A negative electrode active material, a method for preparing the same, and a lithium ion battery

Abstract

The application discloses a negative electrode active material and a preparation method thereof and a lithium ion battery, relates to the technical field of battery material preparation, and the negative electrode active material comprises a core material and a coating layer material which at least partially coats the core material; the core material comprises porous carbon, a modification layer and a nano-silicon layer, and the modification layer and the nano-silicon layer are sequentially arranged on the surface of the porous carbon; the modification layer comprises a first modification layer and a second modification layer, the first modification layer comprises a heteroatom modification layer, the second modification layer comprises a lithium modification layer, and the first modification layer is arranged on the side close to the porous carbon. The two modification layers improve the defects of the porous carbon and improve the electronic conductivity and the initial efficiency of the material; the porous carbon, the heteroatom modification layer and the lithium modification layer are bonded through C-heteroatom-Li to form a structure bonded layer by layer, so that lithium is indirectly connected to the surface of the porous carbon in a stable manner; and the rate performance of the material can be obviously improved in the charging and discharging process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery material preparation, and particularly relates to a negative electrode active material, a preparation method thereof and a lithium ion battery. BACKGROUND

[0002] Silicon-carbon material is an important negative electrode material of lithium ion battery.

[0003] The current silicon-carbon material is mainly composed of porous carbon, nano-silicon deposited in the pores of the porous carbon, and an amorphous carbon coating layer. During the cycle process, the expansion of the nano-silicon will cause the repeated recombination and repair of the solid electrolyte interphase (SEI) film, thereby causing gas production and reducing the cycle performance.

[0004] At present, the surface of the porous carbon in which the nano-silicon is deposited can be coated with titanium niobate to reduce the expansion of the nano-silicon. However, titanium niobate has the disadvantage of high cost. SUMMARY

[0005] The main purpose of the present application is to provide a negative electrode active material, a preparation method thereof and a lithium ion battery, which aims to solve the problem of high expansion rate of the silicon-carbon negative electrode material in the prior art.

[0006] To achieve the above-mentioned purpose, the present application provides a negative electrode active material, which comprises a core material and a coating layer material at least partially coating the outer surface of the core material:

[0007] The core material comprises porous carbon, a modification layer and a nano-silicon layer, and the modification layer and the nano-silicon layer are sequentially arranged on the surface of the porous carbon.

[0008] The modification layer comprises a first modification layer and a second modification layer, the first modification layer comprises a heteroatom modification layer, the second modification layer comprises a lithium modification layer, and the first modification layer is arranged on the side close to the porous carbon.

[0009] The coating layer material comprises a first coating layer material, the first coating layer material comprises a carbon coating layer material, and the carbon coating layer material comprises a first carbon coating layer material.

[0010] In an embodiment, the carbon coating layer material further comprises a second carbon coating layer material, and the second carbon coating layer material at least partially coats the first carbon coating layer material.

[0011] The degree of disorder of carbon in the first carbon coating layer material is 0.8 < ID / IG < 1.2, and the degree of disorder of carbon in the second carbon coating layer material is 0.2 ≤ ID / IG ≤ 0.8.

[0012] In an embodiment, the coating layer material further comprises a second coating layer material, which is arranged on a side of the first coating layer material away from the core material:

[0013] The second coating layer material comprises a solid-state electrolyte material, the chemical formula of which is Li 5+x La3Zr x M 2-x O 12 wherein M is selected from any one of Ta, Nb, Al, Si, Ga, Sc, Ti, V, Y and Sn, and x is 0.01-0.6.

[0014] In an embodiment, the second carbon coating layer material further comprises an inorganic carbon conductive agent and / or a thermal sensitive material.

[0015] In an embodiment, the mass ratio of the core material, the first coating layer material and the second coating layer material is 80-90:5-10:5-10; and / or,

[0016] In the core material, the mass ratio of the porous carbon, the first modification layer, the second modification layer and the nano-silicon layer is 40-45:5-10:5-10:40-45; and / or,

[0017] The second carbon coating layer material comprises an inorganic carbon conductive agent and a thermal sensitive material, the conductive agent comprises at least one of graphene, carbon nanotube and carbon fiber; the thermal sensitive material comprises a mixture of polyimide and carbon black, the mass ratio of the polyimide and the carbon black is 1:0.5-2; and / or,

[0018] The particle size of the negative electrode active material is 5-10 μm; and / or,

[0019] The thickness of the first carbon coating layer material is 10-100 nm; and / or,

[0020] The thickness of the second carbon coating layer material is 50-200 nm; and / or,

[0021] The thickness of the second coating layer material is 500-1000 nm.

[0022] The application further provides a preparation method of a negative electrode active material, the preparation method comprising:

[0023] S1, obtaining porous carbon, preparing a heteroatom source precursor into a heteroatom source gas, and performing first deposition on the porous carbon by the heteroatom source gas to form a heteroatom modification layer precursor on the surface of the porous carbon, thereby obtaining first modified porous carbon;

[0024] S2, preparing an organic lithium source precursor into an organic lithium source gas, and performing second deposition on the first modified porous carbon by the organic lithium source gas to form a lithium modification layer precursor in the surface of the porous carbon, to obtain a second modified porous carbon;

[0025] S3, performing third deposition on the second modified porous carbon by a silane gas under an inert atmosphere to deposit nano-silicon in the pores of the second modified porous carbon, and performing fourth deposition by a carbon source gas to form a first carbon coating layer material, to obtain the negative electrode active material.

[0026] In an embodiment, step S3 comprises:

[0027] S301, performing third deposition on the second modified porous carbon by a silane gas under an inert atmosphere to deposit nano-silicon in the pores of the second modified porous carbon, and performing fourth deposition by a carbon source gas to form a first carbon coating layer material, to obtain a first intermediate material;

[0028] S302, mixing the first intermediate material and a coating liquid, and drying to form a second carbon coating layer material on the surface of the first intermediate material, to obtain the negative electrode active material, wherein the coating liquid comprises a conductive polymer.

[0029] In an embodiment, step S302 comprises:

[0030] S3021, mixing the first intermediate material and a coating liquid, and drying to form a second carbon coating layer material on the surface of the first intermediate material, to obtain a second intermediate material, wherein the coating liquid comprises a conductive polymer;

[0031] S3022, depositing a solid-state electrolyte material on the surface of the second intermediate material by an atomic layer deposition technology to form a second coating layer material, to obtain the negative electrode active material.

