Carbon-based negative electrode material and preparation method and application thereof

Abstract

The application discloses a carbon-based negative electrode material and a preparation method and application thereof. The carbon-based negative electrode material comprises a porous carbon base and an encapsulant for converting open pores on the surface of the porous carbon base into closed pores; and the encapsulant is discrete encapsulating particles and / or a continuous encapsulating layer. The carbon-based negative electrode material disclosed by the application has high capacity, high initial efficiency, super-long cycle stability, excellent rate performance and wide temperature range adaptability.

Description

Technical Field

[0001] This invention relates to the technical field of anode materials, specifically to a carbon-based anode material, its preparation method, and its application. Background Technology

[0002] Graphite-based anode materials, with their mature and stable layered structure, have become the absolute mainstream anode material for lithium batteries. Their advantages are significant: the volume change during lithium ion insertion and extraction is minimal, only about 10%; the electrode structure is less prone to pulverization; and the initial charge-discharge efficiency is high, generally exceeding 95%. Furthermore, the production process is mature, raw materials are readily available, costs are low, and safety is more guaranteed. However, they also have significant drawbacks: the theoretical specific capacity is only 372 mAh / g, and the actual commercial application is around 330-360 mAh / g. Capacity improvement is nearing its limit, making it difficult to meet the demands of high-energy-density batteries. Additionally, they are prone to lithium dendrite formation during high-current charging, and their performance degrades significantly at low temperatures.

[0003] Silicon-based anode materials are a promising next-generation anode material, with their core advantage being extremely high theoretical specific capacity. Pure silicon can reach 4200 mAh / g, more than 10 times that of graphite, while silicon suboxide has approximately 2600 mAh / g, significantly improving battery energy density and meeting the needs of long-range electric vehicles and high-capacity consumer electronics. However, their disadvantages are equally significant. The volume expansion rate during lithium intercalation is as high as 300%-400%, which easily leads to electrode pulverization, repeated SEI film rupture, and a significant reduction in cycle life.

[0004] Therefore, it is crucial to develop an anode material that can maintain high capacity while also having long cycle performance.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention discloses a carbon-based anode material that combines high capacity, high initial efficiency, ultra-long cycle stability, excellent rate performance, and wide temperature range adaptability.

[0007] The specific technical solution is as follows:

[0008] In a first aspect, the present invention provides a carbon-based anode material, comprising a porous carbon substrate and an encapsulant for sealing the openings on the surface of the porous carbon substrate;

[0009] The encapsulation material is discrete encapsulation particles and / or continuous encapsulation layers.

[0010] In an optional embodiment, the carbon-based anode material has a cavity inside.

[0011] In an optional embodiment, the carbon-based anode material satisfies at least one of the following conditions:

[0012] (a) Specific surface area of ​​0.1~100 m² 2 / g;

[0013] (b) The pore volume is 0.001~0.15 cm. 3 / g;

[0014] (c) Particle size Dv50 is 2~18 μm;

[0015] (d) Tap density is 0.1~1.2 g / cm³ 3 .

[0016] Optionally, the carbon-based anode material satisfies at least one of the following conditions:

[0017] (a) Specific surface area of ​​0.1~80 m² 2 / g;

[0018] (b) The pore volume is 0.005~0.05cm 3 / g;

[0019] (c) Particle size Dv50 is 7.0 ± 1.0 μm;

[0020] (d) Tap density is 0.35~0.75 g / cm³ 3 .

[0021] In an optional embodiment, the battery assembled with the carbon-based negative electrode material satisfies at least one of the following conditions:

[0022] (1) The discharge capacity in the first week shall not be less than 1400mAh / g;

[0023] (2) After 500 cycles, the capacity retention rate is not less than 85% and the expansion rate is not more than 5%; optionally, the capacity retention rate is not less than 90% and the expansion rate is not more than 4%.

[0024] (3) At a current density of 1.0 A / g, the capacity retention rate is not less than 80% after 2000 cycles and not less than 72% after 5000 cycles; optionally, the capacity retention rate is not less than 83% after 2000 cycles and not less than 77% after 5000 cycles.

[0025] (4) At a current density of 5.0 A / g, the capacity retention rate after 200 cycles is not less than 60%; optionally, the capacity retention rate is not less than 65%.

[0026] (5) At -20℃, the capacity retention rate after 500 cycles is not less than 68%, and at -40℃, the capacity retention rate after 500 cycles is not less than 40%; optionally, the capacity retention rate after 500 cycles at -20℃ is not less than 72%, and at -40℃, the capacity retention rate after 500 cycles is not less than 50%.

[0027] In an optional embodiment, the mass percentage of the encapsulated material is no more than 20% based on the mass of the carbon-based anode material being 100%; alternatively, the mass percentage is 8-20%.

[0028] In an optional embodiment, the porous carbon substrate is prepared as follows:

[0029] The carbon material precursor is sintered at high temperature to remove impurities, and then pores are formed to obtain a porous carbon substrate; pore forming includes methods such as strong alkali corrosion, carbon dioxide activation or water vapor activation.

[0030] In optional embodiments, the type of carbon material precursor is not particularly limited and may include, but is not limited to, pitch-based carbon material precursors, pitchene-based carbon material precursors, coal-based carbon material precursors, coke-based carbon material precursors, biochar-based carbon material precursors, carbon black-based carbon material precursors, oil-based carbon material precursors, tar-based carbon material precursors, polymer-based carbon material precursors, protein-based carbon material precursors, carbohydrate-based carbon material precursors, cotton-based carbon material precursors, fat-based carbon material precursors, waste-based carbon material precursors, graphite-based carbon material precursors, melamine-based carbon material precursors, wood-based carbon material precursors, porous graphene, porous graphene oxide, activated carbon, and combinations thereof.

[0031] Porous carbon materials with this type of carbon material precursor can be easily prepared to have the following properties: particle size, specific surface area, pore volume, tap density, etc.

[0032] In an optional embodiment, the porous carbon substrate satisfies at least one of the following conditions:

[0033] (a) Specific surface area of ​​100~2500 m² 2 / g;

[0034] (b) The pore volume is 0.5~3.0 cm. 3 / g;

[0035] (c) Particle size Dv50 is 1~20 μm;

[0036] (d) The average pore size is 1~10 nm;

[0037] (e) Aperture concentration ≥ 1, Aperture concentration = Pv50 / (Pv90 - Pv10).

[0038] In this invention, the pore size concentration is Pv50 / (Pv90-Pv10), where Pv50 is 0.5~1.5nm, Pv90 is 1.5~2.2nm, and Pv10 is 0.4~1.0nm.

[0039] The ASAP2460 physical adsorption analyzer was used for testing. The dried and degassed porous carbon material samples were placed in liquid nitrogen, and the adsorption amount of nitrogen was measured by adjusting different experimental pressures. Adsorption and desorption isotherms were plotted. The pore shape was determined based on the shape of the hysteresis loop, and the pore distribution was calculated using different pore models. The BJH model was used to fit the pore size distribution curve of mesopores, and the DFT model was used to fit the pore size distribution curve of micropores. In this invention, Pv90 includes particles with a pore size smaller than its volume accounting for 90%, Pv10 includes particles with a pore size smaller than its volume accounting for 10%, and Pv50 includes particles with a pore size larger than its volume accounting for 50%, and particles smaller than its volume also accounting for 50%. This is also known as the median diameter, which is usually used to represent the average particle size.

