Carbon negative electrode material and preparation method thereof, negative electrode sheet, battery and electrical device

Abstract

The present application discloses a carbon negative electrode material and a preparation method thereof, a negative electrode plate, a battery and an electrical device. In the scheme, the porosity of the macropores of the carbon negative electrode material is greater than or equal to 30%, and the macropores are pores with a pore size greater than 50nm. In the scheme of the present application, by increasing the porosity of the macropores, that is, increasing the number of macropores, the internal pores of the carbon negative electrode material can be enriched, and then the ion channels can be increased to facilitate the embedding and extraction of ions, so that the carbon negative electrode material exhibits relatively good charge and discharge performance, and the fast charging ability of the carbon negative electrode material is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a carbon negative electrode material and a preparation method thereof, a negative electrode sheet, a battery and an electrical device. Background Art

[0002] With the rapid development of the current society, people's demand for green new energy and high-performance energy storage equipment is becoming more and more urgent. As a new generation of green energy storage and conversion devices, batteries have been widely used in portable electronic devices and power vehicles. And the batteries used are generally secondary batteries that can be charged and discharged repeatedly. However, the charging efficiency of existing secondary batteries is low, which greatly limits its application. Therefore, it is urgent to develop batteries with fast charging capabilities. Summary of the invention

[0003] In view of the above technical problems, the present application provides a carbon negative electrode material and a preparation method thereof, a negative electrode plate, a battery and an electrical device, which can improve the fast charging capability of the carbon negative electrode material.

[0004] In a first aspect, the present application provides a carbon negative electrode material, wherein the porosity of macropores of the carbon negative electrode material is greater than or equal to 30%, and the pore size of the macropores is greater than 50 nm.

[0005] In the technical solution of the embodiment of the present application, the porosity of the macropores in the carbon negative electrode material is increased, that is, the number of macropores is increased, which can enrich the internal channels of the carbon negative electrode material and further increase the ion channels to facilitate the embedding and detachment of ions, so that the carbon negative electrode material exhibits relatively good charge and discharge performance and improves the fast charging capability of the carbon negative electrode material.

[0006] In some embodiments, the porosity of the macropores of the carbon negative electrode material is greater than or equal to 30% and less than or equal to 80%.

[0007] In some embodiments, the carbon negative electrode material includes a graphite material, which includes one or more of graphitized mesophase carbon microspheres, mesophase pitch carbon fibers, gas-grown carbon fibers, graphitized fibers carbonized from biomass materials, hard carbon, and soft carbon. These carbon materials have relatively abundant internal pores and can provide more ion channels.

[0008] In some embodiments, the specific surface area of ​​the carbon negative electrode material is 0.5-25 m 2 / g. By increasing the specific surface area of ​​the carbon negative electrode material, the carbon negative electrode material can expose its internal ion channels to facilitate the insertion and extraction of ions, so that the carbon negative electrode material exhibits relatively good charge and discharge performance and improves the fast charging ability of the carbon negative electrode material.

[0009] In a second aspect, the present application provides a negative electrode plate, comprising a negative electrode material and a negative electrode current collector, wherein the negative electrode material comprises any of the above carbon negative electrode materials.

[0010] In a third aspect, the present application provides a battery, comprising a positive electrode plate, a separator and a negative electrode plate, wherein the separator is located between the positive electrode plate and the negative electrode plate to perform an isolation function, and the negative electrode plate comprises any of the negative electrode plates described above.

[0011] In a fourth aspect, the present application provides an electrical device, the electrical device comprising any of the above batteries.

[0012] In a fifth aspect, the present application provides a method for preparing a carbon negative electrode material, the preparation method comprising: providing a pore-forming agent and a carbon source material; mixing the pore-forming agent and the carbon source material and heating them in an inert gas atmosphere to obtain any of the above carbon negative electrode materials.

