Negative electrode material and preparation method therefor, negative electrode, battery, electronic device, and energy storage device

Abstract

A negative electrode material and a preparation method therefor, a negative electrode, a battery, an electronic device, and an energy storage device. The present application intends to solve the problem of porous carbon powder having low purity, a low degree of graphitization, and a poor lithium ion battery performance. The negative electrode material comprises a porous carbon powder, wherein an oxygen-containing functional group in the porous carbon powder is less than or equal to 0.4 mmol / g, the mass fraction of carbon in the porous carbon powder is greater than or equal to 95%, and the 002 peak position in an XRD pattern of the porous carbon is greater than or equal to 25 degrees. Increasing the mass fraction of carbon in the porous carbon powder while decreasing the oxygen-containing functional group leads to high purity of the porous carbon powder, which helps improve first-cycle efficiency of the negative electrode material. Moreover, increasing the degree of graphitization of the porous carbon powder further improves the first-cycle efficiency and the electronic conductivity of the negative electrode material, thereby improving electrochemical performance.

Description

Negative electrode material, preparation method thereof, negative electrode, battery, electronic device and energy storage device

[0001] The present application claims priority to the Chinese patent application No. 202410628398.7, filed on May 20, 2024, and entitled "Negative electrode material, preparation method thereof, negative electrode, battery, electronic device and energy storage device", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] Embodiments of the present application relate to the technical field of batteries, in particular to a negative electrode material, a preparation method thereof, a negative electrode, a battery, an electronic device and an energy storage device. BACKGROUND

[0003] With the gradual development of battery technology, lithium ion batteries have been gradually applied to electronic devices and energy storage devices. Silicon-carbon negative electrode material is a typical lithium ion battery negative electrode material. However, the current carbon component of the silicon-carbon negative electrode has low purity and low graphitization degree, which affects the play of its electrochemical performance. SUMMARY

[0004] Embodiments of the present application provide a negative electrode material, a preparation method thereof, a negative electrode, a battery, an electronic device and an energy storage device, which can increase the purity and graphitization degree of the carbon component in the negative electrode material and improve the play of the electrochemical performance.

[0005] In a first aspect, embodiments of the present application provide a negative electrode material, comprising a porous carbon powder, the oxygen-containing functional group in the porous carbon powder being less than or equal to 0.4 mmol / g, and the mass fraction of carbon in the porous carbon powder being greater than or equal to 95%.

[0006] Through the above setting, the purity of the porous carbon powder is high, and the defects are less, so that the initial efficiency of the corresponding negative electrode material will be improved. The porous carbon powder has a high graphitization degree, which is represented by the 002 peak position of graphite in XRD being greater than or equal to 25°. The formation of the high-graphitized carbon component means that the material has good electronic conductivity and good lithium ion deintercalation capacity, further enhancing the play of the electrochemical initial efficiency and the rate.

[0007] In some embodiments that can include the above embodiments, the negative electrode material further comprises a functional layer and a coating layer. The functional layer covers the pore side wall in the porous carbon powder; the specific capacity of the functional layer is greater than that of the porous carbon powder, and the functional layer includes but is not limited to silicon, tin, etc. The coating layer is filled in the pores of the porous carbon powder, and the functional layer is located between the coating layer and the pore side wall.

[0008] In this way, compared with the negative electrode material containing only the porous carbon powder, the negative electrode material has a larger capacity. The capacity of the negative electrode material can be controlled by adjusting the material and mass fraction of the functional layer.

[0009] In some embodiments that can include some of the above embodiments, the porous carbon powder has a pore volume greater than 0.08 g / cc, for example, the porous carbon powder has a pore volume greater than 0.6 g / cc, or the porous carbon powder has a pore volume greater than 0.8 g / cc.

[0010] In this way, the pore volume of the porous carbon powder enables the porous carbon powder to have adsorption capacity, and the porous carbon powder can adsorb silane gas into the pores, and the silane gas can be cracked on the side wall of the pores to form a silicon layer. By changing the size of the pore volume and the mass ratio of carbon and silicon in the porous carbon powder, the capacity of the negative electrode can be controlled, and thus the capacity of the battery can be changed.

[0011] In some embodiments that can include some of the above embodiments, the average pore size of the porous carbon powder is less than 5 nm.

[0012] In this way, the pore structure of the porous carbon powder has a certain threshold effect on the silicon particles. When lithium is completely inserted into the silicon particles, the silicon particles will expand a lot, which will reduce the cycle life and power of the electrode. The small pore size of the porous carbon powder enables the silicon particles to enter the pores in a small size, so that the expansion of the silicon particles is small, thereby improving the cycle life and power of the battery.

[0013] In some embodiments that can include some of the above embodiments, the material of the coating layer can include amorphous carbon.

[0014] In this way, the amorphous carbon can passivate the silicon particles, reduce the activity of the silicon particles, and improve the stability of the negative electrode. At the same time, the amorphous carbon has good electrical conductivity, and can realize fast transmission of lithium ions. Compared with the coating layer prepared by other inorganic materials, the coating layer using amorphous carbon has better toughness, can better adapt to the stress change caused by the volume expansion of the silicon particles, and has a certain ductility. In addition, the coating layer of amorphous carbon can be obtained by a gas source deposition process, and compared with other materials, the coating layer has a simpler manufacturing process.

[0015] In a second aspect, the embodiments of the present application provide a negative electrode, which includes a conductor and the negative electrode material described above, and the negative electrode material is coated on the conductor.

[0016] The negative electrode provided by the embodiments of the present application includes the negative electrode material in any of the above embodiments, so the two can solve the same technical problems and achieve the same technical effects.

[0017] In a third aspect, the embodiments of the present application provide a battery, which includes a positive electrode, a separator, and the negative electrode described above, and the separator is arranged between the positive electrode and the negative electrode.

[0018] The battery provided by the embodiments of the present application comprises the negative electrode in any of the above embodiments, and thus the two can solve the same technical problem and achieve the same technical effect.

[0019] In a fourth aspect, the embodiments of the present application provide an electronic device comprising a shell and the above battery, wherein the battery is arranged in the shell.

[0020] The electronic device provided by the embodiments of the present application comprises the battery in any of the above embodiments, and thus the two can solve the same technical problem and achieve the same technical effect.

[0021] In a fifth aspect, the embodiments of the present application provide an energy storage device comprising a plurality of the above batteries, wherein the plurality of batteries are connected in series or in parallel.

