Negative electrode active material and preparation method therefor, electrode, and battery
By uniformly depositing nano-silicon on a porous carbon framework and coating it with an amorphous carbon film, the non-uniformity problem of porous silicon-carbon anode materials during the preparation process was solved, thereby improving the performance and lifespan of the battery.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- BERZELIUS CO LTD
- Filing Date
- 2025-12-17
- Publication Date
- 2026-07-30
AI Technical Summary
In the prior art, porous silicon-carbon anode materials have uneven distribution of under-silicon particles during the preparation process, which leads to a decrease in battery performance, including a reduction in coulombic efficiency, cycle performance and rate performance.
By controlling the deposition of nano-silicon on a porous carbon framework and the coating of amorphous carbon films, the proportion of under-silicon particles is limited, and process parameters are optimized to achieve uniform deposition, ensuring that the product of silicon mass content and the proportion of under-silicon particles is within a reasonable range, thus forming a dense and uniform material structure.
It improves the mechanical strength and compressive strength of the negative electrode active material, reduces volume change, enhances coulombic efficiency and cycle stability, extends battery cycle life, and reduces expansion rate.
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Figure CN2025143254_30072026_PF_FP_ABST
Abstract
Description
A negative electrode active material and its preparation method, electrode, and battery Technical Field
[0001] This application relates to the field of batteries, specifically to a negative electrode active material for secondary batteries, a method for preparing the same, an electrode, and a battery. Background Technology
[0002] With the rapid development of electric vehicles, portable electronic devices, and other fields, higher demands are being placed on battery energy density. Traditional graphite anode materials can no longer meet the ever-increasing energy density requirements; therefore, the development of novel high-capacity anode materials has become a research hotspot. Silicon materials have extremely high theoretical specific capacity, thus being considered an ideal choice for next-generation high-energy-density battery anode materials. However, silicon materials suffer from severe volume expansion and contraction during battery cycling, leading to performance degradation. Porous silicon-carbon anode materials, by introducing a porous structure, effectively alleviate the volume expansion problem of silicon materials, improve battery cycle stability, and have become a powerful candidate material for improving battery energy density.
[0003] Porous silicon-carbon anode materials can be prepared using various methods, including sand milling, template method, and chemical vapor deposition (CVD). Among these, the core of CVD involves introducing a silicon source gas (such as silane) into the pores of porous carbon particles. High-temperature pyrolysis causes the gas to deposit, forming silicon nanoparticles dispersed within the pores of the porous carbon. This method allows for molecular-scale control of the prepared nanomaterials, while also producing relatively uniform and dense silicon-carbon materials. Therefore, this structure effectively mitigates the volume changes of silicon materials during charge and discharge, improving the material's cycle stability and rate performance.
[0004] In the vapor-phase silicon-carbon deposition process, the silicon source gas needs to be uniformly deposited within the porous carbon to form a uniformly distributed silicon-carbon composite material. However, achieving uniform deposition is challenging due to the differences in the pore structure and surface properties of porous carbon, as well as the limitations of mass and heat transfer during the deposition process. In fact, in existing rotary kiln and fluidized bed processes, porous carbon particles are difficult to achieve sufficient fluidization or dispersion, resulting in insufficient contact between some particles and the silicon source gas. These particles become under-silicon particles, meaning they have almost no silicon deposition or only a very small amount of silicon deposition. These under-silicon particles still have a large number of pores, a large specific surface area, and poor mechanical properties. They are prone to breakage under compression, further exposing a large number of internal pores. This leads to a significant increase in side reactions with the electrolyte, reducing the coulombic efficiency, cycle performance, and rate performance of the battery.
[0005] Besides the presence of under-silicon particles, the distribution of silicon within and on the surface of porous carbon particles, the uniformity of silicon distribution among different particles, and key parameters such as silicon utilization rate of the pore volume within the porous carbon particles and the remaining pore volume all significantly affect the cycle stability and volume expansion rate of this material in batteries. Therefore, strengthening the research on deposition mechanisms and optimizing the control of process parameters to achieve uniform deposition, minimize the proportion of under-silicon particles, and optimize the distribution of silicon on porous carbon structures have become critical issues that urgently need to be addressed in the industry.
[0006] The content of the background section is merely the technology known to the inventor and does not necessarily represent the prior art in this field. Summary of the Invention
[0007] To address at least one of the aforementioned technical problems, this application provides a negative electrode active material for secondary batteries, a method for preparing the same, an electrode, and a battery.
[0008] The negative electrode active material provided in this application comprises negative electrode active material particles, characterized in that the negative electrode active material particles include a porous carbon framework, nano-silicon and an amorphous carbon film.
[0009] The negative electrode active material particles include silicon-deficient particles, wherein the silicon content in the silicon-deficient particles is ≤15% by mass, and the percentage of silicon-deficient particles in the total negative electrode active material particles is [not specified]. ≤35%, preferably ≤30%, further preferably ≤25%, and even more preferably ≤20%;
[0010] The mass content of silicon in the negative electrode active material The percentage of the number of the under-silicon particles The product DS ≤ 0.15, preferably ≤ 0.125, and even more preferably ≤ 0.1.
[0011] In some embodiments of this application, the nano-silicon is deposited within the pores of the porous carbon skeleton and / or on the surface of the porous carbon skeleton.