[0013] In some embodiments, the pore-forming agent includes one or more of alkali metal hydroxides, alkaline earth metal hydroxides, thallium hydroxide, diammine silver hydroxide, choline, thallium hydroxide, quaternary ammonium base compounds, Grignard reagents, alkyl copper lithium, sodium alcoholate, potassium alcoholate, and guanidine.

[0014] In the technical solution of the embodiment of the present application, a strong alkaline substance is used as a pore-forming agent to chemically corrode the carbon source material, or in other words, the specific surface area of ​​the carbon source material is increased by chemical erosion to expose the ion channels inside the carbon negative electrode material, thereby facilitating the embedding and extraction of ions, improving the charging capacity, and achieving fast charging.

[0015] In some embodiments, the mass ratio of the pore former to the carbon source material is 1:500 to 1:3. By adjusting the amount of the pore former, the pore size of the formed pores and the porosity of the obtained carbon negative electrode material can be controlled, providing more ion channels, thereby facilitating the insertion and extraction of ions and improving the fast charging capability.

[0016] In some embodiments, the heat treatment time is 300-1200° C., and the heat treatment temperature is 0.5-48 hours. In this way, the reaction rate can be controlled to ensure that the pore size of the obtained pore is larger, and to prevent rapid reaction and too small pore size.

[0017] In some embodiments, after the pore-forming agent and the carbon source material are mixed and before the heat treatment in an inert gas atmosphere, the process includes: stirring and mixing the pore-forming agent and the carbon source material, the stirrer used includes any one of a turbine, paddle, propeller, screw, and planetary stirrer, and the stirring time is 0.25 to 48 hours. By fully mixing the pore-forming agent and the carbon source material, the surface reaction of the material can be made more uniform, and the pores obtained have a balanced pore size.

[0018] In some embodiments, after mixing the pore-forming agent and the carbon source material and heating them in an inert gas atmosphere, the process includes: mixing the heated mixture with deionized water to form a suspension, stirring for 0.5 h to 1 h, filtering, and drying the obtained solid to obtain a carbon negative electrode material. In this way, the reaction impurities remaining on the surface of the carbon negative electrode material can be cleaned and removed, the purity of the obtained negative electrode material can be improved, and the impact on the battery performance can be avoided.

[0019] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0021] Figure 1 A schematic diagram of the structure of a vehicle according to some embodiments of the present application;

[0022] Figure 2 A schematic diagram of the exploded structure of a battery according to some embodiments of the present application;

[0023] Figure 3 A schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application;

[0024] Figure 4 This is a morphology image of the carbon negative electrode material of Comparative Example 1 of the present application tested using a scanning electron microscope;

[0025] Figure 5 This is a morphology image of the carbon negative electrode material of Example 1 of the present application tested using a scanning electron microscope;

[0026] Figure 6 This is a morphology image of the carbon negative electrode material of Example 3 of the present application tested using a scanning electron microscope. DETAILED DESCRIPTION

[0027] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0029] 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 "multiple" is more than two, unless otherwise clearly and specifically defined.

[0030] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0031] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0032] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0033] As a new generation of green energy storage and conversion devices, lithium-ion batteries have the advantages of high energy density, long cycle life, high discharge voltage, no memory effect, low self-discharge rate and low environmental pollution. They have been widely used in portable electronic devices and power vehicles. Lithium-ion batteries include positive electrode materials, negative electrode materials, isolation membranes, electrolytes and current collectors. Among them, the characteristics of positive electrode materials and negative electrode materials will directly affect the performance of the battery.

[0034] As people's demand for high-power and high-energy-density lithium-ion batteries becomes more and more urgent, the performance requirements for electrode materials are also increasing, such as fast charging, high safety performance, high energy density, high power density, etc. In order to obtain electrode materials with high comprehensive performance, researchers have proposed a variety of coping strategies, such as surface coating of electrode materials and construction of electrode materials with multi-level particles.

