Carbon anode active materials and preparation methods, secondary batteries and power devices

Abstract

This invention discloses a carbon anode active material and its preparation method, a secondary battery, and an electrical device. The carbon anode active material has a porous structure and an active specific surface area of ​​0.03 m². 2 / g-0.12m 2 / g, and the pore volume of the carbon anode active material is greater than or equal to 0.005cm³. 3 / g. Therefore, carbon anode active materials have suitable active specific surface area and high pore volume. When used as battery anode active materials, they can form an effective SEI film during the first charge cycle. Furthermore, during battery cycle charging and discharging, carbon anode active materials consume less active lithium, which can effectively improve the long-term electrical performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery anode materials, specifically to carbon anode active materials and their preparation methods, secondary batteries, and electrical devices. Background Technology

[0002] Secondary batteries have advantages such as high energy density, long cycle life, and good rate performance, and are widely used in portable electronic devices, electric vehicles, and energy storage systems. During the cycling process of secondary batteries, the negative electrode active material (such as carbon materials like graphite) expands and continuously exposes new interfaces of internal pores. These new interfaces continue to react with the electrolyte, leading to the growth of the SEI film (solid electrolyte interphase) and accelerated battery capacity degradation.

[0003] Therefore, current carbon anode active materials and preparation methods, as well as secondary batteries and power devices, still need improvement. Summary of the Invention

[0004] This invention is based on the inventor's discoveries and understanding of the following facts and problems:

[0005] During battery cycling, as the carbon anode active materials such as graphite expand, the anode active materials will continuously expose new interfaces of internal pores (active sites that are easy to react with the electrolyte). These new interfaces of pores will continue to react with the electrolyte, causing the SEI film to continue to grow and consuming more active lithium, resulting in rapid decline in battery capacity and a significant decrease in battery cycle performance.

[0006] In view of this, the present invention aims to at least alleviate or solve at least one of the aforementioned problems to some extent.

[0007] In one aspect, the present invention provides a carbon anode active material. According to an embodiment of the present invention, the carbon anode active material has a porous structure, and the active specific surface area of ​​the carbon anode active material is 0.03 m². 2 / g-0.12m 2 / g, and the pore volume of the carbon anode active material is greater than or equal to 0.005cm³. 3 / g. Therefore, carbon anode active materials have suitable active specific surface area and high pore volume. When used as battery anode active materials, they can form an effective SEI film during the first charge cycle. Furthermore, during battery cycle charging and discharging, carbon anode active materials consume less active lithium, which can effectively improve the long-term electrical performance of the battery.

[0008] According to an embodiment of the present invention, the active specific surface area of ​​the carbon anode active material is 0.03 m². 2 / g-0.08m 2 / g, which is beneficial for further improving the long-term electrical performance of the battery (e.g., cycle performance and storage performance).

[0009] According to an embodiment of the present invention, the pore volume of the carbon anode active material is 0.005 cm³. 3 / g-0.1cm 3 / g.

[0010] According to embodiments of the present invention, the carbon anode active material contains one or more of micropores, mesopores, or macropores. This allows the carbon anode active material to have a more suitable pore volume, thereby improving the long-term electrical performance of the battery.

[0011] According to embodiments of the present invention, based on the total pore volume in the carbon anode active material, the volume content of the micropores is less than or equal to 10%, optionally less than or equal to 5%; and / or, based on the total pore volume in the carbon anode active material, the volume content of the mesopores is 60%-95%, optionally 70%-90%; and / or, based on the total pore volume in the carbon anode active material, the volume content of the macropores is less than or equal to 25%, optionally 5%-20%.

[0012] According to an embodiment of the present invention, the carbon anode active material satisfies at least one of the following conditions (1)-(3): (1) the specific surface area of ​​the carbon anode active material is 1.0 m². 2 / g-8.0m 2 / g, optional 2m 2 / g-5m 2 / g; (2) The volume distribution particle size Dv50 of the carbon anode active material is 5μm-50μm, and can be selected as 10μm-30μm; (3) The porosity of the carbon anode active material is 20%-40%, and can be selected as 25%-35%. Therefore, it is beneficial to further improve the electrochemical performance of the carbon anode active material.

[0013] According to embodiments of the present invention, the carbon anode active material contains oxygen-containing functional groups, including one or more of lactones, ethers, phenols, carboxyl groups, acid anhydrides, and carbonyl groups. The presence of these oxygen-containing functional groups facilitates the reaction of the carbon anode active material with the electrolyte during the first charging cycle to form an effective SEI film.

[0014] In another aspect, the present invention provides a method for preparing the aforementioned carbon anode active material. According to an embodiment of the present invention, the method for preparing the aforementioned carbon anode active material includes: providing a carbon material; oxidizing the carbon material using an oxidizing gas probe to obtain an intermediate carbon material; and reducing the intermediate carbon material using a reducing gas to obtain the carbon anode active material, wherein the carbon anode active material has a porous structure and an active specific surface area of ​​0.03 m². 2 / g-0.12m 2 / g, and the pore volume of the carbon anode active material is greater than or equal to 0.005cm³. 3 / g. Therefore, the carbon anode active material prepared by this method has a suitable active specific surface area and pore volume. The carbon anode active material can not only form an effective SEI film during the first charge cycle, but also consume less active lithium during the charge-discharge cycle, thereby effectively improving the long-term electrical performance of the battery.