[0040] Experiments have shown that controlling the pore size concentration of the porous carbon substrate is particularly important in this invention. If the pore size concentration is too low (below 1), the pore distribution is too scattered, resulting in incomplete encapsulation, reduced closed pores, less lithium storage, significantly reduced first-time efficiency, and worsened stability during subsequent encapsulation.

[0041] Optionally, the carbon source precursor is subjected to high-temperature carbonization treatment, followed by two activation treatments to obtain porous carbon materials; or the carbon source precursor is mixed with a template agent and then directly subjected to high-temperature carbonization treatment.

[0042] The process involves two activation treatments: the first activation uses alkali, acid, or carbon dioxide as the activating agent, and the second activation uses water vapor as the activating agent; the pore volume ratio of the first activation is ≤50%; and the pore volume ratio of the second activation is ≥50%.

[0043] If the initial activation is to produce an acid or alkali, it needs to be discharged at room temperature until it is neutral, with no acid or alkali residue, and dried until the moisture content is less than 1% for secondary activation. Secondary activation involves vacuum treatment followed by the introduction of a steam-nitrogen mixture to a slightly positive pressure until the pressure increase exceeds 50%. Then, the pressure is continuously reduced to a vacuum, and the steam-nitrogen mixture is reintroduced. This process is repeated until the desired pore structure is achieved.

[0044] Alternatively, a template method can be used, with template agents including but not limited to mesoporous molecular sieves and other materials that meet the above-mentioned pore characteristics requirements.

[0045] In a further optional embodiment, the porous carbon substrate satisfies at least one of the following conditions:

[0046] (a) Specific surface area of ​​1000~2100 m² 2 / g;

[0047] (b) The pore volume is 0.6~2.5 cm. 3 / g;

[0048] (c) Particle size Dv50 is 7.0 ± 1.0 μm;

[0049] (d) The average pore size is 2.0 ± 1.0 nm;

[0050] (e) Aperture concentration ≥ 1.5.

[0051] Further optional:

[0052] The pore size concentration of the porous carbon substrate is 1.6~2.5.

[0053] Experiments have shown that continuous optimization of pore size concentration can ensure higher closed-pore conversion efficiency, resulting in batteries with superior electrochemical performance.

[0054] In an optional embodiment, the material of the encapsulating particles is selected from one or more of metals, non-metals, metal oxides, and inorganic salts;

[0055] In an optional embodiment, the metal is selected from one or more of iron, cobalt, nickel, and calcium;

[0056] In an optional embodiment, the nonmetal is selected from one or more of phosphorus, silicon, carbon, and sulfur;

[0057] In an optional embodiment, the metal oxide is selected from one or more of lithium oxide, iron oxide, nickel oxide, cobalt oxide, and zinc oxide;

[0058] In an optional embodiment, the inorganic salt is selected from inorganic lithium salts; more preferably, it is lithium carbonate, lithium silicate, lithium sulfate, lithium fluoride, etc.

[0059] In an optional embodiment, the average particle size of the encapsulated particles is 1~10 nm; more preferably, the average particle size is 2.0~7.0 nm.

[0060] In an optional embodiment, the encapsulation layer is selected from thin films having conductive and / or ion-conducting properties.

[0061] Further optionally, the encapsulation layer is selected from a polymer film, or a polymer film doped with a conductive material; or a polymer carbon film converted from the above-mentioned polymer film by carbonization. In an optional embodiment, the polymer film is selected from one or more of polyacrylic acid, polypyrrole, and polyaniline;

[0062] In an optional embodiment, the conductive material is selected from one or more of carbon nanotubes, carbon black, graphene, and metallic lithium.

[0063] Alternatively, the polymer raw material used in the polymer film has a molecular weight of not less than 1000 Da.

[0064] Experiments have shown that if carbon prepared by vapor deposition using small molecule carbon sources (such as ethylene, acetylene, etc.) is used as encapsulation particles or encapsulation layers, or if encapsulation particles or encapsulation layers prepared by liquid phase deposition using low molecular weight carbon sources (such as glucose, etc.) are used, the pores on the surface of the porous carbon substrate cannot be fully sealed, or the internal cavities of the porous carbon substrate cannot be effectively preserved, resulting in the inability to achieve high capacity and ultra-long cycle stability.

[0065] In an optional embodiment, the thickness of the encapsulation layer is no greater than 100 nm; more preferably, the thickness is no greater than 20 nm.

[0066] Secondly, the present invention provides a method for preparing the carbon-based anode material, comprising:

[0067] Using a porous carbon substrate as raw material, it is encapsulated. After encapsulation, the openings on the surface of the porous carbon substrate are closed, and the closure rate is not less than 85%.

[0068] ;

[0069] R1 is the pore volume of the porous carbon substrate, and R2 is the pore volume of the carbon-based anode material obtained after encapsulation.

[0070] After encapsulation, the encapsulated material retains the internal cavity of the porous carbon substrate while only sealing the outermost pores, thus preventing the continuous channels inside the porous carbon substrate from directly contacting the electrolyte.

[0071] In an optional embodiment, the encapsulation process includes one or more of the following: vapor deposition, liquid deposition, liquid adsorption, ionization adsorption, and spray coating.

[0072] Optionally, the spraying treatment includes, but is not limited to, one or more combinations of spray drying, surface self-polymerization, freeze drying, etc.

[0073] In an optional implementation, the encapsulation process is selected from vapor deposition:

[0074] The precursor, which serves as the gas source, is introduced into a reactor containing a porous carbon substrate, and the vapor deposition temperature is controlled at T.

[0075] In an optional embodiment, the flow rate of the precursor is not higher than 20 L / min; more preferably, the flow rate of the precursor is not higher than 10 L / min.

[0076] In an optional embodiment, T is related to the decomposition temperature Tprecursor. d The temperature difference ΔT = 100~500℃, T>T d .

[0077] Further optionally, ΔT = 100~400℃. By adjusting the vapor deposition temperature, the particle size of the deposited encapsulated particles can be controlled to adapt to different average particle sizes of porous carbon substrates to obtain high closed-cell conversion rates.

[0078] In an optional embodiment, when the encapsulating particles are selected from phosphorus, the precursor is selected from common types in the art, such as phosphine, ethionine, and phosphorus oxychloride.

[0079] In an optional embodiment, when the encapsulating particles are selected from silicon, the precursor is selected from common types in the art, such as silane, silane, monochlorosilane, trichlorosilane, etc.

[0080] In an optional embodiment, when the encapsulating particles are selected from carbon, the precursor is selected from methane, acetylene, ethylene, propane, pitch vapor, anthracene, pyrene, etc.

[0081] In an optional embodiment, when the encapsulating particles are selected from sulfur, the precursor is selected from hydrogen sulfide, methanethiol, dimethyl disulfide, etc.

[0082] In an optional implementation, the encapsulation process is selected from liquid phase deposition:

[0083] A porous carbon substrate, a precursor, and a solvent are mixed and subjected to a water bath and stirring process to adsorb ionic substances into the pores for sealing.

[0084] In an optional embodiment, when the encapsulating particles are selected from iron oxide particles, the precursor is selected from common types in the art, such as ferric nitrate, ferric chloride, ferric oxalate, and ferric isopropoxide.