[0022] The energy storage device provided by the embodiments of the present application comprises the battery in any of the above embodiments, and thus the two can solve the same technical problem and achieve the same technical effect.

[0023] In a sixth aspect, the embodiments of the present application provide a negative electrode material preparation method comprising: mixing a carbon-containing precursor and an alkali activator, and preheating; activating the preheated carbon-containing precursor and alkali activator mixture to obtain a first product; washing and drying the first product, and then performing heat treatment, wherein the heat treatment temperature is greater than or equal to 900 DEG C, and the heat treatment time is greater than or equal to 1 h, to obtain a porous carbon powder.

[0024] In this way, the heat treatment temperature and the heat treatment time will affect the formation of the porous carbon powder structure, so that the properties of the porous carbon powder change. The graphitization degree of the porous carbon powder generated by the heat treatment temperature greater than or equal to 900 DEG C and the heat treatment time greater than or equal to 1 h is obviously improved. For example, the heat treatment temperature is greater than 1200 DEG C. BRIEF DESCRIPTION OF DRAWINGS

[0025] FIG. 1 is a structural schematic diagram of an energy storage device provided by the embodiments of the present application;

[0026] FIG. 2 is a structural schematic diagram of an electronic device provided by the embodiments of the present application;

[0027] FIG. 3 is a structural schematic diagram of a battery provided by the embodiments of the present application;

[0028] FIG. 4 is a structural schematic diagram of a negative electrode provided by the embodiments of the present application;

[0029] FIG. 5 is a structural schematic diagram of a negative electrode material provided by the embodiments of the present application;

[0030] FIG. 6 is a structural schematic diagram of a negative electrode material provided by the embodiments of the present application;

[0031] Fig. 7 is a flow chart of a method for preparing a negative electrode material according to an embodiment of the present application;

[0032] Fig. 8 is a flow chart of a method for preparing a negative electrode material according to another embodiment of the present application;

[0033] Fig. 9 is a flow chart of forming a functional layer on the sidewall of the pores in the porous carbon powder;

[0034] Fig. 10 is a flow chart of a method for preparing a negative electrode material after forming a silicon layer;

[0035] Fig. 11 is a flow chart of a method for preparing a negative electrode material after passivating the negative electrode material;

[0036] Fig. 12 is a flow chart of a method for preparing a negative electrode according to an embodiment of the present application;

[0037] Fig. 13 is a flow chart of a method for preparing a battery according to an embodiment of the present application;

[0038] Fig. 14 is a graph of the adsorption and desorption curve of the porous carbon powder according to an embodiment of the present application;

[0039] Fig. 15 is a graph of the adsorption and desorption curve of the porous carbon powder according to another embodiment of the present application;

[0040] Fig. 16 is a graph of the adsorption and desorption curve of the porous carbon powder according to another embodiment of the present application;

[0041] Fig. 17 is an XRD graph of the porous carbon powder according to an embodiment of the present application.

[0042] Legend of reference signs: 10: battery; 20: negative electrode; 30: negative electrode material; 31: porous carbon powder; 32: functional layer; 33: coating layer; 21: conductor; 11: positive electrode; 12: battery cell; 40: electronic device; 41: housing; 42: circuit board; 50: energy storage device. DETAILED DESCRIPTION

[0043] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0044] Hereinafter, the terms "first", "second", and the like are used only for the purpose of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second", and the like can explicitly or implicitly include one or more of the features.

[0045] Referring to FIG. 1, an embodiment of the present application provides an energy storage device 50, which includes a plurality of batteries 10 connected in series or in parallel. It can be understood that the voltage of the energy storage device 50 can be adjusted by changing the connection mode between the batteries 10. It can be understood that the energy storage device 50 is not specifically limited in the embodiment of the present application, and for example, the energy storage device 50 can include an energy storage station, a battery pack on an electric vehicle, etc.

[0046] Referring to FIG. 2, an embodiment of the present application provides an electronic device 40, which includes a housing 41 and a battery 10, and the battery 10 is arranged in the housing 41. It can be understood that the material of the housing 41 can include aluminum, steel, etc.; the housing 41 can include a regular shape such as a cuboid or a cylinder, and of course the housing 41 can also have other irregular shapes. The housing 41 can support and protect the battery 10, so as to avoid damage to the battery 10 by external force. The electronic device 40 can further include a circuit board 42, and the circuit board 42 is electrically connected with the battery 10, and the battery 10 can provide energy for each component on the circuit board 42, so that the component works. It can be understood that the electronic device 40 is not specifically limited in the embodiment of the present application, and for example, the electronic device 40 can include a mobile phone, a tablet computer, etc.

[0047] Referring to FIG. 3, an embodiment of the present application further provides a battery 10, which includes a positive electrode 11, a separator and a negative electrode 20, and the separator is arranged between the positive electrode 11 and the negative electrode 20. The separator is used to absorb electrolyte, so as to ensure that the positive electrode 11 and the negative electrode 20 are filled with electrolyte. It can be understood that the specific structure of the battery 10 is not limited in the embodiment of the present application, and for example, the battery 10 includes a battery cell 12. In an implementation mode in which the battery cell 12 adopts a winding core, the positive electrode 11, the separator and the negative electrode 20 can constitute a diaphragm, and the diaphragm forms a winding core after being wound or folded. In an implementation mode in which the battery cell 12 adopts a stacking core, the positive electrode 11, the negative electrode 20 and the separator constitute a diaphragm, and the diaphragm forms a stacking core after being folded at least once.

[0048] When the battery 10 is charged, metal ions are released from the positive electrode 11, migrate to the negative electrode 20 through the electrolyte, and are embedded in the negative electrode 20 to form a composite compound, and for example, in an embodiment in which the negative electrode 20 includes graphite, lithium carbide can be formed; at the same time, electrons flow from the positive electrode 11 to the negative electrode 20 through an external circuit, the open circuit voltage of the battery 10 is increased, and the electrical energy is stored. When the battery 10 is discharged, the metal ions in the negative electrode 20 undergo a de-embedding reaction, return to the positive electrode 11 through the electrolyte, and the electrons migrate from the negative electrode 20 to the positive electrode 11 through the external circuit, the voltage is reduced, and the electrical energy is released.

