Porous carbon and preparation method thereof, silicon carbon material, electrode and battery

Abstract

The invention discloses porous carbon and a preparation method thereof, a silicon carbon material, an electrode and a battery, and relates to the technical field of new energy. The porous carbon comprises resin-derived carbon, strip-shaped dopant-derived carbon and granular dopant-derived carbon. According to the porous carbon provided by the invention, by optimizing the compactness, crystallinity and crosslinking degree of a carbon skeleton, a porous carbon material with mechanical strength, toughness and structural stability far higher than those of a single component is obtained while proper porosity is maintained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy, in particular to a porous carbon, a preparation method thereof, a silicon-carbon material, an electrode and a battery. BACKGROUND

[0002] The porous carbon is a kind of porous material composed of carbon elements and containing a large number of hole structures inside. The porous carbon is often combined with silicon particles to form a silicon-carbon material to be used as a material of a battery. The pore structure of the porous carbon can effectively relieve the volume expansion of silicon after lithium intercalation, provide a "physical constraint space" for the silicon particles, and the carbon material has good electrical conductivity, which can ensure the electrical conductivity of the battery.

[0003] In the related art, although the porous carbon can buffer the volume expansion of silicon through the pores, the porous carbon itself has high porosity, and the carbon skeleton is usually loose and has high brittleness. If the strength of the porous carbon itself is insufficient, the carbon skeleton will be continuously subjected to "fatigue stress" due to the repeated expansion-shrinkage of silicon in the long-term charge-discharge cycle of the battery, resulting in the fracture of the carbon skeleton and the collapse of the pores, and further leading to the failure of the electrode.

[0004] Therefore, the structural strength of the porous carbon material still needs to be further improved. SUMMARY

[0005] Therefore, the present application provides a porous carbon, a preparation method thereof, a silicon-carbon material, an electrode and a battery.

[0006] In the embodiments of the present application, a porous carbon includes resin-derived carbon, long-strip dopant-derived carbon and granular dopant-derived carbon.

[0007] Optionally, in some embodiments of the present application, the average length of the long-strip dopant-derived carbon is 0.08 μm to 100 μm; The average particle size of the granular dopant-derived carbon is 0.8 nm to 1000 nm; The average particle size of the granular dopant-derived carbon is less than or equal to the average length of the long-strip dopant-derived carbon.

[0008] Optionally, in some embodiments of the present application, the porous carbon has pores with an average particle size of 4 nm to 12 nm; The average particle size of the porous carbon is 1 μm to 100 μm; In the porous carbon, the mass ratio of the resin-derived carbon, the long-strip dopant-derived carbon and the granular dopant-derived carbon is 100: (0.1-5): (10-40).

[0009] Correspondingly, the present application also provides a preparation method of the porous carbon, which includes the following steps: The mixed slurry comprises resin, long strip dopant, granular dopant and solvent; The dopant is sequentially subjected to solidification, carbonization and activation treatment to obtain porous carbon.

[0010] Optionally, in some embodiments of the present application, the average length of the long strip dopant is 0.1 μm to 100 μm; The average particle size of the granular dopant is 1 nm to 1000 nm; The average particle size of the granular dopant is less than or equal to the average length of the long strip dopant; The resin is selected from one or more of phenolic resin, epoxy resin, urea-formaldehyde resin, polyurethane resin, furfural resin; The long strip dopant is selected from one or more of carbon nanotube, cellulose, lignin, carbon fiber, aramid fiber, glass fiber; The granular dopant is selected from one or more of carbon black, graphite particle, ordered mesoporous carbon.

[0011] Optionally, in some embodiments of the present application, the solvent comprises water; In the mixed slurry, the mass fraction of the resin is 30% to 60%; The mixed slurry further comprises a dispersing aid; the dispersing aid is selected from hydrogen peroxide; the volume ratio of the solvent to the dispersing aid is 100: (0.01 to 10); In the mixed slurry, the mass ratio of the resin, the long strip dopant and the granular dopant is 100: (0.1 to 5): (10 to 40).

[0012] Optionally, in some embodiments of the present application, the solidification comprises gradient solidification, which comprises: heating the mixed slurry to a first temperature, maintaining for a first time period; heating to a second temperature again, maintaining for a second time period; heating to a third temperature again, maintaining for a third time period and then first cooling; wherein, The first temperature is 80℃ to 90℃, and the first time period is 12h to 24h; The second temperature is 95℃ to 100℃, and the second time period is 24h to 48h; The third temperature is 105℃ to 110℃, and the third time period is 12h to 24h; The first cooling comprises cooling to 20℃ to 40℃.

[0013] Optionally, in some embodiments of the present application, the carbonization comprises gradient carbonization; after the solidification, the solidified particles are heated to a fourth temperature at a first heating rate, and kept for a fourth time period; then heated to a fifth temperature at a second heating rate, and kept for a fifth time period before second cooling; wherein, the first heating rate is 2-3℃ / min, the fourth temperature is 400-600℃, and the fourth time period is 1-2h; the second heating rate is 3-5℃ / min, the fifth temperature is 1000-1200℃, and the fifth time period is 1-2h; the second cooling comprises cooling to 20-40℃.

[0014] Optionally, in some embodiments of the present application, the activation comprises gradient activation; after the carbonization, the carbonized particles are heated to a sixth temperature at a third heating rate, and then heated to a seventh temperature at a fourth heating rate, and activated for a sixth time period before third cooling; wherein, the activation agent is selected from one or more of water vapor and carbon dioxide; the volume flow rate of the activation agent is 0.01-100L / min; the third heating rate is 5-10℃ / min, and the sixth temperature is 700-800℃; the fourth heating rate is 2-5℃ / min, the seventh temperature is 800-1200℃, and the sixth time period is 1-20h; the third cooling comprises cooling to 20-40℃.

