Method for preparing uniformly modified negative electrode material for silicon-based lithium-ion battery

Abstract

The present invention provides a uniformly modified silicon-based negative electrode material for lithium-ion batteries, and its preparation method and application. [Solution] The present invention relates to a uniformly modified silicon-based lithium ion battery anode material and its preparation method and application. The structure of the silicon-based lithium ion battery anode material is such that carbon atoms are uniformly distributed in a silicon monoxide matrix at the atomic level, and in the measurement of the silicon-based lithium ion battery anode material using a focused ion beam-transmission electron microscope (FIB-TEM), EDS analysis of the particle cross section shows that the carbon, oxygen and silicon elements inside the particles are uniformly distributed, and the average particle size D of the silicon-based lithium ion battery anode material is 1.0 μm. 50 The particle size is 1 nm to 100 μm, and the specific surface area is 0.5 m 2 / g~40m 2 / g, and the mass of the carbon atoms accounts for 0.1%-40% of the mass of the silicon monoxide matrix. In the present invention, a carbon-containing gas source is introduced during the preparation of silicon monoxide, and the distribution of carbon atoms in silicon monoxide belongs to bulk phase distribution, so that the negative electrode material has the advantage of carbon bulk phase doping, and the electrical conductivity of the material and the cycle stability of lithium ion batteries are improved.

Description

Technical Field

[0001] Cross-reference This application claims the priority of a Chinese patent application with an application number of 202110524182.2, filed with the China National Intellectual Property Administration on May 13, 2021, and titled "Anode Material for Uniformly Modified Silicon-based Lithium-ion Batteries, Its Preparation Method and Application".

[0002] The present invention relates to the technical field of materials, and particularly to an anode material for uniformly modified silicon-based lithium-ion batteries, its preparation method and application.

Background Art

[0003] With the demands of economic and social development, natural resources are constantly being consumed. Non-renewable resources mainly such as oil and natural gas are gradually in short supply and are depleting day by day. Also, the environmental pollution problems caused during the excessive extraction and utilization of oil should not be underestimated. Therefore, for scientists, finding clean, environmentally friendly and highly efficient energy has become the top priority. Lithium-ion battery technology is one of the clean and environmentally friendly new energy technologies.

[0004] The anode material is one of the most important materials in lithium-ion battery technology. The currently commercially available graphite anode has reached a technical bottleneck due to its low capacity per unit mass. Silicon, on the other hand, is one of the most promising lithium-ion anode materials. Silicon-based anode materials with a high specific capacity of 4200 mAh / g and silicon-based anode materials with three-dimensional diffusion channels are gradually showing the advantage of high energy density. Although silicon-based anode materials can achieve a satisfactory energy density, there are also technical bottlenecks as materials. A series of drawbacks such as the volume expansion effect and low conductivity of silicon-based anode materials themselves limit their actual applications.

[0005] Carbon coating is a common modification method. Currently, commercially available silicon monoxide is generally carbon-coated, which improves the conductivity of the material surface, avoids direct contact with the electrolyte, and improves the cycle performance of the material. Carbon coating can only change the surface conductivity, and it is also necessary to improve the conductivity inside the particles to achieve fast charging performance.

Summary of the Invention

Problems to be Solved by the Invention

[0006] Embodiments of the present invention provide a uniformly modified negative electrode material for silicon-based lithium-ion batteries, a preparation method thereof, and applications. The carbon element, oxygen element, and silicon element inside the negative electrode material are uniformly distributed. Due to the bulk phase doping of the carbon element, 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 negative electrode material for a silicon-based lithium-ion battery, the structure of which is such that carbon atoms are uniformly distributed at the atomic level in a silicon monoxide matrix. In the measurement of the focused ion beam-transmission electron microscope (FIB-TEM) of the negative electrode material for the silicon-based lithium-ion battery, it is shown by the EDS mapping of the particle cross-section that the carbon element, oxygen element, and silicon element inside the particles are uniformly distributed. The average particle size D of the particles of the negative electrode material for the silicon-based lithium-ion battery 50 is from 1 nm to 100 μm, the specific surface area is 0.5 m 2 / g to 40 m 2 / g, and the mass of the carbon atoms accounts for 0.1% to 40% of the mass of the silicon monoxide matrix.

[0008] Preferably, the outside of the negative electrode material for the silicon-based lithium-ion battery 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 monoxide matrix.

