Uniformly modified silicon-based composite material, preparation method thereof, negative electrode sheet, and lithium battery

Abstract

An object of the present invention is to provide a uniformly modified silicon-based composite material, a preparation method thereof, and an application thereof. 【Solution means】The general formula of the silicon-based composite material is SiC x A y O z where 0 < x < 20, 0 < y < 10, 0 < z < 10, where A is one or more of B, Al, Mg, Ca, Fe, Co, Ni, Cu, Zn, Ge, Sn, Li, and C is distributed so as to be uniformly dispersed inside the particles of the silicon-based composite material at the atomic level, and there is no aggregation of carbon of 20 nm or more, and some or all of the carbon atoms are bonded to silicon atoms to form an amorphous Si-C bond. In the measurement of the focused ion beam-transmission electron microscope FIB-TEM of the silicon-based composite material, the EDS (Energy Dispersive X-ray Spectroscopy) mapping of the particle cross-section shows that the silicon element, carbon element, element A, and oxygen element inside the particle are uniformly distributed. The microstructure of the silicon-based composite material is a multiphase dispersion structure, and the average particle size D 50 of the particles of the silicon-based composite material is 1 nm to 100 μm, and the specific surface area is 0.5 m 2 / g to 40 m 2 / g, the mass of the carbon atoms accounts for 0.1% to 40% of the mass of the silicon-based composite material, and the mass of the element A accounts for 3% to 40% of the mass of the composite particles.

Description

Technical Field

[0001] (Cross-reference) This application claims the priority of a Chinese patent application with an application number of 202110668605.8, filed with the China National Intellectual Property Administration on June 16, 2021, and titled "Uniformly Modified Silicon-Based Composite Material, Its Preparation Method and Application".

[0002] (Technical Field) The present invention relates to the technical field of materials, and in particular, to a uniformly modified silicon-based composite material, its preparation method and application.

Background Art

[0003] With the rapid development of the application of lithium-ion batteries and the increasing need for high energy density, the development of electrode materials with high specific capacity has become the current research focus in the field of lithium-ion batteries. The negative electrode material is one of the four major main materials of lithium-ion batteries, and the magnitude of its capacity greatly affects the magnitude of the energy density of lithium-ion batteries. Silicon and lithium form an alloy at a low potential and react to form Li 3.75 Si, and the specific capacity at this time can reach 3975 mAh / g. However, silicon undergoes a volume change of up to 300% during the lithium insertion and desorption process, significantly limiting the application of this material.

[0004] Compared with the large volume change of silicon, the volume expansion of silicon oxide (SiO x ) in the lithium-inserted state is about 150%, and its specific capacity (~1700 mAh / g) is lower than that of silicon materials but much higher than that of currently commercially available graphite (372 mAh / g). Therefore, it has become one of the research hotspots of negative electrode materials. However, the initial Coulomb efficiency of silicon oxide is low (~78%), and due to the volume change of 150%, it still faces the problem of material pulverization.

[0005] Carbon coating is a common modification method, and the electrolyte and SiO xAvoid direct contact with it, reduce the formation of the solid electrolyte interface (SEI) film, improve the reversible capacity of the material, and the mechanical action of the surface carbon on the insertion and extraction process of lithium can buffer the volume change of SiO x particles, which can not only improve the cycle characteristics of the material, but also improve the electron conductivity of the material surface. As a result, the rate characteristics of the material are improved. However, carbon coating can only change the surface conductivity, and in order to achieve rapid charging performance, it is also necessary to improve the conductivity inside the particles.

Summary of the Invention

Problems to be Solved by the Invention

[0006] Embodiments of the present invention provide a uniformly modified silicon-based composite material, a preparation method thereof and an application. Due to the bulk phase doping distribution of carbon and element A, the conductivity of the material and the cycle stability of the lithium-ion battery are improved.

Means for Solving the Problems

[0007] In a first aspect, an embodiment of the present invention is a uniformly modified silicon-based composite material, and the general formula of the silicon-based composite material is SiC x A y O z where 0 < x < 20, 0 < y < 10, 0 < z < 10, where A is one or more of B, Al, Mg, Ca, Fe, Co, Ni, Cu, Zn, Ge, Sn, Li, and C is distributed so as to be uniformly dispersed inside the particles of the silicon-based composite material at the atomic level, and there is no aggregation of carbon of 20 nm or more. Part or all of the carbon atoms are bonded to silicon atoms to form an amorphous Si-C bond. In the measurement of the focused ion beam-transmission electron microscope FIB-TEM of the silicon-based composite material, the EDS (Energy Dispersive X-ray Spectroscopy) mapping of the particle cross-section shows that the silicon element, carbon element, element A, and oxygen element inside the particles are uniformly distributed. The microstructure of the silicon-based composite material is a multiphase dispersion structure. The average particle size D of the particles of the silicon-based composite material 50 is from 1 nm to 100 μm, and the specific surface area is 0.5 m 2 / g to 40 m 2 / g. The mass of the carbon atoms accounts for 0.1% to 40% of the mass of the silicon-based composite material, and the mass of the element A accounts for 3% to 40% of the mass of the composite particles.

[0008] Preferably, the outside of the silicon-based composite material further has a carbon coating layer, and the mass of the carbon coating layer accounts for 0 to 20% of the mass of the silicon-based composite material.

[0009] More preferably, the mass of the carbon atoms accounts for 0.5% to 10% of the mass of the silicon-based composite material, and the mass of the carbon coating layer accounts for 0 to 10% of the mass of the silicon-based composite material.

[0010] In a second aspect, an embodiment of the present invention is a method for preparing the uniformly modified silicon-based composite material described in the first aspect, and the preparation method includes a one-step vapor phase growth method or a two-step vapor phase growth method.

[0011] Preferably, the one-step vapor phase growth method specifically includes: uniformly mixing silicon powder, silicon dioxide powder, elemental A powder and / or A oxide powder in required amounts and putting them into a vacuum furnace; after reducing the pressure of the vacuum furnace, heating it to 1200°C to 1700°C to obtain a mixed vapor containing silicon element, oxygen element, and element A; under a protective atmosphere, blowing a carbon-containing gas source into the vacuum furnace and performing a gas phase reaction with the mixed vapor for 1 to 24 hours; cooling the material obtained by the gas phase reaction to room temperature, taking out the material, pulverizing it, and performing sieving to obtain a silicon-based composite material SiC x A y O z in which carbon is uniformly distributed at the atomic level; is included.

