Negative electrode material, and preparation method therefor and use thereof

Abstract

A negative electrode material (100) comprises a silicon-carbon core (10) and a coating layer (20) that coats the silicon-carbon core (10), wherein the silicon-carbon core (10) comprises a porous carbon matrix (11) and an amorphous silicon material (12) arranged in pores of the porous carbon matrix (11), the volume of micropores in the porous carbon matrix (11) accounting for 80-90% of the total pore volume of the porous carbon matrix (11); and the amorphous silicon material (12) is doped with nitrogen, the nitrogen accounting for 0.2-1% of the total mass of the negative electrode material (100). By means of the arrangement of the micropores and the doping of amorphous silicon, the formation and growth of a crystalline phase during a reaction of the negative electrode material (100) with a metal can be effectively inhibited, thereby improving the structural stability and cycling stability of the negative electrode material (100), which is conducive to improving the cycling performance of a negative electrode sheet (200) and prolonging the cycle life of a battery.

Description

Anode materials, their preparation methods and applications

[0001] This application claims priority to Chinese Patent Application No. 202410700650.0, filed on May 30, 2024, entitled “Anode Material and Preparation Method Thereof and Application”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, specifically to a negative electrode material, its preparation method, and its application. Background Technology

[0003] Silicon anode materials have a significantly higher capacity than graphite anode materials, making them promising for a wide range of applications. During battery operation, the reaction between silicon and metal is essential for energy storage. However, the continuous reaction between silicon and metal leads to the formation of a crystalline phase, causing the anode material to expand in volume, resulting in cracking and pulverization of the anode sheet. It also makes the anode prone to violent reactions with the electrolyte, negatively impacting the battery's cycle life. In related technologies, filling a porous carbon matrix with nano-silicon and adding a coating layer can shorten the ion diffusion path, improve the conductivity and stability of the anode material, and alleviate silicon volume expansion. However, during long-term use, silicon and metal will still undergo alloying reactions, and as the reaction intensifies, a crystalline phase forms and grows, leading to expansion of the anode material and reducing the cycle stability of the anode sheet. Therefore, a cathode material with excellent cycle stability is needed that can effectively suppress the formation and growth of the crystalline phase during the reaction between silicon and metal. Summary of the Invention

[0004] This application discloses an anode material, its preparation method, and its application. In this anode material, an amorphous silicon material is filled in a porous carbon matrix. The amorphous silicon material is doped with nitrogen. Silicon and nitrogen can form silicon-nitrogen bonds, which reduces the occurrence of side reactions. In addition, the micropore volume ratio in the porous carbon matrix is ​​large, which limits the formation and growth of the crystalline phase during use and improves the cycle stability of the anode material.

[0005] In a first aspect, this application discloses a negative electrode material comprising a silicon-carbon core and a coating layer covering the silicon-carbon core. The silicon-carbon core comprises a porous carbon matrix and an amorphous silicon material disposed within the pores of the porous carbon matrix. The micropore volume in the porous carbon matrix accounts for 80%-90% of the total pore volume of the porous carbon matrix. The amorphous silicon material is doped with nitrogen, and the nitrogen accounts for 0.2%-1% of the total mass of the negative electrode material.

[0006] Optionally, the coating material includes at least one of carbon materials, metal oxides, and metal sulfides.

[0007] Optionally, the thickness of the coating layer is 5nm-30nm.

[0008] Optionally, in the negative electrode material, the mass ratio of carbon to silicon is 1:(0.5-1).

[0009] Optionally, the specific surface area of ​​the porous carbon matrix is ​​1500 m² / g to 2000 m² / g.

[0010] Optionally, the Dv50 particle size of the porous carbon matrix is ​​1μm-20μm.

[0011] Optionally, in the negative electrode material, the mass ratio of the coating layer to the silicon-carbon core is 1:(19-99).

[0012] Optionally, the specific surface area of ​​the negative electrode material is 1 m² / g to 5 m² / g.

[0013] Optionally, the Dv50 particle size of the negative electrode material is 3μm-10μm.

[0014] Optionally, the amorphous silicon material and the nitrogen element form a silicon-nitrogen bond.

[0015] The negative electrode material provided in this application has a porous carbon matrix filled with amorphous silicon material, and the amorphous silicon material is doped with nitrogen element to form silicon-nitrogen bonds; the high volume ratio of micropores in the porous carbon matrix is ​​beneficial to avoid the formation and growth of crystalline phase when the amorphous silicon material reacts with the metal, thereby reducing the volume expansion of the negative electrode material and improving the cycle stability of the negative electrode material.

[0016] Secondly, this application discloses a method for preparing a negative electrode material, including:

[0017] A silicon-containing gas and a nitrogen-containing gas are sequentially introduced into a porous carbon matrix. After a first reaction, a silicon-carbon core is obtained.

[0018] A coating material gas is introduced into the silicon-carbon core, and a negative electrode material is obtained after a second reaction. The negative electrode material includes a silicon-carbon core and a coating layer covering the silicon-carbon core. The silicon-carbon core includes a porous carbon matrix and an amorphous silicon material disposed in the pores of the porous carbon matrix. The micropore volume in the porous carbon matrix accounts for 80%-90% of the total pore volume of the porous carbon matrix. The amorphous silicon material is doped with nitrogen, and the nitrogen accounts for 0.2%-1% of the total mass of the negative electrode material.

[0019] Optionally, the temperature of the first reaction is 400℃-900℃, and the reaction time is 15min-10h.

[0020] Optionally, the temperature of the second reaction is 500℃-800℃, and the reaction time is 1h-12h.

[0021] Optionally, the gas flow rate ratio of the silicon-containing gas to the nitrogen-containing gas is (5-10):1.

[0022] Optionally, the coating layer feed gas includes at least one of methane, ethane, ethylene, and acetylene.

[0023] Optionally, the reaction chamber is purged with an inert gas before each introduction of the silicon-containing gas, and the reaction chamber is purged with an inert gas before each introduction of the nitrogen-containing gas.

[0024] The method for preparing the anode material provided in this application is novel, the preparation process is simple, and the prepared anode material has excellent cycle stability.

[0025] Thirdly, this application discloses a negative electrode sheet, which includes a current collector and a negative electrode active material layer disposed on the surface of the current collector. The negative electrode active material layer includes the negative electrode material described in the first aspect and the negative electrode material prepared by the preparation method described in the second aspect.

[0026] The negative electrode provided in this application has good cycle stability and excellent overall performance.

[0027] Fourthly, this application discloses a battery comprising a positive electrode and a negative electrode as described in the third aspect.

[0028] The battery provided in this application has good stability, high safety performance, and long service life.

[0029] Fifthly, this application discloses an electrical device, which includes the battery described in any of the preceding claims.

[0030] The electrical equipment provided in this application has excellent overall performance, significantly improved safety performance, and strong product competitiveness. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0032] Figure 1 is a schematic cross-sectional structure diagram of the negative electrode material provided in an embodiment of this application;

[0033] Figure 2 is a schematic cross-sectional structure diagram of a porous carbon matrix provided in an embodiment of this application;

[0034] Figure 3 is a schematic cross-sectional view of the silicon-carbon core provided in one embodiment of this application;

[0035] Figure 4 is a flowchart of the preparation method of the negative electrode material provided in one embodiment of this application;

[0036] Figure 5 is a schematic cross-sectional view of the negative electrode sheet provided in one embodiment of this application;

[0037] Figure 6 is a graph showing the change in conductivity of the negative electrode materials prepared in Example 1 and Comparative Example 1 of this application as a function of pressure.

