Silicon-based negative electrode material and preparation method and application thereof

Abstract

The embodiment of the invention relates to a silicon-based negative electrode material as well as a preparation method and application thereof. The silicon-based negative electrode material comprises a silicon-carbon substrate and doping elements which are uniformly distributed in the silicon-carbon substrate at an atomic level, the silicon-carbon substrate comprises porous carbon and silicon uniformly distributed in pores and on the surface of the porous carbon; the doping elements comprise one or more of C, N, B, F, S, C l, A l and P; a chemical bond is formed between silicon in the silicon-carbon substrate and the doped element; the average particle size Dv50 of the silicon-based negative electrode material particles is 1 nm to 100 [mu] m, and the specific surface area is 0.5 m < 2 > / g to 45 m < 2 > / g; the mass of the doped element accounts for 0.1%-15% of the mass of the silicon-carbon substrate; when the silicon-based negative electrode material is applied to the lithium battery, the cycle performance of the lithium battery can be improved.

Description

Technical Field

[0001] The present invention relates to the field of material technology, and in particular to a silicon-based negative electrode material and a preparation method and application thereof. Background Art

[0002] With the rapid development of the power battery industry, energy density requirements for upstream materials are increasing. Due to the low theoretical gram capacity of graphite anodes, shipments of silicon-based anode materials have increased significantly. Furthermore, silicon-based materials offer advantages such as abundant reserves, environmental friendliness, and low cost, making them considered one of the most promising anode materials.

[0003] However, silicon-based materials experience significant volume expansion (>300%) during cycling, which can cause silicon particles to break up, further leading to electrode pulverization, structural damage, and rapid capacity degradation. Furthermore, low electrical conductivity further limits the commercial application of silicon-based anodes.

[0004] Therefore, it is necessary to develop a negative electrode material that can solve the problems of volume expansion rate and poor conductivity of silicon negative electrode materials and is suitable for commercial applications. Summary of the Invention

[0005] The present invention provides a silicon-based negative electrode material and its preparation method and application, the purpose of which is to inhibit the volume expansion of the silicon-based negative electrode material during battery cycling, improve the conductive properties of the material, and thus improve the electrochemical performance of lithium batteries.

[0006] To achieve the above objectives, in a first aspect, an embodiment of the present invention provides a silicon-based negative electrode material, the silicon-based negative electrode material comprising: a silicon-carbon matrix, and a doping element uniformly distributed in the silicon-carbon matrix at the atomic level;

[0007] The silicon-carbon matrix includes porous carbon and silicon uniformly distributed in the pores and on the surface of the porous carbon;

[0008] The doping element includes one or more of C, N, B, F, S, Cl, Al, and P; a chemical bond is formed between the silicon in the silicon-carbon matrix and the doping element;

[0009] The average particle size Dv50 of the silicon-based negative electrode material particles is 1nm-100μm, and the specific surface area is 0.5m 2 / g-45m 2 / g; the mass of the doping element accounts for 0.1%-15% of the mass of the silicon-carbon matrix.

[0010] Preferably, the porosity of the porous carbon is 35%-90%; the pore diameter of the porous carbon is 1nm-10nm;

[0011] The average particle size Dv50 of the porous carbon is 5 μm-20 μm; the specific surface area of ​​the porous carbon is 500 m 2 / g-3000m 2 / g.

[0012] Preferably, the mass percentage of the silicon to the mass percentage of the silicon-based negative electrode material is 30%-70%.

[0013] Preferably, the outer surface of the silicon-based negative electrode material further has a carbon coating layer; the mass of the carbon coating layer accounts for 0%-20% of the total mass of the silicon-based negative electrode material.

[0014] In a second aspect, an embodiment of the present invention provides a method for preparing the silicon-based negative electrode material described in the first aspect, the method comprising:

[0015] Step S1, placing porous carbon on a substrate in a first furnace chamber of a vapor deposition furnace, and placing a material containing doping elements in a second furnace chamber of the vapor deposition furnace;

[0016] Step S2: Under a protective atmosphere, the temperature in the second furnace chamber of the vapor deposition furnace is raised to 600° C. to 950° C. to vaporize the material containing the doping element, and a gas containing the silicon element is introduced to obtain a mixed gas source; alternatively, a mixed gas containing the silicon element and the doping element is introduced into the second furnace chamber at a temperature of 600° C. to 950° C. via a carrier gas to obtain a mixed gas source;

[0017] Step S3: introducing the mixed gas source into the first furnace chamber and depositing it in the pores of the porous carbon to obtain a silicon-based negative electrode material.

