Porous carbon for negative electrode material and composite material for lithium ion secondary battery

Abstract

The present application relates to a kind of porous carbon for negative material and its preparation method, wherein, in the Raman spectrogram of the porous carbon, the ratio (I D / I G ) of D peak intensity (I D ) and G peak intensity (I G ) is 0.10-1.50, the diffraction angle 2 theta of (002) crystal face in the X-ray diffraction pattern of the porous carbon is 24.00°-26.53°, the specific surface area BET of the porous carbon is 600-3000 m 2 / g.The present application also relates to composite material comprising the porous carbon and negative electrode sheet and lithium ion secondary battery comprising the composite material.The porous carbon material of the present application has desired properties (such as graphitization degree and pore structure).Composite material can be used as battery negative material, and can significantly improve the electrical performance of battery.The method for preparing porous carbon and composite material of the present application is simple and easy to operate, and can be applied to mass production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a vapor-deposited silicon-carbon negative electrode material for lithium-ion secondary batteries. BACKGROUND

[0002] Lithium-ion batteries are one of the most widely used secondary battery systems. Compared with other rechargeable batteries such as nickel-cadmium batteries and nickel-hydrogen batteries, lithium-ion batteries have the characteristics of high energy density, high working voltage, limited self-discharge, low maintenance requirement, etc. However, the commercial graphite negative electrode has a theoretical specific capacity of only 372 mAh g -1 , which cannot meet the increasing demand for energy density, operation reliability and system integration of portable electronic devices, electric vehicles and energy storage applications.

[0003] Among all potential lithium-ion battery negative electrode materials, silicon is one of the most promising candidate materials to replace graphite, for the following reasons: (1) silicon has the highest weight specific capacity (4200 mAh / g) and volume specific capacity (9786 mAh / cm 3 ); (2) the discharge voltage of silicon is about 0.4 V on average, which achieves a good balance between maintaining a reasonable open-circuit voltage and avoiding adverse lithium metal; (3) silicon has a rich reserve (second in the earth's crust), with potential advantages of low cost, environmental friendliness and non-toxicity.

[0004] However, with the lithium intercalation and deintercalation process of silicon, the volume of silicon will experience a sharp expansion and contraction (volume change > 360%) and generate a huge stress, which can cause the following problems: (1) the electrode structural integrity is destroyed during repeated charge and discharge processes; (2) the interface stress induces the disconnection of the electrode and the current collector; (3) the solid electrolyte interface (SEI) layer is continuously consumed in the continuous formation-breakage-reformation process. These problems can also accelerate the electrode collapse and capacity decay in a synergistic manner.

[0005] Nanotechnology of silicon can effectively alleviate the impact of volume expansion on the electrode. Currently, silicon can be deposited in the pores of a porous matrix material (such as porous carbon) to achieve nanotechnology of silicon. For example, CN113795945A discloses an electroactive material for metal-ion batteries, which is a particulate material composed of a plurality of composite particles, the composite particles comprising: (a) a porous carbon framework comprising micropores and mesopores and (b) a plurality of nanoscale elemental silicon domains located within the pores of the porous carbon framework.

[0006] In order to improve the performance of the battery to better meet market demand, it is necessary to further develop suitable porous carbon materials and nanosilicon-porous carbon composite materials. SUMMARY

[0007] To further improve the battery performance, the present application provides a porous carbon for negative electrode material and a preparation method thereof, and further provides a composite material comprising the porous carbon and an application thereof.

[0008] In one aspect, the present application relates to a porous carbon for negative electrode material, wherein the ratio (I D / I G ) of the intensity of D peak (I D ) to the intensity of G peak (I G ) in the Raman spectrum of the porous carbon is 0.10-1.50; the diffraction angle 2θ of (002) crystal plane in the X-ray diffraction pattern of the porous carbon is 24.00°-26.53°; and the specific surface area BET of the porous carbon is 600-3000 m 2 / g.

[0009] In one embodiment, the ratio (I D / I G ) of the intensity of D peak (I D ) to the intensity of G peak (I G ) in the Raman spectrum of the porous carbon is 0.10-1.10, preferably 0.20-0.80, and more preferably 0.20-0.70.

[0010] In one embodiment, the specific surface area BET of the porous carbon is 800-2800 m 2 / g, preferably 900-2750 m 2 / g.

[0011] In one embodiment, the pore volume of the porous carbon is 0.50 cm 3 / g or more, preferably 0.60 cm 3 / g or more.

[0012] In one embodiment, the diffraction angle 2θ of (002) crystal plane in the X-ray diffraction pattern of the porous carbon is 24.15°-26.50°.

[0013] In another aspect, the present application relates to a method for preparing the porous carbon, comprising the following steps: providing a porous carbon precursor; and performing alkali activation on the porous carbon precursor to prepare the porous carbon of the present application.

[0014] In one embodiment, the alkali for alkali activation of the porous carbon precursor comprises: a hydroxide of an alkali metal or an alkaline earth metal, preferably comprises: potassium hydroxide, sodium hydroxide or a combination thereof.

[0015] In yet another aspect, the present application relates to a composite material for lithium ion secondary battery, comprising: the porous carbon of the present application and nano-silicon dispersed in the porous carbon.

[0016] In yet another aspect, the present application relates to a method for preparing the composite material of the present application, comprising the steps of: providing a porous carbon; performing silicon deposition in the porous carbon to form nanosilicon dispersed in the porous carbon; optionally, coating the outer surface of the porous carbon having the nanosilicon dispersed therein to form a shell layer.

[0017] In another aspect, the present application relates to a negative electrode tab comprising the composite material of the present application.

[0018] In yet another aspect, the present application relates to a lithium ion secondary battery comprising the negative electrode tab of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 XRD pattern of biomass-based porous carbon precursor A.

[0020] Figure 2 XRD pattern of resin-based porous carbon precursor B.

[0021] Figure 3 XRD pattern of coke-based porous carbon precursor C3.

[0022] Figure 4 Raman spectrum of porous carbon A1.

[0023] Figure 5 Raman spectrum of porous carbon B1.

[0024] Figure 6 Raman spectrum of porous carbon C1.

[0025] Figures 7-9 Graph of the results of the de-lithiation GITT test of the half-cells assembled using the negative electrode tabs prepared from each sample of the present application.

[0026] Figure 10 Cycle curves of the full cells assembled using the negative electrode tabs prepared from each sample of the present application.

[0027] Figure 11 Cycle curves of the full cells assembled using the negative electrode tabs with different electrode tab compaction densities.

[0028] Figure 12 Cycle curves of the full cells assembled using the negative electrode tabs with different electrode tab compaction densities.

[0029] Figures 13-15 Cycle curves of the full cells assembled using the negative electrode tabs prepared from each sample of the present application under a low temperature environment. DETAILED DESCRIPTION

[0030] General definitions and terminology

[0031] All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety unless otherwise indicated.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. If there is a conflict between the definitions provided in this document and those provided in the patents, applications, and other references mentioned herein, the definitions provided in this document control.

[0033] Unless otherwise indicated, all percentages, parts, ratios, etc., are by weight.

[0034] When a number, concentration, or other value or parameter is given as a range, preferred range or a range of preferred ranges, it is intended to include every narrower range that falls within the broader range. Unless otherwise stated, the use of a range or preferred range includes the end points of the range and all integers and fractions within the range. The ranges of values are not intended to be limited to the specific values that are cited, unless expressly stated otherwise. For example, "1 to 8" is intended to cover, inter alia, 1, 2, 3, 4, 5, 6, 7, 8, as well as any sub-range that falls within the broader range, e.g., 2 to 6, 3 to 5.

[0035] The terms "about," "approximately," when used in connection with a numerical value, generally mean that the value of the variable and all values of the variable are within experimental error (e.g., within a 95% confidence interval of the mean) or within ±10% of the stated value, or within a broader range.

[0036] The terms "comprising," "including," "containing," "having," or "involving" and any variations thereof, are inclusive or open-ended and do not exclude additional, unrecited elements or method steps. Those skilled in the art will understand that a recited element, step, or ingredient need not be present in a composition, method, or article for the composition, method, or article to be encompassed by a claim. The terms "comprising," "including," and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to," "comprising, but not limited to," or "containing, but not limited to"). The term "consisting of" is to be construed as a closed term meaning "only the recited elements are present." The term "consisting essentially of" is to be construed as a closed term meaning "the recited elements are present, but the composition, method or article can also include other elements that do not materially affect the basic and novel characteristics of the claimed composition, method or article." It will be understood that the term "comprising" encompasses the terms "consisting of" and "consisting essentially of."

[0037] The term "selected from the group consisting of" means one or more elements from the group listed thereafter, independently selected, and can include combinations of two or more elements.

[0038] When numerical values or ranges are described herein, it is to be understood that the disclosure is intended to encompass the particular value or end point recited, as well as any value or end point within the range.

[0039] As used herein, the term "one or more" or "at least one" means one, two, three, four, five, six, seven, eight, nine, or more.

[0040] The terms "combination thereof and "mixture thereof, unless otherwise indicated, refer to a multi-component mixture of the individual elements, e.g., two, three, four, and up to the maximum possible multi-component mixture.

[0041] Further, where the number of a component or constituent of the application is not otherwise specified, it is intended to mean that there is no limit to the number of occurrences (or presence) of the component or constituent. Thus, it is to be interpreted to include one or at least one, and the singular word form of the component or constituent also includes the plural unless the number clearly dictates the singular.

[0042] As used herein, the term "optional" or "optionally" means that the subsequently described event or circumstance can or can not occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

[0043] "Carburizing," "pyrolyzing," "carburization," and "pyrolysis" all refer to the process of heating a carbon-containing substance in an inert atmosphere (e.g., argon or nitrogen) or in a vacuum at a pyrolysis soak temperature such that the target material collected at the end of the process is primarily carbon. "Pyrolyzed" refers to a material or substance (e.g., a carbon material) that has undergone the process of pyrolysis.

