Carbon-based composite negative electrode material and preparation method thereof, negative electrode plate and battery

Abstract

The invention relates to a carbon-based composite negative electrode material and a preparation method thereof, a negative electrode plate and a battery. The carbon-based composite negative electrode material comprises a carbon material, a conductive agent and carbon aerogel, the carbon aerogel meets the following relational expression: (m2 * S2 + m3 * S3) / (m1 * S1) is more than or equal to 1 and less than or equal to 2; in the relational expression, S1 is the specific surface area of the carbon material, and the unit is m < 2 > / g; m1 is the addition amount of the carbon material, and the unit is g; s2 is the specific surface area of the conductive agent, and the unit is m < 2 > / g; m2 is the addition amount of the conductive agent, and the unit is g; s3 is the specific surface area of the carbon aerogel, and the unit is m < 2 > / g; m3 is the addition amount of the carbon aerogel, and the unit is g. According to the scheme provided by the invention, the first coulombic efficiency, the rate capability and the cycle performance of the battery can be improved.

Description

Technical Field

[0001] This application relates to the technical field of batteries, and particularly to a carbon-based composite negative electrode material, a preparation method thereof, a negative electrode sheet and a battery. Background Art

[0002] Lithium-ion batteries are widely used in fields such as consumer electronics, new energy vehicles and energy storage. With the rapid development of the new energy vehicle industry, consumers have put forward higher requirements for the charging and discharging speed and service life of batteries, that is, the batteries have higher rate performance and cycling performance.

[0003] In related technologies, in order to enable batteries to achieve higher rate performance and cycling performance, it is a common method to use fast charge and discharge type graphite. Most of the fast charge and discharge type graphite adopts secondary granulation to improve kinetics, but asphalt is used as a binder in the granulation process, and there are many surface defects in asphalt, which increases the irreversible capacity and reduces the first Coulomb efficiency of the battery; moreover, the particles are bonded together by asphalt, and during long-term cycling, as lithium ions continuously intercalate and deintercalate from the graphite material, the material volume expands, stress is generated inside the particles, and when the stress reaches a certain level, cracks appear on the material surface, the particles are peeled off, and the material is pulverized, resulting in the loss of electrical contact between the active material and the current collector, and ultimately leading to a sharp decline in capacity.

[0004] Therefore, it is urgent to develop a negative electrode material that can improve the first Coulomb efficiency, rate performance and cycling performance of batteries. Summary of the Invention

[0005] To solve or partially solve the problems existing in related technologies, this application provides a carbon-based composite negative electrode material, a preparation method thereof, a negative electrode sheet and a battery, which can improve the first Coulomb efficiency, rate performance and cycling performance of the battery.

[0006] In the first aspect of this application, a carbon-based composite negative electrode material is provided, wherein the carbon-based composite negative electrode material includes a carbon material, a conductive agent and a carbon aerogel; The carbon material, the conductive agent, and the carbon aerogel satisfy the following relationship: 1 ≤ (m 2 × S 2 + m 3 × S 3 ) / (m 1 × S 1 ) ≤ 2; In the relationship, S 1 is the specific surface area of the carbon material, with the unit of m 2 / g; m 1 is the addition amount of the carbon material, with the unit of g; S 2 is the specific surface area of the conductive agent, with the unit of m 2 / g; m 2 is the addition amount of the conductive agent, with the unit of g; S 3 is the specific surface area of the carbon aerogel, with the unit of m 2 / g; m 3 is the addition amount of the carbon aerogel, with the unit of g.

[0007] For the carbon-based composite negative electrode material as described above, wherein, the carbon material, the conductive agent, and the carbon aerogel satisfy 1.3 ≤ (m 2 ×S 2 + m 3 ×S 3 ) / (m 1 ×S 1 ) ≤ 1.8.

[0008] For the carbon-based composite negative electrode material as described above, wherein, m 2 : m 3 = (1 to 5):1; Preferably, m 2 : m 3 = (2:1) to (3:1).

[0009] For the carbon-based composite negative electrode material as described above, wherein, the conductive agent includes carbon nanotubes and / or carbon fiber tubes; Preferably, the conductive agent is carbon nanotubes; Further preferably, the carbon nanotubes are selected from one or more of array tubes or multi-walled tubes; and / or, the diameter of the carbon nanotubes is 3 nm to 20 nm; and / or, the specific surface area of the carbon nanotubes is 200 m 2 / g to 400 m 2 / g; and / or, the specific surface area of the carbon aerogel is 800 m 2 / g to 1600 m 2 / g; and / or, the average pore diameter of the carbon aerogel is 1.4 nm to 2.3 nm; and / or, the carbon material includes at least one of graphite, hard carbon, and soft carbon; Preferably, the carbon material is graphite; and / or, the specific surface area of the graphite is 1 m 2 / g to 3 m 2 / g; Further preferably, the graphite includes at least one of petroleum coke, pitch coke, and needle coke.

[0010] The second aspect of the present application provides a preparation method of a carbon-based composite negative electrode material, which includes the following steps: S1. Weigh carbon material with a specific surface area of S 1 , conductive agent with a specific surface area of S 1 , and m 2 , conductive agent with a specific surface area of S 2 , and m 3 with a specific surface area of S3 The carbon aerogel is mixed in a solvent and then ultrasonically treated to obtain an intermediate; S2. The intermediate is calcined to obtain a carbon-based composite anode material; Wherein, the carbon material, the conductive agent, and the carbon aerogel satisfy the following relational expression: 1 ≤ (m 2 × S 2 + m 3 × S 3 ) / (m 1 × S 1 ) ≤ 2.

[0011] The preparation method of the carbon-based composite anode material as described above, wherein the ultrasonic temperature of the ultrasonic treatment is 35°C to 55°C, and the ultrasonic time is 0.5 h to 2 h; And / or, the calcination treatment includes the following steps: under an H 2 atmosphere, the temperature is raised to 600°C to 1100°C at a heating rate of 5°C / min to 10°C / min, and held for 2 h to 6 h; And / or, m 2 : m 3 = (1 to 5):1; preferably, m 2 : m 3 = (2:1) to (3:1); And / or, 1m 2 / g ≤ S 1 ≤ 3m 2 / g And / or, 200m 2 / g ≤ S 2 ≤ 400m 2 / g; And / or, 800m 2 / g ≤ S 3 ≤ 1600m 2 / g.