[0085] In an optional embodiment, the spraying process is selected from spray drying.

[0086] Alternatively, after encapsulation, the sealing rate shall not be less than 95%.

[0087] Thirdly, the present invention provides a negative electrode sheet comprising the aforementioned carbon-based negative electrode material.

[0088] Fourthly, the present invention provides a secondary battery, including the aforementioned negative electrode sheet.

[0089] Fifthly, the present invention provides an electrical device, including the aforementioned secondary battery.

[0090] Compared with the prior art, the present invention has the following beneficial effects:

[0091] (1) Ion storage function: The three-dimensional confined space formed inside the closed hole can effectively store lithium ions. During the first lithium insertion process, the electrolyte can penetrate into the closed hole to form a solid electrolyte interface (SEI). The SEI layer exists stably and can continuously provide a transport channel for lithium ions inside the closed hole, thereby realizing the efficient lithium storage function of the closed hole and obtaining a high initial capacity.

[0092] (2) Rapid extraction and high first efficiency: Lithium ions in the closed pore can be rapidly extracted during the delithiation process. Due to the complete closed pore structure and unobstructed channels, the resistance during the insertion and extraction process is small and the kinetic performance is excellent. Therefore, a first coulombic efficiency of up to 85%~100% can be obtained.

[0093] (3) Zero strain volume expansion: The porous carbon skeleton itself hardly undergoes volume expansion during lithium intercalation. The expansion mainly comes from the small deformation caused by lithium ion storage in the closed pores. The overall volume expansion rate can be controlled within 5%, achieving near-zero strain.

[0094] (4) Ultra-long cycle stability: The closed pore structure completely encapsulates the active storage sites, greatly reducing side reactions with the electrolyte. At the same time, the mechanical stability of the porous carbon skeleton ensures the structural integrity during cycling. The capacity retention rate is ≥85% after 500 cycles, and can reach up to 94%; the capacity retention rate is ≥80% after 2000 cycles, and can reach up to 88%; the capacity retention rate is ≥72% after 5000 cycles, and can reach up to 79%.

[0095] (5) High compaction resistance: The high mechanical strength support material of the porous carbon skeleton can withstand a compaction density of more than 2.0 g / cm³, and the closed pore structure is intact and does not collapse, meeting the requirements of high energy density batteries.

[0096] (6) Excellent rate performance: ensures rapid lithium-ion transport, and the capacity retention rate at 5C (1C=1A / g) discharge can reach more than 60%, and up to 70%.

[0097] (7) Wide temperature range adaptability: It is suitable for the temperature range of -40℃ to 60℃. It has excellent low temperature discharge performance. The capacity retention rate is ≥68% after 500 cycles at -20℃, and can reach up to 80% at the highest. The capacity retention rate is ≥40% after 500 cycles at -40℃, and can reach up to 69% at the highest. Attached Figure Description

[0098] Figure 1 This is a schematic diagram of the encapsulation of a porous carbon substrate in this invention;

[0099] Figure 2 SEM images of the commercially available porous carbon material in Example 1;

[0100] Figure 3 SEM image of the carbon-based anode material prepared in Example 1;

[0101] Figure 4 SEM image of the carbon-based anode material prepared in Example 4. Detailed Implementation

[0102] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially. The features and performance of the present invention will be further described in detail below with reference to the embodiments.

[0103] In a first aspect, the present invention provides a carbon-based anode material, comprising a porous carbon substrate and an encapsulant for sealing the openings on the surface of the porous carbon substrate;

[0104] The encapsulation material is discrete encapsulation particles and / or continuous encapsulation layers.

[0105] In an optional embodiment, the carbon-based anode material has a cavity inside.

[0106] In an optional embodiment, the carbon-based anode material satisfies at least one of the following conditions:

[0107] (a) Specific surface area of ​​0.1~100 m² 2 / g, specifically 0.1 m 2 / g, 0.5 m 2 / g, 1.0 m 2 / g, 5.0m 2 / g、10 m 2 / g、20 m 2 / g、30 m 2 / g、40 m 2 / g、50 m 2 / g、60 m 2 / g、70 m 2 / g、80m 2 / g、90 m 2 / g, 100m 2 / g or any value within the above range; optionally, the specific surface area is 0.1~80 m². 2 / g; further optionally, the specific surface area is 0.1~55 m². 2 / g.

[0108] (b) The pore volume is 0.001~0.15 cm. 3 / g, specifically 0.001 cm 3 / g, 0.003 cm 3 / g, 0.005cm 3 / g, 0.008 cm 3 / g, 0.01 cm 3 / g, 0.03 cm 3 / g, 0.05 cm 3 / g, 0.08 cm 3 / g, 0.1 cm 3 / g, 0.12cm 3 / g, 0.15 cm 3 / g or any value within the above range; optionally, the pore volume is 0.005~0.05 cm³. 3 / g.

[0109] (c) The particle size Dv50 is 2~18 μm, specifically 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm or any value within the above range; optionally, the particle size Dv50 is 7.0±1.0 μm.

[0110] (d) Tap density is 0.1~1.2 g / cm³ 3 Specifically, it can be 0.1 g / cm³. 3 0.2 g / cm 3 0.3 g / cm 3 0.4 g / cm 3 0.5 g / cm 3 0.6 g / cm 3 0.7 g / cm 3 0.8 g / cm 3 0.9 g / cm 3 1.0 g / cm 3 1.1 g / cm 3 1.2 g / cm 3 Or any value within the above range; optionally, the tap density is 0.35~0.75 g / cm³. 3 .

[0111] In an optional embodiment, the battery assembled with the carbon-based negative electrode material satisfies at least one of the following conditions:

[0112] (1) The discharge capacity in the first week shall not be less than 1400 mAh / g, specifically selected from 1400 mAh / g, 1500 mAh / g, 1600 mAh / g, 1700 mAh / g, 1800 mAh / g, 1900 mAh / g, 2000 mAh / g, 2100 mAh / g, 2200 mAh / g or higher, and any value within the above range; the maximum value can reach 2200 mAh / g.

[0113] (2) After 500 cycles, the capacity retention rate is not less than 85%, specifically selectable from 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94% or any value within the above range; optionally, the capacity retention rate is not less than 90%, and can reach a maximum of 94%; after 500 cycles, the expansion rate is not higher than 5%, specifically selectable from 5%, 4.5%, 4.0%, 3.5%, 3.0%, 2.5%, 2.0%, 1.5% or any value within the above range; optionally, the expansion rate is not higher than 4%, and can reach a minimum of 1.9%.

[0114] (3) At a current density of 1.0 A / g, the capacity retention rate after 2000 cycles is not less than 80%, specifically selectable from 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88% or any value within the above range; optionally, the capacity retention rate is not less than 83%, and can reach up to 88%;

[0115] After 5000 cycles, the capacity retention rate is not less than 72%, specifically selectable from 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88% or any value within the above range; optionally, the capacity retention rate is not less than 77%, and can reach up to 79%.

[0116] (4) At a current density of 5.0 A / g, the capacity retention rate after 200 cycles is not less than 60%, specifically selectable from 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70% or any value within the above range; optionally, the capacity retention rate is not less than 65%, and can reach up to 70%.

