Porous carbon, silicon-carbon negative electrode material and preparation method and application thereof

Abstract

The present application relates to the technical field of battery, in particular to a kind of porous carbon, silicon-carbon negative electrode material and its preparation method and application.The present application provides a kind of porous carbon, the porous carbon includes micropore, and the percentage of micropore pore volume in total pore volume is greater than or equal to 85%, in the pore distribution curve of the abscissa being pore size, ordinate being differential pore volume dV / dW obtained by nitrogen adsorption method test, the porous carbon in the interval of pore size 1 ~ 2nm, differential pore volume dV / dW > 0.05cm 3 ·g ‑1 ·nm ‑1 The porous carbon of the present application has suitable microporosity and a luan-type pore size distribution, which can effectively improve the loading efficiency of silicon, reserve a part of space for the volume increase of silicon caused by expansion during the cycle process of nanoscale silicon, has the effect of relieving the volume expansion when silicon inserts lithium, can reduce the volume expansion rate of silicon-based negative electrode material, and improve the cycle stability of battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a porous carbon / silicon-carbon anode material, its preparation method, and its application. Background Technology

[0002] With the rapid development of electric vehicles, the demand for batteries is increasing daily. Batteries typically contain a positive electrode, a negative electrode, and a separator. Among these, the negative electrode material has a significant impact on the overall electrical performance of the battery. Silicon-carbon anode materials are a relatively new type of anode material developed in recent years. However, silicon anode materials undergo significant volume changes during battery charging and discharging, leading to the shedding and pulverization of active electrode materials, and even damage to the electrode structure. This results in rapid capacity decay, severely restricting their industrial application. To address this, carbon and silicon materials are often combined to create silicon-carbon composite materials, aiming to improve the volume effect of silicon and enhance its electrochemical stability. However, current silicon-carbon anode materials still face technical challenges, including unsatisfactory capacity and insufficient improvement of the silicon volume effect.

[0003] In view of this, the present invention is hereby proposed. Summary of the Invention

[0004] The primary objective of this invention is to provide a porous carbon with a high microporosity and a pore size distribution in the range of 1-2 nm, which can effectively improve the loading efficiency of silicon, effectively alleviate the volume expansion during silicon lithium intercalation, reduce the volume expansion rate of silicon-based anode materials, and improve their capacity and first-time efficiency.

[0005] Another objective of this invention is to provide a silicon-carbon anode material that has the characteristics of high capacity, high initial efficiency, and low volume expansion rate.

[0006] Another objective of this invention is to provide a simple and easy method for preparing silicon-carbon anode materials.

[0007] Another object of the present invention is to provide an electrode.

[0008] Another object of the present invention is to provide a lithium-ion battery.

[0009] Another object of the present invention is to provide an electrical appliance.

[0010] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0011] A porous carbon comprising micropores, wherein the pore volume of the micropores accounts for a percentage of the total pore volume greater than or equal to 85%, and in a pore distribution curve obtained by nitrogen adsorption method with pore size as the x-axis and differential pore volume dV / dW as the y-axis, the porous carbon exhibits a differential pore volume dV / dW > 0.05 cm⁻¹ in the pore size range of 1–2 nm. 3 ·g -1 ·nm -1 .

[0012] In some embodiments, the porous carbon has at least one peak in the pore size range of 1 to 2 nm.

[0013] In some embodiments, the porous carbon has at least one peak and valley within the pore size range of 1–2 nm, and the differential pore volume dV / dW corresponding to the lowest point of the peak and valley is greater than 0.1 cm³. 3 ·g -1 ·nm -1 .

[0014] In some embodiments, the pore volume of pores with a diameter of less than 0.7 nm in the porous carbon accounts for less than 30% of the total pore volume.

[0015] In some embodiments, the porous carbon has a pore volume of 0.7–1.2 cm³. 3 / g.

[0016] In some embodiments, the specific surface area of ​​the porous carbon is 1500–2500 m². 2 / g.

[0017] In some embodiments, the porous carbon has a particle size Dv50 of 3 to 10 μm, a particle size Dv99 of 10 to 25 μm, and a particle size Dn10 of 0.5 to 5 μm.

[0018] In some embodiments, the tap density of the porous carbon is 0.3–0.5 g / cm³. 3 .

[0019] In some embodiments, the porous carbon powder has a conductivity of 0.5 to 10 S / mm.

[0020] In some embodiments, the mass content of elemental oxygen in the porous carbon is less than 2%.

[0021] A silicon-carbon anode material, the silicon-carbon anode material comprising porous carbon and nano-silicon located in the pores of the porous carbon.

[0022] In some embodiments, the nano-silicon content in the silicon-carbon anode material is 5% to 85% by mass.

[0023] In some embodiments, the particle size Dv50 of the silicon-carbon anode material is 3 to 10 μm, the particle size Dv99 of the silicon-carbon anode material is 10 to 25 μm, and the particle size Dn10 of the silicon-carbon anode material is 0.5 to 5 μm.

[0024] In some embodiments, the specific surface area of ​​the silicon-carbon anode material is 0.5–30 m². 2 / g.

[0025] In some embodiments, the tap density of the silicon-carbon anode material is 0.5–2 g / cm³. 3 .

[0026] In some embodiments, the surface of the silicon-carbon anode material further includes a coating layer; the coating layer comprises at least one of amorphous carbon, a fast ion conductor, and a polymer.

[0027] The preparation method of the silicon-carbon anode material as described above includes the following steps:

[0028] The silicon-carbon anode material is obtained by vapor deposition of porous carbon in an atmosphere containing a silicon source.

[0029] In some embodiments, the method further includes: coating the silicon-carbon anode material to obtain a coating layer on the surface of the silicon-carbon anode material, the coating layer comprising at least one of amorphous carbon, fast ion conductor and polymer.

[0030] An electrode comprising the porous carbon, or the silicon-carbon anode material, or the silicon-carbon anode material prepared by the method for preparing the silicon-carbon anode material.