[0035] Specifically, surface coating is widely used to improve the cycle stability of negative electrode materials. Currently, there are public composite negative electrode materials that can be formed by coating graphite with niobium pentoxide. By using niobium pentoxide to form a uniformly distributed coating layer on the negative electrode material, the coating layer is used to reduce the interface resistance and improve the cycle stability and fast charging ability of the negative electrode material. The method of constructing multi-level particles can not only artificially construct channels for lithium ion diffusion, reduce the free travel of active ions, improve the internal diffusion dynamics of negative electrode materials, and improve the fast charging performance, rate performance and cycle performance of the battery. It can also increase the compaction density of the negative electrode material, thereby increasing the energy density of the battery.

[0036] However, the process of surface coating and constructing multi-level particles is relatively complicated, and only the surface of the negative electrode material is improved without modifying the inside of the material. As a result, its performance does not reach a better state. Based on this, the present application provides a carbon negative electrode material, which can not only enrich the internal pores of the carbon negative electrode material and provide more ion channels; but also treat the surface of the carbon negative electrode material to expose more of the internal pore structure and expose the ion channels to facilitate the insertion and extraction of ions, so that the carbon negative electrode material exhibits better charge and discharge performance and improves the fast charging ability of the carbon negative electrode material.

[0037] The battery disclosed in the embodiments of the present application can be used in an electrical device that uses the battery as a power source or in various energy storage systems that use the battery as an energy storage element. The electrical device can be, but is not limited to, a mobile phone, a tablet, a laptop, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft, and the like. Among them, the electric toy can include a fixed or mobile electric toy, for example, a game console, an electric car toy, an electric ship toy, and an electric airplane toy, and the like, and the spacecraft can include an airplane, a rocket, a space shuttle, and a spacecraft, and the like.

[0038] For the convenience of description, the following embodiments are described by taking a vehicle 1000 as an example of an electrical device according to an embodiment of the present application.

[0039] Please refer to Figure 1 , Figure 1A schematic diagram of the structure of a vehicle 1000 provided for some embodiments of the present application. The vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 may be provided at the bottom, head or tail of the vehicle 1000. The battery 100 may be used to power the vehicle 1000, for example, the battery 100 may be used as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to power the motor 300, for example, for starting, navigating and driving the vehicle 1000.

[0040] In some embodiments of the present application, the battery 100 can not only serve as an operating power source for the vehicle 1000, but also serve as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0041] Please refer to Figure 2 , Figure 2 Schematic diagram of the exploded structure of the battery 100 provided for some embodiments of the present application. The battery 100 includes a box 10 and a battery cell 20, and the battery cell 20 is contained in the box 10. Among them, the box 10 is used to provide a storage space for the battery cell 20, and the box 10 can adopt a variety of structures. In some embodiments, the box 10 may include a first part 11 and a second part 12, the first part 11 and the second part 12 cover each other, and the first part 11 and the second part 12 jointly define a storage space for accommodating the battery cell 20. The second part 12 can be a hollow structure with one end open, the first part 11 can be a plate-like structure, and the first part 11 covers the open side of the second part 12, so that the first part 11 and the second part 12 jointly define a storage space; 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 covers 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 be in a variety of shapes, such as a cylinder, a cuboid, etc.

[0042] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a mixed connection. A mixed connection means that the multiple battery cells 20 are both connected in series and in parallel. The multiple battery cells 20 may be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple battery cells 20 is accommodated in the box 10; of course, the battery 100 may also be a battery module formed by connecting multiple battery cells 20 in series, in parallel, or in a mixed connection, and then the multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole, and accommodated in the box 10. The battery 100 may also include other structures, for example, the battery 100 may also include a busbar component for realizing electrical connection between the multiple battery cells 20.

[0043] Each battery cell 20 may be a secondary battery or a primary battery, or a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto. The battery cell 20 may be cylindrical, flat, rectangular, or in other shapes.

