Silicon-based composite materials, their preparation methods and applications

Abstract

This invention discloses a silicon-based composite material, the general chemical formula of which is: Li x SiO y N z The parameters are: 0 < x < 20, 0 < y < 5, 0 < z < 10; lithium accounts for 2%–20% of the mass of the silicon-based composite material; nitrogen accounts for 0.1%–20% of the mass of the silicon-based composite material. Scanning electron microscopy of particle cross-sections shows that the microstructure of the silicon-based composite material is a multiphase dispersed structure, obtained by mixing gaseous raw materials, including gaseous silicon source material, gaseous lithium source material, and gaseous nitrogen source material. The average particle size D of the silicon-based composite material particles is... 50 Within the range of 1nm-100μm, the specific surface area is 0.5m². 2 / g-40m 2 The silicon-based anode material disclosed in this invention exhibits high initial coulombic efficiency and good cycle performance.

Description

TECHNICAL FIELD

[0001] The present application relates to a lithium ion battery negative electrode material, in particular to a silicon-based composite material and a preparation method and application thereof. BACKGROUND

[0002] Under the background of developing clean, efficient and sustainable energy, lithium ion batteries have become the focus of research in various countries because of their high energy density, long cycle life, high output voltage, green environmental protection and no memory effect. As one of the important components of lithium ion batteries, the performance of the negative electrode material directly affects the overall energy density of the battery. At present, the main negative electrode of lithium ion battery is graphite negative electrode, and its capacity has approached the theoretical specific capacity (372 mAh·g -1 Therefore, it is urgent to develop a negative electrode material with higher specific capacity.

[0003] Silicon is considered as a potential next-generation negative electrode material due to its excellent theoretical specific capacity (4200 mAh·g -1 ), suitable voltage platform (0.4 V vs. Li / Li+), abundant reserves in the earth's crust (26.4%), environmental friendliness and other advantages. Among them, silicon monoxide SiO x (0 < x < 2) as a form of silicon-based negative electrode has become one of the research hotspots of lithium ion battery negative electrode materials because of its high specific capacity, low charge-discharge potential, low volume expansion rate, low price and environmental friendliness. However, the silicon monoxide material generates Li2O and Li4SiO4 inactive products during lithium intercalation, which causes part of Li to lose activity, resulting in low first efficiency, generally only about 70%, and inevitable volume expansion during charge and discharge, which makes SiO x still faces the problems of material pulverization and poor electrical conductivity.

[0004] Carbon coating is the most common material modification method. Carbon coating of the material can provide a stable chemical and electrochemical reaction interface, avoid direct contact of the electrolyte with SiO x , and buffer the volume change of SiO x particles during lithium deintercalation. On the other hand, it can improve the electrical conductivity of the material surface. However, in order to achieve fast charging performance, the electrical conductivity of the particles also needs to be improved.

[0005] Compared with traditional modification methods, heteroatom doping can significantly change the elemental composition of silicon-based materials, control their surface activity, and improve their electrochemical performance. Among them, nitrogen atom is N-type doping, i.e. donor-type doping, and nitrogen atom can provide excess electrons, thereby increasing the carrier concentration and electrical conductivity, so that the nitrogen-doped silicon-based material exhibits excellent electrochemical performance. SUMMARY

[0006] The embodiment of the present application provides a silicon-based composite material and a preparation method and application thereof, aiming at uniformly dispersing nitrogen element, silicon element and lithium element by mixing gaseous nitrogen source material with gaseous raw material, and providing excess electrons by N type doping of nitrogen atoms, so as to improve carrier concentration and conductivity, and improve the first coulomb efficiency and cycle performance of the silicon-based composite material.

[0007] In a first aspect, the embodiment of the present application provides a silicon-based composite material, and a chemical general formula of the silicon-based composite material is Li x SiO y N z , 0 < x < 20, 0 < y < 5, 0 < z < 10; the mass of lithium element accounts for 2% to 20% of the mass of the silicon-based composite material; the mass of nitrogen element accounts for 0.1% to 20% of the mass of the silicon-based composite material;

[0008] The microstructure of the silicon-based composite material is a multiphase dispersion structure; the multiphase dispersion structure is obtained by mixing gaseous raw material; the gaseous raw material comprises gaseous silicon source material, gaseous lithium source material and gaseous nitrogen source material;

[0009] The average particle size D 50 of the silicon-based composite material particle is between 1 nm and 100 microns; the specific surface area is between 0.5 m 2 / g and 40 m 2 / g.

[0010] Preferably, the gaseous silicon source material comprises gaseous silicon powder and / or gaseous silicon dioxide;

[0011] The gaseous lithium source material comprises gaseous inorganic lithium source material and / or gaseous organic lithium source material;

[0012] The gaseous nitrogen source material comprises nitrogen-containing gas source and / or gaseous nitrogen-containing compound.

[0013] Preferably, the mass of the lithium element accounts for 5% to 15% of the mass of the silicon-based composite material; the mass of the nitrogen element accounts for 0.5% to 10% of the mass of the silicon-based composite material;

[0014] The silicon source material comprises silicon powder and / or silicon dioxide;

[0015] The lithium source material comprises inorganic lithium source material and / or organic lithium source material;

[0016] The inorganic lithium source material comprises one or more of lithium carbonate, lithium nitride, lithium phosphate, lithium manganate or metallic lithium;

[0017] The organic lithium source material comprises butyl lithium and / or phenyl lithium;

[0018] The nitrogen source material comprises: a nitrogen source and / or a nitrogen-containing compound;

[0019] The nitrogen source comprises: one or more of nitrogen, nitric oxide, nitrogen dioxide or ammonia.

