Porous carbon, silicon-carbon negative electrode material, electrode sheet, lithium-ion battery, and electric device

Abstract

The present disclosure relates to the technical field of electrode materials, and in particular to a porous carbon, a silicon-carbon negative electrode material, an electrode sheet, a lithium-ion battery, and an electric device. The porous carbon has micropores and mesopores, wherein pores with a pore size of less than 3 nm account for more than 85% of the total pore volume, and pores with a pore size of less than 0.7 nm account for less than 15% of the total pore volume; and the porous carbon exhibits a Luan-type pore size distribution, wherein the Luan-type distribution is defined as: within a pore size range of 1-3 nm, a pore size distribution curve has a Dv / Dw value greater than 0.05 cm3·g-1·nm-1. The porous carbon provided in the present disclosure is a micro-mesoporous carbon, exhibits the Luan-type distribution, and has low pore resistance, thereby improving silicon loading efficiency, and ensuring intercalation and deintercalation of lithium ions while ensuring adsorption capacity. The silicon-carbon negative electrode material prepared by using the porous carbon exhibits high capacity and efficiency, and low expansion.

Description

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

[0001] Cross-reference to Related Applications

[0002] The present application claims priority to the Chinese patent application No. 202411381145.0 filed on September 30, 2024, and entitled "Porous carbon, silicon-carbon negative electrode material, electrode sheet, lithium ion battery and electric appliance", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present disclosure relates to the technical field of electrode materials, in particular, to a porous carbon, a silicon-carbon negative electrode material, an electrode sheet, a lithium ion battery and an electric appliance. BACKGROUND

[0004] Porous carbon materials are widely used in gas separation, water purification, heterogeneous catalyst support materials, high-performance thermal field materials, etc. due to their unique surface properties and structures. They also show broad application prospects in the fields of new energy materials such as high-performance materials for lithium ion batteries and high-performance materials for sodium ion batteries. The main reasons for their advantages in various fields are their rich pore structure, large specific surface area and low cost.

[0005] The silicon-carbon negative electrode material prepared by depositing nano-silicon in a porous carbon matrix is a new type of silicon-containing negative electrode material, which has smaller volume effect and better cycle performance than pure silicon. However, the existing porous carbon matrix has poor silicon loading efficiency, which affects the performance of the silicon-carbon negative electrode material.

[0006] SUMMARY

[0007] The present disclosure found through in-depth research that:

[0008] As the matrix of a new type of silicon-carbon material, the material structure of the porous carbon is a key factor affecting the performance of the silicon-carbon. The specific surface area and pore size distribution are the two most important factors affecting the electrochemical performance of the porous carbon. Currently, the porous carbon matrix does not have transport pores matching the adsorption pore volume, has large pore channel resistance, has low silicon loading efficiency, cannot simultaneously have large adsorption capacity and high adsorption rate, and cannot balance the adsorption force and lithium ion deintercalation.

[0009] In view of the above, the present disclosure is proposed.

[0010] The first object of the present disclosure is to provide a porous carbon, which includes micropores and mesopores, and has a stack distribution of pore size distribution in the interval of 1-3 nm, small pore channel resistance, high silicon loading efficiency, and can ensure lithium ion deintercalation while ensuring adsorption force.

[0011] A second object of the present disclosure is to provide a silicon-carbon negative electrode material including the porous carbon as described above and nano-silicon in pores of the porous carbon, the silicon-carbon negative electrode material having high capacity, high initial efficiency and small expansion.

[0012] A third object of the present disclosure is to provide an electrode sheet including the silicon-carbon negative electrode material as described above.

[0013] A fourth object of the present disclosure is to provide a lithium ion battery including the electrode sheet as described above.

[0014] A fifth object of the present disclosure is to provide an electric appliance including the lithium ion battery as described above.

[0015] In the present disclosure, the electric appliance can be, but is not limited to, a mobile phone, a tablet, a notebook computer, an electric toy, an electric tool, an electric vehicle, an electric automobile, a ship, a spacecraft, etc.

[0016] In order to achieve the above objects of the present disclosure, the following technical solutions are adopted:

[0017] A porous carbon including micropores and mesopores, and having a percentage of pore volume of pores with a pore diameter < 3 nm higher than 85% of the total pore volume, and a percentage of pore volume of pores with a pore diameter < 0.7 nm lower than 15% of the total pore volume; in a pore distribution curve with pore diameter as the horizontal coordinate and differential pore volume dV / dW as the vertical coordinate obtained by nitrogen adsorption method, the porous carbon has a differential pore volume dV / dW > 0.05 cm 3 ·g -1 ·nm -1 .

[0018] Further, the porous carbon has at least one peak in the interval of pore diameter 1-3 nm;

[0019] and / or, the porous carbon has at least one peak valley in the interval of pore diameter 1-3 nm, and the dV / dW at the lowest point of the peak valley > 0.1 cm 3 ·g -1 ·nm -1 .

[0020] Further, the microporosity of the porous carbon is 50%-90%.

[0021] Further, the pore volume of the porous carbon is 0.6-1.2 cc / g.

[0022] Further, the BET specific surface area of the porous carbon is 1500-2500 m 2 / g.