[0009] More preferably, the mass of the carbon atoms accounts for 0.5% to 10% of the mass of the silicon monoxide matrix, and the mass of the carbon coating layer accounts for 0 to 10% of the mass of the silicon monoxide matrix.

[0010] In a second aspect, an embodiment of the present invention is a method for preparing a negative electrode material for a silicon-based lithium-ion battery according to the first aspect, wherein the preparation method comprises: Under a protective atmosphere, a carbon-containing gas source and a mixed vapor of preheated silicon and silicon dioxide are subjected to a gas-phase reaction for 1 to 24 hours to obtain a material in which carbon atoms are uniformly distributed at the atomic level in a silicon monoxide matrix; cooling the material to room temperature, taking out the material, pulverizing it, and performing sieving to obtain particles in which carbon atoms are uniformly distributed at the atomic level in a silicon monoxide matrix, that is, the negative electrode material for a silicon-based lithium-ion battery; and

[0011] Preferably, the carbon-containing gas source includes one or more of methane, propane, butane, acetylene, ethylene, propylene, butadiene, or carbon monoxide.

[0012] Preferably, after cooling the material to room temperature, taking out the material, pulverizing it, and performing sieving, the preparation method further includes subjecting the sieved material to carbon coating, classifying it, and then obtaining the negative electrode material.

[0013] More preferably, the carbon coating includes at least one of vapor-phase coating, liquid-phase coating, and solid-phase coating.

[0014] In a third aspect, an embodiment of the present invention relates to a negative electrode sheet including the negative electrode material for a silicon-based lithium-ion battery according to the first aspect.

[0015] In a fourth aspect, an embodiment of the present invention relates to a lithium battery including the negative electrode sheet according to the third aspect.

Advantages of the Invention

[0016] The negative electrode material for a silicon-based lithium-ion battery according to the present invention, in which carbon atoms are uniformly distributed at the atomic level inside, improves the conductivity inside the silicon monoxide particles due to the bulk phase distribution of carbon in the silicon monoxide, is advantageous for the rapid charging performance of the material, and alleviates the volume expansion and contraction of the silicon monoxide during the lithium insertion / extraction process, relieves the deformation stress, and is advantageous for enhancing the cycle characteristics of the material.

Brief Description of the Drawings

[0017] Hereinafter, the technical solutions in the embodiments of the present invention will be described in more detail with reference to the drawings and examples.

[0018] [Figure 1] It is a flowchart of a method for preparing a negative electrode material for a silicon-based lithium-ion battery according to an embodiment of the present invention. [Figure 2] It is an EDS mapping of FIB-TEM of a silicon-based negative electrode material in which carbon atoms are uniformly distributed at the atomic level inside according to Example 1 of the present invention. [Figure 3] It is a high-resolution electron microscope image of FIB-TEM of a silicon-based negative electrode material in which carbon atoms are uniformly distributed at the atomic level inside according to Example 1 of the present invention.

Modes for Carrying Out the Invention

[0019] Hereinafter, the present invention will be further described with reference to the drawings and specific examples, but it should be understood that these examples 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.

[0020] The structure of the negative electrode material for the silicon-based lithium-ion battery of the present invention is such that carbon atoms are distributed uniformly at the atomic level in the silicon monoxide matrix. In the measurement of the focused ion beam-transmission electron microscope (FIB-TEM) of the negative electrode material for the silicon-based lithium-ion battery, it is shown by the EDS mapping of the particle cross-section that the carbon element, oxygen element, and silicon element inside the particles are uniformly distributed. The average particle size D of the particles of the negative electrode material for the silicon-based lithium-ion battery 50 is from 1 nm to 100 μm, and the specific surface area is 0.5 m 2 / g to 40 m 2 / g, and the mass of the carbon atoms accounts for 0.1% to 40% of the mass of the silicon monoxide matrix. Preferably, the mass of the carbon atoms accounts for 0.5% to 10% of the mass of the silicon monoxide matrix.

[0021] The outer layer 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 monoxide matrix. Preferably, the mass of the carbon coating layer accounts for 0 to 10% of the mass of the silicon monoxide matrix.

[0022] The negative electrode material for the silicon-based lithium-ion battery of the present invention is obtained by the following preparation method. The main method steps are as shown in FIG. 1 and include the following steps.