[0020] The nitrogen-containing compound comprises: one or more of methylamine, carbamide, isocyanate or aniline.

[0021] Preferably, the outer layer of the silicon-based composite material has a carbon coating layer; the mass of the carbon coating layer accounts for 0%-20% of the mass of the silicon-based composite material.

[0022] In a second aspect, the present application provides a preparation method of the silicon-based composite material of the first aspect, and the preparation method comprises:

[0023] The silicon source material and the lithium source material are mixed uniformly in proportion, placed in a first furnace cavity, vacuumized to 60-180 Pa, heated to a temperature of 1000-2000 ℃, and a first gas source is obtained;

[0024] The first gas source is introduced into a second furnace cavity;

[0025] The gaseous nitrogen source material is used as a second gas source and is introduced into the second furnace cavity, so that the first gas source and the second gas source are mixed uniformly and react for 2-6 hours, and a mixed gas is obtained;

[0026] The mixed gas is cooled and deposited on a stainless steel substrate, and after the deposited material is crushed and sieved, a silicon-based composite material is obtained;

[0027] The silicon-based composite material is Li x SiO y N z , 0

[0028] The microstructure of the silicon-based composite material is a multiphase dispersion structure; the average particle size D 50 is 1 nm-100 μm, and the specific surface area is 0.5 m 2 / g-40 m 2 / g.

[0029] The gaseous nitrogen source material comprises: a nitrogen source and / or a gaseous nitrogen-containing compound; and the gaseous nitrogen-containing compound has a gasification temperature of 25-800 ℃.

[0030] Preferably, the lithium element accounts for 5-15% of the mass of the silicon-based composite material; and the nitrogen element accounts for 0.5-10% of the mass of the silicon-based composite material.

[0031] The silicon source material comprises silicon powder and / or silicon dioxide.

[0032] The lithium source material comprises inorganic lithium source material and / or organic lithium source material.

[0033] The inorganic lithium source material comprises one or more of lithium carbonate, lithium nitride, lithium phosphate, lithium manganese oxide or metallic lithium.

[0034] The organic lithium source material comprises butyl lithium and / or phenyl lithium.

[0035] The nitrogen source material comprises a nitrogen source and / or a nitrogen-containing compound.

[0036] The nitrogen source comprises one or more of nitrogen, nitric oxide, nitrogen dioxide or ammonia.

[0037] The nitrogen-containing compound comprises one or more of methylamine, carbamide, isocyanate or aniline.

[0038] Preferably, the preparation method further comprises carbon coating the silicon-based composite material; the mass of the carbon coating layer accounts for 0-20% of the mass of the silicon-based composite material; and the carbon coating method comprises one of gas-phase coating, liquid-phase coating or solid-phase coating.

[0039] Preferably, the mass of the carbon coating layer accounts for 0.5-10% of the mass of the silicon-based composite material.

[0040] In a third aspect, an embodiment of the present application provides a negative electrode sheet comprising the silicon-based composite material of the first aspect.

[0041] In a fourth aspect, an embodiment of the present application provides a lithium battery comprising the negative electrode sheet of the third aspect.

[0042] The silicon-based composite material provided by the present application uses a gaseous nitrogen source material mixed with a gaseous raw material to uniformly disperse the nitrogen element, silicon element and lithium element, and the nitrogen atom is N-type doped to provide excess electrons, thereby improving the carrier concentration and conductivity, and making the silicon-based composite material have high initial coulombic efficiency and good cycle performance. BRIEF DESCRIPTION OF DRAWINGS

[0043] The technical solutions of the embodiments of the present application are described in further detail below with reference to the drawings and examples.

[0044] Figure 1This is a flowchart of a method for preparing silicon-based composite materials provided in an embodiment of the present invention;

[0045] Figure 2a This is a focused ion beam scanning electron microscope (FIB-SEM) image of the interior of silicon-based composite material particles provided in Embodiment 1 of the present invention;

[0046] Figure 2b The image shows the FI B-SEM image of the Si element inside the silicon-based composite material particles provided in Embodiment 1 of the present invention.

[0047] Figure 2c The image shows the FI B-SEM image of the O element inside the silicon-based composite material particles provided in Embodiment 1 of the present invention.

[0048] Figure 2d This is a FI B-SEM image of the nitrogen element inside the silicon-based composite material particles provided in Embodiment 1 of the present invention. Detailed Implementation

[0049] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. However, it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any way, that is, not intended to limit the scope of protection of the present invention.

[0050] This invention provides a silicon-based composite material, the general chemical formula of which is: Li x SiO y N z , 0 < x < 20, 0 < y < 5, 0 < z < 10; lithium content of 2%-20% of the silicon-based composite material, preferably 5%-15%; nitrogen content of 0.1%-20% of the silicon-based composite material, preferably 0.5%-10%; average particle size D 50 Within the range of 1nm-100μm, the specific surface area is 0.5m². 2 / g-40m 2 Between / g.

