Carbon material, negative electrode material and battery

Abstract

The present application relates to a carbon material, a negative electrode material and a battery. The carbon material has pores, and the length-diameter ratio of particles of the carbon material is 3-15. The particles of the carbon material of the present application are of a rod-shaped structure, and the rod-shaped particles of the carbon material can be arranged and stacked together to reduce gaps among the carbon material particles and improve the compaction density of the carbon material, thereby improving the surface capacity density of a carbon material electrode sheet.

Description

Carbon materials, negative electrode materials and batteries

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on August 30, 2023, with application number 202311109379.5 and invention name “Carbon materials and preparation methods thereof, negative electrode materials, and batteries”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of negative electrode materials, and more specifically, to carbon materials, negative electrode materials and batteries. Background Art

[0003] Porous carbon negative electrode materials are one of the most critical materials for improving the cyclic expansion performance of lithium-ion batteries. The cavities or pore structures inside the commonly used porous carbon negative electrode materials are mostly mesoporous or macroporous structures. Such pore structures often lead to low efficiency of porous carbon negative electrode materials when compounded with active substances such as silicon, tin, lead, sulfur, etc., and are accompanied by safety hazards. In the process of compounding porous carbon negative electrode materials with active substances, it is difficult for the active substances to completely fill the macropores and mesopores in the porous carbon negative electrode materials, and it is difficult for the active substances to be evenly distributed in the pore structure of the porous carbon. On the one hand, this leads to limited improvement in the compaction density and energy density of the composite material. On the other hand, it leads to uneven distribution of expansion tension of the composite material during the cycle, thereby causing the composite material to split and pulverize, creating safety hazards. At the same time, there are many pore structures between the particles of porous carbon negative electrode materials. These pore structures will cause the mechanical properties of the material to deteriorate, and it will break under stress during compaction and the process of making pole pieces, reducing the coulombic efficiency of the material.

[0004] Therefore, how to reduce the large number of pore structures between the particles of porous carbon negative electrode materials, improve the mechanical properties and energy density of negative electrode materials, and reduce the breakage of particles during the electrode pressing process are problems that still need to be solved.

[0005] Application Contents

[0006] The present application provides a carbon material, a negative electrode material, and a battery. The carbon material particles of the present application have an average aspect ratio of 3 to 15, and the carbon material particles have a rod-like structure. The arrangement and stacking of the rod-like carbon material particles can reduce gaps between the carbon material particles, increase the compaction density of the carbon material, and thereby improve the areal capacity density and mechanical properties of the carbon material electrode.

[0007] In a first aspect, the present application provides a carbon material having pores, and the average aspect ratio of particles of the carbon material is 3-15.

[0008] In some embodiments, the average length of the carbon material particles is 0.3 μm to 5 μm.

[0009] In some embodiments, the average diameter of the carbon material particles is 0.1 μm to 3 μm.

[0010] In some embodiments, the total pore volume of the carbon material is 0.2 cm 3 / g~0.8cm 3 / g.

[0011] In some embodiments, the average pore diameter of the pores in the carbon material is 0.8 nm to 2.5 nm.

[0012] In some embodiments, the pores in the carbon material include micropores, and the volume of the micropores accounts for 80% to 95% of the total pore volume.

[0013] In some embodiments, the pores in the carbon material further include at least one of mesopores and macropores.

[0014] In some embodiments, the volume of the mesopores accounts for 5% to 15% of the total pore volume.

[0015] In some embodiments, the volume of the macropores accounts for 0% to 5% of the total pore volume.

[0016] In some embodiments, the battery assembled from the carbon material has a charge capacity of 250 mAh / g to 400 mAh / g.

[0017] In some embodiments, the coulombic efficiency of a battery assembled from the carbon material is 40% to 55%.

[0018] In some embodiments, the mass content of oxygen in the carbon material is 1% to 5.5%.

[0019] In a second aspect, the present application provides a negative electrode material, which includes the carbon material and an active substance as described in the first aspect, and at least a portion of the active substance is filled in the pores of the carbon material.

[0020] In a third aspect, the present application provides a negative electrode material, which includes a carbon material and an active substance. After removing the active substance, the negative electrode material has pores, and the average aspect ratio of the particles of the negative electrode material after removing the active substance is 3 to 15.

[0021] In some embodiments, the mass content of carbon in the negative electrode material is 70% to 98%;

[0022] In some embodiments, the active material includes silicon-based active particles.

[0023] In some embodiments, the active material includes silicon-based active particles, and the silicon-based active particles include at least one of amorphous silicon, crystalline silicon, silicon oxide, silicon alloy, and a composite of crystalline silicon and amorphous silicon.

[0024] In some embodiments, the active material includes silicon-based active particles, and the median particle size of the silicon-based active particles is 0.85 nm to 2.45 nm.

[0025] In some embodiments, the pore volume of the negative electrode material is 0.001 cm 3 / g~0.020cm 3 / g.

[0026] In a fourth aspect, the present application provides a battery, comprising the carbon material described in the first aspect or the negative electrode material described in the second or third aspect.

[0027] Compared with the prior art, the technical solution of this application has at least the following beneficial effects:

[0028] The carbon material provided in this application has an average aspect ratio of 3 to 15 in its particles, and the particles are rod-shaped. The arrangement and stacking of the rod-shaped particles can reduce the gaps between the particles, thereby reducing the pore structure in the carbon material after the particles are stacked, thereby improving the compaction density and mechanical properties of the carbon material, and thereby improving the surface capacity density and mechanical properties of the carbon material electrode. During the roll-pressing process for preparing the negative electrode electrode, this carbon material can reduce the probability of carbon material rupture caused by rolling and squeezing between particles, thereby improving the mechanical properties of the carbon material negative electrode electrode. By controlling the aspect ratio of the carbon material particles, this can provide a continuous axial electron transmission path and a shorter radial ion diffusion path, significantly improving the rate performance of batteries using this carbon material. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present application is further described below with reference to the accompanying drawings and examples.