[0015] Optionally, in some embodiments of the present application, after the solidification, before the carbonization, the method for preparing the porous carbon further comprises: performing first crushing treatment on the solidified mixed slurry to obtain solidified particles; the average particle size of the solidified particles is less than or equal to 2cm; after the activation, activated particles are obtained, and the method for preparing the porous carbon further comprises: performing second crushing treatment on the activated particles to obtain the porous carbon; the average particle size of the porous carbon is 1-100μm.

[0016] Correspondingly, the embodiments of the present application further provide a silicon-carbon material, which comprises silicon and the above-mentioned porous carbon, or the porous carbon prepared by the above-mentioned method for preparing the porous carbon.

[0017] Correspondingly, the embodiments of the present application further provide an electrode, the material of which comprises the above-mentioned silicon-carbon material.

[0018] Correspondingly, the application also provides a battery, which comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein the material of the negative electrode comprises the silicon-carbon material or the negative electrode comprises the electrode.

[0019] The porous carbon provided by the application comprises a plurality of different shapes of derived carbon, wherein the resin derived carbon forms a preliminary carbon skeleton structure as a porous carbon matrix, and the resin has a certain strength by cross-linking; the long strip-shaped dopant can alleviate the problem of "brittleness" of the resin derived carbon and significantly improve the toughness and tensile strength; and the granular dopant can improve the problems of "softness" and "porosity" of the resin derived carbon and improve the rigidity and hardness. In the porous carbon, the resin derived carbon, the long strip-shaped dopant derived carbon and the granular dopant derived carbon are mutually coordinated to form a complete structure of "concrete + steel + stone". Specifically, the resin is a liquid or a solid that can be melted and solidified in the precursor stage, can fully wrap and infiltrate the long strip-shaped dopant and the granular dopant, and is similar to "concrete". When the porous carbon is stressed to produce micro-cracks, the long strip-shaped dopant can be bridged at both ends of the crack to prevent crack propagation. The crack propagation needs to overcome a large amount of energy to pull the long strip-shaped dopant out of the "concrete", so the long strip-shaped dopant is similar to "steel" and can significantly improve the toughness of the porous carbon. The granular dopant is similar to "stone" and can be filled into the micro-defects or the gaps in the long strip-shaped dopant to effectively hinder the dislocation and movement of the internal structure of the porous carbon and improve the overall rigidity and strength.

[0020] The porous carbon provided by the application has mechanical strength, toughness and structural stability far exceeding that of a single component by optimizing the compactness, crystallinity and cross-linking degree of the carbon skeleton while maintaining appropriate porosity. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0022] Figure 1 It is a preparation method flow chart of a porous carbon provided by the application. DETAILED DESCRIPTION

[0023] With reference to the drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, any other embodiments obtained by a person of ordinary skill in the art without creative effort should fall within the scope of the present application. In addition, it should be understood that the specific implementation described herein is only used to illustrate and explain the present application, and is not used to limit the present application.

[0024] In the present application, the orientation words such as "upper" and "lower" generally refer to the upper and lower in the actual use or working state of the device, specifically the drawing surface direction in the drawings, and "inner" and "outer" refer to the contour of the device. In addition, in the description of the present application, the term "comprising" means "including but not limited to". The terms first, second, third, etc. are only used as labels and do not impose numerical requirements or establish an order.

[0025] In the present application, "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B, which means that there can be A alone, A and B together, and B alone. Wherein A and B can be singular or plural.

[0026] In the present application, "at least one" means one or more, and "multiple" means two or more. "One or more", "at least one of the following" or similar expressions mean any combination of these items, including any combination of single item or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0027] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is only for the convenience and brevity, and should not be understood as a hard limit on the scope of the present application; therefore, it should be considered that the described range has been specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated in the present application, it means that any cited number (fraction or integer) within the indicated range is included.

[0028] The technical solutions of the present application are as follows: In a first aspect, the embodiments of the present application provide a porous carbon, which comprises resin-derived carbon, long-strip dopant-derived carbon and granular dopant-derived carbon.

[0029] It should be noted that the resin-derived carbon refers to the product after carbonization of resin, the long-strip dopant-derived carbon refers to the product after carbonization of long-strip dopant, and the granular dopant-derived carbon refers to the product after carbonization of granular dopant.

[0030] It should also be noted that after carbonization, the resin, long-strip dopant and granular dopant remove organic matter and volatile matter. In other words, the long-strip dopant is still long-strip after carbonization, but the average length is reduced to a certain extent due to the removal of organic matter and volatile matter. Correspondingly, the granular dopant is still granular after carbonization, but the average particle size is reduced to a certain extent due to the removal of organic matter and volatile matter.

[0031] The porous carbon provided by the embodiments of the present application comprises a plurality of different shapes of derived carbon, wherein the resin-derived carbon serves as the matrix of the porous carbon to form a preliminary carbon skeleton structure, and the resin has a certain strength by cross-linking; the long-strip dopant serves as the core of cross-linking to alleviate the problem of "brittleness" of the resin-derived carbon and significantly improve the toughness and tensile strength; and the granular dopant improves the problems of "softness" and "porosity" of the resin-derived carbon and improves the rigidity and hardness. In the porous carbon, the resin-derived carbon, long-strip dopant-derived carbon and granular dopant-derived carbon cooperate with each other to form a complete structure of "concrete + steel bars + stones". Specifically, the resin is a liquid or a solid that can be melted and solidified in the precursor stage, which can fully wrap and infiltrate the long-strip dopant and the granular dopant, similar to "concrete". When the porous carbon is stressed to produce micro-cracks, the long-strip dopant can bridge the two ends of the crack to prevent the crack from expanding, and the crack expansion needs to overcome a large amount of energy to pull the long-strip dopant out of the "concrete", so the long-strip dopant is similar to "steel bars" and can significantly improve the toughness of the porous carbon. The granular dopant is similar to "stones" and can be filled into the micro-defects or the gaps in the long-strip dopant to effectively hinder the dislocation and movement of the internal structure of the porous carbon, share the pressure load and limit the shrinkage of the resin, and improve the overall rigidity and strength.