[0031] A lithium-ion battery, comprising the aforementioned electrodes.

[0032] An electrical appliance, comprising the aforementioned lithium-ion battery.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] (1) The porous carbon of the present invention has a high microporosity and a pore size distribution in the range of 1-2 nm. It can effectively improve the loading efficiency of silicon and reserve some space for the nano-silicon cycling process to alleviate the volume increase caused by the lithium intercalation expansion of silicon. It has the effect of alleviating the volume expansion during silicon lithium intercalation, reducing the volume expansion rate of silicon-based anode materials, and improving the capacity and first efficiency of silicon-carbon anode materials.

[0035] (2) The silicon-carbon anode material of the present invention has the characteristics of high capacity and high first efficiency, which can improve the cycle stability of the battery.

[0036] (3) The preparation method of the silicon-carbon anode material of the present invention is simple and easy to implement. The silicon-carbon anode material can be obtained by depositing silicon source vapor onto porous carbon. The silicon-carbon anode material obtained by this method has the characteristics of high capacity and high first-time efficiency, which can improve the cycle performance and safety performance of the battery. Attached Figure Description

[0037] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 The diagram shows the pore size distribution of porous carbon in Embodiment 1 of the present invention (the vertical axis represents the differential pore volume dV / dW, and the secondary axis represents the cumulative pore volume), which is a purplish-brown pore.

[0039] Figure 2 The pore size distribution curve of porous carbon in Embodiment 2 of the present invention (the main vertical axis is the differential pore volume dV / dW, and the secondary axis is the cumulative pore volume), is a purplish-brown pore;

[0040] Figure 3 The pore size distribution curve of porous carbon in Embodiment 3 of the present invention (the vertical axis is the differential pore volume dV / dW, and the secondary axis is the cumulative pore volume), is a purplish-brown pore;

[0041] Figure 4 The pore size distribution curve of the porous carbon in Comparative Example 1 of the present invention is shown (the main vertical axis is the differential pore volume dV / dW, and the secondary axis is the cumulative pore volume), which is a peak-shaped pore.

[0042] Figure 5 The pore size distribution curve of the porous carbon in Comparative Example 2 of the present invention is shown (the main vertical axis is the differential pore volume dV / dW, and the secondary axis is the cumulative pore volume), which is a purplish-brown pore.

[0043] Figure 6 The pore size distribution curve of the porous carbon in Comparative Example 3 of the present invention is shown (the main vertical axis is the differential pore volume dV / dW, and the secondary axis is the cumulative pore volume), which is a purplish-brown pore.

[0044] Figure 7 This is a schematic diagram of the goldenrain tree's morphological distribution.

[0045] Figure 8 This is a schematic diagram of a peak-shaped distribution. Detailed Implementation

[0046] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0047] According to one aspect of the present invention, the present invention relates to a porous carbon comprising micropores, wherein the pore volume of the micropores accounts for a percentage of the total pore volume greater than or equal to 85%, and in a pore distribution curve obtained by nitrogen adsorption method with pore size as the abscissa and differential pore volume dV / dW as the ordinate, the porous carbon has a differential pore volume dV / dW > 0.05 cm² in the pore size range of 1–2 nm. 3 ·g -1 ·nm -1 .

[0048] In other words, the pore distribution curve does not intersect the horizontal axis within the pore size range of 1-2 nm (excluding endpoints) (the pore distribution curve does not intersect the horizontal axis when the differential pore volume dV / dW ≠ 0), and the pore distribution curve does not approach the horizontal axis within the pore size range of 1-2 nm (the pore distribution curve approaches the horizontal axis when the differential pore volume dV / dW ≤ 0.05 cm). 3 ·g -1 ·nm -1 ).

[0049] In this invention, according to the definition of the International Union of Pure and Applied Chemistry (IUPAC), micropores refer to pores with a diameter of less than 2 nm.

[0050] Unconstrained by theory, the severe volume effect and other fundamental problems of silicon during charging and discharging seriously hinder the effective realization of its advantages. In the porous carbon of this invention, the percentage of pore volume of pores (micropores) with a pore size of less than 2 nm (i.e., microporosity) to the total pore volume is large, which can effectively improve the efficiency of silicon loading. It also reserves some space for the nanoscale silicon cycling process to alleviate the volume increase caused by silicon expansion, and has the effect of mitigating the volume expansion during silicon lithium intercalation. This can reduce the volume expansion rate of silicon-based anode materials and improve the cycle stability of the battery.

[0051] Unbound by theory, pores with a diameter in the range of 1 to 2 nm (excluding endpoint values) exhibit two types of pore distribution: peak-shaped distribution and elliptic-shaped distribution.

[0052] The peak-shaped pore structure is mainly characterized within the pore size range of 1-2 nm (excluding endpoint values). The pore distribution curve intersects the horizontal axis at more than one point or is close to the horizontal axis. Furthermore, in most cases, the peak-shaped pore structure has at least one peak within the pore size range of 1-2 nm, and / or, porous carbon has at least one valley within the pore size range of 1-2 nm, with the lowest point of the valley, Dv / Dw, < 0.05 cm. 3 ·g -1 ·nm -1 The characteristic of peak-shaped pore distribution is mainly manifested in the fact that as the pore diameter increases, the pore distribution exhibits a peak-valley pattern with abrupt changes in height, and the transition between pore diameters is relatively steep. In peak-shaped pore structures, the pore diameter distribution is discontinuous, and the total number of pores is insufficient, such as... Figure 8 As shown, peak-shaped pores can suddenly change diameter. When the pore is deep and the diameter is small, the resistance that nano-silicon has to overcome to enter is greater, and the relative distance that it can diffuse (compared to the pore depth) is shorter. Therefore, the utilization rate of the pore is also lower.