[0038] Figure 7 is a charging differential capacitance curve of the battery prepared in Example 1 and Comparative Example 1 of this application after 100 cycles.

[0039] Figure 8 is a scanning electron microscope image of the negative electrode material prepared in Example 1 of this application.

[0040] Figure reference numerals: 10: Silicon-carbon core; 11: Porous carbon matrix; 12: Amorphous silicon material; 20: Coating layer; 30: Negative electrode current collector; 40: Negative electrode active material layer; 100: Negative electrode material; 200: Negative electrode sheet; Detailed Implementation

[0041] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0042] In some embodiments of this application, a negative electrode material 100 is disclosed. Referring to Figures 1 and 2, the negative electrode material 100 includes a silicon-carbon core 10 and a coating layer 20 covering the silicon-carbon core 10. The silicon-carbon core 10 includes a porous carbon matrix 11 and an amorphous silicon material 12 disposed in the pores of the porous carbon matrix 11. In the porous carbon matrix 11, the micropore volume accounts for 80%-90% of the total pore volume of the porous carbon matrix 11. The amorphous silicon material 12 is doped with nitrogen, and the nitrogen accounts for 0.2%-1% of the total mass of the negative electrode material 100.

[0043] In this application, the porous carbon matrix 11 can improve the conductivity of the negative electrode material 100; the porous carbon matrix 11 contains an amorphous silicon material 12, which can improve the capacity of the negative electrode material 100. The amorphous silicon material 12 is doped with nitrogen, and the amorphous silicon material 12 and nitrogen can form silicon-nitrogen bonds, which can effectively suppress the reaction between the amorphous silicon material 12 and metals (such as lithium metal) to form a crystalline phase and the continuous growth of the crystalline phase, reduce the volume expansion of the negative electrode material 100, and help improve the conductivity and cycle stability of the negative electrode material 100; the porous carbon... In the substrate 11, micropores account for 80%-90% of the total pore volume of the porous carbon substrate 11. This means that the porous carbon substrate 11 has a large number of pores with a diameter less than 2 nm. This restricts the continuous reaction between the amorphous silicon material 12 disposed within the pores and the metal to form a crystalline phase, as well as the aggregation and growth of the crystalline phase, thus improving the cycle stability of the negative electrode material 100. The coating layer 20 reduces the contact between the silicon-carbon core 10 and other substances, reduces the occurrence of interfacial side reactions, improves the structural stability of the negative electrode material 100, and enhances the safety performance of the battery. The negative electrode material 100 provided in this application exhibits no crystalline phase formation or growth when reacting with the metal, demonstrating good structural stability and excellent cycle stability, which is beneficial for improving battery safety performance and lifespan.

[0044] In some embodiments of this application, please refer to Figures 2 and 3. The silicon-carbon core 10 includes a porous carbon matrix 11 and an amorphous silicon material 12 disposed in the pores of the porous carbon matrix 11. The amorphous silicon material 12 is doped with nitrogen.

[0045] In this application, the micropore volume accounts for 80%-90% of the total pore volume of the porous carbon matrix 11. The porous carbon matrix 11 includes micropores, mesopores, and macropores. Micropores are pores with a diameter less than 2 nm, mesopores are pores with a diameter between 2 nm and 50 nm, and macropores are pores with a diameter greater than 50 nm. A higher proportion of micropore volume, meaning a greater number of pores with a diameter less than 2 nm within the porous carbon matrix 11, effectively inhibits the reaction between the amorphous silicon material 12 and the metal within the pores to form a crystalline phase and to promote agglomeration and growth. This reduces the volume expansion rate of the negative electrode material 100 and is beneficial for improving the cycle stability of the negative electrode material 100.

[0046] Specifically, the micropore volume accounts for, but is not limited to, 80%, 82%, 84%, 86%, 88%, or 90% of the total volume of the porous carbon matrix 11.

[0047] In one embodiment of this application, the micropore volume in the porous carbon matrix 11 can account for 80%-86% of the total pore volume of the porous carbon matrix 11.

[0048] In specific applications, the ratio of micropore volume to the total pore volume of the porous carbon matrix 11 can be set to any value or a range between any two values, such as 80%, 81%, 82%, 83%, 84%, 85%, 86%.

[0049] In another embodiment of this application, the micropore volume in the porous carbon matrix 11 can account for 84%-90% of the total pore volume of the porous carbon matrix 11.

[0050] In specific applications, the ratio of micropore volume to the total pore volume of the porous carbon matrix 11 can be set to any value or a range between any two values, such as 84%, 85%, 86%, 87%, 88%, 90%.

[0051] In some embodiments, the micropore volume accounts for 85% of the total pore volume of the porous carbon matrix 11, and the mesopores and macropores account for 15% of the total pore volume of the porous carbon matrix. The volume ratio between mesopores and macropores is not specifically limited.

[0052] In one embodiment of this application, the specific surface area of ​​the porous carbon matrix 11 is 1500 m2 / g-2000 m2 / g.

[0053] In this embodiment, a larger specific surface area and a greater number of micropores in the porous carbon matrix 11 are beneficial to improving the cycle stability of the negative electrode material 100. Specific surface area was measured using nitrogen isothermal adsorption-desorption curves (BET).

[0054] Specifically, the specific surface area of ​​the porous carbon matrix 11 includes, but is not limited to, 1500 m² / g, 1600 m² / g, 1700 m² / g, 1800 m² / g, 1900 m² / g, or 2000 m² / g.

[0055] In one embodiment of this application, the specific surface area of ​​the porous carbon matrix 11 can be 1500 m2 / g to 1850 m2 / g.

[0056] In specific applications, the specific surface area of ​​the porous carbon matrix 11 can be set to any value or a range between any two values, such as 1500 m2 / g, 1600 m2 / g, 1700 m2 / g, 1800 m2 / g, or 1850 m2 / g.

[0057] In another embodiment of this application, the specific surface area of ​​the porous carbon matrix 11 can be 1800 m2 / g-2000 m2 / g.

[0058] In specific applications, the specific surface area of ​​the porous carbon matrix 11 can be set to any value or a range between any two values, such as 1800 m2 / g, 1850 m2 / g, 1900 m2 / g, 1950 m2 / g, 2000 m2 / g.

[0059] In one embodiment of this application, the Dv50 particle size of the porous carbon matrix 11 is 1μm-20μm. A suitable Dv50 particle size of the porous carbon matrix 11 can improve the conductivity of the negative electrode material 100, which is beneficial for increasing the compaction density of the negative electrode sheet 200, thereby improving the energy density of the battery. A wet testing method was used, in which the porous carbon matrix 11 was dispersed in alcohol, and a laser particle size analyzer was used for testing.

[0060] Specifically, the Dv50 particle size of the porous carbon matrix 11 includes, but is not limited to, 1μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm or 20μm.

[0061] In one embodiment of this application, the Dv50 particle size of the porous carbon matrix 11 can be 1μm-8μm.