[0049] It can be understood that the capacity of the battery 10 is related to how much material can accommodate metal ions, for example, the capacity of the battery 10 is related to the mass, volume and compaction density of the electrode. Under other conditions, the greater the mass of the electrode, the greater the capacity of the battery 10; the greater the volume of the electrode, the greater the capacity of the battery 10; the greater the compaction density of the electrode, the greater the capacity of the battery 10.

[0050] In some embodiments, the battery 10 can include a lithium ion battery, the metal ions include lithium ions, and accordingly, the material of the positive electrode 11 can include at least one of lithium cobaltate, lithium iron phosphate, lithium manganate, ternary material lithium nickel cobalt manganate, lithium nickel cobalt aluminum acid, etc., and the material of the electrolyte can include at least one of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, lithium tetrafluoroborate, lithium hexafluorophosphate, vinylene carbonate, fluoroethylene carbonate, etc.

[0051] Referring to FIG. 4, the embodiment of the application further provides a negative electrode 20, which includes a conductor 21 and a negative electrode material 30 coated on the conductor 21. It can be understood that the conductor 21 can be a copper foil, a cobalt foil, or a lithium foil.

[0052] Referring to FIG. 5, the embodiment of the application provides a negative electrode material 30, which includes a porous carbon powder 31 containing oxygen functional groups less than or equal to 0.4 mmol / g, and the mass fraction of carbon in the porous carbon powder 31 is greater than or equal to 95%. It can be understood that the greater the mass fraction of carbon in the porous carbon powder 31, the fewer the oxygen-containing functional groups, the higher the purity of the carbon component, and the fewer the defects, which can improve the initial efficiency of the negative electrode material 30. The negative electrode material 30 also has a high graphitization degree, and the main peak position of graphite (002) in its XRD is greater than or equal to 25°. The porous carbon material with high graphitization degree has high electronic conductivity, and accordingly, the fast charging performance is improved. In addition, compared with low-graphitization amorphous carbon, the carbon material with high graphitization degree has high order degree, and the compaction density can also be improved to a certain extent.

[0053] It can be understood that the first efficiency refers to the percentage of the ratio of the first full discharge capacity to the first full charge capacity of the battery 10 in the first charge and discharge process. The electronic conductivity refers to the conductivity of the negative electrode material 30. The compaction density includes the powder compaction density and the electrode sheet compaction density. The powder compaction density is usually tested by applying a certain pressure, such as (5T), to the density of the powder under the pressure. The electrode sheet compaction density refers to the ratio of the area density of the battery 10 to the difference between the thickness of the electrode sheet after rolling and the thickness of the current collector. That is, the compaction density = area density / (thickness of the electrode sheet after rolling - thickness of the current collector). Generally speaking, a high powder compaction density is beneficial to the improvement of the electrode sheet compaction density. Under the same negative electrode 20 (as shown in FIG. 4) capacity, the higher the compaction density of the porous carbon powder 31, the smaller the volume of the negative electrode 20, which is beneficial to the volume energy density.

[0054] In some implementations, the characteristic peak of the porous carbon powder 31 in the X-ray diffraction (XRD) spectrum is greater than 25°C. It can be understood that, in addition to detecting the graphitization degree of the porous carbon powder 31 by X-ray diffraction method, the graphitization degree of the porous carbon powder 31 can also be detected by other methods such as Raman spectroscopy. In the implementation of detecting the porous carbon powder 31 by X-ray diffraction method, the characteristic peak refers to the 002 peak, and the peak position refers to the abscissa 2θ of the XRD spectrum. The abscissa 2θ of the 002 peak is greater than 23°, which indicates that the porous carbon powder 31 has a certain degree of graphitization. In the present technical solution, when the oxygen-containing functional group in the porous carbon powder 31 is less than or equal to 0.4 mmol / g and the mass fraction of carbon is greater than or equal to 95%, the corresponding 2θ is greater than 25°. The 2θ of the standard graphite is about 26.5°. The closer the 2θ is to 26.5°, the higher the peak value of the 002 peak, and the higher the graphitization degree of the corresponding porous carbon powder 31.

[0055] In some implementations, the D50 of the porous carbon powder 31 can include 1um-10um, the Dmax is less than 40um, and the Dmin is greater than 0.1um. It can be understood that the D50 refers to the particle size corresponding to the cumulative particle size distribution percentage of 50% of the porous carbon powder 31, the Dmax refers to the maximum particle size of the porous carbon powder 31, and the Dmin refers to the minimum particle size of the porous carbon powder 31.

[0056] With continued reference to FIG. 5, in some implementations, the negative electrode material 30 further includes a functional layer 32 and a coating layer 33. The functional layer 32 covers the pore sidewalls in the porous carbon powder 31; the specific capacity of the functional layer 32 is greater than that of the porous carbon powder 31. The material of the functional layer includes, but is not limited to, silicon, phosphorus, etc. The coating layer 33 fills in the pores of the porous carbon powder 31, and the functional layer 32 is located between the coating layer 33 and the pore sidewalls. It can be understood that the greater the specific capacity, the greater the capacity of the negative electrode material 30, and the negative electrode material 30 including the functional layer 32 has a greater capacity than the negative electrode material 30 including only the porous carbon powder 31. In this way, the capacity of the negative electrode material 30 can be controlled by adjusting the material and mass fraction of the functional layer 32.

[0057] It can be understood that the porous carbon powder 31 is not limited to the shape shown in FIG. 5, and the embodiments of the present application do not limit the specific shape of the porous carbon powder 31. For example, the porous carbon powder 31 can include a spherical shape, a rod shape, a cuboid shape, and a rose shape. As shown in FIG. 6, the surface of the porous carbon powder 31 is arranged with pores of various sizes and shapes, the functional layer 32 covers the pore sidewalls in the porous carbon powder 31, and the coating layer 33 fills in the pores of the porous carbon powder 31 and the entire particle exterior.

[0058] In some implementations, the functional layer 32 includes at least one of a silicon layer, a phosphorus layer, and a tin layer. The theoretical specific capacity of silicon is 4200 mAh / g, the theoretical specific capacity of phosphorus is 2596 mAh / g, the theoretical specific capacity of tin is 990 mAh / g, and the theoretical specific capacity of carbon is 372 mAh / g. The theoretical specific capacity refers to the amount of charge released or absorbed per unit mass of active material in the electrode under complete reaction, and is used to characterize the theoretical charge capacity that the electrode can accommodate. It can be understood that the theoretical specific capacity of silicon, phosphorus, and tin is greater than that of carbon, and the negative electrode 20 including at least one of silicon, phosphorus, and tin (as shown in FIG. 4) can accommodate a greater theoretical charge capacity than the negative electrode 20 including only carbon, and the capacity of the negative electrode 20 including at least one of silicon, phosphorus, and tin is greater under the condition that the mass of the negative electrode material 30 is the same.

