Negative electrode material and preparation method, battery and electric device

Abstract

The application discloses a negative electrode material and a preparation method thereof, a battery and an electric device. The negative electrode material comprises porous carbon, iron elements and / or sulfur elements are included in the porous carbon, and active materials are included in the pores of the porous carbon. In this way, the negative electrode material has good conductivity, small volume expansion and high surface activity, so that the battery has high capacity, excellent rate performance and cycle performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery materials, and particularly relates to a negative electrode material, a preparation method thereof, a battery and an electric device. BACKGROUND

[0002] With the rapid development of the current society, people's demand for green new energy and high-performance energy storage devices is becoming more and more urgent. As a new generation of green energy storage and conversion device, batteries have been widely used in portable electronic devices, electric vehicles and other fields. Batteries include positive electrode materials, negative electrode materials, separators, electrolytes and current collectors. At present, the negative electrode material of the battery has problems such as volume expansion and poor conductivity, which greatly shortens the service life of the battery and reduces the performance of the battery. Therefore, higher requirements are put forward on how to inhibit volume expansion, increase cycle performance and improve conductivity. SUMMARY

[0003] In view of the above technical problems, the present application provides a negative electrode material, a preparation method thereof, a battery and an electric device, which can make the negative electrode material have good conductivity and small expansion rate, so as to realize that the battery using the negative electrode material has excellent rate performance and cycle performance and high capacity.

[0004] In a first aspect, the present application provides a negative electrode material, which comprises porous carbon, the porous carbon comprises iron elements and / or sulfur elements, and the pores of the porous carbon comprise active materials.

[0005] In the technical scheme of the present application, the base material of the negative electrode material is porous carbon, and the pore structure in the porous carbon can buffer the volume expansion of the active material and improve the problems caused by the volume expansion. Further, the porous carbon comprises iron elements, which can improve the conductivity of the porous carbon and the negative electrode material. On the one hand, iron itself is a good conductor, and on the other hand, iron has a catalytic graphitization effect at high temperature, which improves the conductivity of the carbon material. That is, the conductivity of the porous carbon and the negative electrode material can be improved. Furthermore, the porous carbon comprises sulfur elements, which can improve the surface activity of the porous carbon material and improve the deposition of the active material. At the same time, because the atomic radius of sulfur (110 pm) is much larger than that of carbon (70 pm), the micropore volume of the porous carbon will be effectively increased, and the expansion space of the active material will be reserved. Furthermore, the simultaneous presence of iron elements and sulfur elements can improve the capacity of the negative electrode material and enhance the rate performance.

[0006] In some embodiments, the content of iron elements in the negative electrode material is 50 ppm-3000 ppm. If the content of iron is too low, the improvement effect on the conductivity of the negative electrode material will be poor. If the content of iron is too high, the specific capacity of the active material will be reduced, and there is a risk of iron precipitation, which affects the safety performance of the battery material.

[0007] In some embodiments, the content of sulfur element in the negative electrode material is 100 ppm-1500 ppm. Too low sulfur content is poor for improving the surface activity of the porous carbon material, and too high sulfur content will make the micropore volume and the content of micropores of the porous carbon too large.

[0008] In some embodiments, the average pore diameter of the porous carbon is 2 nm-50 nm. By designing the pore diameter of the porous carbon, the deposition of the active material can be facilitated, and the deposition difficulty can be reduced.

[0009] In some embodiments, the pore volume of the porous carbon is 0.1-2.0 cm 3 / g. Too low pore volume of the porous carbon is not conducive to the deposition of the active material inside the porous carbon, and too high pore volume of the porous carbon will significantly reduce the strength of the porous carbon, resulting in that the negative electrode material is not pressure-resistant.

[0010] In some embodiments, the content ratio of micropores, mesopores and macropores in the porous carbon is (5%-25%):(65%-90%):(5%-15%). The micropores have small pore volume, and the active material is difficult to deposit into the micropores, but the micropores can be reserved as expansion space. Too large content ratio of the micropores will result in too large unused pore volume, and too small content ratio of the micropores will result in insufficient reserved expansion space. Too large content ratio of the mesopores / macropores will result in that the strength of the porous carbon is significantly reduced, resulting in that the negative electrode material is not pressure-resistant. Too low content ratio of the mesopores is not conducive to the deposition of the active material, resulting in that the effective active material deposition amount is too low, and too small content ratio of the macropores is not conducive to the synthesis of the porous carbon material and is difficult to realize. By controlling the content ratio of the micropores, mesopores and macropores in the porous carbon, the above problems can be balanced.

[0011] In some embodiments, the active material includes a silicon-carbon material, and the silicon-carbon material includes nano-silicon particles and nano-carbon particles. By depositing the nano-silicon and nano-carbon in the pores of the porous carbon material, the size of the nano-silicon particles can be effectively controlled, and the nano-silicon and nano-carbon are uniformly distributed in the pores of the porous carbon, which can effectively improve the conductivity of the negative electrode material, and further reserve the expansion space of the nano-silicon, thereby further reducing the expansion of the negative electrode material.

[0012] In the technical scheme of the embodiments of the present application, by depositing the nano-silicon particles and nano-carbon particles in the pores of the porous carbon material, the size of the nano-silicon particles can be effectively controlled, and the nano-silicon and nano-carbon are uniformly distributed in the pores of the porous carbon, which can effectively improve the conductivity of the negative electrode material, and further reserve the expansion space of the nano-silicon, thereby further reducing the expansion of the negative electrode material.

[0013] In some embodiments, the particle size of the nano-silicon particles is less than or equal to 10 nm. By reducing the size of the nano-silicon particles, the cycle performance of the negative electrode material is improved, the local stress of the negative electrode material is reduced, and the structural stability of the negative electrode material during the charging and discharging process is increased.

[0014] In some embodiments, the particle size of the nano-carbon particles is less than or equal to 30 nm. By reducing the particle size of the nano-carbon particles, the nano-scale mixing of the nano-silicon and the nano-carbon is improved, and the conductivity of the negative electrode material is improved.

[0015] In some embodiments, the mass ratio of silicon element and carbon element in the negative electrode material is Si:C = (20-55):(40-75). By limiting the silicon content, the negative electrode material has a higher capacity, and the carbon content can promote the effective formation of porous carbon and effectively isolate the subsequently deposited nano-silicon particles.

[0016] In some embodiments, the mass ratio of silicon element, carbon element and oxygen element in the negative electrode material is Si:C:O = (20-55):(40-75):(0.5-5). By limiting the oxygen content, the flexibility of the porous carbon and the connection stability of the porous carbon and the nano-silicon are improved.