[0117] (5) At -20℃, the capacity retention rate after 500 cycles is not less than 68%, specifically selectable from 68%, 69%, 70%, 72%, 75%, 78%, 80% or any value within the above range; optionally, the capacity retention rate after 500 cycles at -20℃ is not less than 72%, and can reach up to 80%;

[0118] At -40℃, the capacity retention rate after 500 cycles is not less than 40%, specifically selectable from 40%, 45%, 50%, 55%, 60%, 65%, 70% or any value within the above range; optionally, the capacity retention rate after 500 cycles at -40℃ is not less than 50%, and can reach up to 69%.

[0119] In an optional embodiment, based on the mass of the carbon-based anode material as 100%, the mass percentage of the encapsulant is no more than 20%, specifically it can be 20%, 19%, 18%, 17%, 16%, 15%, 12%, 10%, 8%, 5%, 2%, 1%, 0.1% or any value within the above range; optionally, the mass percentage is 8~20%.

[0120] In an optional embodiment, the porous carbon substrate is prepared as follows:

[0121] The carbon material precursor is sintered at high temperature to remove impurities, and then pores are formed to obtain a porous carbon substrate; pore forming includes methods such as strong alkali corrosion, carbon dioxide activation or water vapor activation.

[0122] In optional embodiments, the type of carbon material precursor is not particularly limited and may include, but is not limited to, pitch-based carbon material precursors, pitchene-based carbon material precursors, coal-based carbon material precursors, coke-based carbon material precursors, biochar-based carbon material precursors, carbon black-based carbon material precursors, oil-based carbon material precursors, tar-based carbon material precursors, polymer-based carbon material precursors, protein-based carbon material precursors, carbohydrate-based carbon material precursors, cotton-based carbon material precursors, fat-based carbon material precursors, waste-based carbon material precursors, graphite-based carbon material precursors, melamine-based carbon material precursors, wood-based carbon material precursors, porous graphene, porous graphene oxide, activated carbon, and combinations thereof.

[0123] Porous carbon materials with this type of carbon material precursor can be easily prepared to have the following properties: particle size, specific surface area, pore volume, tap density, etc.

[0124] In an optional embodiment, the porous carbon substrate satisfies at least one of the following conditions:

[0125] (a) Specific surface area of ​​100~2500 m² 2 / g, specifically 100 m 2 / g、200 m 2 / g、500 m 2 / g、800m 2 / g, 1000 m 2 / g、1200 m2 / g, 1500 m 2 / g、1800 m 2 / g、2000 m 2 / g、2200 m 2 / g、2500 m 2 / g or any value within the above range; optionally, the specific surface area is 1000~2100 m². 2 / g; further optionally, the specific surface area is 1500~2100 m² 2 / g.

[0126] (b) The pore volume is 0.5~3.0 cm. 3 / g, specifically 0.5 cm 3 / g, 0.55 cm 3 / g, 0.6 cm 3 / g, 0.65cm 3 / g, 0.7 cm 3 / g, 0.75 cm 3 / g, 0.8 cm 3 / g, 0.85 cm 3 / g, 0.9 cm 3 / g, 0.95 cm 3 / g, 1.0 cm 3 / g, 1.5 cm 3 / g, 2.0 cm 3 / g, 2.5 cm 3 / g, 3.0 cm 3 / g or any value within the above range; optionally, the pore volume is 0.6~2.5 cm³. 3 / g; further optionally, the pore volume is 0.6~1.2 cm³. 3 / g.

[0127] (c) The particle size Dv50 is 1~20 μm, specifically it can be 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm or any value within the above range; optionally, the particle size Dv50 is 7.0±1.0 μm.

[0128] (d) The average pore size is 1~10 nm, specifically 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm, 8.5 nm, 9 nm, 9.5 nm, 10 nm or any value within the above range; optionally, the average pore size is 2.0±1.0 nm.

[0129] (e) Aperture concentration ≥ 1, specifically can be 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.5, 3.0 or any value within the above range; optionally, aperture concentration ≥ 1.5, and further optionally, aperture concentration is selected from 1.6 to 2.5.

[0130] In this invention, the pore size concentration is Pv50 / (Pv90-Pv10), where Pv50 is 0.5~1.5nm, Pv90 is 1.5~2.2nm, and Pv10 is 0.4~1.0nm.

[0131] The ASAP2460 physical adsorption analyzer was used for testing. The dried and degassed porous carbon material samples were placed in liquid nitrogen, and the adsorption amount of nitrogen was measured by adjusting different experimental pressures. Adsorption and desorption isotherms were plotted. The pore shape was determined based on the shape of the hysteresis loop, and the pore distribution was calculated using different pore models. The BJH model was used to fit the pore size distribution curve of mesopores, and the DFT model was used to fit the pore size distribution curve of micropores. In this invention, Pv90 includes particles with a pore size smaller than its volume accounting for 90%, Pv10 includes particles with a pore size smaller than its volume accounting for 10%, and Pv50 includes particles with a pore size larger than its volume accounting for 50%, and particles smaller than its volume also accounting for 50%. This is also known as the median diameter, which is usually used to represent the average particle size.

[0132] Experiments have shown that controlling the pore size concentration of the porous carbon substrate is particularly important in this invention. If the pore size concentration is too low (below 1), the pore distribution is too scattered, resulting in incomplete encapsulation, reduced closed pores, less lithium storage, significantly reduced first-time efficiency, and worsened stability during subsequent encapsulation.

[0133] Experiments have shown that continuous optimization of pore size concentration can ensure higher closed-pore conversion efficiency, resulting in batteries with superior electrochemical performance.

[0134] Optionally, the carbon source precursor is subjected to high-temperature carbonization treatment, followed by two activation treatments to obtain porous carbon materials; or the carbon source precursor is mixed with a template agent and then directly subjected to high-temperature carbonization treatment.

[0135] The process involves two activation treatments: the first activation uses alkali, acid, or carbon dioxide as the activating agent, and the second activation uses water vapor as the activating agent; the pore volume ratio of the first activation is ≤50%; and the pore volume ratio of the second activation is ≥50%.

[0136] If the initial activation is to produce an acid or alkali, it needs to be discharged at room temperature until it is neutral, with no acid or alkali residue, and dried until the moisture content is less than 1% for secondary activation. Secondary activation involves vacuum treatment followed by the introduction of a steam-nitrogen mixture to a slightly positive pressure until the pressure increase exceeds 50%. Then, the pressure is continuously reduced to a vacuum, and the steam-nitrogen mixture is reintroduced. This process is repeated until the desired pore structure is achieved.

[0137] Alternatively, a template method can be used, with template agents including but not limited to mesoporous molecular sieves and other materials that meet the above-mentioned pore characteristics requirements.

[0138] In an optional embodiment, the material of the encapsulating particles is selected from one or more of metals, non-metals, metal oxides, and inorganic salts;

[0139] In an optional embodiment, the metal is selected from one or more of iron, cobalt, nickel, and calcium.

[0140] In an optional embodiment, the nonmetal is selected from one or more of phosphorus, silicon, carbon, and sulfur; optionally, the nonmetal is selected from phosphorus and / or silicon.

[0141] In an optional embodiment, the metal oxide is selected from one or more of lithium oxide, iron oxide, nickel oxide, cobalt oxide, and zinc oxide.