[0062] In specific applications, the Dv50 particle size of the porous carbon matrix 11 can be set to any value or a range between any two values, such as 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm.

[0063] In another embodiment of this application, the Dv50 particle size of the porous carbon matrix 11 can be 7μm-20μm.

[0064] In specific applications, the Dv50 particle size of the porous carbon matrix 11 can be set to any value or a range between any two values, such as 7μm, 10μm, 12μm, 14μm, 16μm, 18μm, 19μm, 19.5μm, 20μm.

[0065] In this application, amorphous silicon material 12 is disposed within the pores of porous carbon matrix 11. Amorphous silicon material 12 is doped with nitrogen, which can form silicon-nitrogen bonds with silicon, suppressing the formation and orderly arrangement of silicon-silicon bonds. When amorphous silicon material 12 reacts with a metal (such as lithium metal), it can maintain the amorphous state of amorphous silicon material 12, limiting the degree of reaction (metallization) between amorphous silicon material 12 and metal (such as lithium metal), which is conducive to the formation of amorphous phase compounds (such as LixSiy, x < 3.75, y = 1), avoiding the amorphous silicon material 12 from fully reacting with metal (such as lithium metal) to form a crystalline phase (Li15Si4). This helps to reduce the volume expansion rate and stress change of the negative electrode material 100, and improve the conductivity, capacity, structural stability and cycle stability of the negative electrode material 100.

[0066] In some embodiments of this application, nitrogen accounts for 0.2%-1% of the total mass of the negative electrode material 100. Appropriate nitrogen doping can improve the conductivity of the negative electrode material 100, and can form chemical bonds with silicon to improve the cycle stability of the negative electrode material 100.

[0067] Specifically, the nitrogen content in the negative electrode material is, but is not limited to, 0.2%, 0.4%, 0.5%, 0.6%, 0.8%, or 1% of the total mass.

[0068] In one embodiment of this application, nitrogen can account for 0.2%-0.7% of the total mass of the negative electrode material 100.

[0069] In specific applications, the nitrogen content in 100% of the total mass of the negative electrode material can be set to any value or a range between any two values, such as 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, or 0.7%.

[0070] In another embodiment of this application, nitrogen can account for 0.6%-1% of the total mass of the negative electrode material 100.

[0071] In specific applications, the nitrogen content in 100% of the total mass of the negative electrode material can be set to any value or a range between any two values, such as 0.6%, 0.7%, 0.8%, 0.9%, or 1%.

[0072] In one embodiment of this application, the amorphous silicon material 12 has high reactivity in its amorphous state, which can promote the uniform reaction between the amorphous silicon material 12 and the metal, avoid excessive reaction in local areas, and prevent the formation of a crystalline phase. This is beneficial to alleviate the volume expansion of the negative electrode material 100 and improve the cycle stability of the negative electrode material 100.

[0073] In one embodiment of this application, the amorphous silicon material 12 is nano-amorphous silicon, which can not only fully fill the porous carbon matrix 11, but also promote the uniform reaction of the amorphous silicon material 12 with the metal, thereby improving the cycle stability of the negative electrode material 100.

[0074] In one embodiment of this application, the mass ratio of carbon to silicon in the negative electrode material 100 is 1:(0.5-1).

[0075] Specifically, in the negative electrode material 100, the mass ratio of carbon to silicon is, but is not limited to, 1:0.5, 1:0.85, 1:0.92, 1:0.95, 1:0.98, or 1:1.

[0076] In one embodiment of this application, the mass ratio of carbon to silicon in the negative electrode material 100 can be 1:(0.5-0.93).

[0077] In practical applications, the mass ratio of carbon to silicon can be set to any value or a range between any two values, such as 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:0.93.

[0078] In another embodiment of this application, the mass ratio of carbon to silicon in the negative electrode material 100 can be 1:(0.9-1).

[0079] In practical applications, the mass ratio of carbon to silicon can be set to any value or a range between any two values, such as 1:0.9, 1:0.92, 1:0.94, 1:0.96, 1:0.98, 1:1, etc.

[0080] In this application, the coating layer 20 can reduce the contact between the silicon-carbon core 10 and other substances, reduce the occurrence of interfacial side reactions, improve the structural stability of the negative electrode material 100, and enhance the safety performance of the battery.

[0081] Specifically, the material of the coating layer 20 may include, but is not limited to, at least one of carbon materials, metal oxides and metal sulfides.

[0082] In one embodiment of this application, the material of the coating layer 20 can be carbon material, and the coating layer 20 is a carbon coating layer.

[0083] In another embodiment of this application, the material of the coating layer 20 can be a metal oxide, and the metal can be lithium metal.

[0084] In one embodiment of this application, the thickness of the coating layer 20 is 5nm-30nm. A suitable coating layer 20 thickness can improve the structural stability of the negative electrode material 100 and also improve the conductivity of the negative electrode material 100.

[0085] Specifically, the thickness of the coating layer 20 includes, but is not limited to, 5nm, 10nm, 12nm, 14nm, 16nm, 18nm or 30nm.

[0086] In one embodiment of this application, the thickness of the coating layer 20 can be 5nm-16nm.

[0087] In specific applications, the thickness of the coating layer 20 can be set to any value or a range between any two values, such as 5nm, 7nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm.

[0088] In another embodiment of this application, the thickness of the coating layer 20 can be 15nm-30nm.

[0089] In specific applications, the thickness of the coating layer 20 can be set to any value or a range between any two values, such as 15nm, 18nm, 20nm, 22nm, 24nm, 26nm, 28nm, 30nm.

[0090] In one embodiment of this application, the coating layer 20 has a coating rate of 80%-100%. The coating rate is the percentage of the area of ​​the coating layer 20 covering the silicon-carbon core 10 to the total surface area of ​​the silicon-carbon core 10, which reflects the degree of coating of the silicon-carbon core by the coating layer 20. This can further improve the structural stability of the negative electrode material 100 and is beneficial to improving the cycle stability of the negative electrode material 100.

[0091] Specifically, the coverage rate of the coating layer 20 includes, but is not limited to, 80%, 85%, 90%, 92%, 95%, or 100%.

[0092] In one embodiment of this application, the coverage rate of the coating layer 20 can be 80%-95%.

[0093] In specific applications, the coverage rate of the coating layer 20 can be set to any value or a range between any two values, such as 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 95%.

[0094] In another embodiment of this application, the coverage of the coating layer 20 can be 90%-100%.

[0095] In specific applications, the coverage rate of the coating layer 20 can be set to any value or a range between any two values, such as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%.

[0096] In one embodiment of this application, the mass ratio of the coating layer 20 to the silicon-carbon core 10 in the negative electrode material 100 is 1:(19-99).

[0097] Specifically, in the negative electrode material 100, the mass ratio of the coating layer 20 to the silicon-carbon core 10 includes, but is not limited to, 1:19, 1:20, 1:30, 1:40, 1:60, 1:80, or 1:99.

[0098] In one embodiment of this application, the mass ratio of the coating layer 20 to the silicon-carbon core 10 in the negative electrode material 100 can be 1:(19-50).

[0099] In specific applications, the mass ratio of the cladding layer 20 to the silicon-carbon core 10 can be set to any value or a range between any two values, such as 1:19, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:49, or 1:50.