[0044] "Soak temperature" refers to the furnace temperature during the portion of the process reserved for maintaining a relatively constant temperature (i.e., not increasing or decreasing the temperature). For example, a pyrolysis soak temperature refers to a relatively constant furnace temperature during the pyrolysis process, and an activation soak temperature refers to a relatively constant furnace temperature during the activation process.

[0045] "Porosity structure" refers to the surface layout of internal pores within a carbon material. The composition of the porosity structure includes pore size, pore volume, surface area, density, pore size distribution, and pore length. Typically, the porosity structure of a porous carbon material includes micropores, mesopores, and macropores. "Mesopores" refer to pores having a pore size of 2-50 nm, "micropores" refer to pores having a pore size of less than 2 nm, and "macropores" refer to pores having a pore size of greater than 50 nm.

[0046] "Surface area" refers to the total specific surface area of a substance that can be measured by BET techniques. Typically, surface area is expressed in m 2 / g. BET techniques use an inert gas (e.g., nitrogen) to measure the amount of gas adsorbed on a material and are commonly used in the art to determine the accessible surface area of a material.

[0047] "Composite material" refers to a composition that contains multiple (2 or more) different chemical substances within the same particle, e.g., a particle that includes a porous carbon material and a silicon material.

[0048] "Soft carbon" also known as "easy graphitizable carbon" refers to carbon materials that can be graphitized after high temperature treatment (e.g., 2200 °C, 2500 °C, etc.) and its disordered structure can be eliminated.

[0049] "Hard carbon" also known as "difficult graphitizable carbon" refers to carbon that is difficult to be completely graphitized even after high temperature treatment (e.g., above 2800 °C) and its disordered structure is difficult to be eliminated at high temperature.

[0050] "Coulombic efficiency" refers to the ratio of the discharge capacity to the charge capacity of the energy storage device of lithium ions. Coulombic efficiency is a percentage or fraction (e.g., 99% = 0.99).

[0051] Porous carbon

[0052] In one aspect, the present disclosure relates to a porous carbon for use in an anode material. The porous carbon can be used as a porous matrix for deposition of silicon, which can be uniformly dispersed in the internal pores of the porous carbon, thereby forming nanosilicon.

[0053] Without being bound by theory, the porous carbon provides superior performance for batteries based on the following aspects: the porous structure of the porous carbon provides suitable void space for the volume expansion process of silicon, thereby reducing the overall particle expansion at the electrode level. The porous structure of the porous carbon can act as a template for silicon deposition to achieve nanosilicon of desired size, distribution, and morphology.

[0054] In the prior art, it is generally taught that low graphitization degree materials are advantageous anode materials, for example, Liu Y, Xue, JS, Zheng T, Dahn, JR. Carbon 1996, 34: 193-200; Wu, YP, Fang, SB, Jiang, YY. 1998, 75: 201-206; Buiel E, Dahn JR. Electrochim Acta 1999 45: 121-130. The disordered nature of the graphene layers can allow lithium ions to be intercalated on either side of the graphene plane, thus, such intercalation can theoretically increase the lithium ion content relative to high graphitization degree materials. In addition, the disordered structure of low graphitization degree materials allows lithium ions to be intercalated isotropically, which improves the rate capability of the material. The disordered graphene network can provide increased electrical conductivity for silicon, thereby enabling faster charge / discharge rates.

[0055] Unlike the teachings in the prior art, the present application finds that the composite material prepared from a porous carbon material having a specific graphitization degree, in particular a higher graphitization degree, and a specific pore structure, has an unexpectedly advantageous effect on improving the performance of the battery, in particular: the battery assembled therefrom can have a higher lithium extraction rate, low-temperature charge-discharge performance, and more excellent cycle performance, etc. Such an advantageous effect makes the application scenarios of the battery be significantly widened. Without being bound by theory, the advantageous effect is derived from the synergistic effect of the specific pore structure and the specific graphitization degree in the porous carbon.

[0056] The graphitization degree of the porous carbon can be investigated by means known in the art, including but not limited to X-ray diffraction (XRD) and Raman spectroscopy. For XRD, the graphitization degree of the carbon material can be evaluated by monitoring the peak intensity at each 2theta corresponding to each Miller index. The higher the graphitization degree of the material, the larger the diffraction angle 2theta of the (002) crystal plane corresponding to graphite in the material, and the more prominent the diffraction peak at this position (i.e., in the form of a narrow and high peak). In one embodiment, the diffraction angle 2theta of the (002) crystal plane in the X-ray diffraction spectrum of the porous carbon of the present application is 24.00°-26.53°, preferably 24.15°-26.50°, such as 24.00°, 24.05°, 24.10°, 24.14°, 24.19°, 24.25°, 24.50°, 24.75°, 25.00°, 25.25°, 24.50°, 24.75°, 25.84°, 26.00°, 24.25°, 26.28°, 26.47°, 26.50°, 26.53°, etc.

[0057] For Raman spectroscopy, the graphitization degree of the carbon material can be evaluated by monitoring the ratio of the peak intensity of the D band (about 1300-1400 cm -1 ) to the G band (about 1550-1650 cm - 1). For the ratio of the D peak intensity (I D ) to the G peak intensity (I G ) (I D / I G ), the material with a higher I D / I G generally has a lower graphitization degree, while a lower I D / I G generally corresponds to a material with a higher graphitization degree. In one embodiment, the ratio of the D peak intensity (I D ) to the G peak intensity (I G ) (I D / I G) is 0.10-1.50, preferably 0.10-1.10, more preferably 0.20-0.80, even more preferably 0.20-0.70, for example 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.38, 0.40, 0.45, 0.50, 0.55, 0.56, 0.58, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.00, 1.10, 1.20, 1.30, etc. Furthermore, the suitable pore structure of the porous carbon is advantageous to provide void space for the deposited silicon, to reserve space for the expansion of silicon, and to increase the content of the depositable silicon in the composite, thereby improving the battery performance, for example, the specific charge capacity.

[0058] In one embodiment, the specific surface area BET of the porous carbon is 600-3000 m 2 / g, preferably 800-2800 m 2 / g, more preferably 900-2750 m 2 / g, for example 600 m 2 / g, 700 m 2 / g, 800 m 2 / g, 900 m 2 / g, 1000 m 2 / g, 1100 m 2 / g, 1200 m 2 / g, 1300 m 2 / g, 1400 m 2 / g, 1500 m 2 / g, 1600 m 2 / g, 1700 m 2 / g, 1800 m 2 / g, 1900 m 2 / g, 2000 m 2 / g, 2100 m 2 / g, 2200 m 2 / g, 2300 m 2 / g, 2400 m 2 / g, 2500 m 2 / g, 2600 m 2 / g, 2700 m 2 / g, 2800 m 2 / g, 2900 m 2 / g, 3000 m 2 / g, 1844 m 2 / g, 1286 m 2 / g, 2703 m 2 / g, etc.

[0059] In one embodiment, the porous carbon has a pore volume of 0.50 cm³. 3 / g or more, preferably 0.60cm 3 / g or more, for example, 0.50cm 3 / g, 0.60cm 3 / g, 0.70cm 3 / g, 0.80cm 3 / g, 0.90cm 3 / g, 1.00cm 3 / g, 1.10cm 3 / g, 1.20cm 3 / g, 1.30cm 3 / g, 1.40cm 3 / g, 1.50cm 3 / g, 2.00cm 3 / g, 2.50cm 3 / g, 0.85cm 3 / g, 1.02cm 3 / g, 0.97cm 3 / g, 1.31cm 3 / g etc.

[0060] In one embodiment, the tap density of the porous carbon is 0.2-1.4 g / cm³. 3 For example, 0.2 g / cm³ 3 0.3g / cm 3 0.4g / cm 3 0.5g / cm 3 0.6g / cm 3 0.7g / cm 3 0.8g / cm 3 0.9g / cm 3 1.0g / cm 3 1.1g / cm 3 1.2g / cm 3 1.3g / cm 3 1.4g / cm 3 In one embodiment, the minimum particle size Dmin of the porous carbon can be 0.1-1.0 μm, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, etc.

[0061] In one embodiment, the D10 particle size of the porous carbon is 2.0-5.0 μm, for example, 2.0 μm, 2.5 μm, 3.0 μm, 3.5 μm, 4.0 μm, 4.5 μm, 5.0 μm, etc.

[0062] In one embodiment, the porous carbon has a D50 particle size of 5.0-15.0 μm, such as 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm, 10.0 μm, 11.0 μm, 12.0 μm, 13.0 μm, 14.0 μm, 15.0 μm, etc.

[0063] In one embodiment, the porous carbon has a D90 particle size of 10.0-30.0 μm, such as 10.0 μm, 15.0 μm, 20.0 μm, 25.0 μm, 30.0 μm, etc.

[0064] In one embodiment, the porous carbon has a D100 particle size of 20.0-50.0 μm; such as 20.0 μm, 25.0 μm, 30.0 μm, 35.0 μm, 40.0 μm, 45.0 μm, 50.0 μm, etc.

[0065] The porous carbon of the present application has suitable graphitization degree, pore structure and particle size distribution, and overcomes the disadvantage of poor conductivity of conventional porous carbon materials. The porous carbon of the present application has low powder resistivity and good conductivity. In one embodiment, the powder resistivity of the porous carbon is 900 mΩ-cm or less, preferably 800 mΩ-cm or less, such as 900 mΩ-cm, 850 mΩ-cm, 800 mΩ-cm, 750 mΩ-cm, 700 mΩ-cm, 600 mΩ-cm, 500 mΩ-cm, 400 mΩ-cm, 300 mΩ-cm, 200 mΩ-cm, 100 mΩ-cm, 50 mΩ-cm, etc.

[0066] Preparation of porous carbon

[0067] In the present application, a specific porous carbon precursor and preparation process are used to obtain the target porous carbon. Therefore, in another aspect, the present application is a method for preparing porous carbon, which comprises: providing a porous carbon precursor and alkali-activating the porous carbon precursor.

[0068] As described above, in order to obtain improved battery performance, porous carbon having suitable properties (such as graphitization degree, pore structure and particle size distribution) is preferred, and for this purpose, the present application uses a specific porous carbon precursor to prepare the porous carbon.

