10 mL acid solution, the same below), keep stirring at 80 °C for 6 h, after suction filtration, wash with deionized water until neutral, then place it in 40 wt% HF, keep stirring at 80 °C for 6 h, after suction filtration, wash with deionized water until neutral, and then dry at 70 °C. After drying, cool to room temperature and then dry to obtain the deashed sample SY-RVRC3.

[0142] S4: Place the prepared deashed sample in a tubular furnace, heat up to 275 °C, introduce air for pre-oxidation for 3 h, then introduce steam at 0.8 L / min in a small rotary furnace for activation at 935 °C for 3 h, and finally roast in an inert atmosphere of nitrogen at 1200 °C for 4.5 h to obtain the carbon negative electrode material SY-RVC-H3.

[0143] Comparative Example 1:

[0144] This comparative example provides a carbon anode material. The difference in the treatment process from Example 1 is that in step S2, the flotation is natural flotation.

[0145] S1: The raw coal SY is naturally air-dried and then undergoes coarse crushing and grinding. Then, according to the national standard GB / T 477-2008 "Coal Screening Test Method", the raw coal is screened, and the original sample is obtained by passing through a 200-mesh sieve.

[0146] S2: The flotation original sample is mixed with water in a ratio of 50 g: 1000 cm 3 and filtered by suction and dried to obtain a mixture of the floating matter SY-RV4 and the sinking matter SY-RI4.

[0147] S3: The obtained floating matter SY-RV4 is placed in a 5 mol / L HCl solution (ratio: 1 g solid sample: 10 mL acid solution, the same below), and stirred at a constant temperature of 80 °C for 6 h. After suction filtration, it is washed with deionized water until neutral and then placed in 40 wt% HF and stirred at a constant temperature of 80 °C for 6 h. After suction filtration, it is washed with deionized water until neutral, and then dried at 70 °C. After drying is completed, it is cooled to room temperature and dried to obtain the deashed sample SY-RVRC4.

[0148] S4: The prepared deashed sample is placed in a tubular furnace, heated to 275 °C, and pre-oxidized with air for 3 h. Then, water vapor is introduced at a rate of 0.5 L / min in a small rotary furnace for activation at 915 °C for 4 h. Finally, it is calcined in an inert atmosphere of nitrogen at 1250 °C for 3 h to obtain the carbon anode material SY-RVC-H4.

[0149] Comparative Example 2:

[0150] This comparative example provides a carbon anode material. The difference in the treatment process from Example 1 is that the negative electrode raw material is changed from the vitrinite concentrate SY-RV1 to the inertinite concentrate SY-RI1.

[0151] S1: The raw coal SY is naturally air-dried and then undergoes coarse crushing and grinding. Then, according to the national standard GB / T 477-2008 "Coal Screening Test Method", the raw coal is screened, and the flotation original sample is obtained by passing through a 200-mesh sieve.

[0152] S2: The flotation original sample is mixed with water in a ratio of 50 g: 1000 cm 3 and a quantitative collector is added during the flotation process and stirred for 1 min, and then a quantitative foaming agent is added. The floating foam and the sinking matter are collected, filtered by suction and dried to obtain the vitrinite concentrate SY-RV1 and the inertinite concentrate SY-RI1 (wherein, the collector is oleic acid and the foaming agent is n-octanol, and their dosages are 0.3 g / L and 0.1 g / L respectively).

[0153] S3: Place the obtained inertinite concentrate SY-RI1 in a 5 mol / L HCl solution (ratio: 1 g solid sample : 10 mL acid solution, the same below), keep stirring at 80 °C for 6 h, after suction filtration, wash with deionized water until neutral, then place it in 40 wt% HF, keep stirring at 80 °C for 6 h, after suction filtration, wash with deionized water until neutral, and after suction filtration, dry at 70 °C. After drying is completed, cool to room temperature and then dry to obtain the deashed sample SY-RIRC1.

[0154] S4: Place the prepared deashed sample in a tubular furnace, heat up to 275 °C, pass in air for pre-oxidation for 3 h, then pass in steam at 0.5 L / min in a small rotary furnace for activation at 915 °C for 4 h, and finally roast in an inert atmosphere of nitrogen at 1250 °C for 3 h to obtain the carbon negative electrode material SY-RIC-H1. The Raman spectrum is as Figure 3 shown.