[0032] In an embodiment, in step S1, the heteroatom source precursor comprises at least one of furan, thiophene, pyrrole, imidazole, indole, pyridine, and pyrimidine; and / or,

[0033] In step S1, 300-1500 mL of the heteroatom source gas is used for the first deposition per 100 g of the porous carbon; and / or,

[0034] In step S1, the temperature of the first deposition is 300-500°C; and / or,

[0035] In step S1, the time of the first deposition is 30-300 min; and / or,

[0036] In step S1, the gas flow rate of the first deposition is 10-50 mL / min; and / or,

[0037] In step S2, the organic lithium source precursor includes at least one of n-butyllithium, methyllithium, phenyllithium, sec-butyllithium, tert-butyllithium; and / or,

[0038] In step S2, 300-1500 mL of the organic lithium source gas is used for the second deposition per 100 g of the porous carbon; and / or,

[0039] In step S2, the temperature of the second deposition is 600-1100°C; and / or,

[0040] In step S2, the time of the second deposition is 30-300 min; and / or,

[0041] In step S2, the gas flow rate of the second deposition is 10-50 mL / min; and / or,

[0042] In step S301, the silane gas includes at least one of silane, disilane, dichlorosilane, chlorosilane; and / or,

[0043] In step S301, the volume ratio of the inert gas of the inert atmosphere to the silane gas is 10:1-5; and / or,

[0044] In step S301, the carbon source gas includes at least one of acetylene, ethylene, methane; and / or,

[0045] In step S301, 3-150 L of the silane gas is used for the third deposition per 1 kg of the second modified porous carbon; and / or,

[0046] In step S301, the temperature of the third deposition is 450-550°C; and / or,

[0047] In step S301, the time of the third deposition is 30-300 min; and / or,

[0048] In step S301, the gas flow rate of the third deposition is 100-500 mL / min; and / or,

[0049] In step S301, 10-50 mL / min of the carbon source gas is used for the fourth deposition per 1 kg of the second modified porous carbon; and / or,

[0050] In step S301, the temperature of the fourth deposition is 700-900°C; and / or,

[0051] In step S301, the time of the fourth deposition is 30-300 min; and / or,

[0052] In step S301, the fourth deposition gas flow rate is 10-50 mL / min; and / or,

[0053] In step S3021, the coating liquid further comprises inorganic carbon conductive agent and / or heat-sensitive material; and / or,

[0054] In step S3021, the drying method is spray drying; and / or,

[0055] In step S3021, the drying temperature is 300-1000 K; and / or,

[0056] In step S3021, the drying time is 5-30 min; and / or,

[0057] In step S3022, the atomic layer deposition technology temperature is 300-1000 K; and / or,

[0058] In step S3022, the atomic layer deposition technology pressure is <0.01 atm; and / or,

[0059] In step S3022, the atomic layer deposition technology time is 10-600 s.

[0060] The application also provides a lithium ion battery comprising the aforementioned negative electrode active material or the negative electrode active material prepared by the aforementioned preparation method.

[0061] In the technical scheme of the application, the first modification layer and the second modification layer are arranged between the porous carbon and the nano-silicon, the two modification layers improve the defects of the porous carbon and improve the electronic conductivity and the initial efficiency of the material; the porous carbon and the heteroatom modification layer in the first modification layer are connected through C-heteroatom bonds, and the heteroatom modification layer and the lithium modification layer in the second modification layer are connected through N-Li bonds, so that the porous carbon, the heteroatom modification layer and the lithium modification layer are bonded through C-heteroatom-Li bonds to form a layer-by-layer bonded structure, so that the lithium is stably and indirectly connected to the surface of the porous carbon, and the rate performance of the material can be obviously improved in the charging and discharging process, and the electrochemical performance is better than that of a single modification layer in which the heteroatom and the lithium are mixed. BRIEF DESCRIPTION OF DRAWINGS

[0062] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can also obtain other drawings according to the structures shown in these drawings without creative labor.

[0063] Figure 1 A scanning electron microscope image of the negative electrode active material of Example 1 provided by the present application.

[0064] The object, functional characteristics and advantages of the present application will be further described with reference to the embodiments in combination with the drawings. DETAILED DESCRIPTION

[0065] In order to make the object, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturers are adopted. If the manufacturers of the reagents or instruments are not specified, the conventional products that can be purchased in the market are adopted. In addition, the meaning of “and / or” appearing in the whole text includes three parallel solutions. Taking “A and / or B” as an example, it includes the A solution, or the B solution, or the solution in which A and B are satisfied at the same time. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the premise that the technical solutions can be realized by the ordinary skilled in the art. When the combination of the technical solutions appears contradictory or unachievable, it should be considered that the combination of the technical solutions does not exist and is not within the protection scope required by the present application. Based on the embodiments in the present application, all other embodiments obtained by the ordinary skilled in the art without making creative efforts are within the protection scope of the present application.

[0066] Silicon-carbon material is an important negative electrode material of lithium ion battery. The current silicon-carbon material is mainly composed of porous carbon, nano-silicon deposited in the pores of the porous carbon, and an amorphous carbon coating layer. During the cycle process, the expansion of the nano-silicon will cause the repeated recombination and repair of the solid electrolyte interphase (SEI) film, thereby causing gas production and reducing the cycle performance. At present, the surface of the porous carbon in which the nano-silicon is deposited can be coated with titanium niobate to reduce the expansion of the nano-silicon. However, titanium niobate has the disadvantage of high cost.

[0067] In view of this, the present application provides a negative electrode active material, which comprises a core material and a coating layer material at least partially coating the outer surface of the core material: the core material comprises porous carbon, a modification layer and a nano-silicon layer, the modification layer and the nano-silicon layer are sequentially arranged on the surface of the porous carbon; the modification layer comprises a first modification layer and a second modification layer, the first modification layer comprises a heteroatom modification layer, the second modification layer comprises a lithium modification layer, and the first modification layer is arranged on the side close to the porous carbon; the coating layer material comprises a first coating layer material, and the first coating layer material comprises a carbon coating layer material, and the carbon coating layer material comprises a first carbon coating layer material.

[0068] In the technical scheme of the present application, the first modification layer and the second modification layer are arranged between the porous carbon and the nano-silicon layer, the two modification layers improve the defects of the porous carbon and improve the electronic conductivity and the initial efficiency of the material; the porous carbon and the heteroatom modification layer in the first modification layer are connected through C-heteroatom bonds, and the heteroatom modification layer and the lithium modification layer in the second modification layer are connected through N-Li bonds, so that the porous carbon, the heteroatom modification layer and the lithium modification layer are bonded through C-heteroatom-Li bonds to form a layer-by-layer bonded structure, so that the lithium is indirectly connected to the surface of the porous carbon more stably, and the ionic conductivity of the porous carbon is improved, and the rate performance of the material can be obviously improved in the charging and discharging process, and the electrochemical performance is better than that of a single modification layer in which the heteroatoms and lithium are mixed with each other; the first carbon coating layer material is coated on the outer surface of the core material, which can better bind the volume expansion of the nano-silicon in the core material and prevent the leakage of the nano-silicon from causing a side reaction.

[0069] The single modification layer in which the heteroatoms and lithium are mixed with each other in the prior art is obtained by simultaneously dissolving a nitrogen source and a lithium source in a solution, and then realizing the synchronous introduction of nitrogen and lithium through steps such as immersion, stirring and drying. This method is prone to cause uneven distribution of doped elements, and it is difficult to accurately control the doping depth and interface structure in the liquid phase process.

