Biomass porous carbon and preparation method thereof, silicon-carbon composite material and preparation method thereof, secondary battery, battery module, battery pack and electric device

Abstract

The embodiment of the invention provides biomass porous carbon and a preparation method thereof, a silicon-carbon composite material and a preparation method thereof, a secondary battery, a battery module, a battery pack and an electric device. The preparation method of the biomass porous carbon comprises the following steps: activating and washing a biomass carbonized material in which Dn10 is more than or equal to 0.8 mu m and less than or equal to 2 mu m and (Dv90-Dv10) / Dv50 is more than or equal to 0.8 mu m and less than or equal to 1.5. The preparation method can effectively improve the activation uniformity and the powder compaction density of the biomass carbonized material after activation treatment; when the silicon-carbon composite material is applied to the hollow porous structure silicon-carbon composite material, the deposition uniformity of silicon particles can be improved, the cycle life of a battery can be prolonged, and the energy density of the battery can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium batteries, in particular to a biomass porous carbon and a preparation method thereof, a silicon-carbon composite material and a preparation method thereof, a secondary battery, a battery module, a battery pack and a power utilization device. BACKGROUND

[0002] In recent years, with the application range of lithium ion batteries becoming more and more extensive, lithium ion batteries are widely used in energy storage power supply systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. Since lithium ion batteries have achieved great development, higher requirements have been put forward for their cycle performance.

[0003] Silicon-based materials have attracted attention due to their much higher capacity than carbon-based materials. However, silicon-based materials undergo a huge volume change (>300%) during charging and discharging, which will cause material structure damage, particle pulverization, and thus lead to rapid decay of electrode capacity and even electrode failure. Therefore, silicon-based materials are often used in combination with carbon-based materials during the production of electrode sheets. The commonly used is a hollow porous structure silicon-carbon composite material (hereinafter referred to as a silicon-carbon composite material), that is, amorphous nano-silicon particles are distributed in a biomass porous carbon matrix, the pores of the biomass porous carbon provide space for the expansion of the silicon particles, and can inhibit the contact between silicon and electrolyte, reduce the occurrence of side reactions, and prolong the cycle life of the silicon-based negative electrode. However, the current silicon-carbon composite material has problems of being unable to balance the cycle performance and energy density in actual battery applications. SUMMARY

[0004] The present application is carried out in view of the above-mentioned problems, and aims to provide a biomass porous carbon and a preparation method thereof, a silicon-carbon composite material and a preparation method thereof, a secondary battery, a battery module, a battery pack and a power utilization device, which can improve the problem of being unable to balance the cycle performance and energy density of the silicon-carbon composite material in actual battery applications.

[0005] In order to achieve the above-mentioned purpose, the present application provides a biomass carbon with high uniformity of activation and high powder compaction density, which, when applied in a hollow porous structure silicon-carbon composite material, is not only beneficial to improving the uniformity of silicon particle deposition, thereby being beneficial to improving the cycle life of the battery, but also being beneficial to improving the energy density of the battery.

[0006] A first aspect of the present application provides a preparation method of a biomass porous carbon, comprising: activating and washing a biomass carbonization material with 0.8 μm≤Dn10≤2 μm, 0.8≤(Dv90-Dv10) / Dv50≤1.5.

[0007] Therefore, by improving the preparation method, by controlling the pre-screening to obtain biomass carbonized material with 0.8 pm≤Dn10≤2 pm, 0.8≤(Dv90-Dv10) / Dv50≤1.5, and then performing activation treatment, the activation uniformity and the powder compaction density of the biomass carbonized material can be effectively improved, so that when the biomass carbonized material is applied to the hollow porous structure silicon-carbon composite material, it is not only beneficial to improve the uniformity of silicon particle deposition, thereby being beneficial to improve the battery cycle life, but also beneficial to improve the energy density of the battery.

[0008] In any embodiment, the biomass carbonized material has 0.8≤(Dv90-Dv10) / Dv50≤1.2. Controlling the span of the biomass carbonized material within the above range is beneficial to further improve the activation uniformity of the biomass carbonized material and is beneficial to improve the battery cycle life.

[0009] In any embodiment, before the activation treatment, the preparation method comprises: pre-carbonizing the biomass material at 400-700°C, then sintering at 800-1000°C, crushing, and then screening to obtain the biomass carbonized material. By controlling the carbonization temperature, the carbonization effect is good, and the yield is improved.

[0010] In any embodiment, the activation treatment comprises: mixing the activation agent and the biomass carbonized material, and performing activation treatment at 900-1100°C; wherein the activation agent comprises at least one of oxygen, water vapor, carbon dioxide gas, and air. The above activation treatment has a good effect, and can further sinter and carbonize the biomass carbonized material.

[0011] The second aspect of the present application also provides a biomass porous carbon, wherein the pore volume deviation of the biomass porous carbon is greater than or equal to 0 and less than 0.1 cm 3 / g, and the powder compaction density of the biomass porous carbon at 5T is 0.55-1.2 g / cm 3 .

[0012] Therefore, the biomass porous carbon provided by the present application has good activation uniformity and good powder compaction density. The good activation uniformity makes the activation degree of different particles of the biomass carbonized material comparable, so that when the biomass carbonized material is applied to the hollow porous structure silicon-carbon composite material, it is beneficial to improve the uniformity of silicon particle deposition, thereby being beneficial to improve the battery cycle life. The good powder compaction density makes it beneficial to improve the energy density of the battery when the biomass carbonized material is applied to the hollow porous structure silicon-carbon composite material.

[0013] In any embodiment, the pore volume deviation of the biomass porous carbon is 0≤pore volume deviation≤0.05 cm 3 / g. Controlling the pore volume deviation of the biomass porous carbon within the above range can further optimize the battery cycle life.

[0014] In any embodiment, the biomass porous carbon has a pore volume of 0.5 cm 3 / g-0.8 cm 3 / g; and / or, the biomass porous carbon has a specific surface area of 1600 m 2 / g-1850 m 2 / g. Controlling the pore volume and / or the specific surface area of the biomass porous carbon within the above ranges is beneficial to improve the capacity and other performances of the silicon-carbon negative electrode material, and further to improve the electrochemical performance of the battery.

[0015] The third aspect of the present application provides a silicon-carbon composite material, which comprises the biomass porous carbon prepared by the method of the first aspect of the present application or the biomass porous carbon of the second aspect of the present application, and silicon particles attached to the pore walls of the biomass porous carbon.

[0016] The silicon-carbon composite material provided by the present application uses biomass carbon with uniform activation and high powder compaction density as a substrate, which is not only beneficial to improve the uniformity of silicon particle deposition, but also beneficial to improve the cycle life and energy density of the battery when the silicon-carbon composite material is applied to the battery.

[0017] In any embodiment, the silicon-carbon composite material satisfies at least one of (a1)-(a2):

[0018] (a1) the volume of the silicon particles accounts for 40%-60% of the pore volume of the biomass porous carbon;

[0019] (a2) the mass percentage of the silicon particles in the biomass porous carbon is 42%-52%.

[0020] Controlling the silicon-carbon composite material to satisfy at least one of (a1)-(a2) is beneficial to improve the cycle life of the battery when the silicon-carbon composite material is applied to the battery.

[0021] In any embodiment, taking the biomass porous carbon and the silicon particles together as a body, the silicon-carbon negative electrode material further comprises a carbon coating layer coated on the body. Wrapping the carbon coating layer on the surface of the body can not only close the pores to become closed pores, so that the external electrolyte cannot enter the internal pores, and reduce the specific surface area, reduce the loss of active lithium when the SEI film is formed on the surface of the silicon-carbon negative electrode material, but also prevent the capacity loss caused by the oxidation of silicon on the surface of the material from causing the first coulombic efficiency of the battery to decrease and other problems.

[0022] In any embodiment, the silicon-carbon composite material has a powder resistance of 4 Ω·cm-100 Ω·cm at 4 MPa. Controlling the powder resistance within the above range makes the battery using the silicon-carbon composite material have low DCR and good rate performance.