[0023] Further, the porous carbon has a particle size Dv50 of 3-10 μm, a particle size Dv99 of 10-25 μm, and a particle size Dn10 of 0.5-5 μm.

[0024] A silicon-carbon negative electrode material, comprising the porous carbon according to any one of the preceding embodiments, and nano-silicon in the pores of the porous carbon.

[0025] Further, the silicon-carbon negative electrode material has a particle size Dv50 of 3-10 μm, a particle size Dv99 of 10-25 μm, and a particle size Dn10 of 0.5-5 μm.

[0026] Further, the silicon-carbon negative electrode material has a BET specific surface area of 0.5-30 m 2 / g.

[0027] Further, the silicon-carbon negative electrode material has a tap density of 0.5-2 g / cm 3 .

[0028] Further, the surface of the silicon-carbon negative electrode material further comprises a coating layer; the coating layer comprises at least one of amorphous carbon, fast ion conductor, and high polymer.

[0029] Further, the silicon content of the silicon-carbon negative electrode material is 5wt%-85wt%.

[0030] A method for preparing the silicon-carbon negative electrode material, comprising the following steps:

[0031] Performing vapor deposition on the porous carbon in an atmosphere containing a silicon source to obtain the silicon-carbon negative electrode material.

[0032] Further, the method further comprises: performing coating treatment on the silicon-carbon negative electrode material to obtain a coating layer on the surface of the silicon-carbon negative electrode material, the coating layer comprising at least one of amorphous carbon, fast ion conductor, and high polymer.

[0033] An electrode sheet, comprising the silicon-carbon negative electrode material according to any one of the preceding embodiments.

[0034] A lithium ion battery, comprising the electrode sheet according to the preceding embodiments.

[0035] An electric appliance, comprising the lithium ion battery according to the preceding embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the specific embodiments of the present disclosure or the prior art, the accompanying drawings needed to be used in the specific embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description are part of the embodiments of the present disclosure, and all other embodiments obtained by those of ordinary skill in the art without creative work based on these accompanying drawings also belong to the protection scope of the present disclosure. The specific conditions are not specified in the embodiments, and the conventional conditions or the conditions recommended by the manufacturer are used. The reagents or instruments used are not specified by the manufacturer, and are conventional products that can be purchased on the market.

[0037] FIG. 1 is a pore distribution diagram of the porous carbon in Example 1 of the present disclosure (the main coordinate axis of the vertical coordinate is differential pore volume dV / dW, and the secondary coordinate axis is cumulative pore volume);

[0038] FIG. 2 is a pore distribution diagram of the porous carbon in Example 2 of the present disclosure (the main coordinate axis of the vertical coordinate is differential pore volume dV / dW, and the secondary coordinate axis is cumulative pore volume);

[0039] FIG. 3 is a pore distribution diagram of the porous carbon in Example 3 of the present disclosure (the main coordinate axis of the vertical coordinate is differential pore volume dV / dW, and the secondary coordinate axis is cumulative pore volume);

[0040] FIG. 4 is a pore distribution diagram of the porous carbon in Comparative Example 1 of the present disclosure (the main coordinate axis of the vertical coordinate is differential pore volume dV / dW, and the secondary coordinate axis is cumulative pore volume);

[0041] FIG. 5 is a pore distribution diagram of the porous carbon in Comparative Example 2 of the present disclosure (the main coordinate axis of the vertical coordinate is differential pore volume dV / dW, and the secondary coordinate axis is cumulative pore volume);

[0042] FIG. 6 is a pore distribution diagram of the porous carbon in Comparative Example 3 of the present disclosure (the main coordinate axis of the vertical coordinate is differential pore volume dV / dW, and the secondary coordinate axis is cumulative pore volume);

[0043] FIG. 7 is a schematic diagram of the pore size change of a larch-shaped pore;

[0044] FIG. 8 is a schematic diagram of the pore size change of a peak-shaped pore. DETAILED DESCRIPTION

[0045] The technical solutions of the present disclosure will be described clearly and completely in combination with the accompanying drawings and specific embodiments, but those skilled in the art will understand that the following described embodiments are part of the embodiments of the present disclosure, not all the embodiments, and are only used to illustrate the present disclosure, and should not be regarded as limiting the scope of the present disclosure. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative work also belong to the protection scope of the present disclosure. The specific conditions are not specified in the embodiments, and the conventional conditions or the conditions recommended by the manufacturer are used. The reagents or instruments used are not specified by the manufacturer, and are conventional products that can be purchased on the market.

[0046] The first aspect of the present disclosure provides a porous carbon, which comprises micropores and mesopores, and the percentage of pore volume of pores with pore diameter < 3 nm to the total pore volume is higher than 85%, for example, specifically can be 88%, 90%, 92%, 95%, 97%, 99%, 100%, etc., and can also be other values within the range; the percentage of pore volume of pores with pore diameter < 0.7 nm to the total pore volume is lower than 15%, for example, specifically can be 14%, 13%, 12%, 11%, 10%, 8%, 5%, 1%, 0, etc., and can also be other values within the range; in the pore distribution curve with pore diameter as the horizontal coordinate and differential pore volume dV / dW as the vertical coordinate obtained by nitrogen adsorption method, the differential pore volume dV / dW of the porous carbon is > 0.05 cm 3 ·g -1 ·nm -1 That is, the pore distribution curve does not intersect with the horizontal coordinate axis (does not intersect with the horizontal coordinate axis refers to differential pore volume dV / dW ≠ 0) and does not approach the horizontal coordinate axis (approaching the horizontal coordinate axis refers to differential pore volume dV / dW ≤ 0.05 cm 3 ·g -1 ·nm -1 ) in the range of 1-3 nm.