[0017] In some embodiments, the particle size Dv50 of the negative electrode material is 3-8 μm; the porosity of the negative electrode material is 5%-30%; and the specific surface area of the negative electrode material is less than or equal to 5.0 m 2 / g. By limiting the particle size of the negative electrode material, the problems of poor cycle performance caused by too small particle size and poor conductivity caused by too large particle size are reduced. By reserving the porosity, the expansion space of the silicon material during charging is reserved, the expansion is buffered, and the cycle performance of the negative electrode material is improved. Too high specific surface area (BET) will affect the performance of the material, and too low specific surface area will be difficult to achieve in the porous carbon material.

[0018] In a second aspect, the present application provides a battery comprising a positive electrode sheet, a separator and a negative electrode sheet, the separator being between the positive electrode sheet and the negative electrode sheet to play a separating role, and the negative electrode sheet comprising a negative electrode material and a negative electrode current collector, the negative electrode material comprising any one of the above negative electrode materials.

[0019] Since the battery of the present application comprises the negative electrode material provided by the present application, it at least has the same advantages as the negative electrode material.

[0020] In a third aspect, the present application provides an electric device comprising the battery of any one of the above.

[0021] Since the electric device of the present application comprises the battery provided by the present application, it at least has the same advantages as the battery.

[0022] In a fourth aspect, the present application provides a preparation method of the negative electrode material, comprising: providing a porous carbon precursor, the porous carbon precursor comprising a carbon precursor, and an iron precursor and / or a sulfur precursor; processing the porous carbon precursor to obtain a porous carbon; and depositing an active material in the pores of the porous carbon to obtain the negative electrode material of any one of the above.

[0023] In some embodiments, the depositing the active material in the pores of the porous carbon comprises: depositing the nano-silicon particles and the nano-carbon particles in the pores of the porous carbon by gas-phase co-deposition; and the volume ratio of the silicon source gas to the carbon source gas in the silicon-carbon co-deposition is greater than or equal to 6:1. By using the co-deposition method, the nano-silicon particles and the nano-carbon particles can be deposited more uniformly; if the volume ratio of the silicon source gas to the carbon source gas is too low, the amount of carbon deposited will be too large, which will affect the silicon-carbon co-deposition and the specific capacity of the negative electrode material. If the volume ratio of the silicon source gas to the carbon source gas is too high, the amount of carbon deposited will be too small, which will not effectively isolate the nano-silicon from growing and will not effectively improve the conductivity of the negative electrode material.

[0024] In some embodiments, the concentration of the silicon source gas in the gas source for the silicon-carbon co-deposition is 5%-80%. If the concentration of the silicon source gas is too low, the deposition time will be long, which is not conducive to improving the production efficiency. If the concentration of the silicon source gas is too high, the production safety risk will be high, the nano-silicon will be prone to agglomeration, and the silicon-carbon co-deposition will also be affected.

[0025] In some embodiments, the silicon source gas comprises one or more of monosilane, disilane, trisilane, monochlorosilane, dichlorosilane, and trichlorosilane; and the carbon source gas comprises one or more of methane, ethane, butane, propane, ethylene, propylene, butylene, and acetylene.

[0026] In some embodiments, the iron precursor comprises one or more of ferric chloride, ferric nitrate, ferric sulfate, carbonyl iron, and ferrocene; and the sulfur precursor comprises one or more of hydrogen sulfide (H2S), thiophene, a thiophene compound, a mercaptan, a sulfenol, and a sulfide.

[0027] In some embodiments, the preparation method further comprises: forming a carbon coating layer on the porous carbon by gas-phase deposition; wherein the deposition gas for the gas-phase deposition is a mixed gas of C2H2 and N2, the volume ratio of C2H2 is 2%-20%, the gas flow rate is 100-300 mL / min, the reaction temperature is 800-1000℃, and the deposition reaction time is 0.5-2h. By forming the carbon coating layer, the conductivity of the negative electrode material can be improved.

[0028] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, the specific embodiments of the present application can be implemented in accordance with the content of the description, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0029] Various other advantages and benefits will become apparent to those of ordinary skill in the art, upon reading the following detailed description of the preferred embodiment. The accompanying drawings are included to provide a better understanding of the preferred embodiment, and are not intended to be limiting of the application. Moreover, in the drawings, like reference numerals denote same or similar components. In the drawings:

[0030] Figure 1 Structure diagram of a vehicle for some embodiments of the application;

[0031] Figure 2 Structure diagram of a battery for some embodiments of the application;

[0032] Figure 3 Structure diagram of a battery cell for some embodiments of the application. DETAILED DESCRIPTION

[0033] The embodiments of the technical solutions of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application; the terms "comprising" and "having," and any variations thereof, as used in the specification and claims and the aforementioned drawings, are intended to cover not exclusive inclusions.

[0035] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0036] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearance of the phrase in various places in the specification are not necessarily all referring to the same embodiment, or are necessarily mutually exclusive or alternative embodiments to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0037] In the description of the embodiments of the present application, the term "and / or" is merely an association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are in an "or" relationship.

[0038] In the description of the embodiments of the present application, the term "a plurality of" refers to two or more (including two), and similarly, "a plurality of groups" refers to two or more groups (including two groups), and "a plurality of pieces" refers to two or more pieces (including two pieces).

[0039] In recent years, to meet the demand for multifunctional products, people have put forward higher and higher requirements for the performance of battery endurance time, safety and capacity. Lithium ion battery has the advantages of high voltage, light weight, long cycle life, no memory effect, good safety, etc., and is widely used. Lithium ion battery includes positive electrode material, negative electrode material, separator, electrolyte and current collector, etc. Commercialized lithium ion battery negative electrode material can use graphite material or silicon material. However, the theoretical specific capacity of graphite is low, which cannot meet the demand of high energy density equipment. Silicon as a negative electrode material has the advantages of high specific capacity, high safety, abundant raw material sources, etc., and is considered as a new type of high-performance lithium ion battery negative electrode material. However, as a negative electrode material, silicon will cause huge volume expansion of lithium alloy in the battery during charging and discharging, greatly shortening the battery life. In addition, the silicon material has relatively low conductivity as a semiconductor, and the electron transfer rate is slow. Therefore, higher requirements are put forward on how to inhibit volume expansion, increase cycle performance and improve conductivity.

[0040] To solve the above technical problems, the prior art uses coating technology, for example, using a catalyst to coat the carbon substrate, using a mixed gas containing a carbon source and a silicon source to perform vapor deposition on the pretreated substrate, after pre-lithiation treatment, using a graphitized carbon source for coating, and after carbonization, a silicon-carbon negative electrode material is obtained. The silicon-carbon negative electrode material can improve the process compatibility of negative electrode sheet preparation and battery preparation to a certain extent, reduce the volume expansion rate, and prolong the cycle life. However, the silicon content of the silicon-carbon negative electrode material only exists in the coating layer, and the silicon content is ≤25%, that is, the capacity of the silicon-carbon material is low, which will be greatly limited in actual application, and the synthesis temperature of the crystalline carbon layer in the silicon-carbon material is relatively high, which will cause the silicon grains to grow, resulting in excessive expansion of local silicon, particle rupture, and deterioration of the cycle performance of the material. On the other hand, the synthesis process of the silicon-carbon material is too complex, and the bonding strength between the substrate and the coating layer, and between the coating layers is weak, which will cause the cycle performance of the silicon-carbon material to deteriorate in the actual application process.