[0012] The preparation method of the carbon-based composite anode material as described above, wherein the conductive agent is selected as carbon nanotubes; before step S1, the following steps of acidifying carbon nanotubes are further included: The carbon nanotubes are mixed with a nitric acid solution and a sulfuric acid solution and then stirred to obtain the acidified carbon nanotubes; Preferably, the mass ratio of the carbon nanotubes, the nitric acid solution, and the sulfuric acid solution is 1:(30 to 35):(100 to 120); Preferably, the carbon nanotubes include array tubes and / or multi-walled tubes; Preferably, the stirring temperature of the stirring treatment is 100°C to 150°C, and the stirring time is 2 h to 4 h.

[0013] In the third aspect of the present application, a negative electrode sheet is provided, wherein the negative electrode active material layer in the negative electrode sheet comprises the carbon-based composite negative electrode material as described above or a carbon-based composite negative electrode material prepared by the preparation method of the carbon-based composite negative electrode material as described above.

[0014] For the negative electrode sheet as described above, wherein the negative electrode active material layer further comprises a dispersant and a binder, and the mass ratio of the carbon-based composite negative electrode material, the dispersant and the binder is (96.3 - 97.5):(1 - 1.7):(1.5 - 2).

[0015] In the fourth aspect of the present application, a battery is provided, comprising the negative electrode sheet as described above.

[0016] The technical solution provided by the present application may include the following beneficial effects: The carbon-based composite negative electrode material provided by the present application satisfies (m 2 ×S 2 +m 3 ×S 3 ) / (m 1 ×S 1 ) within the range of 1 to 2, realizing the three-dimensional network construction of carbon materials, carbon aerogels and conductive agents. The layers of the carbon aerogel are evenly separated, the conductive agent is evenly spread out, and the conductive agent penetrates between the carbon aerogel layers, avoiding the accumulation of carbon aerogels and the agglomeration of conductive agents. At the same time, the carbon material particles are confined within the network formed by the conductive agent and the carbon aerogel, enabling strong adhesion between the carbon material particles, enhancing the isotropy of the carbon material, significantly improving the multi-directional lithium ion deintercalation channels and diffusion rate, and at the same time being able to alleviate the volume expansion of the carbon material during the cycling process, improving the first Coulomb efficiency, rate performance and cycling performance of the battery; in the carbon-based composite negative electrode material, the carbon material is covered by carbon nanotubes and carbon aerogels, which can reduce the contact between the carbon material and the electrolyte, reduce the side reaction between the carbon material and the electrolyte, and improve the first Coulomb efficiency, rate performance and cycling performance of the battery. In addition, the carbon-based composite negative electrode material has high conductivity. When used in the negative electrode active material layer, a conductive agent can be not added and directly compounded with the binder, increasing the addition amount of the negative electrode active material in the negative electrode active material layer and improving the energy density of the battery. If (m 2 ×S 2 +m 3 ×S 3 ) / (m 1 ×S 1 )<1, the conductive agent and the carbon aerogel cannot completely cover the carbon material, resulting in more side reactions between the carbon material and the electrolyte, leading to a decrease in the first Coulomb efficiency, rate performance and cycling performance of the battery; if (m 2 ×S 2 +m 3 ×S3 ) / ( m 1 × S 1 When ( ) / ( m × S ) > 2, the addition amounts of the conductive agent and the carbon aerogel are excessive, and excessive carbon nanotubes and carbon aerogels agglomerate to form an uneven and dense network structure, which hinders the diffusion and insertion processes of lithium ions and restricts the rapid migration of lithium ions. In addition, excessive carbon nanotubes and carbon aerogels may undergo structural changes or fall off during repeated charge and discharge processes, damaging the originally formed stable interface.

[0017] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this application. Specific Embodiments

[0018] To make the present invention easy to understand, the present invention will be described in detail below. However, before describing the present invention in detail, it should be understood that the present invention is not limited to the described specific embodiments. It should also be understood that the terms used herein are only for describing specific embodiments and do not represent restrictive.

[0019] When a numerical range is provided, it should be understood that each intermediate value between the upper and lower limits of the range and any other specified or intermediate value in the specified range is covered within the present invention. The upper and lower limits of these smaller ranges can be independently included in the smaller ranges and are also covered within the present invention, subject to any explicit exclusions in the specified range. When the specified range includes one or both of the limits, ranges excluding either or both of the included limits are also included in the present invention.

[0020] Unless otherwise defined, all terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, the preferred methods and materials are now described.

[0021] In related technologies, in order to enable a battery to achieve higher rate performance and cycling performance, it is a common method to use fast charge and discharge type graphite. Most fast charge and discharge type graphite adopts a secondary granulation form to improve kinetics, but asphalt is used as a binder during the granulation process, and there are many surface defects in the asphalt, which increases the irreversible capacity and results in a decrease in the first Coulomb efficiency of the battery. Moreover, the particles are bonded together with asphalt. During long-term cycling, as lithium ions continuously intercalate and deintercalate from the graphite material, the material volume expands, stress is generated inside the particles. When the stress reaches a certain level, cracks appear on the material surface, the particles are peeled off, and the material is pulverized, resulting in the loss of electrical contact between the active material and the current collector, and ultimately leading to a sharp decline in capacity.

[0022] In view of the above problems, an embodiment of the present application provides a carbon-based composite anode material, which includes a carbon material, a conductive agent, and a carbon aerogel; the carbon material, the conductive agent, and the carbon aerogel satisfy the following relational expression: 1 ≤ (m 2 × S 2 + m 3 × S 3 ) / (m 1 × S 1 ) ≤ 2; In the relational expression, S 1 is the specific surface area of the carbon material, with the unit of m 2 / g; m 1 is the addition amount of the carbon material, with the unit of g; S 2 is the specific surface area of the conductive agent, with the unit of m 2 / g; m 2 is the addition amount of the conductive agent, with the unit of g; S 3 is the specific surface area of the carbon aerogel, with the unit of m 2 / g; m 3 is the addition amount of the carbon aerogel, with the unit of g.

[0023] In the carbon-based composite anode material of the present application, the carbon material refers to a material mainly composed of carbon elements, such as graphite, hard carbon, soft carbon, etc. The conductive agent in the present application refers to a material that can improve the conductivity of the carbon-based composite anode material. The conductive agents are easy to overlap with each other to form a conductive network. For example, the conductive agent includes carbon nanotubes, carbon fiber tubes, carbon fibers, etc. The carbon aerogel in the present application is a gel material with a three-dimensional network structure formed by the connection of carbon nanoparticles. The carbon aerogel has a layered structure and contacts in a face-to-face form, increasing the contact area.