[0012] Preferably, the two-step vapor phase growth method specifically includes: Mix silicon powder and silicon dioxide powder in the required amounts uniformly and put them into a vacuum furnace, After reducing the pressure of the vacuum furnace, heat it to 1200°C to 1700°C to obtain a mixed vapor containing silicon element and oxygen element, Under a protective atmosphere, blow a carbon-containing gas source into the vacuum furnace and carry out a gas-phase reaction with the mixed vapor for 1 to 24 hours, Cool the material obtained by the gas-phase reaction to room temperature, take out the material, pulverize it, and perform sieving to obtain a composite material SiC x O z in which carbon is uniformly distributed at the atomic level, SiC x O z Mix uniformly with single crystal A powder and / or A oxide powder, put it into a high-temperature furnace, and heat-treat it at 600°C to 1500°C for 2 to 24 hours to obtain a silicon-based composite material SiC x A y O z in which carbon is uniformly distributed at the atomic level, is included.

[0013] More preferably, the carbon-containing gas source includes one or more of methane, propane, butane, acetylene, ethylene, propylene, butadiene, or carbon monoxide.

[0014] Preferably, after cooling the material to room temperature, taking out the material, pulverizing it, and performing sieving, the preparation method further includes performing carbon coating on the sieved material, classifying it, and then obtaining the negative electrode material.

[0015] More preferably, after cooling the material to room temperature, taking out the material, pulverizing it, and performing sieving, the preparation method further includes performing carbon coating on the sieved material, where the carbon coating includes at least one of gas-phase coating, liquid-phase coating, and solid-phase coating.

[0016] In a third aspect, an embodiment of the present invention relates to a negative electrode sheet including the uniformly modified silicon-based composite material described in the first aspect.

[0017] In a fourth aspect, an embodiment of the present invention relates to a lithium battery including the negative electrode sheet described in the third aspect.

Advantages of the Invention

[0018] The uniformly modified silicon-based composite material SiC according to the present invention x A y O z improves the conductivity of the bulk phase of the silicon-based material due to the bulk-phase doping distribution of element C and element A, provides a buffer space in which the bulk phase is uniformly distributed with respect to the volume expansion of the silicon-based material, and improves the rapid charging performance, initial Coulomb efficiency, and cycle stability of the material.

Brief Description of the Drawings

[0019] Hereinafter, the technical solutions in the embodiments of the present invention will be described in more detail with reference to the drawings and embodiments.

[0020]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0021] Hereinafter, the present invention will be further described with reference to the drawings and specific embodiments, but it should be understood that these embodiments are only for explaining the present invention in more detail and are not intended to limit the present invention in any form, that is, they are not intended to limit the protection scope of the present invention.

[0022] The general formula of the uniformly modified silicon-based composite material according to the present invention is SiC x A y O z where 0 < x < 20, 0 < y < 10, 0 < z < 10, and A is one or more of B, Al, Mg, Ca, Fe, Co, Ni, Cu, Zn, Ge, Sn, Li; C is distributed so as to be uniformly dispersed inside the particles of the silicon-based composite material at the atomic level, and there is no aggregation of carbon of 20 nm or more. Part or all of the carbon atoms are bonded to silicon atoms to form amorphous Si-C bonds. In the measurement of the focused ion beam-transmission electron microscope FIB-TEM of the silicon-based composite material, the EDS mapping of the particle cross-section shows that the silicon element, carbon element, element A, and oxygen element inside the particles are uniformly distributed, the microstructure of the silicon-based composite material is a multiphase dispersion structure, the average particle size D of the particles of the silicon-based composite material 50 is 1 nm to 100 μm, the specific surface area is 0.5 m 2 / g to 40 m 2 / g, the mass of the carbon atoms accounts for 0.1% to 40% of the mass of the silicon-based composite material, preferably 0.5% to 10%, and the mass of element A accounts for 3% to 40% of the mass of the composite particles.

[0023] The outer side of the above material may be coated with a carbon coating layer, and the mass of the carbon coating layer accounts for 0 to 20% of the mass of the silicon-based composite material, preferably, the mass of the carbon coating layer accounts for 0 to 10% of the mass of the silicon-based composite material.

[0024] The above uniformly modified silicon-based composite material of the present invention can be obtained by a one-step vapor phase growth method or a two-step vapor phase growth method.

[0025] The one-step vapor phase growth method includes the following steps as shown in Figure 1.

[0026] In step 110, silicon powder, silicon dioxide powder, elemental A powder and / or oxide powder of A are uniformly mixed in required amounts and put into a vacuum furnace. In step 120, after reducing the pressure of the vacuum furnace, it is heated to 1200 °C to 1700 °C to obtain a mixed vapor containing silicon element, oxygen element, and element A. Here, the pressure of the vacuum furnace is reduced to 300 Pa or less.

[0027] In step 130, under a protective atmosphere, a carbon-containing gas source is blown into the vacuum furnace, and a gas-phase reaction is carried out with the mixed vapor for 1 to 24 hours. Here, the protective atmosphere may be an N2 or Ar atmosphere. The carbon-containing gas source contains one or more of methane, propane, butane, acetylene, ethylene, propylene, butadiene, or carbon monoxide.

[0028] In step 140, the material obtained by the gas-phase reaction is cooled to room temperature, the material is taken out and pulverized, and sieved to obtain a silicon-based composite material SiC in which carbon is uniformly distributed at the atomic level. x A y O z is obtained.

[0029] The two-step gas-phase growth method includes the following steps, as shown in Figure 2.

[0030] In step 210, silicon powder and silicon dioxide powder are uniformly mixed in required amounts and put into a vacuum furnace. In step 220, after reducing the pressure of the vacuum furnace, it is heated to 1200 °C to 1700 °C to obtain a mixed vapor containing silicon element and oxygen element. Here, the pressure of the vacuum furnace is reduced to 300 Pa or less.

[0031] In step 230, under a protective atmosphere, a carbon-containing gas source is blown into the vacuum furnace, and a gas-phase reaction is carried out with the mixed vapor for 1 to 24 hours. Here, the protective atmosphere may be an N2 or Ar atmosphere. The carbon-containing gas source contains one or more of methane, propane, butane, acetylene, ethylene, propylene, butadiene, or carbon monoxide.

