Porous carbon, silicon-carbon negative electrode material, electrode sheet, lithium-ion battery and electrical appliance

Abstract

The present invention relates to the field of electrode material technology, and more specifically, to a porous carbon, a silicon-carbon negative electrode material, an electrode sheet, a lithium-ion battery, and an electrical appliance. The porous carbon has micropores and mesopores, and the pore volume of pores with a pore diameter of less than 3 nm accounts for more than 85% of the total pore volume; the pore volume of pores with a pore diameter of less than 0.7 nm accounts for less than 15% of the total pore volume; the pore size distribution of the porous carbon is a Luan-shaped distribution, which means that within the pore diameter range of 1-3 nm, the pore size distribution curve Dv / Dw>0.05 cm 3 ·g ‑1 nm ‑1 The porous carbon provided by the present invention is micro-mesoporous porous carbon with a Luan-shaped distribution and low pore resistance, which can improve the silicon loading efficiency, ensure the adsorption capacity while also ensuring the deintercalation of lithium ions. The silicon-carbon negative electrode material prepared using the porous carbon has high capacity and efficiency, and lower expansion performance.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode materials, and in particular to a porous carbon, silicon-carbon negative electrode material, an electrode sheet, a lithium-ion battery and an electrical appliance. Background Art

[0002] Due to their unique surface properties and structure, porous carbon materials are widely used in gas separation, water purification, heterogeneous catalytic support materials, high-performance thermal field materials, and other fields. They also show broad application prospects in new energy materials such as high-performance materials for lithium-ion batteries and sodium-ion batteries. Their rich pore structure, large specific surface area, and low cost are the main reasons for their advantages in various fields.

[0003] Silicon-carbon anode materials, prepared by depositing nanosilicon within a porous carbon matrix, are a new type of silicon-containing anode material. They offer a smaller volume effect and better cycling performance than pure silicon. However, existing porous carbon matrices have low silicon loading efficiency, which in turn affects the electrochemical performance of silicon-carbon anode materials. Summary of the Invention

[0004] After in-depth research, the inventors of the present invention found that:

[0005] As the matrix of new silicon-carbon materials, porous carbon's material structure is a key factor influencing its performance. Specific surface area and pore size distribution are the two most important factors affecting its electrochemical performance. Currently, the porous carbon matrix used lacks transport pores that match the adsorption pore volume. This results in high pore resistance and low silicon loading efficiency, making it impossible to achieve both high adsorption capacity and high adsorption rate, and unable to balance adsorption and lithium ion deintercalation.

[0006] In view of this, the present invention is proposed.

[0007] The first purpose of the present invention is to provide a porous carbon, which includes micropores and mesopores, and in the range of pore diameter of 1-3nm, the pore size distribution presents a Luan-shaped distribution, the pore resistance is small, the silicon loading efficiency is high, and the adsorption force can be guaranteed while also ensuring the deintercalation of lithium ions.

[0008] The second object of the present invention is to provide a silicon-carbon negative electrode material, which includes the porous carbon as described above and nano-silicon located in the pores of the porous carbon. The silicon-carbon negative electrode material has high capacity, high first efficiency and small expansion.

[0009] A third object of the present invention is to provide an electrode sheet comprising the silicon-carbon negative electrode material as described above.

[0010] A fourth object of the present invention is to provide a lithium-ion battery comprising the electrode sheet described above.

[0011] A fifth object of the present invention is to provide an electrical appliance comprising the lithium-ion battery described above.

[0012] In the present invention, the electrical appliances may be, but are not limited to, mobile phones, tablet computers, laptop computers, electric toys, electric tools, battery vehicles, electric vehicles, ships, spacecraft, and the like.

[0013] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0014] A porous carbon, comprising micropores and mesopores, wherein the pore volume of pores with a pore diameter less than 3 nm accounts for more than 85% of the total pore volume, and the pore volume of pores with a pore diameter less than 0.7 nm accounts for less than 15% of the total pore volume; in a pore distribution curve obtained by a nitrogen adsorption method, in which the abscissa is the pore diameter and the ordinate is the differential pore volume dV / dW, the porous carbon has a differential pore volume dV / dW greater than 0.05 cm in the pore diameter range of 1-3 nm. 3 ·g -1 nm -1 .

[0015] Preferably, the porous carbon has at least one peak in the pore diameter range of 1-3 nm;

[0016] And / or, the porous carbon has at least one peak-valley in the pore diameter range of 1-3 nm, and the dV / dW of the lowest point of the peak-valley is greater than 0.1 cm 3 ·g -1 nm -1 .

[0017] Preferably, the microporosity of the porous carbon is 50%-90%.

[0018] Preferably, the pore volume of the porous carbon is 0.6-1.2 cc / g.

[0019] Preferably, the BET specific surface area of ​​the porous carbon is 1500-2500 m 2 / g.

[0020] Preferably, the particle size Dv50 of the porous carbon is 3-10 μm, the particle size Dv99 of the porous carbon is 10-25 μm, and the particle size Dn10 of the porous carbon is 0.5-5 μm.

[0021] A silicon-carbon negative electrode material comprises the porous carbon according to any one of the aforementioned embodiments, and nano-silicon located in the pores of the porous carbon.

