Silicon carbon anode material and method for manufacturing the same

Abstract

This invention relates to a silicon-carbon anode material and a method for manufacturing the same. The silicon-carbon anode material comprises a carbon skeleton having a porous structure and a silicon-based material provided within the porous structure, wherein the content of high-valence silicon in the region from the surface to 10 nm inward of the silicon-carbon anode material is less than 25% of the total amount of low-valence silicon and the high-valence silicon, the low-valence silicon is silicon with a valency of 0 to 2, and the high-valence silicon is silicon with a valency of 3 to 4. The silicon-carbon anode material can improve the capacity per gram and initial Coulomb efficiency in lithium desorption of the silicon-carbon anode material, and improve the capacity per gram and initial Coulomb efficiency in the discharge of a secondary battery.

Description

[Technical Field]

[0001] (Cross-reference of related applications) This disclosure is based on and claims priority to a Chinese patent application with application number 202311619241.X, filed on November 28, 2023, and titled "Silicon Carbon Anode Material and Method for Manufacturing the Same." All contents of the said Chinese patent application are incorporated herein by reference.

[0002] This disclosure relates to the battery technology field, and more particularly to silicon carbon anode materials and methods for manufacturing the same. [Background technology]

[0003] As the output of electrical devices such as mobile phones, computers, power tools, and electric vehicles continues to increase, the demand for energy density in secondary batteries is also rising. Silicon-based anode materials have a high capacity per gram, so the industry is currently working to increase the energy density of secondary batteries by adding silicon-based anode materials to anode sheets. However, because the volume expansion rate of silicon-based anode materials increases after lithium is inserted, cracks may occur in the anode sheet.

[0004] To address the relatively high volume expansion coefficient of silicon-based anode materials, silicon-carbon anode materials are now often used, which are formed by depositing silicon inside porous carbon. The gaps within the porous carbon reduce the expansion of the silicon-based material. However, because the silicon in the silicon-carbon anode material is oxidized to high-valence silicon, the capacity per gram of the silicon-carbon anode material decreases, affecting the initial Coulomb efficiency of the secondary battery. [Overview of the project] [Means for solving the problem]

[0005] This disclosure has been made in view of the above-mentioned problems, and its purpose is to provide a silicon carbon anode material and a method for manufacturing the same that have high capacity per gram and initial Coulomb efficiency in lithium desorption, and that can improve capacity per gram and initial Coulomb efficiency in the discharge of a secondary battery.

[0006] To achieve the above objective, a first aspect of this disclosure provides a silicon-carbon anode material comprising a carbon skeleton having a porous structure and a silicon-based material provided within the porous structure. In the region from the surface to 10 nm inward of the silicon-carbon anode material, the content of high-valence silicon is less than 25% of the total amount of low-valence silicon and the high-valence silicon, the low-valence silicon is silicon with a valency of 0 to 2, and the high-valence silicon is silicon with a valency of 3 to 4.

[0007] The silicon-carbon anode material of this disclosure suppresses the content of high-valence silicon to a low level and increases the content of low-valence silicon, thereby increasing the capacity per gram and initial Coulomb efficiency in lithium desorption of the anode material, and effectively improving the capacity per gram and initial Coulomb efficiency in the discharge of the secondary battery.

[0008] In some embodiments, the high-valence silicon content in the region from the surface to 10 nm in the interior of the silicon-carbon anode material is 20% or less of the total amount of low-valence silicon and the high-valence silicon. Therefore, the anode material has a higher capacity per gram and initial Coulomb efficiency in lithium desorption, and the resulting secondary battery has a better capacity per gram and initial Coulomb efficiency in discharge.

[0009] In some embodiments, in the region from a position 10 nm away from the surface of the silicon-carbon negative electrode material to a position 20 nm away from the surface of the silicon-carbon negative electrode material, the content of high-valence silicon is 20% or less, and selectively 10% or less, based on the total amount of low-valence silicon and the high-valence silicon. Therefore, the content of high-valence silicon in the silicon-carbon negative electrode material of the present disclosure is further suppressed to a lower level, which is further helpful for improving the capacity per gram and the initial Coulomb efficiency in lithium desorption of the negative electrode material.

[0010] In some embodiments, in the region from a position 20 nm away from the surface of the silicon-carbon negative electrode material to a position 30 nm away from the surface of the silicon-carbon negative electrode material, the content of high-valence silicon is 10% or less, and selectively 5% or less, based on the total amount of low-valence silicon and the high-valence silicon. Therefore, the content of high-valence silicon in the silicon-carbon negative electrode material of the present disclosure is further suppressed to a lower level, which is further helpful for improving the capacity per gram and the initial Coulomb efficiency in lithium desorption of the negative electrode material.

[0011] In some embodiments, the silicon-carbon negative electrode material has the following properties: (1) the volume distribution particle size Dv50 of the silicon-carbon negative electrode material is 5 μm to 10 μm, and selectively 6 μm to 9 μm; (2) the specific surface area of the silicon-carbon negative electrode material is 5 m 2 / g or less, and selectively 2 m 2 / g or less; (3) the powder bulk density of the silicon-carbon negative electrode material under a pressure of 3000 N is 0.8 g / cm 3 to 1.2 g / cm 3 , and selectively 0.9 g / cm 3 to 1.2 g / cm 3 ; (4) the tap density of the silicon-carbon negative electrode material is 0.9 g / cm 3 to 1.1 g / cm 3 , and selectively 1.0 g / cm 3 to 1.1 g / cm 3(5) The silicon carbon anode material satisfies at least one of the following conditions: (6) The lithium desorption capacity per gram of the silicon carbon anode material is 800 mAh / g to 2500 mAh / g, and selectively 1000 mAh / g to 2000 mAh / g. By setting the particle size, pressure density, and tap density of the silicon carbon anode material within the above range, the pressure density of the electrode sheet can be effectively increased, and the energy density of the cell can be improved. In addition, the specific surface area is 5 m². 2 By reducing the particle size to less than / g, the contact area between the particles and the electrolyte can be minimized, improving initial Coulomb efficiency, cycle performance, and storage performance.

[0012] In some embodiments, the pore volume of the carbon skeleton is 0.4 cm³. 3 / g~1.5cm 3 It is / g and selectively 0.6cm 3 / g~1.2cm 3 The volume is such that the volume ratio of micropores with a pore diameter of less than 2 nm is 60% or more of the pore volume, and selectively 80% or more. Therefore, silicon-based material is mainly deposited in the micropores, and as the proportion of micropores increases, the amount of deposited silicon-based material increases, and accordingly the volume per gram in lithium desorption increases.

[0013] In some embodiments, the surface of the silicon-carbon anode material has a coating layer, which is selectively a carbon coating layer. This disclosure significantly reduces the risk of oxidizing silicon in the anode material via the coating layer to form high-valence silicon, thereby reducing the high-valence silicon content in the silicon-carbon anode material.

[0014] A second aspect of this disclosure provides a method for manufacturing a silicon carbon anode material according to the first aspect, the method comprising: A silicon carbon particle formation step involves reacting a carbon skeleton having a porous structure with a silicon source gas to form silicon carbon particles having a silicon-based material within the porous structure, A silicon carbon particle treatment step comprising introducing a mixed gas containing a carbon source gas and an inert gas into the silicon carbon particles at a permeability rate greater than 0 L / min and less than or equal to 10 L / min, under conditions of a temperature of 500°C to 800°C and a pressure of 0 kPa to 1 kPa, wherein the carbon source gas is at least one selected from ethane, ethylene, acetylene, and methane.