[0023] The fourth aspect of the present application provides a preparation method of a silicon-carbon composite material, which comprises: introducing the biomass porous carbon prepared by the preparation method of the first aspect of the present application or the biomass porous carbon of the second aspect of the present application into a fluidized bed reactor, and performing deposition under the conditions that the mass concentration of the silicon source gas is 8%-18%, the superficial gas velocity is 0.03 m / s-0.07 m / s, and the deposition temperature is 500°C-700°C.

[0024] The silicon source gas comprises a silane-containing hydrocarbon.

[0025] The preparation method of the silicon-carbon composite material is advantageous for uniformly depositing silicon particles in the biomass porous carbon material, and is advantageous for further improving the uniformity of the deposition of the silicon particles, so that the silicon-carbon composite material is advantageous for improving the cycle life of the battery when applied to the battery.

[0026] The fifth aspect of the present application provides a secondary battery comprising any one of the biomass porous carbon prepared by the preparation method of the first aspect of the present application, the biomass porous carbon of the second aspect of the present application, or the silicon-carbon composite material of the third aspect of the present application.

[0027] The sixth aspect of the present application provides a battery module comprising the secondary battery of the third aspect of the present application.

[0028] The seventh aspect of the present application provides a battery pack comprising the battery module of the fourth aspect of the present application.

[0029] The sixth aspect of the present application provides an electric device comprising at least one selected from the secondary battery of the third aspect of the present application, the battery module of the fourth aspect of the present application, or the battery pack of the fifth aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 A scanning electron microscope image of the biomass porous carbon prepared for Example 1;

[0031] Figure 2 A scanning electron microscope image of the biomass porous carbon prepared for Comparative Example 1;

[0032] Figure 3 A scanning electron microscope image of the coarse powder after grading of the biomass porous carbon prepared for Comparative Example 1;

[0033] Figure 4 A 1k times particle cross-section backscattering image of the silicon-carbon composite material prepared for Example 1;

[0034] Figure 5 A 1k times particle cross-section backscattering image of the silicon-carbon composite material prepared for Comparative Example 1;

[0035] Figure 6 A cycle performance comparison diagram of the secondary batteries corresponding to Example 1 and Comparative Examples 1-2.

[0036] Figure 7 This is a schematic diagram of a secondary battery according to one embodiment of this application;

[0037] Figure 8 yes Figure 7 An exploded view of a secondary battery according to an embodiment of this application is shown.

[0038] Figure 9 This is a schematic diagram of a battery module according to one embodiment of this application;

[0039] Figure 10 This is a schematic diagram of a battery pack according to one embodiment of this application;

[0040] Figure 11 yes Figure 10 An exploded view of a battery pack according to one embodiment of this application is shown;

[0041] Figure 12 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0042] Explanation of reference numerals in the attached figures:

[0043] 1-Battery pack; 2-Upper housing; 3-Lower housing; 4-Battery module; 5-Secondary battery; 51-Housing shell; 52-Electrode assembly; 53-Top cover assembly. Detailed Implementation

[0044] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the biomass porous carbon and its preparation method, silicon-carbon composite materials, secondary batteries, battery modules, battery packs, and electrical devices of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0045] The ranges disclosed herein are meant to be inclusive of the endpoints and include the end values in the range. Ranges can be combined to form new ranges, e.g., a range of "60-120 and 80-110" is understood to include 60-110 and 80-120. Further, if a minimum range value is listed as 1 and a maximum range value is listed as 3, 4, and 5, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise indicated, a numerical range "a-b" means a range of any combination of the numbers a and b, wherein both a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between 0 and 5 have been listed herein, and "0-5" is merely a shorthand for listing all of those numbers. Also, when a parameter is stated to be an integer > 2, it is equivalent to state that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0046] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, unless otherwise specified.

[0047] All technical features and optional technical features of the present application can be combined with each other to form new technical solutions, unless otherwise specified.

[0048] All steps of the present application can be performed in sequence or randomly, preferably in sequence, unless otherwise specified. For example, a method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, it is mentioned that the method can further comprise step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0049] Unless otherwise specified, "including" and "comprising" mentioned in the present application means open-ended, and can also be closed-ended. For example, "including" and "comprising" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0050] If not specifically stated, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": A is true (or present) and B is false (or not present); A is false (or not present) and B is true (or present); or both A and B are true (or present).

[0051] The main factor affecting the poor cycle performance of the hollow porous structure silicon-carbon composite material in actual battery applications is the selection of the biomass porous carbon substrate. The hollow porous structure silicon-carbon composite material with a resin-based carbon substrate generally has better cycle performance. If a biomass-based carbon substrate is used, it is easy to cause the cycle performance of the battery to decrease. Therefore, how to effectively improve the problem of the poor cycle performance of the hollow porous structure silicon-carbon composite material with a biomass-based carbon substrate as the biomass porous carbon substrate in actual battery applications is a difficulty.

[0052] One of the main factors affecting the cycle performance of silicon in silicon-carbon composite materials in actual battery applications is that the silicon in the silicon-carbon composite material is uniformly distributed at a suitable proportion. Since the preparation process of the silicon-carbon composite material is carried out at high temperature in a reactor, the heat distribution between the inside of the reactor and the shell is inevitably uneven. At the same time, the thermal capacity difference between the dense and sparse regions of the particles also causes uneven heat distribution. Therefore, different thermal zones exist in the reactor. The carbon materials with similar porosities and similar densities are distributed in the same thermal zone, that is, the particle distribution concentration is high, and the deposition uniformity between the particles is improved. Among them, the prepared biomass porous carbon can be classified to obtain carbon materials with similar porosities and similar densities. However, this method has the problems of low compaction density of the prepared carbon material powder, high difficulty and cost of screening.

[0053] Based on this, the first aspect of the embodiments of the present application provides a preparation method of biomass porous carbon, which comprises: activating and washing the biomass carbonized material with 0.8 μm≤Dn10≤2 μm and 0.8≤(Dv90-Dv10) / Dv50≤1.5.

[0054] It can be understood that the biomass carbonized material refers to the process of slow decomposition of biomass material under oxygen-free (such as vacuum atmosphere), oxygen-deficient or inert atmosphere (such as nitrogen or argon atmosphere) to produce solid coke, wherein the solid coke is the biomass carbonized material in the present application. The biomass material refers to various organisms produced by photosynthesis. Representative biomass materials include but are not limited to crop straw, rice husk, sawdust, and shells of various plants, etc., which can be selected according to actual needs.

[0055] The activation treatment is used to expand the pore structure formed by the carbonization process in the biomass carbonization material and form new pores, so as to optimize the pore structure and pore distribution. In the process of activation treatment, part of the large particles can be broken to produce small particles.

[0056] The washing is used to remove impurities, wherein the washing includes but is not limited to: first using acid washing to remove organic matter, etc., then using alkaline aqueous solution to adjust pH and then washing to neutral, or directly washing to neutral after acid washing. The acid washing method includes but is not limited to soaking or rinsing, and the acid used in the acid washing includes but is not limited to hydrochloric acid or permanganic acid, etc.

[0057] Dn10, Dv10, Dv50 and Dv90 all have the meanings known in the art, and can be tested by the methods known in the art. For example, a laser diffraction particle size distribution measuring instrument is used to measure according to the particle size distribution laser diffraction method (for details, refer to GB / T19077-2016). Dn10 refers to the particle size when the cumulative number of particles is 10% from the small particle size in the particle size distribution measurement by laser scattering method. Dv10 refers to the particle size when the cumulative volume is 10% from the small diameter in the particle size distribution measurement by laser scattering method, Dv50 refers to the particle size when the cumulative volume is 50% from the small diameter in the particle size distribution measurement by laser scattering method, and Dv90 refers to the particle size when the cumulative volume is 90% from the small diameter in the particle size distribution measurement by laser scattering method.

[0058] (Dv90-Dv10) / Dv50 represents the particle size distribution width, also known as the diameter distance.

