Carbon material and preparation method thereof, secondary battery and electric device

Abstract

The invention provides a carbon material and a preparation method thereof, a secondary battery and an electric device. The carbon material has a porous structure, and the interlayer spacing of a 002 crystal face is 0.3523 nm to 0.3671 nm. The carbon material is used as a negative electrode active material, so that a secondary battery has relatively long cycle life, and meanwhile, the fast charging performance of the battery is improved.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and in particular to a modified carbon material and a preparation method thereof, a secondary battery and an electrical device using the carbon material as a negative electrode active material. Background Art

[0002] In recent years, as the application scope of lithium-ion batteries has become more and more extensive, lithium-ion batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. As lithium-ion batteries have made great progress, higher requirements have been put forward for their fast charging and discharging performance.

[0003] Generally, a carbon material including a porous structure is used as a negative electrode active material. However, the current preparation method of the porous carbon material has high energy consumption, and the kinetic performance of the secondary battery is not ideal, and it is difficult to take into account the cycle performance. Therefore, there is still a need to provide an improved carbon material and a preparation method. Summary of the invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a carbon material that can improve the fast charging performance of a secondary battery and at the same time make the battery have a better cycle life. This application also provides a method for preparing the carbon material, and a secondary battery and an electrical device using the carbon material as a negative electrode active material.

[0005] To this end, the first aspect of the present application provides a carbon material having a porous structure, and the interlayer spacing of the 002 crystal plane of the carbon material is 0.3523-0.3671 nm.

[0006] The porous structure of the carbon material and the enlarged carbon layer spacing jointly promote the diffusion of active ions, and the porous structure reserves pores for the expansion of the carbon material, alleviating the expansion of the material during the battery charging and discharging process, thereby improving the rapid charging performance of the secondary battery and taking into account good cycle performance.

[0007] In any embodiment, the interlayer spacing of the 002 crystal plane of the carbon material is 0.3523-0.3581 nm. Carbon materials with interlayer spacing within this range have relatively better active ion diffusion effect, thereby being able to obtain better rapid charging performance of secondary batteries.

[0008] In any embodiment, the porous structure includes micropores and mesopores. The porous structure of the carbon material including micropores and mesopores is conducive to the diffusion of active ions to a wider range of parts of the material, thereby increasing the reaction sites between the active ions and the carbon material.

[0009] In any embodiment, the percentage of the mesopore volume of the carbon material to the total pore volume of the carbon material is 35%-60%, optionally 45%-60%. When the mesopore volume of the carbon material is within the above range, the fast charging performance and cycle life of the secondary battery can be improved, and the capacity of the secondary battery can be further improved.

[0010] In any embodiment, the percentage of the micropore volume of the carbon material to the total pore volume of the carbon material is 20%-30%. When the micropore volume of the carbon material is within the above range, on the one hand, it will not lead to a decrease in cycle performance, and on the other hand, it can further improve the capacity performance of the secondary battery.

[0011] In any embodiment, the average pore size is 16-40 nm, and further optionally 16-30 nm. The appropriate average pore size of the carbon material can enable the secondary battery to obtain a relatively balanced fast charging performance and cycle performance.

[0012] In any embodiment, the ID / IG value of the carbon material is 0.749-0.889, optionally 0.749-0.820, wherein ID represents the Raman spectrum at 1350±50cm -1 The D peak intensity at 1580±50cm -1 The G peak intensity at .

[0013] The second aspect of the present application provides a method for preparing the carbon material of the first aspect. The method comprises: mixing a carbon source with a basic carbonate of a transition metal to obtain a mixture; performing a first sintering of the mixture at a first temperature of 200°C to 300°C in an inert atmosphere; heating the mixture to a second temperature of 700°C to 1000°C to perform a second sintering; and washing the product obtained by the second sintering with an acid.

[0014] In the above preparation method, only carbon source and basic carbonate of transition metal are used as reaction raw materials, and sintering is performed at two temperatures, and the raw materials and process are simple. In the first sintering at a lower temperature, the basic carbonate of transition metal decomposes to produce carbon dioxide and metal oxide. In the second sintering at a higher temperature, carbon dioxide reacts with the carbon source to activate the material, forming a large number of pore structures, and the interlayer spacing of the 002 crystal plane is expanded under the action of the gas. At the same time, the metal oxide reacts with carbon and is reduced to a transition metal, and the transition metal in situ catalyzes carbon graphitization. In this way, the activation and graphitization of the carbon source are achieved simultaneously, thereby forming a channel of a mixture of ordered carbon and disordered carbon, and improving the electrical conductivity of the material. Then in the pickling, the transition metal is removed, and the position occupied by the metal is vacated, further expanding the pore size. The carbon material thus obtained has a suitable porous structure, an expanded interlayer spacing of the 002 crystal plane and a high degree of graphitization.