[0051] The microstructure of the silicon-based composite material is a multiphase dispersed structure; the multiphase dispersed structure is obtained by mixing gaseous raw materials, including gaseous silicon source material, gaseous lithium source material and gaseous nitrogen source material;

[0052] Among them, the gaseous silicon source materials include: vaporized silicon powder and / or vaporized silicon dioxide;

[0053] Gaseous lithium source materials include: vaporized inorganic lithium source materials and / or vaporized organic lithium source materials;

[0054] Gaseous nitrogen source materials include: nitrogen-containing gas sources and / or vaporized nitrogen-containing compounds.

[0055] The outer layer of the silicon-based composite material further has a carbon coating layer; the mass of the carbon coating layer accounts for 0%-20% of the mass of the silicon-based composite material, preferably 0.5%-10%.

[0056] The embodiment provides a preparation method of a silicon-based composite material, comprising:

[0057] In step 110, the silicon source material and the lithium source material are uniformly mixed in proportion, are placed into a first furnace cavity, are vacuum-extracted to 60 Pa-180 Pa, and are heated at a temperature of 1000°C-2000°C to obtain a first gas source;

[0058] The silicon source material comprises silicon powder and / or silicon dioxide.

[0059] The lithium source material comprises inorganic lithium source material and / or organic lithium source material.

[0060] The inorganic lithium source material comprises one or more of lithium carbonate, lithium nitride, lithium phosphate, lithium manganese oxide or metallic lithium.

[0061] The organic lithium source material comprises butyl lithium and / or phenyl lithium.

[0062] In step 120, the first gas source is introduced into a second furnace cavity.

[0063] In step 130, gaseous nitrogen source material is introduced into the second furnace cavity as a second gas source, the first gas source and the second gas source are uniformly mixed and fully react for 2-6 hours to obtain a mixed gas.

[0064] The gaseous nitrogen source material comprises nitrogen-containing gas source and / or gasified nitrogen-containing compound, and the gasification temperature of the nitrogen-containing compound is 25°C-800°C.

[0065] The nitrogen source material comprises nitrogen-containing gas source and / or nitrogen-containing compound.

[0066] The nitrogen-containing gas source comprises one or more of nitrogen, nitric oxide, nitrogen dioxide or ammonia.

[0067] The nitrogen-containing compound comprises one or more of methylamine, carbamide, isocyanate or aniline.

[0068] In step 140, the mixed gas is cooled and deposited on a stainless steel substrate, and after the deposited material is crushed and screened, a silicon-based composite material is obtained.

[0069] The silicon-based composite material is Li x SiO y N z, 0 < x < 20, 0 < y < 5, 0 < z < 10; the mass of lithium element accounts for 2%-20% of the mass of the silicon-based composite material, preferably 5%-15%; the mass of nitrogen element accounts for 0.1%-20% of the mass of the silicon-based composite material, preferably 0.5%-10%; and the microstructure of the silicon-based composite material is a multiphase dispersion structure.

[0070] The preparation method of the silicon-based composite material provided in the embodiment further includes carbon coating of the silicon-based composite material, and the method of carbon coating 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 mass of the silicon-based composite material, preferably 0.5%-10%.

[0071] The embodiment provides a negative electrode tab including the silicon-based composite material, and the negative electrode tab can be applied to a lithium battery.

[0072] In order to better understand the technical solutions provided in the present application, the following describes the preparation process and characteristics of the silicon-based composite material in multiple specific examples.

[0073] Embodiment 1

[0074] The embodiment provides a preparation process, application and performance test of a silicon-based composite material.

[0075] The specific preparation process is as follows:

[0076] (1) 1 kg of silicon powder, 1 kg of silicon dioxide powder and 332 g of lithium nitride are uniformly mixed and placed in a first furnace cavity, vacuumized to 60 Pa, and heated to 1600 ℃, so that the raw materials are gasified after vacuum heating to obtain a first gas source.

[0077] (2) The first gas source is introduced into a second furnace cavity.

[0078] (3) Nitrogen is used as a second gas source, 5 L of nitrogen is slowly introduced into the second furnace cavity, the first gas source and the second gas source are uniformly mixed and fully reacted for 4 hours to obtain a mixed gas.

[0079] (4) The mixed gas is deposited on a stainless steel substrate, and after discharging, crushing and screening, a silicon-based composite material is obtained.

[0080] The silicon-based composite material prepared in the embodiment is tested by an organic element analyzer, and the nitrogen content is 2.5%.

[0081] The silicon-based composite material prepared in the embodiment is tested by FIB-SEM, and the distribution of Si, O and N elements in the particles is observed by energy spectrum detection, as shown in Figures 2a-2d It can be seen that the three elements of Si, O and N are uniformly distributed.

[0082] The silicon-based composite prepared in this embodiment is carbon-coated:

[0083] 2 kg of material is placed in a rotary furnace, heated to 800°C in an argon atmosphere, argon and propylene are introduced at a volume ratio of 1:1 for gas phase coating, and the organic gas source is turned off after 2 hours of heat preservation. After cooling and grading, the silicon-based composite with a carbon-coated layer is obtained, and the total carbon content is 3.3%.