[0024] The carbon material, the conductive agent, and the carbon aerogel satisfy the following relational expression: 1 ≤ (m 2 × S 2 + m 3 × S 3 ) / (m 1 × S 1 ) ≤ 2; For example, (m 2 × S 2 + m 3 × S 3 ) / (m 1 × S 1 ) can be 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2, etc.

[0025] It can be understood that S 1 is the specific surface area of the carbon material, and m 1 is the addition amount of the carbon material. Therefore, m 1 × S 1refers to the total area of the carbon material in the carbon-based composite anode material; similarly, m 2 ×S 2 refers to the total area of the conductive agent in the carbon-based composite anode material, m 3 ×S 3 refers to the total area of the carbon aerogel in the carbon-based composite anode material. Therefore, based on experience and experiments, it is found that the physical meaning of (m 2 ×S 2 +m 3 ×S 3 ) / (m 1 ×S 1 ) is the degree of coating of the conductive agent and the carbon aerogel on the carbon material.

[0026] The carbon-based composite anode material provided by this application satisfies (m 2 ×S 2 +m 3 ×S 3 ) / (m 1 ×S 1 ) within the range of 1 to 2, realizing the three-dimensional network construction of the carbon material, the carbon aerogel, and the conductive agent. The layers of the carbon aerogel are evenly separated, the conductive agent is evenly dispersed, and the conductive agent is interspersed between the layers of the carbon aerogel, avoiding the accumulation of the carbon aerogel and the agglomeration of the conductive agent. At the same time, the carbon material particles are confined within the network formed by the conductive agent and the carbon aerogel, enabling strong adhesion between the carbon material particles, enhancing the isotropy of the carbon material, significantly improving the multi-directional lithium-ion deintercalation channels and diffusion rate, and at the same time being able to alleviate the volume expansion of the carbon material during the cycling process, improving the first Coulombic efficiency, rate performance, and cycling performance of the battery; the carbon material in the carbon-based composite anode material is covered by the conductive agent and the carbon aerogel, which can reduce the contact between the carbon material and the electrolyte, reduce the side reaction between the carbon material and the electrolyte, and improve the first Coulombic efficiency, rate performance, and cycling performance of the battery. In addition, the carbon-based composite anode material has high electrical conductivity. When used in the negative electrode active material layer, it can be directly compounded with the binder without adding additional conductive materials, increasing the addition amount of the negative electrode active material in the negative electrode active material layer and improving the energy density of the battery. If (m 2 ×S 2 +m 3 ×S 3 ) / (m 1 ×S 1 ) < 1, the conductive agent and the carbon aerogel cannot completely cover the carbon material, resulting in more side reactions between the carbon material and the electrolyte, leading to a decrease in the first Coulombic efficiency, rate performance, and cycling performance of the battery; if (m 2 ×S 2 +m 3 ×S 3 ) / (m 1 ×S 1When it is greater than 2, the addition amounts of the conductive agent and the carbon aerogel are excessive. The excessive carbon nanotubes and carbon aerogel agglomerate, forming an uneven and dense network structure, which hinders the diffusion and insertion process of lithium ions and restricts the rapid migration of lithium ions. In addition, the excessive carbon nanotubes and carbon aerogel may undergo structural changes or fall off during repeated charge and discharge processes, damaging the originally formed stable interface. Therefore, in this application, it is controlled that (m 2 ×S 2 +m 3 ×S 3 ) / (m 1 ×S 1 )is in the range of 1 to 2, which can improve the first Coulomb efficiency, rate performance, and cycle performance of the battery.

[0027] In a preferred embodiment, 1.3 ≤ (m 2 ×S 2 +m 3 ×S 3 ) / (m 1 ×S 1 )≤ 1.8. When (m 2 ×S 2 +m 3 ×S 3 ) / (m 1 ×S 1 )is in the range of 1.3 to 1.8, the conductive agent and the carbon aerogel can better cover the carbon material, can further reduce the side reaction between the conductive agent and the electrolyte, and at the same time can greatly improve the lithium ion conduction rate in the composite material, relieve the volume expansion of the composite material during the cycle, and make the first Coulomb efficiency, rate performance, and cycle performance of the battery better.

[0028] In a specific embodiment, m 2 :m 3 = (1 to 5):1. For example, m 2 :m 3 can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, or 5:1, etc. When the mass ratio of the conductive agent to the carbon aerogel is within the above range, the conductive agent and the carbon aerogel can be better matched, so that the layers of the carbon aerogel are evenly separated, the conductive agent is spread out, the conductive agent is interspersed between the carbon aerogel layers, and the accumulation of the carbon aerogel and the agglomeration of the conductive agent are avoided to a greater extent, thereby better realizing the construction of the three-dimensional network, and further making the first Coulomb efficiency, rate performance, and cycle performance of the battery higher.

[0029] In a preferred embodiment, m 2 :m 3 = (2 to 3):1. For example, m 2 :m3 It can be 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1 or 3:1, etc. When the mass ratio of the conductive agent to the carbon aerogel is within the above range, the compounding of the conductive agent and the carbon aerogel is more uniform, further avoiding the accumulation of the carbon aerogel and the agglomeration of the conductive agent, making the distribution of carbon nanotubes and carbon aerogel in the three-dimensional network more reasonable, thereby improving the first Coulomb efficiency, rate performance and cycling performance of the battery.

[0030] In a specific embodiment, the conductive agent includes carbon nanotubes and / or carbon fiber tubes. The carbon nanotubes or carbon fiber tubes have a high aspect ratio and are easy to overlap with each other, making it easier to form a conductive network.

[0031] Preferably, the conductive agent is carbon nanotubes. The carbon nanotubes and the carbon aerogel can be better compounded, enabling the carbon nanotubes to better penetrate between the carbon aerogel layers, further avoiding the accumulation of the carbon aerogel and the agglomeration of the carbon nanotubes, thereby better coating the carbon material and forming a carbon-based composite negative electrode material with a more stable structure.

[0032] In a specific embodiment, the carbon nanotube raw material includes array tubes and / or multi-walled tubes. When the carbon nanotube raw material is array tubes and / or multi-walled tubes, the carbon nanotubes have high conductivity, high mechanical properties and strong performance controllability, which is beneficial to the preparation of acidified carbon nanotubes and can improve the conductivity of the carbon-based composite negative electrode material, thereby improving the electrochemical performance of the battery.

[0033] In a specific embodiment, the diameter of the carbon nanotubes is 3 nm to 20 nm. For example, the diameter of the carbon nanotubes can be 3 nm, 4 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm or 20 nm, etc.