[0100] In another embodiment of this application, the mass ratio of the coating layer 20 to the silicon-carbon core 10 in the negative electrode material 100 can be 1:(45-99).

[0101] In specific applications, the mass ratio of the cladding layer 20 to the silicon-carbon core 10 can be set to any value or a range between any two values, such as 1:45, 1:50, 1:55, 1:60, 1:65, 1:70, 1:75, 1:80, 1:85, 1:88, or 1:99.

[0102] In one embodiment of this application, the specific surface area of ​​the negative electrode material 100 is 1m2 / g-5m2 / g, and the amorphous silicon material 12 has a good filling effect, which improves the conductivity and cycle stability of the negative electrode material 100.

[0103] In specific applications, the specific surface area can be tested using nitrogen isotherm adsorption-desorption curves (BET). Specifically, the specific surface area of ​​the negative electrode material 100 includes, but is not limited to, 1 m² / g, 2 m² / g, 3 m² / g, 4 m² / g, or 5 m² / g.

[0104] In one embodiment of this application, the specific surface area of ​​the negative electrode material 100 can be 1 m² / g to 4 m² / g.

[0105] In specific applications, the specific surface area of ​​the negative electrode material 100 can be set to any value or a range between any two values, such as 1 m² / g, 1.5 m² / g, 2 m² / g, 2.5 m² / g, 3 m² / g, 3.5 m² / g, 3.9 m² / g, 4 m² / g.

[0106] In another embodiment of this application, the specific surface area of ​​the negative electrode material 100 can be 3m² / g-5m² / g.

[0107] In specific applications, the specific surface area of ​​the negative electrode material 100 can be set to any value or a range between any two values, such as 3m² / g, 3.5m² / g, 3.9m² / g, 4m² / g, 4.5m² / g, 4.9m² / g, 5m² / g.

[0108] In one embodiment of this application, the Dv50 particle size of the negative electrode material 100 is 1μm-20μm. A suitable Dv50 particle size of the negative electrode material 100 can increase the compaction density of the negative electrode material 100, which is beneficial to improving the energy density of the battery.

[0109] In specific applications, a wet method can be used, in which the negative electrode material 100 is dispersed in alcohol and tested using a laser particle size analyzer.

[0110] Specifically, the Dv50 particle size of the negative electrode material 100 includes, but is not limited to, 1μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm or 20μm.

[0111] In one embodiment of this application, the Dv50 particle size of the negative electrode material 100 can be 1μm-8μm.

[0112] In specific applications, the Dv50 particle size of the negative electrode material 100 can be set to any value or a range between any two values, such as 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm.

[0113] In another embodiment of this application, the Dv50 particle size of the negative electrode material 100 can be 7μm-20μm.

[0114] In specific applications, the Dv50 particle size of the negative electrode material 100 can be set to any value or a range between any two values, such as 7μm, 8μm, 9μm, 10μm, 12μm, 14μm, 16μm, 18μm, 19μm, 20μm.

[0115] Please refer to Figure 4. In some embodiments of this application, a flowchart of a method for preparing a negative electrode material 100 is disclosed, including:

[0116] S101: Silicon-containing gas and nitrogen-containing gas are sequentially introduced into the porous carbon matrix 11. After the first reaction, a silicon-carbon core 10 is obtained.

[0117] S102: The coating material gas is introduced into the silicon-carbon core 10, and the negative electrode material 100 is obtained after the second reaction.

[0118] In this embodiment, silicon-containing gas contacts the porous carbon matrix 11 and deposits in the pores of the porous carbon matrix 11, subsequently decomposing to form silicon nuclei. Nitrogen-containing gas also contacts the porous carbon matrix 11 and deposits in the pores of the porous carbon matrix 11. However, due to the small size of the silicon nuclei and the presence of dangling bonds on the surface, the reactivity of the amorphous silicon material 12 is improved. The introduced nitrogen-containing gas reacts with silicon to form silicon-nitrogen bonds, resulting in nitrogen-doped amorphous silicon material 12, which can reduce the volume expansion rate of the negative electrode material 100. Finally, the coating layer raw material gas is introduced and pyrolyzes on the surface of the porous carbon matrix 11 to form a coating layer 20, improving the structural stability of the negative electrode material 100.

[0119] In the embodiments of this application, the preparation method of the negative electrode material 100 is novel and the preparation process is simple. The obtained negative electrode material 100 is not prone to side reactions, has a small volume expansion rate, and exhibits excellent cycle stability. The negative electrode material 100 described in any of the above embodiments can be prepared by this method.

[0120] In one embodiment of this application, silicon-containing gas can enable the deposition of amorphous silicon material 12 in a porous carbon matrix 11, which helps to alleviate the volume expansion phenomenon of the negative electrode material 100.

[0121] Specifically, the silicon-containing gas may be, but is not limited to, at least one of silane, disilane, trisilane, tetrasilane, and chlorosilane.

[0122] In one embodiment of this application, the silicon-containing gas may be silane.

[0123] In another embodiment of this application, the silicon-containing gas may be tetrasilane.

[0124] In one embodiment of this application, the silicon-containing gas is introduced for 10 min to 60 min. A suitable silicon-containing gas introduction time can promote the deposition of silicon-containing gas in the porous carbon matrix 11, improve the deposition uniformity, and help improve the capacity of the negative electrode material 100.

[0125] Specifically, the introduction time of silicon-containing gas includes, but is not limited to, 10 min, 20 min, 30 min, 40 min, 50 min, or 60 min.

[0126] In one embodiment of this application, the introduction time of silicon-containing gas can be 10 min to 40 min.

[0127] In specific applications, the time for introducing silicon-containing gas can be set to any value or a range between any two values, such as 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, or 40 min.

[0128] In another embodiment of this application, the introduction time of silicon-containing gas can be 30 min to 60 min.

[0129] In specific applications, the time for introducing silicon-containing gas can be set to any value or a range between any two values, such as 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min.

[0130] In one embodiment of this application, the silicon-containing gas also includes an inert gas, which can prevent the porous carbon matrix 11 from being contaminated during the reaction process.

[0131] Specifically, the inert gas may include, but is not limited to, at least one of argon, helium, and neon.

[0132] In one embodiment of this application, the silicon-containing gas includes silane and argon.

[0133] In one embodiment of this application, nitrogen-containing gas can be used to dope the amorphous silicon material 12 with nitrogen within the pores of the porous carbon matrix 11, forming silicon-nitrogen bonds and improving the cycle stability of the anode material 100.

[0134] Specifically, the nitrogen-containing gas may be, but is not limited to, at least one of ammonia and nitrogen.

[0135] In one embodiment of this application, the nitrogen-containing gas may be ammonia.

[0136] In one embodiment of this application, the nitrogen-containing gas introduction time can be, but is not limited to, 5 min to 60 min. A suitable nitrogen-containing gas introduction time can promote the uniform doping of nitrogen in amorphous silicon materials and further improve the cycle stability of the anode material.

[0137] Specifically, the time for introducing nitrogen-containing gas includes, but is not limited to: 5 min, 10 min, 20 min, 30 min, 40 min, 52 min, or 60 min.

[0138] In one embodiment of this application, the nitrogen-containing gas can be introduced for 5 min to 45 min.

[0139] In specific applications, the nitrogen-containing gas introduction time can be set to any value or a range between any two values, such as 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min.