[0084] The silicon-based composite with a carbon-coated layer prepared in this embodiment and internal lithium and nitrogen elements dispersedly distributed is used to make negative electrode sheets and assemble batteries for testing, and the specific process is as follows:

[0085] The silicon-based composite with a carbon-coated layer described above is used as a negative electrode material, and conductive carbon black (SP) and adhesive polyvinylidene fluoride (PVDF) are weighed in a mass ratio of 95:2:3. The slurry is prepared in a beater at room temperature. The prepared slurry is uniformly coated on a copper foil. After drying in a forced air drying oven at 50°C for 2 hours, the electrode sheet is cut into 8x8mm, and vacuum drying is carried out at 100°C for 10 hours in a vacuum drying oven. The dried electrode sheet is immediately transferred to a glove box for battery assembly.

[0086] The assembly of the battery is carried out in a glove box containing high-purity Ar atmosphere, using metallic lithium as the counter electrode, and a solution of 1 mole of LiPF6 in ethylene carbonate / dimethyl carbonate (EC / DMC v:v=1:1) as the electrolyte. The battery is assembled. The constant current charge and discharge mode test is carried out using a charge and discharge instrument, the discharge cut-off voltage is 0.005V, the charge cut-off voltage is 1.5V, the first week charge and discharge test is carried out at C / 10 current density, and the second week discharge test is carried out at C / 10 current density. The test data are shown in Table 1.

[0087] Example 2

[0088] This embodiment provides a preparation process, application and performance test of a silicon-based composite.

[0089] The specific preparation process is as follows:

[0090] (1) Mix 1 kg of silicon powder, 1 kg of silicon dioxide powder and 1.1 kg of lithium phosphate uniformly, place in the first furnace cavity, vacuum to 60 Pa, heat to 1600°C, and the raw materials are gasified after vacuum heating to obtain a first gas source.

[0091] (2) Introduce the first gas source into the second furnace cavity.

[0092] (3) Nitrogen dioxide is used as a second gas source, and 22.5L of nitrogen dioxide is slowly introduced into the second furnace cavity. The first gas source and the second gas source are mixed uniformly and fully reacted for 4 hours to obtain a mixed gas.

[0093] (4) The mixed gas is deposited on a stainless steel substrate, and after discharging, crushing and screening, a silicon-based composite material is obtained.

[0094] The silicon-based composite material prepared in this embodiment is tested by an organic element analyzer, and the nitrogen content is 4.5%.

[0095] The silicon-based composite material prepared in this embodiment is carbon-coated:

[0096] 2 kg of material is placed in a rotary furnace, heated to 900 DEG C in an argon atmosphere, and argon and a mixed gas of argon and methane in a volume ratio of 1:1 are introduced for gas phase coating, wherein the volume ratio of acetylene and methane is 3:1. After 3 hours of heat preservation, the organic gas source is closed, and after cooling, discharging and grading, a silicon-based composite material with a carbon-coated layer is obtained, wherein the total carbon content is 4.2%.

[0097] The silicon-based composite material prepared in this embodiment is used to make a negative electrode sheet and assemble a battery for testing, and the specific process is the same as that of Example 1. The test data is shown in Table 1.

[0098] Example 3

[0099] This embodiment provides a preparation process, application and performance test of a silicon-based composite material.

[0100] The specific preparation process is as follows:

[0101] (1) 1 kg of silicon powder, 1 kg of silicon dioxide powder and 1 kg of lithium carbonate are mixed uniformly and placed in a first furnace cavity, vacuumized to 90 Pa, and heated to 1450 DEG C. After vacuum heating, the raw materials are gasified to obtain a first gas source.

[0102] (2) The first gas source is introduced into a second furnace cavity.

[0103] (3) Nitric oxide is used as a second gas source, and 19.8 L of nitric oxide is slowly introduced into the second furnace cavity. The first gas source and the second gas source are mixed uniformly and fully reacted for 6 hours to obtain a mixed gas.

[0104] (4) The mixed gas is deposited on a stainless steel substrate, and after discharging, crushing and screening, a silicon-based composite material is obtained.

[0105] The silicon-based composite material prepared in this embodiment is tested by an organic element analyzer, and the nitrogen content is 6.1%.

[0106] The silicon-based composite material prepared in this embodiment is carbon-coated:

[0107] 2kg material is placed in a rotary furnace, heated to 800℃ in argon atmosphere, argon and acetylene are introduced at a volume ratio of 1:1 for gas phase coating. After 4 hours of heat preservation, the organic gas source is turned off, the material is cooled and graded, and the silicon-based composite material with carbon coating layer is obtained, wherein the total carbon content is 4.7%.

[0108] The silicon-based composite material with carbon coating layer and internal lithium and nitrogen elements dispersedly distributed prepared in this example is used to make negative electrode sheets and assemble batteries for testing. The specific process is the same as that in Example 1. The test data are shown in Table 1.

[0109] Example 4

[0110] This example provides a preparation process, application and performance test of a silicon-based composite material.

[0111] The specific preparation process is as follows:

[0112] (1) 1kg of silicon powder, 1kg of silicon dioxide powder and 2.4kg of phenyllithium are mixed uniformly, placed in a first furnace cavity, vacuumized to 120Pa, and heated to 1250℃. The raw materials are gasified after vacuum heating to obtain a first gas source.

[0113] (2) The first gas source is introduced into a second furnace cavity.

[0114] (3) Ammonia is used as a second gas source, 4L of ammonia is slowly introduced into the second furnace cavity, the first gas source and the second gas source are mixed uniformly and fully reacted for 5 hours to obtain a mixed gas.