[0059] In this way, the capacity of the negative electrode 20 can be improved by the functional layer 32, and the size of the capacity of the negative electrode 20 can be controlled by adjusting the content of the functional layer 32 and the component ratio of the functional layer 32 and the porous carbon powder 31.

[0060] In some implementations, the porous carbon powder 31 has a pore volume greater than 0.08 g / cc. For example, the porous carbon powder 31 has a pore volume greater than 0.6 g / cc, or greater than 0.8 g / cc. It can be appreciated that the porous carbon powder 31 has a pore volume such that the porous carbon powder 31 has an adsorption capacity to adsorb, for example, silane gas into the pores and to decompose on the pore walls to form a silicon layer. It can be appreciated that the shape of the pores of the porous carbon powder 31 varies, and correspondingly, the state of the silicon particles varies. The porous carbon powder 31 can have a pore volume including 0.08-0.4 g / cc, for example, the pore volume can include 0.1 g / cc, 0.2 g / cc, 0.3 g / cc, etc. The porous carbon powder 31 can have a pore volume including 0.8 g / cc-1.2 g / cc, for example, the pore volume can include 0.9 g / cc, 1.0 g / cc, 1.1 g / cc, etc.

[0061] In this way, the pore volume of the porous carbon powder 31 is such that the porous carbon powder 31 has an adsorption capacity to adsorb, for example, silane gas into the pores and to decompose on the pore walls to form a silicon layer. By varying the size of the pore volume, the mass ratio of carbon and silicon in the porous carbon powder 31 can be varied to control the size of the capacity of the anode 20, and thus the size of the capacity of the battery 10.

[0062] In some implementations, the porous carbon powder 31 has an average pore size less than 5 nm. For example, the porous carbon powder 31 can have an average pore size including 4 nm, 3 nm, 2 nm, 1 nm. It can be appreciated that the pore structure of the porous carbon powder 31 has a certain threshold effect on the silicon particles. The silicon particles will expand greatly when lithium is fully inserted, and this expansion leads to a decrease in the cycle life and power of the electrode. The small pore size of the porous carbon powder 31 allows the size of the silicon particles entering the pores to be small, and the expansion of the silicon particles is small, which can improve the cycle life and power of the battery 10.

[0063] In some implementations, the material of the coating layer 33 can include amorphous carbon. It can be appreciated that the material of the coating layer 33 can also include high-molecular resins, metals, and metal oxides. It can be appreciated that the silicon particles exist in the form of nanoparticles in the pores of the porous carbon powder 31, and the silicon particles are relatively active, which is not conducive to the stability of the anode 20. Amorphous carbon can passivate the silicon particles and reduce the activity of the silicon particles. At the same time, amorphous carbon has good electrical conductivity and can achieve fast transmission of lithium ions. Compared with other inorganic material prepared coating layers 33, the coating layer 33 using amorphous carbon has better toughness and can better adapt to the stress changes caused by the volume expansion of the silicon particles, has a certain ductility, and the coating layer 33 of amorphous carbon can be obtained by a gas source deposition process, and compared with other material coating layers 33, the manufacturing process is simpler.

[0064] Referring to FIG. 7, the embodiment of the present application provides a preparation method of the negative electrode material 30 (as shown in FIG. 5), including the following steps.

[0065] S101: mixing the carbon-containing precursor and the alkali activator, and preheating;

[0066] In some embodiments, the carbon-containing precursor and the alkali activator are mixed in a mass ratio of 1:1-1:20. For example, the mass ratio of the carbon-containing precursor and the alkali activator can be 1:2, 1:5, 1:10, or 1:15. The preheating temperature is 200-350°C. For example, the preheating temperature can be 200°C or 300°C. After preheating, the mixture needs to be kept for 0.5-2h. For example, the mixture can be kept for 1h or 1.5h. It can be understood that h is the unit of time, hour.

[0067] S103: activating the mixture of the preheated carbon-containing precursor and the alkali activator to obtain a first product;

[0068] It can be understood that the mixture after activation needs to be washed and dried before obtaining the first product. In some embodiments, the mixture of the preheated carbon-containing precursor and the alkali activator is transferred to an activation furnace and heated to 500-1200°C and kept for 1-48h to achieve sufficient activation. For example, the mixture can be heated to 500°C, 600°C, 800°C, 1000°C, or 1200°C. The keeping time can be 1h, 2h, 10h, 12h, 24h, 36h, or 48h.

[0069] S105: heat treating the first product at a temperature greater than or equal to 900°C for a time greater than or equal to 1h to obtain a porous carbon powder.

[0070] For example, the heat treatment temperature is greater than 1200°C. It can be understood that the heat treatment temperature and the heat treatment time will affect the formation of the porous carbon powder 31 (as shown in FIG. 6), so that the pore structure and internal structure of the porous carbon powder 31 change.

[0071] In some implementations, the carbon-containing precursor includes at least one of petroleum coke and coal. The alkali activator includes at least one of sodium hydroxide, potassium hydroxide, potassium carbonate, and potassium chloride. The alkali activator can carbonize the carbon-containing precursor at high temperature and react to form a pore structure.

[0072] It can be understood that the carbon-containing precursor further includes a pitch precursor, a resin precursor, and a biomass precursor. The pitch precursor includes fossil fuels. For example, the pitch precursor can include pitch. The resin precursor can include phenolic resin and epoxy resin. The biomass precursor can include bio-based polymer materials. For example, the biomass precursor can include coconut shell, walnut shell, sugar, and starch.

[0073] Compared with other carbon-containing precursors, the pitch precursor has low cost, raw materials are easy to obtain, and cost performance is high, but the pitch needs to be pretreated. For example, the microstructure of the pitch can be changed by a crosslinking agent. Due to the high volatile content in the pitch, additional tail gas treatment is required, which increases the cost.

[0074] Compared with pitch precursors and biomass precursors, the molecular structure of the resin precursor is simpler and more controllable. The molecular structure can be designed as needed to precisely construct adjustable pore structures, so that the porous carbon powder 31 has better capacity retention rate and cycle stability. However, the price of the resin precursor is relatively high, and the cost pressure of mass production is large.