[0012] In some embodiments of this application, the amorphous carbon film coats the surface of the nano-silicon and / or the porous carbon skeleton, and / or the amorphous carbon film fills the pores of the porous carbon skeleton.
[0013] In some embodiments of this application, the powder resistivity of the negative electrode active material particles is ≤60. Preferred size ≤40 Further optimization of ≤20 More preferably ≤10 .
[0014] In some embodiments of this application, the specific surface area of the negative electrode active material particles is ≤60. Preferably ≤35 Further preferably ≤20 More preferably ≤10 .
[0015] In some embodiments of this application, the median particle size of the negative electrode active material particles is 1~15μm, preferably 2~12μm.
[0016] In some embodiments of this application, the mass content of silicon in the negative electrode active material is... The content is 30-80%, preferably 35-65%.
[0017] In some embodiments of this application, the median particle size of the nano-silicon is ≤10nm, preferably ≤5nm, and more preferably ≤3nm.
[0018] The electrode provided in this application includes any of the negative electrode active materials described above.
[0019] The battery provided in this application includes the electrodes described above.
[0020] The method for preparing a negative electrode active material provided in this application, wherein the negative electrode active material comprises negative electrode active substance particles, and the preparation method includes:
[0021] The preparation of the negative electrode active material particles includes:
[0022] Prepare a porous carbon framework;
[0023] Nano-silicon is deposited on the porous carbon framework; and
[0024] An amorphous carbon film is coated onto a porous carbon framework on which the nano-silicon is deposited.
[0025] The negative electrode active material particles contain silicon-deficient particles, wherein the silicon content of the silicon-deficient particles is ≤15% by mass, and the percentage of silicon-deficient particles in the negative electrode active material particles is [not specified]. ≤35%, preferably ≤30%, further preferably ≤25%, and even more preferably ≤20%;
[0026] The mass content of silicon in the negative electrode active material The percentage of the number of the under-silicon particles The product DS ≤ 0.15, preferably ≤ 0.125, and even more preferably ≤ 0.1.
[0027] The negative electrode active material provided in this application controls the proportion of under-silicon particles, improves the deposition uniformity of nano-silicon in the negative electrode active material, avoids the presence of a large number of ineffective porous carbon particles, and also avoids the situation of severe enrichment of nano-silicon in some particles. Therefore, the material has a more dense and uniformly distributed structure, reduces the specific surface area of the material, improves the mechanical strength and compressive strength, effectively alleviates the volume change of silicon material during charging and discharging, improves the coulombic efficiency and cycle stability of the material, and reduces cycle expansion.
[0028] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description
[0029] The embodiments of this application are described in detail below with reference to the accompanying drawings. These drawings, which form part of this application, are used to provide a further understanding of the application. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application.
[0030] Figure 1 is a process flow diagram of the preparation process of negative electrode active material particles of an exemplary embodiment of the present application.
[0031] Figure 2 is the X-ray diffraction pattern of the negative electrode active material prepared in Example 1 of this application.
[0032] Figure 3 shows the scanning electron microscope image and partial results of energy dispersive spectroscopy (EDS) of the negative electrode active material prepared in Example 1 of this application at 20 kV. Embodiments of the present invention
[0033] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of this application. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.
[0034] The following disclosure provides many different embodiments or examples for implementing different structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.
[0035] The specific embodiments of this application will be described in more detail below with reference to the accompanying drawings and examples, so as to better understand the solution of this application and its advantages in various aspects. However, the specific embodiments and examples described below are for illustrative purposes only and are not intended to limit this application.
[0036] Negative electrode active materials
[0037] The negative electrode active material provided in this application comprises negative electrode active material particles. These particles include a porous carbon framework, nano-silicon, and an amorphous carbon film.
[0038] The porous carbon framework has a large number of pores. Optionally, nano-silicon is deposited within the pores of the porous carbon framework and / or on the surface of the porous carbon framework. For example, nano-silicon is deposited on the bottom surface of the pores of the porous carbon framework, or on the pore walls of the pores of the porous carbon framework, or on the surface of the porous carbon framework.
[0039] Optionally, an amorphous carbon film is coated on the surface of nano-silicon and / or a porous carbon framework, and / or the amorphous carbon film fills the pores of the porous carbon framework. For example, the amorphous carbon film is coated on the surface of nano-silicon, or on the surface of the porous carbon framework, or on the bottom surface of the pores of the porous carbon framework, or on the sidewalls of the pores of the porous carbon framework.
[0040] The negative electrode active material particles contain under-silicon particles. In this application, negative electrode active material particles with a silicon mass content ≤15% are referred to as under-silicon particles. Optionally, the silicon mass content in the negative electrode active material particles (also referred to as porous carbon particles in this application) is measured using a scanning electron microscope at 20kV.