[0115] (4) The mixed gas is deposited on a stainless steel substrate, and after discharging, crushing and sieving, a silicon-based composite material is obtained.

[0116] The silicon-based composite material prepared in this example is tested by an organic element analyzer, and the nitrogen content is 0.5%.

[0117] The silicon-based composite material prepared in this example is carbon-coated:

[0118] 2kg of material is mixed with petroleum pitch at a mass ratio of 12:1, placed in a high-temperature furnace, heat-treated at 1200℃ in a nitrogen atmosphere for 3 hours, and after cooling and grading, a silicon-based composite material with carbon coating layer is obtained, wherein the total carbon content is 5.8%.

[0119] The silicon-based composite material with carbon coating layer and internal lithium and nitrogen elements dispersedly distributed prepared in this example is used to make negative electrode sheets and assemble batteries for testing. The specific process is the same as that in Example 1. The test data are shown in Table 1.

[0120] Example 5

[0121] The embodiment provides a preparation process and application and performance test of a silicon-based composite material.

[0122] The specific preparation process is as follows:

[0123] (1) 1 kg of silicon powder, 1 kg of silicon dioxide powder and 1.8 kg of butyl lithium are uniformly mixed, placed in a first furnace cavity, vacuumized to 150 Pa, heated to 1700 DEG C, and after the raw materials are gasified by vacuum heating, a first gas source is obtained.

[0124] (2) The first gas source is introduced into a second furnace cavity.

[0125] (3) 60 L of isocyanate is gasified at 380 DEG C as a second gas source, the gasified isocyanate is slowly introduced into the second furnace cavity, the first gas source and the second gas source are uniformly mixed and fully reacted for 4.5 hours, and a mixed gas is obtained.

[0126] (4) The mixed gas is deposited on a stainless steel substrate, and after discharging, crushing and screening, a silicon-based composite material is obtained.

[0127] The silicon-based composite material prepared in the embodiment is tested by an organic element analyzer, and the nitrogen content is 7.6%.

[0128] The silicon-based composite material prepared in the embodiment is carbon-coated.

[0129] 2 kg of material is mixed with petroleum pitch at a mass ratio of 10:1, placed in a high-temperature furnace, heat-treated at 1400 DEG C in a nitrogen atmosphere for 2 hours, and after cooling, discharging and grading, a silicon-based composite material with a carbon-coated layer is obtained, and the total carbon content is 5.2%.

[0130] The silicon-based composite material prepared in the embodiment is used to prepare a negative electrode sheet and assemble a battery for testing, and the specific process is the same as that in embodiment 1. The test data are shown in Table 1.

[0131] Embodiment 6

[0132] The embodiment provides a preparation process and application and performance test of a silicon-based composite material.

[0133] The specific preparation process is as follows:

[0134] (1) 1 kg of silicon powder, 1 kg of silicon dioxide powder and 5 kg of lithium manganate are uniformly mixed and placed in a furnace cavity A, vacuumized to 180 Pa, heated to 1700 DEG C, and after the raw materials are gasified by vacuum heating, a first gas source is obtained.

[0135] (2) The first gas source is introduced into a second furnace cavity.

[0136] (3) 1 kg of carbonamide is vaporized at 560°C and used as a second gas source. The vaporized carbonamide is slowly introduced into the second furnace chamber. The first gas source and the second gas source are mixed evenly and reacted fully for 5.5 hours to obtain a mixed gas.

[0137] (4) The mixed gas is cooled and deposited on a stainless steel substrate, and after discharge, crushing and sieving, a silicon-based composite material is obtained.

[0138] The silicon-based composite material prepared in this embodiment was tested using an organic elemental analyzer, and the nitrogen content was found to be 9.7%.

[0139] The silicon-based composite material prepared in this embodiment is carbon-coated:

[0140] 2 kg of material and graphene were dissolved in ethanol at a ratio of 15:1 and stirred for 8 hours to form a homogeneous slurry. The slurry was then dried directly and placed in a high-temperature furnace. The mixture was sintered at 1000°C under a nitrogen protective atmosphere for 2 hours. After cooling and grading, a silicon-based composite material with a carbon coating layer was obtained, in which the total carbon content was 3.5%.

[0141] The silicon-based composite material with a carbon-containing coating layer and dispersed lithium and nitrogen elements prepared in this embodiment was used to fabricate the negative electrode sheet and assemble the battery for testing. The specific process is the same as in Example 1. Test data are detailed in Table 1.

[0142] Example 7

[0143] This embodiment provides a preparation process, application, and performance testing of a silicon-based composite material.

[0144] The specific preparation process is as follows:

[0145] (1) Mix 1kg silicon powder, 1kg silicon dioxide powder and 10g lithium metal evenly, place them in the first furnace chamber, evacuate to 120Pa, heat to 1500℃, and the raw materials are vaporized after vacuum heating to obtain the first gas source.

[0146] (2) Introduce the first gas source into the second furnace chamber.

[0147] (3) Using methylamine as the second gas source, 43L of methylamine is slowly introduced into the second furnace chamber. The first gas source and the second gas source are mixed evenly and reacted fully for 2 hours to obtain a mixed gas.

[0148] (4) The mixed gas is cooled and deposited on a stainless steel substrate, and after discharge, crushing and sieving, a silicon-based composite material is obtained.