[0015] According to embodiments of the present invention, the oxidizing gas probe includes one or more of oxygen, air, chlorine, nitrogen oxides, sulfur trioxide, and argon plasma. Thus, all of the above gas probes possess a certain degree of oxidizing property, enabling them to locate active sites (including unexposed sites) on the surface of carbon materials such as graphite, and oxidize the active sites in the carbon materials, facilitating the passivation of some sites through subsequent reduction of oxygen-containing functional groups.

[0016] According to embodiments of the present invention, the reducing gas includes one or more of hydrogen, carbon monoxide, hydrogen sulfide, sulfur dioxide, ammonia, olefins, and alkynes. All of the above gases have good reducing properties and can reduce oxygen-containing functional groups, thereby reducing the active sites in the carbon material.

[0017] According to embodiments of the present invention, the oxidizing gas probe comprises oxygen and the reducing gas comprises hydrogen; or, the oxidizing gas probe comprises air and the reducing gas comprises carbon monoxide; or, the oxidizing gas probe comprises argon plasma and the reducing gas comprises ammonia. Thus, the reducing gas and the oxidizing gas probe are well-matched, and the reducing gas can react more specifically with oxygen-containing functional groups, thereby reducing and passivating the active sites on the surface of the carbon material.

[0018] According to an embodiment of the present invention, the oxidation treatment temperature is 300°C-500°C, and / or the oxidation treatment time is 8h-16h. Thus, most, or even almost all, of the edge sites of carbon materials can be oxidized through oxidation treatment.

[0019] According to an embodiment of the present invention, the reduction treatment temperature is 800℃-1000℃, and / or the reduction treatment time is 6h-15h. Thus, the reduction treatment can reduce and passivate some oxygen-containing functional groups, while retaining some sites to react with the electrolyte during the first charging cycle to form an effective SEI film.

[0020] According to embodiments of the present invention, the carbon material includes one or more of natural graphite, artificial graphite, hard carbon, soft carbon, carbon fiber, and mesophase carbon microspheres. All of the above-mentioned carbon materials can be treated by the method proposed in this invention, and the electrochemical performance of the treated carbon materials can be significantly improved.

[0021] In another aspect, the present invention provides a secondary battery comprising a negative electrode sheet, the negative electrode sheet comprising the aforementioned carbon negative electrode active material. Thus, the secondary battery possesses all the characteristics and advantages of the aforementioned carbon negative electrode active material, which will not be repeated here. In summary, the carbon negative electrode active material can react with the electrolyte during the first charge cycle of the secondary battery to form an effective SEI film. Furthermore, during cycling and storage, the carbon negative electrode active material in the negative electrode sheet consumes less active lithium, which is beneficial for improving the long-term cycle performance and storage performance of the battery.

[0022] In another aspect, the present invention provides an electrical device. According to an embodiment of the invention, the electrical device includes the aforementioned secondary battery. Thus, the electrical device possesses all the features and advantages of a secondary battery, which will not be repeated here. Attached Figure Description

[0023] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0024] Figure 1 A flowchart of a method for preparing a carbon anode active material according to an embodiment of the present invention is shown. Detailed Implementation

[0025] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0026] In one aspect, the present invention provides a carbon anode active material. According to an embodiment of the present invention, the carbon anode active material has a porous structure, and the active specific surface area of ​​the carbon anode active material can be 0.03 m². 2 / g-0.12m 2 / g, for example, the active specific surface area of ​​a carbon anode active material can be 0.03m². 2 / g, 0.05m 2 / g, 0.07m 2 / g, 0.09m 2 / g, 0.10m 2 / g, 0.12m 2 / g, and the pore volume of the carbon anode active material is greater than or equal to 0.005cm³. 3 / g, for example, the pore volume of a carbon anode active material can be 0.005 cm³. 3 / g, 0.0053cm 3 / g, 0.0055cm 3 / g, 0.0058cm 3 / g, 0.006cm 3 / g etc. Therefore, the carbon anode active material possesses a suitable active specific surface area and pore volume. Using this carbon anode active material as the battery's anode active material, it can fully react with the electrolyte during the first charge cycle to form an effective SEI film. Furthermore, during subsequent charge and discharge cycles, this carbon anode active material does not expose excessive active sites, thereby reducing the consumption of active lithium during subsequent charge and discharge cycles. This effectively improves the battery's long-term electrical performance, resulting in excellent cycle stability and a longer service life.

[0027] Preferably, the active specific surface area of ​​the carbon anode active material can be 0.03 m². 2 / g-0.08m 2 / g, for example, the active specific surface area of ​​a carbon anode active material can be 0.03m². 2 / g, 0.04m 2 / g, 0.05m 2 / g, 0.06m 2 / g, 0.07m 2 / g, 0.08m 2 / g etc., which is conducive to further improving the performance of carbon anode active materials. Using carbon anode active materials as the anode active materials of batteries can further improve the cycle stability of batteries and extend the service life of batteries.

[0028] Preferably, the pore volume of the carbon anode active material can be 0.005 cm³. 3 / g-0.1cm 3 / g, for example, the pore volume of a carbon anode active material can be 0.005 cm³. 3 / g, 0.007cm 3 / g, 0.01cm 3 / g, 0.03cm 3 / g, 0.05cm 3 / g, 0.08cm 3 / g, 0.1cm 3 / g, etc., thus, the carbon anode active material has a large pore volume, which is beneficial to further improve the performance of the carbon anode active material.