[0053] The characteristic of the pore distribution in the Luan-shaped structure is mainly manifested in the mountain-like variation of the pore distribution as the pore diameter increases. The transition in pore diameter is relatively smooth and gradual. Within the pore diameter range of 1-2 nm, the pore distribution curve does not intersect with the horizontal axis and is not close to it, indicating a relatively uniform pore distribution. The pores in the Luan-shaped structure have a continuous and uninterrupted pore diameter distribution, a large total number of pores, and a generally consistent pore depth. Figure 7 As shown, the depth of the convex-shaped pores does not exhibit the abrupt diameter changes seen in peak-shaped pores. Therefore, it reduces the local resistance caused by diameter changes, which facilitates the entry of precursor molecules (such as silane molecules) for vapor-phase silicon deposition, thereby improving silicon loading efficiency. Porous carbon with these characteristics is beneficial for enabling silicon-carbon to possess higher capacity and efficiency, and lower expansion performance.

[0054] In some embodiments, the pore size distribution curve of the porous carbon has at least one peak corresponding to the pore size range of 1–2 nm; and / or, the porous carbon has at least one valley within the pore size range of 1–2 nm, and the differential pore volume dV / dW corresponding to the lowest point of the valley is greater than 0.1 cm³. 3 ·g -1 ·nm -1 Including but not limited to 0.11cm 3 ·g -1 ·nm -1 0.12cm 3 ·g -1 ·nm -1 0.15cm 3 ·g -1 ·nm -1 0.2cm 3 ·g -1 ·nm -10.5cm 3 ·g -1 ·nm -1 etc., or a range of values ​​between any two of the above.

[0055] In some embodiments, the percentage of pores with a diameter less than 0.7 nm in the porous carbon is less than 30% of the total pore volume. In some embodiments, the percentage of pores with a diameter less than 0.7 nm in the porous carbon includes, but is not limited to, 1%, 2%, 5%, 8%, 10%, 15%, 20%, 25%, 28%, 29%, or any value between these two ranges. Micropores with a diameter less than 0.7 nm are difficult for silane molecules to enter during deposition; therefore, the percentage of micropores must be limited. The present invention's porous carbon, with a pore size less than 0.7 nm accounting for less than 30%, is more conducive to ensuring the silicon loading efficiency of the porous carbon, thereby facilitating the performance of the electrical properties of the silicon-carbon material.

[0056] In some embodiments, the porous carbon has a pore volume greater than 0.7 cm³. 3 / g. In some embodiments, the pore volume of the porous carbon includes, but is not limited to, 0.72 cm³. 3 / g, 0.75cm 3 / g, 0.8cm 3 / g, 0.85cm 3 / g, 0.9cm 3 / g, 1cm 3 / g, or a value within a range of either of the above. In some embodiments, the pore volume of the porous carbon is 0.7–1.0 cm³. 3 / g. The porous carbon of the present invention has a suitable pore volume, which is beneficial to ensuring its physicochemical properties and subsequent loading of silicon materials, ensuring that it has a suitable silicon loading rate, so as to improve the capacity and first-efficiency of silicon-carbon composite materials.

[0057] In some embodiments, the specific surface area of ​​the porous carbon is 1500–2500 m². 2 / g. In some embodiments, the specific surface area of ​​the porous carbon includes, but is not limited to, 1500 m². 2 / g, 1600m 2 / g, 1700m 2 / g、1800m 2 / g、1900m 2 / g、2000m 2 / g、2100m 2 / g、2200m 2 / g、2500m 2 / g, or a value within the range of any two of the above. The porous carbon of the present invention has a suitable specific surface area, which is beneficial for ensuring the loading effect on silicon materials.

[0058] In some embodiments, the porous carbon of the present invention has a suitable particle size. The particle size Dv50 of the porous carbon is 3–10 μm, including but not limited to 3 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or any value between the two. The particle size Dv99 of the porous carbon is 10–25 μm, including but not limited to 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 25 μm, or any value between the two. The particle size Dn10 of the porous carbon is 0.5–5 μm, including but not limited to 0.5 μm, 1 μm, 2 μm, 5 μm, or any value between the two.

[0059] In some embodiments, the porous carbon of the present invention has a suitable tap density of 0.3–0.5 g / cm³. 3 In some embodiments, the tap density of the porous carbon includes, but is not limited to, 0.32 g / cm³. 3 0.33g / cm 3 0.35g / cm 3 0.38g / cm 3 etc., or a range of values ​​between any two of the above.

[0060] In some embodiments, the porous carbon powder of the present invention has a conductivity of 0.5 to 10 S / mm. In other embodiments, the conductivity of the porous carbon powder includes, but is not limited to, 2.2 S / mm, 2.5 S / mm, 2.8 S / mm, 3 S / mm, 3.5 S / mm, 4 S / mm, 5 S / mm, 8 S / mm, 10 S / mm, or values ​​within any range of the above. The porous carbon of the present invention has a high conductivity.

[0061] In some embodiments, the porous carbon contains less than 2% oxygen by mass, including but not limited to 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, or any value between the two.

[0062] In some specific embodiments of the present invention, porous carbon includes at least one of biomass-derived carbon, resin-derived carbon, petroleum coke-derived carbon, coal-derived carbon, metal-modified carbon materials, and metal oxide-modified carbon materials.

[0063] The specific embodiments of the present invention use a porous carbon preparation method, which is illustrated by the following porous carbon preparation method, but is not limited thereto.

[0064] The method for preparing the porous carbon includes the following steps:

[0065] (1) Dry the mangosteen peel and grind it into powder.

[0066] (2) The powder ground in step (1) is stirred in HCl, then washed with deionized water until the water is colorless, and then dried.

[0067] (3) Disperse the dried mangosteen peel powder and KOH in water at a mass ratio of 1:1 to 1:4, stir, and then freeze dry to remove moisture.

[0068] (4) In an argon atmosphere, the mixed precursor obtained in step (3) is rapidly heated to 200°C in a tube furnace, then slowly heated to 550°C, then rapidly heated to 600-1000°C, and heated at 600-1000°C for 1 hour.

[0069] (5) The calcined product is washed with deionized water and dried under vacuum to obtain the porous carbon.