[0032] In step 240, the material obtained by the gas-phase reaction is cooled to room temperature, the material is taken out, pulverized, and sieved, so as to obtain a composite material SiC in which carbon is uniformly distributed at the atomic level. x O z to obtain. In step 250, SiC x O z is uniformly mixed with single A powder and / or A oxide powder, put into a high-temperature furnace, and heat-treated at 600°C to 1500°C for 2 to 24 hours, so as to obtain a silicon-based composite material SiC x A y O z in which carbon is uniformly distributed at the atomic level.

[0033] In addition to the above two methods, when preparing a silicon-based composite material further having a carbon coating layer on the outside, a carbon coating is applied to the pulverized material and classified, so as to obtain a silicon-based composite material. The specific method of carbon coating may include at least one of vapor-phase coating, liquid-phase coating, and solid-phase coating. The above method is a coating method often used in the preparation process of battery materials, and the description is omitted here.

[0034] The silicon-based composite material having carbon uniformly distributed at the atomic level inside the particles according to the present invention improves the bulk-phase conductivity of the silicon-based material due to the bulk-phase doping distribution of element C and element A, and provides a buffer space in which the bulk-phase is uniformly distributed with respect to the bulk expansion of the silicon-based material, improving the rapid charging performance, initial Coulomb efficiency, and cycle stability of the material.

[0035] The silicon-based composite material according to the present invention can be used to prepare a negative electrode sheet applicable to a lithium battery.

[0036] In order to better understand the technical solution according to the present invention, hereinafter, a plurality of specific examples will be given to explain the specific process of preparing a silicon-based composite material by the method according to the above embodiment of the present invention, and the method and characteristics applicable to a lithium secondary battery, respectively.

[0037] (Example 1) Put 1 kg of silicon powder, 1 kg of silicon dioxide and 0.3 kg of copper oxide into a high-temperature reactor, evacuate to 50 Pa, heat it up to 1500 °C to turn it into vapor. Slowly blow in 1.6 L of methane with an argon gas flow and react for 3 hours, then cool to room temperature. After taking out the material and pulverizing it, a silicon-based composite material in which carbon and copper elements are uniformly distributed at the atomic level is obtained. As a result of measurement with a carbon-sulfur analyzer, the carbon content in this is 1.5%.

[0038] Perform FIB-TEM measurement on the obtained silicon-based composite material and observe the elemental distribution inside the particles by EDS analysis. Figure 3 is the EDS mapping of FIB-TEM. It can be seen from the EDS mapping in Figure 3 that four elements, Si, C, Cu, and O, are uniformly distributed in the particles.

[0039] Then, apply carbon coating to the silicon-based composite material, put 2 kg of the material into a rotary furnace, heat it up to 1000 °C under an argon atmosphere, blow in argon and propylene at a volume ratio of 1:1 to perform vapor phase coating, keep the temperature for 2 hours, close the organic gas source, lower the temperature, take out the material, classify it, and obtain a silicon-based composite material containing a carbon coating layer, and the total carbon content in this is 4.5%.

[0040] Use the above silicon-based composite material containing a carbon coating layer as the negative electrode material, weigh conductive carbon black (SP) as the conductive additive and polyvinylidene fluoride (PVDF) as the binder at a ratio of 95%:2%:3%, and prepare a slurry in a beaker at room temperature. Apply the prepared slurry uniformly on the copper foil. After drying in a blower dryer at 50 °C for 2 hours, cut it into 8×8 mm electrode sheets, evacuate and dry in a vacuum dryer at 100 °C for 10 hours. For battery assembly, transfer the dried electrode sheets into a glove box immediately for preparation.

[0041] The assembly of the simulated battery was carried out in a glove box containing a high-purity Ar atmosphere. Using lithium metal as the counter electrode and a solution of ethylene carbonate / dimethyl carbonate (volume ratio of EC / DMC is 1:1) containing 1 mol / L of LiPF6 as the electrolyte, it was assembled into a battery. A constant current charge-discharge mode test was implemented using a charger. The discharge cut-off voltage was 0.005 V, the charge cut-off voltage was 1.5 V. The first cycle of charge-discharge test was carried out at a C / 10 current density, and the second cycle of discharge test was carried out at a C / 10 current density. The test results of the initial Coulomb efficiency, 0.1C reversible capacity, and cycle characteristics at a 0.1C rate are shown in Table 1.

[0042] (Example 2) 1 kg of silicon powder and 1 kg of silicon dioxide mixed powder were put into a vacuum furnace, evacuated to 50 Pa, heated and raised to 1500 °C to turn it into vapor. Then, 1.6 L of methane was gradually blown in with an argon gas flow and reacted for 3 hours, and then cooled to room temperature. After taking out the material and pulverizing it, a silicon-based composite material with carbon uniformly dispersed at the atomic level inside was obtained. As a result of measurement with a carbon-sulfur analyzer, the carbon content in it was 1.8%.

[0043] The obtained silicon-based material powder with carbon uniformly dispersed at the atomic level inside and copper oxide were uniformly mixed at a molar ratio of 1:0.4, and then heat-treated at 1000 °C for 4 hours to obtain a silicon-based composite material containing carbon and copper elements inside.

[0044] After that, carbon coating was applied to the silicon-based composite material. 2 kg of the silicon-based composite material was put into a rotary furnace, heated to 1000 °C under an argon atmosphere, and argon and propylene were blown in at a volume ratio of 1:1 to carry out vapor phase coating. The temperature was maintained for 2 hours, and then the organic gas source was closed. The temperature was lowered, the material was taken out and classified to obtain a silicon-based composite material containing a carbon coating layer, and the total carbon content in it was 4.6%.

[0045] The manufacturing process of the negative electrode sheet, battery assembly, and battery test are the same as in Example 1. The test results of the initial Coulomb efficiency, 0.1C reversible capacity, and cycle characteristics at 0.1C rate are shown in Table 1.