[0069] The type of suitable porous carbon precursor helps to obtain a porous carbon with desired properties. In one embodiment, the porous carbon precursor is a soft carbon material. Preferably, the porous carbon precursor is selected from the group consisting of pitch-based and coal-based materials. The pitches useful herein include, but are not limited to, petroleum coke, pitch coke, needle coke, green coke, semi-coke, and the like. More preferably, the porous carbon precursor is petroleum coke. The preferred precursor material is capable of ensuring that the porous carbon produced is further capable of obtaining a desired pore structure by a suitable pore-making process, on the basis of obtaining a desired degree of graphitization.

[0070] In one embodiment, the porous carbon precursor has a diffraction angle 2Θ of the (002) crystal plane in the range of 25.00° to 26.50°, preferably in the range of 25.25° to 26.25°, more preferably in the range of 25.40° to 26.00°, such as 25.00°, 25.50°, 25.70°, 25.78°, 25.80°, 25.90°, 25.96°, 26.00°, 26.10°, 26.20°, 26.30°, 26.40°, 26.50°, and the like, in the X-ray diffraction pattern thereof.

[0071] In one embodiment, the porous carbon precursor has a ratio (I D / I G ) of the intensity of the D peak (I D ) to the intensity of the G peak (I G ) in the range of 0.30 to 0.50, preferably in the range of 0.35 to 0.48, such as 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.50, and the like, in the Raman spectrum thereof.

[0072] The suitable diffraction angle 2Θ of the (002) crystal plane and the suitable ratio (I D / I G ) of the intensity of the D peak (I D ) to the intensity of the G peak (I G ) of the porous carbon precursor enables the porous carbon to have a desired higher degree of graphitization, on the basis of ensuring the pore structure of the porous carbon. A porous carbon precursor with too high a degree of graphitization is not capable of obtaining a desired pore structure by a pore-making process; and a porous carbon precursor with too low a degree of graphitization also causes a decrease in the performance of a battery product.

[0073] The lower powder resistivity of the porous carbon precursor helps to improve the conductive properties of the resulting porous carbon. In one embodiment, the powder resistivity of the porous carbon precursor is 5.0 mW-cm or less, such as about 5.0 mW-cm, 4.9 mW-cm, 4.5 mW-cm, 4.0 mW-cm, 3.5 mW-cm, 3.1 mW-cm, 2.9 mW-cm, 2.0 mW-cm, 1.5 mW-cm, 1.0 mW-cm, etc.

[0074] The porous carbon precursor is subjected to a suitable pore forming process to obtain the target pore structure. In the present application, the porous carbon precursor is preferably subjected to an alkali activation process. For coke-based and coal-based materials, the alkali activation process has excellent pore forming efficiency and helps to ensure the structural stability of the porous carbon. An inorganic base can be used for the alkali activation process, such as a hydroxide of an alkali or alkaline earth metal. Suitable bases include, but are not limited to, potassium hydroxide, sodium hydroxide, etc.

[0075] It should be understood that the preparation of the porous carbon can also include conventional steps for preparing porous carbon in the art, including but not limited to: crushing, washing, etc.

[0076] The crushing process is used to break larger size materials into materials having a desired size. Before the alkali activation pore forming treatment of the porous carbon precursor, the porous carbon precursor can be subjected to a crushing process to break larger size (e.g., centimeter level) porous carbon precursor into smaller size (e.g., micron level) porous carbon precursor. Such size of the porous carbon precursor facilitates the pore forming process. After the pore forming process is completed, a secondary crushing can be performed to obtain a porous carbon material having a desired particle size distribution. Compared to a single crushing, the use of multiple crushing in the present application is advantageous for the pore forming process, while also shortening the crushing time of the porous carbon after the pore forming, and reducing the possible adverse effects of the crushing process on the pore structure.

[0077] The washing process can remove impurities from the material. For example, after the pore forming, the impurities (e.g., alkali) in the material can be removed by a washing process to remove the adverse effects of the impurity residues.

[0078] It has been found in the present application that the use of a specific porous carbon precursor in combination with the pore forming and crushing processes can obtain a desired porous carbon material. In particular, by selecting a suitable precursor in the present application, an additional graphitization step (e.g., graphitization by high temperature) is not required, thereby avoiding possible adverse consequences (e.g., pore collapse, low pore volume, low specific surface area) due to the graphitization process (e.g., high temperature). Therefore, in one embodiment, the method for preparing the porous carbon in the present application does not include a graphitization step, preferably does not include a high temperature heating step, such as a heating step at a temperature of 2500°C or higher, or 2000°C or higher, or 1600°C or higher, or 1200°C or higher.

[0079] Composite materials for secondary lithium-ion batteries

[0080] In one aspect, the present application relates to a composite material for lithium ion secondary battery, the composite material comprising: porous carbon and nano-silicon dispersed in the porous carbon.

[0081] In the present application, the silicon is uniformly dispersed in the inner pores of the porous carbon to form nano-silicon (i.e. nano-silicon particles), and the outer surface of the porous carbon is substantially free of silicon, which is beneficial to the full play of the advantages of nano-silicon.

[0082] In one embodiment, the nano-silicon dispersed in the porous carbon is hydrogen-containing nano-silicon. In the present application, the silicon dispersed in the porous carbon retains part of the Si-H bond, and therefore the silicon dispersed in the porous carbon is also referred to as hydrogen-containing silicon. The hydrogen-containing silicon of the present application refers to all the nano-silicon dispersed in the porous carbon. In the hydrogen-containing silicon, at least part of the nano-silicon particles are nano-silicon particles with Si-H bond. The presence of Si-H bond in the hydrogen-containing silicon can effectively improve the stability of the composite material during the charging and discharging process and prolong the cycle life of the battery. The Si-H bond in the hydrogen-containing silicon can be determined by any means in the art, including but not limited to infrared testing. For example, the infrared spectrum of the composite material can have a vibration peak at 625-640 cm -1 , and the infrared spectrum of the composite material can also have a vibration peak at one or more of the following positions: 845-885 cm -1 , 1990-2010 cm -1 .

[0083] In the Raman spectrum of the composite material of the present application, the ratio (I D / I G ) of the intensity of D peak (I D ) to the intensity of G peak (I G ) is 0.20-1.50, preferably 0.20-1.00, for example 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, 1.18, 1.32, 1.46, 1.50, etc.

[0084] The suitable particle size of the nano-silicon is beneficial to the improvement of the performance of the composite material. The particle size of the nano-silicon can range from 0.1 nm to 60 nm, preferably from 0.1 nm to 20 nm, and more preferably from 1 nm to 5 nm.

[0085] The ratio of silicon dispersed in the porous carbon to the porous carbon also affects the performance of the composite material. A suitable content of silicon dispersed in the porous carbon can impart good electrical properties (e.g., excellent specific charge capacity) to the product, while also reserving some pores in the porous carbon to provide space for the expansion of the silicon later, avoiding rupture or even pulverization of the composite material due to the volume expansion of the silicon. In one embodiment, the weight ratio of nanosilicon to porous carbon is 0.3-0.7, preferably 0.5-0.7, such as about 0.30, 0.40, 0.50, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.60, 0.70, etc.

[0086] The pore structure of the porous carbon in which the nanosilicon is deposited can indicate the deposition of silicon in the porous carbon. The performance of the material is better with suitable pores. If the porous carbon in which the nanosilicon is deposited has too high a porosity, the content of silicon is insufficient, resulting in poor performance, and if the porosity is too low, there is insufficient space for the expansion of the silicon.

[0087] In one embodiment, the specific surface area BET of the porous carbon in which the nanosilicon is deposited is 30-300 m 2 / g, such as 30 m 2 / g, 50 m 2 / g, 100 m 2 / g, 150 m 2 / g, 200 m 2 / g, 250 m 2 / g, 300 m 2 / g, etc. In one embodiment, the pore volume of the porous carbon in which the nanosilicon is deposited is 0.2 cm 3 / g or less.

[0088] In one embodiment, the powder resistivity of the porous carbon in which the nanosilicon is deposited is 1500 Ω·cm or less, such as 1500 Ω·cm, 1200 Ω·cm, 800 Ω·cm, 300 Ω·cm, 100 Ω·cm, 60 Ω·cm, 20 Ω·cm, etc.

[0089] The outer surface of the porous carbon in which the nanosilicon is deposited can be coated with a shell layer, which serves as the outer layer of the composite material. The shell layer coated on the outer surface of the porous carbon not only prevents the oxidation and spontaneous combustion of the high-activity nanosilicon in the pores of the porous carbon in the air, but also ensures that the porous carbon and the nanosilicon inside it do not directly contact the electrolyte during use of the composite material, which is conducive to the formation of a stable SEI film.

[0090] The porous carbon in which the nanosilicon is dispersed can be subjected to a reaction treatment to form the shell layer, or another material can be attached to the surface of the porous carbon to form the shell layer.

[0091] The components of the shell layer can include, but are not limited to, amorphous carbon, graphene, carbon nanotubes, conductive polymers, titanium carbide, aluminum oxide, aluminum nitride, silicon carbide, silicon nitride, silicon oxide (e.g., silicon dioxide), silicon oxynitride, or combinations thereof. In certain embodiments, the shell layer of the composite material of the present application is a carbon shell.

[0092] The shell layer can be a single layer or multiple layers. For any layer in the shell layer, the component can not be limited to one of the above-mentioned components, but can be a combination of several components.

[0093] The shell layer can have a suitable thickness to sufficiently perform the function of the shell layer. The thickness of the shell layer can be 1-1000 nm. In some embodiments, the shell layer of the composite material has a thickness of 1-10 nm. In certain embodiments, the shell layer of the composite material has a thickness of 10-50 nm. In certain embodiments, the shell layer of the composite material has a thickness of 50-100 nm. In certain embodiments, the shell layer of the composite material has a thickness of 100-500 nm. In certain embodiments, the shell layer of the composite material has a thickness of 500-1000 nm.

[0094] It should be understood that the "shell layer coated on the outer surface of the porous carbon" described herein does not mean that the shell layer material is only located on the outside of the porous carbon. For example, the shell layer material can enter the pores of the porous carbon near the outer surface. For another example, the shell layer can be formed by reacting the outer layer portion of the porous carbon having dispersed nanosilicon.