[0015] In any embodiment, the weight ratio of the carbon source to the basic carbonate of the transition metal is 1:(1-8), optionally 1:(1-4). When the weight ratio of the carbon source to the basic carbonate of the transition metal is within the above range, a pore structure with appropriate size and quantity can be obtained, and a suitable interlayer spacing of the 002 crystal plane and a suitable ratio of disordered carbon to ordered carbon can be obtained (I D / I G value); and the graphitization degree of the final carbon material product is also high.

[0016] In any embodiment, the carbon source includes microcrystalline graphite and / or flake graphite, wherein microcrystalline graphite is abundant in mineral resources and is more advantageous as a carbon source.

[0017] In any embodiment, the basic carbonate of the transition metal includes basic copper carbonate and / or basic nickel carbonate. Both copper and nickel can achieve catalytic graphitization at a sintering temperature of 1000° C. or lower, thereby reducing energy consumption.

[0018] In any embodiment, the first sintering is carried out at the first temperature for 2-3 hours; optionally, the temperature is raised to the first temperature at a rate of 2-8°C / min, optionally, 2-5°C / min. The first sintering under the above conditions can fully decompose the basic carbonate.

[0019] In any embodiment, the second sintering is carried out at the second temperature for 2-5 hours, optionally, for 2-3 hours; optionally, the temperature is increased to the second temperature at a rate of 5-20°C / min, optionally, at a rate of 5-15°C / min.

[0020] In any embodiment, the acid comprises nitric acid and / or hydrochloric acid.

[0021] The third aspect of the present application provides a secondary battery, which comprises the carbon material provided in the first aspect of the present application as a negative electrode active material, or comprises the carbon material prepared by the preparation method of the carbon material provided in the second aspect of the present application as a negative electrode active material.

[0022] The fourth aspect of the present application provides an electrical device, comprising the secondary battery provided in the third aspect of the present application.

[0023] The carbon material provided in the present application has a porous structure, and the interlayer spacing of the 002 crystal plane is 0.3523-0.3671nm. The porous structure of the carbon material and the appropriately increased interlayer spacing of the 002 crystal plane shorten the diffusion path of the active ions, increase the transmission channel of the active ions, and are conducive to the diffusion of the active ions. The suitable porous structure provides a reserved space for the expansion of the material, alleviates the instability of the particle structure caused by the expansion of the material during the charge and discharge cycle, thereby improving the fast charging performance of the secondary battery while taking into account the cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of a battery cell according to an embodiment of the present application.

[0025] Figure 2 yes Figure 1 An exploded view of a battery cell according to an embodiment of the present application is shown.

[0026] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0027] Figure 4 It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0028] Figure 5 yes Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0029] Figure 6 FIG. 1 is a schematic diagram of an electric device using a secondary battery according to an embodiment of the present application as a power source.

[0030] Description of reference numerals:

[0031] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 top cover assembly DETAILED DESCRIPTION

[0032] Hereinafter, the carbon material and its manufacturing method, secondary battery and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings, and the embodiments thereof are specifically disclosed. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0033] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0034] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0035] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0036] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0037] In order to improve the kinetic performance of secondary batteries, a variety of schemes have been proposed to improve the negative electrode active materials to provide a fast transmission path for active ions. Among them, porous carbon materials, as negative electrode active materials, can provide a diffusion path for active ions, thereby improving the rate performance of secondary batteries. However, the current methods for preparing porous carbon materials mostly require high-temperature sintering, which has high energy consumption. In addition, the obtained carbon material has too high porosity and is easy to expand, resulting in unsatisfactory cycle performance of the secondary battery. For this reason, further improvements are needed to obtain carbon materials with suitable structures, so as to improve the kinetic performance of secondary batteries and take into account the cycle performance.

[0038] Based on this, the present application proposes a modified porous carbon material having a porous structure and an interlayer spacing of 002 crystal plane of 0.3523-0.3671 nm.

[0039] The porous structure of the carbon material and the enlarged carbon interlayer spacing jointly promote the diffusion of active ions, thereby improving the rapid charging performance of the secondary battery. The porous structure provides more diffusion paths for active ions, allowing the active ions to diffuse rapidly and facilitating the infiltration of the electrolyte. A larger interlayer spacing is also conducive to the rapid diffusion of active ions to more reaction sites. In addition, the rich pore structure gives the material a higher specific surface area and increases the sites of electrochemical reactions. The carbon material having the above structure has a shortened transmission path for active ions, which is conducive to the rapid diffusion of active ions, thereby improving the rate performance of the secondary battery and facilitating rapid charging and discharging. In addition, the porous structure provides reserved space for the expansion of the material, alleviates the instability of the particle structure caused by the expansion of the material during the charge and discharge cycle, and improves the cycle life of the secondary battery.