[0140] In another embodiment of this application, the nitrogen-containing gas can be introduced for 30-60 minutes.

[0141] In specific applications, the nitrogen-containing gas introduction time can be set to any value or a range between any two values, such as 30min, 35min, 40min, 45min, 50min, 55min, 59min, 60min.

[0142] In one embodiment of this application, the nitrogen-containing gas also includes an inert gas, which can prevent the porous carbon matrix from being contaminated during the reaction process.

[0143] Specifically, inert gases also include at least one of argon, helium, and neon.

[0144] In one embodiment of this application, the nitrogen-containing gas includes ammonia and argon.

[0145] In some embodiments, the inert gas in the silicon-containing gas may be the same as or different from the inert gas in the nitrogen-containing gas.

[0146] In one embodiment of this application, silicon-containing gas and nitrogen-containing gas are sequentially introduced at least once. That is, the number of times silicon-containing gas and nitrogen-containing gas are introduced can be once or multiple times, with multiple times ranging from 2 to 5 times. For example, silicon-containing gas and nitrogen-containing gas can be sequentially introduced into the porous carbon matrix 11; or silicon-containing gas, nitrogen-containing gas, silicon-containing gas, nitrogen-containing gas, silicon-containing gas and nitrogen-containing gas can be sequentially introduced into the porous carbon matrix 11, in which case silicon-containing gas and nitrogen-containing gas are introduced three times.

[0147] In one embodiment of this application, the gas flow rate ratio of silicon-containing gas to nitrogen-containing gas is (5-10):1.

[0148] In the embodiments of this application, a suitable flow ratio can promote uniform doping of nitrogen in amorphous silicon material 12, form silicon-nitrogen bonds, prevent amorphous silicon material 12 from reacting with metal to form a crystalline phase, reduce the volume expansion rate of negative electrode material 100, and improve the cycle stability of negative electrode material 100.

[0149] Specifically, the gas flow ratio of silicon-containing gas and nitrogen-containing gas includes, but is not limited to, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1.

[0150] In one embodiment of this application, the gas flow ratio of silicon-containing gas to nitrogen-containing gas can be (5-8):1.

[0151] In specific applications, the gas flow ratio of silicon-containing gas and nitrogen-containing gas can be set to any value or a range between any two values, such as 5:1, 5.5:1, 6:1, 7:1, 7.5:1, 8:1.

[0152] In another embodiment of this application, the gas flow ratio of silicon-containing gas to nitrogen-containing gas can be (7-10):1.

[0153] In specific applications, the gas flow ratio of silicon-containing gas and nitrogen-containing gas can be set to any value or a range between any two values, such as 7:1, 7.5:1, 8:1, 9:1, 9.5:1, 10:1.

[0154] In one embodiment of this application, before introducing the silicon-containing gas and before introducing the nitrogen-containing gas, an inert gas is also introduced. The inert gas is used for gas washing to improve the safety of the reaction, prevent the reactants from being contaminated, and improve the cycle stability of the negative electrode material 100.

[0155] Specifically, the inert gas may include, but is not limited to, at least one of argon, helium, and neon.

[0156] In one embodiment of this application, the inert gas is argon.

[0157] In some embodiments, the inert gas in the silicon-containing gas, the inert gas in the nitrogen-containing gas, and the inert gas in the purge gas may be the same or different.

[0158] In one embodiment of this application, the inert gas is introduced for 10-30 minutes. A suitable third inert gas introduction time is beneficial to improving reaction efficiency.

[0159] Specifically, the inert gas introduction time includes, but is not limited to, 10 min, 15 min, 20 min, 25 min, or 30 min.

[0160] In one embodiment of this application, the inert gas can be introduced for 10-20 minutes.

[0161] In specific applications, the inert gas introduction time can be set to any value or a range between any two values, such as 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min.

[0162] In one embodiment of this application, the inert gas can be introduced for 15-30 minutes.

[0163] In specific applications, the inert gas introduction time can be set to any value or a range between any two values, such as 15min, 16min, 17min, 18min, 19min, 20min, 22min, 24min, 26min, 28min, 30min.

[0164] In one embodiment of this application, the gas introduction sequence can be inert gas, silicon-containing gas, inert gas, and nitrogen-containing gas, and can be introduced at least once in this gas introduction sequence. That is, the gas can be introduced once or multiple times in this gas introduction sequence, with multiple times ranging from 2 to 5 times, to promote the uniform deposition of amorphous silicon material and nitrogen doping in the porous carbon matrix, and further improve the cycle stability of the negative electrode material 100.

[0165] Specifically, the number of repetitions includes, but is not limited to, 1 time, 2 times, 3 times, 4 times, or 5 times.

[0166] In one embodiment of this application, the repetition can be twice. For example, the gas introduction sequence can be inert gas, silicon-containing gas, inert gas, nitrogen-containing gas, inert gas, silicon-containing gas, inert gas, and nitrogen-containing gas, in which case the gas is introduced twice in this sequence.

[0167] In one embodiment of this application, the temperature of the first reaction is 400°C-900°C.

[0168] In the embodiments of this application, a suitable reaction temperature can cause the silicon-containing gas to decompose at high temperature, forming silicon crystal nuclei, promoting the deposition of amorphous silicon material 12 in the pores of the porous carbon matrix 11, and improving the deposition uniformity of amorphous silicon material 12.

[0169] Specifically, the temperature of the first reaction includes, but is not limited to, 400℃, 500℃, 600℃, 700℃, 800℃, or 900℃.

[0170] In one embodiment of this application, the temperature of the first reaction can be 400℃-700℃.

[0171] In practical applications, the temperature of the first reaction can be set to any value or a range between any two values, such as 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃.

[0172] In another embodiment of this application, the temperature of the first reaction can be 600℃-900℃.

[0173] In practical applications, the temperature of the first reaction can be set to any value or a range between any two values, such as 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃.

[0174] In one embodiment of this application, the time for the first reaction is 15 min to 10 h.

[0175] Specifically, the time for the first reaction includes, but is not limited to: 15 min, 30 min, 1 h, 2 h, 4 h, 6 h, 8 h, or 10 h.

[0176] In one embodiment of this application, the time for the first reaction can be 15 min to 5 h.

[0177] In practical applications, the time for the first reaction can be set to any value or a range between any two values, such as 15min, 30min, 1h, 2h, 3h, 4h, 5h.

[0178] In another embodiment of this application, the time for the first reaction can be 4h-10h.

[0179] In practical applications, the time for the first reaction can be set to any value or a range between any two values, such as 4h, 5h, 6h, 7h, 8h, 9h, 10h.

[0180] In one embodiment of this application, the coating material gas can form a coating layer 20 on the surface of the silicon-carbon core 10, thereby improving the structural stability of the negative electrode material 100.

[0181] Specifically, the feed gas for the coating layer may include, but is not limited to, at least one of methane, ethane, ethylene, and acetylene.

[0182] In one embodiment of this application, the raw material gas for the coating layer can be methane.

[0183] In another embodiment of this application, the raw material gas for the coating layer can be a mixture of ethane and ethylene.

[0184] In one embodiment of this application, the temperature of the second reaction is 500°C-800°C.