[0015] The above manufacturing method allows for the formation of a uniform and dense coating layer on the surface of silicon carbon particles, significantly reducing the risk of oxidation of silicon in the anode material to form high-valence silicon. This makes it possible to obtain a silicon carbon anode material with high capacity per gram and high initial Coulomb efficiency in lithium desorption.

[0016] In some embodiments, during the silicon carbon particle processing step, the mixed gas is introduced to the silicon carbon particles at a flow rate of 0.5 L / min to 4 L / min under conditions of a temperature of 550°C to 650°C and a pressure of 0 kPa to 0.5 kPa. This helps to form a more uniform and dense coating layer, resulting in a silicon carbon anode material with higher capacity per gram and initial Coulomb efficiency in lithium desorption.

[0017] In some embodiments, the mixed gas comprises 10% to 70% by volume of acetylene, 0% to 20% by volume of methane, and 10% to 90% by volume of an inert gas, and selectively comprises 15% to 60% by volume of acetylene, 5% to 10% by volume of methane, and 30% to 80% by volume of an inert gas. Thus, a specific mixed gas can be used to control the decomposition rate, allow the carbon to slowly coat the particle surface, and make the coating layer denser.

[0018] In some embodiments, the silicon-carbon particle formation step includes evacuating the reactor and then introducing an inert gas. This removes oxygen from the reactor and significantly reduces the risk of oxidizing the silicon deposited in the negative electrode material with oxygen in the reactor to form high-valence silicon.

[0019] In some embodiments, the silicon carbon particle formation step includes heating a carbon skeleton having a porous structure to 400°C to 550°C in a reactor to remove oxygen gas from the carbon skeleton. Therefore, by removing oxygen adsorbed on the carbon skeleton itself, the risk of oxidizing the silicon deposited in the negative electrode material with the oxygen adsorbed on the carbon skeleton itself to form high-valence silicon can be significantly reduced.

[0020] In some embodiments, the silicon carbon particle formation step includes introducing a mixed gas of a silicon source gas and an inert gas into a reactor and depositing it at a temperature of 400°C to 550°C for 2 to 10 hours to form silicon carbon particles. Thus, silicon can be uniformly deposited within porous carbon.

[0021] In some embodiments, the silicon source gas is one or more selected from silane, disilane, dichlorosilane, and trichlorosilane, wherein the silicon source gas is selectively silane.

[0022] In some embodiments, the inert gas is argon. This ensures that the silicon source gas is non-flammable and prevents the silicon from being oxidized.

[0023] A third aspect of this disclosure further provides an anode sheet comprising a silicon carbon anode material according to the first aspect of this disclosure or a silicon carbon anode material obtained by manufacturing according to the second aspect.

[0024] A fourth aspect of the present disclosure further provides a secondary battery comprising a negative electrode sheet according to a third aspect of the present disclosure, which has excellent initial Coulomb efficiency.

[0025] A fifth aspect of this disclosure further provides an electrical device including a secondary battery according to a fourth aspect of this disclosure. [Brief explanation of the drawing]

[0026] [Figure 1] This is a schematic diagram of a battery cell according to one embodiment of the present disclosure. [Figure 2] Figure 1 is an exploded view of a battery cell according to one embodiment of this application. [Figure 3] This is a schematic diagram of a battery module according to one embodiment of the present disclosure. [Figure 4] This is a schematic diagram of a battery pack according to one embodiment of the present disclosure. [Figure 5] Figure 4 is an exploded view of a battery pack according to one embodiment of the present disclosure. [Figure 6] This is a schematic diagram of an electrical device in which a secondary battery is used as a power source according to one embodiment of the present disclosure. [Figure 7] This is an XPS graph showing the analysis of the region from the surface to the interior of the silicon carbon anode material according to Example 1 of this disclosure, up to 10 nm. [Figure 8] This is an XPS graph showing the analysis of the region from the surface to the interior of the silicon carbon anode material according to Comparative Example 1 of this disclosure, up to 10 nm. [Modes for carrying out the invention]

[0027] Embodiments of the silicon carbon anode material and its manufacturing method disclosed herein will be described in detail below with appropriate reference to the accompanying drawings. However, unnecessary detailed explanations may be omitted. For example, detailed explanations of well-known matters and redundant explanations of identical structures may be omitted. This is to avoid unnecessarily verbose explanations, making them easy for those skilled in the art to understand. Furthermore, the accompanying drawings and the following explanation are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter described in the claims.

[0028] The “ranges” disclosed in this disclosure are limited in the form of lower and upper bounds, and a given range is limited by selecting one lower bound and one upper bound, and the selected lower and upper bounds define the boundaries of a particular range. Such limited ranges may or may not include endpoint values ​​and can be combined in any way, that is, any lower bound and any upper bound can be combined to form a single range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, the ranges 60-110 and 80-120 are also understood to be predictable. Similarly, if the minimum range values ​​are listed as 1 and 2, and the maximum range values ​​are listed as 3, 4 and 5, then the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all predictable. In this disclosure, unless otherwise specified, a numerical range of “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where both a and b are real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0 to 5" are listed in this specification, and "0 to 5" is merely an abbreviated representation of combinations of these numbers. Furthermore, when a parameter is described as being an integer of 2 or more, it is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12.

[0029] Unless otherwise specified, all embodiments and optional embodiments of this disclosure can be combined to form new technical solutions.

[0030] Unless otherwise specified, all technical features and optional technical features of this disclosure can be combined to form new technical solutions.

[0031] Unless otherwise specified, all steps of this disclosure may be performed sequentially or randomly, preferably in order. For example, when a method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, a method referred to may further include step (c), meaning that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), or otherwise.

[0032] Unless otherwise specified, terms used in this disclosure have the meanings generally understood by those skilled in the art.

[0033] Unless otherwise specified, the values ​​of each parameter mentioned in this disclosure may be measured using various test methods commonly used in the art, for example, according to the test methods given in this disclosure.

[0034] Extensive research on silicon-carbon anode materials has led to increased demands for their performance. The inventors have discovered that increasing the content of low-valence silicon in silicon-carbon anode materials helps improve the capacity per gram in lithium desorption. However, in current silicon-carbon anode materials, low-valence silicon is inevitably oxidized to form high-valence silicon, leading to a decrease in the capacity per gram and initial Coulomb efficiency in lithium desorption. Furthermore, these high-valence silicon particles readily form irreversible lithium silicate with lithium ions, reducing the amount of active lithium that repeatedly inserts and deinserts between the positive and negative electrode sheets, resulting in lithium loss and a decrease in the capacity per gram and initial Coulomb efficiency in secondary battery discharge.

[0035] In view of this, the present disclosure provides a silicon-carbon anode material comprising a carbon skeleton having a porous structure and a silicon-based material provided within the porous structure. In the region from the surface to 10 nm inward of the silicon-carbon anode material, the content of high-valence silicon is less than 25% of the total amount of low-valence silicon and the high-valence silicon, the low-valence silicon is silicon with a valency of 0 to 2, and the high-valence silicon is silicon with a valency of 3 to 4.