[0070] In some specific embodiments of the present invention, in step (4): in an argon atmosphere, the mixed precursor obtained in step (3) is rapidly heated to 200°C at a heating rate of 10°C / min in a tube furnace, and then slowly heated to 550°C for 10 hours, and then rapidly heated to 600-1000°C at a heating rate of 10°C / min, and heated to 600-1000°C for 1 hour.

[0071] In some specific embodiments of the present invention, step (5) further includes a sieving process after vacuum drying.

[0072] In some specific embodiments of the present invention, the particle size distribution of porous carbon can be controlled by the grinding process in step (1) and / or the sieving process after vacuum drying in step (5). This is well known in the art and will not be elaborated further.

[0073] According to another aspect of the present invention, the present invention relates to a silicon-carbon anode material comprising porous carbon and nano-silicon located in the pores of the porous carbon.

[0074] In this invention, the nano-silicon is a silicon material with a size less than 100 nm in at least one dimension. For example, the nano-silicon may have at least one dimension of 99 nm, 90 nm, 80 nm, 70 nm, 60 nm, 50 nm, 40 nm, 30 nm, 20 nm, 10 nm, 9 nm, 8 nm, 7 nm, 6 nm, 5 nm, 4 nm, 3 nm, 2 nm, 1.5 nm, 1 nm, 0.5 nm, 0.1 nm, 0.01 nm, etc., or other values ​​within that range.

[0075] In some specific embodiments of the present invention, the nano-silicon can be nano-silicon particles with a crystal domain size of 0 nm to 3 nm, specifically 0.01 nm, 0.1 nm, 0.5 nm, 1 nm, 1 nm, 3 nm or any value between 0 nm and 3 nm; small particles have a higher specific surface area and a shorter diffusion path, which can release pressure more quickly and reduce the degree of volume expansion, which is beneficial to improving coulombic efficiency. For example, a typical but non-limiting range can be nano-silicon particles with a particle size of 1-3 nm.

[0076] This invention uses porous carbon as a carrier to load nano-silicon, which can effectively improve the loading efficiency of nano-silicon and reserve some space for the expansion of silicon during the nano-scale silicon cycling process, thus alleviating the volume expansion during silicon lithium intercalation and reducing the volume expansion rate of silicon-based anode materials. The silicon-carbon anode material of this invention has the characteristics of high capacity and high first-time efficiency, improving the cycle stability of the battery.

[0077] In some embodiments, the mass content of nano-silicon in the silicon-carbon anode material is 5% to 85%, including but not limited to 5%, 10%, 20%, 3%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 80%, 85%, or any value between the above two. In the silicon-carbon anode material of the present invention, the nano-silicon has a suitable mass content, which is more conducive to ensuring the overall electrical performance of the silicon-carbon anode material.

[0078] In some embodiments, the particle size Dv50 of the silicon-carbon anode material of the present invention is 3–10 μm, including but not limited to 3 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or any value between the two. The particle size Dv99 of the silicon-carbon anode material is 10–25 μm, including but not limited to 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 25 μm, or any value between the two. The particle size Dn10 of the silicon-carbon anode material is 0.5–5 μm, including but not limited to 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or any value between the two. The silicon-carbon anode material of the present invention has the above-mentioned suitable particle size, which is more conducive to ensuring the performance of the slurry and improving the volumetric energy, charge-discharge performance and cycle performance of the battery.

[0079] In some embodiments, the silicon-carbon anode material of the present invention has a suitable specific surface area, which is 0.5 to 30 m². 2 / g. In some embodiments, the specific surface area of ​​the silicon-carbon anode material includes, but is not limited to, 0.5m². 2 / g、1m 2 / g、3m 2 / g、5m2 / g, 10m 2 / g, 15m 2 / g、30m 2 / g, or any value within a range of the above two.

[0080] In some embodiments, the tap density of the silicon-carbon anode material of the present invention is 0.5–2 g / cm³. 3 In some embodiments, the tap density of the silicon-carbon anode material includes, but is not limited to, 0.5 g / cm³. 3 0.72g / cm 3 0.75g / cm 3 0.78g / cm 3 0.8g / cm 3 0.85g / cm 3 0.9g / cm 3 The values ​​are either equal to or within a range of either of the above. The silicon-carbon anode material of the present invention has a suitable tap density to facilitate obtaining high capacity and high first-efficiency.

[0081] In some embodiments, the surface of the silicon-carbon anode material of the present invention further includes a coating layer; the coating layer comprises at least one of amorphous carbon, fast ion conductor and polymer, which is more conducive to improving the overall electrical performance of the anode material.

[0082] According to another aspect of the present invention, the present invention also relates to a method for preparing the silicon-carbon anode material as described above, comprising the following steps:

[0083] Porous carbon is vapor-deposited in an atmosphere containing a silicon source to obtain silicon-carbon anode materials.

[0084] The method for preparing the silicon-carbon anode material of the present invention is simple and easy to implement. The silicon-carbon anode material can be obtained by depositing silicon source vapor onto porous carbon. The silicon-carbon anode material obtained by this method has the characteristics of high capacity and high initial efficiency.

[0085] In some embodiments, the temperature of the vapor deposition is 300–1200°C, including but not limited to 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, or any range between the two.

[0086] In some embodiments, the silicon source of the present invention includes at least one of silane (SiH4), propane, silane, dimethylsilane, dichlorosilane, hexamethyldisilane, silicon tetrachloride, trichlorosilane, and silicon tetrafluoride.

[0087] In some embodiments, the method further includes: coating the silicon-carbon anode material to obtain a coating layer on the surface of the silicon-carbon anode material, the coating layer comprising at least one of amorphous carbon, a fast ion conductor, and a polymer. This invention improves the electrical performance of the silicon-carbon anode material by further coating it with a carbon coating layer.

[0088] In some embodiments, the coating treatment temperature is 300–1200°C, including but not limited to 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, or any value between two of these; the deposition time for the coating treatment is 20 min–6 h, including but not limited to 20 min, 1 h, 2 h, 3 h, 4 h, 5 h, or 6 h, or any value between two of these. By employing suitable coating treatment conditions, this invention is more conducive to obtaining a uniform and high-quality carbon coating layer, which is beneficial to the final electrical performance of the negative electrode material.