[0034] In a specific embodiment, the specific surface area S of the carbon nanotubes 2 is 200 m 2 / g to 400 m 2 / g. For example, S 2 can be 200 m 2 / g, 220 m 2 / g, 240 m 2 / g, 260 m 2 / g, 280 m 2 / g, 300 m 2 / g, 320 m 2 / g, 340 m 2 / g, 360 m 2 / g, 380 m 2 / g or 400 m 2 / g, etc. When the tube diameter and specific surface area of the carbon nanotubes are within the above ranges, it is beneficial to construct the three-dimensional network of the carbon-based composite anode material, improve the stability of the carbon-based composite anode material, and make the electrochemical performance of the battery better.

[0035] In a specific embodiment, the specific surface area S of the carbon aerogel 3 is 800 m 2 / g to 1600 m 2 / g. For example, the specific surface area of the carbon aerogel can be 800 m 2 / g, 900 m 2 / g, 1000 m 2 / g, 1100 m 2 / g, 1200 m 2 / g, 1300 m 2 / g, 1400 m 2 / g, 1500 m 2 / g or 1600 m 2 / g, etc.

[0036] In a specific embodiment, the average pore diameter of the carbon aerogel is 1.4 nm to 2.3 nm. For example, the average pore diameter of the carbon aerogel can be 1.4 nm, 1.5 nm, 1.6 nm, 1.7 nm, 1.8 nm, 1.9 nm, 2 nm, 2.1 nm, 2.2 nm or 2.3 nm, etc.

[0037] When the specific surface area and average pore diameter of the carbon aerogel are within the above ranges, the carbon aerogel and carbon nanotubes can better cooperate and better coat the carbon material, which is beneficial to the construction of the three-dimensional network of the carbon-based composite anode material, and further improves the first Coulomb efficiency, rate performance and cycle performance of the battery.

[0038] In a specific embodiment, the carbon material includes at least one of graphite, hard carbon, and soft carbon.

[0039] Preferably, the carbon material is graphite. When the carbon material is graphite, the graphite particles can be better incorporated into the conductive agent and the network of the carbon aerogel to achieve adhesion between the graphite particles, thereby better improving the multi-directional deintercalation channels and diffusion rate of lithium ions. Moreover, graphite has high stability and fewer side reactions with the electrolyte, thus further improving the first Coulomb efficiency, rate performance and cycle performance of the battery to a greater extent.

[0040] In a specific embodiment, the specific surface area of the graphite is 1 m 2 / g to 3 m 2 / g. For example, the specific surface area of the graphite can be 1 m 2 / g, 1.2 m 2 / g, 1.4 m 2 / g, 1.6 m2 / g, 1.8 m 2 / g, 2 m 2 / g, 2.2 m 2 / g, 2.4 m 2 / g, 2.6 m 2 / g, 2.8 m 2 / g or 3 m 2 / g etc. When the specific surface area of the graphite is within the above range, the specific surface area of the carbon-based composite anode material can be further improved, which is beneficial to the deintercalation and migration of lithium ions, thereby further improving the first Coulomb efficiency, rate performance and cycling performance of the battery.

[0041] In a specific embodiment, the graphite includes at least one of petroleum coke, pitch coke and needle coke. Petroleum coke, pitch coke and needle coke have low cost, high energy density, good chemical stability and mechanical properties, which can reduce the side reaction between graphite and electrolyte in the carbon-based composite anode material, improve the electrochemical performance of the battery, and at the same time help to reduce the cost of the carbon-based composite anode material, and are suitable for the industrial production of the carbon-based composite anode material.

[0042] This application also provides a preparation method of a carbon-based composite anode material, including the following steps: S1. Weigh m 1 with a specific surface area of S 1 of carbon material, m 2 with a specific surface area of S 2 of conductive agent, m 3 with a specific surface area of S 3 of carbon aerogel, mix them in a solvent, and then perform ultrasonic treatment to obtain an intermediate; S2. Calcinate the intermediate to obtain the carbon-based composite anode material; Among them, the carbon material, conductive agent and carbon aerogel satisfy the following relationship: 1 ≤ (m 2 × S 2 + m 3 × S 3 ) / (m 1 × S 1 ) ≤ 2.

[0043] Step S1: Mix the carbon material in a solvent to form a carbon material suspension. Subsequently, add a conductive agent and carbon aerogel and mix them, and then perform ultrasonic treatment to evenly separate the layers of the carbon aerogel by the conductive agent. At the same time, the layered structure of the carbon aerogel spreads out the conductive agent, preventing the accumulation of the carbon aerogel and the agglomeration of the conductive agent. The two cross-combine, with the conductive agent interspersed between the layers of the carbon aerogel, and the carbon material particles are confined within the network formed by the conductive agent and the carbon aerogel, forming a substance with a composite structure. Among them, the specific surface areas and addition amounts of the carbon material, carbon aerogel, and conductive agent satisfy the above relational formula. Subsequently, clean and dry this substance to obtain an intermediate product.

[0044] The intermediate product in this application refers to the intermediate product obtained after ultrasonic treatment of the carbon material, carbon aerogel, and conductive agent.

[0045] This application does not make specific limitations on the selection of the solvent, which can be selected according to actual needs. For example, a mixed solution of water and ethanol can be selected, and the volume ratio of water to ethanol is (5~6):(3~4), which is beneficial to the dispersion of the carbon material, carbon aerogel, and conductive agent.

[0046] This application does not make specific limitations on the selection of the physical parameters of the carbon material, carbon aerogel, and conductive agent, which can be selected according to actual needs.

[0047] This application does not make specific limitations on the selection of the parameters of the ultrasonic treatment, which can be selected according to actual needs.

[0048] Step S2: Place the intermediate product in a tube furnace, heat it for calcination treatment, and cool it to room temperature after the calcination ends to obtain a carbon-based composite anode material. During the calcination treatment process, the composite structure of the intermediate product is solidified, improving the stability of the carbon-based composite anode material. At the same time, the defects and impurities in the intermediate product can be removed, improving the purity of the carbon-based composite anode material.

[0049] This application does not make specific limitations on the selection of the parameters of the calcination treatment, which can be selected according to actual needs.

[0050] Through the above preparation method of the carbon-based composite anode material, this application can evenly separate the layers of the carbon aerogel, spread out the conductive agent, with the conductive agent interspersed between the layers of the carbon aerogel, avoiding the accumulation of the carbon aerogel and the agglomeration of the conductive agent. At the same time, the carbon material particles are confined within the network formed by the carbon nanotubes and the carbon aerogel. Subsequently, the composite structure including the carbon material, carbon aerogel, and conductive agent is structurally solidified, improving the stability of the carbon-based composite anode material. This preparation method has simple process, low equipment requirements, and low cost, which is beneficial to industrial production.