[0036] In the silicon-carbon anode material of this disclosure, the high-valence silicon content is suppressed to a low level, allowing the low-valence silicon content to be 75% or more, thereby improving the capacity per gram and initial Coulomb efficiency in lithium desorption of the anode material. Furthermore, due to the low high-valence silicon content, the formation of lithium silicate is reduced, significantly decreasing lithium loss and effectively improving the capacity per gram and initial Coulomb efficiency in the discharge of the secondary battery.

[0037] In this disclosure, the high-valence silicon and low-valence silicon described above can be quantified by XPS. In the XPS graph, the binding energy of low-valence silicon is 98 to 102 eV, the corresponding valence states are 0, 1, and 2, and the area enclosed by the curve and baseline (S1) is the amount of atomic molars of low-valence silicon. The binding energy of high-valence silicon is 102 eV to 106 eV, the corresponding valence states are 3 and 4, and the area enclosed by the curve and baseline (S2) is the amount of atomic molars of high-valence silicon. The content of high-valence silicon = S2 / (S1+S2) × 100% of the total amount of low-valence silicon and high-valence silicon, and the content of low-valence silicon = S1 / (S1+S2) × 100%. The baseline is the line connecting two points on the test curve, where the two points are X=98 eV and X=106 eV, respectively.

[0038] In some embodiments, in a region from the surface to the interior of the silicon carbon anode material up to 10 nm, high-valence silicon (C) 10The content of (as indicated) is within the range of 24%, 23%, 22%, 21%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or any two values, but is not limited to these. In some embodiments, in the region from the surface to 10 nm inside the silicon carbon anode material, C 10 It is preferably 20% or less, C 10 The content of high-valence silicon in the region from the surface to 10 nm inside the silicon-carbon anode material decreases, the content of low-valence silicon increases, and the capacity per gram in lithium desorption of the silicon-carbon anode material increases. In addition, because the content of high-valence silicon is low, the formation of lithium silicate is reduced, which significantly improves the capacity per gram and the initial Coulomb efficiency in the discharge of the secondary battery.

[0039] In some embodiments, in the region from 10 nm away from the surface of the silicon carbon anode material to 20 nm away from the surface of the silicon carbon anode material, high-valence silicon (C) 20 The content of (indicated as) is 20% or less. For example, the content of high-valence silicon is within the range of 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or any two values, but is not limited to these. In some embodiments, in the region from 10 nm away from the surface of the silicon-carbon anode material to 20 nm away from the surface of the silicon-carbon anode material, C 20 It is preferably less than 10%.

[0040] In some embodiments, in the region from 20 nm away from the surface of the silicon carbon anode material to 30 nm away from the surface of the silicon carbon anode material, high-valence silicon (C 30 The content of (as indicated by C) is 10% or less. For example, the content of high-valence silicon (C) 30) may be a value within the range of 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or any two numbers, but is not limited to these. Preferably, in the region from 20 nm away from the surface of the silicon carbon anode material to 30 nm away from the surface of the silicon carbon anode material, C 30 It is less than 5%.

[0041] C above 10 , C 20 , C 30 For specific measurement methods, please refer to the section on examples.

[0042] In some embodiments, the silicon carbon anode material has the following characteristics: (1) The volume distribution particle size Dv50 of the silicon carbon anode material is 5 μm to 10 μm, for example, 5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, or 9 μm, preferably 6 μm to 9 μm; and (2) The specific surface area of ​​the silicon carbon anode material is 5 m². 2 / g or less, for example 5m 2 / g, 4m 2 / g, 3m 2 / g, 2m 2 / g, 1.5m 2 / g, 1m 2 It may also be / g, preferably 2m 2 (3) The powder pressure density of the silicon carbon anode material under a pressure of 3000N is 0.8 g / cm³. 3 ~1.2g / cm 3 For example, 0.8 g / cm³ 3 , 0.9 g / cm³ 3 0.95 g / cm³ 3 1.0 g / cm³ 3 , 1.1 g / cm³ 3 , 1.15 g / cm³ 3 , 1.2 g / cm³ 3 It may be, preferably 0.9 g / cm³ 3 ~1.2g / cm 3 (4) The tap density of the silicon carbon anode material is 0.9 g / cm³ 3 ~1.1 g / cm³3 For example, 0.9 g / cm³ 3 0.95 g / cm³ 3 1.0 g / cm³ 3 1.05 g / cm³ 3 , 1.1 g / cm³ 3 It may be, preferably 1.0 g / cm³ 3 ~1.1 g / cm³ 3 (5) The silicon carbon anode material satisfies at least one of the following conditions: (6) The capacity per gram in lithium desorption is 800 mAh / g to 2500 mAh / g, and may be, for example, 800 mAh / g, 900 mAh / g, 1000 mAh / g, 1100 mAh / g, 1200 mAh / g, 1300 mAh / g, 1400 mAh / g, 1500 mAh / g, 1600 mAh / g, 1700 mAh / g, 1800 mAh / g, 1900 mAh / g, 2000 mAh / g, 2100 mAh / g, and preferably 1000 mAh / g to 2000 mAh / g. By setting the particle size, pressure density, and tap density of the silicon carbon anode material within the above range, the pressure density of the electrode sheet can be effectively increased, and the energy density of the cell can be improved. Also, the specific surface area is 5 m². 2 By reducing the particle size to less than / g, the contact area between the particles and the electrolyte can be minimized, improving initial Coulomb efficiency, cycle performance, and storage performance.

[0043] In this disclosure, the volume distribution particle size Dv50 of the material has a meaning known in the art, representing the particle size corresponding to when the cumulative volume distribution of the material reaches 50%, and can be measured using instruments and methods known in the art. For example, it can be measured using a laser particle size analyzer, referring to GB / T19077-2016. The test instrument may be a Mastersizer 3000 laser particle size analyzer manufactured by Malvern Ltd., UK.

[0044] In this disclosure, the specific surface area of ​​a material has the meaning known in the art and can be measured using instruments and methods known in the art. For example, it can be measured using a specific surface area analysis test method by nitrogen adsorption, referring to GB / T19587-2017, or calculated using the Brunauer Emmett Teller (BET) method. The test instrument may be a Tri-Star 3020 specific surface area pore size analyzer manufactured by Micromeritics, Inc., USA.

[0045] In this disclosure, the powder pressure density of the material has a meaning known in the art and can be measured using instruments and methods known in the art. For example, it can be measured using an electronic pressure tester (e.g., an electronic pressure tester UTM7305), referring to GB / T24533-2009. An exemplary test method is as follows: Weigh 1 g of sample powder and measure the pressure density of a sample powder over a base area of ​​1.327 cm². 2 In addition to the mold, the material is pressurized to 300 kg, the pressure is maintained for 30 seconds, then the pressure is released and maintained for 10 seconds. After that, the powder pressure density of the material under a pressure of 3000 N is recorded and calculated.

[0046] In this disclosure, the tap density of a material has the meaning known in the art and can be measured using instruments and methods known in the art. For example, it can be measured using a powder tap density tester, referring to GB / T5162-2006. The tester may be a BT-301 manufactured by Dandong Baite, with test parameters of vibration frequency of 250 ± 15 times / min, amplitude of 3 ± 0.2 mm, number of vibrations of 5000, and a graduated cylinder of 25 mL.

[0047] In this disclosure, the volume per gram in lithium desorption of the material has a meaning known in the art and can be measured using methods known in the art. For specific test methods, please refer to those described in the examples.