[0018] Preferably, the material containing doping elements includes one or more of glucose, ammonium chloride, melamine, red phosphorus, ammonium fluoride, boron oxide, ammonium sulfide, aluminum oxide, and ammonium chloride;

[0019] The gas containing doping elements includes one or more of acetylene, propylene, methane, and ammonia;

[0020] The silicon-containing gas includes one or more of monosilane, disilane, chlorosilane, tetrafluorosilane, hexamethyldisilane, tris(trimethylsilyl)silane, and methylvinyldichlorosilane.

[0021] Preferably, the protective atmosphere includes nitrogen atmosphere or argon atmosphere;

[0022] The carrier gas is nitrogen or argon; the flow rate of the carrier gas is 15L / min-65L / min.

[0023] The deposition time in step S3 is 0.5 hours to 10 hours.

[0024] Preferably, the preparation method further comprises performing a carbon coating treatment on the silicon-based negative electrode material to form a carbon coating layer on the surface of the silicon-based negative electrode material;

[0025] The carbon coating treatment method includes: any one of gas phase coating, liquid phase coating or solid phase coating.

[0026] In a third aspect, an embodiment of the present invention provides a negative electrode plate, wherein the negative electrode plate includes the silicon-based negative electrode material described in the first aspect.

[0027] In a fourth aspect, an embodiment of the present invention provides a lithium battery, comprising the negative electrode sheet described in the third aspect.

[0028] An embodiment of the present invention provides a silicon-based negative electrode material, a preparation method thereof, and an application thereof. The method comprises the following steps: heating and vaporizing a material containing different doping elements or introducing a gas containing doping elements, and then forming a mixed gas source with a gas containing silicon elements, which is deposited in the pores of porous carbon. The doping elements form chemical bonds with Si at the atomic level through gas phase mixing to obtain a silicon-based negative electrode material. The silicon-based negative electrode material of the present invention is applied to lithium batteries. On the one hand, the chemical bonds formed between the doping elements and Si at the atomic level can inhibit the volume expansion of the material to ensure structural stability. On the other hand, the ionic conductivity of the material can be improved, thereby improving the cycle performance of the battery. In addition, the silicon-based negative electrode material of the present invention optionally also has a carbon coating layer, which can effectively limit the direct contact between the electrolyte and silicon, reduce the irreversible capacity caused by the first insertion and extraction of lithium, and improve the first coulombic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Flowchart of the method for preparing silicon-based negative electrode materials provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings. It is apparent that the embodiments described are only some, not all, of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0031] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0032] An embodiment of the present invention provides a silicon-based negative electrode material, which includes: a silicon-carbon matrix, and doping elements uniformly distributed in the silicon-carbon matrix at the atomic level; the silicon-carbon matrix includes porous carbon and silicon uniformly distributed in the pores and on the surface of the porous carbon. The mass percentage of silicon in the silicon-based negative electrode material is 30%-70%. The average particle size Dv50 of the silicon-based negative electrode material particles is 1nm-100μm, and the specific surface area is 0.5m 2 / g-45m 2 / g.

[0033] The porosity of the porous carbon is 35%-90%; the pore size of the porous carbon is 1nm-10nm; the average particle size Dv50 of the porous carbon is 5μm-20μm; the specific surface area of ​​the porous carbon is 500m 2 / g-3000m 2 / g.

[0034] The doping elements include one or more of C, N, B, F, S, Cl, Al, and P. The mass of the doping elements accounts for 0.1% to 15% of the mass of the silicon-carbon matrix, preferably 2% to 5%. A chemical bond is formed between the silicon in the silicon-carbon matrix and the doping elements.

[0035] When the doping element is C, in the X-ray photoelectron spectrum XPS of the silicon-based negative electrode material, after the C 1s spectrum is split, there is a binding peak belonging to the Si-C bond at the position of 283.5±1.0eV.

[0036] When the doping element is N, in the X-ray photoelectron spectrum XPS of the silicon-based negative electrode material, after the N 1s spectrum is split, there is a binding peak belonging to the Si-N bond at the position of 398.0±1.0eV.

[0037] When the doping element is B, in the X-ray photoelectron spectrum XPS of the silicon-based negative electrode material, after the B 1s energy spectrum is split, there is a binding peak belonging to the Si-B bond at the position of 188.5±0.5eV; after the F 1s energy spectrum is split, there is a binding peak belonging to the Si-F bond at the position of 686.0±1eV.