[0095] It should also be understood that there can be a clear interface between the shell layer and the porous carbon described herein. There can also be no clear interface between the shell layer and the porous carbon described herein, for example, there is a certain thickness of the interface region between the shell layer and the porous carbon.

[0096] It should also be understood that the thickness of the shell layer described herein can be uniform at various positions, or there can be differences.

[0097] In one embodiment, the tap density of the porous carbon having deposited nanosilicon coated with the shell layer can be 0.5-2 g / cm 3 , for example, 0.5 g / cm 3 , 0.6 g / cm 3 , 0.8 g / cm 3 , 1.0 g / cm 3 , 1.2 g / cm 3 , 1.4 g / cm 3 , 1.6 g / cm 3 , 1.8 g / cm 3 , 2.0 g / cm 3 , etc.

[0098] In one embodiment, the porous carbon having nanosilicon deposited therein and coated with a shell layer has a specific surface area BET of 10 m2 / g or less, for example, 10 m2 / g, 9 m2 / g, 8 m2 / g, 7 m2 / g, 6 m2 / g, 5 m2 / g, 4 m2 / g, 3 m2 / g, 2 m2 / g, 1 m2 / g, or 0.5 m2 / g or less. 2 / g or less, for example, 10 m 2 / g or less, 9 m 2 / g or less, 8 m 2 / g or less, 7 m 2 / g or less, 6 m 2 / g or less, 5 m 2 / g or less, etc.

[0099] In one embodiment, the porous carbon having nanosilicon deposited therein and coated with a shell layer has a pore volume of 0.1 cm3 / g or less, for example, 0.1 cm3 / g, 0.08 cm3 / g, 0.06 cm3 / g, 0.05 cm3 / g, 0.04 cm3 / g, 0.03 cm3 / g, 0.02 cm3 / g, 0.01 cm3 / g, or 0.005 cm3 / g or less. 3 / g or less, for example, 0.1 cm 3 / g or less, 0.1 cm 3 / g or less, 0.08 cm 3 / g or less, 0.06 cm 3 / g or less, 0.05 cm 3 / g or less.

[0100] In one embodiment, the porous carbon having nanosilicon deposited therein and coated with a shell layer has a powder resistivity of 100 Ω-cm or less, for example, 100 Ω-cm, 60 Ω-cm, 30 Ω-cm, 10 Ω-cm, 2 Ω-cm, or the like.

[0101] The carbon content can be 30-70 wt%, preferably 30-50 wt%, for example, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, or the like, based on the total weight of the porous carbon having nanosilicon deposited therein and coated with a shell layer.

[0102] The hydrogen content can be 0-10 wt%, preferably 0.3-5 wt%, for example, 0.1 wt%, 0.3 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or the like, based on the total weight of the porous carbon having nanosilicon deposited therein and coated with a shell layer.

[0103] The oxygen content can be 0-3 wt%, 0.1 wt%, 0.3 wt%, 1 wt%, 2 wt%, 3 wt%, or the like, based on the total weight of the porous carbon having nanosilicon deposited therein and coated with a shell layer.

[0104] The nanosilicon can be crystalline silicon or amorphous silicon. In certain embodiments, the nanosilicon comprises crystalline nanosilicon. In certain embodiments, the nanosilicon comprises polycrystalline nanosilicon. In certain other embodiments, the nanosilicon comprises amorphous nanosilicon. In certain other embodiments, the nanosilicon comprises both crystalline nanosilicon and amorphous nanosilicon.

[0105] The crystallinity of silicon in the nanosilicon can be determined by any means in the art, for example, by electrochemical curve. For the test sample obtained from the composite material, the platform of the charge curve at 0.4-0.5V and the characteristic peak of the corresponding DQ / DV curve at 0.4-0.5V are related to the crystallinity of the nanosilicon. The higher the proportion of crystalline silicon in the nanosilicon, the more obvious the platform of the charge curve at 0.4-0.5V, and the stronger the characteristic peak of the DQ / DV curve at 0.4-0.5V.

[0106] In some embodiments, the lithium ion half-cell test prepared from the composite material of the secondary lithium ion battery of the present application has a platform at 0.4-0.5V in the electrochemical charge curve. In some embodiments, the lithium ion half-cell test prepared from the composite material of the secondary lithium ion battery of the present application has a characteristic peak at 0.4-0.5V in the electrochemical charge curve.

[0107] In another aspect, the present application relates to a method of the above-mentioned composite material, comprising the following steps: providing a porous carbon; depositing silicon in the porous carbon to form nanosilicon dispersed in the porous carbon; and optionally, coating the outer surface of the porous carbon with the nanosilicon dispersed therein to form a shell layer.

[0108] The dispersion process of silicon can be achieved by any means in the art, including but not limited to CVD deposition method, liquid immersion method. Suitable parameters in the dispersion process help to obtain the desired composite material.

[0109] There is no special limitation on the coating method herein, and the outer surface of the porous carbon can be coated by reactive coating, adhesive coating, or a combination of reactive coating and adhesive coating, or other methods that can form a shell layer on the surface of the porous substrate with the nanosilicon dispersed therein. Reactive coating refers to forming a shell layer by reaction treatment to achieve coating. For example, a shell layer can be formed by reaction treatment of the porous carbon with the nanosilicon dispersed therein, specifically, the reaction treatment can be carried out by partial oxidation, nitridation, carbonization of the nanosilicon to achieve coating. Adhesive coating refers to attaching a material to the surface of the porous carbon to form a shell layer. The outer surface of the porous carbon can be coated by a combination of reactive coating and adhesive coating.

[0110] The present application finds that the composite material prepared from the porous carbon material with a specific graphitization degree as the raw material exhibits better performance in terms of delithiation rate, discharge capacity retention rate, and low-temperature discharge capacity percentage in the battery assembled therefrom, while these performances are usually difficult to improve by the conventional means in the art (for example, adjusting the content of silicon in the composite material, etc.).

[0111] In one embodiment, the half-cell assembled by the negative electrode sheet made of the composite material of the present application can perform at room temperature 0.1C / 0.1C, and the de-lithiation GITT can be calculated according to the following formula:

[0112]

[0113] wherein, D - diffusion coefficient; τ - relaxation time; R s - active particle radius; ΔE s - voltage change caused by pulse; ΔE t - voltage change of constant current charge ((dis) charge). The peak value of the de-lithiation GITT test curve of the half-cell assembled by the composite material of the present application is 1.30 or more, preferably 1.40 or more, more preferably 1.45 or more.

[0114] In one embodiment, the full cell assembled by the composite material of the present application measures the discharge capacity percentage under the following conditions: room temperature (25℃) 1C charge, low temperature (-20℃) 0.2C discharge; voltage range: 2.8-4.25V. The discharge capacity percentage of the full cell assembled by the negative electrode sheet made of the composite material of the present application is 70% or more.

[0115] In one embodiment, the full cell assembled by the composite material of the present application measures the discharge capacity retention rate under the following conditions: room temperature (25℃) 1C charge, 0.2C discharge to 2.5V, measure the discharge capacity, repeat three times and take the average value, which is recorded as the room temperature discharge capacity. After room temperature 1C charge, low temperature (-20℃) storage for 6-12h, 0.2C discharge to 2.5V, measure the discharge capacity, and the ratio of this value to the room temperature discharge capacity is the discharge capacity retention rate. The discharge capacity retention rate of the full cell assembled by the negative electrode sheet made of the composite material of the present application is 70% or more, preferably 73% or more.

[0116] The present application also includes the following embodiments:

[0117] Embodiment 1: A porous carbon for negative electrode material, characterized in that the ratio (ID / IG) of the intensity (ID) of the D peak to the intensity (IG) of the G peak in the Raman spectrum of the porous carbon is 0.10-1.10; the diffraction angle 2θ of the (002) crystal face in the X-ray diffraction spectrum of the porous carbon is 24.00°-26.53°; and the specific surface area BET of the porous carbon is 600-3000m2 / g.

[0118] Embodiment 2: The porous carbon according to Embodiment 1, characterized in that the ratio (ID / IG) of the intensity (ID) of the D peak to the intensity (IG) of the G peak in the Raman spectrum of the porous carbon is 0.20-0.80, preferably 0.25-0.70. ​

[0119] Implementation Scheme 3: The porous carbon according to Implementation Scheme 1, characterized in that the specific surface area (BET) of the porous carbon is 800-2800 m2 / g, preferably 900-2750 m2 / g.

[0120] Implementation Scheme 4: The porous carbon according to Implementation Scheme 1, characterized in that the pore volume of the porous carbon is 0.50 cm3 / g or more, preferably 0.60 cm3 / g or more.

[0121] Implementation Scheme 5: The porous carbon according to Implementation Scheme 1 is characterized in that the diffraction angle 2θ of the (002) crystal plane in the X-ray diffraction pattern of the porous carbon is 24.15°-26.50°.

[0122] Implementation Scheme 6: The porous carbon according to Implementation Scheme 1, characterized in that the powder resistivity of the porous carbon is below 900 mΩ·cm, preferably below 800 mΩ·cm.

[0123] Implementation Scheme 7: The porous carbon according to Implementation Scheme 1, characterized in that the porous carbon has one or more of the following characteristics: (a) the tap density of the porous carbon is 0.2-1.4 g / cm³. 3 (b) The minimum particle size Dmin of the porous carbon is 0.1-1.0 μm; (c) The D10 particle size of the porous carbon is 2.0-5.0 μm; (d) The D50 particle size of the porous carbon is 5.0-15.0 μm; (e) The D90 particle size of the porous carbon is 10.0-30.0 μm; (f) The D100 particle size of the porous carbon is 20.0-50.0 μm.

[0124] Implementation Scheme 8: The porous carbon according to Implementation Scheme 1, characterized in that the porous carbon is obtained by alkali activation of a porous carbon precursor; preferably, the alkali includes: hydroxides of alkali metals or alkaline earth metals; more preferably, the alkali includes: potassium hydroxide, sodium hydroxide or a combination thereof.