[0155] Comparative Example 3:

[0156] This comparative example provides a carbon negative electrode material. The difference in the treatment process from Example 1 is that it is directly carbonized without acid washing and deashing.

[0157] S1: After the raw coal SY is naturally air-dried, it is roughly broken and then crushed and ground. Then, according to the national standard GB / T 477-2008 "Coal Screening Test Method", the raw coal is screened, and the flotation original sample is obtained by passing through a 200-mesh sieve.

[0158] S2: Mix the flotation original sample with water at a ratio of 50 g : 1000 cm 3 In the flotation process, add a certain amount of collector and stir for 1 min, then add a certain amount of foaming agent. Collect the floating foam and the sinking material, perform suction filtration and drying to obtain the vitrinite concentrate SY-RV1 and the inertinite concentrate SY-RI1. (Among them, the collector is oleic acid and the foaming agent is n-octanol, and their dosages are 0.3 g / L and 0.1 g / L respectively).

[0159] S3: Place the obtained vitrinite concentrate SY-RI1 in a tubular furnace, heat up to 275 °C, pass in air for pre-oxidation for 3 h, then pass in steam at 0.5 L / min in a small rotary furnace for activation at 915 °C for 4 h, and finally roast in an inert atmosphere of nitrogen at 1250 °C for 3 h to obtain the carbon negative electrode material SY-RVC-H5.

[0160] Comparative Example 4:

[0161] This comparative example provides a carbon negative electrode material. The difference in the treatment process from Example 1 is that steam is not passed in for activation in step S4.

[0162] S1: The raw coal SY is naturally air-dried, then roughly broken and ground. Subsequently, according to the national standard GB / T 477-2008 "Coal Screening Test Method", the raw coal is screened, and the flotation original sample is obtained by passing through a 200-mesh sieve.

[0163] S2: The flotation original sample is mixed with water in a ratio of 50 g: 1000 cm 3 proportion. During the flotation process, a certain amount of collector is added and stirred for 1 min, then a certain amount of foaming agent is added. The floating foam and the sinking matter are collected, filtered by suction and dried to obtain the vitrinite concentrate SY-RV1 and the inertinite concentrate SY-RI1. (Among them, the collector is oleic acid, and the foaming agent is n-octanol, and their dosages are 0.3 g / L and 0.1 g / L respectively).

[0164] S3: The obtained vitrinite concentrate SY-RV1 is placed in a 5 mol / L HCl solution (ratio: 1 g solid sample: 10 mL acid solution, the same below), and stirred at a constant temperature of 80 °C for 6 h. After suction filtration, it is washed with deionized water until neutral, then placed in 40 wt% HF and stirred at a constant temperature of 80 °C for 6 h. After suction filtration, it is washed with deionized water until neutral, and then dried at 70 °C. After drying is completed, it is cooled to room temperature and then dried in an oven to obtain the deashed sample SY-RVRC1.

[0165] S4: The obtained deashed sample is placed in a tube furnace, heated to 275 °C, and pre-oxidized with air for 3 h, and then calcined in an inert atmosphere of nitrogen at 1250 °C for 3 h to obtain the carbon negative electrode material SY-RVC-H6.

[0166] Comparative Example 5:

[0167] This comparative example provides a carbon negative electrode material. The difference in the treatment process from Example 1 is that: the final carbonization degree in S4 is higher.

[0168] S1: The raw coal SY is naturally air-dried, then roughly broken and ground. Subsequently, according to the national standard GB / T 477-2008 "Coal Screening Test Method", the raw coal is screened, and the flotation original sample is obtained by passing through a 200-mesh sieve.

[0169] S2: The flotation original sample is mixed with water in a ratio of 50 g: 1000 cm 3 proportion. During the flotation process, a certain amount of collector is added and stirred for 1 min, then a certain amount of foaming agent is added. The floating foam and the sinking matter are collected, filtered by suction and dried to obtain the vitrinite concentrate SY-RV1 and the inertinite concentrate SY-RI1. (Among them, the collector is oleic acid, and the foaming agent is n-octanol, and their dosages are 0.3 g / L and 0.1 g / L respectively).