[0030] FIG1 is a schematic diagram of the structure of the carbon material provided in an embodiment of the present application;

[0031] FIG2 is a flow chart of the preparation process of the carbon material provided in an embodiment of the present application;

[0032] FIG3 is a scanning electron microscope image of the carbon material provided in Example 1 of the present application;

[0033] FIG4 is a scanning electron microscope image of the carbon material provided in Example 2 of the present application;

[0034] FIG5 is a scanning electron microscope image of the carbon material provided in Comparative Example 1 of the present application;

[0035] FIG6 is a scanning electron microscope image of the carbon material provided in Comparative Example 2 of the present application;

[0036] FIG7 is a pore size distribution diagram of the carbon material provided in Example 1 of the present application;

[0037] FIG8 is a pore size distribution diagram of the carbon material provided in Example 2 of the present application;

[0038] FIG9 is a pore size distribution diagram of the carbon material provided in Comparative Example 1 of the present application;

[0039] FIG10 is a pore size distribution diagram of the carbon material provided in Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0040] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0041] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0042] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0043] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0044] In a first aspect, as shown in FIG1 , the present application provides a carbon material, wherein particles of the carbon material have a rod-like structure, the carbon material has pores, and the average aspect ratio of the particles of the carbon material is 3 to 15.

[0045] The carbon material provided in the present application has an average aspect ratio of 3 to 15 in the particles of the carbon material, and the particles of the carbon material have a rod-like structure. The arrangement and stacking of the particles of the rod-like carbon material can reduce the gaps between the particles of the carbon material, and can reduce the pore structure in the carbon material after the particles of the carbon material are stacked, thereby improving the compaction density and mechanical properties of the carbon material, and thus improving the surface capacity density and mechanical properties of the carbon material electrode. The carbon material can reduce the probability of carbon material rupture caused by rolling and squeezing between particles during the roll-pressing preparation process of the negative electrode, which is beneficial to improving the mechanical properties of the carbon material negative electrode; by controlling the aspect ratio of the particles of the carbon material, it is beneficial to provide a continuous axial electron transmission path and a shorter radial ion diffusion path, thereby greatly improving the rate performance of the battery using the carbon material. Axial refers to the length direction of the carbon material, and radial refers to the diameter direction of the carbon material.

[0046] Specifically, the average aspect ratio of the carbon material particles can be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15, etc., which is not limited here. Preferably, the average aspect ratio of the carbon material is 5-10.

[0047] In some embodiments, the average length of the carbon material particles is 0.3 μm to 5 μm, specifically 0.3 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm, etc., and of course other values ​​within the above range are also possible, and are not limited here. Preferably, the average length of the carbon material is 1 μm to 3 μm.

[0048] In some embodiments, the average diameter of the carbon material particles is 0.1 μm to 3 μm, specifically 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm or 3 μm, etc., and of course other values ​​within the above range are also possible, and are not limited here. Preferably, the average diameter of the carbon material is 0.3 μm to 0.5 μm.

[0049] In some embodiments, the total pore volume of the carbon material is 0.2 cm 3 / g~0.8cm 3 / g. The total pore volume of the carbon material can be specifically 0.2cm 3 / g, 0.3cm 3 / g, 0.4cm 3 / g, 0.5cm 3 / g, 0.6cm 3 / g, 0.7cm 3 / g or 0.8cm 3 / g, etc., which are not limited here. Preferably, the total pore volume of the carbon material is 0.5cm3 / g~0.8cm 3 / g.

[0050] In some embodiments, the specific surface area of ​​the carbon material is 500 m 2 / g~1600m 2 / g. The specific surface area of ​​the carbon material can be 500m 2 / g、600m 2 / g、700m 2 / g、800m 2 / g、900m 2 / g、1000m 2 / g、1100m 2 / g、1200m 2 / g、1300m 2 / g、1400m 2 / g、1500m 2 / g or 1600m 2 / g, etc., of course, it can also be other values ​​within the above range, which is not limited here. Preferably, the specific surface area of ​​the carbon material is 600m 2 / g~900m 2 / g.

[0051] In some embodiments, the average pore diameter of the pores in the carbon material is 0.8 nm to 2.5 nm, and specifically can be 0.8 nm, 0.9 nm, 1 nm, 1.1 nm, 1.3 nm, 1.5 nm, 1.6 nm, 1.8 nm, 2 nm, 2.3 nm, or 2.5 nm, etc. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the average pore diameter of the carbon material is 1 nm to 1.5 nm.

[0052] In some embodiments, the pores in the carbon material include micropores, and the pore volume of the micropores accounts for 80% to 95% of the total pore volume, specifically 80%, 81%, 83%, 85%, 87%, 90%, 91%, 92%, 93%, 94% or 95%, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0053] It can be understood that carbon materials have a large number of microporous structures. In the process of compounding with active materials, the chemical vapor infiltration advantages of micropores can be effectively utilized, which is conducive to the uniform and efficient distribution of active materials in the pores of carbon materials during the compounding process, and is conducive to the uniform dispersion of the expansion stress of the active materials, reducing the splitting and breakage of the negative electrode materials, and is conducive to the improvement of the compaction density and energy density of the negative electrode materials. Controlling the volume ratio of micropores in carbon materials within the above range improves the composite uniformity of carbon materials and active materials, so that the active materials can be evenly distributed in the pore structure of carbon materials during the compounding process, improving the uniformity of the distribution of expansion tension during the cycle of negative electrode materials, reducing the splitting and breakage of negative electrode materials, and reducing the safety risks of negative electrode materials; at the same time, the microporous structure of carbon materials can be filled as completely as possible by active materials, which is conducive to the improvement of the compaction density and energy density of negative electrode materials. Preferably, the volume ratio of the pore volume of micropores in carbon materials to the total pore volume is 90% to 95%.

[0054] In some embodiments, the pores in the carbon material further include mesopores, and the volume of the mesopores accounts for 5% to 15% of the total pore volume, specifically 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%, etc., and other values ​​within the above range are also possible, and are not limited here. Preferably, the volume of the mesopores in the carbon material accounts for 5% to 10% of the total pore volume.