[0038] When the doping element is S, in the X-ray photoelectron spectrum XPS of the silicon-based negative electrode material, after the S2p spectrum is split, there is a binding peak belonging to the Si-S bond at the position of 162.4±1.0eV.

[0039] When the doping element is Cl, in the X-ray photoelectron spectroscopy XPS of the silicon-based negative electrode material, after the Cl 2p spectrum is split, there is a binding peak belonging to the Si-Cl bond at the position of 201.7±1.0eV.

[0040] When the doping element is Al, in the X-ray photoelectron spectroscopy XPS of the silicon-based negative electrode material, after the Al 2p spectrum is separated, there is a binding peak belonging to the Si-Al bond at the position of 75.3±0.5eV.

[0041] When the doping element is P, in the X-ray photoelectron spectrum XPS of the silicon-based negative electrode material, after the P 2p spectrum is split, there is a binding peak belonging to the Si-P bond at the position of 134.6±1.0eV.

[0042] In an optional solution, the outer surface of the silicon-based negative electrode material further has a carbon coating layer; the mass of the carbon coating layer accounts for 0%-20% of the total mass of the silicon-based negative electrode material, preferably 0%-10%.

[0043] The present invention provides a method for preparing the silicon-based negative electrode material. Figure 1 As shown, the specific steps include:

[0044] Step S1, placing porous carbon on a substrate in a first furnace chamber of a vapor deposition furnace, and placing a material containing doping elements in a second furnace chamber of the vapor deposition furnace;

[0045] The material containing doping elements includes one or more of glucose, ammonium chloride, melamine, red phosphorus, ammonium fluoride, boron oxide, ammonium sulfide, aluminum oxide, and ammonium chloride.

[0046] Step S2: Under a protective atmosphere, the temperature in the second furnace chamber of the vapor deposition furnace is raised to 600° C. to 950° C. to vaporize the material containing the doping element, and a gas containing the silicon element is introduced to obtain a mixed gas source; alternatively, a mixed gas containing the silicon element and the doping element is introduced into the second furnace chamber at a temperature of 600° C. to 950° C. via a carrier gas to obtain a mixed gas source;

[0047] The gas containing doping elements includes one or more of acetylene, propylene, methane, and ammonia;

[0048] The gas containing silicon element includes one or more of monosilane, disilane, chlorosilane, tetrafluorosilane, hexamethyldisilane, tris(trimethylsilyl)silane, and methylvinyldichlorosilane.

[0049] The protective atmosphere includes nitrogen atmosphere or argon atmosphere;

[0050] The carrier gas is nitrogen or argon; the flow rate of the carrier gas is 15L / min-65L / min.

[0051] Step S3, introducing the mixed gas source into the first furnace chamber and depositing it in the pores of the porous carbon to obtain a silicon-based negative electrode material;

[0052] The deposition time is 0.5 hours to 10 hours.

[0053] In an optional scheme, the above-mentioned preparation method also includes: performing carbon coating treatment on the silicon-based negative electrode material to form a carbon coating layer on the surface of the silicon-based negative electrode material; the carbon coating treatment method includes: one of gas phase coating, liquid phase coating or solid phase coating; the mass of the carbon coating layer accounts for 0%-20% of the total mass of the silicon-based negative electrode material, preferably 0%-10%.

[0054] In the present invention, a chemical bond is formed between the silicon and the doping element in the silicon-carbon matrix of the silicon-based negative electrode material prepared above. This chemical bond is a covalent bond, and its formation mechanism is: when the same or different non-metallic element atoms in the silicon-carbon matrix meet, under certain temperature conditions, the outermost electron configuration of the atoms has not reached a stable state, and the atoms are likely to form covalent bonds through shared electron pairs.

[0055] In the present invention, the temperature in the second furnace chamber of the vapor deposition furnace in step S2 is 600°C.

[0056] -950℃, for example, it can be 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, but it is not limited to the listed temperature values. Other values ​​not listed in this temperature range are also applicable. The inventors found that within this temperature range, chemical bonds are easily formed between silicon and doping elements. In addition, if the temperature is higher than 950℃, silicon and carbon are likely to form a SiC phase, resulting in a decrease in material performance. The silicon-based negative electrode material prepared by the above preparation method of the embodiment of the present invention can be used as a negative electrode material active substance to prepare a negative electrode plate for a lithium battery.

[0057] The negative electrode sheet of the present invention also includes a negative electrode current collector. The present invention has no particular limitation on the negative electrode current collector as long as it can achieve the purpose of the present application. For example, it may include but is not limited to copper foil, copper alloy foil, nickel foil, stainless steel foil or a composite current collector.