[0044] Please refer to Figure 3 , Figure 3 The schematic diagram of the exploded structure of the battery cell 20 provided in some embodiments of the present application. The battery cell 20 refers to the smallest unit that constitutes the battery. Figure 3 The battery cell 20 includes an end cover 21, a shell 22, a battery cell assembly 23 and other functional components.

[0045] The end cap 21 refers to a component that covers the opening of the shell 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cap 21 can be adapted to the shape of the shell 22 to match the shell 22. Optionally, the end cap 21 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap 21 is not easily deformed when squeezed and collided, so that the battery cell 20 can have a higher structural strength and the safety performance can also be improved. Functional components such as electrode terminals 21a can be provided on the end cap 21. The electrode terminal 21a can be used to electrically connect to the battery cell assembly 23 for outputting or inputting electrical energy of the battery cell 20. In some embodiments, the end cap 21 can also be provided with a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The material of the end cap 21 can also be a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not impose special restrictions on this. In some embodiments, an insulating member may be provided inside the end cap 21, and the insulating member may be used to isolate the electrical connection components in the housing 22 from the end cap 21 to reduce the risk of short circuit. For example, the insulating member may be plastic, rubber, or the like.

[0046] The shell 22 is a component used to cooperate with the end cover 21 to form the internal environment of the battery cell 20, wherein the formed internal environment can be used to accommodate the battery cell assembly 23, electrolyte and other components. The shell 22 and the end cover 21 can be independent components, and an opening can be set on the shell 22, and the internal environment of the battery cell 20 is formed by covering the opening with the end cover 21 at the opening. 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 connection surface before other components are put into the shell, and when the interior of the shell 22 needs to be encapsulated, the end cover 21 covers the shell 22. The shell 22 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the shell 22 can be determined according to the specific shape and size of the battery 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 embodiment of the present application does not impose any special restrictions on this.

[0047] The battery cell assembly 23 is a component in the battery cell 100 where electrochemical reactions occur. One or more battery cell assemblies 23 may be contained in the housing 22. The battery cell assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and a separator is usually provided between the positive and negative electrode sheets. The parts of the positive and negative electrode sheets with active materials constitute the main body of the battery cell assembly, and the parts of the positive and negative electrode sheets without active materials each constitute a tab 23a. The positive tab and the negative tab may be located together at one end of the main body or respectively at both ends of the main body. During the charge and discharge process of the battery, the positive active material and the negative active material react with the electrolyte, and the tab 23a connects the electrode terminals to form a current loop.

[0048] According to some embodiments of the present application, a carbon negative electrode material is provided, wherein the porosity of macropores of the carbon negative electrode material is greater than or equal to 30%, and the pore size of the macropores is greater than 50 nm.

[0049] Among them, according to the pore size, pores can be divided into three categories: large pores (pore size > 50nm), mesopores (2nm≤pore size≤50nm), and micropores (pore size <2nm). Compared with small pores and mesopores, large pores allow large molecules / ions to enter the pores, and the setting of large pores can increase ion channels. In addition, large pores can also serve as buffers for electrolytes, shortening the distance for electrolytes to reach the inner surface.

[0050] In some embodiments, the porosity of the macropores is greater than or equal to 30%. Preferably, the porosity of the macropores is 30%-80%. For example, the porosity of the macropores can be 42%, 51%, 59%, 67%, 73%, etc.

[0051] Specifically, the porosity test can be performed using a mercury intrusion method. The mercury intrusion instrument used in the experiment can be PoreMaster 60 (Quantachrome Instruments, USA). The pressure applied in the low pressure station (LP) is about 0.6PSI to 50PSI (corresponding to a pore diameter of 355 microns to 4 microns), and the pressure applied in the high pressure station (HP) is 20PSI to 60,000PSI (corresponding to a pore diameter of 10 microns to 0.004 microns). The porosity of the pore structure within a suitable pore size range can be measured by adjusting the pressure.