[0029] According to some embodiments of the present invention, the specific surface area of ​​the carbon anode active material can be 1.0 m². 2 / g-8.0m 2 / g, for example, the specific surface area of ​​a carbon anode active material can be 1.0m². 2 / g, 2.0m 2 / g, 4.0m 2 / g, 6.0m 2 / g, 8.0m 2 The carbon anode active material has a suitable specific surface area, allowing for sufficient contact with the electrolyte during charge and discharge, which is beneficial for improving the battery's charge and discharge performance. Preferably, the specific surface area of ​​the carbon anode active material can be 2 m² / g. 2 / g-5m 2 / g, for example, the specific surface area of ​​carbon anode active materials can be 2m². 2 / g、3m 2 / g、4m 2 / g、5m 2 / g, etc., which is beneficial to further improve the performance of carbon anode active materials.

[0030] According to some embodiments of the present invention, the volume distribution particle size Dv50 of the carbon anode active material is 5μm-50μm. For example, the volume distribution particle size Dv50 of the carbon anode active material can be 5μm, 8μm, 10μm, 20μm, 30μm, 40μm, 50μm, etc. Thus, the carbon anode active material has a suitable volume distribution particle size, enabling it to have sufficient contact with the electrolyte during charging and discharging, thereby improving the battery's electrical performance. Preferably, the volume distribution particle size Dv50 of the carbon anode active material can be 10μm-30μm. For example, the volume distribution particle size Dv50 of the carbon anode active material can be 10μm, 12μm, 15μm, 18μm, 22μm, 25μm, 27μm, 30μm, etc. Thus, the carbon anode active material has an even better volume distribution particle size, which is beneficial for further improving the performance of the carbon anode active material.

[0031] According to some embodiments of the present invention, the carbon anode active material contains one or more of the following: micropores (typically with a pore size less than 2 nm), mesopores (typically with a pore size of 2 nm to 50 nm), and / or macropores (typically with a pore size greater than 50 nm), thereby giving the carbon anode active material a more suitable pore volume, which is more conducive to improving the long-term electrical performance of the battery.

[0032] According to some embodiments of the present invention, based on the total pore volume in the carbon anode active material, the micropore volume content is less than or equal to 10%, and optionally less than or equal to 5%.

[0033] According to some embodiments of the present invention, based on the total pore volume in the carbon anode active material, the mesopore volume content is 60%-95%, optionally 70%-90%.

[0034] According to some embodiments of the present invention, based on the total pore volume in the carbon anode active material, the volume content of macropores is less than or equal to 25%, and can be selected as 5%-20%.

[0035] When the carbon anode active material has an appropriate amount of micropores, mesopores and / or macropores, it is beneficial to further increase the contact area between the carbon anode active material and the electrolyte, thereby further improving the overall performance of the battery.

[0036] According to some embodiments of the present invention, the porosity of the carbon anode active material can be 20%-40%, for example, 20%, 22%, 26%, 30%, 32%, 36%, 38%, 40%, etc. This high porosity is beneficial for increasing the contact area between the carbon anode active material and the electrolyte, thereby improving battery performance. Preferably, the porosity of the carbon anode active material can be 25%-35%, for example, 25%, 28%, 31%, 33%, 35%, etc. This suitable porosity results in a larger contact area between the active material and the electrolyte, further improving battery performance.

[0037] According to an embodiment of the present invention, the carbon anode active material contains oxygen-containing functional groups, wherein the oxygen-containing functional groups include one or more of lactones, ethers, phenols, carboxyl groups, acid anhydrides, and carbonyl groups, thereby enabling the oxygen-containing functional groups to fully react with the electrolyte during the first charge cycle of the battery to form an effective SEI film.

[0038] In another aspect, the present invention provides a method for preparing carbon anode active materials. According to embodiments of the present invention, refer to... Figure 1 The method for preparing carbon anode active materials may include the following steps:

[0039] S100: Provides carbon materials.

[0040] According to embodiments of the present invention, the carbon material may include one or more of natural graphite, artificial graphite, hard carbon, soft carbon, carbon fiber, and mesophase carbon microspheres. According to some embodiments of the present invention, the carbon material may be natural graphite, artificial graphite, hard carbon, soft carbon, carbon fiber, or mesophase carbon microspheres. According to other embodiments of the present invention, the carbon material may include two or more of natural graphite, artificial graphite, hard carbon, soft carbon, carbon fiber, and mesophase carbon microspheres.

[0041] Carbon materials typically contain oxygen-containing functional groups, which readily react with the electrolyte during battery charging and discharging. Furthermore, carbon materials tend to expand during battery cycling, continuously exposing new interfaces within their internal pores. These new interfaces readily react with the electrolyte, leading to an increase in the electrolyte-exposed area (SEI) and the consumption of a significant amount of active lithium. Taking graphite anode materials as an example, during battery cycling, graphite expands, exposing new interfaces within its internal pores. These new interfaces readily react with the electrolyte, causing the SEI to continue to increase and further consuming active lithium, resulting in a decline in battery cycle performance and storage capacity.

[0042] S200: Carbon materials are oxidized using an oxidizing gas probe to obtain intermediate carbon materials;

[0043] According to embodiments of the present invention, carbon materials are oxidized using an oxidizing gas probe. The oxidizing gas probe can locate the end faces of the carbon material, search for active sites on the surface of the carbon material, and find interfaces that are easily exposed due to expansion (active sites that are easily exposed but not initially exposed). These active sites are then oxidized to oxygen-containing functional groups, resulting in intermediate carbon material. Subsequent reduction treatment can passivate some of these oxygen-containing functional groups. After the aforementioned interfacial active sites are passivated, they are less likely to react with the electrolyte during battery cycle charging and discharging, thereby improving the long-term cycle performance and storage performance of the battery. It should be noted that the more active sites on the surface of the carbon material, the larger the active specific surface area. In this invention, by using an oxidizing gas probe to locate active sites and oxidize them to oxygen-containing functional groups, followed by reduction treatment to passivate some of these oxygen-containing functional groups, the content of active sites can be controlled, and the active specific surface area of ​​the material can be kept within a suitable range, thereby improving the long-term electrical performance of the battery.