[0023] In step 110, under a protective atmosphere, a carbon-containing gas source and a mixed vapor of preheated silicon and silicon dioxide are subjected to a gas-phase reaction for 1 to 24 hours to obtain a material in which carbon atoms are distributed uniformly at the atomic level in the silicon monoxide matrix. Specifically, the protective atmosphere may be an N2 or Ar atmosphere.

[0024] The carbon-containing gas source includes one or more of methane, propane, butane, acetylene, ethylene, propylene, butadiene, or carbon monoxide.

[0025] In step 120, the material is cooled to room temperature, taken out, pulverized, and sieved, so as to obtain particles in which carbon atoms are uniformly distributed at the atomic level in the silicon monoxide matrix, that is, the negative electrode material for a silicon-based lithium ion battery.

[0026] Furthermore, when preparing a negative electrode material for a silicon-based lithium ion battery further having a carbon coating layer on the outside, by applying a carbon coating to the pulverized material, after classification, a negative electrode material for a silicon-based lithium ion battery can be obtained. Specific methods of carbon coating may include at least one of vapor phase coating, liquid phase coating, and solid phase coating. The above three methods are all coating methods commonly used in the process of preparing battery materials, and the description thereof is omitted here.

[0027] The negative electrode material for a silicon-based lithium ion battery according to the present invention, in which carbon atoms are uniformly distributed at the atomic level inside, improves the conductivity inside the silicon monoxide particles due to the bulk phase distribution of carbon in the silicon monoxide, is advantageous for the rapid charging performance of the material, and relaxes the volume expansion and contraction of the silicon monoxide during the lithium insertion and extraction process, relaxes the deformation stress, and is advantageous for enhancing the cycle characteristics of the material.

[0028] The negative electrode material for a silicon-based lithium ion battery according to the present invention can be used to produce a negative electrode sheet applied to a lithium battery.

[0029] 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 the negative electrode material for a silicon-based lithium ion battery by the method according to the above embodiment of the present invention, and the method and characteristics applied to a lithium secondary battery respectively.

Example

[0030] 1 kg of silicon powder and 1 kg of silicon dioxide were put into a high-temperature reactor, heated to 1300 °C until they turned into vapor, and 1.6 L of methane was slowly blown in with a stream of argon gas and reacted for 3 hours, then cooled to room temperature. After taking out the material and pulverizing it, a silicon monoxide negative electrode material with carbon atoms uniformly distributed at the atomic level inside was obtained. As a result of measurement with a carbon-sulfur analyzer, the carbon content in this was 2%.

[0031] Perform FIB-TEM measurement on the silicon monoxide negative electrode material with carbon atoms uniformly distributed at the atomic level inside, and observe the carbon distribution inside the particles by EDS analysis. Figure 2 is the EDS mapping of FIB-TEM, and Figure 3 is the high-resolution electron microscope image of FIB-TEM. From the EDS element mapping in Figure 2, it can be seen that three elements, Si, O, and C, are uniformly distributed inside the particles. From the high-resolution electron microscope image in Figure 3, it can be seen that the internal atoms of silicon monoxide with carbon atoms uniformly distributed at the atomic level inside are arranged disorderly and have an amorphous structure.

[0032] After that, carbon coating was applied to the silicon monoxide negative electrode material. 2 kg of the material was put into a rotary furnace, heated to 1000 °C under an argon atmosphere, and argon and a mixed gas of propylene and acetylene equal in amount to argon were blown in at a volume ratio of 1:1 to perform vapor phase coating. Here, the volume ratio of propylene to acetylene is 1:1. Keep the temperature for 2 hours, 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 and with carbon atoms uniformly distributed at the atomic level inside was obtained, and the total carbon content in this was 5%.

[0033] Using a silicon monoxide material having carbon atoms distributed uniformly at the atomic level inside the above carbon coating as the anode material, conductive carbon black (SP) as the conductive additive and polyvinylidene fluoride (PVDF) as the binder are weighed in a ratio of 95%:2%:3%, and a slurry is prepared in a beater at room temperature. The prepared slurry is uniformly coated on a copper foil. After drying in a hot air dryer at 50 °C for 2 hours, it is cut into 8×8 mm electrode sheets and dried under vacuum at 100 °C in a vacuum dryer for 10 hours. For battery assembly, the dried electrode sheets are immediately transferred into a glove box and prepared.