[0070] In some embodiments, the carbon coating layer material further comprises a second carbon coating layer material, and the second carbon coating layer material at least partially coats the first carbon coating layer material; the degree of disorder of carbon in the first carbon coating layer material is 0.8 < ID / IG ≤ 1.2, and the degree of disorder of carbon in the second carbon coating layer material is 0.2 ≤ ID / IG ≤ 0.8.

[0071] In the technical scheme of the present application, the first carbon coating layer material and the second carbon coating layer material are coated on the outer surface of the core material, and the two carbon layers can better bind the volume expansion of the nano-silicon in the core material and prevent the leakage of the nano-silicon from causing a side reaction. The first carbon coating layer material is a first type of amorphous carbon formed after carbonization of a carbon source gas, which closely adheres to the surface of silicon, provides structural support and electronic conduction path, and preliminarily inhibits the volume expansion of the nano-silicon; the second carbon coating layer material is a second type of amorphous carbon formed after carbonization of a high molecular material, which has poorer electrical conductivity than the first type of amorphous carbon, and provides mechanical buffering, inhibits volume expansion and adjusts interface reaction, and the two types of amorphous carbon can jointly inhibit the volume expansion of the nano-silicon and improve the electronic conductivity.

[0072] It should be noted that the first type of amorphous carbon has relatively high brittleness and may crack under the huge volume expansion of silicon; while the second type of amorphous carbon has high elasticity and can provide a buffer space to better bind the expansion of the nano-silicon and prevent the nano-silicon from directly contacting the electrolyte.

[0073] In some embodiments, the coating layer material further comprises a second coating layer material disposed on a side of the first coating layer material distal to the core material; the second coating layer material comprises a solid-state electrolyte material having a chemical formula of Li 5+x La3Zr x M 2-x O 12 wherein M is selected from any one of Ta, Nb, Al, Si, Ga, Sc, Ti, V, Y, and Sn, and x is 0.01-0.6.

[0074] In the technical solution of the present application, the second coating layer material is disposed on the outer surface of the first coating layer material, and the solid-state electrolyte material Li 5+x La3Zr x M 2-x O 12 has high ionic conductivity and extremely low electronic conductivity, improves the fast-charging performance of the material, avoids the accumulation of lithium during charging and discharging, reduces the interface thickening caused by the repeated rupture and regeneration of the SEI film, and effectively inhibits the “irreversible expansion at the electrode level” and “cyclic degradation expansion” caused by lithium accumulation and gas production; at the same time, it provides mechanical restraint and buffers the stress transmission of the volume expansion of the nanosilicon. The first coating layer material and the second coating layer material can synergistically inhibit the expansion rate of the negative electrode active material during battery cycling.

[0075] In some embodiments, the second carbon coating layer material further comprises an inorganic carbon conductive agent and / or a thermosensitive material. Since the second type of amorphous carbon in the second carbon coating layer material has poor electrical conductivity, the addition of an inorganic carbon conductive agent can improve the electronic conductivity of the second carbon coating layer material. After adding the thermosensitive material, at normal use temperature, the thermosensitive material has a very low resistance value; when the battery material temperature is too high and rises to a certain temperature, the resistance value of the thermosensitive material will increase sharply, with a stepwise increase, and the system current will not increase but decrease, reducing the battery heat production, preventing further thermal runaway of the system, interrupting the vicious cycle of thermal runaway, and effectively improving the safety performance of the battery.

[0076] In some embodiments, the mass ratio of the core material, the first coating layer material, and the second coating layer material is 80-90:5-10:5-10. The mass ratio can be 80:10:10, 85:7:7, or 90:5:5, and the mass ratio within the above range can ensure a low expansion rate of the negative electrode active material during cycling.

[0077] In some embodiments, the mass ratio of the porous carbon, the first modification layer, the second modification layer, and the nano-silicon in the core material is 40-45:5-10:5-10:40-45. The mass ratio can be 40:10:10:40, 45:5:5:45, or 40:10:5:45. The mass ratio in the above range can ensure that the lithium modification layer has more connection sites, that is, more heteroatom sites, so that the lithium is more stably and indirectly connected to the surface of the porous carbon, thereby improving the rate performance of the material.

[0078] In some embodiments, the second carbon coating layer material comprises an inorganic carbon conductive agent and a heat-sensitive material, the conductive agent comprises at least one of graphene, carbon nanotubes, and carbon fibers; and the heat-sensitive material comprises a mixture of polyimide and carbon black, and the mass ratio of the polyimide to the carbon black is 1:0.5-2.

[0079] In some embodiments, the particle size of the negative electrode active material is 5-10 μm. The particle size in the above range can ensure a smaller pore size, reduce the contact area with the electrolyte, inhibit the excessive formation of SEI, and improve the initial efficiency.

[0080] In some embodiments, the thickness of the first carbon coating layer material is 10-100 nm; and / or, the thickness of the second carbon coating layer material is 50-200 nm; and / or, the thickness of the second coating layer material is 500-1000 nm. Controlling the thickness of the first carbon coating layer material, the second carbon coating layer material, and the second coating layer material in the above range can ensure that the negative electrode active material has a lower expansion rate and good cycle stability.

[0081] The application also provides a preparation method of a negative electrode active material, which comprises the following steps: S1, obtaining porous carbon, preparing a heteroatom source precursor into a heteroatom source gas, and performing first deposition on the porous carbon by using the heteroatom source gas to form a heteroatom modification layer precursor on the surface of the porous carbon, thereby obtaining first modified porous carbon; S2, preparing an organic lithium source precursor into an organic lithium source gas, and performing second deposition on the first modified porous carbon by using the organic lithium source gas to form a lithium modification layer precursor on the surface of the porous carbon, thereby obtaining second modified porous carbon; and S3, performing third deposition on the second modified porous carbon by using silane gas in an inert atmosphere, so that nano-silicon is deposited in the pores of the second modified porous carbon, and then performing fourth deposition by using a carbon source gas to form a first carbon coating layer material, thereby obtaining the negative electrode active material.

[0082] In the technical scheme of the present application, in step S1: first, a heteroatom source gas is deposited on the surface of the porous carbon, the heteroatom including at least one of N, S and O, the heteroatom replacing part of the carbon atoms in the porous carbon framework to form a heteroatom modification layer precursor through C-heteroatom bonding on the surface of the porous carbon, reducing the defects of the porous carbon, improving the electronic conductivity and the initial efficiency of the material, and obtaining a first modified porous carbon, the heteroatom modification layer precursor being converted into a final heteroatom modification layer at a fourth deposition temperature; in step S2: an organic lithium source gas is deposited on the surface of the heteroatom modification layer precursor, lithium atoms being preferentially bonded to the heteroatom modification layer precursor through heteroatom-Li bonding, the bonding being relatively stable, so that the lithium ion doping on the surface of the porous carbon is relatively uniform and a lithium ion modification layer precursor is formed, obtaining a second modified porous carbon, the precursor being converted into a final lithium modification layer at the fourth deposition temperature, the lithium modification layer improving the ionic conductivity and the rate performance of the material; in step S3: under an inert atmosphere, a silane gas is deposited on the surface of the lithium modification layer precursor to form nano-silicon, the nano-silicon and the lithium modification layer precursor being in close contact, the overall silicon-carbon negative electrode active material constituting a pre-lithiated silicon-carbon material, and then the material is subjected to a fourth deposition, the fourth deposition not only being capable of depositing a first carbon coating layer material, but also being capable of simultaneously removing unnecessary elements (oxygen elements and hydrogen elements, etc.) in the heteroatom modification layer precursor and the lithium modification layer precursor, obtaining a heteroatom modification layer and a lithium modification layer, and the final material having good initial coulombic efficiency and good cycle stability.