[0047] In the present disclosure, according to the definition of International Union of Pure and Applied Chemistry (IUPAC), micropores refer to pores with pore diameter less than 2 nm, and mesopores refer to pores with pore diameter of 2-50 nm. Without being bound by theory, the relationship of various pore volumes of the porous carbon plays an important role in the dynamic adsorption performance and use performance of the porous carbon. If the porous carbon only has developed adsorption pore volume and no matching transport pores, the adsorption rate cannot be improved and the adsorption pores cannot be well utilized, and vice versa, although there are sufficient transport pores, but there are not enough adsorption pores, the adsorption performance is poor. As a silicon deposition substrate, the porous carbon not only needs to have large adsorption capacity, but also needs to have high adsorption rate.

[0048] The porous carbon provided by the present disclosure comprises micropores and mesopores (which can be recorded as microporous mesoporous porous carbon), and as a carrier, the porous carbon needs to adsorb the cracked nanosilicon into the pore channel, so it needs to have a certain amount of micropores as adsorption pores to ensure the adsorption force field; but it cannot be all micropores, and lithium ions are easy to enter but difficult to exit in the porous carbon material with high micropore rate (for example, micropore rate > 90%), so a certain amount of small mesopores are also needed to provide a transport channel to improve the adsorption rate while ensuring the deintercalation of lithium ions; and without being bound by theory, the microporous mesopores can also effectively inhibit the expansion of silicon.

[0049] Without being bound by theory, for pores with a pore size < 0.7 nm, the gas-phase silicon precursor molecules (e.g., silane molecules) have difficulty entering the pores due to the small pore size, resulting in pores with a pore size < 0.7 nm being difficult to utilize, and thus, too many pores with a pore size < 0.7 nm can result in low micropore utilization, which needs to be controlled to be within 15%.

[0050] Without being bound by theory, pores with a size < 3 nm have two types of pore distribution, one is a peak type distribution, and the other is a stack type distribution.

[0051] The peak type pore structure is mainly manifested in the interval of 1-3 nm (not including the end point value) of the pore size, the pore distribution curve has more than one intersection with the abscissa axis or is close to the abscissa axis, and further, in most cases, the peak type pore structure has at least one peak in the interval of 1-3 nm of the pore size, and / or the porous carbon has at least one peak valley in the interval of 1-3 nm of the pore size, and the lowest point of the peak valley dV / dW < 0.05 cm 3 ·g -1 ·nm -1 The peak type pore distribution is mainly manifested in that as the pore size increases, the pore distribution changes in a peak valley type with a sudden high and a sudden low, and the pore size transition is relatively steep. In the peak type pore structure, the pore size distribution is discontinuous, and the total pore number is insufficient. As shown in FIG. 8, the peak type pore can have a sudden change in diameter, and when the pore is deep and the diameter is small, the resistance to be overcome by the nanosilicon is greater, and the relative distance that can be diffused (compared with the pore depth) is shorter, and thus, the utilization rate of the pore is also lower.

[0052] The stack type pore distribution is mainly manifested in that as the pore size increases, the pore distribution changes in a mountain type, and the pore size transition is relatively smooth and gentle, and in the interval of 1-3 nm of the pore size, the pore distribution curve does not intersect with the abscissa axis or is close to the abscissa axis, and the pore channel distribution is relatively uniform. The stack type structure has continuous and uninterrupted pore size distribution, a large total pore number, and a substantially consistent pore depth. As shown in FIG. 7, the stack type pore depth does not have a sudden change in diameter like the peak type pore, and thus, the local resistance generated by the change in diameter can be reduced, which is conducive to the entry of the gas-phase silicon precursor molecules (e.g., silane molecules) and improves the silicon loading efficiency.

[0053] The porous carbon provided by the present disclosure has a < 3 nm pore ratio of > 85%, and in the interval of 1-3 nm of the pore size, the pore size distribution is a stack type distribution, the pore channel resistance is small, the silicon loading efficiency is high, and the silicon-carbon negative electrode material prepared by using the porous carbon has good electrochemical performance.

[0054] In some specific embodiments of the present disclosure, the pore distribution curve of the porous carbon has at least one peak in the interval of 1-3 nm of the pore size; and / or the porous carbon has at least one peak valley in the interval of 1-3 nm of the pore size, and the differential pore volume dV / dW of the lowest point of the peak valley is > 0.1 cm 3·g -1 ·nm -1 The pore distribution is more uniform, which is more conducive to the entry of gas-phase silicon deposition precursor molecules (for example, silane molecules) and the deposition of nanosilicon.