[0089] In some specific embodiments, the preparation method of silicon-carbon anode material includes the following steps:

[0090] (a) Dry the mangosteen peel and grind it into powder; stir the powder in HCl, then wash it with deionized water until the water is colorless and dry it; disperse the dried mangosteen peel powder and KOH in water at a mass ratio of 1:1 to 1:4, stir, and then freeze-dry to remove moisture to obtain a mixed precursor; in an argon atmosphere, rapidly heat the obtained mixed precursor to 200°C at 10°C / min in a tube furnace, then slowly heat it to 550°C for 10 hours, and then rapidly heat it to 600-1000°C at a heating rate of 10°C / min, and heat it at 600-1000°C for 1 hour to obtain a calcined product; wash the calcined product with deionized water, then vacuum dry and sieve it to obtain porous carbon.

[0091] (b) The porous carbon from step (a) is placed in a heat treatment apparatus and preheated at a temperature of 90–120°C and kept at that temperature for 20–40 min under vacuum. Then, a protective gas is introduced and the temperature is increased to 300–1200°C at a rate of 1–8°C / min. Silicon source gas is then introduced at a flow rate of 0.4–12 L / min for 2–5 h. The silicon source valve is then closed to obtain the first material.

[0092] (c) The obtained first material is heated to 300-1200°C, and carbon source gas is introduced for 20 min-6 h to obtain silicon-carbon anode material.

[0093] According to another aspect of the present invention, the present invention also relates to an electrode comprising the porous carbon, or the silicon-carbon anode material, or the silicon-carbon anode material prepared by the method for preparing the silicon-carbon anode material.

[0094] The electrode of the present invention comprises the aforementioned porous carbon and exhibits excellent electrical properties. The electrode includes a current collector and a negative electrode material layer located on the surface of the current collector, the negative electrode material layer containing the aforementioned porous carbon or silicon-carbon negative electrode material.

[0095] According to another aspect of the invention, the invention also relates to a lithium-ion battery comprising the aforementioned electrodes.

[0096] The lithium-ion battery of the present invention has high capacity, high initial efficiency, excellent cycle performance, and safety performance.

[0097] According to another aspect of the invention, the invention also relates to an electrical appliance comprising the aforementioned lithium-ion battery.

[0098] In this invention, the electrical appliance can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc.

[0099] The following explanation, combined with specific embodiments and comparative examples, further illustrates the point.

[0100] Example 1

[0101] A method for preparing a silicon-carbon anode material includes the following steps:

[0102] S1. Preparation of porous carbon:

[0103] (1) Dry the mangosteen peel at 80℃ for 24 hours and grind it into powder.

[0104] (2) Stir in 1M HCl overnight, then wash with deionized water until the water is colorless, and dry at 80°C for 12 hours.

[0105] (3) Disperse the dried mangosteen peel powder and KOH evenly in water at a mass ratio of 1:3, stir overnight, and then freeze dry to remove moisture.

[0106] (4) In an argon atmosphere, the mixed precursor is heated to 200°C in a tube furnace at a heating rate of 10°C / min, then heated to 550°C for 10 hours, and then heated to 780°C at a heating rate of 10°C / min for 1 hour.

[0107] (5) Finally, the calcined product was washed with deionized water, dried under vacuum at 80°C for 12 hours, and sieved to obtain the porous carbon.

[0108] In this embodiment, the porous carbon has a particle size D50 of 7.6 μm, a Dv99 of 22.7 μm, a Dn10 of 3.1 μm, and a specific surface area of ​​1946 m². 2 / g, pore volume is 0.91cm 3 / g, with an electrical conductivity of 2.7S / mm, has the following pore structure: pores smaller than 2nm account for 94% of the total pore volume (microporosity), and pores smaller than 0.7nm account for 25% of the total pore volume (microporosity). The pore size distribution is of the Luan type.

[0109] S2. Vapor phase silicon deposition: Porous carbon is placed in a rotary kiln and heated to 100°C. It is kept at this temperature for 30 minutes under vacuum. Then, nitrogen gas is introduced for protection. The temperature is then increased to 550°C at a rate of 5°C / min. Silane is then introduced at a flow rate of 10L / min for 4 hours. After the reaction is complete, the silicon source valve is closed.

[0110] S3. Carbon coating: After silicon deposition, the temperature is raised to 700℃, and acetylene is introduced at a flow rate of 5L / min for 3 hours to obtain silicon-carbon anode material.

[0111] Example 2

[0112] The preparation method of the negative electrode material provided in this embodiment is the same as in Example 1, except that:

[0113] S1. Preparation of porous carbon:

[0114] (1) Dry the mangosteen peel at 80℃ for 24 hours and grind it into powder.

[0115] (2) Stir in 1M HCl overnight, then wash with deionized water until the water is colorless, and dry at 80°C for 12 hours.

[0116] (3) Disperse the dried mangosteen peel powder and KOH evenly in water at a mass ratio of 1:2, stir overnight, and then freeze dry to remove moisture.

[0117] (4) In an argon atmosphere, the mixed precursor is heated to 200°C in a tube furnace at a heating rate of 10°C / min, then heated to 550°C for 10 hours, and then heated to 650°C at a heating rate of 10°C / min for 1 hour.

[0118] (5) Finally, the calcined product was washed with deionized water, dried under vacuum at 80°C for 12 hours, and sieved to obtain the porous carbon.

[0119] In this embodiment, the porous carbon has a particle size D50 of 7.3 μm, a Dv99 of 21.1 μm, a Dn10 of 0.5 μm, and a specific surface area of ​​1669 m². 2 / g, pore volume is 0.74cm 3 / g, with an electrical conductivity of 1.9S / mm, has the following pore structure: pores smaller than 2nm account for 93% of the total pore volume (microporosity), and pores smaller than 0.7nm account for 28% of the total pore volume (microporosity). Its pore size distribution is of the Luan type.

