Carbon material and preparation method thereof, negative electrode material, negative electrode and battery

Abstract

The invention discloses a carbon material and a preparation method thereof, a negative electrode material, a negative electrode and a battery, the carbon material comprises porous carbon and a carbon layer coated on the surface of the porous carbon, the pore size distribution curve of the porous carbon has only one peak at 1-3nm, the carbon material has a convex peak in an X-ray small angle scattering spectrum, and the convex peak is a convex peak. The value from the central position of the convex peak to the curve base line corresponding to the intensity is defined as the peak height H, the half H position is used as a base line parallel line, the difference value of two points intersected with the peak is defined as the half peak width FWHM, and the value of the FWHM is 0.5-0.7 nm <-1 >. The carbon material disclosed by the invention has relatively high electrochemical properties such as specific capacity.

Description

Technical Field

[0001] The present application relates to the field of new energy technology, and in particular to a carbon material and a preparation method thereof, a negative electrode material, a negative electrode and a battery. Background Art

[0002] With the rapid growth of energy demand and increasing environmental awareness, the development of high-efficiency, long-life energy storage devices has become particularly important. In the battery field, the choice of anode materials directly affects the battery's energy density, charge and discharge efficiency, and cycle stability.

[0003] Porous carbon has a porous structure, which gives it a higher specific surface area, which can increase the storage sites and transmission channels of ions, thereby improving the energy density of the battery; the porous structure can also provide abundant surface active sites, accelerating the embedding and extraction speed of ions during the charging and discharging process, so that the porous carbon performs well at high current density and the battery has better rate performance; the porous carbon structure also helps to maintain the integrity of the material and reduce particle breakage, thereby maintaining stable cycle performance, extending the battery life, and making the battery have better cycle performance.

[0004] However, the specific capacity of existing porous carbon is relatively low and needs to be further improved. Summary of the Invention

[0005] In view of this, the present application provides a carbon material and a preparation method thereof, a negative electrode material, a negative electrode and a battery.

[0006] The present invention provides a carbon material comprising porous carbon and a carbon layer coated on the surface of the porous carbon. The porous carbon has a pore size distribution curve with only one peak at 1-3 nm. The carbon material has a convex peak in the X-ray small-angle scattering spectrum. The value from the intensity corresponding to the center position of the convex peak to the baseline of the curve is defined as the peak height H. A line parallel to the baseline is drawn at half H, and the difference between the two points intersecting the peak is defined as the half-maximum width FWHM. The FWHM value is 0.5-0.7 nm. -1 .

[0007] Optionally, in some embodiments, the carbon material has closed pores, and the pore diameter of the closed pores ranges from 0.2 to 1.6 nm.

[0008] Optionally, in some embodiments, the center position of the protrusion peak is between 0.6 and 1.8 nm. -1 within the scope; The specific surface area of ​​the carbon material is less than or equal to 10 m 2 / g; The D of the carbon material V50 5~15 μm; The thickness of the carbon layer ranges from 10 to 30 nm.

[0009] Optionally, in some embodiments, the carbon material includes one or more of hard carbon and soft carbon, wherein the hard carbon includes one or more of hard coke, biomass-based hard carbon, asphalt-based hard carbon, resin-based hard carbon, and coal-based hard carbon, and the soft carbon includes one or more of soft coke, biomass-based soft carbon, asphalt-based soft carbon, resin-based soft carbon, and coal-based soft carbon.

[0010] Accordingly, the present invention also provides a method for preparing a carbon material, comprising the following steps: Providing porous carbon, wherein the porous carbon has a pore size distribution curve with only one peak at 1-3 nm; A carbon layer is deposited on the surface of the porous carbon to obtain a carbon material.

[0011] Optionally, in some embodiments, the specific surface area of ​​the porous carbon is 500-3000 m 2 / g; The mesoporosity of the porous carbon is 5% to 30%; The pore size of the porous carbon is in the range of 1 to 5 nm.