[0034] The assembly of the simulated battery is 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, the battery is assembled. A constant current charge-discharge mode test is carried out using a charger. The discharge cut-off voltage is 0.005 V and the charge cut-off voltage is 1.5 V. The first cycle charge-discharge test is carried out at a C / 10 current density, and the second cycle discharge test is carried out at a C / 10 current density. The test results of the initial Coulomb efficiency, 5C reversible capacity, and cycle characteristics at a 5C rate are shown in Table 1.

Example

[0035] 3 kg of silicon powder and 3 kg of silicon dioxide were put into a high-temperature reactor, heated to 1350 °C until vaporized, and 23.4 L of propane was slowly blown in with an argon gas flow and reacted for 8 hours, then cooled to room temperature. After taking out the material and pulverizing it, a silicon monoxide negative electrode material with carbon atoms 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 was 1.5%. Then, the silicon monoxide negative electrode 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 an argon and a mixed gas of propylene and methane equal to the amount of argon were blown in at a volume ratio of 1:1 to perform vapor phase coating. Here, the volume ratio of propylene to methane was 2:3. After maintaining the temperature for 3 hours, closing the organic gas source and lowering the temperature, a silicon monoxide negative electrode material containing a carbon coating layer and with carbon atoms uniformly dispersed at the atomic level inside was obtained, and the total carbon content in this was 6.5%.

[0036] 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 coulombic efficiency, 5C reversible capacity, and cycle characteristics at the 5C rate are shown in Table 1.

Example

[0037] 2 kg of silicon powder and 2 kg of silicon dioxide were put into a high-temperature reactor, heated to 1350 °C until vaporized, and 1 L of propylene was slowly blown in with an argon gas flow and reacted for 5 hours, then cooled to room temperature. After taking out the material and pulverizing it, a silicon monoxide negative electrode material with carbon atoms 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 was 3.1%. Then, the silicon monoxide negative electrode material was coated with carbon. 2 kg of the material was put into a rotary furnace, heated to 950 °C under an argon atmosphere, and an argon and an equal amount of propane were blown in at a volume ratio of 1:1 to perform vapor phase coating. After maintaining the temperature for 2.5 hours, closing the organic gas source and lowering the temperature, a silicon monoxide negative electrode material containing a carbon coating layer and with carbon atoms uniformly dispersed at the atomic level inside was obtained, and the total carbon content in this was 8.2%.

[0038] The preparation 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, 5C reversible capacity, and cycle characteristics at a 5C rate are shown in Table 1.

Example

[0039] 2 kg of silicon powder and 2 kg of silicon dioxide were put into a high-temperature reactor, heated to 1300 °C until vaporized, and 1 L of ethylene was slowly blown in with an argon gas flow and reacted for 5 hours, then cooled to room temperature. After taking out the material and pulverizing it, a silicon monoxide negative electrode material with carbon atoms 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 2.8%. Then, carbon coating was applied to the silicon monoxide negative electrode material. 2 kg of the material was put into a rotary furnace, heated to 1150 °C under an argon atmosphere, and argon and propane equal in amount to argon were blown in at a volume ratio of 1:1 to perform vapor phase coating. The temperature was maintained for 2.5 hours, the organic gas source was closed, and after the temperature was lowered, a silicon monoxide negative electrode material containing a carbon coating layer and with carbon atoms uniformly dispersed at the atomic level inside was obtained, and the total carbon content in this was 7.8%.

[0040] 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, 5C reversible capacity, and cycle characteristics at a 5C rate are shown in Table 1.

Example

[0041] 3 kg of silicon powder and 3 kg of silicon dioxide were put into a high-temperature reactor, heated to 1400 °C until they became vapor, and a mixed gas of 11.7 L of acetylene and 5 L of methane was slowly blown in with an argon gas flow and reacted for 8 hours, then cooled to room temperature. After taking out the material and pulverizing it, a silicon monoxide negative electrode material in which carbon atoms were uniformly dispersed at the atomic level was obtained. As a result of measurement with a carbon-sulfur analyzer, the carbon content in this was 1.5%. Then, carbon coating was applied to the silicon monoxide negative electrode material, 2 kg of the material was put into a rotary furnace, heated to 1100 °C under an argon atmosphere, and a mixed gas of argon and propylene and methane in an amount equal to argon was blown in at a volume ratio of 1:1 to perform vapor phase coating. Here, the volume ratio of propylene to methane was 2:3. After maintaining the temperature for 3 hours, closing the organic gas source and lowering the temperature, a silicon monoxide negative electrode material containing a carbon coating layer and in which carbon atoms were uniformly dispersed at the atomic level was obtained, and the total carbon content in this was 6.5%.