[0059] The preparation method of the biomass carbonization material 0.8≤Diameter≤1.5 and 0.8 μm≤Dn10≤2 μm, and then the biomass carbonization material is activated and washed. On the one hand, by pre-limiting the diameter and Dn10 of the biomass carbonization material in the above range, the biomass carbonization material that is too large or too small is removed, the difference between the biomass carbonization materials is reduced, and the particles of different sizes are uniformly distributed, so that the activation uniformity of the biomass carbonization material after activation can be effectively improved, the activation degree of different particles of the biomass carbonization material is equivalent, and when the biomass carbonization material is applied to the hollow porous structure silicon-carbon composite material, the uniformity of the silicon particle deposition is improved, and the battery cycle life is improved. On the other hand, since the present application adopts screening before activation, the activated biomass porous carbon can be obtained without further classification, the yield is higher than that of the screening method after activation, the production cost is effectively reduced, and since the particles of the biomass carbonization material are large and small and the activation process also causes a certain degree of crushing, the final prepared biomass porous carbon has particles of different sizes with appropriate particle size, so that the powder compaction density can be effectively improved based on the compounding of particles of different sizes, and the battery energy density is improved.

[0060] Exemplarily, the Dn10 of the biomass carbonization material is any one of 0.8 μm, 1.0 μm, 1.2 μm, 1.5 μm, 1.7 μm, 2.0 μm or between any two values.

[0061] Exemplarily, the diameter of the biomass carbonization material is any one of 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or between any two values.

[0062] In summary, the preparation method provided by the present application can effectively improve the activation uniformity and powder compaction density of the biomass carbonization material by controlling the pre-screening to obtain 0.8 μm≤Dn10≤2 μm, 0.8≤(Dv90-Dv10) / Dv50≤1.5, and then activating the biomass carbonization material. When the biomass carbonization material is applied to the hollow porous structure silicon-carbon composite material, it is not only beneficial to improve the uniformity of the silicon particle deposition and improve the battery cycle life, but also beneficial to improve the energy density of the battery. It can be understood that the preparation method also includes drying and washing the biomass carbonization material.

[0063] In some embodiments, the biomass carbonization material has 0.8≤(Dv90-Dv10) / Dv50≤1.2.

[0064] Controlling the diameter of the biomass carbonization material in the above range is beneficial to further improve the activation uniformity of the biomass carbonization material and improve the battery cycle life.

[0065] Exemplarily, the diameter of the biomass carbonized material is any one of 0.8, 0.9, 1.0, 1.1, 1.2 or between any two values.

[0066] In some embodiments, before the activation treatment, the preparation method comprises: pre-carbonizing the biomass material at 400-700°C, then sintering at 800-1000°C, crushing and sieving to obtain the biomass carbonized material.

[0067] Through pre-carbonization and sintering, carbonization of the biomass material is achieved, which refers to a process of slow decomposition of the biomass material under the action of heat in an oxygen-free (such as a vacuum atmosphere), oxygen-deficient or inert atmosphere (such as an atmosphere of nitrogen or argon) to produce solid coke.

[0068] Through pre-carbonization and sintering in combination and controlling the temperature of both to achieve carbonization, not only the carbonization effect is good, but also the yield is improved.

[0069] Exemplarily, the temperature of pre-carbonization is any one of 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C or between any two values.

[0070] Optionally, the temperature of pre-carbonization is 400-600°C. Exemplarily, the temperature of sintering is any one of 800°C, 850°C, 900°C, 950°C, 1000°C or between any two values.

[0071] The upper limit of the total carbonization time of pre-carbonization and sintering can include ten hours, and the lower limit of the total carbonization time can be any time as long as the biomass material is reliably carbonized.

[0072] It should be noted that before carbonizing the biomass material, it also includes selecting a suitable biomass raw material according to actual needs, then placing the biomass raw material in a drying oven for drying treatment to control the water content, then stirring and crushing the dried single biomass raw material with a pulverizer or stirring and crushing the dried multiple biomass raw materials with a pulverizer, then sieving to obtain a powdered biomass material for carbonization, wherein the particle size range of the powdered biomass material for carbonization can be selected according to actual needs.

[0073] The activation treatment method can include a gas activation method and a chemical activation treatment.

[0074] The chemical activation method refers to activation by using chemical activators such as sodium hydroxide, potassium hydroxide, zinc chloride, iron chloride, calcium phosphate, calcium hydroxide, magnesium carbonate, potassium carbonate, sulfuric acid, etc. The specific operation can refer to related technologies.

[0075] The gas activation method refers to: using oxygen, water vapor, carbon dioxide gas, air and the like as an activation agent, heating the biomass carbonization material at 700-1400°C, optionally 700-1100°C for tens of minutes to several hours in this atmosphere, thereby forming fine structures of volatile components or carbon molecules in the biomass carbonization material.

[0076] In some embodiments, the activation treatment comprises: mixing the activation agent and the biomass carbonization material, and performing the activation treatment at 900-1100°C.

[0077] The activation agent comprises at least one of oxygen, water vapor, carbon dioxide gas, air, and potassium hydroxide.

[0078] It should be noted that the activation temperature can be appropriately adjusted within the range of 900-1100°C based on the type of biomass material, the type of gas, the concentration of the gas, and the like.

[0079] The above activation treatment has good effects and can further sinter and carbonize the biomass carbonization material.

[0080] For example, the temperature of the activation treatment is any one of 900°C, 920°C, 950°C, 980°C, 1000°C, 1020°C, 1050°C, 1080°C, 1100°C or between any two values.

[0081] The second aspect of the embodiments of the present application provides a biomass porous carbon, the pore volume deviation of the biomass porous carbon is greater than or equal to 0 and less than 0.1 cm 3 / g, and the powder compaction density of the biomass porous carbon at 5T is 0.55-1.2 g / cm 3 .

[0082] The pore volume deviation refers to grading the biomass porous carbon according to the Dv50 range to obtain multiple samples with different Dv50 ranges, obtaining the pore volumes between the samples, and expressing the pore volume deviation between any two samples as the pore volume difference between the two samples.

[0083] It can be understood that the pore volume deviation of the biomass porous carbon is greater than or equal to 0 and less than 0.1 cm 3 / g refers to: after grading, the pore volume difference between different samples needs to be greater than or equal to 0 and less than 0.1 cm 3 / g.

[0084] The pore volume deviation is used to characterize the activation uniformity of the biomass porous carbon, wherein the smaller the pore volume deviation, the higher the activation uniformity of the biomass porous carbon.

[0085] The biomass porous carbon provided in the application has preferable activation uniformity and preferable powder compaction density. The preferable activation uniformity makes the activation degree of different particles of the biomass carbonization material comparable, which is conducive to improving the uniformity of silicon particle deposition when the biomass porous carbon is applied to a hollow porous structure silicon-carbon composite material, and thus is conducive to improving the battery cycle life. The preferable powder compaction density is conducive to improving the battery energy density when the biomass porous carbon is applied to the hollow porous structure silicon-carbon composite material.

[0086] For example, the pore volume deviation of the biomass porous carbon is any value or between any two values in the range of 0, 0.01 cm 3 / g, 0.03 cm 3 / g, 0.05 cm 3 / g, 0.08 cm 3 / g, 0.10 cm 3 / g.

[0087] For example, the powder compaction density of the biomass porous carbon at 5T is any value or between any two values in the range of 0.55 g / cm 3 , 0.58 g / cm 3 , 0.60 g / cm 3 , 0.63 g / cm 3 , 0.65 g / cm 3 , 0.68 g / cm 3 , 0.70 g / cm 3 , 0.73 g / cm 3 , 0.75 g / cm 3 , 0.78 g / cm 3 , 0.80 g / cm 3 , 0.85 g / cm 3 , 0.90 g / cm 3 , 0.95 g / cm 3 , 1.00 g / cm 3 , 1.05 g / cm 3 , 1.10 g / cm 3 , 1.15 g / cm 3 , 1.20 g / cm 3 .