[0044] According to embodiments of the present invention, the oxidizing gas probe may include one or more of oxygen, air, chlorine, nitrogen oxides, sulfur trioxide, and argon plasma. These oxidizing gases can effectively search for active sites in carbon materials such as graphite, and can locate most or almost all easily exposed active sites, oxidizing them to oxygen-containing functional groups so that the active sites can be passivated by subsequent reduction. According to some embodiments of the present invention, the oxidizing gas probe may be oxygen, air, chlorine, nitrogen oxides, sulfur trioxide, or argon plasma. According to other embodiments of the present invention, the oxidizing gas probe may include two or more of oxygen, air, chlorine, nitrogen oxides, sulfur trioxide, and argon plasma.

[0045] According to embodiments of the present invention, the oxygen-containing functional groups may include one or more of lactones, ethers, phenols, carboxyl groups, acid anhydrides, and carbonyl groups. Thus, a certain amount of the above-mentioned oxygen-containing functional groups can react with the electrolyte during the first charge cycle of the battery to form an effective SEI film. According to some embodiments of the present invention, the oxygen-containing functional groups in the intermediate carbon material may be lactones, ethers, phenols, carboxyl groups, acid anhydrides, or carbonyl groups. According to other embodiments of the present invention, the oxygen-containing functional groups in the intermediate carbon material may include two or more of lactones, ethers, phenols, carboxyl groups, acid anhydrides, and carbonyl groups. It should be noted that the carbon material itself may also contain a certain amount of oxygen-containing functional groups, and the oxygen-containing functional groups present in the carbon material itself may also include one or more of lactones, ethers, phenols, carboxyl groups, acid anhydrides, and carbonyl groups.

[0046] According to embodiments of the present invention, the oxidation temperature of the carbon material can be between 300°C and 500°C. For example, the oxidation temperature can be 300°C, 320°C, 350°C, 370°C, 400°C, 430°C, 450°C, 480°C, 500°C, etc. When the temperature is set within the above range, the oxidizing gas probe can oxidize most or even almost all of the active sites on the end face of the carbon material. This facilitates the partial reduction of the active sites on the surface of the carbon material (including active sites that may be exposed when the carbon material expands during cycling) through subsequent reduction. The reduced active sites are less likely to react with the electrolyte, thereby improving the cycle performance and storage performance of the battery. The inventors have found that if the oxidation temperature of the carbon material is too high, for example, above 800°C, the carbon material may burn; if the oxidation temperature is too low, for example, below 100°C, it is difficult to achieve oxidation of the active sites of the carbon material.

[0047] According to embodiments of the present invention, the oxidation treatment time for carbon materials can be 8-16 hours, for example, 8 hours, 10 hours, 12 hours, 15 hours, 16 hours, etc. When the oxidation treatment time is set within the above range, the oxidizing gas probe can fully react with the carbon material, causing most or even almost all active sites to be oxidized. The inventors have found that if the oxidation treatment time for carbon materials is too short, for example, less than 1 hour, it is difficult to ensure sufficient reaction between the oxidizing gas probe and the carbon material; if the oxidation treatment time for carbon materials is too long, for example, greater than 24 hours, it may cause the exfoliation of graphite and other carbon materials, resulting in the loss of lithium intercalation activity of the carbon material.

[0048] S300: The intermediate carbon material is reduced by a reducing gas to obtain a carbon anode active material.

[0049] According to an embodiment of the present invention, after oxidizing a carbon material to obtain an intermediate carbon material, the intermediate carbon material is then reduced using a reducing gas to partially reduce the oxygen-containing functional groups in the intermediate carbon material, thereby obtaining a carbon anode active material. This carbon anode active material has a porous structure and an active specific surface area of ​​0.03 m². 2 / g-0.12m 2 / g, and the pore volume of the carbon anode active material is greater than or equal to 0.005cm³. 3 / g. During the oxidation process, the active sites on the surface of the carbon material, as well as those easily exposed during expansion, can be oxidized by an oxidizing gas probe to generate oxygen-containing functional groups. Reduction treatment of the intermediate carbon material with a reducing gas can passivate some of these oxygen-containing functional groups. After the oxidation-reduction process, the active sites are less likely to react with the electrolyte during battery cycling, thus reducing the consumption of active lithium during cycling and significantly improving the long-term cycle performance and storage performance of the battery. Furthermore, the retained oxygen-containing functional groups can still react with the electrolyte during the first charge cycle to form an effective SEI film. After oxidation and reduction treatments of the carbon material, the active specific surface area of ​​the resulting carbon anode active material is 0.03 m². 2 / g-0.12m 2 / g, and the pore volume of the carbon anode active material is greater than or equal to 0.005cm³. 3 / g, the carbon anode active material has good long-term electrical properties.

[0050] According to embodiments of the present invention, the reducing gas may include one or more of hydrogen, carbon monoxide, hydrogen sulfide, sulfur dioxide, ammonia, alkenes, and alkynes. These reducing gases can react with oxygen-containing functional groups, reducing and passivating oxygen-containing functional groups such as lactones, ethers, phenols, carboxyl groups, acid anhydrides, and carbonyl groups. According to some embodiments of the present invention, the reducing gas may be hydrogen, carbon monoxide, hydrogen sulfide, sulfur dioxide, ammonia, alkenes, or alkynes. According to other embodiments of the present invention, the reducing gas may include two or more of hydrogen, carbon monoxide, hydrogen sulfide, sulfur dioxide, ammonia, alkenes, and alkynes.