[0048] In some embodiments, the pore volume of the carbon skeleton is 0.4 cm³. 3 / g~1.5cm 3 It is / g and selectively 0.6cm 3 / g~1.2cm 3 The volume is / g, and / or the volume ratio of micropores with a pore diameter of less than 2 nm relative to the above pore volume is 60% or more, and selectively 80% or more. Therefore, silicon-based material is mainly deposited in the micropores, and the higher the proportion of micropores, the more silicon-based material is deposited, and accordingly the volume per gram in lithium desorption increases. In some embodiments, the silicon-based material may be amorphous hard carbon.

[0049] In some embodiments, the surface of the silicon-carbon anode material has a coating layer, which is selectively a carbon coating layer. The disclosure further prevents oxygen from entering the anode material by providing a uniform and dense coating layer, significantly reducing the risk of oxidation of silicon in the silicon-carbon anode material to form high-valence silicon, and thus reducing the high-valence silicon content in the silicon-carbon anode material.

[0050] Furthermore, this disclosure provides a method for manufacturing the silicon carbon anode material described above. This manufacturing method includes a silicon carbon particle forming step (step (a)) in which a carbon skeleton having a porous structure is reacted with a silicon source gas to form silicon carbon particles having a silicon-based material in the porous structure, and a silicon carbon particle processing step (step (b)) in which a mixed gas containing a carbon source gas and an inert gas is introduced into the silicon carbon particles at a permeability rate greater than 0 L / min and less than or equal to 10 L / min under conditions of a temperature of 500°C to 700°C and a pressure of 0 kPa to 1 kPa, wherein the carbon source gas is at least one selected from ethane, ethylene, acetylene, and methane.

[0051] Therefore, by using specific temperatures, pressures, airflow rates, and gas mixtures, the decomposition rate of the carbon source gas can be effectively controlled, which helps to form a uniform and dense coating layer on the surface of the silicon carbon particles. In this way, the risk of oxidizing silicon in the silicon carbon particles with oxygen in the air to form high-valence silicon is effectively reduced, and the content of high-valence silicon in the particles is reduced, C10 , C 20 and C 30 This can be kept within the above range. By selecting the above carbon source gas, the coating can be made uniform and complete.

[0052] In some embodiments, in step (b), the temperature may be, for example, 500°C, 550°C, 600°C, 650°C, 700°C, or any two of these values ​​within that range. The pressure may be, for example, 0kPa, 50Pa, 100Pa, 150Pa, 200Pa, 250Pa, 300Pa, 350Pa, 400Pa, 450Pa, 500Pa, 550Pa, 600Pa, 650Pa, 700Pa, 750kPa, 800Pa, 850Pa, 900Pa, 950Pa, 1000Pa (1kPa), or any two of these values ​​within that range. By keeping the temperature and pressure within the above ranges, the decomposition rate of the carbon source gas can be effectively controlled, which helps to form a uniform and dense coating layer.

[0053] In some embodiments, in step (b), the airflow rate may be, for example, 0.5 L / min, 1.0 L / min, 1.5 L / min, 2.0 L / min, 2.5 L / min, 3.0 L / min, 3.5 L / min, 4.0 L / min, 4.5 L / min, 5.0 L / min, 5.5 L / min, 6.0 L / min, 6.5 L / min, 7.0 L / min, 7.5 L / min, 8.0 L / min, 8.5 L / min, 9.0 L / min, 9.5 L / min, 10.0 L / min, or any two of these values ​​within a range. By keeping the airflow rate within the above range, the carbon source gas can be sufficiently reacted, increasing the utilization rate of the carbon source gas and helping to form a uniform and dense coating layer.

[0054] In some embodiments, it is preferable in step (b) to introduce the mixed gas under the conditions of a temperature of 550°C to 650°C, a pressure of 0 kPa to 500 Pa, and an airflow rate of 0.5 L / min to 4 L / min. Under these conditions, a denser coating layer is formed, further reducing the possibility of oxygen from the air penetrating the inside of the particles and oxidizing the silicon. 10 , C 20 , C 30 This can be further reduced.

[0055] In some embodiments, the mixed gas preferably contains 10% to 70% acetylene, 0% to 20% methane, and 10% to 90% inert gas, and more preferably contains 15% to 60% acetylene, 5% to 10% methane, and 30% to 80% inert gas. Acetylene has a low decomposition temperature and decomposes rapidly. Adding a certain amount of methane allows for control of the decomposition rate of acetylene, slow coating of the particle surface with carbon, and densification of the coating layer.

[0056] An inert gas is a gas that does not react with silicon materials. Examples of inert gases, though not limited to them, include helium, neon, argon, krypton, xenon, and radon. By using an inert gas as a protective gas, the formation of Si3N4 can be reduced.

[0057] In some embodiments, step (a) above may include the following steps (a1) to (a3).

[0058] Step (a1): In a reaction apparatus, a carbon skeleton having a porous structure is heated to 400°C to 550°C to remove oxygen gas from the carbon skeleton.

[0059] The above-mentioned reaction apparatus is not particularly limited, but may be an apparatus commonly used in this field, such as a medium-frequency furnace, roller hearth kiln, rotary kiln, pusher kiln, vertical granulator, horizontal granulator, vertical reaction vessel, horizontal reaction vessel, or drum furnace.

[0060] In step (a1), the carbon skeleton is heated to 400°C to 550°C, for example, within the range of 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, or any two of these values, but is not limited to these. Preferably, the carbon skeleton is heated to 450°C to 550°C. By heating the carbon skeleton within the above range, oxygen adsorbed on the carbon skeleton itself is removed, the risk of oxidizing the silicon deposited in the negative electrode material with oxygen adsorbed on the carbon skeleton itself and forming high-valence silicon is greatly reduced, the content of low-valence silicon in the silicon carbon negative electrode material can be maintained at a high level, and the content of high-valence silicon can be reduced, C 10 , C 20 , and C 30 This helps to bring the above range into place and obtain a silicon-carbon anode material with high lithium desorption capacity per gram.

[0061] Step (a2): The reactor is evacuated, and then an inert gas is introduced.

[0062] This step removes oxygen from the reactor, significantly reducing the risk of oxidizing the silicon deposited in the negative electrode material with oxygen in the reactor and forming high-valence silicon, thereby maintaining a high level of low-valence silicon content in the silicon-carbon negative electrode material and reducing the high-valence silicon content. 10 , C 20 , and C 30 This helps to bring it within the above range.

[0063] In some embodiments, the vacuum level inside the reactor is reduced to 1 × 10⁻⁶ by vacuuming. -3 Pa~1×10 -6 Let Pa be, for example, 1 × 10 -5 The pressure may also be expressed as Pa. The lower the pressure value in the reactor, the less oxygen remains in the reactor, and the lower the content of high-valence silicon in the silicon-carbon anode material produced.

[0064] In some embodiments, in step (a2), after the pressure in the reactor reaches the above-mentioned pressure and the pressure is maintained for the above-mentioned time, an inert gas is introduced into the reactor to further reduce the amount of residual oxygen in the reactor.

[0065] In some embodiments, step (a2) (vacuuming, pressure maintenance, and introduction of inert gas) may be repeated. The number of times this step can be performed is not limited, but includes 1, 2, and 3.