[0142] In an optional embodiment, the inorganic salt is selected from inorganic lithium salts; more preferably, it is lithium carbonate, lithium silicate, lithium sulfate, lithium fluoride, etc.

[0143] In an optional embodiment, the average particle size of the encapsulated particles is 1~10 nm, specifically selectable from 1.0 nm, 1.5 nm, 2.0 nm, 2.5 nm, 3.0 nm, 3.5 nm, 4.0 nm, 4.5 nm, 5.0 nm, 5.5 nm, 6.0 nm, 6.5 nm, 7.0 nm, 7.5 nm, 8.0 nm, 8.5 nm, 9.0 nm, 9.5 nm, 10 nm or any value within the above range; optionally, the average particle size is 2.0~7.0 nm.

[0144] In an optional embodiment, the encapsulation layer is selected from thin films having conductive and / or ion-conducting properties.

[0145] Further optionally, the encapsulation layer is selected from a polymer film, or a polymer film doped with conductive materials; or a polymer carbon film converted from the above-mentioned polymer film by carbonization.

[0146] In an optional embodiment, the polymer film is selected from one or more of polyacrylic acid, polypyrrole, and polyaniline;

[0147] In an optional embodiment, the conductive material is selected from one or more of carbon nanotubes, carbon black, graphene, and metallic lithium.

[0148] Alternatively, the polymer raw material used in the polymer film has a molecular weight of not less than 1000 Da.

[0149] Experiments have shown that if carbon prepared by vapor deposition using small molecule carbon sources (such as ethylene, acetylene, etc.) is used as encapsulation particles or encapsulation layers, or if encapsulation particles or encapsulation layers prepared by liquid phase deposition using low molecular weight carbon sources (such as glucose, etc.) are used, the pores on the surface of the porous carbon substrate cannot be fully sealed, or the internal cavities of the porous carbon substrate cannot be effectively preserved, resulting in the inability to achieve high capacity and ultra-long cycle stability.

[0150] In an optional embodiment, the thickness of the encapsulation layer is no greater than 100 nm, and can be selected from 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm or any value within the above range; further optionally, the thickness is no greater than 20 nm.

[0151] Secondly, the present invention provides a method for preparing the carbon-based anode material, comprising:

[0152] Using a porous carbon substrate as raw material, it is encapsulated. After encapsulation, the surface of the porous carbon substrate is sealed, and the sealing rate is not less than 85%. Specifically, it can be selected from 85%, 88%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or any value within the above range.

[0153] ;

[0154] R1 is the pore volume of the porous carbon substrate, and R2 is the pore volume of the carbon-based anode material obtained after encapsulation.

[0155] Optionally, after encapsulation, the sealing ratio is not less than 95%. Experiments have shown that the higher the sealing ratio, the better the electrochemical performance of the battery finally assembled from the prepared carbon-based anode material.

[0156] In an optional embodiment, the encapsulation process includes one or more of the following: vapor deposition, liquid deposition, liquid adsorption, ionization adsorption, and spray coating.

[0157] Optionally, the spraying treatment includes, but is not limited to, one or more combinations of spray drying, surface self-polymerization, freeze drying, etc.

[0158] In an optional implementation, the encapsulation process is selected from vapor deposition:

[0159] The precursor, which serves as the gas source, is introduced into a reactor containing a porous carbon substrate, and the vapor deposition temperature is controlled at T.

[0160] In an optional embodiment, the flow rate of the precursor is not higher than 20 L / min, specifically selected from 20 L / min, 18 L / min, 16 L / min, 15 L / min, 13 L / min, 11 L / min, 10 L / min, 8 L / min, 6 L / min, 5 L / min, 3 L / min, 1 L / min, 0.1 L / min or any value within the above range; further optionally, the flow rate of the precursor is not higher than 10 L / min.

[0161] In an optional embodiment, T is related to the decomposition temperature Tprecursor. d The temperature difference ΔT = 100~500℃, specifically selectable from 100℃, 150℃, 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, 500℃ or any value within the above range, and T > T0. d Alternatively, ΔT = 100~400℃.

[0162] The particle size of the deposited encapsulated particles can be controlled by adjusting the vapor deposition temperature to adapt to different average particle sizes of porous carbon substrates and achieve high sealing efficiency.

[0163] In an optional embodiment, when the encapsulating particles are selected from phosphorus, the precursor is selected from common types in the art, such as phosphine, ethionine, and phosphorus oxychloride.

[0164] In an optional embodiment, when the encapsulating particles are selected from silicon, the precursor is selected from common types in the art, such as silane, silane, monochlorosilane, trichlorosilane, etc.

[0165] In an optional embodiment, when the encapsulating particles are selected from carbon, the precursor is selected from methane, acetylene, ethylene, propane, pitch vapor, anthracene, pyrene, etc.

[0166] In an optional embodiment, when the encapsulating particles are selected from sulfur, the precursor is selected from hydrogen sulfide, methanethiol, dimethyl disulfide, etc.

[0167] In an optional implementation, the encapsulation process is selected from liquid phase deposition:

[0168] A porous carbon substrate, a precursor, and a solvent are mixed and subjected to a water bath and stirring process to adsorb ionic substances into the pores for sealing.

[0169] In an optional embodiment, when the encapsulating particles are selected from iron oxide particles, the precursor is selected from common types in the art, such as ferric nitrate, ferric chloride, ferric oxalate, and ferric isopropoxide.

[0170] In an optional embodiment, the spraying process is selected from spray drying.

[0171] Thirdly, the present invention provides a negative electrode sheet comprising the aforementioned carbon-based negative electrode material.

[0172] Fourthly, the present invention provides a secondary battery, including the aforementioned negative electrode sheet.

[0173] Fifthly, the present invention provides an electrical device, including the aforementioned secondary battery.

[0174] Example 1

[0175] (1) Commercially available porous carbon material (specific surface area of ​​1850 m²) was used. 2 / g, pore volume 0.9 cm³ 3 / g, average pore size 1.82 nm, pore size distribution 1.6 (obtained by BET test); tap density 0.3 g / cm³ 3 After sieving, the particle size Dv50 is controlled to be 7 μm;

[0176] (2) Take 300 g of the above-treated porous carbon material as a substrate and place it in a CVD rotary deposition furnace. Adjust the furnace temperature to 500℃, evacuate to -0.095MPa, backfill with nitrogen, maintain a nitrogen atmosphere, and maintain a pressure ≥500Pa. Use phosphine (PH3) as the encapsulation gas source, with a total flow rate of 6 L / min. Adjust the rotary furnace speed to a low speed of 5Hz (the highest speed of 50Hz corresponds to 3r / min). Continuously circulate gas for 20 min to carry out chemical vapor deposition. After completion, introduce nitrogen and cool to room temperature to obtain carbon-based anode material.

[0177] The carbon-based anode material prepared in this embodiment was characterized for properties such as specific surface area, phosphorus content, and phosphorus grain size. The results are as follows:

[0178] The specific surface area of ​​the carbon-based anode material prepared in this embodiment is 10 m². 2 / g, pore volume 0.03 cm³ 3 / g, sealing rate 96.7%; particle size Dv50 7.5µm; tap density 0.35 g / cm³ 3 .