[0032] The porous carbon provided by the present application has mechanical strength, toughness and structural stability far exceeding that of a single component by optimizing the compactness, crystallinity and cross-linking degree of the carbon skeleton while maintaining appropriate porosity.

[0033] It can be understood that, when the raw materials are mixed, the resin, the long strip-shaped dopant and the granular dopant are cooperated with each other to form a structure of "concrete + steel + stone", and after carbonization, the resin-derived carbon, the long strip-shaped dopant-derived carbon and the granular dopant-derived carbon are cooperated with each other to form a corresponding structure of "concrete + steel + stone" due to the fact that the raw materials still maintain the original shape.

[0034] In some embodiments, the average length of the long strip-shaped dopant-derived carbon is 0.08 μm to 100 μm, for example, 0.08 μm, 0.1 μm, 1 μm, 10 μm, 20 μm, 50 μm, 80 μm, 100 μm or a range between any two of the above values. Within the range of the average length, the long strip-shaped dopant-derived carbon can effectively play the role of "steel" to improve the toughness of the porous carbon. It should be noted that, in the present application, the length of the long strip-shaped dopant-derived carbon is tested by a scanning electron microscope.

[0035] In some embodiments, the average particle size of the granular dopant-derived carbon is less than or equal to the average length of the long strip-shaped dopant-derived carbon. In this way, the granular dopant-derived carbon and the long strip-shaped dopant-derived carbon are cooperated with each other in structure to improve the strength of the porous carbon.

[0036] In some embodiments, the average particle size of the granular dopant-derived carbon is 0.8 nm to 1000 nm, for example, 0.8 nm, 1 nm, 10 nm, 100 nm, 500 nm, 800 nm, 1000 nm or a range between any two of the above values. Within the range of the average length, the granular dopant-derived carbon can effectively play the role of "stone" to improve the rigidity and hardness of the porous carbon. It should be noted that, in the present application, the particle size of the granular dopant-derived carbon is tested by a scanning electron microscope.

[0037] In some embodiments, the porous carbon has pores with an average particle size of 4 nm to 12 nm, for example, 4 nm, 6 nm, 8 nm, 10 nm, 12 nm or a range between any two of the above values. Within the range of the particle size, the porous carbon can improve the charge storage capacity and ion transmission efficiency, and also has good strength to effectively inhibit the volume expansion of silicon.

[0038] In some embodiments, the average particle size of the porous carbon is 1 μm to 100 μm, for example, 1 μm, 10 μm, 20 μm, 50 μm, 80 μm, 100 μm or a range between any two of the above values. Within the range of the particle size, it is beneficial for the application of the porous carbon to form a silicon-carbon material together with silicon.

[0039] In some embodiments, the mass ratio of the resin-derived carbon, the long-strip dopant-derived carbon and the granular dopant-derived carbon in the porous carbon is 100: (0.1-5): (10-40), for example, can be 100:0.1:40, 100:1:30, 100:2:25, 100:3:20, 100:4:15, 100:5:10 or a range between any two of the above ratios, etc. Within the range of the mass ratio, the resin-derived carbon, the long-strip dopant-derived carbon and the granular dopant-derived carbon can synergistically cooperate with each other to form a structure with high strength like "concrete + steel bars + stones", thereby improving the stability of the porous carbon.

[0040] In a second aspect, referring to Figure 1 The embodiments of the present application also provide a preparation method of the porous carbon, comprising the following steps: Step S11, providing a mixed slurry, wherein the mixed slurry comprises resin, long-strip dopant, granular dopant and solvent; Step S12, sequentially performing solidification, carbonization and activation treatment on the dopant to obtain the porous carbon.

[0041] In the step S11, It should be noted that the mixed slurry can be obtained by dissolving the resin in the solvent and then adding the long-strip dopant and the granular dopant. The long-strip dopant and the granular dopant can be directly added or can be dissolved and then added.

[0042] It should be further noted that the resin can be a liquid resin or a solid resin which is crushed and sieved before use.

[0043] In some embodiments, the resin in the resin-derived carbon is selected from one or more of phenolic resin, epoxy resin, urea-formaldehyde resin, polyurethane resin and furfural resin. Among them, the phenolic resin is a preferable raw material due to its low price, wide purchase channels and high carbonization yield.

[0044] In some embodiments, the average length of the long-strip dopant is 0.1-100 pm, for example, can be 0.1 pm, 1 pm, 10 pm, 20 pm, 50 pm, 80 pm, 100 pm or a range between any two of the above values, etc. Within the range of the average length, the long-strip dopant can effectively play the role of "steel bars" to improve the toughness of the porous carbon. It should be noted that in the present application, the length of the long-strip dopant is tested by a scanning electron microscope.

[0045] In some embodiments, the long-strip dopant is selected from one or more of carbon nanotubes, cellulose, lignin, carbon fiber and aramid fiber.

[0046] In some embodiments, the average particle size of the particulate dopant is less than or equal to the average length of the long strip dopant. In this way, the particulate dopant and the long strip dopant are structurally synergistic, improving the strength of the porous carbon.