[0120] Example 3

[0121] The preparation method of the negative electrode material provided in this embodiment is the same as in Example 1, except that:

[0122] S1. Preparation of porous carbon:

[0123] (1) Dry the mangosteen peel at 80℃ for 24 hours and grind it into powder.

[0124] (2) Stir in 1M HCl overnight, then wash with deionized water until the water is colorless, and dry at 80°C for 12 hours.

[0125] (3) Disperse the dried mangosteen peel powder and KOH evenly in water at a mass ratio of 1:2.5, stir overnight, and then freeze dry to remove moisture.

[0126] (4) In an argon atmosphere, the mixed precursor is heated to 200°C in a tube furnace at a heating rate of 10°C / min, then heated to 550°C for 10 hours, and then heated to 700°C at a heating rate of 10°C / min for 1 hour.

[0127] (5) Finally, the calcined product was washed with deionized water, dried under vacuum at 80°C for 12 hours, and sieved to obtain the porous carbon.

[0128] The porous carbon in this embodiment has a particle size D50 of 6.4 μm, a Dv99 of 18.7 μm, a Dn10 of 2.5 μm, and a specific surface area of ​​1911 m². 2 / g, pore volume is 0.81cm 3 / g, with an electrical conductivity of 2.7S / mm, has the following pore structure: the percentage of pore volume smaller than 2nm (microporosity) is 100%, the percentage of pore volume smaller than 0.7nm (microporosity) is 29%, and its pore size distribution is elliptical.

[0129] Comparative Example 1

[0130] The difference between the preparation method of the negative electrode material in this comparative example and that in Example 1 is that the porous carbon used for vapor-phase silicon deposition is different. The porous carbon used in this comparative example was purchased from Jiangsu Pustar Environmental Protection Technology Co., Ltd., model PAC-A1. The remaining process parameters for vapor-phase silicon deposition and carbon coating are the same as in Example 1.

[0131] The porous carbon in this comparative example has a particle size D50 of 7.2 μm, a Dv99 of 23 μm, a Dn10 of 3.5 μm, and a specific surface area of ​​1297 m². 2 / g, pore volume is 0.94cm 3 / g, with an electrical conductivity of 0.33S / mm, in its pore structure, the pore volume of pores smaller than 2nm accounts for 54% of the total pore volume, and the pore volume of pores smaller than 0.7nm accounts for 25% of the total pore volume (microporosity). The pore structure of porous carbon has a peak-shaped structure.

[0132] Comparative Example 2

[0133] The difference between the preparation method of the negative electrode material in this comparative example and that in Example 1 is that the porous carbon used for vapor-phase silicon deposition is different. The porous carbon used in this comparative example was purchased from Dachao Carbon Energy Co., Ltd. The remaining process parameters for vapor-phase silicon deposition and carbon coating are the same as in Example 1.

[0134] The porous carbon in this comparative example has a particle size D50 of 7.6 μm, a Dv99 of 22 μm, a Dn10 of 0.5 μm, and a specific surface area of ​​2053 m². 2 / g, pore volume is 0.84cm 3 / g, with an electrical conductivity of 2.92S / mm, in its pore structure, the pore volume of pores smaller than 2nm accounts for 100% of the total pore volume, and the pore volume of pores smaller than 0.7nm accounts for 33% of the total pore volume (microporosity). The pore structure of porous carbon has a lattice-shaped structure.

[0135] Comparative Example 3

[0136] The difference between the preparation method of the silicon-carbon anode material in this comparative example and that in Example 1 is that the porous carbon used for vapor-phase silicon deposition is different. The porous carbon used in this comparative example was purchased from Jiangsu Pustar Environmental Protection Technology Co., Ltd., model PAC-SP40. The remaining process parameters for vapor-phase silicon deposition and carbon coating are the same as in Example 1.

[0137] The porous carbon in this comparative example has a particle size D50 of 6.6 μm, a Dv99 of 20.8 μm, a Dn10 of 3.4 μm, and a specific surface area of ​​1282 m². 2 / g, pore volume 0.72cm 3 / g, with an electrical conductivity of 4.3 S / mm, in its pore structure, the pore volume of pores smaller than 2 nm accounts for 50% of the total pore volume, and the pore volume of pores smaller than 0.7 nm accounts for 21% of the total pore volume (microporosity). The pore structure of porous carbon has a lattice-shaped structure.

[0138] Experimental Example

[0139] 1. Performance testing of porous carbon

[0140] The test methods for the specific surface area, pore volume, and proportion of <2nm pores of porous carbon in each embodiment and comparative example are as follows:

[0141] Specific surface area and pore volume: Tested according to GB / T 19587-2017. Measurements were performed using an ASAP 2460 (from Micromeritics), which operates according to the Sorption Method with Adaptive Dosing Rate (SMART method). For the reference material, standard material GB13905 (9.01m) can be used. 2 / g, based on multi-point BET method), GB13913 (5.78m 2 / g, based on multi-point BET method) and GB13909 (Mesoporous SiO2 specific surface area, total pore volume and pore size standard material).

[0142] To reduce dead volume, a packing rod was added to both the reference and sample tubes. The tubes were mounted on the BET apparatus. The saturated vapor pressure of nitrogen (N2 4.0) was measured. A certain amount of sample was weighed into the glass tube, ensuring the tube containing the packing rod was completely filled and producing the minimum dead volume. To dry the sample, it was held at 200°C under vacuum for 2 hours. After cooling, the sample weight was recorded. The glass tube containing the sample was mounted on the measuring apparatus. To degas the sample, it was evacuated at a selected pumping rate until no material was drawn into the pump, reaching a final pressure of 200 mTorr.