[0051] According to one embodiment of the present invention, the oxidizing gas probe includes oxygen, and the reducing gas includes hydrogen. According to another embodiment of the present invention, the oxidizing gas probe includes air, and the reducing gas includes carbon monoxide. According to yet another embodiment of the present invention, the oxidizing gas probe includes argon plasma, and the reducing gas includes ammonia. The oxidizing gas probes and reducing gases in the above embodiments have good matching, which can better achieve the reduction and passivation of oxygen-containing functional groups, thereby being more beneficial to improving the long-term cycle performance and storage performance of the battery.

[0052] According to embodiments of the present invention, the reduction treatment temperature can be 800℃-1000℃, for example, 800℃, 830℃, 850℃, 880℃, 900℃, 920℃, 950℃, 970℃, 1000℃, etc. When the reduction treatment temperature is set within the above range, the reducing gas can reduce the oxygen-containing functional groups, causing some of the oxygen-containing functional groups to be reduced. The oxidized active sites are reduced and passivated. The passivated sites are less likely to react with the electrolyte during battery cycling, thereby effectively improving the long-term cycle performance and storage performance of the battery. The inventors have found that if the reduction treatment temperature is too low, for example, below 800℃, it is difficult to achieve reduction passivation; if the reduction treatment temperature is too high, the carbon material may undergo methanation or carbon deposition, which is detrimental to improving battery performance.

[0053] According to embodiments of the present invention, the reduction treatment time can be 6h-15h, for example, 6h, 8h, 10h, 13h, 15h, etc. The reduction treatment time is set within the above range. The reducing gas can reduce and passivate the oxidized active sites, while retaining some sites to react with the electrolyte during the first charging cycle to form an effective SEI film. The inventors have found that if the reduction treatment time is too short, for example, less than 6h, too many oxidation sites will remain, consuming more active lithium and hindering battery performance improvement. If the reduction treatment time is too long, for example, more than 15h, insufficient sites may occur, making it difficult to ensure the formation of an effective SEI film during the first charging cycle.

[0054] In another aspect, the present invention provides a secondary battery comprising a negative electrode sheet, the negative electrode sheet comprising the aforementioned carbon negative electrode active material. Thus, this secondary battery possesses all the characteristics and advantages of the aforementioned carbon negative electrode active material, which will not be repeated here. In summary, this secondary battery exhibits excellent long-term cycle performance and storage performance.

[0055] According to embodiments of the present invention, in a secondary battery, the negative electrode sheet may further include a first conductive agent, a first binder, a thickener, etc. According to some embodiments of the present invention, the first conductive agent may include one or more of carbon nanotubes, carbon black, carbon fibers, graphene, etc.; the first binder may include one or more of polyvinyl alcohol, polyurethane, polyacrylate, polyvinylidene fluoride, nitrile rubber, epoxy resin, vinyl acetate resin, chlorinated rubber, etc.; and the thickener may include sodium carboxymethyl cellulose, etc.

[0056] According to some embodiments of the present invention, in a secondary battery, the negative electrode sheet may further include a negative current collector, which may be copper foil, aluminum foil, etc.

[0057] According to embodiments of the present invention, the battery may further include a positive electrode sheet, a separator, and an electrolyte. According to some embodiments of the present invention, the positive electrode sheet includes a positive current collector and a positive active material layer. The positive current collector may be copper foil, aluminum foil, etc. The positive active material layer may include a positive active material, a second conductive agent, and a second binder. The positive active material may include one or more of lithium iron phosphate, nickel-cobalt-manganese ternary materials, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium vanadium oxide, lithium ferrite, etc. The second conductive agent may include one or more of carbon nanotubes, carbon black, carbon fibers, graphene, etc. The second binder may include one or more of polyvinyl alcohol, polyurethane, polyacrylate, polyvinylidene fluoride, nitrile rubber, epoxy resin, vinyl acetate resin, chlorinated rubber, etc.

[0058] The present invention does not impose any particular limitation on the specific material of the separator, and those skilled in the art can select it according to actual needs. Similarly, the present invention does not impose any particular limitation on the specific components of the electrolyte, and those skilled in the art can select and adjust them according to actual needs.

[0059] In another aspect, the present invention provides an electrical device. According to an embodiment of the invention, the electrical device includes the aforementioned secondary battery. Thus, the electrical device possesses all the features and advantages of the aforementioned secondary battery, which will not be repeated here. In general, the electrical device has good overall performance and good stability.

[0060] According to some embodiments of the present invention, the electrical device can be a vehicle. According to some embodiments of the present invention, the vehicle may further include a chassis and a body disposed on the upper part of the chassis, and the electrical device satisfies at least one of the following conditions: the electrical device is located on the side of the chassis closer to the body; the electrical device is located on the side of the chassis away from the body; the electrical device is located inside the chassis.

[0061] The present invention will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments below are merely illustrative and do not limit the scope of the invention in any way. Furthermore, in the following embodiments, unless otherwise specified, the materials and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the later embodiments, conditions and methods known in the art can be used for processing.