[0083] It should be noted that the first carbon coating layer material is actually amorphous carbon, and the degree of disorder thereof can be obtained by Raman spectrum testing, and the degree of disorder being represented by the intensity ratio of D peak and G peak in the Raman spectrum.

[0084] In some embodiments, step S3 includes: S301, under an inert atmosphere, a silane gas is used for third deposition on the second modified porous carbon to deposit nano-silicon in the pores of the second modified porous carbon, and then a carbon source gas is used for fourth deposition to form a first carbon coating layer material, obtaining a first intermediate material; S302, the first intermediate material is mixed with a coating liquid and dried to form a second carbon coating layer material on the surface of the first intermediate material, obtaining the negative electrode active material, the coating liquid including a conductive polymer.

[0085] In the technical solution of the present application, step S301: after the nano-silicon is deposited, a first amorphous carbon layer is formed on the surface of the nano-silicon layer by depositing a carbon source gas, which is used to preliminarily bind the nano-silicon expansion and ensure good electronic conductivity; step S302: a second amorphous carbon layer is formed on the surface of the first amorphous carbon layer by mixing a coating liquid containing a conductive polymer with the first intermediate material and removing the solvent, which provides a larger accommodation space for the nano-silicon expansion and is used to further bind the nano-silicon expansion, and the method for removing the solvent can be drying treatment, preferably spray drying treatment, which ensures that the structure of the second amorphous carbon layer is relatively stable and has fewer defects, and the negative electrode active material is obtained.

[0086] In some embodiments, step S302 comprises:

[0087] S3021, mixing the first intermediate material and the coating liquid, and drying to form a second carbon coating layer material on the surface of the first intermediate material, to obtain a second intermediate material, wherein the coating liquid comprises a conductive polymer;

[0088] S3022, depositing a solid-state electrolyte material on the surface of the second intermediate material by atomic layer deposition technology to form a second coating layer material, to obtain the negative electrode active material.

[0089] In the technical solution of the present application, the solid-state electrolyte is deposited on the surface of the second intermediate material by atomic layer deposition technology, which can improve the ion diffusion coefficient of the material on the one hand because the solid-state electrolyte has the characteristics of high density and strong ion conductivity; on the other hand, the solid-state electrolyte can accelerate the migration of lithium ions through the ion diffusion coefficient and reduce the residence time at the interface, thus effectively inhibiting the “irreversible expansion at the electrode level” and “cyclic degradation expansion” caused by the repeated regeneration of SEI, lithium accumulation, and gas production, and reducing the expansion rate of the negative electrode active material. The atomic layer deposition technology has the advantages of controllable preparation process and high preparation efficiency.

[0090] In some embodiments, in step S1, the heteroatom source precursor comprises at least one of furan, thiophene, pyrrole, imidazole, indole, pyridine, and pyrimidine. The heteroatom source precursor can be any one of furan, thiophene, pyrrole, imidazole, indole, pyridine, and pyrimidine, or two or more of furan, thiophene, pyrrole, imidazole, indole, pyridine, and pyrimidine, all of which are within the protection scope of the present application. The heteroatoms in the above-mentioned heteroatom source precursor can rapidly replace part of the carbon atoms in the porous carbon skeleton, thereby completing the modification of the porous carbon.

[0091] In some embodiments, in step S1, 300-1500 mL of the heteroatom source gas is used for the first deposition per 100 g of the porous carbon; and / or, in step S1, the temperature of the first deposition is 300-500 °C; and / or, in step S1, the time of the first deposition is 30-300 min; and / or, in step S1, the gas flow rate of the first deposition is 10-50 mL / min. Controlling the amount of the heteroatom source gas, the temperature, the time and the gas flow rate of the first deposition within the above ranges can ensure that sufficient heteroatoms are bonded to the surface of the porous carbon, providing bonding sites for the subsequent doping of lithium atoms.

[0092] In some embodiments, in step S2, the organic lithium source precursor includes at least one of n-butyllithium, methyllithium, phenyllithium, sec-butyllithium, tert-butyllithium. The organic lithium source precursor can be any one of n-butyllithium, methyllithium, phenyllithium, sec-butyllithium, tert-butyllithium, or two or more of n-butyllithium, methyllithium, phenyllithium, sec-butyllithium, tert-butyllithium, all within the protection scope of the present application. The above-mentioned organic lithium source precursor can quickly adsorb and grow on the surface of the heteroatom modification layer precursor and the porous carbon, reducing defects and improving ionic conductivity.

[0093] In some embodiments, in step S2, 300-1500 mL of the organic lithium source gas is used for the second deposition per 100 g of the porous carbon; and / or, in step S2, the temperature of the second deposition is 600-1100 °C; and / or, in step S2, the time of the second deposition is 30-300 min; and / or, in step S2, the gas flow rate of the second deposition is 10-50 mL / min. Controlling the amount of the organic lithium source gas, the temperature, the time and the gas flow rate of the second deposition within the above ranges can ensure that lithium atoms are bonded to the heteroatoms more quickly, more stably, more uniformly and more, forming a lithium modification layer, thereby improving the ionic conductivity and rate performance of the material.

[0094] In some embodiments, in step S301, the silane gas includes at least one of monosilane, disilane, dichlorosilane, chlorosilane; and / or, in step S301, the volume ratio of the inert gas of the inert atmosphere to the silane gas is 10:1-5. The silane gas can be any one of monosilane, disilane, dichlorosilane, chlorosilane, or two or more of monosilane, disilane, dichlorosilane, all within the protection scope of the present application. The volume ratio of the inert gas of the inert atmosphere to the silane gas can be 10:1, 10:3 or 10:5. Controlling the volume ratio of the inert gas to the silane gas and the type of the silane gas can ensure that nano-silicon with a uniform distribution and controllable particle size is formed on the surface of the lithium modification layer.

[0095] In some embodiments, in step S301, 3-150 L of the silane gas is used for the third deposition per 1 kg of the second modified porous carbon; and / or, in step S301, the temperature of the third deposition is 450-550 DEG C; and / or, in step S301, the time of the third deposition is 30-300 min; and / or, in step S301, the gas flow of the third deposition is 100-500 mL / min. Controlling the amount of silane gas, the temperature, the time and the gas flow of the third deposition within the above ranges can ensure that a first carbon coating layer material with a relatively uniform and high coverage is formed on the surface of the nano-silicon.

[0096] In some embodiments, in step S301, the carbon source gas comprises at least one of acetylene, ethylene and methane.