[0125] Implementation Scheme 9: The porous carbon according to Implementation Scheme 8 is characterized in that the porous carbon precursor is a soft carbon material, preferably a coke or coal-based material, and more preferably petroleum coke.

[0126] Implementation Scheme 10: The porous carbon according to Implementation Scheme 8, characterized in that, in the X-ray diffraction pattern of the porous carbon precursor, the diffraction angle 2θ of the (002) crystal plane is 25.00°-26.50°, preferably 25.25°-26.25°, and more preferably 25.40°-26.00°.

[0127] Implementation Scheme 11: The porous carbon according to Implementation Scheme 8, characterized in that, in the Raman spectrum of the porous carbon precursor, the D peak intensity (I D ) and G peak intensity (I G The proportion of (I) D / I G The value is 0.35-0.48, preferably 0.41-0.47.

[0128] Implementation Scheme 12: The porous carbon according to Implementation Scheme 8, characterized in that the powder resistivity of the porous carbon precursor is below 5.0 mΩ·cm.

[0129] Implementation Scheme 13: A method for preparing porous carbon according to any one of Implementation Schemes 1-12, comprising the following steps: providing a porous carbon precursor; and alkali-activating the porous carbon precursor to prepare the porous carbon.

[0130] Implementation Scheme 14: A composite material for lithium-ion secondary batteries, characterized in that the composite material comprises: porous carbon as described in any one of Implementation Schemes 1-12, and nano-silicon dispersed in the porous carbon; preferably, the nano-silicon dispersed in the porous carbon is hydrogen-containing nano-silicon.

[0131] Implementation Scheme 15: The composite material according to Implementation Scheme 14, characterized in that, in the Raman spectrum of the composite material, the D peak intensity (I D ) and G peak intensity (I G The proportion of (I) D / I G The value is 0.35-1.10, preferably 0.40-1.00.

[0132] Implementation Scheme 16: The composite material according to Implementation Scheme 14 is characterized in that the composite material has one or more of the following features: (a) the particle size range of the nano-silicon is 0.1-60 nm, preferably 0.1-20 nm, more preferably 1-5 nm; (b) the weight ratio of the nano-silicon to the composite material is 0.3-0.7, preferably 0.5-0.7; (c) the powder resistivity of the composite material is below 1500 Ω·cm; (d) the specific surface area (BET) of the composite material is 30-300 m². 2 / g; (e) The pore volume of the composite material is 0.2 cm³. 3 / g or less.

[0133] Embodiment 17: The composite material according to Embodiment 14, further comprising: a shell layer coated on the outer surface of the porous carbon; preferably, the component of the shell layer comprises: amorphous carbon, graphene, carbon nanotube, conductive polymer, titanium carbide, aluminum oxide, aluminum nitride, carbide of silicon, nitride of silicon, oxide of silicon, oxynitride of silicon, or a combination thereof.

[0134] Embodiment 18: The composite material according to Embodiment 17, wherein the carbon content is 30-70 wt%, preferably 30-50 wt%, based on the total weight of the composite material; the hydrogen content is 0-10 wt%, preferably 0.3-5 wt%, based on the total weight of the composite material; the oxygen content is 0-3 wt%, based on the total weight of the composite material.

[0135] Embodiment 19: The composite material according to Embodiment 17, wherein the tap density of the composite material is 0.5-2 g / cm3; the powder resistivity of the composite material is 100 Ω-cm or less; the specific surface area BET of the composite material is 10 m2 / g or less; the pore volume of the composite material is 0.1 cm3 / g or less. 3 2 3

[0136] Embodiment 20: The composite material according to Embodiment 17, wherein the prepared half-cell of the composite material has a platform at 0.4-0.5 V in the electrochemical charge curve; and / or the prepared half-cell of the composite material has a characteristic peak at 0.4-0.5 V in the DQ / DV curve.

[0137] Embodiment 21: A method for preparing the composite material according to any one of Embodiments 14-20, comprising the steps of: providing a porous carbon; performing silicon deposition in the porous carbon to form nanosilicon dispersed in the porous carbon; optionally, coating the outer surface of the porous carbon with nanosilicon dispersed therein to form a shell layer.

[0138] Embodiment 22: A negative electrode sheet, comprising the composite material according to any one of Embodiments 14-20.

[0139] Embodiment 23: A lithium ion secondary battery, comprising the negative electrode sheet according to Embodiment 22.

[0140] Beneficial effects

[0141] ​​​In the present application, a specific porous carbon precursor is used in combination with a pore-forming and crushing process to obtain a porous carbon material with desired properties (e.g., high graphitization degree, rich pore structure), which can achieve a desired silicon deposition process. The composite material of the present application can be used as a battery negative electrode material and significantly improves the electrical performance of the battery. In the preparation method of the present application, by selecting a suitable precursor, no additional graphitization step (e.g., graphitization by high temperature) is needed, thereby avoiding the adverse consequences (e.g., pore collapse, low pore volume, low specific surface area) that may be caused by the graphitization process (e.g., high temperature). Moreover, the preparation method of the present application is simple and easy to operate, and can be applied to mass production.

[0142] Examples

[0143] The technical solutions of the present application will be further described in detail below in combination with specific examples.

[0144] It should be noted that the following examples are merely examples for clearly illustrating the technical solutions of the present application, and are not intended to limit the present application. Based on the above description, other different forms of changes or modifications can be made by those skilled in the art, and here it is not necessary or possible to exhaust all the embodiments, and the changes or modifications derived therefrom are still within the protection scope of the present application. Unless otherwise specified, the instruments and reagent materials used herein are commercially available.

[0145] Test methods

[0146] 1. Powder resistivity test

[0147] The test was performed using an automatic powder resistivity tester (ST2742B type), and the test standard referred to Appendix G of GB / T 30835-2014.

[0148] (1) Sample weighing: the sample to be tested was weighed on the weighing paper using a balance, and the porous carbon sample was weighed at 0.25-0.3 g (accurate to 0.01 g); the deposited silicon porous carbon sample and the deposited silicon porous carbon sample coated with a shell layer were weighed at 0.5-0.6 g (accurate to 0.01 g);

[0149] (2) Parameter setting: open the test software of the ST2742B powder resistivity tester, click "connect instrument" in the measurement interface, the software switches to the instrument setting interface, set the lower limit of the test pressure to 8 MPa, the upper limit to 10 MPa, the pressure holding time to 10 s, input the sample mass, click "set" to save the data;

[0150] (3) Test: Pour the sample into the sample loader, hold the loader, gently tap the table to make the sample in the cup vibrate and compact, place the loaded loader on the lifting platform, switch to the measurement control interface, fill in the "measurement identification", "tester", etc. in the lower right corner of the software. Click the "start" button in the software under the conditions of "automatic" and "up", start the automatic measurement, and the measurement interface displays the test results after the test is completed. After the measurement is completed, remove the loader, clean the loader, and then shut down or test the next sample.

[0151] 2. Raman spectrum test

[0152] The test was performed using a Raman spectrometer (HORIBA XploRA PLUS).

[0153] (1) Sample preparation: Take an appropriate amount of powder sample and place it in the middle of the slide, cover it with another slide, and use the tablet press at 10 MPa for 30 s to make the sample uniformly compacted on the slide;

[0154] (2) Test: Set the test wavelength range to 0-3000 cm -1 , the grating is 1200 gr / mm, the slit width is 0.1 mm at a wavelength of 532 nm, and the integration time is 25 s. Three positions are selected for each sample for testing.

[0155] 3. XRD test

[0156] The test was performed using an X-ray diffractometer (SmartLab SE).

[0157] The sample powder was placed in the XRD diffractometer, 10-65°, 5° / min, X-ray using a copper target, wavelength 0.154 nm, and tested.

[0158] Preparation

[0159] Preparation of porous carbon

[0160] Porous carbon was prepared from the porous carbon precursors shown in Table 1. The precursors were prepared by crushing, pore making, secondary crushing, and washing steps to prepare porous carbon samples. Biomass-based precursor materials were activated by water vapor or carbon dioxide activation methods. Resin-based precursor materials were activated by water vapor or carbon dioxide methods. Char-based materials were activated by alkali activation methods. Graphite materials cannot be activated by any conventional pore-making method. The parameters of the obtained porous carbon samples are shown in Tables 2 and 3.

[0161] Preparation of sample A1-SC and sample A1-SC-BF

[0162] Into the fluidized bed, 12 kg of porous carbon (No. porous carbon A1) was added as a deposition substrate (the parameters of the porous carbon used are shown in Tables 2 and 3), and nitrogen gas was introduced to replace the air in the fluidized bed at a flow rate of 21 L / min.

[0163] After the fluidized bed was raised to 500°C at a temperature increase rate of 2°C / min, silane SiH4 was introduced into the fluidized bed to perform vapor deposition on the porous carbon, the silane gas flow rate was 35 L / min, and the deposition time was 6 hours, thereby obtaining a porous carbon sample with deposited silicon (No. A1-SC).

[0164] After the deposition of silicon was completed, the gas carbon source ethyne was introduced to perform carbon coating on the porous carbon sample with deposited silicon (No. A1-SC) by vapor deposition, thereby obtaining a porous carbon sample with deposited silicon coated with a shell layer (No. A1-SC-BF).

[0165] Preparation of sample A2-SC and sample A2-SC-BF

[0166] Into the fluidized bed, 12 kg of porous carbon (No. porous carbon A2) was added as a deposition substrate (the parameters of the porous carbon used are shown in Tables 2 and 3), and nitrogen gas was introduced to replace the air in the fluidized bed at a flow rate of 24 L / min.

[0167] After the fluidized bed was raised to 400°C at a temperature increase rate of 1°C / min, silane SiH4 was introduced into the fluidized bed to perform vapor deposition on the porous carbon, the silane gas flow rate was 40 L / min, and the deposition time was 5 hours, thereby obtaining a porous carbon sample with deposited silicon (No. A2-SC).

[0168] After the deposition of silicon was completed, the gas carbon source propane was introduced to perform carbon coating on the porous carbon sample with deposited silicon (No. A2-SC) by vapor deposition, thereby obtaining a porous carbon sample with deposited silicon coated with a shell layer (No. A2-SC-BF).