[0041] For example, using the energy dispersive spectroscopy (EDS) function of a Hitachi SU8010 scanning electron microscope (SEM), the particles were scanned at 20 kV to obtain information on the types and contents of elements in the particles. To statistically analyze the uniformity of the silicon-carbon anode active material, the sample particles were laid flat on a conductive carbon paste during EDS sample preparation, ensuring that only one layer of particles was present on the carbon paste to avoid multi-layer particle stacking. When collecting the EDS signals of the particles, at 1000x magnification, all particles with a diameter ≥2 μm in the image were scanned, and the EDS signals of all particles were collected, ensuring that the number of collected particles was ≥500 (if there were fewer than 500 particles in one image, the EDS signals of particles from multiple regions were collected). Statistical analysis was performed on the collected particle EDS signals, defining particles with a silicon mass content ≤15% as under-silicon particles, and the proportion of under-silicon particles was statistically analyzed. .
[0042] Optionally, in this application, the proportion of silicon-deficient particles in the negative electrode active material particles is... ≤35%, preferably ≤30%, further preferably ≤25%, and even more preferably ≤20%.
[0043] In the deposition of vapor-phase silicon-carbon, the silicon source gas is first adsorbed by the porous carbon framework, then decomposes at high temperature to form nano-silicon, which is then deposited. Achieving uniform deposition is challenging due to differences in the pore structure and surface properties of the porous carbon framework, as well as limitations in mass and heat transfer during deposition. In fact, in existing rotary kiln and fluidized bed processes, it is difficult to achieve sufficient fluidization or dispersion of the porous carbon framework, resulting in insufficient contact between some particles and the silicon source gas, creating fluidization or dispersion "dead zones." These particles become under-silicon particles, meaning they have almost no or only a small amount of silicon deposition. Furthermore, some porous carbon frameworks, limited by differences in their pore structure and surface properties, exhibit poor kinetics during silicon deposition, with adsorption and decomposition reactions significantly slower than other particles, also leading to under-silicon particles. These under-silicon particles still possess a large number of pores and a large specific surface area, but their mechanical properties are poor, making them prone to breakage under pressure, further exposing numerous internal pores. This leads to a significant increase in side reactions with the electrolyte, reducing the battery's coulombic efficiency, cycle performance, and rate performance. In this application, the proportion of silicon-deficient particles to negative electrode active material particles is... Controlling the content to ≤35%, preferably ≤30%, further preferably ≤25%, and more preferably ≤20% can effectively improve the uniformity of nano-silicon distribution in the negative electrode active material, reduce the specific surface area of the material, improve mechanical strength and compressive strength, effectively reduce the volume change of silicon material during charging and discharging, and improve the coulombic efficiency and cycle stability of the material.
[0044] Furthermore, in this application, the mass content of silicon in the negative electrode active material is... The proportion of under-silicon particles The product DS ≤ 0.15, preferably ≤ 0.125, and even more preferably ≤ 0.1.
[0045] Due to the structural limitations imposed by the pore volume and pore size distribution within the porous carbon framework, there is an upper limit to the mass content of silicon that each porous carbon framework can accommodate. When the actual mass content of silicon in the deposition is lower than this upper limit, the porous carbon framework still retains residual pore structures. These residual pore structures may be partially filled during subsequent amorphous carbon coating processes or may remain in the final product. These residual pore structures are beneficial for improving the silicon-carbon material's ability to accommodate and buffer the expansion and contraction of silicon nanoparticles in the battery, effectively reducing its volume change during charge and discharge, improving cycle stability, and reducing expansion. Conversely, when the actual mass content of silicon in the deposition exceeds the upper limit that the porous carbon particles can accommodate, the excess silicon will form a layer of elemental silicon of a certain thickness on the particle surface, or form elemental silicon particles, leading to severely aggravated side reactions with the electrolyte, significantly deteriorated cycle performance, and significantly increased expansion.
[0046] When DS≤0.15 (preferably ≤0.125, further preferred)≤0.1, the presence of a large number of ineffective porous carbon particles can be effectively avoided, and the situation of severe enrichment of nano-silicon in some particles can also be avoided.
[0047] Optionally, the powder resistivity of the negative electrode active material particles is ≤60. Preferred size ≤40 Further optimization of ≤20 More preferably ≤10 .
[0048] As mentioned above, when the actual silicon content deposited on porous carbon particles exceeds their maximum capacity, the excess silicon will form a layer of elemental silicon of a certain thickness on the particle surface, leading to a significant increase in the powder resistivity of the material. When the powder resistivity of the negative electrode active material particles is controlled to ≤60 Ω... Preferred size ≤40 Further optimization of ≤20 More preferably ≤10 This indicates that the elemental silicon layer on the particle surface is thin, or there is no elemental silicon layer on the particle surface, thus significantly improving the cycle.
[0049] Optionally, the specific surface area (BET) of the negative electrode active material particles is ≤60. Preferably ≤35 Further optimization of ≤20 More preferably ≤10 .
[0050] Optionally, the median particle size of the negative electrode active material particles The value is 1~15μm, preferably 2~12μm.
[0051] Optionally, the mass content of silicon in the negative electrode active material The content is 30-80%, preferably 35-65%. At this value, the material has a high reversible capacity, as well as excellent cycle performance and low expansion rate.
[0052] Optionally, the median particle size of the nano-silicon is ≤10nm, preferably ≤5nm, and more preferably ≤3nm. Silicon nanoparticles within this range exhibit minimal expansion and are less prone to breakage during lithium-ion insertion / extraction cycles, resulting in minimal cycle expansion and stable cycling performance in lithium-ion secondary batteries using this material. Since nano-silicon is primarily deposited within or coated on the pore surface of a porous carbon framework, the pore size and distribution structure of the porous carbon framework determine the size of the nano-silicon particles.