[0097] In some embodiments, in step S301, 10-50 mL / min of the carbon source gas is used for the fourth deposition per 1 kg of the second modified porous carbon; and / or, in step S301, the temperature of the fourth deposition is 700-900 DEG C; and / or, in step S301, the time of the fourth deposition is 30-300 min; and / or, in step S301, the gas flow of the fourth deposition is 10-50 mL / min. Controlling the amount of carbon source gas, the temperature, the time and the gas flow of the fourth deposition within the above ranges can ensure that a second carbon coating layer material with a relatively uniform and high coverage is formed on the surface of the first carbon coating layer material.

[0098] In some embodiments, in step S3021, the coating liquid further comprises an inorganic carbon conductive agent and / or a heat-sensitive material. The inorganic carbon conductive agent and the heat-sensitive material are introduced into the second carbon coating layer material through the coating liquid and a drying process.

[0099] In some embodiments, in step S3021, the drying method is spray drying. The drying method is preferably spray drying, which has the advantages of high drying efficiency and little damage to the structure of the material.

[0100] In some embodiments, in step S3021, the drying temperature is 300-1000 K; and / or, in step S3021, the drying time is 5-30 min. Controlling the temperature and the time of the carbonization process within the above ranges can ensure that the first carbon coating layer material and the second carbon coating layer material are better converted into amorphous carbon while reducing impurity components in the system.

[0101] In some embodiments, in step S3022, the temperature of the atomic layer deposition technique is 300-1000K; and / or, in step S3022, the pressure of the atomic layer deposition technique is <0.01 atm; and / or, in step S3022, the time of the atomic layer deposition technique is 10-600s. Controlling the temperature, time and pressure of the atomic layer deposition technique within the above ranges can ensure that the solid-state electrolyte is uniformly distributed on the surface of the second carbon-coated layer material.

[0102] The application also provides a lithium ion battery comprising the aforementioned negative electrode active material or the negative electrode active material prepared by the aforementioned method for preparing a negative electrode active material. Therefore, all the beneficial effects of the aforementioned negative electrode active material or the aforementioned method for preparing a negative electrode active material are possessed.

[0103] The technical solutions of the application will be further described in detail below in combination with specific embodiments and drawings. It should be understood that the following embodiments are only used to explain the application and do not limit the application.

[0104] Embodiment 1

[0105] A negative electrode active material, which comprises porous carbon and, sequentially arranged in an inside-out direction of the porous carbon, a nitrogen atom modification layer, a lithium modification layer, a nano-silicon layer and a first carbon-coated layer material;

[0106] The method for preparing the aforementioned negative electrode active material comprises the following steps:

[0107] Step (1): 100g of porous carbon is transferred into a tube furnace and heated to 400℃. A furan gas is introduced at a flow rate of 30mL / min for 150min to form a heteroatom modification layer precursor on the surface of the porous carbon, obtaining a first modified porous carbon. Then, the temperature is continuously increased to 900℃, and a n-butyl lithium gas compound is introduced at a flow rate of 30mL / min for 150min to form a lithium modification layer precursor on the surface of the heteroatom modification layer precursor, obtaining a second modified porous carbon.

[0108] Step (2): 1kg of the second modified porous carbon is transferred into a fluidized bed and heated to 500℃. A mixed gas of disilane and nitrogen (volume ratio, disilane:nitrogen=3:10) is introduced at a flow rate of 300mL / min for 150min to deposit nano-silicon on the surface of the lithium modification layer precursor. Then, the temperature is increased to 800℃, and acetylene gas is introduced at a flow rate of 30mL / min for 150min to deposit a first carbon-coated layer material on the surface of the nano-silicon, obtaining a first intermediate material, i.e., a negative electrode active material.

[0109] Embodiment 2

[0110] Compared with Embodiment 1, Embodiment 2 is different in that:

[0111] After step (2), step (3) is added, which is: 100 g of polyacetylene is added to 2000 g of N-methylpyrrolidone to prepare a solution with a mass concentration of 5 wt% and dispersed uniformly, to obtain a coating liquid;

[0112] 100 g of the first intermediate material is added to 150 g of the coating liquid and dispersed uniformly, and spray drying (inlet temperature 220°C, outlet temperature 100°C, flow rate 0.2 kg / h, 2 h) is performed to obtain the second intermediate material, i.e., the negative electrode active material.

[0113] Example 3

[0114] Compared with Example 2, the difference of Example 3 is that:

[0115] The second carbon coating layer material is formed first, and then the first carbon coating layer material is formed, i.e., after the formation of the nano-silicon, the second carbon coating layer material is formed by spray drying of the coating layer, and then the first carbon coating layer material is formed by deposition of acetylene gas.

[0116] Example 4

[0117] Compared with Example 2, the difference of Example 4 is that:

[0118] After step (3), step (4) is added, which is: 100 g of the second intermediate material is dispersed in an atomic layer deposition (ALD) reaction chamber, and heated to a temperature of 500 K (Kelvin) in the reaction chamber, and kept at this temperature for 20 min, and the gas pressure in the reaction chamber is less than 0.01 atm; then the gas outlet valve is opened, and the pulse purge gas is opened for 30 s; the gas outlet valve is closed, and Li 5.5 La3Zr 0.5 Ta 1.5 O 12 is deposited by argon carrier gas, the deposition time is 5 seconds, and then kept for 30 seconds; then the gas outlet valve is opened, and the pulse purge gas is opened for 0.5 minutes; the gas outlet valve is closed, and the vacuum is removed, and the excess reaction byproducts are removed; the above steps are repeated 5 times to form a solid electrolyte layer, and the negative electrode active material is obtained.

[0119] Example 5

[0120] Compared with Example 1, the difference of Example 5 is that:

[0121] In step (2), after the formation of the nano-silicon, the solid electrolyte layer is formed by referring to the method of step (4) in Example 4, and the negative electrode active material is obtained.

[0122] Example 6

[0123] Compared with Example 2, the difference of Example 6 is that:

[0124] The mass of the coating solution in step (3) is 50 g.

[0125] Example 7

[0126] Example 7 differs from Example 2 in that:

[0127] Step (3) is: 100 g of polyacetylene is added to 2000 g of N-methylpyrrolidone to configure a solution with a mass concentration of 5 wt%, and then 50 g of a 2.5 wt% carbon nanotube conductive agent solution (solvent: N-methylpyrrolidone) is added and uniformly dispersed to obtain a coating solution;

[0128] 100 g of the first intermediate material is added to 150 g of the coating solution and uniformly dispersed, and spray drying (inlet temperature 220°C, outlet temperature 100°C, flow rate 0.2 kg / h, 2 h) is performed to obtain the second intermediate material;

[0129] The rest is the same as in Example 2.