[0046] (Example 3) Put 3 kg of silicon powder, 3 kg of silicon dioxide, and 1 kg of boron oxide mixed powder into a vacuum furnace, evacuate to 100 Pa, heat up to 1350 °C to turn it into vapor, and gradually blow 23.4 L of propane into it with an argon gas flow and react for 8 hours, then cool to room temperature. After taking out the material and pulverizing it, a silicon-based composite material with carbon and boron uniformly dispersed at the atomic level inside was obtained. As a result of measurement with a carbon-sulfur analyzer, the carbon content in this is 2.0%.

[0047] Then, carbon coating was applied to the silicon-based composite material. 2 kg of the material was put into a rotary furnace, heated up to 900 °C under an argon atmosphere, and argon and a mixed gas of propylene and methane equal in amount to argon were blown in at a volume ratio of 1:1 to perform vapor phase coating, where the volume ratio of propylene to methane is 2:3. Keep the temperature for 3 hours, close the organic gas source, lower the temperature, take out the material, and after classification, a silicon-based composite material containing a carbon coating layer was obtained, and the total carbon content in this is 4.7%.

[0048] The manufacturing process of the negative electrode sheet, battery assembly, and battery test are the same as in Example 1. The test results of the initial Coulomb efficiency, 0.1C reversible capacity, and cycle characteristics at 0.1C rate are shown in Table 1.

[0049] (Example 4) Put 2 kg of silicon powder and 2 kg of silicon dioxide mixed powder into a vacuum furnace, evacuate to 150 Pa, heat up to 1400 °C to turn it into vapor. Gradually blow 1 L of methylpropylene into it with an argon gas flow and react for 5 hours, then cool to room temperature. After taking out the material and pulverizing it, a silicon-based composite material with carbon uniformly dispersed at the atomic level inside was obtained. As a result of measurement with a carbon-sulfur analyzer, the carbon content in this is 2.0%.

[0050] The obtained silicon-based composite material with carbon uniformly dispersed at the atomic level and metallic aluminum were uniformly mixed at a molar ratio of 2:1, and then heat-treated at 1200 °C for 4 hours to obtain a silicon-based composite material containing carbon and aluminum inside.

[0051] The manufacturing process of the negative electrode sheet, battery assembly, and battery test are the same as those in Example 1. The test results of the initial Coulomb efficiency, 0.1C reversible capacity, and cycle characteristics at a 0.1C rate are shown in Table 1.

[0052] (Example 5) A mixed powder of 3 kg of silicon, 3 kg of silicon dioxide, and 1 kg of metallic magnesium was placed in a vacuum furnace, evacuated to 150 Pa, heated to raise the temperature to 1400 °C to turn it into vapor, and a mixed gas of 11.7 L of acetylene and 5 L of methane was gradually blown in with an argon gas flow and reacted for 4 hours, then cooled to room temperature. After taking out the material and pulverizing it, a silicon-based composite material with carbon and magnesium elements uniformly dispersed at the atomic level inside was obtained. As a result of measurement with a carbon-sulfur analyzer, the carbon content therein was 1.8%.

[0053] Thereafter, the silicon-based composite material was coated with carbon. 2 kg of the material was put into a rotary furnace, heated to 1100 °C under an argon atmosphere, and a gas-phase coating was carried out by blowing in argon and a mixed gas of propylene and methane equal in amount to argon at a volume ratio of 1:1, where the volume ratio of propylene to methane was 2:3. The temperature was maintained for 3 hours, the organic gas source was closed, the temperature was lowered, the material was taken out and classified, and a silicon-based composite material containing a carbon coating layer was obtained, and the total carbon content therein was 6.5%.

[0054] The manufacturing process of the negative electrode sheet, battery assembly, and battery test are the same as those in Example 1. The test results of the initial Coulomb efficiency, 0.1C reversible capacity, and cycle characteristics at a 0.1C rate are shown in Table 1.

[0055] (Example 6) Put 5 kg of silicon powder and 5 kg of silicon dioxide powder into a vacuum furnace, evacuate to 150 Pa, heat and raise the temperature to 1400 °C to turn it into vapor. Slowly blow 1 L of acetylene into it with an argon gas flow and react for 5 hours, then cool to room temperature. After taking out the material and pulverizing it, a silicon-based composite material was obtained in which carbon was uniformly distributed at the atomic level. As a result of measurement with a carbon-sulfur analyzer, the carbon content in this was 0.8%.

[0056] The obtained silicon-based material powder in which carbon was uniformly distributed at the atomic level and calcium oxide were uniformly mixed at a molar ratio of 3:1, and then heat-treated at 1200 °C for 4 hours to obtain a silicon-based composite material containing carbon and calcium inside.

[0057] After that, the silicon-based composite material was coated with carbon. 1.5 kg of the material was put into a rotary furnace, the temperature was raised to 850 °C under an argon atmosphere, and argon and propane in an amount equal to that of argon were blown in at a volume ratio of 1:1 to perform vapor phase coating. The temperature was maintained for 1.5 hours, the organic gas source was closed, the temperature was lowered, the material was taken out and classified, and a silicon-based composite material containing a carbon coating layer was obtained. The total carbon content in this was 5.5%.

[0058] The manufacturing process of the negative electrode sheet, battery assembly and battery test are the same as in Example 1. The test results of the initial Coulomb efficiency, 0.1C reversible capacity, and cycle characteristics at 0.1C rate are shown in Table 1.

[0059] (Example 7) Put 2 kg of silicon, 3 kg of silicon dioxide and 0.5 kg of metallic iron mixed powder into a vacuum furnace, evacuate to 100 Pa, heat and raise the temperature to 1600 °C to turn it into vapor, and slowly blow 1 L of butane into it with an argon gas flow and react for 3 hours, then cool to room temperature. After taking out the material and pulverizing it, a silicon-based composite material was obtained in which carbon and iron elements were uniformly distributed at the atomic level. As a result of measurement with a carbon-sulfur analyzer, the carbon content in this was 2%.

[0060] Subsequently, the silicon-based composite material is coated with carbon. 2 kg of the material is placed in a rotary furnace, heated to 700 °C under an argon atmosphere, and argon and acetylene are blown in at a volume ratio of 1:2 to perform vapor phase coating. The temperature is maintained for 2 hours, the organic gas source is closed, the temperature is lowered, the material is taken out and classified, and a silicon-based composite material containing a carbon coating layer is obtained, and the total carbon content therein is 4.5%.