[0047] In some embodiments, the average particle size of the particulate dopant is 1 nm to 1000 nm, such as 1 nm, 10 nm, 100 nm, 500 nm, 800 nm, 1000 nm, or a range between any two of the foregoing values. Within the range of the average length, the particulate dopant can effectively play the role of "stone", improving the rigidity and hardness of the porous carbon. It should be noted that in this application, the particle size of the particulate dopant is tested by scanning electron microscopy.

[0048] In some embodiments, the particulate dopant in the particulate dopant-derived carbon is selected from one or more of carbon black, graphite particles, and ordered mesoporous carbon. It should be noted that ordered mesoporous carbon is a mesoporous material with a regular pore structure, combining high specific surface area and adjustable pore size characteristics. The particulate dopant has high electrical conductivity, which can further improve the electrical conductivity of the porous carbon.

[0049] In some embodiments, the solvent includes water.

[0050] In some embodiments, the mass fraction of the resin in the mixed slurry is 30% to 60%, such as 30%, 40%, 50%, 60%, or a range between any two of the foregoing values. Within the range of the mass fraction, it is beneficial for the resin to be uniformly dispersed, and to ensure that the subsequent curing and solvent removal time is appropriate.

[0051] In some embodiments, the mixed slurry further includes a dispersing aid. Further, the dispersing aid is selected from hydrogen peroxide.

[0052] In some embodiments, the volume ratio of the solvent to the dispersing aid is 100:(0.01-10), such as 100:0.01, 100:0.1, 100:1, 100:2, 100:2, 100:8, 100:10, or a range between any two of the foregoing values. Within the range of the volume ratio, it is beneficial for the dispersing aid to further promote the dispersion of the resin.

[0053] In some embodiments, the mass ratio of the resin, the long strip dopant and the granular dopant in the mixed slurry is 100: (0.1-5): (10-40), for example, it can be 100:0.1:40, 100:1:30, 100:2:25, 100:3:20, 100:4:15, 100:5:10 or a range between any two of the above ratios, etc. Within the range of the mass ratio, the resin, the long strip dopant and the granular dopant are beneficial to synergize with each other to form a structure with high strength of "concrete + steel + stone".

[0054] In the step S12: It should be noted that the curing is based on the "thermosetting" nature of the resin. After mixing with the long strip dopant and the granular dopant, high-temperature curing makes the resin form a three-dimensional cross-linked structure that is "insoluble and infusible", and then broken into a form that meets the subsequent process requirements. The carbonization process is a process of orderly arrangement of carbon atoms mainly by removing water and non-carbon elements. The activation treatment is a process of making pores with appropriate pore size.

[0055] In some embodiments, the curing includes gradient curing.

[0056] Further, the gradient curing includes: heating the mixed slurry to a first temperature, and keeping the temperature for a first time period; then heating to a second temperature, and keeping the temperature for a second time period; then heating to a third temperature, and keeping the temperature for a third time period before first cooling.

[0057] In some embodiments, the first temperature is 80-90℃, for example, it can be 80℃, 82℃, 85℃, 88℃, 90℃ or a range between any two of the above values, etc.; the first time period is 12-24h, for example, it can be 12h, 15h, 18h, 20h, 24h or a range between any two of the above values, etc.

[0058] The second temperature is 95-100℃, for example, it can be 95℃, 96℃, 97℃, 98℃, 99℃, 100℃ or a range between any two of the above values, etc.; the second time period is 24-48h, for example, it can be 24h, 28h, 30h, 35h, 40h, 45h, 48h or a range between any two of the above values, etc.

[0059] The third temperature is 105-110℃, for example, it can be 105℃, 106℃, 107℃, 108℃, 100℃, 100℃ or a range between any two of the above values, etc.; the third time period is 12-24h, for example, it can be 12h, 15h, 18h, 20h, 24h or a range between any two of the above values, etc.

[0060] The first temperature decrease includes decreasing to room temperature, and specifically, can decrease to 20-40℃, for example, 20℃, 25℃, 30℃, 35℃, 40℃ or a range between any two of the above values.

[0061] Thus, under the above gradient curing conditions, most of the solvent can be effectively removed, and the resin molecular chain can be converted from a linear, flowable low molecular weight state to a three-dimensional network, insoluble and infusible high molecular crosslinked structure through chemical reaction; and the segmented curing can avoid the foaming and expansion of the resin caused by rapid heating, and reduce the residual solvent and monomers in the resin.

[0062] In some embodiments, the curing can include pouring the mixed slurry into a tray or a mold, and curing in a high-temperature oven or oven room. After the curing, the cured mixed slurry is subjected to a first crushing treatment to obtain cured particles. The crushing can use conventional tools and methods known in the art, such as hammer crushing, cutter crushing or universal crushing.

[0063] Further, in order to meet the requirement of uniform heating, the average particle size of the cured particles is less than or equal to 2 cm.

[0064] In some embodiments, the carbonization includes gradient carbonization.

[0065] Further, the gradient carbonization includes: heating the cured particles to a fourth temperature at a first heating rate, and holding for a fourth time period; then heating to a fifth temperature at a second heating rate, and holding for a fifth time period before second temperature decrease.

[0066] In some embodiments, the first heating rate is 2-3℃ / min, for example, 2℃ / min, 2.2℃ / min, 2.5℃ / min, 2.8℃ / min, 3℃ / min or a range between any two of the above values; the fourth temperature is 400-600℃, for example, 400℃, 450℃, 500℃, 550℃, 600℃ or a range between any two of the above values; and the fourth time period is 1-2h, for example, 1h, 1.2h, 1.5h, 1.8h, 2h or a range between any two of the above values.