[0185] In this embodiment, a suitable temperature for the second reaction can promote the pyrolysis of the coating material, forming a coating layer 20 on the surface of the porous carbon matrix 11.

[0186] Specifically, the temperature of the second reaction includes, but is not limited to, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, or 800℃.

[0187] In one embodiment of this application, the temperature of the second reaction can be 500°C-700°C.

[0188] In practical applications, the temperature of the second reaction can be set to any value or a range between any two values, such as 500℃, 550℃, 600℃, 650℃, or 700℃.

[0189] In another embodiment of this application, the temperature of the second reaction can be 600°C-800°C.

[0190] In practical applications, the temperature of the second reaction can be set to any value or a range between any two values, such as 600℃, 650℃, 700℃, 750℃, or 800℃.

[0191] In one embodiment of this application, the second reaction takes 1-12 hours.

[0192] In the embodiments of this application, an appropriate reaction time can promote the complete coating of the coating layer 20 by the coating material, which is beneficial to improving the conductivity and structural stability of the coating layer 20.

[0193] Specifically, the time for the second reaction includes, but is not limited to: 1h, 2h, 4h, 6h, 8h, 10h, or 12h.

[0194] In one embodiment of this application, the second reaction time can be 1h-6h.

[0195] In practical applications, the time for the second reaction can be set to any value or a range between any two values, such as 1h, 2h, 3h, 4h, 5h, 6h.

[0196] In one embodiment of this application, the second reaction time can be 5h-12h.

[0197] In practical applications, the time for the second reaction can be set to any value or a range between any two values, such as 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h.

[0198] In one embodiment of this application, both the first reaction and the second reaction are carried out in a high-temperature furnace.

[0199] Specifically, high-temperature furnaces can be, but are not limited to, fluidized bed furnaces or rotary kilns.

[0200] In one embodiment of this application, the high-temperature furnace may be a fluidized bed.

[0201] Please refer to Figure 5. This application also discloses a negative electrode sheet 200, which includes a negative electrode current collector 30 and a negative electrode active material layer 40 disposed on the surface of the negative electrode current collector 30. The negative electrode active material layer 40 includes the negative electrode material 100 described in any of the above embodiments.

[0202] In the embodiments of this application, the negative electrode 200 has improved cycle life and safety performance due to the presence of a negative electrode material 100 that is not easily reactive with metals, has good cycle stability and low volume expansion rate.

[0203] In one embodiment of this application, the negative electrode current collector 30 includes, but is not limited to, at least one of copper, aluminum, nickel, and stainless steel.

[0204] In one embodiment of this application, the negative electrode current collector 30 can be a copper foil.

[0205] In one embodiment of this application, the negative electrode active material layer 40 further includes a negative electrode binder, which can improve the bonding ability of each component in the negative electrode active material layer 40 and improve the bonding ability between the negative electrode active material layer 40 and the negative electrode current collector 30.

[0206] Specifically, the negative electrode binder includes, but is not limited to, one or more of the following: polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, polybutadiene, acrylic resin, epoxy resin, polyethylene oxide, sodium carboxymethyl cellulose, and styrene-butadiene latex.

[0207] In one embodiment of this application, the negative electrode binder may be polyvinylidene fluoride.

[0208] In another embodiment of this application, the negative electrode binder may be sodium carboxymethyl cellulose.

[0209] In one embodiment of this application, the negative electrode active material layer 40 further includes a negative electrode conductive agent, which can increase the conductivity of the negative electrode material and improve the electronic conductivity.

[0210] Specifically, the negative electrode conductive agent includes, but is not limited to, at least one of graphite, carbon black, acetylene black, and graphene.

[0211] In one embodiment of the application, the negative electrode conductive agent may be graphite.

[0212] In another embodiment of this application, the negative electrode conductive agent may be carbon black.

[0213] In some embodiments of this application, this application also discloses a battery, including a positive electrode and a negative electrode 200 as described in any of the above embodiments.

[0214] In the embodiments of this application, the negative electrode 200 has a long cycle life and high safety performance because it has a negative electrode material 100 that is not easily reacted with metals, has good cycle stability and low volume expansion rate. Therefore, the battery disclosed in this application has excellent cycle performance, long service life and high safety, which is conducive to the widespread application of the battery.

[0215] In one embodiment of this application, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on the surface of the positive current collector, wherein the positive active material layer includes a positive active material.

[0216] Specifically, the positive electrode current collector includes, but is not limited to, at least one of copper, aluminum, nickel, and stainless steel; the positive electrode active material includes, but is not limited to, at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium manganese oxide, nickel cobalt manganese, and nickel cobalt aluminum.

[0217] In one embodiment of this application, the positive electrode current collector can be aluminum foil, and the positive electrode active material can be lithium cobalt oxide.

[0218] In one embodiment of this application, the positive electrode active material layer further includes a positive electrode conductive agent. The positive electrode conductive agent can increase the conductivity between active materials and improve electronic conductivity.

[0219] Specifically, the positive electrode conductive agent includes, but is not limited to, at least one of graphite, carbon black, acetylene black, and graphene.

[0220] In one embodiment of this application, the positive electrode conductive agent may be graphite.

[0221] In another embodiment of this application, the positive electrode conductive agent may be carbon black.

[0222] In one embodiment of this application, the positive electrode active material layer further includes a positive electrode binder, which can improve the bonding ability of each component in the positive electrode active material layer and improve the bonding ability between the positive electrode active material layer and the positive electrode current collector.

[0223] Specifically, the positive electrode binder includes, but is not limited to, one or more of the following: polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, polybutadiene, acrylic resin, epoxy resin, polyethylene oxide, sodium carboxymethyl cellulose, and styrene-butadiene latex.

[0224] In one embodiment of this application, the positive electrode binder may be polyvinylidene fluoride.

[0225] In one embodiment of this application, the battery further includes a separator disposed between the positive electrode and the negative electrode 200.

[0226] Specifically, the diaphragm can be, but is not limited to, woven membrane, nonwoven fabric, microporous membrane, composite membrane, rolled membrane, or diaphragm paper.

[0227] In one embodiment of this application, the battery further includes an electrolyte. At least a portion of the positive electrode and at least a portion of the negative electrode 200 are immersed in the electrolyte. The electrolyte used in this application is not particularly limited and can be, but is not limited to, any substance in the art that can be used as a battery electrolyte.

[0228] In some embodiments of this application, this application also discloses an electrical device, which includes the battery described in any of the above embodiments.

[0229] In the embodiments of this application, the battery has excellent cycle performance, long service life, and high safety, which makes the electrical device have excellent overall performance and strong market competitiveness.

[0230] In specific applications, electrical equipment can refer to vehicles, electronic devices, energy storage systems, etc., and the aforementioned electrochemical devices can be installed in the electrical equipment in the form of single cells, battery modules, battery packs, capacitors, etc.

[0231] In one embodiment of this application, the battery can be used in a vehicle to improve the safety of vehicle power supply.

[0232] In another embodiment of this application, the battery can also be used in electronic devices, which can increase the battery cycle stability of electronic devices and improve battery life.

[0233] The effects of the technical solution in this application will be further illustrated below with specific examples.