[0022] Preferably, the particle size Dv50 of the silicon-carbon negative electrode material is 3 to 10 μm, the particle size Dv99 of the silicon-carbon negative electrode material is 10 to 25 μm, and the particle size Dn10 of the silicon-carbon negative electrode material is 0.5 to 5 μm.

[0023] Preferably, the BET specific surface area of ​​the silicon-carbon negative electrode material is 0.5-30 m 2 / g.

[0024] Preferably, the tap density of the silicon-carbon negative electrode material is 0.5-2 g / cm 3 .

[0025] Preferably, the surface of the silicon-carbon negative electrode material further includes a coating layer; the coating layer contains at least one of amorphous carbon, a fast ion conductor and a high molecular polymer.

[0026] Preferably, the silicon content of the silicon-carbon negative electrode material is 5wt%-85wt%.

[0027] The method for preparing the silicon-carbon negative electrode material comprises the following steps:

[0028] The porous carbon is vapor-deposited in an atmosphere containing a silicon source to obtain the silicon-carbon negative electrode material.

[0029] Preferably, the method further comprises: coating the silicon-carbon negative electrode material to obtain a coating layer on the surface of the silicon-carbon negative electrode material, wherein the coating layer comprises at least one of amorphous carbon, a fast ion conductor and a high molecular polymer.

[0030] An electrode sheet comprising the silicon-carbon negative electrode material according to any one of the aforementioned embodiments.

[0031] A lithium-ion battery comprises the electrode sheet described in the above embodiment.

[0032] An electrical appliance comprises the lithium-ion battery described in the foregoing embodiment.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The porous carbon provided by the present invention includes micropores and mesopores (which can be recorded as micro-mesoporous porous carbon), and the pore size distribution is a Luan-shaped distribution within the pore diameter range of 1-3nm. During the adsorption process, the adsorption pores (micropores) and the transport pores (small mesopores that match the micropores) cooperate with each other, and the pore resistance is low, ensuring the adsorption of silicon sources (such as silane gases, etc.), which can improve the silicon loading efficiency. The uniformly variable pore diameter (Luan-shaped distribution) also ensures the deintercalation and extraction of lithium ions. The silicon-carbon negative electrode material prepared using this porous carbon has high capacity and efficiency, and a lower expansion rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 : This is a pore distribution diagram of the porous carbon in Example 1 of the present invention (the primary axis of the vertical coordinate is the differential pore volume dV / dW, and the secondary axis is the cumulative pore volume);

[0037] Figure 2 : This is a pore distribution diagram of the porous carbon in Example 2 of the present invention (the primary axis of the vertical coordinate is the differential pore volume dV / dW, and the secondary axis is the cumulative pore volume);

[0038] Figure 3 : This is a pore distribution diagram of the porous carbon in Example 3 of the present invention (the primary axis of the vertical coordinate is the differential pore volume dV / dW, and the secondary axis is the cumulative pore volume);

[0039] Figure 4 The pore distribution diagram of the porous carbon in Comparative Example 1 of the present invention (the primary axis of the vertical coordinate is the differential pore volume dV / dW, and the secondary axis is the cumulative pore volume);

[0040] Figure 5 The pore distribution diagram of the porous carbon in Comparative Example 2 of the present invention (the primary axis of the vertical coordinate is the differential pore volume dV / dW, and the secondary axis is the cumulative pore volume);

[0041] Figure 6 The pore distribution diagram of the porous carbon in Comparative Example 3 of the present invention (the primary axis of the vertical coordinate is the differential pore volume dV / dW, and the secondary axis is the cumulative pore volume);

[0042] Figure 7 Schematic diagram of the diameter change of Luan-shaped pore;

[0043] Figure 8 Schematic diagram of the pore size change of peak-shaped pores. DETAILED DESCRIPTION

[0044] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0045] A first aspect of the present invention provides a porous carbon, wherein the porous carbon includes micropores and mesopores, and the pore volume of pores with a pore diameter of less than 3 nm accounts for more than 85% of the total pore volume, for example, specifically 88%, 90%, 92%, 95%, 97%, 99%, 100%, etc., or other values ​​within the range; the pore volume of pores with a pore diameter of less than 0.7 nm accounts for less than 15% of the total pore volume, for example, specifically 14%, 13%, 12%, 11%, 10%, 8%, 5%, 1%, 0, etc., or other values ​​within the range; in a pore distribution curve obtained by a nitrogen adsorption method, in which the horizontal axis is the pore diameter and the vertical axis is the differential pore volume dV / dW, the porous carbon has a differential pore volume dV / dW>0.05cm in the pore diameter range of 1-3 nm. 3 ·g -1 nm -1 That is to say, the pore distribution curve has no intersection with the horizontal axis in the pore diameter range of 1-3nm (excluding the endpoint value) (the pore distribution curve has no intersection with the horizontal axis, which means that the differential pore volume dV / dW ≠ 0), and the pore distribution curve will not be close to the horizontal axis in the pore diameter range of 1-3nm (the pore distribution curve is close to the horizontal axis, which means that the differential pore volume dV / dW ≤ 0.05cm 3 ·g -1 nm -1 ).