[0062] Example 1

[0063] Preparation of carbon anode active materials

[0064] Weigh out NG-II-18-365 type graphite (Dv50 is 18.0μm±2.0μm, interlayer spacing d002 is 0.3358nm±0.0003nm, tap density is 1.05g / cm³). 3 The compaction density at 40000N is 1.60 g / cm³. 3 The true density is 2.22 g / cm³. 3 ±0.02g / cm 3 Its specific surface area is 2.0 m². 2 / g±0.5m 21000g of a carbon anode active material (with an initial discharge specific capacity of 365.0 mA·h / g) was placed in a tube furnace. Oxygen was continuously introduced at a flow rate of 50 mL / min at room temperature, and then the temperature was increased to 300℃ at a heating rate of 10℃ / min and held for 12 h (oxidation treatment). The temperature was then reduced to room temperature. Hydrogen was continuously introduced at a flow rate of 50 mL / min for 1 h, and then the temperature was increased to 800℃ at a heating rate of 10℃ / min and held for 6 h (reduction treatment). The temperature was then reduced to room temperature.

[0065] Preparation of the positive electrode sheet

[0066] A lithium-containing nickel-cobalt-manganese (NCM811) ternary material, conductive agent carbon black, binder polyvinylidene fluoride (PVDF), and N-methylpyrrolidone (NMP) were mixed evenly in a weight ratio of 97.36:28.86:2.7:1.1 to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto a positive electrode current collector, followed by drying, cold pressing, and slitting to obtain a positive electrode sheet.

[0067] Preparation of the negative electrode sheet

[0068] The carbon anode active material, conductive carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) prepared above were dissolved in deionized water at a weight ratio of 96.2:0.8:0.8:1.2 and mixed evenly to prepare a negative electrode slurry. The negative electrode slurry was uniformly coated on the negative electrode current collector copper foil, and then dried, cold-pressed, and slit to obtain the negative electrode sheet.

[0069] Preparation of Electrolyte

[0070] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed uniformly at a volume ratio of 3:7. Based on 100 parts by mass of the total mass of the mixed organic solvent, 12.5 parts by mass of lithium LiPF6 were added to dissolve LiPF6 in the organic solvent. The mixture was stirred evenly to obtain the electrolyte.

[0071] [Preparation of Lithium-ion Batteries]

[0072] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide insulation. The cells are then wound to obtain a bare cell. Tabs are welded onto the bare cell, which is then placed in an aluminum casing and baked at 80°C to remove moisture. Electrolyte is then injected and the casing is sealed, resulting in a non-charged battery. This non-charged battery then undergoes a series of processes including settling, hot and cold pressing, formation, shaping, and capacity testing to obtain the lithium-ion battery product of Example 1.

[0073] Example 2

[0074] In the preparation process of the carbon negative electrode active material in Example 2, the oxidation atmosphere was air, the oxidation temperature was 500℃, and the oxidation time (the holding time of the oxidation process) was 16h; the reduction atmosphere was carbon monoxide, the reduction temperature was 1000℃, and the reduction time (the holding time of the reduction process) was 10h. The other steps of Example 2 were the same as those of Example 1.

[0075] Example 3

[0076] In the preparation process of the carbon negative electrode active material in Example 3, the oxidation atmosphere was argon plasma, the oxidation treatment temperature was 300℃, and the oxidation treatment time was 8h; the reduction atmosphere was ammonia, the reduction treatment temperature was 900℃, and the reduction treatment time was 15h. The other steps of Example 3 were the same as those of Example 1.

[0077] Example 4

[0078] In the preparation of the carbon anode active material in Example 4, the oxidation treatment temperature was 400℃, and the other steps were the same as in Example 1.

[0079] Blank example 1

[0080] NG-II-18-365 type graphite was used as the carbon anode active material, and the other steps were the same as in Example 1.

[0081] Blank example 2

[0082] Using NG-I-18-363 type graphite (Dv50 18.0μm±2.0μm, interlayer spacing d002 0.3358nm±0.0003nm, tap density 1.05g / cm³), 3 The compaction density at 40000N is 1.65 g / cm³. 3 The true density is 2.23 g / cm³. 3 ±0.03g / cm 3 Its specific surface area is 2.0 m². 2 / g±0.5m 2 The carbon anode active material is selected with a first discharge specific capacity ≥363.0 mA·h / g, and the other steps are the same as in Example 1.

[0083] Comparative Example 1

[0084] The reduction treatment temperature of Comparative Example 1 was 500°C, and the other steps of Comparative Example 1 were the same as those of Example 1.

[0085] Comparative Example 2

[0086] The oxidation treatment temperature of Comparative Example 2 was 600°C, and the other steps of Comparative Example 2 were the same as those of Example 2.

[0087] Comparative Example 3

[0088] The oxidation treatment temperature of Comparative Example 3 was 100°C, and the other steps of Comparative Example 3 were the same as those of Example 3.

[0089] Comparative Example 4

[0090] Using NG-I-18-363 graphite as the carbon material, the preparation process and other steps were the same as in Example 1.

[0091] To more clearly compare the graphite processing conditions in each embodiment, comparative example, and blank example, the corresponding data are recorded in Table 1 below.

[0092] Table 1. Graphite processing conditions in each embodiment, comparative example, and blank example.

[0093]

[0094] [Battery Performance Test]

[0095] 1. Battery capacity retention test

[0096] Taking Example 1 as an example, the battery capacity retention rate test process is as follows: At 25°C, the lithium-ion battery of Example 1 is charged to 4.3V at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 4.3V, left to rest for 5 minutes, and then discharged to 2.8V at 1 / 3C. The resulting capacity is recorded as the initial capacity C0. The above steps are repeated for the same battery, and the discharge capacity Cn of the battery after the nth cycle is recorded. Then, the battery capacity retention rate Pn after each cycle is Pn = Cn / C0*100%. With the 100 points P1, P2...P100 as the vertical axis and the corresponding number of cycles as the horizontal axis, the capacity retention rate of the lithium-ion battery of Example 1 versus the number of cycles can be obtained as a curve.