[0058] In the present invention, the negative electrode sheet may further include a conductive agent. The present invention has no particular limitation on the conductive agent, as long as the purpose of the present application can be achieved.

[0059] Lithium batteries assembled using the negative electrode sheet containing the silicon-based negative electrode material of the present invention include, but are not limited to: lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries or lithium ion polymer secondary batteries.

[0060] The silicon-based negative electrode material obtained by the present invention is different from the material obtained by the traditional mechanical mixing method. Through vapor deposition, the doping elements can be evenly distributed in the material at the atomic level. On the one hand, at a certain temperature, chemical bonds are formed between the doping elements and silicon, which can stabilize the material structure and inhibit volume expansion. On the other hand, the doping elements can also improve the electrical conductivity of the material itself and enhance the material's cycling and fast charging performance.

[0061] In order to better understand the technical solution provided by the present invention, the preparation process and characteristics of the silicon-based negative electrode material of the present invention are respectively described below with multiple specific examples.

[0062] Example 1

[0063] This embodiment provides a preparation process and performance test of a silicon-based negative electrode material. The specific process is as follows:

[0064] (1) 1 kg of porous carbon was placed on a substrate in the first chamber of a vapor deposition furnace, and 200 g of carbon black was placed in the second chamber of the vapor deposition furnace. The porous carbon had a porosity of 65%, a particle size Dv50 of 15 μm, and a specific surface area of ​​1000 m 2 / g.

[0065] (2) Under a nitrogen atmosphere, the temperature in the second furnace chamber of the vapor deposition furnace was raised to 600°C to gasify the carbon black, and monosilane was introduced into the second furnace chamber by nitrogen at a flow rate of 25 L / min for 4 hours to obtain a mixed gas source.

[0066] (3) The mixed gas source is introduced into the first furnace chamber, cooled and deposited in the pores of the porous carbon. The deposition time is 3 hours, and a silicon-based negative electrode material with Si and C deposited in the pores is obtained.

[0067] The silicon-based negative electrode material prepared in this embodiment was subjected to carbon coating treatment. The specific process was as follows: 1 kg of silicon-based negative electrode material was placed in a rotary kiln, heated to 800°C under an argon atmosphere, and argon and acetylene gas were introduced at a volume ratio of 3:1 for vapor phase coating. After keeping warm for 125 minutes, the gas source was turned off, and the material was discharged after cooling to room temperature to obtain a silicon-based negative electrode material containing a carbon coating layer.

[0068] XPS analysis of the silicon-carbon material prepared in this embodiment, which has carbon atoms uniformly distributed at the atomic level, yielded a C1s spectrum. Peak fitting revealed a Si-C binding peak at 283.35 eV.

[0069] The silicon-based negative electrode material containing a carbon coating layer prepared in this embodiment was used to prepare a negative electrode sheet and assembled into a button-type half-cell for testing. The specific process is as follows.

[0070] The silicon-based negative electrode material containing a carbon coating layer, the conductive additive carbon black, and the adhesive (sodium carboxymethyl cellulose and styrene-butadiene rubber in a mass ratio of 1:1) were weighed according to a mass ratio of 93%:3%:4%, and the slurry was prepared using a beater. After that, the slurry was coated, dried, and cut into pieces, and assembled into button-type half-cells in a glove box.

[0071] The assembly of the button half-cell was carried out in a glove box filled with argon atmosphere, using metallic lithium as the counter electrode and a solution of 1 mol of LiPF6 in ethylene carbonate (EC) / diethyl carbonate (DEC) (v:v=1:1) as the electrolyte to assemble the half-cell.

[0072] A constant current charge and discharge mode test was performed using a charge and discharge instrument. The discharge cut-off voltage was 0.005V and the charge cut-off voltage was 2V. The first week of charge and discharge tests was performed at a current density of C / 10, and subsequent cycle tests were performed at a current density of 4C.

[0073] The test data of the first-week coulombic efficiency, initial reversible capacity, and cycle capacity retention rate of the button half-cell after 100 and 500 cycles at a 4C rate are shown in Table 1.

[0074] Example 2

[0075] This embodiment provides a preparation process and performance test of a silicon-based negative electrode material. The specific process is as follows:

[0076] (1) 1.2 kg of porous carbon was placed on a substrate in a first furnace chamber of a vapor deposition furnace, and 300 g of melamine was placed in a second furnace chamber of the vapor deposition furnace.