[0051] In a specific embodiment, the ultrasonic temperature for ultrasonic treatment is 35°C to 55°C. For example, the ultrasonic temperature can be 35°C, 40°C, 45°C, 50°C, 55°C, etc. The ultrasonic time is 0.5 h to 2 h. For example, the ultrasonic time can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, 2 h, etc. When the ultrasonic temperature and ultrasonic time for ultrasonic treatment are within the above ranges, the carbon material, carbon aerogel, and conductive agent can be better mixed, enabling the carbon aerogel and the conductive agent to form an intercalation structure, and at the same time enabling the carbon material to be fully coated by the conductive agent and the carbon aerogel, thereby forming a stable three-dimensional network structure, improving the stability of the carbon-based composite negative electrode material, and further improving the initial Coulomb efficiency, rate performance, and cycling performance of the battery.

[0052] In a specific embodiment, the calcination treatment includes the following steps: in an H 2 atmosphere, heating at a heating rate of 5°C / min to 10°C / min to 600°C to 1100°C, and holding for 2 h to 6 h. For example, the heating rate can be 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, or 10°C / min, etc. The calcination temperature can be 600°C, 700°C, 800°C, 900°C, 1000°C, or 1100°C, etc. The calcination time can be 2 h, 3 h, 4 h, 5 h, or 6 h, etc. When the parameters of the calcination treatment are within the above ranges, the calcination treatment can fully solidify the structure of the composite structure including the carbon material, carbon aerogel, and conductive agent, and can remove the defects and impurities in the intermediate obtained by ultrasonic treatment, improving the purity of the carbon-based composite negative electrode material, thereby improving the electrochemical performance of the battery.

[0053] In a specific embodiment, m 2 : m 3 = (1 to 5):1. For example, m 2 : m 3 can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, or 5:1, etc.

[0054] In a preferred embodiment, m 2 : m 3 = (2 to 3):1. For example, m 2 : m 3 can be 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, or 3:1, etc.

[0055] In a specific embodiment, the specific surface area S of graphite1 is 1 m² / g ~ 3 m² / g 2 / g~3m 2 / g. For example, the specific surface area of graphite can be 1 m² / g, 2 1.2 m² / g, 2 1.4 m² / g, 2 1.6 m² / g, 2 1.8 m² / g, 2 2 m² / g, 2 2.2 m² / g, 2 2.4 m² / g, 2 2.6 m² / g, 2 2.8 m² / g, 2 or 3 m² / g, etc. 2 / g etc.

[0056] In a specific embodiment, the specific surface area S of the carbon nanotubes 2 is 200 m² / g ~ 400 m² / g, 2 / g~400m 2 / g. For example, S 2 can be 200 m² / g, 2 220 m² / g, 2 240 m² / g, 2 260 m² / g, 2 280 m² / g, 2 300 m² / g, 2 320 m² / g, 2 340 m² / g, 2 360 m² / g, 2 380 m² / g, 2 or 400 m² / g, etc. 2 / g etc.

[0057] In a specific embodiment, the specific surface area S of the carbon aerogel 3 is 800 m² / g ~ 1600 m² / g, 2 / g~1600m 2 / g. For example, the specific surface area of the carbon aerogel is 800 m² / g, 2 900 m² / g, 2 1000 m² / g, 2 1100 m² / g, 2 1200 m² / g, 2 1300 m² / g, 2 1400 m² / g, 2 1500 m² / g, 2 or 1600 m² / g, etc. 2 / g etc.

[0058] In a specific embodiment, the conductive agent is carbon nanotubes; before step S1, the following steps for acidifying carbon nanotubes are further included: mixing carbon nanotubes with nitric acid solution and sulfuric acid solution and then performing stirring treatment to obtain acidified carbon nanotubes. The nitric acid solution and sulfuric acid solution in this application are concentrated nitric acid solution and concentrated sulfuric acid solution. In the preparation process of the acidified carbon nanotubes in this application, hydroxyl groups, carboxyl groups and other oxygen-containing functional groups are introduced onto the surface of the carbon nanotubes through concentrated nitric acid and concentrated sulfuric acid, promoting the dispersion of the acidified carbon nanotubes and reducing the degree of self-aggregation of the acidified carbon nanotubes. At the same time, under the action of concentrated nitric acid and concentrated sulfuric acid, the weak defect part of the carbon nanotube raw material will preferentially undergo an acidification reaction, causing the carbon nanotubes to be cut and shortened, further promoting the dispersion of the acidified carbon nanotubes, so as to better improve the stability of the carbon-based composite negative electrode material, and then improve the first Coulomb efficiency, rate performance and cycle performance of the battery.

[0059] In a preferred embodiment, the mass ratio of carbon nanotubes, nitric acid solution, and sulfuric acid solution is 1:(30 - 35):(100 - 120). For example, the mass ratio of carbon nanotubes, nitric acid solution, and sulfuric acid solution can be 1:30:100, 1:31:100, 1:32:100, 1:33:100, 1:34:100, 1:35:100, 1:30:110, 1:31:110, 1:32:110, 1:33:110, 1:34:110, 1:35:110, 1:30:120, 1:31:120, 1:32:120, 1:33:120, 1:34:120 or 1:35:120, etc. When the mass ratio of carbon nanotubes, nitric acid solution, and sulfuric acid solution is within the above range, the concentrated nitric acid solution and concentrated sulfuric acid solution can introduce hydroxyl groups, carboxyl groups and other oxygen-containing functional groups onto the surface of the carbon nanotubes faster, and can further remove impurities and shorten the carbon nanotube raw material, to a greater extent improve the dispersibility of the acidified carbon nanotubes, inhibit the aggregation of the acidified carbon nanotubes, so as to better improve the conductivity of the carbon-based composite negative electrode material, and to a greater extent improve the first Coulomb efficiency, rate performance and cycle performance of the battery.

[0060] In a preferred embodiment, the carbon nanotube raw material includes array tubes and / or multi-walled tubes.

[0061] In a preferred embodiment, the stirring temperature for the stirring treatment is 100°C to 150°C. For example, the stirring temperature can be 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, or 150°C, etc. The stirring time is 2h to 4h. For example, the stirring time can be 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h, or 4h, etc. When the stirring temperature and stirring time for the stirring treatment are within the above ranges, the acidification treatment of the carbon nanotubes is more complete, resulting in higher dispersibility of the acidified carbon nanotubes. This avoids a decrease in the dispersibility of the acidified carbon nanotubes due to too low a temperature or insufficient stirring time, or a decrease in the length and structural damage of the acidified carbon nanotubes, as well as a reduction in the stability of the carbon-based composite negative electrode material due to too high a temperature or excessive stirring time, thereby being able to better improve the electrochemical performance of the battery.