[0046] In the present invention, according to the definition of the International Association of Pure and Applied Chemistry (IUPAC), micropores refer to pores with a pore diameter of less than 2 nm, and mesopores refer to pores with a pore diameter of 2-50 nm. Without being bound by theory, the relationship between the various pore volumes of porous carbon has an important influence on the dynamic adsorption performance and performance of porous carbon. If the porous carbon only has a developed adsorption pore volume but no transport pores to match it, the adsorption rate cannot be improved, and the role of the adsorption pores cannot be well played. On the contrary, although there are enough transport pores, there are not enough adsorption pores, and the adsorption performance is poor. As a porous carbon substrate for silicon deposition, it is necessary not only to have a large adsorption capacity, but also a higher adsorption rate.

[0047] The porous carbon provided by the present invention includes micropores and mesopores (which can be recorded as micro-mesoporous porous carbon). The porous carbon serves as a carrier and needs to adsorb and crack nano-silicon into the pores. Therefore, a certain amount of micropores is required as adsorption pores to ensure the adsorption force field; however, not all of them can be micropores. Lithium ions are easy to enter but difficult to exit when deintercalating in porous carbon materials with high microporosity (for example, microporosity > 90%). Therefore, a certain number of small mesopores are also required to provide transport channels to increase the adsorption rate while ensuring the deintercalation of lithium ions; and, without being bound by theory, micro-mesopores can also effectively inhibit the expansion of silicon.

[0048] Not subject to theoretical constraints, for pores with a pore size of less than 0.7 nm, since the pore size is too small, it is difficult for vapor-phase silicon deposition precursor molecules (such as silane molecules) to enter, resulting in pores with a pore size of less than 0.7 nm being difficult to utilize. Therefore, too many pores with a pore size of less than 0.7 nm will lead to low micropore utilization, which needs to be controlled within 15%.

[0049] Without being bound by theory, pores smaller than 3 nm have two types of pore distributions: a peak-shaped distribution and a Luan-shaped distribution.

[0050] Among them, the peak-type pore structure is mainly manifested in the range of pore diameter of 1-3nm (excluding the endpoint value), the pore distribution curve has more than one intersection with the horizontal axis or is close to the horizontal axis, further, in most cases, the peak-type pore structure has at least one peak in the range of pore diameter of 1-3nm, and / or, the porous carbon has at least one peak-valley in the range of pore diameter of 1-3nm, and the lowest point of the peak-valley dV / dW is less than 0.05cm 3 ·g -1 nm -1 The main feature of the peak pore distribution is that as the pore size increases, the pore distribution changes in a peak-to-valley pattern, with the pore size transition being relatively steep. In the peak pore structure, the pore size distribution is discontinuous and the total number of pores is insufficient, such as Figure 8 As shown in the figure, the peak-shaped pores will suddenly change in diameter. When the pores are deeper and smaller in diameter, the resistance that nano-silicon has to overcome for entry is greater, and the relative distance that can diffuse (compared to the pore depth) is shorter. Therefore, the utilization rate of the pores is also lower.

[0051] The main characteristics of Luan-shaped pore distribution are that as the pore diameter increases, the pore distribution changes in a mountainous manner, and the pore diameter transition is relatively smooth and gentle. In the range of pore diameters of 1-3nm, the pore distribution curve has no intersection with the horizontal axis, nor is it close to the horizontal axis, and the pore distribution is relatively uniform. The pores of the Luan-shaped structure have continuous and uninterrupted pore diameter distribution, a large number of total pores, and basically consistent pore depths. Figure 7 As shown, the Luan-shaped pore depth will not suddenly change in diameter like the peak-shaped pore. Therefore, the local resistance caused by the diameter change can be reduced, which is conducive to the entry of vapor-phase silicon deposition precursor molecules (such as silane molecules) and improves the silicon loading efficiency.

[0052] The porous carbon provided by the present invention has pores less than 3 nm accounting for more than 85%, and in the range of pore diameters of 1-3 nm, the pore size distribution is a Luan-shaped distribution, the pore resistance is small, and the silicon loading efficiency is high. The silicon-carbon negative electrode material prepared using the porous carbon has good electrochemical performance.

[0053] In some embodiments of the present invention, the pore distribution curve of the porous carbon has at least one peak in the pore diameter range of 1-3 nm; and / or, the porous carbon has at least one peak and valley in the pore diameter range of 1-3 nm, and the differential pore volume dV / dW at the lowest point of the peak and valley is greater than 0.1 cm 3 ·g -1 nm -1 The pore distribution is more uniform, which is more conducive to the entry of vapor phase silicon precursor molecules (such as silane molecules) and the deposition of nano-silicon.

[0054] In some specific embodiments of the present invention, the microporosity of the porous carbon is 50-90%, for example, it can be 50%, 60%, 70%, 80%, 90%, etc., or other values ​​within the range; the pore volume of pores (micropores) with a pore size of <2nm is controlled to be 50-90%, firstly, to provide sufficient adsorption pores and ensure the adsorption force field, so as to facilitate the adsorption and cracking of nano-silicon into the pores; secondly, to avoid the phenomenon that porous carbon with high microporosity (for example, microporosity>90%) shows easy entry and difficult exit during the deintercalation of lithium ions.