[0012] Optionally, in some embodiments, depositing a carbon layer on the surface of the porous carbon comprises: placing the porous carbon in a cavity, introducing a carbon source gas, heating the cavity to a temperature T, and maintaining the temperature at T for a time t to deposit carbon on the surface of the porous carbon to form a carbon layer covering the porous carbon, wherein: The temperature T is 800-1200° C. The time t is 12 to 16 hours; The heating rate to temperature T is 2-10°C / min.

[0013] Optionally, in some embodiments, the carbon source gas further includes a carrier gas, and the carrier gas includes an inert gas; The carbon source gas includes C1~C3 hydrocarbons, C5~C 10 One or more of hydrocarbon vapor and aromatic compound vapor with 6 to 60 ring atoms.

[0014] Optionally, in some embodiments, the volume ratio of the carbon source gas to the carrier gas is 1:(1-10); The flow rate of the mixed gas formed by the carbon source gas and the carrier gas is 10~20 mL / min / g; The C1-C3 hydrocarbons include one or more of methane, ethylene, acetylene, propane, propylene, and propyne; The C5~C 10The hydrocarbon vapor includes one or more of hexane vapor and cyclohexane vapor; The aromatic compound vapor having 6 to 60 ring atoms includes one or more of benzene vapor and toluene vapor; The inert gas includes one or more of nitrogen, argon, helium, neon, krypton, and xenon.

[0015] Correspondingly, the present application also provides a negative electrode material, including the carbon material, or including the carbon material prepared by the preparation method.

[0016] Correspondingly, the present application also provides a negative electrode, comprising the negative electrode material.

[0017] Correspondingly, the present application also provides a battery comprising the negative electrode.

[0018] Beneficial effect: The FWHM value of the convex peak in the X-ray small angle scattering spectrum of the carbon material described in this application is 0.5~0.7 nm -1 This facilitates the formation of closed pores with appropriate pore sizes, inducing the formation of high-density pseudometals within lithium / sodium ions, thereby significantly improving energy density. Furthermore, when the carbon material undergoes volume changes (such as lithium / sodium ion insertion / deinsertion), these closed pores can absorb at least some of the stress, relieving the internal pressure of the carbon material, thereby improving the cycling stability and mechanical integrity of the carbon material, and thus comprehensively enhancing the carbon material's electrochemical properties, such as specific capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 This is a flow chart of a method for preparing a carbon material provided in an embodiment of the present application; Figure 2 is the pore size distribution curve of the porous carbon in step 1 of carbon material embodiment 1 of the present application; Figure 3 This is the small-angle X-ray scattering spectrum of the carbon material of carbon material Example 1 of the present application. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of this application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0022] In this application, "and / or" describes the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural.

[0023] It should be noted that the average particle size in this application is measured by a Malvern laser particle size analyzer.

[0024] Carbon-based closed-pore materials are urgently needed for the development of lithium / sodium batteries. Traditional graphite negative electrodes are prone to lithium precipitation (lithium dendrites) during fast charging, posing a safety hazard, and have poor sodium ion storage capacity (sodium ions are difficult to embed between graphite layers). Closed-pore materials may provide a more stable ion transport path. For porous carbon, the specific capacity and first-cycle efficiency are affected by the open pore structure, and there are problems of irreversible sodium storage, lithium storage, and electrolyte side reactions. Closed pores are pores inside the material that are not connected to the outside world. They can reduce side reactions, improve the first-cycle coulomb efficiency, buffer volume expansion, and reduce damage to the electrode structure. However, the controllable synthesis of closed pores is difficult, and the specific capacity of existing carbon materials with closed pores is low.