[0088] In some embodiments, the pore volume deviation of the biomass porous carbon is ≤0.05 cm 3 / g.

[0089] The pore volume deviation of the biomass porous carbon is controlled within the above range, which can further optimize the activation uniformity of the biomass porous carbon, make the activation degree of different particles of the biomass carbonization material more comparable, and when the biomass porous carbon is applied to the hollow porous structure silicon-carbon composite material, it is beneficial to further improve the uniformity of silicon particle deposition, and thus further improve the battery cycle life.

[0090] Exemplarily, the pore volume deviation of the biomass porous carbon is any value or between any two values in 0, 0.01 cm 3 / g, 0.02 cm 3 / g, 0.03 cm 3 / g, 0.04 cm 3 / g, 0.05 cm 3 / g.

[0091] In some embodiments, the pore volume of the biomass porous carbon is 0.5 cm 3 / g-0.8 cm 3 / g; and / or,

[0092] The specific surface area of the biomass porous carbon is 1600 m 2 / g-1850 m 2 / g.

[0093] The pore volume refers to the total volume of pores per unit mass of biomass porous carbon. The test method of the pore volume is nitrogen BET-full pore test.

[0094] The specific surface area is tested by gas adsorption method, and is tested by BET method according to GB / T 19587-2017 test standard.

[0095] It can be understood that the pore volume of the biomass porous carbon corresponds to the deposition amount of silicon particles. Therefore, by limiting the pore volume of the biomass porous carbon to 0.5 cm 3 / g-0.8 cm 3 / g, it is beneficial to deposit a target amount of silicon in the biomass porous carbon to improve the capacity of the silicon-carbon negative electrode material, and after the silicon is deposited to the target amount, the biomass porous carbon still has sufficient pores to buffer the volume expansion caused by the silicon particles, thereby improving the initial discharge capacity and cycle performance of the battery.

[0096] Exemplarily, the pore volume of the biomass porous carbon is any value or between any two values in 0.5 cm 3 / g, 0.6 cm 3 / g, 0.7 cm 3 / g, 0.8 cm 3 / g.

[0097] The specific surface area range is conducive to the deposition of silicon particles in the pores of the biomass porous carbon, and is conducive to improving the cycle performance of the battery.

[0098] For example, the specific surface area of the biomass porous carbon is 1600 m 2 / g, 1650 m 2 / g, 1680 m 2 / g, 1700 m 2 / g, 1730 m 2 / g, 1750 m 2 / g, 1780 m 2 / g, 1800 m 2 / g, 1830 m 2 / g, 1850 m 2 / g, or between any two values.

[0099] The third aspect of the embodiments of the present application provides a silicon-carbon composite material, which comprises the biomass porous carbon prepared by the preparation method of the first aspect of the embodiments of the present application or the biomass porous carbon of the second aspect of the embodiments of the present application, and silicon particles attached to the pore wall of the biomass porous carbon.

[0100] It can be understood that the silicon particles attached to the pore wall of the biomass porous carbon means that the silicon particles are attached to the pore wall of the biomass porous carbon and the space of the pores is not filled with the silicon particles. That is, the biomass porous carbon with the silicon particles attached to the pore wall still has certain pores, which reserve space for the expansion of the silicon particles and inhibit the contact between the silicon and the electrolyte, reduce the occurrence of side reactions, and prolong the cycle life of the silicon-based negative electrode.

[0101] The silicon-carbon composite material provided by the present application uses biomass carbon with uniform activation and high powder compaction density as a substrate, which is not only conducive to improving the uniformity of silicon particle deposition, but also conducive to improving the cycle life of the battery when the silicon-carbon composite material is applied to the battery, and conducive to improving the energy density of the battery.

[0102] In the preparation process of the silicon-carbon composite material, the silicon particles can be deposited in the biomass porous carbon by using a chemical vapor deposition method in a heating chamber of a gas phase deposition furnace, or the silicon particles can be deposited in the biomass porous carbon by using a gas phase deposition method in a gas fluidized bed.

[0103] In some embodiments, the silicon-carbon composite material satisfies at least one of (a1)-(a2):

[0104] (a1) the volume of the silicon particles accounts for 40%-60% of the pore volume of the biomass porous carbon;

[0105] When the proportion of the silicon particles is too small, the large specific surface area of the residual porous carbon substrate affects the first coulomb efficiency of the material. When the proportion of the silicon particles is too large, the surface rich in silicon leads to a large degree of attenuation in long-term cycles.

[0106] Therefore, by limiting the volume proportion of the silicon particles to the pore volume proportion of the biomass porous carbon, the pores of the biomass porous carbon after the silicon particles are attached to the pore wall can be controlled, so that the silicon-carbon composite material is beneficial to improve the cycle life of the battery when applied to the battery.

[0107] Exemplarily, the volume proportion of the silicon particles to the pore volume of the biomass porous carbon is any one of 40%, 42%, 45%, 47%, 50%, 53%, 55%, 56%, 57%, 58%, 59%, 60% or between any two values.

[0108] (a2) The mass percentage of the silicon particles in the biomass porous carbon is 42%-52%.

[0109] By limiting the mass percentage of the silicon particles in the biomass porous carbon within the above range, the silicon-carbon composite material is beneficial to improve the cycle life of the battery when applied to the battery.

[0110] Exemplarily, the mass percentage of the silicon particles in the biomass porous carbon is any one of 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52% or between any two values.

[0111] Alternatively, the mass percentage of the silicon particles in the biomass porous carbon is 42%-52%.

[0112] In some embodiments, the silicon-carbon negative electrode material further comprises a carbon coating layer coated on the body with the biomass porous carbon and the silicon particles as the body.

[0113] Since the silicon particles have high activity, the carbon coating layer is used to wrap the surface of the body, which on one hand closes the pores to become closed pores, so that the external electrolyte cannot enter the internal pores, and reduces the specific surface area, reduces the loss of active lithium when the SEI film is formed on the surface of the silicon-carbon negative electrode material, and on the other hand, can prevent the capacity loss caused by the oxidation of silicon on the surface of the material from causing the first coulomb efficiency of the battery to decrease and other problems.

[0114] The thickness of the carbon coating layer can be limited according to actual needs, and exemplarily, the thickness of the carbon coating layer is 0.5-40 nm.

[0115] In some embodiments, the silicon-carbon composite material has a powder resistance of 4Ω-100Ω at 4Mpa.

[0116] Controlling the powder resistance of the silicon-carbon composite material within the above range allows the battery using the silicon-carbon composite material to have low DCR and good rate performance.

[0117] For example, the silicon-carbon composite material has a powder resistance of any one of 4 Ω·cm, 10 Ω·cm, 30 Ω·cm, 50 Ω·cm, 70 Ω·cm, 90 Ω·cm, 100 Ω·cm or between any two values at 4 MPa.

[0118] The fourth aspect of the present application provides a silicon-carbon composite material, and a preparation method of the silicon-carbon composite material includes: introducing the biomass porous carbon prepared by the preparation method of the first aspect of the present application or the biomass porous carbon of the second aspect of the present application into a fluidized bed reactor, and depositing under the conditions that the mass concentration of the silicon source gas is 8%-18%, the superficial gas velocity is 0.03 m / s-0.07 m / s, and the deposition temperature is 500°C-700°C.

[0119] The silicon source gas includes a silane hydrocarbon.

[0120] The silane hydrocarbon includes but is not limited to one or more of silane, dichlorosilane, trichlorosilane, and tetrachlorosilane.

[0121] The above preparation method is beneficial to the uniform deposition of silicon particles in the biomass porous carbon material, and is beneficial to further improving the uniformity of the deposition of silicon particles, so that the silicon-carbon composite material is beneficial to improving the cycle life of the battery when applied to the battery.

[0122] For example, the mass concentration of the silicon source gas is any one of 8%, 10%, 13%, 15%, 18% or between any two values, the superficial gas velocity is any one of 0.03 m / s, 0.04 m / s, 0.05 m / s, 0.06 m / s, 0.07 m / s or between any two values, and the deposition temperature is any one of 500°C, 550°C, 600°C, 650°C, 700°C or between any two values.