[0061] The manufacturing process of the negative electrode sheet, battery assembly, and battery test are the same as in Example 1. The test results of the initial Coulomb efficiency, 0.1C reversible capacity, and cycle characteristics at a 0.1C rate are shown in Table 1.

[0062] (Example 8) 3 kg of silicon powder and 5 kg of silicon dioxide mixed powder are placed in a vacuum furnace, evacuated to 150 Pa, heated to 1400 °C to turn it into vapor. 1.5 L of butadiene is gradually blown in with an argon gas flow and reacted for 6 hours, and then cooled to room temperature. After taking out and pulverizing the material, a silicon-based material powder in which carbon is uniformly dispersed at the atomic level is obtained. As a result of measurement with a carbon-sulfur analyzer, the carbon content therein is 1.3%.

[0063] The obtained silicon-based material powder in which carbon is uniformly dispersed at the atomic level and metallic cobalt are uniformly mixed at a molar ratio of 5:1, and then heat-treated at 1200 °C for 4 hours to obtain a silicon-based composite material containing carbon and cobalt inside.

[0064] Subsequently, the silicon-based composite material is coated with carbon. 1.5 kg of the material is placed in a rotary furnace, heated to 850 °C under an argon atmosphere, and argon and a mixed gas of argon and an equal amount of acetylene and propane are blown in at a volume ratio of 1:1 to perform vapor phase coating. Here, the volume ratio of acetylene to propane is 3:1. The temperature is maintained for 3 hours, the organic gas source is closed, the temperature is lowered, the material is taken out and classified, and a silicon-based composite material containing a carbon coating layer is obtained, and the total carbon content therein is 5.5%.

[0065] The manufacturing process of the negative electrode sheet, battery assembly, and battery test are the same as in Example 1. The test results of the initial Coulomb efficiency, 0.1C reversible capacity, and cycle characteristics at 0.1C rate are shown in Table 1.

[0066] (Example 9) Put 5 kg of silicon, 4 kg of silicon dioxide, and 1 kg of metallic nickel mixed powder into a vacuum furnace, evacuate to 100 Pa, heat and raise the temperature to 1700 °C to turn it into vapor, and gradually blow 1.4 L of carbon monoxide gas with an argon gas flow for 12 hours of reaction, then cool to room temperature. After taking out the material and pulverizing it, a silicon-based composite material with carbon and iron elements uniformly dispersed at the atomic level inside was obtained. As a result of measurement with a carbon-sulfur analyzer, the carbon content in this is 0.6%.

[0067] After that, carbon coating was applied to the silicon-based composite material. Put 2 kg of the material into a rotary furnace, raise the temperature to 600 °C under an argon atmosphere, and blow in argon and acetylene in a volume ratio of 1:3 to perform vapor phase coating. Keep the temperature for 2 hours, close the organic gas source, lower the temperature, take out the material, and after classification, a silicon-based composite material containing a carbon coating layer was obtained, and the total carbon content in this is 3.5%.

[0068] The manufacturing process of the negative electrode sheet, battery assembly, and battery test are the same as in Example 1. The test results of the initial Coulomb efficiency, 0.1C reversible capacity, and cycle characteristics at 0.1C rate are shown in Table 1.

[0069] (Example 10) Put 5 kg of silicon powder and 5 kg of silicon dioxide mixed powder into a vacuum furnace, evacuate to 150 Pa, heat and raise the temperature to 1400 °C to turn it into vapor. Gradually blow in a mixed gas of 2.0 L of carbon monoxide and 1.2 L of acetylene with an argon gas flow for 10 hours of reaction, then cool to room temperature. After taking out the material and pulverizing it, a silicon-based material powder with carbon uniformly dispersed at the atomic level inside was obtained. As a result of measurement with a carbon-sulfur analyzer, the carbon content in this is 3%.

[0070] The obtained silicon-based material powder with carbon uniformly dispersed at the atomic level and metallic zinc were uniformly mixed at a molar ratio of 2:1, and then heat-treated at 1200 °C for 4 hours to obtain a silicon-based anode material containing carbon and zinc inside.

[0071] After that, the silicon-based anode material was coated with carbon. 2 kg of the material and petroleum pitch were mixed at a mass ratio of 10:1, put into a high-temperature furnace, heat-treated at 900 °C for 2 hours under a nitrogen atmosphere, the temperature was lowered, the material was taken out and classified, and then a silicon-based composite material containing a carbon coating layer was obtained. The total carbon content in this was 4.2%.

[0072] Using the above silicon-based composite material containing a carbon coating layer as the anode material, conductive carbon black (SP) as the conductive additive and polyvinylidene fluoride (PVDF) as the adhesive were weighed at a ratio of 95%:2%:3%. A slurry was prepared in a beater at room temperature. The prepared slurry was uniformly coated on a copper foil. After drying in a blower dryer at 50 °C for 2 hours, it was cut into 8×8 mm electrode sheets and vacuumed at 100 °C in a vacuum dryer and dried for 10 hours. For battery assembly, the dried electrode sheets were immediately transferred into a glove box and prepared.

[0073] The assembly of the simulated battery was carried out in a glove box containing a high-purity Ar atmosphere. Using the above electrode as the negative electrode, the ternary cathode material NCM811 as the counter electrode, and garnet-type Li7La3Zr2O 12 (LLZO) as the solid electrolyte, it was assembled into a button-shaped all-solid-state battery in a glove box, and it was charged to evaluate its electrochemical performance. A constant current charge-discharge mode test was carried out using a charge-discharge device. The discharge cut-off voltage was 0.005 V, the charge cut-off voltage was 1.5 V, the first-cycle charge-discharge test was carried out at a C / 10 current density, and the second-cycle discharge test was carried out at a C / 10 current density. The test results of the initial Coulomb efficiency, 0.1C reversible capacity, and cycle characteristics at a 0.1C rate are shown in Table 1.

[0074] (Example 11) Put a mixed powder of 4 kg of silicon, 4 kg of silicon dioxide and 2 kg of copper oxide into a vacuum furnace, evacuate to 100 Pa, heat and raise the temperature to 1700 °C to turn it into vapor, and gradually blow in a mixed gas of 0.9 L of methane, 1.2 L of propylene and 1.7 L of propane with an argon gas flow and react for 6 hours, then cool to room temperature. After taking out the material and pulverizing it, a silicon-based composite material in which carbon and copper elements are uniformly dispersed at the atomic level was obtained. As a result of measurement with a carbon-sulfur analyzer, the carbon content in this is 3.6%.