[0169] Preparation of sample A3-SC and sample A3-SC-BF

[0170] Into the fluidized bed, 12 kg of porous carbon (No. porous carbon A3) was added as a deposition substrate (the parameters of the porous carbon used are shown in Tables 2 and 3), and nitrogen gas was introduced to replace the air in the fluidized bed at a flow rate of 23 L / min.

[0171] After the fluidized bed was raised to 480°C at a temperature increase rate of 5°C / min, silane SiH4 was introduced into the fluidized bed to perform vapor deposition on the porous carbon, the silane gas flow rate was 35 L / min, and the deposition time was 6 hours, thereby obtaining a porous carbon sample with deposited silicon (No. A3-SC).

[0172] After the silicon deposition, a gaseous carbon source, propane, was introduced to the fluidized bed to perform carbon coating on the silicon-deposited porous carbon sample (No. A4-SC) by gas-phase deposition, obtaining the shell-coated silicon-deposited porous carbon sample (No. A4-SC-BF).

[0173] Preparation of sample A4-SC and sample A4-SC-BF

[0174] Into the fluidized bed, 12 kg of porous carbon (No. Porous Carbon B2) was added as a deposition substrate (the parameters of the porous carbon used are shown in Tables 2 and 3), and nitrogen gas was introduced to replace the air in the fluidized bed at a flow rate of 27 L / min.

[0175] After the fluidized bed was raised to 425°C at a temperature raising rate of 4°C / min, silane SiH4 was introduced into the fluidized bed to perform gas-phase deposition on the porous carbon, the flow rate of the silane gas was 30 L / min, and the deposition time was 8 hours, obtaining a silicon-deposited porous carbon sample (No. B1-SC).

[0176] After the silicon deposition, a gaseous carbon source, propane, was introduced to the fluidized bed to perform carbon coating on the silicon-deposited porous carbon sample (No. B1-SC) by gas-phase deposition, obtaining the shell-coated silicon-deposited porous carbon sample (No. B1-SC-BF).

[0177] Preparation of sample B1-SC and sample B1-SC-BF

[0178] Into the fluidized bed, 12 kg of porous carbon (No. Porous Carbon B2) was added as a deposition substrate (the parameters of the porous carbon used are shown in Tables 2 and 3), and nitrogen gas was introduced to replace the air in the fluidized bed at a flow rate of 27 L / min.

[0179] After the fluidized bed was raised to 425°C at a temperature raising rate of 4°C / min, silane SiH4 was introduced into the fluidized bed to perform gas-phase deposition on the porous carbon, the flow rate of the silane gas was 30 L / min, and the deposition time was 8 hours, obtaining a silicon-deposited porous carbon sample (No. B1-SC).

[0180] After the silicon deposition, a gaseous carbon source, propane, was introduced to the fluidized bed to perform carbon coating on the silicon-deposited porous carbon sample (No. B1-SC) by gas-phase deposition, obtaining the shell-coated silicon-deposited porous carbon sample (No. B1-SC-BF).

[0181] Preparation of sample B2-SC and sample B2-SC-BF

[0182] Into the fluidized bed, 12 kg of porous carbon (No. Porous Carbon B2) was added as a deposition substrate (the parameters of the porous carbon used are shown in Tables 2 and 3), and nitrogen gas was introduced to replace the air in the fluidized bed at a flow rate of 27 L / min.

[0183] After the fluidized bed was raised to 450°C at a temperature raising rate of 5°C / min, silane SiH4 was introduced into the fluidized bed to perform vapor deposition on the porous carbon, the silane gas flow rate was 50 L / min, and the deposition time was 4 hours, to obtain a porous carbon sample with deposited silicon (No. B2-SC).

[0184] After the silicon deposition was completed, a gaseous carbon source, acetylene, was introduced to perform carbon coating on the porous carbon sample with deposited silicon (No. B2-SC) by vapor deposition, to obtain a porous carbon sample with deposited silicon coated with a shell layer (No. B2-SC-BF).

[0185] Preparation of sample C1-SC and sample C1-SC-BF

[0186] Into the fluidized bed, 12 kg of porous carbon (No. Porous Carbon C1) was added as a deposition substrate (the parameters of the porous carbon used are shown in Tables 2 and 3), and nitrogen gas was introduced to replace the air in the fluidized bed, at a nitrogen gas flow rate of 23 L / min.

[0187] After the fluidized bed was raised to 525°C at a temperature raising rate of 6°C / min, silane SiH4 was introduced into the fluidized bed to perform vapor deposition on the porous carbon, the silane gas flow rate was 30 L / min, and the deposition time was 6 hours, to obtain a porous carbon sample with deposited silicon (No. C2-SC).

[0188] After the silicon deposition was completed, a gaseous carbon source, acetylene, was introduced to perform carbon coating on the porous carbon sample with deposited silicon (No. C2-SC) by vapor deposition, to obtain a porous carbon sample with deposited silicon coated with a shell layer (No. C2-SC-BF).

[0189] Preparation of sample C2-SC and sample C2-SC-BF

[0190] Into the fluidized bed, 12 kg of porous carbon (No. Porous Carbon C1) was added as a deposition substrate (the parameters of the porous carbon used are shown in Tables 2 and 3), and nitrogen gas was introduced to replace the air in the fluidized bed, at a nitrogen gas flow rate of 23 L / min.

[0191] After the fluidized bed was raised to 525°C at a temperature raising rate of 6°C / min, silane SiH4 was introduced into the fluidized bed to perform vapor deposition on the porous carbon, the silane gas flow rate was 30 L / min, and the deposition time was 6 hours, to obtain a porous carbon sample with deposited silicon (No. C2-SC).

[0192] After the silicon deposition was completed, a gaseous carbon source, acetylene, was introduced to perform carbon coating on the porous carbon sample with deposited silicon (No. C2-SC) by vapor deposition, to obtain a porous carbon sample with deposited silicon coated with a shell layer (No. C2-SC-BF).

[0193] Preparation of sample C3-SC and sample C3-SC-BF

[0194] Into the fluidized bed, 12 kg of porous carbon (No. porous carbon C3) was added as a deposition substrate (the parameters of the porous carbon used are shown in Tables 2 and 3), and nitrogen gas was introduced to replace the air in the fluidized bed at a flow rate of 25 L / min.

[0195] After the fluidized bed was raised to 525°C at a temperature raising rate of 5°C / min, silane SiH4 was introduced into the fluidized bed to perform vapor deposition on the porous carbon, the flow rate of the silane gas was 30 L / min, and the deposition time was 8 hours, thereby obtaining a porous carbon sample with deposited silicon (No. C3-SC).

[0196] After the deposition of silicon was completed, a gaseous carbon source, propylene, was introduced to perform carbon coating on the porous carbon sample with deposited silicon (No. C3-SC) by vapor deposition, thereby obtaining a porous carbon sample with deposited silicon coated with a shell layer (No. C3-SC-BF).

[0197] Preparation of sample B1-SC and sample B1-SC-BF

[0198] Into the fluidized bed, 12 kg of porous carbon (No. porous carbon C4) was added as a deposition substrate (the parameters of the porous carbon used are shown in Tables 2 and 3), and nitrogen gas was introduced to replace the air in the fluidized bed at a flow rate of 23 L / min.

[0199] After the fluidized bed was raised to 450°C at a temperature raising rate of 6°C / min, silane SiH4 was introduced into the fluidized bed to perform vapor deposition on the porous carbon, the flow rate of the silane gas was 35 L / min, and the deposition time was 10 hours, thereby obtaining a porous carbon sample with deposited silicon (No. C4-SC).

[0200] After the deposition of silicon was completed, a gaseous carbon source, acetylene, was introduced to perform carbon coating on the porous carbon sample with deposited silicon (No. C4-SC) by vapor deposition, thereby obtaining a porous carbon sample with deposited silicon coated with a shell layer (No. C4-SC-BF).

[0201] Preparation of sample B1-SC and sample B1-SC-BF

[0202] Into the fluidized bed, 12 kg of porous carbon (No. porous carbon C5) was added as a deposition substrate (the parameters of the porous carbon used are shown in Tables 2 and 3), and nitrogen gas was introduced to replace the air in the fluidized bed at a flow rate of 27 L / min.

[0203] After the fluidized bed was raised to 450°C at a temperature raising rate of 5°C / min, silane SiH4 was introduced into the fluidized bed to perform vapor deposition on the porous carbon, the flow rate of the silane gas was 36 L / min, and the deposition time was 5 hours, thereby obtaining a porous carbon sample with deposited silicon (No. C5-SC).

[0204] After the silicon deposition, the sample of porous carbon with deposited silicon (No. C5-SC) was carbon-coated by gas-phase deposition method using the gaseous carbon source acetylene, to obtain the sample of porous carbon with deposited silicon coated with a shell (No. C5-SC-BF).

[0205] Preparation of sample C6-SC and sample C6-SC-BF

[0206] Into the fluidized bed, 12 kg of porous carbon (No. Porous carbon C6) was added as the deposition substrate (the parameters of the porous carbon used are shown in Tables 2 and 3), and nitrogen gas was introduced to replace the air in the fluidized bed at a flow rate of 23 L / min.

[0207] After the fluidized bed was raised to 550 °C at a temperature raising rate of 5 °C / min, silane SiH4 was introduced into the fluidized bed to perform gas-phase deposition on the porous carbon, the flow rate of the silane gas was 35 L / min, and the deposition time was 6 hours, to obtain the sample of porous carbon with deposited silicon (No. C6-SC).

[0208] After the silicon deposition, the sample of porous carbon with deposited silicon (No. C6-SC) was carbon-coated by gas-phase deposition method using the gaseous carbon source acetylene, to obtain the sample of porous carbon with deposited silicon coated with a shell (No. C6-SC-BF).

[0209] Preparation of sample C7-SC and sample C7-SC-BF

[0210] Into the fluidized bed, 12 kg of porous carbon (No. Porous carbon C7) was added as the deposition substrate (the parameters of the porous carbon used are shown in Tables 2 and 3), and nitrogen gas was introduced to replace the air in the fluidized bed at a flow rate of 23 L / min.