[0123] When the biomass porous carbon and the silicon particles are collectively used as the body, and the silicon-carbon negative electrode material further includes a carbon coating layer coated on the body, the preparation method of the carbon coating layer includes but is not limited to: placing the body in a mixed gas atmosphere of a carbon source and an inert gas, and pyrolyzing the carbon source to form a carbon coating layer coated on the body, wherein the carbon source includes one or more of alkane, alkyne, and alkene. The inert gas includes but is not limited to nitrogen or argon. The alkane includes but is not limited to methane, the alkene includes but is not limited to ethylene, and the alkyne includes but is not limited to acetylene.

[0124] In addition, the secondary battery, the battery module, the battery pack, and the power utilization device of the present application are described below with appropriate reference to the accompanying drawings.

[0125] [Secondary battery]

[0126] The fifth aspect of the embodiments of the present application provides a secondary battery.

[0127] The secondary battery according to the present application is not particularly limited, and for example, the secondary battery can be a lithium ion battery or the like.

[0128] Generally, the secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During charging and discharging of the battery, active ions are inserted and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet, and mainly plays a role of preventing short circuit between the positive electrode and the negative electrode, while allowing ions to pass through.

[0129] The electrolyte according to the present application is not particularly limited, and can be selected according to actual needs. For example, the electrolyte can be selected from at least one of a solid-state electrolyte and a liquid-state electrolyte (i.e., electrolyte solution). The secondary battery using the electrolyte solution, and some secondary batteries using the solid-state electrolyte.

[0130] [Positive electrode sheet]

[0131] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0132] As an example, the positive electrode current collector has two opposite surfaces in the thickness direction thereof, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0133] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0134] In some embodiments, when the secondary battery is a lithium ion battery, the positive electrode active material can employ a positive electrode active material for a lithium ion battery known in the art. As an example, the positive electrode active material can include at least one of a lithium-containing phosphate of an olivine structure, a lithium transition metal oxide, and a modified compound of each thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material can also be used. These positive electrode active materials can be used alone only one or in combination of two or more. Among them, examples of the lithium transition metal oxide can include, but are not limited to, lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3Mn 1 / 3 O2(also can be simply referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2(also can be simply referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2(also can be simply referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2(also can be simply referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2(also can be simply referred to as NCM 811 )、LiNi 0.85 Co 0.15 Al 0.05 O2) and a modified compound thereof, etc. Examples of the lithium-containing phosphate of an olivine structure can include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4(also can be simply referred to as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon.

[0135] In some embodiments, in order to further improve the energy density of the secondary battery, the positive electrode active material for the lithium ion battery can include a general formula of Li a Ni b Co c M d O e A fOne or more of lithium transition metal oxides and their modified compounds. 0.8 ≤ a ≤ 1.2, 0.5 ≤ b < 1, 0 < c < 1, 0 < d < 1, 1 ≤ e ≤ 2, 0 ≤ f ≤ 1, M is selected from one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is selected from one or more of N, F, S, and Cl.

[0136] In some embodiments, by way of example, the positive electrode active material for a lithium-ion battery may include one or more of LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 O2, LiFePO4, and LiMnPO4.

[0137] In the present application, the modified compounds of the above positive electrode active materials may be doping modification and / or surface coating modification of the positive electrode active materials.

[0138] As an optional technical solution of the present application, the polyanionic compound may be Li 1+x Mn 1-y A y P 1-z R z O4; wherein, x is any value within the range of -0.100 to 0.100, y is any value within the range of 0.001 to 0.500, z is any value within the range of 0.001 to 0.100, A includes one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and R includes one or more elements of B, S, Si, and N.

[0139] As an optional technical solution of the present application, the polyanionic compound may be Li a A e Mn 1-f B f P 1-g Cg O 4-n D n wherein A comprises one or more elements of Zn, Al, Na, K, Mg, Nb, Mo and W; B comprises one or more elements of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge; C comprises one or more elements of B, S, Si and N; D comprises one or more elements of S, F, Cl and Br; a is selected from the range of 0.9 to 1.1, e is selected from the range of 0.001 to 0.1, f is selected from the range of 0.001 to 0.5, g is selected from the range of 0.001 to 0.1, n is selected from the range of 0.001 to 0.1, and the second positive electrode active material is electrically neutral.

[0140] The battery will be accompanied by Li de-intercalation and consumption during charging and discharging process, and the molar content of Li is different when the battery is discharged to different states. In the enumeration of the positive electrode material in the present application, the molar content of Li is the initial state of the material, i.e. the state before feeding, and the positive electrode material is applied to the battery system. After charging and discharging cycle, the molar content of Li will change.

[0141] In the enumeration of the positive electrode material in the present application, the molar content of O is only the theoretical state value, and the release of oxygen from the lattice will cause the change of the molar content of oxygen, and the actual molar content of O will appear floating.

[0142] As an optional technical manner of the present application, the polyanionic compound can be Na 4+x R 3-y P 4-m O 15 / C; wherein 0 < x < 0.5, 0≤y≤0.5, 0≤m≤0.2, R comprises at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Cr, Nb, Mo, In, Ga, Sn, Hf, Ta, W and Pb.

[0143] As an optional technical manner of the present application, the polyanionic compound can be Na x-a A a V y-b M b (PO4) 2-2c (DO4) 2c F z-d Q dwherein the A element represents an alkali metal element that dopes and substitutes the Na element, the M element represents a metal element that substitutes the V element, the D element represents a doping element that substitutes the P element, the Q element represents a doping element that substitutes the F element, the D element includes at least one of Si and S, and the Q element includes at least one of Cl and O; 3.5≤x≤4.5, 0≤a≤0.15x, 0.8≤y≤1.1, 0≤b≤0.3y, 0≤c≤0.15, 0.8≤z≤1.1, and 0≤d≤0.2z. Optionally, the A element includes at least one of K and Li; and the M element includes at least one of Fe, Cr, Al, Sc, Ga, In, Ti, Zr, Mn, Zn, Ni, Cu, and Co.

[0144] As an optional technical solution of the present application, the transition metal in the sodium transition metal oxide can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The sodium transition metal oxide is, for example, NaM0, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0

[0145] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions, and tetrahedral (Y04) n- The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; and n represents the valence of (Y04) n- .

[0146] The Prussian blue compound can be a compound having sodium ions, transition metal ions, and cyanide ions (CN - ). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The Prussian blue compound is, for example, Na a Me b Me’ c (CN)6, where Me and Me’ are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0

[0147] In some embodiments, the positive electrode film layer can also optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin.

[0148] In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0149] In some embodiments, the positive electrode tab can be prepared by dispersing the above-mentioned components for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., N-methyl pyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector; and subjecting the positive electrode current collector to drying, cold pressing, and the like to obtain the positive electrode tab.

[0150] [Positive electrode tab]

[0151] In some embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material. The negative electrode active material is the silicon-carbon composite material provided in the first aspect of the present application. Thus, the negative electrode tab of the present application is beneficial to improving the cycle life of the battery when applied in the battery, and can also effectively improve the powder compaction density, which is beneficial to improving the energy density of the battery.

[0152] As an example, the negative electrode current collector has two opposite surfaces in the thickness direction thereof, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0153] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base layer (such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.). In some embodiments, the negative electrode film layer further optionally includes a binder. The binder can be selected from at least one of 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).

[0154] In some embodiments, the negative electrode film layer further optionally includes a conductive agent. The conductive agent can be selected from at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0155] In some embodiments, the negative electrode film layer can also optionally include other additives, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

[0156] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative electrode current collector, and after processes such as drying, cold pressing, and the like, the negative electrode sheet can be obtained.