[0055] In some embodiments of the present disclosure, the microporosity of the porous carbon is 50%-90%, for example, specifically 50%, 60%, 70%, 80%, 90%, etc., and other values in the range are also possible; the proportion of pore volume of pores with a pore size of <2nm (micropores) is 50-90%, which is to provide sufficient adsorption pores to ensure the adsorption force field to facilitate the entry of adsorbed and cracked nanosilicon into the pores; and to avoid the phenomenon of easy entry and difficult exit of high microporosity (for example, microporosity >90%) porous carbon in the deintercalation of lithium ions.

[0056] In some embodiments of the present disclosure, the pore volume of the porous carbon is greater than or equal to 0.6cc / g, for example, specifically 0.6cc / g, 0.7cc / g, 0.8cc / g, 0.9cc / g, 1.0cc / g, 1.1cc / g, 1.2cc / g, etc., and other values in the range are also possible; in some embodiments, the pore volume of the porous carbon is 0.6-1.2cc / g; the pore volume affects the silicon loading amount, and a higher silicon content can obtain a high enough capacity and efficiency.

[0057] In some embodiments of the present disclosure, the BET specific surface area of the porous carbon is 1500-2500m 2 / g, for example, specifically 1500m 2 / g, 1600m 2 / g, 1800m 2 / g, 2000m 2 / g, 2200m 2 / g, 2500m 2 / g, etc., and other values in the range are also possible.

[0058] In some embodiments of the present disclosure, the particle size Dv50 of the porous carbon is 3-10μm, for example, 3μm, 5μm, 7μm, 9μm, 10μm, etc., and other values in the range are also possible; the particle size Dv99 of the porous carbon is 10-25μm, for example, 10μm, 15μm, 20μm, 25μm, etc., and other values in the range are also possible; the particle size Dn10 of the porous carbon is 0.5-5μm, for example, 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, etc., and other values in the range are also possible.

[0059] In some embodiments of the present disclosure, the porous carbon comprises at least one of biomass-derived carbon, resin-derived carbon, petroleum coke-derived carbon, coal-derived carbon, metal-modified carbon material, and metal oxide-modified carbon material.

[0060] In the present disclosure, the preparation method of the porous carbon is described below by way of example, but is not limited thereto.

[0061] The preparation method of the porous carbon comprises the following steps:

[0062] (1) Dry the mangosteen peel and grind it into powder;

[0063] (2) Stir the powder obtained in step (1) in HCl, and then wash it with deionized water until the water is colorless, and dry it;

[0064] (3) Disperse the dried mangosteen peel powder obtained in step (2) and KOH in water at a mass ratio of 1:1 to 1:4, stir, and then freeze-dry to remove water;

[0065] (4) Then heat the mixed precursor obtained in step (3) in a tube furnace, and heat at 200, 300, and 400°C respectively for 1.5h, and then heat at 600-1000°C for 1h in argon;

[0066] (5) Finally, wash the calcined product with deionized water, and vacuum dry to obtain the porous carbon.

[0067] In some embodiments of the present disclosure, step (5) further comprises a process of sieving after vacuum drying.

[0068] In some embodiments of the present disclosure, the particle size distribution of the porous carbon can be controlled through the process of grinding into powder in step (1) and / or the process of sieving after vacuum drying in step (5). This is well known in the art and will not be described here.

[0069] The second aspect of the present disclosure provides a silicon-carbon negative electrode material, which comprises the porous carbon of any one of the preceding embodiments, and nano-silicon located in the pores of the porous carbon.

[0070] In the present disclosure, the nano-silicon is a silicon material with a size of less than 100nm in at least one dimension. For example, the nano-silicon has a size of 99nm, 90nm, 80nm, 70nm, 60nm, 50nm, 40nm, 30nm, 20nm, 10nm, 9nm, 8nm, 7nm, 6nm, 5nm, 4nm, 3nm, 2nm, 1.5nm, 1nm, 0.5nm, 0.1nm, 0.01nm, etc., or other values within the range.

[0071] In some embodiments of the present disclosure, the nano-silicon can be nano-silicon particles, the nano-silicon particles have a crystalline domain size of 0 nm to 3 nm, and specifically can be 0.01 nm, 0.1 nm, 0.5 nm, 1 nm, 2 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, can release pressure faster, and reduce the degree of volume expansion, which is beneficial to the improvement of coulombic efficiency.

[0072] The silicon-carbon negative electrode material provided by the present disclosure has high capacity, high initial efficiency, and low expansion rate.

[0073] In some embodiments of the present disclosure, the particle size Dv50 of the silicon-carbon negative electrode material is 3 to 10 μm, for example, 3 μm, 5 μm, 7 μm, 9 μm, 10 μm, or a range value composed of any one point value or 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.

[0074] In some embodiments of the present disclosure, the BET specific surface area of the silicon-carbon negative electrode material is 0.5-30 m 2 / g, for example, specifically can be 30 m 2 / g, 25 m 2 / g, 20 m 2 / g, 15 m 2 / g, 10 m 2 / g, 5 m 2 / g, 4.9 m 2 / g, 4.7 m 2 / g, 4.5 m 2 / g, 4.2 m 2 / g, 4 m 2 / g, 3.5 m 2 / g, 3 m 2 / g, 2.5 m 2 / g, 2 m 2 / g, 1 m 2 / g, 0.5 m 2 / g, etc., or other values within the range.