[0040] According to some embodiments, the interlayer spacing of the 002 crystal plane of the carbon material is 0.3523-0.3581 nm, preferably 0.3561 nm. Carbon materials with interlayer spacing within this range have relatively better active ion diffusion effects, thereby being able to obtain better rapid charging performance of secondary batteries.

[0041] According to some embodiments, the porous structure includes micropores and mesopores.

[0042] The porous structure of the carbon material includes micropores and mesopores, providing pores of different pore sizes. The mesopores have a larger pore size, allowing active ions to pass and diffuse more easily; the micropores have a relatively small pore size, which is conducive to the diffusion of active ions to a wider range of parts of the material, increasing the reaction sites between active ions and carbon materials. In addition to mesopores and micropores, carbon material particles can also have macropores.

[0043] The micropores mentioned in this article usually refer to pores with a pore size less than 2 nm; mesopores usually refer to pores with a pore size between 2 and 50 nm; and macropores usually refer to pores with a pore size greater than 50 nm.

[0044] In some embodiments, the mesoporous volume of the carbon material accounts for 35%-60% of the total pore volume of the carbon material, optionally 45%-60%, especially 48%-58%. Exemplarily, the mesoporous volume ratio may be 40%, 43%, 45%, 48%, 50%, 53%, 55%, 58%, etc., but is not limited thereto. The mesopore diameter is relatively large, providing a channel for the rapid transmission of active ions and providing reserved space for the expansion of the carbon material. And a suitable mesoporous volume ratio can increase the compaction density of the material and improve the capacity of the battery. Therefore, when the mesoporous volume ratio of the carbon material is within the above range, the fast charging performance and cycle life of the secondary battery can be improved, and the capacity of the secondary battery can be further improved.

[0045] In some embodiments, the micropore volume of the carbon material accounts for 20%-30% of the total pore volume of the carbon material. Exemplarily, the micropore volume ratio may be 20%, 22%, 25%, 28%, 30%, etc., but is not limited thereto. The micropores of the carbon material have a relatively low pore size, which increases the surface area of ​​the carbon material, further increases the reactivity of the material, and improves the fast charging performance of the secondary battery. When the micropore volume ratio of the carbon material is within the above range, on the one hand, it will not lead to a decrease in the cycle performance, and on the other hand, it can further improve the capacity performance of the secondary battery.

[0046] In some embodiments, the average pore size of the carbon material is in the range of 16-40nm, optionally in the range of 16-30nm. Exemplarily, the lower limit of the average pore size may be 16nm, 18nm, 20nm, 22nm, 24nm, etc. Exemplarily, the upper limit of the average pore size may be 40nm, 36nm, 34nm, 32nm, 30nm, 28nm, etc. Too small pore size in carbon materials should be avoided, because too small pore size is not conducive to the transmission of active ions, but will increase the expansion of the material, resulting in a decrease in material stability. Similarly, too large pore size in carbon materials will also cause insufficient material strength and a decrease in stability. According to some embodiments, the average pore size of the carbon material is 16-40nm, optionally 16-30nm, especially in the range of 22-30nm, which can enable the secondary battery to obtain a more balanced fast charging performance and cycle performance.

[0047] The carbon material has the above-mentioned porous structure, which enables the secondary battery to obtain better dynamic performance while taking into account the cycle performance.

[0048] According to some embodiments, the carbon material I D / I GThe value is 0.749-0.889, optionally 0.749-0.820. D Indicates that the Raman spectrum is at 1350±50cm -1 The D peak intensity at I G Indicates that the Raman spectrum is at 1580±50cm -1 The ratio of the two peak intensities is used to reflect the order of carbon in the carbon material. The order of carbon is beneficial to improving the conductivity of the material, thereby improving the kinetic performance of the secondary battery. D / I G The value makes the carbon material have good conductivity, effectively reduces the electron transfer resistance, and further facilitates the rapid charging and discharging of the material at a large rate.

[0049] The multi-level pore structure of the carbon material of the present invention, the larger carbon layer spacing and the higher I D / I G The two values ​​jointly improve the transmission efficiency of active ions, increase the number of reactive sites and the reaction speed, thereby effectively improving the fast charging performance of the secondary battery.

[0050] In the present application, the interlayer spacing of the 002 crystal plane of the carbon material has a well-known meaning in the art and can be tested using instruments and methods known in the art. For example, an X-ray diffractometer (such as Bruker D8 Discover) can be used for testing, and the test can refer to JIS K 0131-1996 and JB / T 4220-2011 to obtain the interlayer spacing of the C (002) crystal plane in the crystal structure of the material.

[0051] The average pore size of the carbon material in this application is a well-known meaning in the art and can be tested using instruments and methods known in the art. For example, the average pore size in the carbon material can be obtained by using an ASAP 2460 surface analyzer and a BJH pore size test.