[0157] In other embodiments, the current collector of the negative electrode sheet can generally include a current collector body and a primer layer, which can be provided on at least one side of the current collector body, the primer layer is substantially free of negative electrode active material, and can include a small amount of carbon material, but the carbon material forms a coating layer with a thickness that is too thin to function as a negative electrode active material. In this embodiment, the negative electrode sheet can be a sheet without a negative electrode active material layer. For the negative electrode sheet without a negative electrode active material layer, when the current collector of the negative electrode sheet does not include a primer layer, the film layer can be provided on the surface of at least one side of the current collector; when the current collector of the negative electrode sheet includes a primer layer, the film layer can be provided on the surface of the side of the primer layer away from the current collector.

[0158] In some embodiments, the film layer can also include a binder for fixing the additives to the negative electrode sheet. The type of the binder is not particularly limited, and can be selected as desired by those skilled in the art.

[0159] [Electrolyte]

[0160] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The type of the electrolyte is not particularly limited in the present application, and can be selected as desired. For example, the electrolyte can be in a liquid state, a gel state, or a full solid state.

[0161] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0162] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorodioxalate phosphate.

[0163] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl 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, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0164] In some embodiments, the electrolyte solution can further optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain performance of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0165] [Separator]

[0166] In some embodiments, the secondary battery further includes a separator. The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0167] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0168] In some embodiments, the positive electrode tab, the negative electrode tab, and the separator can be made into an electrode assembly through a winding process or a stacking process.

[0169] In some embodiments, the secondary battery can include an outer package. The outer package can be used to package the above-described electrode assembly and the electrolyte solution.

[0170] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as the plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, etc. can be listed.

[0171] The shape of the secondary battery is not particularly limited in the present application, and it can be cylindrical, square, or any other shape. For example, Figure 7 is a battery cell 5 in a square structure as an example.

[0172] In some embodiments, with reference to Figure 8The outer package can include a housing 51 and a cover plate 53. The housing 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be arranged on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator film can form the electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and the number can be selected by a person skilled in the art according to the actual needs.

[0173] In some embodiments, the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery module.

[0174] Figure 9 The battery module 4 is an example. Referring to Figure 9 In the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be used. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0175] Optionally, the battery module 4 can also include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0176] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery pack.

[0177] Figure 10 And Figure 11 The battery pack 1 is an example. Referring to Figure 10 And Figure 11 The battery pack 1 can include a battery box and a plurality of battery modules 6 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be arranged on the lower box body 3 to form a closed space for receiving the battery module 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0178] In addition, the application also provides a power utilization device, which comprises at least one of the secondary battery, the battery module, or the battery pack provided by the application. The secondary battery, the battery module, or the battery pack can be used as a power supply of the power utilization device, and can also be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0179] As the power utilization device, the secondary battery, the battery module, or the battery pack can be selected according to the use requirement thereof.

[0180] Figure 12 The power utilization device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of the power utilization device for high power and high energy density of the secondary battery, the battery pack or the battery module can be used.

[0181] The device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and the secondary battery can be used as a power supply.

[0182] Hereinafter, the embodiments of the application are described. The embodiments described below are exemplary and are only used to explain the application, and cannot be understood as a limitation of the application. If the specific technology or condition is not indicated in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument used is not indicated by the manufacturer, it is a conventional product that can be obtained by purchase.

[0183] The following parameters are tested in the following manner:

[0184] 1. Dn10, Dv10, Dv50, Dv90

[0185] The laser diffraction particle size distribution measuring instrument is used to measure according to the particle size distribution laser diffraction method (for details, refer to GB / T19077-2016).

[0186] 2. Specific surface area

[0187] According to GB / T 19587-2017, the specific process is to weigh 1-8 g of sample (the minimum sample weight is 1 / 3 of the volume of the sphere) and place it in a 1 / 2 inch long tube with a ball bubble (the diameter of the spherical part of the tube is 12 mm), and then place it in the test equipment TriStar3030 (USA Mac company) after pretreatment at 200 DEG C for 2 h, and the adsorption gas used is N2 (purity: 99.999%), and the test condition is carried out at 77K, and the specific surface area is tested by BET calculation method.

[0188] 3, pore volume.

[0189] The N2 gas adsorption method is used to determine the adsorption / desorption data, and the NRDFT model is used for pore structure fitting.

[0190] 4, 5T powder compaction density powder.

[0191] The test standard refers to GB / T 24533-2009 "Lithium ion battery graphite negative electrode material". The specific test method is: weigh 1.0000±0.0500 g of negative electrode material sample and place it in the test mold (CARVER #3619 (13 mm)), then place the sample in the test equipment, the test equipment is TriStar vertical and horizontal UTM7305 test tonnage 0.3t, 0.5t, 0.75t, 1.0t, 1.5t, 2.0t, 2.5t, 3.0t, 4.0t, 5.0t, the pressure increasing rate is 10 mm / min, the pressure increasing holding time is 30 s, the pressure releasing rate is 30 mm / min, and the pressure releasing holding time is 10 s.

[0192] In this application, the powder compaction density is the compaction density measured after 5t pressure release. The calculation formula of the compaction density is: compaction density = material mass / (material force area x sample thickness).

[0193] 5, mass percentage of silicon particles in porous carbon

[0194] Weigh 0.1 g of sample into a PTFE beaker, drop 10 mL of nitric acid, heat to digest. Drop 10 mL of nitric acid again, heat and repeat digestion once. After cooling, filter the digestion solution to remove the residue, and dilute to 100 mL in a volumetric flask. Add the prepared solution to the atomization chamber and test by inductively coupled plasma emission spectrometry.

[0195] 6, volume of silicon particles in the pore volume of porous carbon

[0196] The volume of silicon particles in the pore volume of porous carbon is set in advance, and it is realized through process control.

[0197] The process control implementation process includes: the pore volume of the porous carbon is obtained in advance by the N2 gas adsorption method to obtain the pore volume of the porous carbon.

[0198] The required volume of the silicon particles is obtained by the volume of the silicon particles in the pore volume of the porous carbon, and the required volume of the silicon particles is converted by the density to obtain the preset deposition mass of the silicon particles, and the actual deposition mass of the silicon particles in the silicon deposition process is controlled to be the preset deposition mass.

[0199] 7. Powder resistance

[0200] According to GB / T 30835-2014, use ST2722-SZ powder resistance tester: take a certain amount of sample powder to be tested in a special mold, set the test pressure to 4Mpa, and the powder resistivity under the pressure of 4Mpa can be obtained.

[0201] Example 1

[0202] I. Preparation of silicon-carbon composite material

[0203] The preparation of the silicon-carbon composite material includes:

[0204]

Biomass porous carbon

[0205] The dried straw is crushed into a powder-like biomass material with a particle size range of 3mm-4mm, the biomass material is pre-carbonized at 500℃ under nitrogen atmosphere, sintered at 900℃, crushed and sieved, and a biomass carbonized material with Dn10=1.5μm, (Dv90-Dv10) / Dv50=1.3 is obtained, then the biomass carbonized material is activated in steam at 900℃ for 3h; the obtained product is cooled at room temperature, soaked in permanganic acid for 24h, washed with distilled water to neutral, and dried.

[0206]

Silicon-carbon composite material

[0207] 1kg of the above biomass porous carbon is introduced into a fluidized bed reactor, and deposited under the conditions of a gaseous silane mass concentration of 15%, an apparent gas velocity of 0.04m / s, and a deposition temperature of 540℃, to obtain a body.

[0208] The body is placed in a heating chamber under a nitrogen atmosphere, mixed gas is introduced at a gas flow ratio of nitrogen:acetylene gas of 2:1, and the heating chamber is heated for 1h, and carbon coating treatment is performed on the surface of the body.

[0209] II. Preparation of secondary battery

[0210] The silicon-carbon composite material obtained in Example 1 above is prepared into a secondary battery as follows.

[0211] Preparation of secondary battery includes:

[0212]

Preparation of positive electrode sheet

[0213] LiNi 0.8 Co 0.1 Mn 0.1O2 (NCM811), conductive agent carbon black (Super P), binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 97:1:2 in an appropriate amount of solvent NMP to form a uniform positive electrode slurry; the positive electrode slurry was uniformly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained.