[0055] In some specific embodiments of the present invention, the pore volume of the porous carbon is greater than or equal to 0.6cc / g, for example, it can be 0.6cc / g, 0.7cc / g, 0.8cc / g, 0.9cc / g, 1.0cc / g, 1.1cc / g, 1.2cc / g, etc., or other values ​​within the range; in some specific embodiments, the pore volume of the porous carbon is 0.6-1.2cc / g; the pore volume affects the silicon loading, and a higher silicon content can obtain sufficiently high capacity and efficiency.

[0056] In some embodiments of the present invention, the BET specific surface area of ​​the porous carbon is 1500-2500 m 2 / g, for example, it can be 1500m 2 / g、1600m 2 / g、1800m 2 / g、2000m 2 / g、2200m 2 / g、2500m 2 / g, etc., or other values ​​within the range.

[0057] In some specific embodiments of the present invention, the particle size Dv50 of the porous carbon is 3-10 μm, for example, 3 μm, 5 μm, 7 μm, 9 μm, 10 μm, etc., and may also be other values ​​within the range; the particle size Dv99 of the porous carbon is 10-25 μm, for example, 10 μm, 15 μm, 20 μm, 25 μm, etc., and may also be other values ​​within the range; the particle size Dn10 of the porous carbon is 0.5-5 μm, for example, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, etc., and may also be other values ​​within the range.

[0058] In some embodiments of the present invention, the porous carbon comprises 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.

[0059] In the specific embodiment of the present invention, the preparation method of porous carbon is described by taking the following preparation method of porous carbon as an example, but is not limited thereto.

[0060] The method for preparing the porous carbon comprises the following steps:

[0061] (1) Dry the mangosteen peel and grind it into powder;

[0062] (2) The powder obtained in step (1) was stirred in HCl, then washed with deionized water until the water was colorless, and dried;

[0063] (3) uniformly dispersing the dried mangosteen peel powder obtained in step (2) and KOH in water at a mass ratio of 1:1-1:4, stirring, and then freeze-drying to remove moisture;

[0064] (4) The mixed precursor obtained in step (3) was then heated in a tube furnace at 200, 300, and 400°C for 1.5 h, respectively, and then at 600-1000°C for 1 h, in argon;

[0065] (5) Finally, the calcined product was washed with deionized water and vacuum dried to obtain the porous carbon.

[0066] In some specific embodiments of the present invention, step (5) further includes a screening process after vacuum drying.

[0067] In some embodiments of the present invention, the particle size distribution of the porous carbon can be controlled by grinding into powder in step (1) and / or sieving after vacuum drying in step (5). This is well known in the art and will not be described in detail.

[0068] A second aspect of the present invention provides a silicon-carbon negative electrode material, comprising the porous carbon according to any one of the aforementioned embodiments, and nano-silicon located in the pores of the porous carbon.

[0069] In the present invention, the nano-silicon is a silicon material having at least one dimension less than 100 nm. For example, at least one dimension of the nano-silicon is 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 a range.

[0070] In some specific embodiments of the present invention, the nano-silicon can be nano-silicon particles, and the crystal domain size of the nano-silicon particles is 0nm to 3nm, specifically 0.01nm, 0.1nm, 0.5nm, 1nm, 2nm, 3nm or any value between 0nm and 3nm; small particles have a higher specific surface area and a shorter diffusion path, can release pressure faster, and reduce the degree of volume expansion, which is conducive to improving the coulombic efficiency.

[0071] The silicon-carbon negative electrode material provided by the present invention has high capacity, high initial efficiency and low expansion rate.

[0072] In some specific embodiments of the present invention, the particle size Dv50 of the silicon-carbon negative electrode material is 3 to 10 μm, for example, any point value among 3 μm, 5 μm, 7 μm, 9 μm, and 10 μm, or a range value composed of any two point values; the particle size Dv99 of the silicon-carbon negative electrode material is 10-25 μm, for example, 10 μm, 15 μm, 20 μm, 25 μm, etc., or other values ​​within the range; the particle size Dn10 of the silicon-carbon negative electrode material is 0.5-5 μm, for example, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, etc., or other values ​​within the range.

[0073] In some specific embodiments of the present invention, the BET specific surface area of ​​the silicon-carbon negative electrode material is 0.5-30 m 2 / g, for example, it can be 30m 2 / g, 25m 2 / g, 20m 2 / g、15m 2 / g、10m 2 / g、5m 2 / g, 4.9m 2 / g, 4.7m 2 / g, 4.5m 2 / g, 4.2m 2 / g、4m 2 / g, 3.5m 2 / g、3m 2 / g, 2.5m2 / g, 2m 2 / g、1m 2 / g, 0.5m 2 / g, etc., or other values ​​within the range.