[0053] The negative electrode active material provided in this application controls the proportion of under-silicon particles, improves the deposition uniformity of nano-silicon in the negative electrode active material, avoids the presence of a large number of ineffective porous carbon particles, and also avoids the severe enrichment of nano-silicon in some particles. Therefore, the material has a more dense and uniformly distributed structure, reduces the specific surface area of the material, improves mechanical strength and compressive strength, effectively alleviates the volume change of silicon material during charging and discharging, improves the coulombic efficiency and cycle stability of the material, and also makes the battery using the negative electrode active material have higher energy density, better cycle life and lower expansion rate.
[0054] Preparation methods for negative electrode active materials
[0055] Figure 1 illustrates a method for preparing negative electrode active material particles according to an embodiment of the present application, including the following steps S1 to S3.
[0056] S1: Prepare a porous carbon framework.
[0057] Porous carbon frameworks refer to carbon materials with pore structures of varying sizes. Based on pore size, porous carbon frameworks can be classified into three types: microporous carbon frameworks (pore size less than 2 nanometers), mesoporous carbon frameworks (pore size between 2 and 50 nanometers), and macroporous carbon frameworks (pore size greater than 50 nanometers). Porous carbon frameworks possess characteristics such as tunable pore structure, large specific surface area, good electrical conductivity, and good stability. Furthermore, by controlling the preparation methods and process parameters, porous carbon materials with different pore sizes, pore volumes, and porosities can be obtained.
[0058] Currently, commonly used porous carbon frameworks include biomass porous carbon, resin-based porous carbon, graphite-based porous carbon, and coal-based porous carbon. There are many methods for preparing porous carbon frameworks, including template methods, laser ablation methods, activation methods, gel crystallization methods, salting-out methods, co-precipitation methods, and emulsion film methods. Among these, activation methods include physical activation methods and chemical activation methods. Physical activation methods utilize high temperatures (usually above 800℃) to carbonize the carbon precursor, and then use water vapor or carbon dioxide as an activating agent to react with the carbon precursor to achieve the purpose of pore formation. Chemical activation methods utilize chemical reagents (such as KOH, etc.) , , or (etc.) react with carbon precursors under high temperature conditions to achieve the purpose of pore formation.
[0059] In this application, the specific surface area of the selected porous carbon framework can be 1000~3000. The preferred value is 1400~3000 The pore volume of the selected porous carbon framework can be 0.5~1.5 pores. The preferred value is 0.55~1.4. The average adsorption pore size of the selected porous carbon framework can be ≤10 nm, more preferably ≤5 nm, and even more preferably ≤3 nm. The average adsorption pore size mentioned here specifically refers to the average adsorption pore size calculated by a surface area analyzer (BET model). The porous carbon framework can simultaneously contain micropores, mesopores, and macropores, and can also simultaneously contain closed pores and open pores.
[0060] In this application, the median particle size of the porous carbon framework selected is... The particle size can be 1~15μm, preferably 2~12μm. The particle size distribution span of the selected porous carbon framework can be ≤2, preferably ≤1.6, and more preferably ≤1.4.
[0061] S2: Depositing nano-silicon on a porous carbon framework.
[0062] A porous carbon framework is placed in a reactor, and a silicon source gas is then introduced. The silicon source gas is adsorbed into the porous carbon framework and then undergoes a pyrolysis reaction at high temperature to generate nano-silicon. The reactor may include a vertical fluidized bed, a horizontal fluidized bed, a stirred fluidized bed, a vibrating fluidized bed, a rotary kiln, a tube furnace, or a vapor deposition furnace, etc. The silicon source gas may include silane (…). ), dichlorosilane ( ), trichlorosilane ( silicon tetrachloride ( In this reaction process, silicon-carbon anode active materials with varying degrees of uniformity in nano-silicon distribution can be obtained by controlling the reaction temperature, gas flow rate, silicon source gas concentration (ratio of silicon source gas to protective gas), stirring intensity, rotation speed, fluidization intensity, reaction time, and equipment structure design. The reaction temperature can be 460~580℃. Protective gases may include nitrogen, argon, etc.
[0063] To further optimize the structure and uniformity of the negative electrode active material, a multi-step silicon infiltration method can be used to achieve the deposition of nano-silicon.
[0064] S3: Coating an amorphous carbon film onto a porous carbon framework with deposited nano-silicon.
[0065] After the deposition of nano-silicon, an amorphous carbon layer can be coated onto the porous carbon framework and nano-silicon within the original reactor, or the porous carbon material with deposited nano-silicon can be transferred to another carbon-coating reactor via an inert gas-protected transfer device for coating with an amorphous carbon layer. The carbon-coating reactor can include a fluidized bed, rotary kiln, tube furnace, or vapor deposition furnace, etc. The carbon source used in this step can be a hydrocarbon gas, and the decomposition temperature of the hydrocarbon gas can be 480~750℃. Simultaneously, a multi-step carbon coating method can also be used to achieve effective coating of the amorphous carbon film.