[0025] The technical solution of this application is as follows: In a first aspect, the present application provides a carbon material comprising porous carbon and a carbon layer coated on the surface of the porous carbon, wherein the pore size distribution curve of the porous carbon has one and only one peak at 1-3 nm, and the carbon material has a convex peak in the X-ray small-angle scattering spectrum, and the value corresponding to the intensity at the center position of the convex peak to the baseline of the curve is defined as the peak height H, and a baseline parallel line is drawn at half H, and the difference between the two points intersecting with the peak is defined as the half-maximum width FWHM, and the FWHM value is 0.5-0.7 nm -1 .

[0026] It should be noted that if Figure 3 As shown, the center position of the convex peak in this application refers to the highest point of the convex peak, and the curve baseline refers to the bottom tangent line of the convex peak.

[0027] In some embodiments, the FWHM may be 0.5 nm -1 , 0.55 nm -1 , 0.6 nm-1 , 0.65 nm -1 , 0.7nm -1 And the numerical value or range between any two numerical values, etc.

[0028] It should be noted that the small-angle X-ray scattering spectrum of the present application is obtained by detection using a small-angle X-ray scattering instrument (SAXS).

[0029] The surface of the porous carbon in the carbon material described in the present application is coated with a carbon layer, so the carbon material has a closed-pore structure and has the characteristics of a carbon material with a closed-pore structure, for example, it has a good storage capacity for lithium ions or sodium ions, can provide a relatively stable ion transmission path, reduce side reactions, improve the initial coulombic efficiency, buffer volume expansion, reduce electrode structure damage, etc.

[0030] Furthermore, the FWHM value of the convex peak in the small-angle X-ray scattering spectrum of the carbon material described in this application is 0.5-0.7 nm. -1 This facilitates the formation of closed pores with appropriate pore sizes, inducing the formation of high-density pseudometals within lithium / sodium ions, thereby significantly improving energy density. Furthermore, when the carbon material undergoes volume changes (such as lithium / sodium ion insertion / deinsertion), these closed pores can absorb at least some of the stress, relieving the internal pressure of the carbon material, thereby improving the cycling stability and mechanical integrity of the carbon material, and thus comprehensively enhancing the carbon material's electrochemical properties, such as specific capacity.

[0031] In some embodiments, the pore size range of the closed pores in the carbon material is 0.2~1.6 nm, for example, 0.2 nm, 0.3 nm, 0.5 nm, 0.6 nm, 0.8 nm, 1.0 nm, 1.2 nm, 1.3 nm, 1.5 nm, 1.6 nm, and values ​​or ranges between any two of the values.

[0032] In some embodiments, the center position of the protrusion peak is between 0.6 and 1.8 nm. -1 range, for example, 0.6 nm -1 , 0.7 nm -1 , 0.8 nm -1 , 0.9 nm -1 , 1.0 nm -1 , 1.1 nm -1 , 1.2 nm -1 , 1.3 nm -1 , 1.4 nm -1 , 1.5 nm -1 , 1.6 nm -1 , 1.7 nm -1 , 1.8 nm-1 As well as the numerical value or range between any two numerical values, etc. In this way, the pore size distribution of the closed pores in the carbon material is advantageously made to be within the range of 0.2-1.6 nm.

[0033] In some embodiments, the specific surface area of ​​the carbon material is less than or equal to 10 m 2 / g, for example, it can be 10 m 2 / g, 9 m 2 / g, 8 m 2 / g, 7 m 2 / g, 6 m 2 / g, 5 m 2 / g, 4 m 2 / g, 3 m 2 / g, etc.

[0034] In some embodiments, the D of the carbon material V50 (50% volume average particle size) is 5-15 μm, for example, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, and values ​​or ranges between any two of the above values.

[0035] In some embodiments, the thickness of the carbon layer ranges from 10 to 30 nm, for example, 10 nm, 12 nm, 13 nm, 15 nm, 16 nm, 18 nm, 20 nm, 22 nm, 23 nm, 25 nm, 26 nm, 28 nm, 30 nm, and values ​​or ranges between any two of the values.