[0075] After that, carbon coating was applied to the silicon-based composite material. 3 kg of the pulverized sample and phenol resin were dissolved in an alcohol solvent at a ratio of 20:1 and stirred for 6 hours to form a uniform slurry. Then, the slurry was directly dried, put into a high-temperature furnace, and the mixture was sintered at 900 °C for 2 hours under a nitrogen atmosphere. After cooling, classification and sieving were carried out to obtain a silicon-based composite material containing a carbon coating layer, and the total carbon content in this is 6.5%.

[0076] Using the above silicon-based composite material containing a carbon coating layer as the negative electrode material, weigh conductive carbon black (SP) as the conductive additive and polyvinylidene fluoride (PVDF) as the binder at a ratio of 95%:2%:3%. Prepare a slurry in a beaker at room temperature. Apply the prepared slurry uniformly on the copper foil. After drying in a blower dryer at 50 °C for 2 hours, cut it into 8×8 mm electrode sheets, evacuate in a vacuum dryer at 100 °C and dry for 10 hours. For battery assembly, transfer the dried electrode sheets immediately into a glove box and prepare them.

[0077] The assembly of the simulated battery was carried out in a glove box containing a high-purity Ar atmosphere. The above electrode was used as the negative electrode, the ternary cathode material NCM811 was used as the counter electrode, the polyolefin-based polymer gel electrolyte membrane was used as the semi-solid electrolyte, and it was assembled into a button-shaped semi-solid battery in the glove box, which was then charged to evaluate its electrochemical performance. A constant current charge-discharge mode test was carried out using a charger. The discharge cut-off voltage was 0.005 V, the charge cut-off voltage was 1.5 V. The first-cycle charge-discharge test was carried out at a C / 10 current density, and the second-cycle discharge test was carried out at a C / 10 current density. The test results of the initial Coulomb efficiency, 0.1C reversible capacity, and cycle characteristics at a 0.1C rate are shown in Table 1.

[0078] (Example 12) 3 kg of silicon powder and 5 kg of silicon dioxide mixed powder were put into a vacuum furnace, evacuated to 150 Pa, heated to 1500 °C to turn it into vapor. A mixed gas of 1.7 L of methane and 1.5 L of propylene was gradually blown in with an argon gas flow and reacted for 3 hours, and then cooled to room temperature. After taking out the material and pulverizing it, a silicon-based material powder with carbon uniformly dispersed at the atomic level inside was obtained. As a result of measurement with a carbon-sulfur analyzer, the carbon content in this was 1.5%.

[0079] The obtained silicon-based material powder with carbon uniformly dispersed at the atomic level inside and metallic germanium were uniformly mixed at a molar ratio of 5:1, and then heat-treated at 1200 °C for 4 hours to obtain a silicon-based composite material containing carbon and germanium inside.

[0080] The manufacturing process of the negative electrode sheet, battery assembly, and battery test were the same as in Example 1. The test results of the initial Coulomb efficiency, 0.1C reversible capacity, and cycle characteristics at a 0.1C rate are shown in Table 1.

[0081] (Example 13) Put a mixed powder of 4 kg of silicon, 4 kg of silicon dioxide, and 2 kg of tin oxide into a vacuum furnace, evacuate to 100 Pa, heat it to raise the temperature to 1700 °C to turn it into vapor, and gradually blow in a mixed gas of 5 L of acetylene and 5 L of ethylene with an argon gas flow, react for 6 hours, and then cool to room temperature. After taking out the material and pulverizing it, a silicon-based composite material in which carbon and tin are uniformly dispersed at the atomic level was obtained. As a result of measurement with a carbon and sulfur analyzer, the carbon content in this is 3%.

[0082] The manufacturing process of the negative electrode sheet, battery assembly, and battery test are the same as in Example 1. The test results of the initial Coulomb efficiency, 0.1C reversible capacity, and cycle characteristics at a 0.1C rate are shown in Table 1.

[0083] (Example 14) Put a mixed powder of 5 kg of silicon powder and 5 kg of silicon dioxide into a vacuum furnace, evacuate to 150 Pa, heat it to raise the temperature to 1500 °C to turn it into vapor. Gradually blow in 2 L of butadiene gas with an argon gas flow, react for 4 hours, and cool to room temperature. After taking out the material and pulverizing it, a silicon-based material powder in which carbon is uniformly dispersed at the atomic level was obtained. As a result of measurement with a carbon and sulfur analyzer, the carbon content in this is 0.5%.

[0084] After uniformly mixing the obtained silicon-based material powder in which carbon is uniformly dispersed at the atomic level and lithium oxide at a molar ratio of 5:1, heat-treat at 1000 °C for 2 hours to obtain a silicon-based composite material containing carbon and lithium elements inside.

[0085] The manufacturing process of the negative electrode sheet, battery assembly, and battery test are the same as in Example 1. The test results of the initial Coulomb efficiency, 0.1C reversible capacity, and cycle characteristics at a 0.1C rate are shown in Table 1.

[0086] (Comparative Example 1) Put 1 kg of silicon powder and 1 kg of silicon dioxide mixed powder into a vacuum furnace, evacuate to 50 Pa, heat up to 1500 °C to turn it into vapor. After taking out the material and pulverizing it, a silicon monoxide negative electrode material was obtained. Then, carbon coating was applied to the silicon monoxide negative electrode material. Put 2 kg of the material into a rotary furnace, heat up to 1000 °C under an argon atmosphere, blow in argon and propylene at a volume ratio of 1:1 to carry out vapor phase coating, keep the temperature for 2 hours, and then close the organic gas source. Lower the temperature, take out the material, classify it, and obtain a silicon-based negative electrode material containing a carbon coating layer, and the carbon content in this is 3%.

[0087] The manufacturing process of the negative electrode sheet, battery assembly, and battery test are the same as in Example 1. The test results of the initial Coulomb efficiency, 0.1C reversible capacity, and cycle characteristics at 0.1C rate are shown in Table 1.