[0214]

Preparation of negative electrode sheet

[0215] The above-mentioned silicon-carbon composite material, graphite, conductive agent conductive carbon black and carbon nanotube, and binder polyacrylic acid were mixed uniformly in a mass ratio of 3:92:1.9:0.1:3, then added to the solvent deionized water, and stirred under the action of a rapid stirrer until the system was uniform, obtaining a negative electrode slurry with a solid content of 45%; the negative electrode slurry was uniformly coated on the negative electrode current collector copper foil and dried at 85°C, and then cold pressed to obtain a negative electrode sheet.

[0216]

Separator

[0217] Celgard2400 separator.

[0218]

Preparation of electrolyte

[0219] Ethylene carbonate (EC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC) were mixed uniformly in a volume ratio of 20:20:60 as an organic solvent, then LiPF6 was dissolved in the above-mentioned organic solvent, and fluoroethylene carbonate (FEC) was added, the concentration of LiPF6 in the electrolyte was 1 mol / L, and the mass percentage of FEC was 5wt%. Ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent, then the dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0220]

Preparation of secondary battery

[0221] The above-mentioned positive electrode sheet, separator and negative electrode sheet were stacked in order, with the separator between the positive and negative electrode sheets to play a separating role, then wound to obtain a bare cell; the bare cell was placed in an outer packaging shell, dried and then injected with electrolyte, and then subjected to vacuum packaging, standing, formation, shaping and other processes to obtain a secondary battery.

[0222] III. Preparation of button-type half-cell

[0223] The above-mentioned silicon-carbon composite material obtained in Example 1 was prepared into a button-type half-cell as follows.

[0224] The preparation of the button-type half cell comprises:

[0225]

Preparation of the negative electrode sheet

[0226] The above-mentioned silicon-carbon composite material, conductive agent conductive carbon black, and binder polyacrylic acid are mixed in a mass ratio of 8:1:1, and then added to a solvent deionized water. The system is stirred to be uniform under the action of a rapid stirrer to obtain a negative electrode slurry with a solid content of 45%. The negative electrode slurry is uniformly coated on a negative electrode current collector copper foil, and then dried at 85°C and cold-pressed to obtain a negative electrode sheet.

[0227]

Separator film

[0228] Celgard2400 separator film.

[0229]

Preparation of the electrolyte

[0230] The electrolyte is a mixture of ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC, and DEC is 20:20:60. Then LiPF6 is dissolved in the above-mentioned organic solvent, and an additive fluoroethylene carbonate (FEC) is added, wherein the concentration of LiPF6 is 1 mol / L, and the mass fraction of FEC in the electrolyte is 5%.

[0231]

Counter electrode

[0232] The metal lithium is used as the counter electrode.

[0233]

Button-type half cell

[0234] The above-mentioned negative electrode sheet, separator film, and counter electrode are assembled, and the electrolyte is injected to obtain a button-type battery.

[0235] Comparative Example 1

[0236] The difference between Comparative Example 1 and Example 1 is only:

[0237] In the preparation process of the biomass porous carbon, the biomass material is pre-carbonized at 500°C under a nitrogen atmosphere, sintered at 900°C, and then directly activated in steam at 900°C for 3h after being broken. The obtained product is cooled at room temperature, soaked in potassium permanganate for 24h, washed with distilled water until neutral, and dried. (That is, Comparative Example 1 does not perform a classification treatment)

[0238] Among them, Figure 1 is the SEM image of the biomass porous carbon prepared in Example 1, Figure 2 is the SEM image of the biomass porous carbon prepared in Comparative Example 1. It can be seen that both of them are composed of particles with different particle sizes, but the gap between the particles in Example 1 is obviously smaller than that in Comparative Example 1.

[0239] The biomass porous carbon prepared in Comparative Example 1 was fractionated using the same fractionation process as Example 1 to obtain fine powder (Dv50: 2.5-4 μm), intermediate material (Dv50: 6-9 μm), and coarse powder (Dv50: 11-13 μm), and the Dv10, Dv50, Dv90, BET, span, and pore volume of the fine powder, intermediate material, and coarse powder were tested and obtained, and the results are shown in Table 1.

[0240] wherein, Figure 3 FIG. 2 is a SEM image of the coarse powder of the biomass porous carbon prepared in Comparative Example 1 after fractionation, and it can be seen that the particle size is uniform.

[0241] The biomass porous carbon prepared in Example 1 and Comparative Example 1 was fractionated using the fractionation process to obtain fine powder (Dv50: 2.5-4 μm), intermediate material (Dv50: 6-9 μm), and coarse powder (Dv50: 11-13 μm), and the Dv10, Dv50, Dv90, BET, span, and pore volume of the fine powder, intermediate material, and coarse powder were tested and obtained, and the results are shown in Table 1.

[0242] Table 1: Results of the parameters of the biomass porous carbon in Example 1 and Comparative Example 1

[0243]

[0244] As can be seen from Table 2, the pore volume deviation of any two fractionated samples of the fine powder, intermediate material, and coarse powder in Example 1 is less than 0.05 cm 3 / g, and the pore volume deviation of the fine powder and intermediate material in Comparative Example 1 is as high as 0.128 cm 3 / g, and the pore volume deviation between the fine powder and coarse powder is as high as 0.201 cm 3 / g.

[0245] That is, the activation uniformity of the biomass porous carbon prepared in Example 1 is significantly higher than that of the biomass porous carbon in Comparative Example 1.

[0246] Since the raw material in Comparative Example 1 was not fractionated before activation, the fine powder and large particles were more, resulting in that the median particle size of the fine powder after fractionation of Comparative Example 1 was smaller than that of the fine powder of the present application, and the median particle size of the intermediate material was larger, so it was assumed that the fine powder and coarse powder in Comparative Example 1 were removed and only the intermediate material was retained, although a sample with high activation uniformity could be obtained, but since the span of the intermediate material in Comparative Example 1 was too narrow, the powder compaction density of the obtained mixture would be significantly lower than that of Example 1, and the raw material utilization rate was low, and the cost was high.

[0247] That is, the biomass porous carbon prepared in Example 1 not only has high activation uniformity, but also has high powder compaction density, which is beneficial to improve the energy density of the battery.

[0248] wherein, Figure 1 SEM image of the biomass porous carbon prepared in Example 1, Figure 2 SEM image of the biomass porous carbon prepared in Comparative Example 1, it can be seen that both are composed of particles of different particle sizes, but the gap between the particles of Example 1 is obviously smaller than that of Comparative Example 1.

[0249] Figure 4 1k times particle cross-section backscattering image of the silicon-carbon composite material prepared in Example 1, Figure 5 1k times particle cross-section backscattering image of the silicon-carbon composite material prepared in Comparative Example 1, Figure 4 and Figure 5 The brighter in the middle represents the higher atomic number, Figure 4 , 5 The whiter in the middle is the silicon-carbon with silicon deposited, and the darker is the biomass porous carbon without silicon deposited or with a small amount of silicon deposited. According to Figure 4 and Figure 5 It can be seen that the silicon deposition of the silicon-carbon composite material of Example 1 is more uniform than that of Comparative Example 1.

[0250] Examples 2-11 and Comparative Example 2

[0251] The difference between Example 2-10 and Example 1 is only that the preparation parameters of the silicon-carbon composite material are shown in Table 2 as follows.

[0252] Among them, the difference between Example 2-7 and Example 1 is only that the Dn10 and the diameter interval of the biomass carbonized material are different.

[0253] Examples 8-10 use the biomass carbonized material prepared in Example 1 to prepare the silicon-carbon composite material, and the difference is only that the volume of the silicon particles accounts for the pore volume of the biomass porous carbon and the mass percentage of the silicon particles in the biomass porous carbon is different.

[0254] The difference between Example 11 and Example 1 is only that KOH is used instead of water vapor as the activating agent during the activation treatment.

[0255] Comparative Example 2 uses resin-based porous carbon instead of biomass porous carbon.