[0036] In some embodiments, the carbon material includes one or more of hard carbon and soft carbon. The hard carbon includes one or more of hard coke, biomass-based hard carbon, pitch-based hard carbon, resin-based hard carbon, and coal-based hard carbon. The soft carbon includes one or more of soft coke, biomass-based soft carbon, pitch-based soft carbon, resin-based soft carbon, and coal-based soft carbon.

[0037] Second, see Figure 1 , the present application also provides a method for preparing a carbon material, comprising the following steps: Step S11, providing porous carbon, wherein the pore size distribution curve of the porous carbon has only one peak at 1-3 nm; Step S12: depositing a carbon layer on the surface of the porous carbon to obtain a carbon material.

[0038] The carbon material is as described above and will not be described again here.

[0039] In the step S11: In some embodiments, the specific surface area of ​​the porous carbon is 500-3000 m 2 / g, for example, 500 m 2 / g、1000m 2 / g, 1500 m 2 / g, 2000 m 2 / g, 2500 m 2 / g, 3000 m 2 / g and the value or range between any two values, etc.

[0040] In some embodiments, the mesoporosity of the porous carbon is 5% to 30%, for example, 5%, 10%, 15%, 20%, 25%, 30%, and a value or range between any two of the values.

[0041] In some embodiments, the pore size of the porous carbon is in the range of 1 to 5 nm, for example, 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, and any value or range between any two of the above values. Within the pore size range, it is advantageous to make the FWHM value of the convex peak of the prepared carbon material in the small-angle X-ray scattering spectrum be between 0.5 and 0.7 nm. -1 within the range.

[0042] The porous carbon is prepared using a known preparation method. In some embodiments, the preparation method of the porous carbon includes: providing a carbon precursor, and activating the carbon precursor to obtain the porous carbon.

[0043] In some embodiments, the carbon precursor includes, but is not limited to, one or more of char-derived carbon, resin-derived carbon, pitch-derived carbon, or biomass-derived carbon.

[0044] In some embodiments, the activation treatment includes one or more of alkali activation, steam activation, and carbon dioxide activation.

[0045] In some embodiments, the temperature of the activation treatment is 400~1000℃, for example, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, and a value or range between any two of the values; the time of the activation treatment is 1~48 h, for example, 1 h, 5 h, 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, 48 h, and a value or range between any two of the values.

[0046] In the step S12: In some embodiments, depositing a carbon layer on the surface of the porous carbon includes: placing the porous carbon in a cavity, introducing a carbon source gas, heating the cavity to a temperature T, and maintaining the temperature at T for a time t to deposit carbon on the surface of the porous carbon to form a carbon layer covering the porous carbon.

[0047] In some embodiments, the carbon source gas includes but is not limited to C1~C3 hydrocarbons, C5~C 10 One or more of hydrocarbon steam and aromatic compound steam with 6 to 60 ring atoms. The C1 to C3 hydrocarbons include but are not limited to one or more of methane, ethylene, acetylene, propane, propylene, and propyne. The C5 to C 10 The hydrocarbon vapor includes but is not limited to one or more of hexane vapor and cyclohexane vapor, and the aromatic compound vapor with 6 to 60 ring atoms includes but is not limited to one or more of benzene vapor and toluene vapor.

[0048] In some embodiments, the carbon source gas further includes a carrier gas, and the carrier gas includes an inert gas, including but not limited to one or more of nitrogen, argon, helium, neon, krypton, and xenon.

[0049] In some embodiments, the volume ratio of the carbon source gas to the carrier gas is 1:(1-10), for example, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, and ratios or ranges between any two of these ratios. In at least one preferred embodiment, the volume ratio of the carbon source gas to the carrier gas is 1:(4-6).

[0050] In some embodiments, the flow rate of the mixed gas formed by the carbon source gas and the carrier gas is 10-20 mL / min / g, for example, 10 mL / min / g, 11 mL / min / g, 12 mL / min / g, 13 mL / min / g, 14 mL / min / g, 15 mL / min / g, 16 mL / min / g, 17 mL / min / g, 18 mL / min / g, 19 mL / min / g, 20 mL / min / g, and values ​​or ranges between any two of these values. In at least one preferred embodiment, the flow rate of the mixed gas formed by the carbon source gas and the carrier gas is 12-14 mL / min / g.