[0170] S3: Place the obtained vitrinite concentrate SY-RV1 in a 5 mol / L HCl solution (ratio: 1 g solid sample : 10 mL acid solution, the same below), keep stirring at 80 °C for 6 h, after suction filtration, wash with deionized water until neutral, then place it in 40 wt% HF and keep stirring at 80 °C for 6 h, after suction filtration, wash with deionized water until neutral, after suction filtration, dry at 70 °C, and after drying is completed, cool to room temperature and then dry to obtain the deashed sample SY-RVRC1.

[0171] S4: Place the prepared deashed sample in a tubular furnace, heat up to 275 °C, introduce air for pre-oxidation for 3 h, then introduce steam at 0.5 L / min in a small rotary furnace for activation at 915 °C for 4 h, and finally roast at 1350 °C for 5 h in an inert atmosphere of nitrogen to obtain the carbon negative electrode material SY-RVC-H7.

[0172] Example 4:

[0173] This example provides a carbon negative electrode material. The difference in the treatment process from Example 1 is that: S4, the degree of carbonization is lower.

[0174] S1: After the raw coal SY is naturally air-dried, it undergoes coarse crushing and grinding, and then the raw coal is screened according to the national standard GB / T 477 - 2008 "Coal Screening Test Method", and the flotation original sample is obtained by passing through a 200-mesh sieve.

[0175] S2: Mix the flotation original sample with water in a ratio of 50 g:1000 cm 3 proportion, during the flotation process, add a certain amount of collector and stir for 1 min, then add a certain amount of foaming agent, collect the floating foam and the sinking material, carry out suction filtration and drying to obtain the vitrinite concentrate SY-RV1 and the inertinite concentrate SY-RI1, (wherein, the collector is oleic acid, the foaming agent is n-octanol, and their dosages are 0.3 g / L and 0.1 g / L respectively).

[0176] S3: Place the obtained vitrinite concentrate SY-RV1 in a 5 mol / L HCl solution (ratio: 1 g solid sample : 10 mL acid solution, the same below), keep stirring at 80 °C for 6 h, after suction filtration, wash with deionized water until neutral, then place it in 40 wt% HF and keep stirring at 80 °C for 6 h, after suction filtration, wash with deionized water until neutral, after suction filtration, dry at 70 °C, and after drying is completed, cool to room temperature and then dry to obtain the deashed sample SY-RVRC1.

[0177] S4: Place the prepared deashed sample in a tubular furnace, heat up to 275 °C, introduce air for pre-oxidation for 3 h, then introduce steam at 0.5 L / min in a small rotary furnace for activation at 915 °C for 4 h, and finally roast at 1200 °C for 2 h in an inert atmosphere of nitrogen to obtain the carbon negative electrode material SY-RVC-H8.

[0178] Example 5:

[0179] This embodiment provides a carbon negative electrode material. The difference in the treatment process from that of Embodiment 1 lies in: S4. Increase the degree of steam activation.

[0180] S1: After the raw coal SY is naturally air-dried, it is roughly broken and then ground. Then, according to the national standard GB / T477 - 2008 "Coal Screening Test Method", the raw coal is screened, and the flotation original sample is obtained by passing through a 200-mesh sieve.

[0181] S2: Mix the flotation original sample with water at a ratio of 50g:1000cm 3 proportion. During the flotation process, a certain amount of collector is added and stirred for 1 minute, and then a certain amount of foaming agent is added. The floating foam and the sinking matter are collected, filtered by suction and dried to obtain the vitrinite concentrate SY-RV1 and the inertinite concentrate SY-RI1. (Among them, the collector is oleic acid, and the foaming agent is n-octanol, and their dosages are 0.3g / L and 0.1g / L respectively).

[0182] S3: Place the obtained vitrinite concentrate SY-RV1 in a 5mol / L HCl solution, (ratio: 1g solid sample: 10mL acid solution, the same below), keep stirring at 80°C for 6 hours, filter by suction, wash with deionized water until neutral, then place it in 40wt% HF and keep stirring at 80°C for 6 hours, filter by suction, wash with deionized water until neutral, filter by suction and dry at 70°C. After drying is completed, cool to room temperature and then dry to obtain the deashed sample SY-RVRC1.