[0062] The third aspect of the present application provides a negative electrode sheet. The negative electrode active material layer in the negative electrode sheet includes the above-mentioned carbon-based composite negative electrode material or a carbon-based composite negative electrode material prepared by the preparation method of the above-mentioned carbon-based composite negative electrode material. The negative electrode sheet of the present application has high conductivity, and has a small volume expansion and few side reactions during the cycling process, thereby being able to improve the first Coulomb efficiency, rate performance, and cycling performance of the battery.

[0063] In a specific embodiment, the negative electrode active material layer further includes a dispersant and a binder. The mass ratio of the carbon-based composite negative electrode material, the dispersant, and the binder is (96.3 to 97.5):(1 to 1.7):(1.5 to 2). For example, the mass ratio of the carbon-based composite negative electrode material, the dispersant, and the binder can be 96.3:1.7:2, 96.5:1.5:2, 97:1:2, 97.5:1:1.5, 97.5:1:1.5, etc. No conductive material is added to the negative electrode active material layer of the present application, which increases the addition amount of the carbon-based composite negative electrode material, thereby being beneficial to improving the energy density of the battery.

[0064] In a specific embodiment, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on the surface of the negative electrode current collector. Among them, there are no special restrictions on the negative electrode current collector in the embodiments of the present application, as long as the purpose of the present application can be achieved. For example, it can be a copper foil, a copper alloy foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, or a composite current collector, etc. The dispersant and binder in the negative electrode active material layer in the embodiments of the present application can be conventional materials in the art.

[0065] The fourth aspect of the present application provides a battery, including the above-mentioned negative electrode sheet. The battery of the present application has excellent first Coulomb efficiency, rate performance, and cycling performance.

[0066] In a specific embodiment, the battery further includes a positive electrode sheet, which includes a positive electrode current collector and a positive electrode active material layer coated on the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes lithium iron phosphate, ternary positive electrode material, and lithium cobaltate. When the positive electrode active material selects the above compounds, the positive electrode active material can fully exert its performance and improve the electrochemical performance of the lithium-ion battery.

[0067] In the embodiments of the present application, there is no particular limitation on the type of the positive electrode current collector, and it can be any known material suitable for use as the positive electrode current collector. In one embodiment, the positive electrode current collector includes metal materials such as aluminum, stainless steel, nickel plating, titanium, tantalum, etc., and carbon materials such as carbon cloth and carbon paper. Preferably, the positive electrode current collector is a metal material.

[0068] In a specific embodiment, the positive electrode material layer further includes a conductive agent and a binder. The conductive agent includes at least one of carbon materials such as acetylene black, Ketjen black, carbon nanotubes, and graphene. The binder includes at least one of polyvinylidene fluoride, polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose.

[0069] In a specific embodiment, the lithium-ion battery further includes a separator. In the embodiments of the present application, there is no particular limitation on the material and shape of the separator, as long as the effects of the present application are not significantly damaged. It may include substances in the form of porous sheets or non-woven fabrics with excellent liquid retention properties, etc. The materials of the resin or glass fiber separator include, but are not limited to, polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, etc., and can be specifically set according to needs.

[0070] In a specific embodiment, the lithium-ion battery may include an outer package, which can be used to encapsulate the above electrode assembly and electrolyte.

[0071] In a specific embodiment, the outer package of the lithium-ion battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as flexible encapsulation using an aluminum-plastic film.

[0072] The present application has no particular limitation on the shape of the secondary battery, and it can be cylindrical, square, or any other arbitrary shape.

[0073] The present application has no particular limitation on the field of the secondary battery, and it can be used in fields such as consumer electronics, new energy vehicles, and energy storage.

[0074] Hereinafter, the present application will be further described in detail through specific examples.

[0075] Example 1 1. Preparation of carbon-based composite negative electrode material 1) Weigh 0.5 g of the array tube and place it in a beaker. Add concentrated HNO 3 solution and stir evenly. Then slowly add concentrated H 2 SO 4 solution. The mass ratio of the carbon-based composite material, concentrated HNO 3 , and concentrated H 2 SO 4 is 1:30:110. Heat up to 100 °C and stir for 3 h. After the reaction is completed, wash with anhydrous ethanol until the pH is neutral, and dry to obtain acidified carbon nanotubes.

[0076] 2) Weigh 1 g (m 1 ) of graphite and dissolve it in 30 mL of deionized water and 15 mL of ethanol. Then add 0.0028 g (m 2 ) of acidified carbon nanotubes and 0.0014 g (m 3 ) of carbon aerogel and mix them. Among them, the specific surface area (S 1 ) of graphite is 1.5 m 2 / g, the specific surface area (S 2 ) of acidified carbon nanotubes is 300 m 2 / g, the tube diameter of acidified carbon nanotubes is 8 nm - 11 nm, the specific surface area (S 3 ) of carbon aerogel is 1000 m 2 / g, and the average pore diameter of carbon aerogel is 1.5 nm - 1.8 nm. Therefore, the mass ratio of carbon nanotubes to carbon aerogel is 2:1, and the usage amounts of graphite, carbon nanotubes, and carbon aerogel satisfy the relationship: (m 2 ×S 2 +m 3 ×S 3 ) / (m 1 ×S 1 ) = 1.5.

[0077] Ultrasonicate the above mixed solution at 55 °C for 1 h. After ultrasonicating, wash with deionized water and ethanol, and place it in a vacuum drying oven to dry to obtain an intermediate.

[0078] 3) Place the intermediate in a crucible and calcine it in a tube furnace. Under a H 2 atmosphere, heat it up to 1000 °C at a heating rate of 10 °C / min, hold for 5 h, cool down, and take out the sample after the temperature in the furnace drops to room temperature to obtain the carbon-based composite negative electrode material.

[0079] 2. Preparation of the negative electrode sheet The carbon-based composite anode material, sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are mixed evenly at a mass ratio of 97:1.3:1.7, and uniformly dispersed in deionized water to form a uniform anode slurry. After the mixed slurry is coated on both sides of a copper foil current collector, it is baked, rolled, and cut into pieces to obtain an anode sheet.

[0080] 3. Preparation of the cathode sheet The cathode active material lithium iron phosphate, carbon black (SP), carbon nanotubes (CNTs), and binder polyvinylidene fluoride (PVDF) are mixed evenly at a mass ratio of 95.7:1.5:0.5:2.3, and uniformly dispersed with N-methylpyrrolidone (NMP) to form a uniform cathode slurry. After the mixed slurry is coated on both sides of an aluminum foil current collector, it is baked, rolled, and cut into pieces to obtain a cathode sheet.