[0097] In this test, the first cycle corresponds to n=1, the second cycle to n=2, ..., the 100th cycle to n=100. P100 is the capacity retention rate of the battery after 100 cycles under the above test conditions.

[0098] The battery capacity retention rate test methods for other embodiments, comparative examples, and blank examples are the same as above. The capacity retention rate of the battery in blank example 1 after 100 cycles is taken as 100% as the baseline. The capacity retention rate of each embodiment and comparative example after 100 cycles is divided by the capacity retention rate of the battery in blank example 1 after 100 cycles, and the result is taken as the capacity retention improvement rate and recorded in Table 2.

[0099] 2. Battery DC impedance test

[0100] Taking Example 1 as an example, the DC impedance test process of the battery is as follows: At 25°C, the lithium-ion battery of Example 1 is charged to 4.3V at a constant current of 1 / 3C, and then charged to a current of 0.05C at a constant voltage of 4.3V. After resting for 5 minutes, the voltage V1 is recorded. Then, it is discharged at 1 / 3C for 30 seconds, and the voltage V2 is recorded. Then, (V2-V1) / (1 / 3C) is used to obtain the internal resistance DCR1 of the battery after the first cycle. The above steps are repeated for the same battery, and the internal resistance DCRn of the battery after the nth cycle (n=1, 2, 3……100) is recorded at the same time. The 100 points of DCR1, DCR2, DCR3……DCR100 are plotted on the vertical axis, and the corresponding number of cycles is plotted on the horizontal axis to obtain the curve of the discharge DCR of the lithium-ion battery of Example 1 versus the number of cycles.

[0101] In this test, the first cycle corresponds to n=1, the second cycle to n=2, ..., the 100th cycle to n=100. The increase rate of battery internal resistance = (DCRn-DCR1) / DCR1*100%.

[0102] The battery DC impedance testing process for other embodiments, comparative examples, and blank examples is the same as above. Taking the internal resistance increase rate of the battery in blank example 1 after 100 cycles as 100%, the internal resistance increase rate of each embodiment and comparative example after the 100th cycle is divided by the internal resistance increase rate of the battery in blank example 1 after 100 cycles, and the result is recorded as the internal resistance improvement rate in Table 2.

[0103] 3. Battery first-efficiency test

[0104] At 25°C, the secondary batteries prepared in each blank example, example, and comparative example were charged at a constant current rate of 1C to the charging cutoff voltage V3 (e.g., 5mV), then charged at a constant voltage until the current ≤0.05C, and allowed to stand for 5 minutes. Next, the secondary batteries prepared in each blank example, example, and comparative example were discharged at a constant current rate of 1C to the cutoff voltage V4 (e.g., 2.0V), and allowed to stand for 5 minutes. This constitutes the first charge-discharge cycle. The first charge capacity and first discharge capacity of each secondary battery were recorded. The first efficiency (first coulombic efficiency) is the ratio of the first discharge capacity to the first charge capacity. The first efficiency test results are recorded in Table 2.

[0105] [Physicochemical Properties Testing]

[0106] 1. BET specific surface area and pore volume test

[0107] The specific surface area of ​​the negative electrode active material is a well-known concept in the art, and can be tested using methods known in the art for each blank example, embodiment, and comparative sample. For example, it can be tested using the nitrogen adsorption specific surface area analysis method according to GB / T 19587-2017, and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis can be performed using a Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, USA, and the test results are recorded in Table 2.

[0108] According to GB / T 21650.2-2008, the nitrogen adsorption-desorption pore volume analysis test method was used to test the samples of each blank example, example and comparative example, and the results were calculated by the BJH (Barrett-Joiner-Halenda) method. The nitrogen adsorption-desorption volume analysis test can be performed by the ASAP 2460 whole pore size analyzer of Micromeritics, USA. The test results are recorded in Table 2.

[0109] 2. Active specific surface area test

[0110] Taking Example 1 as an example, the test was conducted using an AUTOCHEM II 2920 fully automated chemisorption analyzer from Micromeritics, USA. A 0.1g sample of the negative electrode active material was placed in a sample tube and tested under a vacuum of 10... -4 After treatment at 950℃ for 2 hours, oxygen adsorption was carried out at 300℃ for 10 hours. Mass spectrometry signals of desorbed CO and CO2 from 300℃ to 950℃ were collected, and the area S was obtained by integration. Based on the oxygen atom adsorption area of ​​0.083 nm... 2 Calculate the active specific surface area (ASA). The calculation formula is as follows:

[0111] ASA(m 2 / g)=0.083×S×10 12 m 2 / g.

[0112] The testing process for the active specific surface area of ​​the negative electrode active material in other embodiments, comparative examples, and blank examples was the same as above, and the test results are recorded in Table 2.

[0113] Table 2 Performance test results for each embodiment, comparative example, and blank example

[0114]

[0115] As shown in Table 2, the method proposed in this invention for preparing carbon anode active materials has no significant impact on the BET specific surface area of ​​the carbon materials. However, the active specific surface area of ​​the materials changes significantly after treatment. The carbon anode active materials prepared in Examples 1-4 have suitable active specific surface areas, resulting in high initial battery efficiency and high capacity retention after 100 cycles. The following explanation assumes that the capacity retention rate of the battery in Blank Example 1 after 100 cycles reaches 95%. Taking this as a benchmark of 100%, the capacity retention improvement rate in Example 3 reaches 105.1% of the benchmark. Therefore, the capacity retention rate of the battery in Example 3 after 100 cycles reaches 99.85%, demonstrating a significant improvement in capacity retention. In contrast, the capacity retention rates of the batteries in Comparative Examples 1-4 after 100 cycles are all below 95%. The materials in Blank Example 1, Blank Example 2, and Comparative Examples 1-4 cannot simultaneously possess suitable active specific surface area and pore volume, resulting in poor cycle performance of the prepared batteries.