[0149] The silicon-based composite material prepared in this embodiment was tested using an organic elemental analyzer, and the nitrogen content was found to be 8%.

[0150] The silicon-based composite material prepared in this embodiment is carbon-coated:

[0151] 2 kg of material and phenolic resin were dissolved in tetrahydrofuran at a ratio of 18:1 and stirred for 5 hours to form a homogeneous slurry. The slurry was then dried directly and placed in a high-temperature furnace. The mixture was sintered at 900°C under a nitrogen protective atmosphere for 4 hours. After cooling and grading, a silicon-based composite material with a carbon coating layer was obtained, in which the total carbon content was 4%.

[0152] The negative electrode sheet was fabricated using the carbon-containing coating layer prepared in this embodiment, with lithium and nitrogen elements dispersed internally in the silicon-based composite material, and the battery was assembled and tested. The specific process is the same as in Example 1. Test data are detailed in Table 1.

[0153] Example 8

[0154] This embodiment provides a preparation process, application, and performance testing of a silicon-based composite material.

[0155] The specific preparation process is as follows:

[0156] (1) Mix 1kg silicon powder, 1kg silicon dioxide powder and 800g lithium carbonate evenly, place them in the first furnace chamber, evacuate to 150Pa, heat to 1500℃, and the raw materials are vaporized after vacuum heating to obtain the first gas source.

[0157] (2) Introduce the first gas source into the second furnace chamber.

[0158] (3) 50L of aniline is vaporized at 200℃ and used as the second gas source. The vaporized aniline is slowly introduced into the second furnace chamber. The first gas source and the second gas source are mixed evenly and reacted fully for 5 hours to obtain a mixed gas.

[0159] (4) The mixed gas is cooled and deposited on a stainless steel substrate, and after discharge, crushing and sieving, a silicon-based composite material is obtained.

[0160] The silicon-based composite material prepared in this embodiment was tested using an organic elemental analyzer, and the nitrogen content was found to be 7.8%.

[0161] The silicon-based composite material prepared in this embodiment is carbon-coated:

[0162] Two kilograms of material were placed in a rotary kiln and heated to 700°C under a protective argon atmosphere. Argon and an equal volume of acetylene-propane were introduced at a volume ratio of 1:2 for gas-phase coating. The volume ratio of acetylene to propane was 3:2. After holding at this temperature for 2 hours, the organic gas source was turned off. The material was then cooled, discharged, and graded to obtain a silicon-based composite material with a carbon coating layer, containing a total carbon content of 4.2%.

[0163] The silicon-based composite material with a carbon-containing coating layer and dispersed lithium and nitrogen elements prepared in this embodiment was used to fabricate the negative electrode sheet and assemble the battery for testing. The specific process is the same as in Example 1. Test data are detailed in Table 1.

[0164] Example 9

[0165] This embodiment provides a preparation process, application, and performance testing of a silicon-based composite material.

[0166] The specific preparation process is as follows:

[0167] (1) Mix 1kg silicon powder, 1kg silicon dioxide powder and 500g lithium nitride evenly, place them in the first furnace chamber, evacuate to 100Pa, heat to 1800℃, and the raw materials are vaporized after vacuum heating to obtain the first gas source.

[0168] (2) Introduce the first gas source into the second furnace chamber.

[0169] (3) Using ammonia as the second gas source, slowly introduce 25L of ammonia into the second furnace chamber. The first gas source and the second gas source are mixed evenly and reacted fully for 3 hours to obtain a mixed gas.

[0170] (4) The mixed gas is cooled and deposited on a stainless steel substrate, and after discharge, crushing and sieving, a silicon-based composite material is obtained.

[0171] The silicon-based composite material prepared in this embodiment was tested using an organic elemental analyzer, and the nitrogen content was found to be 8.1%.

[0172] The silicon-based composite material prepared in this embodiment is carbon-coated:

[0173] 2 kg of material was mixed with asphalt emulsion at a mass ratio of 12:1 and stirred for 3 hours to form a uniform slurry. The slurry was then placed in a high-temperature furnace and heat-treated at 1000℃ in a nitrogen atmosphere for 5 hours. After cooling and grading, a silicon-based composite material with a carbon coating layer was obtained, with a total carbon content of 5.9%.

[0174] The silicon-based composite material with a carbon-containing coating layer and dispersed lithium and nitrogen elements prepared in this embodiment was used to fabricate the negative electrode sheet and assemble the battery for testing. The specific process is the same as in Example 1. Test data are detailed in Table 1.

[0175] To better illustrate the effects of the embodiments of the present invention, comparative examples 1, 2 and 3 are compared with the above embodiments.

[0176] Comparative Example 1

[0177] This comparative example provides a preparation process, application, and performance testing of a silicon-based anode material. The silicon-based anode material in this comparative example does not contain lithium or nitrogen.

[0178] The specific preparation process is as follows:

[0179] (1) Mix 1 kg of silicon powder and 1 kg of silicon dioxide powder evenly, place them in the first furnace chamber, evacuate to 150 Pa, heat to 1400 °C, and the raw materials will be vaporized after vacuum heating.

[0180] (2) The gasified raw material is cooled and deposited on a stainless steel substrate, and then discharged, crushed and screened to obtain silicon-based anode material.