[0179] SEM images of commercially available porous carbon materials used as raw materials, such as... Figure 2 As shown, the SEM images of the prepared carbon-based anode material are as follows: Figure 3 As shown, the grain size of the nano-phosphorus particles used as encapsulation in the obtained carbon-based anode material is about 2.2 nm, as determined by SEM and TEM. The loading of the encapsulation is 10% based on the mass of the carbon-based anode material as 100%.

[0180] Example 2

[0181] (1) Commercially available porous carbon material (specific surface area of ​​1850 m²) was used. 2 / g, pore volume 1.2 cm³ 3 / g, average pore size is 2.5 nm, pore size distribution is 1.8 (obtained by BET test); tap density is 0.25 g / cm³. 3 After sieving, the particle size Dv50 is controlled to be 7 μm;

[0182] (2) Take 300 g of the above-treated porous carbon material as a substrate and place it in a CVD rotary deposition furnace. Adjust the furnace temperature to 750℃, evacuate to -0.095MPa, backfill with nitrogen, maintain a nitrogen atmosphere, and maintain a pressure ≥500Pa. Use silane (SiH4) as the silicon source gas, with a total flow rate of 8 L / min. Adjust the rotary furnace speed to a low speed of 10Hz (the highest speed of 50Hz corresponds to 3r / min), and continuously ventilate for 0.5h for chemical vapor deposition. After completion, introduce nitrogen and cool to room temperature to obtain carbon-based anode material.

[0183] The carbon-based anode material prepared in this embodiment has a specific surface area of ​​25 m², as determined by testing. 2 / g, pore volume 0.05 cm³ 3 / g, sealing rate 95.8%; particle size Dv50 7.5 μm; tap density 0.35 g / cm³ 3 .

[0184] According to the Debye-Scherrer formula, the grain size of the nano-silicon particles used as encapsulation in the obtained carbon-based anode material is 4.2 nm; and the loading of the encapsulation is 15% based on the mass of the carbon-based anode material as 100%.

[0185] Example 3

[0186] (1) Commercially available porous carbon material (specific surface area of ​​1550 m²) was used. 2 / g, pore volume 0.6 cm³3 / g, average pore size is 1.62 nm, pore size distribution is 1.8 (obtained by BET test); tap density is 0.25 g / cm³. 3 After sieving, the particle size Dv50 is controlled to be 7 μm;

[0187] (2) Take 300 g of the above-treated porous carbon material as a substrate and disperse it in 2000 mL of deionized water. Add ferric nitrate (Fe(NO3)3·9H2O) to control the Fe concentration in the dispersion. 3+ The concentration was 0.5 mol / L; after stirring in an oil bath at 120℃ for 2 hours, it was transferred to a vacuum drying oven and dried at 120℃ for 12 hours, and then heat-treated at 500℃ for 2 hours under nitrogen protection to allow Fe to... 3+ It is converted into nano-iron oxide particles to obtain carbon-based anode materials.

[0188] The carbon-based anode material prepared in this embodiment has a specific surface area of ​​80 m², as determined by testing. 2 / g, pore volume 0.02 cm³ 3 / g, sealing rate 96.7%; particle size Dv50 7.5 μm; tap density 0.5 g / cm³ 3 .

[0189] Characterized by SEM and TEM, the grain size of the nano-iron oxide particles used as encapsulants in the obtained carbon-based anode material is 5.1 nm, and the loading of the encapsulants is 20% based on the mass of the carbon-based anode material as 100%.

[0190] Example 4

[0191] (1) Commercially available porous carbon material (specific surface area of ​​2108 m²) was used. 2 / g, pore volume 1.1 cm 3 The average pore size is 2.32 nm, and the pore size distribution is 1.9 (obtained by BET measurement); the tap density is 0.22 g / cm³. 3 After sieving, the particle size Dv50 is controlled to be 7 μm;

[0192] (2) Take 500 g of the above-treated porous carbon material as a substrate and disperse it in 800 mL of deionized water. Add 1.85 L of 100 g / L polyacrylic acid aqueous solution. Place the suspension in a 60℃ water bath and heat and stir for 4 h to ensure that the polyacrylic acid and porous carbon are in full contact. Then spray dry the suspension with the outlet temperature set at 90℃ and the hot air temperature at 200℃. Take out the polyacrylic acid-porous carbon composite after one spray drying and perform carbonization treatment in a nitrogen atmosphere at 300℃ to carbonize the polyacrylic acid on its surface. Then disperse the material in deionized water, add polyacrylic acid solution, and repeat the spraying 10 times to obtain carbon-based anode material.

[0193] The carbon-based anode material prepared in this embodiment has a specific surface area of ​​30 m², as determined by testing. 2 / g, pore volume 0.05 cm³ 3 / g, sealing rate 95.5%; particle size Dv50 7.5 μm; tap density 0.35 g / cm³ 3 .

[0194] Figure 4 The image shows the SEM image of the carbon-based anode material prepared in this embodiment. Characterized by SEM and TEM, the carbon used as an encapsulant in the obtained carbon-based anode material is a continuous thin film with an average thickness of about 18 nm. The loading of the encapsulant is 15% based on the mass of the carbon-based anode material as 100%.

[0195] Example 5

[0196] (1) Commercially available porous carbon material (specific surface area of ​​1850 m²) was used. 2 / g, pore volume 0.85 cm³ 3 The average pore size is 1.82 nm, and the pore size distribution is 1.7 (obtained by BET testing); the tap density is 0.27 g / cm³. 3 After sieving, the particle size Dv50 is controlled to be 7 μm;

[0197] (2) Take 300 g of the treated porous carbon as a substrate, disperse it in 3000 mL of deionized water, add 30 g of lithium carbonate (analytical grade, corresponding to a Li⁺ concentration of 0.5 mol / L), and mechanically stir in a 15℃ water bath for 2 hours to ensure that the lithium carbonate is fully dissolved and penetrates into the pores of the porous carbon. Filter the suspension to separate the solids, and dry the solid part in a 120℃ vacuum drying oven for 12 hours to completely remove moisture. Heat the dried material to 500℃ at 5℃ / min under nitrogen protection and hold for 2 hours. This process promotes the sintering of lithium carbonate at the pore openings of the porous carbon, forming a sealed plugging layer. After cooling, the carbon-based anode material is obtained.

[0198] The carbon-based anode material prepared in this embodiment has a specific surface area of ​​55 m², as determined by testing. 2 / g, pore volume is 0.04cm 3 / g, sealing rate 95.3%; particle size Dv50 7.8 μm; tap density 0.45 g / cm³ 3 .

[0199] Characterized by SEM and TEM, the lithium carbonate particles used as encapsulants in the obtained carbon-based anode material have a grain size of 7.0 nm, and the loading of the encapsulants is 8% based on the mass of the carbon-based anode material as 100%.

[0200] Example 6

[0201] The preparation process is basically the same as in Example 1, except that the porous carbon in step (1) is replaced with a raw material having the following parameters:

[0202] Specific surface area is 1912 m² 2 / g, pore volume 0.9 cm³ 3 / g, average pore size is 1.75 nm, pore size distribution is 2.2 (obtained by BET test); tap density is 0.27 g / cm³. 3 .

[0203] The specific surface area of ​​the carbon-based anode material prepared in this embodiment was tested to be 0.9 m². 2 / g, pore volume is 0.008 cm³ 3 / g, sealing rate 99%; particle size Dv50 7.5 μm; tap density 0.45 g / cm³ 3 .