[0081] 4. Preparation of the electrolyte Under an environment with a water content of less than 10 ppm, ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are mixed at a mass ratio of 30:10:60, and then lithium hexafluorophosphate (LiPF 6 ) is added to the solvent. The molar concentration of LiPF 6 in the electrolyte is 1.2 mol / L, and it is dissolved and mixed evenly. Then, vinylene carbonate (VC) with a mass concentration of 2%, fluoroethylene carbonate (FEC) with a mass concentration of 1%, and divinyl sulfite (DTD) with a mass concentration of 1% are added and mixed evenly to obtain the electrolyte.

[0082] 5. Fabrication of the lithium-ion battery The above-prepared anode and cathode sheets are successively processed through procedures such as Z-type laminating, encapsulation, polymerization, formation, degassing, and grading to fabricate a lithium iron phosphate-based fast-charging and fast-discharging lithium-ion battery.

[0083] The preparation methods of the lithium-ion batteries provided in Examples 2 to 23 and Comparative Examples 1 to 15 are basically the same as those in Example 1, and the specific parameters are shown in Tables 1 and 2.

[0084] Table 1

[0085] Table 2

[0086] Example 24 The difference between this example and Example 1 lies in the preparation of the anode sheet: the mass ratio of the carbon-based composite anode material, sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) is 96.3:1.7:2.

[0087] Test example Performance test of the lithium-ion battery: 1. First Coulomb efficiency test: After the formation and grading of the lithium-ion battery are completed, record the formation charging capacity C 0 , the charging capacity C of the first grading cycle 1 , and the discharging capacity C of the first grading cycle 2 . The first efficiency = C 2 / (C 0 + C 1 ) × 100%, and take the average value and record it in Table 3.

[0088] 2. Rate charge and discharge test: (1) The rate charging test method is as follows: 1) Perform a 1C calibration test on the battery cell at room temperature; 2) Discharge the battery cell at a constant current of 1C to 2.5V, and let it stand for 30 min; charge it at a constant current of XC rate to 3.65V, and then charge it at a constant voltage until it is cut off at 0.05C, and let it stand for 30 min; 3) Repeat step 2), with X taking 1C, 2C, 4C, and 6C respectively, to test the charging performance of the battery cell at different rates; 4) After the test is completed, perform a re-grading test.

[0089] Note: The constant current ratio % = constant current charging capacity / (constant current charging capacity + constant voltage charging capacity) × 100% (2) The rate discharging test method is as follows: 1) Perform a 1C calibration test on the battery cell at room temperature; 2) Discharge the battery cell at a constant current of XC to 2.5V, and let it stand for 30 min; charge it at a constant current of 1C rate to 3.65V, and then charge it at a constant voltage until it is cut off at 0.05C, and let it stand for 30 min; 3) Repeat step 2), with X taking 1C, 2C, 4C, and 6C respectively, to test the discharging performance of the battery cell at different rates; 4) After the test is completed, perform a re-grading test.

[0090] Note: Based on the 1C rate discharge, the rate discharge capacity retention rate % = XC discharge capacity / 1C discharge capacity × 100%.

[0091] 3. Rate cycle test: 1) Perform a 1C calibration test on the battery cell at room temperature: discharge it at a constant current of 1C to 2.5V, and let it stand for 10 min; charge it at a constant current of 1C rate to 3.65V, and then charge it at a constant voltage until it is cut off at 0.05C, and let it stand for 10 min. Repeat this three times, and record the last discharge capacity as the initial capacity Q 1 ; 2) Charge the battery cell at a constant current of 3C rate until it reaches 20%Q 1 cut-off, and let it stand for 10 min; charge the battery cell at a constant current of 3C rate until it reaches 60%Q 1Cut off and let it stand for 20 min; discharge at a constant current of 3C until the capacity reaches 60%Q 1 Cut off and let it stand for 20 min; 3) Repeat step 2) to conduct the cell rate cycling test; 4) Perform a calibration every 100 cycles: discharge at a constant current of 1C to 2.5V, let it stand for 10 min; charge at a constant current of 1C rate to 3.65V, charge at a constant voltage until cut off at 0.05C, let it stand for 10 min, repeat three times, and record the discharge capacity of the last time as the real-time capacity Q at this time n , where n represents the number of cycles corresponding to the rate cycle; 5) Cycle capacity retention rate % = Q n / Q 1 × 100%.

[0092] Table 3

[0093] Table 4

[0094] It can be seen from Table 3 and Table 4 that: According to the comparison of Examples 1 to 5 and Comparative Examples 1, 2, and 5, when the mass ratio of carbon nanotubes to carbon aerogel is in the range of (1 to 5):1, the first Coulomb efficiency, rate performance, and cycle performance of the battery are improved; when the mass ratio of carbon nanotubes to carbon aerogel is in the preferred range of (2 to 3):1, the first Coulomb efficiency, rate performance, and cycle performance of the battery are better.

[0095] According to the comparison of Examples 2, 6, and 7 and Comparative Examples 6 and 7, when the specific surface area S of carbon nanotubes 2 is 200 m 2 / g to 400 m 2 / g, it is beneficial to improve the first Coulomb efficiency, rate performance, and cycle performance of the battery.

[0096] According to the comparison of Examples 2, 8, and 9 and Comparative Examples 8 and 9, when the specific surface area S of carbon aerogel 3 is 800 m 2 / g to 1600 m 2 / g, the first Coulomb efficiency, rate performance, and cycle performance of the battery can be further improved.

[0097] According to the comparison of Examples 2, 10, and 11 and Comparative Examples 10 and 11, when the specific surface area S of graphite 1 is 1 m 2 / g to 3 m 2When it is [specific value] / g, it can improve the first Coulombic efficiency, rate performance, and cycling performance of the battery.

[0098] According to the comparison between Example 2, Examples 12 - 15 and Comparative Examples 3, 4, when (m 2 ×S 2 +m 3 ×S 3 ) / (m 1 ×S 1 )is in the range of 1 - 2, the coating of carbon nanotubes and carbon aerogel on graphite is better, which is beneficial to improving the first Coulombic efficiency, rate performance, and cycling performance of the battery; when (m 2 ×S 2 +m 3 ×S 3 ) / (m 1 ×S 1 )is in the range of 1.3 - 1.8, the first Coulombic efficiency, rate performance, and cycling performance of the battery are better.