[0052] In this embodiment of the present application, by adjusting the porosity of the macropores, a larger specific surface area can be provided. The larger specific surface area allows a large number of lithium ions to attach to the inner and outer surfaces of the carbon negative electrode material, which is conducive to the rapid transmission of lithium ions and achieves a larger capacitance value. At the same time, it can enrich the internal pores of the carbon negative electrode material, thereby increasing the ion channels to facilitate the insertion and extraction of ions, so that the carbon negative electrode material exhibits relatively good charge and discharge performance and improves the rapid charging ability of the carbon negative electrode material.

[0053] In some embodiments, the specific surface area of ​​the carbon negative electrode material ranges from 0.5 to 25 m 2 / g. Specifically, it can be 3m 2 / g, 7m 2 / g, 11m 2 / g, 15m 2 / g, 18m 2 / g, 23m 2 / g, etc. By increasing the specific surface area of ​​the carbon negative electrode material, the carbon negative electrode material can expose its internal ion channels to facilitate the insertion and extraction of ions, so that the carbon negative electrode material exhibits relatively good charge and discharge performance and improves the fast charging ability of the carbon negative electrode material.

[0054] In some embodiments, the carbon negative electrode material includes a graphite material. Preferably, the graphite material includes one or more of graphitized mesophase carbon microbeads, mesophase asphalt carbon fibers, vapor-grown carbon fibers, graphitized fibers carbonized from biomass materials, hard carbon, soft carbon, and the like.

[0055] Among them, the carbon negative electrode material is graphite material. Graphite materials are divided into natural graphite materials and artificial graphite materials. Natural graphite materials have different particle sizes, many surface defects, poor compatibility with electrolytes, and many side reactions. Artificial graphite materials show more advantages, such as high purity and a structure that is more suitable for smooth insertion and extraction of lithium ions. Therefore, artificial graphite materials are currently the most successful negative electrode materials for commercial applications because of their excellent conductivity, stable charging and discharging platform, good capacity, abundant resources, and low cost.

[0056] However, as people's demand for high-power and high-energy-density lithium-ion batteries becomes more and more urgent, traditional artificial graphite negative electrode materials face huge challenges, such as how to achieve fast charging, high safety performance, high energy density, and high power density.

[0057] Specifically, although the internal structure of existing graphite materials is rich in pores, the internal pore structure is difficult to expose in the electrolyte, and the specific surface area is too low, which affects its fast charging performance. Current research has only improved the surface of graphite particles or graphite fibers, but has not improved the inside of graphite particles. The ion channels inside graphite particles or fibers are very limited. Based on this, the present application scheme increases the specific surface area on the basis of the existing graphite negative electrode, exposes the internal ion channels, and facilitates the insertion and removal of ions, so that the carbon negative electrode material exhibits relatively good charge and discharge performance, and improves the fast charging ability of the carbon negative electrode material.

[0058] According to some embodiments of the present application, the present application also provides a negative electrode plate, the negative electrode plate includes a negative electrode material and a negative electrode current collector, and the negative electrode material includes any of the above carbon negative electrode materials.

[0059] According to some embodiments of the present application, the present application also provides a battery, the battery includes a positive electrode plate, a separator and a negative electrode plate, the separator is located between the positive electrode plate and the negative electrode plate to play an isolation role, and the negative electrode plate includes any of the negative electrode plates described above.

[0060] According to some embodiments of the present application, the present application further provides an electrical device, which includes a battery according to any of the above schemes, and the battery is used to provide electrical energy to the electrical device.

[0061] The power-consuming device may be any of the aforementioned devices or systems using batteries.

[0062] According to some embodiments of the present application, the present application also provides a method for preparing a carbon negative electrode material. The method for preparing the carbon negative electrode material is to contact a pore-forming agent with a carbon source material to produce a chemical reaction, use chemical etching to form pores, construct a porous structure, increase the specific surface area of ​​the carbon negative electrode material, and improve the fast charging performance of the carbon negative electrode material.