[0066] In some embodiments, step (a2) may detect the oxygen content in the exhaust gas discharged from the reactor at a predetermined frequency. If the oxygen content in the exhaust gas falls below 200 ppm, step (a2) is stopped. For example, if the oxygen content in the exhaust gas is within the range of 0 ppm, 20 ppm, 40 ppm, 60 ppm, 80 ppm, 100 ppm, 120 ppm, 140 ppm, 160 ppm, 180 ppm, 190 ppm, or any two of these values, step (a2) can be stopped.

[0067] The order of steps (a1) and (a2) above is not particularly limited; step (a1) may be performed first, followed by step (a2), or step (a2) may be performed first, followed by step (a1). These two steps maximize the removal of oxygen contained in the raw materials and the reactor.

[0068] Step (a3): A mixture of silicon source gas and inert gas is introduced into the reactor and deposited at a temperature of 400°C to 550°C for 2 to 10 hours to form silicon carbon particles.

[0069] The silicon source gas described above includes a gas capable of supplying silicon atoms. For example, it may be one or more of silane, disilane, dichlorodihydrosilane, and trichlorosilane. Selectively, the silicon source gas is silane. The inert gas used in this step is defined in the same way as the inert gas in step (b) above, and argon is preferably used.

[0070] In some embodiments, a rotary kiln is used as the reaction apparatus, and a mixed gas of silane and argon is introduced into the rotary kiln at an aeration rate of 0.1 L / min to 4 L / min. The reaction is carried out under slightly positive pressure of 0 to 0.5 kPa and a rotation frequency of 0 Hz to 80 Hz. The rotation frequency of the reaction apparatus may be within the range of 0 Hz, 5 Hz, 10 Hz, 20 Hz, 30 Hz, 40 Hz, 50 Hz, 60 Hz, 70 Hz, 80 Hz, or any two of these values. By setting the rotation frequency within the above range, the powder can be sufficiently rotated in the kiln, increasing the contact between the powder and the gas, and allowing for a thorough reaction.

[0071] Step (a3) ​​is performed after steps (a1) and (a2) described above. Since oxygen contained in the reaction materials and reaction apparatus has already been removed by steps (a1) and (a2) described above, the risk of oxidation of the deposited silicon in step (a3) ​​can be greatly reduced.

[0072] Furthermore, the present disclosure provides a negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector. The negative electrode film layer comprises a negative electrode active material, which comprises the silicon carbon negative electrode material of the present disclosure or a silicon carbon negative electrode material obtained by manufacturing according to the manufacturing method of the present disclosure.

[0073] For example, the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0074] In some embodiments, a metal foil or a composite current collector can be used as the negative electrode current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys) on a polymer material substrate (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0075] In some embodiments, the negative electrode film layer further selectively comprises a binder. The binder may be at least one selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0076] In some embodiments, the negative electrode film layer further selectively comprises a conductive agent. The conductive agent may be at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0077] In some embodiments, the negative electrode film layer further comprises other additives, such as a selective thickener (e.g., sodium carboxymethylcellulose (CMC-Na)).

[0078] In some embodiments, the negative electrode sheet can be manufactured as follows: Components for manufacturing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry. The negative electrode slurry is then applied onto a negative electrode current collector, and the negative electrode sheet can be obtained through processes such as oven drying and cold pressing.

[0079] Furthermore, the secondary battery and electrical device of this disclosure will be described below with reference to the attached drawings as appropriate.

[0080] In one embodiment of this disclosure, a secondary battery is provided.

[0081] In this specification, the term "secondary battery" refers to a battery cell, battery module, or battery pack. Each of these is described below.

[0082] Typically, a secondary battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During charging and discharging of the battery, active ions repeatedly insert and withdraw between the positive and negative electrode sheets. The electrolyte plays a role in conducting ions between the positive and negative electrode sheets. The separator is placed between the positive and negative electrode sheets and primarily serves to prevent short circuits between the positive and negative electrodes, while also allowing ions to pass through.

[0083] [Positive electrode sheet] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material according to a first embodiment of the present disclosure.

[0084] For example, a positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode film layer is provided on one or both of the two opposing surfaces of the positive electrode current collector.

[0085] In some embodiments, a metal foil or a composite current collector can be used as the positive electrode current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material substrate (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0086] In some embodiments, when the battery cell is a lithium-ion battery, known positive electrode active materials for lithium-ion batteries in the art may be used as the positive electrode active material. For example, the positive electrode active material may include at least one of olivine-structured lithium-containing phosphates, lithium transition metal oxides, and modified compounds of each thereof. However, this disclosure is not limited to these materials, and other conventional materials usable as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used individually or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide (LiCoO2, etc.), lithium nickel oxide (LiNiO2, etc.), lithium manganese oxide (LiMnO2, LiMn2O4, etc.), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 (Also abbreviated as LiNi) 0.5 Co 0.2 Mn 0.3 O2(NCM 523 (Also abbreviated as LiNi) 0.5 Co 0.25 Mn 0.25 O2(NCM 211 (Also abbreviated as LiNi)0.6 Co 0.2 Mn 0.2 O2 (NCM 622 also abbreviated as), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM 811 also abbreviated as), lithium nickel cobalt aluminum oxide (LiNi 0.85 Co 0.15 Al 0.05 O2, etc.), and at least one of their modified compounds, etc. Examples of olivine-structured lithium-containing phosphates include, but are not limited to, lithium iron phosphate (LiFePO4 (also abbreviated as LFP), etc.), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (LiMnPO4, etc.), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and at least one of a composite material of lithium iron manganese phosphate and carbon.

[0087] In some embodiments, the positive electrode film layer optionally further comprises a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of vinylidene fluoride, tetrafluoroethylene, and propylene, a terpolymer of vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene, a copolymer of tetrafluoroethylene and hexafluoropropylene, and a fluorine-containing acrylate resin.

[0088] In some embodiments, the positive electrode film layer optionally further comprises a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0089] In some embodiments, the positive electrode sheet can be manufactured as follows: Components for manufacturing the above-mentioned positive electrode sheet, such as a positive electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, the positive electrode slurry is applied onto a positive electrode current collector, and the positive electrode sheet can be obtained through processes such as oven drying and cold pressing.

[0090] [Electrolyte] The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The type of electrolyte is not specifically limited in this disclosure and can be selected as needed. For example, the electrolyte may be liquid, gel-like, or all-solid.

[0091] In some embodiments, an electrolyte solution is used as the electrolyte. The electrolyte solution contains an electrolyte salt and a solvent.

[0092] In some embodiments, the electrolyte salt may be at least one selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0093] In some embodiments, the solvent may be at least one selected from ethylene carbonate, propylene carbonate, ethylmethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, ethylmethyl sulfone, and diethyl sulfone.

[0094] In some embodiments, the electrolyte further selectively includes additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may further include additives that can improve certain aspects of the battery's performance, such as additives that can improve the battery's overcharge performance or additives that can improve the battery's high-temperature or low-temperature performance.

[0095] [Separator] In this disclosure, the type of separator is not particularly limited, and any known porous structure separator having good chemical and mechanical stability can be selected. In some embodiments, the material of the separator may be at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. If the separator is a multilayer composite film, the materials of each layer may be the same or different, and is not particularly limited.

[0096] In some embodiments, the positive electrode sheet, negative electrode sheet, and separator can be assembled into an electrode assembly by a winding process or a lamination process.

[0097] In some embodiments, the battery cell may include an outer casing. This casing can be used to enclose the electrode assembly and electrolyte.