[0183] S4: Place the prepared deashed sample in a tubular furnace, heat up to 275°C, introduce air for pre-oxidation for 3 hours, then introduce steam at a rate of 1L / min in a small rotary furnace for activation at 915°C for 6 hours, and finally roast in an inert atmosphere of nitrogen at 1250°C for 2 hours to obtain the carbon negative electrode material SY-RVC-H9.

[0184] The microcrystalline parameters of the samples prepared in the above embodiments and comparative examples are shown in Table 3.

[0185] Table 3

[0186]

[0187] The Raman carbon structure parameters of the samples prepared in the above embodiments and comparative examples are shown in Table 4, and the electrical properties are shown in Table 4 and Figures 5-6 as shown.

[0188] Table 4

[0189]

[0190]

[0191] From the above Table 3 and Table 4 andFigure 5 It can be seen that when the prepared carbon negative electrode material simultaneously satisfies the characteristics ① 0.4 ≤ I G / I D ≤ 0.5, characteristic ② 0.35 ≤ I D3+D4 / I All ≤ 0.42 and I D3 / I G`+D2+D3 ≥ 0.14, the reversible specific capacity, the first-cycle discharge specific capacity, and the first efficiency all have good performances. Compared with Examples 1-3, Examples 4 and 5 only satisfy the characteristics ① and characteristic ② 0.35 ≤ I D3+D4 / I All ≤ 0.42 or I D3 / I G`+D2+D3 ≥ 0.14. Although the reversible specific capacity, the first-cycle discharge specific capacity, and the first efficiency have good performances, there is an obvious gap compared with Examples 1-3.

[0192] It can be seen from the comparison between Comparative Examples 1-2 and the Examples that the carbon negative electrode materials prepared with raw coal or sinkage as carbon raw materials cannot meet the requirements of this application, which will further lead to obvious decreases in the reversible specific capacity, the first-cycle discharge specific capacity, and the first efficiency compared with Examples 4-5. It can be seen from the comparison between Comparative Examples 3-5 and Example 1 that pickling, steam activation, and carbonization degree will all affect the microstructure of the carbon material. The omission or unreasonable setting of pickling, steam activation, and carbonization degree will lead to the obtained carbon material negative electrode material not meeting the requirements of this application, which will further lead to obvious decreases in the reversible specific capacity, the first-cycle discharge specific capacity, and the first efficiency compared with Examples 4-5.

[0193] From Figure 6 the analysis of the rate performance test results, it can be known that compared with the Comparative Examples, the obtained products show better capacity retention rates at different charge and discharge currents, that is, the negative electrode materials obtained by the preparation process provided in this application have good rate performance.

[0194] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A carbon material for the negative electrode of a sodium-ion battery, characterized in that, The Raman spectrum of the carbon material satisfies Feature ① and Feature ②: Characteristic ① 0.4 ≤ I G / I D ≤ 0.5; Feature ② 0.35 ≤ I D3+D4 / I All ≤ 0.42; and / or, I D3 / I Gˋ+D2+D3 ≥ 0.14; Among them, I G is the area of the G peak in the Raman spectrum; I D is the area of the D peak in the Raman spectrum; I D3+D4 is the total area of the D3 and D4 peaks in the fitted Raman spectrum; I All is the total area of the Gˋ, D1, D2, D3 and D4 peaks in the fitted Raman spectrum; I D3 is the area of the D3 peak in the fitted Raman spectrum; I Gˋ+D2+D3 is the total area of the Gˋ, D2 and D3 peaks in the fitted Raman spectrum; The fitted Raman spectrum is obtained by deconvoluting the Raman spectrum; the peak value of the Gˋ peak is at 1560 cm -1 ~1600 cm -1 ; the peak value of the D1 peak is at 1330 cm -1 ~1370 cm -1 ; the peak value of the D2 peak is at 1480 cm -1 ~1520 cm -1 ; the peak value of the D3 peak is at 1610 cm -1 ~1640 cm -1 ; the peak value of the D4 peak is at 1180 cm -1 ~1220 cm -1 .