[0067] The second temperature increasing rate is 3-5°C / min, for example, 3°C / min, 3.5°C / min, 4°C / min, 4.5°C / min, 5°C / min, or a range between any two of the above values, etc. The fifth temperature is 1000-1200°C, for example, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, or a range between any two of the above values, etc. The fifth time period is 1-2h, for example, 1h, 1.2h, 1.5h, 1.8h, 2h, or a range between any two of the above values, etc.

[0068] The second temperature decreasing includes decreasing to room temperature, specifically, 20-40°C, for example, 20°C, 25°C, 30°C, 35°C, 40°C, or a range between any two of the above values, etc. The second temperature decreasing can be air cooling, i.e., using air as medium for cooling.

[0069] In this way, under the above gradient carbonization conditions, the raw materials are carbonized to prepare the derived carbon. It can be understood that the resin is carbonized to obtain the resin derived carbon, the long strip dopant is carbonized to obtain the long strip dopant derived carbon, and the granular dopant is carbonized to obtain the granular dopant derived carbon. The first temperature increasing rate is slow to remove as much moisture and volatile matter as possible. Slow temperature increasing is beneficial for small molecules to separate from macromolecular chains, and the second temperature increasing rate is fast to shorten the carbonization time.

[0070] In some embodiments, the carbonization can be performed in a rotary kiln, and the carbonization is performed in an inert atmosphere.

[0071] In some embodiments, the activation includes gradient activation.

[0072] Further, after the carbonization, carbonized particles are obtained, and the gradient activation includes: increasing the temperature of the carbonized particles to a sixth temperature at a third temperature increasing rate, increasing the temperature to a seventh temperature at a fourth temperature increasing rate, introducing an activation agent, and performing third temperature decreasing after a sixth time period.

[0073] In some embodiments, the activation agent is selected from one or more of water vapor and carbon dioxide.

[0074] In some embodiments, the volume flow rate of the activation agent is 0.01-100L / min, for example, 0.01L / min, 0.1L / min, 1L / min, 10L / min, 50L / min, 100L / min, or a range between any two of the above values, etc.

[0075] In some embodiments, the third temperature increasing rate is 5-10℃ / min, for example, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min or a range between any two of the above values; and the sixth temperature is 700-800℃, for example, 700℃, 720℃, 750℃, 780℃, 800℃ or a range between any two of the above values.

[0076] The fourth temperature increasing rate is 2-5℃ / min, for example, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min or a range between any two of the above values; the seventh temperature is 800-1200℃, for example, 800℃, 900℃, 1000℃, 1100℃, 1200℃ or a range between any two of the above values; and the sixth time period is 1-20h, for example, 1h, 5h, 10h, 15h, 20h or a range between any two of the above values.

[0077] The third temperature decreasing includes decreasing to room temperature, specifically, 20-40℃, for example, 20℃, 25℃, 30℃, 35℃, 40℃ or a range between any two of the above values. The third temperature decreasing can be air cooling.

[0078] In this way, under the above gradient activation conditions, the carbonized particles are activated to form pores, and the porous carbon with suitable pore size is prepared. It should be noted that the activation etching pore formation basically occurs above 700℃, and it is difficult to reach the required entropy value at too low temperature, so the temperature can be increased rapidly in the early stage, and the temperature increasing rate is decreased in the later stage to concentrate the pore size in the activation temperature range. Too large temperature change will increase the extreme value of the pore size, which is not conducive to the stability of the porous carbon.

[0079] In some embodiments, the activation can be performed in a rotary kiln, and the activation is performed in an inert atmosphere.

[0080] In some embodiments, after the activation, the activated particles are obtained, and the method for preparing the porous carbon further comprises: performing a second crushing treatment on the activated particles to obtain the porous carbon. The crushing can be performed by using conventional tools and methods known in the art, such as jet mill, impact mill or ball mill.

[0081] Further, in order to facilitate the formation of a composite material of the porous carbon and silicon, the average particle size of the porous carbon is 1-100μm.

[0082] The resin, the long strip dopant and the granular dopant are used as the porous carbon raw material in the embodiment of the application, and the hard structure of "concrete + steel bars + stones" is formed, and then solidification, carbonization and activation are performed to prepare the porous carbon with high mechanical strength, high toughness and high structural stability.

[0083] In a third aspect, the embodiment of the application further provides a silicon-carbon material, which comprises silicon and the porous carbon described above, or the porous carbon prepared by the preparation method described above.

[0084] In a fourth aspect, the embodiment of the application further provides an electrode, the material of which comprises the silicon-carbon material described above, or the silicon-carbon material prepared by the preparation method described above.

[0085] In a fifth aspect, the embodiment of the application further provides a battery, which comprises a positive electrode, a negative electrode, a separator and an electrolyte, the material of the negative electrode comprises the silicon-carbon material described above, or the negative electrode comprises the electrode described above.

[0086] The positive electrode, the separator and the electrolyte can adopt conventional materials in the technical field.

[0087] The porous carbon provided by the embodiment of the application is applied to the negative electrode of the battery after being combined with silicon, and the high-strength porous carbon improves the comprehensive performance of the silicon-carbon negative electrode through "structure-performance" matching from the aspects of volume control (restricting the volume expansion of silicon), improving the conductivity, accelerating the ion transmission and stabilizing the SEI film. The pore structure of the porous carbon can effectively limit the expansion of silicon and help Li + diffusion, the high conductivity of the porous carbon itself compensates for the electronic transmission defects of silicon, the chemical stability of the porous carbon guarantees the long-term stability of the SEI film (the porous carbon can protect the SEI film by physically isolating and inhibiting the rupture of the SEI film), and the low cost and easy controllability make it a "bridge" for the industrial application of the silicon-carbon negative electrode from the laboratory. The strength of the porous carbon provided by the application is high, which can effectively limit the repeated expansion of silicon in the long-term charge and discharge cycle of the battery, and the strength of the porous carbon itself is sufficient, and the pore structure will not collapse due to the extrusion of the expansion of silicon, and can withstand the long-term stress impact caused by the expansion of silicon, thereby prolonging the service life of the battery.