[0074] In some specific embodiments of the present invention, the tap density of the silicon-carbon negative electrode material is 0.5-2 g / cm 3 , for example, it can be 0.5g / cm 3 , 0.6g / cm 3 , 0.7g / cm 3 , 0.75g / cm 3 , 0.8g / cm 3 , 0.85g / cm 3 , 0.9g / cm 3 , 0.95g / cm 3 , 1.0g / cm 3 , 1.1g / cm 3 , 1.2g / cm 3 , 1.3g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 , 1.7g / cm 3 , 1.8g / cm 3 , 1.9g / cm 3 , 2g / cm 3 It can also be other values ​​within the range.

[0075] In some embodiments of the present invention, 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 high molecular weight polymer. The present invention further coats the surface of the silicon-carbon anode material with the coating layer to further improve the electrical performance of the silicon-carbon anode material.

[0076] In some specific embodiments of the present invention, the silicon content of the silicon-carbon negative electrode material is 5wt%-85wt%, for example, it can be 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, etc., or it can be other values ​​within the range.

[0077] In some specific embodiments of the present invention, the silicon content of the silicon-carbon negative electrode material may be 40 wt%-60 wt%.

[0078] In some specific embodiments of the present invention, the method for preparing the silicon-carbon negative electrode material comprises the following steps: vapor-depositing porous carbon in an atmosphere containing a silicon source to obtain the silicon-carbon negative electrode material.

[0079] In some specific embodiments of the present invention, the temperature of the vapor deposition is 300-1200°C, for example, it can be 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, etc., or it can be other values ​​within the range.

[0080] In some specific embodiments of the present invention, the silicon source can be one or more of monosilane, disilane, trisilane, dimethylsilane, hexamethyldisilane, dichlorodihydrosilane, trichlorosilane, silicon tetrachloride, and silicon tetrafluoride.

[0081] In some specific embodiments of the present invention, the silicon-carbon negative electrode material is coated to obtain a coating layer on the surface of the silicon-carbon negative electrode material, and the coating layer contains at least one of amorphous carbon, a fast ion conductor and a high molecular polymer.

[0082] In some specific embodiments of the present invention, the coating layer includes a carbon coating layer, which is obtained by chemical vapor deposition. A gaseous carbon source is introduced under a protective gas atmosphere to carbon-coat the porous carbon after silicon deposition.

[0083] In some specific embodiments of the present invention, the temperature of carbon coating is 300-1200°C, for example, it can be 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, etc., or other values ​​within the range; the deposition time of carbon coating is 20min-6h, for example, 20min, 1h, 2h, 3h, 4h, 5h, 6h, etc., or other values ​​within the range.

[0084] In some specific embodiments of the present invention, the gaseous carbon source may be at least one of acetylene, methane, ethane or ethylene. In other embodiments, other carbon sources may also be used.

[0085] A third aspect of the present invention provides an electrode sheet, which includes the silicon-carbon negative electrode material according to any one of the aforementioned embodiments.

[0086] A fourth aspect of the present invention provides a lithium-ion battery, comprising the electrode sheet described in the aforementioned embodiment.

[0087] A fifth aspect of the present invention provides an electrical appliance comprising the lithium-ion battery described in the foregoing embodiment.

[0088] The following describes some embodiments of the present invention in detail with reference to specific examples. The raw materials used in the examples can be purchased from the market unless otherwise specified.

[0089] Example 1

[0090] S1. Preparation of porous carbon:

[0091] (1) Dry the mangosteen peel at 80°C for 24 h and grind it into powder;

[0092] (2) Stir in 1 M HCl overnight, then wash with deionized water until the water is colorless, and dry at 80 °C for 12 h;

[0093] (3) The dried mangosteen peel powder and KOH were evenly dispersed in water at a mass ratio of 1:3, stirred overnight, and then freeze-dried to remove moisture;

[0094] (4) The mixed precursor was then heated in a tube furnace at 200, 300, and 400 °C for 1.5 h, respectively, and then at 850 °C for 1 h in argon at a heating rate of 3 °C / min;

[0095] (5) Finally, the calcined product was washed with deionized water, dried in vacuum at 80° C. for 12 h, and sieved to obtain the porous carbon.

[0096] The particle size Dv50 of the porous carbon in this embodiment is 6.6 μm, Dv99 is 16.2 μm, and Dn10 is 3.3 μm; the specific surface area, pore volume, and pore structure information are shown in Table 1;

[0097] Depend on Figure 1 It can be seen that the pore distribution of the porous carbon in this embodiment in the range of 1-3 nm is a Luan-shaped distribution;

[0098] S2. Vapor-Phase Silicon Deposition: The porous carbon was placed in a rotary furnace, heated to 100°C, and held under vacuum for 30 minutes. Nitrogen was then introduced for protection. The temperature was then raised to 550°C at a rate of 5°C / min. Monosilane (SiH4) was then introduced at a flow rate of 10 L / min for 4 hours. After the reaction was complete, the silicon source valve was closed.

[0099] S3. Carbon coating: After silicon deposition is completed, the temperature is raised to 700°C, and acetylene (C2H2) is introduced at a flow rate of 5 L / min for 3 hours to obtain a silicon-carbon negative electrode material.