[0066] In this application, the content of silicon-deficient particles in the negative electrode active material particles can be controlled by adjusting the specific process parameters of steps S1 to S3, thereby increasing the proportion of silicon-deficient particles in the negative electrode active material particles. ≤35%, and the mass content of silicon in the negative electrode active material The proportion of low-silicon particles The product DS ≤ 0.15. Specifically, by controlling the appropriate stirring frequency and gas flow rate, the material can be fully fluidized, agglomerates can be broken up, and the reactant gas and material particles can be fully contacted to achieve uniform and efficient adsorption and reaction, while avoiding channeling and excessive bubbling fluidization. In addition, by designing the reaction temperature zone, the material can achieve the adsorption of silicon-containing reactant gases (such as silanes) and the deposition of silicon nanoparticles at different temperatures in the reactor, which is beneficial to improving the uniformity of the reaction.
[0067] Characterization methods for negative electrode active materials
[0068] 1. Material Testing: The following equipment was used to characterize the negative electrode active materials prepared in each embodiment and comparative example: A BetterSize 2600 laser particle size analyzer (Dandong BetterSize) was used to test the particle size distribution of the negative electrode active materials. A Rigaku miniFlex 600 powder X-ray diffractometer (XRD) was used to test the composition and crystal structure of the obtained negative electrode materials. A Quantachrome Instruments NOVA 4200e specific surface area analyzer was used to test the specific surface area of the negative electrode active materials. The specific surface area testing requirements were as follows: the sample was weighed using a sample tube, nitrogen gas was used, and the specific surface area of the sample was tested using a multi-point method within a relative pressure range of p / p0 = 0.05~0.3. The carbon content W of the sample was tested using an ELEMENTRAC CS-i carbon-sulfur analyzer. c The standard sample contained 41% carbon by mass, and the equipment was calibrated using the standard sample before the carbon content test was performed. The silicon content in the negative electrode active material was also tested. The mass content of silicon is calculated using the following formula. =1-W c The resistivity of the negative electrode active material under different pressures was determined using the ST2722-SD powder low-resistivity tester from Suzhou Jingge, with the resistivity at 20 MPa taken as the powder resistivity of the material.
[0069] The surface morphology of the anode active material was observed using a Hitachi SU8010 scanning electron microscope (SEM). Simultaneously, the energy dispersive spectroscopy (EDS) function of the SEM was used to perform spot scanning of the particles at 20 kV to obtain information on the elemental types and contents within the particles. To statistically analyze the uniformity of the silicon-carbon anode active material, the sample particles were laid flat on a conductive carbon paste during EDS sample preparation, ensuring that only one layer of particles was present on the carbon paste to avoid multi-layer particle stacking. When collecting the EDS signals of the particles, all particles with a diameter ≥2 μm in the image were spot-scanned at 1000x magnification, and the EDS signals of all particles were collected, ensuring that the number of collected particles was ≥500 (if less than 500 particles were present in one image, the EDS signals of multiple regions were collected). Statistical analysis was performed on the collected particle EDS signals. Particles with a silicon mass content ≤15% were defined as under-silicon particles, and the proportion of under-silicon particles was statistically analyzed. .
[0070] 2. Half-cell electrode preparation and testing: Take 80 parts of the above-mentioned negative electrode active material, 9.7 parts of conductive carbon black, 0.3 parts of single-walled carbon nanotubes, and 10 parts of binder, and coat them in an aqueous system. Then dry and roll them to obtain a negative electrode containing the negative electrode active material of this application.
[0071] The negative electrode sheet containing the negative electrode active material of this application was stacked sequentially with a separator, lithium sheet, and stainless steel gasket, and 200 μL of electrolyte was added before sealing to form a 2016-type lithium-ion half-cell. The capacity and discharge efficiency were tested using a small (micro) current range device from Wuhan Landian Electronics Co., Ltd. The capacity and first-cycle efficiency of the pure material half-cell containing the negative electrode active material of this application were measured.
[0072] 3. Full cell electrode sheet fabrication and testing: Take 20 parts of the above-mentioned negative electrode active material, 74 parts of artificial graphite, 2.5 parts of conductive additive, and 3.5 parts of binder, and coat them in an aqueous system, then dry and roll them to obtain a negative electrode sheet containing the negative electrode active material of this application.
[0073] The negative electrode sheets prepared with negative electrode active materials in each embodiment and comparative example were slit, vacuum baked, wound together with paired ternary positive electrode sheets and separators, and packed into an aluminum-plastic shell of appropriate size. A certain amount of electrolyte was injected, and the shell was degassed and sealed. After formation, a lithium-ion full battery of approximately 3.2 Ah was obtained. The battery was then subjected to 1C / 1C cycling at 45°C to obtain the capacity retention rate after 1000 cycles, and the cell expansion rate after 1000 cycles was also tested.
[0074] The present invention will now be described with reference to specific embodiments. The process conditions and values used in the following embodiments and comparative examples are exemplary, and their possible ranges are as shown in the foregoing description of the invention. For process parameters not specifically noted, conventional techniques can be used. Unless otherwise specified, the reagents and instruments used in the technical solutions provided by the present invention can all be purchased from conventional channels or the market. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.