[0077] (2) Under a nitrogen atmosphere, the temperature in the second furnace chamber of the vapor deposition furnace was raised to 700°C to vaporize the melamine, and disilane was introduced into the second furnace chamber by nitrogen at a flow rate of 25 L / min for 4 hours to obtain a mixed gas source.

[0078] (3) The mixed gas source is introduced into the first furnace chamber, cooled and deposited in the pores of the porous carbon for 3 hours to obtain a silicon-based negative electrode material with Si and N deposited in the pores.

[0079] The silicon-based negative electrode material prepared in this embodiment was subjected to carbon coating treatment. The specific process was as follows: 1 kg of silicon-based negative electrode material was placed in a rotary kiln, heated to 550°C under an argon atmosphere, and argon and propane gases were introduced at a volume ratio of 2:1 for vapor phase coating. After keeping warm for 150 minutes, the gas source was turned off and the material was discharged after cooling to room temperature to obtain a silicon-based negative electrode material containing a carbon coating layer.

[0080] XPS analysis of the silicon-carbon material prepared in this embodiment, which has nitrogen atoms uniformly distributed at the atomic level, yielded an N1s spectrum. Peak fitting revealed a Si-N binding peak at 398.0 eV.

[0081] The silicon-based negative electrode material containing a carbon coating layer prepared in this example was used to prepare a negative electrode sheet and assembled into a button half-cell for testing. The assembly and testing processes were the same as in Example 1. The test data are detailed in Table 1.

[0082] Example 3

[0083] This embodiment provides a preparation process and performance test of a silicon-based negative electrode material. The specific process is as follows:

[0084] (1) 1.3 kg of porous carbon was placed on a substrate in the first furnace chamber of a vapor deposition furnace, and 330 g of black phosphorus was placed in the second furnace chamber of the vapor deposition furnace.

[0085] (2) Under a nitrogen atmosphere, the temperature in the second furnace chamber of the vapor deposition furnace was raised to 950°C to vaporize the black phosphorus, and hexamethyldisilane was introduced into the second furnace chamber by nitrogen at a flow rate of 25 L / min for 4 hours to obtain a mixed gas source.

[0086] (3) The mixed gas source is introduced into the first furnace chamber, cooled and deposited in the pores of the porous carbon. The deposition time is 3 hours, and a silicon-based negative electrode material with Si and P deposited in the pores is obtained.

[0087] The silicon-based negative electrode material prepared in this embodiment was subjected to carbon coating treatment. The specific process was as follows: the silicon-based negative electrode material and petroleum asphalt were mixed in a mass ratio of 20:3, placed in a high-temperature furnace, and heat treated at 940°C in a nitrogen atmosphere for 2 hours. After cooling to room temperature, the material was discharged to obtain a silicon-based negative electrode material containing a carbon coating layer.

[0088] XPS analysis of the silicon-carbon material prepared in this example, which has atomically uniformly distributed phosphorus atoms, yielded a P 2p spectrum. Peak fitting revealed a Si-P binding peak at 134.6 eV.

[0089] The silicon-based negative electrode material containing a carbon coating layer prepared in this embodiment was used to prepare a negative electrode sheet and assembled into a button half-cell for testing. The assembly and testing process were the same as in Example 1. The test data are detailed in Table 1.

[0090] Example 4

[0091] This embodiment provides a preparation process and performance test of a silicon-based negative electrode material. The specific process is as follows:

[0092] (1) 2 kg of porous carbon was placed on a substrate in the first chamber of a vapor deposition furnace, and 150 g of boron oxide was placed in the second chamber of the vapor deposition furnace.

[0093] (2) Under a nitrogen atmosphere, the temperature in the second furnace chamber of the vapor deposition furnace was raised to 950°C to vaporize the boron oxide, and tetrafluorosilane was introduced into the second furnace chamber by nitrogen at a flow rate of 25 L / min for 4 hours to obtain a mixed gas source.

[0094] (3) The mixed gas source is introduced into the first furnace chamber, cooled and deposited in the pores of the porous carbon for 3 hours, and a silicon-based negative electrode material with Si and B deposited in the pores is obtained.

[0095] The silicon-based negative electrode material prepared in this example was subjected to carbon coating treatment. The specific process was as follows: 1 kg of silicon-based negative electrode material was placed in a rotary kiln, heated to 750°C under an argon atmosphere, and a mixed gas of argon, natural gas, and propylene was introduced at a volume ratio of 5:3 for gas phase coating, wherein the volume ratio of natural gas to propylene was 3:2. After keeping the temperature for 120 minutes, the gas source was turned off.