[0256] Among them, the differences between the biomass carbonized materials, porous carbons, and prepared carbon composite materials in Examples 1-11 and Comparative Examples 1-2 are shown in Table 2.

[0257] Table 2. Comparison of biomass carbonization material, porous carbon silicon and carbon composite material prepared in Examples 1-11 and Comparative Examples 1-2

[0258]

[0259]

[0260] In Table 2, the porous carbon of Examples 1-11, Comparative Example 1, Comparative Examples 3-6 is biomass porous carbon, and the porous carbon of Comparative Example 2 is resin-based porous carbon.

[0261] As can be seen from Table 2, the selection of biomass carbonization material will affect the parameters of the prepared porous carbon and the parameters and performance of the silicon-carbon composite material.

[0262] The batteries prepared in Examples 1-11 and Comparative Examples 1-2 were tested for performance, and the performance test method was as follows:

[0263] (1) Secondary battery cycle test method:

[0264] The secondary batteries prepared in Examples and Comparative Examples were charged at 1C rate to the charge cut-off voltage V1 at 5°C, then charged at constant voltage to the current ≤0.05C, rested for 5 min, discharged at 0.33C rate to the discharge cut-off voltage V2, rested for 5 min, which was one charge-discharge cycle. The battery was tested for cycle charge-discharge according to this method until the battery capacity decayed to 80%.

[0265] (2) Button cell initial efficiency test method:

[0266] After the assembled button cell was rested for 60 min, it was tested by the process of 0.05C constant current discharge to 5mV, 50μA discharge to 5mV, rested for 10 min, and 0.1C charge to 0.8V, wherein the delithiation capacity of 0.8V represents the capacity size of the silicon-carbon material, and the initial efficiency % = 0.08V delithiation capacity / lithium intercalation capacity.

[0267] The test results are shown in Table 3 below.

[0268] Table 3. Battery test results

[0269]

[0270]

[0271] As shown in Tables 2 and 3, activation treatment of biomass carbonized materials with 0.8μm≤Dn10≤2μm and 0.8≤(Dv90-Dv10) / Dv50≤1.5 can effectively improve the activation uniformity and powder compaction density of the biomass carbonized materials after activation treatment. This is beneficial for improving battery cycle life and energy density when applied to hollow porous silicon-carbon composite materials.

[0272] According to Example 1 and Comparative Examples 1-2, when the silicon-carbon composite materials prepared by porous carbon in Example 1, Comparative Examples 1 and 2 are applied to batteries, the number of battery cycles in Example 1 is slightly greater than that in Comparative Example 2, and the number of battery cycles in Comparative Example 2 is significantly greater than that in Comparative Example 1.

[0273] in, Figure 6 This is a comparison chart of the cycle performance of the secondary batteries corresponding to Example 1 and Comparative Examples 1-2. According to... Figure 6 It can be seen that the silicon-carbon composite material prepared from biomass porous carbon in Example 1 has significantly improved recycling performance compared to Comparative Example 1, achieving effects comparable to the silicon-carbon composite material prepared from resin-based porous carbon. Figure 6 As can be seen from the data, the silicon-carbon composite material prepared by resin-based porous carbon in Example 1 is superior to that in Comparative Example 2 when the secondary battery has been operated for about 600 cycles or more.

[0274] As can be seen from Examples 1-7 and Comparative Examples 3-4, biomass carbonization materials must simultaneously meet the ranges of 0.8μm≤Dn10≤2μm and 0.8≤(Dv90-Dv10) / Dv50≤1.5. Failure to meet any of these conditions will affect the activation uniformity, and the hollow porous silicon-carbon composite material made based on it will lead to a significant reduction in battery cycle life when applied to batteries.

[0275] As shown in Examples 1 and 8-10, the volume ratio of silicon particles in the pore volume of the biomass porous carbon and the mass percentage of silicon particles in the biomass porous carbon affect the battery cycle life and energy density. When the volume ratio of silicon particles in the biomass porous carbon is 40%-60% and the mass percentage of silicon particles in the biomass porous carbon is between 42%-52%, the battery has better cycle life and better energy density when it is used in the battery.

[0276] As can be seen from Examples 1 and 11, when the Dn10 and diameter of the biomass carbon material are controlled within the scope of this application, even if different activators are used to activate the biomass carbon material, the activation uniformity and powder compaction density of the biomass carbon material after activation treatment can be improved, which is beneficial to improving the battery cycle life and energy density when applied to silicon-carbon composite materials.

[0277] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration, function, and effect as the technical idea of the present application are included in the technical scope of the present application. Furthermore, other modes constructed by applying various modifications that can be thought of by those skilled in the art to the embodiments, or by combining part of the constituent elements of the embodiments, are also included in the scope of the present application without departing from the spirit of the present application.

Claims

1. A method for preparing a biomass porous carbon, characterized by, Comprising: activating the biomass carbonized material with 0.8 μm≤Dn10≤2 μm, 0.8≤(Dv90-Dv10) / Dv50≤1.5, and washing.

2. The production method according to claim 1, characterized by, The biomass carbonized material has 0.8≤(Dv90-Dv10) / Dv50≤1.

2.

3. The preparation method according to claim 1, characterized in that, Before the activating, the preparation method comprises: pre-carbonizing the biomass material at 400-700 ℃, sintering at 800-1000 ℃, crushing, and sieving to obtain the biomass carbonized material.

4. The method of claim 1, wherein, The activating comprises: mixing an activating agent with the biomass carbonized material, and activating at 900-1100 ℃. The activating agent comprises at least one of oxygen, water vapor, carbon dioxide gas, air, and potassium hydroxide.

5. A biomass porous carbon, characterized by, The biomass porous carbon has a pore volume deviation greater than or equal to 0 and less than 0.1 cm 3 / g, and a powder compaction density of 0.55-1.2 g / cm 3 at 5T.

6. The biomass-based porous carbon of claim 5, wherein, 0 < the pore volume deviation of the biomass-based porous carbon is < 0.05 cm3 / g 3 / g.

7. The biomass-based porous carbon of claim 5, wherein, The biomass porous carbon has a pore volume of 0.5 cm 3 / g-0.8 cm 3 / g; and / or, The biomass porous carbon has a specific surface area of 1600 m 2 / g-1850 m 2 / g.

8. A silicon-carbon composite material, characterized by, The biomass porous carbon prepared by the preparation method of any one of claims 1-4 or the silicon particles of any one of claims 5-7.

9. The silicon-carbon composite of claim 8, wherein, The silicon-carbon composite material satisfies at least one of (a1)-(a2): (a1) the volume of the silicon particles accounts for 40-60% of the pore volume of the biomass porous carbon; (a2) the mass percentage of the silicon particles in the biomass porous carbon is 42-52%.

10. The silicon-carbon composite material according to claim 8 or 9, characterized in that, The silicon-carbon negative electrode material further comprises a carbon coating layer coated on the body.

11. The silicon-carbon composite of claim 10, wherein, The silicon-carbon composite material has a powder resistance of 4-100 Ω at 4 MPa.

12. A method of producing a silicon-carbon composite material as claimed in claims 8-11, characterized in that, The biomass porous carbon prepared by the preparation method of any one of claims 1-4 or the biomass porous carbon of any one of claims 5-7 is introduced into a fluidized bed reactor, and is deposited under the conditions of a silicon source gas mass concentration of 8-18%, an apparent gas velocity of 0.03-0.07 m / s, and a deposition temperature of 500-700 ℃. The silicon source gas comprises a silane-containing hydrocarbon.

13. A secondary battery characterized by comprising: Any one of the biomass porous carbon prepared by the preparation method of any one of claims 1-4, the biomass porous carbon of any one of claims 5-7, or the silicon-carbon composite material of any one of claims 8-11.

14. A battery module, characterized by The secondary battery of claim 13.

15. A battery pack, characterized by The secondary battery of claim 13 or the battery module of claim 14.

16. An electrical device, comprising: At least one selected from the secondary battery of claim 13, the battery module of claim 14, or the battery pack of claim 15.

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