[0234] Example 1

[0235] A porous carbon matrix 11 (Dv50 of 8 μm, micropore volume accounting for 85% of the total pore volume of the porous carbon matrix, and specific surface area of ​​1800 m2 / g) was placed in a fluidized bed and purged with 100 sccm of argon gas for 30 minutes. The first reaction temperature was maintained at 500℃. A silicon-containing gas (a mixture of 50 sccm of silane and 100 sccm of argon gas) was introduced for 10 minutes, followed by purging with 100 sccm of argon gas for 30 minutes. A nitrogen-containing gas (a mixture of 10 sccm of ammonia and 100 sccm of argon gas) was introduced for 5 minutes, followed by purging with 100 sccm of argon gas for 30 minutes. This process was repeated five times to obtain the silicon-carbon core 10.

[0236] The temperature of the second reaction was adjusted to 700°C, and the raw material gas for the coating layer (a mixture of acetylene at 50 sccm and argon at 100 sccm) was introduced for 6 hours to obtain the negative electrode material 100.

[0237] Example 2

[0238] The difference from Example 1 is that in the porous carbon matrix 11, the micropore volume accounts for 80% of the total pore volume of the porous carbon matrix 11, and the specific surface area is 1500 m2 / g.

[0239] Example 3

[0240] The difference from Example 1 is that in the porous carbon matrix 11, the micropore volume accounts for 90% of the total pore volume of the porous carbon matrix 11, and the specific surface area is 2000 m2 / g.

[0241] Example 4

[0242] The difference from Example 1 is that nitrogen-containing gas was introduced for 1 minute.

[0243] Example 5

[0244] The difference from Example 1 is that the silicon-containing gas is a mixture of silane at 30 sccm and argon at 100 sccm. The gas flow ratio of the silicon-containing gas to the nitrogen-containing gas is 3:1.

[0245] Example 6

[0246] The difference from Example 1 is that the second reaction takes 2 hours.

[0247] Example 7

[0248] The difference from Example 1 is that the second reaction takes 12 hours.

[0249] Example 8

[0250] The difference from Example 1 is that no argon purging is performed.

[0251] Example 9

[0252] The difference from Example 1 is that the temperature of the first reaction is 900°C.

[0253] Comparative Example 1

[0254] The difference from Example 1 is that no nitrogen-containing gas is introduced.

[0255] Comparative Example 2

[0256] The difference from Example 1 is that no silicon-containing gas is introduced.

[0257] Comparative Example 3

[0258] The difference from Example 1 is that no silicon-containing gas or nitrogen-containing gas is introduced.

[0259] Comparative Example 4

[0260] The difference from Example 1 is that no coating material gas is introduced.

[0261] Comparative Example 5

[0262] The difference from Example 1 is that in the porous carbon matrix 11, the micropore volume accounts for 50% of the total pore volume of the porous carbon matrix 11, and the specific surface area is 1200 m2 / g.

[0263] Comparative Example 6

[0264] The difference from Example 1 is that nitrogen-containing gas was introduced for 65 minutes.

[0265] Comparative Example 7

[0266] The difference from Example 1 is that the silicon-containing gas is a mixture of 10 sccm of silane and 100 sccm of argon. The gas flow ratio of the silicon-containing gas to the nitrogen-containing gas is 1:1.

[0267] Performance testing

[0268] The anode materials 100 prepared in Examples 1-9 and Comparative Examples 1-7 were tested for nitrogen content using a nitrogen-oxygen analyzer according to GB / T14265-2017. The test results are shown in Table 1.

[0269] The negative electrode materials 100 prepared in Examples 1-9 and Comparative Examples 1-7 were subjected to BET testing according to GB / T19587-2017. The testing procedure was as follows: the mass of the empty sample tube was weighed, approximately 2g of negative electrode material 100 was weighed and placed into the sample tube, the sample tube was heated at 200℃ for 2 hours in a degassing station, and after cooling, the mass of the sample tube was weighed again. The sample tube was then vertically installed onto the analysis port of the testing instrument, and the bottom of the sample tube was immersed in a Dewar flask containing an appropriate amount of liquid nitrogen. The amount of nitrogen adsorbed by the sample was measured at different pre-set pressure points to obtain adsorption isotherms. The data was processed by computer, and the specific surface area was calculated based on the adsorption isotherms. The test results are shown in Table 1.

[0270] The negative electrode materials 100 prepared in Examples 1-9 and Comparative Examples 1-7 were analyzed according to GB / T14265-2017 using a nitrogen-oxygen analyzer and a carbon-sulfur analyzer to determine the content of carbon, nitrogen, oxygen, and sulfur elements in the negative electrode material 100, with the remainder being silicon element content. The mass ratio of carbon to silicon was then calculated. The nitrogen-oxygen analyzer test procedure was as follows: an appropriate amount of negative electrode material 100 was weighed and placed in a graphite crucible, helium gas was introduced, and the mixture was heated to 4700℃ to melt. The oxygen in the negative electrode material 100 reacted with the carbon in the graphite crucible to generate carbon monoxide, and the nitrogen in the negative electrode material 100 escaped as nitrogen gas. The specific content was detected by infrared spectroscopy. The carbon-sulfur analyzer test procedure was as follows: an appropriate amount of negative electrode material 100 was weighed and placed in a ceramic crucible, and heated to 1500℃ under an oxygen-rich atmosphere. The carbon in the negative electrode material 100 was oxidized to carbon dioxide and escaped, and the sulfur in the negative electrode material 100 was oxidized to sulfur dioxide and escaped. The specific content was detected by infrared spectroscopy. The specific results are shown in Table 1.

[0271] The conductivity of the negative electrode materials prepared in Examples 1-9 and Comparative Examples 1-7 was tested using a PRCD3100 (I EST-Yuaneng Technology). The testing procedure was as follows: 1g of negative electrode material 100 was weighed and placed into the test mold of the instrument. A four-probe mode was used, with a pressure range of 10-200MPa and a holding time of 10s. The conductivity curves of the powder as a function of pressure were obtained. The conductivity test results for Examples 1-9 and Comparative Examples 1-7 when the applied pressure was 20MPa are shown in Table 1. Figure 6 shows the conductivity curves of the negative electrode material 100 prepared in Example 1 and Comparative Example 1 as a function of pressure. It can be seen that the conductivity of the negative electrode material in Example 1 is much higher than that in Comparative Example 1.

[0272] The negative electrode material 100 prepared in Examples 1-9 and Comparative Examples 1-7 was mixed with a conductive agent (conductive graphite Super P) and a binder (polystyrene) at a mass ratio of 8:1:1. A solvent (water) was added to obtain a negative electrode slurry, which was coated onto a negative electrode current collector 30 (copper foil) and dried at 100°C for 24 hours to obtain a negative electrode sheet 200. The negative electrode sheet 200, the positive electrode sheet (lithium sheet), the battery separator (Celgard 2400 polypropylene film), the electrolyte (1 mol / L lithium hexafluorophosphate (LiPF6) in ethylene carbonate and diethyl carbonate, with a volume ratio of ethylene carbonate and diethyl carbonate of 1:1) and the electrolyte additive (5.0 wt% fluoroethylene carbonate) were assembled into a CR2032 coin cell.