2. The carbon material for the negative electrode of a sodium ion battery according to claim 1, wherein The carbon material satisfies at least one of the following features a-i: a.d 002 is 0.36 nm - 0.39 nm; b. Lc is 1.20 nm - 1.4 nm; c.Lc / d 002 is 3.35 - 3.65; d. The closed pore rate is 40% - 65%; e. The carbon material includes amorphous carbon; f. The reversible specific capacity > 300 mAh / g; h. The discharge specific capacity of the first cycle > 320 mAh / g; i. The first efficiency > 90%.

3. A method for preparing the carbon material for the negative electrode of a sodium-ion battery according to claim 1 or 2, characterized in that, It includes: Float the slurry containing raw coal powder to obtain the floating matter and the sinking matter; Pickle the floating matter to obtain the ash-removed floating matter; Subject the ash-removed floating matter to pre-oxidation, activation, and roasting in sequence to obtain the carbon material.

4. The preparation method of the carbon material for the negative electrode of a sodium-ion battery according to claim 3, characterized in that, The particle size of the raw coal powder is less than 200 mesh; And / or, in the flotation step, the ratio of raw coal powder to water in the slurry is 1 g:(15 - 25) cm 3 ; And / or, the slurry further includes a collector and / or a foaming agent; And / or, in the flotation step, the enrichment rate of the floating matter is 60% - 80%, and the enrichment rate of the sinking matter is 10% - 40%.

5. The preparation method of the carbon material for the negative electrode of a sodium-ion battery according to claim 3, characterized in that, The collector is selected from at least one of oleic acid, cetyltrimethylammonium bromide, and sodium dodecyl sulfate; And / or, the content of the collector in the slurry is 0.25 g / L - 0.3 g / L; And / or, the foaming agent includes one or more of n-octanol, sec-octanol, cyclohexanol, pine oil, industrial miscellaneous alcohols, or methyl isobutyl carbinol; And / or, the content of the foaming agent in the slurry is 0.08 g / L - 0.1 g / L.

6. The preparation method of the carbon material for the negative electrode of a sodium-ion battery according to claim 3, characterized in that, The pickling includes hydrochloric acid pickling and hydrofluoric acid pickling of the floating matter in sequence; And / or, after the hydrochloric acid pickling and hydrofluoric acid pickling, the floating matter is washed with deionized water until neutral.

7. The preparation method of the carbon material for the negative electrode of a sodium-ion battery according to claim 6, characterized in that, The concentration of the hydrochloric acid solution used for hydrochloric acid pickling is 3 mol / L - 7 mol / L, and the amount of the hydrochloric acid solution corresponding to each gram of the floating matter in the hydrochloric acid pickling step is less than 10 mL; And / or, the concentration of the hydrofluoric acid solution used for hydrofluoric acid pickling is 35 wt% - 45 wt%, and the amount of the hydrofluoric acid solution corresponding to each gram of the floating matter in the hydrofluoric acid pickling step is less than 10 mL.

8. The preparation method of the carbon material for the negative electrode of a sodium ion battery according to claim 3, characterized in that, The pre-oxidation temperature is 250°C - 300°C, the time is 3 h - 6 h, and the atmosphere is an oxidizing atmosphere; And / or, the activation temperature is 900°C - 950°C, and the time is 2 h - 5 h; And / or, the activation method is physical activation, the activation gas is water vapor and / or carbon dioxide, and the flow rate of the activation gas is 0.1 L / min - 2 L / min; And / or, the activation method is chemical activation, the activator is selected from at least one of KOH, NaOH, phosphoric acid, and potassium bicarbonate, and the addition amount of the activator is 5 wt% - 40% of the ash-removed floating matter after pre-oxidation; And / or, the roasting temperature is 1200°C - 1300°C, and the time is 2 h - 4 h.

9. A negative electrode sheet, characterized in that, It includes the carbon material described in Claim 1 or 2.

10. A sodium-ion battery, characterized in that, It includes the negative electrode plate described in Claim 9.

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