[0052] In the present application, the mesopore volume fraction and micropore volume fraction of the carbon material have well-known meanings in the art and can be tested using instruments and methods known in the art. For example, the ASAP 2460 surface area analyzer can be used to measure the volume fraction of each level of pores using nitrogen as the adsorption medium and the model can be used to calculate the volume fraction of each level of pores.

[0053] In this application, the I of the carbon material D / I G The value can be tested using a Raman spectrometer. D The Raman spectrum of the material is 1350±50cm -1 The D peak intensity at I G The Raman spectrum of the material is 1580±50cm -1The test conditions are: excitation wavelength of 532nm, grating of 600 lines, objective lens of 50 times, integration time of 10s, accumulation times of 3 times, surface scanning, obtain the D peak and G peak intensity of 100 points, calculate the I of 100 points D / I G , remove the largest and smallest 30 I D / I G The average value of the remaining 40 points is the I D / I G The testing instrument may be a Horiba LabRAM HR800 Raman spectrometer.

[0054] The present application also provides a method for preparing the above carbon material. The method comprises the following steps: mixing a carbon source with a basic carbonate of a transition metal to obtain a mixture; performing a first sintering of the mixture at a first temperature of 200°C to 300°C in an inert atmosphere; heating the mixture to a second temperature of 700°C to 1000°C for a second sintering; and washing the product obtained by the second sintering with an acid.

[0055] Unlike traditional porous carbon materials that use activators such as zinc chloride and potassium hydroxide to form pores, the preparation method of the present application only uses carbon sources and basic carbonates of transition metals as reaction raw materials. The basic carbonate of the transition metal decomposes to produce carbon dioxide in the first sintering at a relatively low temperature, and when the second sintering is performed at a further elevated temperature, the carbon dioxide produced reacts with the carbon in the carbon source to activate the material and form a large number of pore structures in the material. At the same time, the metal oxide produced by the decomposition of the basic carbonate of the transition metal reacts with carbon in the second sintering and is reduced to a transition metal, and the transition metal catalyzes carbon graphitization in situ. Therefore, in the method of the present application, only the basic carbonate of the transition metal is used to perform a decomposition reaction at a relatively low temperature and a catalytic and activation effect at a relatively high temperature, thereby achieving catalytic graphitization and CO2 activation at the same time. After in-situ catalytic graphitization, the metal remains in the material, and the metal can be removed by pickling, thereby leaving vacancies in the material. These vacancies produced by removing the metal further expand the pore size and increase the surface area of ​​the carbon material.

[0056] In addition, in the traditional method, potassium hydroxide is used as an activator to modify anthracite particles, and graphitization is performed at a temperature above 2000°C. Through the etching action of the alkali, pores are formed in the material, and channels of amorphous carbon are formed, resulting in poor conductivity of the final material. When the method of the present invention is used, the generated CO2 is used as an activator, and the gas is easily diffused into the pores of the carbon source material, so that the entire carbide particles are more uniformly activated, and amorphous carbon (i.e., disordered carbon) is generated through the physical activation; at the same time, the transition metal can evenly catalyze the entire carbide particles, making the particles more uniformly graphitized (i.e., ordered carbon), and after the transition metal is removed by acid washing, the original transition metal position further becomes part of the pores, thereby obtaining a mixed channel of disordered carbon and ordered carbon, and obtaining better conductivity.

[0057] Since no chemical activator is required, the method of the present application also avoids the problem of corrosion of equipment and pollution of the environment by alkaline substances such as potassium hydroxide.

[0058] The carbon material prepared by the above method can form a porous structure as mentioned above. In addition, the carbon dioxide gas and the gas further formed in the reaction with the carbon can expand the interlayer spacing of the 002 crystal plane of the carbon material, further providing favorable conditions for the diffusion of active ions.

[0059] According to some embodiments, the carbon source used is not particularly limited. According to some specific embodiments, the carbon source can be microcrystalline graphite and / or flake graphite. Among them, microcrystalline graphite mineral resources are abundant and it is more advantageous to use it as a carbon source.

[0060] According to some embodiments, the basic carbonate of the transition metal may be basic copper carbonate and / or basic nickel carbonate. Both copper and nickel can be catalytically graphitized at a sintering temperature of 1000°C or lower. Compared with the conventional preparation method using a temperature higher than 1000°C or even close to 2000°C, it reduces energy consumption and industrial difficulty, which is conducive to reducing costs and achieving industrial production.

[0061] In some embodiments, the weight ratio of the carbon source to the basic carbonate of the transition metal is 1:(1-8), optionally 1:(1-4). For example, the weight ratio of the carbon source to the basic carbonate of the transition metal is 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, etc., but is not limited thereto, and can also be a value between any two ratios.

[0062] When the weight ratio of the carbon source to the basic carbonate of the transition metal is within the above range, a pore structure with appropriate size and quantity can be obtained, and a suitable interlayer spacing of the 002 crystal plane can be obtained; and the graphitization degree of the final carbon material product can also be improved.