[0041] The battery disclosed by the embodiments of the present application can be used in a power consumption device using the battery as a power source or a variety of energy storage systems using the battery as an energy storage element. The power consumption device can be, but is not limited to, a mobile phone, a tablet, a notebook computer, an electric toy, an electric tool, an electric vehicle, an electric automobile, a ship, a spacecraft, and the like. Among them, the electric toy can include a fixed or mobile electric toy, such as a game console, an electric automobile toy, an electric ship toy, and an electric aircraft toy, and the like, and the spacecraft can include an airplane, a rocket, a space shuttle, a spacecraft, and the like.

[0042] The following embodiments are described by taking a power consumption device of an embodiment of the present application as a vehicle 1000 for convenience of description.

[0043] Please refer to Figure 1 , Figure 1 A structural schematic diagram of the vehicle 1000 provided by some embodiments of the present application is shown. The vehicle 1000 can be a fuel automobile, a gas automobile, or a new energy automobile, and the new energy automobile can be a pure electric automobile, a hybrid electric automobile, or a range extended automobile, etc. The vehicle 1000 is internally provided with a battery 100, which can be arranged at the bottom, the head, or the tail of the vehicle 1000. The battery 100 can be used for power supply of the vehicle 1000, for example, the battery 100 can be used as an operating power source of the vehicle 1000. The vehicle 1000 can further include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the working power demand of the vehicle 1000 during starting, navigation, and driving.

[0044] In some embodiments of the present application, the battery 100 can not only be used as an operating power source of the vehicle 1000, but also be used as a driving power source of the vehicle 1000, to replace or partially replace fuel or natural gas to provide driving power for the vehicle 1000.

[0045] Please refer to Figure 2 , Figure 2A schematic diagram of a battery 100 is provided in some embodiments of the present application. The battery 100 includes a box 10 and a battery cell 20, which is accommodated in the box 10. The box 10 is used to provide an accommodation space for the battery cell 20, and the box 10 can adopt various structures. In some embodiments, the box 10 can include a first part 11 and a second part 12, the first part 11 and the second part 12 are overlapped with each other, and the first part 11 and the second part 12 jointly define an accommodation space for accommodating the battery cell 20. The second part 12 can be a hollow structure with one end open, and the first part 11 can be a plate structure, which is overlapped with the open side of the second part 12 to jointly define the accommodation space with the second part 12. The first part 11 and the second part 12 can also be hollow structures with one side open, and the open side of the first part 11 is overlapped with the open side of the second part 12. Of course, the box 10 formed by the first part 11 and the second part 12 can have various shapes, such as a cylinder, a cuboid, etc.

[0046] In the battery 100, the battery cell 20 can be multiple, and the multiple battery cells 20 can be connected in series, in parallel, or in a mixed connection. The mixed connection means that there are both series connection and parallel connection among the multiple battery cells 20. The multiple battery cells 20 can be directly connected in series, in parallel, or in a mixed connection, and then the whole of the multiple battery cells 20 is accommodated in the box 10. Of course, the battery 100 can also be that the multiple battery cells 20 are first connected in series, in parallel, or in a mixed connection to form a battery module, and then multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole, which is accommodated in the box 10. The battery 100 can also include other structures, for example, the battery 100 can also include a busbar component for realizing the electrical connection among the multiple battery cells 20.

[0047] Each battery cell 20 can be a secondary battery or a primary battery, and can also be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto. The battery cell 20 can be in the shape of a cylinder, a flat body, a cuboid, or other shapes, etc.

[0048] Please refer to Figure 3 , Figure 3 A schematic diagram of a battery cell 20 is provided in some embodiments of the present application. The battery cell 20 refers to the smallest unit that constitutes a battery. As Figure 3 , the battery cell 20 includes an end cover 21, a shell 22, an electrode assembly 23, and other functional components.

[0049] The end cover 21 refers to a component that covers the opening of the shell 22 to isolate the internal environment of the battery monomer 20 from the external environment. Without limitation, the shape of the end cover 21 can be adapted to the shape of the shell 22 to fit the shell 22. Optionally, the end cover 21 can be made of a material with certain hardness and strength, such as aluminum alloy, so that the end cover 21 is not easily deformed when subjected to extrusion collision, so that the battery monomer 20 can have higher structural strength, and the safety performance can also be improved. The end cover 21 can be provided with functional components such as electrode terminals 21a. The electrode terminals 21a can be used to electrically connect with the cell assembly 23 for output or input of the electrical energy of the battery monomer 20. In some embodiments, the end cover 21 can also be provided with a pressure relief mechanism for relieving the internal pressure of the battery monomer 20 when the internal pressure or temperature of the battery monomer 20 reaches a threshold value. The material of the end cover 21 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not make special limitations. In some embodiments, an insulating member can also be provided on the inner side of the end cover 21, which can be used to isolate the electrical connection components in the shell 22 from the end cover 21 to reduce the risk of short circuit. For example, the insulating member can be plastic, rubber, etc.

[0050] The shell 22 is a component for fitting the end cover 21 to form the internal environment of the battery monomer 20, wherein the formed internal environment can be used to accommodate the cell assembly 23, electrolyte and other components. The shell 22 and the end cover 21 can be independent components, and an opening can be provided on the shell 22, and the end cover 21 is covered on the opening to form the internal environment of the battery monomer 20. Without limitation, the end cover 21 and the shell 22 can also be integrated, specifically, the end cover 21 and the shell 22 can form a common connecting surface before other components enter the shell, and when it is necessary to encapsulate the internal environment of the shell 22, the end cover 21 is covered on the shell 22. The shell 22 can be various shapes and various sizes, such as rectangular parallelepiped, cylindrical, hexagonal prism, etc. Specifically, the shape of the shell 22 can be determined according to the specific shape and size of the cell assembly 23. The material of the shell 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not make special limitations.

[0051] The electrode assembly 23 is a component in which electrochemical reactions occur in the battery cell 100. One or more electrode assemblies 23 can be included in the housing 22. The electrode assembly 23 is mainly formed by winding or layering a positive electrode sheet and a negative electrode sheet, and a separator is generally provided between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet and the negative electrode sheet have portions with active materials that constitute a main body of the electrode assembly, and portions without active materials that each constitute a tab 23a. The positive electrode tab and the negative electrode tab can be located together at one end of the main body or at opposite ends of the main body. During charging and discharging of the battery, the positive active material and the negative active material react with the electrolyte, and the tabs 23a connect the electrode terminals to form a current loop.