[0088] The application will be specifically described below through specific embodiments. The following embodiments are only part of the embodiments of the application, and are not a limitation on the application.

[0089] Porous carbon embodiment 1 The porous carbon provided by the embodiment of the application is prepared by the following steps. Step S21, 10 kg of liquid phenolic resin is provided, 10 kg of deionized water and 1000 mL of hydrogen peroxide are added thereto, after stirring uniformly, 0.2 kg of carbon nanotubes (the average length of the carbon nanotubes is 20 μm) and 2 kg of carbon black powder (the average particle size of the carbon black is 50 nm) are added, and the stirring is continued for 12 h to make the dispersion uniform, to obtain a mixed slurry; Step S22, the mixed slurry is poured into a tray with a polytetrafluoroethylene film interlayer, the thickness of the mixed slurry is kept <3 cm, then the tray is placed in an oven for curing, first heated to 90℃ for 12 h, then heated to 100℃ at a rate of 2℃ / min for 24 h, finally heated to 110℃ at a rate of 2℃ / min for 24 h, then reduced to room temperature, the cured material is broken to below 2 cm using a universal breaker, to obtain cured particles; Step S23, 1 kg of the cured particles is placed in an industrial batch rotary furnace for carbonization, heated to 600℃ at a rate of 3℃ / min, then heated to 900℃ at a rate of 5℃ / min for 1 h, then reduced to room temperature, the whole process is kept in an inert atmosphere by passing N2, to obtain carbonized particles; Step S24, 200 g of the carbonized particles is placed in a tube furnace, N2 is passed at a rate of 0.2 L / min, after 30 min, heated to 800℃ at a rate of 8℃ / min, then heated to 900℃ at a rate of 5℃ / min, then activated by passing water vapor, the water vapor gas flow is set to 5 L / min, and the temperature is kept for 10 h, finally reduced to room temperature, to obtain activated particles, the activated particles are broken by using an air jet mill, to obtain porous carbon with an average particle size D50=10±2 μm.

[0090] Porous carbon example 2 This porous carbon example is basically the same as porous carbon example 1, the only difference is that in this porous carbon example, the carbon nanotubes in step S21 are replaced by cellulose (the average length is 60 μm).

[0091] Porous carbon example 3 This porous carbon example is basically the same as porous carbon example 1, the only difference is that in this porous carbon example, the carbon nanotubes in step S21 are replaced by lignin (the average length is 100 μm).

[0092] Porous carbon example 4 This porous carbon example is basically the same as porous carbon example 1, the only difference is that in this porous carbon example, the carbon nanotubes in step S21 are replaced by glass fiber (the average length is 10 μm).

[0093] Porous carbon example 5 This porous carbon example is basically the same as porous carbon example 1, the only difference is that in this porous carbon example, the carbon black in step S21 is replaced by graphite particles (the average particle size is 30 nm).

[0094] Porous carbon example 6 The porous carbon example is basically the same as the porous carbon example 1, the difference is that in the porous carbon example, the carbon black in step S21 is replaced by ordered mesoporous carbon (average particle size is 20 nm).

[0095] Porous carbon example 7 The porous carbon example is basically the same as the porous carbon example 1, the difference is that in the porous carbon example, the mass of carbon nanotubes in step S21 is 0.01 kg.

[0096] Porous carbon example 8 The porous carbon example is basically the same as the porous carbon example 1, the difference is that in the porous carbon example, the mass of carbon nanotubes in step S21 is 0.5 kg.

[0097] Porous carbon example 9 The porous carbon example is basically the same as the porous carbon example 1, the difference is that in the porous carbon example, the mass of carbon black powder in step S21 is 1 kg.

[0098] Porous carbon example 10 The porous carbon example is basically the same as the porous carbon example 1, the difference is that in the porous carbon example, the mass of carbon black powder in step S21 is 4 kg.

[0099] Porous carbon example 11 The porous carbon example is basically the same as the porous carbon example 1, the difference is that in the porous carbon example, the liquid phenolic resin in step S21 is replaced by solid epoxy resin, and the solid epoxy resin is first crushed and sieved into 30 mesh particles before use.

[0100] Porous carbon comparative example 1 The porous carbon comparative example is basically the same as the porous carbon example 1, the difference is that in the porous carbon comparative example, only the phenolic resin is solidified, carbonized and activated, and does not include carbon nanotubes and carbon black.

[0101] Porous carbon comparative example 2 The porous carbon comparative example is basically the same as the porous carbon example 1, the difference is that in the porous carbon comparative example, only the phenolic resin and carbon nanotubes are solidified, carbonized and activated, and do not include carbon black.

[0102] Porous carbon comparative example 3 The porous carbon comparative example is basically the same as the porous carbon example 1, the difference is that in the porous carbon comparative example, only the phenolic resin and carbon black are solidified, carbonized and activated, and do not include carbon nanotubes.

[0103] Porous carbon comparative example 4 The porous carbon of the present application is substantially the same as the porous carbon of Example 11, except that the porous carbon of the present application is only cured, carbonized and activated, without carbon nanotubes and carbon black.

[0104] The porous carbon of Examples 1-10 and Comparative Examples 1-3 was subjected to a crush test to obtain the crush strength of the porous carbon. The test results are shown in Table 1.