[0075] In some embodiments of the present disclosure, the tap density of the silicon-carbon negative electrode material is 0.5-2 g / cm 3 , for example, specifically can be 0.5 g / cm 3 , 0.6 g / cm 30.7g / 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 "etc." can also be other values ​​within the range.

[0076] In some specific embodiments of this disclosure, 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. Further coating the surface of the silicon-carbon anode material with the aforementioned coating layer can further improve the electrical performance of the silicon-carbon anode material.

[0077] In some specific embodiments of this disclosure, the silicon content of the silicon-carbon anode 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 other values ​​within the range.

[0078] In some specific embodiments of this disclosure, the silicon content of the silicon-carbon anode material can be 40wt%-60wt%.

[0079] In some specific embodiments of this disclosure, the method for preparing the silicon-carbon anode material includes the following steps: performing vapor deposition of porous carbon in an atmosphere containing a silicon source to obtain the silicon-carbon anode material.

[0080] In some embodiments of the present disclosure, the temperature for the vapor deposition is 300-1200℃, for example, specifically, 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, etc., and other values within the range are also possible.

[0081] In some embodiments of the present disclosure, the silicon source can be one or more of monosilane, disilane, trisilane, dimethylsilane, hexamethyldisilane, dichlorodisilane, trichlorosilane, silicon tetrachloride, silicon tetrafluoride.

[0082] In some embodiments of the present disclosure, the silicon-carbon negative electrode material is subjected to a coating treatment to obtain a coating layer on the surface of the silicon-carbon negative electrode material, and the coating layer comprises at least one of amorphous carbon, fast ion conductor and high molecular polymer.

[0083] In some embodiments of the present disclosure, the coating layer comprises a carbon coating layer, which is obtained by a chemical vapor deposition method, and gaseous carbon source is introduced into a protective gas atmosphere to coat the porous carbon after silicon deposition.

[0084] In some embodiments of the present disclosure, the temperature for the carbon coating is 300-1200℃, for example, specifically, 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃, 1200℃, etc., and other values within the range are also possible; the deposition time for the carbon coating is 20min-6h, for example, 20min, 1h, 2h, 3h, 4h, 5h, 6h, etc., and other values within the range are also possible.

[0085] In some embodiments of the present disclosure, the gaseous carbon source can be at least one of acetylene, methane, ethane or ethylene, and other carbon sources can also be used in other embodiments.

[0086] The third aspect of the present disclosure provides an electrode sheet comprising the silicon-carbon negative electrode material according to any one of the preceding embodiments.

[0087] The fourth aspect of the present disclosure provides a lithium ion battery comprising the electrode sheet according to the preceding embodiments.

[0088] The fifth aspect of the present disclosure provides an electric appliance comprising the lithium ion battery according to the preceding embodiments.

[0089] Some embodiments of the present disclosure will be described in detail below with specific reference on the basis of specific examples. The raw materials used in the examples, such as the materials without special instructions, can be purchased on the market.

[0090] Example 1

[0091] S1. Preparation of porous carbon:

[0092] (1) Dry the mangosteen peel at 80℃ for 24h, and grind into powder;

[0093] (2) Stir in 1M HCl overnight, then wash with deionized water until the water is colorless, and dry at 80℃ for 12h;

[0094] (3) Disperse the dried mangosteen peel powder and KOH in water at a mass ratio of 1:3, stir overnight, and then freeze-dry to remove water;

[0095] (4) Then heat the mixed precursor in a tube furnace at a heating rate of 3℃ / min at 200, 300, 400℃ for 1.5h respectively, and then at 850℃ for 1h, under argon atmosphere;

[0096] (5) Finally, wash the calcined product with deionized water, vacuum dry at 80℃ for 12h, and sieve to obtain the porous carbon.

[0097] The particle size Dv50 of the porous carbon in this example is 6.6μm, the Dv99 is 16.2μm, and the Dn10 is 3.3μm; the specific surface area, pore volume and pore structure information are shown in Table 1;

[0098] As can be seen from Figure 1, the pore distribution of the porous carbon in this example in the range of 1-3nm is in a luan type distribution;

[0099] S2. Gas phase silicon deposition: Place the porous carbon in a rotary furnace, heat to 100℃, and keep vacuum for 30min, then introduce nitrogen protection, then heat to 550℃ at a rate of 5℃ / min, then introduce silane (SiH4) at a flow rate of 10L / min, the introduction time is 4h, and after the reaction is completed, close the silicon source valve;

[0100] S3. Carbon coating: After the silicon deposition is completed, heat to 700℃, and introduce acetylene (C2H2) at a flow rate of 5L / min, the introduction time of acetylene is 3h, to obtain a silicon-carbon negative electrode material.