[0181] The silicon-based anode material prepared in this comparative example was carbon-coated:

[0182] Two kilograms of material were placed in a rotary kiln and heated to 1300°C under a protective argon atmosphere. Argon and propylene were introduced at a volume ratio of 1:2 for gas-phase coating. The mixture was held at this temperature for 3 hours, and then the organic gas source was turned off. After cooling and grading, a silicon-based anode material with a carbon coating layer was obtained, containing 3% carbon.

[0183] The silicon-based anode material with a carbon coating prepared in this embodiment was used to fabricate anode sheets and assemble batteries for testing. The specific process was the same as in Example 1. Test data are detailed in Table 1.

[0184] Comparative Example 2

[0185] This comparative example provides a preparation process, application, and performance testing of a silicon-based composite material. The lithium-silicon-based composite material in this comparative example does not contain nitrogen but contains lithium.

[0186] The specific preparation process is as follows:

[0187] (1) Mix 1 kg of silicon powder, 1 kg of silicon dioxide powder and 1 kg of lithium carbonate evenly, place them in the first furnace chamber, evacuate to 130 Pa, heat to 1600 °C, and the raw materials are vaporized after vacuum heating.

[0188] (2) The gasified raw material is cooled and deposited on a stainless steel substrate, and then discharged, crushed and screened to obtain a silicon-based composite material.

[0189] The silicon-based composite material prepared in this comparative example was carbon-coated:

[0190] 2 kg of material was mixed with petroleum asphalt at a mass ratio of 12:1, placed in a high-temperature furnace, and heat-treated at 900°C for 2 hours in a nitrogen atmosphere. After cooling, discharge and grading, a lithium-ion silicon-based composite material with a carbon coating layer was obtained, in which the total carbon content was 4.2%.

[0191] The silicon-based composite material with carbon coating prepared in this comparative example was used to fabricate a negative electrode sheet and assemble a battery for testing. The specific process was the same as in Example 1. Test data are detailed in Table 1.

[0192] Comparative Example 3

[0193] This comparative example provides a preparation process, application, and performance testing of a silicon-based composite material. The silicon-based composite material in this comparative example does not contain lithium but contains nitrogen.

[0194] The specific preparation process is as follows:

[0195] (1) Mix 1 kg of silicon powder and 1 kg of silicon dioxide powder evenly, place them in the first furnace chamber, evacuate to 100 Pa, heat to 1800 °C, and the raw materials are vaporized after vacuum heating to obtain the first gas source.

[0196] (2) Introduce the first gas source into the second furnace chamber.

[0197] (3) Using ammonia as the second gas source, 6L of ammonia is slowly introduced into the second furnace chamber. The first gas source and the second gas source are mixed evenly and reacted fully for 3 hours to obtain a mixed gas.

[0198] (4) The mixed gas is cooled and deposited on a stainless steel substrate, and after discharge, crushing and sieving, a silicon-based composite material is obtained.

[0199] The silicon-based composite material prepared in this comparative example was tested using an organic elemental analyzer, and the nitrogen content was found to be 4%.

[0200] The silicon-based composite material prepared in this comparative example was carbon-coated:

[0201] 2 kg of material and phenolic resin were dissolved in acetone at a ratio of 15:1 and stirred for 7 hours to form a homogeneous slurry. The slurry was then dried directly and placed in a high-temperature furnace. The mixture was sintered at 1000°C under a nitrogen protective atmosphere for 5 hours. After cooling and grading, a silicon-based composite material with a carbon coating layer was obtained, in which the total carbon content was 4.7%.

[0202] The silicon-based composite material with carbon coating prepared in this comparative example was used to fabricate a negative electrode sheet and assemble a battery for testing. The specific process was the same as in Example 1. Test data are detailed in Table 1.

[0203] The initial efficiency, 0.1C reversible capacity, and 0.1C rate cycling performance of the anode materials in Examples 1-9 and Comparative Examples 1-3 were tested, and the results are listed in Table 1.

[0204]

[0205] Table 1

[0206] As can be seen from the data in Comparative Examples 1-3 in the table, Comparative Example 2, which doped the silicon-based composite material with lithium, significantly improved the initial efficiency compared to Comparative Example 1, but its cycle performance was inferior. Comparative Example 3, which doped the silicon-based composite material with nitrogen, significantly improved the cycle capacity retention rate compared to Comparative Example 1, but its initial efficiency was slightly inferior.

[0207] Comparing the data of Examples 1-9 and Comparative Examples 1-3 in the table, it can be seen that the initial efficiency and cycle performance of Comparative Example 1, which is not doped with lithium and nitrogen, are worse than those of Examples 1-9, which are doped with lithium and nitrogen; the cycle performance of Comparative Example 2, which is not doped with nitrogen, is worse than that of Examples 1-9; and the initial efficiency of Comparative Example 3, which is not doped with lithium, is lower than that of Examples 1-9. Therefore, it can be seen that Examples 1-9, by dispersively doping the material with lithium and nitrogen in bulk, increased the conductivity inside the particles, provided a buffer space for the expansion of the material, and improved the initial efficiency and cycle life of the material.

[0208] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment 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 within the scope of protection of the present invention.