[0105] Crush test is a common characterization method. It can evaluate the compression resistance of the material under pressure, which helps to understand the crush strength of the material and the stress distribution during the fracture process. The crush strength refers to the maximum bearing stress value of the sample under quasi-static compression conditions when permanent deformation or structural collapse occurs. The test method of the crush test is as follows: disperse the porous carbon sample into ethanol, drop onto a glass slide, position a single particle under an optical microscope, control the uniform speed of the pressure head, collect the force and displacement curve during the particle compression process, and record the force-displacement curve to find the "failure" point, i.e. the force at which the particle is crushed (fails).

[0106] Table 1

[0107] As can be seen from Table 1, the porous carbon of Examples 1-6 and Comparative Examples 1-3, the present application forms a hard structure of "concrete, steel bars and stones" by the cooperation of resin, long strip-shaped dopant and granular dopant, effectively improving the mechanical strength, toughness and structural stability of the porous carbon material; the various long strip-shaped dopants and various granular dopants provided by the present application can cooperate with each other to improve the strength of the porous carbon; As can be seen from the porous carbon of Examples 1, 7-10 and Comparative Example 1, within the dosage range of the resin, long strip-shaped dopant and granular dopant provided by the present application, the "concrete, steel bars and stones" can be effectively cooperated to build a stable "building structure", so that the porous carbon can resist large deformation and fracture, improve the overall stiffness and strength, and fix the porous structure, thereby improving the structural stability of the porous carbon; As can be seen from the porous carbon of Example 11 and Comparative Example 4, the composite material provided by the present application is suitable for various resins in various states, and the cooperation of the long strip-shaped dopant and the granular dopant can effectively improve the structural strength of the porous carbon.

[0108] Battery Example 1 The present battery example provides a battery, and the preparation method of the battery comprises the following steps: Step S31, using a fluidized bed to carry out a silane deposition experiment: 200 g of the porous carbon of the porous carbon example 1 was taken as a precursor and placed in a fluidized bed sample bin, after the bin was filled and sealed, 30 min of carrier gas N2 was introduced to exhaust the air in the bin, then it was heated to 600℃ at a rate of 3℃ / min, and then 12 L / min of silane gas (SiH4) was introduced for deposition for 1 h; in order to avoid oxidation of the exposed silane, after the silane deposition was completed, acetylene was introduced for surface coating, 18 L / min of 30% acetylene-N2 mixed gas was introduced for 6 h, and finally it was cooled to room temperature to obtain a silicon-carbon material; Step S32, the silicon-carbon material was mixed with conductive agent (SP), binder (CMC, sodium carboxymethyl cellulose), and binder (SBR, butadiene-styrene rubber) according to a ratio of 96:0.5:2.3:1.2, and was coated on a copper foil, with a compacted density of 1.60 g / cm 3 After vacuum drying, it was used as a negative electrode, lithium metal was used as a counter electrode, an electrolyte used a mixed slurry of ethylene carbonate (EC) and dimethyl carbonate (DMC) of IMLiPP6 in a mass ratio of 1:1, and a separator was a PE / PPPE composite membrane, to assemble a button cell.

[0109] Battery examples 2-11 Battery examples 2-11 were basically the same as battery example 1, except that in battery examples 2-11, the porous carbon of the porous carbon example 1 was replaced by the porous carbon of the porous carbon examples 2-11.

[0110] Battery comparative examples 1-4 Battery comparative examples 1-4 were basically the same as battery example 1, except that in battery comparative examples 1-4, the porous carbon of the porous carbon example 1 was replaced by the porous carbon of the porous carbon comparative examples 1-4.

[0111] The first coulombic efficiency and the battery life of the battery of battery examples 1-11 and battery comparative examples 1-4 were tested, and the test results are shown in Table 2.

[0112] The test method for the first coulombic efficiency was as follows: under the condition of 25±2℃, the voltage range was 0.005V-2V, and the first coulombic efficiency was tested at a charge-discharge rate of 0.05C.

[0113] The test method for the battery life was as follows: under the condition of 25±2℃, step S1, charging at a constant current of 1C to a charging cutoff voltage of 4.2V, and then charging at a constant voltage until the current was 0.05C, and standing for 10 min; step S2, discharging at a constant current of 1C to a discharge cutoff voltage of 3V, and recording the initial capacity as C0; then steps S1-S2, recording the discharge capacity C n of each cycle. After 100 cycles, the cycle capacity retention rate (C n / C0x100%). Generally, the capacity retention of more than 80% proves that the material is not affected or less affected by the silicon-carbon expansion, and the battery life is effectively guaranteed.

[0114] Table 2

[0115] As can be seen from Table 2, the porous carbon provided by the battery embodiments 1-6 and the battery comparative examples 1-3 has high strength, which can effectively limit the expansion of silicon, thereby increasing the cycle number of the battery and prolonging the service life of the battery; the long strip dopant and the granular dopant used in the application also have good electrical conductivity, which can further improve the electrical conductivity of the battery, thereby improving the first coulomb efficiency of the battery; As can be seen from the battery embodiments 9-10 and the battery comparative example 3, the appropriate amount of resin, long strip dopant and granular dopant provided by the application cooperate with each other to prepare the porous carbon with high strength, which can effectively share the repeated expansion-shrinkage of silicon in the long-term charge-discharge cycle of the battery, avoid the collapse of the pore channel, and withstand the long-term stress impact caused by the expansion of silicon, thereby effectively improving the stability of the battery; As can be seen from the battery embodiment 11 and the battery comparative example 3, various resins are suitable for carbonization to form porous carbon and form silicon-carbon materials with silicon as the negative electrode of the battery. The battery in the embodiment still has a high capacity retention rate after 100 cycles, while the capacity retention rate of the comparative example decreases, which indicates that the battery provided by the embodiment of the application has a long service life and better performance.