[0101] Example 2

[0102] The preparation method of the negative electrode material provided in this example refers to Example 1, except for the following differences:

[0103] Preparation of porous carbon in this example:

[0104] (1) The mangosteen peel was dried at 80°C for 24h, and ground into powder;

[0105] (2) Stirred in 1M HCl overnight, then washed with deionized water until the water was colorless, and dried at 80°C for 12h;

[0106] (3) The dried mangosteen peel powder and KOH were uniformly dispersed in water at a mass ratio of 1:2, stirred overnight, and then freeze-dried to remove water;

[0107] (4) Then the mixed precursors were heated in a tube furnace at a heating rate of 3°C / min, at 200, 300, 400°C for 1.5h respectively, and then at 680°C for 1h, heated in argon;

[0108] (5) Finally, the calcined product was washed with deionized water, dried at 80°C under vacuum for 12h, and sieved to obtain the porous carbon.

[0109] The particle size Dv50 of the porous carbon in this example was 7.5μm, Dv99 was 16.9μm, and Dn10 was 0.5μm; the specific surface area, pore volume, and pore structure information are shown in Table 1;

[0110] As shown in FIG. 2, the porous carbon of this example showed a luan-type distribution in the 1-3nm range.

[0111] Example 3

[0112] The preparation method of the negative electrode material provided in this example refers to Example 1, except that:

[0113] Preparation of the porous carbon in this example:

[0114] (1) The mangosteen peel was dried at 80°C for 24h, and ground into powder;

[0115] (2) Stirred in 1M HCl overnight, then washed with deionized water until the water was colorless, and dried at 80°C for 12h;

[0116] (3) The dried mangosteen peel powder and KOH were uniformly dispersed in water at a mass ratio of 1:2.5, stirred overnight, and then freeze-dried to remove water;

[0117] (4) Then the mixed precursors were heated in a tube furnace at a heating rate of 3°C / min, at 200, 300, 400°C for 1.5h respectively, and then at 730°C for 1h, heated in argon;

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

[0119] The particle size Dv50 of the porous carbon in the embodiment is 5.5 μm, the Dv99 is 15.2 μm, and the Dn10 is 0.5 μm; the specific surface area, pore volume, and pore structure information are shown in Table 1.

[0120] As shown in FIG. 3, the porous carbon in the embodiment has a luan-type distribution of pores in the range of 1-3 nm.

[0121] Embodiment 4

[0122] The preparation method of the negative electrode material in the embodiment refers to Embodiment 1, except that:

[0123] Preparation of the porous carbon in the embodiment:

[0124] (1) The mangosteen peel was dried at 80°C for 24 h and ground into powder;

[0125] (2) The powder was stirred in 1M HCl overnight, then washed with deionized water until the water was colorless, and dried at 80°C for 12 h;

[0126] (3) The dried mangosteen peel powder and KOH were uniformly dispersed in water at a mass ratio of 1:1.5, stirred overnight, and then freeze-dried to remove water;

[0127] (4) Then the mixed precursor was heated in a tube furnace at a heating rate of 3°C / min at 200, 300, and 400°C for 1.5 h, respectively, and then at 600°C for 1 h, under argon;

[0128] (5) Finally, the calcined product was washed with deionized water, vacuum dried at 80°C for 12 h, and sieved to obtain the porous carbon.

[0129] The particle size Dv50 of the porous carbon in the embodiment is 6.5 μm, the Dv99 is 17.2 μm, and the Dn10 is 2.3 μm; the specific surface area, pore volume, and pore structure information are shown in Table 1.

[0130] The porous carbon in the embodiment has a luan-type distribution of pores in the range of 1-3 nm.

[0131] Comparative Example 1

[0132] The difference between the preparation method of the silicon-carbon negative electrode material in Comparative Example 1 and Embodiment 1 is that the porous carbon used for gas-phase silicon deposition is different. The porous carbon used in Comparative Example 1 is purchased from Tianjin Chenxiangfengkai Company, model G25; the remaining process parameters for gas-phase silicon deposition and carbon coating are the same as those in Embodiment 1.

[0133] The particle size Dv50 of the porous carbon in Comparative Example 1 is 6.2 μm, the Dv99 is 21 μm, and the Dn10 is 2.4 μm; the specific surface area, pore volume, and pore structure information are shown in Table 1.

[0134] As can be seen from FIG. 4, the pore distribution of the porous carbon of the present comparative example in the range of 1-3 nm is in a peak type.

[0135] Comparative Example 2

[0136] The difference between the preparation method of the silicon-carbon negative electrode material in Comparative Example 2 and that in Example 1 is that the porous carbon used for the vapor-phase silicon deposition is different, and the porous carbon used in Comparative Example 2 is provided by Jiangsu Pusida Company; the rest of the process parameters for the vapor-phase silicon deposition and the carbon coating are the same as those in Example 1.

[0137] The particle size Dv50 of the porous carbon in Comparative Example 2 is 7.6 μm, the Dv99 is 18.9 μm, and the Dn10 is 2.6 μm; the specific surface area, pore volume and pore structure information are shown in Table 1.

[0138] As can be seen from FIG. 5, the pore distribution of the porous carbon of the present comparative example in the range of 1-3 nm is in a peak type.

[0139] Comparative Example 3

[0140] The difference between the preparation method of the silicon-carbon negative electrode material in Comparative Example 3 and that in Example 1 is that the porous carbon used for the vapor-phase silicon deposition is different, and the porous carbon used in Comparative Example 3 is provided by Fujian Tianli Company; the rest of the process parameters for the vapor-phase silicon deposition and the carbon coating are the same as those in Example 1.