[0052] According to some embodiments of the present application, a negative electrode material is provided, the negative electrode material comprising a porous carbon, the porous carbon comprising iron and / or sulfur elements, and the porous carbon comprising an active material in pores of the porous carbon.

[0053] The porous carbon refers to a carbon material with different pore structures. The porous carbon can be a biomass porous carbon or a resin porous carbon. Different pore structures allow different molecules / ions to enter the inside of the pore channel. The porous carbon can serve as a base material to provide a base for the deposition and attachment of the active material.

[0054] In some embodiments, the active material is deposited in the pores of the porous carbon, and the active material can be one or more of a silicon-carbon material, an aluminum-containing material, a tin-containing material, and an antimony-containing material. Further, the silicon-carbon material comprises nano-silicon particles and nano-carbon particles, and the resulting negative electrode material is a composite material of nano-silicon, nano-carbon, and porous carbon. The nano-silicon / nano-carbon / porous carbon are tightly combined together, improving the stability of the structure of the negative electrode material.

[0055] The nano-silicon is a nano-sized amorphous elemental silicon, and the nano-carbon is a nano-sized carbon particle, such as carbon black. The nano-silicon particles and the nano-carbon particles are deposited in the pores of the porous carbon in a stacked, blended, and uniform manner.

[0056] In this embodiment of the present application, by depositing nano-silicon particles and nano-carbon particles in the pores of the porous carbon material, the size of the nano-silicon particles can be effectively controlled. At the same time, the nano-silicon and the nano-carbon are uniformly distributed in the pores of the porous carbon, which can effectively improve the electrical conductivity of the negative electrode material, and further reserve space for the expansion of the nano-silicon, thereby further reducing the expansion effect of the negative electrode material.

[0057] In some embodiments, the average pore size of the porous carbon is 2-50 nm. Preferably, it is 20-30 nm. Specifically, it can be 5 nm, 8 nm, 13 nm, 19 nm, 26 nm, 33 nm, 41 nm, 49 nm, etc. By designing the pore size of the porous carbon, the deposition of the active material can be facilitated, and the difficulty of deposition can be reduced.

[0058] In some embodiments, the particle size of the nano-silicon particles is less than or equal to 10 nm. Specifically, it can be 1 nm, 2.5 nm, 3 nm, 4.2 nm, 6 nm, 7.3 nm, 8 nm, 9 nm, etc. By reducing the size of the nano-silicon particles, the cycle performance of the negative electrode material can be improved, the local stress of the silicon-carbon composite material (i.e. the negative electrode material) can be reduced, and the structural stability of the negative electrode material during the charging and discharging process can be increased.

[0059] In some embodiments, the particle size of the nano-carbon particles is less than or equal to 30 nm. Specifically, it can be 3 nm, 5 nm, 9 nm, 11 nm, 14 nm, 17 nm, 22 nm, 28 nm, etc. By reducing the particle size of the carbon nano-particles, the nano-scale mixing of nano-silicon and nano-carbon can be improved, and the conductivity of the negative electrode material can be improved.

[0060] In some embodiments, the porous carbon includes iron elements and / or sulfur elements.

[0061] Specifically, the iron source and / or the sulfur source can be mixed with the resin precursor of the resin porous carbon, and then the mixture can be treated to obtain the porous carbon containing the iron elements and / or the sulfur elements.

[0062] In an embodiment, the porous carbon can be resin porous carbon, and the iron elements and / or the sulfur elements can be added to the resin precursor of the resin porous carbon, so that the obtained porous carbon contains the iron elements and / or the sulfur elements.

[0063] Specifically, the iron source and / or the sulfur source can be mixed with the resin precursor of the resin porous carbon, and then the mixture can be treated to obtain the porous carbon containing the iron elements and / or the sulfur elements.

[0064] Specifically, the iron source and / or the sulfur source can be mixed with the resin precursor of the resin porous carbon, and then the mixture can be treated to obtain the porous carbon containing the iron elements and / or the sulfur elements.

[0065] In this embodiment, the iron elements can improve the conductivity of the porous carbon and the negative electrode material. On the one hand, iron itself is a good conductor, and on the other hand, iron has a catalytic graphitization effect at high temperatures, which improves the conductivity of the carbon material. The sulfur elements can improve the surface activity of the porous carbon material and improve the deposition of nano-silicon and nano-carbon. At the same time, because the atomic radius of sulfur (110 pm) is much larger than that of carbon (70 pm), the micropore volume and the micropore content ratio of the porous carbon can be effectively increased, and more expansion space for the negative electrode material can be reserved.

[0066] In some embodiments, the content of iron element in the porous carbon is 50-3000 ppm. Specifically, it can be 100 ppm, 200 ppm, 300 ppm, 600 ppm, 1000 ppm, 1700 ppm, 2200 ppm, 2800 ppm, etc. Too low iron content has poor effect on improving the conductivity of the negative electrode material, and too high iron content will lead to the decrease of the specific capacity of the negative electrode material, and there is a risk of iron precipitation, which affects the safety performance of the battery.

[0067] In some embodiments, the content of sulfur element in the porous carbon is 100-1500 ppm. Specifically, it can be 150 ppm, 210 ppm, 360 ppm, 530 ppm, 690 ppm, 820 ppm, 970 ppm, 1450 ppm, etc. Too low sulfur content has poor effect on improving the surface activity of the porous carbon material, and too high sulfur content will make the micropore volume of the porous carbon too large.

[0068] In some embodiments, the mass ratio of silicon element and carbon element in the negative electrode material is Si:C=(20-55):(40-75). Specifically, it can be 22:43, 27:56, 35:62, 43:69, 54:71, etc. By limiting the content of silicon, the negative electrode material can have a higher capacity, and the content of carbon can promote the effective formation of the porous carbon and effectively isolate the subsequently deposited nano-silicon particles.

[0069] In some embodiments, the mass ratio of silicon element, carbon element and oxygen element in the negative electrode material is Si:C:O=(20-55):(40-75):(0.5-5). Specifically, it can be 22:43:0.6, 27:56:1.3, 35:62:2.8, 43:69:3.7, 54:71:4.6, etc. By limiting the content of oxygen, the flexibility of the porous carbon and the connection stability of the porous carbon and nano-silicon and nano-carbon can be improved.

[0070] In some embodiments, the pore volume of the porous carbon is 0.1-2.0 cm 3 / g. Specifically, it can be 0.2 cm 3 / g, 0.34 cm 3 / g, 0.41 cm 3 / g, 0.5 cm 3 / g, 0.63 cm 3 / g, 0.7 cm 3 / g, 0.85 cm 3 / g, 0.97 cm 3 / g, 1.07 cm 3 / g, 1.27 cm 3 / g, 1.47 cm 3 / g, 1.67 cm 3 / g, 1.87 cm 3 / g, 1.97 cm 3 / g, etc. Among them, too low pore volume of the porous carbon is not conducive to the deposition of nano-silicon and nano-carbon inside the porous carbon; too high pore volume of the porous carbon will significantly reduce the strength of the porous carbon, resulting in poor pressure resistance of the negative electrode material.