[0063] The present application does not particularly limit the mixing method, and any method that can make the two mixed evenly can be used. In some embodiments, the carbon source and the basic carbonate of the transition metal can be ball-milled to make the two mixed evenly. In addition, the raw materials can also obtain a predetermined particle size by ball milling.

[0064] According to some embodiments, the first sintering is performed at a first temperature of 200-300°C for 2-3 hours. The temperature may be raised to the first temperature at a rate of 2-8°C / min, optionally, at a rate of 2-5°C / min. For example, the first sintering temperature may be 200°C, 220°C, 250°C, 280°C, 300°C, etc., or a value between any two ranges.

[0065] Sintering is performed at the first temperature for a certain period of time, and the basic carbonate decomposes to produce carbon dioxide, water and metal oxides. Taking basic copper carbonate as an example, the reaction formula is as follows:

[0066] Cu2(OH)2CO3→2CuO+H2O↑+CO2↑.

[0067] Under the above first sintering conditions, the basic carbonate can be fully decomposed to fully activate the carbon source. If the first sintering temperature is too low, the basic carbonate will not be fully decomposed, which will in turn lead to insufficient activation of the carbon source and insufficient formation of sufficient pores.

[0068] According to some embodiments, the second sintering is performed at a second temperature of 700-1000°C for 2-5 hours, optionally 2-3 hours. The temperature may be raised from the first temperature to the second temperature at a rate of 5-20°C / min, optionally 5-15°C / min. According to some embodiments, the second sintering temperature is 800-900°C, the sintering time is 2-3 hours, and the heating rate is 5-15°C / min, optionally 5-10°C / min.

[0069] It can be listed that the second temperature can be 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, etc., or a value between the ranges formed by any two values. As long as the second sintering temperature is within the above range, the transition metal can produce a better catalytic effect. It can be listed that the time of the second sintering can be 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 5 hours, etc., or a value between the ranges formed by any two values. It can be listed that the heating rate from the first temperature to the second temperature can be 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, 15°C / min, etc., but not limited to this. During the second sintering process, the carbon dioxide generated in the first sintering undergoes an oxidation-reduction reaction with C in the carbon source, consuming a portion of C, thereby further generating abundant pores in the material. At the same time, carbon dioxide, as a gas, and the gas further generated in the reaction, expand the interlayer spacing of the 002 crystal plane of the material.

[0070] At the same time, the transition metal oxide produced in the first sintering undergoes an oxidation-reduction reaction with the C in the carbon source to generate metal. Taking basic copper carbonate as an example, the reaction is as follows:

[0071] 2CuO+C→2Cu+CO2↑.

[0072] The generated transition metal in situ catalyzes the graphitization of the carbon source, thereby increasing the graphitization degree of the final carbon material and thus improving the conductivity.

[0073] According to some embodiments, the first and second sintering are both performed in a flowing inert atmosphere. The present application has no particular limitation on the inert atmosphere, which may be, for example, a nitrogen atmosphere.

[0074] Both steps of sintering can be carried out in a tubular furnace, for example. The present application has no particular limitation on the sintering device.

[0075] According to some embodiments, the acid used for washing the product obtained by the second sintering with an acid is nitric acid or hydrochloric acid. There is no particular limitation on the concentration of the acidity, and conventionally, the molar concentration of the acid may be 0.5 to 2M, and optionally 1 to 1.5M.

[0076] The metal in the product obtained by the second sintering can be removed by washing with an acid. By removing the metal, vacancies can be generated at the location where the metal was located, thereby further expanding the pore size.

[0077] After washing with acid, the carbon material can be obtained by washing, drying, etc. Optionally, the particle size of the carbon material can be reduced by further grinding (such as ball milling) to provide a product with a predetermined particle size.

[0078] Through the carbon dioxide activation and transition metal catalytic graphitization carried out simultaneously in the second sintering, the carbon source constructs a mixed channel of disordered carbon and ordered carbon, increases the diffusion rate of active ions, reduces the polarization effect, and the active ions diffuse quickly into the ordered graphite interlayer. In addition, the rich pore structure is also conducive to the infiltration of the electrolyte. The carbon material obtained by the above method can improve the rate performance of the secondary battery and take into account the cycle performance. In addition, the method has simple and easy raw materials, simple process, low sintering temperature, and thus low energy consumption, good economy, and is conducive to industrial production.

[0079] The present application also provides a secondary battery and an electric device. The secondary battery and the electric device of the present application are described below with reference to the accompanying drawings as appropriate.

[0080] The term "secondary battery" mentioned herein refers to a battery cell, a battery module or a battery pack, which are described below.

[0081] Generally, a secondary battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0082] The “active ions” mentioned herein refer to metal ions that participate in the electrochemical reaction of the battery, including, but not limited to, one or more of lithium ions, nickel ions, cobalt ions, sodium ions, and the like.