[0141] The particle size Dv50 of the porous carbon in Comparative Example 3 is 6.5 μm, the Dv99 is 19.1 μm, and the Dn10 is 3.0 μm; the specific surface area, pore volume and pore structure information are shown in Table 1.

[0142] As can be seen from FIG. 6, the pore distribution of the porous carbon of the present comparative example in the range of 1-3 nm is in a peak type.

[0143] Comparative Example 4

[0144] The difference between the preparation method of the silicon-carbon negative electrode material in Comparative Example 4 and that in Example 1 is that the porous carbon used for the vapor-phase silicon deposition is different, and the active carbon used in Comparative Example 4 is provided by Jiangsu Pusida Company; the rest of the process parameters for the vapor-phase silicon deposition and the carbon coating are the same as those in Example 1.

[0145] The particle size Dv50 of the porous carbon in Comparative Example 4 is 7.6 μm, the Dv99 is 18.9 μm, and the Dn10 is 0.6 μm; the specific surface area, pore volume and pore structure information are shown in Table 1.

[0146] Test Example

[0147] (1) Test of the specific surface area, pore volume and pore ratio of the porous carbon

[0148] The specific surface area, pore volume and pore fraction of the porous carbons in each example and each comparative example were tested according to GB / T 19587-2017 by BET method; the measurement was performed using an ASAP 2460 (from Micromeritics) working according to the Sorption Method with Adaptive dosing Rate (SMART method). As reference materials, the standard materials GB13905 (9.01 m 2 / g based on the multipoint BET method), GB13913 (5.78 m 2 / g based on the multipoint BET method) and GB13909 (mesoporous SIO2 specific surface area, total pore volume and pore size standard material) can be used.

[0149] To reduce the dead volume, a packing rod was added to the reference and sample tubes. The tubes were installed on the BET apparatus. The saturated vapor pressure of nitrogen (N2 4.0) was determined. An amount of sample was weighed into a glass tube such that the tube containing the packing rod was completely filled and the smallest dead volume was created. To dry the sample, the sample was kept at 200 °C under vacuum for 2 hours. After cooling, the sample weight was recorded. The glass tube containing the sample was installed on the measurement apparatus. To degas the sample, it was evacuated at a selected pumping speed such that no material was drawn into the pump, reaching a final pressure of 200 mTorr.

[0150] Test method: Nitrogen adsorption measurements were performed using a Micromeritics ASAP 2460 instrument at liquid nitrogen temperature (77.3 K). Prior to the measurement, the sample was degassed at 443 K until a static vacuum of less than 0.01 Torr was reached. The adsorption point-site distribution was calculated from the adsorption isotherm using the standard instrument software DFT (NLDFT) software.

[0151] Pore fraction test method: Nitrogen adsorption method was used to test the percentage of the pore volume of the pores with a pore size less than 3 nm, or less than 0.7 nm, or other pore (volume) fraction in the porous carbon.

[0152] The test results are shown in Table 1.

[0153] Table 1

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

[0155] Test method:

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

[0157] Test method: Nitrogen adsorption measurements were performed using an ASAP 2460 instrument from Micromeritics at liquid nitrogen temperature (77.3 K). Prior to the measurement, the sample was degassed at 443 K until a static vacuum of less than 0.01 Torr was achieved. The adsorption point distribution was calculated from the adsorption isotherm using the standard instrument software DFT (NLDFT) software. To reduce the dead volume, a packing rod was added to the reference and sample tubes (same test method as for the specific surface area of the porous carbon).

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

[0159] Tap density: Tested using a Dandong Bit BT313 tap density instrument device according to the national standard GB / T 24533-2019.

[0160] Silicon content:

[0161] The silicon content was determined using a thermogravimetric analyzer in air at 1000°C for 1 h, which completely oxidized the carbon and converted the silicon to silicon dioxide. The weight of the added oxygen was then used to calculate the silicon content in the silicon-carbon material. The details are as follows:

[0162] (1) Weigh about 2 g of silicon-carbon material, and record the actual mass 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, and heat at a rate of 10°C / min to 600°C, maintain for 1 h, and then heat at the same rate to 1000°C for 1 h;

[0164] (3) After natural cooling to room temperature, remove the crucible and weigh the mass as m2;

[0165] (4) Calculate the Si content Si% = (m2-m1) x MSi ÷ MSiO2 ÷ m0 x 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 rate% = [amount of collected material (g) x silicon content (%)] / [volume of silane passed in (L) x density of silane (g / L)].

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

[0169] Table 2

[0170] (3) Electrochemical performance test

[0171] The preparation method of the button half-cell is as follows: the active material, SP, CNT, and PAA glue solution are mixed in a mass ratio of 80:9:1:10, and deionized water is used to prepare a slurry, which is uniformly coated on a copper foil, and then vacuum dried at 80°C for 24h to obtain the battery pole piece for experiment. Then, a lithium sheet is used as a counter electrode, 1.1mol / L LiPF6 is used as an electrolyte, a four-component mixed solvent is used as a 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 a separator, and then a CR2025 button half-cell is assembled in a vacuum glove box.