[0055] In some embodiments, the pores in the carbon material further include macropores, and the volume of the macropores accounts for 0% to 5% of the total pore volume, specifically 0%, 0.5%, 1%, 1%, 3%, 4%, or 5%. Of course, other values ​​within the above ranges are also possible and are not limited here. Preferably, the volume of the macropores in the carbon material accounts for 0% to 1% of the total pore volume.

[0056] In some embodiments, the carbon material contains oxygen, and the mass content of oxygen in the carbon material is 1% to 5.5%, specifically 1%, 1.2%, 1.5%, 1.8%, 2%, 2.4%, 2.6%, 2.9%, 3%, 3.5%, 4%, 4.5%, 5%, 5.1%, 5.2%, 5.3% or 5.5%, etc., and of course other values ​​within the above range are also possible, which are not limited here. Controlling the mass content of oxygen in the carbon material within the above range is beneficial to improving the conductive properties of the carbon material. Preferably, the mass content of oxygen in the carbon material is 1% to 4.2%.

[0057] In some embodiments, the charge capacity of the carbon material is 250 mAh / g to 400 mAh / g, specifically 250 mAh / g, 260 mAh / g, 280 mAh / g, 300 mAh / g, 320 mAh / g, 330 mAh / g, 350 mAh / g, 360 mAh / g, 370 mAh / g, 380 mAh / g, 390 mAh / g or 400 mAh / g, etc., without limitation herein. Preferably, the charge capacity of the carbon material is 320 mAh / g to 390 mAh / g.

[0058] In some embodiments, the coulombic efficiency of the carbon material is 40% to 55%, specifically 40%, 43%, 45%, 48%, 50%, 51%, 52%, 53%, 54%, or 55%, etc., and other values ​​within the above range are also possible, and are not limited here. Preferably, the coulombic efficiency of the carbon material is 48% to 55%.

[0059] In a second aspect, the present application provides a negative electrode material, which includes the carbon material and an active substance described in the first aspect, and at least a portion of the active substance is filled in the pores of the carbon material.

[0060] In a third aspect, the present application provides a negative electrode material, which includes a carbon material and an active substance. After removing the active substance, the negative electrode material has pores, and the average aspect ratio of the particles of the negative electrode material after removing the active substance is 3 to 15.

[0061] The active material is removed by etching. For example, when the active material is silicon-based active particles, the negative electrode material is added to a 1M nitric acid solution and soaked for 4 hours. Then, a 20% mass fraction HF acid solution is dripped dropwise into the negative electrode material, which will produce yellow smoke. The dripping is repeated several times until no yellow smoke is produced in the solution. Finally, the residue is digested with a 1M nitric acid solution, and then washed and dried to obtain the negative electrode material after removing the active material.

[0062] In some embodiments, the average aspect ratio of the particles of the negative electrode material after removing the active material is 3 to 15, specifically 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0063] In some embodiments, the active material refers to a substance that can react with lithium to deintercalate and deintercalate lithium. Specifically, the active material includes at least one of Li, Na, K, Sn, Ge, Si, Fe, SiO, Mg, Ti, Zn, Al, P, and Cu. The active material can be a single metal.

[0064] In some embodiments, the active material can specifically be Si particles, Sn particles, Ge particles, and Al particles. In other embodiments, the active material can also be silicon-lithium alloy, silicon-magnesium alloy, etc. Of course, it should be noted that in some cases, the active material includes elemental particles and alloys.

[0065] In some embodiments, the mass content of carbon element in the negative electrode material is 70% to 98%, specifically 70%, 75%, 80%, 85%, 90%, 92%, 95%, 96%, 97% or 98%, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0066] In some embodiments, the active material includes silicon-based active particles.

[0067] In some embodiments, the silicon-based active particles include at least one of amorphous silicon, crystalline silicon, silicon oxide, silicon alloy, and a composite of crystalline silicon and amorphous silicon.

[0068] In some embodiments, the average particle size of the silicon-based active particles is 0.85 nm to 2.45 nm, specifically 0.85 nm, 0.9 nm, 0.95 nm, 1 nm, 1.2 nm, 1.5 nm, 1.8 nm, 2.0 nm, 2.1 nm, 2.2 nm, 2.3 nm, 2.4 nm or 2.45 nm, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0069] In some embodiments, the specific surface area of ​​the negative electrode material is 0.5 m 2 / g~5m 2 / g, specifically 0.5m 2 / g、1m 2 / g, 1.5m 2 / g, 2m 2 / g, 2.5m 2 / g、3m 2 / g, 3.5m 2 / g、4m 2 / g, 4.5m 2 / g or 5m 2 / g, etc., and of course, it can also be other values ​​within the above range, which is not limited here.

[0070] In some embodiments, the pore volume of the negative electrode material is 0.001 cm 3 / g~0.020cm 3 / g, specifically 0.001cm 3 / g, 0.005cm 3 / g, 0.01cm 3 / g, 0.015cm 3 / g or 0.02cm 3 / g, etc., and of course, it can also be other values ​​within the above range, which is not limited here.

[0071] In some embodiments, the compacted density of the negative electrode material is 0.90 g / cm 3 ~1.10g / cm 3 , specifically 0.9g / cm 3 , 0.92g / cm 3 , 0.95g / cm 3 , 0.98g / cm 3 , 1g / cm 3 or 1.1 g / cm 3 Of course, it can also be other values ​​within the above range, which is not limited here.

[0072] In a fourth aspect, the present application provides a method for preparing a carbon material, as shown in FIG2 , comprising the following steps:

[0073] Step S10, subjecting a mixed solution containing an inorganic zinc salt and a polymer monomer to an in-situ polymerization reaction and a coprecipitation reaction to obtain a complex containing a polymer and zinc hydroxide, wherein the concentration of the inorganic zinc salt is 0.045 mol / L to 0.400 mol / L;

[0074] Step S20, drying the composite to form a precursor comprising a polymer and zinc oxide;

[0075] In step S30 , the precursor is subjected to a stepwise temperature-raising heat treatment under an inert gas atmosphere to obtain a carbon material with a rod-like structure, wherein the average aspect ratio of the carbon material is 3-15.