[0071] In some embodiments, the content ratio of micropores, mesopores, and macropores in the porous carbon is (5%-25%):(65%-90%):(5%-15%). Specifically, it can be 6%:68%:7%, 10%:73%:9%, 13%:81%:10%, 19%:85%:13%, 24%:89%:15%, etc.

[0072] Among them, according to the pore size, the pores can be divided into three categories: macropores (pore size > 50 nm), mesopores (mesopores) (2 nm ≤ pore size ≤ 50 nm), and micropores (pore size < 2 nm). The pore volume of the micropores is too small, and it is difficult for nano-silicon particles to deposit into the micropores, but the micropores can become reserved expansion space; too large content ratio of the micropores will result in too large unutilized pore volume, and too small content ratio of the micropores will result in insufficient reserved expansion space. Too large content ratio of the mesopores / macropores will result in reduced strength of the porous carbon, resulting in poor pressure resistance of the negative electrode material. Too low content ratio of the mesopores will not be conducive to the deposition of silicon, resulting in too low effective silicon deposition amount, and too small content ratio of the macropores will not be conducive to the synthesis of the porous carbon. By controlling the content ratio of the micropores, mesopores, and macropores in the porous carbon, the above problems can be balanced.

[0073] In some embodiments, the particle size Dv50 of the negative electrode material is 3-8 μm. Dv50 is the particle size corresponding to the cumulative volume percentage of 50% of the material. Specifically, it can be 3.3 μm, 3.9 μm, 4.2 μm, 4.8 μm, 5.5 μm, 6 μm, 7 μm, 7.4 μm, etc. By limiting the particle size of the negative electrode material, the problems of poor cycle performance due to too small particle size and poor conductivity due to too large particle size can be reduced.

[0074] In some embodiments, the porosity of the negative electrode material is 5%-30%. Specifically, it can be 8%, 12%, 15%, 18%, 23%, 26%, 28%, etc. By reserving the porosity, the expansion space of the silicon material during charging can be reserved, the expansion can be buffered, and the cycle performance of the negative electrode material can be improved.

[0075] In some embodiments, the specific surface area of the negative electrode material is less than or equal to 5.0 m 2 / g. The specific surface area refers to the total area possessed by unit mass of material. Specifically, it can be 0.5 m 2 / g, 1.3 m 2 / g, 1.8 m 2 / g, 2.5 m 2 / g, 3.2 m2 / g, 4.5 m 2 / g, etc. Too high specific surface area (BET) will affect the performance of the negative electrode material, and too low specific surface area (BET) is not conducive to the formation of porous carbon.

[0076] In the above embodiments, the negative electrode material provided by the application contains nano-silicon / nano-carbon in the pores of the porous carbon material, which can effectively control the size of the silicon particles, so that the silicon particles are controlled in a small range, and the close combination of nano-silicon / nano-carbon / porous carbon is achieved, thereby improving the structural stability of the negative electrode material. The negative electrode material can achieve high silicon proportion incorporation, realize high capacity of the negative electrode material, and has small volume expansion and good cycle performance. Further, the negative electrode material also contains iron and sulfur elements, so that the negative electrode material also has good electrical conductivity and small volume expansion, thereby realizing excellent rate performance and cycle performance of the negative electrode material.

[0077] According to some embodiments of the application, the application further provides a negative electrode tab, the negative electrode tab comprising a negative electrode material and a negative electrode current collector, the negative electrode material comprising any one of the above negative electrode materials.

[0078] According to some embodiments of the application, the application further provides a battery, the battery comprising a positive electrode tab, a separator, and a negative electrode tab, the separator being located between the positive electrode tab and the negative electrode tab to play a separating role, and the negative electrode tab comprising any one of the above negative electrode tabs.

[0079] According to some embodiments of the application, the application further provides an electric device, the electric device comprising the battery of any one of the above solutions, and the battery being used to provide electric energy for the electric device.

[0080] The electric device can be a device or system of any one of the above applications.

[0081] According to some embodiments of the application, the application further provides a preparation method of a negative electrode material, the preparation method comprising: providing a porous carbon; and depositing an active material in the pores of the porous carbon to obtain the negative electrode material of any one of the above.

[0082] Specifically, the porous carbon can be biomass porous carbon or resin porous carbon.

[0083] In an embodiment, the providing of the porous carbon comprises: providing a porous carbon precursor, the porous carbon precursor comprising a carbon precursor, and an iron precursor and / or a sulfur precursor; and treating the porous carbon precursor to obtain the porous carbon.

[0084] The iron precursor includes one or more of ferric chloride, ferric nitrate, ferric sulfate, carbonyl iron, and ferrocene; the sulfur precursor includes one or more of hydrogen sulfide (H2S), thiophene, a thiophene compound, a mercaptan, a sulfenol, and a sulfide. The carbon precursor includes one or more of furan resin, urea-formaldehyde resin, melamine resin, phenol-formaldehyde resin, epoxy resin, polyformaldehyde methyl acrylate resin, and polyacrylonitrile.

[0085] In this embodiment, the iron precursor, the sulfur precursor, and the resin precursor are mixed, so that the iron and the sulfur can be uniformly distributed in the porous carbon matrix, and the conduction is more uniform.

[0086] Specifically, the iron source solution and the sulfur source solution are added to the resin precursor solution and stirred to be uniformly dispersed, to obtain a mixed solution A. The mass ratio of the iron source, the sulfur source, and the resin precursor is adjusted according to the design requirements of the material.

[0087] The mixed solution A is placed in an oven at 70-140°C for pre-curing for 3-12h, and the cured material is crushed to obtain a powder B.

[0088] The powder B is placed in an oven and protected by nitrogen, and is fully cured at 150-220°C for 8-20h to obtain a powder C.

[0089] The powder C is placed in a high-temperature furnace and protected by nitrogen, and is carbonized at 900-3000°C for 2-4h to form a porous carbon powder D.

[0090] In an embodiment, active material is deposited in the pores of the porous carbon, and the active material includes nano-silicon particles and nano-carbon particles. The specific method includes: using a gas-phase co-deposition method to deposit nano-silicon particles and nano-carbon particles in the pores of the porous carbon. By using the co-deposition method, the nano-silicon particles and the nano-carbon particles can be more uniformly deposited.

[0091] Specifically, the powder D is subjected to silicon-carbon deposition by a chemical vapor deposition method, the volume ratio of a silicon source gas to a carbon source gas in the silicon-carbon co-deposition is adjusted, and at least one of N2, H2, and Ar can be introduced for dilution to adjust the concentration of the silicon source gas. The flow rate of the mixed gas introduced is 100-1000mL / min, the reaction temperature is 400-1000°C, and the deposition reaction time is 2-10h. The final product, a nano-silicon / nano-carbon / porous carbon composite material E, is obtained.