Claims

1. A silicon-based composite material, characterized by, The chemical general formula of the silicon-based composite material is: Li x SiO y N z , 0 < x < 20, 0 < y < 5, 0 < z < 10; the mass of lithium element accounts for 2%-20% of the mass of the silicon-based composite material; the mass of nitrogen element accounts for 0.1%-20% of the mass of the silicon-based composite material; The microstructure of the silicon-based composite material is a multiphase dispersion structure; The multiphase dispersion structure is obtained by mixing gaseous raw materials; the gaseous raw materials include: gaseous silicon source material, gaseous lithium source material and gaseous nitrogen source material; The silicon-based composite material is specifically obtained by reacting a mixed gas obtained by reacting the silicon source material and the lithium source material heated under vacuum to form a first gas source with the gaseous nitrogen source material, and then cooling and depositing on a stainless steel substrate; The lithium source material includes: inorganic lithium source material and / or organic lithium source material; the inorganic lithium source material includes: one or more of lithium carbonate, lithium nitride, lithium phosphate, lithium manganate or metallic lithium; the organic lithium source material includes: butyl lithium and / or phenyl lithium; The average particle size D of the silicon-based composite particles is between 1 nm and 100 μm 50 The specific surface area is between 0.5 m 2 / g and 40 m 2 / g.

2. The silicon-based composite material of claim 1, wherein The gaseous silicon source material includes: gasified silicon powder and / or gasified silicon dioxide; The gaseous lithium source material includes: gasified inorganic lithium source material and / or gasified organic lithium source material; The gaseous nitrogen source material includes: nitrogen-containing gas source and / or gasified nitrogen-containing compound.

3. The silicon-based composite material of claim 1, wherein The mass of lithium element accounts for 5%-15% of the mass of the silicon-based composite material; the mass of nitrogen element accounts for 0.5%-10% of the mass of the silicon-based composite material; The silicon source material includes: silicon powder and / or silicon dioxide; The nitrogen source material includes: nitrogen gas source and / or nitrogen-containing compound; The nitrogen gas source includes: one or more of nitrogen gas, nitric oxide, nitrogen dioxide or ammonia gas; The nitrogen-containing compound includes: one or more of methylamine, carbamide, isocyanate or aniline.

4. The silicon-based composite material of claim 1, wherein The outer layer of the silicon-based composite material has a carbon coating layer; the mass of the carbon coating layer accounts for 0%-20% of the mass of the silicon-based composite material.

5. A method of producing a silicon-based composite material according to any one of claims 1 to 4, characterized by, The preparation method includes: Mixing the silicon source material and the lithium source material uniformly according to a proportion, placing them into a first furnace cavity, vacuumizing to 60Pa-180Pa, heating at a temperature of 1000℃-2000℃ to obtain a first gas source; Introducing the first gas source into a second furnace cavity; The gaseous nitrogen source material as a second gas source is introduced into the second furnace cavity, so that the first gas source and the second gas source are mixed uniformly and react for 2-6 hours to obtain a mixed gas; Cooling and depositing the mixed gas on a stainless steel substrate, crushing and screening the deposited material to obtain a silicon-based composite material; The silicon-based composite material is: Li x SiO y N z , 0 < x < 20, 0 < y < 5, 0 < z < 10; the mass of lithium element accounts for 2%-20% of the mass of the silicon-based composite material; the mass of nitrogen element accounts for 0.1%-20% of the mass of the silicon-based composite material; The microstructure of the silicon-based composite material is a multiphase dispersion structure; the average particle size D 50 is 1 nm-100 μm, and the specific surface area is 0.5 m 2 / g-40 m 2 / g; The gaseous nitrogen source material includes: nitrogen-containing gas source and / or gasified nitrogen-containing compound; the gasification temperature of the nitrogen-containing compound is between 25℃-800℃.

6. The method of producing a matrix composite according to claim 5, wherein The mass of lithium element accounts for 5%-15% of the mass of the silicon-based composite material; the mass of nitrogen element accounts for 0.5%-10% of the mass of the silicon-based composite material; The silicon source material includes: silicon powder and / or silicon dioxide; The lithium source material includes: inorganic lithium source material and / or organic lithium source material; The inorganic lithium source material includes: one or more of lithium carbonate, lithium nitride, lithium phosphate, lithium manganate or metallic lithium; The organic lithium source material includes: butyl lithium and / or phenyl lithium; The nitrogen source material includes: nitrogen gas source and / or nitrogen-containing compound; The nitrogen gas source includes: one or more of nitrogen gas, nitric oxide, nitrogen dioxide or ammonia gas; The nitrogen-containing compound includes: one or more of methylamine, carbamide, isocyanate or aniline. The nitrogen-containing compound includes one or more of methylamine, carbamide, isocyanate, or aniline.

7. The method of claim 5, wherein the silicon-based composite material is prepared by a process comprising: The preparation method further includes carbon-coating the silicon-based composite material; the mass of the carbon-coating layer accounts for 0%-20% of the mass of the silicon-based composite material. The method of carbon-coating includes one of gas-phase coating, liquid-phase coating, or solid-phase coating.

8. The method of claim 7, wherein the silicon-based composite material is prepared by a process comprising: The mass of the carbon-coating layer accounts for 0.5%-10% of the mass of the silicon-based composite material.

9. A negative electrode sheet characterized by comprising: The silicon-based composite material of any one of claims 1-4.

10. A lithium battery, characterized by, The negative electrode sheet of claim 9.

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