[0088] (Comparative Example 2) Put 1 kg of silicon powder, 1 kg of silicon dioxide, and 0.3 kg of copper oxide mixed powder into a vacuum furnace, evacuate to 50 Pa, heat up to 1500 °C to turn it into vapor, react for 3 hours, and then cool to room temperature. After taking out the material and pulverizing it, a silicon monoxide negative electrode material with copper elements uniformly dispersed at the atomic level inside was obtained. Then, carbon coating was applied to the silicon monoxide negative electrode material. Put 2 kg of the material into a rotary furnace, heat up to 1000 °C under an argon atmosphere, blow in argon and propylene at a volume ratio of 1:1 to carry out vapor phase coating, keep the temperature for 2 hours, and then close the organic gas source. Lower the temperature, take out the material, classify it, and obtain a silicon monoxide negative electrode material containing a carbon coating layer, and the total carbon content in this is 3%.

[0089] The manufacturing process of the negative electrode sheet, battery assembly, and battery test are the same as in Example 1. The test results of the initial Coulomb efficiency, 0.1C reversible capacity, and cycle characteristics at 0.1C rate are shown in Table 1.

[0090] (Comparative Example 3) Put 1 kg of silicon powder and 1 kg of silicon dioxide mixed powder into a vacuum furnace, evacuate to 50 Pa, heat and raise the temperature to 1500 °C to turn it into vapor. Slowly blow in 1.6 L of methane with an argon gas flow and react for 3 hours, then cool to room temperature. After taking out the material and pulverizing it, a silicon monoxide negative electrode material with carbon uniformly dispersed at the atomic level inside was obtained. As a result of measurement with a carbon and sulfur analyzer, the carbon content in this is 1.7%. Then, apply carbon coating to the silicon monoxide negative electrode material. Put 2 kg of the material into a rotary furnace, raise the temperature to 1000 °C under an argon atmosphere, blow in argon and propylene at a volume ratio of 1:1 to carry out vapor phase coating, keep the temperature for 2 hours, and close the organic gas source. Lower the temperature, take out the material, and after classification, a silicon monoxide negative electrode material containing a carbon coating layer was obtained, and the total carbon content in this is 4.7%.

[0091] The manufacturing process of the negative electrode sheet, battery assembly, and battery test are the same as in Example 1. The test results of the initial Coulomb efficiency, 0.1C reversible capacity, and cycle characteristics at 0.1C rate are shown in Table 1.

[0092] The test results of the initial Coulomb efficiency, 0.1C reversible capacity, and cycle characteristics at 0.1C rate of the negative electrode materials in Examples 1 to 14 and Comparative Examples 1 to 3 are as follows.

[0093]

Table 1

[0094] As can be seen from the data of Comparative Examples 1 to 3 in the table, in Comparative Example 2, silicon monoxide was doped with copper element, and the initial Coulomb efficiency was significantly improved compared with Comparative Example 1, but the cycle characteristics were inferior. In Comparative Example 3, silicon monoxide was doped with carbon, and the cycle capacity retention rate was significantly improved compared with Comparative Example 1, but the initial Coulomb efficiency was slightly inferior. In Examples 1 to 14, by performing bulk phase doping of carbon and element A on the material, the conductivity inside the particles was increased, a buffer space was provided for the expansion of the material, and at the same time, the initial Coulomb efficiency and cycle life of the material were improved.

[0095] In the above specific embodiments, the object, technical solution and beneficial effects of the present invention are further described in detail. The above are only specific embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0096] (Supplementary Note) (Supplementary Note 1) A silicon-based composite material uniformly modified, The general formula of the silicon-based composite material is SiC x A y O z where 0 < x < 20, 0 < y < 10, 0 < z < 10, Here, A is one or more of B, Al, Mg, Ca, Fe, Co, Ni, Cu, Zn, Ge, Sn, Li, and C is distributed so as to be uniformly dispersed inside the particles of the silicon-based composite material at the atomic level, and there is no aggregation of carbon of 20 nm or more. Part or all of the carbon atoms are bonded to silicon atoms to form an amorphous Si-C bond. In the measurement of the focused ion beam-transmission electron microscope FIB-TEM of the silicon-based composite material, the EDS (Energy Dispersive X-ray Spectroscopy) mapping of the particle cross-section shows that the silicon element, carbon element, element A, and oxygen element inside the particles are uniformly distributed. The microstructure of the silicon-based composite material is a multi-phase dispersion structure. The average particle size D of the particles of the silicon-based composite material 50 is 1 nm to 100 μm, the specific surface area is 0.5 m 2 / g to 40 m 2 / g, the mass of the carbon atoms accounts for 0.1% to 40% of the mass of the silicon-based composite material, and the mass of the element A accounts for 3% to 40% of the mass of the composite particles. A silicon-based composite material characterized by the above.

[0097] (Supplementary Note 2) On the outside of the silicon-based composite material, there is further a carbon coating layer, and the mass of the carbon coating layer accounts for 0 to 20% of the mass of the silicon-based composite material. The silicon-based composite material according to Supplementary Note 1 is characterized in this regard.

[0098] (Supplementary Note 3) The mass of the carbon atoms accounts for 0.5% to 10% of the mass of the silicon-based composite material, and the mass of the carbon coating layer accounts for 0 to 10% of the mass of the silicon-based composite material. The silicon-based composite material according to Supplementary Note 2 is characterized in this regard.

[0099] (Supplementary Note 4) A method for preparing a uniformly modified silicon-based composite material according to any one of Supplementary Notes 1 to 3 above, characterized in that it includes a one-step vapor-phase growth method or a two-step vapor-phase growth method.

[0100] (Supplementary Note 5) Specifically, the one-step vapor-phase growth method is as follows: Mix silicon powder, silicon dioxide powder, elemental A powder and / or A oxide powder in required amounts uniformly and put them into a vacuum furnace. After reducing the pressure of the vacuum furnace, heat it to 1200°C to 1700°C to obtain a mixed vapor containing silicon element, oxygen element, and element A. Under a protective atmosphere, blow a carbon-containing gas source into the vacuum furnace and carry out a gas-phase reaction with the mixed vapor for 1 to 24 hours. Cool the material obtained by the gas-phase reaction to room temperature, take out the material, pulverize it, and perform sieving to obtain a silicon-based composite material SiC in which carbon is uniformly distributed at the atomic level. x A y O z To obtain Including The preparation method according to Supplementary Note 4 is characterized in this regard.