[0204] Characterized by SEM and TEM, the grain size of the nano-phosphorus particles used as encapsulants in the obtained carbon-based anode material is about 2.0 nm; the loading of the encapsulants is 11% based on the mass of the carbon-based anode material of 100%.

[0205] Example 7

[0206] The preparation process is basically the same as in Example 1, except that the porous carbon in step (1) is replaced with a raw material having the following parameters:

[0207] Specific surface area is 1835 m² 2 / g, pore volume 0.9 cm³ 3 / g, average pore size is 2.05 nm, pore size distribution is 1.0 (obtained by BET test); tap density is 0.35 g / cm³. 3 .

[0208] The carbon-based anode material prepared in this embodiment has a specific surface area of ​​95 m², as determined by testing. 2 / g, pore volume is 0.135 cm³ 3 / g, sealing rate 85%; particle size Dv50 7.5 μm; tap density 0.75 g / cm³ 3 .

[0209] Characterized by SEM and TEM, the grain size of the nano-phosphorus particles used as encapsulants in the obtained carbon-based anode material is about 2.0 nm; the loading of the encapsulants is 11% based on the mass of the carbon-based anode material of 100%.

[0210] Comparative Example 1

[0211] The preparation process is basically the same as in Example 1, except that the porous carbon in step (1) is replaced with a raw material having the following parameters:

[0212] Specific surface area is 1790 m² 2 / g, pore volume 0.9 cm³ 3 / g, average pore size is 2.33 nm, pore size distribution is 0.8 (obtained by BET test); tap density is 0.35 g / cm³. 3 .

[0213] The specific surface area of ​​the carbon-based anode material prepared in this comparative example is 190 m². 2 / g, pore volume is 0.198 cm³ 3 / g, with a blocking rate of 78%; particle size Dv50 is 7.5 μm.

[0214] Characterized by SEM and TEM, the grain size of the nano-phosphorus particles used as encapsulation in the obtained carbon-based anode material is about 2.1 nm; the loading of the encapsulation is 12% based on the mass of the carbon-based anode material as 100%.

[0215] Comparative Example 2

[0216] Commercially available porous carbon material (specific surface area of ​​1850 m²) was used. 2 / g, pore volume 0.9 cm³ 3 The average pore size is 1.82 nm, and the pore size distribution is 1.6 (obtained by BET testing); the tap density is 0.3 g / cm³. 3 After sieving, the particle size Dv50 was controlled to be 7 μm. The porous carbon material was then used for subsequent electrochemical performance testing.

[0217] Comparative Example 3

[0218] Step (1) is the same as in Example 1;

[0219] (2) Take 300 g of the above-treated porous carbon material as a substrate and place it in a CVD rotary deposition furnace. Adjust the furnace temperature to 500℃, evacuate to -0.095MPa, backfill with nitrogen, maintain a nitrogen atmosphere, and maintain a pressure ≥500Pa. Use acetylene as the encapsulation gas source, with a total flow rate of 10L / min. Adjust the rotary furnace speed to a low speed of 5Hz (the highest speed of 50Hz corresponds to 3r / min), and continuously circulate gas for 20min for chemical vapor deposition. After completion, introduce nitrogen and cool to room temperature.

[0220] The specific surface area of ​​the anode material prepared in this comparative example was tested to be 1590 m². 2 / g, pore volume is 0.71 cm³ 3 / g, with a blocking rate of 21%; particle size Dv50 is 7.5 μm.

[0221] The grain size of the deposited carbon could not be calculated; the loading of the encapsulated material was 12% based on 100% carbon-based anode material mass.

[0222] Experiments revealed that acetylene has a small molecular weight and is extremely unstable. Although the deposited carbon forms a continuous thin film covering the surface of the porous carbon material, it is prone to grow on the inner wall of the pores, encroaching on the lithium storage space. The surface of the porous carbon material still retains a large pore structure and does not form a complete closed pore.

[0223] Comparative Example 4

[0224] The preparation process is basically the same as that of Comparative Example 3, with the only difference being:

[0225] In step (2), the chemical vapor deposition time is extended to 20 hours.

[0226] The specific surface area of ​​the negative electrode material prepared in this comparative example was tested to be 1.0 m². 2 / g, pore volume is 0.007cm 3 / g, with a blocking rate of 99%; particle size Dv50 is 7.5 μm.

[0227] Based on the carbon-based anode material as 100% by mass, the loading of the encapsulation is 48%.

[0228] Experiments revealed that at this point, the deposited carbon completely entered the pore structure of the porous carbon material, occupying the entire pore volume and failing to provide space for subsequent lithium storage.

[0229] Comparative Example 5

[0230] The preparation process is basically the same as in Example 2, with the only difference being:

[0231] Replace the chemical vapor deposition temperature in step (2) with 450℃.

[0232] The specific surface area of ​​the anode material prepared in this comparative example was tested to be 1135 m². 2 / g, pore volume 0.8cm 3 / g, with a blocking rate of 33%; particle size Dv50 is 7.5 μm.

[0233] According to the Debye-Scherrer formula, the grain size of the vapor-deposited silicon nanoparticles in the obtained anode material is about 1.3 nm; with the carbon-based anode material as 100% by mass, the loading of the encapsulant is 14%.

[0234] Experiments revealed that at this point, the nano-silicon particles were deposited on the inner wall of the pores, but did not form large particles to externally seal the porous carbon material.

[0235] Electrochemical performance testing:

[0236] CR2025 coin cells were assembled using the negative electrode materials prepared in each embodiment and comparative example, specifically:

[0237] (1) Preparation of positive electrode sheet: commercially available pure lithium sheet with a diameter of 18 mm and a thickness of 0.5 mm was used.

[0238] (2) Preparation of negative electrode sheet:

[0239] 1. Ingredients: Using a mixer, the negative electrode active material, Super P, SW CNT, and PAA binder are added to pure water at a mass ratio of 80:9:1:10. After high-speed stirring and dispersion, a uniform and stable negative electrode slurry is formed with a solid content of 13.07%.

[0240] 2. Coating: The thoroughly stirred negative electrode slurry is uniformly coated onto a 0.9-micron thick copper foil current collector, and then baked at 120℃ for 5 minutes to form an areal density of 1.6~2.0 mg / cm³. 2 The dense and flat negative electrode sheet between them.

[0241] 3. Sheet Forming: The dried negative electrode sheet is compacted using a roller press to improve coating density and adhesion, ensuring the electrode sheet is flat and dense. During roller pressing, the compaction density of the electrode sheet should be maintained at 0.6-0.8 g / cm³. 3 Between. After rolling, the electrode sheet is punched into several small round pieces with a diameter of 16mm by a slicing machine.

[0242] 4. Baking: Place the qualified negative electrode sheets (small round sheets) into a vacuum oven and bake at 85℃ for 10-15 hours to dry the moisture in the electrode sheets.

[0243] 5. Weighing: After baking, the electrode sheets are weighed using a 1 / 100,000 electronic balance, and 5 electrode sheets of the same weight are selected for backup.