[0076] The preparation method of the carbon material provided by the present application comprises the following steps: subjecting a mixed solution containing an inorganic zinc salt and a polymer monomer to an in-situ polymerization reaction; during the in-situ polymerization process, the inorganic zinc salt in the solution precipitates to form zinc hydroxide, and simultaneously the polymer monomer polymerizes to form a polymer, and the polymer and the zinc hydroxide are co-precipitated to form a composite comprising the polymer and zinc hydroxide through the co-precipitation; in addition, the aspect ratio of the carbon material is controlled by controlling the concentration of the inorganic zinc salt in the mixed solution, thereby controlling the carbon material to have a rod-like structure; the composite is dried, and during the drying process, the zinc hydroxide decomposes to form zinc oxide with a rod-like structure, and simultaneously the polymer particles are stacked and arranged using the zinc oxide as a template. The invention relates to a method for preparing a rod-shaped precursor comprising a polymer and zinc oxide; performing a step-by-step temperature heat treatment on the precursor under an inert gas atmosphere, wherein the structure of the rod-shaped precursor can be preliminarily solidified during the heat treatment process to reduce the situation where the rod-shaped structure is damaged due to excessive temperature increase; and then performing a carbonization treatment by heating the precursor. The polymer in the precursor is cracked during the high-temperature carbonization process to form a carbon material containing zinc oxide, and then the zinc oxide is reduced to a single zinc substance by part of the carbon in the carbon material; finally, the zinc is vaporized at a high temperature and released from the interior of the carbon material; the zinc vapor can act as a pore-forming agent to form uniform pores in the carbon material, and the pores extend from the interior of the carbon material to the surface of the carbon material, thereby forming a carbon material with a rod-shaped structure having pores.

[0077] The preparation method of the present application is described in detail below with reference to the examples:

[0078] Step S10: subjecting a mixed solution containing an inorganic zinc salt and a polymer monomer to an in-situ polymerization reaction to obtain a complex containing a polymer and zinc hydroxide, wherein the concentration of the inorganic zinc salt is 0.045 mol / L to 0.400 mol / L.

[0079] In step S10, the concentration of the inorganic zinc salt can specifically be 0.045mol / L, 0.048mol / L, 0.05mol / L, 0.10mol / L, 0.20mol / L, 0.24mol / L, 0.30mol / L, 0.35mol / L or 0.40mol / L etc., but is not limited to the numerical value enumerated, and other numerical values ​​in this numerical range are equally applicable. When the concentration of the inorganic zinc salt in the mixed solution is too high, the longitudinal growth of the zinc oxide of the rod-like structure begins to be suppressed by the shear force generated by stirring, the lateral growth of zinc oxide prevails, the aspect ratio decreases, and the particles begin to agglomerate, causing the rod-like structure to disappear, thereby being unable to form the carbon material of the rod-like structure. Controlling the concentration of the inorganic zinc salt in the mixed solution within the above-mentioned range is conducive to controlling the aspect ratio of the carbon material, and is conducive to the formation of the carbon material rod-like structure.

[0080] In some embodiments, the inorganic zinc salt includes at least one of zinc chloride, zinc nitrate, zinc acetate, zinc sulfate, zinc fluorosilicate, zinc fluoroborate, and zinc gluconate. It is understood that during the formation of the carbon material, the inorganic zinc salt can form zinc oxide with a rod-like structure, and the rod-like structure of zinc oxide facilitates the formation of a rod-like structure of the carbon material.

[0081] In some embodiments, the polymer monomers include a first monomer and a second monomer.

[0082] In some embodiments, the polymer monomer includes a first monomer including phenol and its derivatives, melamine and its derivatives, or benzoic acid and its derivatives.

[0083] In some embodiments, the polymer monomer includes a first monomer including at least one of phenol, resorcinol, catechol, hydroquinone, phloroglucinol, p-aminophenol, and dopamine.

[0084] In some embodiments, the polymer monomer includes a first monomer including at least one of melamine, benzoguanamine, trichloromelamine, and hexamethylene melamine.

[0085] In some embodiments, the polymer monomer includes a first monomer including at least one of benzoic acid, p-toluic acid, p-fluorobenzoic acid, and 3-chlorobenzoic acid.

[0086] In some embodiments, the polymer monomer includes a second monomer including at least one of formaldehyde, furfural, acetaldehyde, propionaldehyde, and butyraldehyde.

[0087] In some embodiments, the mixed solution further includes a surfactant, and the surfactant includes at least one of cetyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, sodium carboxymethyl cellulose, and polyvinyl pyrrolidone.

[0088] It can be understood that adding a surfactant to the mixed solution can enhance the adsorption of zinc hydroxide on the polymer particles and improve the co-precipitation efficiency of the polymer and zinc hydroxide.

[0089] In some embodiments, the mixed solution further includes a surfactant, and the concentration of the surfactant is 0.10 mol / L to 0.15 mol / L, specifically 0.1 mol / L, 0.11 mol / L, 0.12 mol / L, 0.13 mol / L, 0.14 mol / L or 0.15 mol / L, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0090] In some embodiments, the mixed solution further includes a pH adjuster, and the pH adjuster includes at least one of ammonia water, sodium hydroxide, and potassium hydroxide.

[0091] In some embodiments, the pH value of the mixed solution is 10-14, specifically 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5 or 14, etc., which is not limited here.

[0092] In some embodiments, the reaction temperature of the in situ polymerization reaction is 28°C to 50°C, specifically 28°C, 30°C, 35°C, 40°C, 43°C, 45°C, 46°C, 48°C or 50°C, etc., which is not limited here.