[0075] Compared with other carbon-containing precursors, the raw materials of the biomass precursor are diverse. However, the molecular structure and molecular weight of different biomass precursors differ significantly, which affects the composition and internal structure of the prepared porous carbon powder 31, and further affects the performance of the negative electrode 20 (as shown in FIG. 4). Therefore, when using a biomass precursor, the corresponding biomass raw material needs to be selected according to the porous carbon powder 31.

[0076] Please refer to FIG. 8. In some implementations, after obtaining the porous carbon powder 31 (as shown in FIG. 6), the method for preparing the negative electrode material 30 (as shown in FIG. 5) further includes:

[0077] S107: forming a functional layer on the pore side wall in the porous carbon powder;

[0078] S109: forming a coating layer in the pores of the porous carbon powder.

[0079] Please refer to FIG. 9. In some implementations, forming the functional layer 32 (as shown in FIG. 6) on the pore side wall in the porous carbon powder 31 (as shown in FIG. 6) includes:

[0080] S201: placing the porous carbon powder in a first reaction cavity, introducing nitrogen into the first reaction cavity and preheating to 400-500°C;

[0081] It can be understood that the nitrogen is a protective gas, and the introduction of nitrogen can discharge the air in the first reaction cavity to prevent the air from affecting the structure and stability of the porous carbon powder 31.

[0082] S203: introducing silane into the first reaction cavity and heat preserving the first reaction cavity to form a silicon layer on the pore side wall in the porous carbon powder.

[0083] It can be understood that the silane gas can include methylsilane gas, and the heat preservation time includes 2-3h.

[0084] Referring to FIG. 10, in some implementations, after forming the silicon layer, the method for preparing the negative electrode material 30 (as shown in FIG. 5) further comprises:

[0085] S205: heating the first reaction cavity to 450-800°C, and adding a carbon source into the first reaction cavity to form amorphous carbon in the pores of the porous carbon powder, so as to passivate the negative electrode material.

[0086] It can be understood that the carbon source comprises at least one of methane, ethane, acetylene, benzene, and amine. The first reaction cavity comprises a rotary furnace and a fluidized bed device, and the formation of amorphous carbon can be directly performed on the first reaction cavity by switching the gas.

[0087] Continuing to refer to FIG. 10, in some implementations, after forming the silicon layer, the method for preparing the negative electrode material 30 (as shown in FIG. 5) further comprises:

[0088] S207: introducing oxygen and nitrogen into the first reaction cavity to passivate the negative electrode material;

[0089] wherein the mass fraction of oxygen is less than 10%.

[0090] It can be understood that the passivation of the negative electrode material 30 can prevent the negative electrode material 30 from suddenly contacting air and causing exothermic combustion of the silicon particles.

[0091] Referring to FIG. 11, in some implementations, after passivating the negative electrode material, the method for preparing the negative electrode material 30 (as shown in FIG. 5) further comprises:

[0092] S301: placing the porous carbon powder into a second reaction cavity;

[0093] S303: heating the second reaction cavity to 450-800°C, and adding a carbon source into the second reaction cavity to form amorphous carbon in the pores of the porous carbon powder.

[0094] It can be understood that, before placing the porous carbon powder 31 (as shown in FIG. 6) into the second reaction cavity, the porous carbon powder 31 needs to be passivated so that it is covered with a part of passivation material, so as to avoid oxidation loss of the silicon layer after being taken out from the first reaction cavity. The oxidation loss refers to the exothermic combustion of the silicon layer after contacting oxygen.

[0095] In some implementations, the passivation of the negative electrode material can be achieved by S205, so that the negative electrode material is covered with a part of carbon material, and then the passivated porous carbon powder 31 is placed into the second reaction cavity to form amorphous carbon. In some implementations, the passivation of the negative electrode material can be achieved by S207, so that the negative electrode material is covered with a part of carbon material, and then the passivated porous carbon powder 31 is placed into the second reaction cavity to form amorphous carbon. In some implementations, the passivation of the negative electrode material can be achieved by S205, so that the negative electrode material is covered with a part of carbon material, and then the passivated porous carbon powder 31 is placed into the second reaction cavity to form amorphous carbon. In some implementations, the passivation of the negative electrode material can be achieved by S207, so that the negative electrode material is covered with a part of carbon material, and then the passivated porous carbon powder 31 is placed into the second reaction cavity to form amorphous carbon.

[0096] It can be understood that, in the implementation mode in which the porous carbon powder 31 forms amorphous carbon in the first reaction cavity, the first reaction cavity can be directly heated to 450-800℃, and a carbon source is introduced into the first reaction cavity to form amorphous carbon.

[0097] Referring to FIG. 12, the application further provides a preparation method of the negative electrode 20 (as shown in FIG. 4), comprising:

[0098] S401: The negative electrode material is used as an active material, and is mixed with super P carbon conductive agent and adhesive carboxymethyl cellulose (CMC) in a mass ratio of 8:1:1 in a water solvent, and is uniformly stirred to obtain a negative electrode slurry;

[0099] S403: The negative electrode slurry is coated on the conductor 21, vacuum dried at 110℃ for 12h, and then rolled to obtain a negative electrode.

[0100] Referring to FIG. 13, the application further provides a preparation method of the battery 10 (as shown in FIG. 3), comprising:

[0101] S501: The lithium sheet is used as a positive electrode, a polyethylene (PE) diaphragm and 1mol / L LiPF6 / (EC+DEC) electrolyte are used;

[0102] It can be understood that the electrolyte comprises lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC) and diethyl carbonate (DEC), wherein the volume ratio of the mixed solution of LiPF6, EC and DEC is 1:1.

[0103] S503: The negative electrode and the above-mentioned materials are assembled into a battery in an argon-protected glove box.

[0104] In the embodiment 1 in which the carbon-containing precursor comprises petroleum coke, the alkali activator comprises potassium hydroxide, the ratio of the carbon-containing precursor to the alkali activator comprises 1:2, the activation temperature comprises 650℃, and the heat treatment temperature comprises 600℃, the mass fraction of carbon in the porous carbon powder 31 is 91%, the pore volume is 0.8g / cc, the powder conductivity is 26S / m, and the oxygen-containing functional group is 0.55mmol / g.