[0042] 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, 5C reversible capacity, and cycle characteristics at a 5C rate are shown in Table 1.

Example

[0043] 2 kg of silicon powder and 2 kg of silicon dioxide were put into a high-temperature reactor, heated to 1250 °C until they became vapor, and 1 L of acetylene was slowly blown in with an argon gas flow and reacted for 5 hours, then cooled to room temperature. After taking out the material and pulverizing it, a silicon monoxide negative electrode material in which carbon atoms were uniformly dispersed at the atomic level was obtained. As a result of measurement with a carbon-sulfur analyzer, the carbon content in this was 2.8%. Then, carbon coating was applied to the silicon monoxide negative electrode material, 2 kg of the material was put into a rotary furnace, heated to 1150 °C under an argon atmosphere, and argon and propane in an amount equal to argon were blown in at a volume ratio of 1:1 to perform vapor phase coating. After maintaining the temperature for 2.5 hours, closing the organic gas source and lowering the temperature, a silicon monoxide negative electrode material containing a carbon coating layer and in which carbon atoms were uniformly dispersed at the atomic level was obtained, and the total carbon content in this was 5.8%.

[0044] 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, 5C reversible capacity, and cycle characteristics at the 5C rate are shown in Table 1.

Example

[0045] 2 kg of silicon powder and 2 kg of silicon dioxide were put into a high-temperature reactor, heated to 1200 °C until they became vapor, and 1 L of butane was slowly blown in with an argon gas flow and reacted for 5 hours, then cooled to room temperature. After taking out the material and pulverizing it, a silicon monoxide negative electrode material in which carbon atoms were uniformly distributed at the atomic level inside was obtained. As a result of measurement with a carbon-sulfur analyzer, the carbon content in this was 3.1%. Then, carbon coating was applied to the silicon monoxide negative electrode material. 2 kg of the material was put into a rotary furnace, heated to 1100 °C under an argon atmosphere, and argon and acetylene were blown in at a volume ratio of 1:2 to perform vapor phase coating. The temperature was maintained for 3 hours, the organic gas source was closed, and after the temperature was lowered, a silicon monoxide negative electrode material containing a carbon coating layer and in which carbon atoms were uniformly distributed at the atomic level inside was obtained, and the total carbon content in this was 6.2%.

[0046] 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, 5C reversible capacity, and cycle characteristics at the 5C rate are shown in Table 1.

Example

[0047] 1 kg of silicon powder and 1 kg of silicon dioxide were put into a high-temperature reactor, heated to 1500 °C until vaporized, and 2 L of butadiene was slowly blown in with an argon gas flow and reacted for 6 hours, then cooled to room temperature. After taking out the material and pulverizing it, a silicon monoxide negative electrode material with carbon atoms 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 2.6%. Thereafter, the silicon monoxide negative electrode material was coated with carbon. 2 kg of the material was put into a rotary furnace, heated to 1000 °C under an argon atmosphere, and argon and acetylene 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. Here, the volume ratio of acetylene to propane was 3:1. After maintaining the temperature for 3 hours, closing the organic gas source and lowering the temperature, a silicon monoxide negative electrode material containing a carbon coating layer and with carbon atoms uniformly dispersed at the atomic level inside was obtained, and the total carbon content in this was 4.9%.

[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, 5C reversible capacity, and cycle characteristics at a 5C rate are shown in Table 1.

Example

[0049] 3 kg of silicon powder and 3 kg of silicon dioxide were put into a high-temperature reactor, heated to 1300 °C until vaporized, and 1.4 L of carbon monoxide was slowly blown in with an argon gas flow and reacted for 12 hours, then cooled to room temperature. After taking out the material and pulverizing it, a silicon monoxide negative electrode material with carbon atoms 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 3.3%. Thereafter, the silicon monoxide negative electrode material was coated with carbon. 2 kg of the material was put into a rotary furnace, heated to 1200 °C under an argon atmosphere, and argon and acetylene were blown in at a volume ratio of 1:2 to perform vapor phase coating. After maintaining the temperature for 3 hours, closing the organic gas source and lowering the temperature, a silicon monoxide negative electrode material containing a carbon coating layer and with carbon atoms uniformly dispersed at the atomic level inside was obtained, and the total carbon content in this was 8.3%.