[0172] The test method of the battery performance is as follows: the capacity and the first charge-discharge efficiency (first efficiency) are tested by using a battery test system (a half-cell test American Arbin multi-channel battery test system, a Labstar (1200 / 780) type glove box of Braun Company in Germany).

[0173] The test procedure is as follows: 0.1C DC to 5mV, standing for 5min; 0.02C DC to 5mV, standing for 5min; 0.01C DC to 5mV, standing for 5min; 0.1C CC to 0.8V, 0.1C CC to 2V.

[0174] The test results are shown in Table 3.

[0175] Table 3

[0176] As can be seen from the data in Table 3, the capacity and the first efficiency of the lithium ion battery assembled by using the silicon-carbon negative electrode material prepared by using the porous carbon in the present disclosure are both significantly improved.

[0177] The beneficial effects of the present disclosure are as follows:

[0178] The porous carbon provided by the present disclosure includes micropores and mesopores (which can be recorded as microporous-mesoporous porous carbon), and the pore size distribution in the interval of 1-3nm is in a luan type distribution. In the adsorption process, the adsorption pores (micropores) and the transport pores (small mesopores matched with the micropores) cooperate with each other, the channel resistance is low, the adsorption force on the silicon source (such as silane gas, etc.) is ensured, and the silicon loading efficiency can be improved. The uniformly variable diameter channel (luan type distribution) also ensures the deintercalation of lithium ions. The silicon-carbon negative electrode material prepared by using the porous carbon has high capacity and efficiency, and the expansion rate is lower.

[0179] Although the present disclosure has been illustrated and described with respect to specific embodiments, it is noted that the above examples are intended to illustrate the technical solutions of the present disclosure, and are not intended to limit the present disclosure; it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be replaced equivalently, without departing from the spirit and scope of the present disclosure; and these modifications or replacements do not make the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present disclosure; therefore, this means that all these replacements and modifications within the scope of the present disclosure are included in the appended claims. Industrial applicability

[0180] The porous carbon of the present disclosure includes micropores and mesopores, the micropores as adsorption pores can ensure the adsorption force field, and the small mesopores provide transport channels to improve the adsorption rate while ensuring the deintercalation of lithium ions; the pore size distribution is in the range of 1-3 nm, the channel resistance is low, and the silicon loading efficiency is high. It can be used to prepare silicon-carbon negative electrode materials, electrode sheets and lithium ion batteries, and the prepared lithium ion batteries have high capacity and high initial efficiency; the lithium ion battery can be used for electrical appliances, such as mobile phones, tablets, notebook computers, electric toys, electric tools, electric vehicles, electric vehicles, ships, spacecraft, etc.

Claims

1. A porous carbon, characterized by, The porous carbon includes micropores and mesopores, and the percentage of pore volume of pores with pore diameter < 3 nm to the total pore volume is higher than 85%, and the percentage of pore volume of pores with pore diameter < 0.7 nm to the total pore volume is lower than 15%; in a pore distribution curve with pore diameter as the horizontal coordinate and differential pore volume dV / dW as the vertical coordinate obtained by nitrogen adsorption method, the differential pore volume dV / dW of the porous carbon in the interval with pore diameter of 1-3 nm is > 0.05 cm 3 ·g -1 ·nm -1 .

2. The porous carbon according to claim 1, characterized in that, The porous carbon has at least one peak in the pore size range of 1-3 nm. And / or, the porous carbon has at least one peak valley in the interval of pore size 1-3 nm, and the differential pore volume dV / dW of the peak valley minimum point is >0.1 cm 3 • g -1 • nm -1 .

3. The porous carbon according to claim 1 or 2, characterized in that, The microporosity of the porous carbon is 50%-90%.

4. The porous carbon according to any one of claims 1 to 3, characterized in that, At least one of the following features is included: (1) The pore volume of the porous carbon is 0.6-1.2 cc / g; (2) the porous carbon has a BET specific surface area of 1500-2500 m 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. A silicon-carbon negative electrode material, characterized by, The silicon-carbon negative electrode material comprises the porous carbon according to any one of claims 1-4, and nano-silicon in the pores of the porous carbon.

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

7. The method of producing a silicon-carbon negative electrode material according to claim 5 or 6, characterized in that, The steps include: Carrying out vapor deposition of the porous carbon in an atmosphere containing a silicon source to obtain the silicon-carbon negative electrode material.

8. The method of claim 7, wherein the silicon-carbon negative electrode material is prepared by a process comprising: Further comprising: Carrying out coating treatment on the silicon-carbon negative electrode material to obtain a coating layer on the surface of the silicon-carbon negative electrode material, the coating layer comprising at least one of amorphous carbon, fast ion conductor and high molecular polymer.

9. An electrode sheet, characterized by The electrode sheet comprises the silicon-carbon negative electrode material according to claim 5 or 6.

10. A lithium-ion battery, characterized by, The lithium ion battery comprises the electrode sheet according to claim 9.

11. An electric appliance characterized by comprising: The electric appliance comprises the lithium ion battery according to claim 10.

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