[0083] [Negative electrode]

[0084] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0085] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0086] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0087] The negative electrode active material includes the carbon material provided in the above embodiment, or includes the carbon material prepared by the preparation method provided in the above embodiment.

[0088] In some embodiments, the negative electrode active material further includes a negative electrode active material for a battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0089] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0090] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0091] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0092] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0093] [Positive electrode]

[0094] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.

[0095] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0096] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0097] In some embodiments, when the battery cell is a lithium-ion battery, the positive electrode active material may adopt a positive electrode active material for lithium-ion batteries that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05O2) and its modified compounds, etc. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0098] In some embodiments, when the battery cell is a sodium ion battery, the positive electrode active material may be a positive electrode active material for lithium ion batteries known in the art. As an example, the positive electrode active material may include at least one of the following materials: sodium transition metal oxide, polyanionic compound, Prussian blue compound, but is not limited thereto.

[0099] The battery will be accompanied by Li deintercalation and consumption during the charge and discharge process, and the molar content of Li is different when the battery is discharged to different states. In the list of positive electrode materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode material is used in the battery system, and the molar content of Li will change after charge and discharge cycles.

[0100] In the list of positive electrode materials in this application, the molar content of O is only a theoretical value. The release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0101] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0102] In some embodiments, the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0103] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0104] [Electrolytes]

[0105] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0106] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0107] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0108] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0109] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0110] [Isolation film]

[0111] In some embodiments, the battery cell further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0112] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0113] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0114] In some embodiments, the battery cell may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0115] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0116] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square or any other shape. Figure 1 The battery cell 5 is a square structure as an example.

[0117] In some embodiments, reference Figure 2 , the outer packaging may include a shell 51 and a top cover assembly 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0118] In some embodiments, battery cells may be assembled into a battery module. The number of battery cells contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0119] Figure 3 4 is an example of a battery module. Figure 3 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0120] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0121] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0122] Figure 4 and Figure 5 1 is a battery pack 1 as an example. Figure 4 and Figure 5The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0123] In addition, the present application also provides an electric device, which includes a secondary battery provided in the present application. The secondary battery can be used as a power source for the electric device, or as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0124] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0125] Figure 6 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the high power and high energy density requirements of the power consumption device for the secondary battery, a battery pack or a battery module can be used.

[0126] As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is usually required to be light and thin, and a battery cell may be used as a power source.

[0127] Example

[0128] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be obtained commercially.

[0129] Example 1

[0130] Place microcrystalline graphite and basic copper carbonate in a ball mill at a mass ratio of 1:1 (C:M mass ratio) and grind at 600 rpm for 2 hours. Then transfer the material to a tubular furnace in a flowing nitrogen atmosphere, maintain a heating rate of 5°C, heat it to 200°C, and sinter for 1 hour. Continue to heat it to 850°C at a heating rate of 10°C and sinter for 2h. Put the cooled carbon material into 1M nitric acid to clean and remove excess metals and their compounds, wash it with pure water and dry it to obtain the carbon material of the present application.

[0131] Embodiments 2 to 8

[0132] The carbon materials of Examples 2 to 8 were prepared in the same manner as in Example 1, with the amount ratio of microcrystalline graphite to basic copper carbonate (C:M mass ratio) being changed as shown in Table 1.

[0133] Comparative Example 1

[0134] Place the microcrystalline graphite in a ball mill and grind it at 600 rpm for 2 hours. Then transfer the material to a tubular furnace in a flowing nitrogen atmosphere, maintain a heating rate of 5°C, heat it to 200°C, and sinter it for 1 hour. Continue to heat it to 850°C at a rate of 10°C and sinter it for 2 hours. Put the cooled carbon material into 1M nitric acid to clean and remove excess metals and their compounds, wash it with pure water and dry it to obtain the carbon material of Comparative Example 1.

[0135] Comparative Example 2

[0136] Place the microcrystalline graphite in a ball mill and grind it at 600 rpm for 2 hours. Then transfer the material to a tubular furnace in a flowing nitrogen atmosphere, maintain a heating rate of 5°C, heat it to 200°C, and sinter it for 1 hour. Continue to heat it to 850°C at a heating rate of 10°C, pass 40mL / min of CO2 gas, sinter it for 2h, and then switch to nitrogen to naturally cool to room temperature. The cooled carbon material is placed in 1M nitric acid to clean and remove excess metals and their compounds, and then cleaned with pure water and dried to obtain the carbon material of Comparative Example 2.

[0137] Comparative Example 3

[0138] The carbon material of Comparative Example 3 was prepared in a similar manner to Example 1, except that the first sintering was performed at 180° C. The specific amount ratio of the raw materials used and the preparation process conditions are shown in Table 1.