[0098] In some embodiments, the battery cell casing may be a rigid case, such as a hard plastic case, an aluminum case, or a steel case. The battery cell casing may also be a soft pack, such as a pouch-type soft pack. The material of the soft pack may be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0099] In this disclosure, the shape of the battery cell is not particularly limited and may be cylindrical, rectangular, or any other shape. For example, Figure 1 shows a rectangular battery cell 5 as an example.

[0100] In some embodiments, referring to Figure 2, the casing may include a case 51 and a top cover assembly 53. Here, the case 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and side plates surround the casing to form a housing cavity. The case 51 has an opening that communicates with the housing cavity, and the top cover assembly 53 may be fitted over the opening to seal the housing cavity. The positive electrode sheet, negative electrode sheet and separator can be formed into an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is sealed within the housing cavity. The electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, and a person skilled in the art can select according to specific practical needs.

[0101] In some embodiments, the battery cells may be assembled as a battery module, and the number of battery cells included in the battery module may be one or more, the specific number of which can be selected by those skilled in the art depending on the application and capacity of the battery module.

[0102] Figure 3 shows an example of a battery module 4. Referring to Figure 3, in the battery module 4, the multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the multiple battery cells 5 may be fixed by fastening members.

[0103] Selectively, the battery module 4 may further include a housing having a housing space, in which a plurality of battery cells 5 are housed.

[0104] In some embodiments, the battery modules may be assembled as a battery pack, and the number of battery modules included in the battery pack may be one or more, the specific number of which can be selected by those skilled in the art depending on the application and capacity of the battery pack.

[0105] Figures 4 and 5 show an example of a battery pack 1. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided within the battery box. The battery box includes an upper box 2 and a lower box 3, the upper box 2 covering the lower box 3 and forming a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged within the battery box in any manner.

[0106] The Disclosure also provides an electrical device including a secondary battery provided herein. The secondary battery may be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships and satellites, energy storage systems, etc.

[0107] The aforementioned electrical device can be selected as a battery cell, battery module, or battery pack, depending on its intended use.

[0108] Figure 6 shows an example of an electrical device. This electrical device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the requirements for high power output and high energy density of secondary batteries, this electrical device may use a battery pack or battery module.

[0109] Other examples of devices may include mobile phones, tablet computers, and laptop computers. Such devices are typically required to be lightweight and thin, and may use battery cells as a power source. [Examples]

[0110] Examples Examples of the present disclosure are described below. The examples described below are illustrative and are for interpretive purposes only, and should not be understood as limiting the present disclosure. Unless otherwise specified in the examples, specific techniques or conditions are followed in accordance with the techniques or conditions described in the literature in the art or in the product specifications. Unless otherwise specified, the reagents or equipment used are all common products available commercially.

[0111] Example 1 Regarding the manufacturing of silicon carbon anode materials Step (a1): 500 g of porous carbon was weighed, placed in a rotary kiln, heated to 500°C (T1) under argon protection conditions, and kept warm for 2 hours to desorb the air adsorbed on the porous carbon.

[0112] Step (a2): Vacuum the rotary kiln to 1 × 10 -5 The system was vacuumed to Pa, the pressure was maintained for 5 minutes, and then argon was introduced. The vacuuming and argon introduction steps were repeated until the oxygen content in the exhaust gas was less than 200 ppm.

[0113] Step (a3): A mixed gas of silane and argon (with a volume ratio of silane to argon of 1:4) was introduced into the rotary kiln at a flow rate of 4 L / min, a slight positive pressure of 200 Pa was maintained, and the rotary kiln was rotated at a rotation frequency of 40 Hz to obtain silicon carbon particles.

[0114] Step (b): The temperature of the rotary kiln was raised to 500°C (T2), a mixed gas of acetylene, methane, and argon was introduced at a pressure of 0.2 kPa (P) and an airflow rate of 3 L / min (V), and the rotary kiln was rotated at a rotation frequency of 40 Hz to coat it with the silicon carbon particles described above.

[0115] After natural cooling, the silicon-carbon anode material was obtained by sieving it through a 200-mesh sieve.

[0116] C content of high-valence silicon in silicon-carbon anode material 10 , C 20 , C 30 Regarding the measurement (1) X-rays were used as an excitation source to act on the surface of the silicon-carbon anode material, and the region from the surface to a depth of 10 nm was detected to obtain the XPS graph shown in Figure 7. The region S1 enclosed by the curve and baseline corresponding to the binding energy 98-102 eV represents the amount of low-valence silicon, and the region S2 enclosed by the curve and baseline corresponding to the binding energy 102 eV-106 eV represents the amount of high-valence silicon. Based on S2 / (S1+S2), the high-valence silicon content C 10 This was calculated to be 17.5%.

[0117] (2) Using an argon ion gun, the surface of the silicon carbon anode material described in (1) above was etched at an etching rate of approximately 4 nm / min, and the etching time was adjusted to 2.5 min, thereby removing the analysis region described in (1) above (i.e., the region from the surface to a depth of 10 nm) by etching. Subsequently, X-rays were used as an excitation source and acted upon the new surface of the silicon carbon anode material that had undergone the above etching, and photoelectron distribution information was obtained at a depth of 10 nm. Following the same method as in (1) above, silicon valence state information was obtained in the region from 10 nm away from the surface to 20 nm away from the surface, and C 20 The figure was 9.6%.

[0118] (3) Using an argon ion gun, the surface of the silicon carbon anode material described in (2) above was further etched at an etching rate of approximately 4 nm / min, and the etching time was adjusted to 2.5 min, thereby removing the analysis region described in (2) above by etching. Subsequently, X-rays were used as an excitation source to act on the new surface of the etched silicon carbon anode material, and photoelectron distribution information was obtained at a depth of 10 nm. Following the same method as in (1) above, silicon valence state information was obtained in the region from 20 nm away from the surface to 30 nm away from the surface, and C 30 The figure was 4.2%.

[0119] Regarding the manufacture of secondary batteries (a) Manufacturing of negative electrode sheets The silicon-carbon composite material obtained above, conductive carbon black, carboxymethylcellulose sodium (CMC) as a thickener, and styrene-butadiene rubber emulsion (SBR) as a binder were thoroughly stirred and mixed in an appropriate amount of deionized water in a weight ratio of 96.5:1.0:1.0:1.5 to form a uniform negative electrode slurry. The negative electrode slurry was applied onto a negative electrode current collector, and a negative electrode sheet was obtained through processes such as oven drying.

[0120] (b) Manufacturing of positive electrode sheets An 8μm thick aluminum foil was used as the positive electrode current collector. The positive electrode active material was LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were dissolved in the solvent N-methylpyrrolidone (NMP) in a weight ratio of 93:2:5. After thorough stirring and mixing until homogeneous, a positive electrode slurry was obtained. Subsequently, the positive electrode slurry was uniformly applied to a positive electrode current collector, and a positive electrode sheet was obtained by oven drying, cold pressing, and cutting.

[0121] (c) Preparation of the electrolyte The electrolyte was a mixture of ethylene carbonate (EC), ethylmethyl carbonate (EMC), and diethyl carbonate (DEC), with a volume ratio of EC, EMC, and DEC of 20:20:60. Subsequently, LiPF6 was dissolved in the above organic solvent, and fluoroethylene carbonate (FEC) was added as an additive. The concentration of LiPF6 was 1 mol / L, and the mass percentage of FEC in the electrolyte was 5%.