[0105] Referring to FIG. 14, FIG. 14 is a graph of the adsorption and desorption curves of the porous carbon powder 31 (as shown in FIG. 6) generated in the present embodiment, in which the abscissa represents the relative pressure, which refers to the ratio of the gas pressure in the adsorption (desorption) process to the saturated vapor pressure of the gas, and the ordinate represents the adsorption (desorption) amount at the standard temperature and pressure (STP). It can be understood that the STP refers to the state at a temperature of 0°C and a pressure of 101.325 kPa. In FIG. 14, the solid line with crosses is the adsorption curve, and the solid line with hollow circles is the desorption curve. The adsorption curve and the desorption curve in FIG. 14 almost completely coincide, indicating that the pores in the porous carbon powder 31 generated in the present embodiment are all micropores. It can be understood that micropores refer to pores less than 2 nm, mesopores refer to pores between 2 nm and 50 nm, macropores refer to pores between 50 nm and 7500 nm, and megapores refer to pores greater than 7500 nm.

[0106] The porous carbon powder 31 generated in the present embodiment is prepared into the negative electrode 20 (as shown in FIG. 4) and assembled into the battery 10 (as shown in FIG. 3), the compact density of the negative electrode 20 is 1.15 g / cc, the mass fraction of silicon is 46%, the reversible capacity of the battery 10 is 1490 mAh / g, the initial efficiency is 83%, and the capacity retention rate is 0.5. It can be understood that the capacity retention rate of the battery 10 refers to the ratio of the capacity of the battery 10 under the condition of 1C delithiation to the capacity of the battery 10 under the condition of 0.1C delithiation. The greater the ratio, the higher the capacity retention rate of the battery 10, indicating that the fast-charging performance of the battery 10 is better. It can be understood that the mass fraction of silicon can be controlled by setting the deposition time. For example, the longer the deposition time, the greater the mass fraction of silicon.

[0107] In the embodiment 2 in which the carbon-containing precursor includes petroleum coke, the alkali activator includes potassium hydroxide, the ratio of the carbon-containing precursor to the alkali activator includes 1:2, the activation temperature includes 650°C, and the heat treatment temperature includes 900°C, the mass fraction of carbon in the porous carbon powder 31 is 95%, the pore volume is 0.7 g / cc, the powder conductivity is 66 S / m, the oxygen-containing functional group is 0.38 mmol / g, and the microporosity is 80%.

[0108] The porous carbon powder 31 generated in the present embodiment is prepared into the negative electrode 20 and assembled into the battery 10, the compact density of the negative electrode 20 is 1.2 g / cc, the mass fraction of silicon is 44%, the reversible capacity of the battery 10 is 1480 mAh / g, the initial efficiency is 86%, and the capacity retention rate is 0.65.

[0109] Compared with the previous embodiment, the heat treatment temperature of the present embodiment is increased to 900°C, the mass fraction of carbon in the generated porous carbon powder 31 is increased, the oxygen-containing functional groups are reduced, and the powder conductivity is greatly increased. The compaction density of the corresponding negative electrode 20 is increased, and the initial efficiency and capacity retention rate of the battery 10 under high rate are increased. It can be understood that after the heat treatment temperature reaches 900°C, the mass fraction of carbon in the porous carbon powder 31 is increased, the oxygen-containing functional groups are reduced, the order degree of the porous carbon powder 31 is increased, and the graphitization degree is increased, thereby causing the initial efficiency and capacity retention rate of the battery 10 to be increased.

[0110] In the embodiment 3, the carbon-containing precursor includes petroleum coke, the alkali activator includes potassium hydroxide, the ratio of the carbon-containing precursor to the alkali activator includes 1:3, the activation temperature includes 650°C, and the heat treatment temperature includes 900°C. In the porous carbon powder 31, the mass fraction of carbon is 94%, the pore volume is 0.8 g / cc, the powder conductivity is 63 S / m, the oxygen-containing functional group is 0.35 mmol / g, and the microporosity is 85%.

[0111] The porous carbon powder 31 generated in the present embodiment is prepared into a negative electrode 20 and assembled into a battery 10. The compaction density of the negative electrode 20 is 1.18 g / cc, the mass fraction of silicon is 46%, the reversible capacity of the battery 10 is 1550 mAh / g, the initial efficiency is 86%, and the capacity retention rate is 0.62.

[0112] Compared with the previous embodiment, the ratio of the alkali activator in the present embodiment is increased, and the pore volume of the generated porous carbon powder 31 is slightly increased. It can be understood that the increase of the ratio of the alkali activator increases the activation depth, and the pore volume and pore size of the porous carbon powder 31 are increased, thereby causing the adsorption capacity of the porous carbon powder 31 to the silicon particles to be increased, and the mass fraction of silicon and the reversible capacity of the battery 10 to be increased.

[0113] In the embodiment 4, the carbon-containing precursor includes petroleum coke, the alkali activator includes potassium hydroxide, the ratio of the carbon-containing precursor to the alkali activator includes 1:3, the activation temperature includes 750°C, and the heat treatment temperature includes 900°C. In the porous carbon powder 31, the mass fraction of carbon is 95%, the pore volume is 0.9 g / cc, the powder conductivity is 60 S / m, and the oxygen-containing functional group is 0.37 mmol / g.

[0114] The porous carbon powder 31 generated in the present embodiment is prepared into a negative electrode 20 and assembled into a battery 10. The compaction density of the negative electrode 20 is 1.15 g / cc, the mass fraction of silicon is 46%, the reversible capacity is 1530 mAh / g, the initial efficiency is 85%, and the capacity retention rate is 0.6.

[0115] Compared with the previous embodiment, the activation temperature of the present embodiment is increased, and the pore volume of the generated porous carbon powder 31 is increased. It can be understood that the increase of the activation temperature makes the activation reaction more intense, the pore volume of the porous carbon powder 31 is increased, and the adsorption capacity of the silicon particles is increased, which is beneficial to the improvement of the mass fraction of silicon and the reversible capacity of the battery 10.

[0116] In the embodiment 5, the carbon mass fraction of the porous carbon powder 31 is 96%, the pore volume is 0.75 g / cc, the powder conductivity is 85 S / m, and the oxygen-containing functional group is 0.21 mmol / g, when the carbon-containing precursor includes petroleum coke, the alkali activator includes potassium hydroxide, the ratio of the carbon-containing precursor to the alkali activator is 1:3, the activation temperature is 750°C, and the heat treatment temperature is 1200°C.