[0093] In some embodiments, the reaction time of the in situ polymerization is 4 h to 12 h, specifically 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h or 12 h, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0094] In some embodiments, the in situ polymerization reaction is carried out under stirring, and the stirring rate is controlled to be 100 r / min to 1500 r / min, specifically 100 r / min, 200 r / min, 300 r / min, 400 r / min, 500 r / min, 800 r / min, 1000 r / min, 1200 r / min, 1300 r / min or 1500 r / min, etc., but is not limited to the listed values, and other values ​​within this numerical range are also applicable.

[0095] In some embodiments, the specific steps of subjecting a mixed solution containing an inorganic zinc salt and a polymer monomer to an in-situ polymerization reaction to obtain a composite containing a polymer and zinc hydroxide are:

[0096] Adding polymer monomers, inorganic zinc salts, surfactants and ammonia water into a solvent and mixing them to obtain a mixed solution containing inorganic zinc salts and polymer monomers;

[0097] The mixed solution is subjected to in-situ polymerization reaction and coprecipitation reaction, and solid-liquid separation is performed to obtain a composite containing a polymer and zinc hydroxide.

[0098] In some embodiments, the solvent includes at least one of water, ethanol, methanol, and propanol.

[0099] In some embodiments, the solid-liquid separation comprises at least one of filtration separation or centrifugal separation.

[0100] In step S20 , the composite is dried to form a precursor comprising a polymer and zinc oxide.

[0101] In some embodiments, the drying temperature is 60°C to 90°C, specifically 60°C, 65°C, 70°C, 75, 80°C, 85°C or 90°C, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0102] In some embodiments, the drying time is 6 h to 24 h, specifically 6 h, 8 h, 10 h, 12 h, 15 h, 18 h, 20 h or 24 h, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0103] In step S30 , the precursor is subjected to a stepwise temperature increase heat treatment in an inert gas atmosphere to obtain a carbon material with a rod-like structure, wherein the average aspect ratio of particles of the carbon material is 3-15.

[0104] In some embodiments, the stepwise temperature increase heat treatment comprises: subjecting the precursor to a heat treatment at 300°C to 400°C for 1 to 3 hours, then heating it to 600°C to 900°C for 1 to 6 hours, and finally heating it to 950°C to 1100°C for 3 to 6 hours.

[0105] Specifically, by subjecting the precursor to a heat treatment at 300°C to 400°C, the structure of the rod-shaped precursor can be preliminarily solidified, thereby reducing the occurrence of damage to the rod-shaped structure caused by excessively rapid heating. During the heat treatment at 600°C to 900°C, the polymer in the precursor is carbonized and cracked to form a rod-shaped carbon material containing zinc oxide. Then, before the temperature is raised to 950°C to 1100°C, the zinc oxide is reduced to elemental zinc by part of the carbon in the carbon material. Finally, during the heat treatment stage at 950°C to 1100°C, the zinc oxide is gasified and dezincified, and the elemental zinc is removed from the interior of the carbon material, forming pores in the carbon material that extend from the interior to the surface, thereby forming a carbon material with a rod-shaped structure having a large number of micropores.

[0106] In some embodiments, the heating rate of the step-by-step heat treatment is 1°C / min to 5°C / min, specifically 1°C / min, 1.5°C / min, 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, 4°C / min, 4.5°C / min or 5°C / min, etc., which is not limited here.

[0107] In some embodiments, the inert gas atmosphere includes at least one of helium, nitrogen, and argon.

[0108] In some embodiments, the method further comprises cooling, shaping and screening the product after the step-by-step temperature increase heat treatment, wherein the shaping comprises at least one of mechanical crushing, grinding, ball milling or air flow crushing.

[0109] In a fifth aspect, the present application provides a battery, comprising the carbon material described in the first aspect or the negative electrode material described in the second and third aspects, or a carbon material prepared according to the preparation method of the carbon material described in the fourth aspect.

[0110] Example

[0111] Example 1

[0112] (1) 950 ml of ethanol and 400 ml of water were mixed to form a mixed solvent. 10 g of resorcinol, 60 g of cetyltrimethylammonium bromide (CTAB), and 5 ml of ammonia water were added to the mixed solvent in sequence, and the mixture was stirred at 30°C for 0.5 h to mix evenly. Then, 15 ml of formaldehyde and 40 ml of a saturated zinc acetate solution at 25°C (the reaction system concentration was 0.0484 mol / L) were added to the mixed solvent to obtain a mixed solution containing resorcinol, formaldehyde, and saturated zinc acetate (pH 12.4).

[0113] (2) The mixed solution (pH 12.4) was stirred at 30° C. for 24 h, the stirring rate was controlled at 1000 r / min, and the mixture was filtered and separated to obtain a complex containing resorcinol formaldehyde resin and zinc hydroxide.

[0114] (3) The composite containing resorcinol formaldehyde resin and zinc hydroxide is vacuum dried at 60° C. for 12 h to form a precursor containing resorcinol formaldehyde resin and zinc oxide.

[0115] (4) A precursor containing resorcinol formaldehyde resin and zinc oxide is placed in a carbonization furnace, nitrogen is introduced, and the temperature is increased to 350°C at 1.5°C / min for heat treatment for 2 h, then the temperature is increased to 600°C at 1.5°C / min for further heat treatment for 2 h, and finally the temperature is increased to 950°C at 1.5°C / min for further heat treatment for 4 h. The carbon material is cooled, ground and sieved to obtain a rod-shaped carbon material.

[0116] The carbon material prepared in this example has rod-like particles and pores. The average length, average diameter, total pore volume, specific surface area, average pore diameter, and the volume fraction of micropores, mesopores, and macropores in the total pore volume of the carbon material are detailed in Table 1.

[0117] FIG3 is a scanning electron microscope image of the carbon material prepared in this embodiment. As shown in FIG3 , the particles of the carbon material have a rod-like structure.

[0118] The carbon material was tested using the Lihua Lianke iPore620 pore size tester and the BET pore size distribution test method. The pore size distribution data of the carbon material was obtained by DFT simulation analysis using the isothermal adsorption characteristic curve of nitrogen. Figure 7 is a pore size distribution test chart of the carbon material prepared in this embodiment. As shown in Figure 7, the pore structure of the carbon material includes micropores less than 2 nm.