[0051] In some embodiments, the temperature T is 800-1200° C., for example, 800° C., 900° C., 1000° C., 1100° C., 1200° C., and any value or range between any two values. Preferably, the temperature T is 800-1000° C.

[0052] In some embodiments, the time t is 12 to 16 hours, for example, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, and a value or range between any two of the values.

[0053] In some embodiments, the heating rate to temperature T is 2~10℃ / min, for example, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min and values ​​or ranges between any two values.

[0054] In some embodiments, the device used to deposit the carbon layer on the surface of the porous carbon can be a rotary kiln, a kiln, a fluidized bed, or other devices that have been used for carbon deposition, which is not limited here.

[0055] The preparation method of the carbon material described in the present application uses porous carbon having only one peak at 1-3 nm in the pore size distribution curve to prepare the carbon material, so that the FWHM value of the convex peak in the X-ray small angle scattering spectrum of the prepared carbon material is 0.5-0.7 nm. -1 range, so that the prepared carbon material has better electrochemical properties.

[0056] In a third aspect, an embodiment of the present application further provides a negative electrode material, comprising the carbon material described above.

[0057] In some embodiments, the negative electrode material further includes a binder and a conductive additive.

[0058] The conductive additive is a known conductive additive used in negative electrode materials, and may include, but is not limited to, one or more of conductive carbon black (SP), carbon nanotubes (CNTs), and graphene.

[0059] The binder is a known binder for negative electrode materials, and may include, but is not limited to, one or more of polyacrylate lithium (PAA-Li), polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), hydroxypropyl methyl cellulose (HPMC), and polyacrylate (PAA).

[0060] In a fourth aspect, an embodiment of the present application further provides a negative electrode, comprising a negative electrode current collector and an active material layer bonded to at least one surface of the negative electrode current collector, wherein the active material layer comprises the negative electrode material described above.

[0061] In a fifth aspect, an embodiment of the present application further provides a battery comprising a positive electrode, a separator, an electrolyte and the negative electrode described above.

[0062] In some embodiments, the battery may be a lithium-ion battery or a sodium-ion battery.

[0063] The negative electrode of the battery described in the present application includes the carbon material described above and has high specific capacity and first coulombic efficiency and other properties.

[0064] The present invention is described in detail below by means of specific examples, which are only some examples of the present invention and are not intended to limit the present invention. The materials or reagents used in the examples and comparative examples of the present invention are commercially available.

[0065] Carbon Material Example 1 The preparation method of the carbon material of this embodiment includes: Step 1: Providing porous carbon, wherein the porous carbon is resin-based hard carbon, the resin-based hard carbon is prepared from phenolic resin-derived carbon, the pore size distribution of the porous carbon is between 1 and 5 nm, and the pore size distribution curve of the porous carbon has only one peak at 1 to 3 nm; Step 2: Place the porous carbon in a rotary furnace and heat it to 800°C at a heating rate of 2°C / min. A mixed gas of carbon source gas and helium at a flow rate of 12 mL / min / g is introduced, wherein the volume ratio of carbon source gas to helium is 1:4. Heat treat for 12 hours to prepare a carbon material.

[0066] The carbon material of this embodiment includes porous carbon and a carbon layer coated on the surface of the porous carbon. The carbon material of this embodiment is resin-based hard carbon.

[0067] Carbon Material Example 2 This embodiment is basically the same as the carbon material embodiment 1, except that, in this embodiment, the temperature is heated to 1000° C. in step 2.

[0068] Carbon Material Example 3 This embodiment is basically the same as the carbon material embodiment 1, except that, in this embodiment, the temperature is heated to 1200° C. in step 2.