[0096] XPS analysis of the silicon-carbon material prepared in this example, which has atomically uniformly distributed boron atoms, yielded a B1s spectrum. Peak fitting revealed a Si-B binding peak at 188.5 eV.

[0097] The silicon-based negative electrode material containing a carbon coating layer prepared in this embodiment was used to prepare a negative electrode sheet and assembled into a button half-cell for testing. The assembly and testing process were the same as in Example 1. The test data are detailed in Table 1.

[0098] Example 5

[0099] This embodiment provides a preparation process and performance test of a silicon-based negative electrode material. The specific process is as follows:

[0100] (1) 2 kg of porous carbon was placed on a substrate in the first chamber of a vapor deposition furnace, and 400 g of ammonium fluoride was placed in the second chamber of the vapor deposition furnace.

[0101] (2) Under a nitrogen atmosphere, the temperature in the second furnace chamber of the vapor deposition furnace was raised to 700°C to vaporize the ammonium fluoride, and chlorosilane was introduced into the second furnace chamber by nitrogen at a flow rate of 25 L / min for 4 hours to obtain a mixed gas source.

[0102] (3) The mixed gas source is introduced into the first furnace chamber, cooled and deposited in the pores of the porous carbon for 3 hours to obtain a silicon-based negative electrode material with Si, F, and N deposited in the pores.

[0103] The silicon-based anode material prepared in this example was carbon-coated. The specific process was as follows: 1 kg of silicon-based anode material and graphene were dissolved in ethanol at a ratio of 15:2 and stirred for 6 hours to achieve a uniform slurry. The slurry was then dried and placed in a rotary kiln. The temperature was raised to 800°C in a protective atmosphere, maintained for 1 hour, and then cooled to room temperature before being discharged. This yielded a silicon-based anode material with a carbon coating.

[0104] XPS analysis of the silicon-carbon material with atomically uniformly distributed fluorine atoms prepared in this example yielded F1s and N1s spectra. Peak fitting revealed a Si-F binding peak at 686.0 eV in the F 1s spectrum and a Si-N binding peak at 398.0 eV in the N 1s spectrum.

[0105] The silicon-based negative electrode material containing a carbon coating layer prepared in this embodiment was used to prepare a negative electrode sheet and assembled into a button half-cell for testing. The assembly and testing process were the same as in Example 1. The test data are detailed in Table 1.

[0106] Example 6

[0107] This embodiment provides a preparation process and performance test of a silicon-based negative electrode material. The specific process is as follows:

[0108] (1) 1.2 kg of porous carbon was placed on a substrate in the first furnace chamber of a vapor deposition furnace, and 100 g of aluminum oxide was placed in the second furnace chamber of the vapor deposition furnace.

[0109] (2) Under a nitrogen atmosphere, the temperature in the second furnace chamber of the vapor deposition furnace was raised to 950°C to vaporize the aluminum oxide, and monosilane was introduced into the second furnace chamber by nitrogen at a flow rate of 25 L / min for 4 hours to obtain a mixed gas source.

[0110] (3) The mixed gas source is introduced into the first furnace chamber, cooled and deposited in the pores of the porous carbon. The deposition time is 3 hours, and a silicon-based negative electrode material with Si and Al deposited in the pores is obtained.

[0111] The silicon-based negative electrode material prepared in this example was subjected to carbon coating. The specific process was as follows: 2 kg of the material was placed in a rotary kiln and heated to 1000°C under an argon atmosphere. Argon and a mixture of propylene and methane in equal amounts were introduced at a volume ratio of 1:1 for vapor phase coating, with the volume ratio of propylene to methane being 2:3. After cooling to room temperature, the material was discharged to obtain a silicon-based negative electrode material with a carbon coating layer.

[0112] XPS analysis of the silicon-carbon material prepared in this example, which has aluminum atoms uniformly distributed at the atomic level, yielded an Al 2p spectrum. Peak fitting revealed a Si-Al binding peak at 75.3 eV.

[0113] The silicon-based negative electrode material containing a carbon coating layer prepared in this embodiment was used to prepare a negative electrode sheet and assembled into a button half-cell for testing. The assembly and testing process were the same as in Example 1. The test data are detailed in Table 1.

[0114] Example 7

[0115] This embodiment provides a preparation process and performance test of a silicon-based negative electrode material. The specific process is as follows:

[0116] (1) 2 kg of porous carbon was placed on a substrate in the first furnace chamber of a vapor deposition furnace, and 200 g of ammonium sulfide was placed in the second furnace chamber of the vapor deposition furnace.