[0099] According to the comparison between Example 2, Examples 16, 17 and Comparative Example 12, when the mass ratio of carbon nanotubes, nitric acid solution, and sulfuric acid solution is 1:(30 - 35):(100 - 120), the prepared acidified carbon nanotubes have better dispersibility, can better improve the conductivity of the carbon - based composite anode material, and thus improve the first Coulombic efficiency, rate performance, and cycling performance of the battery.

[0100] According to the comparison between Example 2, Examples 18, 19 and Comparative Example 13, when the stirring temperature during the acidification treatment is 100℃ - 150℃ and the stirring time is 2h - 4h, the acidification treatment of carbon nanotubes is more complete, the dispersibility of acidified carbon nanotubes is better, and the electrochemical performance of the battery is improved.

[0101] According to the comparison between Example 2, Examples 20, 21 and Comparative Example 14, when the ultrasonic temperature of the ultrasonic treatment is 35℃ - 55℃ and the ultrasonic time is 0.5h - 2h, the carbon material, carbon aerogel, and conductive agent can be better mixed to form a stable three - dimensional network structure, improving the stability of the carbon - based composite anode material, which is beneficial to improving the first Coulombic efficiency, rate performance, and cycling performance of the battery.

[0102] According to the comparison between Example 2, Examples 22, 23 and Comparative Example 15, when the heating rate of the calcination treatment is 5℃ / min - 10℃ / min, the calcination temperature is 600℃ - 1100℃, and the calcination time is 2h - 6h, the first Coulombic efficiency, rate performance, and cycling performance of the battery are better.

[0103] According to Embodiments 2 and 24, when the mass ratio of the carbon-based composite anode material, the dispersant, and the binder is (96.3 to 97.5):(1 to 1.7):(1.5 to 2), the initial Coulombic efficiency, rate performance, and cycling performance of the battery are better.

[0104] The embodiments of the present application have been described above. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of the terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other ordinary skill in the art to understand the disclosed embodiments.

Claims

1. A carbon-based composite negative electrode material, characterized in that: The carbon-based composite negative electrode material comprises a carbon material, a conductive agent and a carbon aerogel; the carbon material, the conductive agent and the carbon aerogel satisfy the following relationship: 1≤(m2×S2+m3×S3) / (m1×S1)≤2; In the relationship, S1 is the specific surface area of ​​the carbon material, in m 2 / g; m1 is the amount of carbon material added, in g; S2 is the specific surface area of ​​the conductive agent, in m 2 / g; m2 is the amount of the conductive agent added, in g; S3 is the specific surface area of ​​the carbon aerogel, in m 2 / g; m3 is the added amount of the carbon aerogel, in g.

2. The carbon-based composite negative electrode material according to claim 1, characterized in that: The carbon material, the conductive agent, and the carbon aerogel satisfy 1.3≤(m2×S2+m3×S3) / (m1×S1)≤1.

8.

3. The carbon-based composite negative electrode material according to claim 1 or 2, characterized in that: m2:m3=(1~5):1; preferably, m2:m3=(2:1)~(3:1).

4. The carbon-based composite negative electrode material according to claim 1, characterized in that: The conductive agent includes carbon nanotubes and / or carbon fiber tubes; preferably, the conductive agent is selected from carbon nanotubes; further preferably, the carbon nanotubes are selected from one or more of array tubes or oligo-walled tubes; and / or, the diameter of the carbon nanotubes is 3nm~20nm; and / or, the specific surface area of ​​the carbon nanotubes is 200m 2 / g~400m 2 / g; and / or, The specific surface area of ​​the carbon aerogel is 800 m 2 / g~1600m 2 / g; and / or, the average pore size of the carbon aerogel is 1.4nm~2.3nm; and / or, The carbon material includes at least one of graphite, hard carbon and soft carbon; preferably, the carbon material is graphite; and / or the specific surface area of ​​the graphite is 1m 2 / g~3m 2 / g; Further preferably, the graphite includes at least one of petroleum coke, asphalt coke and needle coke.

5. A method for preparing a carbon-based composite negative electrode material, characterized in that: The following steps are involved: S1, weighing a carbon material m1 with a specific surface area of ​​S1, a conductive agent m2 with a specific surface area of ​​S2, and a carbon aerogel m3 with a specific surface area of ​​S3, mixing them in a solvent, and then subjecting them to ultrasonic treatment to obtain an intermediate; S2, calcining the intermediate to obtain a carbon-based composite negative electrode material; Wherein, the carbon material, the conductive agent, and the carbon aerogel satisfy the following relationship: 1≤(m2×S2+m3×S3) / (m1×S1)≤2.

6. The method for preparing a carbon-based composite negative electrode material according to claim 5, characterized in that: The ultrasonic temperature of the ultrasonic treatment is 35°C to 55°C, and the ultrasonic time is 0.5h to 2h; And / or, the calcination treatment comprises the following steps: in a H2 atmosphere, heating to 600°C~1100°C at a heating rate of 5°C / min~10°C / min, and keeping the temperature for 2h~6h; and / or, m2:m3=(1-5):1; preferably, m2:m3=(2:1)-(3:1); and / or, 1m 2 / g≤S1≤3m 2 / g; and / or, 200m 2 / g≤S2≤400m 2 / g; and / or, 800m 2 / g≤S3≤1600m 2 / g.

7. The method for preparing a carbon-based composite negative electrode material according to claim 5, characterized in that: The conductive agent is selected from carbon nanotubes; before step S1, the following step of acidifying the carbon nanotubes is also included: The carbon nanotubes are mixed with a nitric acid solution and a sulfuric acid solution and then stirred to obtain the acidified carbon nanotubes; Preferably, the mass ratio of the carbon nanotubes, the nitric acid solution, and the sulfuric acid solution is 1: (30-35): (100-120); Preferably, the carbon nanotubes include array tubes and / or oligo-walled tubes; Preferably, the stirring temperature of the stirring treatment is 100° C. to 150° C., and the stirring time is 2 h to 4 h.

8. A negative electrode sheet, characterized in that: The negative electrode active material layer in the negative electrode sheet comprises the carbon-based composite negative electrode material according to any one of claims 1 to 4 or a carbon-based composite negative electrode material prepared by the method for preparing the carbon-based composite negative electrode material according to any one of claims 5 to 7.

9. The negative electrode sheet according to claim 8, characterized in that: The negative electrode active material layer also includes a dispersant and a binder, and the mass ratio of the carbon-based composite negative electrode material, the dispersant and the binder is (96.3-97.5): (1-1.7): (1.5-2).

10. A battery, characterized in that: The battery comprises the negative electrode sheet according to claim 8 or 9.

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