[0092] In an embodiment, the volume ratio of the silicon source gas to the carbon source gas in the silicon-carbon co-deposition is greater than or equal to 6:1. Optionally, the volume ratio is 7:1-40:1, and specifically, the volume ratio can be 8:1, 13:1, 17:1, 21:1, 29:1, 33:1, 38:1, 43:1, etc. If the volume ratio of the silicon source gas to the carbon source gas is too low, the amount of carbon deposition will be too large, which will affect the silicon-carbon co-deposition and the gravimetric capacity of the silicon-carbon composite material. If the volume ratio of the silicon source gas to the carbon source gas is too high, the amount of carbon deposition will be too small, which will not effectively isolate the growth of the nanosilicon and will not effectively improve the conductivity of the silicon-carbon composite material.

[0093] In an embodiment, at least one of N2, H2, and Ar can be introduced to dilute the silicon source gas and the carbon source gas, so that the concentration of the silicon source gas in the gas source for the silicon-carbon co-deposition is 5%-80%. Specifically, the concentration of the silicon source gas can be 8%, 10%, 18%, 25%, 31%, 43%, 57%, 65%, 78%, etc. If the concentration of the silicon source gas is too low, the deposition time will be long, which is not conducive to improving the production efficiency. If the concentration of the silicon source gas is too high, the production safety risk will be high, and the nanosilicon will be prone to agglomeration, which will also affect the silicon-carbon co-deposition.

[0094] In some embodiments, the silicon source gas includes one or more of monosilane, disilane, trisilane, monochlorosilane, dichlorosilane, and trichlorosilane; and the carbon source gas includes one or more of methane, ethane, butane, propane, ethylene, propylene, butylene, and acetylene.

[0095] In some embodiments, the method further includes forming a carbon coating layer on the porous carbon by gas phase deposition; wherein the deposition gas for the gas phase deposition is a mixed gas of C2H2 and N2, the volume ratio of C2H2 is 2%-20%, the flow rate of the introduced gas is 100-300 mL / min, the reaction temperature is 800-100°C, and the deposition reaction time is 0.5-2h. By setting the carbon coating layer, the conductivity of the negative electrode material can be improved.

[0096] In the above embodiments, the preparation method of the negative electrode material provided by the present application is used to uniformly distribute the iron and sulfur elements in the porous carbon matrix, so that the conductivity is more uniform. The gas phase co-deposition is used to make the nanosilicon particles and the nanocarbon particles more uniformly deposited. The appropriate volume ratio of the silicon source gas to the carbon source gas is used to improve the gravimetric capacity of the silicon-carbon composite material and effectively improve the conductivity of the silicon-carbon composite material. The inert gas is introduced to dilute the gas source for the silicon-carbon co-deposition, and the concentration of the silicon source gas in the gas source for the silicon-carbon co-deposition is controlled, which is conducive to improving the production efficiency and safety. The carbon coating layer is set, which can improve the conductivity of the silicon-carbon negative electrode material.

[0097] In the above embodiments, the negative electrode material provided by the present application is prepared by co-deposition of nano-silicon and nano-carbon in the pores of the porous carbon material, which can effectively control the size of the silicon particles, realize the control of the silicon particles in a small range, and realize the close combination of nano-silicon / nano-carbon / porous carbon. The material structure is stable, and the material can realize high-silicon proportion doping, realize high capacity of the negative electrode material, and has small expansion and good cycle performance. Further, the negative electrode material includes Fe elements and S elements, by realizing the nanoscale mixing of nano-silicon and nano-carbon, and element doping, the negative electrode material also has good conductivity and small expansion, so as to realize excellent rate performance and cycle performance of the material.

[0098] The beneficial effects of the present application will be further illustrated in combination with the embodiments.

[0099] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application more clear, the following will be further described in combination with the embodiments and the drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all. The description of at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0100] 1. Preparation of porous carbon

[0101] A predetermined proportion of iron source material, sulfur source material and resin material is weighed, and in this embodiment, ferrocene is selected as the iron source material, hydrogen sulfide is selected as the sulfur source material, and phenolic resin is selected as the resin material. After dissolution, a mixed solution A is obtained. The mixed solution A is placed in an oven for pre-curing, the pre-curing temperature is 80℃, and the pre-curing time is 10h. The pre-cured material is crushed to obtain powder B. The powder B is placed in an oven and protected by nitrogen gas for full curing, the full curing temperature is 160℃, and the full curing time is 15h, to obtain powder C. The powder C is placed in a high-temperature furnace and protected by nitrogen gas for carbonization, the carbonization temperature is 1000℃, and the carbonization time is 4h, to form porous carbon powder D. The characteristic parameters of each embodiment and the comparative example are shown in Table 1.

[0102] 2. Preparation of silicon-carbon negative electrode material

[0103] The powder D is subjected to silicon-carbon co-deposition by chemical vapor deposition method to obtain a silicon-carbon negative electrode material. The volume ratio of silicon source gas to carbon source gas for silicon-carbon co-deposition is 30:1, and the silicon source gas concentration is 30%. In this embodiment, silane is selected as the silicon source gas, and acetylene is selected as the carbon source gas.

[0104] 3. Preparation of battery

[0105] 1) Preparation of negative electrode sheet

[0106] The silicon-carbon negative electrode material, artificial graphite, binder styrene-butadiene rubber (SBR), binder polyacrylic acid (PAA), dispersant (CMC-Na), and conductive carbon black (Super-P, SP), carbon nanotube (CNT) prepared in each of the above examples and comparative examples were mixed in a weight ratio of 10%:85%:2%:1%:1%:0.7%:0.3% in an appropriate amount of deionized water to prepare a negative electrode slurry. The negative electrode slurry was coated on the surface of a negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode sheet was obtained.

[0107] 2) Preparation of positive electrode sheet

[0108] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), conductive agent Super P, and binder PVDF were mixed in a mass ratio of 96.5:1.5:2 in an appropriate amount of NMP to form a positive electrode slurry; the positive electrode slurry was coated on the surface of a positive electrode current collector aluminum foil, and after drying, cold pressing, and slitting, a positive electrode sheet was obtained.

[0109] 3) Separation film

[0110] A PP / PE composite separation film was used.

[0111] 4) Electrolyte

[0112] Ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte. In the electrolyte, the concentration of LiPF6 was 1 mol / L.

[0113] 5) Assembly of battery

[0114] The above positive electrode sheet, separation film, and negative electrode sheet were stacked and wound in order to obtain an electrode assembly; the electrode assembly was placed in an outer package, and the above prepared electrolyte was added, and after processes such as packaging, standing, formation, and aging, a secondary battery was obtained.