[0101] (Supplementary Note 6) Specifically, the two-step vapor-phase growth method is as follows: Mix silicon powder and silicon dioxide powder in required amounts uniformly and put them into a vacuum furnace. After evacuating the vacuum furnace, heat it to 1200°C to 1700°C to obtain a mixed vapor containing silicon and oxygen elements, and Under a protective atmosphere, blow a carbon-containing gas source into the vacuum furnace and carry out a gas-phase reaction with the mixed vapor for 1 to 24 hours, and Cool the material obtained by the gas-phase reaction to room temperature, take out the material, pulverize it, and perform sieving, whereby a composite material SiC in which carbon is uniformly dispersed at the atomic level is obtained. x O z To obtain, and SiC x O z And uniformly mix the single crystal A powder and / or the oxide powder of A, put it into a high-temperature furnace, and heat-treat it at 600°C to 1500°C for 2 to 24 hours, whereby a silicon-based composite material SiC in which carbon is uniformly dispersed at the atomic level is obtained. x A y O z To obtain, and Including, The preparation method according to Supplementary Note 4, characterized by the above.

[0102] (Supplementary Note 7) The carbon-containing gas source includes at least one of methane, propane, butane, acetylene, ethylene, propylene, butadiene, or carbon monoxide, and the preparation method according to Supplementary Note 5 or 6, characterized by this.

[0103] (Supplementary Note 8) After cooling the material to room temperature, taking out the material, pulverizing it, and performing sieving, it further includes applying a carbon coating to the sieved material, where the carbon coating includes at least one of a gas-phase coating, a liquid-phase coating, and a solid-phase coating, and the preparation method according to Supplementary Note 5 or 6, characterized by this.

[0104] (Supplementary Note 9) A negative electrode sheet including the uniformly modified silicon-based composite material according to any one of Supplementary Notes 1 to 3 above.

[0105] (Supplementary Note 10) A lithium battery including the negative electrode sheet according to Supplementary Note 9 above.

Claims

1. A silicon-based composite material uniformly modified, wherein The general formula of the silicon-based composite material is SiC ｘ A ｙ O ｚ where 0 < x < 20, 0 < y < 10, 0 < z < 10, here, A is one or more of B, Al, Mg, Ca, Fe, Co, Ni, Cu, Zn, Ge, Sn, Li; C is distributed so as to be uniformly dispersed inside the particles of the silicon-based composite material at the atomic level, and there is no aggregation of carbon of 20 nm or more, and a part or all of the carbon atoms are bonded to silicon atoms to form an amorphous Si-C bond. In the measurement of the focused ion beam-transmission electron microscope (FIB-TEM) of the silicon-based composite material, the EDS (Energy Dispersive X-ray Spectroscopy) mapping of the particle cross-section shows that the silicon element, carbon element, element A, and oxygen element inside the particles are uniformly distributed, The average particle size D of the particles of the silicon-based composite material ５０ is from 1 nm to 100 μm, and the specific surface area is 0.5 m ２ / g to 40 m ２ / g, the mass of the carbon atoms accounts for 0.1% to 40% of the mass of the silicon-based composite material, and the mass of the element A accounts for 3% to 40% of the mass of the composite particles. A silicon-based composite material characterized by the above.

2. The silicon-based composite material according to claim 1, further having a carbon coating layer on the outside of the silicon-based composite material, wherein the mass of the carbon coating layer accounts for 0 to 20% of the mass of the silicon-based composite material.

3. The silicon-based composite material according to claim 2, wherein the mass of the carbon atoms accounts for 0.5% to 10% of the mass of the silicon-based composite material, and the mass of the carbon coating layer accounts for 0 to 10% of the mass of the silicon-based composite material.

4. A method for preparing the uniformly modified silicon-based composite material according to any one of claims 1 to 3 above, including a one-step vapor phase growth method or a two-step vapor phase growth method, Specifically, the one-step vapor phase growth method is uniformly mixing silicon powder, silicon dioxide powder, elemental A powder and / or oxide powder of A in required amounts and putting them into a vacuum furnace, after reducing the pressure of the vacuum furnace, heating it to 1200°C to 1700°C to obtain a mixed vapor containing silicon element, oxygen element, and element A, blowing a carbon-containing gas source into the vacuum furnace under a protective atmosphere, and performing a gas phase reaction with the mixed vapor for 1 to 24 hours, cooling the material obtained by the gas phase reaction to room temperature, taking out the material, pulverizing it, and performing sieving to obtain a silicon-based composite material SiCx Ay Oz in which carbon is distributed so as to be uniformly dispersed at the atomic level, and Specifically, the two-step vapor phase growth method is uniformly mixing silicon powder and silicon dioxide powder in required amounts and putting them into a vacuum furnace, after reducing the pressure of the vacuum furnace, heating it to 1200°C to 1700°C to obtain a mixed vapor containing silicon element and oxygen element, Under a protective atmosphere, a carbon-containing gas source is blown into a vacuum furnace, and a gas-phase reaction is carried out with the mixed vapor for 1 to 24 hours. The material obtained by the gas-phase reaction is cooled to room temperature, the material is taken out, pulverized, and sieved to obtain a composite material SiCxOz in which carbon is uniformly distributed at the atomic level. SiCxOz is uniformly mixed with single A powder and / or A oxide powder, put into a high-temperature furnace, and heat-treated at 600°C to 1500°C for 2 to 24 hours to obtain a silicon-based composite material SiCx AyOz in which carbon is uniformly distributed at the atomic level. A preparation method characterized by the above.

5. The preparation method according to claim 4, wherein the carbon-containing gas source contains one or more of methane, propane, butane, acetylene, ethylene, propylene, butadiene, or carbon monoxide.

6. The method further includes cooling the material to room temperature, taking out the material, pulverizing it, sieving it, and then applying a carbon coating to the sieved material, where the carbon coating includes at least one of a gas-phase coating, a liquid-phase coating, and a solid-phase coating. The preparation method according to claim 4.

7. A negative electrode sheet including the uniformly modified silicon-based composite material according to any one of claims 1 to 3 above.

8. A lithium battery including the negative electrode sheet according to claim 7 above.

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