[0139] Material performance testing

[0140] The carbon materials obtained in the above examples and comparative examples were subjected to the following tests respectively.

[0141] (1) Interlayer spacing of 002 crystal plane

[0142] The X-ray diffractometer (Bruker D8 Discover) was used to test and obtain the interlayer spacing of the C (002) crystal plane in the material crystal structure.

[0143] (2) Raman spectroscopy

[0144] The Raman spectra of the materials were measured using a Horiba Lab RAM HR800 Raman spectrometer. The test conditions were: excitation wavelength of 532 nm, grating of 600 lines, objective lens of 50 times, integration time of 10 s, accumulation times of 3 times, surface scanning, obtaining the D peak and G peak intensities of 100 points, and calculating the I peaks of 100 points. D / I G , remove the largest and smallest 30 I D / I G The average value of the remaining 40 points is the I D / I G .

[0145] (3) Porous structure

[0146] The pore size and pore structure of Example 2 and Comparative Example 2 were measured using an ASAP 2460 specific surface analyzer with N2 as the adsorption medium. The micropore volume of the carbon material prepared in Example 2 accounted for 26%, the mesopore volume accounted for 57%, and the average pore diameter was 24.62 nm; the micropore volume of the carbon material prepared in Comparative Example 2 accounted for 31%, the mesopore volume accounted for 45%, and the average pore diameter was 20.62 nm.

[0147] Battery performance test

[0148] In addition, the carbon materials obtained in the above Examples 1-8 and Comparative Examples 1-2 were respectively prepared into secondary batteries as shown below, and the battery performance tests were performed. The test results are shown in Table 2 below.

[0149] Preparation of secondary batteries

[0150] The carbon material prepared in the above examples and comparative examples was used as the negative electrode active material, the conductive agent carbon black (Super P), the thickener sodium carboxymethyl cellulose, and the binder styrene butadiene rubber were fully stirred and mixed in an appropriate amount of solvent deionized water at a weight ratio of 96.4:1:1.2:1.4 to form a negative electrode slurry. The negative electrode slurry was coated on both surfaces of the negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode sheet was obtained.

[0151] LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523) is mixed with conductive agent carbon black (Super P) and binder polyvinylidene fluoride in a weight ratio of 96:2:2, and an appropriate amount of solvent NMP is added and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is coated on both surfaces of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained.

[0152] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then LiPF6 is dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0153] A polyethylene film is used as an isolation film, and is placed in order with the positive electrode sheet and the negative electrode sheet prepared as above, so that the isolation film is located between the positive electrode sheet and the negative electrode sheet to play an isolation role, and then the electrode assembly is wound; the electrode assembly is placed in an outer package, and after drying, the electrolyte is injected, and a secondary battery is obtained after vacuum packaging, standing, forming, shaping and other processes.

[0154] (1) Fast charging test

[0155] The preparation and lithium plating of the three-electrode battery are consistent with the preparation of the lithium-ion battery mentioned above. During the preparation of the lithium-ion battery, a copper wire is connected to the battery as a reference electrode, and the negative electrode is lithium plated at a current of 20μA for 6 hours. After the lithium plating is completed, the battery is charged at the same rate of 1 / 3C at 25°C, and the anode potential is recorded. At the same rate, the higher the anode potential, the better the fast charging performance.

[0156] (2) Cyclic performance test

[0157] At 25°C, the prepared secondary battery was discharged at 1C constant current to 2.5V, and then charged at 1C constant current to an upper cut-off voltage of 4.4V, and the charging capacity at this time (i.e., 1C charging capacity) was recorded, and then constant voltage charging was performed to a current of 0.05C. After standing for 5 minutes, the secondary battery was discharged at 1C constant current to a lower cut-off voltage of 2.5V, and the discharge capacity at this time was recorded, which was the discharge capacity of the first cycle. The secondary battery was subjected to a cyclic charge and discharge test according to the above method, and the discharge capacity after 1000 cycles was recorded.

[0158] Capacity retention rate (%) of secondary battery after 1000 cycles at 25° C.=discharge capacity after 1000 cycles / discharge capacity at the first cycle×100%.

[0159] The above test results are shown in Table 1.

[0160] Table 1: Carbon material preparation process conditions and performance test results of the embodiments and comparative examples

[0161]