[0069] Carbon Material Example 4 This embodiment is basically the same as the carbon material embodiment 1, except that, in this embodiment, the flow rate in step 2 is 10 mL / min / g.

[0070] Carbon Material Example 5 This embodiment is basically the same as the carbon material embodiment 1, except that, in this embodiment, the flow rate in step 2 is 20 mL / min / g.

[0071] Carbon Material Example 6 This embodiment is substantially the same as the carbon material embodiment 1, except that, in this embodiment, bamboo-derived carbon (biomass-based hard carbon) is used to replace the phenolic resin-derived carbon in embodiment 1.

[0072] Carbon Material Comparative Example 1 This comparative example is substantially the same as the carbon material example 1, except that the porous carbon in step 1 of this comparative example has two peaks at 1-3 nm.

[0073] Carbon Material Comparative Example 2 This comparative example is substantially the same as the carbon material example 1, except that, in step 1 of this comparative example, the pore size distribution of the porous carbon is between 10 and 20 nm.

[0074] Carbon Material Comparative Example 3 This comparative example is basically the same as carbon material embodiment 1, except that in step 2 of this comparative example, heating is performed to 1400°C.

[0075] Carbon Material Comparative Example 4 This comparative example is basically the same as carbon material embodiment 1, except that in step 2 of this comparative example, heating is performed to 700°C.

[0076] Carbon Material Comparative Example 5 This comparative example is basically the same as carbon material example 1, except that in step 2 of this comparative example, the flow rate is 25 mL / min / g.

[0077] Carbon Material Comparative Example 6 This comparative example is basically the same as carbon material example 1, except that in step 2 of this comparative example, the flow rate is 8 mL / min / g.

[0078] Lithium-ion battery embodiment 1 Step 01. The carbon material of Carbon Material Example 1 was mixed with styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), and conductive carbon black (SP) in a mass ratio of 94.5:2.5:1.5:1.5, respectively. The mixture was prepared into a slurry with ultrapure water and applied to a copper foil. The prepared slurry coating was placed in a vacuum drying oven and dried at 90°C for 24 hours. After being rolled with a 5T roller, a circular electrode sheet with a diameter of 12 mm was pressed using a tablet press to produce the battery negative electrode. Step S02: Use a lithium sheet as a counter electrode, a glass fiber disc as a separator, 1.0 mol / L LiPF6 mixed in a mixed solvent of EC:DMC:EMC with a volume ratio of 1:1:1 as the electrolyte, add a spring and a gasket, and assemble into a 2032 model button battery in a glove box.

[0079] Lithium-ion battery examples 2 to 6 Lithium ion battery embodiments 2 to 6 are substantially the same as lithium ion battery embodiment 1, except that lithium ion battery embodiments 2 to 6 use the carbon materials of carbon material embodiments 2 to 6 to replace the carbon material of carbon material embodiment 1.

[0080] Lithium-ion battery comparison examples 1 to 6 Lithium ion battery comparative examples 1 to 6 are substantially the same as lithium ion battery embodiment 1, except that the carbon materials of carbon material comparative examples 1 to 6 are used to replace the carbon materials of carbon material embodiment 1.

[0081] Sodium ion battery example 1 The sodium ion battery embodiment 1 is basically the same as the lithium ion battery embodiment 1, except that the sodium ion battery embodiment 1 uses lithium sheets to replace the sodium sheets in the lithium ion battery embodiment 1, and uses NaPF6 to replace the LiPF6 in the lithium ion battery embodiment 1.

[0082] Sodium Ion Battery Examples 2-6 Sodium ion battery embodiments 2 to 6 are substantially the same as sodium ion battery embodiment 1, except that sodium ion battery embodiments 2 to 6 use the carbon materials of carbon material embodiments 2 to 6 to replace the carbon materials of carbon material embodiment 1.