[0117] (2) Under a nitrogen atmosphere, the temperature in the second furnace chamber of the vapor deposition furnace was raised to 600°C to vaporize the ammonium sulfide, and disilane was introduced into the second furnace chamber through nitrogen at a flow rate of 25 L / min for 4 hours to obtain a mixed gas source.

[0118] (3) The mixed gas source is introduced into the first furnace chamber, cooled and deposited in the pores of the porous carbon for 3 hours to obtain a silicon-based negative electrode material with Si, S, and N deposited in the pores.

[0119] XPS analysis of the silicon-carbon material prepared in this example, which contained uniformly distributed atomically distributed sulfur atoms, yielded S2p and N1s spectra. Peak fitting revealed a Si-S binding peak at 162.4 eV in the S2p spectrum and a Si-N binding peak at 398.0 eV in the N1s spectrum.

[0120] The silicon-based negative electrode material containing a carbon coating layer prepared in this embodiment was used to prepare a negative electrode sheet and assembled into a button half-cell for testing. The assembly and testing process were the same as in Example 1. The test data are detailed in Table 1.

[0121] Example 8

[0122] This embodiment provides a preparation process and performance test of a silicon-based negative electrode material. The specific process is as follows:

[0123] (1) 1.2 kg of porous carbon was placed on a substrate in the first furnace chamber of a vapor deposition furnace, and 160 g of ammonium chloride was placed in the second furnace chamber of the vapor deposition furnace.

[0124] (2) Under a nitrogen atmosphere, the temperature in the second furnace chamber of the vapor deposition furnace was raised to 950°C to vaporize the ammonium chloride, and fluorosilane was introduced into the second furnace chamber by nitrogen at a flow rate of 25 L / min for 4 hours to obtain a mixed gas source.

[0125] (3) The mixed gas source is introduced into the first furnace chamber, cooled and deposited in the pores of the porous carbon for 3 hours to obtain a silicon-based negative electrode material with Si, Cl, and N deposited in the pores.

[0126] XPS analysis of the silicon-carbon material prepared in this example, which has uniformly distributed chlorine and nitrogen atoms at the atomic level, yielded Cl 2p and N 1s spectra. Peak fitting revealed a Si-Cl binding peak at 201.7 eV in the Cl 2p spectrum and a Si-N binding peak at 398.0 eV in the N 1s spectrum.

[0127] The silicon-based negative electrode material containing a carbon coating layer prepared in this embodiment was used to prepare a negative electrode sheet and assembled into a button half-cell for testing. The assembly and testing process were the same as in Example 1. The test data are detailed in Table 1.

[0128] In order to better illustrate the effects of the embodiments of the present invention, Comparative Example 1 is compared with the above embodiments.

[0129] Comparative Example 1

[0130] This comparative example provides a preparation process and performance test of a silicon-carbon composite material. The specific process is: 1.2 kg of porous carbon is placed on a substrate in the first furnace chamber of a vapor deposition furnace. Under a nitrogen atmosphere, the temperature in the first furnace chamber of the vapor deposition furnace is raised to 700°C. Monosilane is introduced into the first furnace chamber through nitrogen to deposit silicon in the pores of the porous carbon, thereby obtaining a silicon-carbon composite material with Si deposited in the pores.

[0131] The prepared silicon-carbon composite material is carbon-coated, specifically: 1 kg of the silicon-carbon composite material is placed in a rotary kiln, the temperature is raised to 900°C under an argon atmosphere, argon and ethylene gas are introduced at a volume ratio of 3:1 for gas phase coating, the heat is kept for 3 hours, the gas source is turned off, and the material is discharged and classified after cooling to room temperature to obtain a silicon-carbon composite material containing a carbon coating layer.

[0132] The silicon-carbon composite material containing a carbon coating layer prepared in this comparative example was used to prepare a negative electrode sheet and assembled into a button half-cell for testing. The assembly and testing processes were the same as in Example 1. The test data are detailed in Table 1.

[0133] Table 1 is a summary of the test data of the first-week coulombic efficiency, initial reversible capacity, and cycle capacity retention rate after 100 and 500 cycles at a 4C rate of the button batteries assembled in Example 1 and Comparative Example 1.