[0050] 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, 5C reversible capacity, and cycle characteristics at the 5C rate are shown in Table 1.

Example

[0051] 3 kg of silicon powder and 3 kg of silicon dioxide were placed in a high-temperature reactor and heated to 1300 °C until they turned into vapor. A mixed gas of 1.2 L of carbon monoxide and 1.2 L of acetylene was slowly blown in with the flow of argon gas and reacted for 10 hours, and then cooled to room temperature. After taking out the material and pulverizing it, a silicon monoxide negative electrode material in which carbon atoms were uniformly distributed at the atomic level was obtained. As a result of measurement with a carbon-sulfur analyzer, the carbon content in this was 3.3%. Then, the silicon monoxide negative electrode material was coated with carbon. The pulverized sample and petroleum pitch were mixed at a mass ratio of 20:1, put into a high-temperature furnace, heat-treated at 900 °C for 2 hours under a nitrogen atmosphere, cooled, and classified. After that, a silicon monoxide negative electrode material containing a carbon coating layer and in which carbon atoms were uniformly distributed at the atomic level was obtained, and the total carbon content in this was 5%.

[0052] Using the silicon monoxide negative electrode material containing the above carbon coating layer and in which carbon atoms were uniformly distributed at the atomic level as the negative electrode material, conductive carbon black (SP) as a conductive additive and polyvinylidene fluoride (PVDF) as an adhesive were weighed at a ratio of 95%:2%:3%, and a slurry was prepared in a beaker 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 vacuum-dried in a vacuum dryer at 100 °C for 10 hours. For battery assembly, the dried electrode sheets were immediately transferred into a glove box and prepared.

[0053] 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 and the ternary cathode material NCM811 as the counter electrode, garnet-type Li7La3Zr2O 12(LLZO) was used as a solid electrolyte and assembled into a button-shaped all-solid-state battery in a glove box, which was then 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 of charge-discharge test was performed at a C / 10 current density, and the second cycle of discharge test was performed at a C / 10 current density. The test results of the initial Coulomb efficiency, 5C reversible capacity, and cycle characteristics at a 5C rate are shown in Table 1.

Example

[0054] 2 kg of silicon powder and 2 kg of silicon dioxide were put into a high-temperature reactor and heated to 1300 °C to turn them into vapor. A mixed gas of 0.9 L of methane, 1.2 L of propylene, and 1.3 L of propane was slowly blown in with the flow of argon gas and reacted for 6 hours, and then cooled to room temperature. After taking out the material and pulverizing it, a silicon monoxide negative electrode material in which carbon atoms were uniformly distributed at the atomic level inside was obtained. As a result of measurement with a carbon-sulfur analyzer, the carbon content in this was 3.1%. Then, the silicon monoxide negative electrode material was coated with carbon. 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 monoxide negative electrode material containing a carbon coating layer and in which carbon atoms were uniformly distributed at the atomic level inside, and the total carbon content in this was 4.8%.

[0055] Using the silicon monoxide negative electrode material containing the above carbon coating layer and having silicon atoms uniformly dispersed at the atomic level inside as the negative electrode material, conductive carbon black (SP) as the conductive additive and polyvinylidene fluoride (PVDF) as the binder are weighed in a ratio of 95%:2%:3%, and a slurry is prepared in a beaker at room temperature. The prepared slurry is uniformly coated on a copper foil. After drying in a blower dryer at 50 °C for 2 hours, it is cut into 8×8 mm electrode sheets, and vacuum dried in a vacuum dryer at 100 °C for 10 hours. For battery assembly, the dried electrode sheets are immediately transferred into a glove box and prepared.

[0056] The assembly of the simulated battery is 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 a polyolefin-based polymer gel electrolyte membrane as the semi-solid electrolyte, it is assembled into a button-shaped semi-solid battery in the glove box, and then charged to evaluate its electrochemical performance. A constant current charge-discharge mode test is carried out using a charge-discharge device. The discharge cut-off voltage is 0.005 V, the charge cut-off voltage is 1.5 V. The first cycle charge-discharge test is carried out at a C / 10 current density, and the second cycle discharge test is carried out at a C / 10 current density. The test results of the initial Coulomb efficiency, 5C reversible capacity, and cycle characteristics at a 5C rate are shown in Table 1.