[0083] Sodium ion battery comparative examples 1 to 6 Sodium ion battery comparative examples 1 to 6 are substantially the same as sodium ion battery embodiment 1, except that the carbon materials of carbon material comparative examples 1 to 6 are used to replace the carbon materials of carbon material embodiment 1.

[0084] The carbon materials of carbon material examples 1 to 6 and carbon material comparative examples 1 to 6 were subjected to X-ray small angle scattering test and specific surface area test, and the porous carbon in step 1 of carbon material examples 1 to 6 and carbon material comparative examples 1 to 6 were subjected to specific surface area test, mesoporosity test and pore size distribution test, respectively. The center position of the protrusion peak and FHWM were recorded during the X-ray small angle scattering test. The test results are shown in Table 1. The pore size distribution curve of the porous carbon in step 1 of carbon material example 1 is shown in Table 1. Figure 2 The X-ray small angle scattering spectrum of the carbon material of carbon material embodiment 1 is shown in Figure 3 .

[0085] The small-angle X-ray scattering spectrum was obtained by using a small-angle X-ray scattering instrument (SAXS), wherein the copper target had a 30W light tube power and a wavelength of 1.54189 Å; the detector model was Pilatus 3R 300K, and the single pixel size was 172 μm.

[0086] Depend on Figure 2 It can be seen that the pore size distribution curve of the porous carbon in step 1 of carbon material example 1 has only one peak at 1-3 nm.

[0087] The specific capacity and initial coulombic efficiency tests were performed on the lithium-ion battery examples 1 to 6 and the lithium-ion battery comparative examples 1 to 6, respectively. The test results are shown in Table 2.

[0088] The specific capacity and initial coulombic efficiency tests were performed on the sodium ion battery examples 1 to 6 and the sodium ion battery comparative examples 1 to 6, respectively. The test results are shown in Table 3.

[0089] Specific surface area and pore size distribution were measured using nitrogen adsorption-desorption isotherms at 77 K using a Micromeritics Tristar 3030 instrument. Samples were vacuum degassed at 200°C for 10 h before measurement. Surface area was calculated using the Brunauer-Emmett-Teller (BET) method using adsorption curve branch data within a relative pressure range of P / P0 of 0.005-1. Pore size distribution was analyzed from the adsorption curve using the Density Function Theory (DFT) model.

[0090] Test method for first efficiency and specific capacity: Discharge specific capacity: Under a constant temperature environment of 25℃, use blue electric test equipment to test, charge and discharge twice at 0.01C in the voltage range of 0.01~2.00V, record the ratio of charge gram capacity / discharge gram capacity in the first cycle as the first efficiency, and the discharge gram capacity in the second cycle as the specific capacity.

[0091] Table 1:

[0092] Table 2:

[0093] Table 3:

[0094] From Table 1, Table 2 and Table 3 we can see that: Compared with the lithium-ion batteries of lithium-ion battery comparative examples 1 to 6, the lithium-ion batteries of lithium-ion battery embodiments 1 to 6 have higher first coulombic efficiency and specific capacity; compared with the sodium-ion batteries of sodium-ion battery comparative examples 1 to 6, the sodium-ion batteries of sodium-ion battery embodiments 1 to 6 have higher first coulombic efficiency and specific capacity. It can be seen that the use of the carbon material described in this application to prepare the negative electrode of the battery can effectively improve the first coulombic efficiency and specific capacity of the battery. The reason may be that the FWHM value of the convex peak in the small-angle X-ray scattering spectrum of the carbon material described in this application is 0.5 to 0.7 nm -1This is conducive to obtaining closed pores with appropriate pore size, inducing lithium / sodium ions to form high-density pseudometals therein, thereby greatly improving the energy density; in addition, when the carbon material undergoes volume changes (such as lithium / sodium ion insertion / deinsertion), these closed pores can absorb at least part of the stress and relieve the internal pressure of the carbon material, thereby improving the cycle stability and mechanical integrity of the carbon material, and then comprehensively improving the electrochemical properties of the carbon material such as the specific capacity.