[0119] Example 2

[0120] The difference from Example 1 is that 80 mL of 25° C. saturated zinc acetate solution (concentration in the reaction system is 0.0969 mol / L) is added in step (1), and the remaining operations are the same as in Example 1.

[0121] The carbon material prepared in this example has rod-like particles and pores. The average length, average diameter, total pore volume, specific surface area, average pore diameter, and the volume fraction of micropores, mesopores, and macropores in the total pore volume of the carbon material are detailed in Table 1.

[0122] FIG4 is a scanning electron microscope image of the carbon material prepared in this embodiment. As shown in FIG4 , the particles of the carbon material have a rod-like structure. Since the microporous structure exceeds the resolution of the scanning electron microscope, the microporous structure on the carbon material is difficult to observe.

[0123] The carbon material was tested using the Lihua Lianke iPore620 pore size tester and the BET pore size distribution test method. The pore size distribution data of the carbon material was obtained by DFT simulation analysis using the isothermal adsorption characteristic curve of nitrogen. Figure 8 is a pore size distribution diagram of the carbon material prepared in this embodiment. As shown in Figure 8, the pore structure of the carbon material is mainly micropores less than 2 nm.

[0124] Example 3

[0125] The difference from Example 1 is that 120 mL of 25° C. saturated zinc acetate solution (concentration in the reaction system is 0.1452 mol / L) is added in step (1), and the remaining operations are the same as in Example 1.

[0126] The carbon material prepared in this example has rod-like particles and pores. The average length, average diameter, total pore volume, specific surface area, average pore diameter, and the volume fraction of micropores, mesopores, and macropores in the total pore volume of the carbon material are detailed in Table 1.

[0127] Example 4

[0128] The difference from Example 1 is that 160 mL of 25° C. saturated zinc acetate solution (concentration in the reaction system is 0.1936 mol / L) is added in step (1), and the remaining operations are the same as in Example 1.

[0129] The carbon material prepared in this example has rod-like particles and pores. The average length, average diameter, total pore volume, specific surface area, average pore diameter, and the volume fraction of micropores, mesopores, and macropores in the total pore volume of the carbon material are detailed in Table 1.

[0130] Example 5

[0131] The difference from Example 1 is that 200 mL of 25° C. saturated zinc acetate solution (concentration in the reaction system is 0.2420 mol / L) is added in step (1), and the remaining operations are the same as in Example 1.

[0132] The carbon material prepared in this example has rod-like particles and pores. The average length, average diameter, total pore volume, specific surface area, average pore diameter, and the volume fraction of micropores, mesopores, and macropores in the total pore volume of the carbon material are detailed in Table 1.

[0133] Example 6

[0134] The difference from Example 1 is that 240 mL of 25° C. saturated zinc acetate solution (concentration in the reaction system is 0.2904 mol / L) is added in step (1), and the remaining operations are the same as in Example 1.

[0135] The carbon material prepared in this example has rod-like particles and pores. The average length, average diameter, total pore volume, specific surface area, average pore diameter, median particle size, and the volume fractions of micropores, mesopores, and macropores in the total pore volume of the carbon material are detailed in Table 1.

[0136] Example 7

[0137] The difference from Example 1 is that 280 mL of 25° C. saturated zinc acetate solution (concentration in the reaction system is 0.3388 mol / L) is added in step (1), and the remaining operations are the same as in Example 1.

[0138] The carbon material prepared in this example has rod-like particles and pores. The average length, average diameter, total pore volume, specific surface area, average pore diameter, and the volume fraction of micropores, mesopores, and macropores in the total pore volume of the carbon material are detailed in Table 1.

[0139] Example 8

[0140] The difference from Example 1 is that 320 mL of 25° C. saturated zinc acetate solution (concentration in the reaction system is 0.3872 mol / L) is added in step (1), and the remaining operations are the same as in Example 1.

[0141] The carbon material prepared in this example has rod-like particles and pores. The average length, average diameter, total pore volume, specific surface area, average pore diameter, and the volume fraction of micropores, mesopores, and macropores in the total pore volume of the carbon material are detailed in Table 1.

[0142] Comparative Example 1

[0143] The difference from Example 1 is that 360 mL of 25° C. saturated zinc acetate solution (concentration in the reaction system is 0.4425 mol / L) is added in step (1), and the remaining operations are the same as in Example 1.

[0144] Comparative Example 2

[0145] (1) 950 ml of ethanol and 400 ml of water were mixed to form a mixed solvent. 10 g of resorcinol, 60 g of hexadecyltrimethylammonium bromide (CTAB), and 5 ml of ammonia water were added to the mixed solvent in sequence, and the mixture was stirred at 30 ° C for 0.5 h to mix them evenly. Then, 15 ml of formaldehyde and 40 ml of tetraethyl silicate were added to the mixed solvent to obtain a mixed solution containing resorcinol, formaldehyde, and tetraethyl silicate (pH 12.6).

[0146] (2) The mixed solution (pH 12.6) was stirred at 30° C. for 24 h, and filtered to obtain a composite of resorcinol formaldehyde resin and silica.

[0147] (3) The composite was vacuum dried at 60° C. for 12 h to form a precursor comprising resorcinol formaldehyde resin and silica.

[0148] (4) The precursor was placed in a carbonization furnace, nitrogen was introduced, and the temperature was increased to 350°C at a rate of 1.5°C / min for heat treatment for 2 h, then the temperature was increased to 600°C at a rate of 1.5°C / min for further heat treatment for 2 h, and finally the temperature was increased to 950°C at a rate of 1.5°C / min for further heat treatment for 4 h. The product was cooled, ground and sieved to obtain a carbonized product powder with a spherical structure.

[0149] (5) The carbonized product powder with a spherical structure is placed in hydrofluoric acid for etching, and then filtered, washed and dried to obtain a carbon material with a spherical structure.