[0162] According to the above results, compared with the carbon material obtained in Comparative Example 1 without adding basic copper carbonate but undergoing the same sintering process, Examples 1-8 can obtain carbon materials with a porous structure and interlayer spacings of different 002 crystal planes by changing the mass ratio of the carbon source and the basic carbonate. In Examples 1-4, due to the appropriate amount of basic carbonate added, a suitable amount of activator and catalyst are generated during sintering, so that the carbon material has a suitable pore size structure and carbon order (I D / I G value), so the battery not only has good capacity and capacity retention rate of 1000 cycles, but also has better anode potential, that is, fast charging performance. Specifically, the amount of basic copper carbonate added in Example 1 is relatively small, resulting in insufficient activation of the carbon source, insufficient expansion of the interlayer spacing of the 002 crystal plane, and failure to achieve a better pore structure, but the battery already has better capacity, cycle performance and anode potential. The amount of basic copper carbonate added in Examples 2-8 gradually increases. However, if the amount of basic copper carbonate added is further increased, it will lead to the generation of too many porous structures, and too many pores will cause the collapse of part of the pore structure. Therefore, the mass ratio of carbon source to basic carbonate should not exceed 1:8. Examples 1-4, especially Example 2, have the best addition ratio of carbon source to basic carbonate, so that the secondary battery obtains a balanced and better capacity, cycle performance and fast charging performance.

[0163] In contrast, the material of Comparative Example 1 has a low carbon interlayer spacing and a high degree of graphitization, but has not been activated and modified at all, and has insufficient pore structure, which cannot provide many active sites and diffusion paths, and has poor electrical properties. Comparative Example 2 only introduces CO2 for physical activation and modification, and obtains a rich pore structure, but is accompanied by the generation of more disordered carbon (I D / I G The value of the carbon material is significantly increased), and the degree of graphitization of the material is reduced. The volume proportion of mesopores in the obtained carbon material (compared with Example 2) is reduced, and the volume proportion of micropores is increased, so that the average pore size is smaller. Compared with Comparative Example 1, the carbon material prepared by the method of Comparative Example 2 improves the battery capacity, cycle performance and anode potential to a certain extent, but the degree of improvement is limited and cannot achieve satisfactory results.

[0164] Although the best mass ratio of carbon source and basic copper carbonate was used in Comparative Example 3, the first sintering temperature was low, resulting in insufficient activation, too small interlayer spacing of the 002 crystal plane, and insufficient pores. The carbon material thus obtained had insufficient reactivity and could not provide satisfactory kinetic properties.

[0165] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A carbon material, characterized in that: The carbon material has a porous structure, and the interlayer spacing of the 002 crystal plane of the carbon material is 0.3523-0.3671 nm.

2. The carbon material according to claim 1, wherein The interlayer spacing of the 002 crystal plane of the carbon material is 0.3523-0.3581 nm.

3. The carbon material according to claim 1 or 2, wherein The porous structure includes micropores and mesopores; optionally, the percentage of the mesopore volume of the carbon material to the total pore volume of the carbon material is 35%-60%, optionally 45%-60%.

4. The carbon material according to claim 3, wherein The percentage of the micropore volume of the carbon material to the total pore volume of the carbon material is 20%-30%.

5. The carbon material according to any one of claims 1 to 4, wherein The average pore diameter of the porous structure is 16-40 nm, and further optionally 16-30 nm.

6. The carbon material according to any one of claims 1 to 5, wherein I of the carbon material D / I G The value is 0.749-0.889, optionally 0.749-0.820, where I D Indicates that the Raman spectrum is at 1350±50cm -1 The D peak intensity at I G Indicates that the Raman spectrum is at 1580±50cm -1 The G peak intensity at .

7. A method for preparing the carbon material according to any one of claims 1 to 6, characterized in that: The method comprises: mixing a carbon source with a basic carbonate of a transition metal to obtain a mixture; The mixture is first sintered at a first temperature of 200° C. to 300° C. in an inert atmosphere; Heating the mixture to a second temperature of 700° C. to 1000° C. for a second sintering; and The product obtained by the second calcination is washed with an acid.

8. The method according to claim 7, wherein: The mixing weight ratio of the carbon source to the basic carbonate of the transition metal is 1:(1-8), optionally 1:(1-4).

9. The method according to claim 7 or 8, wherein: The carbon source includes microcrystalline graphite and / or flake graphite.

10. The method according to any one of claims 7 to 9, wherein: The basic carbonate of the transition metal includes basic copper carbonate and / or basic nickel carbonate.

11. The method according to any one of claims 7 to 10, wherein: The first sintering is carried out at the first temperature for 2-3 hours; Optionally, the temperature is raised to the first temperature at a rate of 2-8°C / min, optionally, at a rate of 2-5°C / min.

12. The method according to any one of claims 7 to 11, wherein: The second sintering is carried out at the second temperature for 2-5 hours, optionally, 2-3 hours; Optionally, the temperature is raised to the second temperature at a rate of 5-20°C / min, optionally, at a rate of 5-15°C / min.

13. The method according to any one of claims 7 to 12, wherein: The acid includes nitric acid and / or hydrochloric acid.

14. A secondary battery, characterized in that: The negative electrode active material comprises the carbon material described in any one of claims 1 to 6, or comprises the carbon material prepared by the method described in any one of claims 7 to 13 as the negative electrode active material.

15. An electrical device, characterized in that: Includes the secondary battery as claimed in claim 14.

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