[0115] 4. The test method for the related parameters of the negative electrode material and the battery of the examples and comparative examples of the present application is as follows:

[0116] (1) Test of pore size, pore volume of micropores, mesopores, and macropores in the porous carbon matrix:

[0117] The pore size and pore volume evaluation method can refer to GB / T 19587-2017 and GB / T21650.2-2008, and is tested by using a TriStar II 3020 pore size distribution instrument. By adsorbing gas on the material to be tested under a series of gradually increasing pressures at a constant temperature, the pore size and pore volume distribution of the porous carbon matrix material can be characterized through the curve of the volume of each pore size and the corresponding partial pressure. Further calculation can obtain the average pore size.

[0118] The pore volume of the porous carbon obtained in each example and the comparative example is 0.8 cm 3 / g, and the content ratio of micropores, mesopores and macropores obtained is 20:70:10. The pore size of the porous carbon obtained in each example and the comparative example is shown in Table 1.

[0119] (2) Porosity test

[0120] The true density of the material is obtained by testing with a true density instrument (such as an AccuPyc II 1340). Specifically, a certain mass of sample is weighed and placed in the true density tester. The closed test system is filled with helium gas according to the program. The gas pressure in the sample chamber and the expansion chamber is detected, and then the real volume Vr is calculated according to the Boyle's law (PV=nRT). Then the real density pr = m / Vr. The apparent density of the material can be obtained by loading a certain mass of powder into a cylindrical mold with an inner diameter of 10 mm, and applying a pressure of 200 MPa to obtain the corresponding apparent volume V0. Then the apparent density of the material is p0 = m / V0.

[0121] The porosity P of the material is 1-p0 / pr x 100%.

[0122] The porosity of the porous carbon obtained in each example and the comparative example is shown in Table 1.

[0123] (3) Specific surface area test

[0124] The specific surface area SSA of the negative electrode material refers to GB / T 19587-2017 "Gas adsorption BET method for testing specific surface area of solid materials". The specific surface area tester (such as TriStar II 3020) is used to test the adsorption amount of gas on the surface of solid at different relative pressures at a constant temperature. Based on the Brunauer-Emmett-Teller (BET) multilayer adsorption theory, the monolayer adsorption amount of the sample is obtained, and the specific surface area of the solid is calculated. The specific surface area of the negative electrode material obtained in each example and the comparative example is 4.5 m 2 / g.

[0125] (4) Volume distribution particle size Dv50 test

[0126] Dv50 can be obtained by referring to the standard GB / T 19077.1-2016, using a laser particle size analyzer (for example, Malvern Master Size 3000). Dv50 is physically defined as the particle size corresponding to the cumulative volume distribution percentage of 50% of the material. The Dv50 of the negative electrode material obtained in each example and the comparative example is 7 μm.

[0127] (5) Test of average particle size

[0128] The particle size of 100 nano-silicon particles and nano-carbon particles can be tested by transmission electron microscopy (for example, ThermoFisher F200i S / TEM) (TEM test), and the average particle size is obtained by measuring and averaging. For irregularly shaped particles, the particle size at the largest particle size is used as the reference. The average particle size of the nano-silicon particles in the negative electrode material obtained in each example and the comparative example is 8 nm, and the average particle size of the nano-carbon particles is 12 nm.

[0129] (6) Test of element mass ratio

[0130] The oxygen content is evaluated based on the "Microbeam Analysis Energy Spectrum Method Quantitative Analysis" in GB / T 17359-2012, using cross-section EDS spectrum. The specific operation is as follows: the powder to be tested is placed in an ion polisher (for example, IB-19500CP type), under vacuum conditions, argon ions are generated by ionization of argon by an ion source, after acceleration and focusing, high-speed argon ions will knock out the atoms or molecules on the surface of the sample, achieving ion polishing, so that cross-section detection can be achieved. The cross-section of the obtained powder is placed in a spectrum analyzer (for example, OXFORD type), and the oxygen content of each point on the cross-section of the material is tested. The average value of 10 points can be obtained to obtain the oxygen content of the material.

[0131] The silicon content is evaluated by referring to the standard EPA 6010D-2018 of the United States Environmental Protection Agency, using an inductively coupled plasma emission spectrometer (ICP). The specific operation is as follows: the powder to be tested is placed in a microwave digestion instrument (for example, CEM-Mars6 type) for digestion. After digestion, the solution is introduced into an ICP tester (for example, ICAP7400 type). By comparing the silicon concentration in the standard solution, the silicon content in the material is calculated.

[0132] The carbon content is tested by using a carbon-sulfur analyzer (for example, DEKAI HCS-140 infrared carbon-sulfur analyzer) and referring to GB / T 20123-2006 / ISO 15350:200. The principle is as follows: the sample is heated and combusted by a high-frequency furnace under oxygen-rich conditions, so that the carbon is oxidized to carbon dioxide. The gas enters the absorption cell, absorbs the corresponding infrared radiation, and then is converted into a corresponding signal by a detector. The carbon content in the material is calculated. The mass ratio Si:C:O of the silicon-carbon negative electrode material obtained in each example and the comparative example is 45:50:5.

[0133] Process and performance parameters of negative electrode materials of each example and comparative example in Table 1

[0134]

[0135] (7) Cycle performance test of battery

[0136] 45℃ cycle performance test:

[0137] The prepared secondary battery was charged at 1C rate to a voltage of 4.25V at a constant temperature of 45℃, then charged at a constant voltage of 4.25V until the current was less than or equal to 0.05mA, then rested for 5min, then discharged at 1C rate to a voltage of 2.5V, and rested for 5min. This was one cycle of charge and discharge process. The discharge capacity of this time was recorded as the discharge capacity of the first cycle of the secondary battery. The secondary battery was subjected to 300 cycles of charge and discharge test according to the above method, and the discharge capacity of the 300th cycle was recorded.

[0138] The capacity retention rate CR45℃(%) of the secondary battery after 300 cycles at 45℃ was calculated as follows: CR45℃(%) = discharge capacity of the 300th cycle / discharge capacity of the first cycle x 100%. The cycle performance of the batteries obtained in each example and comparative example is shown in Table 2.

[0139] Cycle expansion performance test of electrode sheet of secondary battery at 45℃:

[0140] The thickness of the negative electrode sheet of the secondary battery when the cold pressing process was completed was recorded as h0. The secondary battery was cycled for 300 cycles according to the above cycle performance test method at 45℃, and then charged at 1C rate to a voltage of 4.25V, then charged at a constant voltage of 4.25V until the current was less than or equal to 0.05mA, then rested for 5min. The cycled battery was disassembled in a dry room, and the thickness of the negative electrode sheet after 300 cycles was recorded as h300. The cycle expansion rate of the electrode sheet of the secondary battery at 45℃ was Δh300.

[0141] Δh300(%) = (h300-h0) / h0*100%. The expansion performance of the batteries obtained in each example and comparative example is shown in Table 2.