Example

[0057] 1 kg of silicon powder and 1 kg of silicon dioxide are put into a high-temperature reactor, heated to 1400 °C until vaporized, and a mixed gas of 0.9 L of methane and 1.2 L of propylene is slowly blown in with an argon gas flow and reacted for 8 hours, and then cooled to room temperature. After taking out the material and pulverizing it, a silicon monoxide negative electrode material with carbon atoms uniformly dispersed at the atomic level inside is obtained.

[0058] 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, 5C reversible capacity, and cycle characteristics at a 5C rate are shown in Table 1.

Example

[0059] 3 kg of silicon powder and 3 kg of silicon dioxide were placed in a high-temperature reactor, heated to 1350 °C until vaporized, and a mixed gas of 5 L of acetylene and 5 L of ethylene was slowly blown in under a stream of argon gas. After reacting for 6 hours, it was cooled to room temperature. After taking out the material and pulverizing it, a silicon monoxide negative electrode material in which carbon atoms were uniformly distributed at the atomic level was obtained. As a result of measurement with a carbon and sulfur analyzer, the carbon content in this was 3.5%.

[0060] 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, 5C reversible capacity, and cycle characteristics at a 5C rate are shown in Table 1.

Example

[0061] 3 kg of silicon powder and 3 kg of silicon dioxide were placed in a high-temperature reactor, heated to 1400 °C until vaporized, and 5 L of butadiene was slowly blown in under a stream of argon gas. After mixing the above vapors with each other and reacting for 4 hours, it was cooled to room temperature. After taking out the material and pulverizing it, a silicon monoxide negative electrode material in which carbon atoms were uniformly distributed at the atomic level was obtained. As a result of measurement with a carbon and sulfur analyzer, the carbon content in this was 2.7%.

[0062] 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, 5C reversible capacity, and cycle characteristics at a 5C rate are shown in Table 1.

[0063] (Comparative Example 1) 1 kg of silicon powder and 1 kg of silicon dioxide were placed in a high-temperature reactor, heated to 1300 °C until vaporized, reacted for 3 hours, and then cooled to room temperature. After taking out the material and pulverizing it, a silicon monoxide negative electrode material was obtained.

[0064] Thereafter, carbon coating was applied to the silicon monoxide negative electrode material. 2 kg of the material was placed in a rotary furnace, heated to 1000 °C under an argon atmosphere, and argon and a mixed gas of propylene and acetylene equal in amount to argon were blown in at a volume ratio of 1:1 to perform vapor phase coating. Here, the volume ratio of propylene to acetylene was 1:1. The temperature was maintained for 2 hours, the organic gas source was closed, the temperature was lowered, the material was taken out, and after classification, a silicon monoxide negative electrode material containing a carbon coating layer was obtained, and the total carbon content therein was 3%.

[0065] 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, 5C reversible capacity, and cycle characteristics at a 5C rate are shown in Table 1.

[0066] The test results of the initial Coulomb efficiency, 5C reversible capacity, and cycle characteristics at a 5C rate of the negative electrode materials in Examples 1 to 14 and Comparative Example 1 are as follows.

[0067]

Table 1

[0068] As can be seen from the data in the table, under the same test conditions, in Examples 1 to 14, bulk phase doping modification was performed on the silicon-based negative electrode material using a carbon-containing gas source, and the cycle characteristics were all very high. In Comparative Example 1, only the surface of the silicon monoxide was carbon-coated, and the cycle characteristics were significantly inferior to those of Examples 1 to 10.

[0069] As can be seen from the EDS element mapping in Figure 2, in Example 1, carbon atoms were doped during the preparation process of the negative electrode material, belonging to bulk phase doping. Therefore, uniformly distributed carbon atoms existed inside the particles, which was beneficial to the cycle characteristics of the material.