[0143] Micropore percentage (microporosity) test method: The percentage of pore volume with a pore size less than 2 nm in porous carbon was measured using nitrogen adsorption. Nitrogen adsorption measurements were performed using an ASAP 2460 instrument from Micron Instruments at liquid nitrogen temperature (77.3 K). Before measurement, the sample was degassed at 443 K until a static vacuum of less than 0.01 Torr was achieved. The adsorption potential distribution was calculated based on the adsorption isotherm and analyzed using the standard instrument software DFT. (NLDFT) software.

[0144] The test results of the porous carbon in Examples 1-3 and Comparative Examples 1-3 are shown in Table 1.

[0145] Table 1 Physical parameters of porous carbon

[0146]

[0147] The pore size distribution curve of the porous carbon in Example 1 of this invention is shown in the figure below. Figure 1 As shown in the figure, the pore size distribution curve of the porous carbon in Example 2 is as follows. Figure 2 As shown in the figure, the pore size distribution curve of the porous carbon in Example 3 is as follows. Figure 3As shown, in the porous carbon of this invention, the pore distribution exhibits a mountain-like variation with increasing pore size. Within the pore size range of 1–2 nm, the pore size distribution curve does not intersect with the horizontal axis, and the transition between pore sizes is relatively smooth and gentle, indicating that the micropores of the porous carbon have relatively uniform channels. The porous carbon of this invention exhibits a rhomboid pore size distribution, as shown... Figure 7 As shown, the pore size distribution is continuous and uninterrupted, with a large total number of pores and basically consistent pore depth. This can reduce the local resistance caused by the change in diameter, which is conducive to the entry of silane molecules, improves silicon loading efficiency, and is beneficial to improving the electrochemical performance of silicon-carbon anode materials.

[0148] The pore size distribution curve of the porous carbon in Comparative Example 1 of this invention is shown in the figure below. Figure 4 As shown, within the pore size range of 1–2 nm, the pore size curve intersects the horizontal axis at multiple points. With increasing pore size, the pore distribution exhibits a peak-valley pattern with sharp increases and decreases, and the transitions in pore size are relatively steep, indicating that the micropore channels are non-uniform and exhibit significant diameter variation. A schematic diagram of the peak-shaped pores of porous carbon in Comparative Example 1 is shown below. Figure 8 As shown, the pore size distribution is discontinuous and the total number of pores is insufficient. When the pores are deep and the pore diameter is small, the resistance that nano-silicon needs to overcome to enter is greater, and the relative distance that it can diffuse (compared to the pore depth) is shorter. Therefore, the utilization rate of the pores is also lower, which is not conducive to the loading of silicon materials and the performance of silicon-carbon anode materials.

[0149] The porous carbon in Comparative Example 2 of this invention was purchased from Dachao Carbon Energy Co., Ltd., and the pore size distribution curve of the porous carbon is shown in the figure below. Figure 5 As shown, the percentage of pore volume in the total pore volume is relatively high for pores with a diameter of less than 0.7 nm.

[0150] The porous carbon in Comparative Example 3 of this invention was purchased from Jiangsu Pustar Environmental Protection Technology Co., Ltd., and the pore size distribution curve of the porous carbon is shown in the figure below. Figure 6 As shown, the specific surface area is relatively low and the microporosity is low.

[0151] 2. Performance testing of silicon-carbon anode materials

[0152] The particle size, specific surface area, tap density, silicon content, and silane utilization of the silicon-carbon anode materials in each embodiment and comparative example were tested. The test methods are as follows:

[0153] Specific surface area testing: The BET method was used, and the specific surface area was tested according to GB / T 19587-2017, including: Nitrogen adsorption measurement was performed using an ASAP 2460 instrument from Micron Instruments at liquid nitrogen temperature (77.3 K). Before measurement, the sample was degassed at 443 K until a static vacuum of less than 0.01 Torr was achieved. The adsorption site distribution was calculated based on the adsorption isotherm using the standard instrument software DFT. (NLDFT) software. To reduce dead volume, filler rods were added to the reference and sample tubes (the specific testing method is the same as that for the porous carbon specific surface area test).

[0154] Particle size testing: Tested using Malvern 3000 equipment according to national standard GB / T 19077-2016.

[0155] Tap density test: The test was conducted using a Dandong Baite BT313 tap density meter, in accordance with the national standard GB / T 24533-2019.

[0156] Silicon content testing: The silicon content was determined using a thermogravimetric analyzer by calcining the silicon-carbon material at 1000℃ in air for 1 hour. This process completely oxidized the carbon, causing weight loss, and completely converted the silicon into silicon dioxide. The increased weight of oxygen was then used to calculate the silicon content in the silicon-carbon material. Details are as follows:

[0157] (1) Weigh about 2g of silicon-carbon material, and record the actual mass as m0; place it in a crucible with a mass of m1;

[0158] (2) Place the crucible in a tube furnace or muffle furnace, continuously pass compressed air through it, raise the temperature to 600℃ at 10℃ / min, hold for 1h, and then raise the temperature to 1000℃ at the same rate and hold for 1h.

[0159] (3) After naturally cooling to room temperature, remove the crucible and weigh it as m2;

[0160] (4) Calculate the Si content: Si% = (m2-m1)×MSi÷MSiO2÷m0×100%;

[0161] Note: MSiO2 is the relative molecular mass of SiO2, which is 60.084 g / mol; MSi is the relative molecular mass of Si, which is 28.0855 g / mol.

[0162] Silane utilization rate % = [Received amount (g) × Silicon content (%)] / [Silane volume introduced (L) × Silane density (g / L)].

[0163] The performance test results of the silicon-carbon anode material are shown in Table 2.

[0164] Table 2 Performance test results of silicon-carbon anode materials

[0165]

[0166] As shown in Table 2, the silicon-carbon anode materials obtained by the methods in the various embodiments of the present invention have suitable particle size, specific surface area, tap density, and silicon content, and high silane utilization rate, which is 93% or higher. The silicon-carbon anode materials obtained in Comparative Examples 1 to 3 have relatively low silane utilization rates.