[0122] (d) Manufacturing of batteries A positive electrode sheet, a separator, and a negative electrode sheet were sequentially stacked so that the separator acts to isolate them from each other. These were then wound together to obtain a bare cell. Tabs were welded to the bare cell, and the bare cell was placed in an aluminum case. After baking at 80°C to remove water, the electrolyte was injected and the case was sealed to obtain an uncharged battery. The uncharged battery underwent sequential processes such as standing, hot and cold pressing, chemical conversion, shaping, and capacity testing to obtain the lithium-ion secondary battery of Example 1.

[0123] Examples 2-5 and Comparative Examples 1-2 Except for changing the temperature (T2) in step (b) as shown in Table 1 below, the silicon carbon anode material was manufactured in the same manner as in Example 1, and C 10 , C 20 , C 30 We measured the parameters and manufactured rechargeable batteries.

[0124] For the silicon-carbon anode material of Comparative Example 1, X-rays were used as an excitation source to act on the surface of the silicon-carbon anode material, and the region from the surface to a depth of 10 nm was detected, obtaining the XPS graph shown in Figure 8. Calculations were performed in the same manner as in Example 1, and the high-valence silicon content C was found to be 10 The figure was 30.3%.

[0125] The following performance tests were performed on the above-mentioned examples and comparative examples.

[0126] <Performance Test> (1) Volume per gram and initial Coulomb efficiency in lithium desorption of silicon carbon anode material a. Manufacturing of button-type batteries: The silicon-carbon negative electrode material, conductive carbon black, and polyacrylic acid binder were mixed in a mass ratio of 8:1:1, and then deionized water was added as a solvent. The mixture was stirred using a high-speed mixer until the solution system was homogeneous, and a negative electrode slurry with a solid content of 45% was obtained. The negative electrode slurry was uniformly coated onto the copper foil of the negative electrode current collector, oven-dried at 85°C, and cold-pressed to obtain an electrode sheet. A button-type battery was assembled using metallic lithium as the counter electrode, a Celgard 2400 separator, and electrolyte. The electrolyte was a mixture of ethylene carbonate (EC), ethylmethyl carbonate (EMC), and diethyl carbonate (DEC), where the volume ratio of EC, EMC, and DEC was 20:20:60. Subsequently, LiPF6 was dissolved in the above organic solvent, and fluoroethylene carbonate (FEC) was added as an additive. The concentration of LiPF6 was 1 mol / L, and the mass percentage of FEC in the electrolyte was 5%.

[0127] b. Button cell battery testing process: Assembled button cells were left standing for 60 minutes, then discharged to 5mV with a constant current of 0.05C, discharged to 5mV with 50μA, left standing for 10 minutes, and then charged to 2.0V with 0.1C. Here, the capacity per gram of the silicon carbon anode material in lithium insertion was the capacity per gram C1 when discharged to 5mV, the capacity per gram in lithium desorption was the capacity per gram C2 when charged to 2.0V, and the initial Coulomb efficiency of the silicon carbon anode material was C2 / C1.

[0128] (2) Capacity per gram and initial Coulomb efficiency in the discharge of secondary batteries The secondary batteries obtained in the above examples and comparative examples were maintained at a constant temperature of 25°C for 60 minutes, then charged to 4.25V with a constant current of 0.1C, and then charged to 0.05C with a constant voltage of 4.25V. The charge capacity per gram at this time was recorded as Q1. After standing for 10 minutes, the batteries were discharged to 2.5V with a constant current of 0.1C, and then discharged to 0.05C with a constant voltage of 2.5V. The capacity per gram at this discharge was recorded as Q2, and the initial Coulomb efficiency of the secondary batteries was recorded as Q2 / Q1.

[0129] [Table 1]

[0130] As can be seen from the results in Table 1, in step (b), by satisfying specific conditions for the temperature, pressure, airflow rate and gas mixture of the rotary kiln, C 10 A silicon-carbon anode material with less than 25% C was obtained. In Examples 1-5, when the rotary kiln temperature was controlled to 500°C to 700°C, the high-valence silicon content in the obtained silicon-carbon anode material was low, and C 10 The results showed that all of these values ​​were less than 25%. The silicon-carbon anode material showed high capacity per gram and initial Coulomb efficiency in lithium desorption, and the resulting secondary battery showed high capacity per gram and initial Coulomb efficiency in discharge. In particular, when the rotary kiln temperature was controlled to 550°C to 650°C, the resulting silicon-carbon anode material showed high C 10 These figures have fallen further, with all falling below 20%, and also C 20 and C 30 The performance of secondary batteries has also improved further.

[0131] In comparative examples 1 and 2, when the temperature inside the rotary kiln was too low (200°C) or too high (1000°C) compared to examples 1 to 5, the C content of the silicon carbon anode material was affected. 10 If the percentage exceeded 30%, the technical effects of this disclosure were not achieved in any of the cases.

[0132] Examples 6-8 and Comparative Example 3 Except for changing the pressure (P) in step (b) as shown in Table 2 below, the silicon carbon anode material was manufactured in the same manner as in Example 3, and C 10 , C 20 , C 30 We measured the parameters and manufactured rechargeable batteries.

[0133] Performance evaluation was conducted in the same manner as in Example 3. The details are shown in Table 2.

[0134] [Table 2]

[0135] As can be seen from the results in Table 2, by keeping the rotary kiln pressure within the range of 0kPa to 1kPa in step (b), the high-valence silicon content in the obtained silicon-carbon anode material is low, C 10 In particular, when the rotary kiln pressure was kept within the range of 0kPa to 0.5kPa, the resulting silicon-carbon anode material was less than 25%. 10 It has fallen even further to below 20%, and also C 20 and C 30 Furthermore, the values ​​decreased even more. The silicon-carbon anode material showed high capacity per gram and initial Coulomb efficiency in lithium desorption, and the resulting secondary battery showed high capacity per gram and initial Coulomb efficiency in discharge.

[0136] In Comparative Example 3, when the pressure inside the rotary kiln was too high (5 kPa), the C of the silicon carbon anode material... 10 If the percentage exceeds 25%, the technical effects of this disclosure were not achieved.

[0137] Examples 9-11 and Comparative Examples 4, 5 Except for changing the air permeability (V) in step (b) as shown in Table 3 below, the silicon carbon anode material was manufactured in the same manner as in Example 3, and C 10 , C 20 , C 30 We measured the parameters and manufactured rechargeable batteries.

[0138] Performance evaluation was conducted in the same manner as in Example 3. The details are shown in Table 3.

[0139] [Table 3]

[0140] As can be seen from the results in Table 3, by keeping the airflow rate (V) of the rotary kiln greater than 0 L / min and within the range of 10 L / min or less in step (b), the content of high-valence silicon in the obtained silicon-carbon anode material is low, C 10 The percentage was less than 25%. In Comparative Examples 4 and 5, the technical effects of this disclosure were not obtained when the airflow rate was too high or when no mixed gas was introduced.

[0141] Examples 12-15 and Comparative Example 6 Except for changing the composition of the mixed gas in step (b) as shown in Table 4 below, the silicon carbon anode material was manufactured in the same manner as in Example 3, and C 10 , C 20 , C 30 We measured the parameters and manufactured rechargeable batteries.

[0142] Performance evaluation was conducted in the same manner as in Example 3. The details are shown in Table 4.