[0117] The porous carbon powder 31 generated in the present embodiment is prepared into the negative electrode 20 and assembled into the battery 10, the compact density of the negative electrode 20 is 1.25 g / cc, the mass fraction of silicon is 45%, the reversible capacity is 1540 mAh / g, the initial efficiency is 87%, and the capacity retention rate is 0.7.

[0118] Compared with the previous embodiment, the heat treatment temperature of the present embodiment is increased, the carbon mass fraction of the generated porous carbon powder 31 is increased, the pore volume is decreased, and the oxygen-containing functional group is reduced. Correspondingly, the compact density of the negative electrode 20 is increased, the initial efficiency of the battery 10 is increased, and the capacity retention rate is increased. It can be understood that the increase of the heat treatment temperature increases the carbon mass fraction of the porous carbon powder 31 and reduces the oxygen-containing functional group, which increases the order degree and the graphitization degree of the porous carbon powder 31, increases the powder conductivity of the porous carbon powder 31, and increases the compact density of the negative electrode 20, the initial efficiency of the battery 10, and the capacity retention rate.

[0119] In the embodiment 6, the carbon mass fraction of the porous carbon powder 31 is 97%, the pore volume is 0.65 g / cc, the powder conductivity is 105 S / m, and the oxygen-containing functional group is 0.15 mmol / g, when the carbon-containing precursor includes petroleum coke, the alkali activator includes potassium hydroxide, the ratio of the carbon-containing precursor to the alkali activator is 1:3, the activation temperature is 750°C, and the heat treatment temperature is 1500°C.

[0120] Please refer to FIG. 15, which is the adsorption-desorption curve of the porous carbon powder 31 (as shown in FIG. 6) generated in the present embodiment, the horizontal coordinate is the relative pressure, and the vertical coordinate is the adsorption (desorption) amount. The solid line with crosses in FIG. 15 is the adsorption curve, and the solid line with hollow circles is the desorption curve. The adsorption curve and the desorption curve in FIG. 15 almost completely coincide, indicating that the pores in the porous carbon powder 31 generated in the present embodiment are all micropores.

[0121] The porous carbon powder 31 generated in this example was prepared into the negative electrode 20 (as shown in FIG. 4) and assembled into the battery 10 (as shown in FIG. 3), the compacted density of the negative electrode 20 was 1.4 g / cc, the mass fraction of silicon was 40%, the reversible capacity of the battery 10 was 1380 mAh / g, the initial efficiency was 88%, and the capacity retention rate was 0.75.

[0122] Compared with the previous example, the heat treatment temperature of this example was increased, the mass fraction of carbon in the generated porous carbon powder 31 was increased, the pore volume was decreased, and the oxygen-containing functional groups were reduced. The compacted density of the corresponding negative electrode 20 was increased, the initial efficiency of the battery 10 was increased, and the capacity retention rate was increased. It can be understood that, as the heat treatment temperature is increased, the mass fraction of carbon in the porous carbon powder 31 is increased, the oxygen-containing functional groups are reduced, the order degree of the porous carbon powder 31 is increased, and the graphitization degree is increased, so that the powder conductivity of the porous carbon powder 31 is increased, and the compacted density, the initial efficiency, and the capacity retention rate of the negative electrode 20 are all increased. However, as the heat treatment temperature is increased, the pore volume is decreased, the adsorption capacity for silicon particles is weakened, the mass fraction of silicon in the negative electrode 20 is reduced, and the reversible capacity of the battery 10 is reduced.

[0123] In Example 7, the mass fraction of carbon in the porous carbon powder 31 was 98%, the pore volume was 0.3 g / cc, the powder conductivity was 118 S / m, and the oxygen-containing functional groups were 0.1 mmol / g, where the carbon-containing precursor included petroleum coke, the alkali activator included potassium hydroxide, the ratio of the carbon-containing precursor to the alkali activator included 1:3, the activation temperature included 750°C, and the heat treatment temperature included 1800°C.

[0124] Referring to FIG. 16, FIG. 16 is a sorption-desorption curve diagram of the porous carbon powder 31 (as shown in FIG. 6) generated in this example, the abscissa is the relative pressure, and the ordinate is the sorption (desorption) amount. The solid line with crosses in FIG. 16 is the adsorption curve, and the solid line with hollow circles is the desorption curve. The adsorption curve and the desorption curve in FIG. 16 do not coincide, forming a hysteresis loop, indicating that the pores in the porous carbon powder 31 generated in this example include micropores and mesopores, and have a slit pore structure.

[0125] The porous carbon powder 31 generated in this example was prepared into the negative electrode 20 (as shown in FIG. 4) and assembled into the battery 10 (as shown in FIG. 3), the compacted density of the negative electrode 20 was 1.6 g / cc, the mass fraction of silicon was 15%, the reversible capacity of the battery 10 was 560 mAh / g, the initial efficiency was 90%, and the capacity retention rate was 0.8.

[0126] Compared with the previous embodiment, the heat treatment temperature of the present embodiment is increased, the mass fraction of carbon in the generated porous carbon powder 31 is increased, the pore volume is decreased, and the oxygen-containing functional groups are reduced. The compaction density of the corresponding negative electrode 20 is increased, the initial efficiency is increased, and the capacity retention rate is increased. It can be understood that, as the heat treatment temperature is increased, the mass fraction of carbon in the porous carbon powder 31 is increased, the oxygen-containing functional groups are reduced, the order degree of the porous carbon powder 31 is increased, and the graphitization degree is increased, so that the powder conductivity of the porous carbon powder 31 is increased, and the compaction density of the negative electrode 20, the initial efficiency of the battery 10, and the capacity retention rate are all increased. However, as the heat treatment temperature is increased, the pore volume is decreased, the adsorption capacity of the silicon particles is weakened, the mass fraction of silicon in the negative electrode 20 is reduced, and the reversible capacity of the battery 10 is reduced.

[0127] In the embodiment 8 in which the carbon-containing precursor includes petroleum coke, the alkali activator includes potassium hydroxide and potassium chloride, the ratio of the carbon-containing precursor to the alkali activator includes 1:3, the activation temperature includes 650°C, and the heat treatment temperature includes 900°C, the mass fraction of carbon in the porous carbon powder 31 is 95%, the pore volume is 0.85 g / cc, the powder conductivity is 68 S / m, and the oxygen-containing functional groups are 0.34 mmol / g.