[0075] Example 1-1
[0076] Take 1000g of biomass activated carbon, its The surface area is 7 μm, the span is 1.3, and the specific surface area of the raw material is 2000. The average adsorption pore size is 2 nm, and the pore volume is 0.72. The porous carbon raw material was fed into a vertical fluidized bed with a stirring frequency of 30 Hz and a nitrogen flow rate of 10 L / min. The temperature was increased to 540 °C at a rate of 5 °C / min, then silane was introduced at a flow rate of 5 L / min, and the temperature was maintained at 540 °C for 150 min. After the holding period, the silane was turned off, and the temperature was further increased to 640 °C. Acetylene was then introduced at a flow rate of 5 L / min, and the temperature was maintained for 150 min before the acetylene was turned off, allowing the furnace to cool naturally.
[0077] The above steps yielded a negative electrode active material, which, after testing with a carbon-sulfur analyzer, showed a carbon content of 57.33%. Since the material contains almost only carbon and silicon, the silicon content is also relatively low. It is 42.67%. The specific surface area of this material is 60. The powder resistivity is 51.97. Its XRD pattern is shown in Figure 2.
[0078] The morphology and elemental composition of the material were analyzed using scanning electron microscopy (SEM), and the SEM images and energy dispersive spectroscopy (EDS) results are shown in Figure 3. Figure 3 only shows the EDS results of 18 particles in this region. It can be seen that 6 of these particles have a silicon mass content of less than 15%, classifying them as silicon-deficient particles. Using the statistical method mentioned above, EDS were performed on more than 500 particles with a diameter ≥ 2 μm, and the percentage of silicon-deficient particles was statistically analyzed to obtain... The mass content is 34.8%. Therefore, the mass content of silicon is... and the percentage of under-silicon particles The product DS is 0.148.
[0079] The first efficiency (FCE) of the anode active material was 88.4% in a half-cell test. Then, the silicon-carbon anode and graphite were mixed (20% silicon-carbon anode was added) and assembled into a 3.2Ah pouch full cell for cycling test at 45°C. After 1000 cycles of 1C / 1C, the cycle retention rate was 80.5% and the cell expansion rate was 25.4%.
[0080] The results are shown in Table 1.
[0081] Examples 1-2
[0082] Using raw materials and processes similar to those in Example 1-1, only the stirring frequency was adjusted to 35Hz, the silane flow rate to 4L / min, and the silicon deposition holding time to 188min.
[0083] The above steps yielded a negative electrode active material, which, after testing with a carbon-sulfur analyzer, showed a carbon content of 57.17% and a silicon content of 42.83%. The specific surface area of this material was 53.8 mm. The powder resistivity is 34.48. Using the characterization methods and statistical approaches described above, we obtain... The mass content is 32.2%. Therefore, the mass content of silicon is... and the percentage of under-silicon particles The product DS is 0.138.
[0084] The first-cycle efficiency of the negative electrode active material was 89.1% in half-cell tests. The full cell containing the negative electrode active material was subjected to a 45°C cycle test, and the cycle retention rate was 81.2% after 1000 cycles, with a cell expansion rate of 23.5%.
[0085] The results are shown in Table 1.
[0086] Examples 1-3
[0087] Using a process similar to that of Example 1-1, only the raw materials are changed to... Biomass activated carbon particles with a diameter of 8.5 μm and a span of 1.3 were selected. The results are shown in Table 1.
[0088] Examples 1-4
[0089] Using similar raw materials and processes as in Example 1-1, only the silane flow rate was adjusted to 3 L / min and the silicon deposition holding time was adjusted to 260 min. The results are shown in Table 1.
[0090] Examples 1-5
[0091] Using similar raw materials and processes as in Examples 1-4, only the silicon deposition holding time was adjusted to 280 min. The results are shown in Table 1.
[0092] Examples 1-6
[0093] Using similar raw materials and processes as in Examples 1-2, only the flow rate of silane was adjusted to 3.5 L / min, and the holding time for silicon deposition was adjusted to 240 min. The results are shown in Table 1.
[0094] Examples 1-7
[0095] Using raw materials and processes similar to those in Examples 1-6, the stirring frequency was adjusted to 45Hz, and the results are shown in Table 1.
[0096] Examples 1-8
[0097] Using raw materials and processes similar to those in Examples 1-7, the silicon deposition temperature was adjusted to 510°C and the stirring frequency was adjusted to 50Hz. The results are shown in Table 1.
[0098] Examples 1-9
[0099] Using raw materials and processes similar to those in Examples 1-8, the holding time for silicon deposition was adjusted to 265 min. The results are shown in Table 1.
[0100] Examples 1-10
[0101] Using a similar raw material process as 1-6, the silicon deposition temperature was adjusted to 520℃, the nitrogen flow rate was adjusted to 15L / min, and the stirring frequency was adjusted to 55Hz. The results are shown in Table 1.
[0102] Examples 1-11
[0103] Take 1000g of resin-activated carbon, its The thickness is 6.5 μm, the span is 1.2, and the specific surface area of the raw material is 2050. The average adsorption pore size is 2 nm, and the pore volume is 0.95. The porous carbon raw material was fed into a rotary kiln with a stirring frequency of 15 Hz and a nitrogen flow rate of 7 L / min. The temperature was increased to 550 °C at a rate of 5 °C / min, followed by the introduction of silane at a flow rate of 3 L / min. The kiln was held at 550 °C for 290 min. After this holding period, the silane flow was stopped, and the temperature was further increased to 640 °C. Acetylene was then introduced at a flow rate of 3 L / min and held for 250 min. The acetylene flow was then stopped, and the furnace was allowed to cool naturally. The results of the obtained materials are shown in Table 1.