[0100] Example 2

[0101] The preparation method of the negative electrode material provided in this embodiment refers to that in Example 1, except that:

[0102] Preparation of porous carbon in this embodiment:

[0103] (1) Dry the mangosteen peel at 80°C for 24 h and grind it into powder;

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

[0105] (3) The dried mangosteen peel powder and KOH were evenly dispersed in water at a mass ratio of 1:2, stirred overnight, and then freeze-dried to remove moisture;

[0106] (4) The mixed precursor was then heated in a tube furnace at 200, 300, and 400 °C for 1.5 h, respectively, and then at 680 °C for 1 h in argon at a heating rate of 3 °C / min;

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

[0108] The particle size Dv50 of the porous carbon in this embodiment is 7.5 μm, Dv99 is 16.9 μm, and Dn10 is 0.5 μm; the specific surface area, pore volume, and pore structure information are shown in Table 1;

[0109] Depend on Figure 2 It can be seen that the pore distribution of the porous carbon in this embodiment in the range of 1-3 nm is a Luan-shaped distribution.

[0110] Example 3

[0111] The preparation method of the negative electrode material provided in this embodiment refers to that in Example 1, except that:

[0112] Preparation of porous carbon in this embodiment:

[0113] (1) Dry the mangosteen peel at 80°C for 24 h and grind it into powder;

[0114] (2) Stir in 1 M HCl overnight, then wash with deionized water until the water is colorless, and dry at 80 °C for 12 h;

[0115] (3) The dried mangosteen peel powder and KOH were evenly dispersed in water at a mass ratio of 1:2.5, stirred overnight, and then freeze-dried to remove moisture;

[0116] (4) The mixed precursor was then heated in a tube furnace at 200, 300, and 400 °C for 1.5 h, respectively, and then at 730 °C for 1 h in argon at a heating rate of 3 °C / min;

[0117] (5) Finally, the calcined product was washed with deionized water, dried in vacuum at 80° C. for 12 h, and sieved to obtain the porous carbon.

[0118] The particle size Dv50 of the porous carbon in this embodiment is 5.5 μm, Dv99 is 15.2 μm, and Dn10 is 0.5 μm; the specific surface area, pore volume, and pore structure information are shown in Table 1;

[0119] Depend on Figure 3 It can be seen that the pore distribution of the porous carbon in this embodiment in the range of 1-3 nm is a Luan-shaped distribution.

[0120] Example 4

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

[0122] Preparation of porous carbon in this embodiment:

[0123] (1) Dry the mangosteen peel at 80°C for 24 h and grind it into powder;

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

[0125] (3) The dried mangosteen peel powder and KOH were evenly dispersed in water at a mass ratio of 1:1.5, stirred overnight, and then freeze-dried to remove moisture;

[0126] (4) The mixed precursor was then heated in a tube furnace at 200, 300, and 400 °C for 1.5 h, respectively, and then at 600 °C for 1 h in argon at a heating rate of 3 °C / min;

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

[0128] The particle size Dv50 of the porous carbon in this embodiment is 6.5 μm, Dv99 is 17.2 μm, and Dn10 is 2.3 μm; the specific surface area, pore volume and pore structure information are shown in Table 1.

[0129] The pore distribution of the porous carbon in this embodiment in the range of 1-3 nm is Luan-shaped.

[0130] Comparative Example 1

[0131] The difference between the preparation method of the silicon-carbon negative electrode material in Comparative Example 1 and Example 1 is that the porous carbon used for vapor phase silicon deposition is different. The porous carbon used in Comparative Example 1 was purchased from Tianjin Chenxiang Fengkai Company, model G25; the remaining process parameters of vapor phase silicon deposition and carbon coating are the same as in Example 1.

[0132] The particle size Dv50 of the porous carbon in Comparative Example 1 is 6.2 μm, Dv99 is 21 μm, and Dn10 is 2.4 μm; the specific surface area, pore volume, and pore structure information are shown in Table 1;

[0133] Depend on Figure 4 It can be seen that the pore distribution of the porous carbon in this comparative example in the range of 1-3 nm presents a peak distribution.

[0134] Comparative Example 2

[0135] The difference between the preparation method of the silicon-carbon negative electrode material in Comparative Example 2 and Example 1 is that the porous carbon used for vapor phase silicon deposition is different. The porous carbon used in Comparative Example 2 is provided by Jiangsu Pushida Company; the remaining process parameters of vapor phase silicon deposition and carbon coating are the same as those in Example 1.

[0136] The particle size Dv50 of the porous carbon in Comparative Example 2 is 7.6 μm, Dv99 is 18.9 μm, and Dn10 is 2.6 μm; the specific surface area, pore volume, and pore structure information are shown in Table 1;

[0137] Depend on Figure 5 It can be seen that the pore distribution of the porous carbon in this comparative example in the range of 1-3 nm is a Luan-shaped distribution.

[0138] Comparative Example 3

[0139] The difference between the preparation method of the silicon-carbon negative electrode material in Comparative Example 3 and Example 1 is that the porous carbon used for vapor phase silicon deposition is different. The porous carbon used in Comparative Example 3 is provided by Fujian Tianli Company; the remaining process parameters of vapor phase silicon deposition and carbon coating are the same as those in Example 1.