[0130] Example 8

[0131] Example 8 differs from Example 2 in that:

[0132] Step (3) is: 100 g of polyacetylene is added to 2000 g of N-methylpyrrolidone to configure a solution with a mass concentration of 5 wt%, and then 50 g of a 2.5 wt% carbon nanotube conductive agent solution (solvent: N-methylpyrrolidone) and 5 g of a polyimide thermal sensitive composite material (mass ratio, polyimide: carbon black = 1:1) are added and uniformly dispersed to obtain a coating solution;

[0133] 100 g of the first intermediate material is added to 150 g of the coating solution and uniformly dispersed, and spray drying (inlet temperature 220°C, outlet temperature 100°C, flow rate 0.2 kg / h, 2 h) is performed to obtain the second intermediate material;

[0134] The rest is the same as in Example 2.

[0135] Example 9

[0136] A method for preparing a negative electrode active material includes the following steps:

[0137] Step (1): 100 g of porous carbon is transferred to a tube furnace and heated to 300°C, and then thiophene gas is introduced at a flow rate of 10 mL / min for 300 min to form a heteroatom modification layer on the surface of the porous carbon to obtain a first modified porous carbon; then the temperature is continuously increased to 600°C, and methyl lithium gas compound is introduced at a flow rate of 10 mL / min for 300 min to form a lithium modification layer on the surface of the heteroatom modification layer to obtain a second modified porous carbon;

[0138] Step (2): 1 kg of the second modified porous carbon is transferred into a fluidized bed and heated to 450°C, and a mixed gas of silane and nitrogen (volume ratio, silane: nitrogen = 1:10) is passed at a flow rate of 100 mL / min to deposit for 300 min to form a nano-silicon on the surface of the lithium modification layer; then the temperature is raised to 700°C, and acetylene gas is passed at a flow rate of 10 mL / min to deposit for 300 min to form a first carbon coating layer material on the surface of the nano-silicon, thereby obtaining a first intermediate material;

[0139] Step (3): 100 g of polyaniline is added to 10,000 g of chloroform organic solvent to configure a solution with a mass concentration of 1 wt%, and then 10 g of a 5 wt% graphene conductive agent solution and 1 g of a polyimide thermal sensitive composite material (mass ratio, polyimide: carbon black = 1:0.5) are uniformly dispersed to obtain a coating liquid;

[0140] 100 g of the first intermediate material is added to 100 g of the coating liquid and uniformly dispersed, and then spray dried (inlet temperature 220°C, outlet temperature 100°C, flow rate 0.2 kg / h, 2 h) to obtain a second intermediate material;

[0141] Step (4): In an ALD reaction chamber, 100 g of the second intermediate material is dispersed, and the reaction chamber is heated to a temperature of 300 Kelvin, and kept at the set temperature for 5 min, and the gas pressure in the reaction chamber is less than 0.01 atm; then the gas outlet valve is opened, and the pulse purge gas is cleaned for 3 s; the gas outlet valve is closed, and Li 5.5 La3Zr 0.5 Al 1.5 O 12 is deposited for a time of 0.01 s, and then kept for a time of 60 s; then the gas outlet valve is opened, and the pulse purge gas is cleaned for 0.1 min; the gas outlet valve is closed, and vacuum is applied to remove excess reaction byproducts; the above steps are repeated 10 times to form a solid electrolyte layer, thereby obtaining a negative electrode active material.

[0142] Example 10

[0143] A negative electrode active material, and a preparation method of the negative electrode active material includes the following steps:

[0144] Step (1): 100 g of porous carbon is transferred into a tube furnace and heated to 500°C, and imidazole gas is passed at a flow rate of 50 mL / min for 30 min to form a heteroatom modification layer precursor on the surface of the porous carbon, thereby obtaining a first modified porous carbon; then the temperature is continuously raised to 1100°C, and phenyllithium gas compound is passed at a flow rate of 50 mL / min for 30 min to form a lithium modification layer precursor on the surface of the heteroatom modification layer precursor, thereby obtaining a second modified porous carbon;

[0145] Step (2): 1 kg of the second modified porous carbon is transferred into a fluidized bed and heated to 550°C. A mixed gas of dichlorosilane and nitrogen (volume ratio, dichlorosilane: nitrogen = 5: 10) is passed at a flow rate of 500 mL / min to deposit for 30 min to form a nano-silicon on the lithium modification layer precursor surface. Then, the temperature is raised to 900°C. Acetylene gas is passed at a flow rate of 50 mL / min to deposit for 30 min to form a first carbon coating layer material on the nano-silicon surface, obtaining a first intermediate material;

[0146] Step (3): 100 g of polypyrrole is added to 1000 g of toluene organic solvent to configure a solution with a mass concentration of 10 wt%. Then, 100 g of a 1 wt% carbon fiber conductive agent solution and 10 g of a polyimide heat-sensitive composite material (mass ratio, polyimide: carbon black = 1:2) are added and uniformly dispersed to obtain a coating liquid;

[0147] 100 g of the first intermediate material is added to 200 g of the coating liquid and uniformly dispersed. Spray drying (inlet temperature 220°C, outlet temperature 100°C, flow rate 0.2 kg / h, 2 h) is performed to obtain a second intermediate material;

[0148] Step (4): In an ALD reaction chamber, 100 g of the second intermediate material is dispersed and heated to a temperature of 1000 Kelvin. The temperature is maintained for 30 min at the set temperature, and the gas pressure in the reaction chamber is less than 0.01 atm. Then, the gas outlet valve is opened, and the pulse purge gas is cleaned for 60 s. The gas outlet valve is closed, and 10 g of Li 5.5 La3Zr 0.5 Ga 1.5 O 12 is deposited for 10 seconds, followed by a holding time of 10 seconds. Then, the gas outlet valve is opened, and the pulse purge gas is cleaned for 1 min. The gas outlet valve is closed, and the vacuum is removed to remove excess reaction byproducts. The above steps are repeated once to form a solid electrolyte layer, obtaining a negative electrode active material.

[0149] Comparative Example 1

[0150] Comparative Example 1 and Example 1 differ in that:

[0151] The modification layer of a mixture of heteroatoms and lithium atoms is obtained by a one-step liquid phase method. The specific steps are as follows:

[0152] 100 g of porous carbon is transferred into a tube furnace and heated to 900°C. A mixed gas of furan gas and n-butyllithium gas compound (volume ratio 1:1) is passed at a flow rate of 30 mL / min for 300 min to form a heteroatom-lithium mixed modification layer precursor on the surface of the porous carbon, obtaining a first modified porous carbon;

[0153] 1kg of the first modified porous carbon was transferred into a fluidized bed, heated to 500℃, and a mixed gas of disilane and nitrogen (volume ratio, disilane: nitrogen = 3:10) was passed at a flow rate of 300mL / min to deposit for 150min to form a nanosilicon on the surface of the heteroatom-lithium mixed modification layer precursor; then heated to 800℃, and acetylene gas was passed at a flow rate of 30mL / min to deposit for 150min to form a first carbon coating layer material on the surface of the nanosilicon, thereby obtaining a first intermediate material, i.e., a negative electrode active material.

[0154] Comparative Example 2

[0155] Comparative Example 2 differs from Example 1 in that:

[0156] In step S1, no furan gas and n-butyllithium gas were passed for deposition, and the other steps were the same as in Example 1.