[0116] The above describes the technical solutions provided by the embodiments of the application in detail. The principles and implementation manners of the application are described by applying specific examples. The above description of the embodiments is only used to help understand the method of the application and its core idea; meanwhile, for those skilled in the art, the specific implementation manner and application range can be changed according to the idea of the application. In summary, the content of the specification should not be understood as a limitation of the application.

Claims

1. A porous carbon, characterized by, The porous carbon comprises resin-derived carbon, long-strip dopant-derived carbon and granular dopant-derived carbon. 2.The porous carbon of claim 1, wherein, The average length of the long-strip dopant-derived carbon is 0.08 μm to 100 μm. The average particle size of the granular dopant-derived carbon is 0.8 nm to 1000 nm. The average particle size of the granular dopant-derived carbon is less than or equal to the average length of the long-strip dopant-derived carbon. 3.The porous carbon of claim 1 or 2, wherein, The porous carbon has pores with an average particle size of 4 nm to 12 nm. The average particle size of the porous carbon is 1 μm to 100 μm. The mass ratio of the resin-derived carbon, the long-strip dopant-derived carbon and the granular dopant-derived carbon in the porous carbon is 100: (0.1-5): (10-40).

4. A method for producing a porous carbon, characterized by, The method comprises the following steps: Providing a mixed slurry comprising resin, long-strip dopant, granular dopant and solvent; Carrying out solidification, carbonization and activation treatment on the dopants in sequence to obtain the porous carbon. 5.The method of claim 4, wherein, The average length of the long-strip dopant is 0.1 μm to 100 μm. The average particle size of the granular dopant is 1 nm to 1000 nm. The average particle size of the granular dopant is less than or equal to the average length of the long-strip dopant. The resin is selected from one or more of phenol-formaldehyde resin, epoxy resin, urea-formaldehyde resin, polyurethane resin and furfural resin. The long-strip dopant is selected from one or more of carbon nanotube, cellulose, lignin, carbon fiber and aramid fiber. The granular dopant is selected from one or more of carbon black, graphite particle and ordered mesoporous carbon. 6.The method of claim 4, wherein, The solvent comprises water. The mass fraction of the resin in the mixed slurry is 30% to 60%. The mixed slurry further comprises a dispersing aid selected from hydrogen peroxide; the volume ratio of the solvent to the dispersing aid is 100: (0.01-10). The mass ratio of the resin, the long-strip dopant and the granular dopant in the mixed slurry is 100: (0.1-5): (10-40).

7. The production method according to claim 4, wherein The solidification comprises gradient solidification, which comprises: heating the mixed slurry to a first temperature, keeping the temperature for a first time period; heating to a second temperature again, keeping the temperature for a second time period; heating to a third temperature again, keeping the temperature for a third time period and then performing first temperature reduction; wherein, The first temperature is 80 ℃ to 90 ℃, and the first time period is 12 h to 24 h. The second temperature is 95 ℃ to 100 ℃, and the second time period is 24 h to 48 h. The third temperature is 105 ℃ to 110 ℃, and the third time period is 12 h to 24 h. The first temperature reduction comprises reducing the temperature to 20 ℃ to 40 ℃.

8. The production method according to claim 4, wherein The carbonization comprises gradient carbonization; after the solidification, solidified particles are obtained, the gradient carbonization comprises: heating the solidified particles to a fourth temperature at a first heating rate, keeping for a fourth time period; then heating to a fifth temperature at a second heating rate, keeping for a fifth time period, and then secondly cooling; wherein, The first heating rate is 2-3 ℃ / min, the fourth temperature is 400-600 ℃, and the fourth time period is 1-2 h; The second heating rate is 3-5 ℃ / min, the fifth temperature is 1000-1200 ℃, and the fifth time period is 1-2 h; The second cooling comprises cooling to 20-40 ℃.

9. The production method according to claim 4, wherein The activation comprises gradient activation; after the carbonization, carbonized particles are obtained, the gradient activation comprises: heating the carbonized particles to a sixth temperature at a third heating rate, then heating to a seventh temperature at a fourth heating rate, introducing an activation agent, keeping for a sixth time period, and then thirdly cooling; wherein, The activation agent is selected from one or more of water vapor and carbon dioxide; The volume flow rate of the activation agent is 0.01-100 L / min; The third heating rate is 5-10 ℃ / min, and the sixth temperature is 700-800 ℃; The fourth heating rate is 2-5 ℃ / min, the seventh temperature is 800-1200 ℃, and the sixth time period is 1-20 h; The third cooling comprises cooling to 20-40 ℃.

10. The preparation method of claim 4, wherein, After the solidification and before the carbonization, the preparation method of the porous carbon further comprises: performing first crushing treatment on the solidified mixed slurry to obtain solidified particles; the average particle size of the solidified particles is less than or equal to 2 cm; After the activation, activated particles are obtained, and the preparation method of the porous carbon further comprises: performing second crushing treatment on the activated particles to obtain the porous carbon; the average particle size of the porous carbon is 1-100 μm.

11. A silicon-carbon material, characterized in that, The silicon-carbon material comprises silicon and the porous carbon of any one of claims 1-3, or the porous carbon prepared by the preparation method of any one of claims 4-10.

12. An electrode characterized by The material of the electrode comprises the silicon-carbon material of claim 11.

13. A battery, characterized by The battery comprises a positive electrode, a negative electrode, a separator, and an electrolyte, the material of the negative electrode comprises the silicon-carbon material of claim 11, or the negative electrode comprises the electrode of claim 12.

Images