[0140] The particle size Dv50 of the porous carbon in Comparative Example 3 is 6.5 μm, Dv99 is 19.1 μm, and Dn10 is 3.0 μm; the specific surface area, pore volume, and pore structure information are shown in Table 1;

[0141] Depend on Figure 6 It can be seen that the pore distribution of the porous carbon in this comparative example in the range of 1-3 nm presents a peak distribution.

[0142] Comparative Example 4

[0143] The difference between the preparation method of the silicon-carbon negative electrode material in Comparative Example 4 and Example 1 is that the porous carbon used for vapor phase silicon deposition is different, and the activated carbon used in Comparative Example 4 is provided by Jiangsu Pushida Company; the remaining process parameters of vapor phase silicon deposition and carbon coating are the same as those in Example 1.

[0144] The particle size Dv50 of the porous carbon in Comparative Example 4 is 7.6 μm, Dv99 is 18.9 μm, and Dn10 is 0.6 μm; the specific surface area, pore volume and pore structure information are shown in Table 1.

[0145] Test example

[0146] (1) Specific surface area, pore volume and pore ratio test of porous carbon

[0147] The specific surface area, pore volume and pore ratio of the porous carbon in each embodiment and each comparative example were measured using the BET method according to GB / T 19587-2017; the measurement was performed using ASAP 2460 (from Micromeritics), which works according to the Sorption Method with Adaptive Dosing Rate (SMART method). As a reference material, the standard material GB13905 (9.01 m 2 / g, based on multi-point BET method), GB13913 (5.78m 2 / g, based on the multi-point BET method) and GB13909 (specific surface area, total pore volume and pore size standard materials of mesoporous SIO2).

[0148] To reduce dead volume, filler rods are added to the reference and sample test tubes. The test tubes are mounted on the BET apparatus. The saturated vapor pressure of nitrogen (N2 4.0) is measured. A certain amount of sample is weighed into the glass test tube so that the test tube containing the filler rod is completely filled and the dead volume is minimized. To dry the sample, the sample is kept under vacuum at 200°C for 2 hours. After cooling, the sample weight is recorded. The glass test tube containing the sample is mounted on the measuring instrument. To degas the sample, it is evacuated at a selected pumping speed so that no material is drawn into the pump, to a final pressure of 200 mTorr.

[0149] Test Method: Nitrogen adsorption measurements were performed using a Micromeritics ASAP 2460 instrument at liquid nitrogen temperature (77.3K). Prior to measurement, the sample was degassed at 443K until a static vacuum of less than 0.01 Torr was reached. The adsorption site distribution was calculated based on the adsorption isotherm using the standard instrument software DFT. (NLDFT) software.

[0150] Pore ​​ratio test method: Nitrogen adsorption method is used to test the percentage of pore volume with pore diameter less than 3 nm or less than 0.7 nm in porous carbon to the total pore volume, or the proportion of other pores (volume).

[0151] The test results are shown in Table 1.

[0152] Table 1

[0153]

[0154] (2) Testing of particle size, specific surface area, tap density, silicon content and silane utilization of silicon-carbon negative electrode materials

[0155] Test method:

[0156] Specific surface area: The specific surface area of ​​silicon carbon in each embodiment and each comparative example was tested using the BET method according to GB / T 19587-2017;

[0157] Test Method: Nitrogen adsorption measurements were performed using a Micromeritics ASAP 2460 instrument at liquid nitrogen temperature (77.3K). Prior to measurement, the sample was degassed at 443K until a static vacuum of less than 0.01 Torr was reached. The adsorption site distribution was calculated based on the adsorption isotherm using the standard instrument software DFT. To reduce the dead volume, filler rods were added to the reference and sample test tubes (the specific test method is the same as that for the specific surface area of ​​porous carbon).

[0158] Particle size: tested using Malvern 3000 equipment according to the national standard GB / T 19077-2016.

[0159] Tap density: tested using Dandong Better BT313 tap density meter equipment, tested according to the national standard GB / T24533-2019.

[0160] Silicon content:

[0161] The silicon content is determined by calcining the material at 1000°C in air for 1 hour using a thermogravimetric analyzer to completely oxidize the carbon and convert the silicon into silicon dioxide. The weight of the added oxygen is then used to calculate the silicon content in the silicon-carbon material.

[0162] (1) Weigh about 2g of silicon-carbon material, the actual mass is recorded as m0; place it in a crucible with a mass of m1;

[0163] (2) Place the crucible in a tube furnace or muffle furnace, continuously pass compressed air, heat it to 600°C at 10°C / min, hold it for 1 hour, then heat it to 1000°C at the same rate and hold it for 1 hour;

[0164] (3) After cooling naturally to room temperature, take out the crucible and weigh its mass m2;

[0165] (4) Calculate the Si content: Si% = (m2-m1) × MSi÷MSiO2÷m0×100%;

[0166] Note: MSiO2 is the relative molecular mass of SiO2, 60.084 g / mol; MSi is the relative molecular mass of Si, 28.0855 g / mol.

[0167] Silane utilization % = [received material amount (g) × silicon content (%)] / [volume of silane introduced (L) × silane density (g / L)].

[0168] The test results are shown in Table 2.