[0150] Test Method

[0151] (1) Test method for average aspect ratio of carbon materials:

[0152] The carbon material was photographed using a Hitachi S-4800 scanning electron microscope in Japan, and 200 carbon material particles were randomly selected from the photographed images for measurement to obtain the length and diameter of each particle. The aspect ratio of each particle was calculated based on the length and diameter, and then the average aspect ratio of the 200 particles was calculated.

[0153] (2) Test method for pore size distribution of carbon materials:

[0154] The carbon material was tested using the Lihua Lianke iPore620 pore size tester and the BET pore size distribution test method. The isothermal adsorption characteristic curve of nitrogen was used to obtain the pore size distribution data of the carbon material through DFT simulation analysis, and then the average pore size, total pore volume, BET specific surface area of ​​the carbon material, and the volume ratio of the pore volume of micropores, mesopores and macropores in the total pore volume were obtained.

[0155] (3) Test method for the mass content of oxygen in carbon materials:

[0156] Using a German Verder oxygen, nitrogen, and hydrogen element analyzer ONH 2000, the carbon material was wrapped with a flux and then melted in a graphite crucible in an inert atmosphere. The oxygen-containing elements in the carbon material were reduced to carbon dioxide by the carbon in the graphite crucible. The generated carbon dioxide entered the infrared detector along with the carrier gas, and the changes in the carbon dioxide infrared signal were quantitatively analyzed to calculate the oxygen content.

[0157] (4) Electrochemical performance test:

[0158] The carbon materials, conductive carbon black (super P), and binder (LA133) prepared in Examples 1 to 8 and Comparative Examples 1 to 2 were mixed into a slurry in a ratio of 91:3:6 and evenly coated on a copper foil. After drying, the slurry was prepared into electrode sheets, which were assembled into button cells and their charging capacity and coulombic efficiency were tested on a Blue Electric battery test cabinet M340A.

[0159] The above test results are detailed in Table 1 and Table 2.

[0160] Table 1 Performance parameters of carbon materials in various embodiments and comparative examples

[0161] Table 2 Electrochemical performance test results of carbon materials prepared in various embodiments and comparative examples

[0162] As shown in Table 1, during the preparation process of the carbon materials of Examples 1 to 8 and Comparative Example 1, as the concentration of zinc acetate in the reaction system continued to increase, the longitudinal growth of the generated rod-shaped zinc oxide template became dominant, and the aspect ratio of the synthesized rod-shaped carbon material continued to increase. However, in Example 7, Example 8 and Comparative Example 1, as the concentration of zinc acetate in the reaction system increased excessively, the longitudinal growth of the rod-shaped zinc oxide began to be inhibited by the shear force generated by stirring, and its lateral growth became dominant, and the aspect ratio began to decrease continuously. When the amount of saturated zinc acetate used reached 360 mL of Comparative Example 1, the particles agglomerated and the rod-shaped structure disappeared. In this process, as the concentration of zinc acetate in the reaction system continues to increase, more pores are formed in the carbon material, and its total pore volume increases. However, the increase in the concentration of zinc acetate in the reaction system also causes the pore-forming effect to intensify, resulting in the collapse and merging of some micropores in the carbon material, a decrease in the proportion of micropores, and an increase in the average pore size of the carbon material. As the concentration of zinc acetate in the reaction system increases excessively, the zinc distribution in the carbon material is uneven, some zinc agglomerates, and the pore-forming ability is weakened, resulting in the total pore volume of the carbon material beginning to decrease, the proportion of micropores increasing, and the average pore size of the carbon material also beginning to decrease. Therefore, the average pore size, specific surface area, total pore volume, and macropore volume ratio of the rod-shaped carbon materials formed in Examples 1 to 8 and Comparative Example 1 show a trend of gradually increasing and then gradually decreasing, while the micropore ratio shows the opposite trend of gradually decreasing and then gradually increasing.

[0163] It can be seen from Tables 1 and 2 that during the preparation process of the carbon materials of Examples 1 to 8, as the concentration of zinc acetate in the reaction system increases, zinc acetate is thermally decomposed to produce zinc oxide, the zinc oxide is reduced by the carbon material, and the oxygen element is transferred to the carbon material, so that the mass content of oxygen and the zinc content in the carbon material are increased, the pore-forming effect of zinc is increased, more pores are formed in the carbon material, the total pore volume is increased, the ability of the carbon material to embed lithium is increased, and the charging capacity is also improved accordingly; a small amount of oxygen doped in the carbon material can also provide lone pairs of electrons, which interact with the π electrons in the carbon material to form a conjugated system, thereby improving the conductivity of the carbon material.

[0164] According to the test data of Example 7 and Example 1, the concentration of zinc acetate in the reaction system is relatively high, and the mass content of oxygen in the carbon material also increases accordingly, and its charging capacity also increases accordingly; however, the relatively high oxygen content may cause the continuity of the C=C conjugated system in the carbon material to decrease, resulting in the breakage of the C=C conjugated system and the decrease in conductivity. After the carbon material is applied to the negative electrode material, the amount of active lithium ions consumed in the negative electrode material during the cycle increases, resulting in a decrease in the first coulombic efficiency of the carbon material compared to Example 1. Therefore, considering the first effective coulombic efficiency and charging capacity of the carbon material, the mass content of oxygen in the carbon material is preferably 1% to 4.2%.

[0165] Figure 5 is a scanning electron microscope image of the carbon material provided in comparative example 1 of the present application. As shown in Figure 5, the particles in the carbon material form agglomerates and the rod-like structure disappears; Figure 9 is a pore size distribution diagram of the carbon material provided in comparative example 1 of the present application. As shown in Figure 9, the pores in the carbon material are only micropores and mesopores, and there are no macropores.

[0166] During the preparation process of the carbon material of Comparative Example 1, due to the high concentration of zinc acetate in the reaction system, the longitudinal growth of the rod-shaped zinc oxide began to be inhibited by the shear force generated by stirring, the lateral growth of zinc oxide dominated, the aspect ratio decreased, and the particles began to agglomerate, resulting in the disappearance of the rod-shaped structure, and thus the carbon material with a rod-shaped structure could not be formed.