[0063] Specifically, a certain mass ratio of pore-forming agent and carbon source material is uniformly mixed, heated to a high temperature in an inert gas atmosphere, and maintained for a certain period of time, and the surface of the carbon material is significantly rougher than the surface of the carbon material before treatment. The porosity of the macropores of the obtained carbon negative electrode material is greater than 30%, and the pore size of the macropores is greater than 50nm.

[0064] In some embodiments, the pore-forming agent includes: (1) alkali metal hydroxides: one or more of lithium hydroxide LiOH, sodium hydroxide NaOH, rubidium hydroxide RbOH, cesium hydroxide CsOH, and francium hydroxide FrOH. (2) alkaline earth metal hydroxides: one or more of slaked lime Ca(OH)2, strontium hydroxide Sr(OH), barium hydroxide Ba(OH)2, and radium hydroxide Ra(OH)2. (3) other strong bases: thallium hydroxide TlOH, diammine silver hydroxide AgOH·2NH3, choline C5H 14 NO + , thallium hydroxide Tl(OH)3, one or more of quaternary ammonium base NR4OH compounds; (4) organic compounds: Grignard reagent, alkyl copper lithium, etc., one or more of sodium alcoholate or potassium alcoholate, and guanidine.

[0065] In this embodiment, by using strong alkaline substances as pore-forming agents to chemically corrode the carbon source material, the internal pore structure of the material can be enriched. At the same time, the specific surface area of ​​the carbon source material can be increased by chemical etching to expose the ion channels inside the carbon negative electrode material, thereby facilitating the embedding and removal of ions, improving the charging capacity, and achieving fast charging.

[0066] In some embodiments, the mass ratio of the pore former to the carbon source material is in the range of 1:500-1:3. For example, it may be 1:450, 1:400, 1:300, 1:100, 1:50, 1:30, 1:20, 1:10, 1:6, etc. By adjusting the amount of the pore former, the pore size of the formed pores and the porosity of the obtained carbon negative electrode material can be controlled, providing more ion channels, thereby facilitating the insertion and extraction of ions and improving the fast charging capability.

[0067] In some embodiments, the heat treatment time is 300-1200°C, and the heat treatment temperature is 0.5h-48h. For example, the temperature is 400°C, 600°C, 700°C, 850°C, 920°C, 1040°C, 1100°C, etc. The time is 3h, 15h, 26h, 33h, 42h, etc. In this way, the reaction rate can be controlled to ensure that the pore size of the obtained pore is large, and to prevent rapid reaction and too small pore size.

[0068] In some embodiments, the heating method is to place the carbon source material and the pore-forming agent in a tube furnace or a muffle furnace protected by a gas atmosphere for heating. During the heating process, the temperature may be continuously raised to the target temperature or may be raised to the target temperature in steps.

[0069] In some embodiments, the inert gas atmosphere is one or more of nitrogen, helium, neon, and argon.

[0070] In some embodiments, after the pore-forming agent and the carbon source material are mixed and before the heat treatment in an inert gas atmosphere, the process includes: stirring and mixing the pore-forming agent and the carbon source material, the stirrer used includes any one of a turbine, paddle, propeller, screw, and planetary stirrer, and the stirring time is 0.25h to 48h. By fully mixing the pore-forming agent and the carbon source material, the surface reaction of the material can be made more uniform, and the pores obtained have a balanced pore size.

[0071] In some embodiments, after mixing the pore-forming agent and the carbon source material and heating them in an inert gas atmosphere, the process includes: mixing the heated mixture with deionized water to form a suspension, stirring for 0.5 h to 1 h, filtering, and drying the obtained solid to obtain a carbon negative electrode material. In this way, the reaction impurities remaining on the surface of the carbon negative electrode material can be cleaned and removed, the purity of the obtained negative electrode material can be improved, and the impact on the battery performance can be avoided.