[0273] The batteries prepared in Examples 1-9 and Comparative Examples 1-7 were tested for electrochemical performance using a Blue Electric testing system (model CT2011A). The testing process involved discharging the battery at a constant current of 100 mA / g to 0.005V at room temperature, followed by charging at a constant current of 100 mA / g to 1.5V. The discharge specific capacity and charge specific capacity of the battery were recorded after the first cycle and after 100 cycles. The coulombic efficiency (%) of the battery in the first cycle was calculated as: charge specific capacity / discharge specific capacity × 100%, and the capacity retention rate (%) was calculated as: discharge specific capacity after 100 cycles / discharge specific capacity in the first cycle × 100%. The test results are shown in Table 2. The differential capacitance curve (dQ / dV) was obtained by differentiating the charge specific capacity Q with respect to the voltage V after 100 cycles, with V as the abscissa. Figure 7 shows the differential capacitance curves of the batteries prepared in Example 1 and Comparative Example 1 after 100 cycles. It can be seen that the characteristic peaks of the crystalline phase (Li15Si4) were not observed in the negative electrode material of Example 1 at a voltage of 0.45V.

[0274] Figure 8 is a scanning electron microscope image of the negative electrode material 100 prepared in Example 1 of this application. It can be seen that no obvious pores appear on the surface of the negative electrode material 100, indicating that the surface of the porous carbon matrix 11 has a coating layer 20, which improves the density of the negative electrode material 100; no obvious amorphous silicon material 12 agglomeration phenomenon is also found on the surface of the negative electrode material 100, indicating that the amorphous silicon material 12 is uniformly deposited in the porous carbon matrix 11 and distributed in the micropores.

[0275] Table 1 Performance Tests of Anode Materials

[0276] Table 2 Battery performance test results

[0277] As can be seen from Examples 1-9 and Comparative Examples 1-7, the negative electrode material 100 provided in this application has high capacity and good cycle stability, which is beneficial to improving the battery's lifespan. As can be seen from Examples 1-3 and Comparative Example 5, in the porous carbon matrix 11, an appropriate micropore volume ratio is beneficial to improving the uniform deposition of amorphous silicon material 12 on the porous carbon matrix 11, which is beneficial to improving the conductivity, capacity, and cycle stability of the negative electrode material 100.

[0278] As can be seen from Examples 1, 4-9, and Comparative Examples 6-7, appropriate reaction conditions can promote the deposition of amorphous silicon material 12 in the porous carbon matrix 11 and the doping of nitrogen in amorphous silicon material 12, thereby improving the cycle stability of the anode material 100. Specifically, an appropriate nitrogen-containing gas introduction time can increase the nitrogen content in the anode material 100, strengthen the bonding between amorphous silicon material 12 and nitrogen, suppress side reactions, and avoid the formation of byproducts (silicon nitride). This improves the capacity retention of the anode material 100 while maintaining its high capacity and first-cycle coulombic efficiency. An appropriate gas flow ratio of silicon-containing gas to nitrogen-containing gas can increase the nitrogen doping content, prevent passivation of the amorphous silicon material, strengthen the formation of silicon-nitrogen bonds, and improve the cycle stability and capacity of the anode material.

[0279] Using the preparation method of Comparative Example 4, a stable negative electrode material 100 that can be stored for a long time cannot be obtained. The prepared negative electrode material 100 is easily oxidized, which leads to spontaneous combustion of the negative electrode material 100 and makes performance testing impossible. As can be seen from Example 1 and Comparative Example 4, the negative electrode material 100 with the coating layer 20 can improve the structural stability of the negative electrode material 100, avoid the silicon carbon core 10 from directly contacting the outside world and causing oxidation, and is beneficial to the storage and application of the negative electrode material 100.

[0280] The above description represents the preferred embodiments of this application, but should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various improvements, changes, modifications, substitutions, and variations without departing from the principles of this application, and these improvements, changes, modifications, substitutions, and variations are also considered to be within the scope of protection of this application.

Claims

1. A negative electrode material, wherein, The negative electrode material includes a silicon-carbon core and a coating layer covering the silicon-carbon core. The silicon-carbon core includes a porous carbon matrix and an amorphous silicon material disposed within the pores of the porous carbon matrix. The micropore volume in the porous carbon matrix accounts for 80%-90% of the total pore volume of the porous carbon matrix. The amorphous silicon material is doped with nitrogen, and the nitrogen accounts for 0.2%-1% of the total mass of the negative electrode material.

2. The negative electrode material as described in claim 1, wherein, The coating layer is made of at least one of carbon materials, metal oxides and metal sulfides, and the thickness of the coating layer is 5nm-30nm.

3. The negative electrode material as described in claim 1, wherein, In the negative electrode material, the mass ratio of carbon to silicon is 1:(0.5-1).

4. The negative electrode material as described in claim 1, wherein, The specific surface area of ​​the porous carbon matrix is ​​1500 m². 2 / g-2000m 2 / g.

5. The negative electrode material as described in claim 1, wherein, The Dv50 particle size of the porous carbon matrix is ​​1μm-20μm.

6. The negative electrode material as described in claim 1, wherein, In the negative electrode material, the mass ratio of the coating layer to the silicon-carbon core is 1:(19-99).

7. The negative electrode material as described in claim 1, wherein, The specific surface area of ​​the negative electrode material is 1m². 2 / g-5m 2 / g.

8. The negative electrode material as described in claim 1, wherein, The particle size of the negative electrode material Dv50 is 1μm-20μm.

9. The negative electrode material as described in claim 1, wherein, The amorphous silicon material and the nitrogen element form a silicon-nitrogen bond.

10. A method for preparing a negative electrode material, wherein, include: A silicon-containing gas and a nitrogen-containing gas are sequentially introduced into a porous carbon matrix. After a first reaction, a silicon-carbon core is obtained. A coating material gas is introduced into the silicon-carbon core, and a negative electrode material is obtained after a second reaction. The negative electrode material includes a silicon-carbon core and a coating layer covering the silicon-carbon core. The silicon-carbon core includes a porous carbon matrix and an amorphous silicon material disposed in the pores of the porous carbon matrix. The micropore volume in the porous carbon matrix accounts for 80%-90% of the total pore volume of the porous carbon matrix. The amorphous silicon material is doped with nitrogen, and the nitrogen accounts for 0.2%-1% of the total mass of the negative electrode material.

11. The preparation method according to claim 10, wherein, The temperature of the first reaction is 400℃-900℃, and the reaction time is 15min-10h; The temperature of the second reaction is 500℃-800℃, and the reaction time is 1h-12h.

12. The preparation method according to claim 10, wherein, The gas flow rate ratio of the silicon-containing gas to the nitrogen-containing gas is (5-10):1; The raw material gas for the coating layer includes at least one of methane, ethane, ethylene, and acetylene.

13. The preparation method according to claim 10, wherein, The reaction chamber is purged with inert gas before each introduction of the silicon-containing gas, and the reaction chamber is purged with inert gas before each introduction of the nitrogen-containing gas.

14. A negative electrode plate, wherein, The negative electrode sheet includes a current collector and a negative electrode active material layer disposed on the surface of the current collector. The negative electrode active material layer includes the negative electrode material as described in any one of claims 1-9 and the negative electrode material prepared by the preparation method as described in any one of claims 10-13.

15. A battery, wherein, The battery includes a positive electrode and a negative electrode as described in claim 14.

16. An electrical appliance, wherein, The electrical device includes the battery as described in claim 15.

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