[0116] In summary, the active specific surface area of ​​the carbon anode active material proposed in this invention can reach 0.03 m². 2 / g-0.12m 2 / g, and the pore volume of the carbon anode active material is greater than or equal to 0.005cm³. 3 / g, the content of active sites in the negative electrode active material is appropriate, which can react with the electrolyte during the first charge of the battery to form an effective SEI film. Furthermore, during battery cycling, it is not easy to generate more active sites to react with the electrolyte, leading to SEI growth and accelerated battery capacity decline. Applying carbon negative electrode active materials to batteries can effectively improve the long-term cycle performance and storage performance of the battery.

[0117] In the description of this specification, the terms "one embodiment," "a specific embodiment," "another specific embodiment," "yet another specific embodiment," "some embodiments," "other embodiments," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment, which are included in at least one embodiment of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0118] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A carbon anode active material, characterized in that, The carbon anode active material has a porous structure, and its active specific surface area is 0.03 m². 2 / g-0.12m 2 / g, and the pore volume of the carbon anode active material is greater than or equal to 0.005cm³. 3 / g.

2. The carbon anode active material according to claim 1, characterized in that, The active specific surface area of ​​the carbon anode active material is 0.03 m². 2 / g-0.08m 2 / g.

3. The carbon anode active material according to claim 1, characterized in that, The pore volume of the carbon anode active material is 0.005 cm³. 3 / g-0.1cm 3 / g.

4. The carbon anode active material according to claim 1, characterized in that, Carbon anode active materials contain one or more of the following: micropores, mesopores, or macropores.

5. The carbon anode active material according to claim 4, characterized in that, Based on the total pore volume in the carbon anode active material, the volume content of the micropores is less than or equal to 10%; and / or, Based on the total pore volume in the carbon anode active material, the volume content of the mesopores is 60%-95%; and / or, Based on the total volume of pores in the carbon anode active material, the volume content of the macropores is less than or equal to 25%.

6. The carbon anode active material according to claim 5, characterized in that, Based on the total pore volume in the carbon anode active material, the volume content of the micropores is less than or equal to 5%; and / or, Based on the total pore volume in the carbon anode active material, the volume content of the mesopores is 70%-90%; and / or, Based on the total volume of pores in the carbon anode active material, the volume content of the macropores is 5%-20%.

7. The carbon anode active material according to claim 1, characterized in that, The carbon anode active material satisfies at least one of the following conditions (1)-(3): (1) The specific surface area of ​​the carbon anode active material is 1.0 m². 2 / g-8.0m 2 / g; (2) The volume distribution particle size Dv50 of the carbon anode active material is 5μm-50μm; (3) The porosity of the carbon negative electrode active material is 20%-40%.

8. The carbon anode active material according to claim 7, characterized in that, The carbon anode active material satisfies at least one of the following conditions: The specific surface area of ​​the carbon anode active material is 2m². 2 / g-5m 2 / g; The volume distribution particle size Dv50 of the carbon anode active material is 10μm-30μm; The porosity of the carbon anode active material is 25%-35%.

9. The carbon anode active material according to any one of claims 1-8, characterized in that, The carbon anode active material contains oxygen-containing functional groups, which include one or more of lactones, ethers, phenols, carboxyl groups, acid anhydrides, and carbonyl groups.

10. A method for preparing the carbon anode active material according to any one of claims 1-9, characterized in that, include: Provide carbon materials; The carbon material was oxidized using an oxidizing gas probe to obtain an intermediate carbon material; The intermediate carbon material is reduced using a reducing gas to obtain a carbon anode active material. This carbon anode active material has a porous structure and an active specific surface area of ​​0.03 m². 2 / g-0.12m 2 / g, and the pore volume of the carbon anode active material is greater than or equal to 0.005cm³. 3 / g.

11. The method according to claim 10, characterized in that, The oxidizing gas probe includes one or more of oxygen, air, chlorine, nitrogen oxides, sulfur trioxide, and argon plasma.

12. The method according to claim 10, characterized in that, The reducing gas includes one or more of hydrogen, carbon monoxide, hydrogen sulfide, sulfur dioxide, ammonia, olefins, and alkynes.

13. The method according to claim 10, characterized in that, The oxidizing gas probe includes oxygen, and the reducing gas includes hydrogen. Alternatively, the oxidizing gas probe may include air, and the reducing gas may include carbon monoxide; Alternatively, the oxidizing gas probe may include argon plasma, and the reducing gas may include ammonia.

14. The method according to any one of claims 10-13, characterized in that, The oxidation treatment temperature is 300℃-500℃, and / or the oxidation treatment time is 8h-16h.

15. The method according to any one of claims 10-13, characterized in that, The reduction treatment is performed at a temperature of 800℃-1000℃ and / or for a duration of 6h-15h.

16. The method according to any one of claims 10-13, characterized in that, The carbon material includes one or more of natural graphite, artificial graphite, hard carbon, soft carbon, carbon fiber, and mesophase carbon microspheres.

17. A secondary battery, comprising a negative electrode, characterized in that, The negative electrode sheet comprises the carbon negative electrode active material according to any one of claims 1-9.

18. An electrical appliance, characterized in that, Includes the secondary battery as described in claim 17.

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