[0169] Table 2

[0170]

[0171] (3) Electrochemical performance test

[0172] Preparation method of button half-cell: active material: SP: CNT: PAA glue is mixed in a mass ratio of 80:9:1:10, made into a slurry with deionized water, evenly coated on copper foil, and vacuum dried at 80°C for 24 hours to prepare the battery electrode for the experiment. Then, the lithium sheet is used as the counter electrode, and 1.1 mol / L LiPF6 electrolyte is used. The solvent is a four-component mixed solvent, ethylene carbonate (EC): vinylene carbonate (VC): dimethyl carbonate (DMC): fluoroethylene carbonate (FEC) = 1:1:1:1 (volume ratio), and a polypropylene microporous film is used as the diaphragm. The CR2025 button half-cell is assembled in a vacuum glove box.

[0173] The battery performance test method is: use a battery test system (half-cell test US Arbin multi-channel battery test system, German Braun Labstar (1200 / 780) glove box) to test the capacity and the first charge and discharge efficiency (first efficiency).

[0174] The test steps are: 0.1C DC to 5mV, let it stand for 5 minutes; 0.02C DC to 5mV, let it stand for 5 minutes; 0.01C DC to 5mV, let it stand for 5 minutes; 0.1C CC to 0.8V, 0.1C CC to 2V.

[0175] The test results are shown in Table 3.

[0176] Table 3

[0177]

[0178]

[0179] It can be seen from the data in Table 3 that the capacity and initial efficiency of the lithium-ion battery assembled with the silicon-carbon negative electrode material prepared using the porous carbon in the present invention are significantly improved.

[0180] Although the present invention has been illustrated and described using specific embodiments, it should be appreciated that the above embodiments are merely intended to illustrate the technical solutions of the present invention rather than to limit them. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents, without departing from the spirit and scope of the present invention. However, these modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A silicon-carbon negative electrode material, characterized in that: The silicon-carbon negative electrode material comprises porous carbon and nano-silicon located in the pores of the porous carbon; The porous carbon includes micropores and mesopores, and the pore volume of pores with a pore diameter of less than 3 nm accounts for more than 85% of the total pore volume, and the pore volume of pores with a pore diameter of less than 0.7 nm accounts for less than 15% of the total pore volume; in a pore distribution curve obtained by a nitrogen adsorption method, in which the abscissa is the pore diameter and the ordinate is the differential pore volume dV / dW, the porous carbon has a differential pore volume dV / dW greater than 0.05 cm in the pore diameter range of 1-3 nm. 3 ·g -1 nm -1 .

2. The silicon-carbon negative electrode material according to claim 1, characterized in that The porous carbon has at least one peak in the range of pore diameter of 1-3 nm; And / or, the porous carbon has at least one peak-valley in the pore diameter range of 1-3 nm, and the differential pore volume dV / dW at the lowest point of the peak-valley is greater than 0.1 cm 3 ·g -1 nm -1 .

3. The silicon-carbon negative electrode material according to claim 1, characterized in that The microporosity of the porous carbon is 50-90%.

4. The silicon-carbon negative electrode material according to claim 1, characterized in that Contains at least one of the following characteristics: (1) The pore volume of the porous carbon is 0.6-1.2 cc / g; (2) The BET specific surface area of ​​the porous carbon is 1500-2500m 2 / g; (3) The particle size Dv50 of the porous carbon is 3-10 μm, the particle size Dv99 of the porous carbon is 10-25 μm, and the particle size Dn10 of the porous carbon is 0.5-5 μm.

5. The silicon-carbon negative electrode material according to claim 1, characterized in that Contains at least one of the following characteristics: (1) The particle size Dv50 of the silicon-carbon negative electrode material is 3 to 10 μm, the particle size Dv99 of the silicon-carbon negative electrode material is 10 to 25 μm, and the particle size Dn10 of the silicon-carbon negative electrode material is 0.5 to 5 μm; (2) The BET specific surface area of ​​the silicon-carbon negative electrode material is 0.5-30m 2 / g; (3) The tap density of the silicon-carbon negative electrode material is 0.5-2 g / cm 3 ; (4) The surface of the silicon-carbon negative electrode material further includes a coating layer; the coating layer comprises at least one of amorphous carbon, a fast ion conductor, and a high molecular polymer; (5) The silicon content of the silicon-carbon negative electrode material is 5wt%-85wt%.

6. The method for preparing the silicon-carbon negative electrode material according to any one of claims 1 to 5, characterized in that: The following steps are involved: The porous carbon is vapor-deposited in an atmosphere containing a silicon source to obtain the silicon-carbon negative electrode material.

7. The method for preparing the silicon-carbon negative electrode material according to claim 6, characterized in that: Also includes: The silicon-carbon negative electrode material is subjected to coating treatment to obtain a coating layer on the surface of the silicon-carbon negative electrode material, wherein the coating layer contains at least one of amorphous carbon, a fast ion conductor and a high molecular polymer.

8. An electrode sheet, characterized in that: The electrode sheet comprises the silicon-carbon negative electrode material according to any one of claims 1 to 5.

9. A lithium-ion battery, characterized in that: The lithium-ion battery comprises the electrode sheet according to claim 8.

10. An electrical appliance, characterized in that: The electrical appliance comprises the lithium-ion battery according to claim 9.

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