[0104] Examples 1-12
[0105] Using similar raw materials and processes as in Examples 1-11, only the silicon deposition holding time was adjusted to 250 min. The results are shown in Table 1.
[0106] Examples 1-13
[0107] Using similar raw materials and processes as in Examples 1-11, only the stirring frequency was adjusted to 20Hz, and the holding time for silicon deposition was extended to 301min. The results are shown in Table 1.
[0108] Examples 1-14
[0109] Using raw materials and processes similar to those in Examples 1-13, only the stirring frequency was adjusted to 17Hz, the silane flow rate to 1.5L / min, and the silicon deposition holding time to 602min. The results are shown in Table 1.
[0110] Examples 1-15
[0111] Using raw materials and process parameters similar to those in Examples 1-11, but changing the equipment to a horizontal fluidized bed, which has both the function of rotating a rotary kiln and the function of fluidizing powder in a fluidized bed, and other process parameters similar to those in Examples 1-11, the results are shown in Table 1.
[0112] Examples 1-16
[0113] Similar raw materials and process parameters as in Examples 1-15 were used, but the holding time for silicon deposition was adjusted to 235 min. Simultaneously, the material obtained after discharge from the horizontal fluidized bed was reintroduced into the rotary kiln. The stirring frequency was 15 Hz, the nitrogen flow rate was 7 L / min, and the temperature was increased to 600 °C at a rate of 5 °C / min. Then, acetylene was introduced at a rate of 3 L / min, held for 100 min, and then the acetylene was turned off, allowing the furnace to cool naturally. The results of the obtained materials are shown in Table 1.
[0114] Examples 1-17
[0115] The raw materials and process parameters were similar to those in Examples 1-15, but the holding time for silicon deposition was adjusted to 326 min. The results of the obtained materials are shown in Table 1.
[0116] Examples 1-18
[0117] Using similar raw materials and processes as in Examples 1-15, only the silane flow rate was adjusted to 1.5 L / min, the silicon deposition temperature to 530 °C, and the silicon deposition time to 580 min. The results are shown in Table 1.
[0118] Examples 1-19
[0119] Using similar raw materials and processes as in Examples 1-18, only the stirring frequency was adjusted to 20Hz and the nitrogen flow rate was adjusted to 11L / min. The results are shown in Table 1.
[0120] Examples 1-20
[0121] Using a process similar to Examples 1-19, except that the raw material is replaced with spherical resin carbon, its The thickness is 6.2 μm, the span is 1.4, and the specific surface area of the raw material is 1950. The average adsorption pore size is 2 nm, and the pore volume is 0.80. The results are shown in Table 1.
[0122] Examples 1-21
[0123] Using a process and raw materials similar to those in Examples 1-20, only the raw materials are... The value was adjusted to 8μm and the span was adjusted to 1.2. The results are shown in Table 1.
[0124] Examples 1-22
[0125] Take 1000g of resin-activated carbon, its The thickness is 9 μm, the span is 1.1, and the specific surface area of the raw material is 2150. The average adsorption pore size is 2 nm, and the pore volume is 0.90. The porous carbon raw material was fed into a vertical fluidized bed at a stirring speed of 50 Hz and a nitrogen flow rate of 15 L / min. The temperature was increased to 540 °C at a rate of 5 °C / min, followed by a holding period. Silane was then introduced at a flow rate of 5 L / min and held for 100 min. The silane flow rate was then turned off, and the nitrogen flow rate was adjusted to 30 L / min with a stirring speed of 75 Hz for 15 min. The nitrogen flow rate was then adjusted back to 15 L / min, and the stirring speed returned to 50 Hz. Silane was introduced again at a flow rate of 2 L / min and held for 185 min. After the holding period, the silane flow rate was turned off, and the temperature was increased to 640 °C. Acetylene was then introduced at a flow rate of 3 L / min and held for 250 min before the acetylene flow rate was turned off, and the furnace was allowed to cool naturally. The results of the obtained materials are shown in Table 1.
[0126] Examples 1-23
[0127] Using a process similar to that of Examples 1-22 and the raw materials of Examples 1-21, the results of the obtained materials are shown in Table 1.
[0128] Comparative Example 1-1
[0129] Using a process and raw materials similar to those in Example 1-1, only the stirring frequency was adjusted to 20Hz and the nitrogen flow rate was adjusted to 5L / min. The resulting materials are shown in Table 1.
[0130] Comparative Examples 1-2
[0131] Using a process and raw materials similar to those in Examples 1-2, but with the silicon deposition holding time extended to 210 min, the resulting materials are shown in Table 1.
[0132] Comparative Examples 1-3
[0133] Using a process and raw materials similar to those in Examples 1-5, but with the silicon deposition holding time extended to 336 min, the resulting materials are shown in Table 1.