[0167] 3. Battery performance test results

[0168] Coin cells were prepared using silicon-carbon anode materials from each embodiment and comparative example, including the following steps:

[0169] The active material, SP, CNT and PAA adhesive were mixed in a mass ratio of 80:9:1:10, and the mixture was prepared into a slurry with deionized water. The slurry was then uniformly coated onto copper foil and dried under vacuum at 80°C for 24 hours to obtain the negative electrode sheet for the experimental battery. A lithium sheet was used as the counter electrode, and a 1.1 mol / L LiPF6 electrolyte was used. The solvent was a four-component mixed solvent with ethylene carbonate (EC): vinylene carbonate (VC): dimethyl carbonate (DMC): fluoroethylene carbonate (FEC) = 1:1:1:1 (volume ratio). A polypropylene microporous membrane was used as the separator, and the CR2025 coin cell was assembled in a vacuum glove box.

[0170] The battery performance testing method is as follows: the capacity and first charge / discharge efficiency (first efficiency) are tested using a battery testing system (half-cell testing: Arbin multi-channel battery testing system from the United States, and Labstar (1200 / 780) glove box from Braun GmbH, Germany).

[0171] The test steps are as follows: 0.1C DC to 5mV, stand for 5 minutes; 0.02C DC to 5mV, stand for 5 minutes; 0.01C DC to 5mV, stand for 5 minutes; 0.1C CC to 0.8V, 0.1C CC to 2V.

[0172] The battery performance test results are shown in Table 3.

[0173] Table 3 Battery performance test results

[0174] Group 1.5V discharge capacity (mAh) 1.5V Efficiency (%) Example 1 2135 92.7 Example 2 1992 90.8 Example 3 2022 91.5 Comparative Example 1 1680 78.2 Comparative Example 2 1922 89.8 Comparative Example 3 1890 86.1

[0175] The porous carbon of this invention exhibits a convex-shaped pore size distribution, possessing suitable microporosity, specific surface area, pore volume, and particle size. The silicon-carbon anode material prepared using this material exhibits high capacity, high initial efficiency, and low silicon expansion rate. As shown in Table 3, the resulting battery demonstrates excellent discharge capacity and efficiency, with a 1.5V discharge capacity exceeding 1990mAh and a 1.5V efficiency exceeding 90%. In Comparative Example 1, the silicon-carbon anode material was prepared from porous carbon with a peak-shaped pore structure. The resulting battery had low capacity and poor efficiency, with a 1.5V discharge capacity of 1680mAh and a 1.5V efficiency of 78.2%. Comparative Examples 2 and 3 used conventional porous carbon to prepare silicon-carbon anode materials and batteries, resulting in batteries with reduced capacity and efficiency compared to Example 1.

[0176] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A silicon-carbon anode material, characterized in that, The silicon-carbon anode material comprises porous carbon and nano-silicon located within the pores of the porous carbon. The porous carbon includes micropores, and the pore volume of the micropores accounts for a percentage of the total pore volume greater than or equal to 85%. In the pore distribution curve obtained by nitrogen adsorption method, with pore size as the x-axis and differential pore volume dV / dW as the y-axis, the differential pore volume dV / dW of the porous carbon is greater than 0.05 cm⁻¹ in the pore size range of 1–2 nm. 3 ·g -1 ·nm -1 .

2. The silicon-carbon anode material according to claim 1, characterized in that, It includes at least one of the following features (1) to (4): (1) The porous carbon has at least one peak in the range of pore size of 1~2nm; (2) The porous carbon has at least one peak and valley in the pore size range of 1~2nm, and the differential pore volume dV / dW corresponding to the lowest point of the peak and valley is greater than 0.1cm. 3 ·g -1 ·nm -1 ; (3) In the porous carbon, the percentage of pore volume with a pore size less than 0.7 nm in the total pore volume is less than 30%; (4) The porous carbon has a pore volume of 0.7~1.2 cm³. 3 / g.

3. The silicon-carbon anode material according to claim 1, characterized in that, It includes at least one of the following features (1) to (5): (1) The specific surface area of ​​the porous carbon is 1500~2500 m². 2 / g; (2) The porous carbon has a particle size Dv50 of 3~10μm, a particle size Dv99 of 10~25μm, and a particle size Dn10 of 0.5~5μm; (3) The tap density of the porous carbon is 0.3~0.5 g / cm³. 3 ; (4) The conductivity of the porous carbon powder is 0.5~10 S / mm; (5) The mass content of elemental oxygen in the porous carbon is less than 2%.

4. The silicon-carbon anode material according to any one of claims 1 to 3, characterized in that, It includes at least one of the following features (1) to (5): (1) The mass content of the nano-silicon in the silicon-carbon anode material is 5-85%; (2) The particle size Dv50 of the silicon-carbon anode material is 3~10μm, the particle size Dv99 of the silicon-carbon anode material is 10~25μm, and the particle size Dn10 of the silicon-carbon anode material is 0.5~5μm; (3) The specific surface area of ​​the silicon-carbon anode material is 0.5~30m². 2 / g; (4) The tap density of the silicon-carbon anode material is 0.5~2 g / cm³. 3 ; (5) The surface of the silicon-carbon anode material further includes a coating layer; the coating layer contains at least one of amorphous carbon, fast ion conductor and polymer.

5. The method for preparing the silicon-carbon anode material according to any one of claims 1 to 4, characterized in that, Includes the following steps: The silicon-carbon anode material is obtained by vapor deposition of porous carbon in an atmosphere containing a silicon source.

6. The method for preparing the silicon-carbon anode material according to claim 5, characterized in that, Also includes: The silicon-carbon anode material is coated to obtain a coating layer on the surface of the silicon-carbon anode material, the coating layer comprising at least one of amorphous carbon, fast ion conductor and polymer.

7. An electrode, characterized in that, The silicon-carbon anode material includes any one of claims 1 to 4, or the silicon-carbon anode material prepared by the method described in claim 5 or 6.

8. A lithium-ion battery, characterized in that, Includes the electrode as described in claim 7.

9. An electrical appliance, characterized in that, Including the lithium-ion battery as described in claim 8.

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