[0095] The above is a detailed introduction to the technical solutions provided in the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for those skilled in the art, based on the ideas of the present application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A carbon material, characterized in that The porous carbon comprises a carbon layer coated on the surface of the porous carbon, wherein the pore size distribution curve of the porous carbon has only one peak at 1-3 nm, wherein: The carbon material has a convex peak in the X-ray small-angle scattering spectrum, and the value from the corresponding intensity at the center of the convex peak to the baseline of the curve is defined as the peak height H, and a baseline parallel line is drawn at half H, and the difference between the two points intersecting the peak is defined as the half-maximum width FWHM, and the value of FWHM is 0.5~0.7 nm. -1 .

2. The carbon material according to claim 1, wherein The carbon material has closed pores, and the pore diameter of the closed pores ranges from 0.2 to 1.6 nm.

3. The carbon material according to claim 1, wherein The center position of the protrusion peak is between 0.6 and 1.8 nm -1 within the scope; and / or The specific surface area of ​​the carbon material is less than or equal to 10 m 2 / g; and / or The D of the carbon material V50 5-15 μm; and / or The thickness of the carbon layer ranges from 10 to 30 nm.

4. The carbon material according to claim 1, wherein The carbon material includes one or more of hard carbon and soft carbon, wherein the hard carbon includes one or more of hard coke, biomass-based hard carbon, asphalt-based hard carbon, resin-based hard carbon, and coal-based hard carbon, and the soft carbon includes one or more of soft coke, biomass-based soft carbon, asphalt-based soft carbon, resin-based soft carbon, and coal-based soft carbon.

5. A method for preparing a carbon material, characterized in that: The steps include: Providing porous carbon, wherein the porous carbon has a pore size distribution curve with only one peak at 1-3 nm; A carbon layer is deposited on the surface of the porous carbon to obtain a carbon material.

6. The preparation method according to claim 5, wherein The specific surface area of ​​the porous carbon is 500-3000 m 2 / g; and / or The mesoporosity of the porous carbon is 5% to 30%; and / or The pore size of the porous carbon is in the range of 1 to 5 nm.

7. The preparation method according to claim 5, wherein Depositing a carbon layer on the surface of the porous carbon comprises: placing the porous carbon in a cavity, introducing a carbon source gas, heating the porous carbon to a temperature T, and maintaining the temperature at T for a time t to deposit carbon on the surface of the porous carbon to form a carbon layer covering the porous carbon, wherein: The temperature T is 800-1200° C.; and / or The time t is 12 to 16 hours; and / or The heating rate to temperature T is 2-10°C / min.

8. The preparation method according to claim 7, wherein The carbon source gas further includes a carrier gas, and the carrier gas includes an inert gas; and / or The carbon source gas includes C1~C3 hydrocarbons, C5~C 10 One or more of hydrocarbon vapor and aromatic compound vapor with 6 to 60 ring atoms.

9. The preparation method according to claim 8, wherein The volume ratio of the carbon source gas to the carrier gas is 1:(1-10); and / or The flow rate of the mixed gas formed by the carbon source gas and the carrier gas is 10-20 mL / min / g; and / or The C1-C3 hydrocarbons include one or more of methane, ethylene, acetylene, propane, propylene, and propyne; and / or The C5~C 10 The hydrocarbon vapor includes one or more of hexane vapor and cyclohexane vapor; and / or The aromatic compound vapor having 6 to 60 ring atoms includes one or more of benzene vapor and toluene vapor; and / or The inert gas includes one or more of nitrogen, argon, helium, neon, krypton, and xenon.

10. A negative electrode material, characterized in that The carbon material comprises the carbon material according to any one of claims 1 to 4, or the carbon material prepared by the preparation method according to any one of claims 5 to 9.

11. A negative electrode, characterized in that: Comprising the negative electrode material according to claim 10.

12. A battery, characterized in that: The negative electrode according to claim 11 is included.

Images