[0244] (3) Battery assembly: Place the positive electrode, negative electrode, electrolyte, separator, nickel foam, positive and negative electrode shells and other materials required for battery assembly into a sealed glove box with a water and oxygen content of less than 0.1 ppm; stack the negative electrode shell-negative electrode-electrolyte-separator-electrolyte-positive electrode (lithium sheet)-nickel foam-positive electrode shell on the operating platform in sequence for assembly; place the assembled battery on the battery sealing machine for sealing.

[0245] 1. Routine performance testing: At 1.5 V and 25 °C, the electrode was first discharged to 0.005 V at 0.1 C, then discharged to 0.001 V at 0.08 C, then to 0.001 V at 0.05 C, and then to 0.001 V at 0.02 C, and left to stand for 10 min. Then it was charged to 1.5 V at 0.1 C and left to stand for 10 min. The charge-discharge capacity after the first cycle was recorded, and the initial coulombic efficiency was calculated. The electrode was cycled 500 times in the same manner, and the charge-discharge capacity after 500 cycles was recorded. The capacity retention rate after 500 cycles was calculated. The electrode expansion was obtained by measuring the thickness change before and after the cycle. The discharge capacity of the first cycle, the initial coulombic efficiency, the capacity retention rate after 500 cycles, and the expansion rate of the negative electrode are listed in Table 1.

[0246] Table 1

[0247]

[0248] 2. Long-cycle performance test: The capacity retention rate after 2000 cycles and after 5000 cycles was tested at a high current density of 1.0 A / g. The data are listed in Table 2.

[0249] Table 2

[0250]

[0251] 3. High compaction performance test: The initial coulombic efficiency under different compaction densities was tested, and the data are listed in Table 3.

[0252] Table 3

[0253]

[0254] 4. Rate performance test: The discharge capacity and capacity retention rate after 200 cycles were tested at different current densities from 0.1 to 5.0 A / g. The retention rate data are listed in Table 4.

[0255] Table 4

[0256]

[0257] 5. Low temperature performance test: The capacity retention rate was tested after 500 cycles at -20℃ and -40℃ and 0.1C. The data are listed in Table 5.

[0258] Table 5

[0259]

[0260] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. The specific examples used above to illustrate the present invention are only for the purpose of helping to understand the present invention and are not intended to limit the present invention. Those skilled in the art to which this invention pertains can make several simple deductions, modifications, substitutions, or combinations based on the concept of the present invention. These deductions, modifications, substitutions, or combinations also fall within the scope of the claims of the present invention.

Claims

1. A carbon-based anode material, characterized in that, It includes a porous carbon substrate and an encapsulation for closing the openings on the surface of the porous carbon substrate; The encapsulation material is discrete encapsulation particles and / or continuous encapsulation layers.

2. The carbon-based anode material according to claim 1, characterized in that, The carbon-based anode material has a cavity inside.

3. The carbon-based anode material according to claim 1, characterized in that, At least one of the following conditions must be met: (a) Specific surface area of ​​0.1~100 m² 2 / g; (b) The pore volume is 0.001~0.15 cm. 3 / g; (c) Particle size Dv50 is 2~18 μm; (d) Tap density is 0.1~1.2 g / cm³ 3 .

4. The carbon-based anode material according to claim 3, characterized in that, At least one of the following conditions must be met: (a) Specific surface area of ​​0.1~80 m² 2 / g; (b) The pore volume is 0.005~0.05cm 3 / g; (c) Particle size Dv50 is 7.0 ± 1.0 μm; (d) Tap density is 0.35~0.75 g / cm³ 3 .

5. The carbon-based anode material according to claim 1, characterized in that, A battery assembled with the aforementioned carbon-based anode material satisfies at least one of the following conditions: (1) The discharge capacity in the first week shall not be less than 1400mAh / g; (2) After 500 cycles, the capacity retention rate is not less than 85%, and the expansion rate is not higher than 5%; (3) At a current density of 1.0 A / g, the capacity retention rate is not less than 80% after 2000 cycles and not less than 72% after 5000 cycles; (4) At a current density of 5.0 A / g, the capacity retention rate is not less than 60% after 200 cycles; (5) At -20℃, the capacity retention rate after 500 cycles is not less than 68%, and at -40℃, the capacity retention rate after 500 cycles is not less than 40%.

6. The carbon-based anode material according to claim 1, characterized in that, Based on the mass of the carbon-based anode material being 100%, the mass percentage of the encapsulated material is no more than 20%.

7. The carbon-based anode material according to claim 1, characterized in that, The porous carbon substrate satisfies at least one of the following conditions: (a) Specific surface area of ​​100~2500 m² 2 / g; (b) The pore volume is 0.5~3.0 cm. 3 / g; (c) Particle size Dv50 is 1~20 μm; (d) The average pore size is 1~10 nm; (e) Aperture concentration ≥ 1, Aperture concentration = Pv50 / (Pv90 - Pv10).

8. The carbon-based anode material according to claim 7, characterized in that, The porous carbon substrate satisfies at least one of the following conditions: (a) Specific surface area of ​​1000~2100 m² 2 / g; (b) The pore volume is 0.6~2.5 cm. 3 / g; (c) Particle size Dv50 is 7.0 ± 1.0 μm; (d) The average pore size is 2.0 ± 1.0 nm; (e) Aperture concentration ≥ 1.

5.

9. The carbon-based anode material according to claim 8, characterized in that: The pore size concentration of the porous carbon substrate is 1.6~2.

5.

10. The carbon-based anode material according to claim 1, characterized in that: The material of the encapsulation particles is selected from one or more of the following: metals, non-metals, metal oxides, and inorganic salts. The encapsulation layer is selected from thin films with conductive and / or ion-conducting properties.

11. The carbon-based anode material according to claim 1, characterized in that: The metal is selected from one or more of iron, cobalt, nickel, and calcium; The nonmetal is selected from one or more of phosphorus, silicon, carbon, and sulfur; The metal oxide is selected from one or more of lithium oxide, iron oxide, nickel oxide, cobalt oxide, and zinc oxide; The inorganic salt is selected from inorganic lithium salts; The average particle size of the encapsulated particles is 1~10 nm.

12. The carbon-based anode material according to claim 10, characterized in that: The encapsulation layer is selected from polymer films or polymer films doped with conductive materials. The thickness of the encapsulation layer is no greater than 100 nm; The polymer film is selected from one or more of polyacrylic acid, polypyrrole, and polyaniline; The conductive material is selected from one or more of carbon nanotubes, carbon black, graphene, and lithium metal.

13. A method for preparing a carbon-based anode material according to any one of claims 1 to 12, characterized in that, include: Using a porous carbon substrate as raw material, it is encapsulated. After encapsulation, the openings on the surface of the porous carbon substrate are closed, and the closure rate is not less than 85%. ； R1 is the pore volume of the porous carbon substrate, and R2 is the pore volume of the carbon-based anode material obtained after encapsulation.

14. The method for preparing the carbon-based anode material according to claim 13, characterized in that, The encapsulation process includes one or more of the following: vapor deposition, liquid adsorption, and spray coating.

15. The method for preparing the carbon-based anode material according to claim 13, characterized in that, The closure rate shall not be less than 95%.

16. A negative electrode sheet, characterized in that, Including the carbon-based anode material according to any one of claims 1 to 12.

17. A secondary battery, characterized in that, Includes the negative electrode sheet according to claim 16.

18. An electrical-related device, characterized in that, Includes the secondary battery according to claim 17.

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