[0070] 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. [Additional Note] [Additional Note 1] A negative electrode material for a silicon-based lithium-ion battery that is uniformly modified, The structure of the negative electrode material for the silicon-based lithium-ion battery is such that carbon atoms are distributed uniformly at the atomic level in the silicon monoxide matrix. In the measurement of the focused ion beam - transmission electron microscope (FIB-TEM) of the negative electrode material for the silicon-based lithium-ion battery, the EDS analysis of the particle cross-section shows that the carbon element, oxygen element, and silicon element inside the particles are uniformly distributed. The average particle size D of the particles of the negative electrode material for the silicon-based lithium-ion battery 50 is from 1 nm to 100 μm, the specific surface area is 0.5 m 2 / g to 40 m 2 / g, and the mass of the carbon atoms accounts for 0.1% to 40% of the mass of the silicon monoxide matrix. A negative electrode material for a silicon-based lithium-ion battery, characterized by the above. [Additional Note 2] The negative electrode material for the silicon-based lithium-ion battery further has a carbon coating layer on the outside, and the mass of the carbon coating layer accounts for 0% to 20% of the mass of the silicon monoxide matrix. The negative electrode material for the silicon-based lithium-ion battery according to Additional Note 1, characterized by the above. [Additional Note 3] The mass of the carbon atoms accounts for 0.5% to 10% of the mass of the silicon monoxide matrix, and the mass of the carbon coating layer accounts for 0% to 10% of the mass of the silicon monoxide matrix. The negative electrode material for the silicon-based lithium-ion battery according to Additional Note 2, characterized by the above. [Additional Note 4] A method for preparing the negative electrode material for a silicon-based lithium-ion battery according to any one of the above Additional Notes 1 to 3, Under a protective atmosphere, a carbon-containing gas source and a mixed vapor of preheated silicon and silicon dioxide are subjected to a gas-phase reaction for 1 to 24 hours to obtain a material in which carbon atoms are distributed uniformly at the atomic level in the silicon monoxide matrix. Cool the material to room temperature, take out the material, pulverize it, and perform sieving to obtain particles in which carbon atoms are distributed uniformly at the atomic level in the silicon monoxide matrix, that is, the negative electrode material for the silicon-based lithium-ion battery. including A preparation method characterized by the above. [Additional Note 5] The carbon-containing gas source includes one or more of methane, propane, butane, acetylene, ethylene, propylene, butadiene, or carbon monoxide. The preparation method according to Additional Note 4, characterized by the above. [Additional Note 6] The preparation method according to supplementary note 4, further comprising cooling the material to room temperature, taking out the material, pulverizing it, performing sieving, subjecting the sieved material to carbon coating, and classifying to obtain the negative electrode material. [Supplementary note 7] The preparation method according to supplementary note 6, wherein the carbon coating includes at least one of vapor phase coating, liquid phase coating, and solid phase coating. [Supplementary note 8] A negative electrode sheet including the negative electrode material for a silicon-based lithium ion battery according to any one of supplementary notes 1 to 3 above. [Supplementary note 9] A lithium battery including the negative electrode sheet according to supplementary note 8 above.

Claims

A method for preparing a uniformly modified negative electrode material for a silicon-based lithium-ion battery, comprising: The structure of the negative electrode material for the silicon-based lithium-ion battery is such that carbon atoms are distributed uniformly at the atomic level in the silicon monoxide matrix. In the measurement of the focused ion beam-transmission electron microscope (FIB-TEM) of the negative electrode material for the silicon-based lithium-ion battery, the EDS analysis of the particle cross-section shows that the carbon, oxygen, and silicon elements inside the particles are uniformly distributed. The average particle size D50 of the particles of the negative electrode material for the silicon-based lithium-ion battery is 1 nm to 100 μm, the specific surface area is 0.5 m2 / g to 40 m2 / g, and the mass of the carbon atoms accounts for 0.1% to 40% of the mass of the silicon monoxide matrix. Under a protective atmosphere, a gas-phase mixing reaction is carried out for 1 to 24 hours on a carbon-containing gas source and a mixed vapor of preheated silicon and silicon dioxide, so that carbon atoms are distributed uniformly at the atomic level in the silicon monoxide matrix to form a target material. After the gas-phase mixing reaction, the target material is cooled to room temperature, taken out, pulverized, and sieved to obtain particles in which carbon atoms are distributed uniformly at the atomic level in the silicon monoxide matrix, that is, the negative electrode material for the silicon-based lithium-ion battery. The preparation method is characterized by including the above steps.

2. The preparation method according to claim 1, characterized in that the carbon-containing gas source includes one or more of methane, propane, butane, acetylene, ethylene, propylene, butadiene, or carbon monoxide.

3. After cooling the target material to room temperature, taking out the material, pulverizing it, and sieving it, the preparation method further includes subjecting the sieved material to carbon coating, classifying it, and then obtaining the negative electrode material. The preparation method is characterized by including the above steps.

4. The preparation method according to claim 3, characterized in that the carbon coating includes at least one of gas-phase coating, liquid-phase coating, and solid-phase coating.

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