[0211] After the fluidized bed was raised to 420 °C at a temperature raising rate of 5 °C / min, silane SiH4 was introduced into the fluidized bed to perform gas-phase deposition on the porous carbon, the flow rate of the silane gas was 35 L / min, and the deposition time was 6 hours, to obtain the sample of porous carbon with deposited silicon (No. C7-SC).

[0212] After the silicon deposition, the sample of porous carbon with deposited silicon (No. C7-SC) was carbon-coated by gas-phase deposition method using the gaseous carbon source acetylene, to obtain the sample of porous carbon with deposited silicon coated with a shell (No. C7-SC-BF).

[0213] Preparation of sample C8-SC and sample C8-SC-BF

[0214] Into the fluidized bed, 12 kg of porous carbon (No. Porous carbon C8) was added as the deposition substrate (the parameters of the porous carbon used are shown in Tables 2 and 3), and nitrogen gas was introduced to replace the air in the fluidized bed at a flow rate of 23 L / min.

[0215] After the fluidized bed was raised to 405°C at a temperature raising rate of 5°C / min, silane SiH4 was introduced into the fluidized bed to perform vapor deposition on the porous carbon, the silane gas flow rate was 35 L / min, and the deposition time was 6 hours, to obtain a porous carbon sample with deposited silicon (No. C8-SC).

[0216] After the silicon deposition was completed, a gaseous carbon source, acetylene, was introduced to perform carbon coating on the porous carbon sample with deposited silicon (No. C8-SC) by vapor deposition, to obtain a porous carbon sample with deposited silicon coated with a shell layer (No. C8-SC-BF).

[0217] Preparation of sample C9-SC and sample C9-SC-BF

[0218] Into the fluidized bed, 12 kg of porous carbon (No. Porous Carbon C9) was added as a deposition substrate (the parameters of the porous carbon used are shown in Tables 2 and 3), and nitrogen gas was introduced to replace the air in the fluidized bed, at a nitrogen gas flow rate of 23 L / min.

[0219] After the fluidized bed was raised to 500°C at a temperature raising rate of 5°C / min, silane SiH4 was introduced into the fluidized bed to perform vapor deposition on the porous carbon, the silane gas flow rate was 35 L / min, and the deposition time was 6 hours, to obtain a porous carbon sample with deposited silicon (No. C9-SC).

[0220] After the silicon deposition was completed, a gaseous carbon source, acetylene, was introduced to perform carbon coating on the porous carbon sample with deposited silicon (No. C9-SC) by vapor deposition, to obtain a porous carbon sample with deposited silicon coated with a shell layer (No. C9-SC-BF).

[0221] Preparation of sample C10-SC and sample C10-SC-BF

[0222] Into the fluidized bed, 12 kg of porous carbon (No. Porous Carbon C10) was added as a deposition substrate (the parameters of the porous carbon used are shown in Tables 2 and 3), and nitrogen gas was introduced to replace the air in the fluidized bed, at a nitrogen gas flow rate of 27 L / min.

[0223] After the fluidized bed was raised to 450°C at a temperature raising rate of 5°C / min, silane SiH4 was introduced into the fluidized bed to perform vapor deposition on the porous carbon, the silane gas flow rate was 35 L / min, and the deposition time was 6 hours, to obtain a porous carbon sample with deposited silicon (No. C10-SC).

[0224] After the silicon deposition was completed, a gaseous carbon source, acetylene, was introduced to perform carbon coating on the porous carbon sample with deposited silicon (No. C10-SC) by vapor deposition, to obtain a porous carbon sample with deposited silicon coated with a shell layer (No. C10-SC-BF).

[0225] Table 1

[0226]

[0227] Table 2

[0228]

[0229] Table 3

[0230]

[0231] Performance tests

[0232] Half-cell test

[0233] The porous carbon sample of deposited silicon or the porous carbon sample of deposited silicon coated with a shell layer prepared using the embodiments of the present application was used to prepare negative electrode sheet assembly button half-cells, which were tested as follows:

[0234] Preparation of negative electrode sheet: The prepared porous carbon sample of deposited silicon or the porous carbon sample of deposited silicon coated with a shell layer, conductive additive carbon black, conductive additive carbon black, binder (carboxymethyl cellulose sodium and butadiene rubber with a mass ratio of 1:1), were weighed according to a mass ratio of 95:2:3, and slurry preparation was carried out in a beater at room temperature. The prepared slurry was uniformly coated on a copper foil, which was dried in a blast drying oven at a temperature of 50°C for 2 hours, then cut into a sheet with a diameter of 8 mm, and vacuum dried at a temperature of 100°C for 10 hours in a vacuum drying oven. The dried sheet was immediately transferred into a glove box for use in assembling a battery.

[0235] Assembly of battery: The assembly of the battery was simulated and carried out in a glove box containing high-purity Ar atmosphere. A metal lithium was used as a counter electrode, and a solution of 1 mol LiPF6 in ethylene carbonate (EC) / dimethyl carbonate (DMC) (volume ratio v:v = 1:1) was used as an electrolyte to assemble a battery.

[0236] Half-cell test conditions: The constant current charge and discharge mode test was carried out using a charge and discharge instrument, the discharge cut-off voltage was 0.005 V, the charge cut-off voltage was 1.5 V, the charge and discharge test was carried out at a current density of C / 10, and the relevant test data (charge specific capacity, first coulombic efficiency) obtained are shown in Tables 4 and 5.

[0237] Half-cell test conditions: room temperature 0.1C / 0.1C. The delithiation GITT was calculated according to the following formula: Figures 7-9 The delithiation GITT comparison results of the half-cells assembled by the negative electrode sheets prepared from the relevant samples are shown, and the peak values of the test curves are shown in Table 5.

[0238]

[0239] wherein, D - diffusion coefficient; τ - relaxation time; R s— Active particle radius; ΔE s — Pulse-induced voltage change; ΔE t — Voltage change during constant current charge (discharge).

[0240] Full cell testing

[0241] The porous carbon sample of deposited silicon or the porous carbon sample of deposited silicon coated with a shell layer prepared using the embodiments of the present application was used to prepare negative electrode sheets for assembling batteries, which were tested as follows:

[0242] Preparation of positive electrode sheets: formulation parameters: 96.2wt% LiNi 0.6 Co 0.2 Mn 0.2 O2(622 positive material) + 1.1wt% PVDF (binder) + 2.7wt% Super P (conductive agent); batching parameters: dry mixing, high-speed dispersion (solid content 72%), viscosity adjustment to a viscosity of about 5000 cP for coating; coating parameters: single-sided area density 21 mg / cm 2 After slitting into 15 cm wide strips, the positive electrode sheets with a size of 73 mm x 44 mm were obtained by die cutting.

[0243] Preparation of negative electrode sheets: formulation parameters: 95.0wt% negative electrode material (the prepared porous carbon sample of deposited silicon or the porous carbon sample of deposited silicon coated with a shell layer) + 3.5wt% binder (mass ratio 1:1 of sodium carboxymethyl cellulose and butadiene rubber) + 1.5wt% conductive agent carbon black; batching parameters: dry mixing and kneading (solid content 65%), high-speed dispersion (solid content 45%), viscosity adjustment to a viscosity of about 5000 for coating; coating parameters: single-sided area density 9 mg / cm 2 After slitting into 15 cm wide strips, the negative electrode sheets with a size of 75 mm x 46 mm were obtained by die cutting.

[0244] Assembled battery: The process is as follows: laminating: 9 pieces of negative electrode and 8 pieces of positive electrode are laminated in Z shape; welding the tabs: the positive and negative tabs are welded (positive: aluminum; negative: nickel); hot and cold pressing: hot pressing at 80°C for 1 min, cold pressing at room temperature for 1 min; aluminum mold punching: the punching depth is 3 mm; top sealing, side sealing: the hot sealing temperature is 190°C, and the hot sealing time is 6 seconds; baking: at 95°C for 3 days, and nitrogen replacement is carried out during the period to ensure that the sample is in an inert atmosphere; water content test: about 1 g of positive electrode and negative electrode is heated to remove water at 120°C, so that the water content is less than 200 ppm; liquid injection: 1 mole of LiPF6 in ethylene carbonate (EC) / dimethyl carbonate (DMC) (volume ratio v:v = 1:1) forms a solution as an electrolyte, which is injected between the positive electrode and the negative electrode, and the injection coefficient calculated according to the first charge is 3.5; sealing: hot sealing temperature 190°C, hot sealing time 3 seconds, vacuum degree-90; soak for 2 days at 45°C to obtain an assembled battery sample.

[0245] Full battery test conditions: cycle conditions: room temperature (25°C), 1C / 1C; voltage range: 2.8-4.25V. Figure 10 The cycle curve of the soft-pack full battery assembled by the negative electrode tab prepared by the sample is shown. Figure 11 The cycle curve of the soft-pack full battery assembled by the negative electrode tab with different tab compaction densities prepared by C1-SC-BF is shown. Figure 12 The cycle curve of the soft-pack full battery assembled by the negative electrode tab with different tab compaction densities prepared by sample A1-SC-BF is shown.

[0246] Full battery test conditions: room temperature (25°C) 1C charging, low temperature (-20°C) 0.2C discharging; voltage range:

[0247] 2.8-4.25V. Figures 13-15 The discharge capacity percentage of the full battery assembled by the negative electrode tab prepared by the related sample at -20°C is shown.

[0248] Full battery test conditions: room temperature (25°C) 1C charging, 0.2C discharging to 2.5V, measuring the discharge capacity, repeating three times to take the average value, and recording as the room temperature discharge capacity. After room temperature 1C charging, low temperature (-20°C) for 6-12h, 0.2C discharging to 2.5V, measuring the discharge capacity, and the ratio of this value to the room temperature discharge capacity is the discharge capacity retention rate. The discharge capacity retention rate of the full battery assembled by the negative electrode tab prepared by the related sample is shown in Table 5.