[0134] Table 1
[0135]
[0136] As shown in Table 1, when The larger the anode material, the more silicon-deficient particles there are. These silicon-deficient particles still have a large number of porous structures, resulting in a large specific surface area. At the same time, their mechanical properties are poor, and they are prone to breakage under compression, further exposing a large number of internal pores. This leads to a significant increase in side reactions with the electrolyte. Therefore, the first efficiency of a half-cell made from pure materials is often low, and the high-temperature cycling performance of a full-cell using this anode material is poor, with a large cycling expansion.
[0137] On the other hand, besides the proportion of silicon-deficient particles, the distribution of silicon within and on the surface of porous carbon particles, as well as the uniformity of distribution among different particles, also significantly impacts performance. When simultaneously satisfying… The concentration of silicon nanoparticles is ≤35%, preferably ≤30%, more preferably ≤25%, and even more preferably ≤20%, with the DS controlled at ≤0.15, preferably ≤0.125, and even more preferably ≤0.1. This effectively avoids the presence of a large number of ineffective porous carbon particles, prevents severe enrichment of nano-silicon in some particles, and avoids the formation of a certain thickness of elemental silicon layer on the surface of some particles. Therefore, it can effectively improve the uniformity of nano-silicon distribution in the negative electrode active material, reduce the specific surface area and powder resistance of the material, improve mechanical strength and compressive strength, effectively reduce the volume change of silicon material during charge and discharge, and improve the coulombic efficiency and cycle stability of the material.
[0138] Example 2-1
[0139] Using a process and raw materials similar to those in Examples 1-10, only the nitrogen flow rate was adjusted to 14 L / min and the silicon deposition time was delayed by 10 min. The results are shown in Table 2.
[0140] Example 2-2
[0141] The process of Example 2-1 is adopted, only the raw materials are replaced with The surface area is 7 μm, the span is 1.3, and the specific surface area of the raw material is 2500. The average adsorption pore size is 1.2 nm, and the pore volume is 0.68. The results are shown in Table 2.
[0142] Example 2-3
[0143] The process of Example 2-1 is adopted, only the raw materials are replaced with The thickness is 7 μm, the span is 1.3, and the specific surface area of the raw material is 1580. The average adsorption pore size is 3.6 nm, and the pore volume is 0.92. The results are shown in Table 2.
[0144] Table 2
[0145]
[0146] As shown in Table 2, the average adsorption pore size of the porous carbon framework determines the average particle size of the nano-silicon. The average particle size of the nano-silicon is preferably ≤5nm, and more preferably ≤3nm, which can obtain better battery performance.
[0147] The above descriptions are merely illustrative embodiments of this application and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A negative electrode active material comprising negative electrode active substance particles, characterized in that, The negative electrode active material particles include a porous carbon framework, nano-silicon, and an amorphous carbon film. The negative electrode active material particles contain silicon-deficient particles, wherein the silicon content of the silicon-deficient particles is ≤15% by mass, and the percentage of silicon-deficient particles in the negative electrode active material particles is [not specified]. ≤35%, preferably ≤30%, further preferably ≤25%, and even more preferably ≤20%; The mass content of silicon in the negative electrode active material The percentage of the number of the under-silicon particles The product DS ≤ 0.15, preferably ≤ 0.125, and even more preferably ≤ 0.
1.
2. The negative electrode active material according to claim 1, characterized in that, The nano-silicon is deposited within the pores of the porous carbon skeleton and / or on the surface of the porous carbon skeleton.
3. The negative electrode active material according to claim 1, characterized in that, The amorphous carbon film coats the surface of the nano-silicon and / or the porous carbon skeleton, and / or the amorphous carbon film fills the pores of the porous carbon skeleton.
4. The negative electrode active material according to claim 1, characterized in that, The powder resistivity of the negative electrode active material particles is ≤60. Preferred size ≤40 Further optimization of ≤20 More preferably ≤10 ; and / or The specific surface area of the negative electrode active material particles is ≤60. Preferably ≤35 Further optimization of ≤20 More preferably ≤10 。 5. The negative electrode active material according to claim 1, characterized in that, The median particle size of the negative electrode active material particles is 1~15μm, preferably 2~12μm.
6. The negative electrode active material according to claim 1, characterized in that, The mass content of silicon in the negative electrode active material The content is 30-80%, preferably 35-65%.
7. The negative electrode active material according to claim 1, characterized in that, The median particle size of the nano-silicon is ≤10nm, preferably ≤5nm, and more preferably ≤3nm.
8. An electrode, characterized in that, Includes the negative electrode active material as described in any one of claims 1 to 7.
9. A battery, characterized in that, Includes the electrode as described in claim 8.
10. A method for preparing a negative electrode active material, wherein the negative electrode active material comprises negative electrode active substance particles, characterized in that, The preparation method includes: The preparation of the negative electrode active material particles includes: Prepare a porous carbon framework; Nano-silicon is deposited on the porous carbon framework; and An amorphous carbon film is coated onto a porous carbon framework on which the nano-silicon is deposited. The negative electrode active material particles contain silicon-deficient particles, wherein the silicon content of the silicon-deficient particles is ≤15% by mass, and the percentage of silicon-deficient particles in the negative electrode active material particles is [not specified]. ≤35%, preferably ≤30%, further preferably ≤25%, and even more preferably ≤20%; The mass content of silicon in the negative electrode active material The percentage of the number of the under-silicon particles The product DS ≤ 0.15, preferably ≤ 0.125, and even more preferably ≤ 0.1.