[0072] In the above embodiments, the fast charging performance of the graphite negative electrode is improved, and the chemical etching effect increases the specific surface area of ​​the graphitized spherical particles or carbon fibers, causing the ion channels inside the spheres or fibers to be exposed, thereby facilitating the embedding and detachment of lithium ions in the graphite, thereby exhibiting better performance at high rates.

[0073] The scheme of the present application is explained below by taking lithium-ion batteries as an example and combining them with specific embodiments. Those skilled in the art will understand that the carbon negative electrode materials and preparation methods described in the present application are only examples, and any other suitable preparation methods are within the scope of the present application.

[0074] 1. Preparation of carbon negative electrode materials

[0075] The strong alkaline pore-forming agent and the carbon source material in a predetermined mass ratio are uniformly mixed together, heated to T1 in a muffle furnace in an argon atmosphere, and maintained at the temperature for t1 time to obtain a carbon negative electrode material. The specific mass ratio, the strong alkaline pore-forming agent used, the carbon source material and the preparation process parameters are shown in Table 1.

[0076] 2. Battery production

[0077] The positive electrode active material is mixed with an appropriate amount of solvent, stirred evenly, and a positive electrode slurry is obtained. The positive electrode slurry is coated on aluminum foil, and dried after coating to obtain a positive electrode sheet. The carbon negative electrode active material is mixed with an appropriate amount of solvent to form a uniform negative electrode slurry, and the negative electrode slurry is evenly coated on the surface of the negative electrode collector copper foil. After drying and cold pressing, a negative electrode sheet is obtained. The positive electrode sheet, negative electrode sheet and isolation film prepared above are placed in order, so that the isolation film is in the middle of the positive electrode sheet and the negative electrode sheet to play an isolating role, processed into shape, and packaged. The electrolyte is injected, and the battery is obtained after packaging. The positive electrode material, negative electrode material, and electrolyte used are detailed in Table 2.

[0078] 3. The relevant parameter testing methods of the carbon negative electrode materials and batteries of the embodiments and comparative examples of the present application are as follows:

[0079] (1) Porosity test

[0080] The treated carbon negative electrode material was cut into small pieces and placed in a sample container. A cone probe made of glass was used as the sample container, and a PoreMaster 60 (Quantachrome Instruments, USA) mercury intrusion instrument was used to apply pressure to the sample for measurement. The applied pressure was about 0.6PSI to 50PSI (corresponding to a pore diameter of 355 microns to 4 microns). The test results are detailed in Table 1.

[0081] (2) Specific surface area test

[0082] According to GB / T 19587-2004 gas adsorption BET method, after the sample is heated and degassed, the adsorption amount of gas on the solid surface under different adsorption pressures is measured at a constant low temperature. The sample monolayer adsorption amount is obtained based on the BET multilayer adsorption theory and its formula, and the specific surface area per unit mass of the solid sample is calculated. The test results are shown in Table 1.

[0083] (3) Morphology test

[0084] The carbon negative electrode materials of all the embodiments and comparative examples were tested using a ZEISS sigma 300 scanning electron microscope, and then tested according to the standard JY / T010-1996 to observe the sample morphology. The test results are detailed in the attached drawings.

[0085] (4) Battery cycle performance test

[0086] The specific test conditions and test results are shown in Table 2.

[0087] Table 1: Performance and preparation process parameters of carbon negative electrode materials in examples and comparative examples

[0088]

[0089] Table 2: Battery performance parameters of the examples and comparative examples

[0090]

[0091] Please refer to the attached Figure 4-5 , Figure 4 This is a morphology image of the carbon negative electrode material of Comparative Example 1 of the present application tested using a scanning electron microscope; Figure 5 This is a morphology image of the carbon negative electrode material of Example 1 of the present application tested using a scanning electron microscope; Figure 6This is a morphology image of the carbon negative electrode material of Example 3 of the present application tested by a scanning electron microscope. After the strong alkali treatment, the surface of the graphite material becomes rough and the specific surface area increases. Please refer to the data in Table 2. After the strong alkali treatment, the negative electrode formed by the graphite material has a higher charging efficiency and a greater cyclability after being prepared into a battery.