[0249] Table 4

[0250]

[0251] Table 5

[0252]

[0253]

[0254] As can be seen from Table 4-5, the battery samples prepared from the composite samples obtained from the porous carbon materials prepared from the coke-based precursor all have excellent specific charge capacity, first coulombic efficiency and lithium extraction rate, and all have good discharge capacity retention rate in low temperature environment.

[0255] According to the lithium extraction GITT results of Figures 7-9 , it can be seen that, compared to the porous carbon materials obtained from biomass or resin-based precursors, the battery samples prepared from the composite samples obtained from the porous carbon materials prepared from the coke-based precursor have higher lithium extraction rate.

[0256] The battery samples prepared from the composite samples obtained from the porous carbon materials prepared from the coke-based precursor have excellent cycle performance. Figure 10 As can be seen from the cycle curves shown, the capacity retention rate of the battery samples prepared from the composite samples of the present application is better.

[0257] From the cycle curves of the soft-pack full batteries under different electrode compactness shown in Figures 11-12 , it can be seen that, the battery samples prepared from the composite samples obtained from the porous carbon materials prepared from the coke-based precursor have basically no capacity retention rate degradation with the increase of electrode compactness, and can maintain excellent cycle performance. However, the battery samples prepared from the composite samples obtained from the biomass precursor have worse cycle performance with the increase of electrode compactness.

[0258] Figures 13-15 The discharge capacity percentage of different test samples in low temperature environment is shown. From the results of Figures 13-15 , it can be seen that, compared to the porous carbon materials obtained from biomass or resin-based precursors, the battery samples prepared from the composite samples obtained from the porous carbon materials prepared from the coke-based precursor have higher discharge capacity percentage in low temperature, i.e., the battery samples prepared from the composite materials of the present application have better tolerance to low temperature environment.

[0259] It will be apparent to those skilled in the art that numerous modifications and variations can be made to the present application without departing from the spirit and scope of the application. The specific embodiments described herein are offered by way of example only, and are not meant to be limiting in any way. The true scope and spirit of the application are set forth in the appended claims, and the specification and examples are merely illustrative.

Claims

1. A porous carbon for use as a negative electrode material of a lithium ion secondary battery, characterized by, The ratio (I D / I G ) of the intensity (I D ) of the D peak and the intensity (I G ) of the G peak in the Raman spectrum of the porous carbon is 0.10-1.

50. the porous carbon having a diffraction angle 2Θ of a (002) plane in an X-ray diffraction pattern of 24.00° to 26.53°; The specific surface area BET of the porous carbon is comprised between 600 and 3000 m2 / g. 2 / g; wherein, The porous carbon is prepared by alkali activation of coke or coal-based materials. In the Raman spectrum of the coke or coal-based materials, the D peak intensity (I) is shown. D ) and G peak intensity (I G The proportion of (I) D / I G The value is 0.30-0.48; and the porous carbon is used as a porous matrix for depositing silicon.

2. The porous carbon according to claim 1, characterized by, The ratio (I D / I G ) of the intensity (I D ) of the D peak and the intensity (I G ) of the G peak in the Raman spectrum of the porous carbon is 0.10-1.

10.

3. The porous carbon according to claim 1, characterized by, The ratio (I D / I G ) of the intensity of the D peak (I D ) to the intensity of the G peak (I G ) in the Raman spectrum of the porous carbon is 0.20-0.

80.

4. The porous carbon according to claim 1, characterized by, The ratio (I D / I G ) of the intensity (I D ) of the D peak to the intensity (I G ) of the G peak in the Raman spectrum of the porous carbon is 0.20-0.

70. D ) with the intensity (I G ) of the G peak is 0.20-0.

70.

5. The porous carbon according to claim 1, characterized by, The specific surface area BET of the porous carbon is comprised between 800 and 2800 m2 / g. 2 / g.

6. The porous carbon according to claim 1, characterized by, The specific surface area BET of the porous carbon is comprised between 900 and 2750 m2 / g. 2 / g.

7. The porous carbon according to claim 1, characterized by, The porous carbon has a pore volume of 0.50 cm 3 / g or more.

8. The porous carbon according to claim 1, characterized by, The porous carbon has a pore volume of 0.60 cm 3 / g or more.

9. The porous carbon according to claim 1, characterized by, the porous carbon having a diffraction angle 2Θ of a (002) plane in an X-ray diffraction pattern of 24.15° to 26.50°.

10. The porous carbon according to claim 1, characterized by, the porous carbon having a powder resistivity of 900 mΩ-cm or less.

11. The porous carbon according to claim 1, characterized by, the porous carbon having a powder resistivity of 800 mΩ-cm or less.

12. The porous carbon of claim 1, wherein, the porous carbon having one or more of the following characteristics: The tap density of the porous carbon is 0.2-1.4 g / cm 3 ; the porous carbon having a minimum particle size Dmin of 0.1 to 1.0 μm; the porous carbon having a D10 particle size of 2.0 to 5.0 μm; the porous carbon having a D50 particle size of 5.0 to 15.0 μm; the porous carbon having a D90 particle size of 10.0 to 30.0 μm; the porous carbon having a D100 particle size of 20.0 to 50.0 μm.

13. The porous carbon according to claim 1, characterized by, the base including a hydroxide of an alkali metal or an alkaline earth metal.

14. The porous carbon according to claim 1, characterized by, the base including potassium hydroxide, sodium hydroxide, or a combination thereof.

15. The porous carbon according to claim 1, characterized by, the cokes being petroleum cokes.

16. The porous carbon according to claim 1, characterized by, the cokes or coal-based material having a diffraction angle 2Θ of a (002) plane in an X-ray diffraction pattern of 25.00° to 26.50°.

17. The porous carbon according to claim 1, characterized by, the cokes or coal-based material having a diffraction angle 2Θ of a (002) plane in an X-ray diffraction pattern of 25.25° to 26.25°.

18. The porous carbon according to claim 1, characterized by, the cokes or coal-based material having a diffraction angle 2Θ of a (002) plane in an X-ray diffraction pattern of 25.40° to 26.00°.

19. The porous carbon according to claim 8, characterized by, The ratio (I D / I G ) of the D peak intensity (I D ) to the G peak intensity (I G ) in the Raman spectrum of the coking or coal-based material is 0.35-0.

48.

20. The porous carbon according to claim 1, characterized by, the cokes or coal-based material having a powder resistivity of 5.0 mΩ-cm or less.

21. A method for producing the porous carbon according to any one of claims 1 to 20, comprising the steps of: providing a porous carbon precursor; subjecting the porous carbon precursor to alkali activation to produce the porous carbon.

22. A composite material for lithium ion secondary batteries, the composite material comprising: the porous carbon of any one of claims 1-21, and nanosilicon dispersed in the porous carbon.

23. The composite material of claim 22, wherein: the nanosilicon dispersed in the porous carbon is hydrogen-containing nanosilicon. The ratio (I D / I G ) of the intensity of the D peak (I D ) to the intensity of the G peak (I G ) in the Raman spectrum of the composite material is 0.20-1.

50.

24. The composite material of claim 22, wherein: The ratio (I D / I G ) of the intensity of the D peak (I D ) to the intensity of the G peak (I G ) in the Raman spectrum of the composite material is 0.20-1.

00.

26. The composite material of claim 22, wherein, the nanosilicon dispersed in the porous carbon is hydrogen-containing nanosilicon.

25. The composite material of claim 22, wherein: the composite material has one or more of the following characteristics: the nanosilicon has a particle size ranging from 0.1 nm to 60 nm; The specific surface area BET of the composite is between 30 and 300 m 2 / g; The composite has a pore volume of 0.2 cm 3 below 0.1 g / cm2. the weight ratio of the nanosilicon to the composite material is from 0.3 to 0.7; the powder resistivity of the composite material is 1500 Ω-cm or less; 27. The composite material of claim 22, wherein:

28. The composite material of claim 22, wherein, the nanosilicon has a particle size ranging from 0.1 nm to 20 nm; and / or the weight ratio of the nanosilicon to the composite material is from 0.5 to 0.

7. the nanosilicon has a particle size ranging from 1 nm to 5 nm.

29. The composite material of claim 22, wherein: the composite material further comprises a shell layer coated on the outer surface of the porous carbon.

30. The composite material of claim 29, wherein: the shell layer comprises amorphous carbon, graphene, carbon nanotube, conductive polymer, titanium carbide, aluminum oxide, aluminum nitride, silicon carbide, silicon nitride, silicon oxide, silicon oxynitride, or a combination thereof.

31. The composite material of claim 29, wherein: the carbon content of the composite material is from 30 wt% to 70 wt% based on the total weight of the composite material; the hydrogen content of the composite material is from 0 wt% to 10 wt% based on the total weight of the composite material; the oxygen content of the composite material is from 0 wt% to 3 wt% based on the total weight of the composite material.

32. The composite material of claim 29, wherein:

33. The composite material of claim 29, wherein, the carbon content of the composite material is from 30 wt% to 50 wt% based on the total weight of the composite material; The tap density of the composite material is 0.5-2 g / cm 3 ; the hydrogen content of the composite material is from 0.3 wt% to 5 wt% based on the total weight of the composite material. The specific surface area BET of the composite is 10 m 2 / g or less; The composite material has a pore volume of 0.1 cm 3 below. the composite material has one or more of the following characteristics: the powder resistivity of the composite material is 100 Ω-cm or less; 34. The composite material of claim 29, wherein: the electrochemical charge curve of a half-cell prepared from the composite material has a plateau at 0.4 V to 0.5 V; and / or the DQ / DV curve of a half-cell prepared from the composite material has a characteristic peak at 0.4 V to 0.5 V.

35. A method of preparing the composite material of any one of claims 22-34, the method comprising the steps of: providing a porous carbon; depositing silicon in the porous carbon to form nanosilicon dispersed in the porous carbon; optionally, coating the outer surface of the porous carbon having the nanosilicon dispersed therein to form a shell layer.

36. A negative electrode sheet, the negative electrode sheet comprising: the composite material of any one of claims 22-34.

37. A lithium-ion secondary battery, characterized by comprising: the negative electrode sheet according to claim 36.

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