[0128] The porous carbon powder 31 generated in the present embodiment is prepared into a negative electrode 20 and assembled into a battery 10, the compaction density of the negative electrode 20 is 1.16 g / cc, the mass fraction of silicon is 46%, the reversible capacity of the battery 10 is 1548 mAh / g, the initial efficiency is 86%, and the capacity retention rate is 0.61.

[0129] Compared with the above-mentioned embodiment 3, the composition of the alkali activator is changed, and a composite alkali activator is used, so that the pore volume of the porous carbon powder 31 is increased, the adsorption capacity of the porous carbon powder 31 to the silicon particles is increased, and the mass fraction of silicon and the reversible capacity of the battery 10 are increased.

[0130] In the embodiment 9 in which the carbon-containing precursor includes petroleum coke, the alkali activator includes potassium hydroxide and potassium carbonate, the ratio of the carbon-containing precursor to the alkali activator includes 1:3, the activation temperature includes 650°C, and the heat treatment temperature includes 900°C, the mass fraction of carbon in the porous carbon powder 31 is 94%, the pore volume is 0.82 g / cc, the powder conductivity is 65 S / m, and the oxygen-containing functional groups are 0.38 mmol / g.

[0131] The porous carbon powder 31 generated in the present embodiment is prepared into a negative electrode 20 and assembled into a battery 10, the compaction density of the negative electrode 20 is 1.18 g / cc, the mass fraction of silicon is 46%, the reversible capacity of the battery 10 is 1552 mAh / g, the initial efficiency is 86%, and the capacity retention rate is 0.63.

[0132] Compared with the above-mentioned embodiment 3, the components of the activator are changed in this embodiment, and a composite alkali activator is used, so that the pore volume of the porous carbon powder 31 is increased, the adsorption capacity of the silicon particles is increased, and the mass fraction of silicon and the reversible capacity of the battery 10 are improved.

[0133] Please refer to FIG. 17, which is the XRD diagram of the porous carbon powder 31 (as shown in FIG. 6) generated by the above-mentioned embodiment. The abscissa is 2θ, which is twice the incident angle of X-rays, and the ordinate is the intensity after diffraction. As can be seen from FIG. 17, the peak value of the 002 peak corresponding to embodiment 7 is the highest, that is, the graphitization degree of embodiment 7 is the highest.

[0134] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A negative electrode material for preparing a negative electrode, characterized in that, The porous carbon powder contains less than or equal to 0.4 mmol / g of oxygen-containing functional groups, and the mass fraction of carbon in the porous carbon powder is greater than or equal to 95%. The characteristic peak of the porous carbon powder in the X-ray diffraction pattern is greater than or equal to 25℃.

2. The negative electrode material according to claim 1, characterized in that, Also included are:

3. The negative electrode material according to claim 1 or 2, characterized in that, The D50 of the porous carbon powder can include 1 um - 10 um, D max less than 40 um, D min greater than 0.1 um.

4. The negative electrode material according to any one of claims 1 to 3, characterized in that, a functional layer covering the pore side wall in the porous carbon powder; the specific capacity of the functional layer is greater than that of the porous carbon powder; a cladding layer filled in the pores of the porous carbon powder; the functional layer is located between the cladding layer and the pore side wall. The functional layer includes at least one of a silicon layer, a phosphorus layer, and a tin layer.

5. The negative electrode material according to claim 4, characterized in that, The pore volume of the porous carbon powder is greater than 0.08 g / cc.

6. The negative electrode material according to any one of claims 1 to 5, characterized in that, The average pore size of the porous carbon powder is less than 5 nm.

7. The negative electrode material according to any one of claims 1 to 6, characterized in that, The material of the cladding layer can include amorphous carbon.

8. The negative electrode material according to any one of claims 1 to 7, characterized in that, The negative electrode material of any one of claims 1-8 is coated on the conductor.

9. A negative electrode, characterized in that, The negative electrode of claim 9 is sandwiched between the positive electrode and the negative electrode. The battery of claim 10 is disposed in the shell.

10. A battery, characterized by A plurality of batteries of claim 10 are connected in series or parallel. A method for preparing a negative electrode material includes:

11. An electronic device, comprising: mixing a carbon-containing precursor and an alkali activator, and preheating; activating the preheated carbon-containing precursor and alkali activator mixture to obtain a first product; 12. An energy storage device, comprising: heat treating the first product at a temperature greater than or equal to 900℃ for a time greater than or equal to 1 h to obtain a porous carbon powder. The carbon-containing precursor includes at least one of petroleum coke and coal coke; 13. A method for preparing a negative electrode material, characterized in that, The alkali activator includes at least one of sodium hydroxide, potassium hydroxide, potassium carbonate, and potassium chloride. After obtaining the porous carbon powder, the method for preparing a negative electrode material further includes: forming a functional layer on the void side wall in the porous carbon powder; forming a cladding layer in the void of the porous carbon powder.

14. The method of claim 13, wherein the method further comprises the step of: Forming a functional layer on the void side wall in the porous carbon powder includes: ​ placing the porous carbon powder in a first reaction cavity, introducing nitrogen into the first reaction cavity and preheating to 400-500℃; 15. The method of claim 13 or 14, wherein the method is characterized by, introducing silane into the first reaction cavity and holding the first reaction cavity to form a silicon layer on the void side wall in the porous carbon powder. After forming the silicon layer, the method for preparing a negative electrode material further includes: increasing the temperature of the first reaction cavity to 450-800° and adding a carbon source to the first reaction cavity to form amorphous carbon in the void of the porous carbon powder, thereby passivating the negative electrode material.

16. The method of claim 15, wherein the method further comprises the step of: After forming the silicon layer, the method for preparing a negative electrode material further includes: introducing oxygen and nitrogen into the first reaction cavity to passivate the negative electrode material; wherein the mass fraction of oxygen is less than 10%.

17. The method of claim 16, wherein the method further comprises the step of: After passivating the negative electrode material, the method for preparing a negative electrode material further includes: ​ placing the porous carbon powder in a second reaction cavity; 18. The method of claim 16, wherein the method further comprises the step of: ​ ​ ​ ​ 19. The method of claim 17 or 18, wherein the method further comprises a step of adding a binder to the mixture. ​ ​ The second reaction chamber is heated to 450-800° and a carbon source is added to the second reaction chamber to form amorphous carbon in the voids of the porous carbon powder.

20. The method of claim 17-19, wherein the method further comprises, The carbon source includes at least one of methane, ethane, acetylene, benzene, and an amine.

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