[0143] [Table 4]

[0144] As can be seen from the results in Table 4, by using at least one selected from ethane, ethylene, acetylene, and methane as the carbon source gas in step (b), the high-valence silicon content in the resulting silicon-carbon anode material is low, and C 10 The content was less than 25%. In Comparative Example 6, a mixed gas of propane, methane, and argon was used, and the decomposition temperature of propane was excessively high, resulting in poor uniformity and completeness of the coating. This led to an excessively high content of high-valence silicon, and the technical effects of this disclosure were not obtained.

[0145] This disclosure is not limited to the embodiments described above. The embodiments described above are merely illustrative, and any embodiment having substantially the same configuration as the technical idea and producing the same functions and effects within the scope of the technical solutions of this disclosure is included within the technical scope of this disclosure. Furthermore, other forms constructed by adding various modifications to the embodiments that a person skilled in the art could conceive of, and by combining some of the components of the embodiments, are also included within the scope of this disclosure, without departing from the gist of this disclosure. [Industrial applicability]

[0146] This disclosure provides a silicon-carbon anode material and a method for manufacturing the same. The silicon-carbon anode material comprises a carbon skeleton having a porous structure and a silicon-based material provided within the porous structure, wherein the content of high-valence silicon in the region from the surface to 10 nm in the interior of the silicon-carbon anode material is less than 25% of the total amount of low-valence silicon and the high-valence silicon, the low-valence silicon is silicon with a valency of 0 to 2, and the high-valence silicon is silicon with a valency of 3 to 4. Therefore, the capacity per gram and initial Coulomb efficiency in lithium desorption of the silicon-carbon anode material can be improved, and the capacity per gram and initial Coulomb efficiency in discharge of a secondary battery can be improved. [Explanation of Symbols]

[0147] 1 Battery pack 2. Top box 3. Lower box 4 Battery Modules 5 battery cells 51 cases 52 Electrode assembly 53 Lid plate

Claims

1. A silicon-carbon anode material comprising a carbon skeleton having a porous structure and a silicon-based material provided within the porous structure, wherein in a region from the surface to 10 nm inside the silicon-carbon anode material, the content of high-valence silicon is less than 25% of the total amount of low-valence silicon and the high-valence silicon, the low-valence silicon is silicon with a valency of 0 to 2, and the high-valence silicon is silicon with a valency of 3 to 4.

2. The silicon carbon anode material according to claim 1, wherein the content of high-valence silicon in the region from the surface to 10 nm in the interior of the silicon carbon anode material is 20% or less relative to the total amount of low-valence silicon and the high-valence silicon.

3. The silicon carbon anode material according to claim 1 or 2, wherein in the region from 10 nm away from the surface of the silicon carbon anode material to 20 nm away from the surface of the silicon carbon anode material, the content of high-valence silicon is 20% or less of the total amount of low-valence silicon and the high-valence silicon, and selectively 10% or less.

4. The silicon carbon anode material according to any one of claims 1 to 3, wherein in the region from 20 nm away from the surface of the silicon carbon anode material to 30 nm away from the surface of the silicon carbon anode material, the content of high-valence silicon is 10% or less relative to the total amount of low-valence silicon and the high-valence silicon, and selectively 5% or less.

5. The aforementioned silicon carbon anode material is (1) The volume distribution particle size Dv50 of the silicon carbon anode material is 5 μm to 10 μm, and selectively Dv50 is 6 μm to 9 μm. (2) The specific surface area of ​​the silicon carbon anode material is 5 m² ２ It is less than / g and selectively 2m ２ It must be less than or equal to / g. (3) The powder pressure density of the silicon carbon anode material under a pressure of 3000 N is 0.8 g / cm³. ３ ~1.2 g / cm ３ Therefore, selectively 0.9 g / cm³ ３ ~1.2 g / cm ３ Being (4) The tap density of the silicon-carbon negative electrode material is 0.9 g / cm ３ to 1.1 g / cm ３ and selectively 1.0 g / cm ３ to 1.1 g / cm ３ being that, (5) The lithium desorption capacity per gram of the silicon carbon anode material is 800 mAh / g to 2500 mAh / g, and selectively 1000 mAh / g to 2000 mAh / g. A silicon carbon anode material according to any one of claims 1 to 4, satisfying at least one of the following conditions.

6. The pore volume of the carbon skeleton is 0.4 cm³. ３ / g to 1.5cm ３ It is / g, and selectively 0.6cm ３ / g to 1.2cm ３ / g and / or The silicon carbon anode material according to any one of claims 1 to 5, wherein the volume ratio of micropores with a pore diameter of less than 2 nm is 60% or more of the pore volume, and selectively 80% or more.

7. The silicon carbon anode material according to any one of claims 1 to 6, wherein the surface of the silicon carbon anode material has a coating layer, and selectively, the coating layer is a carbon coating layer.

8. A silicon carbon particle formation step involves reacting a carbon skeleton having a porous structure with a silicon source gas to form silicon carbon particles having a silicon-based material within the porous structure, A silicon carbon particle processing step comprising introducing a mixed gas containing a carbon source gas and an inert gas into the silicon carbon particles at a permeability rate greater than 0 L / min and less than or equal to 10 L / min, under conditions of a temperature of 500°C to 700°C and a pressure of 0 kPa to 1 kPa, wherein the carbon source gas is at least one selected from ethane, ethylene, acetylene, and methane. A method for producing a silicon carbon anode material according to any one of claims 1 to 7, including the method described in any one of claims 1 to 7.

9. The manufacturing method according to claim 8, wherein in the silicon carbon particle processing step, the mixed gas is introduced to the silicon carbon particles at a permeability of 0.5 L / min to 4 L / min under conditions of a temperature of 550°C to 650°C and a pressure of 0 kPa to 0.5 kPa.

10. The mixed gas comprises 10% to 70% by volume of acetylene, 0% to 20% by volume of methane, and 10% to 90% by volume of an inert gas. Selectively, the mixed gas comprises 15% to 60% by volume of acetylene, 5% to 10% by volume of methane, and 30% to 80% by volume of an inert gas. The manufacturing method according to claim 8 or 9.

11. In the silicon carbon particle formation step, A manufacturing method according to any one of claims 8 to 10, comprising the step of evacuating the reaction apparatus and then introducing an inert gas.

12. In the silicon carbon particle formation step, A manufacturing method according to any one of claims 8 to 11, comprising the step of heating a carbon skeleton having a porous structure to 400°C to 550°C in a reaction apparatus and removing oxygen gas from the carbon skeleton.

13. In the silicon carbon particle formation step, A manufacturing method according to any one of claims 8 to 12, comprising the step of introducing a mixed gas of a silicon source gas and an inert gas into a reaction apparatus and depositing it at a temperature of 400°C to 550°C for 2 to 10 hours to form silicon carbon particles.

14. The manufacturing method according to any one of claims 8 to 13, wherein the silicon source gas is one or more selected from silane, disilane, dichlorosilane, and trichlorosilane, and selectively the silicon source gas is silane.

15. The manufacturing method according to any one of claims 8 to 14, wherein the inert gas is argon gas.

16. A negative electrode sheet comprising a silicon carbon negative electrode material according to any one of claims 1 to 7, or a silicon carbon negative electrode material manufactured by a manufacturing method according to any one of claims 8 to 15.

17. A secondary battery comprising the negative electrode sheet described in claim 16.

18. An electrical device comprising the secondary battery described in claim 17.

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