[0092] In summary, porous carbon negative electrode materials can be constructed through physical and chemical methods to improve the fast charging performance of graphite negative electrode materials. The preparation method is to use a pore-forming agent, that is, a strong alkaline substance and a carbon source to react chemically to form pores. A small amount of metallic lithium block or metallic lithium powder is compounded with spherical and fibrous carbon by melting or pressurizing, and lithium atoms diffuse into the graphite fibers, causing the graphite fibers to crack and expose more internal area, making it easier for lithium ions to be embedded and removed, and at the same time, the specific capacity of the graphite negative electrode material can be significantly improved.

[0093] The above description is only an implementation method of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A carbon negative electrode material, characterized in that: The carbon negative electrode material includes a graphite material, the porosity of the macropores of the graphite material is greater than or equal to 30% and less than or equal to 45%, and the pore size of the macropores is greater than 50 nm.

2. The carbon negative electrode material according to claim 1, characterized in that The graphite material includes one or more of graphitized mesophase carbon microspheres, mesophase pitch carbon fibers, carbon fibers grown in the vapor phase, graphitized fibers carbonized from biomass materials, hard carbon, and soft carbon.

3. The carbon negative electrode material according to claim 1, characterized in that The specific surface area of ​​the carbon negative electrode material is 0.5-25 m 2 / g.

4. A negative electrode plate, characterized in that: It comprises a negative electrode material and a negative electrode current collector, wherein the negative electrode material comprises the carbon negative electrode material as claimed in any one of claims 1 to 3.

5. A battery, characterized in that: It comprises a positive electrode sheet, a separator and a negative electrode sheet, wherein the separator is located between the positive electrode sheet and the negative electrode sheet to play an isolating role, and the negative electrode sheet comprises the negative electrode sheet as claimed in claim 4.

6. An electrical device, characterized in that: Comprising the battery as claimed in claim 5.

7. A method for preparing a carbon negative electrode material, characterized in that: include: Providing pore formers and carbon source materials; The pore former and the carbon source material are mixed and then heat-treated in an inert gas atmosphere, the heat treatment time is 300-1200° C., and the heat treatment temperature is 0.5-48 h to obtain the carbon negative electrode material according to any one of claims 1-3.

8. The method for preparing a carbon negative electrode material according to claim 7, characterized in that: The pore-forming agent includes one or more of alkali metal hydroxides, alkaline earth metal hydroxides, thallium hydroxide, diammine silver hydroxide, choline, thallium hydroxide, quaternary ammonium base compounds, Grignard reagents, alkyl copper lithium, sodium alcoholate, potassium alcoholate, and guanidine.

9. The method for preparing a carbon negative electrode material according to claim 7, characterized in that: The mass ratio of the pore former to the carbon source material is 1:500 to 1:

3.

10. The method for preparing a carbon negative electrode material according to claim 7, characterized in that: The step of mixing the pore former and the carbon source material and then heating them in an inert gas atmosphere comprises: The pore former and the carbon source material are stirred and mixed, and the stirrer used includes any one of a turbine type, a paddle type, a propeller type, a screw type, and a planetary type stirrer, and the stirring time is 0.25 h to 48 h.

11. The method for preparing a carbon negative electrode material according to claim 7, characterized in that: The mixing of the pore former and the carbon source material and the heating treatment in an inert gas atmosphere comprises: The heated mixture is mixed with deionized water to form a suspension, stirred for 0.5 h to 1 h, filtered, and the obtained solid is dried to obtain the carbon negative electrode material.

Images