[0157] Performance test

[0158] 1. Negative electrode active material test:

[0159] The negative electrode active material prepared in Example 1 was observed by scanning electron microscopy, and the results are shown in Figure 1

[0160] As can be seen from Figure 1 , the negative electrode active material prepared in Example 1 has a spherical structure, with uniform size distribution and a particle size of 5-10μm.

[0161] The negative electrode active materials prepared in Examples 1-10 and Comparative Examples 1-2 were tested for physical and chemical properties. The test methods were as follows: the pore volume and pore size of each negative electrode active material were tested according to the national standards GB / T-38949-2020 "Standard Particle Method for Determining Pore Size of Porous Membrane" and GB / T7702.20-2008 "Coal Activated Carbon Pore Volume Detection"; the specific surface area and tap density of the negative electrode active material were tested according to the national standard GB / T38823-2020 "Silicon Carbon"; and the powder conductivity of the negative electrode active material was tested using a four-probe tester. The test results are shown in Table 1.

[0162] Table 1 Physical and chemical property characterization of the negative electrode active materials prepared in Examples 1-10 and Comparative Examples 1-2.

[0163]

[0164] As can be seen from Table 1, since the heteroatom modification layer and lithium modification layer are sequentially arranged on the surface of the porous carbon in the examples, the powder resistivity of the material is reduced, and the electronic and ionic conductivity of the material is improved; at the same time, the specific surface area of the material of the examples of the present application is higher.

[0165] 2. Button cell test​

[0166] The negative electrode active materials prepared in Examples 1-10 and Comparative Examples 1-2 were respectively used as the lithium ion battery negative electrode active material, and the coin batteries were prepared according to the following method: the negative electrode active material, binder, conductive agent and solvent were mixed (in the amount ratio of 70 g: 15 g: 15 g: 300 mL), and then stirred to make a slurry, and then coated on a copper foil, and then dried and rolled to obtain a negative electrode sheet; wherein the binder used was LA132, the conductive agent was SP (conductive carbon black), and the solvent was NMP (N-methyl pyrrolidone); the electrolyte was a solution with LiPF6 as the electrolyte, and the concentration was 1 mol / L, wherein the solvent was a mixture of EC (ethylene carbonate) and DEC (diethyl carbonate) in a volume ratio of 1:1; the lithium metal sheet was the counter electrode, and the separator was a polypropylene (PP) film. Each coin battery was assembled in an argon-filled glove box. Then each coin battery was subjected to the following performance tests:

[0167] (1) The electrochemical performance was tested on a Wuhan Lan electric CT2001A battery tester, the charge and discharge voltage range was 0.005V to 2.0V, the charge and discharge rate was 0.1C, the discharge specific capacity and the first efficiency of the corresponding coin battery were tested, and at the same time, the charge direct current resistance (DCR) (50%, 0.1C rate) of the corresponding coin battery was tested.

[0168] (2) Full charge expansion test: the thickness D1 of the rolled electrode sheet was tested, the thickness D2 of the electrode sheet was tested when fully charged to 100% SOC (State of Charge), and the full charge expansion was (D2-D1) / D1.

[0169] (3) The lithium ion diffusion coefficient of the material was tested by GITT (constant current intermittent titration technique). The test results are shown in Table 2.

[0170] Table 2 Performance characterization of the coin batteries corresponding to Examples 1-10 and Comparative Examples 1-2.

[0171]

[0172] As can be seen from Table 2, in Examples 1-10, as the shell is arranged layer by layer, the proportion of the coating layer of the negative active material increases, the specific capacity decreases, and the discharge specific capacity shows a decreasing trend, but overall is better than that of Comparative Examples 1 and 2. As can be seen from Examples 1 and 2, when the first carbon coating layer material and the second carbon coating layer material are arranged at the same time, the full charge expansion can be reduced; in addition, in Example 4, the solid-state electrolyte is arranged, the lithium ion diffusion coefficient is good, the full charge expansion and DCR are low; however, when the first carbon coating layer material and the second carbon coating layer material are arranged and only the solid-state electrolyte layer is arranged (Example 5), the lithium ion diffusion coefficient of the material is reduced instead, which shows that the first shell and the second coating layer material in the present application have a synergistic effect of inhibiting the volume expansion of nano-silicon.

[0173] 3. Soft package battery test

[0174] The negative active materials prepared in Examples 1-10 and Comparative Examples 1-2 were respectively prepared into negative electrode sheets, and a ternary material LiNi 0.6 Co 0.2 Mn 0.2 O2 was used as the positive electrode material; LiPF6 was used as the electrolyte in the electrolyte, and a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1 was used as the solvent; and Celgard 2400 film was used as the separator, and 5Ah soft package batteries were respectively prepared. Then each soft package battery was respectively tested for the following performance:

[0175] (1) Cycle performance: the 500th cycle performance of the battery was tested at a charge / discharge rate of 1C / 1C, a voltage range of 2.5V-4.2V, and a temperature of 25±3℃.

[0176] (2) Fast charging performance: constant current charging was carried out at a rate of 2C to 4.2V, constant voltage charging was carried out at 4.2V for 2h to reach 100% SOC (full charge state), and then the constant current ratio = constant current capacity / (constant current capacity+constant voltage capacity) was calculated. The test results are shown in Table 3.

[0177] Table 3 Performance characterization of soft package batteries corresponding to Examples 1-10 and Comparative Examples 1-2.

[0178]

[0179] As can be seen from Table 3, the rate and cycle performance of the soft package lithium ion battery prepared from the silicon-carbon composite material of the examples are better than those of the comparative examples.

[0180] 4. Safety performance:

[0181] Puncture experiment: 10 soft package batteries of each of examples 1-10 and comparative examples 1-2 were taken, the batteries were fully charged, a nail with a diameter of 5 mm was passed through the center of the battery, a temperature tester was installed at the battery pole, and the nail was left in the battery, the battery condition was observed, and the battery temperature when the nail penetrated the battery was measured, as shown in Table 4 below.

[0182] Table 4 Safety performance characterization of batteries of examples 1-10 and comparative examples 1-2.

[0183]

[0184] As can be seen from Table 4, the group without adding a heat-sensitive material and a solid-state electrolyte (examples 1-3, 6, 7 and comparative examples 1-2) has the highest temperature and the highest ignition rate. The group adding only a solid-state electrolyte (examples 4-5) has a slightly higher temperature and a reduced ignition rate. The group adding only a heat-sensitive material (example 8) has a slightly lower temperature and a lower ignition rate. The group adding a solid-state electrolyte and a heat-sensitive material (examples 9-10) has the lowest temperature and the lowest ignition rate. The heat-sensitive material mainly reduces the temperature and reduces the ignition rate. The solid-state electrolyte is mainly high-temperature resistant, so the temperature is relatively high, and there is a certain ignition rate. The present application coats a heat-sensitive material on the surface of the material, sharply increases the resistance when the battery is punctured and short-circuited, and reduces the probability of combustion; and coats a solid-state electrolyte on the surface of the material, which is an inorganic material with high-temperature resistance, can reduce the temperature of thermal runaway, and further improves the safety performance.