[0167] According to the test data of Example 1 and Comparative Example 1, it can be seen that in Comparative Example 1, due to the high concentration of zinc acetate in the reaction system, and during the step-by-step temperature increase heat treatment, the carbon material is oxidized and etched by zinc oxide, zinc oxide is reduced by the carbon material, and oxygen is transferred to the carbon material, so that the mass content of oxygen and zinc in the carbon material is too high. The increase in the mass content of oxygen in the carbon material will destroy the continuity of the C=C conjugated system in the material, causing the C=C conjugated system to break, resulting in a significant decrease in the conductivity of the carbon material; at the same time, the excessively high zinc content in the carbon material leads to uneven distribution of zinc in the carbon material, partial zinc agglomeration, and weakened pore-forming ability, resulting in the total pore volume of the carbon material beginning to decrease. After the carbon material is applied to the negative electrode material, the lithium insertion ability of the negative electrode material is reduced, and the capacity and coulombic efficiency of the carbon material are reduced; at the same time, the proportion of mesopores in the carbon material is also greatly increased, resulting in a decrease in the structural stability of the carbon material. The particles are easily broken when the electrode is roller-pressed, and the side reaction between the carbon material and the electrolyte is intensified, causing the SEI interface film to be continuously generated, further reducing the capacity and coulombic efficiency of the carbon material.

[0168] Figure 6 is a scanning electron microscope image of the carbon material provided in comparative example 2 of the present application. As shown in Figure 6, the particles in the carbon material agglomerate to form spherical carbon material; Figure 10 is a pore size distribution diagram of the carbon material provided in comparative example 2 of the present application. As shown in Figure 10, the proportion of mesopores and macropores in the carbon material increases significantly.

[0169] According to the test data of Example 3, Example 4 and Comparative Example 2, the carbon material prepared in Comparative Example 2 is

[0170] The carbon materials prepared in Examples 3 and 4 have similar average pore diameters, specific surface areas, and total pore volumes. However, since the inorganic zinc salt is replaced with tetraethyl silicate in the carbon material of Comparative Example 2 during the preparation process, the generated carbon material is spherical porous carbon, and the proportion of mesopores and macropores in the carbon material is relatively high, while the micropores are relatively few. The gaps between the carbon material particles are large, and the mechanical properties are weakened, which results in some particles of the spherical porous carbon being broken when the electrode is roller-pressed, thereby increasing the specific surface area of ​​the carbon material and intensifying the side reaction between the carbon material and the electrolyte, causing the SEI film thickness to further increase, thereby causing the charging capacity of the carbon material to decay, and its coulombic efficiency is also greatly reduced.

[0171] The applicant declares that while the above-mentioned embodiments are used to illustrate the detailed process equipment and process flow of the present application, the present application is not limited to the above-mentioned detailed process equipment and process flow, which does not mean that the present application must rely on the above-mentioned detailed process equipment and process flow in order to be implemented. Those skilled in the art should understand that any improvements to the present application, equivalent replacements for the raw materials of the present application's products, addition of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present application.

Claims

1. A carbon material, characterized in that The carbon material has pores, and the average aspect ratio of particles of the carbon material is 3-15.

2. The carbon material according to claim 1, characterized in that The carbon material meets at least one of the following technical characteristics: (1) The average length of the carbon material particles is 0.3 μm to 5 μm; (2) The average diameter of the carbon material particles is 0.1 μm to 3 μm.

3. The carbon material according to claim 1, characterized in that The total pore volume of the carbon material is 0.2 cm 3 / g~0.8cm 3 / g.

4. The carbon material according to claim 1, characterized in that The average pore diameter of the pores in the carbon material is 0.8 nm to 2.5 nm.

5. The carbon material according to claim 1, characterized in that The pores in the carbon material include micropores, and the volume of the micropores accounts for 80% to 95% of the total pore volume.

6. The carbon material according to claim 1, characterized in that The pores in the carbon material further include at least one of mesopores and macropores.

7. The carbon material according to claim 6, characterized in that The carbon material meets at least one of the following technical characteristics: (1) The volume of the mesopores accounts for 5% to 15% of the total pore volume; (2) The volume of the macropores accounts for 0% to 5% of the total pore volume.

8. The carbon material according to claim 1, characterized in that The carbon material meets at least one of the following technical characteristics: (1) The charging capacity of the battery assembled from the carbon material is 250 mAh / g to 400 mAh / g; (2) The coulombic efficiency of the battery assembled from the carbon material is 40% to 55%.

9. The carbon material according to claim 1, characterized in that The mass content of oxygen in the carbon material is 1% to 5.5%.

10. A negative electrode material, characterized in that: The negative electrode material comprises the carbon material according to any one of claims 1 to 9 and an active substance, and at least a portion of the active substance is filled in the pores of the carbon material.

11. A negative electrode material, characterized in that: The negative electrode material includes a carbon material and an active material. The negative electrode material after removing the active material has pores, and the aspect ratio of particles of the negative electrode material after removing the active material is 3-15.

12. The negative electrode material according to claim 10 or 11, characterized in that: The mass content of carbon element in the negative electrode material is 70% to 98%.

13. The negative electrode material according to claim 10 or 11, characterized in that: The negative electrode material meets at least one of the following technical characteristics: (1) The active material includes silicon-based active particles; (2) The active material includes silicon-based active particles, and the silicon-based active particles include at least one of amorphous silicon, crystalline silicon, silicon oxide, silicon alloy, and a composite of crystalline silicon and amorphous silicon; (3) The active material includes silicon-based active particles, and the average particle size of the silicon-based active particles is 0.85 nm to 2.45 nm.

14. The negative electrode material according to claim 10 or 11, characterized in that: The pore volume of the negative electrode material is 0.001 cm 3 / g~0.020cm 3 / g.

15. A battery, characterized in that: The battery comprises the carbon material according to any one of claims 1 to 9 or the negative electrode material according to any one of claims 10 to 14.

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