[0134]

[0135]

[0136] Table 1

[0137] By comparing the test data in Table 1, it can be seen that under the same test conditions, the first-week coulombic efficiency and initial reversible capacity of the button batteries of Examples 1-6 are similar to the test data of Comparative Example 1, and the initial efficiency of Examples 7-8 is lower. This is because the carbon coating formed on the surface of the silicon-based negative electrode material in Examples 1-6 can effectively limit the direct contact between the electrolyte and silicon, reduce the irreversible capacity caused by the first lithium insertion and extraction, and improve the first coulombic efficiency. In addition, the button batteries prepared in Examples 1-8 have a higher cycle capacity retention rate after 100 cycles and 400 cycles at a 4C rate than Comparative Example 1. This is because the doping elements are combined with silicon through chemical bonds. The bond energy of the chemical bonds constrains silicon during the battery formation process, which can effectively alleviate the volume expansion of the material and stabilize the structure of the material. In addition, the doping elements uniformly dispersed in the bulk phase can also improve the ionic conductivity of the material, thereby improving the cycle performance of the battery.

[0138] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A silicon-based negative electrode material, characterized in that: The silicon-based negative electrode material comprises: a silicon-carbon matrix, and doping elements uniformly distributed in the silicon-carbon matrix at the atomic level; The silicon-carbon matrix includes porous carbon and silicon uniformly distributed in the pores and on the surface of the porous carbon; The doping element includes one or more of C, N, B, F, S, Cl, Al, and P; a chemical bond is formed between the silicon in the silicon-carbon matrix and the doping element; The average particle size Dv50 of the silicon-based negative electrode material particles is 1nm-100μm, and the specific surface area is 0.5m 2 / g-45m 2 / g; the mass of the doping element accounts for 0.1%-15% of the mass of the silicon-carbon matrix.

2. The silicon-based negative electrode material according to claim 1, characterized in that The porosity of the porous carbon is 35%-90%; the pore diameter of the porous carbon is 1nm-10nm; The average particle size Dv50 of the porous carbon is 5 μm-20 μm; the specific surface area of ​​the porous carbon is 500 m 2 / g-3000m 2 / g.

3. The silicon-based negative electrode material according to claim 1, characterized in that The mass percentage of the silicon to the mass percentage of the silicon-based negative electrode material is 30%-70%.

4. The silicon-based negative electrode material according to claim 1, characterized in that The outer surface of the silicon-based negative electrode material further has a carbon coating layer; the mass of the carbon coating layer accounts for 0%-20% of the total mass of the silicon-based negative electrode material.

5. A method for preparing the silicon-based negative electrode material according to any one of claims 1 to 4, characterized in that: The preparation method comprises: Step S1, placing porous carbon on a substrate in a first furnace chamber of a vapor deposition furnace, and placing a material containing doping elements in a second furnace chamber of the vapor deposition furnace; Step S2: Under a protective atmosphere, the temperature in the second furnace chamber of the vapor deposition furnace is raised to 600° C. to 950° C. to vaporize the material containing the doping element, and a gas containing the silicon element is introduced to obtain a mixed gas source; alternatively, a mixed gas containing the silicon element and the doping element is introduced into the second furnace chamber at a temperature of 600° C. to 950° C. via a carrier gas to obtain a mixed gas source; Step S3: introducing the mixed gas source into the first furnace chamber and depositing it in the pores of the porous carbon to obtain a silicon-based negative electrode material.

6. The preparation method according to claim 5, characterized in that The material containing doping elements includes one or more of glucose, ammonium chloride, melamine, red phosphorus, ammonium fluoride, boron oxide, ammonium sulfide, aluminum oxide, and ammonium chloride; The gas containing doping elements includes one or more of acetylene, propylene, methane, and ammonia; The silicon-containing gas includes one or more of monosilane, disilane, chlorosilane, tetrafluorosilane, hexamethyldisilane, tris(trimethylsilyl)silane, and methylvinyldichlorosilane.

7. The preparation method according to claim 5, characterized in that The protective atmosphere includes nitrogen atmosphere or argon atmosphere; The carrier gas is nitrogen or argon; the flow rate of the carrier gas is 15L / min-65L / min; The deposition time in step S3 is 0.5 hours to 10 hours.

8. The preparation method according to claim 5, characterized in that The preparation method further comprises performing a carbon coating treatment on the silicon-based negative electrode material to form a carbon coating layer on the surface of the silicon-based negative electrode material; The carbon coating treatment method includes: any one of gas phase coating, liquid phase coating or solid phase coating.

9. A negative electrode plate, characterized in that: The negative electrode plate comprises the silicon-based negative electrode material according to any one of claims 1 to 4.

10. A lithium battery, characterized in that: The lithium battery includes the negative electrode sheet according to claim 9.

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