[0142] Rate performance test method:

[0143] The prepared secondary battery was charged at 0.33C (i.e. the current value of fully discharging the theoretical capacity within 3h) to a charge cut-off voltage of 4.25V at 25℃, then charged at a constant voltage until the current was 0.05C, rested for 5min, then discharged at 0.33C to a discharge cut-off voltage of 2.5V, and the actual capacity was recorded as C0.

[0144] Then the battery was charged at 0.33C constant current to the charge cut-off voltage 4.25V, then charged at constant voltage to the current of 0.05C, rested for 5min, then discharged at 3C constant current to the discharge cut-off voltage 2.5V, and the actual capacity C3 was recorded.

[0145] The rate performance of the secondary battery can be characterized as DR = C3 / C0 x 100%. The higher the DR value, the better the rate performance of the material. The rate performance of the batteries obtained in each of the examples and the comparative examples is shown in Table 2.

[0146] Table 2: Performance parameters of the batteries of each of the examples and the comparative examples

[0147]

[0148] As can be seen from the data in Table 2, the capacity retention rate of the batteries of Examples 1-15 after 300 cycles at 45℃ was 95.6%-97.5%, the cycle expansion rate Ah300 was 32.6%-36.4%, the rate performance DR was 82.1%-85.9%, the secondary battery had good cycle stability and small volume expansion, and had good kinetic performance. The content of iron in the negative electrode material of Example 16 was 20ppm, and the content of sulfur was 30ppm, the content of iron and sulfur elements was very low, the capacity retention rate after 300 cycles at 45℃ was 92.3%, the cycle expansion rate Ah300 was 39.1%, and the rate performance DR was 79.8%. The content of iron in the negative electrode material of Example 17 was 5000ppm, and the content of sulfur was 30ppm, the capacity retention rate after 300 cycles at 45℃ was 88.4%, the cycle expansion rate Ah300 was 40.5%, and the rate performance DR was 88.9%. The content of iron in the negative electrode material of Example 18 was 20ppm, and the content of sulfur was 2500ppm, the capacity retention rate after 300 cycles at 45℃ was 85.7%, the cycle expansion rate Ah300 was 30.7%, and the rate performance DR was 75.2%. Although the cycle performance, cycle expansion and kinetic performance of Examples 16-18 were not as good as those of Examples 1-15, it can be seen that the content of iron and sulfur elements has a great influence on the performance of the silicon-carbon negative electrode material. The silicon-carbon negative electrode material has good electrical conductivity, and the secondary battery has small expansion effect, and can have excellent cycle performance and rate performance.

[0149] The above description is merely an embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation using the content of the specification and the drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A negative electrode material, characterized in that, It includes porous carbon, which contains iron, or iron and sulfur, and the pores of the porous carbon contain active materials.

2. The negative electrode material according to claim 1, characterized in that, The iron content in the negative electrode material is 50 ppm to 3000 ppm; and / or The sulfur content in the negative electrode material is 100 ppm to 1500 ppm.

3. The negative electrode material according to claim 1 or 2, characterized in that, The average pore size of the porous carbon is 2-50 nm.

4. The negative electrode material according to any one of claims 1-3, characterized in that, The porous carbon has a pore volume of 0.1-2.0 cm³. 3 / g.

5. The negative electrode material according to any one of claims 1-4, characterized in that, The content ratio of micropores, mesopores and macropores in the porous carbon is (5%-25%):(65%-90%):(5%-15%).

6. The negative electrode material according to any one of claims 1-5, characterized in that, The active material includes silicon-carbon material, which includes silicon nanoparticles and carbon nanoparticles.

7. The negative electrode material according to claim 6, characterized in that, The particle size of the silicon nanoparticles is less than or equal to 10 nm; and / or The particle size of the carbon nanoparticles is less than or equal to 30 nm.

8. The negative electrode material according to claim 6 or 7, characterized in that, The mass ratio of silicon to carbon in the negative electrode material is Si:C = (20-55):(40-75).

9. The negative electrode material according to any one of claims 6-8, characterized in that, The mass ratio of silicon, carbon, and oxygen in the negative electrode material is Si:C:O = (20-55):(40-75):(0.5-5).

10. The negative electrode material according to any one of claims 1-9, characterized in that, The particle size Dv50 of the negative electrode material is 3-8 μm; and / or The porosity of the negative electrode material is 5%-30%; and / or The specific surface area of ​​the negative electrode material is less than or equal to 5.0 m². 2 / g.

11. A battery, characterized in that, It includes a positive electrode, a separator, and a negative electrode. The separator is located between the positive electrode and the negative electrode and serves to isolate them. The negative electrode includes a negative electrode material and a negative electrode current collector. The negative electrode material includes the negative electrode material as described in any one of claims 1-10.

12. An electrical appliance, characterized in that, Includes the battery as described in claim 11.

13. A method for preparing a negative electrode material, characterized in that, include: A porous carbon precursor is provided, the porous carbon precursor comprising a carbon precursor and an iron precursor, or the porous carbon precursor comprising a carbon precursor, an iron precursor and a sulfur precursor. The porous carbon precursor is processed to obtain porous carbon; An active material is deposited in the pores of the porous carbon to obtain the anode material as described in any one of claims 1-10.

14. The method for preparing the negative electrode material according to claim 13, characterized in that, The iron precursor includes one or more of ferric chloride, ferric nitrate, ferric sulfate, ferric carbonyl, and ferrocene; and / or The sulfur precursor includes one or more of hydrogen sulfide (H2S), thiophene, thiophene compounds, thiols, thiophenols, and thioethers.

15. The method for preparing the negative electrode material according to claim 13 or 14, characterized in that, The active material deposited in the pores of the porous carbon includes: Nano-silicon particles and nano-carbon particles are deposited in the pores of the porous carbon using a vapor phase co-deposition method.

16. The method for preparing the negative electrode material according to claim 15, characterized in that, The volume ratio of silicon source gas to carbon source gas in silicon-carbon co-deposition is greater than or equal to 6:1; and / or The concentration of silicon source gas in the gas source for silicon-carbon co-deposition is 5%-80%.

17. The method for preparing the negative electrode material according to claim 16, characterized in that, The silicon source gas includes one or more of the following: methane, ethylsilane, propane, monochlorosilane, dichlorosilane, and trichlorosilane; and / or The carbon source gas includes one or more of methane, ethane, butane, propane, ethylene, propylene, butene, and acetylene.

18. The method for preparing the negative electrode material according to any one of claims 13-17, characterized in that, Also includes: A carbon coating layer is formed by vapor deposition on the porous carbon; The deposition gas in the vapor phase deposition is a mixture of C2H2 and N2, with the volume ratio of C2H2 being 2%-20%. The gas flow rate is 100-300 mL / min, the reaction temperature is 800-1000℃, and the deposition reaction time is 0.5-2 h.

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