[0185] The above is only a preferred embodiment of the present application, and does not limit the patent scope of the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the patent protection scope of the present application.

Claims

1. A negative electrode active material, characterized by, The negative electrode active material comprises a core material and a coating layer material at least partially coating an outer surface of the core material: The core material comprises porous carbon, a modification layer, and a nano-silicon layer, the modification layer and the nano-silicon layer are sequentially arranged on the surface of the porous carbon; The modification layer is a first modification layer and a second modification layer, the first modification layer is a heteroatom modification layer, the second modification layer is a lithium modification layer, and the first modification layer is arranged on the side close to the porous carbon; the heteroatom of the heteroatom modification layer comprises at least one of N, S, and O; The coating layer material comprises a first coating layer material, and the first coating layer material comprises a carbon coating layer material, and the carbon coating layer material comprises a first carbon coating layer material; The carbon coating layer material further comprises a second carbon coating layer material, and the second carbon coating layer material at least partially coats the first carbon coating layer material: The degree of disorder of carbon in the first carbon coating layer material is 0.8 < ID / IG ≤ 1.2, and the degree of disorder of carbon in the second carbon coating layer material is 0.2 ≤ ID / IG ≤ 0.

8.

2. The negative electrode active material according to claim 1, wherein The coating layer material further comprises a second coating layer material, and the second coating layer material is arranged on the side of the first coating layer material away from the core material: The second cladding layer material includes a solid-state electrolyte material having a chemical formula of Li 5+ x La3Zr x M 2-x O 12 wherein M is selected from any one of Ta, Nb, Al, Si, Ga, Sc, Ti, V, Y, and Sn, and x is 0.01-0.

6.

3. The negative electrode active material according to claim 2, wherein The second carbon coating layer material further comprises an inorganic carbon conductive agent and / or a heat-sensitive material.

4. The negative electrode active material according to claim 3, wherein The mass ratio of the core material, the first coating layer material, and the second coating layer material is 80-90:5-10:5-10; and / or, In the core material, the mass ratio of the porous carbon, the first modification layer, the second modification layer, and the nano-silicon layer is 40-45:5-10:5-10:40-45; and / or, The second carbon coating layer material comprises an inorganic carbon conductive agent and a heat-sensitive material, the conductive agent comprises at least one of graphene, carbon nanotubes, and carbon fibers; the heat-sensitive material comprises a mixture of polyimide and carbon black, and the mass ratio of the polyimide to the carbon black is 1:0.5-2; and / or, The particle size of the negative electrode active material is 5-10 μm; and / or, The thickness of the first carbon coating layer material is 10-100 nm; and / or, The thickness of the second carbon coating layer material is 50-200 nm; and / or, The thickness of the second coating layer material is 500-1000 nm.

5. A method for producing the negative electrode active material according to any one of claims 1 to 4, characterized by, The preparation method of the negative electrode active material comprises: S1, obtaining porous carbon, preparing a heteroatom source precursor into a heteroatom source gas, and performing first deposition on the porous carbon by the heteroatom source gas to form a heteroatom modification layer precursor on the surface of the porous carbon, thereby obtaining first modified porous carbon; the heteroatom source precursor comprises at least one of furan, thiophene, pyrrole, imidazole, indole, pyridine, and pyrimidine; S2, preparing an organic lithium source precursor into an organic lithium source gas, and performing second deposition on the first modified porous carbon by the organic lithium source gas to form a lithium modification layer precursor in the surface of the porous carbon, thereby obtaining second modified porous carbon; Step S3 comprises: S301. Under an inert atmosphere, the second modified porous carbon is deposited a third time using silane gas to deposit nano-silicon in the pores of the second modified porous carbon, and then a fourth deposition is performed using carbon source gas to form a first carbon coating material, thereby obtaining a first intermediate material. S302. The first intermediate material and the coating liquid are mixed and dried to form a second carbon coating layer on the surface of the first intermediate material, thereby obtaining the negative electrode active material. The coating liquid includes a conductive polymer.

6. The method for producing a negative electrode active material according to claim 5, wherein Step S302 includes: S3021. The first intermediate material and the coating liquid are mixed and dried to form a second carbon coating layer material on the surface of the first intermediate material, thereby obtaining the second intermediate material. The coating liquid includes a conductive polymer. S3022. Solid electrolyte material is deposited on the surface of the second intermediate material using atomic layer deposition technology to form a second coating layer material, thereby obtaining the negative electrode active material.

7. The method for producing a negative electrode active material according to claim 6, wherein In step S1, 300-1500 mL of the heteroatom source gas is used for the first deposition of every 100 g of the porous carbon; and / or, In step S1, the temperature of the first deposition is 300-500℃; and / or, In step S1, the first deposition time is 30-300 min; and / or, In step S1, the gas flow rate for the first deposition is 10-50 mL / min; and / or, In step S2, the organic lithium source precursor includes at least one selected from n-butyllithium, methyllithium, phenyllithium, sec-butyllithium, and tert-butyllithium; and / or, In step S2, 300-1500 mL of the organic lithium source gas is used for a second deposition per 100 g of the porous carbon; and / or, In step S2, the temperature of the second deposition is 600-1100℃; and / or, In step S2, the second deposition time is 30-300 min; and / or, In step S2, the gas flow rate for the second deposition is 10-50 mL / min; and / or, In step S301, the silane gas includes at least one of methylsilane, disilane, dichlorosilane, and chlorosilane; and / or, In step S301, the volume ratio of the inert gas in the inert atmosphere to the silane gas is 10:1-5; and / or, In step S301, the carbon source gas includes at least one of acetylene, ethylene, and methane; and / or, In step S301, 3-150 L of the silane gas is used for a third deposition per 1 kg of the second modified porous carbon; and / or, In step S301, the temperature of the third deposition is 450-550℃; and / or, In step S301, the third deposition time is 30-300 min; and / or, In step S301, the gas flow rate for the third deposition is 100-500 mL / min; and / or, In step S301, a fourth deposition is performed using the carbon source gas at a rate of 10-50 mL / min for every 1 kg of the second modified porous carbon; and / or, In step S301, the temperature of the fourth deposition is 700-900℃; and / or, In step S301, the fourth deposition time is 30-300 min; and / or, In step S301, the fourth deposition gas flow is 10-50 mL / min; and / or, In step S3021, the coating solution further comprises inorganic carbon conductive agent and / or heat-sensitive material; and / or, In step S3021, the drying method is spray drying; and / or, In step S3021, the drying temperature is 300-1000 K; and / or, In step S3021, the drying treatment time is 5-30 min; and / or, In step S3022, the atomic layer deposition technology temperature is 300-1000 K; and / or, In step S3022, the atomic layer deposition technology pressure is <0.01 atm; and / or, In step S3022, the atomic layer deposition technology time is 10-600 s.

8. A lithium-ion battery, characterized by The lithium ion battery comprises the negative electrode active material as claimed in any one of claims 1 to 4 or the negative electrode active material prepared by the preparation method as claimed in any one of claims 5 to 7.

Images